Effect of chronic consumption of a high-fat diet on mammary metabolism

Rapid and selective manipulation of milk fatty acid composition in mice through the maternal diet during lactation

Dietary fatty acid (FA) composition in early postnatal life can modulate growth and development and later metabolic health. Investigating programming effects of early dietary FA manipulations in rodents may be stressful and complicated due to the need of artificial feeding techniques. It is largely unknown to what extent breast milk (BM) FA composition can be directly manipulated by the diet. We exposed dams to different dietary FA compositions from postnatal day (PN) 2 until PN28. Dams with litters were randomly assigned to control (CTRL), high-medium-chain FA (MCFA), low-linoleic acid (LowLA), high-n-3 long-chain PUFA (n-3LCP) or high-n-3LCP and MCFA (n-3LCP/MCFA) diets, and diets were continued after weaning until PN28. FA compositions were determined in feeds, milk and in erythrocytes. BM MCFA content was independent from dietary MCFA intake. In contrast, the LowLA diet reduced BM LA content by about 50 % compared with the CTRL diet at PN7. BM of dams fed the n-3LCP or n-3LCP/MCFA diet contained about 6-fold more n-3 LCP than BM of the dams fed the CTRL diet at PN7. These changes in milk FA composition established after 5 d of dietary exposure did not further change over the lactation period. At PN28, the erythrocyte FA composition of the male pups correlated with analysed milk FA profiles. In conclusion, manipulation of the diet of lactating mice can strongly and rapidly affect BM FA composition, in particular of n-6 LA and n-3 LCP. Our present findings will facilitate mechanistic studies on the programming of adult metabolic health by dietary FA in the early postnatal period via direct and selective manipulation of the maternal diet.

Regulation of milk lipid secretion and composition

Triacylglycerols make up 98% of the lipid content of milk, ranging in different species from 0 to 50% of the total milk volume. The fatty aid composition of the triacylglycerols depends on the species, the dietary fatty acid composition, and the carbohydrate-to-lipid ratio of the diet. The rate of lipid synthesis in the lactating mammary gland depends on the stage of mammary development and is decreased by fasting and starvation in ruminants and rodents but not in species that fast during lactation, such as seals and hibernating bears. Regulatory agents include insulin, prolactin, and non-esterified fatty acids. Dietary trans fatty acids may depress milk lipid synthesis under certain conditions. Evidence is presented that fatty acids may play a major regulatory role in acute changes in de novo mammary fatty acid synthesis, acting primarily on the activity of acetyl coenzyme A carboxylase.

Alterations in the activities of rat tissue hexose monophosphate dehydrogenases in response to premature weaning and dietary restriction at mid-lactation

The activities of the hexose monophosphate dehydrogenases increased in adipose tissue, remained unchanged in liver and decreased in mammary gland following the weaning of rats at mid-lactation (day 14). When dietary intake was restricted at mid-lactation, the activities of the hexose monophosphate dehydrogenases increased in adipose tissue, decreased in liver, but were unaltered in mammary gland. Premature weaning on day 14 postpartum resulted in maternal increases in both plasma insulin and glucose, which peaked at day 16. The plasma insulin levels decreased from day 14 to day 18 postpartum in the normal lactating rat, and a similar trend was observed for animals on a restricted dietary intake. Daily food consumption in the lactating rat decreased from 50 g to 20 g after premature weaning. The live weight of pups raised on dams given a restricted food intake from day 14 had decreased by day 17 postpartum, whereas an increase in daily live weight gain was recorded for the litters from the lactating controls. The results demonstrate that the activities of the hexose monophosphate dehydrogenases are regulated differentially between tissues of the lactating rat.