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Obesity is a major public health burden worldwide and is characterized by chronic low-grade inflammation driven by the cooperation of the innate immune system and dysregulated metabolism in adipose tissue and other metabolic organs. Receptor-interacting serine/threonine-protein kinase 1 (RIPK1) is a central regulator of inflammatory cell function that coordinates inflammation, apoptosis and necroptosis in response to inflammatory stimuli. Here we show that genetic polymorphisms near the human RIPK1 locus associate with increased RIPK1 gene expression and obesity. We show that one of these single nucleotide polymorphisms is within a binding site for E4BP4 and increases RIPK1 promoter activity and RIPK1 gene expression in adipose tissue. Therapeutic silencing of RIPK1 in vivo in a mouse model of diet-induced obesity dramatically reduces fat mass, total body weight and improves insulin sensitivity, while simultaneously reducing macrophage and promoting invariant natural killer T cell accumulation in adipose tissue. These findings demonstrate that RIPK1 is genetically associated with obesity, and reducing RIPK1 expression is a potential therapeutic approach to target obesity and related diseases.

Reverse causality has made it difficult to establish the causal directions between obesity and prediabetes and obesity and insulin resistance. To disentangle whether obesity causally drives prediabetes and insulin resistance already in non-diabetic individuals, we utilized the UK Biobank and METSIM cohort to perform a Mendelian randomization (MR) analyses in the non-diabetic individuals. Our results suggest that both prediabetes and systemic insulin resistance are caused by obesity (p = 1.2×10-3 and p = 3.1×10-24). As obesity reflects the amount of body fat, we next studied how adipose tissue affects insulin resistance. We performed both bulk RNA-sequencing and single nucleus RNA sequencing on frozen human subcutaneous adipose biopsies to assess adipose cell-type heterogeneity and mitochondrial (MT) gene expression in insulin resistance. We discovered that the adipose MT gene expression and body fat percent are both independently associated with insulin resistance (p≤0.05 for each) when adjusting for the decomposed adipose cell-type proportions. Next, we showed that these 3 factors, adipose MT gene expression, body fat percent, and adipose cell types, explain a substantial amount (44.39%) of variance in insulin resistance and can be used to predict it (p≤2.64×10-5 in 3 independent human cohorts). In summary, we demonstrated that obesity is a strong determinant of both prediabetes and insulin resistance, and discovered that individuals' adipose cell-type composition, adipose MT gene expression, and body fat percent predict their insulin resistance, emphasizing the critical role of adipose tissue in systemic insulin resistance., Competing Interests: The authors have declared that no competing interests exist.

Obesity is an important public health concern with limited effective treatment options. Internet-based technologies offer a cost-effective means to treat obesity. However, most of the online programs have been of short duration, have focused on a limited number of treatment modalities, and have not utilized the potential of coaching as part of the intervention. In this paper, we present the design, methods and participants' baseline characteristics in a real-life internet-based weight management program. Healthy Weight Coaching (HWC) is a 12-month web-based intervention for the management of obesity. The program is based on the Acceptance and Commitment Therapy and includes themes important for weight loss, including diet, physical activity, psychological factors, and sleep. In addition to the automated, interactive program, a personal coach is allocated to each participant. The participants are nationally enrolled through referrals from primary care, occupational health, hospitals, and private health care units. Adult individuals with BMI ≥25 kg/m 2 without severe complications are included. On a weekly basis, participants submit their weight logs, training sessions, and lifestyle targets to the internet portal and are scheduled to have online discussions with their coaches 26 times over the course of a year. Questionnaires on lifestyle, diet, physical activity, psychological factors, sleep, and quality of life are completed at baseline, 3, 6, 9, and 12 months, and thereafter yearly until 5 years. Additionally, log data on the use of the service and discussions with the coach are collected. The main outcome is weight change from baseline to 12 months. Recruitment to the HWC is ongoing. Baseline data of the participants recruited between Oct 2016 and Mar 2019 (n = 1189) are provided. This research will bring insight into how internet-based technologies can be implemented in the virtual management of obesity., Trial Registration: The trial is registered at clinicaltrials.cov (Clinical Trials Identifier NCT04019249)., Competing Interests: The authors declare no conflicts of interests. Alcohol consumption., (© 2020 The Authors. Published by Elsevier Inc.)

Single-nucleus RNA sequencing (snRNA-seq) measures gene expression in individual nuclei instead of cells, allowing for unbiased cell type characterization in solid tissues. We observe that snRNA-seq is commonly subject to contamination by high amounts of ambient RNA, which can lead to biased downstream analyses, such as identification of spurious cell types if overlooked. We present a novel approach to quantify contamination and filter droplets in snRNA-seq experiments, called Debris Identification using Expectation Maximization (DIEM). Our likelihood-based approach models the gene expression distribution of debris and cell types, which are estimated using EM. We evaluated DIEM using three snRNA-seq data sets: (1) human differentiating preadipocytes in vitro, (2) fresh mouse brain tissue, and (3) human frozen adipose tissue (AT) from six individuals. All three data sets showed evidence of extranuclear RNA contamination, and we observed that existing methods fail to account for contaminated droplets and led to spurious cell types. When compared to filtering using these state of the art methods, DIEM better removed droplets containing high levels of extranuclear RNA and led to higher quality clusters. Although DIEM was designed for snRNA-seq, our clustering strategy also successfully filtered single-cell RNA-seq data. To conclude, our novel method DIEM removes debris-contaminated droplets from single-cell-based data fast and effectively, leading to cleaner downstream analysis. Our code is freely available for use at https://github.com/marcalva/diem.

Background & Aim: Lifestyle changes focusing on diet and exercise remain the cornerstone of the treatment of non-alcoholic fatty liver disease (NAFLD). The present co-twin control study of monozygotic (MZ) twin pairs was designed to identify nutritional factors potentially involved in the pathogenesis of NAFLD., Methods: Cross-sectional study of 50 MZ twin pairs (age range: 23-36 years), of which ten pairs were discordant for liver fat (liver fat percentage of one twin ≤5% and his/her co-twin >5% and a difference between co-twins of >5%) as determined by magnetic resonance spectroscopy. Nutrient intake was calculated from 3-day food records., Results: Among the ten liver fat-discordant twin pairs, the n-6: n-3 ratio was significantly higher in the twins with higher liver as compared to their co-twins with lower liver fat (6.6:1 vs. 3.2:1, p-value = 0.005). In multiple regression analysis of within-pair differences including all 50 twin pairs, a higher n-6: n-3 ratio was significantly associated with a higher liver fat percentage within MZ twin pairs after adjustment for body mass index, energy intake and other covariates (standardized beta = 0.43, p-value = 0.001)., Conclusions: Our findings suggest that the n-6: n-3 ratio is a promising dietary agent for the prevention and treatment of NAFLD. Clinical trials are required to better understand causal relationships and required doses., (Copyright © 2019 Elsevier Ltd and European Society for Clinical Nutrition and Metabolism. All rights reserved.)

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

We present Bisque, a tool for estimating cell type proportions in bulk expression. Bisque implements a regression-based approach that utilizes single-cell RNA-seq (scRNA-seq) or single-nucleus RNA-seq (snRNA-seq) data to generate a reference expression profile and learn gene-specific bulk expression transformations to robustly decompose RNA-seq data. These transformations significantly improve decomposition performance compared to existing methods when there is significant technical variation in the generation of the reference profile and observed bulk expression. Importantly, compared to existing methods, our approach is extremely efficient, making it suitable for the analysis of large genomic datasets that are becoming ubiquitous. When applied to subcutaneous adipose and dorsolateral prefrontal cortex expression datasets with both bulk RNA-seq and snRNA-seq data, Bisque replicates previously reported associations between cell type proportions and measured phenotypes across abundant and rare cell types. We further propose an additional mode of operation that merely requires a set of known marker genes.

Background and Aims: Plasma apolipoprotein C3 (ApoC3) is associated with higher plasma triglyceride and type 2 diabetes incidence. We evaluated whether body mass index (BMI) or glucose metabolism were associated with ApoC3 in healthy monozygotic (MZ) twins., Methods and Results: Forty-seven MZ twin-pairs (20 man, 27 women), aged 23-42 years, were divided in subgroups according to discordance or concordance for (a) BMI (within-pair difference (Δ) in BMI≥3.0 or<3.0 kg/m 2 ), or (b) 2-h glucose iAUC, during oral glucose tolerance test (ΔGlucose iAUC ≥97.5 or<97.5 mmol × 120 minutes). Within these discordant or concordant subgroups, we tested (Wilcoxon signed-rank test) co-twin differences in ApoC3, adiposity measures, insulin-resistance and beta-cell function indices, and plasma and lipoprotein lipids. In BMI-Discordant (p = 0.92) or BMI-Concordant (p = 0.99) subgroups, ApoC3 did not differ between leaner and heavier co-twins. In the Glucose-Discordant subgroup, ApoC3 was significantly higher in twins with higher Glucose iAUC than in their co-twins with the lower Glucose iAUC (10.03 ± 0.78 vs. 8.48 ± 0.52 mg/dl; M ± SE; p = 0.032). Co-twins with higher Glucose iAUC also had higher waist circumference, body fat percentage, liver fat content, worse insulin-sensitivity and beta-cell function and higher cholesterol and triglyceride in plasma VLDL, IDL, and LDL. In Glucose-Concordant twin-pairs, no significant differences were observed in the explored variables. In all twin-pairs, ΔApoC3 correlated with Δ in lipids and glucose metabolism variables, the closest relationship being between ΔApoC3 and ΔVLDL triglyceride (r = 0.74, p < 0.0001)., Conclusions: While ApoC3 was not related to acquired differences in BMI, it associated with early dysregulation of glucose metabolism independently of obesity and genetic background., Competing Interests: Declaration of Competing Interest The authors declare that they have no conflict of interest associated with this manuscript., (Copyright © 2019. Published by Elsevier B.V.)

