An inflammatory cascade leading to hyperresistinemia in humans

The burden of type 2 diabetes: strategies to prevent or delay onset

Type 2 diabetes is widespread and its prevalence is increasing rapidly. In the US alone, approximately 41 million individuals have prediabetes, placing them at high risk for the development of diabetes. The pathogenesis of type 2 diabetes involves inadequate insulin secretion and resistance to the action of insulin. Suggestive data link insulin resistance and accompanying hyperglycemia to an excess of abdominal adipose tissue, a link that appears to be mediated partially by adipocyte secretion of multiple adipokines that mediate inflammation, thrombosis, atherogenesis, hypertension, and insulin resistance. The adipokine adiponectin has reduced expression in obesity and appears to be protective against the development of type 2 diabetes. Current recommendations to prevent type 2 diabetes center on lifestyle modifications, such as diet and exercise. Clinical trials have established the efficacy of lifestyle intervention, as well as pharmacologic interventions that target glycemic control or fat metabolism. However, diabetes did develop in a substantial percentage of individuals who received intensive intervention in these trials. Thus there is an unmet need for additional strategies in high-risk individuals. Recent data suggest thiazolidinediones and blockade of the endocannabinoid system represent novel therapeutic approaches that may be used for the prevention of diabetes.

Nonalcoholic fatty liver disease: from pathogenesis to patient care

Nonalcoholic fatty liver disease (NAFLD) is the most common liver disease in Western countries. It encompasses a wide spectrum of liver lesions, from pure steatosis to end-stage liver disease with cirrhosis and hepatocellular carcinoma. Nonalcoholic steatohepatitis corresponds only to one stage of NAFLD. As NAFLD can be considered a liver manifestation of the metabolic syndrome, its prevalence is high in obese people and in patients who have type 2 diabetes-insulin resistance is one of the key elements of the pathogenesis of NAFLD. This disease is often asymptomatic in the absence of decompensated cirrhosis, but should be suspected in patients with elevated aminotransferase levels or radiological evidence of a fatty liver or hepatomegaly. Liver fibrosis is associated with age over 50 years, obesity, diabetes and high triglyceride levels. Liver biopsy is the only way to assess the histologic features of necrotic inflammation and fibrosis that define nonalcoholic steatohepatitis and to determine its probable prognosis. The prognosis is good for pure steatosis, whereas the presence of necrotic inflammation is associated with a significant risk of progression to cirrhosis and, possibly, hepatocellular carcinoma. Lifestyle changes, such as dietary modifications and exercise, are recommended. To date, there have been very few randomized, placebo-controlled trials of drug treatments for NAFLD.

Pronounced elevation of resistin correlates with severity of disease in severe sepsis and septic shock

OBJECTIVE

Resistin induces insulin resistance in mice. In humans, recent data suggest that resistin functions as a proinflammatory cytokine. Here, we studied resistin up to 2 wks after admission in patients with septic shock and/or severe sepsis.

DESIGN

Two prospective studies of patients with sepsis and in vitro studies of resistin interaction with monocytes.

SETTING

Intensive care unit at Karolinska University Hospital and Center for Infectious Medicine, Karolinska Institute, Huddinge, Sweden.

PATIENTS

Twenty-nine patients with severe sepsis and 66 with septic shock.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Ninety-five patients were studied, 25 of whom died within 28 days. Resistin and cytokine levels and routine biochemistry were measured at three to six defined time points during the first 2 wks after admission and were correlated to other cytokines, glucose levels, body mass index, Acute Physiology and Chronic Health Evaluation II, and Sepsis-related Organ Failure Assessment scores. Serum resistin was significantly elevated compared with healthy controls (p < .000001) and correlated with severity of disease as measured by Acute Physiology and Chronic Health Evaluation II and Sepsis-related Organ Failure Assessment scores, with an increasingly strong degree of correlation over time. Median levels were four- to eight-fold higher than controls and remained high up to 2 wks after admission to the intensive care unit. Levels correlated with interleukin-6, interleukin-8, interleukin-10, tumor necrosis factor-alpha, creatinine, D-dimer, and lactate, but not with p-glucose or body mass index. In vitro, resistin was released from monocytes after stimulation with either lipopolysaccharide or high mobility group box 1 protein. Recombinant resistin itself up-regulated intercellular adhesion molecule-1 on monocytes.

CONCLUSIONS

This is the first study assessing systemic levels of resistin in patients with septic shock/severe sepsis. We show that resistin is a marker of severity of disease and possibly a mediator of the prolonged inflammatory state seen in infected critically ill patients. Further exploration of resistin as a therapeutic target and marker of disease is merited.

Expression and regulation of resistin in osteoblasts and osteoclasts indicate a role in bone metabolism

The adipose tissue is the site of expression and secretion of a range of biologically active proteins, called adipokines, for example, leptin, adiponectin, and resistin. Leptin has previously been shown to be expressed in osteoblasts and to promote bone mineralization, whereas adiponectin expression is enhanced during osteoblast differentiation. In the present study we explored the possible role of resistin in bone metabolism. We found that resistin is expressed in murine preosteoclasts and preosteoblasts (RAW 264.7, MC3T3-E1), in primary human bone marrow stem cells and in mature human osteoblasts. The expression of resistin mRNA in RAW 264.7 was increased during differentiation and seemed to be regulated through PKC- and PKA-dependent mechanisms. Recombinant resistin increased the number of differentiated osteoclasts and stimulated NFkappaB promoter activity, indicating a role in osteoclastogenesis. Resistin also enhanced the proliferation of MC3T3-E1 cells in a PKA and PKC-dependent manner, but only weakly interfered with genes known to be upregulated during differentiation of MC3T3-E1 into osteoblasts. All together, our results indicate that resistin may play a role in bone remodeling.

Plasma resistin, associated with single nucleotide polymorphism -420, is correlated with insulin resistance, lower HDL cholesterol, and high-sensitivity C-reactive protein in the Japanese general population

OBJECTIVE

Resistin, secreted from adipocytes, causes insulin resistance in rodents. We previously reported that the G/G genotype of a resistin gene promoter single nucleotide polymorphism (SNP) at -420 increases type 2 diabetes susceptibility by enhancing promoter activity. We report here on the relation between plasma resistin and either SNP -420 genotype or factors related to insulin resistance.

RESEARCH DESIGN AND METHODS

We cross-sectionally analyzed 2,078 community-dwelling Japanese subjects attending a yearly medical checkup. The SNP -420 genotype was determined by TaqMan analysis. Fasting plasma resistin was measured using an enzyme-linked immunosorbent assay kit.

RESULTS

Plasma resistin was associated with the SNP -420 genotype (P < 0.0001), which was highest in G/G followed by C/G and C/C. Plasma resistin was higher in elderly individuals, female subjects, nondrinkers, and subjects with high blood pressure (P < 0.001, 0.003, <0.001, and 0.001, respectively). Simple regression analysis revealed that age, female sex, homeostasis model assessment of insulin resistance (HOMA-IR) index, systolic blood pressure, low HDL cholesterol, and high-sensitivity C-reactive protein (hs-CRP) were positively correlated with plasma resistin (P < 0.001, 0.003, <0.001, 0.004, <0.001, and 0.003, respectively). Multiple regression analysis adjusted for age, sex, and BMI revealed that plasma resistin was an independent factor for HOMA-IR, low HDL cholesterol, and hs-CRP (P = 0.001, <0.001, and 0.006, respectively).

CONCLUSIONS

Plasma resistin was associated with SNP -420 and was correlated with insulin resistance, low serum HDL cholesterol, and high hs-CRP in the Japanese general population.

Innate immunity modulates adipokines in humans

CONTEXT

Chronic inflammation converges in type 2 diabetes and atherosclerosis. Modulation of adipokine signaling by innate immunity in humans is of considerable interest given the role of adipokines in insulin resistance and atherosclerosis.

OBJECTIVE

The aim of the study was to examine effects of low-grade endotoxemia, a model of human inflammation, on adipokines in vivo.

DESIGN/SETTING

An open-label, placebo-controlled, fixed-sequence clinical study was conducted at a General Clinical Research Center.

PATIENTS

There were 20 healthy male (50%) and female volunteers aged 18-40 yr.

INTERVENTION

Serial blood sampling and adipose biopsies were performed for 24 h before and after iv bolus endotoxin [lipopolysaccharide (LPS), 3 ng/kg].

MAIN OUTCOME MEASURES

We measured plasma leptin, adiponectin, resistin, soluble leptin receptor, cytokines, insulin, and glucose; distribution of adiponectin among multimeric complexes; whole blood, monocyte and adipose mRNA for adipokines and their receptors.

RESULTS

LPS induced fever, blood, and adipose TNF and IL-6 and increased homeostasis model assessment of insulin resistance. These were associated with increases in plasma leptin (from 4.1 +/- 1.1 to 6.1 +/- 1.9 ng/ml in men; 21.1 +/- 4.4 to 27.4 +/- 4.7 ng/ml in women; P < 0.005), doubling of the leptin:soluble leptin receptor ratio, and marked induction of whole blood resistin mRNA (13.7 +/- 7.3-fold; P < 0.001) and plasma resistin (8.5 +/- 2.75 to 43.2 +/- 15.3 ng/ml; P < 0.001). Although total adiponectin levels and low and high molecular weight adiponectin complexes were unaltered by LPS treatment, whole blood mRNA for adiponectin receptors 1 (49%; P < 0.005) and 2 (65%; P < 0.001) was suppressed.

