Brief hypoglycemia alters morphology, function, and metabolism of the embryonic mouse heart

This study examined effects of brief embryonic exposure to hypoglycemia on the developing mouse heart during organogenesis. Mouse embryos were exposed in whole-embryo culture to brief periods (2, 4, or 6 h) of hypoglycemia (20, 40, or 80 mg/dL glucose) at three developmental stages (10, 20, or 30 somites), and hearts were examined for morphologic, functional, and metabolic effects. Hypoglycemia produced abnormal cardiac structure and expansion and pericardial edema, and it disrupted histologic integrity and growth of the heart, particularly at 20 somites. Embryonic heart rate was decreased by hypoglycemia at all three stages. Cardiac glucose uptake and glycolysis were increased by hypoglycemia, suggesting a compensatory response to glucose deficiency, with little effect on ATP levels. In summary, brief embryonic exposure to hypoglycemia affects the morphology, function, and metabolism of the developing heart. Mechanisms by which metabolic responses are related to morphologic and functional effects are currently unclear.