451
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Iwai H, Ohno Y, Aoki N. The effect of leptin, tumor necrosis factor-alpha (TNF-alpha), and nitric oxide (NO) production on insulin resistance in Otsuka Long-Evans fatty rats. Endocr J 2003; 50:673-80. [PMID: 14709837 DOI: 10.1507/endocrj.50.673] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Adipocytokines and nitric oxide (NO) play important roles in type 2 diabetes; however, the regulatory mechanism has not been fully clarified. To investigate the role of adipocytokines and NO production on insulin resistance in type 2 diabetes, the LETO rats and the OLETF rats were fed a control diet or a high-fat diet for 4 weeks. After 4 weeks the blood levels of leptin, tumor necrosis factor-alpha (TNF-alpha), and NO were measured. As an indicator of insulin resistance, the homeostasis model assessment for insulin resistance (HOMA-R) was applied. Food intake in high-fat diet group rats was lower than in control diet group rats. The high fat diet increased body weight (BW), but did not significantly affect the HOMA-R and blood pressure (BP). Leptin and TNF-alpha levels were significantly higher in the OLETF rats than in the LETO rats, while NO levels did not change between the two groups. The high-fat diet elevated blood leptin levels, but not TNF-alpha and NO levels. The HOMA-R in the OLETF rats was correlated with leptin, but not with BP, BW, TNF-alpha or NO. NO showed an inverse correlation with BP. In conclusion, leptin, TNF-alpha, and NO may each regulate insulin sensitivity through their own unique pathways. The elucidation of the regulatory mechanism of adipocytokines and NO may give a clue to clarify the pathophysiology of insulin resistance.
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Affiliation(s)
- Hiroshi Iwai
- Department of Endocrinology, Metabolism, and Diabetology, Kinki University School of Medicine
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452
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Wakimoto K, Chiba H, Michibata H, Seishima M, Kawasaki S, Okubo K, Mitsui H, Torii H, Imai Y. A novel diacylglycerol acyltransferase (DGAT2) is decreased in human psoriatic skin and increased in diabetic mice. Biochem Biophys Res Commun 2003; 310:296-302. [PMID: 14521909 DOI: 10.1016/j.bbrc.2003.09.015] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Psoriasis is a skin disease with epidermal keratinocyte hyperproliferation and altered differentiation. To identify novel psoriasis-related genes, we investigated differentially expressed genes between normal and psoriatic skin. We identified a novel acyl CoA:diacylglycerol acyltransferase 2 (DGAT2) gene, which was decreased in human psoriatic skin. DGAT2 mRNA was expressed in sebaceous glands of normal human skin. DGAT2 protein was detected on endoplasmic reticulum. DGAT2 catalyzes the final step in the production of triglycerides and the accumulation of triglycerides in the tissues is considered to be related to insulin resistance. Therefore, we also investigated the expression of the DGAT2 gene in diabetic mice. DGAT2 mRNA was increased in the adipose, small intestine, and skeletal muscle in diabetic mice.
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Affiliation(s)
- Koji Wakimoto
- Discovery Research Laboratory, Advanced Medical Research Department, Tanabe Seiyaku Co., Ltd, 3-16-89 Kashima, Yodogawa-ku, Osaka 532-8505, Japan.
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453
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Rangwala SM, Rhoades B, Shapiro JS, Rich AS, Kim JK, Shulman GI, Kaestner KH, Lazar MA. Genetic modulation of PPARgamma phosphorylation regulates insulin sensitivity. Dev Cell 2003; 5:657-63. [PMID: 14536066 DOI: 10.1016/s1534-5807(03)00274-0] [Citation(s) in RCA: 173] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Obesity-associated diabetes is epidemic in industrialized societies. The nuclear receptor peroxisome proliferator-activated receptor gamma (PPARgamma) is highly expressed in adipose tissue and the presumed molecular target for antidiabetic thiazolidinedione drugs that reverse insulin resistance but also promote weight gain. Phosphorylation reduces the activity of PPARgamma in vitro, but physiological relevance has not been demonstrated. We have studied mice homozygous for a mutation (S112A) that prevents PPARgamma phosphorylation. Surprisingly, the weights and adipose mass of PPARgamma-S112A mice are not greater than wild-type. Remarkably, however, genetic prevention of PPARgamma phosphorylation preserves insulin sensitivity in the setting of diet-induced obesity. Underlying this protection are smaller fat cells, elevated serum adiponectin, and reduced free fatty acid levels. Thus, the phosphorylation state of PPARgamma modulates insulin sensitivity. Compounds that prevent PPARgamma phosphorylation or ligands that induce the conformation of nonphosphorylated PPARgamma may selectively enhance insulin sensitivity without increasing body weight.
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MESH Headings
- Adiponectin
- Adipose Tissue/metabolism
- Adipose Tissue, Brown
- Alanine/genetics
- Amino Acid Substitution
- Animals
- Blood Glucose/metabolism
- Blotting, Southern
- Body Weight
- Cell Size
- Cells, Cultured
- Culture Media, Conditioned/pharmacology
- Dose-Response Relationship, Drug
- Embryo, Mammalian
- Fatty Acids, Nonesterified/blood
- Female
- Gene Expression
- Glucose/metabolism
- Glucose Tolerance Test
- Immunoblotting
- Insulin/metabolism
- Insulin/pharmacology
- Insulin/physiology
- Insulin Resistance
- Intercellular Signaling Peptides and Proteins
- Leptin/blood
- Male
- Mice
- Mice, Inbred C57BL
- Mice, Transgenic/blood
- Mice, Transgenic/genetics
- Mutation
- Obesity/blood
- Obesity/chemically induced
- Phosphorylation
- Proteins/genetics
- Proteins/metabolism
- Receptors, Cytoplasmic and Nuclear/genetics
- Receptors, Cytoplasmic and Nuclear/metabolism
- Receptors, Cytoplasmic and Nuclear/physiology
- Serine/genetics
- Time Factors
- Transcription Factors/genetics
- Transcription Factors/metabolism
- Transcription Factors/physiology
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Affiliation(s)
- Shamina M Rangwala
- Division of Endocrinology, Diabetes, and Metabolism, Department of Medicine, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA
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454
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Hattori Y, Suzuki M, Hattori S, Kasai K. Globular adiponectin upregulates nitric oxide production in vascular endothelial cells. Diabetologia 2003; 46:1543-9. [PMID: 14551684 DOI: 10.1007/s00125-003-1224-3] [Citation(s) in RCA: 157] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/10/2003] [Revised: 09/04/2003] [Indexed: 11/30/2022]
Abstract
AIMS/HYPOTHESIS Adiponectin, also called ACRP30, is a novel adipose tissue-specific protein that has been shown to improve insulin sensitivity and to exert anti-atherogenic effects. It is known that knockout mice lacking endothelial NO synthase (eNOS) develop hypertension, insulin resistance, hyperlipidaemia, and show augmented ischaemia-reperfusion damage. Thus, we examined whether globular adiponectin activates eNOS to produce NO. METHODS To analyze NO production in bovine aortic endothelial cells (BAE), NOx (nitrite and nitrate) was measured in the medium with an automated NO detector/high-performance liquid chromatography system. eNOS activation was assessed by phosphorylation of the enzyme and its activity was evaluated by citrulline synthesis in human umbilical vein endothelial cells (HUVEC). eNOS mRNA and protein expressions in HUVEC were evaluated by Realtime PCR and Western blot analysis. RESULTS Gobular adiponectin increased NO production in BAE. It also caused eNOS phosphorylation and potentiated eNOS activity in HUVEC. In addition, globular adiponectin up-regulated the eNOS gene to increase protein expression in HUVEC. CONCLUSION/INTERPRETATION Globular adiponectin increases NO production through two mechanisms, namely, by activation of eNOS enzyme activity and via an increase in eNOS expression. Activation and up-regulation of eNOS could explain some of the observed vasoprotective properties of globular adiponectin, as well as its beneficial effects on the cardiovascular system.
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Affiliation(s)
- Y Hattori
- Departments of Endocrinology and Metabolism, Dokkyo University School of Medicine, Mibu, Tochigi, Japan.
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455
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Hoenig M, Ferguson DC. Effect of darglitazone on glucose clearance and lipid metabolism in obese cats. Am J Vet Res 2003; 64:1409-13. [PMID: 14620778 DOI: 10.2460/ajvr.2003.64.1409] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
OBJECTIVE To examine the effect of darglitazone, a compound of the thiazolidinedione class, on glucose clearance and lipid metabolism in obese cats. ANIMALS 18 obese and 4 lean adult neutered female cats. PROCEDURE IV glucose tolerance tests with measurements of glucose, insulin, and nonesterified fatty acid (NEFA) concentrations were performed before and 42 days after daily administration of darglitazone (9 obese cats) or placebo (9 obese and 4 lean cats). Additionally, cholesterol, triglyceride, leptin, and glycosylated hemoglobin concentrations were measured. RESULTS Darglitazone-treated cats had significantly lower cholesterol, triglyceride, and leptin concentrations, compared with placebo-treated obese cats. A significant decrease in the area under the curve for NEFAs, glucose, and insulin during an i.v. glucose tolerance test was seen in darglitazone-treated cats. The drug was well tolerated. CONCLUSION AND CLINICAL RELEVANCE The response of obese cats to darglitazone was similar to the response to thiazolidinediones in obese humans and rodents Darglitazone was effective in improving insulin sensitivity and glucose and lipid metabolism in obese cats.
