Effects of high-fat overfeeding on mitochondrial function, glucose and fat metabolism, and adipokine levels in low-birth-weight subjects

Association of birth weight with type 2 diabetes mellitus and the mediating role of fatty acids traits: a two-step mendelian randomization study

BACKGROUND

Observational studies have suggested an association between birth weight and type 2 diabetes mellitus, but the causality between them has not been established. We aimed to obtain the causal relationship between birth weight with T2DM and quantify the mediating effects of potential modifiable risk factors.

METHODS

Two-step, two-sample Mendelian randomization (MR) techniques were applied using SNPs as genetic instruments for exposure and mediators. Summary data from genome-wide association studies (GWAS) for birth weight, T2DM, and a series of fatty acids traits and their ratios were leveraged. The inverse variance weighted (IVW) method was the main analysis approach. In addition, the heterogeneity test, horizontal pleiotropy test, Mendelian randomization pleiotropy residual sum and outlier (MR-PRESSO) test, and leave-one-out analysis were carried out to assess the robustness.

RESULTS

The IVW method showed that lower birth weight raised the risk of T2DM (β: -1.113, 95% CI: -1.573 ∼ -0.652). Two-step MR identified 4 of 17 candidate mediators partially mediating the effect of lower birth weight on T2DM, including ratio of polyunsaturated fatty acids to monounsaturated fatty acids (proportion mediated: 7.9%), ratio of polyunsaturated fatty acids to total fatty acids (7.2%), ratio of omega-6 fatty acids to total fatty acids (8.1%) and ratio of linoleic acid to total fatty acids ratio (6.0%).

CONCLUSIONS

Our findings supported a potentially causal effect of birth weight against T2DM with considerable mediation by modifiable risk factors. Interventions that target these factors have the potential to reduce the burden of T2DM attributable to low birth weight.

Mechanical Bowel Preparation Is a Risk Factor for Postoperative Delirium as It Alters the Gut Microbiota Composition: A Prospective Randomized Single-Center Study

Background and Objective

Postoperative delirium (POD) is a frequent complication in patients undergoing gastrectomy. Increasing evidence suggests that abnormal gut microbiota composition may contribute to its morbidity. However, it is unclear whether mechanical bowel preparation would cause postoperative delirium by altering the gut microbiota of patients. This study aimed to investigate the association between mechanical bowel preparation and postoperative delirium in patients undergoing gastrectomy.

Methods

A prospective randomized single-center study was performed. A total of 81 patients with gastric cancer were enrolled and randomly assigned to two groups: preparation group and non-preparation group according to whether the patient received MBP before surgery. To diagnose postoperative delirium, we used the 3-Min Diagnostic Interview for Confusion Assessment Method-defined delirium for five successive days after surgery. 16s rRNA gene sequencing was used to investigate changes in the intestinal bacteria. The linear discriminant analysis and effect size (LefSe) analysis were also used to identify the different taxa of fecal microbiota between the postoperative delirium and non-postoperative delirium groups.

Results

We found that there was a significant difference in β-diversity of the gut microbiota between the preparation group and non-preparation group (P = 0.048). Furthermore, patients in the preparation group had a much higher rate of postoperative delirium (13/40, 32.5%) compared with that in non-preparation groups (4/41, 9.8%). Multivariate regression analysis adjusted by other risk factors indicated that mechanical bowel preparation was associated with the occurrence of delirium (odds ratio = 4.792; 95% confidence interval: 1.274–18.028; P = 0.020). When comparing the gut microbiota of patients with and without POD, Bacteroides and Veillonella (genus), which were higher in the preparation group, were also higher in delirium patients (P < 0.05). Genus Olsenella was both relatively higher in the non-preparation group and non-POD group (P < 0.05).

Conclusion

Mechanical bowel preparation not only altered the gut microbiota composition of patients with gastric cancer but also increased the incidence of postoperative delirium. Among all the gut microbiota altered by mechanical bowel preparation, Bacteroides and Veillonella genus might be a risk factor of POD. Genus Olsenella might be a beneficial bacteria to reduce the incidence of POD.

Influence of placental and peripheral malaria exposure in fetal life on cardiometabolic traits in adult offspring

INTRODUCTION

Fetal malaria exposure may lead to intrauterine growth restriction and increase the risk of developing diabetes and cardiovascular diseases in adulthood. We investigated the extent to which fetal peripheral and placental malaria exposure impacts insulin sensitivity and secretion, body composition and cardiometabolic health 20 years after in utero malaria exposure.

RESEARCH DESIGN AND METHODS

We traced 101 men and women in Muheza district, Tanga region whose mothers participated in a malaria chemosuppression during a pregnancy study in 1989-1992. All potential participants were screened for malaria, hepatitis B and HIV to ascertain study eligibility. Seventy-six individuals (44 men, 32 women) were included in this cohort study. The participants underwent a thorough clinical examination including anthropometric measurements, ultrasound scanning for abdominal fat distribution, blood pressure, 75 g oral glucose tolerance test, an intravenous glucose tolerance test followed by a hyperinsulinemic euglycemic clamp and a submaximal exercise test.

RESULTS

Offspring exposed to placental malaria during pregnancy had significantly higher 30-minute plasma post-glucose load levels, but no significant difference in peripheral insulin resistance, insulin secretion or other cardiometabolic traits compared with non-exposed individuals.

CONCLUSIONS

Using the state-of-the-art euglycemic clamp technique, we were unable to prove our a priori primary hypothesis of peripheral insulin resistance in young adult offspring of pregnancies affected by malaria. However, the subtle elevations of plasma glucose might represent an early risk marker for later development of type 2 diabetes if combined with aging and a more obesogenic living environment.

The role of CD36-Fabp4-PPARγ in skeletal muscle involves insulin resistance in intrauterine growth retardation mice with catch-up growth

BACKGROUND

Studies have shown that the high incidence of type 2 diabetes in China is associated with low birth weight and excessive nutrition in adulthood, which occurred during the famine years of the 1950s and 1960s, though the specific molecular mechanisms are unclear. In this study, we proposed a severe maternal caloric restriction during late pregnancy, followed by a post weaning high-fat diet in mice. After weaning, normal and high-fat diets were provided to mice to simulate the dietary pattern of modern society.

METHODS

The pregnant mice were divided into two groups: normal birth weight (NBW) group and low birth weight (LBW) group. After 3 weeks for weaning, the male offspring mice in the NBW and LBW groups were then randomly divided into four subgroups: NC, NH, LC and LC groups. The offspring mice in the NC, NH, LC and LC groups were respectively fed with normal diet, normal diet, high-fat diet and high-fat diet for 18 weeks. After 18 weeks of dietary intervention, detailed analyses of mRNA and protein expression patterns, signaling pathway activities, and promoter methylation states were conducted for all relevant genes.

RESULTS

After dietary intervention for 18 weeks, the expressions of CD36, Fabp4, PPARγ, FAS, and ACC1 in the skeletal muscle tissue of the LH group were significantly increased compared with the LC and NH groups (P < 0.05). The level of p-AMPK/AMPK in the skeletal muscle tissue of the LH group was significantly decreased compared with the LC and NH groups (P < 0.05). CPT1 and PGC-1α protein expressions were up-regulated in the LH group (P < 0.05) compared to the LC group. Additionally, the DNA methylation levels of the PGC-1α and GLUT4 gene promoters in the skeletal muscle of the LH groups were higher than those of the LC and NH groups (P < 0.05). However, PPARγ DNA methylation level in the LH group was lower than those of the LC and NH groups (P < 0.05).

CONCLUSIONS

LBW combined with high-fat diets may increase insulin resistance and diabetes through regulating the CD36-related Fabp4-PPARγ and AMPK/ACC signaling pathways.

