Adipose tissue secreted proteins are collectively named adipocytokines and include leptin, adiponectin, resistin, collagenous repeat-containing sequence of 26-kDa protein (CORS-26) and omentin. Several of these adipocytokines influence insulin sensitivity and glucose metabolism and therefore systemic levels may be affected by oral glucose uptake. Whereas contradictory results have been published for leptin and adiponectin, resistin has not been extensively investigated and no reports on omentin and CORS-26 do exist.
Therefore the plasma levels of these proteins before and 120 min after an oral glucose load were analyzed in 20 highly-insulin sensitive, young adults by ELISA or immunoblot.
Circulating leptin was reduced 2 h after glucose uptake whereas adiponectin and resistin levels are not changed. Distribution of adiponectin and CORS-26 isoforms were similar before and after glucose ingestion. Omentin is highly abundant in plasma and immunoblot analysis revealed no alterations when plasma levels before and 2 h after glucose intake were compared.
Taken together our data indicate that only leptin is reduced by glucose uptake in insulin-sensitive probands whereas adiponectin and resistin are not altered. CORS-26 was demonstrated for the first time to circulate as high molecular weight form in plasma and like omentin was not influenced by oral glucose load. Omentin was shown to enhance insulin-stimulated glucose uptake but systemic levels are not correlated to postprandial blood glucose.
Adipose-derived cytokines, including tumor necrosis factor α, may contribute to the inflammation that occurs in the metabolic syndrome. We investigated the effects of inhibition of tumor necrosis factor α with etanercept in patients with the metabolic syndrome.
Fifty-six subjects with the metabolic syndrome were randomized to administration of either etanercept or identical placebo, 50 mg subcutaneously once a week for 4 weeks. The C-reactive protein level was the primary end point. Effects on other inflammatory markers (including fibrinogen, interleukin 6, and adiponectin), insulin sensitivity, lipid levels, and body composition were also determined.
Baseline characteristics were similar between the groups. Two subjects dropped out of each group, and etanercept was well tolerated throughout the study. The C-reactive protein levels decreased significantly in the treated compared with the placebo group (−2.4 ± 0.4 vs 0.5 ± 0.7 mg/L; P<.001). Adiponectin levels rose significantly in the etanercept group compared with the placebo group (0.8 ± 0.4 vs −0.3 ± 0.3 µg/mL; P=.03). Fibrinogen levels decreased (−68 ± 16 vs −2 ± 31 mg/dL [−2.0 ± 0.47 vs −0.06 ± 0.91 µmol/L]; P=.04) and interleukin 6 levels tended to decrease (−1.2 ± 0.8 vs 0.5 ± 0.5 ng/L; P=.07) in the etanercept-treated subjects compared with placebo, respectively. No changes occurred in body composition parameters or insulin sensitivity, but high-density lipoprotein levels tended to decrease in the etanercept group (−1 ± 1 vs 2 ± 1 mg/dL [−0.03 ± 0.03 vs 0.05 ± 0.03 mmol/L]; P=.06) compared with the placebo group.
Etanercept reduces C-reactive protein levels and tends to improve other inflammatory cardiovascular risk indexes in patients with the metabolic syndrome. Etanercept may interrupt the inflammatory cascade that occurs with abdominal obesity. Further, longer-term studies are needed to determine the effects of tumor necrosis factor α inhibition on cardiovascular disease in patients with the metabolic syndrome.
Insulin resistance, which implies impairment of insulin signaling in the target tissues, is a common cause of type 2 diabetes. Adipose tissue plays an important role in insulin resistance through the dysregulated production and secretion of adipose-derived proteins, including tumor necrosis factor-α, plasminogen activator inhibitor-1, leptin, resistin, angiotensinogen, and adiponectin. Adiponectin was estimated to be a protective adipocytokine against atherosclerosis, and also to have an anti-inflammatory effect. In this study, the relationship between fasting plasma adiponectin concentration and adiposity, body composition, insulin sensitivity (ITT, HOMAIR, QUICK), lipid profile, fasting insulin concentration were examined in Korean type 2 diabetes. The difference in the adiponectin concentrations was also examined in diabetic and non-diabetic subjects, with adjustment for gender, age and body mass index. 102 type 2 diabetics and 50 controls were examined. After a 12-h overnight fast, all subjects underwent a 75gram oral glucose tolerance test. Baseline blood samples were drawn for the determinations of fasting plasma glucose, insulin, adiponectin, total cholesterol, triglyceride, LDL-cholesterol, and HDL-cholesterol. The body composition was estimated using a bioelectric impedance analyzer (Inbody 2.0). The insulin sensitivity was estimated using the insulin tolerance test (ITT), HOMAIR and QUICK methods. In the diabetic group, the fasting adiponectin concentrations were significantly lower in men than in women. They were negatively correlated with BMI (r=-0.453), hip circumference (r=-0.341), fasting glucose concentrations (r=-0.277) and HOMAIR (r=-0.233). In addition, they were positively correlated with systolic blood pressure (r=0.321) and HDL-cholesterol (r=0.291). The systolic blood pressure and HDL-cholesterol were found to be independent variables, from a multiple logistic regression analysis, which influenced the adiponectin concentration. Compared with the non-diabetic group, the adiponectin concentrations were significantly lower in the diabetic group, with the exception of obese males. In conclusion, the plasma adiponectin concentrations were closely related to the insulin resistance parameters in Korean type 2 diabetic patients.
