Cardiovascular outcomes associated with a new once-weekly GLP-1 receptor agonist vs. traditional therapies for type 2 diabetes: a simulation analysis.

AIM: The effect of glucose-lowering agents on diabetes-related complications including cardiovascular (CV) events is of major importance. In the absence of a long-term study, we simulated such a trial using a mathematical model where subjects were given exenatide once-weekly (EQW), which has been shown to improve glycaemic control and reduce weight, systolic blood pressure (SBP) and lipids in patients with type 2 diabetes mellitus (T2DM). METHODS: Using the Archimedes Model, we followed a simulated population derived from individuals with T2DM in NHANES who were drug-naïve or on oral agents only. We modelled the effects of four treatment strategies including standard care (SC, maintaining levels of control seen in NHANES), intensive glycaemic control (IGC, target HbA1c < 7% with conventional antidiabetic agents) and two versions of EQW added to SC: one with glycaemic and weight reduction only (EQW-1) and one with additional improvements in SBP and lipids (EQW-2). EQW strategies were derived from 52-week clinical trial data. Endpoints included macrovascular and microvascular outcomes. RESULTS: Simulated EQW treatment resulted in earlier benefit and 2-3 times greater relative reductions in major adverse CV events than IGC when compared to SC (6% relative reduction by year 20 for IGC vs. 12 and 17% for the EQW strategies). For microvascular complications, EQW showed comparable benefit to IGC for neuropathy but significantly greater impact on renal complications. CONCLUSIONS: This analysis shows that the novel drug EQW has the potential to greatly reduce CV events through its combined effects on glycaemia, weight and other CV risk factors.

The effect of pramlintide on hormonal, metabolic or symptomatic responses to insulin-induced hypoglycaemia in patients with type 1 diabetes.

BACKGROUND: Pramlintide, a human amylin analogue, is a potential new adjunctive therapy to insulin for patients with type 1 diabetes and insulin-using patients with type 2 diabetes. Early clinical trials have shown a transient increased risk of hypoglycaemia in some patients at the time of initiating pramlintide therapy. This may be the result of combining the postprandial glucose, lowering effect of pramlintide with the existing hypoglycaemic potential of insulin without appropriate adjustment of insulin doses. However, the possibility that pramlintide may exert an independent detrimental effect on the physiological responses to insulin-induced hypoglycaemia needs to be excluded. METHODS: We conducted three separate randomized, placebo-controlled studies in patients with type 1 diabetes treated with adjunctive pramlintide. These studies utilized pramlintide at high doses (either 0.1-1 mg pramlintide daily or 0.1-0.8 mg pramlintide four times a day for 5 or 6 days) as well as doses closer to those anticipated for therapeutic usage (30, 100 or 300 microg three times daily for 14 days), and examined the hormonal, metabolic and symptomatic responses to an insulin-infusion hypoglycaemic challenge conducted at baseline and after days of therapy. RESULTS AND CONCLUSION: Pramlintide had no effect on the counter-regulatory hormonal, metabolic and symptomatic responses to hypoglycaemia. These findings demonstrated that pramlintide, when used as adjunctive therapy to insulin in patients with type 1 diabetes, has no independent effect on the response to hypoglycaemia.

Adjunctive therapy with pramlintide lowers HbA1c without concomitant weight gain and increased risk of severe hypoglycemia in patients with type 1 diabetes approaching glycemic targets.

AIMS: In long-term clinical trials in patients with type 1 diabetes spanning a wide range of HbA1c, addition of pramlintide to existing insulin regimens led to reductions in HbA1c that were accompanied by weight loss and no increase in overall severe hypoglycemia event rates. Given that weight gain and increased hypoglycemia risk contribute to the difficulty of attaining HbA1c targets (<7 %), the question arose whether pramlintide could benefit patients approaching, but not reaching glycemic targets with insulin alone. To address this question, we conducted a pooled analysis from 3 long-term clinical trials, including all patients with an entry HbA1c between 7.0 % and 8.5 %. METHODS: Within the subset of patients with an entry HbA1c between 7.0 % and 8.5 % (approximately 28 % of all patients enrolled in the 3 studies), 196 were treated with placebo + insulin (baseline HbA1c 7.9+/-0.4 %, body weight 76.0+/-14.3 kg [mean+/-SD]) and 281 with pramlintide+insulin (baseline HbA1c 7.9+/-0.4 %, body weight 75.4+/-13.1 kg). Endpoints included placebo-corrected changes from baseline to week 26 in HbA1c, body weight, and the event rate of severe hypoglycemia. RESULTS: Adjunctive therapy with pramlintide resulted in significant reductions in HbA1c and body weight from baseline to week 26 (0.3 % and 1.8 kg, placebo-corrected treatment differences, respectively, both p

Amylin replacement with pramlintide as an adjunct to insulin therapy improves long-term glycaemic and weight control in Type 1 diabetes mellitus: a 1-year, randomized controlled trial.

