scholarly journals Regulation of mitochondrial trifunctional protein modulates nonalcoholic fatty liver disease in mice

2018 ◽  
Vol 59 (6) ◽  
pp. 967-973 ◽  
Author(s):  
Fatiha Nassir ◽  
Justin J. Arndt ◽  
Sarah A. Johnson ◽  
Jamal A. Ibdah
Keyword(s):  
Liver Disease ◽  
Fatty Liver ◽  
Nonalcoholic Fatty Liver Disease ◽  
Hepatic Steatosis ◽  
Mitochondrial Function ◽  
Fatty Liver Disease ◽  
Critical Role ◽  
Acid Oxidation ◽  
Nonalcoholic Fatty Liver ◽  
Mitochondrial Trifunctional Protein

Mitochondrial trifunctional protein (MTP) plays a critical role in the oxidation of long-chain fatty acids. We previously reported that aging mice (>9 months old) heterozygous for an MTP defect (MTP+/−) develop nonalcoholic fatty liver disease (NAFLD). We tested whether a high-fat diet (HFD) accelerates NAFLD in young MTP+/−mice, and whether overexpression of the nicotinamide adenine dinucleotide (NAD+)-dependent deacetylase sirtuin 3 (SIRT3) deacetylates MTP and improves mitochondrial function and NAFLD. Three-month-old WT and MTP+/− mice were fed HFD (60% cal fat) for 16 weeks and livers were assessed for fatty acid oxidation (FAO) and NAFLD. Compared with WT, MTP+/− mice displayed reduced hepatic SIRT3 levels and reduced FAO, with increased hepatic steatosis and the inflammatory marker CD68. Hepatic overexpression of SIRT3 in HFD-fed MTP+/− mice increased hepatic MTP protein levels at the posttranscriptional level. Immunoprecipitation of MTP from liver mitochondria followed by Western blot with acetyl-lysine antibody showed higher acetylation of MTP in MTP+/− compared with WT mice. Overexpression of SIRT3 in MTP+/− mice significantly reduced the acetylation of MTP compared with β-galactosidase controls, increased mitochondrial FAO, and reduced hepatic steatosis, CD68, and serum ALT levels. Taken together, our data indicate that deacetylation of MTP by SIRT3 improves mitochondrial function and rescues NAFLD in MTP+/− mice.

scholarly journals Acetylation of Mitochondrial Trifunctional Protein α-Subunit Enhances Its Stability To Promote Fatty Acid Oxidation and Is Decreased in Nonalcoholic Fatty Liver Disease

2016 ◽  
Vol 36 (20) ◽  
pp. 2553-2567 ◽  
Author(s):  
Liang Guo ◽  
Shui-Rong Zhou ◽  
Xiang-Bo Wei ◽  
Yuan Liu ◽  
Xin-Xia Chang ◽  
...  
Keyword(s):  
Fatty Acid ◽  
Liver Disease ◽  
Fatty Liver ◽  
Nonalcoholic Fatty Liver Disease ◽  
Fatty Acid Oxidation ◽  
Fatty Liver Disease ◽  
Acid Oxidation ◽  
Α Subunit ◽  
Nonalcoholic Fatty Liver ◽  
Mitochondrial Trifunctional Protein

Nonalcoholic fatty liver disease (NAFLD) has become the most common liver disease, and decreased fatty acid oxidation is one of the important contributors to NAFLD. Mitochondrial trifunctional protein α-subunit (MTPα) functions as a critical enzyme for fatty acid β-oxidation, but whether dysregulation of MTPα is pathogenically connected to NAFLD is poorly understood. We show that MTPα is acetylated at lysine residues 350, 383, and 406 (MTPα-3K), which promotes its protein stability by antagonizing its ubiquitylation on the same three lysines (MTPα-3K) and blocking its subsequent degradation. Sirtuin 4 (SIRT4) has been identified as the deacetylase, deacetylating and destabilizing MTPα. Replacement of MTPα-3K with either MTPα-3KR or MTPα-3KQ inhibits cellular lipid accumulation both in free fatty acid (FFA)-treated alpha mouse liver 12 (AML12) cells and primary hepatocytes and in the livers of high-fat/high-sucrose (HF/HS) diet-fed mice. Moreover, knockdown of SIRT4 could phenocopy the effects of MTPα-3K mutant expression in mouse livers, and MTPα-3K mutants more efficiently attenuate SIRT4-mediated hepatic steatosis in HF/HS diet-fed mice. Importantly, acetylation of both MTPα and MTPα-3K is decreased while SIRT4 is increased in the livers of mice and humans with NAFLD. Our study reveals a novel mechanism of MTPα regulation by acetylation and ubiquitylation and a direct functional link of this regulation to NAFLD.

