Greater expression of key microbial genes may lower cardiovascular disease risk

A study published in Clinical Nutrition set out to assess the effect of walnut-related modulation of gut microbiota composition on microbiota functionality. Specifically, the researchers characterized the effect on bacterial gene expression of a walnut-enriched diet containing 18% of energy from walnuts (57 grams/day) compared to a fatty acid-matched diet devoid of walnuts and a diet where oleic acid replaced alpha-linolenic acid.

This randomized, crossover, controlled-feeding study included 35 participants, 40% of whom were female. In the first stage, participants were given a standard Western diet for two weeks. Subsequently, participants were given the walnut-enriched diet, the fatty acid-matched diet and the oleic acid diet in random order. Metatranscriptomic analyses were performed as an exploratory outcome.

The results showed greater expression of many bacterial genes following the walnut-enriched diet compared to the fatty acid-matched diet and the oleic acid diet. In particular, greater expression of metabolism-related genes encoding glycine amidinotransferase and arginine deiminase was observed compared to the fatty acid-matched diet. Greater expression of glycine amidinotransferase by Gordonibacter was also observed following the walnut-enriched diet versus the other two diets.

The findings suggest that walnut intake may increase endogenous production of homoarginine through gut microbiota-mediated upregulation of glycine amidinotransferase, which is a novel mechanism by which walnuts may lower cardiovascular disease risk.

This study was funded by the California Walnut Commission.

Petersen, K. S., Chandra, M., Chen See, J. R., Leister, J., Jafari, F., Tindall, A., Kris-Etherton, P. M., & Lamendella, R. (2023). Walnut consumption and gut microbial metabolism: Results of an exploratory analysis from a randomized, crossover, controlled-feeding study. Clinical Nutrition (Edinburgh, Scotland), 42(11), 2258–2269.

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