Project description:High-protein diets are known to reduce adiposity in the context of high carbohydrate and Western diets. However, few studies have investigated the specific high-protein effect on lipogenesis induced by a high-sucrose (HS) diet or fat deposition induced by high-fat feeding. We aimed to determine the effects of high protein intake on the development of fat deposition and partitioning in response to high-fat and/or HS feeding. A total of thirty adult male Wistar rats were assigned to one of the six dietary regimens with low and high protein, sucrose and fat contents for 5 weeks. Body weight (BW) and food intake were measured weekly. Oral glucose tolerance tests and meal tolerance tests were performed after 4th and 5th weeks of the regimen, respectively. At the end of the study, the rats were killed 2 h after ingestion of a calibrated meal. Blood, tissues and organs were collected for analysis of circulating metabolites and hormones, body composition and mRNA expression in the liver and adipose tissues. No changes were observed in cumulative energy intake and BW gain after 5 weeks of dietary treatment. However, high-protein diets reduced by 20 % the adiposity gain induced by HS and high-sucrose high-fat (HS-HF) diets. Gene expression and transcriptomic analysis suggested that high protein intake reduced liver capacity for lipogenesis by reducing mRNA expressions of fatty acid synthase (fasn), acetyl-CoA carboxylase a and b (Acaca and Acacb) and sterol regulatory element binding transcription factor 1c (Srebf-1c). Moreover, ketogenesis, as indicated by plasma β-hydroxybutyrate levels, was higher in HS-HF-fed mice that were also fed high protein levels. Taken together, these results suggest that high-protein diets may reduce adiposity by inhibiting lipogenesis and stimulating ketogenesis in the liver.
Project description:High-protein diets are known to reduce adiposity in the context of high carbohydrate and Western diets. However, few studies have investigated the specific high-protein effect on lipogenesis induced by a high-sucrose (HS) diet or fat deposition induced by high-fat feeding. We aimed to determine the effects of high protein intake on the development of fat deposition and partitioning in response to high-fat and/or HS feeding. A total of thirty adult male Wistar rats were assigned to one of the six dietary regimens with low and high protein, sucrose and fat contents for 5 weeks. Body weight (BW) and food intake were measured weekly. Oral glucose tolerance tests and meal tolerance tests were performed after 4th and 5th weeks of the regimen, respectively. At the end of the study, the rats were killed 2 h after ingestion of a calibrated meal. Blood, tissues and organs were collected for analysis of circulating metabolites and hormones, body composition and mRNA expression in the liver and adipose tissues. No changes were observed in cumulative energy intake and BW gain after 5 weeks of dietary treatment. However, high-protein diets reduced by 20 % the adiposity gain induced by HS and high-sucrose high-fat (HS-HF) diets. Gene expression and transcriptomic analysis suggested that high protein intake reduced liver capacity for lipogenesis by reducing mRNA expressions of fatty acid synthase (fasn), acetyl-CoA carboxylase a and b (Acaca and Acacb) and sterol regulatory element binding transcription factor 1c (Srebf-1c). Moreover, ketogenesis, as indicated by plasma β-hydroxybutyrate levels, was higher in HS-HF-fed mice that were also fed high protein levels. Taken together, these results suggest that high-protein diets may reduce adiposity by inhibiting lipogenesis and stimulating ketogenesis in the liver. Adult male Wistar rats were fed diets with varying amounts of protein, carbohydrates and fat for 5 weeks. At the end of the experiment, rats were killed and tanscriptome analysis was performed on pooled liver samples.
Project description:In order to study the heart disorder that the long term, high energy diet caused, Bama miniature pigs were fed a high-fat, high-sucrose diet for 23 months. These pigs developed symptoms of metabolic syndrome and showed cardiac steatosis and hypertrophy with a greatly increased heart weight (1.82-fold, P<0.05) and heart volume (1.60-fold, P<0.05) compared with the control pigs. To understand the molecular mechanisms of cardiac steatosis and hypertrophy, nine pig heart cRNA samples were hybridized to porcine GeneChips.
