The dual PPARalpha/gamma agonist tesaglitazar blocks progression of pre-existing atherosclerosis in APOE*3Leiden.CETP transgenic mice.

BACKGROUND AND PURPOSE: We have evaluated the effects of a peroxisome proliferator-activated receptor (PPAR)alpha/gamma agonist on the progression of pre-existing atherosclerotic lesions in APOE*3Leiden.cholesteryl ester transfer protein (E3L.CETP) transgenic mice. EXPERIMENTAL APPROACH: E3L.CETP mice were fed a high-cholesterol diet for 11 weeks to induce atherosclerosis, followed by a low-cholesterol diet for 4 weeks to obtain a lower plasma total cholesterol level of approximately 10 mmol.L(-1). Mice were divided into three groups, which were either killed before (baseline) or after an 8 week treatment period with low-cholesterol diet without (control) or with the PPARalpha/gamma agonist tesaglitazar (10 microg.kg(-1).day(-1)). Atherosclerosis was assessed in the aortic root. KEY RESULTS: Treatment with tesaglitazar significantly reduced plasma triglycerides, total cholesterol, CETP mass and CETP activity, and increased high-density lipoprotein-cholesterol. At baseline, substantial atherosclerosis had developed. During the 8 week low-cholesterol diet, atherosclerosis progressed in the control group with respect to lesion area and severity, whereas tesaglitazar inhibited lesion progression during this period. Tesaglitazar reduced vessel wall inflammation, as reflected by decreased monocyte adhesion and macrophage area, and modified lesions to a more stabilized phenotype, with increased smooth muscle cell content in the cap and collagen content. CONCLUSIONS AND IMPLICATIONS: Dual PPARalpha/gamma agonism with tesaglitazar markedly improved the atherogenic triad by reducing triglycerides and very low-density lipoprotein-cholesterol and increasing high-density lipoprotein-cholesterol and additionally reduced cholesterol-induced vessel wall activation. These actions resulted in complete inhibition of progression and stabilization of pre-existing atherosclerotic lesions in E3L.CETP mice.

Echocardiographic aortic valve area formula for the estimation of obstruction in stenosis.

We have investigated the use of M-mode echocardiography for the quantification of aortic valve stenosis through the application of a hydraulic orifice equation using only noninvasively determined hemodynamic variables. The new equation is A = (2/5)SV/(t3/2 dP1/4HR), where A is the effective aortic valve area in cm2, SV is the stroke volume in ml, t is the systolic ejection period in seconds, dP is the echographically estimated aortic valve gradient and HR is the heart rate. The predicted valve areas correspond with those derived by conventional cardiac catheterization studies at a level of r = 0.84, SE = 0.14 cm2, N = 10. The results suggest that M-mode echocardiography may have application to the quantitative diagnosis of aortic stenosis.

Some properties of Ca-binding microsomal subfractions isolated from rabbit colon muscle.

From a homogenate of rabbit colon smooth muscle a microsomal fraction was isolated, which was divided into subfractions by centrifugation on a discontinuous sucrose gradient. The Ca-binding properties of the subfractions were investigated under different conditions. In the presence of 0.35 mM ATP the Ca binding of the fractions amounted to 4--8 nmol/mg protein. The 35% fraction bound more Ca per mg protein than the 35--45% fraction. The Ca accumulation was comparatively higher both in the presence of 5 mM ATP and in the presence of 5 mM oxalate. The two fractions showed about the same sensitivity for oxalate. This substance stimulated the Ca uptake at 5 mM but not at lower concentrations. The amount and the rate of Ca binding were more dependent on variations in the exogenous ATP concentration in the 35% fraction than was the case for the 35--45% fraction. The Ca binding was completely inhibited by salyrgan when the microsomal fractions were pretreated with this agent. Sodium azide did not influence the Ca-binding capacity of the fractions. It is suggested that the microsomal subfractions of the rabbit colon muscle represent physiologically important parts of the Ca sequestering system of the muscle, since Ca binding takes place at Ca- and ATP-concentrations which are believed to be present in the myoplasm.

Biochemical and morphological characterization of subcellular fractions isolated from rabbit colon muscle.

From a homogenate of rabbit colon muscle subcellular fractions were isolated by differential centrifugation. The crude microsomal fraction could be separated into subfractions, a fraction of vesicular microsomes at 35% sucrose, a fraction containing sarcolemma, mitochondrial fragments and microsomal vesicles at 35--45% sucrose and a small protein fraction at 45--55% sucrose. Their biochemical properties and their morphological characterization were investigated. The cholesterol and the phospholipid content was equally distributed between the microsomal fractions 35% and 35--45% while the RNA was localized to the mitochondria and the microsomal fraction 35%. The enzyme cytochrome c oxidase was found to be concentrated in the mitochondria while a high contamination was found in the microsomal fractions 35--45%. The NADH-oxidase activity was highest in the 35% fraction and the 5'-nucleotidase activity in the 40,000 X g supernatant. The microsomal subfractions contained the enzymes ATPase, adenylate cyclase and phosphodiesterase. In the 35% fraction Ca stimulated the hydrolysis of ATP. The binding of [3H]-ouabain and the incorporation of [3H]-leucine was most pronounced in the 35% fraction. In a K+-free Krebs Ringer medium the binding of the glucoside was stimulated in all the fractions. From these results we concluded that the fraction 35% sucrose may be mainly derived from the endoplasmic reticulum and the plasma membrane while the 35--45% originates from the plasma membrane, mitochondria and to a lesser extent the endoplasmic reticulum.

Cyclic AMP and Ca-binding in microsomal fractions isolated from rabbit colon smooth muscle.

From a homogenate of rabbit colon muscle two ATP dependent Ca-accumulating microsomal fractions were isolated by differential centrifugation on a sucrose density grandient at 35% and 35-45% sucrose. Adenylate cyclase and phosphodiesterase activities were found in the fractions. The Ca-accumulation and the ATPase activity of these fractions were stimulated by cyclic AMP (10(-5)M) at an ATP concentration of 0.35 mM ATP. In the presence of higher concentrations of ATP (5 mM) cyclic AMP had no effect on the Ca-binding. The higher concentration of ATP markedly increased the cyclic AMP formation in relation to the activity found at the lower concentration of ATP. Isoprenaline (2 X 10(-6)M) stimulated the Ca-accumulation in the 35-45% fraction and increased the hydrolysis of ATP. These effects were absent in the fraction isolated at 35% sucrose. In the former fraction isoprenaline also stimulated the adenylate cyclase activity at 0.35 mM but not at 5 mM ATP. Both the effect of isoprenaline on the Ca-binding and the adenylate cyclase activity were inhibited by the adrenergic beta-receptor blocking agent sotalol. In the 35-45% fraction papaverine (1 X 10(-3)M) stimulated the Ca-accumulation and inhibited the phosphodiesterase activity. It is suggested that cyclic AMP and agents which influence the cyclic AMP metabolism in the microsomes may have a regulatory role on the Ca-binding of the microsomes.