HFD-induced Hepatic Lipid Accumulation Research Articles

Impacts of Non- and Whole-fat Milk Supplementation on Metabolism-Associated Fatty Liver Disease (MAFLD) in C57BL/6 Mice

Background: Metabolism-associated fatty liver disease (MAFLD) is a widespread metabolic disease affecting 25% of the global adult population following Westernized lifestyles. Lifestyle modifications, specifically adherence to healthy dietary patterns, are pivotal in preventing and mitigating this disease. Consuming milk and dairy products is considered a cornerstone of a healthy dietary pattern, gathering significant attention due to compelling evidence from observational studies. These studies suggest that a higher intake of milk and certain dairy products is associated with a reduced risk of MAFLD. However, the relative health benefits of high- compared to lower-fat milk is a current topic of interest, with ongoing debates about their equivalency in promoting metabolic health. Aims & Hypothesis: In a MAFLD mouse model, we aim to determine the dependence of milk’s fat content on hepatic steatosis and lipid metabolic pathways by comparing whole- (WFM) to non-fat (NFM) milk supplementation in high-fat diet-fed mice (HFD). We hypothesize that both WFM and NFM will significantly improve HFD-induced hepatic lipid accumulation but via differential molecular mechanisms. Methods: Two cohorts of n=24 and n=36 6-week-old male C57BL/6 mice were acclimatized for one week, then randomly assigned to a HFD (45 kcal% fat) or a low-fat diet (LFD; 10 kcal% fat) control group. The HFD mice were randomized to either a WFM or NFM treatment of 0.425 mL milk for 8 weeks. At the end of the study, mice underwent an insulin tolerance and pyruvate tolerance test and body composition was measured. The animals were then euthanized, tissues were collected, and hepatic lipid metabolism was compared using western blot, histology, hepatic lipid assays, gas chromatography, and qPCR. Statistics were then completed using GraphPad Prism software 7.0, utilizing T-test, one-way ANOVA, and Tukey’s post-hoc tests with a p-value ≤ 0.05 considered as statistically significant. Results: Body weight gain was significantly reduced in NFM groups compared to HFD and WFM, accounted for by a significant reduction in fat mass. ITT was unaltered when corrected to baseline, but NFM groups had significantly higher PTT values when corrected to baseline. Overnight-fasted blood glucose was significantly reduced in NFM animals compared to WFM animals, suggesting an altered metabolic state between the two treatment groups. Histological results indicate a significant reduction in lipid accumulation by the NFM group compared to the HFD group (p<0.05), with WFM trending towards a similar reduction (p=0.051). Hepatic triglyceride concentrations were significantly reduced in NFM animals compared to WFM and HFD animals, suggesting a greater effect of NFM in reducing hepatic steatosis. Hepatic molecular results display an enhancement of enzymes involved in fatty acid oxidation and export pathways in the NFM group. In contrast, WFM displays an enhancement of de novo lipogenesis, fatty acid uptake, and fatty acid oxidation. Conclusion: The findings suggest that NFM may be more effective at reducing hepatic steatosis through enhanced fatty acid oxidation and export. WFM may reduce steatosis less effectively because of counteractive effects on fatty acid uptake and de novo lipogenesis versus beta-oxidation. These results provide mechanistic evidence of the protective effects of milk on MAFLD. The funding sources for this project include the Alberta Diabetes Institute Studentship Grant, CIHR Canadian Graduate Studentship, and Dairy Farmers of Canada. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Astragalus polysaccharide attenuates nonalcoholic fatty liver disease through THDCA in high-fat diet-fed mice

Ethnopharmacological relevanceAstragalus polysaccharide (APS) extracted from Astragalus membranaceus (Fisch.) Bunge was proven to be effective in preventing high-fat diet (HFD) induced nonalcoholic fatty liver disease (NAFLD). However, the exact mechanisms were not completely elucidated. Aim of the studyThe aim was to reveal the mechanisms of APS on preventing NAFLD from the aspects of regulating bile acids (BAs) homeostasis. Materials and methodsSerum and liver BAs in HFD fed mice with or without APS intervention were quantified with an ultra-performance liquid chromatography coupled to tandem mass spectrometry (UPLC-MS/MS) system. The effect of APS on hepatic proteins involved in BAs synthesis were analyzed with Western blot. Finally, the effect of identified taurohyodeoxycholic acid (THDCA) that was significantly increased by APS on hepatic triglyceride (TG) accumulation was explored in vivo and in vitro. ResultsAPS regulated serum and liver BA profiles in HFD fed mice, especially increased serum THDCA. The levels of hepatic cholesterol 7a-hydroxylase (CYP7A1) and sterol 12a-hydroxylase (CYP8B1) which catalyzed the classical BAs synthesis pathway were significantly decreased by APS, while oxysterol 7a-hydroxylase (CYP7B1) which catalyzed the alternative BAs synthesis pathway was significantly increased by APS. THDCA reduced HFD-induced hepatic lipid accumulation and improved glucose homeostasis in mice, and decreased TG level in palmitic acid/oleic acid treated alpha mouse liver 12 (AML-12) cells. THDCA significantly downregulated the protein level of cluster of differentiation 36 (CD36) involved in fatty acid transport into the liver. Importantly, THDCA showed similar effect with APS in upregulating hepatic CYP7B1 and downregulating CYP7A1. ConclusionThis study revealed the protective effect of APS on NAFLD was associated with the regulation on BA profiles, and proved the potential anti-NAFLD effect of THDCA, highlighting the involvement of BA metabolism in efficacy of herb-derived polysaccharides on metabolism.

