Glucose counterregulation, hypoglycemia, and intensive insulin therapy in diabetes mellitus

Prediction of severe hypoglycemia

OBJECTIVE

Prevention of severe hypoglycemia (SH) is premised partially on the ability to accurately anticipate its occurrence. This study prospectively tests methods for predicting SH using blood glucose meter readings.

RESEARCH DESIGN AND METHODS

One hundred adults with type 1 diabetes were followed for 6 months, and 79 insulin-using adults with type 2 diabetes were followed for 4 months. During this time, subjects' routine self-monitored blood glucose (SMBG) readings were stored on and retrieved from memory meters, and participants were queried biweekly about occurrence of SH. Respective demographics for the two groups were age 40.7 and 50.2 years, duration of diabetes 20.0 and 12.2 years, A1C 7.6 and 8.8%, and male sex 43 and 39%, respectively.

RESULTS

Relative risk for SH, quantified by the ratio of an individual's low blood glucose index (LBGI) based on the previous 150 SMBG readings to the LBGI based on recent SMBG readings, increased significantly in the 24 h before SH episodes in individuals with type 1 and type 2 diabetes (t = 10.3, P < 0.0001, and t = 4.2, P < 0.001, respectively). A sliding algorithm detected 58% of imminent (within 24 h) SH episodes in the type 1 diabetic group and 60% of those in the type 2 diabetic group when three SMBG readings were available in the 24 h before an episode. Detection increased to 63 and 75%, respectively, if five SMBG readings were available in the 24 h before an episode.

CONCLUSIONS

SH often follows a specific blood glucose fluctuation pattern that is identifiable from SMBG. Thus, partial prediction of imminent SH is possible, providing a potential tool to trigger self-regulatory prevention of significant hypoglycemia.

Hypoglycemia reduces the blood-oxygenation level dependent signal in primary auditory and visual cortex: a functional magnetic resonance imaging study

Studies of the effects of hypoglycemia on the brain using neurocognitive testing have suggested that mainly complex functions subserved by secondary and tertiary cortex are affected by mild to moderate hypoglycemia and that intensively treated patients with Type I diabetes mellitus (T1DM) may have altered sensitivity to the central nervous system effects of hypoglycemia. Functional magnetic resonance imaging provides a sensitive, regionally-specific probe of possible neurophysiologic changes related to hypoglycemia in the brain. Eleven intensively-treated T1DM patients and 11 matched non-diabetic controls took part in a 2-day protocol in which functional magnetic resonance imaging (MRI) was used to measure changes in the patterns of brain activation produced by simple auditory and visual stimuli in different conditions. On one day, participants were euglycemic the entire time. On the other day, an initial 50-min euglycemic period was followed by a 50-min hypoglycemic period. Results indicated that hypoglycemia reduced the amplitude of the blood-oxygenation level dependent response in primary auditory and visual cortex to simple auditory and visual stimuli. The latency and duration of the transient hemodynamic response function were not affected. Responses to hypoglycemia were similar in diabetic and non-diabetic participants. These results suggest that mild to moderate hypoglycemia may alter the balance of blood flow and oxygen extraction when glucose levels are lowered. Intensively-treated T1DM, with its attendant frequent hypoglycemic episodes, did not seem to alter hypoglycemic responses in primary visual and auditory cortex.

Effects of glycemic control on target organ responses to epinephrine in type 1 diabetes

Severe hypoglycemia occurs in intensively treated patients with type 1 diabetes mellitus (T1DM) due in part to deficient epinephrine counterregulatory responses. Previously, we have found that T1DM patients demonstrated a spectrum of altered responses to epinephrine at a variety of target organs compared with nondiabetic healthy subjects. What is not known is whether intensive glycemic control further modifies target organ responses in individuals with T1DM. Therefore, the aim of this study is to assess whether there is tissue specific (liver, muscle, adipose tissue, pancreas and cardiovascular) resistance to epinephrine in intensively controlled (IC) T1DM compared with those with conventional control (CC). Eight IC patients (age 33 +/- 4 yr, BMI 24 +/- 2 kg/m2, Hb A1C 6.7 +/- 0.1%), and 11 CC patients (age 35 +/- 3 yr, BMI 25 +/- 1 kg/m2, Hb A1C 9.6 +/- 0.1%) underwent two separate randomized, single-blind, 2-h hyperinsulinemic euglycemic clamp studies with (EPI) and without (NO EPI) epinephrine infusion. Epinephrine levels during EPI were similar in all groups (5,197 +/- 344 pmol/l). Glucose (5.3 +/- 0.1 mmol/l) and insulin levels (515 +/- 44 pmol/l) were similar in all groups during the glucose clamps. Endogenous glucose production (EGP) and glucose uptake (R(d)) were determined using [3-H3]glucose. Muscle biopsy was performed at the end of each study. IC had a significantly reduced EGP and R(d) responses to EPI compared with CC. Glucagon responses to EPI were similarly blunted in both IC and CC. Free fatty acid and glycerol response to EPI was greater in CC compared with IC. There was a significantly greater systolic blood pressure response to EPI in CC. We conclude that, despite similar epinephrine, insulin, and glucose levels, intensively treated T1DM patients had reduced cardiovascular, skeletal muscle, hepatic, and adipose target organ responses to EPI compared with conventionally treated T1DM patients.

Hypoglykämie trotz Hyperglykämie

Hypoglycemia represents the most frequent endocrinologic emergency situation in prehospital patient care. As the patients are usually unconscious on arrival of emergency medical personnel, often the only way to establish a diagnosis is by determination of the blood glucose concentration. However, even normoglycemic or hyperglycemic levels cannot definitively exclude the diagnosis of a previous hypoglycemia as the cause of the acute cerebral deficiency. Therefore, and especially in the case of insulin-dependent diabetes mellitus, a differential diagnosis should be considered. We report a case of emergency treatment of a hypoglycemic episode in a female patient with prolonged neuroglycopenia together with cerebrovascular dementia and Alzheimer's disease.

Potent hypoglycaemic activity of the aqueous extract of Chamaemelum nobile in normal and streptozotocin-induced diabetic rats

The purpose of this study was to investigate the effect of both a single dose and daily oral administration for 15 days of the aqueous extract of the aerial part of Chamaemelum nobile (C. nobile) at a dose of 20mg/kg body weight on blood glucose concentrations and basal insulin levels in normal and streptozotocin-induced diabetic rats (STZ). Single oral administration of C. nobile aqueous extract reduced blood glucose levels from 6.0 +/- 0.3 mmol/l to 4.9 +/- 0.09 mmol/l (P < 0.05) 6h after administration in normal rats and from 21.1 +/- 1.3 mmol/l to 14.5 +/- 0.9 mmol/l (P < 0.001) in STZ diabetic rats. Furthermore, blood glucose levels were decreased from 6.1 +/- 0.06 mmol/l to 4.6 +/- 0.17 mmol/l (P < 0.01) and from 21.1 +/- 1.31 mmol/l to 13.7 +/- 0.9 mmol/l (P < 0.01) in normal and STZ diabetic rats, respectively, after 15 days of treatment. Basal plasma insulin concentrations remain unchanged after treatment in both normal and STZ diabetic rats so the mechanism of this pharmacological activity seems to be independent of insulin secretion. We conclude that the aqueous extract of C. nobile exhibits a significant hypoglycaemic effect in normal and STZ diabetic rats without affecting basal plasma insulin concentrations and support, therefore, its traditional use by the Moroccan population.

Survivors of childhood acute lymphoblastic leukaemia, with radiation-induced GH deficiency, exhibit hyperleptinaemia and impaired insulin sensitivity, unaffected by 12 months of GH treatment

OBJECTIVE

Adult survivors of childhood acute lymphoblastic leukaemia (ALL) often exhibit GH deficiency (GHD), due to prophylactic cranial radiotherapy (CRT). It is not known whether the observed risk for adiposity in these patients is associated with impaired insulin sensitivity and whether the insulin sensitivity is affected by GH replacement therapy.

