Elective abdominal surgery depresses muscle protein synthesis and increases subjective fatigue: effects lasting more than 30 days

The utility of the rodent synergist ablation model in identifying molecular and cellular mechanisms of skeletal muscle hypertrophy

Skeletal muscle exhibits remarkable plasticity to adapt to stimuli such as mechanical loading. The mechanisms that regulate skeletal muscle hypertrophy due to mechanical overload have been thoroughly studied. Remarkably, our understanding of many of the molecular and cellular mechanisms that regulate hypertrophic growth were first identified using the rodent synergist ablation (SA) model and subsequently corroborated in human resistance exercise training studies. To demonstrate the utility of the SA model, we briefly summarize the hypertrophic mechanisms identified using the model and the following translation of these mechanism to human skeletal muscle hypertrophy induced by resistance exercise training.

The effect of spinal versus general anaesthesia on perioperative muscle weakness in patients having bilateral total hip arthroplasty: a single center randomized clinical trial

BACKGROUND

Perioperative neuro-endocrine stress response may contribute to acquired muscle weakness. Regional anaesthesia has been reported to improve the outcome of patients having total hip arthroplasty. In this study, it was hypothesized that spinal anaesthesia (SA) decreases the perioperative neuro-endocrine stress response and perioperatively acquired muscle weakness (PAMW), as compared to general anaesthesia (GA).

METHODS

Fifty subjects undergoing bilateral total hip arthroplasty (THA) were randomly allocated to receive a standardized SA (n = 25) or GA (n = 25). Handgrip strength was assessed preoperatively, on the first postoperative day (primary endpoint) and on day 7 and 28. Respiratory muscle strength was measured by maximal inspiratory pressure (MIP). Stress response was assessed by measuring levels of Adrenocorticotropic hormone (ACTH), cortisol and interleukin-6 (IL-6).

RESULTS

Handgrip strength postoperatively (day 1) decreased by 5.4 ± 15.9% in the SA group, versus 15.2 ± 11.7% in the GA group (p = 0.02). The handgrip strength returned to baseline at day 7 and did not differ between groups at day 28. MIP increased postoperatively in patients randomized to SA by 11.7 ± 48.3%, whereas it decreased in GA by 12.2 ± 19.9% (p = 0.04). On day 7, MIP increased in both groups, but more in the SA (49.0 ± 47.8%) than in the GA group (14.2 ± 32.1%) (p = 0.006). Postoperatively, the levels of ACTH, cortisol and IL-6 increased in the GA, but not in the SA group (p < 0.004).

CONCLUSION

In patients having bilateral THA, SA preserved the postoperative respiratory and peripheral muscle strength and attenuated the neuro-endocrine and inflammatory responses.

TRIAL REGISTRATION

clinicaltrials.gov NCT03600454.

Endothelial Damage and Muscle Wasting in Cardiac Surgery Patients

This is a post-hoc analysis to assess the effect of anesthesia, surgical trauma, and extracorporeal circuit on endothelial integrity, microvascular permeability, and extracellular fluid balance, as well as on skeletal muscle catabolism, in patients undergoing elective cardiac surgery. We included 127 well-nourished patients undergoing “on-pump” elective cardiac surgery. One day prior to surgery (D0) and again on postoperative day 7 (POD7), body mass index, body composition assessment, hand-grip strength (HGS), and mid-upper arm muscle circumference (MAMC) were measured. Patients were assigned to early recovery (ER) and late recovery (LR) groups, depending on the duration of ICU stay (cut-off 48 hours). The magnitude of change (Δ) in all parameters studied was assessed in ER versus LR groups, regarding (i) epithelial tissue dysfunction (Δ-Extra-Cellular Water percentage (Δ-ECW%), Δ-Phase Angle (Δ-PhA)), (ii) skeletal muscle mass catabolism (Δ-Skeletal muscle mass reduction%, Δ-Hand Grip Strength (Δ-HGS) and Δ-Mid Upper-Arm Muscle Circumference (Δ-MAMC)). Baseline measurements were similar in both groups. A significant difference was observed in all Δ-parameters studied (Δ-ECW%, Δ-PhA and muscle catabolism, Δ-HGS, Δ-MAMC), the worse results being correlated to the LR group. The results raise the issue that patients with early recovery may silently have pathological conditions, continuing even on the day of discharge - further research should be planned.

Effects of Various Muscle Disuse States and Countermeasures on Muscle Molecular Signaling

Skeletal muscle is capable of changing its structural parameters, metabolic rate and functional characteristics within a wide range when adapting to various loading regimens and states of the organism. Prolonged muscle inactivation leads to serious negative consequences that affect the quality of life and work capacity of people. This review examines various conditions that lead to decreased levels of muscle loading and activity and describes the key molecular mechanisms of muscle responses to these conditions. It also details the theoretical foundations of various methods preventing adverse muscle changes caused by decreased motor activity and describes these methods. A number of recent studies presented in this review make it possible to determine the molecular basis of the countermeasure methods used in rehabilitation and space medicine for many years, as well as to identify promising new approaches to rehabilitation and to form a holistic understanding of the mechanisms of gravity force control over the muscular system.

Massage as a mechanotherapy promotes skeletal muscle protein and ribosomal turnover but does not mitigate muscle atrophy during disuse in adult rats

AIM

Interventions that decrease atrophy during disuse are desperately needed to maintain muscle mass. We recently found that massage as a mechanotherapy can improve muscle regrowth following disuse atrophy. Therefore, we aimed to determine if massage has similar anabolic effects when applied during normal weight bearing conditions (WB) or during atrophy induced by hindlimb suspension (HS) in adult rats.

METHODS

Adult (10 months) male Fischer344-Brown Norway rats underwent either hindlimb suspension (HS, n = 8) or normal WB (WB, n = 8) for 7 days. Massage was applied using cyclic compressive loading (CCL) in WB (WBM, n = 9) or HS rats (HSM, n = 9) and included four 30-minute bouts of CCL applied to gastrocnemius muscle every other day.

RESULTS

Massage had no effect on any anabolic parameter measured under WB conditions (WBM). In contrast, massage during HS (HSM) stimulated protein turnover, but did not mitigate muscle atrophy. Atrophy from HS was caused by both lowered protein synthesis and higher degradation. HS and HSM had lowered total RNA compared with WB and this was the result of significantly higher ribosome degradation in HS that was attenuated in HSM, without differences in ribosomal biogenesis. Also, massage increased protein turnover in the non-massaged contralateral limb during HS. Finally, we determined that total RNA degradation primarily dictates loss of muscle ribosomal content during disuse atrophy.

