Bridging the Gut Microbiota and the Brain, Kidney, and Cardiovascular Health: The Role of Probiotics

The symbiosis between intestinal bacteria and the human body's physiological processes can modulate health. The intestinal microbiota is linked to the development of neurotrophic factors; therefore, it is increasingly related to the modulation of nervous system pathologies. Moreover, microbiota can interfere with inflammation and oxidative stress, which are closely linked to cardiovascular risk factors and several other inflammatory conditions, such as kidney and neurodegenerative diseases. Probiotics are live microorganisms that help regulate and maintain healthy microbiota; thus, they can help prevent these diseases. Due to these reasons, this review aimed to evaluate the effects of probiotics on the gut, kidneys, brain, and heart homeostasis. Clinical trials showed several positive results with the treatment. In the brain, probiotics reduce depressive symptoms (decreases in HAMA, GAD-7, and BDI-II scales), improving patients' sleep quality and fatigue, enhancing cognitive subscales while slowing brain atrophy, and reducing IL-6 levels in the central areas, also modulating REM delta power to reduce high-frequency brain waves. Probiotics can also reduce cardiovascular risk factors, such as inflammation. Probiotics can also benefit the heart by decreasing TMAO, LDL-c, TG, CRP, MDA, TNF-α, IL-6, and urea levels, improving dyslipidemia and toxin profiles. Probiotics also increase HDL-c, ApoE, and insulin sensitivity, decreasing BMI, body fat, and the risk of developing chronic hyperglycemia while increasing lean mass. Besides, probiotic supplementation helped reduce toxic uremic toxins (serum urea) and sodium levels, bringing benefits to the kidneys, and improve energy/amino acid metabolism. Probiotics can also modulate and enhance kidney function due to decreased pro-inflammatory TGFβ-1 and TNF-α levels and RUNX2. Furthermore, enhanced gastrointestinal motility and diversity have been reported using specific bacteria. Although probiotics can bring several health benefits, there are still challenges regarding these supplements, such as dose, frequency, and pharmaceutical formula. Therefore, new studies are welcome to deepen the understanding of these microorganisms.