Muscle fibre length and bone length in adult mice during dietary restriction and refeeding

Abstract

The dietary intake of male mice was restricted to 70% by weight of the ad lib intake of control littermates between days 75 and 96 post partum. Eight mice were killed at 96 days of age and compared with controls. A further group of eight mice then resumed ad lib feeding until they had regained the control body weight, when they were killed and also compared with controls. Muscle weight, fibre length, sarcomere length and sarcomere number per fibre were measured in the biceps brachii and tibialis anterior muscles. The lengths of the femur, tibia, humerus and radius were measured and remained unchanged throughout the study. Muscle weight, fibre length and the number of sarcomeres per fibre were significantly reduced in both muscles following dietary restriction but regained their control values after a return to normal feeding. Sarcomere length remained unchanged throughout the study. The pattern of fibre length changes, due entirely to alterations in sarcomere number, is similar to that reported in young mice. The reduction in sarcomere number during dietary restriction was due to a loss of established sarcomeres.