Serum resistin is reduced by glucose and meal loading in healthy human subjects

What is the effect of a Mediterranean compared with a Fast Food meal on the exercise induced adipokine changes? A randomized cross-over clinical trial

Background

Adipose tissue-derived adipokines are pro-inflammatory cytokines involved in metabolic-related diseases and can be influenced by diet and exercise. We aimed to compare the effect of a Mediterranean (MdM) compared with Fast Food (FFM) meal on the exercise induced adipokines changes.

Methods

In a double blinded cross over trial, 46 participants were randomly assigned to one of two standardized iso-energy pre-exercise meals: FFM or MdM-type. Three hours after each meal, participants completed a treadmill exercise test (EC). Serum adiponectin, resistin, PAI-1, lipocalin-2/NGAL and adipsin were determined by Luminex magnetic bead immunoassay. Wilcoxon signed rank test compared changes before/after meal and before/after EC and a linear mixed model evaluated the effect of meals on the adipokine response to exercise, adjusted for confounders.

Results

Thirty-nine participants (mean age of 25, with a standard deviation of 5 years) completed the trial (56% females). For both interventions, a significant reduction of adipsin after each meal and a significant increase of lipocalin, PAI-1, adipsin and resistin, after exercise was observed. When exercise was preceded by a MdM meal a higher increase in adipsin levels was seen.

Conclusion

Acute exercise induced an increase of circulatory levels of adipsin, resistin, lipocalin and PAI-1, but not adiponectin. A pre-exercise Mediterranean meal potentiated the increase of adipsin after the exercise test, which possibly relates to the immune regulatory role of adipsin. These changes suggest a cross-talk between the immune and metabolic immediate response to exercise and its modulation by the pre-exercise diet composition.

Serum resistin is causally related to mortality risk in patients with type 2 diabetes: preliminary evidences from genetic data

Resistin has been firmly associated with all-cause mortality. We investigated, whether, in patients with type 2 diabetes (T2D), this association is sustained by a cause-effect relationship. A genotype risk score (GRS), created by summing the number of resistin increasing alleles of two genome-wide association studies (GWAS)-derived single nucleotide polymorphisms (SNPs), serum resistin measurements and all-cause death records were obtained in 1,479 (403 events/12,454 person-years), patients with T2D from three cohorts, Gargano Heart Study-prospective design (n = 350), Gargano Mortality Study (n = 698) and Foggia Mortality Study (n = 431), from Italy. GRS was strongly associated with serum resistin in a non-linear fashion (overall p = 3.5 * 10^-7) with effect size modest for GRS = 1 and 2 and much higher for GRS >3, with respect to GRS = 0. A significant non-linear association was observed also between GRS and all-cause mortality (overall p = 3.3 * 10^-2), with a low effect size for GRS = 1 and 2, and nearly doubled for GRS ≥ 3, with respect to GRS = 0. Based on the above-reported associations, each genetic equivalent SD increase in log-resistin levels showed a causal hazard ratio of all-cause mortality equal to 2.17 (95%CI: 1.22-3.87), thus providing evidence for a causal role of resistin in shaping the risk of mortality in diabetic patients.

Serum resistin and glomerular filtration rate in patients with type 2 diabetes

Background

High serum levels of the pro-inflammatory adipokine resistin have been associated with decreased renal function in the general population. The goal of this study was to investigate whether such association is also present among diabetic subjects, who are at increased risk of renal function loss.

Methods

The cross-sectional association between serum resistin levels and estimated glomerular filtration rate (eGFR) was investigated in 1,560 type 2 diabetic (T2D) patients of European ancestry comprised in two different cohorts: 762 patients from San Giovanni Rotondo (SGR; Italy) and 798 patients from Boston (US).

