Pycnogenol, a standardized extract from the bark of the French maritime pine, consists of phenolic compounds including catechin, taxifolin, procyanidins, and phenolic acids (1).
We investigated whether Pycnogenol has a glucose-lowering effect because of personal verbal communication from patients reporting no need for insulin following supplementation with Pycnogenol.
The study was designed as an open, controlled, dose-finding study and was approved by the ethical committee of Guangnamen Hospital. Patients gave written informed consent. We recruited 18 men and 12 women among outpatients of the Guangnamen Hospital and Municipal Dental Hospital. Patients were 28–64 years of age and had a BMI 22–34 kg/m2. Patients with type 2 diabetes were included with fasting plasma glucose between 7 and 10 mmol/l after participation in a diet and sports program for 1 month. Exclusion criteria were type 1 diabetes, manifest or malignant hypertension and any diseases requiring continuous treatment with drugs, and pregnant or lactating women.
During the first and last visit, a physical examination and assessment of demographic data, medical history, body weight, height, vital signs, blood pressure, electrocardiogram, diet, and medication was carried out. Samples for fasting blood glucose, HbA1c, insulin, and endothelin-1 were taken. Blood samples were taken to measure postprandial blood glucose 2 h after breakfast.
Glucose was measured enzymatically, HbA1c by high-performance liquid chromatography, and insulin and endothelin-1 by immunoassays. Statistical analysis was done with SPSS 16.0 software using one-factorial ANOVA with Fisher projected least significant difference test. Patients received in succession 50, 100, 200, and 300 mg Pycnogenol in intervals of 3 weeks. Every 3 weeks, fasting and postprandial glucose, endothelin-1, HbA1c, and insulin were analyzed.
No changes were observed in vital signs, electroencephalogram, or blood pressure over the 12-week period.
Fasting blood glucose was lowered dose dependently until a dose of 200 mg Pycnogenol was administered. Increasing the dose from 200 to 300 mg did not further decrease blood glucose. Compared with baseline, 100–300 mg lowered fasting glucose significantly from 8.64 ± 0.93 to 7.54 ± 1.64 mmol/l (P < 0.05). Fifty milligrams of Pycnogenol lowered postprandial glucose significantly from 12.47 ± 1.06 to 11.16 ± 2.11 mmol/l (P < 0.05). Maximum decrease of postprandial glucose was observed with 200 mg to 10.07 ± 2.69 mmol/l; 300 mg had no stronger effect.
HbA1c levels decreased continuously from 8.02 ± 1.04 to 7.37 ± 1.09%. Difference to baseline became significant after 9 and 12 weeks of treatment with 200 or 300 mg Pycnogenol (P < 0.05). Endothelin-1 decreased significantly after 100–300 mg Pycnogenol from 104 ± 16 to 91 ± 15 pg/ml (P < 0.05). There was no additional decrease with 300 mg. Insulin levels were not changed at any dosage level of Pycnogenol.
Four patients reported dizziness, two headache, two gastric discomfort, and one mouth ulcer. None of the patients discontinued the study. All unwanted effects were minor and transitory.
Stimulation of insulin secretion can be excluded as a cause for lower glucose levels because insulin secretion was not affected. Mechanistic investigations are underway to elucidate the mechanism of glucose lowering with Pycnogenol.
The decrease of endothelin-1 following supplementation with Pycnogenol points to an ameliorated function of the endothelium.
This dose-finding study encourages further mechanistic and clinical studies with Pycnogenol to explore its potential in obtaining metabolic control in patients with mild type 2 diabetes. A double-blind placebo-controlled study with 77 patients confirmed the glucose-lowering effect of Pycnogenol (2).
The study was sponsored by Horphag Research, Guernsey, Channel Islands.
P.R. is a paid consultant of Horphag Research. X.L. receives research funds from Horphag Research.