AMPD2 plays important roles in regulating hepatic glucose and lipid metabolism

Dysregulation of hepatic glucose and lipid metabolism can instigate the onset of various metabolic disorders including obesity, dyslipidemia, insulin resistance, type 2 diabetes, and fatty liver disease. Adenosine monophosphate (AMP) deaminase (AMPD), which converts AMP to inosine monophosphate, plays a key role in maintaining adenylate energy charge. AMPD2 is the major isoform present in the liver. However, the mechanistic link between AMPD2 and hepatic glucose and lipid metabolism remains elusive. In this study, we probed into the hepatic glucose and lipid metabolism in AMPD2-deficient (A2−/−) mice. These mice exhibited reduced body weight, fat accumulation, and blood glucose levels, coupled with enhanced insulin sensitivity while maintaining consistent calorie intake and spontaneous motor activity compared with wild type mice. Furthermore, A2−/− mice showed mitigated obesity and hyper-insulinemia induced by high-fat diet (HFD) but elevated levels of the serum triglyceride and cholesterol. The hepatic mRNA levels of several fatty acid and cholesterol metabolism-related genes were altered in A2−/− mice. RNA sequencing unveiled multiple alterations in lipid metabolic pathways due to AMPD2 deficiency. These mice were also more susceptible to fasting or HFD-induced hepatic lipid accumulation. The liver exhibited elevated AMP levels but unaltered AMP/ATP ratio. In addition, AMPD2 deficiency is not associated with the adenosine production. In summary, this study established a link between purine metabolism and hepatic glucose and lipid metabolism via AMPD2, providing novel insights into these metabolic pathways.

Garcinia cambogia water extract alleviates insulin resistance and hepatic lipid accumulation in mice fed a high-fat diet.

Garcinia cambogia is widely used as a weight-loss supplement, and it is reported to be negatively associated with metabolic diseases including insulin resistance (IR), type 2 diabetes mellitus (T2DM), non-alcoholic fatty liver disease (NAFLD), and dyslipidemia. This study aimed to investigate the effect of G. cambogia water extract (GE) on high-fat diet (HFD)-induced obesity, IR, and hepatic lipid accumulation. C57BL/6 male mice were fed HFD with or without GE, GED and GEP for 16 weeks, and the mice were subjected to insulin tolerance tests and liver histological analysis. The hydroxycitric acid (HCA) levels of GE, GED, and GEP were measured by high-performance liquid chromatography. The results showed that GE significantly reduced HFD-induced body weight gain (P < 0.001), alleviated IR (P < 0.01), reduced serum total cholesterol (TC) (P < 0.001), and attenuated HFD-induced hepatic lipid accumulation. To investigate the constituent that was responsible for these effects, we separated GE into the component that dissolved in ethanol (GED) and the component that was precipitated by ethanol (GEP). Further mouse experiments showed that both GED and GEP were effective, but GED (which was used at a dose of 4 g/L) was more effective than GEP (which was used at a lower dose of 1 g/L). The HCA levels in GED and GEP were similar, although less than in GE. HCA may be the effective component in GE. This study provides evidence that G. cambogia can be used as a natural supplement to alleviate IR and hepatic lipid accumulation.

Corilagin prevents non-alcoholic fatty liver disease via improving lipid metabolism and glucose homeostasis in high fat diet-fed mice.

