Role of adipocytokines in metabolism and disease

The fatty acid profile of adipose tissue as a predictor of the ponderal and inflammatory response in adult women six years after bariatric surgery

Background

Adipose tissue is involved in several metabolic changes. This study investigated the association between the fatty acid (FA) composition of subcutaneous (SAT) and visceral (VAT) adipose tissue pre-surgery and the postsurgical response regarding the evolution of weight and concentrations of tumour necrosis factor alpha (TNF) and interleukin 6 (IL-6) in adult women who underwent Roux-en-Y gastric bypass (RYGB, n = 14) or sleeve gastrectomy (SG, n = 19) at one (T1), three (T3) and six (T6) years after surgery.

Methods

Blood samples were collected to obtain plasma for the measurement of IL-6 and TNF. Anthropometric measurements were performed, collecting samples of VAT and SAT during surgery to assess the FA profiles.

Results

Weight loss had a positive correlation with the percentage of VAT-C17:0 (T1, T3) and SAT-C18:2 (T1, T3, T6), and it had a negative correlation with SAT-C22:0 (T1, T3) and VAT-C22:0 (T3). Regarding the inflammatory response, SAT-C14:0 (T6), VAT-C14:0 (T6), SAT-C14:1 (baseline), SAT-C15:0 (T6), SAT-C16:1 (T6), VAT-C16:1 (baseline), SAT-C17:1 (T6), VAT-C17:1 (baseline), VAT-C18:1 (T6), and VAT-C20:1 (T6) exhibited positive correlations with the concentration of IL-6, which were different from the correlations of IL-6 concentrations with SAT-C18:2, VAT-C18:2 (T6), and VAT-C18:3 (T6). The FA SAT-C18:0 (T1) was negatively correlated with TNF concentrations.

Conclusions

Saturated FAs were predominantly proinflammatory, primarily in the late postoperative period. Alternately, the polyunsaturated FAs exhibited anti-inflammatory potential and predicted weight loss. Thus, the FA profile of the adipose tissue of obese adult women may be a predictor of the ponderal and inflammatory response 6 years after bariatric surgery.

Trial registration

This study was approved by the ethics committee of Federal University of Viçosa; Registration n. 17287913.2.0000.5153; Date: 07/05/2013.

Benefits of aerobic training in girls with precocious puberty: involvement of CRP and cortisol

Background The aim of this study was to investigate the effect of 12 weeks of aerobic training, 4 weeks of detraining and use gonadotropin-releasing hormone agonist (GnRHa) on serum C-reactive protein (CRP) and cortisol levels in girls with central precocious puberty (CPP). Methods Forty-five girls (aged 6-8 years) with precocious puberty were randomly divided into three groups (medication, training and medicine + training groups). Fifteen healthy girls (without precocious puberty) were also included as the control group. Serum CRP and cortisol levels were measured at baseline by the enzyme-linked immunosorbent assay (ELISA) technique. Then, the experimental groups performed an aerobic training program for 3 days/week 20-75 min per day at 45-75% maximum heart rate for 12 weeks. The medication groups also received GnRHa during the study, once a month (1 mL every 4 weeks) by intramuscular injection. Serum CRP and cortisol levels were measured again 48 h after the last training session and also after 4 weeks of detraining. Results Analysis of variance (ANOVA) with repeated measures showed a significant decrease in CRP (p = 0.02) and cortisol levels (p = 0.01) in the training group and the medicine + training group. Detraining led to return of CRP and cortisol levels to the pre-training levels (p = 0.001). No significant difference in serum CRP (p = 0.43) and cortisol levels (p = 0.06) was observed in the medication group. Further, no significant difference was observed between groups in CRP and cortisol. Conclusions Long-term regular moderate training decreases inflammation indices, and detraining eliminates the benefits of training in girls with precocious puberty.

