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The aim of our study was to establish whether the well-known defective or absent secretion of glucagon in type 1 diabetes in response to hypoglycaemia is selective or includes lack of responses to other stimuli, such as amino acids. Responses of glucagon to hypoglycaemia were measured in eight patients with type 1 diabetes and six non-diabetic subjects during hyperinsulinaemic (insulin infusion 0.5 mU kg−1 min−1) and eu-, hypo- and hyperglycaemic clamp studies (sequential steps of plasma glucose 5.0, 2.9, 5.0, 10 mmol/l). Subjects were studied on three randomised occasions with infusion of low- or high-dose alanine, or saline. With saline, glucagon increased in hypoglycaemia in non-diabetic subjects but not in diabetic subjects. Glucagon increased further with low-dose (181 ± 16 ng l−1 min−1) and high-dose alanine (238 ± 20 ng l−1 min−1) in non-diabetic subjects, but only with high-dose alanine in diabetic subjects (area under curve 112 ± 5 ng l−1 min−1). The alanine-induced glucagon increase in diabetic subjects paralleled the spontaneous glucagon response to hypoglycaemia in non-diabetic subjects not receiving alanine. The greater responses of glucagon to hypoglycaemia with alanine infusion were offset by recovery of eu- or hyperglycaemia. In type 1 diabetes, the usually deficient responses of glucagon to hypoglycaemia may improve after increasing the concentration of plasma amino acids. Amino acid-enhanced secretion of glucagon in response to hypoglycaemia remains under physiological control since it is regulated primarily by the ambient plasma glucose concentration. These findings might be relevant to improving counter-regulatory defences against insulin-induced hypoglycaemia in type 1 diabetes. [ABSTRACT FROM AUTHOR]

The widespread availability and reliability of immunohistochemical techniques in the last three decades have allowed researchers to identify cells with common neuroendocrine markers in virtually every organ. As a whole, these neuroendocrine cells form the so-called diffuse neuroendocrine system. Tumours arising from the cells of the diffuse neuroendocrine system are defined as (neuro)endocrine tumours (NETs). NETs have been increasingly described in recent years. However, despite the increase in the number of published papers focused on NET, we still lack adequate epidemiological data, particularly for non-gastroenteropancreatic (GEP) NETs. Furthermore, the real incidence of neuroendocrine differentiation for most sites is not completely known and is probably underestimated. As a consequence, data on the clinical features of many NET subgroups are not well known or confusing. For all of these reasons, we have attempted to evaluate the epidemiology of non-GEP NETs, reviewing the limited data available in the literature. [ABSTRACT FROM AUTHOR]

Activating mutations of the BRAF gene are the most common genetic alterations in papillary thyroid carcinomas (PTCs) and the T1799A transversion, resulting in BRAFV600E, appeared virtually unique in this cancer type. Here, we report on the identification in a classic PTC of a novel BRAF mutation, namely a 1795GTT insertion, resulting in BRAFV599Ins, and describe its biochemical and molecular characterization. Kinase assays carried out on BRAFV599Ins and BRAFV600E revealed a three- to five-fold increase in the enzymatic activity of both mutants with respect to BRAFWT. Similarly, evaluation of BRAF-induced phosphorylation of MEK, MAPK and RSK revealed a significant MAPK cascade activation in cells expressing BRAFV599Ins or BRAFV600E, but not in cells expressing BRAFWT. Molecular dynamic simulations showed a destabilization of the inactive conformation of the enzyme in both BRAFV599Ins and BRAFV600E mutants, but not in BRAFWT. The analysis of the interaction energies inside the catalytic site allowed to demonstrate the presence of repulsive electrostatic forces acting on the activation loop and moving from inward to outward of the mutant enzymes. Finally, focus assays in NIH-3T3 cells confirmed a high transformation rate in the cells transfected either with BRAFV599Ins or BRAFV600E. In conclusion, this study demonstrated that BRAFV599Ins, as BRAFV600E, is a ‘gain of function’ mutation, characterized by a constitutive catalytic activation, which accounts for its causative role in the studied PTC.Oncogene (2006) 25, 4235–4240. doi:10.1038/sj.onc.1209448; published online 27 February 2006 [ABSTRACT FROM AUTHOR]

