A fifteen-month double-blind cross-over study of the efficacy and antigenicity of human and pork insulins

100 years on: the impact of the discovery of insulin on clinical outcomes

Throughout history, up to the early part of the 20th century, diabetes has been a devastating disorder, particularly when diagnosed in childhood when it was usually fatal. Consequently, the successful pancreatic extraction of insulin in 1921 was a miraculous, life-changing advance. In this review, the truly transformative effect that insulin has had on the lives of people with type 1 diabetes and on those with type 2 diabetes who are also dependent on insulin is described, from the time of its first successful use to the present day. We have highlighted in turn how each of the many facets of improvements over the last century, from advancements in the properties of insulin and its formulations to the evolution of different methods of delivery, have led to continued improvement in clinical outcomes, through the use of illustrative stories from history and from our own clinical experiences. This review concludes with a brief look at the current challenges and where the next century of technological innovation in insulin therapy may take us.

The evolution of insulin therapy

Evolution in medicine is generally driven by clinical need, hand in hand with opportunities generated by novel chemical and mechanical engineering technologies. Since 1921 that has been a continuing paradigm for insulin therapy, some advances being a continual process, and others arising from external scientific or engineering developments. Purification of insulin preparations was an early issue, resolved in the 1970s, then challenged by the switch to manufacture in microorganisms. The nature of insulin was established serially, in 1928 as a polypeptide, in 1955 by amino acid sequence, and later by 3-dimensional structure (1969), laying foundations for understandings on routes of administration, and later the engineering of novel insulins. Insulin was the first, and remains the predominant, pharmaceutical therapy to benefit from scientific advances underlying the genetic code, and thus recombinant DNA technology. Advances in mechanical and chemical engineering have contributed to important changes in insulin delivery devices. Biological science, including both cellular mechanisms and whole organism physiology, has led to considerable understandings of clinical defects in insulin action, but currently has been disappointing in its applicability to the insulins available for clinical practice, something perhaps now changing. The pathways of these changes are reviewed here.

Immunogenicity of human and bovine insulin in type 1 diabetes mellitus patients

BACKGROUND

The advantages of synthetic insulin (human insulin) over bovine insulin in the treatment of type 1 diabetes mellitus (DM) are much debated in terms of potency and purity. Immunogenicity is one of several factors that determine potency and safety. This study was designed to investigate and study the difference in immunogenicity of human and bovine insulin. We investigated anti-insulin antibody (AIAB) status in 69 type 1 DM patients receiving insulin therapy. Group 1 had 33 patients treated with bovine insulin, and group 2 had 32 patients treated with human insulin. All patients had received their respective insulin therapy for a minimum period of 1 year and had no history of change in insulin type. Forty-three subjects from the normal population were the control group.

METHODS

AIABs were assayed in serum samples of all subjects using a semiquantitative radioimmunoassay kit. The Kruskal-Wallis non-parametric and Mann-Whitney U tests were used to study the difference in immunogenicity of human and bovine insulins.

RESULTS

The Kruskal-Wallis test showed that antibody titers in the three groups significantly differed (P<0.001). The Mann-Whitney U test showed no significant difference in AIAB titer between the treatment groups. AIAB titers in the two treatment groups differed significantly from that of the control group, independently (P<0.001). High titers of AIABs are present in patients receiving bovine and human insulin compared to that of the normal population.

CONCLUSIONS

Bovine and human insulins are antigenic, and there is no significant difference in AIAB titer. Prospective studies are required to determine the long-term clinical significance of these antibodies.

Immunogenicity of xenopeptide hormone therapies

Peptides are a growing class of agents whose therapeutic use originated with non-human treatments such as animal insulins. Xenopeptides continue to be explored for biotherapeutic development using genetic engineering, and through the rich resource of animal and plant polypeptides. One of the major concerns of therapeutic administration of xenopeptides is the potential for untoward immune responses that may lead to loss of drug efficacy or adverse events in recipients. An increased risk of immunogenicity is perceived with xenopeptides, however, human-derived therapies also induce antibody formation that in some cases has been associated with severe clinical sequelae. In this review, antibody responses to xenopeptides are highlighted looking at current hormone therapies used to treat endocrine disorders. Similar to clinical experiences with peptide-based agents in general, antibody responses against xenopeptide hormone therapies in majority of cases have been benign in nature with minimal clinical impact.

