Journal Name:
Am. J. Physiol. Renal Physiol.
Article Title:
Omega-3 fatty acid rich diet prevents diabetic renal disease.
Date Written:
2009
Volume:
296
Number:
2
Page:
F306
Author(s):
Garman, J.H.; Mulroney, S.; Manigrasso, M.; Flynn, E.; Maric, C.
Article:
Diabetic nephropathy is the leading cause of chronic renal disease, end-stage renal disease, and the need for kidney dialysis and transplantation in the Western world. Epidemiological studies have reported that omega-3 polyunsaturated fatty acids (n-3 PUFA) reduce renal dysfunction by preventing declines in creatinine clearance in healthy older people and the risk of albuminuria in young type 1 diabetic patients and in older patients with type 2 diabetes. The mechanisms responsible for these effects are unclear. The aim of the present study was to assess the effects of a diet rich in canola, a source of n-3 PUFA alpha-linolenic acid (ALA), reduces the development of diabetic renal disease.
Male Sprague-Dawley rats were randomly divided into four treatment groups: nondiabetic (ND), streptozotocin-induced diabetic (D), diabetic and fed a high n-3 PUFA diet (D+canola), and diabetic and fed a high n-6 (omega-6) PUFA diet (D+corn). Study treatments were carried out for 30 wk. The data showed that a diet high in n-3 PUFA (in canola oil), but not n-6 PUFA completely prevents the development of renal disease characteristic of longer-term (30 wk) diabetes. Animals fed the canola oil diet did not exhibit increased urine albumin excretion, glomerulosclerosis, tubulointerstitial fibrosis, hypertension, and inflammation characteristic of diabetic renal disease. D+canola significantly decreased diabetes-associated increases in urine albumin excretion; systolic blood pressure; glomerulosclerosis and tubulointerstitial fibrosis in the renal cortex and the inner stripe of the outer medulla. D+corn also exerted renoprotection, but not to the same degree as D+canola. The D+canola attenuated diet-associated increases in collagen type I and type IV, IL-6, MCP-1, transforming growth factor-beta, and CD68 expression.
In humans, albuminuria is a strong predictor of progressive decline in renal function. In this study, diabetic animals showed a significant increase in urine albumin excretion, while treatment with canola reduced urine albumin excretion to levels of those observed in nondiabetic animals. The current study also demonstrated an increase in systolic blood pressure in diabetic animals compared with non-diabetic animals after 30 wk of diabetes, which was not observed in diabetic animals fed either an n-3 PUFA or an n-6 PUFA diet. Diabetic animals showed increased glomerulosclerosis and tubulointerstitial fibrosis after 32 wk of treatment. This pathology was completely prevented by treatment with canola oil, demonstrating that in addition to being able to prevent albuminuria and hypertension, canola is also effective in alleviating renal structural damage associated with diabetes.
The present study showed an increased density of activated macrophages and IL-6, and MCP-1 protein expression in the diabetic renal cortex, consistent with increased tissue inflammation. Treatment with canola oil attenuated these changes, demonstrating their anti-inflammatory effects in diabetes. In summary, this study demonstrated that canola oil prevents albuminuria, glomerulosclerosis, tubulointerstitial fibrosis, inflammation, and increased systolic blood pressure associated with long-term diabetes in an animal model. Further research is emphasized to assess the effects that canola oil could have on the prevention of diabetic organ complications.
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