Intramuscular Injection of miR-1 Reduces Insulin Resistance in Obese Mice

The role of microRNAs in metabolic diseases has been recognized and modulation of them could be a promising strategy to treat obesity and obesity-related diseases. The major purpose of this study was to test the hypothesis that intramuscular miR-1 precursor replacement therapy could improve metabolic parameters of mice fed a high-fat diet. To this end, we first injected miR-1 precursor intramuscularly in high-fat diet-fed mice and evaluated glucose tolerance, insulin sensitivity, and adiposity. miR-1-treated mice did not lose weight but had improved insulin sensitivity measured by insulin tolerance test. Next, using an in vitro model of insulin resistance by treating C2C12 cells with palmitic acid (PA), we overexpressed miR-1 and measured p-Akt content and the transcription levels of a protein related to fatty acid oxidation. We found that miR-1 could not restore insulin sensitivity in C2C12 cells, as indicated by p-Akt levels and that miR-1 increased expression of Pgc1a and Cpt1b in PA-treated cells, suggesting a possible role of miR-1 in mitochondrial respiration. Finally, we analyzed mitochondrial oxygen consumption in primary skeletal muscle cells treated with PA and transfected with or without miR-1 mimic. PA-treated cells showed reduced basal respiration, oxygen consumption rate-linked ATP production, maximal and spare capacity, and miR-1 overexpression could prevent impairments in mitochondrial respiration. Our data suggest a role of miR-1 in systemic insulin sensitivity and a new function of miR-1 in regulating mitochondrial respiration in skeletal muscle.

Targeting Mitochondria in Diabetes

Type 2 diabetes (T2D), one of the most prevalent noncommunicable diseases, is often preceded by insulin resistance (IR), which underlies the inability of tissues to respond to insulin and leads to disturbed metabolic homeostasis. Mitochondria, as a central player in the cellular energy metabolism, are involved in the mechanisms of IR and T2D. Mitochondrial function is affected by insulin resistance in different tissues, among which skeletal muscle and liver have the highest impact on whole-body glucose homeostasis. This review focuses on human studies that assess mitochondrial function in liver, muscle and blood cells in the context of T2D. Furthermore, different interventions targeting mitochondria in IR and T2D are listed, with a selection of studies using respirometry as a measure of mitochondrial function, for better data comparison. Altogether, mitochondrial respiratory capacity appears to be a metabolic indicator since it decreases as the disease progresses but increases after lifestyle (exercise) and pharmacological interventions, together with the improvement in metabolic health. Finally, novel therapeutics developed to target mitochondria have potential for a more integrative therapeutic approach, treating both causative and secondary defects of diabetes.

The biology of human overfeeding: A systematic review

This systematic review has examined more than 300 original papers dealing with the biology of overfeeding. Studies have varied from 1 day to 6 months. Overfeeding produced weight gain in adolescents, adult men and women and in older men. In longer term studies, there was a clear and highly significant relationship between energy ingested and weight gain and fat storage with limited individual differences. There is some evidence for a contribution of a genetic component to this response variability. The response to overfeeding was affected by the baseline state of the groups being compared: those with insulin resistance versus insulin sensitivity; those prone to obesity versus those resistant to obesity; and those with metabolically abnormal obesity versus those with metabolically normal obesity. Dietary components, such as total fat, polyunsaturated fat and carbohydrate influenced the patterns of adipose tissue distribution as did the history of low or normal birth weight. Overfeeding affected the endocrine system with increased circulating concentrations of insulin and triiodothyronine frequently present. Growth hormone, in contrast, was rapidly suppressed. Changes in plasma lipids were influenced by diet, exercise and the magnitude of weight gain. Adipose tissue and skeletal muscle morphology and metabolism are substantially altered by chronic overfeeding.

Gut DYSBIOSIS and altered barrier function precedes the appearance of metabolic syndrome in a rat model of nutrient-induced catch-up growth

Nutritional restriction early in life followed by catch-up growth has been associated with increased risk of metabolic syndrome in adulthood. To elucidate whether altered gut colonization underlies the mechanisms responsible of this predisposition gut microbiome was studied before or afterwards catch-up growth. Offspring of dams fed ad libitum (C) or undernourished during pregnancy and suckling (U), were weaned onto high-fat diet (HFD) for 22 weeks (CHF and UHF, respectively) or continued on their diet. HF-feeding induced glucose intolerance (P<.05), insulin resistance (P<.001), and white adipose tissue inflammation (P<.001) in UHF rats compared to CHF. Analyses of gut microbial composition before catch-up growth revealed reduced F/B ratio and significant expansion of the mucolytic genera Akkermansia (P<.05) and Desulfovibrio (P<.05) in U pups. Although relative abundance of Akkermansia remained elevated to adulthood in U rats, HFD normalized its levels to C and CHF. Food-restriction increased intestinal permeability causing disorganization on the tight-junction proteins of colonic epithelium, Zonula Occludens-1 (ZO-1) and occludin, and reducing the mucus thickness layer in U adult rats. The levels of ZO-1 and occludin were not recovered in U rats after HF-feeding. This event was correlated with increased circulating levels of bacterial lipopolysaccharides in both U and UHF adult rats. Even more, serum lipopolysaccharides were already elevated in U rats compared to C group (P<.001) at weaning. Thus, gut dysbiosis and chronic endotoxemia observed in U rats, even before catch-up growth, might anticipate a pro-inflammatory milieu promoting metabolic diseases when fed hyperlipidic diets.

Effect of liquid ubiquinol supplementation on glucose, lipids and antioxidant capacity in type 2 diabetes patients: a double-blind, randomised, placebo-controlled trial

Ubiquinone is a lipid antioxidant, and a novel liquid ubiquinol (a hydro-soluble, reduced form of coenzyme Q10) supplement was recently developed. The purpose of this study was to examine the levels of glucose, lipids and antioxidant capacity of type 2 diabetes patients after liquid ubiquinol supplementation. This study was designed as a randomised, double-blind, placebo-controlled trial. In all, fifty participants were randomly assigned to a placebo (n 25) or liquid ubiquinol (100 mg/d, n 25) group, and the intervention lasted for 12 weeks. Plasma coenzyme Q10, glucose homoeostasis parameters, lipid profiles, oxidative stress and antioxidative enzyme activities were measured during the study. After 12 weeks of supplementation, glyco Hb (HbA1c) value was significantly decreased in the liquid ubiquinol group (P=0·03), and subjects in the liquid ubiquinol group had significantly lower anti-glycaemic medication effect scores (MES) compared with those in the placebo group (P=0·03). The catalase (P<0·01) and glutathione peroxidase (P=0·03) activities were increased significantly after supplementation. Plasma coenzyme Q10 was correlated with the insulin level (P=0·05), homoeostatic model assessment-insulin resistance (P=0·07), quantitative insulin sensitivity check index (P=0·03) and the anti-hyperglycaemic agents' MES (P=0·03) after supplementation. Lipid profiles did not change after supplementation; however, the subjects in the placebo group had a significantly lower level of HDL-cholesterol after 12 weeks of intervention. In conclusion, oral intake of 100 mg/d liquid ubiquinol might benefit type 2 diabetes patients by increasing antioxidant enzyme activity levels, reducing HbA1c levels and maintaining HDL-cholesterol levels.

Fasting unmasks differential fat and muscle transcriptional regulation of metabolic gene sets in low versus normal birth weight men

Background

Individuals born with low birth weight (LBW) have an increased risk of metabolic diseases when exposed to diets rich in calories and fat but may respond to fasting in a metabolically preferential manner. We hypothesized that impaired foetal growth is associated with differential regulation of gene expression and epigenetics in metabolic tissues in response to fasting in young adulthood.

Methods

Genome-wide expression and DNA methylation were analysed in subcutaneous adipose tissue (SAT) and skeletal muscle from LBW and normal birth weight (NBW) men after 36 h fasting and after an isocaloric control study using microarrays.

Findings

Transcriptome analyses revealed that expression of genes involved in oxidative phosphorylation (OXPHOS) and other key metabolic pathways were lower in SAT from LBW vs NBW men after the control study, but paradoxically higher in LBW vs NBW men after 36 h fasting. Thus, fasting was associated with downregulated OXPHOS and metabolic gene sets in NBW men only. Likewise, in skeletal muscle only NBW men downregulated OXPHOS genes with fasting. Few epigenetic changes were observed in SAT and muscle between the groups.

Interpretation

Our results provide insights into the molecular mechanisms in muscle and adipose tissue governing a differential metabolic response in subjects with impaired foetal growth when exposed to fasting in adulthood. The results support the concept of developmental programming of metabolic diseases including type 2 diabetes.

Fund

The Swedish Research Council, the Danish Council for Strategic Research, the Novo Nordisk foundation, the Swedish Foundation for Strategic Research, The European Foundation for the Study of Diabetes, The EU 6th Framework EXGENESIS grant and Rigshospitalet.

