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Mental Disorders Linked to Crosstalk between The Gut Microbiome and The Brain.
Choi, TY, Choi, YP, Koo, JW
Experimental neurobiology. 2020;29(6):403-416
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Plain language summary
The gut microbiome may have a role in regular brain function and mental health and this review paper aimed to determine the mechanisms through which this may be possible. There are several mental health disorders that may be affected by the gut microbiome, major depressive disorder (MDD), anxiety disorder, autism spectrum disorder (ASD), Alzheimer’s disease (AD), and addiction. It appears that there is a correlation between a disordered gut microbiome (known as dysbiosis) and MDD, ASD and addiction. Anxiety symptoms in healthy individuals and cognitive deficits in individuals with AD have reportedly been improved with probiotics. How the gut microbiome communicates with the brain was also discussed with the enteric nervous system, vagus nerve, spinal chord, immune system and brain signalling molecules all being implicated as possible routes. Finally, the paper discussed the use of probiotics for the prevention or treatment of mental disorders, with Bifidobacteria, Lactobacillus and specifically L. reuteri, L. plantarum and L. helveticus all shown in animal models to improve aspects associated with mental disorders. Amongst the human research B. longum has been shown to relieve stress and increase cognitive function in healthy individuals. It was concluded that studies have elucidated a relationship between the gut microbiome and mental health through various routes of communication. Research should focus on how gut microbiome changes are involved in mental illness. This study could be used by healthcare professionals to further knowledge on the potential relationship between the gut microbiome and mental health.
Abstract
Often called the second brain, the gut communicates extensively with the brain and vice versa. The conversation between these two organs affects a variety of physiological mechanisms that are associated with our mental health. Over the past decade, a growing body of evidence has suggested that the gut microbiome builds a unique ecosystem inside the gastrointestinal tract to maintain the homeostasis and that compositional changes in the gut microbiome are highly correlated with several mental disorders. There are ongoing efforts to treat or prevent mental disorders by regulating the gut microbiome using probiotics. These attempts are based on the seminal findings that probiotics can control the gut microbiome and affect mental conditions. However, some issues have yet to be conclusively addressed, especially the causality between the gut microbiome and mental disorders. In this review, we focus on the mechanisms by which the gut microbiome affects mental health and diseases. Furthermore, we discuss the potential use of probiotics as therapeutic agents for psychiatric disorders.
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Gut microbiota varies by opioid use, circulating leptin and oxytocin in African American men with diabetes and high burden of chronic disease.
Barengolts, E, Green, SJ, Eisenberg, Y, Akbar, A, Reddivari, B, Layden, BT, Dugas, L, Chlipala, G
PloS one. 2018;13(3):e0194171
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Obesity and type 2 diabetes (T2D) can lead to alterations of the composition of the gut microbiota. The gut microbiota, in turn, has been suggested to play a role in the development of psychological conditions, such as anxiety, depression and drug addiction. This cross-sectional study included 99 mostly overweight/obese African American men, with or without T2D, and with or without opioid addiction and other psychiatric disorders. The aim of the study was to determine, whether the gut microbiota composition was linked to T2D and the use of opioids in these patients. Furthermore, the researchers looked at the associations between leptin and oxytocin levels in the blood and the gut microbiota, and whether these hormone biomarkers could be indicative of obesity and psychosocial behaviour, such as opioid addiction. The authors found that some bacterial species in the gut were affected by T2D, diabetes medication and opioid use in the studied subjects. A relationship was also observed between leptin and oxytocin levels and the abundance of certain bacteria in the gut in subjects without T2D. The authors conclude that targeting the gut microbiota could be used for the management of T2D and associated psychiatric disorders. However, more studies are needed to provide further understanding of the connections between the gut microbiota and the brain.
Abstract
OBJECTIVE The gut microbiota is known to be related to type 2 diabetes (T2D), psychiatric conditions, and opioid use. In this study, we tested the hypothesis that variability in gut microbiota in T2D is associated with psycho-metabolic health. METHODS A cross-sectional study was conducted among African American men (AAM) (n = 99) that were outpatients at a Chicago VA Medical Center. The main outcome measures included fecal microbiota ecology (by 16S rRNA gene sequencing), psychiatric disorders including opioid use, and circulating leptin and oxytocin as representative hormone biomarkers for obesity and psychological pro-social behavior. RESULTS The study subjects had prevalent overweight/obesity (78%), T2D (50%) and co-morbid psychiatric (65%) and opioid use (45%) disorders. In the analysis of microbiota, the data showed interactions of opioids, T2D and metformin with Bifidobacterium and Prevotella genera. The differential analysis of Bifidobacterium stratified by opioids, T2D and metformin, showed significant interactions among these factors indicating that the effect of one factor was changed by the other (FDR-adjusted p [q] < 0.01). In addition, the pair-wise comparison showed that participants with T2D not taking metformin had a significant 6.74 log2 fold increase in Bifidobacterium in opioid users as compared to non-users (q = 2.2 x 10-8). Since metformin was not included in this pair-wise comparison, the significant 'q' suggested association of opioid use with Bifidobacterium abundance. The differences in Bifidobacterium abundance could possibly be explained by opioids acting as organic cation transporter 1 (OCT1) inhibitors. Analysis stratified by lower and higher leptin and oxytocin (divided by the 50th percentile) in the subgroup without T2D showed lower Dialister in High-Leptin vs. Low-Leptin (p = 0.03). Contrary, the opposite was shown for oxytocin, higher Dialister in High-Oxytocin vs. Low-Oxytocin (p = 0.04). CONCLUSIONS The study demonstrated for the first time that Bifidobacterium and Prevotella abundance was affected by interactions of T2D, metformin and opioid use. Also, in subjects without T2D Dialister abundance varied according to circulating leptin and oxytocin.