Exercise-induced hypoglycaemia in IDDM patients treated with a short-acting insulin analogue

Examining the Acute Glycemic Effects of Different Types of Structured Exercise Sessions in Type 1 Diabetes in a Real-World Setting: The Type 1 Diabetes and Exercise Initiative (T1DEXI)

OBJECTIVE

Maintenance of glycemic control during and after exercise remains a major challenge for individuals with type 1 diabetes. Glycemic responses to exercise may differ by exercise type (aerobic, interval, or resistance), and the effect of activity type on glycemic control after exercise remains unclear.

RESEARCH DESIGN AND METHODS

The Type 1 Diabetes Exercise Initiative (T1DEXI) was a real-world study of at-home exercise. Adult participants were randomly assigned to complete six structured aerobic, interval, or resistance exercise sessions over 4 weeks. Participants self-reported study and nonstudy exercise, food intake, and insulin dosing (multiple daily injection [MDI] users) using a custom smart phone application and provided pump (pump users), heart rate, and continuous glucose monitoring data.

RESULTS

A total of 497 adults with type 1 diabetes (mean age ± SD 37 ± 14 years; mean HbA1c ± SD 6.6 ± 0.8% [49 ± 8.7 mmol/mol]) assigned to structured aerobic (n = 162), interval (n = 165), or resistance (n = 170) exercise were analyzed. The mean (± SD) change in glucose during assigned exercise was -18 ± 39, -14 ± 32, and -9 ± 36 mg/dL for aerobic, interval, and resistance, respectively (P < 0.001), with similar results for closed-loop, standard pump, and MDI users. Time in range 70-180 mg/dL (3.9-10.0 mmol/L) was higher during the 24 h after study exercise when compared with days without exercise (mean ± SD 76 ± 20% vs. 70 ± 23%; P < 0.001).

CONCLUSIONS

Adults with type 1 diabetes experienced the largest drop in glucose level with aerobic exercise, followed by interval and resistance exercise, regardless of insulin delivery modality. Even in adults with well-controlled type 1 diabetes, days with structured exercise sessions contributed to clinically meaningful improvement in glucose time in range but may have slightly increased time below range.

Placebo controlled phase II clinical trial: Safety and efficacy of combining intranasal insulin & acute exercise

A growing number of investigations are exploring the utility of intranasal insulin as a means of mitigating cognitive decline. However, as a basic tenant of dementia prevention programs is increasing physical activity, it is essential to obtain a preliminary assessment of the safety profile of combining intranasal insulin with physical activity; to ensure that undue risks are not incurred. Utilizing a randomized double-blind placebo-controlled design, a sample of 116 non-diabetic, fasted college-aged adults were randomly assigned to receive a dose of 0-to-120 IU of NovoLog (Insulin Aspart) before being randomized to 20 min of exercise or sitting control condition. The safety of intranasal insulin was assessed by examining the incidence of potential symptoms of hypoglycemia and changes in peripheral blood glucose. The efficacy of a combination therapeutic approach was assessed using behavioral measures of inhibition and sustained attention alongside neuroelectric indices of attentional engagement. The frequency of symptoms reported following administration of intranasal insulin were not observed to interact with exercise so as to make their occurrence any more or less prominent, nor was the frequency observed to relate to the dose of intranasal insulin. However, doses of intranasal insulin of 100 IU or more were observed to result in a 7-fold increase in the likelihood of a level 1 hypoglycemic event for those individuals in the exercise condition. This study provides preliminary evidence to suggest that exercise is not associated with an increase in risk when combined with lower doses of intranasal insulin.Clinical trial registration The trial is registered at ClinicalTrials.gov, number NCT04292535.

Delayed effect of different exercise modalities on glycaemic control in type 1 diabetes mellitus: A systematic review and meta-analysis

BACKGROUND AND AIMS

Despite the crucial role of exercise in the prevention of comorbidities and complications in type 1 diabetes mellitus (T1DM), people living with the disease are often insufficiently physically active, mainly due to the fear of hypoglycaemia. Research using continuous glucose monitoring (CGM) devices has shown that exercise affects glycaemic control in T1DM for over 24 h. The aim of this systematic review and meta-analysis is, therefore, to investigate the delayed effects of different exercise modalities on glycaemic control in adults with T1DM.

METHODS AND RESULTS

The literature search of experimental studies was conducted on PubMed, SPORTDiscus and EMBASE from January 2000 to September 2019. Twelve studies using CGM devices were included. Compared to endurance, intermittent exercise increased the time spent in hypoglycaemia (0.62, 0.07 to 1.18; standardised effect size, 95% CI) and reduced the mean interstitial glucose concentration (-0.88, -1.45 to -0.33). No differences emerged in the time spent in hyperglycaemia (-0.07, -0.58 to 0.45) or in the proportion of exercisers experiencing hypoglycaemic events (0.82, 0.45 to 1.49; proportion ratio, 95% CI) between conditions. The systematic review also found a reduced risk of hypoglycaemia if exercise is performed in the morning rather than in the afternoon, and with a 50% rapid-acting insulin reduction. It was not possible to determine the benefits of resistance exercise.

CONCLUSIONS

For the first time, we systematically investigated the delayed effect of exercise in adults with T1DM, highlighted undetected effects, shortcomings in the existing literature, and provided suggestions to design future comparable studies.

