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Qiu Y, Gan M, Wang X, Liao T, Chen Q, Lei Y, Chen L, Wang J, Zhao Y, Niu L, Wang Y, Zhang S, Zhu L, Shen L. The global perspective on peroxisome proliferator-activated receptor γ (PPARγ) in ectopic fat deposition: A review. Int J Biol Macromol 2023; 253:127042. [PMID: 37742894 DOI: 10.1016/j.ijbiomac.2023.127042] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2023] [Revised: 09/20/2023] [Accepted: 09/21/2023] [Indexed: 09/26/2023]
Abstract
Excessive expansion of adipocytes can have unhealthy consequences as excess free fatty acids enter other tissues and cause ectopic fat deposition by resynthesizing triglycerides. This lipid accumulation in various tissues is harmful and can increase the risk of related metabolic diseases such as type II diabetes, cardiovascular disease, and insulin resistance. Peroxisome proliferator-activated receptors (PPARs) are members of the nuclear hormone receptor superfamily that play a key role in energy metabolism as fatty acid metabolism sensors, and peroxisome proliferator-activated receptor γ (PPARγ) is the main subtype responsible for fat cell differentiation and adipogenesis. In this paper, we introduce the main structure and function of PPARγ and its regulatory role in the process of lipogenesis in the liver, kidney, skeletal muscle, and pancreas. This information can serve as a reference for further understanding the regulatory mechanisms and measures of the PPAR family in the process of ectopic fat deposition.
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Affiliation(s)
- Yanhao Qiu
- Farm Animal Genetic Resource Exploration and Innovation Key Laboratory of Sichuan Province, Sichuan Agricultural University, Chengdu 611130, China; Key Laboratory of Livestock and Poultry Multi-omics, Ministry of Agriculture and Rural Affairs, College of Animal and Technology, Sichuan Agricultural University, Chengdu 611130, China
| | - Mailin Gan
- Farm Animal Genetic Resource Exploration and Innovation Key Laboratory of Sichuan Province, Sichuan Agricultural University, Chengdu 611130, China; Key Laboratory of Livestock and Poultry Multi-omics, Ministry of Agriculture and Rural Affairs, College of Animal and Technology, Sichuan Agricultural University, Chengdu 611130, China
| | - Xingyu Wang
- Farm Animal Genetic Resource Exploration and Innovation Key Laboratory of Sichuan Province, Sichuan Agricultural University, Chengdu 611130, China; Key Laboratory of Livestock and Poultry Multi-omics, Ministry of Agriculture and Rural Affairs, College of Animal and Technology, Sichuan Agricultural University, Chengdu 611130, China
| | - Tianci Liao
- Farm Animal Genetic Resource Exploration and Innovation Key Laboratory of Sichuan Province, Sichuan Agricultural University, Chengdu 611130, China; Key Laboratory of Livestock and Poultry Multi-omics, Ministry of Agriculture and Rural Affairs, College of Animal and Technology, Sichuan Agricultural University, Chengdu 611130, China
| | - Qiuyang Chen
- Farm Animal Genetic Resource Exploration and Innovation Key Laboratory of Sichuan Province, Sichuan Agricultural University, Chengdu 611130, China; Key Laboratory of Livestock and Poultry Multi-omics, Ministry of Agriculture and Rural Affairs, College of Animal and Technology, Sichuan Agricultural University, Chengdu 611130, China
| | - Yuhang Lei
- Farm Animal Genetic Resource Exploration and Innovation Key Laboratory of Sichuan Province, Sichuan Agricultural University, Chengdu 611130, China; Key Laboratory of Livestock and Poultry Multi-omics, Ministry of Agriculture and Rural Affairs, College of Animal and Technology, Sichuan Agricultural University, Chengdu 611130, China
| | - Lei Chen
- Farm Animal Genetic Resource Exploration and Innovation Key Laboratory of Sichuan Province, Sichuan Agricultural University, Chengdu 611130, China; Key Laboratory of Livestock and Poultry Multi-omics, Ministry of Agriculture and Rural Affairs, College of Animal and Technology, Sichuan Agricultural University, Chengdu 611130, China
| | - Jinyong Wang
- Chongqing Academy of Animal Science, Rongchang, Chongqing 402460, China
| | - Ye Zhao
- Farm Animal Genetic Resource Exploration and Innovation Key Laboratory of Sichuan Province, Sichuan Agricultural University, Chengdu 611130, China; Key Laboratory of Livestock and Poultry Multi-omics, Ministry of Agriculture and Rural Affairs, College of Animal and Technology, Sichuan Agricultural University, Chengdu 611130, China
| | - Lili Niu
- Farm Animal Genetic Resource Exploration and Innovation Key Laboratory of Sichuan Province, Sichuan Agricultural University, Chengdu 611130, China; Key Laboratory of Livestock and Poultry Multi-omics, Ministry of Agriculture and Rural Affairs, College of Animal and Technology, Sichuan Agricultural University, Chengdu 611130, China
| | - Yan Wang
- Farm Animal Genetic Resource Exploration and Innovation Key Laboratory of Sichuan Province, Sichuan Agricultural University, Chengdu 611130, China; Key Laboratory of Livestock and Poultry Multi-omics, Ministry of Agriculture and Rural Affairs, College of Animal and Technology, Sichuan Agricultural University, Chengdu 611130, China
| | - Shunhua Zhang
- Farm Animal Genetic Resource Exploration and Innovation Key Laboratory of Sichuan Province, Sichuan Agricultural University, Chengdu 611130, China; Key Laboratory of Livestock and Poultry Multi-omics, Ministry of Agriculture and Rural Affairs, College of Animal and Technology, Sichuan Agricultural University, Chengdu 611130, China
| | - Li Zhu
- Farm Animal Genetic Resource Exploration and Innovation Key Laboratory of Sichuan Province, Sichuan Agricultural University, Chengdu 611130, China; Key Laboratory of Livestock and Poultry Multi-omics, Ministry of Agriculture and Rural Affairs, College of Animal and Technology, Sichuan Agricultural University, Chengdu 611130, China.
| | - Linyuan Shen
- Farm Animal Genetic Resource Exploration and Innovation Key Laboratory of Sichuan Province, Sichuan Agricultural University, Chengdu 611130, China; Key Laboratory of Livestock and Poultry Multi-omics, Ministry of Agriculture and Rural Affairs, College of Animal and Technology, Sichuan Agricultural University, Chengdu 611130, China.
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Yoo HS, Moss KO, Cockrum MA, Woo W, Napoli JL. Energy status regulates levels of the RAR/RXR ligand 9-cis-retinoic acid in mammalian tissues: Glucose reduces its synthesis in β-cells. J Biol Chem 2023; 299:105255. [PMID: 37714463 PMCID: PMC10582780 DOI: 10.1016/j.jbc.2023.105255] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2023] [Revised: 09/01/2023] [Accepted: 09/10/2023] [Indexed: 09/17/2023] Open
Abstract
9-cis-retinoic acid (9cRA) binds retinoic acid receptors (RAR) and retinoid X receptors (RXR) with nanomolar affinities, in contrast to all-trans-retinoic acid (atRA), which binds only RAR with nanomolar affinities. RXR heterodimerize with type II nuclear receptors, including RAR, to regulate a vast gene array. Despite much effort, 9cRA has not been identified as an endogenous retinoid, other than in pancreas. By revising tissue analysis methods, 9cRA quantification by liquid chromatography-tandem mass spectrometry becomes possible in all mouse tissues analyzed. 9cRA occurs in concentrations similar to or greater than atRA. Fasting increases 9cRA in white and brown adipose, brain and pancreas, while increasing atRA in white adipose, liver and pancreas. 9cRA supports FoxO1 actions in pancreas β-cells and counteracts glucose actions that lead to glucotoxicity; in part by inducing Atg7 mRNA, which encodes the key enzyme essential for autophagy. Glucose suppresses 9cRA biosynthesis in the β-cell lines 832/13 and MIN6. Glucose reduces 9cRA biosynthesis in 832/13 cells by inhibiting Rdh5 transcription, unconnected to insulin, through cAMP and Akt, and inhibiting FoxO1. Through adapting tissue specifically to fasting, 9cRA would act independent of atRA. Widespread occurrence of 9cRA in vivo, and its self-sufficient adaptation to energy status, provides new perspectives into regulation of energy balance, attenuation of insulin and glucose actions, regulation of type II nuclear receptors, and retinoid biology.
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Affiliation(s)
- Hong Sik Yoo
- Department of Nutritional Sciences and Toxicology, Graduate Program in Metabolic Biology, University of California, Berkeley, Berkeley, California, USA
| | - Kristin Obrochta Moss
- Department of Nutritional Sciences and Toxicology, Graduate Program in Metabolic Biology, University of California, Berkeley, Berkeley, California, USA
| | - Michael A Cockrum
- Department of Nutritional Sciences and Toxicology, Graduate Program in Metabolic Biology, University of California, Berkeley, Berkeley, California, USA
| | - Wonsik Woo
- Department of Nutritional Sciences and Toxicology, Graduate Program in Metabolic Biology, University of California, Berkeley, Berkeley, California, USA
| | - Joseph L Napoli
- Department of Nutritional Sciences and Toxicology, Graduate Program in Metabolic Biology, University of California, Berkeley, Berkeley, California, USA.
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Chen G. The Interactions of Insulin and Vitamin A Signaling Systems for the Regulation of Hepatic Glucose and Lipid Metabolism. Cells 2021; 10:cells10082160. [PMID: 34440929 PMCID: PMC8393264 DOI: 10.3390/cells10082160] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2021] [Revised: 08/17/2021] [Accepted: 08/19/2021] [Indexed: 02/07/2023] Open
Abstract
The pandemics of obesity and type 2 diabetes have become a concern of public health. Nutrition plays a key role in these concerns. Insulin as an anabolic hormonal was discovered exactly 100 years ago due to its activity in controlling blood glucose level. Vitamin A (VA), a lipophilic micronutrient, has been shown to regulate glucose and fat metabolism. VA's physiological roles are mainly mediated by its metabolite, retinoic acid (RA), which activates retinoic acid receptors (RARs) and retinoid X receptors (RXRs), which are two transcription factors. The VA status and activations of RARs and RXRs by RA and synthetic agonists have shown to affect the glucose and lipid metabolism in animal models. Both insulin and RA signaling systems regulate the expression levels of genes involved in the regulation of hepatic glucose and lipid metabolism. Interactions of insulin and RA signaling systems have been observed. This review is aimed at summarizing the history of diabetes, insulin and VA signaling systems; the effects of VA status and activation of RARs and RXRs on metabolism and RAR and RXR phosphorylation; and possible interactions of insulin and RA in the regulation of hepatic genes for glucose and lipid metabolism. In addition, some future research perspectives for understanding of nutrient and hormone interactions are provided.
