Metabolic and hormonal effects of muscular exercise in juvenile type diabetics

The effects of acute hyperglycaemia on sports and exercise performance in type 1 diabetes: A systematic review and meta-analysis

OBJECTIVES

People with type 1 diabetes (T1D) are advised by health care professionals to target mild hyperglycaemia before and during exercise, to reduce the risk of hypoglycaemia. This review aimed to summarise the available evidence on the effects of acute hyperglycaemia on sports and exercise performance in T1D.

DESIGN

Systematic review and meta-analysis.

METHODS

Medline, EMBASE, CENTRAL, and Web of Science were searched until 29th May 2023 for studies investigating the effects of acute hyperglycaemia on any sports or exercise performance outcome in T1D. Random-effects meta-analysis was performed using standardised mean differences (SMD) when more than one study reported data for similar outcomes. Certainty of evidence for each outcome was assessed using GRADE.

RESULTS

Seven studies were included in the review, comprising data from 119 people with T1D. Meta-analysis provided moderate-certainty evidence that acute hyperglycaemia does not significantly affect aerobic exercise performance (SMD -0.17; 95 % CI -0.59, 0.26; p = 0.44). There is low- or very-low certainty evidence that acute hyperglycaemia has no effect on anaerobic (two outcomes), neuromuscular (seven outcomes) or neurocognitive performance (three outcomes), except impaired isometric knee extension strength. One study provided low-certainty evidence that the performance effects of hyperglycaemia may depend on circulating insulin levels.

CONCLUSIONS

Acute hyperglycaemia before or during exercise appears unlikely to affect aerobic performance to an extent that is relevant to most people with T1D, based on limited evidence. Future research in this field should focus on anaerobic, neuromuscular and neurocognitive performance, and examine the relevance of circulating insulin levels.

Exercise in adults with type 1 diabetes mellitus

Regular physical activity improves cardiometabolic and musculoskeletal health, helps with weight management, improves cognitive and psychosocial functioning, and is associated with reduced mortality related to cancer and diabetes mellitus. However, turnover rates of glucose in the blood increase dramatically during exercise, which often results in either hypoglycaemia or hyperglycaemia as well as increased glycaemic variability in individuals with type 1 diabetes mellitus (T1DM). A complex neuroendocrine response to an acute exercise session helps to maintain circulating levels of glucose in a fairly tight range in healthy individuals, while several abnormal physiological processes and limitations of insulin therapy limit the capacity of people with T1DM to exercise in a normoglycaemic state. Knowledge of the acute and chronic effects of exercise and regular physical activity is critical for the formulation of clinical strategies for the management of insulin and nutrition for active patients with T1DM. Emerging diabetes-related technologies, such as continuous glucose monitors, automated insulin delivery systems and the administration of solubilized glucagon, are demonstrating efficacy for preserving glucose homeostasis during and after exercise in this population of patients. This Review highlights the beneficial effects of regular exercise and details the complex endocrine and metabolic responses to different types of exercise for adults with T1DM. An overview of basic clinical strategies for the preservation of glucose homeostasis using emerging technologies is also provided.

The complex relationship between physical activity and diabetes: an overview

Diabetes mellitus (DM) is a widespread condition, representing a challenging disease to manage. Exercise is being increasingly recommended as part of the therapeutic regimen for DM but the management of different forms of physical activity is difficult for individuals with diabetes, trainers, and physicians. Regular exercise can improve health and well-being, helping individuals to achieve their target lipid profile, body composition, cardio-respiratory fitness, and glycemic goals. People with diabetes tend to be as inactive as the general population, with a large percentage of individuals not achieving the minimum amount of recommended physical activity levels. Indeed, several barriers to exercise exist for persons with diabetes, including sports eligibility, multi-modality management of diabetic athletes, and inadequate knowledge about adequate type and intensity of exercise. The aim of the present review is to provide the current understanding of mechanisms, recommendations, and beneficial effects of different modalities of exercise for the treatment of DM.

