Inverse relationship of serum adiponectin concentration with type 2 diabetes mellitus incidence in middle-aged Japanese workers: six-year follow-up

Low levels of spexin and adiponectin may predict insulin resistance in patients with non-alcoholic fatty liver

Adipose tissue is endocrine organ that responds by secreting numerous hormones that regulate metabolism in skeletal muscle and the liver. The aim of this study was to compare the levels of spexin and adiponectin in patients with non-alcoholic fatty liver and evaluate the relationship between circulating adipocytokines and insulin resistance. Two groups of subjects were evaluated: 41 non-alcoholic fatty liver subjects (age 35.17 ​± ​12.29 year, BMI 30.97 ​± ​2.75 ​kg/m2) and 38 normal controls (age 38.47 ​± ​11.63 year, BMI 22.83 ​± ​3.00 ​kg/m2). Plasma concentrations of spexin and adiponectin were determined using immunosorbent assay kits. Insulin resistance was assessed using the homeostasis model assessment (HOMA-IR) formula derived from fasting insulin and glucose levels. Compared to normal controls, plasma concentrations of spexin and adiponectin were significantly lower in patients with non-alcoholic fatty liver (P ​< ​0.001). Spexin did not correlate with BMI but did significantly correlate with HOMA-IR (r ​= ​-0.368; P ​= ​0.018) and adiponectin (r ​= ​0.378; P ​= ​0.043), and this correlation remained significant after adjustment for gender and BMI. In this small group of patients with non-alcoholic fatty liver we demonstrated that insulin resistance correlated strongly with spexin and adiponectin levels.

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The plasma spexin levels were decreased in patients with NAFLD.

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A negative correlation was shown between spexin and HOMA-IR.

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A negative correlation was shown between adiponectin and HOMA-IR.

Activation of central galanin receptor 2 mitigated insulin resistance in adipocytes of diabetic rats

PURPOSE

Our and other's studies showed that administration of neuropeptide galanin may mitigate insulin resistance via promoting glucose transporter 4 (GLUT4) expression and translocation in rats. The objective of this study is to investigate whether galanin receptor 2 (GAL2-R) in brain mediates the ameliorative effect of galanin on insulin resistance in adipose tissues of type 2 diabetic rats.

METHODS

In this study galanin, GAL2-R agonist M1145 and GAL2-R antagonist M871 were respectively or cooperatively injected into intracerebroventricles of type 2 diabetic rats once a day for successive fifteen days. Then the plasma and fat tissues of rats were used to estimate the alterations of insulin resistance indexes.

RESULTS

The central administration of galanin enhanced 2-deoxy-[3H]-D-glucose, peroxisome proliferator-activated receptor γ and adiponectin levels, food intake and body weight, GLUT4 mRNA expression and GLUT4 concentration in plasma membranes, as well as homeostasis model assessment-insulin resistance index. Those effects of galanin may be blocked by M817, and imitated by M1145 except for food intake and body weight.

CONCLUSION

Those results suggest that central GAL2-R mediates the beneficial effects of galanin on insulin sensitivity in type 2 diabetic rats. GAL2-R agonist may be taken as a potential antidiabetic agent to treat insulin resistance and type 2 diabetes.

Serum adiponectin and insulin secretion: A direct or inverse association?

We investigated the association between serum high molecular weight (HMW) adiponectin and insulin secretion in a population-based study, with or without adjustment for insulin sensitivity. A total of 488 participants (263 women) were included in the present study. Insulin secretion was estimated using the homeostasis model assessment of β-cell function ± adjustment for insulin resistance using the disposition index. Multivariate analysis showed that HMW adiponectin was significantly and inversely associated with homeostasis model assessment of β-cell function (partial regression coefficient -0.19, 95% confidence interval -0.28, -0.10, P < 0.0001). However, HMW adiponectin was significantly and positively associated with disposition index (partial regression coefficient 0.15, 95% confidence interval 0.06, 0.24, P = 0.0016). The present study showed that a positive association between HMW adiponectin levels and insulin secretion evaluated using an index incorporating adjustment for insulin resistance was identified, and vice versa using an index that did not adjust for insulin resistance.

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.

Smoking and diabetes: is the association mediated by adiponectin, leptin, or C-reactive protein?

Background

Although the association between cigarette smoking and risk of type 2 diabetes is well established, its mechanisms are yet to be clarified. This study examined the possible mediating effects of adiponectin, leptin, and C-reactive protein (CRP) concentrations on the smoking-diabetes association.

Methods

Between 2002 and 2011, we followed 3338 Japanese workers, aged 35–66 years, who were enrolled in the second Aichi workers’ cohort study. We used multivariable-adjusted Cox regression models to determine the hazard ratios and respective 95% confidence intervals (CIs) of the association between smoking status and risk of diabetes. A multiple mediation model with bootstrapping was used to estimate the magnitude and the respective bias-corrected (BC) 95% CIs of the indirect effects of smoking on diabetes through the three biomarkers.

