Glucose Tolerance and Related Factors in Dogs Fed Diets of Suboptimal Protein Value

Abstract

Littermate dogs were fed from weaning on high-protein diets (HP) or on dietswhich were adequate in calories but marginally deficient in protein (LP). The LP animals grew at a slightly retarded rate but showed no other outward abnormality. In the HP animals, intravenous glucose tolerance (K) increased steadily up to twelve months of age (K = 6) and then declined to the adult value (K = 4.7). These changes were accelerated and exaggerated in LP dogs so that, from seven months onwards, the K values for the LP dogs became progressively lower than those of their HP littermates. Although the LP diet was adequate for adult maintenance and other biochemical signs of proteincalorie deficiency were corrected in the adult, glucose tolerance remained impaired (mean K for HP adults = 4.7 and for LP adults = 3.3). In the LP dog decreasing glucose tolerance was associated with increasing resistance to exogenous insulin. During pregnancy, the HP animals showed an early increase in K followed by a progressive fall. The LP animals showed little change in K during pregnancy, but after lactation both glucose tolerance and sensitivity to insulin increased. Pups born to LP mothers showed signs of congenital malnutrition; they also showed greatly enhanced glucose tolerance in early life. Young dogs, whether fed HP or LP diets, showed rapid impairment of glucosetolerance when acutely infected with toxocara canis. The findings for dogs are compared with those reported in human diabetes mellitus.