Influence of atorvastatin on fractional and subfractional composition of serum lipoproteins and MMP activity in mice with Triton WR 1339-induced lipaemia

Hypolipidemic Effects of β-Glucans, Mannans, and Fucoidans: Mechanism of Action and Their Prospects for Clinical Application

The search for lipid-lowering drugs is important for clinical medicine. This review summarizes our research findings regarding the hypolipidemic activity of polysaccharides. There are several validated agents altering lipid levels which reduce the risk of atherosclerotic cardiovascular events. Nonetheless, for many people, the risk of such an event remains unacceptably high despite treatment with these agents. This situation has prompted the search for new therapies to reduce the residual cardiovascular risk. The lipid-lowering effect of β-glucans consumed with food was demonstrated in patients with atherosclerosis. The mechanism of the protective effect of β-glucans is poorly studied. The effects of β-glucans are mediated by Toll-like receptors, by dectin-1, and possibly by other receptors. Nevertheless, the mechanism of the protective action of β-glucan in lipemic mice has been studied insufficiently. This review will present up-to-date information regarding experimental hypolipidemic polysaccharide compounds that hold promise for medicine. Phagocyte-specific chitotriosidase in humans contributes to innate immune responses against chitin-containing fungi. This enzyme has been first described in patients with Gaucher disease and serves as an important diagnostic biomarker. It has been reported that, in mice, chitin particles of certain size are recognized by macrophages through Toll-like receptors, dectin-1, and to a lesser extent through mannose receptor.

Early-stage atherosclerosis in poloxamer 407-induced hyperlipidemic mice: pathological features and changes in the lipid composition of serum lipoprotein fractions and subfractions

Background

The aims of this study were to evaluate the effect of poloxamer 407 administration on atherogenic serum lipoprotein fractions and subfractions associated with cholesterol, triglycerides and phospholipids, as well as the onset of early atherosclerosis, in mice.

Methods

Mice were administered either sterile saline or poloxamer 407 (to induce a dose-controlled hyperlipidemia) for 1 month and then sacrificed at 1, 4 and 10 days after the last dose of poloxamer 407. Systolic and diastolic blood pressure, the activity of a cysteine protease (cathepsin B) in cardiac and liver tissue, and histological/morphological examination of heart and liver specimens was performed for each group of mice at each time point. Lastly, small angle X-ray scattering was utilized to analyze the lipoprotein fractions and subfractions associated with cholesterol, triglycerides and phospholipids for both groups of mice at each time point. Statistical analysis was performed using one-way, analysis-of-variance with post hoc analysis to determine significantly different mean values, while correlation analysis employed the Spearman test.

Results

Poloxamer 407-treated mice revealed significant hyperlipidemia, moderately elevated blood pressure, general lipidosis in liver cells, increased cysteine protease activity in heart tissue, and contractile-type changes in cardiomyocytes. Similar to humans, the onset of atherosclerosis in poloxamer 407-treated mice was characterized by a steady increase in serum low-density, intermediate-density and very-low-density lipoprotein fractions, as well as very-low-density lipoprotein subfractions.

Conclusions

We would propose that the sustained elevation of serum atherogenic lipoprotein fractions and subfractions induced by the administration of poloxamer 407 to mice resulted in the morphological changes we observed in both heart and liver cells, which are suggested to precede atherosclerosis, since this is a well-established mouse model of atherosclerosis. Since most of the cellular, biochemical and physiological changes documented in the present study using poloxamer 407-treated mice are related to the symptoms of early atherosclerosis in humans, it is suggested that the poloxamer 407-induced mouse model of hyperlipidemia and atherosclerosis might prove beneficial as an experimental animal model with which to evaluate the pathological features observed in early-stage atherosclerosis.

Thiomorpholine Derivatives with Hypolipidemic and Antioxidant Activity

A number of thiomorpholine derivatives that are structurally similar to some substituted morpholines possessing antioxidant and hypocholesterolemic activity were synthesized. The new compounds incorporate an antioxidant moiety as the thiomorpholine N-substituent. The derivatives were found to inhibit the ferrous/ascorbate-induced lipid peroxidation of microsomal membrane lipids, with IC50 values as low as 7.5 µΜ. In addition, these compounds demonstrate hypocholesterolemic and hypolipidemic action. The most active compound (5) decreases the triglyceride, total cholesterol, and low-density lipoprotein levels in the plasma of Triton WR-1339-induced hyperlipidemic rats, by 80, 78, and 76%, respectively, at 56 mmol/kg (i.p.). They may also act as squalene synthase inhibitors. The above results indicate that the new molecules may be useful as leads for the design of novel compounds as potentially antiatherogenic factors.

