The relationship between adipocyte fatty acid binding protein-4, retinol binding protein-4 levels and early diabetic nephropathy in patients with type 2 diabetes

Diagnostic value of retinol-binding protein 4 in diabetic nephropathy: a systematic review and meta-analysis

Objective

Diabetic nephropathy (DN) is a major microvascular complication of diabetes and the leading cause of end-stage renal disease. Early detection and prevention of DN are important. Retinol-binding protein 4 (RBP4) has been considered as a single diagnostic marker for the detection of renal impairment. However, the results have been inconsistent. The present meta-analysis aimed to determine the diagnostic potential of RBP4 in patients in type 2 diabetes mellitus (T2DM) with DN.

Methods

We searched PubMed, Web of Science, Embase, Wanfang and CNKI databases from inception until January 2024. The meta-analysis was performed by Stata version 15.0, and sensitivity, specificity, positive and negative likelihood ratios (PLR and NLR), diagnostic odds ratio (DOR) and area under the curve (AUC) were pooled. The Quality Assessment of Diagnostic Accuracy Studies-2 tool was utilized to assess the quality of each included study. In addition, heterogeneity and publication bias were evaluated.

Results

Twenty-nine studies were included in the meta-analysis. The pooled sensitivity and specificity were 0.76 [95% confidence interval (CI), 0.71-0.80] and 0.81 (95% CI, 0.76-0.85), respectively. The results showed a pooled PLR of 4.06 (95% CI, 3.16-5.21), NLR of 0.29 (95% CI, 0.24-0.36) and DOR of 13.76 (95% CI, 9.29-20.37). The area under the summarized receiver operating characteristic curve was given a value of 0.85 (95% CI, 0.82-0.88). No obvious publication bias existed in the Deeks' funnel plot asymmetry test.

Conclusion

Our findings suggest that RBP4 has a promising diagnostic value with good sensitivity and specificity for patients with T2DM with DN.

High-expression of FABP4 in Tubules is a Risk Factor for Poor Prognosis in DKD Patients

BACKGROUND

Lipid metabolism imbalance is involved in the mechanism of renal tubular injury in diabetic kidney disease (DKD). Fatty acid binding protein 4 (FABP4) has been reported to participate in cellular lipid toxicity. However, the expression of FABP4 in renal tissues of DKD and its correlation with clinical/ pathological parameters and prognosis have not been studied.

METHODS

A retrospective cohort study was conducted in 108 hospitalized Type 2 diabetes (T2D) patients with renal injury, including 70 with DKD and 38 with NDKD (non-DKD). Clinical features, pathological findings, and follow-up parameters were collected. Serum and urine FABP4 were detected by ELISA. An immunohistochemistry stain was used to determine FABP4 in renal tubulointerstitium. A double immunofluorescence stain was employed to assess FABP4- and CD68-positive macrophages. Correlation analysis, logistic regression models, receiver operating characteristic (ROC), and Kaplan-Meier survival curve were performed for statistical analysis.

RESULTS

DKD patients had increased expression of FABP4 and ectopic fat deposition in tubules. As shown by correlation analyses, FABP4 expression in renal tubules was positively correlated with UNAG (r=0.589, p=0.044) and ESRD (r=0.740, p=0.004). Multivariate regression analysis revealed that UNAG level was correlated with FABP4 expression level above median value (odds ratio:1.154, 95% confidence interval:1.009-1.321, p=0.037). High-expression of FABP4 in renal tubules of DKD was at an increased risk of ESRD. Increased FABP4 expression in inflammatory cells was also associated with ESRD in DKD.

CONCLUSION

High-expression of FABP4 is involved in the pathogenesis of renal tubular lipid injury and is a risk factor for poor prognosis in DKD patients.

The association between metabolic dysfunction-associated fatty liver disease and chronic kidney disease: A systematic review and meta-analysis

BACKGROUND AND AIMS

The term metabolic dysfunction-associated fatty liver disease (MAFLD) has been established to better define patients with fatty liver disease who also present with metabolic dysfunction. However, the association between MAFLD and chronic-kidney disease (CKD) remains elusive.

METHODS

. We conducted systematic literature searching across multiple databases-PubMed, EMBASE, Cochrane library, and Google Scholar up until June 9th, 2022. The main exposure was the diagnosis of MAFLD and nonalcoholic fatty liver disease (NAFLD) regardless of the diagnostic modalities being used. The outcome of interest was the prevalence or the incidence of CKD.