The competitive athlete with type 1 diabetes

Regular exercise is important for health, fitness and longevity in people living with type 1 diabetes, and many individuals seek to train and compete while living with the condition. Muscle, liver and glycogen metabolism can be normal in athletes with diabetes with good overall glucose management, and exercise performance can be facilitated by modifications to insulin dose and nutrition. However, maintaining normal glucose levels during training, travel and competition can be a major challenge for athletes living with type 1 diabetes. Some athletes have low-to-moderate levels of carbohydrate intake during training and rest days but tend to benefit, from both a glucose and performance perspective, from high rates of carbohydrate feeding during long-distance events. This review highlights the unique metabolic responses to various types of exercise in athletes living with type 1 diabetes. Graphical abstract.

A Prospective, Randomized Trial Testing Different Regimens of Carbohydrate Administration to Prevent Major Reduction in Plasma Glucose Follwing a Standardized Bout of Moderate Physical Activity in Patients with Type 1 Diabetes

AIM/HYPOTHESIS

It was the aim to prospectively study regimes of "preventive" carbohydrate administration to avoid major reduction in plasma glucose during physical activity.

METHODS

24 patients with type 1 diabetes (age 41±12 years; 11 women, 13 men; BMI 26.5±4.7 kg/m²; HbA_1c 9.1±1.5%; insulin dose 0.64±0.22 IU/kg body weight and day) participated in one experiment without physical activity and in three experiments with a 4 km, 60 min hike starting at 2 p.m.. No "preventive" carbohydrates, 2×10 g or 2×20 g carbohydrates (muesli bars) were taken when starting and after 30 min (randomized order). Plasma glucose was determined.

RESULTS

Within 30 min after starting physical activity, plasma glucose fell by approximately 70 mg/dl, making additional carbohydrate intake necessary in 70% of the subjects. This drop was not prevented by any regimens of "preventive" carbohydrate intake. After the nadir, plasma glucose rose faster after the 2×20 g carbohydrate regime (the largest amount tested; p=0.0036). With "preventive" administration of carbohydrates, significantly (p<0.05) less additional "therapeutic" carbohydrates needed to be administered in 6 h following the initiation of the hike.

CONCLUSIONS/INTERPRETATION

In conclusion, in the setting of 2 h postprandial exercise in type 1 diabetes, preventive carbohydrate supplementation alone will not completely eliminate the risk of brisk falls in plasma glucose concentrations or hypoglycaemic episodes. Else, higher amounts or repeated administration of carbohydrates may be necessary.

CarbMetSim: A discrete-event simulator for carbohydrate metabolism in humans

This paper describes CarbMetSim, a discrete-event simulator that tracks the blood glucose level of a person in response to a timed sequence of diet and exercise activities. CarbMetSim implements broader aspects of carbohydrate metabolism in human beings with the objective of capturing the average impact of various diet/exercise activities on the blood glucose level. Key organs (stomach, intestine, portal vein, liver, kidney, muscles, adipose tissue, brain and heart) are implemented to the extent necessary to capture their impact on the production and consumption of glucose. Key metabolic pathways (glucose oxidation, glycolysis and gluconeogenesis) are accounted for in the operation of different organs. The impact of insulin and insulin resistance on the operation of various organs and pathways is captured in accordance with published research. CarbMetSim provides broad flexibility to configure the insulin production ability, the average flux along various metabolic pathways and the impact of insulin resistance on different aspects of carbohydrate metabolism. The simulator does not yet have a detailed implementation of protein and lipid metabolism. This paper contains a preliminary validation of the simulator's behavior. Significant additional validation is required before the simulator can be considered ready for use by people with Diabetes.

Carbohydrate Restriction in Type 1 Diabetes: A Realistic Therapy for Improved Glycaemic Control and Athletic Performance?

