Effect of exercise training on A-FABP, lipocalin-2 and RBP4 levels in obese women

Effect of weight loss and liraglutide on neutrophil gelatinase-associated lipocalin levels among individuals with overweight and knee osteoarthritis: Exploratory analyses of a randomized controlled trial

Objective

Obesity is a major risk factor for osteoarthritis (OA). Adipose tissues may be linked to OA development through secretion of potential proinflammatory cytokines including neutrophil gelatinase-associated lipocalin (NGAL). Our objective was to assess changes in serum NGAL after a low-calorie diet (LCD) and subsequent glucagon-like peptide 1 receptor agonist (GLP-1 RA) treatment.

Design

A secondary analysis of a randomized, double-blinded, placebo-controlled trial in adults with overweight (BMI≥27 ​kg/m2) and symptomatic, early-to-moderate radiographic knee OA. Prior to randomization, participants underwent an 8-week LCD (week -8 to 0). Participants who lost min. 5 ​% of initial bodyweight were randomized 1:1 to liraglutide 3 ​mg/d or placebo for 52 weeks. Main outcome was change in serum NGAL from enrollment (week -8) to randomization (week 0). Other outcome was change in serum NGAL from week 0 to week 52 comparing liraglutide and placebo.

Results

168 participants were enrolled to the initial intensive diet intervention; 127 participants, with NGAL samples, were randomized. Following the 8-week diet intervention, NGAL concentrations rose by 93.0 ​ng/mL (95 ​% CI: 18.9 to 167.1, P ​= ​0.015), with no correlation to weight loss magnitude. 52 weeks of treatment with either liraglutide or placebo, liraglutide did not cause a greater decrease in serum NGAL (14.9 ​ng/ml, 95%CI: -92.1 to 121.7 ​ng/mL, P ​= ​0.78).

Conclusion

An intensive 8-week calorie restriction was associated with a rise in serum NGAL. Compared to placebo, 52 weeks of liraglutide did not cause additional changes in NGAL. This indicates a complex pattern of proinflammatory cytokine-release during hypocaloric diet interventions.

Trial registration

Clinicaltrials.gov: NCT02905864.

Association of Initial and Changes in Serum A-FABP Level With the Development and Improvement of Presarcopenia

CONTEXT

Several cross-sectional studies have reported the association between serum adipocyte fatty acid-binding protein (A-FABP) level and presarcopenia. However, data on the effects of serum A-FABP level and its changes over time on the development and improvement of presarcopenia are scarce.

OBJECTIVE

This study aimed to explore the association of serum A-FABP level with the incidence and improvement of presarcopenia in a community-based cohort, and further investigated the association of changes in serum A-FABP level with the incidence and improvement of presarcopenia.

METHODS

This longitudinal cohort study included 1496 adults (41.2% men; median age, 58 [53-63] years) in 2013 to 2014 and was followed up to 2015 to 2016. Participants underwent serum A-FABP level measurements at baseline and a follow-up visit. Visceral fat area (VFA) was measured using magnetic resonance imaging. Skeletal muscle mass (SMM) was estimated by bioelectrical impedance analysis and converted to a skeletal muscle index (SMI). Presarcopenia was defined as SMI less than 1 SD of the sex-specific mean for the young reference group.

RESULTS

During an average follow-up period of 2.1 years, baseline serum A-FABP level was positively associated with the incidence of presarcopenia (standardized by weight: risk ratio [RR] 3.22; 95% CI, 1.96-5.38; standardized by VFA: RR 2.11, 95% CI, 1.29-3.51) and negatively associated with the improvement of presarcopenia (standardized by weight: RR 0.66; 95% CI, 0.45-0.97; standardized by VFA: RR 0.71; 95% CI, 0.54-0.94), regardless of whether SMM was standardized by weight or VFA. Moreover, changes in serum A-FABP level provided additional information on the incidence and improvement of presarcopenia, independent of baseline serum A-FABP level (all P < .05).

CONCLUSION

Baseline serum A-FABP level and its changes were positively associated with the incidence and negatively associated with the improvement of presarcopenia.

The effect of 60 days of 6° head-down-tilt bed rest on circulating adropin, irisin, retinol binding protein-4 (RBP4) and individual metabolic responses in young, healthy males

Background

Alterations in the circulating concentrations and target-tissue action of organokines underpin the development of insulin resistance in microgravity and gravity deprivation. The purpose of this study was to examine changes in circulating adropin, irisin, retinol binding protein-4 (RBP4), and the metabolic response of healthy young males following 60 days of 6° head-down-tilt (HDT) bed rest, with and without reactive jump training (RJT), to explore links with whole-body and tissue-specific insulin sensitivity. To our knowledge, this is the first time that adropin, irisin, and RBP4 have been studied in HDT bed rest.

Methods

A total of 23 male subjects (29 ± 6 years, 181 ± 6 cm, 77 ± 7 kg) were exposed to 60 days of 6° HDT bed rest and randomized to a control (CTRL, n = 11) or a RJT (JUMP, n = 12) group (48 sessions with ≤4 min total training time per session). Circulating adropin, irisin, and RBP4 were quantified in fasting serum before and after HDT bed rest. A subanalysis was performed a posteriori to investigate individual metabolic responses post-HDT bed rest based on subjects that showed an increase or decrease in whole-body insulin sensitivity (Matsuda index).

Results

There were significant main effects of time, but not group, for decreases in adropin, irisin, Matsuda index, and liver insulin sensitivity following HDT bed rest (p < 0.05), whereas RBP4 did not change. The subanalysis identified that in a subgroup with decreased whole-body insulin sensitivity (n = 17), RBP4 increased significantly, whereas adropin, irisin, and liver insulin sensitivity were all decreased significantly following HDT bed rest. Conversely, in a subgroup with increased whole-body insulin sensitivity (n = 6), liver insulin sensitivity increased significantly after HDT bed rest, whereas adropin, irisin, and RBP4 did not change.

Conclusion

Investigating individual metabolic responses has provided insights into changes in circulating adropin, irisin, RBP4, in relation to insulin sensitivity following HDT bed rest. We conclude that adropin, irisin, and RBP4 are candidate biomarkers for providing insights into whole-body and tissue-specific insulin sensitivity to track changes in physiological responsiveness to a gravity deprivation intervention in a lean male cohort.

Enhancing cardiometabolic health: unveiling the synergistic effects of high-intensity interval training with spirulina supplementation on selected adipokines, insulin resistance, and anthropometric indices in obese males

This study investigated the combined effects of 12 weeks of high-intensity interval training (HIIT) and spirulina supplementation on adipokine levels, insulin resistance, anthropometric indices, and cardiorespiratory fitness in 44 obese males (aged 25-40 years). The participants were randomly assigned to one of four groups: control (CG), supplement (SG), training (TG), or training plus supplement (TSG). The intervention involved daily administration of either spirulina or a placebo and HIIT three times a week for the training groups. Anthropometric indices, HOMA-IR, VO2peak, and circulating adipokines (asprosin and lipocalin2, omentin-1, irisin, and spexin) were measured before and after the 12-week intervention. Post-intervention analysis indicated differences between the CG and the three interventional groups for body weight, fat-free mass (FFM), percent body fat (%BF), HOMA-IR, and adipokine levels (p < 0.05). TG and SG participants had increased VO2peak (p < 0.05). Spirulina supplementation with HIIT increased VO2peak, omentin-1, irisin, and spexin, while causing decreases in lipocalin-2 and asprosin levels and improvements in body composition (weight, %fat), BMI, and HOMA-IR. Notably, the combination of spirulina and HIIT produced more significant changes in circulating adipokines and cardiometabolic health in obese males compared to either supplementation or HIIT alone (p < 0.05). These findings highlight the synergistic benefits of combining spirulina supplementation with HIIT, showcasing their potential in improving various health parameters and addressing obesity-related concerns in a comprehensive manner.