Objective: To establish the impact of different amounts of increased energy expenditure on type 2 diabetes care.Research Design and Methods: Post hoc analysis of long-term effects of different amounts of increased energy expenditure (metabolic equivalents [METS] per hour per week) through voluntary aerobic physical activity was performed in 179 type 2 diabetic subjects (age 62 +/- 1 years [mean +/- SE]) randomized to a physical activity counseling intervention. Subjects were followed for 2 years and divided into six groups based on their increments in METs per hour per week: group 0 (no activity, n = 28), group 1-10 (6.8 +/- 0.3, n = 27), group 11-20 (17.1 +/- 0.4, n = 31), group 21-30 (27.0 +/- 0.5, n = 27), group 31-40 (37.5 +/- 0.5, n = 32), and group >40 (58.3 +/- 1.8, n = 34).Results: At baseline, the six groups did not differ for energy expenditure, age, sex, diabetes duration, and all parameters measured. After 2 years, in group 0 and in group 1-10, no parameter changed; in groups 11-20, 21-30, 31-40, and >40, HbA(1c), blood pressure, total serum cholesterol, triglycerides, and estimated percent of 10-year coronary heart disease risk improved (P < 0.05). In group 21-30, 31-40, and >40, body weight, waist circumference, heart rate, fasting plasma glucose, serum LDL and HDL cholesterol also improved (P < 0.05). METs per hour per week correlated positively with changes of HDL cholesterol and negatively with those of other parameters (P < 0.001). After 2 years, per capita yearly costs of medications increased (P = 0.008) by USD393 in group 0, did not significantly change in group 1-10 (USD 206, P = 0.09), and decreased in group 11-20 (USD -196, P = 0.01), group 21-30 (USD -593, P = 0.009), group 31-40 (USD -660, P = 0.003), and group >40 (USD -579, P = 0.001).Conclusions: Energy expenditure >10 METs . h(-1) . week(-1) obtained through aerobic leisure time physical activity is sufficient to achieve health and financial advantages, but full benefits are achieved with energy expenditure >20 METs . h(-1) . week(-1). [ABSTRACT FROM AUTHOR]

SummaryAims Little information is available on the relationship betweeen glycated haemoglobin levels and the source or amount of dietary carbohydrate. The present study compares the association of carbohydrate intake with HbA1c between European individuals with Type 1 diabetes mellitus injecting insulin once or twice per day and those with ≥ 3 daily injections. Methods The relation of carbohydrate intake (total, cereal, fruit, vegetable, milk, and potato carbohydrate assessed by a 3-day dietary record) to HbA1c was examined in 2084 patients (age 32.6 ± 10.2 years, duration of diabetes 14.8 ± 9.5 years) included in the EURODIAB Complications Study. Results In both insulin injection regimens, an increased intake of total carbohydrate (% of energy) and a higher consumption of potato carbohydrates (g) were associated with higher levels of HbA1c, whereas an increased intake of vegetable carbohydrate (g) was inversely related to HbA1c. These tendencies were all more pronounced in persons with one or two daily insulin injections. Consumption of cereal and fruit carbohydrates (g) was not related to HbA1c, irrespective of the insulin injection regimen. A trend of HbA1c to increase with higher intakes of milk carbohydrate was confined to those with one or two insulin injections per day (test for interaction: P = 0.01). Conclusions In particular, subjects with only 1 or 2 daily insulin injections per day should receive specific advice to correctly consider milk and potato carbohydrates. On the other hand, people with Type 1 diabetes may profit from a higher consumption of vegetable carbohydrates for their levels of HbA1c. [ABSTRACT FROM AUTHOR]

Summary Aims The aim of the study was to evaluate the efficacy and safety of acarbose in patients with Type 1 diabetes mellitus (DM). Methods A multicentre double-blind, randomized, placebo-controlled study was performed. After a 6-week run-in, 121 patients were randomized to acarbose or placebo and to high- or low-fibre diet for 24 weeks. Acarbose dose was 50 mg t.d.s. for the first 2 weeks and 100 mg t.d.s. for the subsequent weeks. Results At the end of 24 weeks of treatment the intention to treat analysis showed that acarbose compared with placebo decreased 2 h postprandial plasma glucose levels (12.23 ± 0.83 vs. 14.93 ± 0.87 mmol/l; F = 6.1, P < 0.02) (least square means ± sem). No significant effect of acarbose was recorded on HbA1c or on the number of hypoglycaemic episodes. The effect of acarbose on blood glucose control was not influenced by the amount of carbohydrate and/or fibre intake. The incidence of adverse events were 75% and 39% in acarbose and placebo groups, respectively; they were mild and confined to the gastrointestinal tract. Conclusions The use of acarbose in combination with insulin reduces postprandial plasma glucose levels in Type 1 diabetic patients who are not satisfactorily controlled with insulin alone but without significant effect on HbA1c. Diabet. Med. 16, 228–232 (1999). [ABSTRACT FROM AUTHOR]

