C-peptide secretion and insulin antibodies as determinants of stability in diabetes mellitus

Urinary C-peptide as an index of unstable glycemic control in insulin-dependent diabetes mellitus (IDDM)

In order to investigate whether urinary C-peptide (UCP) excretion can be a useful index of insulin-dependent diabetes mellitus (IDDM) with unstable glycemic control, UCP was measured in nine IDDM patients with unstable glycemic control, nine IDDM patients with stable glycemic control, and 12 non-insulin-dependent diabetic (NIDDM) patients treated with insulin. The UCPs in overnight urine (U1) and fasting single void urine (U2) in IDDM patients with unstable glycemic control were significantly lower than those in IDDM patients with stable glycemic control (U1: 0.03 +/- 0.03 vs 0.24 +/- 0.20 nmol/mmol-Creatinine, U2: 0.02 +/- 0.01 vs 0.20 +/- 0.20 nmol/mmol-Cr, mean +/- SD, both P less than 0.01). The UCPs in U1 and U2 in both groups of IDDM were significantly lower than those in NIDDM (U1: 0.97 +/- 0.52, U2: 0.73 +/- 0.41 nmol/mmol-Cr, both P less than 0.01). The UCPs in U1 and U2 significantly correlated with incremental C-peptide response to intravenous glucagon injection and with glycemic stability assessed by the standard deviation of 10 previous fasting plasma glucose levels. These results suggest that UCP reflects their residual insulin secretory capacity and that UCP can be a useful index which distinguishes patients with unstable IDDM from those with stable diabetes mellitus.

The relevance of persistent C-peptide secretion in type 1 (insulin-dependent) diabetes mellitus to glycaemic control and diabetic complications

The effect of residual C-peptide secretion in longer standing IDDM on glycaemic control and the prevalence and evolution of complications over 2 years was evaluated. Thirty-one subjects with IDDM of 15.4 (1.5) years duration (mean SEM)) and residual C-peptide secretion, were matched for age, duration of diabetes and body mass index with 31 subjects without detectable C-peptide secretion. At trial entry and over 2 years, levels of HbA1, fructosamine and mean blood glucose were essentially similar in both groups. Levels of glycated albumin (GSA) were significantly higher in the C-peptide negative group after 3 and 9 months (P less than 0.05). An increased prevalence of proliferative retinopathy in the C-peptide negative group and of peripheral vascular disease in the C-peptide secretor group was apparent at entry to the study (both P less than 0.05), although no significant differences were observed after 1 or 2 years. There was no difference in the prevalence of peripheral or autonomic neuropathy, hypertension, nephropathy or ischaemic heart disease. Subjects with C-peptide concentrations greater than 0.100 pmol/ml at entry to this study had lower daily insulin requirements after 1 and 2 years, but behaved like the larger group with any detectable C-peptide secretion in all other respects. Residual C-peptide secretion was lost after 1 year in 7 patients, in whom glycaemic control during the year had been particularly poor. Insulin antibody titres were no different in the 2 groups at any time point. This study suggests that residual C-peptide secretion in longer standing IDDM confers the potential for limited improvements in glycaemic control. This effect appears to be insufficient to prevent the evolution of microvascular complications over a 2-year period. Residual C-peptide secretion and relative hyperinsulinaemia may be associated with an excess of peripheral vascular disease.

