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Query: UNIPROT:P06889 (
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630,302
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Polycystic ovary syndrome (PCOS) is associated with an increased incidence of insulin resistance (IR), obesity, and type 2 diabetes. Resistin, an adipocytokine, may represent a link between obesity, and these metabolic disorders. There is also evidence that inflammation is a hyperresistinemic state in humans, and cytokine induction of resistin may contribute to insulin resistance in endotoxemia, obesity, and other inflammatory states. In contrast,
adiponectin
, increases insulin sensitivity, improves glucose tolerance, inhibits inflammatory pathways, while adenovirus-expressed
adiponectin
reduces atherosclerotic lesions in a mouse model of atherosclerosis. We aimed to assess, in women with PCOS, whether there is a relationship between
adiponectin
and resistin and the indices of IR, and whether serum levels of these adipocytokines are altered by glucose-induced hyperinsulinaemia. Serum levels of resistin and
adiponectin
were measured at 0, 60, and 120 min during 75 g oral glucose tolerance test (OGTT), in 19 women with PCOS, age 36.3+/-11.4 years (mean+/-SD), body mass index (BMI) 29.3+/-7.7 kg/m2, and correlated with the indices of IR, such as HOMA-IR, QUICKI, and the insulin resistance index calculated from glucose and insulin levels obtained during OGTT. There was no change in resistin concentrations (7.31+/-4.58, 7.47+/-5.40, 7.22+/-5.12 pg/ml, at 0, 60, and 120 min of OGTT, respectively, P = 0.77), but there was an increase in
adiponectin
from 11.32+/-4.64 microg/ml at baseline to 14.78+/-7.41 microg/ml, at 120 min of OGTT (P < 0.01). The magnitude of the overall rise in
adiponectin
was greater from 60 to 120 min (from 12.31+/-5.72 to 14.78+/-7.41 microg/ml, P < 0.006). Neither resistin, nor
adiponectin
correlated with the indices of IR, lipids, or other hormonal parameters of the PCOS. There was, however, a significant negative correlation between serum resistin and
adiponectin
(P = 0.001). In conclusion, we observed a strong negative correlation between serum
adiponectin
and resistin, despite the lack of direct correlation with the indices of IR. Given the opposite effects of resistin and
adiponectin
on the inflammatory process, we speculate that relative proportion of
adiponectin
-to-resistin might potentially influence cardiometabolic risk in women with the PCOS independently of IR parameters. The observed increase in
adiponectin
during OGTT requires further study.
Mol
Genet Metab 2005 May
PMID:Adiponectin and resistin serum levels in women with polycystic ovary syndrome during oral glucose tolerance test: a significant reciprocal correlation between adiponectin and resistin independent of insulin resistance indices. 1586 82
Adiponectin, an adipocyte-derived protein, is an essential modulator of insulin sensitivity and several studies suggest an important role of
adiponectin
in the processes leading to atherosclerosis, thus indicating the
adiponectin
gene as a potential candidate for coronary artery disease (CAD). In the present study we have studied the association between two single nucleotide polymorphisms (SNPs) (+45T>G and +276 G>T) of the
adiponectin
gene and CAD, looking also into the possible influence of these SNPs on
adiponectin
plasma levels. The SNPs were analysed in a first cohort of 595 subjects, 325 with CAD and 270 matched controls. We observed a significant association (p<0.001) between the SNP +276G>T in the
adiponectin
gene and CAD. In multivariate analysis, carriers of the +276G>T SNP had an odds ratio (OR) for CAD of 4.99 (p<0.0007). A strong interaction between the +276G>T SNP and age was also present (OR, 1.03; p<0.0001). The increase in CAD risk was most evident among individuals with early-onset CAD (age <or=50 years), whereas in older CAD subjects other factors, and not the
adiponectin
SNP, were the major determinants. Furthermore, in CAD subjects with early-onset disease this SNP was also a significant determinant of lower levels of serum
adiponectin
levels. This association resulted independent from the other variables known to be associated with CAD in our population, including sex, body mass index, high-density lipoprotein and Homeostasis Model Assessment for insulin resistance. To confirm the results the +276G>T SNP was analysed in a second cohort of CAD and controls. The difference between CAD and controls in the +276G>T SNP frequencies showed a similar trend as before, although not significant. The combination of the two cohorts (1,046 subjects: 580 CAD and 466 controls) showed a statistically significant association, particularly in CAD subjects with early-onset of disease. In addition, we confirmed that in younger CAD subjects the SNP was a significant determinant of lower levels of
adiponectin
. In view of these results, it could be speculated that the
adiponectin
gene variant, or a mutation in linkage with it, determines lower
adiponectin
gene expression, causing in turn an increased risk to develop insulin resistance, atherosclerosis and cardiovascular disease. The significant association of the
adiponectin
gene in subjects with early-onset CAD also suggests that that genetic factors for late-onset diseases may exert a greater influence in younger persons, when other risk factors are not as prevalent as in older age groups.
