Relationship between serum resistin concentrations and insulin resistance in nonobese, obese, and obese diabetic subjects

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.

Resistin and adiponectin in major depression: the association with free cortisol and effects of antidepressant treatment

Major depression is associated with an increased risk for myocardial infarction. Adipokines have been shown to link obesity with metabolic disturbances. Based on this finding the present study was designed to investigate the effect of antidepressive treatment with either amitriptyline or paroxetine on circulating concentrations of resistin and adiponectin in depressed patients, and to establish, whether these adipokines are associated with the activation of the hypothalamic-pituitary-adrenal (HPA)-system. Thirty-seven depressed in-patients were treated in a double-blind, randomized protocol with either amitriptyline or paroxetine over a period of five weeks. After six drug free days blood was drawn on day 1 and again 36 days after antidepressive treatment for the measurement of resistin and adiponectin, fasting glucose and insulin concentrations. For quantification of free cortisol levels saliva was obtained daily at 0800 hours during weeks 1 and 5. While resistin concentrations decreased in patients remitting under amitriptyline and paroxetine (p<0.03), no changes were observed in non-remitters. At baseline, though not during treatment, circulating resistin concentrations correlated positively with free cortisol levels and with BMI (p<0.01). Adiponectin levels, however, did not change during treatment and were not associated with free cortisol concentrations but were instead positively related to QUICKI (p<0.03). In conclusion, the present data revealed resistin but not adiponectin to be related to free cortisol concentrations and to decline in remitters to antidepressive treatment.

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.

Implications of resistin plasma levels in subjects undergoing coronary angiography

BACKGROUND

The adipokine resistin, which is thought to serve as a link between obesity and insulin resistance, was recently shown to exert proatherosclerotic features.

OBJECTIVE

Our study aimed to explore the involvement of resistin in cardiovascular disease by investigating the associations of resistin with angiographic coronary artery disease (CAD), cardiovascular risk factors and mortality.

DESIGN

The Ludwigshafen Risk and Cardiovascular Health (LURIC) study is a prospective study of white subjects who had undergone coronary angiography.

PATIENTS AND MEASUREMENTS

Resistin levels were determined in 1162 subjects with (n = 911) and without (n = 251) angiographic CAD. During a mean follow-up period of 5.47 years, 198 deaths occurred among our probands.

RESULTS

Resistin was positively correlated with C-reactive protein (CRP; r = 0.245, P < 0.001), vascular adhesion molecule-1 (VCAM-1; r = 0.327, P < 0.001) and intercellular adhesion molecule-1 (ICAM-1; r = 0.197, P < 0.001) and was negatively correlated with glomerular filtration rate (GFR; r = -0.438, P < 0.001) and high density lipoprotein (HDL; r = -0.196, P < 0.001). Multiple regression analysis revealed that GFR was the strongest predictive variable for resistin. Angiographic CAD, type 2 diabetes, smoking, hypertension and body mass index (BMI) were not associated with resistin. Compared to the first quartile, we observed an increased risk for cardiovascular and noncardiovascular mortality at the fourth quartile of resistin, but only the association between resistin and noncardiovascular mortality remained significant after multivariable adjustments [hazard ratio (HR) 4.92, 95% confidence interval (CI) 1.66-14.6, P = 0.004].

CONCLUSIONS

Resistin plasma concentrations are related to inflammatory processes and renal function but our study does not support the hypothesis of resistin as an independent cardiovascular risk factor. The unexpected association of resistin with noncardiovascular mortality still warrants further study.

Ethnicity, insulin resistance, and inflammatory adipokines in women at high and low risk for vascular disease

OBJECTIVE

We sought to compare the relationship between body composition, insulin resistance, and inflammatory adipokines in Aboriginal Canadian women, who are at high risk of vascular disease, with white women.

RESEARCH DESIGN AND METHODS

A subgroup of the First Nations Bone Health Study population, consisting of 131 Aboriginal women and 132 matched white women, was utilized. Body composition was determined by whole-body dual X-ray absorptiometry, and blood analytes were measured after an overnight fast.

RESULTS

After excluding individuals with diabetes, A1C, BMI, percent trunk fat, and homeostasis model assessment of insulin resistance (HOMA-IR) were greater in First Nation women compared with white women, whereas adiponectin, retinol binding protein (RBP)4, and insulin-like growth factor binding protein-1 (IGFBP-1) were lower. First Nation women had more trunk fat for any given level of total fat than white women. There were no differences in resistin, leptin, tumor necrosis factor (TNF)-alpha, or C-reactive protein (CRP) levels between First Nation and white women. Insulin resistance correlated with leptin and inversely with adiponectin levels in both First Nation and white women. There were weak correlations between insulin resistance and TNF-alpha, interleukin-6, and CRP, but these were not significant after correction for body fat. No correlation was found between RBP4 and insulin resistance. ANCOVA revealed a higher HOMA-IR adjusted for total body fat in First Nation women than in white women (P = 0.015) but not HOMA-IR adjusted for trunk fat (P > 0.2).

CONCLUSIONS

First Nation women are more insulin resistant than white women, and this is explained by trunk fat but not total fat. Despite the increased insulin resistance, inflammatory adipokines are not significantly increased in First Nation women compared with white women.

Adipocyte resistin mRNA levels are down-regulated by laparoscopic ovarian electrocautery in both obese and lean women with polycystic ovary syndrome

BACKGROUND

The aim of this study was to investigate serum and adipocyte mRNA expression of resistin in lean and obese women with polycystic ovary syndrome (PCOS) before and 3 months after laparoscopic ovarian electrocauterization (LOE).

METHODS

Adipose tissue obtained from 12 women with PCOS (six obese and six lean, body mass index > 27 kg m(-1) as threshold point) before and after LOE was analysed. Gene expression of resistin was measured by semi-quantitative RT-PCR. Ten lean, age-matched healthy women served as controls.

RESULTS

Both lean and obese women with PCOS had significantly higher fasting and 2 h insulin and homeostasis model insulin resistance index (HOMA(IR)) values and lower fasting glucose-to-insulin ratios (G(0)/I(0)) than did the controls. The serum levels of glucose and insulin and HOMA(IR) were significantly decreased, and the G(0)/I(0) ratio was significantly increased 3 months after LOE. No difference was found in serum resistin levels between controls and either obese or lean women with PCOS before LOE, nor between PCOS patients before and after LOE. However, resistin mRNA expression levels in both lean and obese women with PCOS before LOE were significantly higher than that in controls and were decreased significantly after LOE back to control levels.

CONCLUSION

Local resistin activity may be actively involved in the pathogenesis of PCOS. LOE reduces insulin resistance and down-regulates resistin mRNA expression in lean and obese women with PCOS.

Resistin: a hormone which induces insulin resistance is increased in normal pregnancy

AIMS

Resistin, a newly discovered adipokine, is thought to play a key role in the regulation of insulin resistance. The objectives of this study were to develop a nomogram of maternal plasma concentrations of resistin from 11 weeks of gestation to term and to determine whether resistin concentrations differ between normal and overweight pregnant women.

METHODS

In this cross-sectional study, plasma concentrations of resistin were determined in normal pregnant women of normal body mass index (BMI 18.5-24.9; n=261), overweight pregnant women (BMI > or =25; n=140), and non-pregnant women of normal BMI (n=40). Blood samples were collected once from each woman between the first trimester and term. Percentiles for resistin concentration were determined for five pre-specified windows of gestational age. Plasma resistin concentration was determined by immunoassay. Non-parametric statistics were used for analysis.

