scholarly journals Pathophysiological importance of bile cholesterol reabsorption: hepatic NPC1L1-exacerbated steatosis and decreasing VLDL-TG secretion in mice fed a high-fat diet

2019 ◽  
Vol 18 (1) ◽  
Author(s):  
Yu Toyoda ◽  
Tappei Takada ◽  
Yoshihide Yamanashi ◽  
Hiroshi Suzuki
Keyword(s):  
High Fat Diet ◽  
Early Stage ◽  
Lipid Homeostasis ◽  
Mrna Levels ◽  
Hepatic Cholesterol ◽  
Wild Type ◽  
High Fat ◽  
Wild Type Littermate ◽  
Alcoholic Fatty Liver ◽  
Hepatic Expression

Abstract Background Non-alcoholic fatty liver disease (NAFLD) is one of the most common liver diseases worldwide, although its pathogenesis remains to be elucidated. A recent study revealed that hepatic Niemann-Pick C1-Like 1 (NPC1L1), a cholesterol re-absorber from bile to the liver expressed on the bile canalicular membrane, is an exacerbation factor of NAFLD. Indeed, transgenic mice with hepatic expression of human NPC1L1 under a liver-specific promoter (L1-Tg mice) developed steatosis with a high-fat diet (HFD) containing cholesterol within a few weeks. However, the mechanism underlying diet-induced hepatic NPC1L1-mediated lipid accumulation is poorly defined. Methods To achieve a deeper understanding of steatosis development in L1-Tg mice, the biochemical features of hepatic NPC1L1-mediated steatosis were investigated. Hemizygous L1-Tg mice and wild-type littermate controls fed a HFD or control-fat diet were used. At the indicated time points, the livers were evaluated for cholesterol and triglyceride (TG) contents as well as mRNA levels of hepatic genes involved in the maintenance of lipid homeostasis. The hepatic ability to secrete very low-density lipoprotein (VLDL)-TG was also investigated. Results Unlike the livers of wild-type mice that have little expression of hepatic Npc1l1, the livers of L1-Tg mice displayed time-dependent changes that indicated steatosis formation. In steatosis, there were three different stages of development: mild accumulation of hepatic cholesterol and TG (early stage), acceleration of hepatic TG accumulation (middle stage), and further accumulation of hepatic cholesterol (late stage). In the early stage, between WT and L1-Tg mice fed a HFD for 2 weeks, there were no significant differences in the hepatic expression of Pparα, Acox1, Fat/Cd36, Srebf1, and Srebf2; however, the hepatic ability to secrete VLDL-TG decreased in L1-Tg mice (P < 0.05). Furthermore, this decrease was completely prevented by administration of ezetimibe, an NPC1L1-selective inhibitor. Conclusion Hepatic NPC1L1 exacerbates diet-induced steatosis, which was accompanied by decreased hepatic ability of VLDL-TG secretion. The obtained results provide a deeper understanding of L1-Tg mice as a promising NAFLD animal model that is able to re-absorb biliary-secreted cholesterol similar to humans. Furthermore, this work supports further studies of the pathophysiological impact of re-absorbed biliary cholesterol on the regulation of hepatic lipid homeostasis.

scholarly journals MicroRNA-29a Suppresses CD36 to Ameliorate High Fat Diet-Induced Steatohepatitis and Liver Fibrosis in Mice

Cells ◽  
2019 ◽  
Vol 8 (10) ◽  
pp. 1298 ◽  
Author(s):  
Hung-Yu Lin ◽  
Feng-Sheng Wang ◽  
Ya-Ling Yang ◽  
Ying-Hsien Huang
Keyword(s):  
Transcription Factor ◽  
Liver Fibrosis ◽  
High Fat Diet ◽  
Critical Role ◽  
Luciferase Reporter ◽  
Hepatic Tissue ◽  
Wild Type ◽  
High Fat ◽  
Alcoholic Fatty Liver ◽  
Mesenchymal Transition

