Diet Rx: How can antioxidant diets protect against diabetic kidney disease?
By Andrea Gibson
More than 150 million people worldwide have been diagnosed with type 2 diabetes, and experts project that the incidence will skyrocket to 300 million by 2025. Kidney disease is a common complication; 50 percent of patients with end-stage kidney disease in the United States are also diabetic.
With the disease and its complications becoming more and more prevalent, Ohio University scientists Felicia Nowak and Sharon Inman and colleagues began examining whether an antioxidant diet could mitigate the symptoms of diabetes.
The Heritage College of Osteopathic Medicine researchers received a three-year grant from the National Institutes of Health for the project, which examined 144 diabetic and healthy rats. The scientists fed the rats a diet fortified with selenium, manganese, Vitamin C, and other antioxidant vitamins and minerals, and then monitored various biomedical markers of health at six, 13, and 20 weeks.
The team was surprised to find that while the antioxidant diet didn’t alleviate the symptoms of diabetes or prevent the development of kidney disease in male rats, it did provide some protection to the female rats under study. The female subjects had significantly lower blood glucose, less severe kidney problems, lower blood pressure, and better production of nitric oxide (which reduces oxidative stress in the body) than their male counterparts throughout the study. The health status of all diabetic subjects, however, worsened with age, the researchers report.
In human populations, men are more likely than women to have diabetic kidney disease.
“Some people think that women have protection because of their elevated estrogen levels and lower levels of androgen,” Nowak says. “I’m not convinced that that’s the reason.”
Nowak notes that the beneficial effect of the antioxidants could have gone unnoticed in most conventional studies, which typically use only male rats.
The team is hoping to attract additional funding to support a new version of the study that would tweak the antioxidant diet. After the initial study was underway, Nowak says, new research was published that suggested that copper could be detrimental to the diabetic kidney, whereas alpha-lipoic acid could be beneficial. The team also plans to use Inman’s expertise with a specialized technique called video microscopy to take a closer look at the new diet’s impact on kidney microcirculation.
In the meantime, Inman’s lab has received funding through two Centers for Osteopathic Research and Education (CORE) research grants to further examine the nitric oxide pathways and the effect of adding a niacin-chromium complex supplement to the rat diet. Niacin and chromium appear to have many beneficial properties, including antioxidant, anti-inflammatory, and anti-dyslipidemia (abnormal concentrations of lipids in the blood) effects, which may slow the progression of kidney disease, Inman explains. Dietary supplementation would be an inexpensive, well-tolerated treatment for patients with type 2 diabetes, she notes.
Nowak also has embarked on a new study, funded by the Ohio University Research Committee and the medical college’s Research and Scholarly Affairs Committee, to examine whether paternal diet and obesity can impact offspring. This relatively unexplored research area has potential applications for human health and therapeutics for metabolic disease, including diabetes.
This article appears in the Spring/Summer 2012 issue of Ohio University's Perspectives magazine.