Obesity-associated nonalcoholic fatty liver disease

Nonalcoholic Fatty Liver Disease Review: Diagnosis, Treatment, and Outcomes

Nonalcoholic fatty liver disease (NAFLD) is the most common cause of abnormal serum aminotransferase levels in both developed and developing countries. Patients with nonalcoholic steatohepatitis (NASH), a subset of NAFLD, are at risk for progressive liver disease and in need of effective treatment options. A practical approach may be pursued by identifying patients with NAFLD with the highest likelihood for histologic evidence of NASH. Despite decades of clinical trials, no single treatment can be recommended to all patients with NASH. Importantly, there is no evidence that pioglitazone or vitamin E improves fibrosis. Bariatric surgeries may improve hepatic histology in morbidly obese patients with NASH, although randomized clinical trials are lacking. Currently, NASH is the second leading etiology of liver disease among adults awaiting liver transplantation in the United States. The primary and secondary prevention of NAFLD may require aggressive strategies for managing obesity, diabetes, and metabolic syndrome.

NKT cell modulates NAFLD potentiation of metabolic oxidative stress-induced mesangial cell activation and proximal tubular toxicity

Obesity and nonalcoholic fatty liver disease (NAFLD) are associated with the development and progression of chronic kidney disease. We recently showed that NAFLD induces liver-specific cytochrome P-450 (CYP)2E1-mediated metabolic oxidative stress after administration of the CYP2E1 substrate bromodichloromethane (BDCM) (Seth RK, Das S, Kumar A, Chanda A, Kadiiska MB, Michelotti G, Manautou J, Diehl AM, Chatterjee S. Toxicol Appl Pharmacol 274: 42-54, 2014; Seth RK, Kumar A, Das S, Kadiiska MB, Michelotti G, Diehl AM, Chatterjee S. Toxicol Sci 134:291-303, 2013). The present study examined the effects of CYP2E1-mediated oxidative stress in NAFLD leading to kidney toxicity. Mice were fed a high-fat diet for 12 wk to induce NAFLD. NAFLD mice were exposed to BDCM, a CYP2E1 substrate, for 4 wk. NAFLD + BDCM increased CYP2E1-mediated lipid peroxidation in proximal tubular cells compared with mice with NAFLD alone or BDCM-treated lean mice, thus ruling out the exclusive role of BDCM. Lipid peroxidation increased IL-1β, TNF-α, and interferon-γ. In parallel, mesangial cell activation was observed by increased α-smooth muscle actin and transforming growth factor-β, which was blocked by the CYP2E1 inhibitor diallyl sulphide both in vivo and in vitro. Mice lacking natural killer T cells (CD1d knockout mice) showed elevated (>4-fold) proinflammatory mediator release, increased Toll-like receptor (TLR)4 and PDGF2 mRNA, and mesangial cell activation in the kidney. Finally, NAFLD CD1D knockout mice treated with BDCM exhibited increased high mobility group box 1 and Fas ligand levels and TUNEL-positive nuclei, indicating that higher cell death was attenuated in TLR4 knockout mice. Tubular cells showed increased cell death and cytokine release when incubated with activated mesangial cells. In summary, an underlying condition of progressive NAFLD causes renal immunotoxicity and aberrant glomerular function possibly through high mobility group box 1-dependent TLR4 signaling and mesangial cell activation, which, in turn, is modulated by intrinsic CD1D-dependent natural killer T cells.

Epigenetics of obesity: beyond the genome sequence

PURPOSE OF REVIEW

After the study of the gene code as a trigger for obesity, epigenetic code has appeared as a novel tool in the diagnosis, prognosis and treatment of obesity, and its related comorbidities. This review summarizes the status of the epigenetic field associated with obesity, and the current epigenetic-based approaches for obesity treatment.

