Physiological, pharmacological, and nutritional regulation of circulating adiponectin concentrations in humans

Is there a link between obesity and asthma?

Increasing epidemiological data identify a link between obesity and asthma incidence and severity. Based on experimental data, it is possible that shared inflammatory mechanisms play a role in determining this linkage. Although controversial, the role of adipokines may be central to this association and the maintenance of the asthma phenotype. While leptin and adiponectin have a causal link to experimental asthma in mice, data in humans are less conclusive. Recent studies demonstrate that adipokines can regulate the survival and function of eosinophils and that these factors can affect eosinophil trafficking from the bone marrow to the airways. In addition, efferocytosis, the clearance of dead cells, by airway macrophages or blood monocytes appears impaired in obese asthmatics and is inversely correlated with glucocorticoid responsiveness. This review examines the potential mechanisms linking obesity to asthma.

The Effect of Leptin and Adiponectin on KiSS-1 and KissR mRNA Expression in Rat Islets of Langerhans and CRI-D2 Cell Line

BACKGROUND

Leptin and adiponectin are the two key metabolic hormones secreted from adipocytes to control food intake and energy expenditure. The action of both hormones in regulation of Gonadotropin Releasing Hormone (GnRH) secretion from the hypothalamus is mediated through Kisspeptins. Kisspeptins are products of KiSS-1 gene. Leptin and adiponectin are modulators of KiSS-1 expression in the hypothalamus. These peptides have also important roles in pancreatic β-cells to control insulin synthesis and secretion and their receptors are detected in Langerhans islets. We hypothesized that leptin and adiponectin might alter KiSS-1 and Kiss Receptor mRNA expression in the islets.

OBJECTIVES

The aim of this study is to investigate any modulatory effect that leptin and adiponectin may have on the expression of Kiss-1 and KiSSR gene in Langerhans islets.

MATERIALS AND METHODS

We isolated the islets from adult male rats by collagenase and cultured CRI-D2 cell lines to investigate the effect of leptin and adiponectin. Then, we incubated them with different concentrations of leptin and adiponectin for 24 hours. After that, RNA was extracted from the islets and CRI-D2 cells and transcripted to cDNA. KiSS-1 and KissR expression levels were evaluated by real time PCR.

RESULTS

In islet and CRI-D2 cells, leptin increased the KiSS-1 mRNA expression significantly, but adiponectin decreased it was expected.

CONCLUSIONS

These findings indicated the possibility that KiSS-1 mRNA expression is a mediator of leptin and adiponectin function in the islets.

Differential effects of adiponectin in osteoblast-like cells

The skeleton should maintain an adequate volume, vigour and strength to carry out the role for which it is designed: to hold the whole soft tissue mass that shapes the body and to protect the vital organs. To fulfil this task a satisfactory food intake is required and regulators that are released in the feeding and fasting states, among other signals indicate how much soft mass needs to be built up. Those signals include the secretion of adipocytokines which could represent a relevant link between soft mass (adipose tissue) and skeleton. We studied the presence of adiponectin receptors (AdipoR1, AdipoR2) and its direct effects in osteosarcoma cell line Saos-2. The results indicated that adiponectin receptors were present in the osteoblastic cells with a higher expression of AdipoR1. Human recombinant globular adiponectin was able to increase viability levels and decrease cytotoxicity rates in cell cultures. Also, adiponectin significantly inhibited alkaline phosphatase activity in supernatants. Osteoprotegerin mRNA expression was significantly reduced after 72 h treatment. The FOS induction was studied and the results exhibited a significant increase caused by adiponectin. In conclusion, all these observations suggest that adiponectin influences bone metabolism decreasing the levels of bone formation. Regulators of adiponectin or its receptors could be circulating to modulate the activities of this peptide.

Early effects of neutering on energy expenditure in adult male cats

The initial cause of post-neutering weight gain in male cats is not entirely known. There is evidence that energy intake (EI) increases rapidly post-neutering, but it is not clear if neutering also decreases energy expenditure (EE) prior to weight gain. Thus, the purpose of this study was to determine if a decrease in EE contributes to the initial shift toward positive energy balance in neutered male cats. To determine the influence of neutering on EE independent of changes in EI and body weight (BW), male cats were fed at their pre-neutering maintenance EI and EE was measured at 4 days pre-neutering, 3–4 days post-neutering, and 9 days post- neutering. Ad libitum food access was then provided for 6 months. Body composition was measured and blood samples collected for serum chemistry at pre-neutering and 7 days, 13 days and 6 months post-neutering. Total energy expenditure (TEE) adjusted for lean body mass (LBM) did not change in cats from pre-neutering to 9 days post-neutering. However, TEE adjusted for BW and resting energy expenditure adjusted for either LBM or BW showed a small, but significant (P<0.05) increase from pre-neutering to 9 days post-neutering. When allowed free choice food access, cats showed significant increases of food intake (FI) and BW. Circulating concentrations of ghrelin increased, while adiponectin levels decreased following neutering. The results of this study indicate that initial post-neutering weight gain in male cats results from increased FI and not decreased EE. Long-term control of FI should be initiated after neutering to prevent hyperphagia and weight gain in male cats.

Adiponectin gene polymorphisms and acute respiratory distress syndrome susceptibility and mortality

RATIONALE

Adiponectin is an anti-inflammatory adipokine that is the most abundant gene product of adipose tissue. Lower levels have been observed in obesity, insulin resistance, and in critical illness. However, elevated levels early in acute respiratory failure have been associated with mortality. Polymorphisms in adiponectin-related genes (ADIPOQ, ADIPOR1, ADIPOR2) have been examined for relationships with obesity, insulin resistance and diabetes, cardiovascular disease, and to circulating adipokine levels, but many gaps in knowledge remain. The current study aims to assess the association between potentially functional polymorphisms in adiponectin-related genes with acute respiratory distress syndrome (ARDS) risk and mortality.

METHODS

Consecutive patients with risk factors for ARDS admitted to the ICU were enrolled and followed prospectively for development of ARDS. ARDS cases were followed through day 60 for all-cause mortality. 2067 patients were successfully genotyped using the Illumina CVD BeadChip high-density platform. Of these, 567 patients developed ARDS. Forty-four single nucleotide polymorphisms (SNPs) on ADIPOQ, ADIPOR1 and ADIPOR2 were successfully genotyped. Of these, 9 SNPs were hypothesized to be functional based on their location (promoter, exon, or 3' untranslated region). These 9 SNPs were analyzed for association with ARDS case status and mortality among ARDS cases.

RESULTS

After multivariable analysis and adjustment for multiple comparisons, no SNPs were significantly associated with ARDS case status. Among ARDS cases, homozygotes for the minor allele of rs2082940 (ADIPOQ) had increased mortality (hazard ratio 2.61, 95% confidence interval 1.36-5.00, p = 0.0039) after adjustment for significant covariates. The significance of this association persisted after adjustment for multiple comparisons (FDR_q = 0.029).

CONCLUSIONS

A common and potentially functional polymorphism in ADIPOQ may impact survival in ARDS. Further studies are required to replicate these results and to correlate genotype with circulating adiponectin levels.

Cot/tpl2 participates in the activation of macrophages by adiponectin

Whereas the main function of APN is to enhance insulin activity, it is also involved in modulating the macrophage phenotype. Here, we demonstrate that at physiological concentrations, APN activates Erk1/2 via the IKKβ-p105/NF-κΒ1-Cot/tpl2 intracellular signal transduction cassette in macrophages. In peritoneal macrophages stimulated with APN, Cot/tpl2 influences the ability to phagocytose beads. However, Cot/tpl2 did not modulate the known capacity of APN to decrease lipid content in peritoneal macrophages in response to treatment with oxLDL or acLDL. A microarray analysis of gene-expression profiles in BMDMs exposed to APN revealed that APN modulated the expression of ∼3300 genes; the most significantly affected biological functions were the inflammatory and the infectious disease responses. qRT-PCR analysis of WT and Cot/tpl2 KO macrophages stimulated with APN for 0, 3, and 18 h revealed that Cot/tpl2 participated in the up-regulation of APN target inflammatory mediators included in the cytokine-cytokine receptor interaction pathway (KEGG ID 4060). In accordance with these data, macrophages stimulated with APN increased secretion of cytokines and chemokines, including IL-1β, IL-1α, TNF-α, IL-10, IL-12, IL-6, and CCL2. Moreover, Cot/tpl2 also played an important role in the production of these inflammatory mediators upon stimulation of macrophages with APN. It has been reported that different types of signals that stimulate TLRs, IL-1R, TNFR, FcγR, and proteinase-activated receptor-1 activate Cot/tpl2. Here, we demonstrate that APN is a new signal that activates the IKKβ-p105/NF-κΒ1-Cot/tpl2-MKK1/2-Erk1/2 axis in macrophages. Furthermore, this signaling cassette modulates the biological functions triggered by APN in macrophages.