SUBJECTS AND DESIGN

Eleven patients with GHD (median age 29 years), previously given prophylactic CRT for ALL, and 11 sex-, age- and body mass index (BMI)-matched controls were investigated with bioimpedance analysis (BIA) and analysis of serum leptin, serum free fatty acids (FFA) and serum insulin. Insulin sensitivity was measured by a euglycaemic-hyperinsulinaemic clamp technique (IS-clamp). Moreover, the effects of 12 months of individually titrated GH treatment (median dose 0.5 mg/day) on these parameters were investigated.

RESULTS

At baseline, the patients had lower fat free mass (FFM) (P = 0.003), higher percentage fat mass (FM) (P = 0.05), serum insulin (P = 0.02) and serum leptin/kg FM (P = 0.01) than controls. The patients had a tendency towards impaired IS-clamp (P = 0.06), which disappeared after correction for body composition (IS-clamp/kg FFM; P > 0.5). In the patients, time since CRT was positively correlated with percentage FM (r = 0.70, P = 0.02), and there was an independent negative association between serum FFA and IS-clamp (P = 0.05). Twelve months of GH treatment increased serum IGF-I (P = 0.003) and FFM (P = 0.02) and decreased percentage FM (P = 0.03), but no significant changes were seen in serum leptin/kg FM, serum FFA, FFA-clamp, serum insulin or IS-clamp (all, P > or = 0.2).

CONCLUSIONS

Young adult survivors of childhood ALL with GHD had increased fat mass, hyperleptinaemia and impaired insulin sensitivity, which could be a consequence of radiation-induced impairment of GH secretion or mediated by other hypothalamic dysfunctions, such as leptin resistance or other unknown factors, affected by CRT. Twelve months of individualized GH replacement therapy led to positive effects on body composition, but the hyperleptinaemia, hyperinsulinaemia and the impaired insulin sensitivity remained unchanged.

Glucose-responsive hepatic insulin gene therapy of spontaneously diabetic BB/Wor rats

Hepatic insulin gene therapy (HIGT) ameliorates hyperglycemia in multiple rodent models of diabetes mellitus, with variable degrees of glucose control. We demonstrate here that adenoviral delivery of a glucose-regulated transgene into rat hepatocytes produces near-normal glycemia in spontaneously diabetic BB/Wor rats without administration of exogenous insulin. We compared growth, glycemia, counterregulatory hormones, and lipids in HIGT-treated diabetic rats to nondiabetic rats and diabetic rats treated with either insulin injections or sustained-release insulin pellets. HIGT-treated rats achieved near-normal blood glucose levels within 1 week and maintained glycemic control for up to 3 months. Rats treated with sustained release insulin implants had similar blood sugars, but more hypoglycemia and gained more weight than HIGT-treated rats. HIGT-treated rats normalized blood glucose within 2 hr after a glucose load, and tolerated a 24-hr fast without hypoglycemia. HIGT treatment suppressed ketogenesis similarly to peripheral insulin. However, glucagon levels and free fatty acids were increased in HIGT-treated rats compared to either nondiabetic controls or rats treated with exogenous insulin. In addition to extending successful application of HIGT to a rat model of autoimmune diabetes, these findings emphasize the relative contribution of hepatic insulin effect in the metabolic stabilization of diabetes mellitus.

Pulmonary oedema in Swedish hunting dogs

A syndrome of acute dyspnoea after hunting in 16 Swedish hunting dogs is characterised. Radiographic pulmonary infiltrates interpreted as pulmonary oedema were found in the acute stage. In 12 dogs, the infiltrates regressed after five to 14 days. Subendocardial necrosis and pulmonary oedema were found at postmortem examination in four other dogs with acute and recurrent dyspnoea after hunting, and myocardial fibrosis in a further three dogs with a history of recurrent dyspnoea after hunting; none of these pathological changes was seen in dogs which had no previous history of dyspnoea after hunting. A pathogenetic mechanism is proposed whereby high catecholamine levels, present during hunting due to the stress of excitement and exercise, cause acute cardiac and pulmonary lesions in some susceptible dogs, similar to neurogenic or postictal pulmonary oedema.

Defective activation of skeletal muscle and adipose tissue lipolysis in type 1 diabetes mellitus during hypoglycemia

The increased risk of hypoglycemia during intensified treatment of type 1 diabetes mellitus (T1DM) patients, who have a deficient glucagon secretory response, is largely attributed to the development of suppressed adrenomedullary responses. A consequence of this impairment of catecholamine secretion might be reduced lipolysis in major target tissues (muscle and adipose) and, in turn, increased glucose metabolism. To test this hypothesis, we used microdialysis to monitor glycerol (index of lipolysis) in the extracellular fluid of skeletal muscle and adipose tissue and assessed whole-body glucose use by measuring [6,6-(2)H(2)]glucose enrichment in plasma in seven intensively treated T1DM patients and eight nondiabetic subjects who received a 3-h insulin infusion (0.8 mU/kg.min) on two occasions: during mild-moderate hypoglycemia or euglycemia. In the hypoglycemic study, the rise in plasma epinephrine was approximately 50% less in the T1DM patients despite a greater fall in plasma glucose (to 3.0 vs. 3.5 mM in controls; P < 0.05). Moreover, the rate of glucose flux and the plasma-extracellular fluid glucose gradient in muscle was increased during hypoglycemia in T1DM subjects compared with controls. Glycerol levels in muscle, adipose, and plasma fell similarly in both groups in the first hour. Thereafter, tissue glycerol remained suppressed in the T1DM patients but rebounded significantly (P < 0.01) in the control subjects. The glycerol response in muscle and adipose tissue was significantly correlated with plasma epinephrine concentration (r = 0.73, P = 0.002; and r = 0.52, P = 0.04, respectively), and inversely correlated with whole-body glucose disposal (r = -0.51, P = 0.05; and r = -0.50, P = 0.05). To determine whether the absence of the lipolytic response is limited to deficient catecholamine release, we perfused muscle and adipose tissue in situ with the selective beta(2)-agonist terbutaline during hyperinsulinemic euglycemia. Local addition of agonist increased glycerol and blood flow in both muscle and adipose (P < 0.01 and P < 0.05, respectively) similarly in T1DM and control subjects. We conclude that deficient release of (rather than impaired responsiveness to) catecholamines in T1DM prevents the local fat breakdown within muscle and adipose tissue that normally occurs during mild-moderate hypoglycemia. This defect within peripheral tissues may lead to a delayed increase in glucose disposal that could contribute to the severity of hypoglycemia when it is prolonged.

Algorithmic evaluation of metabolic control and risk of severe hypoglycemia in type 1 and type 2 diabetes using self-monitoring blood glucose data

The optimization of metabolic control in Type 1 and Type 2 diabetes mellitus (T1DM and T2DM, respectively) [i.e., the maintenance of near-normal hemoglobin A(1c) (HbA(1c)) without increasing the risk of hypoglycemia] could be enhanced by analysis of self-monitoring blood glucose (SMBG) data assessing complementary processes: exposure to hyperglycemia and hypoglycemia. We present algorithms that simultaneously estimate HbA(1)c and risk for significant hypoglycemia using 45-60 days of SMBG. The algorithms were developed using a primary data for 96 subjects with T1DM (n = 48) and T2DM, and were validated in an external data for 520 subjects with T1DM (n = 231) and T2DM. All subjects were on insulin. In the primary (external) data the estimation of HbA(1c) had absolute error of 0.5 (0.7) units of HbA(1c) and percent error of 6.8% (8.1%); 96% (96%) of all estimates were within 20% from reference HbA(1c). The SMBG-estimated value of HbA(1c) was closer to current reference HbA(1c) than a reference HbA(1c) value taken only 2-3 months ago. The results in T1DM and T2DM were similar. Linear model predicted future significant hypoglycemia (R(2) = 62%, p < 0.0001). The leading predictor was a previously introduced Low Blood Glucose Index, which alone had R(2) = 55%. Probability model assessed accurately the odds for future moderate/severe hypoglycemia (coefficients of determination 92%/94%). Four risk categories were identified; within moderate- and high-risk category, there was no difference between T1DM and T2DM in the occurrence of prospective significant hypoglycemia. SMBG data allow for accurate estimation of the two most important markers of metabolic control in T1DM and T2DM - HbA(1c) and risk for hypoglycemia.