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Affiliation(s)
- Margarethe Hoenig
- Department of Physiology and Pharmacology, College of Veterinary Medicine, University of Georgia, Athens, GA 30602, USA
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456
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Luquet S, Lopez-Soriano J, Holst D, Fredenrich A, Melki J, Rassoulzadegan M, Grimaldi PA. Peroxisome proliferator-activated receptor delta controls muscle development and oxidative capability. FASEB J 2003; 17:2299-301. [PMID: 14525942 DOI: 10.1096/fj.03-0269fje] [Citation(s) in RCA: 397] [Impact Index Per Article: 18.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Peroxisome proliferator-activated receptors (PPARs) are nuclear receptors exerting several functions in development and metabolism. The physiological functions of PPARdelta remain elusive. By using a CRE-Lox recombination approach, we generated an animal model for muscle-specific PPARdelta overexpression to investigate the role of PPARdelta in this tissue. Muscle-specific PPARdelta overexpression results in a profound change in fiber composition due to hyperplasia and/or shift to more oxidative fiber and, as a consequence, leads to the increase of both enzymatic activities and genes implicated in oxidative metabolism. These changes in muscle are accompanied by a reduction of body fat mass, mainly due to a large reduction of adipose cell size. Furthermore, we demonstrate that endurance exercise promotes an accumulation of PPARdelta protein in muscle of wild-type animals. Collectively, these results suggest that PPARdelta plays an important role in muscle development and adaptive response to environmental changes, such as training exercise. They strongly support the idea that activation of PPARdelta could be beneficial in prevention of metabolic disorders, such as obesity or type 2 diabetes.
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Affiliation(s)
- Serge Luquet
- Inserm U470, Centre de Biochimie, Parc Valrose, Université de Nice-Sophia Antipolis, 06108 Nice cedex 2, France
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457
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Satoh N, Ogawa Y, Usui T, Tagami T, Kono S, Uesugi H, Sugiyama H, Sugawara A, Yamada K, Shimatsu A, Kuzuya H, Nakao K. Antiatherogenic effect of pioglitazone in type 2 diabetic patients irrespective of the responsiveness to its antidiabetic effect. Diabetes Care 2003; 26:2493-9. [PMID: 12941708 DOI: 10.2337/diacare.26.9.2493] [Citation(s) in RCA: 238] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
OBJECTIVE Thiazolidinediones (TZDs), a class of insulin-sensitizing agents used clinically to treat type 2 diabetes, are also antiatherogenic. This study was designed to elucidate the relationship between the antiatherogenic and antidiabetic effects of pioglitazone, a TZD, in type 2 diabetic patients. RESEARCH DESIGN AND METHODS A total of 136 Japanese type 2 diabetic patients were included and divided into two groups: the pioglitazone-treated group (30 mg daily for 3 months) (n = 70) and the untreated control group (n = 66). The changes in glycolipid metabolism as well as plasma high-sensitivity C-reactive protein (CRP), leptin, adiponectin, and pulse wave velocity (PWV) were monitored to analyze the relationship between the antiatherogenic and antidiabetic effects of pioglitazone. RESULTS The pioglitazone treatment significantly reduced hyperglycemia, hyperinsulinemia, and HbA(1c) levels and increased plasma adiponectin concentrations relative to the control group (P < 0.01). It also significantly decreased CRP and PWV (P < 0.01). The antiatherogenic effect was observed in both the nonresponders showing <1% of reduction in HbA(1c) (n = 30) and responders showing >1% of reduction (n = 40). ANCOVA revealed that treatment with pioglitazone was associated with a low CRP and PWV, independent of the changes in parameters related to glucose metabolism. CONCLUSIONS This study represents the first demonstration of the antiatherogenic effect of pioglitazone in both nonresponders and responders with respect to its antidiabetic effect and suggests that pioglitazone can exert its antiatherogenic effect independently of its antidiabetic effect.
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Affiliation(s)
- Noriko Satoh
- Diabetes Center and Clinical Research Institute of Kyoto National Hospital, Kyoto, Japan
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458
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Niki I. [Contribution of diabetic research to versatile strategies for the treatment of diabetes mellitus]. Nihon Yakurigaku Zasshi 2003; 122:228-35. [PMID: 12939540 DOI: 10.1254/fpj.122.228] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Diabetes mellitus is a very common life-style-related disease. Both genetic and environmental factors are strongly involved in its etiology and pathogenesis, and patients suffering from this disease are rapidly increasing in number. Since the discoveries of insulin in the 1920s and of antidiabetic sulphonylureas in the 1950s, these agents have been widely used for the treatment of diabetes mellitus. For the use of insulin, however, diabetic patients are imposed to inject insulin daily, and long-term use of sulphonylureas is suggested to impair pancreatic B cell functions. In order to overcome these problems and to achieve the fine control of blood glucose levels, many attempts for novel antidiabetic treatments are currently ongoing, and versatile therapeutic strategies for the treatment are expected to prevent the progression of this disease and resultant diabetic complications that severely affect the individuals' QOL. This paper overviews what diabetic research has done for its treatment and what it will do in the future.
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Affiliation(s)
- Ichiro Niki
- Department of Pharmacology, Oita Medical University, Hasama, Japan.
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459
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Fujita Y, Yamada Y, Kusama M, Yamauchi T, Kamon J, Kadowaki T, Iga T. Sex differences in the pharmacokinetics of pioglitazone in rats. Comp Biochem Physiol C Toxicol Pharmacol 2003; 136:85-94. [PMID: 14522601 DOI: 10.1016/s1532-0456(03)00194-7] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Clinical studies have suggested that pioglitazone, an insulin sensitizer, has a stronger effect in women than in men. To determine the sex difference in the pharmacokinetics of pioglitazone, we examined the plasma and white adipose tissue levels of pioglitazone and its active metabolites (M-II, M-III and M-IV) in male and female rats treated with a single or repeated oral administration of pioglitazone (10 mg/kg). The AUCs of pioglitazone (149.6+/-22.6 vs. 103.3+/-14.0 microg.h/ml; P<0.01), M-III (31.4+/-8.1 vs. 20.2+/-4.7 microg.h/ml; P<0.05) and M-IV (41.9+/-15.5 vs. 14.1+/-1.6 microg.h/ml; P<0.01) were larger in female rats than in male rats, but the levels of M-II were similar. Any of the compounds did not accumulate in plasma after repeated administration. According to kinetic model analysis, the apparent elimination rate of pioglitazone and the formation rate of M-II were faster in male rats than in female rats. No significant sex difference was found in the tissue-to-plasma concentration ratios of pioglitazone or its active metabolites in white adipose tissue. These results suggest that there are sex differences in the plasma levels of pioglitazone and some of its active metabolites and that those differences are reflected in differences in white adipose tissue levels.
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Affiliation(s)
- Yukiyoshi Fujita
- Department of Pharmacy, The University of Tokyo Hospital, Faculty of Medicine, University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo, Japan
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460
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Abstract
Diabetes, obesity, atherosclerosis and cancer are the principal contributors to morbidity and mortality in Western society. Emerging evidence indicates that a nuclear receptor, the peroxisome proliferator-activated receptor gamma (PPARgamma), plays a role in these pathological processes. Furthermore, modulation of receptor action in these diseases may be of therapeutic value, as exemplified by the recent introduction of the thiazolidinediones, a novel class of insulin-sensitizing agent for the treatment of type 2 diabetes mellitus. The availability of such high-affinity ligands has facilitated the study of signalling pathways through which PPARgamma regulates metabolic processes; these analyses have been complemented by the study of human subjects harbouring (naturally occurring) mutations and polymorphisms within the receptor. The latter have provided unique genetic evidence for a link between PPARgamma and mammalian glucose homeostasis, lipid metabolism and regulation of fat mass. This review highlights recent studies which have advanced our understanding of the pivotal role that this receptor plays in metabolism, with particular reference to the consequences of inherited variation in the human receptor gene.
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Affiliation(s)
- Mark Gurnell
- Department of Medicine, University of Cambridge, Addenbrooke's Hospital, Cambridge, UK.
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461
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Seo JB, Noh MJ, Yoo EJ, Park SY, Park J, Lee IK, Park SD, Kim JB. Functional characterization of the human resistin promoter with adipocyte determination- and differentiation-dependent factor 1/sterol regulatory element binding protein 1c and CCAAT enhancer binding protein-alpha. Mol Endocrinol 2003; 17:1522-33. [PMID: 12730330 DOI: 10.1210/me.2003-0028] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Recent studies with murine models propose that resistin would be a possible mediator to link between obesity and insulin resistance. Although it has been reported that resistin is highly expressed and secreted by adipocytes, transcription factors that are involved in resistin gene expression have not been well characterized. To investigate the molecular mechanisms of resistin gene expression, we cloned and characterized the human resistin promoter. Sequence analysis of the resistin promoter revealed several putative binding sites for adipogenic transcription factors including adipocyte determination- and differentiation-dependent factor 1 (ADD1)/sterol regulatory element binding protein 1c (SREBP1c) and CCAAT enhancer binding protein-alpha (C/EBP alpha). EMSA and chromatin immunoprecipitation assays demonstrated that ADD1/SREBP1c binds to the human resistin promoter in vitro and in vivo. Expression of ADD1/SREBP1c transactivated the luciferase reporter gene activity, the promoter region of which contains a human resistin promoter in a sterol regulatory element (SRE)-dependent manner. Furthermore, ectopic expression of ADD1/SREBP1c by adenovirus significantly increased the expression of resistin mRNA in adipocytes. Human resistin promoter was also activated by C/EBP alpha expression, although ectopic expression of both transcription factors did not show any synergistic effects on the activation of resistin promoter. Together, these data suggest that ADD1/SREBP1c and C/EBP alpha may play discrete roles in the regulation of the resistin gene expression.
