Association of 25 (OH) Vitamin D and Leptin in Individuals with Insulin Resistance

Asian-Indian individuals with diabetes have been shown to have low vitamin D levels. Whether this hypovitamonisis D is associated with hyperleptinaemia is unclear. Also, whether this association is different in those with and without insulin resistance has not been ascertained. The present study aimed to investigate the association of 25-hydroxy vitamin D [25(OH) vitamin D] and leptin in individuals with and without insulin resistance.

Ninety two individuals were recruited in two study groups (n = 46 each group). First group included individuals with insulin resistance (homeostasis model assessment of insulin resistance [HOMA-IR] ≥2.0). Second group included those without insulin resistance (HOMA-IR <2.0). Comparison of 25(OH) vitamin D, leptin, anthropometry, and biochemical parameters was done between two groups and correlations between 25(OH) vitamin D, leptin, and HOMA-IR were studied.

Individuals with insulin resistance were of simiar age (39.6 ± 5.3 years) and body mass index (24.4 ± 3.2 kg/m²) as those without (39.5 ± 5.2 years and 23.6 ± 3.2 kg/m²). Individuals with insulin resistance showed significantly lower 25(OH) vitamin D (17.8 ± 7.1 vs. 22.3 ± 11.6 ng/mL, P = .03) and significantly higher leptin levels (16.9 ± 15.8 vs. 9.6 ± 9.3 ng/mL, P = .09) compared to those without. Significant negative correlation was observed between 25(OH) vitamin D and leptin levels overall (r = -0.3, P = .008). HOMA-IR showed significantly negative correlation with 25(OH) vitamin D levels in individuals with insulin resistance (r = -0.33, P = .027).

The present study found higher circulating leptin levels and lower 25(OH) vitamin D levels in individuals with insulin resistance. 25(OH) vitamin D levels were inversely associated with leptin levels particularly in women.