Inhibition of muscle glutamine formation in hypercatabolic patients.

Glutamine is synthesized primarily in skeletal muscle, and enables transfer of nitrogen to the liver, as well as serving other functions. There is increasing evidence for beneficial clinical effects of glutamine supplementation in critically ill patients. However, the response of endogenous glutamine formation to severe stress is poorly understood. The rates of net protein balance, leucine oxidative decarboxylation, and alanine and glutamine synthesis de novo were determined in leg skeletal muscle of 20 severely burned patients and 19 normal controls in the post-absorptive state. Patients were studied at 14+/-5 days post-burn, and their mean burn size was 66+/-18% of total body surface area. Methods were based on the leg arteriovenous balance technique in combination with biopsies of the vastus lateralis muscle. In the post-absorptive state, patients with severe burns, as compared with healthy control subjects, exhibited accelerated muscle loss (+150%) (i.e. proteolysis minus synthesis) and leucine oxidative decarboxylation (+117%), and depletion of the intramuscular free glutamine pool (-63%). The average rate of glutamine synthesis de novo was decreased by 48%, whereas net alanine synthesis de novo was increased by 174%, in skeletal muscle of burned patients. In conclusion, in severely hypercatabolic burned patients, muscle glutamine formation was suppressed, whereas alanine was the major vehicle for inter-organ nitrogen transport. These changes account for a decreased glutamine availability during prolonged severe stress.     

Hyperglycemia exacerbates muscle protein catabolism in burn-injured patients

OBJECTIVE: The purpose of this study was to assess if hyperglycemia influences energy expenditure or the extent of muscle protein catabolism in severely burned adults. DESIGN: Retrospective study. SETTING: Burn intensive care unit at a university hospital. PATIENTS: Adults with burns on >/=40% of their body surface area. INTERVENTIONS: Simultaneous measurement of indirect calorimetry and leg net balance of phenylalanine (as an index of muscle protein catabolism). Patients were stratified by plasma glucose values at the time of metabolic measurements (i.e., normal, glucose at 200 mg/dL). MEASUREMENTS AND MAIN RESULTS: Normal (n = 9; plasma glucose, 109 +/- 13 mg/dL [mean +/- sd]), mildly hyperglycemic (n = 13l plasma glucose, 156 +/- 17 mg/dL), and severely hyperglycemic subjects (n = 7, glucose 231 +/- 32 mg/dL) were similar in age, body weight, extent of burn area, and daily caloric intake. Severe hyperglycemia was associated with significantly higher arterial concentrations of phenylalanine (normal, 0.079 +/- 0.027 micromol/L; severe hyperglycemia, 0.116 +/- 0.028; p <.05) and a significantly greater net efflux of phenylalanine from the leg (normal, -0.067 +/- 0.072 micromol.min(-1).100 mL(-1) leg volume; severe hyperglycemia, -0.151 +/- 0.080 micromol.min(-1).100 mL(-1) leg volume; p <.05). Resting energy expenditure and respiratory quotient were similar between patient groups. CONCLUSIONS: These findings demonstrate an association between hyperglycemia and an increased rate of muscle protein catabolism in severely burned patients. This suggests a possible link between resistance of muscle to the action of insulin for both glucose clearance and muscle protein catabolism.     

Glutamine: a major gluconeogenic precursor and vehicle for interorgan carbon transport in man.

To compare glutamine and alanine as gluconeogenic precursors, we simultaneously measured their systemic turnovers, clearances, and incorporation into plasma glucose, their skeletal muscle uptake and release, and the proportion of their appearance in plasma directly due to their release from protein in postabsorptive normal volunteers. We infused the volunteers with [U-14C] glutamine, [3-13C] alanine, [2H5] phenylalanine, and [6-3H] glucose to isotopic steady state and used the forearm balance technique. We found that glutamine appearance in plasma exceeded that of alanine (5.76 +/- 0.26 vs. 4.40 +/- 0.33 mumol.kg-1.min-1, P < 0.001), while alanine clearance exceeded glutamine clearance (14.7 +/- 1.3 vs. 9.3 +/- 0.8 ml.kg-1.min-1, P < 0.001). Glutamine appearance in plasma directly due to its release from protein was more than double that of alanine (2.45 +/- 0.25 vs. 1.16 +/- 0.12 mumol.kg-1.min-1, P < 0.001). Although overall carbon transfer to glucose from glutamine and alanine was comparable (3.53 +/- 0.24 vs 3.47 +/- 0.32 atoms.kg-1.min-1), nearly twice as much glucose carbon came from protein derived glutamine than alanine (1.48 +/- 0.15 vs 0.88 +/- 0.09 atoms.kg-1.min-1, P < 0.01). Finally, forearm muscle released more glutamine than alanine (0.88 +/- 0.05 vs 0.48 +/- 0.05 mumol.100 ml-1.min-1, P < 0.01). We conclude that in postabsorptive humans glutamine is quantitatively more important than alanine for transporting protein-derived carbon through plasma and adding these carbons to the glucose pool.     