CONCLUSION

We conclude that massage is an effective mechanotherapy to impact protein turnover during muscle disuse in both the massaged and non-massaged contralateral muscle, but it does not attenuate the loss of muscle mass.

Perioperatively Acquired Weakness

BACKGROUND

Skeletal muscle failure in critical illness (intensive care unit-acquired weakness) is a well-known complication developing early during intensive care unit stay. However, muscle weakness during the perioperative setting has not yet been investigated.

METHODS

We performed a subgroup investigation of a prospective observational trial to investigate perioperative muscle weakness. Eighty-nine patients aged 65 years or older were assessed for handgrip strength preoperatively, on the first postoperative day, at intensive care unit discharge, at hospital discharge, and at 3-month follow-up. Functional status was evaluated perioperatively via Barthel index, instrumental activities of daily living, Timed Up and Go test, and functional independence measure. After exclusion of patients with intensive care unit-acquired weakness or intensive care unit stay of ≥72 hours, 59 patients were included into our analyses. Of these, 14 patients had additional pulmonary function tests preoperatively and on postoperative day 1. Blood glucose was measured intraoperatively every 20 minutes.

RESULTS

Handgrip strength significantly decreased after surgery on postoperative day 1 by 16.4% (P < .001). Postoperative pulmonary function significantly decreased by 13.1% for vital capacity (P = .022) and 12.6% for forced expiratory volume in 1 second (P = .001) on postoperative day 1. Handgrip strength remained significantly reduced at hospital discharge (P = .016) and at the 3-month follow-up (P = .012). Perioperative glucose levels showed no statistically significant impact on muscle weakness. Instrumental activities of daily living (P < .001) and functional independence measure (P < .001) were decreased at hospital discharge, while instrumental activities of daily living remained decreased at the 3-month follow-up (P = .026) compared to preoperative assessments.

CONCLUSIONS

Perioperatively acquired weakness occurred, indicated by a postoperatively decreased handgrip strength, decreased respiratory muscle function, and impaired functional status, which partly remained up to 3 months.

Impaired Ribosomal Biogenesis by Noncanonical Degradation of β-Catenin during Hyperammonemia

Increased ribosomal biogenesis occurs during tissue hypertrophy, but whether ribosomal biogenesis is impaired during atrophy is not known. We show that hyperammonemia, which occurs in diverse chronic disorders, impairs protein synthesis as a result of decreased ribosomal content and translational capacity. Transcriptome analyses, real-time PCR, and immunoblotting showed consistent reductions in the expression of the large and small ribosomal protein subunits (RPL and RPS, respectively) in hyperammonemic murine skeletal myotubes, HEK cells, and skeletal muscle from hyperammonemic rats and human cirrhotics. Decreased ribosomal content was accompanied by decreased expression of cMYC, a positive regulator of ribosomal biogenesis, as well as reduced expression and activity of β-catenin, a transcriptional activator of cMYC. However, unlike the canonical regulation of β-catenin via glycogen synthase kinase 3β (GSK3β)-dependent degradation, GSK3β expression and phosphorylation were unaltered during hyperammonemia, and depletion of GSK3β did not prevent ammonia-induced degradation of β-catenin. Overexpression of GSK3β-resistant variants, genetic depletion of IκB kinase β (IKKβ) (activated during hyperammonemia), protein interactions, and in vitro kinase assays showed that IKKβ phosphorylated β-catenin directly. Overexpressing β-catenin restored hyperammonemia-induced perturbations in signaling responses that regulate ribosomal biogenesis. Our data show that decreased protein synthesis during hyperammonemia is mediated via a novel GSK3β-independent, IKKβ-dependent impairment of the β-catenin-cMYC axis.

Regulation of Protein Synthesis in Inactivated Skeletal Muscle: Signal Inputs, Protein Kinase Cascades, and Ribosome Biogenesis

Disuse atrophy of skeletal muscles is characterized by a significant decrease in the mass and size of muscle fibers. Disuse atrophy develops as a result of prolonged reduction in the muscle functional activity caused by bed rest, limb immobilization, and real or simulated microgravity. Disuse atrophy is associated with the downregulation of protein biosynthesis and simultaneous activation of protein degradation. This review is focused on the key molecular mechanisms regulating the rate of protein synthesis in mammalian skeletal muscles during functional unloading.

Relation between the Disability of the Arm, Shoulder and Hand Score and Muscle Strength in Post-Cardiac Surgery Patients

Background: The Disabilities of the Arm, Shoulder, and Hand (DASH) questionnaire is a valid and reliable patient-reported outcome measure. DASH can be assessed by self-reported upper extremity disability and symptoms. We aimed to examine the relationship between the physiological outcome of muscle strength and the DASH score after cardiac surgery. Methods: This cross-sectional study assessed 50 consecutive cardiac patients that were undergoing cardiac surgery. Physiological outcomes of handgrip strength and knee extensor muscle strength and the DASH score were measured at one month after cardiac surgery and were assessed. Results were analyzed using Spearman correlation coefficients. Results: The final analysis comprised 43 patients (men: 32, women: 11; age: 62.1 ± 9.1 years; body mass index: 22.1 ± 4.7 kg/m²; left ventricular ejection fraction: 53.5 ± 13.7%). Respective handgrip strength, knee extensor muscle strength, and DASH score were 27.4 ± 8.3 kgf, 1.6 ± 0.4 Nm/kg, and 13.3 ± 12.3, respectively. The DASH score correlated negatively with handgrip strength (r = -0.38, p = 0.01) and with knee extensor muscle strength (r = -0.32, p = 0.04). Conclusion: Physiological outcomes of both handgrip strength and knee extensor muscle strength correlated negatively with the DASH score. The DASH score appears to be a valuable tool with which to assess cardiac patients with poor physiological outcomes, particularly handgrip strength as a measure of upper extremity function, which is probably easier to follow over time than lower extremity function after patients complete cardiac rehabilitation.

Inflammatory response to surgical trauma in patients with minilaparotomy cholecystectomy versus laparoscopic cholecystectomy: a randomised multicentre study

OBJECTIVE

The aim of the study was to evaluate the inflammatory response to surgical trauma in minilaparotomy cholecystectomy (MC) compared to laparoscopic cholecystectomy (LC). Assessment of inflammatory response to surgical trauma in MC has not been addressed properly. Therefore, we investigated five interleukins (IL) and C-reactive protein (CRP) in MC versus LC group in a prospective randomised trial.

METHODS

Initially, 106 patients with non-complicated symptomatic gallstone disease were randomised into MC (n = 56) or LC (n = 50) groups. Plasma levels of five interleukins (IL-1β, IL-1ra, IL-6, IL-8, IL-10) and hs-CRP were measured at three time points; before operation (PRE), immediately after operation (POP1) and six hours after operation (POP2). The primary end-point of the study was to compare the plasma levels of five interleukins and CRP in LC versus MC group.