Endogenous peptides as risk markers to assess the development of insulin resistance

Insulin resistance, the reciprocal of insulin sensitivity, is known to be a characteristic of type 2 diabetes mellitus, and is regarded as an important mechanism in the pathogenesis. The hallmark of insulin resistance is a gradual break-down of insulin-regulative glucose uptake by muscle and adipose tissues in subjects. Insulin resistance is increasingly estimated in various disease conditions to examine and assess their etiology, pathogenesis and consequences. Although our understanding of insulin resistance has tremendously been improved in recent years, certain aspects of its estimation and etiology still remain elusive to clinicians and researchers. There are numerous factors involved in pathogenesis and mechanisms of insulin resistance. Recent studies have provided compelling clues about some peptides and proteins, including galanin, galanin-like peptide, ghrelin, adiponectin, retinol binding protein 4 (RBP4) and CRP, which may be used to simplify and to improve the determination of insulin resistance. And alterations of these peptide levels may be recognized as risk markers of developing insulin resistance and type 2 diabetes mellitus. This review examines the updated information for these peptides, highlighting the relations between these peptide levels and insulin resistance. The plasma high ghrelin, RBP4 and CRP as well as low galanin, GALP and adiponectin levels may be taken as the markers of deteriorating insulin resistance. An increase in the knowledge of these marker proteins and peptides will help us correctly diagnose and alleviate insulin resistance in clinic and study.

Fish oil supplementation ameliorates fructose-induced hypertriglyceridemia and insulin resistance in adult male rhesus macaques

Fish oil (FO) is a commonly used supplemental source of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), 2 n-3 (ω-3) polyunsaturated fatty acids (PUFAs) that have been shown to have a variety of health benefits considered to be protective against cardiometabolic diseases. Although the effects of EPA and DHA on lipid metabolism have been extensively studied, not all of the metabolic effects of FO-derived n-3 PUFAs have been characterized. Our laboratory recently showed that a high-fructose diet in rhesus monkeys induces the features of metabolic syndrome (MetS) similar to those observed in humans. Thus, we specifically wanted to evaluate the effects of FO in rhesus monkeys fed a high-fructose diet and hypothesized that FO supplementation would mitigate the development of fructose-induced insulin resistance, dyslipidemia, and other cardiometabolic risk factors. In this study, adult monkeys (aged 12-20 y) received either a standard unpurified diet plus 75 g fructose/d (control group; n = 9) or a standard unpurified diet, 75 g fructose/d, and 4 g FO (16% EPA + 11% DHA)/d (treatment group; n = 10) for 6 mo. Importantly, our results showed that daily FO supplementation in the monkeys prevented fructose-induced hypertriglyceridemia and insulin resistance as assessed by intravenous-glucose-tolerance testing (P ≤ 0.05). Moreover, FO administration in the monkeys prevented fructose-induced increases in plasma apolipoprotein (Apo)C3, ApoE, and leptin concentrations and attenuated decreases in circulating adropin concentrations (P ≤ 0.05). No differences between the control and FO-treated monkeys were observed in body weight, lean mass, fat mass, or fasting glucose, insulin, and adiponectin concentrations. In conclusion, FO administration in a nonhuman primate model of diet-induced MetS ameliorates many of the adverse changes in lipid and glucose metabolism induced by chronic fructose consumption.

Effects of sugar-sweetened beverages on plasma acylation stimulating protein, leptin and adiponectin: relationships with metabolic outcomes

OBJECTIVE

The effects of fructose and glucose consumption on plasma acylation stimulating protein (ASP), adiponectin, and leptin concentrations relative to energy intake, body weight, adiposity, circulating triglycerides, and insulin sensitivity were determined.

DESIGN AND METHODS

Thirty two overweight/obese adults consumed glucose- or fructose-sweetened beverages (25% energy requirement) with their ad libitum diets for 8 weeks, followed by sweetened beverage consumption for 2 weeks with a standardized, energy-balanced diet. Plasma variables were measured at baseline, 2, 8, and 10 weeks, and body adiposity and insulin sensitivity at baseline and 10 weeks.

RESULTS

Fasting and postprandial ASP concentrations increased at 2 and/or 8 weeks. ASP increases correlated with changes in late-evening triglyceride concentrations. At 10 weeks, fasting adiponectin levels decreased in both groups, and decreases were inversely associated with baseline intra-abdominal fat volume. Sugar consumption increased fasting leptin concentrations; increases were associated with body weight changes. The 24-h leptin profiles increased during glucose consumption and decreased during fructose consumption. These changes correlated with changes of 24-h insulin levels.

CONCLUSIONS

The consumption of fructose and glucose beverages induced changes in plasma concentrations of ASP, adiponectin, and leptin. Further study is required to determine if these changes contribute to the metabolic dysfunction observed during fructose consumption.

Low prepregnancy adiponectin concentrations are associated with a marked increase in risk for development of gestational diabetes mellitus

OBJECTIVE

To examine whether circulating total and high-molecular weight (HMW) adiponectin concentrations, measured before pregnancy, are associated with subsequent risk of gestational diabetes mellitus (GDM).

RESEARCH DESIGN AND METHODS

This was a nested case-control study among women who participated in the Kaiser Permanente Northern California Multiphasic Health Check-up exam (1984-1996) with a serum sample obtained and who had a subsequent pregnancy (1984-2009). Eligible women were free of recognized diabetes. Case subjects were the 256 women who developed GDM. Two control subjects were selected for each case and matched for year of blood draw, age at exam, age at pregnancy, and number of intervening pregnancies.

RESULTS

Compared with the highest quartile of adiponectin, the risk of GDM increased with decreasing quartile (odds ratio [OR] 1.5 [95% CI 0.7-2.9], 3.7 [1.9-7.2], and 5.2 [2.6-10.1]; P(trend) <0.001) after adjustment for family history of diabetes, BMI, parity, race/ethnicity, cigarette smoking, and glucose and insulin concentrations. Similar estimates were observed for HMW (P(trend) <0.001). The combined effects of having total adiponectin levels below the median (<10.29 mg/mL) and being overweight or obese (BMI ≥25.0 kg/m(2)) were associated with a sevenfold increased risk of GDM compared with normal-weight women with adiponectin levels above the median (OR 6.7 [95% CI 3.6-12.5]).

CONCLUSIONS

Prepregnancy low adiponectin concentrations, a marker of decreased insulin sensitivity and altered adipocyte endocrine function, is associated with reduced glucose tolerance during pregnancy and may identify women at high risk for GDM to target for early intervention.

