Guanine Nucleotide-Binding Protein G(i) Subunit Alpha 2 Exacerbates NASH Progression by Regulating Peroxiredoxin 1-Related Inflammation and Lipophagy.

BACKGROUND AND AIMS: NASH is an advanced stage of liver disease accompanied by lipid accumulation, inflammation, and liver fibrosis. Guanine nucleotide-binding protein G(i) subunit alpha-2 (GNAI2) is a member of the "inhibitory" class of α-subunits, and recent studies showed that Gnai2 deficiency is known to cause reduced weight in mice. However, the role of GNAI2 in hepatocytes, particularly in the context of liver inflammation and lipid metabolism, remains to be elucidated. Herein, we aim to ascertain the function of GNAI2 in hepatocytes and its impact on the development of NASH. APPROACH AND RESULTS: Human liver tissues were obtained from NASH patients and healthy persons to evaluate the expression and clinical relevance of GNAI2. In addition, hepatocyte-specific Gnai2-deficient mice (Gnai2hep-/- ) were fed either a Western diet supplemented with fructose in drinking water (WDF) for 16 weeks or a methionine/choline-deficient diet (MCD) for 6 weeks to investigate the regulatory role and underlying mechanism of Gnai2 in NASH. GNAI2 was significantly up-regulated in liver tissues of patients with NASH. Following feeding with WDF or MCD diets, livers from Gnai2hep-/- mice had reduced steatohepatitis with suppression of markers of inflammation and an increase in lipophagy compared to Gnai2flox/flox mice. Toll-like receptor 4 signals through nuclear factor kappa B to trigger p65-dependent transcription of Gnai2. Intriguingly, immunoprecipitation, immunofluorescence, and mass spectrometry identified peroxiredoxin 1 (PRDX1) as a binding partner of GNAI2. Moreover, the function of PRDX1 in the suppression of TNF receptor-associated factor 6 ubiquitin-ligase activity and glycerophosphodiester phosphodiesterase domain-containing 5-related phosphatidylcholine metabolism was inhibited by GNAI2. Suppression of GNAI2 combined with overexpression of PRDX1 reversed the development of steatosis and fibrosis in vivo. CONCLUSIONS: GNAI2 is a major regulator that leads to the development of NASH. Thus, inhibition of GNAI2 could be an effective therapeutic target for the treatment of NASH.

Modulation of IR as a therapeutic target to prevent NASH using NRF from Diceratella elliptica (DC.) jonsell. Strong Nrf2 and leptin inducer as well as NF-kB inhibitor.

BACKGROUND: Insulin resistance (IR) and lipotoxicity were evidenced as the major nonalcoholic steatohepatitis (NASH) initiators. However, absence of the effective treatment against NASH progression raised our aim to discover a new promising insulin modulator and NSH preventer. PURPOSE: Our study aimed to extract and prepare a nitriles rich fraction (NRF) from Diceratella elliptica (DC.) Jonsell, investigate its insulin-sensitizing & anti-NASH potentialities and address its molecular targets in IR-NASH pathogenesis. STUDY DESIGN: NRF was prepared using natural autolysis method and compounds were identified. Then, seventy male Wistar rats were feed high fat diet (HFD) or normal pellets for 35 days. In day 14th, HFD rats were injected by Streptozotocin (STZ) once and treatment was started in day 21st with either NRF (30, 60 and 120 mg/kg; orally) or pioglitazone (PioG) (10 mg/kg; i.p) beside HFD. While, NRF-alone rats were treated with NRF (120 mg/kg; orally) beside the normal pellets. Body weight, glucose homeostasis, hepatopathological examinations were performed. METHODS: Gas liquid chromatography-mass spectrophotometry (GLC/MS) was used for compounds' identification while spectrophotometer was used for total glucosinolates (GLS) quantification. Also, the biochemical and molecular investigations concerned with liver lipotoxicity, oxidative stress, inflammation and insulin signaling pathway were investigated and confirmed with the computational prediction of the major compounds' targets. RESULTS: Butenyl and benzyl GLS were the major along with other volatile compounds. NRF had significantly increased the insulin sensitivity and improved NASH-hisptopathology showing hepatoprotective effect. While, the fraction's anti-NASH potentiality was evidenced in the normalized hepatic steatosis markers, inflammation and oxidative stress key transcriptional factors resulting in induction of insulin receptor substrates (IRSs) phosphorylation and its downstream effectors. CONCLUSION: NRF has reversed IR, stimulated leptin secretion and prevented NASH initiation showing promising anti-NASH and anti-fibrotic effects.