Serum retinol-binding protein 4 concentrations in response to short-term overfeeding in normal-weight, overweight, and obese men

The biology of human overfeeding: A systematic review

This systematic review has examined more than 300 original papers dealing with the biology of overfeeding. Studies have varied from 1 day to 6 months. Overfeeding produced weight gain in adolescents, adult men and women and in older men. In longer term studies, there was a clear and highly significant relationship between energy ingested and weight gain and fat storage with limited individual differences. There is some evidence for a contribution of a genetic component to this response variability. The response to overfeeding was affected by the baseline state of the groups being compared: those with insulin resistance versus insulin sensitivity; those prone to obesity versus those resistant to obesity; and those with metabolically abnormal obesity versus those with metabolically normal obesity. Dietary components, such as total fat, polyunsaturated fat and carbohydrate influenced the patterns of adipose tissue distribution as did the history of low or normal birth weight. Overfeeding affected the endocrine system with increased circulating concentrations of insulin and triiodothyronine frequently present. Growth hormone, in contrast, was rapidly suppressed. Changes in plasma lipids were influenced by diet, exercise and the magnitude of weight gain. Adipose tissue and skeletal muscle morphology and metabolism are substantially altered by chronic overfeeding.

Retinol binding protein 4 in relation to diet, inflammation, immunity, and cardiovascular diseases

Retinol binding protein 4 (RBP4), previously called retinol binding protein (RBP), is considered a specific carrier of retinol in the blood. It is also an adipokine that has been implicated in the pathophysiology of insulin resistance. RBP4 seems to be correlated with cardiometabolic markers in inflammatory chronic diseases, including obesity, type 2 diabetes, metabolic syndrome, and cardiovascular diseases (CVDs). It has recently been suggested that inflammation produced by RBP4 induces insulin resistance and CVD. The clinical relevance of this hypothesis is discussed in this review. Knowledge concerning the association of RBP4 with inflammation markers, oxidative stress, and CVDs as well as concerning the role of diet and antioxidants in decreasing RBP4 concentrations are discussed. Special attention is given to methodologies used in previously published studies and covariates that should be controlled when planning new studies on this adipokine.

Relationship between circulating visfatin/NAMPT, nutritional status and insulin resistance in an elderly population - results from the PolSenior substudy

BACKGROUND

Circulating visfatin/nicotinamide phosphoribosyltransferase (visfatin/NAMPT) levels according to some studies are related to nutritional status and insulin resistance. These associations have not been studied in large elderly populations. Therefore, the aim of our study was to assess the relationships between circulating visfatin/NAMPT levels, nutritional status, and insulin resistance in a large population of the elderly.

MATERIALS AND METHODS

Concentrations of glucose, albumin, creatinine, CRP, interleukin-6, insulin, and visfatin/NAMPT (by ELISA) were assessed, and HOMA-IR calculated in 3050 elderly participants of the PolSenior study.

RESULTS

The highest plasma visfatin/NAMPT levels were observed in obese, as well as in non-diabetic insulin resistant subjects; however there were only significant differences found in women. The regression models showed that plasma visfatin/NAMPT levels decline with age and increased with waist circumference, BMI, and hs-CRP. Waist circumference was better correlated than BMI for visfatin/NAMPT levels in statistical models not adjusted by sex, and just the opposite in models which were. We demonstrated a 0.023ng/mL increase of Visfatin/NAMPT levels for 1mg/L increase of hs-CRP, and a 0.007ng/mL decline for each year of age.

CONCLUSION

Our study revealed that in elderly subjects, circulating visfatin/NAMPT levels are related to age, nutritional status, especially visceral obesity, and inflammation.

The effect of a short-term high-intensity circuit training program on work capacity, body composition, and blood profiles in sedentary obese men: a pilot study

The objective of this study was to determine how a high-intensity circuit-training (HICT) program affects key physiological health markers in sedentary obese men. Eight obese (body fat percentage >26%) males completed a four-week HICT program, consisting of three 30-minute exercise sessions per week, for a total of 6 hours of exercise. Participants' heart rate (HR), blood pressure (BP), rating of perceived exertion, total work (TW), and time to completion were measured each exercise session, body composition was measured before and after HICT, and fasting blood samples were measured before throughout, and after HICT program. Blood sample measurements included total cholesterol, triacylglycerides, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, glucose, and insulin. Data were analyzed by paired t-tests and one-way ANOVA with repeated measures. Statistical significance was set to P < 0.05. Data analyses revealed significant (P < 0.05) improvements in resting HR (16% decrease), systolic BP (5.5% decrease), TW (50.7%), fat tissue percentage (3.6%), lean muscle tissue percentage (2%), cholesterol (13%), triacylglycerol (37%), and insulin (18%) levels from before to after HICT program. Overall, sedentary obese males experienced a significant improvement in biochemical, physical, and body composition characteristics from a HICT program that was only 6 hours of the total exercise.

