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Thomas MM, Zaki ME, Youness E, Hamed K, Khedr AA, Abd El-Massieh PM, Abdo SM, El-Bassyouni HT. Measurement of Serum Chemerin, Oxidized LDL, and Vitamin D Levels in Prader–Willi Syndrome: A Cross-Sectional Study in Pediatric Egyptian Patients. JOURNAL OF CHILD SCIENCE 2020. [DOI: 10.1055/s-0040-1718896] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
AbstractPrader–Willi syndrome (PWS) is the commonest genetic cause of obesity. Oxidative stress and chronic low-grade inflammation play a crucial role in the pathogenesis of obesity. Alterations of vitamin D (25-OHD) levels are commonly encountered with obesity. The aim of this study was to analyze serum chemerin, oxidized low-density lipoprotein (ox-LDL), and 25-OHD values in pediatric PWS patients in comparison with obese healthy children and nonobese control groups, highlighting possible correlations with body mass index (BMI) and obesity. Twenty-six PWS Egyptian patients and 26 obese healthy individuals referred to the outpatient clinic of the Clinical Genetics Department, National Research Centre, Cairo, Egypt, and 20 control patients with matching age and sex were enrolled in the study. Patients were clinically diagnosed and confirmed by routine cytogenetic and fluorescence in-situ hybridization analysis. Anthropometric measurements were performed, and BMI was calculated by weight/height2 (kg/m2), and BMI z score was also determined. Serum chemerin, ox-LDL, and vitamin D were determined by enzyme-linked immunosorbent assay. Chemerin levels, which reflected chronic inflammation, were significantly elevated as compared with obese and nonobese controls (p ≤ 0.0001). Concerning oxidative damage, children with PWS showed higher Ox-LDL levels compared with obese and nonobese controls (p < 0.0001). Vitamin D levels were significantly lower in PWS patients compared with obese and nonobese controls (p ≤ 0.0001). Our data showed that obesity in PWS is associated with oxidative stress and chronic low-grade inflammation. Ox-LDL is a good indicator of oxidative stress, and chemerin could be used as a biomarker for the chronic inflammatory state. Furthermore, vitamin D supplementation is recommended in PWS patients
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Affiliation(s)
- Manal M. Thomas
- Clinical Genetics Department, Center of Scientific Excellence, National Research Centre, Cairo, Egypt
| | - Moushira E. Zaki
- Department of Biological Anthropology, National Research Centre, Cairo, Egypt
| | - Eman Youness
- Department of Biological Anthropology, National Research Centre, Cairo, Egypt
| | - Khaled Hamed
- Clinical Genetics Department, Center of Scientific Excellence, National Research Centre, Cairo, Egypt
| | - Azzah A. Khedr
- Human Genetics and Genome Research Division, Human Cytogenetics Department, National Research Centre, Cairo, Egypt
| | - Phoebe M. Abd El-Massieh
- Human Genetics and Genome Research Division, Oro-dental Genetics Department, National Research Centre, Cairo, Egypt
| | - Sara M. Abdo
- Biochemistry Division, Chemistry Department, Faculty of Science, Helwan University, Cairo, Egypt
| | - Hala T. El-Bassyouni
- Clinical Genetics Department, Center of Scientific Excellence, National Research Centre, Cairo, Egypt
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Oxidized LDL Modify the Human Adipocyte Phenotype to an Insulin Resistant, Proinflamatory and Proapoptotic Profile. Biomolecules 2020; 10:biom10040534. [PMID: 32244787 PMCID: PMC7226150 DOI: 10.3390/biom10040534] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2020] [Revised: 03/19/2020] [Accepted: 03/25/2020] [Indexed: 12/17/2022] Open
Abstract
Little information exists in humans on the regulation that oxidized low-density lipoprotein (oxLDL) exerts on adipocyte metabolism, which is associated with obesity and type 2 diabetes. The aim was to analyze the oxLDL effects on adipocytokine secretion and scavenger receptors (SRs) and cell death markers in human visceral adipocytes. Human differentiated adipocytes from visceral adipose tissue from non-obese and morbidly obese subjects were incubated with increasing oxLDL concentrations. mRNA expression of SRs, markers of apoptosis and autophagy, secretion of adipocytokines, and glucose uptake were analyzed. In non-obese and in morbidly obese subjects, oxLDL produced a decrease in insulin-induced glucose uptake, a significant dose-dependent increase in tumor necrosis factor-α (TNF-α), IL-6, and adiponectin secretion, and a decrease in leptin secretion. OxLDL produced a significant increase of Lox-1 and a decrease in Cxcl16 and Cl-p1 expression. The expression of Bnip3 (marker of apoptosis, necrosis and autophagy) was significantly increased and Bcl2 (antiapoptotic marker) was decreased. OxLDL could sensitize adipocytes to a lower insulin-induced glucose uptake, a more proinflammatory phenotype, and could modify the gene expression involved in apoptosis, autophagy, necrosis, and mitophagy. OxLDL can upregulate Lox-1, and this could lead to a possible amplification of proinflammatory and proapoptotic effects of oxLDL.
