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Coculture Analysis of Extracellular Protein Interactions Affecting Insulin Secretion by Pancreatic Beta Cells
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Insulin regulates circulating insulin-like growth factors and some of their binding proteins in lactating cows

M A McGuire1, D A Dwyer, R J Harrell

  • 1Department of Animal Sciences, Cornell University, Ithaca, New York 14853, USA.

The American Journal of Physiology
|October 1, 1995
PubMed

Insights

Insulin significantly impacts growth factors in cows. This study found that insulin infusion increased insulin-like growth factor I (IGF-I) while decreasing insulin-like growth factor II (IGF-II) and specific binding proteins (IGFBP).

Area of Science:

  • Animal Science
  • Endocrinology
  • Metabolic Research

Background:

  • Insulin plays a crucial role in metabolic regulation.
  • Insulin-like growth factors (IGF) and their binding proteins (IGFBP) are key regulators of growth and metabolism.
  • Understanding insulin's effects on IGFs and IGFBPs in lactating animals is important for productivity and health.

Purpose of the Study:

  • To investigate the impact of a hyperinsulinemic-euglycemic clamp on circulating concentrations of IGF-I, IGF-II, and their binding proteins (IGFBP) in lactating Holstein cows.
  • To determine whether insulin directly influences IGF and IGFBP levels or if secondary metabolic changes are responsible.

Main Methods:

  • Four lactating Holstein cows underwent a 4-day hyperinsulinemic-euglycemic clamp.
  • Insulin was infused at 1 microgram/kg body weight/hour, with glucose infused to maintain euglycemia.
  • Blood samples were collected regularly to measure IGFs and IGFBPs using Western blot densitometry.

Main Results:

  • Hyperinsulinemia-euglycemia approximately doubled IGF-I concentrations (145 to 286 ng/ml).
  • Circulating IGF-II concentrations decreased significantly (285 to 180 ng/ml).
  • IGFBP-2 and a 26,000 M(r) IGFBP decreased by 73% and 58%, respectively, while IGFBP-3 remained unchanged.

Conclusions:

  • Insulin administration in lactating cows increases circulating IGF-I levels.
  • Insulin decreases circulating IGF-II, IGFBP-2, and a specific 26,000 M(r) IGFBP.
  • These findings highlight insulin's complex regulatory role in the IGF axis in dairy cattle.

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