Effect of insulin and contraction up on glucose transport in skeletal muscle.
Level 5 - mechanism / opinion, no new human data
Narrative review of physiological and molecular mechanisms
PubMed 14642866 · doi:10.1016/s0079-6107(03)00055-5
What was done
This narrative review synthesized literature on the molecular pathways governing GLUT4 translocation and glucose transport in skeletal muscle in response to insulin, acute muscle contraction, endurance exercise training, and resistance training.
What was found
The abstract reports no numerical data or effect sizes. Qualitatively, insulin promotes GLUT4 translocation via a phosphatidylinositol 3-kinase-dependent pathway, whereas contraction-stimulated translocation operates through separate, insulin-independent pathways (potentially involving sarcoplasmic reticulum calcium release or autocrine/paracrine signals). Endurance training increases total GLUT4 content but reduces glucose utilization during sub-maximal exercise, likely due to reduced translocation efficiency. Resistance training effects remain debated, though studies link improved insulin sensitivity to increases in muscle mass.
Why it matters
Clarifying that exercise stimulates glucose uptake via pathways independent of insulin provides the mechanistic rationale for using exercise to bypass insulin resistance in metabolic disorders.
Limits
The abstract provides no primary human data, quantitative values, sample sizes, or systematic review methodology. Molecular mechanisms underlying adaptations to endurance and resistance training remain incompletely elucidated.
Cited by
- supports Physical activity stimulates glucose transporters and allows muscles to take up glucose directly without requiring insulin.