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Dias S, Paredes S, Ribeiro L. Drugs Involved in Dyslipidemia and Obesity Treatment: Focus on Adipose Tissue. Int J Endocrinol 2018; 2018:2637418. [PMID: 29593789 PMCID: PMC5822899 DOI: 10.1155/2018/2637418] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/05/2017] [Revised: 09/28/2017] [Accepted: 10/11/2017] [Indexed: 12/15/2022] Open
Abstract
Metabolic syndrome can be defined as a state of disturbed metabolic homeostasis characterized by visceral obesity, atherogenic dyslipidemia, arterial hypertension, and insulin resistance. The growing prevalence of metabolic syndrome will certainly contribute to the burden of cardiovascular disease. Obesity and dyslipidemia are main features of metabolic syndrome, and both can present with adipose tissue dysfunction, involved in the pathogenic mechanisms underlying this syndrome. We revised the effects, and underlying mechanisms, of the current approved drugs for dyslipidemia and obesity (fibrates, statins, niacin, resins, ezetimibe, and orlistat; sibutramine; and diethylpropion, phentermine/topiramate, bupropion and naltrexone, and liraglutide) on adipose tissue. Specifically, we explored how these drugs can modulate the complex pathways involved in metabolism, inflammation, atherogenesis, insulin sensitivity, and adipogenesis. The clinical outcomes of adipose tissue modulation by these drugs, as well as differences of major importance for clinical practice between drugs of the same class, were identified. Whether solutions to these issues will be found in further adjustments and combinations between drugs already in use or necessarily in new advances in pharmacology is not known. To better understand the effect of drugs used in dyslipidemia and obesity on adipose tissue not only is challenging for physicians but could also be the next step to tackle cardiovascular disease.
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Affiliation(s)
- Sofia Dias
- Department of Biomedicine, Faculty of Medicine, University of Porto, 4200-319 Porto, Portugal
| | - Sílvia Paredes
- Department of Endocrinology, Hospital de Braga, 4710-243 Braga, Portugal
- Department of Public Health and Forensic Sciences, and Medical Education, Faculty of Medicine, University of Porto, 4200-319 Porto, Portugal
| | - Laura Ribeiro
- Department of Biomedicine, Faculty of Medicine, University of Porto, 4200-319 Porto, Portugal
- Department of Public Health and Forensic Sciences, and Medical Education, Faculty of Medicine, University of Porto, 4200-319 Porto, Portugal
- I3S-Instituto de Investigação e Inovação em Saúde, University of Porto, 4200-135 Porto, Portugal
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Song G, Wu X, Zhang P, Yu Y, Yang M, Jiao P, Wang N, Song H, Wu Y, Zhang X, Liu H, Qin S. High-density lipoprotein inhibits ox-LDL-induced adipokine secretion by upregulating SR-BI expression and suppressing ER Stress pathway. Sci Rep 2016; 6:30889. [PMID: 27468698 PMCID: PMC4965769 DOI: 10.1038/srep30889] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2016] [Accepted: 07/12/2016] [Indexed: 02/06/2023] Open
Abstract
Endoplasmic reticulum stress (ERS) in adipocytes can modulate adipokines secretion. The aim of this study was to explore the protective effect of high-density lipoprotein (HDL) on oxidized low-density lipoprotein (ox-LDL)-induced ERS-C/EBP homologous protein (CHOP) pathway-mediated adipokine secretion. Our results showed that serum adipokines, including visfatin, resistin and TNF-α, correlated inversely with serum HDL cholesterol level in patients with abdominal obesity. In vitro, like ERS inhibitor 4-phenylbutyric acid (PBA), HDL inhibited ox-LDL- or tunicamycin (TM, an ERS inducer)-induced increase in visfatin and resistin secretion. Moreover, HDL inhibited ox-LDL-induced free cholesterol (FC) accumulation in whole cell lysate and in the