Structural characterisation and cholesterol efflux improving capacity of the novel polysaccharides from Cordyceps militaris.

Water extracts of the edible mushroom Cordyceps militaris possess a lipid-lowering effect. However, the types of components and how they exert this effect are not clear. In this study, two novel polysaccharides, CM1 and CMS, were isolated, and their cholesterol efflux improving capacity was investigated in vitro. The molecular weight of CM1 was approximately 700 kDa, and its main chain was consisted of (1 → 4)-ß-D-Glcp and (1 → 2)-α-D-manp branched at the O-6 positions of (1 → 2,6)-α-D-manp with (1 → 2) linked-ß-D-galf, (1 → 2)-α-D-manp or methyl and terminated with ß-D-Galf and α-D-Manp. The molecular weight of CMS was approximately 18.2 kDa, and it was a novel (1 → 6)-ß-D-Glcp linked glucan. Both CM1 and CMS significantly increased [3H]-cholesterol efflux by activating the protein expression of ATP-binding cassette (ABC) G1. However, they showed no significant influence on the proteins expression of ABCA1 and scavenger receptor B type 1. Therefore, CM1 and CMS are effective water-soluble components with potential lipid-lowering activity. They may be exploited as potential candidates for dyslipidaemia-related diseases such as atherosclerosis.

Exogenous supplement of N-acetylneuraminic acid improves macrophage reverse cholesterol transport in apolipoprotein E-deficient mice.

BACKGROUND: N-acetylneuraminic acid (NANA) is the major form of sialic acid in mammals, and the plasma NANA level is increased in patients with cardiovascular diseases. Exogenous supplement of NANA has been demonstrated to reduce hyperlipidaemia and the formation of atherosclerotic lesions; however, the underlying mechanisms have not yet been clarified. The aim of this study is to investigate whether exogenous supplement of NANA improves reverse cholesterol transprot (RCT) in vivo. METHODS: Apolipoprotein E-deficient mice fed a high-fat diet were used to investigate the effect of NANA on RCT by [3H]-cholesterol-loaded macrophages, and the underlying mechanism was further investigated by various molecular techniques using fenofibrate as a positive control. RESULTS: Our novel results demonstrated that exogenous supplement of NANA significantly improved [3H]-cholesterol transfer from [3H]-cholesterol-loaded macrophages to the plasma (an increase of > 42.9%), liver (an increase of 35.8%), and finally to the feces (an increase of 50.4% from 0 to 24 h) for excretion in apolipoprotein E-deficient mice fed a high-fat diet. In addition, NANA up regulated the protein expression of ATP-binding cassette (ABC) G1 and peroxisome proliferator-activated receptor α (PPARα), but not the protein expression of ABCA1and scavenger receptor B type 1 in the liver. Therefore, the underlying mechanism of NANA in improving RCT may be partially due to the elevated protein levels of PPARα and ABCG1. CONCLUSION: Exogenous supplement of NANA improves RCT in apolipoprotein E-deficient mice fed a high-fat diet mainly by improving the protein expression of PPARα and ABCG1. These results are helpful in explaining the lipid-lowering effect of NANA.

Ubiquitin ligase TRAF2 attenuates the transcriptional activity of the core clock protein BMAL1 and affects the maximal Per1 mRNA level of the circadian clock in cells.

The ubiquitin-proteasome system (UPS) modulates the ubiquitination and degradation of many proteins and thus alters their abundance and biological functions. The core clock protein, aryl hydrocarbon receptor nuclear translocator-like protein 1 (ARNTL or BMAL1), is the master regulator of the circadian clock and plays important roles in the regulation of many biological processes, such as protein synthesis, cell senescence, and circadian rhythms. However, the influence of the UPS on BMAL1 is not fully understood. Here, we find an E3 ubiquitin ligase, TNF receptor-associated factor 2 (TRAF2), as an interacting protein of BMAL1 to reduce its stability. Biochemical experiments demonstrate that this regulation is achieved through the ubiquitination and subsequent degradation of BMAL1. We further reveal that BMAL1 preferentially interacts with the zinc finger domain but not the conventional substrate recognition domain in TRAF2. Functional studies find that TRAF2 expression reduces the BMAL1 transcriptional activity and Traf2 knockdown elevates the maximal Per1 mRNA level of the circadian clock in a neuroblastoma cell line. This work discovers TRAF2 as a novel regulatory factor for BMAL1 and reveals a new domain in TRAF2 for substrate binding, which may extend the regulatory functions of TRAF2 and BMAL1 in many biological processes, such as circadian rhythm.

