Semester

Spring

Date of Graduation

2011

Document Type

Dissertation

Degree Type

PhD

College

Davis College of Agriculture, Natural Resources and Design

Department

Animal and Nutritional Sciences

Committee Chair

Janet C Tou

Abstract

The occurrence of kidney failure in the US has drastically increased over the past decade. The decline in health associated with chronic kidney disease can be prevented if detected early in disease progression. However, substantial damage has often occurred before detection of renal disease is possible. Therefore, disease prevention (as in all diseases) is the optimal treatment.;In regards to the kidneys, dietary habits can have a profound influence on the function and overall kidney health. This is particularly evident in female rats due to their susceptibility to diet induced renal disease. In female rats, the initiation of chronic kidney disease typically involves nephrocalcinosis (NC). NC is characterized by increased renal calcium (Ca) content, and involves the pathological deposition of mineral deposits in renal tissue. Fluctuations in dietary Ca and phosphorus (P) content are the major consideration in managing NC. However, other dietary components can mediate the development and severity of this disease in rats.;Based on our study results, the source of dietary protein and lipid can influence the development of NC in female rats. Our initial study compared the nutritional quality of a novel protein source derived from krill to the milk protein, casein. Rats fed krill protein concentrate (KPC) had lower kidney weights (P<0.001), lower kidney Ca content (P =0.002), and lower incidence of renal damage than rats fed casein based diets. These changes occurred in the absence of fluctuating urinary mineral content, which is a major cause of NC. Further analysis showed that KPC contained residual krill oil, which is rich in omega-3 polyunsaturated fatty acids (o-3 PUFAs). The next study involved isolation and characterization of krill oil. Krill oil is a unique lipid with high (>65%) polar lipid content including phospholipids, whereas other dietary sources of o-3 PUFAs were found to be predominately triacyglyceride. In the final study, the characterized oils were added to casein-based diets and fed to female rats to determine if lipid content influences the development of NC. While rats fed KPC appeared to be protected from NC, rats fed the high fat diet as krill oil were the only rats who developed NC. The high inclusion of krill oil resulted in elevated dietary P content due to its high phospholipid content. Aside from NC, the renal fatty acid content was influenced by the diet and lead to an apparent decrease in urinary prostaglandin production in all rats consuming the long-chain o-3 polyunsaturated fatty acids (o-3 LCPUFAs) eicosapentaenoic (EPA) and docosahexaenoic acid (DHA). The consumption of the different o-3 PUFA sources also resulted in reduced activity of the proinflammatory transcription factor NFkappaB, and expression of the proinflammatory cyclooxygenase -2 (COX-II) and transforming growth factor-beta (TGF-beta). Despite these observed results, no differences were noted in serum measures of kidney function. We concluded that changing the source of dietary protein and lipid can mediate renal health in female rats. It appears that o-3 PUFAs do not influence the nephrocalcigenic nature of casein. However, providing dietary o-3 PUFAs resulted in decreased renal inflammatory activity as compared to rats fed corn oil. This supports the benefit of o-3 PUFA supplementation in reducing the onset of diseases caused by inflammatory processes, and suggests that different dietary sources of o- PUFAs vary in regards to biological activity.

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