The impact of leptin and adiponectin on incident type 2 diabetes is modified by sex and insulin resistance

Adipokines are possible risk markers for aortic stenosis requiring surgery

OBJECTIVES

Aortic stenosis (AS) is the most prevalent valvular heart disease among adults. The adipocyte-derived hormones, leptin and adiponectin, have profound metabolic actions. We examined whether these adipokines are independently associated with future aortic valve replacement (AVR).

DESIGN

In this longitudinal case-control study, we identified 336 cases who had undergone AVR due to AS, and who had previously participated in population-based health surveys. Two referents were matched to each case and leptin and adiponectin concentrations were analysed from stored baseline survey samples. Uni- and multivariable logistic regression analyses were used to estimate the risk of future AVR. An additional cohort was identified for validation including 106 cases with AVR and 212 matched referents.

RESULTS

Median age (interquartile range (IQR)) in years at survey was 59.9 (10.4) and at surgery 68.3 (12.7), and 48% were women. An elevated concentration of leptin was not associated with future AVR (odds ratio [95% confidence interval]) (1.10 [0.92-1.32]), although leptin was associated with a higher risk in patients with coronary artery disease (CAD) having more than 5 years between survey and AVR (1.41 [1.08-1.84]). Adiponectin was not associated with higher risk for future AVR (0.95 [0.82-1.11]), although after stratification for age, higher levels were associated with reduced risk for AVR in persons aged ≥60 years at surgery (0.79 [0.64-0.98]). In the validation study, leptin was associated with future AVR whereas adiponectin was not. None of the associations remained significant after adjustment for body mass index (BMI).

CONCLUSIONS

The adipokine leptin may promote the development of AS.

Effect of Gender on Serum Leptin in Type 2 Diabetes Mellitus: A System Review and Meta-Analysis

Objective

To assess the effect of gender factors on serum leptin levels in patients with diabetes mellitus.

Methods

To remove any studies that indicated a relationship between leptin-based inflammatory variables and the prevalence of type 2 diabetes in particular patient categories, a comprehensive search of all articles published between July 2019 and June 2021 was performed on PubMed/MEDLINE, Web of Science, Scopus, and EBSCO Host, including Academic Search Premier, Africa-Wide Information, and Cumulative Index to Nursing and Allied Health Literature. A summary description of the combined analysis across multiple centers, regions, and continents will help us better understand the effect of gender on serum leptin levels in patients with diabetes. The meta-analysis was performed using RevMan 5.2 software on the literature that satisfied the inclusion and exclusion criteria.

Results

Plasma CRP levels in women with type 2 diabetes were found to be no different from those in males with type 2 diabetes, with an OR of 0.12, 95 percent confidence interval (CI) of 0.12 to 0.12, P = 0.01. There was no statistically significant difference in the plasma level of interleukin-6 (IL-6) between women with type 2 diabetes and males with type 2 diabetes However, the “inverted funnel” diagram is asymmetrical, indicating a publication bias in the included studies, despite the fact that there was no statistically significant difference in abnormal leptin levels between men with type 2 diabetes and women patients (OR = −0.69, 95 percent CI (0.88, 1.00), P < 0.05).

Conclusion

Gender factors did not affect the level of inflammatory factors and leptin level in type 2 diabetes.

Comparative efficacy of a 12 week yoga-based lifestyle intervention and dietary intervention on adipokines, inflammation, and oxidative stress in adults with metabolic syndrome: a randomized controlled trial

The present randomized controlled trial (RCT) evaluated the comparative efficacy of 12 week yoga-based lifestyle intervention (YBLI) and dietary intervention (DI) alone on adipokines, inflammation, and oxidative stress in Indian adults with metabolic syndrome (Met S). A parallel, two arm, RCT was conducted in Integral Health Clinic (IHC), All India Institute of Medical Sciences, India from 2012 to 2014. IHC is an outpatient facility conducting YBLI programs for prevention and management of chronic diseases. Two hundred sixty men and women (20-45 years) visiting the outpatient department of a tertiary care hospital were diagnosed with Met S and randomized 1:1 to receive 12 week YBLI (n = 130) or DI (n = 130). Primary outcomes were change in plasma levels of adipokines (leptin, adiponectin, and leptin:adiponectin ratio), markers of inflammation (tumor necrosis factor [TNF]-α, interleukin [IL]-6), markers of oxidative stress (thiobarbituric acid reactive substances [TBARS], 8-hydroxy-2'-deoxyguanosine [8-OHdG], and superoxide dismutase [SOD]) measured at baseline, 2 weeks, and 12 weeks. YBLI group showed a significant decrease in leptin, leptin:adiponectin ratio, IL-6, 8-OHdG, and TBARS levels, whereas there was a significant increase in adiponectin and SOD levels. No significant changes were noticed in DI alone group. YBLI showed significantly greater reduction in TBARS levels than in DI group, suggestive of reduced oxidative stress in adults with Met S. A 12 week YBLI had a positive impact on oxidative stress versus DI alone in adults with Met S.

