scholarly journals Absence of gravin-mediated signaling inhibits development of high-fat diet-induced hyperlipidemia and atherosclerosis

2019 ◽  
Vol 317 (4) ◽  
pp. H793-H810 ◽  
Author(s):  
Qiying Fan ◽  
Xing Yin ◽  
Abeer Rababa’h ◽  
Andrea Diaz Diaz ◽  
Cori S. Wijaya ◽  
...  
Keyword(s):  
Lipid Metabolism ◽  
Protein Kinase ◽  
Lipid Accumulation ◽  
High Fat Diet ◽  
Regulatory Element ◽  
Plaque Formation ◽  
High Fat ◽  
Element Binding Protein ◽  
Sterol Regulatory Element

Gravin, an A-kinase anchoring protein, is known to play a role in regulating key processes that lead to inflammation and atherosclerosis development, namely, cell migration, proliferation, and apoptosis. We investigated the role of gravin in the development of high-fat diet (HFD)-induced atherosclerosis and hyperlipidemia. Five-week-old male wild-type (WT) and gravin-t/t mice were fed a normal diet or an HFD for 16 wk. Gravin-t/t mice showed significantly lower liver-to-body-weight ratio, cholesterol, triglyceride, and very low-density lipoprotein levels in serum as compared with WT mice on HFD. Furthermore, there was less aortic plaque formation coupled with decreased lipid accumulation and liver damage, as the gravin-t/t mice had lower levels of serum alanine aminotransferase and aspartate aminotransferase. Additionally, gravin-t/t HFD-fed mice had decreased expression of liver 3-hydroxy-3-methyl-glutaryl-CoA reductase, an essential enzyme for cholesterol synthesis and lower fatty acid synthase expression. Gravin-t/t HFD-fed mice also exhibited inhibition of sterol regulatory element binding protein-2 (SREBP-2) expression, a liver transcription factor associated with the regulation of lipid transportation. In response to platelet-derived growth factor receptor treatment, gravin-t/t vascular smooth muscle cells exhibited lower intracellular calcium transients and decreased protein kinase A- and protein kinase C-dependent substrate phosphorylation, notably involving the Erk1/2 signaling pathway. Collectively, these results suggest the involvement of gravin-dependent regulation of lipid metabolism via the reduction of SREBP-2 expression. The absence of gravin-mediated signaling lowers blood pressure, reduces plaque formation in the aorta, and decreases lipid accumulation and damage in the liver of HFD mice. Through these processes, the absence of gravin-mediated signaling complex delays the HFD-induced hyperlipidemia and atherosclerosis. NEW & NOTEWORTHY The gravin scaffolding protein plays a key role in the multiple enzymatic pathways of lipid metabolism. We have shown for the first time the novel role of gravin in regulating the pathways related to the initiation and progression of atherosclerosis. Specifically, an absence of gravin-mediated signaling decreases the lipid levels (cholesterol, triglyceride, and VLDL) that are associated with sterol regulatory element binding protein-2 downregulation.

Contribution of high fat diet induced PCSK9 upregulation to a mouse model of PCOS is mediated partly by SREBP2

Reproduction ◽  
2021 ◽  
Author(s):  
Wen-jing Guo ◽  
Yi-cheng Wang ◽  
Yong-dan Ma ◽  
Zhi-hui Cui ◽  
Li-xue Zhang ◽  
...  
Keyword(s):  
High Fat Diet ◽  
Cholesterol Metabolism ◽  
Regulatory Element ◽  
Follicular Development ◽  
Cholesterol Homeostasis ◽  
High Fat ◽  
Prevention And Treatment ◽  
Element Binding Protein ◽  
Sterol Regulatory Element