Methods for quantifying self-monitoring blood glucose profiles exemplified by an examination of blood glucose patterns in patients with type 1 and type 2 diabetes

The maintenance of glycemic control in patients with type 1 or type 2 diabetes mellitus (T1DM and T2DM, respectively) is commonly assisted by devices for self-monitoring of blood glucose (SMBG) that store multiple BG determinations. However, besides average BG, no other SMBG characteristics are routinely computed. We describe several SMBG-based measures that quantify the extent and rate of patients' BG excursions into hypoglycemia and hyperglycemia and can be used as markers for patients' vulnerability to hypoglycemia and BG irregularity. These markers are applied to analyze data from patients with T1DM (n = 277) and T2DM (n = 323), all of whom used insulin. T1DM and T2DM patients were matched by HbA(1c), gender, and number of SMBG readings/day. On average, 230 SMBG readings and three HbA(1c) assays were collected for each subject over 3 months. Compared with T2DM, patients with T1DM diabetes had (1) more extreme low and high BGs, (2) greater risk for severe hypoglycemia as quantified by the Low BG Index, (3) faster descent into hypoglycemia as quantified by the risk rate of change/hour, and (4) greater BG irregularity as computed by BG rate of change/hour and BG SD (all p levels < 0.0001). SMBG data allow for computing and frequent updating of various idiosyncratic diabetes characteristics and risk factors. The use of such computations may assist in optimizing patients' glycemic control.

Effect of acute and antecedent hypoglycemia on sympathetic neural activity and catecholamine responsiveness in normal rats

Adrenergic responsiveness to acute hypoglycemia is impaired after prior episodes of hypoglycemia. Although circulating epinephrine responses are blunted, associated alterations in adrenal sympathetic nerve activity (SNA) have not been reported. We examined adrenal nerve traffic in normal conscious rats exposed to acute insulin-induced hypoglycemia compared with insulin with (clamped) euglycemia. We also examined adrenal SNA and catecholamine responses to insulin-induced hypoglycemia in normal conscious rats after two antecedent episodes of hypoglycemia (days -2 and -1) compared with prior episodes of sham treatment. Acute insulin-induced hypoglycemia increased adrenal sympathetic nerve traffic compared with insulin administration with clamped euglycemia (165 +/- 12 vs. 118 +/- 21 spikes/s [P < 0.05]; or to 138 +/- 8 vs. 114 +/- 10% of baseline [P < 0.05]). In additional experiments, 2 days of antecedent hypoglycemia (days -2 and -1) compared with sham treatment significantly enhanced baseline adrenal SNA measured immediately before subsequent acute hypoglycemia on day 0 (180 +/- 11 vs. 130 +/- 12 spikes/s, respectively; P < 0.005) and during subsequent acute hypoglycemia (229 +/- 17 vs. 171 +/- 16 spikes/s; P < 0.05). However, antecedent hypoglycemia resulted in a nonsignificant reduction in hypoglycemic responsiveness of adrenal SNA when expressed as percent increase over baseline (127 +/- 5% vs. 140 +/- 14% of baseline). Antecedent hypoglycemia, compared with sham treatment, resulted in diminished epinephrine responsiveness to subsequent hypoglycemia. Norepinephrine responses to hypoglycemia were not significantly altered by antecedent hypoglycemia. In summary, prior hypoglycemia in normal rats increased adrenal sympathetic tone, but impaired epinephrine responsiveness to acute hypoglycemia. Hence, these data raise the intriguing possibility that increased sympathetic tone resulting from antecedent hypoglycemia downregulates subsequent epinephrine responsiveness to hypoglycemia. Alternatively, it is possible that the decrease in epinephrine responsiveness after antecedent hypoglycemia could be the result of reduced adrenal sympathetic nerve responsiveness.

Exercise in diabetes management: maximizing benefits, controlling risks

Exercise is a recommended component of diabetes management. In both type 1 and type 2 diabetes mellitus, exercise can increase insulin sensitivity, lower blood glucose, and have positive psychological effects. More markedly in type 2 than in type 1, regular physical activity improves glycemic control, reduces hypertension, and normalizes lipids. Adjustments in insulin dosage, careful blood glucose monitoring, and attention to diet around the time of exercise will help prevent hypoglycemia and hyperglycemia, which are common hazards of exercise in type 1 diabetes. Special precautions are necessary for those who have diabetic complications such as retinopathy or peripheral neuropathy.

Plasma glucose alone does not predict neurologic dysfunction in hypoglycemic nondiabetic subjects

STUDY OBJECTIVE

To assess the value of plasma glucose concentration alone as a predictor of neurologic dysfunction in nondiabetic subjects with normal baseline neurologic examination and electroencephalographic (EEG) findings.

METHODS

Neurologic function and EEG results were evaluated in 17 subjects before and during insulin-induced hypoglycemia using relevant and reliable clinical tools for bedside use.

RESULTS

Hypoglycemia (mean nadir concentration, 30 mg/dL) was without effect on level of consciousness or cranial nerve, motor, sensory, vestibulocerebellar, language, or simple visuospatial functions. Attention was minimally impaired in all subjects, but memory in only 3. EEG results remained normal in 5 subjects; minimal to moderate nonspecific changes occurred in the rest. All patients manifested signs of sympathetic stimulation from hypoglycemia, including tremor, tachycardia, and diaphoresis. The manifestations of neuroglycopenia did not correlate significantly with nadir plasma glucose or duration of hypoglycemia.

CONCLUSION

Moderately severe hypoglycemia of short duration can be neurologically occult, or subtle inattention can be its first and only clinical manifestation. Our findings are at variance with reports in the emergency medicine literature in which marked deficits are universally present at glucose concentrations equal to those attained in this study. This discrepancy suggests that the expression of neuroglycopenia is multifactorially determined and that plasma glucose concentration alone does not predict neurologic dysfunction in nondiabetic subjects with normal baseline neurologic examinations.

Counterregulatory hormones oscillate during steady-state hypoglycemia

During hypoglycemia, the magnitude of the counterregulatory response depends on the extent of plasma glucose reduction. However, our clinical observations during steady-state hypoglycemia indicate that symptom severity can change independently of plasma glucose concentrations, i.e., symptoms appeared to fluctuate despite stable glucose levels. This study was therefore designed to test the hypothesis that hormonal and symptomatic responses to hypoglycemia are pulsatile. Seven healthy subjects had serial blood sampling at 3-min intervals during 90 min of insulin-induced hypoglycemia. Mean +/- SE plasma glucose levels plateaued at 62 +/- 3 mg/dl. Counterregulatory hormones were significantly elevated (P < 0.05-0. 01, except norepinephrine) and strikingly pulsatile. Cluster analysis revealed pulses of large magnitude in plasma glucagon, epinephrine, and norepinephrine concentrations. Amplitudes were, respectively, 72 +/- 4, 64 +/- 8, and 48 +/- 3% of the mean. Interpeak intervals were 27 +/- 7, 19 +/- 4, and 25 +/- 5 min, respectively. Symptom score and cardiovascular responses were also pulsatile; their peaks were found to coincide with epinephrine peaks. We conclude that hormonal and symptomatic counterregulation in hypoglycemia, while critically driven by plasma glucose levels, is also influenced by an endogenous pulsatility that exists despite steady-state glucose concentrations.

Responsiveness of glycogen catabolism to adrenergic agonists during insulin-induced hypoglycemia in rat livers

1. Insulin-induced hypoglycemia (IIH) promoted decreased responsiveness of hepatic glycogen catabolism to phenylephrine and isoproterenol, but not to glucagon and cyanide. 2. In addition, glycogen phosphorylase activity and glycogen levels were not affected by IIH. 3. It was concluded that hypoglycemia promoted changes in hepatic responsiveness to adrenergic agonists. 4. However, the ability of the liver to mobilize glycogen was not influenced by hypoglycemia.