Results

Serum resistin was inversely associated with eGFR in SGR [β (SE) for one SD of resistin increment = -1.01 (0.70) ml/min/1.73m², p = 0.019] and in Boston [β (SE) = -5.31 (0.74) ml/min/1.73m², p < 0.001] samples, as well as in the two studies combined [β (SE) = -3.42 (0.52) ml/min/1.73m², p < 0.001]. The association was unaffected by adjustment for smoking habits, BMI, waist circumference, diabetes duration, HbA1c, insulin treatment, hypertension and lipid-lowering therapy: β (SE) for one SD of resistin increment = -1.07 (0.70), p = 0.02; -5.50 (0.88), p < 0.001; and -2.81 (0.55) ml/min/1.73m², p < .001, in SGR, Boston and the two studies combined, respectively. The association was significantly stronger in men than in women (p for resistin-by-gender interaction = 0.003). For each resistin SD increment, the odds of having eGFR < 0 ml/min/1.73m² increased by 22% (OR = 1.22; 95% CI 1.02–1.44; p = 0.025) in SGR sample, 69% (OR = 1.69; 95% CI 1.38–2.07; p < 0.001) in Boston sample, and 47% (OR = 1.47; 95% CI 1.29–1.68; p < 0.001) in the two studies considered together. Similar associations were observed in the adjusted model: OR 95% CI for each SD resistin increment being 1.23 (1.03–1.46), p = 0.021; 1.52 (1.20–1.92), p < 0.001; 1.33 (1.16–1.53), p < 0.001, in SGR, Boston and the two studies combined, respectively.

Conclusions

This is the first report of an association between high serum resistin and low eGFR in patients with T2D of European ancestry.

A physiology-based model describing heterogeneity in glucose metabolism: the core of the Eindhoven Diabetes Education Simulator (E-DES)

Current diabetes education methods are costly, time-consuming, and do not actively engage the patient. Here, we describe the development and verification of the physiological model for healthy subjects that forms the basis of the Eindhoven Diabetes Education Simulator (E-DES). E-DES shall provide diabetes patients with an individualized virtual practice environment incorporating the main factors that influence glycemic control: food, exercise, and medication. The physiological model consists of 4 compartments for which the inflow and outflow of glucose and insulin are calculated using 6 nonlinear coupled differential equations and 14 parameters. These parameters are estimated on 12 sets of oral glucose tolerance test (OGTT) data (226 healthy subjects) obtained from literature. The resulting parameter set is verified on 8 separate literature OGTT data sets (229 subjects). The model is considered verified if 95% of the glucose data points lie within an acceptance range of ±20% of the corresponding model value. All glucose data points of the verification data sets lie within the predefined acceptance range. Physiological processes represented in the model include insulin resistance and β-cell function. Adjusting the corresponding parameters allows to describe heterogeneity in the data and shows the capabilities of this model for individualization. We have verified the physiological model of the E-DES for healthy subjects. Heterogeneity of the data has successfully been modeled by adjusting the 4 parameters describing insulin resistance and β-cell function. Our model will form the basis of a simulator providing individualized education on glucose control.

Polymorphisms in RETN gene and susceptibility to colon cancer in Saudi patients

BACKGROUND AND OBJECTIVES

Resistin is an adipocytokine, which has been studied for its role in insulin resistance and recently in inflammation. Several single-nucleotide polymorphisms (SNPs) have been identified in the human resistin gene (RETN). This study aims to investigate the association of RETN rs1862513 (C-420G) and rs3745367 (G+299A) SNPs with the colon cancer risk in Saudi patients.

DESIGN AND SETTING

This is a case-control study conducted among Saudi adult colon cancer patients recruited from King Abdulaziz Hospital and Oncology Center in Jeddah, Saudi Arabia.

SUBJECTS AND METHODS

In this study, 120 Saudi volunteers (60 colon cancer patients and 60 disease-free controls) were studied. The SNPs were determined by polymerase chain reaction (PCR) and genotyping using PCR- restriction fragment length polymorphism analysis.

RESULTS

In comparing the result obtained for the patient group with that of the controls, colon cancer group displayed different genotype distribution of the RETN C-420G and G+299A SNPs. The study indicated that the SNP-420 heterozygous (CG) genotype (odds ratio [OR]=2.48, 95% CI 1.07-5.74, P=.03) and the SNP +299 heterozygous (GA) genotype (OR=6.5, 95% CI 1.77-24.18, P=.002) significantly increased the risk of colon cancer. A further analysis of the genotype combination of SNPs RETN C-420G and G+299A showed a larger increase in the colon cancer risk.

