[A study on microproteinuria among diabetic and obese subjects without clinically overt proteinuria]

In metabolic disorders such as diabetes mellitus (DM) and obesity, renal abnormalities may also occur even when renal dysfunction is not be detected by conventional urinalysis. By use of immunological technique, an investigation was made on the subclinical abnormality in the excretion of urinary proteins in DM and obese (OB) subjects. Urinary excretion of the proteins (albumin, IgG, IgG4, beta 2-microglobulin) and fractional clearances (clearance ratios to creatinine clearance) at sitting position were respectively measured. Albumin excretion rate (AER) and fractional albumin clearance were higher in DM and OB than normal controls (NC). In non-diabetic subjects (OB+NC), body mass index (BMI) significantly positively correlated with AER and fractional albumin clearance. In DM, not only AER and fractional albumin clearance but also IgG4 excretion rate and fractional IgG4 clearance positively correlated with BMI. In DM with BMI less than 22 Kg/m2, HbA1C significantly correlated with AER, IgG4 excretion rate, and fractional albumin and IgG4 clearances. The data suggest that microproteinuria in DM and OB may be of glomerular origin. In DM, in the light of an increase in urinary excretion of negatively charged IgG4, it is also suggested that proteinuria is attributed to the alteration of charge barrier as well as to that of glomerular hemodynamics. Lastly but not least , obesity-related factor should also be taken into account in the development of microalbuminuria of the diabetic patient.