Exercise and type 2 diabetes mellitus : peripheral sensory neuropathy in humans and regulation of blood glucose control in rodents.
PART ONE A prospective cohort study was conducted on eight previously inactive diabetic volunteers (34 – 47 yr) with a mean pre-trial HbA1c of 7.45 (±1.34) %, who completed an 8-week endurance exercise intervention of moderate intensity (Active Group, AG) as well as two passive controls (age 45-46 yr) with a sedentary lifestyle and one active control (AC; age 40yr) who continued with a prior exercise programme. All participants were requested to maintain their usual diet during the exercise intervention. The intervention in the AG included a 30-minute cycling program, during which the heart rate fluctuated between 60-80 % of age-predicted maximum, repeated three times per week. The effects of this endurance exercise program on signs and symptoms of Diabetic Peripheral Neuropathy (DPN) and possible associations between exercise-induced changes in mean resting heart rate (RHR), blood pressure (BP), body mass index (BMI), waist circumference, percentage body fat, eight subjective ratings of symptoms of pedal discomfort (SRPD), six objective neurological measures of DPN and changes in HbA1c, plasma brain- derived neurotrophic factor (BDNF) and adiponectin concentrations were determined in all participants (n=11). The exercise programme resulted in significant improvements (p<0.05) in the mean RHR, systolic BP and patellar and ankle reflexes in AG (n=8). It is concluded that the 8-week endurance exercise programme which was not combined with dietary intervention, was not successful in improving BMI and abdominal fat indexes, glucose homeostasis and neurological measures of DPN, but improved reflex action in the T2DM patients with DPN. PART TWO Six-week old male Spraque-Dawley rats (BW: 276.3± 14.5g) were divided into three groups as Normal Control (NC, n=7), Diabetic Control (DBC, n=6) and Exercising Diabetic (DBE; n=7) groups. Diabetes was induced in the animals in DBC and DBE groups by feeding a 10% fructose solution ad libitum for first two weeks followed by an intraperitoneal injection of streptozotocin (STZ) (40 mg/kg BW), while the animals in NC group were given normal drinking water and injected with vehicle buffer. One week after the STZ injection, animals with 3 h fasting blood glucose (3hFBG) of more than 16 and 12 mmol.L-1 were considered as diabetic and pre-diabetic, respectively. After the confirmation of diabetes, a progressive 5-week endurance exercise programme (20-22 m/min, 0-4° incline for 60 minutes.day-1) was implemented for five days per week in the DBE group and a prediabetic (PDBE) rat, only. Daily food and water intake, weekly 3hFBG and body mass, and post-trial plasma insulin, fructosamine, adiponectin and BDNF concentrations were measured in all rats. Following the exercise programme, elevated 3hFBG, plasma fructosamine and BDNF concentrations (p>0.05), but hypoinsulinaemia (p<0.05) with unchanged plasma adiponectin concentrations (p> 0.05) were recorded in the DBE group (n=6), while elevated plasma insulin concentrations was recorded in the PDBE rat with reduced 3hFBG and plasma fructosamine and elevated plasma adiponectin and BDNF levels. Data of this study suggest that although endurance exercise when combined with fructose withdrawal, is not effective in reversing STZ-induced diabetes, it may be effective in improving glycaemic status in the pre-diabetic stage.