Circulating lipocalin-2 and features of metabolic syndrome in community-dwelling older women: A cross-sectional study

Lipocalin-2 (LCN2) is released by several cell types including osteoblasts and adipocytes and has been suggested as a marker of renal dysfunction, metabolic syndrome (MetS) and type 2 diabetes (T2D). Whether LCN2 is linked to these diseases in older women remains unknown. This study investigated whether LCN2 is related to features of MetS and T2D in older women. This cross-sectional study included 705 non-diabetic women (mean age 75.1 ± 2.6 years) for MetS analysis and 76 women (mean age 75.4 ± 2.8 years) with T2D. Total circulating LCN2 levels were analysed using a two-step chemiluminescent microparticle monoclonal immunoassay. MetS was determined by a modified National Cholesterol Education Program Adult Treatment Panel III classification. Multivariable-adjusted logistic regression analysis was used to assess odds ratios between LCN2 quartiles and MetS. Women in the highest LCN2 quartile had approximately 3 times greater risk for MetS compared to women in the lowest quartile (OR 3.05; 95%CI 1.86-5.02). Women with T2D or MetS scores of ≥ 3 had higher LCN2 levels compared to women with a MetS score of 0 (p < 0.05). Higher LCN2 correlated with higher body mass index, fat mass, triglycerides and glycated haemoglobin and lower high-density lipoprotein cholesterol and estimated glomerular filtration rate (p < 0.05). Higher circulating levels of LCN2 are associated with worsened cardio-metabolic risk factors and increased odds of MetS and T2D in older women. Whether it can be used as a biomarker for identifying those at risk for MetS and T2D should be explored further.

Serum Osteocalcin, Sclerostin and Lipocalin-2 Levels in Adolescent Boys with Obesity over a 12-Week Sprint Interval Training

The aim of the study was to examine the effects of supervised cycling sprint interval training (SIT) on serum osteocalcin, lipocalin-2 and sclerostin levels, and bone mineral characteristics among obese adolescent boys. Untrained obese adolescent boys aged 13.4 ± 0.3 were assigned to either a 12-week SIT group (3 sessions/week), or a non-exercising control group who continued with their habitual everyday life. Serum osteocalcin, lipocalin-2 and sclerostin concentrations, and bone mineral values were assessed before and after intervention. After 12-week intervention, where 14 boys in both groups ended the study, there were no significant differences in serum osteokine levels between the groups after 12 weeks, while whole body bone mineral content and lower limb bone mineral density increased in the SIT group (p < 0.05). Change in body mass index was negatively correlated with the change in osteocalcin (r = -0.57; p = 0.034), and positively correlated with the change in lipocalin-2 levels (r = 0.57; p = 0.035) in the SIT group. Supervised 12-week SIT intervention improved bone mineral characteristics, but did not change osteocalcin, lipocalin-2 or sclerostin levels in adolescent boys with obesity.

Fecal and Urinary Adipokines as Disease Biomarkers

The use of biomarkers is of great clinical value for the diagnosis and prognosis of disease and the assessment of treatment efficacy. In this context, adipokines secreted from adipose tissue are of interest, as their elevated circulating levels are associated with a range of metabolic dysfunctions, inflammation, renal and hepatic diseases and cancers. In addition to serum, adipokines can also be detected in the urine and feces, and current experimental evidence on the analysis of fecal and urinary adipokine levels points to their potential as disease biomarkers. This includes increased urinary adiponectin, lipocalin-2, leptin and interleukin-6 (IL-6) levels in renal diseases and an association of elevated urinary chemerin as well as urinary and fecal lipocalin-2 levels with active inflammatory bowel diseases. Urinary IL-6 levels are also upregulated in rheumatoid arthritis and may become an early marker for kidney transplant rejection, while fecal IL-6 levels are increased in decompensated liver cirrhosis and acute gastroenteritis. In addition, galectin-3 levels in urine and stool may emerge as a biomarker for several cancers. With the analysis of urine and feces from patients being cost-efficient and non-invasive, the identification and utilization of adipokine levels as urinary and fecal biomarkers could become a great advantage for disease diagnosis and predicting treatment outcomes. This review article highlights data on the abundance of selected adipokines in urine and feces, underscoring their potential to serve as diagnostic and prognostic biomarkers.

Effect of 8 Weeks Aerobic Training and Saffron Supplementation on Inflammation and Metabolism in Middle-Aged Obese Women with Type 2 Diabetes Mellitus

Background: This study aimed to investigate the effects of 8-week aerobic training (AT) and saffron supplementation on inflammation and metabolism in middle-aged obese women with type 2 diabetes mellitus (T2DM). Methods: Thirty-two obese women with T2DM were randomly divided into four groups (n = 8 in all groups): saffron + training (ST), placebo + training (PT), saffron supplementation (SS), and placebo (P). The ST and PT groups performed eight weeks of aerobic training (AT) (three sessions/week at 60−75% HRmax). A daily dose of 400 mg saffron powder was consumed by the ST and SS groups for 8 weeks. Blood samples were taken after 12 h of fasting, 48 h before the first AT session, 48 h and two weeks after the last AT session. Results: AT, saffron supplementation, and their combination affected body mass index (BMI), homeostatic model assessment for insulin resistance (HOMA-IR), and serum levels of insulin, adiponectin, interleukin-6 (IL-6), high-density lipoprotein cholesterol (HDL-C), cholesterol, and triglyceride (TG) (p < 0.05). However, body weight, body fat percentage, and serum levels of glucose, resistin, tumor necrosis factor-alpha (TNF-α), irisin, and low-density lipoprotein cholesterol (LDL-C) showed significant changes in the ST group only (p < 0.05). In addition, a significant difference was seen between all factors in post-training and follow-up in the ST group (p < 0.05). Conclusions: Saffron supplementation at a dose of 400 mg/day, when combined with AT, could improve inflammation, metabolism, glycemic status, and lipid profile in T2DM patients, and these changes are sustainable at up to 2 weeks of detraining.

The effect of interval training on adipokine plasmatic levels in rats with induced myocardial infarction

Context: Exercise has been demonstrated to reduce pro-inflammatory while boosting anti-inflammatory adipokines; yet research in relation to Myocardial infarction (MI) is limited.Objective: The aim of this study was to investigate the effect of an interval exercise-training programme on concentrations of Lipocalin-2 and Adiponectin plasmatic levels in rats with induced MI.Materials and methods: The experimental study design comprised of three groups, including: a control group, MI control group and MI training group that participated in an interval training protocol for six weeks.Results: There was a significant increase in Lipocalin-2 levels in the MI interval training group when compared to the other groups.Discussion and conclusion: Although interval training has beneficial effects on adiponectin, it also increases Lipocalin-2 concentrations. Because Lipocalin-2 significantly contributes to the pathogenesis of atherosclerosis and adverse cardiac conditions, our findings suggest that interval training might be a counterproductive strategy to improve MI-related cardiac damage.

Blood and Urinary Biomarkers of Antipsychotic-Induced Metabolic Syndrome

Metabolic syndrome (MetS) is a clustering of at least three of the following five medical conditions: abdominal obesity, high blood pressure, high blood sugar, high serum triglycerides, and low serum high-density lipoprotein (HDL). Antipsychotic (AP)-induced MetS (AIMetS) is the most common adverse drug reaction (ADR) of psychiatric pharmacotherapy. Herein, we review the results of studies of blood (serum and plasma) and urinary biomarkers as predictors of AIMetS in patients with schizophrenia (Sch). We reviewed 1440 studies examining 38 blood and 19 urinary metabolic biomarkers, including urinary indicators involved in the development of AIMetS. Among the results, only positive associations were revealed. However, at present, it should be recognized that there is no consensus on the role of any particular urinary biomarker of AIMetS. Evaluation of urinary biomarkers of the development of MetS and AIMetS, as one of the most common concomitant pathological conditions in the treatment of patients with psychiatric disorders, may provide a key to the development of strategies for personalized prevention and treatment of the condition, which is considered a complication of AP therapy for Sch in clinical practice.

Effect of 6 weeks Pilates training along with dill supplementation on serum concentrations of nesfatin-1, lipocalin-2, and insulin resistance in females with overweight and obesity: A randomized controlled trial

Background:

This study aimed to investigate the effect of 6 weeks’ pilates training along with dill supplementation on serum concentrations of nesfatin-1, lipocaline-2, and insulin resistance in females with overweight and obesity.

Materials and Methods:

In this randomized controlled trial study, 45 overweight and obese females are randomly assigned to four groups: Pilates training + dill group (PDG) (n = 12), pilates training + placebo group (PPG) (n = 11), dill supplementation group (DG) (n = 11), and placebo group (PG) (n = 11). Participants of PDG and PPG performed pilates training for 6 weeks (60 min, 3 sessions per week). PDG and DG received dill tablet (three times a day, 6 weeks). Anthropometric measurements, glycemic markers, and blood samples were assessed before (pretest) and after (posttest) 6 weeks of intervention.

