Sex-Specific Associations of Trimethylamine-N-Oxide and Zonulin with Signs of Depression in Carbohydrate Malabsorbers and Nonmalabsorbers

Beck Depression InventoryBiomarkerscarbohydrate malabsorptionDepressionGut Microbiome

Sex-Specific Associations of Trimethylamine-N-Oxide and Zonulin with Signs of Depression in Carbohydrate Malabsorbers and Nonmalabsorbers

Why this matters for your gut health

The gut-brain axis is increasingly linked to mental health, and this study explores whether two microbiome-related biomarkers — TMAO (a metabolite from gut bacteria) and zonulin (a marker of gut permeability, i.e., “leaky gut”) — relate to depressive symptoms. It also asks whether carbohydrate malabsorption (a common digestive condition) changes that relationship, and whether the effects differ between men and women — a nuance often missed in gut-brain research.

Summary

Researchers measured serum TMAO and zonulin in 251 participants (115 with carbohydrate malabsorption, 136 without), tested for lactase gene polymorphism and fructose malabsorption via breath testing, and assessed depressive symptoms using the Beck Depression Inventory (BDI-II). They then examined correlations between the biomarkers and depression scores, separately by sex and malabsorption status.

Key findings

Median TMAO: 2.66 μmol/L; median zonulin: 40.83 ng/mL
Serum TMAO was positively correlated with depressive symptoms overall (P=0.011, ρ=0.160)
The strongest TMAO–depression correlations appeared in people without carbohydrate malabsorption (CMA): females (P=0.010, ρ=0.274) and males (P=0.027, ρ=0.315)
No significant correlations were found in the 115 participants with CMA
Zonulin showed a near-significant negative correlation with depression scores in males without CMA (P=0.062, ρ=-0.269)
Conclusion: TMAO is positively linked to depression severity in both sexes without CMA; zonulin is negatively linked to depression in males without CMA — pointing to a sex-specific gut-brain relationship

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Citation

Meinitzer, S., Baranyi, A., Holasek, S., Schnedl, W. J., Zelzer, S., Mangge, H., Herrmann, M., Meinitzer, A., & Enko, D. (2020). Sex-Specific Associations of Trimethylamine-N-Oxide and Zonulin with Signs of Depression in Carbohydrate Malabsorbers and Nonmalabsorbers. Disease Markers, 2020, Article 7897240.