Elevated levels of liver methylglyoxal and d-lactate in early-stage hepatitis in rats

Methylglyoxal (MGO) is highly cytotoxic and its levels are elevated in diabetes, nephropathy and atherosclerosis. However, it has never been studied in liver disease. For this reason, we aimed to assess the levels of MGO and its metabolite d-lactate in an early hepatitis model. Wistar rats were administered CCl4 (0.75mL/kg, i.p.) to induce hepatitis. In either CCl4-treated or untreated rats, alanine transaminase and aspartate transaminase levels did not change over the course of the study, indicating that significant liver damage did not occur following CCl4 treatment. However, the levels of MGO and d-lactate were higher in the livers of CCl4-treated animals than in untreated animals (MGO: 128.2±18.8 and 248.1±64.9μg/g protein, p<0.01; d-lactate: 0.860±0.040 and 1.293±0.078μmol/g protein, respectively p<0.01). Furthermore, in untreated and treated animals, serum d-lactate levels were 57.65±2.59 and 92.16±16.69μm and urine d-lactate levels were 1.060±0.007 and 1.555±0.366μmol/mg UCr, respectively (p<0.01). These data show that in this model of early-stage liver damage, the levels of MGO and its metabolite d-lactate are elevated and that d-lactate could be useful as a reference marker for the early stage of hepatitis.