Obesity: Shimomura I

Maeda N, Funahashi T, Shimomura I. · Graduate School of Medicine, Osaka University, Osaka, Japan. · Nat Clin Pract Endocrinol Metab. · Pubmed #18852723 No free full text.

Abstract: The discovery of aquaporins, which are plasma-membrane-associated water channels, has greatly influenced the medical sciences. So far, thirteen aquaporins have been identified in humans. Among them, types 3, 7, 9, and 10 are subcategorized as aquaglyceroporins, which enable the transport of glycerol as well as water. Although aquaporins have a proven crucial role in water homeostasis, the physiological and pathological importance of aquaporins as glycerol channels is not fully understood. Adipocytes are a major source of glycerol, one of the substrates for hepatic gluconeogenesis. Aquaporin subtypes 7 and 9 (AQP7 and AQP9) are the glycerol channels in adipocytes and hepatocytes, respectively. The coordinated regulation of these channels leads to the optimum balance between release of glycerol by adipocytes and its uptake by the liver. In addition, studies of AQP7 and AQP9 knockout or knockdown mice have clearly demonstrated in vivo the pathophysiological relevance of glycerol channels through effects on glycerol metabolism. Associations between various AQP7 gene mutations and obesity in humans have also been shown. Thus, further research of these two aquaporins might uncover novel targets for therapy.

Nishida M, Funahashi T, Shimomura I. · Health Care Center, Osaka University 1-17 Machikaneyama, Toyonaka, Osaka, 560-0043, Japan. · Med Mol Morphol. · Pubmed #17572841 No free full text.

Abstract: Adipose tissue, which classically has been considered as an energy-storing organ, is now viewed as a massive source of bioactive substances such as leptin, tumor necrosis factor (TNF)-alpha, and adiponectin. Adiponectin was discovered to be the most abundant adipose-specific transcript. Its function had been unclear, but epidemiological and clinical studies have demonstrated that serum levels of adiponectin are inversely associated with body weight, especially abdominal visceral fat accumulation. In addition, adiponectin was inversely related to cardiovascular risk factors, such as insulin resistance, blood pressure, and low-density lipoprotein (LDL) cholesterol and triglyceride levels, and was positively related to high-density lipoprotein (HDL) cholesterol levels. Moreover, low adiponectin concentration is associated with a high incidence of cardiovascular disease (CVD), diabetes, some kinds of cancer, and other various diseases. These associations suggest the clinical significance of adiponectin, and a number of investigations are now being conducted to clarify the biological functions of adiponectin. Recent studies have revealed that adiponectin exhibits antiinflammatory, antiatherogenic, and antidiabetic properties. In addition, adiponectin has been thought to be a key molecule in "metabolic syndrome," which is an epidemiological target for preventing cardiovascular disease. Various functions of adiponectin may possibly serve to prevent and treat obesity-related diseases and CVD. Furthermore, enhancement of adiponectin secretion or action may become a promising therapeutic target.

Oshima K, Shimomura I, Iwahashi H. · Osaka University, Graduate School of Medicine, Department of Medicine and Pathophysiology. · Clin Calcium. · Pubmed #16883042 No free full text.

Abstract: The number of obesity and diabetes mellitus in the world has been rapidly increasing in population. Current lifestyle initiates obesity, especially visceral fat accumulation, and leads to the onset of metabolic syndrome, such as cardiovascular events, hyperlipidemia and diabetes mellitus, based on insulin resistance. Several studies of adipocyte function have revealed that adipose tissue is not merely an energy-storing organ but it secretes a variety of biologically active molecules, conceptualized as "adipocytokines", including tumor necrosis factor-alpha, estrogen, leptin and adiponectin and that abnormal secretion of these adipocytokines causes metabolic syndrome. Adipocytes exist not only in the visceral and subcutaneous tissue but also in the bone marrow. Therefore, it is important to know their effects not only on glucose and lipid metabolism but also on bone metabolism. This report aims to review some of the effects of visceral fat accumulation by diabetes mellitus on bone metabolism.

Matsuda M, Shimomura I. · Department of Medicine and Pathophysiology, Graduate School of Frontier Bioscience and Graduate School of Medicine, Osaka University. · Nippon Rinsho. · Pubmed #15206145 No free full text.

Abstract: Recent progress in adipocyte-biology shows that adipocytes are not merely fat-storing cells but that they secrete a variety of hormones, cytekines, growth factors and other bioactive substabces, conceptualized as adipocytokines. These include plasminogen activator inhibitor 1(PAI-1), tumor necrosis factor(TNF-alpha), leptin and adiponectin. Dysregulated productions of these adipocytekines participate in the pathogenesis of obesity-associated metabolic syndrome such as insulin resistance, type 2 diabetes, hyperlipidemia, and vascular diseases. Increased productions of PAI-1 and TNF-alpha from accumulated fat contribute to the formation of thrombosis and insulin resistance in obesity, respectively. Lack of leptin causes metabolic syndrome. Adiponectin exerts insulin-sensitizing and anti-atherogenic effects, hence decrease of plasma adiponectin is causative for insulin resistance and atherosclerosis in obesity.

