Lumacaftor/ivacaftor in cystic fibrosis: effects on glucose metabolism and insulin secretion

PURPOSE

The question whether the new cystic fibrosis transmembrane conductance regulator (CFTR) modulator drugs aimed at restoring CFTR protein function might improve glucose metabolism is gaining attention, but data on the effect of lumacaftor/ivacaftor treatment (LUMA/IVA) on glucose tolerance are limited. We evaluated the variation in glucose metabolism and insulin secretion in CF patients homozygous for Phe508del CFTR mutation after one-year treatment with LUMA/IVA in comparison to patients with the same genotype who did not receive such treatment.

METHODS

We performed a retrospective case-control study on 13 patients with a confirmed diagnosis of CF, homozygous for the Phe508del CFTR mutation, who received LUMA/IVA for one year (cases) and 13 patients with identical genotype who did not receive this treatment (controls). At the beginning and conclusion of the follow-up, all subjects received a modified 3 h OGTT, sampling at baseline, and at 30 min intervals for plasma glucose, serum insulin, and c-peptide concentrations to evaluate glucose tolerance, and quantify by modeling beta-cell insulin secretion responsiveness to glucose, insulin clearance and insulin sensitivity.

RESULTS

LUMA/IVA did not produce differences in glucose tolerance, insulin secretory parameters, clearance and sensitivity with respect to matched controls over one-year follow-up.

CONCLUSION

We found no evidence of improvements in glucose tolerance mechanisms in patients with CF after one-year treatment with LUMA/IVA.

Association between ratio indexes of body composition phenotypes and metabolic risk in Italian adults

The ratio between fat mass (FM) and fat-free mass (FFM) has been used to discriminate individual differences in body composition and improve prediction of metabolic risk. Here, we evaluated whether the use of a visceral adipose tissue-to-fat-free mass index (VAT:FFMI) ratio was a better predictor of metabolic risk than a fat mass index to fat-free mass index (FMI:FFMI) ratio. This is a cross-sectional study including 3441 adult participants (age range 18-81; men/women: 977/2464). FM and FFM were measured by bioelectrical impedance analysis and VAT by ultrasonography. A continuous metabolic risk Z score and harmonised international criteria were used to define cumulative metabolic risk and metabolic syndrome (MetS), respectively. Multivariate logistic and linear regression models were used to test associations between body composition indexes and metabolic risk. In unadjusted models, VAT:FFMI was a better predictor of MetS (OR 8.03, 95%CI 6.69-9.65) compared to FMI:FFMI (OR 2.91, 95%CI 2.45-3.46). However, the strength of association of VAT:FFMI and FMI:FFMI became comparable when models were adjusted for age, gender, clinical and sociodemographic factors (OR 4.06, 95%CI 3.31-4.97; OR 4.25, 95%CI 3.42-5.27, respectively). A similar pattern was observed for the association of the two indexes with the metabolic risk Z score (VAT:FFMI: unadjusted b = 0.69 ± 0.03, adjusted b = 0.36 ± 0.03; FMI:FFMI: unadjusted b = 0.28 ± 0.028, adjusted b = 0.38 ± 0.02). Our results suggest that there is no real advantage in using either VAT:FFMI or FMI:FFMI ratios as a predictor of metabolic risk in adults. However, these results warrant confirmation in longitudinal studies.

Identification of insulin secretory defects and insulin resistance during oral glucose tolerance test in a cohort of cystic fibrosis patients

BACKGROUND

Cystic fibrosis (CF)-related diabetes is a leading complication of CF and is associated with pulmonary and nutritional deterioration, years before an evident hyperglycemia, possibly because of insulin deficiency and resistance.

AIM

To evaluate glucose tolerance, insulin secretion, and insulin sensitivity by a widely applicable method suitable for accurate and prospective measurements in a CF population.

METHODS

A total of 165 CF subjects (80 females) aged 17±5 years and 18 age- and sex-matched healthy controls (CON) received an oral glucose tolerance test with glucose, insulin and C-peptide determinations. Insulin sensitivity was defined on the basis of glucose and insulin concentrations using the oral glucose insulin sensitivity index, whereas β-cell function was determined on the basis of a model relating insulin secretion (C-peptide profile) to glucose concentration.

RESULTS

Fifteen percent of CF patients had glucose intolerance and 6% had diabetes without fasting hyperglycemia and 3% had diabetes with fasting hyperglycemia. β-cell function was reduced in CF patients compared with CON (70.0±4.1 vs 117.9±11.6  pmol/min per m(2) per mM, P<0.001) and decreased significantly with age by -2.7  pmol/min per m(2) per mM per year (confidence interval (CI) -4.5 to -0.82), i.e. almost 4% yearly. The early insulin secretion index was also reduced. Insulin sensitivity was similar to CON. CF patients who attained glucose tolerance comparable to CON had lower β-cell function and higher insulin sensitivity.

CONCLUSION

The major alteration in insulin secretion and insulin sensitivity of CF patients is slowly declining β-cell function, consisting of delayed and reduced responsiveness to hyperglycemia, that in CF patients with normal glucose tolerance may be compensated by an increased insulin sensitivity.

Estimated height from knee-height in Caucasian elderly: implications on nutritional status by mini nutritional assessment

OBJECTIVES

To investigate if the use of estimated height (EH) by currently available prediction formulas might affect the screening and outcome prediction attitudes of both the Mini Nutritional Assessment (MNA) and its short-form version (MNA-SF).

DESIGN

A 6-month observational study.

SETTING

Two long-term cares of the province of Como.

PARTICIPANTS

266 resident elderly (102 men, 164 women; mean age +/- SD: 80.4 +/- 8.6 years).

MEASUREMENTS

Subjects were studied by anthropometry (weight, standing height, knee-height, arm and calf circumferences, triceps skinfold) and biochemistry (albumin and prealbumin). Nutritional status was assessed using both MNA and MNA-SF. At 6 months, major outcome were: death, infections and bedsores.

RESULTS

In overall population, prediction formulas significantly underestimated real height. The bias by Italian-specific equation was higher than that by nationally-representative formulas for white Americans. The use of EHs produced significant differences in body mass index (BMI) but these did not affect nutritional status scoring by MNA and MNA-SF (r > or =0.99, p < 0.0001). Cohen's kappa statistic also showed an almost perfect concordance (kappa > 0.9). Moreover, similar degrees of correlation were found between nutritional parameters and both MNA and MNA-SF scores by BMI from SH and EHs. After 6 months, major complications occurred in twenty-eight patients (11.6%). The use EHs did not affect the distribution of events among MNA and MNA-SF nutritional classes.

CONCLUSION

In Italian elderly, height prediction by nationally representative equations for white Americans should be preferred to that by ethnic-specifc formula. However, the use of both models does not seem to affect nutritional screening and outcome prediction by MNA and MNA-SF.

Protein and glutamine kinetics during counter-regulatory failure in type 1 diabetes

BACKGROUND AND AIMS

Healthy individuals counteract insulin-induced hypoglycaemia by increasing glutamine utilization but not proteolysis. Glucagon is important to this response because it increases glutamine uptake. In type 1 diabetes (T1DM) glucagon and epinephrine responses to hypoglycaemia are defective. We investigated whether glutamine and amino acid utilization during hypoglycaemia is altered in T1DM with defective counter-regulatory responses.