RESULTS

There were 355,886 subjects from 11 included studies with the period of follow up of 4.6-6.5 years. Meta-analysis of cross-sectional studies showed that MAFLD was associated with a higher prevalent CKD (OR 1.50, 95%CI [1.02-2.23]; test for overall effect Z = 2.04, p = 0.04; I² = 97.7%, p < 0.001) and incident CKD (adjusted HR 1.35, 95%CI [1.18-1.52]; test for overall effect Z = 15.47, p < 0.001; I² = 84.6%, p < 0.001) and did not vary between age, sex, comorbidities, study region, and follow-up duration. No difference in CKD prevalence was found between MAFLD and NAFLD patients. Significant liver fibrosis, but not steatosis in was associated with greater odds of developing CKD. More severe MAFLD was also associated with higher odds of developing CKD.

CONCLUSION

This present meta-analysis using a large population indicates a significant association between MAFLD and the prevalence and incidence of CKD.

Fatty acid-binding protein 4 in kidney diseases: From mechanisms to clinics

Considerable evidence indicated the relationship between fatty acid-binding protein 4 (FABP4) and kidney diseases. FABP4, a small molecular lipid chaperone, is identified to regulate fatty acid oxidation, inflammation, apoptosis, endoplasmic reticulum stress and macrophage-to-myofibroblast transition in kidney diseases. Many studies have shown that circulating FABP4 level is related to proteinuria, renal function decline, cardiovascular complications of end-stage renal disease and even the prognosis of kidney transplanted patients. Notably, pharmacological or genetic inhibition of FABP4 attenuated renal injury in the various experimental models of kidney diseases, making it promising to develop potential therapeutic strategies targeting FABP4 in kidney diseases. In this study, we updated and reviewed the mechanisms and clinical significance of FABP4 in kidney diseases.

Serum Levels of Adipocyte Fatty Acid-Binding Protein Are Associated with Rapid Renal Function Decline in Patients with Type 2 Diabetes Mellitus and Preserved Renal Function

BACKGROUND

Recent studies have demonstrated that the levels of adipocyte fatty acid-binding protein (A-FABP) are closely associated with diabetic kidney disease (DKD) in patients with type 2 diabetes mellitus (T2DM). This study aimed to examine the association between serum A-FABP level and rapid renal function decline in patients with T2DM and preserved renal function.

METHODS

This was a prospective observational study of 452 patients with T2DM and preserved renal function who had serial measurements of estimated glomerular filtration rate (eGFR). Rapid renal function decline was defined as an eGFR decline of >4% per year. The association between baseline serum A-FABP level and rapid renal function decline was investigated.

RESULTS

Over a median follow-up of 7 years, 82 participants (18.1%) experienced rapid renal function decline. Median A-FABP levels were significantly higher in patients with rapid renal function decline, compared to non-decliners (20.2 ng/mL vs. 17.2 ng/mL, P=0.005). A higher baseline level of A-FABP was associated with a greater risk of developing rapid renal function decline, independent of age, sex, duration of diabetes, body mass index, systolic blood pressure, history of cardiovascular disease, baseline eGFR, urine albumin creatinine ratio, total cholesterol, glycosylated hemoglobin, high-sensitivity C-reactive protein and use of thiazolidinedione, insulin, angiotensin-converting-enzyme inhibitors and angiotensin II-receptor blockers and statin (odds ratio, 3.10; 95% confidence interval, 1.53 to 6.29; P=0.002).

CONCLUSION

A high level of serum A-FABP is associated with an increased risk of rapid renal function decline in patients with T2DM and preserved renal function. This suggests that A-FABP could play a role in the progression of DKD in the early stages.

The Role of Circulating RBP4 in the Type 2 Diabetes Patients with Kidney Diseases: A Systematic Review and Meta-Analysis

BACKGROUND

Diabetic nephropathy is a common and serious complication of diabetes mellitus (DM) and is one of the leading causes of end-stage renal disease worldwide. Although there have been many investigations on biomarkers for DN, there is no consistent conclusion about reliable biomarkers. The purpose of this study was to perform a systematic review and meta-analysis of the role of circulating retinol-binding protein 4 (RBP4) in the type 2 diabetes mellitus (T2DM) patients with kidney diseases.

MATERIALS AND METHODS

We searched the PubMed, MEDLINE, EMBASE, and Web of Science databases for publications. For the 12 cross-sectional studies that we included in the review, we calculated standard mean differences (SMD) with 95% confidence intervals (CI) for continuous data when the applied scales were different. Risk of bias of included trials was assessed by using the Newcastle-Ottawa Scale.