AIMS: The autoimmune-mediated destruction of pancreatic beta-cells in Type 1 diabetes mellitus renders patients deficient in two glucoregulatory peptide hormones, insulin and amylin. With insulin replacement alone, most patients do not achieve glycaemic goals. We aimed to determine the long-term efficacy and safety of adjunctive therapy with pramlintide, a synthetic human amylin analogue, in patients with Type 1 diabetes. METHODS: In a double-blind, placebo-controlled, parallel-group, multicentre study, 651 patients with Type 1 diabetes (age 41 +/- 13 years, HbA(1c) 8.9 +/- 1.0%, mean +/- sd) were randomized to mealtime injections of placebo or varying doses of pramlintide, in addition to their insulin therapy, for 52 weeks. RESULTS: Addition of pramlintide [60 microg three times daily (TID) or four times daily (QID)] to insulin led to significant reductions in HbA(1c) from baseline to Week 52 of 0.29% (P < 0.011) and 0.34% (P < 0.001), respectively, compared with a 0.04% reduction in placebo group. Three times the proportion of pramlintide- than placebo-treated patients achieved an HbA(1c) of < 7%. The greater reduction in HbA(1c) with pramlintide was achieved without an increase in concomitant insulin use and was accompanied by a significant reduction in body weight from baseline to Week 52 of 0.4 kg in the 60 microg TID (P < 0.027) or QID (P < 0.040) pramlintide treatment groups, compared with a 0.8-kg gain in body weight in the placebo group. The most common adverse event in pramlintide-treated patients was transient, mild-to-moderate nausea. CONCLUSIONS: These results show that mealtime amylin replacement with pramlintide, as an adjunct to insulin therapy, improves long-term glycaemic and weight control in patients with Type 1 diabetes.

The human amylin analog, pramlintide, reduces postprandial hyperglucagonemia in patients with type 2 diabetes mellitus.

AIMS: Amylin is a second beta-cell hormone that is normally co-secreted with insulin in response to meals; it complements the effects of insulin in postprandial glucose control, in part by suppressing glucagon secretion. In patients with type 2 diabetes, mealtime administration of the human amylin analog pramlintide markedly improves postprandial glucose excursions. The aim of this study was to examine whether pramlintide reduces the postprandial hyperglucagonemia that is often seen in this patient population. METHODS: Utilizing a single-blind, placebo-controlled crossover design, 24 patients with type 2 diabetes, 12 insulin-treated and 12 non-insulin-treated, underwent a standardized mixed meal test on 2 occasions during which they received, in randomized order, a five-hour intravenous infusion of placebo or pramlintide (100 microg/h). RESULTS: During the placebo infusion, plasma glucose and plasma glucagon concentrations increased substantially after the meal. During the pramlintide infusion, postprandial plasma glucose and plasma glucagon responses were significantly (p < 0.05, all) reduced following ingestion of the same meal, both in the insulin-treated and non-insulin-treated subgroups. CONCLUSION: Supplementation of mealtime amylin with pramlintide reduces postprandial hyperglucagonemia in patients with type 2 diabetes, a mechanism that likely contributes to pramlintide's postprandial glucose-lowering effect.

The human amylin analog, pramlintide, corrects postprandial hyperglucagonemia in patients with type 1 diabetes.