Shimomura I. · Department of Medicine and Pathophysiology, Graduate School of Frontier Bioscience, Graduate School of Medicine, Osaka University, Suita 565-0871. · Rinsho Byori. · Pubmed #14679787 No free full text.

Abstract: The adipose tissue produces and secretes many bioactive substances, which we conceptualized as Adipocytokines (Nature Medicine 1996). Adiponectin is a novel adipocytokine, which we identified by screening the adipose-specific genes from human fat. Adiponectin is a secreted protein, the concentration of which reaches as high as 5-15 micrograms/ml in human plasma. Adiponectin mRNA is expressed exclusively in adipose tissues. The adiponectin mRNAs and its plasma levels are reduced in obesity, type 2 diabetes and atherosclerosis. Hyperinsulinemic euglycemic clamp studies in humans and monkeys, and several recent studies from others revealed that adiponectin is an insulin-sensitizing hormone. Furthermore, adiponectin exhibited anti-atherogenic moieties, decreasing the attachment of monocytes to endothelial cells through inhibiting the expression levels of adhesion molecules. It reduced the lipid accumulation in macrophages through reducing the expression of scavenger receptor, and inhibited the cytokine-stimulated proliferation of smooth muscle cells. The genetic mutation of the adiponectin gene accompanying hypoadiponectinemia was strongly associated with the incidence of type 2 diabetes and atherosclerosis in Japanese subjects. Hypoadiponectinemia was the strongest predictor for the development of type 2 diabetes in humans. Adiponectin knockout mice exhibited diet-induced diabetes and severer atherosclerotic response by vascular injury. Adiponectin supplement reversed the insulin resistance syndrome including diabetes and atherosclerotic change in the knockout mice. We conclude that "Hypoadiponectinemia" stands upstream of the pathophysiology of metabolic syndrome, hence, can be a direct target of drug intervention to tackle life style-related disease rampant in developed countries.

Matsuzawa Y, Shimomura I, Kihara S, Funahashi T. · Department of Internal Medicine and Molecular Science, Graduate School of Medicine, Osaka University, Osaka, Japan. · Horm Res. · Pubmed #14671398 No free full text.

Abstract: To elucidate the biological characteristics of adipose tissue, we analyzed the gene expression profile of visceral and subcutaneous fat. Unexpectedly, adipose tissue, especially visceral fat, expressed a variety of genes for secretory proteins. About 30% of the genes expressed in visceral adipose tissue encoded secretory proteins and most were biologically active molecules, which we called adipocytokines. We found plasminogen activator inhibitor type 1 and heparin binding EGF-like growth factor. Production of these atherogenic adipocytokines was shown to increase with the accumulation of visceral fat, which may be one of the mechanisms of vascular disease in visceral obesity. We found a unique and novel collagen-like protein, adiponectin, encoded by the most abundantly expressed gene in adipose tissue, termed APM1 (adipose most abundant gene transcript-1). Plasma levels of adiponectin ranged from 0.3 to approximately 3 mg/dl but were decreased in patients with visceral obesity, type 2 diabetes and coronary artery disease (CAD). Screening for mutations in the adiponectin gene revealed that patients carrying a missense mutation showed markedly decreased plasma levels of adiponectin and had CAD. These data suggest that hypoadiponectinemia may be considered an important risk factor for CAD. Cell biology studies revealed that adiponectin has a potent inhibitory effect on the expression of adhesion molecules in endothelial cells and an inhibitory effect on the expression in macrophages. In order to confirm these antidiabetic and antiatherogenic functions of adiponectin, we developed adiponectin knockout mice. Adiponectin knockout mice showed severe insulin resistance and impaired glucose metabolism when fed a high-fat, high-sucrose diet. Knockout mice also developed intimal thickening in response to endothelial injury.

Matsuzawa Y, Funahashi T, Kihara S, Shimomura I. · Department of Internal Medicine and Molecular Science, Osaka University Graduate School, Sumitomo Hospital, Osaka, Japan. · Arterioscler Thromb Vasc Biol. · Pubmed #14551151 links to  free full text

Abstract: In this review article, the crucial roles of adipocytes in the development of so-called metabolic syndrome and vascular disease are reviewed, focusing on adipocyte-derived bioactive substances, adipocytokines. Recent progress in adipocyte biology shows that adipocytes are not merely energy-storing cells but that they secrete a variety of hormones cytokines, growth factors, and other bioactive substances. To search for novel adipocytokines by the large-scale random sequence analysis of expressed genes in adipocytes, we identified an adipose-specific collagen-like molecule, adiponectin. This novel adipocytokine has plural biofunctions, such as antidiabetic, antiatherosclerotic, and antiinflammatory functions. Adiponectin plasma levels decrease with the accumulation of visceral adipose tissue. In this review, we discuss the link of adiponectin to visceral adiposity, insulin resistance, and vascular diseases.