Leukocyte telomere length (LTL) is a heritable biomarker of genomic aging. In this study, we perform a genome-wide meta-analysis of LTL by pooling densely genotyped and imputed association results across large-scale European-descent studies including up to 78,592 individuals. We identify 49 genomic regions at a false dicovery rate (FDR) < 0.05 threshold and prioritize genes at 31, with five highlighting nucleotide metabolism as an important regulator of LTL. We report six genome-wide significant loci in or near SENP7, MOB1B, CARMIL1, PRRC2A, TERF2, and RFWD3, and our results support recently identified PARP1, POT1, ATM, and MPHOSPH6 loci. Phenome-wide analyses in >350,000 UK Biobank participants suggest that genetically shorter telomere length increases the risk of hypothyroidism and decreases the risk of thyroid cancer, lymphoma, and a range of proliferative conditions. Our results replicate previously reported associations with increased risk of coronary artery disease and lower risk for multiple cancer types. Our findings substantially expand current knowledge on genes that regulate LTL and their impact on human health and disease., (Copyright © 2020 The Author(s). Published by Elsevier Inc. All rights reserved.)

Introduction: Data on postoperative bile reflux after one anastomosis gastric bypass (OAGB) is lacking. Bile reflux scintigraphy (BRS) has been shown to be a reliable non-invasive tool to assess bile reflux after OAGB. We set out to study bile reflux after OAGB with BRS and endoscopy in a prospective series (RYSA Trial)., Methods: Forty patients (29 women) underwent OAGB between November 2016 and December 2018. Symptoms were reported and upper gastrointestinal endoscopy (UGE) was done preoperatively. Six months after OAGB, bile reflux was assessed in UGE findings and as tracer activity found in gastric tube and esophagus in BRS (follow-up rate 95%)., Results: Twenty-six patients (68.4%) had no bile reflux in BRS. Twelve patients (31.6%) had bile reflux in the gastric pouch in BRS and one of them (2.6%) had bile reflux also in the esophagus 6 months postoperatively. Mean bile reflux activity in the gastric pouch was 5.2% (1-21%) of total activity. De novo findings suggestive of bile reflux (esophagitis, stomal ulcer, foveolar inflammation of gastric pouch) were found for 15 patients (39.5%) in postoperative UGE. BRS and UGE findings were significantly associated (P = 0.022). Eight patients experienced de novo reflux symptoms at 6 months, that were significantly associated with BRS and de novo UGE findings postoperatively (P = 0.033 and 0.0005, respectively)., Conclusion: Postoperative bile reflux in the gastric pouch after OAGB is a common finding in scintigraphy and endoscopy. The long-term effects of bile exposure will be analyzed in future reports after a longer follow-up., Trial Registration: Clinical Trials Identifier NCT02882685.

White adipose tissue is one of the largest organs of the body. It plays a key role in whole-body energy status and metabolism; it not only stores excess energy but also secretes various hormones and metabolites to regulate body energy balance. Healthy adipose tissue capable of expanding is needed for metabolic well-being and to prevent accumulation of triglycerides to other organs. Mitochondria govern several important functions in the adipose tissue. We review the derangements of mitochondrial function in white adipose tissue in the obese state. Downregulation of mitochondrial function or biogenesis in the white adipose tissue is a central driver for obesity-associated metabolic diseases. Mitochondrial functions compromised in obesity include oxidative functions and renewal and enlargement of the adipose tissue through recruitment and differentiation of adipocyte progenitor cells. These changes adversely affect whole-body metabolic health. Dysfunction of the white adipose tissue mitochondria in obesity has long-term consequences for the metabolism of adipose tissue and the whole body. Understanding the pathways behind mitochondrial dysfunction may help reveal targets for pharmacological or nutritional interventions that enhance mitochondrial biogenesis or function in adipose tissue., (© 2019 World Obesity Federation.)

Introduction: There is a lack of prospective studies comparing Roux-en-Y gastric bypass (RYGB) and one-anastomosis gastric bypass (OAGB). Also, the effects of bariatric surgery and weight loss need a deeper understanding through metabolic studies. We describe the trial protocol and interim analysis of a prospective randomized controlled study comparing RYGB and OAGB: the RYSA trial., Materials and Methods: In total, 120 bariatric patients will be randomized between RYGB and OAGB in two academic centers. All patients will be followed up for 10 years with analysis and measurements of weight, comorbidities, blood tests, body composition and questionnaires. Extensive metabolic analyses (mixed meal tests, energy expenditure, biopsies of muscle and subcutaneous fat, urine, saliva and fecal samples) will be carried out in the Obesity Research Unit, University of Helsinki, for all patients treated at the Helsinki University Hospital (80 patients) at baseline, 6 months and 12 months. Bile reflux will be studied for the OAGB group at the Helsinki University Hospital at 6 months with gastroscopy and scintigraphy., Results: At an interim analysis at 3 months (half-way) through recruitment (30 RYGB and 30 OAGB patients) there have been no deaths and no intensive care unit admittances. One patient in both groups required additional gastroscopy, with anastomosis dilatation in the RYGB group but with no additional intervention in the OAGB group., Conclusion: The trial can be safely carried out. Recruitment is estimated to be complete by the end of 2019., Trial Registration: Clinical Trials Identifier NCT02882685. Registered on August 30th 2016.

The purpose of this review is to provide a detailed and updated description of the FinnTwin16 (FT16) study and its future directions. The Finnish Twin Cohort comprises three different cohorts: the Older Twin Cohort established in the 1970s and the FinnTwin12 and FT16 initiated in the 1990s. FT16 was initiated in 1991 to identify the genetic and environmental precursors of alcoholism, but later the scope of the project expanded to studying the determinants of various health-related behaviors and diseases in different stages of life. The main areas addressed are alcohol use and its consequences, smoking, physical activity, overall physical health, eating behaviors and eating disorders, weight development, obesity, life satisfaction and personality. To date, five waves of data collection have been completed and the sixth is now planned. Data from the FT16 cohort have contributed to several hundred studies and many substudies, with more detailed phenotyping and collection of omics data completed or underway. FT16 has also contributed to many national and international collaborations.

We constructed a food-based diet quality score (DQS) and examined its association with obesity measures, eating styles and nutrient intakes. Participants were 3592 individuals (764 dizygotic [DZ] and 430 monozygotic [MZ] twin pairs) from the FinnTwin16 study. The DQS (0-12 points) was constructed from a short 14 item food frequency questionnaire. Anthropometric measures and eating styles were self-reported. Nutrient intakes were calculated from food diaries completed in a subsample of 249 individuals (45 same-sex DZ and 60 MZ twin pairs). Twins were analyzed both as individuals and as twin pairs. The DQS was inversely associated with body mass index (β = -0.12, per one-unit increase in DQS, p < 0.001), waist circumference (β = -0.34, p < 0.001), obesity (odds ratio [OR]: 0.95, p = 0.004) and abdominal obesity (OR: 0.88, p < 0.001), independent of sex, age, physical activity and education. A higher DQS was associated with health-conscious eating, having breakfast, less snacking, fewer evening meals, and a higher frequency and regularity of eating. The DQS was positively correlated with the intakes of protein, fiber and magnesium and negatively correlated with the intakes of total fat, saturated fat and sucrose. Within twin pairs, most of the associations between the DQS with eating styles and some nutrients remained, but the DQS was not associated with obesity measures within twin pairs. The DQS is an easy-to-use tool for ranking adults according to diet quality and shows an association with obesity measures, eating styles and key nutrients in the expected direction., Competing Interests: The authors declare no conflict of interest.

Objective: To provide further knowledge about the longitudinal association between sleep duration and overweight in infants., Study Design: The data for this study are from the CHILD-SLEEP birth cohort (n = 1679). The sleep data are based on parent-reported total sleep duration collected at 3, 8, 18, and 24 months. For a subgroup of 8-month old participants (n = 350), an actigraph recording was also made. Growth data were derived from the child health clinic records. A logistic regression model was used to study the association between sleep duration and later weight development., Results: Shorter sleep duration in 3-month-old infants was cross-sectionally associated with lower weight-for-length/height (all P values ≤ .026) and body mass index (all P values ≤ .038). Moreover, short sleep duration at the age of 3 months was associated with greater weight-for-length/height z score at the age of 24 months (aOR 1.56; 95% CI 1.02-2.38) as well as with a predisposition to gain excess weight between 3 and 24 months of age (aOR 2.61; 95% CI 1.75-3.91). No significant associations were found between sleep duration at 8, 18, or 24 months and concurrent or later weight status. Actigraph-measured short night-time sleep duration at the age of 8 months was associated with greater weight-for-length at the age of 24 months (aOR 1.51; 95% CI 1.02-2.23)., Conclusions: Short total sleep duration at the age of 3 months and short night-time sleep duration at the age of 8 months are associated with the risk of gaining excess weight at 24 months of age., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Aims: To investigate how apolipoprotein C-III (apoC-III) metabolism is altered in subjects with type 2 diabetes, whether the perturbed plasma triglyceride concentrations in this condition are determined primarily by the secretion rate or the removal rate of apoC-III, and whether improvement of glycaemic control using the glucagon-like peptide-1 analogue liraglutide for 16 weeks modifies apoC-III dynamics., Materials and Methods: Postprandial apoC-III kinetics were assessed after a bolus injection of [5,5,5- 2 H 3 ]leucine using ultrasensitive mass spectrometry techniques. We compared apoC-III kinetics in two situations: in subjects with type 2 diabetes before and after liraglutide therapy, and in type 2 diabetic subjects with matched body mass index (BMI) non-diabetic subjects. Liver fat content, subcutaneous abdominal and intra-abdominal fat were determined using proton magnetic resonance spectroscopy., Results: Improved glycaemic control by liraglutide therapy for 16 weeks significantly reduced apoC-III secretion rate (561 ± 198 vs. 652 ± 196 mg/d, P = 0.03) and apoC-III levels (10.0 ± 3.8 vs. 11.7 ± 4.3 mg/dL, P = 0.035) in subjects with type 2 diabetes. Change in apoC-III secretion rate was significantly associated with the improvement in indices of glucose control (r = 0.67; P = 0.009) and change in triglyceride area under the curve (r = 0.59; P = 0.025). In line with this, the apoC-III secretion rate was higher in subjects with type 2 diabetes compared with BMI-matched non-diabetic subjects (676 ± 208 vs. 505 ± 174 mg/d, P = 0.042)., Conclusions: The results reveal that the secretion rate of apoC-III is associated with elevation of triglyceride-rich lipoproteins in subjects with type 2 diabetes, potentially through the influence of glucose homeostasis on the production of apoC-III., (© 2019 John Wiley & Sons Ltd.)

