EFFECTS OF FLAXSEED AND FLAX OIL DIETS IN A RAT-5 6 RENAL ABLATION MODEL/

The objective of this study was to assess the effects of flaxseed and flax oil diets in the rat renal ablation model. Flaxseed is a rich sou rce of alpha-linolenic acid, an 18:3n3 omega-3 fatty acid, which has a nti-atherogenic and anti-inflammatory properties. Flaxseed, but not fl ax oil, is also rich in lignans, which are platelet-activating factor- receptor antagonists. Rats were subjected to 5/6 nephrectomy, fed a re gular laboratory diet (RLD) for 1 week, then divided into three groups to receive either the RLD (n = 8), a 15% flaxseed diet (n = 8), or a 15% flax oil diet (n = 7). Blood pressure, proteinuria, glomerular fil tration rate, and urinary prostaglandins (thromboxane B-2 and 6-keto p rostaglandin F1(alpha) were measured presurgery and at 1 week (before dietary allotment) and 20 weeks postnephrectomy when blood for plasma lipids and kidneys for histology and tissue-phospholipid analyses were obtained. Blood pressure increased progressively in the RLD group but not in the flax diet groups. Plasma triglycerides and cholesterol inc reased in all groups, but this increase was significantly attenuated b y both flax diets. Proteinuria increased 1 week postsurgery and contin ued to increase in the RLD group but not in the flax diet groups. Glom erular filtration rate decreased progressively, but this decline in re nal function was attenuated significantly by the flax diets. Both of t he flax diets prevented glomerulosclerosis and mesangial expansion. Re nal alpha-linolenic acid was increased by both the flax diets (flax oi l > flaxseed), but eicosapentaenoic acid increased in the flax oil gro up only. The flaxseed group had greater renal-arachidonic acid levels than the flax oil and RLD groups. The total omega-3 fatty acids increa sed twofold to threefold in the flax oil group compared with the two o ther groups. The total saturated fatty acids were lower and the polyun saturated fatty acids were increased in both flax diet groups. A progr essive increase in urinary thromboxane B-2 occurred in the RLD group b ut not in the flaxseed group; the level decreased in the flax oil grou p. The ratio of prostaglandin F(1 alpha)thromboxane B-2 was preserved in the flax oil group only. In conclusion, the dietary flax seed and f lax oil attenuated the decline in renal function and reduced glomerula r injury with favorable effects on blood pressure, plasma lipids, and urinary prostaglandins. While we have not proven any specific synergis tic effects of the constituents of the flaxseed diet, the benefits of flax-derived alpha-linolenic acid with or without lignans in the rat-5 /6 renal ablation model seem clear from this experiment. (C) 1995 by t he National Kidney Foundation, Inc.