scholarly journals Dissociation of hepatic insulin resistance from susceptibility of nonalcoholic fatty liver disease induced by a high-fat and high-carbohydrate diet in mice

2014 ◽  
Vol 306 (6) ◽  
pp. G496-G504 ◽  
Author(s):  
Akihiro Asai ◽  
Pauline M. Chou ◽  
Heng-Fu Bu ◽  
Xiao Wang ◽  
M. Sambasiva Rao ◽  
...  
Keyword(s):  
Liver Disease ◽  
Fatty Liver ◽  
Nonalcoholic Fatty Liver Disease ◽  
Hepatic Steatosis ◽  
Fatty Liver Disease ◽  
Diet Group ◽  
High Fat ◽  
Nonalcoholic Fatty Liver ◽  
Akt Phosphorylation ◽  
High Carbohydrate

Liver steatosis in nonalcoholic fatty liver disease is affected by genetics and diet. It is associated with insulin resistance (IR) in hepatic and peripheral tissues. Here, we aimed to characterize the severity of diet-induced steatosis, obesity, and IR in two phylogenetically distant mouse strains, C57BL/6J and DBA/2J. To this end, mice (male, 8 wk old) were fed a high-fat and high-carbohydrate (HFHC) or control diet for 16 wk followed by the application of a combination of classic physiological, biochemical, and pathological studies to determine obesity and hepatic steatosis. Peripheral IR was characterized by measuring blood glucose level, serum insulin level, homeostasis model assessment of IR, glucose intolerance, insulin intolerance, and AKT phosphorylation in adipose tissues, whereas the level of hepatic IR was determined by measuring insulin-triggered hepatic AKT phosphorylation. We discovered that both C57BL/6J and DBA/2J mice developed obesity to a similar degree without the feature of liver inflammation after being fed an HFHC diet for 16 wk. C57BL/6J mice in the HFHC diet group exhibited severe pan-lobular steatosis, a marked increase in hepatic triglyceride levels, and profound peripheral IR. In contrast, DBA/2J mice in the HFHC diet group developed only a mild degree of pericentrilobular hepatic steatosis that was associated with moderate changes in peripheral IR. Interestingly, both C57BL/6J and DBA/2J developed severe hepatic IR after HFHC diet treatment. Collectively, these data suggest that the severity of diet-induced hepatic steatosis is correlated to the level of peripheral IR, not with the severity of obesity and hepatic IR. Peripheral rather than hepatic IR is a dominant factor of pathophysiology in nonalcoholic fatty liver disease.

scholarly journals Reproductive Endocrinology of Nonalcoholic Fatty Liver Disease

2018 ◽  
Vol 40 (2) ◽  
pp. 417-446 ◽  
Author(s):  
Mathis Grossmann ◽  
Margaret E Wierman ◽  
Peter Angus ◽  
David J Handelsman
Keyword(s):  
Liver Disease ◽  
Fatty Liver ◽  
Nonalcoholic Fatty Liver Disease ◽  
Hepatic Steatosis ◽  
Fatty Liver Disease ◽  
Energy Homeostasis ◽  
Sex Hormone Binding Globulin ◽  
Sex Steroid ◽  
Receptor Signaling ◽  
Nonalcoholic Fatty Liver

