Effects of the type of dietary fat at two levels of vitamin E in Wistar male rats during development and aging. IV. Biochemical and morphometric parameters of the heart

The object of this study was to explore the possible influence of the type of dietary fat at two extreme levels of vitamin E on several biochemically determined changes in the whole brain as well as on a number of quantitatively analyzed ultrastructural variations with age in neurons of the dorso-lateral parietal cortex and in the cerebellar Purkinje cells. For this purpose, six groups of weaning Wistar male rats were fed ad libitum isoenergetic diets containing similar amounts (15 g per 100 g of diet) of saturated fat (coconut oil), unsaturated fat (safflower oil) or a combination of both at two levels of dl-α-tocopherol (2 or 200 mg per 100 g of diet). The determinations were carried out in rats killed at 3, 6, 12, 18 and 24 months. Although in relation to age and irrespective of the type of diet several of the biochemical parameters significantly fluctuated with time, comparisons of the results between the youngest and oldest rats showed no changes in the concentration of RNA, triglycerides, phospholipids, cholesterol and collagen, a significant increase in DNA and vitamin E, and a significant decrease in total protein. While in vitro lipoperoxidation of whole brain homogenates (malonaldehyde production) increased from 3 to 18 months, there was a precipitous decline at 24 months. None of these biochemical changes were consistently influenced by the type of diet. In vivo peroxidation in the total lipids of the whole brain (conjugated dienes) was never observed in rats fed the saturated fat diets and was only detected at 6, 12 and 18 months in some of the rats fed unsaturated or combined fat diets. At 24 months, however, none of the rats from the various dietary groups showed in vivo lipoperoxidation. It would appear that the dietary levels of vitamin E had no effect on the extent of in vivo lipoperoxidation in rats fed the unsaturated fat diets but may have had some preventive effect in rats fed the combined fat diets for 18 months. The possible nosologic implications, if any, of the eventual occurrence of in vivo lipoperoxidation remained uncertain since no correlation could be found between this phenomenon and the other biochemical and morphometric parameters. In the cerebral cortex, the numerical density of neurons, astrocytes and dark oligodendrocytes did not change with age, but microglial cells increased and light oligodendrocytes significantly decreased. No major quantitative variations were found in mitochondria and rough endoplasmic reticulum of cortical neurons with age. The numerical density of Purkinje cells decreased with age and, while in these cells the numerical density of mitochondria decreased, the fractional volume of these organelles as well as the density of rough endoplasmic reticulum remained unchanged with age. The fractional cytoplasmic volume of lipofuscin significantly increased almost linearly with time in cortical neurons and Purkinje cells. While no correlation was found between lipofuscin accumulation in the cerebral cortical neurons and the variations in the other morphometric parameters of these cells, a highly significant negative correlation was detected between the increment of lipofuscin and the decrement of Purkinje cell number (r = −0.96) as well as with the decrement in the number of mitochondria in these cells (r = −0.90), suggesting a possible deleterious effect of this pigment. None of the morphometric parameters, including lipofuscin, were clearly influenced by either the type of dietary fat or by the levels of vitamin E.