Metabolic syndrome (MetS) is a precursor to the major health diseases associated with high mortality in industrialized countries: cardiovascular disease and diabetes. An important component of the pathogenesis of the metabolic syndrome is mitochondrial dysfunction, which is associated with tissue hypoxia, disruption of mitochondrial integrity, increased production of reactive oxygen species, and a decrease in ATP, leading to a chronic inflammatory state that affects tissues and organ systems. The mitochondrial AAA + protease Lon (Lonp1) has a broad spectrum of activities. In addition to its classical function (degradation of misfolded or damaged proteins), enzymatic activity (proteolysis, chaperone activity, mitochondrial DNA (mtDNA)binding) has been demonstrated. At the same time, the spectrum of Lonp1 activity extends to the regulation of cellular processes inside mitochondria, as well as outside mitochondria (nuclear localization). This mitochondrial protease with enzymatic activity may be a promising molecular target for the development of targeted therapy for MetS and its components. The aim of this review is to elucidate the role of mtDNA in the pathogenesis of metabolic syndrome and its components as a key component of mitochondrial dysfunction and to describe the promising and little-studied AAA + LonP1 protease as a potential target in metabolic disorders.

Monocytes play a key role in the development of metabolic syndrome, and especially obesity. Given the complex features of their development from progenitor cells, whose regulation is mediated by their interactions with bone marrow adipocytes, the importance of a detailed study of the heterogeneous composition of monocytes at the molecular and systemic levels becomes clear. Research argues for monocytes as indicators of changes in the body’s metabolism and the possibility of developing therapeutic strategies to combat obesity and components of metabolic syndrome based on manipulations of the monocyte compound of the immune response. An in-depth study of the heterogeneity of bone-marrow-derived monocytes and adipocytes could provide answers to many questions about the pathogenesis of obesity and reveal their therapeutic potential.

Metabolic syndrome (MetS) is a complex of serious pathologies with a high prevalence worldwide. Disruption of mitochondrial biogenesis and its interaction with other cell organelles plays an important role in the development of MetS. Studies have revealed the phenotypic and functional heterogeneity of mitochondria that exist within a single cell and can regulate metabolic signaling pathways, influencing the development of metabolic diseases. Excessive intake of fatty acids leads to changes in fatty acid metabolism that affect the biology of important cell organelles - the lipid droplets, whose specific biology is not fully understood. Perhaps targeted molecular genetic stimulation aimed at regulating the contact between mitochondria and lipids can break the vicious cycle of inflammation in MetS and restore normal cell function, reducing the risk of developing concomitant pathologies. The review describes potential (promising) therapeutic molecular targets associated with mitochondria and lipid droplets, focusing on the proteins involved in their contact and emphasizing their role in the pathogenesis of MetS.

Background: Epidermal growth factor receptor 4 (ERBB4) and neuregulin 4 (NRG4) have been shown to reduce steatosis and prevent the development of non-alcoholic steatohepatitis in mouse models, but little to nothing is known about their role in non-alcoholic fatty liver disease (NAFLD) in humans. This study is the first to investigate the expression of ERBB4 and NRG4 mRNAs and their role in lipid metabolism in the livers of individuals with obesity, type 2 diabetes and biopsy-proven NAFLD. Methods: Liver biospecimens were obtained intraoperatively from 80 individuals. Quantitative reverse transcription polymerase chain reaction was used to measure the expression levels of mRNAs ERBB4 and NRG4, as well as key lipogenesis genes in the liver tissue of the donors. Histological analysis was conducted on liver biopsies from 36 subjects, and the levels of the examined transcripts were compared with the stage of NAFLD. Results: In individuals with elevated body mass index (BMI), ERBB4 and NRG4 levels decreased, while ACACA levels increased. A strong negative correlation was observed between NRG4 and ACACA levels. No deregulation of the analyzed transcripts was detected in NAFLD. Conclusions: The study demonstrates a decrease in ERBB4 and NRG4 mRNA expression in the livers of subjects with high BMI but not in those with NAFLD. The correlation of the studied transcripts with major lipogenesis genes was assessed, and on this basis a putative scheme for NRG4-mediated suppression of hepatic de novo lipogenesis was hypothesised, offering new research vectors in this field.