CONCLUSION

These preliminary results suggested a potential role for RETN C-420G and G+299A polymorphisms in the genetic predisposition to colon cancer disease.

Acute intake of a high-fructose diet alters the balance of adipokine concentrations and induces neutrophil influx in the liver

The postprandial state is a period of metabolic fluxes, biosynthesis and oxidative metabolism. A considerable amount is known about the inflammatory response to the chronic consumption of fructose, but little is known about its effects in the postprandial state. The aim of the present study was to investigate the inflammatory effects of a single meal containing fructose on healthy mice. Male BALB/c and LysM-eGFP mice at 12-14 weeks were divided into three groups: fasted, control (mice fed with a sucrose-containing diet) and fructose (mice fed with a fructose-containing diet). One, 2 or 4 h postprandial, the BALB/c mice were killed, and samples were collected. LysM-eGFP mice were submitted to intravital microscopy. The fed mice showed a low-grade inflammatory response apart from dietary composition, which was characterized by increased numbers of leukocytes and high serum concentrations of pentraxin 3, leptin and resistin. TNF-α and CCL2 concentrations rose in the liver after the meal. IL-6 concentration increased and IL-10 decreased in the adipose tissue of the fed mice. Mice fed with the fructose-containing diet showed an intensification of the inflammatory response. Furthermore, the adiponectin concentration dropped, and the liver influx of neutrophils increased after fructose intake. Overall, this study showed a rapid increase in the systemic and tissue-specific immune response after a balanced meal. The study also showed an increased neutrophil influx in liver associated with an imbalance of adipokine concentrations and an increase of cytokine in the liver and adipose tissue following a fructose-containing meal.

The complex interaction between obesity, metabolic syndrome and reproductive axis: a narrative review

The aim of this narrative review is to provide current evidence for the interaction between obesity, metabolic syndrome (MS) and reproductive axis. Gonadotropin-releasing hormone (GnRH) pulses and, consequently, normal function of reproductive (hypothalamus-pituitary-gonadal) axis depend on normal energy balance, which presupposes sufficient food intake, reasonable energy consumption and average thermoregulatory costs. In case of an energy imbalance, reproductive dysfunction may occur. In young women, excessive leanness is accompanied by puberty delay, whereas premature puberty might be a manifestation of obesity. In a similar way, obesity in men affects fertility. Excess adipose tissue results in increased conversion of testosterone to estradiol, which may lead to secondary hypogonadism through reproductive axis suppression. Moreover, oxidative stress at the level of the testicular micro-environment may result in decreased spermatogenesis and sperm damage. Products of the adipocyte, such as leptin, adiponectin and resistin, and gut peptides, such as ghrelin, are considered to be crucial in the interaction between energy balance and reproduction. Finally, an indirect evidence for the interplay between MS and reproductive axis is the fact that when treating components of one, parameters of the other can be improved as well. These therapeutic interventions include lifestyle modifications, pharmacological agents, such as sex hormone replacement therapy, and surgical procedures. Although many issues remain unclear, the elucidation of the complex interaction between MS and reproductive axis will have obvious clinical implications in the therapeutic approach of both entities.

Serum adipokines as biomarkers of beta-cell function in patients with type 1 diabetes: positive association with leptin and resistin and negative association with adiponectin

BACKGROUND

We investigated the adipokines adiponectin, leptin and resistin as serum biomarkers of beta-cell function in patients with type 1 diabetes.

METHODS

One hundred and eighteen patients with type 1 diabetes (20.3 ± 7.5 years) diagnosed <5 years underwent standardized mixed meal test (MMTT) for 2 h. Systemic concentrations of C-peptide, adiponectin, leptin and resistin obtained during MMTT were measured and compared between patient groups by multiple regression analysis.

RESULTS

Patients were divided by their adipokine levels in subgroups above or below the median level ('high versus low'). High adiponectin levels (>10.6 µg/mL) were associated with lower C-peptide compared to the low adiponectin subgroup (p < 0.03). Increased leptin or resistin concentrations associated positively with beta-cell function even after adjustment for metabolic confounders (p < 0.04). The described associations between adipokines and C-peptide concentrations persisted in Spearman correlation tests (p < 0.05). Serum adipokines fell during MMTT (p < 0.05).