Results:

Results showed a significant increase in serum concentrations of nesfatin-1 in PDG compared to pretest (P = 0.001). Differences in the serum concentrations of nesfatin-1 in PDG were greater than PPG, DG, and PG (P = 0.01). Furthermore, results found in significant reduction in serum concentrations of lipocalin-2, body mass index (BMI), and waist-hip ratio (WHR) in PDG, PPG, and DG as compared to pretest (P > 0.05). Fasting glucose plasma (FGP) was significantly decreased in all three intervention groups PDG (P < 0.001), PPG (P < 0.001), and DG (P < 0.001) as compared to pretest. Differences in FGP were significantly higher in PDG than PPG, DG, and PG (P = 0.001). A significant reduction was found for insulin only in PDG after 6 weeks of intervention as compared to pretest (P = 0.03). Insulin resistance significantly decreased in PDG (P = 0.03) and PPG (P = 0.04) as compared to pretest. Body fat percent (BFP) was significantly decreased in PDG (P = 0.003), PPG (P = 0.006), and DG (P = 0.01). However, there were no significant inter-group differences in insulin resistance, insulin, serum concentrations of lipocalin-2, BMI, BFP, and WHR after 6 weeks of Pilates training along with dill supplementation (P > 0.05).

Conclusion:

We concluded that 6 weeks of Pilates training along with dill may be beneficial for improvements in serum concentrations of nesfatin-1 and FGP.

Lipocalin 2 as a link between ageing, risk factor conditions and age-related brain diseases

Chronic (neuro)inflammation plays an important role in many age-related central nervous system (CNS) diseases, including Alzheimer's disease, Parkinson's disease and vascular dementia. Inflammation also characterizes many conditions that form a risk factor for these CNS disorders, such as physical inactivity, obesity and cardiovascular disease. Lipocalin 2 (Lcn2) is an inflammatory protein shown to be involved in different age-related CNS diseases, as well as risk factor conditions thereof. Lcn2 expression is increased in the periphery and the brain in different age-related CNS diseases and also their risk factor conditions. Experimental studies indicate that Lcn2 contributes to various neuropathophysiological processes of age-related CNS diseases, including exacerbated neuroinflammation, cell death and iron dysregulation, which may negatively impact cognitive function. We hypothesize that increased Lcn2 levels as a result of age-related risk factor conditions may sensitize the brain and increase the risk to develop age-related CNS diseases. In this review we first provide a comprehensive overview of the known functions of Lcn2, and its effects in the CNS. Subsequently, this review explores Lcn2 as a potential (neuro)inflammatory link between different risk factor conditions and the development of age-related CNS disorders. Altogether, evidence convincingly indicates Lcn2 as a key constituent in ageing and age-related brain diseases.

High-Intensity Interval Training Improves Lipocalin-2 and Omentin-1 Levels in Men with Obesity

We investigated the effects of 12 weeks of high-intensity interval training (HIIT) on selected circulating adipokines and other cardiovascular diseases risks factors in men with obesity. Thirty men with obesity (age: 24.96 ± 3.11 year, BMI: 30.92 ± 1.04 kg/m2) were randomly assigned to HIIT and control groups. The HIIT group participated in a 12-week HIIT program (5×2 min interval bout at an intensity of 85-95% HRmax interspersed by 1 min passive recovery, three times per week), while the control group maintained their usual lifestyles. Blood lipids, insulin resistance, and select serum adipokines were assessed before and after 12 weeks of the intervention period. HIIT improved body composition and lipid profiles (p<0.05) and also decreased fasting insulin levels (p=0.001) and HOMA-IR (p=0.002) levels. Furthermore, HIIT increased levels of lipocalin-2 (p=0.002) while decreasing omentin-1 levels (p=0.001) in men with obesity. Changes in lcn2 and omentin-1 concentrations correlated with the changes in risk factors in the HIIT group (p<0.05). The results indicate that 12 weeks of supervised HIIT significantly improves both circulating concentrations of lcn2 and omentin-1, two recently described adipokines, and risk markers of cardiovascular diseases in men with obesity. Further research is necessary to understand the molecular mechanisms involved with these changes.

Sex-related differences of fatty acid-binding protein 4 and leptin levels in atrial fibrillation

AIMS

Adiposity plays a key role in the pathogenesis of atrial fibrillation (AF). Our aim was to study the sex differences in adipokines levels according to AF burden.

METHODS AND RESULTS

Two independent cohorts of patients were studied: (i) consecutive patients with AF undergoing catheter ablation (n = 217) and (ii) a control group (n = 105). (i) Adipokines, oxidative stress, indirect autonomic markers, and leucocytes mRNA levels were analysed; (ii) correlation between biomarkers was explored with heatmaps and Kendall correlation coefficients; and (iii) logistic regression and random forest model were used to determine predictors of AF recurrence after ablation. Our results showed that: (i) fatty acid-binding protein 4 (FABP4) and leptin levels were higher in women than in men in both cohorts (P < 0.01). In women, FABP4 levels were higher on AF cohort (20 ± 14 control, 29 ± 18 paroxysmal AF and 31 ± 17 ng/mL persistent AF; P < 0.01). In men, leptin levels were lower on AF cohort (22 ± 15 control, 13 ± 16 paroxysmal AF and 13 ± 11 ng/mL persistent AF; P < 0.01). (ii) In female with paroxysmal AF, there was a lower acetylcholinesterase and higher carbonic anhydrase levels with respect to men (P < 0.05). (iii) Adipokines have an important role on discriminate AF recurrence after ablation. In persistent AF, FABP4 was the best predictor of recurrence after ablation (1.067, 95% confidence interval 1-1.14; P = 0.046).

CONCLUSION

The major finding of the present study is the sex-based differences of FABP4 and leptin levels according to AF burden. These adipokines are associated with oxidative stress, inflammatory and autonomic indirect markers, indicating that they may play a role in AF perpetuation.

Understanding the role of oxidative stress in the incidence of metabolic syndrome and obstructive sleep apnea

BACKGROUND

Understanding the causes and risk factors of metabolic syndrome is important for promoting population health. Oxidative stress has been associated with metabolic syndrome, and also obstructive sleep apnea. These are two diseases which have common prognostic characteristics for heart disease. The aim of this study was to examine the role of oxidative stress in the concurrent presence of metabolic syndrome and obstructive sleep apnea in a working population.

METHODS

Participants were 163 artisan bakers in Shahroud, Iran, routinely exposed to significant heat stress and other oxidative stress indicators on a daily basis as part of their work. Using a cross-sectional design, data relevant to determining metabolic syndrome status according to International Diabetes Federation criteria, and the presence of obstructive sleep apnea according to the STOP-Bang score, was collected. Analyses included hierarchical binary logistic regression to yield predictors of the two diseases.

RESULTS

Hierarchical binary logistic regression showed that oxidative stress - alongside obesity, no regular exercise, and smoking - was an independent predictor of metabolic syndrome, but not obstructive sleep apnea. Participants who were obese were 28 times more likely to have metabolic syndrome (OR 28.59, 95% CI 4.91-63.02) and 44 times more likely to have obstructive sleep apnea (OR 44.48, 95% CI 4.91-403.28). Participants meeting metabolic syndrome criteria had significantly higher levels of malondialdehyde (p <  0.05) than those who did not. No difference in oxidative stress index levels were found according to obstructive sleep apnea status.

CONCLUSIONS

Our findings suggest that oxidative stress contributes to the onset of metabolic syndrome, and that obstructive sleep apnea is involved in oxidative stress. Whilst obesity, exercise, and smoking remain important targets for reducing the incidence of metabolic syndrome and obstructive sleep apnea, policies to control risks of prolonged exposure to oxidative stress are also relevant in occupations where such environmental conditions exist.

The effect of combined exercises on the plasma levels of retinol-binding protein 4 and its relationship with insulin resistance and hepatic fat content in postmenopausal women with nonalcoholic fatty liver disease

BACKGROUND

Evidence suggests increased serum levels of retinol-binding protein 4 (RBP4) in postmenopausal women with nonalcoholic fatty liver disease (NAFLD). This study investigated the effect of combined exercises on the plasma levels of RBP4 and its relationship with insulin resistance and hepatic fat content in these women.

