Hyperglycemia suppresses Lactate Clearance during Exercise in Type 1 Diabetes.

CONTEXT:Circulating lactate concentration is an important determinant of exercise tolerance. OBJECTIVE:To determine the role of hyperglycemia on lactate metabolism during exercise in type 1 diabetes (T1D). DESIGN:Protocol involved compared T1D participants and participants without diabetes (ND) at euglycemia [5.5mM] or hyperglycemia [9.2mM] in random order in T1D and at euglycemia in ND. SETTING:Clinical Research Unit, University of Virginia, Charlottesville, VA. PARTICIPANTS:7 T1D and 7 ND. INTERVENTION:[1-13C] lactate infusion, exercise at 65% VO2max, euglycemia and hyperglycemia visits. MAIN OUTCOME MEASURE:Lactate turnover before, during and after 60 min of exercise at 65% VO2max. RESULTS:A two-compartment model with loss only from the peripheral compartment described lactate kinetics. Volume of distribution of the accessible compartment was similar between T1D and ND (p=0.76) and concordant to plasma volume (∼40ml/kg). Circulating lactate concentrations were higher (p<0.001) in T1D participants during exercise at hyperglycemia than euglycemia. Exercise induced lactate appearance did not differ (p=0.13) between hyperglycemia and euglycemia. However, lactate clearance was lower (p=0.03) during hyperglycemia than euglycemia in T1D. There were no differences in any of the above parameters between T1D and ND during euglycemia. CONCLUSIONS:Hyperglycemia modulates lactate metabolism during exercise by lowering lactate clearance leading to higher circulating lactate concentrations in T1D. This novel observation implies that exercise during hyperglycemia can lead to higher circulating lactate concentrations thus increasing the likelihood of reaching the lactate threshold sooner in T1D, and has high translational relevance for both providers and recreationally active people with Type 1 diabetes.