TCF7L2 Expression Is Regulated by Cell Differentiation and Overfeeding in Human Adipose Tissue

Aim: The TCF7L2 gene variant rs7903146 has the largest effect on type 2 diabetes risk reported in genome-wide association studies, however its role in adipose tissue development and function is unknown. We investigate the association between gene variant rs7903146 and metabolic parameters and examine in vitro and ex vivo gene expression of TCF7L2 in human adipose tissue and progenitor cells from two independent populations of young healthy men with increased risk of type 2 diabetes due to low birth weight (LBW). Design: Adipose tissue biopsies were excised from 40 healthy young men with low and normal birth weights (NBW) after a control and 5-day high-fat overfeeding diet. In another cohort including 13 LBW and 13 NBW men, adipocyte progenitor cells were isolated and cultivated. Transcriptome-wide expression was performed on RNA extracted from biopsies or cell cultures. Results: Diet-induced peripheral insulin resistance is more pronounced in carriers of the T-risk allele rs7903146, whereas no association with hepatic insulin resistance was shown. TCF7L2 expression increased during adipogenesis in isolated preadipocytes from both LBW and NBW men (p < 0.001) and correlated positively with markers of progenitor cell proliferation and maturation capacity. In the mature adipose tissue, LBW men had lower expression of TCF7L2 compared to NBW men at baseline (p = 0.03) and TCF7L2 expression was suppressed by short-term overfeeding in NBW men (p = 0.005). Conclusions: The results suggest a regulation of TCF7L2 expression during adipogenesis and in mature adipose tissue upon overfeeding, and further that young men exposed to an adverse intrauterine environment have reduced mature adipose tissue TCF7L2 expression.

Leukocyte telomere length is associated with elevated plasma glucose and HbA1c in young healthy men independent of birth weight

Telomeres are protein-bound regions of repetitive nucleotide sequences (TTAGGG) at the end of human chromosomes, and their length is a marker of cellular aging. Intrauterine growth restriction is associated with shorter blood cell telomeres at birth and individuals with type 2 diabetes have shorter telomeres. Individuals with a low birth weight (LBW) have an increased risk of metabolic disease and type 2 diabetes. Therefore, we aimed to investigate the relationship between birth weight and telomere length and the association between birth weight, telomere length and cardiometabolic phenotype in adulthood. Young, healthy men with LBW (n = 55) and normal birth weight (NBW) (n = 65) were examined including blood pressure, blood samples and body composition. Leukocyte telomere length was determined using a high-throughput qPCR method. The LBW men were more insulin resistant as determined by the HOMA-IR index. There was no difference in telomere length between LBW and NBW subjects. When adjusting for birth weight and cohort effect, significant negative associations between telomere length and fasting glucose (P = 0.003) and HbA1c (P = 0.0008) were found. In conclusion, no significant difference in telomere length was found between LBW and NBW men. The telomere length was negatively associated with glucose concentrations and HbA1c levels within the normal non-diabetic range independent of birth weight.

Exposure to Gestational Diabetes Is a Stronger Predictor of Dysmetabolic Traits in Children Than Size at Birth

CONTEXT AND OBJECTIVE

Being born small or large for gestational age and intrauterine exposure to gestational diabetes (GDM) increase the risk of type 2 diabetes in the offspring. However, the potential combined deleterious effects of size at birth and GDM exposure remains unknown. We examined the independent effect of size at birth and the influence of GDM exposure in utero on cardiometabolic traits, body composition, and puberty status in children.

DESIGN, PARTICIPANTS, AND METHODS

The present study was a longitudinal birth cohort study. We used clinical data from 490 offspring of mothers with GDM and 527 control offspring aged 9 to 16 years, born singleton at term from the Danish National Birth Cohort with available birthweight data.

RESULTS

We found no evidence of a U-shaped association between size at birth (expressed as birthweight, sex, and gestational age adjusted z-score) and cardiometabolic traits. Body size in childhood and adolescence reflected the size at birth but was not reflected in any metabolic outcome. No synergistic adverse effect of being born small or large for gestational age and exposure to GDM was shown. However, GDM was associated with an adverse metabolic profile and earlier onset of female puberty in childhood and adolescence independently of size at birth.

CONCLUSION

In childhood and adolescence, we found GDM was a stronger predictor of dysmetabolic traits than size at birth. The combination of being born small or large and exposed to GDM does not exacerbate the metabolic profile in the offspring.

Plasma ceramide levels are altered in low and normal birth weight men in response to short-term high-fat overfeeding

Low birth weight (LBW) individuals have an increased risk of developing insulin resistance and type 2 diabetes compared with normal birth weight (NBW) individuals. We hypothesised that LBW individuals exhibit an increased fatty acid flux into lipogenesis in non-adipose tissue with a resulting accumulation of lipotoxic lipids, including ceramides, in the blood. Therefore, we measured fasting plasma levels of 27 ceramides in 18 young, healthy, LBW men and 25 NBW controls after an isocaloric control diet and a 5-day high-fat, high-calorie diet by HPLC-HRMS. LBW men did not show elevated plasma ceramide levels after the control or high-fat, high-calorie diet. An increased fatty acid oxidation rate in these individuals during both diets may limit ceramide synthesis and thereby compensate for a likely increased fatty acid load to non-adipose tissue. Interestingly, LBW and NBW men decreased d18:0-18:1/d18:1-18:0 and d18:1-24:2/d18:2-24:1 levels and increased the d18:0-24:1a level in response to overfeeding. Plasma d18:0-24:1a and total ceramide levels were positively associated with the fasting blood glucose level and endogenous glucose production after the control diet, and the total ceramide level was in addition positively associated with hepatic insulin resistance. Further studies are needed to determine if lipotoxicity contributes to insulin resistance in LBW individuals.

Effectiveness of Coenzyme Q10 Supplementation for Type 2 Diabetes Mellitus: A Systematic Review and Meta-Analysis

OBJECTIVE

To evaluate the effectiveness and safety of coenzyme Q10 for patients with type 2 diabetes mellitus (T2DM).

METHODS

Data from randomized controlled trials were obtained to assess the effects of coenzyme Q10 versus placebo or western medicine on patients with T2DM. The study's registration number is CRD42018088474. The primary outcomes included glycosylated hemoglobin, fasting blood glucose, and fasting insulin.

RESULT

Thirteen trials involving 765 patients were included. Compared with the control group, coenzyme Q10 may decrease the HbA1c (WMD -0.29; 95% CI -0.54, -0.03; P = 0.03) and the fasting blood glucose (WMD -11.21; 95% CI -18.99, -3.43; P = 0.005). For fasting insulin, there is also not strong evidence that confirms which one is better because there was no statistical difference (WMD -0.48; 95% CI -2.54, 1.57; P = 0.65).

CONCLUSION

Based on current evidence, coenzyme Q10 may assist glycemic control, decrease TG, and improve HDL-C in patients with T2DM.

Plasma acylcarnitine profiling indicates increased fatty acid oxidation relative to tricarboxylic acid cycle capacity in young, healthy low birth weight men

We hypothesized that an increased, incomplete fatty acid beta‐oxidation in mitochondria could be part of the metabolic events leading to insulin resistance and thereby an increased type 2 diabetes risk in low birth weight (LBW) compared with normal birth weight (NBW) individuals. Therefore, we measured fasting plasma levels of 45 acylcarnitine species in 18 LBW and 25 NBW men after an isocaloric control diet and a 5‐day high‐fat, high‐calorie diet. We demonstrated that LBW men had higher C2 and C4‐OH levels after the control diet compared with NBW men, indicating an increased fatty acid beta‐oxidation relative to the tricarboxylic acid cycle flux. Also, they had higher C6‐DC, C10‐OH/C8‐DC, and total hydroxyl‐/dicarboxyl‐acylcarnitine levels, which may suggest an increased fatty acid omega‐oxidation in the liver. Furthermore, LBW and NBW men decreased several acylcarnitine levels in response to overfeeding, which is likely a result of an upregulation of fatty acid oxidation due to the dietary challenge. Moreover, C10‐OH/C8‐DC and total hydroxyl‐/dicarboxyl‐acylcarnitine levels tended to be negatively associated with the serum insulin level, and the total hydroxyl‐/dicarboxyl‐acylcarnitine level additionally tended to be negatively associated with the hepatic insulin resistance index. This indicates that an increased fatty acid omega‐oxidation could be a compensatory mechanism to prevent an accumulation of lipid species that impair insulin signaling.

