Adrenergic mechanisms contribute to the late phase of hypoglycemic glucose counterregulation in humans by stimulating lipolysis

Diurnal Cycling of Insulin Sensitivity in Type 2 Diabetes: Evidence for Deviation From Physiology at an Early Stage

The aim of this study was to establish the contribution of insulin resistance to the morning (a.m.) versus afternoon (p.m.) lower glucose tolerance of people with type 2 diabetes (T2D). Eleven subjects with T2D (mean [SD] diabetes duration 0.79 [0.23] years, BMI 28.3 [1.8] kg/m2, A1C 6.6% [0.26%] [48.9 (2.9) mmol/mol]), treatment lifestyle modification only) and 11 matched control subjects without diabetes were monitored between 5:00 and 8:00 a.m. and p.m. (in random order) on one occasion (study 1), and on a subsequent occasion, they underwent an isoglycemic clamp (a.m. and p.m., both between 5:00 and 8:00, insulin infusion rate 10 mU/m2/min) (study 2). In study 1, plasma glucose, insulin, C-peptide, and glucagon were higher and insulin clearance lower in subjects with T2D a.m. versus p.m. and versus control subjects (P < 0.05), whereas free fatty acid, glycerol, and β-hydroxybutyrate were lower a.m. versus p.m. However, in study 2 at identical hyperinsulinemia a.m. and p.m. (∼150 pmol/L), glucose Ra and glycerol Ra were both less suppressed a.m. versus p.m. (P < 0.05) in subjects with T2D. In contrast, in control subjects, glucose Ra was more suppressed a.m. versus p.m. Leucine turnover was no different a.m. versus p.m. In conclusion, in subjects with T2D, insulin sensitivity for glucose (liver) and lipid metabolism has diurnal cycles (nadir a.m.) opposite that of control subjects without diabetes already at an early stage, suggesting a marker of T2D.

ARTICLE HIGHLIGHTS

In people with type 2 diabetes (T2D), fasting hyperglycemia is greater in the morning (a.m.) versus the afternoon (p.m.), and insulin sensitivity for glucose and lipid metabolism is lower a.m. versus p.m. This pattern is the reverse of the physiological diurnal cycle of people without diabetes who are more insulin sensitive a.m. versus p.m. These new findings have been observed in the present study in people without obesity but with recent-onset T2D, with good glycemic control, and in the absence of confounding pharmacological treatment. It is likely that the findings represent a specific marker of T2D, possibly present even in prediabetes before biochemical and clinical manifestations.

Pharmacokinetic and Pharmacodynamic Head-to-Head Comparison of Clinical, Equivalent Doses of Insulin Glargine 300 units · mL-1 and Insulin Degludec 100 units · mL-1 in Type 1 Diabetes

OBJECTIVE

To prove equivalence of individual, clinically titrated basal insulin doses of glargine 300 units ⋅ mL^-1 (Gla-300) and degludec 100 units ⋅ mL^-1 (Deg-100) under steady state conditions in a single-blind, randomized, crossover study, on the glucose pharmacodynamics (PD) in people with type 1 diabetes (T1D).

RESEARCH DESIGN AND METHODS

Subjects with T1D (N = 22, 11 men, age 44.3 ± 12.4 years, disease duration 25.5 ± 11.7 years, A1C 7.07 ± 0.63% [53.7 ± 6.9 mmol ⋅ mL^-1], BMI 22.5 ± 2.7 kg · m^-2), naïve to Gla-300 and Deg-100, underwent 24-h euglycemic clamps with individual clinical doses of Gla-300 (0.34 ± 0.08 units ⋅ kg^-1) and Deg-100 (0.26 ± 0.06 units ⋅ kg^-1), dosing at 2000 h, after 3 months of optimal titration of basal (and bolus) insulin.

RESULTS

At the end of 3 months, Gla-300 and Deg-100 reduced slightly and, similarly, A1C versus baseline. Clamp average plasma glucose (0-24 h) was euglycemic with both insulins. The area under curve of glucose infused (AUC-GIR_{[0-24 h]}) was equivalent for the two insulins (ratio 1.04, 90% CI 0.91-1.18). Suppression of endogenous glucose production, free fatty acids, glycerol, and β-hydroxybutyrate was 9%, 14%, 14%, and 18% greater, respectively, with Gla-300 compared with Deg-100 during the first 12 h, while glucagon suppression was no different. Relative within-day PD variability was 23% lower with Gla-300 versus Deg-100 (ratio 0.77, 90% CI 0.63-0.92).

CONCLUSIONS

In T1D, individualized, clinically titrated doses of Gla-300 and Deg-100 at steady state result in similar glycemic control and PD equivalence during euglycemic clamps. Clinical doses of Gla-300 compared with Deg-100 are higher and associated with quite similar even 24-h distribution of PD and antilipolytic effects.

Metabolomic, hormonal and physiological responses to hypoglycemia versus euglycemia during exercise in adults with type 1 diabetes

INTRODUCTION

This study sought to compare the metabolomic, hormonal and physiological responses to hypoglycemia versus euglycemia during exercise in adults with type 1 diabetes (T1D).

RESEARCH DESIGN AND METHODS

Thirteen individuals with T1D (hemoglobin; 7.0%±1.3% (52.6±13.9 mmol/mol), age; 36±15 years, duration diabetes; 15±12 years) performed a maximum of 45 min submaximal exercise (60%±6% V̇O_2max). Retrospectively identified exercise sessions that ended in hypoglycemia ((HypoEx) blood glucose (BG)≤3.9 mmol/L) were compared against a participant-matched euglycemic condition ((EuEx) BG≥4.0, BG≤10.0 mmol/L). Samples were compared for detailed physiological and hormonal parameters as well as metabolically profiled via large scale targeted ultra-high-performance liquid chromatography coupled to tandem mass spectrometry. Data were assessed using univariate and multivariate analysis techniques with false discovery rate adjustment. Significant results were considered at p≤0.05.

RESULTS

Cardiorespiratory and counterregulatory hormone responses, whole-body fuel use and perception of fatigue during exercise were similar under conditions of hypoglycemia and euglycemia (BG 3.5±0.3 vs 5.8±1.1 mmol/L, respectively p<0.001). HypoEx was associated with greater adenosine salvage pathway activity (5'-methylthioadenosine, p=0.023 and higher cysteine and methionine metabolism), increased utilization of glucogenic amino acids (glutamine, p=0.021, alanine, aspartate and glutamate metabolism and homoserine/threonine, p=0.045) and evidence of enhanced β-oxidation (lower carnitine p<0.001, higher long-chain acylcarnitines).

CONCLUSIONS

Exposure to acute hypoglycemia during exercise potentiates alterations in subclinical indices of metabolic stress at the level of the metabolome. However, the physiological responses induced by dynamic physical exercise may mask the symptomatic recognition of mild hypoglycemia during exercise in people with T1D, a potential clinical safety concern that reinforces the need for diligent glucose management.

TRIAL REGISTRATION NUMBER

DRKS00013509.

Greater Suppression of Glucagon, Lipolysis, and Ketogenesis with Insulin Glargine U300 as Compared with Glargine U100 in Type 1 Diabetes Mellitus

The aim of this study was to establish the effects of clinical doses of Gla-300 versus Gla-100 on suppression of glucagon, lipolysis, and ketogenesis in type 1 diabetes mellitus (T1DM). Eighteen persons with T1DM (age 40 ± 12 years, diabetes duration 26 ± 12 years, body mass index 23.4 ± 2 kg/m², A1C 7.19% ± 0.52% [55 ± 6 mmol/mol]) were studied after 3 months of titration with Gla-300 and Gla-100 (randomized, crossover design) with a 24-h euglycemic clamp (s.c. injection of individual insulin daily doses used by subjects for previous 2 weeks, Gla-300 0.35 ± 0.08 and Gla-100 0.28 ± 0.07 U/kg). Gla-300 resulted in (1) less increase in insulin concentration for 0-12 h, but greater insulin concentration in 12-24 h (no differences for 24 h); (2) greater glucagon suppression; (3) greater prehepatic insulin-to-glucagon molar ratio, primarily in 12-24 h (ratio 1.78, 90% confidence intervals [CIs] 1.5-2.1); and (4) lower 24-h free fatty acid (0.81; 90% CI 0.73-0.89), glycerol (0.78; 90% CI 0.65-0.94), and β-hydroxybutyrate (0.72; 90% CI 0.58-0.90). Over the 24 h postinjection, as compared with Gla-100, clinical doses of Gla-300 exhibit greater suppressive effects on glucagon, lipolysis, and ketogenesis, whereas the effects on glucose metabolism are equivalent.

Impact of Hypoglycemia on Brain Metabolism During Diabetes

Diabetes is a metabolic disease afflicting millions of people worldwide. A substantial fraction of world's total healthcare expenditure is spent on treating diabetes. Hypoglycemia is a serious consequence of anti-diabetic drug therapy, because it induces metabolic alterations in the brain. Metabolic alterations are one of the central mechanisms mediating hypoglycemia-related functional changes in the brain. Acute, chronic, and/or recurrent hypoglycemia modulate multiple metabolic pathways, and exposure to hypoglycemia increases consumption of alternate respiratory substrates such as ketone bodies, glycogen, and monocarboxylates in the brain. The aim of this review is to discuss hypoglycemia-induced metabolic alterations in the brain in glucose counterregulation, uptake, utilization and metabolism, cellular respiration, amino acid and lipid metabolism, and the significance of other sources of energy. The present review summarizes information on hypoglycemia-induced metabolic changes in the brain of diabetic and non-diabetic subjects and the manner in which they may affect brain function.