METHODS

This quasi-experimental study randomly assigned 24 women with fatty liver and a mean age of 56.18±4.58 years to an experimental group and a control group. The experimental group participated in ten-week incremental endurance-resistance training as combined exercises three sessions a week. Fatty liver was diagnosed with ultrasound, RBP4 levels were measured and insulin resistance was determined using the Homeostatic Model Assessment for Insulin Resistance (HOMA-IR). Between-group data were analyzed using ANCOVA, within-group data using the dependent t-test and Wilcoxon test and relationships between RBP4 and variables using Spearman and Pearson correlation coefficients.

RESULTS

Ten weeks of combined exercises significantly decreased RBP4 levels (P=0.000), HOMA-IR (P=0.011) and hepatic fat levels (P=0.000) in the experimental group compared to in the controls. The posttest showed significant correlations between RBP4 levels and hepatic fat levels (P=0.002) and no correlations between RBP4 levels and insulin resistance (P=0.116).

CONCLUSIONS

Combined exercises significantly reduced serum levels of RBP4 in postmenopausal women with fatty liver. RBP4 was not related to insulin resistance and effects of RBP4 on hepatic fat regulation were independent of the effects of insulin resistance.

Recent advances and future avenues in understanding the role of adipose tissue cross talk in mediating skeletal muscle mass and function with ageing

Sarcopenia, broadly defined as the age-related decline in skeletal muscle mass, quality, and function, is associated with chronic low-grade inflammation and an increased likelihood of adverse health outcomes. The regulation of skeletal muscle mass with ageing is complex and necessitates a delicate balance between muscle protein synthesis and degradation. The secretion and transfer of cytokines, long non-coding RNAs (lncRNAs) and microRNAs (miRNAs), both discretely and within extracellular vesicles, have emerged as important communication channels between tissues. Some of these factors have been implicated in regulating skeletal muscle mass, function, and pathologies and may be perturbed by excessive adiposity. Indeed, adipose tissue participates in a broad spectrum of inter-organ communication and obesity promotes the accumulation of macrophages, cellular senescence, and the production and secretion of pro-inflammatory factors. Pertinently, age-related sarcopenia has been reported to be more prevalent in obesity; however, such effects are confounded by comorbidities and physical activity level. In this review, we provide evidence that adiposity may exacerbate age-related sarcopenia and outline some emerging concepts of adipose-skeletal muscle communication including the secretion and processing of novel myokines and adipokines and the role of extracellular vesicles in mediating inter-tissue cross talk via lncRNAs and miRNAs in the context of sarcopenia, ageing, and obesity. Further research using advances in proteomics, transcriptomics, and techniques to investigate extracellular vesicles, with an emphasis on translational, longitudinal human studies, is required to better understand the physiological significance of these factors, the impact of obesity upon them, and their potential as therapeutic targets in combating muscle wasting.

Association between adipocyte fatty acid-binding protein with left ventricular remodelling and diastolic function in type 2 diabetes: a prospective echocardiography study

Background

The relationship between adipocyte fatty acid-binding protein (AFABP) and cardiac remodelling has been reported in cross-sectional studies, although with conflicting results. Type 2 diabetes mellitus (T2DM) is associated with left ventricular (LV) hypertrophy and diastolic dysfunction, as well as elevated circulating AFABP levels. Here we investigated prospectively the association between AFABP with the longitudinal changes of cardiac remodelling and diastolic dysfunction in T2DM.

Methods

Circulating AFABP levels were measured in 176 T2DM patients without cardiovascular diseases (CVD) at baseline. All participants received detailed transthoracic echocardiography both at baseline and after 1 year. Multivariable linear and Cox regression analyses were used to evaluate the associations of circulating AFABP levels with changes in echocardiography parameters and incident major adverse cardiovascular events (MACE), respectively.

Results

The median duration between baseline and follow-up echocardiography assessments was 28 months. Higher sex-specific AFABP quartiles at baseline were associated with increase in LV mass and worsening of average E/e′ (all P < 0.01). Multivariable linear regression demonstrated that AFABP in the highest quartile was independently associated with both increase in LV mass (β = 0.89, P < 0.01) and worsening of average E/e′ (β = 0.57, P < 0.05). Moreover, multivariable Cox regression analysis showed that elevated baseline circulating AFABP level independently predicted incident MACE (HR 2.65, 95% CI 1.16–6.05, P < 0.05) after adjustments for age, sex, body mass index, glycated haemoglobin, hypertension, dyslipidemia and presence of chronic kidney disease.

Conclusion

Circulating AFABP level at baseline predicted the development of LV hypertrophy, diastolic dysfunction and MACE in T2DM patients without CVD.

Lipid chaperones and associated diseases: a group of chaperonopathies defining a new nosological entity with implications for medical research and practice

Fatty acid-binding proteins (FABPs) are lipid chaperones assisting in the trafficking of long-chain fatty acids with functions in various cell compartments, including oxidation, signaling, gene-transcription regulation, and storage. The various known FABP isoforms display distinctive tissue distribution, but some are active in more than one tissue. Quantitative and/or qualitative changes of FABPs are associated with pathological conditions. Increased circulating levels of FABPs are biomarkers of disorders such as obesity, insulin resistance, cardiovascular disease, and cancer. Deregulated expression and malfunction of FABPs can result from genetic alterations or posttranslational modifications and can be pathogenic. We have assembled the disorders with abnormal FABPs as chaperonopathies in a distinct nosological entity. This entity is similar but separate from that encompassing the chaperonopathies pertaining to protein chaperones. In this review, we discuss the role of FABPs in the pathogenesis of metabolic syndrome, cancer, and neurological diseases. We highlight the opportunities for improving diagnosis and treatment that open by encompassing all these pathological conditions within of a coherent nosological group, focusing on abnormal lipid chaperones as biomarkers of disease and etiological-pathogenic factors.

Effects of FABP knockdown on flight performance of the desert locust, Schistocerca gregaria

During migratory flight, desert locusts rely on fatty acids as their predominant source of energy. Lipids mobilized in the fat body are transported to the flight muscles and enter the muscle cells as free fatty acids. It has been postulated that muscle fatty acid binding protein (FABP) is needed for the efficient translocation of fatty acids through the aqueous cytosol towards mitochondrial β-oxidation. To assess whether FABP is required for this process, dsRNA was injected into freshly emerged adult males to knock down the expression of FABP. Three weeks after injection, FABP and its mRNA were undetectable in flight muscle, indicating efficient silencing of FABP expression. At rest, control and treated animals exhibited no morphological or behavioral differences. In tethered flight experiments, both control and treated insects were able to fly continually in the initial, carbohydrate-fueled phase of flight, and in both groups, lipids were mobilized and released into the hemolymph. Flight periods exceeding 30 min, however, when fatty acids become the main energy source, were rarely possible for FABP-depleted animals, while control insects continued to fly for more than 2 h. These results demonstrate that FABP is an essential element of skeletal muscle energy metabolism in vivo.

Investigation of galectin-3, lipocalin 2, retinol binding protein (RBP), small dense low-density lipoprotein (sdLDL) in patients with hirsutism

Introduction

Hirsutism is defined as excessive terminal hair in androgen-dependent areas in women. Adipose tissue is no longer regarded as a storage site for triglycerides or as a source of free fatty acids but is currently emerging as a key constituent of energy metabolism secreting numerous enzymes, cytokines, growth factors, and hormones.

Aim

To evaluate serum levels of galectin-3 (Gal3), lipocalin-2 (LCN2), retinol binding protein (RBP), and small dense low-density lipoprotein (sdLDL) in patients with hirsutism and patients co-presenting with polycystic ovary syndrome (PCOS) and hirsutism.

Material and methods

The study included 90 patients that were divided into three groups: (I) patients with idiopathic hirsutism (IH) (n = 30), (II) PCOS patients with hirsutism (H-PCOS) (n = 30), and (III) the control group (n = 30). Informed consent was obtained from each participant. Idiopathic hirsutism was scored using the modified Ferriman-Gallwey (mFG) scoring system and the diagnosis of PCOS was established based on the modified Rotterdam criteria. Human Gal3, LCN2, RBP, and sdLDL levels were analysed using a commercially available double-antigen sandwich enzyme-linked immunosorbent assay.

