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Phoenixin-14 (PNX) is a neuropeptide that has been shown to prevent oxidative damage and stimulates insulin secretion. We investigated the effects of PNX on pancreatic injury induced by streptozotocin (STZ), and nicotinamide (NAD). Male Sprague-Dawley rats, in control (C) and diabetic (STZ) groups, were treated with either saline, or PNX (0.45 nmol/kg, or 45 nmol/kg) daily for 3 days 1 week after STZ injection. Fasting blood glucose (FBG) and gastric emptying rate (GER) were measured. Tissue and blood samples were collected. PNX treatments prevented pancreatic damage and β cell loss. Increased luminol and lucigenin levels in the pancreas, ileum and liver tissues of STZ groups were alleviated by PNX treatment in pancreatic and ileal tissues. PNX0.45 decreased FBG without any change in insulin blood level and pancreatic mRNA. GER increased in all diabetic rats while PNX0.45 delayed GER only in the C group. PNX diminishes pancreatic damage and lowers FBG by reducing oxidative load.

Various metabolic processes in the body oscillate throughout the natural day, driven by a biological clock. Circadian rhythms are also influenced by time cues from the environment (light exposure) and behaviour (eating and exercise). Recent evidence from diurnal- and circadian-rhythm studies indicates rhythmicity in various circulating metabolites, insulin secretion and -sensitivity and energy expenditure in metabolically healthy adults. These rhythms have been shown to be disturbed in adults with obesity-related metabolic disturbances. Moreover, eating and being (in)active at a time that the body is not prepared for it, as in night-shift work, is related to poor metabolic outcomes. These findings indicate the relevance of 24-h metabolism in obesity-related metabolic alterations and have also led to novel strategies, such as timing of food intake and exercise, to reinforce the circadian rhythm and thereby improving metabolic health. This review aims to deepen the understanding of the influence of the circadian system on metabolic processes and obesity-related metabolic disturbances and to discuss novel time-based strategies that may be helpful in combating metabolic disease.

Despite the pivotal role played by elevated circulating triglyceride levels in the pathophysiology of cardio-metabolic diseases many of the indices used to quantify metabolic health focus on deviations in glucose and insulin alone. We present the Mixed Meal Model, a computational model describing the systemic interplay between triglycerides, free fatty acids, glucose, and insulin. We show that the Mixed Meal Model can capture deviations in the post-meal excursions of plasma glucose, insulin, and triglyceride that are indicative of features of metabolic resilience; quantifying insulin resistance and liver fat; validated by comparison to gold-standard measures. We also demonstrate that the Mixed Meal Model is generalizable, applying it to meals with diverse macro-nutrient compositions. In this way, by coupling triglycerides to the glucose-insulin system the Mixed Meal Model provides a more holistic assessment of metabolic resilience from meal response data, quantifying pre-clinical metabolic deteriorations that drive disease development in overweight and obesity.

Objective Skeletal muscle mitochondrial function and energy metabolism displays day-night rhythmicity in healthy, young individuals. Twenty-four-hour rhythmicity of metabolism has been implicated in the etiology of age-related metabolic disorders. Whether day-night rhythmicity in skeletal muscle mitochondrial function and energy metabolism is altered in older, metabolically comprised humans remains unknown. Methods Twelve male overweight volunteers with impaired glucose tolerance and insulin sensitivity stayed in a metabolic research unit for 2 days under free living conditions with regular meals. Indirect calorimetry was performed at 5 time points (8 AM, 1 PM, 6 PM, 11 PM, 4 AM), followed by a muscle biopsy. Mitochondrial oxidative capacity was measured in permeabilized muscle fibers using high-resolution respirometry. Results Mitochondrial oxidative capacity did not display rhythmicity. The expression of circadian core clock genes BMAL1 and REV-ERBα showed a clear day-night rhythm (p, Highlights • Diurnal rhythmicity of mitochondrial function is attenuated in older and metabolically compromised men. • Rhythmicity of the biological clock gene PER2 is disturbed in skeletal muscle of these volunteers. • Metabolic flexibility in 24-h metabolism is diminished, with a lack of a typical feeding-fasting cycle.