DNA methylation links genetics, fetal environment, and an unhealthy lifestyle to the development of type 2 diabetes

Type 2 diabetes is a complex trait with both environmental and hereditary factors contributing to the overall pathogenesis. One link between genes, environment, and disease is epigenetics influencing gene transcription and, consequently, organ function. Genome-wide studies have shown altered DNA methylation in tissues important for glucose homeostasis including pancreas, liver, skeletal muscle, and adipose tissue from subjects with type 2 diabetes compared with nondiabetic controls. Factors predisposing for type 2 diabetes including an adverse intrauterine environment, increasing age, overweight, physical inactivity, a family history of the disease, and an unhealthy diet have all shown to affect the DNA methylation pattern in target tissues for insulin resistance in humans. Epigenetics including DNA methylation may therefore improve our understanding of the type 2 diabetes pathogenesis, contribute to development of novel treatments, and be a useful tool to identify individuals at risk for developing the disease.

Birth weight and type 2 diabetes: A meta-analysis

The prevalence of T2DM is increasing around the world on a yearly basis. A meta-analysis was conducted to analyze the association between birth weight and incidence of type 2 diabetes mellitus (T2DM). A literature search was performed from January 1990 to June 2016 in PubMed, ScienceDirect, SpringerLink, China National Knowledge Infrastructure and Chinese Biomedical Literature Database. After reviewing characteristics of all the included studies systematically, a meta-analytical method was employed to calculate the pooled odds ratios (ORs) and associated 95% confidence intervals (CI) from random-effects models. Heterogeneity was assessed by Q-statistic test. Funnel plot, Begg's and Egger's linear regression tests were applied to evaluate publication bias. A sensitivity analysis was also performed to assess the robustness of results. According to inclusion and exclusion criteria, 8 studies were selected to be included in the meta-analysis. Compared with normal birth weight (2,500–4,000 g), low birth weight (<2,500 g) was associated with an increased risk of T2DM (OR, 1.55; 95% CI, 1.39–1.73; P<0.001). No significant difference was observed between high birth weight (>4,000 g) and normal birth weight in terms of the risk of T2DM (OR, 0.98; 95% CI, 0.79–1.22). Compared with high birth weight, low birth weight was associated with an increased risk of diabetes mellitus (OR, 1.58; 95% CI, 1.30–1.93; P<0.001). These findings indicated that there may be an inverse linear association between birth weight and T2DM.

Complement factors C4 and C3 are down regulated in response to short term overfeeding in healthy young men

Insulin resistance is associated with high circulating level of complement factor C3. Animal studies suggest that improper complement activation mediates high-fat-diet-induced insulin resistance. Individuals born with low birth weight (LBW) are at increased risk of developing insulin resistance. We hypothesized that high-fat overfeeding (HFO) increase circulating C3 and induce complement activation in a birth weight differential manner. Twenty LBW and 26 normal birth weight (NBW) young men were studied using a randomised crossover design. Insulin resistance was measured after a control-diet and after 5-days HFO by a hyperinsulinemic-euglycemic-clamp. Circulating C4, C3, ficolins, mannose-binding-lectin, complement activation products C3bc, terminal complement complex (TCC) and complement activation capacity were determined using turbidimetry and ELISA. HFO induced peripheral insulin resistance in LBW individuals only, while both groups had the same degree of hepatic insulin resistance after HFO. Viewing all individuals circulating levels of C4, C3, C3bc, TCC and complement activation capacity decreased paradoxically along the development of insulin resistance after HFO (P = 0.0015, P < 0.0001, P = 0.01, P < 0.0001, P = 0.0002, P < 0.0001, P = 0.0006). Birth weight did not influence these results. This might reflect a hitherto unrecognized down-regulatory mechanism of the complement system. More human studies are needed to understand the underlying physiology and the potential consequences of these findings.

36 h fasting of young men influences adipose tissue DNA methylation of LEP and ADIPOQ in a birth weight-dependent manner

Background

Subjects born with low birth weight (LBW) display a more energy-conserving response to fasting compared with normal birth weight (NBW) subjects. However, the molecular mechanisms explaining these metabolic differences remain unknown. Environmental influences may dynamically affect epigenetic marks, also in postnatal life. Here, we aimed to study the effects of short-term fasting on leptin (LEP) and adiponectin (ADIPOQ) DNA methylation and gene expression in subcutaneous adipose tissue (SAT) from subjects with LBW and NBW.

Methods

Twenty-one young LBW men and 18 matched NBW controls were studied during 36 h fasting. Eight subjects from each group completed a control study (overnight fast). We analyzed SAT LEP and ADIPOQ methylation (Epityper MassARRAY), gene expression (q-PCR), and adipokine plasma levels.

Results

After overnight fast (control study), LEP and ADIPOQ DNA methylation levels were higher in LBW compared to those in NBW subjects (p ≤ 0.03) and increased with 36 h fasting in NBW subjects only (p ≤ 0.06). Both LEP and ADIPOQ methylation levels were positively associated with total body fat percentage (p ≤ 0.05). Plasma leptin levels were higher in LBW versus NBW subjects after overnight fasting (p = 0.04) and decreased more than threefold in both groups after 36 h fasting (p ≤ 0.0001).

Conclusions

This is the first study to demonstrate that fasting induces changes in DNA methylation. This was shown in LEP and ADIPOQ promoters in SAT among NBW but not LBW subjects. The altered epigenetic flexibility in LBW subjects might contribute to their differential response to fasting, adipokine levels, and increased risk of metabolic disease.

Electronic supplementary material

The online version of this article (doi:10.1186/s13148-017-0340-8) contains supplementary material, which is available to authorized users.

MECHANISMS IN ENDOCRINOLOGY: Skeletal muscle lipotoxicity in insulin resistance and type 2 diabetes: a causal mechanism or an innocent bystander?

Dysfunctional adipose tissue is associated with an increased risk of developing type 2 diabetes (T2D). One characteristic of a dysfunctional adipose tissue is the reduced expandability of the subcutaneous adipose tissue leading to ectopic storage of fat in organs and/or tissues involved in the pathogenesis of T2D that can cause lipotoxicity. Accumulation of lipids in the skeletal muscle is associated with insulin resistance, but the majority of previous studies do not prove any causality. Most studies agree that it is not the intramuscular lipids per se that causes insulin resistance, but rather lipid intermediates such as diacylglycerols, fatty acyl-CoAs and ceramides and that it is the localization, composition and turnover of these intermediates that play an important role in the development of insulin resistance and T2D. Adipose tissue is a more active tissue than previously thought, and future research should thus aim at examining the exact role of lipid composition, cellular localization and the dynamics of lipid turnover on the development of insulin resistance. In addition, ectopic storage of fat has differential impact on various organs in different phenotypes at risk of developing T2D; thus, understanding how adipogenesis is regulated, the interference with metabolic outcomes and what determines the capacity of adipose tissue expandability in distinct population groups is necessary. This study is a review of the current literature on the adipose tissue expandability hypothesis and how the following ectopic lipid accumulation as a consequence of a limited adipose tissue expandability may be associated with insulin resistance in muscle and liver.

Plasma amino acid levels are elevated in young, healthy low birth weight men exposed to short-term high-fat overfeeding

Low birth weight (LBW) individuals exhibit a disproportionately increased, incomplete fatty acid oxidation and a decreased glucose oxidation, compared with normal birth weight (NBW) individuals, and furthermore have an increased risk of developing insulin resistance and type 2 diabetes. We hypothesized that changes in amino acid metabolism may occur parallel to alterations in fatty acid and glucose oxidation, and could contribute to insulin resistance. Therefore, we measured fasting plasma levels of 15 individual or pools of amino acids in 18 LBW and 25 NBW men after an isocaloric control diet and after a 5-day high-fat, high-calorie diet. We demonstrated that LBW and NBW men increased plasma alanine levels and decreased valine and leucine/isoleucine levels in response to overfeeding. Also, LBW men had higher alanine, proline, methionine, citrulline, and total amino acid levels after overfeeding compared with NBW men. Alanine and total amino acid levels tended to be negatively associated with the insulin-stimulated glucose uptake after overfeeding. Therefore, the higher amino acid levels in LBW men could be a consequence of their reduction in skeletal muscle insulin sensitivity due to overfeeding with a possible increased skeletal muscle proteolysis and/or could potentially contribute to an impaired insulin sensitivity. Furthermore, the alanine level was negatively associated with the plasma acetylcarnitine level and positively associated with the hepatic glucose production after overfeeding. Thus, the higher alanine level in LBW men could be accompanied by an increased anaplerotic formation of oxaloacetate and thereby an enhanced tricarboxylic acid cycle activity and as well an increased gluconeogenesis.