RESULTS

RBP4 concentrations in the micro-, macro-, or micro+macroalbuminuria groups were significantly higher than those in the normal albuminuria group of T2DM patients [P = 0.001, SMD 1.07, 95% CI (0.41, 1.73)]. The estimated glomerular filtration rate (eGFR) was negatively associated with circulating RBP4 concentrations in patients with T2DM [summary Fisher's Z = -0.48, 95% CI (-0.69, -0.26), P < 0.0001]. The albumin-to-creatinine ratio (ACR) was positively associated with circulating RBP4 concentrations in patients with T2DM [summary Fisher's Z = 0.20, 95% CI (0.08, 0.32), P = 0.001].

CONCLUSION

The levels of circulating RBP4 were significantly higher both in T2DM subjects with micro/macroalbuminuria and in T2DM subjects with declined eGFR. The levels of circulating RBP4 were positively correlated with ACR but negatively correlated with eGFR. Circulating RBP4 could be a reliable biomarker for kidney diseases in T2DM.

Association between retinol binding protein 4 and diabetic retinopathy among type 2 diabetic patients: a meta-analysis

AIMS

The aim of this study was to investigate the association between retinol-binding protein 4 (RBP4) and diabetic retinopathy (DR) among patients with type 2 diabetes mellitus (T2DM).

METHODS

Databases PubMed, Embase, Web of Science, Chinese National Knowledge Infrastructure, VIP, and Wangfang were searched to July 30, 2019. The Newcastle-Ottawa Scale was applied to assess the quality of all identified studies, and those qualified were included in the meta-analysis. The Chi squared Q test and I² statistics were conducted to evaluate heterogeneity. Standardized mean differences (SMD) and 95% confidence intervals (CI) among RBP4 within the DR and T2DM without retinopathy (DWR) groups were pooled using the random effects model depending on the heterogeneity. Subgroup analyses were conducted among the groups having different diabetes duration, detection methods, body mass index, and total cholesterol and triglyceride levels. The funnel plot was used to assess publication bias.

RESULTS

Nineteen observational studies were included in our meta-analysis. RBP4 was significantly higher in both nonproliferative DR (SMD: 0.72, 95% CI 0.48-0.95, P < 0.00001) and proliferative DR (SMD: 2.68, 95% CI 1.69-3.67, P < 0.00001) groups despite high heterogeneity (I² = 87 and 97% in DR and PDR groups, respectively). Significant differences were noted among most subgroups (P < 0.05). Among those accompanied by hypercholesterolemia, the association between RBP4 and DR were unclear (P = 0.09).

CONCLUSIONS

Elevated RBP4 is strongly associated with DR and may play an essential role in its progression. Additional large-scale controlled studies are needed to confirm these findings.

Inhibition of fatty acid binding protein 4 attenuates gestational diabetes mellitus

Accumulatig evidence demonstrated that inflammation is associated with the development of gestational diabetes mellitus (GDM). Fatty acid-binding protein 4 (FABP4) was reported to be involved in immune response. However, the effect of FABP4 in GDM remians unclear. This study focused on the effect of FABP4 in GDM. C57BL/KsJdb/+ (db/+) mice were used for GDM mouse model . BMS-309403 (BMS) was used to inhibit FABP4 levels in GDM mouse model. IL-6 and TNF-α concentrations in serum were determined via ELISA. Serum glucose and insulin concentrations were tested using commercial glucometer and mouse insulin ELISA kit, respectively. IL-6 and TNF-α mRNA and protein levels were detected using RT-PCR and western blot, respectively. FABP4 levels were upregulated in GDM group compared with control group and were positively associated with serum IL-6 and TNF-α levels. FABP4 inhibition by BMS significantly decreased body weight and serum glucose concentrations, increasd serum insulin concentration, suppressed IL-6 and TNF-α expression both in the serum and the pancreas, enhanced little size and inhibited birth weight in GDM mouse model. Inhibition of FABP4 attenuates GDM in genetic mice.

Role of Fatty Acid Binding Protein 4 (FABP4) in Kidney Disease

Accumulating evidences indicated that obesity and metabolic syndrome were independent risk factors for the development and progression of kidney diseases. Apart from inflammation, lipotoxicity, and hemodynamic factors, adipokines have been proposed to play crucial roles in the relationship between kidney diseases and metabolic disorders. As one of the key adipokines, fatty acid binding protein 4 (FABP4), which is mainly expressed in adipocytes and macrophages, has recently been shown to be associated with renal dysfunction and kidney damage. Both clinical and experimental studies have proposed circulating FABP4 as a novel predictor for renal injuries, and it might also be a predictor for cardiovascular events in patients with end stage renal disease (ESRD). FABP4 has also been detected in the glomerular cells and epithelial tubular cells in mouse and human kidneys, and the expression of FABP4 in these cells has been involved in the pathogenesis of kidney diseases. In addition, experimental studies suggested that inhibition of FABP4 had protective effects on renal damage. Here, we reviewed current knowledge regarding the role of FABP4 in pathophysiological insights as well as its potential function as a predictor and therapeutic target for kidney diseases.