Results

Relative to never smokers, the risk of diabetes was significantly elevated in current (hazard ratio 1.75, 95% CI 1.25–2.46) and ex-smokers (hazard ratio 1.54, 95% CI 1.07–2.22). The indirect effects of smoking on diabetes through adiponectin levels were statistically significant among light (point estimate 0.033, BC 95% CI 0.005–0.082), moderate (point estimate 0.044, BC 95% CI 0.010–0.094), and heavy smokers (point estimate 0.054, BC 95% CI 0.013–0.113). In contrast, neither the indirect effects of smoking on diabetes through leptin nor CRP levels were significant, as the corresponding BC 95% CIs included zero.

Conclusions

In our analysis, adiponectin concentration appeared to partially mediate the effect of smoking on diabetes, while leptin and CRP levels did not.

Role of serum vaspin in progression of type 2 diabetes: a 2-year cohort study

Vaspin is a novel adipocytokine that has potential insulin-sensitizing effects. The aim of this study is to explore the role of vaspin in the progression of type 2 diabetes mellitus (T2DM) in humans through a longitudinal process. This was a 2-year follow-up study that included 132 patients with T2DM and 170 non-diabetic subjects. The serum vaspin and adiponectin levels were determined with ELISA. Anthropometric measurements, circulating glucose, hemoglobin A1c, insulin level, liver function, kidney function, and lipid profile were measured for each participant. The new onset of T2DM was counted in non-diabetic subjects and the glycemic control was analyzed in T2DM patients at follow-up. At enrollment, the serum vaspin and adiponectin levels were lower in T2DM patients compared with non-diabetic subjects. Significant positive correlation between serum vaspin and HDL-C levels (r = 0.23, P = 0.006) was observed in non-diabetic controls. The serum vaspin concentration was also significantly correlated with body mass index (BMI) (r = 0.19, P = 0.028), waist-hip ratio (WHR) (r = 0.17, P = 0.035) and homeostasis model assessment of insulin resistance (HOMA-IR) (r = 0.14, P = 0.029) in T2DM patients. In cohort analyses, it was found that lower serum vaspin [odds ratio (OR) = 0.52, 95% confidence interval (CI): 0.10–0.87, P = 0.015] and adiponectin (OR = 0.35, 95% CI: 0.20–0.72, P = 0.015) levels at baseline were risk factors for new onset of T2DM at follow-up. The percentage of insulin treatment in T2DM patients was higher in the sub-group with lower serum vaspin level than that in the sub-group with higher vaspin level at follow-up (55.3% vs. 44.7%, P = 0.020). Our study indicates that low serum concentration of vaspin is a risk factor for the progression of T2DM.

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

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

Adiponectin as predictor for diabetes among pre-diabetic groups

Adiponectin is found to associate with diabetes in studies apart from cohort studies. This prospective cohort study is to evaluate the predictive role of adiponectin in diabetes among participants with impaired fasting glucose (IFG). A total of 42,845 participants who visited 7 health examination centers located in Seoul and Kyunggi province, South Korea, during 2004-2008 were first included. Of the 42,845 participants, 5,085 participants had IFG. IFG was categorized as stage 1 (fasting glucose 100-109 mg/dL) or stage 2 (110-125 mg/dL). The incidence rates of diabetes were followed up to December, 2011. Hazard ratios (HRs) and 95 % confidence intervals (CI) were performed by Cox proportional hazard model. Of the 5,085 participants, 652 participants developed diabetes during a mean follow-up of 4.4 years. Low adiponectin was associated with diabetes among men with stage 2 IFG (HR, 1.78; 95 %CI, 1.33-2.38) while it was associated with diabetes among women with stage 1 IFG (HR, 2.64; 95 %CI, 1.38-5.03) and stage 2 IFG (HR, 2.17; 95 %CI, 1.07-4.42). When combined men and women, the association between adiponectin and diabetes was statistically significant in stage 2 IFG with an increase of about 82 % (HR, 1.82; 95 %CI, 1.40-2.39) after adjusting for age, sex, body mass index, waist circumference, and fasting serum glucose. There was an interaction by sex and stage 1 IFG in the association between adiponectin and risk of diabetes (P < 0.001). Adiponectin was independently associated with diabetes among participants with IFG. This association was apparent in stage 2 IFG. Adiponectin may be used as a predictor of diabetes in patients having IFG.

Incidence of type 2 diabetes in Japan: a systematic review and meta-analysis

BACKGROUND

The definition of incident type 2 diabetes varies across studies; hence, the actual incidence of type 2 diabetes in Japan is unclear. Here, we reviewed the various definitions of incident type 2 diabetes used in previous epidemiologic studies and estimated the diabetes incidence rate in Japan.

METHODS

We searched for related literature in the MEDLINE, EMBASE, and Ichushi databases through September 2012. Two reviewers selected studies that evaluated incident type 2 diabetes in the Japanese population.

