Absence of peroxisome proliferator-activated receptor-alpha abolishes hypertension and attenuates atherosclerosis in the Tsukuba hypertensive mouse

Peroxisome proliferator-activated receptor-alpha is widely distributed in the vasculature where it is believed to exert pleiotropic antiatherogenic effects. Its role in the regulation of blood pressure is still unresolved; however, some evidence suggests that it may affect the renin-angiotensin system. We investigated its role in angiotensin II-induced hypertension in the Tsukuba hypertensive mouse (THM). This is a model of hypertension and atherosclerosis because of high angiotensin II and aldosterone levels as a result of the transgenic expression of the entire human renin-angiotensin system. Making the THM animals deficient in Peroxisome proliferator-activated receptor-alpha (THM/PPARKO) totally abolished hypertension and myocardial hypertrophy. This was accompanied by a reduction in plasma human active renin in THM/PPARKO mice compared with THM animals from 3525+/-128 mU/L to 1910+/-750 mU/L (P<0.05) and by a normalization of serum aldosterone (1.6+/-0.29 nmol/L versus 3.4+/-0.69 nmol/L; P=0.003). In the THM/PPARKO mice, the extent of atherosclerosis at the aortic sinus after a 12-week period on an atherogenic diet was decreased by >80%. In addition, the spontaneous formation of foam cells from peritoneal macrophages, a blood pressure-independent event, was reduced by 92% in the THM/PPARKO mice, suggesting protection from the usual oxidative stress in these animals, possibly because of lower prevailing angiotensin II levels. Finally, chronic fenofibrate treatment further elevated blood pressure in THM animals but not in THM/PPARKO animals. Taken together, these data indicate that peroxisome proliferator-activated receptor-alpha may regulate the renin-angiotensin system. They raise the possibility that its activation may aggravate hypertension and hasten atherosclerosis in the context of an activated renin-angiotensin system.     

MRI of the Budd-Chiari syndrome

Five of six patients with angiographically proved Budd-Chiari syndrome (hepatic venous outflow obstruction) showed multiple specific MRI abnormalities: striking reduction in caliber or complete absence of the hepatic veins, "comma-shaped" intrahepatic collateral vessels, and/or marked constriction of the intrahepatic inferior vena cava. The sixth patient had angiographically proven sinusoidal hepatic venous obstruction and patent central hepatic veins; MRI showed ascites but revealed no specific features of the Budd-Chiari syndrome. Patients with end-stage cirrhosis also showed compressed, distorted hepatic veins; however, these cirrhotic livers were distinguished by their small size, nodular surface, and extrahepatic collateral varices. In patients without cirrhosis or the Budd-Chiari syndrome, normal hepatic, portal, and inferior caval veins were routinely seen when technically adequate MRI examinations were obtained (94 of 100 cases). Four of the six patients with Budd-Chiari syndrome had been treated surgically. In three, MRI identified patent portocaval shunts. In the fourth, angiographically confirmed shunt stenosis was demonstrated by MRI.