Maternal low-protein diet affects bone mass and mineral metabolism in suckling rats

This study was performed to analyse the effects of low-protein diet (7%) on bone mass and mineral metabolism in rat pups whose mothers were submitted to protein-restricted diet during late pregnancy and early post-natal periods. For this purpose, 12 pregnant Wistar rats were divided into two groups of six animals each: a control group with free access to standard diet (20% protein) and protein-restricted group (PR) fed with low-protein diet (7% protein) from the 14th day of pregnancy until day 14 after delivery. Body weight, femur bone mass, plasma thyroid hormones (FT4 and FT3), biochemical bone marker levels [alkaline phosphatase (ALP), tartrate-resistant acid phosphatase (ACP)] and bone DNA content were recorded. In undernourished pups, a decrease in body weight (-47%, p < 0.001) in skeletal growth (-11%, p < 0.001) and in bone DNA content (-48%, p < 0.001) were observed. Plasma protein and albumin levels and thyroid status were also decreased in undernourished rat pups compared with those of control group. The circulating amino acid levels were decreased in pups. While in their mothers, some of them were increased and the others were decreased. A positive correlation was observed between bone mass and plasma thyroid hormone levels and ALP activity and plasma protein levels, and a negative correlation with ACP activity. Plasma ALP levels were decreased by 19%, whereas plasma tartrate-resistant ACP levels were increased by 33% indicating a hyperactivity of bone remodelling. These results showed that protein-restricted diet given to mothers during late pregnancy and early post-natal periods induced changes in body weight, skeletal growth and bone metabolism in their offspring.