Metabolic effect of islet B-cell function in insulin-treated diabetes

We studied the relationship between endogenous insulin secretion and fasting levels of plasma free fatty acids (FFA), plasma acetoacetate plus plasma 3-hydroxybutyrate (total ketone bodies), blood glucose, and HbA1 in 132 diabetic outpatients treated with conventional insulin regimens. Patients were divided into four groups according to plasma C-peptide concentration after intravenous stimulation with glucagon: one group with C-peptide stimulation less than 0.06 nmol/l, one group with C-peptide stimulation 0.06- less than 0.32 nmol/l, one group with C-peptide stimulation 0.32- less than 0.60 nmol/l, and one group with C-peptide stimulation greater than 0.60 nmol/l. According to clinical criteria the prevalence of insulin-dependent diabetes mellitus was approximately 90% in patients with C-peptide stimulation less than 0.32 nmol/l, approximately 25% in patients with C-peptide stimulation from 0.32- less than 0.60 nmol/l, and approximately 10% in patients with C-peptide stimulation greater than 0.60 nmol/l. All metabolic variables were significantly higher in patients without detectable C-peptide in plasma when compared to values found in patients with C-peptide stimulation from 0.06- less than 0.32 nmol/l. These two patient groups also had similar peripheral plasma free insulin levels and were comparable according to age, sex, and body mass index.(ABSTRACT TRUNCATED AT 250 WORDS)

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)

Metabolic instability in type I diabetic patients. Studies on insulin absorption, hepatic production of metabolites and glucose counterregulation

In order to investigate the causes underlying metabolic instability in type I diabetes mellitus, we studied 8 unstable (group 1) and 4 well-controlled (group 2) diabetic patients, matched for age and duration of diabetes. Subjects were connected overnight to an artificial pancreas and brought to normoglycemia. On the following morning, insulin administration was discontinued for 6 hours and both metabolic and hormonal studies were carried out during this period. After insulin withdrawal, group 1 showed a faster rise of blood glucose (peak: 324.63 +/- 24.93 vs 175.25 +/- 42.63 mg/dl, p less than 0.01), beta-OH-butyrate (peak: 2,273.25 +/- 415.78 vs 550.50 +/- 158.17 mumol/l, p less than 0.01), and glycerol (164.10 +/- 38.90 vs 28.25 +/- 10.6 mumol/l, p less than 0.01). C-peptide secretion increased in group 2 from 0.09 +/- 0.052 to 0.22 +/- 0.099 pmol/ml whereas it remained almost undetectable in group 1 (p less than 0.01, group 1 vs group 2). Growth hormone, cortisol and immunoreactive glucagon were not significantly different in the two groups at any time after insulin withdrawal. Free insulin, after repeated s.c. or i.m. injection of porcine monocomponent insulin (10 IU), was not different in the two groups. We concluded that type I diabetic patients showing severe metabolic instability produced more glucose, ketone bodies and glycerol after insulin withdrawal than control 'stable' patients. This difference could not be accounted for by an excessive secretion of counterregulatory hormones or by an erratic insulin absorption from the injection sites and may have been related to the degree of B-cell failure, as measured by the absence of C-peptide and/or to the degree of insulin resistance.

Instability of fasting blood glucose values in noninsulin-dependent diabetic patients with long-term insulin treatment

We studied serum free C-peptide immunoreactivity (CPR) and the coefficient of variation (CV) of fasting blood glucose values (FBG) in 26 insulin-treated patients with non-insulin-dependent diabetes mellitus (NIDDM) in relation to the duration of insulin treatment. Serum free CPR responses during 100 g oral glucose tolerance test (OGTT) were significantly lower in patients with insulin treatment for five years or more than in those with insulin treatment for less than five years although their previous immunoreactive insulin (IRI) responses during OGTT before insulin treatment showed no significant difference. CV of FBG was found to be significantly higher at the time of this study (20.6 +/- 7.8%, mean +/- SD) than at the second year of insulin treatment (15.3 +/- 7.7%, P less than 0.05) in the patients with insulin treatment for five or more years but did not show any significant difference in patients with insulin treatment for less than five years at the corresponding times. Thus we measured CV of the FBG in NIDDM patients at various intervals during the long-term insulin or oral hypoglycemic agent treatment in another study. In 20 patients with insulin treatment, CV of FBG was found to be significantly different among the various intervals during insulin treatment (P less than 0.0025). It was significantly higher at the eight year (22.2 +/- 8.6%) and 12th year (21.9 +/- 9.1%) than at the second year (14.9 +/- 6.1%) and fifth year (15.0 +/- 6.7%) of insulin treatment (P less than 0.025, P less than 0.025; P less than 0.05, P less than 0.01, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