We aimed to study the eating behavioral traits that associate with body mass index (BMI) among BMI-discordant twin pairs. This cross-sectional study examined self-reported eating behaviors in 134 healthy young adult twin pairs (57 monozygotic [MZ] and 77 same-sex dizygotic [DZ]), of whom 29 MZ and 46 DZ pairs were BMI discordant (BMI difference ≥ 3 kg/m2). In both MZ and DZ BMI-discordant pairs, the heavier co-twins reported being less capable of regulating their food intake optimally than their leaner co-twins, mainly due to 'frequent overeating'. Furthermore, the heavier co-twins reported augmented 'disinhibited eating', 'binge-eating scores' and 'body dissatisfaction'. The twins agreed more frequently that the heavier co-twins (rather than the leaner co-twins) ate more food in general, and more fatty food, in particular. No significant behavioral differences emerged in BMI-concordant twin pairs. Overeating - measured by 'frequent overeating', 'disinhibited eating' and 'binge-eating score' - was the main behavioral trait associated with higher BMI, independent of genotype and shared environment.

Previous reports link differential DNA methylation (DNAme) to environmental exposures that are associated with lung function. Direct evidence on lung function DNAme is, however, limited. We undertook an agnostic epigenome-wide association study (EWAS) on pre-bronchodilation lung function and its change in adults.In a discovery-replication EWAS design, DNAme in blood and spirometry were measured twice, 6-15 years apart, in the same participants of three adult population-based discovery cohorts (n=2043). Associated DNAme markers (p<5×10 -7 ) were tested in seven replication cohorts (adult: n=3327; childhood: n=420). Technical bias-adjusted residuals of a regression of the normalised absolute β-values on control probe-derived principle components were regressed on level and change of forced expiratory volume in 1 s (FEV 1 ), forced vital capacity (FVC) and their ratio (FEV 1 /FVC) in the covariate-adjusted discovery EWAS. Inverse-variance-weighted meta-analyses were performed on results from discovery and replication samples in all participants and never-smokers.EWAS signals were enriched for smoking-related DNAme. We replicated 57 lung function DNAme markers in adult, but not childhood samples, all previously associated with smoking. Markers not previously associated with smoking failed replication. cg05575921 ( AHRR (aryl hydrocarbon receptor repressor)) showed the statistically most significant association with cross-sectional lung function (FEV 1 /FVC: p discovery =3.96×10 -21 and p combined =7.22×10 -50 ). A score combining 10 DNAme markers previously reported to mediate the effect of smoking on lung function was associated with lung function (FEV 1 /FVC: p=2.65×10 -20 ).Our results reveal that lung function-associated methylation signals in adults are predominantly smoking related, and possibly of clinical utility in identifying poor lung function and accelerated decline. Larger studies with more repeat time-points are needed to identify lung function DNAme in never-smokers and in children., Competing Interests: Conflict of interest: M. Imboden has nothing to disclose. Conflict of interest: M. Wielscher has nothing to disclose. Conflict of interest: F.I. Rezwan has nothing to disclose. Conflict of interest: A.F.S. Amaral has nothing to disclose. Conflict of interest: E. Schaffner has nothing to disclose. Conflict of interest: A. Jeong has nothing to disclose. Conflict of interest: A. Beckmeyer-Borowko has nothing to disclose. Conflict of interest: S.E. Harris reports grants from Medical Research Council, Biotechnology and Biological Sciences Research Council, Age UK and The Wellcome Trust, during the conduct of the study. Conflict of interest: J.M. Starr has nothing to disclose. Conflict of interest: I.J. Deary reports grants from Age UK and Medical Research Council, during the conduct of the study. Conflict of interest: C. Flexeder has nothing to disclose. Conflict of interest: M. Waldenberger has nothing to disclose. Conflict of interest: A. Peters has nothing to disclose. Conflict of interest: H. Schulz reports grants from German Federal Ministry of Education and Research (BMBF), during the conduct of the study. Conflict of interest: S. Chen has nothing to disclose. Conflict of interest: S.K. Sunny has nothing to disclose. Conflict of interest: W.J.J. Karmaus has nothing to disclose. Conflict of interest: Y. Jiang has nothing to disclose. Conflict of interest: G. Erhart has nothing to disclose. Conflict of interest: F. Kronenberg has nothing to disclose. Conflict of interest: R. Arathimos has nothing to disclose. Conflict of interest: G.C. Sharp has nothing to disclose. Conflict of interest: A.J. Henderson reports grants from Medical Research Council and Wellcome Trust, during the conduct of the study. Conflict of interest: Y. Fu has nothing to disclose. Conflict of interest: P. Piirilä has nothing to disclose. Conflict of interest: K.H. Pietiläinen has nothing to disclose. Conflict of interest: M. Ollikainen has nothing to disclose. Conflict of interest: A. Johansson has nothing to disclose. Conflict of interest: U. Gyllensten has nothing to disclose. Conflict of interest: M de Vries has nothing to disclose. Conflict of interest: D.A. van der Plaat has nothing to disclose. Conflict of interest: K. de Jong has nothing to disclose. Conflict of interest: H.M. Boezen has nothing to disclose. Conflict of interest: I.P. Hall reports grants from GSK and Boehringer Ingelheim, outside the submitted work. Conflict of interest: M.D. Tobin reports grants from Pfizer and GSK, outside the submitted work. Conflict of interest: M-R. Jarvelin has nothing to disclose. Conflict of interest: J.W. Holloway reports grants from European Union and National Institutes of Health, during the conduct of the study. Conflict of interest: D. Jarvis reports grants from European Union, Medical Research Council and Asthma UK, during the conduct of the study. Conflict of interest: N.M. Probst-Hensch has nothing to disclose., (Copyright ©ERS 2019.)

Purpose: The purpose of this study is to elucidate the effect of excess body weight and liver fat on the plasma proteome without interference from genetic variation., Experimental Design: The effect of excess body weight is assessed in young, healthy monozygotic twins from pairs discordant for body mass index (intrapair difference (Δ) in BMI > 3 kg m -2 , n = 26) with untargeted LC-MS proteomics quantification. The effect of liver fat is interrogated via subgroup analysis of the BMI-discordant twin cohort: liver fat discordant pairs (Δliver fat > 2%, n = 12) and liver fat concordant pairs (Δliver fat < 2%, n = 14), measured by magnetic resonance spectroscopy., Results: Seventy-five proteins are differentially expressed, with significant enrichment for complement and inflammatory response pathways in the heavier co-twins. The complement dysregulation is found in obesity in both the liver fat subgroups. The complement and inflammatory proteins are significantly associated with adiposity measures, insulin resistance and impaired lipids., Conclusions and Clinical Relevance: The early pathophysiological mechanisms in obesity are incompletely understood. It is shown that aberrant complement regulation in plasma is present in very early stages of clinically healthy obese persons, independently of liver fat and in the absence of genetic variation that typically confounds human studies., (© 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Waist-to-hip ratio (WHR) is a prominent cardiometabolic risk factor that increases cardio-metabolic disease risk independently of BMI and for which multiple genetic loci have been identified. However, WHR is a relatively crude proxy for fat distribution and it does not capture all variation in fat distribution. We here present a study of the role of coding genetic variants on fat mass in 6 distinct regions of the body, based on dual-energy X-ray absorptiometry imaging on more than 17k participants. We find that the missense variant CCDC92S70C, previously associated with WHR, is associated specifically increased leg fat mass and reduced visceral but not subcutaneous central fat. The minor allele-carrying transcript of CCDC92 is constitutively more highly expressed in adipose tissue samples. In addition, we identify two coding variants in SPATA20 and UQCC1 that are associated with arm fat mass. SPATA20K422R is a low-frequency variant with a large effect on arm fat only, and UQCC1R51Q is a common variant reaching significance for arm but showing similar trends in other subcutaneous fat depots. Our findings support the notion that different fat compartments are regulated by distinct genetic factors., Competing Interests: The authors have declared that no competing interests exist.

