Serum IRI in insulin-treated diabetics during a 24-hour period

Hypertension in diabetes mellitus

Hypertension should be detected and treated early in diabetic patients. It has a marked contribution to the morbidity and mortality of diabetic individuals due to both atherosclerosis and microvascular disease. Antihypertensive treatment is an effective tool in slowing the progression of early and advanced diabetic nephropathy. Prospective studies addressing the effects of antihypertensive regimens on the incidence of CHF, stroke, and coronary artery disease in the diabetic population are not available. We assume that the beneficial effects of therapy apply to both diabetic and nondiabetic subjects. Glycemic control and the lipid profile are major concerns when selecting an antihypertensive drug. Because hyperinsulinemia and insulin resistance have been advocated as hypertensive and atherosclerotic risk factors, the effects of antihypertensive drugs on insulin action and plasma insulin levels may also become an important element in the selection of an antihypertensive agent. ACE inhibitors, calcium channel blockers, and alpha-adrenergic blockers probably offer the most favorable metabolic profile when compared with diuretics and beta-blockers and should be used as the initial drugs in most clinical settings.

Insulin excess counteracts the effects of HDL on intracellular sterol accumulation in cultured human skin fibroblasts

Both Type 1 (insulin-dependent) and Type 2 (non-insulin-dependent) diabetic individuals are at increased risk of developing ischaemic heart disease. Insulin excess, present in both diabetic groups, may play an important pathophysiologic role in accelerating the atherogenic process. In this study, cultured human skin fibroblasts were incubated with varying concentrations of insulin to test the role of insulin on cell cholesterol homeostasis and on HDL3-mediated removal of excess cholesterol from cells. Insulin excess (1-100 nmol/l) resulted in a significant dose-dependent reduction in HDL3-mediated cholesterol efflux from the intracellular unesterified cholesterol pool of cultured human skin fibroblasts. Similar insulin concentrations resulted in impaired HDL-mediated cholesterol efflux from the cell membrane but had no effect on non-HDL-mediated efflux. The effect of insulin on cholesterol esterification and biosynthesis was assessed by 14C-oleate labelling. The addition of HDL3 (50 micrograms) resulted in a significant decrease in 14C-labelled cholesterol ester, reflecting a decrease in intracellular unesterified cholesterol, which was partially reversed by the addition of insulin. Insulin had no effect on the incorporation of 14C-oleate into unesterified cholesterol. During simultaneous incubation of fibroblasts with LDL and HDL, insulin resulted in an increase in cholesterol esterification and inhibited ability of HDL to promote the decrease in esterification. Thus, we have shown that insulin excess counteracts the beneficial effects of HDL that involve removal of cellular cholesterol and may in part promote atherogenesis by this mechanism.

Augmentation of synthesis of plasminogen activator inhibitor type 1 by insulin and insulin-like growth factor type I: implications for vascular disease in hyperinsulinemic states

Accelerated atherosclerosis accompanying diabetes mellitus, obesity, and some types of hypertension has been associated with hyperinsulinemia, augmented plasma plasminogen activator inhibitor type 1 (PAI-1), or both. We hypothesized that insulin and insulin-like growth factor type I (IGF-I) can influence synthesis of PAI-1, thereby potentially attenuating fibrinolysis. In HepG2 cells used as a model system, concentrations of insulin and IGF-I consistent with those seen in plasma independently stimulated PAI-1 synthesis. Accumulation of PAI-1 protein in conditioned medium over 24 hr was stimulated more with insulin alone than with the combination. Synergistic increases were evident, however, in the accumulation of PAI-1 protein over 48 hr with a concomitant increase in PAI-1 mRNA. A 10- to 20-fold increase in IGF binding protein I mRNA was seen 16-48 hr after exposure of the HepG2 cells to insulin and IGF-I, an increase abolished by cycloheximide. The results obtained are consistent with the hypothesis that hyperinsulinemia coupled with physiologic concentrations of IGF-I may attenuate fibrinolytic activity in vivo, thereby contributing to accelerated atherosclerosis.