CONCLUSIONS

Modulation of adipokine signaling may contribute to the insulin resistant, atherogenic state associated with human inflammatory syndromes. Targeting of individual adipokines or their upstream regulation may prove effective in preventing acute and chronic inflammation-related metabolic complications.

Elevated serum acylated (biologically active) ghrelin and resistin levels associate with pregnancy-induced weight gain and insulin resistance

AIM

To study fasting biologically active serum ghrelin (RIA) and resistin (ELISA) levels in different trimesters of pregnancy (HP, n=45, 15 in each) and in gestational diabetes mellitus (GDM, n=30) compared to non-pregnant healthy women (NP, n=40) in correlation with TNF-alpha, soluble (s)TNF-receptor (R)-1, -2, leptin (ELISA), C-peptide (Cp, RIA) and Cp/blood glucose ratio (bg).

STUDY DESIGN

Cross-sectional case control study.

RESULTS

Acylated ghrelin levels were significantly increased (p<0.0001) in the 2nd (377+/-38pg/ml, X+/-S.D.) and decreased in the 3rd trimester (252+/-36) and in GDM (226+/-21) compared to NP controls (309+/-20) and HP women in the 1st trimester (314+/-41). Serum resistin levels were higher in the 1st (8.5+/-2.6ng/ml), 2nd (10.2+/-2.1) and 3rd (13.1+/-3.6) trimesters of pregnancy and in GDM (15.7+/-3.5) than in NP controls (6.5+/-2.3). Significant (p<0.01) negative linear correlations were found among fasting serum ghrelin and body mass index (BMI), the fasting C-peptide (Cp) level, C-peptide/blood glucose (Cp/bg) ratio, TNF-alpha, soluble (s)TNFR-2, leptin and resistin concentrations in both, HP and GDM groups. Significant positive correlations were observed between serum acylated ghrelin and adiponectin, and between BMI and fasting Cp, Cp/bg, TNF-alpha, sTNFR-1, -2 and leptin levels in both pregnant groups.

CONCLUSION

Increased fasting serum acylated ghrelin concentrations in the 2nd trimester may associate with weight gain during pregnancy. Hyperresistinemia may also be associated with the pregnancy-induced insulin resistance. A negative regulatory feed-back mechanism between resistin, TNF-alpha and ghrelin may be hypothesized.

Hypothalamic resistin induces hepatic insulin resistance

Circulating resistin stimulates endogenous glucose production (GP). Here, we report that bi-directional changes in hypothalamic resistin action have dramatic effects on GP and proinflammatory cytokine expression in the liver. The infusion of either resistin or an active cysteine mutant in the third cerebral ventricle (icv) or in the mediobasal hypothalamus stimulated GP independent of changes in circulating levels of glucoregulatory hormones. Conversely, central antagonism of resistin action markedly diminished the ability of circulating resistin to enhance GP. We also report that centrally mediated mechanisms partially control resistin-induced expression of TNF-alpha, IL-6, and SOCS-3 in the liver. These results unveil what we believe to be a novel site of action of resistin on GP and inflammation and suggest that hypothalamic resistin action can contribute to hyperglycemia in type 2 diabetes mellitus.

The emerging role of adipokines as mediators of inflammation and immune responses

Interest in the biology of white adipose tissue (WAT) has increased dramatically since the discovery of leptin in 1994. The identification of the product of the gene obese (ob) threw light on the role of adipose tissue in the physiopathology of obesity-related diseases, and spurred the identification of numerous other adipokines, many of a pro-inflammatory nature. It has become increasingly evident that WAT-derived cytokines mediate between obesity-related exogenous factors (nutrition and lifestyle) and the molecular events that lead to metabolic syndrome and inflammatory and/or autoimmune conditions. Here, we review recent adipokine research, with particular attention to the roles of leptin, adiponectin, resistin, visfatin, apelin, vaspin and hepcidin in such conditions.

Associations of resistin with inflammation and insulin resistance in patients with type 2 diabetes mellitus

OBJECTIVE

Resistin has been linked to obesity, type 2 diabetes, inflammation and atherosclerosis but the results of animal and human studies have been at variance. The purpose of this study was to investigate the potential roles of resistin in patients with type 2 diabetes and to evaluate the correlation between resistin and markers of obesity, inflammation, insulin resistance, metabolic parameters, diabetes control and complications.

MATERIAL AND METHODS

Fasting resistin, leptin, insulin, glucose, HbA1c, full lipid profile, C-reactive protein (CRP) (high sensitivity assay) and complete blood count were determined in 135 patients with type 2 diabetes. Univariate regression and multivariate logistic regression analyses were used to relate resistin with indices of obesity, inflammation, insulin resistance (homeostasis model, HOMA), insulin sensitivity, diabetic control, coronary heart disease (CHD) and degree of microalbuminuria.

RESULTS

Resistin showed significant (p<0.05) correlations with body mass index (BMI) "(Spearman r=0.67), waist circumference (r=0.54), fasting insulin (0.51), insulin sensitivity (r=-0.29), HOMA (r=0.30), leptin (r=0.39), CRP (r=0.29), white cell count (r=0.25) and lipid parameters but showed no significant correlation with glucose and HbA1c. Partial correlation analysis, with correction for BMI, abolished the correlation of resistin with insulin sensitivity and HOMA but not with the white cell count. When confounding factors were fixed using multiple logistic regression, resistin was not independently associated with CHD (odds ratio=1.05, p=0.08) and degree of microalbuminuria (odds ratio=1.06, p=0.24).

CONCLUSIONS

Resistin showed significant BMI-dependent associations with insulin resistance and factors linked with obesity and inflammation in patients with type 2 diabetes. Resistin may represent a link between obesity and insulin resistance via pro-inflammatory pathways.

Efficacy of antioxidant treatment in reducing resistin serum levels: a randomized study

Objectives:

Few in vitro studies have examined the participation of resistin, a recently discovered adipokine, in oxidative processes. We investigated whether in vivo treatment with the antioxidant vitamin C might affect resistin serum levels.

Design:

Randomized prospective open trial.

Setting:

San Giovanni Battista Hospital, Turin, Italy.

Participants:

Eighty healthy individuals.

Intervention:

Administration of 2 g of ascorbic acid orally for 2 wk (n = 40; experimental group) or no supplementation (n = 40; control group).

Outcome measures:

The primary end point was the between-group difference in the before–after change in resistin serum level after vitamin C supplementation. Secondary endpoints were the within- and between-group changes in glucose, insulin, lipid parameters, C-reactive protein fasting values, and markers of oxidative stress.

Results:

In the experimental group, vitamin C supplementation was significantly associated with both resistin concentration reduction (from 4.3 ± 1.5 to 2.9 ± 0.8 ng/ml; 95% confidence interval [CI] −1.87, −1.03) and ascorbic acid level increase (from 9.4 ± 2.9 to 19.0 ± 5.2 mg/l; 95% CI 7.9, 11.2). In the control group, resistin levels did not change significantly (from 4.2 ± 1.0 to 4.3 ± 0.9 ng/ml; 95% CI −0.07, 0.37). The between-group differences were highly significant (p < 0.001). Vitamin C supplementation was also associated with a statistically significant reduction in nitrotyrosine level and incremental increase in reduced glutathione. In a linear regression model, within-individual changes in vitamin C concentrations were inversely correlated with changes in resistin levels in both groups (each unit increase of vitamin C corresponded to a decrease of about 0.10 units of resistin levels (95% CI 0.13, 0.08; p < 0.001).

Conclusion:

This is to our knowledge the first randomized trial in humans that has demonstrated that short-term vitamin C supplementation could significantly reduce resistin levels, independent of changes in inflammatory or metabolic variables. Future investigations of resistin participation in oxidative processes are warranted.

Background: Resistin is a hormone that is produced by fat cells. Much of the work on resistin has been done in mice, and as a result of this research the hormone was thought to explain the link between obesity and development of diabetes. In obese mice, higher levels of resistin are seen, and this hormone seems to interfere with the normal role of insulin in reducing blood sugar levels. However, the exact biochemical pathways in mice and humans seem to be very different, and it is not obvious whether resistin plays the same role in the development of diabetes in humans as it does in mice. At the same time, some researchers have suggested links between resistin and oxidative stress, which is thought to be involved in the development of certain diseases, particularly cardiovascular disease. The researchers here wanted to more fully explore these links by finding out whether an antioxidant, vitamin C, affected levels of resistin in blood. The researchers carried out a trial in healthy human participants, who were randomized to receive 2 g of vitamin C daily for two weeks, or no treatment. The primary outcome of the trial was the change in resistin levels in blood, and the researchers also looked at the levels of other biochemical variables in blood, such as fasting glucose, insulin, cholesterol, fatty acids, and nitrotyrosine.

What the trial shows: The researchers recruited 80 participants into the trial, and 40 were randomized to receive 2 g of vitamin C supplementation for two weeks. Forty individuals acted as “controls” and received no intervention over the two weeks of the trial. Outcomes were assessed for all but two individuals in the control group. Overall, levels of resistin in blood fell substantially over the course of the trial among the individuals in the vitamin C supplementation group, but not in the control arm of the trial, and this difference between groups was statistically significant. The levels of many other biochemical markers in blood, such as glucose, cholesterol, fatty acids, and insulin, did not show statistically significant changes between the randomized groups. However, levels of two markers of oxidative stress did change: levels of nitrotyrosine, which is associated with cell damage and inflammation, seemed to drop in the vitamin C group relative to the control group, and levels of reduced glutathione (an antioxidant) seemed to increase in the vitamin C group relative to the control group.