Biomarkers of cadmium, lead and mercury exposure in relation with early biomarkers of renal dysfunction and diabetes: Results from a pilot study among aging Canadians

Cadmium (Cd), lead (Pb) and mercury (Hg) are known nephrotoxicants that have been associated with the risk of developing type-2 diabetes (T2D). The aim of this pilot study was to explore relations between biomarkers of Cd, Pb and Hg exposure, early urinary biomarkers of renal dysfunction (kidney-injured molecule-1 (KIM-1), N-acetylglucosaminidase and retinol-binding protein (RBP)) and plasma biomarkers deemed predictive of the risk of developing T2D (adiponectin, leptin, branched-chain and aromatic amino acids), among 70 participants (age range: (46-87 yrs)) from the Canadian Longitudinal Study on Aging (CLSA) with normal glycemic control (glycated haemoglobin ≤ 6.5%) in all but four of them. Significant (p < 0.05) Spearman correlation coefficients were obtained between: plasma adiponectin and RBP (r = 0.42), urinary Cd (r = 0.32), blood Cd (r = 0.36); KIM-1 and CdU (r = 0.33) as well as HgU (r = 0.37); RBP and isoleucine (r = -0.28), leucine (r = -0.33), tyrosine (r = -0.3) and valine (r = -0.44); CdU and isoleucine and valine (r = -0.27 for both). Multiple linear regression analyses showed that some T2D-related biomarkers are confounders of associations between RBP and Hg or Cd biomarkers. Path analyses support a mediating effect of adiponectin on the relation between urinary Cd and RBP. Concluding, this pilot study originally investigated a comprehensive set of biomarkers on complex interactions between toxic metal exposure, renal function and T2D in a group of aging Canadians. Its findings warrant further investigation of longitudinal data in a greater number of participants.

Leptin: Adiponectin ratio discriminated the risk of metabolic syndrome better than adiponectin and leptin in Southwest Nigeria

AIM

To assess the ability of leptin, adiponectin and leptin: adiponectin ratio (LAR) to discriminate apparently healthy subjects with metabolic syndrome in Southwest Nigeria.

METHODS

One hundred and twenty three subjects with metabolic syndrome (cases) were age matched with 123 subjects without metabolic syndrome. The serum adiponectin and leptin levels were measured using standard procedures. The ability of serum adiponectin, leptin and LAR to discriminate metabolic syndrome and its components were determined using the receiver operating curve and linear regression.

RESULTS

The median age of the cases (49 IQR 42, 56 years) was not significantly different from the controls (48 IQR 39, 56 years) p = 0.252. The adiponectin levels was reduced with increasing number of the components of metabolic syndrome from 11.6 (IQR 9.6, 13.5) among subjects without any component of metabolic syndrome to 6.5 (IQR 5.7, 7.7) in subjects with more than three components of metabolic syndrome. For leptin and LAR, the values increased with increasing components (p < 0.001). LAR (AUC 0.960) discriminated metabolic syndrome better than adiponectin (AUC 0.865) and leptin (AUC = 0.918) in males and females (LAR AUC = 0.966, adiponectin AUC = 0.888, leptin AUC = 0.929).

CONCLUSION

LAR had better ability to discriminate the risk of metabolic syndrome than adiponectin and leptin alone in males and females among apparently healthy subjects from Southwest Nigeria.

Adipokine levels are associated with insulin resistance in antipsychotics users independently of BMI

BACKGROUND

The prevalence of obesity, metabolic syndrome and type 2 diabetes mellitus is increased among patients with severe mental disorders, and particularly use of second generation antipsychotic drugs is associated with metabolic side effects. Antipsychotics have been found to alter levels of adipokines which regulate insulin sensitivity, but their role in antipsychotic-associated insulin resistance is not established, and it is unclear whether adipokines affect insulin resistance independently of body mass index (BMI).

METHODS

We included 1050 patients with severe mental disorders and 112 healthy controls aged 18-65 years from the Oslo area, Norway. Clinical variables, BMI and use of medication were assessed, fasting blood samples were obtained for calculation of the leptin/adiponectin ratio (L/A ratio) and estimate of insulin resistance using the Homeostatic Model Assessment for Insulin Resistance (HOMA-IR). Case-control analyses were followed by mediation analyses to evaluate the possible direct effect of antipsychotics on HOMA-IR and indirect effect mediated via the L/A ratio. This was performed both with and without adjustment for BMI, in the total sample and in an antipsychotic monotherapy subsample (N = 387).

RESULTS

BMI, L/A ratio and HOMA-IR were significantly higher in patients than controls (p < 0.001-p = 0.01). There was a significant direct effect from use of antipsychotics in general on HOMA-IR both without (b = 0.03, p = 0.007) and with adjustment for BMI (b = 0.03, p = 0.013), as well as a significant mediating effect via L/A ratio both without (b = 0.03, p < 0.001) and with adjustment for BMI (b = 0.01, p = 0.041). Use of olanzapine (b = 0.03, p < 0.001) or aripiprazole (b = 0.04, p < 0.001) in monotherapy showed significant effects on HOMA-IR mediated via L/A ratio.

CONCLUSIONS

The study suggests that use of antipsychotics may alter adipokine levels, and that increased L/A ratio may play a role in the development of insulin resistance associated with use of antipsychotics also independently of BMI.

Legume consumption increase adiponectin concentrations among type 2 diabetic patients: A randomized crossover clinical trial

BACKGROUND AND OBJECTIVE

This randomized crossover clinical trial investigated the effects of substituting legumes for meat consumption in the therapeutic lifestyle change (TLC) diet on leptin and adiponectin concentrations among type 2 diabetic patients.

MATERIAL AND METHODS

Thirty-one type 2 diabetic patients (24 women, age: 58.1±6.0 years) were randomly assigned to groups designated to consume a legume-free TLC diet or a legume-based TLC diet for 8 weeks. Both diets were similar except for the replacement of two servings of red meat with legumes 3 days per week in the legume-based TLC group. Leptin and adiponectin concentrations were measured at baseline and after the 8-week intervention.

RESULTS

The legume-based TLC diet significantly increased adiponectin concentrations in comparison with the legume-free TLC diet. There was no significant change in leptin concentrations after both intervention diets.

CONCLUSIONS

Legumes increased serum adiponectin concentrations in type 2 diabetic patients. Registration number: IRCT201202251640N7.

