Effects of feed restriction on mammary gland development of pubertal mice and the involved mechanisms

Objective  To investigate the effect of feed restriction on mammary gland development of pubertal mice and explore the involved mechanisms, and provide a scientific basis for nutritional regulation during mammary gland development of animals.

Method  Twenty-four 4-week-old C57BL/6J female mice were randomly divided into the control group and feed restriction group. The trial lasted for four weeks. The body weight, feed intake and water intake were recorded weekly, and the body imaging and body composition of mice were examined before the end of the trial. At the end of the trial, the mouse mammary gland was collected and weighed. The blood was collected and the levels of insulin-like growth factor (IGF-1) and estradiol (E2) in serum were measured. The mammary gland development was observed and assessed by using whole-mount staining and the numbers of mammary gland terminal end bud (TEB) and duct branches were analyzed. Immunofluorescence staining was used to detect the expression of proliferating cell nuclear antigen (PCNA) in the mammary gland tissue of pubertal mice.

Result  The body weight, body weight gain, average daily feed intake and average daily energy intake of mice in feed restriction group were significantly lower than those of mice in control group (P<0.001), while the water intake of feed restriction group was significantly higher than that of control group (P<0.05). Feed restriction had no effect on muscle and fat contents. In addition, feed restriction significantly decreased the mammary gland weight by 29%(P<0.05), with no effect on mammary gland index. The results of whole-mount staining showed that feed restriction significantly inhibited the development of mammary gland, with significant lower number of TEB and duct branches (P<0.05). Furthermore, feed restriction significantly reduced the serum level of IGF-1 by 34%(P<0.05), with no influence on serum E2 level. Feed restriction significantly inhibited PCNA protein expression in the mammary gland of pubertal mice.

Conclusion  Feed restriction significantly inhibits mammary gland development of pubertal mice, which might be associated with the decreased level of IGF-1 in serum and expression of proliferation-associated protein PCNA in mammary gland tissue.