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Affiliation(s)
- Guoxun Chen
- Department of Nutrition, University of Tennessee at Knoxville, Knoxville, TN 37996, USA
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Guan D, Sun H, Wang J, Wang Z, Li Y, Han H, Li X, Fang T. Rosiglitazone promotes glucose metabolism of GIFT tilapia based on the PI3K/Akt signaling pathway. Physiol Rep 2021; 9:e14765. [PMID: 33650786 PMCID: PMC7923568 DOI: 10.14814/phy2.14765] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2020] [Revised: 01/28/2021] [Accepted: 01/30/2021] [Indexed: 11/24/2022] Open
Abstract
The study aimed to explore the effects of rosiglitazone on glucose metabolism of GIFT tilapia based on the PI3K/Akt signaling pathway. The experiment was divided into five groups: normal starch group (32%, LC), high starch group (53%, HC), high starch +rosiglitazone group 1 (10 mg/kg, R1), high starch + rosiglitazone group 2 (20 mg/kg, R2), and high starch + rosiglitazone group 3 (30 mg/kg, R3). The results showed that a high starch diet supplemented with 10-20 mg/kg rosiglitazone had a better specific growth rate and protein efficiency that was beneficial for the growth of the tilapia. Rosiglitazone had no significant effect on the contents of crude lipid, crude protein, crude ash, and moisture of the whole fish body (p > 0.05). The contents of triglycerides and total cholesterol in the R1, R2, and R3 groups were lower than those in the HC group. The levels of glutamic oxaloacetic transaminase (GOT) and glutamic pyruvic transaminase (GPT) in R1 and R2 groups were significantly lower than those in the HC groups (p < 0.05). However, the GOT and GPT levels in the R3 groups were significantly higher than those in the R1 and R2 groups (p < 0.05). With an increase in the rosiglitazone concentration, the contents of serum glucose, insulin, and hepatic glycogen in the R1, R2, and R3 groups decreased gradually. Meanwhile, the muscle glycogen content in the R1, R2, and R3 groups increased gradually. The mRNA expression of the IRS-1, PI3K, GLUT-4, and Akt proteins in the R1, R2, and R3 groups was significantly higher than that in the HC group (p < 0.05). Compared with the HC group, the expression of the GSK-3 mRNA in the R1, R2, and R3 groups was significantly reduced (p < 0.05). The protein expression of p-Akt in the R1 and R2 groups was higher than that in the HC group (p > 0.05). The protein expression of p-GSK-3β in the R1 and R2 groups was significantly higher than that in the HC group (p < 0.05). In conclusion, a high starch diet supplemented with rosiglitazone can improve growth, enhance the serum biochemical indices, and increase the muscle glycogen content in the GIFT tilapia. It benefits in upregulating the IRS-1, PI3K, and GLUT-4 mRNA levels in the skeletal muscle and promotes glucose uptake. Meanwhile, the phosphorylation of Akt and GSK-3β increased significantly and resulted in the inactivation of GSK-3β and alleviation of insulin resistance.
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Affiliation(s)
- Dong‐Yan Guan
- Shandong Provincial Key Lab. of Animal Biotechnology and Disease Control and PreventionLab of Aquatic Animal Nutrition & Environmental HealthShandong Agricultural UniversityTaian CityShandong ProvinceChina
| | - Hui‐Wen Sun
- Shandong Provincial Key Lab. of Animal Biotechnology and Disease Control and PreventionLab of Aquatic Animal Nutrition & Environmental HealthShandong Agricultural UniversityTaian CityShandong ProvinceChina
| | - Ji‐Ting Wang
- Shandong Provincial Key Lab. of Animal Biotechnology and Disease Control and PreventionLab of Aquatic Animal Nutrition & Environmental HealthShandong Agricultural UniversityTaian CityShandong ProvinceChina
| | - Zhen Wang
- Shandong Provincial Key Lab. of Animal Biotechnology and Disease Control and PreventionLab of Aquatic Animal Nutrition & Environmental HealthShandong Agricultural UniversityTaian CityShandong ProvinceChina
| | - Yang Li
- Shandong Provincial Key Lab. of Animal Biotechnology and Disease Control and PreventionLab of Aquatic Animal Nutrition & Environmental HealthShandong Agricultural UniversityTaian CityShandong ProvinceChina
| | - Hao‐Jun Han
- Shandong Provincial Key Lab. of Animal Biotechnology and Disease Control and PreventionLab of Aquatic Animal Nutrition & Environmental HealthShandong Agricultural UniversityTaian CityShandong ProvinceChina
| | - Xiang Li
- Shandong Provincial Key Lab. of Animal Biotechnology and Disease Control and PreventionLab of Aquatic Animal Nutrition & Environmental HealthShandong Agricultural UniversityTaian CityShandong ProvinceChina
| | - Ting‐Ting Fang
- Shandong Provincial Key Lab. of Animal Biotechnology and Disease Control and PreventionLab of Aquatic Animal Nutrition & Environmental HealthShandong Agricultural UniversityTaian CityShandong ProvinceChina
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Ren G, Kim T, Kim HS, Young ME, Muccio DD, Atigadda VR, Blum SI, Tse HM, Habegger KM, Bhatnagar S, Coric T, Bjornsti MA, Shalev A, Frank SJ, Kim JA. A Small Molecule, UAB126, Reverses Diet-Induced Obesity and its Associated Metabolic Disorders. Diabetes 2020; 69:2003-2016. [PMID: 32611548 PMCID: PMC7458036 DOI: 10.2337/db19-1001] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/04/2019] [Accepted: 06/18/2020] [Indexed: 12/13/2022]
Abstract
Targeting retinoid X receptor (RXR) has been proposed as one of the therapeutic strategies to treat individuals with metabolic syndrome, as RXR heterodimerizes with multiple nuclear receptors that regulate genes involved in metabolism. Despite numerous efforts, RXR ligands (rexinoids) have not been approved for clinical trials to treat metabolic syndrome due to the serious side effects such as hypertriglyceridemia and altered thyroid hormone axis. In this study, we demonstrate a novel rexinoid-like small molecule, UAB126, which has positive effects on metabolic syndrome without the known side effects of potent rexinoids. Oral administration of UAB126 ameliorated obesity, insulin resistance, hepatic steatosis, and hyperlipidemia without changes in food intake, physical activity, and thyroid hormone levels. RNA-sequencing analysis revealed that UAB126 regulates the expression of genes in the liver that are modulated by several nuclear receptors, including peroxisome proliferator-activated receptor α and/or liver X receptor in conjunction with RXR. Furthermore, UAB126 not only prevented but also reversed obesity-associated metabolic disorders. The results suggest that optimized modulation of RXR may be a promising strategy to treat metabolic disorders without side effects. Thus, the current study reveals that UAB126 could be an attractive therapy to treat individuals with obesity and its comorbidities.
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Affiliation(s)
- Guang Ren
- Division of Endocrinology, Diabetes, and Metabolism, Department of Medicine, University of Alabama at Birmingham, Birmingham, AL
- UAB Comprehensive Diabetes Center, University of Alabama at Birmingham, Birmingham, AL
| | - Teayoun Kim
- Division of Endocrinology, Diabetes, and Metabolism, Department of Medicine, University of Alabama at Birmingham, Birmingham, AL
- UAB Comprehensive Diabetes Center, University of Alabama at Birmingham, Birmingham, AL
| | - Hae-Suk Kim
- Division of Endocrinology, Diabetes, and Metabolism, Department of Medicine, University of Alabama at Birmingham, Birmingham, AL
- UAB Comprehensive Diabetes Center, University of Alabama at Birmingham, Birmingham, AL
| | - Martin E Young
- UAB Comprehensive Diabetes Center, University of Alabama at Birmingham, Birmingham, AL
- Division of Cardiovascular Disease, Department of Medicine, University of Alabama at Birmingham, Birmingham, AL
| | - Donald D Muccio
- Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, Birmingham, AL
| | - Venkatram R Atigadda
- Department of Chemistry, University of Alabama at Birmingham, Birmingham, AL
- Department of Dermatology, University of Alabama at Birmingham, Birmingham, AL
| | - Samuel I Blum
- UAB Comprehensive Diabetes Center, University of Alabama at Birmingham, Birmingham, AL
- Department of Microbiology, University of Alabama at Birmingham, Birmingham, AL
| | - Hubert M Tse
- UAB Comprehensive Diabetes Center, University of Alabama at Birmingham, Birmingham, AL
- Department of Microbiology, University of Alabama at Birmingham, Birmingham, AL
| | - Kirk M Habegger
- Division of Endocrinology, Diabetes, and Metabolism, Department of Medicine, University of Alabama at Birmingham, Birmingham, AL
- UAB Comprehensive Diabetes Center, University of Alabama at Birmingham, Birmingham, AL
| | - Sushant Bhatnagar
- Division of Endocrinology, Diabetes, and Metabolism, Department of Medicine, University of Alabama at Birmingham, Birmingham, AL
- UAB Comprehensive Diabetes Center, University of Alabama at Birmingham, Birmingham, AL
| | - Tatjana Coric
- Department of Pharmacology and Toxicology, University of Alabama at Birmingham, Birmingham, AL
| | - Mary-Ann Bjornsti
- Department of Pharmacology and Toxicology, University of Alabama at Birmingham, Birmingham, AL
| | - Anath Shalev
- Division of Endocrinology, Diabetes, and Metabolism, Department of Medicine, University of Alabama at Birmingham, Birmingham, AL
- UAB Comprehensive Diabetes Center, University of Alabama at Birmingham, Birmingham, AL
| | - Stuart J Frank
- Division of Endocrinology, Diabetes, and Metabolism, Department of Medicine, University of Alabama at Birmingham, Birmingham, AL
- UAB Comprehensive Diabetes Center, University of Alabama at Birmingham, Birmingham, AL
| | - Jeong-A Kim
- Division of Endocrinology, Diabetes, and Metabolism, Department of Medicine, University of Alabama at Birmingham, Birmingham, AL
- UAB Comprehensive Diabetes Center, University of Alabama at Birmingham, Birmingham, AL
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Tan YQ, Li Q, Wang L, Chiu-Leung LC, Leung LK. The livestock growth-promoter zeranol facilitates GLUT4 translocation in 3T3 L1 adipocytes. CHEMOSPHERE 2020; 253:126772. [PMID: 32464760 DOI: 10.1016/j.chemosphere.2020.126772] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/14/2020] [Revised: 03/23/2020] [Accepted: 04/08/2020] [Indexed: 06/11/2023]
Abstract
Zeranol is an approved but controversial growth-promoting agent for livestock in North America. It is a mycotoxin metabolite secreted by the Fusarium family fungi. The regulatory bodies in this region have established the acceptable daily intake and exposure below the level would not significantly increase the health risk for humans. However, their European counterparts have yet to establish an acceptable level and do not permit the use of this agent in farm animals. Given the growth-promoting ability of zeranol, its effect on energy metabolism was investigated in the current study. Our results indicated that zeranol could induce glucose transporter type 4 (GLUT4) expression in 3T3 L1 cells at 10 μM and initiate the translocation of the glucose transporter to the membrane as assayed by confocal microscopy. The translocation was likely triggered by the increase of GLUT4 and p-Akt. The insulin signal transduction pathway of glucose translocation was analyzed by Western blot analysis. Since no increase in the phosphorylated insulin receptor substrate in zeranol-treated cells was evidenced, the increased p-Akt and GLUT4 amount should be the mechanism dictating the GLUT4 translocation. In summary, this study showed that zeranol could perturb glucose metabolism in differentiated 3T3 L1 adipocytes. Determining the growth-promoting mechanism is crucial to uncover an accepted alternative to the general public.
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Affiliation(s)
- Yan Qin Tan
- Food and Nutritional Sciences Programme, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong
| | - Qing Li
- Department of Biochemistry, School of Life Sciences, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong
| | - Lin Wang
- Cell and Molecular Biology Programme, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong
| | - Leo C Chiu-Leung
- Marine Science, School of Life Sciences, Faculty of Science, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong
| | - Lai K Leung
- Food and Nutritional Sciences Programme, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong; Department of Biochemistry, School of Life Sciences, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong.