Strengths and limitations: In this trial, all individuals were randomized at once to the two study groups. While this is unconventional (normally, participants are randomized one by one, as they are screened and deemed eligible for a study), the process would be likely to prevent bias in allocation of individuals to the study groups. Although participants were not blinded to which study group they were assigned to, the laboratory staff measuring biochemical marker levels in blood were blinded to the study groups. A key limitation of this study is that the participants in the control arm did not receive placebo tablets, but rather received no treatment. A placebo control group would have enabled the researchers to blind participants as to whether they received vitamin C or no active intervention. Participants' knowledge of their group assignment (e.g., to receive vitamin C or no intervention) may have affected their response in the trial. Finally, the trial was conducted on a small group of healthy individuals, and no clinical outcomes were examined. Therefore, although the findings are intriguing, their clinical meaning is not clear.

Contribution to the evidence: There are few other studies that have been carried out in humans examining the possibility of a link between resistin levels and oxidative stress. This study suggests that vitamin C administration reduces blood levels of resistin in humans. This finding does not yet clearly point to a specific role for resistin in disease processes or human disease, but raises questions for further study.

The adipocyte as an active participant in energy balance and metabolism

Obesity is responsible for the mounting incidence of metabolic disease in adult and pediatric populations. Understanding of the pathogenesis and maintenance of the obese state has advanced rapidly over the past 10 years. Bodily energy reserves are managed actively by complex systems that regulate food intake, substrate partitioning, and energy expenditure. An underlying assumption that circulating factors released from storage organs were able to signal bodily energy reserves was confirmed with the discovery of the leptin system. This proof of concept has spurred on the discovery of a multitude of other adipocyte-generated factors. These circulating factors signal to the brain and other organs of metabolic importance, including adipose tissue, liver, muscle, and the immune system. Adipose-derived factors have numerous implications for the basic biology of obesity and provide prospective targets for the amelioration of obesity and its adverse metabolic consequences. In this review we detail the current understanding of leptin as a prototypical adipose tissue-derived hormone related to appetite and obesity. We also describe other important adipose-derived factors in relation to their metabolic effect.

Basic endocrine products of adipose tissue in states of thyroid dysfunction

Over the past decade it has been established that adipose tissue is capable of secreting a variety of hormones, cytokines, growth factors, and other peptides that are capable of changing adipocyte biology as well as different organ systems, like the central nervous system, liver, pancreas, and skeletal muscles. Also, it is well known that changes of thyroid function are associated with marked changes in both body weight and energy expenditure. In recent years an extensive research is under way to explore the mutual roles of different adipokines and thyroid hormones. The aim of this review is to summarize our current knowledge on the role of basic peptides of adipose tissue, such as adiponectin, interleukin-6, tumor necrosis factor-alpha, and resistin, in states of altered thyroid function.

Plasma and urine levels of resistin and adiponectin in chronic kidney disease

BACKGROUND

Subjects with chronic kidney disease (CKD) have an increased risk of developing coronary atherosclerosis. Adipocyte hormones, resistin and adiponectin are implicated in insulin resistance and atherosclerosis. However, few studies in the literature address the role of adipocyte hormones in CKD. The aim of this study was to compare the levels of resistin, adiponectin and other inflammatory markers in subjects with CKD with those of the control subjects.

MATERIALS AND METHODS

In a cross-sectional study, we measured basal metabolic panel, fasting lipid panel and levels of glucose, resistin, adiponectin, insulin, C-reactive protein (CRP) and TNF-alpha in 43 subjects with CKD compared with those of 34 control subjects. We also measured the resistin and adiponectin levels in urine samples (16).

RESULTS

Subjects with CKD have increased insulin levels and insulin resistance index (IRI). Compared with controls, subjects with CKD had increased levels of resistin (5.12+/-3.2 vs.7.5+/-5.9; p<0.05), CRP (1.7+/-2.2 vs. 5.97+/-6.0; p<0.0005), and TNF-alpha (3.4+/-2.0 vs. 5.2+/-3.5; p<0.005). Resistin levels correlate with CRP and TNF-alpha, even with BMI as a covariate. Although 60% of subjects with CKD have CAD, e plasma levels of adiponectin were not decreased in subjects with CKD compared with controls (17.02+/-9.8 vs. 16.40+/-9.0 with p value 0.78). Urinary adiponectin levels correlate inversely with GFR (r=-0.4; p<0.05) and plasma adiponectin levels (r=0.9; p<0.0001).

CONCLUSIONS

Subjects with CKD had normal levels of plasma adiponectin despite the adverse metabolic environment for CAD. In addition, this study demonstrates the relationship between resistin and TNF-alpha in subjects with CKD and suggests that resistin may play a role in the sub-clinical inflammation associated with CKD, suggesting that adiponectin clearance may be decreased as shown by the inverse correlation of urinary adiponectin with GFR.

A novel role for Oct-2 in the lipopolysaccharide-mediated induction of resistin gene expression in RAW264.7 cells

Although resistin was first suggested as a possible link between obesity and diabetes, we have demonstrated previously that expression of resistin is induced by LPS (lipopolysaccharide). In the present study, we showed that LPS increased levels of resistin mRNA and promoter activity in murine RAW264.7 macrophages. Investigation of cis-regulatory elements in the mouse resistin promoter required for LPS-mediated induction showed that an Octamer (ATTTGCAT) element, located at -914 to -907, was required for maximal promoter activity in response to LPS stimulation. Co-transfection of RAW264.7 cells with a resistin promoter-luciferase construct and an Oct-1 or Oct-2 expression plasmid (pCG-Oct-1 or pCG-Oct-2) showed that Oct-2, but not Oct-1, activated the resistin promoter upon LPS treatment. Binding of Oct-2 to the Octamer element was demonstrated by supershift DNA-affinity precipitation and chromatin immunoprecipitation assays. Reverse transcription-PCR and Western blot results showed that levels of Oct-2 mRNA and protein were both up-regulated by LPS in RAW264.7 cells. The LPS-induced increase in Oct-2 protein was inhibited by LY294002 (a phosphoinositide 3-kinase inhibitor) post-transcriptionally, and the inhibition also resulted in a lower response of both resistin mRNA and promoter activity to LPS treatment. Moreover, specific knockdown of Oct-2 by RNA interference impaired the LPS-induced increase in resistin mRNA and promoter activity. Together, these results indicate that Oct-2 is involved in the LPS-mediated induction of resistin gene expression in macrophages and suggest that activation of Oct-2 is a part of LPS signalling pathways in macrophages.

Prolonged exposure to resistin inhibits glucose uptake in rat skeletal muscles

AIM

To assess the effects and mechanisms of the action of resistin on basal and insulin-stimulated glucose uptake in rat skeletal muscle cells.

METHODS

Rat myoblasts (L6) were cultured and differentiated into myotubes followed by stimulation with single commercial resistin (130 ng/mL, 0-24 h) or cultured supernatant from 293-T cells transfected with resistin-expressing vectors (130 ng/mL, 0-24 h). Liquid scintillation counting was used to quantitate [3H] 2-deoxyglucose uptake. The translocation of insulin-sensitive glucose transporters GLUT4 and GLUT1, synaptosomal-associated protein 23 (SNAP23) and GLUT protein content, as well as the tyrosine phosphorylation status and protein content of insulin receptor substrate (IRS)-1, were assessed by Western blotting.

RESULTS

Treatment of L6 myotubes with single resistin or cultured supernatant containing recombinant resistin reduced basal and insulin-stimulated 2-deoxyglucose uptake and impaired insulin-stimulated GLUT4 translocation. While SNAP23 protein content was decreased, no effects were noted in GLUT4 or GLUT1 protein content. Resistin also diminished insulin-stimulated IRS-1 tyrosine phosphorylation levels without affecting its protein content. The effects of recombinant resistin from 293-T cells transfected with resistin-expressing vectors were greater than that of single resistin treatment.

CONCLUSION

Resistin regulated IRS-1 function and decreased GLUT4 translocation and glucose uptake in response to insulin. The downregulated expression of SNAP23 may have been partly attributed to the decrease of glucose uptake by resistin treatment. These observations highlight the potential role of resistin in the pathophysiology of type 2 diabetes related to obesity.

