| Objective: Previous studies revealed critical associations of adipocyte fatty acid binding protein(A-FABP) and serum vitamin D levels with obesity and obesity related disorders. The study aimed to assess the relationships between serum A-FABP, vitamin D levels and subclinical atherosclerosis as well as fat distribution.Methods: The study population was all selected from the Shanghai Obesity Study(SHOS). A sandwich enzyme-linked immunosorbent assay was used to determine serum A-FABP level and the electrochemiluminescence immunoassay was used to determine serum 25-hydroxy vitamin D3(25(OH)D3) level. Carotid intima-media thickness(C-IMT), a marker used to assess subclinical atherosclerosis, was measured by Carotid ultrasound. Each subject underwent a bioelectrical impedance analysis in order to quantify fat mass, free fat mass and fat percentage(fat%). While magnetic resonance imaging, which is recommended by International Diabetes Federation(IDF), was carried out to determine the abdominal fat distribution(including the subcutaneous fat area [SFA] and the visceral fat area [VFA]). In addition, B mode ultrasound was used to diagnose the non-alcoholic fatty liver disease(NAFLD), and fatty liver index(FLI) was calculated to evaluate liver steatosis. NAFLD was diagnosed according to the Guidelines for the Diagnosis and Management of NAFLD(2010). The glucose tolerance was mady by the criteria of the 1999 World Health Organization. In addition, visceral obesity was defined by VFA ≥ 80 cm2, while a high SFA was defined as a SFA above the upper quartile of the menopause-specific subjects, respectively.Results:(1) Among the 2253(835 men and 1418 women) cardiovascular disease-free normal glucose tolerance(NGT) participants, women had significantly higher serum level of A-FABP than men(P < 0.001). Compared with premenopausal women, postmenopausal women also had higher serum level of A-FABP(P < 0.001). In men, pre- and postmenopausal women, there were significantly increased trends in C-IMT accompanied with the quartiles of serum A-FABP levels(P for all trend < 0.001). Stepwise regression analyses revealed that serum A-FABP concentrations were correlated with C-IMT in preand postmenopausal women(Standardized β = 0.077 and 0.113, respectively; P = 0.044 and 0.001, respectively), but not in men. In addition, the independent associations of serum A-FABP level with C-IMT in both premenopausal and postmenopausal women still remained in a normal body mass index(BMI) subgroup(Standardized β = 0.162 and 0.100, respectively; P < 0.001 and P = 0.012, respectively).(2) Among the 2108 women(including 760 pre- and 1348 postmenopausal women) without diabetes and cardiovascular diasease, those with isolated increased VFA showed a higher serum A-FABP level than subjects with isolated increased SFA in both pre- and postmenopausal status(both P < 0.05). Moreover, regardless of the menopausal status, women with increased VFA also had a higher serum level of A-FABP than those with normal VFA in both BMI< 25 kg/m2 and BMI ≥ 25 kg/m2 group(all P < 0.01). As revealed by the multiple stepwise regression analyses, serum A-FABP levels were positively and independently correlated with fat mass in both menopausal status(both P < 0.001). In addition, VFA(Standardized β = 0.114, P = 0.001) was demonstrated as a risk factor of serum A-FABP level only in postmenopausal women. Application of the same multiple regression analyses to both the two BMI subgroups(< 25 kg/m2 and ≥ 25 kg/m2) yield the similar results(all P < 0.05).(3) In a total of 1001 middle-aged men aged more than 45 years, serum 25(OH)D3 level was lower in subjects with carotid plaque compared with those without carotid plaque [13.80(10.82–17.68) ng/m L vs. 14.74(10.87–19.08) ng/m L, P = 0.029]. In addition, in both with plaque and without plaque groups, decreased serum level of 25(OH)D3 was found in increased C-IMT subgroup [without carotid plaque: 13.90(9.99–17.09) ng/m L vs. 14.99(11.17–19.43) ng/m L, P < 0.01; with carotid plaque:13.24(9.91–16.81) ng/m L vs. 14.45(11.40–18.51) ng/m L, P < 0.05]. Furthermore, Logistic regression analyses showed that serum 25(OH)D3 level was independently associated with the carotid plaque [OR(95%CI): 0.972(0.946–0.998), P = 0.032] as well as increased C-IMT among subjects with and without plaque [without carotid plaque: OR(95%CI): 0.944(0.908–0.981), P = 0.004; with carotid plaque: OR(95%CI): 0.900(0.849–0.955), P = 0.001].(4) Among the 567 men with NGT, overweight/obese participants had a lower serum level of 25(OH)D3 than their non-overweight/non-obese participants(P = 0.029). Serum 25(OH)D3 levels decreased with VFA and fat mass increased(P for both trends < 0.01). Among the overweight/obese participants, those with fat ≥ 25% had lower level of serum 25(OH)D3. In addition, those with VFA ≥ 80 cm2 also had lower serum level of serum 25(OH)D3 in both BMI subgroups(both P < 0.05). Multiple stepwise regression analysis found an independent relationship between VFA(Standardized β =-0.163, P < 0.001), triglycerides(Standardized β =-0.086, P = 0.041) and serum 25(OH)D3 level.(5) Among the 514 subjects with normal liver enzymes and BMI, the NAFLD subjects had a lower level of serum 25(OH)D3(P < 0.01). Logistic regression analysis demonstrated that serum level of 25(OH)D3 independently and negatively correlated with NAFLD(OR: 0.937, 95%CI: 0.884–0.993,P = 0.028). In addition, stepwise multiple regression analysis found that FLI correlated with serum 25(OH)D3 level(Standardized β =-0.023, P = 0.040).Conclusions: Serum A-FABP level positively and independently correlate with subclinical atherosclerosis assessed by C-IMT in both premenopausal and postmenopausal women with normal glucose tolerance. In addition, serum level of A-FABP was influenced by fat mass, and was also associated with VFA in postmenopausal women. Serum levels of 25(OH)D3 inversely and independently correlated with VFA and NAFLD in men. Furthermore, serum level of 25(OH)D3 was inversely and independently associated with subclinical atherosclerosis in men. |
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