The influences of larger physical constitutions including obesity on the amount of urine protein excretion in primary glomerulonephritis: research of the Japan Renal Biopsy Registry

Background: This study aimed to describe the influences of larger physical constitutions including obesity on the amount of urine protein excretion (AUPE) in primary glomerulonephritis. The distinct effects on the AUPE in various types of glomerulonephritis were evaluated. Methods: Using the database of the Japan Renal Biopsy Registry (J-RBR) from 2007 to 2010, 4060 cases with primary glomerulonephritis including MCNS, FSGS, MN, MPGN, IgAN, and non-IgA were reviewed. The AUPEs were compared between high and low Body Mass Index (BMI) groups, and larger and smaller body surface area (BSA) groups using the indexes of BMI 25.0 kg/m² and BSA 1.73 m² in all cases and in each histological group. Multivariable analysis was performed to evaluate the predominant contributors to the AUPE. Results: The larger physical constitution groups (BMI ≥25.0 kg/m² or BSA ≥1.73 m²) had significantly higher AUPEs in all cases with primary glomerulonephritis. When compared in each histological group, the mean AUPEs were significantly higher in the larger physical constitution groups, excluding the FSGS and non-IgA groups. Multiple regression analysis revealed that the significant contributors to the AUPE were BMI and BSA in MCNS and MN, whereas BMI and BSA were not significant and mean blood pressure and serum creatinine were significant in FSGS and non-IgA. Conclusion: Larger physical constitutions including obesity had a significant impact on the increase in the AUPE in primary glomerulonephritis, especially in MCNS and MN. However, FSGS and non-IgA were distinct for having blood pressure and renal dysfunction as possibly the major causes of proteinuria.