RECENT FINDINGS

Thanks to technical advances, novel and key obesity-associated polymorphisms have been described by genome-wide association studies, but there are limitations with their predictive power. Epigenetics is also studied for disease association, which involves decoding of the genome information, transcriptional status and later phenotypes. Obesity could be induced during adult life by feeding and other environmental factors, and there is a strong association between obesity features and specific epigenetic patterns. These patterns could be established during early life stages, and programme the risk of obesity and its comorbidities during adult life. Furthermore, recent studies have shown that DNA methylation profile could be applied as biomarkers of diet-induced weight loss treatment.

SUMMARY

High-throughput technologies, recently implemented for commercial genetic test panels, could soon lead to the creation of epigenetic test panels for obesity. Nonetheless, epigenetics is a modifiable risk factor, and different dietary patterns or environmental insights during distinct stages of life could lead to rewriting of the epigenetic profile.

Duodenal jejunal bypass attenuates non-alcoholic fatty liver disease in western diet-obese rats

PURPOSE

To evaluate the effects of duodenal-jejunal bypass (DJB) on serum and hepatic profiles of obese rats fed on a western diet (WD).

METHODS

Twenty eight male Wistar rats were fed a standard rodent chow diet (CTL group) or WD ad libitum. After 10 weeks, WD rats were submitted to sham (WD SHAM) or duodenal-jejunal bypass (WD DJB). Body weight, fat pad depots, glycemia, insulinemia, HOMA-IR, TyG, lipids profile and hepatic analyses were evaluated two months after surgery.

RESULTS

The WD SHAM group presented greater obesity, hyperglycemia, hyperinsulinemia, insulin resistance, hypertriglyceridemia and hepatic steatosis than the CTL group. WD DJB rats presented decreased serum glucose and insulin resistance, when compared to WD SHAM animals, without changes in insulinemia. In addition, DJB surgery normalized serum TG and attenuated TG accumulation and steatosis in the liver of the WD DJB group. Hepatic ACC and FAS protein expressions were similar in all groups.

CONCLUSION

Duodenal-jejunal bypass attenuates hepatic parameters of non-alcoholic fatty liver disease in obese rats fed on a western diet.

Proximal Roux-en-Y gastric bypass alters drug absorption pattern but not systemic exposure of CYP3A4 and P-glycoprotein substrates

STUDY OBJECTIVES

To evaluate the effect of Roux-en-Y gastric bypass surgery (RYGB) on the pharmacokinetics of midazolam (a CYP3A4 substrate) and digoxin (a P-glycoprotein substrate).

DESIGN

Prospective, nonblinded, longitudinal, single-dose pharmacokinetic study in three phases: presurgery baseline and postoperative assessments at 3 and 12 months.

PATIENTS

Twelve obese patients meeting current standards for bariatric surgery.

MEASUREMENTS AND MAIN RESULTS

At each study visit, patients received a single dose of oral digoxin and midazolam at 8 a.m. Blood samples were collected at regular intervals for 24 hours after dosing. Continuous 12-lead electrocardiogram (EKG), heart rate, blood pressure, and respiratory rate were monitored, and pharmacokinetic parameters from the three visits were compared. The peak plasma concentration (Cmax ) of midazolam increased by 66% and 71% at 3- and 12-month post-RYGB (p=0.017 and p=0.001, respectively), whereas the median time to peak concentration (Tmax ) was reduced by 50%. The mean Cmax for 1'-hydroxymidazolam increased by 87% and 80% at 3 and 12 months (p=0.001 and p<0.001, respectively). However, neither the area under the concentration-time curve (AUC) for midazolam nor the metabolite-to-parent AUC ratio changed significantly over time. For digoxin, the median Tmax decreased from 40 minutes at baseline to 30 and 20 minutes at 3 and 12 months, respectively. The mean AUC for digoxin, heart rate, and EKG patterns were similar across the three study phases.

CONCLUSION

Contemporary proximal RYGB increases the rate of drug absorption without significantly changing the overall exposure to midazolam and digoxin. The Cmax of a CYP3A4 substrate with a high extraction ratio was substantially increased after RYGB.

