Conversations and Reactions Around Severe Hypoglycaemia (CRASH): Results from the German Cohort of a Global Survey of People with Type 1 Diabetes or Insulin-Treated Type 2 Diabetes and Caregivers.

BACKGROUND: A global cross-sectional survey (CRASH) was designed to provide information about the experiences of people with diabetes (PWD) and their caregivers in relation to severe hypoglycaemic events. METHODS: Adults with type 1 diabetes or insulin-treated type 2 diabetes who had experienced one or more severe hypoglycaemic events within the past 3 years, and adult caregivers for such people, were recruited from medical research panels using purposive sampling. We present here results from Germany. RESULTS: Approximately 100 individuals in each of the four participant groups completed a 30-minute online survey. Survey results indicated that the most recent severe hypoglycaemic event made many participants feel scared (80.4%), unprepared (70.4%), and/or helpless (66.5%). Severe hypoglycaemia was discussed by healthcare professionals at every visit with only 20.2% of participants who had ever had this conversation, and 53.5% of participants indicated that their insulin regimen had not changed following their most recent event. 37.1% of PWD/people with diabetes cared for by caregivers owned a glucagon kit at the time of survey completion. CONCLUSIONS: The survey identified areas for improvement in the prevention and management of severe hypoglycaemic events. For healthcare professionals, these include enquiring more frequently about severe hypoglycaemia and adjusting blood glucose-lowering medication after a severe hypoglycaemic event. For individuals with diabetes and their caregivers, potential improvements include ensuring availability of glucagon at all times. Changes in these areas could lead not only to improved patient wellbeing but also to reduced use of emergency services/hospitalisation and, consequently, lower healthcare costs.

Metabolic and Cognitive Outcomes of Subchronic Once-Daily Intranasal Insulin Administration in Healthy Men.

Insulin acts in the brain to limit food intake and improve memory function. We have previously shown that 8 weeks of intranasal insulin delivered in four daily doses of 40 IU decrease body weight and enhance word list recall. In the present study, we investigated the effect on body composition, endocrine parameters, and memory performance of 8 weeks of once-daily administration of 160 IU in healthy men. We assumed that intranasal insulin administered before nocturnal sleep, a period of relative metabolic inactivity that moreover benefits memory formation, would be superior to insulin delivery in the morning and placebo administration. After a 2-week baseline period, healthy male normal-weight subjects (mean age, 27.1 ± 0.9 years) received either placebo, 160 IU intranasal insulin in the morning, or 160 IU in the evening (n = 12 per group) for 8 consecutive weeks. Throughout the experiment, we measured body weight and body composition as well as circulating concentrations of glucose, insulin, adrenocorticotropin, cortisol, growth hormone, insulin-like growth-factor 1, adiponectin, and leptin. Declarative and procedural memory function was repeatedly assessed by means of, respectively, word list recall and word-stem priming. We found that neither morning nor evening insulin compared to placebo administration induced discernible changes in body weight and body composition. Delayed recall of words showed slight improvements by insulin administration in the evening, and serum cortisol concentrations were reduced after 2 weeks of insulin administration in the morning compared to the other groups. Results indicate that catabolic long-term effects of central nervous insulin delivery necessitate repetitive, presumably pre-meal delivery schedules. The observed memory improvements, although generally weaker than previously found effects, suggest that sleep after intranasal insulin administration may support its beneficial cognitive impact.

Relationship between cerebrospinal fluid concentrations of orexin A/hypocretin-1 and body composition in humans.