MicroRNA-29 (miR-29) has been shown to play a critical role in reducing inflammation and fibrosis following liver injury. Non-alcoholic fatty liver disease (NAFLD) occurs when fat is deposited (steatosis) in the liver due to causes other than excessive alcohol use and is associated with liver fibrosis. In this study, we asked whether miR-29a could reduce experimental high fat diet (HFD)-induced obesity and liver fibrosis in mice. We performed systematical expression analyses of miR-29a transgenic mice (miR-29aTg mice) and wild-type littermates subjected to HFD-induced NAFLD. The results demonstrated that increased miR-29a not only alleviated HFD-induced body weight gain but also subcutaneous, visceral, and intestinal fat accumulation and hepatocellular steatosis in mice. Furthermore, hepatic tissue in the miR-29aTg mice displayed a weak fibrotic matrix concomitant with low fibrotic collagen1α1 expression within the affected tissues compared to the wild-type (WT) mice fed the HFD diet. Increased miR-29a signaling also resulted in the downregulation of expression of the epithelial mesenchymal transition-executing transcription factor snail, mesenchymal markers vimentin, and such pro-inflammation markers as il6 and mcp1 within the liver tissue. Meanwhile, miR-29aTg-HFD mice exhibited significantly lower levels of peroxisome proliferator-activated receptor γ (PPARγ), mitochondrial transcription factor A TFAM, and mitochondria DNA content in the liver than the WT-HFD mice. An in vitro luciferase reporter assay further confirmed that miR-29a mimic transfection reduced fatty acid translocase CD36 expression in HepG2 cells. Conclusion: Our data provide new insights that miR-29a can improve HDF-induced obesity, hepatocellular steatosis, and fibrosis, as well as highlight the role of miR-29a in regulation of NAFLD.

SO023HEPATOCYTE GROWTH FACTOR (HGF) PRECLUDE HIGH-FAT DIET-INDUCED OBESITY AND IMPROVED INSULIN RESISTANCE IN MICE

2020 ◽  
Vol 35 (Supplement_3) ◽  
Author(s):  
Jun Muratsu ◽  
Yoshiaki Taniyama ◽  
Fumihiro Sanada ◽  
Atsuyuki Morishima ◽  
Katsuhiko Sakaguchi ◽  
...  
Keyword(s):  
Insulin Resistance ◽  
Body Weight ◽  
Adipose Tissue ◽  
Growth Factor ◽  
Inflammatory Mediators ◽  
High Fat Diet ◽  
Neutralizing Antibody ◽  
Mrna Levels ◽  
Wild Type ◽  
High Fat

Abstract Background and Aims Obesity and its associated chronic inflammation in adipose tissue initiate insulin resistance, which is related to several pathologies including hypertension and atherosclerosis. Previous reports demonstrated that circulating hepatocyte growth factor (HGF) level was associated with obesity and type 2 diabetes. However, its precise role in obesity and related-pathology is unclear. Method In this experiment, cardiac-specific over-expression of human HGF in mice (HGF-Tg mice) which showed 4-5 times higher serum HGF levels than wild-type mice were used. We chose cardiac specific HGF overexpression, as other strain of HGF transgenic mice such as liver and kidney specific HGF overexpression mice develop cancer and cystic diseases, which are rare in the heart. In the present study, using HGF-Tg mice and anti-HGF neutralizing antibody (HGF-Ab), we explored the role of HGF in obese and insulin resistance induced by high fat diet (HFD) for 14 weeks (200 or 400ug/week). Results With normal chow diet (ND), there were no significant changes in body weight between WT and HGF-Tg mice. While body weight in wild-type mice fed with HFD for 14 weeks was significantly increased accompanied with insulin resistance, HGF-Tg mice prevented body weight gain and insulin resistance. Insulin resistance in obesity arises from the combination of altered functions of insulin target cells (e.g., liver, skeletal muscle, and adipose tissue) and the accumulation of macrophages that secrete pro-inflammatory mediators in adipose tissue. The accumulation of macrophages and elevated levels of inflammatory mediators in adipose tissue were significantly inhibited in HGF-Tg mice as compared to wild-type mice. In the gWAT, the mRNA levels of the mature macrophage marker F4/80, the chemoattractants, MCP-1 and CXCL2, and the inflammatory cytokines, such as TNF-α and iNOS, were significantly increased in WT mice fed with HFD. However, these levels were markedly reduced in HGF-Tg mice fed with HFD. Additionally, activation of Akt by insulin administration was significantly reduced in the gWAT SM, and liver by HFD; however, this activation was restored in HGF-Tg mice. Moreover, insulin-induced Akt signaling was decreased in HGF-Ab groups as compared to saline group under HFD condition. Importantly, HFD significantly increased the level of HGF mRNA by approximately 2 fold in gWAT, SM, and liver without changing cMet expression. All together, these data indicate that the HGF as one of the systemic gWAT, SM, and liver-derived growth factor plays a role in compensatory mechanism against insulin-resistance through the at least anti-inflammatory effect in adipose tissue. The HFD-induced obesity in wild-type mice treated with HGF-neutralizing antibody showed an exacerbated response to the glucose tolerance test. Conclusion HGF suppresses inflammation in adipose tissue induced by a high-fat diet, and as a result improves systemic insulin resistance. These gain-of-function and loss-of-function studies demonstrated that the elevated HGF level induced by HFD have protective role against obesity and insulin resistance.