METHODS AND RESULTS

Eight T1DM patients (duration of diabetes 14+/-4 years and therefore with presumed defective counter-regulatory response) and eight controls (CON) received a 3h hypoglycaemic hyperinsulinaemic (0.65mU/kg per min) clamp coupled to [6,6-(2)H(2)]glucose, [1-(13)C]leucine and [2-(15)N]glutamine to trace the relative kinetics. Post-absorptive plasma glucose and glucose uptake were increased in T1DM (9.09+/-0.99 vs 5.01+/-0.22mmol/l and 19.5+/-0.9 vs 12.6+/-0.8micromol/kg per min, p<0.01). During the clamp T1DM but not CON required exogenous glucose (4.4+/-1.7micromol/kg per min) to maintain the hypoglycaemic plateau because the endogenous glucose production was significantly suppressed (p<0.01). In T1DM the leucine and phenylalanine concentrations were less suppressed from basal (p<0.05) despite a similar insulin suppression of proteolysis (-16+/-2 vs -20+/-4%, p=ns) indicating a defective stimulation of leucine metabolic clearance from basal (+18+/-3% vs +55+/-9%, p<0.01). Glutamine concentration remained unchanged from basal (-7+/-3% vs -35+/-3%, p<0.01) and the clearance of glutamine was markedly defective in T1DM (+6+/-2%) in comparison with controls (+22+/-4%; p=0.02).

CONCLUSIONS

In T1DM, the counter-regulatory failure to hypoglycaemia seems to be associated with a defective glutamine utilization. The failure to clear circulating amino acids, specifically glutamine, during hypoglycaemia may adversely affect gluconeogenesis.

Nutritional counselling in disabled people: effects on dietary patterns, body composition and cardiovascular risk factors

AIM

Disabled persons are frequently affected by nutritional status impairment, consequent to quantitative and qualitative inadequacy of diet and physical inactivity, resulting in a significant reduction of fat-free mass and bone mineral density (BMD), and an over-expression of fat mass and an increased number of biochemical risk factors for chronic degenerative diseases. The aim of this study was to analyse the applicability and the efficacy of a nutritional counselling intervention in order to improve dietary intake and nutritional status in disabled people.

METHODS

Thirty-seven disabled subjects (24 with physical disability and 13 with both mental retardation and physical disability; age 33.5+/-9.2 years) underwent an assessment of nutritional status, and an intervention with nutritional counselling was proposed to each patient for one year. Anthropometric measurements, indirect calorimetry, dual-energy X-ray absorptiometry, dietary intake, and biochemical analysis at baseline (T0) and after one year (T1) of counselling intervention were performed.

RESULTS

Sixty-five percent of patients dropped out. Overall, no significant improvement in cardiovascular risk factors, body composition and dietary patterns was reported at T1 in completer subjects. Six subjects who were obese or overweight at T0, reported significant weight and fat mass (FM) reduction at T1 (P=0.01 and P=0.00, respectively).

CONCLUSION

Nutritional counselling seems to be ineffective and poorly applicable to disabled people. Further studies should be directed towards a treatment program associated with careful screening, motivation analysis, and follow-up in this patient population.

Poor agreement between a portable armband and indirect calorimetry in the assessment of resting energy expenditure

BACKGROUND & AIMS

To evaluate the agreement between resting energy expenditure (REE) estimated by a portable armband and measured by indirect calorimetry.

METHODS

One-hundred and twenty-seven women and 42 men with a mean (SD) age of 44 (12) years and a body mass index of 30.2 (5.4) kg/m(2) were studied. REE was estimated using the Sense Wear Pro 2 Armband (SWA), measured using the Sensor Medics 29 metabolic cart (V(max)), and estimated using Schofield's equation. The limits of agreement (LOA) and the concordance correlation coefficient (CCC) were used to evaluate the interchangeability of the methods.

RESULTS

The LOA between REE(SWA) and REE(Vmax) were wide in both women (-269 to 378 kcal/day) and men (-330 to 545 kcal/day) and CCC was low (0.579 in females and 0.583 in males, p<0.0001 for both). REE(Schofield) agreed with REE(Vmax) to a similar degree (CCC=0.563 in females and 0.500 in males, p<0.0001 for both).

CONCLUSIONS

SWA and indirect calorimetry are not interchangeable methods for the assessment of REE in normal-weight and obese subjects.

Evaluation of air-displacement plethysmography and bioelectrical impedance analysis vs dual-energy X-ray absorptiometry for the assessment of fat-free mass in elderly subjects

OBJECTIVE

To evaluate air-displacement plethysmography (ADP) and bioelectrical impedance analysis (BIA) vs dual-energy X-ray absorptiometry (DXA) for the assessment of fat-free mass (FFM) in healthy elderly subjects.

SUBJECTS

Forty-two women and twenty-six men aged 60-84 years.

METHODS

FFM was measured by DXA and ADP. Body impedance (Z) was measured by four-polar BIA and the impedance index (ZI) was calculated as stature(2)/Z. Selection of predictors (gender, age, weight and ZI at 5, 50 and 100 kHz) for BIA algorithms was carried out using bootstrapped stepwise linear regression on 1000 samples of 68 subjects. Limits of agreement were used as measures of interchangeability of ADP and BIA with DXA.

RESULTS

The limits of agreement of ADP vs DXA were -11.0 to 2.4 kg in males and -4.8 to 2.2 kg in females. Gender, weight and ZI(100) were selected as predictors of FFM by bootstrapped stepwise linear regression. In males, ZI(100) (-12.2 to 12.2 kg) was much less accurate than weight (-6.0 to 6.0 kg) at predicting FFM and their combination did not improve the estimate (-6.0 to 6.0 kg). In females, ZI(100) (-6.8 to 6.8 kg) was less accurate than weight (-5.6 to 5.6 kg) at predicting FFM and their combination improved the estimate only slightly (-5.0 to 5.0 kg).

CONCLUSIONS

In healthy elderly subjects, (1) ADP and DXA are not interchangeable for the assessment of FFM, especially in males; and (2) ZI(100) is not superior to weight for the prediction of FFM and their combination is of little advantage and only in females.

Atrial Natriuretic Peptide in Diabetic and Nondiabetic Patients With and Without Heart Transplantation

BACKGROUND

Natriuretic peptides are useful markers for risk stratification of patients with heart disease. However, conflicting results have been reported about circulating atrial natriuretic peptide (ANP) concentration in heart transplant recipients.

METHODS

To ascertain the effects of diabetes and acute insulin administration on plasma ANP concentrations in a model of heart denervation, we studied 12 diabetic (D-OHT) and 6 nondiabetic heart-transplanted (OHT) patients using the euglycemic-hyperinsulinemic clamp and oral glucose tolerance tests. Five patients with type 2 diabetes without heart transplantation (D) and 9 healthy subjects (NOR) matched for anthropometric features served as the controls.

RESULTS

Means baseline plasma ANP concentration was higher in D-OHT (82 +/- 15 pg/mL) than in OHT or NOR (27 +/- 4 or 30 +/- 5; P < .01), but was not different than D (69 +/- 12; P = .82). During the clamp plasma ANP showed similar increases in all groups (49 +/- 4, 39 +/- 3, 59 +/- 4, and 49 +/- 3% in D-OHT, OHT, D, and NOR; P < .02 vs basal, P = NS among groups). Plasma osmolarity and catecholamines were also not different among groups and did not increase during the clamp. Fasting plasma ANP concentrations correlated with plasma glucose concentrations measured 120 minutes after oral glucose tolerance testing.

CONCLUSIONS

Among heart transplantation recipients fasting plasma ANP concentrations were not different at 5 to 6 years after the surgical procedure than in nondiabetic controls. Increased ANP concentrations were observed among recipients with diabetes and among nontransplanted diabetic patients. Although the insulin-induced increment in ANP concentrations was not different among groups, circulating ANP was strongly associated with glucose tolerance status.

Circulating salicylic acid is related to fruit and vegetable consumption in healthy subjects

Salicylic acid (SA) is a natural phenolic compound known as the active principle of aspirin. Its presence in vegetal sources suggests that fruit and vegetable (FV) consumption could produce measurable SA serum concentrations in human subjects not taking aspirin. The aim of this study was to investigate the relationship between FV intake and circulating SA in healthy subjects. Thirty-eight volunteers (twenty-two males and sixteen females) were recruited from an Italian university campus. They recorded their food intake for 7 d to evaluate dietary consumption and, in particular, FV intake; fasting blood samples were taken on the morning of the eighth day to measure SA serum concentration, using a sensitive stable isotope dilution and GC-MS method. Median SA serum concentration was 0.124 mumol/l (range 0.028-0.295). Circulating SA was significantly related to FV consumption, both to the mean daily intake (r2 0.13, P = 0.03) and to the last day intake (r2 0.16, P = 0.01). The subjects in the highest FV intake quartile in the preceding day (>4.75 servings) had significantly higher SA concentrations than in the lowest quartile ( < 2.3 servings) (median concentrations 0.188 and 0.112 mumol/l, respectively; P = 0.04). This study proved that, after overnight fast, human subjects not taking aspirin display circulating SA in amounts related to the FV consumption. It is therefore possible that the beneficial effects of regular FV consumption in man could also depend on low chronic SA exposure.

