Prolonged high-fat-diet feeding promotes non-alcoholic fatty liver disease and alters gut microbiota in mice

Abstract

BACKGROUND Non-alcoholic fatty liver disease (NAFLD) has become an epidemic largely due to the worldwide increase in obesity. While lifestyle modifications and pharmacotherapies have been used to alleviate NAFLD, successful treatment options are limited. One of the main barriers to finding safe and effective drugs for long-term use in NAFLD is the fast initiation and progression of disease in the available preclinical models. Therefore, we are in need of preclinical models that (1) mimic the human manifestation of NAFLD and (2) have a longer progression time to allow for the design of superior treatments. AIM To characterize a model of prolonged high-fat diet (HFD) feeding for investigation of the long-term progression of NAFLD. METHODS In this study, we utilized prolonged HFD feeding to examine NAFLD features in C57BL/6 male mice. We fed mice with a HFD (60% fat, 20% protein, and 20% carbohydrate) for 80 wk to promote obesity (Old-HFD group, n = 18). A low-fat diet (LFD) (14% fat, 32% protein, and 54% carbohydrate) was administered for the same duration to age-matched mice (Old-LFD group, n = 15). An additional group of mice was maintained on the LFD (Young-LFD, n = 20) for a shorter duration (6 wk) to distinguish between age-dependent and age-independent effects. Liver, colon, adipose tissue, and feces were collected for histological and molecular assessments. RESULTS Prolonged HFD feeding led to obesity and insulin resistance. Histological analysis in the liver of HFD mice demonstrated steatosis, cell injury, portal and lobular inflammation and fibrosis. In addition, molecular analysis for markers of endoplasmic reticulum stress established that the liver tissue of HFD mice have increased phosphorylated Jnk and CHOP. Lastly, we evaluated the gut microbial composition of Old-LFD and Old-HFD. We observed that prolonged HFD feeding in mice increased the relative abundance of the Firmicutes phylum. At the genus level, we observed a significant increase in the abundance of Adercreutzia, Coprococcus, Dorea , and Ruminococcus and decreased relative abundance of Turicibacter and Anaeroplasma in HFD mice. CONCLUSION Overall, these data suggest that chronic HFD consumption in mice can mimic pathophysiological and some microbial events observed in NAFLD patients.

Diabetic phenotype in mouse and humans with β-amyloid pathology reduces the number of microglia around β-amyloid plaques

“…We successfully induced obesity and diabetic phenotype in all of the mouse lines used by applying a six-month TWD regime, starting at the age of seven months, which is in line with previous reports [26,36,73,94]. Furthermore, TWD strongly increased fatty liver changes, emphasizing the robust effect of TWD on the metabolism of not only in the brain but also in peripheral tissues, as also shown previously [97]. Our results related to the behavioral assessments strongly suggest that TWD-induced obesity and diabetic phenotype impair memory and learning, which are also supported by the previous findings [24,26,33,34,38,47,81].…”

NAFLD Preclinical Models: More than a Handful, Less of a Concern?

“…Diet-induced obesity is known to be the most common risk factor for NAFLD in humans [17]. The experimental NAFLD/NASH models are often based on overnutrition, a condition that can be induced by means of diets varying in macronutrient composition, amongst others.…”

“…While after long-term (34-36 weeks) HFD feeding, significant increases in circulating liver enzyme levels, i.e., alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were observed [19], these mice showed only minor signs of inflammation and fibrosis [21], even after prolonged administration up to 50 weeks [19]. Yet, after chronic feeding (80 weeks) of HFD, which mimics lifetime HFD consumption and enables proper design of treatment options, Velázquez et al [17] demonstrated that mice displayed obesity and insulin resistance. In addition, these mice were shown to develop NAFLD features, including hepatic steatosis, cell injury, portal and lobular inflammation, hepatic ER stress, as well as fibrosis [17].…”

“…Yet, after chronic feeding (80 weeks) of HFD, which mimics lifetime HFD consumption and enables proper design of treatment options, Velázquez et al [17] demonstrated that mice displayed obesity and insulin resistance. In addition, these mice were shown to develop NAFLD features, including hepatic steatosis, cell injury, portal and lobular inflammation, hepatic ER stress, as well as fibrosis [17]. In line with Chen et al [22], which showed a deterioration in NAFLD when germ-free mice were inoculated with the Firmicutes phyla, they also found increases in the Firmicutes phyla in response to prolonged HFD [17].…”

“…In addition, these mice were shown to develop NAFLD features, including hepatic steatosis, cell injury, portal and lobular inflammation, hepatic ER stress, as well as fibrosis [17]. In line with Chen et al [22], which showed a deterioration in NAFLD when germ-free mice were inoculated with the Firmicutes phyla, they also found increases in the Firmicutes phyla in response to prolonged HFD [17]. Though intestinal permeability was not measured in this study, these data pointed towards diet-induced gut-microbial dysbiosis [17], a well-known microbial event that has been previously observed in NAFLD patients [23].…”