Short-term overfeeding increases circulating adiponectin independent of obesity status

Background

Adiponectin is an adipose tissue derived hormone which strengthens insulin sensitivity. However, there is little data available regarding the influence of a positive energy challenge (PEC) on circulating adiponectin and the role of obesity status on this response.

Objective

The purpose of this study was to investigate how circulating adiponectin will respond to a short-term PEC and whether or not this response will differ among normal-weight(NW), overweight(OW) and obese(OB).

Design

We examined adiponectin among 64 young men (19-29 yr) before and after a 7-day overfeeding (70% above normal energy requirements). The relationship between adiponectin and obesity related phenotypes including; weight, percent body fat (%BF), percent trunk fat (%TF), percent android fat (%AF), body mass index (BMI), total cholesterol, HDLc, LDLc, glucose, insulin, homeostatic model assessment insulin resistance (HOMA-IR) and β-cell function (HOMA-β) were analyzed before and after overfeeding.

Results

Analysis of variance (ANOVA) and partial correlations were used to compute the effect of overfeeding on adiponectin and its association with adiposity measurements, respectively. Circulating Adiponectin levels significantly increased after the 7-day overfeeding in all three adiposity groups. Moreover, adiponectin at baseline was not significantly different among NW, OW and OB subjects defined by either %BF or BMI. Baseline adiponectin was negatively correlated with weight and BMI for the entire cohort and %TF, glucose, insulin and HOMA-IR in OB. However, after controlling for insulin resistance the correlation of adiponectin with weight, BMI and %TF were nullified.

Conclusion

Our study provides evidence that the protective response of adiponectin is preserved during a PEC regardless of adiposity. Baseline adiponectin level is not directly associated with obesity status and weight gain in response to short-term overfeeding. However, the significant increase of adiponectin in response to overfeeding indicates the physiological potential for adiponectin to attenuate insulin resistance during the development of obesity.

Circulating glucagon-like peptide-1 increases in response to short-term overfeeding in men

BACKGROUND

Glucagon-like Peptide-1 (GLP-1) is an incretin hormone secreted from the gastrointestinal tract that facilitates the glucose-dependent insulin response. Additionally, GLP-1 is thought to be involved in energy homeostasis. Currently little is known about GLP-1's responsiveness to an energy surplus, a fundamental cause of obesity and diabetes. Our objective was to examine the response of serum GLP-1 to short-term (7 day) overfeeding in young men.

METHODS

Seventy-two young men from the Canadian province of Newfoundland were recruited for the study. For 7-days, the subjects consumed 70% more calories than required at baseline.Various measurements including: anthropometrics, body composition, markers of glucose/lipid metabolism and serum total GLP-1, were taken at a fasted state before (day 1) and after (day 8) the challenge. Paired t-test analyses were used to assess the change in variables after the overfeeding period. Additionally, the relationship between serum GLP-1 and the measured variables at baseline and change due to overfeeding were analyzed.

RESULTS

Serum GLP-1 was significantly increased in all groups in response to the 7-day energy surplus, indicating the increase was independent of adiposity status. There was no significant difference in fasting GLP-1 at baseline between the normal weight and overweight/obese groups. At baseline, GLP-1 concentration negatively correlated with HDL-cholesterol and positively correlated with triacylglycerols and markers of insulin resistance in the overweight/obese group. Also GLP-1 was negatively correlated with change in percent gynoid fat in the overweight/obese subjects. Percent change in GLP-1 was negatively associated with percent change in gynoid fat in the normal weight group and positively associated with percent change in cholesterol in the overweight/obese group. Percentage change of circulating triacylglycerols was positively associated with percent change in GLP-1 in both adiposity groups.

CONCLUSION

Our findings showed that GLP-1 serum concentration is not a significant factor in determining obesity status. The increase of GLP-1 in all subjects regardless of obesity status, suggest GLP-1 serves as a protective role, counteracting energy surplus.

