[Obesity and diabetes - are they always together?]

Obesity and type 2 diabetes mellitus (DM 2) are two interrelated metabolic diseases widespread throughout the developed world. However, up to 30% of individuals with a long history of obesity do not have a carbohydrate metabolism disorder. This article presents the results of a multi-year study of adipose tissue biology in obese individuals with DM 2 compared with individuals with the same history of obesity without DM 2. Comparative analysis of hormonal, cellular, and genetic factors in two groups of patients showed that DM 2 occurs in individuals with abnormal proliferation and adipogenic differentiation of mesenchymal stem cells (MSCs) of adipose tissue. It leads to adipocyte hypertrophy and inflammatory infiltration of adipose tissue macrophages, resulting in increased insulin resistance and diabetogenic effects. These disorders are due to abnormal expression of genes responsible for the proliferation and adipogenic differentiation of MSCs. The study of the possible reversibility of abnormal changes in adipose tissue MSCs in obese patients after significant weight loss and DM 2 remission appears to be a promising research direction. The ability to control adipose tissue progenitor cells may represent a new target for treating and preventing metabolic disorders in obesity.

Features of the Population of Mouse Peritoneal Macrophages Isolated after Stimulation with Concanavalin A and Thioglycolate.

Murine peritoneal macrophages isolated from the lavage fluid after administration of thioglycolate and concanavalin A are presented by two populations of cells of different diameters. Polarization of macrophages into a proinflammatory (M1) phenotype is accompanied by an increase in number of small cells. Macrophages obtained after administration of thioglycolate demonstrate higher tendency to anti-inflammatory (M2) phenotype, while macrophages isolated after administration of concanavalin A are committed in the proinflammatory direction. Lactate level is increased in M1 macrophages in comparison with M2 cells, which indicates predominance of glycolytic metabolism. Macrophages obtained after administration of concanavalin A have reduced mitochondrial potential, which reflects a tendency to apoptosis. Autophagy activation and inhibition neutralize the differences in pro- and anti-inflammatory properties of polarized macrophages obtained after thioglycolate administration, but have less pronounced effect on macrophages obtained after administration concanavalin A. Autophagy inhibitor increases mitochondrial potential in non-polarized macrophages obtained after administration of concanavalin A. These results demonstrate divergent properties of macrophages obtained after administration of glycolate and concanavalin A due to the difference in the mechanisms of experimental peritonitis.

Mitochondrial dynamics keep balance of nutrient combustion in thermogenic adipocytes.

Non-shivering thermogenesis takes place in brown and beige adipocytes and facilitates cold tolerance and acclimation. However, thermogenesis in adipose tissue also was found to be activated in metabolic overload states for fast utilization of nutrients excess. This observation spurred research interest in mechanisms of thermogenesis regulation for metabolic overload and obesity prevention. One of proposed regulators of thermogenic efficiency in adipocytes is the dynamics of mitochondria, where thermogenesis takes place. Indeed, brown and beige adipocytes exhibit fragmented round-shaped mitochondria, while white adipocytes have elongated organelles with high ATP synthesis. Mitochondrial morphology can determine uncoupling protein 1 (UCP1) content, efficiency of catabolic pathways and electron transport chain, supplying thermogenesis. This review will highlight the co-regulation of mitochondrial dynamics and thermogenesis and formulate hypothetical ways for excessive nutrients burning in response to mitochondrial morphology manipulation.

Latent Inflammation and Defect in Adipocyte Renewal as a Mechanism of Obesity-Associated Insulin Resistance.

Obesity is a major risk factor for type 2 diabetes and metabolic syndrome and an essential medical and social problem. In the first part of the review, we briefly highlight the biochemical basis of metabolic disbalance in obesity and evolution of our views on the mechanisms of insulin resistance development in insulin-sensitive tissues. Because obesity relates to the disturbance in the normal physiology of fat tissue, the second part of the review focuses on latent inflammation that develops in obesity and is supported by immune cells. Finally, the problem of adipocyte hypertrophy, reduced regenerative potential of fat progenitor cells, and impaired renewal of fat depots is discussed in the context of type 2 diabetes pathogenesis.

The Role of Urokinase, Tumor Necrosis Factor, and Matrix Metalloproteinase-9 in Monocyte Activation.

