The Intestinal Microbiome

The intestinal microbiome is a collection of microorganisms that live in the human gut.

Intestinal micro-organisms process complex nutrients, such as plant fiber and Mucins, into simple sugars. The microbiome plays an important role in maintaining the self-regulation function of intestinal immune cells, the synthesis of vitamins, and preventing mucosa colonization with pathogens.

Maintaining the gut’s balance of microbiome is crucial for human health and preventing heart disease, type-2 diabetes, cancer, and obesity.

One of the microbiome functions is the production of short-chain fatty acids (SCFA).

SCFA – Short-Chain Fatty Acids

SCFA is produced by the intestinal microbiome during the prebiotics (dietary fiber, indigestible carbohydrates, or resistant starch) fermentation process.

The most common acids in the large intestine are acetic, propionic, and butyric acid (in a molar ratio of 3: 1: 1).

An imbalance of the intestinal microbiome and SCFA bacteria decreasing is often diagnosed in patients with inflammatory bowel disease, irritable bowel syndrome, type-2 diabetes, obesity, bacterial infections, autoimmune diseases, or cancer.

Functions of Short-Chain Fatty Acids (SCFA)

  • It improves the energy metabolism of mammals, which use them together with glucose as an energy source. SCFA can provide up to 10% of your daily calories. However, the production of these acids requires prebiotics used in fermentation
  • It is the main source of epithelial cells energy in colon mucosa
  • By stimulating the growth of saprophytic microflora, it suppresses the development of pathogenic microorganisms (Escherichia coli, Salmonella or Campylobacter) competing for colonization sites
  • It enhances the barrier function of the intestinal epithelium and regulates the immune system
  • It affects the differentiation of regulatory T-cells that control the strength and duration of the immune response, as well as the production of anti-inflammatory interleukin-10
  • It affects the maintenance of normal intestinal structure, integrity, and function
  • It regulates pH, increasing the absorption of calcium, iron, and magnesium
  • It is useful for the metabolism of glucose and protein in the liver
  • Increases the amount of mucus and blood flow rate
  • Regulates the appetite
  • Affects on markers of cardiovascular disease risk
SCFA Type of salt/ester Effect on human health
Acetic Acetate
  • Escherichia coli O157:H7
  • Participates in the cholesterol synthesis
Butyrate Oil
  • A source of 70% energy used by intestinal epithelial cells
  • Increases MUC2 gene expression and mucin production
  • Inhibits the development of tumor cells and triggers its death
  • Suppresses the genotoxic activity of nitroamides and hydrogen peroxide
  • Has an immunoregulatory effect
  • Plays a role in the prevention and treatment of distal ulcerative colitis, Crohn’s disease and cancer
  • Reduces symptoms of ulcerative colitis
Oily / Acetic / Propionic Butyrate / Acetate / Propionate
  • Reduces macroscopic and histological signs of inflammation
Formic Formate
  • The presence is associated with methanogenesis, and its concentration may be increased during inflammation
Propionic Propionate
  • Reduces the synthesis of cholesterol in the liver, improves lipid metabolism
  • Has an antiproliferative effect: it suppresses excessive cell division
Valerian Valerate
  • Stimulates the intestinal epithelium growth
  • Has a beneficial effect on the pathogenesis of diseases such as colitis, cardio-metabolic diseases, and cancer

Probiotics Effectiveness

Probiotics are live bacteria that improve the intestinal microflora.

Intestinal micro-organisms affect metabolism. The balance of the microbiome is necessary to maintain body health and prevent many diseases.

Scientists have suggested that deliberately multiplying or introducing certain groups of microorganisms may be useful to people who have a significant lack of them.

Anti-inflammatory effect of probiotics. The effect of Symprove aqueous probiotic suspension on bacterial diversity was tested in vitro of the human gut. Symprove probiotic contains 4 types of lactic acid bacteria: L. rhamnoses, L. Acidophilus, L. Plantarum, and Enterococcus faecium. After 3 weeks of taking Symprove, the SCFA production (especially oil acid) and the number of anti-inflammatory molecules IL-10 and IL-6 (cytokines) have increased, while the inflammatory molecules-chemokines IL-8, CXCL 10 and MCP-1 production were decreased.

Probiotics as pathogens killers. In another study, 33 volunteers aged 26 to 76 years consumed Lactobacillus Plantarum for 4 weeks. As a result, the number of beneficial bacteria increased, and the number of conditionally pathogenic microorganisms decreased. Production of acetic and propionic SCFA has increased in all age groups showing peak indicators after 5 weeks of probiotic intake.

Anti-aging effect of probiotics. 15 aging mice were receiving a probiotic for 12 weeks with three lactic acid bacteria: L. paracasei, L. plantarum and thermophilic Streptococcus. As a result, SCFA production has increased, while cell death and brain damage process began to slow. Aging mice have improved memory and learning ability.

