Emodin Corrects Type II Diabetes Metabolic Imbalance in Mouse Model

The pancreas typically produces enough insulin, but cells are resistant to the insulin and it may not work as effectively. Type II is the most common form of diabetes, and most individuals with the disease are adults. However, children and adolescents can develop the disease, particularly if they are overweight and have a history of type II diabetes in their family. Type II diabetes is treated with diet, exercise, and in some cases, oral medication and/or insulin. Self-monitoring of blood glucose levels is important to assess efficacy of the treatment.

The compound under investigation in the current study is emodin, which can be extracted from various Chinese herbs including Rheum palmatum (Turkey or Chinese rhubarb) and Polygonum cuspidatum (Japanese knotweed). Japanese knotweed in particular is a concentrated source of emodin, used as a nutritional supplement to regulate bowel motility. The roots of Japanese knotweed are used in traditional Chinese and Japanese herbal medicines as a natural laxative. The active principle responsible for the laxative effect is emodin, present in its natural form as a complex of its analogs. Emodin has a mild laxative effect in doses of 20 mg to 50 mg per day. In addition, Japanese knotweed is a commercial source of resveratrol supplements.

Investigators at the Shanghai Institute of Materia Medica (China) studied the relationship between emodin and the enzyme 11-beta-hydroxysteroid dehydrogenase type 1 (11-beta-HSD1). This enzyme stimulates the activity of glucocorticoids, which have the opposite effect on glucose metabolism than insulin does.

The investigators used a scintillation proximity assay to evaluate inhibition of emodin against recombinant human and mouse 11-beta-HSDs. The ability of emodin to inhibit prednisone- or dexamethasone-induced insulin resistance was investigated in C57BL/6J mice, and its effect on metabolic abnormalities was observed in DIO (diabetes induced obese) mice.

They reported in the August 11, 2010, issue of the British Journal of Pharmacology that emodin was a potent and selective 11-beta-HSD1 inhibitor, and that a single oral administration of the compound inhibited 11-beta-HSD1 activity in the livers and fat of the mice. This effect was evinced by lowered blood glucose and serum insulin, improved insulin resistance, and healthier levels of lipid in the blood. It also decreased body weight and reduced central fat mass.

"Our work showed that this natural extract from Chinese herbs could point the way to a new way of helping people with type II diabetes as well as other metabolic disorders. To develop it further, researchers would need to develop chemicals that have similar effects as emodin, and see which if any of these could be used as a therapeutic drug,” said senior author Dr. Ying Leng, professor of pharmacology at the Shanghai Institute of Materia Medica. "If repeated in humans, all of these changes would be beneficial for people affected by type II diabetes or other metabolic diseases associated with insulin resistance.”

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Shanghai Institute of Materia Medica