Effect of Three Levels of Dietary Protein on Metabolic Phenotype of Healthy Individuals With 8 Weeks of Overfeeding

CONTEXT

Obesity is associated with insulin resistance and other metabolic changes that might be modified by overfeeding diets with different protein levels.

OBJECTIVE

The objective of the study was to determine the effect of overfeeding diets with 5%, 15%, or 25% energy from protein on insulin sensitivity and compartments of body fat in healthy men and women.

METHODS

Fifteen men and five women were overfed by approximately 40% for 56 days with 5% (low protein), 15% (normal protein), or 25% (high protein) protein diets. Insulin sensitivity was measured using a two-step insulin clamp at baseline and at 8 weeks. Body composition and fat distribution were measured by dual-energy x-ray absorptiometry and multislice computed tomography scan and abdominal sc fat cell size was determined on osmium-fixed fat cells.

SETTING

This was an in-patient metabolic ward study.

MAIN OUTCOME MEASURES

Insulin sensitivity and free fatty acids during low and high levels of insulin infusion before and after 8 weeks after overfeeding and changes in body fat distribution from computed tomography were measured.

RESULTS

Total body fat mass, fat-free mass (FFM), visceral adipose tissue (VAT), and deep sc fat all increased with overfeeding. FFM and intrahepatic lipid increased more on the high protein diet, whereas percentage BF and fasting free fatty acids (FFAs) increased more on the low protein diet. Baseline fat cell size predicted the increase in VAT and the magnitude of FFA suppression during the high-dose insulin clamp. Acute release of insulin at baseline predicted the increase in deep sc fat but not VAT. Fasting insulin and glucose increased with overfeeding, but glucose disposal as measured by the clamp was not changed. Suppression of FFAs was less complete during the high-dose insulin infusion after overfeeding.

CONCLUSION

Eight weeks of overfeeding, which increased fat mass including expansion of visceral and deep sc tissues and intrahepatic lipid, increased fasting insulin and glucose, impaired the suppression of FFA but did not produce whole-body insulin resistance.

Adipose tissue transcriptomics and epigenomics in low birthweight men and controls: role of high-fat overfeeding

AIMS/HYPOTHESIS

Individuals who had a low birthweight (LBW) are at an increased risk of insulin resistance and type 2 diabetes when exposed to high-fat overfeeding (HFO). We studied genome-wide mRNA expression and DNA methylation in subcutaneous adipose tissue (SAT) after 5 days of HFO and after a control diet in 40 young men, of whom 16 had LBW.

METHODS

mRNA expression was analysed using Affymetrix Human Gene 1.0 ST arrays and DNA methylation using Illumina 450K BeadChip arrays.

RESULTS

We found differential DNA methylation at 53 sites in SAT from LBW vs normal birthweight (NBW) men (false discovery rate <5%), including sites in the FADS2 and CPLX1 genes previously associated with type 2 diabetes. When we used reference-free cell mixture adjustments to potentially adjust for cell composition, 4,323 sites had differential methylation in LBW vs NBW men. However, no differences in SAT gene expression levels were identified between LBW and NBW men. In the combined group of all 40 participants, 3,276 genes (16.5%) were differentially expressed in SAT after HFO (false discovery rate <5%) and there was no difference between LBW men and controls. The most strongly upregulated genes were ELOVL6, FADS2 and NNAT; in contrast, INSR, IRS2 and the SLC27A2 fatty acid transporter showed decreased expression after HFO. Interestingly, SLC27A2 expression correlated negatively with diabetes- and obesity-related traits in a replication cohort of 142 individuals. DNA methylation at 652 CpG sites (including in CDK5, IGFBP5 and SLC2A4) was altered in SAT after overfeeding in this and in another cohort.

CONCLUSIONS/INTERPRETATION

Young men who had a LBW exhibit epigenetic alterations in their adipose tissue that potentially influence insulin resistance and risk of type 2 diabetes. Short-term overfeeding influences gene transcription and, to some extent, DNA methylation in adipose tissue; there was no major difference in this response between LBW and control participants.

From fatalism to mitigation: A conceptual framework for mitigating fetal programming of chronic disease by maternal obesity

Prenatal development is recognized as a critical period in the etiology of obesity and cardiometabolic disease. Potential strategies to reduce maternal obesity-induced risk later in life have been largely overlooked. In this paper, we first propose a conceptual framework for the role of public health and preventive medicine in mitigating the effects of fetal programming. Second, we review a small but growing body of research (through August 2015) that examines interactive effects of maternal obesity and two public health foci - diet and physical activity - in the offspring. Results of the review support the hypothesis that diet and physical activity after early life can attenuate disease susceptibility induced by maternal obesity, but human evidence is scant. Based on the review, we identify major gaps relevant for prevention research, such as characterizing the type and dose response of dietary and physical activity exposures that modify the adverse effects of maternal obesity in the offspring. Third, we discuss potential implications of interactions between maternal obesity and postnatal dietary and physical activity exposures for interventions to mitigate maternal obesity-induced risk among children. Our conceptual framework, evidence review, and future research directions offer a platform to develop, test, and implement fetal programming mitigation strategies for the current and future generations of children.

Maternal Betaine Supplementation during Gestation Enhances Expression of mtDNA-Encoded Genes through D-Loop DNA Hypomethylation in the Skeletal Muscle of Newborn Piglets

Betaine has been widely used in animal and human nutrition to promote muscle growth and performance, yet it remains unknown whether maternal betaine supplementation during gestation affects the metabolic characteristics of neonatal skeletal muscles. In the present study, feeding sows with betaine-supplemented diets throughout gestation significantly upregulated the expression of mtDNA-encoded OXPHOS genes (p < 0.05), including COX1, COX2, and ND5, in the muscle of newborn piglets, which was associated with enhanced mitochondrial COX enzyme activity (p < 0.05). Concurrently, maternal betaine supplementation increased the plasma betaine concentration and muscle expression of methyl transfer enzymes (p < 0.05), BHMT and GNMT, in offspring piglets. Nevertheless, Dnmt3a was downregulated at the level of both mRNA and protein, which was associated with a hypomethylated mtDNA D-loop region (p < 0.05). These results suggest that maternal betaine supplementation during gestation enhances expression of mtDNA-encoded genes through D-loop DNA hypomethylation in the skeletal muscle of newborn piglets.

Uteroplacental insufficiency leads to hypertension, but not glucose intolerance or impaired skeletal muscle mitochondrial biogenesis, in 12-month-old rats

Growth restriction impacts on offspring development and increases their risk of disease in adulthood which is exacerbated with “second hits.” The aim of this study was to investigate if blood pressure, glucose tolerance, and skeletal muscle mitochondrial biogenesis were altered in 12-month-old male and female offspring with prenatal or postnatal growth restriction. Bilateral uterine vessel ligation induced uteroplacental insufficiency and growth restriction in offspring (Restricted). A sham surgery was also performed during pregnancy (Control) and some litters from sham mothers had their litter size reduced (Reduced litter), which restricted postnatal growth. Growth-restricted females only developed hypertension at 12 months, which was not observed in males. In Restricted females only homeostasis model assessment for insulin resistance was decreased, indicating enhanced hepatic insulin sensitivity, which was not observed in males. Plasma leptin was increased only in the Reduced males at 12 months compared to Control and Restricted males, which was not observed in females. Compared to Controls, leptin, ghrelin, and adiponectin were unaltered in the Restricted males and females, suggesting that at 12 months of age the reduction in body weight in the Restricted offspring is not a consequence of circulating adipokines. Skeletal muscle PGC-1α levels were unaltered in 12-month-old male and female rats, which indicate improvements in lean muscle mass by 12 months of age. In summary, sex strongly impacts the cardiometabolic effects of growth restriction in 12-month-old rats and it is females who are at particular risk of developing long-term hypertension following growth restriction.

