Effect of ascorbic acid administration on B and E apoproteins in rats fed a cholesterol enriched diet

The Effect of Coconut Water on Adipocyte Differentiation and Lipid Accumulation in 3T3-L1 Cells

Coconut water is reported to have lipid-lowering effects in animal studies. However, there is lack of published reports regarding its effect on adipocytes. This study observed the effect of coconut water on adipocyte differentiation and lipid accumulation in 3T3-L1 cells. The sample used in this study was mature coconut water from tall variety. Based on a preliminary study, the sample was heat-treated and added with certain amino acids as precursors for Maillard reaction to improve its original flavor. As a comparison, aromatic coconut water was used since it is highly preferred as a fresh beverage. Six samples were supplemented to 3T3-L1 cells, which were then analyzed for cell proliferation, lipid accumulation, triglyceride content, and gene expression. Arginine and vitamin C contents of the samples were also determined. The data were analyzed with ANOVA and followed by Tukey's test. Results showed that aromatic coconut water could slightly suppress lipid accumulation, while mature coconut water had a significantly lower percentage of accumulation compared to the control sample (p<0.05). Canned and fresh samples had no significant difference in terms of lipid-lowering activity (p>0.05). Similarly, the addition of lysine and proline in canned samples did not significantly affect the cells' differentiation. There was no significant effect on expressions of C/EBP-α and PPARγ, indicating the possibility of other pathways involved in hypolipidemic effect of coconut water. This study showed that coconut water might have potential to inhibit adipogenesis in 3T3-L1 cells due to its bioactive compounds.

Beneficial Effects of Coconut Water Feeding on Lipid Metabolism in Cholesterol-Fed Rats

The purpose of this study was to determine the effect of coconut water feeding in cholesterol-fed rats. Male albino rats were fed tender coconut water and mature coconut water at a dose level of 4 mL/100 g of body weight. Cholesterol feeding caused a marked increase in total cholesterol, very low-density lipoprotein (VLDL) + low-density lipoprotein (LDL) cholesterol, and triglycerides in serum. Administration of coconut water counteracts the increase in total cholesterol, VLDL + LDL cholesterol, and triglycerides, while high-density lipoprotein cholesterol was higher. Lipid levels in the tissues viz. liver, heart, kidney, and aorta were markedly decreased in cholesterol-fed rats supplemented with coconut water. Feeding coconut water resulted in increased activities of 3-hydroxy-3-methylglutaryl-CoA reductase in liver, lipoprotein lipase in heart and adipose tissue, and plasma lecithin:cholesterol acyl transferase, while lipogenic enzymes showed decreased activities. An increased rate of cholesterol conversion to bile acid and an increased excretion of bile acids and neutral sterols were observed in rats fed coconut water. Histopathological studies of liver and aorta revealed much less fatty accumulation in these tissues in cholesterol-fed rats supplemented with coconut water. Feeding coconut water resulted in increased plasma L-arginine content, urinary nitrite level, and nitric oxide synthase activity. These results indicate that both tender and mature coconut water has beneficial effects on serum and tissue lipid parameters in rats fed cholesterol-containing diet.

Vitamin C intake and apolipoproteins in a healthy elderly Japanese population

BACKGROUND

Adequate vitamin C (AsA) intake may lower the risk of arteriosclerotic cardiovascular disease, but little is known about its influence on the progression of atherogenic disease in the elderly.

METHODS

We examined whether AsA intake was associated with serum lipids, apolipoprotein A-1 (ApoA1) and apolipoprotein B (ApoB), in 680 Japanese elderly persons.

RESULTS

There were no significant gender differences among mean serum lipids and apolipoprotein concentrations and intakes of macronutrients. AsA intake had a significant positive association with serum concentrations of high-density cholesterol and ApoA1, but an inverse association with serum concentrations of low-density cholesterol and ApoB, after adjusting for age, body mass index, total energy, and macronutrients. AsA intake was strongly inversely related to ApoA1/ApoB.

CONCLUSION

Increased AsA intake could play an important role in lipid composition and could be of potential importance in the genesis and prevention of atherogenic disease in the elderly.

Dietary and hypothyroid hypercholesterolemia induces hepatic apolipoprotein E expression in the rat: direct role of cholesterol

Apolipoprotein E (apo E) exerts a protective effect against atherosclerosis, related to its role in intracellular cholesterol removal and remnants clearance. In this study we investigated the effect of dietary and hypothyroid hypercholesterolemia, induced respectively by a high cholesterol diet and by propylthiouracil, on hepatic apo E expression in Wistar male rats. The Northern and Western blot analysis of hepatic mRNA and protein levels showed a 2-3-fold increase of apo E in hypercholesterolemic rats compared to controls. The incubation of FAO rat hepatoma cells with 25-OH cholesterol and mevalonate led to a three-fold increase of apo E mRNA, demonstrating a direct role of cholesterol on apo E expression. This effect was completely abolished by elevating intracellular cAMP levels with forskolin. Immunoblot and immunofluorescence analysis revealed that 25-OH cholesterol/mevalonate strongly increased also apo E protein synthesis and secretion in FAO cells. Our data demonstrate that hypercholesterolemia, apart of the cause (diet or hypothyroidism) induces liver apo E expression in the rat and that this effect can be directly related, via cAMP, to cholesterol.