RESULTS

The demographic variables and the surgical data were similar in the study groups. The patients in the MC group had higher elevation of the CRP mean values post-operatively (p = 0.01). However, the patients in the MC group had higher elevation of the IL-1ra mean values post-operatively, the mean pre-/post-operative IL-1ra values being 299/614 pg/ml in the MC group versus 379/439 pg/ml in the LC group (p = 0.003). There was no statistical significance in IL-6 mean values between the MC and LC groups pre- and post-operatively (POP1). However, the patients in the MC group had higher IL-6 mean values six hours post-operatively (POP2), the mean IL-6 values being 27.6 pg/ml in the MC group versus 14.8 pg/ml in the LC group (p = 0.037). In addition, the patients in the MC group had higher elevation of the IL-6 mean values post-operatively, the mean pre-/post-operative IL-6 values being 4.1/27.6 pg/ml in the MC group versus 3.8/14.8 pg/ml in the LC group (p = 0.04). There was no statistical significance in IL-8, IL-10, and IL-1β mean values between the MC and LC groups pre- and post-operatively.

CONCLUSION

Our results suggest that the inflammatory response in MC versus LC groups was similar based on the IL-8, IL-10, and IL-1β values. A new finding with possible clinical relevance in the present work is higher relative elevation of the IL-1ra and IL-6 mean values post-operatively in the MC group.

Ribosome biogenesis: emerging evidence for a central role in the regulation of skeletal muscle mass

The ribosome is a supramolecular ribonucleoprotein complex that functions at the heart of the translation machinery to convert mRNA into protein. Ribosome biogenesis is the primary determinant of translational capacity of the cell and accordingly has an essential role in the control of cell growth in eukaryotes. Cumulative evidence supports the hypothesis that ribosome biogenesis has an important role in the regulation of skeletal muscle mass. The purpose of this review is to, first, summarize the main mechanisms known to regulate ribosome biogenesis and, second, put forth the hypothesis that ribosome biogenesis is a central mechanism used by skeletal muscle to regulate protein synthesis and control skeletal muscle mass in response to anabolic and catabolic stimuli. The mTORC1 and Wnt/β-catenin/c-myc signaling pathways are discussed as the major pathways that work in concert with each of the three RNA polymerases (RNA Pol I, II, and III) in regulating ribosome biogenesis. Consistent with our hypothesis, activation of these two pathways has been shown to be associated with ribosome biogenesis during skeletal muscle hypertrophy. Although further study is required, the finding that ribosome biogenesis is altered under catabolic states, in particular during disuse atrophy, suggests that its activation represents a novel therapeutic target to reduce or prevent muscle atrophy. Lastly, the emerging field of ribosome specialization is discussed and its potential role in the regulation of gene expression during periods of skeletal muscle plasticity.

Albumin synthesis rates are not responsive to hyperglycemic hyperinsulinemia in postoperative patients

BACKGROUND

Insulin regulates albumin synthesis in vitro and in various experimental models. The current study was undertaken to determine the effects of a physiologic hyperinsulinemia on albumin synthesis in postoperative patients in whom plasma albumin concentrations are decreased.

METHODS

Studies were performed in postabsorptive patients after major abdominal operations. Mass spectrometry techniques were used to directly determine the incorporation rate of 1-[(13)C]-leucine into albumin. Consecutive blood samples were taken during a continuous isotope (D-Glc) infusion (0.16 µmol/kg/min). Isotopic enrichments were determined at baseline (period I) and after a 4-hour D-glucose (D-Glc) infusion at currently recommended rates (170 mg/kg/h, n = 10) or after infusion of saline (control group, n = 8) (period II).

RESULTS

After D-Glc infusion, plasma insulin concentrations increased significantly (period I, 6.6 ± 1.8 µU/mL; period II, 21.4 ± 2.1 µU/mL; P < .01). In contrast, plasma insulin concentration remained constant in control patients (period I, 3.8 ± 0.9 µU/mL(-1); period II, 5.9 ± 1.1 µU/mL; not significant vs period I, but P < .005 vs the corresponding value at the end of period II in the control group). Hyperinsulinemia was without effect on fractional albumin synthesis (period I, 12.8% ± 1.9%/d; period II, 11.9% ± 1.9%/d; not significant), and synthesis rates corresponded to those measured in controls (period I, 13.0% ± 1.2%/d; period II, 12.1% ± 0.1%/d; not significant vs period I and vs D-Glc infusion).

CONCLUSIONS

A standard D-Glc infusion is insufficient to increase albumin synthesis in postoperative patients.

Effects of short-term application of low-dose growth hormone on trace element metabolism and blood glucose in surgical patients

AIM: To investigate the effects of short-term application of low-dose growth hormone on trace element metabolism and blood glucose in surgical patients

METHODS: A total of 48 consecutive patients undergoing abdominal operations were randomized to receive either subcutaneous rhGH (0.15 IU/kg) or placebo (menstruum) injections daily for 7 d after surgery. The two groups had similar nutrition intake. Blood, feces, urine and drain samples were collected to measure zincum, cuprum and ferrum as well as glucose levels. Accumulative intake, excretion and balance of zincum, cuprum and ferrum, apparent absorption (AA) and apparent utilization (AU) of zincum, cuprum and ferrum, blood glucose levels and adverse events were estimated.

RESULTS: There were no differences in accumulative intake and drain excretion between the two groups. The feces excretion and accumulative excretion of cuprum were lower in the rhGH group (P < 0.05). The urinary excretion of zincum, cuprum and ferrum was all significantly decreased in the rhGH group (P < 0.05) and the accumulative balance of zincum, cuprum and ferrum was improved compared with the placebo group (P < 0.05). AA of cuprum in the rhGH group was almost twice as much as the placebo group (P < 0.05), and AU of zincum, cuprum and ferrum was all improved in the rhGH group (P < 0.05). The mean blood glucose level was significantly higher in the rhGH group than in the placebo group from d 3 to d 6 after operation (P < 0.05).

CONCLUSION: Postoperative low-dose rhGH treatment improves the retention of zincum, cuprum and ferrum and decreases the excretion of zincum, cuprum and ferrum, improves the balance of zincum, cuprum and ferrum, and promotes the AA and AU of zincum, cuprum and ferrum. rhGH can be well tolerated without significant adverse effects and the blood glucose level can be well controlled.

