Regular exercise reduces the development of painful diabetic neuropathy in animals—apparently related to increased expression of a protective substance called "heat shock protein" 72 (Hsp72), reports an experimental study in the February issue of Anesthesia & Analgesia, official journal of the International Anesthesia Research Society (IARS).
The observations add to previous studies suggesting that "progressive exercise training markedly decreased diabetes associated neuropathic pain," write Yu-Wen Chen, PhD, of China Medical University, Taichung, Taiwan, and colleagues. The link to Hsp72 offers a clue as to how exercise can prevent or slow the development of neuropathy—a major complication of diabetes.
Exercise Reduces Diabetic Nerve Pain in Rats
Neuropathic pain is a common and difficult-to-treat type of pain related to nerve damage—most commonly caused by diabetes. Affecting about half of patients with diabetes, diabetic neuropathy causes symptoms such as numbness, tingling, or pain in the arms and legs.
Dr Chen and colleagues examined the effects of exercise on neuropathy caused by chemically-induced diabetes in rats. For a few weeks after induction of diabetes, some animals were assigned to a progressive treadmill exercise program.
Within two weeks, the diabetic rats that did not exercise showed signs of diabetic neuropathy, based on observable pain behaviors. These included abnormal responses to temperature and pressure (thermal and tactile hypersensitivity)—both characteristic of neuropathic pain.
"In contrast, diabetic rats undergoing exercise demonstrated delayed progress of tactile and thermal hypersensitivity," Dr Chen and colleagues write. The reduction in painful diabetic neuropathy was associated with lesser increases in blood glucose levels after induction of diabetes.
Previous studies have suggested that neuropathic pain may be related to expression of certain inflammation-promoting cytokines—such as tumor necrosis factor-alpha and interleukin-6—which might be reduced by exercise. In the new experiments, expression of TNF-alpha and IL-6 in nerve tissue were significantly increased after induction of diabetes, with no difference for exercising versus non-exercising animals.