Food Restriction Ameliorates Hepatic Metabolic Dysfunction In Chronic Postnatal Overnutrition-induced Obese Mice

Background: Insulin resistance results in dysregulated hepaticgluconeogenesis that contributes to obesity-related hyperglycemia andprogression of type2diabetes mellitus (T2DM). However, there have beenfew literatures about the influences of reducing body weight though foodrestriction on the expression of gluconeogenic genes. In the present study,we used a well-characterized mouse model to investigate whether foodrestriction could ameliorate the metabolic dysfunction, especially theabnormal gluconeogenesis in the liver of postnatal overfeeding-inducedobese mice.Methods: In the present study, we used two independent mousemodels:1) Wild-type male C56BL/6J mice served as control, male ob/obobese mice with C57BL/6J genetic background were used as obese model.At the age of150days, the histological feature of liver tissue was examinedby H&E. Macrohoages were detected by immunohistochmistry stainingwith using F4/80antibody. The mRNA expression levels of related genes were detected through quantitative real-time PCR (Q-PCR).2) Maleoffspring from ICR mice were used in our study. Chronic postnatalovernutrition (CPO) was induced by reducing litters to5pups per dam onpostnatal day3(P3) and3pups per dam on P6, while in control (CTR),10pups per litter were maintained. On P21, the pups were weaned ontostandard chow diet and the male pups were housed3per cage. CPO malemice were divided randomly into two groups on P45, i e. CPO withCPO-FR free access to standand chow diet (CPO) and CPO food restriction(CPO-FR). In CPO-FR group, animals were fed with2/3food as much asthat in CPO group. Therefore all the animals were set into three subgroups:CTR, CPO and CPO-FR. GTT and PTT were performed on P100and P120to assess the condition of insulin sensitivity and gluconeogenic capacity.Body weight was monitored. These mice were sacrificed by decapitation onP150. Morphologic analysis was performed by H&E staining to identifylipid droplets and the degree of inflammation in liver tissue. Theultrastructure characteristics of hepatocyte were observed by transmissionelectron microscope (TEM). The mRNA levels were analyzed by Q-PCR.Western blot analysis was performed to assess the protein levels ofperoxisome proliferator activated receptor γ coactivator-1α (PGC-1α)、Uncoupling protein2(UCP2) and Cytochrome c (Cyt-C).Results:1) Both liver weight and body weight of the ob/ob mice weresignificantly higher than those of control group. H&E staining showed obvious lipid accumulation in the liver of ob/ob mice.Immunohistochmistry staining for F4/80showed more macrophage cellinfiltration in the liver of ob/ob. Compared with control group, the PGC-1α,PPARα, NRF1mRNA levels in ob/ob group were elevated significantly.2)Body weight, fat mass and liver weight were significantly reduced inCPO-FR mice in comparison with CPO. Compared with CTR, CPO miceshowed typical changes of metabolic dysfunction, characterized by imparedinsulin sensitivity and increased hepatic glucose production; obvious lipidsaccumulation and macrovesicular steatosis in liver tissue; changes ofhepatocyte ultrastructure, such as typical mitochondrial swelling andendoplasmic reticulum expansion; up-regulated genes mRNA expressionlevels in liver, which are involved in mitochondrial biogenesis andgluconeogenesis. While food restriction could ameliorate the livermetabolic dysfunction in the obese mice. Compared with CPO, CPO-FRmice showed enhanced insulin sensitivity, attenuated hepatic glucoseproduction and relatively mild hepatic lipid accumulation. Hepatocyteultra-structure and mRNA levels of key genes related to glucosemetabolism also suggested food restriction might help to protect metabolicdysfunction induced by CPO. But the differences for the degree of UCP2and Cyt-C protein level in all groups were not reached the statisticalsignificance.Conclusions:1) There were obvious lipid accumulation and inflammatory cells infiltration in the liver tissue of ob/ob mice. PGC-1α,PPARα and NRF1that are related to hepatic energy metabolism, weresignificantly upregulated which could resulted in enhanced hepaticgluconeogenesis and the liver lipid accumulation.2) Food restriction couldameliorate the chronic postnatal overnutrition induced dysfunction ofhepatic glucose metabolism, though the improvement of hepaticgluconeogensis pathway.