Adiponectin: A novel adipokine linking adipocytes and vascular function

Relationship of Serum Adiponectin Level to Adverse Cardiovascular Events in Patients Who Undergo Percutaneous Coronary Intervention

BACKGROUND

Hypoadiponectinemia has been reported to indicate an increased risk of cardiovascular disease, so the present study investigated the significance of serum adiponectin (APN) levels for predicting clinical outcomes after percutaneous coronary intervention (PCI).

METHODS AND RESULTS

The APN levels were evaluated in 184 consecutive patients who underwent PCI. The patients were divided into Group A [the lowest quartile of APN levels (APN < or =4.5 microg/ml), n=46] and Group B [the upper 3 quartiles of APN levels (APN >4.5 microg/ml), n=138]. During a mean follow-up period of 27.3 months, the rate of major adverse cardiac and cerebrovascular events (MACCE: death from any cause, re-infarction, repeat coronary revascularization, hospitalization because of congestive heart failure, and cerebral infarction) was higher in Group A (58.7%) than in Group B (37.0%, p=0.0101). Moreover, when the APN levels were calculated by adjusting for sex, age, body mass index, and triglyceride levels, patients in the lowest quartile of residual APN levels had a higher risk of MACCE (p=0.0405). Multiple logistic analyses showed that hypoadiponectinemia (APN < or =4.5 microg/ml) was independently correlated with MACCE. Kaplan-Meier analysis demonstrated a higher MACCE rate in Group A than in Group B (Log-rank chi(2)=7.89, p=0.0050).

CONCLUSION

The APN level may be helpful for predicting clinical outcomes after PCI.

Circulating leptin and adiponectin levels in patients with primary hyperparathyroidism

Primary hyperparathyroidism (PHPT) has been associated with high cardiovascular morbidity and mortality; its pathogenesis is not fully understood. Moreover, many metabolic abnormalities are frequently present in patients with PHPT. Several substances (such as leptin and adiponectin) are secreted from adipocytes, which may contribute to regulate energy homeostasis and the development of cardiovascular diseases. We examined the relationship between leptin and adiponectin levels and metabolic disorders in 67 newly diagnosed never-treated patients with PHPT and in 46 healthy subjects (HS). Twenty (29.8%) patients with PHPT presented a metabolic syndrome (as defined by Adult Treatment Panel III criteria). Serum leptin and adiponectin levels in HS were 6.28 +/- 3.3 ng/mL (range, 1.7-19.2 ng/mL) and 6.65 +/- 1.7 microg/mL (range, 3.72-10.86 microg/mL), respectively. In all patients with PHPT, the mean leptin levels (34.28 +/- 20.4 ng/mL) were significantly higher than those of HS (P < .01) and, in particular, in PHPT patients with metabolic syndrome (52.63 +/- 31.2 ng/mL) and positively correlated with body mass index, waist circumference, and cholesterol. The mean adiponectin level was significantly lower (4.34 +/- 3.5 mug/mL) only in PHPT patients with metabolic syndrome (P < .005) and negatively correlated with waist circumference and fasting glucose. We concluded that increased serum level of leptin and decreased serum level of adiponectin coexist in patients with PHPT and may represent a pathogenetic factor for cardiovascular disease in this condition.

Dual PPAR α/γ Agonists: Promises and Pitfalls in Type 2 Diabetes

Type 2 diabetes mellitus is a disease of complex pathogenesis and pleiotropic clinical manifestations. The greatest clinical challenge in this disease is the prevention of the long-term complications, many of which involve cardiovascular outcomes. The peroxisome proliferator-activated receptor (PPAR) alpha and gamma isoforms of the family of nuclear transcription factors are pharmaceutical targets for therapeutic intervention because they can potentially ameliorate not only the hyperglycemia of diabetes, but also the dyslipidemia that is characteristic of this disorder (low high-density lipoprotein cholesterol, high triglycerides, small, dense low-density lipoprotein particles). Novel drugs with dual PPAR alpha and gamma activity have been under clinical development for type 2 diabetes, and they have shown promise in early studies with regard to glucose lowering and improved lipid profile when compared with the PPAR-gamma-specific thiazolidinediones. Unfortunately, the dual PPARs available to date have some of the PPAR-gamma-associated side effect profile, including fluid retention and weight gain, which have limited the further clinical development of higher doses that show improved efficacy. This review will briefly summarize our understanding of the pathogenesis of type 2 diabetes, the role of the PPAR family of receptors, and the potential for clinical use of this novel emerging class of agents that serve as dual activators of both PPAR-alpha and PPAR-gamma.

Type 2 diabetes and cardiovascular disease: getting to the fat of the matterThis paper is one of a selection of papers published in this Special Issue, entitled Young Investigators' Forum

The increasing national prevalence of obesity is a major public health concern and a substantial burden on the health care resources of Canada. In addition to the direct health impact of obesity, this condition is a well-established risk factor for the development of various prevalent comorbidities including type 2 diabetes, hypertension, and cardiovascular disease. Historically, adipose tissue has been regarded primarily as an organ for energy storage. However, the discovery of leptin in the mid 1990’s revolutionized our understanding of this tissue and has focused attention on the endocrine function of adipose tissue as a source of secreted bioactive peptides. These compounds, collectively termed adipokines, regulate a number of biological functions including appetite and energy balance, insulin sensitivity, lipid metabolism, blood pressure, and inflammation. The physiological importance of adipokines has led to the hypothesis that changes in the synthesis and secretion of these compounds in the obese are a causative factor contributing to the development of obesity and obesity-related diseases in these individuals. Following from this it has been proposed that pharmacologic manipulation of adipokine levels may provide novel effective therapeutic strategies to treat and prevent obesity, type 2 diabetes, and cardiovascular disease.

Percutaneous coronary intervention increases leptin and decreases adiponectin levels

OBJECTIVE

The study was designed to examine the effect of percutaneous coronary intervention (PCI) on adiponectin and leptin levels. We have previously demonstrated that PCI triggers a systemic inflammatory response. We hypothesized that inflammation participates in the pathogenesis of diabetes mellitus and the metabolic syndrome by modulating levels of adiponectin and leptin.

DESIGN

Prospective study in which inflammation was induced by PCI.

PATIENTS

Forty-eight patients with stable coronary artery disease and without diabetes mellitus.

MEASUREMENTS

High-sensitivity C-reactive protein (hs-CRP), interleukin-6 (IL-6), leptin and adiponectin were measured at baseline and 48 h after the procedure.

RESULTS

Following PCI, hs-CRP increased by 211%, IL-6 by 87% and leptin by 19%, while adiponectin decreased by 14% (P < 0.001 for all). The change in IL-6 correlated with that in hs-CRP (rho = 0.32; P = 0.027), as did the changes in IL-6 and leptin (rho = 0.31; P = 0.03). The change in adiponectin, however, did not correlate with the change in any of the other markers.

CONCLUSION

This study demonstrates that PCI affects the levels of adiponectin and leptin within 48 h. These effects may be secondary to the inflammatory response triggered by PCI.

The entero-insular axis and adipose tissue-related factors in the prediction of weight gain in humans

Obesity has now reached epidemic proportions. Epidemiological studies in the past decades have shown that adults gain weight and adiposity from the early twenties until their sixties. In the paediatric population, growing numbers of children and adolescents put on unhealthy weight. Many environmental, socio-economical and biological determinants that predispose to weight gain have been identified thus far. The aim of the present review is to summarize the current knowledge on the role of the circulating levels of adipokines and other entero-insular hormones and biological markers of obesity to predict weight gain in humans. The review focuses on relationship between hormonal and biochemical markers (insulin, insulin-like growth factors, gastrointestinal hormones, leptin, adiponectin, resistin, inflammatory proteins and cytokines) and weight gain in prospective studies. The complex relationships displayed by these hormonal factors with future weight gain in humans are critically reviewed and integrative models are proposed. Overall, most of the studies reported to date made adjustments for baseline body mass index but failed to consider dietary intake and physical activity as confounding factors. Outstanding questions are raised and new directions for future prospective studies are proposed in order to improve our understanding of the role of biological determinants of energy balance and development of obesity in humans.

