How does the gut brain axis affect emotions and blood sugar levels? How important are probiotics? The intestine has always been affecting the brain
Among them, probiotics represented by lactic acid bacteria and bifidobacteria play an irreplaceable role in nutrient absorption, immune maintenance, and even emotional regulation through a series of unique biological reactions.
1、 The core skill of probiotics is a series of precise biological reactions that enable them to function effectively.
（1） Helping the body digest and absorb carbohydrates is the key skill of probiotics.
Taking Bifidobacterium as an example, it can produce β - galactosidase, fructosidase, etc., which break down oligosaccharides (such as oligofructose and galactose oligosaccharides) that we cannot digest into short chain fatty acids (mainly acetic acid, propionic acid, and butyrate).
Probiotics are also highly targeted for the processing of amino acids.
Lactobacillus can convert tryptophan into a precursor of serotonin (a substance closely related to emotions);
The energy produced by the breakdown of glutamine by bifidobacteria can also help repair damaged intestinal mucosa.
（2） The cell wall components of probiotics that regulate immunity, such as peptidoglycan and lipoteichoic acid, are recognized by Toll like receptors on the surface of intestinal epithelial cells and macrophages, which activate the NF - κ B signaling pathway to maintain a balance between pro-inflammatory and anti-inflammatory factors.
The "occupancy strategy" of probiotics is crucial in combating pathogenic bacteria.
For example, Lactobacillus rhamnosus GG (LGG) secretes a bacteriocin called "plantaricin", which directly inhibits the attachment of Escherichia coli and Salmonella to the intestinal wall; It can also stimulate the secretion of defense hormones by Paneth cells in the intestine.
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（3） Cross organ communication ": There is an" information highway "(also known as the" gut brain axis ") from the gut to the brain, liver, gut, and brain, through which probiotics can exert their effects.
Clinical studies have shown that Bifidobacterium longum 1714 can regulate tryptophan metabolism in the intestine, increasing serotonin (a "pleasure hormone") in the brain, thereby alleviating anxiety - this was discovered by Slyepchenko et al. in 2019, which may be related to the activation of the vagus nerve and the secretion of neuropeptides (such as CCK and GLP-1) by intestinal endocrine cells.
The metabolites of probiotics can also affect blood sugar. CanFora et al.'s 2015 study found that propionic acid produced by probiotics can reach the liver through the portal vein, activate the AMPK signaling pathway, reduce liver glucose synthesis, and improve insulin resistance - indicating that probiotics may have an adjuvant intervention effect on metabolic syndrome.
2、 What will happen if the microbiota is disrupted?
How to 'adjust' once the gut microbiota is imbalanced (such as fewer probiotics and more bad bacteria), beneficial biological reactions will 'deviate', which may cause a series of problems: in obese people, the proportion of Firmicutes and Bacteroidetes is often higher, which makes the body more 'good' at absorbing energy, leading to the accumulation of substances such as endotoxins and branched chain amino acids;
Autistic patients often have excessive amounts of Desulfovibrio in their intestines, and the hydrogen sulfide they produce may interfere with neural development through the gut brain axis.
There are currently several regulatory approaches to address these issues: supplementing probiotics: the key is to select the right strains (such as Lactobacillus reuteri DSM 17938, which is helpful for children with irritable bowel syndrome), and to ensure that they can reach the intestine alive (microencapsulation technology has better formulation effects);
Eat some prebiotics: substances such as galactooligosaccharides (GOS) and inulin can specifically "feed" probiotics. The clinical trial conducted by Makras et al. in 2005 showed that consuming 5-10 grams per day significantly increased the number of bifidobacteria in feces.