Hypothesis: insulin is responsible for the vascular complications of diabetes

It is proposed that the systemic hyperinsulinemia and hepatic portal hypoinsulinemia that occurs with conventional injectable preparations of insulin currently used in the treatment of patients with diabetes mellitus is largely responsible for the morbidity associated with this disease. Epidemiological evidence and animal experimentation strongly support systemic hyperinsulinemia as a major factor in genesis of atherosclerosis in diabetic patients. In addition, in vitro studies demonstrate a direct effect of insulin on endothelial cell and arterial smooth muscle proliferation. On the other hand, inadequate hepatic delivery of insulin is associated with overproduction of renal vasoregulatory factors leading to glomerular hyperfiltration and ultimately to glomerulosclerosis and its clinical endpoint--end-stage renal disease. In the absence of widespread success of pancreatic and islet-cell transplantation as a means to deliver insulin physiologically into the hepatic portal circulation, methods must be devised and perfected to accomplish such delivery using approaches such as orally administering insulin in intestinal-enzyme protected capsules. Until such methods of delivery are available for safe and widespread use, one should abandon the illusory goal of rigid glucose control in favor of methods that reduce insulin requirement. Along these lines, dietary restriction and aerobic exercise should be the major life style changes advised for diabetic patients. Reduction of glomerular hyperfiltration in diabetic patients can be promoted with the use of low protein diets and/or angiotensin converting enzyme inhibitors.

Prevalence of anti-insulin antibodies and its relation to severe hypoglycaemia in insulin-treated diabetic patients

The prevalence of anti-insulin antibodies (AIABs) and their association with clinical parameters, metabolic control and severe hypoglycaemia were investigated in a geographically defined population of insulin-treated diabetic patients. Eighty per cent of the patients (479) delivered venous blood samples and answered a questionnaire on severe hypoglycaemic problems during a 12-month period. Circulating AIABs were demonstrable in 78% of the patients, being more common among those with type 1 diabetes and in long-duration patients. High levels of AIABs were also more frequent in patients in whom insulin treatment had been initiated prior to the era of highly purified insulins. The AIABs did not correlate to metabolic control, insulin dose or severe hypoglycaemia. It is concluded that AIABs is not a risk factor for severe hypoglycaemia in insulin-treated diabetic patients.

Atherosclerosis in diabetes: the role of hyperinsulinemia

Non-insulin-dependent diabetes (NIDDM) is a major cause of premature morbidity and mortality among adults. Macrovascular disease of coronary and peripheral vessels is the primary cause of death in these patients. Numerous experimental and epidemiologic studies have suggested that hyperinsulinemia accelerates the development of atherosclerosis. In experimental models, insulin promotes diet-induced lesion development and overrides lesion regression and estrogen protection against atherosclerosis. Local hyperinsulinemia induced by selected arterial infusion accelerates atherosclerosis in the perfused artery. Insulin has been shown to stimulate subintimal smooth muscle and fibroblast cells in culture, and to increase the uptake and local synthesis of lipid by these cells. Insulin may also induce inhibition of fibrinolysis. Several prospective studies performed on nondiabetic patients show that either fasting or postprandial insulin levels are a sensitive predictor of the development of coronary disease independent of other risk factors. Two recent studies in NIDDM patients confirm this finding and suggest that glycemic control may not be a significant factor in the development of macrovascular disease. Diseases of carbohydrate tolerance, ie, NIDDM, impaired glucose tolerance, obesity, are frequently associated with elevated circulating insulin levels, either physiologically or secondary to treatment. Given the high prevalence of cardiovascular disease in these populations, modifying therapy to minimize hyperinsulinemia should be an important consideration in a treatment program. Use of oral agents such as glipizide or gliclazide, which induce less diurnal hyperinsulinemia, may be advantageous when compared to traditional oral agent or insulin therapy.