3H-DHT binding was examined in cultured skin fibroblasts from a patient with complete testicular feminisation (CTF), from his heterozygote mother, and his clinically normal sister, who menstruated normally. Binding parameters were: Bmax less than 1 fmol/mg protein and KD unmeasurable in CTF; Bmax = 24 fmol/mg protein and KD = 3.63 X 10(-9) mol/l in the mother; and Bmax = 46 fmol/mg protein and KD = 3.7 X 10(-9) mol/l in the sister. Five cultures obtained from genital and non-genital skin of normal male and female subjects were used as controls, in which Bmax ranged from 37 to 62 fmol/mg and KD from 2.0 to 3.6 X 10(-9) mol/l. The considerable reduction of Bmax in the obligate heterozygote and the normal binding capacity in the sister, a probable heterozygote, suggests that it may be possible to use the DHT-receptor assay to identify carriers in families with androgen resistance. [ABSTRACT FROM PUBLISHER]

Proteinuria and nephropathy have been found to cluster in families of non-insulin-dependent diabetic (NIDDM) Pima Indian, and in Caucasian insulin-dependent diabetic (IDDM) patients. No information is at present available for Caucasian NIDDM patients. The aim of the present study was to determine whether micro-macroalbuminuria (AER + ) is associated with albumin excretion rate abnormalities in diabetic and non-diabetic siblings of probands with NIDDM and AER + . We identified 169 Caucasian families with one NIDDM proband (the patient with longest known NIDDM duration) (101 families with only NIDDM siblings, 33 families with both NIDDM and non-NIDDM siblings and 35 families with only non-NIDDM siblings). Of the probands 56 had AER + [Prob-NIDDM-(AER + )], 78 had AER– [Prob-NIDDM-(AER–)], 74 siblings of Prob-NIDDM-(AER + ), and 113 siblings of Prob-NIDDM-(AER–) also had NIDDM. Data on albuminuria and retinopathy from multiple sibling pairs when the size of the sibship was more than two was adjusted according to a weighting factor. The odds ratio for AER + , in siblings of Prob-NIDDM-(AER + ) adjusted for age, hypertension, glycated haemoglobin A1 c and other confounding variables was 3.94 (95 % confidence intervals: 1.93–9.01) as compared to siblings of Prob-NIDDM-(AER–). The 74 siblings of Prob-NIDDM-(AER + ) had higher prevalence of proliferative retinopathy than siblings of Prob-NIDDM-(AER–) (14 vs 2 %; p < 0.01). We also identified 66 non-diabetic siblings of 41 NIDDM probands with AER + and 36 non-diabetic siblings of 27 NIDDM probands with AER–. Albumin excretion was two times higher, although still within the normal range, in the non-diabetic siblings of Prob-NIDDM-(AER + ) than in siblings of Prob-NIDDM-(AER–) [median = 13.5 (range 0.5–148) vs 6.6 (range 1–17) μg/min ( p < 0.05)]. In conclusion higher rates of albumin excretion aggregate in Caucasian families with NIDDM. Proliferative retinopathy is more frequently observed in families showing a clustering of AER + and NIDDM. These findings suggest that familial factors play a role in the pathogenesis of renal and retinal complications in NIDDM. [Diabetologia (1997) 40: 816–823] [ABSTRACT FROM AUTHOR]