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7
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Zhao Q, Yang D, Gao L, Zhao M, He X, Zhu M, Tian C, Liu G, Li L, Hu C. Downregulation of peroxisome proliferator-activated receptor gamma in the placenta correlates to hyperglycemia in offspring at young adulthood after exposure to gestational diabetes mellitus. J Diabetes Investig 2019; 10:499-512. [PMID: 30187673 PMCID: PMC6400209 DOI: 10.1111/jdi.12928] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/01/2017] [Revised: 08/14/2018] [Accepted: 08/28/2018] [Indexed: 01/08/2023] Open
Abstract
AIMS/INTRODUCTION Children who are exposed to gestational diabetes mellitus (GDM) in utero are at high risk of developing related illnesses, such as type 2 diabetes mellitus in young adulthood, but the underlying mechanism and related predictive biomarkers are not known. MATERIALS AND METHODS The present study identified the related biomarkers of hyperglycemia in young adults from the relationship between fetal blood glucose and placental lipid transporters at messenger ribonucleic acid (mRNA) and protein expression levels. We recruited patients from a prospective cohort, and determined the mRNA and protein levels of placental fatty acid transporters. Diet-induced mouse models of GDM were established, and the mRNA and protein levels of the same transporters in placentas were validated. RESULTS Only the mRNA levels of peroxisome proliferator-activated receptor gamma correlated with the levels of neonatal blood glucose in GDM patients using linear regression and Spearman's correlation analyses (r = 0.774, P = 0.001). The mRNA levels of peroxisome proliferator-activated receptor gamma, matrix metalloproteinase-2 and fatty acid transport protein-6 correlated with blood glucose levels in mouse offspring (r = 0.82, P = 0.001, r = 0.737, P = 0.006 and r = -0.891, P = 0.001, respectively) at young adulthood using the same analyses. Notably, we observed significantly higher blood glucose levels in GDM offspring at 12 weeks-of-age compared with the control and rosiglitazone-supplemented groups (P < 0.05). CONCLUSIONS The downregulation of peroxisome proliferator-activated receptor gamma in the placenta might predict hyperglycemia in offspring at young adulthood.
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Affiliation(s)
- Qihong Zhao
- Department of Nutrition and Food HygieneSchool of Public HealthAnhui Medical UniversityAnhuiHefeiChina
| | - Dong Yang
- Department of Nutrition and Food HygieneSchool of Public HealthAnhui Medical UniversityAnhuiHefeiChina
| | - Lei Gao
- Department of Nutrition and Food HygieneSchool of Public HealthAnhui Medical UniversityAnhuiHefeiChina
| | - Mingqiu Zhao
- Department of Nutrition and Food HygieneSchool of Public HealthAnhui Medical UniversityAnhuiHefeiChina
| | - Xiujie He
- Department of Nutrition and Food HygieneSchool of Public HealthAnhui Medical UniversityAnhuiHefeiChina
| | - Meng Zhu
- Department of Nutrition and Food HygieneSchool of Public HealthAnhui Medical UniversityAnhuiHefeiChina
| | - Chaoqing Tian
- Department of Nutrition and Food HygieneSchool of Public HealthAnhui Medical UniversityAnhuiHefeiChina
| | - Gang Liu
- Department of Nutrition and Food HygieneSchool of Public HealthAnhui Medical UniversityAnhuiHefeiChina
| | - Li Li
- Department of Nutrition and Food HygieneSchool of Public HealthAnhui Medical UniversityAnhuiHefeiChina
| | - Chuanlai Hu
- Department of Nutrition and Food HygieneSchool of Public HealthAnhui Medical UniversityAnhuiHefeiChina
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Lee YS, Choi SS, Yonezawa T, Teruya T, Woo JT, Kim HJ, Cha BY. Honokiol, magnolol, and a combination of both compounds improve glucose metabolism in high-fat diet-induced obese mice. Food Sci Biotechnol 2015. [DOI: 10.1007/s10068-015-0189-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022] Open
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Pan J, Guleria RS, Zhu S, Baker KM. Molecular Mechanisms of Retinoid Receptors in Diabetes-Induced Cardiac Remodeling. J Clin Med 2014; 3:566-94. [PMID: 26237391 PMCID: PMC4449696 DOI: 10.3390/jcm3020566] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2014] [Revised: 03/17/2014] [Accepted: 03/25/2014] [Indexed: 02/07/2023] Open
Abstract
Diabetic cardiomyopathy (DCM), a significant contributor to morbidity and mortality in diabetic patients, is characterized by ventricular dysfunction, in the absence of coronary atherosclerosis and hypertension. There is no specific therapeutic strategy to effectively treat patients with DCM, due to a lack of a mechanistic understanding of the disease process. Retinoic acid, the active metabolite of vitamin A, is involved in a wide range of biological processes, through binding and activation of nuclear receptors: retinoic acid receptors (RAR) and retinoid X receptors (RXR). RAR/RXR-mediated signaling has been implicated in the regulation of glucose and lipid metabolism. Recently, it has been reported that activation of RAR/RXR has an important role in preventing the development of diabetic cardiomyopathy, through improving cardiac insulin resistance, inhibition of intracellular oxidative stress, NF-κB-mediated inflammatory responses and the renin-angiotensin system. Moreover, downregulated RAR/RXR signaling has been demonstrated in diabetic myocardium, suggesting that impaired RAR/RXR signaling may be a trigger to accelerate diabetes-induced development of DCM. Understanding the molecular mechanisms of retinoid receptors in the regulation of cardiac metabolism and remodeling under diabetic conditions is important in providing the impetus for generating novel therapeutic approaches for the prevention and treatment of diabetes-induced cardiac complications and heart failure.
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Affiliation(s)
- Jing Pan
- Division of Molecular Cardiology, Department of Medicine, College of Medicine, Texas A & M Health Science Center, Baylor Scott & White Health, Central Texas Veterans Health Care System, Temple, TX, 76504, USA.
| | - Rakeshwar S Guleria
- Division of Molecular Cardiology, Department of Medicine, College of Medicine, Texas A & M Health Science Center, Baylor Scott & White Health, Central Texas Veterans Health Care System, Temple, TX, 76504, USA.
| | - Sen Zhu
- Division of Molecular Cardiology, Department of Medicine, College of Medicine, Texas A & M Health Science Center, Baylor Scott & White Health, Central Texas Veterans Health Care System, Temple, TX, 76504, USA.
| | - Kenneth M Baker
- Division of Molecular Cardiology, Department of Medicine, College of Medicine, Texas A & M Health Science Center, Baylor Scott & White Health, Central Texas Veterans Health Care System, Temple, TX, 76504, USA.
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Zhang Q, Schmandt R, Celestino J, McCampbell A, Yates MS, Urbauer DL, Broaddus RR, Loose DS, Shipley GL, Lu KH. CGRRF1 as a novel biomarker of tissue response to metformin in the context of obesity. Gynecol Oncol 2014; 133:83-9. [PMID: 24680596 DOI: 10.1016/j.ygyno.2013.12.006] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2013] [Revised: 11/26/2013] [Accepted: 12/04/2013] [Indexed: 01/18/2023]
Abstract
OBJECTIVE Obesity-associated hyperestrogenism and hyperinsulinemia contribute significantly to the pathogenesis of endometrial cancer. We recently demonstrated that metformin, a drug long used for treatment of type 2 diabetes, attenuates both insulin- and estrogen-mediated proliferative signaling in the obese rat endometrium. In this study, we sought to identify tissue biomarkers that may prove clinically useful to predict tissue response for both prevention and therapeutic studies. We identified CGRRF1 (cell growth regulator with ring finger domain 1) as a novel metformin-responsive gene and characterized its possible role in endometrial cancer prevention. METHODS CGRRF1 mRNA expression was evaluated by RT-qPCR in the endometrium of obese and lean rats, and also in normal and malignant human endometrium. CGRRF1 levels were genetically manipulated in endometrial cancer cells, and its effects on proliferation and apoptosis were evaluated by MTT and Western blot. RESULTS CGRRF1 is significantly induced by metformin treatment in the obese rat endometrium. In vitro studies demonstrate that overexpression of CGRRF1 inhibits endometrial cancer cell proliferation. Analysis of human endometrial tumors reveals that CGRRF1 expression is significantly lower in hyperplasia, Grade 1, Grade 2, Grade 3, MMMT, and UPSC endometrial tumors compared to normal human endometrium (p<0.05), suggesting that loss of CGRRF1 is associated with the presence of disease. CONCLUSION CGRRF1 represents a novel, reproducible tissue marker of metformin response in the obese endometrium. Furthermore, our preliminary data suggests that up-regulation of CGRRF1 expression may prove clinically useful in the prevention or treatment of endometrial cancer.
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Affiliation(s)
- Qian Zhang
- Department of Gynecologic Oncology and Reproductive Medicine, The University of Texas M.D. Anderson Cancer Center, Houston, TX 77030, USA
| | - Rosemarie Schmandt
- Department of Gynecologic Oncology and Reproductive Medicine, The University of Texas M.D. Anderson Cancer Center, Houston, TX 77030, USA
| | - Joseph Celestino
- Department of Gynecologic Oncology and Reproductive Medicine, The University of Texas M.D. Anderson Cancer Center, Houston, TX 77030, USA
| | - Adrienne McCampbell
- Department of Pathology, The University of Texas M.D. Anderson Cancer Center, Houston, TX 77030, USA
| | - Melinda S Yates
- Department of Gynecologic Oncology and Reproductive Medicine, The University of Texas M.D. Anderson Cancer Center, Houston, TX 77030, USA
| | - Diana L Urbauer
- Department of Biostatistics, The University of Texas M.D. Anderson Cancer Center, Houston, TX 77030, USA
| | - Russell R Broaddus
- Department of Pathology, The University of Texas M.D. Anderson Cancer Center, Houston, TX 77030, USA
| | - David S Loose
- Department of Integrative Biology and Pharmacology, The University of Texas Medical School at Houston, Houston, TX 77030, USA
| | - Gregory L Shipley
- Department of Integrative Biology and Pharmacology, The University of Texas Medical School at Houston, Houston, TX 77030, USA
| | - Karen H Lu
- Department of Gynecologic Oncology and Reproductive Medicine, The University of Texas M.D. Anderson Cancer Center, Houston, TX 77030, USA.
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A transcriptomic network identified in uninfected macrophages responding to inflammation controls intracellular pathogen survival. Cell Host Microbe 2014; 14:357-68. [PMID: 24034621 PMCID: PMC4180915 DOI: 10.1016/j.chom.2013.08.004] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2013] [Revised: 06/04/2013] [Accepted: 08/06/2013] [Indexed: 12/11/2022]
Abstract
Intracellular pathogens modulate host cell function to promote their survival. However, in vitro infection studies do not account for the impact of host-derived inflammatory signals. Examining the response of liver-resident macrophages (Kupffer cells) in mice infected with the parasite Leishmania donovani, we identified a transcriptomic network operating in uninfected Kupffer cells exposed to inflammation but absent from Kupffer cells from the same animal that contained intracellular Leishmania. To test the hypothesis that regulated expression of genes within this transcriptomic network might impact parasite survival, we pharmacologically perturbed the activity of retinoid X receptor alpha (RXRα), a key hub within this network, and showed that this intervention enhanced the innate resistance of Kupffer cells to Leishmania infection. Our results illustrate a broadly applicable strategy for understanding the host response to infection in vivo and identify Rxra as the hub of a gene network controlling antileishmanial resistance. Leishmania infection rapidly activates infected and uninfected Kupffer cells in mice Transcriptomics of inflamed and infected KC uncover distinct and overlapping networks A network centered on RXRα is uniquely activated in inflammation-exposed uninfected KCs Manipulation of RXRα function leads to a reduction in early parasite burden
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12
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Abstract
Retinoid X Receptors (RXR) were initially identified as nuclear receptors binding with stereo-selectivity the vitamin A derivative 9-cis retinoic acid, although the relevance of this molecule as endogenous activator of RXRs is still elusive. Importantly, within the nuclear receptor superfamily, RXRs occupy a peculiar place, as they are obligatory partners for a number of other nuclear receptors, thus integrating the corresponding signaling pathways. In this chapter, we describe the structural features allowing RXR to form homo- and heterodimers, and the functional consequences of this unique ability. Furthermore, we discuss the importance of studying RXR activity at a genome-wide level in order to comprehensively address the biological implications of their action that is fundamental to understand to what extent RXRs could be exploited as new therapeutic targets.