Myostatin, activin receptor IIb, and follistatin-like-3 gene expression are altered in adipose tissue and skeletal muscle of obese mice

2008 ◽  
Vol 294 (5) ◽  
pp. E918-E927 ◽  
Author(s):  
David L. Allen ◽  
Allison S. Cleary ◽  
Kristin J. Speaker ◽  
Sarah F. Lindsay ◽  
Jill Uyenishi ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Adipose Tissue ◽  
High Fat Diet ◽  
Growth Inhibitor ◽  
Mrna Levels ◽  
Wild Type ◽  
Reporter Construct ◽  
High Fat ◽  
Visceral Adipose ◽  
Activin Receptor Iib

Myostatin (MSTN) is a secreted growth inhibitor expressed in muscle and adipose. We sought to determine whether expression of MSTN, its receptor activin RIIb (ActRIIb), or its binding protein follistatin-like-3 (FSTL3) are altered in subcutaneous or visceral adipose or in skeletal muscle in response to obesity. MSTN and ActRIIb mRNA levels were low in subcutaneous (SQF) and visceral fat (VF) from wild-type mice but were 50- to 100-fold higher in both SQF and VF from ob/ob compared with wild-type mice. FSTL3 mRNA levels were increased in SQF but decreased in VF in ob/ob compared with wild-type mice. Moreover, MSTN mRNA levels were twofold greater in tibialis anterior (TA) from ob/ob mice, whereas ActRIIb and FSTL3 mRNA levels were unchanged. MSTN mRNA levels were also increased in TA and SQF from mice on a high-fat diet. Injection of ob/ob mice with recombinant leptin caused FSTL3 mRNA levels to decrease in both VF and SQF in ob/ob mice; MSTN and ActRIIb mRNA levels tended to decrease only in VF. Finally, MSTN mRNA levels and promoter activity were low in adipogenic 3T3-L1 cells, but an MSTN promoter-reporter construct was activated in 3T3-L1 cells by cotransfection with the adipogenic transcription factors SREBP-1c, C/EBPα, and PPARγ. These results demonstrate that expression of MSTN and its associated binding proteins can be modulated in adipose tissue and skeletal muscle by chronic obesity and suggest that alterations in their expression may contribute to the changes in growth and metabolism of lean and fat tissues occurring during obesity.

scholarly journals MON-642 Genetic Knockout of Intestinal Hexokinase Domain-Containing Protein 1 Affects Whole-Body Glycemic Control and Triglyceride Metabolism

2020 ◽  
Vol 4 (Supplement_1) ◽  
Author(s):  
Joseph Louis Zapater ◽  
Wasim Khan ◽  
Brian T Layden
Keyword(s):  
Glycemic Control ◽  
Olive Oil ◽  
High Fat Diet ◽  
Normal Diet ◽  
Whole Body ◽  
Lipid Homeostasis ◽  
Glucose Load ◽  
Wild Type ◽  
High Fat ◽  
Glucose And Lipid Homeostasis

