Non-alcoholic fatty liver disease is associated with high prevalence of gastro-oesophageal reflux symptoms

Background

Gastro-oesophageal reflux symptoms are usually reported by patients with obesity and metabolic syndrome. Aim of this study was to assess the prevalence and clinical characteristics of gastro-oesophageal reflux symptoms in subjects with non-alcoholic fatty liver disease.

Methods

Cross-sectional, case–control study of 185 consecutive patients with non-alcoholic fatty liver disease and an age- and sex-matched control group of 112 healthy volunteers. Participants were interviewed with the aid of a previously validated questionnaire to assess lifestyle and reflux symptoms in the 3 months preceding enrolment. Odds ratios were determined before and after adjustment for body mass index, increased waist circumference, physical activity, metabolic syndrome and proton pump inhibitors and/or antiacid medication.

Results

The prevalence of heartburn and/or regurgitation and of at least one of gastro-oesophageal reflux symptoms was significantly higher in the non-alcoholic fatty liver disease group. Non-alcoholic fatty liver disease subjects were associated to higher prevalence of heartburn (adjusted odds ratios: 2.17, 95% confidence intervals: 1.16–4.04), regurgitation (adjusted odds ratios: 2.61, 95% confidence intervals: 1.24–5.48) and belching (adjusted odds ratios: 2.01, 95% confidence intervals: 1.12–3.59) and had higher prevalence of at least one GER symptom (adjusted odds ratios: 3.34, 95% confidence intervals: 1.76–6.36).

Conclusion

Non-alcoholic fatty liver disease is associated with a higher prevalence of gastro-oesophageal reflux symptoms.     

高脂饲料诱发非酒精性脂肪肝实验研究

目的探讨正常饮食和高脂肪饮食对小鼠体重、血糖、葡萄糖耐受、血脂、脂肪肝的影响。方法雄性C57BL/6小鼠随机分为MD10%和MD45%脂肪含量饲料组,喂养3个月,检测动物体重、血糖、葡萄糖耐受、血脂,以及主要脏器重量及肝脏脂质含量。结果与正常组（MD10%脂肪含量）相比,高脂组（MD45%脂肪含量）动物体重显著增加,出现明显的糖耐量异常和血脂水平升高,同时伴有肝脏脂质含量增加。结论高脂饮食对非酒精性脂肪肝有较强的诱导作用。     

Bromelain activates the AMP-activated protein kinase-autophagy pathway to alleviate hepatic lipid accumulation

Bromelain, a cysteine protease found in pineapple, is known to exert protective effects against non-alcoholic fatty liver disease (NAFLD); however, the underlying mechanism is unclear. In this study, we aimed to investigate the molecular mechanisms underlying the beneficial effects of bromelain using in vivo and in vitro models. C57BL/6 mice were fed a high-fat diet (HFD) with or without bromelain (20 mg/kg/day) for 12 weeks. We found that treatment with bromelain alleviated hepatic lipid accumulation accompanied by the activation of AMP-activated protein kinase (AMPK) and autophagy flux, as evidenced by the elevated levels of phosphorylated AMPK, ATG5, ATG7, LC3-II, and lysosome-associated membrane protein 2 (LAMP2), and the decreased levels of p62 in the liver of HFD-fed mice. In human hepatoma Huh 7 cells, bromelain prevented oleic acid (OA)-induced lipid accumulation and increased the levels of phosphorylated AMPK, ATG5, ATG7, LC3-II, and LAMP2 but decreased the levels of p62. Inhibition of AMPK and autophagy flux by specific inhibitors or small interfering RNAs suppressed bromelain-mediated protective effect on lipid accumulation. Moreover, inhibition of AMPK activity abolished the activation of autophagy flux in OA-treated hepatocytes. Collectively, these findings suggest a new molecular mechanism involving the AMPK-autophagy pathway through which bromelain confers protection against the deregulation of lipid metabolism in the liver.     

Accumulation of lipids and oxidatively damaged DNA in hepatocytes exposed to particles

Exposure to particles has been suggested to generate hepatosteatosis by oxidative stress mechanisms. We investigated lipid accumulation in cultured human hepatocytes (HepG2) and rat liver after exposure to four different carbon-based particles. HepG2 cells were exposed to particles for 3 h and subsequently incubated for another 18 h to manifest lipid accumulation. In an animal model of metabolic syndrome we investigated the association between intake of carbon black (CB, 14 nm) particles and hepatic lipid accumulation, inflammation and gene expression of Srebp-1, Fasn and Scd-1 involved in lipid synthesis. There was a concentration-dependent increase in intracellular lipid content after exposure to CB in HepG2 cells, which was only observed after co-exposure to oleic/palmitic acid. Similar results were observed in HepG2 cells after exposure to diesel exhaust particles, fullerenes C₆₀ or pristine single-walled carbon nanotubes. All four types of particles also generated oxidatively damaged DNA, assessed as formamidopyrimidine DNA glycosylase (FPG) sensitive sites, in HepG2 cells after 3 h exposure. The animal model of metabolic syndrome showed increased lipid load in the liver after one oral exposure to 6.4 mg/kg of CB in lean Zucker rats. This was not associated with increased iNOS staining in the liver, indicating that the oral CB exposure was associated with hepatic steatosis rather than steatohepatitis. The lipid accumulation did not seem to be related to increased lipogenesis because there were unaltered gene expression levels in both the HepG2 cells and rat livers. Collectively, exposure to particles is associated with oxidative stress and steatosis in hepatocytes.     

The Influence of Dietary Fat on Liver Fat Accumulation

Obesity is a known risk factor for the development of non-alcoholic fatty liver disease (NAFLD); however, it has been suggested that dietary fat, both amount and composition, may play a pivotal role in its development, independent of body fatness. Studies that have investigated the role of dietary fat on liver fat accumulation are reasonably sparse. We review here the available work that has investigated the impact of dietary fat: amount, composition and frequency, on liver fat accumulation in human observational and intervention studies. Overall, it would seem that total calorie consumption, rather than dietary fat composition, is an important factor in the development of fatty liver disease in humans.     

白芍总苷对NAFLD大鼠肝脏的保护作用及其机制研究

目的研究白芍总苷对NAFLD模型大鼠肝脏保护的机制。方法 SD大鼠50只,随机分为正常对照组10只,模型组40只。高脂饲料喂养建模后,模型组随机分为模型对照组、非诺贝特组、白芍总苷高剂量组、白芍总苷低剂量组各10只。连续灌胃给药4周后,测定大鼠血清中ALT、AST、GST、SOD和GSH-PX酶的活性及MDA含量;测定血清中IL-1、TNF-α和TGF-β的水平;各组取肝脏做HE染色,观察肝脏组织学病变。结果与正常对照组比较,NAFLD模型对照组大鼠ALT、AST、GST活性和IL-1、TNF-α、TGF-β含量显著升高,经非诺贝特和白芍总苷干预后,模型组大鼠的ALT、AST、GST活性和IL-1、TNF-α、TGF-β含量均降低回正常水平,差异有统计学意义(P<0.05);与正常对照组比较,NALFD模型大鼠SOD、GSH-PX活性显著降低,MDA含量明显升高,干预治疗后,模型组大鼠SOD、GSH-PX活性大大提高,MDA含量显著降低(P<0.05)。结论白芍总苷对高脂引起的NAFLD模型大鼠有肝脏保护作用,其作用机制可能与其提高抗氧化能力、降低异常细胞因子水平有关。