Acute Hypoglycemia in Healthy Humans Impairs Insulin-Stimulated Glucose Uptake and Glycogen Synthase in Skeletal Muscle: A Randomized Clinical Study

Hypoglycemia is the leading limiting factor in glycemic management of insulin-treated diabetes. Skeletal muscle is the predominant site of insulin-mediated glucose disposal. Our study used a crossover design to test to what extent insulin-induced hypoglycemia affects glucose uptake in skeletal muscle and whether hypoglycemia counterregulation modulates insulin and catecholamine signaling and glycogen synthase activity in skeletal muscle. Nine healthy volunteers were examined on three randomized study days: 1) hyperinsulinemic hypoglycemia (bolus insulin), 2) hyperinsulinemic euglycemia (bolus insulin and glucose infusion), and 3) saline control with skeletal muscle biopsies taken just before, 30 min after, and 75 min after insulin/saline injection. During hypoglycemia, glucose levels reached a nadir of ∼2.0 mmol/L, and epinephrine rose to ∼900 pg/mL. Hypoglycemia impaired insulin-stimulated glucose disposal and glucose clearance in skeletal muscle, whereas insulin signaling in glucose transport was unaffected by hypoglycemia. Insulin-stimulated glycogen synthase activity was completely ablated during hyperinsulinemic hypoglycemia, and catecholamine signaling via cAMP-dependent protein kinase and phosphorylation of inhibiting sites on glycogen synthase all increased.

Effects of insulin-induced hypoglycaemia on lipolysis rate, lipid oxidation and adipose tissue signalling in human volunteers: a randomised clinical study

AIMS/HYPOTHESIS

The aims of this study were to determine the role of lipolysis in hypoglycaemia and define the underlying intracellular mechanisms.

METHODS

Nine healthy volunteers were randomised to treatment order of three different treatments (crossover design). Treatments were: (1) saline control; (2) hyperinsulinaemic hypoglycaemia (HH; i.v. bolus of 0.1 U/kg insulin); and (3) hyperinsulinaemic euglycaemia (HE; i.v. bolus of 0.1 U/kg insulin and 20% glucose). Inclusion criteria were that volunteers were healthy, aged >18 years, had a BMI between 19 and 26 kg/m², and provided both written and oral informed consent. Exclusion criteria were the presence of a known chronic disease (including diabetes mellitus, epilepsy, ischaemic heart disease and cardiac arrhythmias) and regular use of prescription medication. The data was collected at the medical research facilities at Aarhus University Hospital, Denmark. The primary outcome was palmitic acid flux. Participants were blinded to intervention order, but caregivers were not.

RESULTS

Adrenaline (epinephrine) and glucagon concentrations were higher during HH than during both HE and control treatments. NEFA levels and lipid oxidation rates (determined by indirect calorimetry) returned to control levels after 105 min. Palmitate flux was increased to control levels during HH (p = NS) and was more than twofold higher than during HE (overall mean difference between HH vs HE, 114 [95% CI 64, 165 μmol/min]; p < 0.001). In subcutaneous adipose tissue biopsies, we found elevated levels of hormone-sensitive lipase (HSL) and perilipin-1 phosphorylation 30 min after insulin injection during HH compared with both control and HE. There were no changes in the levels of adipose triglyceride lipase (ATGL), comparative gene identification-58 (CGI-58) or G₀/G₁ switch gene 2 (G0S2) proteins. Insulin-stimulated phosphorylation of Akt and mTOR were unaffected by hypoglycaemia. Expression of the G0S2 gene increased during HE and HH compared with control, without changes in ATGL (also known as PNPLA2) or CGI-58 (also known as ABHD5) mRNA levels.

CONCLUSIONS/INTERPRETATION

These findings suggest that NEFAs become a major fuel source during insulin-induced hypoglycaemia and that lipolysis may be an important component of the counter-regulatory response. These effects appear to be mediated by rapid stimulation of protein kinase A (PKA) and HSL, compatible with activation of the β-adrenergic catecholamine signalling pathway.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01919788 FUNDING: : The study was funded by Aarhus University, the Novo Nordisk Foundation and the KETO Study Group/Danish Agency for Science Technology and Innovation (grant no. 0603-00479, to NM).

Biomarkers of Insulin for the Diagnosis of Hyperinsulinemic Hypoglycemia in Infants and Children

OBJECTIVE

To evaluate thresholds of various biomarkers for defining excess insulin activity to recognize congenital hyperinsulinism.

STUDY DESIGN

This was a retrospective chart review of diagnostic fasting tests in children with ketotic hypoglycemia (n = 30) and genetically/pathology confirmed congenital hyperinsulinism (n = 28). Sensitivity and specificity for congenital hyperinsulinism were determined for plasma insulin, β-hydroxybutyrate, free fatty acids (FFA), C-peptide, insulin-like growth factor binding protein-1 (IGFBP-1), and the glycemic response to glucagon (through the glucagon stimulation test [GST]) at the time of hypoglycemia.

RESULTS

Only 23 of the 28 subjects with congenital hyperinsulinism had detectable insulin (median, 6.7 μIU/mL), and insulin was undetectable in all subjects with ketotic hypoglycemia. Compared with ketotic hypoglycemia, subjects with congenital hyperinsulinism had higher GST values (57 vs 13 mg/dL; ΔGST ≥30 mg/dL in 24 of 27 subjects with congenital hyperinsulinism vs 0 of 30 subjects with ketotic hypoglycemia) and C-peptide levels (1.55 vs 0.11 ng/mL), with lower levels of FFA (0.82 vs 2.51 mM) and IGFBP-1 (59.5 vs 634 ng/mL). At the time of hypoglycemia, the upper limits of β-hydroxybutyrate and FFA in subjects with congenital hyperinsulinism were higher than reported previously (β-hydroxybutyrate <1.8 mM and FFA <1.7 mM), providing the best sensitivity for congenital hyperinsulinism vs ketotic hypoglycemia. A C-peptide level ≥0.5 ng/mL was 89% sensitive and 100% specific, and an IGFBP-1 level ≤110 ng/mL was 85% sensitive and 96.6% specific.

CONCLUSION

Because low or undetectable insulin level during hypoglycemia does not exclude the diagnosis of hyperinsulinism, C-peptide and IGFBP-1 may inform the diagnosis of congenital hyperinsulinism. In this group of children with well-defined congenital hyperinsulinism, thresholds for "suppressed" β-hydroxybutyrate and FFA are higher than previously reported levels.

Cortisol response to individualised graded insulin infusions: a reproducible biomarker for CNS compounds inhibiting HPA activation

AIM

To determine the potential of cortisol secretion, in response to a physiological stressor, as a biomarker for centrally active compounds targeting the hypothalamic-pituitary-adrenocortical (HPA) axis.

METHODS

Cortisol response to hypoglycaemia was measured in 26 healthy males in two stages: firstly to derive an algorithm for individualized, graded insulin infusion rates to achieve defined hypoglycaemic targets over 3 h and secondly to determine the inter- and intra-subject variability of cortisol response to hypoglycaemia over two identical periods by measuring the maximum (t(max) ), time to maximum (C(max) ) response and cortisol area under the response curve (AUC).

RESULTS

Hypoglycaemia induced a consistent cortisol response starting at approximately 1 h, corresponding to blood glucose concentrations of approximately 3.3 mmol l⁻¹, and peaking approximately 3 h after the start of infusion. The inter- and intra-subject coefficients of variation (CVs) of cortisol response were approximately 19 and 19% (AUC), 15 and 19 % (C(max) ) and 10 and 14% (t(max) ), respectively. The intra-subject CVs for the ratio of maximum cortisol response to baseline concentration and rate of initial cortisol response between study days were more variable (32.8% and 59.0%, respectively). The blood glucose-cortisol response model derived from the study was predictive of the individual observed cortisol responses, and estimated a blood glucose EC(50) associated with onset of the cortisol response of 3.3 mmol l⁻¹.

CONCLUSIONS

Gradual hypoglycaemia is an effective, reproducible and well-tolerated method of stimulating a cortisol response and may therefore be useful in assessing the neuroendocrine response to HPA axis inhibitors, such as corticotropin-releasing hormone-1 (CRH-1) antagonists.

Hypoglycemia: A Possible Link between Insulin Resistance, Metabolic Dyslipidemia, and Heart and Kidney Disease (the Cardiorenal Syndrome)

Resistance to insulin metabolic signaling in adipose tissue contributes to the lipid abnormalities in obese, hyperinsulinemic, insulin-resistant patients who develop the cardiorenal syndrome. These same metabolic dyslipidemic abnormalities can be found in conditions of caloric energy restriction with decreased adiposity or normal insulin levels, such as anorexia, starvation or non-diabetic kidney disease. In this review, we assess hypoglycemia as an alternative physiological explanation for the biochemical and lipid findings in conditions of insulin resistance (IR). Therefore, PubMed databases (1961-2010) were searched for articles on the effect of hypoglycemia and starvation on non-esterified fatty acid (NEFA) elevation and abnormalities in insulin signaling in muscles as well as abnormal kidney metabolism. The search included articles on NEFA and their role in triglyceride (TG) and high-density lipoprotein (HDL) metabolism, as well as kidney and heart disease. Available studies support that hypoglycemia increases NEFA generation from adipose tissue. Elevated levels of NEFA induce increased plasma levels of TG and decreased levels of HDL cholesterol, and may cause direct kidney and myocardial damage. IR of adipose and skeletal muscle tissue, and the elevation in insulin levels in obese, insulin-resistant patients could be explained by an adaptation to their carbohydrate intake. These molecular abnormalities in insulin metabolic signaling can also be found in hypoglycemia or starvation. In conclusion, IR of adipose tissue cannot fully explain the lipid abnormalities observed in the cardiorenal syndrome. Decreased blood glucose levels (e.g. hypoglycemia) occur frequently in patients at risk for this syndrome. Hypoglycemia-induced increases in NEFA levels can promote lipid abnormalities that contribute to IR and the cardiorenal syndrome.

Mechanisms of insulin resistance after insulin-induced hypoglycemia in humans: the role of lipolysis

OBJECTIVE

Changes in glucose metabolism occurring during counterregulation are, in part, mediated by increased plasma free fatty acids (FFAs), as a result of hypoglycemia-activated lipolysis. However, it is not known whether FFA plays a role in the development of posthypoglycemic insulin resistance as well.

