Saudi date cultivars' seed extracts inhibit developing hepatic steatosis in rats fed a high-fat diet

This research aim was to assess the impact of the seed extracts of the date cultivars (Qatara, Barhi, and Ruthana) on rat’s liver steatosis, oxidative stress, and inflammation triggered by feeding a high-fat diet (HFD). The experimental design was based on random partitioning into two groups; one that received the standard diet and another that received the HFD diet. The HFD rats were orally administered Lipitor or date seed extracts at 300 or 600 mg/kg/day for 4 weeks. Accordingly, feeding rats HFD significantly increased body and liver weights, hepatic and serum lipid levels, glucose, insulin, HOMA-IR, liver function enzymes, and inflammation markers, and decreased oxidative stress enzymes. Oral administration of Barhi and Ruthana date seed extracts significantly decreased body and liver weights. Serum and liver total cholesterol TC, Triglycerides TGs, and free fatty acids FFAs were also decreased as were AST, ALT, MAD, leptin, and CRP, with a concomitant increase in SOD, GSH, and CAT. Furthermore, similar to Lipitor, oral administration of the extracts reduced inflammation markers such as TNF-α, serum CRP, IL-6, IL-1β, and leptin while increasing IL-10 and adiponectin levels. Histological observation revealed that extract administration improved hepatocyte and parenchymal structures and decreased lipid deposition. In conclusion, both Barhi and Ruthana seed extracts showed strong hepatoprotective, anti-inflammatory, and antioxidant effects against HFD-induced liver steatosis. And date seeds have other beneficial potential for prevention and treatment of various diseases, which can be studied in the future.     

Liver-directed microRNA-7a depletion induces nonalcoholic fatty liver disease by stabilizing YY1-mediated lipogenic pathways in zebrafish

Nonalcoholic fatty liver disease (NAFLD) has been associated with the function and changes in expression levels of microRNAs (miRs). MiR-7 has been proven to play an important role in many cellular processes; however, its functions in the context of liver lipogenesis remain unknown. We applied the microRNA-sponge (miR-SP) technology and generated transgenic miR-7a-SP models (hC7aSP and bC7aSP), which disrupted the activities of hepatic miR-7a and induced the early onset of NAFLD and nonalcoholic steatohepatitis (NASH) in zebrafish. We identified a novel miR-7a target, YY1, and demonstrated novel miR-7a functions to regulate zebrafish hepatic lipid metabolism by controlling YY1 stabilization through the regulation of the expression of lipogenic signaling pathways. Correspondingly, liver specific miR-7a depletion functionally promoted lipid accumulation in hC7ASP livers. NASH hC7aSP increased the expression of inflammatory genes (il-1b, il-6, tnf-α, ifn-γ, nfkb2, and NF-kB) and endoplasmic reticulum stress markers (atf6, ern2, ire1, perk, hspa5 and ddit3). Molecular analysis revealed that miR-7a-SP can stabilize YY1 expression and contribute to the accumulation of hepatic triglycerides by reducing the CHOP-10 expression in the hC7aSP and then inducing the transactivation of C/EBP-α and PPAR-γ expression. PPAR-γ antagonists and miR-7a mimic treatment ameliorate hC7aSP NASH phenotypes. Conclusion: Our results suggest that miR-7a-SP acts as a lipid enhancer by directly increasing YY1 stability to disrupt CHOP-10-dependent suppression of lipogenic pathways, resulting in increased lipid accumulation. MiR-7a expression improves liver steatosis and steatohepatitis in hC7aSPs, which suggests a novel strategy for the prevention and early treatment of NASH in humans.     

The sex-specific effects of blood lead,mercury, and cadmium levels on hepatic steatosis and fibrosis: Korean nationwide cross-sectional study

AimThe potential effects of heavy metals on non-alcoholic fatty liver disease (NAFLD) remain unknown. We investigated the sex-specific relationships of blood lead (BPb), mercury (BHg), and cadmium (BCd) levels with hepatic steatosis (HS) and fibrosis (HF).MethodWe included 4420 participants from the 2016–2017 Korea National Health and Nutrition Examination Survey. High-risk alcoholics and patients with chronic hepatitis B or C infections or liver cirrhosis were excluded. We calculated the hepatic steatosis index (HSI) and fibrosis-4 index (FIB-4) values; we defined the presence of HS and HF as an HSI ≥ 36 and FIB-4 score >2.67, respectively. We adjusted for age, smoking and alcohol consumption statuses, hypertension, obesity, diabetes, hypertriglyceridemia, and BPb, BHg, and BCd levels.ResultIn males (n = 1860), the HSI was correlated negatively with the BPb level and positively with the BHg level (both p < 0.01). The FIB-4 score was correlated positively with the BPb and BCd levels (both p < 0.01). In females (n = 2560), the HSI and FIB-4 score were correlated positively with the BPb, BHg, and BCd levels (all p < 0.01). After adjustments, the BHg level increased the risk of HS in both males (OR = 1.065, p = 0.003) and females (OR = 1.061, p = 0.048), and the BCd level increased the risk of HF in females (OR = 1.668, p = 0.012).ConclusionBlood heavy metal levels were generally correlated positively with the HSI and FIB4 score, more so in females than males. The BHg level was associated with HS in males and females, and the BCd level was associated with HF in females. Further studies on NAFLD progression according to heavy metal status and sex are warranted.     

