Selective CETP inhibition and PPARalpha agonism increase HDL cholesterol and reduce LDL cholesterol in human ApoB100/human CETP transgenic mice.

Cholesteryl ester transfer protein (CETP) plays a key role in high-density lipoprotein (HDL) cholesterol metabolism, but normal mice are deficient in CETP. In this study, transgenic mice expressing both human apolipoprotein B 100 (ApoB-100) and human CETP (hApoB100/hCETP) were used to characterize the effects of CETP inhibition and peroxisome proliferator-activated receptor alpha (PPARalpha) agonism on lipid profiles. Torcetrapib (3, 10, and 30 mg/kg), a CETP inhibitor, fenofibrate (30 mg/kg), a weak PPARalpha agonist, and GW590735 (3 and 10 mg/kg), a potent and selective PPARalpha agonist were given orally for 14 days to hApoB100/hCETP mice and lipid profiles were assessed. The average percentages of HDL, low-density lipoprotein (LDL), and very-low-density lipoprotein (VLDL) cholesterol fractions in hApoB100/hCETP mice were 34.8%, 61.6%, and 3.6%, respectively, which is similar to those of normolipidemic humans. Both torcetrapib and fenofibrate significantly increased HDL cholesterol and reduced LDL cholesterol, and there was a tendency for torcetrapib to reduce VLDL cholesterol and triglycerides. GW590735 significantly increased HDL cholesterol, decreased LDL and VLDL cholesterol, and significantly reduced triglycerides. Maximal increases in HDL cholesterol were 37%, 53%, and 84% with fenofibrate, torcetrapib, and GW590735, respectively. These results, in mice that exhibit a more human-like lipid profile, demonstrate an improved lipid profile with torcetrapib, fenofibrate, and GW590735, and support the use of selective PPARalpha agonism for the treatment of lipid disorders. In addition, these data demonstrate the use of hApoB100/hCETP transgenic mice to identify, characterize, and screen compounds that increase HDL cholesterol.

SB 234551 selective ET(A) receptor antagonism: perfusion/diffusion MRI used to define treatable stroke model, time to treatment and mechanism of protection.

Mismatches between tissue perfusion-weighted imaging (PWI; an index of blood flow deficit) and cellular diffusion-weighted imaging (DWI; an index of tissue injury) provide information on potentially salvageable penumbra tissue in focal stroke and can identify "treatable" stroke patients. The present pre-clinical studies were conducted to: a.) Determine PWI (using perfusion delay) and DWI measurements in two experimental stroke models, b.) Utilize these measurements to characterize selective ET(A) receptor antagonism (i.e., determine efficacy, time-to-treatment and susceptibility to treatment in the different stroke models), and c.) Determine if increasing the reduced blood flow following a stroke is a mechanism of protection. Permanent middle cerebral artery occlusion (MCAO) or sham surgeries were produced in Sprague Dawley rats (SD; proximal MCAO; hypothesized to be a model of slowly evolving brain injury with a significant penumbra) and in spontaneously hypertensive rats (SHR; distal MCAO; hypothesized to be a model of rapidly evolving brain injury with little penumbra). Infusions of vehicle or SB 234551 (3, 10, or 30 microg/kg/min) were initiated at 0, 75, and/or 180 min post-surgery and maintained for the remainder of 24 h post-surgery. Hyper-intense areas of perfusion delay (PWI) in the forebrain were measured using Gadolinium (Gd) bolus contrast. DWI hyper-intense areas were also measured, and the degree of forebrain DWI-PWI mismatch was determined. Region specific analyses (ROI) were also conducted in the core ischemic and low perfusion/penumbra areas to provide indices of perfusion and changes in the degree of tissue perfusion due to SB 234551 treatment. At 24 h post-surgery, final infarct volume was measured by DWI and by staining forebrain slices. Following SD proximal MCAO, there was a significant mismatch in the ischemic forebrain PWI compared to DWI (PWI>DWI) at 60 min which was maintained up to 150 min (all p<0.05). By 24 h post-stroke, infarct volume was identical to the area of early perfusion deficit/PWI, suggesting a slow progression of infarct development that expanded into the significant, earlier cortical penumbra (i.e., model with salvageable tissue with potential for intervention). When SB 234551 was administered within the period of peak mismatch (i.e., at 75 min post-stroke), SB 234551 provided significant dose-related reductions in cortical (penumbral) progression to infarction (p<0.05). Cortical protection was related to an increased/normalization of the stroke-induced decrease in tissue perfusion in cortical penumbra areas (p<0.05). No SB 234551-induced changes in reduced tissue perfusion were observed in the striatum core ischemic area. Also, when SB-234551 was administered beyond the time of mismatch, no effect on cortical penumbra progression to infarct was observed. In comparison and strikingly different, following SHR distal MCAO there was no mismatch between PWI and DWI (PWI=DWI) as early as 60 min post-stroke, with this early change in SHR DWI being identical to the final infarct volume at 24 h, suggesting a rapidly occurring brain injury with little cortical penumbra (i.e., model with little salvageable tissue or potential for intervention). In distal MCAO, SB 234551 administered immediately at the time of stroke did not have any effect on infarct volume in SHR. These data demonstrate that selective blockade of ET(A) receptors is protective following proximal MCAO in SD (i.e. a model similar to "treatable" clinical patients). The protective mechanism appears to be due to enhanced collateral blood flow and salvage of penumbra. Therefore, the use of PWI-DWI mismatch signatures can identify treatable stroke models characterized by a salvageable penumbra and can define appropriate time to treatment protocols. In addition, tissue perfusion information obtained under these conditions might clarify mechanism of protection in the evaluation of protective compounds for focal stroke.

Comparison of mitochondrial and macrophage content between subcutaneous and visceral fat in db/db mice.

Central (visceral) obesity is more closely associated with insulin resistance, type 2 diabetes, and cardiovascular disease than peripheral (subcutaneous) obesity, however the underlying differences in morphology and pathophysiology between subcutaneous and visceral adipose are largely unknown. To evaluate the effects of diabetes and rosiglitazone (RSG) treatment, the expression of mitochondrial Hsp60, UCP-1 and F4/80 in inguinal subcutaneous (SC) fat, composed of white and brown adipose tissues, and epididymal (EP) fat, mainly white adipose tissue, were evaluated. In diabetic db/db mice, there was significant increased number of aggregated macrophage foci compared to db/+ mice, especially in EP fat. On the other hand, the expression of mitochondrial Hsp60 protein was suppressed in both SC and EP fat of db/db mice compared to db/+ mice, and the expression level of mitochondrial Hsp60 in db/+ mice was lower in EP fat compared with SC. In db/db mice, RSG suppressed the number of aggregated macrophage foci in EP fat, but not in SC fat. RSG ameliorated the mitochondrial Hsp60 expression and induced the expression of UCP-1 in both SC and EP fat. Taken together, these data suggest that differences exist in mitochondrial and macrophage content, and in the response to RSG between visceral and subcutaneous adipose tissue, and adipose type and distribution may be important for obesity-linked insulin resistance.