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Dietary lipid and postnatal development. II. Palmityl coenzyme A oxidation in heart and liver
Insights
Postnatal dietary lipid content does not affect the cellular capacity for fatty acid oxidation. Rabbit pups fed high-fat or low-fat diets showed no differences in palmityl coenzyme A oxidation rates.
Area of Science:
- Biochemistry
- Mitochondrial Metabolism
- Nutritional Science
Background:
- Perinatal development of fatty acid oxidation pathways is poorly understood.
- Indirect evidence suggests dietary lipids may regulate this development postpartum.
Purpose of the Study:
- To directly investigate the influence of postnatal dietary lipid on fatty acid oxidation capacity.
- To determine if varying lipid intake affects key mitochondrial enzyme activities.
Main Methods:
- Rabbit pups were fed either a low-fat (14.2%) or high-fat (77.6%) diet.
- Palmityl coenzyme A oxidation rates were measured in heart and liver homogenates.
- Cytochrome oxidase activity and respiration supported by glutamate + malate were also assessed.
Main Results:
- No significant differences in palmityl coenzyme A oxidation rates were observed between high-fat and low-fat diet groups.
- Carnitine dependency of oxidation was consistent across groups and similar to mother-fed animals.
- Normalized oxidation rates and cytochrome oxidase activity showed no diet-related variations.
Conclusions:
- Large variations in postnatal dietary lipid proportion do not impact the cellular capacity to oxidize palmityl coenzyme A.
- The study found no evidence that diet influences the rate-limiting steps of fatty acid oxidation beyond acyl activation.
Abstract:
There is only indirect evidence to suggest that the sudden postpartum appearance of dietary lipid regulates the perinatal development of the enzyme pathways required for fatty acid oxidation. To test this idea directly, rabbit pups were maintained on diets containing lipid to equal either 14.2% (LF) or 77.6% (HF) of the total caloric intake. Palmityl coenzyme A oxidation rates in the presence of excess ADP and carnitine were measured polarographically in heart and liver homogenates. No significant difference in oxidation rates between HF and LF groups was observed even at 10 days of age. Palmityl coenzyme A oxidation in both groups was carnitine dependent and was in general the same as that of mother-fed animals. Similarly, an evaluation of cytochrome oxidase activity and glutamate + malate-supported respiration in heart and liver homogenates revealed no difference attributable to diet. To consider the possibility that fatty acid oxidation might be specifically increased or decreased over other mitochondrial respiratory activity as a function of diet, palmityl coenzyme A oxidation rates were normalized with respect to glutamate + malate oxidation rates. A similar comparison was made relative to cytochrome oxidase activity. Still no differences were observed between HF and LF groups. By studying the maximum rate of oxygen utilization in the presence of excess carnitine and palmityl-coenzyme A we would have detected any change in a rate-limiting step for fatty acid oxidation beyond acyl activation. We must conclude, therefore, that large differences in the proportion of postnatal dietary lipid do no influence the cellular capacity to oxidize palmityl coenzyme A.