Protein glycation in diabetes as determined by mass spectrometry

Diabetes is a common endocrine disorder characterized by hyperglycemia leading to nonenzymatic glycation of proteins, responsible for chronic complications. The development of mass spectrometric techniques able to give highly specific and reliable results in proteome field is of wide interest for physicians, giving them new tools to monitor the disease progression and the possible complications related to diabetes, as well as the effectiveness of therapeutic treatments. This paper reports and discusses some of the data pertaining protein glycation in diabetic subjects obtained by matrix-assisted laser desorption ionization (MALDI) mass spectrometry (MS). The preliminary studies carried out by in vitro protein glycation experiments show clear differences in molecular weight of glycated and unglycated proteins. Then, the attention was focused on plasma proteins human serum albumin (HSA) and immunoglobulin G (IgG). Enzymatic degradation products of in vitro glycated HSA were studied in order to simulate the in vivo enzymatic digestion of glycated species by the immunological system leading to the highly reactive advanced glycation end-products (AGEs) peptides. Further studies led to the evaluation of glycated Apo A-I and glycated haemoglobin levels. A different MALDI approach was employed for the identification of markers of disease in urine samples of healthy, diabetic, nephropathic, and diabetic-nephropathic subjects.

Characteristics of urinary and serum soluble Klotho protein in patients with different degrees of chronic kidney disease

Background

Klotho is a single-pass transmembrane protein, which appears to be implicated in aging. The purpose of the present study was to characterize the relationship between the soluble Klotho level and renal function in patients with various degrees of chronic kidney disease (CKD).

Methods

The levels of soluble Klotho in the serum and urine obtained from one hundred thirty-one CKD patients were determined by a sandwich enzyme-linked immunosorbent assay system.

Results

The amount of urinary excreted Klotho during the 24 hr period ranged from 1.6 to 5178 ng/day (median 427 ng/day; interquartile range [IR] 56.8-1293.1), and the serum Klotho concentration ranged from 163.9 to 2123.7 pg/ml (median 759.7 pg/ml; IR 579.5-1069.1). The estimated glomerular filtration rate (eGFR) was significantly correlated with the log-transformed values of the amount of 24 hr urinary excreted Klotho (r = 0.407, p < 0.01) and the serum Klotho levels (r = 0.232, p < 0.01). However, a stepwise multiple regression analysis identified eGFR to be a variable independently associated only with the log-transformed value of the amount of 24-hr urinary excreted Klotho but not with the log-transformed serum Klotho concentration. Despite the strong correlation between random urine protein-to-creatinine ratio and the 24 hr urinary protein excretion (r = 0.834, p < 0.01), a moderate linear association was observed between the log-transformed value of the amount of 24 hr urinary excreted Klotho and that of the urinary Klotho-to-creatinine ratio (Klotho/Cr) in random urine specimens (r = 0.726, p < 0.01).

Conclusions

The amount of urinary Klotho, rather than the serum Klotho levels, should be linked to the magnitude of the functioning nephrons in CKD patients. The use of random urine Klotho/Cr as a surrogate for the amount of 24-hr urinary excreted Klotho needs to be evaluated more carefully.

Clear association between serum levels of adipokines and T-helper 17-related cytokines in patients with psoriasis

BACKGROUND

Psoriasis represents one of the T-helper (Th)17-mediated autoimmune diseases, and has been shown to be associated with metabolic syndrome (MetS). It has been reported that some adipokines and Th17-related cytokines are altered in patients with psoriasis.

AIM

To examine the relationship between levels of adipokines and Th17-related cytokines in the serum of patients with psoriasis compared with healthy controls.

METHODS

We enrolled 30 patients with psoriasis and 30 normal controls in the study, and used ELISA to measure serum adipokines and Th17-related cytokines. The association between each adipokine and each cytokine was determined using Pearson correlation analysis. Multiple regression analysis using all adipokines and Th17-related cytokines as covariates was also performed.

RESULTS

Pearson correlation analysis showed a strong positive association between chemerin and resistin levels and between adiponectin and high molecular weight adiponectin in normal controls. By contrast, in patients with psoriasis, resistin levels were significantly positively associated with tumour necrosis factor-α, while there was a strong negative association between retinol binding protein-4 and interleukin (IL)-6 levels. Interestingly, a marked positive correlation between IL-22 and adiponectin was also found in patients with psoriasis. Leptin levels correlated positively with IL-6 in patients with psoriasis, but this did not reach significance. The correlations identified by the multiple regression analyses were almost identical to those from the Pearson analyses.

CONCLUSIONS

These data suggest that distinct interaction between adipokines and Th17 cytokines is involved in the pathogenesis of psoriasis.

Serum acylated ghrelin concentrations in response to short-term overfeeding in normal weight, overweight, and obese men

Background

Ghrelin, an orexigenic gut hormone secreted primarily from the stomach, is involved in energy homeostasis. However, little data is available regarding its response to energy surplus and the development of human obesity.

Objective

The present study investigated the response of circulating acylated ghrelin to a 7-day positive energy challenge.