Background: Obesity is related to a myriad of cardiometabolic outcomes, each of which may have a specific metabolomic signature and a genetic basis. We identified plasma metabolites associating with different cardiometabolic risk factors (adiposity, cholesterol, insulin resistance, and inflammation) in monozygotic (MZ) twins. Additionally, we assessed if metabolite profiling can identify subgroups differing by cardiometabolic risk factors., Methods: We quantified 111 plasma metabolites (Acquity UPLC-triple quadrupole mass spectrometry), and measured blood lipids, HOMA index, CRP, and adiposity (BMI, %bodyfat by DEXA, fat distribution by MRI) in 40 MZ twin pairs (mean BMI 27.9 kg/m 2 , age 30.7). We determined associations among individuals (via linear regression) between metabolites and clinical phenotypes, and assessed, with within-twin pair analysis, if these associations were free from genetic confounding. We also performed cluster analysis to identify distinct subgroups based on subjects' metabolite profiles., Results: We identified 42 metabolite-phenotype associations (FDR < 0.05), 19 remained significant after controlling for shared factors within the twin pairs. Aspartate, propionylcarnitine, tyrosine hexanoylcarnitine, and deoxycytidine associated positively with two or more adiposity measures. HDL cholesterol (HDL-C) associated negatively and BMI positively with the most numbers of metabolites; 12 were unique for HDL-C and 3 for BMI. Metabolites associating with HDL-C had the strongest effect size. Metabolite profiling revealed two distinct subgroups of individuals, differing by 32 metabolites (p < 0.05), and by total and LDL cholesterol (LDL-C). Forty-two metabolites predicted subgroup membership in correlation with total cholesterol and 45 metabolites predicted subgroup membership in correlation with LDL-C., Conclusions: Different fat depots share metabolites associating with general adiposity. BMI and HDL-C associated with the most pronounced and specific metabolomic signature. Metabolomics profiling can be used to identify distinct subgroups of individuals that differ by cholesterol measures. Most of the observed metabolite-phenotype associations are free of confounding by genetics and environmental factors shared by the co-twins.

Objective: Obesity may alter serum steroid concentrations and metabolism. We investigated this in healthy young women with increased body fat and their leaner co-twin sisters., Design: Age and genetic background both strongly influence serum steroid levels and body composition. This is a cross-sectional study of 13 female monozygotic twin pairs (age, 23-36 years), ten of which were discordant for body mass index (median difference in body weight between the co-twins, 19 kg)., Methods: We determined body composition by dual energy X-ray absorptiometry and magnetic resonance imaging, serum androgens by liquid chromatography-tandem mass spectrometry, and mRNA expression of genes in subcutaneous adipose tissue and adipocytes., Results: The heavier women had lower serum dehydroepiandrosterone (DHEA), dihydrotestosterone (DHT), and sex hormone-binding globulin (SHBG) (P < 0.05 for all) compared to their leaner co-twins with no differences in serum testosterone or androstenedione levels. Serum DHEA correlated inversely with %body fat (r = -0.905, P = 0.002), and DHT positively with SHBG (r = 0.842, P = 0.002). In adipose tissue or adipocytes, expressions of STS (steroid sulfatase) and androgen-related genes were significantly higher in the heavier compared to the leaner co-twin, and within pairs, correlated positively with adiposity but were not related to serum androgen levels. None of the serum androgen or SHBG levels correlated with indices of insulin resistance., Conclusions: Serum DHEA levels were best predicted by %body fat, and serum DHT by SHBG. These or other serum androgen concentrations did not reflect differences in androgen-related genes in adipose tissue. General or intra-abdominal adiposity were not associated with increased androgenicity in young women., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Mitochondrial disorders (MDs) are inherited multi-organ diseases with variable phenotypes. Inclusion body myositis (IBM), a sporadic inflammatory muscle disease, also shows mitochondrial dysfunction. We investigated whether primary and secondary MDs modify metabolism to reveal pathogenic pathways and biomarkers. We investigated metabolomes of 25 mitochondrial myopathy or ataxias patients, 16 unaffected carriers, six IBM and 15 non-mitochondrial neuromuscular disease (NMD) patients and 30 matched controls. MD and IBM metabolomes clustered separately from controls and NMDs. MDs and IBM showed transsulfuration pathway changes; creatine and niacinamide depletion marked NMDs, IBM and infantile-onset spinocerebellar ataxia (IOSCA). Low blood and muscle arginine was specific for patients with m.3243A>G mutation. A four-metabolite blood multi-biomarker (sorbitol, alanine, myoinositol, cystathionine) distinguished primary MDs from others (76% sensitivity, 95% specificity). Our omics approach identified pathways currently used to treat NMDs and mitochondrial stroke-like episodes and proposes nicotinamide riboside in MDs and IBM, and creatine in IOSCA and IBM as novel treatment targets. The disease-specific metabolic fingerprints are valuable "multi-biomarkers" for diagnosis and promising tools for follow-up of disease progression and treatment effect., (© 2018 The Authors. Published under the terms of the CC BY 4.0 license.)

Aims: The PREVIEW lifestyle intervention study (ClinicalTrials.gov Identifier: NCT01777893) is, to date, the largest, multinational study concerning prevention of type-2 diabetes. We hypothesized that the initial, fixed low-energy diet (LED) would induce different metabolic outcomes in men vs women., Materials and Methods: All participants followed a LED (3.4 MJ/810 kcal/daily) for 8 weeks (Cambridge Weight Plan). Participants were recruited from 8 sites in Europe, Australia and New Zealand. Those eligible for inclusion were overweight (BMI ≥ 25 kg/m 2 ) individuals with pre-diabetes according to ADA-criteria. Outcomes of interest included changes in insulin resistance, fat mass (FM), fat-free mass (FFM) and metabolic syndrome Z-score., Results: In total, 2224 individuals (1504 women, 720 men) attended the baseline visit and 2020 (90.8%) completed the follow-up visit. Following the LED, weight loss was 16% greater in men than in women (11.8% vs 10.3%, respectively) but improvements in insulin resistance were similar. HOMA-IR decreased by 1.50 ± 0.15 in men and by 1.35 ± 0.15 in women (ns). After adjusting for differences in weight loss, men had larger reductions in metabolic syndrome Z-score, C-peptide, FM and heart rate, while women had larger reductions in HDL cholesterol, FFM, hip circumference and pulse pressure. Following the LED, 35% of participants of both genders had reverted to normo-glycaemia., Conclusions: An 8-week LED induced different effects in women than in men. These findings are clinically important and suggest gender-specific changes after weight loss. It is important to investigate whether the greater decreases in FFM, hip circumference and HDL cholesterol in women after rapid weight loss compromise weight loss maintenance and future cardiovascular health., (© 2018 The Authors. Diabetes, Obesity and Metabolism published by John Wiley & Sons Ltd.)

Background: Tobacco smoking is a risk factor for multiple diseases, including cardiovascular disease and diabetes. Many smoking-associated signals have been detected in the blood methylome, but the extent to which these changes are widespread to metabolically relevant tissues, and impact gene expression or metabolic health, remains unclear., Methods: We investigated smoking-associated DNA methylation and gene expression variation in adipose tissue biopsies from 542 healthy female twins. Replication, tissue specificity, and longitudinal stability of the smoking-associated effects were explored in additional adipose, blood, skin, and lung samples. We characterized the impact of adipose tissue smoking methylation and expression signals on metabolic disease risk phenotypes, including visceral fat., Results: We identified 42 smoking-methylation and 42 smoking-expression signals, where five genes (AHRR, CYP1A1, CYP1B1, CYTL1, F2RL3) were both hypo-methylated and upregulated in current smokers. CYP1A1 gene expression achieved 95% prediction performance of current smoking status. We validated and replicated a proportion of the signals in additional primary tissue samples, identifying tissue-shared effects. Smoking leaves systemic imprints on DNA methylation after smoking cessation, with stronger but shorter-lived effects on gene expression. Metabolic disease risk traits such as visceral fat and android-to-gynoid ratio showed association with methylation at smoking markers with functional impacts on expression, such as CYP1A1, and at tissue-shared smoking signals, such as NOTCH1. At smoking-signals, BHLHE40 and AHRR DNA methylation and gene expression levels in current smokers were predictive of future gain in visceral fat upon smoking cessation., Conclusions: Our results provide the first comprehensive characterization of coordinated DNA methylation and gene expression markers of smoking in adipose tissue. The findings relate to human metabolic health and give insights into understanding the widespread health consequence of smoking outside of the lung.

Background: The genetic architecture of birth size may differ geographically and over time. We examined differences in the genetic and environmental contributions to birthweight, length and ponderal index (PI) across geographical-cultural regions (Europe, North America and Australia, and East Asia) and across birth cohorts, and how gestational age modifies these effects., Methods: Data from 26 twin cohorts in 16 countries including 57 613 monozygotic and dizygotic twin pairs were pooled. Genetic and environmental variations of birth size were estimated using genetic structural equation modelling., Results: The variance of birthweight and length was predominantly explained by shared environmental factors, whereas the variance of PI was explained both by shared and unique environmental factors. Genetic variance contributing to birth size was small. Adjusting for gestational age decreased the proportions of shared environmental variance and increased the propositions of unique environmental variance. Genetic variance was similar in the geographical-cultural regions, but shared environmental variance was smaller in East Asia than in Europe and North America and Australia. The total variance and shared environmental variance of birth length and PI were greater from the birth cohort 1990-99 onwards compared with the birth cohorts from 1970-79 to 1980-89., Conclusions: The contribution of genetic factors to birth size is smaller than that of shared environmental factors, which is partly explained by gestational age. Shared environmental variances of birth length and PI were greater in the latest birth cohorts and differed also across geographical-cultural regions. Shared environmental factors are important when explaining differences in the variation of birth size globally and over time.

