AMP-activated protein kinase (AMPK) functions as a sensor of cellular energy status, acting as a key regulator of metabolism. AMPK stimulates ATP production, primarily through increased glycolysis and fatty acid oxidation. We postulated that AMPK may act as a regulator of embryo development, mediated by glucose metabolism. This study aimed to determine the effect of AMPK activation on in vitro embryo development, metabolism and outgrowth potential, through the addition of the AMPK agonist AICAR.

F₁ hybrid (C57BL/6xCBA) mice were stimulated, mated and their zygotes cultured for 48h in G1 medium. Morulae were randomly allocated into G2 medium ± AICAR at varying concentrations, and cultured for 24h. Subsequently, embryos were either maintained for 24h in group culture or incubated individually in 1 μl of modified G2 for later analysis of glucose and lactate concentrations using microfluorescence. Blastocyst cell number was determined or embryos cultured to assess outgrowth area. Data were considered statistically significant at α=0.05.

Glucose consumption increased (P<0.05) in the presence of 2.5, 5 and 10 μM AICAR, while lactate production only increased in 5 and 10 μM AICAR concentrations (n>20 embryos per treatment). Addition of 10 μM AICAR increased glycolytic rate relative to control and 1 μM AICAR, and reduced total cell number (P<0.0001, n>20). Low (1 and 2.5 μM) AICAR did not alter total cell number. Embryo outgrowth area was reduced by the addition of 5 and 10 μM AICAR, decreasing by almost 30 and 50% respectively after 43h (P<0.0001, n=60 per treatment). Reduced outgrowth area in 5 and 10 μM treated embryos was maintained through 137h of culture. In contrast, 1 μM AICAR increased outgrowth area, although not significantly compared to untreated embryos.

Data suggest overstimulation of AMPK adversely impacts embryo development, manifested through altered carbohydrate metabolism. Initial blastocyst invasion is affected by modulation of AMPK activity, reflecting the reduction in blastocyst cell numbers. Appropriate regulation of energy sensing pathways is therefore critical for embryo viability and is of significance to culture- and diet-induced alterations in embryo physiology.