Conjoint regulation of glucagon concentrations via plasma insulin and glucose in dairy cows

Zarrin, Mousa; Wellnitz, Olga; Bruckmaier, Rupert (2015). Conjoint regulation of glucagon concentrations via plasma insulin and glucose in dairy cows. Domestic animal endocrinology, 51, pp. 74-77. Elsevier 10.1016/j.domaniend.2014.11.004

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Insulin and glucagon are glucoregulatory hormones that contribute to glucose homeostasis. Plasma insulin is elevated during normoglycemia or hyperglycemia and acts as a suppressor of glucagon secretion. We have investigated if and how insulin and glucose contribute to the regulation of glucagon secretion through long term (48 h) elevated insulin concentrations during simultaneous hypoglycemia or euglycemia in mid-lactating dairy cows. Nineteen Holstein dairy cows were randomly assigned to 3 treatment groups: an intravenous insulin infusion (HypoG, n = 5) to decrease plasma glucose concentrations (2.5 mmol/L), a hyperinsulinemic-euglycemic clamp to study effects of insulin at simultaneously normal glucose concentrations (EuG, n = 6) and a 0.9% saline infusion (NaCl, n = 8). Plasma glucose was measured at 5-min intervals, and insulin and glucose infusion rates were adjusted accordingly. Area under the curve of hourly glucose, insulin, and glucagon concentrations on day 2 of infusion was evaluated by analysis of variance with treatments as fixed effect. Insulin infusion caused an increase of plasma insulin area under the curve (AUC)/h in HypoG (41.9 ± 8.1 mU/L) and EuG (57.8 ± 7.8 mU/L) compared with NaCl (13.9 ± 1.1 mU/L; P < 0.01). Induced hyperinsulinemia caused a decline of plasma glucose AUC/h to 2.3 ± 0.1 mmol/L in HypoG (P < 0.01), whereas plasma glucose AUC/h remained unchanged in EuG (3.8 ± 0.2 mmol/L) and NaCl (4.1 ± 0.1 mmol/L). Plasma glucagon AUC/h was lower in EuG (84.0 ± 6.3 pg/mL; P < 0.05) and elevated in HypoG (129.0 ± 7.0 pg/mL; P < 0.01) as compared with NaCl (106.1 ± 5.4 pg/mL). The results show that intravenous insulin infusion induces elevated glucagon concentrations during hypoglycemia, although the same insulin infusion reduces glucagon concentrations at simultaneously normal glucose concentrations. Thus, insulin does not generally have an inhibitory effect on glucagon concentrations. If simultaneously glucose is low and insulin is high, glucagon is upregulated to increase glucose availability. Therefore, insulin and glucose are conjoint regulatory factors of glucagon concentrations in dairy cows, and the plasma glucose status is the key factor to decide if its concentrations are increased or decreased. This regulatory effect can be important for the maintenance of glucose homeostasis if insulin secretion is upregulated by other factors than high glucose such as high plasma lipid and protein concentrations at simultaneously low glucose.

Item Type:

Journal Article (Original Article)

Division/Institute:

05 Veterinary Medicine > Department of Clinical Research and Veterinary Public Health (DCR-VPH) > Veterinary Physiology
05 Veterinary Medicine > Department of Clinical Research and Veterinary Public Health (DCR-VPH)

UniBE Contributor:

Zarrin, Mousa; Wellnitz, Olga and Bruckmaier, Rupert

Subjects:

600 Technology > 610 Medicine & health
600 Technology > 630 Agriculture

ISSN:

0739-7240

Publisher:

Elsevier

Language:

English

Submitter:

Lorenzo Enrique Hernandez Castellano

Date Deposited:

07 Apr 2015 15:57

Last Modified:

12 Oct 2015 15:43

Publisher DOI:

10.1016/j.domaniend.2014.11.004

PubMed ID:

25577602

Uncontrolled Keywords:

Dairy cow, Glucagon, Glucose, Homeostasis, Insulin, Metabolism

BORIS DOI:

10.7892/boris.66018

URI:

https://boris.unibe.ch/id/eprint/66018

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