Spontaneous hypoglycemia in patients with cystic fibrosis

OBJECTIVE

Diabetes frequently complicates cystic fibrosis (CF) without fasting hyperglycemia or despite spontaneous hypoglycemia (anecdotally ascribed to malnutrition), whose prevalence, clinical meaning, and relationship with glucose tolerance and clinical/nutritional status were not previously investigated. The relationship of CF genotype with insulin secretion control is also unclear.

DESIGN AND METHODS

A total of 129 CF patients without stable diabetes received 188 oral glucose tolerance tests. Distribution of fasting plasma glucose (FPG), glucose, insulin and C-peptide responses, clinical/nutritional variables, and their relationships were analyzed.

RESULTS

FPG < 60 mg/dl (3.3 mmo/l) was detected in 14% of studies and reactive hypoglycemia (PG < 50 mg/dl (2.8 mmo/l)) in 15%. OGTT-based diabetes frequency was similar in the lowest quartile (Q1) and Q2-3 for FPG (10 and 8%), with higher glucose increment and area under the curve in Q1. Insulin and C-peptide levels were similar among FPG quartiles. Class I cystic fibrosis transmembrane conductance regulator mutation carriers had higher insulin concentrations than class II, especially in Q1 for FPG. Age, sex, nutritional, and anthropometric parameters including fat and lean body mass were unrelated to FPG. Lower FPG was associated with more frequent hospitalization rates (P = 0.002) and lower Shwachman scores (P = 0.041). Steroids weaning was accurately evaluated but then excluded as a possible cause of hypoglycemia.

CONCLUSIONS/INTERPRETATION

Fasting asymptomatic hypoglycemia is frequent and possibly related to inappropriate insulin secretion control in class I mutation carriers. Low FPG does not exclude impaired glucose tolerance (IGT) and diabetes in CF and reflects worse clinical status.

Is ghrelin a signal of decreased fat-free mass in elderly subjects?

OBJECTIVE

Aging is associated with appetite decline, weight loss, reduced fat-free mass (FFM), and increased fat mass (FM). Ghrelin and leptin are short- and long-term determinants of energy balance respectively, whose dysregulation could alter food intake. We evaluate the relationship of circulating ghrelin and leptin responses to standardized oral mixed nutrient load (SOMNL) with body composition, daily food intake, and insulin sensitivity in healthy elderly subjects (ES).

DESIGN AND METHODS

Twenty-six ES (12/14 M/F, 69+/-4 years) and ten young healthy controls (LY) (5/5 M/F, 27+/-3 years) were studied at the International Center for the Assessment of Nutritional Status (Milan, Italy) with air plethysmography, dual energy X-ray absorptiometry, indirect calorimetry, and dietary intake assessment. Basal and postprandial ghrelin, leptin, testosterone, glucose, insulin and C-peptide concentrations, and insulin resistance (homeostasis model assessment (HOMA-R)) and sensitivity (quantitative insulin-sensitivity check index (QUICKI)) were evaluated.

RESULTS

Basal ghrelin levels were similar in ES and LY, whereas leptin was higher in ES than LY, in agreement with the higher amount of FM. Basal and percentage change in ghrelin were inversely related to FFM, appendicular skeletal muscle mass (SMM), and QUICKI, but not to FM. Basal and percentage change in leptin were directly related to FM and not to FFM indexes. Ghrelin basal concentration was negatively correlated with energy and protein intake and with QUICKI. Percentage change in Ghrelin after SOMNL correlated negatively with protein intake, but positively with resting energy expenditure and energy intake, and glucose, insulin, C-peptide basal concentrations, and HOMA-R.

CONCLUSION

In ES, basal and postprandial ghrelin increases with FFM, specifically SMM, reduction, whereas leptin increases with relative FM increases.

Measurement of salicylic acid in human serum using stable isotope dilution and gas chromatography–mass spectrometry

A simple, highly selective, and sensitive method using stable isotope dilution and gas chromatography-mass spectrometry has been developed to quantify salicylic acid (SA) at concentrations naturally occurring in biological fluids, such as in the serum of subjects not taking aspirin. After extraction of liquid-liquid with diethyl ether and ethyl acetate and preparation of the tert-butyldimethylsilyl derivative, SA content was detected using deuterated SA as internal standard. The mean recovery of SA from serum was 85 +/- 6%. Intra- and interday precision and % relative error were <15% in all cases. With a detection limit of 0.6 ng and a quantification limit of 2 ng, the method is therefore also adequate for population studies because of the small amount of blood necessary to perform the analyses.

Nutritional status and dietary patterns in disabled people

BACKGROUND AND AIM

Obesity, cardiovascular diseases, diabetes and osteoporosis are the most frequent pathologies among people with a severe reduction of physical activity. The impairment in nutritional status, consequent to quantitative and qualitative inadequacy of diet, could be one of the first steps in the development of co-morbidities in disabled subjects. In order to evaluate this hypothesis we investigated the nutritional status and the food intake in patients with physical or mental disabilities.

METHODS AND RESULTS

Thirty-seven disabled subjects (24 with exclusively physical inactivity and 13 with mental retardation and physical inactivity) mean age 33.5+/-9.2 years and 25 healthy subjects (mean age 31.0+/-9.3 years) were enrolled. Anthropometric measurements, indirect calorimetry, dual-energy X-ray absorptiometry, dietary intake and biochemical parameters were collected for each subject. Forty percent of disabled were overweight and 14% were obese. Fat free mass (FFM) and bone mineral content (BMC) was lower and fat mass (FM) was higher than able-bodied control. Absolute resting energy expenditure (REE) was lower in disabled subjects, but this difference disappeared when REE was normalized to FFM. Dietary intake resulted unbalanced (16%, 31%, 50% of total daily energy intake derived from protein, lipid and carbohydrate respectively) with a distribution of dietary fatty acid quite far from the recommended ratio [3.1(SFA):4.1(MUFA):1.0(PUFA)] and an excessive consumption of simple carbohydrates (mean intake 17.5+/-4.9%). Insufficient intake of fibre, iron, calcium, potassium and zinc was also found. Finally, alterations in the cholesterol profile were evident in more than one third of the disabled subjects, whereas fasting glucose intolerance was evident in one fourth.

CONCLUSION

This study shows a consistent nutritional status impairment in disabled patients resulting in an reduction of FFM and BMC, in an over-representation of FM and in a number of biochemical risk factors for cardiovascular disease. The altered nutritional status is counterparted by a widespread inadequacy of dietary patterns. This nutritional and dietary impairment occurs both in subjects with mental and physical diseases.

Time course of total and distrectual weight gain after refeeding in anorexia nervosa

Anorectic patients who achieve complete recovery from the eating disorder can obtain a favorable psychosocial outcome but the long-term nutritional outcome is ill-defined. We investigated the time course of total and distrectual body composition during and after refeeding in 32 female patients with anorexia nervosa. Patients were enrolled at their lowest weight (T0) and re-examinated after a 15% weight gain (at a mean of 3 months, T1; n=17) and after 3 years of stable weight recovery (T2; n=8). At T2 patients were compared to a control group of 8 healthy females matched for age and body mass index. All subjects underwent dual X-ray absorptiometry and anthropometry at each visit. At T0, the 32 subjects were at 61%+/-8% of ideal body weight (IBW) with severe reductions in fat mass (FM; 7.1%+/-4.5%), fat free mass (FFM) and bone mineral content (BMC). At T2, the 8 subjects had gained 40% of initial weight, but remained at 85.1%+/-7.7% of IBW ( p<0.01 vs. controls), with a percent FM comparable to that of controls and an absolute FFM still deficient. BMC did not improve at T2 and remained 79% of that in controls. FM depletion was more severe in the limbs than in the trunk and at T2 the trunk/limb FM ratio remained greater than that in controls. These data strongly suggest that continued nutritional surveillance and support is necessary throughout these patients' lives, even after correction of the psychiatric illness and of severe underweight.