endoplasmic reticulum. Additionally, like PBA, HDL inhibited ox-LDL- or TM-induced activation of ERS response as assessed by the decreased phosphorylation of protein kinase-like ER kinase and eukaryotic translation initiation factor 2α and reduced nuclear translocation of activating transcription factor 6 as well as the downregulation of Bip and CHOP. Furthermore, HDL increased scavenger receptor class B type I (SR-BI) expression and SR-BI siRNA treatment abolished the inhibitory effects of HDL on ox-LDL-induced FC accumulation and CHOP upregulation. These data indicate that HDL may suppress ox-LDL-induced FC accumulation in adipocytes through upregulation of SR-BI, subsequently preventing ox-LDL-induced ER stress-CHOP pathway-mediated adipocyte inflammation.
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Affiliation(s)
- Guohua Song
- Institute of Atherosclerosis, Key Laboratory of Atherosclerosis in Universities of Shandong, TaiShan Medical University, Taian, China
| | - Xia Wu
- Institute of Atherosclerosis, Key Laboratory of Atherosclerosis in Universities of Shandong, TaiShan Medical University, Taian, China.,Institute of Nursing, TaiShan Medical University, Taian, China.,Central Hospital of Taian City, Taian, China
| | - Pu Zhang
- Central Hospital of Taian City, Taian, China
| | - Yang Yu
- Institute of Atherosclerosis, Key Laboratory of Atherosclerosis in Universities of Shandong, TaiShan Medical University, Taian, China
| | - Mingfeng Yang
- Institute of Atherosclerosis, Key Laboratory of Atherosclerosis in Universities of Shandong, TaiShan Medical University, Taian, China
| | - Peng Jiao
- Institute of Atherosclerosis, Key Laboratory of Atherosclerosis in Universities of Shandong, TaiShan Medical University, Taian, China
| | - Ni Wang
- Maternal and child health hospital of Daiyue District, Taian, China
| | - Haiming Song
- Maternal and child health hospital of Daiyue District, Taian, China
| | - You Wu
- Institute of Atherosclerosis, Key Laboratory of Atherosclerosis in Universities of Shandong, TaiShan Medical University, Taian, China
| | - Xiangjian Zhang
- Hebei Collaborative Innovation Center for Cardio-cerebrovascular Disease and Hebei Key Laboratory of Vascular Homeostasis, Shijiazhuang, 050000, China
| | - Huaxia Liu
- Institute of Nursing, TaiShan Medical University, Taian, China
| | - Shucun Qin
- Institute of Atherosclerosis, Key Laboratory of Atherosclerosis in Universities of Shandong, TaiShan Medical University, Taian, China
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Effects of homocysteine on adipocyte differentiation and CD36 gene expression in 3T3-L1 adipocytes. J Cell Commun Signal 2015; 10:55-60. [PMID: 26691520 DOI: 10.1007/s12079-015-0316-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2015] [Accepted: 12/13/2015] [Indexed: 10/22/2022] Open
Abstract
The aim of this study was to investigate the effects of homocysteine (Hcy), a risk factor for cardiovascular diseases, hypertension, stroke and obesity, on expression of CD36 that regulates uptake of oxidized low-density lipoprotein (Ox-LDL) by adipocytes and differentiation of 3T3-L1 cells to adipocytes. Cell viability was determined using MTT assay, and density of triglycerides were measured with Oil Red O staining. The expression levels of CD36 were analyzed using SYBR green assay by quantitative RT-PCR. Our results showed that the addition of Hcy inhibited differentiation of 3T3-L1 preadipocytes in a dose-dependent manner without a significant cell toxicity (p < 0.05). Percentage CD36 gene expression increased in the Hcy treatment groups, but not statistically significantly (p > 0.05) compared to differentiated adipocytes. Hcy reduced adipocyte differentiation, but had no effect on the expression level of CD36 in vitro conditions. The effect of Hcy on uptake and clearance of Ox-LDL by adipose tissue now needs to be investigated in vivo.