Incidence and predictive criteria of nocturnal hypoglycemia in young children with insulin-dependent diabetes mellitus

OBJECTIVE

To determine the incidence of significant nocturnal hypoglycemia occurring at home in young children with insulin-dependent diabetes mellitus using conventional therapy.

DESIGN

Sixty-one children (aged 2.6 to 8.5 years) were studied on one night, at home, with blood collection occurring at dinner, bedtime/supper, 11 PM, 2 AM, and breakfast, with subsequent laboratory analysis.

RESULTS

The proportion of subjects with blood glucose levels less than 64, 55, 45, and 36 mg/dl (3.5, 3.0, 2.5, and 2.0 mmol/L) was 37.8%, 17%, 13%, and 8%, respectively. Nocturnal hypoglycemia was associated with younger age (< 5 years 57% vs 5 to 8.5 years 36%; p < 0.001) and lowered glycosylated hemoglobin levels (HbA1c) with a greater than 50% incidence of hypoglycemia seen in subjects with HbA1c levels of less than 8.5%. The average HbA1c concentration was lower in the hypoglycemic group than in the nonhypoglycemic group (7.8 vs 8.3%; p < 0.02). Nocturnal hypoglycemia occurred with increasing frequency throughout the night in subjects less than 5 years of age (dinner, supper, 11 PM, 2 AM, and breakfast incidences being 0%, 12.5%, 26%, 33%, and 30%, respectively) but not in those older than 5 years. Carbohydrate intake at supper did not prevent subsequent hypoglycemia. Blood glucose levels at 11 PM were poor predictors of subsequent hypoglycemia at 2 AM in either the group as a whole or in the children less than 5 years of age. Symptom recognition of nocturnal hypoglycemia was decreased in younger children (< 5 years (36%) > 5 years (58%)), in those with a lower HbA1c, and when hypoglycemia occurred at breakfast rather than at dinner (0% vs 50%).

CONCLUSIONS

The incidence of nocturnal hypoglycemia in young children with insulin-dependent diabetes mellitus receiving conventional therapy is unacceptably high and is increased with lowered age and HbA1c concentration; the condition is often asymptomatic. Early-morning hypoglycemia is poorly predicted by a blood glucose determination at 11 PM and is not prevented by carbohydrate intake at supper. In younger children, blood glucose profiles should include early-morning measurements.

Interactive educational simulators in diabetes care

Since the Diabetes Control and Complications Trial demonstrated the substantial benefits of tight glycaemic control there has been renewed interest in the application of information technology (IT) based techniques for improving the day-to-day care of patients with diabetes mellitus. Computer-based educational approaches have a great deal of potential for patients use, and may offer a means of training more health-care professionals to deliver such improved care. In this article the potential role of IT in diabetes education is reviewed, focusing in particular on the application of compartmental models in both computer-based interactive simulators and educational video games. Close attention is devoted to practical applications-available today-for use by patients, their relatives, students and health-care professionals. The novel features and potential benefits of such methodologies are highlighted and some of the limitations of currently available software are discussed. The need for improved graphical user interfaces, and for further efforts to evaluate such programs and demonstrate an educational benefit from their use are identified as hurdles to their more widespread application. The review concludes with a look to the future and the type of modelling features which should be provided in the next generation of interactive diabetes simulators and educational video games.

Quantification of insulin release from implantable polymer-based delivery systems and augmentation of therapeutic effect with simultaneous release of somatostatin

Insulin injections control diabetes mellitus but do not reproduce physiologic regulation. Polymer-based controlled-release technology has enabled us to demonstrate: that the controlled release of insulin from polymer matrices can indeed be used to control diabetes mellitus but does so at the expense of hyperinsulinemia and hypoglycemia; and that somatostatin can be delivered in similar fashion, so as to provide glucose homeostasis in a more physiologic range, at lower insulin levels and at somatostatin doses below those used in intermittent infusion studies; and, that microgram quantities of a drug can be delivered successfully in vivo with intact biological function and in a manner that can be monitored continuously. In the present study the simultaneous polymer-matrix-controlled release of insulin with somatostatin extended glycemic control in diabetic rats. Eleven rats received subcutaneous polymer matrix implants containing insulin alone and 11 rats received implants containing insulin and somatostatin. Plasma and urinary glucose control were improved in both groups. Glucose concentrations in the insulin alone group remained depressed for 5 days until insulin release from the matrices declined below 11.6 units/kg/day. When somatostatin was delivered at 0.75-1.1 micrograms/kg/day together with insulin, plasma glucose control persisted for 12 days until insulin release decreased below 3.6 units/kg/day. It is our hope that further experiments regarding the potential role of both controlled-release devices and somatostatin will be performed to provide continuing therapeutic alternatives to the insulin-dependent diabetic. This is also the first in vivo demonstration of the simultaneous release of two biologically active peptide hormones from polymer matrices. The use of the polymer matrix systems may not only have profound effects on the ambulatory care of diabetes but might also permit the investigation of the synergistic effects of other families of compounds.

Analysing the hypoglycaemic counter-regulation: a clinically relevant phenomenon?

This paper describes an analysis of the temporal relation between episodes of low blood glucose (hypoglycaemia) and counter-regulations, i.e., episodes of elevated blood glucose (hyperglycaemia), in patients with insulin dependent diabetes. The relation was assessed by statistical methods based on a metabolic computer model of the human glucose metabolism. The study material was standard collected clinical data on meals, insulin injections, and measured blood glucose from hospitalised patients. We have found that a typical hypoglycaemic counter-regulation begins 6-8 h after the hypoglycaemia, that it lasts 16-18 h, giving a total duration of 24 h, and that it elevates the blood glucose by 4-10 mmol/l. The phenomenon was demonstrated in the data from more than half of the patients with hypoglycaemic episodes.

Severe hypoglycemia in insulin-dependent diabetic children treated by multiple injection insulin regimen

The occurrence and risk factors of severe hypoglycemic attacks were analyzed during a 4-year study in a group of children and adolescents who received human insulin and followed a multiple daily injection regimen (three or four injections per day); 29 patients experienced severe hypoglycemia at least once in 4 years. Of these, 13 suffered recurrent episodes: 8 had two episodes, 4 had four episodes, and 1 patient had seven episodes. For comparative purposes, the nonhypoglycemic population (217 diabetic children) was used as a control group. The hypoglycemic children received insulin doses which were significantly higher than for nonhypoglycemic patients (1.05 +/- 0.6 U/kg daily vs 0.87 +/- 0.7; P < 0.05). Moreover, the hypoglycemic group had a significantly higher mean number of previous episodes of severe hypoglycemia than the nonhypoglycemic group (0.98 +/- 1.2 vs 0.26 +/- 0.7; P < 0.001). There was no significant difference in age, sex, duration of disease, and metabolic control between hypoglycemic and nonhypoglycemic children. There was no association between severe hypoglycemia and the presence of retinopathy, persistent microalbuminuria, or autonomic neuropathy. Severe hypoglycemia is a recurrent problem, not related to the quality of metabolic control nor to the presence of long-term microvascular complications, and diabetic children with a personal history of severe hypoglycemia are at risk for future episodes.

Evaluation and outcomes of patients with palpitations

PURPOSE

To determine: (1) the etiologies of palpitations, (2) the usefulness of diagnostic tests in determining the etiologies of palpitations, and (3) the outcomes of patients with palpitations.

PATIENTS AND METHODS

One hundred and ninety consecutive patients presenting with a complaint of palpitations at a university medical center were enrolled in this prospective cohort study. Patients underwent a structured clinical interview and psychiatric screening. The charts were abstracted for results of the physical exam and tests ordered by the primary physician. Assignment of an etiology of palpitations was based on strict adherence to predetermined criteria and achieved by consensus of the two physician investigators. One-year follow-up was obtained in 96% of the patients.

