From Normal to Obesity and Back: The Associations between Mitochondrial DNA Copy Number, Gender, and Body Mass Index.

Mitochondrial DNA (mtDNA) encodes core subunits of oxidative phosphorylation complexes and, as a result of intricate regulatory crosstalk between nuclear and mitochondrial genomes, the total number of mtDNA copies fits the requirements of each cell type. Deviations from the physiological number of mtDNA copies are expected to be deleterious and might cause some inherited diseases and normal ageing. We studied 46 obese patients with type 2 diabetes (T2DM) one year after a laparoscopic sleeve gastrectomy (LSG) and Roux-en-Y gastric bypass (RYGB). The results were compared with normal-weight patients without T2DM (control group 1) (body mass index (BMI) = 22.5 ± 3.01 kg/m <sup>2</sup> ) and patients with obesity without T2DM (control group 2) (BMI = 36 ± 3.45 kg/m <sup>2</sup> ). We detected an increase of mtDNA copy number in the cells of the buffy coat obtained from peripheral blood, sampled one year after bariatric surgery. We also found that average mtDNA copy number as well as its dynamics (before and after the surgery) are gender-specific. To the best of our knowledge, this is the first evidence for the restoration of mtDNA copy number in obese patients after LSG and RYGB

CHEMERIN AS A POTENTIAL REGULATOR OF MITOCHONDRIAL QUALITY CONTROL IN OBESE PATIENTS

In obese patients, the relationship between the content of chemerin in blood plasma and the expression of genes TFAM, Drp1, MFN2, SOD, BAX, responsible for quality control of mitochondria, in insulin-dependent tissues (adipose tissue, liver) was revealed. The tissue-specific features of gene expression (TFAM, Drp1, MFN2, SOD, BAX), the number of mtDNA copies in the studied depots in obese patients were established. It has been proven that a change (decrease) in the number of mtDNA copies in insulin-dependent tissues can have a protective effect on mitochondria under conditions of increased oxidative stress. It was found that in patients without type 2 diabetes, an increase in chemerin production promotes the activation of the antioxidant system in the visceral adipose tissue but not in the liver. On the contrary, all obese patients with type 2 diabetes showed a decrease (compared with patients without type 2 diabetes) in the plasma level of chemerin. Thus, the low content of chemerin in the blood plasma in patients with type 2 diabetes mediates the formation of mitochondrial dysfunction in insulin-dependent tissues (adipose tissue, liver)