Non-alcoholic fatty liver disease (NAFLD) has been considered to be one of the most common chronic liver diseases. However, no validated pharmacological therapies have been officially proved in clinic due to its complex pathogenesis. The purpose of this study was to examine the protective effects of Corilagin (referred to Cori) against NAFLD in mice under a high fat diet (HFD) condition. Mice were fed either a normal control diet (NCD) or HFD with or without Cori (5 or 10 mg/kg body weight) for 15 weeks. In our results, Cori treatment significantly attenuated HFD-induced hepatic steatosis, high NAFLD activity score (NAD) and liver injury. Consistently, Cori treatment remarkably alleviated HFD-induced hepatic lipid accumulation (e.g., triglycerides (TG) and total cholesterol (TC) contents in liver), and improved plasma lipid concentrations (e.g., plasma TG, TC, low-density lipoprotein cholesterol (LDL-c), high-density lipoprotein cholesterol (HDL-c)). Moreover, Cori treatment ameliorated NAFLD associated metabolic disorders such as glucose intolerance and insulin resistance in HFD-fed mice. Additionally, Cori treatment dramatically changed HFD-induced liver gene expression profiles, and identified overlapped differentially expressed genes (DEGs) between NCD vs. HFD group and HFD vs. HCR (high fat diet plus treatment with Cori) group. With these DEGs, we observed a marked enrichment of Gene Ontology (GO) terms and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways, which were closely associated with the metabolic balance in liver. Particularly, we found several potential hub proteins against NAFLD development with analyses of protein-protein interaction (PPI) network and qPCR assays. Collectively, our results revealed the important protective effects of Cori against the progress of NAFLD, which was probably mediated through improving dysregulated lipid metabolism and insulin resistance in HFD-fed mice. Additionally, Cori-dependent overlapped DEGs might serve as a featured NAFLD-associated gene expression signature for the diagnosis, treatment, as well as drug discovery and development of NAFLD in the near future.

Transcription factor CREB3 is a potent regulator of high-fat diet-induced obesity and energy metabolism.

The endoplasmic reticulum senses alterations to cellular homeostasis that activates the unfolded protein response (UPR). UPR proteins are known to aid in regulating glucose and lipid metabolism. CREB3 is a UPR-associated transcription factor whose potential role in regulating energy metabolism remains unclear. Eight-week-old wild-type (WT) and Creb3+/- mice were placed on control and high-fat diets (HFD) for 8 weeks, and metabolic phenotypes characterized by weekly weighing, indirect calorimetry, body composition scans, glucose tolerance tests, plasma analysis, tissue lipid quantifications and gene/protein expression analysis. HFD weight gain in Creb3+/- males was reduced by 34% (p < 0.0001) and females by 39.5% (p = 0.014) from their WT counterparts. No differences were found in HFD food intake or total fecal lipids between genotypes. Creb3+/- mice had increased energy expenditure and respiratory exchange ratios (p = 0.002) relative to WT. Creb3+/- mice had significant reductions in absolute fat and lean tissue, while Creb3+/- females had significant reductions in body fat% and increased lean% composition (p < 0.0001) compared to WT females. Creb3+/- mice were protected from HFD-induced basal hyperglycemia (males p < 0.0001; females p = 0.0181). Creb3+/- males resisted HFD-induced hepatic lipid accumulation (p = 0.025) and glucose intolerance compared to WT (p < 0.0001) while Creb3+/- females were protected from lipid accumulation in skeletal muscle (p = 0.001). Despite the metabolic differences of Creb3+/- mice on HFD, lipid plasma profiles did not significantly differ from WT. Fasted Creb3+/- mice additionally revealed upregulation of hepatic energy expenditure and gluconeogenic genes such as Pgc-1a and Gr (glucocorticoid receptor) (p < 0.05), respectively. Reduced expression of CREB3 increased energy expenditure and the respiratory exchange ratio, and protected mice from HFD-induced weight gain, basal hyperglycemia, and sex-specific tissue lipid accumulation. We postulate that CREB3 is a novel key regulator of diet-induced obesity and energy metabolism that warrants further investigation as a potential therapeutic target in metabolic disorders.

The effects of brewers’ spent grain on high-fat diet-induced fatty liver

Obesity drives nonalcoholic fatty liver disease (NAFLD). This study investigated the effects of dietary brewers’ spent grain (BSG) supplementation on obesity-induced NAFLD. Mice fed a high-fat diet supplemented with 30% BSG (HFD30) had reduced body weight and decreased plasma total cholesterol (TC) concentrations compared with HFD-fed mice. Retroperitoneal white adipose tissue (RWAT) and liver weights were reduced. Consistent with reduced hepatic triacylglycerol, TC, and non-esterified fatty acid concentrations, HFD30-fed mice showed reduced hepatic steatosis. 3-hydroxy-3-methylglutaryl-CoA reductase and low-density lipoprotein receptor genes were increased, whereas carnitine palmitoyltransferase 1 alpha, ATP-binding cassette subfamily A member 1 (Abca1), and cholesterol 7 alpha-hydroxylase genes were upregulated in the liver of HFD30-fed mice. Abca1 gene expression was also increased in epididymal WAT and RWAT of HFD30-fed mice. BSG supplementation increased and decreased fecal fat and bile acid concentrations, respectively. Taken together, BSG supplementation reduced HFD-induced hepatic lipid accumulation by increasing fatty acid oxidation and bile acid synthesis in the liver as well as decreasing lipid absorption in the intestine.