Intestinal parasites: Associations with intestinal and systemic inflammation

The aim of the present study was to evaluate associations between intestinal parasitic infection with intestinal and systemic inflammatory markers in school-aged children with high rates of obesity. Plasma concentrations of C-Reactive Protein (CRP), leptin, TNF-α, IL-6 and IL-10 were measured as systemic inflammation markers and count of stool leukocytes as marker of intestinal inflammation in 291 children (6-10 years). Intestinal parasitic infection was measured by stool examination. Logistic regression analyses were performed to determine the odds of having high inflammatory markers for each parasite or group of parasites as compared to parasite-free children while adjusting for sex, age, mother's educational level and percentage of body fat. The prevalence of soil-transmitted helminths and intestinal protozoa infections was 12% and 36%, respectively. Parasitic infection was not associated with CRP, IL-6, IL-10 or TNF-α. Children infected with Ascaris lumbricoides (aOR: 5.91, 95% CI: 1.97-17.70) and Entamoeba coli (aOR: 8.46, 95% CI: 2.85-25.14) were more likely to have higher stool leucocytes than parasite-free children. Children with multiple infections (aOR: 10.60, 95% CI: 2.85-25.14) were more likely to have higher leptin concentrations than parasite-free children. Intestinal parasitic infection was not associated with systemic inflammation, but was associated with intestinal inflammation. Having multiple infections were associated with higher leptin concentrations.

Plasma adiponectin levels and type 2 diabetes risk: a nested case-control study in a Chinese population and an updated meta-analysis

Results from previous prospective studies assessing the relation between adiponectin and type 2 diabetes (T2D) were not entirely consistent, and evidence in Chinese population is scarce. Moreover, the last meta-analysis did not examine the impact of metabolic variables on the adiponectin-T2D association. Therefore, we prospectively evaluated the adiponectin-T2D association among 571 T2D cases and 571 age-sex-matched controls nested within the Singapore Chinese Health Study (SCHS). Furthermore, we conducted an updated meta-analysis by searching prospective studies on Pubmed till September 2016. In the SCHS, the odds ratio of T2D, comparing the highest versus lowest tertile of adiponectin levels, was 0.30 (95% confidence interval: 0.17, 0.55) in the fully-adjusted model. The relation was stronger among heavier participants (body mass index ≥23 kg/m²) compared to their leaner counterparts (P for interaction = 0.041). In a meta-analysis of 34 prospective studies, the pooled relative risk was 0.53 (95% confidence interval: 0.47, 0.61) comparing the extreme tertiles of adiponectin with moderate heterogeneity (I² = 48.7%, P = 0.001). The adiponectin-T2D association remained unchanged after adjusting for inflammation and dyslipidemia markers, but substantially attenuated with adjustment for insulin sensitivity and/or glycaemia markers. Overall evidence indicates that higher adiponectin levels are associated with decreased T2D risk in Chinese and other populations.

Is There Any Relationship between Plasma 25-Hydroxyvitamin D₃, Adipokine Profiles and Excessive Body Weight in Type 2 Diabetic Patients?

A growing interest in the role of vitamin D in metabolic diseases led us to study the relationships between 25-hydroxyvitamin D₃ (25(OH)D₃) and the profiles of selected adipokines in type 2 diabetic (T2DM) patients. The study comprised 92 type 2 diabetics divided into quartiles regarding 25(OH)D₃ concentration. Each group was divided into male and female subgroups. All the studied patients had their anthropometric and biochemical parameters determined. Plasma 25-hydroxyvitamin D₃ concentration was determined by HPLC, while the selected adipokines (leptin, adiponectin, resistin and visfatin) by ELISA methods. The ratio of leptin to adiponectin (L/A) was calculated for all the patients. In 85.3% of diabetics a full (<20 ng/mL) or moderate (20-30 ng/mL) vitamin D deficit was found. Irrespective of sex, plasma leptin concentration decreased across increasing quartiles of 25(OH)D₃ level. In women, 25(OH)D₃ was negatively correlated with BMI, leptin level as well as L/A ratio, and positively with adiponectin concentration. In men, 25(OH)D₃ was positively correlated with HDL and negatively with systolic blood pressure (SBP), leptin level and L/A ratio. Considering all the patients, there ocurred a significant negative correlation between 25(OH)D₃ and SBP, BMI, WHR, TG, leptin and L/A ratio and positive ones between 25(OH)D₃ and both adiponectin and HDL. The results of the study support the existence of the relationship among vitamin D, obesity and leptin in type 2 diabetic patients.

Leptin independently predicts development of sepsis and its outcome

Background

Sepsis is a life-threatening condition and obesity is related to the clinical outcome. The underlying reasons are incompletely understood, but the adipocyte derived hormones leptin and adiponectin may be involved.

Methods

Patients aged 18 years or more with documented first time sepsis events were included in a nested case-referent study if they had participated in previous health surveys. Two matched referents free of known sepsis were identified. Circulating levels of leptin and adiponectin were determined in stored plasma, and their impact on a future sepsis event and its outcome was evaluated.

Results

We identified 152 patients (62% women) with a sepsis event and a previous participation in a health survey. Eighty-three % had also blood samples from the acute event. Hyperleptinemia at health survey associated with a future sepsis event (OR 1.77, 95% CI 1.04–3.00) and with hospital death. After adjustment for BMI leptin remained associated with sepsis in men, but not in women. High levels in the acute phase associated with increased risk for in hospital death in women (OR 4.18, 95% CI 1.17–15.00), while being protective in men (OR 0.05, 95% CI 0.01–0.48). Furthermore, leptin increased more from baseline to the acute phase in men than in women. Adiponectin did not predict sepsis and did not relate to outcome.