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Affiliation(s)
- Jong Bae Seo
- School of Biological Sciences, Seoul National University, NS-70, San 56-1, Seoul 151-742, Korea
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462
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Norris AW, Chen L, Fisher SJ, Szanto I, Ristow M, Jozsi AC, Hirshman MF, Rosen ED, Goodyear LJ, Gonzalez FJ, Spiegelman BM, Kahn CR. Muscle-specific PPARgamma-deficient mice develop increased adiposity and insulin resistance but respond to thiazolidinediones. J Clin Invest 2003; 112:608-18. [PMID: 12925701 PMCID: PMC171387 DOI: 10.1172/jci17305] [Citation(s) in RCA: 312] [Impact Index Per Article: 14.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2002] [Accepted: 06/03/2003] [Indexed: 12/12/2022] Open
Abstract
Activation of peroxisome proliferator-activated receptor gamma (PPARgamma) by thiazolidinediones (TZDs) improves insulin resistance by increasing insulin-stimulated glucose disposal in skeletal muscle. It remains debatable whether the effect of TZDs on muscle is direct or indirect via adipose tissue. We therefore generated mice with muscle-specific PPARgamma knockout (MuPPARgammaKO) using Cre/loxP recombination. Interestingly, MuPPARgammaKO mice developed excess adiposity despite reduced dietary intake. Although insulin-stimulated glucose uptake in muscle was not impaired, MuPPARgammaKO mice had whole-body insulin resistance with a 36% reduction (P < 0.05) in the glucose infusion rate required to maintain euglycemia during hyperinsulinemic clamp, primarily due to dramatic impairment in hepatic insulin action. When placed on a high-fat diet, MuPPARgammaKO mice developed hyperinsulinemia and impaired glucose homeostasis identical to controls. Simultaneous treatment with TZD ameliorated these high fat-induced defects in MuPPARgammaKO mice to a degree identical to controls. There was also altered expression of several lipid metabolism genes in the muscle of MuPPARgammaKO mice. Thus, muscle PPARgamma is not required for the antidiabetic effects of TZDs, but has a hitherto unsuspected role for maintenance of normal adiposity, whole-body insulin sensitivity, and hepatic insulin action. The tissue crosstalk mediating these effects is perhaps due to altered lipid metabolism in muscle.
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Affiliation(s)
- Andrew W Norris
- Research Division, Joslin Diabetes Center, One Joslin Place, Boston, Massachusetts 02215, USA
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463
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Ruan H, Pownall HJ, Lodish HF. Troglitazone antagonizes tumor necrosis factor-alpha-induced reprogramming of adipocyte gene expression by inhibiting the transcriptional regulatory functions of NF-kappaB. J Biol Chem 2003; 278:28181-92. [PMID: 12732648 DOI: 10.1074/jbc.m303141200] [Citation(s) in RCA: 150] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Troglitazone (TGZ), a member of the thiazolidinedione class of anti-diabetic compounds and a peroxisome proliferator activator receptor-gamma (PPAR-gamma) agonist, restores systemic insulin sensitivity and improves the full insulin resistance syndrome in vivo. The mechanisms underlying its in vivo function are not understood. Here we investigated the potential functional interaction between PPAR-gamma and NF-kappaB in adipocytes. We show that TGZ selectively blocked tumor necrosis factor-alpha-induced and NF-kappaB-dependent repression of multiple adipocyte-specific genes and induction of growth phase and other genes. This occurs without interfering with NF-kappaB expression, activation, nuclear translocation, or DNA binding and without suppressing NF-kappaB-dependent survival signals. Notably, the expressions of some tumor necrosis factor-alpha-induced genes in adipocytes were unaffected by PPAR-gamma activation. In reporter gene assays in HeLa cells, ectopic expression of PPAR-gamma abolished induction of a NF-kappaB-responsive reporter gene by the p65 subunit (RelA) of NF-kappaB, and the inhibition was further enhanced in the presence of TGZ. Conversely, overexpression of p65 inhibited induction of a PPAR-gamma-responsive reporter gene by activated PPAR-gamma in a dose-dependent manner. The inhibitory effect was independent of the presence of NF-kappaB-binding sites in the promoter region. Other NF-kappaB family members, p50 and c-Rel as well as the S276A mutant of p65, blocked PPAR-gamma-mediated gene transcription less effectively. Thus, p65 antagonizes the transcriptional regulatory activity of PPAR-gamma in adipocytes, and PPAR-gamma activation can at least partially override the inhibitory effects of p65 on the expression of key adipocyte genes. Our data suggest that inhibition of NF-kappaB activity is a mechanism by which PPAR-gamma agonists improve insulin sensitivity in vivo and that adipocyte NF-kappaB is a potential therapeutic target for obesity-linked type 2 diabetes.
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Affiliation(s)
- Hong Ruan
- Whitehead Institute for Biomedical Research, Cambridge, Massachusetts 02142, USA
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464
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Rybczynski PJ, Zeck RE, Combs DW, Turchi I, Burris TP, Xu JZ, Yang M, Demarest KT. Benzoxazinones as PPARgamma agonists. part 1: SAR of three aromatic regions. Bioorg Med Chem Lett 2003; 13:2359-62. [PMID: 12824034 DOI: 10.1016/s0960-894x(03)00401-3] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
A series of benzoxazinones was synthesized as PPARgamma agonists. The compounds were obtained in seven steps, and SAR was developed by variations to the core shown below. The compounds were tested as functional agonists in the induction of the aP2 gene in preadipocytes, and the most potent compound in the series has an EC(50)=0.51 microM. The potency was further confirmed through a PPAR-Gal4 construct. Efficacy has been demonstrated in the db/db mouse model of hyperglycemia.
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Affiliation(s)
- Philip J Rybczynski
- Johnson and Johnson Pharmaceutical Research and Development, LLC, 08869, Raritan, NJ, USA.
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465
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Muller YL, Bogardus C, Beamer BA, Shuldiner AR, Baier LJ. A functional variant in the peroxisome proliferator-activated receptor gamma2 promoter is associated with predictors of obesity and type 2 diabetes in Pima Indians. Diabetes 2003; 52:1864-71. [PMID: 12829658 DOI: 10.2337/diabetes.52.7.1864] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Peroxisome proliferator-activated receptor gamma (PPARgamma)-2 is a member of the nuclear hormone receptor superfamily that is expressed predominantly in adipocytes and is thought to have a role in energy homeostasis, adipogenesis, and insulin sensitivity. A functional single nucleotide polymorphism (SNP) that predicts a proline to alanine substitution (Pro12Ala) within the coding region of this gene has previously been associated with obesity and type 2 diabetes in several populations. In this study, we identified several novel SNPs in the promoter region of PPARgamma2 and genotyped them, along with the previously identified Pro12Ala SNP. In 241 nondiabetic Pima subjects, the Pro12Ala was associated with whole-body insulin action (P = 0.05), hepatic insulin action (P = 0.03), and fasting plasma insulin concentrations (P = 0.01). One of the promoter SNPs positioned within a putative E2 box was in high linkage disequilibrium (/D'/ = 0.98) with the Pro12Ala. This promoter SNP was similarly associated with whole-body insulin action (P = 0.04) and hepatic insulin action (P = 0.05), but not fasting plasma insulin concentrations. Functional studies in transfected 3T3-L1 cells demonstrated that this single base substitution in the putative E2 box significantly altered transcriptional activity from a luciferase reporter construct. These data indicate that this promoter SNP, via its effect on PPARgamma2 expression, may also have functional consequences on PPARgamma2-activated pathways, and perhaps both the promoter SNP and the Pro12Ala contribute to PPARgamma2-related phenotypes.
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Affiliation(s)
- Yunhua Li Muller
- Phoenix Epidemiology and Clinical Research Branch, National Institute of Diabetes and Digestive and Kidney Disease, National Institutes of Health, Phoenix, Arizona 85016, USA
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466
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Chen HC, Jensen DR, Myers HM, Eckel RH, Farese RV. Obesity resistance and enhanced glucose metabolism in mice transplanted with white adipose tissue lacking acyl CoA:diacylglycerol acyltransferase 1. J Clin Invest 2003; 111:1715-22. [PMID: 12782674 PMCID: PMC156099 DOI: 10.1172/jci15859] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Recent studies have identified the white adipose tissue (WAT) as an important endocrine organ that regulates energy and glucose metabolism via a number of secreted factors. Mice lacking acyl CoA:diacylglycerol acyltransferase 1 (DGAT1), a key enzyme in mammalian triglyceride synthesis, are protected against diet-induced obesity and glucose intolerance because of increased energy expenditure and enhanced insulin sensitivity. Because DGAT1 is highly expressed in WAT, we hypothesized that DGAT1 deficiency affects the expression of adipocyte-derived factors that regulate energy and glucose metabolism. Here we show that the transplantation of DGAT1-deficient WAT decreases adiposity and enhances glucose disposal in wild-type mice. Analysis of DGAT1-deficient WAT revealed a twofold increase in the expression of adiponectin, a molecule that enhances fatty acid oxidation and insulin sensitivity, and this increase may account in part for the transplantation-induced metabolic changes. Our results highlight the importance of the endocrine function of WAT and suggest that an alteration in this function contributes to the increased energy expenditure and insulin sensitivity in DGAT1-deficient mice.
