Hepatic and Whole-Body Insulin Metabolism during Proestrus and Estrus in Mongrel Dogs.
Insulin resistance occurs during various stages of the estrus cycle in dogs. To quantify the effects of proestrus-estrus (PE) and determine whether PE affects liver insulin sensitivity, 11 female mongrel dogs were implanted with sampling and intraportal infusion catheters. Five of the dogs (PE group) entered proestrus after surgery; those remaining in anestrus were controls. The dogs were fasted overnight, [3-(3)H]glucose and somatostatin were infused through peripheral veins, and glucagon was infused intraportally. Insulin was infused intraportally, with the rate adjusted to maintain arterial plasma glucose at basal levels (PE, 294±25 μU/kg/min; control, 223±21 μU/kg/min). Subsequently the insulin infusion rate was increased by 0.2 mU/kg/min for 120 min (P1) and then to 1.5 mU/kg/min for the last 120 min (P2); glucose was infused peripherally as needed to maintain euglycemia. Insulin concentrations did not differ between groups at any time; they increased 3 μU/mL over baseline during P1 and to 3 times baseline during P2. The glucose infusion rate in PE dogs during P2 was 63% of that in control dogs. Net hepatic glucose output and the endogenous glucose production rate declined 40% to 50% from baseline in both groups during P1; during P2, both groups exhibited a low rate of net hepatic glucose uptake with full suppression of endogenous glucose production. The glucose disappearance rate during P1 and P2 was 35% greater in control than PE dogs. Therefore, PE in canines is associated with loss of nonhepatic (primarily muscle) but not hepatic insulin sensitivity.
Departments of Pathology, Microbiology, Immunology, and Division of Animal Care, Vanderbilt University School of Medicine, Nashville, Tennessee, USA.
Erin Nz
EN
Yu
Departments of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee, USA.
Jason J
JJ
Winnick
Departments of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee, USA; Diabetes Research and Training Center, Vanderbilt University School of Medicine, Nashville, Tennessee, USA.
Dale S
DS
Edgerton
Departments of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee, USA.
Melanie F
MF
Scott
Departments of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee, USA.
Marta S
MS
Smith
Departments of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee, USA; Diabetes Research and Training Center, Vanderbilt University School of Medicine, Nashville, Tennessee, USA.
Ben
B
Farmer
Diabetes Research and Training Center, Vanderbilt University School of Medicine, Nashville, Tennessee, USA; Department of Surgery, Vanderbilt University School of Medicine, Nashville, Tennessee, USA.
Phillip E
PE
Williams
Departments of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee, USA.
Alan D
AD
Cherrington
Departments of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee, USA. genie.moore@vanderbilt.edu.
Mary Courtney
MC
Moore
D000818:Animals; D004285:Dogs / Q000378:metabolism*; D004971:Estrus / Q000378:metabolism*; D007328:Insulin / Q000378:metabolism*; D007333:Insulin Resistance; D008099:Liver / Q000378:metabolism*; D011359:Proestrus / Q000378:metabolism*
D007328:Insulin