Diabetes mellitus; insulin resistance; adiponectin
Circulating adiponectin reflects the degree of energy homeostasis and insulin sensitivity of adult individuals. Low abundance of the high molecular mass multimers (HMW), the most active forms mediating the insulin-sensitizing effects of adiponectin, is indicative of impaired metabolic status. The increase in fetal adiponectin HMW compared with adults is a distinctive features of human neonates. In order to further understand the functional properties of adiponectin during fetal life, we have evaluated the associations of adiponectin with insulin sensitivity, body composition and gender. Umbilical cord adiponectin, adiponectin complexes and metabolic parameters were measured at term by elective Cesarean section. The associations between adiponectin, measures of body composition and insulin sensitivity were evaluated in relation to fetal gender in 121 singleton neonates. Higher total adiponectin concentrations in females compared with male fetuses (34.3±9.5 vs 24.9±8.6, p<0.001) were associated with a 3.2-fold greater abundance in circulating HMW complexes (0.20±0.03 vs 0.08±0.03, p<0.001, n=9). Adiponectin was positively correlated with neonatal fat mass (r= 0.27, p< 0.04) and percent body fat in female fetuses (r= 0.28, p<0.03) and with lean mass in males (r= 0.28, p<0.03). There was no significant correlation between cord adiponectin and fasting insulin concentrations or fetal insulin sensitivity as estimated by HOMA-IR. The gender dimorphism for plasma adiponectin concentration and complex distribution first appears in utero. In sharp contrast to the inverse correlation found in adults, the positive relationship between adiponectin and body fat is a specific feature of the fetus.
Adiponectin complexes; insulin sensitivity; body composition; adiposity; human; fetus
Insulin resistance is frequent in human immunodeficiency virus (HIV) infection and may be related to antiretroviral therapy. Cytokines secreted by adipose tissue (adipokines) are linked to insulin sensitivity. The present study is aimed to assess the prevalence of insulin resistance (IR) and its association with several adipokines, in a non-diabetic Romanian cohort of men and women with HIV-1 infection, undergoing combination antiretroviral therapy (cART).
A cross-sectional study was conducted in an unselected sample of 89 HIV-1-positive, non-diabetic patients undergoing stable cART for at least 6 months. Metabolic parameters were measured, including fasting plasma insulin, and circulating adiponectin, leptin, resistin, tumor necrosis factor alpha (TNF-alpha) and interleukin-6 (IL-6) levels. Insulin resistance was estimated by measuring the Quantitative Insulin Sensitivity Check Index (QUICKI), using a cut-off value of 0.33. A linear regression model was fitted to QUICKI to test the association of IR and adipokines levels.
A total of 89 patients (aged 18–65, median: 28 years) including 51 men (57.3%) and 38 women (42.7%) were included in the study. Fifty nine patients (66.3%) were diagnosed with IR based on QUICKI values lower than the cut-off point. IR prevalence was 72.5% in men and 57.6% in women. The presence of the IR was not influenced by either the time of the HIV diagnosis or by the duration of cART. Decreased adiponectin and increased serum triglycerides were associated with increased IR in men (R=0.43, p=0.007). Hyperleptinemia in women was demonstrated to be associated with the presence of IR (R=0.33, p=0.03).
Given the significant prevalence of the IR in our young non-diabetic cohort with HIV infection undergoing antiretroviral therapy reported in our study and the consecutive risk of diabetes and cardiovascular events, we suggest that the IR management should be a central component of HIV-infection therapeutic strategy. As adipokines play major roles in regulating glucose homeostasis with levels varying according to the sex, we suggest that further studies investigating adipokines should base their analyses on gender differences.
Adipokines; Adiponectin; Leptin; Antiretroviral therapy; Insulin resistance; HIV
Adipose tissue secreted cytokines (adipocytokines) have significant effects on the physiology and pathology of human metabolism relevant to diabetes and cardiovascular disease. We determined the relationship of the pattern of these circulating hormones with obesity-related phenotypes and whether such pattern is transmitted from parent to offspring. A combined total of 403 individuals from 156 consenting Saudi families divided into initial (119 families with 123 adults and 131 children) and replication (37 families with 58 adults and 91 children) cohorts were randomly selected from the RIYADH Cohort study. Anthropometrics were evaluated and metabolic measures such as fasting serum glucose, lipid profiles, insulin, leptin, adiponectin, resistin, tumor necrosis factor alpha (TNFα), activated plasminogen activator inhibitor 1 (aPAI1), high sensitivity C-reactive protein (hsCRP) and angiotensin II were also assessed. Parent-offspring regressions revealed that with the exception of hsCRP, all hormones measured showed evidence for significant inheritance. Principal component (PC) analysis of standardized hormone levels demonstrated surprising heritability of the three most common axes of variation. PC1, which explained 21% of the variation, was most strongly loaded on levels of leptin, TNFα, insulin, and aPAI1, and inversely with adiponectin. It was significantly associated with body mass index (BMI) and phenotypically stronger in children, and showed a heritability of ∼50%, after adjustment for age, gender and generational effects. We conclude that adipocytokines are highly heritable and their pattern of co-variation significantly influences BMI as early as the pre-teen years. Investigation at the genomic scale is required to determine the variants affecting the regulation of the hormones studied.