Integral role of PTP1B in adiponectin-mediated inhibition of oncogenic actions of leptin in breast carcinogenesis

The molecular effects of obesity are mediated by alterations in the levels of adipocytokines. High leptin level associated with obese state is a major cause of breast cancer progression and metastasis, whereas adiponectin is considered a "guardian angel adipocytokine" for its protective role against various obesity-related pathogenesis including breast cancer. In the present study, investigating the role of adiponectin as a potential inhibitor of leptin, we show that adiponectin treatment inhibits leptin-induced clonogenicity and anchorage-independent growth. Leptin-stimulated migration and invasion of breast cancer cells is also effectively inhibited by adiponectin. Analyses of the underlying molecular mechanisms reveal that adiponectin suppresses activation of two canonical signaling molecules of leptin signaling axis: extracellular signal-regulated kinase (ERK) and Akt. Pretreatment of breast cancer cells with adiponectin protects against leptin-induced activation of ERK and Akt. Adiponectin increases expression and activity of the physiological inhibitor of leptin signaling, protein tyrosine phosphatase 1B (PTP1B), which is found to be integral to leptin-antagonist function of adiponectin. Inhibition of PTP1B blocks adiponectin-mediated inhibition of leptin-induced breast cancer growth. Our in vivo studies show that adenovirus-mediated adiponectin treatment substantially reduces leptin-induced mammary tumorigenesis in nude mice. Exploring therapeutic strategies, we demonstrate that treatment of breast cancer cells with rosiglitazone results in increased adiponectin expression and inhibition of migration and invasion. Rosiglitazone treatment also inhibits leptin-induced growth of breast cancer cells. Taken together, these data show that adiponectin treatment can inhibit the oncogenic actions of leptin through blocking its downstream signaling molecules and raising adiponectin levels could be a rational therapeutic strategy for breast carcinoma in obese patients with high leptin levels.

Adipose tissue depot and cell size dependency of adiponectin synthesis and secretion in human obesity

Adiponectin is an insulin sensitizing fat cell (FC) hormone whose levels are related to adipose tissue (AT) mass and depot distribution. We hypothesized that the nature of AT expansion (hypertrophy vs. hyperplasia) contributes to obesity-related reductions in serum adiponectin and that this effect is influenced by the regional distribution of AT to subcutaneous (S) and visceral (V) depots. Thirteen obese subjects provided paired AT biopsies. Serum total and high molecular weight (HMW) adiponectin levels were determined by ELISA. Secretion was quantified following 24-h explant culture. FC size, number, % large, and % small FC were determined by microscopic analysis. Secretion of total adiponectin was highest by SAT (P = 0.008) and correlated more strongly with serum adiponectin (total: P = 0.015, r = 0.77; HMW: P = 0.005, r = 0.83) than did secretion by VAT (P = 0.05, r = 0.66 for both). FC size was greatest in SAT and correlated negatively with both serum (total: P = 0.01, r = −0.74; HMW: P = 0.03, r = −0.69) and secreted (total: P = 0.05, r = −0.72; HMW: P = 0.02, r = −0.87) adiponectin. The % small FC in SAT correlated positively with both serum (total: P = 0.006, r = 0.87; HMW: P = 0.009, r = 0.79) and secreted (total: P = 0.03, r = 0.75; HMW: P = 0.01, r = 0.92) adiponectin. VAT FC size correlated negatively with serum HMW adiponectin (P = 0.01, r = −0.76) but not with any measure of secretion. VAT had the greatest % small FC, which related positively to serum HMW (P = 0.004, r = 0.81) and to secreted total adiponectin (P = 0.02, r = 0.78). These studies indicate that differences in fat cell size and depot distribution of AT expansion are important influences on adiponectin in obesity.

Anti-inflammatory cytokines and risk of type 2 diabetes

Proinflammatory processes have been investigated extensively in the development of type 2 diabetes, but our knowledge on anti-inflammatory proteins is rather limited. This article summarizes studies that investigated associations between circulating levels of anti-inflammatory cytokines and incident type 2 diabetes preferably in prospective epidemiological studies. Adiponectin is the only known anti-inflammatory protein whose circulating levels are decreased before type 2 diabetes. In contrast, concentrations of interleukin-1 receptor antagonist (IL-1RA), transforming growth factor-β1 (TGF-β1) and growth differentiation factor-15 (GDF-15) are increased and indicate the presence of a compensatory, but eventually futile, counter-regulation of proinflammatory stimuli. Importantly, a proof-of-principle study using recombinant IL-1RA to improve metabolic control in patients with type 2 diabetes demonstrated that a more pronounced upregulation of this protein than that found in the natural course of diabetes development may have clinical relevance. Other interesting candidates like omentin (which shows similar associations with metabolic parameters as adiponectin), interleukin-10 (IL-10) and secreted frizzled-related protein-5 (Sfrp5) are currently less well studied with sometimes conflicting results regarding their association with type 2 diabetes. Thus, further research is required to better understand the causal role of proinflammatory cytokines, hypoadiponectinaemia and the upregulation of anti-inflammatory proteins before the onset of type 2 diabetes.

Simple anthropometrics are more correlated with health variables than are estimates of body composition in Yup'ik people

OBJECTIVES

To (1) evaluate the relationships between several indices of obesity with obesity-related risk factors; (2) compare the accuracy of body composition estimates derived from anthropometry and bioimpedance analysis (BIA) to estimates of body composition assessed by doubly-labeled water (DLW); and (3) establish equations for estimating fat mass (FM), fat-free mass (FFM), and percent body fat (PBF) in Yup'ik people.

DESIGN AND METHODS

Participants included 1,056 adult Yup'ik people from 11 communities in Southwestern Alaska. In a sub-study of 30 participants, we developed population-specific linear regression models for estimating FM, FFM, and PBF from anthropometrics, age, sex, and BIA against criterion measures derived from total body water assessed with DLW. These models were then used with the population cohort and we analyzed the relationships between obesity indices and several health-related and disease status variables: (1) fasting plasma lipids, (2) glucose, (3) HbA1c, (4) adiponectin, (5) blood pressure, (6) diabetes (DM), and (7) cerebrocoronary vascular disease (CCVD) which includes stroke and heart disease.

RESULTS

The best model for estimating FM in the sub-study used only three variables-sex, waist circumference (WC), and hip circumference and had multiple R(2) = 0.9730. FFM and PBF were calculated from FM and body weight.

CONCLUSION

WC and other anthropometrics were more highly correlated with a number of obesity-related risk factors than were direct estimates of body composition. Body composition in Yup'ik people can be accurately estimated from simple anthropometrics.

Adiponectin gene polymorphisms and susceptibility to atherosclerosis: A meta-analysis

Previous studies have inspected the associations between Adiponectin (ADIPOQ) 276G/T polymorphisms and atherosclerosis, but the results are inconclusive. The aim of this study was to explore the relationship between polymorphism +276 G > T (rs1501299) in ADIPOQ and atherosclerosis. A widespread search was directed to identify all studies on the association of ADIPOQ 276G/T polymorphism with atherosclerosis risk. The fixed effect pooled measures according to odds ratio (OR) and 95% confidence interval (CI) were calculated in the meta-analysis. Heterogeneity among studies was evaluated using Q test and the I(2). Publication bias was estimated using modified Egger's linear regression test and Fuunel plot. Nine studies regarding the associations between the ADIPOQ 276G/T polymorphism and atherosclerosis risk were enrolled in this meta-analysis, including 1959 cases and 3739 controls. The 276G/T polymorphism was not significantly associated with atherosclerosis, yielding pooled ORs of 0.925 (95% CI: 0.728-1.178) and 0.921 (95% CI: 0.804-1.054), for TT versus GG, and TG versus GG, respectively. Significant between-study heterogeneity was not found in our meta-analysis. Furthermore there was no evidence of publication bias in the meta-analysis. The present meta-analysis showed that there is no association between ADIPOQ 276G/T polymorphism and atherosclerosis. High quality studies are still needed to add for more investigation of the association between ADIPOQ 276G/T polymorphisms and atherosclerosis.

The effects of Leptin and Adiponectin on Pdx1, Foxm1, and PPARγ Transcription in Rat Islets of Langerhans

BACKGROUND

Leptin and adiponectin are two hormones, which are released from adipocytes in order to control energy expenditure. Both hormones are also involved in glucose homeostasis through control of insulin secretion from pancreatic islets. Since Pdx1, PPARγ, and foxm1 play important roles in islets function, it is essential to understand how these genes are regulated in the islets of Langerhans.

OBJECTIVES

We have designed an experiment to identify the effect of leptin and adiponectin treatment on Pdx1, PPARγ, and foxm1 transcription.

MATERIALS AND METHODS

Islets were isolated from adult male rats by collagenase and incubated with different concentrations of leptin and adiponectin for 24 hours. Next, by means of real time PCR, we evaluated the gene transcription related to a housekeeping gene. The effect of leptin and adiponectin on insulin secretion was evaluated by ELISA.

