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There has been 100 years of research detailing the role of insulin in glucose, protein and free fatty acid metabolism. We explore the learnings though evolution and changes in management with an understanding of how it has impacted the care of people with diabetes. The discrimination endured is described and recent advances to empower and counter this are highlighted., (© 2021 The Authors. Diabetic Medicine published by John Wiley & Sons Ltd on behalf of Diabetes UK.)

Diabetes mellitus (DM) is a metabolic disease characterized by chronic hyperglycemia due to multiple etiological factors. In diabetics, lipid accumulation may cause lipid peroxidation and cell membrane lipid oxidation, leading to cellular injuries and triggering dysfunctions. Lipid accumulation may also lead to kidney injury in diabetics, such as glomerulosclerosis, tubular injury and loss of podocytes. As a water-soluble low molecular glycoprotein, apolipoprotein C3 (APOC3) is an important factor in the regulation of human lipid metabolism. It is closely involved in the development of diabetes mellitus and related complications through insulin resistance, lipid metabolism disorders, inflammation and oxidative stress. This review summarized the role and mechanism of APOC3 in diabetes and diabetic kidney disease.

Objective: Cancer cells must maintain lipid supplies for their proliferation and do so by upregulating lipogenic gene programs. The sterol regulatory element-binding proteins (SREBPs) act as modulators of lipid homeostasis by acting as transcriptional activators of genes required for fatty acid and cholesterol synthesis and uptake. SREBPs have been recognized as chemotherapeutic targets in multiple cancers, however it is not well understood which SREBP target genes are essential for tumorigenesis. In this study, we examined the requirement of SREBP target genes for pancreatic ductal adenocarcinoma (PDAC) tumor growth. Methods: Here we constructed a custom CRISPR knockout library containing known SREBP target genes and performed in vitro 2D culture and in vivo orthotopic xenograft CRISPR screens using a patient-derived PDAC cell line. In vitro, we grew cells in medium supplemented with 10% fetal bovine serum (FBS) or 10% lipoprotein-deficient serum (LPDS) to examine differences in gene essentiality in different lipid environments. In vivo, we injected cells into the pancreata of nude mice and collected tumors after 4 weeks. Results: We identified terpenoid backbone biosynthesis genes as essential for PDAC tumor development. Specifically, we identified the non-sterol isoprenoid product of the mevalonate pathway, geranylgeranyl diphosphate (GGPP), as an essential lipid for tumor growth. Mechanistically, we observed that restricting mevalonate pathway activity using statins and SREBP inhibitors synergistically induced apoptosis and caused disruptions in small G protein prenylation that have pleiotropic effects on cellular signaling pathways. Finally, we demonstrated that geranylgeranyl diphosphate synthase 1 (GGPS1) knockdown significantly reduces tumor burden in an orthotopic xenograft mouse model. Conclusions: These findings indicate that PDAC tumors selectively require GGPP over other lipids such as cholesterol and fatty acids and that this is a targetable vulnerability of pancreatic cancer cells.

Objectives: Compromised hepatic fatty acid oxidation (FAO) has been observed in human MASH patients and animal models of MASLD/MASH. It remains poorly understood how and when the hepatic FAO pathway is suppressed during the progression of MASLD towards MASH. Hepatic ChREBP⍺ is a classical lipogenic transcription factor that responds to the intake of dietary sugars. Methods: We examined its role in regulating hepatocyte fatty acid oxidation (FAO) and the impact of hepatic Chrebpa deficiency on sensitivity to diet-induced MASLD/MASH in mice. Results: We discovered that hepatocyte ChREBP⍺ is both necessary and sufficient to maintain FAO in a cell-autonomous manner independently of its DNA-binding activity. Supplementation of synthetic PPAR⍺/δ agonist is sufficient to restore FAO in Chrebp−/− primary mouse hepatocytes. Hepatic ChREBP⍺ was decreased in mouse models of diet-induced MAFSLD/MASH and in patients with MASH. Hepatocyte-specific Chrebp⍺ knockout impaired FAO, aggravated liver steatosis and inflammation, leading to early-onset fibrosis in response to diet-induced MASH. Conversely, liver overexpression of ChREBP⍺-WT or its non-lipogenic mutant enhanced FAO, reduced lipid deposition, and alleviated liver injury, inflammation, and fibrosis. RNA-seq analysis identified the CYP450 epoxygenase (CYP2C50) pathway of arachidonic acid metabolism as a novel target of ChREBP⍺. Over-expression of CYP2C50 partially restores hepatic FAO in primary hepatocytes with Chrebp⍺ deficiency and attenuates preexisting MASH in the livers of hepatocyte-specific Chrebp⍺-deleted mice. Conclusions: Our findings support the protective role of hepatocyte ChREBPa against diet-induced MASLD/MASH in mouse models in part via promoting CYP2C50-driven FAO.

Objective: Metabolic-associated fatty liver disease (MAFLD) represents one of the most prevalent chronic liver conditions worldwide, but its precise pathogenesis remains unclear. This research endeavors to elucidate the involvement and molecular mechanisms of polyribonucleotide nucleotidyltransferase 1 (PNPT1) in the progression of MAFLD. Methods: The study employed western blot and qRT-PCR to evaluate PNPT1 levels in liver specimens from individuals diagnosed with MAFLD and in mouse models subjected to a high-fat diet. Cellular studies investigated the effects of PNPT1 on lipid metabolism, apoptosis, and mitochondrial stability in hepatocytes. Immunofluorescence was utilized to track the subcellular movement of PNPT1 under high lipid conditions. RNA immunoprecipitation and functional assays were conducted to identify interactions between PNPT1 and Mcl-1 mRNA. The role of PPARα as an upstream transcriptional regulator of PNPT1 was investigated. Recombinant adenoviral vectors were utilized to modulate PNPT1 expression in vivo. Results: PNPT1 was found to be markedly reduced in liver tissues from MAFLD patients and HFD mice. In vitro, PNPT1 directly regulated hepatic lipid metabolism, apoptosis, and mitochondrial stability. Under conditions of elevated lipids, PNPT1 relocated from mitochondria to cytoplasm, modifying its physiological functions. RNA immunoprecipitation revealed that the KH and S1 domains of PNPT1 bind to and degrade Mcl-1 mRNA, which in turn affects mitochondrial permeability. The transcriptional regulator PPARα was identified as a significant influencer of PNPT1, impacting both its expression and subsequent cellular functions. Alterations in PNPT1 expression were directly correlated with the progression of MAFLD in mice. Conclusions: The study confirms the pivotal function of PNPT1 in the development of MAFLD through its interactions with Mcl-1 and its regulatory effects on lipid metabolism and mitochondrial stability. These insights highlight the intricate association between PNPT1 and MAFLD, shedding light on its molecular pathways and presenting a potential new therapeutic avenue for MAFLD management.

