What is unknown in using microbiota as a therapeutic?

The influence of the gut-brain axis on anxiety and depression: A review of the literature on the use of probiotics

This review aims to argue how using probiotics can improve anxiety and depressive behaviour without adverse effects, also exploring the impact of postbiotics on it. Specifically, probiotics have drawn more attention as effective alternative treatments, considering the rising cost of antidepressant and anti-anxiety drugs and the high risk of side effects. Depression and anxiety disorders are among the most common mental illnesses in the world's population, characterised by low mood, poor general interest, and cognitive or motor dysfunction. Thus, this study analysed published literature on anxiety, depression, and probiotic supplementation from PubMed and Scopus, focusing on the last twenty years. This study focused on the effect of probiotics on mental health as they have drawn more attention because of their extensive clinical applications and positive impact on various diseases. Numerous studies have demonstrated how the gut microbiota might be critical for mood regulation and how probiotics can affect host health by regulating the gut-brain axis. By comparing the different works analysed, it was possible to identify a strategy by which they are selected and employed and, at the same time, to assess how the effect of probiotics can be optimised using postbiotics, an innovation to improve mental well-being in humans.

Personalized Clostridioides difficile engraftment risk prediction and probiotic therapy assessment in the human gut

Clostridioides difficile colonizes up to 30-40% of community-dwelling adults without causing disease. C. difficile infections (CDIs) are the leading cause of antibiotic-associated diarrhea in the U.S. and typically develop in individuals following disruption of the gut microbiota due to antibiotic or chemotherapy treatments. Further treatment of CDI with antibiotics is not always effective and can lead to antibiotic resistance and recurrent infections (rCDI). The most effective treatment for rCDI is the reestablishment of an intact microbiota via fecal microbiota transplants (FMTs). However, the success of FMTs has been difficult to generalize because the microbial interactions that prevent engraftment and facilitate the successful clearance of C. difficile are still only partially understood. Here we show how microbial community-scale metabolic models (MCMMs) accurately predicted known instances of C. difficile colonization susceptibility or resistance in vitro and in vivo. MCMMs provide detailed mechanistic insights into the ecological interactions that govern C. difficile engraftment, like cross-feeding or competition involving metabolites like succinate, trehalose, and ornithine, which differ from person to person. Indeed, three distinct C. difficile metabolic niches emerge from our MCMMs, two associated with positive growth rates and one that represents non-growth, which are consistently observed across 15,204 individuals from five independent cohorts. Finally, we show how MCMMs can predict personalized engraftment and C. difficile growth suppression for a probiotic cocktail (VE303) designed to replace FMTs for the treatment rCDI. Overall, this powerful modeling approach predicts personalized C. difficile engraftment risk and can be leveraged to assess probiotic treatment efficacy. MCMMs could be extended to understand the mechanistic underpinnings of personalized engraftment of other opportunistic bacterial pathogens, beneficial probiotic organisms, or more complex microbial consortia.

The Influence of Probiotic Supplementation on the Obesity Indexes, Neuroinflammatory and Oxidative Stress Markers, Gut Microbial Diversity, and Working Memory in Obese Thai Children

Obesity is a worldwide health problem with a complex interaction between gut microbiota and cognition. Several studies have demonstrated that probiotic treatments improve characteristics linked to obesity. The present study aimed to evaluate the effects of probiotic supplementation on the obesity indexes, inflammatory and oxidative stress markers, gut microbiota, and working memory in obese children. Ten obese children were assigned to receive the probiotics (8 × 109 CFU of Lactobacillus paracasei HII01 and Bifidobacterium animalis subsp. lactis) for 12 weeks. Demographic data were recorded. Urine and fecal samples were collected to evaluate biomarkers related to obesity and cognition. Behavioral working memory was assessed using the visual n-back test. Electroencephalography was employed to measure electrical activity during the visual n-back test. All parameters were evaluated at the baseline and after 12 weeks. The results revealed that probiotic supplementation significantly altered some gut microbial metabolites, gut microbiota, total antioxidant capacity, and neuroinflammatory markers. However, no significant changes were observed in the visual n-back test or electroencephalographic recordings after 12 weeks. In conclusion, the use of probiotics might be an alternative treatment that could improve the gut microbial ecosystem and microbial metabolites, as well as host antioxidant and neuroinflammation levels. The preliminary results indicated that further detailed prolonged studies are needed in order to determine the beneficial effects of the studied probiotics.

Narrative Review: The Effect of Vitamin A Deficiency on Gut Microbiota and Their Link with Autism Spectrum Disorder

Autism spectrum disorder (ASD) is a group of neurodevelopmental disorders defined by a lack of social behaviors, repetitive behaviors and nonverbal interactions, such as limited eye contact, facial expression, and body gesturing. It is not a single condition, but rather a multi-factorial disorder caused by hereditary and non-genetic risk factors, as well as their interaction. According to several studies, the gut microbiota may have a role in the pathophysiology of autism spectrum disorder. Various studies have found differences in the composition of the gastrointestinal (GI) microbiota in children with ASD compared to unaffected siblings and/or healthy unrelated controls. The processes that relate the gut microbiota to brain dysfunctions (the gut-brain axis) in ASD are yet to be fully understood. However, the differences in the gastrointestinal composition might be due to vitamin A deficiency because vitamin A (VA) plays a role in the regulation of the intestinal microbiota. This narrative review discusses the impact of vitamin A deficiency on the gut microbiota composition and tries to understand how this may contribute for the development and severity of ASD.