We investigated cardiovascular function and plasma catecholamine response during incremental exercise and recovery in diabetic patients with (DAN+) and without autonomic neuropathy (DAN−). The former group was divided according to the presence of parasympathetic (DAN+PH−) or associated parasympathetic and sympathetic (DAN+PH+) damage to the autonomic nervous system. A group of healthy volunteers was studied as a control group. All the patients and control subjects underwent a submaximal or symptom-limited incremental exercise test using a cycle-ergometer. Air flow and respiratory gas fractions were sampled at the level of the mouth allowing a breath-by-breath analysis of oxygen consumption (VO). Heart rate and systolic blood pressure were recorded and venous blood samples were obtained from the patients at rest and during each minute of exercise and recovery to measure norepinephrine and epinephrine plasma levels. Haemodynamic parameters and plasma catecholamines were computed at rest and at 25, 50, 75 and 100% of the peak VO (VO). The breath-by-breath relationships among VO, heart rate and VO/heart rate against work were assessed during exercise for patients and control subjects. While VO in absolute values was not significantly different among the diabetic groups, VO was much less in diabetic patients than in control subjects ( p<0.01). During exercise the rate of heart rate, systolic blood pressure, norepinephrine and epinephrine increase was different among the diabetic groups, being significantly blunted in DAN+PH+. The VO/work relationship of the three diabetic groups was similar but markedly reduced in respect to that of control subjects ( p<0.001). The relationship between oxygen pulse (VO/heart rate) and work showed no differences among the diabetic groups, whereas its slope was significantly steeper in control subjects ( p<0.01 vs DAN−; p<0.05 vs DAN+PH− and DAN+PH+). In conclusion during incremental exercise both DAN+PH− and DAN+PH+ exhibit abnormal heart rate, systolic blood pressure and catecholamine responses which, however, appear clearly distinct between the two groups of DAN+. In DAN+ the VO increment is reduced during exercise. Since DAN−show the same impairment, this particular finding seems most likely to be influenced by factors (i.e.: diabetic cardiomyopathy) other than overt autonomic neuropathy. [ABSTRACT FROM AUTHOR]

Hypoglycaemia unawareness, is a major risk factor for severe hypoglycaemia and a contraindication to the therapeutic goal of near-normoglycaemia in IDDM. We tested two hypotheses, first, that hypoglycaemia unawareness is reversible as long as hypoglycaemia is meticulously prevented by careful intensive insulin therapy in patients with short and long IDDM duration, and that such a result can be maintained long-term. Second, that intensive insulin therapy which strictly prevents hypoglycaemia, can maintain long-term near-normoglycaemia. We studied 21 IDDM patients with hypoglycaemia unawareness and frequent mild/severe hypoglycaemia episodes while on 'conventional' insulin therapy, and 20 nondiabetic control subjects. Neuroendocrine and symptom responses, and deterioration in cognitive function were assessed in a stepped hypoglycaemia clamp before, and again after 2 weeks, 3 months and 1 year of either intensive insulin therapy which meticulously prevented hypoglycaemia (based on physiologic insulin replacement and continuous education, experimental group, EXP, n=16), or maintenance of the original 'conventional' therapy (control group, CON, n=5). At entry to the study, all 21 IDDM-patients had subnormal neuroendocrine and symptom responses, and less deterioration of cognitive function during hypoglycaemia. After intensive insulin therapy in EXP, the frequency of hypoglycaemia decreased from 0.5±0.05 to 0.045±0.02 episodes/patient-day; HbA increased from 5.83±0.18 to 6.94±0.13% (range in non-diabetic subjects 3.8-5.5%) over a 1-year period; all counterregulatory hormone and symptom responses to hypoglycaemia improved between 2 weeks and 3 months, with the exception of glucagon which improved at 1 year; and cognitive function deteriorated further as early as 2 weeks ( p<0.05). The improvement in responses was maintained at 1 year. The improvement in plasma adrenaline and symptom responses inversely correlated with IDDM duration. In contrast, in CON, neither frequency of hypoglycaemia, nor neuroendocrine responses to hypoglycaemia improved. Thus, meticulous prevention of hypoglycaemia by intensive insulin therapy reverses hypoglycaemia unawareness even in patients with long-term IDDM, and is compatible with long-term near-normoglycaemia. Because carefully conducted intensive insulin therapy reduces, not increases the frequency of moderate/severe hypoglycaemia, intensive insulin therapy should be extended to the majority of IDDM patients in whom it is desirable to prevent/delay the onset/progression of microvascular complications. [ABSTRACT FROM AUTHOR]