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Affiliation(s)
- Federica Gilardi
- Center for Integrative Genomics, University of Lausanne, Genopode Building, 1015, Lausanne, Switzerland,
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13
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Álvarez R, Vaz B, Gronemeyer H, de Lera ÁR. Functions, therapeutic applications, and synthesis of retinoids and carotenoids. Chem Rev 2013; 114:1-125. [PMID: 24266866 DOI: 10.1021/cr400126u] [Citation(s) in RCA: 149] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Affiliation(s)
- Rosana Álvarez
- Departamento de Química Orgánica, Centro de Investigación Biomédica (CINBIO), and Instituto de Investigación Biomédica de Vigo (IBIV), Universidade de Vigo , 36310 Vigo, Spain
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14
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Zhang Q, Celestino J, Schmandt R, McCampbell AS, Urbauer DL, Meyer LA, Burzawa JK, Huang M, Yates MS, Iglesias D, Broaddus RR, Lu KH. Chemopreventive effects of metformin on obesity-associated endometrial proliferation. Am J Obstet Gynecol 2013; 209:24.e1-24.e12. [PMID: 23500454 DOI: 10.1016/j.ajog.2013.03.008] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2012] [Revised: 01/30/2013] [Accepted: 03/07/2013] [Indexed: 12/30/2022]
Abstract
OBJECTIVE Obesity is a significant contributing factor to endometrial cancer risk. We previously demonstrated that estrogen-induced endometrial proliferation is enhanced in the context of hyperinsulinemia and insulin resistance. In this study, we investigate whether pharmacologic agents that modulate insulin sensitivity or normalize insulin levels will diminish the proliferative response to estrogen. STUDY DESIGN Zucker fa/fa obese rats and lean controls were used as models of hyperinsulinemia and insulin resistance. Insulin levels were depleted in ovariectomized rats following treatment with streptozotocin, or modulated by metformin treatment. The number of BrdU-incorporated cells, estrogen-dependent proliferative and antiproliferative gene expression, and activation of mTOR and ERK1/2 MAPK signaling were studied. A rat normal endometrial cell line RENE1 was used to evaluate the direct effects of metformin on endometrial cell proliferation and gene expression in vitro. RESULTS Streptozotocin lowered circulating insulin levels in obese rats and decreased the number of BrdU-labeled endometrial cells even in the presence of exogenous estrogen. Treatment with the insulin-sensitizing drug metformin attenuated estrogen-dependent proliferative expression of c-myc and c-fos in the obese rat endometrium compared to untreated controls and was accompanied by inhibition of phosphorylation of the insulin and IGF1 receptors (IRβ/IGF1R) and ERK1/2. In vitro studies indicated metformin inhibited RENE1 proliferation in a dose-dependent manner. CONCLUSION These findings suggest that drugs that modulate insulin sensitivity, such as metformin, hinder estrogen-mediated endometrial proliferation. Therefore, these drugs may be clinically useful for the prevention of endometrial cancer in obese women.
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Abstract
Retinoid acid is a metabolite of vitamin A and functions as an important factor in cell survival, differentiation and death. Most previous studies on retinoid metabolism have focused on its association with cancer, hematologic and dermatologic disorders. Given the special concern over the recent increase in the prevalence of diabetes worldwide, the role of retinoid metabolism on glucose metabolism and insulin resistance in the human body is of marked importance. Therefore, in this issue, we review the literature on the association of retinoid metabolism with glucose tolerance, with regard to insulin secretion, pancreatic autoimmunity, insulin sensitivity and lipid metabolism. Further, we tried to assess the possibility of using retinoids as a novel therapeutic strategy for diabetes.
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Affiliation(s)
- Eun-Jung Rhee
- Department of Endocrinology and Metabolism, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine, Seoul, Korea
| | - Jorge Plutzky
- Cardiovascular Division, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA
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16
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Kotani H, Tanabe H, Mizukami H, Amagaya S, Inoue M. A Naturally Occurring Rexinoid, Honokiol, Can Serve as a Regulator of Various Retinoid X Receptor Heterodimers. Biol Pharm Bull 2012; 35:1-9. [DOI: 10.1248/bpb.35.1] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Affiliation(s)
- Hitoshi Kotani
- Laboratory of Medicinal Resources, School of Pharmacy, Aichi Gakuin University
- Laboratory of Pharmacognosy, Graduate School of Pharmaceutical Sciences, Nagoya City University
| | - Hiroki Tanabe
- Laboratory of Medicinal Resources, School of Pharmacy, Aichi Gakuin University
| | - Hajime Mizukami
- Laboratory of Pharmacognosy, Graduate School of Pharmaceutical Sciences, Nagoya City University
| | - Sakae Amagaya
- Department of Kampo Pharmaceutical Sciences, Nihon Pharmaceutical University
| | - Makoto Inoue
- Laboratory of Medicinal Resources, School of Pharmacy, Aichi Gakuin University
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17
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Sugita S, Kamei Y, Akaike F, Suganami T, Kanai S, Hattori M, Manabe Y, Fujii N, Takai-Igarashi T, Tadaishi M, Oka JI, Aburatani H, Yamada T, Katagiri H, Kakehi S, Tamura Y, Kubo H, Nishida K, Miura S, Ezaki O, Ogawa Y. Increased systemic glucose tolerance with increased muscle glucose uptake in transgenic mice overexpressing RXRγ in skeletal muscle. PLoS One 2011; 6:e20467. [PMID: 21655215 PMCID: PMC3105070 DOI: 10.1371/journal.pone.0020467] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2011] [Accepted: 04/26/2011] [Indexed: 01/27/2023] Open
Abstract
Background Retinoid X receptor (RXR) γ is a nuclear receptor-type transcription
factor expressed mostly in skeletal muscle, and regulated by nutritional
conditions. Previously, we established transgenic mice overexpressing
RXRγ in skeletal muscle (RXRγ mice), which showed lower blood
glucose than the control mice. Here we investigated their glucose
metabolism. Methodology/Principal Findings RXRγ mice were subjected to glucose and insulin tolerance tests, and
glucose transporter expression levels, hyperinsulinemic-euglycemic clamp and
glucose uptake were analyzed. Microarray and bioinformatics analyses were
done. The glucose tolerance test revealed higher glucose disposal in
RXRγ mice than in control mice, but insulin tolerance test revealed no
difference in the insulin-induced hypoglycemic response. In the
hyperinsulinemic-euglycemic clamp study, the basal glucose disposal rate was
higher in RXRγ mice than in control mice, indicating an
insulin-independent increase in glucose uptake. There was no difference in
the rate of glucose infusion needed to maintain euglycemia (glucose infusion
rate) between the RXRγ and control mice, which is consistent with the
result of the insulin tolerance test. Skeletal muscle from RXRγ mice
showed increased Glut1 expression, with increased glucose uptake, in an
insulin-independent manner. Moreover, we performed in vivo
luciferase reporter analysis using Glut1 promoter
(Glut1-Luc). Combination of RXRγ and PPARδ
resulted in an increase in Glut1-Luc activity in skeletal
muscle in vivo. Microarray data showed that RXRγ
overexpression increased a diverse set of genes, including glucose
metabolism genes, whose promoter contained putative PPAR-binding motifs. Conclusions/Significance Systemic glucose metabolism was increased in transgenic mice overexpressing
RXRγ. The enhanced glucose tolerance in RXRγ mice may be mediated at
least in part by increased Glut1 in skeletal muscle. These results show the
importance of skeletal muscle gene regulation in systemic glucose
metabolism. Increasing RXRγ expression may be a novel therapeutic
strategy against type 2 diabetes.