The aim of this study was to determine whether retinol-binding protein 4 (RBP4), adiponectin and high molecular weight (HMW) adiponectin are associated with insulin resistance (IR) and metabolic parameters in non-diabetic hypertensive patients. Also, we sought to compare the predictive values of these adipocytokines for IR in non-diabetic hypertensive patients.
Materials and Methods
Analyses of RBP4, adiponectin, and HMW adiponectin were performed on 308 non-diabetic hypertensives (148 males, age 58 ± 10 years, 189 non-metabolic syndrome and 119 metabolic syndrome). The homeostasis model assessment (HOMA) index for IR, lipid profiles, and anthropometric measure-ments were assessed.
There was no significant difference in RBP4 levels according to the presence of metabolic syndrome, although adiponectin and HMW adiponectin were significantly lower in metabolic syndrome. Correlation analysis of log RBP4 with IR and metabolic indices revealed that there was no significant correlation of RBP4 with waist circumference (r = 0.056, p = 0.324), HDL cholesterol (r = 0.005, p = 0.934), ApoB/ApoAI ratio (r = 0.066, p = 0.270), and the HOMA index (r = 0.017, p = 0.756). However, adiponectin and HMW adiponectin showed significant correlations with the HOMA index (r = - 0.247, p < 0.001; r = - 0.296, p < 0.001) and metabolic parameters. With IR defined as HOMA index ≥ 2.5, HMW adiponectin did not demonstrate a superior predictive value for IR compared to adiponectin (AUC = 0.680 vs. 0.648, p = 0.083). The predictive value of RBP4 for IR was minimal (AUC = 0.534).
RBP4 was not associated with IR or metabolic indices and the predictive value for IR was minimal in hypertensives. HMW adiponectin didn't have a superior predictive value for IR compared to adiponectin. Therefore, we can suggest that RBP4 and HMW adiponectin don't have more additive information than adiponectin in non-diabetic hypertensives.
Retinol-binding proteins; adiponectin; hypertension; insulin resistance
Adiponectin—an adipose tissue-derived protein—may provide a molecular link between obesity and colorectal cancer (CRC), but evidence from large prospective studies is limited. In particular, no epidemiological study explored high-molecular weight (HMW) and non-HMW adiponectin fractions in relation to CRC risk, despite them being hypothesized to have differential biological activities, i.e. regulating insulin sensitivity (HMW adiponectin) versus inflammatory response (non-HMW adiponectin). In a prospective, nested case–control study, we investigated whether prediagnostic serum concentrations of total, HMW and non-HMW adiponectin are associated with risk of CRC, independent of obesity and other known CRC risk factors. A total of 1206 incident cases (755 colon and 451 rectal) were matched to 1206 controls using incidence-density sampling. In conditional logistic regression, adjusted for dietary and lifestyle factors, total adiponectin and non-HMW adiponectin concentrations were inversely associated with risk of CRC [relative risk (RR) comparing highest versus lowest quintile = 0.71, 95% confidence interval (CI) = 0.53–0.95, P
trend = 0.03 for total adiponectin and RR = 0.45, 95% CI = 0.34–0.61, P
trend < 0.0001 for non-HMW adiponectin]. HMW adiponectin concentrations were not associated with CRC risk (RR = 0.91, 95% CI = 0.68–1.22, P
trend = 0.55). Non-HMW adiponectin was associated with CRC risk even after adjustment for body mass index and waist circumference (RR = 0.39, 95% CI = 0.26–0.60, P
trend < 0.0001), whereas the association with total adiponectin was no longer significant (RR = 0.81, 95% CI = 0.60–1.09, P
trend = 0.23). When stratified by cancer site, non-HMW adiponectin was inversely associated with both colon and rectal cancer. These findings suggest an important role of the relative proportion of non-HMW adiponectin in CRC pathogenesis. Future studies are warranted to confirm these results and to elucidate the underlying mechanisms.
Adiponectin is an adipocyte hormone that links visceral adiposity with insulin resistance and atherosclerosis. It is unique among adipocyte-derived hormones in that its circulating concentrations are inversely proportional to adiposity, and low adiponectin concentrations predict the development of type 2 diabetes and cardiovascular disease. Consequently, in the decade since its discovery, adiponectin has generated immense interest as a potential therapeutic target for the metabolic syndrome and diabetes.
This review summarizes current research regarding the regulation of circulating adiponectin concentrations by physiological, pharmacological, and nutritional factors, with an emphasis on human studies. In humans, plasma adiponectin concentrations are influenced by age and gender, and are inversely proportional to visceral adiposity. In vitro studies suggest that adiponectin production may be determined primarily by adipocyte size and insulin sensitivity, with larger, insulin-resistant adipocytes producing less adiponectin. While adiponectin concentrations are unchanged after meal ingestion, they are increased by significant weight loss, such as after bariatric surgery. In addition, adiponectin production is inhibited by a number of hormones, including testosterone, prolactin, glucocorticoids and growth hormone, and by inflammation and oxidative stress in adipose tissue. Smoking decreases, while moderate alcohol consumption increases, circulating adiponectin concentrations. Dietary fatty acid composition in rodents influences adiponectin production via ligand-activated nuclear receptors (PPARs); however, current evidence in humans is equivocal. In addition to PPAR agonists (such as thiazolidinediones and fibrates), a number of pharmacological agents (angiotensin receptor type 1 blockers, ACE inhibitors, and cannabinoid receptor antagonists) used in treatment of the metabolic syndrome also increase adiponectin concentrations in humans.