Disproportionately increased 24-h energy expenditure and fat oxidation in young men with low birth weight during a high-fat overfeeding challenge

BACKGROUND

Low birth weight (LBW) associates with increased risk of developing type 2 diabetes. LBW individuals exhibit disproportionately reduced peripheral insulin action and increased fat oxidation after a 5-day high-fat overfeeding (HFO) challenge. Furthermore, LBW men exhibit increased nocturnal fat oxidation during energy balance and low energy expenditure (EE) during fasting. We hypothesized that short-term HFO could further unmask key defects of whole-body energy metabolism in LBW men.

METHODS

Eighteen LBW (2717 ± 268 g) and 26 normal birth weight (NBW) (3893 ± 207 g) healthy young men were included in a 5-day HFO (60 E % fat, +50 % calories) study. The 24-h EE, respiratory quotient and substrate oxidation rates were assessed by indirect calorimetry using respiratory chambers.

RESULTS

After adjusting for body composition, the LBW subjects displayed increased nighttime EE (P = 0.02) compared with NBW controls during HFO. Nighttime glucose oxidation rate was decreased (P = 0.06, adjusted P = 0.05), while both adjusted 24-h (P = 0.07) and nighttime (P = 0.02) fat oxidation rate was elevated in LBW subjects. The relative contribution of fat oxidation to EE was increased in LBW compared with NBW men during the entire 24-h period (P = 0.06) and during nighttime (P = 0.03).

CONCLUSIONS

We suggest that disproportionally enhanced fat oxidation in LBW individuals during short-term HFO represents a compensatory response to reduced subcutaneous adipose tissue expandability and storage capacity. The extent to which this mechanism may lead to, or be replaced by insulin resistance, ectopic fat accumulation and/or glucose intolerance during long-term HFO in LBW needs further studies.

Supplementation of Coenzyme Q10 among Patients with Type 2 Diabetes Mellitus

Type 2 diabetes mellitus (T2DM) is a major cause of morbidity and mortality with ever increasing prevalence in the United States and worldwide. There is growing body of evidence suggesting that mitochondrial dysfunction secondary to oxidative stress plays a critical role in the pathogenesis of T2DM. Coenzyme Q10 is an important micronutrient acting on the electron transport chain of the mitochondria with two major functions: (1) synthesis of adenosine triphosphate (ATP); and (2) a potent antioxidant. Deficiency in coenzyme Q10 is often seen in patients with T2DM. Whether restoration of coenzyme Q10 will help alleviate oxidative stress, preserve mitochondrial function, and thus improve glycemic control in T2DM is unclear. This article reviews the relationships among oxidative stress, mitochondrial dysfunction, and T2DM and examines the evidence for potential use of coenzyme Q10 as a supplement for the treatment of T2DM.

Developmental Programming: Priming Disease Susceptibility for Subsequent Generations

Racial and/or ethnic minorities carry the highest burden of many adverse health outcomes intergenerationally We propose a paradigm in which developmental programming exacerbates the effects of racial patterning of adverse environmental conditions, thereby contributing to health disparity persistence. Evidence that developmental programming induces a heightened response to adverse exposures ("second hits") encountered later in life is considered. We evaluated the evidence for the second hit phenomenon reported in animal and human studies from three domains (air, stress, nutrition). Original research including a gestational exposure and a childhood or adulthood second hit exposure was reviewed. Evidence from animal studies suggest that prenatal exposure to air pollutants is associated with an exaggerated reaction to postnatal air pollution exposure, which results in worse health outcomes. It also indicates offspring exposed to prenatal maternal stress produce an exaggerated response to subsequent stressors, including anxiety and hyper-responsiveness of the hypothalamic-pituitary-adrenal axis. Similarly, prenatal and postnatal Western-style diets induce synergistic effects on weight gain, metabolic dysfunction, and atherosclerotic risk. Cross-domain second hits (e.g., gestational air pollution followed by childhood stressor) were also considered. Suboptimal gestational environments induce exaggerated offspring responses to subsequent environmental and social exposures. These developmental programming effects may result in enhanced sensitivity of ongoing, racially patterned, adverse exposures in race/ethnic minorities, thereby exacerbating health disparities from one generation to the next. Empirical assessment of the hypothesized role of priming processes in the propagation of health disparities is needed. Future social epidemiology research must explicitly consider synergistic relationships among social environmental conditions to which gestating females are exposed and offspring exposures when assessing causes for persistent health disparities.

Metabolic response to 36 hours of fasting in young men born small vs appropriate for gestational age

AIMS/HYPOTHESIS

Being born small for gestational age (SGA) is associated with an increased risk of type 2 diabetes in an affluent society, but could confer an improved chance of survival during sparse living conditions. We studied whether insulin action and other metabolic responses to prolonged fasting differed between 21 young adults born SGA and 18 matched controls born appropriate for gestational age (AGA).

METHODS

A frequently sampled IVGTT and indirect calorimetry measurements were performed after a 36 h fast. Endogenous glucose production, insulin sensitivity (SI), first-phase insulin secretion and glucose effectiveness were estimated by stable isotope tracer techniques and minimal modelling. Muscle and fat biopsies were obtained after 35 h of fasting.

RESULTS

During fasting, SGA individuals experienced a more pronounced decrease in serum insulin and lower plasma triacylglycerol levels compared with AGA individuals. In addition, energy expenditure decreased in SGA but increased in AGA individuals. After fasting, SGA individuals displayed lower fat oxidation than AGA individuals. SG was reduced in SGA compared with AGA individuals, whereas hepatic or whole body insulin action (SI) did not differ between groups. SGA individuals had increased muscle PPARGC1A DNA methylation. We found no differences in adipose tissue PPARGC1A DNA methylation, muscle and adipose tissue PPARGC1A mRNA expression, or muscle glycogen levels between the groups.

CONCLUSION

Compared with AGA individuals, SGA individuals displayed a more energy-conserving and potentially beneficial [corrected] cardiometabolic response to 36 h fasting. The role of increased muscle PPARGC1A DNA methylation in mediating this response requires further study.

Effects of an outdoor bicycle-based intervention in healthy rural Indian men with normal and low birth weight

Physical inactivity and low birth weight (LBW) may lead to an increased risk for developing type 2 diabetes. The extent to which LBW individuals may benefit from physical exercise training when compared with those with normal birth weight (NBW) controls is uncertain. We assessed the impact of an outdoor exercise intervention on body composition, insulin secretion and action in young men born with LBW and NBW in rural India. A total of 61 LBW and 56 NBW healthy young men were recruited into the study. The individuals were instructed to perform outdoor bicycle exercise training for 45 min every day. Fasting blood samples, intravenous glucose tolerance tests and bioimpedance body composition assessment were carried out. Physical activity was measured using combined accelerometry and heart rate monitoring during the first and the last week of the intervention. Following the exercise intervention, the LBW group displayed an increase in physical fitness [55.0 ml (O2)/kg min (52.0-58.0)-57.5 ml (O2)/kg min (54.4-60.5)] level and total fat-free mass [10.9% (8.0-13.4)-11.4% (8.0-14.6)], as well as a corresponding decline in the ratio of total fat mass/fat-free mass. In contrast, an increase in total fat percentage as well as total fat mass was observed in the NBW group. After intervention, fasting plasma insulin levels, homoeostasis model assessments (HOMA) of insulin resistance (HOMA-IR) and insulin secretion (HOMA-IS), improved to the same extent in both the groups. In summary, young men born with LBW in rural India benefit metabolically from exercise training to an extent comparable with NBW controls.