Individuals affected with two genetic syndromes identified in Ecuador have severe short stature and diminished insulin secretion, along with essentially different GH counterregulatory effects on insulin action, which leads to the appearance of opposing metabolic phenotypes. In the case of Laron syndrome, subjects have enhanced insulin sensitivity and diminished incidence of type 2 diabetes mellitus. In the other clinical entity, individuals have innate insulin resistance, a varying degree of carbohydrate metabolism disturbances, glucose intolerance, and eventually insulin-resistant diabetes mellitus. Since both groups have diminished insulin secretion, the standard homeostatic minimal models for assessment of insulin sensitivity and resistance were used to see if they could properly identify the metabolic status, especially considering that these methodologies are simple and non-invasive procedures. Methods Fasting insulin concentrations, fasting glucose/fasting insulin ratio and various minimal models were determined in individuals from the two syndromic cohorts, as well as in a control group made of first-degree normal relatives of the insulin-resistant phenotype subjects. Results The metabolic characteristics of enhanced insulin sensitivity in one of the syndromes and innate insulin resistance in the other could not be properly ascertained by the selected methodology. Furthermore, results were confusing and even discrepant with the clinical findings. Conclusions The standard homeostatic minimal models could not properly identify or discriminate insulin sensitivity and resistance in subjects with inherently diminished secretion. It is thereby suggested that these models should be used with caution in clinical situations where reduced secretion of the metabolic peptide is found or suspected.

Various metabolic processes in the body oscillate throughout the natural day, driven by a biological clock. Circadian rhythms are also influenced by time cues from the environment (light exposure) and behaviour (eating and exercise). Recent evidence from diurnal- and circadian-rhythm studies indicates rhythmicity in various circulating metabolites, insulin secretion and -sensitivity and energy expenditure in metabolically healthy adults. These rhythms have been shown to be disturbed in adults with obesity-related metabolic disturbances. Moreover, eating and being (in)active at a time that the body is not prepared for it, as in night-shift work, is related to poor metabolic outcomes. These findings indicate the relevance of 24-h metabolism in obesity-related metabolic alterations and have also led to novel strategies, such as timing of food intake and exercise, to reinforce the circadian rhythm and thereby improving metabolic health. This review aims to deepen the understanding of the influence of the circadian system on metabolic processes and obesity-related metabolic disturbances and to discuss novel time-based strategies that may be helpful in combating metabolic disease.

Purpose Artificially sweetened and sugar-sweetened beverage consumptions have both been reported to be associated with type 2 diabetes mellitus (T2D) risk. The aim of the current study was to investigate the potential underlying associations with dynamic pancreatic β-cell function (BCF) and insulin sensitivity. Methods We evaluated cross-sectional associations in 2240 individuals (mean ± SD age 59.6 ± 8.18, 49.4% male, 21.9% T2D) participating in a diabetes-enriched population-based cohort. Artificially sweetened and sugar-sweetened soft drinks and juice consumption were assessed by a food-frequency questionnaire. Glucose metabolism status, insulin sensitivity, and BCF were measured by a seven-point oral glucose tolerance test. Regression analyses were performed to assess associations of artificially and sugar-sweetened beverage consumption with measures of glucose homeostasis. Associations were adjusted for potential confounders, and additionally with and without total energy intake and BMI, as these variables could be mediators. Results Moderate consumption of artificially sweetened soft drink was associated with lower β-cell glucose sensitivity [standardized beta (95% CI), − 0.06 (− 0.11, − 0.02)], total insulin secretion [β − 0.06 (− 0.10, − 0.02)], and with lower β-cell rate sensitivity [odds ratio (95% CI), 1.29 (1.03, 1.62)] compared to abstainers. Daily artificially sweetened soft drink consumption was associated with lower β-cell glucose sensitivity [β − 0.05 (− 0.09, 0.00)], and total insulin secretion [β − 0.05 − 0.09, − 0.01)] compared to abstainers. Conclusions Moderate and daily consumption of artificially sweetened soft drinks was associated with lower BCF, but not with insulin sensitivity. No evidence was found for associations of sugar-sweetened soft drink and juice consumption with BCF or insulin sensitivity in this middle-aged population. Prospective studies are warranted to further investigate the associations of artificially and sugar-sweetened beverage consumption with non-fasting insulin sensitivity and multiple BCF aspects.