RESULTS

Leptin decreased PPARγ transcription and insulin secretion, while adiponectin significantly increased Pdx1 and PPARγ transcription and insulin secretion in rat islets. The transcription of foxm1 did not change in the islet cells treated with leptin or adiponectin.

CONCLUSIONS

These findings indicate the possibility that Pdx1 and PPARγ transcription is a mediator of leptin and adiponectin function in control of insulin secretion and glucose homeostasis in pancreatic islets.

Prospective study of serum adiponectin and incident metabolic syndrome: the ARIRANG study

OBJECTIVE

Increased adiponectin levels may play a protective role in the development of metabolic abnormalities, but prospective studies of the predictive value of serum adiponectin to identify individuals at high risk of new-onset metabolic syndrome are lacking. We investigated whether serum adiponectin predicts incident cases of the metabolic syndrome in a population-based longitudinal study.

RESEARCH DESIGN AND METHODS

A prospective cohort study was conducted of 2,044 adults (831 men and 1,213 women) aged 40-70 years without metabolic syndrome examined in 2005-2008 (baseline) and 2008-2011 (follow-up). Baseline serum adiponectin concentrations were measured by radioimmunoassay.

RESULTS

During an average of 2.6 years of follow-up, 153 men (18.4%) and 199 women (16.4%) developed metabolic syndrome. In multivariable-adjusted models, the odds ratio for incident metabolic syndrome comparing the highest with the lowest quartiles of adiponectin levels was 0.25 (95% CI 0.14-0.47) in men and 0.45 (0.28-0.74) in women. While serum adiponectin did not improve the area under the ROC curve for predicting new-onset metabolic syndrome based on information from metabolic syndrome components, the net reclassification improvement and the integrated discrimination improvement of prediction models including adiponectin were significantly higher compared with those of models not including adiponectin among men, with a significant difference between men and women (P = 0.001).

CONCLUSIONS

Increased adiponectin is an independent protective factor for incident metabolic syndrome in men and women, and it may have a clinical role in predicting new-onset metabolic syndrome among men.

Alterations of adiponectin in the course of inflammation and severe sepsis

The adipocyte-specific protein adiponectin reveals anti-inflammatory, antioxidant, antiatherosclerotic and vasoprotective effects. This study aims to investigate adiponectin expression in cultured human adipocytes within an inflammatory model and in patients with severe sepsis and evaluates treatment effects of drotrecogin α (activated) (DAA). In an in vitro inflammatory model of adipocyte cell culture, the effect of DAA on adiponectin mRNA expression was evaluated. Synthesis of mRNA was measured by quantitative polymerase chain reaction. Supernatants of these adipocytes and serum levels of adiponectin were measured in blood of 104 patients by enzyme-linked immunosorbent assay on days 1, 3, and 5 of severe sepsis. Twenty-six patients were treated with DAA (DAA), 78 patients without DAA (DAA). Stimulation of human adipocytes with tumor necrosis factor α over 6 and 24 h resulted in a significant decrease in adiponectin mRNA transcripts. After 24 h of incubation, adiponectin mRNA expression was significantly upregulated according to applied dosages of DAA at 50 ng/mL and 5 μg/mL (P < 0.05). Accordingly, adiponectin levels of supernatants of adipocyte culture increased after 24 h (P < 0.05). DAA patients revealed significantly higher adiponectin serum levels compared with healthy controls (P < 0.1) and DAA patients (P < 0.05) at days 1 and 3. On day 5 after 96-h infusion of DAA (24 μg/kg per hour), adiponectin levels significantly increased in DAA patients and equalized toward DAA patients (P > 0.1). Adiponectin might be involved in the pathogenesis of the systemic inflammatory response during sepsis. Administration of DAA upregulates adiponectin expression under circumstances of systemic inflammation.

Influence of androgens on circulating adiponectin in male and female rodents

Several endocrine factors, including sex-steroid hormones are known to influence adiponectin secretion. Our purpose was to evaluate the influence of testosterone and of the synthetic non-aromatizable/non-5α reducible androgen 17β-hydroxyestra-4,9,11-trien-3-one (trenbolone) on circulating adiponectin and adiponectin protein expression within visceral fat. Young male and female F344 rats underwent sham surgery (SHAM), gonadectomy (GX), or GX plus supraphysiologic testosterone-enanthate (TE) administration. Total circulating adiponectin was 39% higher in intact SHAM females than SHAM males (p<0.05). GX increased total adiponectin by 29-34% in both sexes (p<0.05), while TE reduced adiponectin to concentrations that were 46-53% below respective SHAMs (p≤0.001) and ablated the difference in adiponectin between sexes. No differences in high molecular weight (HMW) adiponectin were observed between sexes or treatments. Adiponectin concentrations were highly and negatively associated with serum testosterone (males: r = -0.746 and females: r = -0.742, p≤0.001); however, no association was present between adiponectin and estradiol. In separate experiments, trenbolone-enanthate (TREN) prevented the GX-induced increase in serum adiponectin (p≤0.001) in young animals, with Low-dose TREN restoring adiponectin to the level of SHAMs and higher doses of TREN reducing adiponectin to below SHAM concentrations (p≤0.001). Similarly, TREN reduced adiponectin protein expression within visceral fat (p<0.05). In adult GX males, Low-dose TREN also reduced total adiponectin and visceral fat mass to a similar magnitude as TE, while increasing serum HMW adiponectin above SHAM and GX animals (p<0.05). Serum adiponectin was positively associated with visceral fat mass in young (r = 0.596, p≤0.001) and adult animals (r = 0.657, p≤0.001). Our results indicate that androgens reduce circulating total adiponectin concentrations in a dose-dependent manner, while maintaining HMW adiponectin. This change is directionally similar to the androgen-induced lipolytic effects on visceral adiposity and equal in magnitude between TE and TREN, suggesting that neither the aromatization nor the 5α reduction of androgens is required for this effect.

Vascular disease in diabetic women: Why do they miss the female protection?

Gender plays a pivotal role in the onset as well as in the progression of the cardiovascular disease with a higher morbidity and mortality being detected in men with respect to women. Type 2 Diabetes Mellitus (T2DM) may reduce gender-related differences in the prevalence of cardiovascular disease by fading the vascular protective effects afforded by estrogen in females. This article will discuss the role of sex and sex hormones on the incidence and mechanisms involved in vascular dysfunction associated to T2DM, which might explain why women with T2DM lack the vascular protection.

Identification of gene pathways altered by deletion of the androgen receptor specifically in mineralizing osteoblasts and osteocytes in mice

Androgens play a key role in skeletal growth and maintenance in males and can mediate their actions, at least in part, via the androgen receptor (AR) in osteoblasts. To investigate the mechanisms by which androgens exert their effects via the AR in mineralizing osteoblasts and osteocytes, we identified gene targets/pathways regulated by the AR using targeted gene expression and microarray approaches on bone isolated from mice in which the AR is specifically deleted in mineralizing osteoblasts and osteocytes (mOBL-ARKOs). Gene ontology mining indicated a number of biological processes to be affected in the bones of mOBL-ARKOs including skeletal and muscular system development and carbohydrate metabolism. All genes identified to have altered expression in the bones of mOBL-ARKOs were confirmed by Q-PCR for their androgen responsiveness in an androgen deprivation and replacement mouse model. The osteoblast genes Col1a1 and Bglap and the osteoclast genes Ctsk and RANKL (Tnfs11) were upregulated in the bones of mOBL-ARKOs, consistent with the increased matrix synthesis, mineralization, and bone resorption observed previously in these mice. Of significant interest, we identified genes involved in carbohydrate metabolism (adiponectin and Dpp4) and in growth and development (GH, Tgfb (Tgfb2), Wnt4) as potential targets of androgen action via the AR in mineralizing osteoblasts.