RESULTS

An etiology of palpitations was determined in 84% of the patients. The etiology of palpitations was cardiac in 43%, psychiatric in 31%, miscellaneous in 10%, and unknown in 16%. Forty percent of the etiologies could be determined with the history and physical examination, an electrocardiogram, and/or laboratory data. The 1-year mortality rate was 1.6% (95% confidence interval [CI] 0% to 3.4%) and the 1-year stroke rate was 1.1% (95% CI 0% to 2.6%). Within the first year, 75% of the patients experienced recurrent palpitations. At 1-year follow-up, 89% reported that their health was the same or improved compared to that at enrollment, 19% reported that their work performance was impaired, 12% reported that workdays were missed, and 33% reported accomplishing less than usual work at home.

CONCLUSIONS

The etiology of palpitations can often be diagnosed with a simple initial evaluation. Psychiatric illness accounts for the etiology in nearly one third of all patients. The short-term prognosis of patients with palpitations is excellent with low rates of death and stroke at 1 year, but there is a high rate of recurrence of symptoms and a moderate impact on productivity.

Inhibition of muscle glycogen synthase activity and non-oxidative glucose disposal during hypoglycaemia in normal man

The purpose of the present study was to evaluate the role of muscle glycogen synthase activity in the reduction of glucose uptake during hypoglycaemia. Six healthy young men were examined twice; during 120 min of hyperinsulinaemic (1.5 mU.kg-1. min-1) euglycaemia followed by: 1)240 min of graded hypoglycaemia (plasma glucose nadir 2.8 mmol/l) or 2) 240 min of euglycaemia. At 350-360 min a muscle biopsy was taken and indirect calorimetry was performed at 210-240 and 330-350 min. Hypoglycaemia was associated with markedly increased levels of adrenaline, growth hormone and glucagon and also with less hyperinsulinaemia. During hypoglycaemia the fractional velocity for glycogen synthase was markedly reduced; from 29.8 +/- 2.3 to 6.4 +/- 0.9%, p < 0.05. Total glucose disposal was decreased during hypoglycaemia (5.58 +/- 0.55 vs 11.01 +/- 0.75 mg.kg-1. min-1 (euglycaemia); p < 0.05); this was primarily due to a reduction of non-oxidative glucose disposal (2.43 +/- 0.41 vs 7.15 +/- 0.7 mg.kg-1 .min-1 (euglycaemia); p < 0.05), whereas oxidative glucose disposal was only suppressed to a minor degree. In conclusion hypoglycaemia virtually abolishes the effect of insulin on muscle glycogen synthase activity. This is in keeping with the finding of a marked reduction of non-oxidative glucose metabolism.

Exercise prescription for individuals with metabolic disorders. Practical considerations

Regular exercise has been recognised as an important component in the management of patients with diabetes mellitus. In addition to acutely lowering blood glucose, exercise training improves glucose tolerance and peripheral insulin sensitivity, contributes to weight loss and reduces several risk factors for cardiovascular disease. When proper precautions are taken to prevent hypoglycaemia, individuals with diabetes can enjoy the same benefits from exercise as nondiabetic healthy individuals. As a guideline, moderate intensity, aerobic endurance activities should be performed for 20 to 40 minutes at least 3 times a week. Blood glucose should be monitored, and insulin dose and carbohydrate intake adjusted based on the blood glucose response to the type and duration of exercise. This review will summarise current understanding of the therapeutic role of exercise in the treatment of diabetes and will present guidelines for prescribing exercise in diabetic patients.

Long-term recovery from unawareness, deficient counterregulation and lack of cognitive dysfunction during hypoglycaemia, following institution of rational, intensive insulin therapy in IDDM

Hypoglycaemia unawareness, is a major risk factor for severe hypoglycaemia and a contraindication to the therapeutic goal of near-normoglycaemia in IDDM. We tested two hypotheses, first, that hypoglycaemia unawareness is reversible as long as hypoglycaemia is meticulously prevented by careful intensive insulin therapy in patients with short and long IDDM duration, and that such a result can be maintained long-term. Second, that intensive insulin therapy which strictly prevents hypoglycaemia, can maintain long-term near-normoglycaemia. We studied 21 IDDM patients with hypoglycaemia unawareness and frequent mild/severe hypoglycaemia episodes while on "conventional" insulin therapy, and 20 nondiabetic control subjects. Neuroendocrine and symptom responses, and deterioration in cognitive function were assessed in a stepped hypoglycaemia clamp before, and again after 2 weeks, 3 months and 1 year of either intensive insulin therapy which meticulously prevented hypoglycaemia (based on physiologic insulin replacement and continuous education, experimental group, EXP, n = 16), or maintenance of the original "conventional" therapy (control group, CON, n = 5). At entry to the study, all 21 IDDM-patients had subnormal neuroendocrine and symptom responses, and less deterioration of cognitive function during hypoglycaemia. After intensive insulin therapy in EXP, the frequency of hypoglycaemia decreased from 0.5 +/- 0.05 to 0.045 +/- 0.02 episodes/patient-day; HbA1c increased from 5.83 +/- 0.18 to 6.94 +/- 0.13% (range in non-diabetic subjects 3.8-5.5%) over a 1-year period; all counterregulatory hormone and symptom responses to hypoglycaemia improved between 2 weeks and 3 months with the exception of glucagon which improved at 1 year; and cognitive function deteriorated further as early as 2 weeks (p < 0.05). The improvement in responses was maintained at 1 year. The improvement in plasma adrenaline and symptom responses inversely correlated with IDDM duration. In contrast, in CON, neither frequency of hypoglycaemia, nor neuroendocrine responses to hypoglycaemia improved. Thus, meticulous prevention of hypoglycaemia by intensive insulin therapy reverses hypoglycaemia unawareness even in patients with long-term IDDM, and is compatible with long-term near-normoglycaemia. Because carefully conducted intensive insulin therapy reduces, not increases the frequency of moderate/severe hypoglycaemia, intensive insulin therapy should be extended to the majority of IDDM patients in whom it is desirable to prevent/delay the onset/progression of microvascular complications.

Involvement of the autonomic nervous system in the in vivo memory to glucose of pancreatic beta cell in rats

The fact that the potentiating effect of prolonged hyperglycemia on the subsequent insulin secretion is observed in vivo but not in vitro suggests the involvement of extrapancreatic factors in the in vivo memory of pancreatic beta cells to glucose. We have investigated the possible role of the autonomic nervous system. Rats were made hyperglycemic by a 48-h infusion with glucose (HG rats). At the end of glucose infusion as well as 6 h postinfusion, both parasympathetic and sympathetic nerve activities were profoundly altered: parasympathetic and sympathetic activities, assessed by the firing rate either of the thoracic vagus nerve or the superior cervical ganglion, were dramatically increased and decreased, respectively. Moreover, 6 h after the end of glucose infusion, insulin secretion in response to a glucose load was dramatically increased in HG rats compared to controls. To determine whether these changes could be responsible for the increased sensitivity of the beta cell to glucose, insulin release in response to glucose was measured in HG and control rats, either under subdiaphragmatic vagotomy or after administration of the alpha 2A-adrenergic agonist oxymetazoline. Both treatments partially abolished the hyperresponsiveness of the beta cell to glucose in HG rats. Therefore chronic hyperglycemia brings about changes in the activity of the autonomic nervous system, which in turn are responsible, at least in part, for the generation of enhanced beta cell responsiveness to glucose in vivo.

Presence and further development of retinal dysfunction after 3-year follow up in IDDM patients without angiographically documented vasculopathy

Abnormalities in neuroretinal function may play a role in the development of diabetic retinopathy. The natural course of diabetic retinal dysfunction in a group of subjects with insulin-dependent diabetes mellitus and with no apparent microvascular alterations in the retina was followed-up with fluorescein angiography and a sensitive electrophysiological technique, i.e., steady-state focal electroretinogram at the macula, for 3 years. Before the beginning and throughout our study, strict glycaemic control was maintained by three or four daily insulin injections under careful monitoring. Analysis of macular electroretinogram provided information from different neural layers. At the first examination, functional activities of postreceptoral neurons were significantly decreased with respect to those of age-matched control subjects. Diabetic patients showed a functional loss of both ganglion cell (0.53 +/- 0.09 vs 0.42 +/- 0.11 microV; t = 5; p = 0.0001) and preganglion cell (0.51 +/- 0.13 vs 0.42 +/- 0.14 microV; t = 2.8; p = 0.007) layers. Diabetes did not alter photoreceptor activity. After 3 years, dysfunction was significantly greater in the preganglion cell layer (0.28 +/- 0.11 microV; t = 6.3; p = 0.0001). Although in some patients further impairment of ganglion cell function was shown, no significant difference was found in 3 years. Photoreceptor function remained unaltered. No vascular abnormalities in the retina were noted after 3 years in this group of patients. Metabolic control was not correlated to functional changes. Our findings suggest that the middle retinal layer is the most sensitive physiological locus of progressive diabetes-induced dysfunction in the absence of angiographically documented abnormalities.