Adrenarche in Prader-Willi syndrome appears not related to insulin sensitivity and serum adiponectin

Prader-Willi syndrome (PWS) is a genetic disorder characterized by dysmorphic features, obesity, hypogonadism, hypotonia and mental retardation. Obesity has been linked to insulin resistance and the latter has also been associated with premature adrenarche. Since up to date a controlled study to investigate adrenarche and its hormonal regulation was lacking in PWS, our aim was to assess whether prepubertal PWS patients develop premature adrenarche and its relationship with markers of insulin sensitivity. Fourteen prepubertal children with PWS (6 M, 8 F) and 10 non-syndromal simple obese matched controls (5 M, 5 F) participated (mean age: 7.62 +/- 1.84 years). A fasting blood sample was obtained for adrenal and ovarian androgens, sex hormone binding globulin, insulin-like growth factor-I (IGF-I), insulin-like growth factor binding protein-1, leptin, adiponectin and a lipid profile. Thereafter an oral glucose tolerance test was performed. PWS patients were smaller at birth and a higher proportion displayed premature pubarche. No differences were found in testosterone, androstenedione, sex hormone binding globulin, free androgen index, homeostatic model assessment-IR, 2-hour insulin, leptin or adiponectin levels. 17-hydroxyprogesterone and DHEAS levels however, were significantly higher in PWS. IGF-I levels were significantly lower in PWS and correlated significantly with height SDS (p < 0.05). In conclusion, a higher proportion of premature adrenarche in our PW patients was observed, which was not explained by differences in insulin sensitivity or plasma levels of adipokines and IGF-I.

Adiponectin inhibits superoxide generation by human neutrophils

Adiponectin (Ad), a member of the adipocytokine family, has been reported to possess antiinflammatory properties. We investigated the effects of full-length human Ad (hAd) on phorbol 12-myristate 13-acetate (PMA)-induced O2-* generation by human neutrophils. hAd, even at the lowest tested concentration of 0.001 microg/ml, after 30-min pretreatment of cells, significantly inhibited O2-* generation by neutrophils stimulated with PMA (100 nM). However, no relation between the dose of hAd and extent of inhibition of PMA-induced O2-* generation was observed with increasing the concentration of hAd up to 1 microg/ml. hAd also significantly inhibited neutrophil O2-* generation stimulated by N-formyl-methionyl-leucyl-phenylalanine (100 microM) and diacylglycerol (500 nM), as well as the PMA-induced neutrophil nitroblue tetrazolium reduction and H2O2 formation. Pretreatment of neutrophils with pronase-digested hAd failed to inhibit the PMA-induced O2-* generation. For the first time, this study revealed that Ad inhibited O2-* generation by neutrophils, possibly through regulation of NADPH oxidase.

Relationship between adipokines, inflammation, and vascular reactivity in lean controls and obese subjects with metabolic syndrome

PURPOSE

Metabolic syndrome is an important risk factor for cardiovascular disease. Adipokines interfere with insulin action and endothelial cell function. We investigated the relationship among adipokines, metabolic factors, inflammatory markers, and vascular reactivity in obese subjects with metabolic syndrome and lean controls.

METHODS

Cross-sectional study of 19 obese subjects with metabolic syndrome and 8 lean volunteers evaluated as controls. Vascular reactivity was assessed by venous occlusion pletysmography measuring braquial forearm blood flow (FBF) and vascular resistance (VR) responses to intra-arterial infusions of endothelium-dependent (acetylcholine-Ach) and independent (sodium nitroprusside-SNP) vasodilators. Blood samples were obtained to evaluate C reactive protein (CRP), plasminogen activator inhibitor 1 (PAI-1), fibrinogen, adiponectin, resistin, and lipid profile. Patients were classified with regard to insulin resistance through the HOMA-IR index.

RESULTS

PAI-1, CRP and fibrinogen were higher and adiponectin was lower in metabolic syndrome subjects compared to controls. Metabolic syndrome subjects had impaired vascular reactivity. Adiponectin and PAI-1 were associated with insulin, HOMA-IR, triglycerides, and HDLc; and resistin with CRP. Adiponectin was associated with VR after Ach in the pooled group and resistin with D FBF after Ach in the metabolic syndrome group.

CONCLUSION

Metabolic syndrome subjects exhibited low levels of adiponectin and high levels of CRP, fibrinogen, and PAI-1. Adiponectin and PAI-1 correlated with insulin resistance markers. Adiponectin and resistin correlated with vascular reactivity parameters. An adipocyte-endothelium interaction might be an important mechanism of inflammation and vascular dysfunction.

Sex-specific association of the androgen to oestrogen ratio with adipocytokine levels in older adults: the Rancho Bernardo Study

OBJECTIVE

Androgens and oestrogens have opposing effects on some adipocyte functions. Thus, the androgen to oestrogen balance may be as important as the individual hormones in determining the biological interaction between endogenous sex hormones and adipocyte-derived factors such as adiponectin and leptin. We tested this hypothesis by evaluating the sex-specific, cross-sectional association of sex hormones and androgen to oestrogen ratios with serum adiponectin and leptin in older men and postmenopausal women.

DESIGN

Cross-sectional.

PARTICIPANTS

A total of 1510 community dwelling men and postmenopausal women aged 50-92 years.

MEASUREMENTS

Serum leptin, adiponectin and sex hormone levels.

RESULTS

Adiponectin and leptin levels were higher in women than men (P < 0.001). In both sexes, adiponectin concentrations were lower, and leptin levels higher, with increasing BMI and waist girth (all P < 0.001). Although the ratio of total testosterone to total oestradiol was significantly associated with both adipocytokines in both sexes, the strongest and most consistent hormone-adipocytokine associations were observed when the androgen to oestrogen ratio was expressed as total testosterone to bioavailable oestradiol. In linear regressions, the testosterone to bioavailable oestradiol ratio was positively related to adiponectin and inversely related to leptin, with nearly identical standardized beta-coefficients for men and women (all P < 0.001). The strength of the hormone ratio-adipocytokine associations was reduced, but not eliminated, after adjustment for age, adiposity and cardiovascular disease risk factors, including insulin resistance.

CONCLUSIONS

The striking similarity of the hormone ratio-adipocytokine associations for men and women, despite wide differences in sex hormone and adipocytokine levels, suggests these results reflect underlying physiological mechanisms common to both sexes.

Complex actions of sex steroids in adipose tissue, the cardiovascular system, and brain: Insights from basic science and clinical studies

Recent publications describing the results of the Women's Health Initiative (WHI) and other studies reporting the impact of hormone therapy on aging women have spurred reexamination of the broad use of estrogens and progestins during the postmenopausal years. Here, we review the complex pharmacology of these hormones, the diverse and sometimes opposite effects that result from the use of different estrogenic and progestinic compounds, given via different delivery routes in different concentrations and treatment sequence, and to women of different ages and health status. We examine our new and growing appreciation of the role of estrogens in the immune system and the inflammatory response, and we pose the concept that estrogen's interface with this system may be at the core of some of the effects on multiple physiological systems, such as the adipose/metabolic system, the cardiovascular system, and the central nervous system. We compare and contrast clinical and basic science studies as we focus on the actions of estrogens in these systems because the untoward effects of hormone therapy reported in the WHI were not expected. The broad interpretation and publicity of the results of the WHI have resulted in a general condemnation of all hormone replacement in postmenopausal women. In fact, careful review of the extensive literature suggests that data resulting from the WHI and other recent studies should be interpreted within the narrow context of the study design. We argue that these results should encourage us to perform new studies that take advantage of a dialogue between basic scientists and clinician scientists to ensure appropriate design, incorporation of current knowledge, and proper interpretation of results. Only then will we have a better understanding of what hormonal compounds should be used in which populations of women and at what stages of menopausal/postmenopausal life.

