Hypoglycaemia and human insulin

Insulin: evolution of insulin formulations and their application in clinical practice over 100 years

The first preparation of insulin extracted from a pancreas and made suitable for use in humans after purification was achieved 100 years ago in Toronto, an epoch-making achievement, which has ultimately provided a life-giving treatment for millions of people worldwide. The earliest animal-derived formulations were short-acting and contained many impurities that caused adverse reactions, thereby limiting their therapeutic potential. However, since then, insulin production and purification improved with enhanced technologies, along with a full understanding of the insulin molecule structure. The availability of radio-immunoassays contributed to the unravelling of the physiology of glucose homeostasis, ultimately leading to the adoption of rational models of insulin replacement. The introduction of recombinant DNA technologies has since resulted in the era of both rapid- and long-acting human insulin analogues administered via the subcutaneous route which better mimic the physiology of insulin secretion, leading to the modern basal-bolus regimen. These advances, in combination with improved education and technologies for glucose monitoring, enable people with diabetes to better meet individual glycaemic goals with a lower risk of hypoglycaemia. While the prevalence of diabetes continues to rise globally, it is important to recognise the scientific endeavour that has led to insulin remaining the cornerstone of diabetes management, on the centenary of its first successful use in humans.

The uptake of recombinant Factor VIII in the Netherlands

In comparison with other biotechnology substitutions, the adoption of recombinant Factor VIII (rFVIII) has been relatively slow. We sent a postal questionnaire to all Dutch haemophilia patients and haemophilia-treating physicians, to determine which factors predict whether a patient uses plasma-derived FVIII (pdFVIII) or rFVIII and to investigate patients' and doctors' opinions on both products. Fifty-six per cent of patients received rFVIII. This percentage varied widely between centres. Only one doctor would choose to use pdFVIII if he suffered from haemophilia A himself, and 74% would choose to use rFVIII. Younger patients, those not infected with the human immunodeficiency virus or hepatitis C, and those who did not have family members who used pdFVIII switched more often from pdFVIII to rFVIII. Patients who rated themselves as innovative, who had family members who used rFVIII, and those who were treated in a large haemophilia treatment centre were also more likely to have switched. For physicians and patients alike, the respondents generally did not see large differences between rFVIII and pdFVIII, except for the risk of infections and the knowledge of long-term effects (both larger for pdFVIII). Although haemophilia patients represent one of the most empowered patient groups, physicians appear to have been influential in choosing between pdFVIII and rFVIII.

Changing from porcine to human insulin

The development of hypoglycaemia unawareness is associated with long duration of diabetes, improved glycaemic control, alcohol intake and recurrent hypoglycaemia. However, current evidence suggests that neither frequency of severe episodes nor mortality from hypoglycaemia are increased following a change from animal to human insulin. Nevertheless, a small number of patients continue to report an alteration in the nature of hypoglycaemic warning symptoms following a change in insulin species. This is possibly a consequence of a reduced catecholamine response to lowering blood glucose levels or to species differences in the effect of insulin on central nervous system function. In practical terms, it seems sensible to warn patients that the nature of the symptoms associated with hypoglycaemia might alter following conversion from porcine to human insulin. At the time of the changeover, patients should be encouraged to perform frequent blood glucose measurements. Also, the usual insulin dose should be reduced by 10% at the start of human insulin treatment. Other aspects of insulin treatment including injection technique, meal timing, exercise, etc. should be discussed. For patients who are convinced that loss of warning of hypoglycaemia occurred after conversion from porcine to human insulin, a change back to animal insulin would be preferred to relaxing glycaemic control in the first instance. Pressure should be brought to bear on the pharmaceutical industry to maintain the availability of animal insulins for the small number of patients who have experienced problems with human insulin.

Diabetic death bed: post-mortem determination of hypoglycaemia

The post-mortem biochemical determination of hypoglycaemia in the practice of forensic medicine is notoriously imprecise and attracts perennial criticisms, particularly from those who may be alien to the peculiarities of medical jurisprudence. There has been re-emphasis recently on the neuropathological pathoclisis ascribed to prolonged hypoglycaemia. Unfortunately, the value perceived is limited by pathognomonic unreliability owing to agonal multifactorial influences and rapidly fatal nocturnal hypoglycaemia. The predicament is oppressive to a consideration of preponderant evidence and an unpopular diagnosis of peri-mortem hypoglycaemia, unless audacious, may be precluded simply because the proof is difficult. This is likely to contribute to diagnostic under-estimation of enigmatic diabetic deaths. A suspected case of lethal nocturnal hypoglycaemia in a young diabetic on 'animal' insulin is presented to restore some perspective to the clinico-pathological deference for an endangered post-mortem diagnosis of hypoglycaemia inferred from minimal evidence.