Interaction between glucose and free fatty acid metabolism in human skeletal muscle.

The mechanism by which FFA metabolism inhibits intracellular insulin-mediated muscle glucose metabolism in normal humans is unknown. We used the leg balance technique with muscle biopsies to determine how experimental maintenance of FFA during hyperinsulinemia alters muscle glucose uptake, oxidation, glycolysis, storage, pyruvate dehydrogenase (PDH), or glycogen synthase (GS). 10 healthy volunteers had two euglycemic insulin clamp experiments. On one occasion, FFA were maintained by lipid emulsion infusion; on the other, FFA were allowed to fall. Leg FFA uptake was monitored with [9,10-3H]-palmitate. Maintenance of FFA during hyperinsulinemia decreased muscle glucose uptake (1.57 +/- 0.31 vs 2.44 +/- 0.39 mumol/min per 100 ml tissue, P < 0.01), leg respiratory quotient (0.86 +/- 0.02 vs 0.93 +/- 0.02, P < 0.05), contribution of glucose to leg oxygen consumption (53 +/- 6 vs 76 +/- 8%, P < 0.05), and PDH activity (0.328 +/- 0.053 vs 0.662 +/- 0.176 nmol/min per mg, P < 0.05). Leg lactate balance was increased. The greatest effect of FFA replacement was reduced muscle glucose storage (0.36 +/- 0.20 vs 1.24 +/- 0.25 mumol/min per 100 ml, P < 0.01), accompanied by decreased GS fractional velocity (0.129 +/- 0.26 vs 0.169 +/- 0.033, P < 0.01). These results confirm in human skeletal muscle the existence of competition between glucose and FFA as oxidative fuels, mediated by suppression of PDH. Maintenance of FFA levels during hyperinsulinemia most strikingly inhibited leg muscle glucose storage, accompanied by decreased GS activity.     

Splanchnic and systemic hemodynamic effects of sustained euglycemic hyperinsulinemia in rats

Insulin, in addition to its metabolic function, was found to induce skeletal muscle vasodilatation after acute administration. The vasoactive effects of sustained euglycemic hyperinsulinemia, especially in the splanchnic circulation, are less well known. The aim of this study was to evaluate the systemic and splanchnic hemodynamic effects of sustained euglycemic hyperinsulinemia. Hyperinsulinemia was induced by a sustained-release insulin implant in the scurf area of male rats (release rate -1 U/day). Beginning on the 3rd day, the study group was fed a glucose-rich diet. Hemodynamic studies were performed on the 5th day using the radioactive microsphere technique. Serum insulin was measured by radioimmunoassay. At the time of the hemodynamic measurements, plasma insulin level was higher in the insulin-treated (n=8) compared to control rats (n=8) (23.6 +/- 4.7 vs. 13.2+/-3.9 microu/mL, respectively; p<0.001). Plasma glucose level of the two groups was similar (5.43 +/- 1.07 vs. 5.83 +/- 1.44 mmol/L, respectively). Abdominal skeletal muscle blood flow was higher in the insulin-treated group (0.11 +/- 0.05 vs. 0.05 +/- 0.04 mL x min(-1) x g(-1), respectively; p<0.02). No significant changes were observed in cardiac output and renal blood flow. In the splanchnic circulation: stomach, pancreatic, intestinal, splenic, hepatic arterial and total hepatic blood flow were also not significantly different. In summary, short-term, sustained euglycemic hyperinsulinemia in rats increased blood flow to skeletal muscle but had no hemodynamic effects on cardiac output or splanchnic circulation.     

Impaired free fatty acid utilization by skeletal muscle in non-insulin-dependent diabetes mellitus.

This study was undertaken to assess utilization of FFA by skeletal muscle in patients with non-insulin-dependent diabetes mellitus (NIDDM). 11 NIDDM and 9 nondiabetic subjects were studied using leg balance methods to measure the fractional extraction of [3H]oleate. Limb indirect calorimetry was used to estimate RQ. Percutaneous muscle biopsy samples of vastus lateralis were analyzed for muscle fiber type distribution, capillary density, and metabolic potential as reflected by measurements of the activity of seven muscle enzyme markers of glycolytic and aerobic-oxidative pathways. During postabsorptive conditions, fractional extraction of oleate across the leg was lower in NIDDM subjects (0.31 +/- 0.08 vs. 0.43 +/- 0.10, P < 0.01), and there was reduced oleate uptake across the leg (66 +/- 8 vs. 82 +/- 13 nmol/min, P < 0.01). Postabsorptive leg RQ was increased in NIDDM (0.85 +/- 0.03 vs. 0.77 +/- 0.02, P < 0.01), and rates of lipid oxidation by skeletal muscle were lower while glucose oxidation was increased (P < 0.05). In subjects with NIDDM, proportions of type I, IIa, and IIb fibers were 37 +/- 2, 37 +/- 6, and 26 +/- 5%, respectively, which did not differ from nondiabetics; and capillary density, glycolytic, and aerobic-oxidative potentials were similar. During 6 h after ingestion of a mixed meal, arterial FFA remained greater in NIDDM subjects. Therefore, despite persistent reduced fractional extraction of oleate across the leg in NIDDM (0.34 +/- 0.04 vs. 0.38 +/- 0.03, P < 0.05), rates of oleate uptake across the leg were greater in NIDDM (54 +/- 7 vs. 45 +/- 8 nmol/min, P < 0.01). In summary, during postabsorptive conditions there is reduced utilization of FFA by muscle, while during postprandial conditions there is impaired suppression of FFA uptake across the leg in NIDDM. During both fasting and postprandial conditions, NIDDM subjects have reduced rates of lipid oxidation by muscle.     

