Atherosclerosis is enhanced by testosterone deficiency and attenuated by CETP expression in transgenic mice

The sex-specific metabolic signature of C57BL/6NRj mice during aging

Due to intact reactive oxygen species homeostasis and glucose metabolism, C57BL/6NRj mice are especially suitable to study cellular alterations in metabolism. We applied Nuclear Magnetic resonance spectroscopy to analyze five different tissues of this mouse strain during aging and included female and male mice aged 3, 6, 12, and 24 months. Metabolite signatures allowed separation between the age groups in all tissues, and we identified the most prominently changing metabolites in female and male tissues. A refined analysis of individual metabolite levels during aging revealed an early onset of age-related changes at 6 months, sex-specific differences in the liver, and a biphasic pattern for various metabolites in the brain, heart, liver, and lung. In contrast, a linear decrease of amino acids was apparent in muscle tissues. Based on these results, we assume that age-related metabolic alterations happen at a comparably early aging state and are potentially associated with a metabolic switch. Moreover, identified differences between female and male tissues stress the importance of distinguishing between sexes when studying age-related changes and developing new treatment approaches. Besides, metabolomic features seem to be highly dependent on the genetic background of mouse strains.

Cholesteryl Ester Transfer Protein and Lipid Metabolism and Cardiovascular Diseases

In this chapter, we present the major advances in CETP research since the detection, isolation, and characterization of its activity in the plasma of humans and several species. Since CETP is a major modulator of HDL plasma levels, the clinical importance of CETP activity was recognized very early. We describe the participation of CETP in reverse cholesterol transport, conflicting results in animal and human genetic studies, possible new functions of CETP, and the results of the main clinical trials on CETP inhibition. Despite major setbacks in clinical trials, the hypothesis that CETP inhibitors are anti-atherogenic in humans is still being tested.

CETP Inhibition Improves HDL Function but Leads to Fatty Liver and Insulin Resistance in CETP-Expressing Transgenic Mice on a High-Fat Diet

In clinical trials, inhibition of cholesteryl ester transfer protein (CETP) raises HDL cholesterol levels but does not robustly improve cardiovascular outcomes. Approximately two-thirds of trial participants are obese. Lower plasma CETP activity is associated with increased cardiovascular risk in human studies, and protective aspects of CETP have been observed in mice fed a high-fat diet (HFD) with regard to metabolic outcomes. To define whether CETP inhibition has different effects depending on the presence of obesity, we performed short-term anacetrapib treatment in chow- and HFD-fed CETP transgenic mice. Anacetrapib raised HDL cholesterol and improved aspects of HDL functionality, including reverse cholesterol transport, and HDL's antioxidative capacity in HFD-fed mice was better than in chow-fed mice. Anacetrapib worsened the anti-inflammatory capacity of HDL in HFD-fed mice. The HDL proteome was markedly different with anacetrapib treatment in HFD- versus chow-fed mice. Despite benefits on HDL, anacetrapib led to liver triglyceride accumulation and insulin resistance in HFD-fed mice. Overall, our results support a physiologic importance of CETP in protecting from fatty liver and demonstrate context selectivity of CETP inhibition that might be important in obese subjects.

Sex Hormones and Sex Chromosomes Cause Sex Differences in the Development of Cardiovascular Diseases

This review summarizes recent evidence concerning hormonal and sex chromosome effects in obesity, atherosclerosis, aneurysms, ischemia/reperfusion injury, and hypertension. Cardiovascular diseases occur and progress differently in the 2 sexes, because biological factors differing between the sexes have sex-specific protective and harmful effects. By comparing the 2 sexes directly, and breaking down sex into its component parts, one can discover sex-biasing protective mechanisms that might be targeted in the clinic. Gonadal hormones, especially estrogens and androgens, have long been found to account for some sex differences in cardiovascular diseases, and molecular mechanisms mediating these effects have recently been elucidated. More recently, the inherent sexual inequalities in effects of sex chromosome genes have also been implicated as contributors in animal models of cardiovascular diseases, especially a deleterious effect of the second X chromosome found in females but not in males. Hormonal and sex chromosome mechanisms interact in the sex-specific control of certain diseases, sometimes by opposing the action of the other.

