Exercise tolerance is lower in type I diabetics compared with normal young men

Effects of Involuntary and Voluntary Exercise in Combination with Acousto-Optic Stimulation on Adult Neurogenesis in an Alzheimer's Mouse Model

Single-factor intervention, such as physical exercise and auditory and visual stimulation, plays a positive role on the prevention and treatment of Alzheimer's disease (AD); however, the therapeutic effects of single-factor intervention are limited. The beneficial effects of these multifactor combinations on AD and its molecular mechanism have yet to be elucidated. Here, we investigated the effect of multifactor intervention, voluntary wheel exercise, and involuntary treadmill running in combination with acousto-optic stimulation, on adult neurogenesis and behavioral phenotypes in a mouse model of AD. We found that 4 weeks of multifactor intervention can significantly increase the production of newborn cells (BrdU⁺ cells) and immature neurons (DCX⁺ cells) in the hippocampus and lateral ventricle of Aβ oligomer-induced mice. Importantly, the multifactor intervention could promote BrdU⁺ cells to differentiate into neurons (BrdU⁺ DCX⁺ cells or BrdU⁺ NeuN⁺ cells) and astrocytes (BrdU⁺GFAP⁺ cells) in the hippocampus and ameliorate Aβ oligomer-induced cognitive impairment and anxiety- and depression-like behaviors in mice evaluated by novel object recognition, Morris water maze tests, elevated zero maze, forced swimming test, and tail suspension test, respectively. Moreover, multifactor intervention could lead to an increase in the protein levels of PSD-95, SYP, DCX, NeuN, GFAP, Bcl-2, BDNF, TrkB, and pSer473-Akt and a decrease in the protein levels of BAX and caspase-9 in the hippocampal lysates of Aβ oligomer-induced mice. Furthermore, sequencing analysis of serum metabolites revealed that aberrantly expressed metabolites modulated by multifactor intervention were highly enriched in the biological process associated with keeping neurons functioning and neurobehavioral function. Additionally, the intervention-mediated serum metabolites mainly participated in glutamate metabolism, glucose metabolism, and the tricarboxylic acid cycle in mice. Our findings suggest the potential of multifactor intervention as a non-invasive therapeutic strategy for AD to anti-Aβ oligomer neurotoxicity.

Sex-related differences in fuel utilization and hormonal response to exercise: implications for individuals with type 1 diabetes

Sex-related differences in metabolic and neuroendocrine response to exercise in individuals without diabetes have been well established. Men and women differ in fuel selection during exercise, in which women rely to a greater extent on fat oxidation, whereas males rely mostly on carbohydrate oxidation for energy production. The difference in fuel selection appears to be mediated by sex-related differences in hormonal (including catecholamines, growth hormone, and estrogen) response to different types and intensities of exercise. In general, men exhibit an amplified counter-regulatory response to exercise, with elevated levels of catecholamines compared with women. However, women exhibit greater sensitivity to the lipolytic action of the catecholamines and deplete less of their glycogen stores than men during exercise, which suggests that women may experience a greater defense in blood glucose control after exercise than men. Conversely, little is known about sex-related differences in response to exercise in individuals with type 1 diabetes (T1D). A single study investigating sex-related differences in response to moderate aerobic exercise in individuals with T1D found sex-related differences in catecholamine response and fuel selection, but changes in blood glucose were not measured. To our knowledge, there are no studies investigating sex-related differences in blood glucose responses to different types and intensities of exercise in individuals with T1D. This review summarizes sex-related differences in exercise responses that could potentially impact blood glucose levels during exercise in individuals with T1D and highlights the need for further research.