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Affiliation(s)
- Hubert C Chen
- Gladstone Institute of Cardiovascular Disease, San Francisco, California 94141-9100, USA
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467
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Waring JF, Ciurlionis R, Clampit JE, Morgan S, Gum RJ, Jolly RA, Kroeger P, Frost L, Trevillyan J, Zinker BA, Jirousek M, Ulrich RG, Rondinone CM. PTP1B antisense-treated mice show regulation of genes involved in lipogenesis in liver and fat. Mol Cell Endocrinol 2003; 203:155-68. [PMID: 12782412 DOI: 10.1016/s0303-7207(03)00008-x] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Protein tyrosine phosphatases are important regulators of insulin signal transduction. Our studies have shown that in insulin resistant and diabetic ob/ob and db/db mice, reducing the levels of protein tyrosine phosphatase 1B (PTP1B) protein by treatment with a PTP1B antisense oligonucleotide resulted in improved insulin sensitivity and normalized plasma glucose levels. The mechanism by which PTP1B inhibition improves insulin sensitivity is not fully understood. We have used microarray analysis to compare gene expression changes in adipose tissue, liver and muscle of PTP1B antisense-treated ob/ob mice. Our results show that treatment with PTP1B antisense resulted in the downregulation of genes involved in lipogenesis in both fat and liver, and a downregulation of genes involved in adipocyte differentiation in fat, suggesting that PTP1B antisense acts through a different mechanism than thiazolidinedione (TZD) treatment. In summary, microarray results suggest that reduction of PTP1B may alleviate hyperglycemia and enhance insulin sensitivity by a different mechanism than TZD treatment.
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Affiliation(s)
- Jeffrey F Waring
- Abbott Laboratories, 100 Abbott Park Road, Abbott Park, IL 60064-6123, USA.
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468
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Pellmé F, Smith U, Funahashi T, Matsuzawa Y, Brekke H, Wiklund O, Taskinen MR, Jansson PA. Circulating adiponectin levels are reduced in nonobese but insulin-resistant first-degree relatives of type 2 diabetic patients. Diabetes 2003; 52:1182-6. [PMID: 12716750 DOI: 10.2337/diabetes.52.5.1182] [Citation(s) in RCA: 104] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Adiponectin, one of the most abundant gene transcript proteins in human fat cells, has been shown to improve insulin action and is also suggested to exert antiatherogenic effects. We measured circulating adiponectin levels and risk factors for atherosclerosis in 45 healthy first-degree relatives of type 2 diabetic subjects (FDR) as well as 40 healthy control subjects (CON) without a known family history of diabetes. Insulin sensitivity (S(i)) was studied with the minimal model, and measurements of adiponectin, metabolic variables, inflammatory markers, and endothelial injury markers, as well as lipoprotein concentrations, were performed. FDR were insulin resistant (3.3 +/- 2.4 vs. 4.5 +/- 2.6 x 10(-4) x min(-1) per microU/ml [mean +/- SD], P < 0.01), and their circulating plasma adiponectin levels (6.6 +/- 1.8 vs. 8.1 +/- 3.0 microg/ml, P < 0.03) were decreased. After adjustments for age in FDR, adiponectin levels were negatively correlated with fasting proinsulin (r -0.64, P < 0.001), plasminogen activator inhibitor (PAI)-1 activity (r -0.56, P < 0.001), fasting insulin (r -0.55, P < 0.001), and acute insulin response (r -0.40, P < 0.05); they were positively related to HDL cholesterol (r 0.48, P < 0.01) and S(i) (r 0.41, P < 0.01). Furthermore, when adjusted for age, waist, and S(i), adiponectin was associated with HDL cholesterol and proinsulin, which explained 51% of the variation in adiponectin in multiple regression analyses in that group. In conclusion, circulating plasma adiponectin levels were decreased in nonobese but insulin-resistant FDR and, in addition, related to several facets of the insulin resistance syndrome (IRS). Thus, hypoadiponectinemia may be an important component of the association between cardiovascular disease and IRS.
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Affiliation(s)
- F Pellmé
- The Lundberg Laboratory for Diabetes Research, Sahlgrenska Academy at Göteborg University, Sahlgrenska University Hospital, S-413 45 Göteborg, Sweden
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469
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Wang YX, Lee CH, Tiep S, Yu RT, Ham J, Kang H, Evans RM. Peroxisome-proliferator-activated receptor delta activates fat metabolism to prevent obesity. Cell 2003; 113:159-70. [PMID: 12705865 DOI: 10.1016/s0092-8674(03)00269-1] [Citation(s) in RCA: 1046] [Impact Index Per Article: 49.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
In contrast to the well-established roles of PPARgamma and PPARalpha in lipid metabolism, little is known for PPARdelta in this process. We show here that targeted activation of PPARdelta in adipose tissue specifically induces expression of genes required for fatty acid oxidation and energy dissipation, which in turn leads to improved lipid profiles and reduced adiposity. Importantly, these animals are completely resistant to both high-fat diet-induced and genetically predisposed (Lepr(db/db)) obesity. As predicted, acute treatment of Lepr(db/db) mice with a PPARdelta agonist depletes lipid accumulation. In parallel, PPARdelta-deficient mice challenged with high-fat diet show reduced energy uncoupling and are prone to obesity. In vitro, activation of PPARdelta in adipocytes and skeletal muscle cells promotes fatty acid oxidation and utilization. Our findings suggest that PPARdelta serves as a widespread regulator of fat burning and identify PPARdelta as a potential target in treatment of obesity and its associated disorders.
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MESH Headings
- Adipose Tissue/metabolism
- Adipose Tissue, Brown/metabolism
- Animals
- Body Weight/genetics
- Dietary Fats/pharmacology
- Energy Metabolism/genetics
- Fatty Acids/metabolism
- Food, Formulated
- Genetic Vectors
- Lipid Metabolism
- Mice
- Mice, Knockout
- Mice, Transgenic
- Obesity/genetics
- Obesity/metabolism
- Obesity/physiopathology
- Receptors, Cell Surface/deficiency
- Receptors, Cell Surface/genetics
- Receptors, Cytoplasmic and Nuclear/agonists
- Receptors, Cytoplasmic and Nuclear/drug effects
- Receptors, Cytoplasmic and Nuclear/metabolism
- Receptors, Leptin
- Recombinant Fusion Proteins
- Thiazoles/pharmacology
- Transcription Factors/agonists
- Transcription Factors/drug effects
- Transcription Factors/metabolism
- Transgenes/genetics
- Triglycerides/metabolism
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Affiliation(s)
- Yong-Xu Wang
- Gene Expression Laboratory, The Salk Institute, 10010 North Torrey Pines Road, La Jolla, CA 92037, USA
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470
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Berger JP, Petro AE, Macnaul KL, Kelly LJ, Zhang BB, Richards K, Elbrecht A, Johnson BA, Zhou G, Doebber TW, Biswas C, Parikh M, Sharma N, Tanen MR, Thompson GM, Ventre J, Adams AD, Mosley R, Surwit RS, Moller DE. Distinct properties and advantages of a novel peroxisome proliferator-activated protein [gamma] selective modulator. Mol Endocrinol 2003; 17:662-76. [PMID: 12554792 DOI: 10.1210/me.2002-0217] [Citation(s) in RCA: 273] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Antidiabetic thiazolidinediones (TZDs) and non-TZD compounds have been shown to serve as agonists of the peroxisome proliferator-activated receptor gamma (PPARgamma). Here, we report the identification and characterization of a novel non-TZD selective PPARgamma modulator (nTZDpa). nTZDpa bound potently to PPARgamma with high selectivity vs. PPARalpha or PPARdelta. In cell-based assays for transcriptional activation, nTZDpa served as a selective, potent PPARgamma partial agonist and was able to antagonize the activity of PPARgamma full agonists. nTZDpa also displayed partial agonist effects when its ability to promote adipogenesis in 3T3-L1 cells was evaluated. Assessment of protein conformation using protease protection or solution nuclear magnetic resonance spectroscopy methods showed that nTZDpa produced altered PPARgamma conformational stability vs. full agonists, thereby establishing a physical basis for its observed partial agonism. DNA microarray analysis of RNA from 3T3-L1 adipocytes treated with nTZDpa or several structurally diverse PPARgamma full agonists demonstrated qualitative differences in the affected gene expression profile for nTZDpa. Chronic treatment of fat-fed, C57BL/6J mice with nTZDpa or a TZD full agonist ameliorated hyperglycemia and hyperinsulinemia. However, unlike the TZD, nTZDpa caused reductions in weight gain and adipose depot size. Feed efficiency was also substantially diminished. Unlike TZDs, nTZDpa did not cause cardiac hypertrophy in mice. When a panel of PPARgamma target genes was examined in white adipose tissue, nTZDpa produced a different in vivo expression pattern vs. the full agonist. These findings establish that novel selective PPARgamma modulators can produce altered receptor conformational stability leading to distinctive gene expression profiles, reduced adipogenic cellular effects, and potentially improved in vivo biological responses. Such compounds may lead to preferred therapies for diabetes, obesity, or metabolic syndrome.
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Affiliation(s)
- Joel P Berger
- RY80N-C31, Merck Research Laboratories, 126 East Lincoln Avenue, Rahway, New Jersey 07065, USA.
