Circulating FABP4 is a marker of metabolic and cardiovascular risk in SLE patients.

The aim of this study is to determine if circulating fatty acid-binding protein 4 (FABP4) plasma levels are a possible marker of metabolic risk in SLE patients. Circulating levels of adipose FABP4 are associated with adiposity, insulin resistance (IR), metabolic syndrome, diabetes and cardiovascular diseases. Patients affected by systemic lupus erythematosus (SLE) show an accelerated atherosclerosis that cannot be entirely explained by traditional cardiovascular risk factors. Sixty consecutive patients with SLE and 34 non-SLE age-matched controls were recruited for the study. Total plasma lipids and circulating FABP4 were determined. Subclinical atherosclerosis was evaluated by measuring carotid intimae-media thickness (c-IMT) by sonography, and the distribution of lipoprotein subclasses was analysed by nuclear magnetic resonance (NMR) spectroscopy. In the SLE group, FABP4 was associated with IR, atherogenic dyslipidaemia, as measured by NMR, and the presence of subclinical atherosclerosis. In multivariate analyses FABP4 was associated with increased c-IMT independent of the inflammatory state of the patient. In sum, circulating FABP4 is involved in the metabolic disturbances of SLE affecting lipid metabolism and IR, and it could be a biomarker of atherosclerosis in this population.

The APOA5-1131 T>C variant enhances the association between RBP4 and hypertriglyceridemia in diabetes.

BACKGROUND AND AIM: Type 2 diabetic patients have an increased prevalence of hypertriglyceridemia. RBP4 has been associated with insulin resistance and hypertriglyceridemia in obesity, the metabolic syndrome and type 2 diabetes. APOA5 is proposed to be a genetic modulator of triglycerides. The aim of this study was to evaluate the relationship between RBP4 plasma levels and lipid disturbances and to determine the impact of the APOA5-1131 T>C variant on this relationship in type 2 diabetic patients. METHODS AND RESULTS: A total of 165 type 2 diabetic patients were included in the study. RBP4 plasma levels and the APOA5-1131 T>C variant were determined and the complete lipid profile was assessed by sequential ultracentrifugation. RBP4 was positively correlated with triglyceride levels in plasma and with all the components of triglyceride-rich lipoproteins. Despite the fact that a statistically significant relationship between the APOA5 genetic variant and RBP4 plasma levels was not found, the hypertriglyceridemic effect of high RBP4 levels was enhanced by the presence of the APOA5-1131 T>C genetic variant. Correlation coefficients were 2-fold higher for TC carriers compared to TT carriers with regard to RBP4 plasma levels and all the components of triglyceride-rich lipoproteins. Those type 2 diabetic patients with high RBP4 plasma concentrations and who were TC carriers showed an increased incidence of hypertriglyceridemia (OR=7.46, P=0.010). CONCLUSION: RBP4 is associated with hypertriglyceridemia in type 2 diabetic patients. The RBP4 effect is conditioned by the presence of the APOA5-1131 T>C genetic variant.

Retinol-binding protein 4 as a plasma biomarker of renal dysfunction and cardiovascular disease in type 2 diabetes.

OBJECTIVE: The retinol-binding protein 4 (RBP4) has been linked to the insulin resistance state in obesity and type 2 diabetes in animal studies. Data in humans are controversial and their relationship with organ damage in diabetic patients is lacking. We studied the association of plasma RBP4 with organ complications in type 2 diabetic patients. SETTING: Sant Joan University Hospital, Reus, Spain. SUBJECTS: 165 nonsmoker type 2 diabetic subjects according to American Diabetes Association criteria, aged 36-79 years, without proteinuria or severely decreased glomerular filtration rates (MDRD-GFR <30 mL min(-1) 1.73 m(-2)), were included in the study. MAIN OUTCOME MEASURE: Plasma RBP4 concentrations were the primary outcome variable. Statistics were performed in relation to clinical and subclinical arteriosclerosis, renal function parameters and biochemical data. RESULTS: Plasma RBP4 concentrations were positively correlated with serum creatinine levels (r = 0.322, P < 0.001) and inversely correlated with MDRD-GFR (r = -0.468, P = 0.009). Patients with moderately renal dysfunction (MDRD-GFR <60 mL min(-1) 1.73 m(-2)) had higher plasma RBP4 concentrations than those with normal to mildly decreased GFR (55.3 +/- 24.6 vs. 40.8 +/- 15.4, P <0.001). Patients in the top quartile of RBP4 concentrations had an increased adjusted odds ratio for moderately renal dysfunction compared with lower quartiles (4.68; 95% CI: 1.52-14.36, P = 0.007). The presence of microalbuminuria was not associated with RBP4. Plasma RBP4 concentrations were higher in those subjects with previous clinical arteriosclerosis than in event-free subjects (48.8 +/- 24.2 vs. 40.6 +/- 13.9, P = 0.045). The presence of retinopathy or polyneuropathy did not differ across RBP4 quartiles. CONCLUSIONS: Plasma RBP4 concentration might be a biomarker of nephropathy and cardiovascular disease in type 2 diabetic subjects.

Fatty acid binding protein 4 is increased in metabolic syndrome and with thiazolidinedione treatment in diabetic patients.

OBJECTIVE: To study the role of FABP4 in the plasma of type 2 diabetic (T2D) subjects with and without metabolic syndrome (MS) and the impact of thiazolidinedione (TZD) treatment. METHODS AND RESULTS: FABP4 was analyzed in 274 individuals (169 T2D subjects and 105 controls). MS-T2D subjects had higher FABP4 levels than non-MS-T2D subjects and controls (53% and 76% increase, respectively, p<0.005). FABP4 levels in T2D subjects were positively correlated to the number of MS elements, obesity degree, adiponectin, triglycerides, lipoperoxides, C-reactive protein, age, systolic blood pressure and diabetes duration (p<0.05). Neither clinical or subclinical atherosclerosis, nor plasma levels of insulin, glucose or RBP4 were associated to FABP4. TZD-treated T2D subjects showed >30% higher FABP4 levels (p<0.05) than non-TZD-treated T2D. A subgroup study confirmed that TZD treatment prospectively increased FABP4 levels (p<0.05) along with an increase of peripheral blood mononuclear cell PPARgamma activity (p<0.05). Furthermore, in vitro studies showed that TZD treatment increased FABP4 mRNA, intracellular protein levels and extracellular secretion from human adipocytes. CONCLUSIONS/INTERPRETATION: FABP4 plasma concentrations are increased with the early presence of MS components, as well as inflammation and oxidation markers in T2D subjects. TZD increases FABP4 plasma concentrations, reflecting PPARgamma activation. FABP4 plasma measurements could be useful in the management of T2D subjects.