Abstract Hexokinase domain-containing protein 1 (HKDC1) is a recently discovered putative fifth hexokinase that is widely expressed in a variety of human and mouse tissues. Previous work indicate that HKDC1 is important for whole-body glucose homeostasis and utilization in pregnancy and aging, and suggest roles for HKDC1 in nonalcoholic fatty liver disease development and progression of hepatocellular carcinoma. Prior work in the lab further showed that global heterozygous-deleted HKDC1 mice exhibit blunted uptake of triglycerides following an olive oil bolus compared to wild-type mice, suggesting a role for intestinal HKDC1 expression in intestinal lipid metabolism (unpublished results). To specifically study the significance of intestinal HKDC1 on whole-body glucose and lipid homeostasis, we utilized Cre-mediated recombination of HKDC1 in which Cre was expressed under the control of the villin gene promoter, creating a mouse model in which HKDC1 expression is specifically deleted in the intestinal epithelium. Quantitative RT-PCR data confirmed the knockout of HKDC1 within the mouse intestine in young and aged mice, while HKDC1 expression in other tissues was comparable to wild-type mice. Next, intestinal HKDC1 knockout mice and their wild-type littermate controls were either maintained on a normal diet or were switched to a high fat diet at 6 weeks of age to simulate the state of impaired glucose tolerance, and the effects of intestinal HKDC1 on glucose and lipid homeostasis were analyzed between 28-34 weeks of age. Mice fed a normal diet did not exhibit any differences in serum glucose or triglyceride during oral/intraperitoneal glucose tolerance tests or oral olive oil bolus, respectively, regardless of intestinal HKDC1 status. Interestingly, mice lacking intestinal HKDC1 that were on a high fat diet demonstrated improved overall glycemic control compared to wild-type mice after the administration of an oral glucose load, all while there were no changes in insulin levels, gluconeogenesis or insulin tolerance related to HKDC1 status. Additionally, introduction of an intraperitoneal glucose load to mice fed a high fat diet did not alter glucose control in the presence or absence of intestinal HKDC1. However, high fat diet-fed mice lacking intestinal HKDC1 did not have a significant increase in serum triglyceride following an oral olive oil bolus, while their stool fat and triglyceride content were comparable to wild-type. Collectively, these data indicate that intestinal HKDC1 has important roles in glucose and triglyceride metabolism within the intestinal epithelium, and further suggest a role in whole-body glucose homeostasis and in the development of insulin resistance and diabetes.

scholarly journals Aspirin reduces hypertriglyceridemia by lowering VLDL-triglyceride production in mice fed a high-fat diet

2011 ◽  
Vol 301 (6) ◽  
pp. E1099-E1107 ◽  
Author(s):  
Janna A. van Diepen ◽  
Irene O. C. M. Vroegrijk ◽  
Jimmy F. P. Berbée ◽  
Steven E. Shoelson ◽  
Johannes A. Romijn ◽  
...  
Keyword(s):  
High Fat Diet ◽  
Particle Production ◽  
Wild Type ◽  
High Fat ◽  
Hepatic Expression ◽  
Human Apolipoprotein ◽  
The Metabolic Syndrome ◽  
Expression Of Genes ◽  
Vldl Particle ◽  
Vldl Triglyceride

Systemic inflammation is strongly involved in the pathophysiology of the metabolic syndrome, a cluster of metabolic risk factors that includes hypertriglyceridemia. Aspirin treatment lowers inflammation via inhibition of NF-κB activity but also reduces hypertriglyceridemia in humans. The aim of this study was to investigate the mechanism by which aspirin improves hypertriglyceridemia. Human apolipoprotein CI (apoCI)-expressing mice ( APOC1 mice), an animal model with elevated plasma triglyceride (TG) levels, as well as normolipidemic wild-type (WT) mice were fed a high-fat diet (HFD) and treated with aspirin. Aspirin treatment reduced hepatic NF-κB activity in HFD-fed APOC1 and WT mice, and in addition, aspirin decreased plasma TG levels (−32%, P < 0.05) in hypertriglyceridemic APOC1 mice. This TG-lowering effect could not be explained by enhanced VLDL-TG clearance, but aspirin selectively reduced hepatic production of VLDL-TG in both APOC1 (−28%, P < 0.05) and WT mice (−33%, P < 0.05) without affecting VLDL-apoB production. Aspirin did not alter hepatic expression of genes involved in FA oxidation, lipogenesis, and VLDL production but decreased the incorporation of plasma-derived FA by the liver into VLDL-TG (−24%, P < 0.05), which was independent of hepatic expression of genes involved in FA uptake and transport. We conclude that aspirin improves hypertriglyceridemia by decreasing VLDL-TG production without affecting VLDL particle production. Therefore, the inhibition of inflammatory pathways by aspirin could be an interesting target for the treatment of hypertriglyceridemia.