Increased Serum Levels of Tumor Necrosis Factor-Alpha, Resistin, and Visfatin in the Children with Autism Spectrum Disorders: A Case-Control Study

Background. Autism spectrum disorders (ASDs) are complex disorders where the pathogenesis is not fully understood. Several proinflammatory and immunoinflammatory disturbances have been observed in the etiology of ASD. There is, however, limited knowledge on variations of adipokines in ASD. The present study aimed to analyze the serum levels of resistin, visfatin, and tumor necrosis factor-alpha (TNF-α) in children with ASD in relation to body weight, gender, and ASD severity level. Method. In total, 30 children with ASD (mean age: 7.72 ± 2.65 y; range; 4-12 y) and 30 healthy children (mean age: 8.4 ± 2.66 y; range: 4-12 y), including males and females, were matched for age, gender, and body mass index (BMI). Serum samples were collected, and visfatin, resistin, and TNF-α serum levels were measured using an enzyme-linked immunosorbent assay (ELISA) kit. Result. Serum visfatin, resistin, and TNF-α levels in children with ASD were significantly higher than that in the healthy patients (p < 0.05). Two significant correlations were found: a correlation between resistin and visfatin with TNF-α in children with ASD (R = 0.8 and R = 0.62, resp.) and a correlation between resistin and visfatin in children with ASD (R = 0.66). Conclusion. Higher TNF-α, resistin, and visfatin levels were found in children with ASD in comparison with controls, suggesting that elevated levels of serum proinflammatory agents may be implicated in the pathophysiology of ASD.

[Occupational semicircular lipoatrophy associated with serum adipokine abnormalities]

OBJECTIVES

The aim of this study was to examine the relationship between semicircular lipoatrophy (SL), inflammation marker (high sensibility C-reactive protein [hs-CRP]), adipokines (leptine, chemerine and vaspine) and autoimmune markers (rheumatoid factor [RF], C3 and C4 complement fractions, antinuclear antibodies [ANA], HLA DR3, and DR4). Chemerine is an adipokine, but also is an immunity marker.

METHODS

A case-control study was performed in May 2013; 21 cases were included. The closest healthy coworker to each case was used as a control. We calculated Kruskal-Wallis nonparametric test.

RESULTS

We found statistical significance (P<.05) between SL and raised hs-CRP, raised leptine and low chemerine.

CONCLUSIONS

i) There seems to be an underlying inflammatory component (raised hs-CRP) in SL; ii) adipokine alteration (raised leptine and low chemerine) supports the idea that adipocytic differentiation is affected in SL, and iii) we have not found any immune marker associated with SL, except chemerine itself, which could explain a possible association between SL and immunity.

Increased peroxisome proliferator-activated receptor γ expression levels in visceral adipose tissue, and serum CCL2 and interleukin-6 levels during visceral adipose tissue accumulation

This study was conducted to determine the mRNA and protein expression levels of peroxisome proliferator-activated receptors (PPARs) in visceral adipose tissue, as well as serum adipokine levels, in Sprague Dawley rats. The rats were fed either a normal (control rats) or excessive (experimental rats) intake of food for 8 or 16 weeks, then sacrificed, at which time visceral and subcutaneous adipose tissues, as well as blood samples, were collected. The mRNA and protein expression levels of PPARs in the visceral adipose tissues were determined using reverse transcription-polymerase chain reaction and Western blotting, respectively. In addition, the levels of adipokines in the serum samples were determined using commercial ELISA kits. The results revealed that at 8 weeks, the mass of subcutaneous adipose tissue was higher than that of the visceral adipose tissue in the experimental rats, but the reverse occurred at 16 weeks. Furthermore, at 16 weeks the experimental rats exhibited an upregulation of PPARγ mRNA and protein expression levels in the visceral adipose tissues, and significant increases in the serum levels of CCL2 and interleukin (IL)-6 were observed, compared with those measured at 8 weeks. In conclusion, this study demonstrated that the PPARγ expression level was likely correlated with serum levels of CCL2 and IL-6, molecules that may facilitate visceral adipose tissue accumulation. In addition, the levels of the two adipokines in the serum may be useful as surrogate biomarkers for the expression levels of PPARγ in accumulated visceral adipose tissues.