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Affiliation(s)
- Satoshi Sugita
- Department of Molecular Medicine and
Metabolism, Medical Research Institute, Tokyo Medical and Dental University,
Tokyo, Japan
| | - Yasutomi Kamei
- Department of Molecular Medicine and
Metabolism, Medical Research Institute, Tokyo Medical and Dental University,
Tokyo, Japan
- * E-mail:
| | - Fumiko Akaike
- Department of Molecular Medicine and
Metabolism, Medical Research Institute, Tokyo Medical and Dental University,
Tokyo, Japan
- Laboratory of Pharmacology, Faculty of
Pharmaceutical Sciences, Tokyo University of Science, Chiba, Japan
| | - Takayoshi Suganami
- Department of Molecular Medicine and
Metabolism, Medical Research Institute, Tokyo Medical and Dental University,
Tokyo, Japan
| | - Sayaka Kanai
- Department of Molecular Medicine and
Metabolism, Medical Research Institute, Tokyo Medical and Dental University,
Tokyo, Japan
| | - Maki Hattori
- Department of Molecular Medicine and
Metabolism, Medical Research Institute, Tokyo Medical and Dental University,
Tokyo, Japan
- Laboratory of Pharmacology, Faculty of
Pharmaceutical Sciences, Tokyo University of Science, Chiba, Japan
| | - Yasuko Manabe
- Graduate School of Human Health Sciences,
Tokyo Metropolitan University, Tokyo, Japan
| | - Nobuharu Fujii
- Graduate School of Human Health Sciences,
Tokyo Metropolitan University, Tokyo, Japan
| | - Takako Takai-Igarashi
- Department of Bioinformatics, Graduate School
of Biomedical Science, Tokyo Medical and Dental University, Tokyo,
Japan
| | - Miki Tadaishi
- Nutritional Science Program, National
Institute of Health and Nutrition, Tokyo, Japan
- Department of Nutritional Science, Faculty of
Applied Bioscience, Tokyo University of Agriculture, Tokyo, Japan
| | - Jun-Ichiro Oka
- Laboratory of Pharmacology, Faculty of
Pharmaceutical Sciences, Tokyo University of Science, Chiba, Japan
| | - Hiroyuki Aburatani
- Research Center for Advanced Science and
Technology, University of Tokyo, Tokyo, Japan
| | - Tetsuya Yamada
- Department of Metabolic Diseases, Center for
Metabolic Diseases, Tohoku University Graduate School of Medicine, Miyagi,
Japan
| | - Hideki Katagiri
- Department of Metabolic Diseases, Center for
Metabolic Diseases, Tohoku University Graduate School of Medicine, Miyagi,
Japan
| | - Saori Kakehi
- Department of Medicine, Metabolism and
Endocrinology, School of Medicine, Juntendo University, Tokyo, Japan
| | - Yoshifumi Tamura
- Department of Medicine, Metabolism and
Endocrinology, School of Medicine, Juntendo University, Tokyo, Japan
- Sportology Center, Juntendo University,
Tokyo, Japan
| | | | | | - Shinji Miura
- Nutritional Science Program, National
Institute of Health and Nutrition, Tokyo, Japan
| | - Osamu Ezaki
- Nutritional Science Program, National
Institute of Health and Nutrition, Tokyo, Japan
| | - Yoshihiro Ogawa
- Department of Molecular Medicine and
Metabolism, Medical Research Institute, Tokyo Medical and Dental University,
Tokyo, Japan
- Global Center of Excellence Program,
International Research Center for Molecular Science in Tooth and Bone Diseases,
Medical Research Institute, Tokyo Medical and Dental University, Tokyo,
Japan
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Modulation of RXR function through ligand design. Biochim Biophys Acta Mol Cell Biol Lipids 2011; 1821:57-69. [PMID: 21515403 DOI: 10.1016/j.bbalip.2011.04.003] [Citation(s) in RCA: 122] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2011] [Revised: 04/06/2011] [Accepted: 04/07/2011] [Indexed: 12/22/2022]
Abstract
As the promiscuous partner of heterodimeric associations, retinoid X receptors (RXRs) play a key role within the Nuclear Receptor (NR) superfamily. Some of the heterodimers (PPAR/RXR, LXR/RXR, FXR/RXR) are "permissive" as they become transcriptionally active in the sole presence of either an RXR-selective ligand ("rexinoid") or a NR partner ligand. In contrast, "non-permissive" heterodimers (including RAR/RXR, VDR/RXR and TR/RXR) are unresponsive to rexinoids alone but these agonists superactivate transcription by synergizing with partner agonists. Despite their promiscuity in heterodimer formation and activation of multiple pathways, RXR is a target for drug discovery. Indeed, a rexinoid is used in the clinic for the treatment of cutaneous T-cell lymphoma. In addition to cancer RXR modulators hold therapeutical potential for the treatment of metabolic diseases. The modulation potential of the rexinoid (as agonist or antagonist ligand) is dictated by the precise conformation of the ligand-receptor complexes and the nature and extent of their interaction with co-regulators, which determine the specific physiological responses through transcription modulation of cognate gene networks. Notwithstanding the advances in this field, it is not yet possible to predict the correlation between ligand structure and physiological response. We will focus on this review on the modulation of PPARγ/RXR and LXR/RXR heterodimer activities by rexinoids. The genetic and pharmacological data from animal models of insulin resistance, diabetes and obesity demonstrate that RXR agonists and antagonists have promise as anti-obesity agents. However, the treatment with rexinoids raises triglycerides levels, suppresses the thyroid hormone axis, and induces hepatomegaly, which has complicated the development of these compounds as therapeutic agents for the treatment of type 2 diabetes and insulin resistance. The discovery of PPARγ/RXR and LXR/RXR heterodimer-selective rexinoids, which act differently than PPARγ or LXR agonists, might overcome some of these limitations.
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Kotani H, Tanabe H, Mizukami H, Makishima M, Inoue M. Identification of a naturally occurring rexinoid, honokiol, that activates the retinoid X receptor. JOURNAL OF NATURAL PRODUCTS 2010; 73:1332-1336. [PMID: 20695472 DOI: 10.1021/np100120c] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Screening of a total of 86 crude drugs for retinoid X receptor (RXR) ligands demonstrated that the methanol extract of the bark of Magnolia obovata markedly activated the transcriptional activity of RXRalpha in luciferase reporter assays. Thereafter, honokiol (1) was isolated as a constituent able to activate RXR selectively as a natural rexinoid, but not RARalpha. The activity of 1 was more potent than those of phytanic acid and docosahexaenoic acid, both of which are known to be natural RXR agonists. Honokiol (1) is capable of activating a RXR/LXR heterodimer, resulting in the induction of ATP-binding cassette transporter A1 mRNA and protein expression in RAW264.7 cells, as well as an increase in [(3)H]cholesterol efflux from peritoneal macrophages. These effects of 1 were enhanced synergistically in the presence of an LXR agonist, 22(R)-hydroxycholesterol. The results obtained demonstrate that 1, a newly identified natural rexinoid, regulates the functions of RXR/LXR heterodimer and abrogates foam cell formation by the induction of ABCA1 via activation of the RXR/LXR heterodimer.
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Affiliation(s)
- Hitoshi Kotani
- Laboratory of Medicinal Resources, School of Pharmacy, Aichi Gakuin University, 1-100 Kusumoto-cho, Chikusa-ku, Nagoya 464-8650, Japan
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20
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Abstract
Many different drugs affect thyroid function. Most of these drugs act at the level of the thyroid in patients with normal thyroid function, or at the level of thyroid hormone absorption or metabolism in patients requiring exogenous levothyroxine. A small subset of medications including glucocorticoids, dopamine agonists, somatostatin analogues and rexinoids affect thyroid function through suppression of TSH in the thyrotrope or hypothalamus. Fortunately, most of these medications do not cause clinically evident central hypothyroidism. A newer class of nuclear hormone receptors agonists, called rexinoids, cause clinically significant central hypothyroidism in most patients and dopamine agonists may exacerbate 'hypothyroidism' in patients with non-thyroidal illness. In this review, we explore mechanisms governing TSH suppression of these drugs and the clinical relevance of these effects.
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Affiliation(s)
- Bryan R Haugen
- University of Colorado Denver, School of Medicine, Department of Medicine, Division of Endocrinology, Metabolism and Diabetes, MS 8106, PO box 6511, Aurora, CO 80045, USA.
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21
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Zhou J, He X, Huang K. Bidirectional regulation of insulin receptor autophosphorylation and kinase activity by peroxynitrite. Arch Biochem Biophys 2009; 488:1-8. [DOI: 10.1016/j.abb.2009.06.014] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2009] [Revised: 06/19/2009] [Accepted: 06/22/2009] [Indexed: 01/23/2023]
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Transcriptional activity of the murine retinol-binding protein gene is regulated by a multiprotein complex containing HMGA1, p54 nrb/NonO, protein-associated splicing factor (PSF) and steroidogenic factor 1 (SF1)/liver receptor homologue 1 (LRH-1). Int J Biochem Cell Biol 2009; 41:2189-203. [PMID: 19389484 DOI: 10.1016/j.biocel.2009.04.011] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2009] [Revised: 04/08/2009] [Accepted: 04/15/2009] [Indexed: 11/24/2022]
Abstract
Retinol-binding protein (RBP4) transports retinol in the circulation from hepatic stores to peripheral tissues. Since little is known regarding the regulation of this gene, we analysed the cis-regulatory sequences of the mouse RBP4 gene. Our data show that transcription of the gene is regulated through a bipartite promoter: a proximal region necessary for basal expression and a distal segment responsible for cAMP-induction. This latter region contains several binding sites for the structural HMGA1 proteins, which are important to promoter regulation. We further demonstrate that HMGA1s play a key role in basal and cAMP-induction of Rbp4 transcription and the RBP4 and HMGA1 genes are coordinately regulated in vitro and in vivo. HMGA1 acts to recruit transcription factors to the RBP4 promoter and we specifically identified p54(nrb)/NonO and protein-associated splicing factor (PSF) as components that interact with this complex. Steroidogenic factor 1 (SF1) or the related liver receptor homologue 1 (LRH-1) are also associated with this complex upon cAMP-induction. Depletion of SF1/LRH-1 by RNA interference resulted in a dramatic loss of cAMP-induction. Collectively, our results demonstrate that basal and cAMP-induced Rbp4 transcription is regulated by a multiprotein complex that is similar to ones that modulate expression of genes of steroid hormone biosynthesis. Since genes related to glucose metabolism are regulated in a similar fashion, this suggests that Rbp4 expression may be regulated as part of a network of pathways relevant to the onset of type 2 diabetes.
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Zhang Q, Shen Q, Celestino J, Milam MR, Westin SN, Lacour RA, Meyer LA, Shipley GL, Davies PJ, Deng L, McCampbell AS, Broaddus RR, Lu KH. Enhanced estrogen-induced proliferation in obese rat endometrium. Am J Obstet Gynecol 2009; 200:186.e1-8. [PMID: 19185100 DOI: 10.1016/j.ajog.2008.08.064] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2008] [Revised: 06/04/2008] [Accepted: 08/30/2008] [Indexed: 11/24/2022]
Abstract
OBJECTIVE We tested the hypothesis that the proliferative estrogen effect on the endometrium is enhanced in obese vs lean animals. STUDY DESIGN Using Zucker fa/fa obese rats and lean control, we examined endometrial cell proliferation and the expression patterns of certain estrogen-regulated proproliferative and antiproliferative genes after short-term treatment with estradiol. RESULTS No significant morphologic/histologic difference was seen between the obese rats and the lean rats. Estrogen-induced proproliferative genes cyclin A and c-Myc messenger RNA expression were significantly higher in the endometrium of obese rats compared with those of the lean control. Expression of the antiproliferative gene p27Kip1 was suppressed by estrogen treatment in both obese and lean rats; however, the decrease was more pronounced in obese rats. Estrogen more strongly induced the antiproliferative genes retinaldehyde dehydrogenases 2 and secreted frizzled-related protein 4 in lean rats but had little or no effect in obese rats. CONCLUSION Enhancement of estrogen-induced endometrial proproliferative gene expression and suppression of antiproliferative gene expression was seen in the endometrium of obese vs lean animals.
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Hwang SL, Yang BK, Lee JY, Kim JH, Kim BD, Kim BH, Suh KH, Kim DY, Kim DY, Kim MS, Song H, Park BS, Huh TL. Isodihydrocapsiate stimulates plasma glucose uptake by activation of AMP-activated protein kinase. Biochem Biophys Res Commun 2008; 371:289-93. [PMID: 18435912 DOI: 10.1016/j.bbrc.2008.04.061] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2008] [Accepted: 04/15/2008] [Indexed: 01/22/2023]
Abstract
AMP-activated protein kinase (AMPK) is an energy-sensing enzyme that is implicated as a key factor in controlling whole body homeostasis, including fatty acid oxidation and glucose uptake. We report that a synthetic structural isomer of dihydrocapsiate, isodihydrocapsiate (8-methylnonanoic acid 3-hydroxy-4-methoxy benzyl ester) improves type 2 diabetes by activating AMPK through the LKB1 pathway. In L6 myotube cells, phosphorylation of AMPK and acetyl-CoA carboxylase (ACC) and glucose uptake were significantly increased, whereas these effects were attenuated by an AMPK inhibitor, compound C. In addition, increased phosphorylation of AMPK and ACC by isodihydrocapsiate was significantly reduced by radicicol, an LKB1 destabilizer, suggesting that increased glucose uptake in L6 cells with isodihydrocapsiate treatment is predominantly accomplished by a LKB1-mediated AMPK activation pathway. Oral administration of isodihydrocapsiate to diabetic (db/db) mice reduced blood glucose levels by 40% after a 4-week treatment period. Our results support the development of isodihydrocapsiate as a potential therapeutic agent to target AMPK in type 2 diabetes.
