Romain Barrès

Chronic high-fat diet in fathers programs β-cell dysfunction in female rat offspring

The global prevalence of obesity is increasing across most ages in both sexes. This is contributing to the early emergence of type 2 diabetes and its related epidemic. Having either parent obese is an independent risk factor for childhood obesity. Although the detrimental impacts of diet-induced maternal obesity on adiposity and metabolism in offspring are well established, the extent of any contribution of obese fathers is unclear, particularly the role of non-genetic factors in the causal pathway. Here we show that paternal high-fat-diet (HFD) exposure programs β-cell ‘dysfunction’ in rat F1 female offspring. Chronic HFD consumption in Sprague–Dawley fathers induced increased body weight, adiposity, impaired glucose tolerance and insulin sensitivity. Relative to controls, their female offspring had an early onset of impaired insulin secretion and glucose tolerance that worsened with time, and normal adiposity. Paternal HFD altered the expression of 642 pancreatic islet genes in adult female offspring (P < 0.01); genes belonged to 13 functional clusters, including cation and ATP binding, cytoskeleton and intracellular transport. Broader pathway analysis of 2,492 genes differentially expressed (P < 0.05) demonstrated involvement of calcium-, MAPK- and Wnt-signalling pathways, apoptosis and the cell cycle. Hypomethylation of the Il13ra2 gene, which showed the highest fold difference in expression (1.76-fold increase), was demonstrated. This is the first report in mammals of non-genetic, intergenerational transmission of metabolic sequelae of a HFD from father to offspring.

Skeletal Muscle PGC-1α1 Modulates Kynurenine Metabolism and Mediates Resilience to Stress-Induced Depression

Depression is a debilitating condition with a profound impact on quality of life for millions of people worldwide. Physical exercise is used as a treatment strategy for many patients, but the mechanisms that underlie its beneficial effects remain unknown. Here, we describe a mechanism by which skeletal muscle PGC-1α1 induced by exercise training changes kynurenine metabolism and protects from stress-induced depression. Activation of the PGC-1α1-PPARα/δ pathway increases skeletal muscle expression of kynurenine aminotransferases, thus enhancing the conversion of kynurenine into kynurenic acid, a metabolite unable to cross the blood-brain barrier. Reducing plasma kynurenine protects the brain from stress-induced changes associated with depression and renders skeletal muscle-specific PGC-1α1 transgenic mice resistant to depression induced by chronic mild stress or direct kynurenine administration. This study opens therapeutic avenues for the treatment of depression by targeting the PGC-1α1-PPAR axis in skeletal muscle, without the need to cross the blood-brain barrier.

Obesity and Bariatric Surgery Drive Epigenetic Variation of Spermatozoa in Humans.

Obesity is a heritable disorder, with children of obese fathers at higher risk of developing obesity. Environmental factors epigenetically influence somatic tissues, but the contribution of these factors to the establishment of epigenetic patterns in human gametes is unknown. Here, we hypothesized that weight loss remodels the epigenetic signature of spermatozoa in human obesity. Comprehensive profiling of the epigenome of sperm from lean and obese men showed similar histone positioning, but small non-coding RNA expression and DNA methylation patterns were markedly different. In a separate cohort of morbidly obese men, surgery-induced weight loss was associated with a dramatic remodeling of sperm DNA methylation, notably at genetic locations implicated in the central control of appetite. Our data provide evidence that the epigenome of human spermatozoa dynamically changes under environmental pressure and offers insight into how obesity may propagate metabolic dysfunction to the next generation.

ZBED6, a novel transcription factor derived from a domesticated DNA transposon regulates IGF2 expression and muscle growth.

This study identifies a previously uncharacterized protein, encoded by a domesticated DNA transposon, called ZBED6 that regulates the expression of the insulin-like growth factor 2 (IGF2) gene, and possibly numerous others, in all placental mammals including human.

DNA methylation in metabolic disorders

DNA methylation is a major epigenetic modification that controls gene expression in physiologic and pathologic states. Metabolic diseases such as diabetes and obesity are associated with profound alterations in gene expression that are caused by genetic and environmental factors. Recent reports have provided evidence that environmental factors at all ages could modify DNA methylation in somatic tissues, which suggests that DNA methylation is a more dynamic process than previously appreciated. Because of the importance of lifestyle factors in metabolic disorders, DNA methylation provides a mechanism by which environmental factors, including diet and exercise, can modify genetic predisposition to disease. This article considers the current evidence that defines a role for DNA methylation in metabolic disorders.

High-fat diet reprograms the epigenome of rat spermatozoa and transgenerationally affects metabolism of the offspring

Objectives Chronic and high consumption of fat constitutes an environmental stress that leads to metabolic diseases. We hypothesized that high-fat diet (HFD) transgenerationally remodels the epigenome of spermatozoa and metabolism of the offspring. Methods F0-male rats fed either HFD or chow diet for 12 weeks were mated with chow-fed dams to generate F1 and F2 offspring. Motile spermatozoa were isolated from F0 and F1 breeders to determine DNA methylation and small non-coding RNA (sncRNA) expression pattern by deep sequencing. Results Newborn offspring of HFD-fed fathers had reduced body weight and pancreatic beta-cell mass. Adult female, but not male, offspring of HFD-fed fathers were glucose intolerant and resistant to HFD-induced weight gain. This phenotype was perpetuated in the F2 progeny, indicating transgenerational epigenetic inheritance. The epigenome of spermatozoa from HFD-fed F0 and their F1 male offspring showed common DNA methylation and small non-coding RNA expression signatures. Altered expression of sperm miRNA let-7c was passed down to metabolic tissues of the offspring, inducing a transcriptomic shift of the let-7c predicted targets. Conclusion Our results provide insight into mechanisms by which HFD transgenerationally reprograms the epigenome of sperm cells, thereby affecting metabolic tissues of offspring throughout two generations.