Results

No significant difference was found between the three groups with regard to serum Gal3, LCN2, RBP, and sdLDL levels (p > 0.05). Median values were higher in the H-PCOS group than in the other two groups: body weight (median: 76.5 kg) (p < 0.001), waist circumference (median: 82.5 cm) (p = 0.001).

Conclusions

No significant correlation was found between the adipokines that play a role in the aetiology of numerous diseases and some mediators of the lipid metabolism and hirsutism.

Effect of Training with or without Ziziphus Jujuba Extract on Cardiokines in Heart Tissue of Myocardial Infarcted Rats

BACKGROUND

Today, the importance of physical activity as a preventative way for cardiovascular disease has attracted much attention.The aim of this study is to investigate the effect of 6 weeks of interval training with or without extract of Ziziphus jujuba on lipocalcin-2 (LCN2) and adiponectin levels in heart tissue in male Wistar rats with myocardial infarction.

METHODS

Thirty male Wistar rats (mean weight, 180-220 g and age, 2-3 months) were divided into five groups, including (1) Healthy control; (2) Isoprenaline-treated group (ISO); (3) ISO + jujube extracts (JE); (4) Trained ISO rats; and (5) Trained ISO rats + JE. Exercise was performed (5 days/week, for 6 week including 54-min cycles with speed of 23 m/min and 54-min cycles with speed of 15 m/min). After 48 h of the last training session, the rats were sacrificed, and their heart tissue was excised. The significant level of statistical data was analyzed by one-way ANOVA test.

RESULTS

LCN2 levels significantly decreased in trained ISO rats + JE group after 6 weeks of interval training with JE consumption, compared to ISO group. However, the consumption of jujuba extracts with and without interval training did not show any significant changes in adiponectin levels of rat's heart tissue, compared to ISO (P < 0.05).

CONCLUSIONS

Because the LCN2 inflammatory factor decreased after 6 weeks of exercise and consumption of the extract, it seems that performing interval training with JE consumption can be an effective method in the cardiac rehabilitation phase after a heart attack.

Plasma retinol-binding protein-4 and tumor necrosis factor-α are reduced in postmenopausal women after combination of different intensities of circuit resistance training and Zataria supplementation

Purpose

Zataria is a plant with anti-inflammatory properties, which has been used for the treatment of many diseases. This study investigated the effect of different intensities of circuit resistance training and Zataria supplementation on plasma retinol-binding protein-4 (RBP-4) and tumor necrosis factor-α (TNF-α) in postmenopausal women.

Methods

Seventy-two postmenopausal women were divided on randomized order into six groups: Control (McGinley and Bishop in J Appl Physiol 121(6):1290-1305, 2016), Training 35% (T35%), Training 55% (T55%), Zataria (Özgünen et al. in Scand J Med Sci Sports 20:140-147, 2010), Zataria/Training 35% (ZT35%), and Zataria/Training 55% (ZT55%). Resist-ance training program included 12 exercise stations (each: 30 s, intensity: 35% and 55% of 1-RM) for 8 weeks (3 sessions/week). Daily (500 mg) Zataria was used after breakfast by participants in ZG, ZT35%, and ZT55% groups. Blood samples were taken 48 h before and after the first and last sessions of training.

Results

After the training period the percentage of body fat decreased significantly (P < 0.001) in all trained groups, whereas muscle mass increased significantly (P < 0.01) only in T55% and ZT55% groups. A significant decrease was observed for RBP-4 values (P < 0.05) after training in all groups except for ZG and CG. Also, RBP-4 was significantly lower (P < 0.05) in all groups as compared to CG at the post-test except for ZG. Moreover, significantly lower values (P < 0.05) were found in T55%, ZT35%, and ZT55% as compared to ZG in post-intervention. TNF-α values decreased significantly (P < 0.05) at the post-test as compared to pre-intervention in ZT35% and ZT55%. Also, TNF-α was significantly lower (P < 0.05) in ZT55% compared to CG and T35% in post-test.

Conclusions

The results demonstrate clearly that in postmenopausal women, circuit resistance training both at low and moderate intensities cause a greater reduction in RBP-4 and TNF-α when Zataria is supplemented in the diet during training.

Adapted Moderate Training Exercise Decreases the Expression of Ngal in the Rat Kidney: An Immunohistochemical Study

Neutrophil gelatinase-associated lipocalin (NGAL) is a biomarker of several injuries and is upregulated in inflammatory conditions. Vitamin D was shown to have anti-inflammatory effects and to increase after physical activity. This work aimed to assess, through immunohistochemistry, the effects of an adapted moderate training exercise (AMTE) on the expression of NGAL and vitamin D receptor (VDR) in the kidney and heart of rats. Sixteen rats were distributed into two groups: the sedentary control group and the experimental group, subjected to AMTE on the treadmill for 12 weeks. The results showed the basal expression of NGAL and VDR in both the heart and the kidney in sedentary rats; no differences in the expression of both NGAL and VDR in the heart; and a decreased NGAL and an increased VDR expression in the kidney of rats subjected to AMTE. These results suggest a possible protective role of AMTE on NGAL-associated injuries in the kidney, probably through the vitamin D signaling pathway. Our results represent an interesting preliminary data that may open new horizons in the management of NGAL-associated kidney injuries. However, further studies are needed to confirm these results and to comprehend the specific interaction between NGAL and VDR pathways in the kidney.

Fatty Acid-Binding Protein 4 in Cardiovascular and Metabolic Diseases

Fatty acid-binding proteins (FABPs), a family of lipid chaperones, contribute to systemic metabolic regulation via several lipid signaling pathways. Fatty acid-binding protein 4 (FABP4), known as adipocyte FABP (A-FABP) or aP2, is mainly expressed in adipocytes and macrophages and plays important roles in the development of insulin resistance and atherosclerosis in relation to metabolically driven low-grade and chronic inflammation, referred to as ‘metaflammation’. FABP4 is secreted from adipocytes in a non-classical pathway associated with lipolysis and acts as an adipokine for the development of insulin resistance and atherosclerosis. Circulating FABP4 levels are associated with several aspects of metabolic syndrome and cardiovascular disease. Ectopic expression and function of FABP4 in cells and tissues are also related to the pathogenesis of several diseases. Pharmacological modification of FABP4 function by specific inhibitors, neutralizing antibodies or antagonists of unidentified receptors would be novel therapeutic strategies for several diseases, including obesity, diabetes mellitus, atherosclerosis and cardiovascular disease. Significant roles of FABP4 as a lipid chaperone in physiological and pathophysiological conditions and the possibility of FABP4 being a therapeutic target for metabolic and cardiovascular diseases are discussed in this review.

Cord Blood Adipocyte Fatty Acid-Binding Protein Levels Correlate With Gestational Age and Birth Weight in Neonates

CONTEXT

Infants born small for gestational age (SGA) have increased risk for obesity and metabolic syndrome, but the underlying mechanisms are not fully elucidated. Adipocyte fatty acid-binding protein (AFABP) is an adipokine that has been implicated in modulation of insulin sensitivity and lipid metabolism. Higher plasma AFABP levels are associated with increased risk of metabolic syndrome and cardiovascular morbidity in adults. Alterations in AFABP levels during fetal growth have not been characterized.

OBJECTIVE

To examine AFABP levels in neonatal cord blood in relation to gestational age and birth weight.

DESIGN

A cross-sectional study of 361 neonates born at a tertiary academic center.

OUTCOME MEASURES

Plasma AFABP levels were measured by enzyme-linked immunosorbent assay. For comparison, venous samples from 26 adults were analyzed.

RESULTS

AFABP levels were higher in neonates compared with adults (P < 0.01). Preterm infants had higher AFABP levels [48.2 (31.2 to 73.3) ng/mL] compared with full-term infants [35.8 (25.1 to 51.5)] ng/mL, P < 0.01). There was a negative correlation between AFABP and gestational age (r = 0.28, P = 0.02). Among full-term infants, AFABP levels in SGA infants were lower [28.6 (24.2 to 37.3) ng/mL], compared with appropriate for gestational age [36.1 (25.5 to 50.4) ng/mL] and large for gestational age infants [45.0 (24.6 to 62.4) ng/mL, P < 0.05].

CONCLUSIONS

These associations may reflect the higher metabolic activity during fetal development. AFABP may also be involved in fetal growth and the association between SGA status and obesity and metabolic syndrome in later life.

