The Effects of Overnight Fasting Duration on Glucose and Lipid Metabolism in a Sprague-Dawley Rat Model of Nonalcoholic Steatohepatitis with Advanced Fibrosis

Nonalcoholic steatohepatitis (NASH) can progress to hepatic fibrosis, and is associated with cardiovascular and liver-related mortality. To understand the pathogenesis of NASH, reliable animal models of the disease are useful. In animal studies, the animals are usually fasted overnight before biospecimens are taken, but little is known about the effects of fasting. Here, we investigated the impact of overnight fasting for approximately 9 to 17 h on glucose and lipid metabolism in a Sprague-Dawley (SD) rat model of diet-induced moderate and advanced NASH in comparison to normal SD rats. Our results revealed that in the moderate NASH model rats, the fasting duration did not affect glucose and lipid metabolism, the histopathological findings, or the hepatic mRNA expression levels of genes related to lipid metabolism, cholesterol metabolism, inflammation, fibrosis, and oxidative stress. In contrast, in the normal rats, significant fasting time-dependent reductions were observed in the epididymal fat pad weight and the hepatic mRNA expression levels of adipose differentiation-related protein and heme oxygenase-1. Moreover, in the advanced NASH model rats, a significant fasting time-dependent reduction and increase were observed in the serum insulin level and mRNA expression level of alpha-smooth muscle actin, respectively. Our present results suggest that the influence of the overnight fasting duration differs among the healthy condition, moderate NASH, and advanced NASH statuses. Further studies are needed in humans to determine the appropriate overnight fasting duration for the accurate evaluation of glucose and lipid metabolism in NASH patients.