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Lactate and glucose interactions during rest and exercise in men: effect of exogenous lactate infusion
Author(s) -
Miller Benjamin F.,
Fattor Jill A.,
Jacobs Kevin A.,
Horning Michael A.,
Navazio Franco,
Lindinger Michael I.,
Brooks George A.
Publication year - 2002
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.2002.027128
Subject(s) - glycogenolysis , chemistry , medicine , endocrinology , blood lactate , lactic acid , anaerobic exercise , carbohydrate , carbohydrate metabolism , glycogen , oxygen , metabolism , biochemistry , heart rate , biology , blood pressure , organic chemistry , bacteria , genetics , physiology
To test the hypothesis that lactate plays a central role in the distribution of carbohydrate (CHO) potential energy for oxidation and glucose production (GP), we performed a lactate clamp (LC) procedure during rest and moderate intensity exercise. Blood [lactate] was clamped at ≈4 m m by exogenous lactate infusion. Subjects performed 90 min exercise trials at 65 % of the peak rate of oxygen consumption (V̇ O2 ,peak ; 65 %), 55 % V̇ O2 ,peak (55 %) and 55 % V̇ O2 ,peak with lactate clamped to the blood [lactate] that was measured at 65 % V̇ O2 ,peak (55 %‐LC). Lactate and glucose rates of appearance ( R a ), disappearance ( R d ) and oxidation ( R ox ) were measured with a combination of [3‐ 13 C]lactate, H 13 CO 3 − , and [6,6‐ 2 H 2 ]glucose tracers. During rest and exercise, lactate R a and R d were increased at 55 %‐LC compared to 55 %. Glucose R a and R d were decreased during 55 %‐LC compared to 55 %. Lactate R ox was increased by LC during exercise (55 %: 6.52 ± 0.65 and 55 %‐LC: 10.01 ± 0.68 mg kg −1 min −1 ) which was concurrent with a decrease in glucose oxidation (55 %: 7.64 ± 0.4 and 55 %‐LC: 4.35 ± 0.31 mg kg −1 min −1 ). With LC, incorporation of 13 C from tracer lactate into blood glucose (L → GNG) increased while both GP and calculated hepatic glycogenolysis (GLY) decreased. Therefore, increased blood [lactate] during moderate intensity exercise increased lactate oxidation, spared blood glucose and decreased glucose production. Further, exogenous lactate infusion did not affect rating of perceived exertion (RPE) during exercise. These results demonstrate that lactate is a useful carbohydrate in times of increased energy demand.