Plasma glutamine and glutamate concentrations in Gabonese children with Plasmodium falciparum infection

BACKGROUND: Low plasma glutamine levels in critical illness, neonates and burns patients are associated with poor outcome and increased risk of intercurrent infection. AIM: To investigate the relationship between plasma glutamine/glutamate levels and severity/outcome of malaria. DESIGN: Two-hospital prospective study, with both febrile and healthy controls. METHODS: We measured plasma glutamine and glutamate concentrations in 239 Gabonese patients: 145 children with malaria (86 with severe, 36 with moderate and 23 with uncomplicated disease), 42 healthy children, 44 febrile controls and eight healthy adults, and related findings to conventional markers of disease severity such as plasma lactate. RESULTS: Median (IQR) plasma glutamine was lower in uncomplicated falciparum malaria and in moderate malaria than in healthy controls: 353 (287-474) and 379 (293-448) vs. 485 (428-531) micromol/l, respectively; p<0.01 for both malaria groups vs. controls. In contrast, plasma glutamine was within the normal range in those with severe malaria and in febrile control children: 431 (342-525) and 472 (338-547) micromol/l, respectively. Furthermore, plasma glutamine was significantly higher in the children who died with malaria than in survivors: 514 (374-813) (n=12) vs. 399 (316-475) micromol/l (n=133), respectively; p=0.001. There were no significant differences in plasma glutamate concentrations between any of the study groups. DISCUSSION: In severe malaria, there was a positive correlation between plasma glutamine and lactate levels (p=0.009, r=0.281). This correlation may reflect impaired gluconeogenesis. Glutamine supplementation is probably not justified in severe P. falciparum infection.     

Role of blood flow in regulating insulin-stimulated glucose uptake in humans. Studies using bradykinin, [15O]water, and [18F]fluoro-deoxy-glucose and positron emission tomography.

Defects in insulin stimulation of blood flow have been used suggested to contribute to insulin resistance. To directly test whether glucose uptake can be altered by changing blood flow, we infused bradykinin (27 microgram over 100 min), an endothelium-dependent vasodilator, into the femoral artery of 12 normal subjects (age 25+/-1 yr, body mass index 22+/-1 kg/m2) after an overnight fast (n = 5) and during normoglycemic hyperinsulinemic (n = 7) conditions (serum insulin 465+/-11 pmol/liter, 0-100 min). Blood flow was measured simultaneously in both femoral regions using [15O]-labeled water ([15O]H2O) and positron emission tomography (PET), before and during (50 min) the bradykinin infusion. Glucose uptake was measured immediately after the blood flow measurement simultaneously in both femoral regions using [18F]-fluoro-deoxy-glucose ([18F]FDG) and PET. During hyperinsulinemia, muscle blood flow was 58% higher in the bradykinin-infused (38+/-9 ml/kg muscle x min) than in the control leg (24+/-5, P<0.01). Femoral muscle glucose uptake was identical in both legs (60.6+/-9.5 vs. 58.7+/-9.0 micromol/kg x min, bradykinin-infused vs control leg, NS). Glucose extraction by skeletal muscle was 44% higher in the control (2.6+/-0.2 mmol/liter) than the bradykinin-infused leg (1.8+/-0.2 mmol/liter, P<0.01). When bradykinin was infused in the basal state, flow was 98% higher in the bradykinin-infused (58+/-12 ml/kg muscle x min) than the control leg (28+/-6 ml/kg muscle x min, P<0.01) but rates of muscle glucose uptake were identical in both legs (10.1+/-0.9 vs. 10.6+/-0.8 micromol/kg x min). We conclude that bradykinin increases skeletal muscle blood flow but not muscle glucose uptake in vivo. These data provide direct evidence against the hypothesis that blood flow is an independent regulator of insulin-stimulated glucose uptake in humans.     