Association of adiponectin and amino terminal proBNP in peripheral arterial disease

BACKGROUND

The aim of the present study was to investigate the relationship of adiponectin, a novel adipocytokine, and amino terminal proBNP (NT-proBNP) in patients with peripheral arterial disease (PAD).

METHODS

Serum concentrations of adiponectin and NT-proBNP were measured in 487 patients with symptomatic PAD from the Linz Peripheral Arterial Disease (LIPAD) study.

RESULTS

Correlation analysis revealed an association of adiponectin and NT-proBNP (r, +0.47; p<0.001). Even after adjustment for age, sex, body mass index, diabetes mellitus, smoking, arterial hypertension, estimated glomerular filtration rate (eGFR), fasting glucose, LDL-cholesterol, HDL-cholesterol, triglycerides, high-sensitivity C-reactive protein, and total homocysteine the relationship of adiponectin and NT-proBNP remained significant (r, +0.35; p<0.001). Furthermore, a subgroup analysis of patients with first manifestation of symptomatic PAD (n=287) demonstrated that disease severity (classified by Fontaine stages) was positively related to adiponectin (r, +0.13; p=0.003) and NT-proBNP (r, +0.28; p<0.001).

CONCLUSION

Adiponectin was positively associated with NT-proBNP in symptomatic atherosclerotic PAD, independent of traditional and non-traditional risk factors. Moreover, adiponectin and NT-proBNP were related to disease severity, indicating a possible role for assessment of future morbidity and mortality in patients with PAD.

Association of adiponectin gene variations with risk of incident myocardial infarction and ischemic stroke: a nested case-control study

BACKGROUND

Adiponectin (ADIPOQ) gene variations are associated with risk of cardiovascular disease in patients with diabetes. No prospective data are available, however, on the risk of atherothrombotic disorders in persons with ADIPOQ variations who do not have diabetes.

METHODS

From a group of DNA samples collected at baseline in a prospective cohort of 14 916 initially healthy American men, we assessed the presence of 5 ADIPOQ genetic variants (rs266729, rs182052, rs822396, rs2241766, and rs1501299) in samples from 600 Caucasian men who subsequently suffered an atherothrombotic event (incident myocardial infarction or ischemic stroke) and from 600 age- and smoking-matched Caucasian men who remained free of reported vascular disease during follow-up (controls).

RESULTS

Genotype distributions for the variations tested were in Hardy-Weinberg equilibrium. Marker-by-marker conditional logistic regression analysis, adjusted for potential risk factors, showed an association of rs266729 [recessive: odds ratio (OR), 0.26; 95% confidence interval (CI), 0.10-0.64; P=0.004] and rs182052 (recessive: OR, 0.40; 95% CI, 0.21-0.76; P=0.006) with decreased risk of ischemic stroke. These findings remained significant after Bonferroni correction. Haplotype-based (constituted by rs266729, rs182052, and rs822396) conditional logistic regression analysis, adjusted for the same potential risk factors, showed an association of haplotype G-A-G (OR, 0.28; 95% CI, 0.09-0.87; P=0.03) with decreased risk of ischemic stroke. Prespecified analysis limited to participants without baseline diabetes showed similar significant findings.

CONCLUSIONS

The present prospective investigation provides further evidence for a protective role of adiponectin gene variation in the risk of ischemic stroke that was independent of the presence of diabetes.

Short-term caloric restriction improves ischemic tolerance independent of opening of ATP-sensitive K+ channels in both young and aged hearts

Ischemic tolerance decreases with aging and the cardioprotective effect of ischemic preconditioning (IPC) is impaired in aged animals. Although lifelong caloric restriction (CR) profoundly affects the physiological and pathophysiological modifications induced by aging and markedly increases life span in several species, it is unclear whether short-term CR affects ischemic tolerance and IPC in aged hearts. Six-month-old (Y) and 24-month-old (O) Fischer 344 male rats were randomly divided into two groups; AL rats were fed ad libitum, whereas CR rats were fed 90% of the caloric intake of AL for 2 weeks followed by 65% of the caloric intake for 2 weeks. Isolated perfused hearts were subjected to 25 min of ischemia followed by 30 min of reperfusion with or without IPC. The recovery of LV function after reperfusion improved with IPC in ALY but not in ALO. CR improved the recovery of LV function in both CRY and CRO but the cardioprotective effect of IPC was not additive to that of CR. Neither 5-hydroxydecanoate nor glibenclamide abrogated the protective effect of CR in either CRY or CRO. The recovery of myocardial high-energy phosphates after reperfusion was better with CR in both generations. There was no difference in myocardial expression levels of AMP-activated kinase (AMPK) but AMPK-alpha phosphorylated at Thr172 increased with CR in both Y and O. In conclusion, short-term CR improves myocardial ischemic tolerance independent of the opening of KATP channels in both Y and O. CR-induced cardioprotection is associated with an increase in activated AMPK.

Associations between aortic calcification and components of body composition in elderly men

OBJECTIVE

To investigate associations among body composition, cardiovascular risk factors, and atherosclerosis in middle-aged and elderly men for the identification of potential pathogenic links.

RESEARCH METHODS AND PROCEDURES

The study included 168 white men 44 to 86 years old. Severity of aortic calcification (AC) was graded on lateral radiographs, and body fat and lean mass were measured by DXA. Information on demographic and lifestyle characteristics also was gathered.

RESULTS

A strong and independent inverse association was found between AC and peripheral lean mass (PLM), even after adjusting for age and BMI (p < 0.05). Independently of the influence of PLM, AC was directly correlated with truncal fat mass (p < 0.05). Furthermore, AC was inversely associated with tertiles of the free androgen index (p < 0.05). In a multiple regression model, age and serum cholesterol (p < 0.01) contributed directly, and truncal fat mass tended also to contribute directly (p = 0.09), whereas PLM contributed borderline inversely (p = 0.06) to the variation of AC (R = 0.635, p < 0.0001).

DISCUSSION

Severity of AC is strongly dependent on age and further modulated by an array of traditional cardiovascular risk factors. Sarcopenia and truncal fat mass are reciprocal correlates of atherosclerosis of borderline statistical significance in multivariate models. To clarify whether sarcopenia is an atherogenic risk factor or rather a parallel consequence of low-grade inflammation also promoting atherogenic trends, further longitudinal studies in larger sample sizes of men and women are needed.

Relationship between serum adiponectin level and lipid composition in each lipoprotein fraction in adolescent children

The association of lipid composition in each lipoprotein fraction with adiponectin level in relation to body fatness was investigated. The subjects were 283 children (144 boys and 139 girls) aged 11.6 years (S.D. 1.5). Cholesterol (C) and triglyceride (TG) levels in each lipoprotein fraction were measured by a combination of agarose gel electrophoresis and differential staining. Adiponectin level was not significantly different between girls and boys. In simple regression analyses, an association of adiponectin level with lipoprotein lipid profile was shown only in girls, and not in boys at all. In girls, very low-density lipoprotein (VLDL)-C, low-density lipoprotein (LDL)-C, VLDL-TG and LDL-TG were negatively correlated with adiponectin level, and high-density lipoprotein (HDL)-C and HDL-C/TG ratio were positively correlated. Multiple regression analyses including adiponectin level and body mass index (BMI) as predictors for the lipoprotein lipid profile demonstrated that adiponectin level was a significant independent predictor of VLDL-TG, LDL-C, LDL-TG, HDL-C and HDL-C/TG ratio. In conclusion, adiponectin level correlates with lipoprotein lipid profile independent of body fatness in adolescent girls.

