Dynamic modulation of mitochondrial membrane physical properties and ATPase activity by diet lipid

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Abstract
The relationship of dietary lipid composition to the membrane lipid environment and activity of mitochondrial ATPase in vivo was studied. Rats were fed a polyunsaturated fatty-acid-rich oil (soybean oil) for 12 days, crossed-over to a monounsaturated fatty-acid-rich oil (rapeseed oil) for the next 11 days, then returned to soybean oil for 11 more days. Additional rats were fed either soybean oil or rapeseed oil throughout. Rats fed rapeseed oil had lower rates of ATPase-catalyzed ATP/[32P]Pi exchange than rats fed soybean oil. Arrhenius plots showed higher transition temperature (Tt) and activation energy (Ea) for rats fed rapeseed oil. Switching from soybean oil to rapeseed oil was dynamically followed by changes in the thermotropic and kinetic properties of the mitochondrial ATPase exchange reaction. Returning to soybean oil reversed these changes. The rapid and reversible modulation of Tt caused by a change of the type of fat ingested suggests that membrane physicochemical properties are not under rigid intrinsic control but are continually modified by the profile of exogenously derived fatty acids. Apparently, in vivo the activity of mitochondrial ATPase is in part determined by dietary lipid via its influence on the microenvironment of the enzyme. The rapidity and ready reversibility of changes observed for this subcellular-membrane-bound enzyme suggest that dietary fatty-acid balance may be an important determinant of other membrane functions in the body.