The Gut-Brain Connection: A New Horizon in Neurological Health

The human body is a complex system, and one of its most fascinating connections is the gut-brain axis. This bidirectional communication between the gastrointestinal (GI) tract and the central nervous system (CNS) has recently gained traction in the scientific community, especially concerning acute neurological diseases like stroke, multiple sclerosis, Alzheimer's disease, and migraine.

The gut-brain axis is not just a physical connection between the gut and the brain; it's a complex network involving proinflammatory cells, gut metabolites, hormones, and neural pathways. Key metabolites include trimethylamine N-oxide (TMAO) and short-chain fatty acids (SCFAs), which are believed to play a central role in gut-brain axis dysfunction. 

Over 50% of ischemic stroke survivors experience GI complications, with dysphagia, constipation, and GI bleeding being the most common. Diarrhea, constipation, and gastroesophageal reflux are also more frequent in patients with migraine. These complications are not merely side effects but may contribute to poor functional neurologic outcomes. It is postulated that the propagation of proinflammatory cells and gut metabolites (including trimethylamine N-oxide and short-chain fatty acids) from the GI tract to the central nervous system play a central role in gut-brain axis dysfunction. In fact, plasma trimethylamine N-oxide (TMAO) levels might predict early neurological deterioration (END) in individuals with acute ischemic stroke. 

Stroke itself can lead to gut dysbiosis, alterations in the normal host intestinal microbiome. This dysbiosis may further perpetuate neurological impairments, creating a vicious cycle that challenges recovery.

Cognition is one of the most evaluated neurologic subjects linked to the gut microbiome. Cognitive impairment is particularly prevalent in patients with multiple sclerosis (MS), a chronic neurological disorder.

Referenced reviews discuss the known GI complications in acute ischemic stroke and multiple sclerosis, emerging therapeutics and lifestyle modifications that target the gut-brain axis. 

REFERENCES

Yong HYF, Ganesh A, Camara-Lemarroy C. Gastrointestinal Dysfunction in Stroke. Semin Neurol. 2023 Aug 10. doi: 10.1055/s-0043-1771470. Epub ahead of print. PMID: 37562458.

Ghadiri F, Ebadi Z, Asadollahzadeh E, Moghadasi AN. Gut microbiome in multiple sclerosis-related cognitive impairment. Multiple Sclerosis and Related Disorders. 2022 Sep 7:104165.

La Rosa G, Lonardo MS, Cacciapuoti N, Muscariello E, Guida B, Faraonio R, Santillo M, Damiano S. Dietary Polyphenols, Microbiome, and Multiple Sclerosis: From Molecular Anti-Inflammatory and Neuroprotective Mechanisms to Clinical Evidence. International Journal of Molecular Sciences. 2023 Apr 14;24(8):7247.

He Q, Wang W, Xiong Y, Tao C, Ma L, Ma J, You C. A causal effects of gut microbiota in the development of migraine. The Journal of Headache and Pain. 2023 Dec;24(1):1-7.

Stealth Care System for IBS

The term "stealth care" was coined in a political context, referring to the idea of certain words being disguised or hidden and the fact that not all types of caring for someone's wellbeing are within (or approved by) traditional health care. 

This term has been also used in the computer security context - to describe the Honeynet Project. A honeynet is a network of Honeypots, computer systems set up to look like regular ones, but with a caveat. Honeypots allow themselves to be attacked by hackers in order to capture their every move, learn the tools, tactics and motives; being used to track down and stop attacks before they happen. 

A new paper from McMaster University describes a cellular delivery system that can safely carry potent antibiotics throughout the body to selectively attack and kill bacteria. Physicists at McMaster University are essentially using red blood cells to conceal this antibiotic within turning them into stealth vehicles. The platform could help to address the ongoing antibiotic resistance crisis while avoiding the toxicity and harmful side effects of antibiotics. The technology could be used to fight particularly dangerous and often drug-resistant bacteria such as E. coli, which is responsible for many serious conditions such as pneumonia, gastroenteritis and bloodstream infections.