Around 80% of individuals with Type 1 diabetes (T1D) in the United States do not achieve glycaemic targets and the prevalence of comorbidities suggests that novel therapeutic strategies, including lifestyle modification, are needed. Current nutrition guidelines suggest a flexible approach to carbohydrate intake matched with intensive insulin therapy. These guidelines are designed to facilitate greater freedom around nutritional choices but they may lead to higher caloric intakes and potentially unhealthy eating patterns that are contributing to the high prevalence of obesity and metabolic syndrome in people with T1D. Low carbohydrate diets (LCD; <130 g/day) may represent a means to improve glycaemic control and metabolic health in people with T1D. Regular recreational exercise or achieving a high level of athletic performance is important for many living with T1D. Research conducted on people without T1D suggests that training with reduced carbohydrate availability (often termed "train low") enhances metabolic adaptation compared to training with normal or high carbohydrate availability. However, these "train low" practices have not been tested in athletes with T1D. This review aims to investigate the known pros and cons of LCDs as a potentially effective, achievable, and safe therapy to improve glycaemic control and metabolic health in people with T1D. Secondly, we discuss the potential for low, restricted, or periodised carbohydrate diets in athletes with T1D.

Individual glucose responses to prolonged moderate intensity aerobic exercise in adolescents with type 1 diabetes: The higher they start, the harder they fall

OBJECTIVE

To evaluate the pattern of change in blood glucose concentrations and hypoglycemia risk in response to prolonged aerobic exercise in adolescents with type 1 diabetes (T1D) that had a wide range in pre-exercise blood glucose concentrations.

METHODS

Individual blood glucose responses to prolonged (~60 minutes) moderate-intensity exercise were profiled in 120 youth with T1D.

RESULTS

The mean pre-exercise blood glucose concentration was 178 ± 66 mg/dL, ranging from 69 to 396 mg/dL, while the mean change in glucose during exercise was -76 ± 55 mg/dL (mean ± SD), ranging from +83 to -257 mg/dL. Only 4 of 120 youth (3%) had stable glucose levels during exercise (ie, ± ≤10 mg/dL), while 4 (3%) had a rise in glucose >10 mg/dL, and the remaining (93%) had a clinically significant drop (ie, >10 mg/dL). A total of 53 youth (44%) developed hypoglycemia (≤70 mg/dL) during exercise. The change in glucose was negatively correlated with the pre-exercise glucose concentration (R² = 0.44, P < 0.001), and tended to be greater in those on multiple daily insulin injections (MDI) vs continuous subcutaneous insulin infusion (CSII) (-98 ± 15 vs -65 ± 7 mg/dL, P = 0.05). No other collected variables appeared to predict the change in glucose including age, weight, height, body mass index, disease duration, daily insulin dose, HbA_1c , or sex.

CONCLUSION

Youth with T1D have variable glycemic responses to prolonged aerobic exercise, but this variability is partially explained by their pre-exercise blood glucose levels. When no implementation strategies are in place to limit the drop in glycemia, the incidence of exercise-associated hypoglycemia is ~44% and having a high pre-exercise blood glucose concentration is only marginally protective.

Exercise management in type 1 diabetes: a consensus statement

Type 1 diabetes is a challenging condition to manage for various physiological and behavioural reasons. Regular exercise is important, but management of different forms of physical activity is particularly difficult for both the individual with type 1 diabetes and the health-care provider. People with type 1 diabetes tend to be at least as inactive as the general population, with a large percentage of individuals not maintaining a healthy body mass nor achieving the minimum amount of moderate to vigorous aerobic activity per week. Regular exercise can improve health and wellbeing, and can help individuals to achieve their target lipid profile, body composition, and fitness and glycaemic goals. However, several additional barriers to exercise can exist for a person with diabetes, including fear of hypoglycaemia, loss of glycaemic control, and inadequate knowledge around exercise management. This Review provides an up-to-date consensus on exercise management for individuals with type 1 diabetes who exercise regularly, including glucose targets for safe and effective exercise, and nutritional and insulin dose adjustments to protect against exercise-related glucose excursions.