Exercise as medicine - evidence for prescribing exercise as therapy in 26 different chronic diseases

This review provides the reader with the up-to-date evidence-based basis for prescribing exercise as medicine in the treatment of 26 different diseases: psychiatric diseases (depression, anxiety, stress, schizophrenia); neurological diseases (dementia, Parkinson's disease, multiple sclerosis); metabolic diseases (obesity, hyperlipidemia, metabolic syndrome, polycystic ovarian syndrome, type 2 diabetes, type 1 diabetes); cardiovascular diseases (hypertension, coronary heart disease, heart failure, cerebral apoplexy, and claudication intermittent); pulmonary diseases (chronic obstructive pulmonary disease, asthma, cystic fibrosis); musculo-skeletal disorders (osteoarthritis, osteoporosis, back pain, rheumatoid arthritis); and cancer. The effect of exercise therapy on disease pathogenesis and symptoms are given and the possible mechanisms of action are discussed. We have interpreted the scientific literature and for each disease, we provide the reader with our best advice regarding the optimal type and dose for prescription of exercise.

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.

Glucagon responses to exercise-induced hypoglycaemia are improved by somatostatin receptor type 2 antagonism in a rat model of diabetes

AIMS/HYPOTHESIS

Regular exercise is at the cornerstone of care in type 1 diabetes. However, relative hyperinsulinaemia and a blunted glucagon response to exercise promote hypoglycaemia. Recently, a selective antagonist of somatostatin receptor 2, PRL-2903, was shown to improve glucagon counterregulation to hypoglycaemia in resting streptozotocin-induced diabetic rats. The aim of this study was to test the efficacy of PRL-2903 in enhancing glucagon counterregulation during repeated hyperinsulinaemic exercise.

METHODS

Diabetic rats performed daily exercise for 1 week and were then exposed to saline (154 mmol/l NaCl) or PRL-2903, 10 mg/kg, before hyperinsulinaemic exercise on two separate occasions spaced 1 day apart. In the following week, animals crossed over to the alternate treatment for a third hyperinsulinaemic exercise protocol.

RESULTS

Liver glycogen content was lower in diabetic rats compared with control rats, despite daily insulin therapy (p < 0.05). Glucagon levels failed to increase during exercise with saline but increased three-to-six fold with PRL-2903 (all p < 0.05). Glucose concentrations tended to be higher during exercise and early recovery with PRL-2903 on both days of treatment; this difference did not achieve statistical significance (p > 0.05).

CONCLUSIONS/INTERPRETATION

PRL-2903 improves glucagon counterregulation during exercise. However, liver glycogen stores or other factors limit the prevention of exercise-induced hypoglycaemia in rats with streptozotocin-induced diabetes.

Insulin therapy in type 1 diabetes

Although not curable, type 1 diabetes is eminently controllable. IIT, as guided by the results of landmark studies such as the DCCT, provides primary care providers with a blueprint for reducing the frequency of the devastating complications of diabetes that were all too common in the recent past. Considering the remarkable advances in contemporary therapy, including MDI and CSII, the likelihood of even greater future improvements in quality of life and survivability can be anticipated. Success requires patient engagement and education, an informed primary care provider, and an interdisciplinary team to maximize the benefits of insulin therapy and avoid the risks of hypoglycemia.

The Impact of Accelerometer and Heart Rate Data on Hypoglycemia Mitigation in Type 1 Diabetes

Aerobic exercise can lower blood glucose levels and alter insulin sensitivity both during and several hours after exercise, creating challenges for a closed-loop artificial pancreas. Predictive low glucose suspend (PLGS) algorithms are a first step toward an artificial pancreas, but few of these have been successfully applied to exercise. This study incorporates physical activity measurements from a combined accelerometer/heart rate monitor (HRM) to improve the performance of an existing PLGS algorithm at mitigating exercise-associated hypoglycemia in participants with type 1 diabetes. In all, 22 subjects with type 1 diabetes on insulin pump therapy were provided a combined accelerometer/HRM and (if not already using one) a continuous glucose monitor (CGM), then instructed to go about their everyday lives while wearing the devices. After the monitoring period, each subject's insulin pump, CGM, and accelerometer/HRM were downloaded and the data were used to augment an existing PLGS algorithm to incorporate activity. Using a computer simulator, the accelerometer-augmented algorithm was compared to the HRM-augmented algorithm to determine which was most effective at mitigating hypoglycemia. Mean length of monitoring was 4.9 days. Across all subjects, 11 061 CGM readings were recorded during the monitoring period. In the simulator analysis, the PLGS algorithm reduced hypoglycemia by 62%, compared to 71% and 74% reductions for the HRM-augmented and accelerometer-augmented algorithms, respectively; combined accelerometer and HRM augmentation provided a 76% reduction. In a simulated setting, the accelerometer-augmented pump suspension algorithm decreases the incidence of exercise-related hypoglycemia by a meaningful amount compared to the PLGS algorithm alone. Results also failed to justify the additional user burden of a HRM.

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.

Glucose or intermittent high-intensity exercise in glargine/glulisine users with T1DM

INTRODUCTION

The effects of glargine/glulisine insulin regimen on exercise blood glucose (BG) and strategies to limit exercise-induced hypoglycemia are not well documented. Intermittent high-intensity exercise has been proposed to prevent hypoglycemia, but its effect in participants with type 1 diabetes using glargine/glulisine is unknown.

