Inflammation,a link between obesity and atrial fibrillation

Inflammation Research - Despite the long belief that the role of the adipose tissue was restricted to that of a passive store of triglycerides and a rich source of fatty acids, accumulating data...     

脂肪细胞因子与胰岛素抵抗的相关性分析

目的探讨肥胖及糖尿病患者血清脂肪细胞因子即:脂联素、肿瘤坏死因子(TNF)及瘦素水平与发生胰岛素抵抗的关系。方法糖耐量正常者和2型糖尿病患者各60例,其中肥胖受试者60例,体重正常者60例。所有受试者均测其脂联素、TNF-α、瘦素、血糖和血脂的水平以及空腹血清免疫反应性胰岛素(FIRI),并测定血压,腰围臀围比值(WHR)。结果糖尿病组的血清脂联素水平明显低于糖耐量正常组,其值分别为(6·09±3·11)mg/L和(14·12±4·17)mg/L,两者有统计学差异(P<0·001)。血清脂联素水平与BMI、FIRI、WHR和胰岛素抵抗指数(HOMA-IR)均负相关(P<0·01)。血清瘦素水平与BMI、FIRI及HOMA-IR明显正相关(P<0·01)。TNF-α与BMI、WHR、FIRI、HOMA-IR呈显著正相关(P<0·01)。血清脂联素与HDL-C呈正相关,而瘦素和TNF-α与HDL-C呈明显的负相关(P<0·01)。统计学上均具有显著意义。血清脂联素水平与TNF-α及瘦素水平呈明显负相关(分别为r=-0·40,P<0·001;r=-0·40,P<0·001)。结论结果显示,脂肪细胞因子即:脂联素、TNF-α及瘦素水平直接或间接参与正常人和糖尿病患者肥胖及胰岛素抵抗的发生或发展。     

The inflammatory consequences of psychologic stress: relationship to insulin resistance, obesity, atherosclerosis and diabetes mellitus, type II

Inflammation is frequently present in the visceral fat and vasculature in certain patients with cardiovascular disease (CVD) and/or adult onset Diabetes Mellitus Type II (NIDDM). An hypothesis is presented which argues that repeated acute or chronic psychologically stressful states may cause this inflammatory process. The mediators are the major stress hormones norepinephrine (NE) and epinephrine (E) and cortisol together with components of the renin-angiotensin system (RAS), the proinflammatory cytokines (PIC), as well as free fatty acids (ffa), the latter as a result of lipolysis of neutral fat. NE/E commence this process by activation of NF(kappa)B in macrophages, visceral fat, and endothelial cells which induces the production of toll-like receptors which, when engaged, produce a cascade of inflammatory reactions comprising the acute phase response (APR) of the innate immune system (IIS). The inflammatory process is most marked in the visceral fat depot as well as the vasculature, and is involved in the metabolic events which culminate in the insulin resistance/metabolic syndromes (IRS/MS), the components of which precede and comprise the major risk factors for CVD and NIDDM. The visceral fat has both the proclivity and capacity to undergo inflammation. It contains a rich blood and nerve supply as well as proinflammatory molecules such as interleukin 6 (IL-6), tumor necrosis factor alpha (TNFalpha), leptin, and resistin, the adipocytokines, and acute phase proteins (APP) which are activated from adipocytes and/or macrophages by sympathetic signaling. The inflammation is linked to fat accumulation. Cortisol, IL-6, angiotensin II (angio II), the enzyme 11(beta) hydroxysteroid dehydrogenase-1 and positive energy balance, the latter due to increased appetite induced by the major stress hormones, are factors which promote fat accumulation and are linked to obesity. There is also the capacity of the host to limit fat expansion. Sympathetic signaling induces TNF which stimulates the production of IL-6 and leptin from adipocytes; these molecules promote lipolysis and ffa fluxes from adipocytes. Moreover, catecholamines and certain PIC inhibit lipoprotein lipase, a fat synthesizing enzyme. The brain also participates in the regulation of fat cell mass; it is informed of fat depot mass by molecules such as leptin and ffa. Leptin stimulates corticotrophin releasing hormone in the brain which stimulates the SNS and HPA axes, i.e. the stress response. Also, ffa through portal signaling from the liver evoke a similar stress response which, like the response to psychologic stress, evokes an innate immune response (IIR), tending to limit fat expansion, which culminates in inflammatory cascades, the IRS-MS, obesity and disease if prolonged. Thus, the brain also has the capacity to limit fat expansion. A competition apparently exists between fat expansion and fat loss. In "western" cultures, with excessive food ingestion, obesity frequently results. The linkage of inflammation to fat metabolism is apparent since weight loss diminishes the concentration of inflammatory mediators. The linkage of stress to inflammation is all the more apparent since the efferent pathways from the brain in response to fat signals, which results in inflammation to decrease and limit fat cell mass, is the same as the response to psychologic stress, which strengthens the hypothesis presented herein.     

