A newly synthetic chromium complex—Chromium ( d-phenylalanine) 3 activates AMP-activated protein kinase and stimulates glucose transport

Abstract

We synthesized the chromium (phenylalanine) 3 [Cr( d-phe) 3] by chelating chromium(III) with d-phenylalanine ligand in aqueous solution to improve the bioavailability of chromium, and reported that Cr( d-phe) 3 improved insulin sensitivity. AMP-activated protein kinase (AMPK) is a key mediator for glucose uptake and insulin sensitivity. To address the molecular mechanisms by which Cr( d-phe) 3 increases insulin sensitivity, we investigated whether Cr( d-phe) 3 stimulates glucose uptake via activation of AMPK signaling pathway. H9c2 myoblasts and isolated cardiomyocytes were treated with Cr( d-phe) 3 (25 μM). Western blotting was used for signaling determination. The glucose uptake was determined by 2-deoxy- d-glucose- 3H accumulation. HPLC measured concentrations of AMP. The mitochondrial membrane potential (Δ ψ) was detected by JC-1 fluorescence assay. Cr( d-phe) 3 stimulated the phosphorylation of α catalytic subunit of AMPK at Thr 172, as well the downstream targets of AMPK, acetyl-CoA carboxylase (ACC, Ser 212) and eNOS (Ser 1177). Moreover, Cr( d-phe) 3 significantly stimulated glucose uptake in both H9c2 cells and cardiomyocytes. AMPK inhibitor compound C (10 μM) dramatically inhibited the glucose uptake stimulated by Cr( d-phe) 3, while it did not affect insulin stimulation of glucose uptake. Furthermore, in vivo studies showed that Cr( d-phe) 3 also activated cardiac AMPK signaling pathway. The increase of cardiac AMP concentration and the decrease of mitochondrial membrane potential (Δ ψ) may contribute to the activation of AMPK induced by Cr( d-phe) 3. Cr( d-phe) 3 is a novel compound that activates AMPK signaling pathway, which contributes to the regulation of glucose transport during stress conditions that may be associated the role of AMPK in increasing insulin sensitivity.