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The Effects Of Feeding Triacylglycerols On Milk Fat Composition, Lipogenesis And Polymer-Protomer Transition Of Acetyl-Coa Carboxylase In Rat Mammary Gland
Oben, JE; Ngondi, JL; Agbor, GA & Enonchong, E
Abstract
Diets rich in fats produce large quantities of milk with high lipid concentrations, which
may be important for the growth of neonates. The present study investigates the effect
of different fat enriched diets on mammary gland lipogenesis in lactating rats. Rats were
fed for 6 weeks during pregnancy through to mid-lactation with diets containing chow
supplemented with 20% (w/w) coconut oil, olive oil or corn oil. The control animals
were fed with a low fat (0.5%, w/w) diet, or with chow (6.8%, w/w fat). Rats fed either
the 20% (w/w) olive oil-supplemented diet or the 20% (w/w) corn oil-supplemented
diet produced milk with significantly lower total fat concentrations (p<0.05) than rats
fed the low-fat (0.5% (w/w) corn oil) control diet or with chow (6.8% (w/w) fat. Rats on
the olive oil- and corn oil-supplemented diets produced milk that had significantly
lower concentrations of total fat and of C8:0 - C18:0 fatty acids and higher
concentrations of C18:1 - C18:3 acids compared to the low-fat diet, chow, or the
coconut oil-supplemented diets. Compared with the low-fat control diet, all the other
dietary regimes suppressed overall fatty acid synthesis in both the lactating mammary
gland and liver, with the highest suppression being produced by the olive oil- and corn
oil-supplemented diets on mammary fatty acid synthesis. Measurements of the total
activity in the mammary gland of the rate-limiting enzyme, acetyl-CoA carboxylase,
and of the proportions of the polymeric (active) and protomeric (inactive) forms of this
enzyme, showed that the total activity decreased in parallel with the overall rate of fatty
acid synthesis. This trend was, however, not noticed for fatty acid synthetase (another
lipogenic enzyme). By contrast, a constant proportion of polymeric to protomeric
forms was maintained at mid-lactation irrespective of the diet, indicating a possible role
of prolactin in mammary gland acetyl-CoA carboxylase polymerization. This study,
therefore, showed that the fatty acid composition of the diet as well as hormones
involved in lactation may affect mammary gland and liver fatty acid synthesis, through
a modification of the rate limiting enzyme of fatty acid synthesis – acetyl-CoA
carboxylase.
Keywords
Acetyl-CoA carboxylase, milk fat, lipogenesis
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