Epinephrine infusion during moderate intensity exercise increases glucose production and uptake

Gluconeogenesis Flux in Metabolic Disease

Gluconeogenesis is a critical biosynthetic process that helps maintain whole-body glucose homeostasis and becomes altered in certain medical diseases. We review gluconeogenic flux in various medical diseases, including common metabolic disorders, hormonal imbalances, specific inborn genetic errors, and cancer. We discuss how the altered gluconeogenic activity contributes to disease pathogenesis using data from experiments using isotopic tracer and spectroscopy methodologies. These in vitro, animal, and human studies provide insights into the changes in circulating levels of available gluconeogenesis substrates and the efficiency of converting those substrates to glucose by gluconeogenic organs. We highlight ongoing knowledge gaps, discuss emerging research areas, and suggest future investigations. A better understanding of altered gluconeogenesis flux may ultimately identify novel and targeted treatment strategies for such diseases.

Factors Influencing Substrate Oxidation During Submaximal Cycling: A Modelling Analysis

BACKGROUND

Multiple factors influence substrate oxidation during exercise including exercise duration and intensity, sex, and dietary intake before and during exercise. However, the relative influence and interaction between these factors is unclear.

OBJECTIVES

Our aim was to investigate factors influencing the respiratory exchange ratio (RER) during continuous exercise and formulate multivariable regression models to determine which factors best explain RER during exercise, as well as their relative influence.

METHODS

Data were extracted from 434 studies reporting RER during continuous cycling exercise. General linear mixed-effect models were used to determine relationships between RER and factors purported to influence RER (e.g., exercise duration and intensity, muscle glycogen, dietary intake, age, and sex), and to examine which factors influenced RER, with standardized coefficients used to assess their relative influence.

RESULTS

The RER decreases with exercise duration, dietary fat intake, age, VO_2max, and percentage of type I muscle fibers, and increases with dietary carbohydrate intake, exercise intensity, male sex, and carbohydrate intake before and during exercise. The modelling could explain up to 59% of the variation in RER, and a model using exclusively easily modified factors (exercise duration and intensity, and dietary intake before and during exercise) could only explain 36% of the variation in RER. Variables with the largest effect on RER were sex, dietary intake, and exercise duration. Among the diet-related factors, daily fat and carbohydrate intake have a larger influence than carbohydrate ingestion during exercise.

CONCLUSION

Variability in RER during exercise cannot be fully accounted for by models incorporating a range of participant, diet, exercise, and physiological characteristics. To better understand what influences substrate oxidation during exercise further research is required on older subjects and females, and on other factors that could explain additional variability in RER.

Minimizing the Risk of Exercise-Induced Glucose Fluctuations in People Living With Type 1 Diabetes Using Continuous Subcutaneous Insulin Infusion: An Overview of Strategies

Physical activity (PA) is important for individuals living with type 1 diabetes (T1D) due to its various health benefits. Nonetheless, maintaining adequate glycemic control around PA remains a challenge for many individuals living with T1D because of the difficulty in properly managing circulating insulin levels around PA. Although the most common problem is increased incidence of hypoglycemia during and after most types of PA, hyperglycemia can also occur. Accordingly, a large proportion of people living with T1D are sedentary partly due to the fear of PA-associated hypoglycemia. Continuous subcutaneous insulin infusion (CSII) offers a higher precision and flexibility to adjust insulin basal rates and boluses according to the individual's specific needs around PA practice. Indeed, for physically active patients with T1D, CSII can be a preferred option to facilitate glucose regulation. To our knowledge, there are no guidelines to manage exercise-induced hypoglycemia during PA, specifically for individuals living with T1D and using CSII. In this review, we highlight the current state of knowledge on exercise-related glucose variations, especially hypoglycemic risk and its underlying physiology. We also detail the current recommendations for insulin modulations according to the different PA modalities (type, intensity, duration, frequency) in individuals living with T1D using CSII.