Effect of a short-term infusion of glutamine on muscle protein metabolism postoperatively

The acute effect of a short-term postoperative infusion of glucose supplemented with glutamine (0.285 g/kg body weight), on muscle protein metabolism, was studied by analyses of free amino acid concentrations and determinations of protein synthesis. A glutamine-glucose infusion was given for 5.5 h to 6 patients 2-3 days after elective surgery for colon cancer. The free glutamine concentration was 5.72 +/- 0.96 mmol/kg wet weight (ww) before and 6.14 +/- 1.10 mmol/kg ww 4 h after the glutamine infusion. The rate of protein synthesis was 1.26 +/- 0.15%/24 h before the infusion and 1.12 +/- 0.16%/24 h during its latter part. The percentage of polyribosomes was 42.2 +/- 3.4% before and 40.9 +/- 1.3% after the infusion. The results showed no difference in these biochemical parameters, indicating that a short-term infusion of glutamine given postoperatively is insufficient to affect protein metabolism in human skeletal muscle.

Dynamics of albumin synthesis after major rectal operation

BACKGROUND

Major abdominal operations were found to be associated with long-lasting metabolic changes, such as accelerated release of stress hormones and carbohydrate turnover. It is unknown currently whether acute changes of hepatic protein metabolism persist in a similar way. We wanted to determine the long-term dynamics of albumin synthesis and its relationship to whole body protein breakdown and albumin concentration after major rectal operations.

METHODS

We used stable isotope tracer techniques to determine albumin synthesis and whole body protein breakdown (rate of appearance of leucine, Ra) in postoperative patients about 1 week after low anterior rectal resection and also during convalescence (about 4 months after operation), and in healthy controls. Consecutive blood sampling was carried out during continuous isotope infusion (1-[(13)C]-leucine, 0.16 micromol/kg min).

RESULTS

Serum albumin concentrations were close to the lower normal limit in patients early after operation but were comparable to controls in convalescent patients. Simultaneously, albumin synthesis was increased in the early postoperative phase (0.53 +/- 0.0.5%/h) compared with convalescent patients (0.32 +/- 0.04) and controls (0.28 +/- 0.04) (P < .01 each). A significant inverse correlation could be found between plasma albumin concentration and corresponding rates of albumin synthesis. Early after operation patients showed an increased leucine Ra (3.25 +/- 0.23 micromol/kg min) that was greater than that of convalescent patients (2.37 +/- 0.06 micromol/kg min, P < .05). Leucine Ra in both patient groups were greater than the rates in controls (2.01 +/- 0.07 micromol/kg min, P < .01) Albumin synthesis correlated weakly with whole body protein breakdown rate.

CONCLUSIONS

Albumin synthesis and total body protein breakdown are increased after major abdominal operation, but albumin synthesis returns to control values only during convalescence. Hypoalbuminemia after rectal operations may be associated with high rates of albumin synthesis and is, therefore, not necessarily an indicator of insufficient hepatic function or poor nutritional status in that particular situation.

Short-term application of low-dose growth hormone in surgical patients: Effects on nitrogen balance and blood glucose

AIM: To investigate the effectiveness and safety of recombinant human growth hormone (rhGH) in postoperative patients.

METHODS: A total of 48 consecutive patients undergoing abdominal operations were randomized to receive either subcutaneous rhGH (0.15 IU/kg) or placebo (menstruum) injections daily for 7 d after surgery. The two groups had similar nutritional intake. Blood samples for serum fibronectin, albumin, prealbumin, transferrin and the total lymphocyte count, as well as glucose levels were collected to study the rhGH effect. Basal laboratory evaluation, and nutritional status were estimated on d 1 before as baseline and d 3 and 10 after operation using standard laboratory techniques. Nitrogen balance was measured from d 3 to 9 after operation.

RESULTS: The cumulative nitrogen balance was significantly improved in rhGH group compared with the placebo group (11.37 ± 16.82 vs -9.11 ± 17.52, P = 0.0003). Serum fibronectin was also significantly higher in the rhGH group than in the placebo group (104.77 ± 19.94 vs 93.03 ± 16.03, P < 0.05), whereas changes in serum albumin, prealbumin, transferrin and total lymphocyte counts were not statistically significant. Mean blood glucose levels were significantly higher in the rhGH group from d 3 to 6 after operation.

CONCLUSION: If blood glucose can be controlled, low-dose growth hormone together with hypocaloric nutrition is effective on improving positive nitrogen balance and protein conservation and safe is in postoperative patients.

Impact of surgical trauma on human skeletal muscle protein synthesis

Muscle protein catabolism is a considerable clinical problem following surgery. However, the impact of surgical trauma on muscle protein synthesis is not well characterized. In this pilot study, we therefore investigated whether the severity of surgical trauma is related to a decrease in muscle protein synthesis rate in humans. Metabolically healthy patients (n=28) were included in the study. Eight of the patients were day-care patients undergoing minor breast surgery (defined as minor surgery). The other 20 patients were subjected to major abdominal surgery and were therefore scheduled to stay overnight in the recovery room during the first postoperative night (defined as major surgery). Protein FSRs (fractional synthesis rates) in skeletal muscle were determined during a measurement period of 90 min before surgery and immediately after termination of surgery. FSR in skeletal muscle of the minor surgery patients was 1.72±0.25%/24 h before surgery and 1.67±0.29%/24 h after surgery (P=0.68). In the major surgery group, FSR was 1.62±0.30%/24 h before surgery and 1.57±0.40%/24 h (P=0.59) immediately following surgery. The observations made in this pilot study could not confirm a size-related decrease in muscle protein synthesis immediately following minor and major surgery. This finding is discussed in relation to confounders, postoperative course and to muscle protein degradation. The shortage of knowledge in this field is emphasized.

A systematic review and meta-analysis of the incidence and severity of postoperative fatigue

OBJECTIVE

Postoperative fatigue is common following major abdominal surgery. Less is known about its prevalence in other surgical subgroups, and about its long-term prognosis. A systematic review of prospective cohort studies was conducted to clarify these issues.

METHOD

Studies were identified from an extensive literature search. Overall estimates of pre- to postoperative change in fatigue severity and the incidence of clinically significant postoperative fatigue were calculated using meta-analyses.

RESULTS

Eighty-one cohorts were identified. Type of surgery was found to be a possible predictor of fatigue severity, with major abdominal, gynaecological, cardiac and minor surgery apparently associated with greater fatigue than orthopaedic surgery. Limited data were available regarding the long-term persistence of postoperative fatigue.

CONCLUSION

Postoperative fatigue appears to be an important problem following only certain forms of surgery. Why this is so remains unclear, and further work using better fatigue questionnaires is now required to confirm these differences.