Changes in whole body and tissue oxygen consumption during recovery from hypothermia: effect of amino acid infusion

OBJECTIVE: To study the effects of amino acids on whole body and peripheral energy metabolism during recovery from post-operative hypothermia. DESIGN: Clinical study using three randomly assigned patient groups. SETTING: ICU of a university hospital. PATIENTS: Nineteen elective coronary bypass operation patients. INTERVENTIONS: Postoperatively, either glucose alone, glucose and a conventional amino acid solution, or glucose and a branch-chain amino acid enriched solution was infused. After ICU arrival (period 1) both conventional amino acid solution and branch-chain amino acid enriched solution groups received 0.15 g/kg-day of nitrogen as a conventional amino acid mixture (20% branch-chain amino acids). After rewarming (period 2), both groups received 0.18 g of nitrogen/kg-day for 2 hrs (branch-chain amino acid content 20% in the conventional amino acid solution and 35% in the branch-chain amino acid enriched solution), and for the following 2 hrs (period 3), 0.22 g of nitrogen/kg-day (branch-chain amino acid content 20% in the conventional amino acid solution and 50% in the branch-chain amino acid enriched solution). MEASUREMENTS AND MAIN RESULTS: Whole body oxygen consumption (VO2) increased during period 1 and continued to increase during period 2 (baseline, 133 +/- 20 mL/min.m2; period 1, 152 +/- 12 mL/min.m2; period 2, 158 +/- 21 mL/min.m2; period 3, 153 +/- 15 mL/min.m2; p less than .05, period 1 vs. baseline). VO2 in the leg increased during period 1 but remained constant thereafter (baseline, 16 +/- 8 mL/min.m2; period 1, 26 +/- 14 mL/min.m2; period 2, 23 +/- 6 mL/min.m2; period 3, 24 +/- 10 mL/min.m2; p less than .05, period 1 vs. baseline). Amino acid infusions had no thermogenic effect. A two-phase redistribution of VO2 and leg VO2 suggested increased visceral VO2 after rewarming. CONCLUSION: The amino acid infusions had no effect on the leg uptake of glucose, ketone bodies, and pyruvate and the leg release of lactate, free fatty acids, and triglycerides, which remained constant during the study.     

Ischemia-modified albumin concentrations in patients with peripheral vascular disease and exercise-induced skeletal muscle ischemia

BACKGROUND: Ischemia-modified albumin (IMA) is a new marker of myocardial ischemia, there is concern that IMA concentrations may be affected by ischemia occurring in tissues other than the myocardium. METHODS: We assessed 23 consecutive patients (15 males; mean age, 67 years) with typical leg claudication and documented peripheral vascular disease (PVD). All patients underwent both treadmill-exercise stress testing to induce leg ischemia and dobutamine stress echocardiography 1 week apart for the assessment of myocardial ischemia. Blood samples for IMA measurements were obtained at baseline, immediately after peak exercise/stress, and 1 h after exercise/stress. Statistical analysis was performed with the ANOVA repeated-measures test. RESULTS: Compared with baseline, mean (SD) IMA was significantly lower after the induction of skeletal muscle ischemia and returned to baseline values at 1 h: baseline, 74.6 (15.6) kilounits/L; peak stress, 69.5 (14.0) kilounits/L (P <0.0001 vs baseline); 1 h after stress, 75.9 (15.7) kilounits/L (P <0.0001 vs peak stress; P = 0.3 vs baseline). Baseline, peak stress, and 1-h poststress IMA concentrations were inversely correlated with the ankle-brachial index after exercise (r = -0.4; P <0.05). None of the patients showed regional wall motion abnormalities during dobutamine stress echocardiography, and IMA concentrations remained unchanged from baseline. There were no differences in baseline [74.6 (15.6) vs 72.7 (11.5) kilounits/L; P = 0.6], peak stress, or poststress IMA concentrations when exercise testing and dobutamine stress echocardiography values were compared. CONCLUSIONS: The relationship between disease severity (of a noncardiac origin) and baseline IMA values is an important and novel finding. IMA is significantly lower immediately after exercise-induced leg ischemia in patients with PVD and is related to disease severity. IMA concentrations can therefore be affected by the development of skeletal muscle ischemia, and this may have implications regarding the ability of IMA to detect myocardial ischemia in PVD patients.     

Comparison of resting energy expenditures and caloric intake in children with severe burns

Nutritional support is provided to children after severe burn injuries in amounts derived from empirical formulas or measurements of resting energy expenditure. To scrutinize these methods, indirect calorimetry measurements were performed on 74 survivors of burns (greater than or equal to 40% total body surface area) and compared to their actual caloric intake, percent weight change, and optimal caloric requirements formulated from the Curreri and Shriners' equations. These parameters showed that in spite of an initial deficit in actual caloric intake as compared to formulated goals, weight was maintained, whereas resting energy expenditures ranged from 30% to 40% below the actual caloric intake. Furthermore, a subgroup of patients (n = 42) who met +/- 20% of their formulated needs were stratified by extent of burn; this illustrated a significant weight gain in the more severely burned children. In conclusion, nutritional formulas in popular use overestimate caloric requirements in severe burns, whereas resting energy expenditure measurements require an additional factor of 30% to maintain body weight.     