Mealtime amylin replacement with the human amylin analog pramlintide as an adjunct to insulin therapy improves postprandial glycemia and long-term glycemic control in type 1 diabetes. Preclinical animal studies indicate that these complementary effects may result from at least 2 independent mechanisms: a slowing of nutrient delivery to the small intestine and a suppression of nutrient-stimulated glucagon secretion. The former effect of pramlintide has previously been demonstrated in patients with type 1 diabetes. The present studies characterize the effect of pramlintide on postprandial glucagon secretion in this patient population. Plasma glucagon and glucose concentrations were measured before and after a standardized liquid meal in 2 separate randomized, double-blind, placebo-controlled studies of pramlintide administration to patients with type 1 diabetes. In a 2-day crossover study, 18 patients received a 5-hour intravenous infusion of pramlintide (25 microg/h or 50 microg/h) or placebo in addition to subcutaneous (SC) insulin injections. In a 14-day parallel-group study, 84 patients received SC injections of 30, 100, or 300 microg of pramlintide or placebo 3 times daily in addition to SC injections of insulin. In both studies plasma glucagon concentrations increased in response to the meal in the placebo-plus-insulin group but not in any of the pramlintide-treated groups (all pramlintide treatment arms v placebo, P <.05). We conclude that mealtime amylin replacement with pramlintide prevents the abnormal meal-related rise in glucagonemia in insulin-treated patients with type 1 diabetes, an effect that likely contributes to its ability to improve postprandial glucose homeostasis and long-term glycemic control.

Amylin replacement with pramlintide as an adjunct to insulin therapy in type 1 and type 2 diabetes mellitus: a physiological approach toward improved metabolic control.

Destruction and dysfunction of pancreatic beta-cells, resulting in absolute and relative insulin deficiency, represent key abnormalities in the pathogenesis of type 1 and type 2 diabetes, respectively. Following the discovery of amylin, a second beta-cell hormone that is co-secreted with insulin in response to nutrient stimuli, it was realized that diabetes represents a state of bihormonal beta cell deficiency and that lack of amylin action may contribute to abnormal glucose homeostasis. Experimental studies show that amylin acts as a neuroendocrine hormone that complements the effects of insulin in postprandial glucose regulation through several centrally mediated effects. These include a suppression of postprandial glucagon secretion and a vagus-mediated regulation of gastric emptying, thereby helping to control the influx of endogenous and exogenous glucose, respectively. In animal studies, amylin has also been shown to reduce food intake and body weight, consistent with an additional satiety effect. Pramlintide is a soluble, non-aggregating, injectable, synthetic analog of human amylin currently under development for the treatment of type 1 and insulin-using type 2 diabetes. Long-term clinical studies have consistently demonstrated that pre-prandial s.c. injections of pramlintide, in addition to the current insulin regimen, reduce HbA(1c) and body weight in type 1 and type 2 diabetic patients, without an increase in insulin use or in the event rate of severe hypoglycemia. The most commonly observed side effects were gastrointestinal-related, mainly mild nausea, which typically occurred upon initiation of treatment and resolved within days or weeks. Amylin replacement with pramlintide as an adjunct to insulin therapy is a novel physiological approach toward improved long-term glycemic and weight control in patients with type 1 and type 2 diabetes.

Effect of insulin on glycerol production in obese adolescents.

Impaired stimulation of glucose metabolism and reduced suppression of lipolytic activity have both been suggested as important defects related to the insulin resistance of adolescent obesity. To further explore the relationship between these abnormalities, we studied seven obese [body mass index (BMI) 35 +/- 2 kg/m2] and seven lean (BMI 21 +/- 1 kg/m2) adolescents aged 13-15 yr and compared them with nine lean adults (aged 21-27 yr, BMI 23 +/- 1 kg/m2) during a two-step euglycemic-hyperinsulinemic clamp in combination with 1) a constant [2H5]glycerol (1.2 mg.m-2.min-1) infusion to quantify glycerol turnover and 2) indirect calorimetry to estimate glucose and net lipid oxidation rates. In absolute terms, basal glycerol turnover was increased and suppression by insulin was impaired in obese adolescents compared with both groups of lean subjects (P < 0.01). However, when the rates of glycerol turnover were adjusted for differences in body fat mass, the rates were similar in all three groups. Basal plasma free fatty acid (FFA) concentrations were significantly elevated, and the suppression by physiological increments in plasma insulin was impaired in obese adolescents compared with lean adults (P < 0.05). In parallel with the high circulating FFA levels, net lipid oxidation in the basal state and during the clamp was also elevated in the obese group compared with lean adults. Net lipid oxidation was inversely correlated with glucose oxidation (r = -0.50, P < 0.01). In conclusion, these data suggest that lipolysis is increased in obese adolescents (vs. lean adolescents and adults) as a consequence of an enlarged adipose mass rather than altered sensitivity of adipocytes to the suppressing action of insulin.