A clinical comparison of purified bovine and purified porcine insulins

Twenty four patients with established insulin dependent diabetes treated with twice daily soluble and isophane bovine insulins were changed to equivalent doses of either purified bovine Neusulin and Neuphane (Wellcome) or purified porcine Actrapid and Monotard (Novo) insulins. After 6 months treatment the porcine group showed a 35% fall in insulin binding antibodies and a 14% reduction in insulin dosage. The group changed to purified bovine insulins showed no significant change in insulin binding antibodies and no change in insulin dose. Mean blood glucose and glycosylated serum protein fell in both groups during the study period but there was no significant difference between the two groups.

Pathophysiology of insulin secretion in diabetes mellitus

In normal man, glucose serves to regulate basal insulin secretion by its participation with insulin in a feedback loop. In addition, glucose stimulates insulin secretion directly and potentiates insulin responses to nonglucose stimuli such as amino acids, beta-adrenergic stimuli, and gut hormones. Maximal glycemic potentiation of the acute insulin response to IV arginine occurs at a glucose level of approx. 450 mg/dl. In patients with noninsulin dependent diabetes mellitus (NIDDM), basal insulin levels have usually been reported as normal, but if plasma glucose is lowered to normal levels, a deficiency of basal insulin becomes apparent. In addition, the first phase (0-10 min) insulin response to IV glucose is absent in virtually all patients with overt NIDDM. In contrast, the second-phase (greater than 10 min) response is often preserved in NIDDM due to its maintenance by ambient hyperglycemia. Similarly, insulin responses to nonglucose stimuli such as arginine often appear normal in NIDDM because of potentiation by hyperglycemia. However, insulin responses to arginine are lower than those of nondiabetic controls when compared at multiple matched glucose levels. Indeed, maximal potentiation by glucose of the insulin response to arginine is markedly subnormal in NIDDM, suggesting a loss of functional B cell secretory capacity. In patients with long-standing insulin-dependent diabetes mellitus (IDDM), basal insulin secretion and insulin responses to all stimuli are virtually absent. However, in a remission phase, or in IDDM of short duration, basal insulin secretion and insulin responses to nonglucose stimuli may be relatively preserved. Therefore, islet dysfunction in IDDM and NIDDM, while etiologically different, share some common pathophysiological features.

Residual B-cell function in type 1 (insulin-dependent) diabetes mellitus: its relation to clinical and metabolic features

The aim of the present study was to investigate whether or not residual B-cell function could be related to insulin sensitivity as well as to duration of disease, insulin requirement, and indices of metabolic control in a population of Type 1 (insulin-dependent) diabetic patients. A positive correlation was found between fasting C-peptide and age at onset of diabetes, whereas a negative relationship occurred between C-peptide and duration of disease. Fasting C-peptide negatively correlated also to mean daily plasma glucose, 24-h glycosuria, and fasting free fatty acid concentration. Moreover, a negative correlation was found between C-peptide and daily insulin requirement. Conversely, a positive relationship occurred between C-peptide levels and the parameter we used for estimating insulin sensitivity, i.e. glucose disappearance rate after i.v. insulin injection. These results once more emphasize the importance of residual B-cell function in Type 1 (insulin-dependent) diabetes mellitus, and suggest that the residual endogenous insulin secretion might play an important role in glucose homeostasis of Type 1 diabetes by influencing the sensitivity to insulin.

