Cold-induced PGC-1alpha expression modulates muscle glucose uptake through an insulin receptor/Akt-independent, AMPK-dependent pathway.
Level 5 - mechanism / opinion, no new human data
Animal laboratory study
PubMed 15165993 · doi:10.1152/ajpendo.00103.2004
What was done
Rats were exposed to 4°C cold for 4 days and treated acutely with insulin in the presence or absence of an antisense oligonucleotide targeting PGC-1alpha. Researchers measured protein expression of PGC-1alpha, uncoupling protein-3 (UCP-3), and GLUT4, alongside phosphorylation of the insulin receptor (IR), Akt (Ser473), and AMPK (Thr172) across type I and type II gastrocnemius muscle fibers. Glucose uptake and clearance were evaluated using hyperinsulinemic clamps.
What was found
The abstract reports directional findings without raw numbers or effect sizes. Cold exposure significantly increased PGC-1alpha and UCP-3 protein expression, clamp-derived glucose uptake, and GLUT4 expression and membrane localization in both fiber types. Cold-exposed rats exhibited lower insulin-induced IR tyrosine phosphorylation and Akt Ser473 phosphorylation, but an insulin-independent increase in AMPK Thr172 phosphorylation. Antisense inhibition of PGC-1alpha diminished clamp glucose clearance, reduced GLUT4 expression and membrane localization, and lowered AMPK phosphorylation, without altering IR or Akt phosphorylation.
Why it matters
This work demonstrates that cold-induced PGC-1alpha can stimulate skeletal muscle glucose uptake through an AMPK-mediated pathway rather than relying on canonical insulin receptor/Akt signaling.
Limits
Findings are restricted to a rodent model, limiting direct extrapolation to human metabolic physiology. The abstract provides no sample sizes, baseline values, or exact quantitative metrics and confidence intervals for glucose uptake and protein expression.
Cited by
- supports Cold exposure elevates norepinephrine, which increases PGC-1alpha and mitochondrial content in skeletal muscle tissue.