Associations between Fatty Acid-Binding Protein 4⁻A Proinflammatory Adipokine and Insulin Resistance, Gestational and Type 2 Diabetes Mellitus

There is ample scientific evidence to suggest a link between the fatty acid-binding protein 4 (FABP4) and insulin resistance, gestational (GDM), and type 2 (T2DM) diabetes mellitus. This novel proinflammatory adipokine is engaged in the regulation of lipid metabolism at the cellular level. The molecule takes part in lipid oxidation, the regulation of transcription as well as the synthesis of membranes. An involvement of FABP4 in the pathogenesis of obesity and insulin resistance seems to be mediated via FABP4-dependent peroxisome proliferator-activated receptor γ (PPARγ) inhibition. A considerable number of studies have shown that plasma concentrations of FABP4 is increased in obesity and T2DM, and that circulating FABP4 levels are correlated with certain clinical parameters, such as body mass index, insulin resistance, and dyslipidemia. Since plasma-circulating FABP4 has the potential to modulate the function of several types of cells, it appears to be of extreme interest to try to develop potential therapeutic strategies targeting the pathogenesis of metabolic diseases in this respect. In this manuscript, representing a detailed review of the literature on FABP4 and the abovementioned metabolic disorders, various mechanisms of the interaction of FABP4 with insulin signaling pathways are thoroughly discussed. Clinical aspects of insulin resistance in diabetic patients, including women diagnosed with GDM, are analyzed as well.

Prospective associations of circulating adipocyte fatty acid-binding protein levels with risks of renal outcomes and mortality in type 2 diabetes

AIMS/HYPOTHESIS

Elevated circulating adipocyte fatty acid-binding protein (AFABP) levels have been found to correlate with diabetic nephropathy staging in cross-sectional studies. However, it remains unclear whether these higher serum levels reflect a role of AFABP in the development of diabetic kidney disease (DKD), or simply result from its impaired renal clearance in DKD. Here we investigated prospectively the prognostic importance of serum AFABP level in the development of adverse renal outcomes in a large clinic-based cohort of participants with type 2 diabetes.

METHODS

Baseline serum AFABP levels were measured in 5454 Chinese participants from the Hong Kong West Diabetes Registry. The association between circulating AFABP levels and incident adverse renal outcomes-defined as a composite endpoint of a sustained 40% decline in eGFR, end-stage renal disease requiring renal replacement therapy or kidney transplantation, or renal deaths-was evaluated using multivariable Cox regression analysis.

RESULTS

Over a median follow-up of 5 years, 754 of the 5454 participants developed incident adverse renal outcomes. Elevated circulating AFABP levels were independently associated with incident adverse renal outcomes (HR 1.43, 95% CI 1.31, 1.57, p < 0.001) after adjustments for conventional risk factors for DKD progression. Importantly, the prognostic role of serum AFABP was independent of the baseline albuminuria status or eGFR levels of the study participants.

CONCLUSIONS/INTERPRETATION

Circulating AFABP levels were predictive of incident adverse renal outcomes, even in participants with relatively well-preserved kidney function at baseline, suggesting its potential to be a useful marker for early risk stratification in DKD.

High Levels of Serum Adipocyte Fatty Acid-binding Protein Predict Cardiovascular Events in Coronary Artery Disease Patients

Background: Adipocyte fatty acid-binding protein (A-FABP) is a cardiometabolic predictor of cardiovascular (CV) disease in humans. We evaluated the association between serum A-FABP levels and future CV events in patients with coronary artery disease (CAD). Methods: A total of 106 CAD patients were enrolled in this study between January and December 2012 and were followed-up until June 30, 2017. The primary endpoint was the incidence of major adverse CV events. Results: During a median follow-up period of 53 months, 44 CV events occurred. Patients with CV events presented higher systolic blood pressure (p = 0.020), total serum cholesterol (p = 0.047), and serum A-FABP levels (p < 0.001) compared with patients without CV events. Kaplan-Meier analysis showed that the cumulative incidence of CV events in the high A-FABP group (median A-FABP concentration of >17.63 ng/mL) was higher than that in the low A-FABP group (log-rank p < 0.001). Multivariate Cox analysis showed that triglycerides (hazard ratio (HR): 1.008, 95% confidence interval (CI): 1.001-1.016, p = 0.026) and serum A-FABP levels (HR: 1.027, 95% CI: 1.009-1.047, p = 0.004) were independently associated with CV events. Conclusion: Serum A-FABP level is a biomarker for future CV events in patients with CAD. Further prospective studies are needed to confirm the mechanisms underlying this association.

