Changes in gut microbiota and cytokines following laparoscopic sleeve gastrectomy are associated with cognitive function improvement

Altered cognitive function in obese patients: relationship to gut flora

Obesity is a risk factor for non-communicable diseases such as cardiovascular disease and diabetes, which are leading causes of death and disability. Today, China has the largest number of overweight and obese people, imposing a heavy burden on China's healthcare system. Obesity adversely affects the central nervous system (CNS), especially cognitive functions such as executive power, working memory, learning, and so on. The gradual increase in adult obesity rates has been accompanied by a increase in childhood obesity rates. In the past two decades, the obesity rate among children under 5 years of age has increased from 32 to 42 million. If childhood obesity is not intervened in the early years, it will continue into adulthood and remain there for life. Among the potential causative factors, early lifestyle may influence the composition of the gut flora in childhood obesity, such as the rate and intake of high-energy foods, low levels of physical activity, may persist into adulthood, thus, early lifestyle interventions may improve the composition of the gut flora in obese children. Adipose Axis plays an important role in the development of obesity. Adipose tissue is characterized by increased expression of nucleoside diphosphate-linked molecule X-type motif 2 (NUDT2), amphiphilic protein AMPH genes, which encode proteins that all play important roles in the CNS. NUDT2 is associated with intellectual disability. Furthermore, amphiphysin (AMPH) is involved in glutamatergic signaling, ganglionic synapse development, and maturation, which is associated with mild cognitive impairment (MCI) and Alzheimer's disease (AD). All of the above studies show that obesity is closely related to cognitive decline in patients. Animal experiments have confirmed that obesity causes changes in cognitive function. For example, high-fat diets rich in long- and medium-chain saturated fatty acids may adversely affect cognitive function in obese mice. This process may be attributed to the Short-Chain Fatty Acid (SCFA)-rich high-fat diet (HFD) activating enterocyte TLR signaling, especially TLR-2 and TLR-4, altering the downstream MyD88-4 signaling, thereby impacting the downstream MyD88-NF-κB signaling cascade and up-regulating the levels of pro-inflammatory factors and lipopolysaccharide (LPS). These changes result in the loss of integrity of the intestinal mucosa and cause an imbalance in the internal environment. Obesity may lead to the disruption of the intestinal flora and damage the intestinal barrier function, causing intestinal flora dysbiosis. In recent years, a growing number of studies have investigated the relationship between obesity and the intestinal flora. For example, high-fat and high-sugar diets have been found to lead to the thinning of the mucus layer of the colon, a decrease in the number of tight junction proteins, and an increase in intestinal permeability in mice. Such changes alter the composition of intestinal microorganisms, allow endotoxins into the blood circulation, and induce neuroinflammation and brain damage. Therefore, obesity affects cognitive function and is even hereditary. This paper reviews the obesity-induced cognitive dysfunction, the underlying mechanisms, the research progress of intestinal flora dysregulation in obese patients, the relationship between intestinal flora and cognitive function changes, and the research progress on intestinal flora dysregulation in obese patients. We want to regulate the internal environment of obese patients from the perspective of intestinal flora, improving the cognitive function of obese patients, and prevent obesity-induced changes in related neurological functions.

A multi-omics microbiome signature is associated with the benefits of gastric bypass surgery and is differentiated from diet induced weight loss through 2 years of follow-up

Roux-en-Y gastric bypass (GBP) surgery is an effective treatment for reducing body weight and correcting metabolic dysfunction in individuals with severe obesity. Herein, we characterize the differences between very low energy diet (VLED) and GBP induced weight loss by multi-omic analyses of microbiome and host features in a non-randomized, controlled, single-center study. Eighty-eight participants with severe obesity were recruited into two arms - GBP versus VLED with matching weight loss for 6 weeks and 2-years of follow-up. A dramatic shift in the distribution of gut microbial taxa and their functional capacity was seen in the GBP group at Week 2 after surgery and was sustained through 2 years. Multi-omic analyses were performed after 6 weeks of matching weight loss between the GBP and VLED groups, which pointed to microbiome derived metabolites such as indoxyl sulphate as characterizing the GBP group. We also identified an inverse association between Streptococcus parasanguinis (an oral commensal) and plasma levels of tryptophan and tyrosine. These data have important implications, as they reveal a significant robust restructuring of the microbiome away from a baseline dysbiotic state in the GBP group. Furthermore, multi-omics modelling points to potentially novel mechanistic insights at the intersection of the microbiome and host.

Multi-omics insights into the microbiota-gut-brain axis and cognitive improvement post-bariatric surgery

BACKGROUND

Although numerous studies have shown that bariatric surgery results in sustained weight loss and modifications in gut microbiota composition and cognitive function, the exact underlying mechanisms are unclear. This study aimed to investigate the effects of bariatric surgery on cognitive function through the microbiota-gut-brain axis (MGBA).