Exercise and type 1 diabetes (T1DM)

Physical exercise is firmly incorporated in the management of type 1 diabetes (T1DM), due to multiple recognized beneficial health effects (cardiovascular disease prevention being preeminent). When glycemic values are not excessively low or high at the time of exercise, few absolute contraindications exist; practical guidelines regarding amount, type, and duration of age-appropriate exercise are regularly updated by entities such as the American Diabetes Association and the International Society for Pediatric and Adolescent Diabetes. Practical implementation of exercise regimens, however, may at times be problematic. In the poorly controlled patient, specific structural changes may occur within skeletal muscle fiber, which is considered by some to be a disease-specific myopathy. Further, even in well-controlled patients, several homeostatic mechanisms regulating carbohydrate metabolism often become impaired, causing hypo- or hyperglycemia during and/or after exercise. Some altered responses may be related to inappropriate exogenous insulin administration, but are often also partly caused by the "metabolic memory" of prior glycemic events. In this context, prior hyperglycemia correlates with increased inflammatory and oxidative stress responses, possibly modulating key exercise-associated cardio-protective pathways. Similarly, prior hypoglycemia correlates with impaired glucose counterregulation, resulting in greater likelihood of further hypoglycemia to develop. Additional exercise responses that may be altered in T1DM include growth factor release, which may be especially important in children and adolescents. These multiple alterations in the exercise response should not discourage physical activity in patients with T1DM, but rather should stimulate the quest for the identification of the exercise formats that maximize beneficial health effects.

A fermented soy permeate improves the skeletal muscle glucose level without restoring the glycogen content in streptozotocin-induced diabetic rats

Exercise is essential into the therapeutic management of diabetic patients, but their level of exercise tolerance is lowered due to alterations of glucose metabolism. As soy isoflavones have been shown to improve glucose metabolism, this study aimed to assess the effects of a dietary supplement containing soy isoflavones and alpha-galactooligosaccharides on muscular glucose, glycogen synthase (GSase), and glycogen content in a type 1 diabetic animal model. The dietary supplement tested was a patented compound, Fermented Soy Permeate (FSP), developed by the French Company Sojasun Technologies. Forty male Wistar rats were randomly assigned to control or diabetic groups (streptozotocin, 45 mg/kg). Each group was then divided into placebo or FSP-supplemented groups. Both groups received by oral gavage, respectively, water or diluted FSP (0.1 g/day), daily for a period of 3 weeks. At the end of the protocol, glycemia was noticed after a 24-h fasting period. Glucose, total GSase, and the glycogen content were determined in the skeletal muscle (gastrocnemius). Diabetic animals showed a higher blood glucose concentration, but a lower glucose and glycogen muscle content than controls. Three weeks of FSP consumption allowed to restore the muscle glucose concentration, but failed to reduce glycemia and to normalize the glycogen content in diabetic rats. Furthermore, the glycogen content was increased in FSP-supplemented controls compared to placebo controls. Our results demonstrated that diabetic rats exhibited a depleted muscle glycogen content (-25%). FSP-supplementation normalized the muscle glucose level without restoring the glycogen content in diabetic rats. However, it succeeded to increase it in the control group (+20%).

Decreased isometric muscle strength after acute hyperglycaemia in Type 1 diabetic patients

AIMS

Fatigue is a common complaint in diabetic patients during periods of hyperglycaemia. To test whether muscle performance is reduced during acute hyperglycaemia, diabetic patients were studied whilst performing maximal isokinetic and isometric contractions.

METHODS

In this double-blind placebo controlled study, maximal isometric and isokinetic muscle strength was determined in seven Type 1 diabetic patients during normo- and hyperglycaemia using a hyperglycaemic clamp technique. On two separate days, maximal muscle strength of the knee extensors was determined quantitatively using a dynamometer. On both days, muscle strength was determined before a constant blood glucose level was obtained and after the blood glucose level had been kept constant at either 5 or 16 mmol/l for 3 h. Percentage of change from baseline at the two glycaemic levels were calculated and compared. In addition, the changes from baseline at these glycaemic levels were related to glucose turnover.

RESULTS

Following hyperglycaemia, a significant decrease in maximal isometric muscle strength was found as compared with normoglycaemia (86 vs. 104% of the initial level) (P = 0.018). In contrast, no alteration of maximal isokinetic muscle strength was found comparing normo- and hyperglycaemia (96 and 95%) (P = 0.74). Changes in muscle strength were not significantly related to either basal or hyperglycaemic glucose turnover.