Abstract The liver and the reproductive system interact in a multifaceted bidirectional fashion. Sex steroid signaling influences hepatic endobiotic and xenobiotic metabolism and contributes to the pathogenesis of functional and structural disorders of the liver. In turn, liver function affects the reproductive axis via modulating sex steroid metabolism and transport to tissues via sex hormone–binding globulin (SHBG). The liver senses the body’s metabolic status and adapts its energy homeostasis in a sex-dependent fashion, a dimorphism signaled by the sex steroid milieu and possibly related to the metabolic costs of reproduction. Sex steroids impact the pathogenesis of nonalcoholic fatty liver disease, including development of hepatic steatosis, fibrosis, and carcinogenesis. Preclinical studies in male rodents demonstrate that androgens protect against hepatic steatosis and insulin resistance both via androgen receptor signaling and, following aromatization to estradiol, estrogen receptor signaling, through regulating genes involved in hepatic lipogenesis and glucose metabolism. In female rodents in contrast to males, androgens promote hepatic steatosis and dysglycemia, whereas estradiol is similarly protective against liver disease. In men, hepatic steatosis is associated with modest reductions in circulating testosterone, in part consequent to a reduction in circulating SHBG. Testosterone treatment has not been demonstrated to improve hepatic steatosis in randomized controlled clinical trials. Consistent with sex-dimorphic preclinical findings, androgens promote hepatic steatosis and dysglycemia in women, whereas endogenous estradiol appears protective in both men and women. In both sexes, androgens promote hepatic fibrosis and the development of hepatocellular carcinoma, whereas estradiol is protective.

scholarly journals Protective Effect of a Mixture of Astragalus membranaceus and Lithospermum erythrorhizon Extract against Hepatic Steatosis in High Fat Diet-Induced Nonalcoholic Fatty Liver Disease Mice

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Doo Jin Choi ◽  
Seong Cheol Kim ◽  
Gi Eun Park ◽  
Bo-Ram Choi ◽  
Dae Young Lee ◽  
...  
Keyword(s):  
Liver Disease ◽  
Fatty Liver ◽  
Nonalcoholic Fatty Liver Disease ◽  
Hepatic Steatosis ◽  
High Fat Diet ◽  
Fatty Liver Disease ◽  
Density Lipoprotein ◽  
Lithospermum Erythrorhizon ◽  
High Fat ◽  
Nonalcoholic Fatty Liver

The present study aimed to evaluate the potential synergistic and protective effects of ALM16, a mixture of Astragalus membranaceus (AM) and Lithospermum erythrorhizon (LE) extract in a ratio of 7 : 3, against hepatic steatosis in high fat diet (HFD)-induced nonalcoholic fatty liver disease (NAFLD) mice. Forty-eight mice were randomly divided into eight groups and orally administered daily for 6 weeks with a normal diet (ND) or high fat diet alone (HFD), HFD with AM (HFD + 100 mg/kg AM extract), HFD with LE (HFD + 100 mg/kg LE extract), HFD with ALM16 (HFD + 50, 100, and 200 mg/kg ALM16), or HFD with MT (HFD + 100 mg/kg Milk thistle extract) as a positive control. ALM16 significantly decreased the body and liver weight, serum and hepatic lipid profiles, including triglyceride (TG), total cholesterol (TC), high-density lipoprotein-cholesterol (HDL), and low-density lipoprotein-cholesterol (LDL), and serum glucose levels, compared to the HFD group. Moreover, ALM16 significantly ameliorated the HFD-induced increased hepatic injury markers, including aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP), lactate dehydrogenase (LDH), and gamma-glutamyltransferase (GGT)-1. Furthermore, as compared to the mice fed HFD alone, ALM16 increased the levels of phosphorylated AMP-activated protein kinase (p-AMPK) and acetyl-CoA carboxylase (p-ACC), thereby upregulating the expression of carnitine palmitoyltransferase (CPT)-1 and downregulating the expression of sterol regulatory element-binding protein (SREBP)-1c and fatty acid synthase (FAS). These results demonstrated that ALM16 markedly inhibited HFD-induced hepatic steatosis in NAFLD mice by modulating AMPK and ACC signaling pathways, and may be more effective than the single extracts of AM or LE.

scholarly journals Assessment of Hepatic Steatosis in Nonalcoholic Fatty Liver Disease by Using Quantitative US

Radiology ◽  
2020 ◽  
Vol 295 (1) ◽  
pp. 106-113 ◽  
Author(s):  
Aiguo Han ◽  
Yingzhen N. Zhang ◽  
Andrew S. Boehringer ◽  
Vivian Montes ◽  
Michael P. Andre ◽  
...  
Keyword(s):  
Liver Disease ◽  
Fatty Liver ◽  
Nonalcoholic Fatty Liver Disease ◽  
Hepatic Steatosis ◽  
Fatty Liver Disease ◽  
Nonalcoholic Fatty Liver ◽  
Quantitative Us
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