The effects of herbal composition Gambigyeongsinhwan (4) on hepatic steatosis and inflammation in Otsuka Long-Evans Tokushima fatty rats and HepG2 cells

MCAD activation by empagliflozin promotes fatty acid oxidation and reduces lipid deposition in NASH

Medium-chain acyl-CoA dehydrogenase (MCAD) is one of the significant enzymes involved in the β-oxidation of mitochondrial fatty acids. MCAD deficiency affects the β-oxidation of fatty acid and leads to lipid deposition in multiple organs, but little is known about its importance in nonalcoholic steatohepatitis (NASH). Empagliflozin is revealed to effectively improve NASH by increasing research, whereas the specific mechanism still has to be explored. Human liver tissues of patients with or without NASH were obtained for proteomic analysis to screen proteins of interest. db/db mice were given empagliflozin by gavage for 8 weeks. The expression of MCAD and signaling molecules involved in hepatic lipid metabolism was evaluated in human liver, mice and HL7702 cells. We found that the MCAD levels in the liver were significantly reduced in NASH patients compared to patients without NASH. Protein-protein interaction network analysis showed that MCAD was highly correlated with forkhead box A2 (FOXA2) and protein kinase AMP-activated catalytic subunit alpha (PRKAA). AMPK/FOXA2/MCAD signaling pathway was detected to be inhibited in the liver of NASH patients. Decreased expression of MCAD was also observed in the livers of db/db mice and hepatocyte treated with palmitic acid and glucose. Of note, empagliflozin could upregulate MCAD expression by activating AMPK/FOXA2 signaling pathway, reduce lipid deposition and improve NASH in vivo and in vitro. This research demonstrated that MCAD is a key player of hepatic lipid deposition and its targeting partially corrects NASH. MCAD thus may be a potential therapeutic target for the treatment of NASH.

The gene knockout of angiotensin II type 1a receptor improves high-fat diet-induced obesity in rat via promoting adipose lipolysis

Aims

The renin-angiotensin system (RAS) is over-activated and the serum angiotensin II (Ang II) level increased in obese patients, while their correlations were incompletely understood. This study aims to explore the role of Ang II in diet-induced obesity by focusing on adipose lipid anabolism and catabolism.

Methods

Rat model of AT1aR gene knockout were established to investigate the special role of Ang II on adipose lipid metabolism. Wild-type (WT) and AT1aR gene knockout (AT1aR^-/-) SD rats were fed with normal diet or high-fat diet for 12 weeks. Adipose morphology and adipose lipid synthesis and lipolysis were examined.

Results

AT1aR deficiency activated lipolysis-related enzymes and increased the levels of NEFAs and glycerol released from adipose tissue in high-fat diet rats, while did not affect triglycerides synthesis. Besides, AT1aR knockout promoted energy expenditure and fatty acids oxidation in adipose tissue. cAMP levels and PKA phosphorylation in the adipose tissue were significantly increased in AT1aR^-/- rats fed with high-fat. Activated PKA could promote adipose lipolysis and thus improved adipose histomorphology and insulin sensitivity in high-fat diet rats.

Conclusions

AT1aR deficiency alleviated adipocyte hypertrophy in high-fat diet rats by promoting adipose lipolysis probably via cAMP/PKA pathway, and thereby delayed the onset of obesity and related metabolic diseases.

Structural Basis for PPARs Activation by The Dual PPARα/γ Agonist Sanguinarine: A Unique Mode of Ligand Recognition