Early selective neuroretinal disorder in prepubertal type 1 (insulin-dependent) diabetic children without microvascular abnormalities

The duration of diabetes before puberty is not considered relevant to the future development of complications. To evaluate the effects of diabetes on the neural retina, we analysed macular function by steady-state focal electroretinography in 20 prepubescent diabetic children without vascular retinopathy and in 39 sex- and age-matched normal children. The mean (+/- SD) response related to retinal cellular elements between the photoreceptors and ganglion cells was significantly lower in diabetic children than in the control group (0.38 +/- 0.12 vs. 0.51 +/- 0.13 microV; unpaired t-test = 3; P = 0.005). Similarly, ganglion cell function showed a significant impairment in diabetic children with respect to the control group (0.4 +/- 0.13 vs. 0.53 +/- 0.09 microV; unpaired t-test = 5.4; P = 0.0001), whereas the photoreceptors appeared unaffected. Metabolic control and disease duration were not correlated with functional deficits. Our results suggest that before puberty, early diabetes may have a selective effect on the neural retina prior to the appearance of microvascular changes. A focal electroretinogram could identify diabetic children with neurosensory disorders who may have a higher risk of developing microvascular retinopathy.

Adrenocorticotrophic hormone, cortisol and catecholamine concentrations during insulin hypoglycaemia in dogs anaesthetized with thiopentone

Glucose homeostasis is maintained by complex neuroendocrine control mechanisms. Increases in plasma concentrations of various glucose-raising hormones such as glucagon, catecholamines, adrenocorticotrophic hormone (ACTH), and cortisol are observed under certain conditions associated with stress (haemorrhage and hypoglycaemia). The purpose of this study was to determine the effect of thiopentone anaesthesia on the catecholamine, ACTH and cortisol response to insulin hypoglycaemia in dogs. Blood sugar (BS), plasma catecholamine, and ACTH, and serum cortisol concentrations were measured during the course of (1) an intravenous insulin test (ITT) and (2) an ACTH test in conscious and in anaesthetized fasted dogs. During the ITT, the anaesthetized dogs showed a moderate resistance, compared with conscious dogs, to the hypoglycaemic action induced by insulin (blood sugar concentration 30 min after insulin injection: 2.91 +/- 0.25 vs 1.93 +/- 0.12 mM.L-1; P < 0.01). In addition, decreased epinephrine (220 +/- 27 vs 332 +/- 32 pg.ml-1), ACTH (65 +/- 6 vs 90 +/- 5 pg.ml-1) and cortisol (4.48 +/- 0.3 vs 6.25 +/- 0.5 micrograms.ml-1) concentrations were detected 60 min after insulin injection (P < 0.01). The norepinephrine response to hypoglycaemia was not altered by anaesthesia (273 +/- 33 vs 325 +/- 25 pg.ml-1). Anaesthetized dogs showed a decreased cortisol response to ACTH at 45 min (5.68 +/- 0.54 vs 8.87 +/- 0.47 micrograms.ml-1) when compared with control dogs (P < 0.001). Haemodynamic variables during anaesthesia showed little changes (P < NS); while respiratory rate was altered (P < 0.01 between 60 and 105 min).(ABSTRACT TRUNCATED AT 250 WORDS)

Post-hypoglycaemic hyperketonaemia does not contribute to brain metabolism during insulin-induced hypoglycaemia in humans

It is controversial as to whether ketone bodies are utilized by the human brain as a fuel alternative to glucose during hypoglycaemia. To clarify the issue, we studied 10 normal volunteers during an experimental hypoglycaemia closely mimicking the clinical hypoglycaemia of patients with Type 1 (insulin-dependent) diabetes mellitus or insulinoma. Hypoglycaemia was induced by a continuous infusion of insulin (0.40 mU.kg-1.min-1 for 8 h, plasma insulin approximately 180 pmol/l) which decreased the plasma glucose concentration to approximately 3.1 mmol/l during the last 3 h of the studies. Subjects were studied on two occasions, i.e. spontaneous, counterregulatory-induced post-hypoglycaemic increase in 3-beta-hydroxybutyrate (from approximately 0.2 to approximately 1.1 mmol/l at 8 h), or prevention of post-hypoglycaemic hyperketonaemia (plasma beta-hydroxybutyrate approximately 0.1 mmol/l throughout the study) after administration of acipimox, a potent inhibitor of lipolysis. In the latter study, glucose was infused to match the hypoglycaemia observed in the former study. The glycaemic thresholds and overall responses of counterregulatory hormones, symptoms (both autonomic and neuroglycopenic), and deterioration of cognitive function (psychomotor tests) were superimposable in the control study in which ketones increased spontaneously after onset of hypoglycaemic counterregulation, as compared to the study in which ketones were suppressed (p = NS). The fact that responses of counterregulatory hormones, symptoms and deterioration in cognitive function were not exaggerated when posthypoglycaemic hyperketonaemia was prevented, indicate that during hypoglycaemia, the counterregulatory-induced endogenous hyperketonaemia does not provide the human brain with an alternative substrate to glucose. Thus, it is concluded that during hypoglycaemia, endogenous hyperketonaemia does not contribute to brain metabolism and function.

Hypoglycaemia in the diabetic child

Hypoglycaemia is the most frequent acute complication of insulin-dependent diabetes mellitus. The clinical symptoms of insulin-induced hypoglycaemia can be grouped into those attributable to the sympathetic and adrenergic responses, e.g. tremor, pallor, palpitation, sweating, mydriasis ('hypoglycaemia awareness'), and those attributable to brain dysfunction, ranging from headache to convulsions and coma. Hypoglycaemia in diabetic children can occur at any time of the day, but nocturnal hypoglycaemia is a particular fear and worry. The frequency of mild hypoglycaemia is almost impossible to ascertain and the incidence of severe hypoglycaemia varies between 0.07 and 3.6 episodes per patient-year, though most authors report a range of 0.1-0.2 episode per patient-year. The most frequent causes of hypoglycaemia in diabetic children are deviations from treatment routine such as strenuous exercise, omission of snacks or skipped meals, and gross deviations from the prescribed times of insulin injections and recommended doses of insulin. Other predisposing factors include intensified insulin treatment, improved glycaemic control, young age, longer duration of diabetes and defective counterregulation. The available paediatric studies do not seem to support the suggestion that human insulin impairs the perception of hypoglycaemic symptoms ('hypoglycaemia unawareness') and increases the frequency of hypoglycaemic episodes, but further conclusive studies are needed. Prolonged and recurrent severe hypoglycaemia, particularly in younger children, can cause permanent neuropsychological dysfunction (e.g. learning disabilities) and permanent electroencephalographic abnormalities. Mild hypoglycaemia has also been documented to affect cognitive function, and the performance of neuropsychological tasks can remain decreased for some time (up to several hours) after full clinical recovery from hypoglycaemia. An impending hypoglycaemic attack can usually be averted by the ingestion of 20 g of rapidly absorbed carbohydrate. A severe episode can be effectively treated outside hospital with subcutaneous or intramuscular glucagon (0.5-1.0 mg) or in the hospital by an intravenous bolus of 0.2-0.5 g/kg glucose followed by a continuous glucose infusion. Patient and parent education and vigilant application of diabetes self-care principles are perhaps the most effective means of prevention, but in very young children a less strict metabolic control (higher glycosylated haemoglobin levels) may be necessary.