Review: Helping the athlete with type 1 diabetes

Exercise is a significant physiological challenge with markedly increased cardiac output, respiration and fuel mobilisation. Whilst the cardio-respiratory response to exercise is similar in type 1 diabetes to that seen in non-diabetic subjects, the response to mobilisation of fuel source to support exercise is impaired. This effect, when combined with the difficulties of nutrition and insulin therapy in type 1 diabetes may negatively impact on the performance of the athlete with diabetes. Hypoglycaemia both during and following exercise, is a significant risk. Furthermore, hyperglycaemia prior to and following some types of exercises can also be problematic. The effect on blood glucose of varying sports can be predicted, and therefore, pro-active adjustments of insulin therapy and nutrition can be made. This article outlines the important differences seen with exercise in type 1 diabetes and discusses appropriate strategies to normalise performance and reduce the risk of hypoglycaemia.

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.

Glucosim: educational software for virtual experiments with patients with type 1 diabetes

GLUCOSIM is an educational software package that simulates blood glucose and insulin dynamics in healthy individuals and patients with type 1 diabetes. It is being used to assist biomedical and chemical engineering students in visualizing the dynamic variations in blood glucose concentration in response to external variations such as food consumption and insulin administration. A nutritional database has been integrated to GLUCOSIM to provide meal inputs to the simulation. The simulator has been improved by the modification of mathematical models, and it has been adapted to include currently available commercial insulin brands.

Clinical management of the physically active patient with type 1 diabetes

The prevalence and incidence of type 1 diabetes continues to increase worldwide. Most patients with type 1 diabetes are young at the time of diagnosis and wish to continue leading a physically active life. Although regular exercise, insulin therapy, and proper nutrition are the cornerstone of treatment, there are considerable challenges in managing the active individual with type 1 diabetes. The current recommendation for diabetes management is intensive glycemic control for all patients when possible to help prevent secondary complications. Both insulin pump therapy and multiple daily injections are beneficial treatment options to lower average glucose levels; however, without continuous glucose monitoring, these treatment options typically increase the risk of hypoglycemia. In active patients with type 1 diabetes, the challenges of maintaining good glycemia are complicated by the inability to regulate insulin concentrations during and after exercise. Physiological and psychosocial factors during growth and maturation also provide additional challenges. This article highlights challenges and key strategies for diabetes management in the active individual with type 1 diabetes, including the application of the most recent diabetes technologies.

Odyssey between Scylla and Charybdis through storms of carbohydrate metabolism and diabetes: a career retrospective

This research perspective allows me to summarize some of my work completed over 50 years, and it is organized in seven sections. 1) The treatment of diabetes concentrates on the liver and/or the periphery. We quantified hormonal and metabolic interactions involved in physiology and the pathogenesis of diabetes by developing tracer methods to separate the effects of diabetes on both. We collaborated in the first tracer clinical studies on insulin resistance, hypertriglyceridemia, and the Cori cycle. 2) Diabetes reflects insulin deficiency and glucagon abundance. Extrapancreatic glucagon changed the prevailing dogma and permitted precise exploration of the roles of insulin and glucagon in physiology and diabetes. 3) We established the critical role of glucagon-insulin interaction and the control of glucose metabolism during moderate exercise and of catecholamines during strenuous exercise. Deficiencies of the release and effects of these hormones were quantified in diabetes. We also revealed how acute and chronic hyperglycemia affects the expression of GLUT2 gene and protein in diabetes. 4) We outlined molecular and physiological mechanisms whereby exercise training and repetitive neurogenic stress can prevent diabetes in ZDF rats. 5) We and others established that the indirect effect of insulin plays an important role in the regulation of glucose production in dogs. We confirmed this effect in humans and demonstrated that in type 2 diabetes it is mainly the indirect effect. 6) We indicated that the muscle and the liver protected against glucose changes. 7) We described molecular mechanisms responsible for increased HPA axis in diabetes and for the diminished responses of HPA axis, catecholamines, and glucagon to hypoglycemia. We proposed a new approach to decrease the threat of hypoglycemia.