Susceptibility of the right and left canine atria to fibrillation in hyperglycemia and hypoglycemia

The objective of this study was to investigate the changes in the refractory period and in the susceptibility to fibrillation of canine atria associated with different levels of glycemia, and the differences in these parameters between the two atria. In 20 anesthetized, open-chest dogs weighing 24 kg, the effective refractory period was measured by atrial pacing with a run of 8 stimuli (S1-S1 350 ms) followed by a progressively earlier S2 until no stimulation of the atrial tissue occurred. The susceptibility to fibrillation was assessed by applying DC at 2, 3, and 4 V for 3 seconds, 7 times each, on the atrial appendage. If fibrillation occurred and persisted for 3 minutes, a transthoracic synchronized shock was delivered (200 J). The refractory period and the susceptibility to fibrillation were assessed under normoglycemia first, and then under hypo and hyperglycemia, in the right and left atrium successively, in random order. The incidence of induced atrial fibrillation in the right atrium was: hypoglycemia 31.96% (132 of 413 attempts); normoglycemia 24.11% (81 of 336; p < 0.05); and hyperglycemia 20.23% (85 of 420). Results for the left atrium were hypoglycemia 52.06% (215 of 413); normoglycemia 40.18% (135 of 336; p < 0.005); and hyperglycemia 32.86% (138 of 420; p < 0.05). Sustained atrial fibrillation (> 3 minutes) occurred significantly more often under hypo rather than hyperglycemia and stimulated the left rather than the right atrium. The refractory period was shortest under hypoglycemia in the left atrium and longest under normo or hyperglycemia in the right atrium.(ABSTRACT TRUNCATED AT 250 WORDS)

Symptomatic and hormonal hypoglycaemic responses to human and porcine insulin in patients with type I diabetes mellitus

In recent years there has been great concern that human insulin (HI) may induce fewer hypoglycaemic warning symptoms than porcine insulin (PI). We addressed this issue in eight patients aged 25.6 +/- 3.3 (SEM) years with Type I (insulin-dependent) diabetes mellitus of 15.1 +/- 3.7 years duration who complained that hypoglycaemia unawareness had appeared after transferring from PI to HI. Acute induction of hypoglycaemia was induced on two occasions with semisynthetic HI and purified PI under double-blind conditions. Blood glucose was first clamped for 2 h at 4.4-6.7 mmol l-1 with an intravenous infusion of HI or PI at 50 mU kg-1 h-1 and 20% glucose at a variable rate. Thereafter, insulin infusion alone was maintained for 100 minutes. Heart rate, arterial pressure, reflex times, autonomic and neuroglycopenic signs and symptoms were assessed every 10 min. Arterialized venous blood samples were taken to measure blood glucose every 10 min and catecholamines, insulin, glucagon, growth hormone, and cortisol every 20 min. Autonomic symptoms first appeared at a plasma glucose level of 2.92 +/- 0.21 mmol l-1 with HI vs 2.92 +/- 0.48 mmol l-1 with PI (NS). There were no significant differences between the two studies concerning any of the above mentioned clinical parameters or the counterregulatory hormone responses. A differential effect of insulin species on the ability to perceive hypoglycaemia in patients who ascribed diminished perception of hypoglycaemia to the use of HI was thus not observed.

Double-blind crossover comparison of human and porcine insulins in patients reporting lack of hypoglycaemia awareness

There has been much debate about reports that some insulin-treated diabetic patients lose awareness of hypoglycaemic symptoms on changing from porcine to human insulin. In a double-blind, crossover study, we sought differences between porcine and human insulin in the frequency and characteristics of hypoglycaemic episodes among patients who reported a reduction of awareness of hypoglycaemia after changing treatment. We studied 50 patients referred by their physicians because of complaints of lack of awareness of hypoglycaemia on human insulin. They had had diabetes for a mean of 20 (SD 12) years and 70% had good or acceptable glycaemic control. Each patient was treated in a double-blind manner for four 1-month periods, two with human and two with porcine insulin, in random order. Only 2 patients correctly identified the sequence of insulin treatments used; 8 or 9 would have been expected to do so by chance alone. The mean percentage of hypoglycaemic episodes associated with reduced or absent awareness was 64% (SD 30%) for human insulin and 69% (31%) for porcine insulin. We could find no statistically significant differences between the insulin species with respect to glycaemic control or the frequency, timing, severity, or awareness of hypoglycaemia. Reduced hypoglycaemia awareness is common with both human and porcine insulins.

