Catecholamines and the effects of exercise, training and gender

Nutrition and human health from a sex-gender perspective

Nutrition exerts a life-long impact on human health, and the interaction between nutrition and health has been known for centuries. The recent literature has suggested that nutrition could differently influence the health of male and female individuals. Until the last decade of the 20th century, research on women has been neglected, and the results obtained in men have been directly translated to women in both the medicine and nutrition fields. Consequently, most modern guidelines are based on studies predominantly conducted on men. However, there are many sex-gender differences that are the result of multifactorial inputs, including gene repertoires, sex steroid hormones, and environmental factors (e.g., food components). The effects of these different inputs in male and female physiology will be different in different periods of ontogenetic development as well as during pregnancy and the ovarian cycle in females, which are also age dependent. As a result, different strategies have evolved to maintain male and female body homeostasis, which, in turn, implies that there are important differences in the bioavailability, metabolism, distribution, and elimination of foods and beverages in males and females. This article will review some of these differences underlying the impact of food components on the risk of developing diseases from a sex-gender perspective.

Exercise-related hypoglycemia in diabetes mellitus

Current recommendations are that people with Type 1 and Type 2 diabetes mellitus exercise regularly. However, in cases in which insulin or insulin secretagogues are used to manage diabetes, patients have an increased risk of developing hypoglycemia, which is amplified during and after exercise. Repeated episodes of hypoglycemia blunt autonomic nervous system, neuroendocrine and metabolic defenses (counter-regulatory responses) against subsequent episodes of falling blood glucose levels during exercise. Likewise, antecedent exercise blunts counter-regulatory responses to subsequent hypoglycemia. This can lead to a vicious cycle, by which each episode of either exercise or hypoglycemia further blunts counter-regulatory responses. Although contemporary insulin therapies cannot fully mimic physiologic changes in insulin secretion, people with diabetes have several management options to avoid hypoglycemia during and after exercise, including regularly monitoring blood glucose, reducing basal and/or bolus insulin, and consuming supplemental carbohydrates.

Exercise induces a marked increase in plasma follistatin: evidence that follistatin is a contraction-induced hepatokine

Follistatin is a member of the TGF-β super family and inhibits the action of myostatin to regulate skeletal muscle growth. The regulation of follistatin during physical exercise is unclear but may be important because physical activity is a major intervention to prevent age-related sarcopenia. First, healthy subjects performed either bicycle or one-legged knee extensor exercise. Arterial-venous differences were assessed during the one-legged knee extensor experiment. Next, mice performed 1 h of swimming, and the expression of follistatin was examined in various tissues using quantitative PCR. Western blotting assessed follistatin protein content in the liver. IL-6 and epinephrine were investigated as drivers of follistatin secretion. After 3 h of bicycle exercise, plasma follistatin increased 3 h into recovery with a peak of 7-fold. No net release of follistatin could be detected from the exercising limb. In mice performing a bout of swimming exercise, increases in plasma follistatin as well as follistatin mRNA and protein expression in the liver were observed. IL-6 infusion to healthy young men did not affect the follistatin concentration in the circulation. When mice were stimulated with epinephrine, no increase in the hepatic mRNA of follistatin was observed. This is the first study to demonstrate that plasma follistatin is increased during exercise and most likely originates from the liver. These data introduce new perspectives regarding muscle-liver cross talk during exercise and during recovery from exercise.

High-intensity intermittent exercise and fat loss

The effect of regular aerobic exercise on body fat is negligible; however, other forms of exercise may have a greater impact on body composition. For example, emerging research examining high-intensity intermittent exercise (HIIE) indicates that it may be more effective at reducing subcutaneous and abdominal body fat than other types of exercise. The mechanisms underlying the fat reduction induced by HIIE, however, are undetermined. Regular HIIE has been shown to significantly increase both aerobic and anaerobic fitness. HIIE also significantly lowers insulin resistance and results in a number of skeletal muscle adaptations that result in enhanced skeletal muscle fat oxidation and improved glucose tolerance. This review summarizes the results of HIIE studies on fat loss, fitness, insulin resistance, and skeletal muscle. Possible mechanisms underlying HIIE-induced fat loss and implications for the use of HIIE in the treatment and prevention of obesity are also discussed.

Intense exercise training induces adaptation in expression and responsiveness of cardiac β-adrenoceptors in diabetic rats

Background

Informations about the effects of intense exercise training on diabetes-induced myocardial dysfunctions are lacking. We have examined the effects of intense exercise training on the cardiac function of diabetic rats, especially focusing on the Langendorff β-adrenergic responsiveness and on the β-adrenoceptors protein expression.

Methods

Control or Streptozotocin induced-diabetic male Wistar rats were randomly assigned to sedentary or trained groups. The training program consisted of 8 weeks running on a treadmill (10° incline, up to 25 m/min, 60 min/day) and was considered to be intense for diabetic rats.