RESULTS

From 1824 relevant articles, we included 33 studies with 386,803 participants. The follow-up period ranged from 2.3 to 14 years and the studies were initiated between 1980 and 2003. The random-effects model indicated that the pooled incidence rate of diabetes was 8.8 (95% confidence interval, 7.4-10.4) per 1000 person-years. We observed a high degree of heterogeneity in the results (I(2) = 99.2%; p < 0.001), with incidence rates ranging from 2.3 to 52.6 per 1000 person-years. Three studies based their definition of incident type 2 diabetes on self-reports only, 10 on laboratory data only, and 20 on self-reports and laboratory data. Compared with studies defining diabetes using laboratory data (n = 30; pooled incidence rate = 9.6; 95% confidence interval = 8.3-11.1), studies based on self-reports alone tended to show a lower incidence rate (n = 3; pooled incidence rate = 4.0; 95% confidence interval = 3.2-5.0; p for interaction < 0.001). However, stratified analyses could not entirely explain the heterogeneity in the results.

CONCLUSIONS

Our systematic review and meta-analysis indicated the presence of a high degree of heterogeneity, which suggests that there is a considerable amount of uncertainty regarding the incidence of type 2 diabetes in Japan. They also suggested that laboratory data may be important for the accurate estimation of the incidence of type 2 diabetes.

Association of genetic variants in the adiponectin gene with metabolic syndrome: a case-control study and a systematic meta-analysis in the Chinese population

Background

The prevalence of metabolic syndrome has been rising worldwide, including in China, but knowledge on specific genetic determinants of metabolic syndrome is very limited. A number of studies have reported that polymorphisms in the ADIPOQ gene are associated with metabolic syndrome in Chinese Han populations. However, data is still conflicting. The objective of this study was to examine the associations of the adiponectin genetic variants with metabolic syndrome by a case-control study and meta-analyses in Chinese.

Methods

We first investigated the association of ADIPOQ rs2241766 (+45T>G in exon 2), rs266729 (−11377C>G in promoter) and rs1501299 (+276G>T in intron 2) polymorphisms with metabolic syndrome in a Hubei Han Chinese population with 322 metabolic syndrome patients and 161 normal controls recruited from the Yichang, Hubei. Then we comprehensively reviewed the association between ADIPOQ rs2241766/rs266729/rs1501299 and metabolic syndrome in the Chinese populations via a meta-analysis. The strength of association was assessed by odds ratios (ORs) with 95% confidence intervals (CI).

Results

The G allele frequency of rs2241766 in metabolic syndrome patients was significantly higher than those of controls group (29.8% vs 23.3%, OR = 1.40, P = 0.033). The logistic regression analysis adjusted by gender and age showed a nominally significant association for rs2241766 GG+GT genotype (P = 0.065, OR = 1.55) and rs1501299 GG genotype in recessive model (OR = 1.54, P = 0.066). However, no association was observed for rs266729 in our sample. We identified thirteen studies for rs2241766 (2,684 metabolic syndrome patients and 2,864 controls), three studies for rs266729, and eleven studies for rs1501299 (2,889 metabolic syndrome patients and 3,304 controls) in Chinese. Meta-analysis indicated significant associations for the rs2241766 G allele (OR = 1.14, 95%CI = 1.05–1.24, P = 0.003), rs266729 GG+GT genotypes (OR = 0.80, 95%CI = 0.68–0.92, P = 0.003) and rs1501299 GG+TG genotypes (OR = 1.42, 95%CI 1.16–1.75, P = 0.001).

Conclusions

Our results demonstrated ADIPOQ as a pleiotropic locus for metabolic syndrome and its components in the Han Chinese population.

Predictive impact of adiponectin for detecting dysglycemia in non-fasting Japanese employees with metabolic risk factors

The screening of dysglycemia in the non-fasting state is a challenging issue in healthcare practice. We investigated whether the additional measurement of circulating adiponectin levels could improve screening performance. We used a database of 1190 Japanese employees with metabolic risk factors, who underwent a 75-g oral glucose tolerance test (OGTT), following non-fasting health check-ups. Dysglycemia was defined as fasting glucose levels ≥6.1 mmol/L or 2-hr glucose levels ≥7.8 mmol/L during the OGTT. Logistic regression analysis revealed that decreased adiponectin levels were associated with dysglycemia, independently of postprandial glucose (PG) and hemoglobin A1c (HbA1c) levels, as well as other health check-up data (p<0.01). The trivariate model with PG, HbA1c, and adiponectin levels (PG+A1c+ADN model) had a larger area under the receiver operating characteristic curves (AUC) than the bivariate model with only PG and HbA1c levels (0.746 vs. 0.729; p=0.01). However, the AUC of the multivariate model with PG, HbA1c, and other health check-up data, but not adiponectin levels (PG+A1c+Other model) was 0.815, much larger than that of the PG+A1c+ADN model (p<0.01). The addition of adiponectin levels to the PG+A1c+Other model had a significantly larger AUC than the A1c+PG+Other model only in the subgroup without abdominal obesity (p=0.01), but not in the overall population (p=0.06) or in the subgroup with abdominal obesity (p=0.62). In conclusion, circulating adiponectin levels were independently associated with dysglycemia in non-fasting Japanese employees with metabolic risk factors, but they improved the screening capacity only in those without abdominal obesity.