The Effect of Intravenous Lactate on Brain Lactate Concentrations During Hypoglycemia

Patients with type 1 diabetes (T1DM) who are unable to perceive symptoms of hypoglycemia, referred to as impaired awareness of hypoglycemia (IAH), are at very high risk of severe hypoglycemia. IAH affects approximately 25% of patients with T1DM. Brain lactate may be involved in the development of IAH. A recent study indicated increased brain lactate utilization during hypoglycemia in T1DM patients with IAH, which did not occur in patients with normal awareness of hypoglycemia (NAH). Conversely, administration of lactate to patients with NAH has been shown to attenuate counterregulatory hormone responses to and symptomatic awareness of hypoglycemia, thus causing a situation that resembles IAH. It has, however, not been demonstrated whether the excess of lactate is actually taken up or metabolized by the brain, and if so whether this occurs under euglycemic or hypoglycemic conditions or both. This project consists of two related studies. The objective of part 1 is to investigate the effect of elevated plasma lactate levels that are sufficient to impair awareness of hypoglycemia on brain lactate concentrations during euglycemia and hypoglycemia in T1DM patients with NAH. The objective of part 2 is to compare the effect of exogenous lactate on brain lactate concentrations between T1DM patients with NAH and T1DM patients with IAH. Furthermore, this study aims to determine the effect of acute hypoglycemia on the inflammatory function and composition of peripheral blood mononuclear cells.