RESEARCH DESIGN AND METHODS

We conducted a series of studies in eight healthy volunteers using acipimox, an inhibitor of lipolysis. Insulin action was measured during a 2-h hyperinsulinemic-euglycemic clamp (plasma glucose [PG] 5.1 mmo/l) from 5:00 p.m. to 7:00 p.m. or after a 3-h morning hyperinsulinemic-glucose clamp (from 10 a.m. to 1:00 p.m.), either euglycemic (study 1) or hypoglycemic (PG 3.2 mmol/l, studies 2-4), during which FFA levels were allowed to increase (study 2), were suppressed by acipimox (study 3), or were replaced by infusing lipids (study 4). [6,6-(2)H(2)]-Glucose was infused to measure glucose fluxes.

RESULTS

Plasma adrenaline, norepinephrine, growth hormone, and cortisol levels were unchanged (P > 0.2). Glucose infusion rates (GIRs) during the euglycemic clamp were reduced by morning hypoglycemia in study 2 versus study 1 (16.8 +/- 2.3 vs. 34.1 +/- 2.2 micromol/kg/min, respectively, P < 0.001). The effect was largely removed by blockade of lipolysis during hypoglycemia in study 3 (28.9 +/- 2.6 micromol/kg/min, P > 0.2 vs. study 1) and largely reproduced by replacement of FFA in study 4 (22.3 +/- 2.8 micromol/kg/min, P < 0.03 vs. study 1). Compared with study 2, blockade of lipolysis in study 3 decreased endogenous glucose production (2 +/- 0.3 vs. 0.85 +/- 0.1 micromol/kg/min, P < 0.05) and increased glucose utilization (16.9 +/- 1.85 vs. 28.5 +/- 2.7 micromol/kg/min, P < 0.05). In study 4, GIR fell by approximately 23% (22.3 +/- 2.8 micromol/kg/min, vs. study 3, P = 0.058), indicating a role of acipimox per se on insulin action.

CONCLUSION

Lipolysis induced by hypoglycemia counterregulation largely mediates posthypoglycemic insulin resistance in healthy subjects, with an estimated overall contribution of approximately 39%.

Short-term effects of the long-acting insulin analog detemir and human insulin on plasma levels of insulin-like growth factor-I and its binding proteins in humans

OBJECTIVE

The objective of the study was to compare responses of plasma levels of IGF-I and IGF binding proteins (IGFBP-1 and IGFBP-3) induced by human regular insulin (HI) and the long-acting insulin analog detemir (IDet) at doses equivalent with respect to the glucose-lowering effect.

EXPERIMENTAL DESIGN

Ten nondiabetic subjects (six males, four females; age, 36 +/- 7 yr; body mass index, 22.9 +/- 2.6 kg/m(2)) were studied on four randomized occasions with iv infusion of IDet (2 mU/kg . min for 4 h, followed by 4 mU/kg . min for 1 h) or HI (1 mU/kg . min for 4 h, followed by 2 mU/kg . min for 1 h) in euglycemia [plasma glucose (PG), 90 mg/dl] or during stepped hypoglycemia (PG, 90, 78, 66, 54, and 42 mg/dl).

RESULTS

PG was maintained at preselected plateaus, without any significant difference between IDet and HI (P > 0.2). Plasma insulin concentrations were on average approximately nine times greater with IDet than HI (749 +/- 52 vs. 83 +/- 19 muU/ml, respectively). Plasma IGF-I concentrations did not change from baseline during insulin infusion in euglycemia (IDet, 147 +/- 16 ng/ml; HI, 155 +/- 15 ng/ml) and hypoglycemia (IDet, 163 +/- 14 ng/ml; HI, 165 +/- 14 ng/ml) with no differences between the two insulins (P > 0.2). A similar pattern was observed for plasma IGFBP-3 levels. Insulin infusion resulted in a suppression of plasma IGFBP-1 concentrations with no differences between IDet (baseline, 16.6 +/- 3.8 ng/ml; endpoint, 2.0 +/- 0.6 ng/ml) and HI (baseline, 16.6 +/- 4.1 ng/ml; endpoint, 2.6 +/- 1.4 ng/ml) (P > 0.2) and study conditions (P > 0.2).

CONCLUSIONS

The greater plasma insulin concentrations obtained with IDet exert effects on plasma levels of IGF-I, IGFBP-1, and IGFBP-3 similar to those of HI. Additional studies are needed to confirm these short-term results in patients with diabetes mellitus on long-term treatment with IDet.

Portal vein glucose sensors do not play a major role in modulating physiological responses to insulin-induced hypoglycemia in humans

OBJECTIVE

Experimental data from animal studies indicate that portal vein glucose sensors play a key role in the responses to slow-fall hypoglycemia. However, their role in modulating these responses in humans is not well understood. The aim of the present study was to examine in humans the potential role of portal vein glucose sensors in physiological responses to insulin-induced hypoglycemia mimicking the slow fall of insulin-treated diabetic subjects.

RESEARCH DESIGN AND METHODS

Ten nondiabetic subjects were studied on two different occasions during intravenous insulin (2 mU . kg(-1) . min(-1)) plus variable glucose for 160 minutes. In both studies, after 60 min of normal plasma glucose concentrations, hypoglycemia (47 mg/dl) was induced slowly (60 min) and maintained for 60 min. Hypoglycemia was preceded by the ingestion of either oral placebo or glucose (28 g) given at 30 min.

RESULTS

Plasma glucose and insulin were not different with either placebo or glucose (P > 0.2). Similarly, counterregulatory hormones, substrates, and symptoms were not different with either placebo or glucose. The Stroop color and colored words subtest of the Stroop test deteriorated less (P < 0.05) with glucose than placebo.

CONCLUSIONS

In contrast to animals, in humans, prevention of portal hypoglycemia with oral glucose from the beginning of insulin-induced slow-fall hypoglycemia has no effect on sympathoadrenal and symptomatic responses to hypoglycemia.

Effects of the selective serotonin reuptake inhibitor fluoxetine on counterregulatory responses to hypoglycemia in individuals with type 1 diabetes

OBJECTIVE

Previous work has demonstrated that chronic administration of the serotonin reuptake inhibitor (SSRI) fluoxetine augments counterregulatory responses to hypoglycemia in healthy humans. However, virtually no information exists regarding the effects of fluoxetine on integrated physiological counterregulatory responses during hypoglycemia in type 1 diabetes. Therefore, the specific aim of this study was to test the hypothesis that 6-week use of the SSRI fluoxetine would amplify autonomic nervous system (ANS) counterregulatory responses to hypoglycemia in individuals with type 1 diabetes.

RESEARCH DESIGN AND METHODS

Eighteen type 1 diabetic patients (14 men/4 women aged 19-48 years with BMI 25 +/- 3 kg/m(2) and A1C 7.0 +/- 0.4%) participated in randomized, double-blind 2-h hyperinsulinemic (9 pmol . kg(-1) . min(-1))-hypoglycemic clamp studies before and after 6 weeks of fluoxetine administration (n = 8) or identical placebo (n = 10). Glucose kinetics was determined by 3-tritiated glucose. Muscle sympathetic nerve activity (MSNA) was determined by microneurography.

RESULTS

Hypoglycemia (2.8 +/- 0.1 mmol/l) and insulinemia (646 +/- 52 pmol/l) were similar during all clamp studies. ANS, neuroendocrine, and metabolic counterregulatory responses remained unchanged in the placebo group. However, fluoxetine administration significantly (P < 0.05) increased key ANS (epinephrine, norepinephrine, and MSNA), metabolic (endogenous glucose production and lipolysis), and cardiovascular (systolic blood pressure) counterregulatory responses during hypoglycemia.

CONCLUSIONS

This study has demonstrated that 6-week administration of the SSRI fluoxetine can amplify ANS and metabolic counterregulatory mechanisms during moderate hypoglycemia in patients with type 1 diabetes. These data also suggest that the use of fluoxetine may be useful in increasing epinephrine responses during hypoglycemia in clinical practice.

Effect of oral amino acids on counterregulatory responses and cognitive function during insulin-induced hypoglycemia in nondiabetic and type 1 diabetic people

OBJECTIVE

Amino acids stimulate glucagon responses to hypoglycemia and may be utilized by the brain. The aim of this study was to assess the responses to hypoglycemia in nondiabetic and type 1 diabetic subjects after ingestion of an amino acid mixture.

RESEARCH DESIGN AND METHODS

Ten nondiabetic and 10 diabetic type 1 subjects were studied on three different occasions during intravenous insulin (2 mU . kg(-1) . min(-1)) plus variable glucose for 160 min. In two studies, clamped hypoglycemia (47 mg/dl plasma glucose for 40 min) was induced and either oral placebo or an amino acid mixture (42 g) was given at 30 min. In the third study, amino acids were given, but euglycemia was maintained.

RESULTS

Plasma glucose and insulin were no different in the hypoglycemia studies with both placebo and amino acids (P > 0.2). After the amino acid mixture, plasma amino acid concentrations increased to levels observed after a mixed meal (2.4 +/- 0.13 vs. placebo study 1.7 +/- 0.1 mmol/l, P = 0.02). During clamped euglycemia, ingestion of amino acids resulted in transient increases in glucagon concentrations, which returned to basal by the end of the study. During clamped hypoglycemia, glucagon response was sustained and increased more in amino acid studies versus placebo in nondiabetic and diabetic subjects (P < 0.05), but other counter-regulatory hormones and total symptom score were not different. Beta-OH-butyrate was less suppressed after amino acids (200 +/- 15 vs. 93 +/- 9 micromol/l, P = 0.01). Among the cognitive tests administered, the following indicated less deterioration after amino acids than placebo: Trail-Making part B, PASAT (Paced Auditory Serial Addition Test) (2 s), digit span forward, Stroop colored words, and verbal memory tests for nondiabetic subjects; and Trail-Making part B, digit span backward, and Stroop color tests for diabetic subjects.