Plasma Epinephrine Contributes to the Development of Experimental Hypoglycemia-Associated Autonomic Failure

BACKGROUND

Recurrent hypoglycemia blunts counter-regulatory responses to subsequent hypoglycemic episodes, a syndrome known as hypoglycemia-associated autonomic failure (HAAF). Since adrenergic receptor blockade has been reported to prevent HAAF, we investigated whether the hypoglycemia-associated rise in plasma epinephrine contributes to pathophysiology and reported interindividual differences in susceptibility to HAAF.

METHODS

To assess the role of hypoglycemia-associated epinephrine responses in the susceptibility to HAAF, 24 adult nondiabetic subjects underwent two 2-hour hyperinsulinemic hypoglycemic clamp studies (nadir 54 mg/dL; 0-2 hours and 4-6 hours) on Day 1, followed by a third identical clamp on Day 2. We challenged an additional 7 subjects with two 2-hour infusions of epinephrine (0.03 μg/kg/min; 0-2 hours and 4-6 hours) vs saline on Day 1 followed by a 200-minute stepped hypoglycemic clamp (90, 80, 70, and 60 mg/dL) on Day 2.

RESULTS

Thirteen out of 24 subjects developed HAAF, defined by ≥20% reduction in average epinephrine levels during the final 30 minutes of the third compared with the first hypoglycemic episode (P < 0.001). Average epinephrine levels during the final 30 minutes of the first hypoglycemic episode were 2.3 times higher in subjects who developed HAAF compared with those who did not (P = 0.006).Compared to saline, epinephrine infusion on Day 1 reduced the epinephrine responses by 27% at the 70 and 60 mg/dL glucose steps combined (P = 0.04), with a parallel reduction in hypoglycemic symptoms (P = 0.03) on Day 2.

CONCLUSIONS

Increases in plasma epinephrine reproduce key features of HAAF in nondiabetic subjects. Marked interindividual variability in epinephrine responses to hypoglycemia may explain an individual's susceptibility to developing HAAF.

A 40-YEAR FOLLOW-UP OF A PATIENT WITH MULTIPLE PARAGANGLIOMAS AND A SDHD MUTATION

Context

Germline mutations in Succinate Dehydrogenase Complex Subunit D gene (SDHD) predispose to predominantly benign head and neck and/or thoracic-abdominal pelvic paragangliomas (PGLs).

Objective

We present the case of a patient carrying a germline SDHD mutation responsible for multiple PGLs, who was followed for 40 years. He was initially diagnosed with a left cervical PGL at the age of 23 years, treated by surgery. Then, he recurred and developed a multifocal disease. The second-line therapeutic option was a three-dimensional conformal radiotherapy performed in 2008. In 2013 the patient had clinical, hormonal, PET- and SPECT-CT data revealing a disease progression. The treatment with the long-acting somatostatin analogue Octreotide Lar was carried out till the patient's death caused by pulmonary embolism in December 2014.

Results

Complex treatment led to a long clinical and biochemical remission and control of tumor growth.

Conclusions

Despite their usually benign behavior, multicentric SDHD-related PGLs can require a multimodal approach involving surgery, radiotherapy and medical treatment for providing a long-term control of the disease and maintaining a good quality of life.

Is Exercise Training Appropriate for Patients With Advanced Heart Failure Receiving Continuous Inotropic Infusion? A Review

Exercise-based rehabilitation programs have been reported to have beneficial effects for patients with heart failure. However, there is little evidence about whether this is the case in patients with more severe heart failure. In particular, there is a question in the clinical setting whether patients with advanced heart failure and continuous inotropic infusion should be prescribed exercise training. In contrast, many studies conclude that prolonged immobility associated with heart failure profoundly impairs physical function and promotes muscle wasting that could further hasten the course of heart failure. By contrast, exercise training has various effects not only in improving exercise capacity but also on vascular function, skeletal muscle, and autonomic balance. In this review, we summarize the effectiveness and discuss methods of exercise training in patients with advanced heart failure receiving continuous inotropic agents such as dobutamine.