Effect of insulin antibodies and their kinetic characteristics on plasma free insulin dynamics in patients with diabetes mellitus

To determine the influence of insulin antibodies (and their equilibrium kinetic properties) on the pharmacokinetics of insulin, we examined the relationship between insulin antibody binding and the initial rate of increase, time to peak, and return to baseline of therapeutic doses of insulin injected subcutaneously (0.15 U/kg) and the half-life, distribution space, and metabolic clearance rate of intravenously infused insulin (2 mU/kg/min) in insulin-treated patients with diabetes mellitus. Compared to age-weight-matched nondiabetic subjects, the diabetic subjects had reduced initial rates of increase (0.33 +/- 0.2 v 0.44 +/- 0.03 microU/mL/min, P less than 0.05), delayed time to peak (130 +/- 12 v 86 +/- 8 min, p less than 0.02), and prolonged return to baseline (485 +/- 37 v 313 +/- 13 min, P less than 0.01) of plasma free insulin levels after subcutaneous injection of insulin, and a prolonged half-life (19.8 +/- 5.8 v 4.3 +/- 0.3 min, P less than 0.02), increased distribution space (904 +/- 284 v 109 +/- 10 mL/kg, P less than 0.001), and augmented metabolic clearance rate (28.5 +/- 1.8 v 17.3 +/- 0.7 mL/kg/min, P less than 0.001) after intravenously infused insulin. All of these abnormal parameters were significantly correlated with binding of insulin to insulin antibodies at tracer insulin concentrations (Bo) and with the high affinity of insulin antibody binding sites as determined by Scatchard analysis. However, patients with 125I insulin antibody binding (Bo) less than 10 percent had normal or near normal plasma free insulin pharmacokinetics.(ABSTRACT TRUNCATED AT 250 WORDS)

Overview of the association between insulin and atherosclerosis

The suggestion that insulin is associated with atherosclerosis is based on clinical, epidemiologic, and experimental evidence. In general, atherosclerosis of the coronary, cerebral, and peripheral arteries is associated with abnormally high insulin responses to oral glucose. This hyperinsulinemia is not related to acute injury or to tissue necrosis, does not occur in response to intravenous glucose or tolbutamide, and is independent of other cardiovascular risk factors. Populations who are at high risk for cardiovascular disease have higher insulin responses to oral glucose than those at lower risk. Prospective studies carried out in Australia, Finland, and France have shown that elevated insulin levels, either fasting or in response to oral glucose, have a predictive role in the development of cardiovascular disease. This association is independent of the effects of other cardiovascular risk factors. In experimental animals, insulin deficiency retards the development of diet-induced arterial disease, whereas administration of insulin promotes lesion development and prevents lesion regression. Insulin stimulates lipid synthesis in isolated arteries and stimulates proliferation and lipid accumulation in cultured arterial smooth muscle cells. The evidence linking insulin with atherosclerosis has been gathered from nondiabetic subjects; this evidence is unavailable in diabetics. As it is clear that hyperinsulinemia is often present in diabetes, either in relation to mild glucose intolerance or obesity (in noninsulin-dependent diabetes mellitus) or because of insulin therapy (in insulin-dependent diabetes mellitus), it is essential that further consideration should be given to the possibility that hyperinsulinemia may have harmful effects on the arterial wall.

Increased high density lipoproteins in diabetic children

Serum lipoprotein lipid and apolipoprotein concentrations were determined in 27 diabetic children (5-18 years old) and 13 matched healthy controls. The serum cholesterol concentrations in the diabetics were slightly higher than in the controls (P less than 0.05) due to a significantly higher level of the high density lipoprotein cholesterol (P less than 0.01). Also the serum concentration of apolipoprotein A-I, the major protein constituent of the high density lipoprotein fraction, was higher in the diabetic children (P = 0.05). There were no significant differences between the groups with regard to the serum triglyceride concentrations or the apolipoprotein C-II and C-III concentrations. Neither the lipoprotein lipid nor the apolipoprotein levels were significantly correlated with variables related to the degree of regulation of the diabetic disease. No obvious explanation, based on the present data, can be given for the increased high density lipoprotein cholesterol concentrations in insulin-treated diabetics in comparison with the healthy children. It is possible, however, that the increased high density lipoprotein cholesterol concentration may be caused by an increased level of insulin in the circulation of insulin-treated diabetic children.

