Impaired subcutaneous absorption of insulin in 'brittle' diabetics

Twenty-four hour plasma free insulin and blood glucose and intermediary metabolite profiles have been measured in 6 C-peptide deficient 'brittle' diabetic patients, during continuous sc and im insulin infusion. During sc infusion free insulin profiles were erratic and unpredictable. Mean 24 h blood glucose levels were raised at 12.6 +/- 2.1 (SE) mmol/l, and 3-hydroxybutyrate at 0.24 +/- 0.08 mmol/l. Blood lactate (1.88 +/- 0.18 mmol/l) and glycerol (0.084 +/- 0.007) were also elevated. Insulin (im) restored free insulin profiles to the normal pattern as found in 'stable' diabetics on sc infusion, with characteristic post-meal peaks (49 +/- 7, 103 +/- 35, and 95 +/- 34 mU/l) and stable night-time levels. Mean 24 h blood glucose was 6.7 +/- 1.1 mmol/l (P less than 0-.05 compared to sc infusion) and 3-hydroxybutyrate 0.07 +/- 0.02 mmol/l (P less than 0.05). Blood lactate (1.67 +/- 0.08 mmol/l) and glycerol (0.10 +/- 0.02 mmol/l) levels remained abnormal. The ratio of plasma free insulin to insulin dose administered was significantly higher during im infusion. In the 6 'stable' diabetics on sc insulin infusion good blood glucose control (7.1 +/- 0.9 mmol/l) was accompanied by clear post-prandial insulin peaks, and stable nocturnal levels. The results strongly suggest that in one category of 'brittle' diabetics there is defective and erratic sc insulin absorption.     

Glucose metabolism in quinine-treated patients with uncomplicated falciparum malaria

To investigate host and drug effects on glucose metabolism in acute falciparum malaria, 10 previously untreated, fasting Thai males with uncomplicated infections were given a 2-h intravenous glucose infusion (5 mg/kg ideal body weight min) with an infusion of quinine dihydrochloride (10 mg/kg body weight) during the second hour. Eight patients were restudied in convalescence. Fasting plasma glucose (mean +/- SD) and insulin (geometric mean (-SD to + SD] were higher during acute illness (5.5 +/- 1.0 mmol/l and 6.2 (5.0-7.7) mU/l) than in convalescence (4.2 +/- 0.25 mmol/l and 3.7 (2.1-6.7) mU/l; P less than 0.001 and P = 0.058 respectively). After 1 h, both plasma glucose (9.3 +/- 1.4 vs 7.5 +/- 0.8 mmol/l, P less than 0.001) and insulin (21.2 (13.8-32.5) vs 15.2 (11.2-20.8) mU/l, P = 0.089) remained higher during acute illness; mathematical model (CIGMA) assessment of these values indicated lower tissue insulin sensitivity on admission (97% (71-134] than in convalescence (139% (109-178), P less than 0.025) but normal beta-cell function on both occasions. Two-hour plasma glucose (9.5 +/- 2.0 mmol/l) and insulin (81.8 (51.5-129.9) mU/l) concentrations during acute illness were also significantly higher than in convalescence (7.2 +/- 1.2 mmol/l and 40.1 (23.5-68.4) mU/l, P less than or equal to 0.025) despite similar end-infusion free plasma quinine concentrations (P greater than 0.5). Basal plasma free fatty acid concentrations were increased in acute illness (0.68 +/- 0.24 vs 0.21 +/- 0.12 mmol/l, P less than 0.001) but fell to low levels at 2 h in both studies. These data suggest tissue insulin resistance and augmented quinine-stimulated insulin secretion in acute falciparum malaria, factors which are likely to influence the clinical situation in which malaria-associated hypoglycaemia occurs.     

