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P Vicini

Publications and source records attributed to P Vicini.

At least 37 records · Page 2Linked to original sources
PubMed2000

Pubertal adolescent male-female differences in insulin sensitivity and glucose effectiveness determined by the one compartment minimal model.

Most studies of insulin sensitivity in puberty have been cross-sectional and have not been able to longitudinally address changes that might occur. In addition, these studies were unable to separate out glucose's ability to stimulate its own disposal (glucose effectiveness, S(G)) from insulin sensitivity (S(I)) or to separate the hepatic and peripheral effects of insulin. To address these problems, we used the frequently sampled i.v. glucose tolerance test with [6,6]D2 glucose to study S(G)* and S(I)* in 24 children (Tanner stage 1-3) at 6-mo intervals over an 18-mo period. Mean overnight GH and fasting GH binding protein (GHBP), IGF-1, and leptin levels were also measured. S(G)* did not differ between the sexes or Tanner stages. S(I)* did not differ between Tanner stages for either sex and was higher in boys than in girls. Hepatic insulin resistance did not differ between sexes or Tanner stages. S(G)* was not related to any of the other variables measured. S(I)* was negatively related to BMI, GHBP, IGF1, and leptin. These results demonstrate that insulin sensitivity is greater in prepubertal and early pubertal boys than in girls and is primarily determined by body mass effects.

Adolescent↗
PubMed1999

Individual prior information in a physiological model of 2H8-toluene kinetics: an empirical Bayes estimation strategy.

Physiologically-based toxicokinetic (PBTK) models are widely used to quantify whole-body kinetics of various substances. However, since they attempt to reproduce anatomical structures and physiological events, they have a high number of parameters. Their identification from kinetic data alone is often impossible, and other information about the parameters is needed to render the model identifiable. The most commonly used approach consists of independently measuring, or taking fom literature sources, some of the parameters, fixing them in the kinetic model, and then performing model identification on a reduced number of less certain parameters. This results in a substantial reduction of the degrees of freedom of the model. In this study, we show that this method results in final estimates of the free parameters whose precision is overestimated. We then compared this approach with an empirical Bayes approach, which takes into account not only the mean value, but also the error associated with the independently determined parameters. Blood and breath 2H8-toluene washout curves, obtained in 17 subjects, were analyzed with a previously presented PBTK model suitable for person-specific dosimetry. Model parameters with the greatest effect on predicted levels were alveolar ventilation rate QPC, fat tissue fraction VFC, blood-air partition coefficient Kb, fraction of cardiac output to fat Qa/co and rate of extrahepatic metabolism Vmax-p. Differences in the measured and Bayesian-fitted values of QPC, VFC and Kb were significant (p < 0.05), and the precision of the fitted values Vmax-p and Qa/co went from 11 +/- 5% to 75 +/- 170% (NS) and from 8 +/- 2% to 9 +/- 2% (p < 0.05) respectively. The empirical Bayes approach did not result in less reliable parameter estimates: rather, it pointed out that the precision of parameter estimates can be overly optimistic when other parameters in the model, either directly measured or taken from literature sources, are treated as known without error. In conclusion, an empirical Bayes approach to parameter estimation resulted in a better model fit, different final parameter estimates, and more realistic parameter precisions.

Adult↗
PubMed1999

Interferon-alpha improves glucose tolerance in diabetic and non-diabetic patients with HCV-induced liver disease.

This pilot study was initiated to evaluate factors controlling glucose tolerance in patients with hepatitis C virus-induced liver disease before and after therapy with recombinant interferon-alpha (r-INF-alpha). Fifteen patients with histologically and serologically proven hepatitis C infection underwent oral and frequently sampled intravenous glucose tolerance tests (FSIGTT) before and after four months of therapy (6 x 106 U r-INF-alpha, subcutaneously, three times a week). Glucose, insulin and C-peptide data from FSIGTT were analysed using the minimal modeling technique to determine insulin sensitivity, glucose effectiveness and first and second phase insulin secretion. According to the WHO criteria 13 patients, had normal glucose tolerance; diabetes mellitus was diagnosed in 2 patients. In the morning following the last r-INF-alpha injection four months later, insulin sensitivity improved significantly in hepatitis C virus-infected patients with normal glucose tolerance (2.17 +/- 0.37 vs. 6.18 +/- 0.94 10(-4) min(-1) per microU/ml, p < 0.001) and with diabetes mellitus (0.86 to 2.61; 0.46 to 1.06 10(-4) min(-1) per microU/ml). This effect was independent of the extent of fibrosis, virus load before treatment and therapy response. First phase insulin secretion increased in non-diabetic (139.2 +/- 17.1 vs. 200.0 +/- 32.7, p < 0.05) and diabetic patients with HCV infection (55.24 to 118.5; 84.23 to 261.1). Moreover, free fatty acid concentrations in all HCV-infected patients were significantly reduced (0.48 +/- 0.01 vs 0.21 +/- 0.03 mmol/l, p < 0.01). Therapy with recombinant interferon-alpha is associated with an amelioration of glucose tolerance in non-diabetic and diabetic HCV-infected patients.