Longitudinal assessment of Integra in primary burn management: a randomized pediatric clinical trial

BACKGROUND: Early excision with autograft-allograft closure is standard in severe burn management. Cadaver skin is associated with risks such as antigenicity, infection, and limited availability and shelf life. Previous studies have shown that Integra is safe to use in burns of <20% total body surface area. However, the suitability of its use in large burns (>50% total body surface area), its effects on postburn hypermetabolism, and the long-term cosmetic and functional results have not yet been evaluated. MATERIALS AND METHODS: Twenty children with an average burn size of 73 +/- 15% total body surface area (71 +/- 15% full-thickness burn) were randomized to be treated with either Integra or with autograft-allograft technique. Outcome measures such as length of hospital stay, mortality, incidence of infection and sepsis, acute phase protein levels, and muscle fractional synthetic rate were compared between and within groups during the acute stay (admission to discharge). Outcome measures such as resting energy expenditure, body composition data (measured by dual-energy radiograph absorptiometry), cardiac function indexes, and number of reconstructive procedures were compared during acute hospital stay and at long-term follow-up (up to 2 yrs postinjury). Scar evaluation was performed at long-term follow-up. RESULTS: There were no significant differences between Integra and controls in burn size (70 +/- 5% vs. 74 +/- 4% total body surface area), mortality (40% vs. 30%), and length of stay (41 +/- 4 vs. 39 +/- 4 days). In the short term, resting energy expenditure significantly decreased (p < .01), and serum levels of constitutive proteins significantly increased (p < .03) in the Integra group compared with controls. Long-term follow-up revealed a significant increase in bone mineral content and density (24 months postburn, p < .05), as well as improved scarring in terms of height, thickness, vascularity, and pigmentation (12 months and 18-24 months, p < .01) in the Integra group. CONCLUSION: Integra can be used for immediate wound coverage in children with severe burns without the associated risks of cadaver skin.     

Tissue oxygenation and perfusion in patients with systemic sepsis.

OBJECTIVE: Multiple organ dysfunction is associated with systemic sepsis. To investigate whether this is attributable to peripheral tissue hypoperfusion and/or cellular hypoxia, simultaneous measurements of tissue perfusion and oxygenation were made in patients with severe sepsis and in controls. DESIGN: Prospective, observational study. SETTING: Adult intensive care unit, tertiary referral center. PATIENTS: Volunteers (group C, n = 7), patients undergoing cardiopulmonary bypass (group B, n = 6), and patients with severe sepsis (group S, n = 6). INTERVENTIONS: Limb ischemia and reperfusion. MEASUREMENTS AND MAIN RESULTS: Tissue oxygenation and microvascular flow were measured by using microelectrodes inserted into brachoradialis muscle and overlying subcutaneous tissue. Forearm cutaneous red cell flux and regional blood flow were measured simultaneously. Responses to 20 mins of limb ischemia and subsequent reperfusion were observed. Baseline muscle tissue oxygenation was greater in sepsis (1.7 +/- 0.2, 1.5 +/- 0.7, and 4.4 +/- 0.6 kPa for groups C, B, and S, respectively, mean +/- sem, p <.05), although baseline subcutaneous tissue oxygenation did not vary between groups. During ischemia tissue oxygenation, values decreased in muscle (to 1.3 +/- 0.2, 1.0 +/- 0.4, and 1.5 +/- 0.4 kPa for groups C, B, and S, respectively) and subcutaneous tissue (to 2.0 +/- 0.3, 1.7 +/- 0.5, and 2.3 +/- 0.2 kPa for groups C, B, and S, respectively). Decline in tissue oxygen tension was initially more rapid in septic muscle compared with controls (25% decrease, 68 +/- 23 vs. 176 +/- 38 for group S vs. group C, p <.05, and 50% decrease, 126 +/- 34 vs. 398 +/- 72 secs for group S vs. group C, p <.01). However, overall rate of tissue decline was similar (95% decrease, 444 +/- 122 vs. 614 +/- 96 for group S vs. group C, p >.05). After reperfusion, significant differences in muscle tissue oxygenation reappeared between groups (2.0 +/- 0.3, 1.5 +/- 0.7, and 4.0 +/- 0.4 kPa for groups C, B, and S, respectively, p <.05). There were no differences in time to 25%, 50%, or 95% tissue oxygen recovery. Whole limb reperfusion was significantly less in patient groups compared with controls (10.6 +/- 0.9, 4.5 +/- 1.2, and 4.3 +/- 1.6 mL x 100 mL(-1) x min(-1) for groups C, B, and S, respectively, p <.05). CONCLUSIONS: Significant differences in tissue oxygenation distribution between muscle and subcutaneous tissues occur in patients with severe sepsis. High baseline muscle tissue oxygen levels are accompanied by rapid extraction of oxygen during stagnant ischemia.     