Metabolic effects of physical exercise in insulin-dependent diabetics controlled by continuous subcutaneous insulin infusion or conventional injection therapy

The metabolic and hormonal response to moderately severe exercise 2 h after breakfast was assessed in 8 insulin-dependent diabetics during conventional insulin injection therapy and after 3 weeks of continuous sc insulin infusion. Blood glucose fell from 12.1 to 4.4 mmol/l on injection therapy; this was accompanied by a significant rise (P less than 0.05) in free insulin to 57 mU/l. On infusion therapy plasma glucose fell and stabilised at 3.6 mmol/l from pre-exercise levels of 7.1 mmol/l, while free insulin level was unchanged at the end of the exercise period (31 mU/l). The fall in blood glucose on injection therapy was accompanied by an exaggerated growth hormone response to exercise that was normalised by 3 weeks of infusion therapy. Basal and post-prandial levels of intermediary metabolites, catecholamines and glucagon were comparable on the two insulin regimens. Responses during exercise were generally similar and no different from those of normal subjects, with the exception of plasma NEFA levels which became abnormally suppressed. Good metabolic control of diabetes is thus accompanied by nearly normal hormonal and metabolic response to moderately severe exercise.     

The absorption kinetics of subcutaneously infused U 40 and U 100 insulin in diabetics

The influence of U 40 and U 100 insulin on the insulin kinetics during continuous subcutaneous insulin infusion (CSII) was investigated in eight insulin-dependent diabetics. CSII was started at t = -1.5 h with a bolus of 2 IU at the individual treatment infusion rate (22-35 IU/24 h), followed at t = 0 h by a premeal dose of 6 IU. Insulin delivery was interrupted for 120 min at t = 4 h and reinitiated with a loading dose of 2 IU for another 2 h. The incremental peak plasma free insulin levels and the time to reach these levels after the premeal insulin dose were not significantly different: 17 +/- 2 vs. 16 +/- 2 mU/l and 144 +/- 22 vs. 129 +/- 9 min for U 40 and U 100 insulin, respectively. During the 2 h interruption of insulin delivery plasma free insulin levels declined by 5.0 +/- 1.6 and 7.2 +/- 1.3 mU/l (NS) for U 40 and U 100 insulin, respectively. The blood glucose profiles were virtually identical throughout the studies for either insulin concentration. These results indicate that varying the insulin concentration in the range between U 40 and U 100 does not affect the insulin kinetics during CSII in insulin-dependent diabetics.     

Postprandial hyperglycaemia following a morning hypoglycaemia in type 1 diabetes mellitus

The occurrence of hyperglycaemia following a morning hypoglycaemic episode was studied in nine patients with Type 1 diabetes. Each patient was studied twice, once following induced hypoglycaemia and once in a control study when hypoglycaemia was prevented by glucose infusion. After the initial hypoglycaemic/control period the patients were maintained on their regular insulin regimens and were given standard meals. Hypoglycaemia induced postprandial hyperglycaemia (3.1 +/- 0.8 mmol l-1 above control) which lasted for about 8 h. Maximal growth hormone levels were seen 40 min after glucose nadir (control 7.8 +/- 3.2, hypoglycaemia 74.0 +/- 12.3 mU l-1) and the magnitude of the hyperglycaemia was related to the growth hormone levels following the hypoglycaemia (r = 0.80, p less than 0.01).     

The dawn phenomenon and diabetes control in treated NIDDM and IDDM patients.

The effect of glycaemic control on the early morning plasma glucose rise, 'the dawn phenomenon', was assessed in two matching diabetic patient groups each comprising five NIDDM and two IDDM patients per group, who were otherwise considered to be in poor (HbA1 = 11.2 +/- 0.6%) or good (HbA1 = 7.6 +/- 0.2%) glycaemic control. Hourly plasma concentrations of glucose, insulin, glucagon, cortisol, and growth hormone were measured between 03.00 and 09.00 h. In all the poorly controlled diabetic patients the mean rise in plasma glucose between 06.00-08.00 and 03.00 h was greater than or equal to 1.0 mmol/l. In contrast, the plasma glucose increment was less than 1.0 mmol/l in the well controlled diabetics. The overnight mean insulin levels in the poor and well controlled patient groups were 19.3 +/- 0.5 and 25.0 +/- 0.6 mU/l (P less than 0.001) respectively. Glucagon, cortisol, and growth hormone levels in the early morning showed no significant differences between the two groups. The decline in plasma insulin from 03.00 to 08.00 h and mean cortisol level between 03.00 and 06.00 h were both significantly correlated with the increase in plasma glucose between 03.00 and 08.00 h. We concluded that an increase of 1.0 mmol/l or more in plasma glucose during the early morning is of clinical importance.     