The role of adiponectin in cancer: a review of current evidence

Excess body weight is associated not only with an increased risk of type 2 diabetes and cardiovascular disease (CVD) but also with various types of malignancies. Adiponectin, the most abundant protein secreted by adipose tissue, exhibits insulin-sensitizing, antiinflammatory, antiatherogenic, proapoptotic, and antiproliferative properties. Circulating adiponectin levels, which are determined predominantly by genetic factors, diet, physical activity, and abdominal adiposity, are decreased in patients with diabetes, CVD, and several obesity-associated cancers. Also, adiponectin levels are inversely associated with the risk of developing diabetes, CVD, and several malignancies later in life. Many cancer cell lines express adiponectin receptors, and adiponectin in vitro limits cell proliferation and induces apoptosis. Recent in vitro studies demonstrate the antiangiogenic and tumor growth-limiting properties of adiponectin. Studies in both animals and humans have investigated adiponectin and adiponectin receptor regulation and expression in several cancers. Current evidence supports a role of adiponectin as a novel risk factor and potential diagnostic and prognostic biomarker in cancer. In addition, either adiponectin per se or medications that increase adiponectin levels or up-regulate signaling pathways downstream of adiponectin may prove to be useful anticancer agents. This review presents the role of adiponectin in carcinogenesis and cancer progression and examines the pathophysiological mechanisms that underlie the association between adiponectin and malignancy in the context of a dysfunctional adipose tissue in obesity. Understanding of these mechanisms may be important for the development of preventive and therapeutic strategies against obesity-associated malignancies.

A lower proportion of dietary saturated/monounsaturated/polyunsaturated fatty acids reduces the expression of adiponectin in rats fed a high-fat diet

The role for the amount of different dietary fatty acids in regulating expression of adiponectin and metabolism of glucose and lipids has been implicated, but the optimal amount has not been established yet. To address this issue, we fed male Wistar rats with either chow diet or various high-fat diets (HFDs) for 12 weeks. The HFDs contained the same percentage of fat (35% energy from fat) but had different proportions of saturated/monounsaturated/polyunsaturated (S/M/P) (1:1.7:1.2, 1:1:1, 2:1.5:1, 1:2:1, or 1:1:2) fat. Glucose and lipid metabolism and adiponectin expression were subsequently examined. In comparison with chow diet, HFD with any proportion of S/M/P increased energy intake but had no obvious effect on body weight gain. The HFD with the S/M/P proportion at 1:1:1 or 1:1:2 significantly decreased the serum triglyceride level and increased the serum level of high-density lipoprotein cholesterol in comparison with the HFD with the S/M/P proportion at 1:1.7:1.2, 2:1.5:1, or 1:2:1. The HFD containing the highest level of saturated fatty acids (S/M/P proportion at 2:1.5:1) increased levels of total cholesterol, low-density lipoprotein cholesterol, and blood glucose. Levels of serum insulin and the homeostasis model assessment of insulin resistance index were significantly increased by HFD with S/M/P proportions at 1:1.7:1.2, 1:1:1, 2:1.5:1, or 1:2:1 but not by the HFD with the S/M/P proportions at 1:1:2 (containing the highest level of polyunsaturated fatty acids). Levels of adiponectin messenger RNA in subcutaneous and visceral adipose tissues were reduced by the HFD with the S/M/P proportion at 1:1.7:1.2 or 1:1:1 but increased by the HFD with the S/M/P proportion at 1:1:2. These changes in expression of adiponectin were inversely associated with those in levels of triglyceride, insulin, and homeostasis model assessment of insulin resistance. Together, the proportion of different fatty acids in diets plays an important role in expression of adiponectin and metabolism of glucose and lipids. Specifically, the proportion of S/M/P at 1:1:2 can promote expression of adiponectin, improve metabolism of glucose and lipids, and increase insulin sensitivity.

Insulin-sensitive obesity in humans - a 'favorable fat' phenotype?

In most humans, obesity and insulin resistance coexist. However, a unique group of obese individuals, who exhibit better insulin sensitivity than expected for their adiposity, has been the focus of recent research interest. We critically examine cross-sectional and lifestyle intervention studies in obese humans classified as 'insulin-sensitive' versus 'insulin-resistant' and review the few longitudinal studies comparing rates of cardiovascular disease, type 2 diabetes and all-cause mortality in these groups of individuals. We suggest that reduced deposition of fat, particularly of bioactive lipid intermediates, in muscle and liver is potentially protective. We propose that dynamic interventional studies in insulin-sensitive obese humans may increase understanding of the metabolic factors that play a role in obesity-associated insulin resistance in humans.

Testosterone therapy decreases subcutaneous fat and adiponectin in aging men

OBJECTIVE

Testosterone therapy increases lean body mass and decreases total fat mass in aging men with low normal testosterone levels. The major challenge is, however, to determine whether the metabolic consequences of testosterone therapy are overall positive. We have previously reported that 6-month testosterone therapy did not improve insulin sensitivity. We investigated the effect of testosterone therapy on regional body fat distribution and on the levels of the insulin-sensitizing adipokine, adiponectin, in aging men with low normal bioavailable testosterone levels.

DESIGN

A randomized, double-blinded, placebo-controlled study on 6-month testosterone treatment (gel) in 38 men, aged 60-78 years, with bioavailable testosterone <7.3 nmol/l, and a waist circumference >94 cm.

METHODS

Central fat mass (CFM) and lower extremity fat mass (LEFM) were measured by dual X-ray absorptiometry. Subcutaneous abdominal adipose tissue (SAT), visceral adipose tissue (VAT), and thigh subcutaneous fat area (TFA) were measured by magnetic resonance imaging. Adiponectin levels were measured using an in-house immunofluorometric assay. Coefficients (b) represent the placebo-controlled mean effect of intervention.

RESULTS

LEFM was decreased (b = -0.47 kg, P = 0.07) while CFM did not change significantly (b = -0.66 kg, P = 0.10) during testosterone therapy. SAT (b = -3.0%, P = 0.018) and TFA (b = -3.0%, P < 0.001) decreased, while VAT (b = 1.0%, P = 0.54) remained unchanged. Adiponectin levels decreased during testosterone therapy (b = -1.3 mg/l, P = 0.001).

CONCLUSION

Testosterone therapy decreased subcutaneous fat on the abdomen and lower extremities, but visceral fat was unchanged. Moreover, adiponectin levels were significantly decreased during testosterone therapy.

Salivary pH as a marker of plasma adiponectin concentrations in Women

BACKGROUND

Plasma adiponectin is a significant correlate of the pro-inflammatory cardiometabolic risk profile associated with obesity and type 2 diabetes. Salivary pH is influenced by several cardiometabolic risk components such as inflammation, oxidation and numerous oral and systemic health modulators, including the menopausal status. This study aimed to assess the association between plasma adiponectin concentrations and salivary pH in women according to the menopausal status.

METHOD

Unstimulated saliva collection was performed in 151 Caucasian women of French-Canadian origin (53 premenopausal women (PMW) and 98 menopausal women (MW)). Student's t test, ANOVA and linear regression models were used to assess the association between plasma adiponectin concentrations and salivary pH.

RESULTS

Plasma adiponectin levels increased as a function of salivary pH in the whole sample and among MW (r = 0.29 and r = 0.36, p < 0.001). The proportion of the variance of plasma adiponectin levels explained by the salivary pH (R2) was 10.8% (p < 0.001). Plasma adiponectin levels progressively increased across salivary pH quartiles (p = 0.005).

CONCLUSIONS

These results suggest that salivary pH is a significant correlate of plasma adiponectin levels in women. With the increasing prevalence of type 2 diabetes and obesity, new technologies should be developed to more easily monitor health status, disease onset and progression. Salivary pH, a simple, inexpensive and non-invasive measure, could be a very promising avenue.

Acylated and unacylated ghrelin levels in normal weight and obese children: influence of puberty and relationship with insulin, leptin and adiponectin levels

BACKGROUND

Ghrelin circulates in blood as acylated (AG) and unacylated (UAG) ghrelin. The physiological role of the two forms is poorly understood, in particular in childhood. Aim of the study was to evaluate the AG and UAG levels in obese and normal weight (NW) children, pre-pubertal and pubertal, and their relationship with insulin, leptin and adiponectin levels.

