Suppression of apolipoprotein B secretion from HepG2 cells by glucosyl hesperidin.

Our previous study has shown that a soluble hesperidin derivative, glucosyl hesperidin (G-hesperidin), preferentially lowers serum triglyceride (TG) level in hypertriglyceridemic subjects through the improvement of very low-density lipoprotein (VLDL) metabolic abnormality. G-Hesperidin has also been found to decrease an elevated serum apolipoprotein B (apo B) level in the hypertriglyceridemic subjects, suggesting a possibility that this compound suppresses excess VLDL secretion in the liver. In the present study, to gain a better understanding of possible mechanisms by which G-hesperidin lowers serum TG, we examined whether this derivative affects apo B secretion from HepG2 human hepatoma cells, a model of hepatic VLDL secretion. As a result, G-hesperidin significantly reduced apo B secretion from the oleate-stimulated HepG2 cells. Furthermore, G-hesperidin significantly suppressed apo B secretion only in the oleate-stimulated cells and failed to act on the cells incubated without oleate. In the oleate-stimulated cells, G-hesperidin significantly decreased cellular cholesteryl ester (CE), although it had no effect on cellular TG or free cholesterol amounts. Moreover, the oleate-stimulated cells had a decrease in cellular apo B amounts by G-hesperidin exposure. These findings indicate that G-hesperidin down-regulates the assembly of apo B-containing lipoproteins via the reduction of CE synthesis augmented with oleate and results in suppressing excess apo B secretion from the cells. This effect is speculated to be associated with the improvement of VLDL metabolic abnormality in hypertriglyceridemic subjects and considered as a mechanism of lowering serum TG.

Glucosyl hesperidin lowers serum triglyceride level in hypertriglyceridemic subjects through the improvement of very low-density lipoprotein metabolic abnormality.

To examine the serum triglyceride (TG)-lowering effect of a soluble hesperidin derivative, glucosyl hesperidin (G-hesperidin), and its mechanisms, we carried out a G-hesperidin administration test in hypertriglyceridemic subjects. G-Hesperidin was administered to the subjects at 500 mg/d for 24 wk. In this study, the subjects were classified into high-TG type (TG > 150 mg/dL), borderline-TG type (TG 110-150 mg/dL) and normal-TG type (TG < 110 mg/dL) on the basis of their initial serum TG values. Among these phenotypes, serum TG level significantly decreased in the high-TG type during the G-hesperidin administration period. It was also observed that elevated values of serum remnant-like particle cholesterol (RLP-C), apolipoprotein (apo) B, apo C-II, apo C-III and apo E occurred in the high-TG type and that these serum levels were significantly reduced by G-hesperidin administration. Moreover, polyacrylamide gel electrophoresis analysis of serum lipoproteins revealed that the very low-density lipoprotein (VLDL)/low-density lipoprotein (LDL) ratio and LDL migration index of the high-TG type were remarkably higher than those of the other phenotypes but that their high values were significantly reduced by the administration. These results indicate that G-hesperidin preferentially lowers serum TG in hypertriglyceridemic subjects and that this effect is possibly caused by the improvement of VLDL metabolic abnormality, leading to the reduction of small dense LDL.

The Peptide Vaccine Combined with Prior Immunization of a Conventional Diphtheria-Tetanus Toxoid Vaccine Induced Amyloid ß Binding Antibodies on Cynomolgus Monkeys and Guinea Pigs.

The reduction of brain amyloid beta (Aß) peptides by anti-Aß antibodies is one of the possible therapies for Alzheimer's disease. We previously reported that the Aß peptide vaccine including the T-cell epitope of diphtheria-tetanus combined toxoid (DT) induced anti-Aß antibodies, and the prior immunization with conventional DT vaccine enhanced the immunogenicity of the peptide. Cynomolgus monkeys were given the peptide vaccine subcutaneously in combination with the prior DT vaccination. Vaccination with a similar regimen was also performed on guinea pigs. The peptide vaccine induced anti-Aß antibodies in cynomolgus monkeys and guinea pigs without chemical adjuvants, and excessive immune responses were not observed. Those antibodies could preferentially recognize Aß 40, and Aß 42 compared to Aß fibrils. The levels of serum anti-Aß antibodies and plasma Aß peptides increased in both animals and decreased the brain Aß 40 level of guinea pigs. The peptide vaccine could induce a similar binding profile of anti-Aß antibodies in cynomolgus monkeys and guinea pigs. The peptide vaccination could be expected to reduce the brain Aß peptides and their toxic effects via clearance of Aß peptides by generated antibodies.

