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DOI: 10.1055/s-0029-1221956
Nampt (visfatin) associations with insulin metabolism are secondary to strong associations with BMI in children
Rationale: Nampt, also named visfatin, is an important enzyme in cellular NAD metabolism. Besides expression in adipose tissue, Nampt circulates in human serum and was hypothesized to be involved in the regulation of insulin secretion. There are only sparse data on Nampt association with obesity or insulin metabolism in humans applying valid assay systems. In this study we evaluated Nampt levels in normal lean children and adolescents compared to obese children and the relationship with metabolic and cardiovascular comorbidities.
Results: In a cohort of n=138 healthy lean children, Nampt levels were not different between boys and girls matched for pubertal stage and there was also no dependency on pubertal development. Nampt levels were, however, significantly elevated in obese children compared to lean children (3.85±0.28, n=72 vs. 2.95±0.30ng/mL, n=69, P=0.029) and correlated with BMI SDS (r=0.35, P<0.0001) and other parameters of obesity in a case control study. We also identified significant associations with parameters of glucose (120min BG r=0.23, P=0.006) and insulin metabolism (Matsuda ISI r=-0.23, P=0.007) in univariate analyses that were, however, mainly attributed to underlying associations with BMI. Similarly, Nampt associations with endothelial function (RHI r=-0.25, P=0.003) or blood pressure (24h mean systolic BP: r=0.23, P=0.022) were abolished after correcting for BMI. The association with circulating endothelial progenitor cells was, however, robust after correction for BMI (rcorr=-0.26, Pcorr=0.01).
Nampt levels significantly declined in response to a glucose load in an oral glucose tolerance test in obese children (n=28). Time after glucose challenge (b=-0.25, P=0.003) and insulin levels (b=-0.23 P=0.042) were significant predictors of Nampt in multiple regression analyses (r2=0.093, P=0.004), but not blood glucose.
Conclusions: Nampt levels were strongly related with obesity in children in three independent groups of children and adolescents. The association with insulin resistance in obese subjects was secondary to the underlying association with obesity.