Cardioprotective effects of acute normovolemic hemodilution in patients with severe aortic stenosis undergoing valve replacement

BACKGROUND: After acute normovolemic hemodilution (ANH), improvement of the rheologic conditions may contribute to optimize tissue oxygen delivery and attenuate ischemia-reperfusion injuries. It was hypothesized that ANH would confer additional cardioprotection in patients with ventricular hypertrophy undergoing open heart surgery. STUDY DESIGN AND METHODS: This study was a randomized controlled trial. Forty patients scheduled for elective aortic valve replacement were randomly assigned to a control group (standard care) or an ANH group (target hematocrit level of 28%). All patients were managed with standard myocardial preservation techniques (cold blood cardioplegia, anesthetic preconditioning). The outcome measures included the release of myocardial enzymes, perioperative hemodynamic changes, the need for pharmacologic cardiovascular support, and cardiac complications. RESULTS: In the ANH group, the postoperative release of troponin I (mean peak plasma concentrations, 1.7 ng/mL; 95% confidence interval, 1.4-2.1 ng/mL) and myocardial fraction of creatine kinase (22 U/L; range, 18-24 U/L) was significantly lower than in the control group (3.6 [range, 3.0-4.2] ng/mL and 45 [range, 39-51] U/L, respectively). In addition, requirement for inotropic support was significantly lower and fewer hemodiluted patients presented adverse cardiac events. After ANH, there was a significant decrease in heart rate (-11 +/- 6%) and rate-pressure product (-16 +/- 8%) until the aortic cross-clamping time and, at the end of surgery, the circulating levels of erythropoietin (EPO) were higher than in control patients (13.6 +/- 4.2 mUI/mL vs. 7.3 +/- 2.4 mUI/mL; p < 0.05). CONCLUSIONS: Besides conventional cardiac preservation techniques, preoperative ANH further attenuates myocardial injuries. Optimization of preischemic myocardial oxygen delivery and/or consumption and the postconditioning effects of endogenous EPO are potential mechanisms for ANH-induced cardioprotection.     

Effects of body fat distribution on regional lipolysis in obesity.

To determine the contribution of the major body fat depots to systemic free fatty acid (FFA) availability, palmitate ([1-14C]-palmitate) release was measured from leg (lower body) and non-leg (upper body) fat in eight upper body obese (UB Ob), six lower body obese (LB Ob), and six nonobese (Non Ob) age-matched premenopausal women in the overnight postabsorptive state. Splanchnic palmitate release was determined in 16 of these subjects. Results: total palmitate release was greater in UB Ob (P less than 0.005) than LB Ob or Non Ob women (161 +/- 16 vs. 111 +/- 9 vs. 92 +/- 9 mumol/min, respectively). Despite increased leg fat mass in obese women, leg palmitate release was similar in each group. Therefore, leg fat palmitate release was greater in Non Ob women than LB Ob (P less than 0.01) or UB Ob (P = 0.06) women (3.7 +/- 0.3 vs. 2.4 +/- 0.2 vs. 2.7 +/- 0.2 mumol.kg fat-1.min-1, respectively). Upper body fat palmitate release was less (P less than 0.01) in LB Ob than Non Ob or UB Ob women (3.0 +/- 0.4 vs. 5.0 +/- 0.3 vs. 4.9 +/- 0.4 mumol.kg fat-1.min-1, respectively). Splanchnic palmitate release accounted for 20-32% of upper body fat palmitate release in each group (P = NS between groups). Leg fat palmitate release was significantly less than upper body fat palmitate release. We conclude that the major difference in resting FFA metabolism between UB Ob and LB Ob women is the ability of the later to down-regulate upper body fat lipolysis to maintain normal FFA availability.     

Generalised wavelet analysis of cutaneous flowmotion during post-occlusive reactive hyperaemia in patients with peripheral arterial obstructive disease.

