Anti-hypercholesterolemic effect of melatonin in rats

The effects on plasma lipids of daily intraperitoneal injections of 4 mg of melatonin (N-acetyl-5-methoxytryptamine) for 10-27-day periods were examined biochemically and morphologically in rats fed regular and high-cholesterol (1% cholesterol, 0.5% cholic acid) diets. Melatonin administration had no significant effect on plasma lipids and lipoproteins in the rats on a normal diet but blunted the effects of a high-cholesterol diet on these parameters. No effects of melatonin on lipase activity were noted. Melatonin also diminished the fatty infiltration in the liver of animals on the high-cholesterol diet. The high-cholesterol diet produced major increases in VLDL and LDL cholesterol and protein content, and decreases in HDL cholesterol and protein. Melatonin decreased the extent of this plasma lipoprotein increase, although it did not completely prevent the phenomenon. Therefore, the effect is thought to be quantitative and not qualititative in nature.     

Comparison of hydrophobic surfactant and cholestyramine on lipid and sterol balance in the rat

The effects of dietary supplement with hydrophobic surfactant, Pluronic L-81, on sterol and lipid metabolism in rats consuming a high-fat high-cholesterol diet was determined. Results were compared both to rats on the high-fat high-cholesterol diet alone and to other rats on a similar diet supplemented with cholestyramine. All treatment programs were well tolerated. Pluronic L-81 therapy produced reductions of plasma and hepatic cholesterol levels compared to rats on the diet alone. Additionally, plasma triglycerides were reduced. These changes were associated with relatively high fecal outputs of neutral steroids but acidic steroid excretion was less than observed for rats on diet alone. No malabsorption of neutral lipid was observed for detergent-treated rats. Cholestyramine was also effective in limiting hepatic cholesterol accumulation. Fecal losses of both neutral and acidic steroids were greater in this group compared to rats on diet alone. This was associated with a marked increase of hepatic 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) reductase activity in the cholestyramine-treated group. Both types of treatment limit cholesterol accumulation in rats on a high cholesterol diet. Pluronic L-81 treatment, however, does not significantly increase endogenous cholesterol synthesis while it is greatly increased in response to cholestyramine as reflected by hepatic activities of HMG-CoA reductase.     

Effects of short-term melatonin administration on lipoprotein metabolism in normolipidemic postmenopausal women

OBJECTIVE: To investigate the effects of short-term administration of melatonin on lipoprotein metabolism in normolipidemic postmenopausal women. METHODS: Fifteen such women received 6.0 mg melatonin daily for 2 weeks. Blood was sampled before and after treatment. We measured concentrations of total cholesterol and total triglyceride in the plasma, as well as the levels of cholesterol, triglyceride, and protein in the very low-density lipoprotein (VLDL), low-density lipoprotein (LDL), and high-density lipoprotein (HDL). Plasma apolipoprotein levels were determined by immunoturbidimetric assay. Activities of lipoprotein lipase, hepatic triglyceride lipase, and lecithin cholesterol acyltransferase were also determined by enzymatic analysis. RESULTS: Melatonin administration significantly increased the plasma levels of triglyceride by 27.2% (P < 0.05), of VLDL-cholesterol by 37.2% (P < 0.01), of VLDL-triglyceride by 62.2% (P < 0.001), and of VLDL-protein by 30.0% (P < 0.05). However, the plasma total cholesterol level and the concentration of lipid and protein in LDL and HDL were not significantly affected. Melatonin significantly increased the plasma levels of apolipoprotein C-II by 29.5% (P < 0.005), of C-III by 17.1% (P < 0.001), and of E by 7.6% (P < 0.05). The plasma levels of apolipoprotein A-I, A-II, and B were not altered. Melatonin significantly inhibited the activity of lipoprotein lipase by -14.1% (P < 0.05), but did not significantly affect the activities of hepatic triglyceride lipase or of lecithin cholesterol acyltransferase. CONCLUSIONS: Findings indicate that melatonin increases the plasma level of VLDL particles by inhibiting the activity of lipoprotein lipase, but may not affect the plasma levels of LDL and HDL particles in postmenopausal women with normolipidemia.     

