Adiponectin in insulin resistance: lessons from translational research

Probucol ameliorates the development of nonalcoholic steatohepatitis in rats fed high-fat diets

AIMS

We sought to evaluate the effects of probucol on steatohepatitis and associated molecular mechanisms in a rat model of nonalcoholic steatohepatitis (NASH) induced by high-fat diet (HFD).

METHODS

Forty male rats weighing 100-120 g were randomly assigned to the following treatments (n = 10 for each treatment): standard diet + normal saline (NC group), standard diet + 500 mg/kg/day probucol (NP group), HFD + normal saline (HD group), and HFD + 500 mg/kg/day probucol (HP group). All animals received the above treatments for 15 weeks. Lipid metabolism and steatohepatitis were assessed. Systemic insulin resistance, oxidative stress status, serum tumor necrosis factor-alpha (TNF-α) and adiponectin levels, and gene expression were examined.

RESULTS

High-fat feeding resulted in macrovesicular steatosis, lobular inflammation, and hepatocellular ballooning degeneration in the liver, coupled with increased concentrations of serum aspartate aminotransferase and alanine aminotransferase. Probucol exposure attenuated the biochemical and histological changes comparable with NASH. Moreover, probucol treatment significantly prevented the elevations of serum total cholesterol, low-density lipoprotein, and high-density lipoprotein and the increase in the expression of numerous lipid metabolism-related genes in HFD-fed rats. There were increased insulin sensitivity and serum adiponectin levels and enhanced hepatic AMP-activated protein kinase phosphorylation in the HP group. Probucol lessened the HFD-induced elevation of serum TNF-α and hepatic malondialdehyde and reduced antioxidant enzymatic activities.

CONCLUSIONS

Probucol shows beneficial effects on HFD-induced steatohepatitis by improving insulin resistance and attenuating oxidative stress and systemic inflammation.

Homeostasis model assessment of insulin resistance for evaluating insulin sensitivity in patients with type 2 diabetes on insulin therapy

Homeostasis model assessment of insulin resistance (HOMA-IR) is a simple and useful method for evaluating insulin sensitivity. But it is difficult to apply to type2 diabetes patients treated with insulin. We have devised a method for measuring HOMA-IR and investigated the validity of HOMA-IR for evaluating insulin sensitivity in patients with type 2 diabetes on insulin therapy. In the first arm of the study, 19 poorly controlled diabetic subjects were treated with insulin and underwent euglycemic clamp study. Then the relationship between insulin resistance index assessed by the clamp test (clamp-IR) and HOMA-IR was investigated in these subjects. Log transformed HOMA-IR correlated with log transformed M/I values derived from the standard euglycemic clamp (r=-0.753, p=0.002). In the second arm of the study, we investigated the relationship between HOMA-IR and various clinical parameters in 156 patients with poorly controlled diabetes after glycemic control. Log transformed HOMA-IR correlated negatively with age (r=-0.292, p=0.0002), HDL-C (r=-0.342, p<0.0001), log transformed serum adiponectin (r=-0.309, p=0.0006) and log transformed KITT (r=-0.264, p=0.0009), and positively with body mass index (r=0.499, p<0.0001), waist circumstance (r=0.461, p<0.0001), visceral fat area (r=0.401, p<0.0001), diastolic blood pressure (r=0.223, p=0.0054), log transformed triglyceride (r=0.497, p<0.0001), urinary CPR (r=0.216, p=0.0099), ΔCPR of glucagon stimulation test (r=0.496, p<0.0001) and log transformed insulinogenic index (r=0.325, p=0.0002). These results suggest that HOMA-IR is a useful test for the evaluation of insulin sensitivity even in patients with type 2 diabetes treated with insulin.

Maternal and fetal leptin, adiponectin levels and associations with fetal insulin sensitivity

OBJECTIVE

It remains uncertain whether leptin and adiponectin levels are correlated in maternal vs. fetal circulations. Little is known about whether leptin and adiponectin affect insulin sensitivity during fetal life.

DESIGN AND METHODS

In a prospective singleton pregnancy cohort (n = 248), we investigated leptin and adiponectin concentrations in maternal (at 24-28 and 32-35 weeks of gestation) and fetal circulations, and their associations with fetal insulin sensitivity (glucose/insulin ratio, proinsulin level).

RESULTS

Comparing concentrations in cord vs. maternal blood, leptin levels were 50% lower, but adiponectin levels more than doubled. Adjusting for gestational age at blood sampling, consistent and similar positive correlations (correlation coefficients: 0.31-0.34, all P < 0.0001) were observed in leptin or adiponectin levels in maternal (at 24-28 or 32-25 weeks of gestation) vs. fetal circulations. For each SD increase in maternal plasma concentration at 24-28 weeks, cord plasma concentration increased by 12.7 (95% confidence interval 6.8-18.5) ng/ml for leptin, and 2.9 (1.8-4.0) µg/ml for adiponectin, respectively (adjusted P < 0.0001). Fetal insulin sensitivity was negatively associated with cord blood leptin (each SD increase was associated with a 5.4 (2.1-8.7) mg/dl/µU/ml reduction in cord plasma glucose/insulin ratio, and a 5.6 (3.9, 7.4) pmol/l increase in proinsulin level, all adjusted P < 0.01) but not adiponectin (P > 0.4) levels). Similar associations were observed in nondiabetic full-term pregnancies (n = 211).

CONCLUSIONS

The results consistently suggest a maternal impact on fetal leptin and adiponectin levels, which may be an early life pathway in maternal-fetal transmission of the propensity to obesity and insulin resistance.

Adiponectin trajectories before type 2 diabetes diagnosis: Whitehall II study

OBJECTIVE

The role of adiponectin in the natural history of diabetes is not well characterized. We set out to characterize prediagnosis trajectories of adiponectin in individuals who develop type 2 diabetes.

RESEARCH DESIGN AND METHODS

In a case-cohort study (335 incident diabetes case and 2,474 noncase subjects) nested in the Whitehall II study, serum adiponectin was measured up to three times per participant (1991-1993, 1997-1999, and 2003-2004). Multilevel models adjusted for age and ethnicity were fitted to assess 13-year trajectories of log-transformed adiponectin preceding diabetes diagnosis or a randomly selected time point during follow-up (year(0)) based on 755/5,095 (case/noncase) person-examinations.

RESULTS

Adiponectin levels were lower in diabetes case than in noncase subjects (median 7,141 [interquartile range 5,187-10,304] vs. 8,818 [6,535-12,369] ng/mL at baseline, P < 0.0001). Control subjects showed a modest decline in adiponectin throughout follow-up (0.3% per year, P < 0.0001) at higher levels in women than in men (difference at year(0): 5,358 ng/mL, P < 0.0001). Female case and early-onset case (age at diagnosis <52 years) subjects had a steeper decline than control subjects (slope difference -1.1% per year, P = 0.001 in females, -1.6% per year in early-onset case subjects, P = 0.034). In men, adiponectin slopes for case and noncase subjects were parallel. The slope differences by diabetes onset were largely attenuated after adjustment for changes in obesity, whereas the sex-specific slope differences were independent of obesity.

CONCLUSIONS

Lower adiponectin levels were observed already a decade before the diagnosis of diabetes. The marked sex difference in trajectories suggests that sex-specific mechanisms affect the association between adiponectin levels and diabetes development.

Emerging roles of cadmium and heme oxygenase in type-2 diabetes and cancer susceptibility

Many decades after an outbreak of severe cadmium poisoning, known as Itai-itai disease, cadmium continues to pose a significant threat to human health worldwide. This review provides an update on the effects of this environmental toxicant cadmium, observed in numerous populations despite modest exposure levels. In addition, it describes the current knowledge on the link between heme catabolism and glycolysis. It examines novel functions of heme oxygenase-2 (HO-2) that protect against type 2-diabetes and obesity, which have emerged from diabetic/obese phenotypes of the HO-2 knockout mouse model. Increased cancer susceptibility in type-2 diabetes has been noted in several large cohorts. This is a cause for concern, given the high prevalence of type-2 diabetes worldwide. A lifetime exposure to cadmium is associated with pre-diabetes, diabetes, and overall cancer mortality with sex-related differences in specific types of cancer. Liver and kidney are target organs for the toxic effects of cadmium. These two organs are central to the maintenance of blood glucose levels. Further, inhibition of gluconeogenesis is a known effect of heme, while cadmium has the propensity to alter heme catabolism. This raises the possibility that cadmium may mimic certain HO-2 deficiency conditions, resulting in diabetic symptoms. Intriguingly, evidence has emerged from a recent study to suggest the potential interaction and co-regulation of HO-2 with the key regulator of glycolysis: 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase 4 (PFKFB4). HO-2 could thus be critical to a metabolic switch to cancer-prone cells because the enzyme PFKFB and glycolysis are metabolic requirements for cell proliferation and resistance to apoptosis.