The incidence of PCOS due to highfat diet (HFD) consumption has been increasing significantly. However, the mechanism by which an HFD contributes to the pathogenesis of PCOS has not been elucidated. Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a key protein that regulates cholesterol metabolism. Our previous study revealed abnormally high PCSK9 levels in serum from patients with PCOS and in serum and hepatic and ovarian tissues from PCOS model mice, suggesting that PCSK9 is involved in the pathogenesis of PCOS. However, the factor that induces high PCSK9 expression in PCOS remained unclear. In this study, Pcsk9 knockout mice were used to further prove the role of PCSK9 in PCOS. We also studied the effects of an HFD on the expression of PCSK9 and sterol regulatory element-binding protein 2 (SREBP2), a regulator of cholesterol homeostasis and a key transcription factor that regulates the expression of PCSK9, and the roles of these proteins in PCOS pathology. Our results indicated HFD may play an important role by inducing abnormally high PCSK9 expression via SREBP2 upregulation. We further investigated the effects of an effective SREBPs inhibitor, fatostain, and found that it could reduce HFD induced PCSK9 expression, ameliorate hyperlipidemia and improve follicular development in PCOS model mice. Our study thus further elucidates the important role of an HFD in the pathogenesis of PCOS and provides a new clue in the prevention and treatment of this disorder.

Analysis of Sterol-Regulatory Element-Binding Protein 1c Target Genes in Mouse Liver during Aging and High-Fat Diet

2013 ◽  
Vol 6 (2) ◽  
pp. 107-122 ◽  
Author(s):  
Frédéric Capel ◽  
Gaëlle Rolland-Valognes ◽  
Catherine Dacquet ◽  
Manuel Brun ◽  
Michel Lonchampt ◽  
...  
Keyword(s):  
High Fat Diet ◽  
Mouse Liver ◽  
Target Genes ◽  
Binding Protein ◽  
Regulatory Element ◽  
High Fat ◽  
Element Binding Protein ◽  
Sterol Regulatory Element

scholarly journals FoxO3 regulates hepatic triglyceride metabolism via modulation of the expression of sterol regulatory-element binding protein 1c

2019 ◽  
Vol 18 (1) ◽  
Author(s):  
Liu Wang ◽  
Xiaopeng Zhu ◽  
Xiaoyang Sun ◽  
Xinyu Yang ◽  
Xinxia Chang ◽  
...  
Keyword(s):  
High Fat Diet ◽  
Hepg2 Cells ◽  
Transcriptional Activity ◽  
Regulatory Element ◽  
Luciferase Reporter ◽  
Chow Diet ◽  
Hepatic Triglyceride ◽  
High Fat ◽  
Element Binding Protein ◽  
Sterol Regulatory Element

Abstract Background Excessive intrahepatic lipid accumulation is the major characteristic of nonalcoholic fatty liver disease (NAFLD). We sought to identify the mechanisms involved in hepatic triglyceride (TG) homeostasis. Forkhead box class O (FoxO) transcription factors have been shown to play an important role in hepatic metabolism. However, little is known about the effect of FoxO3 on hepatic TG metabolism. Methods Liver biopsy samples from patients with NALFD and liver tissues from high glucose and high sucrose (HFHS) fed mice, ob/ob mice and db/db mice were collected for protein and mRNA analysis. HepG2 cells were transfected with small interfering RNA to mediate FoxO3 knockdown, or adenovirus and plasmid to mediate FoxO3 overexpression. FoxO3-cDNA was delivered by adenovirus to the liver of C57BL/6 J male mice on a chow diet or on a high-fat diet, followed by determination of hepatic lipid metabolism. Sterol regulatory element-binding protein 1c (SREBP1c) luciferase reporter gene plasmid was co-transfected into HepG2 cells with FoxO3 overexpression plasmid. Results FoxO3 expression was increased in the livers of HFHS mice, ob/ob mice, db/db mice and patients with NAFLD. Knockdown of FoxO3 reduced whereas overexpression of FoxO3 increased cellular TG concentrations in HepG2 cells. FoxO3 gain-of-function caused hepatic TG deposition in C57BL/6 J mice on a chow diet and aggravated hepatic steatosis when fed a high-fat diet. Analysis of the transcripts established the increased expression of genes related to TG synthesis, including SREBP1c, SCD1, FAS, ACC1, GPAM and DGAT2 in mouse liver. Mechanistically, overexpression of FoxO3 stimulated the expression of SREBP1c, whereas knockdown of FoxO3 inhibited the expression of SREBP1c. Luciferase reporter assays showed that SREBP1c regulated the transcriptional activity of the SREBP1c promoter. Conclusions FoxO3 promotes the transcriptional activity of the SREBP1c promoter, thus leading to increased TG synthesis and hepatic TG accumulation.

