Fractionation of gamma-glutamyltransferase in patients with nonalcoholic fatty liver disease and alcoholic liver disease

Abstract

Aim: To assess how serum gamma-glutamyltransferase (GGT) fractions vary in patients with alcoholic liver disease (ALD) and non-alcoholic fatty liver disease (NAFLD).

Methods: Serum samples were obtained from 14 patients with biopsy-proven alcoholic liver diseases and 9 patients with biopsy proven non-alcoholic fatty liver disease. In addition to these biopsy-proven cases, 16 obese (body mass index > 25) patients without any history of alcohol consumption but with a fatty liver on ultrasound examination and with elevated GGT were included for an additional analysis. Serum GGT fractionation was conducted by high-performance gel filtration liquid chromatography and was separated into the four fractions, big-GGT, medium-GGT, small-GGT (s-GGT), and free-GGT (f-GGT).

Results: The results were expressed as a ratio of each fraction including the total GGT (t-GGT). The s-GGT/t-GGT ratios were lowest for the control group and highest for the ALD group. The differences between the control and NAFLD groups and also between the NAFLD and ALD groups were statistically significant. In contrast, the f-GGT/t-GGT ratios were highest in the control group and lowest in the ALD group, with the differences being statistically significant. As a result, the s-GGT/f-GGT ratios were markedly increased in the NAFLD group as compared with the control group. The increase of the s-GGT/t-GGT ratios, the decrease of the f-GGT/t-GGT ratios, and the increase of s-GGT/F-GGT ratios as compared with the control group subjects were also found in obese patients with clinically diagnosed fatty change of the liver.

Conclusion: Serum GGT fractionation by high-performance gel filtration liquid chromatography is potentially useful for the differential diagnosis of ALD and NAFLD.

Keywords: Alcoholic liver disease; Gamma-glutamyltransferase; Gel filtration liquid chromatography; Non-alcoholic fatty liver disease; f-GGT/t-GGT ratios.

Figure 1

Gamma-glutamyltransferase-specific elution profiles of representative serum samples (two of each) obtained from the control group subjects (A and B), patients with alcoholic liver disease (C and D), and patients with non-alcoholic fatty liver disease (E and F). On the basis of the molecular weight calibration curve (data not shown), these four peaks are equivalent to big-GGT (MW > 2000 kDa, eluted between 6.25-9.50 mL), medium GGT (MW 940 kDa, eluted between 9.5-12.25 mL), small GGT (MW 140 kDa, eluted between 12.25–15.5 mL) and free-GGT (MW 70 kDa, eluted between 15.5-20 mL), respectively. GGT: Gamma-glutamyltransferase.

Figure 2

Linear correlation between the total area under the chromatograph curve multiplied by serum dilution factors and total serum gamma-glutamyltransferase activity. Elution volume (between 12-38 mL). y = 5.9667x + 15.303; r = 0.988; P < 0.001; n = 49. GGT: Gamma-glutamyltransferase.

Figure 3

Serum b-GGT/t-GGT, s-GGT/t-GGT, f-GGT/t-GGT, b-GGT/s-GGT and s-GGT/f-GGT ratios in patients with biopsy-proven non-alcoholic fatty liver disease, biopsy-proven alcoholic liver disease and the controls group. ALD: Alcoholic liver disease; NAFLD: Non-alcoholic fatty liver disease; GGT: Gamma-glutamyltransferase; b-GGT: Big-GGT; t-GGT: Total-GGT; s-GGT: Small-GGT; f-GGT: Free-GGT; ns: No significant differences.

Figure 4

Serum b-GGT/t-GGT, s-GGT/t-GGT, f-GGT/t-GGT, b-GGT/s-GGT, and s-GGT/f-GGT ratios in patients with non-alcoholic fatty liver disease clinically diagnosed by ultrasonography. GGT: Gamma-glutamyltransferase; b-GGT: Big-GGT; t-GGT: Total-GGT; s-GGT: Small-GGT; f-GGT: Free-GGT; ns: No significant differences.