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Inhibition of the mTOR/p70S6K pathway is not involved in the insulin-sensitizing effect of AMPK on cardiac glucose uptake.
. 2011 Aug; 301(2):H469-77.

Abstract

The AMP-activated protein kinase (AMPK) is known to increase cardiac insulin sensitivity on glucose uptake. AMPK also inhibits the mammalian target of rapamycin (mTOR)/p70 ribosomal S6 kinase (p70S6K) pathway. Once activated by insulin, mTOR/p70S6K phosphorylates insulin receptor substrate-1 (IRS-1) on serine residues, resulting in its inhibition and reduction of insulin signaling. AMPK was postulated to act on insulin by inhibiting this mTOR/p70S6K-mediated negative feedback loop. We tested this hypothesis in cardiomyocytes. The stimulation of glucose uptake by AMPK activators and insulin correlated with AMPK and protein kinase B (PKB/Akt) activation, respectively. Both treatments induced the phosphorylation of Akt substrate 160 (AS160) known to control glucose uptake. Together, insulin and AMPK activators acted synergistically to induce PKB/Akt overactivation, AS160 overphosphorylation, and glucose uptake overstimulation. This correlated with p70S6K inhibition and with a decrease in serine phosphorylation of IRS-1, indicating the inhibition of the negative feedback loop. We used the mTOR inhibitor rapamycin to confirm these results. Mimicking AMPK activators in the presence of insulin, rapamycin inhibited p70S6K and reduced IRS-1 phosphorylation on serine, resulting in the overphosphorylation of PKB/Akt and AS160. However, rapamycin did not enhance the insulin-induced stimulation of glucose uptake. In conclusion, although the insulin-sensitizing effect of AMPK on PKB/Akt is explained by the inhibition of the insulin-induced negative feedback loop, its effect on glucose uptake is independent of this mechanism. This disconnection revealed that the PKB/Akt/AS160 pathway does not seem to be the rate-limiting step in the control of glucose uptake under insulin treatment.

Authors+Show Affiliations

Pole of Cardiovascular Research, Institut de Recherche Expérimentale et Clinique, Université catholique de Louvain, Brussels, Belgium.No affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

21602475

Citation

Ginion, Audrey, et al. "Inhibition of the mTOR/p70S6K Pathway Is Not Involved in the Insulin-sensitizing Effect of AMPK On Cardiac Glucose Uptake." American Journal of Physiology. Heart and Circulatory Physiology, vol. 301, no. 2, 2011, pp. H469-77.
Ginion A, Auquier J, Benton CR, et al. Inhibition of the mTOR/p70S6K pathway is not involved in the insulin-sensitizing effect of AMPK on cardiac glucose uptake. Am J Physiol Heart Circ Physiol. 2011;301(2):H469-77.
Ginion, A., Auquier, J., Benton, C. R., Mouton, C., Vanoverschelde, J. L., Hue, L., Horman, S., Beauloye, C., & Bertrand, L. (2011). Inhibition of the mTOR/p70S6K pathway is not involved in the insulin-sensitizing effect of AMPK on cardiac glucose uptake. American Journal of Physiology. Heart and Circulatory Physiology, 301(2), H469-77. https://doi.org/10.1152/ajpheart.00986.2010
Ginion A, et al. Inhibition of the mTOR/p70S6K Pathway Is Not Involved in the Insulin-sensitizing Effect of AMPK On Cardiac Glucose Uptake. Am J Physiol Heart Circ Physiol. 2011;301(2):H469-77. PubMed PMID: 21602475.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Inhibition of the mTOR/p70S6K pathway is not involved in the insulin-sensitizing effect of AMPK on cardiac glucose uptake. AU - Ginion,Audrey, AU - Auquier,Julien, AU - Benton,Carley R, AU - Mouton,Céline, AU - Vanoverschelde,Jean-Louis, AU - Hue,Louis, AU - Horman,Sandrine, AU - Beauloye,Christophe, AU - Bertrand,Luc, Y1 - 2011/05/20/ PY - 2011/5/24/entrez PY - 2011/5/24/pubmed PY - 2011/10/1/medline SP - H469 EP - 77 JF - American journal of physiology. Heart and circulatory physiology JO - Am. J. Physiol. Heart Circ. Physiol. VL - 301 IS - 2 N2 - The AMP-activated protein kinase (AMPK) is known to increase cardiac insulin sensitivity on glucose uptake. AMPK also inhibits the mammalian target of rapamycin (mTOR)/p70 ribosomal S6 kinase (p70S6K) pathway. Once activated by insulin, mTOR/p70S6K phosphorylates insulin receptor substrate-1 (IRS-1) on serine residues, resulting in its inhibition and reduction of insulin signaling. AMPK was postulated to act on insulin by inhibiting this mTOR/p70S6K-mediated negative feedback loop. We tested this hypothesis in cardiomyocytes. The stimulation of glucose uptake by AMPK activators and insulin correlated with AMPK and protein kinase B (PKB/Akt) activation, respectively. Both treatments induced the phosphorylation of Akt substrate 160 (AS160) known to control glucose uptake. Together, insulin and AMPK activators acted synergistically to induce PKB/Akt overactivation, AS160 overphosphorylation, and glucose uptake overstimulation. This correlated with p70S6K inhibition and with a decrease in serine phosphorylation of IRS-1, indicating the inhibition of the negative feedback loop. We used the mTOR inhibitor rapamycin to confirm these results. Mimicking AMPK activators in the presence of insulin, rapamycin inhibited p70S6K and reduced IRS-1 phosphorylation on serine, resulting in the overphosphorylation of PKB/Akt and AS160. However, rapamycin did not enhance the insulin-induced stimulation of glucose uptake. In conclusion, although the insulin-sensitizing effect of AMPK on PKB/Akt is explained by the inhibition of the insulin-induced negative feedback loop, its effect on glucose uptake is independent of this mechanism. This disconnection revealed that the PKB/Akt/AS160 pathway does not seem to be the rate-limiting step in the control of glucose uptake under insulin treatment. SN - 1522-1539 UR - https://www.unboundmedicine.com/medline/citation/21602475/Inhibition_of_the_mTOR/p70S6K_pathway_is_not_involved_in_the_insulin_sensitizing_effect_of_AMPK_on_cardiac_glucose_uptake_ L2 - https://journals.physiology.org/doi/10.1152/ajpheart.00986.2010?url_ver=Z39.88-2003&rfr_id=ori:rid:crossref.org&rfr_dat=cr_pub=pubmed DB - PRIME DP - Unbound Medicine ER -