Project description:Serine is involved in the regulation of hepatic lipid metabolism. However, whether exogenous or endogenous serine deficiency affects lipid accumulation in the liver and related mechanisms is unclear. Here, we investigated the effects of serine deficiency on hepatic fat accumulation in mice fed a serine-deficient diet or in mice supplemented with the D-3-phosphoglycerate dehydrogenase (PHGDH) inhibitor NCT-503. Both treatments produced an increase in body weight and liver weight and higher triglyceride content in the liver. Both treatments also exacerbated hepatic inflammatory responses and oxidative stress. Importantly, NCT-503 supplementation significantly inhibited PHGDH activity and decreased the serine content in the liver. Dietary serine deficiency significantly affected the colonic microbiota, characterized by a decreased ratio of Firmicutes/Bacteroidetes and decreased proportion of Bifidobacterium. Dietary serine deficiency additionally resulted in significantly decreased colonic and serum acetate and butyrate levels. The collective results indicate that NCT-503 supplementation may contribute to overaccumulation of hepatic lipid, by causing hepatic serine deficiency, while dietary serine deficiency may produce similar outcomes by affecting the gut-microbiota-liver axis.
Project description:Nonalcoholic fatty liver disease (NAFLD) is one of the most common liver diseases worldwide. Although the involvement of chronic overnutrition, systemic inflammation, and insulin resistance in the development of NAFLD is well-established, however, the associations among these remain to be elucidated. Several studies have reported that chronic overnutrition, such as excessive consumption of fats (high-fat diet, HFD), can cause insulin resistance and inflammation. However, the mechanisms by which HFD exerts inflammation and thereby promotes insulin resistance and intrahepatic fat accumulation remain poorly understood. Here, we show that HFD induces the expression of hepatic serine/threonine kinase 38 (STK38), which further induces systemic inflammation leading to insulin resistance. Notably, ectopic expression of STK38 in mouse liver leads to lean NAFLD phenotype with hepatic inflammation, insulin resistance, intrahepatic lipid accumulation, and hypertriglyceridemia in mice fed on a regular chow diet. Further, depletion of hepatic STK38 in HFD-fed mice remarkably reduces proinflammation, improves hepatic insulin sensitivity, and decreases hepatic fat accumulation. Mechanistically, two critical stimuli are elicited by STK38 action. For one stimulus, STK38 binds to Tank-Binding protein Kinase 1 and induces Tank-Binding protein Kinase 1 phosphorylation to promote NF-κβ nuclear translocation that mobilizes the release of proinflammatory cytokines and eventually leads to insulin resistance. The second, stimulus involves intrahepatic lipid accumulation by enhanced de novo lipogenesis via reducing the AMPK-ACC signaling axis. These findings identify STK38 as a novel nutrient-sensitive proinflammatory and lipogenic factor in maintaining hepatic energy homeostasis, and it provides a promising target for hepatic and immune health.
Project description:ObjectiveLipid-laden macrophages or foam cells are characterized by massive cytosolic lipid droplet (LD) deposition containing mostly cholesterol ester (CE) derived from the lipoproteins cleared from the arterial wall. Cholesterol efflux from foam cells is considered to be atheroprotective. Because cholesterol is effluxed as free cholesterol, CE accumulation in LDs may limit free cholesterol efflux. Our objective was to identify proteins that regulate cholesterol trafficking through LDs.Approach and resultsIn a proteomic analysis of the LD fraction of RAW 264.7 macrophages, we identified an evolutionarily conserved protein with a canonical GXSXG lipase catalytic motif and a predicted α/β-hydrolase fold, the RIKEN cDNA 1110057K04 gene, which we named LD-associated hydrolase (LDAH). LDAH association with LDs was confirmed by immunoblotting and immunocytochemistry. LDAH was labeled with a probe specific for active serine hydrolases. LDAH showed relatively weak in vitro CE hydrolase activity. However, cholesterol measurements in intact cells supported a significant role of LDAH in CE homeostasis because LDAH upregulation and downregulation decreased and increased, respectively, intracellular cholesterol and CE in human embryonic kidney-293 cells and RAW 264.7 macrophages. Mutation of the putative nucleophilic serine impaired active hydrolase probe binding, in vitro CE hydrolase activity, and cholesterol-lowering effect in cells, whereas this mutant still localized to the LD. LDAH upregulation increased CE hydrolysis and cholesterol efflux from macrophages, and, interestingly, LDAH is highly expressed in macrophage-rich areas within mouse and human atherosclerotic lesions.ConclusionsThe data identify a candidate target to promote reverse cholesterol transport from atherosclerotic lesions.