The effect of high insulin concentrations on prostacyclin production as measured by 6-keto PGF1 alpha determination

The effect of insulin in varied concentrations on the production of 6-keto PGF1 alpha, the metabolite of prostacyclin, by rat aortic tissue in vitro was assessed by radioimmunoassay. An insulin concentration of 50 microU/ml produced no change in 6-keto PGF1 alpha from the control samples, but concentrations of 100 microU/ml and 250 microU/ml reduced production from a control value of 0.326 +/- 0.031 ng/mg to 0.253 +/- .018 ng/mg (P less than .05) and 0.226 +/- 0.015 ng/mg (P less than .025) respectively. These results suggest that the suppression of PGI2 production may occur in states associated with insulin levels above those normally found in the postprandial state and might be one mechanism by which hyperinsulinemia might favor macrovascular disease.

Insulin-mediated increases in the HDL cholesterol/cholesterol ratio in humans

The role of insulin in the regulation of lipoprotein cholesterol distribution was studied in 18 human volunteers who were of normal weight, normolipemic, and glucose-tolerant. We used the euglycemic clamp technique and made comparisons with six saline-infused controls. While total cholesterol and low density lipoprotein cholesterol levels fell similarly by 6 hours in both groups (p = NS), there was a greater decrease in triglyceride levels (p less than 0.02) but less decrease in high density lipoprotein cholesterol levels (p less than 0.02) in the insulin-infused group. These changes resulted in both a higher high density lipoprotein cholesterol/total cholesterol ratio (p = 0.01) and a higher high density lipoprotein cholesterol/low density cholesterol ratio (p = 0.02) in the insulin-infused group. The timing of this effect of insulin implies a mechanism unrelated to high density lipoprotein turnover. Thus, insulin infusion during euglycemia appears to alter cholesterol distribution favorably in normal subjects.

Free and total insulin integrated concentrations in insulin dependent diabetes

Studies of the 24 hr insulin concentration profiles in diabetic subjects on chronic exogenous insulin have been hampered by the presence of endogenous anti-insulin antibody, which gives spurious estimates of radioimmunoassayable insulin concentrations. The introduction of polyethylene glycol precipitation of endogenous antibody has allowed development of reliable assays for determination of free and total insulin concentration in subjects on insulin therapy. This article reports our observations of plasma free and total insulin concentration in 50 Type I and Type II ambulatory insulin dependent diabetics, utilizing a continuous 24 hr blood withdrawal technique. In response to exogenous insulin, study subjects had marked elevations in insulin concentrations compared to controls. Mean free insulin integrated concentration was 3.5-fold higher in diabetics than nondiabetics. Mean total insulin integrated concentration was 868 microunits/ml, more than 20 times in excess of total insulin concentration in nondiabetics. There was a wide range among diabetics in the percentage of total insulin in the free insulin fraction. Neither free nor total insulin integrated concentration correlated with dose of exogenous insulin. Free and total insulin concentration profiles showed a limited range of variation in insulin concentration during the 24 hr of study, no subject having a profile that mimicked that observed in nondiabetic subjects. Glucose integrated concentration showed no correlation with free insulin integrated concentration, however, it did correlate inversely with the percentage of total insulin in the free insulin fraction. These data emphasize the difficulty in establishing normal patterns of insulin among diabetic subjects on conventional subcutaneous insulin therapy.