Role of adipokines and peroxisome proliferator-activated receptors in nonalcoholic fatty liver disease

Intrahepatic fat deposition has been demonstrated in patients with nonalcoholic fatty liver disease (NAFLD). Genetic and environmental factors are important for the development of NAFLD. Diseases such as obesity, diabetes, and hypertension have been found to be closely associated with the incidence of NAFLD. Evidence suggests that obesity and insulin resistance are the major factors that contribute to the development of NAFLD. In comparing the factors that contribute to the buildup of excess calories in obesity, an imbalance of energy homeostasis can be considered as the basis. Among the peripheral signals that are generated to regulate the uptake of food, signals from adipose tissue are of major relevance and involve the maintenance of energy homeostasis through processes such as lipogenesis, lipolysis, and oxidation of fatty acids. Advances in research on adipose tissue suggest an integral role played by adipokines in NAFLD. Cytokines secreted by adipocytes, such as tumor necrosis factor-α, transforming growth factor-β, and interleukin-6, are implicated in NAFLD. Other adipokines, such as leptin and adiponectin and, to a lesser extent, resistin and retinol binding protein-4 are also involved. Leptin and adiponectin can augment the oxidation of fatty acid in liver by activating the nuclear receptor super-family of transcription factors, namely peroxisome proliferator-activated receptor (PPAR)-α. Recent studies have proposed downregulation of PPAR-α in cases of hepatic steatosis. This review discusses the role of adipokines and PPARs with regard to hepatic energy metabolism and progression of NAFLD.

Gastric bypass and sleeve gastrectomy: the same impact on IL-6 and TNF-α. Prospective clinical trial

BACKGROUND

Due to the association between the quantity of adipose tissue and concentrations of interleukin-6 (IL-6) and tumor necrosis factor (TNF-α), this work aimed to assess the effects of Roux-en-Y gastric bypass (RYGB) and sleeve gastrectomy (SG) procedures on serum IL-6 and TNF-α concentrations.

METHODS

This study evaluated serum IL-6 and TNF-α levels, as well as routine anthropometric and biochemical values, before and 1 year post-bariatric surgery. Fifty percent of patients (n = 24) underwent RYGB, and 50 % (n = 24) underwent SG. Prior to bariatric surgery, IL-6 and TNF-α mRNA expression levels in subcutaneous adipose tissue (SAT) and visceral adipose tissue (VAT) were investigated in obese women.

RESULTS

There was a significant reduction (p < 0.05) in all anthropometric and routine biochemical measurements in patients in the RYGB and SG groups 1 year post-surgery. The serum concentrations of IL-6 and TNF-α were reduced following surgery in both groups (p < 0.05). No differences in the relative expression levels of IL-6 and TNF-α were found between SAT and VAT prior to bariatric surgery.

CONCLUSIONS

RYGB and SG procedures demonstrated a similar impact on adipokine levels in women 1 year post-surgery. Both techniques may improve the course of chronic diseases and the state of inflammation associated with obesity.

In vivo microdialysis sampling of adipokines CCL2, IL-6, and leptin in the mammary fat pad of adult female rats

Adipocytes from white adipose tissue secrete cytokines and other bioactive proteins which are collectively termed adipokines. Adiposity has been linked with increased breast cancer risk as adipokines secreted by adipocytes significantly affect epithelial cells from which breast cancer arises. Measurement of extracellular adipokine concentrations that would be involved in signaling through mammary tissue is therefore of importance. In this work, microdialysis sampling was used to collect adipokines from the interstitial space of the mammary fat pad of female rats under isoflurane anesthesia. The adipokines CCL2 (MCP-1), leptin and IL-6 were quantified from dialysate samples and compared to total tissue concentrations surrounding the implanted probes. After three hours of microdialysis sampling at 1 μL min(-1), the respective median values for these adipokines in dialysate samples were approximately 175 pg mL(-1) (CCL2), 150 pg mL(-1) (IL-6) and 750 pg mL(-1) (leptin). Adipokine protein levels from dialysates were an order of magnitude lower than levels obtained directly from mammary tissue. However, the adipokine concentrations between excised tissue surrounding the microdialysis sampling probes and control tissue without implants did not differ. This work demonstrates the utility of microdialysis sampling to quantify mammary gland adipokine levels, with relevance to understanding mammary physiology.