Background: Consensus on the necessity of esophagogastroduodenoscopy (EGD) before bariatric surgery is lacking. Recommendations and practices vary by country and unit. Several reports have expressed concerns on gastroesophageal reflux disease (GERD) and its consequences after sleeve gastrectomy (SG) and the risk of leaving a premalignant lesion in the excluded stomach after Roux-en-Y gastric bypass (RYGB)., Objectives: We explored the number and types of clinically significant findings in preoperative EGDs and how they associate with preexisting GERD-symptoms (SG) and premalignant lesions (RYGB). We also studied how many reoperations were performed due to postoperative GERD in SG-patients., Setting: University hospital., Methods: We investigated preoperative EGD-findings and gastrointestinal symptoms before bariatric surgery in all patients with a primary bariatric operation in our unit between December 2007 and May 2016., Results: We performed 1474 operations: 1047 (71.0%) RYGB, 407 (27.6%) SG, and 20 (1.4%) others. One thousand two hundred seventy-five (86.5%) preoperative EGD reports were analyzed: 647 (50.7%) EGDs were completely normal. Altogether, 294 patients (23.0% of total) had a clinically significant finding that was relevant for SG (hiatal hernia, esophagitis, Barrett's esophagus, esophageal dysplasia), 144 (49.0%) of whom reported gastrointestinal symptoms. Twenty patients (1.6%) had a significant finding relevant for RYGB (peptic ulcer, atrophic gastritis, gastrointestinal stromal tumor), and 6 (30%) reported gastrointestinal symptoms. Thirteen (3.2%) SGs were converted into RYGB due to GERD., Conclusions: Preoperative EGD is indicated before SG but not before RYGB for asymptomatic patients without a risk for gastric pathology., (Copyright © 2018 American Society for Bariatric Surgery. Published by Elsevier Inc. All rights reserved.)

Background: There is evidence that birth size is positively associated with height in later life, but it remains unclear whether this is explained by genetic factors or the intrauterine environment., Aim: To analyze the associations of birth weight, length and ponderal index with height from infancy through adulthood within mono- and dizygotic twin pairs, which provides insights into the role of genetic and environmental individual-specific factors., Methods: This study is based on the data from 28 twin cohorts in 17 countries. The pooled data included 41,852 complete twin pairs (55% monozygotic and 45% same-sex dizygotic) with information on birth weight and a total of 112,409 paired height measurements at ages ranging from 1 to 69 years. Birth length was available for 19,881 complete twin pairs, with a total of 72,692 paired height measurements. The association between birth size and later height was analyzed at both the individual and within-pair level by linear regression analyses., Results: Within twin pairs, regression coefficients showed that a 1-kg increase in birth weight and a 1-cm increase in birth length were associated with 1.14-4.25 cm and 0.18-0.90 cm taller height, respectively. The magnitude of the associations was generally greater within dizygotic than within monozygotic twin pairs, and this difference between zygosities was more pronounced for birth length., Conclusion: Both genetic and individual-specific environmental factors play a role in the association between birth size and later height from infancy to adulthood, with a larger role for genetics in the association with birth length than with birth weight., (Copyright © 2018 The Authors. Published by Elsevier B.V. All rights reserved.)

It is well established that boys are born heavier and longer than girls, but it remains unclear whether birth size in twins is affected by the sex of their co-twin. We conducted an individual-based pooled analysis of 21 twin cohorts in 15 countries derived from the COllaborative project of Development of Anthropometrical measures in Twins (CODATwins), including 67,850 dizygotic twin individuals. Linear regression analyses showed that boys having a co-twin sister were, on average, 31 g (95% CI 18 to 45) heavier and 0.16 cm (95% CI 0.045 to 0.274) longer than those with a co-twin brother. In girls, birth size was not associated (5 g birth weight; 95% CI -8 to -18 and -0.089 cm birth length; 95% CI -0.202 to 0.025) with the sex of the co-twin. Gestational age was slightly shorter in boy-boy pairs than in boy-girl and girl-girl pairs. When birth size was standardized by gestational age, the magnitude of the associations was attenuated in boys, particularly for birth weight. In conclusion, boys with a co-twin sister are heavier and longer at birth than those with a co-twin brother. However, these differences are modest and partly explained by a longer gestation in the presence of a co-twin sister.

Objectives: We investigated whether (1) subcutaneous adipose tissue (SAT) mitochondrial capacity predicts weight loss success and (2) weight loss ameliorates obesity-related SAT mitochondrial abnormalities., Methods: SAT biopsies were obtained from 19 clinically healthy obese subjects (body mass index (BMI) 34.6±2.7 kg m - 2 ) during a weight loss intervention (0, 5 and 12 months) and from 19 lean reference subjects (BMI 22.7±1.1 kg m -2 ) at baseline. Based on 1-year weight loss outcome, the subjects were divided into two groups: continuous weight losers (WL, n=6) and weight regainers (WR, n=13). Main outcome measures included SAT mitochondrial pathways from transcriptomics, mitochondrial amount (mitochondrial DNA (mtDNA), Porin protein levels), mtDNA-encoded transcripts, oxidative phosphorylation (OXPHOS) proteins, and plasma metabolites of the mitochondrial branched-chain amino-acid catabolism (BCAA) pathway. SAT and visceral adipose tissue (VAT) glucose uptake was measured with positron emission tomography., Results: Despite similar baseline clinical characteristics, SAT in the WL group exhibited higher gene expression level of nuclear-encoded mitochondrial pathways (P=0.0224 OXPHOS, P=0.0086 tricarboxylic acid cycle, P=0.0074 fatty acid beta-oxidation and P=0.0122 BCAA), mtDNA transcript COX1 (P=0.0229) and protein level of Porin (P=0.0462) than the WR group. Many baseline mitochondrial parameters correlated with WL success, and with SAT and VAT glucose uptake. During WL, the nuclear-encoded mitochondrial pathways were downregulated, together with increased plasma metabolite levels of BCAAs in both groups. MtDNA copy number increased in the WR group at 5 months (P=0.012), but decreased to baseline level between 5 and 12 months (P=0.015). The only significant change in the WL group for mtDNA was a reduction between 5 and 12 months (P=0.004). The levels of Porin did not change in either group upon WL., Conclusions: Higher mitochondrial capacity in SAT predicts good long-term WL success. WL does not ameliorate SAT mitochondrial downregulation and based on pathway expression, may paradoxically further reduce it.Data availability:The transcriptomics data generated in this study have been deposited to the Gene Expression Omnibus public repository, accession number GSE103769.

A carbohydrate-restricted diet is a widely recommended intervention for non-alcoholic fatty liver disease (NAFLD), but a systematic perspective on the multiple benefits of this diet is lacking. Here, we performed a short-term intervention with an isocaloric low-carbohydrate diet with increased protein content in obese subjects with NAFLD and characterized the resulting alterations in metabolism and the gut microbiota using a multi-omics approach. We observed rapid and dramatic reductions of liver fat and other cardiometabolic risk factors paralleled by (1) marked decreases in hepatic de novo lipogenesis; (2) large increases in serum β-hydroxybutyrate concentrations, reflecting increased mitochondrial β-oxidation; and (3) rapid increases in folate-producing Streptococcus and serum folate concentrations. Liver transcriptomic analysis on biopsy samples from a second cohort revealed downregulation of the fatty acid synthesis pathway and upregulation of folate-mediated one-carbon metabolism and fatty acid oxidation pathways. Our results highlight the potential of exploring diet-microbiota interactions for treating NAFLD., (Copyright © 2018 Elsevier Inc. All rights reserved.)

This study aims to investigate (i) how monozygotic (MZ) twin pairs who are discordant for body mass index (BMI) differ for objectively and subjectively measured physical activity (PA) and cardiorespiratory fitness (VO 2 max) and (ii) associations of PA and VO 2 max with adiposity and measures of metabolic health, in individual twins and independent of genetic and shared environmental effects within twin pairs. We examined 27 BMI-discordant and 14 BMI-concordant MZ twin pairs. Fat and fat-free mass (ffm) were measured by dual-energy X-ray absorptiometry and VO 2 max by spiroergometry. PA was measured objectively by accelerometers using ActiGraph GT1M for daytime activity and Actiwatch AW7 for 24 h/d. Self-reported PA was obtained through the Baecke and IPAQ long-form questionnaires. Objectively measured moderate-to-vigorous PA (MVPA, min/d), steps/d, and VO 2 max/kg were significantly lower, by 30%, 21%, and 14%, respectively, in the heavier compared with the leaner co-twins of the BMI-discordant twin pairs. There were no significant differences in self-reported PA or VO 2 max/ffm. As expected, PA and VO 2 max/ffm were similar in the BMI-concordant co-twins. Furthermore, the 24-h recording of activity suggested that the heavier co-twins had more restless sleep during the night, whereas the leaner co-twins were more active during the day. Within all twin pairs, higher MVPA and steps per day were associated with lower fat percentage and improved metabolic health measures. Objectively, but not subjectively measured PA is associated with lower fat percentage and better metabolic health, independent of genetic and shared environmental factors., (© 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Background: Few studies have examined both gene expression and DNA methylation profiles in subcutaneous adipose tissue (SAT) during long-term weight loss. Thus, molecular mechanisms in weight loss and regain remain elusive., Participants/methods: We performed a 1-year weight loss intervention on 19 healthy obese participants (mean body mass index (BMI) 34.6 kg m -2 ) and studied longitudinal gene expression (Affymetrix Human Genome U133 Plus 2.0) and DNA methylation (Infinium HumanMethylation450 BeadChip) in SAT at 0, 5 and 12 months. To examine whether weight loss and acquired obesity produce reciprocal profiles, we verified our findings in 26 BMI-discordant monozygotic twin pairs., Results: We found altered expression of 69 genes from 0 to 5' months (short-term) weight loss. Sixty of these genes showed reversed expression in acquired obesity (twins). Altogether 21/69 genes showed significant expression-DNA methylation correlations. Pathway analyses revealed increased high-density lipoprotein-mediated lipid transport characteristic to short-term weight loss. After the fifth month, two groups of participants evolved: weight losers (WLs) and weight regainers (WRs). In WLs five genes were differentially expressed in 5 vs 12 months, three of which significantly correlated with methylation. Signaling by insulin receptor pathway showed increased expression. We further identified 35 genes with differential expression in WLs from 0 to 12 months (long-term) weight loss, with 20 showing opposite expression patterns in acquired obesity, and 16/35 genes with significant expression-DNA methylation correlations. Pathway analyses demonstrated changes in signal transduction, metabolism, immune system and cell cycle. Notably, seven genes (UCHL1, BAG3, TNMD, LEP, BHMT2, EPDR1 and OSTM1) were found to be downregulated during both short- and long-term weight loss., Conclusions: Our study indicates short- and long-term weight loss influences in transcription and DNA methylation in SAT of healthy participants. Moreover, we demonstrate that same genes react in an opposite manner in weight loss and acquired obesity.