The hypothalamic neuropeptide orexin A (hypocretin-1) is a key signal in sleep/wake regulation and promotes food intake. We investigated the relationship between cerebrospinal fluid orexin A concentrations and body composition in non-narcoleptic human subjects with a wide range of body weight to gain insight into the role of orexin A in human metabolism. We collected cerebrospinal fluid and blood samples and measured body composition by bioelectric impedance analysis in 36 subjects (16 women and 20 men) with body mass indices between 16.24 and 38.10 kg/m2 and an age range of 19-80 years. Bivariate Pearson correlations and stepwise multiple regressions were calculated to determine associations between orexin A and body composition as well as biometric variables. Concentrations of orexin A in cerebrospinal fluid averaged 315.6 ±â€¯6.0 pg/ml, were comparable between sexes (p > 0.15) and unrelated to age (p > 0.66); they appeared slightly reduced in overweight/obese compared to normal-weight subjects (p = .07). Orexin A concentrations decreased with body weight (r = -0.38, p = .0229) and fat-free mass (r = -0.39, p = .0173) but were not linked to body fat mass (p > 0.24). They were inversely related to total body water (r = -0.39, p = .0174) as well as intracellular (r = -0.41, p = .0139) and extracellular water (r = -0.35, p = .0341). Intracellular water was the only factor independently associated with cerebrospinal fluid orexin A concentrations (p = .0139). We conclude that cerebrospinal fluid orexin A concentrations do not display associations with body adiposity, but are inversely related to intracellular water content. These cross-sectional findings suggest a link between orexin A signaling and the regulation of water homeostasis in humans.

Self-reported Hypoglycaemic Events in 2 430 Patients with Insulin-treated Diabetes in the German Sub-population of the HAT Study.

Data concerning true hypoglycaemic incidence in insulin-treated patients with diabetes in real-world clinical practice are lacking in Germany. The aim of this analysis was to determine the incidence of hypoglycaemia experienced by the German cohort of patients enrolled in the global Hypoglycaemia Assessment Tool (HAT) study. This was a non-interventional, 6-month retrospective and 4-week prospective study using self-assessment questionnaires and patient diaries assessing patients aged ≥18 years in Germany, with type 1 diabetes (T1D) (n=811) or type 2 diabetes (T2D) (n=1 619) treated with insulin for >12 months. The primary endpoint was the percentage of patients experiencing ≥1 hypoglycaemic event during the prospective observational period (4 weeks after baseline). Predictive and continuous factors (such as age, gender, duration of insulin use and HbA1c) contributing to hypoglycaemia risk were explored.During the prospective period, at least one hypoglycaemic event was reported by 81.3% of patients with T1D and 39.7% of patients with T2D, indicating that hypoglycaemia is a common acute complication among patients with insulin-treated diabetes. Severe hypoglycaemia was reported by 9.1% of patients with T1D and 5.4% of patients with T2D. Higher rates of any and severe hypoglycaemia were reported prospectively than retrospectively, regardless of diabetes type, indicating that patients retrospectively under-report hypoglycaemia. Prospective rates (events per patient-year) of any, nocturnal and severe hypoglycaemia were 80.3, 9.9 and 3.0 for T1D and 15.6, 2.4 and 1.1 for T2D, respectively. Given the potential for recall bias in retrospective reporting, this prospective assessment of hypoglycaemia appears more reliable than retrospective assessment. Trial number: NCT01696266.

Disability-adjusted life years lost due to diabetes in France, Italy, Germany, Spain, and the United Kingdom: a burden of illness study.

AIMS: To compare the burden of disease (BoD) attributable to diabetes expressed in disability-adjusted life years (DALYs) for five European countries in 2010. METHODS: DALYs lost to diabetes as the sum of years of life lost and years lived with disability were estimated by sex and age using country-specific epidemiological data and global disability weights. Data from various secondary sources were combined to estimate health loss due to diabetes for France, Germany, Italy, Spain, and the UK. National statistical databases were used and if necessary, community studies were used to derive the prevalence of diabetes by sex and age group, which were weighted proportionately for a national population burden of disease estimate. All identified data were adapted to the Global Burden of Disease methodology (2010) to calculate the burden attributable to diabetes. No age weighting and discounting was applied. Sensitivity to different sources of variation was examined. Germany and Italy lost the largest number of DALYs due to diabetes, with 5.9 and 5.8 per 1,000 inhabitants, respectively, followed by Spain (4.4), France (3.7), and the UK (2.9). The highest burden was caused by mortality due to diabetes, with the exception of the UK, for which the burden due to disability of diabetes was higher. Mean DALYs lost were higher for women in Germany, Italy, and Spain and shown to increase with age for all countries. Sensitivity analysis in variation in disability weights and uncertainty in epidemiological data were shown to have effects on DALYs lost. CONCLUSION: In spite of data limitations, the estimates reported here show that DALY loss due to diabetes imposes a substantial burden on countries. Cross-national variation in disease epidemiology was the largest source of variation in the burden of diabetes between countries.