RESULTS

The median maternal plasma concentration of resistin between 11 to 14 weeks of gestation in women of normal weight was significantly higher than non-pregnant women; the plasma concentration of resistin increased with gestational age.

CONCLUSIONS

Normal pregnant women have a higher median plasma concentration of resistin than non-pregnant women and the concentration of this adipokine increases with advancing gestation. Alterations in the maternal plasma concentration of resistin during pregnancy could contribute to metabolic changes of pregnancy.

Effect of growth hormone therapy on serum adiponectin and resistin levels in short, small-for-gestational-age children and associations with cardiovascular risk parameters

BACKGROUND

Adiponectin and resistin are fat cell-derived hormones, which are thought to be respectively protective and disadvantageous with regard to the development of cardiovascular disease and diabetes mellitus type 2. Low birth weight has been associated with increased risks for the development of these diseases. In short, small-for-gestational-age (SGA) children, GH therapy has several positive effects regarding cardiovascular risk factors. On the other hand, concern has been expressed about the effects of GH therapy on insulin sensitivity.

METHODS

We measured adiponectin and resistin levels in 136 short prepubertal children born SGA and their association with cardiovascular risk parameters and growth factors. Also, we compared the levels with normal-statured controls. The effect of GH treatment was evaluated in 50 short SGA children vs. baseline and vs. an untreated sex- and age-matched SGA control group.

RESULTS

Short SGA children had similar adiponectin and lower resistin levels, compared with normal-statured controls. In GH-treated SGA children, neither adiponectin nor resistin levels changed significantly during 2 yr of GH treatment. Compared with untreated sex- and age-matched SGA controls, GH-treated SGA children had similar adiponectin and lower resistin levels. Adiponectin correlated inversely with age but not any cardiovascular risk parameter or growth factor. Higher IGF-I levels in GH-treated children were associated with lower resistin levels.

CONCLUSIONS

Compared with normal-statured controls, short prepubertal SGA children had similar adiponectin and lower resistin levels. Two years of GH treatment had no effect on their adiponectin and resistin levels.

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.

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.

High-fat/low-carbohydrate diets regulate glucose metabolism via a long-term transcriptional loop

Insulin sensitivity is characterized by insulin-stimulated glucose metabolism in skeletal muscle. We hypothesized that carbohydrate metabolism and storage might be under transcriptional control. To test this hypothesis, we fed insulin-sensitive males (glucose disposal rate, 14.7 +/- 4.1 mg/kg fat-free mass [FFM] per minute) an isoenergetic high-fat/low-carbohydrate diet (HF/LCD) for 3 days with muscle biopsies before and after intervention. Oligonucleotide microarrays revealed a total of 369 genes of 18861 genes on the arrays were differentially regulated in response to diet (Bonferonni adjusted P < .01). A similar experiment was conducted in mice with a 3-week intervention using a control group and an HF/LCD group to offset the lack of a control group within the human cohort. As part of an analysis of results previously published from this data set, 7 genes in the carbohydrate metabolism pathway changed in response to the HF/LCD, and 3 genes were confirmed by quantitative reverse transcriptase-polymerase chain reaction: fructose-2,6-biphosphatase 3 (PFKFB3), pyruvate dehydrogenase kinase, isoenzyme 4 (PDK4), and glycogen synthase 1 (muscle). In a separate experiment, we fed C57Bl/6J mice an HF/LCD for 3 weeks and found that the same glucose metabolism genes were changed by approximately 70% on average. Fructose-2,6-biphosphatase 3 and pyruvate dehydrogenase kinase, isoenzyme 4 increased and glycogen synthase 1 (muscle) decreased. Combined, these results suggest a mechanism whereby HF/LCD regulates the genes necessary for glucose utilization and storage vis-á-vis transcriptional control.

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.

Resistin concentrations before and after weight loss in obese children

OBJECTIVE

The influences of gender, puberty, and obesity on resistin levels and the longitudinal relationships between insulin resistance, weight loss, and resistin have not yet been studied in childhood.

METHODS

Age, pubertal stage, gender, weight status (standard deviation score-body mass index (SDS-BMI)), resistin levels, and insulin resistance index calculated by homeostasis model assessment (HOMA) were evaluated in 63 obese children and compared to 36 lean children of same age, gender, and pubertal stage. Furthermore, we analyzed the changes of weight status (SDS-BMI, percentage body fat based on skinfold measurements), waist-to-hip ratio, resistin, and HOMA over a 1-year period in 38 obese children.

RESULTS

The resistin levels did not significantly (P = 0.079) differ between obese (median resistin 8.7 ng/ml) and lean children (median resistin 9.7 ng/ml). Resistin concentrations were independent of age and pubertal stage, but girls demonstrated significantly higher resistin levels than boys (P = 0.021). There were no significant correlations between changes of resistin and changes of SDS-BMI (r = 0.14, P = 0.198), changes of percentage body fat (r = -0.01, P = 0.466), changes of waist-to-hip ratio (r = 0.17, P = 0.141), and changes of insulin resistance index (r = 0.01, P = 0.472) over the 1-year period. The weight loss of > or = 0.5 SDS-BMI in 16 children was associated with a significant decrease in HOMA (P = 0.030), while there was no significant change in resistin levels (P = 0.878).

CONCLUSIONS

Girls demonstrated higher resistin concentrations than boys. Our data do not support a relationship between resistin, insulin resistance index, and weight status in childhood.

Secretome of primary cultures of human adipose-derived stem cells: modulation of serpins by adipogenesis

Studies of adipogenic protein induction have led to a new appreciation of the role of adipose tissue as an endocrine organ. Adipocyte-derived "adipokines" such as adiponectin, leptin, and visceral adipose tissue-derived serine protease inhibitor (vaspin) exert hormone-like activities at the systemic level. In this study, we examined the secretome of primary cultures of human subcutaneous adipose-derived stem cells as an in vitro model of adipogenesis. Conditioned media obtained from four individual female donors after culture in uninduced or adipogenic induced conditions were compared by two-dimensional gel electrophoresis and tandem mass spectrometry. Over 80 individual protein features showing > or =2-fold relative differences were examined. Approximately 50% of the identified proteins have been described previously in the secretome of murine 3T3-L1 preadipocytes or in the interstitial fluid derived from human mammary gland adipose tissue. As reported by others, we found that the secretome included proteins such as actin and lactate dehydrogenase that do not display a leader sequence or transmembrane domain and are classified as "cytoplasmic" in origin. Moreover we detected a number of established adipokines such as adiponectin and plasminogen activator inhibitor 1. Of particular interest was the presence of multiple serine protease inhibitors (serpins). In addition to plasminogen activator inhibitor 1, these included pigment epithelium-derived factor (confirmed by Western immunoblot), placental thrombin inhibitor, pregnancy zone protein, and protease C1 inhibitor. These findings, together with the recent identification of vaspin, suggest that the serpin protein family warrants further proteomics investigation with respect to the etiology of obesity and type 2 diabetes.

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.

Diet/Exercise versus pioglitazone: effects of insulin sensitization with decreasing or increasing fat mass on adipokines and inflammatory markers

BACKGROUND

Plasma adipokine concentrations are variably related to fatness/insulin resistance and may act via endocrine mechanisms. We assessed the relationship among plasma adipokine concentrations and their relationship with insulin sensitivity and body composition in obese adults before and after insulin sensitization accomplished using diet/exercise or pioglitazone.

METHODS

Plasma adipokine concentrations, insulin sensitivity, and body composition were assessed in 39 upper-body obese insulin-resistant, nondiabetic adults before and after 19 wk of diet/exercise or 30 mg/d pioglitazone.