TNFα mediates the expression of MMP-9 in THP-1 monocytes induced by urokinase (uPA). Upregulation of MMP-9 caused by uPA and TNFα is suppressed by etanercept, a TNFα inhibitor. In addition, uPA stimulates TNFα mRNA expression. Both uPA and TNFα induce ROS generation in monocytes, while MMP-9 secretion induced by uPA and TNFα is inhibited by antioxidants. Inhibitors of NFκB, ligands of PPARα and PPARγ receptors, and SIRT1 activators negatively affect MMP-9 secretion induced by uPA. MMP-9 secretion during monocyte differentiation into macrophages is downregulated by etanercept and antioxidants. These factors as well as MMP inhibitor GM6001 reduce the number of macrophages attached to substrate during cell differentiation, indicating the role of urokinase, TNFα, and ROS in MMP expression in monocytes and MMP involvement in macrophage maturation.

Combined Action of GDNF and HGF Up-Regulates Axonal Growth by Increasing ERK1/2 Phosphorylation.

A stimulating effect of a combination of hepatocyte growth factor (HGF) and glial neurotrophic factor (GDNF) on the growth of neurites in the spinal ganglion model was demonstrated. The mechanism of neurite growth in the spinal ganglion model is associated with transactivation of HGF c-met receptor in the presence of both HGF and GDNF. The combination of HGF and GDNF significantly activated mitogenic signaling cascade mediated by protein kinases ERK1/2, which can be a mechanism for increasing the number of neurites. Our findings can be used for developing effective methods for restoring impaired peripheral nerve function after traumatic and ischemic injury using a combination of GDNF and HGF.

Chemical Inducers of Obesity-Associated Metabolic Stress Activate Inflammation and Reduce Insulin Sensitivity in 3T3-L1 Adipocytes.

Obesity is accompanied by dyslipidemia, hypoxia, endoplasmic reticulum (ER) stress, and inflammation, representing the major risk factor for the development of insulin resistance (IR) and type 2 diabetes. We modeled these conditions in cultured 3T3-L1 adipocytes and studied their effect on insulin signaling, glucose uptake, and inflammatory response via activation of stress-dependent JNK1/2 kinases. Decreased insulin-induced phosphorylation of the insulin cascade components IRS, Akt, and AS160 was observed under all tested conditions (lipid overloading of cells by palmitate, acute inflammation induced by bacterial lipopolysaccharide, hypoxia induced by Co2+, and ER stress induced by brefeldin A). In all the cases, except the acute inflammation, glucose uptake by adipocytes was reduced, and the kinetics of JNK1/2 activation was bi-phasic exhibiting sustained activation for 24 h. By contrast, in acute inflammation, JNK1/2 phosphorylation increased transiently and returned to the basal level within 2-3 h of stimulation. These results suggest a critical role of sustained (latent) vs. transient (acute) inflammation in the induction of IR and impairment of glucose utilization by adipose tissue. The components of the inflammatory signaling can be promising targets in the development of new therapeutic approaches for preventing IR and type 2 diabetes.

Interleukin-4 Restores Insulin Sensitivity in Lipid-Induced Insulin-Resistant Adipocytes.

Obesity and latent inflammation in adipose tissue significantly contribute to the development of insulin resistance (IR) and type 2 diabetes. Here we studied whether the antiinflammatory interleukin-4 (IL-4) can restore insulin sensitivity in cultured 3T3-L1 adipocytes. The activity of key components of the insulin signaling cascade was assessed by immunoblotting using phospho-specific antibodies to insulin receptor substrate IRS1 (Tyr612), Akt (Thr308 and Ser473), and AS160 (Ser318) protein that regulates translocation of the GLUT4 glucose transporter to the plasma membrane. IR was induced in mature adipocytes with albumin-conjugated palmitate. IR significantly reduced phosphorylation levels of all the above-mentioned proteins. Addition of IL-4 to the culturing medium during IR induction led to a dose-dependent stimulation of the insulin-promoted phosphorylation of IRS1, Akt, and AS160. At the optimal concentration of 50 ng/ml, IL-4 fully restored activation of the insulin cascade in IR cells, but it did not affect insulin signaling activation in the control cells. IL-4 neither upregulated expression of key adipogenesis markers GLUT4 and PPARγ nor caused lipid accumulation in the adipocytes. These results demonstrate that IL-4 can restore insulin sensitivity in adipocytes via mechanisms not associated with induced adipogenesis or de novo formation of lipid depots.

Plasmid-based gene therapy with hepatocyte growth factor stimulates peripheral nerve regeneration after traumatic injury.