Effects of telmisartan and valsartan on insulin sensitivity in obese diabetic mice

Telmisartan and valsartan have angiotensin II receptor blocking activity. Because telmisartan has also an agonistic action for peroxisome proliferators-activator receptor (PPAR)-γ, it is speculated that an effect of telmisartan on insulin sensitivity is different from that of valsartan, which lacks of PPAR-γ agonistic activity. To address the issue, effects of telmisartan and valsartan on insulin sensitivity, adipocytokines and PPAR-γ target genes were evaluated in obese diabetic mice. KK-A(y) mice were treated with telmisartan (5mg/kg) and valsartan (15 mg/kg), once daily for 3 weeks. Insulin tolerance test was performed on day 14, and plasma adiponectin concentration and mRNA expression levels of tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) in adipose tissues were measured on day 21. Time-course of plasma glucose level after the injection of insulin in mice with telmisartan was not significantly different from that of animals with valsartan. In addition, PPAR-γ antagonist did not diminished the improvement of insulin sensitivity by telmisartan. Telmisartan and valsartan elevated plasma adiponectin concentration and suppressed the mRNA expressions of TNF-α and IL-6 in adipose tissues. These variables of the telmisartan- and valsartan-treated groups did not significantly differ. Influence of telmisartan on the PPAR-γ target genes (ap2 and fatty acid synthase) mRNA expressions was not detected in adipose tissues under the present condition. These data suggest that the effect of telmisartan on insulin sensitivity is similar to that of valsartan, and a role of PPAR-γ-mediated stimuli is small in the telmisartan-induced improvement of insulin sensitivity.

Genetic association of adiponectin with type 2 diabetes in Jordanian Arab population

Adiponectin, a protein exclusively secreted by adipose tissue and present at low levels in obese individuals, is now widely recognized as a key determinant of insulin sensitivity and protection against obesity-associated metabolic syndrome. In Jordan, prevalence of diabetes (17.1%) is twice that of the United States (7.8%). In this study, we examined the contribution of the promoter variant rs266729 (-11377C>G) of the ADIPOQ gene as a risk factor for diabetic patients in Jordan. DNA was extracted from blood samples for patients and controls .Polymerase chain reaction and restriction fragment length polymorphism were used to genotype this variant. A total of 420 type 2 diabetic patients and 230 controls were successfully genotyped. The results showed a significant genotypic (p=0.00001) and allelic (p=0.01) association with variant in the diabetic patients as compared to controls. This suggests that the ADIPOQ gene plays a major role in increasing the risk of diabetes, at least in the Jordanian Arab population.

Overview of bariatric surgery for the physician

The worldwide pandemic of obesity carries alarming health and socioeconomic implications. Bariatric surgery is currently the only effective treatment for severe obesity. It is safe, with mortality comparable to that of cholecystectomy, and effective in producing substantial and sustainable weight loss, along with high rates of resolution of associated comorbidities, including type 2 diabetes. For this reason, indications for bariatric surgery are being widened. In addition to volume restriction and malabsorption, bariatric surgery brings about neurohormonal changes that affect satiety and glucose homeostasis. Increased understanding of these mechanisms will help realise therapeutic benefits by pharmacological means. Bariatric surgery improves long-term mortality but can cause long-term nutritional deficiencies. The safety of pregnancy after bariatric surgery is still being elucidated.

A cross-over study of the acute effects of espresso coffee on glucose tolerance and insulin sensitivity in people with type 2 diabetes mellitus

The objective was to determine the effect of a single dose of espresso caffeinated coffee, decaffeinated coffee, or water on glucose tolerance and insulin sensitivity in people with type 2 diabetes mellitus. Eighteen participants who were habitual coffee drinkers, were studied using a random-order cross-over design. After a fasting blood sample participants consumed either a double-shot black espresso coffee, decaffeinated coffee, or hot water. The main outcomes were area under the curve (AUC) glucose and insulin, and insulin sensitivity (Matsuda index) during a 75 g oral glucose tolerance test (OGTT) performed one hour later. Other outcomes were change in glucose and insulin and also the insulinogenic index (IGI) and disposition index (DI). AUC glucose was marginally different between beverages (P=.06) being greater following caffeinated coffee than water, mean difference 104 mmol/L/180 min (95% CI 0.1 to 198.1, P=.031), or decaffeinated coffee, mean difference 92.1 mmol/L/180 min (95% CI -1.9 to 186.1, P=.055). There was no difference in AUC insulin (P=.87) or insulin sensitivity (P=.47), nor in change in glucose or insulin over the hour following beverage consumption. There was a marginal difference in IGI between beverages (P=.097) with coffee having a lower incremental increase in insulin/glucose than water (P=.037) though no difference between coffee and decaffeinated coffee (P=.54) and no difference in DI (P=.23). Black espresso coffee in people with type 2 diabetes mellitus results in a marginally greater excursion of glucose during a following OGTT compared with water or decaffeinated coffee. This effect does not appear to be mediated by changes in insulin sensitivity.

Single-nucleotide polymorphisms and haplotypes in the adiponectin gene contribute to the genetic risk for type 2 diabetes in Tunisian Arabs

Adiponectin is an adipocyte-produced protein involved in regulating glucose, lipid, and energy metabolism, and is encoded by ADIPOQ (APM1) gene. ADIPOQ polymorphisms were previously associated with type 2 diabetes (T2DM) in Caucasian and non-Caucasian populations. We investigated the contribution of 13 polymorphisms in the promoter, coding regions, and 3'untranslated region of ADIPOQ gene to T2DM in 917 patients and 748 normoglycemic control subjects. ADIPOQ genotyping was done by allelic discrimination method. Of the 13 ADIPOQ variants analyzed, higher minor allele frequency of rs16861194 (P<0.001), rs17300539 (P<0.001), rs266729 (P<0.001), rs822396 (P=0.02), rs2241767 (P=0.03), and rs1063538 (P=0.02) were seen in T2DM cases. Varied association of ADIPOQ genotypes with T2DM was seen according to the genetic model used: rs17300539 and rs266729 were significantly associated with T2DM under the three models, while rs16861194 was association with T2DM under additive and dominant models, and rs822396, rs2241766, and rs1063538 were associated with T2DM under the dominant models only. Haploview analysis revealed low linkage disequilibrium between the ADIPOQ variants, resulting in high haplotype diversity, and two blocks were identified, each differentially associated with T2DM. These results support a significant association of ADIPOQ gene polymorphism with T2DM in Tunisian Arabs.

Dietary glycemic index and glycemic load and breast cancer risk in the European Prospective Investigation into Cancer and Nutrition (EPIC)

BACKGROUND

The glycemic potential of a diet is associated with chronically elevated insulin concentrations, which may augment breast cancer (BC) risk by stimulating insulin receptor or by affecting insulin-like growth factor I (IGF-I)-mediated mitogenesis. It is unclear whether this effect differs by BC phenotype.

OBJECTIVE

The objective was to investigate the relation between glycemic index (GI), glycemic load (GL), and total carbohydrate intake with BC by using data from the European Prospective Investigation into Cancer and Nutrition (EPIC).

DESIGN

We identified 11,576 women with invasive BC among 334,849 EPIC women aged 34-66 y (5th to 95th percentiles) at baseline over a median follow-up of 11.5 y. Dietary GI and GL were calculated from country-specific dietary questionnaires. We used multivariable Cox proportional hazards models to quantify the association between GI, GL, and carbohydrate intake and BC risk. BC tumors were classified by receptor status.