Peripheral signalling involved in energy homeostasis control

The alarming prevalence of obesity has led to a better understanding of the molecular mechanisms controlling energy homeostasis. Regulation of energy intake and expenditure is more complex than previously thought, being influenced by signals from many peripheral tissues. In this sense, a wide variety of peripheral signals derived from different organs contributes to the regulation of body weight and energy expenditure. Besides the well-known role of insulin and adipokines, such as leptin and adiponectin, in the regulation of energy homeostasis, signals from other tissues not previously thought to play a role in body weight regulation have emerged in recent years. The role of fibroblast growth factor 21 (FGF21), insulin-like growth factor 1 (IGF-I), and sex hormone-binding globulin (SHBG) produced by the liver in the regulation of body weight and insulin sensitivity has been recently described. Moreover, molecules expressed by skeletal muscle such as myostatin have also been involved in adipose tissue regulation. Better known is the involvement of ghrelin, cholecystokinin, glucagon-like peptide 1 (GLP-1) and PYY(3-36), produced by the gut, in energy homeostasis. Even the kidney, through the production of renin, appears to regulate body weight, with mice lacking this hormone exhibiting resistance to diet-induced obesity. In addition, the skeleton has recently emerged as an endocrine organ, with effects on body weight control and glucose homeostasis through the actions of bone-derived factors such as osteocalcin and osteopontin. The comprehension of these signals will help in a better understanding of the aetiopathology of obesity, contributing to the potential development of new therapeutic targets aimed at tackling excess body fat accumulation.

S-resistin inhibits adipocyte differentiation and increases TNFalpha expression and secretion in 3T3-L1 cells

S-resistin is a non-secretable resistin spliced variant described in white adipose tissue from Wistar rats. Since resistin has been implicated in adipogenesis regulation, here we have investigated the possible role of this new isoform in this process. For that, we have studied the adipocyte development in 3T3-L1 pre-adipocyte cell line stably expressing s-resistin and resistin. Both isoforms are able to restrain 3T3-L1 pre-adipocyte differentiation though affecting differently the expression pattern of pro-adipogenic transcription factors such CCAAT/enhancer binding proteins alpha and beta (C/EBPalpha and C/EBPbeta) and peroxisome proliferator-activated receptor gamma (PPARgamma), as well of proteins implicated in lipid metabolism such perilipin, fatty acid synthase (FAS), adipocyte lipid binding protein (ALBP/aP2) and carnitine palmitoyltransferase1 (CPT1). Likewise, both resistin isoforms impair insulin-stimulated glucose transport by decreasing glucose transport 4 (GLUT4) expression but to a different degree. In addition, s-resistin expressing 3T3-L1 cells display other remarkable differences. Thus, in these cells, endogenous resistin expression falls down while tumor necrosis factor alpha (TNFalpha) and interleukine 6 (IL-6) productions are increased along differentiation. These findings indicate that s-resistin isoform also impairs adipocyte differentiation affecting the expression pattern of key pro-adipogenic transcription factors and insulin sensitivity. Additionally, s-resistin may play a role in inflammatory processes.

Relationship between insulin resistance, inflammation and liver cell apoptosis in patients with severe obesity

BACKGROUND

In obesity, insulin resistance appears frequently after activation of proinflammatory molecules. Caspase-generated cytokeratin-18 (CK-18) fragments are produced during the apoptosis of hepatic cells. The main objective in the present study is to investigate the relationship between insulin resistance and caspase-generated CK-18 fragments in patients with severe obesity.

METHODS

Sixty-two patients selected for bariatric surgery were clinically studied (sex, age, weight, waist diameter, body mass index, arterial pressure and type 2 diabetes mellitus) and analytic parameters were measured in blood (glucose concentration, cholesterol, triglycerides, insulin, glycosylated hemoglobin, aspartate aminotransferase, alanine aminotransferase, high-sensitivity C-reactive protein, adiponectin, interleukin 6, interleukin 18 and CK-18 fragments). Patient group division was based on 70th percentile of insulin resistance as measured by homeostasis model assessment (HOMA) and also according to liver histology.

RESULTS

Patients with greater insulin resistance (percentile > 70th) showed higher values of CK-18 fragments, interleukin 6 and transaminases. A positive correlation between the HOMA score, value of CK-18 fragments and triglyceride level was found. A correlation between CK-18 fragments with interleukin 6, triglycerides and transaminases was also observed. HOMA score and value of CK-18 fragments correlated with the degree of liver fibrosis.