Conclusions

Hyperleptinemia independently predicted the development of sepsis and an unfavourable outcome in men, and inertia in the acute response related to worse outcome.

Body and liver fat content and adipokines in schizophrenia: a magnetic resonance imaging and spectroscopy study

RATIONALE

Although antipsychotic treatment often causes weight gain and lipid abnormalities, quantitative analyses of tissue-specific body fat content and its distribution along with adipokines have not been reported for antipsychotic-treated patients.

OBJECTIVES

The purposes of the present study were to quantitatively assess abdominal and liver fat in patients with schizophrenia on antipsychotic treatment and age- and body mass index (BMI)-matched healthy controls and to evaluate their associations with plasma leptin and adiponectin levels.

METHODS

In 13 schizophrenia patients on antipsychotic treatment and 11 age- and BMI-matched controls, we simultaneously quantified visceral and subcutaneous fat content using T1-weighted magnetic resonance imaging and liver fat content by ¹H magnetic resonance spectroscopy. Associations of tissue-specific fat content with plasma levels of leptin and adiponectin were evaluated.

RESULTS

Plasma adiponectin level (μg/mL) was not statistically different between groups (7.02 ± 2.67 vs. 7.59 ± 2.92), whereas plasma leptin level (ng/mL) trended to be higher in patients than in controls (11.82 ± 7.89 vs. 7.93 ± 5.25). The values of liver fat (%), visceral fat (L), and subcutaneous fat (L) were 9.64 ± 8.03 vs. 7.07 ± 7.35, 4.41 ± 1.64 vs. 3.31 ± 1.97, and 8.37 ± 3.34 vs. 7.16 ± 2.99 in patients vs. controls, respectively. Liver fat content was inversely correlated with adiponectin in controls (r =  - 0.87, p < 0.001) but not in patients (r =  - 0.26, p = 0.39). In both groups, visceral fat was inversely associated with adiponectin (controls : r =  - 0.66, p = 0.03; patients : r =  - 0.65, p = 0.02), while subcutaneous fat was positively correlated with leptin (controls : r = 0.90, p < 0.001; patients : r = 0.67, p = 0.01).

CONCLUSIONS

These findings suggest that antipsychotic treatment may disrupt the physiological relationship between liver fat content and adiponectin but does not essentially affect the associations of adiponectin and leptin with visceral and subcutaneous compartments.

Acute Vitamin D₃ Supplementation in Severe Obesity: Evaluation of Multimeric Adiponectin

Obesity predisposes to vitamin D deficiency (VDD) and glucose abnormalities. It is currently debated if vitamin D administration may improve glucose homeostasis by interacting with modulators of insulin sensitivity, such as adiponectin and its oligomers. In a 4-week inpatient study on a metabolic rehabilitation program, consisting of individualized caloric restriction and aerobic physical exercise in obese subjects with VDD, we assessed the acute effects of 600,000 IU cholecalciferol given per os VD group, 12 subjects; body mass index (BMI) 42.7 ± 1.3 kg/m²) or placebo per os (PL group, 12 subjects, BMI 39.8 ± 0.9 kg/m²) on high (HWM-A), medium (MMW-A), and low molecular weight adiponectin (LMW-A), as quantified by western immunoblot (WIB) and ELISA. During the 4-week study, dieting promoted a similar magnitude of weight loss in VD and PL groups. Compared to the PL group, cholecalciferol administration increased 25(OH)Vit D levels (p < 0.001) and promoted a significant increase of HMW-A expression analyzed by WIB (p = 0.02). In parallel, a significant decrease of leptin/HMW-A ratio (p < 0.05), a biomarker of metabolic homeostasis, was observed. During the study, changes of MMW-A and LMW-A occurred independently of cholecalciferol administration, and were likely explained by weight loss. At odds with these findings, the ELISA assessment of adiponectin oligomers showed no modifications in the VD group or PL group. Current findings suggest that acute cholecalciferol administration selectively modifies HMW-A and the leptin/HMW-A ratio.

The relationship between adipokines and the onset of type 2 diabetes in middle-aged men: The PRIME study

AIMS

Epidemiological evidence suggests that adipokines may be associated with the onset of type 2 diabetes, but the evidence to date is limited and inconclusive. This study examined the association between adiponectin and leptin and the subsequent diagnosis of type 2 diabetes in a UK population based cohort of non-diabetic middle-aged men.

METHODS

Baseline serum levels of leptin and adiponectin were measured in 1839 non-diabetic men aged 50-60years who were participating in the prospective population-based PRIME study. Over a mean follow-up of 14.7years, new cases of type 2 diabetes were determined from self-reported clinical information with subsequent validation by general practitioners.

RESULTS

151 Participants developed type 2 diabetes during follow-up. In Cox regression models adjusted for age, men in the top third of the leptin distribution were at increased risk (hazard ratio (HR) 4.27, 95% CI 2.67-6.83) and men in the top third of the adiponectin distribution at reduced risk (HR 0.24, 95% CI 0.14-0.42) relative to men in the bottom third. However, significance was lost for leptin after additional adjustment for BMI, waist to hip ratio, lifestyle factors and biological risk factors, including C-reactive protein (CRP). Further adjustment for HOMA-IR also resulted in loss of significance for adiponectin.

CONCLUSIONS

This study provides evidence that adipokines are associated with men's future type 2 diabetes risk but not independently of other risk factors.

