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In the news: Can Microbiota Influence Ocular Health? Vitamin D + Mg Improves Vitamin D Status

Gut Microbiota and the Ocular Surface

The potential of the microbiota to influence ocular health is gaining more attention as a promising field of research. Recent studies, for example, have found an association of gut bacteria such as Bacteroides and Eysipelotrichi and AMD, with lower AMD risk in those whose microbiota is enriched with those bacteria(1).

A study published this month provides some insight into the potential role of gut microbiota in maintaining ocular surface homeostasis, with implications for dry eye syndrome(2).

The Baylor University team, who authored the study, are interested in investigating the potential role of microbially produced molecules in mediating the interaction between the intestinal microbiota and the ocular surface. One such molecule is butyrate, a short‐chain fatty acid produced by certain members of the gut microbiota through fermentation of dietary fiber. Butyrate in the gut can enter the bloodstream and has been shown to modulate inflammatory responses in the gut and elsewhere in the body.

Using a mouse model, the team showed, among other findings, that a short-chain fatty acid transporter (SLC5A8) is expressed in vivo in mice conjunctival and corneal epithelium, which suggests that circulating butyrate may directly interact with cells at the ocular surface.

Significantly, they found that pretreatment with butyrate in mice undergoing desiccating stress reduced ocular surface inflammation – an effect which involves SLC5A8 transporter.

Taken together, the findings indicate that butyrate originating in the gut can suppress inflammatory responses at the ocular surface.

Magnesium + Vitamin D May Be Better Than Vitamin D Alone for Some

Inadequate vitamin D levels have been associated with heightened cardiovascular disease, diabetes,and cancer risks. Studies suggest that vitamin D may play a protective role in ocular health as well.

Poor vitamin D status is often observed in over-weight and obese individuals. Magnesium, a cofactor in vitamin D metabolism, is also frequently found to be low in this population group. This led researchers to investigate the effects of a combined magnesium and vitamin D supplement regimen on raising serum vitamin D levels and cardiometabolic outcomes(3).

This 12-week, placebo-controlled trial randomized 95 overweight or obese participants into one of three treatments arms: magnesium (360 mg daily) plus vitamin D (1000 IU daily), vitamin D alone (1000 IU), or placebo. Serum vitamin D, serum PTH, inflammatory markers and blood pressure were measured at base-line and at the study’s conclusion.

Those in the combined magnesium and vitamin D group had the greatest increase in serum vitamin D concentrations (6.3 + 8.36 ng/mL, p < 0.05). For participants who were vitamin D insufficient and deficient at baseline, the increase in serum vitamin D was significantly higher in the combo group vs. the vitamin D-alone group.

There was also a decrease in systolic blood pressure (- 7.5 + 8.26 mmHg p < 0.05) for individuals in the combined nutrient group who started the trial with systolic blood pressure of at least 132 mmHg.

The authors conclude that combining vitamin D with magnesium may be more effective in raising serum vitamin D than vitamin D alone in overweight and obese individuals.

References

1. Yanqun C, et al. Association of nutrients, specific dietary patterns, and probiotics with age-related macular degeneration. Curr Med Chem. Epub ahead of print, May 11, 2022.
2. Schaefer L, et al. Gut-derived butyrate suppresses ocular surface inflammation. Nature Sci Reports 12:4512, 2022.
3. Cheung MM, et al. The effect of combined magnesium and vitamin D supplementation on vitamin D status, systemic inflammation, and blood pressure: A randomized double-blinded controlled trial. Nutrients. Vol 99-100, July–August 2022, 111674.