A morning dose of insulin glargine prevents nocturnal ketosis after postprandial interruption of continuous subcutaneous insulin infusion with insulin lispro

AIM: The aim of this crossover trial was to evaluate the potential of partial substitution of basal insulin with glargine, administered once daily in the morning, to protect against nocturnal ketosis after postprandial interruption of continuous subcutaneous insulin infusion (CSII). METHODS: Seven patients with type 1 diabetes received 4 weeks of treatment with insulin lispro, administered by CSII, and 4 weeks of treatment with CSII and a partial basal replacement dose of insulin glargine administered in the morning. On day 28 of each treatment phase, patients were admitted to the research unit where dinner was served and their usual dinner insulin bolus dose given, after which CSII was discontinued at 7 pm. Plasma (p) beta-hydroxybutyrate and p glucose were measured every hour for 12 h thereafter. RESULTS: Plasma beta-hydroxybutyrate at 7 pm was 0.16+/-0.05 and 0.13+/-0.07 mmol/l with and without glargine, respectively, and increased to 0.17+/-0.10 and 0.60+/-0.3 mmol/l within 6 h (P=0.02). Plasma glucose increased without glargine, from 8.6+/-2.9 to 21.1+/-3.0 mmol/l (P=0.003), but did not rise significantly following glargine (13.6+/-4.7 vs. 12.6+/-5.6 mmol/l; P=0.65). CONCLUSIONS: Partial replacement with a morning dose of insulin glargine protects against the development of ketosis for as much as 12 h after postprandial interruption of CSII. This treatment strategy could, therefore, be useful for patients who are prone to ketosis but, for other reasons, are deemed suitable for CSII.     

Optimal timing of injection of once-daily insulin glargine in people with Type 1 diabetes using insulin lispro at meal-times.

AIMS: To compare blood glucose control when insulin glargine is given at lunch-time, dinner-time, and bed-time in people with Type 1 diabetes using insulin lispro at meal-times. METHODS: In this 16-week, three-way, cross-over study, 23 people with Type 1 diabetes were randomized to insulin glargine injection at lunch-time (L) [mean 12.37 +/- 00.34 (+/- sd) h], dinner-time (D) (18.12 +/- 00.40 h), or bed-time (B) (22.29 +/- 00.40 h), each plus meal-time insulin lispro. Each 4-week treatment period concluded with a 24-h inpatient metabolic profile. RESULTS: Insulin doses, HbA(1c), and fructosamine concentration did not differ between treatment periods. Pre-breakfast self-monitored blood glucose (SMBG) concentration was higher with injection of glargine at lunch-time than at other times [L: 9.2 +/- 0.3 (+/- se) vs. D: 8.2 +/- 0.3 or B: 8.0 +/- 0.3 mmol/l, P = 0.016], as probably was pre-lunch SMBG (L: 8.6 +/- 0.7 vs. D: 6.4 +/- 0.7 or B: 6.4 +/- 0.8 mmol/l, P = 0.051). Pre-dinner SMBG level was higher with dinner-time glargine than other injection times (D: 9.4 +/- 0.9 vs. L: 4.9 +/- 0.9 or B: 7.4 +/- 1.1 mmol/l, P = 0.007). For 22.00 to 02.00 h, mean inpatient plasma glucose concentration was higher with injection of glargine at bed-time than other times (B: 9.1 +/- 0.6 vs. L: 7.8 +/- 0.6 or D: 6.7 +/- 0.6 mmol/l, P = 0.023). Plasma free insulin concentration was lower at the end of the afternoon with dinner-time glargine than other injection times (D: 11.5 +/- 1.4 vs. L: 20.2 +/- 1.3 or B: 16.5 +/- 1.3 mU/l, P < 0.001). Frequency of hypoglycaemia was not different, but timing of hypoglycaemia differed between treatment periods. CONCLUSIONS: Blood glucose levels rise around the time of injection of insulin glargine whether given at lunch-time, dinner-time or bed-time. Bed-time injection leads to hyperglycaemia in the early part of the night which is improved by giving insulin glargine at lunch-time or dinner-time.     