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Zhong Q, Zhao S, Yu B, Wang X, Matyal R, Li Y, Jiang Z. High-density lipoprotein increases the uptake of oxidized low density lipoprotein via PPARγ/CD36 pathway in inflammatory adipocytes. Int J Biol Sci 2015; 11:256-65. [PMID: 25678844 PMCID: PMC4323365 DOI: 10.7150/ijbs.10258] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2014] [Accepted: 12/18/2014] [Indexed: 01/08/2023] Open
Abstract
Aim: Previous studies have demonstrated that the dysregulated-secretion of adipokines by adipocytes may contribute to obesity-associated atherosclerosis (As) and high density lipoprotein (HDL) may protect against atherogenesis through multiple pathways. This study was to explore the effect of HDL on the oxLDL uptake in inflammatory adipocytes stimulated by endotoxin lipopolysaccharide (LPS) and the possible mechanism. Methods and Results: 3T3-L1 adipocytes were cultured and induced to differentiation and maturation. Acute inflammation in adipocytes was induced by LPS (100 ng/ml) for 6 hours. The adipocytes were pretreated with HDL in various concentrations (10, 50, 100 μg/ml) for 16 hours or with specific PPARγ antagonist (GW9662, 10 μM) or agonist (Rosiglitazone, 10 μM) for 30 min before administration of LPS. The results showed that LPS significantly increased the release of inflammation-related adipokines, such as monocyte chemoattractant protein-1 (MCP-1), plasminogen activator inhibitor 1 (PAI-1), tumor necrosis factor-alpha (TNF-α), interleukin (IL)-8 and IL-6, while decreasing the release of leptin and adiponectin. Meanwhile, LPS reduced the uptake and degradation of 125I-oxLDL, and down-regulated the expression of PPARγ and CD36. Pretreatment with HDL dose-dependently affected the release of IL-8 and IL-6 and the reduced uptake and degradation of oxLDL of adipocytes stimulated by LPS, accompanied with marked upregulation of PPARγ and CD36 expression. Pretreatment with GW9662 markedly inhibited the upregulation of CD36 expression mediated by HDL (100 μg/ml), while the effects of Rosiglitazone were opposite to GW9662. Conclusions: HDL may increase oxLDL uptake of inflammatory adipocytes stimulated by LPS via upregulation of PPARγ/CD36 pathway, which may be a new mechanism of anti-atherosclerosis mediated by HDL.
