A recent study conducted in China examined the types of fungi found in the digestive systems of children and teenagers with depression. The researchers compared these individuals to children without depression and found that the depressed group had higher levels of Saccharomyces and Apiotrichum fungi, while having lower levels of Aspergillus and Xeromyces fungi. The study was published in the Journal of Affective Disorders.
The digestive system contains a diverse community of bacteria, archaea, fungi, and viruses known as the gut microbiota. These microorganisms are essential for digesting food, and there is growing evidence suggesting they may also play a role in overall health. Many diseases have been associated with changes in the gut, highlighting the potential importance of the microbiota.
Recent advances in the area of genetics, biochemistry and neuroimaging allowed for the discovery of the microbiota-gut-brain axis. The microbiota-gut-brain axis is a two-directional communication system between the gut microbiota and the central nervous system. It is based on small proteins called cytokines that play a crucial role in the activities of the immune system and a number of other biomolecules, including the hormone cortisol, short-chain fatty acids (SCFAs), tryptophan, and others.
Scientists have been able to study the composition of the gut microbiota by analyzing stool samples using a technique called metagenomics. Numerous studies have utilized this approach in recent years, investigating the connection between changes in gut bacteria and the severity of depression symptoms. They have also explored the relationship between the gut microbiota and other mental health disorders. In one recent study, researchers even attempted to transplant gut microbiota to determine if changes in microbiota composition could cause depression.
The authors of the new study, led by Shao-rui Hao, noticed that while previous research had examined the link between gut bacteria and depression, the connection with fungal species in the gut had received less attention. They conducted a study focusing on the composition of gut microbiota in children and teenagers with depression, specifically looking at the presence of fungal species and their interactions with gut bacteria.
The study included 145 participants with depression, aged between 12 and 18, who were undergoing treatment at two hospitals in China. These individuals were compared to 110 healthy children and teenagers of similar age, gender, body mass index, and ethnicity. The healthy participants were recruited through advertisements.
The researchers collected fresh stool samples from each participant and extracted DNA for analysis. They used a technique called polymerase chain reaction to create multiple copies of the DNA for further examination. The researchers assessed the diversity of fungal species in the samples, calculated the average relative abundance of fungi, and identified the most abundant groups of fungal species. They also analyzed the associations between specific fungal and bacterial species.
The results revealed that most of the participants in the depression group had moderate to severe symptoms of depression. Two participants were regular tobacco smokers, while none reported regular alcohol consumption in the month before the study.
Analysis of the stool samples showed that the diversity of fungal species in the gut was similar between the depression group and the healthy control group. The most common fungal group in both groups was Ascomycota, followed by Basidiomycota.
However, there were differences in the abundance of certain fungal species between the two groups. Saccharomyces and Apiotrichum fungi were more abundant in guts of depressed patients, while the abundance of Aspergillus and Xeromyces was decreased compared to the group of healthy children.
The connections between the abundances of fungi and bacterial species were also altered in the guts of children with depression compared to the healthy group. The abundance of Candida species of fungi was associated with higher abundances of Parasutterella, but lower abundances of Bifidobacterium species in participants with depression, but not in healthy children.
Similarly, higher abundances of Aspergillus were associated with higher abundances of Prevotella, but with lower of Bacteroides and Parasutterella in the depression group, but not in the group of healthy children/adolescents.
“We demonstrated that gut microbiota dysbiosis [disruption in the composition, diversity or function] in children and adolescents with depression manifests as changes in the gut fungal community structure and composition. We also found alterations in the bacterial–fungal interkingdom network, suggesting that the gut mycobiota [fungal community] is a potential therapeutic target for children and adolescents with depression. Targeting gut mycobiota interventions, such as probiotic, prebiotic, antifungal drugs, or fecal fungal transplantation, may prevent the psychiatric disease progression,” the study authors concluded.
While this study contributes valuable information to our understanding of the microbiota-gut-brain pathway, it has some limitations. The study design does not allow for cause-and-effect conclusions, as it was observational. Additionally, the conclusions were based on a single stool sample per participant, and the study did not consider the psychiatric history of the participants’ mothers. Future studies using multiple stool samples over a longer period may provide more comprehensive results.
The study, “Altered gut bacterial–fungal interkingdom networks in children and adolescents with depression“, was authored by Shao-rui Hao, Zhe Zhang, Yuan-yue Zhou, Xue Zhang, Wen-jun Sun, Zi Yang, Jian-hua Zhao, and Hai-yin Jiang.