Diosgenin, 4-hydroxyisoleucine, and fiber from fenugreek: mechanisms of actions and potential effects on metabolic syndrome

Metabolic syndrome and its complications continue to rise in prevalence and show no signs of abating in the immediate future. Therefore, the search for effective treatments is a high priority in biomedical research. Products derived from botanicals have a time-honored history of use in the treatment of metabolic diseases including type 2 diabetes. Trigonella foenum-graecum, commonly known as fenugreek, is an annual herbaceous plant that has been a staple of traditional herbal medicine in many cultures. Although fenugreek has been studied in both clinical and basic research settings, questions remain about its efficacy and biologic mechanisms of action. Diosgenin, 4-hydroxyisoleucine, and the fiber component of the plant are the most intensively studied bioactive constituents present in fenugreek. These compounds have been demonstrated to exert beneficial effects on several physiologic markers including glucose tolerance, inflammation, insulin action, liver function, blood lipids, and cardiovascular health. Although insights into the molecular mechanisms underlying the favorable effects of fenugreek have been gained, we still do not have definitive evidence establishing its role as a therapeutic agent in metabolic disease. This review aims to summarize the currently available evidence on the physiologic effects of the 3 best-characterized bioactive compounds of fenugreek, with particular emphasis on biologic mechanisms of action relevant in the context of metabolic syndrome.

Ipragliflozin, an SGLT2 inhibitor, exhibits a prophylactic effect on hepatic steatosis and fibrosis induced by choline-deficient l-amino acid-defined diet in rats

Ipragliflozin is a selective sodium glucose cotransporter 2 (SGLT2) inhibitor that increases urinary glucose excretion by inhibiting renal glucose reabsorption and thereby causes a subsequent antihyperglycemic effect. As nonalcoholic fatty liver disease (NAFLD), including nonalcoholic steatohepatitis (NASH), is closely linked to metabolic diseases such as obesity and diabetes, we investigated the effect of ipragliflozin on NAFLD in rats fed a choline-deficient l-amino acid-defined (CDAA) diet. Five weeks after starting the CDAA diet, rats exhibited hepatic triglyceride (TG) accumulation, fibrosis, and mild inflammation. Repeated oral administration of ipragliflozin (3mg/g, once daily for 5 weeks) prevented both hepatic TG accumulation (188 vs.290 mg/g tissue vehicle-treated group; P<0.001) and large lipid droplet formation. Further, ipragliflozin exerted a prophylactic effect on liver fibrosis, as indicated by a marked decrease in hydroxyproline content and fibrosis score. Pioglitazone, which is known to be effective on hepatic fibrosis in CDAA diet-fed rats as well as NASH patients with type 2 diabetes mellitus (T2DM), also exerted a mild prophylactic effect on fibrosis, but not on hepatic TG accumulation or inflammation. In conclusion, ipragliflozin prevented hepatic TG accumulation and fibrosis in CDAA-diet rats. These findings suggest the therapeutic potential of ipragliflozin for patients with NAFLD.

Micro-RNA 21 inhibition of SMAD7 enhances fibrogenesis via leptin-mediated NADPH oxidase in experimental and human nonalcoholic steatohepatitis

Hepatic fibrosis in nonalcoholic steatohepatitis (NASH) is the common pathophysiological process resulting from chronic liver inflammation and oxidative stress. Although significant research has been carried out on the role of leptin-induced NADPH oxidase in fibrogenesis, the molecular mechanisms that connect the leptin-NADPH oxidase axis in upregulation of transforming growth factor (TGF)-β signaling have been unclear. We aimed to investigate the role of leptin-mediated upregulation of NADPH oxidase and its subsequent induction of micro-RNA 21 (miR21) in fibrogenesis. Human NASH livers and a high-fat (60% kcal) diet-fed chronic mouse model, where hepatotoxin bromodichloromethane was used to induce NASH, were used for this study. To prove the role of the leptin-NADPH oxidase-miR21 axis, mice deficient in genes for leptin, p47phox, and miR21 were used. Results showed that wild-type mice and human livers with NASH had increased oxidative stress, increased p47phox expression, augmented NF-κB activation, and increased miR21 levels. These mice and human livers showed increased TGF-β, SMAD2/3-SMAD4 colocalizations in the nucleus, increased immunoreactivity against Col1α, and α-SMA with a concomitant decrease in protein levels of SMAD7. Mice that were deficient in leptin or p47phox had decreased activated NF-κB and miR21 levels, suggesting the role of leptin and NADPH oxidase in inducing NF-κB-mediated miR21 expression. Further miR21 knockout mice had decreased colocalization events of SMAD2/3-SMAD4 in the nucleus, increased SMAD7 levels, and decreased fibrogenesis. Taken together, the studies show the novel role of leptin-NADPH oxidase induction of miR21 as a key regulator of TGF-β signaling and fibrogenesis in experimental and human NASH.