Adult↗
PubMed1999

Comparison of in vitro and ex vivo antiplatelet effects of 1,2-benzisothiazolin-3-one and its 2-amino derivative.

The in vitro and ex vivo antiplatelet effects of 2-amino-1,2-benzisothiazolin-3-one (1) are compared with those of its parent compound 1,2-benzisothiazolin-3-one (2) and with acetylsalicylic acid (ASA) against different agonists. 2-Amino-1,2-benzisothiazolin-3-one inhibits adenosine diphosphate (ADP)-, arachidonic acid (AA)- and collagen-induced human platelet aggregation in vitro, with IC50 values of 8.90 x 10(-5), 1.50 x 10(-6) and 5.11 x 10(-8) mol/l, respectively. The strong inhibitory activity is significant not only for collagen but also for AA-induced aggregation. The same compound inhibits ex vivo collagen- and particularly AA-induced rabbit platelet aggregation at the tested dose of 10 mg/kg i.m. In view of the potential use of 2-amino-1,2-benzisothiazolin-3-one as antithrombotic agent, the log P values for both 1,2-benzisothiazolin-3-one derivatives 1 and 2 are determined, to gain an understanding of the significance of the 2-amino group in the 1,2-benzisothiazolin-3-one moiety with respect to the biological activity under study.

Adenosine Diphosphate↗
PubMed1999

Glucose effectiveness and insulin sensitivity from the minimal models: consequences of undermodeling assessed by Monte Carlo simulation.

The unlabeled (cold) minimal model (MM) and the labeled (hot) minimal model (HMM) are a powerful tool to investigate in vivo metabolism from a standard intravenous glucose tolerance test (IVGTT) or hot IVGTT (HIVGTT). They allow to estimate metabolic indexes of the glucose-insulin system, namely glucose effectiveness (GE) and insulin sensitivity (IS) (of uptake and production those of MM, and of uptake only those of HMM). Here, the consequences of the single-compartment glucose kinetics approximation used in the MM's are investigated via Monte Carlo simulation, using a physiologic reference model (RM) of the system. RM allows to generate noisy synthetic plasma concentrations of glucose, tracer glucose, and insulin during IVGTT and HIVGTT, which are then analyzed with MM and HMM. The MM and HMM GE and IS are then compared with the RM ones. Results of 400 runs show that: 1) correlation of MM GE with the RM index is weak; 2) MM IS is well correlated with the RM index, but severely underestimates it; 3) HMM clearance rate is correlated with RM clearance; and 4) HMM IS is well correlated and only slightly overestimates the RM index. These results demonstrate that GE of MM is most affected by the single-compartment approximation and the indexes of HMM are more robust than those of MM.

Blood Glucose↗
PubMed1999

Glucose production during an IVGTT by deconvolution: validation with the tracer-to-tracee clamp technique.

Recently, a new method, based on a two-compartment minimal model and deconvolution [A. Caumo and C. Cobelli. Am. J. Physiol 264 (Endocrinol. Metab. 37): E829-E841, 1993; P. Vicini, G. Sparacino, A. Caumo, and C. Cobelli. Comput. Meth. Prog. Biomed. 52: 147-156, 1997], has been proposed to estimate endogenous glucose production (EGP) from labeled intravenous glucose tolerance test (IVGTT) data. Our aim here is to compare this EGP profile with that independently obtained with the reference method, based on the tracer-to-tracee ratio (TTR) clamp. An insulin-modified (0.03 U/kg body wt infused over 5 min) [6,6-2H2]glucose-labeled IVGTT (0.33 g/kg of glucose) was performed in 10 normal subjects. A second tracer ([U-13C]glucose) was also infused during the test in a variable fashion to clamp endogenous glucose TTR. The TTR clamp was quite successful. As a result, the EGP profile, reconstructed from [U-13C]glucose data with the models of Steele and Radziuk, were almost superimposable. The deconvolution-obtained EGP profile, calculated from [6,6-2H2]glucose data, showed remarkable agreement with that obtained from the TTR clamp. Some differences between the two profiles were noted in the estimated basal EGP and in the initial modalities of EGP inhibition. A high interindividual variability was also observed with both methods in the resumption of EGP to baseline; variability was high in both the timing and the extent of resumption. In conclusion, the use of the two-compartment minimal model of the IVGTT and deconvolution allows the estimation of a profile of EGP that is in very good agreement with that independently obtained with a TTR clamp.