RESULTS

Overall GI, GL, and carbohydrates were not related to BC. Among postmenopausal women, GL and carbohydate intake were significantly associated with an increased risk of estrogen receptor-negative (ER(-)) BC when extreme quintiles (Q) were compared [multivariable HR(Q5-Q1) (95% CI) = 1.36 (1.02, 1.82; P-trend = 0.010) and HR(Q5-Q1) = 1.41 (1.05, 1.89; P-trend = 0.009), respectively]. Further stratification by progesterone receptor (PR) status showed slightly stronger associations with ER(-)/PR(-) BC [HR(Q5-Q1) (95% CI) = 1.48 (1.07, 2.05; P-trend = 0.010) for GL and HR(Q5-Q1) = 1.62 (1.15, 2.30; P-trend = 0.005) for carbohydrates]. No significant association with ER-positive BC was observed.

CONCLUSION

Our results indicate that a diet with a high GL and carbohydrate intake is positively associated with an increased risk of developing ER(-) and ER(-)/PR(-) BC among postmenopausal women.

The role of nocturnin in early adipogenesis and modulation of systemic insulin resistance in human

The deadenylase nocturnin (Noc, Ccrn4l) has been recently found to regulate lipid metabolism and to control preadipocyte differentiation. Here, we showed that among the five deadenylases tested, Noc and Pan2 exhibited a biphasic expression which is out of phase to each other during adipocyte differentiation of 3T3-L1 cells. The expression levels of other deadenylases, including Parn, Ccr4, and Caf1, were relatively unchanged or reduced. The immediate early expressed Noc during 3T3-L1 adipogenesis was involved in regulating mitotic clonal expansion (MCE) and cyclin D1 expression, as demonstrated in Noc-silenced 3T3-L1 cells and Noc(-/-) primary mouse embryonic fibroblasts (MEFs). Transcriptional profiling of Noc-depleted 3T3-L1 adipocytes revealed that most of the differentially expressed genes were related to cell growth and proliferation. In human adipose tissue, NOC mRNA level negatively associated with both fasting serum insulin and homeostasis model assessment of insulin resistance, and positively associated with both adiponectin mRNA levels and circulating adiponectin levels. Taken together, these results suggest the role of Noc in the modulation of early adipogenesis as well as systemic insulin sensitivity.

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.

Weight cycling enhances adipose tissue inflammatory responses in male mice

Background

Obesity is associated with low-grade chronic inflammation attributed to dysregulated production, release of cytokines and adipokines and to dysregulated glucose-insulin homeostasis and dyslipidemia. Nutritional interventions such as dieting are often accompanied by repeated bouts of weight loss and regain, a phenomenon known as weight cycling (WC).

Methods

In this work we studied the effects of WC on the feed efficiency, blood lipids, carbohydrate metabolism, adiposity and inflammatory markers in C57BL/6 male mice that WC two or three consecutive times by alternation of a high-fat (HF) diet with standard chow (SC).

Results

The body mass (BM) grew up in each cycle of HF feeding, and decreased after each cycle of SC feeding. The alterations observed in the animals feeding HF diet in the oral glucose tolerance test, in blood lipids, and in serum and adipose tissue expression of adipokines were not recuperated after WC. Moreover, the longer the HF feeding was (two, four and six months), more severe the adiposity was. After three consecutive WC, less marked was the BM reduction during SC feeding, while more severe was the BM increase during HF feeding.

Conclusion

In conclusion, the results of the present study showed that both the HF diet and WC are relevant to BM evolution and fat pad remodeling in mice, with repercussion in blood lipids, homeostasis of glucose-insulin and adipokine levels. The simple reduction of the BM during a WC is not able to recover the high levels of adipokines in the serum and adipose tissue as well as the pro-inflammatory cytokines enhanced during a cycle of HF diet. These findings are significant because a milieu with altered adipokines in association with WC potentially aggravates the chronic inflammation attributed to dysregulated production and release of adipokines in mice.

Anti-tumour necrosis factor alpha therapy improves insulin sensitivity in normal-weight but not in obese patients with rheumatoid arthritis

INTRODUCTION

Insulin resistance (IR), a risk factor for the development of cardiovascular disease, is common among patients with rheumatoid arthritis (RA). Inflammation, and especially tumour necrosis factor alpha (TNFα), has been associated with IR, and the administration of anti-TNFα agents is suggested to improve insulin sensitivity. However obesity, a potent contributor to IR, may limit the beneficial effects of anti-TNFα medication on IR. The aim of this study is to compare the effects of anti-TNFα therapy on IR between normal-weight and obese patients with RA.

METHODS

Patients who were normal-weight with IR (N+IR) or obese with IR (O+IR) and had embarked on anti-TNFα treatment, participated. Assessments included body mass index (BMI), insulin sensitivity (Homeostasis Model Assessment of insulin resistance, HOMA and the Quantitative Insulin sensitivity Check Index, QUICKI), and RA disease characteristics before and following six months of anti-TNFα treatment. Their results were compared to matched (for age, gender, BMI, disease duration and smoking status) normal-weight patients without IR (N-IR) and obese without IR (N-IR), respectively. In total, 32 patients were assessed for this study, with 8 in each group.

RESULTS

Following six months of treatment, disease activity was significantly reduced in all groups (P < 0.05) to a similar extent (P for differences between groups > 0.05 in all cases). In the total population, changes in HOMA (mean reduction at 6 m = -0.2 ± 0.1; P = 0.088) and QUICKI (mean increase at 6 m = 0.03 ± 0.022; P = 0.092) after treatment were not statistically significant, though a trend towards improvement was observed. However, N+IR patients showed a significant decrease in HOMA (mean reduction at 6 m = -0.54 ± 0.2; P = 0.002) and increase in QUICKI (mean increase at 6 m = 0.046 ± 0.02; P = 0.011). These changes were significantly different compared to the other groups (P < 0.05 in all cases). Multivariable analyses showed that the change in Erythrocyte Sedimentation Rate (ESR), and the change in C-Reactive Protein (CRP) associated with the improvement in HOMA (ESR: F₁₋₇ = 5.143, P = 0.019; CRP: F₁₋₇ = 3.122, P = 0.022) and QUICKI (ESR: F₁₋₇ = 3.814, P = 0.021; CRP: F₁₋₇ = 2.67; P = 0.041) only in the N+IR group.

CONCLUSIONS

Anti-TNFα therapy, through controlling inflammation, seems to improve insulin sensitivity in normal-weight RA patients with insulin resistance, but is not sufficient to achieving the same beneficial effect in obese RA patients with insulin resistance.

Arterial stiffness is associated with increased monocyte expression of adiponectin receptor mRNA and protein in patients with coronary artery disease

BACKGROUND

Arterial stiffness and carotid intima-media thickness (IMT) constitute validated cardiovascular prognostic markers. Adiponectin and its receptors 1 (AdipoR1) and 2 (AdipoR2) are involved in coronary artery disease (CAD). We investigated whether AdipoR1 and R2 mRNA and protein expression are associated with arterial stiffness, IMT and extent of coronary atherosclerosis.

METHODS

We studied 71 patients (61 men, 10 women) with angiographically proven CAD. We measured: (i) monocyte expression of AdipoR1 and AdipoR2 mRNA (quantitative real-time PCR) and protein expression (flow cytometry) (iii) adiponectin, metalloproteinase-9 (MMP-9) and C-reactive protein (CRP) blood levels, (iv) carotid-femoral artery pulse wave velocity (PWV) and carotid IMT.

RESULTS

Patients with multi-vessel CAD had higher AdipoR1 and AdipoR2 mRNA than those with single-vessel (P < 0.05). PWV was associated with AdipoR1 mRNA (r = 0.474), AdipoR1 protein (r = 0.228), AdipoR2 mRNA (r = 0.716), AdipoR2-protein (r = 0.261), adiponectin (r = 0.236), and MMP-9 (r = 0.350) (P < 0.05, for all correlations). After adjustment for age, sex, waist-hip ratio, and mean blood pressure both AdipoR1 and AdipoR2 mRNA remained independent determinants of PWV (R(2) = 0.35 and R(2) = 0.57, P < 0.05). IMT was also associated with AdipoR2 mRNA, AdipoR2 protein, and MMP-9 (P < 0.05). Increased expression of ADR2 mRNA significantly related to MMP-9 (r = 0.210), and CRP (r = 0.531) (P < 0.05).

CONCLUSION

Increased mRNA and protein expression of adiponectin receptors is related with increased aortic stiffness, coronary and peripheral atherosclerosis in patients with CAD. The interrelation of AdipoR2 with inflammatory markers, PWV and IMT suggests a compensatory increase of these receptors to counteract the excess inflammatory and atherogenic process in CAD. Thus, adiponectin receptors may provide a potential therapeutic target of agents activating their beneficial action.American Journal of Hypertension 2012; doi:10.1038/ajh.2012.42.