Hormonal responses to insulin infusion in diabetes mellitus

Summary Twenty diabetic patients and fourteen normal volunteers received infusion of 2.4 U neutral porcine insulin/h until either the blood glucose level was stable, or until hypoglycaemia occurred. As previously reported [1] in the normal group the blood glucose stabilised at 2.8±0.1 mmol/l without any hypoglycaemic symptoms. There was an increase in blood levels of glucagon, cortisol and growth hormone as the blood glucose level fell, the mean peak increments being 167±33 pg/ml, 400±71 nmol/l and 29±7 mU/l, respectively. In ten of the diabetic subjects (Group A) the blood glucose level stabilised at 3.6±0.2 mmol/l during the insulin infusion, with peak increments in plasma glucagon (110±24pg/ml), cortisol (411±71 nmol/l) and growth hormone (22±6 mU/l), not significantly different from those in the normal subjects. These rises in hormone levels occurred during the last hour of infusion after normoglycaemia was reached and maintained. The ten remaining diabetics (Group B) developed symptoms of hypoglycaemia during the infusion. The peak increments in plasma glucagon (19±7 pg/ml), cortisol (183±36 nmol/l) and growth hormone (6±2 mU/l) in this latter group were significantly less than those in the other diabetic group or the normals. The absence of counter-regulatory hormonal responses in the Group B diabetics was related to the development of hypoglycaemia and may be the result of a dysfunction of hypothalamic gluco-regulatory centres.     

A comparison of the effects of semisynthetic human insulin and porcine insulin on transmembrane ion shifts and glucose metabolism during euglycaemic clamping

Disturbances of potassium, calcium, phosphate and magnesium homeostasis in diabetes mellitus are well documented. We have compared the effects of semisynthetic human and pancreatic porcine insulin on transmembrane shifts of these ions, and on glucose metabolism, at two insulin infusion rates, 20 and 50 mU/kg/h, during euglycaemic clamping for 2 h in 6 normal volunteers. The glucose requirements and the changes in blood metabolite concentrations were not significantly different during the porcine and human insulin infusions. Serum potassium levels, however, showed a significant greater decline with infusions of porcine insulin (4.2 +/- 0.1 to 3.5 +/- 0.1 mmol/l) compared with human insulin (4.2 +/- 0.1 to 3.7 +/- 0.1 mmol/l) at 50 mU/kg/h (P less than 0.05). Potassium levels were significantly lower during the porcine insulin infusion at 105 and 120 min and at 15 and 30 min after stopping the infusion. Electrocardiographic T-wave voltage decreased during the porcine and human insulin infusion by 0.13 +/- 0.02 and 0.10 +/- 0.01 mV, respectively (P less than 0.02). Changes in serum levels of magnesium, calcium, phosphate, and red blood cell concentrations of magnesium and 2,3-DPG, were not significantly different between the insulins. Thus a small but significant greater decline in potassium levels with similar glucose requirements was found during iv administration of porcine insulin compared with human insulin.     

Glucagon release and glucose counter-regulation during hypoglycaemia. Modifying effect of the previous glucose level

The importance of a short-term elevation of the ambient glucose level for the release of counter-regulatory hormones and the glucose recovery rate during a subsequent hypoglycaemia was studied in healthy subjects. Hypoglycaemia was induced with insulin infusion after a previous 80 min of euglycaemic (E: 5 mmol/l) or hyperglycaemic (H: 15 mmol/l) glucose clamp. By infusing insulin during the euglycaemic clamp similar levels were reached during both glucose clamps. The same level of hypoglycaemia was reached in both studies (E: 1.5 +/- 0.1, H: 1.5 +/- 0.2 mmol/l) and the insulin levels were also similar both at glucose nadir and during the recovery period. In spite of this, both the mean glucagon levels at nadir at the mean individual maximal increase were significantly lower after the hyperglycaemic clamp (E: 101 +/- 25, H: 54 +/- 7 pg/ml, P less than 0.05). The glucose recovery rate was also significantly impaired following the hyperglycaemic clamp. The results show that a short-term elevation of the ambient glucose level impairs the glucagon release during a subsequent hypoglycaemia. This finding may be of importance for the development of the blunted glucagon release in response to low glucose levels in diabetics.     

