People with type 2 diabetes were eligible if they had diabetic nephropathy that was classified as early stage. Pregnant or breastfeeding women and people with liver disease, psychiatric diseases, or other kidney diseases were excluded from the trial. All subjects were treated with standard medical care, which included diabetic education, a low protein diet, and medications to control blood glucose levels and high blood pressure. This randomized trial was conducted at Jinhua College of Profession and Technology in Jinhua, Zhejiang Province, China.

A total of 64 subjects were randomly allocated to 2 groups. Subjects in the control group continued on with standard medical care only. Subjects in the ginkgo group received standard medical care plus 3 tablets daily of ginkgo leaf extract (Tianbaoning; Kang’enbei Pharmaceutical Company; Zhejiang Province, China). Each tablet contained 19.2 mg flavonol glycosides and 4.8 mg terpene lactones. The methods section does not state if subjects in the ginkgo group knew that they were taking ginkgo tablets.

The study lasted for 8 weeks. Urine tests, blood tests, and ultrasound scans of the brachial artery were performed at baseline and at the end of the 8-week period. The blood tests measured glucose, creatinine (a measure of kidney function), and markers of endothelial function. These markers were von Willebrand factor, which promotes blood clotting; nitric oxide, which promotes dilation of blood vessels; and endothelin-1, which promotes constriction of blood vessels. The urine test evaluated urinary excretion of albumin. The brachial artery ultrasound scans were used to assess endothelial function. The inner diameter of the brachial artery, the major blood vessel in the arm, was measured before and after inflation of a pressure cuff (endothelium-dependent dilation) and before and after oral nitroglycerin (endothelium-independent dilation).

At baseline, there were no significant differences between the 2 groups for age, gender, years of diabetes, or body mass index. The mean age of subjects was 67 years and the mean duration of diabetes was 8 years. The authors do not report how many subjects in each group completed the 8-week trial, so it is not clear if the analysis includes data from all 64 subjects who were enrolled.

Creatinine levels and urinary excretion of albumin decreased significantly (both P < 0.01) in the ginkgo group but not in the control group after 8 weeks. Nitric oxide increased significantly (P < 0.01) and von Willebrand factor decreased significantly (P < 0.01) in the ginkgo group but not in the control group. As the von Willebrand factor was abnormally high in both groups at baseline, the decrease in the ginkgo group means that normalization of this factor can be achieved by this ginkgo extract. Fasting blood glucose and endothelin-1 levels did not change significantly in either group. The increase in brachial artery diameter after inflation of the pressure cuff was significant (P < 0.05) for the ginkgo group, but not for the control group. There was no significant difference between the groups for the increase in brachial artery diameter following the nitroglycerin challenge.

In this study, ginkgo had a protective effect on vascular endothelial function in people with early stage diabetic nephropathy. Eight-week treatment with ginkgo improved kidney function markers, endothelial function markers, and endothelium-dependent dilation as assessed by ultrasound. The authors suggest that adding ginkgo to standard medical care may be helpful in delaying the development of nephropathy in people with early stage diabetic nephropathy.

The authors point out that a previous study reported a decrease in endothelin-1 in people with diabetic nephropathy following treatment with ginkgo, but this study found no change in endothelin-1. This could be due to differences in the ginkgo product, ginkgo dose, or method for determining endothelin-1 between the 2 studies.

The authors do not discuss any limitations of this trial, nor do they report any adverse side effects associated with ginkgo use. Diabetes is a chronic, progressive condition, and long-term trials are needed to evaluate the clinical significance, safety, and effectiveness of ginkgo in people with diabetic nephropathy.