Renal excretion of ascorbic acid in insulin dependent diabetes mellitus.
Serum ascorbic acid (AA) is reduced in diabetic patients. Aim of this study was 1) to verify whether such a decrease might be due to an altered urinary excretion of AA, and 2) whether this latter was modified in presence of early diabetic nephropathy with microalbuminuria (albumin excretion rate [AER] > 20 micrograms/min) in a group of 21 patients affected by insulin-dependent (type 1) diabetes mellitus (IDDM) as compared with 13 healthy controls matched for sex, age, dietary AA intake, and creatinine clearance per 1.73 m2 (CCl). Mean serum AA (+/- SD) was lower in diabetics (40.3 +/- 14 microM/l) than in controls (85.1 +/- 23.5 microM/l; p = 0.0001) and there was no difference between serum AA of patients with or without microalbuminuria. Urinary excretion of AA to creatinine x 100 (UAA/Cr) was higher in micro- (n = 6; 4.6 +/- 1.7) as compared to normoalbuminurics (n = 15; 1.6 +/- 0.9) or controls (1.5 +/- 1.2; p = 0.0001). For values exceeding renal threshold of tubular AA reabsorption (39 microM) the regression line of serum AA to UAA/Cr was significantly (p = 0.001) steeper in diabetics than in controls, suggesting an impaired tubular reabsorption of filtered AA in IDDM. The ratio of AA clearance to CCl was moreover related to AER (r = 0.48; p = 0.03) and to blood glucose (r = 0.51; p = 0.01), being unrelated to uric acid clearance, glycosuria and to urinary excretion of both alanine aminopeptidase and N-acetyl-beta-glucosaminidase.(ABSTRACT TRUNCATED AT 250 WORDS)
Diabetes Unit, Spedali Riuniti, Pistoia, Italy.
G
G
Seghieri
L
L
Martinoli
M
M
Miceli
M
M
Ciuti
G
G
D'Alessandri
A
A
Gironi
L
L
Palmieri
R
R
Anichini
G
G
Bartolomei
F
F
Franconi
D000042:Absorption; D000328:Adult; D000419:Albuminuria / Q000652:urine; D001205:Ascorbic Acid / Q000008:administration & dosage / Q000097:blood / Q000652:urine*; D003404:Creatinine / Q000652:urine; D003922:Diabetes Mellitus, Type 1 / Q000652:urine*; D005260:Female; D006801:Humans; D007668:Kidney / Q000378:metabolism*; D007684:Kidney Tubules / Q000378:metabolism; D008297:Male
D003404:Creatinine; D001205:Ascorbic Acid