IL-6 Linkage to Exercise-Induced Shifts in Lipid-Related Metabolites: A Metabolomics-Based Analysis

Metabolomics profiling and bioinformatics technologies were used to determine the relationship between exercise-induced increases in IL-6 and lipid-related metabolites. Twenty-four male runners (age 36.5 ± 1.8 y) ran on treadmills to exhaustion (2.26 ± 0.01 h, 24.9 ± 1.3 km, 69.7 ± 1.9% VO_2max). Vastus lateralis muscle biopsy and blood samples were collected before and immediately after running and showed a 33.7 ± 4.2% decrease in muscle glycogen, 39.0 ± 8.8-, 2.4 ± 0.3-, and 1.4 ± 0.1-fold increases in plasma IL-6, IL-8, and MCP-1, respectively, and 95.0 ± 18.9 and 158 ± 20.6% increases in cortisol and epinephrine, respectively (all, P < 0.001). The metabolomics analysis revealed changes in 209 metabolites, especially long- and medium-chain fatty acids, fatty acid oxidation products (dicarboxylate and monohydroxy fatty acids, acylcarnitines), and ketone bodies. OPLS-DA modeling supported a strong separation in pre- and post-exercise samples (R2Y = 0.964, Q2Y = 0.902). OPLSR analysis failed to produce a viable model for the relationship between IL-6 and all lipid-related metabolites (R2Y = 0.76, Q2Y = -0.0748). Multiple structure equation models were evaluated based on IL-6, with the best-fit pathway model showing a linkage of exercise time to IL-6, then carnitine, and 13-methylmyristic acid (a marker for adipose tissue lipolysis) and sebacate. These metabolomics-based data indicate that the increase in plasma IL-6 after long endurance running has a minor relationship to increases in lipid-related metabolites.

Effect of antecedent moderate-intensity exercise on the glycemia-increasing effect of a 30-sec maximal sprint: a sex comparison

This study investigated whether a prior bout of moderate-intensity exercise attenuates the glycemia-increasing effect of a maximal 30-sec sprint. A secondary aim was to determine whether the effect of antecedent exercise on the glucoregulatory response to sprinting is affected by sex. Participants (men n = 8; women n = 7) were tested on two occasions during which they either rested (CON) or cycled for 60-min at a moderate intensity of ~65% (EX) before performing a 30-sec maximal cycling effort 195 min later. In response to the sprint, blood glucose increased to a similar extent between EX and CON trials, peaking at 10 min of recovery, with no difference between sexes (P > 0.05). Blood glucose then declined at a faster rate in EX, and this was associated with a glucose rate of disappearance (R_d) that exceeded the glucose rate of appearance (R_a) earlier in EX compared with CON, although the overall glucose R_a and R_d profile was higher in men compared with women (P < 0.05). The response of growth hormone was attenuated during recovery from EX compared with CON (P < 0.05), with a lower absolute response in women compared with men (P < 0.05). The response of epinephrine and norepinephrine was also lower in women compared with men (P < 0.05) but similar between trials. In summary, a prior bout of moderate-intensity exercise does not affect the magnitude of the glycemia-increasing response to a 30-sec sprint; however, the subsequent decline in blood glucose is more rapid. This blood glucose response is similar between men and women, despite less pronounced changes in glucose R_a and R_d, and a lower response of plasma catecholamines and growth hormone to sprinting in women.

Carbohydrate use and reduction in number of balance beam falls: implications for mental and physical fatigue

BACKGROUND

Artistic Gymnastics is a sport where athletes are frequently fatigued. One element that might influence this aspect is carbohydrate, an important energy substrate for the muscles and the CNS. Our goal was to investigate the influence of fatigue over artistic gymnastics athlete's performance and the effects of a carbohydrate supplementation on their performance.

METHODS

We evaluated 15 athletes divided in 2 groups (control and fatigue) from 12 to 14 years old in two different experimental days. On the first day (water day), they did 5 sets of exercises on the balance beam (experimental protocol) ingesting only water, CG (control group) warmed up before the experimental protocol and FG (fatigue group) did a fatigue circuit, warm up exercises and then the experimental protocol. On the second day (carbohydrate day), we used the same protocol but CG ingested a sugar free flavored juice and FG ingested a 20% concentration maltodextrin solution before the protocol on the balance beam.

