Prospective Associations of Vitamin D With β-Cell Function and Glycemia
The PROspective Metabolism and ISlet cell Evaluation (PROMISE) Cohort Study
- Sheena Kayaniyil1,
- Ravi Retnakaran2,
- Stewart B. Harris3,
- Reinhold Vieth1,4,
- Julia A. Knight5,6,
- Hertzel C. Gerstein7,
- Bruce A. Perkins2,
- Bernard Zinman2,6 and
- Anthony J. Hanley1,2,5⇓
- 1Department of Nutritional Sciences, University of Toronto, Toronto, Ontario, Canada
- 2Division of Endocrinology, Department of Medicine, University of Toronto, Toronto, Ontario, Canada
- 3Centre for Studies in Family Medicine, University of Western Ontario, London, Ontario, Canada.
- 4Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario, Canada
- 5Dalla Lana School of Public Health, University of Toronto, Toronto, Ontario, Canada
- 6Samuel Lunenfeld Research Institute, Mount Sinai Hospital, Toronto, Ontario, Canada
- 7Division of Endocrinology and Metabolism and the Population Health Research Institute, Department of Medicine, McMaster University and Hamilton Health Sciences, Hamilton, Ontario, Canada
- Corresponding author: Anthony J. Hanley, .
OBJECTIVE To examine the prospective associations of baseline vitamin D [25-hydroxyvitamin D; 25(OH)D] with insulin resistance (IR), β-cell function, and glucose homeostasis in subjects at risk for type 2 diabetes.
RESEARCH DESIGN AND METHODS We followed 489 subjects, aged 50 ± 10 years, for 3 years. At baseline and follow-up, 75-g oral glucose tolerance tests (OGTTs) were administered. IR was measured using the Matsuda index (ISOGTT) and the homeostasis model assessment of IR (HOMA-IR), β-cell function was determined using both the insulinogenic index divided by HOMA-IR (IGI/IR) and the insulin secretion sensitivity index-2 (ISSI-2), and glycemia was assessed using the area under the glucose curve (AUCglucose). Regression models were adjusted for age, sex, ethnicity, season, and baseline value of the outcome variable, as well as baseline and change in physical activity, vitamin D supplement use, and BMI.
RESULTS Multivariate linear regression analyses indicated no significant association of baseline 25(OH)D with follow-up ISOGTT or HOMA-IR. There were, however, significant positive associations of baseline 25(OH)D with follow-up IGI/IR (β = 0.005, P = 0.015) and ISSI-2 (β = 0.002, P = 0.023) and a significant inverse association of baseline 25(OH)D with follow-up AUCglucose (β = −0.001, P = 0.007). Progression to dysglycemia (impaired fasting glucose, impaired glucose tolerance, or type 2 diabetes) occurred in 116 subjects. Logistic regression analyses indicated a significant reduced risk of progression with higher baseline 25(OH)D (adjusted odds ratio 0.69 [95% CI 0.53–0.89]), but this association was not significant after additional adjustment for baseline and change in BMI (0.78 [0.59–1.02]).
CONCLUSIONS Higher baseline 25(OH)D independently predicted better β-cell function and lower AUCglucose at follow-up, supporting a potential role for vitamin D in type 2 diabetes etiology.
- Received April 6, 2011.
- Accepted August 4, 2011.
- © 2011 by the American Diabetes Association.
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