CONCLUSIONS

Greater degree of insulin resistance induces apoptosis of hepatic cells as measured by the serum levels of CK-18 fragments.

High serum resistin level may be an indicator of the severity of coronary disease in acute coronary syndrome

OBJECTIVE

To investigate the correlation between serum resistin level, cardiovascular risk factors and severity of coronary disease in acute coronary syndrome (ACS).

METHODS

After evaluated by clinical history, electrocardiography, exercise tolerance tests, laboratory tests, and coronary angiography, 220 consecutive patients with suspected chest pain were divided into normal control group, stable angina pectoris (SAP) group, and ACS group, respectively. Baseline clinical characteristics, including height, weight, waist circumference, hip circumference, white blood cell count, high-sensitive C-reactive protein (hsCRP), total cholesterol, triglyceride, low-density lipoprotein cholesterol and high-density lipoprotein cholesterol, were compared among three groups. ELISA was used to detect serum resistin levels. Pearson's correlation coefficient analysis was used to assess association between resistin and other traditional cardiovascular risk factors. Multinomial logistic regression analyses were used to define the relationship between serum resistin level and SAP or ACS.

RESULTS

Serum resistin level in ACS group (1.18+/-0.48 microg/L) was significantly higher than that in normal control and SAP groups (0.49+/-0.40 and 0.66+/-0.40 microg/L; P<0.01). Only in ACS group, increased serum resistin level was significantly correlated with hsCRP (r=0.262, P=0.004) and white blood cell count (r=0.347, P=0.001). Furthermore, serum resistin levels showed a stepwise increase with the number increase of > 50% stenosed coronary vessels. Multinomial logistic regression test demonstrated that serum resistin was a strong risk factor for ACS (OR=29.132, 95 % CI: 10.939-77.581, P<0.001).

CONCLUSION

These findings suggested the potential role of resistin in atherosclerosis and especially its involvement in ACS.

Impaired adiponectin-AMPK signalling in insulin-sensitive tissues of hypertensive rats

AIMS

Adiponectin improves insulin sensitivity by decreasing lipid accumulation in insulin-sensitive tissues. The aim of this study was to investigate whether these effects are altered in hypertension.

MAIN METHODS

Adiponectin receptors (AdipoR1 and AdipoR2) and adiponectin-related enzymes were measured by real-time PCR and Western-blot in insulin-sensitive tissues of 10-week-old male spontaneously hypertensive rats (SHR). Intrahepatic and intramyocellular triglycerides were determined by enzymatic methods.

KEY FINDINGS

SHR showed overweight, dyslipidemia, glucose intolerance and insulin resistance. Circulating concentrations of adiponectin as well as the mRNA and protein expression of adiponectin in epididymal and subcutaneous fat depots were significantly increased in hypertensive rats. Adiponectin mRNA levels were strongly associated with PPARgamma mRNA levels in both epididymal (r=0.54, P<0.05) and subcutaneous (r=0.93, P<0.0001) fat. The expression of AdipoR1 and AdipoR2, acetyl-CoA carboxylase (ACC), as well as carnitine palmitoyl transferase 1 (CPT1), were increased in skeletal muscle of SHR. These changes were not observed in the liver of SHR. In addition, in spite of the hyperadiponectinemia, SHR showed similar activation of AMP-activated protein kinase (AMPK) and a lower phosphorylation degree of its downstream ACC in liver and skeletal muscle. Accordingly, SHR exhibited a significant increase in intrahepatic (approximately 40%) and intramyocellular (approximately 60%) lipid accumulation.

SIGNIFICANCE

These findings suggest that dysregulation of the adiponectin downstream effectors contributes to increased intrahepatic and intramyocellular triglycerides in SHR. Hyperadiponectinemia together with overexpression of adiponectin receptors in skeletal muscle may reflect a defective compensatory mechanism to overcome adiponectin resistance in hypertensive rats.