Obesity and ageing are associated with lower serum testosterone levels in men. How fat distribution or adipose tissue metabolism, independent of genetic factors and age, are related to sex steroid metabolism is less clear. We studied the associations between adiposity and serum sex hormone concentrations, and mRNA expression of genes regulating sex hormone metabolism in adipose tissue in young adult male monozygotic (MZ) twin pairs. The subjects [n=18 pairs; mean age, 32 years; individual body mass indexes (BMIs) 22-36kg/m 2 ] included 9 male MZ twin pairs discordant for BMI [intra-pair difference (Δ) in BMI ≥3kg/m 2 ]. Sex steroid concentrations were determined by liquid chromatography-tandem mass spectrometry, body composition by dual-energy X-ray absorptiometry and magnetic resonance imaging, and mRNA expressions from subcutaneous adipose tissue by Affymetrix. In BMI-discordant pairs (mean ΔBMI=5.9kg/m 2 ), serum dihydrotestosterone (DHT) was lower [mean 1.9 (SD 0.7) vs. 2.4 (1.0) nmol/l, P=0.040] and mRNA expressions of DHT-inactivating AKR1C2 (P=0.021) and cortisol-producing HSD11B1 (P=0.008) higher in the heavier compared to the leaner co-twins. Serum free 17β-estradiol (E2) was higher [2.3 (0.5) vs. 1.9 (0.5) pmol/l, P=0.028], and in all twin pairs, serum E2 and estrone concentrations were higher in the heavier than in the leaner co-twins [107 (28) vs. 90 (22) pmol/l, P=0.006; and 123 (43) vs. 105 (27) pmol/l, P=0.025]. Within all twin pairs, i.e. independent of genetic effects and age, 1) the amount of subcutaneous fat inversely correlated with serum total and free testosterone, DHT, and sex hormone-binding globulin (SHBG) concentrations (P<0.01 for all), 2) intra-abdominal fat with total testosterone and SHBG (P<0.05), and 3) liver fat with SHBG (P=0.006). Also, 4) general and intra-abdominal adiposity correlated positively with mRNA expressions of AKR1C2, HSD11B1, and aromatase in adipose tissue (P<0.05). In conclusion, acquired adiposity was associated with decreased serum DHT and increased estrogen concentrations, independent of genetic factors and age. The reduction of DHT could be linked to its increased degradation (by AKR1C2 and HSD11B1) and increased estrogen levels to increased adiposity-related expression of aromatase in adipose tissue., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Background: Overconsumption of dietary sugars, fructose in particular, is linked to cardiovascular risk factors such as type 2 diabetes, obesity, dyslipidemia and nonalcoholic fatty liver disease. However, clinical studies have to date not clarified whether these adverse cardiometabolic effects are induced directly by dietary sugars, or whether they are secondary to weight gain., Objectives: To assess the effects of fructose (75 g day -1 ), served with their habitual diet over 12 weeks, on liver fat content and other cardiometabolic risk factors in a large cohort (n = 71) of abdominally obese men., Methods: We analysed changes in body composition, dietary intake, an extensive panel of cardiometabolic risk markers, hepatic de novo lipogenesis (DNL), liver fat content and postprandial lipid responses after a standardized oral fat tolerance test (OFTT)., Results: Fructose consumption had modest adverse effects on cardiometabolic risk factors. However, fructose consumption significantly increased liver fat content and hepatic DNL and decreased β-hydroxybutyrate (a measure of β-oxidation). The individual changes in liver fat were highly variable in subjects matched for the same level of weight change. The increase in liver fat content was significantly more pronounced than the weight gain. The increase in DNL correlated positively with triglyceride area under the curve responses after an OFTT., Conclusion: Our data demonstrated adverse effects of moderate fructose consumption for 12 weeks on multiple cardiometabolic risk factors in particular on liver fat content despite only relative low increases in weight and waist circumference. Our study also indicates that there are remarkable individual differences in susceptibility to visceral adiposity/liver fat after real-world daily consumption of fructose-sweetened beverages over 12 weeks., (© 2017 The Association for the Publication of the Journal of Internal Medicine.)

Background: Subcutaneous adipose tissue (SAT) undergoes major changes in obesity, but little is known about the whole-genome scale patterns of these changes or about their variation between different obesity sub-groups. We sought to compare how transcriptomics profiles in SAT differ between monozygotic (MZ) co-twins who are discordant for body mass index (BMI), whether the profiles vary between twin pairs and whether the variation can be linked to clinical characteristics., Methods: We analysed the transcriptomics (Affymetrix U133 Plus 2.0) patterns of SAT in young MZ twin pairs (n=26, intra-pair difference in BMI >3 kg m -2 , aged 23-36), from 10 birth cohorts of adult Finnish twins. The clinical data included measurements of body composition, insulin resistance, lipids and adipokines., Results: We found 2108 genes differentially expressed (false discovery rate (FDR)<0.05) in SAT of the BMI-discordant pairs. Pathway analyses of these genes revealed a significant downregulation of mitochondrial oxidative pathways (P<0.05) and upregulation of inflammation pathways (P<0.05). Hierarchical clustering of heavy/lean twin ratios, representing effects of acquired obesity in the transcriptomics data, revealed three sub-groups with different molecular profiles (FDR<0.05). Analyses comparing these sub-groups showed that, in the heavy co-twins, downregulation of the mitochondrial pathways, especially that of branched chain amino acid degradation was more evident in two clusters while and upregulation of the inflammatory response was most evident in the last, presumably the unhealthiest cluster. High-fasting insulin levels and large adipocyte diameter were the predominant clinical characteristic of the heavy co-twins in this cluster (Bonferroni-adjusted P<0.05)., Conclusions: This is the first study in BMI-discordant MZ twin pairs reporting sub-types of obesity based on both SAT gene expression profiles and clinical traits. We conclude that a decrease in mitochondrial BCAA degradation and an increase in inflammation in SAT co-occur and associate with hyperinsulinemia and large adipocyte size in unhealthy obesity.

Background: Genes and the environment contribute to variation in adult body mass index [BMI (in kg/m 2 )], but factors modifying these variance components are poorly understood. Objective: We analyzed genetic and environmental variation in BMI between men and women from young adulthood to old age from the 1940s to the 2000s and between cultural-geographic regions representing high (North America and Australia), moderate (Europe), and low (East Asia) prevalence of obesity. Design: We used genetic structural equation modeling to analyze BMI in twins ≥20 y of age from 40 cohorts representing 20 countries (140,379 complete twin pairs). Results: The heritability of BMI decreased from 0.77 (95% CI: 0.77, 0.78) and 0.75 (95% CI: 0.74, 0.75) in men and women 20-29 y of age to 0.57 (95% CI: 0.54, 0.60) and 0.59 (95% CI: 0.53, 0.65) in men 70-79 y of age and women 80 y of age, respectively. The relative influence of unique environmental factors correspondingly increased. Differences in the sets of genes affecting BMI in men and women increased from 20-29 to 60-69 y of age. Mean BMI and variances in BMI increased from the 1940s to the 2000s and were greatest in North America and Australia, followed by Europe and East Asia. However, heritability estimates were largely similar over measurement years and between regions. There was no evidence of environmental factors shared by co-twins affecting BMI. Conclusions: The heritability of BMI decreased and differences in the sets of genes affecting BMI in men and women increased from young adulthood to old age. The heritability of BMI was largely similar between cultural-geographic regions and measurement years, despite large differences in mean BMI and variances in BMI. Our results show a strong influence of genetic factors on BMI, especially in early adulthood, regardless of the obesity level in the population., (© 2017 American Society for Nutrition.)