Twenty-four-hour metabolic profiles in diabetic children receiving insulin injections once or twice daily

Twenty-four-hour metabolic profiles were performed twice in each of 15 diabetic children, once when they were receiving single daily injections of insulin (Monotard plus Actrapid) and once on a twice-daily regimen (Semitard plus Actrapid). Before the study control was optimised at home on each regimen. There were no differences in overall 24-hour diabetic control on the two regimens as measured by mean blood glucose concentration, area under the blood glucose curve, M value, and 24-hour urinary glucose excretion. Hyperglycaemia after breakfast occurred on both regimens. Significant differences were noted before breakfast, when blood glucose and ketone concentrations were lower and plasma free insulin higher on the single-injection regimen, and after supper and during the night, when blood glucose values were lower on the two-injection regimen and associated with a rise in plasma free insulin after the evening injection. Once-daily injections provided insufficient circulating insulin after the evening meal, while twice-daily injections did not last through the night. Plasma C peptide, indicating residual endogenous insulin secretion, was just detectable in two children but easily detectable in four children, whose 24-hour diabetic control was significantly better than that in the remaining 11 children.Conclusions about the superiority of one insulin regimen over another must be based on specific differences in diabetic control. Both regimens studied achieved adequate control, and though neither provided physiological control specific modifications to the regimens could help to produce more normal profiles.

Insulin, glucagon, and amino acids during glycemic control by the artificial pancreas in diabetic man

The artificial endocrine pancreas (AEP) can normalize glycemia at rest and with meals. To determine whether insulin, glucagon, and amino acid profiles are also normalized, nine diabetics on subcutaneous insulin (S/C) and AEP control were compared to ten normal controls (NC). Glycemia was monitored continuously over 10 hr during which meals were consumed. Insulin infusion rate, and the levels of immunoreactive insulin (IRI) (in NC), free insulin (in S/C and AEP), C-peptide, glucagon, and amino acids are reported. Glycemia in AEP started at somewhat higher levels than in NC, but with breakfast and thereafter, it was identical. In S/C, hyperglycemia prevailed throughout, with no systematic change in free IRI. In AEP, both basal and peak free insulin levels, measured in four patients, were significantly higher than in NC. C-peptide values were significantly lower in diabetics and did not change with meals. Basal glucagon values were not different in the three groups and changes with meals were of small magnitude. Branched chain amino acids were higher in S/C and did not increase as in NC. In AEP, levels were lower than NC after the first two meals. Similarly, lysine and threonine were lower in AEP than in NC at the same times. Alanine, though similar at the onset, was lower 2 hr postbreakfast and higher 2 hrs postsupper in AEP and S/C compared to NC. These studies demonstrate that glycemic control with AEP is accompanied by hyperinsulinemia, which could account for the amino acid responses and the small alterations in immunoreactive glucagon (IRG) patterns. Further refinement is needed to obtain full normalization of metabolic profiles.

Timing of pre-breakfast insulin injection and postprandial metabolic control in diabetic children

A peak period of hyperglycaemia in insulin-dependent diabetics occurs after breakfast. A randomised crossover study was performed on nine diabetic children at home to study the effect of varying the time of their morning mixed injection of Monotard and Actrapid insulin on this hyperglycaemic peak. Performing the study at home minimised the children's stress.After diabetic control had been improved children injected their insulin 30 minutes (early injection) or five minutes (late injection) before breakfast on two consecutive Saturday mornings. Blood samples were taken at 30-minute intervals over 3(1/2) hours and analysed for concentrations of glucose, insulin, C-peptide, pyruvate, lactate, alanine, and ketones. Diet, insulin dose, and exercise were kept the same on both test days.The mean blood glucose concentration at breakfast (0 minutes) was 11 mmol/l after the early injection and 10 mmol/l after the late injection. Subsequent concentrations were consistently lower with the early injection regimen than the late regimen. The greatest difference between values in the two groups was 3.7 mmol/l at 150 minutes. Mean plasma insulin concentrations were lower in the children on the early regimen than in those on the late regimen at 30 minutes before breakfast but higher at 0 minutes and thereafter. There were no significant differences in mean concentration of intermediary metabolites between the two injection regimens. These were mainly within the normal range for healthy young adults except for the ketone concentrations, which were raised with both injection regimens until 180 minutes after breakfast.These results suggest that the timing of the morning injection of insulin is important in the control of postprandial hyperglycaemia in diabetic children.

