In June 2024, a Tsinghua University team published cryo-electron microscopy structures of human GLUT9, the high-capacity urate transporter that is one of the most promising drug targets in gout. One structure shows GLUT9 bound to urate. The other shows it bound to apigenin, sitting in the same pocket as a competitive inhibitor. That is a genuinely significant structural finding, and it has been widely misread as evidence that apigenin lowers uric acid in people. The animal data are messier than that, and one study points in the opposite direction entirely.
Key Takeaways
- A 2024 Nature Communications paper resolved apigenin bound inside the substrate pocket of human GLUT9 at 3.3 angstrom resolution, confirming it acts as a competitive inhibitor of the urate transporter.
- Two mouse studies found apigenin or its 7-O-glucoside lowered serum uric acid, inhibited xanthine oxidase, and shifted renal urate transporter expression (GLUT9 and URAT1 down, OAT1 up).
- A 2011 study found the opposite: apigenin and four other flavonoids raised serum uric acid in mice, and the authors concluded explicitly that they are not candidates for replacing allopurinol.
- The concentrations used in the structural and cell work are micromolar. Human plasma apigenin after a realistic dose sits in the low nanomolar range, a gap of roughly a thousandfold.
- No human trial has measured apigenin’s effect on serum uric acid or gout flares. Gout has genuinely effective drugs, and untreated hyperuricemia damages joints and kidneys.
What the GLUT9 Structure Actually Established
Urate is a paradox: a potent antioxidant in serum at normal levels, and the direct cause of gout when it accumulates. GLUT9 is the transporter that moves it, and it is a target precisely because blocking urate reabsorption in the kidney increases urinary excretion.
The 2024 structures resolved human GLUT9 in complex with urate at 3.5 angstroms and with apigenin at 3.3 angstroms, both in an inward-open conformation with the substrate pocket facing the cell interior.[1] The paper established two things: why GLUT9 prefers urate over glucose despite belonging to the glucose transporter family, and that apigenin inhibits it by physically occupying the substrate binding site.
What the paper did not claim is that apigenin is a gout treatment. Its stated purpose is to provide structural information for developing specific GLUT9 inhibitors. Apigenin here is a molecular tool that made the pocket visible, and the natural next step is designing a better-binding molecule around what that structure revealed.
The Animal Studies That Support It
Two mouse studies do report urate lowering. A 2022 study in Pharmaceuticals induced acute hyperuricemia with potassium oxonate plus hypoxanthine over seven days. Apigenin lowered serum uric acid, creatinine and blood urea nitrogen, cut IL-1beta, IL-6, IL-18 and TNF-alpha, raised IL-10, and reduced liver xanthine oxidase activity and urine protein.[2]
The transporter findings are the interesting part. Renal GLUT9 and URAT1 expression fell while OAT1 rose, which is the exact pattern you would want: less reabsorption, more secretion. The authors attributed the anti-inflammatory arm to suppression of JAK2/STAT3 signaling.
A 2023 study in Phytomedicine reached a similar conclusion via apigenin 7-O-glucoside, the glycoside form found in peony leaf extract. In hyperuricemic mice it reduced uric acid, creatinine and malondialdehyde, inhibited xanthine oxidase both in vitro and in liver tissue, and modulated all four major renal urate transporters: URAT1, GLUT9, OAT1 and ABCG2.[3]
The Study That Points the Other Way
A 2011 paper in Food and Chemical Toxicology tested genistein, apigenin, quercetin, rutin and astilbin on xanthine oxidase activity and serum uric acid in normal and hyperuricemic mice. Its findings contradict the picture above on both counts.[4]
In vitro, none of the flavonoids significantly affected xanthine oxidase activity. In vivo, serum uric acid in the flavonoid-treated mice was higher than in controls. The authors’ conclusion is blunt: the flavonoids tested are not candidates for replacing allopurinol as a treatment to reduce serum uric acid.
This study is older and smaller than the 2022 and 2023 work, and the models differ. But it is a direct, published contradiction in the same species measuring the same endpoint, and any honest summary has to carry it. Three animal studies, two positive and one negative, is not a settled question. It is an open one.
The Concentration Problem Nobody Mentions
This is the gap that decides how much any of the above matters in practice. Structural and cell studies work at micromolar concentrations. Human pharmacokinetic data put apigenin far below that.
A controlled human ADME study found that free apigenin is poorly absorbed, with metabolites equivalent to only 0.5 percent of intake recovered in urine over 24 hours. Glycoside forms fared much better, with chamomile tea reaching 34 percent and parsley 11.2 percent urinary recovery, but the circulating species were apigenin glucuronides and sulfate rather than free apigenin.[5]
That matters twice over. Plasma concentrations from a realistic dose land roughly a thousandfold below what the GLUT9 and xanthine oxidase experiments used. And the molecule actually circulating is a conjugate, not the free aglycone that was crystallized in the GLUT9 pocket. Whether a glucuronide binds that site the same way is an unanswered question, not a technicality.
What This Means If You Have Gout
Gout is unusual among chronic conditions in that the drugs work well. Allopurinol and febuxostat lower urate reliably, and sustained treatment to target dissolves existing crystal deposits. Untreated hyperuricemia is not a cosmetic problem: it produces joint erosion and contributes to kidney disease.
Against that, apigenin offers a compelling structure, two supportive rodent studies, one contradictory rodent study, and zero human data. Treating it as an alternative to urate-lowering therapy inverts the evidence hierarchy completely.
Two practical notes if you take apigenin for other reasons and also have gout. Apigenin inhibits CYP1A2, CYP2C9 and CYP3A4, so interaction checking matters more than usual if you are on multiple medications. And if you monitor serum urate, note the date you started any new supplement so an unexpected change has a candidate explanation.
Bottom Line
The GLUT9 structure is real, important, and about drug design rather than supplementation. Two mouse studies support urate lowering through combined xanthine oxidase inhibition and renal transporter modulation, and a third found apigenin raised serum uric acid and concluded it cannot replace allopurinol. Human plasma concentrations sit far below the levels used in every one of these experiments, and the circulating form is a conjugate rather than free apigenin. No human has been studied. This is a promising target, not a working remedy.
References
- Shen Z, Xu L, Wu T, et al. Structural basis for urate recognition and apigenin inhibition of human GLUT9. Nature Communications (2024). PMID 38866775
- Liu T, Gao H, Zhang Y, et al. Apigenin Ameliorates Hyperuricemia and Renal Injury through Regulation of Uric Acid Metabolism and JAK2/STAT3 Signaling Pathway. Pharmaceuticals (2022). PMID 36422572
- Zhang Y, Li Y, Li C, et al. Paeonia suffruticosa Andrews leaf extract and its main component apigenin 7-O-glucoside ameliorate hyperuricemia by inhibiting xanthine oxidase activity and regulating renal urate transporters. Phytomedicine (2023). PMID 37478683
- Huang J, Wang S, Zhu M, et al. Effects of genistein, apigenin, quercetin, rutin and astilbin on serum uric acid levels and xanthine oxidase activities in normal and hyperuricemic mice. Food and Chemical Toxicology (2011). PMID 21600261
- Borges G, Fong RY, Ensunsa JL, et al. Absorption, distribution, metabolism and excretion of apigenin and its glycosides in healthy male adults. Free Radical Biology and Medicine (2022). PMID 35452808
These statements have not been evaluated by the Food and Drug Administration. This information is not intended to diagnose, treat, cure, or prevent any disease. Content is for informational purposes only and is not medical advice; consult a qualified healthcare provider before starting any supplement. As an Amazon Associate we earn from qualifying purchases.