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471
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Ye JM, Iglesias MA, Watson DG, Ellis B, Wood L, Jensen PB, Sørensen RV, Larsen PJ, Cooney GJ, Wassermann K, Kraegen EW. PPARalpha /gamma ragaglitazar eliminates fatty liver and enhances insulin action in fat-fed rats in the absence of hepatomegaly. Am J Physiol Endocrinol Metab 2003; 284:E531-40. [PMID: 12556350 DOI: 10.1152/ajpendo.00299.2002] [Citation(s) in RCA: 113] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Peroxisome proliferator-activated receptor (PPAR)alpha and PPARgamma agonists lower lipid accumulation in muscle and liver by different mechanisms. We investigated whether benefits could be achieved on insulin sensitivity and lipid metabolism by the dual PPARalpha/gamma agonist ragaglitazar in high fat-fed rats. Ragaglitazar completely eliminated high-fat feeding-induced liver triglyceride accumulation and visceral adiposity, like the PPARalpha agonist Wy-14643 but without causing hepatomegaly. In contrast, the PPARgamma agonist rosiglitazone only slightly lessened liver triglyceride without affecting visceral adiposity. Compared with rosiglitazone or Wy-14643, ragaglitazar showed a much greater effect (79%, P < 0.05) to enhance insulin's suppression of hepatic glucose output. Whereas all three PPAR agonists lowered plasma triglyceride levels and lessened muscle long-chain acyl-CoAs, ragaglitazar and rosiglitazone had greater insulin-sensitizing action in muscle than Wy-14643, associated with a threefold increase in plasma adiponectin levels. There was a significant correlation of lipid content and insulin action in liver and particularly muscle with adiponectin levels (P < 0.01). We conclude that the PPARalpha/gamma agonist ragaglitazar has a therapeutic potential for insulin-resistant states as a PPARgamma ligand, with possible involvement of adiponectin. Additionally, it can counteract fatty liver, hepatic insulin resistance, and visceral adiposity generally associated with PPARalpha activation, but without hepatomegaly.
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Affiliation(s)
- Ji-Ming Ye
- Diabetes and Obesity Program, Garvan Institute of Medical Research, Sydney, New South Wales 2010, Australia.
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472
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Park Y, Freedman BD, Lee EJ, Park S, Jameson JL. A dominant negative PPARgamma mutant shows altered cofactor recruitment and inhibits adipogenesis in 3T3-L1 cells. Diabetologia 2003; 46:365-77. [PMID: 12687335 DOI: 10.1007/s00125-003-1037-4] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/09/2002] [Revised: 11/12/2002] [Indexed: 10/20/2022]
Abstract
AIMS/HYPOTHESIS PPARgamma, a member of the nuclear hormone receptor family of transcription factors, plays a key role in adipocyte differentiation and insulin sensitivity. The aim of this study was to identify a potential dominant negative murine PPARgamma mutant and to characterize the in vitro functional properties of this mutant. METHODS In vitro transient transfections and mammalian two-hybrid assays in TSA201 cells were used to characterize the transcriptional activity of the L466A mutant and to study the molecular interaction of transcriptional cofactors with the L466A mutant in an attempt to elucidate the mechanism of its dominant negative activity. Adenoviral constructs expressing PPARgamma wild-type (AdWT) or the L466A mutant (AdL466A) were infected into the murine 3T3-L1 cell line to study the mutant's effect on adipogenesis. RESULTS The L466A mutant alone is transcriptionally defective. However, it retains DNA binding and inhibits the ligand-dependent and -independent activity of the wild-type receptor, consistent with dominant negative properties. In mammalian two-hybrid studies, the L466A mutant does not bind nuclear receptor coactivators. However, it more avidly recruits corepressors due to enhanced binding to the corepressor ID1 domain, leading to pronounced transcriptional repression. The AdL466A mutant inhibits adipogenesis induced by either a differentiation cocktail or by thiazolidinedione ligand. AdL466A infection also blocked the upregulation of the adipocyte marker genes aP2 and adipsin. CONCLUSION We conclude that the L466A PPARgamma mutant possesses potent dominant negative activity based on preferential corepressor recruitment and it inhibits adipogenesis and the expression of adipocyte-specific genes.
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Affiliation(s)
- Y Park
- Division of Endocrinology, Metabolism and Molecular Medicine, Northwestern University Medical School, Chicago, USA
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473
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Larsen TM, Toubro S, Astrup A. PPARgamma agonists in the treatment of type II diabetes: is increased fatness commensurate with long-term efficacy? Int J Obes (Lond) 2003; 27:147-61. [PMID: 12586994 DOI: 10.1038/sj.ijo.802223] [Citation(s) in RCA: 204] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
The nuclear hormone receptor peroxisome proliferator-activated receptor gamma (PPARgamma) is a member of the PPAR family. The endogenous activators of all members of the PPAR family are a variety of fatty acids, which suggests that the PPARs are highly involved in lipid metabolism. In the present paper, the current understanding of the involvement of PPARgamma in adipocyte proliferation and adipose tissue formation is extensively reviewed, and it is stressed that PPARgamma seems to be a major regulator in the differentiation of adipocytes. Thiazoledinediones (TZDs) are a group of PPARgamma-agonists used in the treatment of type 2 diabetes (T2D) since 1997. They are characterized by their ability to decrease insulin resistance, and have been suggested to slow down the progression of insulin resistance. Treatment with TZD requires several weeks of treatment to decrease plasma glucose levels, but in addition they markedly decrease plasma triglycerides and free fatty acids. A major drawback of treatment with TZD is body fat gain, but some evidence suggests that the fat is redistributed in a favourable direction, that is, from visceral to subcutaneous depots. However, the effect of long-term treatment on weight gain following TZD treatment is unknown, and it may be questioned whether the use of these 'adipogenic compounds' is appropriate, considering that excess body fat is almost a prerequisite for the development of type 2 diabetes.
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Affiliation(s)
- T M Larsen
- Research Department of Human Nutrition, The Royal Veterinary and Agricultural University, Copenhagen, Denmark.
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474
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Wilson-Fritch L, Burkart A, Bell G, Mendelson K, Leszyk J, Nicoloro S, Czech M, Corvera S. Mitochondrial biogenesis and remodeling during adipogenesis and in response to the insulin sensitizer rosiglitazone. Mol Cell Biol 2003; 23:1085-94. [PMID: 12529412 PMCID: PMC140688 DOI: 10.1128/mcb.23.3.1085-1094.2003] [Citation(s) in RCA: 359] [Impact Index Per Article: 17.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
White adipose tissue is an important endocrine organ involved in the control of whole-body metabolism, insulin sensitivity, and food intake. To better understand these functions, 3T3-L1 cell differentiation was studied by using combined proteomic and genomic strategies. The proteomics approach developed here exploits velocity gradient centrifugation as an alternative to isoelectric focusing for protein separation in the first dimension. A 20- to 30-fold increase in the concentration of numerous mitochondrial proteins was observed during adipogenesis, as determined by mass spectrometry and database correlation analysis. Light and electron microscopy confirmed a large increase in the number of mitochondrion profiles with differentiation. Furthermore, mRNA profiles obtained by using Affymetrix GeneChips revealed statistically significant increases in the expression of many nucleus-encoded mitochondrial genes during adipogenesis. Qualitative changes in mitochondrial composition also occur during adipose differentiation, as exemplified by increases in expression of proteins involved in fatty acid metabolism and of mitochondrial chaperones. Furthermore, the insulin sensitizer rosiglitazone caused striking changes in mitochondrial shape and expression of selective mitochondrial proteins. Thus, although mitochondrial biogenesis has classically been associated with brown adipocyte differentiation and thermogenesis, our results reveal that mitochondrial biogenesis and remodeling are inherent to adipose differentiation per se and are influenced by the actions of insulin sensitizers.
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Affiliation(s)
- Leanne Wilson-Fritch
- Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, Massachusetts 01615, USA
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475
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Laplante M, Sell H, MacNaul KL, Richard D, Berger JP, Deshaies Y. PPAR-gamma activation mediates adipose depot-specific effects on gene expression and lipoprotein lipase activity: mechanisms for modulation of postprandial lipemia and differential adipose accretion. Diabetes 2003; 52:291-9. [PMID: 12540599 DOI: 10.2337/diabetes.52.2.291] [Citation(s) in RCA: 130] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
This study sought to determine whether the adipose depot-specific (subcutaneous [SF] vs. visceral [VF]) action of peroxisome proliferator-activated receptor-gamma (PPAR-gamma) agonists on fat deposition extends to the expression of lipoprotein lipase (LPL) and other key adipose lipid metabolism genes, and whether changes in LPL impact triglyceridemia. Rats were fed a standard diet or an obesity-promoting diet for 3 weeks, with or without treatment with COOH, a nonthiazolidinedione PPAR-gamma agonist. Treatment effects were essentially similar in both dietary cohorts. COOH did not affect weight gain, but increased SF (inguinal) fat mass twofold and reduced VF (retroperitoneal) accretion by half. Corresponding depot-specific alterations were observed in mRNA levels of the glucocorticoid-activating enzyme 11beta-hydroxysteroid dehydrogenase 1 (11beta-HSD-1) and the thermogenic modulator uncoupling protein 1 (UCP-1). COOH increased brown adipose tissue (BAT) weight and LPL availability by five- to eightfold. In rats refed standard diet after a 24-h fast, COOH reduced the insulin excursion by half. The agonist increased SF LPL activity and mRNA levels, but had no effect on VF LPL. The two- to threefold postprandial increase in plasma triglycerides (TGs) was abrogated in COOH-treated rats, likely in part because of increased LPL in SF and BAT. Thus PPAR-gamma agonist treatment had a powerful, site-specific effect on adipose metabolism and lipid deposition, and greatly impacted the postprandial handling of TG-rich lipoproteins. These depot-specific effects may be mediated by differential regulation of key metabolic genes, including LPL, 11beta-HSD-1, and UCP-1.