Identification of differentially expressed genes related to metabolic syndrome induced with high-fat diet in E3 rats

Understanding the genes differentially expressing in aberrant organs of metabolic syndrome (MetS) facilitates the uncovering of molecular mechanisms and the identification of novel therapeutic targets for the disease. This study aimed to identify differentially expressed genes related to MetS in livers of E3 rats with high-fat-diet-induced metabolic syndrome (HFD-MetS). E3 rats were fed with high-fat diet for 24 weeks to induce MetS. Then, suppression subtractive hybridization (SSH) technology was used to identify the genes differentially expressed between HFD-MetS and control E3 rat livers. Twenty positive recombinant clones were chosen randomly from forward subtractive library and sent to sequence. BLAST analysis in GenBank database was used to determine the property of each cDNA fragment. In total, 11 annotated genes, 3 ESTs, and 2 novel gene fragments were identified by SSH technology. The expression of four genes (Alb, Pip4k2a, Scd1, and Tf) known to be associated with MetS and other five genes (Eif1, Rnase4, Rps12, Rup2, and Tmsb4) unknown to be relevant to MetS was significantly up-regulated in the livers of HFD-MetS E3 rats compared with control rats using real-time quantitative PCR (RT-qPCR). By analyzing the correlations between the expression of these nine genes and serum concentrations of TG, Tch, HDL-C, and LDL-C, we found that there were significant positive correlations between TG and the expression of five genes (Alb, Eif1, Pip4k2a, Rps12, and Tmsb4x), Tch and three genes (Rnase4, Scd1, and Tmsb4x), and LDL-C and two genes (Rnase4 and Scd1), as well there were significant negative correlations between HDL-C and the expression of three genes (Rup2, Scd1, and Tf). This study provides important clues for unraveling the molecular mechanisms of MetS.

The Effect of Chlorella vulgaris Supplementation on Liver En-zymes, Serum Glucose and Lipid Profile in Patients with Non-Alcoholic Fatty Liver Disease

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) is becoming a public health problem worldwide and using microalgae is a new approach on its treatment. The aim of this study was to investigate the effect of Chlorella vulgaris supplementation on liver enzymes, serum glucose and lipid profile in patients with NAFLD.

METHODS

This double-blind randomized placebo-controlled clinical trial was conducted on 60 NAFLD patients from specialized clinics of Tabriz University of Medical Sciences from December 2011 to July 2012. The subjects were randomly allocated into 2 groups: 1) "intervention" (n=30) received 400 mg/day vitamin E plus four 300 mg tablets of Chlorella vulgaris and, 2) "placebo" (n=30) received 400 mg/day vitamin E and four placebo tablets per day for 8 weeks. Weight, liver enzymes and metabolic factors were assessed in fasting serum and dietary data was collected at baseline and end of the study.

RESULTS

Weight, liver enzymes, fasting blood sugar (FBS) and lipid profile decreased significantly in both groups (P<0.05). The differences in weight, ALP and FBS between the two groups were statistically significant (P=0.01, P=0.04 and P=0.02, respectively).

CONCLUSION

C. vulgaris seems to improve FBS and lipid profile and therefore could be considered as an effective complementary treatment in NAFLD.