Inflammation: a pivotal link between autoimmune diseases and atherosclerosis

Premature coronary heart disease has emerged as a major cause of morbidity and mortality in systemic autoimmune diseases. Recent epidemiologic and pathogenesis studies have suggested a great deal in common between the pathogenesis of prototypic autoimmune disease such as rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE) and that of atherosclerosis. Some of the most remarkable data in support of a link between autoimmunity and atherosclerosis comes from epidemiological studies of patients with autoimmune disorders (RA and SLE). Many epidemiologic observations have linked systemic inflammation with the cardiovascular events in autoimmune disease such as RA and SLE. Inflammation is increasingly being considered central to the pathogenesis of atherosclerosis and an important risk factor for vascular disease. Systemic inflammation may be regarded as accelerating the atherosclerotic process. Systemic levels of soluble inflammatory mediators such as C-reactive protein (CRP) have been associated with cardiovascular risk in the general population. CRP, or more specifically high sensitivity-hsCRP, is a marker of systemic inflammation that has been identified as a valid biomarker of cardiovascular risk. Furthermore, the immunomodulatory and anti-inflammatory actions of statins may affect their utility in the context of chronic inflammatory autoimmune disease. Thus, effective control or dampening of inflammation, with such agents, should be included in the therapeutic armamentarium of autoimmune diseases with the aim of protecting against cardiovascular disease.     

Macrophages, inflammation, adipose tissue, obesity and insulin resistance

Obesity is associated with a complex systemic inflammatory reaction that has been associated with the development of atherosclerosis and insulin resistance. Obesity also induces macrophage accumulation in adipose tissue. Macrophages produce many of the pro inflammatory molecules released by adipose tissue and have been implicated in the development of obesity-induced adipose tissue inflammation. Monocyte chemoattractant proteins (MCPs) and their receptors play key roles in the development of inflammatory responses and are crucial for the recruitment of immune cells towards inflammation sites. Adipose tissue expression of at least 1 MCP, C-C motif chemokine ligand-2 (CCL2 or MCP1), increases in proportion to adiposity. The C-C motif chemokine receptor-2 (CCR2) regulates monocyte and macrophage recruitment and is necessary for macrophage-dependent inflammatory responses and the development of atherosclerosis. Because CCR2 regulates monocyte and macrophage chemotaxis and local inflammatory responses, it has been hypothesized that monocyte chemoattractant molecules acting through CCR2 might regulate obesity-induced inflammation in adipose tissue. Our study focuses on the molecular and genetic mechanisms that recruit and retain macrophages in adipose tissue.     

Is there a link between insulin resistance and inflammatory activation in preeclampsia?

Preeclampsia is a severe complication of human pregnancy and an insulin resistant state has been demonstrated in this multisystem disorder, although its bases remain unclear. Inositol phosphoglycans P-type belongs to a family of putative insulin mediators and was described to exert many insulin-like effects on lipid and glucose metabolism. A definite association between this molecule and preeclampsia was reported. The systemic inflammatory activation that occurs in preeclampsia as a consequence of the immunological dysfunction can exacerbate placental insulin resistance leading to an over-expression of P-IPG as a counterregulatory mechanism to insulin resistance. Besides, the lipidic form of P-IPG was reported to be similar to endotoxins, and may represent the link between insulin resistance, systemic inflammation and increased angiogenic factors. In this article we propose a new working theory on insulin resistance and preeclampsia.     

