Parvalbumin interneuron loss mediates repeated anesthesia-induced memory deficits in mice

Repeated or prolonged, but not short-term, general anesthesia during the early postnatal period causes long-lasting impairments in memory formation in various species. The mechanisms underlying long-lasting impairment in cognitive function are poorly understood. Here, we show that repeated general anesthesia in postnatal mice induces preferential apoptosis and subsequent loss of parvalbumin-positive inhibitory interneurons in the hippocampus. Each parvalbumin interneuron controls the activity of multiple pyramidal excitatory neurons, thereby regulating neuronal circuits and memory consolidation. Preventing the loss of parvalbumin neurons by deleting a proapoptotic protein, mitochondrial anchored protein ligase (MAPL), selectively in parvalbumin neurons rescued anesthesia-induced deficits in pyramidal cell inhibition and hippocampus-dependent long-term memory. Conversely, partial depletion of parvalbumin neurons in neonates was sufficient to engender long-lasting memory impairment. Thus, loss of parvalbumin interneurons in postnatal mice following repeated general anesthesia critically contributes to memory deficits in adulthood.

Intranasal administration of 40 and 80 units of insulin does not cause hypoglycemia during cardiac surgery: a randomized controlled trial

PURPOSE

Intranasal insulin administration may improve cognitive function in patients with dementia and may prevent cognitive problems after surgery. Although the metabolic effects of intranasal insulin in non-surgical patients have been studied, its influence on glucose concentration during surgery is unknown.

METHODS

We conducted a randomized, double-blind, placebo-contolled trial in patients scheduled for elective cardiac surgery. Patients with type 2 diabetes mellitus (T2DM) and non-T2DM patients were randomly allocated to one of three groups (normal saline, 40 international units [IU] of intranasal insulin, and 80 IU intranasal insulin). Insulin was given after the induction of general anesthesia. Glucose and plasma insulin concentrations were measured in ten-minute intervals during the first hour and every 30 min thereafter. The primary outcome was the change in glucose concentration 30 min after intranasal insulin administration.

RESULTS

A total of 115 patients were studied, 43 of whom had T2DM. In non-T2DM patients, 40 IU intranasal insulin did not affect glucose concentration, while 80 IU intranasal insulin led to a statistically significant but not clinically important decrease in blood glucose levels (mean difference, 0.4 mMol·L^-1; 95% confidence interval, 0.1 to 0.7). In T2DM patients, neither 40 IU nor 80 IU of insulin affected glucose concentration. No hypoglycemia (< 4.0 mMol·L^-1) was observed after intranasal insulin administration in any patients. In non-T2DM patients, changes in plasma insulin were similar in the three groups. In T2DM patients, there was an increase in plasma insulin concentrations ten minutes after administration of 80 IU of intranasal insulin compared with saline.

CONCLUSIONS

In patients with and without T2DM undergoing elective cardiac surgery, intranasal insulin administration at doses as high as 80 IU did not cause clinically important hypoglycemia.

TRIAL REGISTRATION

www.ClinicalTrials.gov (NCT02729064); registered 5 April 2016.

Sexually dimorphic response of mice to the Western-style diet caused by deficiency of fatty acid binding protein 6 (Fabp6)

Bile acids are natural detergents that aid in the absorption of dietary lipids. Fatty acid binding protein 6 (Fabp6) is a component of the bile acid recovery system that operates in the small intestine. The aim of this study was to determine if Fabp6 deficiency causes dietary fat malabsorption. Wild-type and Fabp6-deficient mice were fed a Western-style diet (WSD) or a reference low-fat diet (LFD) for 10 weeks. The body weight gain, bile acid excretion, fat excretion, energy metabolism, and major gut microbial phyla of the mice were assessed at the end of the controlled diet period. Fabp6-/- mice exhibited enhanced excretion of both bile acids and fat on the WSD but not on the LFD diet. Paradoxically, male Fabp6-/- mice, but not female Fabp6-/- mice, had greater adiposity despite increased fat excretion. Analysis of energy intake and of expenditure by indirect calorimetry revealed sex differences in physical activity level and respiratory quotient, but these did not account for the enhanced adiposity displayed by male Fabp6-/- mice. Analysis of stool DNA showed sex-specific changes in the abundance of major phyla of bacteria in response to Fabp6 deficiency and WSD feeding. The results obtained indicate that the malabsorption of bile acids that occurs in Fabp6-/- mice is associated with dietary fat malabsorption on the high-fat diet but not on the low-fat diet. The WSD induced a sexually dimorphic increase in adiposity displayed by Fabp6-/- mice and sexually distinct pattern of change in gut microbiota composition.

Plasma levels of one-carbon metabolism nutrients in women with anorexia nervosa

OBJECTIVE

People who are ill with anorexia nervosa (AN) show altered availability of key plasma nutrients. However, little is known about the patterning of alterations that occurs across diverse nutrients during active phases of illness or about the persistence of any such alterations following remission of illness.

METHOD

We compared plasma levels of one-carbon metabolism nutrients across women with active AN (AN-Active: n = 53), in remission from AN (AN-Remitted: n = 40), or who had no eating-disorder history (NED: n = 36). We also tested associations between body mass index (BMI) changes and changes in pre- to posttreatment nutrient levels, and explored the association between nutrient levels, on the one hand, and BMI and eating symptoms, on the other. Choline, betaine, and methionine were analyzed using mass spectrometry. Folate and B12 were analyzed using the AccuBind® ELISA kit. Eating-disorder symptoms were assessed by interview and self-report.

RESULTS

Compared to NED individuals, AN-Active individuals exhibited significantly elevated B12 and (less-reliably) betaine. In AN-Active individuals, lower BMI was associated with higher B12.

DISCUSSION

The observed alterations run contrary to the intuition that plasma nutrient levels should be directly responsive to nutritional status and suggest, instead, the existence of compensatory adaptations to malnutrition in individuals with active AN. Further study is required to clarify mechanisms that underlie such effects.

Knockout of USP19 Deubiquitinating Enzyme Prevents Muscle Wasting by Modulating Insulin and Glucocorticoid Signaling

Muscle atrophy arises because of many chronic illnesses, as well as from prolonged glucocorticoid treatment and nutrient deprivation. We previously demonstrated that the USP19 deubiquitinating enzyme plays an important role in chronic glucocorticoid- and denervation-induced muscle wasting. However, the mechanisms by which USP19 exerts its effects remain unknown. To explore this further, we fasted mice for 48 hours to try to identify early differences in the response of wild-type and USP19 knockout (KO) mice that could yield insights into the mechanisms of USP19 action. USP19 KO mice manifested less myofiber atrophy in response to fasting due to increased rates of protein synthesis. Insulin signaling was enhanced in the KO mice, as revealed by lower circulating insulin levels, increased insulin-stimulated glucose disposal and phosphorylation of Akt and S6K in muscle, and improved overall glucose tolerance. Glucocorticoid signaling, which is essential in many conditions of atrophy, was decreased in KO muscle, as revealed by decreased expression of glucocorticoid receptor (GR) target genes upon both fasting and glucocorticoid treatment. This decreased GR signaling was associated with lower GR protein levels in the USP19 KO muscle. Restoring the GR levels in USP19-deficient muscle was sufficient to abolish the protection from myofiber atrophy. Expression of GR target genes also correlated with that of USP19 in human muscle samples. Thus, USP19 modulates GR levels and in so doing may modulate both insulin and glucocorticoid signaling, two critical pathways that control protein turnover in muscle and overall glucose homeostasis.