Free insulin, bound insulin, C-peptide and the metabolic control in juvenile onset diabetics: comparison of C-peptide secretors and non-secretors during 24 hours conventional insulin therapy

In two groups of juvenile onset diabetics similar in age, weight, diet and daily insulin dosage (eight without C-peptide, group I; eight with C-peptide, group II) the serum levels of free and antibody bound insulin, C-peptide, glucose, lactate, alanine and FFA were determined over 24 h. In addition the affinity and binding capacity of the insulin antibodies were determined in vitro. No correlation was found between free or bound insulin and glucose. This holds true for the individual profiles as well as for the averaged profiles of the two groups. Free insulin and lactate or alanine were positively correlated in the C-peptide secreting group. C-peptide secretion followed the flucturations of the glucose level during 24 h in each individual patient. As a group, C-peptide secretors were better controlled than non-secretors with respect to mean blood glucose, M-value and the lability index and showed higher free insulin levels despite a similar daily insulin dosage. The possible reasons for this fact are discussed. No correlation was found between the affinity characteristics of the insulin antibodies and the degree of metabolic control or the daily insulin dosage.

Antibody formation and insulin requirements in diabetic children during treatment with purified commercial pork insulins

40 diabetic children (20 female, 20 male, mean age 8.5 ys, ranging from 0.8 to 14.3 ys), were treated with either of two purified porcine insulin preparations, Komb-Insulin CS (Hoechst) "CS": n = 21, and Semilente MC (Novo) "MC": n = 19, the latter being further purified by ion exchange chromatography. Circulating IgG-antibodies formed in 39 out of 40 subjects during the observation period of more than 2 years. Insulin binding-capacities below 2 mU/ml (mean value after 12 months: 0.45 mU/ml) were found following MC and considerably higher concentrations (mean value after 12 months: 5.16 mU/ml) following CS administration. However, only 52% of the CS-group (n = 11) showed high individual responses (subgroup II), many of which exceeded 5 mU/ml, while the other half (subgroup I) exhibited values as low as those in the MC-subjects. The ratio of girls to boys was high (8 vs 3) in subgroup II, and low (2 vs 8) in subgroup I. Despite great differences in antibody formation, no differences in insulin requirements were noted between the MC- and the CS-groups. Within the CS-group, however, some positive relationship between these parameters was found 6 months and 12 months after the start of therapy, but this did not necessarily apply to individual subjects. Short-term (metabolic control) and long-term effects of therapy (growth) were not different in the MC- and CS-subjects. From these results it may be concluded that antibody formation does not affect insulin requirements or metabolic control during relatively short-term treatment. Provided that antibodies have no direct relation to future vascular changes, both insulin preparations used in this study are equally well-situated for long-term treatment in children and adolescents.

Comparison between the plasma insulin and glucose responses to five different insulin regimes in diabetic patients

Diurnal plasma insulin and glucose concentrations were studied in six diabetic patients, each treated with five different insulin regimes. Subcutaneous soluble insulin was too slow and long acting for physiological replacement of the normal insulin response to meals, but the peak insulin levels were higher than the postprandial levels of normal subjects. Intramuscular insulin, though absorbed more quickly than subcutaneous insulin, was not clinically advantageous. Three rather than two injections of soluble insulin gave improved blood glucose control but two combined injections of short and medium acting insulins gave nearly as good results. A long acting insulin was needed to prevent raised plasma glucose levels overnight.