Background: Lipid metabolism disorders are among the most common metabolic diseases that are increasing globally and are associated with chronic metabolic disturbances. The present study aimed to determine the knowledge and practice of internal medicine physicians concerning lipid disorders according to the AHA, AACE, ESC-EAS, and NCEP-ATP-III guidelines. Methods: This descriptive-analytical cross-sectional study selected a convenience sample of 220 internal medicine specialists from January through September 2021 in Tehran and some other Iranian cities. A 25-item researcher-designed questionnaire was used. Suggested scenarios were designed by emphasizing the points of difference in the guidelines. Content validity was approved by 10 tenured faculty members, and reliability was tested with the test-retest method. Results: Women comprised 60% of the population. In addition, 3.2% (n=7) of the physicians had poor knowledge, 95.0% (n=209) had moderate knowledge, and 1.8% (n=4) had good knowledge of lipid disorders based on international guidelines. Moreover, performance regarding lipid disorders was poor in 25 (11.4%), moderate in 164 (74.5%), and good in 31 (14.1%) physicians. The knowledge score decreased, whereas the practice score increased with age. The knowledge score of female physicians was significantly higher than that of their male counterparts. The knowledge score was negatively correlated with the physician's years of experience. Conclusion: The knowledge and performance of internists regarding dyslipidemia were rated moderate according to the AHA, AACE, ESC-EAS and NCEP-ATP III guidelines. [ABSTRACT FROM AUTHOR]

Objective: Lipid metabolism plays an important role in early pregnancy, but its effects on decidualization are poorly understood. Fatty acids (FAs) must be esterified by fatty acyl-CoA synthetases to form biologically active acyl-CoA in order to enter the anabolic and/or catabolic pathway. Long-chain acyl-CoA synthetase 4 (ACSL4) is associated with female reproduction. However, whether it is involved in decidualization is unknown. Methods: The expression of ACSL4 in human and mouse endometrium was detected by immunohistochemistry. ACSL4 levels were regulated by the overexpression of ACSL4 plasmid or ACSL4 siRNA, and the effects of ACSL4 on decidualization markers and morphology of endometrial stromal cells (ESCs) were clarified. A pregnant mouse model was established to determine the effect of ACSL4 on the implantation efficiency of mouse embryos. Modulation of ACSL4 detects lipid anabolism and catabolism. Results: Through examining the expression level of ACSL4 in human endometrial tissues during proliferative and secretory phases, we found that ACSL4 was highly expressed during the secretory phase. Knockdown of ACSL4 suppressed decidualization and inhibited the mesenchymal-to-epithelial transition induced by MPA and db-cAMP in ESCs. Further, the knockdown of ACSL4 reduced the efficiency of embryo implantation in pregnant mice. Downregulation of ACSL4 inhibited FA β-oxidation and lipid droplet accumulation during decidualization. Interestingly, pharmacological and genetic inhibition of lipid droplet synthesis did not affect FA β-oxidation and decidualization, while the pharmacological and genetic inhibition of FA β-oxidation increased lipid droplet accumulation and inhibited decidualization. In addition, inhibition of β-oxidation was found to attenuate the promotion of decidualization by the upregulation of ACSL4. The decidualization damage caused by ACSL4 knockdown could be reversed by activating β-oxidation. Conclusions: Our findings suggest that ACSL4 promotes endometrial decidualization by activating the β-oxidation pathway. This study provides interesting insights into our understanding of the mechanisms regulating lipid metabolism during decidualization.

Abstract Background Increasing evidence suggests that the metabolism of lipids plays a crucial role in the progression of gastric cancer. However, the expression of lipid metabolism-related genes (LMGs) still does not serve as a prognostic biomarker in gastric cancer. Methods We obtained transcriptome data for 751 LMGs and divided STAD patients into two subtypes based on differences in LMGs expression. Then, we analyzed genetic changes in two subtypes as well as immune features to determine their differences. We also constructed a prognostic risk model related to LMGs for individualized comprehensive evaluations. Results In this study, two lipid metabolic (LM) subtypes were identified anchored in the expression profiles of LMGs. Clinical information, genomic alterations, immune features, and immunotherapy response varied significantly between the two LM subtypes. A risk model based on LMGs was also developed to assess prognosis and distinguish patients with high risk from those at low risk. The prognosis differed significantly between the two risk groups of patients. In STAD patients, the risk score was strongly correlated with genomic alterations and immune profile scores. Also, the risk score was an excellent predictor of immune checkpoint inhibitors (ICIs) response. Anchored in preliminary results derived from the aforementioned bioinformatic analysis, we chose CYP19A1 as our target gene and the expression of CYP19A1 was verified in several common gastric cancer cell lines. Then, we carried out the Western blotting, CCK-8 assay, colony formation assay, wound healing assay, and transwell assay to explore the effects of CYP19A1 on malignant biological behavior, and positive consequences were obtained. Conclusions In this study, STAD patients were divided into two subtypes based on LMGs expression. It is possible to assess the prognosis of a patient and the response to immunotherapy using the established prognostic risk model. A series of basic laboratory experiments also verified the functional role of CYP19A1 in gastric cancer.

An overview analysis highlighting the possibilities of solving the problem of preventing the formation of an obesoand diabetogenic environment, preventing inflammatory processes in adipose tissue, imbalance in the mechanisms of neuroendocrine interactions of relationships based on an integrated approach, characterized by a harmonious combination of individualized correction of the applied diet with hypothermic stimulation.

Abstract Objective Dysregulated lipid metabolism enhances the development and advancement of many cancers, including osteosarcoma (OS); however, the underlying mechanisms are still largely unknown. Therefore, this investigation aimed to elucidate novel potential lipid metabolism-related long non-coding RNAs (lncRNAs) that regulate OS development and provide novel signatures for its prognosis and precise treatment. Materials and methods The GEO datasets (GSE12865 and GSE16091) were downloaded and analyzed using R software packages. Immunohistochemistry (IHC) was used to evaluate protein levels in OS tissues while real-time qPCR was used to measure lncRNA levels, and MTT assays were used to assess OS cell viability. Results Two lipid metabolism-associated lncRNAs (LM-lncRNAs), small nucleolar RNA host gene 17 (SNHG17) and LINC00837, were identified as efficient and independent prognostic indicators for OS. In addition, further experiments confirmed that SNHG17 and LINC00837 were significantly elevated in OS tissues and cells than para-cancerous counterparts. Knockdown of SNHG17 and LINC00837 synergistically suppressed the viability of OS cells, whereas overexpression of the two lncRNAs promoted OS cell proliferation. Moreover, bioinformatics analysis was conducted to construct six novel SNHG17-microRNA-mRNA competing endogenous RNA (ceRNA) networks, and three lipid metabolism-associated genes (MIF, VDAC2, and CSNK2A2) were found to be abnormally upregulated in OS tissues, suggesting that they were potential effector genes of SNHG17. Conclusion In summary, SNHG17 and LINC00837 were found to promote OS cell malignancy, suggesting their use as ideal biomarkers for OS prognosis and treatment.

Abstract Objective To identify the genetic mechanisms underlying lipid metabolism-mediated tumor immunity in head and neck squamous carcinoma (HNSC). Materials and methods RNA sequencing data and clinical characteristics of HNSC patients were procured from The Cancer Genome Atlas (TCGA) database. Lipid metabolism-related genes were collected from KEGG and MSigDB databases. Immune cells and immune-related genes were obtained from the TISIDB database. The differentially expressed genes (DEGs) in HNSC were identified and weighted correlation network analysis (WGCNA) was performed to identify the significant gene modules. Lasso regression analysis was performed to identify hub genes. The differential gene expression pattern, diagnostic values, relationships with clinical features, prognostic values, relationships with tumor mutation burden (TMB), and signaling pathways involved, were each investigated. Results One thousand six hundred sixty-eight DEGs were identified as dysregulated between HNSC tumor samples and healthy control head and neck samples. WGCNA analysis and Lasso regression analysis identified 8 hub genes, including 3 immune-related genes (PLA2G2D, TNFAIP8L2 and CYP27A1) and 5 lipid metabolism-related genes (FOXP3, IL21R, ITGAL, TRAF1 and WIPF1). Except CYP27A1, the other hub genes were upregulated in HNSC as compared with healthy control samples, and a low expression of these hub genes indicated a higher risk of death in HNSC. Except PLA2G2D, all other hub genes were significantly and negatively related with TMB in HNSC. The hub genes were implicated in several immune-related signaling pathways including T cell receptor signaling, Th17 cell differentiation, and natural killer (NK) cell mediated cytotoxicity. Conclusion Three immune genes (PLA2G2D, TNFAIP8L2, and CYP27A1) and immune-related pathways (T cell receptor signaling, Th17 cell differentiation, and natural killer (NK) cell mediated cytotoxicity) were predicted to play significant roles in the lipid metabolism-mediated tumor immunity in HNSC.

