Concentrations ofd-lactate and its related metabolic intermediates in liver, blood, and muscle of diabetic and starved rats

Abstract

This is a report investigating the methylglyoxal (MG) bypass in animals, by which D-lactate is produced from triosephosphate via MG. Rats were made diabetic using streptozotocin or starved for 72 h. D-Lactate and various metabolites related to it, such as L-lactate, pyruvate, methylglyoxal, glucose, and inorganic phosphate, were measured in the blood plasma, liver, and skeletal muscle of the rats. Diabetic and starved rats had significantly higher levels of D-lactate in plasma, liver, and skeletal muscle compared with the control group. In contrast, pyruvate levels in plasma, liver, and skeletal muscle was markedly lower than normal in diabetic and starved rats. L-Lactate level lowered markedly in plasma, liver, and skeletal muscle of starved rats and elevated in liver of diabetic rats. Differences between plasma L-lactate level for diabetes and control were not significant. MG level was significantly elevated in plasma and depressed in livers and muscles of starved rats as well as livers of diabetic rats. Hepatic glycerol content was markedly increased in those states. Enzyme activities related to D- and L-lactate, such as pyruvate kinase, phosphofructokinase, aldolase, and glyoxalase I, were measured in the livers of these rats. Pyruvate kinase activity decreased in these states, but other enzyme activities showed no significant changes. D-Lactate was much more excreted than L-lactate in the urine of diabetic and fasted rats compared with normal rats.

Enantiomeric Determination ofd- andl-Lactate in Rat Serum Using High-Performance Liquid Chromatography with a Cellulose-Type Chiral Stationary Phase and Fluorescence Detection

“…The D-lactate concentration of rat serum before fasting was 87.6 Ϯ 26.5, in fasting for 24 h was 35.1 Ϯ 5.2, and in fasting for 48 h was 25.5 Ϯ 7.2 M, while the body weight was 228 Ϯ 9.8, 186 Ϯ 5.8, and 183 Ϯ 6.8, respectively (mean Ϯ SD, n ϭ 5). Differing from the previous report by Kondoh et al (27) in which plasma D-lactate concentrations in fasted rats determined by the enzymatic (LDH) method were about two times higher than those in control rats, we observed the significant decrease of D-lactate concentrations in fasting (less than the half value of control). Although this discrepancy is not clearly explained, it might depend on the difference of the methodology for D-lactate determination.…”

“…Using the present method, we examined the influence of fasting on the D-lactate concentration in rat serum, which was reported to increase (27). The representative chromatograms of serum sample were shown in Fig.…”

Determination of serum d-lactic and l-lactic acids in normal subjects and diabetic patients by column-switching HPLC with pre-column fluorescence derivatization

“…The endogenous D-lactic acid is produced from methyglyoxal mediated by glyoxalase I and II in the metabolic pathway of glucose [1,2]. It has been reported that D-lactic acid concentration was significantly increased in the serum of diabetic animals [3,4] and patients [5]. This has been considered due to the accelerated production of its precursor, methyglyoxal, which causes the patient to develop diabetic complications under the diabetic stage [6,7,8,9,10].…”

Simultaneous determination of D‐lactic acid and 3‐hydroxybutyric acid in rat plasma using a column‐switching HPLC with fluorescent derivatization with 4‐nitro‐7‐piperazino‐2,1,3‐benzoxadiazole (NBD‐PZ)

“…The D-lactic acid concentration has been reported to increase in plasma of experimental animals such as diabetic rats and cats (Christopher et al, 1995;Kondoh et al, 1992Kondoh et al, , 1994, due to the enhanced production of its precurser, methylglyoxal, in diabetes. The increase of D-lactic acid concentration has also been reported in plasma of patients with diabetes mellitus (McLellan et al, 1992(McLellan et al, , 1994Beisswenger et al, 1999), suggesting that D-lactic acid might be one of the possible clinical markers for diabetes mellitus.…”