Ginsenoside Rg3 improves erectile function in streptozotocin-induced diabetic rats

Ginsenoside Rg3 is one of the active ingredients isolated from Panax ginseng C.A. Meyer. Previous studies demonstrated that Rg3 has antioxidant and neuroprotective abilities.

The purpose of this study was to evaluate the protective effect of Rg3 on erectile function in streptozotocin (STZ)-induced diabetic rats.

Two-month-old Sprague-Dawley male rats received a one-time intraperitoneal (IP) STZ (60 mg/kg) or vehicle injection after a 16-hour fast. Three days later, rats were randomly divided into four groups and were treated with daily gavage feedings of a mix of distilled saline water and 0.5% carboxymethylcellulose or Rg3 dissolved in the mix at doses of 10 mg/kg and 100 mg/kg for 3 months. A sham group underwent IP injection of saline followed by daily gavage of the above mix for 3 months.

Erectile function was assessed by cavernosal nerve electrostimulation at 3 months. The penis was then harvested and deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) was performed. Western blot was performed to examine cleaved caspase-3, platelet endothelial cell adhesion molecule (PECAM)-1, and smooth muscle actin (SMA). Neural regeneration was measured by nicotinamide adenine dinucleotide phosphate (NADPH)-diaphorase staining. Superoxide dismutase (SOD) and malondialdehyde (MDA) levels were detected by colorimetry.

In the negative control group, the functional evaluation showed a lower mean intracavernosal pressure (ICP) with cavernosal nerve stimulation than in the sham group; there was a significant change in the expression of cleaved caspase-3, bcl-2, bcl-xl, PECAM-1, and SMA, as well as in the SOD and MDA production in the corpus cavernosum. Histological analysis of specimens stained for NADPH showed a significant change in the staining quality of the neurons in the dorsal nerves; TUNEL showed a greater apoptotic index in corpus cavernosum cells. With daily oral gavage with 100 mg/kg Rg3, the ICP/mean arterial pressure value was significantly higher than in the controls. The level of cleaved caspase-3, bcl-2, bcl-xl, PECAM-1, and SMA and the number of positively stained nerve fibers tended to revert to normal after Rg3 treatment. The apoptotic index in corpus cavernosum cells was lowered.

Oral gavage with Rg3 appears to both prevent degeneration of neurons in the dorsal nerves and exert an antioxidant effect in the corpus cavernosum of rats.