A program to reduce fatigue in convalescing elderly adults

This study is an examination of the influence of a fatigue reduction program on the level of fatigue experienced by elderly individuals convalescing in subacute units after lower extremity injury, surgery, or weakness. Fifty participants with a mean age of 81 were divided into two groups of 25 participants. The experimental group received a fatigue reduction program consisting of planned rest periods after bathing and therapy; high-protein, high-carbohydrate liquid supplement; and a 3-minute back rub at bedtime. Each participant's level of fatigue was tested soon after admission and 1 week later, and data were analyzed using the paired t test. The difference between the change in pre-test and post-test scores of the two groups was significant in all three measures of fatigue. The experimental group exhibited a significantly greater reduction in fatigue. The outcomes reinforced the value of nursing interventions that have been an integral component of nursing care from its beginning: promoting nutrition, alternating periods of activity and rest, and including a back rub in evening care.

Effect of elective abdominal surgery on human colon protein synthesis in situ

OBJECTIVE

To determine the effect of elective abdominal surgery on the rate of human colon fractional protein synthesis in situ.

SUMMARY BACKGROUND DATA

Efficient intestinal protein synthesis plays an important role in the physiology and pathophysiology of the intestinal tract, allowing preservation of gut integrity and thereby preventing bacterial or endotoxin translocation. Because of species differences, animal studies have only limited applicability to human intestinal protein metabolism, and because of methodologic restrictions, no studies on colon protein synthesis in situ are available in humans.

METHODS

The authors used advanced mass spectrometry techniques (capillary gas chromatography and combustion isotope ratio mass spectrometry) to determine directly the incorporation rate of 1-[13C]-leucine into colon mucosal protein in control subjects and nonseptic postoperative patients. All subjects had a colostomy, which allowed easy access to the colon mucosa, and consecutive sampling from the same tissue was performed during continuous isotope infusion (0.16 micromol/kg per minute).

RESULTS

Control subjects demonstrated a colon protein fractional synthetic rate of 0.74 +/- 0.09% per hour. In postsurgical patients, colon protein synthesis was significantly higher and the tissue free leucine enrichment was significantly lower, compatible with an increased colon proteolytic rate.

CONCLUSIONS

Elective abdominal surgery followed by an uncomplicated postoperative course is associated with a stimulation of colon protein synthesis and possibly also of protein degradation. The postoperative rate of colon protein synthesis is, compared with other tissues, among the highest measured thus far in humans.

Determination of protein synthesis in human ileum in situ by continuous [1-(13)C]leucine infusion

Efficient protein synthesis plays an important role in the physiology and pathophysiology of the human gastrointestinal tract. Because of methodological restrictions, no studies on ileal protein synthesis in situ are available in humans. We used advanced mass spectrometry techniques (capillary gas chromatography/combustion isotope ratio mass spectrometry) to determine directly the incorporation rate of [1-(13)C]leucine into ileal mucosal protein in control subjects and postoperative patients. All subjects had an ileostomy, which allowed easy access to the ileal mucosa. To examine changes in ileal protein synthesis during prolonged isotope infusion (0.16 micromol. kg(-1). min(-1), 9.6 micromol/kg prime), studies were performed over a 10-h period. Mucosal biopsies were performed after 3, 6, and 10 h of infusion. Protein synthesis was calculated separately between hour 3 and hour 6 (period 1) and hour 6 and hour 10 (period 2). Control subjects demonstrated an ileal protein fractional synthetic rate of 0.62 +/- 0.06%/h in period 1 and of 0. 52 +/- 0.08%/h in period 2 (not significant). In postsurgical subjects, ileal protein synthesis was significantly higher (1.11 +/- 0.14%/h in period 1, P < 0.01 vs. controls in period 1) but declined markedly in period 2 (0.39 +/- 0.13, P < 0.01 vs. period 1 after surgery). The rate of protein synthesis in the small bowel of control subjects is, thus far, among the lowest measured in mammals and reflects the comparably slow turnover of human ileal mucosa. Postoperative disturbances of gut integrity lead to an accelerated anabolic response. During prolonged isotope infusion, stimulated protein synthesis declines because of diurnal variations or is erroneously reduced by tracer loss due to an accelerated cell turnover.

The metabolic consequences of critical illness: acute effects on glutamine and protein metabolism

Net protein loss and large decreases in plasma glutamine concentration are characteristics of critical illness. We have used [2-15N]glutamine and [1-13C]leucine to investigate whole body glutamine and leucine kinetics in a group of critically ill patients and matched healthy controls. Glutamine appearance rate (Ra,Gln) was similar in both groups. However, in the patients, the proportion of Ra,Gln arising from protein breakdown was higher than in the control group (43 +/- 3 vs. 32 +/- 2%, P < 0.05). Glutamine metabolic clearance rate (MCR) was 92 +/- 8% higher (P < 0.001), whereas plasma glutamine concentration was 38 +/- 5% lower (P < 0.001) than in the control group. Leucine appearance rate (whole body proteolysis) and nonoxidative leucine disposal (whole body protein synthesis) were 59 +/- 14 and 49 +/- 15% higher in the patients (P < 0.001). Leucine oxidation and MCR were increased in the patients by 104 +/- 37 and 129 +/- 39%, respectively (P < 0.05). These results demonstrate that critical illness is associated with a major increase in protein turnover. The acute decrease in plasma glutamine concentration and the unaltered plasma Ra,Gln suggest that the increase in proteolysis is insufficient to meet increased demand for glutamine in this severe catabolic state.

The effect of unloading on protein synthesis in human skeletal muscle

Atrophy of skeletal muscle is observed in response to immobilization and lack of weight-bearing. The aim of this study was to investigate the effect of immobilization on muscle protein synthesis and associated biochemical parameters in skeletal muscle of healthy volunteers employing a standardized model of lower limb unloading. One leg was unloaded for 10 days, and percutaneous muscle biopsies were taken before and at the end of the unloading period. The capacity for protein synthesis, as reflected by the concentration of RNA, decreased by 16% (P < 0.05) although the fractional synthesis rate (FSR) of protein was not significantly changed after 10 days of unloading. Furthermore there was an increase in the concentration of the free branched chain amino acids in muscle by 48% (P < 0.05).

Contrasting plasma free amino acid patterns in elite athletes: association with fatigue and infection

AIM

There is little information on the plasma free amino acid patterns of elite athletes against which fatigue and nutrition can be considered. Therefore the aim was to include analysis of this pattern in the medical screening of elite athletes during both especially intense and light training periods.