The diagnostic specificity of recombinant 21-hydroxylase autoantibodies (21OH-Ab) for Addison's disease was tested in adult patients with either Graves" disease (GD), insulin-dependent diabetes mellitus (IDDM), or polyendocrinopathy, as well as in healthy controls. Using a radiobinding assay with in vitro translated recombinant human 21-hydroxylase, we found 21OH-Ab in 24/28 (86%) idiopathic Addison patients, and using an immunofluorescence assay we found adrenal cortex autoantibodies (ACA) in 12/28 (43%) patients (P = 0.002). All the 12 ACA-positive sera were also positive for 21OHAb and ACA were found in 11/15 (73%) patients with less than 15 years and in 1/13 (8%) patients with 15-38 years of disease duration (P = 0.002). 21OH-Ab were present in 3/92 (3%) patients with GD. in 1/180 (0.6%) with IDDM and in 0/106 healthy subjects. The 2IOH-Ab-positive GD and IDDM patients were also positive for ACA. None of 17 patients with polyendocrinopathy, but without Addison's disease, had 2IOH-Ab. None of the 180 Belgian IDDM patients had Addison's disease or developed an adrenal insufficiency at follow up. In two out of three Graves patients, the presence of 21OH-Ab was associated with clinical and biochemical signs of adrenal insufficiency. Of the 89 21OH-Ab-negative patients with GD none had Addison's disease at the time of blood sampling, and 79 were followed up for 5.6-7.5 years and none developed clinical signs of adrenal insufficiency. We conclude that the presence of 21OH-Ab in patients with endocrine autoimmune diseases is highly, specific for Addison's disease. [ABSTRACT FROM AUTHOR]

The effects of glimepiride, the newest sulphonylureic compound, on pancreatic insulin and glucagon secretion were studied using the classical, isolated, perfused rat pancreas model. The influence of four different environmental glucose conditions (during a glycaemic stimulus with glucose increasing from 5 to 8.33 mM and at stable 0, 5 and 2.22 mM glucose levels) on the effects of glimepiride was also assessed. At a pharmacological concentration glimepiride strongly stimulated beta-cell activity, producing a characteristic biphasic insulin release with a sharp first-phase secretory peak, followed by a prolonged and sustained second phase. Environmental glucose concentrations markedly influenced the extent, but not the pattern of glimepiride-induced insulin secretion, as hormone release dropped significantly when the glucose level was reduced. Glimepiride failed to influence alpha-cell activity at any of the environmental glycaemic levels. [ABSTRACT FROM AUTHOR]

To discriminate between true secondary failure (TF) and pseudo-secondary failure (PF) to oral hypoglycaemic agents, we studied 34 non-obese non-insulin-dependent diabetic patients who were being treated with these drugs. Nine were in good control (GC) with oral treatment, while 25 showed apparent SF. During a controlled hospital diet, fasting blood glucose remained persistently high in 15 of these patients (TF), while in the other 10 patients it clearly improved (PF). Fasting plasma glucose (FPG) and HbA were higher and body mass index (BMI) was lower in TF patients than in PF patients ( P<0.01). C-peptide concentrations differed significantly among the three groups both in the fasting state (TF 0.25±0.02 nmol/l, PF 0.70±0.03 nmol/l, GC 0.74±0.03 nmol/l; P<0.0001) and 6 min after glucagon injection (TF 0.50±0.04 nmol/l, PF 1.02±0.06 nmol/l, GC 1.14±0.07 nmol/l; P<0.0001). C-peptide and plasma insulin curves obtained after a standard mixed meal also showed significant differences ( P<0.001). In particular, there was a statistically significant difference between GC and PF versus TF ( P<0.05), while there was no statistical difference between PF and GC. We conclude that some patients with apparent SF can improve their metabolic control if they strictly adhere to a correct diet (PF); a single measurement of basal C-peptide concentration or examination of the C-peptide and insulin responses to a meal are useful indicators for distinguishing patients with PF from those with TF to oral hypoglycaemic agents. Lower BMI and higher fasting plasma glucose and HbA are additional and simple indicators of TF. [ABSTRACT FROM AUTHOR]