Design

A total of 68 healthy young men were overfed 70% more calories than required, for 1-week. Subjects were classified based on percent body fat (measured by dual-energy X-ray absorptiometry) as normal weight, overweight, and obese. Serum acylated ghrelin concentration was measured before and after the positive energy challenge. Additionally, the relationship between acylated ghrelin and obesity-related phenotypes including weight, body mass index, percent body fat, cholesterol, HDL-c, LDL-c, glucose, insulin and homeostasis model assessment of insulin resistance and β-cell function at baseline and change due to overfeeding, were assessed.

Results

Contrary to our expectations, serum acylated ghrelin was significantly increased in response to overfeeding and the increase was independent of obesity status. There was no significant difference in fasting acylated ghrelin between normal weight, overweight, and obese men at baseline. Acylated ghrelin was negatively correlated with weight and BMI for normal weight and with BMI in overweight men. Also ghrelin was correlated with change in weight and BMI in overweight (negative relationship) and obese (positive relationship) groups.

Conclusion

Our results showed that circulating acylated ghrelin was increased after a 7-day positive energy challenge regardless of adiposity status. However, acylated ghrelin was correlated with change in weight and BMI in opposing directions, in overweight and obese subjects respectively, thus dependent on obesity status.

Role of Retinol-Binding Protein 4 in Obese Asian Indians with Metabolic Syndrome

Retinol-binding protein 4 is an adipocytokine separately implicated in the development of obesity-related insulin resistance and proatherogenic lipid profile, however, its role in humans is unclear. This study was carried out to assess the role of retinol-binding protein 4 as a potential marker of metabolic syndrome in obese Asian Indians (a high-risk population for diabetes). 52 obese (BMI >23 kg/m2) Asian Indians were grouped into those with and without metabolic syndrome based on IDF criteria and compared with healthy controls. The anthropometric and biochemical parameters (fasting blood sugar, lipid profile, serum insulin, high-sensitivity C-reactive protein, and retinol-binding protein 4) were estimated. The obese groups had significantly altered adiposity indices, insulin resistance parameters (fasting blood sugar (only in the metabolic syndrome group), serum insulin, HOMA-IR and QUICKI), index of inflammation (C-reactive protein) and proatherogenic dyslipidemic profile (serum triglycerides, VLDL-cholesterol, and triglyceride/HDL-cholesterol ratio). Retinol-binding protein 4 levels were elevated in the obese groups, but were not significant. Retinol-binding protein 4 levels were correlated with anthro-pometric parameters and atherogenic lipids, while C-reactive protein was correlated with anthropometric and insulin resistance parameters in the entire group of subjects. Although these correlations were not observed in the obese groups, in the control group, retinol-binding protein 4 was correlated to the lipid parameters and C-reactive protein to adiposity indices. Thus, the role of retinol-binding protein 4 as a potential marker of metabolic syndrome is limited to the prediction of proatherogenic risk among Asian Indians.

Visfatin in overweight/obesity, type 2 diabetes mellitus, insulin resistance, metabolic syndrome and cardiovascular diseases: a meta-analysis and systemic review

There are controversies regarding the association of visfatin with overweight/obesity, type 2 diabetes mellitus, insulin resistance (IR), metabolic syndrome and cardiovascular disease in published articles. A meta-analysis was performed to identify the significance of visfatin in these diseases. We searched for relevant articles in Pubmed, Scopus and SCIE. A total of 1035 articles were surveyed and 46 articles were identified, with 14 reports reporting more than one of our investigated diseases. A total of 13 (n = 644), 19 (n = 2405), 20 (n = 2249), 5 (n = 527) and 5 (n = 851) articles/(participants) were included in each meta-analysis regarding the association of visfatin and overweight/obesity, type 2 diabetes mellitus, insulin resistance, metabolic syndrome and cardiovascular diseases, respectively. Plasma visfatin concentrations were increased in participants diagnosed with overweight/obesity, type 2 diabetes mellitus, metabolic syndrome and cardiovascular diseases, with pooled log odds ratios of 1.164 [95% confidence interval (CI): 0.348 to 1.981, p = 0.005], 1.981 (95% CI: 1.377 to 2.584, p < 0.001), 1.094 (95% CI: 0.678 to 1.511, p < 0.001), and 2.902 (95% CI: 0.924 to 4.879, p < 0.005), respectively. The circulating visfatin level was positively associated with insulin resistance, with a Fisher's z of 0.089 (95% CI: 0.013 to 0.165, p = 0.022). No single study was found to affect the overall result of each analysis by sensitivity testing. No publication bias was found by the Egger test. Our study suggests that the use of visfatin may be promising for predicting obesity, diabetes status, insulin resistance, metabolic syndrome and cardiovascular disease.