METHODS

The study used a repeated-measures design with three randomly ordered exercise conditions. Eleven participants completed 60 min of moderate-intensity exercise at 50% VO(2peak) for all conditions. These conditions varied as follows: participants ingested 0 g of glucose preexercise (0G + MOD), 30 g of glucose preexercise (30G + MOD), or 0 g of glucose preexercise but performed brief high-intensity intervals interspersed every 2 min (0G + MOD/INT) during exercise. If BG fell <4 mmol·L(-1), a 20% dextrose solution was started to maintain BG between 4 and 5 mmol·L(-1).

RESULTS

Consuming 30 g of glucose before exercise (30G + MOD) resulted in a higher preexercise BG (11.7 ± 2.7 mmol·L(-1)) compared with 0 g of glucose before exercise (0G + MOD, 7.8 ± 4.0, and 0G + MOD/INT, 9.2 ± 3.5mmol·L(-1)), P < 0.05. A dextrose infusion was required in 7/11, 4/11, and 1/11 participants for 0G + MOD, 0G + MOD/INT, 30G + MOD conditions, respectively, P < 0.02. The duration and the quantity of dextrose infused were greatest in the 0G + MOD condition, moderate in the to 0G + MOD/INT condition, and minimal in the 30G + MOD condition, P < 0.01.

CONCLUSION

Our results suggest that both moderate-intensity exercise with a 30-g preexercise glucose beverage or interspersed with intermittent high-intensity sprints may be safe strategies to prevent hypoglycemia in glargine/glulisine users.

Exercise and glycemic imbalances: a situation-specific estimate of glucose supplement

PURPOSE

The purposes of this study were to describe a newly developed algorithm that estimates the glucose supplement on a patient- and situation-specific basis and to test whether these amounts would be appropriate for maintaining blood glucose levels within the recommended range in exercising type 1 diabetic patients.

METHODS

The algorithm first estimates the overall amount of glucose oxidized during exercise on the basis of the patient's physical fitness, exercise intensity, and duration. The amount of supplemental CHO to be consumed before or during the effort represents a fraction of the burned quantity depending on the patient's usual therapy and insulin sensitivity and on the time of day the exercise is performed. The algorithm was tested in 27 patients by comparing the estimated amounts of supplemental CHO with the actual amounts required to complete 1-h constant-intensity walks. Each patient performed three trials, each of which started at different time intervals after insulin injection (81 walks were performed overall). Glycemia was tested every 15 min.

RESULTS

In 70.4% of the walks, independent of the time of day, the amount of CHO estimated by the algorithm would be adequate to allow the patients to complete the exercise with a glucose level within the selected thresholds (i.e., 3.9-10 mmol·L(-1)).

CONCLUSIONS

The algorithm provided a satisfactory estimate of the CHO needed to complete the exercises. Although the performance of the algorithm still requires testing for different exercise intensities, durations, and modalities, the results indicate its potential usefulness as a tool for preventing immediate exercise-induced glycemic imbalances (i.e., during exercise) in type 1 diabetic patients, in particular for spontaneous physical activities not planned in advance, thus allowing all insulin-dependent patients to safely enjoy the benefits of exercise.

Continuous moderate-intensity exercise with or without intermittent high-intensity work: effects on acute and late glycaemia in athletes with Type 1 diabetes mellitus

AIMS

Individuals with Type 1 diabetes mellitus are susceptible to hypoglycaemia during and after continuous moderate-intensity exercise, but hyperglycaemia during intermittent high-intensity exercise. The combination of both forms of exercise may have a moderating effect on glycaemia in recovery. The aims of this study were to compare the physiological responses and associated glycaemic changes to continuous moderate-intensity exercise vs. continuous moderate-intensity exercise + intermittent high-intensity exercise in athletes with Type 1 diabetes.

METHODS

Interstitial glucose levels were measured in a blinded fashion in 11 trained athletes with Type 1 diabetes during two sedentary days and during 2 days in which 45 min of afternoon continuous moderate-intensity exercise occurred either with or without intermittent high-intensity exercise. The total amount of work performed and the duration of exercise was identical between sessions.

RESULTS

During exercise, heart rate, respiratory exchange ratio, oxygen utilization, ventilation and blood lactate levels were higher during continuous moderate-intensity + intermittent high-intensity exercise vs. continuous moderate-intensity exercise (all P < 0.05). Despite these marked cardiorespiratory differences between trials, there was no difference in the reduction of interstitial glucose or plasma glucose levels between the exercise trials. Nocturnal glucose levels were higher in continuous moderate-intensity + intermittent high-intensity exercise and in sedentary vs. continuous moderate-intensity exercise (P < 0.05). Compared with continuous moderate-intensity exercise alone, continuous moderate-intensity + intermittent high-intensity exercise was associated with less post-exercise hypoglycaemia (5.2 vs. 1.5% of the time spent with glucose < 4.0 mmol/l) and more post-exercise hyperglycaemia (33.8 vs. 20.4% of time > 11.0 mmol/l).

CONCLUSIONS

Although the decreases in glucose level during continuous moderate-intensity exercise and continuous moderate-intensity + intermittent high-intensity exercise are similar, the latter form of exercise protects against nocturnal hypoglycaemia in athletes with Type 1 diabetes.