Type I diabetes and physical exercise

Metabolic effects of physical exercise in type I diabetes are reviewed. Physical training leads to an increased insulin sensitivity but does not seem to influence the metabolic control. However, the metabolic control is of importance for the exercise results. Patients in a good control do not differ from normal individuals concerning working capacity, recovery after hypoglycemia and hormonal balance. Furthermore, abnormalities in the blood glucose homeostasis during exercise in type I diabetes are discussed as well as potential beneficial effects of physical training in the prevention of cardiovascular disease.

Fuel metabolism during exercise in euglycaemia and hyperglycaemia in patients with type 1 diabetes mellitus--a prospective single-blinded randomised crossover trial

AIMS/HYPOTHESIS

We assessed systemic and local muscle fuel metabolism during aerobic exercise in patients with type 1 diabetes at euglycaemia and hyperglycaemia with identical insulin levels.

METHODS

This was a single-blinded randomised crossover study at a university diabetes unit in Switzerland. We studied seven physically active men with type 1 diabetes (mean +/- SEM age 33.5 +/- 2.4 years, diabetes duration 20.1 +/- 3.6 years, HbA1c 6.7 +/- 0.2% and peak oxygen uptake [VO2peak] 50.3 +/- 4.5 ml min(-1) kg(-1)). Men were studied twice while cycling for 120 min at 55 to 60% of VO2peak, with a blood glucose level randomly set either at 5 or 11 mmol/l and identical insulinaemia. The participants were blinded to the glycaemic level; allocation concealment was by opaque, sealed envelopes. Magnetic resonance spectroscopy was used to quantify intramyocellular glycogen and lipids before and after exercise. Indirect calorimetry and measurement of stable isotopes and counter-regulatory hormones complemented the assessment of local and systemic fuel metabolism.

RESULTS

The contribution of lipid oxidation to overall energy metabolism was higher in euglycaemia than in hyperglycaemia (49.4 +/- 4.8 vs 30.6 +/- 4.2%; p < 0.05). Carbohydrate oxidation accounted for 48.2 +/- 4.7 and 66.6 +/- 4.2% of total energy expenditure in euglycaemia and hyperglycaemia, respectively (p < 0.05). The level of intramyocellular glycogen before exercise was higher in hyperglycaemia than in euglycaemia (3.4 +/- 0.3 vs 2.7 +/- 0.2 arbitrary units [AU]; p < 0.05). Absolute glycogen consumption tended to be higher in hyperglycaemia than in euglycaemia (1.3 +/- 0.3 vs 0.9 +/- 0.1 AU). Cortisol and growth hormone increased more strongly in euglycaemia than in hyperglycaemia (levels at the end of exercise 634 +/- 52 vs 501 +/- 32 nmol/l and 15.5 +/- 4.5 vs 7.4 +/- 2.0 ng/ml, respectively; p < 0.05).

CONCLUSIONS/INTERPRETATION

Substrate oxidation in type 1 diabetic patients performing aerobic exercise in euglycaemia is similar to that in healthy individuals revealing a shift towards lipid oxidation during exercise. In hyperglycaemia fuel metabolism in these patients is dominated by carbohydrate oxidation. Intramyocellular glycogen was not spared in hyperglycaemia.

Effect of acute maximal exercise on lymphocyte subgroups in type 1 diabetes

The essential therapy of diabetes mellitus includes medical nutrition therapy (MNT), exercise and medical therapy. Exercise, besides its metabolic effects, has positive influence on the immune system, but some forms of exercise may cause trauma for muscle and skeletal systems, they may also support negative effects on the immune system. Nineteen type 1 diabetic patients (mean age 22.1 +/- 2.8 yrs), followed by Diabetes Outpatient Clinic and twenty age matched male control subjects were included into the study, to demonstrate the effects of maximal, acute exercise on the immune system. The exercise test was performed according to Bruce protocol on treadmill. In diabetic subjects, increased CD19 and CD23 expressions were observed before exercise. In both groups (diabetic/control) CD3, CD4 expressions and CD4/CD8 ratio were decreased following the exercise, however expression of natural killer (NK) cells increased. Compared to type 1 diabetic patients healthy subjects had longer acute exercise that caused the increased level of CD8 expression, however type 1 diabetic patients did not show any difference. These results indicate that submaximal aerobic exercise might be recommended for type 1 diabetics without any complications because of its positive reflection on metabolic control and no negative effects on the immune system.

