Effect of Initial Aging and High-Fat/High-Fructose Diet on Mitochondrial Bioenergetics and Oxidative Status in Rat Brain

Middle age is an early stage of the aging process, during which the consumption of diets rich in saturated fats and/or simple sugars might influence brain function, but only few data are available on this issue. We therefore investigated the impact of a diet rich in saturated fat and fructose (HFF) on mitochondrial physiology in hippocampus and frontal cortex of middle-aged rats (1 year old), by including a group of adult rats (90 days) as a "negative control," lacking the putative effect of aging. Middle-aged rats were fed HFF or control diet for 4 weeks. Mitochondrial function was analyzed by high-resolution respirometry and by assessing the amount of respiratory complexes. Markers of oxidative balance, as well as the protein content of uncoupling protein 2 (UCP2), peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1 alpha), and peroxisome proliferator-activated receptor alpha (PPAR alpha), were also assessed. A decrease in the activity of complex I was detected in both brain areas of middle-aged rats. In hippocampus, mitochondrial respiratory capacity and complex IV content decreased with age and increased with HFF diet. Higher protein oxidative damage, decreased antioxidant defenses, and increased UCP2 and PGC-1 alpha content were found in hippocampus of middle-aged rats. HFF feeding induced a significant reduction in the amount of UCP2, PGC-1 alpha, and PPAR alpha, together with higher protein oxidative damage, in both brain areas. Overall, our results point to middle age as a condition of early brain aging for mitochondrial function, with hippocampus being an area more susceptible to metabolic impairment than frontal cortex.