On the role of vitamin D binding globulin in glucose homeostasis: results from the San Luis Valley diabetes study

• Main Authors: Iyengar, Sudha, Hamman, Richard F., Marshall, Julie A., Majumder, Partha P., Ferrell, Robert E., Rao, D. C., Vogler, G. P.
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: John Wiley and Sons, Inc 1989
• Subjects: QH426 Genetics; Dogrib
• Online Access: http://repository.ias.ac.in/21347/; http://onlinelibrary.wiley.com/doi/10.1002/gepi.1370060606/abstract

Several studies have reported association between noninsulin-dependent diabetes mellitus and GC, the vitamin D binding protein of human plasma, with the GC 1 allele in significant excess among diabetics. Additionally, there is a considerable body of animal data suggesting that vitamin D has a significant impact on insulin secretion. Examination of the insulin levels in Dogrib Indians showed that the lowest levels of fasting insulin were associated with the GC 1F-1F genotype. The present study examined levels of glucose, C-peptide, and insulin at fasting and 1 hr and 2 hr following a 75 g oral glucose challenge, in a population of Hispanic-Americans and Anglos in the San Luis Valley of southern Colorado. The sample comprised a total of 468 individuals with normal glucose tolerance. Of these, 289 were Anglos and 179 were Hispanic-Americans. An analysis of covariance was performed to determine the effect of the GC genotypes on mean levels of the primary variables-glucose, C-peptide, and insulin-and a secondary variable-insulinogenic index adjusting for the covariates age, body mass index (BMI), gender, and ethnicity. The analyses revealed that there is a significant difference in mean levels of glucose at fasting (F value = 2.46; P = 0.033) among the GC genotypes in the sample. Additionally, the differences in mean levels of 1 hr postprandial glucose among the GC genotypes although not significant at a 5% level, were significant at the 10% level. No other significant phenotypic effects were observed. These analyses, are not in concordance the results of an earlier study, where lower fasting insulin was associated with the GC 1F-1F genotype.