The regulation of ketogenesis

Ketone bodies accumulate in the plasma in conditions of fasting and uncontrolled diabetes. The initiating event is a change in the molar ratio of glucagon:insulin. Insulin deficiency triggers the lipolytic process in adipose tissue with the result that free fatty acids pass into the plasma for uptake by liver and other tissues. Glucagon appears to be the primary hormone involved in the induction of fatty acid oxidation and ketogenesis in the liver. It acts by acutely dropping hepatic malonyl-CoA concentrations as a consequence of inhibitory effects exerted in the glycolytic pathway and on acetyl-CoA carboxylase (EC 6.4.1.2). The fall in malonyl-CoA concentration activates carnitine acyltransferase I (EC 2.3.1.21) such that long-chain fatty acids can be transported through the inner mitochondrial membrane to the enzymes of fatty acid oxidation and ketogenesis. The latter are high-capacity systems assuring that fatty acids entering the mitochondria are rapidly oxidized to ketone bodies. Thus, the rate-controlling step for ketogenesis is carnitine acyltransferase I. Administration of food after a fast, or of insulin to the diabetic subject, reduces plasma free fatty acid concentrations, increases the liver concentration of malonyl-CoA, inhibits carnitine acyltransferase I and reverses the ketogenic process.

Exercise for diabetic pregnant women

BACKGROUND

Diabetes in pregnancy may result in unfavourable maternal and neonatal outcomes. Exercise was proposed as an additional strategy to improve glycaemic control. The effect of exercise during pregnancies complicated by diabetes needs to be assessed.

OBJECTIVES

To evaluate the effect of exercise programs, alone or in conjunction with other therapies, compared to no specific program or to other therapies, in pregnant women with diabetes on perinatal and maternal morbidity and on the frequency of prescription of insulin to control glycaemia. To compare the effectiveness of different types of exercise programs on perinatal and maternal morbidity.

SEARCH STRATEGY

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (31 December 2005).

SELECTION CRITERIA

All known randomised controlled trials evaluating the effect of exercise in diabetic pregnant women on perinatal outcome and maternal morbidity.

DATA COLLECTION AND ANALYSIS

We evaluated relevant studies for meeting the inclusion criteria and methodological quality. Three review authors abstracted the data. For all data analyses, we entered data based on the principle of intention to treat. We calculated relative risks and 95% confidence intervals for dichotomous data.

MAIN RESULTS

Four trials, involving 114 pregnant women with gestational diabetes, were included in the review. None included pregnant women with type 1 or type 2 diabetes. Women were recruited during the third trimester and the intervention was performed for about six weeks. The programs generally consisted in exercising three times a week for 20 to 45 minutes. We found no significant difference between exercise and the other regimen in all the outcomes evaluated.

AUTHORS' CONCLUSIONS

There is insufficient evidence to recommend, or advise against, diabetic pregnant women to enrol in exercise programs. Further trials, with larger sample size, involving women with gestational diabetes, and possibly type 1 and 2 diabetes, are needed to evaluate this intervention.

Exercise for diabetic pregnant women

BACKGROUND

Diabetes in pregnancy may result in unfavourable maternal and neonatal outcomes. Exercise was proposed as an additional strategy to improve glycaemic control. The effect of exercise during pregnancies complicated by diabetes needs to be assessed.

OBJECTIVES

To evaluate the effect of exercise programs, alone or in conjunction with other therapies, compared to no specific program or to other therapies, in pregnant women with diabetes on perinatal and maternal morbidity and on the frequency of prescription of insulin to control glycaemia. To compare the effectiveness of different types of exercise programs on perinatal and maternal morbidity.