Retinol-binding protein 4 in young men with low versus normal birth weight: physiological response to short-term overfeeding

Retinol-binding protein 4 (RBP4) is a plasma protein which is elevated in obesity and type 2 diabetes. We aimed to investigate whether RBP4 represents a mechanism underlying the associations between low birth weight (LBW), high-fat diet, and insulin resistance. Forty-six young, lean men with low (n = 20) or normal (n = 26) birth weight underwent a 5-day high-fat high-calorie (HFHC) dietary intervention. In vivo glucose metabolism was assessed by euglycemic-hyperinsulinemic clamp, glucose tracer and intravenous glucose tolerance test techniques. Body composition was measured by a dual-energy x-ray absorptiometry scan, and plasma RBP4 by an enzyme-linked immunosorbent assay. RBP4 was not associated with birth weight, but with BMI (β = 0.9 µg/ml (0.08; 1.8) (95% confidence interval), P = 0.03) and plasma levels of low-density lipoprotein cholesterol (β = 5.3 µg/ml (1.9; 8.7), P = 0.03) and triglycerides (β = 15.4 µg/ml (9.5; 21.3), P < 0.001). Under baseline diet conditions, RBP4 was associated with decreased disposition index (D(i)) (β = -2.4% (-4.5%; -0.2%), P = 0.04) and increased basal hepatic glucose production rate (HGP) (β = 0.02 mg kg(-1) min(-1) (0.002; 0.04), P = 0.03), but not associated with peripheral glucose disposal rate or hepatic insulin resistance index. RBP4 levels were not influenced by overfeeding or related to peripheral and hepatic insulin resistance provoked by the dietary intervention. In conclusion, plasma RBP4 in young men associates with components of the metabolic syndrome, but is not determined by birth weight and seems not to be involved in short-term high-fat diet-induced insulin resistance.

Serum peptide YY in response to short-term overfeeding in young men

BACKGROUND

Peptide YY (PYY), a gut hormone that inhibits appetite, has been linked to the development of obesity.

OBJECTIVE

This study investigated the nutritional regulation of PYY after 7 d of overfeeding (70% above normal energy requirements) in normal-weight, overweight, and obese men.

DESIGN

Sixty-nine men (aged 19-29 y) participated in the study. We analyzed the relation between fasting serum PYY before and after a 7-d overfeeding challenge in normal-weight, overweight, and obese men. In addition, we analyzed PYY with obesity-related phenotypes including weight, percentage body fat (measured by dual-energy X-ray absorptiometry), body mass index (BMI), total cholesterol, HDL, LDL, glucose, insulin, insulin resistance, and β cell function evaluated by the homeostasis model assessment of insulin resistance (HOMA-IR) and β cell function (HOMA-β) at baseline and in response to the energy surplus.

RESULTS

Fasting serum PYY concentrations at baseline were not significantly different between the normal-weight, overweight, and obese subjects on the basis of dual-energy X-ray absorptiometry or BMI. Although the PYY concentration significantly increased due to overfeeding, no differences were observed between adiposity statuses. In addition, basal PYY was negatively correlated with the changes of total cholesterol, HDL, and LDL in normal weight. In addition, the increase in PYY after overfeeding was positively correlated with HDL cholesterol and glucose in normal-weight subjects.

CONCLUSIONS

Our findings suggest that fasting PYY concentrations are not associated with adiposity status. Moreover, the 7-d overfeeding challenge significantly increased fasting PYY, which is likely a protective response to the positive energy balance.

Effect of postprandial lipemia on plasma concentrations of A-FABP, RBP-4 and visfatin

BACKGROUND AND AIMS

Several studies indicate that changes in the plasma concentrations of adipocyte-fatty acid binding protein (A-FABP), retinol binding protein-4 (RBP-4) and visfatin are associated with chronic states of insulin resistance. Recent studies have shown that postprandial lipemia induces an acute state of insulin resistance. The aim of this study was to investigate the effect of postprandial lipemia on the plasma concentrations of A-FABP, RBP-4 and visfatin.

METHODS AND RESULTS

In a within-subject crossover study, we administered a standardized high-fat meal to 24 healthy subjects (12 males and 12 females). Plasma concentrations of adipocytokines were measured in the morning after an overnight fast and during postprandial lipemia, i.e. 2, 4 and 6 hours after meal ingestion (postprandial experiment). To exclude potential confounding factors affecting the adipocytokine plasma concentrations, a control experiment without meal ingestion was performed over the same time period (postabsorptive control experiment). Comparing plasma concentrations of A-FABP, RBP-4 and visfatin between the postprandial and the postabsorptive control experiments, we found no significant differences. Within either of the two experiments, a decrease of A-FABP was noted reaching, however, statistical significance only in the postprandial experiment, i.e. 2 and 4 hours after meal ingestion.

