Inadequate dietary magnesium intake increases atherosclerotic plaque development in rabbits

Epidemiological studies have shown dietary magnesium (Mg) intake and serum Mg levels to be inversely correlated with the development of atherosclerosis. We hypothesized that low levels of Mg would promote atherosclerotic plaque development in rabbits. New Zealand white rabbits (4 months old, n = 22) were fed an atherogenic diet containing 0.12% (−Mg), 0.27% (control), or 0.43% (+Mg) Mg for 8 weeks. Blood samples were obtained at baseline, 2, 4, 6, and 8 weeks and were assayed for total cholesterol, high-density lipoprotein (HDL), non-HDL, triglycerides (TG), C-reactive protein, serum Mg, and erythrocyte Mg. Aortas from −Mg had significantly more plaque, with an intima thickness 42% greater than control and 36% greater than +Mg. Serum cholesterol levels rose over time, and at 8 weeks, −Mg had the highest and +Mg the lowest total and non-HDL cholesterol and TG levels, although these results did not reach significance. Over time, serum Mg levels increased, and erythrocyte Mg levels decreased. C-reactive protein significantly increased in all groups at 4 and 6 weeks but returned to baseline levels by 8 weeks. This study supports the hypothesis that inadequate intake of Mg results in an increase in atherosclerotic plaque development in rabbits.     

Influence of large molecular polymeric pigments isolated from fermented Zijuan tea on the activity of key enzymes involved in lipid metabolism in rat

Influence of large molecular polymeric pigments (LMPP) isolated from fermented Zijuan tea on the activity and mRNA expression of key enzymes involved in lipid metabolism in rat was explored. The results show that intragastric infusion of high-dose LMPP (1.215g/kg body weight) effectively suppressed the elevation in TC and LDL-C (p<0.05), and prevented the reduction in HDL-C (p<0.05), compared with the hyperlipidemia model group. LMPP significantly enhanced the activity of HL and HSL, and increased the HSL mRNA expression in the liver tissue and adipose tissue. High-LMPP treatment significantly reduced the HMG-CoA reductase expression by 56.5% in the liver compared with hyperlipidemia model group. In contrast, LDL-R expression was increased by 120% in the presence of high-LMPP treatment. These results suggest that LMPP have the hypolipidemic effect to some extent and significantly enhance HSL mRNA expression in the liver and adipose tissue, thereby increasing HSL activity in rat.     

Intermittent chylomicronemia caused by intermittent GPIHBP1 autoantibodies

Chylomicronemia caused by a deficiency in lipoprotein lipase (LPL) or GPIHBP1 (the endothelial cell protein that transports LPL to the capillary lumen) is typically diagnosed during childhood and represents a serious, lifelong medical problem. Affected patients have high plasma triglyceride levels (>1500 mg/dL) and a high risk of acute pancreatitis. However, chylomicronemia frequently presents later in life in the absence of an obvious monogenic cause. In these cases, the etiology for the chylomicronemia is presumed to be “multifactorial” (involving diabetes, drugs, alcohol, or polygenic factors), but on a practical level, the underlying cause generally remains a mystery. Here, we describe a 15-year-old female with chylomicronemia caused by GPIHBP1 autoantibodies (which abolish LPL transport to the capillary lumen). Remarkably, chylomicronemia in this patient was intermittent, interspersed between periods when the plasma triglyceride levels were normal. GPIHBP1 autoantibodies were easily detectable during episodes of chylomicronemia but were undetectable during periods of normotriglyceridemia. During the episodes of chylomicronemia (when GPIHBP1 autoantibodies were present), plasma LPL levels were low, consistent with impaired LPL transport into capillaries. During periods of normotriglyceridemia, when GPIHBP1 autoantibodies were absent, plasma LPL levels normalized. Because the chylomicronemia in this patient was accompanied by debilitating episodes of acute pancreatitis, the patient was ultimately treated with immunosuppressive drugs, which resulted in disappearance of GPIHBP1 autoantibodies and normalization of plasma triglyceride levels. GPIHBP1 autoantibodies need to be considered in patients who present with unexplained acquired cases of chylomicronemia.     

