The role of microbiota and inflammation in self-judgement and empathy: implications for understanding the brain-gut-microbiome axis in depression

Abstract

Rationale The gut-brain axis includes bidirectional communication between intestinal microbiota and the central nervous system. Bifidobacterium and Lactobacillus spp. have been implicated in psychological health, such as depression, through various pathways (e.g. inflammation). Research needs a better understanding of direct and indirect effects through examination of psychological factors that make people susceptible to, or offer protection against, depression. Objective This study investigated the relationships between gut microbiota, inflammation and psychological risk and resilience factors for depression. Methods Forty participants (13 m/27 f) recruited from the general population completed self-report questionnaires for depression, self-judgement, over-identification and affective and cognitive empathy. Faecal and blood samples were taken to assay microbiota ( Bifidobacterium ; Lactobacillus spp.) and pro-inflammatory molecules (C-reactive protein, CRP and interleukin-6, IL-6), respectively. Results Hierarchical regression analyses (controlling for sex, age and the shared variance of risk and resilience factors) showed that (i) cognitive depression was significantly predicted by negative self-judgement and reduced cognitive empathy; (ii) abundance of Lactobacillus spp. was directly related to positive self-judgement but only indirectly to cognitive depression and lower affective empathy (both through self-judgement); and (iii) CRP was the strongest predictor of reduced cognitive empathy, with suppression effects seen for age (negative) and IL-6 (positive) after controlling for CRP. Conclusions Findings suggest that lactobacilli and inflammation may be differentially associated with mood disorder via brain mechanisms underpinning self-judgement and cognitive empathy, respectively. Further trials investigating interventions to increase Lactobacillus spp. in depression would benefit from direct measures of self-judgement and affective empathic distress, whilst those that aim to reduce inflammation should investigate cognitive empathy. Electronic supplementary material The online version of this article (10.1007/s00213-019-05230-2) contains supplementary material, which is available to authorized users.

Measuring the Brain-Gut Axis in Psychological Sciences: A Necessary Challenge

“…Microbiota would impact behavior via bottomup pathways, positioning it as a factor to consider in studies attempting the understanding of well-being (O'mahony et al, 2009;Dinan and Cryan, 2012;Dinan et al, 2013). Moreover, increasing evidence has posited microbiota as relevant in the context of autism (Mulle et al, 2013;Sgritta et al, 2019), schizophrenia (Severance et al, 2016), multiple sclerosis (Jangi et al, 2016), bipolar disorder (Evans et al, 2017), irritable bowel disease (Jeffery et al, 2012;Kennedy et al, 2014), obesity (Gomes et al, 2018), neurodegenerative disorders (Boehme et al, 2019), and depression (Naseribafrouei et al, 2014;Jiang et al, 2015;Aizawa et al, 2016;Kelly et al, 2016;Heym et al, 2019). The mechanisms through which microbiota exert its effects over behavior include neural pathways via the vagus nerve, regulation of the stress response, production of short chain fatty acids after fiber fermentation, amino acids metabolism and control of immune function, among others (Cryan and Dinan, 2012;.…”

Spaceship Earth Revisited: The Co-Benefits of Overcoming Biological Extinction of Experience at the Level of Person, Place and Planet

“…With one microbial cell to match each human cell, and impressive numbers of functional microbial genes (quite capable of influencing disease risk as well as vitality [68]), humans are indeed multi-species entities [69,70]. Consider the implications of just a single non-pathogenic microbial strain influencing brain activity during social stress [71] or findings that suggest that our microbial partners could be putting their "weight" on the scale of human cognitive empathy [72] and personality [73]. Moreover, these observations open a door to narrative around very personal biological consequences of large-scale biodiversity loss [63].…”

Prebiotics and the Modulation on the Microbiota-GALT-Brain Axis

“…In addition, it was shown that WD-fed mice had intestinal dysbiosis, which was accompanied by inflammatory signaling in the brain, microglial activation, and reduced neuroplasticity [83]. Therefore, dysbiosis of gut microbiota may increase the cytokines production and neuroinflammation, affecting mood, or it could induce psychiatric disorders such as depression and anxiety as was described in animal models [56] as well as in comparative studies performed in humans [5,84]. Moreover, in maternal immune activation (MIA) mouse model, intestinal dysbiosis induced both higher production of both 4-ethylphenylsulfate (4EPS) and indolepyruvate, leading to autism spectrum disorder (ASD).…”