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Affiliation(s)
- Mathieu Laplante
- Department of Anatomy and Physiology, Laval Hospital Research Center, School of Medicine, Laval University, Québec, Canada
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476
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Kajita K, Ishizuka T, Mune T, Miura A, Ishizawa M, Kanoh Y, Kawai Y, Natsume Y, Yasuda K. Dehydroepiandrosterone down-regulates the expression of peroxisome proliferator-activated receptor gamma in adipocytes. Endocrinology 2003; 144:253-9. [PMID: 12488352 DOI: 10.1210/en.2002-220039] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Dehydroepiandrosterone (DHEA) is expected to have a weight-reducing effect. In this study, we evaluated the effect of DHEA on genetically obese Otsuka Long Evans Fatty rats (OLETF) compared with Long-Evans Tokushima rats (LETO) as control. Feeding with 0.4% DHEA-containing food for 2 wk reduced the weight of sc, epididymal, and perirenal adipose tissue in association with decreased plasma leptin levels in OLETF. Adipose tissue from OLETF showed increased expression of peroxisome proliferator-activated receptor gamma (PPARgamma) protein, which was prevented by DHEA treatment. Further, we examined the effect of DHEA on PPARgamma in primary cultured adipocytes and monolayer adipocytes differentiated from rat preadipocytes. PPARgamma protein level was decreased in a time- and concentration-dependent manner, and DHEA significantly reduced mRNA levels of PPARgamma, adipocyte lipid-binding protein, and sterol regulatory element-binding protein, but not CCAAT/enhancer binding protein alpha. DHEA-sulfate also reduced the PPARgamma protein, but dexamethasone, testosterone, or androstenedione did not alter its expression. In addition, treatment with DHEA for 5 d reduced the triglyceride content in monolayer adipocytes. These results suggest that DHEA down-regulates adiposity through the reduction of PPARgamma in adipocytes.
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Affiliation(s)
- Kazuo Kajita
- The Third Department of Internal Medicine, Gifu University School of Medicine, Tsukasa-machi 40, Gifu 500-8705, Japan
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477
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Wada K, Kamisaki Y. Role of PPAR.GAMMA. in the development of the central nervous system. Nihon Yakurigaku Zasshi 2003; 122:301-8. [PMID: 14501165 DOI: 10.1254/fpj.122.301] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Peroxisome proliferator-activated receptor gamma (PPARgamma) is a nuclear receptor that plays a central role in adipocyte differentiation and insulin sensitivity. Recently, a diversity of the action of PPARgamma on many other cell types or organs is indicated. We summarize here the possible role of PPARgamma in the development of the murine central nervous system. Expressions of PPARgamma in newborn or adult mouse brain are extremely low, but high in embryo or fetal mouse brain. Furthermore, we investigated the role of PPARgamma in proliferation or differentiation of neural stem cells (NSCs) isolated from murine embryonic brains, because NSCs are considered to be a major source of neurons in developmental brains. Administrations of PPARgamma-specific ligands on the NSCs from wild-type mice resulted in the stimulation of cell growth. On the other hand, administration of PPARgamma-antagonist showed the cell death and apoptosis of NSCs. These results may indicate that PPARgamma plays an important role during the early stage of the development of the central nervous system.
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Affiliation(s)
- Koichiro Wada
- Department of Pharmacology, Graduate School of Dentistry, Osaka University, Suita, Japan.
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478
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Eto K, Yamashita T, Matsui J, Terauchi Y, Noda M, Kadowaki T. Genetic manipulations of fatty acid metabolism in beta-cells are associated with dysregulated insulin secretion. Diabetes 2002; 51 Suppl 3:S414-20. [PMID: 12475784 DOI: 10.2337/diabetes.51.2007.s414] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Triacylglyceride (TG) accumulation in pancreatic beta-cells is associated with impaired insulin secretion, which is called lipotoxicity. To gain a better understanding of the pathophysiology of lipotoxicity, we generated three models of dysregulated fatty acid metabolism in beta-cells. The overexpression of sterol regulatory element binding protein-1c induced lipogenic genes and TG accumulation. Under these conditions, we observed a decrease in glucose oxidation and upregulation of uncoupling protein-2, which might be causally related to the decreased glucose-stimulated insulin secretion. The overexpression of AMP-activated protein kinase was accompanied by decreased lipogenesis, increased fatty acid oxidation, and decreased glucose oxidation; insulin secretions to glucose and depolarization stimuli were decreased, probably because of the decrease in glucose oxidation and cellular insulin content. It was notable that the secretory response to palmitate was blunted, which would suggest a role of the fatty acid synthesis pathway, but not its oxidative pathway in palmitate-stimulated insulin secretion. Finally, we studied islets of PPAR-gamma(+/-) mice that had increased insulin sensitivity and low TG content in white adipose tissue, skeletal muscle, and liver. On a high-fat diet, glucose-stimulated insulin secretion was decreased in association with increased TG content in the islets, which might be mediated through the elevated serum free fatty acid levels and their passive transport into beta-cells. These results revealed some aspects about the mechanisms by which alterations of fatty acid metabolism affect beta-cell functions.
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Affiliation(s)
- Kazuhiro Eto
- Department of Metabolic Diseases, Graduate School of Medicine, University of Tokyo, Tokyo, Japan
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479
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Prpic V, Watson PM, Frampton IC, Sabol MA, Jezek GE, Gettys TW. Adaptive changes in adipocyte gene expression differ in AKR/J and SWR/J mice during diet-induced obesity. J Nutr 2002; 132:3325-32. [PMID: 12421846 DOI: 10.1093/jn/132.11.3325] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Obesity-prone (AKR/J) and obesity-resistant (SWR/J) mice were weaned onto low (LF) or high fat (HF) diets to identify adaptive changes in adipocyte gene expression that are associated with differences between the strains in fat deposition. Food consumption was monitored at weekly intervals and all mice were evaluated after consuming their respective diets for 4 wk for analysis of mRNA levels of selected metabolic genes. Despite similar food consumption, body weight and fat deposition were significantly greater in AKR/J than in SWR/J mice, and this difference was greatly accentuated by the HF diet. The HF diet produced distinct differences between strains in gene expression patterns among fat depots. In AKR/J mice, UCP1 mRNA was decreased 10-fold in interscapular brown adipose tissue (BAT) and four- to fivefold in retroperitoneal and inguinal white adipose tissue (WAT). The HF diet also decreased PGC-1 and beta(3)-adrenergic receptor mRNA by two- and ninefold in BAT from AKR/J mice. In contrast, the HF diet either increased uncoupling protein (UCP)1 in BAT or had no effect on expression of these genes in adipose tissues from SWR/J mice. UCP2 mRNA was fourfold higher in WAT from AKR/J compared with SWR/J mice and increased by an additional twofold in WAT from AKR/J mice fed the HF diet. UCP2 was unaffected by diet in SWR/J mice. These studies show that the diet-induced obesity of AKR/J mice is characterized by increased metabolic efficiency and is associated with changes in adipocyte gene expression that limit the adaptive thermogenic response to increased energy density.
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Affiliation(s)
- Veronica Prpic
- Pennington Biomedical Research Center, Baton Rouge, LA, USA
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480
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Abstract
Obesity is a recognized risk factor for cardiovascular disease. Because the prevalence of obesity is rising in industrialized as well as developing nations, it is important to understand the mechanisms by which obesity targets the vascular system. A metabolic syndrome of insulin resistance is provoked by obesity, and this results in the dysregulation of a number of adipocyte-derived factors, which favors atherosclerosis. This review focuses on how products of the adipocyte, including free fatty acids and "adipo"-cytokines, may mediate the effect of obesity on insulin resistance and atherosclerosis.
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Affiliation(s)
- Alexander Sorisky
- Department of Medicine, University of Ottawa, Ottawa Health Research Institute, Ottawa Hospital, Ottawa, Ontario, Canada.
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481
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Sesti G. Searching for type 2 diabetes genes: prospects in pharmacotherapy. THE PHARMACOGENOMICS JOURNAL 2002; 2:25-9. [PMID: 11990377 DOI: 10.1038/sj.tpj.6500078] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Affiliation(s)
- G Sesti
- Department of Experimental and Clinical Medicine, University of Catanzaro-Magna Graecia, Catanzaro, Italy.
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482
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Vaccaro O, Mancini FP, Ruffa G, Sabatino L, Iovine C, Masulli M, Colantuoni V, Riccardi G. Fasting plasma free fatty acid concentrations and Pro12Ala polymorphism of the peroxisome proliferator-activated receptor (PPAR) gamma2 gene in healthy individuals. Clin Endocrinol (Oxf) 2002; 57:481-6. [PMID: 12354130 DOI: 10.1046/j.1365-2265.2002.01618.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
BACKGROUND The Pro12Ala polymorphism of the peroxisome proliferator-activated receptor (PPAR) gamma gene has been associated in some, but not all, studies with lower body mass index (BMI) and improved insulin sensitivity; how an altered transcriptional activity of PPARgamma2 could influence insulin sensitivity is currently unclear. The free fatty acids (FFAs) released from adipose tissue triglycerides via lipolysis are key mediators of impaired insulin sensitivity; however, no study has described the relationship of the Pro12Ala mutation with circulating levels of FFAs under physiological conditions. OBJECTIVE To investigate in a population-based sample of Caucasians the relation of the Pro12Ala polymorphism with plasma concentrations of FFAs and other markers of lipid and glucose metabolism described as components of the insulin resistance syndrome. SUBJECTS Four hundred and thirty-eight nondiabetic employees of the Italian Telephone Company, aged 35-65 years, randomly selected from a total population of 3900 participants in a company-sponsored health screening. MEASUREMENTS The Pro12Ala polymorphism of the PPARgamma was studied together with plasma FFAs, insulin, glucose, triglycerides, high density lipoprotein (HDL) cholesterol, blood pressure and anthropometry. The Homeostatic Model Assessment (HOMA) index was calculated as a measure of insulin resistance. RESULTS Carriers and noncarriers of the Pro12Ala polymorphism showed very similar circulating levels of FFA (0.46 +/- 0.2 vs. 0.47 +/- 0.2, NS); plasma glucose, triglycerides, HDL cholesterol and blood pressure were also similar in the two groups with or without the polymorphism. To allow for the possible confounding effect of obesity, a separate analysis was conducted in overweight (BMI > or = 25 kg/m(2)) and normal-weight people (BMI < 25 kg/m(2)). Circulating plasma FFA concentrations, as well as triglycerides, blood pressure and HOMA, were significantly higher in overweight than normal-weight, as expected, but no significant differences were detected between carriers and noncarriers of the Pro12Ala polymorphism within each BMI group (0.49 +/- 0.2 vs. 0.48 +/- 0.2, NS, and 0.44 +/- 0.2 vs. 0.47 +/- 0.2, NS, in overweight and normal-weight, respectively). The Pro12Ala polymorphism was also analysed across increasing quartiles of FFA concentrations and no relationship was observed between the frequency of the polymorphism and FFA values (overall chi2 = 0.48, NS). CONCLUSION This study does not show any relationship between the Pro12Ala polymorphism of the PPARgamma gene and fasting FFAs in the general population. The possibility of a different handling of FFAs under different conditions (i.e. postprandial) cannot be excluded and remains to be explored.
