Pharmacokinetic and glucodynamic variability: assessment of insulin glargine, NPH insulin and insulin ultralente in healthy volunteers using a euglycaemic clamp technique

Aims/hypothesis This single-dose, double-blind, randomised, parallel-group study evaluated the reproducibility in systemic exposure and glucodynamic effect of insulin glargine, NPH insulin (NPH) and insulin ultralente (ultralente) using the manually adjusted euglycaemic clamp technique.Methods In total, 36 healthy volunteers received two consecutive s.c. injections (0.4 IU/kg) of glargine, NPH or ultralente with a wash-out period of 7 days between treatments.Results In healthy volunteers, glargine presented well-reproduced flat concentration profiles and no pronounced peaks in activity. NPH, by contrast, showed well-defined peaks in concentration and glucose disposal, while ultralente had highly variable profiles. Within-subject variability (ANOVA) for insulin exposure over 24 h was 15% for glargine and 19% for NPH, compared with 67% for ultralente (p<0.05, glargine and NPH vs ultralente). The 49% within-subject variability in total glucose disposal (glucose infusion rate [GIR]-AUC_{0–24 h}) with ultralente was about twice as large as the 22% with NPH (p<0.05), but was intermediate with glargine at 31% (p=NS). By contrast, variability in the diurnal time-action profile (SD of diurnal day-to-day differences in GIR) for glargine was 30% (p<0.05) and 50% (p<0.05) less than with NPH and ultralente, respectively. No serious adverse events were reported.Conclusions/interpretation Although representing insulins of different profiles, glargine and NPH showed a high and similar reproducibility of total absorption and glucodynamic effect, whereas ultralente proved to have poor reproducibility. However, while NPH yields peaks in concentration and activity, glargine shows flat and non-fluctuating profiles resulting in less variation in day-to-day 24-h activity.     

Effects of ritonavir and amprenavir on insulin sensitivity in healthy volunteers

BACKGROUND: Some HIV protease inhibitors (PIs) have been shown to induce insulin resistance in vitro but the degree to which specific PIs affect insulin sensitivity in humans is less well understood. METHODS: In two separate double-blind, randomized, cross-over studies, we assessed the effects of a single dose of ritonavir (800 mg) and amprenavir (1200 mg) on insulin sensitivity (euglycemic hyperglycemic clamp) in healthy normal volunteers. RESULTS: Ritonavir decreased insulin sensitivity (-15%; P = 0.008 versus placebo) and non-oxidative glucose disposal (-30%; P = 0.0004), whereas neither were affected by amprenavir administration. CONCLUSION: Compared to previously performed studies of identical design using single doses of indinavir and lopinavir/ritonavir, a hierarchy of insulin resistance was observed with the greatest effect seen with indinavir followed by ritonavir and lopinavir/ritonavir, with little effect of amprenavir.     

A comparison of the artificial pancreas (glucose controlled insulin infusion system) and a manual technique for assessing insulin sensitivity during euglycaemic clamping

Summary Two main methods are available for assessing insulin sensitivity with the hyperinsulinaemic euglycaemic clamp technique: one employs a glucose-controlled insulin infusion system (the Biostator) with automatic feedback control; the second depends on frequent glucose measurement and the use of an algorithm and a pocket calculator (manual) to determine the glucose infusion rate. The amount of glucose infused is a measure of insulin sensitivity. The efficiency of the two methods was compared in nine normal subjects (seven lean, two obese). After an overnight fast subjects were infused with insulin at 50 mU · kg^-1 · h^-1 for 2 h; this rate was doubled during the first 10 min for the manual technique. Blood glucose averaged 4.7 ± 0.1 and 4.8 ± 0.1 mmol/l from 0 to 120 min for Biostator and manual techniques and did not deviate significantly from the desired level. Variability of the clamp was also similar over the same period (coefficient of variation 5.1 ±0.6% and 6.4 ±0.7%, Biostator and manual). Glucose infused to maintain steady state from 60 to 120 min was higher, however, with the manual than the Biostator method (5.7±0.6 versus 4.4 ± 0.6 mg·kg^-1·min^-1, p< 0.01) even when the loading dose was omitted, although the two methods correlated closely (p< 0.05). Glucose infusion rate varied more from minute to minute with the Biostator (coefficient of variation 28.8 ± 3% versus 12.2 ± 2.1%). Steady-state serum insulin levels (30–120 min) were the same during both methods. Thus both methods give effective clamping but the manual method is simpler and shows less variability in glu cose insulin infusion rate.     