CONCLUSIONS

Oral amino acids improve cognitive function in response to hypoglycemia and enhance the response of glucagon in nondiabetic and diabetic subjects.

Different brain responses to hypoglycemia induced by equipotent doses of the long-acting insulin analog detemir and human regular insulin in humans

OBJECTIVE

The acylated long-acting insulin analog detemir is more lipophilic than human insulin and likely crosses the blood-to-brain barrier more easily than does human insulin. The aim of these studies was to assess the brain/hypothalamus responses to euglycemia and hypoglycemia in humans during intravenous infusion of equipotent doses of detemir and human insulin.

RESEARCH DESIGN AND METHODS

Ten normal, nondiabetic subjects (six men, age 36+/-7 years, and BMI 22.9+/-2.6 kg/m(2)) were studied on four occasions at random during intravenous infusion of either detemir or human insulin in euglycemia (plasma glucose 90 mg/dl) or during stepped hypoglycemia (plasma glucose 90, 78, 66, 54, and 42 mg/dl steps).

RESULTS

Plasma counterregulatory hormone response to hypoglycemia did not differ between detemir and human insulin. The glycemic thresholds for adrenergic symptoms were higher with detemir (51 +/- 7.7 mg/dl) versus human insulin (56 +/- 7.8 mg/dl) (P = 0.029). However, maximal responses were greater with detemir versus human insulin for adrenergic (3 +/- 2.5 vs. 2.4 +/- 1.8) and neuroglycopenic (4 +/- 3.9 vs. 2.7+/-2.5) symptoms (score, P < 0.05). Glycemic thresholds for onset of cognitive dysfunction were lower with detemir versus human insulin (51 +/- 8.1 vs. 47 +/- 3.6 mg/dl, P = 0.031), and cognitive function was more deteriorated with detemir versus human insulin (P < 0.05).

CONCLUSIONS

Compared with human insulin, responses to hypoglycemia with detemir resulted in higher glycemic thresholds for adrenergic symptoms and greater maximal responses for adrenergic and neuroglycopenic symptoms, with an earlier and greater impairment of cognitive function. Additional studies are needed to establish the effects of detemir on responses to hypoglycemia in subjects with diabetes.

Comparison of pharmacokinetics and dynamics of the long-acting insulin analogs glargine and detemir at steady state in type 1 diabetes: a double-blind, randomized, crossover study

OBJECTIVE

To compare pharmacokinetics and pharmacodynamics of insulin analogs glargine and detemir, 24 subjects with type 1 diabetes (aged 38 +/- 10 years, BMI 22.4 +/- 1.6 kg/m2, and A1C 7.2 +/- 0.7%) were studied after a 2-week treatment with either glargine or detemir once daily (randomized, double-blind, crossover study).

RESEARCH DESIGN AND METHODS

Plasma glucose was clamped at 100 mg/dl for 24 h after subcutaneous injection of 0.35 unit/kg. The primary end point was end of action (time at which plasma glucose was >150 mg/dl).

RESULTS

With glargine, plasma glucose remained at 103 +/- 3.6 mg/dl up to 24 h, and all subjects completed the study. Plasma glucose increased progressively after 16 h with detemir, and only eight subjects (33%) completed the study with plasma glucose <180 mg/dl. Glucose infusion rate (GIR) was similar with detemir and glargine for 12 h, after which it decreased more rapidly with detemir (P < 0.001). Estimated total insulin activity (GIR area under the curve [AUC](0-end of GIR)) was 1,412 +/- 662 and 915 +/- 225 mg/kg (glargine vs. detemir, P < 0.05), with median time of end of action at 24 and 17.5 h (glargine vs. detemir, P < 0.001). The antilipolytic action of detemir was lower than that of glargine (AUC free fatty acids(0-24 h) 11 +/- 1.7 vs. 8 +/- 2.8 mmol/l, respectively, P < 0.001).

CONCLUSIONS

Detemir has effects similar to those of glargine during the initial 12 h after administration, but effects are lower during 12-24 h.

Higher glucose uptake in paralysed spastic leg

BACKGROUND

Insulin resistance and diabetes mellitus have been reported in the spinal cord injured (SCI). The group exhibits risk factors, as decreased physical activity, as well as episodes of stimulation of sympathetic nervous system below the level of lesion known to stimulate lipolysis, which in turn could induce insulin resistance. However, data are inconsistent, which might indicate the presence of protective mechanisms.

OBJECTIVE

To investigate the glucose uptake in spastic paralysed SCI legs compared to able-bodied. To investigate regional differences between glucose handling in the arm and leg.

STUDY DESIGN

Experimental controlled study.

SETTINGS

Institution of Clinical Neuroscience and Physiology, Spinal Injures Unit, Sahlgrens University Hospital, Goteborg, Sweden.

METHODS

Nine SCI subjects (2 C7, 7 T1-T4 ASIA A: 8, ASIA B: 1) were compared to 10 weight- and age-matched controls. Plasma flow in arm and leg was analysed by venous occlusion strain gauge plethysmography, and plasma derived from artery and veins in the arm and leg was analysed for glucose, insulin and lactate during fasting resting conditions.

RESULTS

Glucose uptake was higher in SCI legs compared to controls. There was no difference in insulin uptake or lactate production. Plasma flow was higher in SCI legs compared to controls. Controls showed a higher glucose uptake and lactate production in arm than leg.

CONCLUSIONS

Spasticity may counteract the risk of diabetes by inducing an insulin-independent glucose uptake. The regional difference in metabolism in able-bodied make it hazardous to do generalizations to whole body metabolism from arm or leg measurements.

Effect of the amino acid alanine on glucagon secretion in non-diabetic and type 1 diabetic subjects during hyperinsulinaemic euglycaemia, hypoglycaemia and post-hypoglycaemic hyperglycaemia

AIMS/HYPOTHESIS

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.

MATERIALS AND METHODS

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.

RESULTS

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.

CONCLUSIONS/INTERPRETATION

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.

Better long-term glycaemic control with the basal insulin glargine as compared with NPH in patients with Type 1 diabetes mellitus given meal-time lispro insulin

BACKGROUND

Glargine is a long-acting insulin analogue potentially more suitable than NPH insulin in intensive treatment of Type 1 diabetes mellitus (T1 DM), but no study has proven superiority. The aim of this study was to test superiority of glargine on long-term blood glucose (BG) as well as on responses to hypoglycaemia vs. NPH.

METHODS

One hundred and twenty-one patients with T1 DM on intensive therapy on four times/day NPH and lispro insulin at each meal, were randomized to either continuation of NPH four times/day (n = 60), or once daily glargine at dinner-time (n = 61) for 1 year. Lispro insulin at meal-time was continued in both groups. In 11 patients from each group, responses to stepped hyperinsulinaemic-hypoglycaemia were measured before and after 1 year's treatment.

RESULTS

Mean daily BG was lower with glargine [7.6 +/- 0.11 mmol/l (137 +/- 2 mg/dl)] vs. NPH [8.1 +/- 0.22 mmol/l (146 +/- 4 mg/dl)] (P < 0.05). HbA(1c) at 4 months did not change with NPH, but decreased with glargine (from 7.1 +/- 0.1 to 6.7 +/- 0.1%), and remained lower than NPH at 12 months (6.6 +/- 0.1%, P < 0.05 vs. NPH). Frequency of mild hypoglycaemia [self-assisted episodes, blood glucose < or = 4.0 mmol/l (72 mg/dl)] was lower with glargine vs. NPH (7.2 +/- 0.5 and 13.2 +/- 0.6 episodes/patient-month, P < 0.05). After 1 year, NPH treatment resulted in no change of responses to hypoglycaemia, whereas with glargine plasma glucose, thresholds and maximal responses of plasma adrenaline and symptoms to hypoglycaemia improved (P < 0.05).

CONCLUSIONS

The simpler glargine regimen decreases the percentage of HbA(1c) and frequency of hypoglycaemia and improves responses to hypoglycaemia more than NPH. Thus, glargine appears more suitable than NPH as basal insulin for intensive treatment of T1 DM.

Hypoglycaemia in Elderly Patients with Diabetes Mellitus

Achieving target glycaemic goals while avoiding hypoglycaemia is a major challenge in the management of elderly patients with diabetes mellitus. Repeated episodes of hypoglycaemia may cause extreme emotional distress in such patients, even when the episodes are relatively mild. Moreover, evidence is mounting that hypoglycaemia among elderly patients is a very real and costly health concern. The strongest predictors of severe hypoglycaemia in the elderly are advanced age, recent hospitalisation and polypharmacy. Education is the key to preventing recurrent or severe hypoglycaemia. As such, there should be close coordination of care between the patient, physician and all other healthcare providers in identifying the cause of hypoglycaemia in elderly patients, and appropriate steps should be taken to prevent further episodes. Prevention of hypoglycaemia has the potential to improve psychosocial aspects of elderly health, including enhanced quality of life, boosted confidence, improved compliance with antidiabetic regimens and avoidance of long-term complications. Since the elderly population represents a unique group, it is imperative to focus on the aetiologies that are exclusive to this group. Advanced age itself is a risk factor for hypoglycaemia, and elderly patients with comorbidities are at increased risk when they are hospitalised. Elderly patients with diabetes often have compromised renal function, which intereferes with drug elimination and thus predisposes them to prolonged life-threatening hypoglycaemia. In addition, patients on five or more prescription medications are prone to drug-associated hypoglycaemia. Although sulfonylurea-associated hypoglycaemia is common, drugs such as ACE inhibitors and nonselective beta-adrenoceptor antagonists can also predispose patients to hypoglycaemia. Greater attention should be paid to the avoidance of hypgolycaemia in nursing home residents. Recurrent hypoglycaemia in elderly patients is not only detrimental to achieving good glycaemic control, it is also a substantial economic burden. Once the causes of hypoglycaemia have been identified, it is crucial to formulate and institute a prevention plan. Firstly, global evaluation of the patient should be carried out to identify possible predisposing risk factors. Secondly, target glycaemic goals should be tailored to each patient. Thirdly, selection of antidiabetic agents should be judicious, then patients and family should be educated to recognise and treat hypoglycaemia. Finally, coordinated care should be provided to identify, treat and prevent hypoglycaemia.

