Gut fungal composition is temporally stable and mainly determined by age, long-term habitual diet, and host physiological states, according to a study in Gut.

Researchers sought to assess the long-term stability and determinants of the gut mycobiome in middle-aged and elderly adults and hypothesized that gut fungi could interact with bacteria to modulate metabolic health. The analysis included 1244 participants (mean age, 64.9 years) from the Guangzhou Nutrition and Health Study (GNHS) cohort.

A taxonomic profile of the gut mycobiome revealed 204 gut fungal genera, in which Ascomycota, Basidiomycota, and unclassified Fungi sp were the most dominant phyla, with a mean relative abundance of 77.0%, 5.7%, and 17.0%, respectively. After about 3.2 years, long-term stability of the gut mycobiome was determined in 184 participants. Internal transcribed spacer 2 fungal data showed nonsignificant alterations over time in 11 genera of the Ascomycota, suggesting that the abundances of these genera were temporally stable.


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Procrustes analysis found a strong correlation between the data matrix of the gut fungi and bacteria (P =.009). Negative associations were found for most of the α-diversity indices between the 2 entities, indicating an ecobalance between the gut fungal and bacterial communities.

Age, dairy intake, and total cholesterol were significantly associated with the gut fungal composition (P <.05). Blastobotrys and Agaricomycetes spp were depleted and Malassezia was enriched in elderly patients (P <.05), compared with middle-aged participants.

Multivariable linear regression models suggested that habitual diet may be an important determinant of the mycobiome, with most foods associated positively or negatively with specific fungi. Fruits and fish were the only foods not significantly associated with fungi. Dairy intake was positively associated with Saccharomyces and Meyerozyme and inversely associated with Candida (P <.05).

The association between fungi and bacteria was highly variable in taxonomy, and gut fungi may be able to manipulate neighboring bacterial communities or vice versa, noted the researchers.

Linear regression analysis showed a significant interaction of Saccharomycetales spp with bacterial α-diversity on homeostatic model assessment of insulin resistance (P value for interaction <.05) and insulin. Bidirectional mediation analysis revealed that the presence of Pichia may have contributed to a reduction in low-density lipoprotein cholesterol by increasing the bacterial functional levels.

The investigators noted that the findings from their observational study based on the GNHS cohort may or may not be generalizable to patients of other ethnicities.

“These findings show that the gut mycobiome is an essential component of the gut ecosystem, interactive with the bacterial community, and contributes to the overall human metabolic health,” concluded the researchers.

Reference

Shuai M, Fu Y, Zhong H-L, et al. Mapping the human gut mycobiome in middle-aged and elderly adults: multiomics insights and implications for host metabolic health. Gut. Published online January 11, 2022. doi: 10.1136/gutjnl-2021-326298