Peroxisome proliferator-activated receptors (PPARs) play crucial roles in glucose and lipid metabolism and inflammation. Sanguinarine is a natural product that is isolated from Sanguinaria Canadensis, a potential therapeutic agent for intervention in chronic diseases. In this study, biochemical and cell-based promoter-reporter gene assays revealed that sanguinarine activated both PPARα and PPARγ, and enhanced their transcriptional activity; thus, sanguinarine was identified as a dual agonist of PPARα/γ. Similar to fenofibrate, sanguinarine upregulates the expression of PPARα-target genes in hepatocytes. Sanguinarine also modulates the expression of key PPARγ-target genes and promotes adipocyte differentiation, but with a lower adipogenic activity compared with rosiglitazone. We report the crystal structure of sanguinarine bound to PPARα, which reveals a unique ligand-binding mode of sanguinarine, dissimilar to the classic Y-shaped binding pocket, which may represent a new pharmacophore that can be optimized for selectively targeting PPARα. Further structural and functional studies uncover the molecular basis for the selectivity of sanguinarine toward PPARα/γ among all three PPARs. In summary, our study identifies a PPARα/γ dual agonist with a unique ligand-binding mode, and provides a promising and viable novel template for the design of dual-targeting PPARs ligands.

Fenofibrate Regulates Visceral Obesity and Nonalcoholic Steatohepatitis in Obese Female Ovariectomized C57BL/6J Mice

Fibrates, including fenofibrate, are a class of hypolipidemic drugs that activate peroxisome proliferator-activated receptor α (PPARα), which in-turn regulates the expression of lipid and lipoprotein metabolism genes. We investigated whether fenofibrate can reduce visceral obesity and nonalcoholic fatty liver disease via adipose tissue PPARα activation in female ovariectomized (OVX) C57BL/6J mice fed a high-fat diet (HFD), a mouse model of obese postmenopausal women. Fenofibrate reduced body weight gain (-38%, p < 0.05), visceral adipose tissue mass (-46%, p < 0.05), and visceral adipocyte size (-20%, p < 0.05) in HFD-fed obese OVX mice. In addition, plasma levels of alanine aminotransferase and aspartate aminotransferase, as well as free fatty acids, triglycerides, and total cholesterol, were decreased. Fenofibrate also inhibited hepatic lipid accumulation (-69%, p < 0.05) and infiltration of macrophages (-72%, p < 0.05), while concomitantly upregulating the expression of fatty acid β-oxidation genes targeted by PPARα and decreasing macrophage infiltration and mRNA expression of inflammatory factors in visceral adipose tissue. These results suggest that fenofibrate inhibits visceral obesity, as well as hepatic steatosis and inflammation, in part through visceral adipose tissue PPARα activation in obese female OVX mice.

Ganoderic acid A attenuates high-fat-diet-induced liver injury in rats by regulating the lipid oxidation and liver inflammation

Ganoderic Acid A (GA) has many pharmacological effects such as anti-tumor, antibacterial, anti-inflammatory, and immunosuppressive effects. However, the protective effect of GA on liver injury has not been reported. This study aimed to investigate the action of GA on insufficient methionine and choline combined with high-fat diet (HFD)-induced non-alcoholic fatty liver disease (NAFLD) in rats. NAFLD model was established by insufficient methionine and choline combined with high fat feeding to rats. The levels of Acetyl-CoA carboxylase, fatty acid synthase, sterol regulatory element binding protein, liver X receptors, AMP-activated protein kinase, peroxisome proliferator-activated receptor α, PPARg coactivator 1α and NF-κB pathway in the liver were detected by western blot. The results of this study demonstrated that the expression of GA can not only significantly decrease the live weight and liver weight per body weight of HFD mice, but also restore the alanine aminotransferase, aspartate aminotransferase, total bilirubin levels, triglyceride and cholesterol in serum. In addition, the expression of GA increased the levels of high-density lipoprotein cholesterol in serum, ameliorated pathological changes and decreased NAS score of mice's liver. In conclusion, the treatment with GA could improve NAFLD in rats by regulating the levels of signaling events involved in free fatty acid production, lipid oxidation and liver inflammation.

