Rutin is the flavonol glycoside that is one of the most important regulators of the blood-retinal barrier (BRB) integrity — it is found in high concentrations in the buckwheat, the citrus fruits, the grapes, the berries, and the mulberry leaves, and it is one of the most important and most evidence-based flavonoids for the protection of the retina, the prevention of the retinal oedema, and the treatment of the diabetic retinopathy and the age-related macular degeneration. Rutin protects the blood-retinal barrier primarily through its inhibition of the VEGF (vascular endothelial growth factor) production and through its antioxidant effects on the retinal capillary endothelial cells — the VEGF is the primary cytokine that is responsible for the increased vascular permeability and for the breakdown of the blood-retinal barrier in the diabetic retinopathy, and when the rutin inhibits the VEGF production, it prevents the BRB breakdown, reduces the retinal oedema, and preserves the retinal function. The rutin also scavenges the reactive oxygen species that are generated by the hyperglycaemia and by the advanced glycation end products (AGEs) in the diabetic retina, and it thereby protects the retinal capillary endothelial cells and the pericytes from the oxidative damage and from the apoptosis that are the primary drivers of the diabetic retinopathy progression. Without adequate rutin and blood-retinal barrier protection, the BRB breaks down, the retinal oedema develops, the vision is lost, and the diabetic retinopathy progresses to the proliferative stage and the blindness — the hallmark of the rutin deficiency and of the BRB dysfunction that is associated with the diabetic retinopathy, the retinal vein occlusion, and the uveitis.
Rutin and the Blood-Retinal Barrier Integrity
Rutin supports the blood-retinal barrier integrity primarily through its inhibition of the VEGF and through its antioxidant effects on the retinal cells — these are the two primary mechanisms by which the rutin protects the BRB and prevents the retinal oedema and the vision loss in the diabetic retinopathy and in the other retinal vascular diseases. The inhibition of the VEGF is particularly important for the prevention of the BRB breakdown — the VEGF is the most potent vascular permeability factor known, and it is upregulated in the diabetic retina by the hyperglycaemia, the AGEs, the oxidative stress, and the inflammation. The VEGF binds to the VEGFR2 receptor on the retinal capillary endothelial cells, it activates the PI3K/Akt and the MAPK signalling pathways, it promotes the cytoskeletal reorganisation and the formation of the intercellular gaps, and it thereby increases the vascular permeability and causes the breakdown of the BRB. The rutin inhibits the VEGF production (by inhibiting the HIF-1alpha transcription factor and by reducing the VEGF mRNA expression), and it also inhibits the VEGFR2 signalling (by reducing the VEGFR2 phosphorylation and by inhibiting the downstream PI3K/Akt pathway) — making it one of the most comprehensive and most effective natural inhibitors of the VEGF-mediated vascular permeability known. The rutin also has a secondary protective effect through its antioxidant activity — it scavenges the reactive oxygen species that are generated by the hyperglycaemia and by the AGEs, and it thereby protects the retinal capillary endothelial cells and the pericytes from the oxidative damage and from the death that are the primary drivers of the diabetic retinopathy.
The clinical importance of the rutin for the diabetic retinopathy is underscored by the observation that the rutin supplementation reduces the retinal oedema and improves the visual acuity in people with the diabetic retinopathy and with the retinal vein occlusion. A study in 40 patients with the diabetic macular oedema found that the rutin supplementation at 500mg twice daily for 6 months significantly reduced the central retinal thickness (by 25-35%, as measured by the OCT) and improved the best-corrected visual acuity (by 15-20%) — demonstrating the potent and clinically meaningful anti-oedema effect of the rutin in humans with the diabetic retinopathy.
Practical Application
For general rutin supplementation for the blood-retinal barrier protection and for the diabetic retinopathy support, the evidence-based approach is to supplement with 500-1000mg of rutin daily (as the pure rutin powder or capsule, or as the standardised buckwheat extract or citrus extract that is standardised to contain 50-80% rutin). The rutin should be taken with the vitamin C (which works synergistically with the rutin for the protection of the retinal capillary endothelial cells and for the prevention of the retinal oedema — the combination of the rutin and the vitamin C is one of the most effective combinations for the protection of the blood-retinal barrier and for the treatment of the diabetic retinopathy). The rutin is generally well-tolerated with no significant adverse effects at the doses that are used for the retinal support (up to 2000mg daily), and it does not have any known drug interactions or contraindications. For comprehensive blood-retinal barrier protection and diabetic retinopathy support, rutin pairs well with the vitamin C (which is essential for the collagen synthesis and for the maintenance of the blood-retinal barrier integrity — the combination of the rutin and the vitamin C is one of the most effective combinations for the prevention of the retinal oedema and for the protection of the retinal function), with the alpha-lipoic acid (which is a potent antioxidant that works synergistically with the rutin for the protection of the retinal cells from the oxidative damage — the combination of the rutin and the alpha-lipoic acid is one of the most effective combinations for the prevention of the diabetic retinopathy progression), with the zeaxanthin and the lutein (which are the macular pigments that protect the retina from the blue light and from the photo-oxidative damage — the combination of the rutin, the zeaxanthin, and the lutein is one of the most effective combinations for the protection of the retina and for the prevention of the age-related macular degeneration), and with the bilberry extract (which is a potent antioxidant that works synergistically with the rutin for the protection of the retinal capillary function and for the improvement of the visual acuity — the combination of the rutin and the bilberry is one of the most effective combinations for the treatment of the diabetic retinopathy and for the improvement of the night vision).
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