Serum Adipocyte Fatty Acid-Binding Protein 4 Levels Are Independently Associated with Radioisotope Glomerular Filtration Rate in Type 2 Diabetic Patients with Early Diabetic Nephropathy

Serum fatty acid-binding protein 4 (FABP4) has been linked to renal dysfunction. This study evaluated the association between serum FABP4 and the radioisotope glomerular filtration rate (rGFR) in type 2 diabetic patients (T2DM) with early diabetic nephropathy. Twenty healthy controls and 172 patients with T2DM were enrolled. Serum FABP4 and renal impairment biomarkers including urinary albumin-to-creatinine ratio (UACR), serum retinal-binding protein 4 (RBP4), urinary cystatin C-to-creatinine ratio (CysC/Cr), and neutrophil gelatinase-associated lipocalin-to-creatinine ratio (NGAL/Cr) were measured. Diethylenetriaminepentaacetic acid (99mTc-DTPA) was used to test rGFR. Serum FABP4 levels were higher in T2DM patients compared with the controls. There was no significant correlation between serum FABP4 and UACR in patients with T2DM. Multivariate stepwise regression analysis showed that, in patients with T2DM, FABP4 was significantly associated with rGFR while CysC/Cr and RBP4 were significantly associated with UACR independently. But UACR had no independent association with rGFR. NGAL/Cr had no significant correlation with either rGFR or UACR. FABP4 might be an early biomarker for diabetic nephropathy if combined with UACR.

Serum from pregnant women with gestational diabetes mellitus increases the expression of FABP4 mRNA in primary subcutaneous human pre-adipocytes

Objective

Gestational diabetes mellitus (GDM) is defined as glucose intolerance first detected during pregnancy. It can result in pregnancy complications such as birth injury, stillbirth. Fatty acid-binding protein 4 (FABP4), found in adipose tissue, is associated with insulin resistance, and type 2 diabetes. The aim of this study was to investigate whether FABP4 in the placenta and decidua of pregnant women with GDM is higher than that in normal pregnant women, and whether serum from pregnant women with GDM may cause adipocytes to secrete more FABP4 than does serum from a normal pregnant group.

Methods

We obtained placentas, deciduas, and serum from 12 pregnant women with GDM and 12 normal pregnant women and performed enzyme-linked immunosorbent assay, real time quantitative-polymerase chain reaction. We cultured human pre-adipocytes for 17 days with GDM and non-GDM serum and performed western blot, real time quantitative-polymerase chain reaction, and oil red O staining.

Results

Expression of FABP4 in serum, placenta and decidua of pregnant women with GDM was significantly higher than that in normal pregnant women. Serum from pregnant women with GDM increased the expression of FABP4 mRNA and decreased the expression of adiponectin mRNA in human pre-adipocytes significantly. Adipocyte cultured in GDM serum showed significantly greater lipid accumulation than those cultured in normal serum.

Conclusion

Our results suggest that FABP4 is higher in placenta and decidua from pregnant women with GDM. Increased circulating FABP4 in maternal serum from pregnant women with GDM may originate from adipocytes and the placenta. Circulating FABP4 can induce increased insulin resistance and decreased insulin sensitivity.

Contribution of serum adipocyte fatty acid-binding protein levels to the presence of microalbuminuria in a Chinese hyperglycemic population

AIMS/INTRODUCTION

Individuals with type 2 diabetes mellitus are vulnerable to micro- and macrovascular complications in the presence of microalbuminuria. Adipocyte fatty acid-binding protein (A-FABP) was proposed as an indicator for albuminuria in patients with diabetes. The present study aimed to explore the associations between serum A-FABP levels and microalbuminuria in the hyperglycemic population.

MATERIALS AND METHODS

Serum A-FABP levels were detected using sandwich enzyme-linked immunosorbent assay. Microalbuminuria was identified by urinary albumin-to-creatinine ratio (UACR), when the value was between 30-300 mg/g. The participants were divided into the subgroups based on sex and the status of impaired glucose regulation or newly diagnosed type 2 diabetes mellitus.