Funahashi T, Nakamura T, Shimomura I, Maeda K, Kuriyama H, Takahashi M, Arita Y, Kihara S, Matsuzawa Y. · The Second Department of Internal Medicine, Osaka University Medical School, Suita. · Intern Med. · Pubmed #10225688 links to  free full text

Abstract: Obesity which is defined as accumulation of excess body fat, is a major cause of atherosclerotic vascular disease in industrial countries. Recent advances in the biology of adipose tissue have revealed that adipose tissue is not simply an energy storage organ but it also secretes a variety of molecules which affect the metabolism of the whole body. Through a systematic search of active genes in adipose tissue, we found that adipose tissue, especially visceral fat expressed numerous genes for secretory proteins (about 30% of total genes analyzed). Among them, plasminogen activator-1 (PAI-1), which is a regulator of the fibrinolytic system, was overexpressed in the visceral fat in an animal model of obesity. Plasma levels of PAI-1 were closely correlated with visceral fat adiposity. Thus, PAI-1 secreted from visceral fat may play some role in thrombotic vascular disease in visceral obesity. Adiponectin, a novel adipose-specific gene product, which has a matrix-like structure, is abundantly present in the bloodstream. Dysregulated secretion of adiponectin may be related to vascular disease in obesity. Biologically active molecules secreted from adipose tissue (adipocytokines) may have important roles in the development of atherosclerotic disease in obesity.

Ryo M, Maeda K, Onda T, Katashima M, Okumiya A, Nishida M, Yamaguchi T, Funahashi T, Matsuzawa Y, Nakamura T, Shimomura I. · Department of Internal Medicine and Molecular Science, Graduate School of Medicine, Osaka University, 2-2 Yamadaoka, Suita, Osaka 565-0871, Japan. · Diabetes Care. · Pubmed #15677816 links to  free full text

This publication has no abstract.

Shimabukuro M, Higa N, Asahi T, Oshiro Y, Takasu N, Tagawa T, Ueda S, Shimomura I, Funahashi T, Matsuzawa Y. · Second Department of Internal Medicine, University of the Ryukyus, 903-0215 Okinawa, Japan. · J Clin Endocrinol Metab. · Pubmed #12843170 links to  free full text

Abstract: Vascular endothelial dysfunction has been demonstrated in overweight or obese patients, but the molecular basis for this link has not been clarified. We asked what the relationship was between adiponectin, an adipose-specific molecule, and endothelial function. Forearm blood flow (FBF) was measured during reactive hyperemia by using strain-gauge plethysmography in 76 Japanese subjects without a history of cardiovascular or cerebrovascular disease, diabetes mellitus, hepatic, or renal disease. The peak FBF and total reactive hyperemic flow [flow debt repayment (FDR)] during reactive hyperemia were correlated with waist circumference (r = -0.418 and -0.414, respectively) and body mass index (r = -0.597 and -0.626, respectively). After correcting for age, gender, and body mass index, the peak FBF was correlated with systolic blood pressure (r = -0.294; P = 0.010), free fatty acid (FFA) (r = -0.331; P = 0.004), and adiponectin in log 10 (r = 0.492; P < 0.001), and FDR was correlated with adiponectin in log 10 (r = 0.462; P = 0.001). In stepwise multiple regression analyses, predictive variables for peak FBF were adiponectin in log 10 (r = 0.468) and FFA (r = -0.292; r(2) = 0.487; P < 0.0001); and predictive variables for FDR were adiponectin in log 10 (r = 0.474) and FFA (r = -0.275; r(2) = 0.346, P < 0.0001). Endothelial function was impaired in proportion to the severity of obesity, and the level of severity was closely related to plasma adiponectin levels. Adiponectin may play a protective role against the atherosclerotic vascular change, and loss of effects enhances endothelial dysfunction, as in obese people.

Kobayashi H, Matsuda M, Fukuhara A, Komuro R, Shimomura I. · Dept. of Metabolic Medicine, Graduate School of Medicine, Osaka University, 2-2 Yamada-oka, Suita-shi, Osaka 565-0871, Japan. · Am J Physiol Endocrinol Metab. · Pubmed #19366877 No free full text.