Relationships among inflammatory cytokines, obesity, and insulin sensitivity in the horse

Recent studies associate obesity and insulin resistance in horses with development of abnormal reproductive function and debilitating laminitis. The factors contributing to insulin resistance in obese horses are unknown. However, human studies provide evidence that elevated inflammatory cytokines such as tumor necrosis factor alpha (TNFalpha), IL1, and IL6 play direct roles in development of obesity-associated insulin resistance. Thus, inflammation may be a key link between obesity and insulin resistance in horses. The aim of the current investigation was to examine possible relationships between obesity, inflammatory cytokines, and insulin sensitivity (IS) in the horse. Age was recorded and BCS and percent body fat (% FAT) were determined as measures of obesity in 60 mares. In addition, blood mRNA expression of IL1, IL6, and TNFalpha and circulating concentrations of TNFalpha protein (TNFp) were determined in each mare. Finally, fasted concentrations of insulin were determined, and IS was determined using the hyperinsulinemic, euglycemic clamp. Significant correlations between several variables provided evidence for the design of 4 population regression models to estimate relationships between measures of obesity, inflammatory factors, and IS in the sample population. The results of these analyses revealed that IS decreased as BCS and % FAT increased (P < 0.001) in the sample population. Additionally, increased IL1 (P < 0.05) and TNFp (P < 0.01) were associated with decreased IS. However, increased TNFalpha (P < 0.001) was associated with decreased IS only in mares 20 yr of age and older. Increased BCS and % FAT were associated with increased expression of TNFalpha (P = 0.053) and IL1 (P < 0.05), and increased TNFp (P < 0.05). Surprisingly, increased BCS and % FAT were associated with decreased IL6 expression (P = 0.05) in mares <20 yr of age. Finally, evaluation of the influence of obesity and inflammatory cytokines on IS within the same model suggested that BCS and % FAT (P < 0.001) with TNFalpha [mRNA (P = 0.07) and protein (P < 0.05)] are inversely associated with IS independently of one another. Combined, these results provide the first evidence associating obesity with increased inflammatory factors in the horse. Furthermore, the results suggest that an interrelationship exists among obesity, inflammatory cytokines, and IS in the horse and emphasize the need for further studies to elucidate the nature of these relationships.

Resistin as an intrahepatic cytokine: overexpression during chronic injury and induction of proinflammatory actions in hepatic stellate cells

Obesity and insulin resistance accelerate the progression of fibrosis during chronic liver disease. Resistin antagonizes insulin action in rodents, but its role in humans is still controversial. The aims of this study were to investigate resistin expression in human liver and to evaluate whether resistin may affect the biology of activated human hepatic stellate cells (HSCs), key modulators of hepatic fibrogenesis. Resistin gene expression was low in normal human liver but was increased in conditions of severe fibrosis. Up-regulation of resistin during chronic liver damage was confirmed by immunohistochemistry. In a group of patients with alcoholic hepatitis, resistin expression correlated with inflammation and fibrosis, suggesting a possible action on HSCs. Exposure of cultured HSCs to recombinant resistin resulted in increased expression of the proinflammatory chemokines monocyte chemoattractant protein-1 and interleukin-8, through activation of nuclear factor (NF)-kappaB. Resistin induced a rapid increase in intracellular calcium concentration, mainly through calcium release from intracellular inositol triphosphate-sensitive pools. The intracellular calcium chelator BAPTA-AM blocked resistin-induced NF-kappaB activation and monocyte chemoattractant protein-1 expression. In conclusion, this study shows a role for resistin as an intrahepatic cytokine exerting proinflammatory actions in HSCs, via a Ca2+/NF-kappaB-dependent pathway and suggests involvement of this adipokine in the pathophysiology of liver fibrosis.

Resistin as an intrahepatic cytokine: overexpression during chronic injury and induction of proinflammatory actions in hepatic stellate cells

Obesity and insulin resistance accelerate the progression of fibrosis during chronic liver disease. Resistin antagonizes insulin action in rodents, but its role in humans is still controversial. The aims of this study were to investigate resistin expression in human liver and to evaluate whether resistin may affect the biology of activated human hepatic stellate cells (HSCs), key modulators of hepatic fibrogenesis. Resistin gene expression was low in normal human liver but was increased in conditions of severe fibrosis. Up-regulation of resistin during chronic liver damage was confirmed by immunohistochemistry. In a group of patients with alcoholic hepatitis, resistin expression correlated with inflammation and fibrosis, suggesting a possible action on HSCs. Exposure of cultured HSCs to recombinant resistin resulted in increased expression of the proinflammatory chemokines monocyte chemoattractant protein-1 and interleukin-8, through activation of nuclear factor (NF)-kappaB. Resistin induced a rapid increase in intracellular calcium concentration, mainly through calcium release from intracellular inositol triphosphate-sensitive pools. The intracellular calcium chelator BAPTA-AM blocked resistin-induced NF-kappaB activation and monocyte chemoattractant protein-1 expression. In conclusion, this study shows a role for resistin as an intrahepatic cytokine exerting proinflammatory actions in HSCs, via a Ca2+/NF-kappaB-dependent pathway and suggests involvement of this adipokine in the pathophysiology of liver fibrosis.

CXCL16 is a marker of inflammation, atherosclerosis, and acute coronary syndromes in humans

OBJECTIVES

This study was designed to determine the association of CXCL16 with inflammation, atherosclerosis, and acute coronary syndromes.

BACKGROUND

Vascular inflammation coincides with uptake of modified lipoproteins in the pathogenesis of atherosclerosis. CXCL16 is a protein that shares scavenger receptor function, promoting uptake of modified lipids, with the activities of an inflammatory chemokine. However, the role of CXCL16 in atherosclerosis remains uncertain.

METHODS

The effect of inflammatory stimuli on CXCL16 gene and protein expression was studied in macrophages, mice, and humans, and the association of sol-CXCL16 with risk factors, atherosclerosis, and acute coronary syndromes was determined in humans.

RESULTS

Endotoxin induction of CXCL16 in human macrophages was attenuated by aspirin, nuclear factor (NF)-kappa-B inhibition and peroxisome proliferator-activated receptor (PPAR)-gamma agonists. Experimental human endotoxemia (n = 6) led to an 8-fold increase in whole-blood CXCL16 messenger ribonucleic acid (p < 0.001) and a 1.7-fold increase in soluble (sol)-CXCL16 (p < 0.001), a cleaved active chemokine. Rosiglitazone-blocked endotoxin induced sol-CXCL16 in mice (p = 0.001), and pioglitazone (n = 28), compared to placebo (n = 28), lowered plasma sol-CXCL16 in metabolic syndrome subjects (p < 0.05). In a nested case-control study of acute and chronic coronary artery disease (n = 699), sol-CXCL16 levels correlated with inflammatory and metabolic risk factors and were associated with chronic coronary artery disease (odds ratio [OR] [95% confidence interval], above vs. below median; 1.60 [1.01 to 2.58]; p = 0.04) and acute coronary syndromes (OR 2.52 [1.32 to 4.82], p = 0.005) following adjustment for established risk factors, medications, and C-reactive protein levels.

CONCLUSIONS

Our findings suggest that CXCL16 may play a pro-inflammatory role in human atherosclerosis, particularly in acute coronary syndrome.

Resistin-like molecule alpha reduces gallbladder optimal tension

INTRODUCTION

Insulin resistance is associated with increased gallbladder volume and impaired gallbladder emptying. Resistin and resistin-like molecule alpha (RELM-alpha) are adipose-derived hormones that are believed to mediate insulin resistance. Therefore, we tested the hypothesis that administration of resistin or RELM-alpha would cause insulin resistance and diminish gallbladder contractility.

METHODS

In two sequential studies 40 eight-week-old nondiabetic lean mice were fed a chow diet for 4 weeks. In Study A, 10 mice received 20 microg of resistin IP, while in Study B 10 mice received 20 microg of RELM-alpha IP for seven days. In each study, 10 control mice received an equal volume of saline IP for seven days. At 12 weeks animals were fasted and underwent cholecystectomy, and in vitro gallbladder response to neurotransmitters was determined. Serum resistin, RELM-alpha, glucose, and insulin levels were measured. HOMA index, a measure of insulin resistance, was calculated.

RESULTS

RELM-alpha significantly increased HOMA index. RELM-alpha decreased gallbladder optimal tension, but did not alter responses to neurotransmitters. Resistin had no effect on HOMA index or on gallbladder optimal tension or response.

CONCLUSION

These data suggest that in nondiabetic lean mice: 1) resistin does not alter insulin resistance or gallbladder optimal tension, but 2) RELM-alpha increases insulin resistance and reduces gallbladder optimal tension. Therefore, we concluded that RELM-alpha may play a role in insulin-resistance mediated gallbladder dysmotility.

The in vitro effects of resistin on the innate immune signaling pathway in isolated human subcutaneous adipocytes

CONTEXT

Obesity-associated inflammation is a contributory factor in the pathogenesis of type 2 diabetes mellitus (T2DM); the mechanisms underlying the progression to T2DM are unclear. The adipokine resistin has demonstrated proinflammatory properties in relation to obesity and T2DM.

OBJECTIVES

The objectives of this study were to characterize resistin expression in human obesity and address the role of resistin in the innate immune pathway; to examine the influence of lipopolysaccharide, recombinant human resistin (rhResistin), insulin, and rosiglitazone in human adipocytes; and, finally, to analyze the effect of rhResistin on the expression of components of the nuclear factor-kappaB pathway and insulin signaling cascade.

METHODS

Abdominal sc adipose tissue was obtained from patients undergoing elective liposuction surgery (n = 35; age, 36-49 yr; body mass index, 26.5 +/- 5.9 kg/m2). Isolated adipocytes were cultured with rhResistin (10-50 ng/ml). The level of cytokine secretion from isolated adipocytes was examined by ELISA. The effect of rhResistin on protein expression of components of the innate immune pathway was examined by Western blot.

