A single-nucleotide polymorphism in the p110beta gene promoter is associated with partial protection from insulin resistance in severely obese adolescents

Genotypic and phenotypic predictors of inflammation in patients with chronic kidney disease

BACKGROUND

In complex diseases such as chronic kidney disease (CKD), the risk of clinical complications is determined by interactions between phenotypic and genotypic factors. However, clinical epidemiological studies rarely attempt to analyse the combined effect of large numbers of phenotype and genotype features. We have recently shown that the relaxed linear separability (RLS) model of feature selection can address such complex issues. Here, it is applied to identify risk factors for inflammation in CKD.

METHODS

The RLS model was applied in 225 CKD stage 5 patients sampled in conjunction with dialysis initiation. Fifty-seven anthropometric or biochemical measurements and 79 genetic polymorphisms were entered into the model. The model was asked to identify phenotypes and genotypes that, when combined, could separate inflamed from non-inflamed patients. Inflammation was defined as a high-sensitivity C-reactive protein concentration above the median (5 mg/L).

RESULTS

Among the 60 genotypic and phenotypic features predicting inflammation, 31 were genetic. Among the 10 strongest predictors of inflammation, 8 were single nucleotide polymorphisms located in the NAMPT, CIITA, BMP2 and PIK3CB genes, whereas fibrinogen and bone mineral density were the only phenotypic biomarkers.

CONCLUSION

These results indicate a larger involvement of hereditary factors in inflammation than might have been expected and suggest that inclusion of genotype features in risk assessment studies is critical. The RLS model demonstrates that inflammation in CKD is determined by an extensive panel of factors and may prove to be a suitable tool that could enable a much-needed multifactorial approach as opposed to the commonly utilized single-factor analysis.

Serum 25-hydroxyvitamin D concentrations are associated with prevalence of metabolic syndrome and various cardiometabolic risk factors in US children and adolescents based on assay-adjusted serum 25-hydroxyvitamin D data from NHANES 2001-2006

BACKGROUND

The effect of assay drifts over time on serum 25-hydroxyvitamin D [25(OH)D] concentrations were not accounted for in previous national survey studies. Thus, previously reported associations between 25(OH)D with cardiometabolic risk factors using data from NHANES were likely over- or underestimated. Moreover, associations between serum 25(OH)D and metabolic syndrome (MetSyn), insulin resistance (IR), and inflammation are unclear in children.

OBJECTIVE

The relation between serum 25(OH)D and cardiometabolic risk factors in US children was investigated by using updated 25(OH)D data.

DESIGN

This study was based on newly updated serum 25(OH)D data, which were released by the National Center for Health Statistics in November 2010. Data from 3 cycles of NHANES (2001-2002, 2003-2004, and 2005-2006) for 5867 adolescents, aged 12-19 y, were used to study the association, by multivariate-adjusted regression, between serum 25(OH)D and prevalence of MetSyn and several cardiometabolic risk factors.

RESULTS

The likelihood of having MetSyn was significantly higher in the first tertile of serum 25(OH)D than in the third tertile of 25(OH)D (odds ratio: 1.71; 95% CI: 1.11, 2.65; P < 0.01). Waist circumference (P < 0.0001), systolic blood pressure (P = 0.01), and homeostatic model assessment-insulin resistance index (P = 0.001) were inversely related and HDL cholesterol (P < 0.0001) was directly related with serum 25(OH)D. No association was observed between 25(OH)D and C-reactive protein (P = 0.18).

CONCLUSIONS

On the basis of assay-adjusted data, serum 25(OH)D was significantly associated with several cardiometabolic risk factors regardless of obesity. In children, given the negative outcomes associated with poor vitamin D status and MetSyn, consideration of vitamin D supplementation in reversing cardiometabolic risk factors appears to be warranted.

Impact of rs361072 in the phosphoinositide 3-kinase p110beta gene on whole-body glucose metabolism and subunit protein expression in skeletal muscle

OBJECTIVE

Phosphoinositide 3-kinase (PI3K) is a major effector in insulin signaling. rs361072, located in the promoter of the gene (PIK3CB) for the p110beta subunit, has previously been found to be associated with homeostasis model assessment for insulin resistance (HOMA-IR) in obese subjects. The aim was to investigate the influence of rs361072 on in vivo glucose metabolism, skeletal muscle PI3K subunit protein levels, and type 2 diabetes.

RESEARCH DESIGN AND METHODS

The functional role of rs361072 was studied in 196 Danish healthy adult twins. Peripheral and hepatic insulin sensitivity was assessed by a euglycemic-hyperinsulinemic clamp. Basal and insulin-stimulated biopsies were taken from the vastus lateralis muscle, and tissue p110beta and p85alpha proteins were measured by Western blotting. The genetic association with type 2 diabetes and quantitative metabolic traits was investigated in 9,316 Danes with glucose tolerance ranging from normal to overt type 2 diabetes.

RESULTS

While hepatic insulin resistance was similar in the fasting state, carriers of the minor G allele had lower hepatic glucose output (per-allele effect: -16%, P(add) = 0.004) during high physiological insulin infusion. rs361072 did not associate with insulin-stimulated peripheral glucose disposal despite a decreased muscle p85alpha:p110beta protein ratio (P(add) = 0.03) in G allele carriers. No association with HOMA-IR or type 2 diabetes (odds ratio 1.07, P = 0.5) was identified, and obesity did not interact with rs361072 on these traits.

CONCLUSIONS

Our study suggests that the minor G allele of PIK3CB rs361072 associates with decreased muscle p85alpha:p110beta ratio and lower hepatic glucose production at high plasma insulin levels. However, no impact on type 2 diabetes prevalence was found.

Association of CHRNA2 polymorphisms with overweight/obesity and clinical characteristics in a Korean population

BACKGROUND

Genes correlated with nicotine may be important in obesity because of the role of nicotine in food intake.

METHODS

To determine if single nucleotide polymorphisms (SNPs) in the neuronal nicotinic acetylcholine receptor alpha2 subunit gene (CHRNA2) are associated with overweight/obesity, 156 non-obese and 200 overweight/obese Koreans were genotyped for four CHRNA2 SNPs using an Affymetrix Array Chip.

RESULTS

Of four SNPs, only one, rs2043063, was associated with overweight/obesity in the study population (co-dominant, p=0.049; dominant, p=0.027). Associations between the significant SNP and obesity-related clinical characteristics were observed, but these were not significant.

CONCLUSIONS

The CHRNA2 rs2043063 SNP might be a risk factor for overweight/obesity in Koreans. Therefore, further studies are needed to investigate whether mutations or common polymorphisms of the CHRNA2 gene represent a risk factor for obesity.