Abstract: Oxidative stress plays an important role in obesity-related metabolic diseases. Glutathione peroxidase (GPX) is an antioxidant enzyme downregulated in adipose tissue of obese mice. However, the role of GPX in adipocytes remains elusive. The objective of this study was to clarify the pathophysiological changes in GPX activity and glutathione metabolism and their roles in the pathogenesis of insulin resistance in adipocytes. To achieve this goal, we measured cellular GPX activity, glutathione (GSH) contents, GSH/GSSG ratio, and mRNA expression of gamma-glutamylcysteine synthetase (gamma-GCS), a rate-limiting enzyme for de novo GSH synthesis, in adipose tissue of control and ob/ob mice and in 3T3-L1 adipocytes treated with insulin, H(2)O(2), free fatty acid (FFA), or TNFalpha. Furthermore, we investigated the effects of GPX inhibition with a specific GPX inhibitor or RNA interference against GPX, H(2)O(2), and reduced GSH on insulin signaling in 3T3-L1 adipocytes. ob/ob Mice showed not only a decrease in cellular activity of GPXs (GPX1, -4, and -7) but also an increase in gamma-GCS expression, resulting in increased GSH contents in adipose tissue. These alterations in glutathione metabolism were also observed during differentiation of 3T3-L1 cells and their exposure to insulin, FFA, or H(2)O(2). Inhibition of GPX activity, addition of GSH, and H(2)O(2) resulted in impaired insulin signaling in 3T3-L1 adipocytes. These results suggest that decreased GPX activity and increased gamma-GCS expression lead to overaccumulation of GSH, which might be involved in the pathogenesis of insulin resistance in obesity.

Tanabe A, Matsuda M, Fukuhara A, Miyata Y, Komuro R, Shimomura I, Tojo H. · Department of Metabolic Medicine, Osaka University Graduate School of Medicine, 2-2 Yamadaoka, Suita, Osaka 565-0871, Japan. · Biochem Biophys Res Commun. · Pubmed #19116132 No free full text.

Abstract: Obesity is associated with insulin resistance and a mild chronic inflammation in adipose tissues. Recent studies suggested that GM3 ganglioside mediates dysfunction in insulin signaling. However, it has not been determined the ganglioside profiling in adipose tissues of obese animals. Here, we for the first time examined semi-quantitative ganglioside profiles in the adipose tissues of high fat- and high sucrose-induced obese, diabetic C57BL/6J mice by TLC and HPLC/mass spectrometry. In control adipose tissues GM3 dominated with traces of GM1 and GD1a; obesity led to a dramatic increase in GM2, GM1, and GD1a with the GM3 content unchanged. Similar results were obtained in KK and KKAy mice. Adipocytes separated from stromal vascular cells including macrophages contained more of those gangliosides in KKAy mice than in KK mice. These results underscore those gangliosides in the pathophysiology of obesity-related diseases.

Okauchi Y, Iwahashi H, Okita K, Yuan M, Matsuda M, Tanaka T, Miyagawa J, Funahashi T, Horikawa Y, Shimomura I, Yamagata K. · Department of Metabolic Medicine, Graduate School of Medicine, Osaka University, Suita, Osaka, Japan. · Endocr J. · Pubmed #18614852 links to  free full text

Abstract: Peroxisome proliferator-activated receptor-gamma coactivator-1 alpha (PGC-1alpha) is a multifunctional transcriptional regulator for the pathways controlling mitochondrial biogenesis, oxidative metabolism, and glucose homeostasis. Genetic studies have suggested that Gly482Ser polymorphism of the PGC-1alpha gene is associated with a higher risk of type 2 diabetes, obesity, and hypertension. Adiponectin is an antidiabetic and antiatherogenic adipocytokine that is specifically produced by adipose tissue, and the transcription of the adiponectin gene is regulated by PPARgamma. In this study, we examined the effect of Gly482Ser polymorphism on the plasma adiponectin level in Japanese type 2 diabetics. The Gly482Ser genotype was associated with a lower plasma adiponectin level in type 2 diabetic men, but not in type 2 diabetic women. The impact of this variation on the adiponectin promoter was also assessed by a reporter gene assay, but there was no significant difference between activation by the wild type and Gly482Ser- PGC-1alpha proteins, indicating that this variation itself has no functional effect. Evaluation of the pattern of linkage disequilibrium revealed that the Gly482Ser polymorphism is located in the largest linkage disequilibrium block of the PGC-1alpha gene. Therefore the observed gender-specific association between PGC-1alpha and the plasma adiponectin level may reflect linkage disequilibrium of Gly482Ser polymorphism with other causative variations.

Araki H, Nishihara T, Matsuda M, Fukuhara A, Kihara S, Funahashi T, Kataoka TR, Kamada Y, Kiyohara T, Tamura S, Hayashi N, Shimomura I. · Department of Gastroenterology and Hepatology, Graduate School of Medicine, Osaka University, K1, 2-2 Yamadaoka, Suita, Osaka 565-0871, Japan. · Gut. · Pubmed #18579666 No free full text.