Body composition assessment: an indispensable tool for disease management

Recent conceptual and technology advancements fostered a rapid development in the field of body composition assessment and provided new and powerful investigative tools. Densitometry, isotopic dilution, bioelectrical impedance, whole-body counting, neutron activation, X-ray absorptiometry, computed tomography, magnetic resonance imaging, and spectroscopy have been the most widely employed methods. The result of this effort is the discovery that body composition at both molecular and cellular or tissue levels is affected by virtually all the pathologic conditions found in medical textbooks. The field is now mature for the clinical translation of this research. Some applications rely on a very solid base and their clinical use has been fully codified. Others still need reference values diversified on a regional and ethnic scale, consensus for interpretation of values, and guidelines for clinical indications. Only after these requirements are satisfied will it be possible to adopt specific practical guidelines, the most reasonable basis for acceptance and accreditation by care providers. Some applications are already being used in several settings. Therefore, establishing the guidelines for clinical application of body composition assessment methods is not only important for physicians and their patients, but is also urgent so as to prevent misuse and to ensure correct communication with the media in this field.

Feasibility of air plethysmography (BOD POD) in morbid obesity: a pilot study

The assessment of body composition (BC) in morbidly obese patients is a difficult procedure. Air-displacement plethysmography (ADP), which measures body density, is a very promising technique for BC assessment in health and disease. However, there are very few data about the feasibility of applying ADP on morbidly obese patients, which theoretically could be affected by large body size and difficulty in lung volume measurements. The main aim of this pilot study was to evaluate the feasibility of using ADP for BC assessment in morbidly obese patients. We studied nine subjects (6 males and 3 females) who had a mean age (+/-SD) of 47.0+/-13.5 years and body mass index (BMI) of 46.6+/-7.7 kg/m(2) (range 36.4-58.8). All patients could fit into the instrument chamber and perform the manoeuvre for pulmonary plethysmography. Mean lung volume was 3.9+/-1.2 l and mean percent body fat was 53.1+/-6.6 (range 46.0-67.5). These results indicate that ADP appears to be suitable for patients with BMI over 40 kg/m(2) and produces realistic BC data.

Gender factors affect fatty acids-induced insulin resistance in nonobese humans: effects of oral steroidal contraception

Plasma free fatty acids and intramyocellular triglycerides (IMCL) content modulate whole body insulin sensitivity in humans. To test whether the interactions between fatty acid metabolism and insulin action in nonobese humans are related to gender factors, we studied 15 young, normal weight, healthy men and 15 women matched for life habits and whole body insulin sensitivity, determined with the euglycemic-hyperinsulinemic clamp, by means of indirect calorimetry to assess substrate oxidation, localized (1)H nuclear magnetic resonance spectroscopy of calf muscles to assess IMCL content, and dual energy x-ray absorption to assess body composition. In addition, to test whether perturbation of the feminine hormonal milieu modifies these interactions, we studied 15 matched females using oral steroidal contraception (OSC). Insulin sensitivity in women, notwithstanding increased body fatness, plasma free fatty acids, IMCL content, and circulating beta-hydroxybutyrate levels and reduced lipid oxidation, was similar to that in men. Women using OSC showed a 40% reduction of insulin sensitivity associated with increased plasma free fatty acids, beta-hydroxybutyrate, cholesterol, and triglycerides levels and a slight increment in IMCL content compared with women with intact hormonal cycles. In all groups the IMCL content was inversely related to insulin sensitivity. In conclusion, nonobese, healthy, young women are as insulin sensitive as men, notwithstanding the higher levels of postabsorptive circulating and tissue-stored fatty acids; OSC-induced insulin resistance is associated with abnormal fatty acid metabolism and loss of this gender-related feature.

Prediction of the long-term metabolic success of the pancreatic graft function

BACKGROUND

Strategies to prevent the return to the diabetic state for graft loss or failure or any other cause after pancreas transplantation require the identification of the subjects at risk. This study evaluated whether daily glucose, insulin, and c-peptide profiles and studies of insulin sensitivity and secretion after transplantation predict pancreatic graft failure.

METHODS

Fifty-three subjects with type 1 diabetes with end-stage renal failure who received a combined pancreas and kidney transplant underwent the following procedures 1 year after transplantation: 1-day metabolic profiles, sampling every 2 hours for plasma glucose, serum insulin, and c-peptide (n=51); an intravenous glucose tolerance test (IVGTT) to evaluate insulin secretion (n=48); and an euglycemic insulin clamp to evaluate insulin sensitivity (M value, n=14). The recipients were then followed up to 8 years (mean follow-up 4.8+/-0.3 years) to evaluate the return to the diabetic state.

RESULTS

Survival analysis showed that plasma glucose in the profiles and insulin secretion in IVGTT were strongly related to the risk of returning to the diabetic state. A cutoff value of mean daily plasma glucose >127 mg/dL, corresponding to the top quartile of the mean plasma glucose distribution in the profiles, predicted the return to the diabetic state within 4 years from transplantation with a 93% specificity and a 100% sensitivity. A cutoff value of insulin delta peak <32 microU/ml in the IVGTT predicted the return to the diabetic state within 4 years from transplantation with a 75% specificity and a 75% sensitivity. In contrast, the M value in the clamp was devoid of predictive value.

CONCLUSIONS

This study indicates that the mean 24-h plasma glucose 1 year after transplantation is the strongest predictor of the return to the diabetic state. The risk is related to defects in insulin secretion and not to insulin resistance. Metabolic profiles can be used to screen the subjects at risk to strictly monitor the graft function and to investigate early determinants of graft failure.

Metabolic effects of restoring partial beta-cell function after islet allotransplantation in type 1 diabetic patients

Successful intraportal islet transplantation normalizes glucose metabolism in diabetic humans. To date, full function is not routinely achieved after islet transplantation in humans, with most grafts being characterized by only partial function. Moreover, the duration of full function is variable and cannot be sufficiently predicted with available methods. In contrast, most grafts retain partial function for a long time. We hypothesized that partial function can restore normal protein and lipid metabolism in diabetic individuals. We studied 45 diabetic patients after islet transplantation. Labeled glucose and leucine were infused to assess whole-body glucose and protein turnover in 1) 6 type 1 diabetic patients with full function after intraportal islet transplantation (FF group; C-peptide > 0.6 nmol/l; daily insulin dosage 0.03 +/- 0.02 U x kg(-1) body wt x day(-1); fasting plasma glucose < 7.7 mmol/l; HbA1c < or = 6.5%), 2) 17 patients with partial function (PF group; C-peptide > 0.16 nmol/l; insulin dosage < 0.4 U x kg(-1) body wt x day(-1)), 3) 9 patients with no function (NF group; C-peptide < 0.16 nmol/l; insulin dosage > 0.4 U x kg(-1) body wt x day(-1)), and 4) 6 patients with chronic uveitis as control subjects (CU group). Hepatic albumin synthesis was assessed in an additional five PF and five healthy volunteers by means of a primed-continuous infusion of [3,3,3-2H3]leucine. The insulin requirement was 97% lower than pretransplant levels for the FF group and 57% lower than pretransplant levels for the PF group. In the basal state, the PF group had a plasma glucose concentration slightly higher than that of the FF (P = 0.249) and CU groups (P = 0.08), but was improved with respect to the NF group (P < 0.01). Plasma leucine (101.1 +/- 5.9 micromol/l) and branched-chain amino acids (337.6 +/- 16.6 micromol/l) were similar in the PF, FF, and CU groups, and significantly lower than in the NF group (P < 0.01). During insulin infusion, the metabolic clearance rate of glucose was defective in the NF group versus in the other groups (P < 0.01). Both the basal and insulin-stimulated proteolytic and proteosynthetic rates were comparable in the PF, FF, and CU groups, but significantly higher in the NF group (P = 0.05). In addition, the PF group had a normal hepatic albumin synthesis. Plasma free fatty acid concentrations in the PF and FF groups were similar to those of the CU group, but the NF group showed a reduced insulin-dependent suppression during the clamp. We concluded that the restoration of approximately 60% of endogenous insulin secretion is capable of normalizing the alterations of protein and lipid metabolism in type 1 diabetic kidney recipients, notwithstanding chronic immunosuppressive therapy. The results of the present study indicate that "success" of islet transplantation may be best defined by a number of metabolic criteria, not just glucose concentration/metabolism alone.