Exercise Alleviates the Apolipoprotein A5-Toll-Like Receptor 4 Axis Impairment in Mice With High-Fat Diet-Induced Non-alcoholic Steatohepatitis.

Background: Apolipoprotein A5 (ApoA5), an important modulator of plasma and hepatic triglyceride metabolism, has been found to be downregulated by metformin to improve non-alcoholic fatty liver disease. Meanwhile, exercise has been recommended as a therapeutic strategy for non-alcoholic steatohepatitis (NASH). However, no study has yet determined whether exercise affects hepatic ApoA5 expression or the inhibition of ApoA5 to toll-like receptor 4 (TLR4). We herein examined the effects of exercise on hepatic ApoA5 expression and the relevance of ApoA5 and TLR4-mediated pathway in mice with high-fat diet (HFD)-induced NASH.Methods: Male C57BL/6J mice were built NASH model with high-fat diet for 12 weeks, and following mice were subjected to exercise for 12 weeks on a treadmill. Microscopy and enzyme-linked immunosorbent assay were used to measure histological analysis of liver and hepatic lipids, respectively. Quantitative real-time PCR and western blot were used to determined mRNA and protein levels of ApoA5 and TLR4-mediated nuclear factor kappa B (NF-κB) pathway components, respectively. ApoA5 overexpression plasmids transfected into mice to investigate the relevance of ApoA5 and TLR4.Results: 12 weeks of exercise remarkably alleviated HFD-induced hepatic lipid accumulation, inflammation, and fibrosis, as well as reduced serum lipopolysaccharide (LPS), hepatic TLR4, myeloid differentiation factor 88 (MyD88), and NF-κBp65 expression. Importantly, exercise did not reduce ApoA5 expression but instead enhanced its ability to suppress TLR4-mediated NF-κB pathway components by decreasing circulating LPS in our experiments involving transfection of ApoA5 overexpression plasmids and LPS interventions.Conclusion: The results demonstrated that exercise improved HFD-induced NASH by triggering the inhibitory effects of ApoA5 on the TLR4-mediated NF-κB pathway.

Antihyperlipidemic and Hepatoprotective Properties of Vitamin B6 Supplementation in Rats with High-Fat Diet-Induced Hyperlipidemia.

The incidence and mortality of hyperlipidemia are increasing year by year, showing a younger trend. At present, the treatment of hyperlipidemia is mainly dependent on western medicine, but its side effects on liver and kidney function are common in clinics. Therefore, it is necessary to study the treatment of hyperlipidemia by augmenting effective dietary nutrition supplements. Vitamin B6 (VitB6), as an essential cofactor for enzymes, participates in lipid metabolism. The effects of VitB6 on hyperlipidemia, however, have not been reported until now. The present study was to investigate the influence of VitB6 on hepatic lipid metabolism in hyperlipidaemia rats induced by a High-Fat Diet (HFD). Male Sprague-Dawley rats were kept on HFD for two weeks to establish the hyperlipidemia model. The rats in low-dosage and high-dosage groups were received 2.00 and 3.00 mg/kg/- day of VitB6 for eight weeks, respectively. The results showed that both doses of VitB6 reduced HFD-induced hepatic Low-Density Lipoprotein Cholesterol (LDL-C); decreased blood cholesterol (TC), triglycerides, LDL-C, atherogenic index (AI), Atherogenic Index of Plasma (AIP), apolipoprotein B (ApoB) and ApoB/apolipoprotein A-1(ApoA1) ratio; increased liver High-Density Lipoprotein Cholesterol (HDL-C) and serum ApoA1; reduced hepatic steatosis and triglyceride accumulation, lowered fat storage, and recovered heart/body and brain/body ratio to a normal level. In addition, VitB6 supplementation markedly decreased HMGR level, increased the mRNA abundance of LDLR and CYP7A1, and protein expression of SIRT1, following the downregulation of SREBP-1 and PPARγ protein expression in the liver of hyperlipidemia rats. In summary, oral VitB6 supplementation can ameliorate HFD-induced hepatic lipid accumulation and dyslipidemia in SD rats by inhibiting fatty acid and cholesterol synthesis, promoting fatty acid decomposition and cholesterol transport.