Adult↗
PubMed1999

Undermodeling affects minimal model indexes: insights from a two-compartment model.

The classic (hereafter cold) and the labeled (hereafter hot) minimal models are powerful tools to investigate glucose metabolism. The cold model provides, from intravenous glucose tolerance test (IVGTT) data, indexes of glucose effectiveness (SG) and insulin sensitivity (SI) that measure the effect of glucose and insulin, respectively, to enhance glucose disappearance and inhibit endogenous glucose production. The hot model provides, from hot IVGTT data, indexes of glucose effectiveness (SG*) and insulin sensitivity (SI*) that, respectively, measure the effects of glucose and insulin on glucose disappearance only. Recent reports call for a reexamination of some of the assumptions of the minimal models. We have previously pointed out the criticality of the single-compartment description of glucose kinetics on which both the minimal models are founded. In this paper we evaluate the impact of single-compartment undermodeling on SG, SI*, and by using a two-compartment model to describe the glucose system. The relationships of the minimal model indexes to the analogous indexes measured with the glucose clamp technique are also examined. Theoretical analysis and simulation studies indicate that cold indexes are more affected than hot indexes by undermodeling. In particular, care must be exercised in the physiological interpretation of SG, because this index is a local descriptor of events taking place in the initial portion of the IVGTT. As a consequence, SG not only reflects glucose effect on glucose uptake and production but also the rapid exchange of glucose between the accessible and nonaccessible glucose pools that occurs in the early part of the test.

Glucose↗
PubMed1999

alpha-Lipoic acid treatment decreases serum lactate and pyruvate concentrations and improves glucose effectiveness in lean and obese patients with type 2 diabetes.

OBJECTIVE: We examined the effect of lipoic acid (LA), a cofactor of the pyruvate dehydrogenase complex (PDH), on insulin sensitivity (SI) and glucose effectiveness (SG) and on serum lactate and pyruvate levels after oral glucose tolerance tests (OGTTs) and modified frequently sampled intravenous glucose tolerance tests (FSIGTTs) in lean (n = 10) and obese (n = 10) patients with type 2 diabetes. RESEARCH DESIGN AND METHODS: FSIGTT data were analyzed by minimal modeling technique to determine SI and SG before and after oral treatment (600 mg, twice a day, for 4 weeks). Serum lactate and pyruvate levels of diabetic patients after glucose loading were compared with those of lean (n = 10) and obese (n = 10) healthy control subjects in which SI and SG were also determined from FSIGTT data. RESULTS: Fasting lactate and pyruvate levels were significantly increased in patients with type 2 diabetes. These metabolites did not exceed elevated fasting concentrations after glucose loading in lean patients with type 2 diabetes. However, a twofold increase of lactate and pyruvate levels was measured in obese diabetic patients. LA treatment was associated with increased SG in both diabetic groups (lean 1.28 +/- 0.14 to 1.93 +/- 0.13; obese 1.07 +/- 0.11 to 1.53 +/- 0.08 x 10(-2) min-1, P < 0.05). Higher SI and lower fasting glucose were measured in lean diabetic patients only (P < 0.05). Lactate and pyruvate before and after glucose loading were approximately 45% lower in lean and obese diabetic patients after LA treatment. CONCLUSIONS: Treatment of lean and obese diabetic patients with LA prevents hyperglycemia-induced increments of serum lactate and pyruvate levels and increases SG.

Blood Glucose↗
PubMed1998

Preserved relative dispersion but blunted stimulation of mean flow, absolute dispersion, and blood volume by insulin in skeletal muscle of patients with essential hypertension.