Fibroblast growth factor 21 (FGF21) in human cerebrospinal fluid: relationship with plasma FGF21 and body adiposity.

OBJECTIVE: Reports of increased circulating fibroblast growth factor 21 (FGF21) levels in obesity indicate that FGF21 may be implicated in body weight homeostasis. We sought to investigate the existence of FGF21 in human cerebrospinal fluid (CSF) and, if present, the relationship between CSF FGF21 with body adiposity and metabolic parameters. RESEARCH DESIGN AND METHODS: CSF and corresponding plasma FGF21 were measured by an enzyme-linked immunosorbent assay (18 men and 20 women, aged 19-80 years, and BMI 16.2-38.1 kg/m(2)) and correlated to body adiposity and metabolic parameters. RESULTS: CSF and plasma FGF21 increased in particular with rising BMI and fat mass. In CSF, FGF21 was detectable at concentrations ~40% that of plasma levels. CSF and plasma FGF21 levels were significantly positively correlated with BMI and fat mass, body weight, plasma insulin, and homeostasis model assessment of insulin resistance. Plasma FGF21 levels were significantly negatively correlated with plasma adiponectin. When subjected to multiple regression analysis, only fat mass was predictive of plasma FGF21 (ß = 0.758; P = 0.004) and CSF FGF21 (ß = 0.767; P = 0.007). The CSF-to-plasma FGF21 ratio was significantly negatively correlated with BMI, fat mass, and plasma FGF21. Subjects in the highest plasma FGF21 quintile had a lower CSF-to-plasma FGF21 ratio (12.7% [9.7-14.9%]) compared with those in the lowest plasma FGF21 quintile (94.7% [37.3-99.8%]) (P < 0.01). CONCLUSIONS: Our observations have important implications with respect to the potential central actions of FGF21. Future research should seek to clarify whether FGF21 would be beneficial in the management of obesity and its metabolic complications.

Decreased cerebrospinal fluid/plasma ratio of the novel satiety molecule, nesfatin-1/NUCB-2, in obese humans: evidence of nesfatin-1/NUCB-2 resistance and implications for obesity treatment.

CONTEXT: The novel adipokine, nesfatin-1/NUCB-2, reduces food intake, levels of which are elevated in overweight individuals. OBJECTIVES: The aim of the study was to investigate the mechanisms underlying brain nesfatin-1/NUCB-2 uptake and to determine whether reduced uptake may contribute to nesfatin-1/NUCB-2 resistance. DESIGN: Cerebrospinal fluid (CSF) and corresponding plasma nesfatin-1/NUCB-2 were measured by ELISA [18 men and 20 women; age, 19-80 yr; body mass index (BMI), 16.2-38.1 kg/m(2)] and correlated to body adiposity and metabolic parameters. RESULTS: CSF/plasma nesfatin-1/NUCB-2 ratio was significantly negatively associated with BMI, body weight, fat mass, and CSF glucose. BMI was predictive of CSF/plasma nesfatin-1/NUCB-2 ratio (ß = -0.786; P = 0.045). CSF nesfatin-1/NUCB-2 was significantly positively associated with plasma nesfatin-1/NUCB-2 (R = 0.706; P < 0.01). There was a significant linear relation between CSF and plasma nesfatin-1/NUCB-2 in lean (BMI <25 kg/m(2); R = 0.744; P = 0.002) and obese (BMI ≥ 30 kg/m(2); R = 0.693; P = 0.026) subjects. Subjects in the highest plasma nesfatin-1/NUCB-2 quintile had lower CSF/plasma nesfatin-1/NUCB-2 ratio [26.5% (26.0-29.5%)] compared to the lowest plasma nesfatin-1/NUCB-2 quintile [38.5% (34.0-42.0%)] (P < 0.01), corresponding BMI [32.4 (31.0-35.0) vs. 23.3 (19.7-23.5) kg/m(2); P < 0.01], and fat mass [32.8 (29.5-40.6) vs. 30.7 (8.2-20.1) kg/m(2); P < 0.01]. CONCLUSIONS: Our observations have important implications with respect to the potential weight-reducing actions of nesfatin-1/NUCB-2 treatment. Future research should seek to clarify whether nesfatin-1/NUCB-2 would be beneficial in the management of obesity.