SUBJECTS AND METHODS

A population based study in which AG, UAG, leptin, adiponectin, glucose, insulin, testosterone or estradiol levels, insulinemic indexes were evaluated in 82 NW and 58 obese (OB) children.

RESULTS

Both ghrelin forms in NW were higher (AG, p<0.02; UAG, p<0.0001) than in OB subjects, with similar ratio AG/UAG . While no differences were observed for gender, puberty AG (p<0.01) and UAG (p<0.0001) levels were higher in pre-pubertal than pubertal NW and OB subjects. Adiponectin levels in NW subjects were higher (p<0.001), while leptin and insulin levels were lower (p<0.0001) than in OB subjects. NW children showed homeostasis model assessment (HOMA) and HOMAβ indices lower than OB children (p<0.0001) with a higher a quantitative insulin sensitivity check index (p<0.0001). AG and UAG levels correlated to each other (p<0.0001), each showing a negative correlation to age, height, weight and body mass index. Both forms, but more strongly UAG, correlated with adiponectin, leptin, and insulin.

CONCLUSIONS

OB children show lower levels of both AG and UAG when compared to NW subjects, with lower levels during puberty. These results demonstrate a peculiar strong relationship between UAG levels and metabolic parameters in the pediatric population, suggesting a role for UAG in metabolic functions.

Sex differences in the impact of the Mediterranean diet on cardiovascular risk profile

The traditional Mediterranean diet (MedDiet) is now widely recommended in the prevention of CVD. However, it is not known whether the MedDiet has the same beneficial cardiovascular effects in women and in men. The objective of the present study was to investigate sex-related differences with regard to changes in cardiometabolic variables in response to a 4-week isoenergetic MedDiet. Participants were thirty-eight men and thirty-two premenopausal women aged between 25 and 50 years who had slightly elevated LDL-cholesterol (LDL-C) concentrations (3·4–4·9 mmol/l) or total cholesterol:HDL-cholesterol ratio ≥ 5·0. A 4-week run-in period preceded the MedDiet in order to control the inter- and intra-individual variability. Cardiometabolic variables were measured before and after the MedDiet. Total cholesterol, LDL-C, apoB and apoA-1 plasma concentrations as well as diastolic blood pressure decreased (P < 0·05) in both men and women (respectively, 10, 10, 10, 6 and 5 % for men and 6, 7, 9, 4 and 4 % for women). ApoA-2 concentrations and insulin concentrations 2 h after the oral administration of 75 g of glucose demonstrated sex × time interactions (respectively, P = 0·05 and P = 0·03) and only men experienced a decrease for these variables (respectively, 8 and 25 %). In conclusion, consuming a MedDiet led to significant changes in plasma lipid profile in both men and women, while only men had significant improvements in insulin homeostasis. These results support the importance of investigating sex-related differences in response to diet in order to perhaps further individualise dietary guidelines in the prevention of CVD and type 2 diabetes.

Glucocorticoid effects on adiponectin expression

Maintenance of energy metabolism and glucose homeostasis is achieved by the regulatory effects of many hormones and their interactions. Glucocorticoids produced from adrenal cortex and adiponectin produced by adipose tissue play important roles in the production, distribution, storage, and utilization of energy substrates. Glucocorticoids are involved in the activation of a number of catabolic processes by affecting the expression of a plethora of genes, while adiponectin acts primarily as an insulin sensitizer. Both are regulated by a number of physiological and pharmacological factors. Although the effects of glucocorticoids on adiponectin expression have been extensively studied in different in vitro, animal and clinical study settings, no consensus has been reached. This report reviews the primary literature concerning the effects of glucocorticoids on adiponectin expression and identifies potential reasons for the contradictory results between different studies. In addition, methods to gain better insights pertaining to the regulation of adiponectin expression are discussed.

Sleep duration and biomarkers of metabolic function among police officers

OBJECTIVE

To investigate associations between sleep duration and biomarkers of metabolic function among police officers.

METHODS

Metabolic markers were measured using standardized methods and sleep duration was assessed from questionnaire data. Mean levels of leptin and adiponectin were assessed across five levels of sleep duration using ANCOVA and linear regression models.

RESULTS

Police officers (n = 443) who reported an average of less than 5 hours and at least 8 hours of sleep had higher levels of leptin compared to those who reported an average of 5 to 7 hours of sleep. These associations were stronger and statistically significant among women, officers with BMI of 24.9 kg/m or less and smaller abdominal height (< 20 cm), and officers who primarily worked on the day shift.

CONCLUSION

Short and long sleep duration were associated with higher leptin levels and may have implications for obesity-related conditions.

Alteration in body composition in the portacaval anastamosis rat is mediated by increased expression of myostatin

The portacaval anastamosis (PCA) rat is a model to examine nutritional consequences of portosystemic shunting in cirrhosis. Alterations in body composition and mechanisms of diminished fat mass following PCA were examined. Body composition of male Sprague-Dawley rats with end-to-side PCA and pair-fed sham-operated (SO) controls were studied 3 wk after surgery by chemical carcass analysis (n=8 each) and total body electrical conductivity (n=6 each). Follistatin, a myostatin antagonist, or vehicle was administered to PCA and SO rats (n=8 in each group) to examine whether myostatin regulated fat mass following PCA. The expression of lipogenic and lipolytic genes in white adipose tissue (WAT) was quantified by real-time PCR. Body weight, fat-free mass, fat mass, organ weights, and food efficiency were significantly lower (P < 0.001) in the PCA than SO rats. Adipocyte size and triglyceride content of epididymal fat in PCA rats were significantly lower (P < 0.01) than in SO rats. Myostatin expression was higher in the WAT of PCA compared with SO rats and was accompanied by an increase in phospho-AMP kinase Thr(172). Follistatin increased whole body fat and WAT mass, adipocyte size, and expression of lipogenic genes in WAT in PCA, but not in SO rats. Myostatin and phospho-AMP kinase protein and lipolytic gene expression were lower with follistatin. We conclude that PCA results in loss of fat mass due to an increased expression of myostatin in adipose tissue with lower lipogenic and higher fatty acid oxidation gene expression.

Anthropometric, dietary, and hormonal correlates of serum adiponectin in Asian American women

There is increasing evidence that adiponectin has a critical role in the development of breast cancer, but factors that influence adiponectin concentrations have not been well studied. We conducted a cross-sectional study among Asian-American controls who participated in a population-based case-control study of breast cancer. Participants were interviewed in-person and donated a blood specimen. Using multivariate models, we investigated the relationships between serum adiponectin concentrations and lifestyle factors (including adiposity and dietary factors) and serum sex-hormones and growth factors among postmenopausal women who were nonhormone-users at blood draw (n = 196). Adiponectin concentrations were significantly positively associated with green tea intake (P trend = 0.03); levels were 31% higher among those who drank green tea 4 or more times per wk (14.5 ± 1.10 μg/mL) compared with nongreen-tea-drinkers (11.0 ± 1.09 μg/mL); this association remained after adjustment for body mass index (BMI) and waist/hip ratio (WHR), both of which were significantly and inversely associated with adiponectin. Adiponectin concentrations were positively associated with sex-hormone-binding globulin (P trend < 0.0001) and the ratios of total testosterone (T)/total estradiol (E2) (P trend <0.004) after adjustment for BMI and WHR. Confirmation of our findings on green tea and adiponectin is needed.

Functional adiponectin resistance and exercise intolerance in heart failure

The contribution of skeletal muscle myopathy to the phenotype of patients with chronic heart failure (CHF) has become generally accepted. Besides the macro- and microscopic changes that develop during the progressive process of muscular wasting, functional abnormalities manifest in an earlier stage. Analogous to the failing heart, alterations in skeletal muscle energy metabolism, including insulin resistance, are increasingly recognized. In the search for factors causing this observed myopathy, adipokines receive growing attention. In particular, adiponectin is of special interest due to its fundamental role in skeletal muscle energy metabolism. In strong contrast with patients at risk for cardiovascular disease, circulating adiponectin levels are increased in patients with CHF, and this finding is associated with adverse outcome. Recently, the concept of functional skeletal muscle adiponectin resistance has been suggested to explain compensatory elevated adiponectin levels in CHF. Unraveling of adiponectin's complex downstream signalling pathways and insights into the concept of adiponectin resistance hopefully will disengage the road for targeted therapeutic interventions.