BACKGROUND: We examined the integrity of the effects of insulin on mean muscle blood flow, flow heterogeneity, and blood volume in essential hypertension. METHODS AND RESULTS: Positron emission tomography, combined with [15O]H2O and [15O]CO as tracers for direct measurement of blood flow and volume in skeletal muscle, and a new bayesian iterative reconstruction algorithm allowing pixel-by-pixel quantitation of blood flow and flow dispersion, were used. Measurements were performed basally after an overnight fast and under normoglycemic hyperinsulinemic conditions in 11 newly diagnosed, untreated mildly hypertensive men (age, 35 +/- 1 years; body mass index, 25.2 +/- 0.4 kg/m2, blood pressure 141 +/- 4/96 +/- 2 mm Hg, mean +/- SE) and 11 matched normotensive men. Insulin-stimulated whole body glucose uptake was significantly decreased in the hypertensive men (41 +/- 4 mumol/kg per minute) compared with the normotensive (59 +/- 4 mumol/kg per minute, P < 0.005) men. Mean blood flow in skeletal muscle was significantly lower in the hypertensive than the normal subjects basally (1.7 +/- 0.2 versus 2.7 +/- 0.4 mL/0.1 kg per minute, P < 0.05) and during hyperinsulinemia (2.3 +/- 0.2 versus 4.2 +/- 0.8, P < 0.05). The flow response to insulin (0.6 +/- 0.2 versus 1.9 +/- 0.5 mL/0.1 kg per minute, hypertensive versus normal subjects, P < 0.05) was also significantly blunted. Muscle blood volume was significantly lower in the hypertensive than in the normal subjects, both basally (3.0 +/- 0.2 versus 3.5 +/- 0.2 mL/0.1 kg, P < 0.05) and during hyperinsulinemia (3.1 +/- 0.2 versus 4.0 +/- 0.2 mL/0.1 kg muscle, P < 0.02). The increase in muscle blood volume by insulin was significant in the normal (P < 0.05) but not the hypertensive subjects. Regional pixel-by-pixel analysis within femoral muscles revealed significant spatial heterogeneity of blood flow. Insulin increased absolute dispersion of blood flow significantly more in the normal subjects than in the hypertensive subjects (P < 0.05). CONCLUSIONS: True flow heterogeneity, as judged from the coefficients of variation (relative dispersion), was comparable between the groups basally and during hyperinsulinemia. We conclude that mean flow, its absolute dispersion, and blood volume exhibit insulin resistance in patients with essential hypertension.

Adult↗
PubMed1998

Antimicrobial activity of some 1,2-benzisothiazoles having a benzenesulfonamide moiety.

Some sulfonamide and sulfonylurea derivatives of unsubstituted and 5-methylsubstituted 1,2-benzisothiazole were studied in vitro for their antimicrobial properties against bacteria and fungi. Compounds 7 and 8 exhibited good antibacterial activity against Gram positive bacteria. A strong synergism was observed when their growth-inhibitory effect was assayed in combination with trimethoprim by using Bacillus subtilis and Staphylococcus aureus as test microorganisms. The antimycotic action of benzenesulfonylurea derivative 9 was very marked for Madurella mycetomatis and dermatophytes Epidermophyton floccosum, Microsporum gypseum and Trichophyton spp.. Structure-activity relations are discussed.

Anti-Bacterial Agents↗
PubMed1998

Approaches to population kinetic analysis with application to metabolic studies.

Population kinetic analysis is the methodology traditionally used to quantify inter-subject variability in pharmacokinetic studies. In the statistics literature, it is also called analysis of repeated measurement data or analysis of longitudinal data. In this work, we will state the population kinetics problem and give some historical background to its significance. Then we will describe and apply to case studies in intermediary metabolism various two-stage and other parametric methods for nonlinear mixed effects models. We will then briefly review the software available for population kinetic analysis.

Computer Simulation↗
PubMed1998

Biological monitoring of controlled toluene exposure.

