Acute impairment of insulin-mediated capillary recruitment and glucose uptake in rat skeletal muscle in vivo by TNF-alpha.
Level 5 - mechanism / opinion, no new human data
Animal experimental research (rodent model).
PubMed 11078458 · doi:10.2337/diabetes.49.11.1904
What was done
Researchers evaluated the impact of a 3-hour intravenous infusion of TNF-alpha (0.5 microg/h/kg) in control and euglycemic-hyperinsulinemic clamped (10 mU/min/kg for 2 hours) anesthetized rats. Measured outcomes included hind-leg glucose uptake, soleus and plantaris muscle uptake of 2-deoxyglucose (2-DG), femoral blood flow (FBF), vascular resistance (VR), and capillary recruitment assessed via metabolism of infused 1-methylxanthine (1-MX).
What was found
Insulin alone significantly (P < 0.05) increased FBF 1.7-fold, increased capillary recruitment 2.5-fold, decreased VR, and increased hind-leg glucose uptake 4-fold alongside increased soleus and plantaris 2-DG uptake. TNF-alpha alone produced no significant baseline changes. When combined with insulin, TNF-alpha completely prevented the insulin-mediated increases in FBF and capillary recruitment as well as the reduction in VR. Furthermore, TNF-alpha significantly reduced (P < 0.05) insulin-mediated total hind-leg glucose uptake by 61% and muscle 2-DG uptake by at least 50%.
Why it matters
This study provides direct in vivo evidence that acute inflammation via TNF-alpha impairs insulin-stimulated microvascular recruitment in skeletal muscle, suggesting a hemodynamic mechanism contributing to cytokine-induced insulin resistance.
Limits
The experiment was conducted exclusively in anesthetized rats, limiting direct extrapolation to human physiology. Animal sample sizes per group, exact baseline values, and measures of variance were not reported in the abstract. The study tested only acute 3-hour exposure and did not determine whether microvascular impairment directly caused the decrease in glucose uptake or occurred in parallel.
Cited by
- supports Elevated inflammatory cytokines cause rapid insulin resistance in humans, rodents, and cell cultures.