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Affiliation(s)
- O Vaccaro
- Department of Clinical and Experimental Medicine, II Policlinico, Medical School, Federico II University, Via S Pansini 5, 80131 Naples, Italy.
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483
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Abstract
Normal metabolic balance is maintained by a complex homeostatic system involving multiple tissues and organs. Acquired or inherited defects in any part of this system can lead to metabolic disorders, such as diabetes and obesity. Adipose tissue, once thought to function primarily as a passive depot for the storage of excess lipid, is now understood to play a much more active role in metabolic regulation, secreting a variety of metabolic hormones and actively functioning to prevent deleterious lipid accumulation in other tissues. Here, we review new advances in our understanding of adipogenesis and fat-cell function, primarily from the perspective of the transcription factor peroxisome proliferator-activated receptor gamma.
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Affiliation(s)
- Heidi S Camp
- Department of Molecular Sciences and Technology, Pfizer Global Research and Development, 2800 Plymouth Rd, Ann Arbor, MI 48105, USA.
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484
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Martens FMAC, Visseren FLJ, Lemay J, de Koning EJP, Rabelink TJ. Metabolic and additional vascular effects of thiazolidinediones. Drugs 2002; 62:1463-80. [PMID: 12093315 DOI: 10.2165/00003495-200262100-00004] [Citation(s) in RCA: 209] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Several cardiovascular risk factors (dyslipidaemia, hypertension, glucose intolerance, hypercoagulability, obesity, hyperinsulinaemia and low-grade inflammation) cluster in the insulin resistance syndrome. Treatment of these individual risk factors reduces cardiovascular complications. However, targeting the underlying pathophysiological mechanisms of the insulin resistance syndrome is a more rational treatment strategy to further improve cardiovascular outcome. Our understanding of the so-called cardiovascular dysmetabolic syndrome has been improved by the discovery of nuclear peroxisome proliferator-activated receptors (PPARs). PPARs are ligand-activated transcription factors belonging to the nuclear receptor superfamily. As transcription factors, PPARs regulate the expression of numerous genes and affect glycaemic control, lipid metabolism, vascular tone and inflammation. Activation of the subtype PPAR-gamma improves insulin sensitivity. Expression of PPAR-gamma is present in several cell types involved in the process of atherosclerosis. Thus, modulation of PPAR-gamma activity is an interesting therapeutic approach to reduce cardiovascular events. Thiazolidinediones are PPAR-gamma agonists and constitute a new class of pharmacological agents for the treatment of type 2 (non-insulin-dependent) diabetes mellitus. Two such compounds are currently available for clinical use: rosiglitazone and pioglitazone. Thiazolidinediones improve insulin sensitivity and glycaemic control in patients with type 2 diabetes. In addition, improvement in endothelial function, a decrease in inflammatory conditions, a decrease in plasma levels of free fatty acids and lower blood pressure have been observed, which may have important beneficial effects on the vasculature. Several questions remain to be answered about PPAR-gamma agonists, particularly with respect to the role of PPAR-gamma in vascular pathophysiology. More needs to be known about the adverse effects of thiazolidinediones, such as hepatotoxicity, increased low-density lipoprotein cholesterol levels and increased oedema. The paradox of adipocyte differentiation with weight gain concurring with the insulin-sensitising effect of thiazolidinediones is not completely understood. The decrease in blood pressure induced by thiazolidinedione treatment seems incompatible with an increase in the plasma volume, and the discrepancy between the stimulation of the expression of CD36 and the antiatherogenic effects of the thiazolidinediones also needs further explanation. Long-term clinical trials of thiazolidinediones with cardiovascular endpoints are currently in progress. In conclusion, studying the effects of thiazolidinediones may shed more light on the mechanisms involved in the insulin resistance syndrome. Furthermore, thiazolidinediones could have specific, direct effects on processes involved in the development of vascular abnormalities.
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Affiliation(s)
- Fabrice M A C Martens
- Department of Internal Medicine, Section of Vascular Medicine and Diabetology, University Medical Center Utrecht, Room F.02.126, Heidelberglaan 100, PO Box 85500, 3508 GA Utrecht, The Netherlands.
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485
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Abstract
Peroxisome proliferator-activated receptor (PPAR)-gamma is a transcription factor with a key role in adipocyte differentiation. The Ala allele of the common Pro12Ala polymorphism in the isoform PPAR-gamma2 is associated with reduced risk for type 2 diabetes. The effect on the individual is weak, but because of a prevalence of >75% of the high-risk Pro allele, the population-attributable risk is enormous. The in vivo effects of the polymorphism are secondary to alterations in adipose tissue, where PPAR-gamma2 is predominantly expressed. Moderate reduction in transcriptional activity of PPAR-gamma as a result of the polymorphism modulates production and release of adipose-derived factors. Both decreased release of insulin-desensitizing free fatty acids, tumor necrosis factor-alpha, and resistin and increased release of the insulin-sensitizing hormone adiponectin result in secondary improvement of insulin sensitivity of glucose uptake and suppression of glucose production. The population effect of this polymorphism may be modulated by environmental or genetic factors such as obesity, ethnicity, ratio of unsaturated to saturated fatty acids, and genetic background. Once diabetes has developed, the protective effect of the Ala allele may be lost, since increased vascular complications and more pronounced beta-cell dysfunction have been reported. These observations, however, are currently unexplained. In conclusion, the Pro12Ala polymorphism in PPAR-gamma2 represents the first genetic variant with a broad impact on the risk of common type 2 diabetes. The precise understanding of its mechanism may lead to novel diagnostic, preventive, and therapeutic approaches for improving the management of type 2 diabetes.
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Affiliation(s)
- Michael Stumvoll
- University Hospital, Department of Endocrinology, Metabolism and Pathobiochemistry, Eberhard-Karls-Universität, Tübingen, Germany.
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486
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Rondinone CM, Trevillyan JM, Clampit J, Gum RJ, Berg C, Kroeger P, Frost L, Zinker BA, Reilly R, Ulrich R, Butler M, Monia BP, Jirousek MR, Waring JF. Protein tyrosine phosphatase 1B reduction regulates adiposity and expression of genes involved in lipogenesis. Diabetes 2002; 51:2405-11. [PMID: 12145151 DOI: 10.2337/diabetes.51.8.2405] [Citation(s) in RCA: 130] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Protein tyrosine phosphatase 1B (PTP1B) has been implicated as a negative regulator of insulin action. Overexpression of PTP1B protein has been observed in insulin-resistant states associated with obesity. Mice lacking a functional PTP1B gene exhibit increased insulin sensitivity and are resistant to weight gain. To investigate the role of PTP1B in adipose tissue from obese animals, hyperglycemic obese (ob/ob) mice were treated with PTP1B antisense oligonucleotide (ISIS-113715). A significant reduction in adiposity correlated with a decrease of PTP1B protein levels in fat. Antisense treatment also influenced the triglyceride content in adipocytes, correlating with a downregulation of genes encoding proteins involved in lipogenesis, such as sterol regulatory element-binding protein 1 and their downstream targets spot14 and fatty acid synthase, as well as other adipogenic genes, lipoprotein lipase, and peroxisome proliferator-activated receptor gamma. In addition, an increase in insulin receptor substrate-2 protein and a differential regulation of the phosphatidylinositol 3-kinase regulatory subunit (p85alpha) isoforms expression were found in fat from antisense-treated animals, although increased insulin sensitivity measured by protein kinase B phosphorylation was not observed. These results demonstrate that PTP1B antisense treatment can modulate fat storage and lipogenesis in adipose tissue and might implicate PTP1B in the enlargement of adipocyte energy stores and development of obesity.
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Affiliation(s)
- Cristina M Rondinone
- Metabolic Diseases Research, Global Pharmaceutical Research and Development, Abbott Laboratories, Abbott Park, Illinois 60064, USA.
