Access Type

Open Access Dissertation

Date of Award

January 2013

Degree Type

Dissertation

Degree Name

Ph.D.

Department

Nutrition and Food Science

First Advisor

Smiti Gupta

Abstract

ABSTRACT

THE EFFECT OF PROALGAZYME AND ITS SUBFRACTIONS ON LIPID METABOLISM IN DIET INDUCED HYPERCHOLESTEROLEMIC HAMSTRES:

CORREALTION WITH PLASMA METABOLOMIC PROFILE

by

ANDREEA GEAMANU

December 2013

Advisor: Dr. Smiti Gupta

Major: Nutrition and Food Science

Degree: Doctor of Philosophy

Background: Plasma HDL cholesterol levels are inversely related to cardiovascular disease, which is the leading cause of death worldwide. This study investigated the preventative effect of an algae infusion, ProAlgaZyme (PAZ) and its subfractions (F1, F2, F3, F4) on plasma HDL in a hamster model. Further, the study aimed to identify the biologically active fraction of PAZ and to determine the therapeutic efficacy of the fraction in diet induced hypercholesterolemic hamsters over time. Also, the current study investigated the changes in plasma metabolomic profile produced due to the interventions, and correlated the results with the lipoprotein profile of the hamsters.

Methods: Eighty male golden Syrian hamsters (8 weeks old) were randomized into controls (CW and CP) or high fat diet (HW, HP, HF1, HF2, HF3, and HF4). During the preventative intervention, an infusion of either 5% (HF1, HF2, HF3) or 20% (HP, HF4) concentration (v/v) was administered via the drinking water for 4 weeks, while the hamsters were being fed a high-fat diet (30% of calories from fat). Plasma lipids were assayed and liver samples subjected to reverse transcription polymerase chain reaction (RT-PCR) to determine the relative transcription levels of genes involved in HDL/reverse cholesterol transport metabolism, ie, ApoA1, ABCA1, CETP, and SRB1. Lipid profile was correlated with plasma metabolomic profile using 1D 1H NMR spectroscopy and the biologically active fraction has been identified.

Further, the study aimed to determine the therapeutic effect of the active fraction of PAZ. For this, 40 male Golden Syrian hamsters were fed a high fat diet for 4 weeks prior to randomization into 5 groups, based on the number of days they received the treatment. Thus animals in T3, T7, T10, T14, and T21 groups received the active fraction for 3, 7, 10, 14, and 21 days, respectively, as their drinking fluid. HW group from previous study was considered as control (T0, high fat diet and the active fraction for 0 days) for this study. Plasma lipid profile was assayed enzymatically, while RT-PCR provided the alternative transcription levels of Apolipoprotein (Apo) A1 gene. Plasma metabolomic profile was determined using 1H nuclear magnetic resonance (NMR) spectroscopy and results correlated with the lipid profile of the hamsters.

Results: Non-HDL cholesterol was significantly reduced in the HP (P < 0.05), HF3 and HF4 (P < 0.001) groups as compared with the HW group, while HDL cholesterol showed a significant increase in the HP, HF3, and HF4 groups (P < 0.001). Moreover, the total cholesterol/HDL ratio was significantly improved in the HP, HF1, and HF2 (P < 0.05), and HF3 and HF4 (P < 0.001) groups. Real-time quantitative polymerase chain reaction showed a significant increase in hepatic ApoA1 (HP, HF4) and ABCA1 (HF3, HF4) expression, consistent with an increase in HDL production, biogenesis, and maturation. A two-fold increase in SRB1 expression indicates that HF4 further augments the reverse cholesterol transport mechanism. Reduction of CETP expression (HF4) is consistent with a decrease in the transfer of cholesteryl ester to LDL, further increasing the amount of cholesterol held as HDL particles. NMR metabolomics approach showed a significant decrease in the concentration of several small molecular weight molecules, including branched chain amino acids and phosphocholine-containing molecules, in groups HP and HF4, when compared with HW group. Since, F4 exhibited the most influence on plasma lipid and metabolomic profile, it was further tested for its therapeutic effect.

Plasma HDL was significantly increased in T3 (P < 0.05) and T21 (P < 0.001), while non-HDL cholesterol was significantly reduced in T3, T7, T10 (P < 0.001) and T14, T21 (P < 0.01). Moreover, the total cholesterol/HDL was significantly lower in all groups (P < 0.001) as compared with T0. Quantitative RT-PCR showed an increase in Apo A1 expression in T10 (3x) and T21 (6x) groups. NMR data followed by multivariate analysis showed a clear separation between T0 and T21 groups, indicating a difference in their metabolomic profiles. Plasma concentrations of choline, phosphocholine, glycerol-phosphocholine, betaine and carnitine metabolites were significantly lowered in T21 group. These metabolites are associated with a reduced risk for atherosclerosis and cardiovascular disease.

Conclusion: ProAlgaZyme and its subfractions significantly improved the plasma cholesterol profile by lowering non-HDL and increasing HDL, possibly via the reverse cholesterol transport mechanism. Also, the concentration of several pro-atherogenic small molecular weight metabolites has been decreased, indicating that PAZ and F4 can be used as a preventative agent for hypercholesterolemia and atherosclerosis. Moreover, treatment with F4 also significantly improved plasma lipid profile by increasing HDL and lowering non-HDL cholesterol, and reducing key risk factor metabolites for atherosclerosis and cardiovascular disease.

Download

Share

COinS