Serum 25-hydroxyvitamin D and markers of insulin resistance in a Japanese working population

Abstract

BACKGROUND/OBJECTIVES:The association between vitamin D status and insulin resistance (IR) has been less studied among Asians, and it remains elusive whether calcium could modify such an association. We examined the association of serum 25-hydroxyvitamin D (25(OH)D) concentrations with IR markers and the potential effect modification by calcium intake among a Japanese population. SUBJECTS/METHODS: The authors analyzed data (n ¼ 494) from a cross-sectional survey conducted in 2009 among a Japanese working population aged 20-68 years. Fasting serum 25(OH)D and insulin, as well as fasting plasma glucose were determined, and homeostatic model assessment of IR (HOMA-IR) was calculated. Calcium intake was assessed using a validated diet history questionnaire. Multiple linear regression was done with adjustment of potential confounding variables. RESULTS: Fasting insulin and HOMA-IR were significantly inversely associated with 25(OH)D concentration across quartiles of 25(OH)D after fully adjusting for covariates (P trend ¼ 0.04 and 0.02, respectively). Across clinically relevant categories of 25(OH)D, compared with participants in the vitamin D sufficiency group, those in the vitamin D insufficiency group had a 5% higher HOMA-IR score, and those in the hypovitaminosis D group had an 18% higher HOMA-IR score (P trend ¼ 0.01). In an analysis by calcium intake, the HOMA-IR score was highest among participants with both a low calcium intake and lowest 25(OH)D concentrations, with significant inverse trend being observed in the group with lower calcium intake (P trend ¼ 0.02).

Association between Serum 25-Hydroxyvitamin D Level and Insulin Resistance in a Rural Population

“…In a healthy Cree community in Quebec, Canada, no association between serum 25(OH)D and insulin homeostasis indices (HOMA-IR and HOMA-beta) was detected 14. Moreover, even in the Asian studies that reported an inverse association between 25(OH)D and insulin resistance, the association was limited to participants who were overweight or obese 8,9. Lastly, a randomized double-blinded trial in women with polycystic ovary syndrome and vitamin D deficiency also did not find vitamin D supplementation to have any effect on insulin resistance 13…”

“…Several epidemiologic studies have reported associations between lower circulating vitamin D levels and impaired glucose homeostasis 1,6,7,8,9. Analysis of the U.S. National Health and Nutrition Examination Survey datasets revealed that insufficient serum 25(OH)D concentration is significantly associated with type 2 diabetes and insulin resistance 6.…”

“…Analysis of the U.S. National Health and Nutrition Examination Survey datasets revealed that insufficient serum 25(OH)D concentration is significantly associated with type 2 diabetes and insulin resistance 6. As well, lower circulating 25(OH)D levels were associated with higher fasting insulin and HOMA-IR in a middle-aged to elderly Chinese population9 and a Japanese working population 8. The association between lower 25(OH)D concentration and impaired glucose homeostasis was also reported in the Korean population.…”

“…Recently, additional functions for vitamin D have also received greater attention, especially concerning its effect on insulin resistance 3,4,5. Nonetheless, while some previous studies reported a significant association between low circulating vitamin D levels and insulin resistance,1,6,7,8,9 others did not 10,11,12,13,14,15,16,17. Associations thereof have proven inconsistent and dependent upon the characteristics of a particular study population, such as ethnicity, sex, and age 10,11.…”

Vitamin D and its effects on cardiovascular diseases: a comprehensive review

“…Increased insulin resistance is found associated with low vitamin D status in a variety of observational studies, for instance, population-based studies in geographically diverse countries [111,112]. Hypponen and Power [109] reported a statistically significant negative association between vitamin D status and hemoglobin A1c.…”