Obesity, a chronic state of energy overload, is characterized by adipose tissue dysfunction that is considered to be the major driver for obesity associated metabolic complications. The reasons for adipose tissue dysfunction are incompletely understood, but one potential contributing factor is adipose tissue mitochondrial dysfunction. Derangements of adipose tissue mitochondrial biogenesis and pathways associate with obesity and metabolic diseases. Mitochondria are central organelles in energy metabolism through their role in energy derivation through catabolic oxidative reactions. The mitochondrial processes are dependent on the proper NAD + /NADH redox balance and NAD + is essential for reactions catalyzed by the key regulators of mitochondrial metabolism, sirtuins (SIRTs) and poly(ADP-ribose) polymerases (PARPs). Notably, obesity is associated with disturbed adipose tissue NAD + homeostasis and the balance of SIRT and PARP activities. In this review we aim to summarize existing literature on the maintenance of intracellular NAD + pools and the function of SIRTs and PARPs in adipose tissue during normal and obese conditions, with the purpose of comprehending their potential role in mitochondrial derangements and obesity associated metabolic complications. Understanding the molecular mechanisms that are the root cause of the adipose tissue mitochondrial derangements is crucial for developing new effective strategies to reverse obesity associated metabolic complications., (Copyright © 2017 The Authors. Published by Elsevier B.V. All rights reserved.)

Background and Aims: Incretin hormones glucagon-like peptide (GLP)-1 and glucose-dependent insulinotropic polypeptide (GIP) are affected early on in the pathogenesis of metabolic syndrome and type 2 diabetes. Epidemiologic studies consistently link high fructose consumption to insulin resistance but whether fructose consumption impairs the incretin response remains unknown., Methods and Results: As many as 66 obese (BMI 26-40 kg/m 2 ) male subjects consumed fructose-sweetened beverages containing 75 g fructose/day for 12 weeks while continuing their usual lifestyle. Glucose, insulin, GLP-1 and GIP were measured during oral glucose tolerance test (OGTT) and triglycerides (TG), GLP-1, GIP and PYY during a mixed meal test before and after fructose intervention. Fructose intervention did not worsen glucose and insulin responses during OGTT, and GLP-1 and GIP responses during OGTT and fat-rich meal were unchanged. Postprandial TG response increased significantly, p = 0.004, and we observed small but significant increases in weight and liver fat content, but not in visceral or subcutaneous fat depots. However, even the subgroups who gained weight or liver fat during fructose intervention did not worsen their glucose, insulin, GLP-1 or PYY responses. A minor increase in GIP response during OGTT occurred in subjects who gained liver fat (p = 0.049)., Conclusion: In obese males with features of metabolic syndrome, 12 weeks fructose intervention 75 g/day did not change glucose, insulin, GLP-1 or GIP responses during OGTT or GLP-1, GIP or PYY responses during a mixed meal. Therefore, fructose intake, even accompanied with mild weight gain, increases in liver fat and worsening of postprandial TG profile, does not impair glucose tolerance or gut incretin response to oral glucose or mixed meal challenge., (Copyright © 2017 The Italian Society of Diabetology, the Italian Society for the Study of Atherosclerosis, the Italian Society of Human Nutrition, and the Department of Clinical Medicine and Surgery, Federico II University. Published by Elsevier B.V. All rights reserved.)

Inflammation is an important mediator of obesity-related complications such as the metabolic syndrome but its causes and mechanisms are unknown. As the complement system is a key mediator of inflammation, we studied whether it is activated in acquired obesity in subcutaneous adipose tissue (AT) and isolated adipocytes. We used a special study design of genetically matched controls of lean and heavy groups, rare monozygotic twin pairs discordant for body mass index (BMI) [ n  = 26, within-pair difference (Δ) in body mass index, BMI >3 kg/m 2 ] with as much as 18 kg mean Δweight. Additionally, 14 BMI-concordant (BMI <3 kg/m 2 ) served as a reference group. The detailed measurements included body composition (DEXA), fat distribution (MRI), glucose, insulin, adipokines, C3a and SC5b-9 levels, and the expression of complement and insulin signaling pathway-related genes in AT and adipocytes. In both AT and isolated adipocytes, the classical and alternative pathway genes were upregulated, and the terminal pathway genes downregulated in the heavier co-twins of the BMI-discordant pairs. The upregulated genes included C1q, C1s, C2, ficolin-1, factor H, receptors for C3a and C5a (C5aR1), and the iC3b receptor (CR3). While the terminal pathway components C5 and C6 were downregulated, its inhibitor clusterin was upregulated. Complement gene upregulation in AT and adipocytes correlated positively with adiposity and hyperinsulinemia and negatively with the expression of insulin signaling-related genes. Plasma C3a, but not SC5b-9, levels were elevated in the heavier co-twins. There were no differences between the co-twins in BMI-concordant pairs. Obesity is associated with increased expression of the early, but not late, complement pathway components and of key receptors. The twins with acquired obesity have therefore an inflated inflammatory activity in the AT. The results suggest that complement is likely involved in orchestrating clearance of apoptotic debris and inflammation in the AT.

Context: The joint effects of cardiorespiratory fitness (CRF) and body composition on metabolic health are not well known., Objective: To examine the associations of CRF, fat-free mass index (FFMI), and fat mass index (FMI) with metabolic health in individual twins and controlling for genetic and shared environmental effects by studying monozygotic intrapair differences., Design, Setting, and Participants: Two cross-sectional samples of healthy adult monozygotic and dizygotic twins were drawn from population-based Danish and Finnish national twin registries (n = 996 and n = 309)., Main Measures: CRF was defined as VO2max divided by fat-free mass. Insulin sensitivity and acute insulin response indices were derived from an oral glucose tolerance test. A continuous metabolic syndrome score was calculated. Visceral and liver fat were measured in the Finnish sample. Associations were analyzed separately in both cohorts with multivariate linear regression and aggregated with meta-analytic methods., Results: Insulin sensitivity, acute insulin response, metabolic syndrome score, visceral, and liver fat amount had strong and statistically significant associations with FMI (|β| 0.53 to 0.79), whereas their associations with CRF and FFMI were at most weak (|β| 0.02 to 0.15). The results of the monozygotic intrapair differences analysis showed the same pattern., Conclusions: Although FMI is strongly associated with worsening of metabolic health traits, even after controlling for genetic and shared environmental factors, there was little evidence for the effects of CRF or FFMI on metabolic health. This suggests that changing FMI rather than CRF or FFMI may affect metabolic health irrespective of genetic or early environmental determinants., (Copyright © 2017 by the Endocrine Society)

Background: The comparison of traits in twins from opposite-sex (OS) and same-sex (SS) dizygotic twin pairs is considered a proxy measure of prenatal hormone exposure. To examine possible prenatal hormonal influences on anthropometric traits, we compared mean height, body mass index (BMI), and the prevalence of being overweight or obese between men and women from OS and SS dizygotic twin pairs., Methods: The data were derived from the COllaborative project of Development of Anthropometrical measures in Twins (CODATwins) database, and included 68,494 SS and 53,808 OS dizygotic twin individuals above the age of 20 years from 31 twin cohorts representing 19 countries. Zygosity was determined by questionnaires or DNA genotyping depending on the study. Multiple regression and logistic regression models adjusted for cohort, age, and birth year with the twin type as a predictor were carried out to compare height and BMI in twins from OS pairs with those from SS pairs and to calculate the adjusted odds ratios and 95% confidence intervals for being overweight or obese., Results: OS females were, on average, 0.31 cm (95% confidence interval (CI) 0.20, 0.41) taller than SS females. OS males were also, on average, taller than SS males, but this difference was only 0.14 cm (95% CI 0.02, 0.27). Mean BMI and the prevalence of overweight or obesity did not differ between males and females from SS and OS twin pairs. The statistically significant differences between OS and SS twins for height were small and appeared to reflect our large sample size rather than meaningful differences of public health relevance., Conclusions: We found no evidence to support the hypothesis that prenatal hormonal exposure or postnatal socialization (i.e., having grown up with a twin of the opposite sex) has a major impact on height and BMI in adulthood.

Context: The associations of body mass index (BMI) and liver fat (LF) with circulating prandial metabolomic markers are incompletely understood., Objective: We aimed to characterize circulating metabolite excursions during an oral glucose tolerance test (OGTT) and evaluate whether the metabolomic signatures of BMI discordance coassociate with LF content., Design, Setting, and Participants: We measured 80 metabolite parameters by nuclear magnetic resonance, together with glucose and insulin, during a 2-hour OGTT in 64 monozygotic (MZ) and 73 dizygotic (DZ) twin pairs (aged 22.8 to 36.2 years). Metabolite excursions during the OGTT were compared within BMI-discordant (intrapair difference, BMI ≥ 3 kg/m2) cotwins separately within MZ and DZ pairs. Insulin-based indices were calculated from the OGTT. LF was measured by magnetic resonance spectroscopy in 25 BMI-discordant MZ pairs. Metabolite profiles were compared with respect to LF discordance (ΔLF% ≥ 2%)., Results: We replicated many previously reported OGTT-induced metabolite excursions in all 274 individuals and report novel lipoprotein excursions. The associations between some metabolite excursions and BMI differed in MZ and DZ twins. In BMI-discordant MZ pairs (mean ΔBMI = 4.9 kg/m2) who were concordant for LF (Δ0.2%), few metabolites differed between the cotwins: very-low-density lipoprotein (VLDL) cholesterol and apolipoprotein B were elevated, and high-density lipoprotein size and concentration were decreased in the cotwins with higher BMI. In contrast, in BMI-discordant MZ pairs (ΔBMI = 6.1 kg/m2) who were discordant for LF (Δ6.8%), cotwins with higher BMI exhibited lower insulin sensitivity and widespread metabolomic differences: elevations in small VLDL and low-density lipoprotein particles, fatty acids (FAs), and isoleucine. Within all 64 MZ twin pairs, lower insulin sensitivity associated with higher levels of VLDLs, triglycerides, FAs, and isoleucine., Conclusions: BMI-discordant MZ twin pairs who also are discordant for LF have more pronounced within-pair differences in metabolomics profiles during an OGTT than BMI-discordant pairs without LF discordance., (Copyright © 2017 by the Endocrine Society)