Background: Adipose tissue is a veritable "endocrine organ" due to its adipocytokines secretion implied in insulin sensitivity modulation and cardiovascular complications.
Objective: To identify the adipocytokines' plasmatic profile (adiponectin, leptin, resistin, IL-6, TNFα) in obese children and adolescents and to assess their relationship with "classic" clinical/paraclinical markers of metabolic syndrome and insulin resistance.
Material and Methods: A case-control study comparing a study group of 38 obese children and adolescents (age 13.5±2.3 years) to a normal weight age matched control group of 24 children.
We measured body mass index (BMI) and waist circumference (WC), systolic and diastolic blood pressure (BP). The classical metabolic parameters (fasting glycemia, total cholesterol and its fractions, serum triglycerides) were measured in both groups. Insulin sensitivity was evaluated using fasting insulinemia, HOMA-index and insulin-resistance summary score (IRS). Adiponectin, leptin, resistin, IL-6 and TNFα were measured using ELISA method.
Outcomes: Serum levels of leptin, resistin and IL-6 were signficantly higher (42.42±22.58 ng/ml versus 14.4±14.49 ng/ml, p <0.001; 9.69±3.47 ng/ml versus 7.92±2.13ng/ml, p = 0.029 and 2.66 ±2.87 pg/ml versus 0.89 ± 1.16 pg/ml, p = 0.006 respectively), while adiponectin levels were significantly lower (9.05±4.61 µg/ml versus 15.93±9.24 μg/ml, p <0.001) in the obese group compared to control group. TNFα was not statistical different between groups.
In multivariate regression analysis adiponectin was negatively and significantly correlated with WC (r = - 0.463, p = 0.003); leptin was positively and significantly related to WC, diastolic BP, fasting insulinemia and resistin (r = 0.775, p <0.001); resistin was positively related to leptin and IL-6 (r = 0.499, p <0.001), IL-6 was positively and significantly related to diastolic blood pressure (r = 0.333, p = 0.008).
Conclusions: Serum levels of adiponectin, leptin, resistin and IL-6 are significantly different in obese children compared to normal weight controls; leptin was the only adipokine correlated with insulin resistance in children. There are significant correlations between plasmatic levels of leptin, resistin and IL-6.
Simple plasmatic determination of TNFα is not a marker of the degree of obesity or its metabolic complications in pediatric population.
adipokine; cytokine; obesity; children
Adipose tissue-derived inflammation may contribute to metabolic alterations and eventually to the metabolic syndrome (MetS). The purpose of this study was to: 1) examine the role of adipocytokines in the association between obesity and the MetS; and 2) to determine whether the association is different in obese and non-obese persons.
Cross-sectional population-based InCHIANTI study.
944 community-dwelling adults aged 65 years and older living in Tuscany, Italy.
Obesity was defined as body mass index ≥ 30 kg/m2 and MetS as ≥ 3 of the ATP-III criteria. Circulating levels of CRP, IL-6, IL-1ra, IL-18, TNF-α R1, adiponectin, resistin, and leptin were measured. Additionally, insulin resistance was determined using the homeostasis model assessment (HOMA-IR).
The prevalence of the MetS was 32%. Both overall and abdominal obesity were significantly associated with the MetS after adjusting for inflammatory cytokines, adipokines and lifestyle factors. After adjusting for multiple confounders and HOMA-IR, IL-1ra, TNF-α R1 and adiponectin (p < 0.05) remained significantly associated with the MetS. Having multiple cytokines in the highest tertile increased the likelihood of having the MetS in both obese (p for trend 0.002) and non-obese persons (p for trend 0.001) independent of insulin resistance.
Non-obese and obese individuals who develop an intense pro-inflammatory state may be more prone to develop the MetS than those with lower levels of inflammation.
adipocytokines; adiponectin; cytokines; inflammation; metabolic syndrome; obesity
Even though there have been major advances in therapy, atherosclerosis and coronary artery disease retain their lead as one of the major causes of morbidity and mortality in the first decade of 21st century. To add to the woes, we have diabetes, obesity and insulin resistance as the other causes. The adipose tissue secretes several bioactive mediators that influence inflammation, insulin resistance, diabetes, atherosclerosis and several other pathologic states besides the regulation of body weight. These mediators are mostly proteins and are termed “adipocytokines”. Adiponectin, resistin, visfatin, retinol binding protein-4 (RBP-4) and leptin are a few such proteins. Adiponectin is a multimeric protein, acting via its identified receptors, AdipoR1 and AdipoR2. It is a potential biomarker for metabolic syndrome and has several antiinflammatory actions. Adiponectin increases insulin sensitivity and ameliorates obesity. Resistin, another protein secreted by the adipose tissue, derived its name due to its involvement in the development of insulin resistance. It plays a role in the pathophysiology of several conditions because of its robust proinflammatory activity mediated through the activation of extracellular signal regulated kinases 1 and 2 (ERK 1/2). In 2007, resistin was reported to have protective effect in ischemia-reperfusion injury and myocyte-apoptosis in the setting of myocardial infarction (MI). RBP-4 is involved in the developmental pathology of type 2 diabetes mellitus and obesity. Visfatin has been described as an inflammatory cytokine. Increased expression of visfatin mRNA has been observed in inflammatory conditions like atherosclerosis and inflammatory bowel disease. Leptin mainly regulates the food intake and energy homeostasis. Leptin resistance has been associated with development of obesity and insulin resistance. Few drugs (thiazolidinediones, rimonabant, statins, etc.) and some lifestyle modifications have been found to improve the levels of adipocytokines. Their role in therapy has a lot in store to be explored upon.