Efficacy and metabolic effects of metformin and troglitazone in type II diabetes mellitus.

BACKGROUND: Combination therapy is logical for patients with non-insulin-dependent (type 2) diabetes mellitus, because they often have poor responses to single-drug therapy. We studied the efficacy and physiologic effects of metformin and troglitazone alone and in combination in patients with type 2 diabetes. METHODS: We randomly assigned 29 patients to receive either metformin or troglitazone for three months, after which they were given both drugs for another three months. Plasma glucose concentrations during fasting and postprandially and glycosylated hemoglobin values were measured periodically during both treatments. Endogenous glucose production and peripheral glucose disposal were measured at base line and after three and six months. RESULTS: During metformin therapy, fasting and postprandial plasma glucose concentrations decreased by 20 percent (58 mg per deciliter [3.2 mmol per liter], P<0.001) and 25 percent (87 mg per deciliter [4.8 mmol per liter], P<0.001), respectively. The corresponding decreases during troglitazone therapy were 20 percent (54 mg per deciliter [2.9 mmol per liter], P=0.01) and 25 percent (83 mg per deciliter [4.6 mmol per liter], P<0.001). Endogenous glucose production decreased during metformin therapy by a mean of 19 percent (P=0.001), whereas it was unchanged by troglitazone therapy (P=0.04 for the comparison between groups). The mean rate of glucose disposal increased by 54 percent during troglitazone therapy (P=0.006) and 13 percent during metformin therapy (P= 0.03 for the comparison within the group and between groups). In combination, metformin and troglitazone further lowered fasting and postprandial plasma glucose concentrations by 18 percent (41 mg per deciliter [2.3 mmol per liter], P=0.001) and 21 percent (54 mg per deciliter [3.0 mmol per liter], P<0.001), respectively, and the mean glycosylated hemoglobin value decreased 1.2 percentage points. CONCLUSIONS: Metformin and troglitazone have equal and additive beneficial effects on glycemic control in patients with type 2 diabetes. Metformin acts primarily by decreasing endogenous glucose production, and troglitazone by increasing the rate of peripheral glucose disposal.

Metabolic effects of troglitazone monotherapy in type 2 diabetes mellitus. A randomized, double-blind, placebo-controlled trial.

BACKGROUND: Troglitazone is a new insulin-sensitizing agent used to treat type 2 diabetes mellitus. The mechanism by which troglitazone exerts its effect on systemic glucose metabolism is unknown. OBJECTIVE: To determine the effects of 6 months of troglitazone monotherapy on glucose metabolism in patients with type 2 diabetes mellitus. DESIGN: Randomized, double-blind, placebo-controlled trial. SETTING: Six general clinical research centers at university hospitals. PATIENTS: 93 patients (mean age, 52 years) with type 2 diabetes mellitus (mean fasting plasma glucose level, 11.2 mmol/L) who were being treated with diet alone or who had discontinued oral antidiabetic medication therapy. INTERVENTION: Patients were randomly assigned to one of five treatment groups (100, 200, 400, or 600 mg of troglitazone daily or placebo) and had metabolic assessment before and after 6 months of treatment. MEASUREMENTS: Plasma glucose and insulin profiles during a meal tolerance test; basal hepatic glucose production and insulin-stimulated glucose disposal rate during a hyperinsulinemic-euglycemic clamp procedure. RESULTS: Troglitazone at 400 and 600 mg/d decreased both fasting (P < 0.001) and postprandial (P = 0.016) plasma glucose levels by approximately 20%. All four troglitazone dosages also decreased fasting (P = 0.012) and postprandial (P < 0.001) triglyceride levels; 600 mg of the drug per day decreased fasting free fatty acid levels (P = 0.018). Plasma insulin levels decreased in the 200-, 400-, and 600-mg/d groups (P < 0.001), and C-peptide levels decreased in all five study groups (P < 0.001). Basal hepatic glucose production was suppressed in the 600-mg/d group compared with the placebo group (P = 0.02). Troglitazone at 400 and 600 mg/d increased glucose disposal rate by approximately 45% above pretreatment levels (P = 0.003). Stepwise regression analysis showed that troglitazone therapy was the strongest predictor of a decrease in fasting (P < 0.001) or postprandial (P = 0.01) glucose levels. Fasting C-peptide level was the next strongest predictor (higher C-peptide level equaled greater glucose-lowering effect). CONCLUSION: Troglitazone monotherapy decreased fasting and postprandial glucose levels in patients with type 2 diabetes, primarily by augmenting insulin-mediated glucose disposal.