Changes in profile of lipids and adipokines in patients with newly diagnosed hypothyroidism and hyperthyroidism

Changes in profile of lipids and adipokines have been reported in patients with thyroid dysfunction. But the evidence is controversial. The present study aimed to explore the relationships between thyroid function and the profile of lipids and adipokines. A cross-sectional study was conducted in 197 newly diagnosed hypothyroid patients, 230 newly diagnosed hyperthyroid patients and 355 control subjects. Hypothyroid patients presented with significantly higher serum levels of total cholesterol, triglycerides, low-density lipoprotein cholesterol (LDLC), fasting insulin, resistin and leptin than control (p < 0.05). Hyperthyroid patients presented with significantly lower serum levels of high-density lipoprotein cholesterol, LDLC and leptin, as well as higher levels of fasting insulin, resistin, adiponectin and homeostasis model insulin resistance index (HOMA-IR) than control (p < 0.05). Nonlinear regression and multivariable linear regression models all showed significant associations of resistin or adiponectin with free thyroxine and association of leptin with thyroid-stimulating hormone (p < 0.001). Furthermore, significant correlation between resistin and HOMA-IR was observed in the patients (p < 0.001). Thus, thyroid dysfunction affects the profile of lipids and adipokines. Resistin may serve as a link between thyroid dysfunction and insulin resistance.

Second-generation antipsychotics and adiponectin levels in schizophrenia: A comparative meta-analysis

People with schizophrenia treated with second-generation antipsychotics (SGAs) have lower plasma adiponectin levels, as compared with general population, that may lead to metabolic abnormalities. However, the contribution of different SGAs on adiponectin dysregulation is still unclear. The objective of this systematic review and meta-analysis was to estimate differences in adiponectin levels among people with schizophrenia treated with different SGAs. We systematically searched for observational studies published up to March 2015 in main electronic databases. Different SGAs were included if data on adiponectin were available from at least three different samples involving as a minimum five participants per treatment arm. Standardized mean differences with relevant 95% confidence intervals were generated. I(2) was used to test heterogeneity among studies. Eight studies were included with data suitable for carrying out four different comparisons: Clozapine vs. Olanzapine (including n=877 individuals with schizophrenia); Clozapine vs. Risperidone (n=660); Olanzapine vs. Risperidone (n=738); Quetiapine vs. Risperidone (n=186). There were no differences on adiponectin levels between people taking Clozapine and those taking Olanzapine (p=0.86), but high heterogeneity was detected (I(2)=82%). Both individuals taking Clozapine (p<0.001; I(2)=0%) and those taking Olanzapine (p=0.02; I(2)=9%), but not subjects treated with Quetiapine (p=0.47; I(2)=0%), had adiponectin levels significantly lower than people taking Risperidone. Our findings are consistent with previous evidence showing greater metabolic abnormalities attributable to Clozapine and Olanzapine, as compared with other SGAs. Although mechanisms whereby both these SGAs influence adiponectin remain unexplained, its reduction might mediate relevant abnormalities. Prospective evaluations of long-term effects of different SGAs on adiponectin are needed.

Plasma adiponectin levels in schizophrenia and role of second-generation antipsychotics: a meta-analysis

BACKGROUND

People with schizophrenia are more likely than general population to suffer from metabolic abnormalities, with second-generation antipsychotics (SGAs) increasing the risk. Low plasma adiponectin levels may lead to metabolic dysregulations but evidence in people with schizophrenia, especially for the role of SGAs, is still inconclusive.

OBJECTIVE

To compare plasma adiponectin levels between people with schizophrenia and healthy controls, and to estimate the relative effect of schizophrenia and SGAs on adiponectin.

METHODS

We performed a systematic review and meta-analysis of observational studies published up to 13 June 2014 in main electronic databases. Pooled standardized mean differences (SMDs) between index and control groups were generated. Appropriate subanalyses and additional subgroup analyses were carried out.

RESULTS

Data from 2735 individuals, 1013 with and 1722 without schizophrenia, respectively, were analysed. Schizophrenia was not associated with lower adiponectin levels (SMD of -0.28, 95%CI: -0.59, 0.04; p=0.09). However, individuals with schizophrenia taking SGAs had plasma levels significantly lower than controls (p=0.002), which was not the case of drug free/drug naïve subjects (p=0.52). As regards single antipsychotic drugs clozapine (p<0.001) and olanzapine (p=0.04)--but not risperidone (p=0.88)--were associated with adiponectin levels lower than controls.

CONCLUSIONS

People with schizophrenia per se may not have levels of adiponectin lower than controls, though treatment with SGAs is associated with this metabolic abnormality. This bears clinical significance because of hypoadiponectinemia involvement in cardiovascular diseases, even if mechanisms whereby SGAs affect adiponectin remain unexplained. Longitudinal studies evaluating long-term effects of SGAs on adiponectin are needed.

Adipokines and proinflammatory cytokines, the key mediators in the pathogenesis of nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is a condition in which excess fat accumulates in the liver of a patient with no history of alcohol abuse or other causes for secondary hepatic steatosis. The pathogenesis of NAFLD and nonalcoholic steatohepatitis (NASH) has not been fully elucidated. The “two-hit“ hypothesis is probably a too simplified model to elaborate complex pathogenetic events occurring in patients with NASH. It should be better regarded as a multiple step process, with accumulation of liver fat being the first step, followed by the development of necroinflammation and fibrosis. Adipose tissue, which has emerged as an endocrine organ with a key role in energy homeostasis, is responsive to both central and peripheral metabolic signals and is itself capable of secreting a number of proteins. These adipocyte-specific or enriched proteins, termed adipokines, have been shown to have a variety of local, peripheral, and central effects. In the current review, we explore the role of adipocytokines and proinflammatory cytokines in the pathogenesis of NAFLD. We particularly focus on adiponectin, leptin and ghrelin, with a brief mention of resistin, visfatin and retinol-binding protein 4 among adipokines, and tumor necrosis factor-α, interleukin (IL)-6, IL-1, and briefly IL-18 among proinflammatory cytokines. We update their role in NAFLD, as elucidated in experimental models and clinical practice.