Metabolic syndrome (MetS) is associated with a plethora of different comorbidities. Exploring its key molecular mechanisms, such as advanced glycation end product and its receptor (AGE/RAGE) pathway, holds great potential. Numerous sources agree that targeting the AGE/RAGE pathway is a potential therapeutic strategy for MetS. However, the regulation of AGE/RAGE by microRNAs (miRNAs) in the context of MetS is still poorly understood. This review aimed to provide a systematic picture of the influence of miRNAs on AGE/RAGE in the context of MetS, with a particular focus on its ligands and receptors. This review achieves this in two ways: through an inductive “bottom-up” approach realized by a classical descriptive literature search, and through a deductive/synthetic “top-down” approach based on carefully selected miRNA profiling studies in MetS and its comorbidities. Although the initial inductive approach allowed the identification of some miRNAs of interest, almost all articles on this topic focus on the regulation of processes exclusively involved in atherogenesis. The new deductive approach has broadened the research horizon: It has enabled the discovery of new promising miRNAs and allowed for ranking different comorbid pathologies in MetS according to the degree of miRNA dysregulation of AGE/RAGE. Thus, in addition to atherosclerosis, significant miRNA dysregulation of AGE/RAGE was also described in MetS, particularly in immune cells, as well as in subcutaneous adipose tissue in obesity. This review, along with the novel approaches to systematizing the data contained therein may contribute to the understanding of MetS pathogenesis and the search for targets for the treatment of MetS.

Vitamin D plays a major role in bone metabolism regulating body phosphorus and calcium metabolism. Vitamin D binding protein (VDBP) binds to vitamin D metabolites and transports them to target tissues. It is hypothesized that polymorphisms in VDBP affect the absorption of vitamin D in the body. However, the relationship between VDBP polymorphisms and vitamin D levels in individuals with obesity has yet to be sufficiently investigated. This work aimed to identify the relationship between vitamin D [25(OH)D3] blood levels in obese and non-obese individuals and the rs4588 and rs7041 polymorphisms in VDBP. The study included a total of 80 participants from the Kaliningrad region. The sample was stratified based on vitamin D status (normal, insufficiency, deficiency, and acute deficiency) and body mass index (BMI). Vitamin D blood levels were determined using enzyme immunoassay. Genomic DNA was extracted from whole blood samples. VDBP polymorphisms were identified using HaeIII and ErhI restriction endonucleases. No significant differences in vitamin D blood levels between obese and non-obese individuals were revealed. The rs4588 C A genotypes were associated with no significant differences in vitamin D levels between individuals with different body mass index (CC, p=0.147; CA, p=0.646; AA, insufficient data). However, for the VDBP rs4588 polymorphism, a significant difference was demonstrated in allele frequency between the groups with different vitamin D levels, i.e., normal vitamin D level group vs. insufficiency group (p=0.009) and normal vitamin D level group vs. acute deficiency group (p 0.0001). The analysis of the individuals with the VDBP rs7041 T G polymorphism demonstrated that there were no significant differences in the vitamin D levels between the BMI groups with specific genotypes (TG, p=0.502; GG, p=0.283; TT, insufficient data). However, the control and acute deficiency groups differed significantly (p 0.0001) in allele frequencies of individuals with the rs7041 polymorphism. Vitamin D blood levels in obese patients were comparable to those of non-obese individuals. VDBP rs7041 and rs4588 polymorphisms do not correlate with variations in vitamin D blood levels among individuals with different BMI. However, the VDBP rs4588 A polymorphism is associated with low vitamin D levels, while the VDBP rs4588 G polymorphism is more common among individuals with normal vitamin D blood levels.