Dietary essential fatty acid supplementation, urinary calcium excretion and reproductive performance in the diabetic pregnant rat.

Hypercalciuria may be a contributory factor to the disturbed calcium homoeostasis seen in diabetic pregnant rats and their offspring. In diabetes, essential fatty acid metabolism is impaired. We have therefore investigated whether feeding a diet supplemented with essential fatty acids will ameliorate the hypercalciuria of diabetic pregnancy and improve reproductive performance. Female rats were fed a standard rat diet, a fat-free diet plus evening primrose oil or a fat-free diet plus sunflower oil. They were injected with streptozotocin or vehicle and mated. Urine samples were analysed for calcium before injection and during gestation. Term-pregnant diabetic rats fed evening primrose oil showed a 73% reduction in urinary calcium output compared with similar rats fed standard diet (P < 0.001). The corresponding reduction was 44% in diabetic rats fed sunflower oil (P < 0.001). A depletion of essential fatty acids in diabetes may therefore be associated with hypercalciuria; dietary supplementation, particularly with evening primrose oil, appears to correct the problem. Diabetic pregnant rats fed evening primrose oil showed a significantly greater live fetal mass (85 +/- 2 vs 33 +/- 12 g; P < 0.05) compared with similar rats fed standard diet. Such findings may imply a normalization of placental transport by essential fatty acids. Rats fed evening primrose, but not sunflower oil, also showed a reduced incidence of diabetes after streptozotocin injection compared with rats fed standard diet (63 vs 86%). Rats fed on evening primrose oil that did become diabetic were less hyperglycaemic than those on the standard diet (29 +/- 2 vs 37 +/- 2 mmol/l), suggesting that the oil may have anti-diabetic properties.