scholarly journals LECT2 as a hepatokine links liver steatosis to inflammation via activating tissue macrophages in NASH

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Noboru Takata ◽  
Kiyo-aki Ishii ◽  
Hiroaki Takayama ◽  
Mayumi Nagashimada ◽  
Kyoko Kamoshita ◽  
...  
Keyword(s):  
Body Mass Index ◽  
High Fat Diet ◽  
Human Liver ◽  
Liver Steatosis ◽  
Mrna Levels ◽  
Liver Inflammation ◽  
High Fat ◽  
Potential Therapeutic Target ◽  
Hepatic Expression ◽  
Shed Light

AbstractIt remains unclear how hepatic steatosis links to inflammation. Leukocyte cell-derived chemotaxin 2 (LECT2) is a hepatokine that senses fat in the liver and is upregulated prior to weight gain. The aim of this study was to investigate the significance of LECT2 in the development of nonalcoholic steatohepatitis (NASH). In human liver biopsy samples, elevated LECT2 mRNA levels were positively correlated with body mass index (BMI) and increased in patients who have steatosis and inflammation in the liver. LECT2 mRNA levels were also positively correlated with the mRNA levels of the inflammatory genes CCR2 and TLR4. In C57BL/6J mice fed with a high-fat diet, mRNA levels of the inflammatory cytokines Tnfa and Nos2 were significantly lower in Lect2 KO mice. In flow cytometry analyses, the number of M1-like macrophages and M1/M2 ratio were significantly lower in Lect2 KO mice than in WT mice. In KUP5, mouse kupffer cell line, LECT2 selectively enhanced the LPS-induced phosphorylation of JNK, but not that of ERK and p38. Consistently, LECT2 enhanced the LPS-induced phosphorylation of MKK4 and TAB2, upstream activators of JNK. Hepatic expression of LECT2 is upregulated in association with the inflammatory signature in human liver tissues. The elevation of LECT2 shifts liver residual macrophage to the M1-like phenotype, and contributes to the development of liver inflammation. These findings shed light on the hepatokine LECT2 as a potential therapeutic target that can dissociate liver steatosis from inflammation.

scholarly journals Empagliflozin Attenuates Non-Alcoholic Fatty Liver Disease (NAFLD) in High Fat Diet Fed ApoE(-/-) Mice by Activating Autophagy and Reducing ER Stress and Apoptosis

2021 ◽  
Vol 22 (2) ◽  
pp. 818
Author(s):  
Narjes Nasiri-Ansari ◽  
Chrysa Nikolopoulou ◽  
Katerina Papoutsi ◽  
Ioannis Kyrou ◽  
Christos S. Mantzoros ◽  
...  
Keyword(s):  
Er Stress ◽  
High Fat Diet ◽  
Molecular Mechanisms ◽  
Beclin 1 ◽  
Control Group ◽  
Caspase 8 ◽  
Mrna Levels ◽  
High Fat ◽  
Alcoholic Fatty Liver ◽  
The Impact

