Author: Lau Altamiranda, Roxanna Waihan
Title: Immunomodulatory, anti-inflammatory and anti-microbial effects of selected dietary agents : a study using a biomarker approach
Degree: M.Phil.
Year: 2011
Subject: Hong Kong Polytechnic University -- Dissertations
Infection -- Prevention.
Medicine, Preventive.
Anti-infective agents.
Diet therapy.
Herbs -- Therapeutic use.
Department: Department of Health Technology and Informatics
Pages: xviii, 217 p. : ill. (some col.) ; 30 cm.
Language: English
Abstract: There is a well established age-related decline in the protective action of the immune system, and this increases not only risk of infection but risk of cancer. It has been shown that the absolute number of several immune parameters decreases with ageing. These include the absolute number of T lymphocytes subsets and B lymphocytes. Other changes that also occur with ageing can directly affect cells of the immune system. Oxidative stress and glycation for instance are related to the ageing process and these affect DNA, proteins and lipid structures of cells. There is also a worrying increase in antibiotic resistance in both hospital and community acquired infections. Therefore, there is an urgent need for strategies to prevent the age-related decline in immune status, and to boost the compromised immune system. In addition, novel antimicrobial therapies are needed to treat antibiotic resistant infections. Many herbs and dietary agents are reported to have immunomodulatory or anti-inflammatory actions. Some herbs have also been reported to have direct or indirect antimicrobial effects. Multi-dimensional approaches for validating beneficial effects of different herbs/ supplementation on health or body systems are needed. Many studies of well known herbs have been widely carried out in in vitro and animal studies and there is a wide range of anecdotal evidence available. However, there is lack of systematic scientific evaluation showing the effect of herbs on human immune status related to antioxidant balance, and thus controlled intervention trials are needed to determine if the claims of health benefits for these herbs/dietary supplements are justified, and if they have a role in prevention and treatment of increasingly difficult-to-treat infectious disease and age-related immune decline. This study investigated the effect of selected herbs/dietary agents on cellular immunity and its relationship with antioxidant status. The direct and indirect antimicrobial effects (against MRSA strains and VISA strain) of these herbs were also studied. Dietary agents/herbs of interest in this study were Lingzhi (Ganoderma lucidum), bilberry (Vaccinium myrtillus) and green tea (Camellia sinenis). Experimental work included in vitro and controlled human intervention trials.
The methodology for assessing cellular immunity included measurement of immunologic phenotype of lymphocyte sub-sets using monoclonal antibodies against surface antigens of white blood cells by flow cytometry and complete white blood cell count. Plasma antioxidant status was determined by measuring plasma biomarkers [including total antioxidant power, ascorbic acid (FRAP assay) and alpha tocopherol (HPLC)]. Antimicrobial effects were investigated by determining the minimal inhibitory concentration (MIC) of the herbs of interest (alone and in combination with antibiotics) by using the spiral gradient endpoint and the agar dilution method. In the supplementation trials, some potential interesting results were observed in terms of inter-relationships between changes in antioxidant status and changes in some white cell subsets. No convincing evidence of supplementation-related positive effects on white cell numbers and subsets was seen. However, in the green tea study, there was some indication of an anti-inflammatory effect; however variation in the response of hsCRP (inflammation biomarker) was wide. There was some indication of improvement in cytotoxic T cells (CD8+) cells after bilberry supplementation, which could have implications for immune surveillance. In addition, lingzhi was shown to have some potential effect in counteracting the side effects of radiotherapy on cellular immunity. At last, this study provides supporting data showing the potential effect of these natural products as antibacterial agents. Direct antimicrobial effect was found in bilberry (MIC= 0.6 mg/ml), screw-shaped green tea (MIC= 0.6 mg/ml) and loongjin green tea (MIC= 1.2 mg/ml) against MRSA, MSSA and VISA strains. Synergistic effects of lingzhi, bilberry and green tea were found when these were used in combination with oxacillin and vancomycin against VISA and MRSA strains. The outcome of this study relates to the potential health benefits of the dietary agents studied in relation to immune status, antioxidant balance and antimicrobial effects. These data may provide evidence to justify the use of food/herbal supplements for immunomodulation and health maintenance in our ageing population.
Rights: All rights reserved
Access: open access

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