Regulation of sterol regulatory-element binding protein 1 gene expression in liver: role of insulin and protein kinase B/cAkt

2000 ◽  
Vol 349 (1) ◽  
pp. 13-17 ◽  
Author(s):  
Mark FLEISCHMANN ◽  
Patrick B. IYNEDJIAN
Keyword(s):  
Gene Expression ◽  
Protein Kinase ◽  
Recombinant Protein ◽  
Protein Kinase B ◽  
Binding Protein ◽  
Regulatory Element ◽  
Mutant Form ◽  
Element Binding Protein ◽  
Sterol Regulatory Element

Insulin stimulates the transcription of the sterol regulatory- element binding protein (SREBP) 1/ADD1 gene in liver. Hepatocytes in primary culture were used to delineate the insulin signalling pathway for induction of SREBP1 gene expression. The inhibitors of phosphoinositide 3-kinase (PI 3-kinase), wortmannin and LY 294002, abolished the insulin-dependent increase in SREBP1 mRNA, whereas the inhibitor of the mitogen- activated protein kinase cascade, PD 98059, was without effect. To investigate the role of protein kinase B (PKB)/cAkt downstream of PI 3-kinase, hepatocytes were transduced with an adenovirus encoding a PKB-oestrogen receptor fusion protein. The PKB activity of this recombinant protein was rapidly activated in hepatocytes challenged with 4-hydroxytamoxifen (OHT), as was endogenous PKB in hepatocytes challenged with insulin. The addition of OHT to transduced hepatocytes resulted in accumulation of SREBP1 mRNA, with a time-course and magnitude similar to the effect of insulin in non-transduced cells. The level of SREBP1 mRNA was not increased by OHT in hepatocytes expressing a mutant form of the recombinant protein whose PKB activity was not activated by OHT. Thus acute activation of PKB is sufficient to induce SREBP1 mRNA accumulation in primary hepatocytes, and might be the major signalling event by which insulin induces SREBP1 gene expression in the liver.

scholarly journals Not So Slim Anymore—Evidence for the Role of SUMO in the Regulation of Lipid Metabolism

Biomolecules ◽  
2020 ◽  
Vol 10 (8) ◽  
pp. 1154
Author(s):  
Amir Sapir
Keyword(s):  
Lipid Metabolism ◽  
Current Knowledge ◽  
Regulatory Element ◽  
Building Blocks ◽  
Life Forms ◽  
Nonalcoholic Fatty Liver ◽  
Element Binding Protein ◽  
Sterol Regulatory Element ◽  
Nonpolar Organic

One of the basic building blocks of all life forms are lipids—biomolecules that dissolve in nonpolar organic solvents but not in water. Lipids have numerous structural, metabolic, and regulative functions in health and disease; thus, complex networks of enzymes coordinate the different compositions and functions of lipids with the physiology of the organism. One type of control on the activity of those enzymes is the conjugation of the Small Ubiquitin-like Modifier (SUMO) that in recent years has been identified as a critical regulator of many biological processes. In this review, I summarize the current knowledge about the role of SUMO in the regulation of lipid metabolism. In particular, I discuss (i) the role of SUMO in lipid metabolism of fungi and invertebrates; (ii) the function of SUMO as a regulator of lipid metabolism in mammals with emphasis on the two most well-characterized cases of SUMO regulation of lipid homeostasis. These include the effect of SUMO on the activity of two groups of master regulators of lipid metabolism—the Sterol Regulatory Element Binding Protein (SERBP) proteins and the family of nuclear receptors—and (iii) the role of SUMO as a regulator of lipid metabolism in arteriosclerosis, nonalcoholic fatty liver, cholestasis, and other lipid-related human diseases.

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