Overnight basal insulin requirements in insulin dependent diabetics

Programming open loop insulin delivery systems makes necessary the knowledge of patients insulin needs. It is frequently postulated that insulin needs increase at the end of the night in relation to the rise in cortisol secretion. According to this hypothesis is it justified to speed up the insulin infusion rate in the early morning? This question was addressed by studying insulin infusion rate by an artificial pancreas during the night in 12 C. peptide negative insulin dependent diabetics. They were connected to the artificial pancreas from 8 a.m. to 10 a.m. the next morning while on their habitual diabetic diet and slept as usual from 11 p.m. to 7 a.m. approximately. From 11 p.m. to 7 a.m. mean insulin infusion rate was 21.5 +/- 3.3 mU/Kg/h representing 15.6 +/- 1.6% of the dose delivered in 24 hours. Blood glucose was stable around 85 mg/dl. No significant differences were observed in the hourly insulin infusion rate during the night period, in spite of a slight tendency to a rise (from 21.1 +/- 2.8 to 22.1 +/- 2.6 mU/kg/h) tendency to a rise (from 21.1 +/- 2.8 to 22.1 +/- 2.6 mU/kg/h) after 4 a.m. On the basis of these results obtained in patients sleeping as usual it does not appear useful to envisage a systematic acceleration of insulin infusion rate by continuous delivery systems in the early morning.     

Insulin-mediated glucose disposal in type 1 (insulin-dependent) diabetic subjects treated by continuous subcutaneous or intraperitoneal insulin fusion

In order to determine if intraperitoneal insulin infusion could improve the insulin resistance of type 1 diabetic patients we have used the englycaemic insulin clamp technique in order to study the effects of insulin on glucose disposal in four C peptide negative type 1 diabetic patients treated by continuous subcutaneous or intraperitoneal insulin infusion and in five control subjects. Compared to control subjects, the diabetic patients treated by subcutaneous insulin infusion had a decreased maximal capacity of glucose utilization (diabetics: 12.6 +/- 0.3 mg.kg-1.min-1; controls: 15.7 +/- 0.7 mg/kg-1.min-1, p less than 0.01) and a trend towards higher half-maximally effective insulin concentrations (diabetics: 70 +/- 11 mU/l-1, controls: 48 +/- 4 mU/l-1). Treatment of the diabetic patients by intraperitoneal insulin infusion for 2 months decreased their mean peripheral free insulin levels (during subcutaneous infusion: 23.5 +/- 2.2 mU/l-1; during intraperitoneal infusion: 18.4 +/- 1.4 mU/l-1, p less than 0.05). However, mean daily insulin requirements were not decreased (during subcutaneous infusion: 0.59 +/- 0.05 U/kg-1.day-1; during intraperitoneal infusion: 0.57 +/- 0.03 U/kg-1.min-1). Moreover, the diabetic patients had a consistently lower maximal capacity of glucose utilization (12.6 +/- 0.7 mg kg-1.min-1) than control subjects (p less than 0.01) without modification of the half-maximally effective insulin concentration (62 +/- 10 mU.l-1). In conclusion, the only benefit of intraperitoneal insulin infusion was a reduction of peripheral free insulin levels; this decrease of peripheral insulinaemia was not associated with an improvement in the insulin resistance of diabetic patients.     

Twice-daily compared with once-daily insulin glargine in people with Type 1 diabetes using meal-time insulin aspart.

