RD Lawrence Lecture 2015 Old habits are hard to break: lessons from the study of hypoglycaemia

High intensity interval training as a novel treatment for impaired awareness of hypoglycaemia in people with type 1 diabetes (HIT4HYPOS): a randomised parallel-group study

AIMS/HYPOTHESIS

Impaired awareness of hypoglycaemia (IAH) in type 1 diabetes may develop through a process referred to as habituation. Consistent with this, a single bout of high intensity interval exercise as a novel stress stimulus improves counterregulatory responses (CRR) to next-day hypoglycaemia, referred to as dishabituation. This longitudinal pilot study investigated whether 4 weeks of high intensity interval training (HIIT) has sustained effects on counterregulatory and symptom responses to hypoglycaemia in adults with type 1 diabetes and IAH.

METHODS

HIT4HYPOS was a single-centre, randomised, parallel-group study. Participants were identified using the Scottish Diabetes Research Network (SDRN) and from diabetes outpatient clinics in NHS Tayside, UK. The study took place at the Clinical Research Centre, Ninewells Hospital and Medical School, Dundee, UK. Participants were aged 18-55 years with type 1 diabetes of at least 5 years' duration and HbA1c levels <75 mmol/mol (<9%). They had IAH confirmed by a Gold score ≥4, modified Clarke score ≥4 or Dose Adjustment For Normal Eating [DAFNE] hypoglycaemia awareness rating of 2 or 3, and/or evidence of recurrent hypoglycaemia on flash glucose monitoring. Participants were randomly allocated using a web-based system to either 4 weeks of real-time continuous glucose monitoring (RT-CGM) or RT-CGM+HIIT. Participants and investigators were not masked to group assignment. The HIIT programme was performed for 20 min on a stationary exercise bike three times a week. Hyperinsulinaemic-hypoglycaemic (2.5 mmol/l) clamp studies with assessment of symptoms, hormones and cognitive function were performed at baseline and after 4 weeks of the study intervention. The predefined primary outcome was the difference in hypoglycaemia-induced adrenaline (epinephrine) responses from baseline following RT-CGM or RT-CGM+HIIT.

RESULTS

Eighteen participants (nine men and nine women) with type 1 diabetes (median [IQR] duration 27 [18.75-32] years) and IAH were included, with nine participants randomised to each group. Data from all study participants were included in the analysis. During the 4 week intervention there were no significant mean (SEM) differences between RT-CGM and RT-CGM+HIIT in exposure to level 1 (28 [7] vs 22 [4] episodes, p=0.45) or level 2 (9 [3] vs 4 [1] episodes, p=0.29) hypoglycaemia. The CGM-derived mean glucose level, SD of glucose and glucose management indicator (GMI) did not differ between groups. During the hyperinsulinaemic-hypoglycaemic clamp studies, mean (SEM) change from baseline was greater for the noradrenergic responses (RT-CGM vs RT-CGM+HIIT: -988 [447] vs 514 [732] pmol/l, p=0.02) but not the adrenergic responses (-298 [687] vs 1130 [747] pmol/l, p=0.11) in those participants who had undergone RT-CGM+HIIT. There was a benefit of RT-CGM+HIIT for mean (SEM) change from baseline in the glucagon CRR to hypoglycaemia (RT-CGM vs RT-CGM+HIIT: 1 [4] vs 16 [6] ng/l, p=0.01). Consistent with the hormone response, the mean (SEM) symptomatic response to hypoglycaemia (adjusted for baseline) was greater following RT-CGM+HIIT (RT-CGM vs RT-CGM+HIIT: -4 [2] vs 0 [2], p<0.05).

CONCLUSIONS/INTERPRETATION

In this pilot clinical trial in people with type 1 diabetes and IAH, we found continuing benefits of HIIT for overall hormonal and symptomatic CRR to subsequent hypoglycaemia. Our findings also suggest that HIIT may improve the glucagon response to insulin-induced hypoglycaemia.

TRIAL REGISTRATION

ISRCTN15373978.

FUNDING

Sir George Alberti Fellowship from Diabetes UK (CMF) and the Juvenile Diabetes Research Foundation.

High-intensity training as a novel treatment for impaired awareness of hypoglycaemia in type 1 diabetes [HIT4HYPOS]: Protocol for a randomized parallel-group study

Aim

This pilot study aimed to investigate whether a 4-week programme of intermittent high-intensity training (HIT) will improve counterregulatory responses and improve hypoglycaemia awareness in adults with type 1 diabetes who have been exposed to recurrent hypoglycaemia.

Methods

Adults with type 1 diabetes who have been exposed to recurrent hypoglycaemia will be recruited from NHS Tayside, Scotland. All participants have a 4-week run-in period to optimize glycaemic control and to receive instruction in hypoglycaemia avoidance using insulin dose adjustment and real-time continuous glucose monitoring (CGM). Following this, they will undergo a baseline 90-minute hyperinsulinaemic hypoglycaemic clamp to assess symptomatic, cognitive and hormonal counterregulatory responses. Subsequently, participants will be randomized in a parallel-group design to either undergo a 4-week intervention with HIT or to no exercise with both groups using CGM throughout and receiving additional advice on hypoglycaemia avoidance. Participants in the HIT arm of the trial will be instructed to exercise 3 times a week on a cycle ergometer and asked to achieve ≥ 90% max heart rate during each period of exercise. On completion of the intervention period, all subjects then undergo a second matched hyperinsulinaemic hypoglycaemic clamp study.

Discussion

This pilot study will determine whether high-intensity exercise may offer a novel approach to restore hypoglycaemic awareness in type 1 diabetes (International Standard Randomised Controlled Trials No: ISRCTN15373978).