CONCLUSION

Postprandial lipemia has no significant effect on the plasma concentrations of visfatin, A-FABP or RBP-4 in relation to their postabsorptive plasma profiles. We conclude that prolonged states of insulin resistance are required to affect plasma concentrations of these adipocytokines.

Association of RBP4 gene variants and serum HDL cholesterol levels in the Newfoundland population

Retinol-binding protein 4 (RBP4) is a novel adipokine that likely contributes to systemic insulin resistance and dyslipidemia. The role of genetic variations in RBP4 on phenotypes of glucose and lipid metabolism is not clear in humans. The purpose of this study was to examine five single-nucleotide polymorphisms (SNPs) in the RBP4 gene to determine their relationship with markers of insulin resistance and serum lipids in the CODING Study. The CODING Study consists of 1,836 subjects recruited from the genetically homogeneous population of Newfoundland and Labrador (NL), Canada. Serum glucose, insulin, homeostasis model assessment of insulin resistance (HOMA(IR)), HOMA for beta cell function (HOMA(beta)), total cholesterol (Chol), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), and triglycerides were determined after a 12-h fast. Five SNPs within RBP4 (rs3758539, G/A 5' flanking region; rs61461737, A/G intron; rs10882280, C/A intron; rs11187545, A/G intron; and rs12265684, C/G intron) were genotyped using TaqMan validated or functionally tested SNP genotyping assays. After correcting for multiple testing, we observed a significant association between the minor allele of two noncoding SNPs (rs10882280 and rs11187545) and higher serum HDL-C (P = 0.043 and 0.042, respectively). No significant associations were observed with any other parameter related to lipid metabolism. We also found no significant association between any variant sites and markers of insulin resistance. Our results suggest that genetic variations in RBP4 may play a role in the differences in serum HDL-C levels in the NL population.

Discriminated benefits of a Mediterranean dietary pattern within a hypocaloric diet program on plasma RBP4 concentrations and other inflammatory markers in obese subjects

Personalized nutritional strategies to treat obesity may specifically influence inflammatory markers, in addition to reduce body weight. In the present study, we evaluated the effect of a hypocaloric diet based on a Mediterranean dietary pattern (MDP) on nutritional status as well as on plasma concentrations of retinol binding protein-4 (RBP4) and other proinflammatory markers. Fourty-one subjects (24F/17M; age: 37 ± 7 years; BMI: 32.2 ± 3.9 kg/m²) were assigned to follow a MDP within a caloric-restricted diet over an 8-week period. Anthropometrical, clinical, and biochemical variables were measured at baseline and endpoint after the nutritional program. Dietary intervention resulted in a mean weight loss of -4.4 ± 2.5 kg (P < 0.001) and marked reductions (P < 0.05) in plasma concentrations of RBP4, leptin, C-reactive protein, complement C3, and tumor necrosis factor-alpha (TNFα). Individuals with a higher adherence to the MDP during the nutritional intervention presented differentially higher reductions (P < 0.05) in plasma RBP4, IL6, and TNFα. In addition, the increase in the Mediterranean diet score from baseline was a significant and independent predictor factor for the decrease in plasma RBP4 concentration (P < 0.05). In conclusion, our findings suggest that following a hypocaloric diet accompanying a high adherence to a MDP resulted in specific reductions on proinflammatory markers, in addition to a significant improvement in some metabolic syndrome features induced by weight loss, which could be a good combined strategy to treat obesity as well as related metabolic and inflammatory disorders.

Visfatin in human pregnancy: maternal gestational diabetes vis-à-vis neonatal birthweight

OBJECTIVE

Adipose tissue dysfunction, characterized by dysregulation of adipokines production and/or secretion, has been implicated in the pathophysiology of type-2 diabetes mellitus, a metabolic complication closely related to gestational diabetes mellitus (GDM). Recently, an association between circulating maternal visfatin, a novel adipokine with metabolic and immunoregulatory properties, and impaired glucose metabolism as well as with altered fetal growth, has been proposed. The aims of this study were to determine whether there is an association between maternal plasma visfatin concentration, GDM, and a large-for-gestational-age (LGA) newborn.

STUDY DESIGN

This cross-sectional study, included pregnant women at term in the following groups: 1) normal pregnancy and an appropriate-for-gestational-age (AGA) neonate (n=54); 2) normal pregnancy and an LGA newborn (n=47); 3) GDM and an AGA newborn (n=56); 4) GDM and an LGA newborn (n=45). The study population was further stratified by first trimester BMI (<25 vs. > or =25 kg/m(2)). Maternal plasma visfatin concentration was determined by ELISA. Parametric and non-parametric statistics were used for analysis.

