Glucagon, insulin, adrenocorticotropic hormone, and cortisol in response to carbohydrates and fasting in healthy neonatal foals.

Abstract

BACKGROUND\nThe endocrine pancreas and hypothalamic-pituitary-adrenal axis (HPAA) are central to energy homeostasis, but information on their dynamics in response to energy challenges in healthy newborn foals is lacking.\n\n\nOBJECTIVES\nTo evaluate glucagon, insulin, ACTH, and cortisol response to fasting and carbohydrate administration in healthy foals.\n\n\nANIMALS\nTwenty-two healthy Standardbred foals ≤4\u2009days of age.\n\n\nMETHODS\nFoals were assigned to fasted (n = 6), IV glucose (IVGT; n = 5), PO glucose (OGT; n = 5), and PO lactose (OLT; n = 6) test groups. Blood samples were collected frequently for 210\u2009minutes. Nursing was allowed from 180 to 210\u2009minutes. Plasma glucagon, ACTH, serum insulin, and cortisol concentrations were measured using immunoassays.\n\n\nRESULTS\nPlasma glucagon concentration decreased relative to baseline at 45, 90, and 180\u2009minutes during the OLT (P = .03), but no differences occurred in other test groups. Nursing stimulated marked increases in plasma glucagon, serum insulin, and glucose concentrations in all test groups (P\u2009<\u2009.001). Plasma ACTH concentration increased relative to baseline at 180\u2009minutes (P\u2009<\u2009.05) during fasting and OLT, but no differences occurred in other test groups. Serum cortisol concentration increased relative to baseline during OLT at 180\u2009minutes (P = .04), but no differences occurred in other test groups. Nursing resulted in decreased plasma ACTH and serum cortisol concentrations in all test groups (P\u2009<\u2009.01).\n\n\nCONCLUSIONS AND CLINICAL IMPORTANCE\nThe endocrine response to enterally and parenterally administered carbohydrates, including the major endocrine response to nursing, suggests that factors in milk other than carbohydrates are strong stimulators (directly or indirectly) of the endocrine pancreas and HPAA.