To assess the effects of ACE-inhibition on insulin action in Type 2 (non-insulin-dependent) diabetes mellitus associated with essential hypertension, 12 patients with Type 2 diabetes (on diet and oral hypoglycaemic agents) and arterial hypertension were examined on two occasions, in a single blind, cross-over study, after two days of treatment with either captopril or a placebo. The study consisted of a euglycaemic-hyperinsulinaemic clamp (two sequential steps of insulin infusion at the rates of 0.25 mU·kg·min and 1 mU·kg·min, 2 h each step), combined with an infusion of 3-H-glucose to measure the rate of hepatic glucose production and that of peripheral glucose utilization. The results show that blood pressure was lower after captopril (sitting, systolic 148±5 mmHg, diastolic 89±2 mm Hg) compared to placebo (155±6 and 94±2 mm Hg) ( p<0.05). Captopril treatment resulted in a more suppressed hepatic glucose production (2.7±0.4 vs 4.94±0.55 μmol·kg·min), and a lower plasma non-esterified fatty acid concentration (0.143±0.05 vs 0.200±0.05 mmol/l) (captopril vs placebo, p<0.05) at the end of the first step of insulin infusion (estimated portal plasma insulin concentration 305±28 pmol/l); and in a greater glucose utilization (36.5±5.1 vs 28±3.6μmol·kg·min, p<0.001) at the end of the second step of insulin infusion (arterial plasma insulin concentration of 604±33 pmol/l). We conclude that captopril improved insulin sensitivity in Type 2 diabetes associated with hypertension at the level of the liver and extrahepatic tissues, primarily muscle and adipose tissue. Thus, in contrast to other antihypertensive drugs such as diuretics and beta-blockers which may have a detrimental effect on insulin action, ACE-inhibitors appear to improve insulin action in Type 2 diabetes and essential hypertension, at least on a short-term basis. [ABSTRACT FROM AUTHOR]

In 114 subjects with Type 1 (insulin-dependent) diabetes mellitus the nocturnal insulin requirements to maintain euglycaemia were assessed by means of i. v. insulin infusion by a Harvard pump. The insulin requirements decreased after midnight to a nadir of 0.102±0.03 mU·kg·min at 02.40 hours. Thereafter, the insulin requirements increased to a peak of 0.135±0.06mU·kg·min at 06.40 hours ( p<0.05). The dawn phenomenon (increase in insulin requirements by more than 20% after 02.40 hours lasting for at least 90 min) was present in 101 out of the 114 diabetic subjects, and its magnitude (% increase in insulin requirements between 05.00-07.00 hours vs that between 01.00-03.00 hours) was 19.4±0.54% and correlated inversely with the duration of diabetes ( r = −0.72, p<0.001), but not with age. The nocturnal insulin requirements and the dawn phenomenon were highly reproducible on three separate nights. In addition, glycaemic control, state of counterregulation to hypoglycaemia and insulin sensitivity all influenced the magnitude of the dawn phenomenon as follows. In a subgroup of 84 subjects with Type 1 diabetes, the multiple correlation analysis showed that not only duration of diabetes ( t = −9.76, p<0.0001), but also % HbA significantly influenced the magnitude of the dawn phenomenon ( t = 2.03, p<0.05). After 5-9 months of intensive therapy, the magnitude of the dawn phenomenon decreased from 24+-2% to 18±2% ( p<0.05) in seven Type 1 diabetic subjects with initially poor glycaemic control, whereas it increased from 17±2% to 24±3% ( p<0.05) in five Type 1 diabetic subjects in whom glycaemic control had deteriorated for 2 weeks. In 18 Type 1 diabetic subjects the magnitude of the dawn phenomenon correlated with the indices of adequate glucose counterregulation, namely plasma glucose concentration at the hypoglycaemic nadir ( r = −0.79) and the rate of plasma glucose recovery from hypoglycaemia ( r = −0.74) (both p<0.01). Finally, in 10 diabetic subjects in whom insulin sensitivity was examined by the euglycaemic glucose clamp technique, there was a correlation between the residual rate of hepatic glucose production ( r = 0.78, p<0.005) as well as between the rate of peripheral glucose utilization and the magnitude of the dawn phenomenon ( r = −0.70, p<0.025). In conclusion, the dawn phenomenon is a very frequent event in Type 1 diabetes; its magnitude (∼20%) is much lower than that indicated by previous Biostator studies; it is highly reproducible from day to day; it is influenced by the duration of diabetes, glycaemic control, state of the counterregulation system to hypoglycaemia and insulin sensitivity. [ABSTRACT FROM AUTHOR]