Central obesity,type 2 diabetes and insulin: exploring a pathway full of thorns

The prevalence of type 2 diabetes (T2D) is rapidly increasing. This is strongly related to the contemporary lifestyle changes that have resulted in increased rates of overweight individuals and obesity. Central (intra-abdominal) obesity is observed in the majority of patients with T2D. It is associated with insulin resistance, mainly at the level of skeletal muscle, adipose tissue and liver. The discovery of macrophage infiltration in the abdominal adipose tissue and the unbalanced production of adipocyte cytokines (adipokines) was an essential step towards novel research perspectives for a better understanding of the molecular mechanisms governing the development of insulin resistance. Furthermore, in an obese state, the increased cellular uptake of non-esterified fatty acids is exacerbated without any subsequent β-oxidation. This in turn contributes to the accumulation of intermediate lipid metabolites that cause defects in the insulin signaling pathway. This paper examines the possible cellular mechanisms that connect central obesity with defects in the insulin pathway. It discusses the discrepancies observed from studies organized in cell cultures, animal models and humans. Finally, it emphasizes the need for therapeutic strategies in order to achieve weight reduction in overweight and obese patients with T2D.     

The interconnections of molecular mechanisms of hormone actions and their role in pathogenesis of obesity, insulin resistance, and diabetes mellitus

The various hormones, proteins and other compounds related to developing obesity, insulin resistance and type 2 diabetes are analyzed in the paper. 1) Leptin, ciliary neurutrophic factor, adiponectin, glucagon-like peptide 1, peptide YY, neuromedin S, as well as the protein receptors of these hormones decrease the food consumption, increase the energy turnover, and prevent obesity, insulin resistance, and type 2 diabetes development. The mediators of these hormone and receptor actions are melanocyte stimulating hormone (MSH), corticotropin-releasing hormone (CRH), and the others. 2) Ghrelin, endogenose cannabinoides, galanin-like peptide and the mediators of their actions: neuropeptide Y (NPY) and Agouti gene related protein (AGRP) increase the appetite and food consumption. Peroxisome proliferation-activated receptor (PPAR) performs the similar action on food intake. The activation of the first group compound functioning decreases the obesity, increases the energy turnover, facilitates the insulin action and prevents the insulin resistance and type 2 diabetes. Increasing the activities of the second group, as well as, decreasing the actions of the first one of substances induce the opposite effects and facilitate obesity, insulin resistance, and type 2 diabetes developments. The interconnections of the molecular mechanisms of so many hormone actions make the very complicated tusk to study the various endocrine disorders including diabetes mellitus as well.     

Differential expression and signaling activation of insulin receptor isoforms A and B: A link between breast cancer and diabetes

We showed that when insulin-like growth factor II (IGF-II) is highly expressed in breast tissues and cell lines, the IGF-I receptor signaling pathway is highly activated. Since IGF-II activates the insulin receptor (INSR), we propose that the INSR signaling is also activated in this system. We examined the expression of both INSR isoforms, insulin receptor A (INSR-A) and insulin receptor B (INSR-B), and the downstream signaling pathways in breast cancer (BC) cells and in paired (normal/tumor) breast tissues from 100 patients. Analysis was performed by real-time PCR, Western blot, immunohistochemistry, and phospho-ELISA techniques. Tumor tissues and cell lines from African-American patients expressed higher levels of INSR-A, but lower levels of INSR-B. Accordingly, insulin receptor substrate 1 and focal adhesion kinase activation were significantly increased in these women. We conclude that higher INSR-A and lower INSR-B contribute to higher proliferation and lower metabolic response. Thus, differential expression of INSR isoforms represents a potential biological link between BC and diabetes.     