The short insulin tolerance test for determination of insulin sensitivity: a comparison with the euglycaemic clamp.

The glucose clamp technique is currently regarded as the standard test for measuring insulin sensitivity against which other methods are compared but is unsuitable for routine screening of patients outside a hospital base. There is thus a need for a simpler test to measure insulin sensitivity. We have therefore compared the glucose disappearance rate KITT in the first 15 min of the insulin tolerance test (ITT) with the M and M/I values derived from the standard euglycaemic clamp in nine normal subjects and eight subjects with Type 2 (non-insulin dependent) diabetes mellitus and coexisting obesity. All subjects underwent the ITT and euglycaemic clamp in random order. Nine subjects later had a repeat ITT to determine the reproducibility of the test. In the ITT, 0.1 U kg-1 body weight, human Actrapid insulin was given as an IV bolus and simultaneous arterialized and venous blood samples were obtained every minute for 15 min. The first order rate constant for the disappearance of glucose KITT over the period 3-15 min was taken as a measure of insulin sensitivity. The euglycaemic clamp was performed with an insulin infusion of 50 mU kg-1 h-1 for 120 min and a variable rate glucose infusion to maintain blood glucose concentration at 0.5 mmol l-1 below fasting level to minimize the effect of endogenous insulin secretion. The ratio of the mean rate of glucose infused (M, mumol kg-1 min-1) to the plasma insulin over the last 30 min of the clamp was taken as a measure of tissue sensitivity to insulin (M/I) assuming endogenous glucose output was suppressed.(ABSTRACT TRUNCATED AT 250 WORDS)     

Heritability and genetic correlations of insulin sensitivity measured by the euglycaemic clamp.

AIMS: Studies investigating genetic factors influencing insulin sensitivity/insulin resistance have measured this phenotype using a variety of methods. In this study, genetic correlations and heritability of insulin sensitivity measured using the euglycaemic hyperinsulinaemic clamp and related phenotypes were examined. METHODS: The study population included 818 non-diabetic individuals from 297 nuclear families. Genetic correlations and heritability estimates were calculated using variance components methods. RESULTS: Homeostasis model of insulin resistance (HOMA-IR) and fasting insulin were very highly phenotypically and genetically correlated (r = 0.99 and r = 0.99). HOMA-IR and insulin sensitivity measured with the euglycaemic clamp were only moderately genetically correlated (r = -0.53), suggesting that the two traits may be influenced, at least in part, by different genes. Heritabilities for fasting insulin (h2 = 0.36) and HOMA-IR (h2 = 0.38) were consistent with the published literature, but heritability for insulin sensitivity measured by the euglycaemic clamp was slightly lower than other published estimates (h(2) = 0.24). CONCLUSIONS: Because HOMA-IR (or fasting insulin) and insulin sensitivity measured with the euglycaemic clamp are not highly genetically correlated, they should not be used interchangeably in genetic studies. Given the very high correlations between fasting insulin and HOMA-IR, HOMA-IR does not offer any advantage over fasting insulin in analyses of insulin sensitivity in this population.     

Comparison between surrogate indexes of insulin sensitivity/resistance and hyperinsulinemic euglycemic glucose clamps in rhesus monkeys

The euglycemic glucose clamp is the reference method for assessing insulin sensitivity in humans and animals. However, clamps are ill-suited for large studies because of extensive requirements for cost, time, labor, and technical expertise. Simple surrogate indexes of insulin sensitivity/resistance including quantitative insulin-sensitivity check index (QUICKI) and homeostasis model assessment (HOMA) have been developed and validated in humans. However, validation studies of QUICKI and HOMA in both rats and mice suggest that differences in metabolic physiology between rodents and humans limit their value in rodents. Rhesus monkeys are a species more similar to humans than rodents. Therefore, in the present study, we evaluated data from 199 glucose clamp studies obtained from a large cohort of 86 monkeys with a broad range of insulin sensitivity. Data were used to evaluate simple surrogate indexes of insulin sensitivity/resistance (QUICKI, HOMA, Log HOMA, 1/HOMA, and 1/Fasting insulin) with respect to linear regression, predictive accuracy using a calibration model, and diagnostic performance using receiver operating characteristic. Most surrogates had modest linear correlations with SI(Clamp) (r ≈ 0.4-0.64) with comparable correlation coefficients. Predictive accuracy determined by calibration model analysis demonstrated better predictive accuracy of QUICKI than HOMA and Log HOMA. Receiver operating characteristic analysis showed equivalent sensitivity and specificity of most surrogate indexes to detect insulin resistance. Thus, unlike in rodents but similar to humans, surrogate indexes of insulin sensitivity/resistance including QUICKI and log HOMA may be reasonable to use in large studies of rhesus monkeys where it may be impractical to conduct glucose clamp studies.     