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 and glycemic control in diabetes: benefits, challenges, and adjustments to pharmacotherapy

Exercise, along with dietary intervention, represents first-line therapy for diabetes mellitus. Aerobic exercise is recommended for its beneficial effects on glucose control as well as its abilities to retard the progression of other comorbidities common in patients with diabetes, such as cardiovascular disease. The capability of aerobic exercise to improve glycemic control in diabetes is well documented, although adherence to exercise regimens is problematic. More recently, the glucose-lowering effects of resistance training have also been documented; this form of exercise has additional benefits, such as the capability to counteract sarcopenia, which is common in older people with type 2 diabetes. Exercise in people with diabetes, however, also can present significant challenges to glycemic control. Excessive glucose lowering can occur under certain conditions, enhancing the threat of hypoglycemia; in other situations, hyperglycemia can be accentuated. An understanding of the interactions between specific antidiabetic medications and various forms and intensities of exercise is essential to optimizing glycemic control while minimizing the potential for acute derangements in plasma glucose levels. Exogenous forms of insulin and agents that stimulate insulin secretion in a glucose-independent manner (such as sulfonylureas and glinides) increase the propensity for hypoglycemia during low- to moderate-intensity aerobic exercise. In contrast, exercise protocols characterized by high intensity are more likely to result in episodes of hyperglycemia. Strategies to minimize inappropriate swings in glycemic control are reviewed.

[Types of insulin therapy]

Diabetes mellitus is a chronic disease associated with a series of long-term microvascular and macrovascular complications that requires continuing therapeutic control. In recent years, the pharmaceutical industry has developed new types of insulin and administration systems in order to more closely mimic human insulin secretion. In this way, insulin therapy is divided into conventional and intensive regimens according to their complexity. In type 1 diabetes mellitus (T1DM) patients, the treatment of choice is the one which achieves intensive glycemic control. In type 2 diabetes mellitus, we can start with a simplified conventional regimen which could progress into an intensive one similar to that of T1DM treatment. Both types of diabetes require an individualized treatment prescription based on the needs and characteristics of each patient.

Hypoglycemia in type 1 diabetes: a still unresolved problem in the era of insulin analogs and pump therapy

The Diabetes Control and Complications Trial demonstrated that in patients with type 1 diabetes, tight metabolic control achieved with intensive insulin therapy can reduce the risk of long-term microvascular complications. However, strict glycemic control carries an increased risk of severe hypoglycemia. Recurrent episodes of hypoglycemia, especially at young ages, can lead to hypoglycemia unawareness, exert adverse effects on neurocognitive function, and cause significant emotional morbidity in the child and parents. Although the introduction of the new insulin analogs in diabetes therapy and the use of continuous subcutaneous insulin infusion raised hopes for a solution to this problem, these modalities have not been associated with the expected reduction in hypoglycemic episodes. The findings suggest that the prevention of hypoglycemia in patients with type 1 diabetes lies in biologically controlled insulin secretion, as in islet transplantation, or the development of an autonomous closed-loop system that efficiently mimics the action of the pancreatic beta-cells and maintains blood glucose levels within the desired range.

Interventions for being active among individuals with diabetes: a systematic review of the literature

PURPOSE

The purpose of this systematic review is to assess and summarize evidence and gaps in the literature regarding the intervention for being active (exercise) among individuals with diabetes.

METHODS

Twelve electronic databases were searched. Publications eligible for inclusion specifically studied learning, behavioral, clinical, and humanistic outcomes for exercise interventions in adult patients with type 1 and type 2 diabetes.

RESULTS

Seven reviews (2 systematic reviews, 3 meta-analyses, 2 technical reviews) and 34 individual, nonreview studies (18 randomized controlled trials, 16 nonrandomized trials) met inclusion criteria. For type 2 diabetes, findings suggested that exercise had a positive effect on glycemic control and decreased cardiovascular risk, but the impact of exercise on behavioral and humanistic outcomes was unclear; long-term outcomes and adherence to exercise interventions is unknown because most studies were of short duration. The overall impact of varied types of exercise in type 1 diabetes was unclear, especially regarding glycemic control. Potential benefits of exercise in type 1 may include improved cardiovascular health.

CONCLUSION

The review did not identify specific successful intervention details because of the heterogeneity of studies, subjects, and research gaps. General findings suggest that physical activity is better than no exercise at all; intensive regimens, if tolerated by patients, achieved better clinical outcomes than less intensive regimens. Reviewed studies using structured exercise regimens exhibited a more significant impact on outcomes. Substantial gaps in the literature include studies measuring direct effects of exercise in the US minority populations most affected by type 2 diabetes and economic evaluations of exercise interventions. Interventions must be tailored to individual patient needs to succeed.

Aerobic fitness and hand grip strength in Type 1 diabetes: relationship to glycaemic control and body composition

AIM

To clarify the relationship of aerobic fitness and handgrip strength with glycaemic control (HbA1c), body composition and lipid profile in Type 1 diabetes.

METHODS

Aerobic capacity (Chester Step Test), handgrip strength and body composition (bioelectrical impedance) were measured in 141 patients with Type 1 diabetes.

RESULTS

Aerobic capacity correlated positively with HbA1c and lean body mass and negatively with body mass index and fat mass. Handgrip strength correlated positively with aerobic capacity and negatively with HbA1c and fat mass. In addition, there was a positive correlation between HbA1c and total cholesterol.

