The effect of dietary hempseed on atherogenesis and contractile function in aortae from hypercholesterolemic rabbits.

UNLABELLED: Hempseed contains a unique combination of both omega-3 and omega-6 polyunsaturated fatty acids. In other studies, supplementation of the diet with selected polyunsaturated fatty acids has induced significant, beneficial cardiovascular effects. The purpose of the present study is to determine if hempseed ingestion over an 8-week period may provide protection to rabbits against the deleterious effects associated with dietary cholesterol supplementation. METHODS: Male albino New Zealand White rabbits were randomly divided into one of six groups: the control diet (RG), the control diet then supplemented with (wt/wt) 5% coconut oil (CO), or 10% hempseed (HP), or 0.5% cholesterol (OL), or with both 10% hempseed and 0.5% cholesterol (OLHP) or with 10% hempseed that was partially delipidated (SC). Each day the rabbits were fed 125 grams of the appropriate diet over an 8-week period. Fatty acid analysis of tissue and diets was determined using gas chromatography. Vascular function testing of aortic rings was done in order to assess the response of the tissue to both contraction and relaxation stimuli. Aortic atherosclerotic plaque was quantified. RESULTS: Cholesterol supplementation to the diet induced significant aortic plaque development. Dietary hempseed did not generate protection. The aorta obtained from rabbits fed the cholesterol-supplemented chow also exhibited defects in their contractile responses to KCl and norepinephrine and in relaxation to sodium nitroprusside (SNP).The addition of hempseed to this diet did not generate any improvement in contractile responses but had a modest protective effect on the cholesterol-induced defects in SNP-induced relaxation. CONCLUSIONS: Our data demonstrate that dietary hempseed provides mildly beneficial effects against contractile dysfunction associated with atherosclerotic vessels in the cholesterol-fed rabbit.

Cholesterol-induced stimulation of platelet aggregation is prevented by a hempseed-enriched diet.

Hypercholesterolemia indirectly increases the risk for myocardial infarction by enhancing the ability of platelets to aggregate. Diets enriched with polyunsaturated fatty acids (PUFAs) have been shown to reduce the detrimental effects of cholesterol on platelet aggregation. This study investigated whether dietary hempseed, a rich source of PUFAs, inhibits platelet aggregation under normal and hypercholesterolemic conditions. Male New Zealand white rabbits were fed one of 6 dietary interventions: regular control diet (RG); control diet + 10% hempseed (HP); control diet + 10% partially delipidated hempseed (DHP); control diet + 0.5% cholesterol (OL); control diet + 0.5% cholesterol + 10% hempseed (OLHP); control diet + 5% coconut oil (CO). After 8 weeks, blood was collected to measure ADP- and collagen-induced platelet aggregation and plasma levels of fatty acids, cholesterol, and triglycerides. The hempseed-fed animals (HP and OLHP) displayed elevated plasma levels of PUFAs and a prominent enhancement in 18:3n-6 (gamma-linolenic acid, GLA) levels, a unique PUFA found in hempseed. The cholesterol-supplemented groups (OL and OLHP) had significantly elevated plasma levels of cholesterol and triglycerides, but platelet aggregation was significantly augmented only in the OL group. The addition of hempseed to this diet (OLHP) normalized aggregation. The direct addition of GLA to the OL platelet samples blocked the cholesterol-induced stimulation of platelet aggregation. The results of this study demonstrate that when hempseed is added to a cholesterol-enriched diet, cholesterol-induced platelet aggregation returns to control levels. This normalization is not due to a reduction in plasma cholesterol levels, but may be partly due to increased levels of plasma GLA.