The purpose of the present study was to assess whether the generalised wavelet analysis (GWA) of the leg cutaneous laser Doppler (LD) flowmotion waves recorded during baseline (Bsl) and after skin post-occlusive hyperaemia (POH) can provide information on the leg cutaneous microcirculatory adaptation to stage II peripheral arterial obstructive disease (PAOD). With this aim the flowmotion was characterised in 20 healthy subjects (HS) and 20 stage II PAOD patients by GWA of LDF tracings during Bsl and POH test. The vascular endothelial and smooth muscle function was also evaluated exploring the arm skin vasodilatory response to iontophoretically delivered acetylcholine (Ach) and sodium nitroprusside (SNP) using LD. During Bsl there was no significant difference in leg skin perfusion between HS and PAOD patients (7.3+/-5.6 vs. 5.8+/-2.9 AU, respectively). PAOD patients revealed higher peak powers in the frequency interval of 0.007-0.02 Hz (120+/-82 vs. 85+/-62 AU(2)/Hz; P < 0.05), 0.02-0.06 Hz (116+/-128 vs. 63+/-48 AU(2)/Hz, respectively; P < 0.05) and 0.06-0.2 Hz (39+/-49 vs. 14+/-10 AU(2)/Hz; P < 0.05). These flowmotion frequencies are related to vascular endothelium activity, sympathetic activity and vessel wall myogenic activity, respectively. During POH the mean peak power of the flowmotion waves increased significantly (P < 0.05) in HS respect to Bsl with the only exception of the 0.02-0.06 Hz band. In the PAOD patients, compared to Bsl the amplitude of the flowmotion waves did not significantly change during POH. In addition, the PAOD patients presented an increased time from release to peak-flux (18.25+/-15.5 vs. 2.16+/-1.28 s, respectively; P < 0.05), an increased time from release to recovery of the basal perfusion (90.26+/-39.14 vs. 26.55+/-14.05 s, respectively; P < 0.05) and a lower slope of the POH curve (10+/-15 vs. 54+/-17 degrees , respectively; P < 0.05), compared with HS. The cutaneous arm vasodilatory response to Ach and to SNP was reduced in PAOD patients in comparison with HS (P < 0.001). In conclusion, our findings showed an increased amplitude of the frequency interval 0.007-0.02, 0.02-0.06 and 0.06-0.2 Hz during Bsl in PAOD patients which did not change during the POH test. All data suggest that in stage II PAOD patients the leg skin perfusion is not impaired during Bsl because of a compensatory mechanism related to increased endothelial, myogenic and sympathetic activities. However during reactive hyperaemia these mechanisms appear to be exhausted in accordance with the reduced vasoreactivity to Ach and SNP.     

Insulin resistance of glucose uptake in skeletal muscle cannot be ameliorated by enhancing endothelium-dependent blood flow in obesity.

We tested the hypothesis that endothelium-dependent vasodilatation is a determinant of insulin resistance of skeletal muscle glucose uptake in human obesity. Eight obese (age 26+/-1 yr, body mass index 37+/-1 kg/m2) and seven nonobese males (25+/-2 yr, 23+/-1 kg/m2) received an infusion of bradykinin into the femoral artery of one leg under intravenously maintained normoglycemic hyperinsulinemic conditions. Blood flow was measured simultaneously in the bradykinin and insulin- and the insulin-infused leg before and during hyperinsulinemia using [15O]-labeled water ([15O]H2O) and positron emission tomography (PET). Glucose uptake was quantitated immediately thereafter in both legs using [18F]- fluoro-deoxy-glucose ([18F]FDG) and PET. Whole body insulin-stimulated glucose uptake was lower in the obese (507+/-47 mumol/m2 . min) than the nonobese (1205+/-97 micromol/m2 . min, P < 0.001) subjects. Muscle glucose uptake in the insulin-infused leg was 66% lower in the obese (19+/-4 micromol/kg muscle . min) than in the nonobese (56+/-9 micromol/kg muscle . min, P < 0.005) subjects. Bradykinin increased blood flow during hyperinsulinemia in the obese subjects by 75% from 16+/-1 to 28+/-4 ml/kg muscle . min (P < 0.05), and in the normal subjects by 65% from 23+/-3 to 38+/-9 ml/kg muscle . min (P < 0.05). However, this flow increase required twice as much bradykinin in the obese (51+/-3 microg over 100 min) than in the normal (25+/-1 mug, P < 0.001) subjects. In the obese subjects, blood flow in the bradykinin and insulin-infused leg (28+/-4 ml/kg muscle . min) was comparable to that in the insulin-infused leg in the normal subjects during hyperinsulinemia (24+/-5 ml/kg muscle . min). Despite this, insulin-stimulated glucose uptake remained unchanged in the bradykinin and insulin-infused leg (18+/-4 mumol/kg . min) compared with the insulin-infused leg (19+/-4 micromol/kg muscle . min) in the obese subjects. Insulin-stimulated glucose uptake also was unaffected by bradykinin in the normal subjects (58+/-10 vs. 56+/-9 micromol/kg . min, bradykinin and insulin versus insulin leg). These data demonstrate that obesity is characterized by two distinct defects in skeletal muscle: insulin resistance of cellular glucose extraction and impaired endothelium-dependent vasodilatation. Since a 75% increase in blood flow does not alter glucose uptake, insulin resistance in obesity cannot be overcome by normalizing muscle blood flow.     

Transrectal sonographic investigation of urethral and paraurethral structures in women with stress urinary incontinence.

