Testosterone deficiency and dietary therapeutic interventions in the rat model of diet-induced metabolic syndrome

PhD Thesis


Kumar, Senthil Arun. 2014. Testosterone deficiency and dietary therapeutic interventions in the rat model of diet-induced metabolic syndrome. PhD Thesis Doctor of Philosophy. University of Southern Queensland.
Title

Testosterone deficiency and dietary therapeutic interventions in the rat model of diet-induced metabolic syndrome

TypePhD Thesis
Authors
AuthorKumar, Senthil Arun
SupervisorBrown, Lindsay
Kauter, Kate
Institution of OriginUniversity of Southern Queensland
Qualification NameDoctor of Philosophy
Number of Pages238
Year2014
Abstract

Male Wistar rats fed with high carbohydrate (68%) and high fat (24%) diet (H) mimicking 'Western diets' showed enhanced visceral obesity and its associated risk factors of metabolic syndrome such as impaired glucose utilisation, insulin resistance, hypertension, cardiovascular stiffness, collagen deposition, endothelial dysfunction, inflammation of heart and liver, dyslipidaemia and non-alcoholic fatty liver disease compared to low fat (8%) cornstarch diet (C) fed rats. Lowered total testosterone concentrations (2.5-5.8 ng/mL) in castrated rats induced by surgical or chemical castration (leuprolide acetate 2mg/kg body weight every four weeks), showed increased abdominal obesity and its associated metabolic risk factors in response to H diet; thus, testosterone plays a crucial role in regulating abdominal obesity associated metabolic disorders in men.
Current treatments for obesity are aimed at modifying dietary patterns, eating habits and proper workout or physical exercise to increase calorie expenditure and lowering calorie intake. I have investigated the therapeutic effects of seaweeds (Ulva ohnoi, Derbesia tenuissima), microalgae mixture (Scenedesmus dimorphus and Schroederiella apiculata), mineral ions (Mg++, K+) and dietary fibre (inulin and oligofructose) as food-based interventions in rats fed H diet. Ulva ohnoi and Derbesia tenuissima attenuated the metabolic symptoms observed in H fed rats; both seaweeds are rich in dietary polysaccharides (23.4-40.9% of dry algae). Compared to Derbesia tenuissima, Ulva ohnoi contained higher amount of soluble polysaccharides (18.1% vs <0.1 % of dry algae) and lowered total body fat mass by 24% which may be attributed to the inhibition of intestinal absorption of fatty acids. In addition higher magnesium content of UO (4.1% vs 1.3% of dry algae) suggested improving the glucose utilisation. Further, insoluble polysaccharides (19.6% of dry algae) supplementation of microalgae mixture showed increased lean mass and attenuated the visceral adiposity-induced metabolic syndrome in H fed rats, which may be due to the faecal bulking effect associated with increased hepatic and skeletal muscle β-oxidation of fatty acids.
Magnesium treatment specifically increased the faecal lipid excretion by 4.5% suggesting the ability of this divalent cation to form insoluble salt complexes with fatty acids and prevent their intestinal absorption as potential mechanism for reduction in abdominal (53%) and total body fat mass (44%) in H diet fed rats showed a complete reversal of metabolic syndrome. Treatment with 2% potassium chloride in H diet fed rats showed no significant effect on obesity but attenuated the H diet-induced metabolic risk factors which may be due to the increased (38%) circulating concentrations of magnesium. Increased faecal load (1.6 g/12h) and lipid excretion (5.4%) detected with 5% soluble fibre (inulin and oligofructose) mixture supplementation serves as the possible potential mechanism in preventing the abdominal obesity and its associated metabolic syndrome in the H diet fed metabolically sick obese rats. Thus, functional foods including seaweeds and microalgae that are rich in important mineral ions (magnesium and potassium) and fibre (dietary polysaccharides) may attenuate obesity-linked metabolic syndrome.

Keywordstestosterone, deficiency, intervention, rat, metabolic, syndrome, diet-induced
ANZSRC Field of Research 2020429999. Other health sciences not elsewhere classified
Byline AffiliationsSchool of Health and Midwifery
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