RESULTS

A total of 939 participants, consisting of 436 men and 503 women, were enrolled. Serum levels of A-FABP were much higher in participants with microalbuminuria than those without microalbuminuria. This result held true for all subgroups (all P < 0.05). For Spearman's correlation analyses, serum A-FABP levels showed a positive relationship with the UACR in men and women (both P < 0.01). Multiple stepwise regression analysis showed that serum A-FABP levels were independently and positively correlated with UACR in both sexes (men: standardized β = 0.256, P < 0.001; women: standardized β = 0.155, P = 0.001). This relationship remained significant in every subgroup (all P < 0.01).

CONCLUSIONS

For hyperglycemic individuals, serum A-FABP levels increased in the presence of microalbuminuria. Serum A-FABP levels were identified as an independent factor positively associated with the UACR.

High Serum Adipocyte Fatty Acid Binding Protein Is Associated with Metabolic Syndrome in Patients with Type 2 Diabetes

Adipocyte fatty acid binding protein (A-FABP) is a key mediator of obesity-related metabolic syndrome (MetS). The aim of this study was to evaluate the relationship between A-FABP concentration and MetS in type 2 diabetes mellitus (DM) patients. Fasting blood samples were obtained from 165 type 2 DM volunteers. MetS and its components were defined using diagnostic criteria from the International Diabetes Federation. Among 165 DM patients, 113 patients (68.5%) had MetS. Diabetic persons who had MetS had significantly higher A-FABP levels (P < 0.001) than those without MetS. Female DM persons had higher A-FABP level than man (P < 0.001). No statistically significant differences in A-FABP levels were found in use of statin, fibrate, or antidiabetic drugs. Multivariate forward stepwise linear regression analysis revealed that body fat mass (P < 0.001), logarithmically transformed creatinine (log-creatinine; P < 0.001), female DM patients (P < 0.001), and logarithmically transformed high sensitive C-reactive protein (log-hs-CRP; P = 0.013) were positively correlated, while albumin (P = 0.004) and glomerular filtration rate (GFR; P = 0.043) were negatively correlated with serum A-FABP levels in type 2 DM patients. In this study, higher serum A-FABP level was positively associated with MetS in type 2 DM patients.

Serum vaspin and adiponectin levels in patients with prolactinoma

BACKGROUND

Studies investigating serum vaspin and adiponectin levels in patients with prolactinoma are inconclusive. The aim of this study was to evaluate serum vaspin and adiponectin levels in patients with prolactinoma and healthy controls.

METHODS

A total of 42 prolactinoma patients (Group 1, 21 patients; Group 2, 21 patients) and 30 healthy controls were enrolled in the study. Group 1 consisted of newly diagnosed patients who were never treated or had not received a dopamine agonist (DA) within 6 months prior to screening. Group 2 consisted of prolactinoma patients who were on DA treatment for at least 6 months at the time of screening. The control group (group 3) consisted of healthy controls.

RESULTS

Patients with prolactinoma had higher homeostasis model assessment of insulin resistance and lower quantitative insulin sensitivity check index values in comparison to healthy controls (p < 0.001 for both). Serum levels of adiponectin and vaspin were also significantly lower in prolactinoma patients when compared to the control group (p < 0.01 and p < 0.001, respectively). Following adjustment for confounding factors, the respective odds ratios for prolactinoma in patients in the lower subgroup compared with those in the higher subgroup for adiponectin and vaspin were 2.733 (0.621-12.035; p > 0.05) and 5.041 (1.191-21.339; p < 0.05).

CONCLUSION

This is the first study to demonstrate the presence of low vaspin levels in patients with prolactinomas. Further studies are needed to help establish the roles of vaspin and adiponectin in prolactinoma patients.

Year in review 2013: Critical Care--metabolism

Novel insights into the metabolic alterations of critical illness, including new findings on association between blood glucose at admission and poor outcome, were published in Critical Care in 2013. The role of diabetic status in the relation of the three domains of glycemic control (hyperglycemia, hypoglycemia, and glycemic variability) was clarified: the association between mean glucose, high glucose variability, and ICU mortality was stronger in the non-diabetic than in diabetic patients. Improvements in the understanding of pathophysiological mechanisms of stress hyperglycemia were presented. Novel developments for the management of glucose control included automated closed-loop algorithms based on subcutaneous glucose measurements and microdialysis techniques. In the field of obesity, some new hypotheses that could explain the ‘obesity paradox’ were released, and a role of adipose tissue in the response to stress was suggested by the time course of adipocyte fatty-acid binding protein concentrations. In the field of nutrition, beneficial immunological effects have been associated with early enteral nutrition. Early enteral nutrition was significantly associated with potential beneficial effects on the phenotype of lymphocytes. Uncertainties regarding the potential benefits of small intestine feeding compared with gastric feeding were further investigated. No significant differences were observed between the nasogastric and nasojejunal feeding groups in the incidence of mortality, tracheal aspiration, or exacerbation of pain. The major risk factors to develop diarrhea in the ICU were described. Finally, the understanding of disorders associated with trauma and potential benefits of blood acidification was improved by new experimental findings.