RESULTS

Diet/exercise reduced body fat and visceral fat and improved insulin sensitivity parameters; pioglitazone improved insulin sensitivity to a similar degree but increased body fat. Adiponectin increased more after pioglitazone (4770 +/- 487 vs. 8351 +/- 693.6 ng/ml, P < 0.001) than after diet/exercise (4704 +/- 367 to 5426 +/- 325.3 ng/ml, P < 0.01), whereas TNFalpha, IL-6, and resistin did not change. C-reactive protein decreased with diet/exercise. Adipokine concentrations were not correlated with each other at baseline or after insulin sensitization, except TNFalpha and IL-6 (r = 0.43, P < 0.05); IL-6 was inversely correlated with resistin. Only adiponectin was correlated (P < 0.05) with indices of insulin sensitivity. Adiponectin concentrations were inversely correlated with visceral fat and with sc fat depots in men but positively correlated with sc fat in women.

CONCLUSION

Plasma adipokine concentrations were not consistently interrelated, and only adiponectin displayed the expected relationship with insulin sensitivity and sensitization. These findings do not support an endocrine role for resistin, TNFalpha, and IL-6 in mediating changes in insulin resistance after diet/exercise or pioglitazone.

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.

Increased serum resistin in elite endurance athletes with high insulin sensitivity

AIMS/HYPOTHESIS

Resistin is an adipokine associated with obesity and type 2 diabetes in animal models, but in humans its role remains uncertain. This study was undertaken to test whether serum resistin is related to insulin resistance and markers of low-grade inflammation in elite athletes taken as a model of extreme insulin sensitivity. SUBJECTS MATERIALS AND METHODS: In 23 elite athletes (sprinters, middle-distance and marathon runners) and in 72 sedentary men including lean and obese individuals with NGT, and obese individuals with IGT or new-onset type 2 diabetes, we assessed insulin sensitivity using a whole-body insulin-sensitivity index (WBISI) derived from a 3-h OGTT; energy homeostasis was also assessed by means of indirect calorimetry, along with circulating adipokines and low-grade pro-inflammatory cyto-chemokines.

RESULTS

Professional athletes had increased WBISIs (p<0.001) and lipid oxidation (p<0.03); they also showed higher serum resistin concentrations (p<0.001), although the pro-inflammatory chemokines were not increased in comparison with the other study groups. Resistin was independently associated only with fasting plasma NEFA. Increased resistin was detected in the middle-distance and marathon runners, but not in the sprinters when compared with the lean, young, sedentary individuals.

CONCLUSIONS/INTERPRETATION

Serum resistin concentration is increased in elite athletes, providing evidence against the notion that resistin levels reflect insulin resistance in humans, as seen in animal studies. Increased resistin was observed in aerobic-endurance, but not sustained-power athletes and this feature appeared to be independently associated with parameters of fatty acid metabolism.

Plasma adipokines and body composition in response to modest dietary manipulations in the mouse

OBJECTIVE

The relationship between adipokine levels and body composition has not been carefully examined. Most studies in humans are cross-sectional, and the few studies in mice have been restricted to a comparison of control animals with markedly obese, insulin-resistant mice. Our objective was to study changes in adipokine levels and body composition in response to modest dietary intervention.

RESEARCH METHODS AND PROCEDURES

Plasma resistin, adiponectin, and leptin levels were examined in mice fed ad libitum, a 75% restricted diet, or a diet supplemented with 10% sucrose. Body composition was determined by whole-body DXA.

RESULTS

The percentage body fat was reduced in mice subjected to the restricted diet and increased in mice supplemented with 10% dextrose. Adipokine levels were not different in either of these groups compared with the control mice. A significant inverse correlation was observed between resistin levels and total body fat, whereas there was no significant correlation between body fat and adiponectin levels. Positive correlations were observed between leptin levels and percentage body fat, total body fat, and abdominal fat. Leptin levels correlated with plasma glucose, but multivariate analysis revealed that this correlation was the result of a strong positive correlation between leptin and insulin levels. There were no correlations between glycemia and resistin or glycemia and adiponectin levels, and no correlation was observed between any of the adipokine levels and bone mineral content or density.

DISCUSSION

These data suggest that in the mouse, modest dietary perturbations have little effect on resistin and adiponectin levels despite significant effects on glycemia, insulin levels, and bone parameters.

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.

Insulin resistance, adipokines, and oxidative stress in nondiabetic, hypercholesterolemic patients: leptin as an 8-epi-prostaglandin F2alpha determinant

Limited data are available on the association of insulin resistance, adipokines, and in vivo lipid peroxidation. We investigated the relationships between insulin resistance, adipokines (leptin, adiponectin, and resistin), and oxidative stress in nondiabetic, hypercholesterolemic patients. Seventy-six nondiabetic patients with hypercholesterolemia participated in this cross-sectional study. Fasting glucose and insulin concentrations were analyzed. Serum leptin, adiponectin, and resistin concentrations and urinary excretion of 8-epi-prostaglandin F(2alpha) (8-epi-PGF(2alpha)) were determined using enzyme-linked immunosorbent assay. We divided all subjects into 3 groups, classified by the tertiles of homeostasis model assessment of insulin resistance (HOMA-IR) values, and clinical parameter comparisons were made among the 3 groups. The results showed that serum leptin (P < .001) and adiponectin levels (P < .05) were significantly different among the groups, although serum resistin was not different. Furthermore, the group with the highest HOMA-IR had a significantly higher urinary 8-epi-PGF(2alpha) excretion than the group with the lowest HOMA-IR (P = .017). Circulating leptin was positively correlated with urinary 8-epi-PGF(2alpha) (r = 0.323, P < .01) and HOMA-IR (r = 0.524, P < .001). Circulating adiponectin was negatively correlated with body mass index (r = -0.252, P < .05) and HOMA-IR (r = -0.228, P < .05). We could not find a relationship between circulating adiponectin or resistin and urinary 8-epi-PGF(2alpha) excretion. Stepwise multiple linear regression analysis showed that leptin was associated with the urinary 8-epi-PGF(2alpha) excretion after adjusting for age, sex, body mass index, blood lipids, and HOMA-IR (P = .002). In conclusion, our results show that more insulin-resistant state of nondiabetic, hypercholesterolemic patients is associated with decreased adiponectin and increased leptin and urinary 8-epi-PGF(2alpha) levels, although no relationship with resistin was observed. Furthermore, serum leptin independently contributed to urinary 8-epi-PGF(2alpha) excretion.

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.

Obesity and the role of gut and adipose hormones in female reproduction

Reproductive function declines at both extremes of human energy balance. The relationship between obesity and reproductive function is complex and incompletely understood. The literature has established the negative impact of excess energy stores on ovulatory function and investigated the mechanisms whereby this occurs. Furthermore, weight loss in obese anovulatory women increases ovulation and conception. Obesity and anti-obesity therapy effects on the endometrium, implantation and early fetal development have received less attention. The discovery of adipokines and enterokines greatly expands the ability to investigate the relationship between obesity, therapies to produce weight loss and reproductive function. In this review, we discuss select adipose and enteric signals. We focus on in vitro, animal and human data that lend biological plausibility to adipokines and enterokines as mediators of obesity and reproduction. Very little published work exists that directly addresses adipocyte and enteric signals in this specific role; therefore, much of this review is on the basis of a synthesis of the literature in three areas: (i) in vitro and in vivo evidence regarding the reproductive effects of these signals; (ii) adipokine and enterokine changes that occur with weight-loss therapies, focusing on hypocaloric diets, bariatric surgery and drugs that target adipocyte or enteric signals and (iii) reproductive changes produced by these weight-loss therapies.