Abstract Background The interaction between tumor cells and immune or non-immune stromal cells creates a unique tumor microenvironment, which plays an important role in the growth, invasion and metastasis of gastric cancer (GC). Methods The candidate genes were selected to construct risk-score by univariate and multivariate Cox regression analysis. Nomograms were constructed by combining clinical pathological factors, and the model performance was evaluated by receiver operating characteristic curve, decision curve analysis, net reclassification improvement and integrated discrimination improvement. The functional enrichment between high-risk group (HRisk) and low-risk group (LRisk) was explored through GO, KEGG, GSVA and ssGSEA. CIBERSORT, quanTIseq and xCell were used to explore the immune cell infiltration between HRisk and LRisk. The relevant EMT scores, macrophage infiltration scores and various metabolic scores were calculated through the “IOBR” package and analyzed visually. Results Through univariate and multivariate Cox regression analysis, we obtained the risk-score of fittings six lipid metabolism related genes (LMAGs). Through survival analysis, we found that risk-score has significant prognostic significance and can accurately reflect the metabolic level of patients. The AUCs of the nomogram model incorporating risk-score 1, 3 and 5 years were 0.725, 0.729 and 0.749 respectively. In addition, it was found that the inclusion of risk-score could significantly improve the prediction performance of the model. It was found that the arachidonic acid metabolism and prostaglandin synthesis were up-regulated in HRisk, and more tumor metastasis related markers and immune related pathways were also enriched. Further study found that HRisk had higher immune score and M2 macrophage infiltration. More importantly, the immune checkpoints of tumor associated macrophages involved in tumor antigen recognition disorders increased significantly. We also found that ST6GALNAC3 can promote arachidonic acid metabolism and up-regulate prostaglandin synthesis, increase M2 macrophage infiltration, induce epithelial mesenchymal transformation, and affect the prognosis of patients. Conclusions Our research found a novel and powerful LMAGs signature. Six-LMAGs features can effectively evaluate the prognosis of GC patients and reflect the metabolic and immune status. ST6GALNAC3 may be a potential prognostic marker to improve the survival rate and prognostic accuracy of GC patients, and may even be a potential biomarker of GC patients, indicating the response to immunotherapy.

Objective: Thioesterase superfamily member 1 (Them1) is a long chain acyl-CoA thioesterase comprising two N-terminal HotDog fold enzymatic domains linked to a C-terminal lipid-sensing steroidogenic acute regulatory transfer-related (START) domain, which allosterically modulates enzymatic activity. Them1 is highly expressed in thermogenic adipose tissue, where it functions to suppress energy expenditure by limiting rates of fatty acid oxidation, and is induced markedly in liver in response to high fat feeding, where it suppresses fatty acid oxidation and promotes glucose production. Them1−/− mice are protected against non-alcoholic fatty liver disease (NAFLD), suggesting Them1 as a therapeutic target. Methods: A high-throughput small molecule screen was performed to identify promising inhibitors targeting the fatty acyl-CoA thioesterase activity of purified recombinant Them1.Counter screening was used to determine specificity for Them1 relative to other acyl-CoA thioesterase isoforms. Inhibitor binding and enzyme inhibition were quantified by biophysical and biochemical approaches, respectively. Following structure-based optimization, lead compounds were tested in cell culture. Results: Two lead allosteric inhibitors were identified that selectively inhibited Them1 by binding the START domain. In mouse brown adipocytes, these inhibitors promoted fatty acid oxidation, as evidenced by increased oxygen consumption rates. In mouse hepatocytes, they promoted fatty acid oxidation, but also reduced glucose production. Conclusion: Them1 inhibitors could prove attractive for the pharmacologic management of NAFLD.

Objective: Pro-inflammatory polarization of adipose tissue macrophages (ATMs) plays a critical role in the pathogenesis of obesity-associated chronic inflammation. However, little is known about the role of lipids in the regulation of ATMs polarity and inflammation in response to metabolic stress. Deletion of α/β-hydrolase domain-containing 6 (ABHD6), a monoacylglycerol (MAG) hydrolase, has been shown to protect against diet-induced obesity and insulin resistance. Methods: Here we investigated the immunometabolic role of macrophage ABHD6 in response to nutrient excess using whole-body ABHD6-KO mice and human and murine macrophage cell-lines treated with KT203, a selective and potent pharmacological ABHD6 inhibitor. Results: KO mice on high-fat diet showed lower susceptibility to systemic diet-induced inflammation. Moreover, in the setting of overnutrition, stromal vascular cells from gonadal fat of KO vs. control mice contained lower number of M1 macrophages and exhibited enhanced levels of metabolically activated macrophages (MMe) and M2 markers, oxygen consumption, and interleukin-6 (IL-6) release. Likewise, under in vitro nutri-stress condition, inhibition of ABHD6 in MMe-polarized macrophages attenuated the expression and release of pro-inflammatory cytokines and M1 markers and induced the upregulation of lipid metabolism genes. ABHD6-inhibited MMe macrophages showed elevated levels of peroxisome proliferator-activated receptors (PPARs) and 2-MAG species. Notably, among different MAG species, only 2-MAG treatment led to increased levels of PPAR target genes in MMe macrophages. Conclusions: Collectively, our findings identify ABHD6 as a key component of pro-inflammatory macrophage activation in response to excess nutrition and implicate an endogenous macrophage lipolysis/ABHD6/2-MAG/PPARs cascade, as a lipid signaling and immunometabolic pathway, which favors the anti-inflammatory polarization of ATMs in obesity.

Objective: Accumulating evidence suggests that dysfunctional adipose tissue (AT) plays a major role in the risk of developing multiple sclerosis (MS), the most common immune-mediated and demyelinating disease of the central nervous system. However, the contribution of adipose tissue to the etiology and progression of MS is still obscure. This study aimed at deciphering the responses of AT in experimental autoimmune encephalomyelitis (EAE), the best characterized animal model of MS. Results and Methods: We observed a significant AT loss in EAE mice at the onset of disease, with a significant infiltration of M1-like macrophages and fibrosis in the AT, resembling a cachectic phenotype. Through an integrative and multilayered approach, we identified lipocalin2 (LCN2) as the key molecule released by dysfunctional adipocytes through redox-dependent mechanism. Adipose-derived LCN2 shapes the pro-inflammatory macrophage phenotype, and the genetic deficiency of LCN2 specifically in AT reduced weight loss as well as inflammatory macrophage infiltration in spinal cord in EAE mice. Mature adipocytes downregulating LCN2 reduced lipolytic response to inflammatory stimuli (e.g. TNFα) through an ATGL-mediated mechanism. Conclusions: Overall data highlighted a role LCN2 in exacerbating inflammatory phenotype in EAE model, suggesting a pathogenic role of dysfunctional AT in MS.

Objective: The activation of non-shivering thermogenesis (NST) has strong potential to combat obesity and metabolic disease. The activation of NST however is extremely temporal and the mechanisms surrounding how the benefits of NST are sustained once fully activated, remain unexplored. The objective of this study is to investigate the role of 4-Nitrophenylphosphatase Domain and Non-Neuronal SNAP25-Like 1 (Nipsnap1) in NST maintenance, which is a critical regulator identified in this study. Methods: The expression of Nipsnap1 was profiled by immunoblotting and RT-qPCR. We generated Nipsnap1 knockout mice (N1–KO) and investigated the function of Nipsnap1 in NST maintenance and whole-body metabolism using whole body respirometry analyses. We evaluate the metabolic regulatory role of Nipsnap1 using cellular and mitochondrial respiration assay. Results: Here, we show Nipsnap1 as a critical regulator of long-term thermogenic maintenance in brown adipose tissue (BAT). Nipsnap1 localizes to the mitochondrial matrix and increases its transcript and protein levels in response to both chronic cold and β3 adrenergic signaling. We demonstrated that these mice are unable to sustain activated energy expenditure and have significantly lower body temperature in the face of an extended cold challenge. Furthermore, when mice are exposed to the pharmacological β3 agonist CL 316, 243, the N1–KO mice exhibit significant hyperphagia and altered energy balance. Mechanistically, we demonstrate that Nipsnap1 integrates with lipid metabolism and BAT-specific ablation of Nipsnap1 leads to severe defects in beta-oxidation capacity when exposed to a cold environmental challenge. Conclusion: Our findings identify Nipsnap1 as a potent regulator of long-term NST maintenance in BAT.

