Vitamin E is a fat-soluble vitamin known for its antioxidant and anti-inflammatory properties. It has eight biochemical isomers (four tocopherols and four tocotrienols). Although alpha-tocopherol is common in supplements, emerging research supports delta-tocotrienol as the superior isomer with clinically relevant benefits across a variety of tissues. One unique effect of the delta-tocotrienols is that its anti-angiogenic properties (inhibiting new blood vessel formation) has the potential to help support eye health in type 2 diabetes mellitus (T2DM).
Uncontrolled hyperglycemia in T2DM increases oxidative stress, inflammation, thrombosis, and angiogenesis upregulation. Hyperglycemia can contribute to the development and progression of diabetic retinopathy, the most common microvascular complication of T2DM and a main contributor to adult blindness. Globally, 93 million people are affected by diabetic retinopathy.
The pathophysiology of diabetic retinopathy is still being investigated. Studies suggest the upregulation of vascular endothelial growth factor (VEGF), an angiogenic protein, as a hallmark feature of diabetic retinopathy. A systematic review and meta-analysis found serum VEGF to be a reliable biomarker in determining the severity and progression of diabetic retinopathy. Upregulated VEGF with hyperglycemia-induced oxidative stress and neurodegeneration leads to the thinning of retinal layers and the loss of neuronal functions. Tocotrienol reduces VEGF expression, attenuating diabetic retinopathy progression. Alpha-tocopherol does not have these anti-angiogenic properties, and it appears to antagonize the anti-angiogenic effects of tocotrienols.
A recent double-blind, randomized controlled trial of 55 participants with diabetic retinopathy investigated the effects of a tocotrienol-rich vitamin E supplement (200 mg twice daily for 12 months) for the progression of retinal microhemorrhages and diabetic macular edema. The tocotrienol group indicated a 48.38% decrease in diabetic macular edema compared to the placebo group, which had no significant changes to the development of retinal microhemorrhages. The study concluded that tocotrienol may have a significant role in potentially reducing the risk of early diabetic retinopathy progression.
Another common visual impairment in diabetic patients is cataracts. Hyperglycemia in T2DM increases oxidative and nitrosative stress, thereby impairing enzymes that maintain lens water and electrolyte homeostasis. Tocotrienols tend to accumulate in the eye and protect against cataract development, possibly due to their antioxidant properties.
A rodent study by Abdul Nasir and colleagues observed that topical tocotrienol in the range of 0.01% to 0.05% reduced the lenticular oxidative and nitrosative stress and delayed the onset and progression of cataracts. A follow-up rodent study observed that a topical tocotrienol microemulsion formulation restored lens transparency back to normal.
Studies show that tocotrienol supports glycemic control, health inflammatory responses, oxidative stress, and micro-ribonucleic acid expression in diabetic individuals. Therefore, tocotrienol may be considered a potential support for healthy blood glucose metabolism.
By Danielle Moyer, MS, CNS, LDN