Insulin is required for prandial ghrelin suppression in humans

Accumulating evidence indicates that ghrelin plays a role in regulating food intake and energy homeostasis. In normal subjects, circulating ghrelin concentrations decrease after meal ingestion and increase progressively before meals. At present, it is not clear whether nutrients suppress the plasma ghrelin concentration directly or indirectly by stimulating insulin secretion. To test the hypothesis that insulin regulates postprandial plasma ghrelin concentrations in humans, we compared the effects of meal ingestion on plasma ghrelin levels in six C-peptide-negative subjects with type 1 diabetes and in six healthy subjects matched for age, sex, and BMI. Diabetic subjects were studied during absence of insulin (insulin withdrawal study), with intravenous infusion of basal insulin (basal insulin study) and subcutaneous administration of a prandial insulin dose (prandial insulin study). Meal intake suppressed plasma ghrelin concentrations (nadir at 105 min) by 32 +/- 4% in normal control subjects, 57 +/- 3% in diabetic patients during the prandial insulin study (P < 0.002 vs. control subjects), and 38 +/- 8% during basal insulin study (P = 0.0016 vs. hyperinsulinemia; P = NS vs. control subjects) but did not have any effect in the insulin withdrawal study (P < 0.001 vs. other studies). In conclusion, 1). insulin is essential for meal-induced plasma ghrelin suppression, 2). basal insulin availability is sufficient for postprandial ghrelin suppression in type 1 diabetic subjects, and 3). lack of meal-induced ghrelin suppression caused by severe insulin deficiency may explain hyperphagia of uncontrolled type 1 diabetic subjects.

Counterregulatory hormone and symptom responses to insulin-induced hypoglycemia in the postprandial state in humans

Plasma counterregulatory hormones and symptoms were measured during hypoglycemia in the postprandial and in the fasting state in humans to establish differences in physiological responses. We studied 8 nondiabetic subjects and 10 subjects with type 1 diabetes on two different occasions during clamped insulin-induced hypoglycemia (2.4 mmol/l) in the sitting position. On one occasion, subjects ate a standard mixed meal, and on the other they remained fasting. In response to postprandial as compared with fasting hypoglycemia, nondiabetic subjects exhibited lower total symptom scores (6.6 +/- 0.4 vs. 11.5 +/- 0.8, P = 0.001), which was due to less hunger (1.1 +/- 0.1 vs. 4.2 +/- 0.2), lower suppression of plasma C-peptide (0.23 +/- 0.1 vs. 0.08 +/- 0.07 nmol/l, P = 0.032), and greater responses of plasma glucagon (248 +/- 29 vs. 163 +/- 25 ng x l(-1) x min(-1), P = 0.018), plasma adrenaline (4.5 +/- 0.6 vs. 3.1 +/- 0.4 nmol x l(-1) x min(-1), P = 0.037), norepinephrine (3.8 +/- 0.3 vs. 3.2 +/- 0.2 nmol x l(-1) x min(-1), P = 0.037), and pancreatic polypeptide (217 +/- 12 vs. 159 +/- 22 pmol x l(-1) x min(-1), P = 0.08). Except for plasma C-peptide, responses in diabetic subjects were similarly affected. Notably, in diabetic subjects responses of glucagon, which were absent in the fasting state, nearly normalized after a meal. In conclusion, in the postprandial compared with the fasting hypoglycemic state, total symptoms are less, but counterregulatory hormones are greater and responses of glucagon nearly normalize in type 1 diabetic subjects.

Norepinephrine and epinephrine-deficient mice are hyperinsulinemic and have lower blood glucose

Norepinephrine (NE) and epinephrine (Epi) help maintain normal blood glucose levels by stimulating glucagon release, glycogenolysis, and food consumption, and by inhibiting insulin release. The absence of NE and Epi in dopamine beta-hydroxylase-null (Dbh-/-) mice results in chronically low blood glucose levels, an impaired glucagon response to hypoglycemia, and elevated insulin levels. Nevertheless, Dbh-/- mice have normal glycogen levels and degrade it normally during a fast. Dbh-/- mice defend blood glucose levels better than controls in an insulin tolerance test but have increased sensitivity to glucose-stimulated insulin secretion and respond normally in a glucose tolerance test. Pharmacological evidence indicates that the hyperinsulinemia results from lack of alpha2-adrenoreceptor stimulation and increased parasympathetic tone. Dbh-/- mice eat normally after challenges with modest levels of insulin or 2-deoxyglucose but fail to eat under more extreme conditions when control mice still do. We suggest that the primary difference in Dbh-/- mice is chronic hyperinsulinemia associated with an altered glucose set point. However, these animals compensate for NE/Epi-mediated glycogenolysis and feeding.

Defective activation of skeletal muscle and adipose tissue lipolysis in type 1 diabetes mellitus during hypoglycemia

The increased risk of hypoglycemia during intensified treatment of type 1 diabetes mellitus (T1DM) patients, who have a deficient glucagon secretory response, is largely attributed to the development of suppressed adrenomedullary responses. A consequence of this impairment of catecholamine secretion might be reduced lipolysis in major target tissues (muscle and adipose) and, in turn, increased glucose metabolism. To test this hypothesis, we used microdialysis to monitor glycerol (index of lipolysis) in the extracellular fluid of skeletal muscle and adipose tissue and assessed whole-body glucose use by measuring [6,6-(2)H(2)]glucose enrichment in plasma in seven intensively treated T1DM patients and eight nondiabetic subjects who received a 3-h insulin infusion (0.8 mU/kg.min) on two occasions: during mild-moderate hypoglycemia or euglycemia. In the hypoglycemic study, the rise in plasma epinephrine was approximately 50% less in the T1DM patients despite a greater fall in plasma glucose (to 3.0 vs. 3.5 mM in controls; P < 0.05). Moreover, the rate of glucose flux and the plasma-extracellular fluid glucose gradient in muscle was increased during hypoglycemia in T1DM subjects compared with controls. Glycerol levels in muscle, adipose, and plasma fell similarly in both groups in the first hour. Thereafter, tissue glycerol remained suppressed in the T1DM patients but rebounded significantly (P < 0.01) in the control subjects. The glycerol response in muscle and adipose tissue was significantly correlated with plasma epinephrine concentration (r = 0.73, P = 0.002; and r = 0.52, P = 0.04, respectively), and inversely correlated with whole-body glucose disposal (r = -0.51, P = 0.05; and r = -0.50, P = 0.05). To determine whether the absence of the lipolytic response is limited to deficient catecholamine release, we perfused muscle and adipose tissue in situ with the selective beta(2)-agonist terbutaline during hyperinsulinemic euglycemia. Local addition of agonist increased glycerol and blood flow in both muscle and adipose (P < 0.01 and P < 0.05, respectively) similarly in T1DM and control subjects. We conclude that deficient release of (rather than impaired responsiveness to) catecholamines in T1DM prevents the local fat breakdown within muscle and adipose tissue that normally occurs during mild-moderate hypoglycemia. This defect within peripheral tissues may lead to a delayed increase in glucose disposal that could contribute to the severity of hypoglycemia when it is prolonged.

Rat liver responsiveness to gluconeogenic substrates during insulin-induced hypoglycemia

Hepatic responsiveness to gluconeogenic substrates during insulin-induced hypoglycemia was investigated. For this purpose, livers were perfused with a saturating concentration of 2 mM glycerol, 5 mM L-alanine or 5 mM L-glutamine as gluconeogenic substrates. All experiments were performed 1 h after an ip injection of saline (CN group) or 1 IU/kg of insulin (IN group). The IN group showed higher (P<0.05) hepatic glucose production from glycerol, L-alanine and L-glutamine and higher (P<0.05) production of L-lactate, pyruvate and urea from L-alanine and L-glutamine. In addition, ip injection of 100 mg/kg glycerol, L-alanine and L-glutamine promoted glucose recovery. The results indicate that the hepatic capacity to produce glucose from gluconeogenic precursors was increased during insulin-induced hypoglycemia.

Reference intervals for glucose, beta-cell polypeptides, and counterregulatory factors during prolonged fasting

To establish reference intervals for the pancreatic beta-cell response and the counterregulatory hormone response to prolonged fasting, we studied 33 healthy subjects (16 males, 17 females) during a 72-h fast. Glucose, insulin, C-peptide, and proinsulin levels decreased (P < 0.001), and the levels of counterregulatory factors increased during the fast [P < 0.05; glucagon and free fatty acids (FFA) with a linear increase and epinephrine, norepinephrine, and cortisol with a clear underlying circadian rhythm]. Growth hormone secretion increased from the first to third day of fasting (P < 0.05) but actually decreased from the second to third day of fasting (P = 0.03). Males had higher glucose and glucagon levels and lower FFA levels during the fast (P < 0.05), whereas no effect of gender on beta-cell polypeptides was observed. A high body mass index resulted in higher insulin and C-peptide levels during the fast (P < 0.05). In conclusion, we have provided reference intervals for glucoregulatory factors during a 72-h fast. We observed a diminished beta-cell response concomitant with an increased secretion of counterregulatory hormones. These results should be of clinical and scientific value in the investigation of hypoglycemic disorders.

