The Association between Dysbiosis and Neurological Conditions Often Manifesting with Chronic Pain

Abstract

The prevalence of neurological conditions which manifest with chronic pain is increasing globally, where the World Health Organisation has now classified chronic pain as a risk factor for death by suicide. While many chronic pain conditions have a definitive underlying aetiology, non-somatic conditions represent difficult-to-diagnose and difficult-to-treat public health issues. The interaction of the immune system and nervous system has become an important area in understanding the occurrence of neuroinflammation, nociception, peripheral and central sensitisation seen in chronic pain. More recently, however, the role of the resident microbial species in the human gastrointestinal tract has become evident. Dysbiosis, an alteration in the microbial species present in favour of non-beneficial and pathogenic species has emerged as important in many chronic pain conditions, including functional somatic syndromes, autoimmune disease and neurological diseases. In particular, a decreased abundance of small chain fatty acid, e.g., butyrate-producing bacteria, including Faecalibacterium, Firmicutes and some Bacteroides spp., is frequently evident in morbidities associated with long-term pain. Microbes involved in the production of neurotransmitters serotonin, GABA, glutamate and dopamine, which mediate the gut-brain, axis are also important. This review outlines the dysbiosis present in many disease states manifesting with chronic pain, where an overlap in morbidities is also frequently present in patients.

Current understanding of the molecular mechanisms of chemotherapy-induced peripheral neuropathy

“…The 16S rRNA gene sequencing and phylum analysis revealed an increased relative abundance of Verrucomicrobia and drastic change in the ratio of Bacteroidetes and Firmicutes ( Shen et al, 2017 ). Accumulating evidence suggested that the imbalance of Bacteroidetes and Firmicutes ratio contributed to the development of chronic pain ( Garvey, 2023 ). In another study, elevated abundance of Verrucomicrobia was linked to chronic abdominal pain ( Kang et al, 2019 ).…”

The Impact of Early-Life Cecal Microbiota Transplantation on Social Stress and Injurious Behaviors in Egg-Laying Chickens

“…Both human and rodent studies indicated that probiotics reduce chronic-psychological-stress-induced abnormal brain activity and related cognitive dysfunctions by lowering plasma CORT and adrenocorticotropic hormone levels, restoring hippocampal 5-HT and NE levels, and normalizing immunity with low plasma levels of TNF-α but high levels of IL-10, an anti-inflammatory cytokine [ 171 , 172 , 173 ]. Several probiotics, as psychobiotics, for example, Bifidobacterium and Lactobacillus , deliver mental health benefits with neurobehavioral effects, which have been used in humans for improving cognitive function and for preventing and treating patients with behavioral impairment in neurodegenerative diseases, such as Alzheimer’s disease and Parkinson’s disease, and in diseases with neuropsychiatric disorders, such as anxiety, depression, and impulsively and compulsively disrupted social behavior [ 75 , 77 , 78 , 79 , 83 , 84 ]. Based on findings, targeting the gut microbiota has been recognized as a novel therapeutic option for patients with neuropsychiatric disorders [ 63 , 73 , 74 ].…”

“…Targeting the intestinal microbiota with the goal of restoring its balance has been recognized as a novel therapeutic option for patients with neuropsychiatric disorders [ 72 , 73 , 74 ]. Several probiotics, as psychobiotics, such as Bifidobacterium and Lactobacillus , which can benefit mental health, have been used for preventing and treating patients with behavioral impairment, such as anxiety, depression, and impulsively and compulsively disrupted social behavior, via regulating the MGB, MGI, or both axes [ 75 , 76 , 77 , 78 , 79 , 80 , 81 , 82 , 83 , 84 ]. However, the use of purified probiotics benefits has shown mixed results, with several weaknesses including transient beneficial effects, requiring continuous administration over time due to the host’s resident microbial populations and “colonization resistance” [ 85 ].…”

Intestinal Dysbiosis: Microbial Imbalance Impacts on Colorectal Cancer Initiation, Progression and Disease Mitigation

“…The association between the gastrointestinal microbiota, IBD, chronic inflammation, and CRC has become an area of much investigation. Alteration in the resident microbial species of the large intestine appears to greatly impact diseases of the gastrointestinal tract (GIT) [14]. This review aims to outline the relationship between GIT dysbiosis, inflammation, and the development of CRC, where insights into novel treatment approaches are also described.…”