RESULTS

We observed a greater number of falls from the balance beam from the FG on the first day (5.40 ± 1.14 FG vs 3.33 ± 1.37 CG; p = 0.024) and a decrease in the number of falls on the second day (2.29 ± 1.25 FG water day vs 5.40 ± 1.14 FG carbohydrate day; p = 0.0013). Carbohydrate solution was able to supply muscle demands and improve the athlete's focus showed by the reduced number of falls.

The effect of a short sprint on postexercise whole-body glucose production and utilization rates in individuals with type 1 diabetes mellitus

CONTEXT

Recently we showed that a 10-sec maximal sprint effort performed before or after moderate intensity exercise can prevent early hypoglycemia during recovery in individuals with type 1 diabetes mellitus (T1DM). However, the mechanisms underlying this protective effect of sprinting are still unknown.

OBJECTIVE

The objective of the study was to test the hypothesis that short duration sprinting increases blood glucose levels via a disproportionate increase in glucose rate of appearance (Ra) relative to glucose rate of disappearance (Rd). SUBJECTS AND EXPERIMENTAL DESIGN: Eight T1DM participants were subjected to a euglycemic-euinsulinemic clamp and, together with nondiabetic participants, were infused with [6,6-(2)H]glucose before sprinting for 10 sec and allowed to recover for 2 h.

RESULTS

In response to sprinting, blood glucose levels increased by 1.2 ± 0.2 mmol/liter (P < 0.05) within 30 min of recovery in T1DM participants and remained stable afterward, whereas glycemia rose by only 0.40 ± 0.05 mmol/liter in the nondiabetic group. During recovery, glucose Ra did not change in both groups (P > 0.05), but glucose Rd in the nondiabetic and diabetic participants fell rapidly after exercise before returning within 30 min to preexercise levels. After sprinting, the levels of plasma epinephrine, norepinephrine, and GH rose transiently in both experimental groups (P < 0.05).

CONCLUSION

A sprint as short as 10 sec can increase plasma glucose levels in nondiabetic and T1DM individuals, with this rise resulting from a transient decline in glucose Rd rather than from a disproportionate rise in glucose Ra relative to glucose Rd as reported with intense aerobic exercise.

Increased postabsorptive and exercise-induced whole-body glucose production in patients with chronic obstructive pulmonary disease

Skeletal muscle biopsy studies have consistently shown a decreased oxidative phenotype in patients with moderate to severe chronic obstructive pulmonary disease (COPD). Limited information is available regarding potential adaptations or abnormalities in anaerobic metabolism and glucose homeostasis. Whole-body glucose production was assessed at rest and during exercise in COPD patients with moderate disease severity (forced expiratory volume in 1 second, 52% ± 3%), prestratified into normal-weight (n = 7; body mass index [BMI], 27.5 ± 0.9 kg·m(-2)) and underweight subjects (n = 6; BMI, 20.6 ± 0.7 kg·m(-2)), and in 8 healthy controls matched for age and BMI with the normal-weight COPD group. Glucose tolerance was normal in all subjects. Rate of appearance (R(a)) of glucose at rest and during submaximal cycling exercise was measured in postabsorptive state by infusion of stable isotope tracer [6,6-(2)H(2)]glucose. Resting glucose R(a) was significantly enhanced in underweight COPD patients compared with controls (16.7 ± 0.3 vs 15.1 ± 0.4 μmol·kg fat-free mass(-1)·min(-1), P < .05) and was inversely related to fat-free mass (r = -0.75, P < .01). Furthermore, the exercise-induced increase in glucose R(a) was enhanced in COPD patients (81.9% ± 3.4% vs 72.1% ± 2.0%, P = .05), resulting in elevated end-of-exercise glucose output. Differences were most pronounced in underweight patients, who were also characterized by enhanced plasma catecholamine levels and decreased insulin concentrations (all, P < .05). In normal-weight patients, there was evidence for decreased insulin sensitivity assessed by homeostatic modeling technique. Whole-body glucose production is increased in underweight COPD patients with normal glucose tolerance. It is hypothesized that lowered body weight in COPD has unique effects on glucose uptake despite reduced skeletal muscle oxidative capacity, relative hypoxemia, and sympathetic activation.

