Link found between birth weight and kidney health

A Monash University study has found that the number of nephrons in a person's kidney increases with their birth weight, a finding that could explain why Indigenous Australians and African-Americans are at greater risk of kidney disease and high blood pressure.

Nephrons are a vital component of kidneys. They filter the blood, allowing water, some salts, glucose and amino acids to be reabsorbed into the blood capillaries while removing waste products. Human and animal studies have shown that having fewer nephrons creates a risk of developing hypertension and kidney diseases.

Australian Aborigines, Native Americans and African Americans have much higher rates of heart and kidney disease than the general population in the same geographic areas. These groups also have higher rates of low-weight infant births and adult obesity.

Professor John Bertram and Mrs Rebecca Douglas-Denton from Monash's Department of Anatomy and Cell Biology, in collaboration with researchers from the Northern Territory's Menzies School of Health Research and the University of Mississippi Medical Center in the US, examined the autopsy kidneys of black and white Australians and North Americans for the size and number of nephrons. They also looked for any gender differences or correlations with age or birth weight.

"Once people are born, they have all the nephrons they are going to get and will lose them as they age," Prof. Bertram said. "For many years it has been assumed that people have about one million nephrons at birth.

"This autopsy study has shown that there is a huge range in the number of nephrons people might have at birth - from 200,000 up to 1.8 million. More importantly, it has shown that the number of nephrons a person has increases with their birth weight."

When there are few nephrons, certain parts of the kidney become susceptible to scarring which puts people with fewer nephrons at greater risk of kidney disease.

"If low nephron number is a risk factor for high blood pressure, and therefore heart disease and chronic kidney disease, then interventions that emphasise prenatal care and reducing the prevalence of low birth weight deliveries should hopefully reduce this risk."

Item provided courtesy of Monash University