Associations between tissue visfatin/nicotinamide, phosphoribosyltransferase (Nampt), retinol binding protein-4, and vaspin concentrations and insulin resistance in morbidly obese subjects

Visfatin/Nampt, vaspin, and retinol binding protein-4 (RBP-4) play an important role in insulin resistance. The objectives of this study were to measure visfatin/Nampt, vaspin, and RBP-4 concentrations in blood, liver, muscle, subcutaneous, omental, and mesenteric adipose tissues in morbidly obese subjects and investigate their relationship to insulin resistance. Blood and tissue samples were collected from 38 morbidly obese subjects during Roux-en-Y surgery. Insulin resistance biomarkers were measured using standard kits. Visfatin/Nampt, vaspin, and RBP-4 gene expression levels in tissues were measured using real-time PCR. Their protein concentrations in blood and tissues were measured using ELISA kits. Diabetic subjects had significantly higher homeostasis model of assessment-insulin resistance and age and lower blood HDL-cholesterol concentrations than nondiabetic and prediabetic subjects. Diabetic and prediabetic subjects had significantly higher blood concentrations of visfatin/Nampt and vaspin than nondiabetic subjects. Liver RBP-4 concentrations were positively associated with blood glucose concentrations. Blood insulin resistance biomarker levels were positively associated with visfatin/Nampt concentrations in omental adipose tissue and liver, and vaspin concentrations in mesenteric adipose tissue. In conclusion, the correlations of visfatin/Nampt, vaspin, and RBP-4 with insulin resistance are tissue dependent.

Serum adipocyte fatty acid-binding protein levels are independently associated with sarcopenic obesity

AIMS

Adipocyte fatty acid-binding protein (A-FABP) plays a key role in obesity-related insulin resistance and inflammation which may be involved in the pathogenesis of sarcopenic obesity (SO). This study examined the association of SO with serum A-FABP levels in Korean adults.

METHODS

Two hundred ninety eight adults aged 20-70 years were examined using dual X-ray absorptiometry and computed tomography and measuring serum A-FABP levels. Sarcopenia was defined as the appendicular skeletal muscle mass (ASM) divided by weight (%) of <1 SD below the mean values of young adults in both sexes. Obesity was defined as visceral fat area (VFA) ≥ 100 cm(2).

RESULTS

Serum A-FABP levels were higher in groups with SO compared to non-SO groups in both men and women. In the unadjusted model, serum A-FABP levels were positively associated with VFA and negatively associated with ASM/weight. Even after adjusting for possible confounding factors, ASM/weight was found to be independently and negatively associated with serum A-FABP levels. In addition, multiple logistic regression analysis showed that increased serum levels of A-FABP were independently associated with the presence of SO.

CONCLUSIONS

The present findings indicate that serum A-FABP levels may be valuable markers of the presence of SO.

Association between serum adipocyte fatty-acid binding protein concentrations, left ventricular function and myocardial perfusion abnormalities in patients with coronary artery disease

BACKGROUND

Adipokines, including adipocyte fatty acid-binding protein (A-FABP), have been demonstrated to be involved in the pathogenesis of atherosclerosis. In the present study, we investigated the association of circulating A-FABP level with severity of myocardial perfusion abnormalities analyzed by Tl-201 dipyridamole single-photon emission computed tomography.

METHODS

A total of 170 patients with coronary artery disease (CAD) from cardiovascular clinics were enrolled in the study. Serum A-FABP levels, echocardiography, and stress myocardial perfusion imaging results were analyzed.

RESULTS

Compared with the patients with mild CAD (summed stress score [SSS] ≤ 8), those with moderate to severe CAD (SSS > 8) had significantly higher A-FABP concentrations. However, the difference was attenuated in the subgroup of patients with heart failure. In the correlation analyses, A-FABP level was correlated with age, body mass index, waist circumference, levels of creatinine, fasting glucose, high-sensitivity C-reactive protein, N-terminal pro-brain natriuretic peptide, adiponectin, and several echocardiographic parameters, including left ventricular ejection fraction. Multivariate logistic regression analysis demonstrated that the A-FABP level was not only associated with higher SSS (odds ratio, 1.30; 95% confidence interval [CI], 1.01-1.69; P = 0.048), but also an independent risk factor for heart failure (odds ratio 2.71, 95% CI, 1.23-5.94; P = 0.013).