Abstract: BACKGROUND: Obesity is a risk factor for acute pancreatitis (AP), but the molecular mechanism remains unclear. Adiponectin, an adipose tissue-derived secretory factor, has anti-inflammatory properties in addition to various biological functions, and its plasma concentrations are reduced in obese subjects. However, the role of adiponectin in AP has not been investigated. AIM: To determine the effects of adiponectin on AP. METHODS: We investigated the effects of adiponectin on experimental AP by using adiponectin-knockout (APN-KO) mice and adenovirus-mediated adiponectin over-expression. AP was induced by 10 hourly intraperitoneal injections of low-dose caerulein (10 microg/kg) after 2 week feeding of normal chow or a high-fat diet (HFD) in wild-type (WT) and APN-KO mice. We evaluated the severity of AP biochemically and morphologically. RESULTS: Low-dose caerulein treatment did not induce pancreatic damage in either WT or APN-KO mice under normal chow feeding. APN-KO mice, but not WT mice, fed a HFD and then treated with caerulein developed pancreatic damage and inflammation, accompanied by increased macrophage/neutrophil infiltration and upregulation of pro-inflammatory mediators such as tumour necrosis factor alpha in the pancreas. Adenovirus-mediated over-expression of adiponectin attenuated the severity of HFD/caerulein-induced AP in APN-KO mice. CONCLUSIONS: Adiponectin plays a protective role in caerulein-induced AP in HFD-fed mice.

Abe M, Matsuda M, Kobayashi H, Miyata Y, Nakayama Y, Komuro R, Fukuhara A, Shimomura I. · Department of Metabolic Medicine, Graduate School of Medicine, Osaka University, Osaka, Japan. · Arterioscler Thromb Vasc Biol. · Pubmed #18323514 links to  free full text

Abstract: OBJECTIVE: Macrophage-mediated chronic inflammation of adipose tissue is causally linked to insulin resistance in obesity. The beneficial effects of 3-hydroxy-3-methylglutaryl (HMG) coenzyme A (CoA) reductase inhibitors (statins) on glucose metabolism have been suggested, but the effects of these agents on adipose tissue inflammation are unclear. The aim of the present study is to define the effects of statins on adipose tissue inflammation and macrophages. METHODS AND RESULTS: Pravastatin or pitavastatin treatment of obese mice attenuated an increase in mRNA expressions of proinflammatory genes, including MCP1 and IL6, in adipose tissue. The supernatant of TLR4-stimulated RAW264 macrophages strongly induced the expression of these genes in 3T3-L1 adipocytes, which was inhibited by pretreatment of macrophages with either statin. Statins inhibited TLR4-mediated activation of interferon (IFN) regulatory factor (IRF)3 by either lipopolysaccharide (LPS) or palmitic acid, resulting in suppression of IFN-beta expression, but not that of NF-kappaB or JNK. Moreover, statins strongly downregulated TLR3-mediated gene expressions by poly(I:C), but not TLR2-stimulation by zymosan A. Neutralization of IFN-beta attenuated proinflammatory activities of the macrophage supernatant. CONCLUSIONS: Statins partially attenuated the development of adipose tissue inflammation in obese mice, which might be associated with an inhibitory effect of statins on TLR4-triggered expression of IFN-beta via MyD88-independent signaling pathway in macrophages.

Okada T, Nishizawa H, Kurata A, Tamba S, Sonoda M, Yasui A, Kuroda Y, Hibuse T, Maeda N, Kihara S, Hadama T, Tobita K, Akamatsu S, Maeda K, Shimomura I, Funahashi T. · Department of Metabolic Medicine, Graduate School of Medicine, Osaka University, 2-2-B5 Yamadaoka, Suita 565-0871, Japan. · Biochem Biophys Res Commun. · Pubmed #18178152 No free full text.

Abstract: Dysregulated production of adipocytokines in obesity is involved in the development of metabolic syndrome. URB/DRO1 contains N-terminal signal sequence and is thought to play a role in apoptosis of tumor cells. In the present study, we investigated the expression pattern of URB mRNA in adipose tissue and secretion from cultured adipocytes. In human and mouse, URB mRNA was predominantly expressed in adipose tissue and was downregulated in obese mouse models, such as ob/ob, KKAy, and diet-induced obese mice. In 3T3L1 adipocytes, insulin, TNF-alpha, H(2)O(2) and hypoxia decreased URB mRNA level. This regulation was similar to that for adiponectin and opposite to MCP-1. URB protein was secreted in media of URB cDNA-stably transfected cells and endogenous URB was detected in media of cultured human adipocytes. In conclusion, the expression pattern of URB suggests its role in obesity and the results suggest that URB is secreted, at least in part, from adipocytes.

Okuno Y, Matsuda M, Kobayashi H, Morita K, Suzuki E, Fukuhara A, Komuro R, Shimabukuro M, Shimomura I. · Department of Metabolic Medicine, Graduate School of Medicine, Osaka University, 2-2 Yamadaoka, Suita, Osaka 565-0871, Japan. · Biochem Biophys Res Commun. · Pubmed #18073138 No free full text.