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Affiliation(s)
- Qiaoqing Zhong
- 1. Post-doctoral Mobile Stations for Basic Medicine, Institute of Cardiovascular Disease and Key Lab for Arteriosclerology of Hunan Province, University of South China, Hengyang, Hunan, 421001, China ; 2. Department of Cardiology, First People's Hospital of Chenzhou, Chenzhou, 423000, China ; 3. Department of Cardiology, The second Xiangya Hospital of Central South University, Changsha, 410011, China
| | - Shuiping Zhao
- 3. Department of Cardiology, The second Xiangya Hospital of Central South University, Changsha, 410011, China
| | - Bilian Yu
- 3. Department of Cardiology, The second Xiangya Hospital of Central South University, Changsha, 410011, China
| | - Xing Wang
- 4. Department of Cardiology, the First Affiliated Hospital of Sun Yat-sen University, Guangzhou, 510080, China
| | - Robina Matyal
- 5. Department of Anesthesia and Critical Care, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02215, USA
| | - Yunping Li
- 5. Department of Anesthesia and Critical Care, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02215, USA
| | - Zhisheng Jiang
- 1. Post-doctoral Mobile Stations for Basic Medicine, Institute of Cardiovascular Disease and Key Lab for Arteriosclerology of Hunan Province, University of South China, Hengyang, Hunan, 421001, China
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7
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Shen L, Peng H, Zhao S, Xu D. A potent soluble epoxide hydrolase inhibitor, t-AUCB, modulates cholesterol balance and oxidized low density lipoprotein metabolism in adipocytes in vitro. Biol Chem 2014; 395:443-51. [PMID: 24225128 DOI: 10.1515/hsz-2013-0251] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2013] [Accepted: 11/08/2013] [Indexed: 11/15/2022]
Abstract
Abstract
The cholesterol metabolism in adipose tissue is dependent on the balance between cholesterol uptake and efflux. Adipocytes dysfunction and its cholesterol imbalance are associated with obesity. Adipocytes are the site for clearance of oxidized low density lipoprotein (oxLDL) in blood. Soluble epoxide hydrolase (sEH) is highly expressed in adipocytes. sEH converts epoxyeicosatrienoic acids (EETs) into less bioactive dihydroxyeicosatrienoic acids, which regulate cholesterol metabolism in adipocytes and block the development of atherosclerosis. In vitro, 3T3-L1 differentiated adipocytes were incubated with the sEH inhibitor t-AUCB (0, 1, 10, 50 or 100 mmol/l) for 24 h with or without the PPARγ inhibitor GW9662. To determine the effect of t-AUCB on oxLDL endocytosis, degradation and cholesterol efflux from adipocytes, we demonstrated that t-AUCB enhances the CD36-mediated recognition and degradation of oxLDL and improves cholesterol efflux via the upregulation of ABCA1 expression. Furthermore, t-AUCB blocked TNF-α secretion and increased adiponectin levels found in adipocytes culture medium. We provide evidence that these effects are PPARγ-dependent. These results suggest that an increase in EETs because of sEH inhibition could maintain cellular cholesterol homeostasis by the regulation of oxLDL clearance and cholesterol efflux via the EETs–PPARγ pathway.
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Chen Y, Chen M, Wu Z, Zhao S. Ox-LDL induces ER stress and promotes the adipokines secretion in 3T3-L1 adipocytes. PLoS One 2013; 8:e81379. [PMID: 24278099 PMCID: PMC3838420 DOI: 10.1371/journal.pone.0081379] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2013] [Accepted: 10/11/2013] [Indexed: 01/09/2023] Open
Abstract
Adipocytes behave as a rich source of adipokines, which may be the link between obesity and its complications. Endoplasmic reticulum (ER) stress in adipocytes can modulate adipokines secretion. The aim of this study is to evaluate the effect of oxidized low density lipoprotein(ox-LDL)treatment on ER stress and adipokines secretion in differentiated adipocytes. 3T3-L1 pre-adipocytes were cultured and differentiated into mature adipocytes in vitro. Differentiated adipocytes were incubated with various concentrations of ox-LDL (0-100 µg/ml) for 48 hours; 50µg/ml ox-LDL for various times (0-48 hours) with or without tauroursodeoxycholic acid (TUDCA) (0-400µM) pre-treatment. The protein expressions of ER stress markers, glucose regulated protein 78(GRP78) and CCAAT/enhancer binding protein [C/EBP] homologous protein (CHOP) in adipocytes were detected by Western blot. The mRNA expressions of visfatin and resistin were measured by real-time PCR and the protein release of visfatin and resistin in supernatant were determined by ELISA. Treatment with ox-LDL could increase the cholesterol concentration in adipocytes. Ox-LDL induced the expressions of GRP78 and CHOP protein in adipocytes and promoted visfatin and resistin secretion in culture medium in dose and time-dependent manner. TUDCA could attenuate the effect of ox-LDL on GRP78 and CHOP expressions and reduce visfatin and resistin at mRNA and protein level in dose-dependent manner. In conclusion, ox-LDL promoted the expression and secretion of visfatin and resistin through its activation of ER stress, which may be related to the increase of cholesterol load in adipocytes.
