Brown Fat Tissue Related Hormone Levels in Metabolically Healthy and Unhealthy Obese Individuals

There are two types of adipose tissue in humans, white and brown adipose tissue. While the main task of white adipose tissue is energy storage, the main task of brown adipose tissue is energy expenditure. It was previously thought that only infants have brown adipose tissue, however today it is known that metabolically active brown adipose tissue exists in adult humans as well. Brown adipose tissue contributes to metabolic health through both energy expenditure and the cytokines they secrete.

Although obesity is frequently associated with many metabolic dysfunctions and cardiometabolic diseases such as insulin resistance, prediabetes, atherogenic dyslipidemia, metabolic syndrome, some obese individuals have been defined as metabolically healthy obese. The mechanisms underlying the formation of the metabolic healthy obese phenotype are not well understood. In experimental animal studies, it has been suggested that the molecular phenotype of adipose tissue is an important factor affecting metabolic health in obese individuals. One of the most important factors affecting the molecular phenotype of adipose tissue is the browning potential of adipose tissue. Based on this hypothesis, in this study it is aimed to investigate whether the browning of white adipose tissue has an effect on determining the metabolic phenotype of metabolically healthy and unhealthy obese individuals with the same amount of adipose tissue.

It is known that irisin, FGF21 and NRG4 are hormones that have the ability to brown the white adipose tissue. In our study, it was aimed to investigate whether there is a difference in serum FGF21, irisin and Neuregulin4 (NRG4) levels, which have brown adipose tissue browning potential, in metabolically healthy and unhealthy obese. In this way, it will be found out whether serum FGF21, irisin and NRG4 hormones, which have a browning effect on white adipose tissue, have an effect on the metabolic health of obese individuals and whether these hormones can be a treatment target.

In this project, participants who have BMI ≥30 kg/m2 and no criteria other than metabolic syndrome criteria, except increased waist circumference (blood pressure ≥130/85 mmHg, fasting blood glucose ≥100 mg/dl, triglyceride ≥150 mg/dl, HDL <40mg/dl in men, <50 mg/dl in women) and those without prediabetes will be defined as metabolically healthy obese, on the other hand other obese individuals will be defined as metabolic unhealthy. 10 ml blood samples will be taken from at least 60 metabolically healthy and 60 metabolically unhealthy participants. Serum FGF21, irisin and NRG4 levels will be measured and their levels in metabolically healthy and unhealthy obese individuals will be compared.