Maternal high fat diet predisposes offspring to obesity and metabolic disorders in later life. However, previous work in rodent models used a limited set of diets. The impacts of graded levels of dietary fat (of fixed composition) on maternal programming have seldom been addressed, and the mechanisms of this effect remain obscure. Here we aimed to assess the influence of maternal dietary fat levels between 8.3% and 66.6% on the milk energy output (MEO) as well as the alterations in the phenotypes of offspring.
We fed lactating Swiss mice a series of customized diets varying in fat content from 8.3% to 66.6%, but with a constant fatty acid composition designed to mimic the western diet. Maternal body weight, food intake and litter mass were measured daily. Daily Energy Expenditure (DEE) was measured during lactating day 14 to 16 using doubly labeled water method to evaluate the MEO.
Offspring of the mothers fed 41.7%, 58.3% and 66.6% fat diets had increased pup masses compared to the 8.3% and 25% ones. Maternal fat content increased in relation to dietary fat levels with those on the 66.6% fat diet having the highest fat content and the 8.3% ones the lowest. Mice on dietary fat content of 41.7% and above consumed more energy [metabolizable energy intake (MEI) (8.3%: 240.4±41.5 KJ/day, 25%: 296±27.2 KJ/day, 41.7%: 382.2±54.6 KJ/day, 58.3%: 371.8±45.8 KJ/day, 66.6%: 360.1±46.5 KJ/day)], had lower DEE (8.3%: 132.4±15.9 KJ/day, 25%: 134.7±8 KJ/day, 41.7%: 128.2±11.2 KJ/day, 58.3%: 118.4±11.5 KJ/day, 66.6%: 113.7±12.6 KJ/day) and thus delivered more milk energy (8.3%: 108±29.5 KJ/day, 25%: 161.3±26.7 KJ/day, 41.7%: 253.9±53.5 KJ/day, 58.3%: 253.4±42.7 KJ/day, 66.6%: 246.5±41.4 KJ/day) to their pups than the ones of 25% and less.
Maternal fat contents of 41.7% and above in lactating mice led to heavier weaned litters with higher body fat content compared to the ones of 25% and less. This was facilitated by increased MEI and decreased DEE resulting in higher MEO.