CONCLUSION

Patients with Type 1 diabetes who have good aerobic capacity have poorer glycaemic control. However, this was an observational study and the results must be interpreted with caution. Further investigation into how these patients manage blood glucose during exercise is required.

Hyperinsulinaemia during exercise does not suppress hepatic glycogen concentrations in patients with type 1 diabetes: a magnetic resonance spectroscopy study

AIMS/HYPOTHESIS

We compared in vivo changes in liver glycogen concentration during exercise between patients with type 1 diabetes and healthy volunteers.

METHODS

We studied seven men with type 1 diabetes (mean +/- SEM diabetes duration 10 +/- 2 years, age 33 +/- 3 years, BMI 24 +/- 1 kg/m(2), HbA(1c) 8.1 +/- 0.2% and VO(2) peak 43 +/- 2 ml [kg lean body mass](-1) min(-1)) and five non-diabetic controls (mean +/- SEM age 30 +/- 3 years, BMI 22 +/- 1 kg/m(2), HbA(1c) 5.4 +/- 0.1% and VO(2) peak 52 +/- 4 ml [kg lean body mass](-1) min(-1), before and after a standardised breakfast and after three bouts (EX1, EX2, EX3) of 40 min of cycling at 60% VO(2) peak. (13)C Magnetic resonance spectroscopy of liver glycogen was acquired in a 3.0 T magnet using a surface coil. Whole-body substrate oxidation was determined using indirect calorimetry.

RESULTS

Blood glucose and serum insulin concentrations were significantly higher (p < 0.05) in the fasting state, during the postprandial period and during EX1 and EX2 in subjects with type 1 diabetes compared with controls. Serum insulin concentration was still different between groups during EX3 (p < 0.05), but blood glucose concentration was similar. There was no difference between groups in liver glycogen concentration before or after the three bouts of exercise, despite the relative hyperinsulinaemia in type 1 diabetes. There were also no differences in substrate oxidation rates between groups.

CONCLUSIONS/INTERPRETATION

In patients with type 1 diabetes, hyperinsulinaemic and hyperglycaemic conditions during moderate exercise did not suppress hepatic glycogen concentrations. These findings do not support the hypothesis that exercise-induced hypoglycaemia in patients with type 1 diabetes is due to suppression of hepatic glycogen mobilisation.

Effect of intermittent high-intensity compared with continuous moderate exercise on glucose production and utilization in individuals with type 1 diabetes

Previously, the decline in glycemia in individuals with type 1 diabetes has been shown to be less with intermittent high-intensity exercise (IHE) compared with continuous moderate-intensity exercise (MOD) despite the performance of a greater amount of total work. The purpose of the present study was to determine whether this lesser decline in glycemia can be attributed to a greater increment in endogenous glucose production (Ra) or attenuated glucose utilization (Rd). Nine individuals with type 1 diabetes were tested on two separate occasions, during which either a 30-min MOD or IHE protocol was performed under conditions of a euglycemic clamp in combination with the infusion of [6,6-(2)H]glucose. MOD consisted of continuous cycling at 40% VO2 peak, whereas IHE involved a combination of continuous exercise at 40% VO2 peak interspersed with additional 4-s maximal sprint efforts performed every 2 min to simulate the activity patterns of intermittent sports. During IHE, glucose Ra increased earlier and to a greater extent compared with MOD. Similarly, glucose Rd increased sooner during IHE, but the increase by the end of exercise was comparable with that elicited by MOD. During early recovery from IHE, Rd rapidly declined, whereas it remained elevated after MOD, a finding consistent with a lower glucose infusion rate during early recovery from IHE compared with MOD (P<0.05). The results suggest that the lesser decline in glycemia with IHE may be attributed to a greater increment in Ra during exercise and attenuated Rd during exercise and early recovery.

Is early and late post-meal exercise so different in type 1 diabetic lispro users?

To compare blood glucose (BG) responses during a 60 min moderate intensity exercise session performed in early or late postprandial periods. Nine generally well-controlled (HbA(1c): 7.3+/-0.1%) type 1 diabetic patients performed, at least one week apart, two exercise sessions, 60 (early exercise) and 180 min (late exercise) after a standardized breakfast. All subjects were using Humulin N (N) and Humalog (Lispro, LI) insulin. During exercise, the overall decrease in BG was 4.8+/-0.6 mmol/l and 3.6+/-0.8 mmol/l in early and late exercise, respectively (P=0.051). To prevent hypoglycemia, a dextrose infusion was initiated when BG reached 5 mmol/l. The quantity of dextrose infused was 6.2+/-3.0 g and 10.5+/-3.2g in early and late exercise, respectively (NS). The time free of dextrose infusion during exercise was 41.2+/-7.8 min and 31.7+/-7.5 min in early and late exercise, respectively (NS). In N-LI users, overall drop in BG during exercise tends to be greater in the early postprandial period. However, early and late exercise present similar quantity of dextrose infused and time free of dextrose infusion. Consequently, the similar risk of exercise-induced hypoglycemia suggests similar precautions in either exercise times.

The impact of hormone physiology on clinical practice with reference to two papers spanning 40 years of endocrinology

Following the pioneering work of Roger Ekins in describing the methodology for radioimmunoassay of hormone concentrations in plasma a series of publications followed describing variation in plasma hormone concentrations in a number of diseases. Though fluctuations in hormonal concentrations had been suspected, it was not until Hunter and Rigal documented these for the GH axis that it became apparent that the preferred mode of signalling for many hormone systems and in particular the anterior-pituitary hormones was of a pulsatile nature.