Glycosylated haemoglobin and serum insulin antibodies in type I diabetes

Type 1 diabetics receiving once (Group 1, n = 72) and twice (Group 2, n = 48) daily subcutaneous injections of conventional beef insulin were compared, on a cross-sectional basis, in respect of insulin antibody binding by serum and total glycosylated haemoglobin (HbA1). Patients in Group 1 had higher insulin antibody binding (25.2 +/- 15.8% vs 17.0 +/- 13.9%; p less than 0.01) and higher HbA1 levels (12.5 +/- 2.0% vs 11.0 +/- 1.8%; p less than 0.001) than patients in Group 2. An inverse correlation (tau = -0.28, p less than 0.01) was observed between HbA1 and insulin antibody binding in C-peptide non-secretors of Group 1 but not in Group 1 C-peptide secretors, nor in C-peptide secretors and/or non-secretors of Group 2. It is suggested that in Type 1 diabetics who receive a single daily insulin injection and who have no endogenous insulin secretion, insulin antibodies may aid glycaemic control by prolonging insulin action.

C-peptide measurement: methods and clinical utility

Proinsulin is the single chain precursor of insulin. It consists of insulin, plus a peptide which connects the A and B chains of insulin. This peptide is termed C-peptide. C-peptide an insulin are secreted in equimolar amounts from pancreatic beta-cells, Hence, circulating C-peptide levels provide a measure of beta-cell secretory activity. C-peptide measurements are preferable to insulin measurements because of lack of hepatic extraction, slower metabolic clearance rate, and lack of cross reactivity with antibodies to insulin. This article reviews the methods for determination of C-peptide levels in body fluids, and discusses the applications of C-peptide measurement. These include the investigation of hypoglycemia and the assessment of insulin secretory function in insulin-treated and non-insulin-dependent diabetics. The contribution of C-peptide measurement to the understanding of the interrelationships between insulin secretory function and age, sex, obesity, blood lipids, and blood glucose concentrations will also be evaluated.

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.

Residual pancreatic function in insulin dependent diabetics

The relative contributions of alpha and residual beta cell function and the presence of insulin binding antibodies to indices of glucose control have been assessed in a group of 44 patients with insulin dependent disease of variable duration. Residual beta cell secretion was detected in 18 patients (40%) but no patient receiving insulin for more than five years showed evidence of residual function. Indices of glucose control were significantly better (p less than 0.001) in patients demonstrating residual secretion. In contrast, no relation was found between glucose control and either fasting of post prandial plasma glucagon concentrations. Insulin binding antibodies were detected in all but two patients but did not correlate with either daily insulin dose or glucose control. These results are consistent with the view that residual beta cell function contributes to improved glucose control in the yearly years of insulin dependency but alpha cell function and insulin antibodies do not.

The relationship between residual insulin secretion and metabolic stability in type 1 (insulin dependent) diabetes

The purpose of this study was to investigate whether the great differences in metabolic control between labile and stable insulin dependent juvenile diabetics could be explained by differences in residual pancreatic B cell function. Nine labile diabetics, ten stable diabetics on one insulin injection a day and nine stable diabetics on two insulin injections a day were investigated during a 24-h period during which they maintained their usual diet and insulin therapy. Serum C-peptide concentrations were measured after removal of proinsulin bound to insulin antibodies. The labile diabetics did not show any significant change in C-peptide concentrations despite great fluctuations in plasma glucose concentrations. In six patients with stable diabetes, C-peptide responses after the main meals could be demonstrated and there was a significant correlation between the concentrations of C-peptide and glucose (r = 0.85, p less than 0.001). The other stable patients, having the same mean plasma glucose concentration and mean amplitude of glycaemic excursions, did not show any C-peptide response. It is concluded that persistent insulin secretion is not a prerequisite for metabolic stability. Severe lability, however, seems to occur only in the absence of residual insulin secretion.

C-peptide-measurement: a simple method for the improvement of specificity

Sera containing insulin antibodies and proinsulin give artifactual high readings in C-Peptide measurement. This problem can be circumvented by the removal of antibodies and proinsulin prior to C-Peptide assay. A method is described which enables the removal of antibodies and proinsulin from sera without affecting the C-Peptide determination. Furthermore, this method allows a semiquantitative estimation of proinsulin, provided there is enough cross reactivity of the C-Peptide antibody with proinsulin.

