Interleukin (IL)-6 family cytokines act through a receptor complex with gp130 subunits. IL-6 is a pleiotropic cytokine that regulates inflammation and liver regeneration. Mitochondria are the first to respond to stress and adapt their dynamics in conditions of damage. In this regard, the study aimed to investigate the role of the IL-6 cytokine family (sIL-6Ra, gp130/sIL-6Rb, and IL-11) in the regulation of mitochondrial dynamics in the liver in obese patients and to assess the contribution of these cytokines to the pathogenesis of type 2 diabetes mellitus (T2DM). We studied 134 obese patients with and without T2DM and 41 healthy donors. We found that increasing the concentration of sIL-6Ra and gp130/sIL-6Rb protected against carbohydrate disorders in obese patients and prevented non-alcoholic fatty liver disease (NAFLD) progression in obese patients. An increase in plasma IL-6 levels is associated with decreased, mitochondrial transcription factor A (TFAM) protein production in liver biopsies in obese patients with and without T2DM. Replication, transcription, and division processes in liver biopsy were reduced in patients with T2DM. Inflammatory processes stimulate liver cell apoptosis in obese patients with T2DM. The increase in IL-11 levels is associated with decreased pro-apoptotic Bcl-2-associated X protein (BAX) protein production in obese patients with and without T2DM.

Interactions between receptors and ligands of the tumor necrosis factor superfamily (TNFSF) provide costimulatory signals that control the survival, proliferation, differentiation, and effector function of immune cells. All components of the TNF superfamily are associated with NF-kB functions that are not limited to cell death and may promote survival in the face of adipose tissue inflammation in obesity. Inflammation dysfunction of mitochondria is a key factor associated with insulin resistance in obesity. The aim of the study was to analyze the relationship of soluble forms of receptors and ligands of the TNF superfamily in blood plasma with mitochondrial dynamics in adipose tissue (greater omentum (GO) and subcutaneous adipose tissue (Sat)) of obese patients with and without type 2 diabetes mellitus (T2DM). Increased plasma sTNF-R1, sTNF-R2, sTNFRSF8 receptors, and ligands TNFSF12, TNFSF13, TNFSF13B are characteristic of obese patients without T2DM. The TNF-a levels in blood plasma were associated with a decrease in MFN2 gene expression in GO and IL-10 in blood plasma. The TNFSF12 levels contributed to a decrease in glucose levels, a decrease in BMI, and an increase in IL-10 levels by influencing the MFN2 gene expression in GO, which supports mitochondrial fusion.

Steatosis in the liver in obesity increases the work of mitochondria to utilize excess lipids. An overload of β-oxidation of fatty acids, the tricarboxylic acid cycle, and oxidative phosphorylation leads to a decrease in ATP and an increase in the formation of reactive oxygen species. Normally, mitochondria can efficiently remove elevated levels of reactive oxygen species using the cell's antioxidant system and metabolic adaptation to altered conditions. This study aimed to investigate the role of hepatic SOD expression in the pathogenesis of NAFLD in obesity. It was found that the level of SOD1 expression in the liver in obese patients with and without type 2 diabetes with a BMI > 40 kg/m2 was lower than in healthy donors. The copy number of mitochondrial DNA (mtDNA) in the liver in all obese patients was more than two times lower than in the control group. In the liver of obese patients without type 2 diabetes, the SOD1 protein level and the mtDNA copy number were interrelated and negatively correlated with the area of fatty inclusions. Thus, in obese patients, a decrease in antioxidant defense in the liver leads to the vulnerability of mitochondria, which, in turn, contributes to the progression of steatosis and insulin resistance.

Interactions between receptors and ligands of the tumor necrosis factor superfamily (TNFSF) provide costimulatory signals that control the survival, proliferation, differentiation, and effector function of immune cells. All components of the TNF superfamily are associated with NF-kB functions that are not limited to cell death and may promote survival in the face of adipose tissue inflammation in obesity. Inflammation and pro-inflammatory dysfunction of mitochondria are key factors associated with insulin resistance in obesity. The aim of the study was to analyze the relationship of soluble forms of receptors and ligands of the TNF superfam-ily in blood plasma with mitochondrial dynamics in adipose tissue (greater omentum (GO) and subcutaneous adipose tissue (Sat)) of obese patients with and without type 2 diabetes mellitus (T2DM). Increased plasma sTNF-R1, sTNF-R2, sTNFRSF8 receptors and ligands TNFSF12, TNFSF13, TNFSF13B are characteristic of obese patients without T2DM. Increases in TNFSF12, TNFSF13B, and sTNF-R1 levels are associated with decreased glucose concentration and decreased BMI in obese patients. The gene expression levels responsible for regulating mitochondrial dynamics were increased in obese patients without T2DM and were unbalanced in patients with obesity and T2DM.

Background. The pathogenesis of nonalcoholic fatty liver disease (NAFLD), which develops in obesity and type 2 diabetes mellitus (T2DM), is associated with the effects of inflammatory factors on the liver parenchyma and liver mitochondrial dysfunction.Aim. To determine the role of sTNFSF14 in the regulation of liver mitochondrial biogenesis in obese patients with and without T2DM.Materials and methods. The study included 263 obese patients with and without T2DM and 42 apparently healthy donors. Quantitative determination of cytokines in the blood plasma was performed by fluorescence flow cytometry. The level of relative gene expression in the liver biopsy samples was investigated by real-time PCR. Semi-quantitative determination of proteins in the liver biopsy samples was studied by western blotting.Results. The study showed that the levels of sTNFSF14, interleukin (IL)-10, gp130 / sIL-6Rb, and sIL-6Ra in the blood plasma of the obese patients without T2DM significantly exceeded the similar values in the control patients and obese patients with T2DM. In the liver biopsy samples of the obese patients with T2DM and a body mass index (BMI) > 40 kg / m2, the expression level of the dynamin-1-like protein (DRP1 / DNM1L) gene was lower than in the control group, and the expression level of the mitofusin 2 (MFN2) gene tended to be higher. Compared with the control group, an increase in the expression level of the NADH-ubiquinone oxidoreductase chain 4 (MT-ND4) gene was recorded in the liver of all the obese patients. The patients with obesity showed a decrease in the amount of mitochondrial DNA (mtDNA) compared with the control group.Conclusion. Thus, sTNFSF14, interacting with IL-10 and gp130 / sIL-6Rb in the circulation, positively effects the liver in the obese patients without T2DM. A low level of sTNFSF14 in the blood plasma of the obese patients with T2DM results in decreased mitochondrial division and increased cellular respiration.