High dose amino acid administration achieves an anabolic response in type 2 diabetic patients that is independent of glycaemic control: A randomized clinical trial

BACKGROUND & AIMS

Surgical stress provokes protein catabolism and hyperglycaemia that is enhanced in patients with type 2 diabetes (T2DM), and increases perioperative morbidity. This study hypothesized that perioperative administration of high dose intravenous (IV) amino acids (AA) will augment protein balance in T2DM patients receiving tight plasma glucose control via continuous IV insulin compared to standard plasma glucose control via subcutaneous (SC) insulin sliding scale.

METHODS

Eighteen patients with well-controlled T2DM (HbA1C% < 7.1) undergoing colorectal surgery were assigned randomly to receive standard glucose control (6-10 mmol/l, SC insulin, n = 9) or tight glucose control (4-6 mmol/l, IV insulin, n = 9). Both groups received general anaesthesia and epidural analgesia. AA (1 ml/kg h Aminoven™ 10%, ∼2.4 g/kg d) were infused via a peripheral vein for two 3-h periods: at the beginning of surgery and in the post-operative care unit. Whole-body protein and glucose kinetics were assessed by stable isotope tracers, L-[1-¹³C]leucine and [6,6-²H₂]glucose.

RESULTS

Whole-body protein balance was positive after surgery in all patients. Since protein synthesis, breakdown and leucine oxidation were comparable in both groups, whole body protein balance was not different (p = 0.605). Tight glucose control suppressed endogenous glucose production (EGP, p < 0.001) and increased glucose clearance (p < 0.001) compared to standard glucose control during both study periods. No episode of hypoglycaemia occurred in either group.

CONCLUSION

High-dose perioperative AA administration under optimal anti-catabolic care with epidural analgesia was effective in achieving a positive protein balance in T2DM patients undergoing surgery that was independent of glycaemic control strategy. Continuous IV insulin maintained normoglycaemia by inhibiting EGP and increasing glucose clearance. Improved glucose control, without a pronounced increase in protein balance with the intravenous insulin regimen, suggests perioperative protein metabolism may be less sensitive to insulin than is glucose.

Hyperinsulinemic-normoglycemic clamp administered together with amino acids induces anabolism after cardiac surgery

Cardiac surgery triggers an inflammatory stress response, leading to protein catabolism, a process that even high-dose insulin therapy alone cannot reverse. To determine whether hyperinsulinemic-normoglycemic clamp and perioperative amino acid (AA) supplementation improves whole body protein balance, 20 patients scheduled for elective coronary artery bypass grafting surgery were randomly assigned to have intra- and postoperative hyperinsulinemic-normoglycemic clamp, with or without intravenous AA supplementation. Primed continuous infusions of [6,6-²H₂]glucose and l-[1-¹³C]leucine were used to quantify whole body protein and glucose metabolism before and after surgery. Adipose tissue and serum cytokines were also analyzed to measure their responsiveness to the anabolic effect of AA administration. During hyperinsulinemic-normoglycemic clamp, AA supplementation successfully stimulated whole body protein synthesis, resulting in a positive whole body protein balance after surgery (insulin: -13.6 ± 4.5 vs. insulin + AA: 2.1 ± 5.4 μmol·kg^-1·h^-1, P < 0.001). Endogenous glucose production was equally suppressed in both groups (insulin: 0.0 ± 3.8 vs. insulin + AA 1.6 ± 1.6 μmol·kg^-1·min^-1, P = 0.230). AA supplementation led to significant changes in serum and tissue IL-6 (insulin: 246.6 ± 111.2 vs. insulin + AA: 124.5 ± 79.3 pg/ml, P = 0.011). In conclusion, hyperinsulinemic-normoglycemic clamp technique, together with AA supplementation, can induce an anabolic state after open-heart surgery, as quantified by a positive whole body protein balance.

Effect of IV dextrose administration on glucose metabolism during surgery

BACKGROUND

The inhibitory influence of exogenous dextrose on glucose production has been shown to be less pronounced during injury and sepsis. This protocol was designed to investigate the effect of i.v. hypocaloric dextrose on glucose metabolism during elective abdominal surgery.

METHODS

Fourteen patients with rectal cancer were studied under fasting conditions and toward the end of a 3-hour infusion of dextrose (2 mg.kg-1 per minute) either in absence (control group, n = 7) or presence of colonic surgery (surgery group, n = 7). Endogenous glucose production was determined by using primed continuous infusions of [6,6-2H2]glucose before and during dextrose administration. We also measured the plasma concentrations of glucose, lactate, cortisol, glucagon, and insulin.

RESULTS

The administration of dextrose decreased the endogenous glucose production in all patients (p < .05). This decrease was less pronounced during surgery (p < .05). Plasma glucose concentration increased during dextrose infusion in both groups (p < .05), with higher values in the surgery group than in the control group (p < .05). Plasma concentrations of lactate and glucagon remained unaltered. Dextrose infusion increased the plasma insulin concentrations to the same extent in both groups (p < .05). Cortisol plasma levels increased only in the surgery group (p < .05).

CONCLUSIONS

Surgical stress blunts the inhibitory effect of i.v. dextrose on endogenous glucose production.

