The relationship between Insulin resistance and vitamin D deficiency : a cross-sectional study among employees at a private university in Lebanon

Abstract

Insulin resistance plays a fundamental role in the pathophysiology of many chronic diseases including Type II diabetes, cardiovascular and metabolic abnormalities. There is an increasing interest in assessing the association between insulin resistance and vitamin D status. Vitamin D deficiency predominates in the Middle East where more than half of the population is deficient. This cross-sectional study aims to explore the association between vitamin D status and insulin resistance among university employees. In September 2016, an email was sent to all the employees of Notre Dame University (NDU) to invite them to participate in our cross-sectional study. The participants completed a 20-minute face-to-face interview questionnaire. They were then requested to pass by the Nutrition Laboratory-NDU to acquire anthropometric, clinical and biochemical measurements. Homeostatic Model Assessment of Insulin Resistance (HOMA-IR) was performed to assess insulin resistance (IR); a food frequency questionnaire was conducted to assess vitamin D intake; enzyme-linked immunosorbent assay (ELISA) was used to measure serum 25 hydroxyvitamin D (25(OH)D) and a 24h recall multiple pass method recall was filled to estimate energy and nutrient intakes. Statistical analyses were performed using SPSS version 23. The study population consisted of 318 adult participants (48.1% male, 51.9% female) with an average age of 41.5 ± 11.1 years. Among the participants, 33.3% and 61.9% had serum 25(OH) D < 20ng/mL and < 30ng/mL, respectively. A positive proportional association between HOMA-IR and BMI categories in both genders (p<0.001) was observed. Mean glucose level was also significantly higher among participants with IR for both genders (p<0.001). Body fat percentage was higher and risky waist circumference was more prevalent among participants with IR for both genders (p<0.001). A significant inverse association was observed with serum 25(OH)D < 20ng/mL (p=0.028) and HOMA-IR; however, this association was not significant when cutoff of 30ng/mL was used. Stratification based on gender showed a significant inverse association among females (p=0.031) but not males at 25(OH)D < 20ng/mL. After adjusting for confounding factors using multiple logistic regression, the association between vitamin D status and HOMA-IR was no longer significant for both genders. However, there was a significant independent association between HOMA-IR and waist circumference among males (p=0.008); and between HOMA-IR and marital status (p=0.006), hypertriglyceridemia (p=0.010) and body fat percentage (p=0.045) among females. This study contributes towards the limited literature on vitamin D and IR in a Middle-Eastern sample. Further research is needed to better understand the relationship between vitamin D and IR to direct future public health or clinical applications.