Reduced levels of adiponectin in sleep apnea syndrome

BACKGROUND

To investigate adiponectin levels in an obese population with and without obstructive sleep apnea syndrome (OSAS) and the acute modifications in adiponectin after a whole-night control by auto continuous positive air pressure (CPAP).

METHODS

46 obese subjects [22 males, 24 females, age 55.1+/-11.4 yr, body mass index (BMI) 38.9+/-6.5 kg/m2]: 11 OSAS with apnea/hypopnea index (AHI) from 10/h to 30/h, 14 OSAS with AHI >30/h and 21 without OSAS. Thirty-seven normal weight healthy subjects (20 males, 17 females, age 31.3+/-9.5 yr, BMI 21.5+/-1.8 kg/m2). Serum adiponectin levels, biochemical parameters, anthropometric measurements, pulmonary function, pulse-oxymetry and polisomnography.

RESULTS

The 3 groups of obese patients were comparable for gender, BMI, age, fat mass, fat free mass, hip and waist circumference, waist-to-hip ratio (WHR), systolic and diastolic blood pressure and glycometabolic parameters. Adiponectin levels were significantly reduced in obese patients compared to healthy normal weight subjects (8.1+/-3.5 vs 11.3+/-4.8 microg/ml p<0.001) In particular, adiponectin showed a trend to decrease according to the severity of OSAS. No differences in adiponectin levels were found after a whole-night control by Auto CPAP.

CONCLUSIONS

OSAS is associated with reduced levels of adiponectin independently of insulin-resistance and BMI. These low adiponectin levels may contribute to the increased mortality seen in such patients.

Serum adiponectin is related to plasma high-density lipoprotein cholesterol but not to plasma insulin-concentration in healthy children: the FLVS II study

Although low levels of plasma adiponectin were associated with an increase in cardiovascular risk in adults, few data investigated that relationship in children. The aim of this study was to investigate the relationship between plasma adiponectin and cardiovascular risk factors in healthy children. This cross-sectional population-based study was conducted in Fleurbaix and Laventie, 2 cities in the north of France. The main outcome measure was the correlations between plasma adiponectin and adiposity variables (the body mass index, the sum of 4 skinfolds, waist circumference [WC], and percent body fat [bioimpedance]), blood pressure, plasma glucose, triglycerides, high-density lipoprotein (HDL) cholesterol and insulin. In 398 children of both sexes, adiponectin was not significantly related to age and pubertal stage. In boys only, adiponectin correlated with WC (r = -0.19; P = .008) and body mass index (r = -0.15; P = .04) but not with other adiposity variables. After taking into account WC, adiponectin was positively correlated with HDL-cholesterol in boys (r = 0.14; P = .05) and girls (r = 0.25; P = .0004), but was not correlated with insulin and homeostasis model assessment index for insulin resistance in both sexes. These results suggest that, in apparently healthy children, adiponectin is related to the level of HDL-cholesterol independently of fat mass. The relationship between adiponectin and insulin resistance previously reported in obese or diabetic children was not apparent in these subjects and may therefore occur only at later age with fat accumulation.

Smoking is not associated with nonalcoholic fatty liver disease

AIM: To analyze the relationship between smoking and nonalcoholic fatty liver disease (NAFLD).

METHODS: This is a cross-sectional study of a healthy population, carried out in a check-up unit of a university hospital in Mexico City. We enrolled 933 subjects, 368 current smokers (cases) and 565 persons who had never smoked (controls). Demographic, metabolic and biochemical variables were measured in the two groups. NAFLD was determined by ultrasound and metabolic syndrome according to ATPIII.

RESULTS: A total of 548 men (205 cases and 343 controls) and 337 women (114 cases and 223 controls) were included in the analysis. Statistical differences between cases and controls were observed only in high blood pressure prevalence (6.6% vs 11.3%, P < 0.05; cases and controls respectively), high-density lipoproteins (1.00 ± 0.26 vs 1.06 ± 0.28 mmol/L, P < 0.005), triglycerides (2.18 ± 1.49 vs 1.84 ± 1.1 mmol/L, P < 0.001), and erythrocyte sedimentation rate (11.3 ± 9.3 vs 13.5 ± 11.9 mm/h, P < 0.001). No differences were observed in the prevalence of NAFLD (22.27% vs 29.68%, P = NS) and metabolic syndrome (41.69% vs 36.74%, P = NS). Univariate analysis showed that smoking was not a risk factor for NAFLD (OR = 0.89, 95% CI 0.65-1.21).

CONCLUSION: No differences in NAFLD prevalence were observed between current smokers and nonsmokers, and furthermore, no differences were observed in heavy smokers (more than 20 packs/year), indicating that there is no relationship between smoking and NAFLD.

Adiponectin and mortality in patients with chronic kidney disease

Adiponectin is presumed to possess antiatherogenic and cardioprotective properties. Limited data exist on the relationship between adiponectin and mortality in the earlier stages of chronic kidney disease. The Modification of Diet in Renal Disease study was a randomized, controlled trial that was conducted between 1989 and 1993. Adiponectin was measured in frozen samples that were obtained at baseline (N = 820). Survival status and cause of death, up to December 31, 2000, were obtained from the National Death Index. Multivariable Cox models were used to examine the relationship of adiponectin with all-cause and cardiovascular mortality. Mean +/- SD age was 52 +/- 12 yr, and mean +/- SD glomerular filtration rate (GFR) rate was 33 +/- 12 ml/min per 1.73 m2. Eighty-five percent of participants were white, and 60% were male. Mean +/- SD adiponectin was 12.8 +/- 8.0 mug/ml. Triglycerides, insulin resistance, glucose, body mass index, GFR, C-reactive protein, and albumin were inversely related and proteinuria and HDL cholesterol were directly related to adiponectin. During the 10-year follow-up period, 201 (25%) participants died of any cause, and 122 (15%) from cardiovascular disease. In multivariable adjusted Cox models, a 1-mug/ml increase in adiponectin was associated with a 3% (hazard ratio 1.03; 95% confidence interval 1.01 to 1.05; P = 0.02) increased risk for all-cause and 6% (hazard ratio 1.06; 95% confidence interval 1.03 to 1.09; P < 0.001) increased risk for cardiovascular mortality. High, rather than low, adiponectin is associated with increased mortality in this cohort of patients with chronic kidney disease stages 3 to 4. Further studies are necessary to confirm this association and to elucidate the underlying mechanisms.

The importance of catch-up growth after early malnutrition for the programming of obesity in male rat

OBJECTIVE

To investigate whether catch-up growth after maternal malnutrition would favor the development of obesity in adulthood.

RESEARCH METHODS AND PROCEDURES

Pregnant rats were submitted to protein or calorie restriction during the course of gestation. During lactation, pups were protein-restricted, normally fed, or overfed [reduced litter size, control (C) diet]. At weaning, rats were transferred to chow or to a hypercaloric diet (HCD) known to induce obesity. Body weight, food intake, blood parameters, glucose tolerance, adipocyte cellularity, and adipose factors contributing to cardiovascular disease development were measured.

RESULTS

Protein and calorie restriction during gestation led to growth retardation at birth. If malnutrition was prolonged throughout lactation, adult body weight was permanently reduced. However, growth-retarded offspring overfed during the suckling period underwent a rapid catch-up growth and became heavier than the normally fed Cs. Offspring of calorie-restricted rats gained more weight than those of dams fed protein-restricted diet. Feeding an HCD postnatally amplified the effect of calorie restriction, and offspring that underwent catch-up growth became more obese than Cs. The HCD was associated with hyperphagia, hyperglycemia, hyperinsulinemia, glucose intolerance, insulin resistance, and adipocyte hypertrophy. The magnitude of effects varied depending on the type and the timing of early malnutrition. The expression of genes encoding factors implicated in cardiovascular disease was also modulated differently by early malnutrition and adult obesity.

DISCUSSION

Catch-up growth immediately after early malnutrition should be a key point for the programming of obesity.

