Positive effect of vitamin D supplementation on weight loss in obese patients treated with glucagon-like peptide 1 and lifestyle interventions
Authors: Gorobeiko M.B. , Zdorna V.V. , Dinets A.V. 
Published: August 2022

Background. Obesity, prediabetes and type 2 diabetes mellitus (T2DM) are global diseases affecting the population of Ukraine, with an annual increase in morbidity. Insulin resistance occurs in up to 90% of obese patients, contributing to the accumulation of white adipose tissue, and has a risk for the further development of prediabetes and T2DM. However, other factors also play a negative role in the development of obesity, particularly cholecalciferol (vitamin D) deficiency. Vitamin D is a steroid hormone the main function of which is to regulate calcium and phosphorus metabolism, but this molecule also exhibits various properties, including the effects on carbohydrate metabolism. The purpose of this study was to identify and evaluate the role of vitaminD elevation in patients receiving glucagon-like peptide-1 agonists (GLP-1a) in combination with lifestyle interventions for the treatment of obesity and to compare its effectiveness with that in patients treating with metformin and sodium-glucose cotransporter 2 inhibitors (SGLT2i). Materials and methods. A prospective study included 155 obese patients, and follow-up data were available for 49 of them. The study group consisted of 30 patients receiving combination therapy with GLP-1a liraglutide at a dose of 1.2 to 3.0 mg per day. The control group included 19 patients receiving combination therapy with metformin in daily doses of 500 to 2,000 mg, and SGLT2i in daily doses of 10 to 12.5 mg. Treatment of vitamin D deficiency was performed with cholecalciferol at a dose of 4,000 IU/day. Results. In study group GLP-1a, 25 (83.3%) patients had vitamin D insufficiency, which is statistically similar to control group (p>0.05)— 17 (89.5%) cases. All patients with vitamin D insufficiency received 4,000 IU of cholecalciferol daily during the follow-up period. In study group GLP-1a, the mean body mass before the treatment was 104.6 kg, after treatment— 96.36 kg (p=0.000007), the mean weight lost was 7.8% (range is 1–23.71%) of the initial level. Mean body mass index (BMI) before treatment was 37.1 kg/m2, after treatment— 34.11 kg/m2 (p=0.000006). In the control group, the mean weight before the treatment was 99.4 kg, after treatment— 91.74 kg (p=0.000196), the mean weight lost was 7.73% (range is 0–16.9%) of the initial level. BMI before treatment averaged 35.6 kg/m2, after treatment— 34.11 kg/m2 (p=0.000196). The analysis of carbohydrate metabolism parameters showed a significantly lower blood glucose level— 5.75 mmol/l in the study group GLP-1a compared to 8.42 mmol/l in the control group (p=0.00024). It should be noted that a similar clinical picture was also observed after treatment, despite the compensation of T2DM in all patients: a significantly lower blood glucose level— 5.03 mmol/l in the study group GLP-1a compared to 5.99 mmol/l in controls (p=0.002453). However, significantly higher levels of insulin were detected in the study group GLP-1a before treatment— 27.02 mU/L compared to 18.59mU/L in control patients (p=0.003286). After treatment, a similar situation was observed in terms of significantly higher levels of insulin: 19.41 mU/l in patients of the study group GLP-1a compared to 14.42mU/l in controls (p=0.0024). Corresponding changes were also observed for the HOMA index. Conclusions. Our results suggest high effectiveness of increasing the level of vitamin D in case of its insufficiency as a part of measures for the treatment of obese patients with liraglutide, metformin or SGLT2i.