Glucose and insulin administration while maintaining normoglycemia inhibits whole body protein breakdown and synthesis after cardiac surgery

We investigated the effect of insulin administered as part of a hyperinsulinemic-normoglycemic clamp on protein metabolism after coronary artery bypass grafting (CABG) surgery. Eighteen patients were studied, with nine patients in the control group receiving standard metabolic care and nine patients receiving insulin (5 mU·kg(-1)·min(-1)). Whole body glucose production, protein breakdown, synthesis, and oxidation were determined using stable isotope tracer kinetics (l-[1-(13)C]leucine, [6,6-(2)H2]glucose) before and 6 h after the procedure. Plasma amino acids, cortisol, and lactate were also measured. Endogenous glucose production (preoperatively 10.0 ± 1.6, postoperatively 3.7 ± 2.5 μmol·kg(-1)·min(-1); P = 0.0001), protein breakdown (preoperatively 105.3 ± 9.8, postoperatively 85.2 ± 9.2 mmol·kg(-1)·h(-1); P = 0.0005) and synthesis (preoperatively 88.7 ± 8.7, postoperatively 72.4 ± 8.4 mmol·kg(-1)·h(-1); P = 0.0005) decreased in the presence of hyperinsulinemia, whereas both parameters remained unchanged in the control group. A positive correlation between endogenous glucose production and protein breakdown was observed in the insulin group (r(2) = 0.385). Whole body protein oxidation and balance decreased after surgery in patients receiving insulin without reaching statistical significance. In the insulin group the plasma concentrations of 13 of 20 essential and nonessential amino acids decreased to a significantly greater extent than in the control group. In summary, supraphysiological hyperinsulinemia, while maintaining normoglycemia, decreased whole body protein breakdown and synthesis in patients undergoing CABG surgery. However, net protein balance remained negative.

Randomized clinical trial of the impact of insulin therapy on liver function in patients undergoing major liver resection

BACKGROUND

Postoperative liver dysfunction is the major source of morbidity and mortality in patients undergoing partial hepatectomy. This study tested the benefits of a metabolic support protocol based on insulin infusion, for reducing liver dysfunction following hepatic resection.

METHODS

Consecutive consenting patients scheduled for liver resection were randomized to receive preoperative dextrose infusion followed by insulin therapy using the hyperinsulinaemic normoglycaemic clamp protocol (n = 29) or standard therapy (control group, n = 27). Patients in the insulin therapy group followed a strict dietary regimen for 24 h before surgery. Intravenous dextrose was started at 2 mg per kg per min the night before and continued until surgery. Hyperinsulinaemic therapy for a total of 24 h was initiated at 2 munits per kg per min at induction of anaesthesia, and continued at 1 munit per kg per min after surgery. Normoglycaemia was maintained (3.5-6.0 mmol/l). Control subjects received no additional dietary supplement and a conventional insulin sliding scale during fasting. All patients were tested serially to evaluate liver function using the Schindl score. Liver tissue samples were collected at two time points during surgery to measure glycogen levels.

RESULTS

Demographics were similar in the two groups. More liver dysfunction occurred in the control cohort (liver dysfunction score range 0-8 versus 0-4 with insulin therapy; P = 0.031). Median (interquartile range) liver glycogen content was 278 (153-312) and 431 (334-459) µmol/g respectively (P = 0.011). The number of complications rose with increasing severity of postoperative liver dysfunction (P = 0.032) CONCLUSION: The glucose-insulin protocol reduced postoperative liver dysfunction and improved liver glycogen content.

REGISTRATION NUMBER

NCT00774098 (http://www.clinicaltrials.gov).

High-dose insulin therapy reduces postoperative liver dysfunction and complications in liver resection patients through reduced apoptosis and altered inflammation

CONTEXT

An exaggerated inflammatory response in patients undergoing major liver resection coupled with poor nutrition diminishes liver regenerative capacity and increases the risk of postoperative complications.

OBJECTIVES

Our objective was to evaluate the biological context leading to better clinical outcomes in patients undergoing liver resection coupled with hyperinsulinemic-normoglycemic clamp vs. standard care (insulin sliding care).

DESIGN AND SETTING

This study was a fundamental research analysis of a patient subset from a randomized-controlled study at the McGill University Health Center.

PATIENTS AND INTERVENTION

Thirty consenting patients participating in a randomized clinical trial for liver resection received either hyperinsulinemic-normoglycemic clamp technique with 24-h preoperative carbohydrate load (intervention) or standard glucose control through insulin sliding scale treatment (control).

MAIN OUTCOME MEASURES

Liver biopsies and plasma samples were taken at various time points before and after surgery. Primary measures included mRNA quantitation for genes related to insulin signaling, inflammation, and proliferation; proinflammatory cytokines at various time points; and liver function markers. These measurements were associated with clinical outcomes.

RESULTS

The hyperinsulinemic-normoglycemic clamp technique reduced postoperative liver dysfunction, infections, and complications. Markers of energy stores indicated higher substrate availability. Cytokine expression pattern was altered (TNF-α, IL-8, monocyte chemoattractant protein-1, IL-6, IL-10, and C-reactive protein). Apoptosis was markedly reduced, whereas the complement system was unaltered.

CONCLUSION

The hyperinsulinemic-normoglycemic clamp technique reduced postoperative negative outcomes by suppressing apoptosis. This phenomenon appears to be linked with higher substrate availability and altered cytokine secretion profile and may provide a long-term benefit of this therapy on liver resection patients.

High-dose insulin administration is associated with hypoaminoacidemia during cardiac surgery

Although the effects of insulin on glucose homeostasis are well recognized in surgical patients, its effect on perioperative protein metabolism has received little attention. The purpose of this study was to examine the effect of high-dose insulin therapy on the plasma concentrations of amino acids (AAs) in patients undergoing coronary artery bypass grafting surgery. We studied 20 nondiabetic patients scheduled for elective coronary artery bypass grafting surgery. Patients were randomly allocated to receive either standard metabolic care (target glycemia 6.0-10.0 mmol/L, control group, n = 10) or high-dose insulin therapy (insulin group, n = 10). Insulin was administered at 5 mU·kg(-1)·min(-1) beginning at skin incision. Simultaneously, 20% dextrose was infused at a variable rate adjusted to maintain glycemia between 4.0 and 6.0 mmol/L. Plasma AAs, glucose, cortisol, and insulin were measured immediately before surgery and at sternal closure. Differences in mean values were assessed by Student t test. Plasma concentrations of all AAs decreased in the insulin group, with 15 of 22 AAs, including all branched-chain AAs, being significantly lower at sternal closure when compared with the control group. At the end of surgery, plasma glucose concentration was significantly lower in the insulin group (4.2 ± 0.6 vs 7.3 ± 1.0 mmol/L, P = .0001), whereas plasma cortisol levels did not show any difference between groups. High-dose insulin therapy resulted in a significant reduction in plasma AAs, particularly branched-chain AAs, during cardiac surgery.

Glucose and protein kinetics in patients undergoing colorectal surgery: perioperative amino acid versus hypocaloric dextrose infusion

Surgical injury provokes a stress response that leads to a catabolic state and, when prolonged, interferes with the postoperative recovery process. This study tests the impact of 2 nutrition support regimens on protein and glucose metabolism as part of an integrated approach in the perioperative period incorporating epidural analgesia in 18 nondiabetic patients undergoing colorectal surgery. To test the hypothesis that parenteral amino acid infusion (amino acid group, n = 9) maintains glucose homeostasis while maintaining normoglycemia and reduces proteolysis compared with infusion of dextrose alone (DEX group, n = 9), glucose and protein kinetics were measured before and on the second day after surgery using a stable isotope tracer technique. Postoperatively, the rate of appearance of glucose was higher (P < .001) and blood glucose increased more (P < .001) in the DEX group than in the amino acid group. The postoperative increase in the appearance of leucine from protein breakdown tended to be greater (P = .077) in the DEX group. We conclude that perioperative infusion of a nutrition support regimen delivering amino acids alone maintains blood glucose homeostasis and normoglycemia and tends to have a suppressive effect on protein breakdown compared with infusion of dextrose alone.

