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Gut Microbiome and Glaucoma: A New Link Through Trimethylamine (TMA)

Introduction

A study led by Janusz Skrzypecki at the Institute of Biochemistry and Biophysics in 2020 has uncovered a fascinating connection between gut bacteria metabolites and glaucoma. The research found that trimethylamine (TMA), a metabolite produced by gut bacteria, was present in the aqueous humor (the clear fluid in the front of the eye) of glaucoma patients. Notably, TMA levels were significantly higher in patients with advanced open-angle glaucoma compared to a control group undergoing cataract surgery.

This discovery highlights the potential role of TMA in the pathophysiology of glaucoma and raises questions about how diet and lifestyle factors, which influence TMA levels, might contribute to the disease.

Key Findings

• TMA, betaine, and trimethylamine N-oxide (TMAO) were detected in the aqueous humor, but only TMA levels were elevated in glaucoma patients.
• TMA and TMAO are known to impact blood pressure regulation and atherosclerosis, both of which are risk factors for glaucoma. However, emerging evidence suggests that TMA itself may be toxic.
• The study suggests that TMA might have a direct or indirect effect on the optic nerve, potentially influencing glaucoma development.

Authors' Insights

"We believe that TMA and TMAO might constitute a common humoral background which affects not only the cardiovascular system but also has a direct or indirect effect on the structure of the optic nerve."

The researchers emphasize that while TMAO has been linked to cardiovascular issues, it is TMA itself that may play a toxic role in health conditions like glaucoma.

Background

TMA is a metabolite produced when gut bacteria break down specific nutrients, particularly choline, betaine, and carnitine, found in foods like red meat, eggs, and some seafood. Its production and levels in the body are influenced by diet and lifestyle factors.

Lifestyle Factors to Improve TMA Levels

Addressing TMA levels through lifestyle changes could reduce the risk of glaucoma and other health issues. Here are some strategies:

1. Dietary Changes

   • Reduce intake of red meat, eggs, and certain seafood.
   • Increase fiber and plant-based foods to promote a healthier gut microbiome.

2. Probiotics

   • Incorporate probiotics or fermented foods to modulate gut bacteria.
   • Studies show plant-based diets can inhibit TMA production even when consuming TMA-precursor foods.

3. Medications and Supplements

   • Some supplements, such as berberine, may have a beneficial impact on TMA production.

4. Physical Activity

   • Regular exercise can positively influence gut microbiota and reduce TMA production.

5. Maintaining a Healthy Weight

   • Weight loss through diet and exercise can restore gut microbiome balance and lower TMA levels.

Study Abstract

Here is a detailed summary of the study:

Title: Glaucoma patients have an increased level of trimethylamine, a toxic product of gut bacteria, in the aqueous humor: a pilot study
View Abstract on PubMed

• Purpose: To investigate the presence of TMA, betaine, and TMAO in the aqueous humor and plasma of glaucoma patients and controls.
• Methods: Chromatography was used to analyze TMA, betaine, and TMAO levels in aqueous humor and plasma of patients undergoing phacotrabeculectomy (glaucoma surgery) and phacoemulsification (cataract surgery).
• Results:
  • TMA levels were significantly higher in the aqueous humor of glaucoma patients.
  • Plasma levels of TMA, TMAO, and betaine were similar between groups.
  • Betaine and TMA levels were higher in plasma than in aqueous humor for both groups.
• Conclusion: Elevated TMA in aqueous humor suggests a potential role in glaucoma pathogenesis, warranting further investigation.

Keywords: Betaine, Intraocular pressure, TMA, TMAO
DOI: 10.1007/s10792-020-01587-y

Conclusion

This study underscores the intricate connection between gut microbiota and ocular health. While further research is needed, the findings suggest that modifying the gut microbiome through diet and lifestyle could help mitigate risks associated with glaucoma and other health conditions.