The Membrane Theory of Aging proposes that lifespan is inversely related to the
level of unsaturation in membrane phospholipids. Calorie restriction (CR) without
malnutrition extends lifespan in many model organisms, which may be related to alterations
in membrane phospholipids fatty acids. During the last few years our research focused on
studying how altering the predominant fat source affects the outcome of CR in mice. We
have established four dietary groups: one control group fed 95% of a
pre-determined ad libitum intake (in order to prevent obesity), and three
CR groups fed 40% less than ad libitum intake. Lipid source for
the control and one of the CR groups was soybean oil (high in n-6 PUFA) whereas the two
remaining CR groups were fed diets containing fish oil (high in n-3 PUFA), or lard (high
in saturated and monounsaturated fatty acids). Dietary intervention periods ranged from 1
to 18 months. We performed a longitudinal lifespan study and a cross-sectional study set
up to evaluate several mitochondrial parameters which included fatty acid composition,
H+ leak, activities of electron transport chain enzymes, ROS
generation, lipid peroxidation, mitochondrial ultrastructure, and mitochondrial apoptotic
signaling in liver and skeletal muscle. These approaches applied to different cohorts of
mice have independently indicated that lard as a fat source often maximizes the effects of
40% CR on mice. These effects could be due to significant increases of
monounsaturated fatty acids levels, in accordance with the Membrane Theory of Aging.