The decline in blood glucose levels is less with intermittent high-intensity compared with moderate exercise in individuals with type 1 diabetes

OBJECTIVE

To compare the response of blood glucose levels to intermittent high-intensity exercise (IHE) and moderate-intensity exercise (MOD) in individuals with type 1 diabetes.

RESEARCH DESIGN AND METHODS

Seven healthy individuals with type 1 diabetes were tested on two separate occasions, during which either a 30-min MOD or IHE protocol was performed. MOD consisted of continuous exercise at 40% Vo(2peak), while the IHE protocol involved a combination of continuous exercise at 40% Vo(2peak) interspersed with 4-s sprints performed every 2 min to simulate the activity patterns of team sports.

RESULTS

Both exercise protocols resulted in a decline in blood glucose levels. However, the decline was greater with MOD (-4.4 +/- 1.2 mmol/l) compared with IHE (-2.9 +/- 0.8 mmol/l; P < 0.05), despite the performance of a greater amount of total work with IHE (P < 0.05). During 60 min of recovery from exercise, glucose levels remained higher in IHE compared with MOD (P < 0.05). Furthermore, glucose levels remained stable during recovery from IHE, while they continued to decrease after MOD (P < 0.05). The stabilization of blood glucose levels with IHE was associated with elevated levels of lactate, catecholamines, and growth hormone during early recovery from exercise (P < 0.05). There were no differences in free insulin, glucagon, cortisol, or free fatty acids between MOD and IHE.

CONCLUSIONS

The decline in blood glucose levels is less with IHE compared with MOD during both exercise and recovery in individuals with type 1 diabetes.

New advances in insulin treatment of diabetes: overcoming barriers

OBJECTIVE

To discuss the optimal role of insulin in the treatment of patients with diabetes mellitus.

METHODS

We review the complications of diabetes, highlight the attempts to improve control of plasma glucose, and summarize current recommendations for use of insulin in clinical practice.

RESULTS

With the strict new guidelines for the diagnosis of diabetes issued by the American Diabetes Association in July 1997--a plasma glucose level of 126 mg/dL (7 mmol/L) rather than 140 mg/dL (7.8 mmol/L)--an additional 8 million persons will be diagnosed this year, and diabetes and its complications will be at the forefront of public health concerns. Strong evidence indicates that with reduction of plasma glucose levels and tight control of glycohemoglobin, the rate of complications can be considerably decreased. Although insulin replacement therapy is well known to be both the best and the most cost-effective way to control glucose levels in patients with type 1 diabetes, studies have no shown that those with type 2 diabetes can likewise benefit from appropriate insulin therapy. Other investigations have indicated that coronary events are as likely to occur in patients with recently discovered impaired glucose tolerance as in patients with known diabetes (at a 2-hour postprandial glucose threshold of 96 mg/dL [5.3 mmol/L]). Such finding suggest that there may be no such thing as "borderline diabetes" and give impetus to the search for improved types of insulin to treat all patients with diabetes. A recent candidate is the new insulin analogue lispro, which was developed by recombinant DNA techniques, with its design influenced by the structural analogy to another endogenous hormone, insulin-like growth factor I. Lispro is a fast-acting, rapidly dissipating insulin formulation. This profile allows lispro to be given less than 15 minutes before a meal, yet with little risk of postprandial hypoglycemia because its high mealtime peak is followed by rapid disappearance from the bloodstream.

CONCLUSION

Lispro has been shown to improve postprandial control of plasma glucose and to decrease the occurrence of hypoglycemia episodes in comparison with regular insulin. Because of its stability and pharmacokinetic properties, lispro can also be used in insulin pump therapy.

Common problems in outpatient management of patients with diabetes in the age of insulin analogues

Most patients with diabetes are managed in an outpatient primary care setting. This article reviews common dilemmas in outpatient insulin therapy and presents the evidence regarding the rational use of insulin therapy and combination oral agent-insulin therapy.

Insulin lispro: a useful advance in insulin therapy

Insulin lispro, the first insulin analogue to be used clinically, was engineered to incorporate the pharmacological advantages of insulin-like growth factor-1 (IGF-1), which has a reduced tendency to self associate, compared to conventional soluble insulin. It is absorbed more quickly following a subcutaneous injection, reaching peak concentrations (approximately twice as much as conventional insulin) and then falls more rapidly. These more physiological insulin profiles are reflected in the results of clinical trials involving patients with Type 1 diabetes, which generally show comparable glycaemic control but reduced rates of hypoglycaemia, particularly at night. The reduction in the rate of hypoglycaemia in the early trials has been generally fairly modest, but more recent publications suggest that increasing experience and more individualised insulin adjustment may lead to a greater impact. Other indications include its use in continuous subcutaneous insulin infusion and postprandially in young children.

Insulin analogues and other developments in insulin therapy for diabetes

Diabetes mellitus is a common chronic disorder, which is increasing in prevalence on a global scale. Insulin replacement therapy is required for all people with Type 1 diabetes and for many with Type 2 diabetes, to correct the metabolic abnormalities of these disorders. However, the pharmacokinetics and glucodynamics of available insulins have numerous limitations. Problems include delayed absorption from subcutaneous absorption sites (soluble [regular] insulin), and wide variability of absorption characteristics (insulin isophane suspension [NPH] and insulin lente) that is influenced by the adequacy of resuspension, and by a variable and insufficient duration of action, which usually requires intermediate-acting insulins to be administered twice-daily. All insulin preparations are associated with the common side effect of hypoglycaemia, and encourage weight gain.

