Genetic effects of adiponectin SNPs influenced by exercise, insulin resistance
MedWire News: Exercise and insulin resistance may modulate the genetic effect of two single nucleotide polymorphisms (SNPs) in the adiponectin gene on several metabolic risk factors, say researchers.
The team explains that "low adiponectin levels in circulating plasma are associated with Type 2 diabetes mellitus, atherosclerosis, and hypertension."
However, "little is known if lifestyle-related risk factors modulate the adiponectin genetic effects on its outcome phenotypes."
Previous studies have identified two SNPs in the adiponectin (adipocyte-C1q and collagen domain containing [ACDC]) gene: +45T>G (rs2241766) and +276G>T (rs1501299), that affect circulating adiponectin levels, insulin resistance, and Type 2 diabetes.
Therefore, Hyun-Sik Kang (Sungkyunkwan University, Republic of Korea) and colleagues investigated the associations between these SNPs and the clustering of metabolic risk factors, such as waist circumference (WC) and blood pressure (BP), in over 1600 young Korean adults, aged 18-29 years. They then assessed the influence of lifestyle factors, including cardio-respiratory fitness (CRF), on these associations.
The team developed a metabolic syndrome risk score - the sum of Z-scores for individual metabolic risk factors - to calculate the "clustering" of metabolic risk factors in each individual.
With respect to rs2241766, the researchers found that individuals with the TT genotype had a significantly higher mean body mass index (BMI; 23.6 vs 22.9 kg/m2), WC (82.4 vs 81.0 cm), systolic BP (118.6 vs 116.6 mmHg), and triglyceride level (113.2 vs 103.1 mg/dl [1.28 vs 1.17 mmol/l]) than individuals with the TG+GG genotype. The clustered metabolic syndrome risk score was also significantly higher, at 0.51 versus 0.04, respectively, and this remained significant after adjusting for age, gender, and smoking.
However, after additional adjustment for CRF and fasting insulin, the genetic impact of rs2241766 was no longer significant, say Kang et al, suggesting that both of these factors modulate the genetic effect of this SNP on the clustering of metabolic risk factors.
For rs1501299, individuals with the GT+TT genotypes had a significantly higher BMI (23.5 vs 22.9 kg/m2) and triglycerides (111.5 vs 104.4 mg/dl [1.26 vs 1.18 mmol/l]) than those with the GG genotype. No genotype differences were observed for any of the other measured variables, however.
Writing in the European Journal of Applied Physiology, the researchers say: "It seems reasonable to speculate that different metabolic environments, including poor CRF level and insulin resistance… could affect the regulation of the ACDC gene and the influence of SNPs within it."
They conclude that "further studies are needed to elucidate the functional mechanism(s) through which these two common SNPs interact with lifestyle-related risk factors… to modulate susceptibility to a clustering of metabolic risk factors."
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By Nikki Withers