'Human' insulin versus animal insulin in people with diabetes mellitus

BACKGROUND

Human insulin was introduced for the routine treatment of diabetes mellitus in the early 1980s without adequate comparison of efficacy to animal insulin preparations. First reports of altered hypoglycaemia awareness after transfer to human insulin made physicians and especially patients uncertain about potential adverse effects of human insulin.

OBJECTIVES

To assess the effects of different insulin species by evaluating their efficacy (in particular glycaemic control) and adverse effects profile (mainly hypoglycaemia).

SEARCH STRATEGY

A highly sensitive search for randomised controlled trials combined with key terms for identifying studies on human versus animal insulin was performed using The Cochrane Library, MEDLINE and EMBASE. We also searched reference lists and databases of ongoing trials. Date of latest search: July 2004.

SELECTION CRITERIA

We included randomised controlled clinical trials with diabetic patients of all ages that compared human to animal (for the most part purified porcine) insulin. Trial duration had to be at least one month in order to achieve reliable results on the main outcome parameter glycated haemoglobin.

DATA COLLECTION AND ANALYSIS

Trial selection as well as evaluation of study quality was performed by two independent reviewers. The quality of reporting of each trial was assessed according to a modification of the quality criteria as specified by Schulz and by Jadad.

MAIN RESULTS

Altogether 2156 participants took part in the 45 randomised controlled studies that were discovered through extensive search efforts. Though many studies had a randomised, double-blind design, most studies were of poor methodological quality. Purified porcine and semi-synthetic insulin were most often investigated. No significant differences in metabolic control or hypoglycaemic episodes between various insulin species could be elucidated. Insulin dose and insulin antibodies did not show relevant dissimilarities.

AUTHORS' CONCLUSIONS

A comparison of the effects of human and animal insulin as well as of the adverse reaction profile did not show clinically relevant differences. Many patient-oriented outcomes like health-related quality of life or diabetes complications and mortality were never investigated in high-quality randomised clinical trials. The story of the introduction of human insulin might be repeated by contemporary launching campaigns to introduce pharmaceutical and technological innovations that are not backed up by sufficient proof of their advantages and safety.

'Human' insulin versus animal insulin in people with diabetes mellitus

BACKGROUND

Human insulin was introduced for the routine treatment of diabetes mellitus in the early 1980s without adequate comparison of efficacy to animal insulin preparations. First reports of altered hypoglycaemia awareness after transfer to human insulin made physicians and especially patients uncertain about potential adverse effects of human insulin.

OBJECTIVES

To assess the effects of different insulin species by evaluating their efficacy (in particular glycaemic control) and adverse effects profile (mainly hypoglycaemia).

SEARCH STRATEGY

A highly sensitive search for randomised controlled trials combined with key terms for identifying studies on human versus animal insulin was performed using the Cochrane Library (issue 2, 2002), Medline (1966 to May, 2002) and Embase (1974 to February, 2002). We also searched reference lists and databases of ongoing trials. Date of latest search: May 2002.

SELECTION CRITERIA

We included randomised controlled clinical trials with diabetic patients of all ages that compared human to animal (for the most part purified porcine) insulin. Trial duration had to be at least one month in order to achieve reliable results on the main outcome parameter glycated haemoglobin.

DATA COLLECTION AND ANALYSIS

Trial selection as well as evaluation of study quality was performed by two independent reviewers. The quality of reporting of each trial was assessed according to a modification of the quality criteria as specified by Schulz and by Jadad.

MAIN RESULTS

Altogether 2156 participants took part in the 45 randomised controlled studies that were discovered through extensive search efforts. Though many studies had a randomised, double-blind design, most studies were of poor methodological quality. Purified porcine and semi-synthetic insulin were most often investigated. No significant differences in metabolic control or hypoglycaemic episodes between various insulin species could be elucidated. Insulin dose and insulin antibodies did not show relevant dissimilarities.