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487
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Esterbauer H, Oberkofler H, Linnemayr V, Iglseder B, Hedegger M, Wolfsgruber P, Paulweber B, Fastner G, Krempler F, Patsch W. Peroxisome proliferator-activated receptor-gamma coactivator-1 gene locus: associations with obesity indices in middle-aged women. Diabetes 2002; 51:1281-6. [PMID: 11916956 DOI: 10.2337/diabetes.51.4.1281] [Citation(s) in RCA: 92] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Peroxisome proliferator-activated receptor-gamma coactivator-1 (PPARGC1) is a transcriptional coactivator that has been implicated in the regulation of genes involved in energy metabolism. We studied associations of two polymorphisms identified in PPARGC1 transcripts with obesity indices in 591 middle-aged men and 467 middle-aged women of a cross-sectional Austrian population. Because neither polymorphic site was likely to be a functional site, we analyzed sex-specific associations of two loci haplotype combinations with obesity indices. Significant associations with BMI (P = 0.006), waist (P = 0.01) and hip circumference (P = 0.03), and total body fat (P = 0.005) and borderline significant associations with abdominal visceral and subcutaneous fat were observed in women but not men. In women, plasma triglycerides, HDL cholesterol, and glucose significantly differed by haplotype combinations, but these associations were not maintained after statistical consideration of BMI. The haplotype combination of the double-variant allele with the double-wild-type allele was associated with the lowest obesity indices, whereas homozygosity for the double-variant allele was not discriminatory among haplotype combinations. These studies suggest functional differences of PPARGC1 haplotypes in human energy metabolism and support a role of PPARGC1 in obesity.
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488
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Yamauchi T, Oike Y, Kamon J, Waki H, Komeda K, Tsuchida A, Date Y, Li MX, Miki H, Akanuma Y, Nagai R, Kimura S, Saheki T, Nakazato M, Naitoh T, Yamamura K, Kadowaki T. Increased insulin sensitivity despite lipodystrophy in Crebbp heterozygous mice. Nat Genet 2002; 30:221-6. [PMID: 11818964 DOI: 10.1038/ng829] [Citation(s) in RCA: 127] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The CBP protein (cAMP response element binding protein (CREB) binding protein) is a co-activator for several transcription factors with a wide range of important biological functions, such as sterol regulatory element binding proteins (SREBPs), CCAAT/enhancer-binding proteins (C/EBPs), nuclear receptors (including peroxisome proliferator-activated receptors, PPARs), and signal transducers and activators of transcription (STATs). In contrast to these individual transcription factors, the biological roles of CBP are poorly understood. CBP enhances transcriptional activities via histone acetylation and the recruitment of additional co-activators such as SRC (steroid coactivator)-1 (ref. 9). To identify its physiological functions using a loss-of-function mutant, we analyzed CBP-deficient mice. As Crebbp null mice (Crebbp-/-) died during embryogenesis, we used Crebbp+/- mice. Unexpectedly, Crebbp+/- mice showed markedly reduced weight of white adipose tissue (WAT) but not of other tissues. Despite this lipodystrophy, Crebbp+/- mice showed increased insulin sensitivity and glucose tolerance and were completely protected from body weight gain induced by a high-fat (HF) diet. We observed increased leptin sensitivity and increased serum adiponectin levels in Crebbp+/- mice. These increased effects of insulin-sensitizing hormones secreted from WAT may explain, at least in part, the phenotypes of Crebbp+/- mice. This study demonstrates that CBP may function as a 'master-switch' between energy storage and expenditure.
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Affiliation(s)
- Toshimasa Yamauchi
- Department of Internal Medicine, Graduate School of Medicine, University of Tokyo, Tokyo 113-8655, Japan
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489
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Walczak R, Tontonoz P. PPARadigms and PPARadoxes: expanding roles for PPARγ in the control of lipid metabolism. J Lipid Res 2002. [DOI: 10.1016/s0022-2275(20)30159-0] [Citation(s) in RCA: 183] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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490
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Havel PJ. Control of energy homeostasis and insulin action by adipocyte hormones: leptin, acylation stimulating protein, and adiponectin. Curr Opin Lipidol 2002; 13:51-9. [PMID: 11790963 DOI: 10.1097/00041433-200202000-00008] [Citation(s) in RCA: 371] [Impact Index Per Article: 16.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Adipose tissue performs complex metabolic and endocrine functions. This review will focus on the recent literature on the biology and actions of three adipocyte hormones involved in the control of energy homeostasis and insulin action, leptin, acylation-stimulating protein, and adiponectin, and mechanisms regulating their production. Results from studies of individuals with absolute leptin deficiency (or receptor defects), and more recently partial leptin deficiency, reveal leptin's critical role in the normal regulation of appetite and body adiposity in humans. The primary biological role of leptin appears to be adaptation to low energy intake rather than a brake on overconsumption and obesity. Leptin production is mainly regulated by insulin-induced changes of adipocyte metabolism. Consumption of fat and fructose, which do not initiate insulin secretion, results in lower circulating leptin levels, a consequence which may lead to overeating and weight gain in individuals or populations consuming diets high in energy derived from these macronutrients. Acylation-stimulating protein acts as a paracrine signal to increase the efficiency of triacylglycerol synthesis in adipocytes, an action that results in more rapid postprandial lipid clearance. Genetic knockout of acylation-stimulating protein leads to reduced body fat, obesity resistance and improved insulin sensitivity in mice. The primary regulator of acylation-stimulating protein production appears to be circulating dietary lipid packaged as chylomicrons. Adiponectin increases insulin sensitivity, perhaps by increasing tissue fat oxidation resulting in reduced circulating fatty acid levels and reduced intramyocellular or liver triglyceride content. Adiponectin and leptin together normalize insulin action in severely insulin-resistant animals that have very low levels of adiponectin and leptin due to lipoatrophy. Leptin also improves insulin resistance and reduces hyperlipidemia in lipoatrophic humans. Adiponectin production is stimulated by agonists of peroxisome proliferator-activated receptor-gamma; an action may contribute to the insulin-sensitizing effects of this class of compounds. The production of all three hormones is influenced by nutritional status. These adipocyte hormones, the pathways controlling their production, and their receptors represent promising targets for managing obesity, hyperlipidemia, and insulin resistance.
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Affiliation(s)
- Peter J Havel
- Department of Nutrition, University of California, Davis, California 95616, USA.
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491
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Yamauchi T, Waki H, Kamon J, Murakami K, Motojima K, Komeda K, Miki H, Kubota N, Terauchi Y, Tsuchida A, Tsuboyama-Kasaoka N, Yamauchi N, Ide T, Hori W, Kato S, Fukayama M, Akanuma Y, Ezaki O, Itai A, Nagai R, Kimura S, Tobe K, Kagechika H, Shudo K, Kadowaki T. Inhibition of RXR and PPARgamma ameliorates diet-induced obesity and type 2 diabetes. J Clin Invest 2001; 108:1001-13. [PMID: 11581301 PMCID: PMC200951 DOI: 10.1172/jci12864] [Citation(s) in RCA: 214] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2001] [Accepted: 08/21/2001] [Indexed: 01/01/2023] Open
Abstract
PPARgamma is a ligand-activated transcription factor and functions as a heterodimer with a retinoid X receptor (RXR). Supraphysiological activation of PPARgamma by thiazolidinediones can reduce insulin resistance and hyperglycemia in type 2 diabetes, but these drugs can also cause weight gain. Quite unexpectedly, a moderate reduction of PPARgamma activity observed in heterozygous PPARgamma-deficient mice or the Pro12Ala polymorphism in human PPARgamma, has been shown to prevent insulin resistance and obesity induced by a high-fat diet. In this study, we investigated whether functional antagonism toward PPARgamma/RXR could be used to treat obesity and type 2 diabetes. We show herein that an RXR antagonist and a PPARgamma antagonist decrease triglyceride (TG) content in white adipose tissue, skeletal muscle, and liver. These inhibitors potentiated leptin's effects and increased fatty acid combustion and energy dissipation, thereby ameliorating HF diet-induced obesity and insulin resistance. Paradoxically, treatment of heterozygous PPARgamma-deficient mice with an RXR antagonist or a PPARgamma antagonist depletes white adipose tissue and markedly decreases leptin levels and energy dissipation, which increases TG content in skeletal muscle and the liver, thereby leading to the re-emergence of insulin resistance. Our data suggested that appropriate functional antagonism of PPARgamma/RXR may be a logical approach to protection against obesity and related diseases such as type 2 diabetes.
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MESH Headings
- 3T3 Cells
- Adipose Tissue/metabolism
- Animals
- Benzhydryl Compounds
- Benzoates/metabolism
- Benzoates/pharmacology
- Biphenyl Compounds/metabolism
- Biphenyl Compounds/pharmacology
- Diabetes Mellitus, Type 2/metabolism
- Epoxy Compounds/metabolism
- Epoxy Compounds/pharmacology
- Fatty Acids/metabolism
- Hyperglycemia/etiology
- Hyperglycemia/metabolism
- Hypoglycemic Agents/metabolism
- Hypoglycemic Agents/pharmacology
- Insulin Resistance
- Leptin/metabolism
- Mice
- Mice, Knockout
- Nicotinic Acids/metabolism
- Nicotinic Acids/pharmacology
- Obesity/metabolism
- Receptors, Adrenergic, beta-3/metabolism
- Receptors, Cytoplasmic and Nuclear/agonists
- Receptors, Cytoplasmic and Nuclear/antagonists & inhibitors
- Receptors, Cytoplasmic and Nuclear/metabolism
- Receptors, Retinoic Acid/agonists
- Receptors, Retinoic Acid/antagonists & inhibitors
- Receptors, Retinoic Acid/metabolism
- Retinoid X Receptors
- Rosiglitazone
- Tetrahydronaphthalenes/metabolism
- Tetrahydronaphthalenes/pharmacology
- Thiazoles/metabolism
- Thiazoles/pharmacology
- Thiazolidinediones
- Transcription Factors/agonists
- Transcription Factors/antagonists & inhibitors
- Transcription Factors/metabolism
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Affiliation(s)
- T Yamauchi
- Department of Internal Medicine, Graduate School of Medicine, University of Tokyo, Tokyo, Japan
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