CONCLUSIONS

Serum adipokine levels differentially correlate with beta-cell function in type 1 diabetes independent of BMI or metabolic control. Serum adipokines should be investigated as biomarkers of beta-cell function in prospective studies and intervention trials in type 1 diabetes.

Dysregulation of glucose, insulin, triglyceride, blood pressure, and oxidative stress after an oral glucose tolerance test in men with abdominal obesity

Postprandial metabolic dysregulation plays a role in the development of atherosclerosis. Visceral fat accumulation is an important component of various metabolic disorders including glucose intolerance, dyslipidemia, and hypertension, which correlate with atherosclerotic cardiovascular disease. The aim of the present study was to compare the postprandial response of various metabolic parameters, blood pressure, adiponectin, and oxidative stress to 75-g oral glucose tolerance test (OGTT) in men with (n = 23) and without (n = 7) abdominal obesity based on waist circumference (WC) cutoff value of 85 cm (based on the Japanese criteria for the metabolic syndrome). The cross-sectional prospective study included 30 male subjects who were on no medications and newly diagnosed with mild hypertension and/or dyslipidemia. The percentage change in each parameter ([each parameter at 120 minutes after an OGTT - that before an OGTT]/that before an OGTT x 100) was calculated. The percentage systolic blood pressure, percentage diastolic blood pressure, and percentage triglyceride were -6.3% +/- 3.5%, -9.4% +/- 3.0%, and -10.2% +/- 2.1%, respectively, in the WC less than 85 group (vs baseline: P = .10, P < .01, and P < .001) and 2.0% +/- 1.7%, 0.9% +/- 2.4%, and 2.8% +/- 3.3%, respectively, in the WC at least 85 group (vs WC <85 group: P < .05, each). However, there were no significant differences in percentage total cholesterol and percentage high-density lipoprotein cholesterol between the 2 groups. The percentage thiobarbituric acid-reacting substances tended to be lower in the WC less than 85 group (vs baseline: P = .07), but not in the WC at least 85 group, albeit statistically insignificant (WC <85 vs >/=85 group: P = .057). The maximum carotid intima-media thickness was larger in the WC at least 85 group than the WC less than 85 group (P < .05). Evaluation of postprandial changes in obesity-related parameters may be important in preventing atherosclerotic diseases.

Serum high-molecular weight adiponectin decreases abruptly after an oral glucose load in subjects with normal glucose tolerance or impaired fasting glucose, but not those with impaired glucose tolerance or diabetes mellitus

Adiponectin exists in the blood as 3 forms, which are a trimer, a hexamer, and a high-molecular weight (HMW) form. We investigated whether circulating HMW adiponectin levels were altered by oral glucose or fat ingestion. Forty male subjects underwent a 75-g oral glucose loading test (OGTT), and 11 healthy subjects (5 women and 6 men) received a fat loading test. Serum levels of HMW and total adiponectin were measured during the OGTT and the fat loading test. The fat loading test was performed for at least 8 hours. Among the 40 male subjects, 11 had normal glucose tolerance (NGT), 9 had impaired fasting glucose (IFG), 11 had impaired glucose tolerance, and 9 had diabetes mellitus (DM). In all 40 subjects, the serum total adiponectin level did not change significantly, whereas serum HMW adiponectin decreased significantly after a glucose load and reached 92.2% of the basal level at 120 minutes after the OGTT (P < .01). The HMW to total adiponectin ratio decreased significantly from 0.47 +/- 0.15 at baseline to 0.43 +/- 0.13 at 120 minutes after a glucose load (P < .05). Serum HMW adiponectin measured at 120 minutes after the OGTT decreased significantly to 86.0% and 85.6% of the basal level in subjects with NGT or IFG, respectively (both P < .01). In subjects with impaired glucose tolerance or DM, however, serum HMW adiponectin did not change. The area under the curve for insulin at 30 minutes after a glucose load during the OGTT was significantly larger in subjects with NGT or IFG than in those with DM (P < .05). In addition, the insulinogenic index (DeltaI(0-30)/DeltaG(0-30)) was significantly higher in subjects with NGT or IFG than in those with DM (P < .001). Percentage changes in serum HMW adiponectin of the baseline at 120 minutes correlated negatively with those in serum insulin (r = -0.468, P = .0023), but not plasma glucose, of the baseline at 30 minutes in 40 subjects. On the other hand, serum triglycerides increased significantly after an oral fat load in 11 healthy subjects; but neither serum total nor HMW adiponectin changed. In conclusion, serum HMW adiponectin (but not total adiponectin) decreased rapidly after glucose loading in subjects with NGT or IFG; and the decrease of HMW adiponectin may be associated with an increase of serum insulin at 30 minutes.

