Increased expression of inflammatory pathway genes in skeletal muscle during surgery

Preoperative administration of branched-chain amino acids reduces postoperative insulin resistance in rats by reducing liver gluconeogenesis

BACKGROUND

Postoperative insulin resistance (PIR) represents an important characteristic of metabolic response following surgical injury. Clinical outcomes are negatively correlated to postoperative insulin resistance and hyperglycemia, indicating a novel treatment for reducing postoperative insulin resistance is urgently needed. The current work aimed to assess the protective effects of branched-chain amino acids (BCAA) on glucose metabolism disorders induced surgically in a rat model, and to explore the underpinning mechanism.

METHODS AND RESULTS

Rats were randomly assigned to 2 groups, including the control and BCAA groups. Rats were given a compulsory oral 3 mL load by gavage two hours before surgery. The results showed that BCAA remarkably reduced glycemia by suppressing liver gluconeogenesis via reduction of cAMP-response element-binding protein-regulated transcription coactivator 2 (CRTC2) and glucose-6-phosphatase (G6PC) gene and protein expression levels (all Ps < 0.05).

CONCLUSIONS

This study revealed that BCAA lower blood glucose levels by reducing liver gluconeogenesis without significant elevation of plasma insulin levels. We anticipate that preoperative BCAA supplementation may be a means for preventing postoperative insulin resistance.

Unresolved issues in perioperative nutrition: A narrative review

Surgical patients are at an increased risk of negative outcomes if they are malnourished or at risk of malnutrition preoperatively. Optimisation of nutritional status should be a focus throughout the perioperative continuum to promote improved surgical outcomes. Enhanced Recovery after Surgery (ERAS) protocols are increasingly applied in the surgical setting but are not yet widespread. This narrative review focused on areas of perioperative nutrition that are perceived as controversial or are lacking in agreement. A search for available literature was conducted on 1 March 2022 and relevant high-quality articles published since 2015 were considered for inclusion. Most malnutrition screening tools are not specific to the surgical population except for the Perioperative Nutrition Screen (PONS) although more large-scale initiatives are needed to improve the prevalence of preoperative nutrition screening. Poor muscle health is common in patients with malnutrition and further exacerbates negative health outcomes indicating that prevention, detection and treatment is of high importance in this population. Although a lack of consensus remains for who should receive preoperative nutritional therapy, evidence suggests a positive impact on muscle health. Additionally, postoperative nutritional support benefits surgical outcomes, with some patients requiring enteral and/or parenteral feeding routes and showing benefit from immunonutrition. The importance of nutrition extends beyond the time in hospital and should remain a priority post-discharge. The impact of individual or personalised nutrition based on select patient characteristics remains to be further investigated. Overall, the importance of perioperative nutrition is evident in the literature despite select ongoing areas of contention.

Preoperative Oral Carbohydrate Levels in Patients with Type 2 Diabetes Mellitus: The Clinical Guiding Significance of Free Fatty Acids

Background

It is still controversial whether preoperative oral carbohydrate (POC) should be applied to patients with type 2 diabetes mellitus (T2DM) in the enhanced recovery after surgery (ERAS) protocol. There is no relevant consensus or indicators to provide guidance as to whether T2DM patients should take POC.

Methods

In total, 164 T2DM patients who underwent laparoscopic hepatectomy were analyzed. According to the level of blood free fatty acids (FFAs) and whether the patients received POC, the patients were divided into 6 groups: the low FFA carbohydrate group (LFFAC group), low FFA fasting water group (LFFAF group), medium FFA carbohydrate group (MFFAC group), medium FFA fasting water group (MFFAF group), high FFA carbohydrate group (HFFAC group) and high FFA fasting water group (HFFAF group).

Results

Patients with low FFA levels showed better perioperative blood glucose control and a lower incidence of postoperative complications than those in the medium and high FFA groups, especially when patients received POC. Further analyses revealed that the postoperative plasma concentrations of IL-6 and TNF-α were significantly decreased in the POC group compared with the fasting water group, except for patients with high FFA levels. Receiver operating characteristic (ROC) curve analysis revealed that when the FFA concentration was higher than 0.745 mmol/L, the risk of poor blood glucose control during the perioperative period was increased.