New Era of Lipid-Lowering Drugs

There are several established lipid-modifying agents, including statins, fibrates, niacin, and ezetimibe, that have been shown in randomized clinical outcome trials to reduce the risk of having an atherosclerotic cardiovascular event. However, in many people, the risk of having an event remains unacceptably high despite treatment with these established agents. This has stimulated the search for new therapies designed to reduce residual cardiovascular risk. New approaches that target atherogenic lipoproteins include: 1) inhibition of proprotein convertase subtilisin/kexin type 9 to increase removal of atherogenic lipoproteins from plasma; 2) inhibition of the synthesis of apolipoprotein (apo) B, the main protein component of atherogenic lipoproteins; 3) inhibition of microsomal triglyceride transfer protein to block the formation of atherogenic lipoproteins; 4) inhibition of adenosine triphosphate citrate lyase to inhibit the synthesis of cholesterol; 5) inhibition of the synthesis of lipoprotein(a), a factor known to cause atherosclerosis; 6) inhibition of apoC-III to reduce triglyceride-rich lipoproteins and to enhance high-density lipoprotein (HDL) functionality; and 7) inhibition of cholesteryl ester transfer protein, which not only reduces the concentration of atherogenic lipoproteins but also increases the level and function of the potentially antiatherogenic HDL fraction. Other new therapies that specifically target HDLs include infusions of reconstituted HDLs, HDL delipidation, and infusions of apoA-I mimetic peptides that mimic some of the functions of HDLs. This review describes the scientific basis and rationale for developing these new therapies and provides a brief summary of established therapies.

The controversy over the use of cholesteryl ester transfer protein inhibitors: is there some light at the end of the tunnel?

BACKGROUND

According to epidemiological studies, there is no clear relationship between the plasma cholesteryl ester transfer protein (CETP) concentration and the development of atherosclerosis in human populations. Although some studies suggest that increased CETP activity relates to undesirable profiles of plasma lipoproteins, promoting an anti-atherogenic plasma lipoprotein profile by drugs that inhibit CETP has not succeeded in preventing atherosclerosis in humans.

MATERIALS AND METHODS

This review describes 28 investigations in human populations dealing with plasma CETP, 11 in mice that express human CETP and seven in animals (six in rabbits and one in mice) in which plasma CETP activity was inhibited by drugs.

RESULTS

Present review shows that models in mice expressing human CETP are not illuminating because they report increase as well reduction of atherosclerosis. However, investigations in rabbits and mice that develop severe hypercholesterolaemia clearly indicate that impairment of the plasma CETP activity elicits protection against the development of atherosclerosis; in all of these experiments are attained substantial reductions of the atherogenic lipoproteins, namely, plasma apoB containing lipoproteins.

CONCLUSION

These models are strong indicators that the benefit in preventing atherosclerosis should be earned in cases of hyperlipidemia by CETP inhibitors.

Assessment of the clinical effects of cholesteryl ester transfer protein inhibition with evacetrapib in patients at high-risk for vascular outcomes: Rationale and design of the ACCELERATE trial

BACKGROUND

Potent pharmacologic inhibition of cholesteryl ester transferase protein by the investigational agent evacetrapib increases high-density lipoprotein cholesterol by 54% to 129%, reduces low-density lipoprotein cholesterol by 14% to 36%, and enhances cellular cholesterol efflux capacity. The ACCELERATE trial examines whether the addition of evacetrapib to standard medical therapy reduces the risk of cardiovascular (CV) morbidity and mortality in patients with high-risk vascular disease.

STUDY DESIGN

ACCELERATE is a phase 3, multicenter, randomized, double-blind, placebo-controlled trial. Patients qualified for enrollment if they have experienced an acute coronary syndrome within the prior 30 to 365 days, cerebrovascular accident, or transient ischemic attack; if they have peripheral vascular disease; or they have diabetes with coronary artery disease. A total of 12,092 patients were randomized to evacetrapib 130 mg or placebo daily in addition to standard medical therapy. The primary efficacy end point is time to first event of CV death, myocardial infarction, stroke, hospitalization for unstable angina, or coronary revascularization. Treatment will continue until 1,670 patients reached the primary end point; at least 700 patients reach the key secondary efficacy end point of CV death, myocardial infarction, and stroke, and the last patient randomized has been followed up for at least 1.5 years.