Screening and therapy for malnutrition and related gastro-intestinal disorders in systemic sclerosis: recommendations of a North American expert panel

OBJECTIVES

To develop a set of recommendations for clinicians caring for patients with systemic sclerosis (SSc) to guide their approach to the patient with malnutrition and possible malabsorption.

METHODS

The Canadian Scleroderma Research Group convened a meeting of experts in the areas of nutrition, speech pathology, oral health in SSc, SSc and gastroenterology to discuss the nutrition-GI paradigm in SSc. This meeting generated a set of recommendations based on expert opinion.

RESULTS

Physicians should screen ALL patients with SSc for malnutrition. The physician should ask a series of questions that pertain to GI involvement. Patients who screen positive for malnutrition should be referred to a dietitian and gastroenterologist. Referral to a patient support group should be considered and if screening reveals oral health problems, referral to a dentist, preferably with expertise in treating patients with SSc, should be done. All SSc patients should weigh themselves monthly and report any sudden significant changes in weight. They should be assessed by a rheumatologist once a year for signs of malnutrition.

CONCLUSIONS

Malnutrition may be common in SSc and a multidisciplinary approach is important.

Comparison of analgesic methods for total knee arthroplasty: metabolic effect of exogenous glucose

BACKGROUND AND OBJECTIVES

This study was set up to assess whether postoperative suppression of gluconeogenesis by dextrose infusion would be influenced by continuous peripheral nerve block (CPNB) with local anesthetics, in comparison with epidural and with intravenous analgesia.

METHODS

Twenty-seven patients, undergoing elective primary total knee arthroplasty for osteoarthritis, were randomly allocated to one of the three groups of 9 patients each: patient controlled analgesia (PCA) with i.v. morphine, epidural with bupivacaine 0.1% and fentanyl 3mug/ml, or continuous femoral and sciatic blocks with ropivacaine 0.2%. Endogenous glucose production, an index of gluconeogenesis, and glucose clearance, an index of whole body glucose uptake, were assessed on the second postoperative day by measuring [6,6-(2)H(2)]glucose kinetics after an overnight fast (fasted state), and during a 3-h period infusion of dextrose at 4 mg/kg/min (fed state). Visual analog scale (VAS) at rest and at knee flexion, use of morphine, mobilization, nutritional intake, and bowel function were also collected.

RESULTS

Endogenous glucose production was totally suppressed by 3 h of dextrose infusion in all 3 groups (P < .001) while glucose clearance was unchanged. Blood glucose and insulin increased (P < .001), while glucagon decreased, with the greatest change in the epidural group (P < .05). VAS at rest and at knee flexion was significantly lower in patients receiving epidural and CPNB compared to i.v. morphine (P < .05). Restoration of bowel function, assessed as return of bowel movements, was faster in the CPNB group (P < .05).

CONCLUSION

Excellent analgesia was achieved in the epidural and continuous nerve block groups. Postoperative gluconeogenesis was totally suppressed by dextrose infusion independent of the analgesia technique with no change in glucose utilization.

Perioperative amino acid supplementation of hypocaloric glucose does not impair glucose metabolism after surgery

We tested the hypothesis that perioperative amino acid supplementation of hypocaloric dextrose would attenuate the inhibitory effect of glucose on endogenous glucose production after surgery. Sixteen patients undergoing colorectal cancer surgery were randomly assigned to receive intravenous glucose either with or without amino acids. Nutrition was administered over 48 hours from surgical skin incision until the second postoperative day. Glucose provided 50% and amino acids 20% of the patient's measured resting energy expenditure. Glucose rate of appearance was assessed by [6,6-2H2]glucose before and after surgery. Circulating concentrations of glucose, lactate, insulin, and glucagon were also determined. Hypocaloric glucose suppressed postoperative endogenous glucose production to a similar degree in both groups. The circulating concentrations of glucose increased to the same extent, whereas there was no significant change in plasma concentrations of lactate, glucagon, and cortisol. Postoperative plasma levels of insulin were significantly higher in patients receiving amino acids (P = .009). Perioperative amino acid administration does not mitigate the inhibitory effect of glucose on glucose production or aggravate hyperglycemia after colorectal surgery.

The importance of nutrition status assessment: the case of severe acute pancreatitis

Severe acute pancreatitis is associated with high mortality. Adequate nutrition support improves clinical outcome. Nevertheless, several recent trials have focused primarily on the route of nutrition support and neglected the role of nutrition status assessment in tailoring nutrition support to individual needs.

A randomized controlled trial of the anticatabolic effect of epidural analgesia and hypocaloric glucose

BACKGROUND AND OBJECTIVES

The goal of the present study was to investigate whether epidural analgesia exerts a protein-sparing effect after colorectal surgery in the presence of hypocaloric glucose supply initiated with surgical skin incision.

METHODS

We randomly allocated 10 patients to receive general anesthesia combined with epidural anesthesia with bupivacaine, followed by epidural analgesia using bupivacaine/fentanyl, and 10 patients to receive general anesthesia, followed by patient-controlled analgesia with intravenous morphine. All patients received a 48-hour infusion of glucose 10% from surgical skin incision until the second day after surgery. The glucose infusion rate provided 50% of the patient's resting energy expenditure. Kinetics of protein and glucose metabolism were assessed by a stable-isotope tracer technique (L-[1-(13)C]leucine and [6,6-(2)H(2)]glucose).

RESULTS

The rate of appearance of leucine increased in the intravenous-analgesia group (112 +/- 29 to 130 +/- 25 micromol/kg/h) 2 days after surgery, and this increase was more pronounced than in the epidural analgesia group (preoperative 120 +/- 24, postoperative 123 +/- 22 micromol/kg/h, P < .05). Leucine oxidation rate increased in the intravenous analgesia group from 17 +/- 8 to 23 +/- 8 micromol/kg/h and in the epidural group from 17 +/- 6 to 19 +/- 7 micromol/kg/h without the difference between the groups reaching statistical significance (P = .067). Nonoxidative leucine disposal remained unaltered in both groups. No differences in glucose metabolism were seen between the groups.

CONCLUSIONS

Epidural analgesia inhibits the increase in whole-body protein breakdown in patients receiving perioperative hypocaloric glucose infusion initiated with surgical skin incision. However, oxidative protein loss, protein synthesis, and glucose metabolism are not affected by epidural analgesia.