内源性睾酮在雄性高脂血症大鼠早期动脉粥样硬化形成中的作用

目的：研究内源性睾酮对雄性高脂血症大鼠早期动脉粥样硬化形成的影响及其作用机制。方法：雄性Ｗｉｓｔａｒ大鼠随机均分为正常对照组,高脂对照组,高脂去势组（切除双侧睾丸及副睾）。实验时间１２周。结果：高脂去势组与高脂对照组相比,血浆总胆固醇（ＴＣ）,甘油三酯（ＴＧ）浓度相差不明显,低密度脂蛋白（ＨＤＬ）水平较高,低密度脂蛋白（ＬＤＬ）＋极低密度脂蛋白（ＶＬＤＬ）水平较低,血浆脂质过氧化物（ＬＰＯ）水平较     

Effect of melatonin on total food intake and macronutrient choice in rats

Melatonin, a hormone secreted in a rhythmic manner over 24 h mainly by the pineal gland, is used to alleviate the symptoms of jetlag and treat sleeping problems. The objective of the present study was to examine the effects of a 7-h phase-shift from the natural peak of melatonin secretion on total food intake and macronutrient selection. Forty-eight adult Wistar rats of both sexes were divided in three dietary groups, each group offered a simultaneous and different choice of a carbohydrate- and a protein-rich diet. Macronutrient intakes following intraperitoneal administration of four doses of melatonin (3000, 6000, 10 000 and 15 000 pg/ml blood) at dark onset were examined. Melatonin increased short- (4 h postinjection) and long-term (12 h postinjection) nocturnal total food intake in both male and female rats, mainly with the two highest doses. This effect of melatonin was mainly due to a short-term increase of intake across all carbohydrate-rich diet preparations (dextrin/cornstarch, cornstarch, and sucrose/cornstarch) and across genders. This consistent effect of melatonin on the intake of carbohydrate-rich diets with contrasting sensory attributes rules out the possibility that melatonin acts on sensorymotor pathways, thus suggesting that melatonin's effect on food intake is controlled by the carbohydrate content of the diet. In contrast, melatonin could be affecting some sensory or motor processes peculiar to the ingestion of protein since it increased protein-rich diet intake inconsistently across the various preparations (casein, soy isolate, and egg protein) as well as genders. This evidence supports the view that melatonin acts as a time indicator, reinforcing the animals with a “night cue”, and favors predominant carbohydrate intake normally occurring at the beginning of the activity period.     

The Expression of Inflammatory Cytokines on the Aorta Endothelia Are Up-regulated in Pinealectomized Rats

This study was designed to investigate the effect of melatonin on the expression of aortic inflammatory cytokines and its underlying mechanisms in rats. Melatonin deficiency rats (Px, N?=?16) were created by pinealectomy and were fed with normal diet for 16 weeks after the surgery, and compared with sham-operated rats (Con, N?=?14). Serum lipid profile, glucose metabolism parameters, serum oxidative stress and inflammatory biomarkers were evaluated. The expression of inflammatory cytokines in the aorta endothelia was analyzed. To evaluate the signal transduction pathways of melatonin on the expression of cytokines, rat aortic endothelial cell lines (RAECs) were treated with melatonin, and their protein expressions of inflammatory cytokines and phosphorylation levels of relevant signal pathways were detected. At the 16th week after surgery in Px rats, their serum triglyceride, very low density lipoprotein cholesterol, free fatty acid and glucose levels were prominently elevated (all P?<?0.05); serum oxidative stress biomarker malondialdehyde, serum inflammatory biomarkers oxidized low-density lipoprotein, tumor necrosis factor-α, interleukin-6 and C reactive protein were also significantly increased. Meanwhile, the expression of inflammatory cytokines: monocyte chemotactic protein-1 (MCP-1), vascular adhesion molecule 1 (VCAM-1) and matrix metalloproteinase-9 (MMP-9) of the aorta endothelia in Px rats were significantly up-regulated (all P?<?0.05). In vitro, melatonin significantly decreased the expression of MCP-1, VCAM-1 and MMP-9 proteins, along with the suppression of phosphorylation levels of nuclear factor κB (NF-κB)/P65 and p38 mitogen-activated protein kinase (P38-MAPK) in RAECs. Melatonin deficiency elevates the serum inflammatory biomarkers and increases aortic inflammatory responses. Melatonin regulates these inflammatory responses by NF-κB and P38-MAPK involved pathways.     