Changes in blubber contaminant concentrations in California sea lions (Zalophus californianus) associated with weight loss and gain during rehabilitation

California sea lions have high levels of persistent organic pollutants (POPs) in their blubber. Animals affected by domoic acid fast and refeed during their rehabilitation. We studied the effect of decreases in total body mass (16 +/- 7% of initial body mass) on blubber POP contaminant concentrations and estimated POP burdens during fasting (12 +/- 5 days) in 19 California sea lions. The effect of refeeding (92 +/- 8% of initial body mass) was also investigated. Significant increases in the concentration of all POPs were found over the mass loss period and decreases during mass gain. A basic mass balance model indicated that the changes did not conform to a simple concentrating and diluting pattern and a proportion of the contaminants were lost from the lipid pool. During mass loss, the lower chlorinated polychlorinated biphenyl congeners, chlordanes, and hexachlorocyclohexanes were lost at a higher rate than the other contaminant classes (particularly polybrominated diphenyl ethers). During mass gain the behavior of all contaminant classes was more consistent with the dilution model. These results indicate the importance of considering the energetic contextwhen sampling blubberfor long-term contaminant monitoring and suggest an initial approach to adjust for such differences.

Increased leptin expression selectively in the hypothalamus suppresses inflammatory markers CRP and IL-6 in leptin-deficient diabetic obese mice

Low-grade systemic inflammation, as indicated by increased circulating levels of inflammatory markers CRP and IL-6, is linked to increased risks for cardiovascular diseases (CVD) and diabetes mellitus in obese subjects. Whereas hyperleptinemia in obesity are associated with increased CRP and IL-6 release, the hypothalamic versus peripheral site of leptin action has not been ascertained. The effects of increased leptin supply selectively in the hypothalamus by gene therapy on pro-inflammatory CRP and IL-6 levels and on markers of diabetes in the circulation of ob/ob mice displaying either age-related or dietary obesity were assessed. A recombinant adeno-associated viral vector encoding either green-fluorescent protein (control) or leptin gene was injected intracerebroventricularly. Five weeks later, one-half of each of the vector groups was switched to high-fat diet consumption and the other half continued to consume regular low-fat chow diet. Body weight and visceral white adipose tissue were drastically reduced and hyperinsulinemia and hyperglycemia were abrogated by leptin gene therapy, independent of the dietary fat content. The elevated plasma CRP and IL-6 levels seen in obese ob/ob mice receiving the control vector, regardless of the fat content of the diet, were markedly suppressed by increased hypothalamic leptin in both groups. The results show for the first time that leptin deficiency elevates and reinstatement of leptin selectively in the hypothalamus suppresses the release of pro-inflammatory biomarkers, a response likely to alleviate CVD associated with obesity.

Proinflammatory cytokines in obesity: impact of type 2 diabetes mellitus and gastric bypass

BACKGROUND

Obesity and obesity-associated type 2 diabetes mellitus (T2DM) are frequently related to a low-grade chronic inflammatory state, which increases the risk of developing cardiovascular diseases. The aim of the present work was to evaluate the effect of obesity and T2DM on the concentrations of pro-inflammatory factors and to study the effect of weight loss after Roux-en-Y gastric bypass (RYGBP).

METHODS

Plasma concentrations of monocyte chemoattractant protein-1 (MCP-1), tumor necrosis factor-alpha (TNF-alpha), serum amyloid A (SAA) and sialic acid (SA) were measured in 25 female volunteers. The concentrations of these cytokines were determined in 14 female obese patients before and after weight loss following RYGBP. Additionally, visceral adipose tissue (VAT) obtained from 15 females was used to quantify expression levels of MCP-1 and CD68 by Real-Time PCR.

RESULTS

Both obese normoglycemic (NG) and T2DM groups exhibited significantly higher MCP-1 (P < 0.05), TNF-alpha (P < 0.01), SAA (P < 0.05) and SA (P < 0.05) concentrations, compared to the lean group. No differences were found between obese NG and obese T2DM subjects. A significant positive correlation was found between body fat percentage (BF) and all inflammatory markers (P < 0.05) studied. MCP-1 expression levels in VAT were upregulated in obese NG (P = 0.008) and obese T2DM (P = 0.032) patients compared to lean subjects, but no additional detrimental effect of T2DM was observed between both obese groups. After weight loss, SAA (P < 0.001) and SA (P < 0.05) concentrations diminished, whereas circulating levels of MCP-1 showed a tendency to decrease (P = 0.093) and TNF-alpha did not change.