RESULTS

In vitro studies demonstrated that antigenic stimuli increase resistin secretion (P < 0.001) from isolated adipocytes. Proinflammatory cytokine levels were increased in response to rhResistin (P < 0.001); this was attenuated by rosiglitazone (P < 0.01). When examining components of the innate immune pathway, rhResistin stimulated Toll-like receptor-2 protein expression. Similarly, mediators of the insulin signaling pathway, phosphospecific c-Jun NH2-terminal kinase (JNK) 1 and JNK2, were up-regulated in response to rhResistin.

CONCLUSION

Resistin may participate in more than one mechanism to influence proinflammatory cytokine release from human adipocytes, potentially via the integration of nuclear factor-kappaB and JNK signaling pathways.

Human resistin is a systemic immune-derived proinflammatory cytokine targeting both leukocytes and adipocytes

The characteristics of human resistin (RETN) are unclear and controversial despite intensive adipose-focused research. Its transcriptional and functional similarity with the murine myeloid-specific and CCAAT/enhancer binding protein epsilon (Cebpe)-dependent gene, resistin-like gamma (Retnlg), is unexplored. We examined the human CEBPE-regulatory pathway by unbiased reference and custom gene expression assays. Real-time RT-PCR analysis demonstrated lack of both the transcriptional factor CEBPE and RETN expression in adipose and muscle cells. In contrast, primary myelocytic samples revealed a concerted CEBPE-RETN transcription that was significantly elevated in inflammatory synoviocytes relative to intact peripheral blood mononuclear cells (PBMC). Mouse Cebpe and Retnlg were predictably expressed in macrophages, whereas Retn was abundant in adipocytes. Quite the opposite, a low and inconsistent RETN transcription was seen in some human white adipose tissue (WAT) biopsies without any relationship to body mass index, insulin sensitivity, or fat depot. However, in these cases, RETN was co-detected with CEBPE and the leukocyte-specific marker, EMR1, indicating the presence of inflammatory cells and their possible resistin-mediated effect on adipocytes. Indeed, addition of human resistin to WAT in culture induced, like in PBMC, the inflammatory cytokines IL6, IL8 and TNF. Importantly, the expression of the adipose-specific markers CEBPA, FABP4 and SLC2A4 was unchanged, while the expected inhibitory effect was seen with TNF. Both cytokines increased the mRNA level of CCL2 and MMP3, which may further promote inflammation in WAT. Thus, the myeloid-restricted nature of CEBPE precludes the expression of RETN in human adipocytes which, however, are targeted by this innate immune-derived proinflammatory cytokine.

Akt and FOXO dysregulation contribute to infection-induced wasting in Drosophila

BACKGROUND

Studies in Drosophila have taught us a great deal about how animals regulate the immediate innate immune response, but we still know little about how infections cause pathology. Here, we examine the pathogenesis associated with Mycobacterium marinum infection in the fly. M. marinum is closely related to M. tuberculosis, which causes tuberculosis in people.

RESULTS

A microarray analysis showed that metabolism is profoundly affected in M. marinum-infected flies. A genetic screen identified foxo mutants as slower-dying after infection than wild-type flies. FOXO activity is inhibited by the insulin effector kinase Akt; we show that Akt activation is systemically reduced as a result of M. marinum infection. Finally, we show that flies infected with Mycobacterium marinum undergo a process like wasting: They progressively lose metabolic stores, in the form of fat and glycogen. They also become hyperglycemic. In contrast, foxo mutants exhibit less wasting.

CONCLUSIONS

In people, many infections--including tuberculosis--can cause wasting, much as we see in Drosophila. Our study is the first examination of the metabolic consequences of infection in a genetically tractable invertebrate and gives insight into the metabolic consequences of mycobacterial infection, implicating impaired insulin signaling as a key mediator of these events. These results suggest that the fly can be used to study more than the immediate innate immune response to infection; it can also be used to understand the physiological consequences of infection and the immune response.

Resistin increases lipid accumulation and CD36 expression in human macrophages

Excessive lipid accumulation in macrophages plays an important role in the development of atherosclerosis. Recently, several studies have implied that resistin, an adipocytokine which is mainly expressed in human peripheral blood monocytes, may take part in the pathogenesis of atherosclerosis. In this study, we investigated the effects of resistin on lipid accumulation as well as oxLDL on resistin expression in human macrophages. Treatment of macrophages with oxLDL significantly increased resistin mRNA expression, whereas native LDL had no such effect. Resistin pre-treated macrophages contained more and larger lipid droplets stained by Nile red. Resistin increased the expression of CD36 at both mRNA and protein levels, without affecting those of class A macrophage scavenger receptor (SR-A). These results suggest that resistin promotes lipid accumulation in human macrophages through its upregulating CD36 cell surface expression. Also, it is suggested that resistin may act as a modulator for macrophage-to-foam cell transformation.

Relationship between serum resistin concentrations and inflammatory markers in patients with type 2 diabetes mellitus

To examine whether serum resistin concentrations are associated with metabolic or inflammatory markers in patients with type 2 diabetes mellitus, we examined serum concentrations levels and metabolic or inflammatory markers in 56 patients with type 2 diabetes mellitus and 41 healthy subjects. Serum levels of resistin, serum amyloid A, and soluble vascular cell adhesion molecule-1 were measured by enzyme-linked immunosorbent assay. Serum resistin levels were significantly elevated in diabetic patients compared with those in healthy subjects. Serum resistin concentrations did not correlate with body mass index; however, there was a significant positive correlation between resistin and soluble vascular cell adhesion molecule-1 in diabetic patients. Based on the present results, we conclude that resistin appears to be associated with vascular inflammatory markers in patients with type 2 diabetes mellitus.

Resistin, a New Adipokine, Is Related to Inflammation and Renal Function in Kidney Allograft Recipients

BACKGROUND

Among patients without chronic kidney disease, resistin, an adipocytokine, has been related to inflammatory markers, coronary artery disease, and cardiovascular disease in the metabolic syndrome. Moreover, resistin up-regulates adhesion molecules. Since inflammation and endothelial cell damage or injury are invariably associated with thrombosis, atherosclerosis, and their major clinical consequences, resistin may play a role to link inflammation and CVD. The aim of this study was to correlate resistin with markers of inflammation and endothelial cell injury in 96 kidney allograft recipients.

METHODS

We measured resistin and the following markers of endothelial function/injury: vWF, thrombomodulin, VCAM, hsCRP, tumor necrosis factor alpha (TNFalpha), and interleukin-6 (IL-6).

RESULTS

Triglycerides, CRP (assessed by high-sensitivity method), phosphate, creatinine, IL-6, TNFalpha, vWF, prothrombin fragments 1 + 2, and resistin were elevated among kidney transplant recipients compared with the control group. Kidney allograft recipients with coronary artery disease displayed significantly higher resistin levels than those in patients without this complication. Upon univariate analysis resistin levels in kidney allograft recipients were related to hsCRP, IL-6, thrombomodulin, red blood cell count, white blood cell count, platelet count, creatinine, urea, VCAM, CSA, dose and eGFR. Upon multiple regression analysis, resistin was independently related only to creatinine, hsCRP, and white blood cell count in kidney allograft recipients.

CONCLUSIONS

The relation of elevated resistin levels to markers of inflammation may represent a novel link between these conditions and adipocytokines. Renal function was a major determinant of elevated resistin in kidney allograft recipients.

Prognostic significance of plasma resistin levels in patients with atherothrombotic ischemic stroke

BACKGROUND

Resistin (RSN) is an adipocytokine involved in insulin resistance, obesity and atherosclerosis. This study aimed to investigate the association between plasma RSN and outcome after ischemic stroke.

METHODS

RSN measured within 24 h after the event was related to functional outcome and 5-year survival in 211 subjects with first-ever atherothrombotic ischemic stroke. Prognosis was assessed by the Kaplan Meier and the Cox techniques.

RESULTS

The probabilities of death were 80.4%, 46.2% and 15.7% (p<0.001) for patients stratified according to tertiles of RSN (>30 ng/mL, 20-30 ng/mL and<20 ng/mL, respectively). The proportion of dependency (modified Rankin Scale score>or=3) was greater in 5-year survivors with RSN in the upper tertile (6/11 [54.5%]) compared to the middle (20/56 [35.7%]) and the lowest tertile (8/43 [18.6%]; p<0.01). C-reactive protein levels (hazard ratio [HR] 3.96 [95% CI 2.06, 8.91]; p<0.001), coronary heart disease (2.69 [1.62, 6.23]; p<0.001), RSN levels (2.12 [1.31, 5.08] p<0.001), National Institute of Health Stroke Scale score (2.02 [1.23, 4.49]; p<0.01) and age (1.84 [1.19, 3.93]; p<0.01) were independent predictors of death.

CONCLUSIONS

High plasma RSN appears to be associated with increased risk of 5-year mortality or disability after atherothrombotic ischemic stroke, independently of other adverse predictors.