Effect of calorie restriction with or without exercise on insulin sensitivity, beta-cell function, fat cell size, and ectopic lipid in overweight subjects

OBJECTIVE

The purpose of this article was to determine the relationships among total body fat, visceral adipose tissue (VAT), fat cell size (FCS), ectopic fat deposition in liver (intrahepatic lipid [IHL]) and muscle (intramyocellular lipid [IMCL]), and insulin sensitivity index (S(i)) in healthy overweight, glucose-tolerant subjects and the effects of calorie restriction by diet alone or in conjunction with exercise on these variables.

RESEARCH DESIGN AND METHODS

Forty-eight overweight volunteers were randomly assigned to four groups: control (100% of energy requirements), 25% calorie restriction (CR), 12.5% calorie restriction +12.5% energy expenditure through structured exercise (CREX), or 15% weight loss by a low-calorie diet followed by weight maintenance for 6 months (LCD). Weight, percent body fat, VAT, IMCL, IHL, FCS, and S(i) were assessed at baseline and month 6.

RESULTS

At baseline, FCS was related to VAT and IHL (P < 0.05) but not to IMCL. FCS was also the strongest determinant of S(i) (P < 0.01). Weight loss at month 6 was 1 +/- 1% (control, mean +/- SE), 10 +/- 1% (CR), 10 +/- 1% (CREX), and 14 +/- 1% (LCD). VAT, FCS, percent body fat, and IHL were reduced in the three intervention groups (P < 0.01), but IMCL was unchanged. S(i) was increased at month 6 (P = 0.05) in the CREX (37 +/- 18%) and LCD (70 +/- 34%) groups (P < 0.05) and tended to increase in the CR group (40 +/- 20%, P = 0.08). Together the improvements in S(i) were related to loss in weight, fat mass, and VAT, but not IHL, IMCL, or FCS.

CONCLUSIONS

Large adipocytes lead to lipid deposition in visceral and hepatic tissues, promoting insulin resistance. Calorie restriction by diet alone or with exercise reverses this trend.

Resistin

PURPOSE OF REVIEW

Resistin, a cysteine-rich 12.5 kDa polypeptide, is a recently discovered adipocytokine with a controversial history regarding its role in the pathogenesis of obesity-mediated insulin resistance and type 2 diabetes mellitus. Whilst current studies appear to re-affirm the role of resistin on glucose homeostasis in rodent systems, we are still unravelling the functionality of resistin in human biology in respect to glucose metabolism and insulin signalling. This review will summarize the current knowledge, put into context the developments to date and discuss the controversial points.

RECENT FINDINGS

Current evidence appears to suggest that resistin is a pro-inflammatory cytokine. Thus, like many other adipocytokines, resistin may possess a dual role in contributing to metabolic disease: first through its direct effects on substrate metabolism and second, through regulating inflammation within its target tissues. The chemistry of resistin has also been the subject of investigation and like adiponectin, the homo-oligomerization of this protein has a bearing on its function.

SUMMARY

The most recent advances include the identification of circulating higher molecular weight structures of resistin in both rodent and human serum. This has been complemented by work casting light on the function and purpose of multimeric resistin in mice. Resistin appears to have effects on substrate metabolism through impairment of insulin action, particularly in the liver, but in addition, also has effects on insulin independent pathways.

Adipokine profile and C-reactive protein in pregnancy: effects of glucose challenge response versus body mass index

OBJECTIVE

To test the hypothesis that gravidas who have an abnormal response to glucose loading have dysfunctional adipose tissue cells that produce more insulin resistance-inducing and proinflammatory adipokines but less insulin-sensitizing adipokines.

METHODS

We performed a nested case-control study within a larger sample of gravidas who had a glucose challenge test (GCT) at 24-29 weeks; we compared 73 cases with an abnormal GCT (>8.3 mM) and 146 controls with a strictly normal GCT (<7.2 mM) matched for body mass index (BMI) and height (mean difference between cases and controls: 0.1 kg/m(2) and 1 cm, respectively). We measured plasma insulin, adipokines (leptin, adiponectin, resistin, tumor necrosis factor [TNF]-alpha, interleukin [IL]-6), soluble leptin receptor (sOb-R), the main leptin-binding protein, and C-reactive protein (CRP).

RESULTS

The cases showed a 48% increase in insulin concentrations and a 27% increase in TNF-alpha concentrations compared to the controls (both P < .0001), but leptin, sOb-R, IL-6, and adiponectin, as well as CRP, concentrations were comparable between cases and controls. In the whole group (n = 219), BMI was correlated with insulin, leptin, IL-6, and CRP, and inversely with sOb-R and adiponectin concentrations (all P < .0003).

CONCLUSIONS

Plasma leptin, sOb-R, IL-6, and adiponectin, as well as CRP, are strongly related to BMI in gravidas at 24-29 weeks gestational age but not to the glucose loading response. However, TNF-alpha is higher in women with an abnormal GCT. Further studies should disclose the source of increased TNF-alpha in these women, and to assess whether TNF-alpha is causally related to glucose intolerance during pregnancy.

Increase in serum resistin during weight loss in overweight subjects is related to lipid metabolism

OBJECTIVE

Human resistin has been stated to influence preadipocyte cell numbers and to stimulate adipocyte triglyceride lipolysis in vivo and in vitro. However, its role in human obesity remains unclear.

DESIGN

Cross-sectional study for comparisons of lean and obese subjects, and subsequent longitudinal 4-month weight loss intervention study in obese subjects.

SUBJECTS

Healthy subjects, lean (n=20, BMI<25) and overweight (n=43, BMI>or=25).

MEASUREMENTS

Serum resistin, body weight, body fat, waist-to-hip ratio, as well as markers of insulin resistance and lipid metabolism at baseline and after 4 months of intervention.

RESULTS

Serum resistin was positively correlated to HOMA-IR (partial r=0.288; P=0.055), serum fructosamines (partial r=0.280; P=0.062), serum NEFA (partial r=0.276; P=0.066) and negatively to age (partial r=-0.349; P=0.019) and serum apolipoprotein A-1 (partial r=-0.363; P=0.014). During the intervention, serum resistin increased significantly (P<0.001). The increase was inversely related to changes in waist-to-hip ratio (P=0.025) and positively to serum apolipoprotein B (P=0.011). In males only, the increase in resistin during weight loss was predicted by total serum cholesterol at baseline (r=0.703, P=0.007). No relation was observed between changes in resistin and changes in HOMA-IR.

CONCLUSION

The present study indicates an association between serum resistin and markers of abdominal fat distribution as well as the regulation of lipid metabolism. However, human resistin is unlikely to play an independent role in the regulation of glucose metabolism.

Adipokines: implications for female fertility and obesity

Obesity is associated with a diverse set of metabolic disorders, and has reproductive consequences that are complex and not well understood. The adipose tissue-produced leptin has dominated the literature with regards to female fertility complications, but it is pertinent to explore the likely role of other adipokines--adiponectin and resistin--as our understanding of their biological functions emerge. Leptin influences the developing embryo, the functioning of the ovary and the endometrium, interacts with the release and activity of gonadotrophins and the hormones that control their synthesis. In this review such biological actions and potential roles of the adipokines leptin, adiponectin and resistin are explored in relation to female fertility and the complexity of the obese metabolic state.

