Yuriy Slyvka

Epigenetic effects of paternal diet on offspring: emphasis on obesity

Overnutrition, obesity, and the rise in associated comorbidities are widely recognized as preventable challenges to global health. Behavioral, metabolic, and epigenetic influences that alter the epigenome, when passed on to offspring, can increase their risk of developing an altered metabolic profile. This review is focused on the role of paternal inheritance as demonstrated by clinical, epidemiological, and experimental models. Development of additional experimental models that resemble the specific epigenetic sensitive situations in human studies will be essential to explore paternally induced trans-generational effects that are mediated, primarily, by epigenetic effects. Further elucidation of epigenetic marks will help identify preventive and therapeutic targets, which in combination with healthy lifestyle choices, can diminish the growing tide of obesity, type 2 diabetes, and other related disorders.

L-Arginine Supplementation in Type II Diabetic Rats Preserves Renal Function and Improves Insulin Sensitivity by Altering the Nitric Oxide Pathway.

Rat studies demonstrated that type II diabetes mellitus (T2DM) decreases both the production and bioavailability of nitric oxide (NO). L-arginine (LA) provides the precursor for the production of NO. We hypothesized that LA dietary supplementation will preserve NO production via endothelial nitric oxide synthase (eNOS) causing renal microvascular vasodilation and increased glomerular blood flow and thus increasing glomerular filtration rate (GFR). This would impede the formation of reactive oxygen species which contributes to cell damage and death. LA supplementation preserved GFR in the treated diabetic rats compared to untreated diabetic rats. We provide evidence that this effect may be due to increased levels of eNOS and urinary cyclic guanosine monophosphate, which leads to renal microvascular vasodilation. Plasma nitrotyrosine was decreased in the LA treated rats; however, plasma nitrite levels remained unaffected as expected. Marked improvements in glucose tolerance were also observed in the LA treated diabetic rats. These results demonstrate that LA supplementation preserves NO activity and may delay the onset of insulin resistance and renal dysfunction during hyperglycemic stress. These results suggest the importance of the NO pathway in consequent renal dysfunction and in the development of insulin resistance in diabetic rats.

Antioxidant diet, gender and age affect renal expression of nitric oxide synthases in obese diabetic rats.

Development of diabetic nephropathy (DN) is associated with decreased renal nitric oxide production and increased oxidative stress. We studied nitric oxide synthase (NOS) expression in kidney of obese Zucker fa/fa rats, a model of Type 2 obesity-related DN. Male and female rats received a regular (REG) or antioxidant-fortified (AO) diet starting at age 4 weeks. Quantitative PCR and immunoblot analyses were performed on kidney cortex and medulla to determine levels of endothelial, neuronal and inducible NOS at 6, 13 and 20 weeks of age. Multiple antibody-specific proteins were detected for each form. These may represent monomeric splice forms, post-translationally modified forms and their dimers, consistent with the known complexity of regulation of these enzymes. Levels of eNOS and nNOS are higher in males than females at 6 weeks on the REG diet and 13 weeks on either diet; the relationship is reversed in females at 6 weeks on the AO diet. Levels of eNOS and nNOS are lower on the AO diet compared to REG, in males at 6 and 13 weeks and females at 13 weeks; the reverse is seen in 6 week females and 20 week males. All three isoforms show peak levels in the younger animals, at 6 or 13 weeks. Better preservation of kidney function is associated with higher prevalence of dimers with potential to increase production of NO and lower levels of potentially harmful monomers. Differential expression of NOS isoforms may be linked to renal functional and histopathological changes in this rat model of DN.

Antioxidant diet and sex interact to regulate NOS isoform expression and glomerular mesangium proliferation in Zucker diabetic rat kidney.