REVIEWER'S CONCLUSIONS

A comparison of the effects of human and animal insulin as well as of the adverse reaction profile did not show clinically relevant differences. Many patient-oriented outcomes like health-related quality of life or diabetes complications and mortality were never investigated in high-quality randomised clinical trials. The story of the introduction of human insulin might be repeated by contemporary launching campaigns to introduce pharmaceutical and technological innovations that are not backed up by sufficient proof of their advantages and safety.

Human versus animal insulin in people with diabetes mellitus. A systematic review

This review is in accordance with the findings of the systematic review of Airey et al [18] with respect to the absence of a differential effect on hypoglycemia between human and animal insulin. For the first time, however, the review compares the relative efficacies of human and animal insulin, which indicates that human insulin was introduced without proof of being superior to animal insulin. Studies have not assessed patient-centered outcomes [41,42], such as patient satisfaction, health-related quality of life, and diabetes-related morbidity. Randomized trials did not report on qualitative assessments of patients' experiences when using different insulin species. Because history tends to repeat itself, we probably will be faced with other "innovations" (e.g., insulin analogs) evaluated in clinical trials tht focus on surrogate outcomes followed by marketing of insulins "proved" to be effective in short-term, underpowered, and badly executed studies.

Therapeutic targets in the management of Type 1 diabetes

For historical reasons, diabetes has long been linked with blood and urine glucose control, partly because these were clearly linked to acute symptoms, and partly because glucose became measurable around 200 years ago. Today it is recognized that there is far more to diabetes than simply monitoring symptoms and blood glucose. Intensive management has an impact on the quality of life. Late complications have their own risk factors and markers. Monitoring and early detection of these risk factors and markers can lead to changes in treatment before tissue damage is too severe. Accordingly, professionals now find themselves monitoring a range of adverse outcomes, markers for adverse outcomes, risk factors and risk markers for microvascular and arterial disease, acute complications of therapy, and the care structures needed to deliver this. Adverse outcomes lend themselves to targets for complication control in populations, and markers of adverse outcomes (such as retinopathy and raised albumin excretion rate) in treatment cohorts. Surveillance systems will have targets for yearly recall and review of early complications. Metabolic (surrogate) outcomes can be monitored in individual patients, but monitoring is only of value in so far as it guides interventions, and this requires comparison to some intervention level or absolute target. Even for blood glucose control this is not easy, for conventional measures such as glycated haemoglobin have their own problems, and more modern approaches such as post-prandial glucose levels are controversial and less convenient to measure. In many people with type 1 diabetes targets for blood pressure, LDL cholesterol, and serum triglycerides will also be appropriate, and need to be part of any protocol of management.

Hypoglycaemia induced by exogenous insulin--'human' and animal insulin compared

AIMS

A systematic review of the literature was carried out to examine whether published evidence suggests a difference in the frequency and awareness of hypoglycaemia induced by 'human' and animal insulin.

METHODS

The review identified randomized controlled trials and studies of other designs including observational comparisons, case series and case reports in which the use of 'human' insulin was compared to animal insulin in people with diabetes. These were identified from bibliographic databases and hand-searches of key journals. The main outcome measures were frequency, severity, awareness and symptoms of insulin induced hypoglycaemia.

RESULTS

Fifty-two randomized controlled trials, 37 of double-blind design, were identified which included one or more of the relevant outcome measures. Of these, 21 specifically investigated hypoglycaemic frequency and awareness as primary outcomes (six in people with previously reported reduced hypoglycaemic awareness). The remainder of the identified trials reported hypoglycaemic outcomes as a secondary or incidental outcome during comparative investigations of efficacy or immunogenicity. Seven of the double-blind studies reported differences in frequency of hypoglycaemia or awareness of symptoms, although none of the studies which selected subjects on the basis of previously reported impaired awareness demonstrated significant differences between insulin species. Four of the unblinded trials reported differences in hypoglycaemia. This reached statistical significance in two of the studies. A further 56 studies of other designs and case reports were considered. In addition to the 10 case reports describing individuals with impaired hypoglycaemic awareness, nine studies reported differences in the incidence and manifestation of hypoglycaemia during 'human' insulin treatment. Notably, none of the four population time trend studies found any relationship between the increasing use of 'human' insulin and hospital admission for hypoglycaemia or unexplained death among those with diabetes. The largest case series could find no support for the hypothesis that an influence of treatment with 'human' insulin on hypoglycaemia had contributed to any of the 50 deaths investigated. When all types of studies considered are ranked in order of rigour (according to the accepted 'hierarchy of evidence'), it is the least rigorous which lend most support to the notion that treatment with 'human' insulin has an effect on the frequency, severity or symptoms of hypoglycaemia.