Effects of supplemental ascorbic acid on the energy conversion of broiler chicks during heat stress and feed withdrawal

The objectives of this study were 1) to determine the effects of supplemental ascorbic acid (AA) on the energy conversion of broiler chicks maintained at thermoneutral and potential heat stress temperatures using indirect convective calorimetry; and 2) to determine whether changes in energy conversion are reflected in changes in lipid metabolism. In Experiment 1, 120 2-d-old cockerels, housed in two identical environmental chambers, were maintained under constant light (2.0 +/- 0.2 fc) and recommended thermal conditions (29.6 +/- 0.8 C; 33.4 +/- 8.0% RH) and consumed water and feed ad libitum. Beginning on Day 8 posthatch, one-half of the birds inside each chamber were randomly assigned and received feed supplemented with AA. Beginning on Day 9 posthatch, the temperature inside one chamber was increased to 34 C whereas the other chamber remained thermoneutral. This design resulted in four treatments: 1) thermoneutral (TN: 27.7 +/- 0.8 C; 40.9 +/- 9.4% RH) and 0 mg AA/kg feed (ppm); 2) TN and 150 ppm AA; 3) heat stress (H: 33.8 +/- 0.5 C; 43.3 +/- 7.4% RH) and 0 ppm AA; or 4) H and 150 ppm AA. Also beginning on Day 9 posthatch, birds were randomly assigned to one of three identical, indirect convective calorimeters designed to accommodate TN or H. Oxygen consumption, carbon dioxide production, respiratory quotient, and heat production were evaluated daily for 8 h, through Day 17 posthatch. Following calorimetric measurement, birds were returned to their respective caging unit/chamber for the remainder of the study. Weight gain, feed intake, and gain: feed were also measured over the 9-d study. Heat exposure depressed (P < 0.05) weight gain, feed intake, and gain:feed. Ascorbic acid increased (P < 0.10) weight gain. Oxygen consumption and carbon dioxide and heat production per kilogram0.75 decreased (P < 0.05) with age with no change in the respiratory quotient. Heat exposure lowered (P < 0.001) the respiratory quotient. A temperature by AA interaction was detected in which heat-exposed birds expressed lower (P < 0.10) respiratory quotients when consuming the AA-supplemented diet. In Experiment 2, 18 2-d-old cockerels, housed in an environmental chamber, were maintained under constant light and recommended thermal conditions (29.3 +/- 0.4 C; 41.4 +/- 3.3% RH) and consumed water and feed ad libitum. On Day 9 posthatch, birds were deprived of feed for 24 h with ad libitum access to water supplemented with either 0 or 400 mg AA/L. Blood samples were obtained from each bird before and after feed withdrawal and supplementation. Supplemented birds exhibited elevated (P < 0.01) plasma AA, levels that were not affected by feed deprivation. Feed deprivation increased (P < 0.0001) plasma beta-hydroxybutyrate with no effect of AA, and decreased (P < 0.05) plasma triglycerides in the unsupplemented birds. A feed withdrawal by AA interaction was detected in which plasma triglycerides remained elevated in birds supplemented with AA. These data suggest that supplemental AA influences body energy stores that are used for energy purposes during periods of reduced energy intake.

Ascorbate administration to normal and cholesterol-fed rats inhibits in vitro TBARS formation in serum and liver homogenates

We have recently shown that ascorbate has a hypocholesterolemic and hypotriglyceridemic effect on rats fed a diet enriched with 1.5% cholesterol and 25% hydrogenated coconut oil (Nath diet). In this study we evaluated the effect of intraperitoneal ascorbate administration on susceptibility to lipoperoxidation either in rats fed standard or Nath diet. In normal rats ascorbate treatment decreased (p<0.05) the susceptibility to lipoperoxidation induced by incubation of serum for 24 hours with 2.2 mM Cu++, without altering the normal serum fatty acid profile. In rats fed Nath diet we observed a reduced susceptibility of serum to CU++-induced lipoperoxidation (36%), according with their low levels of serum unsaturated fatty acids (40% less than rats fed standard diet). In these animals ascorbate administration affects serum fatty acid profile leading to a decrease of S/U ratio from 1.6 to 1.2 without significantly modifying the susceptibility of serum to lipoperoxidation. Moreover, the production of spontaneous lipid peroxides in liver homogenates, measured as TBARS levels, was strongly inhibited by ascorbate (p<0.01) in rats fed either standard or Nath diet. These data indicate that ascorbate administration exerts an antioxidant effect and that in hypercholesterolemic rats, in addition to a lipid lowering effect, ascorbate exerts a protective role against the peroxidative damage of lipids.