RESULTS

1) Among women who delivered an AGA neonate, the median maternal plasma concentration of visfatin was higher in patients with GDM than in those with a normal pregnancy; 2) Among women with a normal pregnancy, those who delivered an LGA neonate had a higher median maternal plasma visfatin concentration than those who delivered an AGA neonate; 3) among patients with normal BMI, there were no significant differences in the median maternal plasma visfatin concentration between the four study groups; and 4) maternal GDM, as well as delivery of an LGA neonate were independently associated with a higher maternal plasma visfatin concentrations.

CONCLUSION

The linkage between increased maternal circulating visfatin and the presence of GDM or delivery of an LGA neonate supports the hypothesis that perturbation of adipokines homeostasis may play a role in the pathophysiology of GDM or excess fetal growth.

Maternal visfatin concentration in normal pregnancy

OBJECTIVE

Adipose tissue has now emerged as a powerful endocrine organ via the production of adipokines. Visfatin, a novel adipokine with diabetogenic and immuno-modulatory properties has been implicated in the pathophysiology of insulin resistance in patients with obesity and Type-2 diabetes mellitus. The aim of this study was to determine whether there are changes in the maternal plasma concentration of visfatin with advancing gestation and as a function of maternal weight.

STUDY DESIGN

In this cross-sectional study, maternal plasma concentrations of visfatin were determined in normal weight and overweight/obese pregnant women in the following gestational age groups: 1) 11-14 weeks (n=52); 2) 19-26 weeks (n=68); 3) 27-34 weeks (n=93); and 4) >37 weeks (n=60). Visfatin concentrations were determined by ELISA. Non parametric statistics were used for analysis.

RESULTS

1) The median maternal plasma visfatin concentration was higher in pregnant women between 19-26 weeks of gestation than that of those between 11-14 weeks of gestation (P<0.01) and those between 27-34 weeks of gestation (P<0.01); 2) among normal weight pregnant women, the median plasma visfatin concentrations of women between 19-26 weeks of gestation was higher than that of those between 11-14 weeks (P<0.01) and those between 27-34 weeks (P<0.01); and 3) among overweight/obese patients, the median maternal visfatin concentration was similar between the different gestational age groups.

CONCLUSION

The median maternal plasma concentration of visfatin peaks between 19-26 and has a nadir between 27-34 weeks of gestation. Normal and overweight/obese pregnant women differed in the pattern of changes in circulating visfatin concentrations as a function of gestational age.

Changes in the transcriptome of abdominal subcutaneous adipose tissue in response to short-term overfeeding in lean and obese men

BACKGROUND

Obesity is caused by the excessive accumulation of adipose tissue as a result of a chronic energy surplus. Little is known regarding the molecular mechanisms involved in the response to an energy surplus in human adipose tissue at the genomic level.

OBJECTIVE

The objective was to investigate changes in the transcriptome of abdominal subcutaneous adipose tissue after a positive energy challenge induced by overfeeding in both lean and obese subjects to identify novel obesity candidate genes.

DESIGN

A total of 26 men were recruited and classified on the basis of percentage body fat (measured by dual-energy X-ray absorptiometry) as lean (<20%) or obese (>25%) to participate in the baseline comparison. Sixteen men participated in the overfeeding study (8 lean and 8 obese). Adipose tissue biopsy samples were collected from all subjects at the subumbilical region. Global gene expression profiles were determined at baseline and after a 7-d hypercaloric diet at 40% above normal energy requirements by using whole human genome DNA microarrays.

RESULTS

Overfeeding induced differential expression in 45 genes. Six genes displayed a significant interaction effect between adiposity status and overfeeding treatment, including transferrin (TF), stearoyl-CoA desaturase (SCD), transaldolase 1 (TALDO1), cathepsin C (CTSC), insulin receptor substrate 2 (IRS2), and pyruvate dehydrogenase kinase, isozyme 4 (PDK4). Overfeeding resulted in changes in expression of these genes in lean subjects, whereas no significant changes were evident in obese subjects.

CONCLUSIONS

Differential expression of these 6 genes may represent a protective mechanism at the molecular level in lean subjects in response to an energy surplus. These genes represent valuable candidates for downstream studies related to obesity.