Parenteral nutrition and protein sparing after surgery: do we need glucose?

Although capable of inducing an anabolic state after surgery, parenteral nutrition, including glucose, leads to hyperglycemia. Even moderate increases in blood glucose are associated with poor surgical outcome. We examined the hypothesis that amino acids, in the absence of glucose supply, spare protein while preventing hyperglycemia. In this prospective study, 14 patients with colonic cancer were randomly assigned to undergo a 6-hour stable isotope infusion study (3 hours of fasting followed by 3-hour infusions of amino acids, Travasol [Baxter, Montreal, Canada] 10% at 0.02 mL.kg(-1).min(-1), with or without glucose at 4 mg.kg(-1).min(-1)) on the second day after colorectal surgery. Protein breakdown, protein oxidation, protein balance, and glucose production were assessed by stable isotope tracer kinetics using l-[1-(13)C]leucine and [6,6-(2)H2]glucose. Circulating concentrations of glucose, cortisol, insulin, and glucagon were determined. The administration of amino acids increased protein balance from -16+/-4 micromol.kg(-1).h(-1) in the fasted state to 16+/-3 micromol.kg(-1).h(-1). Combined infusion of amino acids and glucose increased protein balance from -17+/-7 to 7+/-5 micromol.kg(-1).h(-1). The increase in protein balance during nutrition was comparable in the 2 groups (P=.07). Combined administration of amino acids and glucose decreased endogenous glucose production (P=.001) and stimulated insulin secretion (P=.001) to a greater extent than the administration of amino acids alone. Hyperglycemia (blood glucose, 10.1+/-1.9 micromol/L) occurred only in the presence of glucose infusion. In summary, excluding glucose from a short-term feeding protocol does not diminish the protein-sparing effect of amino acids and avoids hyperglycemia.

Intraoperative Infusion of Amino Acids Induces Anabolism Independent of the Type of Anesthesia

BACKGROUND

The infusion of dextrose in patients receiving epidural and light general anesthesia or general anesthesia alone failed to achieve a positive protein balance. We sought to verify the hypothesis that nutritional supplementation with i.v. amino acids induced a greater protein balance in patients receiving epidural blockade compared with those receiving general anesthesia.

METHODS

Sixteen patients were randomly assigned to receive either general anesthesia with desflurane (control group) or general anesthesia combined with epidural analgesia (EDA group). A primed constant infusion of stable isotope tracers L-[1-(13)C]leucine and [6,6-(2)H2]glucose was started after a 32-h fast before surgery, (3 h of fasted state), and continued for 3 h during surgery during which amino acids were infused i.v. (fed state).

RESULTS

Compared with the fasted state, the endogenous rate of appearance of leucine decreased to a similar extent in both groups, and protein synthesis increased, with no difference between the two groups. Leucine oxidation did not change in either group. After amino acids infusion, endogenous glucose production remained unchanged and glucose clearance decreased in both groups. Blood glucose, plasma cortisol, serum insulin, and glucagon concentrations increased to the same extent in both groups.

CONCLUSIONS

Epidural anesthesia provided no additional benefit beyond the anabolism obtained with amino acids.

Postoperative infusion of amino acids induces a positive protein balance independently of the type of analgesia used

BACKGROUND

Net loss of body protein is a prominent feature of the catabolic response to surgical tissue trauma. Epidural analgesia with hypocaloric dextrose has been demonstrated to attenuate leucine oxidation but was unable to make protein balance positive. The current study was set to determine whether an infusion of amino acids on the second day after colon surgery would revert the catabolic state and promote protein synthesis while maintaining glucose homeostasis in patients receiving epidural analgesia as compared with patient-controlled analgesia with morphine (PCA).

METHODS

Sixteen patients undergoing colorectal surgery were randomly assigned to receive epidural blockade or PCA as analgesic techniques and underwent a 6-h stable isotope infusion study (3 h fasted, 3 h fed) on the second postoperative day. Whole body glucose kinetics and protein turnover were measured using [6,6-2H2]glucose and l-[1-13C]leucine as tracer.

RESULTS

The infusion of amino acids caused a decrease in endogenous glucose rate of appearance in both groups (P < 0.05), with greater changes in the PCA group (P < 0.05). Administration of amino acids suppressed the appearance of leucine from protein breakdown in both groups (P < 0.05), although the decrease was greater in the PCA group (P < 0.05). Leucine oxidation increased in both groups (P < 0.05), with greater change in the epidural group (P < 0.05). Protein synthesis increased to the same extent in both groups (P < 0.05). Protein balance became positive after the infusion of amino acids, and the effect was greater in the PCA group (P < 0.05).

CONCLUSIONS

Infusion of amino acids decreased the endogenous glucose production and induced a positive protein balance independent of the type of anesthesia provided, although such effects were greater in the PCA group.

Randomized clinical trial of the anabolic effect of hypocaloric parenteral nutrition after abdominal surgery

BACKGROUND

The observed failure of hypocaloric nutrition to establish an anabolic state after surgery may reflect inadequate control for the type and quality of analgesia in the studies performed. This study was designed to test the hypothesis that hypocaloric nutrition induces anabolism in patients who receive effective segmental pain relief using perioperative epidural analgesia.

METHODS

Sixteen patients who underwent colorectal surgery and received epidural analgesia were randomly assigned to receive intravenous glucose either without (glucose only) or with amino acids (nutrition). Feeding was administered over 48 h from surgical skin incision until the second day after operation. Glucose provided 50 per cent of the patient's resting energy expenditure (REE). Amino acids were infused at rates that provided 20 per cent of REE. Leucine rate of appearance (Ra), leucine oxidation and non-oxidative leucine disposal (NOLD) were assessed by measuring L-[1-13C]leucine kinetics. A positive leucine balance, that is the difference between NOLD and leucine Ra, indicated anabolism.

RESULTS

After surgery, leucine Ra in the nutrition group was lower than that in the glucose only group (mean(s.d.) 88(25) versus 131(22) micromol per kg per h). The leucine balance remained negative in the glucose only group, whereas it became positive in the nutrition group (mean(s.d.) -24(3) versus 38(12) micromol per kg per h; P < 0.001).

CONCLUSION

Patients who receive hypocaloric parenteral nutrition can be rendered anabolic after colorectal surgery in the presence of epidural analgesia.

Effect of Laparoscopic Colon Resection on Postoperative Glucose Utilization and Protein Sparing

HYPOTHESIS

Using a stable isotope method to quantify postoperative changes in glucose and protein metabolism, patients undergoing laparoscopic-assisted colon resection and receiving 4 mg . kg(-1) . min(-1) of dextrose intravenously will (1) have more pronounced suppression of endogenous glucose production, leading to (2) a greater reduction in whole-body protein breakdown.