Early postnatal overnutrition increases adipose tissue accrual in response to a sucrose-enriched diet

Both overnutrition and an incorrect nutrient balance have contributed to the rise in obesity. Moreover, it is now clear that poor nutrition during early life augments the possibility of excess weight gain in later years. Our aim was to determine how neonatal overnutrition affects later responses to a sucrose-enriched diet and whether this varies depending upon when the diet is introduced in postnatal life. Male Wistar rats raised in litters of four or 12 pups were given a 33% sucrose solution instead of water from weaning (day 21) or postnatal day (PND) 65. All rats received normal chow ad libitum until they were euthanized on PND 80. Body weight (BW) and food and liquid intake were monitored throughout the study. Fat mass, adipocyte morphology, serum biochemical and hormonal parameters, and hypothalamic neuropeptide mRNA levels were measured at study termination. Neonatal overnutrition increased food intake, BW, and leptin levels, induced adipocyte hypertrophy, and decreased total ghrelin levels. The sucrose-enriched diet increased total energy intake, adipose accrual, and leptin, adiponectin, and acylated ghrelin levels but decreased BW. Most of these responses were accentuated in neonatally overnourished rats, which also had increased insulin and triglyceride levels. However, long-term sucrose intake induced adipocyte hypertrophy in rats from normal-sized litters but not in neonatally overfed rats. The results reported here indicate that neonatal overnutrition increases the detrimental response to a diet rich in sucrose later in life. Moreover, the timing and duration of the exposure to a sucrose-enriched diet alter the adverse metabolic outcomes.

Effects of lipoic acid on AMPK and adiponectin in adipose tissue of low- and high-fat-fed rats

BACKGROUND

Lipoic acid (LA) is an antioxidant with antiobesity and antidiabetic properties. Adiponectin is an adipokine with potent anti-inflammatory and insulin-sensitizing properties. AMP-activated protein kinase (AMPK) is a key enzyme involved in cellular energy homeostasis. Activation of AMPK has been considered as a target to reverse the metabolic abnormalities associated with obesity and type 2 diabetes.

AIM OF THE STUDY

The aim of this study was to determine the effects of LA on AMPK phosphorylation and adiponectin production in adipose tissue of low-fat (control diet) and high-fat diet-fed rats.

RESULTS

Dietary supplementation with LA reduced body weight and adiposity in control and high-fat-fed rats. LA also reduced basal hyperinsulinemia as well as the homeostasis model assessment (HOMA) levels, an index of insulin resistance, in high-fat-fed rats, which was in part independent of their food intake lowering actions. Furthermore, AMPK phosphorylation was increased in white adipose tissue (WAT) from LA-treated rats as compared with pair-fed animals. Dietary supplementation with LA also upregulated adiponectin gene expression in WAT, while a negative correlation between adiposity-corrected adiponectin levels and HOMA index was found. Our present data suggest that the ability of LA supplementation to prevent insulin resistance in high-fat diet-fed rats might be related in part to the stimulation of AMPK and adiponectin in WAT.

Improvement of vitamin D status via daily intake of fortified yogurt drink either with or without extra calcium ameliorates systemic inflammatory biomarkers, including adipokines, in the subjects with type 2 diabetes

CONTEXT

Systemic inflammation is thought to have a central role in diabetic long-term complications.

OBJECTIVE

The aim of this study was to investigate the effects of vitamin D either with or without extra calcium on certain inflammatory biomarkers in the subjects with type 2 diabetes (T2D).

DESIGN, SETTING, AND PARTICIPANTS

This was a double-blind, randomized, controlled trial conducted over 12 wk in 90 T2D subjects aged 30-60 yr from both sexes.

INTERVENTION

Subjects were randomly allocated to one of three groups to receive two 250-ml bottles a day of plain Persian yogurt drink or doogh (PD, containing 150 mg calcium and no detectable vitamin D(3)/250 ml), vitamin D-fortified doogh (DD, containing 500 IU vitamin D(3) and 150 mg calcium/250 ml), or calcium + vitamin D(3)-fortified doogh (CDD, containing 500 IU vitamin D(3) and 250 mg calcium/250 ml).

OUTCOME MEASURES

The changes in inflammatory markers were evaluated.

RESULTS

Compared to the baseline values, highly sensitive C-reactive protein, IL-1β, IL-6, fibrinogen, and retinol binding protein-4 concentrations significantly decreased in both the DD and CDD groups. Although the decrement in highly sensitive C-reactive protein and fibrinogen was more in CDD compared to DD (-4.0 ± 8.5 vs. -1.3 ± 2.8 mg/liter, and -0.40 ± 0.74 and -0.20 ± 0.52 mg/liter, respectively), the differences were not significant. There was a significant increase in serum adiponectin in both the DD and CDD groups (51.3 ± 65.3 vs. 57.1 ± 33.8 μg/liter; P < 0.05). Mean adiponectin changes in CDD were significantly higher than in PD (P = 0.021).

CONCLUSIONS

Daily intake of vitamin D-fortified doogh improved inflammatory markers in T2D subjects, and extra calcium conferred additional benefit only for the antiinflammatory adipokine, i.e. adiponectin.

Adiponectin and skeletal muscle: pathophysiological implications in metabolic stress

Upregulation of muscular adiponectin could act as a local protective mechanism to counteract cellular damage in obesity by weakening inflammation, oxidative stress, and apoptosis. To test this hypothesis, adiponectin-knockout (KO) and wild-type (WT) mice were fed a Western diet (WD). WT mice under WD conditions displayed 63% higher adiponectin expression in myocytes than those under standard laboratory diet (SLD) conditions (P = 0.011). WD-fed KO mice exhibited approximately threefold larger myocyte degeneration than WT mice (P = 0.003). Even under SLD conditions, myotubes of KO mice displayed already moderate immunolabeling for markers of oxidative stress (peroxiredoxin-3/5) and for a lipid peroxidation product (hydroxynonenal). Expression of tumor necrosis factor-α (TNF-α) and caspase-6, a marker of apoptosis, was also present. After WD challenge, immunoreactivity for these markers was strong in muscle of KO mice, although it was detected to a lesser extent in WT mice. Activation of NF-κB and caspase-6 doubled in myocytes of WD-fed KO mice when compared to WT mice (P < 0.001). Furthermore, muscle electrotransfer of the adiponectin gene prevented these abnormalities in WD-fed KO mice. Finally, gene abrogation of the adiponectin receptor 1 (AdipoR1) by siRNA recapitulated a pro-inflammatory state in C2C12 myotubes. Thus, upregulation of muscular adiponectin may be triggered by obesity and be crucial locally to counteract oxidative stress, inflammation, and apoptosis. These effects operate in an autocrine/paracrine manner via AdipoR1 and down-regulation of NF-κB signaling.

Elevated serum visfatin/nicotinamide phosphoribosyl-transferase levels are associated with risk of postmenopausal breast cancer independently from adiponectin, leptin, and anthropometric and metabolic parameters

OBJECTIVE

Obesity has been implicated in the etiology of postmenopausal breast cancer (PBC). We hypothesized that altered secretion of visfatin may underlie this association. We thus investigated the association of serum visfatin with PBC risk, taking into account known risk factors including adipokines and anthropometric and metabolic parameters.

METHODS

In a case-control study, we studied 102 postmenopausal women with pathologically confirmed, incident invasive breast cancer and 102 control women matched on age and time of diagnosis between 2003 and 2010 at Army Share Fund Hospital, Veterans' Hospital (NIMTS). Levels of serum visfatin, adiponectin, leptin, metabolic parameters, carcinoembryonic antigen, and CA 15-3 were determined.

RESULTS

The mean serum visfatin level was significantly higher in case than in control participants (P < 0.001). Women in the highest quartile of visfatin concentration presented significantly higher odds for PBC, adjusting for age, date of diagnosis, education, body mass index, waist circumference, years with menstruation, parity/age at first full-term pregnancy, breast-feeding, family history of cancer, use of exogenous hormones, alcohol consumption, smoking status, homeostasis model assessment score, and serum leptin and adiponectin concentrations (odds ratio, 7.93; 95% CI, 2.52-24.9). In case participants, the visfatin level correlated significantly with the tumor marker CA 15-3 (P = 0.03) but not with metabolic and anthropometric variables (P > 0.05).