Objective: Medium chain fatty acids (MCFAs), which are fatty acids with chain lengths of 8–12 carbon atoms, have been shown to reduce food intake in rodents and humans, but the underlying mechanisms are unknown. Unlike most other fatty acids, MCFAs are absorbed from the intestine into the portal vein and enter first the liver. We thus hypothesized that MCFAs trigger the release of hepatic factors that reduce appetite. Methods: The liver transcriptome in mice that were orally administered MCFAs as C8:0 triacylglycerol (TG) was analyzed. Circulating growth/differentiation factor 15 (GDF15), tissue Gdf15 mRNA and food intake were investigated after acute oral gavage of MCFAs as C8:0 or C10:0 TG in mice. Effects of acute and subchronic administration of MCFAs as C8:0 TG on food intake and body weight were determined in mice lacking either the receptor for GDF15, GDNF Family Receptor Alpha Like (GFRAL), or GDF15. Results: Hepatic and small intestinal expression of Gdf15 and circulating GDF15 increased after ingestion of MCFAs, while intake of typical dietary long-chain fatty acids (LCFAs) had no effect. Plasma GDF15 levels also increased in the portal vein with MCFA intake, indicating that in addition to the liver, the small intestine contributes to the rise in circulating GDF15. Acute oral provision of MCFAs decreased food intake over 24 h compared with a LCFA-containing bolus, and this anorectic effect required the GDF15 receptor, GFRAL. Moreover, subchronic oral administration of MCFAs reduced body weight over 7 days, an effect that was blunted in mice lacking either GDF15 or GFRAL. Conclusions: We have identified ingestion of MCFAs as a novel nutritional approach that increases circulating GDF15 in mice and have revealed that the GDF15-GFRAL axis is required for the full anorectic effect of MCFAs.

Abstract Background Energy metabolism disorder, especially lipid metabolism disorder, is an important biological characteristic of colon cancer. This research sought to examine the association between lipid metabolism-related long non-coding RNAs (lncRNAs) and prognoses among colon cancer patients. Methods The transcriptome profile and clinical data of patients with colon cancer were retrieved from The Cancer Genome Atlas database. Using consensus clustering, cases were divided into two clusters and Kaplan–Meier analysis was executed to analyze differences in their prognoses. The gene set enrichment analysis (GSEA) was used to discover biological processes and signaling pathways. A lipid metabolism-related lncRNA prognostic model (lipid metabolism-LncRM) was created utilizing the least absolute shrinkage and selection operator (LASSO) regression. The tumor microenvironment was evaluated on the basis of the composition of immune and stromal cells. Results The patients in Cluster 2 were found to have a better prognosis and higher expression of programmed cell death 1 (PD-1) and programmed cell death ligand 1 (PD-L1) relative to Cluster 1. The results of GSEA showed the enrichment of energy metabolism pathways in Cluster 2. LASSO regression was used to identify the five LncRNAs that were shown to be most substantially linked to patient prognosis. These were NSMCE1-DT, LINC02084, MYOSLID, LINC02428, and MRPS9-AS1. Receiver operating characteristic (ROC) curves and survival analysis illustrated that the lipid metabolism-LncRM had a significant prognostic value. Further analysis showed that high- and low-risk groups were significantly different in terms of clinical characteristics and immune cells infiltration. Conclusions Lipid metabolism-related lncRNAs could predict the prognoses and tumor microenvironment of colon cancer and might be important biomarkers relevant to immunotherapy.

Objective: Ectopic lipid accumulation is a hallmark of metabolic diseases, linking obesity to non-alcoholic fatty liver disease, insulin resistance and diabetes. The use of zebrafish as a model of obesity and diabetes is raising due to the conserved properties of fat metabolism between humans and zebrafish, the homologous genes regulating lipid uptake and transport, the implementation of the ‘3R’s principle and their cost-effectiveness. To date, a method allowing the conservation of lipid droplets (LDs) and organs in zebrafish larvae to image ectopic lipids is not available. Our objectives were to develop a novel methodology to quantitatively evaluate organ-specific LDs, in skeletal muscle and liver, in response to a nutritional perturbation. Methods: We developed a novel embedding and cryosectioning protocol allowing the conservation of LDs and organs in zebrafish larvae. To establish the quantitative measures, we used a three-arm parallel nutritional intervention design. Zebrafish larvae were fed a control diet containing 14% of nutritional fat or two high fat diets (HFDs) containing 25 and 36% of dietary fats. In muscle and liver, LDs were characterized using immunofluorescence confocal microscopy. In liver, intrahepatocellular lipids were discriminated from intrasinusoid lipids. To complete liver characteristics, fibrosis was identified with Masson’s Trichrome staining. Finally, to confirm the conservation and effect of HFD, molecular players of fat metabolism were evaluated by RT-qPCR. Results: The cryosections obtained after setting up the embedding and cryopreservation method were of high quality, preserving tissue morphology and allowing the visualization of ectopic lipids. Both HFDs were obesogenic, without modifying larvae survival or development. Neutral lipid content increased with time and augmented dietary fat. Intramuscular LD volume density increased and was explained by an increase in LDs size but not in numbers. Intrahepatocellular LD volume density increased and was explained by an increased number of LDs, not by their increased size. Sinusoid area and lipid content were both increased. Hepatic fibrosis appeared with both HFDs. We observed alterations in the expression of genes associated with LD coating proteins, LD dynamics, lipogenesis, lipolysis and fatty acid oxidation. Conclusions: In this study, we propose a reproducible and fast method to image zebrafish larvae without losing LD quality and organ morphology. We demonstrate the impact of HFD on LD characteristics in liver and skeletal muscle accompanied by alterations of key players of fat metabolism. Our observations confirm the evolutionarily conserved mechanisms in lipid metabolism and reveal organ specific adaptations. The methodological advancements proposed in this work open the doors to study organelle adaptations in obesity and diabetes related research such as lipotoxicity, organelle contacts and specific lipid depositions.

Nevertheless, a preliminary study, validating this skin and coat scoring system, showed that intraobserver variability was moderate to substantial.12 Although the latter study aimed at assessing the skin and coat quality in dogs with different hair coats (i.e. long-haired, short-haired and wire-haired dogs), only two wire-haired dogs were included, making it impossible to assess the skin and coat scoring system in dogs with this hair type. Skin biopsies Five of the 10 included dogs had skin biopsies taken at the left side and the remaining five at the right side at the time of surgery. Keywords: canine; dermatology; hair; hepatopathy; internal medicine; lipids EN canine dermatology hair hepatopathy internal medicine lipids 371 377 7 09/09/22 20221001 NES 221001 B Background b - Skin and coat quality can reflect nutritional deficiencies in humans and dogs with liver diseases. [Extracted from the article]