Gender-related differences in counterregulatory responses to antecedent hypoglycemia in normal humans

Compared to men, inherent counterregulatory responses are reduced in healthy and type 1 diabetic women. Despite this, the prevalence of hypoglycemia in patients with type 1 diabetes (type 1 DM) is gender neutral. The aim of this study was to determine the in vivo mechanism(s) responsible for this apparent clinical paradox. The central importance of antecedent hypoglycemia in causing subsequent counterregulatory failure is now established. We, therefore, hypothesized that a gender-related difference to the blunting effects of prior hypoglycemia may exist, and this could explain why type 1 DM women do not have an increased prevalence of hypoglycemia despite reduced counterregulatory responses. Fifteen healthy male and female individuals (eight men and seven women) underwent four separate 2-day experimental protocols in a randomized fashion. Day 1 involved identical morning and afternoon 2-h hyperinsulinemic (9 pmol/kg x min) glucose clamp studies with 5.1 +/- 0.1, 3.9 +/- 0.1, 3.3 +/- 0.1, or 2.9 +/- 0.1 mmol/L. Day 2 consisted of a single 2-h hypoglycemic clamp of 2.9 +/- 0.1 mmol/L. Insulin levels were similar on both days of each protocol in men and women. After day 1 euglycemia (5.1 +/- 0.1 mmol/L), day 2 counterregulatory responses were significantly increased (P < 0.01) in men relative to women. In women, counterregulatory responses were resistant to the effects of day 1 hypoglycemia. Antecedent hypoglycemia of 3.9, 3.3, and 2.9 +/- 0.1 mmol/L produced 3 +/- 2%, 5 +/- 2%, and 25 +/- 4% aggregate reductions in day 2 neuroendocrine, muscle sympathetic nerve activity, and metabolic counterregulatory responses. In marked contrast, identical day 1 hypoglycemia of 3.9, 3.3, and 2.9 +/- 0.1 mmol/L in men produced significantly greater reductions in day 2 counterregulatory responses of 30 +/- 6%, 39 +/- 6%, and 52 +/- 6%, respectively. The net effect of the differential gender effects of antecedent hypoglycemia was to overcome the usually increased (50%) sympathetic nervous system (SNS) counterregulatory responses to hypoglycemia found in men. We conclude that 1) antecedent hypoglycemia produces less blunting of counterregulatory responses to subsequent hypoglycemia in women relative to men; 2) two episodes of antecedent hypoglycemia can overcome the greater SNS response to hypoglycemia usually found in men; and 3) the reduced susceptibility of women to the blunting effects of antecedent hypoglycemia may be the mechanism explaining why, despite inherently reduced SNS counterregulatory responses, female type 1 DM patients have a similar prevalence of hypoglycemia compared to men.

Effect of local sympathetic blockade on forearm blood flow and glucose uptake during hypoglycemia

During hypoglycemia, hepatic glucose production increases and peripheral glucose utilization decreases. Systemic beta-adrenergic blockade during hypoglycemia increases peripheral glucose utilization. To explore the local effects of increased alpha- and beta-adrenergic activity on skeletal muscle glucose utilization, we measured arterial and venous plasma glucose concentrations, forearm blood flow (FBF), and forearm glucose uptake (FGU) during a hyperinsulinemic (40 mU/m2/min) stepped-hypoglycemic clamp with intrabrachial artery infusion of saline, phentolamine, propranolol, or combined phentolamine and propranolol. A control study was also performed with a euglycemic clamp and intraarterial saline. During hypoglycemia with saline and phentolamine, there were significant increases in FBF (130% +/- 38% and 180% +/- 35%, respectively) and FGU (120% +/- 51% and 230% +/- 150%, respectively). During hypoglycemia with propranolol and phentolamine + propranolol, FBF remained constant. FGU during hypoglycemia with propranolol was not different versus hypoglycemia with saline. No differences were found in these studies for forearm lactate output (FLO) or venous free fatty acid concentrations. These results demonstrate that local, as opposed to systemic, blockade during hypoglycemia does not alter peripheral glucose utilization.

Physiology of glucose counterregulation to hypoglycemia

Prevention of hypoglycemia is essential for the preservation of brain metabolism and survival of the whole body. Normally, glucose is the only substrate used by the brain to meet its metabolic requirements. Therefore, a continuous supply of circulatory glucose is a necessary prerequisite for normal cerebral metabolism. When plasma glucose concentration decreases (e.g., during prolonged fasting or after administration of glucose-lowering drugs) several physiologic responses are activated to prevent further decreases in blood glucose. The first response is known as counterregulation, a system that prevents and corrects hypoglycemia through the release of counterregulatory hormones.

Attenuated hepatic glucose production but unimpaired lipolysis in newborn infants of mothers with diabetes

In infants of diabetic mothers, maternal-fetal hyperglycemia induces fetal hyperinsulinemia, which may be sustained for several hours after birth. The inhibitory effect of insulin on glycogenolysis, gluconeogenesis, and lipolysis increases the risk of hypoglycemia in these infants. Eight term infants of diabetic mothers were studied between 3.9 and 8.5 h postnatally. The maternal diabetes was considered well controlled as judged by self-monitoring of blood glucose and Hb Alc. Neonatal plasma concentrations of glucose, glycerol, and insulin were monitored and averaged 2.7 +/- 0.7 mM, 371 +/- 116 microM, and 15.9 +/- 2.8 microU.mL-1, respectively. Stable isotope-gas chromatography/ mass spectrometry techniques were used to determine glucose and glycerol turnover rates and gluconeogenesis from glycerol in the infants. The appearance rates of glucose and glycerol averaged 20.0 +/- 5.4 mumol.kg-1.min-1 (3.6 +/- 1.0 mg.kg-1.min-1), and 8.9 +/- 2.3 mumol.kg-1.min-1, respectively. The fraction of glycerol appearance rate converted to glucose was 68.2 +/- 17.3%, which accounted for 15.5 +/- 4.6% of glucose production. Thus, compared with healthy term infants studied previously under identical conditions, the infants of diabetic mothers had higher insulin concentrations and attenuated glucose production. Despite increased insulin concentrations, lipolysis was unimpaired, and the gluconeogenic contribution from glycerol was higher than in the healthy newborns.

Regulation of lipolysis by the sympathetic nervous system: a microdialysis study in normal and spinal cord-injured subjects

To evaluate the regulation of lipolysis by the sympathetic nervous system, eight spinal cord-injured (SCI) subjects with a lesion above T5 resulting in a decentralization of the lower-body sympathetic nervous system and adrenal medulla (age, 36 +/- 2 years; weight, 82 +/- 5 kg; body fat mass, 26.8 +/- 3.0 kg; all mean +/- SE) and nine control subjects (age, 33 +/- 2; weight, 80 +/- 3; NS; body fat mass, 16.1 +/- 1.5 kg; P < .01) were investigated after fasting overnight. Each subject was studied with subcutaneous microdialysis and 133Xe-clearance adipose tissue blood flow (ATBF) in the umbilical and clavicular regions during postabsorptive rest and after sympathoexcitatory stimulation by means of mental stress and isometric handgrip exercise. SCI subjects had an increased body fat mass, hyperinsulinemia, and an elevated lipolytic rate at rest compared with control subjects. ATBF and lipolysis were activated to a normal extent following mental stress and isometric handgrip exercise in the umbilical region in control subjects. ATBF was increased in tissue above but not below the lesion level in SCI subjects following mental stress. Glycerol release was not different between groups in either tissue region despite significantly lower noradrenaline and adrenaline levels in SCI subjects. This finding argues against a significant adrenergic control of the lipolytic rate at rest. Furthermore, the small differences in stimulated glycerol release between groups, as well as the increased plasma glycerol levels in SCI subjects, cast doubt on the view that interruption of adrenergic activity below the lesion is the sole mechanism underlying the increased body fat mass in SCI subjects.

Long-term intensive insulin therapy in IDDM: effects on HbA1c, risk for severe and mild hypoglycaemia, status of counterregulation and awareness of hypoglycaemia

The present studies were designed to assess the percentage of HbA1c, frequency, and awareness of hypoglycaemia (H) during long-term intensive therapy (IT) of insulin-dependent diabetes mellitus (IDDM). From 1981 to 1994, 112 IDDM patients were on IT. HbA1c was 7.17 +/- 0.16% (non-diabetic subjects 3.8-5.5%), the frequency of severe H 0.01 +/- 0.009 episodes/patient-year, frequency of mild symptomatic H 35.6 +/- 2.9 episodes/patient-year. IDDM patients with HbA1c < or = 5.5% (Group I, n = 10), between 6.1-7.0% (Group II, n = 12), and > or = 7.6% (Group III, n = 11) were studied to assess responses of counterregulatory hormones, symptoms and cognitive function during experimental, stepped H. Compared to 18 non-diabetic subjects, Group I exhibited high thresholds (plasma glucose had to decrease more than normal to evoke responses), and impaired responses of adrenaline, unawareness of H and delayed onset of cognitive dysfunction at the lowest glycaemic plateau (2.3 mmol/l). Group II had normal thresholds and responses, whereas Group III had low thresholds. Frequency of mild H was higher in Group I (54.5 +/- 1.9 episodes/patient-year) than in Group II and III (33.7 +/- 3.5 and 20.4 +/- 2.5 episodes/patient-year, respectively, p < 0.001) and correlated with percentage of HbA1c (r = -0.82).

IN CONCLUSION

IT can maintain near-normal HbA1c and is compatible with low frequency of severe H. However, if HbA1c is less than 6.0%, mild, symptomatic H is excessively frequent and causes impaired counterregulation and H unawareness. Efforts should be made not only to maintain HbA1c < or = 7.0%, but also to prevent, recognize and reverse iatrogenic H unawareness during long-term IT of IDDM by maintaining HbA1c > 6.0%.