CONCLUSIONS

Further prospective studies are needed to determine whether an elevated serum visfatin level is implicated in the etiopathogenesis of PBC or reflects changes during PBC progression and could therefore be used as a biomarker for PBC.

Role of coffee in modulation of diabetes risk

Coffee consumption has been associated with a lower risk of type 2 diabetes. This association does not depend on race, gender, geographic distribution of the study populations, or the type of coffee consumed (i.e., caffeinated or decaffeinated). This review discusses the strength of this relationship, examines the possibility that the pattern of coffee consumption could influence the association, and evaluates the possible relationship between coffee consumption and other risk factors associated with diabetes. Particular attention is paid to the identification, on the basis of the scientific evidence, of the possible mechanisms by which coffee components might affect diabetes development, especially in light of the paradoxical effect of caffeine on glucose metabolism. In addition to the role of coffee in reducing the risk of developing type 2 diabetes, the possible role of coffee in the course of the illness is explored. Finally, the possibility that coffee can also affect the risk of other forms of diabetes (e.g., type 1 diabetes and gestational diabetes) is examined.

Detection of adiponectin and monocyte chemoattractant protein-1 using a calixcrown derivatives-coated protein chip

We used a ProteoChip coated with a calixcrown derivative protein linker to measure adiponectin and monocyte chemoattractant protein-1 (MCP-1) levels and compared the results with commercial enzyme-linked immunosorbent assay (ELISA) kits. Adiponectin and MCP-1 levels in normal human serum and RAW264 cell supernatants, respectively, were measured. The ProteoChip quantification results correlated with those from the ELISA kits; however, the ProteoChip required less sample volume, exhibited higher sensitivity, and had a wider detection range. The ProteoChip was capable of detecting and quantifying small amounts of protein, possibly replacing ELISA kits in evaluating the levels of adiponectin and MCP-1.

Adipokines and central control in adenosine A1 receptor dependent glucose metabolism

Adenosine A1 receptor-deficient mice develop a phenotype of insulin resistance and grow fat. Participating pathophysiological pathways are not understood in detail yet, as discussed in our recent manuscript. This commentary further explores possible pathophysiological mechanisms with emphasis on the roles of the adipokines resistin, retinol-binding protein 4, adiponectin and the function of the gastric hormone ghrelin in adenosine mediated central regulation of energy balance. The postulate of an important function of ghrelin/A1AR axis provides a good hypothetical basis for further investigations to clarify the mechanism of A1AR-dependent metabolic homeostasis.

Short-term walnut consumption increases circulating total adiponectin and apolipoprotein A concentrations, but does not affect markers of inflammation or vascular injury in obese humans with the metabolic syndrome: data from a double-blinded, randomized, placebo-controlled study

Long-term consumption of walnuts is associated with lower cardiovascular disease risk in epidemiological studies, possibly through improvements in lipid profile and endothelial function. It remains to be elucidated how soon after initiation of walnut consumption beneficial effects on lipid profile and biomarkers of inflammation or vascular injury can be observed. Fifteen obese subjects (9 men and 6 women; age, 58 ± 2.5 years; body mass index, 36.6 ± 1.7 kg/m(2)) with the metabolic syndrome participated as inpatients in a randomized, double-blinded, placebo-controlled crossover study involving short-term placebo or walnut-enriched diet (48 g/d for 4 days). Apolipoproteins and markers of inflammation and vascular injury were measured before and after consumption of the experimental diets. Consumption of walnuts was associated with a statistically significant increase in serum apolipoprotein A concentrations (P = .03), but did not affect circulating levels of fetuin A, resistin, C-reactive protein, serum amyloid A, soluble intercellular adhesion molecules 1 and 3, soluble vascular cell adhesion protein 1, interleukins 6 and 8, tumor necrosis factor α, E-selectin, P-selectin, and thrombomodulin. Four days of walnut consumption (48 g/d) leads to mild increases in apolipoprotein A concentrations, changes that may precede and lead to the beneficial effects of walnuts on lipid profile in obese subjects with the metabolic syndrome.

Supplementation of n3 long-chain polyunsaturated fatty acid synergistically decreases insulin resistance with weight loss of obese prepubertal and pubertal children

BACKGROUND AND AIMS

Supplementation with n3 long-chain polyunsaturated fatty acids (n3-LCPUFA) appears to affect body weight, adipokines, and insulin resistance (IR) in obese individuals. However, it is unclear whether the effect on IR is independent of weight loss and if the same effect is observed in children. We undertook this study to analyze the effect of supplementation with n3-LCPUFA on adipokine concentration and IR of prepubertal and pubertal children, independent of weight loss.

METHODS

Included were 76 children, 9- to 18-years of age. Subjects were overweight and insulin resistant, but otherwise healthy. They were randomly assigned to receive 900 mg n3-LCPUFA daily (Omega III, Salmon Oil, GNLD) or placebo for 1 month. No dietary intervention was conducted. Dietary information, anthropometry, and blood samples to measure adipokines and IR were obtained at baseline. Anthropometry and measurement of biochemical parameters were repeated at the end of follow-up. For analysis, children were stratified by treatment (placebo and n3-FA) and according to changes in body weight (increase, decrease, unchanged).

RESULTS

Twenty seven children received placebo and 49 received the n3-LCPUFA. Despite no differences at baseline, only the n3-FA group decreased fasting insulin and HOMA-IR (p <0.010). Significant differences between groups were observed for changes in TNF-α, leptin and adiponectin after supplementation (p <0.050). At the end of the 1-month period, 16 children lost weight and 27 children gained weight. Multiple analysis demonstrated that supplementation with n3-LCPUFA decreased HOMA-IR by 15% after adjusting for puberty, treatment adherence, changes in adipokines, and weight loss. Interaction between supplementation and weight loss was significant (p = 0.007).

CONCLUSIONS

Supplementation with n3-LCPUFA is a potential beneficial tool for obese at-risk children.

Insulin resistance in relation to melanoma risk

Obesity, deregulation of adipocytokines, and insulin resistance are interrelated and have been implicated in carcinogenesis. In search of novel risk factors for melanoma, we explored the association of this disease with insulin resistance in a small size, case-control study. Homeostasis Model Assessment for Insulin Resistance (HOMA-IR), serum leptin, and adiponectin levels were determined in 55 patients with incident melanoma and 165 age-matched and sex-matched controls. Odds ratios were derived after adjusting for skin type, medical history, sociodemographic, lifestyle, and anthropometric parameters. Among the controls, HOMA-IR correlated positively with BMI (r=0.34; P=0.0001), waist-to-hip ratio (r=0.20; P=0.01) and negatively with serum adiponectin (r=-0.21; P=0.006), whereas the correlation with leptin was essentially null (r=0.09; P=0.27). The mean HOMA-IR was approximately 1.5 times higher in cases than in controls (P=0.05). The established positive association of melanoma with skin type was evident in multiple logistic regression models and so was the association with increasing HOMA-IR quintile (odds ratio for the fifth quintile=3.68; 95% confidence intervals 1.15-11.79, P=0.02). The latter persisted after adjustment for anthropometric variables and adiponectin but was attenuated when leptin was introduced in the model. These findings point to insulin resistance as a potentially independent risk factor for melanoma and need to be confirmed by future larger studies, ideally allowing the control of the directionality of the association.

Association between circulating levels of adiponectin and indices of bone mass and bone metabolism in middle-aged post-menopausal women

BACKGROUND

Adiponectin, a fat derived cytokine, is a potential independent contributor to bone mineral density (BMD); however, its action on bone metabolism in humans is still unclear.

AIM

The aim of this study was to investigate the relationship of adiponectin with bone mass indices and bone metabolic markers in middle-aged post-menopausal women without diabetes.

SUBJECTS AND METHODS

A random sample consisted of 81 post-menopausal women (age range 45-61 yr, osteopenic/osteoporotic no.=43) was studied. Lumbar-spine BMD (BMD(L2-L4)) and total-body bone mineral content (TBBMC) were measured with dual X-ray absorptiometry. Plasma levels of total and high-molecular weight (HMW) adiponectin, osteoprotegerin (OPG), soluble receptor activator of nuclear factor-κB ligand (sRANKL) and IGF-I were determined.