Objective: Perfluoroalkyl substances (PFAS) are man-made chemicals with demonstrated endocrine-disrupting properties. Exposure to perfluorooctanoic acid (PFOA) has been linked to disturbed metabolism via the liver, although the exact mechanism is not clear. Moreover, information on the metabolic effects of the new PFAS alternative GenX is limited. We examined whether exposure to low-dose PFOA and GenX induces metabolic disturbances in mice, including NAFLD, dyslipidemia, and glucose tolerance, and studied the involvement of PPARα. Methods: Male C57BL/6J wildtype and PPARα−/− mice were given 0.05 or 0.3 mg/kg body weight/day PFOA, or 0.3 mg/kg body weight/day GenX while being fed a high-fat diet for 20 weeks. Glucose and insulin tolerance tests were performed after 18 and 19 weeks. Plasma metabolite levels were measured next to a detailed assessment of the liver phenotype, including lipid content and RNA sequencing. Results: Exposure to high-dose PFOA decreased body weight and increased liver weight in wildtype and PPARα−/− mice. High-dose but not low-dose PFOA reduced plasma triglycerides and cholesterol, which for triglycerides was dependent on PPARα. PFOA and GenX increased hepatic triglycerides in a PPARα-dependent manner. RNA sequencing showed that the effects of GenX on hepatic gene expression were entirely dependent on PPARα, while the effects of PFOA were mostly dependent on PPARα. In the absence of PPARα, the involvement of PXR and CAR became more prominent. Conclusion: Overall, we show that long-term and low-dose exposure to PFOA and GenX disrupts hepatic lipid metabolism in mice. Whereas the effects of PFOA are mediated by multiple nuclear receptors, the effects of GenX are entirely mediated by PPARα. Our data underscore the potential of PFAS to disrupt metabolism by altering signaling pathways in the liver.

Background: Peroxisomes are single membrane-bound organelles named for their role in hydrogen peroxide production and catabolism. However, their cellular functions extend well beyond reactive oxygen species (ROS) metabolism and include fatty acid oxidation of unique substrates that cannot be catabolized in mitochondria, and synthesis of ether lipids and bile acids. Metabolic functions of peroxisomes involve crosstalk with other organelles, including mitochondria, endoplasmic reticulum, lipid droplets and lysosomes. Emerging studies suggest that peroxisomes are important regulators of energy homeostasis and that disruption of peroxisomal functions influences the risk for obesity and the associated metabolic disorders, including type 2 diabetes and hepatic steatosis. Scope of review: Here, we focus on the role of peroxisomes in ether lipid synthesis, β-oxidation and ROS metabolism, given that these functions have been most widely studied and have physiologically relevant implications in systemic metabolism and obesity. Efforts are made to mechanistically link these cellular and systemic processes. Major conclusions: Circulating plasmalogens, a form of ether lipids, have been identified as inversely correlated biomarkers of obesity. Ether lipids influence metabolic homeostasis through multiple mechanisms, including regulation of mitochondrial morphology and respiration affecting brown fat-mediated thermogenesis, and through regulation of adipose tissue development. Peroxisomal β-oxidation also affects metabolic homeostasis through generation of signaling molecules, such as acetyl-CoA and ROS that inhibit hydrolysis of stored lipids, contributing to development of hepatic steatosis. Oxidative stress resulting from increased peroxisomal β-oxidation-generated ROS in the context of obesity mediates β-cell lipotoxicity. A better understanding of the roles peroxisomes play in regulating and responding to obesity and its complications will provide new opportunities for their treatment.

Background: Resistance to cell death, a protective mechanism for removing damaged cells, is a “Hallmark of Cancer” that is essential for cancer progression. Increasing attention to cancer lipid metabolism has revealed a number of pathways that induce cancer cell death. Scope of review: We summarize emerging concepts regarding lipid metabolic reprogramming in cancer that is mainly involved in lipid uptake and trafficking, de novo synthesis and esterification, fatty acid synthesis and oxidation, lipogenesis, and lipolysis. During carcinogenesis and progression, continuous metabolic adaptations are co-opted by cancer cells, to maximize their fitness to the ever-changing environmental. Lipid metabolism and the epigenetic modifying enzymes interact in a bidirectional manner which involves regulating cancer cell death. Moreover, lipids in the tumor microenvironment play unique roles beyond metabolic requirements that promote cancer progression. Finally, we posit potential therapeutic strategies targeting lipid metabolism to improve treatment efficacy and survival of cancer patient. Major conclusions: The profound comprehension of past findings, current trends, and future research directions on resistance to cancer cell death will facilitate the development of novel therapeutic strategies targeting the lipid metabolism.

Objective: Emerging studies suggest that long non-coding RNAs (lncRNAs) play crucial roles in hepatocellular carcinoma (HCC). A rapidly increasing number of studies have shown that metabolic changes including lipid metabolic reprogramming play a significant role in the progression of HCC. But it remains to be elucidated how lncRNAs affect tumor cell metabolism. Methods: Through analysis and screening of The Cancer Genome Atlas-Liver Hepatocellular Carcinoma (TCGA-LIHC) dataset, we found a novel lncRNA RP11-386G11.10 was overexpressed, related to prognosis, conserved and non-protein-coding in HCC and related to poor prognosis. Then, CCK-8, colony formation, Transwell invasion, wound healing assays were performed and nude mouse subcutaneous tumour formation and lung metastasis models were established to explore the effect of RP11-386G11.10 on HCC tumour growth and metastasis. Chromatography-mass spectrometry (GC-MS) and Nile red staining detected the effect of RP11-386G11.10 on lipid metabolism in HCC. Mechanistically, we clarified the RP11-386G11.10/miR-345-3p/HNRNPU signalling pathway through dual luciferase reporter, RNA immunoprecipitation (RIP) and chromatin immunoprecipitation (ChIP) assays and identified ZBTB7A as a transcription factor of RP11-386G11.10. Results: RP11-386G11.10 was overexpressed in HCC and positively correlated with tumour size, TNM stage, and poor prognosis in HCC patients. RP11-386G11.10 promoted the proliferation and metastasis of HCC cells in vitro and in vivo. Mechanistically, RP11-386G11.10 acted as a competing endogenous RNA (ceRNA) for miR-345-3p to regulate the expression of HNRNPU and its downstream lipogenic enzymes, leading to lipid accumulation in HCC cells and promoting their growth and metastasis. In addition, we identified ZBTB7A as a transcription factor of RP11-386G11.10. Moreover, HNRNPU promoted the expression of ZBTB7A in HCC cells, thereby increasing the transcriptional activity of RP11-386G11.10, and forming a positive feedback loop, ultimately leading continuous lipid accumulation, growth and metastasis in HCC cells. Conclusions: Our results indicated that the lncRNA RP11-386G11.10 was a novel oncogenic lncRNA that was strongly correlated with the poor prognosis of HCC. The ZBTB7A-RP11-386G11.10-HNRNPU positive feedback loop promoted the progression of HCC by regulating lipid anabolism. RP11-386G11.10 may become a new diagnostic and prognostic biomarker and therapy target for HCC.

Objective: Non-alcoholic fatty liver disease (NAFLD) is linked to impaired lipid metabolism and systemic insulin resistance, which is partly mediated by altered secretion of liver proteins known as hepatokines. Regular physical activity can resolve NAFLD and improve its metabolic comorbidities, however, the effects of exercise training on hepatokine secretion and the metabolic impact of exercise-regulated hepatokines in NAFLD remain unresolved. Herein, we examined the effect of endurance exercise training on hepatocyte secreted proteins with the aim of identifying proteins that regulate metabolism and reduce NAFLD severity. Methods: C57BL/6 mice were fed a high-fat diet for six weeks to induce NAFLD. Mice were exercise trained for a further six weeks, while the control group remained sedentary. Hepatocytes were isolated two days after the last exercise bout, and intracellular and secreted proteins were detected using label-free mass spectrometry. Hepatocyte secreted factors were applied to skeletal muscle and liver ex vivo and insulin action and fatty acid metabolism were assessed. Syndecan-4 (SDC4), identified as an exercise-responsive hepatokine, was overexpressed in the livers of mice using adeno-associated virus. Whole-body energy homeostasis was assessed by indirect calorimetry and skeletal muscle and liver metabolism was assessed using radiometric techniques. Results: Proteomics analysis detected 2657 intracellular and 1593 secreted proteins from mouse hepatocytes. Exercise training remodelled the hepatocyte proteome, with differences in 137 intracellular and 35 secreted proteins. Bioinformatic analysis of hepatocyte secreted proteins revealed enrichment of tumour suppressive proteins and proteins involved in lipid metabolism and mitochondrial function, and suppression of oncogenes and regulators of oxidative stress. Hepatocyte secreted factors from exercise trained mice improved insulin action in skeletal muscle and increased hepatic fatty acid oxidation. Hepatocyte-specific overexpression of SDC4 reduced hepatic steatosis, which was associated with reduced hepatic fatty acid uptake, and blunted pro-inflammatory and pro-fibrotic gene expression. Treating hepatocytes with recombinant ectodomain of SDC4 (secreted form) recapitulated these effects with reduced fatty acid uptake, lipid storage and lipid droplet accumulation. Conclusions: Remodelling of hepatokine secretion is an adaptation to regular exercise training that induces changes in metabolism in the liver and skeletal muscle. SDC4 is a novel exercise-responsive hepatokine that decreases fatty acid uptake and reduces steatosis in the liver. By understanding the proteomic changes in hepatocytes with exercise, these findings have potential for the discovery of new therapeutic targets for NAFLD.