Control of glycaemia

Maintenance of plasma glucose concentrations within a narrow range despite wide fluctuations in the demand (e.g. vigorous exercise) and supply (e.g. large carbohydrate meals) of glucose results from coordination of factors that regulate glucose release into and removal from the circulation. On a moment-to-moment basis these processes are controlled mainly by insulin and glucagon, whose secretion is reciprocally influenced by the plasma glucose concentration. In the resting postabsorptive state, release of glucose from the liver (equally via glycogenolysis and gluconeogenesis) is the key regulated process. Glycogenolysis depends on the relative activities of glycogen synthase and phosphorylase, the latter being the more important. The activities of fructose-1,6-diphosphatase, phosphoenolpyruvate carboxylkinase and pyruvate dehydrogenase regulate gluconeogenesis, whose main precursors are lactate, glutamine and alanine. In the postprandial state, suppression of liver glucose output and stimulation of skeletal muscle glucose uptake are the most important factors. Glucose disposal by insulin-sensitive tissues is regulated initially at the transport step and the mainly by glycogen synthase, phosphofructokinase and pyruvate dehydrogenase. Hormonally induced changes in intracellular fructose 2,6-bisphosphate concentrations play a key role in muscle glycolytic flux and both glycolytic and gluconeogenic flux in the liver. Under stressful conditions (e.g. hypoglycaemia, trauma, vigorous exercise), increased secretion of other hormones such as adrenaline, cortisol and growth hormone, and increased activity of the sympathetic nervous system, come into play; their actions to increase hepatic glucose output and to suppress tissue glucose uptake are partly mediated by increases in tissue fatty acid oxidation. In diabetes, the most common disorder of glucose homeostasis, fasting hyperglycaemia, results primarily from excessive release of glucose by the liver due to increased gluconeogenesis; postprandial hyperglycaemia results from both impaired suppression of hepatic glucose release and impaired skeletal muscle glucose uptake. These abnormalities are usually due to the combination of impaired insulin secretion and tissue resistance to insulin, the causes of which remain to be determined.

Glucose counterregulation: prevention and correction of hypoglycemia in humans

The prevention or correction of hypoglycemia in humans is the result of both dissipation of insulin and activation of glucose counterregulatory (glucose-raising) systems. Whereas insulin is the dominant glucose-lowering factor, there are redundant glucose counterregulatory factors. Furthermore, there is a hierarchy among the glucoregulatory factors. The first defense against a decrement in plasma glucose is decreased insulin secretion; this occurs with glucose decrements within the physiological range at a glycemic threshold of 4.6 +/- 0.2 mmol/l. However, biological glucose recovery from hypoglycemia can occur despite mild (approximately 2-fold) peripheral hyperinsulinemia and can occur in the absence of portal hypoinsulinemia. Thus additional (glucose counterregulatory) factors must be involved. Critical glucose counterregulatory systems are activated at glycemic thresholds of approximately 3.8 mmol/l (the level at which brain glucose uptake is first measurably reduced), well above the thresholds for symptoms of hypoglycemia (approximately 3.0 mmol/l) and those for cognitive dysfunction resulting from neuroglycopenia (approximately 2.7 mmol/l). Among the glucose counterregulatory factors, glucagon plays a primary role. Indeed, it may be that hypoglycemia does not occur if the secretion and actions of both glucagon and insulin, among the glucoregulatory hormones, are normal. Epinephrine is not normally critical, but it becomes critical to glucose counterregulation when glucagon is deficient. Because hypoglycemia develops or progresses when both glucagon and epinephrine are deficient and insulin is present, these three hormones stand high in the hierarchy of redundant glucoregulatory factors.(ABSTRACT TRUNCATED AT 250 WORDS)

Initiation and management of insulin pump therapy

Insulin infusion pump therapy is a treatment option that facilitates achieving improved blood glucose control and lifestyle flexibility. These advantages are derived from the physiologic mode of insulin delivery and the pharmacologic advantages of using rapid-acting insulin. Patients who are sufficiently motivated and capable can learn to use the pump so that insulin adjustments can be made to compensate for changing circumstances. Although there are potential risks and side effects of using an insulin pump, these can be avoided through proper education and surveillance. The health care provider should be knowledgeable about the management of infusion pump therapy, including assessment of patient capabilities and practices, education, insulin adjustment, and techniques of use. The knowledge assists the health care provider in counseling patients to consider pump therapy and to manage patients already employing this mode of insulin delivery.

Blood sugar, serum insulin and serum non-esterified fatty acid levels during thiopentone anaesthesia in dogs

The purpose of this study was to determine the effect of thiopentone anaesthesia on glucose metabolism. Blood sugar (BS), serum immunoreactive insulin (IRI) and serum non-esterified fatty acid (NEFA) concentrations were measured during the course of (1) an intravenous glucose tolerance test (IVGTT), and (2) an intravenous insulin test (ITT), in conscious and anaesthetized fasted dogs. The IVGTTs were repeated in dogs under alpha- or beta-adrenergic blockade, induced by phentolamine or propranolol. During the IVGTT, the anaesthetized dogs showed glucose intolerance (blood sugar levels were higher than in the control group) and little serum IRI response to hyperglycaemia was detected. An attenuated initial decrease and a slower rebound of NEFA concentration was observed in anaesthetized animals than in controls. Phentolamine administration (5 mg.kg-1 iv) partly restored the IRI response without affecting the BS levels; propanolol (1 mg.kg-1 iv) had no effect. Anaesthetized dogs showed a moderate resistance to insulin induced hypoglycaemic action and a lack of serum NEFA response during counter-regulation of hypoglycaemia, while in conscious controls an intense rebound was observed. Hyperinsulinaemia after iv insulin administration was longer in anaesthetized dogs than in controls. The insulin distribution space was 78% of body weight and insulin t1/2 in blood group compared with 54% and 16 min, in controls. We conclude that thiopentone provokes disturbances in glucose and serum NEFA metabolisms and abolishes the serum IRI response to hyperglycaemia. These effects are influenced by extrapancreatic factors regulating serum IRI levels and by an alpha-adrenergic mechanism, via the inhibition of insulin secretion.

Pancreatic and pituitary hormonal responses to insulin-induced hypoglycaemia during muscarinic cholinergic blockade in man

To investigate the role of muscarinic cholinergic mechanisms in mediating the pancreatic and pituitary hormonal responses to hypoglycaemia, six normal subjects were studied during acute insulin-induced hypoglycaemia under control conditions, and during blockade with intravenous atropine. During atropine blockade the response of pancreatic polypeptide was suppressed while the maximum response of plasma glucagon was significantly higher. The increment in plasma vasopressin was also increased significantly during cholinergic blockade. During blockade with atropine the responses of plasma prolactin was reduced, with a slight but significant reduction in the growth hormone response, and although a similar maximum response of plasma ACTH was achieved, this rise was delayed. These results implicate involvement of a cholinergic muscarinic inhibitory and stimulatory mechanisms in regulating the responses of pancreatic and pituitary hormones to hypoglycaemia.

Diabetic Ketoacidosis: Pathophysiology, Management and Complications

Diabetic ketoacidosis (DKA) is a common and potentially life-threatening complication of diabetes mellitus, the second most common chronic childhood disease [1]. Prior to the introduction of insulin to clinical medicine by Banting and Best in 1922, DKA had a mortality rate greater than 60% [2]. As insulin was introduced into clinical practice, there was a gradual decrease in mortality associated with DKA over the subsequent 30 years. Recent epidemiological data reveal current mortality varies from 0 to 19% [3,4]. DKA continues to be the most common cause of death in patients younger than 24 years of age; it accounts for as many as 50% of deaths of young diabetic patients [5–7]. In elderly diabetics who have coexisting diseases, DKA carries a high mortality [8]. Despite many advances in the care of diabetic patients, the prevalence of DKA is not declining; it accounts for 14% of all diabetes-related hospital admissions [3, 4, 9].