Increased carbonylation of the lipid phosphatase PTEN contributes to Akt2 activation in a murine model of early alcohol-induced steatosis

The production of reactive aldehydes such as 4-hydroxynonenal (4-HNE) is a key event in the pathogenesis of alcoholic liver disease (ALD), which ranges from simple steatosis to fibrosis. The lipid phosphatase PTEN plays a central role in the regulation of lipid metabolism in the liver. In this study, the effects of chronic ethanol feeding and carbonylation on the PTEN signaling pathway were examined in a 9-week mouse feeding model for ALD. Chronic ethanol consumption resulted in altered redox homeostasis as evidenced by decreased GSH, decreased Trx1, and increased GST activity. Both PTEN expression and PTEN phosphorylation were significantly increased in the livers of ethanol-fed mice. Carbonylation of PTEN increased significantly in the ethanol-fed mice compared to pair-fed control animals, corresponding to decreased PTEN 3-phosphatase activity. Concomitantly, increased expression of Akt2 along with increased Akt phosphorylation at residues Thr³⁰⁸, Thr⁴⁵⁰, and Ser⁴⁷³ was observed resulting in increased Akt2 activity in the ethanol-fed animals. Akt2 activation corresponded to a decrease in cytosolic SREBP and ChREBP. Subsequent LC/MS/MS analysis of 4-HNE-modified recombinant human PTEN identified Michael addition adducts of 4-HNE on Cys⁷¹, Cys¹³⁶, Lys¹⁴⁷, Lys²²³, Cys²⁵⁰, Lys²⁵⁴, Lys³¹³, Lys³²⁷, and Lys³⁴⁴. Computational-based molecular modeling analysis of 4-HNE adducted to Cys⁷¹ near the active site and Lys³²⁷ in the C2 domain of PTEN suggested inhibition of enzyme catalysis via either stearic hindrance of the active-site pocket or prevention of C2 domain-dependent PTEN function. We hypothesize that 4-HNE-mediated PTEN inhibition contributes to the observed activation of Akt2, suggesting a possible novel mechanism of lipid accumulation in response to increased reactive aldehyde production during chronic ethanol administration in mice.     

An increase in liver PPARγ2 is an initial event to induce fatty liver in response to a diet high in butter: PPARγ2 knockdown improves fatty liver induced by high-saturated fat

The effects of a diet rich in saturated fat on fatty liver formation and the related mechanisms that induce fatty liver were examined. C57BL/6J mice were fed butter or safflower oil as a high-fat (HF) diet (40% fat calories) for 2, 4, 10, or 17 weeks. Although both HF diets induced similar levels of obesity, HF butter-fed mice showed a two to threefold increase in liver triacylglycerol (TG) concentration compared to HF safflower oil-fed mice at 4 or 10 weeks without hyperinsulinemia. At 4 weeks, increases in peroxisome proliferator-activated receptor γ2 (PPARγ2), CD36, and adipose differentiation-related protein (ADRP) mRNAs were observed in HF butter-fed mice; at 10 weeks, an increase in sterol regulatory element-binding protein-1c (SREBP-1c) was observed; at 17 weeks, these increases were attenuated. At 4 weeks, a single injection of adenoviral vector-based short hairpin interfering RNA against PPARγ2 in HF butter-fed mice reduced PPARγ protein and mRNA of its target genes (CD36 and ADRP) by 43%, 43%, and 39%, respectively, with a reduction in liver TG concentration by 38% in 5 days. PPARγ2 knockdown also reduced mRNAs in lipogenic genes (fatty-acid-synthase, stearoyl-CoA desaturase 1, acetyl-CoA carboxylase 1) without alteration of SREBP-1c mRNA. PPARγ2 knockdown reduced mRNAs in genes related to inflammation (CD68, interleukin-1β, tumor necrosis factor-α, and monocyte chemoattractant protein-1). In conclusion, saturated fatty acid-rich oil induced fatty liver in mice, and this was triggered initially by an increase in PPARγ2 protein in the liver, which led to increased expression of lipogenic genes. Inactivation of PPARγ2 may improve fatty liver induced by HF saturated fat.     

Interleukin-6 derived from cutaneous deficiency of stearoyl-CoA desaturase- 1 may mediate metabolic organ crosstalk among skin,adipose tissue and liver

Stearoyl-CoA desaturase 1 (SCD1), a lipogenic enzyme that adds a double bond at the delta 9 position of stearate (C18: 0) and palmitate (C16: 0), has been proven to be important in the development of obesity. Mice with skin-specific deficiency of SCD1 (SKO) display increased whole-body energy expenditure, which is protective against adiposity from a high-fat diet because it improves glucose clearance, insulin sensitivity, and hepatic steatosis. Of note, these mice also display elevated levels of the “pro-inflammatory” plasma interleukin-6 (IL-6). In whole skin of SKO mice, IL-6 mRNA levels are increased, and protein expression is evident in hair follicle cells and in keratinocytes. Recently, the well-known role of IL-6 in causing white adipose tissue lipolysis has been linked to indirectly activating the gluconeogenic enzyme pyruvate carboxylase 1 in the liver, thereby increasing hepatic glucose production. In this study, we suggest that skin-derived IL-6 leads to white adipose tissue lipolysis, which contributes to the lean phenotype of SKO mice without the incidence of meta-inflammation that is associated with IL-6 signaling.     