Objective: Polyunsaturated fatty acid (PUFA) supplements have been trialled as a treatment for a number of conditions and produced a variety of results. This variety is ascribed to the supplements, that often comprise a mixture of fatty acids, and to different effects in different organs. In this study, we tested the hypothesis that the supplementation of individual PUFAs has system-level effects that are dependent on the molecular structure of the PUFA. Methods: We undertook a network analysis using Lipid Traffic Analysis to identify both local and system-level changes in lipid metabolism using publicly available lipidomics data from a mouse model of supplementation with FA(20:4n-6), FA(20:5n-3), and FA(22:6n-3); arachidonic acid, eicosapentaenoic acid, and docosahexaenoic acid, respectively. Lipid Traffic Analysis is a new computational/bioinformatics tool that uses the spatial distribution of lipids to pinpoint changes or differences in control of metabolism, thereby suggesting mechanistic reasons for differences in observed lipid metabolism. Results: There was strong evidence for changes to lipid metabolism driven by and dependent on the structure of the supplemented PUFA. Phosphatidylcholine and triglycerides showed a change in the variety more than the total number of variables, whereas phosphatidylethanolamine and phosphatidylinositol showed considerable change in both which variables and the number of them, in a highly PUFA-dependent manner. There was also evidence for changes to the endogenous biosynthesis of fatty acids and to both the elongation and desaturation of fatty acids. Conclusions: These results show that the full biological impact of PUFA supplementation is far wider than any single-organ effect and implies that supplementation and dosing with PUFAs require a system-level assessment.

A high-cholesterol diet can reduce male fertility. However, it is not known whether a high-cholesterol diet can regulate the expression of genes involved in sperm maturation and sperm fertilizing ability. Quercetin, a natural product, is known to have cytoprotective effects by regulating lipid metabolism in various cell types. This study aimed to confirm the expression of genes involved in sperm maturation in the testes of mice fed a high-cholesterol diet and to determine whether quercetin can reverse the genetic regulation of cholesterol. Mice were divided into groups fed a normal chow diet and a high-cholesterol diet. Mice fed the high-cholesterol diet were dose-dependently supplemented with quercetin for 6 weeks. Investigations using quantitative PCR and in situ hybridization revealed that the high-cholesterol diet alters the expression of genes associated with sperm maturation in the testes of mice, and this was reversed with the supplementation of quercetin. In addition, the high-cholesterol diet regulated the expression of genes related to lipid metabolism in the liver of mice. Under a highcholesterol diet, quercetin can improve male fertility by regulating the expression of genes involved in sperm maturation.

Like other bodily materials, lipids such as plasma triacylglycerol, cholesterols, and free fatty acids are in a dynamic state of constant turnover (i.e., synthesis, breakdown, oxidation, and/or conversion to other compounds) as essential processes for achieving dynamic homeostasis in the body. However, dysregulation of lipid turnover can lead to clinical conditions such as obesity, fatty liver disease, and dyslipidemia. Assessment of “snap-shot” information on lipid metabolism (e.g., tissue contents of lipids, abundance of mRNA and protein and/or signaling molecules) are often used in clinical and research settings, and can help to understand one's health and disease status. However, such “snapshots” do not provide critical information on dynamic nature of lipid metabolism, and therefore may miss “true” origin of the dysregulation implicated in related diseases. In this regard, stable isotope tracer methodology can provide the in vivo kinetic information of lipid metabolism. Combining with “static” information, knowledge of lipid kinetics can enable the acquisition of in depth understanding of lipid metabolism in relation to various health and disease status. This in turn facilitates the development of effective therapeutic approaches (e.g., exercise, nutrition, and/or drugs). In this review we will discuss 1) the importance of obtaining kinetic information for a better understanding of lipid metabolism, 2) basic principles of stable isotope tracer methodologies that enable exploration of “lipid kinetics” in vivo, and 3) quantification of some aspects of lipid kinetics in vivo with numerical examples.

Background: Because fatty acid binding proteins (FABPs) and peroxisome proliferator-activated receptor (PPAR) ? physically interact, the ability of FABPs to modulate lipid signaling could be exploited for developing medications, improving therapeutic or prophylactic measures for the control of metabolic disorders, and for controlling the activity of their therapeutic targets such as PPARs. Purpose: To examine PPAR?-mediated differences in energy substrate among type 2 diabetes mellitus (T2DM) patients differing in the stage of diabetic retinopathy. Material and Methods: This study involved 101 T2DM patients (101 eyes) with different stages of diabetic retinopathy (DR) and 40 non-diabetics (controls) who were comparable in age, gender and body mass index. DR was graded using the ETDRS scale. The polymorphism was detected by real-time PCR on a Real-Time Gene Amp® PCR System 7500 (Applied Biosystems). ELISA was used to determine serum L-FABP levels with Human L-FABP ELISA kit (Hycult Biotech). Conclusion: We found a significant variation in fatty acid (FA) concentrations in red blood cell membranes in T2DM patients differing in PPAR?-gene mediated phenotypes. Among wild-type carriers, arachidonic acid concentration increased 1.4-fold in those with the early stage of DR (р < 0.05) compared to controls and decreased 7.5-fold in those with DR progression (р < 0.05). Among carriers of the 12Ala allele, arachidonic acid concentration decreased twofold in those with the early stage of DR (р < 0.05) compared to controls, and further gradually decreased with DR progression. There was a gradual and not significant increase in L-FABP concentration with DR progression in T2DM patients carrying the wild genotype. Among carriers of the 12Ala allele, concentration of the chaperone increased fourfold in those with the early stage of DR compared to controls (р < 0.05), and gradually decreased with DR progression.

