Purified ??-3 fatty acids retard the development of proteinuria in salt-loaded hypertensive rats

Abstract

To determine whether purified omega-3 and omega-6 fatty acids influence the progression of hypertensive renal failure in salt-loaded stroke-prone spontaneously hypertensive rats (SHRSP) with established hypertension or during the developmental stage of their hypertension. Groups of eight SHRSP aged 1 or 4 months were fed, for 12 weeks, synthetic diets containing 2% sodium (wt:wt) and either 5% olive oil or 4.5% gamma-linolenic acid (omega-6), eicosapentaenoic acid (omega-3) or docosahexaenoic acid (omega-3). Urinary protein excretion and blood pressure were measured after 6, 9 and 12 weeks. The rats were killed and their tissues were collected for fatty acid and eicosanoid analysis. Young rats (aged 1 month) fed diets containing gamma-linolenic acid or olive oil developed marked proteinuria by 9 weeks, whereas no change was observed after 12 weeks in rats fed docosahexaenoic acid or eicosapentaenoic acid. Blood pressure was lower in those fed docosahexaenoic acid or eicosapentaenoic acid than in the gamma-linolenic acid or olive oil groups. Adult rats (aged 4 months) fed the docosahexaenoic acid diet had significantly lower proteinuria than those fed gamma-linolenic acid, eicosapentaenoic acid or olive oil, but there were no differences in blood pressure among the groups. Kidneys from rats fed omega-3 fatty acids had increased levels of docosahexaenoic acid or eicosapentaenoic acid, or both, whereas those from rats fed gamma-linolenic acid and olive oil contained virtually no omega-3 fatty acids. Thromboxane B2 and 12-hydroxyeicosatetraenoic acid production in renal cortex extracts was lowest in rats fed docosahexaenoic acid and eicosapentaenoic acid. Dietary omega-3 fatty acids retard the development of hypertension-induced proteinuria. This may be caused by a favourable influence on fatty acid and eicosanoid metabolism and reduction of blood pressure.