SEARCH STRATEGY

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (31 December 2005).

SELECTION CRITERIA

All known randomised controlled trials evaluating the effect of exercise in diabetic pregnant women on perinatal outcome and maternal morbidity.

DATA COLLECTION AND ANALYSIS

We evaluated relevant studies for meeting the inclusion criteria and methodological quality. Three review authors abstracted the data. For all data analyses, we entered data based on the principle of intention to treat. We calculated relative risks and 95% confidence intervals for dichotomous data.

MAIN RESULTS

Four trials, involving 114 pregnant women with gestational diabetes, were included in the review. None included pregnant women with type 1 or type 2 diabetes. Women were recruited during the third trimester and the intervention was performed for about six weeks. The programs generally consisted in exercising three times a week for 20 to 45 minutes. We found no significant difference between exercise and the other regimen in all the outcomes evaluated.

AUTHORS' CONCLUSIONS

There is insufficient evidence to recommend, or advise against, diabetic pregnant women to enrol in exercise programs. Further trials, with larger sample size, involving women with gestational diabetes, and possibly type 1 and 2 diabetes, are needed to evaluate this intervention.

Effects of stress on exacerbation of diabetes mellitus, serum glucose and cortisol levels and body weight in rats

OBJECTIVE

The effects of stress on the serum glucose, serum cortisol levels and body weight were investigated to clarify the possible link between the stress and diabetes.

METHODS

The experiments were performed on nondiabetic and streptozotocin diabetic rats divided to control, sham and stressed groups. Water immersion was used as stressor. After the experiment, blood samples were collected. The serum glucose level (SGL) was measured by the glucose oxidase method and serum cortisol level (SCL) was determined by radioimmunoassay.

RESULTS

Stress caused a significant increase in glucose level in both nondiabetic and diabetic rats. In diabetes rats, a significant increase in SCL was observed. Stress did not cause, however, significant increases in SCL. A significant weight loss took place in rats exposed to stress and that was much greater in diabetic animals.

CONCLUSION

The stress with mainly psychic component exacerbated the diabetes in streptozotocin treated rats and the glucose levels increased significantly also in nondiabetic controls, but no glucose was detected in their urine.

Exercise and Newer Insulins: How Much Glucose Supplement to Avoid Hypoglycemia?

PURPOSE

To determine the glucose supplement required to prevent hypoglycemia during moderate-intensity exercise in Type 1 diabetic patients using newer analog insulins.

METHODS

Nine subjects performed 60 min of ergocycle exercise (50% VO2max), 3 h after a standard breakfast in three different conditions. Subjects were randomly assigned to preexercise liquid glucose supplement of 0 g of glucose (0G), 15 g of glucose (15G), and 30 g of glucose (30G). Blood glucose (BG) was measured before, during, and following the exercise. All subjects used Humulin N (N) and analog insulin Humalog (Lispro). A dextrose infusion was initiated when BG fell below 5 mmol x L(-1).

RESULTS

There was no significant difference in the magnitude of the decrease in BG exercise-induced when comparing the three experimental conditions. However, the quantity of dextrose infused was significantly higher in the 0G (10.5 +/- 3.2 g) than in the 15G (3.5 +/- 1.8 g) or the 30G conditions (1.6 +/- 1.0 g). The addition of a glucose supplement (15G or 30G) significantly prolonged the delay before the need for dextrose infusion (31.7 +/- 7.5, 51.3 +/- 4.2, and 55.6 +/- 2.6 min; 0G, 15G, and 30G, respectively). The quantity of dextrose infusion was plotted against the three preexercise glucose supplements and a regression equation obtained. Solving this equation, a glucose supplement of 40 g was estimated in order to maintain BG levels within the normal range during and after exercise.

CONCLUSION

For 60 min of late postprandial exercise followed by 60 min of recovery, an estimated 40 g of a liquid glucose supplement, ingested 15 min prior exercise, would seem likely to help maintain safe BG levels in subjects using N-Lispro.