To investigate the effects of vitamin K (VK) on pancreatic function, intravenous glucose tolerance tests were performed in rats fed with and without low VK diet (inclucing less than 20% required vitamin K1). Plasma glucose and immuno-reactive insulin (IRI) were determined. It was found that at 0 min., plasma glucose and IRI levels in low VK group were slightly less than in the control (glucose, 204.5 ± 21.7 vs. 229 ± 19.6 mg/dl, IRI, 6.6 ± 1.3 vs. 9.3 ± 1.8 ng/ml mean ± SEM). At 3 min. after glucose administration, plasma glucose was higher (391.8 ± 25.6 vs. 371.8 ± 18.7 mg/dl) and IRI, lower (11.8 ± 2.1 vs. 18.2 ± 3.6 ng/ml) in the low VK group. The disappearance rate of plasma glucose in the low VK group at 5–10 min. was significantly less than in the control (6.7 ± 2.2 vs. 11.9 ± 1.8 mg/ dl/min.). Incremental IRI area at 0 to 5 min. in the low VK group is less than in the control (15.2 ± 4.4 vs. 25.0 ± 9.1 ng/ml/min.), but at 5–60 min. and 0–60 min., it was found to be significantly higher compared to the control (210.3 ± 55.2 vs. 32.5 ± 47.1 ng/ml/min. at 5–60 min.). Dietary low VK intake would thus appear to induce a tendency of poor early insulin response, and late hyperinsulinemia to the glucose load in rats.
Response of plasma glucose, insulin, and nonesterified fatty acids to intravenous glucose tolerance tests in dairy cows during a 670-day lactation