Project description:In order to study the heart disorder that the long term, high energy diet caused, Bama miniature pigs were fed a high-fat, high-sucrose diet for 23 months. These pigs developed symptoms of metabolic syndrome and showed cardiac steatosis and hypertrophy with a greatly increased heart weight (1.82-fold, P<0.05) and heart volume (1.60-fold, P<0.05) compared with the control pigs. To understand the molecular mechanisms of cardiac steatosis and hypertrophy, nine pig heart cRNA samples were hybridized to porcine GeneChips. The control group consisted of 6 Bama pigs fed a control diet, and the HFHSD group comprised 6 pigs that were induced with a HFHS diet, which included 37% sucrose, 53% control diet and 10% pork lard. The pigs were fed twice every day and provided water ad libitum for 23 months. The pigs were fasted for 12 hours and euthanized with ketamine and xylazine. Pig hearts from the HFHSD group pigs (120, 126, 138, 140, 144, and 146) and three control group pigs (157, 159, and 161) were sampled and preserved in liquid nitrogen and then for RNA extraction and hybridization on Affymetrix microarrays.
Project description:Mitochondrial function is an important control variable in the progression of metabolic dysfunction associated fatty liver disease (MAFLD). We hypothesize that organization and function of mitochondrial electron transport chain (ETC) in this pathologic condition is a consequence of shifted substrate availability. Paradoxically, in MAFLD increased de novo lipogenesis (DNL) occurs despite hepatic insulin resistance. Therefore, we addressed this question using our animal model alb-SREBP-1c, which exhibits increased DNL by constitutively active SREBP-1c. Using an omics approach, we show that the abundance of ETC complex subunits and metabolic pathways are altered in liver of these animals. Analyses of cellular metabolic status by functional assays revealed that SREBP-1c-forced DNL induces a limitation of substrates for oxidative phosphorylation that is rescued by enhanced complex II activity. Furthermore, energy metabolism associated gene regulation indicates the counteracting to increase expression of mitochondrial genes and features cell communication by miRNA and exosomal RNA transfer. In conclusion, substrate availability fuels mainly complex II electron flows as a consequence of activated DNL with impact on whole body by liver-specific exosomal RNAs in early stages of MAFLD.https://pubmed.ncbi.nlm.nih.gov/35743314/
Project description:Mitochondrial function is an important control variable in the progression of metabolic dysfunction associated fatty liver disease (MAFLD). We hypothesize that organization and function of mitochondrial electron transport chain (ETC) in this pathologic condition is a consequence of shifted substrate availability. Paradoxically, in MAFLD increased de novo lipogenesis (DNL) occurs despite hepatic insulin resistance. Therefore, we addressed this question using our animal model alb-SREBP-1c, which exhibits increased DNL by constitutively active SREBP-1c. Using an omics approach, we show that the abundance of ETC complex subunits and metabolic pathways are altered in liver of these animals. Analyses of cellular metabolic status by functional assays revealed that SREBP-1c-forced DNL induces a limitation of substrates for oxidative phosphorylation that is rescued by enhanced complex II activity. Furthermore, energy metabolism associated gene regulation indicates the counteracting to increase expression of mitochondrial genes and features cell communication by miRNA and exosomal RNA transfer. In conclusion, substrate availability fuels mainly complex II electron flows as a consequence of activated DNL with impact on whole body by liver-specific exosomal RNAs in early stages of MAFLD.https://pubmed.ncbi.nlm.nih.gov/35743314/
Project description:We find that selective inhibition of one arm of mTORC1 signaling, via deletion of FLCN, promotes activation of the transcription factor TFE3 and profoundly protects against NAFLD and NASH in mice. (1) We performed genome-wide RNA-seq on livers from Control, liver-specific Flcn-null mice (LiFKO), and Flcn/Tfe3 double knock-out (DKO) mice fed either normal chow (NC) or a NAFLD-inducing diet (AMLN). We find TFE3-mediated induction of lysosomal and mitochondrial gene programs, and also suppression of de novo lipogenesis genes. (2) To understand whether TFE3 directly affects gene expression, we performed TFE3 ChIP-seq on livers from Control and LiFKO mice on normal chow. We find TFE3 occupancy on the chromatin at lysosomal genes, Ppargc1a (a driver of mitochondrial genes), and at de novo lipogenesis genes. (3) Finally, we wanted to test whether TFE3 antagonistically competes with the pro-lipogenic transcription factor SREBP-1c on chromatin. We therefore injected HA-tagged constitutively nuclear (active) SREBP-1c (nSREBP-1c), or a control virus, into control and LiFKO mice, treated them with a NAFLD-inducing diet (FPC diet), and collected liver tissue. We consequently performed HA-nSREBP-1c and TFE3 ChIP-seq experiments and observed no evidence of antagonistic competition.