The T allele of TCF7L2 rs7903146 is a common genetic variant associated with type 2 diabetes (T2D), possibly by modulation of incretin action. In this study, we evaluated the effect of the TCF7L2 rs7903146 T allele on the incretin effect and other glucometabolic parameters in normal glucose tolerant individuals (NGT) and participants with T2D. The rs7903146 variant was genotyped in cohorts of 61 NGT individuals (23 were heterozygous (CT) or homozygous (TT) T allele carriers) and 43 participants with T2D (20 with CT/TT). Participants were previously examined by an oral glucose tolerance test (OGTT) and a subsequent isoglycemic intravenous glucose infusion (IIGI). The incretin effect was assessed by quantification of the difference in integrated beta cell secretory responses during the OGTT and IIGI. Glucose and hormonal levels were measured during experimental days, and from these, indices of beta cell function and insulin sensitivity were calculated. No genotype-specific differences in the incretin effect were observed in the NGT group (P = 0.70) or the T2D group (P = 0.68). NGT T allele carriers displayed diminished glucose-dependent insulinotropic polypeptide response during OGTT (P = 0.01) while T allele carriers with T2D were characterized by lower C-peptide AUC after OGTT (P = 0.04) and elevated glucose AUC after OGTT (P = 0.04). In conclusion, our findings do not exclude that this specific TCF7L2 variant increases the risk of developing T2D via diminished incretin effect, but genotype-related defects were not detectable in these cohorts.

Aims/hypothesis The hyperglycaemic clamp technique and the frequently sampled IVGTT are unsuitable techniques to assess beta cell function (BCF) in large cohorts. Therefore, the aim of this study was to evaluate the discriminatory ability of simple OGTT-based BCF indices for prediction of prediabetes (meaning impaired fasting glucose and/or impaired glucose tolerance) and type 2 diabetes. Methods Glucose metabolism status was assessed by 2 h 75 g OGTT at baseline (n = 476, mean age 59.2 years, 38.7% women) and after 7 years of follow-up (n = 416) in the Cohort on Diabetes and Atherosclerosis Maastricht (CODAM) study (1999–2009). Baseline plasma glucose, insulin and C-peptide values during OGTTs were used to calculate 21 simple indices of BCF. Disposition indices (BCF index × Matsuda index), to compensate for the prevailing level of insulin resistance, were calculated for the BCF indices with the best discriminatory abilities. The discriminatory ability of the BCF indices was estimated by the area under the receiver operating characteristics curve (ROC AUC) with an outcome of incident prediabetes (n = 73) or type 2 diabetes (n = 60 and n = 18 cases, respectively, in individuals who were non-diabetic or had normal glucose metabolism at baseline). Results For incident prediabetes (n = 73), all ROC AUCs were less than 70%, whereas for incident type 2 diabetes, I30/I0, CP30/CP0, ΔI30/ΔG30, ΔCP30/ΔG30 (where I, CP and G are the plasma concentrations of insulin, C-peptide and glucose, respectively, at the times indicated), and corrected insulin response at 30 min had ROC AUCs over 70%. In at-baseline non-diabetic individuals, disposition indices ΔI30/ΔG30, ΔCP30/ΔG30 and corrected insulin response at 30 min had ROC AUCs of over 80% for incident type 2 diabetes. Moreover, these BCF disposition indices had significantly better discriminatory abilities for incident type 2 diabetes than the Matsuda index alone. Conclusions/interpretation BCF indices reflecting early-phase insulin secretion have the best ability to discriminate individuals who will develop prediabetes and type 2 diabetes. Of these, ΔCP30/ΔG30, often referred to as the C-peptidogenic index, performed consistently well. Electronic supplementary material The online version of this article (doi:10.1007/s00125-016-4165-3) contains peer-reviewed but unedited supplementary material, which is available to authorised users.