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Affiliation(s)
- Seung-Lark Hwang
- TG Biotech Research Institute, Technobuilding, Kyungpook National University, Daegu 702-832, Republic of Korea
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Montessuit C, Papageorgiou I, Lerch R. Nuclear receptor agonists improve insulin responsiveness in cultured cardiomyocytes through enhanced signaling and preserved cytoskeletal architecture. Endocrinology 2008; 149:1064-74. [PMID: 18063688 DOI: 10.1210/en.2007-0656] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Insulin resistance is the failure of insulin to stimulate the transport of glucose into its target cells. A highly regulatable supply of glucose is important for cardiomyocytes to cope with situations of metabolic stress. We recently observed that isolated adult rat cardiomyocytes become insulin resistant in vitro. Insulin resistance is combated at the whole body level with agonists of the nuclear receptor complex peroxisome proliferator-activated receptor gamma (PPARgamma)/retinoid X receptor (RXR). We investigated the effects of PPARgamma/RXR agonists on the insulin-stimulated glucose transport and on insulin signaling in insulin-resistant adult rat cardiomyocytes. Treatment of cardiomyocytes with ciglitazone, a PPARgamma agonist, or 9-cis retinoic acid (RA), a RXR agonist, increased insulin- and metabolic stress-stimulated glucose transport, whereas agonists of PPARalpha or PPARbeta/delta had no effect. Stimulation of glucose transport in response to insulin requires the phosphorylation of the signaling intermediate Akt on the residues Thr308 and Ser473 and, downstream of Akt, AS160 on several Thr and Ser residues. Phosphorylation of Akt and AS160 in response to insulin was lower in insulin-resistant cardiomyocytes. However, treatment with 9-cis RA markedly increased phosphorylation of both proteins. Treatment with 9-cis RA also led to better preservation of microtubules in cultured cardiomyocytes. Disruption of microtubules in insulin-responsive cardiomyocytes abolished insulin-stimulated glucose transport and reduced phosphorylation of AS160 but not Akt. Metabolic stress-stimulated glucose transport also involved AS160 phosphorylation in a microtubule-dependent manner. Thus, the stimulation of glucose uptake in response to insulin or metabolic stress is dependent in cardiomyocytes on the presence of intact microtubules.
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Affiliation(s)
- Christophe Montessuit
- Division of Cardiology, Geneva University Hospitals, 24 Micheli-du-Crest, 1211 Geneva 14, Switzerland.
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Meissburger B, Wolfrum C. The role of retinoids and their receptors in metabolic disorders. EUR J LIPID SCI TECH 2008. [DOI: 10.1002/ejlt.200700291] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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George J, Liddle C. Nonalcoholic Fatty Liver Disease: Pathogenesis and Potential for Nuclear Receptors as Therapeutic Targets. Mol Pharm 2007; 5:49-59. [DOI: 10.1021/mp700110z] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
- Jacob George
- Storr Liver Unit, Westmead Millennium Institute, University of Sydney, Westmead Hospital, Westmead NSW 2145, Australia
| | - Christopher Liddle
- Storr Liver Unit, Westmead Millennium Institute, University of Sydney, Westmead Hospital, Westmead NSW 2145, Australia
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Altucci L, Leibowitz MD, Ogilvie KM, de Lera AR, Gronemeyer H. RAR and RXR modulation in cancer and metabolic disease. Nat Rev Drug Discov 2007; 6:793-810. [PMID: 17906642 DOI: 10.1038/nrd2397] [Citation(s) in RCA: 397] [Impact Index Per Article: 23.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Retinoic acid receptors (RARs) are ligand-controlled transcription factors that function as heterodimers with retinoid X receptors (RXRs) to regulate cell growth and survival. The success of RAR modulation in the treatment of acute promyelocytic leukaemia (APL) has stimulated considerable interest in the development of RAR and RXR modulators. This has been aided by recent advances in the understanding of the biological role of RARs and RXRs and in the design of selective receptor modulators that might overcome the limitations of current drugs. Here, we discuss the challenges and opportunities for therapeutic strategies based on RXR and RAR modulators, with a focus on cancer and metabolic diseases such as diabetes and obesity.
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Affiliation(s)
- Lucia Altucci
- Dipartimento di Patologia Generale, Seconda Università degli Studi di Napoli, Vico Luigi de Crecchio 7, 80138 Napoli, Italy
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Delage B, Rullier A, Capdepont M, Rullier E, Cassand P. The effect of body weight on altered expression of nuclear receptors and cyclooxygenase-2 in human colorectal cancers. Nutr J 2007; 6:20. [PMID: 17767717 PMCID: PMC2018695 DOI: 10.1186/1475-2891-6-20] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2006] [Accepted: 09/03/2007] [Indexed: 12/13/2022] Open
Abstract
Background Epidemiological studies on risk factors for colorectal cancer (CRC) have mainly focused on diet, and being overweight is now recognized to contribute significantly to CRC risk. Overweight and obesity are defined as an excess of adipose tissue mass and are associated with disorders in lipid metabolism. Peroxisome proliferator-activated receptors (PPARs) and retinoid-activated receptors (RARs and RXRs) are important modulators of lipid metabolism and cellular homeostasis. Alterations in expression and activity of these ligand-activated transcription factors might be involved in obesity-associated diseases, which include CRC. Cyclooxygenase-2 (COX-2) also plays a critical role in lipid metabolism and alterations in COX-2 expression have already been associated with unfavourable clinical outcomes in epithelial tumors. The objective of this study is to examine the hypothesis questioning the relationship between alterations in the expression of nuclear receptors and COX-2 and the weight status among male subjects with CRC. Method The mRNA expression of the different nuclear receptor subtypes and of COX-2 was measured in 20 resected samples of CRC and paired non-tumor tissues. The association between expression patterns and weight status defined as a body mass index (BMI) was statistically analyzed. Results No changes were observed in PPARγ mRNA expression while the expression of PPARδ, retinoid-activated receptors and COX-2 were significantly increased in cancer tissues compared to normal colon mucosa (P ≤ 0.001). The weight status appeared to be an independent factor, although we detected an increased level of COX-2 expression in the normal mucosa from overweight patients (BMI ≥ 25) compared to subjects with healthy BMI (P = 0.002). Conclusion Our findings show that alterations in the pattern of nuclear receptor expression observed in CRC do not appear to be correlated with patient weight status. However, the analysis of COX-2 expression in normal colon mucosa from subjects with a high BMI suggests that COX-2 deregulation might be driven by excess weight during the colon carcinogenesis process.
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Affiliation(s)
- Barbara Delage
- Laboratoire Alimentation et Cancerogenese Colique, Unite de Nutrition et Signalisation Cellulaire, Universite Bordeaux1, France
| | - Anne Rullier
- Departement de Pathologie, Hopital Pellegrin, Bordeaux, France
| | - Maylis Capdepont
- Departement de Chirurgie Digestive, Hopital Saint-André, Bordeaux, France
| | - Eric Rullier
- Departement de Chirurgie Digestive, Hopital Saint-André, Bordeaux, France
| | - Pierrette Cassand
- Laboratoire Alimentation et Cancerogenese Colique, Unite de Nutrition et Signalisation Cellulaire, Universite Bordeaux1, France
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Schaiff WT, Knapp FFR, Barak Y, Biron-Shental T, Nelson DM, Sadovsky Y. Ligand-activated peroxisome proliferator activated receptor gamma alters placental morphology and placental fatty acid uptake in mice. Endocrinology 2007; 148:3625-34. [PMID: 17463056 DOI: 10.1210/en.2007-0211] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The nuclear receptor peroxisome proliferator activated receptor gamma (PPARgamma) is essential for murine placental development. We previously showed that activation of PPARgamma in primary human trophoblasts enhances the uptake of fatty acids and alters the expression of several proteins associated with fatty acid trafficking. In this study we examined the effect of ligand-activated PPARgamma on placental development and transplacental fatty acid transport in wild-type (wt) and PPARgamma(+/-) embryos. We found that exposure of pregnant mice to the PPARgamma agonist rosiglitazone for 8 d (embryonic d 10.5-18.5) reduced the weights of wt, but not PPARgamma(+/-) placentas and embryos. Exposure to rosiglitazone reduced the thickness of the spongiotrophoblast layer and the surface area of labyrinthine vasculature, and altered expression of proteins implicated in placental development. The expression of fatty acid transport protein 1 (FATP1), FATP4, adipose differentiation related protein, S3-12, and myocardial lipid droplet protein was enhanced in placentas of rosiglitazone-treated wt embryos, whereas the expression of FATP-2, -3, and -6 was decreased. Additionally, rosiglitazone treatment was associated with enhanced accumulation of the fatty acid analog 15-(p-iodophenyl)-3-(R, S)-methyl pentadecanoic acid in the placenta, but not in the embryos. These results demonstrate that in vivo activation of PPARgamma modulates placental morphology and fatty acid accumulation.
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Affiliation(s)
- W Timothy Schaiff
- Washington University School of Medicine, Department of Obstetrics and Gynecology, Campus Box 8064, 4566 Scott Avenue, St. Louis, Missouri 63110, USA
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Lessard SJ, Rivas DA, Chen ZP, Bonen A, Febbraio MA, Reeder DW, Kemp BE, Yaspelkis BB, Hawley JA. Tissue-specific effects of rosiglitazone and exercise in the treatment of lipid-induced insulin resistance. Diabetes 2007; 56:1856-64. [PMID: 17440174 DOI: 10.2337/db06-1065] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Both pharmacological intervention (i.e., thiazolidinediones [TZDs]) and lifestyle modification (i.e., exercise training) are clinically effective treatments for improving whole-body insulin sensitivity. However, the mechanism(s) by which these therapies reverse lipid-induced insulin resistance in skeletal muscle is unclear. We determined the effects of 4 weeks of rosiglitazone treatment and exercise training and their combined actions (rosiglitazone treatment and exercise training) on lipid and glucose metabolism in high-fat-fed rats. High-fat feeding resulted in decreased muscle insulin sensitivity, which was associated with increased rates of palmitate uptake and the accumulation of the fatty acid metabolites ceramide and diacylglycerol. Impairments in lipid metabolism were accompanied by defects in the Akt/AS160 signaling pathway. Exercise training, but not rosiglitazone treatment, reversed these impairments, resulting in improved insulin-stimulated glucose transport and increased rates of fatty acid oxidation in skeletal muscle. The improvements to glucose and lipid metabolism observed with exercise training were associated with increased AMP-activated protein kinase alpha1 activity; increased expression of Akt1, peroxisome proliferator-activated receptor gamma coactivator 1, and GLUT4; and a decrease in AS160 expression. In contrast, rosiglitazone treatment exacerbated lipid accumulation and decreased insulin-stimulated glucose transport in skeletal muscle. However, rosiglitazone, but not exercise training, increased adipose tissue GLUT4 and acetyl CoA carboxylase expression. Both exercise training and rosiglitazone decreased liver triacylglycerol content. Although both interventions can improve whole-body insulin sensitivity, our results show that they produce divergent effects on protein expression and triglyceride storage in different tissues. Accordingly, exercise training and rosiglitazone may act as complementary therapies for the treatment of insulin resistance.
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Affiliation(s)
- Sarah J Lessard
- School of Medical Sciences, RMIT University, P.O. Box 71, Bundoora, Victoria 3083, Australia
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Pinaire JA, Reifel-Miller A. Therapeutic potential of retinoid x receptor modulators for the treatment of the metabolic syndrome. PPAR Res 2007; 2007:94156. [PMID: 17497022 PMCID: PMC1852898 DOI: 10.1155/2007/94156] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2006] [Revised: 01/04/2007] [Accepted: 01/04/2007] [Indexed: 01/30/2023] Open
Abstract
The increasing prevalence of obesity is a fundamental contributor
to the growing prevalence of the metabolic syndrome. Rexinoids, a
class of compounds that selectively bind and activate RXR,
are being studied as a potential option for the treatment of
metabolic syndrome. These compounds have glucose-lowering,
insulin-sensitizing, and antiobesity effects in animal models
of insulin resistance and type 2 diabetes. However,
undesirable side effects such as hypertriglyceridemia and
suppression of the thyroid hormone axis also occur.
