Erectile dysfunction (ED) is very common in diabetes mellitus. ED refers to the “inconsistent inability to achieve and maintain penile erection sufficient for adequate sexual relations.” ED is associated with diabetes, aging, high blood cholesterol (hypercholesterolemia,) hypertension, sedentary life style and cigarette smoking.
ED seems to be mainly due to inability of the inner lining cells of the blood vessels to produce enough relaxing chemicals to provide sufficient circulation to the penis. The endothelium refers to the inner lining of blood vessels where relaxation produces an increase in local circulation. ED is considered a warning sign of general circulatory problems, including cardiovascular disease. There are high rates of insulin resistance, metabolic syndrome and obesity in men with ED.
High blood sugar levels (hyperglycemia) reduce a needed enzyme called endothelial nitric oxide synthase (eNOS), which is necessary for nitric oxide (NO) production. NO is a chemical that causes blood vessel relaxation and ED is primarily a sign of insufficient NO.
Insufficient L-arginine is one cause of failure of eNOS activity. One study in diabetic rabbits showed that oral L-arginine resulted in vascular relaxation and increased production of NO. Oxidized LDL (low density lipoprotein) damaged by free radicals can reduce endothelial absorption of l-arginine.
Lowered levels of tetrahydrobiopterin (BH4), a cofactor necessary for eNOS to function, can result from hyperglycemia and failure of NO production. Supplementation with BH4 has been shown to improve endothelial dysfunction in diabetics.
High blood sugar (hyperglycemia) activates oxidative stress, producing free radicals and changing eNOS acivity. This results in the production of harmful reactive oxygen species (ROS) rather than beneficial NO. This oxidative stress can cause damage to the inner lining of blood vessels (endothelial dysfunction) leading to arteriosclerosis.
There are low levels of antioxidants in the penile circulation in erectile dysfunction. Treatment with vitamin E, sodium selenate, ascorbic acid, alpha lipoic acid, gamma linolenic acid (omega-6) and melatonin help restore the penile circulation in diabetics. Superoxide dysmutase (SOD) is an enzyme that improves penile circulation.
CONCLUSION: This article reviews hyperglycemia-induced endothelial dysfunction as a cause of ED. There is a connection between diabetes, obesity, cardiovascular disease and erectile dysfunction. Circulatory problems seem to be due to insufficient nitric oxide in the inner lining of blood vessels, which results in reduced relaxation of the blood vessels and poor circulation. Antioxidants, oral l-arginine, superoxide dysmutase, BH4, melatonin and gamma linolenic acid can relieve erectile dysfunction.
NOTE: Maca from Peru has been found to be useful for erectile dysfuncion. Red onion peel has been found to have phosphodiesterase-5 activity similar to that of Viagra. Hyperprolactinemia (hyperprolactinaemia) can be found in erectile dysfunction.
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