Recent trends in diabetes mortality in England and Wales

Trends in diabetes-related mortality in England and Wales between 1975-6 and 1985-6, and regional and ethnic differences in diabetes-related mortality in 1985-6, have been examined. Data from death certificates mentioning diabetes in 1975-6 were compared with those for 1985-6 for different age groups. Data for 1985-6 were also analysed for different regions of England and Wales, and for country of birth. Between 1975-6 and 1985-6, the age-standardized rate of mentioning diabetes rose by 2.7% (95% confidence interval 1.4%, 4.1%) in men of all ages, and fell by 11.7% (10.6, 12.8) in women of all ages. By contrast, the rate of mentioning diabetes in those below 45 years fell by 30.7% (23.0, 37.7) in men and by 26.7% (16.5, 35.6) in women. Deaths in which the underlying cause was ischaemic heart disease (IHD), and where diabetes was also mentioned on the death certificate, rose by 14.4% (11.5, 16.8) in men and did not change significantly in women of all ages, but fell by 18.4% (-35.1, +2.6) in men, and 23.5% (-49.1, +15.2) in women below age 45. This was less favourable than the trend in the general population, where IHD mortality fell by 9.7% in men and 8.3% in women of all ages, and by 31.1% (28.6, 33.5) in men and 40.5% (35.0, 45.5) in women under 45 years.(ABSTRACT TRUNCATED AT 250 WORDS)

Human insulin and awareness of acute hypoglycaemic symptoms in insulin-dependent diabetes

Some insulin-dependent diabetic patients who have clear symptoms of hypoglycaemia during animal insulin treatment have reported loss of these symptoms when human insulin preparations are introduced. A survey of Mersey Region, UK, identified eleven patients whose awareness of hypoglycaemia was lost after introduction of human insulin but returned with animal insulin treatment; seven took part in the study. Acute hypoglycaemia was induced in these patients on two occasions by intravenous infusion of porcine or human soluble insulin (2.5 mU.kg-1, min-1) in random order. There was no significant difference between porcine and soluble insulin in the plasma glucose profile; mean (SEM) plasma glucose fell from 7.1 (0.4) mmol/l to a nadir of 1.5 (0.1) mmol/l with porcine insulin and from 7.1 (0.5) mmol/l to 1.6 (0.2) mmol/l with human insulin. An acute autonomic reaction occurred in all seven patients, at a similar plasma glucose concentration (1.9 [0.1] mmol/l with porcine insulin; 2.0 [0.2] mmol/l with human insulin). There were no significant differences in the frequency of symptoms or signs of hypoglycaemia between the two insulin species, nor any consistent differences in plasma glucagon, cortisol, growth hormone, adrenaline, or noradrenaline responses to hypoglycaemia. Symptomatic and hormonal responses to acute hypoglycaemia induced by porcine and human soluble insulins therefore seem to be almost indistinguishable, even in patients carefully selected for their apparent loss of hypoglycaemia awareness with human insulin.

Unexplained deaths of type 1 diabetic patients

The suggestion of an increase in the number of sudden deaths of young people with Type 1 diabetes in the UK has been investigated. It was suggested that such deaths were due to hypoglycaemia and related to the increasing use of human insulin. In total we were notified of 50 deaths of people with Type 1 diabetes under age 50 years in the UK in 1989 which our informants (relatives, physicians, and pathologists) considered sudden and unexpected. An autopsy had been done in all cases and we supplemented this with detailed clinical information from relatives and case records. Of the 50 cases we excluded five with a definite cause of death, 11 suicides or self-poisonings, six cases of ketoacidosis, and four in which there was insufficient information about the circumstances of death to drawn any conclusions. Of the other 24 cases, two patients had been found with irreversible hypoglycaemic brain damage and died after a period of artificial ventilation. The most puzzling group were 22, aged 12-43 years, most of whom had gone to bed in apparently good health and been found dead in the morning. Nineteen of the 22 were sleeping alone at the time of death and 20 were found lying in an undisturbed bed. Most had uncomplicated diabetes and in none were anatomical lesions found at autopsy. There are major difficulties in diagnosing hypoglycaemia post-mortem, but the timing of death and other circumstantial evidence suggests that hypoglycaemia or a hypoglycaemia-associated event was responsible. All patients were taking human insulin at the time of death but most had been changed from animal insulin between 6 months and 2 years earlier and there was nothing to implicate the species of insulin as a factor in these deaths.