Selective increase in high molecular weight adiponectin concentration in serum of women with preeclampsia

Total adiponectin concentrations have been shown to increase in serum of preeclamptic women. However, variance of concentrations of different isoforms has not been studied, despite the emerging notion that high, medium and low molecular weight adiponectin exert different functions. We have determined serum concentrations of each adiponectin isoform using a newly developed enzyme immunosorbent assay. High molecular weight (HMW) adiponectin concentrations were significantly higher in women with preeclampsia (n=14; median, 11.2 microg/ml; interquartile range, 9.2-15.8) compared to normal pregnant women (n=14; 6.8 microg/ml, 5.4-10.7; P=0.04). In contrast, medium molecular weight and low molecular weight adiponectin concentrations were substantially equal between the groups. The ratio of HMW adiponectin to total adiponectin was also markedly higher in preeclamptic women (52.3%, 49.5-58.7) than control women (43.0%; 39.8-48.0; P=0.004). Taken together with other reports our findings imply a physiological feedback response to minimize endothelial damage in preeclamptic women.

Expression of adiponectin receptors and its possible implication in the human endometrium

Adiponectin, a pleiotropic cytokine, exerts its effects via the specific receptors AdipoR1 and AdipoR2. Whereas circulating adiponectin concentrations decrease in women with endometriosis and endometrial cancer, possible effects of adiponectin and the presence of the receptors in the endometrium have not been determined. In this study, we examined the expression of adiponectin receptors AdipoR1 and AdipoR2 in the human endometrium and assessed effects of adiponectin in endometrial cells. Expression of AdipoR1 and AdipoR2 in endometrial tissues was evaluated by real-time quantitative PCR, in situ hybridization, and Western blotting. The effects of adiponectin on phosphorylation of AMP-activated protein kinase, a regulator of energy homeostasis, in cultured endometrial stromal cells (ESCs) and epithelial cells (EECs) were studied by Western blotting. The effects of adiponectin on IL-1beta-induced secretion of IL-6, IL-8, and monocyte chemoattractant protein 1 from cultured ESCs were determined using specific ELISAs. The expression of AdipoR1 and AdipoR2 was detected in the endometrium. The expression of both genes was increased in the midluteal phase, the period of embryo implantation. In situ hybridization revealed that both AdipoR1 and AdipoR2 appeared to be equally expressed in the epithelial cells and in the stromal cells. Adiponectin increased phosphorylation of AMP-activated protein kinase in ESCs and EECs. Adiponectin decreased IL-1beta-induced secretion of IL-6, IL-8, and monocyte chemoattractant protein 1 from ESCs. These findings suggest that adiponectin exerts energy-homeostatic and antiinflammatory effects in the endometrium, and these effects might be relevant to pathological and physiological endometrium-related events such as implantation and endometriosis.

Adiponectin and cancer: a systematic review

Recent studies have demonstrated that obesity is a significant risk factor for the development of several malignancies, but the mechanisms underlying this relationship remain to be fully elucidated. Adiponectin, an adipocyte secreted endogenous insulin sensitizer, appears to play an important role not only in glucose and lipid metabolism but also in the development and progression of several obesity-related malignancies. In this review, we present recent findings on the association of adiponectin with several malignancies as well as recent data on underlying molecular mechanisms that provide novel insights into the association between obesity and cancer risk. We also identify important research questions that remain unanswered.

Adiponectin suppression of high-glucose-induced reactive oxygen species in vascular endothelial cells: evidence for involvement of a cAMP signaling pathway

Adiponectin is an abundant adipocyte-derived plasma protein with antiatherosclerotic effects. Vascular signal transduction by adiponectin is poorly understood and may involve 5'-AMP-activated protein kinase (AMPK), cAMP signaling, and other pathways. Hyperglycemia sharply increases the production of reactive oxygen species (ROS), which play a key role in endothelial dysfunction in diabetes. Because the recombinant globular domain of human adiponectin (gAd) reduces the generation of endothelial ROS induced by oxidized LDL, we sought to determine whether adiponectin could also suppress ROS production induced by high glucose in cultured human umbilical vein endothelial cells. Incubation in 25 mmol/l glucose for 16 h increased ROS production 3.8-fold (P<0.05), using a luminol assay. Treatment with gAd for 16 h suppressed glucose-induced ROS in a dose-dependent manner up to 81% at 300 nmol/l (P<0.05). The AMPK activator 5-aminoimidazole-4-carboxamide-1-beta-D-ribofuranoside (AICAR; 1 mmol/l, 16 h) only partially decreased glucose-induced ROS by 22% (P<0.05). Cell pretreatment with AMPK inhibitors, however, failed to block the effect of gAd to suppress glucose-induced ROS, suggesting that the action of gAd was independent of AMPK. Interestingly, activation of cAMP signaling by treatment with forskolin (2 micromol/l) or dibutyryl-cAMP (0.5 mmol/l) reduced glucose-induced ROS generation by 43 and 67%, respectively (both P<0.05). Incubation with the cAMP-dependent protein kinase (PKA) inhibitor H-89 (1 micromol/l) fully abrogated the effect of gAd, but not that of AICAR, on ROS induced by glucose. gAd also increased cellular cAMP content by 70% in an AMPK-independent manner. Full-length adiponectin purified from a eukaryotic expression system also suppressed ROS induced by high glucose or by treatment of endothelial cells with oxidized LDL. Thus, adiponectin suppresses excess ROS production under high-glucose conditions via a cAMP/PKA-dependent pathway, an effect that has implications for vascular protection in diabetes.

Cardiovascular death and the metabolic syndrome: role of adiposity-signaling hormones and inflammatory markers

OBJECTIVE

Levels of adiposity-signaling hormones and inflammatory markers are less favorable in individuals with the metabolic syndrome; their role in the association between the metabolic syndrome and cardiovascular mortality remains unclear.

RESEARCH DESIGN AND METHODS

We conducted a prospective study of 977 men and 1,141 women aged 40-94 years in 1984-1987, followed for mortality for a maximum of 20 years. Adiponectin, leptin, ghrelin, interleukin-6 (IL-6), C-reactive protein (CRP), and Adult Treatment Panel III-defined metabolic syndrome components were measured in fasting blood samples obtained in 1984-1987. Cox-proportional hazards models were used in survival analyses.

RESULTS

The age- and sex-adjusted hazard ratio (HR) (95% CI) for coronary heart disease (CHD) mortality associated with the metabolic syndrome was 1.65 (1.25-2.18) (P < 0.001); this association did not differ significantly by sex, age, or diabetic status (P > 0.2 for each interaction). The association between the metabolic syndrome and CHD mortality was not materially changed after adjustment for adiponectin, leptin, and ghrelin; it was attenuated by 25% after adjustment for IL-6 and 35% after adjustment for CRP. CHD mortality increased linearly with greater levels of IL-6 and CRP (P(trend) < 0.001 for each); the age- and sex-adjusted HRs comparing highest versus lowest quarter were 3.0 (1.87-4.89) for IL-6 and 2.1 (1.41-3.21) for CRP. IL-6, but not CRP, remained a significant predictor of CHD mortality in models including both inflammatory markers and the metabolic syndrome.

CONCLUSIONS

Adiposity-signaling hormones and inflammatory markers explain little to some of the association between the metabolic syndrome and CHD mortality. IL-6 levels predict CHD mortality independently of CRP.