Involvement of adiponectin in early stage of colorectal carcinogenesis

Background

Although altered levels of adiponectin have been reported as a potential risk factor in colorectal cancer (CRC), the importance of the role played by adiponectin in colorectal carcinogenesis has not been established. We sought to examine the expression pattern of adiponectin and adiponectin receptors (AdipoRs) in the normal-adenoma-carcinoma sequence and to assess the implications of adiponectin in colorectal carcinogenesis.

Methods

Serum adiponectin concentrations, and the mRNA and protein expression of adiponectin and AdipoRs were examined using serum and tissues from patients with CRC, advanced adenoma, and a normal colon. mRNA expression of AdipoRs and epithelial-mesenchymal transition regulators including E-cadherin, cyclooxygenase-2 (COX-2) and T-cadherin were examined in HCT116 cells treated with adiponectin.

Results

Serum adiponectin concentrations in patients with advanced adenoma and CRC were lower than those in controls. Adiponectin mRNA was not detected in colonic tissue, whereas AdipoRs mRNA was lower in advanced adenoma and CRC than that in normal colon tissues. Immunohistochemical staining demonstrated that adiponectin was expressed in spindle-shaped cells of the subepithelial layer in normal colon tissues, whereas ill-defined overexpression of adiponectin was seen in the stroma of advanced adenoma and CRC tissues. AdipoRs expression was strong in normal epithelium, but weak to negative in the epithelia of CRC tissues. Adiponectin downregulated COX-2 mRNA expression in vitro, but upregulated T-cadherin in HCT116 cells.

Conclusions

Systemic adiponectin and local AdipoRs expression in the colon may be associated with anti-tumorigenesis during the early stages of CRC. These findings offer new insight into understanding the relationship between adiponectin and colorectal carcinogenesis.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2407-14-811) contains supplementary material, which is available to authorized users.

Obesity attenuates gender differences in cardiovascular mortality

Background

To estimate cardiovascular disease (CVD) mortality in relation to obesity and gender.

Methods

Data from 11 prospective cohorts from four European countries including 23 629 men and 21 965 women, aged 24 to 99 years, with a median follow-up of 7.9 years were analyzed. Hazards ratios (HR) for CVD mortality in relation to baseline body mass index (BMI), waist circumference (WC), waist-to-hip ratio (WHR) and waist-to-height ratio (WHtR) were estimated using Cox proportional hazards models with age as the timescale.

Results

Men had higher CVD mortality than women in all four BMI categories (<25.0, 25.0-29.9, 30.0-34.9 and ≥35.0 kg/m²). Compared with the lowest BMI category in women, multivariable adjusted HRs (95% confidence intervals) for higher BMI categories are 1.0 (0.8-1.4), 1.6 (1.1-2.1) and 2.8 (2.0-3.8) in women and 2.8 (2.2-3.6), 3.1 (2.5-3.9), 3.8 (2.9-4.9) and 5.4 (3.8-7.7) in men, respectively. Similar findings were observed for abdominal obesity defined by WC, WHR or WHtR. The gender difference was slightly smaller in obese than in non-obese individuals; but the interaction was statistically significant only between gender and WC (p = 0.02), and WHtR (p = 0.01). None of the interaction terms was significant among non-diabetic individuals.

Conclusions

Men had higher CVD mortality than women across categories of anthropometric measures of obesity. The gender difference was attenuated in obese individuals, which warrants further investigation.

Electronic supplementary material

The online version of this article (doi:10.1186/s12933-014-0144-5) contains supplementary material, which is available to authorized users.

Leptin levels and risk of type 2 diabetes: gender-specific meta-analysis

This meta-analysis aimed to assess the gender-specific differences in the relationship between circulating leptin levels and risk of type 2 diabetes. Published prospective studies that reported the association of leptin levels with risk of type 2 diabetes for a certain gender or those that reported gender-specific associations were considered. Dose-response relationships were assessed by the generalized least squares trend estimation and summary relative risks (RRs) with 95% confidence interval (CI) were computed with the random-effects model. Stratified and sensitivity analyses were also performed to investigate potential sources of heterogeneity. Overall, 11 prospective studies were identified. The summary RR for an increment in leptin levels of 1-log ng mL(-1) was 1.37 (95% CI, 1.13-1.66) for men and 0.96 (95% CI, 0.90-1.03) for women. The differences between genders were statistically significant (P for interaction = 0.006). Subgroup and sensitivity analyses generally confirmed the robustness of these findings. Furthermore, the increased risk in men appeared non-linear, with a tendency to plateau at high levels (P for non-linearity = 0.03). Little evidence of publication bias was found. Collectively, higher leptin levels were found to be associated with elevated risk of type 2 diabetes in men but not in women.

Association of adipokines, leptin/adiponectin ratio and C-reactive protein with obesity and type 2 diabetes mellitus

OBJECTIVE

Alterations in plasma adipokines and/or inflammatory parameters in Type 2 DM remain vague as to whether they are due to obesity and/or directly associated with the diabetic state. Our objective was to compare plasma adiponectin, leptin, leptin/adiponectin ratio (LAR) and hs-CRP in obese non-diabetic subjects and non-obese Type 2 DM patients, as well as determining the association of these adipokines with MetS and diabetes-related quantitative traits.