CONCLUSIONS

Evidence does not support the contention that treatment with 'human' insulin per se affects the frequency, severity or symptoms of hypoglycaemia. However, a number of studies, mainly those of less rigorous design, describe an effect when people are transferred from animal insulin to 'human' insulin. It is not possible to state how common this is or whether the phenomenon is specific to 'human' insulin or an effect resulting from stricter glycaemic control (perhaps compounded, in some cases, by neurological complications in long-standing diabetes). This remaining uncertainty makes it essential that insulin from animal sources continues to be available so that clinicians and patients may retain this choice of treatment.

Safety of inhaled proteins for therapeutic use

The use of the inhalation route for delivery of inhaled proteins has received increasing attention recently. The purpose of this article is to review the available information related to the safety aspects of inhaled proteins. The review focuses primarily on possible toxicity to the respiratory tract, because usually one is either considering an agent to treat the lung or an agent for which the systemic toxicity has been investigated following subcutaneous (s.c.) administration in its clinical use as a therapeutic agent. Some background is provided on mechanisms of absorption and reasons why inhalation delivery is considered for many proteins. Available data are summarized from clinical trials of proteins and protein-like biomolecules, generally showing minimal, if any, adverse respiratory effects. The results of the animal toxicology studies that have been published are presented. In general, the observed lung toxicity has been relatively low, and it has been difficult to interpret in cases where the animal protein differs considerably from the human protein. Discussion is presented on the possibility of adverse immune reactions, suggesting that this is not likely to be any greater issue than it is for subcutaneously injected materials. Although the safety information is relatively sparse at present, the available data suggest that the inhalation route can be an attractive route to consider for many therapeutic proteins.

Glucose monitoring and insulin therapy during pregnancy

Excellent blood glucose control is necessary to reduce the excess fetal morbidity and mortality associated with the diabetic pregnancy. This article outlines the roles of glucose monitoring and insulin therapy in intensive treatment regimens during gestation. The discussion includes recommended monitoring frequency, glycemic standards, types of insulin and mechanism of action, goals and timing of insulin therapy, as well as the complications of insulin therapy.

Frequency, severity and symptomatology of hypoglycaemia: a comparative trial of human and porcine insulins in type 1 diabetic patients

A randomized, double-blind, cross-over trial was performed to compare the frequency, severity, and symptomatology of hypoglycaemia during treatment with porcine and human insulins. Forty patients with Type 1 diabetes (20 newly diagnosed and 20 with diabetes of 5-20 years duration) were treated with human and porcine insulins for consecutive 3-month periods, in random order. Episodes of hypoglycaemia were recorded prospectively with self-reporting of the presence and intensity of symptoms using a standardized scoring technique. Serial measurements of glycated haemoglobin and review of home blood glucose tests confirmed that similar glycaemic control was achieved with each insulin species. On comparison of the treatment periods with human and porcine insulins, no differences were demonstrated in the total frequency of symptomatic hypoglycaemia (3.10 vs 3.06 episodes patient-1 3-months-1; p = 0.94), the frequency of severe hypoglycaemia (0.1 vs 0.2 episodes patient-1 3-months-1; p = 0.44), the occurrence of asymptomatic biochemical hypoglycaemia (0.75 vs 0.68 episodes patient-1 3-months-1; p = 0.81), and the capillary blood glucose concentration at the onset of hypoglycaemic symptoms (2.6 +/- 0.2 vs 2.4 +/- 0.3 mmol l-1; p = 0.40), with all results being expressed for human vs porcine treatment periods, respectively. The symptoms of hypoglycaemia did not differ during the treatment periods with each insulin species. In conclusion, treatment with human insulin had no effect upon the symptomatic response to hypoglycaemia, did not increase the total frequency of hypoglycaemia, and did not emerge as a significant risk factor for severe hypoglycaemia in these patients.