Identification of nesfatin-1 in human and murine adipose tissue: a novel depot-specific adipokine with increased levels in obesity.

Nesfatin-1 is a recently identified anorexigenic peptide derived from its precursor protein, nonesterified fatty acid/nucleobindin 2 (NUCB2). Although the hypothalamus is pivotal for the maintenance of energy homeostasis, adipose tissue plays an important role in the integration of metabolic activity and energy balance by communicating with peripheral organs and the brain via adipokines. Currently no data exist on nesfatin-1 expression, regulation, and secretion in adipose tissue. We therefore investigated NUCB2/nesfatin-1 gene and protein expression in human and murine adipose tissue depots. Additionally, the effects of insulin, dexamethasone, and inflammatory cytokines and the impact of food deprivation and obesity on nesfatin-1 expression were studied by quantitative RT-PCR and Western blotting. We present data showing NUCB2 mRNA (P < 0.001), nesfatin-1 intracellular protein (P < 0.001), and secretion (P < 0.01) were significantly higher in sc adipose tissue compared with other depots. Also, nesfatin-1 protein expression was significantly increased in high-fat-fed mice (P < 0.01) and reduced under food deprivation (P < 0.01) compared with controls. Stimulation of sc adipose tissue explants with inflammatory cytokines (TNFalpha and IL-6), insulin, and dexamethasone resulted in a marked increase in intracellular nesfatin-1 levels. Furthermore, we present evidence that the secretion of nesfatin-1 into the culture media was dramatically increased during the differentiation of 3T3-L1 preadipocytes into adipocytes (P < 0.001) and after treatments with TNF-alpha, IL-6, insulin, and dexamethasone (P < 0.01). In addition, circulating nesfatin-1 levels were higher in high-fat-fed mice (P < 0.05) and showed positive correlation with body mass index in human. We report that nesfatin-1 is a novel depot specific adipokine preferentially produced by sc tissue, with obesity- and food deprivation-regulated expression.

Euglycemic infusion of insulin detemir compared with human insulin appears to increase direct current brain potential response and reduces food intake while inducing similar systemic effects.

OBJECTIVE: In the treatment of diabetic patients, the long-acting insulin analog insulin detemir is less prone to induce weight gain than other insulin formulations. Assuming that because of its pharmacologic properties, detemir displays stronger central nervous anorexigenic efficacy than human insulin, we compared acute effects of human insulin and detemir on electroencephalography (EEG) measures and food intake. RESEARCH DESIGN AND METHODS: Frontocortical EEG direct current (DC) potentials were recorded in 15 healthy men during two hyperinsulinemic-euglycemic clamps that included an insulin bolus injection (human insulin, 17.75 mU/kg body wt; detemir, 90 mU/kg body wt) followed by a steady 90-min infusion (1.0 vs. 2.0 mU x kg(-1) x min(-1)). A higher dosage was chosen for detemir to compensate for its delay in impact relative to human insulin and to elicit similar systemic effects. At 20 min after infusion, subjects were allowed to eat ad libitum from a test buffet. RESULTS: Mean glucose infusions to maintain euglycemia (P > 0.93) and blood glucose concentrations (P > 0.34) did not differ between conditions. Detemir infusion induced a negative DC-potential shift, averaging -372.2 microV from 21 to 90 min that was not observed during human insulin infusion (146.5 microV, P = 0.02). Detemir, in comparison with human insulin, reduced subsequent food intake by 303 kcal (1,257 vs. 1,560, P < 0.04). CONCLUSIONS: While inducing comparable peripheral effects, detemir exerts stronger acute effects on brain functions than human insulin and triggers a relative decrease in food consumption, suggesting an enhanced anorexigenic impact of detemir compared with human insulin on central nervous networks that control nutrient uptake.

