Associations between vitamin D status and type 2 diabetes measures among Inuit in Greenland may be affected by other factors

• Published in: PLOS ONE
• Main Authors: Nielsen, Nina O, Bjerregaard, Peter, Rønn, Pernille F, Friis, Henrik, Andersen, Stig, Melbye, Mads, Lundqvist, Marika, Cohen, Arieh S, Hougaard, David M, Jørgensen, Marit E
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2016
• Subjects: Greenland; inuit
• Online Access: https://curis.ku.dk/portal/da/publications/associations-between-vitamin-d-status-and-type-2-diabetes-measures-among-inuit-in-greenland-may-be-affected-by-other-factors(49b2cba3-a6de-4d81-814f-2a146b930f19).html; https://doi.org/10.1371/journal.pone.0152763; https://curis.ku.dk/ws/files/160997891/Nielsen_et_al_PLoS_One_2016_Vol_11_4_e0152763.pdf

OBJECTIVE: Epidemiological studies have provided evidence of an association between vitamin D insufficiency and type 2 diabetes. Vitamin D levels have decreased among Inuit in Greenland, and type 2 diabetes is increasing. We hypothesized that the decline in vitamin D could have contributed to the increase in type 2 diabetes, and therefore investigated associations between serum 25(OH)D3 as a measure of vitamin D status and glucose homeostasis and glucose intolerance in an adult Inuit population. METHODS: 2877 Inuit (≥18 years) randomly selected for participation in the Inuit Health in Transition study were included. Fasting- and 2hour plasma glucose and insulin, C-peptide and HbA1c were measured, and associations with serum 25(OH)D3 were analysed using linear and logistic regression. A subsample of 330 individuals who also donated a blood sample in 1987, were furthermore included. RESULTS: After adjustment, increasing serum 25(OH)D3 (per 10 nmol/L) was associated with higher fasting plasma glucose (0.02 mmol/L, p = 0.004), 2hour plasma glucose (0.05 nmol/L, p = 0.002) and HbA1c (0.39%, p<0.001), and with lower beta-cell function (-1.00 mmol/L, p<0.001). Serum 25(OH)D3 was positively associated with impaired fasting glycaemia (OR: 1.08, p = 0.001), but not with IGT or type 2 diabetes. CONCLUSIONS: Our results did not support an association between low vitamin D levels and risk of type 2 diabetes. Instead, we found weak positive associations between vitamin D levels and fasting- and 2hour plasma glucose levels, HbA1c and impaired fasting glycaemia, and a negative association with beta-cell function, underlining the need for determination of the causal relationship.