Physiological and pathophysiological regulation of regional adipose tissue in the development of insulin resistance and type 2 diabetes

AIM

To survey the latest state of knowledge concerning the regulation of regional adipocytes and their role in the development of insulin resistance and type 2 diabetes.

METHODS

Data from the English-language literature on regional adipocytes, including abdominal, intramyocellular, intrahepatic and intra-islet fat as well as the adipokines and their relations to insulin resistance and type 2 diabetes, were reviewed.

RESULTS

It is not the total amount of fat but the fat that resides within skeletal muscle cell (intramyocellular fat), hepatocytes and intra-abdominally (visceral fat), via systemic and local secretion of several adipokines, that influences insulin resistance. Among the adipokines that relate to insulin resistance, adiponectin and leptin appear to have clinical relevance to human insulin resistance and others may also contribute, but their role is still inconclusive. The intra-islet fat also adversely affects beta-cell function and number (beta-cell apoptosis), eventually leading to deterioration of glucose tolerance. The abnormal location of fat observed in patients with type 2 diabetes and their relatives is conceivably partly the results of the genetically determined, impaired mitochondrial fatty acid oxidative capacity. Restriction or elimination of the fat load by weight control, regular exercise and thiazolidinediones has been shown to improve insulin resistance and beta-cell function and to delay the development of type 2 diabetes.

CONCLUSION

These data support the plausibility of an essential role of regional adipose tissue in the development of insulin resistance and type 2 diabetes.

Increased plasma levels of adipokines in preeclampsia: relationship to placenta and adipose tissue gene expression

Adipokines are predominantly secretory protein hormones from adipose tissue but may also originate in placenta and other organs. Cross-sectionally, we monitored maternal plasma concentration of adiponectin, resistin, and leptin and their mRNA expression in abdominal subcutaneous adipose tissue and placenta from preeclamptic (PE; n = 15) and healthy pregnant (HP; n = 23) women undergoing caesarean section. The study groups were similar in age and BMI, whereas HOMA-IR tended to be higher in the PE group. In fasting plasma samples, the PE group had higher concentrations of adiponectin (18.3 +/- 2.2 vs. 12.2 +/- 1.1 microg/ml, P = 0.011), resistin (5.68 +/- 0.41 vs. 4.65 +/- 0.32 ng/ml, P = 0.028), and leptin (34.4 +/- 3.2 vs. 22.7 +/- 2.1 ng/ml, P = 0.003) compared with the HP group. Adiponectin and leptin concentrations were still different between PE and HP after controlling for BMI and HOMA-IR, whereas resistin concentrations differed only after controlling for BMI but not HOMA-IR. We found similar mean mRNA levels of adiponectin, resistin, and leptin in abdominal subcutaneous adipose tissue in PE and HP women. When data were pooled from PE and HP women, resistin mRNA levels in adipose tissue also correlated with HOMA-IR (r = 0.470, P = 0.012) after controlling for BMI and pregnancy duration. Resistin mRNA levels in placenta were not significantly different between PE and HP, whereas leptin mRNA levels were higher in PE placenta compared with HP. Thus increased plasma concentrations of adiponectin and resistin in preeclampsia may not relate to altered expression levels in adipose tissue and placenta, whereas both plasma and placenta mRNA levels of leptin are increased in preeclampsia.

The potential role of resistin in atherogenesis

Resistin, an adipocyte-derived cytokine linked to insulin resistance and obesity, has recently been shown to activate endothelial cells (ECs). Using microarrays, we found that along with numerous other pro-atherosclerotic genes, resistin expression levels are elevated in the aortas of C57BL/6J apoE-/- mice; these findings led us to further explore the relation between resistin and atherosclerosis. Using TaqMan PCR and immunohistochemistry, we found that ApoE-/- mice had significantly higher resistin mRNA and protein levels in their aortas, and elevated serum resistin levels, compared to C57BL/6J wild-type mice. Incubation of murine aortic ECs with recombinant resistin increased monocyte chemoattractant protein (MCP)-1 and soluble vascular cell adhesion molecule (sVCAM)-1 protein levels in the conditioned medium. Furthermore, human carotid endarterectomy samples stained positive for resistin protein, while internal mammary artery did not show strong staining. Patients diagnosed with premature coronary artery disease (PCAD) were found to have higher serum levels of resistin than normal controls. In summary, resistin protein is present in both murine and human atherosclerotic lesions, and mRNA levels progressively increase in the aortas of mice developing atherosclerosis. Resistin induces increases in MCP-1 and sVCAM-1 expression in murine vascular endothelial cells, suggesting a possible mechanism by which resistin might contribute to atherogenesis. Finally, PCAD patients exhibited increased serum levels of resistin when compared to controls. These findings suggest a possible role of resistin in cardiovascular disease.

Pathophysiological levels of the obesity related peptides resistin and ghrelin increase adhesion molecule expression on human vascular endothelial cells

1. In the present study, we sought to determine whether physiological or pathophysiological concentrations of obesity related peptides influence the key early atherogenic events of monocyte adhesion to endothelial cells and adhesion molecule expression using primary human cells. 2. Human umbilical vein endothelial cells were grown to confluence and human monocytes were obtained by elutriation. Adhesion was assessed by automated cell counting and cell adhesion molecule expression (E-selectin, intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1)) was assayed by ELISA. 3. Experimental conditions included untreated control, ghrelin (100, 150, 450 and 1350 pmol/L), resistin (15, 40 and 100 ng/mL) and combined leptin and insulin (combinations of 30 and 120 pmol/L insulin and 5, 50 and 500 ng/mL leptin). 4. Both resistin and ghrelin produced modest but significant increases in VCAM-1 expression (110 +/- 4 and 117 +/- 13% compared with controls, respectively; both P <or= 0.01). Ghrelin also increased ICAM-1 expression (119 +/- 17% of control; P <or= 0.01). 5. However, despite these increases in adhesion molecule expression, neither ghrelin nor resistin altered monocyte adhesion values. 6. Neither leptin nor insulin altered monocyte adhesion to endothelial cells or cell adhesion molecule expression. 7. Pathophysiologically relevant concentrations of ghrelin and resistin, within the range of concentrations exhibited by patients with anorexia nervosa or the Prader-Willi syndrome and type 2 diabetes, respectively, increase endothelial cell adhesion molecule expression, possibly contributing to increased atherosclerosis risk in such subjects.

The role of adipokines as regulators of skeletal muscle fatty acid metabolism and insulin sensitivity

Several adipose-derived cytokines (adipokines) have been suggested to act as a link between accumulated fat mass and altered insulin sensitivity. Resistin and tumour necrosis factor-alpha (TNF-alpha) have been implicated in impairing insulin sensitivity in rodents; conversely, two other adipokines, leptin and adiponectin, increase insulin sensitivity in lean and obese rodents. Currently, there is considerable focus on the concept that lipid accumulation in skeletal muscle leads to the development of insulin resistance. Adiponectin and leptin have each been demonstrated to increase rates of fatty acid (FA) oxidation and decrease muscle lipid content, which may in part be the underlying mechanism to their insulin sensitizing effect. These effects on FA metabolism appear to be mediated in part through the activation of AMP-activated protein kinase. Evidence derived from animal and human studies suggests that the ability of leptin and adiponectin to stimulate FA oxidation in muscle is impaired in the obese condition. Thus, leptin and adiponectin resistance may be an initiating factor in the accumulation of intramuscular lipids, such as diacylglycerol and ceramide, and the ensuing development of insulin resistance. Lifestyle factors such as diet and exercise are able to restore the sensitivity of muscle to leptin. The actual physiological roles of resistin and TNF-alpha in altering muscle lipid metabolism are more controversial, but each has been shown to directly impair insulin signalling and consequently, insulin stimulated glucose uptake in muscle. However, the possibility that resistin and TNF-alpha reduces insulin sensitivity in muscle by directly impairing FA metabolism in this tissue leading to lipid accumulation, has been virtually unexamined. Thus, the contribution of various adipokines to the development of insulin resistance is complex and not fully understood. Finally, the effects of these adipokines on metabolism and insulin sensitivity are generally studied in isolation, making it difficult to predict the interactive effects and the net impact on insulin sensitivity.

