Improvement of erectile function by Korean red ginseng (Panax ginseng) in a male rat model of metabolic syndrome

Abstract

The seriousness of metabolic syndrome is not due to the disease itself but its promotion of other diseases, such as erectile dysfunction and cardiovascular and cerebrovascular diseases. We investigated the effects of Korean red ginseng (KRG, Panax ginseng) extract on erectile function in a rat model of metabolic syndrome. We divided the rats into three groups: control, metabolic syndrome+normal saline (N/S) and metabolic syndrome+KRG. To determine the occurrence of metabolic syndrome in all groups, body weight and various biochemical parameters (e.g., blood glucose, insulin, cholesterol) were measured, and the intra-abdominal glucose tolerance test was performed. To investigate penile erection, the peak intracavernosal pressure (ICP), mean arterial pressure (MAP) and Masson's trichrome stain were evaluated. Erectile function was also investigated by measuring the cyclic guanosine monophosphate (cGMP) levels of the corpus cavernosum. We found that the various biochemical parameters and body weight were similar in the metabolic syndrome+KRG group and the control group, although the values were slightly higher. The peak ICP/MAP ratio of the metabolic syndrome+N/S group was markedly decreased compared to the other groups. The cGMP level of the corpus cavernosum in the metabolic syndrome+N/S group was significantly lower than that of the other groups. As demonstrated in this model of metabolic syndrome with erectile dysfunction, KRG may improve erectile function.

Figure 1

The change of body weight (a) and systolic blood pressure (b) in each group over the 12-week study period. While body weight (P=0.010) and systolic blood pressure (P=0.014) increased significantly in group II compared to group I, those of group III were similar to group I, although they were slightly higher. Group I, control; Group II: metabolic syndrome + normal saline; Group III: metabolic syndrome + Korean red ginseng.

Figure 2

Comparison of the ratio of the peak ICP/MAP in each group. The ratio of peak ICP/MAP decreased significantly in group II (*P=0.016 vs. group I), whereas it was similar in group III and group I. ICP, intracavernosal pressure; MAP, mean arterial pressure. Group I, control; Group II: metabolic syndrome + normal saline; Group III: metabolic syndrome + Korean red ginseng.

Figure 3

The distribution of smooth muscle observed using Masson's trichrome staining of the corpus cavernosum in each group. The ratio of smooth muscle in group II was significantly lower than the other groups (*P=0.023 vs. group I), while it was similar in groups III and I. Group I, control; Group II: metabolic syndrome + normal saline; Group III: metabolic syndrome + Korean red ginseng.

Figure 4

A comparison of the immunohistochemical expression of TGF-β₁ in each group. In group I, normal structures and weak immunoreactivity to TGF-β₁ were observed in the corpus cavernosum tissue. By contrast, in group II, TGF-β₁ immunoreactivity was strong and tended to increase in collagen, fibroblasts and smooth muscle fibres. In group III, TGF-β₁ immunoreactivity was decreased compared with group II. Scale bar=100 μm. Group I, control; Group II: metabolic syndrome + normal saline; Group III: metabolic syndrome + Korean red ginseng.

Figure 5

The cGMP level of the corpus cavernosum in each group. The cGMP level in group II was significantly lower than that of the control group (*P=0.005 vs. group I). cGMP, cyclic guanosine monophosphate. Group I, control; Group II: metabolic syndrome + normal saline; Group III: metabolic syndrome + Korean red ginseng.