In Mice, 1 g/kg Won on Inflammation and 2 g/kg on Tissue

A mouse study of oolong tea polyphenols against high uric acid reported two safety measures that point at different doses. The highest dose cut serum uric acid the furthest and left the best-preserved kidney tissue under the microscope. The middle dose produced the lower inflammatory markers and suppressed the signaling pathway the highest dose switched on.

The work was published August 11 in Frontiers in Nutrition by Fenqi Lin and colleagues, who mapped 59 targets shared between oolong tea polyphenols and hyperuricemia, the excess-uric-acid condition behind gout, and named PI3K-AKT signaling as the hub. Seven compounds were analyzed in the extract: EGCG, GCG, ECG, EGC, caffeine, epicatechin and catechin.

Sixty male Kunming mice of 18 to 20 g received oral potassium oxonate at 300 mg/kg for 15 days to induce hyperuricemia, then the polyphenol extract for 15 days more at 0.5, 1 or 2 g/kg/day.

Serum uric acid ran 180.00 +/- 36.59 micromol/L in normal mice and 600.49 +/- 14.53 in untreated hyperuricemic ones. The 2 g/kg group came in at 405.72 +/- 1.50, the largest reduction of the doses reported and still above normal. At 1 g/kg, renal TNF-alpha fell to 655.94 +/- 23.55 ng/g against 853.73 +/- 9.66 untreated, and xanthine oxidase, the enzyme that produces uric acid, fell to 0.59 +/- 0.01 U/g against 2.05 +/- 0.29.

The 0.5 and 1 g/kg doses suppressed phosphorylation of PI3K, AKT and mTOR. The 2 g/kg dose activated that pathway instead and showed elevated IL-1beta, an inflammatory marker, which the paper describes as a paradox.

The tissue slides ran the other way. In the 1 g/kg group, "moderate tubular degeneration and crystal deposition were observed, accompanied by moderate interstitial inflammation and fibrosis." In the 2 g/kg group, "only mild protein deposition was observed in renal tubules, slight interstitial edema, and well-preserved glomerular architecture."

The study concludes that "a medium dose of TP may represent a feasible dietary strategy against hyperuricemia," and describes the high dose as having "paradoxically elevated interleukin-1beta (IL-1beta) and overactivated PI3K/AKT/mTOR signaling." The histopathology the authors report for that medium dose is the more damaged of the two.

Sixty mice, an isolated polyphenol extract at fixed doses, 15 days. Not brewed tea, and not a trial in people.

Sources: Frontiers in Nutrition, Lin et al., "Oolong tea polyphenols target hyperuricemia through PI3K/AKT/mTOR pathway modulation"