CONCLUSIONS

ACCELERATE will establish whether the cholesteryl ester transfer protein inhibition by evacetrapib improves CV outcomes in patients with high-risk vascular disease.

Regulation of Hepatic Cholesteryl Ester Transfer Protein Expression and Reverse Cholesterol Transport by Inhibition of DNA Topoisomerase II

Cholesteryl ester transfer protein (CETP) transfers cholesteryl esters from high density lipoprotein to triglyceride-rich lipoproteins. CETP expression can be transcriptionally activated by liver X receptor (LXR). Etoposide and teniposide are DNA topoisomerase II (Topo II) inhibitors. Etoposide has been reported to inhibit atherosclerosis in rabbits with un-fully elucidated mechanisms. In this study we determined if Topo II activity can influence cholesterol metabolism by regulating hepatic CETP expression. Inhibition of Topo II by etoposide, teniposide, or Topo II siRNA increased CETP expression in human hepatic cell line, HepG2 cells, which was associated with increased CETP secretion and mRNA expression. Meanwhile, inhibition of LXR expression by LXR siRNA attenuated induction of CETP expression by etoposide and teniposide. Etoposide and teniposide induced LXRα expression and LXRα/β nuclear translocation while inhibiting expression of receptor interacting protein 140 (RIP140), an LXR co-repressor. In vivo, administration of teniposide moderately reduced serum lipid profiles, induced CETP expression in the liver, and activated reverse cholesterol transport in CETP transgenic mice. Our study demonstrates a novel function of Topo II inhibitors in cholesterol metabolism by activating hepatic CETP expression and reverse cholesterol transport.

Mouse models of disturbed HDL metabolism

High-density lipoprotein (HDL) is considered to be an anti-atherogenic lipoprotein moiety. Generation of genetically modified (total body and tissue-specific knockout) mouse models has significantly contributed to our understanding of HDL function. Here we will review data from knockout mouse studies on the importance of HDL's major alipoprotein apoA-I, the ABC transporters A1 and G1, lecithin:cholesterol acyltransferase, phospholipid transfer protein, and scavenger receptor BI for HDL's metabolism and its protection against atherosclerosis in mice. The initial generation and maturation of HDL particles as well as the selective delivery of its cholesterol to the liver are essential parameters in the life cycle of HDL. Detrimental atherosclerosis effects observed in response to HDL deficiency in mice cannot be solely attributed to the low HDL levels per se, as the low HDL levels are in most models paralleled by changes in non-HDL-cholesterol levels. However, the cholesterol efflux function of HDL is of critical importance to overcome foam cell formation and the development of atherosclerotic lesions in mice. Although HDL is predominantly studied for its atheroprotective action, the mouse data also suggest an essential role for HDL as cholesterol donor for steroidogenic tissues, including the adrenals and ovaries. Furthermore, it appears that a relevant interaction exists between HDL-mediated cellular cholesterol efflux and the susceptibility to inflammation, which (1) provides strong support for the novel concept that inflammation and metabolism are intertwining biological processes and (2) identifies the efflux function of HDL as putative therapeutic target also in other inflammatory diseases than atherosclerosis.

The low density lipoprotein receptor modulates the effects of hypogonadism on diet-induced obesity and related metabolic perturbations

Here, we investigated how LDL receptor deficiency (Ldlr(-/-)) modulates the effects of testosterone on obesity and related metabolic dysfunctions. Though sham-operated Ldlr(-/-) mice fed Western-type diet for 12 weeks became obese and showed disturbed plasma glucose metabolism and plasma cholesterol and TG profiles, castrated mice were resistant to diet-induced obesity and had improved glucose metabolism and reduced plasma TG levels, despite a further deterioration in their plasma cholesterol profile. The effect of hypogonadism on diet-induced weight gain of Ldlr(-/-) mice was independent of ApoE and Lrp1. Indirect calorimetry analysis indicated that hypogonadism in Ldlr(-/-) mice was associated with increased metabolic rate. Indeed, mitochondrial cytochrome c and uncoupling protein 1 expression were elevated, primarily in white adipose tissue, confirming increased mitochondrial metabolic activity due to thermogenesis. Testosterone replacement in castrated Ldlr(-/-) mice for a period of 8 weeks promoted diet-induced obesity, indicating a direct role of testosterone in the observed phenotype. Treatment of sham-operated Ldlr(-/-) mice with the aromatase inhibitor exemestane for 8 weeks showed that the obesity of castrated Ldlr(-/-) mice is independent of estrogens. Overall, our data reveal a novel role of Ldlr as functional modulator of metabolic alterations associated with hypogonadism.