AIM: To compare blood glucose control when using insulin glargine twice daily at breakfast- and dinner-times with insulin glargine once daily at dinner time, in unselected people with Type 1 diabetes using insulin aspart at meal-times. METHODS: In this 8-week, two-way, cross-over study, 20 people with Type 1 diabetes were randomized to insulin glargine injection once daily at dinner-time or twice daily at breakfast- and dinner-times, both plus meal-time insulin aspart. Each 4-week treatment period concluded with a 24-h inpatient metabolic profile. RESULTS: Insulin doses, HbA1c, fructosamine concentration and pre-breakfast self-monitored blood glucose (SMBG) concentration did not differ between treatment periods. SMBG concentrations after breakfast, after lunch and before dinner were lower with twice-daily compared with once-daily dinner-time glargine [9.3 +/- 0.5 (+/- se) vs. 6.7 +/- 0.5 mmol/l, P = 0.003; 10.2 +/- 0.9 vs. 7.0 +/- 0.9 mmol/l, P = 0.024; 9.6 +/- 0.5 vs. 6.6 +/- 0.5 mmol/l, P = 0.001]. Mean 24-h SMBG concentration was lower with twice-daily glargine (7.1 +/- 0.5 vs. 8.8 +/- 0.5 mmol/l, P = 0.031). Within-day variability of SMBG concentration was lower with twice-daily glargine (sd 3.2 +/- 0.2 vs. 4.0 +/- 0.3 mmol/l, P = 0.044). Plasma free insulin concentration was higher in the afternoon with twice-daily glargine (21.9 +/- 1.4 vs. 16.1 +/- 1.3 mU/l, P = 0.009), but lower overnight (12.1 +/- 1.7 vs. 17.8 +/- 1.7 mU/l, P = 0.030), compared with once-daily injection. Plasma glucose concentration overnight was higher with twice-daily compared with once-daily glargine (mean 9.0 +/- 0.4 vs. 6.6 +/- 0.4 mmol/l, P = 0.001). CONCLUSIONS: Blood glucose concentration rises in the late afternoon in association with falling plasma insulin levels towards the end of the 24-h period after insulin glargine injection in some people with Type 1 diabetes using once-daily glargine at dinner-time plus a rapid-acting insulin analogue at meal-times. This is prevented by twice-daily injection of insulin glargine.     

Increased plasma pancreatic polypeptide (PP) in diabetic ketoacidosis; normalization following treatment

As both hypoglycaemia and hyperglycaemia may modify plasma levels pancreatic polypeptide (PP), we measured plasma PP by a homologous radioimmunoassay in seven diabetics who were admitted to the hospital in overt diabetic ketoacidosis (initial blood glucose 27.1-55.0 mmol/l). None had circulating PP-antibodies. All were treated with continuous infusion of insulin and fluids. Before starting treatment, plasma PP ranged from 2585-136 mmol/l (mean 629 pmol/l). Following treatment plasma PP decreased gradually in all patients. The following morning mean plasma PP was 242 pmol/l, 67 pmol/l when one ureamic patient was excluded. The normal value is less than 100 pmol/l. This study shows that plasma PP is clearly elevated in diabetic ketoacidosis and decreases following treatment.     

Absence of exercise-induced hypoglycaemia in Type I (insulin-dependent) diabetic patients during maintenance of normoglycaemia by short-term,open-loop insulin infusion

Summary To assess the risk and possible mechanisms of hypoglycaemia during moderate exercise in Type I (insulin-dependent) diabetic patients receiving constant insulin infusion, five insulin-dependent male diabetic patients were exercised 18 h after their last meal and 30 h after their last injection of intermediate acting insulin. Intravenous insulin was initially delivered via a closed-loop infusion system programmed to lower mean blood glucose from 11.3 ± 1.8 to 4.8 ± 0.4 mmol/l over approximately 3.5 h. Blood glucose was then maintained at this level for 4 h. At this time, the closed-loop infusion was discontinued and replaced by an open-loop system. The average amount of insulin infused per min during the 4 h normoglycaemic closed-loop period was calculated and this amount was infused at a constant rate during both a 30 min period of exercise on a bicycle ergometer (approximately 65% maximum oxygen uptake) and a 30 min rest period which followed. Five nondiabetic males served as control subjects. Despite significantly higher free insulin concentrations (p < 0.05) and identical preexercise blood glucose concentrations, blood glucose rose during exercise only in the diabetic group (0.5 ± 0.2 mmol/l; p < 0.01). Changes in the serum concentrations of lactate, glycerol, glucagon, cortisol, non-esterified fatty acids and growth hormone were similar in the two groups and did not account for the increment of blood glucose in the diabetic patients. Beta-hydroxybutyrate concentrations were, however, higher in the diabetic patients at the onset of exercise (p < 0.01) and decreased significantly more than the control subjects during exercise. We conclude that exercise under these conditions in diabetic patients is not attended by hypoglycaemia.     

