25-Hydroxyvitamin D in Obese Youth Across the Spectrum of Glucose Tolerance From Normal to Prediabetes to Type 2 Diabetes

Abstract

OBJECTIVETo 1) determine if plasma 25-hydroxyvitamin D (25[OH]D) concentrations differ among obese youth with normal glucose tolerance (NGT) versus prediabetes versus type 2 diabetes and 2) assess the relationships between 25(OH)D and in vivo insulin sensitivity and β-cell function in this cohort.RESEARCH DESIGN AND METHODSPlasma 25(OH)D concentrations were examined in banked specimens in 9- to 20-year-old obese youth (n = 175; male 42.3%, black 46.3%) (NGT, n = 105; impaired glucose tolerance [IGT], n = 43; type 2 diabetes, n = 27) who had in vivo insulin sensitivity and secretion measured by hyperinsulinemic-euglycemic and hyperglycemic clamp techniques and had an assessment of total body composition and abdominal adiposity.RESULTSThe mean age and BMI of the subjects were 14.3 ± 2.1 years and 35.7 ± 5.6 kg/m2, respectively. BMI, plasma 25(OH)D, and the proportion of vitamin D–deficient and –insufficient children did not differ across the three groups. Furthermore, there was no association between 25(OH)D and in vivo insulin sensitivity or β-cell function relative to insulin sensitivity (disposition index) in all groups combined or in each group separately.CONCLUSIONSOur data in obese youth show 1) no differences in plasma 25(OH)D concentrations across the glucose tolerance groups and 2) no relationship between 25(OH)D and in vivo insulin sensitivity and β-cell function relative to insulin sensitivity in any of the groups. It remains uncertain if enhancement of the vitamin D status could improve pathophysiological mechanisms of prediabetes and type 2 diabetes in obese youth.

The influence of puberty on vitamin D status in obese children and the possible relation between vitamin D deficiency and insulin resistance

“…In recent years, the relationship between vitamin D and glucose metabolism has been widely analyzed, although the results have been conflicting (4,6,8,25,26). In this study, we observed that vitamin D status and HOMA SDS differed between obese subjects during prepuberty and puberty.…”

Prospective Associations of Vitamin D Status With β-Cell Function, Insulin Sensitivity, and Glycemia: The Impact of Parathyroid Hormone Status

“…Although lower 25-OH-D has been associated with incident T2DM (7)(8)(9)43) and decline in b-cell function over time (10,11) in several observational studies, other investigators have noted conflicting results (13,15,16,18). In addition, interventional studies aiming to evaluate the effect of vitamin D supplementation on glucose metabolism have yielded inconsistent conclusions (19)(20)(21)44,45).…”

“…Previous studies have also reported that increased PTH is associated with insulin resistance (12) and metabolic syndrome (4,13), and deterioration of insulin sensitivity and b-cell function has been described in hyperparathyroid states (14). Conversely, however, many investigators have questioned the association of vitamin D and PTH with glucose metabolism, particularly in light of several observational studies (13,(15)(16)(17)(18) and interventional trials (1,(19)(20)(21) that either have been negative or showed only modest beneficial effects of vitamin D supplementation on glucose homeostasis.…”

No association between 25-hydroxyvitamin D levels and prediabetes in Brazilian patients. A cross-sectional study

“…16 However, in a recent study on 175 obese adolescents, of whom 60% were euglycemic, 25% prediabetic and 15% diabetic, Las Heras et al did not find any difference in serum 25OHD3 between these groups, or any association with any metabolic parameters, even though the prevalence of low levels of vitamin D was higher in both groups. 27 Another study, on 150 obese children and adolescents living in the tropics, found vitamin D levels ≥ 20 ng/ml in 88.6%, with no difference in the prevalence of prediabetes in relation to the group with levels lower than 20 ng/ml. 28 In spite of our negative results regarding the correlation between prediabetes and vitamin D, measurement of 25OHD3 levels in patients with prediabetes is important because of the worldwide problem of vitamin D deficiency.…”