Distinct effects of dietary flax compared to fish oil, soy protein compared to casein, and sex on the renal oxylipin profile in models of polycystic kidney disease.

Key Findings

Little is known regarding the effects of dietary protein on oxylipins which are derived form polyunsaturated fatty acids. Soy protein compared to casein feeding reversed some of the disease associated alterations in n-6 PUFA derived oxylipins in rat renal tissues. Soy protein can reduce the activity of Δ6 desaturase, an enzyme that converts LA to longer chain PUFA, and raise the LA levels, and thus could potentially alter the formation of oxylipins from these fatty acids. There were few effects of dietary fish and flax compared to soy oil, soy protein compared to casein, and sex on disease progression in a rat and a mouse model of polycystic kidney disease. Flax oil also is effective in lowering n-6 PUFA derived oxylipins in rodent kidneys and human plasma. The current study uses a larger profile of renal oxylipins in a direct comparison of fish and flax oil. A greater effect of fish compared to flax oil occurred despite the fact that the EPA and DHA content of the fish oil diet was less than half that of the ALA content of the flax oil diet, indicating that EPA and DHA have a greater effect than ALA on the n-6 PUFA derived oxylipins. The n-3 derived oxylipins were increased with both flax and fish oil feeding, but the effect on ALA oxylipins was greater with flax oil, while the effect on EPA and DHA oxylipins was greater with fish oil.  These studies provide novel data directly comparing flax and fish oil on the renal oxylipin profile. Fish compared to flax oil resulted in greater reduction in n-6 PUFA derived oxylipins and greater increase in EPA and DHA derived oxylipins, whereas flax oil was more effective in elevating ALA derived oxylipins. Soy protein resulted in higher levels of oxylipins from LA, while females compared to males displayed higher levels of AA oxylipins. Further studies are required to elucidate how these novel effects of diet and sex on the renal oxylipin profile affect renal health and disease

ABSTRACT:

Oxylipins are bioactive lipids derived from polyunsaturated fatty acids (PUFA) that are important regulators of kidney function and health. Targeted lipidomic analyses of renal oxylipins from four studies of rodent models of renal disease were performed to investigate the differential effects of dietary flax compared to fish oil, soy protein compared to casein, and sex. Across all studies, dietary fish oil was more effective than flax oil in reducing n-6 PUFA derived oxylipins and elevating eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) derived oxylipins, whereas dietary flax oil resulted in higher α-linolenic acid (ALA) oxylipins. Dietary soy protein compared to casein resulted in higher linoleic acid (LA) derived oxylipins. Kidneys from females had higher levels of arachidonic acid (AA) oxylipins, but similar or lower levels of oxylipins from other PUFA. Modulation of the oxylipin profile by diet and sex may help elucidate their effects on renal physiology and health.