CONCLUSION

The present findings suggest that elevated pro-inflammatory cytokine levels found in obese patients relate mainly to obesity rather than to T2DM. Moreover, surgery-induced weight loss reduces circulating concentrations of key pro-inflammatory factors, which contribute to the improvement in the cardiovascular co-morbidity following excess weight loss.

The metabolic syndrome: how to approach differing definitions

Metabolic syndrome (MetS) is a useful tool for identifying individuals at risk for type 2 diabetes and coronary heart disease (CHD). The syndrome has confused practitioners because of differences in definition, though definitions have come closer together over the years; however, the principles are clear: persons who have glucose intolerance, blood pressure elevation, dyslipidemia, and central obesity are at increased risk for type 2 diabetes mellitus and CHD. Identifying the presence in a given patient of the items in the cluster serves as a warning that risk of disease is increased, and should stimulate the practitioner to institute preventive measures early, with lifestyle change initially, and pharmacotherapy subsequently, as indicated by any continued risk factor presence.

The regulation of body mass and its relation to the development of obesity

A testtömeg, ezen belül a zsírtömeg regulálása egy visszacsatolásos rendszerben valósul meg, melyben a zsírtömeg nagyságáról adipositasszignálok (leptin, inzulin, amylin), a pillanatnyi tápláltsági állapotról intestinalis peptidhormonok (ghrelin, PYY, PP, GLP-1, OXM, CCK) és a n. vagus informálják a központi idegrendszert mint központi szabályozót. A hypothalamus nucleus arcuatusának két jól elkülöníthető neuroncsoportja fogadja a zsírtömeg nagyságával arányos mennyiségben termelődő leptin közvetítette afferens információt. A leptinkötődés a sejtek felszínén elhelyezkedő leptinreceptorokhoz intracelluláris szignálmechanizmusokon keresztül a targetgének aktiválódását és anorexigén (POMC, CART) neuropeptidek termelését, majd másodlagos központokon keresztül az energiafelvétel és -leadás folyamatainak efferens regulációs mechanizmusait generálja. A testtömeg-szabályozás összetett és redundáns rendszer, számos más neuroendokrin folyamattal (növekedés, mellékvese- és pajzsmirigyműködés, reproduktív funkciók stb.), memória-, valamint jutalmazási és függőségi mechanizmussal áll kapcsolatban, így a szabályozórendszer egyes elemeinek befolyásolása, pl. gyógyszerekkel, más rendszerek működésére is hatással lehet, mellékhatások felléptére lehet számítani. Az obesitas világméretű epidémiája – mely elsősorban a magas energiasűrűségű élelmiszerek bőségével és a mozgásszegény életmóddal áll összefüggésben, melyhez a testtömeg-szabályozó rendszerünk nem tud megfelelően alkalmazkodni – intenzív kutatásokra ösztönzi az akadémiai és gyógyszeripari kutatóközpontokat annak érdekében, hogy új gyógyszerek, hatékony testsúlycsökkentő kezelési eljárások álljanak rendelkezésre az életmód-változtatási stratégiákon (diéta, fizikai aktivitás, magatartásterápia) túlmenően.