Experimental Models of Impaired Hypoglycaemia-Associated Counter-Regulation

Impaired awareness of hypoglycaemia (IAH) affects around a quarter of patients with diabetes who receive insulin treatment. This condition is characterised by a progressive reduction in symptomatic and behavioural responses to hypoglycaemia, increasing risk of deeper drops in blood glucose, unconsciousness, and collapse. Thus, patients with IAH experience severe hypoglycaemic episodes more frequently, resulting in significant morbidity and mortality. IAH is thought to develop as a consequence of whole-body adaptations to repeated insulin-induced hypoglycaemia (RH), with widespread deficits in the hypoglycaemia counter-regulatory response (CRR). Despite this important insight, the precise pathophysiology by which RH leads to an attenuated CRR is unknown. Studies into the underlying mechanisms of IAH have employed a variety of protocols in humans and experimental species. The use of animal models has many investigational benefits, including the unprecedented increase in the availability of transgenic strains. However, modelling impaired hypoglycaemia-associated counter-regulation remains challenging and appropriate interpretation of findings across species and protocols even more so. Here, we review the experimental modelling of IAH and impaired hypoglycaemia-associated counter-regulation, with a focus on understanding species-specific variation in glucose homeostasis. This review will aid investigators in interpreting outputs from different studies in IAH and aid progress in the field.

Impaired hypoglycaemia awareness in type 1 diabetes: lessons from the lab

Hypoglycaemia remains the most common metabolic adverse effect of insulin and sulfonylurea therapy in diabetes. Repeated exposure to hypoglycaemia leads to a change in the symptom complex that characterises hypoglycaemia, culminating in a clinical phenomenon referred to as impaired awareness of hypoglycaemia (IAH). IAH effects approximately 20-25% of people with type 1 diabetes and increases the risk of severe hypoglycaemia. This review focuses on the mechanisms that are responsible for the much higher frequency of hypoglycaemia in people with diabetes compared with those without, and subsequently how repeated exposure to hypoglycaemia leads to the development of IAH. The mechanisms that result in IAH development are incompletely understood and likely to reflect changes in multiple aspects of the counterregulatory response to hypoglycaemia, from adaptations within glucose and non-glucose-sensing cells to changes in the integrative networks that govern glucose homeostasis. Finally, we propose that the general process that incorporates many of these changes and results in IAH following recurrent hypoglycaemia is a form of adaptive memory called 'habituation'.

An international survey on hypoglycemia among insulin-treated type I and type II diabetes patients: Turkey cohort of the non-interventional IO HAT study

BACKGROUND

Limited real-world data are currently available on hypoglycemia in diabetes patients. The International Operations Hypoglycemia Assessment Tool (IO HAT) study was designed to estimate hypoglycemia in insulin-treated type I (T1DM) and type II (T2DM) diabetes mellitus patients from 9 countries. The data from Turkey cohort are presented here.

METHODS

A non-interventional study to determine the hypoglycemia incidence, retrospectively and prospectively, in Turkish T1DM and T2DM patients using a 2-part self-assessment questionnaire.

RESULTS

Overall, 2348 patients were enrolled in the Turkey cohort (T1DM = 306 patients, T2DM = 2042 patients). In T1DM patients, 96.8% patients reported hypoglycemic events (Incidence rate [IR]: 68.6 events per patient-year [ppy]), prospectively, while 74.0% patients reported hypoglycemic events (IR: 51.7 events ppy), retrospectively. In T2DM patients, 95.9% patients (IR: 28.3 events ppy) reported hypoglycemic events, prospectively, while 53.6% patients (IR: 23.0 events ppy) reported hypoglycemic events, retrospectively. Nearly all patients reported hypoglycemia during the prospective period.

CONCLUSIONS

This is a first patient-reported dataset on hypoglycemia in Turkish, insulin-treated diabetes patients. A high incidence of patient-reported hypoglycemia confirms that hypoglycemia remains under-estimated. Hypoglycemia increased healthcare utilization impacting patients' quality of life. Hypoglycemia remains a common side effect with insulin-treatment and strategies to optimize therapy and reduce hypoglycemia occurrence in diabetes patients are required.

TRIAL REGISTRATION

Clinicaltrials.gov, NCT02306681 (Date of registration: 12 Nov 2014; retrospectively registered).

High-Intensity Exercise as a Dishabituating Stimulus Restores Counterregulatory Responses in Recurrently Hypoglycemic Rodents

Hypoglycemia is a major adverse effect of insulin therapy for people with type 1 diabetes (T1D). Profound defects in the normal counterregulatory response to hypoglycemia explain the frequency of hypoglycemia occurrence in T1D. Defective counterregulation results to a large extent from prior exposure to hypoglycemia per se, leading to a condition called impaired awareness of hypoglycemia (IAH), the cause of which is unknown. In the current study, we investigate the hypothesis that IAH develops through a special type of adaptive memory referred to as habituation. To test this hypothesis, we used a novel intense stimulus (high-intensity exercise) to demonstrate two classic features of a habituated response, namely dishabituation and response recovery. We demonstrate that after recurrent hypoglycemia the introduction of a novel dishabituating stimulus (a single burst of high-intensity exercise) in male Sprague-Dawley rats restores the defective hypoglycemia counterregulatory response. In addition, the rats showed an enhanced response to the novel stimulus (response recovery). We make the further observation using proteomic analysis of hypothalamic extracts that high-intensity exercise in recurrently hypoglycemic rats increases levels of a number of proteins linked with brain-derived neurotrophic factor signaling. These findings may lead to novel therapeutic approaches for individuals with T1D and IAH.