Human insulin and hypoglycaemia: a literature survey

Thirty-nine clinical studies and 12 epidemiological reports comparing human insulin and porcine insulin were reviewed. Twenty-five studies (encompassing 338 subjects) showed identical symptoms and physiological response to acute hypoglycaemia overall. Fifteen studies (encompassing more than 1253 patients) showed identical incidence of hypoglycaemia overall and similar symptoms with the two types of insulin. Twelve studies showed identical incidence of hypoglycaemia overall with the two types of insulin. Thus, the overwhelming evidence from a large number of studies including a large number of patients suggests that: (1) human and porcine insulin do not provoke different hormonal responses to hypoglycaemia; (2) they do not cause different symptoms of hypoglycaemia; (3) the incidence of severe hypoglycaemia with human insulin does not differ from that of porcine insulin.

Insulin regimens for the non-insulin dependent: impact on diurnal metabolic state and quality of life

A randomized prospective study was conducted to determine whether the insulin regimen for NIDDM subjects poorly controlled on oral therapy should be designed primarily to control basal metabolism or to control mealtime hyperglycaemia. Grossly obese subjects were excluded. After a 2-month run-in phase involving intensive education, subjects were randomized to therapy with twice daily isophane or three times daily soluble insulin. Both Protaphane and Actrapid brought about similar improvement in HbA1 (9.5 +/- 0.5 and 9.7 +/- 0.4%) compared with baseline (11.7 +/- 0.5%; p < 0.001). Diurnal blood glucose profiles showed that despite the good post-prandial control achieved by pre-meal soluble insulin, loss of control occurred overnight, resulting in higher fasting blood glucose levels compared with Protaphane therapy (8.0 +/- 0.8 vs 10.6 +/- 0.8 mmol l-1; p < 0.05). The overall rate of hypoglycaemia was 0.44 patient-1 year-1. Thirty-two mild hypoglycaemic episodes occurred on Protaphane therapy and 79 on Actrapid therapy. Using formal psychometric tests it was shown that insulin therapy was associated with improved treatment satisfaction and that this was greater on Protaphane therapy (p < 0.05). Overall well-being increased similarly in the two groups. All subjects wished to continue with insulin therapy after the conclusion of the study. The insulin regimen for moderately or poorly controlled non-insulin-dependent diabetes should primarily be designed to correct the basal insulin deficiency rather than to mimic normal meal-induced insulin secretion.

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.

Double blind clinical and laboratory study of hypoglycaemia with human and porcine insulin in diabetic patients reporting hypoglycaemia unawareness after transferring to human insulin

OBJECTIVES

To compare awareness of hypoglycaemia and physiological responses to hypoglycaemia with human and porcine insulin in diabetic patients who reported loss of hypoglycaemia awareness after transferring to human insulin.

DESIGN

Double blind randomised crossover study of clinical experience and physiological responses during slow fall hypoglycaemic clamping with porcine and human insulin.

SETTING

Clinical investigation unit of teaching hospital recruiting from diabetes clinics of five teaching hospitals and one district general hospital.

SUBJECTS

17 patients with insulin dependent diabetes mellitus of more than five years' duration who had reported altered hypoglycaemia awareness within three months of transferring to human insulin.

MAIN OUTCOME MEASURES

Glycaemic control and frequency of hypoglycaemic episodes during two months' treatment with each insulin. Glucose thresholds for physiological and symptomatic responses during clamping.

RESULTS

Glycaemic control did not change with either insulin. 136 hypoglycaemic episodes (eight severe) were reported with human insulin and 149 (nine severe) with porcine insulin (95% confidence interval -4 to 2.5, p = 0.63). 20 episodes of biochemical hypoglycaemia occurred with human insulin versus 18 with porcine insulin (-0.8 to 1, p = 0.78). During controlled hypoglycaemia the mean adrenaline response was 138 nmol/l/240 min for both insulins; neurohormonal responses were triggered at 3.0 (SE 0.2) versus 3.1 (0.2) mmol/l of glucose for adrenaline and 2.5 (0.1) versus 2.5 (0.1) mmol/l for subjective awareness.