Effects of glucosyl hesperidin on serum lipids in hyperlipidemic subjects: preferential reduction in elevated serum triglyceride level.

Although hesperidin lowers serum total cholesterol (TC) or triglyceride (TG) in animal models, its effect in humans remains unclear. Using a soluble hesperidin derivative, glucosyl hesperidin (G-hesperidin), as a hesperidin source, we examined the efficacy on hyperlipidemic subjects. G-Hesperidin was administered to the subjects at 100 or 500 mg/d for 6 wk. The percentage of subjects who had a change in serum cholesterol levels was less than 20%. However, 45-55% of the total subjects showed a reduction in serum TG level. The subjects were classified into normal (TC<230mg/dL, TG<150mg/dL), high-TC (TC>230 mg/dL, TG<150 mg/dL) and high-TG (TG>150 mg/dL) types. While serum cholesterol levels scarcely changed in any phenotype, TG level was significantly reduced by administration in the high-TG type. In this phenotype, serum apolipoprotein (apo) C-II and E levels decreased by the administration, but non-apo B. G-Hesperidin also raised low-density lipoprotein (LDL)-cholesterol/apo B in the high-TG type. These results indicate that G-hesperidin preferentially lowers serum TG in hypertriglyceridemic subjects and that this effect is possibly caused by the facilitation of catabolism of TG-rich lipoproteins and may contribute to the reduction of small dense LDL.

A novel method for enhancement of peptide vaccination utilizing T-cell epitopes from conventional vaccines.

Peptide vaccines have two fundamental weak points, namely low antigenicity and MHC-restriction. In our previous study, we proposed the design of vaccine peptide to overcome these weakpoints. The vaccine was constructed in the following order, N-terminal, Arg-Gly-Asp (RGD), T-cell epitope peptide, di-lysine linker (KK) to B-cell epitope peptide. Although the vaccine peptide can basically induce B-cell epitope peptide specific antibodies to the host without immune adjuvants via intraperitoneal, subcutaneous and intranasal administration, some peptide antigens require adjuvants for antibody induction. In this study, we propose a novel protocol to enhance the immunogenicity of the peptide utilizing the host immune response to a conventional toxoid vaccine, which are lymphocyte activities to the T-cell epitope peptide. We selected multiagretope-type T-cell epitopes from diphtheria toxoid, a conventional vaccine antigen, and a part of amyloid-beta peptide (Aß) as a B-cell epitope. The conventional toxoid vaccine was immunized before the peptide immunization. Using this protocol, we succeeded in the enhancement of the anti-Aß antibodies induction by intranasal immunization without any immune adjuvants in C57BL/6 and Balb/c mice. Furthermore, the vaccine peptide induced the transformation of peripheral blood lymphocytes collected from healthy volunteers carrying immunities to diphtheria toxoid. These results suggested that our peptide vaccines with the novel protocol would provide an effective method for antibody induction.

Bioavailability of glucosyl hesperidin in rats.

Glucosyl hesperidin (G-hesperidin) is a water-soluble derivative of hesperidin. We compared the absorption and metabolism of G-hesperidin with those of hesperidin in rats. After oral administration of G-hesperidin or hesperidin to rats, hesperetin was detected in sera hydrolyzed with beta-glucuronidase, but it was not detectable in unhydrolyzed sera. Serum hesperetin was found more rapidly in rats administered G-hesperidin than in those administered hesperidin. The area under the concentration-time curve for hesperetin in the sera of rats administered G-hesperidin was approximately 3.7-fold greater than that of rats administered hesperidin. In the urine of both administration groups, hesperetin and its glucuronide were found. Urinary excretion of metabolites was higher in rats administered G-hesperidin than in those administered hesperidin. These results indicate that G-hesperidin presents the same metabolic profile as hesperidin. Moreover, it was concluded that G-hesperidin is absorbed more rapidly and efficiently than hesperidin, because of its high water solubility.

An ingenious design for peptide vaccines.

For humoral immunization, it may be possible to make effective and safe peptide vaccines for various diseases by selection of proper B-cell epitopes. However, a lack of T-cell epitopes on short peptides, such as those associated with major histocompatibility complex (MHC)-restriction, is a major problem for peptide vaccine development. We propose a solution for the design of peptide vaccines that involves induction of broadly reactive T-cell epitopes via agretopes. The strategy involves positioning multi-agretope type peptides on the N-terminal side of a di-lysine linker and B-cell epitopes on the C-terminal side. The addition of the arginine-glysine-aspartate (RGD)-motif to the N terminus of the peptide enhances its immunogenicity, and enables nasal immunization without adjuvants.