The rat, a useful animal model for pharmacological studies on apolipoprotein E

Apolipoprotein E is a major protein component of lipoproteins and plays an important role in cholesterol transport. The structure of the gene and the polymorphism of apolipoprotein E have been studied in human and rat, which show similar structures of apolipoprotein E. The wide tissue distribution of this apolipoprotein suggests diverse functions like cholesterol distribution between cells, intracellular cholesterol trafficking and tissue reparation. Nevertheless, the presence of apolipoprotein E in atherosclerotic plaques and amyloid deposits in brains of Alzheimer's disease patients also indicate pathologic functions staying misunderstood. The aim of this paper is to review the present knowledge on the distribution of apolipoprotein E between the different organs with the related functions and to make an overview of the implications of this apolipoprotein is physiological events and pathological states in the rat. The rat is widely used for drug metabolism studies. Its serum levels are 5-10 times higher than in human and thus this animal provides an useful pharmacological model to elucidate the functions of apo E.

Effect of vitamin C on plasma lipids

OBJECTIVE

To review the effects of vitamin C (ascorbic acid) on plasma lipid concentrations, and to address the proposed mechanisms through which vitamin C may potentially alter lipid concentrations.

DATA SOURCE

A MEDLINE search was performed to identify pertinent English-language literature including studies, abstracts, and review articles. Key search terms were vitamin C, ascorbic acid, lipoproteins, lipids, and atherosclerosis.

STUDY SELECTION AND DATA EXTRACTION

Studies examining the relationships between vitamin C and plasma lipid concentrations including animal, observational, and clinical trials were selected. Because there were no large randomized, controlled clinical trials, data were extracted from all clinical trials, regardless of design. Review articles discussing the effects of vitamin C on plasma lipid concentrations and the atherosclerotic process also were included. Pertinent information, as judged by the authors, was extracted for discussion.

DATA SYNTHESIS

Evidence suggests an inverse relationship between vitamin C intake and the development of atherosclerosis, although the effect has not yet been proven in clinical trials. It has been postulated that this effect might be mediated not only through the antioxidant properties of vitamin C, but also through a plasma lipid-modifying effect. Data from animal and observational trials suggest that high vitamin C concentrations may correlate negatively with concentrations of total cholesterol, triglycerides, and low-density lipoproteins and positively with high-density lipoproteins. Other studies, however, have not confirmed these findings. Similarly, results from clinical trials have been widely variable and inconclusive.

CONCLUSIONS

Analysis of the literature suggests an association between vitamin C and plasma lipid concentrations and a potential role in slowing the development of atherosclerosis. Significant variations and inadequacies in trial design, however, prohibit definitive conclusions. On the basis of these preliminary data, it appears that there is justification for additional well-designed trials to further evaluate the relationship between vitamin C and plasma lipid concentrations.

Changes in apoprotein distribution between lipoprotein classes of hypercholesterolemic rats treated with ascorbate

It is known that ascorbate has a lipid lowering effect, accompanied by a drop of apo B, in rats fed a diet enriched with 1.5% of cholesterol (Nath diet). In order to better clarify the role exerted by ascorbate in lipid metabolism, the effect of ascorbate administration on apolipoprotein pattern in rats fed the Nath diet was investigated. Wistar male rats fed for two months the Nath diet were treated i.p. with 60 mg/kg of body weight of ascorbate for 10 days. Blood collection before and after the treatment was performed by intracardiac puncture. Lipoproteins were prepared by preparative ultracentrifugation and their apoprotein content was obtained by densitometric scanning of the apoprotein electhrophoretic pattern. The decrease of total plasma cholesterol and triglycerides and of cholesterol, triglycerides and protein content of all plasma lipoproteins observed in ascorbate treated rats, is accompanied by a marked modification of the apolipoprotein pattern of all lipoprotein classes studied, with an increase of apo E content in VLDL-IDL and LDL fractions (135 and 44% respectively), and a decrease of C (37%), AI (70%) and B (37.5%) apoproteins in VLDL-IDL and of apo C (36%) in LDL. On the contrary, in HDL fraction ascorbate induces an increase of C apoproteins (26%) and a decrease of E and B apoproteins (47% and 71% respectively). The data reported clearly show that in hypercholesterolemic rats the lipid lowering effect of ascorbate administration, is accompanied by a marked modification of the apoprotein pattern of all lipoprotein classes studied.