A comparison between enalapril and captopril on insulin sensitivity in normotensive healthy volunteers

Background: Captopril has been shown to improve insulin sensitivity in insulin resistant hypertensive individuals and enalapril has been shown to improve insulin sensitivity in a small group of healthy volunteers, but there has been no direct comparison of the effects of the different angiotensin converting enzyme inhibitors (ACEIs) on insulin sensitivity in either insulin sensitive or insulin insensitive populations. Aim: To compare the impact of two different ACEIs (captopril and enalapril) on insulin mediated glucose uptake in normotensive, non-obese, insulin sensitive subjects. Method: A single blind cross-over study comparing captopril (6.25 mg twice daily) and enalapril (5 mg once daily) for 28 days with a 28 day washout period between drugs. Insulin mediated glucose uptake was measured by means of the euglycaemic hyperinsulinaemic clamp at the start and completion of each period of drug therapy. Results: Both drugs resulted in elevations of fasting insulin levels (mean difference ± SEM for combined data, 2.7 ± 1.8; p < 0.05) and a reduction in insulin mediated glucose uptake (mean difference for combined data, - 0.72 ± 0.37 mg/kg¹ minute^-1; p= 0.056). Results were similar for both agents and suggest a class effect. Conclusions: The increase in fasting insulin levels, and reduction in insulin mediated glucose uptake in this study are in contrast to findings in obese and hypertensive subjects, and indicate that studies of insulin sensitivity of ACEIs in non-obese, normotensive subjects are inappropriate for predicting likely effects in clinical practice. (Aust NZ J Med 1993; 23: 652–655.)     

Glucose uptake and pulsatile insulin infusion: euglycaemic clamp and [3-3H]glucose studies in healthy subjects

To test the hypothesis that insulin has a greater effect on glucose metabolism when given as pulsatile than as continuous infusion, a 354-min euglycaemic clamp study was carried out in 8 healthy subjects. At random order soluble insulin was given intravenously either at a constant rate of 0.45 mU/kg X min or in identical amounts in pulses of 1 1/2 to 2 1/4 min followed by intervals of 10 1/2 to 9 3/4 min. Average serum insulin levels were similar during the two infusion protocols, but pulsatile administration induced oscillations ranging between 15 and 62 microU/ml. Glucose uptake expressed as metabolic clearance rate (MCR) for glucose was significantly increased during pulsatile insulin delivery as compared with continuous administration (270-294 min: 8.7 +/- 0.7 vs 6.8 +/- 0.9 ml/kg X min, P less than 0.01, and 330-354 min: 8.9 +/- 0.5 vs 7.4 +/- 0.9 ml/kg X min, P less than 0.05). The superior efficacy of pulsatile insulin delivery on glucose uptake was not consistently found until after 210 min of insulin administration. In both infusion protocols, endogenous glucose production as estimated by the [3-3H]glucose infusion technique was suppressed to insignificant values. Finally, the effect of insulin on endogenous insulin secretion and lipolysis as assessed by changes in serum C-peptide and serum FFA was uninfluenced by the infusion mode. In conclusion, insulin infusion resulting in physiological serum insulin levels enhances glucose uptake in peripheral tissues in healthy subjects to a higher degree when given in a pulsed pattern mimicking that of the normal endocrine pancreas than when given as a continuous infusion.     

Effects of exenatide on circulating glucose, insulin, glucagon, cortisol and catecholamines in healthy volunteers during exercise

Aims/hypothesis  

Exenatide, a glucagon like peptide-1 agonist, is a treatment for type 2 diabetes mellitus that stimulates insulin and suppresses glucagon secretion in a glucose-dependent manner. By contrast, during aerobic exercise, the serum insulin concentration normally falls, with a rise in plasma glucagon. We therefore assessed whether exenatide might predispose to hypoglycaemia during exercise.     

