GIP Identified As Bifunctional Blood Glucose Stabilizer

Glucose-dependent insulinotropic polypeptide infusion affects glucagon levels, insulin release

MONDAY, Nov. 28 (HealthDay News) -- Infusion of glucose-dependent insulinotropic polypeptide (GIP) increases glucagon responses during hypoglycemia and euglycemia, with no effect on insulin secretion, and more than doubles the insulin secretion rate during hyperglycemia, with no effect on glucagon responses, according to a study published in the December issue of Diabetes.

Mikkel Christensen, M.D., from the Gentofte Hospital in Copenhagen, Denmark, and colleagues evaluated the glucose dependency of GIP effects on insulin and glucagon release in 10 healthy adult males (average age, 23 years; average BMI, 23 kg/m²; average hemoglobin A1c, 5.5 percent). Participants were randomized to receive either intravenous saline or physiological doses of GIP during 90 minutes of insulin-induced hypoglycemia, euglycemia, and hyperglycemia.

The investigators found that, compared to saline infusion, GIP infusion resulted in significantly greater glucagon response during the first 30 minutes of hypoglycemia (76 ± 17 versus 28 ± 16 pmol/L per 30 min), with similar peak glucagon levels reached after 60 minutes. Significantly larger glucagon responses were observed with GIP infusion during euglycemia (62 ± 18 versus −11 ± 8 pmol/L per 90 min). GIP and saline infusions showed comparable suppression of plasma glucagon during hyperglycemia (−461 ± 81 versus −371 ± 50 pmol/L per 90 min; P = 0.26). GIP infusion more than doubled the insulin secretion rate during hyperglycemia.

"GIP seems to be a physiological bifunctional blood glucose stabilizer with diverging glucose-dependent effects on the two main pancreatic glucoregulatory hormones," the authors write.

The study was supported by the Novo Nordisk Foundation.

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