The aim of the present studies was to test the hypothesis that the dawn phenomenon in Type 1 (insulin-de-pendent) diabetes mellitus is due to a decrease in insulin sensitivity caused by nocturnal spikes of growth hormone. Twelve subjects with Type 1 diabetes were studied on two different occasions, from 24.00 to 02.00 hours, and from 06.00 to 08.00 hours with the euglycaemic clamp technique at two plasma free insulin levels (≈25 mU/l, n=7; ≈80 mU/l, n=5). To eliminate the confounding factor of insulin waning of previous Biostator studies, prior to clamp experiments the diabetic subjects were infused with i.v. insulin by means of a syringe pump according to their minute-to-minute insulin requirements. Insulin sensitivity decreased at dawn as compared to the early night hours (≈30% increase in the rate of hepatic glucose production, ≈25% decrease in the rate of peripheral glucose utilisation). Plasma insulin clearance did not change overnight. In seven Type 1 diabetic subjects, suppression of nocturnal spikes of growth hormone secretion by somatostatin during basal glucagon and growth hormone replacement resulted in complete abolition of the increased rate of hepatic glucose production at dawn. Replacement of nocturnal spikes of growth hormone faithfully reproduced the increase in hepatic glucose production at dawn of the control study. It is concluded that the dawn phenomenon in Type 1 diabetes mellitus examined during optimal insulin replacement, first, is due solely to a decrease in insulin sensitivity and not to an increase in insulin clearance; second, that the decrease in insulin sensitivity at dawn takes place both in the liver and peripheral tissues; third, that the decrease in hepatic (and most likely extrahepatic) insulin sensitivity at dawn is caused by nocturnal spikes of growth hormone secretion. [ABSTRACT FROM AUTHOR]

These studies were undertaken to assess the influence of storage temperature of insulin vials on pharmacokinetics and pharmacodynamics of a mixture of lente insulin (Monotard HM) and regular insulin (Actrapid HM) injected subcutaneously. Seven subjects with Type 1 (insulin-dependent) diabetes mellitus were studied twice after overnight normalization of plasma glucose. A mixture of lente insulin (0.22 U/kg) and regular insulin (0.11 U/kg) was prepared from insulin vials kept either refrigerated (∼4 °C) or at room temperature (∼18 °C) and injected subcutaneoulsy (abdomen). Euglycaemia was maintained for the following 16 h by glucose infusion at variable rate. With refrigerated insulin, the plasma free insulin peak was greater (53±5 versus 45±6 mU/l) and occurred earlier (2.5±0.2 versus 6±0.3 h), and the glucose infusion rate showed a greater (16.5±1.2 versus 14.5±0.9 μmol·kg·min) and earlier peak (3.2±0.2 versus 6±0.4 h) as compared to that occurring with the non-refrigerated insulin ( p<0.05). However, 6 h after insulin injection, both plasma free insulin and glucose infusion rate were 30% lower with the mixture of refrigerated as compared to that of non-refrigerated insulin ( p<0.05). In contrast, when NPH-insulin (Protaphane HM) was mixed with regular insulin and injected in 4 out of the 7 diabetic patients, the storage temperature of insulin vials had no effect on the pharmacokinetics and pharmacodynamics of the mixture. Thus, the storage temperature of insulin vials profoundly influences the effects of the mixture lente/regular insulin, but does not affect the pharmacokinetics and pharmacodynamics of the mixture NPH/regular insulin. [ABSTRACT FROM AUTHOR]

Hyperglycaemia may enhance insulin resistance typical of non-insulin dependent diabetes mellitus, as well as insulin dependent diabetes mellitus, and thus initiate a vicious pathogenetic cycle. We sought to test the hypothesis that reduction in chronic hyperglycaemia in the diabetic dog by methods that do not employ insulin may improve insulin resistance. We used the glucuretic agent phlorizin in dogs rendered chronically hyperglycaemic and diabetic by alloxan treatment. To analyse glucose disposition the euglycaemic clamp was performed. To minimize the role of counterregulatory influences that might be at play when glucose is reduced, the hyperglycaemic clamp with continuous somatostatin infusion was performed. Although phlorizin normalised plasma glucose in the diabetic dog and reduced plasma glucose in normal, non-diabetic dogs, insulin dependent glucose disposition rate did not improve. While phlorizin itself was associated with insulin resistance in the normal animals, the insulin resistance of diabetes mellitus was not further augmented. We conclude that phlorizin is associated with insulin resistance perhaps by a common pathway shared by chronic hyperglycaemia. Care must be taken when phlorizin is used as an agent to study glucose disposition. [ABSTRACT FROM AUTHOR]