Aims/hypothesis: Low mitochondrial activity in adipose tissue is suggested to be an underlying factor in obesity and its metabolic complications. We aimed to find out whether mitochondrial measures are downregulated in obesity also in isolated adipocytes., Methods: We studied young adult monozygotic (MZ) twin pairs discordant (n = 14, intrapair difference ΔBMI ≥ 3 kg/m 2 ) and concordant (n = 5, ΔBMI < 3 kg/m 2 ) for BMI, identified from ten birth cohorts of 22- to 36-year-old Finnish twins. Abdominal body fat distribution (MRI), liver fat content (magnetic resonance spectroscopy), insulin sensitivity (OGTT), high-sensitivity C-reactive protein, serum lipids and adipokines were measured. Subcutaneous abdominal adipose tissue biopsies were obtained to analyse the transcriptomics patterns of the isolated adipocytes as well as of the whole adipose tissue. Mitochondrial DNA transcript levels in adipocytes were measured by quantitative real-time PCR. Western blots of oxidative phosphorylation (OXPHOS) protein levels in adipocytes were performed in obese and lean unrelated individuals., Results: The heavier (BMI 29.9 ± 1.0 kg/m 2 ) co-twins of the discordant twin pairs had more subcutaneous, intra-abdominal and liver fat and were more insulin resistant (p < 0.01 for all measures) than the lighter (24.1 ± 0.9 kg/m 2 ) co-twins. Altogether, 2538 genes in adipocytes and 2135 in adipose tissue were significantly differentially expressed (nominal p < 0.05) between the co-twins. Pathway analysis of these transcripts in both isolated adipocytes and adipose tissue revealed that the heavier co-twins displayed reduced expression of genes relating to mitochondrial pathways, a result that was replicated when analysing the pathways behind the most consistently downregulated genes in the heavier co-twins (in at least 12 out of 14 pairs). Consistently upregulated genes in adipocytes were related to inflammation. We confirmed that mitochondrial DNA transcript levels (12S RNA, 16S RNA, COX1, ND5, CYTB), expression of mitochondrial ribosomal protein transcripts and a major mitochondrial regulator PGC-1α (also known as PPARGC1A) were reduced in the heavier co-twins' adipocytes (p < 0.05). OXPHOS protein levels of complexes I and III in adipocytes were lower in obese than in lean individuals., Conclusions/interpretation: Subcutaneous abdominal adipocytes in obesity show global expressional downregulation of oxidative pathways, mitochondrial transcripts and OXPHOS protein levels and upregulation of inflammatory pathways., Data Availability: The datasets analysed and generated during the current study are available in the figshare repository, https://dx.doi.org/10.6084/m9.figshare.3806286.v1.

Mitochondrial myopathy (MM) with progressive external ophthalmoplegia (PEO) is a common manifestation of mitochondrial disease in adulthood, for which there is no curative therapy. In mice with MM, ketogenic diet significantly delayed progression of the disease. We asked in this pilot study what effects high-fat, low-carbohydrate "modified Atkins" diet (mAD) had for PEO/MM patients and control subjects and followed up the effects by clinical, morphological, transcriptomic, and metabolomic analyses. All of our five patients, irrespective of genotype, showed a subacute response after 1.5-2 weeks of diet, with progressive muscle pain and leakage of muscle enzymes, leading to premature discontinuation of the diet. Analysis of muscle ultrastructure revealed selective fiber damage, especially in the ragged-red-fibers (RRFs), a MM hallmark. Two years of follow-up showed improvement of muscle strength, suggesting activation of muscle regeneration. Our results indicate that (i) nutrition can modify mitochondrial disease progression, (ii) dietary counseling should be part of MM care, (iii) short mAD is a tool to induce targeted RRF lysis, and (iv) mAD, a common weight-loss method, may induce muscle damage in a population subgroup., (© 2016 The Authors. Published under the terms of the CC BY 4.0 license.)

Background: Obesity has been recognized as a state of subclinical inflammation resulting in a loss of insulin receptors and decreased insulin sensitivity. We here studied in vivo the role of circulating matrix metalloproteinase-8 (MMP-8) among young healthy twin adults. Also, in vitro analysis of the cleavage of human insulin receptor (INSR) by MMP-8 was investigated as well its inhibition by doxycycline and other MMP-8 inhibitor, Ilomastat/GM6001, which are broad-spectrum MMP inhibitors., Materials and Methods: We analysed serum MMP-8 levels by a time-resolved immunofluorometric assay in obese (n = 34), overweight (n = 76) and normal weight (n = 130) twin individuals. The effect of MMP-8 on INSR and the effects of synthetic MMP-8 inhibitors, doxycycline and Ilomastat/GM6001, were studied by SDS-PAGE., Results: We found that in obese individuals relative to normal weight individuals, the serum MMP-8 levels and MMP-8/TIMP-1 ratio were significantly increased (P = 0·0031 and P = 0·031, respectively). Among normal weight and obese individuals, also smoking significantly increases serum MMP-8 and MMP-8/TIMP-1 ratio. In vitro, we found that INSR was degraded by MMP-8 and this was inhibited by doxycycline and Ilomastat/GM6001., Conclusions: Obesity associated with elevated circulating MMP-8 found among young adults may contribute to progression of insulin resistance by cleaving INSR. This INSR cleavage by MMP-8 can be inhibited by synthetic MMP-8 inhibitors such as doxycycline. In addition to obesity, also smoking independently explained increased MMP-8 levels. Our results suggest that MMP-8 is an essential mediator in systemic subclinical inflammatory response in obesity, and a potential drug target., (© 2016 Stichting European Society for Clinical Investigation Journal Foundation.)

Background: Obese twins have lower saturated and higher long-chain polyunsaturated fatty acids (FA) in subcutaneous adipose tissue (SAT) compared to their lean monozygotic (MZ) co-twin. Whether this holds for metabolically distinct deep (DSAT) and superficial (SSAT) depots is unknown. Here we use non-invasive magnetic resonance spectroscopy (MRS) to measure the FA unsaturation in body mass index (BMI) discordant MZ twins in DSAT and SSAT and their relationship to ectopic fat content and body fat distribution. The main finding is further confirmed in an independent cohort using standardized measurement times., Methods: MRS and magnetic resonance imaging were used to measure DSAT and SSAT unsaturation and their relationship to intramyocellular lipids (IMCL), hepatocellular lipids (HCL) and the amount of subcutaneous (SAT) and visceral adipose tissue (VAT) in 16 pairs of healthy monozygotic twins (MZ) discordant for BMI. A second independent cohort of 12 healthy volunteers was used to measure DSAT unsaturation and IMCL with standardized measurement time. One volunteer also underwent repeated random measurements of DSAT unsaturation and IMCL., Results: In accordance with biopsy studies SSAT unsaturation was higher in the heavier twins (15.2±1.0% vs. 14.4±1.5%, P=0.024) and associated with SAT volume (R=0.672, P=0.001). DSAT unsaturation did not differ between twins (11.4±0.8 vs. 11.0±1.0, P=0.267) and associated inversely with IMCL content (R=-0.462, P=0.001). The inverse association between DSAT unsaturation and IMCL was also present in the participants of the second cohort (R=-0.641, P=0.025) and for the repeated sampling at random of one person (R=-0.765, P=0.027)., Conclusions: DSAT and SSAT FA unsaturation shows distinct associations with obesity and IMCL in MZ twins, reflecting compartment-specific metabolic activities. The FA unsaturation in the DSAT depot associates inversely with IMCL content, which raises the possibility of cross talk between the DSAT depot and the rapid turnover IMCL depot., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Background: Biotin acts as a coenzyme for carboxylases regulating lipid and amino-acid metabolism. We investigated alterations of the biotin-dependent functions in obesity and the downstream effects of biotin restriction in adipocytes in vitro., Subjects: Twenty-four monozygotic twin pairs discordant for body mass index (BMI). Mean within-pair difference (heavy-lean co-twin, Δ) of BMI was 6.0 kg m(-2) (range 3.1-15.2 kg m(-)(2))., Methods: Adipose tissue (AT) DNA methylation, gene expression of AT and adipocytes, and leukocytes (real-time quantitative PCR), serum biotin, C-reactive protein (CRP) and triglycerides were measured in the twins. Human adipocytes were cultured in low and control biotin concentrations and analyzed for lipid droplet content, mitochondrial morphology and mitochondrial respiration., Results: The gene expression levels of carboxylases, PCCB and MCCC1, were upregulated in the heavier co-twins' leukocytes. ΔPCCB (r=0.91, P=0.0046) and ΔMCCC1 (r=0.79, P=0.036) correlated with ΔCRP within-pairs. Serum biotin levels were lower in the heavier (274 ng l(-1)) than in the lean co-twins (390 ng l(-1), P=0.034). ΔBiotin correlated negatively with Δtriglycerides (r=-0.56, P=0.045) within-pairs. In AT, HLCS and ACACB were hypermethylated and biotin cycle genes HLCS and BTD were downregulated (P<0.05). Biotin-dependent carboxylases were downregulated (ACACA, ACACB, PCCB, MCCC2 and PC; P<0.05) in both AT and adipocytes of the heavier co-twins. Adipocytes cultured in low biotin had decreased lipid accumulation, altered mitochondrial morphology and deficient mitochondrial respiration., Conclusions: Biotin-dependent functions are modified by adiposity independent of genetic effects, and correlate with inflammation and hypertriglyceridemia. Biotin restriction decreases lipid accumulation and respiration, and alters mitochondrial morphology in adipocytes.