METHODS

Plasma amino acid analysis was undertaken in three situations. (1) A medical screening service was offered to elite athletes during an intense training period before the 1992 Olympics. Screening included a blood haematological/biochemical profile and a microbial screen in athletes who presented with infection. The athletes were divided into three groups who differed in training fatigue and were considered separately. Group A (21 track and field athletes) had no lasting fatigue; group B (12 judo competitors) reported heavy fatigue at night but recovered overnight to continue training; group C (18 track and field athletes, one rower) had chronic fatigue and had been unable to train normally for at least several weeks. (2) Athletes from each group were further screened during a post-Olympic light training period. (3) Athletes who still had low amino acid levels during the light training period were reanalysed after three weeks of additional protein intake.

RESULTS

(1) The pre-Olympics amino acid patterns were as follows. Group A had a normal amino acid pattern (glutamine 554 (25.2) micromol/l, histidine 79 (6.1) micromol/l, total amino acids 2839 (92.1) micromol/l); all results are means (SEM). By comparison, both groups B and C had decreased plasma glutamine (average 33%; p<0.001) with, especially in group B, decreased histidine, glucogenic, ketogenic, and branched chain amino acids (p<0.05 to p<0.001). None in group A, one in group B, but ten athletes in group C presented with infection: all 11 athletes had plasma glutamine levels of less than 450 micromol/l. No intergroup differences in haematological or other blood biochemical parameters, apart from a lower plasma creatine kinase activity in group C than in group B (p<0.05) and a low neutrophil to lymphocyte ratio in the athletes with viral infections (1.2 (0.17)), were found. (2) During post-Olympic light training, group A showed no significant amino acid changes. In contrast, group B recovered normal amino acid levels (glutamine 528 (41.4) micromol/l, histidine 76 (5.3) micromol/l, and total amino acids 2772 (165) micromol/l) (p<0.05 to p<0.001) to give a pattern comparable with that of group A, whereas, in group C, valine and threonine had increased (p<0.05), but glutamine (441 (24.5) micromol/l) and histidine (58 (5.3) micromol/l) remained low. Thus none in group A, two in group B, but ten (53%) in group C still had plasma glutamine levels below 450 micromol/l, including eight of the 11 athletes who had presented with infection. (3) With the additional protein intake, virtually all persisting low glutamine levels increased to above 500 micromol/l. Plasma glutamine rose to 592 (35.1) micromol/l and histidine to 86 (6.0) micromol/l. Total amino acids increased to 2761 (128) micromol/l (p<0.05 to p<0.001) and the amino acid pattern normalised. Six of the ten athletes on this protein intake returned to increased training within the three weeks.

CONCLUSION

Analysis of these results provided contrasting plasma amino acid patterns: (a) a normal pattern in those without lasting fatigue; (b) marked but temporary changes in those with acute fatigue; (c) a persistent decrease in plasma amino acids, mainly glutamine, in those with chronic fatigue and infection, for which an inadequate protein intake appeared to be a factor.

The concentrations of free amino acids in human liver tissue obtained during laparoscopic surgery

The concentrations of the free amino acids in individual tissues gives information concerning amino acid, energy and protein metabolism. In muscle and intestinal mucosa, different metabolic states are distinctly characterized by an altered free amino acid pattern. Furthermore, the patterns are quite different in individual tissues. So far, liver tissue has not been investigated systematically in this respect. The aims of this investigation were to establish a standardized sampling procedure for liver tissue during laparoscopic surgery and to characterize the free amino acid concentrations in human liver tissue. Aspartate was the most abundant amino acid in the liver, followed by taurine, glutamine, glutamate, glycine and alanine. These six, and most abundant, amino acids constitute 90% of the total hepatic amino acid concentration. In the future, liver tissue sampling during laparoscopic surgery may be used as a model for investigating the influence of nutrition and hormones on hepatic amino acid and protein metabolism in man.

Effect of transcutaneous electrical muscle stimulation on postoperative muscle mass and protein synthesis

In an experimental study, 13 patients undergoing major elective abdominal surgery were given postoperative transcutaneous electrical muscle stimulation (TEMS) to the quadriceps femoris muscle on one leg; the opposite leg served as control. Changes in cross-sectional area (CSA) and muscle protein synthesis were assessed by computed tomography and ribosome analysis of percutaneous muscle biopsies before surgery and on the sixth postoperative day. The percentage of polyribosomes in the ribosome suspension decreased significantly (P < 0.03) after operation in control legs, but not in stimulated legs (P > 0.16). The total concentration of ribosomes decreased significantly in legs treated with TEMS (P < 0.03) but not in control legs (P > 0.16). CSA decreased significantly in both legs. The decrease in polyribosomes and CSA after operation was significantly less in stimulated legs than in controls (P < 0.05). TEMS may be a simple and effective method for improving muscle protein synthesis and muscle mass after abdominal surgery and should be evaluated in other catabolic states with muscle wasting.

Laparoscopic cholecystectomy minimally impairs postoperative cardiorespiratory and muscle performance

Surgery elicits a subjective feeling of postoperative fatigue, at least partly related to an impairment in cardiorespiratory function and muscle performance. Laparoscopic surgery is reported to impair the patient's condition minimally. The aim of this study was to assess exercise performance in patients scheduled for elective laparoscopic cholecystectomy. Nine patients assessed as having American Society of Anesthesiologists (ASA) grade I were enrolled in the study. Subjective feelings of fatigue (measured on a visual analogue scale), and heart rate, systemic arterial pressure oxygen consumption and carbon dioxide production responses to graded exercise testing, were assessed before operation and on days 3 and 10 after operation. There were no significant differences in any of these measurements, at rest or during exercise, between the preoperative and postoperative values. Uncomplicated laparoscopic cholecystectomy does not impair postoperative cardiorespiratory and muscle performance or induce significant postoperative fatigue in patients with ASA I, allowing rapid recovery.

The effect of recombinant growth hormone on nitrogen balance in malnourished patients after major abdominal surgery

The effect of recombinant growth hormone (rGH) on nitrogen balance was studied in malnourished patients receiving total parenteral nutrition after major abdominal surgery. Fifteen patients were randomized to receive either subcutaneous rGH (0.2 iu/kg) or placebo (saline) injection daily for seven days after surgery. Positive nitrogen balance was achieved throughout the treatment period with rGH administration and was significant on days 3 and 6. This was associated with increase in mid-arm muscle circumference and significant weight gain. Plasma insulin-like growth factor-1 (IGF-1) concentration was significantly raised in the rGH group at day 7, suggesting its role in the anabolic effect of growth hormone. Plasma pre-albumin and retinol-binding protein concentrations were raised in both the rGH and control groups, indicating improvement in the nutritional status. We conclude that the postoperative catabolic response can be attenuated using recombinant growth hormone.