Project description:In order to determine whether dis-regulation of a genetic pathway could explain the increased apoptosis of parp-2-/- double positive thymocytes, the gene expression profiles in double positive thymocytes derived from wild-type and parp-2-/- mice were analysed using Affymetrix oligonucleotide chips (mouse genome 430 2.0).
Project description:Elevated circulating lipid levels are known risk factors for cardiovascular diseases (CVD). In order to examine the effects of quercetin on hepatic lipid metabolism and detailed serum lipid profiles, mice received a mild-high-fat diet without (control) or with supplementation of 0.33% (w/w) quercetin for 12 weeks. Gas chromatography and 1H nuclear magnetic resonance were used to measure quantitatively serum lipid profiles and whole genome microarray analysis was used to identify the responsible mechanisms in liver. There were no significant differences found in mean body weight, energy intake and hepatic lipid accumulation between the quercetin and control group. In serum of quercetin-fed mice, TG levels were decreased with 15%, poly unsaturated fatty acids (PUFA) were increased with 14% and saturated fatty acids were decreased. Palmitic acid, oleic acid, and linoleic acid were all decreased in quercetin-fed mice by 9-15%. Both palmitic acid and oleic acid can be oxidized by omega-oxidation. Indeed, gene expression profiling showed that quercetin increased hepatic lipid metabolism, especially omega-oxidation. At the gene level, this was reflected by the up regulation of cytochrome P450 (Cyp) 4a10, Cyp4a14, Cyp4a31 and Acyl-CoA thioesterase 3 (Acot3). Two relevant regulators, Cytochrome P450 oxidoreductase (Por, rate limiting for cytochrome P450s) and the transcription factor Constitutive androstane receptor (Car; official symbol Nr1i3) were also up regulated in the quercetin-fed mice. We conclude that quercetin intake increased hepatic lipid omega-oxidation and lowered corresponding circulating lipid levels, a process that may involve Por and Car, and results in a potential beneficial CVD preventive effect. Liver samples were obtained from 36 C57BL/6J male adult mice. All mice started with a three week adaptation phase, in which they were fed a mild-high-fat diet. 12 mice were sacrificed immediately after the adaptation phase (t=0). The other 24 mice received the mild-high-fat diet without (HF) or with supplementation of 0.33% (w/w) quercetin (HF-Q) for 12 weeks.
Project description:Ossification of the posterior longitudinal ligament (OPLL) is formed by heterogeneous ossification of posterior longitudinal ligament. The patho-mechanism of OPLL is still largely unknown. MicroRNAs are small nucleatides that function as regulators of gene expression in almost any biological process. However, few microRNAs are reported to have a role in the pathological process of OPLL. Therefore, we performed high-throughput microRNA sequencing and transcriptome sequencing of primary OPLL and PLL cells in order to decipher the interacting network of microRNAs in OPLL. MRNA and microRNA profiles were done using primary culture cells of human ossification of the posterior longitudinal ligament (OPLL) tissue and normal posterior longitudinal ligament (PLL) tissue.
Project description:Excess lipid accumulation is an early signature of nonalcoholic fatty liver disease (NAFLD). Although liver receptor homolog 1 (LRH-1) (encoded by NR5A2) is suppressed in human NAFLD, evidence linking this phospholipid-bound nuclear receptor to hepatic lipid metabolism is lacking. Here, we report an essential role for LRH-1 in hepatic lipid storage and phospholipid composition based on an acute hepatic KO of LRH-1 in adult mice (LRH-1AAV8-Cre mice). Indeed, LRH-1-deficient hepatocytes exhibited large cytosolic lipid droplets and increased triglycerides (TGs). LRH-1-deficient mice fed high-fat diet displayed macrovesicular steatosis, liver injury, and glucose intolerance, all of which were reversed or improved by expressing wild-type human LRH-1. While hepatic lipid synthesis decreased and lipid export remained unchanged in mutants, elevated circulating free fatty acid helped explain the lipid imbalance in LRH-1AAV8-Cre mice. Lipidomic and genomic analyses revealed that loss of LRH-1 disrupts hepatic phospholipid composition, leading to lowered arachidonoyl (AA) phospholipids due to repression of Elovl5 and Fads2, two critical genes in AA biosynthesis. Our findings reveal a role for the phospholipid sensor LRH-1 in maintaining adequate pools of hepatic AA phospholipids, further supporting the idea that phospholipid diversity is an important contributor to healthy hepatic lipid storage.