Both central, general adiposity lead to higher risks for kidney disease
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Risks for kidney disease rise with increasing adiposity regardless of fat distribution and presence of diabetes, according to a study published in the International Journal of Obesity.
“It is not well appreciated that, compared with the apparent optimum BMI of 20 kg/m2 to 25 kg/m2, a U.K. adult’s risk for advanced chronic kidney disease is increased by about one-third if they are overweight (BMI 25-30 kg/m2), is approximately doubled in early obesity (BMI 30-35 kg/m2) and is tripled at BMI over 35 kg/m2,” William G. Herrington, MD, FRCP, associate professor and Medical Research Council-Kidney Research UK Professor David Kerr Clinician Scientist at the University of Oxford, told Healio.
Herrington and colleagues analyzed data from the UK Biobank collected from 2006 to 2010 on 408,527 adults (218,141 women; mean age, 56.2 years; 23,637 with diabetes; 12,507 with prediabetes; 22,318 with vascular disease; mean systolic blood pressure, 138 mm Hg). The study focused on waist-to-hip ratio to measure central adiposity and BMI for general adiposity.
Most participants did not have a detectable urinary albumin level (< 6.7 mg/L). Those with any albuminuria (mean, 1 mg/mmol) were categorized based on urine albumin-to-creatinine ratio (uACR): low normal (uACR 0.1 to 1 mg/mmoL; n = 61,074), high normal (uACR 1 to 3 mg/mmoL; n = 45,148) and albuminuria (uACR 3 mg/mmoL; n = 20,425).
The researchers found both central and general adiposity were linked to higher risks for albuminuria. For a given BMI, each increase of 0.06 in waist-to-hip ratio was associated with 32% greater odds of being in a higher uACR category for the entire cohort (OR = 1.32; 95% CI, 1.30-1.34), with greater odds for men (OR = 1.39; 95% CI, 1.36-1.42) than for women (OR = 1.27; 95% CI, 1.24-1.30). Odds were also greater for adults with diabetes (OR = 1.45; 95% CI, 1.38-1.52) than for those without diabetes (OR = 1.26; 95% CI, 1.24-1.28) or those with prediabetes (OR = 1.18; 95% CI, 1.09-1.27).
With respect to general adiposity, for a given waist-to-hip ratio, each 5 kg/m2 increase in BMI was associated with 35% greater odds of being in a higher uACR category for the total cohort (OR = 1.35; 95% CI, 1.33-1.37). As with central adiposity, greater odds were found for men (OR = 1.50; 95% CI, 1.47-1.53) than for women (OR = 1.27; 95% CI, 1.25-1.29) and for adults with diabetes (OR = 1.37; 95% CI, 1.33-1.42) compared to those without diabetes (OR = 1.29; 95% CI, 1.28-1.31).
However, the researchers noted the association between adiposity and albuminuria remains strong among adults with no diabetes or prediabetes.
“From these data, we can conclude that fat in any place of the body is linked to increased urinary protein,” Herrington said. “This was true in men and women — with no apparent protective effect of fat around the hips — and in people with and without prediabetes or diabetes.”
Factors such as diabetes, BP and vascular disease explained about 40% of central adiposity-albuminuria associations, according to the researchers.
“The observation of associations between adiposity and proteinuria in people with absolutely normal blood glucose levels, and the fact that traditional risk factors explained less than half of the adiposity-proteinuria associations, raises a hypothesis that unknown mediating mechanisms lie undiscovered,” Herrington said.
Dietary salt was not a factor in explaining the associations, Herrington said. Models incorporating urinary sodium-to-creatinine ratio did not explain any of the associations between BMI or waist-to-hip ratio with albuminuria.
Herrington said the researchers were now generating similar models using genetic epidemiological approaches to explore whether the adiposity-kidney disease associations are causal and then assess the importance of known mediators with established treatments.
For more information:
William G. Herrington, MD, FRCP, can be reached at will.herrington@ndph.ox.ac.uk
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