Intermittent Fasting Inhibits High-Fat Diet-Induced Atherosclerosis by Ameliorating Hypercholesterolemia and Reducing Monocyte Chemoattraction.

Atherosclerosis is a major pathology for cardiovascular diseases (CVDs). Clinically, the intermittent fasting (IF) has been observed to reduce the risk of CVDs. However, the effect of IF on the development of atherosclerosis has not been fully elucidated. Herein, we determined the protection of IF against high-fat diet–induced atherosclerosis in pro-atherogenic low-density lipoprotein receptor deficient (LDLR-/-) mice and the potentially involved mechanisms. The LDLR-/- mice were scheduled intermittent fasting cycles of 3-day HFD feeding ad libitum and 1 day fasting, while the mice in the control group were continuously fed HFD. The treatment was lasted for 7 weeks (∼12 cycles) or 14 weeks (∼24 cycles). Associated with the reduced total HFD intake, IF substantially reduced lesions in the en face aorta and aortic root sinus. It also increased plaque stability by increasing the smooth muscle cell (SMC)/collagen content and fibrotic cap thickness while reducing macrophage accumulation and necrotic core areas. Mechanistically, IF reduced serum total and LDL cholesterol levels by inhibiting cholesterol synthesis in the liver. Meanwhile, HFD-induced hepatic lipid accumulation was attenuated by IF. Interestingly, circulating Ly6Chigh monocytes but not T cells and serum c-c motif chemokine ligand 2 levels were significantly reduced by IF. Functionally, adhesion of monocytes to the aortic endothelium was decreased by IF via inhibiting VCAM-1 and ICAM-1 expression. Taken together, our study indicates that IF reduces atherosclerosis in LDLR-/- mice by reducing monocyte chemoattraction/adhesion and ameliorating hypercholesterolemia and suggests its potential application for atherosclerosis treatment.

Polysaccharide MCP extracted from Morchella esculenta reduces atherosclerosis in LDLR-deficient mice.

The pharmaceutical application of fungal polysaccharides has been extensively studied based on their multiple biological activities. However, the effect of Morchella esculenta polysaccharides on the development of atherosclerosis remains unknown. This study aims to investigate the anti-atherosclerotic effect of a novel polysaccharide (MCP) extracted from Morchella esculenta. The average molecular weight of MCP is 1.69 × 105 Da, and it is composed of glucose, mannose and galactose in the molar ratio of 1 : 1.9 : 0.51. LDLR-deficient (LDLR-/-) mice were fed high-fat diet (HFD) and administered intragastrically (i.g.) with saline or MCP dissolved in saline for 15 weeks. We found that MCP inhibited en face and sinus lesions. Moreover, serum levels of total and low-density lipoprotein cholesterol and triglyceride were decreased by MCP. The HFD-induced hepatic lipid accumulation was also attenuated by MCP. The underlying molecular mechanisms of anti-atherogenic and lipogenic effects of MCP might be attributed to reduced cholesterol synthesis by activating AMPKα signaling pathway and inhibiting SREBP2 expression. In addition, MCP-decreased serum triglyceride level is related to inhibiting LXRα expression. Taken together, these results indicate that MCP markedly alleviates atherosclerosis and M. esculenta can be used as a functional food additive to benefit patients with atherosclerosis.

HFD-induced hepatic lipid accumulation and inflammation are decreased in Factor D deficient mouse

Excessive intake of fat causes accumulation of fat in liver, leading to non-alcoholic fatty liver disease (NAFLD). High-fat diet (HFD) upregulates the expression of Factor D, a complement pathway component, in the liver of mice. However, the functions of Factor D in liver are not well known. Therefore, the current study investigated the relationship between Factor D and hepatic lipid accumulation using CRISPR/Cas9-mediated Factor D knockout (FD-KO) mice. Factor D deficiency downregulated expression of genes related to fatty acid uptake and de novo lipogenesis in the liver. Furthermore, Factor D deficiency reduced the expression of inflammatory factors (Tnf and Ccl2) and fibrosis markers and decreased accumulation of F4/80-positive macrophages. These data suggest that the Factor D deficiency improved hepatic lipid accumulation and hepatic inflammation in HFD-fed mice.