Quercetin improves macrophage reverse cholesterol transport in apolipoprotein E-deficient mice fed a high-fat diet.

BACKGROUND: Quercetin, one of the most widely distributed flavonoids in plants, has been demonstrated to reduce hyperlipidaemia and atherosclerotic lesion formation. Reverse cholesterol transport (RCT) plays a crucial role in exporting cholesterol from peripheral cells, which is one mechanism utilized in the prevention and treatment of atherosclerosis. The aim of this study is to investigate whether quercetin reduces lipid accumulation by improving RCT in vivo. METHODS: Apolipoprotein E-deficient mice fed a high-fat diet were used to investigate the effect of quercetin on RCT by an isotope tracing method, and the underlying mechanisms were clarified by molecular techniques. RESULTS: These novel results demonstrated that quercetin significantly improved [3H]-cholesterol transfer from [3H]-cholesterol-loaded macrophages to the plasma (approximately 34% increase), liver (30% increase), and bile (50% increase) and finally to the feces (approximately 40% increase) for excretion in apolipoprotein E-deficient mice fed a high-fat diet. Furthermore, quercetin markedly increased the cholesterol accepting ability of plasma and high-density lipoprotein (HDL) and dramatically decreased the content of malondialdehyde in plasma and oxidized phosphocholine carried by HDL. Therefore, the underlying mechanisms of quercetin in improving RCT may be partially due to the elevated cholesterol accepting ability of HDL, the increased expression levels of proteins related to RCT, such as ATP-binding cassettes (ABC) A1 and G1, and the improved antioxidant activity of HDL. CONCLUSION: Quercetin accelerates RCT in an atherosclerosis model, which is helpful in clarifying the lipid-lowering effect of quercetin.

Phospholipid transfer protein deficiency in mice impairs macrophage reverse cholesterol transport in vivo.

Phospholipid transfer protein is expressed in various cell types and secreted into plasma, where it transfers phospholipids between lipoproteins and modulates the composition of high-density lipoprotein particles. Phospholipid transfer protein deficiency in vivo can lower high-density lipoprotein cholesterol level significantly and impact the biological quality of high-density lipoprotein. Considering high-density lipoprotein was a critical determinant for reverse cholesterol transport, we investigated the role of systemic phospholipid transfer protein deficiency in macrophage reverse cholesterol transport in vivo After the littermate phospholipid transfer protein KO and WT mice were fed high-fat diet for one month, they were injected intraperitoneally with (3)H-cholesterol-labeled and acLDL-loaded macrophages. Then the appearance of (3)H-tracer in plasma, liver, bile, intestinal wall, and feces over 48 h was determined. Plasma lipid analysis indicated phospholipid transfer protein deficiency lowered total cholesterol, high-density lipoprotein-C and apolipoprotein A1 levels significantly but increased triglyceride level in mice. The isotope tracing experiment showed (3)H-cholesterol of plasma was decreased by 68% for male and 62% for female, and (3)H-tracer of bile was decreased by 37% for male and 21% for female in phospholipid transfer protein KO mice compared with WT mice. However, there was no difference in liver, and (3)H-tracer of intestinal wall was increased by 43% for male and 27% for female. Finally, (3)H-tracer of fecal excretion in phospholipid transfer protein KO mice was reduced significantly by 36% for male and 43% for female during 0-24 h period, but there was no significant difference during 24-48 h period. Meanwhile, Western Blot analysis showed the expressions of reverse cholesterol transport -related protein liver X receptor α (LXRα), ATP binding cassette transporter A1, and cholesterol 7α-hydroxylase A1 were upregulated in liver of phospholipid transfer protein KO mice compared with WT mice. These data reveal that systemic phospholipid transfer protein deficiency in mice impairs macrophage-specific reverse cholesterol transport in vivo.