Effect and mechanism of ginsenoside Rg1-regulating hepatic steatosis in HepG2 cells induced by free fatty acid

Ginsenoside Rg1 (G-Rg1) is a bioactive phytochemical that has been found to be beneficial for the treatment of several diseases including nonalcoholic fatty liver disease (NAFLD). But there is a lack of literature reporting the effect of G-Rg1 on lipid metabolism balance in NAFLD. We investigated the effect and mechanism of G-Rg1 on lipid metabolism in vitro. We found that G-Rg1 decreased the levels of TG, TC, and MDA, and increased activity of SOD. Results of RT-PCR and western blotting showed that supplementation with G-Rg1 downregulated the expression of PPAR γ, FABP1, FATP2/5, CD36, SREBP1 c, and FASN, while the expression of PPAR ɑ, CPT1, ACOX1, MTTP, and ApoB100 was upregulated, after induction by a free fatty acid. Taken together, we conclude that G-Rg1 inhibits lipid synthesis and lipid uptake, and enhances lipid oxidation and lipid export to reduce hepatic steatosis of HepG2 cells by regulating PPAR ɑ and PPAR γ expression.

Isolation and purification of acidic polysaccharides from Agaricus blazei Murill and evaluation of their lipid-lowering mechanism

Polysaccharides are important active constituents of Agaricus blazei Morrill. In the present study, WABM-A was isolated from WABM using DEAE-cellulose, and subsequently purified using sepharose CL-6B to obtain the acidic polysaccharide WABM-A-b. WABM-A-b is mainly composed of Glc dextran, with a molecular weight of 10 KDa and β-1,6-D-Glcp as its main chain. The results of in vivo experiments show that in comparison with the MG, WABM-A significantly reduced the serum levels of TC, TG, and LDL-C, increased the serum levels of HDL-C (P < 0.01), and upregulated the liver expression of PPARγ, LXRα, ABCA1, and ABCG1 in rats with hyperlipidemia (P < 0.05). The results of in vitro experiments show that in comparison with the MG group, WABM-A-b-H significantly reduced the levels of TC and TG in HepG2 cells induced by oleic acid (P < 0.01), and significantly upregulated the protein expression of PPARγ, LXRα, ABCA1, and ABCG1 (P < 0.05). The present study demonstrates that WABM-A-b is an acidic glucan with lipid-lowering activity. The lipid-lowering mechanism of WABM-A-b is via the activation of the PPARγ/LXRα/ABCA1/ABCG1 cholesterol metabolism pathway. This is the first time that the hypolipidemic effect of Agaricus blazei Morrill acidic polysaccharides has been reported.

The Impacts of Herbal Medicines and Natural Products on Regulating the Hepatic Lipid Metabolism

The dysregulation of hepatic lipid metabolism is one of the hallmarks in many liver diseases including alcoholic liver diseases (ALD) and non-alcoholic fatty liver diseases (NAFLD). Hepatic inflammation, lipoperoxidative stress as well as the imbalance between lipid availability and lipid disposal, are direct causes of liver steatosis. The application of herbal medicines with anti-oxidative stress and lipid-balancing properties has been extensively attempted as pharmaceutical intervention for liver disorders in experimental and clinical studies. Although the molecular mechanisms underlying their hepatoprotective effects warrant further exploration, increasing evidence demonstrated that many herbal medicines are involved in regulating lipid accumulation processes including hepatic lipolytic and lipogenic pathways, such as mitochondrial and peroxisomal β-oxidation, the secretion of very low density lipoprotein (VLDL), the non-esterified fatty acid (NEFA) uptake, and some vital hepatic lipogenic enzymes. Therefore, in this review, the pathways or crucial mediators participated in the dysregulation of hepatic lipid metabolism are systematically summarized, followed by the current evidences and advances in the positive impacts of herbal medicines and natural products on the lipid metabolism pathways are detailed. Furthermore, several herbal formulas, herbs or herbal derivatives, such as Erchen Dection, Danshen, resveratrol, and berberine, which have been extensively studied for their promising potential in mediating lipid metabolism, are particularly highlighted in this review.

The polyherbal composition Gyeongshingangjeehwan 18 attenuates glucose intolerance and pancreatic steatosis in C57BL/6J mice on a high-fat diet

Ethnopharmacologic relevance: Gyeongshingangjeehwan 18 (GGEx18) is a polyherbal composition derived from Ephedra sinica Stapf (Ephedraceae), Laminaria japonica Aresch (Laminariaceae), and Rheum palmatum L. (Polygonaceae) that is used as an antiobesity drug in Korean clinics. Its constituents are traditionally known to combat obesity, dyslipidemia, and insulin resistance.