Abstract: In adipose tissue of obese mice, the expression of catalase, an anti-oxidant enzyme, significantly decreases, which may cause insufficient elimination of hydrogen peroxide, but it does not in liver or skeletal muscle. However, the precise regulatory mechanism of catalase expression in adipocytes has not been fully defined. Here, we demonstrated that adipose tissues highly expressed catalase on the level comparable to liver and kidney, and treatment of mice with PPARgamma agonist significantly enhanced catalase expression in adipose tissue but not in liver. In 3T3-L1 cells, mRNA expression of catalase was up-regulated by the induction for adipose differentiation, and down-regulated by TNFalpha, in parallel with alterations in PPARgamma expression. PPARgamma agonist significantly enhanced catalase mRNA and activity. Furthermore, we newly identified a remote enhancer region containing two functional PPARgamma binding sites in mouse catalase gene. Collectively, our findings suggest that PPARgamma plays a crucial role in the expression of catalase in adipocytes.

Nozaki M, Fukuhara A, Segawa K, Okuno Y, Abe M, Hosogai N, Matsuda M, Komuro R, Shimomura I. · Department of Metabolic Medicine, Graduate School of Medicine, Osaka University, 2-2 Yamadaoka, Suita, Osaka 565-0871, Japan. · Biochem Biophys Res Commun. · Pubmed #17931601 No free full text.

Abstract: Obesity is associated with infiltration of macrophages into adipose tissue, and macrophages are an important source of nitric oxide (NO). Dysregulated production of fat-derived secretory factor, adipocytokine, leads to obesity-linked metabolic disorders. However, it has not been fully determined whether NO might have direct effects on adipocytokine expressions. Here, we show that NO donor treatment downregulated gene expression and secretion of adiponectin, and upregulated mRNA levels of PAI-1 and IL-6. NO donor reduced promoter activity of adiponectin through PPARgamma responsive element. Moreover, NO donor activated JNK and NF-kappaB pathways, and inhibitors of these pathways rescued NO-mediated upregulation of PAI-1 and IL-6. Analysis of adipose tissue of high-fat-fed obese mice showed upregulation of PAI-1 and IL-6 expression, increased synthesis of NO, and downregulation of adiponectin. Our results suggest that increased NO synthesis might be partly responsible for dysregulation of adipocytokines in adipose tissue.

Ohashi K, Iwatani H, Kihara S, Nakagawa Y, Komura N, Fujita K, Maeda N, Nishida M, Katsube F, Shimomura I, Ito T, Funahashi T. · Department of Metabolic Medicine, Graduate School of Medicine, Osaka University, 2-2 Yamadaoka, Suita, Osaka 565-0871, Japan. · Arterioscler Thromb Vasc Biol. · Pubmed #17626903 links to  free full text

Abstract: OBJECTIVE: Obesity is recognized increasingly as a major risk factor for kidney disease. We reported previously that plasma adiponectin levels were decreased in obesity, and that adiponectin had defensive properties against type 2 diabetes and hypertension. In this study, we investigated the role of adiponectin for kidney disease in a subtotal nephrectomized mouse model. METHODS AND RESULTS: Subtotal (5/6) nephrectomy was performed in adiponectin-knockout (APN-KO) and wild-type (WT) mice. The procedure resulted in significant accumulation of adiponectin in glomeruli and interstitium in the remnant kidney. Urinary albumin excretion, glomerular hypertrophy, and tubulointerstitial fibrosis were significantly worse in APN-KO mice compared with WT mice. Intraglomerular macrophage infiltration and mRNA levels of vascular cell adhesion molecule (VCAM)-1, MCP-1, tumor necrosis factor (TNF)-alpha, transforming growth factor (TGF)-beta1, collagen type I/III, and NADPH oxidase components were significantly increased in KO mice compared with WT mice. Treatment of APN-KO mice with adenovirus-mediated adiponectin resulted in amelioration of albuminuria, glomerular hypertrophy, and tubulointerstitial fibrosis and reduced the elevated levels of VCAM-1, MCP-1, TNF-alpha, TGF-beta1, collagen type I/III, and NADPH oxidase components mRNAs to the same levels as those in WT mice. CONCLUSIONS: Adiponectin accumulates to the injured kidney, and prevents glomerular and tubulointerstitial injury through modulating inflammation and oxidative stress.

Okauchi Y, Nishizawa H, Funahashi T, Ogawa T, Noguchi M, Ryo M, Kihara S, Iwahashi H, Yamagata K, Nakamura T, Shimomura I, Matsuzawa Y. · Department of Metabolic Medicine, Graduate School of Medicine, Osaka University, Suita, Japan. · Diabetes Care. · Pubmed #17563343 links to  free full text

This publication has no abstract.