Effects of a soy protein product on serum and tissue cholesterol concentrations in swine fed high-fat, high-cholesterol diets

Hypocholesterolemic effect of a soy protein product was studied in swine fed a high-fat, high-cholesterol diet. In the first experiment, a group of swine were fed 42% butter (by calories) and 1055 mg cholesterol daily, with casein as the source for protein, for 6 weeks and this diet resulted in moderately high serum cholesterol concentrations (219 ± 33 mg/dl). Another group fed the same diet except with soy protein product as the protein source instead of casein showed virtual normocholesterolemia at the end (107 ± 3 mg/dl). Cholesterol balance was studied under non-steady state conditions using methods designed for this purpose. Reflecting the serum cholesterol concentration, the total body cholesterol concentration (excluding CNS) was also significantly lower in soy protein group. However, parameters of cholesterol balance, such as fecal neutral and acidic steroid excretions, dietary cholesterol absorption, and whole body cholesterol synthesis were studied and no differences were demonstrated between the casein- and soy protein-fed swine. The experiment was repeated and in Experiment II virtually the same results were obtained. When swine were given the same high-fat, high-cholesterol diets with $\text{1}\text{2}$ casein + $\text{1}\text{2}$ soy protein or casein + soy protein, hypocholesterolemic effects were also observed. Therefore, such action is probably caused principally by soy protein per se rather than simply by replacement of casein by soy protein. Addition of dl-methionine to soy protein containing diet did not alter the hypocholesterolemic effect of soy protein indicating that the effect was not the result of methionine deficiency. In conclusion, we can state that the hypocholesterolemic action of soy protein was clearly demonstrated in swine fed a high-fat, high-cholesterol diet, but that the mechanism of action is yet to be established.     

刺激单核巨噬细胞对肝实质及非实质细胞脂蛋白代谢的影响

本研究结果表明酵母多糖对喂正常饲料大鼠肝非实质细胞及实质细胞的^125I-HDL及^125I-LDL代谢影响不大，但可明显增加喂高脂饲料大鼠细胞对^125I-HDL及^125I-LDL的结合、内移及降解，增加胆汁中总胆酸及胆固醇的排泄，明显降低高脂饲料导致的高胆固醇血症。     

附子多糖预防高胆固醇血症的作用及其对肝脏CYP7α-1表达的影响

目的: 探讨附子多糖(FPS)预防高胆固醇血症的作用及其对肝脏胆固醇7α-羟化酶(CYP7α-1)表达的影响。方法: SPF级雄性Wistar大鼠50只,体重100 g,随机分为正常组(control)、高胆固醇组(HC)和HC+附子多糖(HC+FPS)低、中、高3个剂量组,每组10只,分别给予正常、高胆固醇及高胆固醇加附子多糖(224、448和896mg·kg^-1·d^-1 )饮食,持续2周,检测各组的血脂水平;观察control组、HC组和HC+FPS(224 mg·kg^-1·d^-1)组大鼠的体重、进食量和粪便量的变化,实验结束后取3组大鼠的肝脏行HE染色;并检测3组大鼠肝脏羟甲基戊二酰辅酶A(HMG-CoA)还原酶mRNA水平、CYP7α-1 mRNA和蛋白水平以及粪便总胆汁酸含量等方面的改变。结果: 附子多糖能显著抑制高胆固醇血症大鼠血清中总胆固醇(TC)和低密度脂蛋白胆固醇(LDL-C)的水平(P<0.05);HC+FPS组大鼠肝细胞脂肪变性较HC组轻微;real-time PCR和Western blotting结果显示附子多糖能显著上调高胆固醇大鼠肝脏CYP7α-1 mRNA水平和蛋白表达并明显降低HMG-CoA还原酶的mRNA水平(P<0.01);HC组大鼠粪便中胆汁酸的含量增多而HC+FPS组进一步增加(P<0.05)。结论: 附子多糖具有明显的降血胆固醇作用,其机制与上调CYP7α-1 mRNA及蛋白水平和下调大鼠肝脏HMG-CoA还原酶mRNA水平有关。     