Identification and characterization of a small molecule AMPK activator that treats key components of type 2 diabetes and the metabolic syndrome

AMP-activated protein kinase (AMPK) is a key sensor and regulator of intracellular and whole-body energy metabolism. We have identified a thienopyridone family of AMPK activators. A-769662 directly stimulated partially purified rat liver AMPK (EC50 = 0.8 microM) and inhibited fatty acid synthesis in primary rat hepatocytes (IC50 = 3.2 microM). Short-term treatment of normal Sprague Dawley rats with A-769662 decreased liver malonyl CoA levels and the respiratory exchange ratio, VCO2/VO2, indicating an increased rate of whole-body fatty acid oxidation. Treatment of ob/ob mice with 30 mg/kg b.i.d. A-769662 decreased hepatic expression of PEPCK, G6Pase, and FAS, lowered plasma glucose by 40%, reduced body weight gain and significantly decreased both plasma and liver triglyceride levels. These results demonstrate that small molecule-mediated activation of AMPK in vivo is feasible and represents a promising approach for the treatment of type 2 diabetes and the metabolic syndrome.

Plasma adiponectin, T94G gene polymorphism and PAI-1 in patients with and without hypertension

BACKGROUND

Reduced adiponectin level has been associated with metabolic syndrome, type 2 diabetes, coronary artery disease and gene polymorphisms, but the interrelationships of T94G genotype, plasma adiponectin and plasminogen activator inhibitor-1 (PAI-1) are less understood.

PATIENTS AND METHODS

The T94G genotypes and plasma levels of adiponectin, and PAI-1 were determined in 568 Chinese patients, 212 with and 356 without hypertension, to study the possible associations of T94G genotype, plasma adiponectin, PAI-1 and blood pressure.

RESULTS

Hypertensive patients showed significantly lower plasma adiponectin (9.7 +/- 11.1 vs. 11.5 +/- 10.0 microg/ml, p = 0.04) and higher PAI-1 (p < 0.001) levels but not significantly greater adiponectin TT genotype percentage (38.7 vs. 33.5%) and T allele frequency (0.620 vs. 0.585) than normotensive subjects. Plasma adiponectin was inversely related to PAI-1 activity (r = -0.09, p = 0.03) and antigen (r = -0.202, p < 0.001). Furthermore, the TT genotypic group showed significantly lower plasma adiponectin level (10.4 +/- 10.5 vs. 13.4 +/- 10.8 mug/ml, p = 0.03) and higher plasma PAI-1 activity (17.0 +/- 9.7 vs. 13.5 +/- 7.6 IU/ml, p = 0.003) and antigen (32.3 +/- 22.7 vs. 25.9 +/- 14.7 ng/ml, p = 0.01) than the GG genotypic group. Multiple linear regression analysis in all study subjects, in men and in normotensives documented an impact of adiponectin T94G genotype on plasma levels of adiponectin (p = 0.007, 0.003 and 0.03) and PAI-1 activity (p = 0.02, 0.03 and 0.04) and antigen (p = 0.03, 0.007 and 0.04) after adjustment for potential confounding factors.

CONCLUSIONS

The present study demonstrated a significant correlation of the TT genotype with lower plasma adiponectin and higher plasma PAI-1 levels in a Chinese population. The contribution of this genotype seemed greater in men and normotensives. It suggested the adiponectin gene T94G polymorphism might affect the regulation of circulating adiponectin and PAI-1.

The good fat hormone: adiponectin and cardiovascular disease

New treatments for heart disease continue to be of paramount importance. The newest pandemic facing us is the rise of obesity and diabetes. One new area of research in the field of metabolism is the hormone adiponectin, which is secreted by fat cells. For the most part, this compound seems more likely to be a part of basic science-oriented research; however, it deserves a much closer look. Many compounds such as high-density lipoprotein and others at first were simply markers of disease but later found to be much more important. During this short review, research from basic science to clinical cardiovascular events is discussed in relation to adiponectin.

Reciprocal relationships between insulin resistance and endothelial dysfunction: molecular and pathophysiological mechanisms

Endothelial dysfunction contributes to cardiovascular diseases, including hypertension, atherosclerosis, and coronary artery disease, which are also characterized by insulin resistance. Insulin resistance is a hallmark of metabolic disorders, including type 2 diabetes mellitus and obesity, which are also characterized by endothelial dysfunction. Metabolic actions of insulin to promote glucose disposal are augmented by vascular actions of insulin in endothelium to stimulate production of the vasodilator nitric oxide (NO). Indeed, NO-dependent increases in blood flow to skeletal muscle account for 25% to 40% of the increase in glucose uptake in response to insulin stimulation. Phosphatidylinositol 3-kinase-dependent insulin-signaling pathways in endothelium related to production of NO share striking similarities with metabolic pathways in skeletal muscle that promote glucose uptake. Other distinct nonmetabolic branches of insulin-signaling pathways regulate secretion of the vasoconstrictor endothelin-1 in endothelium. Metabolic insulin resistance is characterized by pathway-specific impairment in phosphatidylinositol 3-kinase-dependent signaling, which in endothelium may cause imbalance between production of NO and secretion of endothelin-1, leading to decreased blood flow, which worsens insulin resistance. Therapeutic interventions in animal models and human studies have demonstrated that improving endothelial function ameliorates insulin resistance, whereas improving insulin sensitivity ameliorates endothelial dysfunction. Taken together, cellular, physiological, clinical, and epidemiological studies strongly support a reciprocal relationship between endothelial dysfunction and insulin resistance that helps to link cardiovascular and metabolic diseases. In the present review, we discuss pathophysiological mechanisms, including inflammatory processes, that couple endothelial dysfunction with insulin resistance and emphasize important therapeutic implications.

Adiponectin--a key adipokine in the metabolic syndrome

Adiponectin is a recently described adipokine that has been recognized as a key regulator of insulin sensitivity and tissue inflammation. It is produced by adipose tissue (white and brown) and circulates in the blood at very high concentrations. It has direct actions in liver, skeletal muscle and the vasculature, with prominent roles to improve hepatic insulin sensitivity, increase fuel oxidation [via up-regulation of adenosine monophosphate-activated protein kinase (AMPK) activity] and decrease vascular inflammation. Adiponectin exists in the circulation as varying molecular weight forms, produced by multimerization. Recent data indicate that the high-molecular weight (HMW) complexes have the predominant action in the liver. In contrast to other adipokines, adiponectin secretion and circulating levels are inversely proportional to body fat content. Levels are further reduced in subjects with diabetes and coronary artery disease. Adiponectin antagonizes many effects of tumour necrosis factor-alpha(TNF-alpha) and this, in turn, suppresses adiponectin production. Furthermore, adiponectin secretion from adipocytes is enhanced by thiazolidinediones (which also act to antagonize TNF-alpha effects). Thus, adiponectin may be the common mechanism by which TNF-alpha promotes, and the thiazolidinediones suppress, insulin resistance and inflammation. Two adiponectin receptors, termed AdipoR1 and AdipoR2, have been identified and these are ubiquitously expressed. AdipoR1 is most highly expressed in skeletal muscle and has a prominent action to activate AMPK, and hence promote lipid oxidation. AdipoR2 is most highly expressed in liver, where it enhances insulin sensitivity and reduces steatosis via activation of AMPK and increased peroxisome-proliferator-activated receptor alpha ligand activity. T-cadherin, which is expressed in endothelium and smooth muscle, has been identified as an adiponectin-binding protein with preference for HMW adiponectin multimers. Given the low levels of adiponectin in subjects with the metabolic syndrome, and the beneficial effect of the adipokine in animal studies, there is exciting potential for adiponectin replacement therapy in insulin resistance and related disorders.

Effects of acquired obesity on endothelial function in monozygotic twins

OBJECTIVE

To determine whether acquired obesity or accompanying metabolic changes such as adiponectin deficiency, insulin resistance, dyslipidemia, or visceral fat are associated, independent of genetic influences, with endothelial dysfunction by studying young adult monozygotic (MZ) twin pairs discordant for obesity.