DESIGN

Randomized protocol study.

SETTING

Tertiary health care center in Montreal, Quebec.

PATIENTS

Twelve patients scheduled for colonic resection were randomly allocated to undergo either laparoscopic (n = 6) or open (n = 6) surgery.

INTERVENTIONS

Patients underwent a 6-hour stable isotope infusion study (3 hours fasted and 3 hours fed with dextrose infusion) on postoperative day 2. Whole-body protein breakdown and synthesis, amino acid oxidation, and endogenous glucose production and clearance were measured during the postabsorptive state using L-[1-(13)C]leucine and [6,6-(2)H(2)]glucose. Gas exchange and plasma concentrations of metabolites and hormones were also measured.

MAIN OUTCOME MEASURES

Endogenous glucose production and whole-body protein breakdown during the fasted and fed states.

RESULTS

In the fasted state, laparoscopy did not affect protein and glucose metabolism. Dextrose infusion suppressed endogenous glucose production in both groups, with the greatest extent in the laparoscopic group (P = .01). Higher respiratory quotients (P = .001) in the latter group also indicated increased exogenous glucose oxidation. Neither surgical approach nor nutrition affected aspects of protein metabolism.

CONCLUSIONS

Laparoscopy for colon resection facilitates whole-body glucose uptake and utilization and oxidation of exogenous glucose with no protein-sparing effect. The laparoscopic approach modulates gluconeogenesis, although it is not sufficient in the presence of exogenous energy to promote nitrogen retention.

Type 2 Diabetes Mellitus and the Catabolic Response to Surgery

Background

The authors tested the hypothesis that the catabolic responses to colorectal surgery are amplified in the presence of type 2 diabetes mellitus.

Methods

Seven nondiabetic and seven diabetic patients underwent a 6-h stable isotope infusion study (3 h fasted, 3-h glucose infusion at 4 mg . kg . min) on the second postoperative day. Leucine rate of appearance (Ra), leucine oxidation, nonoxidative leucine disposal, and glucose Ra were assessed by L-[1-C]leucine and [6,6-H2]glucose. Circulating concentrations of glucose, lactate, insulin, glucagon, and cortisol also were determined.

Results

Diabetic patients had a higher leucine oxidation than nondiabetic patients (P = 0.0003), whereas leucine Ra and nonoxidative leucine disposal were not different. Administration of glucose did not affect leucine kinetics regardless of whether patients were diabetic. In diabetic patients, glucose Ra was greater than in the nondiabetic group (P = 0.0032). Glucose infusion suppressed the endogenous glucose Ra to a lesser extent in diabetic than in nondiabetic patients (P = 0.0048). Plasma glucose concentrations were higher in diabetic than in nondiabetic patients (P = 0.0203), both in the postabsorptive and the fed state. Circulating concentrations of glucagon were higher (P = 0.0065) and concentrations of insulin were lower (P = 0.0146) in the presence of diabetes, resulting in a lower insulin/glucagon ratio (P = 0.0002). In diabetic patients, the insulin/glucagon ratio increased during glucose infusion to a lesser extent than in the nondiabetic group (P = 0.0014).

Conclusion

Protein catabolism after colorectal surgery is increased in patients with type 2 diabetes mellitus as reflected by an increased oxidative protein loss.

Postoperative protein sparing with epidural analgesia and hypocaloric dextrose

OBJECTIVE

We examined the hypothesis that epidural analgesia prevents the increase in amino acid oxidation after elective colorectal surgery in patients receiving hypocaloric infusion of dextrose.

SUMMARY BACKGROUND DATA

Increased oxidative protein loss after surgery may adversely affect postoperative outcome. We have previously shown that effective segmental pain relief by epidural analgesia improves postoperative substrate utilization, resulting in less protein catabolism.

METHODS

We randomly allocated 10 patients to receive general anesthesia combined with epidural analgesia using bupivacaine/fentanyl and 10 to receive general anesthesia followed by patient-controlled analgesia with intravenous morphine. All patients received a peripheral 72-hour infusion of dextrose 10% from the day before until the second day after surgery. The dextrose infusion rate was adjusted to provide 50% of the patients' resting energy expenditure. The primary end point was whole-body leucine oxidation as determined by a stable isotope tracer technique (l-[1-C]leucine).

RESULTS

In the intravenous analgesia group, leucine oxidation increased from 19 +/- 4 to 28 +/- 6 micromol kg h after surgery. Epidural analgesia prevented this increase of leucine oxidation (preoperative 21 +/- 6 micromol kg h, postoperative 21 +/- 5 micromol kg h). This difference was statistically significant (P = 0.01; analysis of variance for repeated measures).

CONCLUSION

Perioperative epidural analgesia and hypocaloric dextrose infusion suppress the postoperative increase in amino acid oxidation, thereby saving more than 100 g of lean body mass per day.

Epidural Ropivacaine versus Epidural Morphine and the Catabolic Response to Colonic Surgery

Background

The authors examined the hypothesis that epidural administration of local anesthetic, in contrast to epidural analgesia with morphine, inhibits postoperative protein oxidation during administration of glucose.

Methods

Fourteen patients were randomly assigned to undergo a 6-h stable isotope infusion study (3 h fasted, 3 h feeding with 4 mg.kg(-1).min(-1) glucose) on the second day after colorectal surgery using epidural analgesia with either continuous ropivacaine or intermittent morphine. Protein synthesis, breakdown and oxidation, and glucose production were measured by L-[L-13C]leucine and [6,6-2H2]glucose. Substrate oxidation rates were determined by indirect calorimetry. Plasma concentrations of metabolic substrates and hormones were also measured.

Results

Whole body protein breakdown, oxidation, synthesis, and glucose production in the fasted state were similar between the two groups. Glucose administration decreased protein breakdown (P = 0.01), protein synthesis (P = 0.001), and glucose production (P = 0.001) to the same extent in both groups, whereas protein oxidation was not significantly affected. The type of epidural analgesia did not significantly influence the circulating concentrations of metabolic substrates and hormones in the fasted or in the fed state. Carbohydrate oxidation rate in the ropivacaine group was greater than in patients receiving morphine (P = 0.04), regardless of whether glucose was infused.

Conclusion

Epidural analgesia achieved with ropivacaine or morphine does not suppress the catabolic response to surgery, either under fasting conditions or in the presence of an energy supply.

Effect of desflurane/remifentanil anaesthesia on glucose metabolism during surgery: a comparison with desflurane/epidural anaesthesia

BACKGROUND

The aim of this study was to investigate the effect of general anaesthesia combined with remifentanil or epidural blockade on glucose metabolism during surgery.