Indirect calorimetry and nutritional problems in clinical practice

Indirect calorimetry is a simple and affordable tool for measuring energy expenditure and for quantifying the utilization of macronutrients. Its use is becoming increasingly widespread, but it is necessary to know its methodological features and its theoretical and practical limitations. Indirect calorimetry measures the rate of resting energy expenditure (REE), the major component of the total daily energy expenditure. Thus, indirect calorimetry reliably estimates the individual energy needs. Coupling the measurement of body composition to that of REE expands the diagnostic potential of indirect calorimetry. Once the lean and fat compartments have been measured, it is possible to establish on the basis of REE whether an individual is hyper- or hypometabolic. The evaluation of substrate oxidation by indirect calorimetry is subject to more severe theoretical constraints, because certain metabolic assumptions must be made. The clinical applications are practically unlimited. In the critically ill, a major goal is to maintain energy balance during the hypermetabolic response following trauma. The REE measurement is valuable from the diagnostic standpoint, because it recognizes discrepancies from the expected time-course of hypermetabolism, for example signaling a potentially catastrophic hypometabolic response. REE is also indispensable for providing correct nutritional support because both hyper- and undernutrition lead to increased mortality. In young or elderly patients, in whom energy consumption may be very different from that predicted from equations based on anthropometric measures, indirect calorimetry is particularly useful.

Effect of hypoglycemia on amino acid and protein metabolism in healthy humans

In response to hypoglycemia, healthy individuals rapidly antagonize insulin action on glucose and lipid metabolism, but the effects on protein metabolism are unclear. Because amino acids are an important substrate for gluconeogenesis and a fuel alternative to glucose for oxidation, we evaluated whether hypoglycemia antagonizes the hypoaminoacidemic and the antiproteolytic effects of insulin and changes the de novo synthesis of glutamine, a gluconeogenic amino acid. To this purpose, in 7 healthy subjects, we performed 2 studies, 3.5 h each, at similar insulin but different glucose concentrations (i.e., 4.9 +/- 0.1 mmol/l [euglycemic clamp] or 2.9 +/- 0.2 mmol/l [hypoglycemic clamp]). As expected, hypoglycemia antagonized the insulin suppression of glucose production achieved in euglycemia (from 21 +/- 15 to 116 +/- 12% of basal, P < 0.001), the stimulation of glucose uptake (from 207 +/- 28 to 103 +/- 7% of basal, P < 0.01) and the suppression of circulating free fatty acids (from 30 +/- 5 to 80 +/- 17% of basal, P < 0.001). In contrast, hypoglycemia increased the insulin suppression of circulating leucine (from 63 +/- 1 to 46 +/- 2% of basal, P < 0.001) and phenylalanine (from 79 +/- 3 to 64 +/- 3% of basal, P < 0.001) concentrations. Hypoglycemia did not change the insulin suppression of proteolysis (from 79 +/- 2 to 82 +/- 4% of basal, P < 0.001). However, hypoglycemia doubled the insulin suppression of the glutamine concentrations (from 84 +/- 3 to 63 +/- 3% of basal, P < 0.01) in the absence of significant changes in the glutamine rate of appearance, but it also caused an imbalance between glutamine uptake and release. This study demonstrates that successful counterregulation does not affect proteolysis. Moreover, it does not increase the availability of circulating amino acids by de novo synthesis. In contrast, despite the lower concentration of circulating amino acids, hypoglycemia increases the uptake of glutamine that can be used for gluconeogenesis and as a fuel alternative to glucose.

Effect of hemipancreatectomy and of pancreatic diversion on the tolerance to a glucose load in humans

BACKGROUND

The role of the pattern, quantity and site of insulin secretion in the tolerance to a glucose challenge is not fully evaluated in humans because it is difficult to obtain appropriate clinical models.

DESIGN

To address this issue, we studied subjects with reduced pancreatic mass (hemipancreatectomized, HEMI), systemic insulin delivery (pancreas transplant recipients, PTX), and two control groups (healthy, CON; and with uveitis on the same immunosuppression as PTX, UVE), with an hyperglycaemic clamp (study 1, + 4.2 mmol L-1), using a repeat experiment (study 2) with a fixed glucose infusion, calculated to increase by 35% that in study 1.

RESULTS

In study 1, CON increased glucose uptake to 20 +/- 3 micromol kg-1 min-1 after a biphasic insulin response. In study 2, CON further increased the glucose uptake via an increment in prehepatic insulin secretion that stimulated insulin sensitivity without changes in peripheral insulin and glucose concentrations. HEMI and PTX had 35% less glucose uptake in study 1, compared to CON, and increased glucose concentrations (+ 1.6 mmol L-1) in study 2. UVE had an intermediate defect. The causes of intolerance were different: HEMI had a defective first-phase insulin secretion (50% peripheral insulin concentrations) but maintained insulin sensitivity; PTX had normal peripheral insulin but only one-third of the insulin sensitivity of CON.

CONCLUSIONS

Hemipancreatectomy and systemic insulin delivery impair first-phase insulin secretion; second-phase peripheral insulinization (HEMI); insulin sensitivity (PTX); and a mechanism evidentiated in study 2 of CON that increases insulin sensitivity in response to prehepatic insulin secretion (both groups). Failure of these mechanisms is largely compensated by hyperglycaemia.

Splanchnic bed utilization of enteral alpha-ketoisocaproate in humans

The branched-chain ketoacids (BCKAs) are used as dietary supplements to spare essential amino acid nitrogen, yet little is known about their absorption and utilization in the body. To study the fate of enterally delivered alpha-ketoisocaproate (KIC), seven healthy adults were infused in the postabsorptive state with [1-(13)C]KIC and [phenyl-2H5]phenylalanine intravenously (NGI) and with [5,5,5-2H3]KIC by nasogastric tube (NG). After 3.5 hours, the routes of tracer infusion were switched for an additional 3.5 hours. Each subject received a second infusion study on a different day with the order of tracer infusion reversed. KIC and phenylalanine kinetics and first-pass uptake and disposal of the enteral tracer by the splanchnic bed were calculated from the tracer enrichments measured in plasma KIC, leucine, and phenylalanine and breath CO2. Phenylalanine flux was 39.5 +/- 1.2 micromol/kg/h during the i.v. infusion periods. KIC flux was 33.1 +/- 1.8 and 30.4 +/- 1.4 micromol/kg/h measured with 13C- and 2H3-KIC, respectively, and these values were significantly different. The fraction of enterally delivered tracer sequestered by the splanchnic bed on the first pass was 30.9% +/- 2.0%, 30.0% +/- 1.4%, and 30.7% +/- 2.7% for 13C-KIC, 2H3-KIC, and 2H5-phenylalanine, respectively. The fraction of infused 13C-KIC tracer recovered as 13CO2 was 27.1% +/- 1.2% and 24.0% +/- 0.9% during i.v. and NG infusion, respectively. From these data, the fraction of ng KIC tracer extracted and oxidized on the first pass was calculated to be 5.1% +/- 1.1%. This fraction was greater than that previously reported for leucine extraction and oxidation (2%), but it was still only a small fraction of the overall extraction (5/30 = 16%). Because the only two fates of the KIC tracer extracted by the splanchnic bed are oxidation or transamination to leucine, the majority (84%) of the KIC tracer was extracted and converted to leucine. These results demonstrate that KIC delivered enterally to postabsorptive humans is rapidly extracted and predominantly converted to leucine by the splanchnic bed. This leucine appears to be available for use by both the splanchnic bed and the whole body.