Costs of managing severe hypoglycaemia in three European countries.

OBJECTIVES: To assess the costs of severe hypoglycaemic events (SHEs) in diabetes patients in Germany, Spain and the UK. METHODS: Healthcare resource use was measured by surveying 639 patients aged ≥ 16 years, receiving insulin for type 1 (n=319) or type 2 diabetes (n=320), who experienced ≥ 1 SHE in the preceding year. Patients were grouped by location of SHE treatment: group 1, community (family/domestic); group 2, community (healthcare professional); group 3, hospital. Costs were calculated from published unit costs applied to estimated resource use. Costs per SHE were derived from patient numbers per subgroup. Weighted average costs were derived using a prevalence database. RESULTS: Hospital treatment was a major cost in all countries. In Germany and Spain, costs per SHE for type 1 patients differed from those for type 2 patients in each group. Average SHE treatment costs were higher for patients with type 2 diabetes (Germany, €533; Spain, €691; UK, €537) than type 1 diabetes patients (€441, €577 and €236, respectively). Telephone calls, visits to doctors, blood glucose monitoring and patient education contributed substantially to costs for non-hospitalised patients. CONCLUSIONS: Treatment of SHEs adds significantly to healthcare costs. Average costs were lower for type 1 than for insulin-treated type 2 diabetes, in all three countries.

Relationship between cerebrospinal fluid visfatin (PBEF/Nampt) levels and adiposity in humans.

OBJECTIVE: Observations of elevated circulating concentrations of visfatin (PBEF/Nampt) in obesity and diabetes suggest that this recently described adipokine is involved in the regulation of body weight and metabolism. We examined in humans whether visfatin is found in cerebrospinal fluid (CSF) and, if so, how CSF visfatin concentrations relate to adiposity and metabolic parameters. RESEARCH DESIGN AND METHODS: We measured visfatin concentrations in the plasma and CSF of 38 subjects (18 men and 20 women; age 19-80 years) with a wide range of body weight (BMI 16.24-38.10 kg/m2). In addition, anthropometric parameters and endocrine markers were assessed. Bivariate correlation coefficients were determined and stepwise multiple regression analyses were performed to detect associations of CSF and plasma visfatin levels with relevant parameters. RESULTS: Plasma visfatin levels increased with rising BMI (P < 0.0001) and body fat mass (P < 0.0001). In contrast, CSF visfatin levels decreased with increasing plasma visfatin concentrations (P < 0.03), BMI (P < 0.001), body fat mass (P < 0.0001), and insulin resistance (P < 0.05). Body fat was the only factor independently associated with CSF visfatin, explaining 58% of the variation of CSF visfatin levels (P < 0.0001). Neither plasma (P > 0.13) nor CSF (P > 0.61) visfatin concentrations differed between men and women. CONCLUSIONS: Our data indicate that visfatin concentrations in human CSF decrease with rising body fat, supporting the assumption that visfatin transport across the blood-brain barrier is impaired in obesity and that central nervous visfatin insufficiency or resistance are linked to pathogenetic mechanisms of obesity.

Early morning rise in hypothalamic-pituitary-adrenal activity: a role for maintaining the brain's energy balance.

