ObjectivesChronic 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.MethodsF0-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.ResultsNewborn 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.ConclusionOur results provide insight into mechanisms by which HFD transgenerationally reprograms the epigenome of sperm cells, thereby affecting metabolic tissues of offspring throughout two generations.

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Insulin exocytosis is regulated in pancreatic ß-cells by a cascade of intracellular signals translating glucose levels into corresponding secretory responses. The mitochondrial enzyme glutamate dehydrogenase (GDH) is regarded as a major player in this process, although its abrogation has not been tested yet in animal models. Here, we generated transgenic mice, named ßGlud1 ؊/؊ , with ß-cell-specific GDH deletion. Our results show that GDH plays an essential role in the full development of the insulin secretory response. In situ pancreatic perfusion revealed that glucose-stimulated insulin secretion was reduced by 37% in ßGlud1 ؊/؊ . Furthermore, isolated islets with either constitutive or acute adenovirus-mediated knock-out of GDH showed a 49 and 38% reduction in glucose-induced insulin release, respectively. Adenovirus-mediated re-expression of GDH in ßGlud1 ؊/؊ islets fully restored glucose-induced insulin release. Thus, GDH appears to account for about 40% of glucose-stimulated insulin secretion and to lack redundant mechanisms. In ßGlud1 ؊/؊ mice, the reduced secretory capacity resulted in lower plasma insulin levels in response to both feeding and glucose load, while body weight gain was preserved. The results demonstrate that GDH is essential for the full development of the secretory response in ß-cells. However, maximal secretory capacity is not required for maintenance of glucose homeostasis in normo-caloric conditions.Pancreatic ß-cells produce the hormone insulin that is essential for glucose homeostasis. Upon nutrient stimulation, elevation of cytosolic calcium in the ß-cell is the primary and necessary signal for insulin exocytosis (1). Then, increasing the magnitude of the secretory response requires amplification of the calcium signal supported by metabolism-derived additive factors (2). The enzyme glutamate dehydrogenase (GDH, 2 EC 1.4.1.3) has been proposed to participate to the development of the secretory response. GDH is a homohexamer located in the mitochondrial matrix that catalyzes the reversible reaction: ␣-ketoglutarate ϩ NH 3 ϩ NAD(P)H % glutamate ϩ NAD(P) ϩ ; inhibited by GTP and activated by ADP (3, 4). Regarding ß-cell, allosteric activation of GDH by L-leucine or its non-metabolized analogue BCH has triggered most of the attention over the last three decades (5).To date, the role of GDH in ß-cell function remains unclear and debated. Specifically, GDH might play a role in glucoseinduced amplifying pathway through generation of glutamate (6, 7). GDH is also an amino acid sensor triggering insulin release upon glutamine stimulation in conditions of GDH allosteric activation (8 -10). Recently, the importance of GDH has been further highlighted by studies showing that SIRT4, a mitochondrial ADP-ribosyltransferase, down-regulates GDH activity and thereby modulates insulin secretion (11,12).GDH is encoded by a well-conserved 45-kb gene named GLUD1, which is organized into 13 exons (13). A decade ago, clinical data and associated genetic studies revealed GDH as a key enzyme for the control ...

Abstract-The mineralocorticoid receptor has been implicated in the development of several cardiac pathologies and could participate in the high incidence of lethal ventricular arrhythmias associated with hyperaldosteronism. We have observed previously that aldosterone markedly increases in vitro the rate of spontaneous contractions of isolated neonate rat ventricular myocytes, a putative proarrhythmogenic condition if occurring in vivo. In the present study, we investigated the effect of glucocorticoids, the involvement of the glucocorticoid receptor, and the modulation of their action by redox agents. Aldosterone and glucocorticoids exerted in vitro a similar, concentration-dependent chronotropic action on cardiomyocytes, which was mediated by both the mineralocorticoid and glucocorticoid receptors. However, the relative contribution of each receptor was different for each agonist, at each concentration. Angiotensin II induced a similar response that was entirely dependent on the activity of the glucocorticoid receptor. Corticosteroid action was modulated by the redox state of the cells, with oxidation increasing the response while reducing conditions partially preventing it. When only the mineralocorticoid receptor was functionally present in the cells, oxidation was necessary to reveal glucocorticoid action, but no obvious competition with mineralocorticoids was observed when both agonists where simultaneously present. In conclusion, corticosteroids exert a strong chronotropic action in ventricular cardiomyocytes, mediated by both the mineralocorticoid and glucocorticoid receptors and modulated by the redox state of the cell. This phenomenon is believed to be because of cell electric remodeling and could contribute in vivo to the deleterious consequence of inappropriate receptor activation, leading to increased susceptibility of patients to arrhythmias.