METHODS

We randomly assigned patients undergoing elective colorectal surgery to receive either desflurane anaesthesia supplemented with intravenous remifentanil (n = 7) or desflurane anaesthesia supplemented with epidural bupivacaine (n = 7). Plasma concentrations of glucose, lactate, free fatty acids (FFA), insulin, glucagon and cortisol were measured before and after 2 h of surgery. Pre- and intraoperative whole body glucose production and glucose clearance, an indicator of glucose uptake, were determined by an isotope dilution technique using [6,6-2H2]glucose.

RESULTS

In both groups intraoperative glucose production ( P< 0.05) and uptake ( P< 0.05) decreased. Plasma glucose concentrations ( P< 0.05) increased during surgery but did not exceed the normal range (remifentanil group: 5.7 +/- 0.7 mmol l-1, epidural group: 5.8 +/- 0.4 mmol l-1). The plasma concentrations of lactate, FFA, insulin and glucagon remained unchanged during the operation. The plasma cortisol concentration in both groups increased intraoperatively (P< 0.05).

CONCLUSION

Both desflurane/remifentanil and desflurane/epidural anaesthesia decrease the intraoperative rate of whole body glucose production, thereby attenuating the hyperglycaemic response to colorectal surgery.

Perioperative glucose infusion and the catabolic response to surgery: the effect of epidural block

Although the nitrogen-sparing properties of epidural block and i.v. glucose on the days after surgical trauma have been well established, their metabolic effects during the acute phase of the stress response remain unclear. Therefore, in this study we investigated the effect of epidural block on glucose and protein kinetics during and immediately after surgery in patients receiving i.v. glucose at 2 mg x kg(-1) x min(-1). Sixteen patients undergoing colorectal surgery received either general anesthesia with epidural block with bupivacaine (EDA; n = 8) or general anesthesia alone (control; n = 8). Glucose and protein kinetics were determined during and 2 h after the operation by stable isotope tracers [6,6-(2)H(2)]glucose and L-[1-(13)C]leucine. Plasma concentrations of glucose, insulin, cortisol, and glucagon were also determined. Epidural block attenuated the perioperative increase in plasma glucose concentration (P < 0.05). The rate of appearance of glucose (R(a) glucose) and endogenous glucose production (EGP) were slower in the EDA group than in control subjects during (R(a) glucose, EDA 13.2 +/- 1.0 versus control 15.3 +/- 1.8 micromol x kg(-1) x min(-1); P < 0.05; EGP, EDA 1.2 +/- 1.2 versus control 3.8 +/- 1.7 micromol x kg(-1) x min(-1); P < 0.05) and after the operation (P > 0.05). Whereas protein breakdown and amino acid oxidation decreased in both groups (P < 0.05), whole-body protein synthesis remained unchanged. Insulin levels increased with both anesthetic techniques (P < 0.05). Intraoperative plasma concentrations of cortisol and glucagon were smaller in the EDA group (P < 0.05). The intraoperative suppression of EGP by exogenous glucose was more pronounced in the presence of epidural block. However, epidural block failed to exert a protein-sparing effect during the acute phase of the stress response in patients receiving i.v. glucose.

The anabolic effect of epidural blockade requires energy and substrate supply

BACKGROUND

The authors examined the hypothesis that continuous thoracic epidural blockade with local anesthetic and opioid, in contrast to patient-controlled intravenous analgesia with morphine, stimulates postoperative whole body protein synthesis during combined provision of energy (4 mg x kg(-1) x min(-1) glucose) and amino acids (0.02 ml x kg(-1) x min(-1) Travasol 10%, equivalent to approximately 2.9 g x kg(-1) x day(-1)).

METHODS

Sixteen patients were randomly assigned to undergo a 6-h stable isotope infusion study (3 h fasted, 3 h feeding) on the second day after colorectal surgery performed with or without perioperative epidural blockade. Protein synthesis, breakdown and oxidation, glucose production, and clearance were measured by L-[1-(13)C]leucine and [6,6-(2)H(2) ]glucose.

RESULTS

Epidural blockade did not affect protein and glucose metabolism in the fasted state. Parenteral alimentation decreased endogenous protein breakdown and glucose production to the same extent in both groups. Administration of glucose and amino acids was associated with an increase in whole body protein synthesis that was modified by the type of analgesia, i.e., protein synthesis increased by 13% in the epidural group (from 93.3 +/- 16.6 to 104.5 +/- 11.1 micromol x kg(-1) x h(-1) ) and by 4% in the patient-controlled analgesia group (from 90.0 +/- 27.1 to 92.9 +/- 14.8 micromol x kg(-1) x h(-1);P = 0.054).

CONCLUSIONS

Epidural blockade accentuates the stimulating effect of parenteral alimentation on whole body protein synthesis.

Epidural blockade modifies perioperative glucose production without affecting protein catabolism

BACKGROUND

Epidural blockade with local anesthetic has been shown to blunt the increase in plasma glucose concentration during and after abdominal surgery. The aim of the study was to test the hypothesis that epidural blockade inhibits this hyperglycemic response by attenuating endogenous glucose production. The authors further examined if the modification of glucose production by epidural blockade has an impact on perioperative protein catabolism.

METHODS

Sixteen patients undergoing colorectal surgery received either general anesthesia and epidural blockade with local anesthetic (n = 8) or general anesthesia alone (control, n = 8). Glucose and protein kinetics were assessed by stable isotope tracer technique ([6,6-2H2]glucose, L-[1-13C]leucine) during and 2 h after surgery. Plasma concentrations of glucose, lactate, free fatty acids (FFA), cortisol, glucagon, and insulin were also determined.

RESULTS

Epidural blockade blunted the perioperative increase in the plasma concentration of glucose, cortisol, and glucagon when compared with the control group (P < 0.05). Plasma concentrations of lactate, FFA, and insulin did not change. Intra- and postoperative glucose production was lower in patients with epidural blockade than in control subjects (intraoperative, epidural blockade 8.2 +/- 1.9 vs. control 10.7 +/- 1.4 micromol x kg(-1) x min(-1), P < 0.05; postoperative, epidural blockade 8.5 +/- 1.8 vs. control 10.5 +/- 1.2 micromol x kg(-1) x min(-1), P < 0.05), whereas glucose clearance decreased to a comparable extent in both groups (P < 0.05). Protein breakdown (P < 0.05), protein synthesis (P < 0.05), and amino acid oxidation (P > 0.05) decreased with both anesthetic techniques.

CONCLUSIONS

Epidural blockade attenuates the hyperglycemic response to surgery through modification of glucose production. The perioperative suppression of protein metabolism was not influenced by epidural blockade.