Project description:Non-alcoholic fatty liver disease (NAFLD) is caused by imbalance in lipid metabolism. In this study, we show that the hepatokine Orosomucoid 2 (ORM2) is a key regulator of de novo lipogenesis in the liver. Hepatic and plasma ORM2 levels are markedly decreased in obese murine models and NAFLD patients. Through multiple loss- and gain-of function studies, we demonstrate that ORM2 is essential to maintain hepatic and systemic lipid homeostasis. At the mechanistic level, ORM2 binds to inositol 1, 4, 5-trisphosphate receptor type 2 (ITPR2) to activate AMP-activated protein kinase (AMPK) signaling, thereby inhibiting sterol regulatory element binding protein 1c (SREBP-1c)-mediated lipogenic gene program. Notably, intraperitoneal injections of recombinant ORM2 protein or stabilized ORM2-FC fusion protein markedly improved liver steatosis, steatohepatitis and atherosclerosis in preclinical mouse models, without adverse effects on body weight or food intake. Thus, these findings suggest that ORM2 may serve as a potential target for therapeutic intervention in NAFLD, NASH and related lipid disorders.
Project description:Background and aim: The Insulin-like growth factor (IGF) axis is increasingly suggested to be involved in fatty liver disease and progression. We identified IGFBP2 as transcriptional regulatory effect network in liver steatosis and conducted a translational approach of its role in liver pathology from mouse to human, and whether it is influenced by conventional clinical intervention that mitigate hepatic steatosis. Methods: Primary hepatocytes from either C57Bl6 controls, alb-SREBP-1c mice with moderate transgene induced hepatic lipid accumulation or aP2-SREBP-1c mice with massive ectopic hepatic lipid accumulation, were analyzed to identify regulatory networks based on differentially regulated hepatic gene expression. In a translational approach, serum of morbidly obese patients with and without diabetes and biopsy-proven NAFLD were used for ELISA-based validation of mouse data. Moreover, sera of patients undergoing intervention were analyzed and correlated to liver fat content. Results: Comparative knowledge-based transcriptome analysis identified IGFBP2 as top score regulatory effect network between moderate and aggravated fatty liver in mouse models. The reduced expression of IGFBP2 in aP2-SREPB-1c progressed fatty liver associated with Igfbp2 promoter hypermethylation. Reduced secretion of IGFBP2 from aP2-SREBP-1c hepatocytes was reflected in the circulation of the animals. In this phenotype, reductions of IGFBP2 were accompanied by reduced fatty acid oxidation and increased methyltransferase and SIRT activity. Physiologically, IGFBP2 has no direct impact on lipid metabolism but might modulate IGF1 action on de novo lipogenesis. In humans, IGFBP2 levels declined from non-obese men to morbidly obese men with NAFLD and NASH. In intervention study reductions in liver fat correlated with restoration of IGFBP2 serum levels to values found in healthy individuals in morbidly obese patients following bariatric surgery. Conclusion: In hepatic metabolism changes of IGFBP2 abundance is connected to lipid metabolism whereas changes in IGFBP2 secretion were directly reflected in the circulation. IGFBP2 serum concentration correlates with the degree of fatty liver, which seems to be related to plasticity of the adipose tissue. These data provide IGFBP2 as a potential non-invasive biomarker for fatty liver disease directly reflecting the degree of impaired liver function with the potential to indicate progressed fatty liver disease.
Project description:To assess the effect of steatosis and oxidative stress on progression of liver fibrosis, we have employed whole genome microarray expression profiling as a discovery platform to identify genes that are related with oxidative stress- and steatosis-induced hepatic fibrogenesis. When wild type mice were fed high-fat/high-sucrose diet for 24 weeks, expression of 69 genes was changed more than 10-fold compared with wild type animals fed normal diet, 11 of which were categorized to lipid metabolic process. Moreover, expression of 208 genes showed more than 5-fold changes in Tet-mev-1 mice fed high-fat/high-sucrose diet compared with the same transgenic animals fed normal diet, and gene ontology analyses indicated significant changes in chemokine activity and chemokine receptor binding as well as defense and immune responses.