Maintenance of euglycemia is impaired in gluconeogenesis-inhibited iron-deficient rats at rest and during exercise.
To evaluate the hypothesis that mild iron deficiency increases dependence upon gluconeogenesis, control and mildly iron-deficient (Hb = 80 +/- 2 g/L) rats were injected with mercaptopicolinic acid (MPA), a known inhibitor of gluconeogenesis, or with injection vehicle (sham) and studied at rest or after 30 min of treadmill running (13.4 m/min, 0% grade). Liver glycogen concentration was lower in resting iron-deficient rats than in resting control rats, but iron deficiency did not influence arterial substrates or hormones in sham-treated rats. Glucose and insulin concentrations were less in resting control and iron-deficient MPA-treated rats than in sham-treated animals. However, arterial lactate was greater in resting iron-deficient MPA-treated rats than control MPA-treated animals, and glucagon and epinephrine were greater in resting iron-deficient MPA-treated rats than in iron-deficient sham-treated animals, indicating that gluconeogenesis is more important to maintenance of euglycemia in resting iron-deficient animals than in controls. Moderate exercise stimulated glucose metabolism in iron-deficient rats, as evidenced by the lower arterial glucose and higher arterial lactate when compared with resting iron-deficient rats. However, MPA treatment did not clearly establish differences between iron-deficient and control rats after exercise. Therefore, changes in substrate and hormone concentrations in resting iron-deficient MPA-treated rats indicate that dependence on gluconeogenesis for maintenance of euglycemia is greater at rest with dietary iron deficiency. Furthermore, consistent with previously published results for severely iron-deficient rats, results from the present investigation indicate that dependence on glucose metabolism is greater during moderate exercise in mildly iron-deficient rats.
Linderman
J K
JK
Department of Human Biodynamics, University of California, Berkeley 94720.
Brooks
G A
GA
Rodriguez
R E
RE
Dallman
P R
PR
D000818:Animals; D001786:Blood Glucose / Q000378:metabolism*; D001835:Body Weight; D004837:Epinephrine / Q000097:blood; D005260:Female; D005943:Gluconeogenesis / Q000187:drug effects / Q000502:physiology*; D007328:Insulin / Q000097:blood; D000090463:Iron Deficiencies; D007773:Lactates / Q000097:blood; D008099:Liver / Q000378:metabolism*; D009638:Norepinephrine / Q000097:blood; D010729:Phosphoenolpyruvate Carboxykinase (GTP) / Q000037:antagonists & inhibitors; D005082:Physical Exertion; D010848:Picolinic Acids / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012146:Rest
D001786:Blood Glucose; D007328:Insulin; D007773:Lactates; D010848:Picolinic Acids; C008363:3-mercaptopicolinic acid; D010729:Phosphoenolpyruvate Carboxykinase (GTP); D009638:Norepinephrine; D004837:Epinephrine