CONCLUSIONS

A few hours of hyperglycaemia in Type 1 diabetic patients leads to a reduction of isometric muscle performance, whereas isokinetic muscle strength is unchanged. The reduction in muscle strength could play a role in the development of fatigue and is related more closely to ambient glucose concentrations than to systemic glucose availability.

Efeito da hidratação com carboidratos na resposta glicêmica de diabéticos tipo 1 durante o exercício

Não está claro se a ingestão de carboidratos (CHO) através de bebidas esportivas pode manter a glicemia em diabéticos tipo 1. A finalidade deste estudo foi examinar a glicemia em adolescentes com diabetes tipo 1 que ingeriram bebidas esportivas com 6% de CHO durante e após o exercício. Dez adolescentes (5 meninas e 5 meninos, 15,3 ± 2,4 anos) com o diabetes controlado (HbA1c < 12%), e sem complicações da doença, exercitaram-se em um cicloergômetro a 55-60% do pico máximo de consumo de O2 (VO2pico) durante 60 minutos em dois dias separados. Em ordem randomizada e desenho duplo-cego, os sujeitos ingeriram (5ml·kg-1 antes do exercício, e 2ml·kg-1 a cada 15 minutos de exercício) bebida esportiva com 6% de CHO ou água com sabor sem CHO (placebo) com cor e sabor similares aos da bebida esportiva. Após uma hora de exercício, a glicemia não diminuiu significativamente quando foi ministrada bebida esportiva (CHO-6%) (221,0 ± 78 para 200,5 ± 111mg·dL-1, p > 0,05), e diminuiu significativamente na situação placebo (282,9 ± 85 para 160,2 ± 77mg·dL-1, p < 0,05) (9 vs. 43,2%). Após 30 minutos de recuperação, a glicemia foi de 177,2 ± 107mg·dL-1 com CHO e 149,1 ± 69,6mg·dL-1 com placebo, representando 20,1% e 47,3% dos níveis pré-exercício. Não foram encontradas diferenças significativas entre as situações na freqüência cardíaca, taxa de percepção de esforço, na insulina e eletrólitos sanguíneos. Não foram encontradas alterações no hematócrito e hemoglobina durante o exercício, indicando que os sujeitos permaneceram euidratados. Em conclusão, o uso de bebidas contendo 6% de CHO atenuou a redução da glicemia induzida pelo exercício em adolescentes com diabetes tipo 1.

Carbohydrate requirement and insulin concentration during moderate exercise in type 1 diabetic patients

The lack in control of insulin release combined with an inadequate carbohydrate (CHO) ingestion accounts for the occurrence of frequent metabolic unbalances during exercise in type 1 diabetic patients. The aim of the study was to quantify, in these patients, the CHO requirement to prevent hypoglycemia during moderate exercise performed at different time intervals after morning subcutaneous insulin injection. Twelve type 1 diabetic patients and 12 well-matched healthy subjects cycled 4 times for 1 hour at a constant workload. The rate of glucose oxidation was calculated continuously by indirect calorimetry throughout the exercise, while blood parameters were assessed periodically and orally given CHO were checked. CHO needed by the patients to prevent hypoglycemia decreased as the time elapsed from insulin administration increased, amounting to 0.63 +/- 0.30, 0.44 +/- 0.32, 0.28 +/- 0.24, and 0.14 +/- 0.18 g/kg after 1, 2.5, 4, and 5.5 hours, respectively. Total glucose requirement during moderate exercise (sum of alimentary and extracellular source) was correlated (r = 0.739, P <.001) to plasma insulin concentration, but not with fitness level. Time elapsed from last insulin dose is not a factor influencing the risk of hypoglycemia during exercise when a proportional, appropriate amount of CHO is ingested.

