Hnf4g invalidation prevents diet-induced obesity via intestinal lipid malabsorption

Changes in dietary habits have occurred concomitantly with a rise of type 2 diabetes (T2D) and obesity. Intestine is the first organ facing nutrient ingestion and has to adapt its metabolism with these dietary changes. HNF-4γ, a transcription factor member of the nuclear receptor superfamily and mainly expressed in intestine, has been suggested to be involved in susceptibility to T2D. Our aim was to investigate the role of HNF-4γ in metabolic disorders and related mechanisms. Hnf4g-/- mice were fed high-fat/high-fructose (HF-HF) diet for 6 weeks to induce obesity and T2D. Glucose homeostasis, energy homeostasis in metabolic cages, body composition and stool energy composition, as well as gene expression analysis in the jejunum were analyzed. Despite an absence of decrease in calorie intake, of increase in locomotor activity or energy expenditure, Hnf4g-/- mice fed with HF-HF are protected against weight gain after 6 weeks of HF-HF diet. We showed that Hnf4g-/- mice fed HF-HF display an increase in fecal calorie loss, mainly due to intestinal lipid malabsorption. Gene expression of lipid transporters, Fatp4 and Scarb1 and of triglyceride-rich lipoprotein secretion proteins, Mttp and ApoB are decreased in gut epithelium of Hnf4g-/- mice fed HF-HF, showing the HNF-4γ role in intestine lipid absorption. Furthermore, plasma GLP-1 and jejunal GLP-1 content are increased in Hnf4g-/- mice fed HF-HF, which could contribute to the glucose intolerance protection. The loss of HNF-4γ leads to a protection against a diet-induced weight gain and to a deregulated glucose homeostasis, associated with lipid malabsorption.

Beneficial Effects of Isoflavones in the Kidney of Obese Rats Are Mediated by PPAR-Gamma Expression

Several studies have demonstrated an important association between altered lipid metabolism and the development of kidney injury because of a high-fat diet. Fructose is also closely associated with renal injury. We opted for a combination of fructose and saturated fats in a diet (DH) that is a model known to induce renal damage in order to evaluate whether soy isoflavones could have promising use in the treatment of renal alterations. After two months of ingestion, there was an expansion of visceral fat, which was associated with long-term metabolic disorders, such as sustained hyperglycemia, insulin resistance, polyuria, dyslipidemia, and hypertension. Additionally, we found a decrease in renal blood flow and an increase in renal vascular resistance. Biochemical markers of chronic kidney disease were detected; there was an infiltration of inflammatory cells with an elevated expression of proinflammatory cytokines (tumor necrosis factor-α, interleukin (IL)-6, and IL-1β), the activation of the renin–angiotensin system, and oxidative/nitrosative stress. Notably, in rats exposed to the DH diet for 120 days, the concomitant treatment with isoflavones after 60 days was able to revert metabolic parameters, renal alterations, and oxidative/nitrosative stress. The beneficial effects of isoflavones in the kidney of the obese rats were found to be mediated by expression of peroxisome proliferator-activated receptor gamma (PPAR-γ).

Beneficial Effects of Lactobacillus plantarum Strains on Non-Alcoholic Fatty Liver Disease in High Fat/High Fructose Diet-Fed Rats

Emerging evidence suggests that probiotics are beneficial in non-alcoholic fatty liver disease (NAFLD). This study aimed to explore the effects of two Lactobacillus plantarum strains, ATG-K2 and ATG-K6 (isolated from Korean fermented cabbage), in a rat model of high fat/high fructose (HF/HF) diet-induced NAFLD. Rats with NAFLD were randomized into four groups (HF/HF diet control, (HC); HF/HF diet with silymarin, (PC); HF/HF diet with ATG-K2, (K2); and HF/HF diet with ATG-K6, (K6)) with healthy rats on a normal diet serving as the negative control. After treatment, histopathological and biochemical analyses of the blood and liver tissue were conducted. In addition, fecal microbiota was analyzed using the MiSeq platform. Compared with HC rats, K2 and K6 rats experienced significantly lower body weight gain, displayed decreased hepatic lipid accumulation, had lower serum levels of aspartate aminotransferase and alanine aminotransferase, and showed increased antioxidant enzyme activities. Moreover, de novo lipogenesis-related genes were downregulated following K2 and K6 administration. The fecal microbiota of K2 and K6 rats contained a higher proportion of Bacteriodetes and a lower proportion of Fimicutes than that of HC rats. Taken together, our results suggest that L. plantarum strains ATG-K2 and ATG-K6 are potential therapeutic agents for NAFLD.