Aims/hypothesis: SGLT-2 inhibitors (SGLT-2i) have been studied as potential treatments against NAFLD, showing varying beneficial effects. The molecular mechanisms mediating these effects have not been fully clarified. Herein, we investigated the impact of empagliflozin on NAFLD, focusing particularly on ER stress, autophagy and apoptosis. Methods: Five-week old ApoE(-/-) mice were switched from normal to a high-fat diet (HFD). After five weeks, mice were randomly allocated into a control group (HFD + vehicle) and Empa group (HFD + empagliflozin 10 mg/kg/day) for five weeks. At the end of treatment, histomorphometric analysis was performed in liver, mRNA levels of Fasn, Screbp-1, Scd-1, Ppar-γ, Pck-1, Mcp-1, Tnf-α, Il-6, F4/80, Atf4, Elf2α, Chop, Grp78, Grp94, Χbp1, Ire1α, Atf6, mTor, Lc3b, Beclin-1, P62, Bcl-2 and Bax were measured by qRT-PCR, and protein levels of p-EIF2α, EIF2a, CHOP, LC3II, P62, BECLIN-1 and cleaved CASPASE-8 were assessed by immunoblotting. Results: Empagliflozin-treated mice exhibited reduced fasting glucose, total cholesterol and triglyceride serum levels, as well as decreased NAFLD activity score, decreased expression of lipogenic enzymes (Fasn, Screbp-1c and Pck-1) and inflammatory molecules (Mcp-1 and F4/80), compared to the Control group. Empagliflozin significantly decreased the expression of ER stress molecules Grp78, Ire1α, Xbp1, Elf2α, Atf4, Atf6, Chop, P62(Sqstm1) and Grp94; whilst activating autophagy via increased AMPK phosphorylation, decreased mTOR and increased LC3B expression. Finally, empagliflozin increased the Bcl2/Bax ratio and inhibited CASPASE-8 cleavage, reducing liver cell apoptosis. Immunoblotting analysis confirmed the qPCR results. Conclusion: These novel findings indicate that empagliflozin treatment for five weeks attenuates NAFLD progression in ApoE(-/-) mice by promoting autophagy, reducing ER stress and inhibiting hepatic apoptosis.

scholarly journals Deficiency of Clusterin Exacerbates High-Fat Diet-Induced Insulin Resistance in Male Mice

Endocrinology ◽  
2014 ◽  
Vol 155 (6) ◽  
pp. 2089-2101 ◽  
Author(s):  
Min Jung Kwon ◽  
Tae-jin Ju ◽  
Jung-Yoon Heo ◽  
Yong-Woon Kim ◽  
Jong-Yeon Kim ◽  
...  
Keyword(s):  
Insulin Resistance ◽  
Skeletal Muscle ◽  
Plasma Levels ◽  
High Fat Diet ◽  
Reactive Oxygen Species Generation ◽  
Area Under The Curve ◽  
Mrna Levels ◽  
Wild Type ◽  
High Fat ◽  
Insulin Levels

The present study examined the role of clusterin in insulin resistance in high fat-fed wild-type and clusterin knockout (KO) mice. The plasma levels of glucose and C-peptide and islet size were increased in clusterin KO mice after an 8-week high-fat diet. In an ip glucose tolerance test, the area under the curve for glucose was not different, whereas the area under the curve for insulin was higher in clusterin KO mice. In a hyperinsulinemic-euglycemic clamp, the clamp insulin levels were higher in clusterin KO mice after the high-fat diet. After adjusting for the clamp insulin levels, the glucose infusion rate, suppression of hepatic glucose production, and glucose uptake were lower in clusterin KO mice in the high fat-fed group. The plasma levels of clusterin and clusterin mRNA levels in the skeletal muscle and liver were increased by the high-fat diet. The mRNA levels of the antioxidant enzymes were lower, and the mRNA levels of nicotinamide adenine dinucleotide phosphate oxidase (NOX) 1 and cytokines and protein carbonylation were higher in the skeletal muscle and liver in clusterin KO mice after the high-fat diet. Palmitate-induced gene expressions of NOX1 and cytokines were higher in the primary cultured hepatocytes of clusterin KO mice compared with the wild-type mice. Clusterin inhibited the gene expression and reactive oxygen species generation by palmitate in the hepatocytes and C2C12. AKT phosphorylation by insulin was reduced in the hepatocytes of clusterin KO mice. These results suggest that clusterin plays a protective role against high-fat diet-induced insulin resistance through the suppression of oxidative stress and inflammation.

scholarly journals Wt1 haploinsufficiency induces browning of epididymal fat and alleviates metabolic dysfunction in mice on high-fat diet

Diabetologia ◽  
2021 ◽  
Author(s):  
Karin M. Kirschner ◽  
Anna Foryst-Ludwig ◽  
Sabrina Gohlke ◽  
Chen Li ◽  
Roberto E. Flores ◽  
...  
Keyword(s):  
Metabolic Disease ◽  
Adipose Tissue ◽  
Glucose Tolerance ◽  
Knockout Mice ◽  
High Fat Diet ◽  
Whole Body ◽  
Mrna Levels ◽  
Wild Type ◽  
High Fat ◽  
Fat Depots