Normal insulin response to short-term intense exercise is abolished in Type 2 diabetic patients treated with gliclazide

BACKGROUND

Physical activity is an essential component of diabetes management; however, exercise is associated with the risk for metabolic decompensation. The aim of the study was to analyze insulin response to the short-term intense exercise in middle-aged Type 2 diabetic patients treated with gliclazide.

MATERIALS AND METHODS

Fourteen Type 2 diabetic patients (47.9+/-1.6 years, mean+/-S.E.M.), treated with gliclazide, and 14 healthy controls (45.1+/-1.0 years) were submitted to standard graduated submaximal (90% HR(max)) exercise treadmill testing at 2 h after standardized breakfast. Serum glucose, insulin, proinsulin, C peptide, growth hormone, insulin-like growth factor-1, and cortisol concentrations; and plasma lactate, glucagon, epinephrine, and norepinephrine concentrations were measured during the periexercise period up to the 60th min of the recovery period.

RESULTS

Significant hemodynamic (heart rate, systolic, and diastolic blood pressure), metabolic (lactate concentration), and hormonal (epinephrine and norepinephrine levels) responses to the exercise were similar in patients and healthy subjects. Glucose, insulin, and proinsulin levels were higher in the diabetic group at the preexercise and at all the next analyzed time points. The insulin concentration increased during the postprandial period in both groups and decreased subsequently during the exercise only in the control group, without concurrent C peptide decline. The C peptide-to-insulin ratio increased during the exercise and decreased immediately postexercise only in the control group.

CONCLUSIONS

The initial decrease of the insulin serum concentration during short-term intense exercise in normal middle-aged men is primarily related to the increased clearance of the hormone. Normal insulin response to the exercise was abolished in Type 2 diabetic patients treated with gliclazide.

Catecholamines and the effects of exercise, training and gender

Stress hormones, adrenaline (epinephrine) and noradrenaline (norepinephrine), are responsible for many adaptations both at rest and during exercise. Since their discovery, thousands of studies have focused on these two catecholamines and their importance in many adaptive processes to different stressors such as exercise, hypoglycaemia, hypoxia and heat exposure, and these studies are now well acknowledged. In fact, since adrenaline and noradrenaline are the main hormones whose concentrations increase markedly during exercise, many researchers have worked on the effect of exercise on these amines and reported 1.5 to >20 times basal concentrations depending on exercise characteristics (e.g. duration and intensity). Similarly, several studies have shown that adrenaline and noradrenaline are involved in cardiovascular and respiratory adjustments and in substrate mobilization and utilization. Thus, many studies have focused on physical training and gender effects on catecholamine response to exercise in an effort to verify if significant differences in catecholamine responses to exercise could be partly responsible for the different performances observed between trained and untrained subjects and/or men and women. In fact, previous studies conducted in men have used different types of exercise to compare trained and untrained subjects in response to exercise at the same absolute or relative intensity. Their results were conflicting for a while. As research progressed, parameters such as age, nutritional and emotional state have been found to influence catecholamine concentrations. As a result, most of the recent studies have taken into account all these parameters. Those studies also used very well trained subjects and/or more intense exercise, which is known to have a greater effect on catecholamine response so that differences between trained and untrained subjects are more likely to appear. Most findings then reported a higher adrenaline response to exercise in endurance-trained compared with untrained subjects in response to intense exercise at the same relative intensity as all-out exercise. This phenomenon is referred to as the 'sports adrenal medulla'. This higher capacity to secrete adrenaline was observed both in response to physical exercise and to other stimuli such as hypoglycaemia and hypoxia. For some authors, this phenomenon can partly explain the higher physical performance observed in trained compared with untrained subjects. More recently, these findings have also been reported in anaerobic-trained subjects in response to supramaximal exercise. In women, studies remain scarce; the results are more conflicting than in men and the physical training type (aerobic or anaerobic) effects on catecholamine response remain to be specified. Conversely, the works undertaken in animals are more unanimous and suggest that physical training can increase the capacity to secrete adrenaline via an increase of the adrenal gland volume and adrenaline content.