Integrated analysis of protein and glucose metabolism during surgery: effects of anesthesia

The aim of this study was to assess dynamic changes in protein and glucose metabolism during surgery. Twelve patients undergoing colorectal surgery received either intravenous propofol anesthesia (n = 6) or inhalational anesthesia with desflurane (n = 6). Pre- and intraoperative protein and glucose kinetics were analyzed by an isotope dilution technique using L-[1-(13)C]leucine and [6,6-(2)H(2)]glucose. Plasma concentrations of glucose, lactate, free fatty acids, insulin, glucagon, and cortisol were measured before and after 2 h of surgery. The rates of appearance of leucine and glucose, leucine oxidation, protein synthesis, and glucose clearance decreased during surgery, independent of the type of anesthesia (P < 0.05). A correlation between the rate of appearance of leucine and glucose was observed (r = 0.755, P < 0.001). Intraoperative plasma cortisol and glucose concentrations increased (P < 0.05), whereas plasma concentrations of lactate, free fatty acids, insulin, and glucagon did not change. Surgery causes a depression of whole body protein and glucose metabolism, independent of the anesthetic technique. There is a correlation between perioperative glucose production and protein breakdown.

Epidural blockade improves substrate utilization after surgery

The purpose of this study was to test the hypothesis that epidural blockade with local anesthetic improves the anticatabolic effects of glucose after colorectal surgery. Sixteen patients were randomly assigned to undergo a 6-h stable isotope infusion study (3 h fasted, 3 h glucose infusion at 4 mg. kg(-1). min(-1)) on the second postoperative day with or without perioperative epidural blockade. Protein synthesis, breakdown and oxidation, and glucose production and clearance were assessed by L-[1-(13)C]leucine and [6, 6-(2)H(2)]glucose. Epidural blockade did not affect protein and glucose metabolism in the fasted state. Glucose infusion increased glucose clearance (P < 0.05), accompanied by an increase in the respiratory quotient (P < 0.05) and a decrease in leucine oxidation (P < 0.05) only in the presence of epidural blockade. An inverse correlation (r = -0.74, P < 0.05) between changes in glucose clearance and leucine oxidation was observed. In conclusion, epidural blockade facilitates whole body glucose uptake and inhibits endogenous protein oxidation after abdominal surgery, indicating a shift from a protein to a more glucose-dominated substrate utilization.

Effect of epidural blockade on protein, glucose, and lipid metabolism in the fasted state and during dextrose infusion in volunteers

BACKGROUND

To interpret correctly the results from studies performed during surgery and anesthesia it is necessary to dissect the separate effect of the anesthetic technique itself. The purpose of this study was to investigate the metabolic effects of epidural blockade (T7-S1) with bupivacaine 0.25% after 12 h fasting and during administration of 4 mg x kg(-1) x min(-1) dextrose in six healthy volunteers.

METHODS

Each volunteer was assigned to randomly undergo a 6-h multiple stable isotope infusion study (3 h fasted, 3 h dextrose infusion) with or without epidural blockade. L-[1-13C]leucine, [6,6-2H2]glucose, and [1,1,2,3,3-2H5]glycerol were infused to measure protein synthesis, breakdown, and amino acid oxidation; glucose production and clearance; and lipolysis. Plasma concentrations of glucose, lactate, glycerol, free fatty acids, insulin, and glucagon were determined.

RESULTS

Epidural blockade with bupivacaine had no influence on protein oxidation, breakdown and synthesis, glucose production, glucose clearance and lipolysis in the fasted state. Plasma concentrations of metabolic substrates and hormones also were not affected. Dextrose infusion significantly increased glucose clearance and plasma concentrations of glucose and insulin, while endogenous glucose production and lipolysis decreased to a similar degree in both groups. Protein synthesis, breakdown, and oxidation did not change during dextrose infusion.

CONCLUSIONS

Epidural blockade with bupivacaine in the absence of surgery has no effect on fasting protein, glucose, and lipid metabolism. Epidural blockade does not modify the inhibitory influence of dextrose administration on endogenous glucose production and lipolysis.

Chronic protein undernutrition and an acute inflammatory stimulus elicit different protein kinetic responses in plasma but not in muscle of piglets

The changes in protein metabolism of severe childhood malnutrition are generally perceived as a metabolic adaptation to chronic protein undernutrition. However, severe malnutrition is invariably accompanied by infections which also have profound effects on protein metabolism. This study aimed to distinguish the effect of protein undernutrition from that of an inflammatory stimulus on muscle and plasma protein synthesis rates. Two groups of five piglets consumed diets containing either 23% or 3% protein for 4 wk. They then were infused intravenously with 2H3-leucine before and 48 h after subcutaneous injections of turpentine to measure the fractional synthesis rates (FSR) of muscle protein and both the FSR and the absolute synthesis rates (ASR) of albumin and fibrinogen. Prior to turpentine injection, compared to control piglets, protein-deficient piglets had significantly lower muscle FSR and plasma concentrations of both albumin and fibrinogen, although only albumin had lower FSR and ASR. Turpentine injection decreased muscle FSR but increased the FSR, ASR and plasma concentrations of both albumin and fibrinogen in control piglets. In protein-deficient piglets, the inflammatory stress caused a further decrease in muscle protein FSR and in plasma albumin concentration despite marked increases in albumin FSR and ASR. Fibrinogen FSR, ASR and plasma concentration were increased. We conclude that protein undernutrition and inflammation elicit the same kinetic response in muscle protein but different kinetic responses in plasma proteins. Furthermore, whereas protein deficiency reduces the plasma albumin pool via a reduction in albumin synthesis, inflammation reduces it through a stimulation of catabolism and/or loss from the intravascular space.

Enteral glutamate is the preferential source for mucosal glutathione synthesis in fed piglets

To measure the source and rate of mucosal glutathione (GSH) synthesis, fed piglets (28 days old; 7.7 kg) received a 6-h infusion of intragastric [U-13C]glutamate (n = 11) either with (n = 5) or without (n = 6) an intragastric infusion of [1-13C]glycine (0-6 h) and [1,2-13C2(U-13C)]glycine (3-6 h). Eighty-four percent of the labeled mucosal GSH-glutamate and 86% of the luminal GSH-glutamate was 13C5. The tracer-to-tracee ratio of GSH-[U-13C]glutamate was 75% of that of mucosal glutamate. Sixty percent of the labeled mucosal glutamate was 13C1, 13C2, or 13C3, but the tracer-to-tracee ratios of these isotopomers in GSH-glutamate were not significantly different from zero. After 3 h of infusion, the tracer-to-tracee ratio of GSH-[U-13C]glycine was 46%, and after 6 h of infusion GSH-[13C1]glycine was 82% of that of mucosal glycine. This suggested that the half-life of mucosal GSH was 2.7 +/- 0.1 h. We concluded that, in fed piglets, mucosal GSH-glutamate derived largely from the direct metabolism of enteral glutamate rather than from glutamate that was metabolized within the mucosa.