OBJECTIVE

This study was undertaken to investigate the effects of GGEx18 on glucose metabolism and pancreatic steatosis in obese C57BL/6 J mice fed a high-fat diet (HFD) and to examine the related cellular and molecular mechanisms.

MATERIALS AND METHODS

The mice were grouped and fed for 13 weeks as follows: 1) low-fat diet, 2) HFD, or 3) HFD supplemented with GGEx18 (500 mg/kg/day). Various factors affecting insulin sensitivity and pancreatic function were then assessed via blood analysis, histology, immunohistochemistry, and real-time polymerase chain reaction.

RESULTS

GGEx18 treatment of obese mice reduced body weight, total fat, and visceral fat mass. GGEx18 inhibited hyperglycemia and hyperinsulinemia and improved glucose and insulin tolerance. GGEx18 also decreased serum leptin levels and concomitantly increased adiponectin levels. Furthermore, GGEx18-treated mice exhibited reduced pancreatic fat accumulation and normalized insulin-secreting β-cell area. GGEx18 increased pancreatic expression of genes promoting fatty acid β-oxidation (i.e., MCAD and VLCAD), whereas expression levels of lipogenesis-related genes (i.e., PPARγ, SREBP-1c, and FAS) declined.

DISCUSSION AND CONCLUSION

GGEx18 curtailed impaired glucose metabolism and pancreatic steatosis in our mouse model by regulating pancreatic genes that govern lipid metabolism and improving insulin sensitivity. This composition may benefit patients with impaired glucose tolerance, insulin resistance, and pancreatic dysfunction.

Ascorbic acid inhibits visceral obesity and nonalcoholic fatty liver disease by activating peroxisome proliferator-activated receptor α in high-fat-diet-fed C57BL/6J mice

BACKGROUND/OBJECTIVES

Ascorbic acid is a known cofactor in the biosynthesis of carnitine, a molecule that has an obligatory role in fatty acid oxidation. Our previous studies have demonstrated that obesity is regulated effectively through peroxisome proliferator-activated receptor α (PPARα)-mediated fatty acid β-oxidation. Thus, this study aimed to determine whether ascorbic acid can inhibit obesity and nonalcoholic fatty liver disease (NAFLD) in part through the actions of PPARα.

DESIGN

After C57BL/6J mice received a low-fat diet (LFD, 10% kcal fat), a high-fat diet (HFD, 45% kcal fat), or the same HFD supplemented with ascorbic acid (1% w/w) (HFD-AA) for 15 weeks, variables and determinants of visceral obesity and NAFLD were examined using metabolic measurements, histology, and gene expression.

RESULTS

Compared to HFD-fed obese mice, administration of HFD-AA to obese mice reduced body weight gain, visceral adipose tissue mass, and visceral adipocyte size without affecting food consumption profiles. Concomitantly, circulating ascorbic acid concentrations were significantly higher in HFD-AA mice than in HFD mice. Ascorbic acid supplementation increased the mRNA levels of PPARα and its target enzymes involved in fatty acid β-oxidation in visceral adipose tissues. Consistent with the effects of ascorbic acid on visceral obesity, ascorbic acid not only inhibited hepatic steatosis but also increased the mRNA levels of PPARα-dependent fatty acid β-oxidation genes in livers. Similarly, hepatic inflammation, fibrosis, and apoptosis were also decreased during ascorbic acid-induced inhibition of visceral obesity. In addition, serum levels of alanine aminotransferase, aspartate aminotransferase, total cholesterol, and LDL cholesterol were lower in HFD-AA-fed mice than in those of HFD-fed mice.

CONCLUSIONS

These results suggest that ascorbic acid seems to suppress HFD-induced visceral obesity and NAFLD in part through the activation of PPARα.