J
Mol
Med (Berl) 2005 Sep
PMID:The adiponectin gene SNP+276G>T associates with early-onset coronary artery disease and with lower levels of adiponectin in younger coronary artery disease patients (age <or=50 years). 1587 15
Obesity is not necessary to observe insulin resistance in humans since severe insulin resistance also characterizes patients lacking subcutaneous fat such as those with HAART (highly-active antiretroviral therapy) - associated lipodystrophy. Both the obese and the lipodystrophic patients have, however, an increase in the amount of fat hidden in the liver. Liver fat content can be non-invasively accurately quantified by proton magnetic resonance spectroscopy. It is closely correlated with fasting insulin and direct measures of hepatic insulin sensitivity while the amount of subcutaneous adipose tissue is not. The causes of interindividual variation in liver fat content independent of obesity are largely unknown but could involve differences in signals from adipose tissue such as in the amount of
adiponectin
produced and differences in fat intake. Adiponectin deficiency characterizes both lipodystrophic and obese insulin resistant individuals, and serum levels correlate with liver fat content. Liver fat content can be decreased by weight loss. In addition, treatment of both lipodystrophic and type 2 diabetic patients with PPARgamma agonists but not metformin decreases liver fat and increases
adiponectin
levels. Markers of liver fat such as serum alanine aminotransferase activity have been shown to predict type 2 diabetes in several studies independent of obesity. The fatty liver thus may help to explain why some but not all obese individuals are insulin resistant and why even lean individuals may be insulin resistant, and thereby at risk of developing type 2 diabetes and cardiovascular disease.
Curr
Mol
Med 2005 May
PMID:The fatty liver and insulin resistance. 1589 48
Diabetic dyslipidemia is a cluster of plasma lipid and lipoprotein abnormalities that are metabolically interrelated. The recognition that the elevation of large VLDL 1 particles initiates a sequence of events that leads to the formation of small dense LDL and HDL species has focused the assembly of VLDL particles on the spotlight as a potential culprit of dyslipidemia. Notably dyslipidemia is associated with insulin resistance, visceral obesity and liver fat content. Insulin resistance is associated with excessive flux of substrates for VLDL assembly to the liver as well as the upregulation of the machinery generating large VLDL particles in excess. The regulation of different molecular steps in this cascade of events are complex and so far poorly understood. The disordered crosstalk between adipose tissue and the liver results in an imbalance of the machinery that orchestrates the regulation of VLDL production. A number of studies indicates that adipocytokines in particular
adiponectin
may be a seminal player in the regulation of fat metabolism in the liver. Future discoveries hopefully will delineate the regulatory steps to allow more targeted treatment of diabetic dyslipidemia.