Effect of poloxamer 407 administration on the serum lipids profile, anxiety level and protease activity in the heart and liver of mice

Chronic administration of the poloxamer 407 (P-407), a block copolymer, to elevate serum lipids in mice is a well-established mouse model of hyperlipidemia and atherosclerosis. We tested the hypothesis that the activity of several types of proteases in heart and liver tissue is changed in the early stages of atherosclerosis development. Additionally, we evaluated whether increased serum lipids would induce anxiety in mice, as determined by using a ‘plus-maze’ test. The mice were administered P-407 by intraperitoneal injection twice a week for one month. P-407 administration to mice resulted in a marked increase in total serum cholesterol, atherogenic non-HDL-cholesterol, and especially in total triglycerides, and it also increased anxiety. Morphological changes observed in P-407-treated mice included contractile type changes in cardiomyocytes and foamy macrophages in liver. A significant increase of cysteine proteases cathepsin B and cathepsin L (at 24 h) and aspartate protease cathepsin D (at both 24 h and 5 days) was determined in heart tissue following P-407 administration. However, no changes were noted in heart matrix metalloproteinase activity. The activity of cysteine and aspartate proteases was significantly increased in liver at both 24 hours and 5 days after P-407 administration. In conclusion, administration of P-407 to mice for one month resulted in increased anxiety, and more importantly, there was an increase in the activity of heart and liver proteases secondary to sustained dyslipidemia. It is suggested that heart and liver cysteine and aspartate proteases may represent potential therapeutic targets in the early stages of atherosclerosis.

The influence of repeated administration of poloxamer 407 on serum lipoproteins and protease activity in mouse liver and heart

The effects of repeated administration of poloxamer 407 (P-407) on lipoprotein-cholesterol (LP-C) and lipoprotein-triglyceride (LP-TG) fractions and subfractions, as well as the effect on liver and heart proteases, were studied. Repeated administration of P-407 to male CBA mice resulted in a model of atherosclerosis with increased diastolic blood pressure; there was a drastic increase in total serum cholesterol and especially TG. A novel small-angle X-ray scattering method for the determination of the fractional and subfractional composition of LP-C and LP-TG was used. In chronically P-407-treated mice, P-407 significantly increased atherogenic low-density lipoprotein C (LDL-C) fractions, as well as intermediate-density lipoprotein C (IDL-C), and LDL₁₋₃-C subfractions, and very-low-density lipoprotein-C (VLDL-C) fractions, as well as VLDL₁₋₂-C and VLDL₃₋₅-C subfractions), to a lesser extent, the total anti-atherogenic high-density lipoprotein C (HDL-C) fraction, as well as HDL₂-C and HDL₃-C subfractions. Additionally, we demonstrated an increase in the serum chitotriosidase activity, without significant changes in serum matrix metalloprotease (MMP) activity. Morphological changes observed in P-407-treated mice included atherosclerosis in the heart and storage syndrome in the liver macrophages. P-407 significantly increased the activity of cysteine, aspartate proteases, and MMPs in the heart, and only the activity of cathepsin B and MMPs in the liver of mice. Thus, repeated administration of P-407 to mice induced atherosclerosis secondary to sustained dyslipidemia and formation of foamy macrophages in liver, and also modulated the activity of heart and liver proteases.

Influence of atorvastatin and carboxymethylated glucan on the serum lipoprotein profile and MMP activity of mice with lipemia induced by poloxamer 407

The effects of atorvastatin and carboxymethylated β-glucan (CMG) on the lipoprotein-cholesterol (LP-C) and lipoprotein-triglyceride (LP-TG) fractions and subfractions at the early stage of murine hyperlipidemia, and its pleiotropic anti-inflammatory effects, were studied. Atorvastatin and CMG were administered in ICR male mice with acute lipemia induced with a single injection of poloxamer 407 (P-407). A novel small-angle X-ray scattering method for the determination of fractional and subfractional composition of LP-C and LP-TG was used. In P-407-treated animals, there was a drastic increase of total cholesterol and especially TG. Atorvastatin decreased both the total cholesterol and TG, but not to control levels. CMG primarily decreased TG and was not as potent as atorvastatin. P-407 increased atherogenic LDL-C (IDL-C and LDL1–3-C subfractions) and very low-density lipoprotein-C (VLDL-C) (VLDL1–2-C and VLDL3–5-C subfractions) fractions, with an increase of the total anti-atherogenic HDL-C fraction (HDL2-C subfraction). Atorvastatin treatment of lipemia was followed by a decrease in the total LP-C, total LDL-C (LDL1–3-C subfraction), and the LDL1–3-TG subfraction. Additionally, atorvastatin treatment resulted in an increase in the serum matrix metalloproteases activity both in control and P-407-treated mice. In general, high-dose atorvastatin therapy exerts its lipid-lowering and pleiotropic effects in the early stages of acute lipemia induced in mice by treatment with P-407.