Associations of objective physical activity with insulin sensitivity and circulating adipokine profile: the Framingham Heart Study

The purpose of this study was to explore the relation of physical activity (PA) and sedentary time (SED) to insulin sensitivity and adipokines. We assessed PA and SED using Actical accelerometers and insulin resistance (HOMA-IR) in 2109 participants (free of type 1 and 2 diabetes mellitus) from Framingham Generation 3 and Omni 2 cohorts (mean age 46 years, 54% women). Systemic inflammation (C-reactive protein [CRP]) and circulating adipokines were measured 6 years earlier. Steps per day, moderate-to-vigorous PA (MVPA) and SED per wear time (%SED) were predictor variables in multivariable regression analyses, with HOMA-IR, CRP and circulating adipokines as outcome measures. We reported that higher MVPA and more steps per day were associated with lower HOMA-IR, adjusting for %SED (β = -0.036, P = 0.002; β = -0.041, P = 0.005). Steps were inversely associated with CRP, but were directly associated with insulin-like growth factor (IGF)-1 levels (β = -0.111, P = 0.002; β = 3.293, P = 0.007). %SED was positively associated with HOMA-IR (β = 0.033, P < 0.0001), but non-significant after adjusting for MVPA (P = 0.13). %SED was associated with higher ratio of leptin/leptin receptor (sOB-R) and higher adipocyte fatty acid-binding protein (FABP)4 (β = 0.096, P < 0.0001; β = 0.593, P = 0.002). Our findings suggest differential influences of PA vs. SED on metabolic pathways, with PA modulating insulin resistance and inflammation, whereas SED influences FABPs.

Lipocalin-2 expression and serum levels as early predictors of type 2 diabetes mellitus in obese women

Obesity and diabetes are increasing in epidemic proportions globally. Lipocalin-2 (LCN-2) is an inflammatory adipocytokine and obesity-related marker of low-grade inflammation. We aimed to investigate, for first time, the possible role of LCN-2 expression and serum levels in prediction of impaired glucose tolerance (IGT) and type 2 diabetes mellitus (T2DM) among obese Egyptian women. This study included 188 obese women and 180 controls. Obese women were subdivided into three subgroups according to their fasting blood glucose, normal glucose tolerance (NGT), IGT and T2DM. Circulating LCN-2 expression levels were determined by real time polymerase chain reaction. Serum LCN-2 concentrations were assessed by ELISA. Our findings revealed that LCN-2 expression and serum levels were higher in obese women compared to lean controls. They were higher in IGT and T2DM obese cases than in NGT obese women. Receiver operating characteristic analyses revealed that LCN-2 expression level was a useful biomarker discriminating IGT from NGT and T2DM from IGT obese women (AUC were 0.735 and 0.740, respectively). It was an independent predictor of IGT and T2DM among obese women. Serum LCN-2 level was a useful biomarker discriminating IGT from NGT and T2DM from IGT obese women (AUC were 0.705 and 0.728, respectively). It was independent predictor of T2DM without predicting IGT among obese women. The power of combined LCN-2 serum levels and expression in discriminating between IGT from NGT and T2DM from IGT obese women was high (AUC = 0.717 and 0.741, respectively). In conclusion, LCN-2 expression and serum levels could discriminate IGT from NGT and T2DM from IGT obese women and early predicting T2DM among obese women. While, LCN-2 expression level was the independent predictor of IGT in obese women. Combination of both LCN-2 expression and serum levels improved their diagnostic value in early detection of IGT and T2DM among obese women. © 2017 IUBMB Life, 69(2):88-97, 2017.

Adipose-specific inactivation of JNK alleviates atherosclerosis in apoE-deficient mice

Both atherosclerosis and obesity, an independent atherosclerotic risk factor, are associated with enhanced systemic inflammation. Obesity is also characterized by increased adipose tissue inflammation. However, the molecular mechanism underlying the accelerated atherosclerosis in obesity remains unclear. In obesity, activation of c-Jun N-terminal kinase (JNK) contributes to adipose tissue inflammation. The present study investigated whether the suppression of fat inflammation through adipose-specific JNK inactivation could protect against atherosclerosis in mice. ApoE−/− mice were cross-bred with transgenic mice with adipose-specific expression of a dominant negative form of JNK (dnJNK) to generate apoE−/−/dnJNK (ADJ) mice. ADJ mice treated with a high-fat–high-cholesterol diet exhibited significant attenuations of visceral fat and systemic inflammation without changes in lipid or glucose metabolism, and were protected against atherosclerosis, when compared with apoE−/− mice. Lean apoE−/− mice that received transplantation of visceral fat from obese wild-type donor mice for 4 weeks showed exacerbated systemic inflammation and atherosclerotic plaque formation. Conversely, apoE−/− recipients carrying a visceral fat graft from obese dnJNK donors were protected against enhanced systemic inflammation and atherogenesis. The beneficial effects of adipose-specific JNK inactivation on atherogenesis in apoE−/− recipients were significantly compromised by continuous infusion of recombinant adipocyte–fatty acid-binding protein (A-FABP), previously shown to interact with JNK via a positive feedback loop to modulate inflammatory responses. Together these data suggested that enhanced atherosclerosis in obesity can be attributed, at least in part, to a distant cross-talk between visceral fat and the vasculature, mediated by the release of proinflammatory cytokines, such as A-FABP, from the inflamed visceral adipose tissue with JNK activation.

Is retinol binding protein 4 a link between adiposity and cancer?

Retinol binding protein 4 (RBP4) is synthesized in the liver where it binds vitamin A, retinol, and transports it to tissues throughout the body. It has been shown in some studies that the level of circulating RBP4 increases with body mass, and the protein has been implicated as a mediator in the development of insulin resistance and the metabolic disease. Adipose tissue serves as another site of RBP4 synthesis, accounting for its designation as an adipokine. In addition to its function as a transport protein, RBP4 serves as a signaling molecule which, by binding to the membrane receptor STRA6, triggers downstream activation of pro-oncogenic pathways including JAK2/STAT3/5. Taken together, available information suggests the possibility that RBP4 may be a link between obesity and cancer.

Biomarkers of Metabolic Syndrome: Biochemical Background and Clinical Significance

Biomarkers of the metabolic syndrome are divided into four subgroups. Although dividing them in groups has some limitations, it can be used to draw some conclusions. In a first part, the dyslipidemias and markers of oxidative stress are discussed, while inflammatory markers and cardiometabolic biomarkers are reviewed in a second part. For most of them, the biochemical background and clinical significance are discussed, although here also a well-cut separation cannot always be made. Altered levels cannot always be claimed as the cause, risk, or consequence of the syndrome. Several factors are interrelated to each other and act in a concerted, antagonistic, synergistic, or modulating way. Most important conclusions are summarized at the end of every reviewed subgroup. Genetic biomarkers or influences of various food components on concentration levels are not included in this review article.

Exercise and Adipose Tissue Macrophages: New Frontiers in Obesity Research?

Obesity is a major public health problem in the twenty-first century. Mutations in genes that regulate substrate metabolism, subsequent dysfunction in their protein products, and other factors, such as increased adipose tissue inflammation, are some underlying etiologies of this disease. Increased inflammation in the adipose tissue microenvironment is partly mediated by the presence of cells from the innate and adaptive immune system. A subset of the innate immune population in adipose tissue include macrophages, termed adipose tissue macrophages (ATMs), which are central players in adipose tissue inflammation. Being extremely plastic, their responses to diverse molecular signals in the microenvironment dictate their identity and functional properties, where they become either pro-inflammatory (M1) or anti-inflammatory (M2). Endurance exercise training exerts global anti-inflammatory responses in multiple organs, including skeletal muscle, liver, and adipose tissue. The purpose of this review is to discuss the different mechanisms that drive ATM-mediated inflammation in obesity and present current evidence of how exercise training, specifically endurance exercise training, modulates the polarization of ATMs from an M1 to an M2 anti-inflammatory phenotype.