Microdialysis techniques in the study of brain and skeletal muscle.

Traditionally, plasma measurements have been used to monitor metabolic events and the actions of hormones that are actually taking place within tissue beds that are anatomically separated from the vascular compartment. It is generally assumed that the extracellular fluid (ECF) within metabolically active tissues is composed of substrates and hormones in concentrations that closely approximate those in plasma. Indeed, this view is implicit in non-steady-state tracer calculations. However, through the use of microdialysis techniques in the study of tissue metabolism this view is being challenged. Our data suggest that there may be substantial concentration gradients for a variety of fuels between plasma and ECF, i.e. fuels (e.g. glucose) removed from the circulation being lower and fuels (e.g. glycerol, lactate, some amino acids) produced by tissues being higher than plasma levels. In short, the metabolic milieu seen by individual tissues (and hormone receptors?) may, at least in some instances, be strikingly different from that in plasma, and as a result, plasma measurements by themselves may not appropriately define the contributions of specific tissues to metabolic events, and overlook the importance of metabolic processes which are largely restricted to individual tissue beds. Through the use of microdialysis as a means of directly sampling ECF from metabolically important body tissues and with the evolution of its use in animal and human research, this technique will continue to offer exciting new insights into tissue metabolism and to investigate fundamental issues that cannot be addressed by other methods.

Counterregulation in peripheral tissues: effect of systemic hypoglycemia on levels of substrates and catecholamines in human skeletal muscle and adipose tissue.

We used microdialysis to distinguish the effects of hyperinsulinemia and hypoglycemia on glucose, gluconeogenic substrate, and catecholamine levels in adipose and muscle extracellular fluid (ECF). Ten lean humans (six males and four females) were studied during baseline and hyperinsulinemic (3 mU x kg-1 x min-1 for 3 h) euglycemia (5.0 mmol/l) and hypoglycemia (2.8 mmol/l). In muscle and adipose, basal ECF glucose was lower (muscle, 3.5 +/- 0.2 mmol/l; adipose tissue, 3.3 +/- 0.2 mmol/l) and lactate was higher (muscle, 2.2 +/- 0.2 mmol/l; adipose, 1.5 +/- 0.3 mmol/l) than respective plasma values (glucose, 4.9 +/- 0.1 mmol/l; lactate, 0.7 +/- 0.1 mmol/l), whereas alanine was higher in muscle ECF (379 +/- 22 micromol/l) than adipose tissue (306 +/- 22 micromol/l) and plasma (273 +/- 33 micromol/l). Plasma catecholamines (unchanged during euglycemia) rose during hypoglycemia with epinephrine, increasing approximately fivefold more than norepinephrine. In contrast, the hypoglycemia-induced increments in muscle dialysate norepinephrine and epinephrine were similar, suggesting local generation of norepinephrine. Compared with euglycemia, hypoglycemia produced a greater increase in lactate and a smaller reduction in alanine in muscle ECF, whereas hypoglycemia caused a greater relative fall in ECF glucose concentrations in muscle (72 +/- 16%) and adipose tissue (69 +/- 9%) than in plasma (42 +/- 3%) (P < 0.05). We conclude that hypoglycemia increases the generation of norepinephrine and gluconeogenic substrates in key target tissues, while increasing the plasma-tissue concentration gradient for glucose. These changes suggest the stimulation of glucose extraction by peripheral tissues, despite systemic counterregulatory hormone release and local sympathetic activation.

Interstitial fluid concentrations of glycerol, glucose, and amino acids in human quadricep muscle and adipose tissue. Evidence for significant lipolysis in skeletal muscle.

