A Mitochondrial VDAC1-Based Peptide Greatly Suppresses Steatosis and NASH-Associated Pathologies in a Mouse Model.
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ABSTRACT:
SUBMITTER: Pittala S
PROVIDER: S-EPMC6822236 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:Mesenchymal stromal cell (MSC) transplantation ameliorated hepatic lipid load; tissue inflammation; and fibrosis in rodent animal models of non-alcoholic steatohepatitis (NASH) by as yet largely unknown mechanism(s). In a mouse model of NASH; we transplanted bone marrow-derived MSCs into the livers; which were analyzed one week thereafter. Combined metabolomic and proteomic data were applied to weighted gene correlation network analysis (WGCNA) and subsequent identification of key drivers. Livers were analyzed histologically and biochemically. The mechanisms of MSC action on hepatocyte lipid accumulation were studied in co-cultures of hepatocytes and MSCs by quantitative image analysis and immunocytochemistry. WGCNA and key driver analysis revealed that NASH caused the impairment of central carbon; amino acid; and lipid metabolism associated with mitochondrial and peroxisomal dysfunction; which was reversed by MSC treatment. MSC improved hepatic lipid metabolism and tissue homeostasis. In co-cultures of hepatocytes and MSCs; the decrease of lipid load was associated with the transfer of mitochondria from the MSCs to the hepatocytes via tunneling nanotubes (TNTs). Hence; MSCs may ameliorate lipid load and tissue perturbance by the donation of mitochondria to the hepatocytes. Thereby; they may provide oxidative capacity for lipid breakdown and thus promote recovery from NASH-induced metabolic impairment and tissue injury.
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Project description:Arazyme, a metalloprotease from the spider Nephila clavata, exerts hepatoprotective activity in CCL4-induced acute hepatic injury. This study investigated the hepatoprotective effects in high-fat diet (HFD)-induced non-alcoholic fatty liver disease-like C57BL/6J mice. The mice were randomly divided into four groups (n = 10/group): the normal diet group, the HFD group, the arazyme group (HFD with 0.025% arazyme), and the milk thistle (MT) group (HFD with 0.1% MT). Dietary supplementation of arazyme for 13 weeks significantly lowered plasma triglyceride (TG) and non-esterified fatty acid levels. Suppression of HFD-induced hepatic steatosis in the arazyme group was caused by the reduced hepatic TG and total cholesterol (TC) contents. Arazyme supplementation decreased hepatic lipogenesis-related gene expression, sterol regulatory element-binding transcription protein 1 (Srebf1), fatty acid synthase (Fas), acetyl-CoA carboxylase 1 (Acc1), stearoyl-CoA desaturase-1 (Scd1), Scd2, glycerol-3-phosphate acyltransferase (Gpam), diacylglycerol O-acyltransferase 1 (Dgat1), and Dgat2. Arazyme directly reduced palmitic acid (PA)-induced TG accumulation in HepG2 cells. Arazyme suppressed macrophage infiltration and tumor necrosis factor ? (Tnfa), interleukin-1? (Il1b), and chemokine-ligand-2 (Ccl2) expression in the liver, and inhibited secretion of TNF? and expression of inflammatory mediators, Tnfa, Il1b, Ccl2, Ccl3, Ccl4, and Ccl5, in PA-induced RAW264.7 cells. Arazyme effectively protected hepatic steatosis and steatohepatitis by inhibiting SREBP-1-mediated lipid accumulation and macrophage-mediated inflammation.
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Project description:Low testosterone (T), a major cause of male hypogonadism and infertility, is linked to mood changes, fatigue, osteoporosis, reduced bone-mass index, and aging. The treatment of choice, T replacement therapy, has been linked with increased risk for prostate cancer and luteinizing hormone (LH) suppression, and shown to lead to infertility, cardiovascular diseases, and obesity. Alternate methods to induce T with lower side effects are desirable. In search of the mechanisms regulating T synthesis in the testes, we identified the 14-3-3? protein adaptor as a negative regulator of steroidogenesis. Steroidogenesis begins in mitochondria. 14-3-3? interacts with the outer mitochondrial membrane voltage-dependent anion channel (VDAC1) protein, forming a scaffold that limits the availability of cholesterol for steroidogenesis. We report the development of a tool able to induce endogenous T formation. Peptides able to penetrate testes conjugated to 14-3-3? site of interaction with VDAC1 blocked 14-3-3?-VDAC1 interactions while at the same time increased VDAC1-translocator protein (18?kDa) interactions that induced steroid formation in rat testes, leading to increased serum T levels. These peptides rescued intratesticular and serum T formation in adult male rats treated with gonadotropin-releasing hormone antagonist, which dampened LH and T production.
