Ketoacids attenuate glucose uptake in human trophoblasts isolated from first-trimester chorionic villi

The objective of this study was to evaluate the hypothesis that ketoacids (acetoacetic acid and beta-hydroxybutyrate) diminish glucose transport in trophoblasts cultured from first-trimester chorionic villi.

First-trimester trophoblasts were obtained by transabdominal chorionic villus sampling for subsequent cytogenetic analysis. The cells were established as a continuous line exhibiting trophoblast characteristics. Trophoblasts were cultured in Ham's F12/Dulbecco's modified Eagle's medium (1:1) supplemented with 15% fetal bovine serum. Experiments were initiated by a 24-hour preincubation in serum-free Ham's F12/Dulbecco's modified Eagle's medium followed by incubation with ketoacids (acetoacetic acid and beta-hydroxybutyrate, 0 to 10 mmol/L) in the presence or absence of insulin-like growth factor-I (100 ng/ml). The cells were challenged with 2-deoxy-[1,2-3H]D-glucose (0.1 mmol/L) for 5 minutes and then cell-associated radioactivity was measured. Total ribonucleic acid was extracted from cells incubated with ketoacids in the presence or absence of insulin-like growth factor-I, and Northern blots were probed with a phosphorus 32-labeled complementary deoxyribonucleic acid fragment encoding the rat GLUT 1.

Ketoacids caused a dose-dependent inhibition of glucose transport. At 5 mmol/L acetoacetic acid there was a > 50% reduction in the rate of glucose transport in both control and insulin-like growth factor-I-treated cells. The diminution in glucose uptake by trophoblasts was not due to cellular toxicity of the ketoacids because there was no significant difference in trypan blue exclusion or lactate dehydrogenase release between control and ketoacid-treated cells. Northern analysis revealed that the steady-state expression of GLUT1 messenger ribonucleic acid was diminished in ketone-treated cells, but this effect was overcome by coincubation of cultures with insulin or insulin-like growth factor-I.

These results indicate that ketoacids can suppress the uptake of glucose into first-trimester human trophoblasts. Because ketoacidosis in pregnant women with diabetes mellitus is a frequent clinical consequence of poor metabolic control, it is possible that elevated levels of acetoacetic acid and beta-hydroxybutyrate may impair the transport of glucose across the placental trophoblast and into the fetal circulation.