Impact of Vitamin E Supplementation on High-Density Lipoprotein in Patients With Haptoglobin Genotype-Stratified Diabetes: A Systematic Review of Randomized Controlled Trials

Background: Vitamin E, an essential micronutrient with antioxidant potential, can dramatically reduce the cardiovascular risk in individuals with haptoglobin (Hp) 2-2 genotype diabetes; however, the underlying mechanism remains unclear. Objective: The objective of this study is to evaluate the effect of vitamin E supplementation on high-density lipoprotein (HDL) levels and function in individuals with diabetes stratified by Hp genotype. Methods: All relevant studies published up to May 2023 were systematically reviewed using PubMed, Cochrane Library, Web of Science, Chinese Wanfang, China Science and Technology Journal, and Chinese National Knowledge Infrastructure databases. Randomized controlled trials that evaluated the effects of vitamin E supplementation on HDL levels were included. The outcomes assessed were changes in HDL concentrations, cholesterol efflux, and HDL-associated lipid peroxides. Results: In total, 163 publications were selected. Based on inclusion and exclusion selection and quality assessment, five studies with 463 participants were included. Vitamin E supplementation did not exert any effect on HDL levels in individuals with diabetes with any Hp genotype. Three of the five studies revealed that vitamin E improved cholesterol efflux and HDL lipid peroxides in individuals with Hp2-2 diabetes but did not positively impact HDL function in Hp1 carriers. Conclusions: Although vitamin E supplementation did not significantly impact HDL levels in individuals with diabetes of any Hp genotype, it may improve HDL function in individuals with Hp2-2 diabetes. These findings indicate a pharmacogenetic interaction between vitamin E and the Hp genotype on HDL function. Moreover, vitamin E supplementation may be an effective strategy for specific individuals with diabetes.