Abstract Aims/hypothesis Despite a similar fat storing function, visceral (intra-abdominal) white adipose tissue (WAT) is detrimental, whereas subcutaneous WAT is considered to protect against metabolic disease. Recent findings indicate that thermogenic genes, expressed in brown adipose tissue (BAT), can be induced primarily in subcutaneous WAT. Here, we investigate the hypothesis that the Wilms tumour gene product (WT1), which is expressed in intra-abdominal WAT but not in subcutaneous WAT and BAT, suppresses a thermogenic program in white fat cells. Methods Heterozygous Wt1 knockout mice and their wild-type littermates were examined in terms of thermogenic and adipocyte-selective gene expression. Glucose tolerance and hepatic lipid accumulation in these mice were assessed under normal chow and high-fat diet conditions. Pre-adipocytes isolated from the stromal vascular fraction of BAT were transduced with Wt1-expressing retrovirus, induced to differentiate and analysed for the expression of thermogenic and adipocyte-selective genes. Results Expression of the thermogenic genes Cpt1b and Tmem26 was enhanced and transcript levels of Ucp1 were on average more than tenfold higher in epididymal WAT of heterozygous Wt1 knockout mice compared with wild-type mice. Wt1 heterozygosity reduced epididymal WAT mass, improved whole-body glucose tolerance and alleviated severe hepatic steatosis upon diet-induced obesity in mice. Retroviral expression of WT1 in brown pre-adipocytes, which lack endogenous WT1, reduced mRNA levels of Ucp1, Ppargc1a, Cidea, Prdm16 and Cpt1b upon in vitro differentiation by 60–90%. WT1 knockdown in epididymal pre-adipocytes significantly lowered Aldh1a1 and Zfp423 transcripts, two key suppressors of the thermogenic program. Conversely, Aldh1a1 and Zfp423 mRNA levels were increased approximately five- and threefold, respectively, by retroviral expression of WT1 in brown pre-adipocytes. Conclusion/interpretation WT1 functions as a white adipocyte determination factor in epididymal WAT by suppressing thermogenic genes. Reducing Wt1 expression in this and other intra-abdominal fat depots may represent a novel treatment strategy in metabolic disease. Graphical abstract

scholarly journals Helix-Loop-Helix Factor Id3 (Inhibitor of Differentiation 3)

2020 ◽  
Author(s):  
Angelina Misiou ◽  
James C. Garmey ◽  
Jack M. Hensien ◽  
Daniel B. Harmon ◽  
Victoria Osinsk ◽  
...  
Keyword(s):  
High Fat Diet ◽  
Promoter Activity ◽  
Visceral Obesity ◽  
Metabolic Dysfunction ◽  
Wild Type ◽  
High Fat ◽  
Wild Type Littermate ◽  
Helix Loop Helix ◽  
The Impact ◽  
Circulating Levels

Objective: The aim of this study was to unravel mechanisms whereby deficiency of the transcription factor Id3 (inhibitor of differentiation 3) leads to metabolic dysfunction in visceral obesity. We investigated the impact of loss of Id3 on hyaluronic acid (HA) production by the 3 HAS (HA synthases; -1, -2, and -3) and on obesity-induced adipose tissue (AT) accumulation of proinflammatory B cells. Approach and Results: Male Id3 −/− mice and respective wild-type littermate controls were fed a 60% high-fat diet for 4 weeks. An increase in inflammatory B2 cells was detected in Id3 −/− epididymal AT. HA accumulated in epididymal AT of high-fat diet–fed Id3 −/− mice and circulating levels of HA were elevated. Has2 mRNA expression was increased in epididymal AT of Id3 −/− mice. Luciferase promoter assays showed that Id3 suppressed Has2 promoter activity, while loss of Id3 stimulated Has2 promoter activity. Functionally, HA strongly promoted B2 cell adhesion in the AT and on cultured vascular smooth muscle cells of Id3 −/− mice, an effect sensitive to hyaluronidase. Conclusions: Our data demonstrate that loss of Id3 increases Has2 expression in the epididymal AT, thereby promoting HA accumulation. In turn, elevated HA content promotes HA-dependent binding of B2 cells and an increase in the B2 cells in the AT, which contributes to AT inflammation.

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