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Project description:Background and aimsIn clinical and experimental NASH, the origin of the scar-forming myofibroblast is the HSC. We used foz/foz mice on a Western diet to characterize in detail the phenotypic changes of HSCs in a NASH model.Approach and resultsWe examined the single-cell expression profiles (scRNA sequencing) of HSCs purified from the normal livers of foz/foz mice on a chow diet, in NASH with fibrosis of foz/foz mice on a Western diet, and in livers during regression of NASH after switching back to a chow diet. Selected genes were analyzed using immunohistochemistry, quantitative real-time PCR, and short hairpin RNA knockdown in primary mouse HSCs. Our analysis of the normal liver identified two distinct clusters of quiescent HSCs that correspond to their acinar position of either pericentral vein or periportal vein. The NASH livers had four distinct HSC clusters, including one representing the classic fibrogenic myofibroblast. The three other HSC clusters consisted of a proliferating cluster, an intermediate activated cluster, and an immune and inflammatory cluster. The livers with NASH regression had one cluster of inactivated HSCs, which was similar to, but distinct from, the quiescent HSCs.ConclusionsAnalysis of single-cell RNA sequencing in combination with an interrogation of previous studies revealed an unanticipated heterogeneity of HSC phenotypes under normal and injured states.
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Project description:Mutations in superoxide dismutase (SOD1) cause amyotrophic lateral sclerosis (ALS), a neurodegenerative disease characterized by loss of motor neurons. With conformation-specific antibodies, we now demonstrate that misfolded mutant SOD1 binds directly to the voltage-dependent anion channel (VDAC1), an integral membrane protein imbedded in the outer mitochondrial membrane. This interaction is found on isolated spinal cord mitochondria and can be reconstituted with purified components in vitro. ADP passage through the outer membrane is diminished in spinal mitochondria from mutant SOD1-expressing ALS rats. Direct binding of mutant SOD1 to VDAC1 inhibits conductance of individual channels when reconstituted in a lipid bilayer. Reduction of VDAC1 activity with targeted gene disruption is shown to diminish survival by accelerating onset of fatal paralysis in mice expressing the ALS-causing mutation SOD1(G37R). Taken together, our results establish a direct link between misfolded mutant SOD1 and mitochondrial dysfunction in this form of inherited ALS.
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Project description:Nonalcoholic fatty liver disease (NAFLD) and its evolution to inflammatory steatohepatitis (NASH) are the most common causes of chronic liver damage and transplantation that are reaching epidemic proportions due to the upraising incidence of metabolic syndrome, obesity, and diabetes. Currently, there is no approved treatment for NASH. The mitochondrial citrate carrier, Slc25a1, has been proposed to play an important role in lipid metabolism, suggesting a potential role for this protein in the pathogenesis of this disease. Here, we show that Slc25a1 inhibition with a specific inhibitor compound, CTPI-2, halts salient alterations of NASH reverting steatosis, preventing the evolution to steatohepatitis, reducing inflammatory macrophage infiltration in the liver and adipose tissue, while starkly mitigating obesity induced by a high-fat diet. These effects are differentially recapitulated by a global ablation of one copy of the Slc25a1 gene or by a liver-targeted Slc25a1 knockout, which unravel dose-dependent and tissue-specific functions of this protein. Mechanistically, through citrate-dependent activities, Slc25a1 inhibition rewires the lipogenic program, blunts signaling from peroxisome proliferator-activated receptor gamma, a key regulator of glucose and lipid metabolism, and inhibits the expression of gluconeogenic genes. The combination of these activities leads not only to inhibition of lipid anabolic processes, but also to a normalization of hyperglycemia and glucose intolerance as well. In summary, our data show for the first time that Slc25a1 serves as an important player in the pathogenesis of fatty liver disease and thus, provides a potentially exploitable and novel therapeutic target.
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