Schaftoside alleviates HFD-induced hepatic lipid accumulation in mice via upregulating farnesoid X receptor

Ethnopharmacology relevanceThe farnesoid X receptor (FXR) is a therapeutic target of for the treatment of non-alcoholic fatty liver disease (NAFLD) owing to its regulatory role in lipid homeostasis. Schaftoside (SS) is a bioactive compound of Herba Desmodii Styracifolii, which has traditionally been used to treat hepatitis and cholelithiasis. However, the potential hepatoprotective effect of SS against NAFLD and the underlying mechanisms remain unknown. Aim of the studyWe investigated whether SS could improve NAFLD-induced liver injury by decreasing lipid accumulation via the activation of FXR signalling. Materials and methodsIn vivo, the effects of SS on high-fat diet (HFD)-induced lipid accumulation in the liver of mice were evaluated by serum biochemical parameters and histopathological analysis. In vitro, the intracellular triglyceride (TG) level and Oil Red O staining were used to evaluate the lipid removal ability of SS in Huh-7 cells or FXR knockout mouse primary hepatocytes (MPHs) induced by oleic acid (OA). Moreover, FXR/sterol regulatory element-binding protein 1 (SREBP1) mRNA and protein expression levels were detected. ResultsSS reduced HFD-induced lipid accumulation in the liver, as indicated by decreased aspartate aminotransferase (AST), cholesterol (Ch), and TG levels in serum and TG levels in liver tissue, and subsequently resulting in attenuation of liver histopathological injury. Gene expression profiles demonstrated that SS dose-dependently prevented HFD-induced decrease of FXR expression and inversely inhibited SREBP1 expression in the nucleus. Furthermore, SS significantly suppressed excessive TG accumulation and decreased intracellular TG level in Huh-7 cells or MPHs via the upregulation of FXR and inhibition of SREBP1 expression in the nucleus. ConclusionOur results suggest that SS ameliorates HFD-induced NAFLD by the decrease of lipid accumulation via the control of FXR-SREBP1 signalling.

MiR-146a Deficiency Accelerates Hepatic Inflammation Without Influencing Diet-induced Obesity in Mice

miR-146a, an anti-inflammatory microRNA, is shown to be a negative regulator of adipocyte inflammation. However, the functional contribution of miR-146a in the development of obesity is not defined. In order to determine whether miR-146a influences diet-induced obesity, mice that were either wild type (WT) or miR-146a deficient (KO) were fed with high (60% kcal) fat diet (HFD) for 16 weeks. Deficiency of miR-146a did not influence obesity measured as HFD-induced body weight and fat mass gain, or metabolism of glucose and insulin tolerance. In addition, adipocyte apoptosis, adipose tissue collagen and macrophage accumulation as detected by TUNEL, Picro Sirius and F4/80 immunostaining, respectively, were comparable between the two groups of mice. Although, miR-146a deficiency had no influence on HFD-induced hepatic lipid accumulation, interestingly, it significantly increased obesity-induced inflammatory responses in liver tissue. The present study demonstrates that miR-146a deficiency had no influence on the development of HFD-induced obesity and adipose tissue remodeling, whereas it significantly increased hepatic inflammation in obese mice. This result suggests that miR-146a regulates hepatic inflammation during development of obesity.

Hepatoprotective Effects of MHY3200 on High-Fat, Diet-Induced, Non-Alcoholic Fatty Liver Disease in Rats.

This study investigated the effects of 2-(4-(5-chlorobenzo[d]thiazol-2-yl)phenoxy)-2,2-difluoroacetic acid (MHY3200) on high-fat diet (HFD)-induced hepatic lipid accumulation and inflammation. The measurement of peroxisome proliferator-activated receptor (PPAR)α activity by using a luciferase assay indicated that MHY3200 was more potent than a known PPARα agonist, WY14643, in AC2F cells. Six-month-old male SD rats were fed chow or HFD for 1 month, and after, with or without added MHY3200 (1 or 2 mg/kg/day) for 4 weeks. The oral administration of MHY3200 caused a significant decrease in serum triglyceride (TG), glucose, alanine aminotransferase, and insulin, as well as a slight decrease in the level of free fatty acid and aspartate transaminase. No weight gain was detected when compared with HFD rats, and hepatic TG content was also attenuated by the administration of MHY3200. Furthermore, phosphorylation of the ER stress marker, inositol-requiring kinase 1 and its downstream gene, c-Jun N-terminal kinase, in addition to serine phosphorylation of insulin receptor substrate 1 were suppressed by MHY3200. Consistent with these results, MHY3200 administration reduced the levels of activation of protein-1, cyclooxygenase-2, and inducible nitric oxide synthase. Our results suggested that MHY3200 ameliorated HFD-induced hepatic lipid accumulation and inflammation, and improved insulin resistance through PPARα activation.