To determine the relationship between circulating metabolic fuels and their local concentrations in peripheral tissues we measured glycerol, glucose, and amino acids by microdialysis in muscle and adipose interstitium of 10 fasted, nonobese human subjects during (a) baseline, (b) euglycemic hyperinsulinemia (3 mU/kg per min for 3 h) and, (c) local norepinephrine reuptake blockade (NOR). At baseline, interstitial glycerol was strikingly higher (P < 0.0001) in muscle (3710 microM) and adipose tissue (2760 microM) compared with plasma (87 microM), whereas interstitial glucose (muscle 3.3, fat 3.6 mM) was lower (P < 0.01) than plasma levels (4.8 mM). Taurine, glutamine, and alanine levels were higher in muscle than in adipose or plasma (P < 0.05). Euglycemic hyperinsulinemia did not affect interstitial glucose, but induced a fall in plasma glycerol and amino acids paralleled by similar changes in the interstitium of both tissues. Local NOR provoked a fivefold increase in glycerol (P < 0.001) and twofold increase in norepinephrine (P < 0.01) in both muscle and adipose tissues. To conclude, interstitial substrate levels in human skeletal muscle and adipose tissue differ substantially from those in the circulation and this disparity is most pronounced for glycerol which is raised in muscle as well as adipose tissue. In muscle, insulin suppressed and NOR increased interstitial glycerol concentrations. Our data suggest unexpectedly high rates of intramuscular lipolysis in humans that may play an important role in fuel metabolism.

Thermoregulatory responses to hyperinsulinemic hypoglycemia and euglycemia in humans.

Hypoglycemia induces physiological changes that influence thermoregulatory mechanisms. We studied such responses in a group of healthy males (mean age 23.5 yr, body mass index 23.7 kg/m2) during hyperinsulinemic euglycemia (E; 4.5 mmol/l) and hypoglycemia (H; 2.5 mmol/l) and under placebo control conditions (P; saline). Plasma epinephrine (P < 0.0001) and norepinephrine (P < 0.01) levels increased during H and were unchanged during P and E. During H, early increases in metabolic rate (P < 0.05), forearm blood flow (P < 0.01), and sweating (P < 0.01) were followed by a fall in skin temperature (from -1.2 to -2.6 degrees C) and blood flow (P < 0.01). Core temperature fell after 40 min of H and continued to fall thereafter (-0.34 +/- 0.08 degrees C). E and P had minimal effect on skin temperature and blood flow. In summary, in healthy human subjects, H causes a fall in core temperature by heat dissipation at the skin surface through evaporative heat loss and conduction of heat to the periphery, despite an increase in metabolic heat production.

Physiological and symptomatic responses to postural change in non-diabetic subjects during hypoglycaemia.

1. Insulin-induced hypoglycaemia is characterized by an autonomic disturbance which produces some of the symptoms of hypoglycaemia. How an additional autonomic stress like postural change may alter physiological responses and symptoms of hypoglycaemia is not known. In 10 healthy male subjects (mean age 24 years) we observed physiological and symptomatic responses to postural change during acute (20 min) and prolonged (60 min) hyperinsulinaemic (60 m-units min-1 m-2) hypoglycaemia (2.5 mmol/l) and euglycaemia (4.5 mmol/l), and placebo control (saline). 2. In all studies standing increased plasma catecholamines (adrenaline, P < 0.001; noradrenaline, P < 0.0001), blood pressure (P < 0.0001) and heart rate (P < 0.0001). Catecholamine responses to standing were augmented by acute hypoglycaemia (adrenaline, P < 0.005; noradrenaline, P < 0.01), but less so by prolonged hypoglycaemia (adrenaline, P < 0.05; noradrenaline, P < 0.05). Supine heart rate was higher before standing during prolonged hypoglycaemia (P < 0.05), but did not increase as much on standing when compared with acute hypoglycaemia and prolonged euglycaemia. 3. During acute hypoglycaemia, autonomic symptoms increased on standing, but during prolonged hypoglycaemia, in the presence of generally higher symptom scores, standing had no effect. Autonomic symptoms, with the exception of hunger, tended to decrease with time (P < 0.05) during prolonged hypoglycaemia. 4. To conclude, posture does modify the catecholamine and symptomatic responses to hypoglycaemia, but this effect is dependent on the duration of hypoglycaemia. Hypoglycaemia and hyperinsulinaemia had little or no effect on the cardiovascular responses to changing posture.

Thermoregulatory responses to hyperinsulinaemic hypoglycaemia and euglycaemia in IDDM.

