Chang liver cell line as a model for Type II Diabetes in the liver and possible reversal of this condition by an indigenous medicinal plant
- Authors: Williams, Saralene Iona
- Date: 2009
- Subjects: Diabetes -- Alternative treatment , Medicinal plants , Traditional medicine , Liver -- Diseases
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10339 , http://hdl.handle.net/10948/d1016179
- Description: The incidence of Type 2 Diabetes Mellittus (T2DM) is increasing world wide. In Africa the limited access to health care and the insidious course of the disease lead to more severe illness and diabetic complications. There is a need to find alternative approaches to treatment and prevention that address the problems and needs of Africa. Sutherlandia frutescens (S.frutescens) is a traditional herbal plant with known anti-diabetic properties, the precise mechanism of action of S.frutescens is not known. In order to develop new approaches for treatment and prevention of T2DM the pathophysiology of T2DM must be understood. T2DM is the final outcome of a multi-organ disease characterized by early defects in muscle, adipocytes, hepatocytes and pancreatic β-cells. In this study the role of the liver was investigated because of its central role in glucose and lipid metabolism. It is hard to differentiate between all the influences in an in vivo model, so the aim of this study was to develop an in vitro model of T2DM in Chang liver cells and to determine if S.frutescens can reverse the state of insulin resistance in this model. Different culture media conditions were screened to identify a method that can be used as the T2DM model in Chang liver cells. Serum free medium (MCBD-201) supplemented with human diabetic serum, (2.5%-10%), high insulin concentrations (0.1μM-1μM), high fructose concentrations (1-10mM). and a combination of high insulin and high fructose was used for this screening. Chang liver cells cultured in MCBD-201 medium supplemented with 1mM fructose and 0.1μM insulin showed reduced glucose uptake and increased lipid accumulation. The effect of two S.frutescens extracts, two anti-diabetic drugs, metformin and ciglitazone, and a hypolipidemic drug ciprofibrate were determined and shown to increase glucose uptake and reduce lipid accumulation. It was postulated that exposing the cells to excess nutrients in the form of high fructose would stimulate the cells to become adipogenic and accumulate lipids, which would interfere with the glucose uptake and induce insulin resistance. Gene expression of PPARγ, PPARα, and SREBP-1 transcription factors regulating lipid metabolism was determined in Chang liver cells cultured in insulin resistance inducing medium over a 48 hour time course. The expression of PPARγ, known to stimulate adipogenesis was increased after 6, 24 and 48 hours of exposure (P(H1)<0.0001). The expression of PPARα, known to stimulate β-oxidation expression, was significantly decreased after 24 hours of exposure (P(H1)<0.0001). The presence of the plant extracts in the insulin resistance inducing media protect against this increase in adipogenesis and decrease in β-oxidation after 48 hours of exposure by increasing PPARα expression and decreasing PPARγ expression. A PCR Array was performed which identified 32 more potential molecular targets of S.frutescens. Five of the 32 targets identified with the PCR Array were validated using qRT-PCR. These genes play a role in lipid and glucose metabolism and protection against oxidative stress and inflammation. In summary a cellular model of insulin resistace in hepatocytes has been established and the capacity of S.frutescens to reverse this process has been demonstrated by acting as a dual PPARγ/α agonist. New genes have been identified in the development of insulin resistance and as targets of S.frutescens.
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- Date Issued: 2009
The effect of tulbaghia violacea plant extract on the growth of aspergillus species
- Authors: Belewa, Xoliswa Vuyokazi
- Date: 2009
- Subjects: Plant products , Plant extracts , Traditional medicine
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10315 , http://hdl.handle.net/10948/d1008186 , Plant products , Plant extracts , Traditional medicine
- Description: Traditional medicine has become an important part of healthcare worldwide. It is estimated that about 25 percent of prescribed medicines contain plant products or active compounds derived from plants. In South Africa, traditional medicine forms part of the culture and tradition of most communities. Garlic compounds have been shown to have a variety of antimicrobial properties. Amongst these are antifungal, antibacterial, antiviral and anti protozoal activities. Allicin and its breakdown products have been shown to be the main active compounds which possess these properties. Tulbaghia violacea has been used for the treatment of a variety of illnesses including asthma, fever, oesophageal cancer, constipation and hypertension. This study investigated the antifungal nature of T.violacea on the morphology, spore germination and lipid synthesis of Aspergillus flavus and Aspergillus parasiticus. The results of this study showed that the plant extract inhibited A. flavus growth at a minimal inhibitory concentration of 15mg/ml and was fungicidal at 20mg/ml and above. A. parasiticus was not inhibited at 25mg/ml indicating resistance to the inhibitory component of the plant extract. A measure of metabolic activity using the XTT assay showed reduced metabolic activity in the presence of increasing concentrations of the plant extract. Higher extract concentrations resulted in higher percentage inhibition of fungal growth for both fungal species with up to 98 percent inhibition being observed for the highest extract concentrations for both fungi. Germination was also delayed in the presence of 15mg/ml plant extract concentration by up to 60hr for A. flavus and 48hr for A. parasititcus. The TEM results showed increased thickening of the cell wall with higher extract concentrations. The thickening was greater for A. flavus than for A. parasiticus. Cell wall thickening may be the reason for the delay in germination in both species. Lipid production was reduced in the presence of plant extracts when compared to the control. The plant extracts inhibited triglyceride production at 15mg/ml for both A. flavus and A. parasiticus. The results therefore indicate that T. violacea extracts are antifungal and probably affect germination through interactions with the cell wall. It is possible that the extract affects lipid production in Aspergillus species.
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- Date Issued: 2009