Inhibition of muscle glycogen synthase activity and non-oxidative glucose disposal during hypoglycaemia in normal man

The purpose of the present study was to evaluate the role of muscle glycogen synthase activity in the reduction of glucose uptake during hypoglycaemia. Six healthy young men were examined twice; during 120 min of hyperinsulinaemic (1.5 mU.kg-1. min-1) euglycaemia followed by: 1)240 min of graded hypoglycaemia (plasma glucose nadir 2.8 mmol/l) or 2) 240 min of euglycaemia. At 350-360 min a muscle biopsy was taken and indirect calorimetry was performed at 210-240 and 330-350 min. Hypoglycaemia was associated with markedly increased levels of adrenaline, growth hormone and glucagon and also with less hyperinsulinaemia. During hypoglycaemia the fractional velocity for glycogen synthase was markedly reduced; from 29.8 +/- 2.3 to 6.4 +/- 0.9%, p < 0.05. Total glucose disposal was decreased during hypoglycaemia (5.58 +/- 0.55 vs 11.01 +/- 0.75 mg.kg-1. min-1 (euglycaemia); p < 0.05); this was primarily due to a reduction of non-oxidative glucose disposal (2.43 +/- 0.41 vs 7.15 +/- 0.7 mg.kg-1 .min-1 (euglycaemia); p < 0.05), whereas oxidative glucose disposal was only suppressed to a minor degree. In conclusion hypoglycaemia virtually abolishes the effect of insulin on muscle glycogen synthase activity. This is in keeping with the finding of a marked reduction of non-oxidative glucose metabolism.

Characterization of the insulin-antagonistic effect of growth hormone in insulin-dependent diabetes mellitus

To characterize its insulin-antagonistic effect, growth hormone (GH) was infused at variable rates (24, 12 or 6 mU kg-1 min-1) for 1 h in 7 IDDM patients. Saline infusion was used as control (C) and all patients participated in all studies. The effect of insulin was measured with the euglycaemic clamp technique for 6 h combined with d-(3-3H)-glucose to evaluate glucose turnover. The insulin levels during the clamps were similar in all studies (23 +/- 3 mU l-1). The infusions produced peak GH levels of (24 rate = 24) 157 +/- 11, (12 rate = 12) 76 +/- 7, and (6 rate = 6) 45 +/- 8 mU l-1 (mean +/- SEM). The insulin-antagonistic effect of GH on glucose uptake was seen after 2 h and was at a maximum 4 to 5 h after the start of the GH infusion (difference in glucose infusion rate between C and 24 was 1.7 +/- 0.4 mg kg-1 min-1, p < 0.01). The resistance was due to a less pronounced effect of insulin to both inhibit rate of appearance and to stimulate rate of disappearance. Infusion of GH at 12 mU kg-1 min-1 induced a less pronounced insulin resistance both with regards to maximal effect (glucose infusion rate C - GH 1.4 +/- 0.5 mg kg-1 min-1, p < 0.05) and duration (3 h). At 6 mU kg-1 min-1, a clear GH-induced insulin-antagonistic effect was only seen during the third hour of the clamp (glucose infusion rate C-GH 1.3 +/- 0.5 mg kg-1 min-1, p < 0.05). GH infusion impaired the effect of insulin to lower both the levels of free fatty acids (NEFA) and glycerol between 2 and 5 h after the start of the infusion (NEFA, C:110 +/- 29, 24:303 +/- 95, p < 0.05: glycerol, C:32 +/- 4, 24:50 +/- 7 mumol l-1, p < 0.05). The present study therefore demonstrates that the insulin-antagonistic effect of GH in IDDM is related to the plasma levels both with regard to duration and response. The results also indicate that GH impairs the effect of insulin on lipolysis in IDDM after physiological peaks.

Paradoxical insulin-induced increase in gluconeogenesis in response to prolonged hypoglycemia in conscious dogs

The aim of this study was to determine the effects of differing insulin concentrations on the gluconeogenic response to equivalent prolonged hypoglycemia. Insulin was infused intraportally, for 3 h, into normal 18-h fasted conscious dogs at 2 (lower, n = 6) or 8 mU.kg-1.min-1 (high, n = 7) on separate occasions. This resulted in steady-state arterial insulin levels of 80 +/- 8 and 610 +/- 55 microU/ml, respectively. Glucose was infused during high dose to maintain the hypoglycemic plateau (50 +/- 1 mg/dl) equivalent to lower. Epinephrine (806 +/- 180 vs. 2,589 +/- 260 pg/ml), norepinephrine (303 +/- 55 vs. 535 +/- 60 pg/ml), cortisol (5.8 +/- 1.2 vs. 12.1 +/- 1.5 micrograms/dl), and pancreatic polypeptide (598 +/- 250 vs. 1,198 +/- 150 pg/ml) were all increased (P < 0.05) in the presence of high-dose insulin. Net hepatic glucose production increased significantly from 2.2 +/- 0.3 to 3.8 +/- 0.5 mg.kg-1.min-1 (P < 0.05) during high-dose infusion but remained at basal levels (2.3 +/- 0.4 mg.kg-1.min-1) during lower-dose insulin. During the 3rd h of hypoglycemia, gluconeogenesis accounted for between 42 and 100% of glucose production during high-dose infusion but only 22-52% during lower-dose insulin. Intrahepatic gluconeogenic efficiency, however, increased similarly during both protocols. Lipolysis, as indicated by arterial blood glycerol levels, increased by a greater amount during high- compared with lower-dose insulin infusion. Six hyperinsulinemic euglycemic control experiments (2 or 8 mU.kg-1.min-1, n = 3 in each) provided baseline data. Gluconeogenesis remained similar to basal levels, but lipolysis was significantly suppressed during both series of hyperinsulinemic euglycemic studies. In summary, these data suggest that 1) the important counterregulatory processes of gluconeogenesis and lipolysis can be significantly increased during prolonged hypoglycemia despite an eightfold increase in circulating insulin levels and 2) the amplified gluconeogenic rate present during the hypoglycemic high-dose insulin infusions was caused by enhanced substrate delivery to the liver rather than an increase in intrahepatic gluconeogenic efficiency.

Forearm muscle insulin resistance during hypoglycemia: role of adrenergic mechanisms and hypoglycemia per se

The forearm perfusion technique was used 1) to quantify the muscle metabolism of glucose and gluconeogenic precursors in response to insulin-induced hypoglycemia and 2) to assess the role of catecholamines and glucose concentration, pe se. Insulin (0.5 mU.kg-1.min-1) was infused for 4 h in three groups of healthy volunteers. In group I (n = 6), blood glucose (BG) was maintained at its basal level (4.5 +/- 0.1 mmol/l). In group II (n = 7), BG was allowed to fall to approximately 3 mmol/l. Group III (n = 6) was similar to group II except that propranolol was infused also. In addition, at 240 min, hypoglycemia was locally corrected by intrabrachial glucose infusion while maintaining the systemic milieu unperturbed. In group I, forearm glucose uptake (FGU) increased from 4.7 +/- 1.3 to a mean value of 37.8 +/- 5.0 mumol.l-1.min-1, whereas in group II it remained unchanged (8.3 +/- 2.0 mumol.l-1.min-1). In group III, propranolol partially prevented the suppression of FGU that increased to 21.6 +/- 5.2 mumol.l-1.min-1 (P < 0.05 vs. group II). Local correction of hypoglycemia normalized the FGU response (36.5 +/- 8.0 mumol.l-1.min-1). Muscle release of lactate, but not of alanine, was slightly higher during hypoglycemia (P = not significant). Forearm blood flow remained unchanged in groups I and III, whereas it increased by approximately 40% in group II (P < 0.05). It is concluded that, during mild hypoglycemia 1) extreme insulin resistance develops in the skeletal muscle, mediated by beta-adrenergic stimulation and reduced glucose mass effect and 2) mobilization of gluconeogenic precursors is only weakly activated.

Evidence that the brain of the conscious dog is insulin sensitive

The aim of this study was to determine whether a selective increase in the level of insulin in the blood perfusing the brain is a determinant of the counterregulatory response to hypoglycemia. Experiments were carried out on 15 conscious 18-h-fasted dogs. Insulin was infused (2 mU/kg per min) in separate, randomized studies into a peripheral vein (n = 7) or both carotid and vertebral arteries (n = 8). This resulted in equivalent systemic insulinemia (84 +/- 6 vs. 86 +/- 6 microU/ml) but differing insulin levels in the head (84 +/- 6 vs. 195 +/- 5 microU/ml, respectively). Glucose was infused during peripheral insulin infusion to maintain the glucose level (56 +/- 2 mg/dl) at a value similar to that seen during head insulin infusion (58 +/- 2 mg/dl). Despite equivalent peripheral insulin levels and similar hypoglycemia; steady state plasma epinephrine (792 +/- 198 vs. 2394 +/- 312 pg/ml), norepinephrine (404 +/- 33 vs. 778 +/- 93 pg/ml), cortisol (6.8 +/- 1.8 vs. 9.8 +/- 1.6 micrograms/dl) and pancreatic polypeptide (722 +/- 273 vs. 1061 +/- 255 pg/ml) levels were all increased to a greater extent during head insulin infusion (P < 0.05). Hepatic glucose production, measured with [3-3H]glucose, rose from 2.6 +/- 0.2 to 4.3 +/- 0.4 mg/kg per min (P < 0.01) in response to head insulin infusion but remained unchanged (2.6 +/- 0.5 mg/kg per min) during peripheral insulin infusion. Similarly, gluconeogenesis, lipolysis, and ketogenesis were increased twofold (P < 0.001) during head compared with peripheral insulin infusion. Cardiovascular parameters were also significantly higher (P < 0.05) during head compared with peripheral insulin infusion. We conclude that during hypoglycemia in the conscious dog (a) the brain is directly responsive to physiologic elevations of insulin and (b) the response includes a profound stimulation of the autonomic nervous system with accompanying metabolic and cardiovascular changes.