Kamada Y, Matsumoto H, Tamura S, Fukushima J, Kiso S, Fukui K, Igura T, Maeda N, Kihara S, Funahashi T, Matsuzawa Y, Shimomura I, Hayashi N. · Department of Gastroenterology and Hepatology, Osaka University, Graduate School of Medicine, 2-2, K1, Yamada-oka, Suita, Osaka 565-0871, Japan. · J Hepatol. · Pubmed #17459514 No free full text.

Abstract: BACKGROUND/AIMS: Adipose tissue produces a number of adipocytokines, including adiponectin, leptin, and tumor necrosis factor-alpha. Obesity, which is associated with low plasma adiponectin levels, is an independent risk factor for various liver diseases including nonalcoholic steatohepatitis (NASH). The aim of this study was to examine the effects of adiponectin on the progression of NASH to cirrhosis and tumor formation using adiponectin-knockout (KO) mice. METHODS: Using a choline-deficient L-amino acid-defined (CDAA) diet-induced mouse NASH model, liver histology and oxidative stress markers were investigated in KO and wild-type (WT) mice. RESULTS: Hepatic steatosis was enhanced to a greater extent in KO mice, compared to WT mice after a 1-week CDAA diet. After 24 weeks, 6 out of 14 KO mice developed liver cirrhosis and hepatic tumors, whereas the 15 WT mice showed only simple steatosis. In KO mice, hepatic cytochrome P450 2E1 levels were upregulated, and markers of oxidative stress (thiobarbituric acid reactive substances, 8-hydroxydeoxyguanosine-positive cells) were significantly increased compared with WT mice. CONCLUSIONS: Our results indicate that lack of adiponectin enhances the progression of hepatic steatosis, fibrosis, and hepatic tumor formation in an animal model of NASH. Hypoadiponectinemia in obesity could be a risk factor for NASH-related hepatic tumor formation.

Hosogai N, Fukuhara A, Oshima K, Miyata Y, Tanaka S, Segawa K, Furukawa S, Tochino Y, Komuro R, Matsuda M, Shimomura I. · Department of Metabolic Medicine, Graduate School of Medicine, Osaka University, 2-2 Yamadaoka, Suita, Osaka 565-0871, Japan. · Diabetes. · Pubmed #17395738 links to  free full text

Abstract: Obesity is linked to a variety of metabolic disorders, such as insulin resistance and atherosclerosis. Dysregulated production of fat-derived secretory factors, adipocytokines, is partly responsible for obesity-linked metabolic disorders. However, the mechanistic role of obesity per se to adipocytokine dysregulation has not been fully elucidated. Here, we show that adipose tissue of obese mice is hypoxic and that local adipose tissue hypoxia dysregulates the production of adipocytokines. Tissue hypoxia was confirmed by an exogenous marker, pimonidazole, and by an elevated concentration of lactate, an endogenous marker. Moreover, local tissue hypoperfusion (measured by colored microspheres) was confirmed in adipose tissue of obese mice. Adiponectin mRNA expression was decreased, and mRNA of C/EBP homologous protein (CHOP), an endoplasmic reticulum (ER) stress-mediated protein, was significantly increased in adipose tissue of obese mice. In 3T3-L1 adipocytes, hypoxia dysregulated the expression of adipocytokines, such as adiponectin and plasminogen activator inhibitor type-1, and increased the mRNAs of ER stress marker genes, CHOP and GRP78 (glucose-regulated protein, 78 kD). Expression of CHOP attenuated adiponectin promoter activity, and RNA interference of CHOP partly reversed hypoxia-induced suppression of adiponectin mRNA expression in adipocytes. Hypoxia also increased instability of adiponectin mRNA. Our results suggest that hypoperfusion and hypoxia in adipose tissues underlie the dysregulated production of adipocytokines and metabolic syndrome in obesity.

Takagi T, Matsuda M, Abe M, Kobayashi H, Fukuhara A, Komuro R, Kihara S, Caslake MJ, McMahon A, Shepherd J, Funahashi T, Shimomura I. · Department of Medicine and Pathophysiology, Graduate School of Frontier Bioscience, Graduate School of Medicine, Osaka University, 2-2 Yamadaoka, Suita, Osaka 565-0871, Japan. · Atherosclerosis. · Pubmed #17391675 No free full text.

Abstract: In the West of Scotland Coronary Prevention Study (WOSCOPS), treatment of hypercholesterolemic men with pravastatin, an inhibitor of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, reduced their likelihood to progress to diabetes mellitus by 30%. However, the mechanism of this effect of pravastatin has not been investigated. In the current study, we examined the effect of pravastatin on the development of diabetes in obese diabetic mice, and on the insulin-induced glucose uptake and adiponectin production. Pravastatin treatment attenuated the development of diabetes in db/db and high fat/high sucrose diet-fed C57BL/6J mice. An in vivo glucose transport assay showed that pravastatin upregulated glucose uptake in adipose tissue. Insulin-stimulated glucose uptake was enhanced in primary adipocytes isolated from pravastatin-treated mice. Pravastatin treatment increased adiponectin production in 3T3-L1 adipocytes. Plasma adiponectin levels were significantly increased in pravastatin-treated mice. Analyses of plasma samples from the WOSCOPS biobank indicated a significant increase of plasma adiponectin levels with pravastatin treatment (placebo -0.28+/-0.34 microg/ml versus pravastatin +1.47+/-0.33 microg/ml, p=0.0003). Taken together, our findings suggest that pravastatin may have beneficial effects on adipose tissue, which may partly explain the reduction of the development of diabetes by pravastatin treatment.