Adipokine; adiponectin; leptin; resistin; retinol binding protein-4; visfatin
The cardioprotective effects of lipid-lowering drugs have been primarily attributed to their effects on blood lipid metabolism. However, emerging evidence indicates that lipid-lowering drugs also modulate the synthesis and secretion of adipose tissue-secreted proteins referred to as adipokines. Adipokines influence energy homeostasis and metabolism and have also been shown to modulate the vascular inflammatory cascade. The purpose of this review will be to examine the reported effects of commonly used lipid-lowering drugs (statins, fibrates, niacin and omega-3-fatty acids) on the circulating concentrations of leptin, adiponectin, tumor necrosis-factor-α (TNF-α), Retinol binding protein 4 (RBP4) and resistin. Overall, the lipid-lowering drugs reviewed have minimal effects on leptin and resistin concentrations.Conversely, circulating adiponectin concentrations are consistently increased by each lipid-lowering drug reviewed with the greatest effects produced by niacin. Studies that have examined the effects of statins, niacin and omega-3-fatty acids on TNF-α demonstrate that these agents have little effect on circulating TNF-α concentrations. Niacin and fibrates appear to lower RBP4 but not resistin concentrations. The results of the available studies suggest that a strong relationship exists between pharmacological reductions in blood lipids and adiponectin that is not obvious for other adipokines reviewed.
Statins; Fibrates; Niacin; Omega-3 fatty acids; Adipokines; Leptin; Adiponectin; Cardiovascular disease; Hyperlipidemia
Obesity, insulin resistance, and dyslipidemia are associated with preeclampsia. Recently, “adipose tissue failure”, characterized by dysregulation of adipokine production, has been implicated in the pathophysiology of these metabolic complications. Adiponectin, an insulin-sensitizing, anti-atherogenic, anti-inflammatory and angiogenic adipokine, circulates in oligomeric complexes including: low-molecular-weight (LMW) trimers, medium-molecular-weight (MMW) hexamers and high-molecular-weight (HMW) isoforms. These multimers exert differential biological effects, and HMW to total adiponectin ratio (SA) has been reported to be a specific marker of adiponectin activity. The aim of this study was to determine whether preeclampsia is associated with changes in circulating adiponectin multimers.
This cross-sectional study included women with: 1) normal pregnancy (n=225); and 2) patients with mild preeclampsia (n=111). The study population was further stratified by first trimester BMI (normal weight <25 kg/m2 vs. overweight/obese ≥25 kg/m2). Serum adiponectin multimers (total, HMW, MMW and LMW) concentrations were determined by ELISA. Non-parametric statistics were used for analysis.
1) The median maternal HMW and LMW adiponectin concentrations were lower in patients with preeclampsia than in those with normal pregnancies (p<0.001 and p=0.01, respectively); 2) patients with preeclampsia had a lower HMW/Total adiponectin ratio (p<0.001) and higher MMW/Total adiponectin and LMW/Total adiponectin ratios than those with a normal pregnancy (p<0.001 and p=0.009, respectively); 3) the presence of preeclampsia was independently associated with lower maternal serum HMW adiponectin concentrations (p=0.001) and with a low HMW/Total adiponectin ratio (p<0.001) after correction for maternal age, maternal BMI, the difference in BMI between the third and the first trimester, and gestational age at sampling; and 4) overweight/obese pregnant women had a lower median total and HMW adiponectin concentration than normal weight pregnant women among women with normal pregnancies, but not among those with preeclampsia.
1) Preeclampsia is associated with a lower median concentration of the HMW adiponectin isoform, the most active form of this adipokine, and a low HMW/Total adiponectin ratio, a specific marker of adiponectin biologic activity; 2) in contrast to normal pregnancy, preeclampsia is not associated with decreased circulating adiponectin multimers in overweight/obese individuals suggesting altered regulation of this adipokine in preeclampsia; 3) collectively, these findings suggest that preeclampsia is characterized by alterations in adiponectin multimers and their relative distribution implying a role for adiponectin multimers in the mechanism of disease in preeclampsia.
Adipokines; Pregnancy; High-molecular-weight (HMW) adiponectin; Medium-molecular-weight (MMW) adiponectin; Low-molecular-weight (LMW) adiponectin; BMI; overweight; obesity
Adiponectin and resistin are adipokines which modulate insulin action, energy, glucose and lipid homeostasis. Meta-analyses showed that hypoadiponectinemia and hyperresistinemia are strongly associated with increased risk of insulin resistance, type 2 diabetes (T2DM), metabolic syndrome (MS) and cardiovascular disease. The aim of this study was to propose a novel adiponectin-resistin (AR) index by taking into account both adiponectin and resistin levels to povide a better indicator of the metabolic homeostasis and metabolic disorders. In addition, a novel insulin resistance (IRAR) index was proposed by integration of the AR index into an existing insulin resistance index to provide an improved diagnostic biomarker of insulin sensitivity.
In this case control study, anthropometric clinical and metabolic parameters including fasting serum total adiponectin and resistin levels were determined in 809 Malaysian men (208 controls, 174 MS without T2DM, 171 T2DM without MS, 256 T2DM with MS) whose ages ranged between 40-70 years old. Significant differences in continuous variables among subject groups were confirmed by ANCOVA or MANCOVA test using 1,000 stratified bootstrap samples with bias corrected and accelerated (BCa) 95% CI. Spearman's rho rank correlation test was used to test the correlation between two variables.