RESULTS

No association was observed between total or HMW adiponectin and BMD(L2-L4) or TBBMC. On the contrary, adiponectin levels were positively associated with OPG levels (partial r=0.276, p=0.015) and negatively with IGF-I (partial r=-0.438, p<0.001), in multiple regression models after adjustment for potential confounders. HMW adiponectin showed a negative association with IGF-I (partial r=-0.266, p=0.049) in the multiple regression models but not with OPG, TBBMC or BMD(L2-L4).

CONCLUSIONS

Although we failed to show statistically significant association between circulating adiponectin levels and indices of bone mass in women during the postmenopausal period, we showed significant associations with OPG and IGF-I levels, suggesting an anabolic role of adiponectin, which may contribute in the understanding of the interplay between adipose tissue-derived hormones and bone metabolism.

Serum adipokines and HIV viral replication in patients undergoing antiretroviral therapy

INTRODUCTION

Several studies have reported that cytokines secreted by adipose tissue (adipokines) may be linked to HIV replication. The aim of the study was to evaluate the relationship between HIV replication and serum levels of adipokines, in a Caucasian HIV-infected population of men and women undergoing complex antiretroviral therapy.

METHODS

A cross-sectional study was conducted in an unselected sample of 77 HIV-1-positive patients. Serum adipokines levels were measured including circulating adiponectin, leptin, resistin, tumor necrosis factor alpha (TNF-alpha) and interleukin-6 (IL-6). Patients were divided into two groups: Group 1 - with undetectable viral load and Group 2 - with persistent HIV viral replication. Differences between groups ? were tested using independent-sample t-test for Gaussian variables and Mann-Whitney-Wilcoxon test for non-parametric variables. Pearson's chi-squared test was used for correlation analysis.

RESULTS

A total of 77 patients (age range: 17-65, mean: 32.5 years) including 44 men (57.1% men, age range: 17-63 years, mean: 34.1 years) and 33 women (42.9% women age range: 19-65 years, mean: 30.3 years) were included in the study. TNF-alpha had significantly higher serum levels in patients with detectable viral load (16.89 vs. 9.35 pg/mL), (p=0.043), but correlation analysis lacked statistical significance. Adiponectin had median serum levels of 9.22 ìg/mL in Group 1 vs. 16.50 ìg/mL in Group 2 but the results lacked statistical significance (p=0.059). Higher leptin, IL-6 and resistin serum levels were noted in patients with undetectable HIV viral load, without statistical significance.

CONCLUSIONS

The present study reported higher TNF-alpha serum levels in patients with persistent HIV viral load. We found no statistically significant correlations between adiponectin, leptin, resistin and IL-6 and HIV viral load in our Caucasian HIV-positive study population, undergoing antiretroviral therapy.

Rosuvastatin and atorvastatin: comparative effects on glucose metabolism in non-diabetic patients with dyslipidaemia

The ever increasing interventional CVD outcome studies have resulted in statins being an essential factor of cardiovascular prevention strategies. The JUPITER study in 2008, despite reducing CVD and overall mortality, highlighted an increase in new onset diabetes in the rosuvastatin treated arm. Since then there have been many meta-analyses of the RCTs and the largest carried out by Sattar et al showed a significant increase in the incidence of diabetes during the trials. The findings from the individual studies when comparing the different statins were less clear. A higher statin dosage and risk factors associated with diabetes appeared to predict this phenomenon. There have been many studies investigating the effects of statins on glycaemic control, but again no clear conclusion is apparent. Despite the increase in new onset diabetes observed, the risk is clearly out-weighed by the CVD benefits observed in nearly all the statin trials. Thus, no change is required to any of the prevention guidelines regarding statins. However, it may be prudent to monitor glycaemic control after commencing statin therapy. This review will focus on atorvastatin which is the most widely used statin worldwide and rosuvastatin which is the most efficacious. This will be against a background of the effects of other statins on glucose metabolism in non-diabetic patients.

Blood pressure decrease with ingestion of a soya product (kinako) or fish oil in women with the metabolic syndrome: role of adiponectin and nitric oxide

The aim of the present study was to verify the effects of fish oil and a soya-based product on inflammatory markers and endothelial function measured by NO in women with the metabolic syndrome (MetS). A total of sixty-five women (mean age: 47·9 (sd9·98) years) were studied in a 90-d parallel, randomised design. A control group maintained their usual diet; the second group received 29 g/d of soyabean (kinako); the third group received 3 g/d of fish oiln-3 fatty acids; and the fourth group received fish oil (3 g/d) and kinako (29 g/d). Anthropometric, blood pressure (BP), inflammatory markers, anti-inflammatory marker (adiponectin) and NO concentrations were evaluated. In relation to the baseline values, the group that received fish oil and kinako concomitantly presented a statistically significant decrease in systolic BP (SBP;P < 0·05), whereas there was a significant decrease in diastolic BP (DBP) in the control group (P < 0·05), kinako group (P < 0·01) and fish oil group (P < 0·01) after 90 d. There was a significant increase in adiponectin (P < 0·01) and NO values (P < 0·05) after 90 d in the kinako and fish oil groups. Differences between treatment groups verified a significant decrease (P < 0·05) in DBP in the kinako group after 90 d when compared to the results obtained from the fish oil and kinako groups. In conclusion, the findings of increased serum adiponectin and NO metabolite levels after 90 d, both in the fish oil and soya groups, reinforce the importance of the influence of adiponectin and NO levels on BP decrease in patients with the MetS.

Calorie restriction and rapamycin inhibit MMTV-Wnt-1 mammary tumor growth in a mouse model of postmenopausal obesity

Obesity is an established risk and progression factor for postmenopausal breast cancer. Interventions to decrease caloric intake and/or increase energy expenditure beneficially impact tumor progression in normoweight humans and animal models. However, despite the increasingly high global prevalence of obesity, the effects and underlying mechanisms of these energy balance modulating interventions are poorly characterized in obese individuals. The goal of this study was to better characterize the mechanism(s) responsible for the link between energy balance and breast cancer progression in the postmenopausal obesity context. We compared the effects of calorie restriction (CR), treadmill exercise (EX), and mammalian target of rapamycin (mTOR inhibitor) treatment on body composition, serum biomarkers, cellular signaling, and mammary tumor growth in obese mice. Ovariectomized C57BL/6 mice were administered a diet-induced obesity regimen for 8 weeks, then randomized into three treatment groups: control (semipurified diet fed ad libitum, maintained the obese state); 30% CR (isonutrient relative to control except 30% reduction in carbohydrate calories); and EX (control diet fed ad libitum plus treadmill exercise). Mice were implanted with syngeneic MMTV-Wnt-1 mammary tumor cells at week 12. Rapamycin treatment (5  mg/kg every 48  h) started at week 14. Tumors were excised at week 18. CR and rapamycin (but not EX) significantly reduced final tumor weight compared to control. In follow-up analysis, constitutive activation of mTOR ablated the inhibitory effects of CR on Wnt-1 mammary tumor growth. We conclude that mTOR inhibition may be a pharmacologic strategy to mimic the anticancer effects of CR and break the obesity-breast cancer progression link.

Total and high-molecular-weight adiponectin and risk of incident diabetes in older people

OBJECTIVE

To delineate the associations of total adiponectin, high-molecular-weight (HMW) adiponectin, and the HMW-to-total adiponectin ratio with diabetes in older adults.

RESEARCH DESIGN AND METHODS

Total and HMW adiponectin were measured in a population-based study of older adults. The relations of total adiponectin, HMW adiponectin, and their ratio with incident diabetes (n = 309) were assessed in 3,802 individuals.

RESULTS

Total and HMW adiponectin were highly correlated (r = 0.94). Analysis using cubic splines revealed that the associations between total and HMW adiponectin and new-onset diabetes were not linear. Specifically, after adjustment for confounders, there were similar inverse relationships for total (hazard ratio per SD 0.49 [95% CI 0.39-0.63]) and HMW adiponectin (0.42 [0.32-0.56]) with diabetes up to values of 20 and 10 mg/L, respectively, above which the associations plateaued. These associations persisted after adjustment for potential mediators (blood pressure, lipids, C-reactive protein, and homeostasis model assessment of insulin resistance [HOMA-IR]). There was, however, evidence of interaction by HOMA-IR in the lower range of adiponectin, with stronger inverse associations among insulin-sensitive than insulin-resistant participants. HMW-to-total adiponectin ratio showed a linear adjusted association with outcome, but this was abolished by inclusion of mediating variables.