The effects of maintenance doses of FK506 versus cyclosporin A on glucose and lipid metabolism after orthotopic liver transplantation

BACKGROUND

Posttransplant diabetes mellitus (PTDM) has gained widespread attention due to the micro and macro-vascular complications that increase the morbidity and mortality of patients receiving solid organs. The higher incidence of PTDM has been mainly attributed to the immunosuppressive therapy. Therefore, this study compares the metabolic side effects of low dose maintenance therapy of FK-506 and Cyclosporin A (CsA) in 14 patients 1 year after orthotopic liver transplant and analyzes possible factors that contribute to the development of PTDM.

METHODS

Two groups (n=7) differing in their immunosuppressive regimen (FK506 or CsA) were matched to eight control subjects and compared to each other. The effects of in vivo insulin action were assessed by means of the euglycemic hyperinsulinemic clamp technique. Arginine stimulation tests at normo- (5.5 mM) and hyperglycemic (15 mM) levels were performed and the acute insulin, C-peptide, and glucagon response (2-5 min) to arginine were determined.

RESULTS

Insulin sensitivity (total glucose disposal) was statistically lower in patients treated with FK-506 and CsA (5.05+/-0.47 and 5.05+/-0.42 mg/kg/min) as compared to controls (6.62+/-0.38 mg/kg/min) (P<0.02), with a significantly higher nonoxidative glucose disposal for the control group (P<0.01), and lower free fatty acid levels (P<0.05). Absolute values for acute insulin response were higher but not significantly different for the transplanted groups. The lower percentage of increase of insulin release after arginine stimulation observed in the FK-506 and CsA groups as compared with controls (754%+/-100, 644%+/-102 vs. 1191%+/-174) (P<0.03 and 0.02, respectively), suggests a reduced beta cell secretory reserve in both treated groups. Also, the acute glucagon response to arginine during hyperglycemia declined less in the FK-506 (28%) and CsA groups (29%) compared with controls (48%) (P<0.05) indicating a defect in the pancreatic beta cell-alpha cell axis.

CONCLUSIONS

There are no major metabolic differences on low maintenance doses between FK-506 and CsA. Both immunosuppressant agents contribute to the development of PTDM at different levels.

Intramyocellular triglyceride content is a determinant of in vivo insulin resistance in humans: a 1H-13C nuclear magnetic resonance spectroscopy assessment in offspring of type 2 diabetic parents

Insulin resistance is the best prediction factor for the clinical onset of type 2 diabetes. It was suggested that intramuscular triglyceride store may be a primary pathogenic factor for its development. To test this hypothesis, 14 young lean offspring of type 2 diabetic parents, a model of in vivo insulin resistance with increased risk to develop diabetes, and 14 healthy subjects matched for anthropomorphic parameters and life habits were studied with 1) euglycemic-hyperinsulinemic clamp to assess whole body insulin sensitivity, 2) localized 1H nuclear magnetic resonance (NMR) spectroscopy of the soleus (higher content of fiber type I, insulin sensitive) and tibialis anterior (higher content of fiber type IIb, less insulin sensitive) muscles to assess intramyocellular triglyceride content, 3) 13C NMR of the calf subcutaneous adipose tissue to assess composition in saturated/unsaturated carbons of triglyceride fatty acid chains, and 4) dual X-ray energy absorption to assess body composition. Offspring of diabetic parents, notwithstanding normal fat content and distribution, were characterized by insulin resistance and increased intramyocellular triglyceride content in the soleus (P < 0.01) but not in the tibialis anterior (P = 0.19), but showed a normal content of saturated/unsaturated carbons in the fatty acid chain of subcutaneous adipocytes. Stepwise regression analysis selected intramyocellular triglyceride soleus content and plasma free fatty acid levels as the main predictors of whole body insulin sensitivity. In conclusion, 1H and 13C NMR spectroscopy revealed intramyocellular abnormalities of lipid metabolism associated with whole body insulin resistance in subjects at high risk of developing diabetes, and might be useful tools for noninvasively monitoring these alterations in diabetes and prediabetic states.

Splanchnic utilization of enteral alanine in humans

The splanchnic bed extracts the majority of the enteral nonessential amino acids glutamine and glutamate, while extracting a much smaller proportion of essential amino acids such as leucine and phenylalanine. Alanine is an abundant nonessential amino acid that plays an important role in hepatic gluconeogenesis and ureagenesis. However, its enteral fate has not been studied. Twelve normal healthy postabsorptive adults received a 7-hour infusion of [1-13C]alanine, 3.5 hours intravenously (IV) and 3.5 hours via a nasogastric tube (NG). The order of infusion was randomized among subjects. Alanine kinetics were calculated from the enrichments of plasma alanine 13C and expired 13CO2. The alanine appearance rate (Ra), measured during the IV tracer infusion, was 279+/-17 micromol/kg/h; 92%+/-2% of the IV-infused and 86%+/-2% of the NG-infused [1-13C]alanine tracer was recovered as 13CO2. From the difference in plasma alanine 13C enrichment between IV-infused and NG-infused tracers, we determined that the splanchnic bed extracted 69%+/-1% of the enterally delivered alanine tracer on the first pass during absorption. Only one third of the enteral alanine passed intact through the splanchnic bed and was made available to systemic tissues. Of the enteral alanine extracted, 83%+/-3% of the carboxyl-carbon label was recovered as CO2, leaving only 17% of the sequestered alanine available for use in splanchnic protein synthesis. Thus, the splanchnic bed, presumably the liver, extracts and metabolizes most of the enterally delivered alanine.

Spontaneous hypoglycaemia after pancreas transplantation in Type 1 diabetes mellitus

Hypoglycaemia is an important complication of insulin treatment in Type 1 diabetes mellitus (DM). Pancreas transplantation couples glucose sensing and insulin secretion, attaining a distinctive advantage over insulin treatment. We tested whether successful transplantation can avoid hypoglycaemia in Type 1 DM. Combined kidney and pancreas transplanted Type 1 DM who complied with good function criteria (KP-Tx, n = 55), and isolated kidney or liver transplanted non-diabetic subjects on the same immunosuppressive regimen (CON-Tx, n = 14), underwent 1-day metabolic profiles in the first 3 years after transplantation, sampling plasma glucose (PG) and pancreatic hormones every 2 hours. KP-Tx had lower PG than CON-Tx in the night and in the morning and higher insulin concentrations throughout the day. KP-Tx had lower PG nadirs than CON-Tx (4.40+/-0.05 vs 4.96+/-0.16 mmol l(-1), ANOVA p = 0.001). Nine per cent of KP-Tx had hypoglycaemic values (PG < or = 3.0 mmol l(-1)) in the profiles, both postprandial and postabsorptive, whereas none of CON-Tx did (p < 0.02). In conclusion, after pancreas transplantation, mild hypoglycaemia is frequent, although its clinical impact is limited. Compared to insulin treatment in Type 1 DM, pancreas transplantation improves but cannot eliminate hypoglycaemia.

