Endocrine Abstracts

Diabetes mellitus (DM) is a disease of epidemic proportions. Most of DM patients are classified as type 2 diabetes mellitus (T2DM) that is linked with resistance to insulin action on target tissues. In 2015, 415 million people were living with DM worldwide with the highest prevalence rates recorded in the Oceania and the Middle East and North Africa (MENA) regions. In Jordan, a MENA country, the prevalence of DM has increased from 13% to 17% over a 10-year period (1994–2014). This highlights the need to identify risk factors associated with the current DM epidemic. This will better inform the public health policy of potential preventive measures to control the disease. Vitamin D, cholecalciferol, is a fat-soluble vitamin and a hormone. Vitamin D traditional role is to maintain calcium homeostasis and bone health. Vitamin D is increasingly recognized for its’ ‘extra-skeletal’ activities including a role in regulating insulin action on target tissues. Vitamin D elicits its action via binding to the vitamin D receptor (VDR). VDR, a nuclear receptor, mediates its action through transcriptional regulation of target genes. Vitamin D deficiency was reported in T2DM patients in several populations but not in Jordan. Herein, we recruited 125 T2DM patients and 125 healthy controls matched by gender and body mass index (BMI). We found that 25-hydroxycholecalciferol (25(OH)D) levels were lower in T2DM patients (P=0.0306). We also genotyped subjects for the following VDR SNPs (rs2228570, rs1544410, rs7975232 and rs731236). We showed that under a dominant inheritance model, the A allele of rs2228570 reduces the risk of DM (P=0.0432; OR 0.597; 95% CI 0.362-0.984). This effect was independent of age and 25(OH)D levels. Haplotype analysis of VDR rs2228570, rs1544410, rs7975232 and rs731236 showed that the ACAA and GAAG haplotypes both reduced the risk of DM in our population (P<0.05). Our findings indicate that vitamin D deficiency/insufficiency may be a risk factor of T2DM in Jordan. Normalizing 25(OH)D levels in the general population may be a feasible and well-tolerated approach to reduce T2DM burden in Jordan.