In healthy subjects hypoglycaemia causes a fall in body temperature through increased sweating and limb blood flow, and despite increased metabolic heat production. We studied thermoregulatory responses to hyperinsulinaemic (100 mU.m-2.min-1) (a) hypoglycaemia (2.5 mmol/l) and (b) euglycaemia (4.5 mmol/l) in insulin-dependent diabetic men of short (< 5 years) and long (> 15 years) diabetes duration. Plasma noradrenaline (p < 0.0001), metabolic rate (p < 0.005), heart rate (p < 0.0001) and skin blood flow (p < 0.05) increased during hypoglycaemia and euglycaemia with a greater rise in noradrenaline during the former (p < 0.05). Plasma adrenaline (p < 0.005), forearm blood flow (p < 0.05) and systolic blood pressure (p < 0.02) increased and diastolic blood pressure decreased (p < 0.005) during hypoglycaemia, with greater changes in adrenaline (p < 0.05) and diastolic blood pressure in patients of short diabetes duration. Only two patients (diabetes duration < 2 years) sweated appropriately, while body temperature changed minimally in the two groups of patients. In summary, thermoregulatory responses to hypoglycaemia are impaired in IDDM due to attenuated sweating and adrenomedullary responses.

Metabolic heat production and cardiovascular responses to an incremental intravenous infusion of adrenaline in healthy subjects.

Increased circulating adrenaline causes a rise in metabolic heat production and well characterized cardiovascular changes. To further characterize these responses we measured metabolic heat production and cardiovascular responses during an incremental infusion of adrenaline (A) in ten healthy subjects (five male; aged 21 to 27 years) and in a placebo controlled (C) study. Plasma adrenaline was unchanged during C, but increased during A (baseline 0.2 nmol/l and low, intermediate and high dose 1.0, 1.9 and 3.1 nmol/l respectively). There was a stepwise increase in metabolic heat production during A (from baseline +0.19, +0.51 and +0.77 kJ/min) with a fall during C (-0.25 kJ/min). During high dose A, plasma adrenaline correlated with increments in metabolic heat production (p < 0.05). Heart rate increased (p < 0.01) and diastolic blood pressure decreased (p < 0.01) at low dose A, and systolic blood pressure increased during intermediate dose A (p < 0.01). Forearm blood flow increased during A and C, with a greater increase in the former during high dose A (p < 0.01). Toe blood flow and toe pulp blood velocity decreased during high dose A (p < 0.05), whereas, skin capillary blood velocity increased at low (p < 0.05) and fell at high (p < 0.01) dose A. In summary, adrenaline increases metabolic heat production and limb blood flow in a dose-dependent fashion. A small increment in plasma adrenaline causes a rise in skin capillary blood flow; and at higher plasma levels blood flow in skin capillaries and arteriovenous anastomoses falls.

Does ethanol cause hypoglycaemia in overnight fasted patients with type 1 diabetes?

Drinking ethanol is widely believed to predispose to hypoglycaemia in patients with Type 1 diabetes, the suggested mechanism being suppression of hepatic gluconeogenesis. The hypoglycaemic effect of ethanol was investigated by measuring steady-state glucose infusion rate during a hypoinsulinaemic (mean plasma insulin 14 +/- 1.3 (SEM) mU l-1), euglycaemic (blood glucose 5 mmol l-1) clamp. Nine patients with Type 1 diabetes fasted overnight and then had, in single-blind fashion, ethanol 0.5 g kg-1 by intravenous bolus followed by 0.25 g kg-1 h-1 or matched volumes of saline. After 1 h of ethanol or saline, all infusions were stopped and blood glucose monitored for a further 90 min. A 60-min ethanol infusion leading to a steady-state blood concentration of 26.2 +/- 1.4 mmol l-1 (120.7 mg %) did not alter the glucose infusion rate needed to maintain euglycaemia (1.22 +/- 0.12 mg kg-1 min-1 before and 1.23 +/- 0.12 during ethanol infusion), the initial rate of fall of blood glucose (ethanol 0.039 mmol l-1 min-1 vs control (0.033), the lowest blood glucose (4.43 mmol l-1 vs 4.31), or the rate of blood glucose recovery (ethanol 0.050 mmol l-1 min-1 vs control 0.054). We conclude that a moderate amount of ethanol, administered intravenously under controlled conditions, does not lead to hypoglycaemia in patients with Type 1 diabetes who have fasted overnight.