Effect of sex and exercise on liver and plasma lipids of the rat

The effect of voluntary exercise on plasma and hepatic lipids was studied in 24 week old male and female Long-Evans rats who were fed a high sucrose (73% of calories) diet containing saturated fat and cholesterol for a 10 week period. Blood lipids were analyzed at week 0, 2, 5 and 10 and liver lipids at week 0 and 10. Half of the animals were housed in individual activity wheels where the females voluntarily ran 4.3 miles/day and the males voluntarily ran 2.4 miles/day. Compared to the males, the females 1. exhibited a greater lipogenic response to the diet, 2. showed a greater lowering of plasma and liver triglyceride and plasma cholesterol ester with exercise, and 3. developed with exercise a higher relative heart weight. Exercise was successful in the males in producing a 75% reduction in the level of hepatic cholesterol ester seen in the non-exercising males. The importance of this study is seen in the lipid-lowering effects of voluntary exercise which avoids food and water deprivation and thus the stress concurrent with forced exercise regimes.     

Effects of Kampo Formulas on the Progression of Hypercholesterolemia and Fatty Liver Induced by High-Cholesterol Diet in Rats

Background

Bofutsushosan is a well known Kampo, traditional Japanese medicine, based on ancient Chinese medicine mainly used in the treatment of hypercholesterolemia in Japan. We selected two Kampo formulas, Boiogito and Keishibukuryogan mainly used in the treatment of hypercholesterolemia in China to compare with Bofutsushosan and cholesterol absorption inhibitor ezetimibe.

Methods

Hypercholesterolemia and fatty liver were induced by high cholesterol (containing 2% cholesterol and 0.5% cholic acid) diet in male Wistar rats for 6 and 12 weeks. Kampo formulas Boiogito, Bofutsushosan, Keishibukuryogan and ezetimibe were added to the high-cholesterol diet, respectively. After 6 and 12 weeks, body and liver weights, blood chemistry, cholesterol concentrations, fat-related and inflammatory-related factors were examined.

Results

High-cholesterol diet increased body and liver weights, and serum cholesterol concentrations. Boiogito and ezetimibe improved them. Serum ICAM-1 and RBP4 were increased in the high cholesterol diet group. Boiogito and ezetimibe improved them too. In the histological examinations of liver and adipose tissues, we observed a significant improvement after treatment. Immunostaining expression of ICAM-1 in aorta was improved by Boiogito, Bofutsushosan, Keishibukuryogan and ezetimibe. The mRNA expression of RBP4, HFABP, CFABP, MCP1 and CCR2 in liver and adipose tissue were decreased by Boiogito and ezetimibe.

Conclusion

Boiogito has a protective effect on the progression of hypercholesterolemia and fatty liver induced by high-cholesterol diet in rats and more effective than Bofutsushosan and Keishibukuryogan. The lipid-lowering effect of Boiogito is not stronger than ezetimibe. But the anti-inflammatory (MCP1, CCR2) and anti-arteriosclerotic (ICAM-1) effects of Boiogito are more potent than ezetimibe.     