MicroRNA-27a/b regulates cellular cholesterol efflux,influx and esterification/hydrolysis in THP-1 macrophages

Rationale

Macrophage cholesterol homeostasis maintenance is the result of a balance between influx, endogenous synthesis, esterification/hydrolysis and efflux. Excessive accumulation of cholesterol leads to foam cell formation, which is the major pathology of atherosclerosis. Previous studies have shown that miR-27 (miR-27a and miR-27b) may play a key role in the progression of atherosclerosis.

Objective

We set out to investigate the molecular mechanisms of miR-27a/b in intracellular cholesterol homeostasis.

Methods and results

In the present study, our results have shown that the miR-27 family is highly conserved during evolution, present in mammals and directly targets the 3′ UTR of ABCA1, LPL, and ACAT1. apoA1, ABCG1 and SR-B1 lacking miR-27 bind sites should not be influenced by miR-27 directly. miR-27a and miR-27b directly regulated the expression of endogenous ABCA1 in different cells. Treatment with miR-27a and miR-27b mimics reduced apoA1-mediated cholesterol efflux by 33.08% and 44.61% in THP-1 cells, respectively. miR-27a/b also regulated HDL-mediated cholesterol efflux in THP-1 macrophages and affected the expression of apoA1 in HepG2 cells. However, miR-27a/b had no effect on total cellular cholesterol accumulation, but regulated the levels of cellular free cholesterol and cholesterol ester. We further found that miR-27a/b regulated the expression of LPL and CD36, and then affected the ability of THP-1 macrophages to uptake Dil-oxLDL. Finally, we identified that miR-27a/b regulated cholesterol ester formation by targeting ACAT1 in THP-1 macrophages.

Conclusion

These findings indicate that miR-27a/b affects the efflux, influx, esterification and hydrolysis of cellular cholesterol by regulating the expression of ABCA1, apoA1, LPL, CD36 and ACAT1.     

载脂蛋白E（apoE）和脂蛋白脂酶（LPL）双基因敲除小鼠（apoE^-／-／LPL^＋/-）用于大豆异黄酮调血脂作用研究

目的探讨大豆异黄酮提取物对高胆固醇合并高甘油三酯血症基因工程小鼠的调血脂作用。方法高脂饮食条件下,以C57BL／6成年小鼠10只（65,早5）为正常对照,载脂蛋白E和脂蛋白脂酶双基因缺陷（apoE^-／-／LPL^＋/-）成年小鼠（ELK小鼠）40只（620,早20）,随机分为4组：高脂模型组,每天200mg/kg大豆异黄酮提取物,每周阳性对照药0．5mg／kg尼尔雌醇和每天20mg/kg洛伐他汀灌胃组。连续灌胃给药4周,测定血清总胆固醇、甘油三酯、高密度脂蛋白胆固醇、低密度脂蛋白胆固醇和血糖含量。结果与C57BL／6空白对照组相比,ELK高脂模型组小鼠的血清TC、TG和LDL—c含量均极显著增高（P〈0．01）。与高脂模型组相比,大豆异黄酮给药4周可显著降低ELK小鼠血清TG含量（P〈0．05）,同时使血清HDL—c增加9．3％,而洛伐他汀和尼尔雌醇组分别降低了13．5％和8．7％;高脂诱导的ELK小鼠血清TC、LDL—c水平极度增高,大豆异黄酮、洛伐他汀和尼尔雌醇均不能显著降低TC、LDL-c含量（P〉0．05）。结论大豆异黄酮有明显调血脂作用。     

脂蛋白脂酶基因PvuⅡ酶切位点多态性与胰岛素抵抗关系的研究

目的旨在探讨脂蛋白脂酶基因第6内含子PvuⅡ酶切位点多态性与胰岛素抵抗、2型糖尿病的发生之间是否有关联。方法随机选取163例2型糖尿病患者作为病例组，106例正常人作为正常对照组，对第6号内含子PvuⅡI酶切位点进行多态性分析。结果病例组中P＋P＋组高密度脂蛋白胆固醇水平明显低于P-P-组，而血清三酰甘油、胰岛素抵抗指数指标水平高于P-P-组。结论PvuⅡ酶切位点多态性与2型糖尿病中胰岛素抵抗有关。