Conclusions

FFAs have clinical guiding significance for the application of POC in patients with T2DM under ERAS administration. T2DM patients with low FFAs are more suitable for receiving POC.

Effects of preoperative oral single-dose and double-dose carbohydrates on insulin resistance in patients undergoing gastrectomy:a prospective randomized controlled trial

BACKGROUND & AIMS

Preoperative oral carbohydrates are strongly recommended for routine use before various elective procedures. The regimen mainly includes preoperative oral single-dose carbohydrate (2-3 h before surgery) and preoperative oral double-dose carbohydrates (10 h before surgery and 2-3 h before surgery). The choice between the two options is still controversial.

METHODS

A total of 139 patients with gastric cancer who underwent radical gastrectomy were recruited from a hospital in Sichuan Province, China. The patients were randomly assigned to a single-dose group (n = 70) or a double-dose group (n = 69). Insulin resistance indicators, subjective comfort indicators, inflammatory mediators, immunological indicators, postoperative recovery indexes, and complications were compared between the two groups.

RESULTS

There were no differences in insulin resistance indicators (fasting plasma glucose, fasting insulin, and homeostasis model assessment indexes), inflammatory mediators (C-reactive protein, interleukin-6, and tumor necrosis factor-α), immunological indicators (CD3+, CD4+, CD8+, and CD4+/CD8+) between the single-dose group and double-dose group (all P > 0.05) at preoperative day 1, preoperative 3 h, and postoperative day 1. There were no differences in subjective comfort indicators (thirst, hunger, anxiety, nausea, fatigue, and weakness) between the two groups (all P > 0.05) at preoperative day 1, preoperative 3 h, preoperative 1 h, and postoperative day 1. The postoperative recovery indexes and complications (exhaust time, liquid intake time, postoperative hospital stay, complication incidence, unplanned readmission rate, and unplanned reoperation rate 30 days after operation) did not significantly differ between the two groups (all P > 0.05). The number of preoperative nighttime urinations in the double-dose group was higher than that in the single-dose group (88.3% VS 48.5%, P < 0.001), and the number of hours of preoperative sleep in the double-dose group was lower than that in the single-dose group (4.56 ± 0.68 VS 5.71 ± 0.57, P < 0.001).

CONCLUSION

Oral carbohydrates administered the night before surgery did not enhance the effects of oral carbohydrates administered 2-3 h before surgery on insulin resistance, subjective comfort, inflammation, and immunity and might affect the patients' night rest. In making a decision between oral carbohydrate regimes, evening carbohydrates could be omitted.

TRIAL REGISTRATION

ChiCTR, ChiCTR1900020608. Registered January 10, 2019, http://www.chictr.org.cn: ChiCTR1900020608.

Major elective abdominal surgery acutely impairs lower limb muscle pyruvate dehydrogenase complex activity and mitochondrial function

BACKGROUND & AIMS

This post hoc study aimed to determine whether major elective abdominal surgery had any acute impact on mitochondrial pyruvate dehydrogenase complex (PDC) activity and maximal mitochondrial ATP production rates (MAPR) in a large muscle group (vastus lateralis -VL) distant to the site of surgical trauma.

METHODS

Fifteen patients undergoing major elective open abdominal surgery were studied. Muscle biopsies were obtained after the induction of anesthesia from the VL immediately before and after surgery for the determination of PDC and maximal MAPR (utilizing a variety of energy substrates).

RESULTS

Muscle PDC activity was reduced by >50% at the end of surgery compared with pre-surgery (p < 0.05). Muscle MAPR were comprehensively suppressed by surgery for the substrate combinations: glutamate + succinate; glutamate + malate; palmitoylcarnitine + malate; and pyruvate + malate (all p < 0.05), and could not be explained by a lower mitochondrial yield.

CONCLUSIONS

PDC activity and mitochondrial ATP production capacity were acutely impaired in muscle distant to the site of surgical trauma. In keeping with the limited data available, we surmise these events resulted from the general anesthesia procedures employed and the surgery related trauma. These findings further the understanding of the acute dysregulation of mitochondrial function in muscle distant to the site of major surgical trauma in patients, and point to the combination of general anesthesia and trauma related inflammation as being drivers of muscle metabolic insult that warrants further investigation.