Oral glucose ingestion increases endurance capacity in normal and diabetic (type I) humans

The effects of an oral glucose administration (1 g/kg) 30 min before exercise on endurance capacity and metabolic responses were studied in 21 type I diabetic patients [insulin-dependent diabetes mellitus (IDDM)] and 23 normal controls (Con). Cycle ergometer exercise (55-60% of maximal O2 uptake) was performed until exhaustion. Glucose administration significantly increased endurance capacity in Con (112 +/- 7 vs. 125 +/- 6 min, P < 0.05) but only in IDDM patients whose blood glucose decreased during exercise (70.8 +/- 8.2 vs. 82.8 +/- 9.4 min, P < 0.05). Hyperglycemia was normalized at 15 min of exercise in Con (7.4 +/- 0.2 vs. 4.8 +/- 0.2 mM) but not in IDDM patients (12.4 +/- 0.7 vs. 15.6 +/- 0.9 mM). In Con, insulin and C-peptide levels were normalized during exercise. Glucose administration decreased growth hormone levels in both groups. In conclusion, oral glucose ingestion 30 min before exercise increases endurance capacity in Con and in some IDDM patients. In IDDM patients, in contrast with Con, exercise to exhaustion attenuates hyperglycemia but does not bring blood glucose levels to preglucose levels.

Defective endogenous opioid response to exercise in type I diabetic patients

Plasma beta-endorphin (beta-E) concentration was determined before, during, and after a standardized incremental exercise test to maximal capacity in eight type I diabetic patients and eight normal control subjects. Diabetic patients were studied under normoglycemic and hyperglycemic conditions in a single-blind random fashion to differentiate between the effects of acute hyperglycemia and of diabetes per se on the beta-E response to exercise. The perceived magnitude of leg effort elicited by exercise was evaluated using a category scale. Whereas plasma beta-E concentrations increased in control subjects with increasing workload, causing significantly higher beta-E levels at the end of exercise than at the beginning (P < .001), no such increase could be observed in the diabetic patients under normoglycemic and hyperglycemic conditions. In addition, baseline plasma beta-E concentrations were significantly lower in normoglycemic (P < .01) and hyperglycemic (P < .001) diabetic patients than in control subjects. Even during the recovery period, patients' beta-E levels remained significantly lower than those of control subjects. At submaximal levels of power output, the perceived intensity of leg effort was significantly higher in normoglycemic and hyperglycemic diabetic patients than in control subjects. We conclude that in type I diabetic patients, the ability of the endogenous opioid system to respond to exercise-induced stress is impaired under hyperglycemic and even under normoglycemic conditions. Considering the effect of endogenous opioids on stress tolerance, such changes may compromise exercise performance in diabetic patients.

Voluntary exercise improves glycemia in non-obese diabetic (NOD) mice

The non-obese diabetic (NOD) mouse was used to investigate the effects of voluntary wheel running exercise on blood glucose levels, glycosylated hemoglobin, and longevity in Type 1 diabetes mellitus. In Experiment 1, diabetic and normoglycemic mice exercised 5 h/day, 5 days/week for 3 weeks matched with non-exercising controls. In diabetic animals a positive correlation was found between blood glucose and the number of revolutions performed (P < or = 0.02). Exercise also significantly lowered blood glucose between baseline and post-exercise in both diabetic and normoglycemic animals. In Experiment 2, mice exercised 2 h/day, 5 days/week. For the diabetic animals, glycosylated hemoglobin was lower than that of matched non-exercising diabetic animals at week 3 (11.1 +/- 0.6% vs. 15.0 +/- 1.6%, P < 0.001). Diabetic runners were able to train and significantly increased running in the first 4 weeks (P < 0.05). At the end of 9 weeks all 5 diabetic runners were alive, compared with 3 of 5 non-running diabetic animals. We conclude: (i) the NOD mouse is a useful model for the study of exercise in Type 1 diabetes, (ii) running exercise is associated with a drop in blood glucose, (iii) the amount of voluntary exercise performed correlates with blood glucose in diabetic animals, and (iv) diabetic mice will increase running distance in the first few weeks after diagnosis.