Low Vitamin K Intake Effects on Glucose Tolerance in Rats

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.