METHODS

In this study, 92 Yemeni male volunteers aged 25-60 years old were enrolled, 31 of whom were healthy subjects with BMI < 25 kg/m(2) served as control; 30 non-diabetic obese subjects BMI ≥ 30 kg/m(2) and FBG < 6.1 mmol/l; and 31 non-obese Type 2 DM with FBG > 7 mmol/l and BMI < 25 kg/m(2).

RESULTS

Adiponectin was lower in obese subjects, with no differences between non-obese Type 2 DM patients and controls. In contrast, leptin, LAR and hs-CRP were higher in both obese subjects and non-obese Type 2 DM patients. Linear regression analysis showed adiponectin to be associated negatively with BMI, waist circumference, insulin, HOMA-β and HOMA-IR; whereas leptin, LAR and hs-CRP were associated positively with BMI, waist circumference, TG, FBG, insulin, HOMA-β and HOMA-IR. Moreover, adiponectin negatively correlated with leptin, LAR and hs-CRP; whereas leptin and LAR positively correlated with hs-CRP and with each other.

CONCLUSION

Plasma adiponectin is not affected by diabetes per se, suggesting that its alterations in Type 2 DM may be due to obesity and may be an important link between adiposity, IR and Type 2 DM.

Adiponectin and waist circumference as predictors of insulin-resistance in women

BACKGROUND AND AIMS

The initial disturbance of insulin resistance seems to focus on adipose tissue is a dynamic organ involved in many physiological and metabolic processes. Expresses and secretes a variety of active peptides, adipocytokines. To evaluate the prevalence of insulin-resistance in an healthy urban middle age population and to explore the role of adiponectin, inflammatory biomarkers (hs-CRP) and traditional cardiovascular risk factors as predictors of the insulin-resistance state.

MATERIALS AND METHODS

We studied of 176 participants (117 women and 59 men, 25-74 years), individuals with diabetes, hypothyroidism or hyperthyroidism, infectious disease, renal, or hepatic neoplasms and pregnant women were excluded. We evaluated glucose, insulin, adiponectin and hs-CRP.

RESULTS

We found that 17.2% of individuals presented insulin-resistance. Correlation was found between waist circumference, body mass index, blood pressure and HOMA index (p<0.01). Adiponectin was associated with the insulin-resistance (p<0.001) but not hs-CRP. Adiponectin (β=0.385, p=0.004) and waist circumference (β=0.116, p=0.02) were predictors of IR only in women, meanwhile none of the analyzed biomarkers predicted insulin-resistance in men. Besides, postmenopausal women presented higher adiponectin levels than premenopausal 7.63 (4.46-9.58) vs 5.50 (3.83-7.40) μg/ml, p=0.01.

CONCLUSIONS

Adiponectin and waist circumference are important predictors of insulin-resistance even in healthy non-diabetic women, they may open a new opportunity to improve current risk estimation.

A rightward shift of the distribution of fasting and post-load glucose in northern Sweden between 1990 and 2009 and its predictors. Data from the Northern Sweden MONICA study

AIMS

Most Swedish studies show stable diabetes prevalence despite increasing obesity, but glucose levels may shift upwards below the diagnostic threshold for diabetes. Our aim was to explore trends in glucose distribution in northern Sweden; whether these trends were uniformly distributed throughout the spectrum of glucose concentrations; and to relate trends to traditional risk factors and the obesity-related adipokine leptin.

METHODS

The project consisted of four cross-sectional surveys between 1990 and 2009, with 7069 participants aged 25-64 years. The overall participation rate was 74.4%. Trend analyses of glucose concentrations along the entire distribution and linear regression in relation to survey years and risk markers were used.

RESULTS

Fasting and post-load glucose increased in women (both P < 0.001) and post-load glucose in men (P = 0.004). The increase was seen in most deciles of glucose concentrations. The prevalence of impaired glucose tolerance doubled in women to 14.5% and tripled in men to 10.1% (both P = 0.004). The prevalence of impaired fasting glucose rose in women from 4.5 to 7.7% (P < 0.001). The prevalence of diabetes was unchanged-6.4% in 2009. In men, leptin, together with traditional risk factors, explained 7.8 and 10.8% of the variance in fasting (P = 0.008) and post-load (P < 0.001) glucose, respectively.

CONCLUSIONS

Increasing fasting and post-load glucose concentrations were seen in most deciles of the glucose distribution, indicating a shift in the entire population. Leptin was significantly associated with fasting and post-load glucose in men.

Childhood obesity and asthma control in the GALA II and SAGE II studies

RATIONALE

Obesity is associated with increased asthma morbidity, lower drug responsiveness to inhaled corticosteroids, and worse asthma control. However, most prior investigations on obesity and asthma control have not focused on pediatric populations, considered environmental exposures, or included minority children.

OBJECTIVES

To examine the association between body mass index categories and asthma control among boys and girls; and whether these associations are modified by age and race/ethnicity.

METHODS

Children and adolescents ages 8-19 years (n = 2,174) with asthma were recruited from the Genes-environments and Admixture in Latino Americans (GALA II) Study and the Study of African Americans, Asthma, Genes, and Environments (SAGE II). Ordinal logistic regression was used to estimate odds ratios (OR) and their confidence intervals (95% CI) for worse asthma control.

MEASUREMENTS AND MAIN RESULTS

In adjusted analyses, boys who were obese had a 33% greater chance of having worse asthma control than their normal-weight counterparts (OR, 1.33; 95% CI, 1.04-1.71). However, for girls this association varied with race and ethnicity (P interaction = 0.008). When compared with their normal-weight counterparts, obese African American girls (OR, 0.65; 95% CI, 0.41-1.05) were more likely to have better controlled asthma, whereas Mexican American girls had a 1.91 (95% CI, 1.12-3.28) greater odds of worse asthma control.