Hormonal and metabolic responses in brittle diabetic patients during feedback intravenous insulin infusion

Twenty-four hour profiles of blood hormones and intermediary metabolites were obtained in seven 'brittle' diabetic subjects during their usual insulin therapy and during feedback intravenous insulin infusion from an artificial pancreas (GCIIS). The results were compared to those in matched stable diabetics and normal controls. Although routine insulin doses were higher in the brittle group than in the stable group (164 +/- 32 (mean +/- SE) vs. 58 +/- 8 U/day, P less than 0.005) during routine therapy, plasma free insulin levels were equal (35 +/- 12 vs. 31 +/- 6 mU/l). In the brittle group feedback i.v. insulin infusion reduced daily requirements to normal levels (80 +/- 13 U/day, P less than 0.025; stable group 71 +/- 4 U/day, NS). On routine therapy blood glucose levels were not different in the two groups (brittle 10.5 +/- 1.6, stable 10.8 +/- 0.6 mmol/l) and were similarly corrected by the GCIIS (6.9 +/- 0.3 and 6.9 +/- 0.3 mmol/l, respectively). Blood lactate and pyruvate levels were markedly abnormal in the brittle group during routine therapy (lactate: brittle group 1.93 +/- 0.27 mmol/l, stable group 0.91 +/- 0.07 mmol/l, P less than 0.025), and this abnormality was not corrected by the GCIIS (1.75 +/- 0.32 and 0.88 +/- 0.08 mmol/l, P less than 0.005). Abnormalities were also found in profiles of blood alanine and glycerol, and serum cortisol. Blood ketone body levels did not differ between the two groups of patients. The results suggest a defect in insulin delivery from subcutaneous tissue into the plasma. These patients have a characteristic metabolic abnormality, unresponsive to short-term normoglycaemia, either as the result of long-term disturbance of diabetic control, or as a marker for the underlying hormonal or biochemical abnormality.     

THE EFFECT OF OXYTOCIN INFUSION ON ADENOHYPOPHYSIAL AND ADRENAL CORTICAL RESPONSES TO INSULIN-INDUCED HYPOGLYCAEMIA

The responses of plasma adrenocorticotrophin (ACTH), cortisol, growth hormone (GH) and prolactin to insulin-induced hypoglycaemia were studied in six lean male subjects (age 22-29 years). Intravenous insulin tests were performed with and without oxytocin infusion. Blood sugar nadir occurred at the onset of symptoms (time S) with no significant differences between oxytocin and saline infusion. During the oxytocin infusion mean plasma oxytocin increased from 1.9 pmol/l to 138 pmol/l. Peak increase in plasma ACTH (oxytocin 266 +/- 54 ng/l; saline 281 +/- 43 ng/l, mean +/- SEM) was at S + 10 min while peak plasma cortisol (oxytocin 680 +/- 47 nmol/l: saline 656 +/- 40 nmol/l) was measured at S +/- 60 min, peak GH (oxytocin 96 +/- 17.8 mU/l; saline 106 +/- 18.6 mU/l) at S + 60 min and prolactin (oxytocin 1332 +/- 239 mU/l; saline 1242 +/- 273 mU/l) at S + 30 min. There were no significant differences in plasma concentrations of ACTH, cortisol, GH or prolactin between saline and oxytocin infusion. The results indicate that oxytocin has no effect on plasma ACTH, cortisol, GH and prolactin responses to insulin-induced hypoglycaemia. In particular they fail to support previous studies which suggested an inhibitory role for oxytocin in ACTH secretion.     