Performance of a continuous glucose monitoring system during controlled hypoglycaemia in healthy volunteers

It has been suggested that the continuous glucose monitoring system may be a useful tool for detecting unrecognised hypoglycaemia, especially at times when finger prick testing is difficult or impossible (e.g., at night). Studies suggest that subcutaneous glucose levels closely mimic blood glucose levels with a lag time of only a few minutes. However, no studies have been published to show how well the sensor performs during sustained or in recovery from hypoglycaemia. This study involved using a hyperinsulinaemic glucose clamp (60 mU/m2) in nine healthy volunteers. Each subject had two sensors inserted the day before the study. Blood glucose levels were maintained at euglycaemia for the first 60 min, then decreased to 45 mg/dL (2.5 mmol/L) for 60 min, and finally restored to euglycaemia. Blood glucose measurements were compared with interstitial values recorded by the sensor. Sensor profiles showed acceptable agreement with blood glucose levels at each of the three plateaus with a correlation coefficient of 0.79, slope of 0.85, and mean absolute error of 7%. The sensor drop closely matched the drop in blood glucose, but the recovery from hypoglycaemia was delayed by an average of 26 min. Continuous glucose sensing provides a useful means of detecting unrecognised hypoglycaemia in type 1 diabetes, although the duration of hypoglycaemia may be overestimated.     

Intrapulmonary administration of insulin to healthy volunteers

Objectives. To study the biological effects of nebulized insulin, administered intrapulmonary, to healthy volunteers.
Design. A double-blind, randomized, controlled intervention study.
Setting. The department of Internal Medicine, University Hospital, Linköping, Sweden.
Subjects. Eight healthy, non-smoking volunteers, with a mean age of 28 (range 22 to 56) years.
Interventions. Regular human insulin 100 U mL^-1 (Actrapid®) or 0.9% saline was given randomly as an oral inhalation. Insulin was given in three different doses (40, 80 and 160 U). Aerosol was generated by a new jet nebulizer.
Main outcome measures. Blood glucose, serum insulin, and serum C-peptide.
Results. After the 160 U insulin dose the blood glucose concentration (mean±SE) fell from 4.3±0.2 to 2.8±0.2 mmol L^-1 ( P <0.001), concomitant with an increase in mean serum insulin concentrations, rising from 9.5±1.5 to 26.1±2.5 mU L^-1 ( P <0.001). Serum C-peptide concentrations simultaneously decreased from 0.48±0.03 to 0.12±0.02 mmol L^-1 ( P <0.001). All changes were dose dependent. No adverse reactions were noted and no significant changes in lung function tests.
Conclusions. Intrapulmonary insulin administration to healthy subjects can induce a significant hypoglycaemia and cause a clinically relevant increase in serum insulin concentrations. If similar results can be obtained when administering insulin to diabetic subjects, this insulin administration route can be a future complement to certain groups of patients.     

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

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

Lack of acute effect of amylin (islet associated polypeptide) on insulin sensitivity during hyperinsulinaemic euglycaemic clamp in humans

Summary It is suggested that amylin (islet associated polypeptide), co-secreted with insulin from the pancreatic beta cells acts as a circulating hormone which opposes the action of insulin on muscle and increases hepatic glucose production. We have tested the effect of amylin in human subjects on postabsorptive glucose homeostasis and on insulin sensitivity using the euglycaemic hyperinsulinaemic clamp. The amylin used opposed insulin-mediated glucose disposal in rat soleus muscle at concentrations of 10 nmol/l. Seven subjects were studied on two occasions and infused with either amylin or placebo for 6 h, initially when postabsorptive and then during a euglycaemic hyperinsulinaemic clamp. Mean plasma amylin concentrations during the first 3 h were 2006±327 pmol/l during amylin infusion and 20±9 pmol/l during the control infusion. Amylin infusion had no effect on postabsorptive plasma concentrations of insulin (control: 32±16 vs amylin: 25±8 pmol/l) or glucose (5.1±0.1 vs 5.3±0.1 mmol/l). During the clamp, amylin concentrations were 1636 ±422 pmol/l when it was infused and 24±6 during control infusions. Plasma glucose and insulin concentrations were well matched during the control and amylin infusions (glucose: 4.7±0.1 vs 4.8±0.1 mmol/l; insulin: 198±37 vs 195±22 pmol/l). Exogenous glucose infusion rates were a mean of 13 % lower than control values during the amylin infusion but were not statistically different (p =0.17). Therefore, an approximately 100-fold elevation of plasma amylin concentration failed to consistently alter glucose metabolism. Our data suggest that amylin does not act as a circulating hormone to influence glucose metabolism in humans. [Diabetologia (1994) 37: 166–169] Received: 1 June 1993 and in revised form: 16 August 1993     

Relative contribution of insulin sensitivity and beta-cell function to plasma glucose and insulin concentrations during the oral glucose tolerance test.