Serum resistin increases in a postprandial state during liquid meal challenge test in healthy human subjects

The role of resistin in humans is controversial although resistin has been linked to atherosclerotic and inflammatory processes. In rodents, resistin expression is suppressed after food restriction while central administration of resistin promotes short-term satiety. However, the nature of postprandial responses in circulating resistin in humans is unknown. Therefore, we investigated postprandial resistin concentrations in a pilot study in 19 healthy subjects and 19 controls matched for age and body mass index (BMI). Serum resistin, insulin and non-esterified fatty acids (NEFA) concentrations as well as plasma glucose and triglycerides were repeatedly assessed before and after ingestion of an isocaloric standardized liquid meal during a 300 min period.After consumption of liquid meal, serum resistin levels increased compared to fasting control (p=0.037). Postprandial plasma glucose and serum insulin increased (p<0.001) with lower glucose responses in females (p=0.001) and lower insulin responses in males (p=0.012). Plasma triglycerides increased and serum NEFA decreased with similar gender responses (p=0.025 and p<0.001, respectively). Serum resistin was not correlated to glucose, insulin, triglyceride, and NEFA responses to liquid meal challenge tests. The present data suggest that serum resistin increases postprandially in healthy humans. Additional studies are needed to elucidate normal 24-h daytime profiles in humans and differential response of serum resistin to macronutrient composition of meals.

Increased subcutaneous and epicardial adipose tissue production of proinflammatory cytokines in cardiac surgery patients: possible role in postoperative insulin resistance

CONTEXT

Hyperglycemia and insulin resistance frequently occur in critically ill patients even without a history of diabetes.

OBJECTIVE

Our objective was to study the role of adipose tissue hormonal production in the development of insulin resistance in cardiac surgery patients. PARTICIPANTS, INTERVENTIONS, AND SETTINGS: Fifteen patients with elective cardiac surgery underwent blood sampling before, at the end, and 6, 12, 24, 48, and 120 h after the end of their operation. Epicardial and sc adipose tissue sampling was done at the beginning and at the end of surgery in the Department of Cardiac Surgery.

MAIN OUTCOME MEASURES

We measured serum concentrations and sc and epicardial adipose tissue mRNA expression of IL-6, monocyte chemoattractant protein-1 (MCP-1), TNF-alpha, leptin, resistin, and adiponectin and sc and epicardial adipose tissue mRNA expression of CD14, CD45, and CD68.

RESULTS

The rate of insulin infusion required to maintain euglycemia increased up to 7-fold 12 h after the operation, suggesting the development of insulin resistance. Serum IL-6 levels increased 43-fold 12 h after surgery. MCP-1 peaked 6-fold at the end of surgery. Smaller peaks of TNF-alpha and leptin appeared 6 and 12 h after surgery, respectively. Resistin levels peaked 4-fold 24 h after surgery, but adiponectin levels were not significantly affected. TNF-alpha and CD45 mRNA expression increased markedly during the operation in sc adipose tissue. IL-6, resistin, and MCP-1 mRNA expression increased in both sc and epicardial adipose tissue. Leptin, adiponectin, CD14, and CD68 mRNA expression did not change significantly.

CONCLUSIONS

Both sc and epicardial adipose tissue is a source of proinflammatory cytokines in cardiac surgery patients and may contribute to the development of postoperative insulin resistance.

Relationship between serum resistin concentration and proinflammatory cytokines in obese women with impaired and normal glucose tolerance

The aim of this study was to investigate the possible role of resistin in obese women with and without insulin resistance. We compared serum concentrations of resistin with interleukin 6 (IL-6), tumor necrosis factor alpha (TNF-alpha), soluble TNF receptors 1 and 2, and certain anthropometric and metabolic parameters in 26 obese women (body mass index [BMI], 35.8 +/- 4.12 kg/m2) and 15 healthy control women (BMI, 22.32 +/- 1.89 kg/m2). Fasting serum resistin and inflammatory cytokine levels were measured by enzyme immunoassay. Insulin resistance was measured by the homeostasis model assessment of insulin resistance (HOMA-R) formula. Compared with lean controls, obese women showed higher HOMA-R values and levels of insulin and increased values of TNF-alpha, soluble TNF receptors, and IL-6. There was no significant difference in resistin levels between the investigated groups of obese women and lean subjects. The results showed that serum resistin concentrations did not correlate with BMI, HOMA, fasting plasma glucose level, or fasting plasma insulin level. Serum resistin correlated with fat mass and IL-6 in the group with impaired glucose tolerance (obese group) (r = 0.51, P < .05, and r = 0.37, P < .05, respectively) and with low-density lipoprotein cholesterol (r = -0.39, P < .05) in the same group. The groups we examined are relatively small; it is likely that with a larger number of subjects, the correlation in other obese women groups may achieve statistical significance. It seems that resistin may be linked with inflammation and obesity and, indirectly, with insulin resistance.

Operative risk factors in the metabolic syndrome: is it lipids and high blood pressure or are there direct vascular effects of insulin resistance and obesity?

The metabolic syndrome is associated with an increased risk for cardiovascular disease. Dyslipidemia, high blood pressure, and impaired glucose tolerance, components of the metabolic syndrome, are all clearly atherogenic. Insulin resistance is an important correlate of other risk factors. Excess abdominal fat, as often seen in overweight people and commonly observed in obese individuals, is the single most important central feature of the metabolic syndrome. In addition to insulin resistance, an excess amount of abdominal fat is associated with all the features of metabolic clustering. Adipocytes secrete several peptide hormones that have been related to the metabolic syndrome and related cardiovascular disease. The role of traditional versus novel adipose tissue-related risk factors in the background of atherosclerosis in the metabolic syndrome are discussed.

Adipocytokines: mediators linking adipose tissue, inflammation and immunity

There has been much effort recently to define the role of adipocytokines, which are soluble mediators derived mainly from adipocytes (fat cells), in the interaction between adipose tissue, inflammation and immunity. The adipocytokines adiponectin and leptin have emerged as the most abundant adipocyte products, thereby redefining adipose tissue as a key component not only of the endocrine system, but also of the immune system. Indeed, as we discuss here, several adipocytokines have a central role in the regulation of insulin resistance, as well as many aspects of inflammation and immunity. Other adipocytokines, such as visfatin, have only recently been identified. Understanding this rapidly growing family of mainly adipocyte-derived mediators might be of importance in the development of new therapies for obesity-associated diseases.

Improvement of insulin sensitivity after peroxisome proliferator-activated receptor-alpha agonist treatment is accompanied by paradoxical increase of circulating resistin levels

We studied the effect of peroxisome proliferator-activated receptor-alpha (PPAR-alpha) activation on serum concentrations and tissue expression of resistin, adiponectin, and adiponectin receptor-1 and -2 (AdipoR1 and AdipoR2) mRNA in normal mice and mice with insulin resistance induced by lipogenic, simple-carbohydrate diet (LD). Sixteen weeks of LD feeding induced obesity with liver steatosis and increased insulin levels but did not significantly affect circulating adiponectin or resistin. Treatment with PPAR-alpha agonist fenofibrate decreased body weight and fat pad weight and ameliorated liver steatosis in LD-fed mice with concomitant reduction in blood glucose, free fatty acid, triglyceride, serum insulin levels, and homeostasis model assessment index values. Euglycemic-hyperinsulinemic clamp demonstrated the development of whole-body and liver insulin resistance in LD-fed mice, which were both normalized by fenofibrate. Fenofibrate treatment markedly increased circulating resistin levels on both diets and adiponectin levels in chow-fed mice only. Fat adiponectin mRNA expression was not affected by fenofibrate treatment. Resistin mRNA expression increased in subcutaneous but not gonadal fat after fenofibrate treatment. In addition to fat, a significant amount of adiponectin mRNA was also expressed in the muscle. This expression markedly increased after fenofibrate treatment in chow- but not in LD-fed mice. Adipose tissue expression of AdipoR1 mRNA was significantly reduced in LD-fed mice and increased after fenofibrate treatment. In conclusion, PPAR-alpha activation ameliorated the development of insulin resistance in LD-fed mice despite a major increase in serum resistin levels. This effect could be partially explained by increased AdipoR1 expression in adipose tissue after fenofibrate treatment.

Is obesity an inflammatory illness? Role of low-grade inflammation and macrophage infiltration in human white adipose tissue

There are at least two scientific evidences of human obesity as a chronic inflammatory illness: first, the well-described moderate increase of inflammatory factors in the circulation in obese subjects, and second, the recent identification of macrophage cells infiltrating the white adipose tissue (WAT). These observations led to a revision of the physiopathology of obesity and its co-morbidities. It has been suggested that the 'low-grade' inflammatory state associates with metabolic and cardiovascular complications of obesity. Weight loss is able to improve this inflammatory state by both significantly decreasing circulating inflammatory molecules and macrophage cell infiltration in WAT depots. However, the mechanisms of WAT macrophage recruitment into the adipose tissue and their role in obesity complications have not been defined. This review aims to point out the knowledge on inflammatory cytokines associated with obesity and focuses on macrophage infiltration in human WAT, discussing their recruitment and role. The interactions of macrophages with adipocytes will certainly be the subject of intense investigations in the future.

Increased subcutaneous and epicardial adipose tissue production of proinflammatory cytokines in cardiac surgery patients: possible role in postoperative insulin resistance

CONTEXT

Hyperglycemia and insulin resistance frequently occur in critically ill patients even without a history of diabetes.

OBJECTIVE

Our objective was to study the role of adipose tissue hormonal production in the development of insulin resistance in cardiac surgery patients. PARTICIPANTS, INTERVENTIONS, AND SETTINGS: Fifteen patients with elective cardiac surgery underwent blood sampling before, at the end, and 6, 12, 24, 48, and 120 h after the end of their operation. Epicardial and sc adipose tissue sampling was done at the beginning and at the end of surgery in the Department of Cardiac Surgery.