Ameliorative effects of black ginseng on nonalcoholic fatty liver disease in free fatty acid-induced HepG2 cells and high-fat/high-fructose diet-fed mice

Background

Black ginseng (BG) is a type of Korean ginseng prepared by steaming and drying raw ginseng to improve the saponin content. This study examined the effects of BG on nonalcoholic fatty liver disease (NAFLD) in HepG2 cells and diet-induced obese mice.

Methods

HepG2 cells were treated with free fatty acids to induce lipid accumulation before supplementation with BG. NAFLD-induced mice were fed different doses (0.5%, 1%, and 2%) of BG for 8 weeks.

Results

BG significantly reduced lipid accumulation and expression of lipogenic genes, peroxisome proliferator–activated receptor gamma, CCAAT/enhancer-binding protein alpha, sterol regulatory element-binding protein-1c, and fatty acid synthase in HepG2 cells, and the livers of mice fed a 45% high-fat diet with 10% fructose in the drinking water (HFHF diet). BG supplementation caused a significant reduction in levels of aspartate aminotransferase and alanine aminotransferase, while antioxidant enzymes activities were significantly increased in 45% high-fat diet with 10% fructose in the drinking water diet-fed mice. Expression of proliferator-activated receptor alpha and carnitine palmitoyltransferase I were upregulated at the transcription and translation levels in both HepG2 cells and diet-induced obese mice. Furthermore, BG-induced phosphorylation of AMP-activated protein kinase and acetyl CoA carboxylase in both models, suggesting its role in AMP-activated protein kinase activation and the acetyl CoA carboxylase signaling pathway.

Conclusion

Our results indicate that BG may be a potential therapeutic agent for the prevention of NAFLD.

Advancing metabolism research to overcome low litter survival in metabolically stressed mice

Elucidating the mechanism underlying the transmission of metabolic disease to subsequent generations requires robust preclinical mouse breeding strategies. Western diets rich in fat and carbohydrates are contributing factors in the rise of diabetes and obesity rates worldwide. Therefore, determining the impact of Western diets consumed by parents on offspring and future generations is critical for understanding the perpetuation of these diseases. Specifically, epigenetic regulation and transgenerational inheritance of metabolic disease is an emerging field of study requiring robust murine models. However, a major challenge to transgenerational studies is offspring mortality, exacerbated by maternal stress during pregnancy. Here, we describe a challenge experienced in our metabolic research in Western diet-fed female mice leading to the loss of litters via pup mortality and cannibalism by the mother. Furthermore, our study evaluates various breeding schemes with pregnancy efficiency and refined husbandry techniques to overcome pup mortality and infanticide, to characterize dams' and pups' metabolic characteristics, and to determine the impact on physiology of dams under detailed breeding schemes.

Zinc supplementation reduces diet-induced obesity and improves insulin sensitivity in rats

Rates of obesity have been growing at alarming rates, compromising the health of the world population. Thus, the search for interventions that address the metabolic repercussions of obesity are necessary. Here we evaluated the metabolic and antioxidant effects of zinc and branched-chain amino acids (BCAA) supplementation on obese rats. Male Wistar rats were fed either a high-fat/high-fructose diet (HFD) or a standard diet (SD) for 19 weeks. From the fifteenth week until the end of the experiment, HFD- and SD-fed rats received zinc (6 mg/kg) or BCAA (750 mg/kg) supplementation. Body weight, abdominal fat, lipid profile, blood glucose, insulin, leptin, and hepatic transaminases were evaluated. In the liver, superoxide dismutase and catalase activities and lipid peroxidation were also analyzed. HFD-fed animals showed increased weight gain, abdominal fat pad, plasma insulin, leptin, and triglycerides levels in comparison with SD-fed rats. Zinc supplementation reduced all these parameters, suggesting a beneficial role for the treatment of obesity. BCAA, on the other hand, did not show any beneficial effect. Liver antioxidant enzymes and hepatic transaminases plasma levels did not change among groups. Lipid peroxidation was higher in HFD-fed rats and was not reverted by zinc or BCAA supplementation. In conclusion, zinc supplementation may be a useful strategy for the treatment of the metabolic dysfunction associated with obesity.

Bitter melon extract ameliorates palmitate-induced apoptosis via inhibition of endoplasmic reticulum stress in HepG2 cells and high-fat/high-fructose-diet-induced fatty liver

Background

Bitter melon (BM) improves glucose level, lipid homeostasis, and insulin resistance in vivo. However, the preventive mechanism of BM in nonalcoholic fatty liver disease (NAFLD) has not been elucidated yet.