Fibrates and fish oil, but not corn oil, up-regulate the expression of the cholesteryl ester transfer protein (CETP) gene

Cholesteryl ester transfer protein (CETP) is a plasma protein that reduces high density lipoprotein (HDL)-cholesterol (chol) levels and may increase atherosclerosis risk. n-3 and n-6 polyunsaturated fatty acids (PUFAs) are natural ligands, and fibrates are synthetic ligands for peroxisome proliferator activated receptor-alpha (PPARα), a transcription factor that modulates lipid metabolism. In this study, we investigated the effects of PUFA oils and fibrates on CETP expression. Hypertriglyceridemic CETP transgenic mice were treated with gemfibrozil, fenofibrate, bezafibrate or vehicle (control), and normolipidemic CETP transgenic mice were treated with fenofibrate or with fish oil (FO; n-3 PUFA rich), corn oil (CO, n-6 PUFA rich) or saline. Compared with the control treatment, only fenofibrate significantly diminished triglyceridemia (50%), whereas all fibrates decreased the HDL-chol level. Elevation of the CETP liver mRNA levels and plasma activity was observed in the fenofibrate (53%) and gemfibrozil (75%) groups. Compared with saline, FO reduced the plasma levels of nonesterified fatty acid (26%), total chol (15%) and HDL-chol (20%). Neither of the oil treatments affected the plasma triglyceride levels. Compared with saline, FO increased the plasma adiponectin level and reduced plasma leptin levels, whereas CO increased the leptin levels. FO, but not CO, significantly increased the plasma CETP mass (90%) and activity (23%) as well as increased the liver level of CETP mRNA (28%). In conclusion, fibrates and FO, but not CO, up-regulated CETP expression at both the mRNA and protein levels. We propose that these effects are mediated by the activation of PPARα, which acts on a putative PPAR response element in the CETP gene.

Effects of anabolic steroids and high-intensity aerobic exercise on skeletal muscle of transgenic mice

In an attempt to shorten recovery time and improve performance, strength and endurance athletes occasionally turn to the illicit use of anabolic-androgenic steroids (AAS). This study evaluated the effects of AAS treatment on the muscle mass and phenotypic characteristics of transgenic mice subjected to a high-intensity, aerobic training program (5d/wk for 6 weeks). The transgenic mice (CETP^+/-LDLr^-/+) were engineered to exhibit a lipid profile closer to humans. Animals were divided into groups of sedentary (Sed) and/or training (Ex) mice (each treated orally with AAS or gum arabic/vehicle: Sed-C, Sed-M, ex-C, ex-M). The effects of AAS (mesterolone: M) on specific phenotypic adaptations (muscle wet weight, cross-sectional area, and fiber type composition) in three hindlimb muscles (soleus:SOL, tibialis anterior:TA and gastrocnemius:GAS) were assessed. In order to detect subtle changes in fiber type profile, the entire range of fiber types (I, IC, IIAC, IIA, IIAD, IID, IIDB, IIB) was delineated using mATPase histochemistry. Body weight gain occurred throughout the study for all groups. However, the body weight gain was significantly minimized with exercise. This effect was blunted with mesterolone treatment. Both AAS treatment (Sed-M) and high-intensity, aerobic training (ex-C) increased the wet weights of all three muscles and induced differential hypertrophy of pure and hybrid fibers. Combination of AAS and training (ex-M) resulted in enhanced hypertrophy. In the SOL, mesterolone treatment (Sed-M and ex-M) caused dramatic increases in the percentages of fiber types IC, IIAC, IIAD, IID, with concomitant decrease in IIA, but had minimal impact on fiber type percentages in the predominantly fast muscles. Overall, the AAS-induced differential adaptive changes amounted to significant fiber type transformations in the fast-to-slow direction in SOL. AAS treatment had a significant effect on muscle weights and fiber type composition in SOL, TA and GAS which was even maximized in animals subjected to metabolically high-intensity aerobic exercise.