CLINICAL TRIAL REGISTRATION

Registered at (NCT01134809).

Preoperative Oral Carbohydrate Reduces Postoperative Insulin Resistance by Activating AMP-Activated Protein Kinase after Colorectal Surgery

BACKGROUND

Postoperative insulin resistance (PIR) is a common response after colorectal surgery and an independent risk factor for recovery. Preoperative oral carbohydrate (POC) has been known to reduce PIR. Herein, we investigated whether its mechanism of action involves AMP-activated protein kinase (AMPK) and mTOR/S6K1/insulin receptor substrate-1 (IRS-1) pathways.

METHODS

Patients undergoing colorectal cancer resection were randomly assigned to a POC, fasting, or placebo group. The exclusion criteria were association with diseases or intake of medication affecting insulin sensitivity. Pre- and postoperative insulin resistance, and protein phosphorylation of AMPK, mTOR, and IRS-1 in the rectus abdominis muscle were evaluated.

RESULTS

From January 2017 to December 2017, 70 patients were randomized and 63 were evaluated. No difference was found in the clinical and operative characteristics among the 3 groups. In the POC group, the levels of blood glucose, blood insulin, and homeostasis model assessment of insulin resistance were significantly lower in the POC group than the fasting and placebo groups, and the insulin sensitivity index was significantly higher. The phosphorylation of AMPK in the POC group was significantly higher than that in the other 2 groups, whereas the phosphorylation of mTOR and IRS-1 was significantly lower.

CONCLUSION

PIR involves AMPK and mTOR/S6K1/IRS-1 pathways. POC reduces PIR by the stimulation of AMPK, which suppresses the phosphorylation of mTOR/IRS-1 and attenuates PIR after colorectal resection.

Supplementation of enteral nutritional powder decreases surgical site infection, prosthetic joint infection, and readmission after hip arthroplasty in geriatric femoral neck fracture with hypoalbuminemia

BACKGROUND

Nearly half of elderly patients with hip fracture were malnourished, indicated with a serum marker of hypoalbuminemia. Malnutrition was a risk factor for poor outcomes in geriatrics after hip replacement. The purpose of this study was to investigate if oral nutritional supplementation after the procedure in geriatrics with hypoalbuminemia was beneficial for outcomes.

METHODS

A retrospective cohort study of older (≥ 65 years old) patients suffering femoral neck fracture and undergoing hip replacement with hypoalbuminemia was conducted. Outcomes were compared between patients with and without postoperative nutritional supplementation.

RESULTS

There were 306 geriatric patients met the criteria. Following adjustment for baseline characteristics, patients with nutritional supplementation showed a lower grade of wound effusion with adjusted OR 0.57 (95% confidence interval (CI), 0.36 to 0.91, P < 0.05). And also a lower rate of surgical site infection (5.5% compared with 13.0% [adjusted OR 0.40, 95% CI, 0.17 to 0.91, P < 0.05]), periprosthetic joint infection (2.8% compared with 9.9% [adjusted OR 0.26, 95% CI, 0.08 to 0.79, P < 0.05]), and 30 days readmission (2.1% compared with 8.7% [adjusted OR 0.22, 95% CI, 0.06 to 0.79, P < 0.05]). The average total hospital stay was longer in patients without nutritional supplementation (10.7 ± 2.0 compared with 9.2 ± 1.8 days, P < 0.05).

CONCLUSIONS

The data suggest that postoperative nutritional supplementation is a protective factor for surgical site infection, periprosthetic joint infection, and 30-days readmission in geriatric with hypoalbuminemia undergoing a hip replacement. Postoperative nutritional supplementation for these patients should be recommended.

Postoperative inflammation and insulin resistance in relation to body composition, adiposity and carbohydrate treatment: A randomised controlled study

Background & aims

The aims of this study were to identify whether differences in distribution of adipose tissue and skeletal muscle in obese and non-obese individuals contribute to the magnitude of the postoperative inflammatory response and insulin resistance, with and without preoperative treatment with carbohydrate drinks.