CONCLUSIONS

These data suggest that human insulin per se does not affect the presentation of hypoglycaemia or the neurohumoral, symptomatic, and cognitive function responses to hypoglycaemia in insulin dependent diabetic patients with a history of hypoglycaemia unawareness.

Influence of human insulin on symptoms and awareness of hypoglycaemia: a randomised double blind crossover trial

OBJECTIVE

To investigate the apparent increased risk of severe hypoglycaemia associated with use of human insulin by comparing the pattern of symptoms of hypoglycaemia with human insulin and porcine insulin.

DESIGN

Randomised controlled double blind crossover trial of treatment with human insulin and porcine insulin, with two treatment periods of six weeks.

SETTING

Diabetes outpatient department of a university teaching hospital in Berne, Switzerland.

PATIENTS

44 patients (25 men, 19 women) aged 14 to 60 years, with insulin dependent diabetes mellitus. All patients met the following criteria: receiving treatment with fast acting soluble insulin and long acting protamine insulin; performing multiple daily fingerstick blood glucose self measurements; and had stable glycaemic control with about one mild hypoglycaemic episode a week during the preceding two months.

INTERVENTION

Patients were randomised to receive either human or porcine insulin for six weeks and were then changed over to the other type of insulin for a further six weeks.

MAIN OUTCOME MEASURE

Questionnaire recording "autonomic" and "neuroglycopenic" symptoms that occurred during hypoglycaemic episodes confirmed by a blood glucose concentration less than or equal to 2.8 mmol/l.

RESULTS

Insulin doses and blood glucose, glycated haemoglobin A1c, and fructosamine concentrations were similar during the two treatment periods. 493 questionnaires on hypoglycaemia (234 during treatment with human insulin and 259 during treatment with porcine insulin) were analysed. With human insulin patients were more likely to report lack of concentration (52% v 35%, p = 0.0003) and restlessness (53% v 45%, p = 0.004) and less likely to report hunger (33% v 42%, p = 0.016) than during treatment with porcine insulin. The difference in the pattern of symptoms during the two treatments was similar to that between the 12 patients with a history of recurrent hypoglycaemic coma and the 32 patients without such a history.

CONCLUSIONS

The pattern of symptoms associated with human insulin could impair patients' ability to take appropriate steps to avoid severe hypoglycaemia. Caution should be exercised when transferring patients from animal insulin to human insulin, and a large scale randomised trial of the two types of insulin may be justified.

Human isophane or lente insulin? A double blind crossover trial in insulin dependent diabetes mellitus

Fifty two children with insulin dependent diabetes mellitus were randomised to receive human isophane or lente insulin preparations in combination with soluble insulin in a double blind trial. Patients were seen every two months, and crossed over after four months of treatment. Control assessed by glycated haemoglobin was significantly lower in children on human isophane insulin, but fasting blood glucose and fructosamine concentrations and the number of episodes of hypoglycaemia were similar on both regimens. In five children on twice daily insulin regimens, insulin profiles throughout a 24 hour period demonstrated greater variability on lente compared with isophane insulin despite identically administered insulin doses. A questionnaire completed at the end of the study showed that two thirds of the children and/or their parents preferred the isophane insulin, and they gave perceived improvement of metabolic control as the major reason for their choice.

A comparison of human ultralente- and lente-based twice-daily injection regimens

The problem of fasting hyperglycaemia remains unresolved on currently used twice-daily injection regimens. Human ultralente insulin is of longer duration than human lente and differs from it only in the nature of the zinc-insulin complex. In a 6-month double-blind crossover study these insulins were compared in 66 patients who were randomized to human ultralente or human lente insulin given together with human soluble insulin in a twice-daily injection regimen. Patients were seen monthly and crossed over after 3 months treatment. Fasting blood glucose concentrations on the ultralente regimen were considerably lower than on the lente regimen, the difference being statistically significant (6.6 +/- 0.5 vs 8.2 +/- 0.5 mmol l-1, p less than 0.05), but only present in those patients with fasting concentrations below the median. Glycosylated haemoglobin was identical on both regimens (9.3 +/- 0.2%). The evening ultralente dose was slightly but significantly lower than the evening lente dose (14.9 +/- 0.8 vs 15.5 +/- 0.8 U, p less than 0.05) thus endorsing the lowering effect of ultralente on the fasting blood glucose concentration. However, the incidence of serious hypoglycaemic events was higher on the ultralente regimen (0.38 +/- 0.10 vs 0.09 +/- 0.04 events per patient-month, p less than 0.02), the majority of nocturnal events occurring between 0500 h and breakfast. We conclude that ultralente insulin can give an improved fasting blood glucose concentration but that in those patients with more marked fasting hyperglycaemia or with a nocturnal hypoglycaemia problem it offers no clinical advantage over human lente insulin in a twice-daily injection regimen.