Intense exercise in type 1 diabetes: exploring the role of continuous glucose monitoring

Development of the external artificial pancreas (AP) is anticipated to be incremental, starting with simple and progressing to more complex applications incorporating exercise periods of various duration and intensity. Most studies investigating the effect of exercise on glucose excursions in subjects with type 1 diabetes either explored moderate exercise, which exerts different effects compared to intense exercise, or did not adopt continuous glucose monitoring combined with frequent plasma glucose measurements. Such studies could provide vital information. Performance of continuous glucose monitors during intense exercise could be evaluated to a greater extent. Frequently sampled blood glucose would facilitate better understanding of the relationship between intense exercise and metabolic processes, providing helpful information to patients with type 1 diabetes, clinicians, and researchers involved in the development of the AP.

Local and systemic effects on blood lactate concentration during exercise with small and large muscle groups

To evaluate the relationship between lactate release and [lac](art) and to investigate the influence of the catecholamines on the lactate release, 14 healthy men [age 25+/-3 (SE) year] were studied by superimposing cycle on forearm exercise, both at 65% of their maximal power reached in respective incremental tests. Handgrip exercise was performed for 30 min at 65% of peak power. In addition, between the tenth and the 22nd minute, cycling with the same intensity was superimposed. The increase in venous lactate concentration ([lac](ven)) (rest: 1.3+/-0.4 mmol.l(-1); 3rd min: 3.9+/-0.8 mmol.l(-1)) begins with the forearm exercise, whereas arterial lactate concentration ([lac](art)) remains almost unchanged. Once cycling has been added to forearm exercise (COMB), [lac](art) increases with a concomitant increase in [lac](ven) (12th min: [lac](art), 3.2+/-1.3 mmol.l(-1); [lac](ven), 5.7+/-2.2 mmol.l(-1)). A correlation between oxygen tension (P(v)O(2)) and [lac](ven) cannot be detected. There is a significant correlation between [lac](art) and norepinephrine ([NE]) (y=0.25x+1.2; r=0.815; p<0.01) but no correlation between lactate release and epinephrine ([EPI]) at moderate intensity. Our main conclusion is that lactate release from exercising muscles at moderate intensities is neither dependent on P(v)O(2) nor on [EPI] in the blood.

Effects of elevated plasma adrenaline levels on substrate metabolism, effort perception and muscle activation during low-to-moderate intensity exercise

The aim of this study was to differentiate the role of raised plasma adrenaline (Adr) concentrations from sympathoadrenal activation associated with moderate-intensity exercise, on muscle activation, cardiopulmonary responses, fuel metabolism, and ratings of perceived exertion (RPE) during low-intensity exercise. Two groups of subjects (MOD, n=6; LOW, n=7) cycled on two occasions for 90 min. MOD cycled at 68% VO(2max) with saline infusion, and at 34% VO(2max) with Adr infusion. LOW cycled twice at 34% VO(2max), with either Adr or saline infusion. Infusions (0.015 g Adr/kg/min) started at 15 min and increased plasma [Adr] somewhat higher than during exercise at 68% VO(2max) (approximately 1.9 vs. 1.4 nM, at 75 min). Mean plasma glucose and lactate concentrations during LOW were significantly higher with Adr than saline infusion (5.1+/-0.6 vs. 4.4+/-0.3 mmol/l, P<0.01 and 2.1+/-0.8 vs. 1.3+/-0.5 mmol/l, P<0.01, respectively). Elevated [Adr], without increased exercise intensity, did not alter glycogenolysis. There were also no effects of Adr infusion at 34% VO(2max) on heart rate, oxygen consumption, [FFA], respiratory exchange ratio, intramuscular triglyceride utilization, muscle activation or RPE. In conclusion, elevated [Adr] similar to those found during moderate-intensity exercise increased plasma glucose and lactate availability, but did not alter intramuscular fuel utilization, effort perception or muscle activation.

Anti-diabetic activities of fucosterol from Pelvetia siliquosa

Fucosterol isolated from Pelvetia siliquosa was tested for its anti-diabetic activity in vivo. Fucosterol, when administered orally at 30 mg/kg in streptozotocin-induced diabetic rats, was caused a significant decrease in serum glucose concentrations, and exhibited an inhibition of sorbitol accumulations in the lenses. Fucosterol, when administered orally at 300 mg/kg in epinephrine-induced diabetic rats, was also caused an inhibition of blood glucose level and glycogen degradation. These results demonstrated that fucosterol is a main anti-diabetic principle from the marine algae P. siliquosa.

