Table 1. Summary of the common pathophysiology of obesity and ED.
| Pathophysiology | Main finding | Experimental models and material | References |
|---|---|---|---|
| IR | Obesity, IR, impaired CC relaxation, decreased cGMP level in CC | High-fat fed mice | [74]a |
| Higher serum level of CRP, TG, and cholesterol and lower IIEF-5 score and testosterone in IR patients than in non-IR patients | Men with ED | [54]b | |
| IR is independently associated with ED and its severity | |||
| Elevated serum level of TNF-α and IL-6 only in obese men with IR | Obese subjects | [53]a,b | |
| Improved vasodilation by superoxide scavenger in mesenteric artery | Mesenteric arteries | ||
| Higher serum level of CRP and insulin in IR subjects than non-IR | Obese subjects | [52]a,b | |
| Impaired vasodilation and increased arteriolar arginase in IR arterioles | Arteriolar tissue | ||
| Impaired endothelium-mediated vasodilation in mesenteric arterioles | Fructose-fed rats (IR animal model) | ||
| Inflammation | Decreased NANC nerve-mediated relaxation and expression of eNOS and nNOS in carvernosal strips | TNF-α infused mice | [41]a |
| Increased endothelium-dependent relaxation and expression of eNOS and nNOS in carvernosal strips | TNF-α deleted mice | [42]a | |
| Increased number of spontaneous erections | |||
| Elevated IL-8 and CRP, which are correlated with severity of ED | Obese men with ED | [36]b | |
| Impaired endothelial function assessed with L-arginine test | |||
| Oxidative stress | Decrease in the number of penile erection | High-fat fed rats | [5]a |
| Attenuated endothelium-relaxation reactivity of CC | |||
| Higher level of oxidized LDL and IL-18 in CC than in venous blood, which are negatively correlated with IIEF scores | Patients (IIEF-EF 6–24) | [40]a,b | |
| TNF-α and IL-18 suppress eNOS expression | HAEC cell (in vitro study) | ||
| Leptin resistance | Suppressed LH surge, delayed male puberty, obesity | Neuronal leptin receptor deleted mice | [25]a |
| Suppressed hCG-stimulated testosterone secretion | Obese men | [26]b | |
| Low testosterone level |
ED: erectile dysfunction, IR: insulin resistance, CC: corpus cavernosum, cGMP: cyclic guanosine monophosphate, CRP: C-reactive protein, TG: triglycerides, IIEF-5: international index of erectile function-5, TNF-α: tumor necrosis factor-alpha, IL: interleukin, NANC: nonadrenergicnoncholinergic, eNOS: endothelial nitric oxide synthase, nNOS: nervous nitric oxide synthase, LDL: low-density lipoprotein, HAEC: human aortic endothelial cell line, LH: lutenizing hormone, hCG: human chorionic gonadotropin.
aBasic research. bClinical research.