Doctor of Philosophy
University of Wollongong, Department of Biological Sciences
Withers, Kerry William, Dietary Omega-6 fatty acids in protein-energy malnutrition, Doctor of Philosophy thesis, University of Wollongong, Department of Biological Sciences, University of Wollongong, 1993. http://ro.uow.edu.au/theses/1044
This thesis examines protein-energy malnutrition (PEM) in rats and the influence of omega-6 polyunsaturated fatty acids (PUFA) on this condition.
In the first of three experiments, rats were assigned to one of four diets, which were all isoenergetic and contained 10% (w/w) fat. One group was fed a control diet (containing 22% w/w protein) ad libitum., the other three diets were reduced in protein (10% w/w ). and at one third the food consumption rate of the control diet rats. These three PEM groups received different amounts of PUFA. Almost all of the PUFA in the diets was Hnoleic acid. The minimum proportion of dietary energy intake supplied by tinoleic acid in the diets was 1.3%. Stearic acid, was chosen to complete the lipid component. Growth, basal metabolic rate and nitrogen and energy balance were determined and tissues analyzed and ion homeostasis examined. Apparent absorption of energy and nitrogen were dramatically reduced in the diet high in stearic acid. A second experiment indicated that substituting coconut oil for stearic acid removed this effect.
In a third experiment, different oils were used, dietary fat content was increased to 15% w/w, the diets were commenced at weaning and the experimental period was extended from six to eight weeks.
Food-restriction lead to a reduced metabolisable energy (as a % of energy intake) and retarded growth. Brain, and the digestive tract were more resistant to growth retardation than the female reproductive organs, skin, fur and spleen. Brain was also less susceptible to changes in composition than other tissues.
PEM reduced apparent absorption of energy and nitrogen, retarding growth to a greater extent than food-restriction. It also increased carcass water content. Increased dietary tinoleic acid seemed to ameliorate some of these effects, notably growth and body water content. Much of the PUFA-induced increased growth was in skin and fur. Net protein utilization improved in PEM, especially with PUFA The PUFA diet gave rise to no obvious negative effects.
Numbers of sodium pumps in soleus muscle and erythrocytes were not affected by food-restriction or PEM. However, they were reduced in erythrocytes during PEM by PUFA. The extracellular compartment of soleus muscle was increased by food-restriction and to a greater extent by PEM. PUFA tended to reverse this effect.
The increases in growth and protein assimilation, combined with a reduced body water content indicate that increased dietary Hnoleic acid during PEM is beneficial. The possible implications of this work on rats for human PEM are, that more attention should be paid to the nature of lipids given during recovery from malnutrition and that the mechanistic differences between kwashiorkor and marasmus m a y be related to essential fatty acid deficiency.
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