The AR index was formulated as 1+log10(R0)-log10(A0). The AR index was more strongly associated with increased risk of T2DM and MS than hypoadiponectinemia and hyperresistinemia alone. The AR index was more strongly correlated with the insulin resistance indexes and key metabolic endpoints of T2DM and MS than adiponectin and resistin levels alone. The AR index was also correlated with a higher number of MS components than adiponectin and resistin levels alone. The IRAR index was formulated as log10(I0G0)+log10(I0G0)log10(R0/A0). The normal reference range of the IRAR index for insulin sensitive individuals was between 3.265 and 3.538. The minimum cut-off values of the IRAR index for insulin resistance assessment were between 3.538 and 3.955.
The novel AR and IRAR indexes are cost-effective, precise, reproducible and reliable integrated diagnostic biomarkers of insulin sensitivity for screening subjects with increased risk of future development of T2DM and MS.
Background and objective
The effect of exercise on the plasma concentration of high-molecular weight (HMW) adiponectin (i.e., the biologically active form of circulating adiponectin) and the possible role of HMW adiponectin in mediating the exercise-induced enhancement of insulin action are not known. The aim of this study was to evaluate the relationship between the post-exercise increase in insulin sensitivity and plasma HMW adiponectin concentration.
Design and methods
We measured total and HMW adiponectin concentrations in plasma by using an enzyme-linked immunosorbent assay, and insulin sensitivity by using the updated homeostasis model assessment of insulin sensitivity (HOMA2-IS) score in the basal, overnight fasted state, once ~12 hours after a single bout of moderate-intensity endurance exercise and once after an equivalent period of rest, in 27 healthy men and women (age: 29 ± 1 years, body mass index: 24.7 ± 0.8 kg/m2).
The HOMA2-IS score was 18 ± 7% greater after exercise than rest (229 ± 20 and 196 ± 17, respectively; P = 0.006), whereas the concentrations of total adiponectin (7.8 ± 0.5 and 7.7 ± 0.5 mg/l, respectively; P = 0.597) and HMW adiponectin (3.0 ± 0.3 and 3.0 ± 0.3 mg/l, respectively; P = 0.625) were not different. The exercise-induced change in HOMA2-IS was not related to changes in total and HMW adiponectin concentrations (P > 0.3).
Changes in HMW adiponectin concentration are not involved in the acute exercise-induced enhancement of insulin action.
adipokines; insulin resistance; physical activity
Adiponectin, an adipokine secreted by adipocytes, exerts beneficial effects on glucose and lipid metabolism and has been found to improve insulin resistance by decreasing triglyceride content in muscle and liver in obese mice. Adiponectin is found in several isoforms and the high-molecular weight (HMW) form has been linked most strongly to the insulin-sensitizing effects. Fat content in skeletal muscle (intramyocellular lipids, IMCL) and liver (intrahepatic lipids, IHL) can be quantified noninvasively using proton magnetic resonance spectroscopy (1H-MRS). The purpose of our study was to assess the relationship between HMW adiponectin and measures of glucose homeostasis, IMCL and IHL, and to determine predictors of adiponectin levels. We studied 66 premenopausal women (mean BMI 31.0 ± 6.6 kg/m2) who underwent 1H-MRS of calf muscles and liver for IMCL and IHL, computed tomography (CT) of the abdomen for abdominal fat depots, dual-energy X-ray absorptiometry (DXA) for fat and lean mass assessments, HMW and total adiponectin, fasting lipid profile and an oral glucose tolerance test (homeostasis model assessment of insulin resistance (HOMAIR), glucose and insulin area under the curve). There were strong inverse associations between HMW adiponectin and measures of insulin resistance, IMCL and IHL, independent of visceral adipose tissue (VAT) and total body fat. IHL was the strongest predictor of adiponectin and adiponectin was a predictor of HOMAIR. Our study showed that in premenopausal obese women HMW adiponectin is inversely associated with IMCL and IHL content. This suggests that adiponectin exerts positive effects on insulin sensitivity in obesity by decreasing intracellular triglyceride content in skeletal muscle and liver; it is also possible that our results reflect effects of insulin on adiponectin.
Adipose tissue is no longer considered to be an inert tissue that stores fat. This tissue is capable of expanding to accommodate increased lipids through hypertrophy of existing adipocytes and by initiating differentiation of pre-adipocytes. Adipose tissue metabolism exerts an impact on whole-body metabolism. As an endocrine organ, adipose tissue is responsible for the synthesis and secretion of several hormones. These are active in a range of processes, such as control of nutritional intake (leptin, angiotensin), control of sensitivity to insulin and inflammatory process mediators (tumor necrosis factor α (TNF-α), interleukin-6 (IL-6), resistin, visfatin, adiponectin, among others) and pathways (plasminogen activator inhibitor 1 (PAI-1) and acylation stimulating protein (ASP) for example). This paper reviews some of the biochemical and metabolic aspects of adipose tissue and its relationship to inflammatory disease and insulin resistance.