Effects of pinealectomy and exogenous melatonin on rat hearts

The effects of pinealectomy and administration of melatonin, the major secretory product of the pineal gland, which is a direct free radical scavenger and an indirect antioxidant, were studied in rat hearts on the basis of cardiac morphology and biochemical findings. Three groups of Wistar rats were used: one group was the sham-operated control, one group consisted of pinealectomized rats and one group consisted of pinealectomized rats that were treated with melatonin. Serum cholesterol, tissue levels of malondialdehyde (MDA) and reduced glutathione (GSH), and heart weight were determined. Histochemical staining with the Van Gieson, PAS/Alcian blue at pH 2.5 and Masson's trichrome methods were performed in addition to hematoxylin-eosin staining. Levels of serum cholesterol and tissue MDA, and heart weight were increased in pinealectomized rats whereas GSH levels did not change. Melatonin administration reversed these effects. Microscopically, myocardial fibrosis and myxomatous degeneration of cardiac valves were detected in all pinealectomized rats. It can be concluded that pinealectomy of rats causes morphological changes in rat hearts, and short-term application of melatonin does not reverse these changes.     

Melatonin and estradiol effects on food intake, body weight, and leptin in ovariectomized rats

OBJECTIVE: The study in ovariectomized (Ovx) rats, as a model of menopausal status, of the effects of melatonin (M) and/or estradiol (E), associated or not with food restriction, on body weight (BW) and serum leptin levels. METHODS: Female SD rats (200-250 g) were Ovx and treated with E, M, E+M or its diluents. Control sham-Ovx rats were treated with E-M diluents. After 7 weeks being fed ad libitum, the animals were exposed for 7 more weeks to a 30% food restriction. We measured: food intake, BW, nocturnal and diurnal urinary excretion of sulphatoxymelatonin (aMT6s), leptin in midday and midnight blood samples, glucose, total cholesterol, LDL, HDL and triglycerides. RESULTS: Day/night rhythm of aMT6s excretion was preserved in all cases. The increase of aMT6s excretion in M-treated animals basically affected the nocturnal period. In animals fed ad libitum, E fully prevented Ovx-induced increase of BW, leptin and cholesterol. Melatonin reduced food intake and partially prevented the increase of BW and cholesterol, without changing leptin levels. Under food restriction, M was the most effective treatment in reducing BW and cholesterol. Leptin levels were similar in M, E or E+M treated rats, and lower than in untreated Ovx rats. CONCLUSIONS: Our result gives a preliminary experimental basis for a post-menopausal co-treatment with estradiol and melatonin. It could combine the effectiveness of estradiol (not modified by melatonin) with the positive effects of melatonin (improvement of sleep quality, prevention of breast cancer, etc.). The possible beneficial effects of melatonin which could justify its use, need to be demonstrated in clinical trials.     

Induction of glomerulosclerosis by dietary lipids. A functional and morphologic study in the rat