Objective: Obesity-related chronic inflammation plays an important role in the development of Metabolic Associated Fatty Liver Disease (MAFLD). Although the contribution of the pro-inflammatory NF-κB signaling pathway to the progression from simple steatosis to non-alcoholic steatohepatitis (NASH) is well-established, its role as an initiator of hepatic steatosis and the underlying mechanism remains unclear. Here, we investigated the hypothesis that the hepatocytic NF-κB signaling pathway acts as a metabolic regulator, thereby promoting hepatic steatosis development. Methods: A murine model expressing a constitutively active form of IKKβ in hepatocytes (Hep-IKKβca) was used to activate hepatocyte NF-κB. In addition, IKKβca was also expressed in hepatocyte A20-deficient mice (IKKβca;A20LKO). A20 is an NF-κB-target gene that inhibits the activation of the NF-κB signaling pathway upstream of IKKβ. These mouse models were fed a sucrose-rich diet for 8 weeks. Hepatic lipid levels were measured and using [1–13C]-acetate de novo lipogenesis and cholesterol synthesis rate were determined. Gene expression analyses and immunoblotting were used to study the lipogenesis and cholesterol synthesis pathways. Results: Hepatocytic NF-κB activation by expressing IKKβca in hepatocytes resulted in hepatic steatosis without inflammation. Ablation of hepatocyte A20 in Hep-IKKβca mice (IKKβca;A20LKO mice) exacerbated hepatic steatosis, characterized by macrovesicular accumulation of triglycerides and cholesterol, and increased plasma cholesterol levels. Both De novo lipogenesis (DNL) and cholesterol synthesis were found elevated in IKKβca;A20LKO mice. Phosphorylation of AMP-activated kinase (AMPK) - a suppressor in lipogenesis and cholesterol synthesis - was decreased in IKKβca;A20LKO mice. This was paralleled by elevated protein levels of hydroxymethylglutaryl-CoA synthase 1 (HMGCS1) and reduced phosphorylation of HMG-CoA reductase (HMGCR) both key enzymes in the cholesterol synthesis pathway. Whereas inflammation was not observed in young IKKβca;A20LKO mice sustained hepatic NF-κB activation resulted in liver inflammation, together with elevated hepatic and plasma cholesterol levels in middle-aged mice. Conclusions: The hepatocytic IKK:NF-κB axis is a metabolic regulator by controlling DNL and cholesterol synthesis, independent of its central role in inflammation. The IKK:NF-κB axis controls the phosphorylation levels of AMPK and HMGCR and the protein levels of HMGCS1. Chronic IKK-mediated NF-κB activation may contribute to the initiation of hepatic steatosis and cardiovascular disease risk in MAFLD patients.

Objective: Type II nuclear hormone receptors, including farnesoid X receptors (FXR), liver X receptors (LXR), and peroxisome proliferator-activated receptors (PPAR), which serve as drug targets for metabolic diseases, are permanently positioned in the nucleus and thought to be bound to DNA regardless of the ligand status. However, recent genome-wide location analysis showed that LXRα and PPARα binding in the liver is largely ligand-dependent. We hypothesized that pioneer factor Foxa2 evicts nucleosomes to enable ligand-dependent binding of type II nuclear receptors and performed genome-wide studies to test this hypothesis. Methods: ATAC-Seq was used to profile chromatin accessibility; ChIP-Seq was performed to assess transcription factors (Foxa2, FXR, LXRα, and PPARα) binding; and RNA-Seq analysis determined differentially expressed genes in wildtype and Foxa2 mutants treated with a ligand (GW4064 for FXR, GW3965, and T09 for LXRα). Results: We reveal that chromatin accessibility, FXR binding, LXRα occupancy, and ligand-responsive activation of gene expression by FXR and LXRα require Foxa2. Unexpectedly, Foxa2 occupancy is drastically increased when either receptor, FXR or LXRα, is bound by an agonist. In addition, co-immunoprecipitation experiments demonstrate that Foxa2 interacts with either receptor in a ligand-dependent manner, suggesting that Foxa2 and the receptor, bind DNA as an interdependent complex during ligand activation. Furthermore, PPARα binding is induced in Foxa2 mutants treated with FXR and LXR ligands, leading to the activation of PPARα targets. Conclusions: Our model requires pioneering activity for ligand activation that challenges the existing ligand-independent binding mechanism. We also demonstrate that Foxa2 is required to achieve activation of the proper receptor – one that binds the added ligand – by repressing the activity of a competing receptor.

Background: Mitochondrial oxidative function plays a key role in the development of non-alcoholic fatty liver disease (NAFLD) and insulin resistance (IR). Recent studies reported that fatty liver might not be a result of decreased mitochondrial fat oxidation caused by mitochondrial damage. Rather, NAFLD and IR induce an elevation in mitochondrial function that covers the increased demand for carbon intermediates and ATP caused by elevated lipogenesis and gluconeogenesis. Furthermore, mitochondria play a role in regulating hepatic insulin sensitivity and lipogenesis by modulating redox-sensitive signaling pathways. Scope of review: We review the contradictory studies indicating that NAFLD and hyperglycemia can either increase or decrease mitochondrial oxidative capacity in the liver. We summarize mechanisms regulating mitochondrial heterogeneity inside the same cell and discuss how these mechanisms may determine the role of mitochondria in NAFLD. We further discuss the role of endogenous antioxidants in controlling mitochondrial H2O2 release and redox-mediated signaling. We describe the emerging concept that the subcellular location of cellular antioxidants is a key determinant of their effects on NAFLD. Major conclusions: The balance of fat oxidation versus accumulation depends on mitochondrial fuel preference rather than ATP-synthesizing respiration. As such, therapies targeting fuel preference might be more suitable for treating NAFLD. Similarly, suppressing maladaptive antioxidants, rather than interfering with physiological mitochondrial H2O2-mediated signaling, may allow the maintenance of intact hepatic insulin signaling in NAFLD. Exploration of the subcellular compartmentalization of different antioxidant systems and the unique functions of specific mitochondrial subpopulations may offer new intervention points to treat NAFLD.

Objective: The endoplasmic reticulum (ER)-resident E3 ligase HRD1 and its co-activator Sel1L are major components of ER-associated degradation (ERAD) machinery. Here, we investigated the molecular mechanism and functional significance underlying the circadian regulation of HRD1/Sel1L-mediated protein degradation program in hepatic energy metabolism. Methods: Genetically engineered animal models as well as gain- and loss-of-function studies were employed to address the circadian regulatory mechanism and functional significance. Gene expression, transcriptional activation, protein–protein interaction, and animal metabolic phenotyping analyses were performed to dissect the molecular network and metabolic pathways. Results: Hepatic HRD1 and Sel1L expression exhibits circadian rhythmicity that is controlled by the ER-tethered transcriptional activator CREBH, the nuclear receptor peroxisome proliferator-activated receptor α (PPARα), and the core clock oscillator BMAL1 in mouse livers. HRD1/Sel1L mediates polyubiquitination and degradation of the CREBH protein across the circadian cycle to modulate rhythmic expression of the genes encoding the rate-limiting enzymes or regulators in fatty acid (FA) oxidation, triglyceride (TG) lipolysis, lipophagy, and gluconeogenesis. HRD1 liver-specific knockout (LKO) mice displayed increased expression of the genes involved in lipid and glucose metabolism and impaired circadian profiles of circulating TG, FA, and glucose due to overproduction of CREBH. The circadian metabolic activities of HRD1 LKO mice were inversely correlated with those of CREBH KO mice. Suppressing CREBH overproduction in the livers of HRD1 LKO mice restored the diurnal levels of circulating TG and FA of HRD1 LKO mice. Conclusion: Our work revealed a key circadian-regulated molecular network through which the E3 ubiquitin ligase HRD1 and its co-activator Sel1L regulate hepatic circadian metabolism.

Objective: White adipose tissue (WAT) expansion regulates energy balance and overall metabolic homeostasis. The absence or loss of WAT occurring through lipodystrophy and lipoatrophy contributes to the development of hepatic steatosis and insulin resistance. We previously demonstrated that sole small ubiquitin-like modifier (SUMO) E2-conjugating enzyme Ube2i represses human adipocyte differentiation. The role of Ube2i during WAT development remains unknown. Methods: To determine how Ube2i impacts body composition and energy balance, we generated adipocyte-specific Ube2i knockout mice (Ube2ia-KO). CRISPR/Cas9 gene editing inserted loxP sites flanking exons 3 and 4 at the Ube2i locus. Subsequent genetic crosses to Adipoq-Cre transgenic mice allowed deletion of Ube2i in white and brown adipocytes. We measured multiple metabolic endpoints that describe energy balance and carbohydrate metabolism in Ube2ia-KO and littermate controls during postnatal growth. Results: Surprisingly, Ube2ia-KO mice developed hyperinsulinemia and hepatic steatosis. Global energy balance defects emerged from dysfunctional WAT marked by pronounced local inflammation, loss of serum adipokines, hepatomegaly, and near absence of major adipose tissue depots. We observed progressive lipoatrophy that commences in the early adolescent period. Conclusions: Our results demonstrate that Ube2i expression in mature adipocytes allows WAT expansion during postnatal growth. Deletion of Ube2i in fat cells compromises and diminishes adipocyte function that induces WAT inflammation and ectopic lipid accumulation in the liver. Our findings reveal an indispensable role for Ube2i during white adipocyte expansion and endocrine control of energy balance.