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Affiliation(s)
- Yaqin Chen
- Department of Cardiology, The Second Xiangya Hospital of Central South University, Central South University, Changsha, Hunan, P.R China
| | - Mingjie Chen
- Department of Cardiology, The Second Xiangya Hospital of Central South University, Central South University, Changsha, Hunan, P.R China
| | - Zhihong Wu
- Department of Cardiology, The Second Xiangya Hospital of Central South University, Central South University, Changsha, Hunan, P.R China
- * E-mail: (ZW); (SZ)
| | - Shuiping Zhao
- Department of Cardiology, The Second Xiangya Hospital of Central South University, Central South University, Changsha, Hunan, P.R China
- * E-mail: (ZW); (SZ)
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Shen L, Peng HC, Xu DY. Soluble epoxide hydrolase inhibitor: A potential target for regulating adipocyte dysfunction. Int J Cardiol 2012; 157:120-2. [DOI: 10.1016/j.ijcard.2012.03.050] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/03/2012] [Accepted: 03/03/2012] [Indexed: 02/03/2023]
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10
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Yu BL, Zhao SP, Hu JR. Cholesterol imbalance in adipocytes: a possible mechanism of adipocytes dysfunction in obesity. Obes Rev 2010; 11:560-7. [PMID: 20025694 DOI: 10.1111/j.1467-789x.2009.00699.x] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Studies of the past decade have increased our understanding of the role of adipose tissue dysfunction in obesity and obesity-related insulin resistance and type 2 diabetes. Although adipose tissue is the body's largest pool of free cholesterol, adipocytes have limited activity in cholesterol synthetic pathway. Thus, the majority of adipocyte cholesterol originates from circulating lipoproteins. To maintain cholesterol homeostasis, adipocytes have developed multiple pathways for cholesterol efflux. Several transcriptional factors, such as sterol regulatory element-binding proteins and liver X receptors may be responsible for the regulation of cholesterol homeostasis in adipocytes. Most notably, because altering cholesterol balance profoundly modifies adipocyte metabolism in a way resembling that seen in hypertrophied adipocytes, cholesterol imbalance is recognized as a characteristic for enlarged adipocytes per se in the obese state. In addition, plasma membrane cholesterol normalization by chromium picolinate can fully restore insulin-stimulated glucose transport, further supporting the role of the adipocyte cholesterol imbalance in obesity and insulin resistance.
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Affiliation(s)
- B-L Yu
- Department of Cardiology, The Second Xiangya Hospital of Central South University, Changsha, Hunan, China
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Scazzocchio B, Varì R, D'Archivio M, Santangelo C, Filesi C, Giovannini C, Masella R. Oxidized LDL impair adipocyte response to insulin by activating serine/threonine kinases. J Lipid Res 2009; 50:832-45. [PMID: 19136667 DOI: 10.1194/jlr.m800402-jlr200] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Oxidized LDL (oxLDL) increase in patients affected by type-2 diabetes, obesity, and metabolic syndrome. Likewise, insulin resistance, an impaired responsiveness of target tissues to insulin, is associated with those pathological conditions. To investigate a possible causal relationship between oxLDL and the onset of insulin resistance, we evaluated the response to insulin of 3T3-L1 adipocytes treated with oxLDL. We observed that oxLDL inhibited glucose uptake (-40%) through reduced glucose transporter 4 (GLUT4) recruitment to the plasma membrane (-70%), without affecting GLUT4 gene expression. These findings were associated to the impairment of insulin signaling. Specifically, in oxLDL-treated cells insulin receptor (IR) substrate-1 (IRS-1) was highly degraded likely because of the enhanced Ser(307)phosphorylation. This process was largely mediated by the activation of the inhibitor of kappaB-kinase beta (IKKbeta) and the c-Jun NH(2)-terminal kinase (JNK). Moreover, the activation of IKKbeta positively regulated the nuclear content of nuclear factor kappaB (NF-kappaB), by inactivating the inhibitor of NF-kappaB (IkappaBalpha). The activated NF-kappaB further impaired per se GLUT4 functionality. Specific inhibitors of IKKbeta, JNK, and NF-kappaB restored insulin sensitivity in adipocytes treated with oxLDL. These data provide the first evidence that oxLDL, by activating serine/threonine kinases, impaired adipocyte response to insulin affecting pathways involved in the recruitment of GLUT4 to plasma membranes (PM). This suggests that oxLDL might participate in the development of insulin resistance.