Meta-analysis: circulating adiponectin levels and risk of colorectal cancer and adenoma

OBJECTIVE

To provide a systematic review with a meta-analysis for addressing the association between circulating adiponectin levels and the risk of colorectal cancer and adenoma.

METHODS

Multiple electronic sources including MEDLINE, EMBASE and the Science Citation Index Expanded databases were searched to identify relevant studies for this systematic review. All existing observational studies that examined the relationship between circulating adiponectin and colorectal cancer or adenoma were included. Weighted mean difference and 95% confidence intervals (CI) were estimated and pooled using meta-analysis methods.

RESULTS

Overall 13 case control or nested case control studies met the inclusion criteria. A total of 6175 participants and 3015 cases of colorectal cancer and adenoma were included in this meta-analysis. The weighted mean difference (95% CI) were -1.084 µg/mL (-1.836, -0.331), P = 0.005 in colorectal cancer and -1.43 µg/mL (-2.231, -0.628), P = 0.000 in adenoma. In men, a 2% decreased risk of colorectal neoplasm for a 1 µg/mL increment in adiponectin levels was observed (OR = 0.98, 95% CI 0.96-0.99) whereas among women there is no evidence of such a trend (OR = 0.99, 95% CI 0.97-1.01).

CONCLUSIONS

Patients with colorectal cancer and adenoma demonstrated markedly lower adiponectin values than controls, yet there was significant heterogeneity among studies. A negative dose response relationship between levels of adiponectin and the risk of colorectal neoplasm was observed in men.

The Effect of Dietary Fish Oil in addition to Lifestyle Counselling on Lipid Oxidation and Body Composition in Slightly Overweight Teenage Boys

Objective. n-3 long-chain polyunsaturated fatty acids (LCPUFAs) have shown potential to increase lipid oxidation and prevent obesity. Subjects. Seventy-eight boys aged 13–15 y with whole-body fat% of 30 ± 9% were randomly assigned to consume bread with fish oil (FO) (1.5 g n-3 LCPUFA/d) or vegetable oil for 16 weeks. All boys were counselled to improve diet and exercise habits. Results. Lifestyle counselling resulted in decreased sugar intake but did not change the physical activity level. Whole-body fat% decreased 0.7 ± 2.5% and 0.6 ± 2.2%, resting metabolic rate after the intervention was 7150 ± 1134 kJ/d versus 7150 ± 1042 kJ/d, and the respiratory quotient was 0.89 ± 0.05 versus 0.88 ± 0.05, in the FO and control group, respectively. No group differences were significant. Conclusion. FO-supplementation to slightly overweight teenage boys did not result in beneficial effects on RMR, lipid oxidation, or body composition.

The potential role of leptin and adiponectin in obesity: a comparative review

Leptin and adiponectin are adipokines produced by the white adipose tissue. The adipokines have been shown to be valuable quantitative markers of adiposity in dogs. Leptin positively correlates with body condition score (BCS) in dogs, regardless of age, sex and breed, and is influenced by feeding state, pharmacological treatment and thyroid gland activity. Conversely, adiponectin negatively correlates with body fat mass and is therefore more abundant in lean animals. The implication of leptin and adiponectin in the pathogenesis of metabolic syndrome is well established in humans, but currently lacking in dogs. Additional studies are necessary to demonstrate their potential usefulness for monitoring the progression of obesity-related diseases and response to treatment. To date, measurement of canine leptin and adiponectin has been used in experimental studies only, whereas bodyweight and BCS are considered the first-approach parameters for the routine assessment of body fat content in obese dogs.

Green tea and breast cancer

The identification of modifiable lifestyle factors that could reduce the risk of breast cancer is a research priority. Despite the enormous chemopreventive potential of green tea and compelling evidence from animal studies, its role in breast cancer development in humans is still unclear. Part of the uncertainty is related to the relatively small number of epidemiological studies on green tea and breast cancer and that the overall results from case-control studies and prospective cohort studies are discordant. In addition, the mechanisms by which green tea intake may influence risk of breast cancer in humans remain not well studied. We review the human studies that have evaluated the relationship between green tea intake and four biomarkers (sex steroid hormones, mammographic density, insulin-like growth factor, adiponectin) that are believed to be important in breast cancer development. Results from these biomarker studies are also inconclusive. Limitations of observational studies and areas of further investigations are discussed.

The complexities of obesity and diabetes with the development and progression of pancreatic cancer

Pancreatic cancer (PC) is one of the most lethal malignant diseases with the worst prognosis. It is ranked as the fourth leading cause of cancer-related deaths in the United States. Many risk factors have been associated with PC. Interestingly, large numbers of epidemiological studies suggest that obesity and diabetes, especially type-2 diabetes, are positively associated with increased risk of PC. Similarly, these chronic diseases (obesity, diabetes, and cancer) are also a major public health concern. In the U.S. population, 50 percent are overweight, 30 percent are medically obese, and 10 percent have diabetes mellitus (DM). Therefore, obesity and DM have been considered as potential risk factors for cancers; however, the focus of this article is restricted to PC. Although the mechanisms responsible for the development of these chronic diseases leading to the development of PC are not fully understood, the biological importance of the activation of insulin, insulin like growth factor-1 (IGF-1) and its receptor (IGF-1R) signaling pathways in insulin resistance mechanism and subsequent induction of compensatory hyperinsulinemia has been proposed. Therefore, targeting insulin/IGF-1 signaling with anti-diabetic drugs for lowering blood insulin levels and reversal of insulin resistance could be useful strategy for the prevention and/or treatment of PC. A large number of studies have demonstrated that the administration of anti-diabetic drugs such as metformin and thiazolidinediones (TZD) class of PPAR-γ agonists decreases the risk of cancers, suggesting that these agents might be useful anti-tumor agents for the treatment of PC. In this review article, we will discuss the potential roles of metformin and TZD anti-diabetic drugs as anti-tumor agents in the context of PC and will further discuss the complexities and the possible roles of microRNAs (miRNAs) in the pathogenesis of obesity, diabetes, and PC.

Obesity and breast cancer: status of leptin and adiponectin in pathological processes

It is well recognized that obesity increases the risk of various cancers, including breast malignancies in postmenopausal women. Furthermore, obesity may adversely affect tumor progression, metastasis, and overall prognosis in both pre- and postmenopausal women with breast cancer. However, the precise mechanism(s) through which obesity acts is/are still elusive and this relationship has been the subject of much investigation and speculation. Recently, adipose tissue and its associated cytokine-like proteins, adipokines, particularly leptin and adiponectin, have been investigated as mediators for the association of obesity with breast cancer. Higher circulating levels of leptin found in obese subjects could be a growth-enhancing factor as supported by in vitro and preclinical studies, whereas low adiponectin levels in obese women may be permissive for leptin's growth-promoting effects. These speculations are supported by in vitro studies which indicate that leptin promotes human breast cancer cell proliferation while adiponectin exhibits anti-proliferative actions. Further, estrogen and its receptors have a definite impact on the response of human breast cancer cell lines to leptin and adiponectin. More in-depth studies are needed to provide additional and precise links between the in vivo development of breast cancer and the balance of adiponectin and leptin.

Erythrocyte membrane phospholipid polyunsaturated fatty acids are related to plasma C-reactive protein and adiponectin in middle-aged German women and men

PURPOSE

Modulation of circulating inflammatory markers and adiponectin may link PUFA to risk of diabetes and cardiovascular diseases. We investigated erythrocyte n-6 and n-3 PUFA in relation to plasma C-reactive protein (CRP) and adiponectin, and whether the Pro12Ala polymorphism in the PPARγ2 gene (PPARG2) modified these associations.

METHODS

We conducted a cross-sectional analysis among 1,222 women and 758 men participating in the EPIC-Potsdam study.