METHODS

Demographic data, serum samples, fecal samples, cognitive assessment scales, and resting-state functional connectivity magnetic resonance imaging (rs-fMRI) scans were obtained from 39 obese patients before and after (6 months) laparoscopic sleeve gastrectomy (LSG). PCA analysis, OPLS-DA analysis, and permutation tests were used to conduct fecal 16 S microbiota profiling, serum metabolomics, and neuroimaging analyses, and a bariatric surgery-specific rs-fMRI brain functional connectivity network was constructed. Spearman correlation analysis and Co-inertia analysis were employed to correlate significant alterations in cognitive assessment scales and resting-state functional connectivity difference networks with differential serum metabolites and 16 S microbiota data to identify key gut microbiota and serum metabolic factors.

RESULTS

LSG significantly reduced the weight of obese patients, with reductions of up to 28%. Furthermore, cognitive assessment scale measurements revealed that LSG enhanced cognitive functions, including memory (HVLT, p = 0.000) and executive function (SCWT, p = 0.008). Also, LSG significantly altered gut microbiota composition (p = 0.001), with increased microbial abundance and diversity (p < 0.05). Moreover, serum metabolite levels were significantly altered, revealing intergroup differences in 229 metabolites mapped to 72 metabolic pathways (p < 0.05, VIP > 1). Spearman correlation analysis among cognitive assessment scales, gut microbiota species, and serum metabolites revealed correlations with 68 gut microbiota species and 138 serum metabolites (p < 0.05). Furthermore, pairwise correlations were detected between gut microbiota and serum metabolites (p < 0.05). Functional neuroimaging analysis revealed that LSG increased functional connectivity in cognitive-related frontotemporal networks (FPN, p < 0.01). Additionally, normalization of the default mode network (DMN) and salience network (SN) connectivity was observed after LSG (p < 0.001). Further canonical correlation and correlation analysis suggested that the cognitive-related brain network changes induced by LSG were associated with key gut microbiota species (Akkermansia, Blautia, Collinsella, Phascolarctobacterium, and Ruminococcus, p < 0.05) and neuroactive metabolites (Glycine, L-Serine, DL-Dopa, SM (d18:1/24:1(15Z), p < 0.05).

CONCLUSION

These findings indicate the pathophysiological role of the microbiota-gut-brain axis in enhancing cognitive function after bariatric surgery, and the study provides a basis for clinical dietary adjustments, probiotic supplementation, and guidance for bariatric surgery, but further research is still needed.

TRIAL REGISTRATION

Chinese Clinical Trial Registry, ChiCTR2100049403. Registered 02 August 2021, https://www.chictr.org.cn/ .

Influence of Bariatric Surgery on Gut Microbiota Composition and Its Implication on Brain and Peripheral Targets

Obesity remains a significant global health challenge, with bariatric surgery remaining as one of the most effective treatments for severe obesity and its related comorbidities. This review highlights the multifaceted impact of bariatric surgery beyond mere physical restriction or nutrient malabsorption, underscoring the importance of the gut microbiome and neurohormonal signals in mediating the profound effects on weight loss and behavior modification. The various bariatric surgery procedures, such as Roux-en-Y gastric bypass (RYGB) and sleeve gastrectomy (SG), act through distinct mechanisms to alter the gut microbiome, subsequently impacting metabolic health, energy balance, and food reward behaviors. Emerging evidence has shown that bariatric surgery induces profound changes in the composition of the gut microbiome, notably altering the Firmicutes/Bacteroidetes ratio and enhancing populations of beneficial bacteria such as Akkermansia. These microbiota shifts have far-reaching effects beyond gut health, influencing dopamine-mediated reward pathways in the brain and modulating the secretion and action of key gut hormones including ghrelin, leptin, GLP-1, PYY, and CCK. The resultant changes in dopamine signaling and hormone levels contribute to reduced hedonic eating, enhanced satiety, and improved metabolic outcomes. Further, post-bariatric surgical effects on satiation targets are in part mediated by metabolic byproducts of gut microbiota like short-chain fatty acids (SCFAs) and bile acids, which play a pivotal role in modulating metabolism and energy expenditure and reducing obesity-associated inflammation, as well as influencing food reward pathways, potentially contributing to the regulation of body weight and reduction in hedonic eating behaviors. Overall, a better understanding of these mechanisms opens the door to developing non-surgical interventions that replicate the beneficial effects of bariatric surgery on the gut microbiome, dopamine signaling, and gut hormone regulation, offering new avenues for obesity treatment.