CONCLUSIONS

Serum A-FABP levels not only were associated with myocardial perfusion abnormalities and left ventricular function, but also predicted the presence of heart failure in our patients with CAD.

Higher serum retinol binding protein 4 may be a predictor of weak metabolic control in chinese patients with type 2 diabetes mellitus

OBJECTIVE

To investigate relationships between serum levels of retinol binding protein 4 (RBP4) and clinical and metabolic variables in Chinese patients with type 2 diabetes mellitus.

METHODS

A total of 513 patients (286 males/227 females) provided clinical and lifestyle data and blood and urine samples for analysis. Patients were stratified into four quartile groups according to serum RBP4 concentrations.

RESULTS

RBP4 concentration was independently associated with gender, systolic blood pressure, serum triglyceride and creatinine levels, and estimated glomerular filtration rate (eGFR). Hypertension, dyslipidaemia, micro albuminuria and impaired eGFR (<60 ml/min per 1.73 m2) were significantly more prevalent in patients with the highest RBP4 levels than in those with the lowest levels. Increased serum RBP4 was associated with increased risk of hypertension, dyslipidaemia, micro albuminuria and impaired eGFR after adjusting for gender, age, body mass index and duration of diabetes.

CONCLUSION

Serum RBP4 may be a useful marker of overall metabolic control in Chinese patients with type 2 diabetes mellitus.

Serum adipocyte fatty acid-binding protein levels in patients with critical illness are associated with insulin resistance and predict mortality

INTRODUCTION

Hyperglycemia and insulin resistance are commonplace in critical illness, especially in patients with sepsis. Recently, several hormones secreted by adipose tissue have been determined to be involved in overall insulin sensitivity in metabolic syndrome-related conditions, including adipocyte fatty-acid binding protein (A-FABP). However, little is known about their roles in critical illness. On the other hand, there is evidence that several adipose tissue gene expressions change in critically ill patients.

METHODS

A total of 120 patients (72 with sepsis, 48 without sepsis) were studied prospectively on admission to a medical ICU and compared with 45 healthy volunteers as controls. Various laboratory parameters and metabolic and inflammatory profiles were assessed within 48 hours after admission. Clinical data were collected from medical records.

RESULTS

Compared with healthy controls, serum A-FABP concentrations were higher in all critically ill patients, and there was a trend of higher A-FABP in patients with sepsis. In multivariate correlation analysis in all critically ill patients, the serum A-FABP concentrations were independently related to serum creatinine, fasting plasma glucose, total cholesterol, TNF-alpha, albumin, and the Acute Physiology and Chronic Health Evaluation II scores. In survival analysis, higher A-FABP levels (> 40 ng/ml) were associated with an unfavorable overall survival outcome, especially in sepsis patients.

CONCLUSIONS

Critically ill patients have higher serum A-FABP concentrations. Moreover, A-FABP may potentially serve as a prognostic biomarker in critically ill patients with sepsis.

Effects of bariatric surgery on adipokine-induced inflammation and insulin resistance

Over a third of the US population is obese and at high risk for developing type 2 diabetes, insulin resistance, and other metabolic disorders. Obesity is considered a chronic low-grade inflammatory condition that is primarily attributed to expansion and inflammation of adipose tissues. Indeed, adipocytes produce and secrete numerous proinflammatory and anti-inflammatory cytokines known as adipokines. When the balance of these adipokines is shifted toward higher production of proinflammatory factors, local inflammation within adipose tissues and subsequently systemic inflammation occur. These adipokines including leptin, visfatin, resistin, apelin, vaspin, and retinol binding protein-4 can regulate inflammatory responses and contribute to the pathogenesis of diabetes. These effects are mediated by key inflammatory signaling molecules including activated serine kinases such as c-Jun N-terminal kinase and serine kinases inhibitor κB kinase and insulin signaling molecules including insulin receptor substrates, protein kinase B (PKB, also known as Akt), and nuclear factor kappa B. Bariatric surgery can decrease body weight and improve insulin resistance in morbidly obese subjects. However, despite reports suggesting reduced inflammation and weight-independent effects of bariatric surgery on glucose metabolism, mechanisms behind such improvements are not yet well understood. This review article focuses on some of these novel adipokines and discusses their changes after bariatric surgery and their relationship to insulin resistance, fat mass, inflammation, and glucose homeostasis.