Comparative Study of the Circadian Rhythmicity in the Urinary Concentration of Glycosaminoglycans in Patients of Calcium Oxalate Nephrolithiasis and in Healthy Adults

Glycosaminoglycans (GAGs) are potent inhibitors of calcium oxalate crystallisation and/or crystal aggregation. Urinary concentration of GAGs has been shown to vary during 24 h; therefore, circadian rhythmicity in urinary concentration of GAGs was investigated in 33 healthy male adults in the age group of 20–40 years and in 27 male patients of a similar age group with calcium nephrolithiasis. Three-hourly urine samples were collected for 24 h beginning from 00.00 h for estimation of urinary concentration of GAGs. The data of each patient was analysed by single cosinor rhythmometry and population mean-cosinor rhythmometry was then applied to each group. Twenty-four-hour urinary excretion of GAGs was significantly less in renal calculus patients (16.867 ± 5.89 µmol) than in healthy subjects (22.588 ± 5.32 µmol; p < 0.001). A statistically validated circadian rhythm in urinary concentration of GAGs was demonstrated in both the groups. However, the amplitude-acrophase test revealed a significant difference between the two groups (F2,57 = 8.305; p < 0.001); the amplitude was 2.354 µmol/l in patients with nephrolithiasis, whereas the amplitude was 7.028 µmol/l in healthy adults. The mesor test also revealed a significant difference in the 3-hour urinary concentration of GAGs between the two groups (18.536 µmol/l in healthy adults vs. 9.728 µmol/l in patients with nephrolithiasis). Thus in patients with nephrolithiasis, not only is the 24-hour urinary excretion of GAGs significantly low but the 3-hourly urinary concentration of GAGs is also significantly decreased as compared to healthy subjects. The amplitude of circadian rhythmicity in 3-hourly urinary concentration of GAGs is also significantly lower in the stone formers than healthy individuals.