RESEARCH METHODS AND PROCEDURES

Nine obesity-discordant (intra-pair difference in BMI, 3.8 to 10.1 kg/m(2)) and nine concordant (0 to 2.3 kg/m(2)) 24- to 27-year-old MZ twin pairs were identified from a population-based FinnTwin16-sample. Endothelial function was measured by blood flow responses to intrabrachial infusions of an endothelium-dependent (acetylcholine) and an endothelium-independent (sodium nitroprusside) vasodilator. Whole body insulin sensitivity was measured using the euglycemic insulin clamp technique, and forearm and body composition were measured with magnetic resonance imaging and DXA. In addition, serum levels of adiponectin, high-sensitivity C-reactive protein, and lipids were determined.

RESULTS

The heavier co-twins of the discordant pairs had significantly lower whole body insulin sensitivity than the leaner co-twins. Blood flows/muscle volume during infusions of acetylcholine and sodium nitroprusside were not altered by obesity. However, intra-pair differences in serum adiponectin, intra-abdominal fat, and C-reactive protein were significantly correlated with those in endothelial function. Only the relationship between intra-pair differences in adiponectin and endothelial function persisted in multiple linear regression analysis. Obesity-concordant co-twins had comparable insulin sensitivity and endothelial function.

DISCUSSION

In young adult MZ twins discordant for obesity, acquired adiponectin deficiency rather than obesity per se is an independent correlate of endothelial dysfunction.

Adiponectin normalizes LPS-stimulated TNF-alpha production by rat Kupffer cells after chronic ethanol feeding

Chronic ethanol feeding sensitizes Kupffer cells to activation by lipopolysaccharide (LPS), leading to increased production of tumor necrosis factor-alpha (TNF-alpha). Adiponectin treatment protects mice from ethanol-induced liver injury. Because adiponectin has anti-inflammatory effects on macrophages, we hypothesized that adiponectin would normalize chronic ethanol-induced sensitization of Kupffer cells to LPS-mediated signals. Serum adiponectin concentrations were decreased by 45% in rats fed an ethanol-containing diet for 4 wk compared with pair-fed rats. Adiponectin dose dependently inhibited LPS-stimulated accumulation of TNF-alpha mRNA and peptide in Kupffer cells from both pair- and ethanol-fed rats. Kupffer cells from ethanol-fed rats were more sensitive to both globular (gAcrp) and full-length adiponectin (flAcrp) than Kupffer cells from pair-fed controls with suppression at 10 ng/ml adiponectin after chronic ethanol feeding. Kupffer cells expressed both adiponectin receptors 1 and 2; chronic ethanol feeding did not change the expression of adiponectin receptor mRNA or protein. gAcrp suppressed LPS-stimulated ERK1/2 and p38 phosphorylation as well as IkappaB degradation at 100-1,000 ng/ml in Kupffer cells from both pair- and ethanol-fed rats. However, only LPS-stimulated ERK1/2 phosphorylation was sensitive to 10 ng/ml gAcrp. gAcrp also normalized LPS-stimulated DNA binding activity of early growth response-1 with greater sensitivity in Kupffer cells from rats fed chronic ethanol. In conclusion, these results demonstrate that Kupffer cells from ethanol-fed rats are more sensitive to the anti-inflammatory effects of both gAcrp and flAcrp. Suppression of LPS-stimulated ERK1/2 signaling by low concentrations of gAcrp was associated with normalization of TNF-alpha production by Kupffer cells after chronic ethanol exposure.

AMPK and cell proliferation--AMPK as a therapeutic target for atherosclerosis and cancer

AMPK is a serine/threonine protein kinase, which serves as an energy sensor in all eukaryotic cell types. Published studies indicate that AMPK activation strongly suppresses cell proliferation in non-malignant cells as well as in tumour cells. These actions of AMPK appear to be mediated through multiple mechanisms including regulation of the cell cycle and inhibition of protein synthesis, de novo fatty acid synthesis, specifically the generation of mevalonate as well as other products downstream of mevalonate in the cholesterol synthesis pathway. Cell cycle regulation by AMPK is mediated by up-regulation of the p53-p21 axis as well as regulation of TSC2-mTOR (mammalian target of rapamycin) pathway. The AMPK signalling network contains a number of tumour suppressor genes including LKB1, p53, TSC1 and TSC2, and overcomes growth factor signalling from a variety of stimuli (via growth factors and by abnormal regulation of cellular proto-oncogenes including PI3K, Akt and ERK). These observations suggest that AMPK activation is a logical therapeutic target for diseases rooted in cellular proliferation, including atherosclerosis and cancer. In this review, we discuss about exciting recent advances indicating that AMPK functions as a suppressor of cell proliferation by controlling a variety of cellular events in normal cells as well as in tumour cells.

O endotélio na síndrome metabólica

O endotélio é responsável pela manutenção da homeostase vascular. Em condições fisiológicas, mantém o tônus vascular, o fluxo sangüíneo laminar, a fluidez da membrana plasmática, o equilíbrio entre coagulação e fibrinólise, a inibição da proliferação e da migração celulares e o controle da resposta inflamatória. A disfunção endotelial é definida como uma alteração do relaxamento vascular por diminuição da biodisponibilidade de fatores de relaxamento derivados do endotélio, principalmente o óxido nítrico (NO). Estas respostas vasomotoras anormais ocorrem na presença de inúmeros fatores de risco para a aterosclerose. A síndrome metabólica é considerada um estado de inflamação crônica que se acompanha de disfunção endotelial e ocasiona aumento na incidência de eventos isquêmicos cardiovasculares e elevada mortalidade. Essa revisão abordará o processo fisiológico de regulação da função vascular pelo endotélio, os métodos disponíveis para avaliação in vivo da disfunção endotelial e as terapias capazes de melhorar a função vascular e conseqüentemente minimizar o risco cardiovascular dessa síndrome tão prevalente no nosso meio.

Citocinas, disfunção endotelial e resistência à insulina

A disfunção endotelial está associada a diversas alterações vasculares, como a aterosclerose, hipertensão arterial, hiperlipidemia e diabetes mellitus, que têm em comum a resistência à insulina (RI). Citocinas são proteínas de baixo peso molecular, com diversas funções metabólicas e endócrinas, que participam da inflamação e resposta do sistema imune. Várias dessas citocinas são consideradas como fatores de risco independentes para doenças da artéria coronária e cerebrovascular. As principais fontes de citocinas (adipocinas) são os tecidos adiposos subcutâneo e visceral. Assim, aumento da massa de tecido adiposo está associado com alterações da produção de adipocina com aumento da expressão de fator de necrose tumoral alfa (TNF-alfa), interleucina 6 (IL-6), inibidor do fator ativador de plasminogênio 1 (PAI-1), e diminuição da expressão de adiponectina no tecido adiposo. A condição pró-inflamatória associada a essas alterações sugere ligação entre RI e disfunção endotelial no estágio inicial do processo de aterosclerose, em indivíduos obesos e em pacientes diabéticos tipo 2. A redução da massa de tecido adiposo, por redução de peso associada a exercício físico, reduz TNF-alfa, IL-6 e PAI-1, aumenta adiponectina, e melhora tanto a sensibilidade à insulina quanto a função endotelial. A interação entre adipocinas e insulina no controle da função endotelial será discutida, bem como o conceito de que a alteração da secreção de adiponectinas na RI e/ou obesidade piora a função endotelial, além de diminuir ainda mais a sensibilidade à insulina.

Endothelial dysfunction in PCOS: role of obesity and adipose hormones

PURPOSE

Polycystic ovary syndrome (PCOS) is an extremely prevalent disorder in which elevated blood markers of cardiovascular risk and altered endothelial function have been found. This study was designed to determine if abnormal carotid intima-media thickness (IMT) and brachial flow-mediated dilation (FMD) in young women with PCOS may be explained by insulin resistance and elevated adipocytokines.

METHODS

A prospective study in 50 young women with PCOS (age: 25.2 +/- 1 years; body mass index [BMI]: 28.7 +/- 0.8) and 50 matched ovulatory controls (age: 25.1 +/- 0.7 years; BMI: 28.5 +/- 0.5) was performed. Carotid IMT, brachial FMD, and blood for fasting glucose, insulin, leptin, adiponectin and resistin were measured.

