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Pu-erh tea hot-water extract activates Akt and induces insulin-independent glucose transport in rat skeletal muscle.

Journal of medicinal food (2013-02-27)
Xiao Ma, Satoshi Tsuda, Xin Yang, Ning Gu, Hiroko Tanabe, Rieko Oshima, Tetsuya Matsushita, Tatsuro Egawa, Ai-Jun Dong, Bei-Wei Zhu, Tatsuya Hayashi
ABSTRACT

Skeletal muscle is a major organ that is important for whole-body glucose metabolism. We found that when isolated rat epitrochlearis muscle was incubated with a Pu-erh tea hot-water extract (PTE) for 30 min, the rate of 3-O-methyl-D-glucose (3MG) transport increased in the absence of insulin. This activation was associated with an increase in Ser(473) phosphorylation of Akt, a signaling intermediary leading to insulin-dependent glucose transport, but not Tyr(458) phosphorylation of phosphoinositide 3-kinase p85, an upstream molecule of Akt. PTE-stimulated 3MG transport was also not accompanied by Thr(172) phosphorylation of the catalytic α-subunit of 5'-AMP-activated protein kinase (AMPK). Gallic acid, a water-soluble ingredient in Pu-erh tea, stimulated Akt phosphorylation, but not AMPK phosphorylation. These results suggest that Pu-erh tea potentially promotes skeletal muscle glucose transport at least in part by activating Akt.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Gallic acid, 97.5-102.5% (titration)
Supelco
Gallic acid, certified reference material, TraceCERT®