Study: Vitamin E may inhibit autoimmunity and prevent insulin resistance

The study, conducted using Swedish case-control data, concludes: “Vitamin E may play a protective role in the incidence of latent autoimmune diabetes in adults (LADA), potentially by inhibiting the development of autoimmunity and preventing insulin resistance.”

The authors suggest that a diet rich in vitamin E should be encouraged as a public health strategy. 

LADA​

LADA is a subtype of diabetes that often falls between types one and two, with an estimated prevalence ranging between 2% and 12% of all people with diabetes.​ 

LADA is characterised by an autoimmune response that gradually destroys insulin-producing cells in the pancreas.

Previous research ​suggests that vitamin E may play a protective role in the incidence of LADA by potentially inhibiting the development of autoimmunity and preventing insulin resistance, as vitamin E helps protect cells from damage caused by free radicals​. 

In the context of LADA, it is believed that vitamin E's antioxidant properties may help reduce oxidative stress ​and inflammation associated with autoimmune responses.

The study ​

The new study assessed cases and controls included in the Swedish population-based case-control Epidemiological Study of Risk Factors for LADA and Type 2 Diabetes (ESTRID) database, between 2010 and 2019.

The authors used two-sample Mendelian randomisation (MR) analyses on 584 LADA cases, 1989 type 2 diabetes cases, and 2276 controls, to assess causality between genetically predicted circulating antioxidants and LADA, using summary statistics from genome-wide association studies. 

Results showed that among the antioxidants, vitamins C and E were inversely associated with high LADA, but not with low LADA or type 2 diabetes. 

Results also showed that Vitamin E was associated with higher homeostasis model assessment of β-cell function (HOMA-β)​, an index of insulin secretory function derived from fasting plasma glucose and insulin concentrations.

The authors hypothesise: “Biological mechanisms linking vitamin C and vitamin E intakes to the risk of LADA, may involve the essential role of these antioxidants in inhibiting lipid peroxidation. 

"This process refers to a chain reaction initiated by free radicals, which leads to the oxidation of phospholipids in the cellular membranes, and has been linked to beta cell dysfunction​.”

Both vitamin C and vitamin E possess characteristics as scavengers of free radicals. Vitamin E is known to be a highly effective lipophilic antioxidant​ that acts as a chain-breaker during lipid peroxidation, thereby hindering the propagation of free radicals within cellular membranes.

Additionally, vitamin C functions as a significant hydrophilic antioxidant​, capable of neutralising free radicals through electron donation and also restoring the antioxidant capacity of vitamin E.

The authors found an inverse relationship between the intake of multivitamins and both LADA and type 2 diabetes, which they hypothesised could reflect the synergistic effects between vitamin C and vitamin E in inhibiting lipid peroxidation​.

They also noted: “We identified a positive association with beta cell function, particularly among individuals with LADA, which provides some support that a causal relationship between vitamin E intake and autoimmune diabetes may exist.”

The authors conclude: “Evidence for a potential protective effect of higher vitamin E intake was supported by the observed association with better beta cell function and lower insulin resistance.”

Limitations​

The authors note some limitations in this study, explaining the study used self-reported dietary information and a retrospective design.

They explain: “Relying on memory to recollect dietary habits can be challenging, particularly among cases who were asked about their diet before diagnosis. 

“It seems possible that those afflicted with diabetes have increased their consumption of antioxidant-rich foods, following medical advice, and may have, thus, over-reported their exposure before diagnosis." 

The authors conclude: “Further studies are certainly needed to confirm our findings and clarify the potential mechanisms for the observed associations.”

Journal: Nutrients

https://www.mdpi.com/2072-6643/15/11/2546​

“Antioxidant Nutrients and Risk of Latent Autoimmune Diabetes in Adults and Type 2 Diabetes: A Swedish Case-Control Study and Mendelian Randomization Analysis”

Authors: Anna-Maria Lampousi, Josefin E. Löfvenborg, Emma Ahlqvist, Tiinamaija Tuomi, Alicja Wolk and Sofia Carlsson.