Curr
Mol
Med 2005 May
PMID:Type 2 diabetes as a lipid disorder. 1589 49
Type 2 diabetes carries a 2-6-fold increased risk of cardiovascular disease (CVD) and death. Indeed, the risk of major cardiovascular events in Type 2 diabetic patients without history of coronary heart disease (CHD) is equivalent to that observed in non-diabetic subjects with CHD. However, atherosclerosis may also precede the development of diabetes, suggesting that both disorders share common genetic and environmental antecedent factors ("common soil" hypothesis). One such a possible ancestor is insulin resistance which constitutes both a major feature of Type 2 diabetes and an independent risk factor for CHD. It is well documented that inflammatory processes play an important role in the causation of atherosclerotic CVD. Inflammatory mediators play a paramount role in the initiation, progression, and rupture of atherosclerotic plaques. Thus, markers of inflammation and endothelial dysfunction may provide additional information about a patient's risk of developing CVD and may become new targets for treatment. On the other hand, evidence has emerged suggesting that inflammation is also involved in the development of Type 2 diabetes. Prospective studies have demonstrated that increased levels of pro-inflammatory markers such as CRP or reduced levels of anti-inflammatory markers such as
adiponectin
predict the development of Type 2 diabetes. Thus, there is accumulating evidence suggesting that inflammation is the bridging link between atherosclerosis and the metabolic syndrome. Interventions by lifestyle modification or agents with anti-inflammatory properties may reduce the risk of both conditions. Drugs exerting anti-inflammatory and vascular effects have future potential to be used within an array of interventions aimed at reducing the enormous cardiovascular burden associated with Type 2 diabetes.
Curr
Mol
Med 2005 May
PMID:Type 2 diabetes as an inflammatory cardiovascular disorder. 1589 50
The role of adipocytes as protein secreting cells has been known for almost 15 years. Most of these proteins have known biological activity and are called adipokines. However, only a few of the adipokines have been shown to regulate insulin sensitivity. The latter effects are direct or indirect. The adipokines regulating insulin sensitivity are tumor necrosis factor alpha,
adiponectin
, interleukin-6, resistin and leptin. This review examines the mechanism how these adipokines influence insulin sensitivity, how the adipocyte production of the adipokines is regulated and if genetic variance in the genes encoding for adipokines is important for the development of type 2 diabetes mellitus.
Curr
Mol
Med 2005 May
PMID:Insulin resistance in type 2 diabetes -- role of the adipokines. 1589 52
Insulin resistance is a principal underlying defect in type 2 DM along with beta-cell dysfunction, and this insulin resistance underpins many of the abnormalities associated with the metabolic syndrome. Peroxisome-proliferator-activated receptor gamma agonists (PPARgamma agonists), also known as glitazones or thiazolidinediones (TZDs) are powerful insulin sensitisers with recent evidence suggesting that they also have a potential to improve pancreatic beta-cell function. TZDs cause a major redistribution of body fat with a decrease in visceral and hepatic fat content with a resultant increase in insulin sensitivity. The glucose lowering effects of TZDs are similar to those seen with the well-established sulphonylureas and metformin. TZDs have a small reducing effect on blood pressure and have been shown to reduce microalbuminuria independent of their blood glucose lowering effect. Both TZDs in clinical practice, pioglitazone and rosiglitazone, reduce small dense LDL-cholesterol and increase HDL-cholesterol levels but pioglitazone would appear to have a more pronounced benefit on these two parameters with a greater reduction in plasma triglycerides. TZDs improved the pro-coagulant state and show benefits in improving endothelial dysfunction and reducing 'non-traditional' inflammatory cytokines and increasing
adiponectin
levels. The greatest benefit for the TZDs is to directly influence atherogenesis itself and the potential that these so-called pleiotrophic effects of TZDs to reduce cardiovascular events in type 2 DM will be tested when the results of outcome trials are published in the next few years. If the results are positive for the reduction in vascular end-points, then TZDs will represent a major advance in improving the prognosis of type 2 DM subjects with the metabolic syndrome.
Curr
Mol
Med 2005 May
PMID:The Clinical Significance of PPAR Gamma Agonism. 1589 54
Glucose-6-phosphate dehydrogenase (G6PD) produces cellular NADPH, which is required for the biosynthesis of fatty acids and cholesterol. Although G6PD is required for lipogenesis, it is poorly understood whether G6PD in adipocytes is involved in energy homeostasis, such as lipid and glucose metabolism. We report here that G6PD plays a role in adipogenesis and that its increase is tightly associated with the dysregulation of lipid metabolism and insulin resistance in obesity. We observed that the enzymatic activity and expression levels of G6PD were significantly elevated in white adipose tissues of obese models, including db/db, ob/ob, and diet-induced obesity mice. In 3T3-L1 cells, G6PD overexpression stimulated the expression of most adipocyte marker genes and elevated the levels of cellular free fatty acids, triglyceride, and FFA release. Consistently, G6PD knockdown via small interfering RNA attenuated adipocyte differentiation with less lipid droplet accumulation. Surprisingly, the expression of certain adipocytokines such as tumor necrosis factor alpha and resistin was increased, whereas that of
adiponectin
was decreased in G6PD overexpressed adipocytes. In accordance with these results, overexpression of G6PD impaired insulin signaling and suppressed insulin-dependent glucose uptake in adipocytes. Taken together, these data strongly suggest that aberrant increase of G6PD in obese and/or diabetic subjects would alter lipid metabolism and adipocytokine expression, thereby resulting in failure of lipid homeostasis and insulin resistance in adipocytes.