Transrectal sonography of the urethra was used in 14 asymptomatic volunteers, 37 women with frequency-urgency syndrome, 42 patients with mild stress urinary incontinence, and 18 with severe stress urinary incontinence. Transverse scanning over the midurethra was performed and cross-sectional images of the urethral and paraurethral structures were compared among the four groups, with P < 0.05 being considered statistically significant. The total cross-sectional area of the midurethra was significantly smaller in patients with stress urinary incontinence than in those without this disorder (86.7+/-29.9 versus 104+/-35.6 mm2, P = 0.005); this difference resulted from a significantly smaller peripheral striated muscle component in patients with stress urinary incontinence (42.8+/-20.7 versus 58.3+/-27.3 mm2, P = 0.001). The thickness of the urethropelvic ligaments was significantly thinner in patients with stress urinary incontinence than in those without (5.9+/-1.7 versus 8.9+/-2.1 mm, P < 0.001). The distribution of the peripheral striated muscle around the urethra was variable: complete surrounding the urethra was noted in 35.7% of the control women and in 48.6% of frequency-urgency patients, but only in 16.7% of patients with mild stress urinary incontinence and 5.3% of patients with severe disease. Bladder neck incompetence was seen in 42 patients with stress urinary incontinence but in none of the control women. The length of the pubourethral ligaments was similar in the four groups. Our finding showed that stress urinary patients had a smaller striated muscle component in the midurethra and thinner urethropelvic ligaments. These defects in the continence mechanisms might have great implications in the pathophysiology of stress urinary incontinence. Transrectal sonography of the urethra is a valuable investigative tool in assessing urethral and paraurethral conditions in patients with stress urinary incontinence before deciding treatment modality.     

Reduced capacity and affinity of skeletal muscle for insulin-mediated glucose uptake in noninsulin-dependent diabetic subjects. Effects of insulin therapy.

We have estimated the capacity and affinity of insulin-mediated glucose uptake (IMGU) in whole body and in leg muscle of obese non-insulin-dependent diabetics (NIDDM, n = 6) with severe hyperglycemia, glycohemoglobin (GHb 14.4 +/- 1.2%), lean controls (ln, n = 7) and obese nondiabetic controls (ob, n = 7). Mean +/- SEM weight (kg) was 67 +/- 2 (ln), 100 +/- 7 (ob), and 114 +/- 11 (NIDDM), P = NS between obese groups. NIDDM were also studied after 3 wk of intensive insulin therapy, GHb post therapy was 10.1 +/- 0.9, P less than 0.01 vs. pretherapy. Insulin (120 mu/m2 per min) was infused and the arterial blood glucose (G) sequentially maintained at approximately 4, 7, 12, and 21 mmol/liter utilizing the G clamp technique. Leg glucose uptake (LGU) was calculated as the product of the femoral arteriovenous glucose difference (FAVGd) and leg blood flow measured by thermodilution. Compared to ln, ob and NIDDM had significantly lower rates of whole body IMGU and LGU at all G levels. Compared to ob, the NIDDM exhibited approximately 50% and approximately 40% lower rates of whole body IMGU over the first two G levels (P less than 0.02) but did not differ at the highest G, P = NS. LGU was 83% lower in NIDDM vs. ob, P less than 0.05 at the first G level only. After insulin therapy NIDDM were indistinguishable from ob with respect to whole body IMGU or LGU at all G levels. A significant correlation was noted between the percent GHb and the EG50 (G at which 1/2 maximal FAVGd occurs) r = 0.73, P less than 0.05. Thus, (a) insulin resistance in NIDDM and obese subjects are characterized by similar decreases in capacity for skeletal muscle IMGU, but differs in that poorly controlled NIDDM display a decrease in affinity for skeletal muscle IMGU, and (b) this affinity defect is related to the degree of antecedent glycemic control and is reversible with insulin therapy, suggesting that it is an acquired defect.     

Glutamine attenuates post-traumatic glutathione depletion in human muscle

Glutathione is quantitatively the most important endogenous scavenger system. Glutathione depletion in skeletal muscle is pronounced following major trauma and sepsis in intensive care unit patients. Also, following elective surgery, glutathione depletion occurs in parallel with a progressive decline in muscle glutamine concentration. The present study was designed to test the hypothesis that glutamine supplementation may counteract glutathione depletion in a human trauma model. A homogeneous group of patients (n = 17) undergoing a standardized surgical procedure were prospectively randomly allocated to receive glutamine (0.56 g x day(-1) x kg(-1)) or placebo as part of isonitrogenous and isocaloric nutrition. Percutaneous muscle biopsies and blood samples were taken pre-operatively and at 24 and 72 h after surgery. The concentrations of muscle glutathione and related amino acids were determined in muscle tissue and plasma. In the control (unsupplemented) subjects, total muscle glutathione had decreased by 47+/-8% and 37+/-11% and reduced glutathione had decreased by 53+/-10% and 45+/-16% respectively at 24 and 72 h after surgery (P < 0.05). In contrast, in the glutamine-supplemented group, no significant post-operative decreases in total or reduced glutathione were seen following surgery. Muscle free glutamine had decreased at 72 h after surgery in both groups, by 41.4+/-14.8% (P < 0.05) in the glutamine-supplemented group and by 46.0+/-14.3% (P < 0.05) in the control group. In conclusion, the present study demonstrates that intravenous glutamine supplementation attenuates glutathione depletion in skeletal muscle in humans following standardized surgical trauma.