Influence of genotype and gender on receptor binding affinity (Kd) for insulin and insulin receptor concentration in skeletal muscle and adipose tissue of growing lambs

Abstract

AbstractDifferences in receptor binding affinity for insulin, and insulin receptor concentration, were found in skeletal muscle and adipose tissue of lambs differing in genotype and gender. The Rouge de l’Ouest lamb genotype had a lower receptor affinity for insulin in m. rectus capitis skeletal muscle compared with both Dutch Texel and Greyface lamb genotypes (P < 0·01). Insulin receptor concentration in m. longissimus dorsi skeletal muscle was greater in the Texel lamb genotype compared with both the Greyface (P < 0·001) and Rouge de l’Ouest (P < 0·05) lamb genotypes. Insulin receptor concentration in perirenal fat tissue was greater in the Rouge de l’Ouest lamb genotype compared with the Texel lamb genotype (P < 0·05).There were no differences in receptor affinity for insulin between individual tissues in male and female lambs. The concentration of insulin receptors in male lambs was greater in m. longissimus dorsi (P < 0·05), subcutaneous adipose tissue (P < 0·05) and perirenal fat (P < 0·001) compared with female lambs. Receptor affinity for insulin in individual tissue depots also demonstrated significant genotype ✕ gender interactions. M. longissimus dorsi had a lower receptor affinity for insulin in Texel male lambs compared with Greyface male lambs (P < 0·05). M. rectus capitis had a lower receptor affinity in Rouge de l’Ouest male lambs compared with Texel male lambs (P < 0·01). M. rectus capitis also had a lower receptor affinity for insulin in Rouge de l’Ouest female lambs compared with both Texel and Greyface female lambs (P < 0·01). Within individual genotypes, m. longissimus dorsi had a lower receptor affinity for insulin in Greyface female lambs compared with Greyface male lambs (P < 0·05) whereas m. rectus capitis had a lower receptor affinity for insulin in Texel female lambs compared with Texel male lambs (P < 0·05).Such differences in tissue receptor affinity for insulin and receptor concentration in lambs differing in genotype and gender could, through effects on tissue sensitivity and/or responsiveness to insulin, manipulate nutrient partitioning between skeletal muscle and fat tissue and hence control, at least in part, the efficiency of lean meat production.