Regulation of insulin signalling, glucose uptake and metabolism in rat skeletal muscle cells upon prolonged exposure to resistin

AIMS/HYPOTHESIS

Debate exists regarding the role of resistin in the pathophysiology of insulin resistance. The aim of this study was to directly assess the effects of resistin (0-24 h) on basal and insulin-stimulated glucose uptake and metabolism in skeletal muscle cells and to investigate the mechanisms responsible for the effects of resistin.

METHODS

We used L6 rat skeletal muscle cells and examined [(3)H]2-deoxyglucose uptake, GLUT4 translocation and GLUT protein content. We assessed glucose metabolism by measuring the incorporation of D-[U-(14)C]glucose into glycogen, (14)CO(2) and lactate production, as well as the phosphorylation level and total protein content of insulin signalling proteins, including insulin receptor beta-subunit (IRbeta), insulin receptor substrate (IRS), Akt and glycogen synthase kinase-3beta (GSK-3beta).

RESULTS

Treatment of L6 rat skeletal muscle cells with recombinant resistin (50 nmol/l, 0-24 h) reduced levels of basal and insulin-stimulated 2-deoxyglucose uptake and decreased insulin-stimulated GLUT4myc content at the cell surface, with no alteration in the production of GLUT4 or GLUT1. Resistin also decreased glycogen synthesis and GSK-3beta phosphorylation. Insulin-stimulated oxidation of glucose via the Krebs cycle was reduced by resistin, whereas lactate production was unaltered. Although insulin receptor protein level and phosphorylation were unaltered by resistin, production of IRS-1, but not IRS-2, was downregulated and a decreased tyrosine phosphorylation of IRS-1 was detected. Reduced phosphorylation of Akt on T308 and S473 was observed, while total Akt and Akt1, but not Akt2 or Akt3, production was decreased.

CONCLUSIONS/INTERPRETATION

Our data show that resistin regulates the function of IRS-1 and Akt1 and decreases GLUT4 translocation and glucose uptake in response to insulin. Selective decreases in insulin-stimulated glucose metabolism via oxidation and conversion to glycogen were also induced by resistin. These observations highlight the potential role of resistin in the pathophysiology of type 2 diabetes in obesity.

Role of resistin in obesity, insulin resistance and Type II diabetes

Resistin is a member of a class of cysteine-rich proteins collectively termed resistin-like molecules. Resistin has been implicated in the pathogenesis of obesity-mediated insulin resistance and T2DM (Type II diabetes mellitus), at least in rodent models. In addition, resistin also appears to be a pro-inflammatory cytokine. Taken together, resistin, like many other adipocytokines, may possess a dual role in contributing to disease risk. However, to date there has been considerable controversy surrounding this 12.5 kDa polypeptide in understanding its physiological relevance in both human and rodent systems. Furthermore, this has led some to question whether resistin represents an important pathogenic factor in the aetiology of T2DM and cardiovascular disease. Although researchers still remain divided as to the role of resistin, this review will place available data on resistin in the context of our current knowledge of the pathogenesis of obesity-mediated diabetes, and discuss key controversies and developments.

Resistin is not associated with insulin sensitivity or the metabolic syndrome in humans

AIMS/HYPOTHESIS

The aim of this study was to further elucidate the relationship between resistin and insulin sensitivity, body fat distribution and the metabolic syndrome in humans.

METHODS

We measured plasma resistin levels in 177 non-diabetic subjects (75 male, 102 female; age 32-75 years). BMI, waist circumference, blood pressure, lipids, glucose, plasminogen-activator inhibitor 1 (PAI-1), adiponectin and leptin levels were also measured. The insulin sensitivity index (S(I)) was quantified using Bergman's minimal model. Intra-abdominal fat (IAF) and subcutaneous fat (SQF) areas were quantified by CT scan. Presence of metabolic syndrome criteria was determined using the National Cholesterol Education Program Adult Treatment Panel III guidelines.

RESULTS

When subjects were divided into categories based on BMI (< or > or =27.5 kg/m(2)) and S(I) (< or > or = 7 x 10(-5) min(-1) [pmol/l](-1)), resistin levels did not differ between the lean, insulin-sensitive (n=53, 5.36+/-0.3 ng/ml), lean, insulin-resistant (n=67, 5.70+/-0.4 ng/ml) and obese, insulin-resistant groups (n=48, 5.94+/-0.4 ng/ml; ANOVA p=0.65). Resistin correlated with age (r=-0.22, p<0.01), BMI (r=0.16, p=0.03) and SQF (r=0.19, p=0.01) but not with S(I) (p=0.31) or IAF (p=0.52). Resistin did not correlate with the number of metabolic syndrome criteria or any of the individual metabolic syndrome criteria. In contrast, adiponectin, PAI-1 and leptin each correlated with IAF, SQF and S(I). Additionally, the number of metabolic syndrome criteria correlated with adiponectin (r=-0.32, p<0.001), leptin (r=0.31, p<0.001) and PAI-1 (r=0.26, p=0.001).

CONCLUSIONS/INTERPRETATION

In contrast to other adipokines, resistin is only weakly associated with body fat and is unlikely to be a major mediator of insulin resistance or the metabolic syndrome in humans.

Resistin SNP-420 determines its monocyte mRNA and serum levels inducing type 2 diabetes

Resistin, secreted from adipocytes, causes insulin resistance in rodents. Its roles and main source in humans remain unknown. The G/G genotype of resistin single nucleotide polymorphism, SNP-420, induces type 2 diabetes mellitus (T2DM) by increasing promoter activity. We elucidated factors correlated with serum resistin and effects of SNP-420 on monocyte resistin mRNA. In 198 T2DM and 157 controls, fasting serum resistin was higher in T2DM. Multiple regression analysis revealed that SNP-420 genotype was the strongest determinant of serum resistin. In T2DM, 1-year duration of T2DM and 1% HbA1c was also correlated with 0.19 and 0.54 ng/ml serum resistin, respectively. Logistic regression analysis revealed that serum resistin was an independent factor for T2DM. In 23 healthy volunteers, monocyte resistin mRNA was positively correlated with its simultaneous serum levels and was higher in G/G genotype. Thus, SNP-420 determines monocyte mRNA and serum levels of resistin, which could induce T2DM.

Distribution and determinants of adiponectin, resistin and ghrelin in a randomly selected healthy population

OBJECTIVE

Adiponectin, resistin, ghrelin and the IGF-I system seem to play an important role in the regulation of body composition throughout life, but the mechanisms are not well understood. The aim of our study was to analyse the distribution among sexes and all decades of the adult life of adiponectin, resistin and ghrelin and their relationship with anthropometric, body composition parameters and the IGF-I system.

SUBJECTS

One hundred and thirty-four men and 127 healthy women were included in the study.

MEASUREMENTS

Plasma concentration of adiponectin, resistin, ghrelin, total IGF-I, free IGF-I and IGFBP-3 were determined in all subjects. Body composition was evaluated by bioelectrical impedance.