Methods

Thirty-two adults (16 obese/16 non-obese) undergoing elective major open abdominal surgery participated in this 2 × 2 factorial, randomised, double-blind, placebo-controlled study. Participants received Nutricia preOp^® or placebo (800 ml on the night before surgery/400 ml 2–3 h preoperatively) after stratifying for obesity. Insulin sensitivity was measured using the hyperinsulinaemic-euglycaemic clamp preoperatively and on the 1st postoperative day. Vastus lateralis, omental and subcutaneous fat biopsies were taken pre- and postoperatively and analysed after RNA extraction. The primary endpoint was within subject differences in insulin sensitivity.

Results

Major abdominal surgery was associated with a 42% reduction in insulin sensitivity from mean(SD) M value of 37.3(11.8) μmol kg⁻¹ fat free mass (FFM) to 21.7(7.4) μmol kg⁻¹ FFM, but this was not influenced by obesity or preoperative carbohydrate treatment. Activation of the triggering receptor expressed on myeloid cells (TREM1) pathway was seen in response to surgery in omental fat samples. In postoperative muscle samples, gene expression differences indicated activation of the peroxisome proliferator-activated receptor (PPAR-α)/retinoid X-receptor (RXR-α) pathway in obese but not in non-obese participants. There were no significant changes in gene expression pathways associated with carbohydrate treatment.

Conclusion

The reduction in insulin sensitivity associated with major abdominal surgery was confirmed but there were no differences associated with preoperative carbohydrates or obesity.

Inflammation-mediated muscle metabolic dysregulation local and remote to the site of major abdominal surgery

Background & aims

Postoperative hyperglycaemia is common in patients having major surgery and is associated with adverse outcomes. This study aimed to determine whether bacteraemia contributed to postoperative systemic inflammation, and whether increases in the expression of muscle mRNAs and proteins reflecting increased muscle inflammation, atrophy and impaired carbohydrate oxidation were evident at the time of surgery, and both local and distant to the site of trauma, and could be associated with impaired glucoregulation.

Methods

Fifteen adult patients without diabetes undergoing major abdominal surgery participated in this observational study set in a university teaching hospital. Arterialised-venous blood samples and muscle biopsies were obtained before and after major elective abdominal surgery, from sites local (rectus abdominis – RA) and remote to the site of surgery (vastus lateralis – VL). The main outcome measures included blood glucose concentrations, gut permeability and changes in expression of muscle mRNAs and proteins linked to inflammation and glucose regulation.

Results

Immediately postoperatively, RA demonstrated markedly increased mRNA expression levels of cathepsin-L (7.5-fold, P < 0.05), FOXO1 (10.5-fold, P < 0.05), MAFbx (11.5-fold, P < 0.01), PDK4 (7.8-fold, P < 0.05), TNF-α (16.5-fold, P < 0.05) and IL-6 (1058-fold, P < 0.001). A similar, albeit blunted, response was observed in VL. Surgery also increased expression of proteins linked to inflammation (IL-6; 6-fold, P < 0.01), protein degradation (MAFbx; 4.5-fold, P < 0.5), and blunted carbohydrate oxidation (PDK4; 4-fold, P < 0.05) in RA but not VL. Increased systemic inflammation (TNF-α, P < 0.05; IL-6, P < 0.001), and impaired postoperative glucose tolerance (P < 0.001), but not bacteraemia (although gut permeability was increased significantly, P < 0.05) or increased plasma cortisol, were noted 48 h postoperatively.

Conclusions

A systemic postoperative proinflammatory response was accompanied by muscle inflammation and metabolic dysregulation both local and remote to the site of surgery, and was not accompanied by bacteraemia.

Clinical trial registration

Registered at http://clinicaltrials.gov (NCT01134809).

Pre-Operative nutrition In Neck of femur Trial (POINT)--carbohydrate loading in patients with fragility hip fracture: study protocol for a randomised controlled trial

Background

Trauma such as hip fracture initiates a neurohumoral stress response that changes the balance between anabolism and catabolism resulting in muscle breakdown and reduced mobilisation. Various studies have demonstrated a reduction in catabolism with pre-operative carbohydrate loading but only in an elective setting.