A profound rise in secretory activity in the early morning hours hallmarks the circadian regulation of the hypothalamic-pituitary-adrenal (HPA) stress axis. Functions and mechanisms underlying this regulation are barely understood. We tested the hypothesis that the early morning rise in HPA axis activity originates in part from a negative energy balance due to nocturnal fasting and concomitant increases in cerebral glucose demands. According to a 2x2 design, healthy men were infused with glucose (4.5mg/kgmin, 2300-0700h) and saline, respectively, during nocturnal sleep (n=9) or wakefulness (n=11). Circulating concentrations of ACTH, cortisol, glucose, insulin, and leptin were measured and food consumption in the next morning was assessed. Independent of sleep, glucose infusion reduced levels of ACTH (P<0.01) and cortisol (P<0.02) during the second night half. In the Sleep group, glucose infusion enhanced rapid eye movement (REM) sleep at the expense of sleep stage 2 (each P<0.05). Glucose infusion increased leptin levels in both groups (P<0.005) and reduced morning food intake in the Wake (P<0.02) but not in the Sleep group (P>0.46). Our findings support the view that increasing energy demands of the brain towards the end of the night essentially contribute to the early morning rise in HPA axis activity. Sleep is not critically involved in this glucose-glucocorticoid feedback loop but may reduce the brain's sensitivity to the anorexigenic effect of enhanced glucose supply.

Towards the therapeutic use of intranasal neuropeptide administration in metabolic and cognitive disorders.

The nose provides an effective way for delivering neuropeptides to the central nervous system, bypassing the blood-brain barrier and avoiding systemic side effects. Thereby intranasal neuropeptide administration enables the modulation of central nervous signaling pathways of body weight regulation and cognitive functions. Central nervous control of energy homeostasis is assumed to rely on hypothalamic neuropeptidergic pathways that are triggered by the peripheral adiposity signals insulin and leptin conveying the amount of body fat to the brain. Melanocortins, including alpha-melanocyte stimulating hormone (alpha-MSH), are essential for inducing anorexigenic/catabolic effects, i.e. for inhibiting caloric intake and increasing energy expenditure. Insulin, in addition to its function as an adiposity signal, also influences memory formation. Here we present a series of studies on the intranasal administration of MSH/ACTH4-10, a melanocortin receptor agonist, and of insulin. Prolonged administration of MSH/ACTH4-10 induced weight loss in normal-weight, but not in overweight humans. Intranasal insulin reduced body fat and improved memory functions in the absence of adverse peripheral side effects. Our results may contribute to the future development of therapeutic strategies in disorders like obesity and cognitive impairments that derive from dysfunctions of central nervous neuropeptidergic pathways.

Differential sensitivity of men and women to anorexigenic and memory-improving effects of intranasal insulin.

CONTEXT: Brain insulin is critically involved in the regulation of body weight and memory processing. Long-term administration of intranasal insulin reduces body weight in men, but not in women, while improving hippocampus-dependent memory processing in both genders. OBJECTIVES: Our objectives were to assess the effects of a single dose of intranasal insulin on food intake and memory function in men and women, and to determine any gender differences. METHODS: A total of 32 healthy, normal-weight subjects (14 men, 18 women) were intranasally administered 160 IU regular human insulin or vehicle before performing a hippocampus-dependent two-dimensional-object location task, a working memory task (digit span), and a hippocampus-independent mirror tracing task. Subsequently, food intake from an ad libitum breakfast buffet was measured. RESULTS: Insulin treatment decreased food intake in men but not in women (difference to placebo condition, men: -192.57 +/- 78.48 kcal, P < 0.03; women: 18.54 +/- 42.89 kcal, P > 0.67). In contrast, hippocampus-dependent memory and working memory were improved in women (P < 0.03, P < 0.05, respectively), whereas men did not benefit from acute insulin treatment (P > 0.17, P > 0.20). Performance on the hippocampus-independent mirror tracing task was not affected by insulin in women or men. CONCLUSIONS: In accordance with animal data, results indicate that men are more sensitive than women to the acute anorexigenic effect of central nervous insulin signaling, whereas insulin's beneficial effect on hippocampus-dependent memory functions is more pronounced in women. Our findings provide support for the notion of a fundamental gender difference in central nervous insulin signaling that pertains to the regulation of energy homeostasis and memory functions.