Steatosis induced by the accumulation of apolipoprotein A-I and elevated ROS levels in H-ras12V transgenic mice contributes to hepatic lesions

Hepatic steatosis is considered to have an important impact on liver tumorigenesis, despite a lack of clear experimental evidence. Histopathological analysis of H-ras12V transgenic mice showed liver lesions on a steatosis background had significantly higher incidence than on a non-steatosis background. Further investigation showed that apolipoprotein A-I was elevated and accumulated around fatty vacuoles. This elevated level of apolipoprotein A-I was coupled with an elevated level of H-ras12V protein and ROS. In conclusion, our results suggest that the expression of H-ras12V oncogene leads to elevated levels of ROS and apolipoprotein A-I that contribute to steatosis. The steatosis, in turn, promotes the development of hepatic lesions induced by H-ras12V oncogene.     

泛素连接酶gp78促进体外肝细胞脂肪变性的作用研究

目的:研究泛素连接酶gp78在体外肝细胞脂肪变性发生过程中的作用。方法:在小鼠肝细胞内转染携带gp78的质粒DNA,400μM油酸刺激肝细胞,油红O染色观察细胞内脂滴形成的情况;测定肝细胞内甘油三酯含量;western blot和RT-PCR检测细胞内gp78的表达水平。结果:与对照组相比,过表达gp78肝细胞内脂滴数目增多,体积增大,甘油三酯含量(4.6±1.56)mol/L升高;而沉默gp78肝细胞内脂滴数目减少,体积减小,甘油三酯含量(0.3±1.37)mol/L明显降低(P0.05)。结论:在肝细胞发生脂肪变性过程中,gp78可能发挥了重要的作用;而其发挥作用的机制还有待进一步研究。     

Role of peroxisome proliferator-activated receptor-α in fasting-mediated oxidative stress

The peroxisome proliferator-activated receptor-α (PPARα) regulates lipid homeostasis, particularly in the liver. This study was aimed at elucidating the relationship between hepatosteatosis and oxidative stress during fasting. Fasted Ppara-null mice exhibited marked hepatosteatosis, which was associated with elevated levels of lipid peroxidation, nitric oxide synthase activity, and hydrogen peroxide accumulation. Total glutathione (GSH), mitochondrial GSH, and the activities of major antioxidant enzymes were also lower in the fasted Ppara-null mice. Consequently, the number and extent of nitrated proteins were markedly increased in the fasted Ppara-null mice, although high levels of protein nitration were still detected in the fed Ppara-null mice while many oxidatively modified proteins were only found in the fasted Ppara-null mice. However, the role of inflammation in increased oxidative stress in the fasted Ppara-null mice was minimal based on the similar levels of tumor necrosis factor-α change in all groups. These results with increased oxidative stress observed in the fasted Ppara-null mice compared with other groups demonstrate a role for PPARα in fasting-mediated oxidative stress and that inhibition of PPARα functions may increase the susceptibility to oxidative damage in the presence of another toxic agent.     

CYP2E1 enhances ethanol-induced lipid accumulation but impairs autophagy in HepG2 E47 cells

The regulation and function of autophagy and lipid metabolism have recently been reported to be reciprocally related. Macroautophagy mediates the breakdown of lipids stored in lipid droplets. An inhibition of autophagy leads to the development of a fatty liver. We evaluated the ability of CYP2E1 to modulate the effects of ethanol on lipid accumulation and autophagy in vitro. The E47 HepG2 cell which expresses CYP2E1 was treated with ethanol at 50, 100 and 150 mM for 4 or 5 days. Ethanol-induced lipid accumulation and an increase of triglycerides (TG) in E47 cells to a greater extent than in control C34 cells which do not express CYP2E1. In contrast, autophagy (LC3 II/LC3 I ratio) was significantly induced by ethanol in C34 cells to a greater extent than in E47 cells. P62 was significantly increased in E47 cells after ethanol treatment. Thus, there is a reciprocal relationship between the effects of ethanol on lipid accumulation and autophagy in the CYP2E1-expressing cells. Inhibition of autophagy by 3-methyladenine (3MA), increased lipid accumulation and TG levels in C34 cells which display elevated autophagy, but enhanced lipid accumulation and TG level to a lesser extent in E47 cells which displayed lower autophagy. Ethanol induced CYP2E1 activity and oxidative stress in E47 cells compared with C34 cells. These experiments suggest that the expression of CYP2E1 may impair autophagy formation which contributes to lipid accumulation in the liver. We hypothesize that CYP2E1-induced oxidative stress promotes the accumulation of lipid droplets by ethanol and this may be responsible for the suppression of autophagy in the liver.