CONCLUSIONS

Worse asthma control is uniformly associated with increased body mass index in boys. Among girls, the direction of this association varied with race/ethnicity.

Higher leptin is associated with hypertension: the Multi-Ethnic Study of Atherosclerosis

Adipokines are secreted from adipose tissue, influence energy homeostasis and may contribute to the association between obesity and hypertension. Among 1897 participants enrolled in the Multi-Ethnic Study of Atherosclerosis, we examined associations between blood pressure and leptin, tumor necrosis factor-α (TNFα), resistin and total adiponectin. The mean age and body mass index (BMI) was 64.7 years and 28.1, respectively, and 50% were female. After adjustment for risk factors, a 1-s.d.-increment higher leptin level was significantly associated with higher systolic (5.0 mm Hg), diastolic (1.9), mean arterial (2.8) and pulse pressures (3.6), as well as a 34% higher odds for being hypertensive (P<0.01 for all). These associations were not materially different when the other adipokines, as well as BMI, waist circumference or waist-to-hip ratio, were additionally added to the model. Notably, the associations between leptin and hypertension were stronger in men, but were not different by race/ethnic group, BMI or smoking status. Adiponectin, resistin and TNFα were not independently associated with blood pressure or hypertension. Higher serum leptin, but not adiponectin, resistin or TNFα, is associated with higher levels of all measures of blood pressure, as well as a higher odds of hypertension, independent of risk factors, anthropometric measures and other selected adipokines.

Association between adiponectin and tumor necrosis factor-alpha levels at eight to fourteen weeks gestation and maternal glucose tolerance: the Parity, Inflammation, and Diabetes Study

OBJECTIVE

Inflammation may influence gestational hyperglycemia, but to date, the data from observational studies is largely limited to results from the third trimester of pregnancy. Our objective was to evaluate first trimester adipocytokine levels. We sought to determine whether first trimester adiponectin and tumor necrosis factor-alpha (TNF)-alpha concentrations were independently associated and predictive of maternal glucose tolerance, as measured by the 1-hour glucose challenge test (GCT), after adjustment for maternal lifestyle behaviors and body mass index (BMI).

MATERIAL AND METHODS

Prospective study of pregnant women (n=211) enrolled in the Parity, Inflammation, and Diabetes Study. Nonfasting serum levels of adiponectin and TNF-r2 were measured at 8-14 weeks of pregnancy. GCT results were abstracted from electronic prenatal records. Multiple linear regression models were developed to determine the association of adiponectin and TNF-r2 levels with response to the GCT, adjusting for demographics, pregravid dietary intake and physical activity, first trimester BMI, and gestational weight gain.

RESULTS

At baseline, higher adiponectin concentrations were inversely and statistically significantly associated with maternal response to the GCT [regression coefficient (β) -0.68; 95% confidence interval (CI): -1.29, -0.06). Adjustment for lifestyle factors did not alter the association of adiponectin with the GCT (β -0.74; 95% CI: -1.43, -0.05). After adjustment for first trimester BMI, the association of adiponectin was attenuated and no longer significant (β -0.46; 95% CI: -1.15, 0.24). TNF-r2 levels were not associated with the GCT (β -0.003; 95% CI: -0.011, 0.005).

CONCLUSIONS

First trimester adiponectin levels are not predictive of the 1-hour GCT response, but may be a marker for the effect of maternal BMI on glucose response to the GCT.

Adiponectin/leptin ratio and insulin resistance in pregnancy

Objective

Pregnancy is characterized by progressive insulin resistance. The present study evaluated whether the adiponectin/leptin ratio is associated with insulin resistance in pregnancy, since this ratio has been shown to be associated with insulin resistance in obesity, type 2 diabetes mellitus, metabolic syndrome and polycystic ovary syndrome.

Methods

In this cross-sectional study, adiponectin and leptin concentrations were measured in pregnant women using enzyme-linked immunosorbent assays. Insulin resistance was assessed using the homeostasis model assessment of insulin resistance (HOMA–IR).

Results

Mean ± SD age of the participants ( n = 74) was 30.76 ± 4.27 years, mean ± SD gestational age was 26.81 ± 3.52 weeks and median body mass index (BMI) before pregnancy was 22.68 kg/m2 (interquartile range 20.75–26.79 kg/m2). There was a significant correlation between the HOMA–IR and leptin concentration, but not between the HOMA–IR and adiponectin concentration. There was a significant inverse correlation between the HOMA–IR and adiponectin/leptin ratio. The adiponectin/leptin ratio was inversely correlated with BMI before pregnancy.

Conclusion

The adiponection/leptin ratio inversely correlates with HOMA–IR in pregnancy.

Interacting epidemics? Sleep curtailment, insulin resistance, and obesity

In the last 50 years, the average self-reported sleep duration in the United States has decreased by 1.5-2 hours in parallel with an increasing prevalence of obesity and diabetes. Epidemiological studies and meta-analyses report a strong relationship between short or disturbed sleep, obesity, and abnormalities in glucose metabolism. This relationship is likely to be bidirectional and causal in nature, but many aspects remain to be elucidated. Sleep and the internal circadian clock influence a host of endocrine parameters. Sleep curtailment in humans alters multiple metabolic pathways, leading to more insulin resistance, possibly decreased energy expenditure, increased appetite, and immunological changes. On the other hand, psychological, endocrine, and anatomical abnormalities in individuals with obesity and/or diabetes can interfere with sleep duration and quality, thus creating a vicious cycle. In this review, we address mechanisms linking sleep with metabolism, highlight the need for studies conducted in real-life settings, and explore therapeutic interventions to improve sleep, with a potential beneficial effect on obesity and its comorbidities.