Results

This intense exercise training amplified the in vivo diabetes-induced bradycardia. It had no effect on Langendorff basal cardiac contraction and relaxation performances in control and diabetic rats. In diabetic rats, it accentuated the Langendorff reduced responsiveness to β-adrenergic stimulation. It did not blunt the diabetes-induced decrease of β1-adrenoceptors protein expression, displayed a significant decrease in the β2-adrenoceptors protein expression and normalized the β3-adrenoceptors protein expression.

Conclusions

Intense exercise training accentuated the decrease in the myocardial responsiveness to β-adrenergic stimulation induced by diabetes. This defect stems principally from the β2-adrenoceptors protein expression reduction. Thus, these results demonstrate that intense exercise training induces specific effects on the β-adrenergic system in diabetes.

Impaired left and right ventricular function following prolonged exercise in young athletes: influence of exercise intensity and responses to dobutamine stress

We examined the effect of intensity during prolonged exercise (PE) on left (LV) and right ventricular (RV) function. Subjects included 18 individuals (mean ± SE: age = 28.1 ± 1.1 yr, maximal aerobic power = 55.1 ± 1.6 ml · kg−1 · min−1), who performed 150 min of exercise at 60 and 80% maximal aerobic power on two separate occasions. Transthoracic echocardiography assessed systolic and diastolic performance, and blood sampling assessed hydration status and noradrenaline levels before (pre), during (15 and 150 min), and 60 min following (post) PE. β-Adrenergic sensitivity pre- and post-PE was assessed by dobutamine stress. High-intensity PE (15 vs. 150 min) induced reductions in LV ejection fraction (69.3 ± 1.3 vs. 63.5 ± 1.3%, P = 0.000), LV strain (−23.5 ± 0.6 vs. −22.3 ± 0.6%, P = 0.034), and RV strain (−26.3 ± 0.6 vs. −23.0 ± 0.6%, P < 0.01). Both exercise intensities induced diastolic reductions (pre vs. post) in the ratio of septal early wave of annular tissue velocities to late/atrial wave of annular tissue velocities (2.15 ± 0.15 vs. 1.62 ± 0.09; 2.21 ± 0.15 vs. 1.48 ± 0.10), ratio of lateral early wave of annular tissue velocities to late/atrial wave of annular tissue velocities (3.84 ± 0.42 vs. 2.49 ± 0.20; 3.56 ± 0.32 vs. 2.08 ± 0.18), ratio of early to late LV strain rate (2.42, ± 0.16 vs. 1.97 ± 0.13; 2.30 ± 0.15 vs. 1.81 ± 0.11), and ratio of early to late RV strain rate (2.03 ± 0.17 vs. 1.51 ± 0.09; 2.16 ± 0.16 vs. 1.44 ± 0.11) ( P < 0.001). Evidence of β-adrenergic sensitivity was supported by a decreased strain, strain rate, ejection fraction, and systolic pressure-volume ratio response to dobutamine ( P < 0.05) with elevated noradrenaline ( P < 0.01). PE-induced reductions in LV and RV systolic function were related to exercise intensity and β-adrenergic desensitization. The clinical significance of exercise-induced cardiac fatigue warrants further research.

Impaired skeletal muscle beta-adrenergic activation and lipolysis are associated with whole-body insulin resistance in rats bred for low intrinsic exercise capacity

Rats selectively bred for high endurance running capacity (HCR) have higher insulin sensitivity and improved metabolic health compared with those bred for low endurance capacity (LCR). We investigated several skeletal muscle characteristics, in vitro and in vivo, that could contribute to the metabolic phenotypes observed in sedentary LCR and HCR rats. After 16 generations of selective breeding, HCR had approximately 400% higher running capacity (P < 0.001), improved insulin sensitivity (P < 0.001), and lower fasting plasma glucose and triglycerides (P < 0.05) compared with LCR. Skeletal muscle ceramide and diacylglycerol content, basal AMP-activated protein kinase (AMPK) activity, and basal lipolysis were similar between LCR and HCR. However, the stimulation of lipolysis in response to 10 mum isoproterenol was 70% higher in HCR (P = 0.004). Impaired isoproterenol sensitivity in LCR was associated with lower basal triacylglycerol lipase activity, Ser660 phosphorylation of HSL, and beta2-adrenergic receptor protein content in skeletal muscle. Expression of the orphan nuclear receptor Nur77, which is induced by beta-adrenergic signaling and is associated with insulin sensitivity, was lower in LCR (P < 0.05). Muscle protein content of Nur77 target genes, including uncoupling protein 3, fatty acid translocase/CD36, and the AMPK gamma3 subunit were also lower in LCR (P < 0.05). Our investigation associates whole-body insulin resistance with impaired beta-adrenergic response and reduced expression of genes that are critical regulators of glucose and lipid metabolism in skeletal muscle. We identify impaired beta-adrenergic signal transduction as a potential mechanism for impaired metabolic health after artificial selection for low intrinsic exercise capacity.