Basal and 24-h C-peptide and insulin secretion rate in normal man

An understanding of the metabolic abnormalities rising from inappropriate insulin delivery in diabetic patients demands a knowledge of 24-h and basal insulin secretion rates in normal man. We have used biosynthetic human C-peptide to determine its kinetic parameters in 10 normal subjects and applied these to measurements of plasma concentrations in the same subjects to determine pancreatic secretion rate. Metabolic clearance rate measured by stepped primed infusion of biosynthetic human C-peptide at rates of 10, 19 and 26 nmol/h was 4.7 +/- 0.7 (+/- SD) ml X kg-1 X min-1, and was independent of infusion rate. Fractional clearance (T1/2, 26 +/- 3 min) and distribution volume (0.178 +/- 0.039 l/kg) were calculated from the decline in concentration after cessation of the highest rate infusion. Basal insulin secretion calculated from the C-peptide metabolic clearance rate and plasma concentrations for the period 02.00 to 07.00 hours was 1.3 +/- 0.4 U/h. Over 24 h total insulin secretion on a standard high carbohydrate diet was 63 +/- 15 U, calculated from the area under the C-peptide concentration curve. Basal insulin secretion, therefore, accounted for 50 +/- 8% of total insulin secretion. Although only 5.6 +/- 1.1% of C-peptide was detected in 24-h urine collections, urinary C-peptide excretion was significantly related to 24-h C-peptide secretion (r = 0.74, p less than 0.02).

Comparative double-blind trial of the effectiveness and antigenicity of semisynthetic human insulin and purified porcine insulin in newly treated diabetic subjects

A double-blind comparative trial of the effectiveness and antigenicity of semisynthetic human insulin (Novo) and highly purified (Monocomponent) porcine insulin was performed over a 12 month period in 20 diabetic subjects newly treated with insulin. Human insulin was shown to be indistinguishable from porcine insulin of comparable purity with respect to plasma glucose and glycosylated hemoglobin levels and insulin dose requirements. Human insulin was no less antigenic than porcine insulin; significant IgG-associated insulin binding activity was detected in six of the ten patients in the human insulin treated group and four of the ten patients in the porcine insulin treated group. In all patients, the binding activity was of low capacity. No adverse reactions to human insulin were noted. It is concluded that semisynthetic human insulin, like purified porcine insulin, is safe and effective. Although there may be advantages for human insulin in the setting of insulin allergy, this study does not indicate that human insulin has advantages over purified porcine insulin with respect to elicitation of antibodies of the IgG class.

Prevalence of morning hyperglycaemia: determinants of fasting blood glucose concentrations in insulin-treated diabetics

A rise in blood glucose concentration at the end of the night, and consequent morning hyperglycaemia, are well recognized events in some diabetic patients. In 94 patients on twice daily insulin injections we have examined the prevalence and extent of morning hyperglycaemia, and its relation to control, insulin therapy, and insulin antibody levels. Blood glucose reached the highest level of the day before or after breakfast in 83% of patients, and in 50% this value was 2 mmol/l greater than any other time of day. Patients with higher fasting concentrations did not have worse blood glucose control over the rest of the day. No correlation was found between fasting blood glucose concentrations and the evening dose of intermediate acting insulin or the level of insulin antibodies. No consistent change in fasting blood glucose concentrations occurred with changes in antibody levels in patients switched between pork and beef insulin. Morning hyperglycaemia was as common with both insulin species. Pre- and post-breakfast hyperglycaemia is common and significant in insulin-treated diabetic patients. It is not directly related to diabetic control at other times of the day, and is independent of insulin species and insulin antibody levels.