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Affiliation(s)
- Beatrice Scazzocchio
- Department of Veterinary Public Health and Food Safety, Istituto Superiore di Sanità, Rome, Italy
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12
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Sun B, Boyanovsky BB, Connelly MA, Shridas P, van der Westhuyzen DR, Webb NR. Distinct mechanisms for OxLDL uptake and cellular trafficking by class B scavenger receptors CD36 and SR-BI. J Lipid Res 2007; 48:2560-70. [PMID: 17876058 DOI: 10.1194/jlr.m700163-jlr200] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Modified forms of LDL, including oxidized low density lipoprotein (OxLDL), contribute to macrophage lipid accumulation in the vessel wall. Despite the pathophysiological importance of uptake pathways for OxLDL, the molecular details of OxLDL endocytosis by macrophages are not well understood. Studies in vitro demonstrate that the class B scavenger receptor CD36 mediates macrophage uptake and degradation of OxLDL. Although the closely related scavenger receptor class B type I (SR-BI) binds OxLDL with high affinity, evidence that SR-BI plays a role in OxLDL metabolism is lacking. In this study, we directly compared OxLDL uptake and degradation by CD36 and SR-BI. Our results indicate that although CD36 and SR-BI internalize OxLDL, SR-BI mediates significantly less OxLDL degradation. Endocytosis of OxLDL by both SR-BI and CD36 is independent of caveolae, microtubules, and actin cytoskeleton. However, OxLDL uptake by CD36, but not SR-BI, is dependent on dynamin. The analysis of chimeric SR-BI/CD36 receptors shows that the CD36 C-terminal cytoplasmic tail is necessary and sufficient for dynamin-dependent OxLDL internalization by class B scavenger receptors. These findings indicate that different mechanisms are involved in OxLDL uptake by SR-BI and CD36, which may segregate these two structurally homologous receptors at the cell surface, leading to differences in intracellular trafficking and degradation.
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Affiliation(s)
- Bing Sun
- Graduate Center for Nutritional Sciences, University of Kentucky Medical Center, Lexington, KY 40536, USA
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Zhao SP, Yu BL, Xie XZ, Dong SZ, Dong J. Dual effects of oxidized low-density lipoprotein on LXR-ABCA1-apoA-I pathway in 3T3-L1 cells. Int J Cardiol 2007; 128:42-7. [PMID: 17643522 DOI: 10.1016/j.ijcard.2007.05.017] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/10/2007] [Revised: 04/23/2007] [Accepted: 05/11/2007] [Indexed: 11/30/2022]
Abstract
BACKGROUND The adipocyte has been proven to recognize and degrade oxidized low-density lipoprotein (oxLDL), while cholesterol efflux from adipocytes to clear excess cholesterol loaded by oxLDL is essential to maintain its normal function. Thus, it is intriguing to explore the effects of oxLDL on cholesterol efflux in adipocytes. METHODS Fully differentiated 3T3-L1 cells were incubated in the medium containing various concentrations of oxLDL (0 to 50 microg/mL) for 8 or 24 h. 10 micromol/L 22(R)-hydroxycholesterol was exposed to preconditioned adipocytes with 25 microg/mL oxLDL for 24 h. Reverse transcription polymerase chain reaction (RT-PCR) was used to evaluate adipocytes mRNA expression. Cholesterol efflux rate was determined through measuring release of radioactivity from (3)H-cholesterol prelabeled cells into medium containing apolipoprotein A-I (apoA-I). RESULTS Low concentrations of oxLDL caused a significant increase in apoA-I-mediated cholesterol efflux via enhancement of ATP binding cassette transporter A1 (ABCA1) pathway, whereas higher concentrations were incapable. In adipocytes preincubated with 25 microg/mL oxLDL for 24 h, 22(R)-hydroxycholesterol could increase ABCA1 and LXR* mRNA levels and apoA-I-mediated cholesterol efflux. CONCLUSION OxLDL has dual effects on ABCA1 pathway in adipocytes. It depends on the concentration and exposure time. The new action of low levels of oxLDL may provide further understanding to its atheroprotective effects.