MAIN OUTCOME MEASURES

We measured serum concentrations and sc and epicardial adipose tissue mRNA expression of IL-6, monocyte chemoattractant protein-1 (MCP-1), TNF-alpha, leptin, resistin, and adiponectin and sc and epicardial adipose tissue mRNA expression of CD14, CD45, and CD68.

RESULTS

The rate of insulin infusion required to maintain euglycemia increased up to 7-fold 12 h after the operation, suggesting the development of insulin resistance. Serum IL-6 levels increased 43-fold 12 h after surgery. MCP-1 peaked 6-fold at the end of surgery. Smaller peaks of TNF-alpha and leptin appeared 6 and 12 h after surgery, respectively. Resistin levels peaked 4-fold 24 h after surgery, but adiponectin levels were not significantly affected. TNF-alpha and CD45 mRNA expression increased markedly during the operation in sc adipose tissue. IL-6, resistin, and MCP-1 mRNA expression increased in both sc and epicardial adipose tissue. Leptin, adiponectin, CD14, and CD68 mRNA expression did not change significantly.

CONCLUSIONS

Both sc and epicardial adipose tissue is a source of proinflammatory cytokines in cardiac surgery patients and may contribute to the development of postoperative insulin resistance.

Adipose tissue resistin levels in patients with anorexia nervosa

OBJECTIVE

Resistin is a specific fat-derived hormone that affects fuel homeostasis and insulin action in rodents. However, its role in human physiology and pathophysiologic conditions, such as malnutrition, remains uncertain.

METHODS

To enhance understanding of the role of resistin in the pathophysiology of anorexia nervosa (AN), we measured plasma resistin levels in 13 women with a restrictive type of AN and in 16 healthy age-matched women (control). Further, we measured resistin levels in the subcutaneous adipose tissue of eight women from the AN group and eight women from the control group with an in vivo microdialysis technique (CMA/107 pump, CMA/60 catheters, CMA Microdialysis AB, Solna, Sweden).

RESULTS

Body mass index, percentage of body fat, fasting plasma leptin and insulin, and homeostasis model assessment index for insulin resistance were severely decreased in patients with AN compared with the control group. Plasma resistin levels were significantly decreased in patients with AN (P < 0.05), whereas subcutaneous adipose tissue resistin levels were significantly increased in patients with AN compared with the control group (P < 0.05). In both groups, plasma resistin levels showed no significant relation to resistin in dialysate, percentage of body fat, body mass index, homeostasis model assessment index for insulin resistance, and fasting plasma leptin levels.

CONCLUSION

We demonstrated that AN is associated with decreased plasma resistin levels and increased resistin levels in extracellular space of the abdominal adipose tissue. Plasma resistin levels in patients with AN or in healthy normal-weight women were not directly related to body mass index, percentage of body fat, plasma leptin levels, and insulin sensitivity.

Elevated resistin levels in cirrhosis are associated with the proinflammatory state and altered hepatic glucose metabolism but not with insulin resistance

The adipokine resistin has been implicated in obesity and insulin resistance. Liver cirrhosis is associated with decreased body fat mass and insulin resistance. We determined plasma resistin levels in 57 patients with cirrhosis, 13 after liver transplantation, and 30 controls and correlated these with hemodynamic as well as hepatic and systemic metabolic parameters. Patients with cirrhosis had, dependent on the clinical stage, an overall 86% increase in resistin levels (P < 0.001) with hepatic venous resistin being higher than arterial levels (P < 0.001). Circulating resistin was significantly correlated with plasma TNF-alpha levels (r = 0.62, P < 0.001). No correlation was observed between resistin and hepatic hemodynamics, body fat mass, systemic energy metabolism, and the degree of insulin resistance. However, plasma resistin in cirrhosis was negatively associated with hepatic glucose production (r = -0.47, P < 0.01) and positively with circulating free fatty acids (FFA; r = 0.40, P < 0.01) and ketone bodies (r = 0.48, P < 0.001) as well as hepatic ketone body production (r = 0.40, P < 0.01). After liver transplantation, plasma resistin levels remained unchanged, whereas insulin resistance was significantly improved (P < 0.01). These data provide novel insights into the role of resistin in the pathophysiological background of a catabolic disease in humans and also indicate that resistin inhibition may not represent a suitable therapeutic strategy for the treatment of insulin resistance and diabetes in patients with liver cirrhosis.

Elevated resistin levels in chronic kidney disease are associated with decreased glomerular filtration rate and inflammation, but not with insulin resistance

In the present study, we explore the role of decreased renal function and a genetic polymorphism on the recently discovered protein resistin, apparently able to inhibit hepatic insulin action in mice. We also investigate possible links with inflammation and the insulin resistance present in patients with chronic kidney disease (CKD). This is a post hoc, cross-sectional study comparing 239 prevalent CKD patients with varying degrees of renal function impairment with an age- and gender-matched randomly selected control group of 25 individuals. Glomerular filtration rate (GFR) was estimated by the mean of urea and creatinine clearance (24-h urine samples) (n=204) or by iohexol clearance (n=60). Plasma analysis of blood lipids, insulin, glucose, inflammatory markers (high-sensitivity C-reactive protein, interleukin-6, tumor necrosis factor-alpha, vascular cellular adhesion molecule, intercellular adhesion molecule) and resistin (kit from LINCO Research, St Charles, MS) was performed using commercially available assays or routine methods. Insulin resistance was estimated by quantitative insulin-sensitivity check index (QUICKI) and homeostasis model assessment for insulin resistance (HOMA-IR) and body composition by dual-energy X-ray absorptiometry. Genotyping of a C/G promoter single nucleotide polymorphism (n=168) at position -180 of the resistin gene was performed by PyroSequencing. Serum levels of resistin were markedly elevated in the CKD patients with both advanced (39.9+/-1.3 ng/ml) and mild to moderate (23.2+/-1.0 ng/ml) renal function impairment, as compared to controls (8.5+/-0.7 ng/ml; P<0.001). In a multiple linear regression model in patients (adjusted r(2)=0.60), only GFR (beta=3.4; P<0.0001), lean body mass (beta=2.2; P<0.001) and the inflammatory markers were independently associated with circulating resistin levels. There was a weak but significant impact of -180 C/G genotype on plasma levels of resistin (median 43.0+/-2.4 ng/ml in CC, 37.5+/-2.0 ng/ml in CG, and 41.1+/-4.9 ng/ml in GG; P<0.05). Univariate analysis of non-diabetic patients and controls showed that serum resistin was associated with markers of glucose metabolism. However, in a multiple regression model, resistin, as well as all the measured markers of inflammation, was only associated with insulin resistance if GFR was not taken into account. Circulating resistin levels are strongly associated with both GFR and inflammatory biomarkers in CKD. As the significant relationship between plasma resistin levels and insulin resistance was lost following the correction for GFR, resistin is not a likely mediator of insulin resistance in patients with CKD. Renal function is an important factor to take into account in clinical studies relating insulin sensitivity to inflammatory biomarkers in CKD as well as in patients with diabetes mellitus, who often have an impaired renal function.

Resistin and adiponectin levels in subjects with coronary artery disease and type 2 diabetes

BACKGROUND

Resistin and adiponectin are implicated in insulin resistance and atherosclerosis. The objective of this study was to evaluate the association between plasma resistin levels and the presence of coronary artery disease (CAD) or diabetes compared to the controls. In a cross-sectional study, we measured glucose, fasting lipid panel, resistin, adiponectin, insulin, C-reactive protein (CRP) and TNF-alpha in 57 subjects with CAD, 58 subjects with diabetes compared to 45 normal control subjects.

RESULTS

Subjects with CAD compared to the control subjects had increased insulin resistance index (39+/-32 vs. 13.45+/-12.73 with p<0.0001), CRP levels (3.8+/-4.03 vs. 2.0+/-2.0 with p<0.05) and decreased levels of adiponectin (12.5+/-4.8 vs. 17.26+/-10.4 with p<0.0003). Subjects with diabetes compared to the controls had had increased insulin resistance index (69+/-19 vs. 13.45+/-12.73 with p<0.001), CRP levels (4.1+/-4.8 vs. 2.0+/-2.0 with p<0.01) and decreased levels of adiponectin (11.58+/-4.8 vs. 17.26+/-10.4 with p<0.001). Compared to the controls, there was no significant difference in the levels of resistin in subjects with CAD (4.92+/-3.2 vs. 4.1+/-2.4) as well as diabetes (4.92+/-3.2 vs. 4.6+/-2.6). Both CRP and resistin levels correlate with TNF-alpha (r=0.557, p<0.000001; r=0.84, p<0.000001).

CONCLUSIONS

The present study shows decreased plasma adiponectin levels in subjects with diabetes as well as in subjects with CAD is similar to the literature. Plasma levels of resistin in subjects with CAD or diabetes are similar to the controls. However, there was a strong correlation of resistin levels with inflammatory markers. This suggests resistin as an inflammatory marker associated with CAD.

High plasma resistin level is associated with enhanced highly sensitive C-reactive protein and leukocytes

OBJECTIVES

Resistin is a newly described hormone with a suggested role in insulin resistance. In humans, inflammatory cells seem to be the major source of resistin. The aim of this study was to find out whether plasma resistin concentration associates with carotid artery atherosclerosis and the risk factors of atherosclerosis.

METHODS

Plasma resistin concentrations were measured in 525 Finnish middle-aged subjects among our population-based cohort. Intima-media thickness was measured from the internal carotid artery, the bifurcation enlargement, and the common carotid artery.

