The effect of dietary flaxseed supplementation on organic anion and osmolyte content and excretion in rat polycystic kidney disease

Progression of chronic renal failure in the Han:SPRD-cy rat polycystic kidn ey disease is associated with renal depletion of citric acid cycle metaboli tes and betaine. Amelioration of this disease by a soy protein diet is asso ciated with retention of citric acid cycle anions, despite increased excret ion, and preservation of tissue levels of betaine. As we have recently foun d that modest dietary supplementation with flaxseed preserves renal functio n and reduces histologic injury in the Han:SPRD-cy rat, we undertook a high -resolution H-1 NMR spectroscopic study of urine and renal tissue extracts from Han:SPRD-cy rats to explore the renal biochemical consequences of a fl axseed diet. There was no significant dietary effect upon organic anion, me thylamine, or osmolyte excretion in healthy animals. There was increased ci trate excretion in Han:SPRD-cy rats fed flaxseed. Urinary ammonium excretio n did not differ, suggesting that the observed increase in citrate excretio n was not due to an alkaline effect of diet. Tissue extract studies reveale d that disease amelioration was associated with tissue retention of succina te and betaine. Amelioration of Han:SPRD-cy rat polycystic kidney disease b y diet is associated with alteration in the handling of citric acid cycle m etabolites. Betaine may have a metabolic role in the reduction of chronic r enal injury.