Objective: Postprandial lipid profiling (PLP), a risk indicator of cardiometabolic disease, is based on frequent blood sampling over several hours after a meal, an approach that is invasive and inconvenient. Non-invasive PLP may offer an alternative for disseminated human monitoring. Herein, we investigate the use of clinical multispectral optoacoustic tomography (MSOT) for non-invasive, label-free PLP via direct lipid-sensing in human vasculature and soft tissues. Methods: Four (n = 4) subjects (3 females and 1 male, age: 28 ± 7 years) were enrolled in the current pilot study. We longitudinally measured the lipid signals in arteries, veins, skeletal muscles, and adipose tissues of all participants at 30-min intervals for 6 h after the oral consumption of a high-fat meal. Results: Optoacoustic lipid-signal analysis showed on average a 63.4% intra-arterial increase at ~ 4 h postprandially, an 83.9% intra-venous increase at ~ 3 h, a 120.8% intra-muscular increase at ~ 3 h, and a 32.8% subcutaneous fat increase at ~ 4 h. Conclusion: MSOT provides the potential to study lipid metabolism that could lead to novel diagnostics and prevention strategies by label-free, non-invasive detection of tissue biomarkers implicated in cardiometabolic diseases.

Objectives: Diet-driven obesity is increasingly widespread. Its consequences pose major challenges to human health and health care systems. There are MAP kinase-interacting kinases (MNKs) in mice, MNK1 and MNK2. Studies have demonstrated that mice lacking either MNK1 or MNK2 were partially protected against high-fat diet (HFD)-induced weight gain and insulin resistance. The aims of this study were to evaluate the phenotype of mice lacking both MNKs when given an HFD, to assess whether pharmacological inhibition of MNK function also protects against diet-induced obesity (DIO) and its consequences and to probe the mechanisms underlying such protection. Methods: Male wild-type (WT) C57Bl6 mice or mice lacking both MNK1 and MNK2 (double knockout, DKO) were fed an HFD or control diet (CD) for up to 16 weeks.In a separate study, WT mice were also given an HFD for 6 weeks, after which half were treated with the recently-developed MNK inhibitor ETC-206 daily for 10 more weeks while continuing an HFD. Metabolites and other parameters were measured, and the expression of selected mRNAs and proteins was assessed. Results: MNK-DKO mice were almost completely protected from HFD-induced obesity. Higher energy expenditure (EE) in MNK-DKO mice was observed, which probably reflects the changes in a number of genes or proteins linked to lipolysis, mitochondrial function/biogenesis, oxidative metabolism, and/or ATP consumption. The MNK inhibitor ETC-206 also prevented HFD-induced weight gain, confirming that the activity of the MNKs facilitates weight gain due to excessive caloric consumption. Conclusions: Disabling MNKs in mice, either genetically or pharmacologically, strongly prevents weight gain on a calorie-rich diet. This finding likely results from increased energy utilisation, involving greater ATP consumption, mitochondrial oxidative metabolism, and other processes.

Objective: Human energy metabolism is under the regulation of the molecular circadian clock; we recently reported that mitochondrial respiration displays a day-night rhythm under study conditions that are similar to real life. Mitochondria are interconnected with lipid droplets, which are of importance in fuel utilization and play a role in muscle insulin sensitivity. Here, we investigated if skeletal muscle lipid content and composition also display day-night rhythmicity in healthy, lean volunteers. Methods: Skeletal muscle biopsies were obtained from 12 healthy lean male volunteers every 5 h over a 24 h period. Volunteers were provided with standardized meals, and biopsies were taken 4.5 h after each last meal. Lipid droplet size and number were investigated by confocal microscopy. Additionally, the muscle lipidome was assessed using UPLC/HRMS-based semi-targeted lipidomics. Results: Confocal microscopy revealed diurnal differences in intramyocellular lipid content (P 50% of all rhythmic species). DAG levels showed a day-night pattern with a trough at 1 PM and a peak at 4 AM. Conclusions: Using two distinct methods, our findings show that myocellular lipid content and whole muscle lipid composition vary across the day-night cycle under normal living conditions. In particular, day-night rhythmicity was present in over half of the DAG lipid species. Future studies are needed to investigate whether rhythmicity in DAG is functionally related to insulin sensitivity and how this might be altered in prediabetes.

Objective: Infants born to mothers with obesity have greater adiposity, ectopic fat storage, and are at increased risk for childhood obesity and metabolic disease compared with infants of normal weight mothers, though the cellular mechanisms mediating these effects are unclear. Methods: We tested the hypothesis that human, umbilical cord-derived mesenchymal stem cells (MSCs) from infants born to obese (Ob-MSC) versus normal weight (NW-MSC) mothers demonstrate altered fatty acid metabolism consistent with adult obesity. In infant MSCs undergoing myogenesis in vitro, we measured cellular lipid metabolism and AMPK activity, AMPK activation in response to cellular nutrient stress, and MSC DNA methylation and mRNA content of genes related to oxidative metabolism. Results: We found that Ob-MSCs exhibit greater lipid accumulation, lower fatty acid oxidation (FAO), and dysregulation of AMPK activity when undergoing myogenesis in vitro. Further experiments revealed a clear phenotype distinction within the Ob-MSC group where more severe MSC metabolic perturbation corresponded to greater neonatal adiposity and umbilical cord blood insulin levels. Targeted analysis of DNA methylation array revealed Ob-MSC hypermethylation in genes regulating FAO (PRKAG2, ACC2, CPT1A, SDHC) and corresponding lower mRNA content of these genes. Moreover, MSC methylation was positively correlated with infant adiposity. Conclusions: These data suggest that greater infant adiposity is associated with suppressed AMPK activity and reduced lipid oxidation in MSCs from infants born to mothers with obesity and may be an important, early marker of underlying obesity risk.

Objective: Hyperglucagonemia is present in many forms of diabetes and contributes to hyperglycemia, and glucagon suppression can ameliorate diabetes in mice. Leptin, a glucagon suppressor, can also reverse diabetes in rodents. Lipid nanoparticle (LNP) delivery of small interfering RNA (siRNA) effectively targets the liver and is in clinical trials for the treatment of various diseases. We compared the effectiveness of glucagon receptor (Gcgr)-siRNA delivered via LNPs to leptin in two mouse models of diabetes. Methods: Gcgr siRNA encapsulated into LNPs or leptin was administered to mice with diabetes due to injection of the β-cell toxin streptozotocin (STZ) alone or combined with high fat diet (HFD/STZ). Results: In STZ-diabetic mice, a single injection of Gcgr siRNA lowered blood glucose levels for 3 weeks, improved glucose tolerance, and normalized plasma ketones levels, while leptin therapy normalized blood glucose levels, oral glucose tolerance, and plasma ketones, and suppressed lipid metabolism. In contrast, in HFD/STZ-diabetic mice, Gcgr siRNA lowered blood glucose levels for 2 months, improved oral glucose tolerance, and reduced HbA1c, while leptin had no beneficial effects. Conclusions: While leptin may be more effective than Gcgr siRNA at normalizing both glucose and lipid metabolism in STZ diabetes, Gcgr siRNA is more effective at reducing blood glucose levels in HFD/STZ diabetes.