Oxidative stress contributes substantially to the pathophysiology of diabetic nephropathy (DN). Consumption of an antioxidant-fortified (AO) diet from an early age prevents or delays later development of DN in the Zucker rat female with type 2 diabetes. We hypothesize this is due to effects on mesangial matrix and renal nitric oxide synthase (NOS) distribution and to sex-specific differences in NOS responses in the diabetic kidney. Total glomerular tuft area (GTA) and PAS-positive tuft area (PTA), endothelial (e), neuronal (n) and inducible (i) NOS were quantified in males and females on AO or regular (REG) diet at 6 and 20 weeks of age. eNOS was observed in glomeruli and tubules. nNOS predominantly localized to tubular epithelium in both cortex and medulla. iNOS was expressed in proximal and distal tubules and collecting ducts. Sex, diabetes duration and AO diet affected the distribution of the three isoforms. GTA and PTA increased with duration of hyperglycemia and showed a negative correlation with renal levels of all NOS isoforms. AO diet in both genders was associated with less PAS-positive staining and less mesangial expansion than the REG diet, an early increase in cortical iNOS in males, and sex-specific changes in cortical eNOS at 20 weeks. These effects of AO diet may contribute to sex-specific preservation of renal function in females.

Paternal high‐fat diet enhances offspring whole‐body insulin sensitivity and skeletal muscle insulin signaling early in life

Evidence suggests that paternal diet can predispose offspring to metabolic dysfunction. Despite this knowledge, little is known regarding the effects of paternal high‐fat feeding on offspring insulin sensitivity. The purpose of this study was to investigate for the first time the effects of paternal high‐fat feeding on whole‐body and skeletal muscle insulin action in young and adult offspring. At 4 weeks of age, founder C57BL6/N males (F0) were fed a high‐fat diet or control diet for 12 weeks and then bred with females on a control diet. Offspring (F1) were euthanized at 6 weeks, 6 months, or 12 months and insulin‐stimulated insulin signaling was measured ex vivo in isolated soleus muscle. At 6 weeks of age, paternal high fat offspring (HFO) had enhanced whole‐body insulin sensitivity (35%, P < 0.05), as well as, increased insulin‐stimulated skeletal muscle phosphorylation of Akt threonine 308 (70%, P < 0.05) and AS160 threonine 642 (80%, P < 0.05) compared to paternal control fed offspring (CFO), despite both offspring groups consuming standard chow. At 6 months of age, HFO had increased percent body fat compared to CFO (74%, P < 0.005) and whole‐body and skeletal muscle insulin signaling normalized to CFO. Body fat was inversely related with insulin signaling in HFO, but not CFO. These findings suggest that paternal high‐fat feeding contributes to enhanced whole‐body and skeletal muscle insulin sensitivity in HFO early in life; however, these benefits are lost by early adulthood, potentially due to premature increases in body fat.

Early antioxidant supplementation in the prevention of diabetic nephropathy: alterations in NOS expression precede renal functional decline

Rat and human studies have shown that good glycemic control alone is not sufficient to prevent the complications associated with diabetes, such as nephropathy. A proposed culprit is excessive oxidative stress in the cells and vasculature of the kidney resulting in endothelial cell dysfunction, which is one of the earliest and most pivotal consequences seen in early diabetes. We hypothesized that an antioxidant (AO) diet would alleviate the oxidative stress and prevent and/or delay the progression of diabetic nephropathy, even with poor glycemic control. Early nephropathy in diabetes is associated with increased intra renal nitric oxide (NO) production. Nitric oxide synthases (NOS) are a family of enzymes that catalyze the production of NO. We report significantly lower endothelial nitric oxide synthase (eNOS) with AO supplementation compared to the other 2 groups, which means the AO diet led to the decrease in eNOS in the early phase of the onset of diabetic nephropathy. Also, we noted a significant decrease in neuronal nitric oxide synthase (nNOS) with AO supplementation, which is consistent with renal protection in the later phase of diabetic nephropathy. Our results reveal evidence of molecular damage to the endothelium and specialized structures of the kidney that precedes the onset of diabetes. These results suggest early AO supplementation safeguards the kidneys from some of the forces that induce hyperfiltration in early-stage diabetic nephropathy.