Plasma glucose, insulin and catecholamine responses to a Wingate test in physically active women and men

The influence of gender on the glucose response to exercise remains contradictory. Moreover, to our knowledge, the glucoregulatory responses to anaerobic sprint exercise have only been studied in male subjects. Hence, the aim of the present study was to compare glucoregulatory metabolic (glucose and lactate) and hormonal (insulin, catecholamines and estradiol only in women) responses to a 30-s Wingate test, in physically active students. Eight women [19.8 (0.7) years] and eight men [22.0 (0.6) years] participated in a 30-s Wingate test on a bicycle ergometer. Plasma glucose, insulin, and catecholamine concentrations were determined at rest, at the end of both the warm-up and the exercise period and during the recovery (5, 10, 20, and 30 min). Results showed that the plasma glucose increase in response to a 30-s Wingate test was significantly higher in women than in men [0.99 (0.15) versus 0.33 (0.20) mmol l(-1) respectively, P<0.05]. Plasma insulin concentrations peaked at 10 min post-exercise and the increase between this time of recovery and the end of the warm-up was also significantly higher in women than in men [14.7 (2.9) versus 2.3 (1.9) pmol l(-1) respectively, P<0.05]. However, there was no gender difference concerning the catecholamine response. The study indicates a gender-related difference in post-exercise plasma glucose and insulin responses after a supramaximal exercise.

Combined infusion of epinephrine and norepinephrine during moderate exercise reproduces the glucoregulatory response of intense exercise

Intense exercise (IE) (>80% O(2max)) causes a seven- to eightfold increase in glucose production (R(a)) and a fourfold increase in glucose uptake (R(d)), resulting in hyperglycemia, whereas moderate exercise (ME) causes both to double. If norepinephrine (NE) plus epinephrine (Epi) infusion during ME produces the plasma levels and R(a) of IE, this would prove them capable of mediating these responses. Male subjects underwent 40 min of 53% O(2max) exercise, eight each with saline (control [CON]), or with combined NE + Epi (combined catecholamine infusion [CCI]) infusion from min 26-40. In CON and CCI, NE levels reached 7.3 +/- 0.7 and 33.1 +/- 2.9 nmol/l, Epi 0.94 +/- 0.08 and 7.06 +/- 0.44 nmol/l, and R(a) 3.8 +/- 0.4 and 12.9 +/- 0.8 mg. kg(-1). min(-1) (P < 0.001), respectively, at 40 min. R(d) increased to 3.5 +/- 0.4 vs. 11.2 +/- 0.8 mg. kg(-1). min(-1) and glycemia 5.2 +/- 0.2 mmol/l in CON vs. 6.5 +/- 0.2 mmol/l in CCI (P < 0.001). The glucagon-to-insulin ratio did not differ. Comparing CCI data to those from 14-min IE (n = 16), peak NE (33.6 +/- 5.1 nmol/l), Epi (5.32 +/- 0.93 nmol/l), and R(a) (13.0 +/- 1.0 mg. kg(-1). min(-1)) were comparable. The induced increments in NE, Epi, and R(a), all of the same magnitude as in IE, strongly support that circulating catecholamines can be the prime regulators of R(a) in IE.

Pharmacological activities of a new glycosaminoglycan, acharan sulfate isolated from the giant African snail Achatina fulica

Acharan sulfate (AS) is a glycosaminoglycan (GAG) prepared from the giant African snail, Achatina fulica. In this study, some biological activities of AS were evaluated on the basis of structural similarities to heparin/heparan sulfate and the biological functions of GAGs. We demonstrated that it exhibited strong immunostimulating activities as measured by carbon clearance test in mice and in vivo phagocytosis. It also exhibited a significant hypoglycemic activity in epinephrine (EP)-induced hyperglycemia as well as antifatigue effects by weight-loaded forced swimming test. And it showed hypolipidemic activities in cholesterol-rich mixture induced hyperlipidemia in rats. The above results indicate that AS has diverse biological activities and suggest therapeutically important target molecules.