Testosterone deficiency induces markedly decreased serum triglycerides, increased small dense LDL, and hepatic steatosis mediated by dysregulation of lipid assembly and secretion in mice fed a high-fat diet

OBJECTIVE

Although low serum testosterone (T) is associated with metabolic disorders, the mechanism of this association is unclear. The objective of the present study was to investigate the combined effects of T deficiency and a high-fat diet (HFD) on hepatic lipid homeostasis in mice.

MATERIALS/METHODS

Orchiectomized (ORX) mice and sham-operated (SHAM) mice were randomly divided into five groups: SHAM mice fed a standard diet (SD), SHAM mice fed HFD, ORX mice fed SD, ORX mice fed HFD, and ORX mice fed HFD with T supplementation. After 4weeks of treatment, we investigated the synthesis and secretion of lipids in the liver and detailed serum lipoprotein profiles in each group.

RESULTS

ORX mice fed HFD showed increased hepatic steatosis, markedly decreased serum triglyceride (TG) and TG-VLDL content, and increased serum very small-LDL content. Gene expression analysis revealed that ORX mice fed HFD showed significantly decreased expression of microsomal triglyceride transfer protein, lipin-1, peroxisome proliferator-activated receptor (PPAR)-α and PPAR-γ coactivator 1-α, and significantly increased sterol regulatory element-binding protein-1, diacylglycerol acyltransferase-2 and fatty acid synthase. Reduction of hepatic AMPK phosphorylation was observed in ORX mice fed HFD. These perturbations in ORX mice fed HFD were normalized to the levels of SHAM mice fed HFD by T supplementation.

CONCLUSION

T deficiency is associated with failure of lipid homeostasis mediated by altered expression of genes involved in hepatic assembly and secretion of lipids.

Atherosclerosis induced by arsenic in drinking water in rats through altering lipid metabolism

Arsenic in drinking water is a global environmental health problem, and the exposure may increase cardiovascular and cerebrovascular diseases mortalities, most likely through causing atherosclerosis. However, the mechanism of atherosclerosis formation after arsenic exposure is still unclear. To study the mechanism of atherosclerosis formation after arsenic exposure and explore the role of high cholesterol diet (HCD) in this process, we fed spontaneous hypertensive rats and Wistar Kyoto rats with basal diet or HCD and provided with them drinking water containing arsenic at different ages and orders for 20 consecutive weeks. We measured high density lipoprotein cholesterol (HDL-C), low density lipoprotein cholesterol (LDL-C), total cholesterol, triglycerides, heat shock protein 70 (HSP 70), and high sensitive C-reactive protein (hs-CRP) at predetermined intervals and determined expressions of cholesteryl ester transfer protein-1 (CETP-1) and liver X receptor β (LXRβ) in the liver. Atherosclerosis was determined by examining the aorta with hematoxylin and eosin stain. After 20 weeks, we found arsenic, alone or combined with HCD, may promote atherosclerosis formation with transient increases in HSP 70 and hs-CRP. Early combination exposure decreased the HDL-C/LDL-C ratio without changing the levels of total cholesterol and triglyceride until 30 weeks old. Both CETP-1 and LXRβ activities were suppressed, most significantly in early combination exposure. In conclusion, arsenic exposure may induce atherosclerosis through modifying reverse cholesterol transport in cholesterol metabolism and suppressing LXRβ and CEPT-1 expressions. For decreasing atherosclerosis related mortality associated with arsenic, preventing exposure from environmental sources in early life is an important element.

A reduction of CETP activity, not an increase, is associated with modestly impaired postprandial lipemia and increased HDL-cholesterol in adult asymptomatic women

Background

The relationship between CETP and postprandial hyperlipemia is still unclear. We verified the effects of varying activities of plasma CETP on postprandial lipemia and precocious atherosclerosis in asymptomatic adult women.