Inhibition of Serotonin Synthesis Induces Negative Hepatic Lipid Balance.

BackgroundHepatic steatosis is caused by metabolic stress associated with a positive lipid balance, such as insulin resistance and obesity. Previously we have shown the anti-obesity effects of inhibiting serotonin synthesis, which eventually improved insulin sensitivity and hepatic steatosis. However, it is not clear whether serotonin has direct effect on hepatic lipid accumulation. Here, we showed the possibility of direct action of serotonin on hepatic steatosis.MethodsMice were treated with para-chlorophenylalanine (PCPA) or LP-533401 to inhibit serotonin synthesis and fed with high fat diet (HFD) or high carbohydrate diet (HCD) to induce hepatic steatosis. Hepatic triglyceride content and gene expression profiles were analyzed.ResultsPharmacological and genetic inhibition of serotonin synthesis reduced HFD-induced hepatic lipid accumulation. Furthermore, short-term PCPA treatment prevented HCD-induced hepatic steatosis without affecting glucose tolerance and browning of subcutaneous adipose tissue. Gene expression analysis revealed that the expressions of genes involved in de novo lipogenesis and triacylglycerol synthesis were downregulated by short-term PCPA treatment as well as long-term PCPA treatment.ConclusionShort-term inhibition of serotonin synthesis prevented hepatic lipid accumulation without affecting systemic insulin sensitivity and energy expenditure, suggesting the direct steatogenic effect of serotonin in liver.

Korean red ginseng (Panax ginseng) inhibits obesity and improves lipid metabolism in high fat diet-fed castrated mice

Ethnopharmacological relevanceKorean red ginseng (Panax ginseng C.A. Meyer, Araliaceae) has been historically used as a traditional drug for the prevention and treatment of most ageing-related diseases, such as obesity, dyslipidemia, diabetes, and cardiovascular disease. Elderly men with testosterone deficiency are strongly associated with many of the aforementioned metabolic diseases. The aim of this study was to determine the effects of ginseng on obesity and lipid metabolism in a mouse model of testosterone deficiency (castrated C57BL/6J mice). Materials and methodsThe effects of ginseng extract (GE) on obesity and lipid metabolism in high-fat diet (HFD)-fed castrated C57BL/6J mice were examined using hematoxylin and eosin staining, serum lipid analysis, and quantitative real-time polymerase chain reaction (PCR). The effects of GE, ginsenosides, and testosterone on adipogenesis were measured using Oil Red O staining, XTT assay, and real-time PCR. ResultsCompared with HFD mice, mice receiving HFD supplemented with GE (HFD-GE) for 8 weeks showed decreased body weight, adipose tissue mass, and adipocyte size without affecting food intake. Serum levels of triglycerides and total cholesterol were lowered in HFD-GE mice than in HFD mice. GE also markedly reduced HFD-induced hepatic lipid accumulation. Concomitantly, HFD-GE decreased mRNA expression of adipogenesis-related genes (SREBP-1C, PPARγ, FAS, SCD1, and ACC1) in visceral adipose tissues compared with HFD alone. Consistent with the in vivo data, GE and major active ginsenosides (Rb1 and Rg1) decreased lipid accumulation and mRNA expression of PPARγ, C/EBPα, and SCD1 in 3T3-L1 adipocytes compared with control. Similarly, testosterone also decreased lipid accumulation and mRNA levels of PPARγ, C/EBPα, and SCD1. These inhibitory effects were further increased by co-treatment of GE or ginsenosides with testosterone. ConclusionsOur results demonstrate that ginseng can inhibit obesity and dyslipidemia in HFD-fed castrated mice, possibly by inhibiting adipogenic gene expression. In addition, our results indicate that ginseng may act like testosterone to inhibit adipogenesis, suggesting that ginseng may be able to prevent obesity, hyperlipidemia, and hepatic steatosis in men with testosterone deficiency.

Electroacupuncture attenuates hepatic lipid accumulation via AMP-activated protein kinase (AMPK) activation in obese rats.