Intense exercise has unique effects on both insulin release and its roles in glucoregulation: implications for diabetes

In intense exercise (>80% VO(2max)), unlike at lesser intensities, glucose is the exclusive muscle fuel. It must be mobilized from muscle and liver glycogen in both the fed and fasted states. Therefore, regulation of glucose production (GP) and glucose utilization (GU) have to be different from exercise at <60% VO(2max), in which it is established that the portal glucagon-to-insulin ratio causes the less than or equal to twofold increase in GP. GU is subject to complex regulation by insulin, plasma glucose, alternate substrates, other humoral factors, and muscle factors. At lower intensities, plasma glucose is constant during postabsorptive exercise and declines during postprandial exercise (and often in persons with diabetes). During such exercise, insulin secretion is inhibited by beta-cell alpha-adrenergic receptor activation. In contrast, in intense exercise, GP rises seven- to eightfold and GU rises three- to fourfold; therefore, glycemia increases and plasma insulin decreases minimally, if at all. Indeed, even an increase in insulin during alpha-blockade or during a pancreatic clamp does not prevent this response, nor does pre-exercise hyperinsulinemia due to a prior meal or glucose infusion. At exhaustion, GU initially decreases more than GP, which leads to greater hyperglycemia, requiring a substantial rise in insulin for 40--60 min to restore pre-exercise levels. Absence of this response in type 1 diabetes leads to sustained hyperglycemia, and mimicking it by intravenous infusion restores the normal response. Compelling evidence supports the conclusion that the marked catecholamine responses to intense exercise are responsible for both the GP increment (that occurs even during glucose infusion and postprandially) and the restrained increase of GU. These responses are normal in persons with type 1 diabetes, who often report exercise-induced hyperglycemia, and in whom the clinical challenge is to reproduce the recovery period hyperinsulinemia. Intense exercise in type 2 diabetes requires additional study.

Adrenaline increases skeletal muscle glycogenolysis, pyruvate dehydrogenase activation and carbohydrate oxidation during moderate exercise in humans

1. To evaluate the role of adrenaline in regulating carbohydrate metabolism during moderate exercise, 10 moderately trained men completed two 20 min exercise bouts at 58 +/- 2 % peak pulmonary oxygen uptake (V(O2,peak)). On one occasion saline was infused (CON), and on the other adrenaline was infused intravenously for 5 min prior to and throughout exercise (ADR). Glucose kinetics were measured by a primed, continuous infusion of 6,6-[(2)H]glucose and muscle samples were obtained prior to and at 1 and 20 min of exercise. 2. The infusion of adrenaline elevated (P < 0.01) plasma adrenaline concentrations at rest (pre-infusion, 0.28 +/- 0.09; post-infusion, 1.70 +/- 0.45 nmol l(-1); means +/- S.E.M.) and this effect was maintained throughout exercise. Total carbohydrate oxidation increased by 18 % and this effect was due to greater skeletal muscle glycogenolysis (P < 0.05) and pyruvate dehydrogenase (PDH) activation (P < 0.05, treatment effect). Glucose rate of appearance was not different between trials, but the infusion of adrenaline decreased (P < 0.05, treatment effect) skeletal muscle glucose uptake in ADR. 3. During exercise muscle glucose 6-phosphate (G-6-P) (P = 0.055, treatment effect) and lactate (P < 0.05) were elevated in ADR compared with CON and no changes were observed for pyruvate, creatine, phosphocreatine, ATP and the calculated free concentrations of ADP and AMP. 4. The data demonstrate that elevated plasma adrenaline levels during moderate exercise in untrained men increase skeletal muscle glycogen breakdown and PDH activation, which results in greater carbohydrate oxidation. The greater muscle glycogenolysis appears to be due to increased glycogen phosphorylase transformation whilst the increased PDH activity cannot be readily explained. Finally, the decreased glucose uptake observed during exercise in ADR is likely to be due to the increased intracellular G-6-P and a subsequent decrease in glucose phosphorylation.