Kinetics of lactate metabolism after submaximal ergometric exercise in HIV-infected patients

It is unknown whether high levels of lactate result from enhanced production or decreased degradation. We therefore investigated differences in the kinetics of plasma lactic acid in HIV-infected patients receiving or not receiving highly active antiretroviral therapy (HAART) and in uninfected controls after submaximal ergometric exercise.

Ten healthy controls, 11 HIV-infected therapy-naïve patients, 15 HIV-infected patients on HAART with normal baseline lactate levels, and nine HIV-infected patients on HAART with elevated baseline lactate levels >2 mmol/L performed 10 min of ergometric exercise, with a heart rate of 200 beats/min minus age. Lactate levels were measured at baseline, at the end of exercise and 15, 30, 45, 60 and 120 min thereafter.

Mean baseline lactate levels were 1.4, 1.5, 1.5 and 2.8 mmol/L in the controls, the therapy-naïve patients, the patients on HAART with normal lactate levels and the patients on HAART with elevated lactate levels, respectively. Maximum lactate levels after exercise were similar in all groups (9.7, 9.4, 9.0 and 10.1 mmol/L, respectively). Significant differences were found in the slope of lactate decline between controls and untreated individuals (P=0.038) and between patients on HAART with normal baseline lactate and patients on HAART with elevated baseline lactate (P=0.028).

Differences in lactate metabolism do exist between healthy controls and HIV-infected therapy-naïve individuals. Thus, HIV infection in itself may influence lactate levels. Elevated baseline lactate levels are associated with a delayed decline of lactate after exercise. These results could be explained by impaired lactate clearance. Lactate production upon exercise does not seem to be affected by baseline lactate levels.