Probiotics against Colon and Rectal Cancer

The colon and rectum malignant tumors (colorectal cancer) are the third most common cause of death from cancer. Colorectal cancer is associated with reduced SCFA levels and intestinal dysbiosis.

The probiotic Butyrivibrio fibrisolvens with high production of butyrate (butyric acid) were introduced into a mouse model of colon cancer. The probiotic has slowed down the tumor development, lowered the cancer marker β-glucuronidase, and increased the immune response.

Many studies have been conducted to estimate the effect of probiotics on tumor growth. While investigating the colon cancer, the following were tested: Pediococcus pentosaceus, Lactobacillus salivarius, Enterococcus faecium, skimmed kefir and ayran. Probiotics have increased the SCFA level and reduced tumor growth.

A diet containing fermentable dietary fibers increases the level of SCFA and could be a possible treatment for colorectal cancer as part of complex therapy.

Probiotics against Obesity

Obesity causes cardiovascular diseases, metabolic disorders, diabetes, cancer, or premature death. There are 1.7 billion overweight people in the world.

The composition of the intestinal microbiome in obese people differs from people with normal weight. Obesity is associated with Bacteroidetes decreasing and an increase in the number of Firmicutes. At the same time, the intestinal microbiome of an obese person is less diverse than that of a thin person.

Studies in mice and rats have shown that probiotics have a significant effect on obesity and diabetes:

  • Increase of intestinal barrier function;
  • Metabolism acceleration;
  • Weight gain suppression and insulin resistance;
  • Food intake lowering;
  • Glucose tolerance improvement.

Proper nutrition and use of probiotics can reduce small intestine inflammation, increase the integrity of the intestinal barrier, increase the number of beneficial bacteria – and lead to weight loss.

Probiotics for type-2 Diabetes

The intestinal microbiome of people with diabetes is altered and the production of SCFA by intestinal bacteria is usually reduced. The use of probiotics inhibits the development of type-2 diabetes.

A probiotic from camel milk was studied on mice. After 6 weeks of administration, the level of bacteria that produce SCFA increased, improved blood glucose and lipids.

Probiotics against Cardiovascular Diseases

Cardiovascular diseases (CVD) are the leading cause of death in the world. CVD is associated with increased in-blood cholesterol. High cholesterol levels provoke hypertension and type 2 diabetes.

For 8 weeks, Daily Body Restore probiotic from lactobacilli, bifidobacteria, and digestive enzymes were applied to mice. They were divided into 3 groups. The first is mice with high cholesterol levels due to a high-fat diet: this group received a probiotic. The second is mice on a low-fat diet. The third was mice on a high-fat diet that did not receive a probiotic. The probiotic has increased the level of propionic acid, reduced the level of harmful low-density lipoproteins, and raised the level of beneficial high-density lipoproteins.

Eating a large amount of fat is associated with intestinal dysbiosis. SCFA reduces the manifestations of cardiovascular diseases by lowering blood pressure and regulating glucose with lipid homeostasis.

Probiotics and Autism Spectrum Disorders

Autism spectrum disorders (ASD) are disorders of the nervous system that are characterized by impaired social interaction and repetitive behaviors.

In patients with ASD, the composition of the intestinal microbiome is changed, and there are often problems with the gastrointestinal tract.

The relationship between gastrointestinal symptoms and ASD was confirmed by a study on 97 children: 29 children with ASD received a probiotic, 29 children with ASD didn’t receive it, and 39 healthy children also did not receive a probiotic. In children with ASD who did not receive a probiotic, SCFA levels were significantly lower than in healthy children and children who received a probiotic.

Probiotics and Atopic Dermatitis

Atopic dermatitis is characterized by intestinal dysbacteriosis with the predominance of such species as Faecalibacterium, Oscillopsia, Bacteroides, Parabacteroides and Sutterella, as well as a decrease in the level or absence of microorganisms that produce SCFA.

Microorganisms that produce SCFA have anti-inflammatory effects are participating in the regulation of the immune system and may play a protective role against atopic dermatitis.

Probiotics and Gastrointestinal Disorders

SCFA prevents colonization of the intestinal epithelium by pathogenic microorganisms. Probiotics also increase the integrity of the intestinal barrier and improve immune regulation.

L. casei has an anti-inflammatory effect on intestinal epithelial cells infected with Shigella. Probiotics can treat and prevent diarrhea caused by bacterial and viral infections.

Probiotics for Human Health

Studies confirm that taking probiotics improves the balance of the intestinal microbiome and normalizes the level of short-chain fatty acids (SCFA) which promotes human health and prevents many diseases.

Researchers emphasize the immunomodulatory effect of SCFA produced by probiotics, but the mechanisms of their action need further study.

 

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