adipose tissue; adipocytes; adipokines
African Americans (AAs) tend to have lower total adiponectin levels compared to European Americans (EA); however, it is not known whether race affects adiponectin multimer distribution and their relationships to metabolic traits. We measured total adiponectin, high molecular weight (HMW), low molecular weight (LMW) (i.e., hexamer), and trimer adiponectin in 132 normoglycemic premenopausal women (75 AAs, 57 EAs), together with measures of total and abdominal fat, plasma lipids, insulin sensitivity (Si), and genetic admixture estimates. We found that lower total adiponectin in AAs was explained by reduced LMW, and trimer forms because levels of HMW did not differ between races. In EAs, HMW was highly correlated with multiple metabolic syndrome traits. In contrast, the LMW and trimer forms were most highly correlated with metabolic traits in AAs, including abdominal adiposity, lipids, and Si. At similar levels of visceral adiposity, AAs exhibited significantly lower LMW adiponectin than EAs. Similarly, at comparable levels of HMW and LMW adiponectin, AAs were more insulin resistant than their EA counterparts. In conclusion, (i) serum adiponectin is lower in AAs predominantly as a result of reduced concentrations of LMW and trimers multimeric forms; (ii) LMW and trimer, not HMW, are most broadly correlated with metabolic traits in AAs. Thus, HMW adiponectin may exert less bioactivity in explaining the metabolic syndrome trait cluster in populations of predominant African genetic background.
Major depressive disorder (MDD) is associated with immune system dysfunction and disruption of multiple circadian systems. Adiponectin is an adipocytokine with anti-inflammatory and anti-atherogenic effects. Circulating concentrations are inversely related to adiposity and risks of metabolic syndrome and diabetes mellitus. Our goals were to: A) establish whether premenopausal women with MDD exhibit decreased plasma adiponectin concentrations and/or disruption of circadian adiponectin rhythmicity; B) assess whether there is a relationship between adiponectin and MDD; C) explore the temporal relationships among adiponectin, leptin, ACTH and cortisol secretion.
Case-control study of community-dwelling premenopausal women with MDD and age- and BMI-matched-control subjects (N=23/group). Main outcome measures were circulating concentrations of adiponectin, leptin, ACTH, and cortisol measured hourly for 24h.
Women with MDD had approximately 30% lower mean 24h concentrations of adiponectin than did control subjects. Adiponectin was inversely related to depression severity and total duration of disease, suggesting a causal link. In contrast, nocturnal leptin concentrations were higher in the MDD versus control groups. Leptin was inversely related to cortisol and adiponectin both in subjects with depression and in control subjects. In cross-correlation analyses, the relationship between ACTH and cortisol was stronger in women with MDD than in control subjects, consistent with HPA-axis activation in MDD.
Reduced daily adiponectin production may increase the risk of diabetes mellitus, and elevated leptin may contribute to osteoporosis, in premenopausal women with MDD.
women’s health; psychosomatic medicine; antidepressants; stress system; circadian rhythmicity; inflammation; adipocytokines: ACTH; cortisol: insulin resistance, cardiovascular risk; osteoporosis; osteopenia
Adiponectin is a protein hormone produced by adipose tissue whose circulating levels are inversely related to adiposity and inflammation. Adiponectin circulates as oligomers, from the low molecular weight trimer to the high molecular weight octodecamer (18mer) Each oligomer has distinct biological activities, which include enhancement of insulin sensitivity and metabolic control, and suppression of inflammation. Adiponectin occurs in human milk at higher concentrations than leptin. The adiponectin in human milk is almost entirely of the high molecular weight form, the form with the highest activity in controlling many types of metabolic processes. Human adiponectin fed to infant mice is transported across the intestinal mucosa into the serum. An inverse relationship between adiponectin levels in milk and adiposity (weight-for-height) of the breastfed infant was observed, and could be due to modulation of infant metabolism by milk adiponectin, and may be related to the observed protection against obesity by breastfeeding. Human milk may be a medium whereby the hormonal milieu (in response to internal factors and the environment) of the mother can be used to communicate with the breastfed infant to modify infant metabolic processes. Transmission of information from mother to infant through milk may allow adaptation to fluctuating environmental conditions.
infant development; body weight; BMI; adiposity
Adiponectin is positively correlated with longevity and negatively correlated with many obesity-related diseases. While there are several circulating forms of adiponectin, the high molecular weight (HMW) version has been suggested to have the predominant bioactivity. Adiponectin gene expression and cognate serum protein levels are of particular interest in mice with altered growth hormone (GH) signaling as these mice exhibit extremes in obesity that are positively associated with insulin sensitivity and lifespan as opposed to the typical negative association of these factors. While a few studies have reported total adiponectin levels in young adult mice with altered GH signaling, much remains unresolved, including changes in adiponectin levels with advancing age, proportion of total adiponectin in the HMW form, adipose depot of origin, and differential effects of GH versus IGF1. Therefore, the purpose of this study was to address these issues using assorted mouse lines with altered GH signaling. Our results show that adiponectin is generally negatively associated with GH activity, regardless of age. Further, the amount of HMW adiponectin is consistently linked with the level of total adiponectin and not necessarily with previously reported lifespan or insulin sensitivity of these mice. Interestingly, circulating adiponectin levels correlated strongly with inguinal fat mass, implying the effects of GH on adiponectin are depot-specific. Interestingly rbGH, but not IGF1, decreased circulating total and HMW adiponectin levels. Taken together, these results fill important gaps in the literature related to GH and adiponectin and question the frequently reported associations of total and HMW adiponectin with insulin sensitivity and longevity.