Carbohydrate restriction has a more favorable impact on the metabolic syndrome than a low fat diet

We recently proposed that the biological markers improved by carbohydrate restriction were precisely those that define the metabolic syndrome (MetS), and that the common thread was regulation of insulin as a control element. We specifically tested the idea with a 12-week study comparing two hypocaloric diets (approximately 1,500 kcal): a carbohydrate-restricted diet (CRD) (%carbohydrate:fat:protein = 12:59:28) and a low-fat diet (LFD) (56:24:20) in 40 subjects with atherogenic dyslipidemia. Both interventions led to improvements in several metabolic markers, but subjects following the CRD had consistently reduced glucose (-12%) and insulin (-50%) concentrations, insulin sensitivity (-55%), weight loss (-10%), decreased adiposity (-14%), and more favorable triacylglycerol (TAG) (-51%), HDL-C (13%) and total cholesterol/HDL-C ratio (-14%) responses. In addition to these markers for MetS, the CRD subjects showed more favorable responses to alternative indicators of cardiovascular risk: postprandial lipemia (-47%), the Apo B/Apo A-1 ratio (-16%), and LDL particle distribution. Despite a threefold higher intake of dietary saturated fat during the CRD, saturated fatty acids in TAG and cholesteryl ester were significantly decreased, as was palmitoleic acid (16:1n-7), an endogenous marker of lipogenesis, compared to subjects consuming the LFD. Serum retinol binding protein 4 has been linked to insulin-resistant states, and only the CRD decreased this marker (-20%). The findings provide support for unifying the disparate markers of MetS and for the proposed intimate connection with dietary carbohydrate. The results support the use of dietary carbohydrate restriction as an effective approach to improve features of MetS and cardiovascular risk.

Retinol to retinol-binding protein (RBP) is low in obese adults due to elevated apo-RBP

Elevated serum retinol-binding protein (RBP) concentration has been associated with obesity and insulin resistance, but accompanying retinol values have not been reported. Assessment of retinol is required to discriminate between apo-RBP, which may act as an adipokine, and holo-RBP, which transports vitamin A. The relations between serum RBP, retinol, retinyl esters, BMI, and measures of insulin resistance were determined in obese adults. Fasting blood (> or =8 h) was collected from obese men and women (n = 76) and blood chemistries were obtained. Retinol and retinyl esters were quantified by HPLC and RBP by ELISA. RBP and retinol were determined in age and sex-matched, nonobese individuals (n = 41) for comparison. Serum apo-RBP was two-fold higher in obese (0.90 +/- 0.62 microM) than nonobese subjects (0.44 +/- 0.56 microM) (P < 0.001). The retinol to RBP ratio (retinol:RBP) was significantly lower in obese (0.73 +/- 0.13) than nonobese subjects (0.90 +/- 0.22) (P < 0.001) and RBP was strongly associated with retinol in both groups (r = 0.71 and 0.90, respectively, P < 0.0001). In obese subjects, RBP was associated with insulin (r = 0.26, P < 0.05), homeostatic model assessment of insulin resistance (r = 0.29, P < 0.05), and quantitative insulin sensitivity check index (r = -0.27, P < 0.05). RBP was associated with BMI only when obese and nonobese subjects were combined (r = 0.25, P < 0.01). Elevated serum RBP, derived in part from apo-RBP, was more strongly associated with retinol than with BMI or measures of insulin resistance in obese adults. Investigations into the role of RBP in obesity and insulin resistance should include retinol to facilitate the measurement of apo-RBP and retinol:RBP. When evaluating the therapeutic potential of lowering serum RBP, consideration of the consequences of vitamin A metabolism is paramount.

Plasma retinol-binding protein is not a marker of insulin resistance in overweight subjects: a three year longitudinal study

OBJECTIVES

This longitudinal study investigated whether or not plasma retinol-binding protein (RBP), recently referred to as RBP4, was a marker of insulin resistance in overweight subjects.

METHODS

We measured anthropometric markers as well as RBP, fasting glucose and insulin in 206 overweight subjects and repeated these measurements 36 months later. Subjects were grouped according to fasting plasma glucose concentration at baseline and 36 months.

RESULTS

Subjects (n=51) with a normal basal fasting glucose (<5.6 mmol/L) who developed impaired fasting glucose (IFG) 3 years later (>or=5.6 mmol/L) showed a highly significant increase in both fasting insulin and insulin resistance, but importantly no change in plasma RBP. This group had a significant increase in body mass index (BMI). Subjects (n=101) with a normal fasting glucose at both baseline (<5.6 mmol/L) and 36 months showed no significant change in fasting insulin, insulin resistance, RBP or BMI. The remaining subjects had impaired basal fasting glucose and were not analysed on a group-wise basis. Overall, RBP correlated significantly, but inversely, with anthropometric measures, but not with fasting glucose, insulin or insulin resistance.

CONCLUSIONS

This is the first report of a long-term longitudinal study on RBP and the major finding is that subjects who developed insulin resistance showed no change in plasma RBP. On the basis of our results we consider that RBP cannot be construed as a marker of insulin resistance in overweight humans.