Lack of glucagon response in glucose counter-regulation in Type 1 (insulin-dependent) diabetics: Absence of recovery after prolonged optimal insulin therapy

Summary Mild hypoglycaemia was induced using an artificial pancreas in five normal subjects (from 5.00 ±0.15 to 2.83±0.15 mmol/l) by infusing 28 mU/m² per min soluble insulin for 60 min. Six Type 1 (insulin-dependent) diabetic patients were stabilized for 14h using an artificial pancreas. They were then rendered hypoglycaemic (from 4.94±0.09 to 2.89±0.11 mmol/l) by infusing 28mU/m² per min plus 16 ±3.8mU/min insulin for 60 min. Before the study, the diabetic patients were in optimal blood glucose control (mean blood glucose 6.72±0.11 mmol/l over the previous 14–20 days; HbA₁ 8.3±0.1%). During the insulin infusion test, blood glucose decrement was slower in the diabetic patients than in the control subjects. The blood glucose nadir was delayed in the diabetics until 75 min compared with 55 min in the control subjects. Blood glucose recovery rate in the diabetic subjects was severely impaired. In Type 1 diabetes, the counter-regulatory hormonal response to insulin induced hypoglycaemia is similar to that of non-diabetics, except for that of glucagon, the blunted response of which is not reversed by prolonged optimisation of blood glucose control. This impaired response of the A cell does not seem to be a consequence of insulin deficiency.     

Effects of morning hypoglycemia on neuroendocrine and metabolic responses to subsequent afternoon hypoglycemia in normal man

There is general agreement that prior hypoglycemia blunts subsequent hypoglycemic counterregulatory responses. However, there is considerable debate concerning the timing and number of prior hypoglycemic episodes required to cause this blunting effect. The aim of this study was to determine whether one episode of hypoglycemia could modify neuroendocrine, metabolic, and symptom responses to hypoglycemia induced 2 h later. A total of 24 (12 male and 12 female) young, healthy, overnight-fasted subjects participated in a series of glucose clamp studies. A total of 16 individuals underwent 2 randomized studies of either identical 2-h morning and afternoon hyperinsulinemic (490 +/- 60 pmol/L) hypoglycemia (2.9 +/- 0.1 mmol/L) separated by 2 h or, at least 2 months later, 2-h morning and afternoon hyperinsulinemic (492 +/- 45 pmol/L) euglycemia (5.1 +/- 0.1 mmol/L). A total of 8 other subjects participated in a single experiment that consisted of 2-h morning hyperinsulinemic (516 +/- 60 pmol/L) euglycemia (5.1 +/- 0.1 mmol/L) and 2-h afternoon hyperinsulinemic (528 +/- 66 pmol/L) hypoglycemia (2.9 +/- 0.1 mmol/L) also separated by 2 h. Morning hypoglycemia significantly (P < 0.01) reduced (33-55%) the responses of epinephrine, norepinephrine, glucagon, GH, cortisol, and pancreatic polypeptide during afternoon hypoglycemia. Hypoglycemic symptoms (primarily neuroglycopenic) were also significantly (P < 0.01) reduced during afternoon hypoglycemia. Plasma glucose, insulin, nonesterified fatty acids, glycerol, lactate, beta-hydroxybutyrate (P < 0.01), GH, and cortisol (P < 0.05) levels were significantly increased at the start of afternoon hypoglycemia following morning hypoglycemia. Morning hypoglycemia created an insulin-resistant state during afternoon hypoglycemia. Despite blunted neuroendocrine responses, glucose infusion rates required to maintain hypoglycemia and increases in glucose oxidation were significantly attenuated during afternoon compared with morning hypoglycemia. This was in marked contrast to euglycemic control experiments where glucose infusion rates and nonoxidative glucose disposal were significantly increased during afternoon relative to morning studies. We conclude that in normal man one episode of prolonged, moderate, morning hypoglycemia can produce substantial blunting of neuroendocrine and symptomatic responses to subsequent near-term hypoglycemia, and the induction of posthypoglycemic insulin resistance can compensate for blunted neuroendocrine responses by limiting glucose flux and specifically glucose oxidation during subsequent near-term hypoglycemia.