Abstract
BackgroundThe active components of Gardenia (Gardenia jasminoides Ellis, GJ) exhibit a hypoglycemic effect by improving insulin secretion and lowering plasma lipids. In the present study, we fed a water extract of gardenia to steroid-induced insulin-resistant (SIIR) rats and observed changes in signaling proteins in order to elucidate the mechanisms of the insulin-sensitizing effect of GJ and evaluate its possibility as an insulin-sensitizing agent.MethodsNormal Wistar rats were randomly divided into a control group (i.e., saline) and experimental groups (GJ 100 and 200 mg/kg). Blood samples were taken at 0, 30, and 60 min for plasma glucose assay in order to determine the optimal dose to induce the hypoglycemic effect. SIIR rats were then randomly divided into a control group (i.e., saline) and an experimental group (optimal dose of gardenia extract) to observe the insulin-sensitizing effect of the extract. Finally, western blot analysis was performed to detect intracellular signaling proteins to elucidate the mechanisms of the insulin-sensitization effect of GJ.ResultsThe normal Wistar rats in the GJ 200 mg/kg group exhibited significant hypoglycemic activity. Meanwhile, the SIIR rats had higher plasma glucose levels than normal rats. There was no obvious change in insulin level, but the insulin sensitivity index and homeostasis model assessment index were significantly elevated. Meanwhile, a significant hypoglycemic effect was observed with GJ 200 mg/kg. In addition, intracellular signaling proteins including insulin receptor substrate-1 (IRS-1) and peroxisome proliferator-activated receptor (PPARγ) were elevated in muscle cells.ConclusionsThe optimal dose of GJ aqueous extract of 200 mg/kg exerts a PPARγ-activating hypoglycemic effect and improves insulin resistance in SIIR rats. Therefore, it is a potential insulin-sensitizing agent in type 2 diabetes mellitus with insulin resistance.
Highlights
The active components of Gardenia (Gardenia jasminoides Ellis, GJ) exhibit a hypoglycemic effect by improving insulin secretion and lowering plasma lipids
Optimal dose of GJ for hypoglycemia In the normal Wistar rats, plasma glucose levels were checked at 0, 30, and 60 min to determine the hypoglycemic effect in the control and 2 experimental groups (i.e., GJ and GJ 200)
The GJ-fed groups exhibited a tendency towards decreasing glucose level with time
Summary
The active components of Gardenia (Gardenia jasminoides Ellis, GJ) exhibit a hypoglycemic effect by improving insulin secretion and lowering plasma lipids. Good control of blood glucose can effectively reduce the microvascular and macrovascular complications of diabetes mellitus (DM). Lifestyle modifications such as deceasing body weight, exercise, and diet control can decrease insulin resistance (IR). This can improve plasma glucose level and decrease the HbA1c level to 1% to 2% [1]. Several factors can induce IR, including decreased physical activity, high-fat diet, medications, and glucose intoxication. Some studies indicate that increased serum free fatty acid induces IR as well as obesity and type 2 DM [4,5]
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