Methods/Design

This is a two-centre, randomised double-blinded trial in the United Kingdom. Sample size will be 30 patients (approximately 15 from each centre).

Randomisation will be web based using computer-generated concealed tables. Both participants and investigators will be blinded to group allocation.

Participants will be >70 years of age, cognitively intact (Abbreviated Mental Score ≥7), able to give informed consent, and admitted directly through the emergency department with fractured neck of femur requiring hemiarthroplasty.

Intervention will consist of two carbohydrate drinks (Nutricia pre-Op) given the night before, and the morning of the surgery. The control will receive two placebo drinks of equal volume.

All participants will receive standard hospital care at the discretion of the clinical team. The primary outcome is the difference between groups in insulin resistance calculated by a glucose tolerance test administered pre-operatively and 24 hours postoperatively. Secondary endpoints will be changes in muscle carbohydrate metabolism (biopsy), mobility (Cumulative Ambulation Score) and subjective measures of tolerability.

Discussion

This is a small-scale pilot study, investigating the benefits and tolerability of carbohydrate loading in an emergency setting in a frail elderly group with known high morbidity and mortality. Positive findings will provide the basis for a larger scale study.

Trial registration

Current Controlled Trials ISRCTN91109766 (7 April 2014); NRES ref: 13/EM/0214

Trial Sponsor: University of Nottingham Ref.13036.

Metabolic conditioning to attenuate the adverse effects of perioperative fasting and improve patient outcomes

PURPOSE OF REVIEW

To review recent articles, published between October 2009 and September 2011, that examined the adverse metabolic consequences of perioperative fasting and interventions that may be utilized to minimize these effects.

RECENT FINDINGS

Fasting induces metabolic stress and insulin resistance consequent upon effects on cellular mitochondria, gene and protein expression. Development of perioperative insulin resistance leads to increased postoperative morbidity and mortality. Preoperative carbohydrate loading attenuates insulin resistance via effects on cellular gene and protein expression, but its effects on clinical outcomes remain unclear. Perioperative arginine-supplemented diets were shown to be associated with significant reductions in infectious complications and length of hospital stay in patients undergoing elective surgery. Perioperative metabolic conditioning using glutamine and L-carnitine may be used to modulate insulin sensitivity but further studies need to determine whether these interventions result in clinical benefit. Finally, energy and protein provision to critically ill patients remains inadequate and is hampered by a number of factors including reliance on inaccurate means of estimating energy expenditure and enteral feed tolerance, conflicting data on the effects of energy deficit on clinical outcomes, and poor methodological quality of studies of perioperative nutritional interventions.

SUMMARY

Numerous perioperative interventions are available, which if utilized should help attenuate the adverse effects of perioperative fasting and lead to improved patient outcomes.

Comparative proteomics and pulmonary toxicity of instilled single-walled carbon nanotubes, crocidolite asbestos, and ultrafine carbon black in mice

Reflecting their exceptional potential to advance a range of biomedical, aeronautic, and other industrial products, carbon nanotube (CNT) production and the potential for human exposure to aerosolized CNTs are increasing. CNTs have toxicologically significant structural and chemical similarities to asbestos (AB) and have repeatedly been shown to cause pulmonary inflammation, granuloma formation, and fibrosis after inhalation/instillation/aspiration exposure in rodents, a pattern of effects similar to those observed following exposure to AB. To determine the degree to which responses to single-walled CNTs (SWCNT) and AB are similar or different, the pulmonary response of C57BL/6 mice to repeated exposures to SWCNTs, crocidolite AB, and ultrafine carbon black (UFCB) were compared using high-throughput global high performance liquid chromatography fourier transform ion cyclotron resonance mass spectrometry (HPLC-FTICR-MS) proteomics, histopathology, and bronchoalveolar lavage cytokine analyses. Mice were exposed to material suspensions (40 micrograms per mouse) twice a week for 3 weeks by pharyngeal aspiration. Histologically, the incidence and severity of inflammatory and fibrotic responses were greatest in mice treated with SWCNTs. SWCNT treatment affected the greatest changes in abundance of identified lung tissue proteins. The trend in number of proteins affected (SWCNT [376] > AB [231] > UFCB [184]) followed the potency of these materials in three biochemical assays of inflammation (cytokines). SWCNT treatment uniquely affected the abundance of 109 proteins, but these proteins largely represent cellular processes affected by AB treatment as well, further evidence of broad similarity in the tissue-level response to AB and SWCNTs. Two high-sensitivity markers of inflammation, one (S100a9) observed in humans exposed to AB, were found and may be promising biomarkers of human response to SWCNT exposure.