RESULTS

Resistin and ghrelin were not affected by age. Plasma adiponectin correlated negatively with age, body mass index (BMI), waist-to-hip ratio (WHR), waist circumference (WC), fat mass (FM) and body fat (BF) in men. Adiponectin correlated negatively with WHR and positively with free IGF-I in women. Resistin correlated positively with BMI and WC only in men, and ghrelin correlated positively with WC, BMI and FM and negatively with free IGF-I in men. In multiple regression analysis adiponectin remained associated with WHR (beta=-0.19, P=0.01) in women. Resistin was positively associated with BMI (beta=0.30, P=0.003) in women and ghrelin was negatively related to free IGF-I (beta=-0.158, P=0.019) in men.

CONCLUSIONS

Plasma adiponectin declines with age and is negatively associated with FM in men. Our data suggest the existence of a positive correlation of adiponectin and the IGF-I axis in women and of an inverse relationship between ghrelin and the IGF-I system in men.

Circulating resistin levels are not associated with fat redistribution, insulin resistance, or metabolic profile in patients with the highly active antiretroviral therapy-induced metabolic syndrome

CONTEXT

The mechanisms underlying the development of the highly active antiretroviral therapy (HAART)-induced metabolic syndrome remain to be fully elucidated.

OBJECTIVE

The objective of this study was to investigate whether the adipocyte-secreted hormone, resistin, is associated with anthropometric and metabolic abnormalities of the HAART-induced metabolic syndrome.

DESIGN, SETTING, AND PATIENTS

We conducted a cross-sectional study of 227 HIV-positive patients (37 women and 190 men) recruited from the infectious diseases clinics. On the basis of history, physical examination, dual-energy x-ray absorptiometry, and single-slice computed tomography, patients were classified into four groups: non-fat redistribution (n = 85), fat accumulation (n = 42), fat wasting (n = 35), and mixed fat redistribution (n = 56).

MAIN OUTCOME MEASURES

The main outcome measures were serum resistin levels and anthropometric and metabolic variables.

RESULTS

Mean serum resistin levels were not significantly different among subjects with fat accumulation, fat wasting, or mixed fat redistribution or between these groups and the non-fat redistribution group. We found a weak, but significant, positive correlation between resistin and percent total body fat (r = 0.20; P < 0.01), total extremity fat (r = 0.18; P < 0.01), and abdominal sc fat (r = 0.19; P < 0.01), but not abdominal visceral fat (r = -0.10; P = 0.16) or waist to hip ratio (r = -0.05; P = 0.43). When adjustments were made for gender (women, 3.92 +/- 2.71 ng/ml; men, 2.96 +/- 2.61 ng/ml; P = 0.05), correlations between resistin and the above parameters were no longer significant. Importantly, resistin levels were not correlated with fasting glucose, insulin, homeostasis model assessment of insulin resistance index, triglycerides, or cholesterol levels in the whole group.

CONCLUSIONS

Resistin is related to gender, but is unlikely to play a major role in the insulin resistance and metabolic abnormalities of the HAART-induced metabolic syndrome.

Resistin stimulation of 17alpha-hydroxylase activity in ovarian theca cells in vitro: relevance to polycystic ovary syndrome

CONTEXT

A newly discovered hormone resistin has been shown to be increased in women with polycystic ovary syndrome (PCOS).

OBJECTIVE

The purpose of this study was to confirm increased resistin concentrations in women with PCOS and to test the direct effect of resistin on human theca cell androgen production.

DESIGN

Resistin was measured in fasting serum samples by RIA. To test the direct effects of resistin on ovarian androgen biosynthesis, human theca cells were cultured with resistin for 3 d in the presence and absence of forskolin and insulin.

PATIENTS

Fasting serum samples were obtained from 45 women with PCOS and 74 regularly cycling premenopausal control women in the follicular phase of their menstrual cycles, and ovarian theca cell cultures were established from two control women.

RESULTS

The mean serum resistin concentration was increased (40%) in women with PCOS. Serum resistin concentrations correlated positively with body mass index and testosterone in PCOS women but not in controls. There were no significant correlations between resistin and fasting insulin or indicators of insulin resistance when corrected for body mass index. In cultured human theca cells, basal 17alpha-hydroxylase activity was unchanged by resistin alone, but resistin enhanced 17alpha-hydroxylase activity in the presence of forskolin or a combination of forskolin plus insulin. Resistin (> or =1 ng/ml) augmented forskolin and forskolin plus insulin stimulation of CYP17 mRNA expression in a concentration-dependent manner.

CONCLUSION

These data indicate that abnormal resistin secretion in PCOS may play a role in causing ovarian hyperandrogenism.

Fat as an endocrine organ: influence of exercise

The prevalence of diabetes and obesity continues to increase. It is therefore important to identify the pathophysiology underlying these disorders. An inability of insulin to stimulate glucose uptake, i.e., insulin resistance, appears to be a common link between diabetes and obesity. The identification of various adipocyte-secreted cytokines (adipocytokines) that influence satiety, energy balance, and insulin sensitivity provide a novel target for the treatment of these disorders. Adipocytokines are differentially expressed with obesity and diabetes, making them a strong candidate for linking insulin resistance to these pathological conditions. This review explores the role of adipocytokines in insulin action and examines the effect of exercise training on adipocytokine content.

Relationships between human serum resistin, inflammatory markers and insulin resistance

OBJECTIVE

Data on the association of resistin levels with markers of insulin resistance are highly contrasting in humans and very few studies about its role in inflammation are available. This study investigates associations between serum resistin levels and markers of insulin resistance, inflammation (C-reactive protein (CRP)) and of oxidative stress (nytrotirosine (NT)).

SUBJECTS

A randomly collected sample of 300 men from a population-based cohort was analysed, separated into two groups according to body mass index (BMI) and waist values.

RESULTS

Correlations between resistin and BMI, waist, triglyceride, uric acid, fasting glucose, insulin and Homeostasis Model Assessment (HOMA) values were significant in subjects with normal BMI, but not in overweight/obese subjects. In a multiple regression model, after multiple adjustments and exclusion of diabetic patients, only fasting glucose remained significantly associated with resistin levels. Otherwise, resistin is associated to CRP levels in all individuals, after multiple adjustments and exclusion of diabetic patients (in normal BMI beta=0.82; 95% CI 0.21, 1.42; in overweight/obese beta=0.43; 95% CI 0.10, 0.76). In the same model, resistin values are negatively related to NT levels in normal weight individuals (beta=-1.61; 95% CI -0.77-2.45).

CONCLUSIONS

Serum resistin is weakly associated with metabolic abnormalities in subjects with normal BMI, while in overweight/obese patients this correlation is not significant, perhaps due to the higher fat content in these subjects. Serum resistin is directly correlated with CRP and inversely to NT. An intriguing hypothesis, which needs to be tested, is that resistin is secreted in response to a chronic low-grade inflammation, and has antioxidant properties.

Serum resistin is associated with C-reactive protein & LDL cholesterol in type 2 diabetes and coronary artery disease in a Saudi population

AIMS

Resistin is an adipocyte-derived factor implicated in obesity-associated type 2 diabetes (T2DM). This study examines the association between human serum resistin, T2DM and coronary heart disease.

METHODS

One hundred and fourteen Saudi Arabian patients (male: female ratio 46:68; age 51.4 (mean +/- SD)11.7 years; median and range: 45.59 (11.7) years and BMI: 27.1 (mean +/- SD) 8.1 Kgm2 median and range: 30.3 (6.3) were studied. Serum resistin and C-reactive protein (CRP), a marker of inflammation CRP levels, were measured in all subjects. (35 patients had type 2 diabetes mellitus (T2DM); 22 patients had coronary heart disease (CHD).

