Chromatographic Analysis of the Amino Acid Composition of Gallstones

Abstract

Cholelithiasis (gallstone disease) is a multifactorial condition characterized by the formation of gallstones. Investigation of the composition of gallstones is essential for understanding the mechanisms of their formation and addressing various practical issues. Currently, it remains unclear which protein components are involved in gallstone formation and how they are related to other components of the stones. This study demonstrates a potential for the qualitative and quantitative determination of amino acids in gallstones of men and women of different ages using gas chromatography (GC-17A chromatograph, Shimadzu, Japan). The analysis of the amino acid composition of gallstones involves the acid hydrolysis of the samples in 6 M HCl at 105°C for 12 h, followed by purification, derivatization of the isolated amino acids, and their determination by gas chromatography. This method allows for the identification of both D- and L-forms of amino acids. A statistical analysis of the obtained data was performed using the STATISTICA 6.0. The study found that cholesterol gallstones in women under the age 50 have the lowest amino acid content. In the amino acid composition of cholesterol gallstones, glycine, along with the L-forms of serine, alanine, and glutamic acid, predominates. Cholesterol gallstones with a mineral component are typical in elderly women (over 60 years old) and middle-aged men (from 37 years old) and exhibit higher amino acid contents than pure cholesterol gallstones. In this type of stones, glycine and the L-forms of leucine, glutamic acid, and aspartic acid predominate. The highest amino acid content was found in pigment stones, both in men and women over the age 55. The amino acid composition of pigment-type stones is dominated by glycine and the L-forms of glutamic acid, aspartic acid, leucine, and alanine. D-amino acids were not detected in cholesterol gallstones. However, D-aspartic acid was found in cholesterol stones with a mineral component and in pigment gallstones. These findings suggest that gas chromatography is a suitable method for studying the amino acid composition of gallstones.