The functional capacity of the mitochondrion is actively regulated to meet the energy requirements of mammalian organisms. The regulation of mitochondrial biogenesis involves multiple transcriptional and signaling pathways that modulate the expression of nuclear and mitochondrial genes that are involved in mitochondrial structure, metabolism and proliferation. The transcriptional co activator, peroxisome proliferator-activated receptor-gamma (PPARy) coactivator-1alpha (PGC-1a) is thought to integrate the molecular regulatory circuitry involved in the transcriptional control of cellular energy metabolism, including mitochondrial function and biogenesis. We have developed a unique transgenic mouse model that over-expresses PGC-1a. Preliminary data suggests this animal exhibits metabolic alterations that are analogous to caloric restriction, which has been shown to alter the aging process and extend lifespan. Thus our hypothesis is over-expression of PGC-1a will have an anti-aging action in mice. Mitochondria have been proposed to be an important link between the age-related accumulation of oxidative damage caused by reactive oxygen species and the alterations of physiological function associated with aging. One of the major actions of PGC-1a is the induction of mitochondrial biogenesis. The first specific aim will therefore be to determine if mitochondrial biogenesis has indeed been induced in skeletal muscle, adipose tissue and liver by measuring mitochondrial enzyme and protein levels utilizing real time-PCR for mRNA and Western blot analysis for protein.
Specific aim 2 will address the question of whether over-expression of PGC-1a has a protective effect against oxidative damage due to mitochondrial production of reactive oxygen species, as caloric restriction does. Oxidative damage of hepatic lipid, DNA and protein will be determined by measuring isoprostane, oxoSdG and carbonyl group formation, respectively.
Specific aim 3 will be a longevity study in which we will determine whether the median life span of the transgenic animals is altered. The long-term objectives of this application are to determine if over-expression of PGC-1a extends the life span of the transgenic animal and, if so, to then determine a mechanism of action for that effect. Insights gained into the mechanisms of life-span extension will increase the likelihood of identifying physiologic or pharmacologic interventions that may enable us to increase human lifespan and/or quality of life. In this context, a better understanding of the molecular processes involved in age-related deteriorative processes, such as oxidative modifications, will uncover approaches for such interventions. ? ? ? ?