Clinical and experimental data indicate that glomerular function and morphology may be influenced by plasma lipids. In familial lecithin-cholesterol-acyltransferase (LCAT) deficiency and in Fabry's disease, lipids accumulate in glomeruli and are assumed to induce sclerosis. The present study was undertaken to examine if dietary lipids could exert effects on the glomeruli of normal, unilaterally nephrectomized rats, and of rats with two-kidney, one clip (2-K,1C) hypertension. In rats with two kidneys on a diet rich in fat and cholesterol, cholesterol concentrations in very low density lipoproteins increased. In these rats the number of glomeruli with sclerotic foci was significantly higher than in rats on a low fat, cholesterol free diet. After 6 months on the diet the percentage of glomeruli with sclerosis (SC) was 13.2 +/- 4.1 (N = 9) in rats with a cholesterol diet and 1.8 +/- 0.6 (N = 11) in control rats (p less than 0.05). The fat and cholesterol diet exacerbated glomerular lesions in the remnant kidney model of uninephrectomized rats. The sclerosis in rats with only one kidney was 38.2 +/- 9.5 (N = 6) on a cholesterol diet compared with 8.7 +/- 3.0 (N = 6) in control rats after 6 months (p less than 0.05). After 3 to 4 months on a fat rich diet cholesterylester was increased in isolated glomeruli. The composition of the dietary lipids influenced the development of glomerular lesions. A linseed oil diet that is rich in unsaturated fatty acids, especially linolenic acid, did not cause major plasma lipid abnormalities and was accompanied by a low sclerosis (1.2 +/- 0.3; N = 9) for rats with two kidneys. In rats with chronic 2-K, 1C hypertension the percentage of glomeruli with partially sclerosed tufts in the unclipped kidney was significantly higher on a fat and cholesterol diet (F) than on a control diet (N) (SC: diet F 31.0 +/- 4.0, N = 13; diet N 12.2 +/- 2.6, N = 12; P less than 0.05). In the clipped kidney, protected against the arterial hypertension, only an increased number of glomeruli with mesangial expansion was noted in rats with the cholesterol diet. Glomerular hemodynamic factors seem to play an important pathogenetic role in the induction of glomerular sclerosis by a lipid rich diet. The fact that dietary lipids can aggravate glomerular lesions in states of arterial hypertension and nephron loss may have implications for the progression of renal disease in humans.     

β-淀粉样蛋白和胆固醇对大鼠大脑类似阿尔茨海默病病理学进程和尼古丁受体的影响

目的探讨β-淀粉样蛋白（Ag）和胆固醇与阿尔茨海默病（AD）病理学进程和神经型尼古丁受体的关系。方法Wistar大鼠经侧脑室注射Aβ1-42（1mg／ml,5μl／只）来建立类似AD动物模型,并饲以5％胆固醇饮食。采用银染、免疫组织化学、水迷宫、Western blot和逆转录聚合酶链反应（RT-PCR）等方法检测实验动物脑组织形态学、学习记忆能力、神经型尼古丁受体亚单位表达水平等方面的改变。结果Aβ侧脑室注射引起大鼠脑组织中AB沉积;高胆固醇饮食造成大鼠明显高胆固醇血症（血胆固醇浓度较对照组增高21％～24％）;Aβ侧脑室注射引起大鼠学习记忆力降低,导致尼古丁受体α3、α4和α7亚单位蛋白水平降低（较对照组分别降低46％、39％及51％）,并引起酊亚单位mRNA表达水平升高41％-73％;高胆固醇饮食能够明显增强Aβ引起的脑组织中Aβ沉积和星形胶质细胞增多、学习记忆能力降低及尼古丁受体表达改变。结论Aβ能明显引起大鼠大脑病理学改变,降低大鼠学习记忆能力和影响神经型尼古丁受体的表达;高胆固醇饮食可增强Aβ的神经毒性作用及对尼古丁受体的影响。     

Effect of photoperiod on the pineal melatonin rhythm in neonatal rats

Photoperiod already modulates pineal melatonin rhythm in neonatal rats. Pineal melatonin content was about 500 fmol during day and increased up to 2000 and 3000 fmol at night in 8- and 12-day-old rats, respectively. On long photoperiods (LD 14:10) melatonin was increased above 1000 fmol for about 8 h while on short photoperiods (LD 8:16) for 12 to 14 h. Melatonin pattern may thus transduce photoperiodic effects in neonatal rats. However, no differences in plasma LH were found in the rats kept on long and short photoperiods.     