Variations of retinol binding protein 4 levels are not associated with changes in insulin resistance during puberty

Retinol binding protein 4 (RBP4) is an adipokine involved in the pathogenesis of insulin resistance in obese adults and children. Since insulin resistance occurs during puberty, independently of adiposity, a role for RBP4 in the onset of this phenomenon may be hypothesized. In order to verify our hypothesis, we studied 90 subjects (45 obese and 45 lean controls). A complete physical examination was assessed, the z-score body mass index (BMI) was calculated, fat mass was assessed by bioelectric impedance analysis, and pubertal stage was assessed according to Tanner. Serum insulin and serum RBP4 levels were assayed. Obese and lean children differed for z-score BMI, fat mass, homeostasis model assessment of insulin resistance (HOMA-IR) and RBP4 levels. z-score BMI and HOMA-IR showed a direct correlation with RBP4 in the total population. When the subjects were divided in lean and obese, this correlation was evident only in obese (r2: 0.2; p=0.009 and r2: 0.2; p=0.01), but not in lean subjects (r2: 0.09; p=0.1 and r2: 0.03; p=0.4). Both in obese and lean HOMA-IR values were higher in pubertal subjects than in pre-pubertal (p<0.001), while serum RBP4 levels were similar in pubertal and in pre-pubertal subjects (>0.1). We conclude that RBP4 is correlated with adiposity and insulin resistance in obese children, but it is not involved in the insulin resistance occurring during puberty.

Association of variants in RETN with plasma resistin levels and diabetes-related traits in the Framingham Offspring Study

OBJECTIVE

The RETN gene encodes the adipokine resistin. Associations of RETN with plasma resistin levels, type 2 diabetes, and related metabolic traits have been inconsistent. Using comprehensive linkage disequilibrium mapping, we genotyped tag single nucleotide polymorphisms (SNPs) in RETN and tested associations with plasma resistin levels, risk of diabetes, and glycemic traits.

RESEARCH DESIGN AND METHODS

We examined 2,531 Framingham Offspring Study participants for resistin levels, glycemic phenotypes, and incident diabetes over 28 years of follow-up. We genotyped 21 tag SNPs that capture common (minor allele frequency >0.05) or previously reported SNPs at r2 > 0.8 across RETN and its flanking regions. We used sex- and age-adjusted linear mixed-effects models (with/without BMI adjustment) to test additive associations of SNPs with traits, adjusted Cox proportional hazards models accounting for relatedness for incident diabetes, and generated empirical P values (Pe) to control for type 1 error.

RESULTS

Four tag SNPs (rs1477341, rs4804765, rs1423096, and rs10401670) on the 3' side of RETN were strongly associated with resistin levels (all minor alleles associated with higher levels, Pe<0.05 after multiple testing correction). rs10401670 was also associated with fasting plasma glucose (Pe = 0.02, BMI adjusted) and mean glucose over follow-up (Pe = 0.01; BMI adjusted). No significant association was observed for adiposity traits. On meta-analysis, the previously reported association of SNP -420C/G (rs1862513) with resistin levels remained significant (P = 0.0009) but with high heterogeneity across studies (P < 0.0001).

CONCLUSIONS

SNPs in the 3' region of RETN are associated with resistin levels, and one of them is also associated with glucose levels, although replication is needed.