Snijder MB, Heine RJ, Seidell JC, Bouter LM, Stehouwer CD, Nijpels G, Funahashi T, Matsuzawa Y, Shimomura I, Dekker JM. · Institute of Health Sciences, Vrije Universiteit Amsterdam, De Boelelaan 1085, 1081 HV Amsterdam, Netherlands. · Diabetes Care. · Pubmed #17065691 links to  free full text

Abstract: OBJECTIVE: Adiponectin is an adipose tissue-derived protein. Low levels are associated with obesity, insulin resistance, and type 2 diabetes. Our objective was to investigate the prospective association between adiponectin levels and the 6.4-year risk of type 2 diabetes and of impaired glucose metabolism (IGM). RESEARCH DESIGN AND METHODS: The Hoorn Study is a cohort study among Caucasians, aged 50-75 years. BMI, waist-to-hip ratio (WHR), fasting glucose, 2-h glucose, triglycerides, HDL cholesterol, LDL cholesterol, alanine aminotransferase, leptin, and adiponectin were measured at baseline. Lifestyle (alcohol intake, smoking, and physical activity) was assessed by questionnaires. After a mean follow-up of 6.4 years, glucose tolerance was assessed by a 75-g oral glucose tolerance test. Analyses were performed in 1,264 subjects (584 men and 680 women) without type 2 diabetes at baseline. For analyses of incident IGM, 239 subjects with IGM at baseline and/or type 2 diabetes at follow-up were excluded. RESULTS: Age- and lifestyle-adjusted odds ratios and 95% CIs comparing highest with lowest adiponectin quartile were 0.52 (0.23-1.18) in men and 0.15 (0.06-0.39) in women for type 2 diabetes and 0.90 (0.51-1.61) and 0.28 (0.16-0.48) for IGM, respectively. The risks were only slightly reduced after adjustment for WHR and leptin as markers of (abdominal) adiposity. Adjustment for baseline fasting and postload glucose levels (potential mediators) substantially diminished these inverse associations with type 2 diabetes (0.79 [0.32-1.91] and 0.62 [0.21-1.81]) and with IGM (1.20 [0.61-2.35] and 0.48 [0.26-0.90]), respectively. CONCLUSIONS: A high adiponectin level was strongly associated with a lower risk of IGM and type 2 diabetes, particularly in women. These results suggest that adiponectin is involved in the pathophysiology linking obesity to type 2 diabetes.

Fujita K, Nishizawa H, Funahashi T, Shimomura I, Shimabukuro M. · Department of Metabolic Medicine, Graduate School of Medicine, Osaka University, Suita, Japan. · Circ J. · Pubmed #17062967 links to  free full text

Abstract: BACKGROUND: The metabolic syndrome (MetS) is a major target for prevention of atherosclerotic cardiovascular diseases and visceral fat accumulation is an underlying component of MetS. The aim of this study was to investigate the association of systemic oxidative stress with visceral fat accumulation and MetS. METHODS AND RESULTS: The study group consisted of Japanese men (n=44; 51.2+/-11.4 years) and women (n=61; 55.4 +/-13.4 years). Urinary 8-epi-prostaglandin F2alpha (8-epi-PGF2 alpha) concentration, a biomarker of systemic oxidative stress, was significantly high in the subjects with MetS. As the urinary concentration of 8-epi-PGF2alpha increased, the number of criteria for MetS were significantly met (abdominal obesity, hypertriglyceridemia, low high-density lipoprotein-cholesterol, hypertension, and high fasting glucose). Among parameters associated with MetS, the correlation coefficient of visceral fat area (VFA) with urinary 8-epi-PGF2alpha concentration was the highest (r=0.636, p<0.0001). In non-obese subjects, the correlation coefficient of VFA with urinary 8-epi-PGF2alpha concentration was higher (r=0.728, p<0.0001), although there was no significant correlation between subcutaneous fat area and urinary 8-epi-PGF2 alpha. Stepwise multiple regression analysis identified VFA as the strongest and independent determinant of urinary 8-epi-PGF2 alpha (p<0.0001) followed by adiponectin (p=0.0212) and, high sensitive C-reactive protein (p=0.0365). CONCLUSIONS: Systemic oxidative stress, as measured by urinary 8-epi-PGF2alpha , is strongly associated with visceral fat accumulation and MetS.