The relation of adipose tissue to cardiometabolic risk

Adipose tissue is an active and complex endocrine organ that secretes numerous bioactive substances, including hormones, growth factors, and cytokines. Central obesity, one of the components of metabolic syndrome, is a cardiometabolic risk factor associated with a state of chronic inflammation and coagulation, one in which the expression of certain adipocytokines, including tumor necrosis factor-alpha (TNF-(alpha), interleukin (IL)-6, and plasminogen activator inhibitor-1 (PAI-1) is more abundantly increased, while adiponectin expression is decreased. TNF-alpha initiates and organizes inflammatory changes in vascular tissue. IL-6, an inflammatory cytokine directly implicated in atherogenesis, exerts pleiotropic effects on a variety of tissues. An increased concentration of PAI-1, an important regulator of the endogenous fibrinolytic system, promotes continued clotting. Adiponectin, on the other hand, has potent vasculoprotective, angiogenic, anti-inflammatory, and antiatherogenic properties. Adiponectin levels are low in obese individuals and increase when weight is lost, thereby serving as a marker for cardioprotection. Weight loss has long been promoted as a means to reduce the risk of type 2 diabetes and cardiovascular disease; for example, exercise and a hypocaloric diet have been shown to decrease PAI-1 levels. Weight loss drugs, such as orlistat, a lipase inhibitor, and sibutramine, a serotonin and norepinephrine reuptake inhibitor, have both been shown to produce a decrease in C-reactive protein levels and an increase in serum adiponectin. Rimonabant, a selective cannabinoid 1 receptor antagonist in Phase III studies, also has been shown to increase adiponectin levels. These agents may play a role in the regulation of adipocytokines, which may directly affect the risk for cardiometabolic disease.

Tumour necrosis factor (TNF)α as a regulator of fat tissue mass in the Mediterranean gilthead sea bream (Sparus aurata L.)

The study was undertaken to analyze the lipolytic effect and transcriptional regulation of tumour necrosis factor (TNF)alpha in gilthead sea bream (Sparus aurata L.). The study was also focused on the transcriptional regulation and analysis of the 5-flanking region of lipoprotein lipase (LPL) in an attempt to identify cis-regulatory elements that would support the TNFalpha-mediated effects. The lipolytic effect of TNFalpha was evidenced by the increased release of glycerol in the culture medium of freshly isolated adipocytes. This observation, in addition to the summer up-regulation of TNFalpha transcripts in liver and mesenteric adipose tissue, supported a key role of TNFalpha as a fish limiting factor of tissue fat mass. Accordingly, TNFalpha expression in liver and mesenteric adipose tissue was reduced by fasting. Furthermore, the up-regulated expression of TNFalpha in the skeletal muscle of older fish can represent an adaptive response to limit the enhanced lipid influx towards muscle. A close positive association between LPL and TNFalpha transcripts supported the contribution of TNFalpha as a part of a regulatory network that exerts an inhibitory tonus upon the expression of LPL, which in turns limits the tissue uptake of fatty acids and the ultimate increase of tissue lipid reservoirs. The precise mechanism for the inhibition of LPL gene expression by TNFalpha remains to be established in fish, but analysis of the 5'-flanking region evidenced the conservation through vertebrate evolution of a functional OCT-1/NF-Y site that would mediate the TNFalpha effects on LPL expression.

Intracellular signalling pathways activated by leptin

Leptin is a versatile 16 kDa peptide hormone, with a tertiary structure resembling that of members of the long-chain helical cytokine family. It is mainly produced by adipocytes in proportion to fat size stores, and was originally thought to act only as a satiety factor. However, the ubiquitous distribution of OB-R leptin receptors in almost all tissues underlies the pleiotropism of leptin. OB-Rs belong to the class I cytokine receptor family, which is known to act through JAKs (Janus kinases) and STATs (signal transducers and activators of transcription). The OB-R gene is alternatively spliced to produce at least five isoforms. The full-length isoform, OB-Rb, contains intracellular motifs required for activation of the JAK/STAT signal transduction pathway, and is considered to be the functional receptor. Considerable evidence for systemic effects of leptin on body mass control, reproduction, angiogenesis, immunity, wound healing, bone remodelling and cardiovascular function, as well as on specific metabolic pathways, indicates that leptin operates both directly and indirectly to orchestrate complex pathophysiological processes. Consistent with leptin's pleiotropic role, its participation in and crosstalk with some of the main signalling pathways, including those involving insulin receptor substrates, phosphoinositide 3-kinase, protein kinase B, protein kinase C, extracellular-signal-regulated kinase, mitogen-activated protein kinases, phosphodiesterase, phospholipase C and nitric oxide, has been observed. The impact of leptin on several equally relevant signalling pathways extends also to Rho family GTPases in relation to the actin cytoskeleton, production of reactive oxygen species, stimulation of prostaglandins, binding to diacylglycerol kinase and catecholamine secretion, among others.