The effect of vitamin D supplementation on glucose metabolism in metabolic syndrome (VitDmet)

In Finland, some 40% of middle-aged men and one third of women have some degree of impairment of glucose metabolism [diagnosed or undiagnosed type 2 diabetes mellitus (T2DM), impaired fasting glycemia (IFG) and impaired glucose tolerance (IGT)]. Only a few studies have been conducted to examine the effect of vitamin D supplementation on glucose tolerance or glycemic control of patients with T2DM. The results have been variable and they could depend on the vitamin D status; supplementation may benefit only those individuals with vitamin D deficiency. Furthermore, recently the discussion about the supplementation dose of vitamin D has been very active, but no consensus has been reached yet.

For the VitDMet trial we will recruit 90 men, who will be randomized to one of the three groups as in the FIND trial: 1) 40 µg/d vitamin D3, 2) 80 µg/d vitamin D3 or 3) placebo. Inclusion criteria are: age ≥60 y, low serum calcidiol (<50 nmol/L), BMI 27-35 kg/m2, and two characteristics of cardio-metabolic syndrome, IFG or IGT, elevated BP (>135/85 mmHg) or dyslipidemia (TG >1.7 mmol/l, HDL <1.0 mmol/l for men and <1.30 mmol/l for women).

The main outcome measures are glucose tolerance, HOMA-IR and HOMA-IS and insulinogenic index. In addition, this study will give new important information of the basic mechanism as for how vitamin D works in adipose tissue and what are its effects on immunological function measured by cytokines, adipokines and gene expression in PBMCs. For our principal aim, this study offers a unique opportunity to examine the effect of vitamin D supplementation on epigenetic changes of key genes and epigenomics.

Optimal vitamin D intake is currently one of the most discussed areas in nutritional science. This study will give new important information of the significance of vitamin D in the prevention and treatment of cardio-metabolic syndrome and related disturbances. Furthermore, this study offers opportunity to find out new early biomarkers for cardio-metabolic syndrome and vitamin D status at gene expression, tissue and serum or plasma levels. The trial will also give important background information for the planned FIND trial.

VitDmet in clinicaltrials.gov (#NCT01479933).

Researchers involved in the project:

Tomi-Pekka Tuomainen, MD, PhD, PI, Matti Uusitupa, MD, PhD, Sari Voutilainen, PhD, Tarja Nurmi, PhD, Jyrki Virtanen, PhD, Ursula Schwab, PhD.