OBJECTIVES: Widespread exposure to toluene occurs in the printing, painting, automotive, shoemaking, and speaker-manufacturing industries. The relationship between air concentrations and the absorbed dose is confounded by dermal exposure, personal protective devices, movement throughout the workplace, and interindividual differences in toluene uptake and elimination. METHODS: To determine the best biological indicator of exposure we examined the blood and alveolar breath concentrations of toluene as well as the urinary excretion rates of hippuric acid and of o-, m-, and p-cresols from 33 controlled human inhalation exposures to 50 ppm for 2 h. RESULTS: Among the metabolites, o-cresol was least influenced by background contributions, whereas the p-cresol and hippuric acid rates were obscured by endogenous and dietary sources. Toluene levels in alveolar breath proved to be the most accurate and noninvasive indicator of the absorbed dose. A physiologic model described blood and breath data using four measured anthropometric parameters and the fit values of extrahepatic metabolism and adipose-tissue blood flow. CONCLUSIONS: After breathing rate and extrahepatic metabolism had been set to conservative (protective) values (the 97.5th and 2.5th percentiles, respectively) the model predicted that pre-final-shift breath levels of < or =10 micromol/m3 and post-final-shift levels of < or =150 micromol/m3 corresponded to average workplace exposure levels of < or =50 ppm toluene. Alternately, we used the distributions and covariances of the measured and fit model parameters to yield conservative pre-final-shift levels of < or =7.3 micromol/m3 and post-final-shift breath levels of < or =120 micromol/m3 that were reflective of workplace exposure levels of < or =50 ppm toluene.

Adult↗
PubMed1998

SAAM II: Simulation, Analysis, and Modeling Software for tracer and pharmacokinetic studies.

Kinetic analysis and integrated systems modeling have contributed substantially to our understanding of the physiology and pathophysiology of metabolic systems and the distribution and clearance of drugs in humans and animals. In recent years, many researchers have become aware of the usefulness of these techniques in the experimental design. With this has come the recognition that the discipline of kinetic analysis requires its own expertise. The expertise can impact experimental design in many ways, from the collaborative and service activities in which individuals interact in formal ways to the development of software tools to aid in kinetic analysis. The purpose of this report is to describe one such software tool, Simulation, Analysis, and Modeling Software II (SAAM II). In the first part, we describe in general how the user can take advantage of the capabilities of the software system, and in the second part, we give three specific examples using multicompartmental models found in lipoprotein (apolipoprotein B [apoB] kinetics) and diabetes (glucose minimal model) research.

Algorithms↗
PubMed1998

A pharmacokinetic/pharmacodynamic comparison of SAAM II and PC/WinNonlin modeling software.

This paper presents a detailed comparison of the kinetic analysis software packages SAAM II and PCNonlin/WinNonlin, based on benchmark modeling problems reported in "Pharmacokinetic andPharmacodynamic Data Analysis: Concepts and Applications" (Gabrielsson and Weiner, 1994) and seven additional models. For each model, both software packages were presented with identical implementations. Models were initially executed in PCNonlin or WinNonlin and automated comparisons with SAAM II made using Microsoft Test. Models investigated included one- and multicompartment models with nonlinearities, multiple inputs and samples, multiple simultaneous experiments, and linear equations. Maximum number of compartments, data sets, and parameters were 9, 5, and 10, respectively. We compared 88 different models, many of them in different configurations, e.g., different weighting schemes or different parameter limits. The total number of attempted comparisons between SAAM II and PCNonlin was 161, of which 142 executed without problems. Parameter estimates, their precision (standard errors), and model predictions were compared; a difference of 1% or less was considered "agreement". Observed differences, mainly in parameter standard errors, can be accounted for in terms of different optimization algorithms, convergence criteria, and individual capabilities. In general, there was good agreement (<1% difference) between SAAM II and PCNonlin in terms of parameter estimates and model predictions. However, due to differences in the optimization procedure, parameter standard errors showed considerable differences. Additionally, there were differences when multiple data sets were fitted, indicating the importance of different fitting procedures for interpreting multiple kinetic data sets. The full results of the comparison and the model files in SAAM II and PCNonlin/WinNonlin formats are available from the authors.

Administration, Oral↗
PubMed1998

Evaluation of compartmental and spectral analysis models of [18F]FDG kinetics for heart and brain studies with PET.

Various models have been proposed to quantitate from [18F]-Fluoro-Deoxy-Glucose ([18F]FDG) positron emission tomography (PET) data glucose regional metabolic rate. We evaluate here four models, a three-rate constants (3K) model, a four-rate constants (4K) model, an heterogeneous model (TH) and a spectral analysis (SA) model. The data base consists of [18F]FDG dynamic data obtained in the myocardium and brain gray and white matter. All models were identified by nonlinear weighted least squares with weights chosen optimally. We show that: 1) 3K and 4K models are indistinguishable in terms of parsimony criteria and choice should be made on parameter precision and physiological plausibility; in the gray matter a more complex model than the 3K one is resolvable; 2) the TH model is resolvable in the gray but not in the white matter; 3) the classic SA approach has some unnecessary hypotheses built in and can be in principle misleading; we propose here a new SA model which is more theoretically sound; 4) this new SA approach supports the use of a 3K model in the heart with a 60 min experimental period; it also indicates that heterogeneity in the brain is modest in the white matter; 5) [18F]FDG fractional uptake estimates of the four models are very close in the heart, but not in the brain; 6) a higher than 60 min experimental time is preferable for brain studies.