Long-term effects of postoperative total parenteral nutrition supplemented with glycylglutamine on subjective fatigue and muscle protein synthesis

Seventeen patients undergoing elective open cholecystectomy were given conventional total parenteral nutrition either with (nine patients) or without (eight) glutamine supplementation of 20 g/day for 3 days after surgery and thereafter ordinary food for the following 27 days. Muscle protein synthesis, as assessed by the total concentration of ribosomes, decreased in control patients on day 3 following surgery and remained low on days 10, 20 and 30 (P < 0.05). In patients who received glutamine the total ribosome concentration was maintained on the third day after operation. Concurrently, the subjective feeling of fatigue increased on days 3 and 10 after surgery and the nitrogen balance was negative after operation in both groups, without any difference related to glutamine supplementation. Intravenous glutamine after surgery counteracts a decline in muscle protein synthesis only for as long as it is provided.

Insulin resistance after abdominal surgery

A study was carried out to determine the time course and degree of postoperative insulin resistance in patients undergoing elective abdominal surgery. Mean(s.e.m.) insulin sensitivity was determined before and on the first (n = 10), fifth, ninth and 20th (n = 5) days after elective open cholecystectomy using the normoglycaemic (4.7(0.1) mmol/l), hyperinsulinaemic (402(12)pmol/l) glucose clamp technique. Preoperative insulin sensitivity expressed as the M value varied from 2.3 to 8.2 mg per kg per min. The relative reduction in insulin sensitivity was most pronounced on the first day after surgery, at a mean(s.e.m.) of 54(2) per cent. Thereafter, a large variation between individuals was found during the course of recovery, and insulin sensitivity returned to normal 20 days after operation. On the first day after surgery, plasma concentrations of glucose, C peptide, noradrenaline and glucagon were slightly but significantly higher than before operation (P < 0.05), whereas insulin, growth hormone, cortisol and adrenaline levels were unaltered. Marked insulin resistance thus develops after elective upper abdominal surgery and persists for at least 5 days after operation. Factors other than simultaneous changes in levels of the hormones studied seem to regulate the maintenance of postoperative insulin resistance.

Acute response of human muscle protein to catabolic hormones

OBJECTIVE

The purpose of this study was to determine the acute in vivo response of human muscle protein to stress.

SUMMARY BACKGROUND DATA

Prior animal and human in vitro studies have suggested that physiologic stress increases muscle protein turnover. In contrast, recent publications using a polyribosomal methodology have demonstrated a reduction in human muscle protein synthesis in vivo after surgery.

METHODS

Five healthy volunteers were given a stable isotopic infusion of 1,2(13)C leucine that allowed for determination of the fractional rate of muscle protein synthesis by measuring the rate of incorporation of 13C label into vastus lateralis muscle biopsies. Simultaneous infusion of 15N lysine and quantitation of leg blood flow by indocyanine green dye dilution allowed for estimation of leg muscle protein breakdown rate (Lys Ra) and synthesis rate (Lys Rd). These measurements were performed before and then at the conclusion of a 4-hour femoral arterial infusion of the catabolic hormones epinephrine, cortisol, and glucagon.

RESULTS

The catabolic hormone infusion elicited a significant (65%) increase in the leg muscle protein breakdown rate and a significant but less marked increase in the rate of muscle protein synthesis, as assessed by both an increase in the fractional rate of muscle protein synthesis of 48.5% and in lysine uptake within the leg of 32%.

CONCLUSIONS

This study conclusively demonstrates that a hormonally induced stress results in a net catabolism of human muscle protein by increasing the rate of protein breakdown in excess of an increased protein synthetic rate.

Comparison of metabolic responses to laparoscopic and minilaparotomy cholecystectomy

This randomized study compared the metabolic responses to laparoscopic cholecystectomy (n = 10) and minilaparotomy cholecystectomy with a 5-7-cm incision (n = 10). Venous blood samples were taken before operation and at 3, 6, 9, 12, 18, 24, 48, 72 and 168 h after incision and analysed for levels of C-reactive protein, interleukin 6, cortisol, albumin, transferrin, iron, fibrinogen, fibrin degradation products and polymorphonuclear elastase, and for neutrophil and lymphocyte counts. Urine samples (24 h) were analysed for urea, creatinine, 3-methylhistidine and catecholamines. The magnitude of the metabolic changes from baseline levels was quantified by calculating areas under each individual curve. A significant metabolic response with a similar time course and magnitude of changes occurred after laparoscopic and minilaparotomy cholecystectomy but with wide variation in magnitude between individuals.

Postoperative fatigue

Uncomplicated major surgery is followed by a pronounced increased feeling of fatigue extending throughout the first month in about one-third of patients. Postoperative fatigue correlates with the degree of surgical trauma but is not related to duration of general anesthesia and surgery or to preoperative nutritional status, age, or sex. Fatigue also correlates with postoperative deterioration in nutritional parameters and impaired adaptability of heart rate during exercise. Furthermore, a postoperative decrease in muscle force and endurance is related to postoperative fatigue, whereas psychological factors are of minor importance. These findings suggest postoperative fatigue to be mediated by the endocrine-metabolic response to surgery, impaired nutritional intake, or immobilization, but the relative role of these factors remains to be established. Until then, therapeutic measures against the development of postoperative fatigue should aim at reducing the surgical stress response, effective treatment of pain to facilitate mobilization, and exercise to increase postoperative nutritional intake.

Is the metabolic response to sepsis in skeletal muscle different in infants and adults? An experimental study in rats

In this study we compared the effect of sepsis on muscle protein metabolism in infant (3 to 4 weeks) and adult (3 to 4 months) rats. Sepsis was induced by cecal ligation and puncture (CLP). Control animals underwent sham operation. Sixteen hours after CLP or sham operation, metabolic studies were performed in incubated intact extensor digitorum longus muscles from infant rats or in strips of the same muscle from adult rats. Protein synthesis rate was determined as incorporation of 3H-phenylalanine into protein; total and myofibrillar protein breakdown rates were determined as release of tyrosine and 3-methylhistidine, respectively. Mortality rate following CLP was similar in both age groups. Basal protein synthesis rate was 3 times higher, total protein breakdown rate was 50% higher, and myofibrillar protein breakdown rate was 3 times higher in infant than in adult animals. However, the relative changes in protein turnover rates induced by sepsis were similar in infant and adult rats: protein synthesis rate decreased by approximately 30%, total protein breakdown increased by 40% to 50%, and myofibrillar protein breakdown increased severalfold. The data suggest that despite prominent differences in basal protein turnover rates between infant and adult rats, the effect of sepsis on muscle protein metabolism is not age dependent.