RESULTS

Among all the subjects, the median resistin concentration was 7.07 ng/ml (interquartile range, 5.82-8.84), women having higher levels than men (P < 0.001) with median values of 7.56 ng/ml (6.18-9.19) and 6.67 ng/ml (5.63-8.31), respectively. Resistin level correlated negatively with mean intima-media thickness, internal carotid artery, and common carotid artery, but the association did not remain significant after adjustments. Plasma resistin concentration was associated positively with leukocytes (P < 0.001), highly sensitive C-reactive protein (P = 0.009), and IGF binding protein 1 (P < 0.001), but not with plasma insulin or glucose levels in analysis of covariance after adjustments for age, sex, and body mass index.

CONCLUSIONS

The results imply that inflammatory factors are more important in the determination of plasma resistin concentration than plasma insulin or glucose values. Resistin is associated with proatherogenic inflammatory markers but not independently with early atherosclerosis.

Heritability of serum resistin and its genetic correlation with insulin resistance-related features in nondiabetic Caucasians

CONTEXT

Serum levels of resistin are believed to modulate insulin resistance in humans.

OBJECTIVE

The aim of this study was to investigate whether serum resistin levels are genetically controlled and whether this control is shared with other insulin resistance traits.

DESIGN AND METHODS

The study cohort included 264 nondiabetic probands, Caucasian from Italy, and their 473 adult family members. Phenotypic characterization included anthropometric variables, blood pressure, fasting glucose and insulin, lipid profile, and resistin levels. Genotypes were determined at position g.-420C-->G (rs1862513), IVS2+181G-->A (rs3745367), and GAT((n)) polymorphisms of the resistin (RETN) gene.

RESULTS

In the 264 unrelated probands, resistin levels were significantly (P < 0.01) correlated with adiposity, blood pressure, C-reactive protein, and the metabolic syndrome score. In a variance component analysis of the 264 probands and their 473 relatives, about 70% of the observed variation of serum resistin levels was heritable (P < 0.0001). A small, but significant (P = 0.004) proportion of this variance was explained by the G-->A variation at position IVS2+181 of the RETN gene. Significant genetic correlations (P < 0.05) were observed between resistin and body mass index (rho(g) = 0.30), waist circumference (rho(g) = 0.32), the insulin resistance index HOMA(IR) (rho(g) = 0.28), and the metabolic syndrome score (rho(g) = 0.35).

CONCLUSIONS

These data indicate that serum resistin is highly heritable and has some common genetic background with traits related to insulin resistance, reinforcing the hypothesis that this adipokine may play a pathogenic role in insulin resistance-related abnormalities, including type 2 diabetes and cardiovascular disease.

Resistin levels are normal in hypothyroidism and remain unchanged after attainment of euthyroidism: relationship with insulin levels and anthropometric parameters

The aim of this controlled prospective study was to investigate resistin levels in hypothyroidism before and after restoration of euthyroidism and correlate the results with body weight (BW), body fat (BF), waist circumference (WC), body mass index (BMI) and serum insulin levels. Fifty-three hypothyroid patients with Hashimoto's disease (6 males, 47 females) and 30 controls matched for age, BMI and BF were investigated. Anthropometric parameters, resistin and insulin levels were measured. All patients were started on levothyroxine treatment and 4 to 5 months after initiation of treatment the investigations were repeated. Hypothyroid patients exhibited normal resistin values, which were no different from controls (mean+/-SD 7.4+/-4.0 vs 5.1+/-3.5 ng/ml, p=0.063). Normalization of circulating thyroid hormone levels produced no significant change in resistin levels (7.4+/-4.0 vs 6.8+/-4.2 ng/ml, p=ns) and post-treatment resistin levels did not differ from euthyroid controls. Furthermore, no gender difference was demonstrated in resistin levels either before (6.4+/-3.7 for males vs 7.6+/-4.1 ng/ml for females, p=ns) or after therapy (7.9+/-4.3 vs 6.7+/-4.3 ng/ml, for males and females respectively, p=ns), nor was there a difference in resistin levels in either sex induced by treatment of hypothyroidism (6.4+/-3.7 vs 7.9+/-4.3 ng/ml for males, p=ns, and 7.6+/-4.1 vs 6.7+/-4.3 ng/ml for females, p=ns). However, a small but significant difference in resistin levels was found between female patients and female controls (7.6+/-4.1 vs 5.0+/-4.0 ng/ml, p=0.047). Insulin levels and homeostasis model assessment insulin resistance (HOMA-IR) index did not differ before and after treatment in hypothyroid patients (13.0+/-10.2 vs 12.6+/-11.8 microU/ml, 22.7+/-1.4 vs 21.8+/-1.3, respectively, p=ns for both) or between patients and controls. In conclusion, our results demonstrate that resistin levels are normal in hypothyroidism and remain within normal range after attainment of euthyroidism. Resistin is not associated with serum insulin and HOMA-IR index, as well as BMI, BF, WC and BW.

Resistin, acute coronary syndrome and prognosis results from the AtheroGene study

OBJECTIVE

Resistin, an adipocyte and macrophage derived cytokine, causes insulin resistance and glucose intolerance. We investigated the impact of resistin as a diagnostic marker in patients with acute coronary syndrome and its prognostic value for future cardiovascular events.

METHODS

Resistin levels were determined in 1153 patients with stable angina (SAP), 380 patients with unstable angina, 278 patients with non-ST-elevation myocardial infarction (NSTEMI) and 111 patients with ST-elevation myocardial infarction (STEMI). All patients have been followed up for a median follow-up of 2.6 years. During follow-up, 70 patients died from cardiovascular causes.

RESULTS

Compared to SAP, resistin levels (5.1 ng/mL in SAP) were elevated in patients with angina at rest (5.89 ng/mL, P=0.001), in patients with NSTEMI (6.00 ng/mL, P<0.001), and in patients with STEMI (5.98 ng/mL, P<0.001). Resistin levels rose at 3-6h after chest pain onset (5.46 ng/mL), persisted elevated among those individuals presenting between 6 and 12h after chest pain onset (5.57 ng/mL) and peaked in individuals presenting more than 12h after chest pain onset (5.74 ng/mL). An increase of one standard deviation of resistin levels was associated with a 1.22-fold (95% CI 1.04-1.43; P=0.02) risk for future fatal cardiovascular events in a model adjusted for risk factors and clinical and therapeutic variables. When adjustment for renal function was applied, this association lost its statistical significance.

CONCLUSIONS

Resistin levels are elevated in patients presenting with unstable angina, NSTEMI and STEMI and might play a role as a diagnostic marker. In addition, systemic resistin level is moderately associated with future cardiovascular death in patients with documented coronary artery disease.

Adipocyte-derived hormones, cytokines, and mediators

Adipose tissue is responsive to both central and peripheral metabolic signals and is itself capable of secreting a number of proteins. These adipocyte-specific or enriched proteins, termed adipokines, have been shown to have a variety of local, peripheral, and central effects. These secreted proteins, which include tumor necrosis factor (TNF)-alpha, resistin, IL-6, IL-8, acylation-stimulating protein (ASP), angiotensinogen, plasminogen activator inhibitor-1 (PAI-1) ("bad" adipokines) and leptin, adiponectin ("good" adipokines) seem to play important regulatory roles in a variety of complex processes, including fat metabolism, feeding behavior, hemostasis, vascular tone, energy balance, and insulin sensitivity, but none is without controversy regarding its respective mechanism and scope of action. The present review is focused on the effects of free fatty acids and a restricted number of adipokines, which have been implicated in vascular (angiotensinogen, PAI-1) and energy and glucose homeostasis (ASP, TNFalpha, IL-6, resistin, leptin, adiponectin).

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.

Leptin and resistin levels and their relationships with glucose metabolism in children with chronic renal insufficiency and undergoing dialysis

AIM

The aim of the present study is: (i) to evaluate the serum concentrations of leptin and resistin in the paediatric patients with chronic renal impairment (CRI), on haemodialysis (HD) and on peritoneal dialysis (PD) treatment; (ii) to examine the relationship between these hormones; and (iii) to investigate the possible influence of these hormones on the insulin resistance and sensitivity indexes as well as on serum insulin-like growth factor-1 (IGF-1) and insulin-like growth factor binding protein-3 (IGFBP-3) levels.

METHODS

In total, 52 patients (15 patients with CRI, 24 PD patients and 13 HD patients) and 23 healthy age- and sex-matched control subjects were included in the present study.

RESULTS

Homeostasis model assessment of insulin resistance (HOMA-IR) was higher than 2.5 in 47.1% of the patients. IGF-1 levels of patients with CRI, PD and HD patients were significantly lower than those in the controls (P < 0.001, P < 0.001, P < 0.001, respectively). The leptin levels of patients with CRI and on PD and HD treatment were significantly higher than the control group (P = 0.038, P = 0.002, P = 0.006, respectively). Similarly, serum resistin levels of patients with CRI and those of PD and HD patients were higher when compared with healthy controls (P = 0.037, P < 0.001, P = 0.005, respectively).

CONCLUSION

Leptin and resistin levels were increased in the children with CRF; however, this elevation was not found to be associated with hyperinsulinism. Further studies to explain the mechanisms and consequences of the accumulation of these hormones in CRF may provide the therapeutical approach aiming to normalize their circulating levels.