RESULTS

PCOS, IMT was increased (P <.01), FMD was decreased (P <.01), fasting insulin was increased (P <.01), QUICKI (a marker of insulin resistance) was decreased (P <.01), and adiponectin was lower (P <.05), whereas leptin and resistin were not different compared with matched controls. Whereas BMI or waist/hip ratios did not correlate with IMT or FMD, insulin and QUICKI correlated positively and negatively with IMT (P <.01). There was a significant negative correlation between adiponectin and IMT (P <.05). These correlations were unchanged when adjusting for BMI and the correlation between IMT and adiponectin was unaffected by insulin resistance parameters.

CONCLUSIONS

These data suggest that young women with PCOS have evidence for altered endothelial function. Adverse endothelial parameters were correlated with insulin resistance and lower adiponectin. Both insulin resistance and adiponectin appear to be important parameters. It is hypothesized that the type of fat distribution may influence these factors.

Adiponectin is an important determinant of apoA-I catabolism

OBJECTIVE

Plasma concentration of adiponectin is positively correlated with high-density lipoprotein (HDL) cholesterol level. However, the role of adiponectin on HDL metabolism remains unknown. This prompted us to perform an in vivo kinetic study of apoA-I, the main apolipoprotein of HDL, using stable isotopes, in 22 subjects with a wide range of plasma adiponectin, including 11 patients with metabolic syndrome (8 with type 2 diabetes, 3 without type 2 diabetes) and 11 normal individuals.

METHODS AND RESULTS

In the 22 studied subjects, plasma adiponectin levels ranged from 2.57 to 14.44 microg/mL and apoA-I fractional catabolic rate (FCR) values ranged from 0.142 to 0.340 day(-1). A strong negative correlation was found between adiponectin and apoA-I FCR (r=-0.66, P<0.001) in the whole studied population and, to a similar extent, in patients with metabolic syndrome (r=-0.73, P=0.010) and normal subjects (r=-0.68, P=0.020), separately. In multivariable analysis, apoA-I FCR was associated negatively with adiponectin (P=0.005) and positively with HDL triglycerides/cholesterol ratio (P=0.006), but not with age, sex, body mass index (BMI), waist circumference, plasma triglycerides, HDL cholesterol, fasting glycemia, and QUICKI. Both adiponectin and HDL triglycerides/cholesterol ratio explained 62% of the variance of apoA-I FCR and adiponectin on its own explained 43%.

CONCLUSIONS

Our kinetic study shows a strong negative correlation between adiponectin and apoA-I FCR, which can explain the positive link between HDL cholesterol and adiponectin. This association is independent of obesity, insulin resistance, and the content of triglycerides within HDL particles. These data suggest that adiponectin may have a direct role on HDL catabolism.

Green tea leaf extract improves lipid and glucose homeostasis in a fructose-fed insulin-resistant hamster model

The present study evaluated the effect of green tea (Camellia sinensis L.) leaf extract on triglyceride and glucose homeostasis in a fructose-fed hypertriglyceridemic, insulin-resistant hamster model. There was a significant decrease in plasma triglyceride levels following supplementation of the green tea epigallocatechin gallate-enriched extract (42% at 150 mg/(kg day) to 62% at 300 mg/(kg day) for 4 weeks). Compared to baseline, the fructose control group at the end of the study showed elevated serum insulin and apolipoprotein B levels, and decreased serum adiponectin levels. The fructose/green tea extract group showed a reversal in all of these metabolic defects, including an improvement in glucose levels during a glucose tolerance test. Triglyceride content was also examined in various tissues and compared to the control fructose group; supplementation of the green tea extract (300 mg/kg) reduced triglyceride content in liver and heart tissues. There was molecular evidence of improved lipid and glucose homeostasis based on peroxisome proliferator-activated receptor (PPAR) protein expression. Compared to the control fructose group, supplementation of the green tea extract (300 mg/kg) significantly increased PPARalpha and PPARgamma protein expression. In summary, the data suggest that intake of the green tea extract ameliorated the fructose-induced hypertriglyceridemia and the insulin-resistant state in part through PPAR.

Adipocyte: a potential target for the treatment of atherosclerosis

Obesity is an independent risk factor for coronary heart disease, whereas the underlying mechanisms have not been fully elucidated. Adipocytes may produce various adipokines with favorable and unfavorable cardiovascular effects. The dysregulated secretion of adipokines by adipocytes may contribute to obese associated atherosclerosis. Adipocytes can also function as phagocytes to uptake and degrade oxidized low-density lipoprotein (Ox-LDL), suggesting that adipocytes possibly involve in clearance of Ox-LDL in blood. The dysfunctional adipocytes might be implicated in the atherogenesis. Some cardioprotective drugs mediate their cardiovascular benefits partly through their direct beneficial effects on adipocytes. Therefore, we hypothesized that adipocytes might be potential target for the treatment of atherosclerosis.

Metabolic actions of adipocyte hormones: focus on adiponectin

The obesity epidemic has focused attention on the endocrine function of adipose tissue. Adipose tissue secretes leptin, cytokines, complement factors, and components of the coagulation cascade, most of which are increased in obesity. In contrast, a strong negative correlation exists between adiponectin and adiposity, insulin sensitivity, diabetes, vascular inflammation, and atherosclerosis. Adiponectin treatment in rodents increases insulin sensitivity and reduces lipids and atherogenesis. Chronic and central adiponectin treatment reduces weight, glucose, and lipids. The insulin-sensitizing action of thiazolidinediones is mediated, in part, through adiponectin. A causal role of adiponectin in diabetes, dyslipidemia, and atherosclerosis has been established in knockout mice. Therefore, adiponectin seems to be a marker of obesity-related diseases and a potential therapeutic target.

Adiponectin is a candidate marker of metabolic syndrome in obese children and adolescents

The aim of this study was to compare the use of several biomarkers to identify obese children and adolescents with increased metabolic risk. One hundred sixty-two Caucasian obese children and adolescents (41% males, 9-18 years old) referred to the Istituto Auxologico Italiano between 2003 and 2004 underwent an oral glucose tolerance test. Circulating levels of adiponectin (AD), plasminogen activator inhibitor 1 (PAI-1), interleukin 18 (IL-18), C-reactive protein (CRP), fibrinogen, uric acid, lipids and insulin were measured. Twenty five percent of obese children had the MS defined using World Health Organization-derived child specific criteria. MS subjects had significantly lower AD (p<0.01) and higher log-PAI-1 (p<0.001), uric acid (p<0.0001), and IL-18 (p<0.001). Subjects with AD levels </=median value had a significantly increased risk of having the MS (p<0.0001), as did subjects with uric acid and PAI-1 levels greater than the median. There was no increased risk with elevated IL-18, CRP, or fibrinogen. Hypoadiponectinemia was independently associated with the MS risk (p<0.0001). In conclusion in obese children and adolescents AD is the best predictor of MS and thus of higher cardiovascular disease risk.

The beneficial effects of high-density lipoprotein on adipocytes may relate to its anti-atherogenic properties

High-density lipoprotein (HDL) has significant anti-atherogenic properties, whereas the underlying mechanisms are complex and have not been completely elucidated. Adipocytes produce a variety of adipokines with cardiovascular effects. The dysregulated secretion of adipokines by adipocytes may contribute to the increased risk of atherosclerosis associated with obesity. Clinical evidences indicate that higher plasma HDL-C levels are associated with a favourable adipokines secretion profile, suggesting that HDL might improve the dysregulated adipokines secretion. HDL may diminish lipid accumulation in adipocytes through phosphorylation of PPARgamma and inhibition of aP2 expression, which possibly account for the favourable effects of HDL on adipokines secretion. Therefore, we hypothesize that HDL might exert several beneficial effects on adipocytes, which may relate to its anti-atherogenic properties.