CONCLUSIONS

In this older cohort, increasing concentrations of total and HMW adiponectin were associated with comparably lower risks of diabetes, but these associations leveled off with further increases above concentrations of 20 and 10 mg/L, respectively. The more pronounced risk decreases at the lower range among participants without insulin resistance support a role for adiponectin that is independent of baseline hyperinsulinemia, but this will require further investigation.

Could serum visfatin be a potential biomarker for postmenopausal breast cancer?

OBJECTIVE

Previous studies have shown that visfatin is significantly elevated in patients with gastric carcinoma and postmenopausal breast cancer (PBC). We thus explored whether serum visfatin could be used as a potential diagnostic and prognostic tool for PBC, taking into account clinicopathological features, serum tumor markers, anthropometric and metabolic parameters.

METHODS

Serum visfatin, tumor marker CA 15-3, carcinoembryonic antigen, metabolic and anthropometric parameters were determined in 103 postmenopausal women with pathologically confirmed, incident invasive breast cancer, 103 controls matched on age and time of diagnosis, and 51 patients with benign breast lesions (BBL).

RESULTS

Mean serum visfatin was significantly higher in cases than in controls and patients with BBL (p<0.001). In cases, visfatin was significantly associated with CA 15-3 (p=0.03), hormone-receptor status (p<0.001), lymph node invasion (p=0.06) but not with metabolic and anthropometric variables (p>0.05). Multivariable regression analysis revealed that absence of estrogen and progesterone receptors (ER-PR-) was the strongest significant determinant of serum visfatin (p<0.001) in cases adjusting for demographic, metabolic and clinicopathological features. Based upon receiver operator characteristic analysis, serum visfatin outperformed CA 15-3 only in discriminating between PBC cases with early cancer stage than those with late stage, and in differentiating particularly patients with ER-PR- breast tumors.

CONCLUSION

Further prospective and longitudinal studies are needed to determine whether serum visfatin could be used as a prognostic tool in the armamentarium of PBC monitoring and management in conjunction with other biomarkers.

Amylin and leptin activate overlapping signalling pathways in an additive manner in mouse GT1-7 hypothalamic, C₂C₁₂ muscle and AML12 liver cell lines

AIMS/HYPOTHESIS

It has been suggested that amylin amplifies leptin's effects and affects energy homeostasis synergistically with leptin in animals and humans. However, no previous study has reported on amylin and leptin signalling in hypothalamic, muscle and liver cells.

METHODS

Leptin and amylin signalling studies were performed in vitro in mouse GT1-7 hypothalamic, C₂C₁₂ muscle and AML12 liver cell lines.

RESULTS

Treatment of mouse GT1-7 and C₂C₁₂ cells with leptin or amylin increased signal transducer and activator of transcription 3 (STAT3) phosphorylation in a dose- and time-dependent manner. In mouse AML12 cells, leptin and amylin produced a biphasic response of STAT3 activity. Importantly, all leptin and amylin signalling pathways were saturable at leptin and amylin concentrations of ∼100 and ∼50 to 100 ng/ml, respectively. Leptin and amylin in combination activated STAT3, AMP-activated protein kinase (AMPK), extracellular signal-regulated kinase (ERK) 1/2 and Akt signalling pathways in an additive manner, effects that were abolished under endoplasmic reticulum (ER) stress. Leptin, but not amylin, increased IRS-1 phosphorylation in GT1-7 hypothalamic, but not in C₂C₁₂ muscle and AML12 liver cell lines.

CONCLUSIONS/INTERPRETATION

Our data suggest that leptin and amylin have overlapping and additive, but not synergistic, effects in the activation of intracellular signalling pathways. ER stress may induce leptin and amylin resistance in hypothalamic, muscle and liver cell lines. These novel insights into the mode of action of leptin and amylin suggest that these hormones may play an additive role in regulating energy homeostasis in humans.

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.

Association of vitamin K status with adiponectin and body composition in healthy subjects: uncarboxylated osteocalcin is not associated with fat mass and body weight

Osteocalcin (OC) is a vitamin K-dependent protein found in bone and in circulation. High serum γ-carboxylated OC reflects a high, and high uncarboxylated OC (ucOC) reflects a low vitamin K status. A revolutionary hypothesis is that ucOC acts as a hormone improving glucose handling and reducing fat mass. The objective was to test the logical extrapolation of the ucOC hormone hypothesis to humans that elevated ucOC is associated with higher body weight, BMI and fat mass. In a cross-sectional analysis, the associations of vitamin K status with circulating adiponectin and body composition were investigated in 244 postmenopausal women (study I). The effects of vitamin K treatment on adiponectin, body weight and BMI were investigated in archived samples from forty-two young men and women who received varying doses of menaquinone-7 during 12 weeks (study II) and from a cohort of 164 postmenopausal women who participated in a 3-year placebo-controlled trial on 45 mg menaquinone-4 (MK-4) (study III). No association was found between vitamin K status and circulating adiponectin before or after vitamin K supplementation. A higher carboxylation of OC was significantly correlated with lower body weight, BMI and fat mass of the trunk. Women taking MK-4 maintained their baseline body weight and BMI, whereas women taking placebo showed significant increases in both indices. These findings demonstrate that a high vitamin K status of bone has no effect on circulating adiponectin in healthy people and long-term vitamin K supplementation does not increase weight in healthy postmenopausal women.

Circulating adiponectin is inversely associated with risk of thyroid cancer: in vivo and in vitro studies

CONTEXT

Circulating adiponectin has been inversely associated with risk for several malignancies. Its association with thyroid cancer has not yet been evaluated.

OBJECTIVE/METHODS

We measured circulating adiponectin levels in 175 thyroid carcinoma patients and 107 controls. We also examined the expression of adiponectin receptors (AdipoR1 and AdipoR2) using immunohistochemistry in 82 thyroid carcinoma tissues and using RT-qPCR in 40 human thyroid carcinoma tissues (32 papillary, six follicular/Hurthle, one anaplastic, one medullary), four normal human thyroid tissue specimens, and the BHP7 and SW579 thyroid cancer cell lines. We then utilized these thyroid cancer cell lines to investigate whether adiponectin could directly regulate cell cycle or apoptosis.

RESULTS

Thyroid cancer patients had lower circulating adiponectin levels than controls (17.00 ± 6.32 vs. 19.26 ± 6.28 μg/ml; P < 0.001). Subjects in the highest tertile of circulating adiponectin concentrations had significantly lower odds of developing any type of thyroid carcinoma (odds ratio = 0.29; 95% confidence interval, 0.16-0.55), or papillary thyroid carcinoma (odds ratio = 0.27; 95% confidence interval, 0.14-0.55), before and after adjustment for potential confounders. Both thyroid carcinoma cell lines and tissues expressed AdipoR1 and AdipoR2. Recombinant adiponectin did not exert a clinically significant direct effect on cell cycle, proliferation, or apoptosis in thyroid cancer cell lines in vitro.

CONCLUSIONS

Circulating adiponectin is independently and inversely associated with the risk of thyroid cancer. Human thyroid carcinomas and cell lines express adiponectin receptors. However, in the absence of a major direct effect of adiponectin on thyroid cancer cell lines in vitro, the negative association observed herein may be attributed to the metabolic effects of adiponectin.

Serum adiponectin and leptin in relation to risk for preeclampsia: results from a large case-control study

Conditions resulting in insulin resistance, as well as metabolic, immune, and angiogenic perturbations, have been associated with an increased risk of preeclampsia (PE). Our purpose was to assess whether the adipose tissue-secreted hormones adiponectin, which has immune-modulating, metabolic, and angiogenic properties, and leptin, which reflects overall fat mass, are associated with PE risk. We performed a case-control design study within a hospital-based cohort of 368 pregnant women (106 with PE and 262 controls; mean age, 26.6 ± 6.8 years; mean gestational age at admission, 38.2 ± 2.8 weeks) between March 2005 and August 2007 at the Hospital of Pennsylvania University. Serum adiponectin and leptin were measured by radioimmunoassay. Statistical analysis of data was performed using simple and multiple regression analyses. No significant differences in adiponectin or leptin levels between preeclamptic and control pregnant women emerged in univariate analyses (P = .57 and P = .15, respectively). Among preeclamptic women, there were also no differences in adipokines between those with mild and severe disease. Serum adiponectin and leptin were not associated with higher risk of PE before and after adjustment for maternal age, race, primigravida, smoking status, body mass index at screening, gestational age at admission, history of PE, chronic hypertension, and gestational diabetes (odds ratio, 0.93; 95% confidence interval, 0.83-1.04 and odds ratio, 1; 95% confidence interval, 0.97-1.03, respectively). Maternal serum adiponectin and leptin levels, drawn at the time of PE diagnosis, were not associated with PE.