Renal accumulation of biglycan and lipid retention accelerates diabetic nephropathy

Hyperlipidemia worsens diabetic nephropathy, although the mechanism by which renal lipids accumulate is unknown. We previously demonstrated that renal proteoglycans have high low-density lipoprotein (LDL) binding affinity, suggesting that proteoglycan-mediated LDL retention may contribute to renal lipid accumulation. The aim of this study was to determine the relative effect of diabetes and hyperlipidemia on renal proteoglycan content. Diabetic and non-diabetic LDL receptor-deficient mice were fed diets containing 0% or 0.12% cholesterol for 26 weeks, and then kidneys were analyzed for renal lipid and proteoglycan content. Diabetic mice on the high-cholesterol diet had accelerated development of diabetic nephropathy with elevations in urine albumin excretion, glomerular and renal hypertrophy, and mesangial matrix expansion. Renal lipid accumulation was significantly increased by consumption of the 0.12% cholesterol diet, diabetes, and especially by both. The renal proteoglycans biglycan and decorin were detectable in glomeruli, with a significant increase in renal biglycan content in diabetic mice on the high-cholesterol diet. Renal biglycan and renal apolipoprotein B were colocalized, and regression analyses showed a significant relation between renal biglycan and renal apolipoprotein B content. The increased renal biglycan content in diabetic nephropathy probably contributes to renal lipid accumulation and the development of diabetic nephropathy.     

Melatonin reduces the production and secretion of prolactin and growth hormone from rat pituitary cells in culture

A culture of clonal tumour cells from rat pituitary gland that secrete both prolactin and growth hormone were used to investigate whether the pineal hormone melatonin can act directly on the pituitary gland to control prolactin production. Melatonin inhibition of prolactin and growth hormone production was significant but mild. Concentrations of between 10(-8) M and 10(-6) M reduced both prolactin and growth hormone production and prolactin secretion by 10-50%. 17 beta-oestradiol (OE) and thyrotrophin-releasing hormone (TRH) stimulated prolactin production but had no significant effect on growth hormone production. Melatonin reduced the effects of both of these compounds. Both TRH and vasoactive intestinal peptide (VIP) stimulated secretion of prolactin, and TRH also of growth hormone. Melatonin reduced these effects significantly. TRH and VIP increased cAMP production two- and 12-fold, respectively. Melatonin had no effect on basal or stimulated cAMP production. The melatonin-induced changes in prolactin and growth hormone production and secretion seen here do not approach the magnitude of the fluctuations seen in plasma in vivo. It is concluded that while melatonin does have a direct effect on the lactotroph in the regulation of prolactin production, its main physiological target must be elsewhere.     

Amlodipine treatment decreases plasma and carotid artery tissue levels of endothelin-1 in atherosclerotic rabbits

Alteration in transferring of calcium ions are seen in atherosclerotic cells and amlodipine can positively influence risk factors associated with atherosclerosis, but all mechanisms are not known. Recent studies indicate that endothelin-1 (ET-1) contributes to the atheroma formation and progression of atherosclerosis. In this study, we have evaluated the effects of amlodipine treatment and/or high-cholesterol diet on blood and carotid artery tissue concentration of ET-1 in the atherosclerotic rabbits. Thirty six male New Zealand white rabbits were randomly divided into four groups: normal-diet control (NC), normal-diet receiving amlodipine (NA), high-cholesterol diet (HC) and high-cholesterol diet receiving amlodipine (HA) groups. After 8 weeks all animals were anesthetized and blood or carotid tissue samples were colleted. Eight weeks of amlodipine treatment reduced significantly total cholesterol, LDL and TG in hypercholesterolemic (HA) group. Significant increase in plasma HDL-C and decrease in TG were the main effects of amlodipine treatment on serum lipid profiles in the control group. The plasma and carotid tissue levels of ET-1 in HC group were significantly increased as compared with the NC group (p < 0.01). Amlodipine treatment significantly reduced ET-1 level in NA and HA rabbits (p < 0.01). Furthermore, high-cholesterol diet induced atherosclerotic lesions as shown by the enhancement of endothelial cell diameter and accumulation of lipid droplets under endothelial cells. Amlodipine treatment reduced atherotic lesions in these rabbits. Amlodipine treatment reduced levels of total cholesterol, LDL and TG as well as plasma and carotid tissue levels of ET-1 in high lipid situation. We suggest that amlodipine treatment by reducing the ET-1 may contribute to reducing the progression of atherosclerotic disease.