Influence of the sympathetic nervous system on insulin sensitivity and adipose tissue metabolism: a study in spinal cord-injured subjects

To evaluate insulin sensitivity and adipose tissue metabolism, seven spinal cord-injured (SCI) subjects (age, 43 +/- 6 years; body mass index, 22.8 +/- 1.4; mean +/- SE) and their seven siblings (age, 45 +/- 6 years; body mass index, 24.8 +/- 0.8) were studied using oral glucose (100-g) tolerance tests (OGTTs), euglycemic insulin clamps (insulin infusion, 1 mU/kg.min), and microdialysis of the subcutaneous tissue. Blood glucose and insulin after oral glucose were significantly increased in SCI subjects as compared with their siblings. During insulin clamping, plasma adrenaline increased significantly in controls, but not in SCI subjects. However, the rates of glucose production (2.02 +/- 0.36 v 1.59 +/- 0.09 mg/kg.min) and utilization (5.13 +/- 0.71 v 5.78 +/- 0.34) were similar in the two groups. Furthermore, interstitial subcutaneous glycerol and lactate concentrations before and after oral glucose were similar in the two groups, even in neurally decentralized tissue with broken connection between the central nervous system and peripheral sympathetic nerves. The data suggest that (1) well-mobilized SCI subjects show minor insulin resistance, and (2) sympathetic nervous activity has a minor influence on adipose tissue metabolism in the postabsorptive state, but may affect insulin sensitivity during euglycemic clamping.

The insulin resistance syndrome in smokers is related to smoking habits

The relationship between smoking habits, insulin resistance, and related risk factors for cardiovascular disease was examined in 57 middle-aged male smokers whose degree of insulin resistance was quantified by using the euglycemic clamp technique. Smoking habits correlated with degree of insulin resistance and consequently with various manifestations of the insulin resistance syndrome including levels of insulin, high-density lipoprotein cholesterol, triglycerides, and plasminogen activator inhibitor-1 (PAI-1) activity. Smoking habits, independent of degree of insulin resistance, were also related to levels of total cholesterol and low-density lipoprotein cholesterol as well as triglycerides. Stepwise regression analyses considering the effects of age, lean body mass, body fat, body mass index, waist/hip ratio, and alcohol consumption showed that only smoking habits and percent body fat were independently related to degree of insulin resistance. This study shows that insulin resistance and the insulin resistance syndrome are important but not unique contributors to the strong risk profile for cardiovascular disease in middle-aged men who smoke.

Long-term recovery from unawareness, deficient counterregulation and lack of cognitive dysfunction during hypoglycaemia, following institution of rational, intensive insulin therapy in IDDM

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; HbA1c 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.

Relative roles of insulin and hypoglycaemia on induction of neuroendocrine responses to, symptoms of, and deterioration of cognitive function in hypoglycaemia in male and female humans

To assess the relative roles of insulin and hypoglycaemia on induction of neuroendocrine responses, symptoms and deterioration of cognitive function (12 cognitive tests) during progressive decreases in plasma glucose, and to quantitate glycaemic thresholds, 22 normal, non-diabetic subjects (11 males, 11 females) were studied on four occasions: prolonged fast (n = 8, saline euglycaemia study, SA-EU), stepped hypoglycaemia (plasma glucose plateaus of 4.3, 3.7, 3 and 2.3 mmol/l) or euglycaemia during insulin infusion at 1 and 2 mU.kg-1.min-1 (n = 22, high-insulin hypoglycaemia and euglycaemia studies, HI-INS-HYPO and HI-INS-EU, respectively), and stepped hypoglycaemia during infusion of insulin at 0.35 mU.kg-1.min-1 (n = 9, low-insulin hypoglycaemia study, LO-INS-HYPO). Insulin per se (SA-EU vs HI-INS-EU), suppressed plasma glucagon (approximately 20%) and pancreatic polypeptide (approximately 30%), whereas it increased plasma noradrenaline (approximately 10%, p < 0.05). Hypoglycaemia per se (HI-INS-HYPO vs HI-INS-EU) induced responses of counterregulatory hormones (CR-HORM), symptoms and deteriorated cognitive function. With the exception of suppression of endogenous insulin secretion, which had the lowest glycaemic threshold of 4.44 +/- 0.06 mmol/l, pancreatic polypeptide, glucagon, growth hormone, adrenaline and cortisol had similar glycaemic thresholds (approximately 3.8-3.6 mmol/l); noradrenaline (3.1 +/- 0.0 mmol/l), autonomic (3.05 +/- 0.06 mmol/l) and neuroglycopenic (3.05 +/- 0.05 mmol/l) symptoms had higher thresholds. All 12 tests of cognitive function deteriorated at a glycaemic threshold of 2.45 +/- 0.06 mmol/l, but 7 out of 12 tests were already abnormal at a glycaemic threshold of 2.89 +/- 0.06 mmol/l. Although all CR-HORM had a similar glycaemic threshold, the lag time of response (the time required for a given parameter to increase) of glucagon (15 +/- 1 min) and growth hormone (14 +/- 3 min) was shorter than adrenaline (19 +/- 3 min) and cortisol (39 +/- 4 min) (p < 0.05). With the exception of glucagon (which was suppressed) and noradrenaline (which was stimulated), insulin per se (HI-INS-HYPO vs LO-INS-HYPO) did not affect the responses of CR-HORM, and did not influence the symptoms or the cognitive function during hypoglycaemia. Despite lower responses of glucagon, adrenaline and growth hormone (but not thresholds) in females than males, females were less insulin sensitive than males during stepped hypoglycaemia.

Pharmacokinetics, pharmacodynamics and glucose counterregulation following subcutaneous injection of the monomeric insulin analogue [Lys(B28),Pro(B29)] in IDDM

The aim of these studies was to compare the pharmacokinetics, pharmacodynamics, counterregulatory hormone and symptom responses, as well as cognitive function during hypoglycaemia induced by s.c. injection of 0.15 IU/kg of regular human insulin (HI) and the monomeric insulin analogue [Lys(B28),Pro (B29)] (MI) in insulin-dependent-diabetic (IDDM) subjects. In these studies glucose was infused whenever needed to prevent decreases in plasma glucose below 3 mmol/l. After MI, plasma insulin increased earlier to a peak (60 vs 90 min) which was greater than after HI (294 +/- 24 vs 255 +/- 24 pmol/l), and plasma glucose decreased earlier to a 3 mmol/l plateau (60 vs 120 min) (p < 0.05). The amount of glucose infused to prevent plasma glucose falling below 3 mmol/l was approximately three times greater after MI than HI (293 +/- 26 vs 90 +/- 25 mumol.kg-1 x 60-375 min-1, p < 0.05). After MI, hepatic glucose production was more suppressed (0.7 +/- 1 vs 5.9 +/- 0.54 mumol.kg-1.min-1) and glucose utilization was less suppressed than after HI (11.6 +/- 0.65 vs 9.1 +/- 0.11 mumol.kg-1.min-1) (p < 0.05). Similarly, plasma NEFA, glycerol, and beta-OH-butyrate were more suppressed after MI than HI (p < 0.05), whereas plasma lactate increased only after MI, but not after HI. Responses of counterregulatory hormones, symptoms and deterioration in cognitive function during plasma glucose plateau of 3 mmol/l were superimposable after MI and HI (p = NS).(ABSTRACT TRUNCATED AT 250 WORDS)

Medium-chain acyl-coenzyme A dehydrogenase deficiency: clinical course in 120 affected children

Medium-chain acyl-coenzyme A dehydrogenase deficiency is an autosomal recessive disorder of beta-oxidation of fatty acids manifested by episodic hypoglycemia, encephalopathy, apnea, and sudden death. Medical data were obtained on 120 patients with medium-chain acyl-coenzyme A dehydrogenase deficiency referred to Duke University Medical Center for biochemical testing. There were 55 male and 65 female subjects ranging from birth to 19 years of age; 118 subjects were white. Twenty-three children (19%) died before the diagnosis was made. Follow-up data were available in the 97 surviving patients for an average of 2.6 years after diagnosis. Psychodevelopmental data were collected on 73 patients older than 2 years of age. Unexpected morbidity included developmental and behavioral disability, chronic muscle weakness, failure to thrive, and cerebral palsy. We conclude that unidentified patients with this disorder have a significant risk of sudden death in early childhood and that survivors have a significant risk of developmental disability and chronic somatic illness.

Post-hypoglycaemic hyperketonaemia does not contribute to brain metabolism during insulin-induced hypoglycaemia in humans

It is controversial as to whether ketone bodies are utilized by the human brain as a fuel alternative to glucose during hypoglycaemia. To clarify the issue, we studied 10 normal volunteers during an experimental hypoglycaemia closely mimicking the clinical hypoglycaemia of patients with Type 1 (insulin-dependent) diabetes mellitus or insulinoma. Hypoglycaemia was induced by a continuous infusion of insulin (0.40 mU.kg-1.min-1 for 8 h, plasma insulin approximately 180 pmol/l) which decreased the plasma glucose concentration to approximately 3.1 mmol/l during the last 3 h of the studies. Subjects were studied on two occasions, i.e. spontaneous, counterregulatory-induced post-hypoglycaemic increase in 3-beta-hydroxybutyrate (from approximately 0.2 to approximately 1.1 mmol/l at 8 h), or prevention of post-hypoglycaemic hyperketonaemia (plasma beta-hydroxybutyrate approximately 0.1 mmol/l throughout the study) after administration of acipimox, a potent inhibitor of lipolysis. In the latter study, glucose was infused to match the hypoglycaemia observed in the former study. The glycaemic thresholds and overall responses of counterregulatory hormones, symptoms (both autonomic and neuroglycopenic), and deterioration of cognitive function (psychomotor tests) were superimposable in the control study in which ketones increased spontaneously after onset of hypoglycaemic counterregulation, as compared to the study in which ketones were suppressed (p = NS). The fact that responses of counterregulatory hormones, symptoms and deterioration in cognitive function were not exaggerated when posthypoglycaemic hyperketonaemia was prevented, indicate that during hypoglycaemia, the counterregulatory-induced endogenous hyperketonaemia does not provide the human brain with an alternative substrate to glucose. Thus, it is concluded that during hypoglycaemia, endogenous hyperketonaemia does not contribute to brain metabolism and function.