Effect of Probiotic Supplementation on Gut Microbiota in Patients with Major Depressive Disorders: A Systematic Review

There is accumulating evidence on the beneficial effects of probiotic supplementation for patients with depressive disorders. However, prior reviews on the topic have largely focused on clinical effectiveness with limited emphasis on the underlying mechanisms of action and effects of probiotics on gut microbiota. In accordance with PRISMA guidelines, a systematic literature search of Medline, EMBASE and the Cochrane Library using combinations of the key words, (“depress*” OR “MDD” OR “suicide”), (“probiotic” OR “Lactobacillus” OR “Bifidobacterium”) AND (“gut” OR “gut micr*” OR “microbiota”), as well as grey literature was performed. We found seven clinical trials involving patients with major depressive disorder (MDD). The small number of studies and heterogeneous sources of data precluded meta-analysis. Most trials (other than one open-label trial) had a low-to-moderate risk of bias, which was largely due to a lack of control for the effects of diet on gut microbiota. Probiotic supplementation yielded only modest effects on depressive symptoms and there were no consistent effects on gut microbiota diversity, and in most instances, no significant alterations in gut microbiota composition were observed after four to eight weeks of probiotic intervention. There is also a lack of systematic reporting on adverse events and no good longer-term data. Patients with MDD may require a longer time to show clinical improvement and the microbial host environment may also need longer than eight weeks to produce significant microbiota alterations. To advance this field, further larger-scale and longer-term studies are required.

Alterations of gut microbiome and effects of probiotic therapy in patients with liver cirrhosis: A systematic review and meta-analysis

BACKGROUND

Alterations in the gut microbiome usually occur in liver cirrhosis. Gut microbiome dysregulation damages the liver and accelerates the development of liver fibrosis. Probiotic treatment has gradually become a major method for improving the prognosis of liver cirrhosis and reducing its complications. However, alterations in the gut microbiome have revealed different results, and the therapeutic effects of various probiotics are inconsistent.

METHODS

We searched the PubMed, Medline, EMBASE, ScienceDirect, and Cochrane databases up to August 2022 and conducted a systematic review and meta-analysis of 17 relevant studies.

RESULTS

The counts of Enterobacter (standardized mean difference [SMD] -1.79, 95% confidence interval [CI]: -3.08 to -0.49) and Enterococcus (SMD -1.41, 95% CI: -2.26 to -0.55) increased significantly in patients with cirrhosis, while the counts of Lactobacillus (SMD 0.63, 95% CI: 0.12-1.15) and Bifidobacterium (SMD 0.44, 95% CI: 0.12-0.77) decreased significantly. Blood ammonia (weighted mean difference [WMD] 14.61, 95% CI: 7.84-21.37) and the incidence of hepatic encephalopathy (WMD 0.40, 95% CI: 0.27-0.61) were significantly decreased in the probiotic group. As for mortality (MD 0.75, 95% CI: 0.48-1.16) and the incidence of spontaneous bacterial peritonitis (WMD -0.02, 95% CI: -0.07 to 0.03), no significant differences were found between the probiotic and placebo groups.

CONCLUSION

In summary, the gut microbiome in cirrhosis manifests as decreased counts of Lactobacillus and Bifidobacterium and increased counts of Enterobacter and Enterococcus. Targeted supplementation of probiotics in cirrhosis, including Lactobacillus combined with Bifidobacterium or Bifidobacterium alone, can reduce blood ammonia and the incidence of hepatic encephalopathy. The effect is similar to that of lactulose, but it has no obvious effect on mortality and spontaneous bacterial peritonitis.

Fecal microbiota transplantation in non-communicable diseases: Recent advances and protocols

Fecal microbiota transplant (FMT) is a therapeutic method that aims to restore normal gut microbial composition in recipients. Currently, FMT is approved in the USA to treat recurrent and refractory Clostridioides difficile infection and has been shown to have great efficacy. As such, significant research has been directed toward understanding the potential role of FMT in other conditions associated with gut microbiota dysbiosis such as obesity, type 2 diabetes mellitus, metabolic syndrome, neuropsychiatric disorders, inflammatory bowel disease, irritable bowel syndrome, decompensated cirrhosis, cancers and graft-versus-host disease. This review examines current updates and efficacy of FMT in treating conditions other than Clostridioides difficile infection. Further, protocols for administration of FMT are also discussed including storage of fecal samples in stool banks, inclusion/exclusion criteria for donors, fecal sample preparation and methods of treatment administration. Overall, understanding the mechanisms by which FMT can manipulate gut microbiota to provide therapeutic benefit as well as identifying potential adverse effects is an important step in clarifying its long-term safety and efficacy in treating multiple conditions in the future.

Lactobacillus spp. for Gastrointestinal Health: Current and Future Perspectives

In recent decades, probiotic bacteria have become increasingly popular as a result of mounting scientific evidence to indicate their beneficial role in modulating human health. Although there is strong evidence associating various Lactobacillus probiotics to various health benefits, further research is needed, in particular to determine the various mechanisms by which probiotics may exert these effects and indeed to gauge inter-individual value one can expect from consuming these products. One must take into consideration the differences in individual and combination strains, and conditions which create difficulty in making direct comparisons. The aim of this paper is to review the current understanding of the means by which Lactobacillus species stand to benefit our gastrointestinal health.