Mol
Cell Biol 2005 Jun
PMID:Overexpression of glucose-6-phosphate dehydrogenase is associated with lipid dysregulation and insulin resistance in obesity. 1592 30
Hepatic lipase (HL) is synthesized in the liver and hydrolyses triglyceride and phospholipids. C-514T polymorphism in HL gene promoter was reported to associate with hepatic lipase activity and plasma lipid levels. We examined whether C-514T polymorphism affects glucose metabolism beyond its effect on plasma lipid levels in nondiabetic Japanese subjects. Gene frequencies of C/C homozygote, C/T heterozygote and T/T homozygote were 18, 51 and 31%, respectively. The allelic frequencies of C and T were 44 and 56%, respectively. T allele frequency was much higher than in Caucasian subjects. Moreover, -514T allele carriers had higher levels of triglyceride (P=0.027), fasting insulin (P=0.016) and HOMA-IR (P=0.033) than non-carriers. In contrast to some former studies, -514T allele affected triglyceride levels and insulin sensitivity. Taken together, HL gene might be one of the important susceptibility genes of type 2 diabetes and the high incidence of type 2 diabetes could be explained by high frequency of -514T allele in the Japanese population. Moreover, since HL and
adiponectin
showed an additive effect on insulin sensitivity, these genetic variations can be independently associated with insulin sensitivity.
Int J
Mol
Med 2005 Sep
PMID:C-514T polymorphism in hepatic lipase gene promoter is associated with elevated triglyceride levels and decreasing insulin sensitivity in nondiabetic Japanese subjects. 1607 49
Epidemiologic studies have shown that serum level of
adiponectin
, a circulating protein secreted by adipocytes, predicts the risk of type 2 diabetes and cardiovascular events. Two single-nucleotide polymorphisms (SNPs) at the
adiponectin
locus (T45G or G276T) of the
adiponectin
gene (APM1) have been associated with insulin resistance, low serum
adiponectin
levels, and diabetes. In the present study, the association of these polymorphisms with serum
adiponectin
level and insulin resistance-associated risk factors was investigated. To this aim, SNP+45 and SNP+276 of APM1 were genotyped in 252 young Finnish men. Serum
adiponectin
level (p < 0.001) and diastolic blood pressure (p = 0.031) were significantly higher in subjects with the T276T genotype of APM1 compared to those with the G276T or G276G genotypes. Mean diastolic blood pressure among the T276T subjects was 80 mmHg and that in subjects with the G276G and G276T genotypes below 75 mmHg. An interaction between triglycerides, diastolic blood pressure, quantitative insulin sensitivity check index, and SNP276 with regard to serum
adiponectin
level was found. After adjustment for other covariates, the interaction between triglycerides and SNP276 remained statistically significant (p = 0.009). Among subjects with the T276T genotype, an increase in triglyceride level was associated with a decrease in
adiponectin
concentration. This result was not observed in other genotype groups. SNP+45 was not significantly related to serum
adiponectin
concentration, but high-density lipoprotein (HDL) cholesterol tended to be higher in subjects with the T45T genotype (p = 0.051) compared to subjects with the X45G genotype. In conclusion, the T276T genotype of the
adiponectin
gene was associated with elevated serum
adiponectin
level and diastolic blood pressure among young Finnish men.
Mol
Genet Metab 2006 Feb
PMID:Common polymorphisms (single-nucleotide polymorphisms SNP+45 and SNP+276) of the adiponectin gene regulate serum adiponectin concentrations and blood pressure in young Finnish men. 1625 87
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