Obesity, insulin resistance and diabetes: sex differences and role of oestrogen receptors

Obesity increases the risk of coronary artery disease through insulin resistance, diabetes, arterial hypertension and dyslipidemia. The prevalence of obesity has increased worldwide and is particularly high among middle-aged women and men. After menopause, women are at an increased risk to develop visceral obesity due to the loss of endogenous ovarian hormone production. Effects of oestrogens are classically mediated by the two nuclear oestrogen receptors (ERs) α and β. In addition, more recent research has shown that the intracellular transmembrane G-protein-coupled oestrogen receptor (GPER) originally designated as GPR30 also mediates some of the actions attributed to oestrogens. Oestrogen and its receptors are important regulators of body weight and insulin sensitivity not only in women but also in men as demonstrated by ER mutations in rodents and humans. This article reviews the role of sex hormones and ERs in the context of obesity, insulin sensitivity and diabetes as well as the related clinical issues in women and men.     

Differential expression and signaling activation of insulin receptor isoforms A and B: A link between breast cancer and diabetes

We showed that when insulin-like growth factor II (IGF-II) is highly expressed in breast tissues and cell lines, the IGF-I receptor signaling pathway is highly activated. Since IGF-II activates the insulin receptor (INSR), we propose that the INSR signaling is also activated in this system. We examined the expression of both INSR isoforms, insulin receptor A (INSR-A) and insulin receptor B (INSR-B), and the downstream signaling pathways in breast cancer (BC) cells and in paired (normal/tumor) breast tissues from 100 patients. Analysis was performed by real-time PCR, Western blot, immunohistochemistry, and phospho-ELISA techniques. Tumor tissues and cell lines from African-American patients expressed higher levels of INSR-A, but lower levels of INSR-B. Accordingly, insulin receptor substrate 1 and focal adhesion kinase activation were significantly increased in these women. We conclude that higher INSR-A and lower INSR-B contribute to higher proliferation and lower metabolic response. Thus, differential expression of INSR isoforms represents a potential biological link between BC and diabetes.     

Contribution of visceral obesity to the insulin resistance syndrome.

A high visceral adipose tissue accumulation has been associated with many metabolic perturbations typical of the insulin resistance syndrome, such as dyslipidemia, impaired glucose-insulin homeostasis, hypertension and impaired fibrinolysis. It has been documented that male gender aging, and a hyperglycemic state are conditions that increase the likelihood of displaying features of the insulin resistance syndrome. Accordingly, studies have demonstrated that the variation in visceral adipose tissue accumulation explains a significant proportion of the gender differences in the metabolic risk profile. Age-related differences in metabolic components of the insulin resistance syndrome have also been shown to be partly explained by the concomitant increase in visceral adipose tissue accumulation found with age. Studies have suggested that a high visceral adipose tissue accumulation contributes significantly to the deterioration in the plasma lipid-lipoprotein profile found in hyperglycemic subjects. Finally, it appears that the clustering of metabolic alterations of the insulin resistance syndrome is more pronounced in obese subjects with high levels of visceral fat that in those with a lower visceral adipose tissue accumulation.     

Inflammation links excess fat to insulin resistance: the role of the interleukin-1 family

A growing body of evidence suggests that cytokines of the interleukin-1 (IL-1) family, particularly IL-1β but also IL-1Ra and IL-18, are involved in obesity-associated inflammation. IL-1β is produced via cleavage of pro-IL-1β by caspase-1, which in turn is activated by a multiprotein complex called the inflammasome. The components of the NLRP3 inflammasome are involved in sensing obesity-associated danger signals, both in mice and in human (obese) subjects, with caspase-1 seemingly the most crucial regulator. Autophagy is upregulated in obesity and may function as a mechanism to control IL-1β gene expression in adipose tissue to mitigate chronic inflammation. All these mechanisms are operative in human adipose tissue and appear to be more pronounced in human visceral compared to subcutaneous tissue. In animal studies, blocking caspase-1 activity results in decreased weight gain, decreased inflammation, and improved insulin sensitivity. Human intervention studies with IL-1Ra (anakinra) have reported beneficial effects in patients with diabetes, yet without significant changes in insulin sensitivity. Clearly, the IL-1 family of cytokines, especially IL-1β, plays an important role in obesity-associated inflammation and insulin resistance and may represent a therapeutic target to reverse the detrimental metabolic consequences of obesity.