Arterial endothelial function in a porcine model of early stage atherosclerotic vascular disease

Abstract

Cardiovascular disease (CVD) is the leading cause of morbidity and mortality in the United States and is projected to become the leading cause of mortality in the world. Atherosclerosis is the most important single factor contributing to this disease burden. In this study, we characterize relationships between endothelial dysfunction and vascular disease in an animal model of diet-induced, early-stage atherosclerotic vascular disease. We tested the hypothesis that hypercholesterolaemia induces vascular disease and impairs endothelium-dependent relaxation (EDR) in conduit arteries of adult male Yucatan pigs. Pigs were fed a normal fat (NF) or high fat cholesterol (HFC) diet for 20-24 weeks. Results indicate that, while the HFC diet did not alter EDR in femoral or brachial arteries, EDR was significantly decreased in both carotid and coronary arteries. Sudanophilic fatty streaks were significantly present in the abdominal aorta and common carotid artery. Histopathology revealed increased intima-media thickness (IMT) and foam cell accumulation in Stary Stage I-III lesions in the abdominal aorta, common carotid artery and femoral arteries. In the coronary arteries, the accumulation of foam cells in Stary Stage I and II lesions resulted in a trend for increased IMT. There was no evidence of vascular disease in the brachial arteries. These results indicate that early stages of CVD (Stary Stage I-III) precede decreases in EDR induced by HFC diet, because femoral arteries exhibited foam cell accumulation and an increased IMT but no change in endothelial function.

Figure 1

(a) Representative photographs of abdominal aorta stained with Sudan IV in pigs fed a normal fat (NF) and a high fat and cholesterol (HFC) diet. (b) The percent Sudanophilia was significantly greater in HFC than NF pigs (*P < 0.001). (c) Representative photographs of sections of abdominal aorta stained with Verhoeff's technique for elastin in pigs fed NF and HFC diet. (d) The aortic intima-media thickness (IMT) was significantly greater in HFC than NF pigs (†P < 0.001).

Figure 2

(a) Representative photographs of common carotid artery stained with Sudan IV in pigs fed a normal fat (NF) and a high fat and cholesterol (HFC) diet. (b) The percent Sudanophilia was significantly greater in HFC than NF pigs (*P = 0.006). (c) Representative photographs of sections of common carotid artery stained with Verhoeff's technique for elastin in pigs fed NF and HFC diet. (d) The carotid intima-media thickness (IMT) was significantly greater in HFC than NF pigs (†P < 0.001).

Figure 3

(a) Representative photographs of femoral artery stained with Verhoeff's technique for elastin in pigs normal fat (NF) and a high fat and cholesterol (HFC) diet. (b) The femoral intima-media thickness (IMT) was significantly greater in HFC than NF pigs (*P < 0.05).

Figure 4

(a) Representative photographs of left anterior descending (LAD) branch of the coronary artery stained with Verhoeff's technique for elastin in pigs normal fat (NF) and a high fat and cholesterol (HFC) diet. (b) The LAD intima-media thickness (IMT) was not different in HFC and NF pigs (P = 0.145).

Figure 5

(a) Representative photographs of brachial artery stained with Verhoeff's technique for elastin in pigs normal fat (NF) and a high fat and cholesterol (HFC) diet. (b) The brachial intima-media thickness (IMT) was not different in HFC and NF pigs (P = 0.86).

Figure 6

Dose-dependent bradykinin (BK)-induced relaxation of carotid artery. Values are means ± SE. Normal fat (NF) (n = 8 pigs); high fat/cholesterol (HFC) (n = 6). Percent relaxation was calculated as percent reduction in force from PGF2-α (30 M)-induced tension. (a) BK-induced relaxation was impaired in HFC at intermediate and high doses of BK (P < 0.05). (b) Effects of N^G-nitro-l-arginine methyl ester (l-NAME) on relaxation. (c) Effects of indomethacin (INDO) on relaxation. (d), Effects of l-NAME plus INDO on relaxation. Mixed-factor anova indicated that l-NAME significantly inhibited BK-induced relaxation.

Figure 7

Dose-dependent acetylcholine (ACH)-induced relaxation of carotid artery. Values are means ± SE. Normal fat (NF) (n = 8 pigs); high fat/cholesterol (HFC) (n = 6). Percent relaxation was calculated as percent reduction in force from PGF2-α (30 M)-induced tension. ACH-induced relaxation was impaired in HFC at intermediate and high doses of ACH (P < 0.05). (a) ACH-induced relaxation was impaired in HFC at intermediate and high doses of BK (P = 0.0001). (b) Effects of N^G-nitro-l-arginine methyl ester (l-NAME) on relaxation. (c) Effects of indomethacin (INDO) on relaxation. (d) Effects of l-NAME plus INDO on relaxation. Mixed-factor anova indicated that l-NAME significantly inhibited ACH-induced relaxation.

Figure 8

Dose-dependent, bradykinin (BK)-induced relaxation of left anterior descending coronary arteries. Values are means ± SE. Normal fat (NF) (n = 12 pigs); high fat/cholesterol (HFC) (n = 11). Percent relaxation was calculated as percent reduction in force from PGF2-α (30 M)-induced tension. (a) BK-induced relaxation was impaired in HFC at intermediate and high doses of BK (P < 0.05). (b) Effects of N^G-nitro-l-arginine methyl ester (l-NAME) on relaxation. (c) Effects of indomethacin (INDO) on relaxation. (d) Effects of l-NAME plus INDO on relaxation. Mixed-factor anova indicated that l-NAME significantly inhibited BK-induced relaxation.

Figure 9

Dose-dependent acetylcholine (ACH) and bradykinin (BK)-induced relaxation of brachial and femoral artery. (a) BK elicited a similar dose-dependent relaxation of brachial arteries from both high fat/cholesterol (HFC) (n = 12) and normal fat (NF) (n = 11) diet groups. (b) BK elicited a similar dose-dependent relaxation of femoral arteries from both HFC (n = 6) and NF (n = 7) diet groups. (c) ACH elicited a similar dose-dependent relaxation of brachial arteries from both HFC (n = 11) and NF (n = 12) diet groups. (d) ACH elicited a similar dose-dependent relaxation of femoral arteries from both HFC (n = 6) and NF (n = 7) diet groups.

Figure 10

Dose-dependent sodium nitroprusside (SNP)-induced relaxation of carotid artery high fat/cholesterol (HFC) (n = 7) and normal fat (NF) (n = 8) diet groups (a). Coronary artery (left anterior descending) HFC (n = 12) and NF (n = 11) diet groups (b). Brachial artery HFC (n = 12) and NF (n = 11) diet groups (c). Femoral artery femoral arteries from both HFC (n = 6) and NF (n = 7) diet groups (d). There were no between group differences in the responses of any artery.