RESULTS

Most notably, in both sexes, higher linoleic acid (LA) was related to lower CRP (geometric mean outcome [mg/L], quintile 1, quintile 5, p for trend ≤ 0.01 unless otherwise stated: 0.95, 0.61 [women], 0.67, 0.51 [men]) and higher adiponectin (7.9, 9.1 [women], 5.3, 6.1 [men]), whereas higher γ-linolenic acid (GLA) and dihomo-γ-linolenic acid (DGLA) were related to higher CRP (GLA: 0.63, 0.92 [women], 0.55, 0.70, p = 0.08 [men], DGLA: 0.55, 1.07 [women], 0.52, 0.76 [men]) and lower adiponectin (GLA: 8.6, 8.0 [women], 5.8, 5.4, p = 0.08 [men], DGLA: 9.2, 7.9 [women], 5.9, 5.4, p = 0.08 [men]) adjusting for age and lifestyle. The associations mostly did neither strongly nor significantly vary by PPARG2 genotype. In women, Pro12Ala appeared to interact with arachidonic acid on CRP (p = 0.04), as well as with docosatetraenoic acid on CRP (p = 0.08) and adiponectin (p = 0.02).

CONCLUSIONS

Our findings suggest that erythrocyte PUFA, particularly LA and n-6 higher unsaturated fatty acids, are related to circulating CRP and adiponectin. They do not indicate that PUFA strongly interact with the PPARG2 Pro12Ala variant on these risk markers.

Chromium dinicocysteinate supplementation can lower blood glucose, CRP, MCP-1, ICAM-1, creatinine, apparently mediated by elevated blood vitamin C and adiponectin and inhibition of NFkappaB, Akt, and Glut-2 in livers of zucker diabetic fatty rats

Chromium and cysteine supplementation can improve glucose metabolism in animal studies. This study examined the hypothesis that a cysteinate complex of chromium is significantly beneficial than either of them in lowering blood glucose and vascular inflammation markers in Zucker diabetic fatty (ZDF) rats. Starting at the age of 6 wk, ZDF rats were supplemented orally (daily gavages for 8 more weeks) with saline-placebo (D) or chromium (400 microg Cr/Kg body weight) as chromium dinicocysteinate (CDNC), chromium dinicotinate (CDN) or chromium picolinate (CP) or equimolar L-cysteine (LC, img/Kg body weight), and fed Purina 5008 diet for 8 wk. ZDF rats of 6 wk age before any supplementations and onset of diabetes were considered as baseline. D rats showed elevated levels of fasting blood glucose, HbA(1), CRP, MCP-1, ICAM-1 and oxidative stress (lipid peroxidation) and lower adiponectin and vitamin C, when compared with baseline rats. In comparison to D group, CDNC group had significantly lower blood glucose, HbA(1), CRP, MCP-1, ICAM-1 and lipid peroxidation and increased vitamin C and adiponectin levels. CDN, CP or LC showed significantly less or no effect on these biomarkers. Only CDNC lowered blood creatinine levels in comparison to D. While CDN and CP had no effect, activation of NFkappaB, Akt and glucose transporter-2 levels were decreased, insulin receptor substrate 1 (IRS-1) activation increased in livers of CDNC-rats. CDNC effect on glycemia, NFkappaB, Akt and IRS-1 in liver was significantly greater compared with LC. Blood chromium levels did not differ between Cr-groups. Exogenous vitamin C supplementation significantly inhibited MCP-1 secretion in U937 monocytes cultured in high-glucose-medium. CDNC is a potent hypoglycemic compound with anti-inflammatory activity apparently mediated by elevated blood vitamin C and adiponectin and inhibition of NFkappaB, Akt, and Glut-2 and increased IRS-1 activation in livers of type 2 diabetic rats.

Long-term, progressive, aerobic training increases adiponectin in middle-aged, overweight, untrained males and females

Adipose tissue secretes the adipokine, adiponectin (ADPN), which increases insulin sensitivity. Because some of the metabolic effects of exercise and ADPN are similar, exercise has been proposed to increase ADPN. However, most short-term (≤3 mos) and constant-effort exercise protocols have not produced increases in ADPN. Furthermore, no direct comparisons of male and female subjects on the effect of exercise on ADPN levels have been reported. We hypothesized that long-term (6 mos), progressive training would increase ADPN levels in both males and females. We recruited middle-aged, untrained males and females to participate in an interventional study employing a marathon training regimen progressing from 9.7 to 88.5 km (6 to 55 miles) per week over 6 mos. At baseline, we matched the mean ages of the male and female groups. We collected and stored fasting plasma samples and recorded body measurements at 0 (baseline) and 6 mos. Stored samples were analysed for insulin, glucose, and ADPN. ADPN increased significantly among both males (from 5.89 ± 2.46 (mean ± SD) to 7.65 ± 3.18 μg/ml; p < 0.05) and females (from 8.48 ± 3.22 to 10.56 ± 4.05 μg/ml; p < 0.05). The extent of the increase in ADPN was similar in the male (40.7 ± 50%; median, 12.1%) and female (27.0 ± 31.1%; median, 22.3%) groups. However, there was no significant reduction in insulin resistance as measured by the HOMA-IR scores in either group. We conclude that long-term, progressive aerobic training increases circulating ADPN levels in middle-aged, untrained males and females.

Variants in the adiponectin gene and serum adiponectin: the Coronary Artery Development in Young Adults (CARDIA) Study

Circulating adiponectin is involved in the atherosclerotic process and has been associated with cardiovascular disease as well as obesity, insulin resistance, metabolic syndrome, and type 2 diabetes. The adiponectin gene (ADIPOQ) encodes the circulating protein adiponectin and affects its expression. Only a small proportion of all known ADIPOQ polymorphisms have been investigated in relation to circulating adiponectin concentrations. Using data from 3,355 African-American and white men and women aged 33-45 at the year 15 examination from the Coronary Artery Development in Young Adults (CARDIA) Study the association between 10 single-nucleotide polymorphisms (SNPs) within ADIPOQ and serum adiponectin was examined using linear regression. SNPs were chosen based on a tagSNP approach. Models were stratified by self-reported race to control for population stratification, and Bonferroni corrected for multiple comparisons. ADIPOQ SNPs rs17300539 (P < 0.0001), rs182052 (P = 0.0013), rs822393 (P = 0.0005), rs9882205 (P = 0.0001), and rs3774261 (P = 0.0001) were strongly associated with serum adiponectin concentrations in whites. In general, there was a dose-response relationship of adjusted mean adiponectin concentrations across genotypes. Only one SNP, rs17300539 was marginally associated with serum adiponectin concentrations (P = 0.0087) in African Americans. Significant interactions were found between waist and rs182052 (P = 0.0029) and between rs9882505 and smoking (P = 0.001) in whites. Many ADIPOQ SNPs have not yet been examined, and additional studies are needed to determine whether these may be functional variants.

Adiponectin and negative mood in healthy premenopausal and postmenopausal women

Negative mood and stress are associated with cardiovascular and metabolic disease. There are likely many physiological mechanisms underlying the poor health outcomes. The relationship of psychological states (negative mood, life stress, and stress-responsive hormones) and adiponectin, an adipokine that promotes insulin sensitivity, was investigated in two separate studies. The two groups of participants included 52 healthy, premenopausal women, and 63 postmenopausal women with a range of stress levels. The relationship between adiponectin and psychological state (perceived stress and negative mood) was examined cross-sectionally in both groups of participants, but also prospectively (1 year later) in the group of postmenopausal women. In premenopausal women, negative mood and nocturnal urinary epinephrine were significantly related to adiponectin, independent of BMI. In postmenopausal women, negative mood was not associated with adiponectin cross-sectionally, but negative mood was a significant predictor for lower levels of adiponectin 1 year later, independent of initial adiponectin concentrations and changes in body mass index. Lastly, having a depressive disorder was related to lower adiponectin. As adiponectin levels are associated with insulin resistance, obesity, and diabetes mellitus, these findings suggest there may be an adiponectin-mediated pathway explaining in part how negative mood affects metabolic health. Mechanistic studies are needed to explore this potential relationship further.