Brain↗
PubMed1998

The HMG-CoA reductase inhibitor atorvastatin increases the fractional clearance rate of postprandial triglyceride-rich lipoproteins in miniature pigs.

We have previously shown in vivo that the 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor atorvastatin decreases hepatic apolipoprotein B (apoB) secretion into plasma. To test the hypothesis that atorvastatin modulates exogenous triglyceride-rich lipoprotein (TRL) metabolism in vivo, an oral fat load (2 g fat/kg body wt) containing retinol (50 000 IU) was given to 6 control miniature pigs and to 6 animals after 28 days of treatment with atorvastatin 3 mg. kg-1. d-1. A multicompartmental model was developed by use of SAAM II and kinetic analysis performed on the plasma retinyl palmitate (RP) data. Peak TRL (d<1.006 g/mL; Sf>20) triglyceride concentrations were decreased 29% by atorvastatin, and the time to achieve this peak was delayed (5.2 versus 2.3 hours; P<0.01). The TRL triglyceride 0- to 12-hour area under the curve was decreased by 24%. In contrast, atorvastatin treatment had no effect on peak TRL RP concentrations, time to peak, or its rate of appearance into plasma; however, the TRL RP 0- to 12-hour area under the curve was decreased by 20%. Analysis of the RP kinetic parameters revealed that the TRL fractional clearance rate was increased significantly, 1.4-fold (3.093 versus 2.276 pools/h; P=0.012), with atorvastatin treatment. The percent conversion of TRL RP from the rapid-turnover to the slow-turnover compartment was decreased by 47% with atorvastatin treatment. The TRL RP fractional clearance rate was negatively correlated with very low density lipoprotein apoB production rate measured in the fasting state (r=-0.49). Thus, although atorvastatin had no effect on intestinal TRL assembly and secretion, plasma TRL clearance was significantly increased, an effect that may relate to a decreased competition for removal processes by hepatic very low density lipoprotein.

Animals↗
PubMed1997

Intact insulin stimulation of skeletal muscle blood flow, its heterogeneity and redistribution, but not of glucose uptake in non-insulin-dependent diabetes mellitus.

We tested the hypothesis that defects in insulin stimulation of skeletal muscle blood flow, flow dispersion, and coupling between flow and glucose uptake contribute to insulin resistance of glucose uptake in non-insulin-dependent diabetes mellitus (NIDDM). We used positron emission tomography combined with [15O]H2O and [18F]-2-deoxy--glucose and a Bayesian iterative reconstruction algorithm to quantitate mean muscle blood flow, flow heterogeneity, and their relationship to glucose uptake under normoglycemic hyperinsulinemic conditions in 10 men with NIDDM (HbA1c 8.1+/-0.5%, age 43+/-2 yr, BMI 27.3+/-0.7 kg/m2) and in 7 matched normal men. In patients with NIDDM, rates of whole body (35+/-3 vs. 44+/-3 micromol/kg body weight.min, P < 0.05) and femoral muscle (71+/-6 vs. 96+/-7 micromol/kg muscle.min, P < 0.02) glucose uptake were significantly decreased. Insulin increased mean muscle blood flow similarly in both groups, from 1.9+/-0.3 to 2.8+/-0.4 ml/100 g muscle.min in the patients with NIDDM, P < 0.01, and from 2.3+/-0.3 to 3.0+/-0.3 ml/100 g muscle.min in the normal subjects, P < 0.02. Pixel-by-pixel analysis of flow images revealed marked spatial heterogeneity of blood flow. In both groups, insulin increased absolute but not relative dispersion of flow, and insulin-stimulated but not basal blood flow colocalized with glucose uptake. These data provide the first evidence for physiological flow heterogeneity in human skeletal muscle, and demonstrate that insulin increases absolute but not relative dispersion of flow. Furthermore, insulin redirects flow to areas where it stimulates glucose uptake. In patients with NIDDM, these novel actions of insulin are intact, implying that muscle insulin resistance can be attributed to impaired cellular glucose uptake.

Adult↗