Aim. This study explored the association of depressive symptoms with indices of insulin sensitivity and insulin secretion in a cohort of non-diabetic men and women aged 30 to 64 years.Methods. The study population was derived from the 3-year follow-up of the Relationship between Insulin Sensitivity and Cardiovascular Disease Risk (RISC) study. Presence of significant depressive symptoms was defined as a Center for Epidemiologic Studies Depression Scale (CES-D) score >= 16. Standard oral glucose tolerance tests were performed. Insulin sensitivity was assessed with the oral glucose insulin sensitivity (OGIS) index. Insulin secretion was estimated using three model-based parameters of insulin secretion (beta-cell glucose sensitivity, the potentiation factor ratio, and beta-cell rate sensitivity).Results. A total of 162 out of 1027 participants (16%) had significant depressive symptoms. Having significant depressive symptoms was not related to either OGIS [standardized beta (beta) -0.033; P=0.24] or beta-cell glucose sensitivity ([3 0.007; P=0.82). Significant depressive symptoms were related to decreased beta-cell rate sensitivity (odds ratio for significant depressive symptoms of the lowest vs. highest quartile of beta-cell rate sensitivity was 2.04; P =0.01). Also, significant depressive symptoms were associated with a statistically significant decrease in the potentiation factor ratio in unadjusted models, but not in the fully adjusted model.Conclusion. Depressive symptoms were not related to insulin sensitivity and tended to be weakly associated to some parameters of insulin secretion in non-diabetic individuals. Prospective studies are needed to study the temporal association between depression and insulin secretion. (C) 2012 Elsevier Masson SAS. All rights reserved.

Lack of physical activity has been related to an increased risk of developing insulin resistance. This study aimed to assess the impact of chronic muscle deconditioning on whole body insulin sensitivity, muscle oxidative capacity, and intramyocellular lipid (IMCL) content in subjects with paraplegia. Nine subjects with paraplegia and nine able-bodied, lean controls were recruited. An oral glucose tolerance test was performed to assess whole body insulin sensitivity. IMCL content was determined both in vivo and in vitro using1H-magnetic resonance spectroscopy and fluorescence microscopy, respectively. Muscle biopsy samples were stained for succinate dehydrogenase (SDH) activity to measure muscle fiber oxidative capacity. Subcellular distributions of IMCL and SDH activity were determined by defining subsarcolemmal and intermyofibrillar areas on histological samples. SDH activity was 57 ± 14% lower in muscle fibers derived from subjects with paraplegia when compared with controls ( P < 0.05), but IMCL content and whole body insulin sensitivity did not differ between groups. In muscle fibers taken from controls, both SDH activity and IMCL content were higher in the subsarcolemmal region than in the intermyofibrillar area. This typical subcellular SDH and IMCL distribution pattern was lost in muscle fibers collected from subjects with paraplegia and had changed toward a more uniform distribution. In conclusion, the lower metabolic demand in deconditioned muscle of subjects with paraplegia results in a significant decline in muscle fiber oxidative capacity and is accompanied by changes in the subcellular distribution patterns of SDH activity and IMCL. However, loss of muscle activity due to paraplegia is not associated with substantial lipid accumulation in skeletal muscle tissue.