Association of weight gain and fifteen adipokines with declining beta-cell function in Mexican Americans.

Obesity and adipokines are associated with development of type 2 diabetes. However, limited longitudinal studies have examined their roles on declining ß-cell function over time. This report assessed three adiposity measures (BMI, percent body fat, trunk fat), insulin resistance, and fifteen adipokines in relationship to longitudinal change in ß-cell function measured by disposition index (DI) from frequently-sampled-intravenous-glucose-tolerance testing. The results showed that three factors were significantly and independently associated with rate of change in DI over time: rate of change in BMI (negative), rate of change in IL-6 (negative), and baseline adiponectin (positive). The association was the strongest for changing BMI and was largely explained by changing insulin resistance; the association with changing IL-6 was also largely explained by changing insulin resistance. Baseline adiponectin remained positively associated after adjustment for changing insulin resistance, suggesting an independent effect of adiponectin to preserve or improve ß-cell function. These findings provide evidence and potential mechanisms for the role of obesity in promoting ß-cell dysfunction, highlighting the potential importance of mitigating obesity and its metabolic effects in preventing and treating type 2 diabetes.

Longitudinal Increases in Adiposity Contribute to Worsening Adipokine Profile over Time in Mexican Americans.

OBJECTIVE: Limited studies have assessed the relationship between longitudinal changes in adiposity and changes in multiple adipokines over time. This study examined changes in BMI, total body fat, and trunk fat associated with changes in 16 circulating adipokines in Mexican Americans at risk for type 2 diabetes. METHODS: Participants included 1,213 individuals with cross-sectional data and a subset of 368 individuals with follow-up measures (mean 4.6 ± 1.5 years from baseline). Joint multivariate associations between 3 adiposity measures and 16 adipokines were assessed by canonical correlation analysis. RESULTS: Longitudinal increases in adiposity were most strongly associated with increasing leptin, C-reactive protein (CRP), and interleukin 1 receptor antagonist (IL-1Ra) and decreasing adiponectin and secreted frizzled protein 5 (SFRP5) over time. Participants with BMI ≥ 30 kg/m2 at baseline had greater increases in leptin, CRP, IL-1Ra, and interleukin 6 (IL-6) and greater decreases in adiponectin and SFRP5, associated with increasing adiposity over follow-up, than those with BMI < 30 kg/m2 . Associations between adiposity and adipokines were most accounted for by leptin; adjustment for leptin greatly reduced the magnitude of all associations between adiposity and remaining adipokines. CONCLUSIONS: Increasing adiposity contributes to a worsening imbalance of pro- and anti-inflammatory adipokines over time, in which leptin may have an important role as a key mediator of metabolic disease risk in Mexican Americans.

Evidence for sex-specific associations between variation in acid phosphatase locus 1 (ACP1) and insulin sensitivity in Mexican-Americans.

CONTEXT: Acid phosphatase locus 1 (ACP1) is a low molecular weight tyrosine phosphatase that has been shown to be an important regulator of insulin receptor signaling. OBJECTIVE: We tested whether variation in ACP1 is associated with type 2 diabetes-related traits in 1035 individuals in 339 Mexican-American families of probands with or without a previous diagnosis of gestational diabetes mellitus (GDM). DESIGN: Study participants were phenotyped by oral glucose tolerance test (for glucose and insulin level) and iv glucose tolerance test (for insulin sensitivity and acute insulin response) and had dual-energy x-ray absorptiometry scans to assess body composition. Six tag single nucleotide polymorphisms (SNPs) were identified from among 15 SNPs genotyped across the ACP1 region. SNPs were tested for association with phenotypes using a likelihood ratio test under a variance components framework. RESULTS: After Bonferroni correction, none of the SNPs were associated with type 2 diabetes mellitus-related phenotypes. However, we observed a significant sex-specific effect of rs3828329. Among males, rs3828329 was significantly associated with fasting insulin (Bonferroni P = 0.007) and insulin sensitivity (Bonferroni P = 0.019) and marginally associated with 2-h insulin (Bonferroni P = 0.058) and percentage body fat (Bonferroni P = 0.09). CONCLUSIONS: There were no significant associations in females. We conclude that variation in ACP1 is associated with fasting insulin and insulin sensitivity in a sex-specific manner.