RESULTS

Serum resistin levels were 1.2-fold higher in type 2 diabetes and 1.3-fold higher in CHD than in controls (p = 0.01). In addition, CRP was significantly increased in both T2DM and CHD patients (p = 0.007 and p = 0.002 respectively). The use of regression analysis also determined that serum resistin correlated with CRP levels (p = 0.04, R2 0.045).

CONCLUSION

The findings from this study further implicate resistin as a circulating protein associated with T2DM and CHD. In addition this study also demonstrates an association between resistin and CRP, a marker of inflammation in type 2 diabetic patients.

Increased serum resistin in adults with prader-willi syndrome is related to obesity and not to insulin resistance

CONTEXT

Determinants of insulin resistance in Prader-Willi syndrome (PWS) are not completely understood. The discovery of several adipokines with relevant effects on insulin resistance and cardiovascular complications of metabolic syndrome offered new tools of investigation of insulin resistance in PWS.

OBJECTIVE

The purpose of this study was to measure serum resistin and mRNA in adipose tissue of patients with PWS, those with simple obesity, and healthy controls and correlate resistin levels with anthropometric and biochemical features.

DESIGN

Twenty-eight adult PWS patients, 29 obese patients, and 25 healthy controls were studied. Anthropometric variables were measured and fasting serum and plasma were collected for measurement of resistin, adiponectin, leptin, lipid profile, glucose, and insulin.

RESULTS

Serum resistin and resistin mRNA expression in adipose tissue was significantly higher in PWS patients, compared with both healthy lean controls and obese patients. Moreover, on regression analysis resistin was significantly correlated with body mass index, whereas no significant association was found between resistin and homeostasis model assessment index. A weak association between resistin and adiponectin was found in the PWS group only. However, on multivariate analysis only the correlation between resistin and body mass index remained significant.

CONCLUSIONS

These results support a link between circulating resistin and obesity in humans but do not support a role for resistin in human insulin resistance.

Effects of diet and/or exercise on the adipocytokine and inflammatory cytokine levels of postmenopausal women with type 2 diabetes

This study examined the independent and combined effects of diet and exercise on adipocytokine and inflammatory cytokines in postmenopausal women with type 2 diabetes. Using a randomized, controlled design, 33 women (age, 50-70 years) were assigned to diet alone (D), exercise alone (EX), or diet + exercise (D + E) for 14 weeks. Before and after the interventions, blood samples for adipocytokines and inflammatory markers were drawn, a meal test was performed, and abdominal fat distribution was measured by magnetic resonance imaging (MRI). Body weight decreased approximately 4.5 +/- 0.6 kg ( P < .05) after the D and D + E interventions, whereas only small changes in body weight were found with the exercise-alone intervention. Plasma C-reactive protein levels were decreased by approximately 15% with all 3 interventions, whereas leptin levels were reduced with the D and D + E intervention (D: pre = 48.7 +/- 6.0, post = 38.9 +/- 5.0 ng/mL; D + E: pre = 38.5 +/- 6.0, post = 22.9 +/- 5.0 ng/mL; P < .05) with no differences between groups. There was a trend for leptin levels to decrease in the EX group ( P = .06). Plasma resistin levels were not altered by the 3 interventions from pre- to posttreatment (D: pre = 6.9 +/- 0.6, post = 6.2 +/- 0.4 ng/mL; D + E: pre = 5.6 +/- 0.6, post = 5.7 +/- 0.4 ng/mL; E: pre = 6.2 +/- 0.6, post = 5.9 +/- 0.6 ng/mL, P > .05), and no differences in adiponectin and tumor necrosis factor alpha (TNF- alpha ) levels were found. Visceral adipose tissue and tumor necrosis factor alpha were the only predictors of calculated insulin resistance ( P < .05), explaining 43% of the variability. A typically prescribed weight loss program with lifestyle changes resulted in few changes in adipocytokines and inflammatory cytokines in older women with type 2 diabetes, suggesting that dramatic weight loss or clinical interventions are needed.

Serum resistin, adiposity and insulin resistance in Saudi women with type 2 diabetes mellitus

BACKGROUND

The role of adipocyte hormones in modulating insulin sensitivity and glucose tolerance are of increasing interest and importance in studies of type 2 diabetes mellitus. Recently a unique signaling molecule, resistin, has been proposed as playing a role in the pathogenesis of obesity-related insulin resistance, but its relevance to human diabetes remains uncertain. Therefore, we assessed the relationship between serum resistin concentrations and insulin resistance in lean, overweight and obese (OW/OB) non-diabetic and diabetic Saudi women.

SUBJECTS AND METHODS

We measured fasting serum resistin levels in 44 diabetic women with a mean body mass index (BMI) of 31.82 +/- 4.35 kg/m2, 21 OW/OB non-diabetic women with a mean BMI 30.71 +/- 3.42 kg/m2 and in 24 lean women with a mean BMI of 23.33 +/- 1.24 kg/m2. Insulin resistance was assessed using the homeostasis model assessment for insulin resistance formula derived from fasting insulin and glucose levels.

RESULTS

The concentrations of fasting serum resistin showed significant differences among the three groups (P<0.001). Mean serum resistin concentrations increased from lean (11.59 +/- 2.08) to OW/OB non-diabetic (16.29 +/- 2.29) to diabetic (19.42 +/- 3.60 ng/mL) women. Significantly higher levels of glucose (P<0.001) and values for the homeostasis model assessment ratio (HOMA-R) (P<0.01) occurred in the diabetic compared to the lean and OW/OB non-diabetic subjects. Furthermore, resistin correlated significantly and positively with hip circumferences (r=0.39, P=0.039), weight (r=0.51, P=0.005), insulin (r=0.40, P=0.033), HOMA-R (r=0.49, P=0.007) and glucose (r=0.39, P=0.038) in diabetic women. In OW/OB non-diabetic subjects, resistin correlated with insulin (r=0.59, P=0.015) and HOMA-R (r=0.616, P=0.011). No correlation was observed with glucose, height, hip, waist, weight, and waist-hip ratio (WHR) in the lean and OW/OB non-diabetic groups.

CONCLUSION

Resistin concentrations are elevated in patients with type 2 diabetes and are associated with obesity and insulin resistance. These data indicate that resistin might be involved in the development of diabetes in humans.

Proteomic Analysis of Primary Cultures of Human Adipose-derived Stem Cells

Adipogenesis plays a critical role in energy metabolism and is a contributing factor to the obesity epidemic. This study examined the proteome of primary cultures of human adipose-derived adult stem (ADAS) cells as an in vitro model of adipogenesis. Protein lysates obtained from four individual donors were compared before and after adipocyte differentiation by two-dimensional gel electrophoresis and tandem mass spectroscopy. Over 170 individual protein features in the undifferentiated adipose-derived adult stem cells were identified. Following adipogenesis, over 40 proteins were up-regulated by > or = 2-fold, whereas 13 showed a > or = 3-fold reduction. The majority of the modulated proteins belonged to the following functional categories: cytoskeleton, metabolic, redox, protein degradation, and heat shock protein/chaperones. Additional immunoblot analysis documented the induction of four individual heat shock proteins and confirmed the presence of the heat shock protein 27 phosphoserine 82 isoform, as predicted by the proteomic analysis, as well as the crystallin alpha phosphorylated isoforms. These findings suggest that the heat shock protein family proteome warrants further investigation with respect to the etiology of obesity and type 2 diabetes.