Methods

Twenty-eight women, selected from a healthy population sample (n = 148) were classified according to three CETP levels, all statistically different: CETP deficiency (CETPd ≤ 4.5%, n = 8), high activity (CETPi ≥ 23.8, n = 6) and controls (CTL, CETP ≥ 4.6% and ≤ 23.7%, n = 14). After a 12 h fast they underwent an oral fat tolerance test (40 g of fat/m² of body surface area) for 8 hours. TG, TG-rich-lipoproteins (TRL), cholesterol and TRL-TG measurements (AUC, AUIC, AR, RR and late peaks) and comparisons were performed on all time points. Lipases and phospholipids transfer protein (PLTP) were determined. Correlation between carotid atherosclerosis (c-IMT) and postprandial parameters was determined. CETP TaqIB and I405V and ApoE-ε3/ε2/ε4 polymorphisms were examined. To elucidate the regulation of increased lipemia in CETPd a multiple linear regression analysis was performed.

Results

In the CETPi and CTL groups, CETP activity was respectively 9 and 5.3 higher compared to the CETPd group. Concentrations of all HDL fractions and ApoA-I were higher in the CETPd group and clearance was delayed, as demonstrated by modified lipemia parameters (AUC, AUIC, RR, AR and late peaks and meal response patterns). LPL or HL deficiencies were not observed. No genetic determinants of CETP deficiency or of postprandial lipemia were found. Correlations with c-IMT in the CETPd group indicated postprandial pro-atherogenic associations. In CETPd the regression multivariate analysis (model A) showed that CETP was largely and negatively predicted by VLDL-C lipemia (R² = 92%) and much less by TG, LDL-C, ApoAI, phospholipids and non-HDL-C. CETP (model B) influenced mainly the increment in ApoB-100 containing lipoproteins (R² = 85% negatively) and phospholipids (R² = 13%), at the 6^thh point.

Conclusion

The moderate CETP deficiency phenotype included a paradoxically high HDL-C and its sub fractions (as earlier described), positive associations with c-IMT, a postprandial VLDL-C increment predicting negatively CETP activity and CETP activity regulating inversely the increment in ApoB100-containing lipoproteins. We hypothesize that the enrichment of TG content in triglyceride-rich ApoB-containing lipoproteins and in TG rich remnants increases lipoproteins' competition to active lipolysis sites,reducing their catabolism and resulting on postprandial lipemia with atherogenic consequences.

Effect of high intensity aerobic exercise and mesterolone on remodeling of Achilles tendon of C57BL/6 transgenic mice

The effect of mesterolone and intensive treadmill training (6 weeks, 5 days/week, means: 15.82 m/min and 45.8 min/day) in Achilles tendon remodeling was evaluated. Sedentary mice treated with mesterolone (Sed-M) or vehicle (Sed-C, placebo/control) and corresponding exercised (Ex-M and Ex-C) were examined. SDS-polyacrylamide gel electrophoresis was used for determining collagen bands and hydroxyproline concentration. Collagen fibril diameter, the area and number of fibrils contained in an area probe, and the ultrastructure of fibroblasts (tenocytes) were determined. The presence of collagen was notable in the tendons of all groups. Collagen alpha(1/)alpha(2) bands in Sed-M, Ex-C, and Ex-M were higher than in Sed-C, as shown by hydroxyproline content, but collagen beta-chain appeared only in Ex-C. Noticeable bands of non-collagenous proteins were found in Sed-M and Ex-M. The number of fibrils in the area probe increased markedly in Sed-M and Ex-C (12-fold), but their diameter and area were unchanged compared with Sed-C. In Ex-M, the fibril number decreased by three-fold to 3.5-fold compared with Sed-M and Ex-C, whereas diameter and area increased. Sed-C tenocytes appeared quiescent, whereas those in the other groups seemed to be engaged in protein synthesis. The density of tenocytes was smaller in Sed-C than in Ex-C, Sed-M, and Ex-M. Thus, mechanical stimuli and mesterolone alter the morphology of tenocytes and the composition of the tendon, probably through fibrillogenesis and/or increased intermolecular cross-links. The ergogenic effect is evidenced by the activation of collagenous and non-collagenous protein synthesis and the increase in the diameter and area of collagen fibrils. This study might be relevant to clinical sports medicine.