Predominant role of GIP in the development of a metabolic syndrome-like phenotype in female Wistar rats submitted to forced catch-up growth

Catch-up growth has been associated with the appearance of metabolic dysfunctions such as obesity and type 2 diabetes in adulthood. Because the entero-insular axis is critical to glucose homeostasis control, we explored the relevance of the incretins glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) in the development of these pathologies. Offspring of rat dams fed ad libitum (control [C]) or 65% food-restricted during pregnancy and suckling time (undernourished [U]) were weaned onto a high-fat (HF) diet (CHF and UHF, respectively) to drive catch-up growth. Both male and female UHF rats showed an obese phenotype characterized by hyperphagy, visceral fat accumulation, and adipocyte hypertrophy. High-fat diet induced deterioration of glucose tolerance in a sex-dependent manner. Female UHF rats experienced much more severe glucose intolerance than males, which was not compensated by insulin hypersecretion, suggesting insulin resistance, as shown by homeostatic model assessment of insulin resistance values. Moreover, female, but not male, UHF rats displayed enhanced GIP but not GLP-1 secretion during oral glucose tolerance test. Administration of the GIP receptor antagonist (Pro3)GIP to UHF female rats over 21 days markedly reduced visceral fat mass and adipocyte hypertrophy without variations in food intake or body weight. These changes were accompanied by improvement of glucose tolerance and insulin sensitivity. In conclusion, the exacerbated production and secretion of GIP after the catch-up growth seems to represent the stimulus for insulin hypersecretion and insulin resistance, ultimately resulting in derangement of glucose homeostasis. Overall, these data evidence the role of GIP as a critical link between catch-up growth and the development of metabolic disturbances.

Young men with low birthweight exhibit decreased plasticity of genome-wide muscle DNA methylation by high-fat overfeeding

AIMS/HYPOTHESIS

The association between low birthweight (LBW) and risk of developing type 2 diabetes may involve epigenetic mechanisms, with skeletal muscle being a prime target tissue. Differential DNA methylation patterns have been observed in single genes in muscle tissue from type 2 diabetic and LBW individuals, and we recently showed multiple DNA methylation changes during short-term high-fat overfeeding in muscle of healthy people. In a randomised crossover study, we analysed genome-wide DNA promoter methylation in skeletal muscle of 17 young LBW men and 23 matched normal birthweight (NBW) men after a control and a 5 day high-fat overfeeding diet.

METHODS

DNA methylation was measured using Illumina's Infinium BeadArray covering 27,578 CpG sites representing 14,475 different genes.

RESULTS

After correction for multiple comparisons, DNA methylation levels were found to be similar in the LBW and NBW groups during the control diet. Whereas widespread DNA methylation changes were observed in the NBW group in response to high-fat overfeeding, only a few methylation changes were seen in the LBW group (χ(2), p < 0.001).

CONCLUSIONS/INTERPRETATION

Our results indicate lower DNA methylation plasticity in skeletal muscle from LBW vs NBW men, potentially contributing to understanding the link between LBW and increased risk of type 2 diabetes.

Exercise as an intervention to improve metabolic outcomes after intrauterine growth restriction

Individuals born after intrauterine growth restriction (IUGR) are at an increased risk of developing diabetes in their adult life. IUGR impairs β-cell function and reduces β-cell mass, thereby diminishing insulin secretion. IUGR also induces insulin resistance, with impaired insulin signaling in muscle in adult humans who were small for gestational age (SGA) and in rodent models of IUGR. There is epidemiological evidence in humans that exercise in adults can reduce the risk of metabolic disease following IUGR. However, it is not clear whether adult IUGR individuals benefit to the same extent from exercise as do normal-birth-weight individuals, as our rat studies suggest less of a benefit in those born IUGR. Importantly, however, there is some evidence from studies in rats that exercise in early life might be able to reverse or reprogram the long-term metabolic effects of IUGR. Studies are needed to address gaps in current knowledge, including determining the mechanisms involved in the reprogramming effects of early exercise in rats, whether exercise early in life or in adulthood has similar beneficial metabolic effects in larger animal models in which insulin resistance develops after IUGR. Human studies are also needed to determine whether exercise training improves insulin secretion and insulin sensitivity to the same extent in IUGR adults as in control populations. Such investigations will have implications for customizing the recommended level and timing of exercise to improve metabolic health after IUGR.

Metabolic profile before and after short-term overfeeding with a high-fat diet: a comparison between South Asian and White men

For the same BMI, South Asians have a higher body fat percentage and an adverse metabolic profile compared with whites. The objective of the present study was to determine the metabolic profiles of South Asian and white men matched for body fat percentage in response to short-term overfeeding with a high-fat diet. A total of ten healthy non-diabetic South Asian men matched for body fat percentage with ten white men were included in the study. A weight-maintenance diet (containing 30 % fat, 55 % carbohydrate and 15 % protein) was provided for 3 d followed by 4 d of overfeeding (150 % of energy requirement) with a high-fat diet (60 % fat, 25 % carbohydrate and 15 % protein). Before and after the overfeeding period, plasma glucose, insulin, TAG, NEFA, total cholesterol and HDL-cholesterol concentrations were determined. Glucose clearance was calculated using a 2 h oral glucose tolerance test. The results revealed that in South Asian and white men, respectively, overfeeding with a high-fat diet decreased plasma TAG concentrations by 0·4 (sd 0·6) and 0·4 (sd 0·5) mmol/l (P diet= 0·008; P ethnicity= 0·24), increased HDL-cholesterol concentrations by 0·12 (sd 0·1) and 0·14 (sd 0·2) mmol/l (P diet= 0·001; P ethnicity= 0·06) and decreased glucose clearance by 48·8 (sd 53·5) and 37·2 (sd 34·2) ml/min per m2 body surface (P diet= 0·004; P ethnicity= 0·18). There was a significant interaction between diet and ethnicity with regard to the changes in total and LDL-cholesterol concentrations (P= 0·01 and 0·007, respectively), which trended towards a larger increase in South Asian subjects than in white subjects. Despite a similar body fat percentage, short-term overfeeding with a high-fat diet had more adverse effects on the lipid profile of South Asians than on that of whites.

PPARGC1A DNA methylation in subcutaneous adipose tissue in low birth weight subjects--impact of 5 days of high-fat overfeeding

OBJECTIVE

Increased DNA methylation of the metabolic regulator peroxisome proliferator-activated receptor gamma coactivator 1 alpha (PPARGC1A) has been reported in skeletal muscle from type 2 diabetes (T2D) subjects and from low birth weight (LBW) subjects with an increased risk of T2D. High-fat overfeeding increases PPARGC1A DNA methylation in muscle in a birth weight dependent manner. However, PPARGC1A DNA methylation in subcutaneous adipose tissue (SAT) in LBW subjects has not previously been investigated. Our objective was to determine PPARGC1A DNA methylation and mRNA expression in basal and insulin-stimulated SAT from LBW and matched normal birth weight (NBW) subjects during control and high-fat overfeeding.

MATERIALS/METHODS

Nineteen young healthy men with LBW and 26 NBW controls were studied after both a 5-day high-fat overfeeding and a control diet in a randomized crossover setting. DNA methylation was assessed with bisulfite sequencing and mRNA expression with quantitative real-time PCR.

RESULTS

Following high-fat overfeeding, increased SAT PPARGC1A DNA methylation was observed in LBW subjects but not in NBW controls. Basal SAT PPARGC1A mRNA expression was unaffected by diet and similar in the two groups. However, LBW subjects showed an increased SAT PPARGC1A mRNA expression during insulin-stimulation. SAT PPARGC1A methylation correlated inversely with mRNA expression during insulin-stimulation.

CONCLUSIONS

The study adds to the increasing awareness of PPARGC1A DNA methylation being flexible and influenced by high-fat overfeeding in a birth weight dependent manner with muscle and fat responding differently. Further data are needed to understand the role of PPARGC1A DNA methylation in insulin resistance and developmental programming of T2D.

Impaired leptin gene expression and release in cultured preadipocytes isolated from individuals born with low birth weight

Low birth weight (LBW) is associated with increased risk of the development of type 2 diabetes (T2D). The appetite-regulating hormone leptin is released from mature adipocytes, and its production may be decreased in immature preadipocytes from LBW individuals. We recruited 14 men born with LBW and 13 controls born with normal birth weight (NBW). Biopsy samples were obtained from subcutaneous abdominal fat depots, and preadipocytes were isolated and cultured. Gene expression of leptin and selected differentiation markers were analyzed during preadipocyte differentiation, and cell culture media were collected to analyze leptin secretion. DNA methylation of CpG sites in the leptin promoter was measured using pyrosequencing. We found that differentiating preadipocytes from LBW individuals showed reduced leptin gene expression and a corresponding reduced leptin release compared with NBW individuals. Mean DNA methylation of the proximal LEP promoter was increased in LBW compared with NBW individuals. The notion of impaired adipocyte maturation in LBW individuals was supported by a lower mRNA expression of the differentiation markers; fatty acid binding protein 4, peroxisome proliferator-activated receptor γ, and GLUT4. Our findings are consistent with impaired preadipocyte maturation, contributing to an increased risk of the development of T2D in LBW subjects.