Targeting metabolic and cognitive pathways of the CNS by intranasal insulin administration.

Intranasal administration effectively delivers neuropeptides to the CNS, bypassing the blood-brain barrier and avoiding systemic side effects. Using this route of administration, direct manipulations of central nervous signalling pathways involved in body weight regulation and cognition are possible. Specifically, the subchronic intranasal administration of insulin has been shown to reduce body fat and improve memory function in the absence of adverse peripheral side effects. These results may fuel the future development of therapeutic strategies in disorders such as obesity and Alzheimer's disease that are promoted by dysfunctions of central nervous neuropeptidergic pathways.

Intranasal insulin to improve memory function in humans.

BACKGROUND: Compelling evidence indicates that central nervous insulin enhances learning and memory and in particular benefits hippocampus-dependent (i.e., declarative) memory. Intranasal administration of insulin provides an effective way of delivering the compound to the central nervous system, bypassing the blood-brain barrier and avoiding systemic side effects. METHODS: Here we review a series of recent studies on the effects of intranasally administered insulin on memory functions in humans. In accordance with the beneficial effects of intravenously administered insulin on hippocampus-dependent declarative memory observed in hyperinsulinemic-euglycemic clamp studies, intranasal insulin administration similarly improves this type of memory, but in the absence of adverse peripheral side effects. RESULT AND CONCLUSION: Considering that cerebrospinal fluid insulin levels are reduced in patients suffering from Alzheimer's disease, these results may be of considerable relevance for future clinical applications of insulin in the treatment of memory disorders.

Defective awakening response to nocturnal hypoglycemia in patients with type 1 diabetes mellitus.

BACKGROUND: Nocturnal hypoglycemia frequently occurs in patients with type 1 diabetes mellitus (T1DM). It can be fatal and is believed to promote the development of the hypoglycemia-unawareness syndrome. Whether hypoglycemia normally provokes awakening from sleep in individuals who do not have diabetes, and whether this awakening response is impaired in T1DM patients, is unknown. METHODS AND FINDINGS: We tested two groups of 16 T1DM patients and 16 healthy control participants, respectively, with comparable distributions of gender, age, and body mass index. In one night, a linear fall in plasma glucose to nadir levels of 2.2 mmol/l was induced by infusing insulin over a 1-h period starting as soon as polysomnographic recordings indicated that stage 2 sleep had been reached. In another night (control), euglycemia was maintained. Only one of the 16 T1DM patients, as compared to ten healthy control participants, awakened upon hypoglycemia (p = 0.001). In the control nights, none of the study participants in either of the two groups awakened during the corresponding time. Awakening during hypoglycemia was associated with increased hormonal counterregulation. In all the study participants (from both groups) who woke up, and in five of the study participants who did not awaken (three T1DM patients and two healthy control participants), plasma epinephrine concentration increased with hypoglycemia by at least 100% (p < 0.001). A temporal pattern was revealed such that increases in epinephrine in all participants who awakened started always before polysomnographic signs of wakefulness (mean +/- standard error of the mean: 7.5 +/- 1.6 min). CONCLUSIONS: A fall in plasma glucose to 2.2 mmol/l provokes an awakening response in most healthy control participants, but this response is impaired in T1DM patients. The counterregulatory increase in plasma epinephrine that we observed to precede awakening suggests that awakening forms part of a central nervous system response launched in parallel with hormonal counterregulation. Failure to awaken increases the risk for T1DM patients to suffer prolonged and potentially fatal hypoglycemia.