C-Peptide reserve in insulin-dependent diabetes. Comparative responses to glucose, glucagon and tolbutamide

Residual beta cell secretory capacity was assessed in short term (2 months to 2 years) and long term (5 to 8 years) insulin-dependent diabetics by measurement of serum C-peptide immunoreactivity during three provocative tests: glucose, tolbutamide, and glucagon. Minimal C-peptide secretion could be detected in only one out of seven long term diabetics by the stimulatory tests. All seven short-term diabetics responded to at least one provocative test of beta cell reserve, although these responses were blunted. The greatest C-peptide responses occurred after glucagon administration (mean increase 0.62 pmol/ml) in short-term responders. Patients who responded to one test did not necessarily respond to another stimulus. There was no correlation between basal C-peptide levels and the ability to provoke further C-peptide secretion by any of the three tests. C-peptide responses did not correlate with % Haemoglobin A1c, mean fasting blood glucose levels, or mean blood glucose concentrations during an oral glucose tolerance test. The data indicate that stimulation tests are only useful in assessing endogenous beta cell reserve in patients with diabetes of less than 5 years duration. In diabetics of longer duration there is little insulin reserve above basal levels.

Pancreatic B-cell response to a test-meal in lean and obese diabetic patients: relation to metabolic control

We have measured fasting C-peptide reactivity (CPR) as well as CPR responses to a test meal in 83 diabetic patients and 41 non diabetic controls. In comparison to controls, basal CPR was decreased in lean insulin-treated diabetics with stable or brittle diabetes and in obese patients with brittle diabetes. Lean and obese maturity-onset diabetics had increased CPR levels and so had obese insulin-treated patients. Nevertheless, the CPR response to the test meal was clearly inadequate in all diabetics. In control patients, there was a positive correlation between fasting blood glucose and CPR levels. On the contrary, lean diabetics demonstrated a negative correlation between these parameters. Hemoglobin A1 levels were negatively correlated to fasting CPR levels in lean diabetics, indicating the importance of residual B-cell function for diabetes control. These correlations were obscured in obese diabetics. In our patients, circulating insulin antibodies had apparently no deleterious effect on metabolic control.

Plasma C-peptide and serum insulin antibodies in diabetic patients receiving pancreatic transplants

Plasma C-peptide and serum insulin antibody levels were determined in 5 diabetic patients undergoing vascularized pancreatic transplantation. The grafts functioned well at first and exogenous insulin could be withdrawn, but one to 7 weeks later the grafts were rejected. After the transplantation there was an increase in the fasting plasma C-peptide level, and B-cell stimulation with glucose or glucagon evoked a C-peptide response. Healing of ischaemic damage was reflected in an increase in the C-peptide level. During graft rejection the C-peptide level fell. Measurement of plasma C-peptide levels provides a direct index of the B-cell function of the pancreatic graft. After transplantation the insulin antibody level fell exponentially, with an apparent half life of 10-11 days, whereas the level of total IgG was variable. The results indicate that formation of insulin antibodies ceases immediately on removal of the immunogenic stimulus, that is, on withdrawal of xenogeneic insulin.

Apparent insulin resistance due to abnormal enzymatic insulin degradation: a new mechanism for insulin resistance

A 16-year-old girl presented with severe, prolonged insulin resistance. Insulin antibodies, initially thought to be responsible for the insulin resistance, were suppressed using monocomponent insulin and immunosuppressive therapy; however insulin resistance persisted. Insulin kinetic studies suggested abnormal metabolism of a bolus injection of 125I insulin and the reappearance in the circulation of radioactive products, demonstrated by chromatography to be of different molecular weight to insulin. These products were of similar molecular weight to material obtained by incubating 125I insulin with protease. Trasylol significantly reduced the patient's insulin requirements and normalised the disappearance of 125I insulin from the circulation. Prolonged treatment with Trasylol resulted in a fall in insulin requirement to non "insulin-resistance" levels. The insulin requirement remained static when Trasylol was ceased. We propose abnormally rapid insulin degradation to be a new mechanism of resistance to insulin therapy.