Biosynthetic human growth hormone preserves both muscle protein synthesis and the decrease in muscle-free glutamine, and improves whole-body nitrogen economy after operation

As a reproducible human trauma model, patients (n = 17) undergoing elective cholecystectomy were studied for 3 postoperative days. They were randomly allocated to receive either recombinant human growth hormone (hGH; 0.3 U/kg/24 hours) or placebo together with total parenteral nutrition, including 0.2 gN/kg/24 hours and 135 kJ/kg/24 hours. Before operation and on the third postoperative day, percutaneous muscle biopsies were performed to determine the concentration and size distribution of ribosomes and the free amino acid concentrations. The significant postoperative decrease in the total ribosome concentration (15.3 +/- 6.4%) and the polyribosome concentration (20.9 +/- 6.5%) in the control group was impeded in the group receiving synthetic hGH. Muscle free glutamine decreased by 35.6 +/- 4.2% in the control group and to a lesser extent in the group that was given hGH after operation (p less than 0.05). The protein content of skeletal muscle was unchanged. The cumulated nitrogen balance for the study period was negative in the control group (-7.09 +/- 0.71 gN), but was not different from zero in the hGH group (-2.32 +/- 1.66 gN). It is concluded that synthetic hGH administered after operation has beneficial effects on the whole-body nitrogen economy, as indicated by the unchanged capacity for protein synthesis in skeletal muscle, the preserved levels of muscle free glutamine, and improvement in the whole-body nitrogen balance. The effects of hGH on skeletal muscle protein and amino acid metabolism can explain the postoperative nitrogen-sparing effect attributed to hGH.

Connective tissue response to major surgery and postoperative infection

Type I and type III collagen are components of a healing wound, and major structural proteins. According to our previous study, wound fluid concentrations of the liberated propeptide extensions of procollagens can be used to monitor collagen synthesis in the wound. Serum concentrations of the carboxyterminal propeptide of type I procollagen (PICP), and the aminoterminal propeptide of type III procollagen (PIIINP) were studied here for up to half a year in 102 patients, admitted for major abdominal surgery. In a frequent follow-up (n = 9), one minimum and two maxima were found for S-PICP, occurring 1 day, 7 days, and 2 months after surgery, respectively. S-PIIINP had a minimum at 1 day and a peak at 10 days. Relative changes (follow-up result/pre-operative concentration) of the propeptides in 50 uncomplicated patients were compared. The 1-day minimum of S-PICP was 0.60 (SD 0.18), and that of S-PIIINP 0.89 (0.27), (P less than 0.0001, 95% CI for the mean difference 0.21 to 0.36). The 7-day peak of S-PICP was 1.4 (0.5), and that of S-PIIINP 2.5 (1.2), (P less than 0.0001, CI 0.81 to 1.42). The 2-month-peak of S-PICP was 1.6 (0.3), and at the same time the relative S-PIIINP was still 1.7 (0.3) without any separate peak. Major infectious (n = 8) and other (12) complications, exploratory procedures (22) and patients with abnormal pre-operative propeptide levels (8) were studied separately. Two early deaths were excluded. Only major infection had a remarkable effect on the responses of S-PICP (3/8) and S-PIIINP (5/8).(ABSTRACT TRUNCATED AT 250 WORDS)

Post-operative fatigue — a real phenomenon attributable to the metabolic effects of surgery on body nutritional stores

Ambulatory monitoring of activity was undertaken in 97 patients before and at intervals following surgery employing a lightweight recorder and sensors to monitor posture and movement over 24h periods. A subjective assessment of fatigue, anthropometric measurements and clinical details were noted prior to each recording. Results were assessed using multiple regression analysis. Few patients exhibited any subjective feeling of fatigue. However, objective assessment did show a reduction in activity, several of the changes correlating with factors related to surgical stress and post-operative nutritional depletion. Reduction in time standing was related to both weight change at 2 weeks (p < 0.005) and duration of surgery (p < 0.05). Increase in time spent lying correlated with muscle loss at 2 weeks (p < 0.005). Number of steps walked was only influenced by weight change at 2 weeks (p < 0.05). Reduction in post-operative mobility may be related to the metabolic consequences of the surgery and its effects on depletion of nutritional stores. Manipulation of the response and aggressive nutritional support might well reduce post-operative fatigue.

Ribosome and free amino acid content in muscle during hemodialysis

Patients (N = 8) with chronic renal failure and uremia treated with hospital hemodialysis were in a pilot study investigated before and after a single hemodialysis session. The extracorporeal dialysis circuit was flushed regularly with saline to avoid clotting and the use of heparin. Percutaneous skeletal muscle biopsies were taken before and after the dialysis to determine the content of free amino acids together with the concentration and size distribution of ribosomes before and after dialysis. After dialysis the alanine concentration in muscle decreased by 20% (P less than 0.05), while all other amino acids were unaffected. The total ribosome concentration per mg of DNA decreased by 31% (P less than 0.01) and the relative proportion of polyribosomes by 7% (P less than 0.05) after the dialysis compared to predialytic values. All individual plasma amino acids decreased during the dialysis procedure except for threonine and arginine, which were unaltered, and leucine and isoleucine, which increased. The decline in ribosome and polyribosome content together with the changes in amino acid levels indicate a low capacity for protein synthesis and increased catabolism in muscle of hemodialyzed patients.

Growth hormone improves muscle protein metabolism and whole body nitrogen economy in man during a hyponitrogenous diet

Healthy male volunteers (n = 12) were given a normocaloric hyponitrogenous diet for a conditioning period of 7 days. Thereafter they were blindly randomized to receive daily injections of methionyl recombinant human growth hormone (met-hGH) 0.06 IU/kg or saline during a second week of hyponitrogenous nutrition. The met-hGH group showed a lower urinary urea excretion and a lower serum concentration of urea as compared with the control group. In skeletal muscle, the polyribosome concentration, indicative of muscle protein synthesis, as well as the concentrations of glutamine, alanine, aspartate, serine, and threonine, decreased in the control group, whereas no such changes were seen in the met-hGH-treated group. Since provision of met-hGH prevented protein catabolism in muscle and improved whole body nitrogen economy, investigations of the possible beneficial effects of met-hGH to prevent skeletal muscle vast after surgical trauma are advocated.

Ribosome profiles from human skeletal muscle as a measure of protein synthesis

The purpose of this overview is to present an outline of ribosome assessment as an estimation of in vivo protein synthesis in human skeletal muscle. The method of analysis will be described and discussed together with a variety of physiological states validating the usefulness of the technique. Applications to several clinical situations will then be described, as well as the co-variation with other techniques for estimating protein metabolism. Finally, the pros and cons of the ribosome technique will be discussed.