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Aims: To study the effects of metformin, as compared to placebo, on serum levels of vitamin D (25‐hydroxyvitamin D [25(OH)D]) in patients with advanced type 2 diabetes. Materials and Methods: In the HOME trial, a randomized placebo‐controlled trial, 390 insulin‐treated patients with type 2 diabetes were treated with 850 mg metformin or placebo thrice daily for 52 months. In a post‐hoc analysis, we examined changes in the combined levels of 25(OH)D2 and 25(OH)D3 at 4 and 16 months during the study. Results: Mean combined 25(OH)D at baseline was 68.2 nmoL/L (95% confidence interval [CI]: 65.5‐71.1). In mixed model analysis, metformin, as compared to placebo, had no effect on 25(OH)D levels during 16 months (coefficient: 1.002 per month, multiplicative model; 95% CI: 0.998‐1.006, P = .30). Metformin was associated with a small increase of 25(OH)D2 (coefficient: 1.012 per month; 95% CI: 1.003‐1.021, P = .008). However, 25(OH)D2 is only a very small fraction (3%) of 25(OH)D. Seasonal variation had the biggest impact on 25(OH)D levels. Vitamin B12 levels were not associated with the levels of 25(OH)D. Conclusion: Metformin had no effect on serum 25(OH)D during 16 months in the setting of a clinical randomized controlled trial in patients with type 2 diabetes. Our results show that metformin doesn't lead to vitamin D deficiency. [ABSTRACT FROM AUTHOR]

Aims: Distorted wall shear stress (WSS) in patients with type 2 diabetes mellitus (T2DM) may be partly explained by an altered red blood cell aggregation tendency (RAT) on viscosity at low shear rate (SR). The present study evaluates viscosity modeling by implementation of hematocrit and RAT in patients with and without T2DM (non-T2DM). Methods: A Couette viscometer and LORCA aggregometer provided viscosity and RAT on 6 shear rates in 55 patients (46–78 yrs, 66% male, T2DM: n = 28), following informed consent. Using a K-fold cross-validation, two linear mixed models predicted by SR and Hct and by SR, Hct and RAT were compared. Results: In non-T2DM modeling was improved in relatively low RATs (48%, p = 1.0 × 10-11) and became worse in relatively high RATs (-18%, p = 0.019). In T2DM the opposite was observed, as modeling became worse in relatively low RATs (-16%, p = 0.001) but was improved in relatively high RATs (22%, p = 0.022). Conclusions: In addition to confirming previous research, major differences in modeling improvement between T2DM and non-T2DM were found. Especially patients with T2DM, a high RAT and often high viscosity at low SR benefit from a more accurate viscosity modeling. Further studies should evaluate how these findings affect WSS in these patients. [ABSTRACT FROM AUTHOR]