adiponectin; high molecular weight adiponectin; growth hormone receptor; growth hormone; growth hormone deficiency; growth hormone antagonist
Adipokines, factors produced by adipose tissue, may be proinflammatory (such as leptin and resistin) or anti-inflammatory (such as adiponectin). Effects of these adipokines on the lungs have the potential to evoke or exacerbate asthma. This review summarizes basic mechanistic data through population-based and clinical studies addressing the potential role of adipokines in asthma. Augmenting circulating concentrations of adiponectin attenuates allergic airway inflammation and airway hyperresponsiveness in mice. Murine data is supported by human data that suggest that low serum adiponectin is associated with greater risk for asthma among women and peripubertal girls. Further, higher serum total adiponectin may be associated with lower clinical asthma severity among children and women with asthma. In contrast, exogenous administration of leptin results in augmented allergic airway hyperresponsiveness in mice. Alveolar macrophages obtained from obese asthmatics are uniquely sensitive to leptin in terms of their potential to augment inflammation. Consistent with this basic mechanistic data, epidemiologic studies demonstrate that higher serum leptin is associated with greater asthma prevalence and/or severity and that these associations may be stronger among women, postpubertal girls, and prepubertal boys. The role of adipokines in asthma is still evolving, and it is not currently known whether modulation of adipokines may be helpful in asthma prevention or treatment.
The metabolic syndrome (MetS) confers an increased risk for diabetes and cardiovascular disease. Although high-sensitive C-reactive protein (hsCRP) concentrations are higher and adiponectin concentrations lower in MetS, there is no reliable biochemical measure that can capture its various features. We evaluated whether hsCRP, adiponectin, or the ratio of adiponectin or its oligomers, especially the high-molecular-weight (HMW) oligomer, to hsCRP predict MetS in 123 subjects with MetS compared with that in 91 healthy control subjects. MetS subjects had significantly higher hsCRP levels and lower total adiponectin and oligomer levels relative to control subjects (P < .0001). The HMW/total adiponectin and adiponectin/CRP ratios were significantly lower in MetS subjects than control subjects (P < .005). The odds ratio (OR) of MetS using the 75th percentile cutoff for CRP was 3.8 (95% confidence interval [CI], 2.1–6.8) and equivalent to low total adiponectin (OR, 2.5; 95% CI, 1.3–4.5), its oligomers, or the adiponectin/hsCRP ratio (OR, 2.6; 95% CI, 1.5, 4.8). Thus, measurements of CRP, adiponectin, or its oligomers provide robust biomarkers for predicting MetS.
C-reactive protein; Adiponectin; Biomarker; Metabolic syndrome
Intra-amniotic and systemic infection/inflammation have been causally linked to preterm parturition and fetal injury. An emerging theme is that adipose tissue can orchestrate a metabolic response to insults, but also an inflammatory response via the production of adipocytokines, and that these two phenomenon are interrelated. Adiponectin, an insulin-sensitizing, anti-inflammatory adipocytokine, circulates in multimeric complexes including low-molecular-weight (LMW) trimers, medium-molecular-weight (MMW) hexamers and high-molecular-weight (HMW) isoforms. Each of these complexes can exert differential biological effects. The aim of this study was to determine whether spontaneous preterm labor (PTL) with intact membranes and intra-amniotic infection/inflammation (IAI) is associated with changes in maternal serum circulating adiponectin multimers.
This cross-sectional study included patients in the following groups: 1) normal pregnant women (n=158); 2) patients with an episode of preterm labor and intact membranes without IAI who delivered at term (n=41); 3) preterm labor without IAI who delivered preterm (n=27); and 4) preterm labor with IAI who delivered preterm (n=36). Serum adiponectin multimers (total, HMW, MMW and LMW) concentrations were determined by ELISA. Non-parametric statistics were used for analyses.
1) Preterm labor leading to preterm delivery or an episode of preterm labor which does not lead to preterm delivery, was associated with a lower median maternal serum concentration of total and HMW adiponectin, a lower median HMW/total adiponectin ratio, and a higher median LMW/total adiponectin ratio than normal pregnancy; 2) among patients with preterm labor, those with IAI had the lowest median concentration of total and HMW adiponectin, as well as the lowest median HMW/total adiponectin ratio; 3) The changes in maternal adiponectin and adiponectin multimers remained significant after adjusting for confounding factors such as maternal age, BMI, gestational age at sampling, and parity.
1) Preterm labor is characterized by a change in the profile of adiponectin multimers concentrations and their relative isoforms. These changes were observed in patients with an episode of preterm labor not leading to preterm delivery, in patients with intra-amniotic inflammation, or in those without evidence of intra-amniotic inflammation; 2) The changes in adiponectin multimer concentrations reported in preterm labor are different from those previously reported in spontaneous labor at term, suggesting that there is a fundamental difference between preterm labor and labor at term; 3) The findings reported herein, provide the first evidence for the participation of adiponectin multimer in preterm parturition. We propose that adiponectins and adipokines in general provide a mechanism to organize the metabolic demands generated by the process of preterm parturition regardless of the nature of the insult (intra-amniotic inflammation or not).
Adiponectin; Adipokines; Pregnancy; High molecular weight (HMW); Medium molecular weight (MMW); Low molecular weight (LMW); Preterm labor; Intra-amniotic infection; Inflammation; Chorioamnionitis; Preterm delivery; Energy Requirements; Energy Expenditure; Preterm Birth; Metabolism; Metaflammation