Morphological changes in murine skeletal muscle in response to exercise and mesterolone

Light and electron microscopy and quantitative morphometry were used to determine the effects of exercise and mesterolone on the soleus muscles of mice. Both exercise and mesterolone caused a significant hypertrophy of extrafusal muscle fibres. The hypertrophy of Type I fibres was greater than that of Type II fibres. There was no hyperplasia. Mitochondria were more numerous and larger than in the muscles of sedentary animals. Capillarity increased and small centrally nucleated muscle fibres appeared, usually in small clusters and most often in the muscles of animals exposed to mesterolone. A small proportion of satellite cells exhibited signs of activation but there were more in the muscles of mesterolone-treated animals than after exercise. Muscles from animals that had been both exercised and treated with mesterolone exhibited the largest changes: muscle mass and muscle fibre hypertrophy was greater than in all other groups of animals, capillarity was higher and >30% of all recognized satellite cells exhibited signs of activation. Groups of small centrally nucleated muscle fibres were commonly seen in these muscles. They appeared to be the result of splits in the form of sprouts from existing muscle fibres. With both exercise and mesterolone, alone or in combination, there was an increase in the proportion of Type I muscle fibres and a decrease in the proportion of Type II.

Lipid transfer proteins: past, present and perspectives

Lipid transfer proteins (PLTP and CETP) play roles in atherogenesis by modifying the arterial intima cholesterol content via altering the concentration and function of plasma lipoproteins and influencing inflammation. In this regard, endotoxins impair the reverse cholesterol transport (RCT) system in an endotoxemic rodent model, supporting a pro-inflammatory role of HDL reported in chronic diseases where atherosclerosis is premature. High PLTP activity related to atherosclerosis in some clinical studies, but the mechanisms involved could not be ascertained. In experimental animals the relation of elevated plasma PLTP concentration with atherosclerosis was confounded by HDL-C lowering and by unfavorable effects on several inflammatory markers. Coincidently, PLTP also increases in human experimental endotoxemia and in clinical sepsis. Human population investigations seem to favor low CETP as atheroprotective; this is supported by animal models where overexpression of huCETP is atherogenic, most likely due to increased concentration of apoB-lipoprotein-cholesterol. Thus, in spite of CETP facilitating the HDL-C-mediated RCT, the reduction of apoB-LP-cholesterol concentration is the probable antiatherogenic mechanism of CETP inhibition. On the other hand, experimental huCETP expression protects mice from the harmful effects of a bacterial polysaccharide infusion and the mortality rate of severely ill patients correlates with reduction of the plasma CETP concentration. Thus, the roles played by PLTP and CETP on atherosclerosis and acute inflammation seem contradictory. Therefore, the biological roles of PLTP and CETP must be carefully monitored when investigating drugs that inhibit their activity in the prevention of atherosclerosis.

Adverse effect of the anabolic-androgenic steroid mesterolone on cardiac remodelling and lipoprotein profile is attenuated by aerobicz exercise training

Abuse of anabolic-androgenic steroids (AAS) for improving physical performance is associated with serious, sometimes fatal, adverse effects. The aim of the present work was to investigate the effects of AAS on the cardiac structure and the plasma lipoprotein profile isolated and in combination with exercise. Transgenic mice with a human lipaemic phenotype (expressing cholesteryl ester transfer protein on the LDL receptor knockout background) were used in this study. Sedentary and exercised mice (treadmill running, five times per week for 6 weeks) were treated with mesterolone (2 microg/g body weight) or vehicle (control-C) in the last 3 weeks. Four groups were compared: (i) exercise + mesterolone (Ex-M), (ii) exercise + vehicle (Ex-C), (iii) sedentary + mesterolone (Sed-M) and (iv) sedentary + vehicle (Sed-C). Arterial blood pressure and body mass increased in all groups along time, but Sed-M reached the highest values and Ex-C the lowest. Treatment with mesterolone increased total cholesterol, triglyceride, low-density lipoprotein cholesterol (LDL-c) and very LDL-c (VLDL-c) plasma levels. However, exercise blunted some of these deleterious effects by increasing high-density lipoprotein cholesterol and decreasing LDL-c, VLDL-c and triglycerides. Exercise training induced beneficial effects, such as physiological cardiomyocyte hypertrophy, increase in myocardial circulation and decrease in cardiac interstitium. However, mesterolone impaired such physiological gains and in addition increased troponin T plasma levels both in sedentary and exercised mice. Thus, while mesterolone induced pro-atherogenic lipoprotein profile and pathogenic cardiac hypertrophy, exercise counteracted these effects and modified favourably both the lipoprotein profile and the cardiac remodelling induced by mesterolone.