The role of diet and exercise in the transgenerational epigenetic landscape of T2DM

Epigenetic changes are caused by biochemical regulators of gene expression that can be transferred across generations or through cell division. Epigenetic modifications can arise from a variety of environmental exposures including undernutrition, obesity, physical activity, stress and toxins. Transient epigenetic changes across the entire genome can influence metabolic outcomes and might or might not be heritable. These modifications direct and maintain the cell-type specific gene expression state. Transient epigenetic changes can be driven by DNA methylation and histone modification in response to environmental stressors. A detailed understanding of the epigenetic signatures of insulin resistance and the adaptive response to exercise might identify new therapeutic targets that can be further developed to improve insulin sensitivity and prevent obesity. This Review focuses on the current understanding of mechanisms by which lifestyle factors affect the epigenetic landscape in type 2 diabetes mellitus and obesity. Evidence from the past few years about the potential mechanisms by which diet and exercise affect the epigenome over several generations is discussed.

Evidence for non-CpG methylation in mammals.

In mammals, the existence of cytosine methylation on non-CpG sequences is controversial. Here, we adapted a LuminoMetric-based Assay (LUMA) to determine global non-CpG methylation levels in rodent and human tissues. We observed that <1% cytosines in non-CpG motifs were methylated in 3T3-L1 fibroblasts, whereas 7-13% cytosines in non-CpG motifs were methylated in mouse tissues or embryonic fibroblasts. Analysis of cytosine methylation in human, rat, and mouse tissues by bisulfite sequencing revealed non-CpG methylation levels up to 7.5% of all non-CpG cytosines. These levels dropped to 1.5% when a second round of PCR was performed prior to bisulfite sequencing, providing an explanation for the common underestimation of non-CpG methylation levels. Collectively, our results provide evidence that non-CpG methylation exists at substantial levels in mammals.

DNA methylation is altered in B and NK lymphocytes in obese and type 2 diabetic human

OBJECTIVE Obesity is associated with low-grade inflammation and the infiltration of immune cells in insulin-sensitive tissues, leading to metabolic impairment. Epigenetic mechanisms control immune cell lineage determination, function and migration and are implicated in obesity and type 2 diabetes (T2D). The aim of this study was to determine the global DNA methylation profile of immune cells in obese and T2D individuals in a cell type-specific manner. MATERIAL AND METHODS Fourteen obese subjects and 11 age-matched lean subjects, as well as 12 T2D obese subjects and 7 age-matched lean subjects were recruited. Global DNA methylation levels were measured in a cell type-specific manner by flow cytometry. We validated the assay against mass spectrometry measures of the total 5-methylcytosine content in cultured cells treated with the hypomethylation agent decitabine (r=0.97, p<0.001). RESULTS Global DNA methylation in peripheral blood mononuclear cells, monocytes, lymphocytes or T cells was not altered in obese or T2D subjects. However, analysis of blood fractions from lean, obese, and T2D subjects showed increased methylation levels in B cells from obese and T2D subjects and in natural killer cells from T2D patients. In these cell types, DNA methylation levels were positively correlated with insulin resistance, suggesting an association between DNA methylation changes, immune function and metabolic dysfunction. CONCLUSIONS Both obesity and T2D are associated with an altered epigenetic signature of the immune system in a cell type-specific manner. These changes could contribute to the altered immune functions associated with obesity and insulin resistance.

Altered promoter methylation of PDK4, IL1 B, IL6, and TNF after Roux-en Y gastric bypass

BACKGROUND Early benefits of Roux-en Y gastric bypass (RYGB) are partly mediated by the caloric restriction that patients undergo before and acutely after the procedure. Altered DNA methylation occurs in metabolic diseases including obesity, as well as in skeletal, muscle eight months after RYGB. The objective of this study was to test whether promoter methylation of peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PPARGC1 A), pyruvate dehydrogenase kinase isozyme-4 (PDK4), transcription factor A (TFAM), interleukin-1 beta (IL1 B), interleukin-6 (IL6) and tumor necrosis factor-α (TNF) is altered in blood after a very low calorie diet (VLCD) or RYGB. METHODS Obese nondiabetic patients (n = 18, body mass index [BMI] 42.3 ± 4.9 kg/m(2)) underwent a 14-day VLCD followed by RYGB. Nonobese patients (n = 6, BMI 25.7 ± 2.1 kg/m(2)) undergoing elective cholecystectomy served as controls. DNA methylation of selected promoter regions was measured in whole blood before and after VLCD. A subgroup of seven patients was studied 1-2 days and 12 ± 3 months after RYGB. Promoter methylation was measured using methylated DNA capture and quantitative real-time polymerase chain reaction (PCR). RESULTS VLCD decreased promoter methylation of PPARGC1 A. Methylation of PPARGC1 A, TFAM, IL1 B, IL6, and TNF promoters was changed two days after RYGB. Similar changes were also seen on day one after cholecystectomy. Moreover, methylation increased in PDK4, IL1 B, IL6, and TNF promoters 12 months after RYGB. CONCLUSION RYGB induced more profound epigenetic changes than VLCD in promoters of the tested genes in whole blood. Changes in DNA methylation may contribute to the improved overall metabolic health after RYGB.