The place for glycemic control in the surgical patient

BACKGROUND

Hyperglycemia is common in surgical patients and is associated with adverse outcomes. Conflicting data exist regarding the best method and the value of glycemic control in various patient populations. The contributions to hyperglycemia and the components of its control are complex and overlapping and likely contribute to the documented variation in outcomes. We provide an overview of the physiologic contributors to hyperglycemia and its control, review the differences in the major randomized trial results, and summarize the data regarding glycemic control in surgical patients.

METHODS

Major reviews of the pathophysiology of hyperglycemia in surgical patients, large randomized trials in critically ill and peri-operative populations, and meta-analyses were reviewed. Summations are provided for the critically ill population and for the peri-operative group.

RESULTS

A substantial physiologic rationale exists for the control of hyperglycemia in surgical patients during critical illness and in the peri-operative period. Randomized, controlled studies are limited predominately to critically ill populations. The data support controlling hyperglycemia to a serum glucose concentration <200 mg/dL, but the absolute target range remains controversial and studied inadequately. The data indicate the benefit of tight glycemic control using insulin to achieve a target of 80-110 mg/dL (intensive insulin therapy [IIT]) vs. a liberal target of 180-200 mg/dL in critically ill surgical patients, although hypoglycemia is more common with IIT. Inadequate studies are available in the peri-operative period to draw conclusions about non-critically ill surgical patients, but the weight of the data suggests control to < 200 mg/dL likely is beneficial.

CONCLUSIONS

Surgical patients benefit from maintaining serum glucose concentrations <200 mg/dL. Intensive insulin therapy (80-110 mg/dL), which appears beneficial in critically ill surgical patients but requires frequent measurement of glucose to avoid hypoglycemia. Further studies are needed to determine the appropriate target range and the influence of nutritional provision and other factors on outcome.

Design and development of a peptide-based adiponectin receptor agonist for cancer treatment

BACKGROUND

Adiponectin, a fat tissue-derived adipokine, exhibits beneficial effects against insulin resistance, cardiovascular disease, inflammatory conditions, and cancer. Circulating adiponectin levels are decreased in obese individuals, and this feature correlates with increased risk of developing several metabolic, immunological and neoplastic diseases. Thus, pharmacological replacement of adiponectin might prove clinically beneficial, especially for the obese patient population. At present, adiponectin-based therapeutics are not available, partly due to yet unclear structure/function relationships of the cytokine and difficulties in converting the full size adiponectin protein into a viable drug.

RESULTS

We aimed to generate adiponectin-based short peptide that can mimic adiponectin action and be suitable for preclinical and clinical development as a cancer therapeutic. Using a panel of 66 overlapping 10 amino acid-long peptides covering the entire adiponectin globular domain (residues 105-254), we identified the 149-166 region as the adiponectin active site. Three-dimensional modeling of the active site and functional screening of additional 330 peptide analogs covering this region resulted in the development of a lead peptidomimetic, ADP 355 (H-DAsn-Ile-Pro-Nva-Leu-Tyr-DSer-Phe-Ala-DSer-NH2). In several adiponectin receptor-positive cancer cell lines, ADP 355 restricted proliferation in a dose-dependent manner at 100 nM-10 μM concentrations (exceeding the effects of 50 ng/mL globular adiponectin). Furthermore, ADP 355 modulated several key signaling pathways (AMPK, Akt, STAT3, ERK1/2) in an adiponectin-like manner. siRNA knockdown experiments suggested that ADP 355 effects can be transmitted through both adiponectin receptors, with a greater contribution of AdipoR1. In vivo, intraperitoneal administration of 1 mg/kg/day ADP 355 for 28 days suppressed the growth of orthotopic human breast cancer xenografts by ~31%. The peptide displayed excellent stability (at least 30 min) in mouse blood or serum and did not induce gross toxic effects at 5-50 mg/kg bolus doses in normal CBA/J mice.

CONCLUSIONS

ADP 355 is a first-in-class adiponectin receptor agonist. Its biological activity, superior stability in biological fluids as well as acceptable toxicity profile indicate that the peptidomimetic represents a true lead compound for pharmaceutical development to replace low adiponectin levels in cancer and other malignancies.

Systemic adiponectin malfunction as a risk factor for cardiovascular disease

Adiponectin (Ad) is an abundant protein hormone regulatory of numerous metabolic processes. The 30 kDa protein originates from adipose tissue, with full-length and globular domain circulatory forms. A collagenous domain within Ad leads to spontaneous self-assemblage into various oligomeric isoforms, including trimers, hexamers, and high-molecular-weight multimers. Two membrane-spanning receptors for Ad have been identified, with differing concentration distribution in various body tissues. The major intracellular pathway activated by Ad includes phosphorylation of AMP-activated protein kinase, which is responsible for many of Ad's metabolic regulatory, anti-inflammatory, vascular protective, and anti-ischemic properties. Additionally, several AMP-activated protein kinase-independent mechanisms responsible for Ad's anti-inflammatory and anti-ischemic (resulting in cardioprotective) effects have also been discovered. Since its 1995 discovery, Ad has garnered considerable attention for its role in diabetic and cardiovascular pathology. Clinical observations have demonstrated the association of hypoadiponectinemia in patients with obesity, cardiovascular disease, and insulin resistance. In this review, we elaborate currently known information about Ad malfunction and deficiency pertaining to cardiovascular disease risk (including atherosclerosis, endothelial dysfunction, and cardiac injury), as well as review evidence supporting Ad resistance as a novel risk factor for cardiovascular injury, providing insight about the future of Ad research and the protein's potential therapeutic benefits.

Oxidative stress as pathogenesis of cardiovascular risk associated with metabolic syndrome

Metabolic syndrome (MetS) is characterized by accumulation of visceral fat associated with the clustering of metabolic and pathophysiological cardiovascular risk factors: impaired glucose tolerance, dyslipidemia, and hypertension. Although the definition of MetS is different among countries, visceral obesity is an indispensable component of MetS. A growing body of evidence suggests that increased oxidative stress to adipocytes is central to the pathogenesis of cardiovascular disease in MetS. Increased oxidative stress to adipocytes causes dysregulated expression of inflammation-related adipocytokines in MetS, which contributes to obesity-associated vasculopathy and cardiovascular risk primarily through endothelial dysfunction. The purpose of present review is to unravel the mechanistic link between oxidative stress and cardiovascular risk in MetS, focusing on insulin resistance, hypertension, and atherosclerosis. Then, therapeutic opportunities translated from the bench to bedside will be provided to develop novel strategies to cardiovascular risk factors in MetS.

Mechanisms of weight maintenance under high- and low-protein, low-glycaemic index diets

SCOPE

Weight maintenance after intended weight loss is a challenge in an obesogenic environment. In a large multicentre dietary intervention study (DiOGenes), it has recently been demonstrated that a high-protein/low-glycaemic index (HP/LGI) diet was slightly more efficient in maintaining weight loss than low-protein/LGI or high-GI (LP/LGI or HGI) diets. Here, we use a proteomic approach to assess the molecular mechanisms behind this positive effect.

METHODS AND RESULTS

A subset of the most successful (weight loser, n=12) and unsuccessful (weight re-gainer, n=12) individuals consuming the LGI diets with either high- or low-protein content (HP or LP/LGI), following an initial calorie deficit run-in weight loss phase, were analyzed at the plasma protein level. Proteomic analysis revealed 18 proteins regulated after 6 months of the dietary weight maintenance phase. Furthermore, 12 proteins were significantly regulated as a function of success rate under an HP diet, arising as candidate biomarkers of mechanisms of successful weight maintenance under an HP/LGI diet. Pregnancy-zone protein (PZP) and protein S (PROS1) were revealed as novel biomarkers of weight maintenance showing opposite effects.

CONCLUSION

Semantic network analysis of the 12 regulated proteins revealed that under an HP/LGI an anti-atherogenic effect and alterations of fat metabolism were associated with the success of maintaining the initial weight loss.