Glucose ingestion attenuates interleukin-6 release from contracting skeletal muscle in humans

Abstract

To examine whether glucose ingestion during exercise affects the release of interleukin-6 (IL-6) from the contracting limb, seven men performed 120 min of semi-recumbent cycling on two occasions while ingesting either 250 ml of a 6.4 % carbohydrate (GLU trial) or sweet placebo (CON trial) beverage at the onset of, and at 15 min intervals throughout, exercise. Muscle biopsies obtained before and immediately after exercise were analysed for glycogen and IL-6 mRNA expression. Blood samples were simultaneously obtained from a brachial artery and a femoral vein prior to and during exercise and leg blood flow was measured by thermodilution in the femoral vein. Net leg IL-6 release, and net leg glucose and free fatty acid (FFA) uptake, were calculated from these measurements. The arterial IL-6 concentration was lower (P < 0.05) after 120 min of exercise in GLU, but neither intramuscular glycogen nor IL-6 mRNA were different when comparing GLU with CON. However, net leg IL-6 release was attenuated (P < 0.05) in GLU compared with CON. This corresponded with an enhanced (P < 0.05) glucose uptake and a reduced (P < 0.05) FFA uptake in GLU. These results demonstrate that glucose ingestion during exercise attenuates leg IL-6 release but does not decrease intramuscular expression of IL-6 mRNA.

Figures

Figure 1. Arterial plasma [IL-6] and leg IL-6 release before and during semi-recumbent cycling with or without the ingestion of glucose

Arterial plasma [IL-6] (top) and leg IL-6 release (bottom) before (0 min) and during 120 min of semi-recumbent cycling at 62 ± 2 % of maximal oxygen uptake with (□) or without (•) the ingestion of glucose throughout exercise.* Significant difference (P < 0.05) between trials. Data expressed as means ±s.e.m. (n = 7).

Figure 2. Arterial plasma [glucose] and leg glucose uptake before and during semi-recumbent cycling with or without the ingestion of glucose

Arterial plasma [glucose ](top) and leg glucose uptake (bottom) before (0 min) and during 120 min of semi-recumbent cycling at 62 ± 2 % of maximal oxygen uptake with (□) or without (•) the ingestion of glucose throughout exercise.* Significant difference (P < 0.05) between trials. Data expressed as means ±s.e.m. (n = 7).

Figure 3. Arterial plasma [FFA] and leg FFA uptake before and during semi-recumbent cycling with or without the ingestion of glucose

Arterial plasma [FFA] (top) and leg FFA uptake (bottom) before (0 min) and during 120 min of semi-recumbent cycling at 62 ± 2 % of maximal oxygen uptake with (□) or without (•) the ingestion of glucose throughout exercise.* Significant difference (P < 0.05) between trials. Data expressed as means ±s.e.m. (n = 7).

Figure 4. Intramuscular muscle glycogen content and IL-6 mRNA during semi-recumbent cycling with or without the ingestion of glucose

Intramuscular muscle glycogen (top) and IL-6 mRNA (bottom) contents before and after 120 min of semi-recumbent cycling at 62 ± 2 % of maximal oxygen uptake with (□) or without (▪) the ingestion of glucose throughout exercise. Data expressed as means ±s.e.m. (n = 7).