Serum insulin-like growth factor (IGF)-I concentrations are reduced by short-term dietary restriction and restored by refeeding in domestic cats (Felis catus).
Nutritional modulation of insulin-like growth factors (IGF) and their binding proteins (IGFBP) is well established. The effect of nutritional restriction on the serum IGF/IGFBP system of adult cats was investigated to evaluate serum IGF-I as a biochemical marker of nutritional status. Assays for measuring feline serum IGF and IGFBP were validated and normal ranges established in a study population of 46 healthy nonobese adult cats. Serum concentrations of IGF-I and IGF-II correlated significantly with body weight (r = 0.75, P < 0. 0001 and r = 0.34, P < 0.03, respectively). Serum IGFBP profiles were similar to other species, including humans, dogs and guinea pigs. IGFBP-3 was the predominant binding protein reflecting IGF-I concentrations and body size. Serum IGFBP-2 concentrations were high relative to the normal human serum pool (NHS) control. Food withdrawal for 18 h followed by refeeding did not alter circulating IGF or IGFBP concentrations, including IGFBP-1, in nine cats. Short-term dietary restriction of nine adult cats to supply initially 56% (56%M) and then 42.5% (42.5%M) of calculated maintenance energy requirements for 14 d resulted in a significant weight loss (P < 0.01). However, serum IGF-I concentrations fell significantly (-51%, P < 0.01) only with 42.5%M restriction. Serum IGF-II, IGFBP, insulin and albumin concentrations were not altered during the study. We conclude that nutrition does modulate the adult feline IGF/IGFBP system, but to a lesser extent than in other species. Further evaluation is required before serum IGF-I can be used for the assessment of nutritional status in adult cats.
Maxwell
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A
Department of Endocrinology, St. Bartholomew's Hospital, London EC1A 7BE, UK.
Butterwick
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R
Batt
R M
RM
Camacho-Hübner
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C
D000818:Animals; D001345:Autoradiography; D015415:Biomarkers; D002415:Cats; D002149:Energy Intake; D005260:Female; D005502:Food; D005508:Food Deprivation / Q000502:physiology*; D018969:Insulin-Like Growth Factor Binding Proteins / Q000097:blood*; D008297:Male; D009752:Nutritional Status; D013002:Somatomedins / Q000378:metabolism*
D015415:Biomarkers; D018969:Insulin-Like Growth Factor Binding Proteins; D013002:Somatomedins