Circulating Lipocalin 2 Levels Predict Fracture-Related Hospitalizations in Elderly Women: A Prospective Cohort Study

Lipocalin 2 (LCN2) or neutrophil gelatinase-associated lipocalin (NGAL) is expressed in a wide range of cells and pathological states. Mounting evidence suggests lipocalin 2 may be an important regulator of bone homeostasis. Recently it has been suggested LCN2 is a novel mechanoresponsive gene central to the pathological response to low mechanical force. We undertook a prospective study of 1009 elderly women over 70 years of age to study the association between circulating LCN2 and potential associated variables, including estimated glomerular filtration rate, physical activity, and baseline measures of hip bone density and heel bone quality. Osteoporotic fractures requiring hospitalizations were identified from the Western Australian Data Linkage System. Over 14.5 years, 272 (27%) of women sustained an osteoporotic fracture-related hospitalization; of these, 101 were hip fractures. Circulating LCN2 levels were correlated with body mass index and estimated glomerular filtration rate (r = 0.249, p < 0.001 and r = -0.481, p < 0.001, respectively) that modified the association with hip and heel bone measures. Per standard deviation increase in LCN2, there was a 30% multivariable-adjusted increase in the risk of any osteoporotic fracture (hazard ratio [HR] = 1.30, 95% confidence interval [CI] 1.13-1.50, p < 0.001). In participants with elevated LCN2 levels above the median (76.6 ng/mL), there was an 80% to 81% increase in the risk of any osteoporotic or hip fracture (HR = 1.81, 95% CI 1.38-2.36, p < 0.001 and HR = 1.80, 95% CI 1.16-2.78, p = 0.008, respectively). These associations remained significant after adjustment for total hip bone mineral density (p < 0.05). In conclusion, we have demonstrated that circulating LCN2 levels predict future risk of osteoporotic fractures requiring hospitalization. Measurement of LCN2 levels may improve fracture prediction in addition to current fracture risk factors in the elderly, particularly in those with impaired renal function.

Obesity, inflammation, and insulin resistance

White adipose tissue (WAT) is considered an endocrine organ. When present in excess, WAT can influence metabolism via biologically active molecules. Following unregulated production of such molecules, adipose tissue dysfunction results, contributing to complications associated with obesity. Previous studies have implicated pro- and anti-inflammatory substances in the regulation of inflammatory response and in the development of insulin resistance. In obese individuals, pro-inflammatory molecules produced by adipose tissue contribute to the development of insulin resistance and increased risk of cardiovascular disease. On the other hand, the molecules with anti-inflammatory action, that have been associated with the improvement of insulin sensitivity, have your decreased production. Imbalance of these substances contributes significantly to metabolic disorders found in obese individuals. The current review aims to provide updated information regarding the activity of biomolecules produced by WAT.

Effect of endurance training on retinol-binding protein 4 gene expression and its protein level in adipose tissue and the liver in diabetic rats induced by a high-fat diet and streptozotocin

AIMS/INTRODUCTION

The present study was designed to investigate from which tissues the decrease in retinol-binding protein 4 (RBP4) expression could contribute to the improvement of serum RBP4 and insulin resistance (IR) after endurance training.

MATERIALS AND METHODS

Male 7-week-old Wistar rats were randomly assigned into four groups including control (C), trained (T), diabetic control (DC) and trained diabetic (TD). At 8 weeks-of-age, diabetes was induced by a high-fat diet and intraperitoneal injection of low-dose streptozotocin (STZ; 35 mg/kg). Rats in the T and TD groups carried out a 7-week exercise program on a motorized treadmill (15-20 m/min for 20 min/day for 5 weeks), whereas the C and DC remained sedentary in their cages. Tissues gene expression and protein levels of RBP4 were assessed by using real-time polymerase chain reaction and western blot, respectively, while serum RBP4 was measured using an enzyme-linked immunosorbent assay kit.

RESULTS

Exercise significantly improved IR and reduced serum concentration of RBP4 in the TD group. This reduction of serum RBP4 was accompanied by decreased RBP4 protein expression in visceral fat tissue. In contrast, exercise had no significant effect on RBP4 expression in liver and subcutaneous fat tissue in the TD group. Exercise also significantly decreased RBP4 gene expression in visceral fat tissue and muscle, whereas the effect of exercise on liver RBP4 messenger ribonucleic acid expression was not significant.

CONCLUSIONS

The present study showed that the mechanism for RBP4 reducing the effect of endurance training could involve decreased RBP4 messenger ribonucleic acid expression and its protein level in adipose tissue in STZ-induced diabetic rats.

Effect of lifestyle modification on serum chemerin concentration and its association with insulin sensitivity in overweight and obese adults with type 2 diabetes

OBJECTIVE

Chemerin, a recently identified adipokine, has been linked to adiposity, insulin resistance, metabolic syndrome risk factors and inflammation. Here, we evaluated whether a 12-week lifestyle intervention in overweight and obese adults with type 2 diabetes could significantly affect the average blood glucose and serum chemerin levels over time.

DESIGN

Thirty-five overweight or obese subjects with type 2 diabetes were randomized to receive intensive lifestyle modification including supervised exercise sessions or usual care for 12 weeks. Anthropometric and clinical data were collected before the intervention and after 12 weeks.

RESULTS

Lifestyle intervention induced a significant decrease in HbA1c (-1·0 ± 0·5 vs 0·1 ± 0·6%, P < 0·001), BMI, total body fat content, serum lipocalin-2 and chemerin levels (-8·1 ± 21·6 vs + 8·2 ± 15·9 ng/ml, P = 0·021) and a significant increase in VO2 max after 12 weeks compared to the usual care group. Baseline chemerin levels were positively correlated with the homoeostasis model of assessment of insulin resistance (HOMA-IR), fasting insulin and the high-sensitivity C-reactive protein (hsCRP) and negatively correlated with insulin sensitivity index (ISI). Changes in the chemerin concentration during 12 weeks were independently negatively correlated with changes in ISI and positively correlated with changes in fasting plasma glucose, total cholesterol and lipocalin-2 levels.

CONCLUSIONS

A 12-week intensive lifestyle intervention significantly decreased serum chemerin level compared to usual care. Decrease in serum chemerin level was associated with improved insulin sensitivity, and this may be involved in the beneficial effects of lifestyle intervention in overweight and obese type 2 diabetic patients.

Short term resistance training enhanced plasma apoA-I and FABP4 levels in Streptozotocin-induced diabetic rats

BACKGROUND

Type 1 diabetes mellitus is associated with a high risk for early atherosclerotic complications. Altered lipids and lipoprotein metabolism in chronic diabetes mellitus is associated with pathogenesis of atherosclerosis and other cardiovascular diseases. The aim of this study was to investigate the effects of 4 weeks resistance training on plasma lipid profile, fatty acid binding protein (FABP) 4 and apolipoprotein (apo) A-I levels in type 1 diabetic rats.

METHODS

Thirty two male Wister rats (12-14 weeks old) were randomly divided into four groups: non-diabetic control; non-diabetic trained; diabetic control; diabetic trained. The rats in training groups were subjected to a resistance training program (3 days/wk, for 4 wk) consisted of climbing a ladder carrying a load suspended from the tail.

RESULTS

Diabetic inducing increased plasma apoA-I and decreased FABP4 levels compared with non-diabetic control group (respectively, P = 0.001 & P = 0.041). After 4 weeks' resistance training, plasma levels of apoA-I and FABP4 in the diabetic trained rats were significantly higher compared with the diabetic control group (respectively, P = 0.003 & P = 0.017). Plasma HDL-C level in diabetic trained group was higher than diabetic control group (P = 0.048). Liver triglycerides concentrations were significantly lower in both trained (non-diabetic and diabetic) groups compared with their control groups (respectively, P = 0.041 and P = 0.002).

CONCLUSION

These data indicated that resistance training may be an efficient intervention strategy to increase plasma apoA-I, HDL-C and FABP4 concentrations, along with decreases liver triglycerides in streptozotocin induced diabetic rats. Further research is needed to elucidate physiological significance of circulating FABP4 levels.

Lipocalin-2 increases fat oxidation in vitro and is correlated with energy expenditure in normal weight but not obese women

OBJECTIVE

The role of lipocalin-2 (Lcn2) was determined in regulating metabolism in cell, animal, and human models.

DESIGN AND METHODS

Adipocytes were treated with recombinant lipocalin-2 (rLcn2) to determine the effect on lipid metabolism. rLcn2 was injected into mice to determine the effect on metabolism in vivo. To assess the relationship between Lcn2 and fat oxidation (FatOx) in humans, normal weight (NW) and obese (OB) women were given three separate high fat (HF) meals followed by indirect calorimetry. The relationship between postprandial Lcn2 with macronutrient metabolism and total energy expenditure (TEE) using Pearson correlations was determined.

