Glucose Ingestion Inhibits Endurance Exercise-Induced IL-6 Producing Macrophage Infiltration in Mice Muscle

Abstract

Background: Carbohydrate (CHO) supplementation during exercise attenuates exercise-induced increases in plasma Interleukin (IL)-6 concentration. However, the effects of CHO supplementation on muscle IL-6 production during endurance exercise is controversial. The purpose of this study was to investigate the effects of CHO supplementation on muscle IL-6 production during endurance exercise with a special focus on the IL-6 producing cells.

Methods: C57BL/6J mice were divided into three groups-sedentary with water ingestion group as the control (Con; n = 10), exercise with water ingestion group (Ex; n = 10), and exercise with 6% glucose ingestion group (Ex + glucose; n = 10). The Ex and Ex + glucose groups completed 3 h of treadmill running (24 m/min, 7% incline) and were sacrificed immediately after exercise.

Results: The exercise-induced increases of plasma IL-6 concentration and gastrocnemius IL-6 gene expression were attenuated by glucose ingestion. However, the increases of soleus IL-6 gene expression and gastrocnemius and soleus IL-6 protein expression were not attenuated by glucose ingestion. Furthermore, we observed that macrophages that infiltrated muscle produce IL-6 and glucose ingestion attenuated the infiltration of IL-6-producing macrophages.

Conclusion: This study revealed that infiltrating macrophages may be one type of IL-6-producing cells during endurance exercise, and the infiltration of these cells in muscle was attenuated by glucose ingestion. However, the effects of glucose ingestion on muscle IL-6 production were limited.

Keywords: endurance exercise; glucose ingestion; interleukin 6 (IL-6); macrophage; monocyte chemotactic protein (MCP)-1.

Figure 1

Effects of exercise and glucose ingestion on plasma Interleukin (IL)-6 concentration. The data are presented as means ± standard error (SE). The differences in IL-6 concentration between Ex and Con or Ex + glucose are presented Δ means ± SE above the bar. p-values for the differences between Ex and Con or Ex + glucose are presented below the bar.

Figure 2

Effects of exercise and glucose ingestion on IL-6 mRNA expression in (A) gastrocnemius and (B) soleus. The data are presented as the fold change ± SE, relative to the values from the Con. * p < 0.05 compared to Con. # p < 0.05, compared to Ex.

Figure 3

Effects of exercise and glucose ingestion on IL-6 protein concentration in (A) gastrocnemius and (B) soleus. The data are presented as means ± SE. * p < 0.05, ** p < 0.01 compared to Con.

Figure 4

Effects of exercise and glucose ingestion on macrophage infiltration in gastrocnemius. (A) Localization of F4/80 [green] and IL-6 [red] of gastrocnemius detected by immunofluorescence staining. Arrows indicate F4/80 and IL-6 double positive cells. Scale bar is 100 µm. (B) The number of F4/80 positive cells and (C) the number of F4/80 and IL-6 double positive cells. (D) Monocyte chemotactic protein (MCP)-1 mRNA expression in gastrocnemius. The data are presented as means ± SE. * p < 0.05, ** p < 0.01 compared to Con. ## p < 0.01, $ p = 0.086 compared to Ex.