This review examines and compares the effects of four RXR-selective
ligands: LGD1069, LG100268, AGN194204, and LG101506, a selective
RXR modulator. Similar to selective modulators of other nuclear
receptors such as the estrogen receptor (SERMs), LG101506
binding to RXR selectively maintains the desirable characteristic
effects of rexinoids while minimizing the undesirable effects.
These recent findings suggest that, with continued research efforts,
RXR-specific ligands with improved pharmacological profiles may
eventually be available as additional treatment options for the
current epidemic of obesity, insulin resistance, type 2 diabetes,
and all of the associated metabolic sequelae.
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Affiliation(s)
- Jane A. Pinaire
- Lilly Research Laboratories, Lilly Corporate Center, Indianapolis, IN 46285, USA
- *Jane A. Pinaire:
| | - Anne Reifel-Miller
- Lilly Research Laboratories, Lilly Corporate Center, Indianapolis, IN 46285, USA
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Germain P, Chambon P, Eichele G, Evans RM, Lazar MA, Leid M, De Lera AR, Lotan R, Mangelsdorf DJ, Gronemeyer H. International Union of Pharmacology. LXIII. Retinoid X receptors. Pharmacol Rev 2007; 58:760-72. [PMID: 17132853 DOI: 10.1124/pr.58.4.7] [Citation(s) in RCA: 376] [Impact Index Per Article: 22.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
The physiological effects of retinoic acids (RAs) are mediated by members of two families of nuclear receptors, the retinoic acid receptors (RARs) and the retinoid X receptors (RXRs), which are encoded by three distinct human genes, RXRalpha, RXRbeta, and RXRgamma. RARs bind both all-trans- and 9-cis-RA, whereas only the 9-cis-RA stereoisomer binds to RXRs. As RXR/RAR heterodimers, these receptors control the transcription of RA target genes through binding to RA-response elements. This review is focused on the structure, mode of action, ligands, expression, and pharmacology of RXRs. Given their role as common partners to many other members of the nuclear receptor superfamily, these receptors have been the subject of intense scrutiny. Moreover, and despite numerous studies since their initial discovery, RXRs remain enigmatic nuclear receptors, and there is still no consensus regarding their role. Indeed, multiple questions about the actual biological role of RXRs and the existence of an endogenous ligand have still to be answered.
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Affiliation(s)
- Pierre Germain
- Centre National de la Recherche Scientifique/Institut National de la Santé et de la Recherche Médicale/Université Louis Pasteur, Illkirch, Communauté Urbaine de Strasbourg, France.
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Golden WM, Weber KB, Hernandez TL, Sherman SI, Woodmansee WW, Haugen BR. Single-dose rexinoid rapidly and specifically suppresses serum thyrotropin in normal subjects. J Clin Endocrinol Metab 2007; 92:124-30. [PMID: 17062760 DOI: 10.1210/jc.2006-0696] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/12/2023]
Abstract
CONTEXT Retinoid X receptor agonists (rexinoids) have demonstrated benefit in patients with certain malignancies but appear to cause central hypothyroidism in some patients with advanced cancer. The influence of rexinoids on thyroid function in healthy subjects is not clear. OBJECTIVE The objective of this study was to determine the effect of a single dose of bexarotene on levels of TSH, T4, and T3 in healthy subjects. DESIGN This study was a randomized, double-blind, placebo-controlled, crossover trial. SETTING This study was conducted at the General Clinical Research Center (University of Colorado Health Sciences Center, Aurora, CO). SUBJECTS Six healthy adults (>18 yr old) were studied. INTERVENTION Single-dose rexinoid (bexarotene, 400 mg/m2) or placebo, with TSH measurements at 0, 1, 2, 4, 8, 12, 24, and 48 h, were used. MAIN OUTCOME MEASURE The main outcome was the serum TSH level at 24 h. RESULTS Single-dose bexarotene suppressed serum TSH (P < 0.001) over time. Compared with placebo, levels of TSH were significantly lower by 12 h (P = 0.043); the nadir of 0.32 +/- 0.02 mU/liter (P < 0.001) was seen at 24 h. Free T4 index and free T3 index were also significantly lower than placebo over time (48 h) (P = 0.029; P = 0.004, respectively). Serum prolactin, cortisol, and triglycerides were not affected (P > 0.05 for all). There was no significant effect of single-dose bexarotene on rT3 or T3/rT3 ratio at 24 h. CONCLUSION A single dose of a rexinoid can rapidly and specifically suppress serum TSH levels in healthy subjects. These data provide insight into the mechanisms by which rexinoids cause central hypothyroidism and potential ways this effect can be used for treatment of disorders such as thyroid hormone resistance and TSH-secreting pituitary tumors.
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Affiliation(s)
- Wendy M Golden
- Division of Endocrinology, Metabolism, and Diabetes, University of Colorado at Denver and Health Sciences Center, Building RC-1 South Tower, MS 8106; 12801 East 17th Avenue, PO Box 6511, Aurora, Colorado 80045, USA
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Abstract
Vitamin A signaling occurs through nuclear receptors recognizing diverse forms of retinoic acid (RA). The retinoic acid receptors (RARs) bind all-trans RA and its 9-cis isomer (9-cis RA). They convey most of the activity of RA, particularly during embryogenesis. The second subset of receptors, the rexinoid receptors (RXRs), binds 9-cis RA only. However, RXRs are obligatory DNA-binding partners for a number of nuclear receptors, broadening the spectrum of their biological activity to the corresponding nuclear receptor-signaling pathways. The present chapter more particularly focuses on RXR-containing transcriptional complexes for which RXR is not only a structural component necessary for DNA binding but also acts as a ligand-activated partner. After positioning RXR among the nuclear receptor superfamily in the first part, we will give an overview of three major signaling pathways involved in metabolism, which are sensitive to RXR activation: LXR:RXR, FXR:RXR, and PPAR:RXR. The third and last part is focused on RXR signaling and its potential role in metabolic regulation. Indeed, while the nature of the endogenous ligand for RXR is still in question, as we will discuss herein, a better understanding of RXR activities is necessary to envisage the potential therapeutic applications of synthetic RXR ligands.
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Affiliation(s)
- Béatrice Desvergne
- Center for Integrative Genomics, Building Génopode, University of Lausanne, CH-1015 Lausanne, Switzerland
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Ziouzenkova O, Orasanu G, Sukhova G, Lau E, Berger JP, Tang G, Krinsky NI, Dolnikowski GG, Plutzky J. Asymmetric cleavage of beta-carotene yields a transcriptional repressor of retinoid X receptor and peroxisome proliferator-activated receptor responses. Mol Endocrinol 2006; 21:77-88. [PMID: 17008383 DOI: 10.1210/me.2006-0225] [Citation(s) in RCA: 106] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
beta-Carotene and its metabolites exert a broad range of effects, in part by regulating transcriptional responses through specific nuclear receptor activation. Symmetric cleavage of beta-carotene can yield 9-cis retinoic acid (9-cisRA), the natural ligand for the nuclear receptor RXR, the obligate heterodimeric partner for numerous nuclear receptor family members. A significant portion of beta-carotene can also undergo asymmetric cleavage to yield apocarotenals, a series of poorly understood naturally occurring molecules whose biologic role, including their transcriptional effects, remains essentially unknown. We show here that beta-apo-14'-carotenal (apo14), but not other structurally related apocarotenals, represses peroxisome proliferator-activated receptors (PPAR) and RXR activation and biologic responses induced by their respective agonists both in vitro and in vivo. During adipocyte differentiation, apo14 inhibited PPARgamma target gene expression and adipogenesis, even in the presence of the potent PPARgamma agonist BRL49653. Apo14 also suppressed known PPARalpha responses, including target gene expression and its known antiinflammatory effects, but not if PPARalpha agonist stimulation occurred before apo14 exposure and not in PPARalpha-deficient cells or mice. Other apocarotenals tested had none of these effects. These data extend current views of beta-carotene metabolism to include specific apocarotenals as possible biologically active mediators and identify apo14 as a possible template for designing PPAR and RXR modulators and better understanding modulation of nuclear receptor activation. These results also suggest a novel model of molecular endocrinology in which metabolism of a parent compound, beta-carotene, may alternatively activate (9-cisRA) or inhibit (apo14) specific nuclear receptor responses.
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Affiliation(s)
- Ouliana Ziouzenkova
- Cardiovascular Division, Brigham and Women's Hospital, Havard University, Boston, Massachusetts 02115, USA
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Hafstad AD, Solevåg GH, Severson DL, Larsen TS, Aasum E. Perfused hearts from Type 2 diabetic (db/db) mice show metabolic responsiveness to insulin. Am J Physiol Heart Circ Physiol 2006; 290:H1763-9. [PMID: 16327015 DOI: 10.1152/ajpheart.01063.2005] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Diabetic ( db/db) mice provide an animal model of Type 2 diabetes characterized by marked in vivo insulin resistance. The effect of insulin on myocardial metabolism has not been fully elucidated in this diabetic model. In the present study we tested the hypothesis that the metabolic response to insulin in db/db hearts will be diminished due to cardiac insulin resistance. Insulin-induced changes in glucose oxidation (GLUox) and fatty acid (FA) oxidation (FAox) were measured in isolated hearts from control and diabetic mice, perfused with both low as well as high concentration of glucose and FA: 10 mM glucose/0.5 mM palmitate and 28 mM glucose/1.1 mM palmitate. Both in the absence and presence of insulin, diabetic hearts showed decreased rates of GLUox and elevated rates of FAox. However, the insulin-induced increment in GLUox, as well as the insulin-induced decrement in FAox, was similar or even more pronounced in diabetic that in control hearts. During elevated FA and glucose supply, however, the effect of insulin was blunted in db/db hearts with respect to both FAox and GLUox. Finally, insulin-stimulated deoxyglucose uptake was markedly reduced in isolated cardiomyocytes from db/db mice, whereas glucose uptake in isolated perfused db/db hearts was clearly responsive to insulin. These results show that, despite reduced insulin-stimulated glucose uptake in isolated cardiomyocytes, isolated perfused db/db hearts are responsive to metabolic actions of insulin. These results should advocate the use of insulin therapy (glucose-insulin-potassium) in diabetic patients undergoing cardiac surgery or during reperfusion after an ischemic insult.