RESULTS

Lcn2 increased expression of genes involved in β-oxidation including peroxisome proliferator-activated receptor-δ in adipocytes, as well as (3) H labeled oleate β-oxidation. Lcn2 injected into chow-fed mice directly increased TEE by 18% after the first dark cycle (232 ± 1.4 cal vs. 341 ± 1.4 cal; PBS vs. Lcn2) and remained significantly elevated by 10% after the second dark cycle (296 ± 1.4 cal vs. 326 ± 1.4 cal; PBS vs. Lcn2). Lcn2 was correlated with TEE in all three HF meal challenges in NW but not OB females.

CONCLUSIONS

Lipocalin-2 is a novel adipokine that promotes FatOx and TEE and its function may be impaired in obesity.

Metabolically protective cytokines adiponectin and fibroblast growth factor-21 are increased by acute overfeeding in healthy humans

CONTEXT

Circulating levels of metabolically protective and adverse cytokines are altered in obese humans and rodent models. However, it is not clear whether these cytokines are altered rapidly in response to over-nutrition, or as a later consequence of the obese state.

METHODS

Forty sedentary healthy individuals were examined prior to and at 3 and 28 days of high fat overfeeding (+1250 kCal/day, 45% fat). Insulin sensitivity (hyperinsulinaemic-euglycaemic clamp), adiposity, serum levels of adiponectin and fibroblast growth factor-21 (FGF21), fatty acid binding protein-4 (FABP4), lipocalin-2 and plasminogen activator factor-1 (PAI1) were assessed. Statistics were performed by repeated measures ANOVA.

RESULTS

Overfeeding increased weight, body fat and liver fat, fasting glucose, insulin and reduced insulin sensitivity by clamp (all P <0.05). Metabolically protective cytokines, adiponectin and FGF21 were increased at day 3 of overfeeding (P ≤0.001) and adiponectin was also elevated at day 28 (P=0.001). FABP4, lipocalin-2 and PAI-1 were not changed by overfeeding at either time point.

CONCLUSION

Metabolically protective cytokines, adiponectin and FGF-21, were increased by over nutrition and weight gain in healthy humans, despite increases in insulin resistance. We speculate that this was in attempt to maintain glucose homeostasis in a state of nutritional excess. PAI-I, FABP4 and lipocalin 2 were not altered by overfeeding suggesting that changes in these cytokines may be a later consequence of the obese state.

CLINICAL TRIAL REGISTRATION

www.clinicaltrials.gov (NCT00562393).

Effects of a combined aerobic and resistance exercise program on C1q/TNF-related protein-3 (CTRP-3) and CTRP-5 levels

OBJECTIVE

To examine the effect of a combined exercise program on C1q/tumor necrosis factor-related protein (CTRP) 3 and CTRP-5 levels and novel adiponectin paralogs suggested to be links between metabolism and inflammation and to evaluate sex differences and association with cardiometabolic risk factors in humans with use of a newly developed ELISA.

RESEARCH DESIGN AND METHODS

This cross-sectional study explored the implications of CTRP-3 and CTRP-5 on cardiometabolic parameters in 453 nondiabetic Korean adults. In addition, we evaluated the impact of a 3-month combined exercise program on CTRP-3 and CTRP-5 levels in 76 obese women. The exercise program consisted of 45 min of aerobic exercise at an intensity of 60-75% of the age-predicted maximum heart rate (300 kcal/session) and 20 min of resistance training (100 kcal/session) five times per week.

RESULTS

Both CTRP-3 and CTRP-5 concentrations were significantly higher in women (P<0.001) than in men (P=0.030). In a multiple stepwise regression analysis, CTRP-3 levels were independently associated with age, sex, and triglyceride, LDL cholesterol, adiponectin, and retinol-binding protein 4 (RBP4) levels (R2=0.182). After 3 months of a combined exercise program, cardiometabolic risk factors, including components of metabolic syndrome, insulin resistance, and RBP4 levels, decreased significantly. In particular, CTRP-3 levels decreased significantly (median [interquartile range] 444.3 [373.8-535.0] to 374.4 [297.2-435.9], P<0.001), whereas CTRP-5 levels were slightly increased (34.1 [28.6-44.3] to 38.4 [29.8-55.1], P=0.048).

CONCLUSIONS

A 3-month combined exercise program significantly decreased CTRP-3 levels and modestly increased CTRP-5 levels in obese Korean women.

Association between plasma neutrophil gelatinase associated lipocalin level and obstructive sleep apnea or nocturnal intermittent hypoxia

BACKGROUND

Both obstructive sleep apnea (OSA) and a novel lipocalin, neutrophil gelatinase associated lipocalin (Ngal), have been reported to be closely linked with cardiovascular disease and loss of kidney function through chronic inflammation. However, the relationship between OSA and Ngal has never been investigated.

OBJECTIVES

To evaluate the relationship between Ngal and OSA in clinical practice.

METHODS

In 102 patients, polysomnography was performed to diagnose OSA and plasma Ngal levels were measured. The correlations between Ngal levels and OSA severity and other clinical variables were evaluated. Of the 46 patients who began treatment with continuous positive airway pressure (CPAP), Ngal levels were reevaluated after three months of treatment in 25 patients.

RESULTS

The Ngal level correlated significantly with OSA severity as determined by the apnea hypopnea index (r = 0.24, p = 0.01) and 4% oxygen desaturation index (ODI) (r = 0.26, p = 0.01). Multiple regression analysis showed that the Ngal level was associated with 4%ODI independently of other clinical variables. Compliance was good in 13 of the 25 patients who used CPAP. Although the OSA (4%ODI: 33.1±16.7 to 1.1±1.9/h, p<0.01) had significantly improved in those with good compliance, the Ngal levels were not significantly changed (60.5±18.1 before CPAP vs 64.2±13.9 ng/ml after CPAP, p = 0.27).

CONCLUSIONS

Plasma Ngal levels were positively associated with the severity of OSA. However, the contribution rate of OSA to systemic Ngal secretion was small and changes in Ngal levels appeared to be influenced largely by other confounding factors. Therefore, it does not seem reasonable to use the Ngal level as a specific biomarker of OSA in clinical practice.

Proteomic analysis of skeletal muscle in insulin-resistant mice: response to 6-week aerobic exercise

Aerobic exercise has beneficial effects on both weight control and skeletal muscle insulin sensitivity through a number of specific signaling proteins. To investigate the targets by which exercise exerts its effects on insulin resistance, an approach of proteomic screen was applied to detect the potential different protein expressions from skeletal muscle of insulin-resistant mice after prolonged aerobic exercise training and their sedentary controls. Eighteen C57BL/6 mice were divided into two groups: 6 mice were fed normal chow (NC) and 12 mice were fed high-fat diet (HFD) for 10 weeks to produce an IR model. The model group was then subdivided into HFD sedentary control (HC, n = 6) and HFD exercise groups (HE, n = 6). Mice in HE group underwent 6 weeks of treadmill running. After 6 weeks, mice were sacrificed and skeletal muscle was dissected. Total protein (n = 6, each group) was extracted and followed by citrate synthase, 2D proteome profile analysis and immunoblot. Fifteen protein spots were altered between the NC and HC groups and 23 protein spots were changed between the HC and HE groups significantly. The results provided an array of changes in protein abundance in exercise-trained skeletal muscle and also provided the basis for a new hypothesis regarding the mechanism of exercise ameliorating insulin resistance.

Adipocyte fatty acid binding protein: a novel adipokine involved in the pathogenesis of metabolic and vascular disease?

Adipocyte fatty acid binding protein (AFABP, also known as aP2 and FABP4) has recently been introduced as a novel fat-derived circulating protein. AFABP serum concentrations are positively correlated with markers of the metabolic syndrome and vascular disease in various cross-sectional and interventional studies. Furthermore, a small set of prospective studies indicates that high AFABP serum levels at baseline predict the risk for metabolic and vascular morbidity and mortality. Studies in Afabp (also known as Fabp4) knockout mice and AFABP inhibitor-treated animals suggest that total AFABP promotes insulin resistance, hypertriacylglycerolaemia and atherosclerosis by ligand/ligand delivery, as well as ligand-independent mechanisms. In contrast, the pathophysiological significance of circulating AFABP and the mechanisms leading to its release remain to be established. The current review summarises recent findings on the regulation and potential role of AFABP in metabolic and vascular disease.