The incidence of insulin-dependent diabetes mellitus continues to increase worldwide and has roughly doubled in each recent decade [10–13]. Because insulin-dependent diabetes mellitus is increasing, and preventative measures to avoid DKA in diabetic patients have not been successful, the incidence of DKA can also be expected to increase in coming years. Prevention of DKA is the ultimate goal (80% of hospital admissions for DKA occur in treated diabetics) [3,8]. It is necessary for clinicians to understand the pathophysiology and treatment of DKA to care for this increasing diabetic population. We discuss the pathophysiology of diabetic ketoacidosis, its management, and its complications.

Adjusting insulins

The teaching of effective insulin adjustment is a formal process that benefits from being carried out in a standardized way. The unique methods outlined in this report have been taught to people with diabetes for over 8 years. Iterative in nature, the methods are safe and work to achieve specified blood glucose or HbA1c targets. They are designed to accommodate each individual's habits, recognizing that acceptance depends on adapting the medication to the life-style rather than vice versa. New technology was used to mediate insulin adjustments at home. Insulin adjustment of itself, however, is but one of five interdependent factors involved in successful self-management. These include (1) choosing sites of insulin injection; (2) choosing species of origin of insulins to be used; (3) reviewing life-style habits, including diet and exercise; (4) implementing dosage titration; and (5) follow-up. Lack of formalized insulin adjustment methods may be a major reason why many diabetes control programs fail to demonstrate significantly better metabolic control in their patients.

Hyperglycaemia, hypoglycaemia, and blood glucose control in diabetes: symptom perceptions and treatment strategies

Recent research has suggested that patients with Type 1 diabetes who are in chronically poor blood glucose control perceive hyperglycaemia differently from those who are in good control. To extend these observations 181 insulin-treated patients with Type 1 or Type 2 diabetes were studied. Patients completed a self-report questionnaire which included items concerning feelings about high and low blood glucose levels and strategies for maintaining blood glucose control. Glycosylated haemoglobin levels were also measured. We hypothesized that level of blood glucose control would: (1) be associated with perceptions of hyperglycaemia and treatment strategies for managing hyperglycaemia and (2) not be associated with perceptions and strategies concerning hypoglycaemia. In comparison with those in 'acceptable' or 'poor' blood glucose control, those in 'good' control perceived symptoms of hyperglycaemia at lower blood glucose levels (p less than 0.001) and felt physically best at lower blood glucose levels (p less than 0.001). They, also began treatment for hyperglycaemia at lower glucose levels (p less than 0.05), set lower minimal (p less than 0.001) and maximal (p less than 0.001) glucose levels as treatment goals, and tested their blood glucose levels more frequently (p less than 0.05). Among Type 1 diabetic patients, those in 'good' control reported experiencing hypoglycaemia at lower glucose levels than those in 'acceptable' or 'poor' control (p less than 0.05). No differences in treatment strategies of hypoglycaemic symptoms were apparent. This study suggests an influence of patients' perceptions of symptoms and treatment in self-care of diabetes.

Endocrine emergencies. Hypoglycaemia

Hypoglycaemia is possibly the most frequent metabolic emergency, in that insulin-induced hypoglycaemia is a common side-effect of treatment of a common disease. The symptoms are partly sympathetic and related to the release of catecholamines. These symptoms include sweating, tremor, palpitations, sensation of hunger, restlessness and anxiety. Other symptoms are caused by an insufficient supply of glucose to the brain, resulting in neuroglucopenia with symptoms like blurred vision, weakness, slurred speech, vertigo and difficulties in concentration. Symptom recognition is the primary and most effective defence against cerebral dysfunction which is the ultimate consequence of hypoglycaemia. Even in insulin-treated diabetic patients symptom failure might occur. Patients who experience severe episodes of hypoglycaemia do not constitute a special subgroup of patients. However, near-normalization of blood glucose levels have resulted in an increase in the incidence of severe hypoglycaemia. Moreover, the threshold for hormonal counter-regulatory responses in adrenaline, growth hormone and cortisol is lowered after a period of strict metabolic control in insulin-dependent diabetic patients. The glucose level at which the patients become subjectively aware of hypoglycaemia is correspondingly reduced. Other reasons for hypoglycaemia to occur are oral hypoglycaemic agents, especially sulfonylureas which may be potentiated by other drugs. Prolonged hypoglycaemia may be seen after first-order sulfonylureas, and may indicate glucose infusion as treatment. Next to insulin and sulfonylurea, ethanol is the most common cause of hypoglycaemia. In non-diabetics, hypoglycaemia will typically develop 6-24 h after a moderate or heavy intake of ethanol by a person who has had an insufficient intake of food for 1 or 2 days. Insulin-producing tumours, insulinomas and non-islet cell tumours may also be reasons for hypoglycaemia in non-diabetics. Treatment of mild episodes of hypoglycaemia is intake of fast-absorbing carbohydrates. Severe episodes can be treated with either i.v. dextrose or glucagon injected i.m. or i.v. The glycaemic response and recovery of a normal level of consciousness is 1-2 min slower after glucagon than after glucose.

Effect of pancreas transplantation on glucose counterregulation in insulin-dependent diabetic patients prone to severe hypoglycaemia

Pancreatic transplantation was performed in three patients with insulin-dependent diabetes mellitus in whom recurrent and severe episodes of hypoglycaemia had been found to be due to defective glucose counterregulation. Thus in these patients the spontaneous blood glucose recovery after insulin-induced hypoglycaemia (0.1 U kg-1 h-1 i.v. insulin until blood glucose levels fell below 2.8 mmol l-1) was delayed, and the responses of glucagon, epinephrine and growth hormone (GH) were absent or diminished. After pancreas transplantation the patients exhibited essentially normal blood glucose control. When the insulin infusion test was repeated 3 months after the transplantation, the blood glucose level recovered rapidly after insulin withdrawal. The glucagon response was restored, and the responses of epinephrine and GH were improved. Plasma C-peptide was suppressed by approximately 50%, which is less than is observed in normal subjects. It is concluded that glucose counterregulation improves after pancreas transplantation. This appears to be mainly due to an improvement in the hypoglycaemia-induced glucagon response, but an amelioration of sympatho-adrenal and hypothalamic-pituitary regulatory mechanisms may also be involved. The apparent failure to suppress completely the insulin release from the denervated pancreas transplant indicates that inhibition of beta-cell secretion during insulin-induced hypoglycaemia may be partly under neural control.

Contribution of adrenergic mechanisms to glucose counterregulation in humans

To assess the role of adrenergic mechanisms during prolonged hypoglycemia, eight normal subjects were studied on six occasions. In study 1, insulin was infused subcutaneously (15 mU.m-2.min-1 for 12 h), and plasma glucose concentration (PG) decreased from 89 +/- 2 to 50 +/- 1 mg/dl. In study 2 (insulin as in study 1 + propranolol and phentolamine + variable glucose to maintain PG as in study 1), the rate of hepatic glucose production (HGO, [3-3H]glucose) was approximately 30% lower after 1.5 h, and the rate of peripheral glucose utilization (GU) was approximately 15% greater after 5 h. To quantitate the effects of adrenergic mechanisms on glucose counterregulation, in a control study (study 3), glucoregulatory hormone secretion was blocked, and the hormones were reinfused to reproduce study 1. When alpha- and beta-blockade plus variable glucose were superimposed to study 3 (study 4), HGO was approximately 25% lower (after 2 h), and GU was approximately 10% greater (after 6 h) vs. study 3. When glucose was not infused to match PG of study 3 (study 5), severe hypoglycemia developed (PG at 7 h 36 +/- 2 vs. 62 +/- 3 mg/dl). Finally, when glucose was not infused during alpha- and beta-blockade of study 2 (study 6), PG was 49 +/- 3 mg/dl at 7 h vs. 65 +/- 3 mg/dl of the control study (study 1), despite greater secretion of glucagon, growth hormone, and cortisol. It is concluded that adrenergic mechanisms play a key counterregulatory role, even in the presence of appropriate responses of glucagon and that greater increases in glucagon (and other counterregulatory hormones) cannot compensate fully for absent contribution of adrenergic mechanisms to counterregulation.