Background Adipocyte fatty acid-binding protein (aFABP) is an intracellular lipid-binding protein expressed in adipocytes and macrophages, particularly in inflammatory conditions. Recently, high circulating serum aFABP levels have been shown to predict the development of carotid atherosclerosis, metabolic syndrome and ischaemic stroke. As an inflammatory disease, circulating aFABP level is expected to be raised in patients with SLE. However, a recent study failed to demonstrate higher aFABP levels in SLE patients than in healthy controls (HC), likely due to the lack of power of study and an optimally matched HC group.
Objectives We aimed to address if serum aFABP level is indeed higher in SLE patients by comparing a larger number of SLE patients with HC stringently matched for age, sex and BMI. In addition, potential associations between serum aFABP levels and clinical and disease-related factors, as well as biophysical markers of cardiovascular (CVS) disease were explored in SLE patients.
Methods Patients with SLE and HC matched for age, gender and BMI were recruited. Subjects with a history of hypertension, diabetes mellitus, renal impairment, CVS and cerebrovascular diseases, and those who were on statins were excluded. Clinical parameters including daily prednisolone dose, SLEDAI, SLICC/ACR DI, and serum C3, C4, anti-dsDNA, total cholesterol (TC) and HDL-c levels were obtained. Serum aFABP levels were determined by commercially available ELISA kit. Endothelial function, arterial stiffness and carotid atherosclerosis were assessed by brachial artery flow-mediated dilation (FMD), pulse-wave velocity (PWV) and carotid intima-media thickness (cIMT) respectively using the Prosound Alpha-10 ultrasound system. Relationships between serum aFABP levels and disease-related factors, FMD, PWV and cIMT were explored by bivariate correlations.
Results Seventy one SLE patients and 71 matched HC (6 men in each group) were studied. The mean±SD age (year), BMI and atherogenic index (TC/HDL-c) of SLE patients and HC were 39.21±13.4 and 40.37±12.9, 22.06±4.3 and 22.86±4.2 and 3.09±1.6 and 3.22±1.4 (p=0.611) respectively. In SLE patients, the mean±SD daily prednisolone dose, SLEDAI and SLICC were 13.43±14.4mg, 6.52±5.4 and 0.17±0.4 respectively. SLE patients had significantly lower FMD than HC (3.82±2.9% vs 4.76±3.0%, p=0.027). PWV and cIMT did not differ between both groups (p=0.739 and p=0.762 respectively). Serum aFABP was significantly higher in SLE patients than that in HC (14.82±3.3ng/ml vs. 13.69±4.6ng/ml, p<0.001). However, no association between serum aFABP levels and serum C3, C4 and anti-dsDNA levels, SLEDAI, SLICC, atherogenic index, daily prednisolone dose, FMD, PWV and cIMT was found in the SLE group. In HC, no association was noted between serum aFABP levels and BMI, FMD, PWV, cIMT and atherogenic index.
Conclusions While we confirmed that SLE patients had significantly higher aFABP levels and lower FMD than age-, sex-, and BMI-matched HC, no association between aFABP and various biophysical markers of CVS disease was found. Prospective studies addressing the CVS impact of aFABP by evaluating adjusted mean aFABP levels over time and CVS events in SLE patients are warranted.
Disclosure of Interest None declared