Myocardial metabolism studied during warm blood antero-retrograde reperfusion in ischaemic human hearts

We propose modified warm blood antegrade-retrograde reperfusion (WBARR) of arrested hearts as a metabolic model with which to study substrate exchange and energy metabolism during the recovery phase after 90 min of ischaemia in man. Eleven anaesthetized patients undergoing aorto-coronary bypass were studied during WBARR. The protocol was designed as follows: period 1, a warm blood reperfusion with potassium (3 min); period 2, a warm blood reperfusion without potassium (2 min). The perfusion flow rate averaged 250+/-2 ml/min at the beginning of period 1 and 218+/-19 ml/min at the beginning and at the end of period 2; the perfusion was performed antegradely and retrogradely in the arrested hearts. Samples were simultaneously taken from the coronary venous sinus (CVS) and from the aortic root needle (AR). At the beginning of WBARR lactate release was 85+/-44 micromol/min and at the end it had significantly decreased to 21+/-99 micromol/min (P<0.03). Simultaneously, non-esterified fatty acids (NEFA) and beta-hydroxy-butyrate were initially released (71+/-61 and 22+/-66 micromol/min, respectively), while at the end of the WBARR there was an uptake of both NEFA (20+/-22 micromol/min; P<0.01) and beta-hydroxy-butyrate (12+/-35 micromol/min; P=0.290). Alanine, glycerol and branched chain amino acid balance across the heart did not significantly change. In summary after 90 min of ischaemia the heart energy metabolism is mainly anaerobic and based on glucose consumption, with lactate, NEFA and amino acids, which are mainly released. After 5 min of WBARR (recovery from ischaemia), lactate release is significantly reduced and NEFA becomes the energy supply of the heart. In conclusion, (1) WBARR is a valuable method with which to study myocardial metabolism in anaesthetized humans and may be combined with the use of tracers; (2) the study of myocardial metabolism in arrested hearts eliminates the imprecisions arising from the noncontinuous coronary blood flow; (3) NEFA become an important source of energy utilized by human hearts in the recovery phase from ischaemia.

Glucagon increases glutamine uptake without affecting glutamine release in humans

Glucagon causes transient hyperglycemia and persistent hypoaminoacidemia, but the mechanisms of this action are unclear. To address this question, the present study measured the effects of glucagon on glucose, leucine, phenylalanine, and glutamine kinetics. Seven healthy subjects each underwent three pancreatic clamp studies (octreotide 30 ng/kg/min, insulin 0.15 mU/kg/min, and glucagon 1.4 ng/kg/min) lasting 7 hours. During the last 3.5 hours of the studies, glucagon infusion was either unchanged (study 0) or increased to 4 and 7 ng/kg/min (studies 1 and 2). The higher glucagon infusion rates increased the glucagon concentration by 50% and 100%, respectively. [6,6-(2)H2]glucose, [2-(15)N]glutamine, 2H5-phenylalanine, and 2H3-leucine were infused to quantify the respective fluxes. Glucagon transiently increased glucose concentrations by stimulating glucose production, which peaked in 15 minutes to 3.82 +/- 0.36 and 4.21 +/- 0.33 mg/kg/min in studies 1 and 2 and then returned to the postabsorptive levels. Glucagon decreased the glutamine concentration (-10% +/- 2% and -22% +/- 2% in studies 1 and 2 v study 0, P < .05), because glutamine uptake became greater than glutamine release (balance from -1.9 +/- 0.9 in study 0 to -8.1 +/- 1.1 and -13.6 +/- 1.0 micromol/kg/h in studies 1 and 2, P < .01). Glucagon decreased the leucine concentration (-11% +/- 3% in study 2 v study 0, P < .02) and caused a small increment in proteolysis (+6% in study 2 v study 0, P < .01) that was related to the decrement in glutamine concentrations. Phenylalanine kinetics were not significantly affected. These results show that glucagon promotes the uptake of gluconeogenic substrates but does not increase their release, suggesting that glucagon-induced hyperglycemia is short-lived because glucagon fails to provide more fuel for gluconeogenesis. The small increase in proteolysis and the depletion of circulating glutamine prove that physiologic hyperglucagonemia can contribute to protein catabolism.

Regulation of glucose homeostasis in humans with denervated livers

The liver plays a major role in regulating glucose metabolism, and since its function is influenced by sympathetic/ parasympathetic innervation, we used liver graft as a model of denervation to study the role of CNS in modulating hepatic glucose metabolism in humans. 22 liver transplant subjects were randomly studied by means of the hyperglycemic/ hyperinsulinemic (study 1), hyperglycemic/isoinsulinemic (study 2), euglycemic/hyperinsulinemic (study 3) as well as insulin-induced hypoglycemic (study 4) clamp, combined with bolus-continuous infusion of [3-3H]glucose and indirect calorimetry to determine the effect of different glycemic/insulinemic levels on endogenous glucose production and on peripheral glucose uptake. In addition, postabsorptive glucose homeostasis was cross-sectionally related to the transplant age (range = 40 d-35 mo) in 4 subgroups of patients 2, 6, 15, and 28 mo after transplantation. 22 subjects with chronic uveitis (CU) undergoing a similar immunosuppressive therapy and 35 normal healthy subjects served as controls. The results showed that successful transplantation was associated with fasting glucose concentration and endogenous glucose production in the lower physiological range within a few weeks after transplantation, and this pattern was maintained throughout the 28-mo follow-up period. Fasting glucose (4. 55+/-0.06 vs. 4.75+/-0.06 mM; P = 0.038) and endogenous glucose production (11.3+/-0.4 vs. 12.9+/-0.5 micromol/[kg.min]; P = 0.029) were lower when compared to CU and normal patients. At different combinations of glycemic/insulinemic levels, liver transplant (LTx) patients showed a comparable inhibition of endogenous glucose production. In contrast, in hypoglycemia, after a temporary fall endogenous glucose production rose to values comparable to those of the basal condition in CU and normal subjects (83+/-5 and 92+/-5% of basal), but it did not in LTx subjects (66+/-7%; P < 0.05 vs. CU and normal subjects). Fasting insulin and C-peptide levels were increased up to 6 mo after transplantation, indicating insulin resistance partially induced by prednisone. In addition, greater C-peptide but similar insulin levels during the hyperglycemic clamp (study 1) suggested an increased hepatic insulin clearance in LTx as compared to normal subjects. Fasting glucagon concentration was higher 6 mo after transplantation and thereafter. During euglycemia/hyperinsulinemia (study 3), the insulin-induced glucagon suppression detectable in CU and normal subjects was lacking in LTx subjects; furthermore, the counterregulatory response during hypoglycemia was blunted. In summary, liver transplant subjects have normal postabsorptive glucose metabolism, and glucose and insulin challenge elicit normal response at both hepatic and peripheral sites. Nevertheless, (a) minimal alteration of endogenous glucose production, (b) increased concentration of insulin and glucagon, and (c) defective counterregulation during hypoglycemia may reflect an alteration of the liver-CNS-islet circuit which is due to denervation of the transplanted graft.