Plasma C-peptide response to arginine in insulin-dependent diabetic subjects

Plasma C-peptide concentrations have been determined in the basal state and in response to intravenous arginine in 10 insulin-dependent diabetics. Five patients had fasting C-peptide levels above 0.08 pmol/ml and responded to the arginine infusion with a rise in C-peptide levels of more than 0.2 pmol/ml (responsive diabetics). The remaining 5 patients had fasting C-peptide below 0.03 pmol/ml and showed no C-peptide response to arginine (nonresponsive diabetics). Fasting blood glucose and the rise in blood glucose in response to arginine were higher in non-responsive than in responsive diabetics. The magnitude of blood glucose rise in response to arginine was inversely correlated with increments in plasma C-peptide. In addition, the fasting levels of FFA and 3-hydroxybutyrate were significantly lower in C-peptide responsive than in nonresponsive patients. These data give further support to the concept that measurements of fasting plasma C-peptide permit to distinguish secretors from nonsecretors, and demonstrate that residual beta-cell function is associated with a lesser degree of aminoacid-induced hyperglycemia.

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.

Bone loss in diabetes: effects of metabolic state

The significance of different risk factors for the development of bone loss in diabetes mellitus was evaluated in a cross sectional study of 215 insulin treated diabetic outpatients. Bone mineral content in the forearms was measured by photon absorptiometry and the metabolic status was evaluated by three indices: residual B-cell function, insulin dosage and fasting blood glucose. The mean bone mineral content was reduced to 90.2% of sex- and age-matched normal mean values (P less than 0.001). Stratification of the patients showed that bone mineral content was 99.3% of that found in sex- and age matched normal subjects in the group with residual B-cell function, low insulin dosage and low fasting blood glucose; it was only 79.3% of normal in the group with no detectable insulin secretion, high insulin dosage and more severe hyperglycaemia. Thus, residual insulin secretion and the quality of metabolic control are major factors in determining bone mineral content in insulin treated diabetic patients.

Metabolism during normal and diabetic pregnancy and its effect on neonatal outcome

Diurnal profile studies have been used to define the fetal carbohydrate and lipid substrate environment in normal and diabetic women during late pregnancy. In women with normal glucose tolerance the diurnal plasma glucose concentration was maintained within close limits (mean +/- S.D., 4.70 +/- 0.38 mmol/l) but in chemical and insulin-dependent diabetics there was a marked increase in both the mean diurnal glucose value and in the variability of the plasma glucose levels observed through the day (mean +/- S.D., 5.61 +/- 5.61 +/- 1.03 and 6.02 +/- 1.26 mmol/l respectively, P less than 0.01). No difference was observed between the peripheral insulin activity of the normal and chemical diabetic women, and the impaired glucose tolerance of the latter group was due to a deficient insulin response to goucose. The diurnal glucose variability, expressed as the standard deviation of the mean, was found to be inversely correlated with the residual C-peptide response in insulin-requiring diabetics. The mean diurnal plasma free fatty acid (FFA) concentration was slightly raised in chemical diabetic subjects compared to normal women (mean +/- S.D., 0.77 +/- 0.34 and 0.68 +/- 0.20 mmol/l respectively) but this difference was not significant. Insulin treatment produced a marked reduction in circulating FFA concentration, with a mean value in the insulin-dependent diabetic group of 0.45 +/- 0.11 mmol/l (P less than 0.001). Neonatal glucose assimilation during the first two hours of life correlated strongly with several functions of maternal carbohydrate tolerance. This was associated with higher plasma insulin concentrations at birth, and a marked tendency to hypoglycaemia in the infants of untreated chemical diabetic women. Impaired mobilization of triglyceride stores was also observed during the two hours after birth in the infants of diabetic women. This, however, appears to be due not to impaired lipolysis but to rapid re-esterification of FFA. These findings all indicate a state of functional hyperinsulinism in the infant of the diabetic women secondary to maternal hyperglycaemia.