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Affiliation(s)
- Anne Dragøy Hafstad
- Department of Medical Physiology, Institute of Medical Biology, Faculty of Medicine, University of Tromsø, N-9037 Tromsø, Norway
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Longnus SL, Ségalen C, Giudicelli J, Sajan MP, Farese RV, Van Obberghen E. Insulin signalling downstream of protein kinase B is potentiated by 5'AMP-activated protein kinase in rat hearts in vivo. Diabetologia 2005; 48:2591-601. [PMID: 16283248 DOI: 10.1007/s00125-005-0016-3] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/14/2005] [Accepted: 08/11/2005] [Indexed: 12/25/2022]
Abstract
AIMS/HYPOTHESIS 5'AMP-activated protein kinase (AMPK) and insulin stimulate glucose transport in heart and muscle. AMPK acts in an additive manner with insulin to increase glucose uptake, thereby suggesting that AMPK activation may be a useful strategy for ameliorating glucose uptake, especially in cases of insulin resistance. In order to characterise interactions between the insulin- and AMPK-signalling pathways, we investigated the effects of AMPK activation on insulin signalling in the rat heart in vivo. METHODS Male rats (350-400 g) were injected with 1 g/kg 5-aminoimidazole-4-carboxamide-1-beta-D-ribofuranoside (AICAR) or 250 mg/kg metformin in order to activate AMPK. Rats were administered insulin 30 min later and after another 30 min their hearts were removed. The activities and phosphorylation levels of components of the insulin-signalling pathway were subsequently analysed in individual rat hearts. RESULTS AICAR and metformin administration activated AMPK and enhanced insulin signalling downstream of protein kinase B in rat hearts in vivo. Insulin-induced phosphorylation of glycogen synthase kinase 3 (GSK3) beta, p70 S6 kinase (p70S6K)(Thr389) and IRS1(Ser636/639) were significantly increased following AMPK activation. To the best of our knowledge, this is the first report of heightened insulin responses of GSK3beta and p70S6K following AMPK activation. In addition, we found that AMPK inhibits insulin stimulation of IRS1-associated phosphatidylinositol 3-kinase activity, and that AMPK activates atypical protein kinase C and extracellular signal-regulated kinase in the heart. CONCLUSIONS/INTERPRETATIONS Our data are indicative of differential effects of AMPK on the activation of components in the cardiac insulin-signalling pathway. These intriguing observations are critical for characterisation of the crosstalk between AMPK and insulin signalling.
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Affiliation(s)
- S L Longnus
- INSERM U145, IFR 50, Faculty of Medicine, Avenue de Valombrose, 06107,, Nice Cedex 2, France.
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Li X, Hansen PA, Xi L, Chandraratna RAS, Burant CF. Distinct Mechanisms of Glucose Lowering by Specific Agonists for Peroxisomal Proliferator Activated Receptor γ and Retinoic Acid X Receptors. J Biol Chem 2005; 280:38317-27. [PMID: 16179348 DOI: 10.1074/jbc.m505853200] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Agonists for the nuclear receptor peroxisomal proliferator-activated receptor-gamma (PPARgamma) and its heterodimeric partner, retinoid X receptor (RXR), are effective agents for the treatment of type 2 diabetes. To gain insight into the antidiabetic action of these compounds, we treated female Zucker diabetic rats (ZFF) with AGN194204, which we show to be a homodimer-specific RXR agonist, or the PPARgamma agonist, troglitazone. Hyperinsulinemic-euglycemic clamps in ZFF showed that troglitazone and AGN194204 reduced basal endogenous glucose production (EGP) approximately 30% and doubled the insulin suppression of EGP. AGN194204 had no effect on peripheral glucose utilization, whereas troglitazone increased insulin-stimulated glucose utilization by 50%, glucose uptake into skeletal muscle by 85%, and de novo skeletal muscle glycogen synthesis by 300%. Troglitazone increased skeletal muscle Irs-1 and phospho-Akt levels following in vivo insulin treatment, whereas AGN194204 increased hepatic Irs-2 and insulin stimulated phospho-Akt in liver. Gene profiles of AGN194204-treated mouse liver analyzed by Ingenuity Pathway Analysis identified increases in fatty acid synthetic genes, including Srebp-1 and fatty acid synthase, a pathway previously shown to be induced by RXR agonists. A network of down-regulated genes containing Foxa2, Foxa3, and G-protein subunits was identified, and decreases in these mRNA levels were confirmed by quantitative reverse transcription-PCR. Treatment of HepG2 cells with AGN194204 resulted in inhibition of glucagon-stimulated cAMP accumulation suggesting the G-protein down-regulation may provide an additional mechanism for hepatic insulin sensitization by RXR. These studies demonstrate distinct molecular events lead to insulin sensitization by high affinity RXR and PPARgamma agonists.
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Affiliation(s)
- Xiangquan Li
- Division of Endocrinology and Metabolism, Department of Internal Medicine, University of Michigan, Ann Arbor, Michigan 48109-0354, USA
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40
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Yang Q, Graham TE, Mody N, Preitner F, Peroni OD, Zabolotny JM, Kotani K, Quadro L, Kahn BB. Serum retinol binding protein 4 contributes to insulin resistance in obesity and type 2 diabetes. Nature 2005; 436:356-62. [PMID: 16034410 DOI: 10.1038/nature03711] [Citation(s) in RCA: 1481] [Impact Index Per Article: 77.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2005] [Accepted: 05/03/2005] [Indexed: 01/08/2023]
Abstract
In obesity and type 2 diabetes, expression of the GLUT4 glucose transporter is decreased selectively in adipocytes. Adipose-specific Glut4 (also known as Slc2a4) knockout (adipose-Glut4(-/-)) mice show insulin resistance secondarily in muscle and liver. Here we show, using DNA arrays, that expression of retinol binding protein-4 (RBP4) is elevated in adipose tissue of adipose-Glut4(-/-) mice. We show that serum RBP4 levels are elevated in insulin-resistant mice and humans with obesity and type 2 diabetes. RBP4 levels are normalized by rosiglitazone, an insulin-sensitizing drug. Transgenic overexpression of human RBP4 or injection of recombinant RBP4 in normal mice causes insulin resistance. Conversely, genetic deletion of Rbp4 enhances insulin sensitivity. Fenretinide, a synthetic retinoid that increases urinary excretion of RBP4, normalizes serum RBP4 levels and improves insulin resistance and glucose intolerance in mice with obesity induced by a high-fat diet. Increasing serum RBP4 induces hepatic expression of the gluconeogenic enzyme phosphoenolpyruvate carboxykinase (PEPCK) and impairs insulin signalling in muscle. Thus, RBP4 is an adipocyte-derived 'signal' that may contribute to the pathogenesis of type 2 diabetes. Lowering RBP4 could be a new strategy for treating type 2 diabetes.
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Affiliation(s)
- Qin Yang
- Division of Endocrinology, Diabetes and Metabolism, Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts 02215, USA
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Gual P, Le Marchand-Brustel Y, Tanti JF. Positive and negative regulation of insulin signaling through IRS-1 phosphorylation. Biochimie 2005; 87:99-109. [PMID: 15733744 DOI: 10.1016/j.biochi.2004.10.019] [Citation(s) in RCA: 619] [Impact Index Per Article: 32.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2004] [Accepted: 10/27/2004] [Indexed: 12/12/2022]
Abstract
This review will provide insight on the current understanding of the regulation of insulin signaling in both physiological and pathological conditions through modulations that occur with regards to the functions of the insulin receptor substrate 1 (IRS1). While the phosphorylation of IRS1 on tyrosine residue is required for insulin-stimulated responses, the phosphorylation of IRS1 on serine residues has a dual role, either to enhance or to terminate the insulin effects. The activation of PKB in response to insulin propagates insulin signaling and promotes the phosphorylation of IRS1 on serine residue in turn generating a positive-feedback loop for insulin action. Insulin also activates several kinases and these kinases act to induce the phosphorylation of IRS1 on specific sites and inhibit its functions. This is part of the negative-feedback control mechanism induced by insulin that leads to termination of its action. Agents such as free fatty acids, cytokines, angiotensin II, endothelin-1, amino acids, cellular stress and hyperinsulinemia, which induce insulin resistance, lead to both activation of several serine/threonine kinases and phosphorylation of IRS1. These agents negatively regulate the IRS1 functions by phosphorylation but also via others molecular mechanisms (SOCS expression, IRS degradation, O-linked glycosylation) as summarized in this review. Understanding how these agents inhibit IRS1 functions as well as identification of kinases involved in these inhibitory effects may provide novel targets for development of strategies to prevent insulin resistance.
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Affiliation(s)
- Philippe Gual
- Inserm U 568 (Molecular signaling and obesity); IFR 50; Faculté de medecine, avenue de Valombrose, 06107 Nice cedex 2, France.
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Szanto A, Narkar V, Shen Q, Uray IP, Davies PJA, Nagy L. Retinoid X receptors: X-ploring their (patho)physiological functions. Cell Death Differ 2005; 11 Suppl 2:S126-43. [PMID: 15608692 DOI: 10.1038/sj.cdd.4401533] [Citation(s) in RCA: 207] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Retinoid X receptor (RXR) belongs to a family of ligand-activated transcription factors that regulate many aspects of metazoan life. A class of nuclear receptors requires RXR as heterodimerization partner for their function. This places RXR in the crossroad of multiple distinct biological pathways. This and the fact that the debate on the endogenous ligand requirement for RXR is not yet settled make RXR still an enigmatic transcription factor. Here, we review some of the biology of RXR. We place RXR into the evolution of nuclear receptors, review structural details and ligands of the receptor. Then processes regulated by RXR are discussed focusing on the developmental roles deduced from studies on knockout animals and metabolic roles in diseases such as diabetes and atherosclerosis deduced from pharmacological studies. Finally, aspects of RXR's involvement in myeloid differentiation and apoptosis are summarized along with issues on RXR's suitability as a therapeutic target.
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Affiliation(s)
- A Szanto
- Department of Biochemistry and Molecular Biology, Research Center for Molecular Medicine, University of Debrecen, Nagyerdei krt. 98, Debrecen H-4012, Hungary
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Carroll R, Carley AN, Dyck JRB, Severson DL. Metabolic effects of insulin on cardiomyocytes from control and diabetic db/db mouse hearts. Am J Physiol Endocrinol Metab 2005; 288:E900-6. [PMID: 15632103 DOI: 10.1152/ajpendo.00491.2004] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Diabetic db/db mice exhibit profound insulin resistance in vivo, but the specific degree of cardiac insensitivity to insulin has not been assessed. Therefore, the effect of insulin on cardiomyocytes from db/db hearts was assessed by measuring two metabolic responses (deoxyglucose uptake and fatty acid oxidation) and the phosphorylation of two enzymes in the insulin-signaling cascade [Akt and AMP-activated protein kinase (AMPK)]. Maximal insulin-stimulated deoxyglucose transport was reduced to 58 and 40% of control in cardiomyocytes from db/db mice at two ages (6 and 12 wk). Insulin-stimulated deoxyglucose uptake was also reduced in myocytes from transgenic db/db mice overexpressing the insulin-sensitive glucose transporter (db/db-hGLUT4). Treatment of db/db mice for 1 wk with an insulin-sensitizing peroxisome proliferator-activated receptor-gamma agonist (COOH) completely normalized insulin-stimulated deoxyglucose uptake. Insulin had no direct effect on palmitate oxidation by either control or db/db cardiomyocytes, but the combination of insulin and glucose reduced palmitate oxidation, likely an indirect effect secondary to increased glucose uptake. Insulin had no effect on AMPK phosphorylation from either control or db/db cardiomyocytes. Insulin increased the phosphorylation of Akt in all cardiomyocyte preparations (control, db/db, COOH-treated db/db) to the same extent. Thus insulin has selective metabolic actions in mouse cardiomyocytes; deoxyglucose uptake and Akt phosphorylation are increased, but fatty acid oxidation and AMPK phosphorylation are unchanged. Insulin resistance in db/db cardiomyocytes is manifested by reduced insulin-stimulated deoxyglucose uptake.
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Affiliation(s)
- Rogayah Carroll
- Department of Pharmacology & Therapeutics, Faculty of Medicine, Univ. of Calgary, 3330 Hospital Dr. N.W., Calgary, Alberta, T2N 4N1, Canada
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