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Affiliation(s)
- Shui-Ping Zhao
- Department of Cardiology, Second Xiangya Hospital of Central South University, Changsha, Hunan, PR China.
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Veltri BC, Backus RC, Rogers QR, Depeters EJ. Adipose fatty acid composition and rate of incorporation of alpha-linolenic acid differ between normal and lipoprotein lipase-deficient cats. J Nutr 2006; 136:2980-6. [PMID: 17116707 DOI: 10.1093/jn/136.12.2980] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Normal adiposity occurs in humans and mice deficient of adipose lipoprotein lipase (LPL) activity. Subnormal adiposity found in LPL-deficient cats is indicative of limited de novo synthesis of fatty acids (FAs). In 14 LPL-deficient (3.0 +/- 0.1 kg) and 8 normal (3.7 +/- 0.1 kg) queens, FAs in triacylglycerol (TAG), phospholipid (PL), and nonesterified FAs (NEFAs) of plasma and inguinal subcutaneous adipose were determined before and after (d 38, 61, 110, 117, and 251) dietary linseed oil supplementation (30 g/kg). By d 60, LPL-deficient queens gained body weight (+0.4 +/- 0.1 kg), developed normal body fat mass (25 +/- 2%), and were enriched in 18:3(n-3) in their plasma and adipose lipids. Adipose TAG 18:3(n-3) enrichment in LPL-deficient queens was subnormal at all sampling times and, as observed in normal queens, apparently not equilibrated by d 251. Adipose FA profiles in TAG but not PL were substantially different (P < 0.05) between LPL-deficient and normal queens; the 16:0 to 18:2(n-6) ratio was high in LPL-deficient (2.4-4.4) relative to normal queens (1.0-1.4). In LPL-deficient queens, fed-state plasma NEFA (n-6) and (n-3) enrichments were similar to those in adipose TAG, and plasma NEFA concentration was high (0.62 +/- 0.05 mmol/L) and similar to that in normal queens after withholding diet for 16 h. These data indicate that LPL deficiency in cats reduces dietary FA storage efficiency, favors storage of saturated over unsaturated FAs, and stimulates de novo FA synthesis substantive enough to support normal adiposity.
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Affiliation(s)
- Brian C Veltri
- Department of Animal Science, University of California, Davis, CA 9561, USA
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Wu ZH, Zhao SP. Adipocyte: a potential target for the treatment of atherosclerosis. Med Hypotheses 2006; 67:82-6. [PMID: 16500036 DOI: 10.1016/j.mehy.2005.12.042] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2005] [Accepted: 12/23/2005] [Indexed: 11/30/2022]
Abstract
Obesity is an independent risk factor for coronary heart disease, whereas the underlying mechanisms have not been fully elucidated. Adipocytes may produce various adipokines with favorable and unfavorable cardiovascular effects. The dysregulated secretion of adipokines by adipocytes may contribute to obese associated atherosclerosis. Adipocytes can also function as phagocytes to uptake and degrade oxidized low-density lipoprotein (Ox-LDL), suggesting that adipocytes possibly involve in clearance of Ox-LDL in blood. The dysfunctional adipocytes might be implicated in the atherogenesis. Some cardioprotective drugs mediate their cardiovascular benefits partly through their direct beneficial effects on adipocytes. Therefore, we hypothesized that adipocytes might be potential target for the treatment of atherosclerosis.
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Affiliation(s)
- Zhi-hong Wu
- Department of Cardiology, The Second Xiangya Hospital of Central South University, Middle Ren-Min Road No. 86, Changsha, Hunan 410011, PR China.
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