Alterations in the gastrocnemius muscle of undernourished suckling rats

Abstract

Protein-energy undernutrition (PEU) during both the gestational and suckling periods causes a reduction in muscle fiber cross-section and a delay in fiber type differentiation. Such changes are not found when PEU occurs after the suckling period. To elucidate the consequences of PEU on muscle during the suckling period, we undernourished (UND) newborn rats by reducing their food intake, including a 6-hour fast every day, and doubling the number of pups suckled by the nursing rat. At day 24 of life, the gastrocnemius muscle showed a discrete reduction in lipids in the fibers of 5 control rats, and in 15 UND rats (P < 0.001). The type 2a and 2b fibers of the UND rats showed a smaller cross-sectional area than control rats (P < 0.05). The distribution frequency histogram for the muscle fibers was skewed to the left in the undernourished rats, and this was significant for type 2a and 2b fibers. PEU during the suckling period may thus induce a delay in muscle fiber maturation but does not produce significant structural alterations.

Maternal protein restriction during pregnancy and lactation affects the development of muscle fibers and neuromuscular junctions in rats

“…Some muscle fibers are not completely formed at birth and are considered undifferentiated. These primitive muscle fibers are known as fetal or type IIc fibers, and are smaller than the remaining fibers …”

Morphological and Morphometric Study of the Muscle Fibers and Neuromuscular Junctions of the Extensor Digitorum Longus in Aged Rats Submitted to Maternal Protein Restriction

“…Other studies with rats subjected to protein restriction have also reported a smaller areas in all fiber types (Nascimento et al, 1990;Silvado & Werneck, 2006;Yan et al, 2012). The literature indicates that protein restriction can compromise the area of type II fibers more than that of type I fibers (Bedi et al;Chopra et al, 1987;Wilson et al, 1988;Dwyer & Stickland, 1992;Oliveira et al;Alves et al).…”

Is the maturation of monosynaptic stretch reflex in rats affected by neonatal malnutrition?

“…A number of studies have demonstrated that malnutrition is able to alter muscle development and structure. 28,29 Through the analysis of biomechanical aspects of muscle, it was found that malnutrition can alter muscular performance in adult rats, even when imposed for short periods, by altering characteristics such as tension, relaxation and fatigue. 30 It remains to be seen whether the elastic properties of tendons and other structures linked to the muscle spindles are also altered by malnutrition, contributing to the lower T-reflexes.…”