Dietary protein decreases exercise endurance through rapamycin-sensitive suppression of muscle mitochondria

Loss of physical performance is linked not only to decreased activity in daily life but also to increased onset of cardiovascular diseases and mortality. A high-protein diet is recommended for aged individuals in order to preserve muscle mass; however, the regulation of muscle mitochondria by dietary protein has not been clarified. We investigated the long-term effects of a high-protein diet on muscle properties, focusing especially on muscle mitochondria. Mice were fed a high-protein diet from the age of 8 wk and examined for mitochondrial properties and exercise endurance at the ages of 20 and 50 wk. Compared with normal chow, a high-protein diet significantly decreased the amount of muscle mitochondria, mitochondrial activity, and running distance at 50 wk, although it increased muscle mass and grip power. Inhibition of TORC1-dependent signal pathways by rapamycin from 8 wk suppressed the decline in mitochondria and exercise endurance observed when mice were fed the high-protein diet in association with preserved AMPK activity. Collectively, these findings suggest a role for dietary protein as a suppressor of muscle mitochondria and indicate that the age-associated decline in exercise endurance might be accelerated by excessive dietary protein through rapamycin-sensitive suppression of muscle mitochondria.

Podocyte energy metabolism and glomerular diseases

Mitochondria are crucial organelles that produce and deliver adenosine triphosphate (ATP), by which all cellular processes are driven. Although the mechanisms that control mitochondrial biogenesis, function and dynamics are complex process and vary among different cell types, recent studies provided many new discoveries in this field. Podocyte injury is a crucial step in the development of a large number of glomerular diseases. Glomerular podocytes are unique cells with complex foot processes that cover the outer layer of the glomerular basement membrane, and are the principle cells composing filtration barriers of glomerular capillaries. Little is known on the modalities and the regulation of podocyte's energetics as well as the type of energy substrate primarily used for their activity, recent studies revealed that dysfunction of energy transduction in podocytes may underlie the podocyte injury associated with numerous glomerular diseases. We herein review and discuss the importance of a fine regulation of energy metabolism in podocytes for maintaining their cellular structure and related kidney function. In the future, understanding these mechanisms will open up new areas of treatment for glomerular diseases.

Link between GIP and osteopontin in adipose tissue and insulin resistance

Low-grade inflammation in obesity is associated with accumulation of the macrophage-derived cytokine osteopontin (OPN) in adipose tissue and induction of local as well as systemic insulin resistance. Since glucose-dependent insulinotropic polypeptide (GIP) is a strong stimulator of adipogenesis and may play a role in the development of obesity, we explored whether GIP directly would stimulate OPN expression in adipose tissue and thereby induce insulin resistance. GIP stimulated OPN protein expression in a dose-dependent fashion in rat primary adipocytes. The level of OPN mRNA was higher in adipose tissue of obese individuals (0.13 ± 0.04 vs. 0.04 ± 0.01, P < 0.05) and correlated inversely with measures of insulin sensitivity (r = -0.24, P = 0.001). A common variant of the GIP receptor (GIPR) (rs10423928) gene was associated with a lower amount of the exon 9-containing isoform required for transmembrane activity. Carriers of the A allele with a reduced receptor function showed lower adipose tissue OPN mRNA levels and better insulin sensitivity. Together, these data suggest a role for GIP not only as an incretin hormone but also as a trigger of inflammation and insulin resistance in adipose tissue. Carriers of the GIPR rs10423928 A allele showed protective properties via reduced GIP effects. Identification of this unprecedented link between GIP and OPN in adipose tissue might open new avenues for therapeutic interventions.

Leptin's role in lipodystrophic and nonlipodystrophic insulin-resistant and diabetic individuals

Leptin is an adipocyte-secreted hormone that has been proposed to regulate energy homeostasis as well as metabolic, reproductive, neuroendocrine, and immune functions. In the context of open-label uncontrolled studies, leptin administration has demonstrated insulin-sensitizing effects in patients with congenital lipodystrophy associated with relative leptin deficiency. Leptin administration has also been shown to decrease central fat mass and improve insulin sensitivity and fasting insulin and glucose levels in HIV-infected patients with highly active antiretroviral therapy (HAART)-induced lipodystrophy, insulin resistance, and leptin deficiency. On the contrary, the effects of leptin treatment in leptin-replete or hyperleptinemic obese individuals with glucose intolerance and diabetes mellitus have been minimal or null, presumably due to leptin tolerance or resistance that impairs leptin action. Similarly, experimental evidence suggests a null or a possibly adverse role of leptin treatment in nonlipodystrophic patients with nonalcoholic fatty liver disease. In this review, we present a description of leptin biology and signaling; we summarize leptin's contribution to glucose metabolism in animals and humans in vitro, ex vivo, and in vivo; and we provide insights into the emerging clinical applications and therapeutic uses of leptin in humans with lipodystrophy and/or diabetes.

Increased nocturnal fat oxidation in young healthy men with low birth weight: results from 24-h whole-body respiratory chamber measurements

OBJECTIVE

Low birth weight (LBW), a marker of disturbed fetal growth, is associated with adiposity and increased risk of type 2 diabetes (T2D). The aim of the study was to investigate whether LBW is associated with changes in 24-h energy expenditure (EE) and/or substrate utilization rates, potentially contributing to the development of adiposity and/or T2D compared to matched control subjects.

MATERIALS/METHODS

Forty-six young, healthy men were included in the study; 20 with LBW (≤ 10th percentile) and 26 control subjects with normal birth weight (NBW) (50th-90th percentile). The subjects were fed a weight maintenance diet and 24-h energy expenditure (EE), respiratory quotient (RQ), and substrate oxidation were assessed in a respiratory chamber.

RESULTS

No differences in 24-h EE, RQ or substrate oxidation were observed between LBW and controls. Interestingly, the LBW group exhibited lower nocturnal RQ compared to controls (0.81 ± 0.01 vs. 0.85 ± 0.01 (mean ± SE), P = 0.01), and hence higher nocturnal fat oxidation (2.55 ± 0.13 vs. 2.09 ± 0.12 kJ/min (mean ± SE), P = 0.02).

CONCLUSIONS

Young LBW men do not exhibit reductions in 24-h EE. However, LBW subjects display increased nocturnal fat oxidation at the expense of reduced glucose oxidation. We speculate that this may be associated with insufficient capability to retain fat in subcutaneous adipose tissue after meals during day time, with an increased rate of nocturnal and morning lipolysis, and potentially with subtle elevations of gluconeogenesis and of fasting glucose levels in the LBW subjects.

Growth arrest specific protein (GAS) 6: a role in the regulation of proliferation and functional capacity of the perinatal rat beta cell

AIMS/HYPOTHESIS

Maternal low-protein (LP) diet during gestation results in a reduced beta cell mass in the offspring at birth and this may hamper the ability to adapt to high-energy food and sedentary lifestyle later in life. To investigate the biology behind the LP-offspring phenotype, this study aimed to identify differentially expressed genes in the pancreas and their potential role in the fetal programming.

METHODS

Wistar rats were given either an LP diet or normal-chow (NC) diet during gestation and differentially expressed genes in the offspring around the time of birth were identified using RNA microarray and quantitative PCR. The role of a differentially expressed gene, growth arrest specific protein 6 (GAS6), was evaluated in vitro using neonatal rat islets.

RESULTS

The mRNA level of Gas6, known to be mitogenic in other tissues, was reduced in LP offspring. The mRNA content of Mafa was increased in LP offspring suggesting an early maturation of beta cells. When applied in vitro, GAS6 increased proliferation of neonatal pancreatic beta cells, while reducing glucose-stimulated insulin secretion without changing the total insulin content of the islets. In addition, GAS6 decreased the mRNA content of Mafa.

CONCLUSIONS/INTERPRETATION

We propose a role for GAS6 in the regulation of pancreatic beta cells in the critical period around the time of birth. Our results support the hypothesis that the reduced beta cell mass seen in LP offspring is caused by a change in the intra-uterine environment that favours premature maturation of the beta cells.