Comparison of insulin lispro with regular human insulin for the treatment of type 1 diabetes in adolescents

BACKGROUND

Although insulin lispro (insulin LP) has been shown to improve postprandial blood glucose (BG) control and reduce hypoglycemic episodes in adult patients with type I diabetes, there appear to have been few clinical studies focusing on its use in adolescents.

OBJECTIVE

This study compared the effects of insulin LP with those of regular human insulin (insulin R) on postprandial BG control and hypoglycemia in adolescents with type diabetes.

METHODS

In this crossover, open-label study, adolescents between the ages of 9 and 18 years who had reached Tanner stage II puberty were randomized to receive either insulin LP immediately before meals or insulin R 30 to 45 minutes before meals, in addition to daily intermediate-acting insulin. After 4 months, patients were switched to the alternate treatment sequence. Eight-point BG profiles, hypoglycemia rate, and glycosylated hemoglobin (HbA1c) were measured at baseline and end point.

RESULTS

Four hundred eighty-one adolescents participated in the study at 53 investigative sites in 15 countries; 463 were randomized to treatment (228 insulin LP, 235 insulin R), and 457 completed the study. Insulin LP given before breakfast resulted in significantly lower mean (+/-SD) 2-hour postprandial BG levels compared with insulin R (9.7 +/- 4.0 mmol/L vs 10.6 +/- 4.3 mmol/L, respectively; P < 0.001). Insulin LP given before dinner resulted in significantly lower 2-hour postprandial BG levels compared with insulin R (8.6 +/- 3.5 mmol/L vs 9.3 +/- 3.7 mmol/L; P = 0.003). No differences were seen between treatments in 2-hour postprandial BG levels after the midday meal. Mean baseline HbA1c values were similar between sequence groups, and no between-group difference in HbA1c was observed at end point (insulin LP, 8.69% +/- 1.52%; insulin R, 8.70% +/- 1.65%). Treatment with insulin LP resulted in a significantly lower incidence of hypoglycemic episodes per patient per 30 days compared with insulin R (4.02 +/- 4.5 vs 4.37 +/- 4.5, respectively; P = 0.023) and significantly fewer hypoglycemic episodes between midnight and 6 AM (1.0 +/- 1.9 vs 1.7 +/- 2.6; P < 0.001).

CONCLUSIONS

In adolescents with type 1 diabetes, insulin LP significantly improved postprandial glycemic control and reduced episodes of nocturnal hypoglycemia compared with insulin R. Insulin LP was well tolerated and effective as part of an intensified insulin regimen in this study population.

Insulin analogues: have they changed insulin treatment and improved glycaemic control?

To improve insulin therapy, new insulin analogues have been developed. Two fast-acting analogues with a more rapid onset of effect and a shorter duration of action combined with a low day-to-day variation in absorption rate are now available. Despite this favourable time-action profile most studies have not been able to show any improvement in overall glycaemic control with the fast-acting analogues. A reduced post-prandial increase in blood glucose has been found in all studies, whereas between 3 and 5 h after the meal and during the night an increased blood glucose level is the normal course. This is probably the main explanation for the absence of improvement in overall glycaemic control when compared with regular human insulin. A tendency to a reduction in hypoglycaemic events during treatment with fast-acting analogues has been observed in most studies. Recent studies have indicated that NPH insulin administered several times daily at mealtimes can improve glycaemic control without increasing the risk of hypoglycaemia. The fast-acting analogues are now also available as insulin mixed with NPH. Insulin glargine is a new long-acting insulin which is soluble and precipitates after injection, resulting in a long half-life with a residual activity of about 50% 24 h after injection. Insulin glargine is a peakless insulin and studies in both type 1 and type 2 diabetic patients indicate that glargine improves fasting blood glucose control and reduces the incidence of nocturnal hypoglycaemia. Surprisingly, the new fast-acting analogues have not achieved the expected commercial success, which emphasises the need for new strategies for basal insulin supplementation, exercise, diet and blood glucose monitoring.

Effects of a fixed mixture of 25% insulin lispro and 75% NPL on plasma glucose during and after moderate physical exercise in patients with type 2 diabetes

OBJECTIVE

To compare the plasma glucose (PG) response with a fixed mixture of 25% insulin lispro and 75% NPL (Mix25), prior to a meal and 3 h before exercise, to human insulin 30/70 (30/70) in patients with type 2 diabetes.

RESEARCH DESIGN AND METHODS

Thirty-seven patients were treated in a randomized, open-label, 8-week, two-period crossover study. Mix25 was injected 5 min before breakfast and dinner throughout the study, as was 30/70 on inpatient test days and on outpatient dose titration days. Following the 4-week outpatient phase, patients were hospitalized, and exercised at a heart rate of 120 beats/min on a cycle ergometer two times for 30 min, separated by 30 min rest, starting 3 h after a 339 kcal breakfast.