It could be also used for conditions such as IBS since traditional antibiotics delivery systems can often bring more harm than good in some cases. Antibiotics can disrupt the balance of the microbiome, leading to further symptoms of IBS and potentially causing new health problems. Additionally, overuse of antibiotics can lead to the development of antibiotic-resistant bacteria, which can make it more difficult to treat future infections effectively.

REFERENCES

Krivic H, Himbert S, Sun R, Feigis M, Rheinstädter MC. Erythro-PmBs: A Selective Polymyxin B Delivery System Using Antibody-Conjugated Hybrid Erythrocyte Liposomes. ACS Infectious Diseases. 2022 Sep 29;8(10):2059-72.

Săndulescu O, Viziteu I, Streinu-Cercel A, Miron VD, Preoțescu LL, Chirca N, Albu SE, Craiu M, Streinu-Cercel A. Novel Antimicrobials, Drug Delivery Systems and Antivirulence Targets in the Pipeline—From Bench to Bedside. Applied Sciences. 2022 Nov 16;12(22):11615.

Săndulescu O, Streinu-Cercel A, Moțoi MM, Streinu-Cercel A, Preoțescu LL. Syndromic Testing in Infectious Diseases: From Diagnostic Stewardship to Antimicrobial Stewardship. Antibiotics. 2023 Jan;12(1):6.

Stealth-care system: Scientists test 'smart' red blood cells to deliver antibiotics that target specific bacteria (2022, October 31) retrieved 6 February 2023 from  https://phys.org/news/2022-10-stealth-care-scientists-smart-red-blood.html

Antibiotics and Bowel Disorders

Frequent use of antibiotics can increase the risk of developing microbiome-associated diseases in all age groups.

Studies have shown that antibiotic exposure in the prenatal period and during the first 2 years of life can significantly impact the risk of developing atopic and metabolic disorders later in life. The first 6 months of life appeared to be a critical period, as this is when the microbiome is most susceptible to irreversible changes. 

Studies of older children (such as 11,000 teens and pre-teens from Finland) have found that, instead of a specific age, the frequency of antibiotic use in the two years prior to the diagnosis of autoimmune disorders, was more strongly associated with risk. Exposures to cephalosporins, macrolides, and amoxicillin-clavulanic acid throughout childhood seemed to increase the likelihood of Juvenile Arthritis (JIA). Exposures to macrolides within two years before diagnosis showed minor association with other autoimmune disorders, including type 1 diabetes (DM), autoimmune thyroiditis (AIT), JIA, and inflammatory bowel diseases (IBD)). 

An article recently accepted for publication found that frequent use of antibiotics later in life also increased the risk of IBD. This study of more than 6 million individuals followed for close to 20 years analyzed 87112328 person-years including 36017 new cases of ulcerative colitis (UC) and 16881 new cases of Crohn’s disease (CD) - two primary types of IBD with different characteristics. This risk was predominantly driven by those diagnosed with CD and was strongest within the first few months of antibiotic use. In a nationwide case–control study of individuals 16-years or older in Sweden, similar results were seen for three or more antibiotic dispensations.

The authors of the study hypothesized that antibiotics contribute to the development of IBD by modulating the intestinal microbiome, but more research is needed to fully understand the mechanism behind this association.

REFERENCES

Semeh Bejaoui, Michael Poulsen, The impact of early life antibiotic use on atopic and metabolic disorders: Meta-analyses of recent insights, Evolution, Medicine, and Public Health, Volume 2020, Issue 1, 2020, Pages 279–289, https://doi.org/10.1093/emph/eoaa039

Räisänen L, Kääriäinen S, Sund R, Engberg E, Viljakainen H, Kolho KL. Antibiotic Exposures and the Likelihood of Developing Pediatric Autoimmune Diseases: a Register-based Matched Case-control Study. (2021). DOI: 10.21203/rs.3.rs-1110501/v1

Faye AS, Allin KH, Iversen AT, et al Antibiotic use as a risk factor for inflammatory bowel disease across the ages: a population-based cohort study Gut Published Online First: 09 January 2023. doi: 10.1136/gutjnl-2022-327845