Central angiotensin AT1 receptors are involved in metabolic adjustments in response to graded exercise in rats

To investigate the influence of central angiotensin AT1-receptors blockade on metabolic adjustments during graded exercise, Losartan (Los) was intracerebroventricularly injected in rats before running until fatigue. Oxygen consumption (VO2) was measured (n=6) and blood samples collected (n=7) to determine variations of glucose, lactate and free fatty acids (FFA). Los-rats exhibited a hyperglycemic response, already observed at 20% of maximal work, followed by a higher lactate levels and FFA mobilization from adipose tissue. Despite the reduced total time to fatigue and the higher VO2 associated with reduced mechanical efficiency, exercise led to the attainment of similar levels of effort in both groups. In summary, central AT1-receptor blockade during graded exercise induces hyperglycemia and higher FFA mobilization from adipose tissue at low exercise intensities in rats running at the same absolute exercise intensity. These data suggest that the central angiotensinergic system is involved in metabolic adjustments during exercise since central blockade of AT1-receptors shifts energy balance during graded exercise, similarly to situations of higher and premature sympathetic activation.

Aerobic exercise training improves autonomic nervous control in patients with COPD

OBJECTIVES

Autonomic modulation is adversely impacted in patients with chronic obstructive pulmonary disease (COPD). The purpose of the present investigation is to assess the effects of a 6-week aerobic exercise training program on autonomic modulation of heart rate in patients with COPD.

METHODS

Forty patients of both sexes with moderate-to-severe COPD were randomly allocated to aerobic exercise training (PT, n=20) or to usual care (Control, n=20). The training program consisted of lower and upper limb stretching and 30 min of treadmill exercise, 3 times per week for a 6-week period. Physiological data during symptom-limited exercise testing and the six-minute walk test (6MWT) were assessed. In addition, R-R intervals were obtained at rest and during the 6MWT. Heart rate variability was analyzed by time (rMSSD and SDNN index) and frequency domains (high frequency--HF, low frequency--LF and HF/LF ratio).

RESULTS

Peak oxygen consumption significantly improved in the training group only (p<0.05). Moreover, the training group demonstrated significant improvements (p<0.05) in blood lactate, minute ventilation, dyspnea at peak exercise, sympathetic activity, and parasympathetic activity at rest and during submaximal exercise. Lastly, a positive and significant correlation was found between change in 6MWT distance and rMSSD index (r=0.65 and p=0.001).

CONCLUSIONS

Neural control of heart rate, in addition to other clinically valuable measures, is positively altered in moderate-severe COPD patients following 6 weeks of aerobic exercise training. The improvement in submaximal performance after exercise training was associated with parasympathetic activity.

Repeated bouts of moderate-intensity aerobic exercise reduce airway reactivity in a murine asthma model

We have reported that moderate-intensity aerobic exercise training attenuates airway inflammation in mice sensitized/challenged with ovalbumin (OVA). The current study determined the effects of repeated bouts of aerobic exercise at a moderate intensity on airway hyperresponsiveness (AHR) in these mice. Mice were sensitized/challenged with OVA or saline and exercised at a moderate intensity 3 times/week for 4 weeks. At protocol completion, mice were analyzed for changes in AHR via mechanical ventilation. Results show that exercise decreased total lung resistance 60% in OVA-treated mice as compared with controls; exercise also decreased airway smooth muscle (ASM) thickness. In contrast, exercise increased circulating epinephrine levels 3-fold in saline- and OVA-treated mice. Because epinephrine binds beta(2)-adrenergic receptors (AR), which facilitate bronchodilatation, the role of beta(2)-AR in exercise-mediated improvements in AHR was examined. Application of the beta(2)-AR antagonist butoxamine HCl blocked the effects of exercise on lung resistance in OVA-treated mice. In parallel, ASM cells were examined for changes in the protein expression of beta(2)-AR and G-protein receptor kinase-2 (GRK-2); GRK-2 promotes beta(2)-AR desensitization. Exercise had no effect on beta(2)-AR expression in ASM cells of OVA-treated mice; however, exercise decreased GRK-2 expression by 50% as compared with controls. Exercise also decreased prostaglandin E(2) (PGE(2)) production 5-fold, but had no effect on E prostanoid-1 (EP1) receptor expression within the lungs of OVA-treated mice; both PGE(2) and the EP1 receptor have been implicated in beta(2)-AR desensitization. Together, these data indicate that moderate-intensity aerobic exercise training attenuates AHR via a mechanism that involves beta(2)-AR.