Aim & Design

To determine the protective mechanism of bitter melon extract (BME), we performed experiments in vitro and in vivo. BME were treated palmitate (PA)-administrated HepG2 cells. C57BL/6J mice were divided into two groups: high-fat/high-fructose (HF/HFr) without or with BME supplementation (100 mg/kg body weight). Endoplasmic reticulum (ER) stress, apoptosis, and biochemical markers were then examined by western blot and real-time PCR analyses.

Results

BME significantly decreased expression levels of ER-stress markers (including phospho-eIF2α, CHOP, and phospho-JNK [Jun N-terminal kinases]) in PA-treated HepG2 cells. BME also significantly decreased the activity of cleaved caspase-3 (a well known apoptotic-induced molecule) and DNA fragmentation. The effect of BME on ER stress-mediated apoptosis in vitro was similarly observed in HF/HFr-fed mice in vivo. BME significantly reduced HF/HFr-induced hepatic triglyceride (TG) and serum alanine aminotransferase (ALT) as markers of hepatic damage in mice. In addition, BME ameliorated HF/HFr-induced serum TG and serum-free fatty acids.

Conclusion

These data indicate that BME has protective effects against ER stress mediated apoptosis in HepG2 cells as well as in HF/HFr-induced fatty liver of mouse. Therefore, BME might be useful for preventing and treating NAFLD.

Postprandial fatty acid uptake and adipocyte remodeling in angiotensin type 2 receptor-deficient mice fed a high-fat/high-fructose diet

The role of the angiotensin type-2 receptor in adipose physiology remains controversial. The aim of the present study was to demonstrate whether genetic angiotensin type-2 receptor-deficiency prevents or worsens metabolic and adipose tissue morphometric changes observed following a 6-week high-fat/high-fructose diet with injection of a small dose of streptozotocin. We compared tissue uptake of nonesterified fatty acid and dietary fatty acid in wild-type and angiotensin type-2 receptor-deficient mice by using the radiotracer 14(R,S)-[(1) (8)F]-fluoro-6-thia-heptadecanoic acid in mice fed a standard or high-fat diet. Postprandial fatty acid uptake in the heart, liver, skeletal muscle, kidney and adipose tissue was increased in wild-type mice after a high-fat diet and in angiotensin type-2 receptor-deficient mice on both standard and high-fat diets. Compared to the wild-type mice, angiotensin type-2 receptor-deficient mice had a lower body weight, an increase in fasting blood glucose and a decrease in plasma insulin and leptin levels. Mice fed a high-fat diet exhibited increased adipocyte size that was prevented by angiotensin type-2 receptor-deficiency. Angiotensin type-2 receptor-deficiency abolished the early hypertrophic adipocyte remodeling induced by a high-fat diet. The small size of adipocytes in the angiotensin type-2 receptor-deficient mice reflects their inability to store lipids and explains the increase in fatty acid uptake in non-adipose tissues. In conclusion, a genetic deletion of the angiotensin type-2 receptor is associated with metabolic dysfunction of white adipose depots, and indicates that adipocyte remodeling occurs before the onset of insulin resistance in the high-fat fed mouse model.

Angiotensin II type 2 receptor promotes adipocyte differentiation and restores adipocyte size in high-fat/high-fructose diet-induced insulin resistance in rats

This study was aimed at establishing whether specific activation of angiotensin II (ANG II) type 2 receptor (AT2R) modulates adipocyte differentiation and function. In primary cultures of subcutaneous (SC) and retroperitoneal (RET) preadipocytes, both AT2R and AT1R were expressed at the mRNA and protein level. Cells were stimulated with ANG II or the AT2R agonist C21/M24, alone or in the presence of the AT1R antagonist losartan or the AT2R antagonist PD123,319. During differentiation, C21/M24 increased PPARγ expression in both RET and SC preadipocytes while the number of small lipid droplets and lipid accumulation solely increased in SC preadipocytes. In mature adipocytes, C21/M24 decreased the mean size of large lipid droplets. Upon abolishment of AT2R expression using AT2R-targeted shRNAs, expressions of AT2R, aP2, and PPARγ remained very low, and cells were unable to differentiate. In Wistar rats fed a 6-wk high-fat/high-fructose (HFHF) diet, a significant shift toward larger adipocytes was observed in RET and SC adipose tissue depots. C21/M24 treatments for 6 wk restored normal adipocyte size distribution in both these tissue depots. Moreover, C21/M24 and losartan decreased hyperinsulinemia and improved insulin sensitivity impaired by HFHF diet. A strong correlation between adipocyte size area and glucose infusion rate during euglycemic-hyperinsulinemic clamp was observed. These results indicate that AT2R is involved in early adipocyte differentiation, while in mature adipocytes and in a model of insulin resistance AT2R activation restores normal adipocyte morphology and improves insulin sensitivity.