Abstract:
Nephrolithiasis or renal stone has been found worldwide; it is also endemic in the northeastern Thailand. Mechanism of stone formation depends upon urinary constituents. In a previous study report that patients with kidney stone excreted urinary lipids higher than in normal individuals and lipid constituents were found in stone matrix. The aim of present research was to investigate the profile of urinary lipids in renal stone patients (RSP) and to elucidate role of lipids in stone formation. A total of 34 kidney stone patients were recruited and collected for 24-hour urine and stone specimens. Thirty-two healthy subjects were participated as control and collected for 24-hour urine. Urine volume, pH, metabolic abnormalities, renal tubular damage and oxidative stress were determined in urine specimens. Mineral composition of stone was analyzed using Fourier transform infrared spectroscopy. Total lipids were extracted from stone and urine samples by chloroform-methanol method and lipid classes were separated using multi-one-dimension-thin layer chromatography. In vitro crystallization and aggregation assays were employed to evaluate the lithogenic role of lipids. The results showed that low urine volume, hypocitraturia and hyperkaliuria were major risk factors of RSP. Tubular damage and oxidative stress were significantly increased in RSP than normal subjects. A trend of increased urinary lipids excretion in RSP was observed although was not statistically significant. Amount of total lipids of each stone type was not significantly different. Excretion of urinary total lipids in RSP was correlated to oxidative stress and renal tubular damage. Urinary lipid profiles in RSP and normal subjects were relatively similar but they greatly differed from stone matrix lipids. Stone formation assay demonstrated that lipids could function as both nucleator and aggregator. This study provided data for better understanding the mechanisms of lithogenesis. Oxidative stress and renal tubular damage caused elevated urinary lipids excretion hence enhancing stone formation potential.