In order to assess whether the metabolic clearance of insulin changes overnight, 11 patients with Type 1 (insulin-dependent) diabetes and low insulin antibody titre, and 6 nondiabetic subjects were studied. In these studies insulin was always infused by a Harvard pump. Initially, the nocturnal insulin requirements were assessed in the diabetic patients by an overnight feedback insulin infusion to maintain euglycaemia. The insulin requirements decreased continuously after midnight to a nadir of 0.115 ± 0.014 mU · kg1 · min at 04.30 hours, but after 05.00 hours the insulin requirements increased nearly 40 percent to a maximum of 0.16 ±0.012 mU · kg · min at 07.00 hours. To assess whether plasma insulin clearance changes overnight, the diabetic patients were studied on two different occasions, from 22.00-02.30 hours and from 04.00-08.30 hours. During each of these two studies insulin was infused in sequential steps of 90 min each at the rate of 0.13, 0.40 and 0.20 mU · kg · min. Despite changes in plasma free insulin concentration, the metabolic clearance of insulin in the interval 22.00-02.30 hours (12.6±0.17 ml · kg · min) was no different from that of the interval 04.00-08.30 hours (12.5 ± 0.19 ml · kg · min). The nondiabetic subjects were studied on two different occasions to assess whether the metabolic clearance of insulin changes overnight. Somatostatin (0.25 mg/h) and insulin (0.3 mU kg · min) were infused from 22.00-02.30 hours on one occasion, and from 04.00-08.30 hours on the other. The metabolic clearance of plasma free insulin in the interval 22.00-02.30 hours was no different from that of the interval 04.00-08.30 hours (12.6 ± 0.20 vs 12.9 ± 0.25 ml · kg · min nor was it different from that of the diabetic patients. It is concluded that, first, the metabolic clearance rate of insulin does not change overnight either in diabetic or in nondiabetic subjects; second, that it is independent of plasma insulin concentration; and third, that its value is comparable in nondiabetic subjects and in diabetic patients with a low titre of insulin antibodies. Thus, changes in insulin sensitivity rather than changes in insulin clearance are implicated in the pathogenesis of the dawn phenomenon. [ABSTRACT FROM AUTHOR]

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/m 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/m 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; HbA 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. [ABSTRACT FROM AUTHOR]

In order to verify whether or not insulininduced blood glucose control can acutely lower glycosylated haemoglobin levels, HbA (HbAI) was measured in 11 diabetics before, during and after 3 days of treatment with an 'artificial endocrine pancreas' (Biostator). Initially 5 patients were in fair glycaemic control (group A), while the other 6 showed poor control (group B). HbAI levels decreased significantly after 3 days in both groups A (from 9.6 ± 0.2% to 8.5 ± 0.3%, mean ± SEM, p < 0.05) and B (from 13.7 ± 0.2% to 12.6 ± 0.3%, p < 0.05). A further HbAI decrease was observed until day 60 following Biostator treatment, during which period glycaemic control inproved, as assessed by fasting and post-lunch plasma glucose values and daily glycosuria determined every 10 days. These results suggest that increased HbAI levels may be reversed early by strict blood glucose control during a 3 day period. It is concluded that HbAI levels not only reflect long-term glycaemic control, but also recent acute variations in mean blood glucose values. [ABSTRACT FROM AUTHOR]

We have determined the stable (irreversibly glycosylated) fraction of haemoglobin A (HbA) on Bio-Rex 70 after incubation of red blood cells in 0.9% saline solution for 6 h at 37 °C. The total (reversibly + irreversibly glycosylated fractions) HbA was determined before each incubation. Labile (reversibly glycosylated) tHbA represented the difference between total and stable HbA fractions. Total and stable HbA fractions were determined during insulin- or meal-induced blood glucose fluctuations in 24 insulin-dependent diabetics and in seven subjects with impaired glucose tolerance. In the diabetics, the maxmial fluctuation of total HbA was 1.47% over 2-12 h, while the simultaneous plasma glucose variation was 21.5 mmol/1. The stable HbA fraction did not change significantly. In diabetics the differences between the maximal and minimal values of plasma glucose and total HbA were significantly correlated. Plasma glucose correlated with simultaneously determined total and labile HbA fractions, but not with stable HbA In subjects with impaired glucose tolerance, similar changes in total but not in stable HbA were observed during an oral glucose tolerance test. We conclude that, although rapid changes in chromatographically determined HbA are relatively small, the determination of stable HbA should be performed to circumvent this problem and to ensure a more accurate index of blood glucose control. [ABSTRACT FROM AUTHOR]