Autori: Mangione E., Giglio E., Salvetti G., Santini F., Donadio C.
Affiliazioni: Dept. Clinical Experimental Medicine, University of Pisa, Italy
Background. It is widely accepted that metabolic syndrome, a cluster of cardiovascular risk factors often related with obesity, is associated with an increased risk of chronic kidney disease (CKD). Obesity itself has been found to be a strong independent risk factor for end stage renal disease even after adjustment for other major risk factors.
The aim of this study is to investigate whether, besides metabolically abnormal obesity (MAO), also metabolically healthy obesity (MHO) phenotype is associated with increased risk of renal dysfunction.
Patients and methods. Retrospective cross-sectional study of 181 obese patients (135 females, 46 males; median age 47 years, IQR 39-56; body weight 125.0 kg, IQR 111.7-146.2; BMI 47.5 Kg/m2, IQR 42.9-53.0; serum creatinine 0.72 mg/dl, IQR 0.63-0.81) admitted to the Department of Endocrinology of Pisa Hospital between 2009 and 2012. Patients were classified as MHO (n=78) or MAO (n=103) according to the absence or presence of metabolic syndrome (Adult Treatment Panel-III criteria); the subjects were also stratified into three groups according to body mass index (BMI): moderate to severe obesity (group 1, BMI 30 to 39.9 kg/m2), pathological obesity (group 2, BMI 40 to 49.9) and extreme obesity (group 3, BMI ≥ 50). Clinical and biochemical parameters were then compared using Mann-Whitney or chi-square test as appropriate. Results are presented as median and interquartile range (25-75). A p value<0.05 was considered significant.
Results. The prevalence of metabolic syndrome was 56.9% (67% of females, 33% of males). No significant differences were observed in age and BMI between the two groups, whereas MAO phenotype was associated with significantly higher values of waist circumference and waist-hip ratio. Also other metabolic parameters (systolic blood pressure, serum glucose, glycated hemoglobin, serum triglycerides, HDL and LDL) were higher in MAO phenotype. Serum urea, uric acid and urine albumin creatinine ratio (uACR) were significantly higher in MAO patients, suggestive of functional kidney alterations. Serum creatinine was slightly higher, eGFR (MDRD-Cr, CKD-EPI-Cr, Salazar Corcoran) and creatinine clearance were lower in MAO phenotype, even if without statistical significance (Table 1). Serum uric acid increased progressively with BMI classes (from 4.8 to 5.5 and 6.2 mg/dl, respectively). The increase in BMI was not associated with an impairment in renal function, which progressively increased according to BMI. Salazar Corcoran CCr and CKD EPI were significantly higher in patients with extreme obesity (mean difference +16 and +20 % respectively, p<0.01). The prevalence of CKD stage III-V was significantly higher in MAO phenotype (13.5% vs 5.1%, p=0.05), as well as the prevalence of micro-macroalbuminuria (23.3% vs 10.3%, p=0.003) (Tables 2-3). The risk for CKD, evaluated from eGFR and uACR (according to National Kidney Foundation Criteria), was higher in MAO phenotype (p=0.01), while no differences were found according to BMI classes (Tables 4-5).
Conclusions: metabolically abnormal obesity phenotype, characterized by the prevalence of abdominal obesity, is associated with an increased risk of renal dysfunction in comparison with metabolically healthy obesity.
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