Electroacupuncture (EA) may offer an effective alternative approach for the treatment of obesity. EA mobilizes energy stores, but its effect on hepatic lipid metabolism is unknown, and the underlying mechanisms remain unclear. To examine the effect of EA on hepatic lipid accumulation in diet-induced obese (DIO) rats, and to explore potential underlying mechanisms. Male Sprague-Dawley rats were fed a normal diet (control group, n=10) or a high-fat diet (HFD) for 12 weeks to induce obesity. Those exhibiting diet-induced obesity were subdivided into two groups, one receiving EA (DIO+EA group, n=10) and one left untreated (DIO group, n=10) and observed for a further 4 weeks. Body, liver and fat pad weight were measured, and liver injury was assessed histologically as well as by measuring serum values of alanine aminotransferase (ALT) and aspartate aminotransferase (AST). Hepatic triglyceride (TG) and total cholesterol were quantified by enzymatic colorimetric methods. Expression of liver AMP-activated protein kinase (AMPK), acetyl-coenzyme A carboxylase (ACC), and carnitine palmitoyltransferase (CPT-1) was measured by Western blotting. EA treatment led to a reduction in body, liver and fat pad weight in DIO rats. This was accompanied by decreases in hepatic TG and total cholesterol values, fatty droplet accumulation, and serum concentrations of ALT and AST. Furthermore, EA treatment restored phosphorylation levels of AMPK (Thr(172)) and ACC (Ser(79)) inhibited by HFD, and increased CPT-1 expression. EA reduces HFD-induced hepatic lipid accumulation, an effect that appears to be mediated through AMPK signalling pathways. Our results shed new light on the mechanisms by which EA may reduce obesity.

Lack of kinin B1 receptor potentiates leptin action in the liver

Kinins B1 and B2 receptors (B1R and B2R) are classically associated with inflammation, but our group has recently demonstrated new roles for B1R in metabolism using a knockout model (B1 (-/-)). B1 (-/-) mice display improvement on leptin and insulin sensitivity and is protected from high fat diet (HFD)-induced obesity. Here, we evaluate the hepatic effects of the B1R ablation and its role on hepatic function. Despite no expression of hepatic B1R, HFD-induced hepatic lipid accumulation was lower than in control animals. B1 (-/-) mice also presented lower hepatic lipogenesis and SCD1 protein content in the liver. When stimulated with exogenous leptin, B1 (-/-) mice exhibited increased hepatic pJAK2. Similarly, leptin signaling was enhanced in the liver of ob/ob-B1 (-/-) mice, as demonstrated by increased levels of pSTAT3 compared to ob/ob. Plasma concentrations of intercellular adhesion molecule 1, fetuin A, leukemia inhibitory factor, tissue inhibitor of metalloprotease-1, resistin, and oncostatin M were reduced in B1 (-/-). Finally, B1 (-/-) mice have increased gene expression of hepatic B2 receptor, but no difference in leptin receptor expression. Our results show that B1 (-/-) mice are protected from non-alcoholic fatty liver disease (NAFLD) after HFD treatment. Since B1R expression was not observed in the liver after HFD, we propose that the cross talk between the adipose tissue and the liver, mainly through leptin, is an important factor contributing to the observed results. Besides that, several other inflammatory mediators already correlated with NAFLD or liver function were found to be altered in our model. Taken together, our data suggest that B1R plays an important role in hepatic steatosis development.

Additive effects of nicotine and high-fat diet on hepatic steatosis in male mice.

Smoking is a major risk factor for diabetes and cardiovascular disease and may contribute to nonalcoholic fatty liver disease. We hypothesize that in the presence of nicotine, high-fat diet (HFD) causes more severe hepatic steatosis in obese mice. Adult C57BL6 male mice were fed a normal chow diet or HFD and received twice daily injections of nicotine (0.75 mg/kg body weight, ip) or saline for 10 wk. Light microscopic image analysis revealed significantly higher lipid accumulation in livers from mice on HFD plus nicotine (190 ± 19 μm(2)), compared with mice on HFD alone (28 ± 1.2 μm(2)). A significant reduction in the percent volume of endoplasmic reticulum (67.8%) and glycogen (49.2%) was also noted in hepatocytes from mice on HFD plus nicotine, compared with mice on HFD alone. The additive effects of nicotine on the severity of HFD-induced hepatic steatosis was associated with significantly greater oxidative stress, increased hepatic triglyceride levels, higher incidence of hepatocellular apoptosis, inactivation (dephosphorylation) of AMP-activated protein kinase, and activation of its downstream target acetyl-coenzyme A-carboxylase. Treatment with acipimox, an inhibitor of lipolysis, significantly reduced nicotine plus HFD-induced hepatic lipid accumulation. We conclude that: 1) greater oxidative stress coupled with inactivation of AMP-activated protein kinase mediate the additive effects of nicotine and HFD on hepatic steatosis in obese mice and 2) increased lipolysis is an important contributor to hepatic steatosis. We surmise that nicotine exposure is likely to exacerbate the metabolic abnormalities induced by high-fat intake in obese patients.