Overexpression of apolipoprotein CIII increases and CETP reverses diet-induced obesity in transgenic mice

OBJECTIVE

We recently described that hypertriglyceridemic apolipoprotein (apo) CIII transgenic mice show increased whole body metabolic rate. In this study, we used these apo CIII-expressing mice, combined or not with the expression of the natural promoter-driven CETP gene, to test the hypothesis that both proteins modulate diet-induced obesity.

MEASUREMENTS AND RESULTS

Mice expressing apo CIII, CIII/CETP, CETP and nontransgenic (NonTg) mice were maintained on a high-fat diet (14% fat by weight) during 20 weeks after weaning. At the end of this period, all groups exhibited the expected lipemic phenotype. Fasting glucose levels were neither affected by the high-fat diet nor by the distinct genotypes. However, apo CIII mice showed significantly higher glycemia ( approximately 35%) and lower insulin levels ( approximately 45%) in the fed state, compared with the NonTg mice. The apo CIII mice presented significantly increased body weight, lipid content of the carcass ( approximately 25%), visceral adipose tissue mass (about twofold) and adipocyte size ( approximately 25%) compared with the CETP and NonTg mice. The CETP expression in the apo CIII background normalized the subcutaneous adipose depot and visceral adipocyte size to the levels of NonTg mice. Plasma leptin levels were lower in CETP groups (25-50%) and higher in the apo CIII mice. Similar core body temperature in all groups and similar liver mitochondrial resting respiration rates in CIII and NonTg mice indicate no differences in basal energy expenditure rates among these mice fed a high-fat diet.

CONCLUSION

The elevation of plasma apo CIII levels aggravates diet-induced obesity and the expression of physiological levels of circulating CETP reverses this adipogenic effect, indicating a novel role for CETP in modulating adiposity.

Soy protein containing isoflavones favorably influences macrophage lipoprotein metabolism but not the development of atherosclerosis in CETP transgenic mice

The possibility that soy protein containing isoflavones influences the development of experimental atherosclerosis has been investigated in ovariectomized mice heterozygous for the human CETP transgene and for the LDL-receptor null allele (LDLr(+/-) CETP(+/-)). After ovariectomy at 8 wk of age they were fed a fat/cholesterol-rich diet for 19 wk and divided into three experimental groups: dietary unmodified soy protein containing isoflavones (mg/g of diet), either at low-dose (Iso Low, 0.272, n = 25), or at high-dose (Iso High, 0.535, n = 28); and the atherogenic diet containing an isoflavone-depleted alcohol-washed soy protein as a control group (n = 28). Aortic root lipid-stained lesion area (mean microm2 x 10(3) +/- SD) did not differ among Iso Low (12.3 +/- 9.9), Iso High (7.4 +/- 6.4), and controls (10.7 +/- 12.8). Autoantibody titers against plasma oxidized LDL did not differ among the experimental groups. Using the control mice as the reference value (100%), in vitro mouse peritoneal macrophage uptake of labeled acetylated LDL-cholesterol was lower in the Iso High (68%) than in the Iso Low (85%) group. The in vitro percent removal by exogenous HDL of labeled unesterified cholesterol from macrophages previously enriched with human [4- 14C]-cholesteryl oleate acetylated LDL was enhanced in the Iso High group (50%). In spite of these in vitro potentially antiatherogenic actions, soy protein containing isoflavones did not modify the average size of lipid-stained area in the aortic root.