Loughman, A. | bioRxiv Science

bioRxiv2024

Associations between oral microbiota pathogens and elevated depressive and anxiety symptoms in men

BackgroundSystemic inflammation has been associated with depression. Certain oral bacterial species contribute to extra oral inflammation, however their potential association with mental disorders remains unclear. This study investigated the associations between oral microbiota pathogens and depressive and anxiety symptoms. MethodsData came from 436 men from the Geelong Osteoporosis Study. Using 16S rRNA gene sequencing, we characterized the oral microbiota composition and created a composite variable representing the prevalence of known oral pathogens, Porphyromonas gingivalis, Treponema denticola, Fusobacterium nucleatum, and Prevotella nigrescens. Binary variables were created representing elevated depressive and anxiety symptoms using the Hospital Anxiety and Depression Scale. Associations between oral pathogens and elevated depressive/anxiety symptoms were analyzed using logistic regression adjusted for confounders (age, socio-economic status, diet, smoking, alcohol, exercise, obesity and hypertension). ResultsWe found limited evidence for an association between the pathogen composite and elevated depressive (N = 39) but not anxiety (N = 66) symptoms. Moreover, some of the comprising species, P. nigrescens (OR 1.61 (95% CI 1.21, 2.13)) and F. nucleatum (subsp. animalis ATCC 51191 (1.54 (1.13, 2.11)), subsp. animalis (1.47 (1.05, 2.08)) and subsp. vincentii (1.47 (1.06, 2.04))) were associated with elevated depressive symptoms. Exploratory analyses revealed several other taxa associated with depression and anxiety. LimitationsThis study focuses on mental health symptoms and not diagnoses in men, and the results may not be generalizable to women. ConclusionsWe identified several taxa within the oral microbiota that were associated with depressive and anxiety symptoms. Further replication and mechanistic studies are needed. HighlightsO_LIA composite of oral pathogens is associated with depressive symptoms in adult men C_LIO_LIAssociations between P. nigrescens and other species and elevated depressive symptoms C_LIO_LIAssociations remain following adjustment for confounders C_LIO_LIOral microbial diversity was not associated with depressive or anxiety symptoms C_LIO_LIFewer associations between oral microbial composition and anxiety than depression C_LI

microbiology↗

bioRxiv2018

An intermittent hypercaloric diet alters gut microbiota, prefrontal cortical gene expression and social behaviours in rats

Excessive consumption of high fat and high sugar (HFHS) diets are known to alter reward processing and aspects of behaviour, and change microbiota profiles. Studies in gnotobiotic mice also provide evidence that gut microorganisms influence social behaviour. To further investigate these interactions, the impact of intermittent access to a HFHS diet on social behaviour, gene expression and microbiota composition was examined. Rats were permitted intermittent daily access (2h / day) to a palatable HFHS diet for 28 days across the adolescent period. Social interaction, social memory and novel object recognition were assessed during this period. Following testing, RT-PCR was conducted on hippocampal and prefrontal cortex (PFC) samples. 16S ribosomal RNA amplicon sequencing was used for identification and relative quantification of bacterial taxa. Reduced social interaction behaviours, and impaired social memory and novel object recognition were observed in HFHS diet rats. Reduced levels of monoamine oxidase A (Maoa), catechol-O-methyltransferase (Comt) and brain derived neurotrophic factor (Bdnf) mRNA were observed in the PFC of HFHS diet rats. The relative abundance of a number of specific taxa differed significantly between the two diet groups, in particular, Lachnospiraceae and Ruminoccoceae bacteria, which also predicted social behaviours, novel object recognition performance and Maoa expression. This is the first study to show that limited daily access to HFHS diet alters social behaviour and cognition in rats. Furthermore, behavioural changes are associated with alterations to cortical gene expression of enzymes involved in monoamine synthesis and neuroplasticity, and microbiota profiles predicted diet-induced changes to behaviour and gene expression.

neuroscience↗