Peripheral nerve injury remains a common clinical problem with no satisfactory treatment options. Numerous studies have shown that hepatocyte growth factor (HGF) exerts neurotrophic effect in motor, sensory, and parasympathetic neurons in addition to mitogenic, morphogenic, angiogenic, antiapoptotic, antifibrotic, and anti-inflammatory effect on various tissues and cells. In our study we examined efficacy of gene therapy with HGF-bearing plasmid (pC4W-hHGF) to improve consequences of traumatic nerve injury in mice. Treatment by pC4W-hHGF led to restoration of nerve structure and functional recovery compared to similar parameters in control animals. Compound action potentials (CAP) in experimental groups treated with 100 or 200 µg of pC4W-hHGF demonstrated increased amplitude and latency decrease compared to spontaneous recovery control group. In HGF-treated mice histological analysis showed a three-fold increase in axon number in nerve portion located distal to the lesion site compared to control. Moreover, significant functional recovery of n. peroneus communis triggered by pC4W-hHGF gene therapy was observed using the footprints analysis. Obtained results provide evidence for plasmid-based HGF gene therapy as a potential treatment for traumatic injury of peripheral nerve.

Latent Inflammation and Insulin Resistance in Adipose Tissue.

Obesity is a growing problem in modern society and medicine. It closely associates with metabolic disorders such as type 2 diabetes mellitus (T2DM) and hepatic and cardiovascular diseases such as nonalcoholic fatty liver disease, atherosclerosis, myocarditis, and hypertension. Obesity is often associated with latent inflammation; however, the link between inflammation, obesity, T2DM, and cardiovascular diseases is still poorly understood. Insulin resistance is the earliest feature of metabolic disorders. It mostly develops as a result of dysregulated insulin signaling in insulin-sensitive cells, as compared to inactivating mutations in insulin receptor or signaling proteins that occur relatively rare. Here, we argue that inflammatory signaling provides a link between latent inflammation, obesity, insulin resistance, and metabolic disorders. We further hypothesize that insulin-activated PI3-kinase pathway and inflammatory signaling mediated by several IκB kinases may constitute negative feedback leading to insulin resistance at least in the fat tissue. Finally, we discuss perspectives for anti-inflammatory therapies in treating the metabolic diseases.

[The Role of Macrophages in Repair of Injured Myocardium and Perspectives of Metabolic Reprogramming of Immune Cells for Myocardial Post-Infarction Recovery].

A new trend in modern experimental cardiology is the development of approaches to correction of reparation after myocardial infarction (MI) with the use of specific effects on immune cells. One of the main targets for such interventions is the process of macrophage's polarization in the infarction zone. Proinflammatory M1­macrophages contribute to hampered myocardial repair, in contrast to M2­macrophages that promote regeneration. Currently, there are two main ways of targeted delivery of agents necessary for macrophage reprogramming - inlipoid and inglycan-encapsulated particles. As modulating agents, small interfering RNA and other genetic constructions are usually used. Both these approaches are currently awaiting their translation into cardiology. The most physiological approach to reprogramming of immune cells may consist in attempts to switch the metabolism of the immune cell from glycolytic to oxidative, which allows macrophages to switch from M1 to M2 phenotype. Among possible targets for macrophage reprogramming, it is worthwhile to isolate the protein complex mTORC1, the blocking of which promotes oxidative metabolism, and the transcription factor HIF-1α, the blocking of which also facilitates the switching of the metabolism from glycolytic to oxidative one.

Molecular Mechanisms of Latent Inflammation in Metabolic Syndrome. Possible Role of Sirtuins and Peroxisome Proliferator-Activated Receptor Type γ.

The problem of metabolic syndrome is one of the most important in medicine today. The main hazard of metabolic syndrome is development of latent inflammation in adipose tissue, which promotes atherosclerosis, non-alcoholic fatty liver disease, myocarditis, and a number of other illnesses. Therefore, understanding of molecular mechanisms of latent inflammation in adipose tissue is very important for treatment of metabolic syndrome. Three main components that arise during hypertrophy and hyperplasia of adipocytes underlie such inflammation: endoplasmic reticulum stress, oxidative stress, and hypoxia. Each of these components mediates activation in different ways of the key factor of inflammation - NF-κB. For metabolic syndrome therapy, it is suggested to influence a number of inflammatory signaling components by activating other cell factors to suppress development of inflammation. Such potential factors are peroxisome proliferator-activated receptors type γ that suppress transcription factor NF-κB through direct contact or via kinase of a NF-κB inhibitor (IKK), and also the antiinflammatory transcription factor AP-1. Other possible targets are type 3 NAD+-dependent histone deacetylases (sirtuins). There are mutually antagonistic relationships between NF-κB and sirtuin type 1 that prevent development of inflammation in metabolic syndrome. Moreover, sirtuin type 1 inhibits the antiinflammatory transcription factor AP-1. Study of the influence of these factors on the relationship between macrophages and adipocytes, macrophages, and adipose tissue-derived stromal cells can help to understand mechanisms of signaling and development of latent inflammation in metabolic syndrome.