Jung, Paul

Life long high fat (HF) diet has been shown to cause more hepatic lipid accumulation in offspring as compared to a post‐weaning HF diet. However, it is still unclear what the epigenetic mechanisms are. We hypothesize that a life long HF diet will cause greater hepatic lipid accumulation as compared to a post‐weaning HF diet. The objective of this study is to understand the epigenetic mechanisms of hepatic lipid accumulation as an outcome of life long HF diet. Timed‐pregnant Sprague‐Dawley rats were given either a control (C, 16% fat) or HF (HF, 45% fat) diet during gestation and lactation. Pups from both C and HF mothers were weaned onto the same HF diet, creating two offspring groups: C/HF and HF/HF. Rats were sacrificed at 12 weeks of age and the left lobe of the liver was used for further analysis. Liver histology showed greater hepatic fat accumulation in the HF/HF group. Gene expression data was measured for multiple genes in the following pathways: glycolysis, gluconeogenesis, fatty acid synthesis, and triacylglycerol synthesis. Only glycerol‐3‐phosphate acyltransferase (GPAM) and fatty acid synthase (FASN) showed higher levels of mRNA. DNA methylation of specific genes was analyzed based on data obtained from methyl‐DNA immunoprecipitation with high‐throughput sequencing. Differential methylation was observed for both GPAM and FASN. Our data suggests that life long HF diet increases lipid storage by increased hepatic GPAM and FASN gene expression in male rats, potentially through epigenetic regulation.

The aim of this study was to determine the effect of prolonged 11β-hydroxysteroid dehydrogenase-1 (11β-HSD1) inhibition on basal and hormone-stimulated glucose metabolism in fasted conscious dogs. For 7 days prior to study, either an 11β-HSD1 inhibitor (HSD1-I; n = 6) or placebo (PBO; n = 6) was administered. After the basal period, a 4-h metabolic challenge followed, where glucagon (3×-basal), epinephrine (5×-basal), and insulin (2×-basal) concentrations were increased. Hepatic glucose fluxes did not differ between groups during the basal period. In response to the metabolic challenge, hepatic glucose production was stimulated in PBO, resulting in hyperglycemia such that exogenous glucose was required in HSD-I ( P < 0.05) to match the glycemia between groups. Net hepatic glucose output and endogenous glucose production were decreased by 11β-HSD1 inhibition ( P < 0.05) due to a reduction in net hepatic glycogenolysis ( P < 0.05), with no effect on gluconeogenic flux compared with PBO. In addition, glucose utilization ( P < 0.05) and the suppression of lipolysis were increased ( P < 0.05) in HSD-I compared with PBO. These data suggest that inhibition of 11β-HSD1 may be of therapeutic value in the treatment of diseases characterized by insulin resistance and excessive hepatic glucose production.

OBJECTIVE—To determine the contribution of liver and viscera to splanchnic cortisol production in humans. RESEARCH DESIGN AND METHODS—D4 cortisol was infused intravenously; arterial, portal venous, and hepatic venous blood was sampled; and liver and visceral fat were biopsied in subjects undergoing bariatric surgery. RESULTS—Ratios of arterial and portal vein D4 cortisol/cortisoltotal (0.06 ± 0.01 vs. 0.06 ± 0.01) and D4 cortisol/D3 cortisol (1.80 ± 0.14 vs. 1.84 ± 0.14) did not differ, indicating that no visceral cortisol production or conversion of D4 cortisol to D3 cortisol via 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD-1) occurred. Conversely, ratios of both D4 cortisol to cortisoltotal (0.05 ± 0.01; P &lt; 0.05) and D4 cortisol to D3 cortisol (1.33 ± 0.11; P &lt; 0.001) were lower in the hepatic vein than in the portal vein, indicating production of both cortisol and D3 cortisol by the liver. The viscera did not produce either cortisol (−8.1 ± 2.6 μg/min) or D3 cortisol (−0.2 ± 0.1 μg/min). In contrast, the liver produced both cortisol (22.7 ± 3.90 μg/min) and D3 cortisol (1.9 ± 0.4 μg/min) and accounted for all splanchnic cortisol and D3 cortisol production. Additionally, 11β-HSD-1 mRNA was approximately ninefold higher (P &lt; 0.01) in liver than in visceral fat. Although 11β-HSD-2 gene expression was very low in visceral fat, the viscera released cortisone (P &lt; 0.001) and D3 cortisone (P &lt; 0.01) into the portal vein. CONCLUSIONS—The liver accounts for all splanchnic cortisol production in obese nondiabetic humans. In contrast, the viscera releases cortisone into the portal vein, thereby providing substrate for intrahepatic cortisol production.