RESULTS

The 2-h postprandial PG was significantly lower with Mix25 ((mean +/- SEM) 10.5 +/- 0.4 mmol/l vs 11.6 +/- 0.4 mmol/l; p = 0.016). Maximum decrease in PG from onset of exercise to end of exercise was significantly less with Mix25 (-3.6 +/- 0.29 mmol/l vs -4.7 +/- 0.31 mmol/l; p = 0.001). The maximum decrease in PG over 6 h, after exercise onset, was significantly less with Mix25 (-4.3 +/- 0.4 mmol/l vs -5.9 +/- 0.4 mmol/l; p < 0.001). The frequency of hypoglycemia (blood glucose (BG) < 3 mmol/l or symptoms) during the inpatient test was not different between treatments. During the outpatient phase, the frequency of patient-recorded hypoglycemia was significantly lower with Mix25 (0.7 +/- 0.2 episodes/30 d vs 1.2 +/- 0.3 episodes/30 d; p = 0.042).

CONCLUSIONS

Mix25 resulted in better postprandial PG control without an increase in exercise-induced hypoglycemia. The smaller decrease in PG during the postprandial phase after exercise may suggest a lower risk of exercise-induced hypoglycemia with Mix25 than with human insulin 30/70, especially for patients in tight glycemic control.

A comparison of insulin lispro and buffered regular human insulin administered via continuous subcutaneous insulin infusion pump

This study compared glycemic control achieved with insulin lispro or buffered regular human insulin in patients with Type 1 diabetes treated with continuous subcutaneous insulin infusion (CSII) using an external insulin pump. In this 24-week multicenter, randomized, two-way crossover, open-label trial, 58 patients on CSII with adequate glycemic control received either insulin lispro or buffered regular human insulin for 12 weeks, followed by the alternate treatment for another 12 weeks. Efficacy and safety measures included hemoglobin A(1c) (HbA(1c)) at baseline and endpoint, home blood glucose monitoring, hypoglycemia, and frequency of pump catheter occlusion. Patients consumed a standard test meal on three occasions, with determinations of fasting, 1- and 2-h postprandial glucose values. Insulin lispro use was associated with a significantly lower HbA(1c) than was buffered regular human insulin (7.41+/-0.97 vs. 7.65+/-0.85 mmol/l; P=.004). Fasting serum glucose values before the test meal were similar between the two therapies. The 1-h (11.16+/-4.29 vs. 13.20+/-4.68 mmol/l; P=.012) and 2-h (9.64+/-4.10 vs. 12.53+/-4.64 mmol/l; P=.001) postprandial glucose concentrations were significantly lower during treatment with insulin lispro. No differences between treatments were observed in basal or bolus insulin doses, weight gain, or the incidence and rate of hypoglycemia, hyperglycemia, or pump occlusions. When used in external pumps, insulin lispro provides better glycemic control than buffered regular human insulin with a similar adverse event profile.

Insulins today and beyond

The advent of insulin almost 80 years ago revolutionised treatment of diabetes and must be one of the most outstanding achievements of twentieth century medicine. Since then, there has been an ever-increasing awareness and acceptance of the need to achieve and sustain near-normoglycaemia to delay onset and retard progression of diabetic angiopathy. Physiological insulin replacement is therefore central to management of patients with diabetes who are unable to make [corrected] insulin. Insulin formulations, treatment strategies, and methods and routes of delivery have changed much, with more and more options for monitoring the effect on blood glucose concentrations. Patients with type 1 and type 2 diabetes need insulin much more aggressively than previously. Parallel developments in glucose-sensing technologies are welcomed as an integral part of safe and optimum implementation of insulin replacement therapy.

Guidelines for premeal insulin dose reduction for postprandial exercise of different intensities and durations in type 1 diabetic subjects treated intensively with a basal-bolus insulin regimen (ultralente-lispro)

OBJECTIVE

To evaluate and validate appropriate premeal insulin dose reductions for postprandial exercises of different intensities and durations to minimize the risk of exercise-induced hypoglycemia in type 1 diabetic subjects.

RESEARCH DESIGN AND METHODS

Eight male type 1 diabetic patients on a basal-bolus insulin regimen of ultralente (UL) as basal insulin and lispro (LP) as premeal insulin were tested in a randomized, crossover fashion during postprandial exercise at 25% VO2max for 60 min, 50% VO2max for 30 and 60 min, and 75% VOmax for 30 min starting 90 min after a standardized mixed breakfast (600 kcal, 75 g carbohydrates). Each subject served as his own control and was rested after a full dose of insulin LP (LP 100%) and/or 50% (LP 50%) and/or 25% (LP 25%) of the current dose.

RESULTS

At all intensities, the full premeal insulin dose was associated with an increased risk of hypoglycemia. At 25% VO2max for 60 min, a 50% reduction in the premeal insulin dose resulted in plasma glucose of -0.62 mmol/l compared with baseline at the end of exercise. At 50% VO2max for 30 and 60 min, 50 and 75% reductions of the premeal insulin dose were associated with plasma glucose of -0.39 and +0.49 mmol/l, respectively, at the end of the exercise. At 75% VO2max, a 75% reduction of the premeal insulin dose was required to achieve appropriate postexercise plasma glucose (+0.71 mmol/l). Such reductions in the premeal insulin dose resulted in a 75% decrease in the incidence of exercise-induced hypoglycemia. CONCLUSIONS In well-controlled type 1 diabetic subjects on intensive insulin therapy with the basal-bolus (UL-LP) insulin regimen, risk of hypoglycemia can be minimized during postprandial exercises of different intensities and different durations by appropriate reduction of premeal insulin LP.