Metabolic effects of liver transplantation in cirrhotic patients

To assess whether liver transplantation (LTx) can correct the metabolic alterations of chronic liver disease, 14 patients (LTx-5) were studied 5+/-1 mo after LTx, 9 patients (LTx-13) 13+/-1 mo after LTx, and 10 patients (LTx-26) 26+/-2 months after LTx. Subjects with chronic uveitis (CU) and healthy volunteers (CON) were also studied. Basal plasma leucine and branched-chain amino acids were reduced in LTx-5, LTx-13, and LTx-26 when compared with CU and CON (P < 0.01). The basal free fatty acids (FFA) were reduced in LTx-26 with respect to CON (P < 0.01). To assess protein metabolism, LTx-5, LTx-13, and LTx-26 were studied with the [1-14C]leucine turnover combined with a 40-mU/m2 per min insulin clamp. To relate changes in FFA metabolism to glucose metabolism, eight LTx-26 were studied with the [1-14C]palmitate and [3-3H]glucose turnovers combined with a two-step (8 and 40 mU/m2 per min) euglycemic insulin clamp. In the postabsorptive state, LTx-5 had lower endogenous leucine flux (ELF) (P < 0.005), lower leucine oxidation (LO) (P < 0.004), and lower non-oxidative leucine disposal (NOLD) (P < 0.03) with respect to CON (primary pool model). At 2 yr (LTx-26) both ELF (P < 0.001 vs. LTx-5) and NOLD (P < 0.01 vs. LTx-5) were normalized, but not LO (P < 0.001 vs. CON) (primary and reciprocal pool models). Suppression of ELF by insulin (delta-reduction) was impaired in LTx-5 and LTx-13 when compared with CU and CON (P < 0.01), but normalized in LTx-26 (P < 0.004 vs. LTx-5 and P = 0.3 vs. CON). The basal FFA turnover rate was decreased in LTx-26 (P < 0.01) and CU (P < 0.02) vs. CON. LTx-26 showed a lower FFA oxidation rate than CON (P < 0.02). Tissue glucose disposal was impaired in LTx-5 (P < 0.005) and LTx-13 (P < 0.03), but not in LTx-26 when compared to CON. LTx-26 had normal basal and insulin-modulated endogenous glucose production. In conclusion, LTx have impaired insulin-stimulated glucose, FFA, and protein metabolism 5 mo after surgery. Follow-up at 26 mo results in (a) normalization of insulin-dependent glucose metabolism, most likely related to the reduction of prednisone dose, and, (b) maintenance of some alterations in leucine and FFA metabolism, probably related to the functional denervation of the graft and to the immunosuppressive treatment.

Metabolic effects of successful intraportal islet transplantation in insulin-dependent diabetes mellitus

The intraportal injection of human pancreatic islets has been indicated as a possible alternative to the pancreas transplant in insulin-dependent diabetic patients. Aim of the present work was to study the effect of intraportal injection of purified human islets on: (a) the basal hepatic glucose production; (b) the whole body glucose homeostasis and insulin action; and (c) the regulation of insulin secretion in insulin-dependent diabetes mellitus patients bearing a kidney transplant. 15 recipients of purified islets from cadaver donors (intraportal injection) were studied by means of the infusion of labeled glucose to quantify the hepatic glucose production. Islet transplanted patients were subdivided in two groups based on graft function and underwent: (a) a 120-min euglycemic insulin infusion (1 mU/kg/min) to assess insulin action; (b) a 120-min glucose infusion (+75 mg/di) to study the pattern of insulin secretion. Seven patients with chronic uveitis on the same immunosuppressive therapy as grafted patients, twelve healthy volunteers, and seven insulin-dependent diabetic patients with combined pancreas and kidney transplantation were also studied as control groups. Islet transplanted patients have: (a) a higher basal hepatic glucose production (HGP: 5.1 +/- 1.4 mg/kg/ min; P < 0.05 with respect to all other groups) if without graft function, and a normal HGP (2.4 +/- 0.2 mg/kg/min) with a functioning graft; (b) a defective tissue glucose disposal (3.9 +/- 0.5 mg/kg/min in patients without islet function and 5.3 +/- 0.4 mg/kg/min in patients with islet function) with respect to normals (P < 0.01 for both comparisons); (c) a blunted first phase insulin peak and a similar second phase secretion with respect to controls. In conclusion, in spite of the persistence of an abnormal pattern of insulin secretion, successful intraportal islet graft normalizes the basal HGP and improves total tissue glucose disposal in insulin-dependent diabetes mellitus.

Oxidation of glutamic acid by the splanchnic bed in humans

[1,2-13C2]glutamate and [ring-2H5]phenylalanine were infused for 7 h into postabsorptive healthy subjects on two occasions. The tracer infusion was by the intravenous route for 3.5 h and by the nasogastric route for 3.5 h. The order of tracer infusion routes was switched between the two occasions. From the plasma tracer enrichment measurements at plateau during the intravenous and enteral infusion periods, we determined that 33 +/- 3% of the enterally delivered phenylalanine and 96 +/- 1% of the glutamate were removed on the first pass by the splanchnic bed; 78 +/- 3% of the enterally delivered [13C]glutamate tracer was recovered as exhaled CO2 compared with 79 +/- 2% of the intravenously infused tracer. The fraction of the enterally delivered tracer that was sequestered specifically on the first pass by the splanchnic bed was 75 +/- 2%. These results verify the previously reported large uptake of [15N]glutamate by the splanchnic bed [Matthews et al. Am. J. Physiol. 264 (Endocrinol. Metab. 27): E848-E854, 1993] and demonstrate that the uptake of tracer is not due to an artifactual loss of the 15N tracer by reversible transamination but to glutamate uptake for oxidation.

Defective insulin action on protein and glucose metabolism during chronic hyperinsulinemia in subjects with benign insulinoma

The ability of chronic endogenous hyperinsulinemia to induce a resistance to insulin action on protein and glucose metabolism was studied in 10 subjects affected by a benign (functioning) insulinoma and 18 healthy subjects by means of infusions of [1-(14)C]leucine and [3-(3)H] glucose. The insulinoma subjects were divided into two groups with moderate (139 +/- 12 pmol/l) (n = 5) and marked (438 +/- 42 pmol/l) (n = 5) hyperinsulinemia and were studied during a euglycemic dextrose infusion. Control subjects were studied postabsorptively and during a low-dose (0.3 mU.kg-1.min-1) (n = 3) and a high-dose (1 mU.kg-1.min-1) (n = 15) euglycemic insulin clamp to match peripheral insulin concentrations with those of insulinoma subjects. In insulinoma subjects there was no correlation among plasma insulin concentration and leucine concentration (r = 0.05), endogenous leucine flux (r = 0.44), hepatic glucose production (r = 0.47), and glucose uptake (r = 0.05). Insulinoma subjects with marked hyperinsulinemia demonstrated a defective suppression of leucine concentrations (100 +/- 11 vs. 65 +/- 5 mumol/l, P < 0.01), endogenous leucine flux (50.1 +/- 6.3 vs. 27.1 +/- 0.9 mumol.m-2.min-1, P < 0.01), and hepatic glucose production (5.4 +/- 2.0 vs. 0.6 +/- 0.6 mumol.kg-1.min-1, P < 0.05), and a defective stimulation of glucose uptake (13.5 +/- 1.6 vs. 41.1 +/- 2.8 mumol.kg-1.min-1, P < 0.001) with respect to normal subjects at a comparable degree of hyperinsulinemia.(ABSTRACT TRUNCATED AT 250 WORDS)

Persistence of counter-regulatory abnormalities in insulin-dependent diabetes mellitus after pancreas transplantation

Conventional insulin therapy does not correct the counter-regulatory abnormalities of insulin-dependent diabetes mellitus. Pancreas transplantation is an alternative therapy that restores the endogenous insulin secretion in diabetes. In this study, the effects of segmental pancreas transplantation on counter-regulation to mild hypoglycaemia were evaluated. Glucose kinetics and the counter-regulatory hormonal responses were assessed in eight insulin-dependent diabetics with end-stage renal failure who had received pancreas and kidney transplantation 1 year previously, seven diabetic uraemic subjects (candidates for combined transplantation), five patients with chronic uveitis on immunosuppressive therapy comparable to pancreas recipients and 10 normal subjects. Insulin (0.3 mU kg-1 min-1) was infused for 2 h to induce mild hypoglycaemia (plasma glucose 3.2-3.5 mmol l-1) and exogenous glucose was infused as required to prevent any glucose decrease below 3.1 mmol l-1. After transplantation, two of eight recipients had hypoglycaemic episodes reported in their medical records. During the study, hepatic glucose production was rapidly suppressed in the controls and in the patients on immunosuppression (-80 +/- 7 and -54 +/- 7%, P < 0.001 vs. basal), and rebounded to the baseline values within 1 h (-3 +/- 1 and -6 +/- 2%, P = NS vs. basal). The transplant recipients had similar suppression in the first hour (-88 +/- 8%, P < 0.001 vs. basal), but the suppression persisted in the second hour (-69 +/- 11%, P < 0.001 vs. basal) indicating a lack of glucose counter-regulatory response.(ABSTRACT TRUNCATED AT 250 WORDS)