Effect of insulin antibodies on free and total plasma-insulin

Insulin administration often causes the development of insulin antibodies. Plasma insulin-binding capacity was assessed and free and total plasma insulin were measured in 96 insulin-dependent diabetic patients. Patients with the highest insulin binding capacity not only had the highest total insulin but also had the lowest free insulin. It is concluded that bound insulin is not unavailable to cells, that sufficient dissociation can occur for this insulin source to make a sizeable contribution to insulin delivery to the cell receptors, and that this can happen at a very low free insulin concentration.

B-cell function and blood glucose control in insulin dependent diabetics within the first month of insulin treatment

Seventeen insulin dependent diabetics were studied after two to four weeks of insulin treatment in a situation approximating to their normal daily life. Some endogenous insulin secretion, assessed by plasma C-peptide determinations, was present in all. Plasma C-peptide concentration was positively correlated with the blood glucose concentration and increased after breakfast, lunch and dinner (p less than 0.01); both peak values and relative increases were lower than those observed in normal subjects (p less than 0.01). The highest insulin secretory capacity was found in subjects with the least unstable blood glucose concentration (r=0.57, p less than 0.03), and these patients required the smallest insulin doses (r=0.54, P less than 0.04). These findings demonstrate the metabolic importance of a preserved B-cell function.

The relationship of abnormal circulating insulin levels to atherosclerosis

The evidence linking insulin with atherosclerosis can be divided into two parts. First, there is evidence that a proportion of subjects who have atherosclerosis or who are at risk of developing atherosclerosis hav elevated circulating insulin levels. The high insulin levels may be associated with another metabolic abnormality such as obesity, hypertriglyceridaemia, uraemia or consumption of oral contraceptives, may be inappropriate to the blood sugar levels as in mild diabetes, or may be of exogenous origin as in insulin-treated diabetics. The tissues of these subjects are exposed to high concentrations of insulin, and it seems reasonable to suggest that elevated insulin levels may have pathological effects on these tissues. Secondly, there is increasing evidence that the arterial wall is an insulin sensitive tissue. Exposure of arterial tissue to insulin results in proliferation of smooth muscle cells, inhibition of lipolysis, and synthesis of cholesterol, phospholipid and triglyceride. Chronic exposure to high concentrations of insulin results in the development of lipid filled lesions similar to those of early atherosclerosis. Thus, insulin has the ability to promote changes in the artery which, in the long term, may progress to atherosclerosis. The two lines of evidence together suggest that high levels of circulating insulin may have a role in the development of atherosclerosis.

Attempted suicide by insulin overdose in insulin-requiring diabetics

Four cases of suicidal insulin overdose in insulin-requiring diabetics presented to one hospital in three years. In three cases there was a history of depression; but despite huge doses of insulin (3,000 and 1,500 units) in two, no patient died and only one had residual signs of clinical brain damage. The estimated plasma insulin level was not well correlated with the severity of the hypoglycaemia. It is probable that suicidal insulin overdose is more common than reports in the literature suggest, and may often be unrecognized. The dissociation between huge doses of insulin and the severity of the subsequent hypoglycaemia in diabetics is unexplained.

Circadian variation of serum glucose, C-peptide immunoreactivity and free insulin normal and insulin-treated diabetic pregnant subjects

To examine differences among pregnant diabetic and nondiabetic subjects, serum glucose, and immunoreactivity of C-peptide, free and total insulin were measured at hourly intervals during a 24--h third trimester metabolic ward evaluation. Six normals, three mild, and four juvenile-onset type diabetics were studied. Diets were identical for all subjects. Mild diabetics differed from juvenile diabetics by having significant residual pancreatic B-cell function, as measured by C-peptide immunoreactivity. Short and intermediate acting insulins given once or twice daily to diabetics maintained serum glucose levels within the normal range throughout the 24 h. Despite wide variation in serum total insulin levels, peripheral free insulin concentrations in well-controlled diabetics fell within a relatively narrow range that was higher than in controls. Infants of the diabetic subjects were comparable to the offpsring of the control women.