Layman’s summary: A function of normal kidneys is to maintain a synergistic balance of the myriad species of bacteria that reside in our gastrointestinal tract. When the balance of the trillions of bacteria is optimal, our immune system is strengthened, our mood is steady, and inflammation is reduced. As kidney disease progresses toward the end stage, the balance of the bacteria living in our gut is upset.
Publication date: February 2013
Published in: Journal of the International Society of Nephrology
Lead author: Nosratola Vazir
Emeritus Professor of Medicine
University of California Irvine

Abstract: The population of microbes (microbiome) in the intestine is a symbiotic ecosystem conferring trophic and protective functions. Since the biochemical environment shapes the structure and function of the microbiome, we tested whether uremia and/or dietary and pharmacologic interventions in chronic kidney disease alters the microbiome.

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Dr. Fisher’s notes:

After nearly four decades, I spoke to Dr. Nick Vaziri, now a retired Professor Emeritus of Medicine, Physiology and Biophysics at the University of California, Irvine. I am proud to say that we worked together at UCLA as renal fellows for two years. He shared with me several of his scientific papers covering diverse disciplines related to kidney diseases.

Kidney patients receive powerful, broad spectrum antibiotics which destroy the protective species of gut flora and upset the delicate balance. In addition, we routinely tell our patients to eat less fiber in the form of fruits and vegetables because of the high potassium content found in them. The good bacteria depend on fiber in the diet to thrive. So in compromised kidneys, the gut flora is diminished.

The bacteria present in the GI tract are responsible for making serotonin which is absolutely necessary for good brain health. Too little may cause a mood disorder such as depression. Depression is very common in our dialysis patients for obvious reasons such as loss of organ function, loss of job, loss of sense of security and well-being, freedom to enjoy their favorite foods much more. Now, compounding the situational depression commonly present, the brain is not receiving adequate serotonin to help stabilize mood.

In the uremic environment, the cells that line the colon develop a leak in the part of the cell called a “tight junction.” (a minute passage between the cell and the internal milieu) This allows bacterial products called endotoxins to pass into the system and do harm. Inflammation is accentuated as inflammatory substances also pass through these leaky junctions. Since Inflammation plays a significant role in producing cardiovascular disease in our kidney patients where heart disease is the most common cause of death. If we can repair the cell and prevent the leak, it may reduce an important cause of the inflammatory state of CRF.

It seems that by changing to a more plant based and high fiber diet, the progression to end stage renal disease may be slowed, the crucial bacterial synergy may be maintained and the inflammatory nature of uremia may be reduced. Dr. Vaziri is working in conjunction with nephrologists to test this hypothesis in clinical studies ongoing. He has called this condition the “Intestinal Renal Syndrome.