Thesis defence in the University of Oulu

Doctoral Candidate

Master of Science Mahmoud Sobhy Elkhwanky

Faculty and research unit

University of Oulu Graduate School, Faculty of Medicine, Research Unit of Biomedicine, Pharmacology and Toxicology

Field of study

Pharmacology and Toxicology

Date and time of the thesis defence

29.5.2020 12:00

Place of the thesis defence

Remote access:

Topic of the dissertation

Regulation of vitamin D metabolism by metabolic state in mice and humans. Discovery of molecular factors repressing vitamin D bioactivation and inducing deficiency in diabetes


Associate professor Enikö Kallay, Medical University of Vienna


Professor of Pharmacology Jukka Hakkola, Research Unit of Biomedicine, Faculty of Medicine, University of Oulu

New molecular explanation for vitamin D deficiency in diabetes and obesity

According to a doctoral study in the University of Oulu, diabetes and obesity impairs the body's ability to utilise vitamin D and consequently cause lower vitamin D levels, namely, vitamin D deficiency. The results provide a novel explanation for the low vitamin D blood levels common in patients with diabetes and obesity.

Vitamin D is essential to the body in many ways, and low vitamin D levels have been connected to a wide range of diseases such as diabetes, skeletal diseases, infections, cancer, and cardiovascular diseases. Epidemiological studies have for long time shown that diabetics often have low blood levels of vitamin D, and low vitamin D levels have been suspected to cause a risk for developing diabetes. However, the mechanisms have remained unknown.

Mahmoud Sobhy Elkhwanky’s doctoral study describes a previously unknown mechanism that regulates the bioactivation of vitamin D in the body. In healthy people, vitamin D, formed in the skin or obtained from nutrition, is converted in the liver to calcidiol (vitamin 25-OH-D), which is regarded as a storage form of vitamin D. According to the current understanding, the concentration of calcidiol reflects the intake and levels of vitamin D in the body. In fact, the blood concentration of calcidiol is used as a measure of vitamin D level.

Mahmoud Sobhy Elkhwanky’s thesis showed that a mechanism activated in diabetes and obesity, prevents conversion of vitamin D into calcidiol, which may result in vitamin D deficiency. Furthermore, the patients with diabetes and obesity may be are less capable to utilise vitamin D that is either produced in their skin or obtained from nutrition or supplementation.

The major implications of the study are 1. The study is the first one to provide a molecular explanation for the vitamin D deficiency associated with diabetes. 2. The study demonstrated that obesity in humans impairs the vitamin D bioactivation in adipose tissue and weight loss promoted by gastric bypass surgery rescues that. 3. Importantly, the study suggests that vitamin D deficiency associated with diabetes is a consequence, not the cause of the disease.



Last updated: 22.5.2020