Cellular deconstruction of the human skeletal muscle microenvironment identifies an exercise-induced histaminergic crosstalk

A comprehensive view of muscle glucose uptake: regulation by insulin, contractile activity, and exercise

Skeletal muscle is the main site of glucose deposition in the body during meals and the major glucose utilizer during physical activity. Although in both instances the supply of glucose from the circulation to the muscle is of paramount importance, in most conditions the rate-limiting step in glucose uptake, storage, and utilization is the transport of glucose across the muscle cell membrane. This step is dependent upon the translocation of the insulin- and contraction-responsive glucose transporter GLUT4 from intracellular storage sites to the sarcolemma and T tubules. Here, we first analyze how glucose can traverse the capillary wall into the muscle interstitial space. We then review the molecular processes that regulate GLUT4 translocation in response to insulin and muscle contractions and the methodologies utilized to unravel them. We further discuss how physical activity and inactivity, respectively, lead to increased and decreased insulin action in muscle and touch upon sex differences in glucose metabolism. Although many key processes regulating glucose uptake in muscle are known, the advent of newer and bioinformatics tools has revealed further molecular signaling processes reaching a staggering level of complexity. Much of this molecular mapping has emerged from cellular and animal studies and more recently from application of a variety of -omics in human tissues. In the future, it will be imperative to validate the translatability of results drawn from experimental systems to human physiology.

Histamine is a molecular transducer of adaptation to endurance exercise training in humans

Histamine is an apparent molecular transducer of physical activity responses and antihistamines modify transcription of many of the genes responding to exercise. The purpose of this study was to determine the role of histamine-receptor activation in adaptations to endurance exercise training. Sixteen healthy, nonsmoking individuals participated in a randomized double-blind placebo-controlled exercise training protocol with an experimental group receiving combined histamine H1/H2-receptor antagonists (blockade) and a control group receiving placebo capsules (placebo) before each exercise training session. Following 6 wk of endurance exercise training (21 training sessions), we determined the effect of blockade versus placebo on improvements in fitness and some of its determinants. The rate of improvement in peak power output over the period of exercise training intervention was 1.62 (0.85, 2.39)% per week in the blockade versus 3.05 (2.27, 3.82)% per week in the placebo group (P < 0.05 blockade vs. placebo). This was paralleled by blunted adaptations in vascular function and oxidative enzyme capacity but not by peak aerobic capacity (V̇o2peak), which increased independent of blockade. Blocking histamine's actions during endurance exercise training via common over-the-counter antihistamines resulted in diminished gains in fitness, indicating that exercise-induced histamine release is important in generating many of the positive adaptations to exercise training that result in improvements in fitness.NEW & NOTEWORTHY Histamine appears to be intimately involved with skeletal muscle responses during and following exercise. Blocking histamine's actions during endurance exercise training by taking common over-the-counter antihistamines resulted in diminished gains in fitness. These results indicate that exercise-induced histamine release is important in generating many of the positive adaptations to exercise training.