Plasma glucose and insulin concentrations have been used in genetic studies as quantitative phenotypic traits and also as surrogates for insulin sensitivity and beta-cell function. However, the significance of these traits in relation to insulin sensitivity and beta-cell function was unknown. We examined how insulin sensitivity and beta-cell function affected plasma glucose and insulin concentrations during the oral glucose tolerance test (OGTT). This is a cross-sectional study enrolling 105 glucose-tolerant subjects (64 females; age, 18 to 40 years; body mass index, 17.58 to 37.57 kg/m(2); waist-to-hip ratio, 0.649 to 1.033 cm/cm). They participated in both OGTTs and hyperglycemic clamps. The relationship between plasma glucose and insulin concentrations and indices of insulin sensitivity and beta-cell function was examined. Univariate analyses showed that insulin sensitivity index (ISI) had some influence on plasma insulin concentrations (r(2) =.2623 to.3814) during the OGTT; however, it had only modest impacts on plasma glucose levels at 60, 90, and 120 minutes (r(2) =.0537 to.1300). Neither first phase (1stIR) nor second phase insulin response (2ndIR) affected plasma glucose concentrations. Multivariate analyses showed an independent impact (all P <.0001) of ISI on plasma glucose concentrations at 60, 90, and 120 minutes and on plasma insulin concentrations at every time point except at 30 minutes. Except for plasma insulin concentration at 30 minutes, of which 24% of the variation can be explained by 1stIR, beta-cell function (either 1stIR or 2ndIR) only had a very modest impact on 30-, 60-, 90- and 120-minute plasma glucose concentrations and on plasma insulin concentration at 60 minutes. In glucose-tolerant subjects, ISI plays an important role in determining postchallenged plasma glucose concentrations at 60, 90, and 120 minutes, as well as plasma insulin concentrations at fasting, 60, 90, and 120 minutes. However, beta-cell function is only reflected in plasma insulin concentration at 30 minutes through 1stIR. Therefore, we conclude that it is essential to measure beta-cell function in vivo if one plans to study the genetic influence of beta-cell dysfunction.     

Measurement of anal cross-sectional area and pressure during anal distension in healthy volunteers

A probe for simultaneous measurement of cross-sectional area and pressure was used to elucidate biomechanical wall properties during anal distension. Measurements in distal sphincter regions demonstrated a high resistance to stretch and a large hysteresis compared to proximal sphincter regions. Resistance to stretch decreased during anal distension indicating an active relaxation mechanism at all recording levels. The zone with high resistance to stretch was located more distal than the high-pressure zone measured by anal-pressure profilometry. In conclusion, biomechanical wall properties of the anal canal cannot be described by classic viscoelastic theories but rather by a loss of sphincter tone caused by reflex mechanism during anal distension.     

Shape of the glucose response curve during an oral glucose tolerance test is associated with insulin clearance and muscle insulin sensitivity in healthy non‐obese men

Individuals with a monophasic glucose response curve (GRC) during a 75‐g oral glucose tolerance test have a higher risk for type 2 diabetes than those with a biphasic GRC. However, no studies have addressed the association between GRC type and insulin clearance. Thus, we studied 49 healthy non‐obese Japanese men. We divided study participants into the monophasic or biphasic group based on the shape of their GRC. We evaluated tissue‐specific insulin sensitivity and insulin clearance using a two‐step hyperinsulinemic‐euglycemic clamp. The monophasic group had more visceral fat, lower insulin clearance and lower muscle insulin sensitivity than the biphasic group, whereas liver and adipose tissue insulin sensitivity, and insulin secretion were comparable. In conclusion, healthy non‐obese men with a monophasic GRC have lower insulin clearance and muscle insulin sensitivity.