Expression of inflammatory and insulin signaling genes in adipose tissue in response to elective surgery

CONTEXT

The mechanisms behind postoperative insulin resistance and impaired glucose utilization are not fully understood.

OBJECTIVE

In this study, we aimed to specifically evaluate the transcription profile of genes in the insulin and adipokine signaling pathways in sc and omental adipose tissue after surgical injury.

DESIGN

Relative expression of 21 target genes was analyzed in both sc and omental adipose tissue sampled at the beginning and at the end of operation.

SETTING

The study was conducted at a university-affiliated hospital.

PATIENTS

Twelve nondiabetic patients [seven females; age, 65 (range, 46-72) yr; body mass index, 24.8 (16.5-29.8) kg/m(2)] undergoing major abdominal surgery were included.

MAIN OUTCOME MEASUREMENTS

The changes in mRNA levels were analyzed.

RESULTS

After surgery, both sc and omental adipose tissue mRNA levels of genes involved in the IL6 and nicotinamide phosphoribosyltransferase pathways were increased, whereas mRNA levels of insulin receptor substrate 1 and adiponectin were reduced (P < 0.05). TNF pathway genes were differently regulated between sc and omental adipose tissue, and glucose transporter 4 mRNA levels were decreased only in omental adipose tissue.

CONCLUSIONS

The transcriptional output of pivotal inflammatory and insulin signaling pathway genes is altered after surgery, and this pattern differs between different fat depots. This could be of importance for the metabolic aberrations associated to postsurgical complications, such as insulin resistance and hyperglycemia.

Modulating postoperative insulin resistance by preoperative carbohydrate loading

The concept of preoperative overnight fasting was challenged and proved to have no benefits over allowing patients to drink clear fluids up until 2 h before surgery. This led to changes in the guidelines for preoperative fasting in many countries around the world. This concept has more recently been developed further. Mounting evidence indicates that instead of being operated in the traditional overnight fasted state, undergoing surgery in the carbohydrate-fed state has many clinical benefits. Many of these clinical effects can be related to reduced postoperative insulin resistance by preoperative carbohydrate loading. This article summarises the present understanding of the mechanisms behind the positive clinical effects and gives an overview of the information available regarding the clinical effects of this treatment. Finally, the article summarises the most recently published national guidelines on preoperative fasting routines where preoperative carbohydrates are recommended for use before a major surgery. These are to be considered for all patients allowed to drink clear fluids and undergoing elective surgery.

Using transcriptomics to identify and validate novel biomarkers of human skeletal muscle cancer cachexia

Background

Cancer cachexia is a multi-organ tissue wasting syndrome that contributes to morbidity and mortality in many cancer patients. Skeletal muscle loss represents an established key feature yet there is no molecular understanding of the disease process. In fact, the postulated molecular regulators of cancer cachexia originate largely from pre-clinical models and it is unclear how these translate to the clinical environment.

Methods

Rectus abdominis muscle biopsies were obtained from 65 upper gastrointestinal (UGI) cancer patients during open surgery and RNA profiling was performed on a subset of this cohort (n = 21) using the Affymetrix U133+2 platform. Quantitative analysis revealed a gene signature, which underwent technical validation and independent confirmation in a separate clinical cohort.

Results

Quantitative significance analysis of microarrays produced an 83-gene signature that was able to identify patients with greater than 5% weight loss, while this molecular profile was unrelated to markers of systemic inflammation. Selected genes correlating with weight loss were validated using quantitative real-time PCR and independently studied as general cachexia biomarkers in diaphragm and vastus lateralis from a second cohort (n = 13; UGI cancer patients). CaMKIIβ correlated positively with weight loss in all muscle groups and CaMKII protein levels were elevated in rectus abdominis. TIE1 was also positively associated with weight loss in both rectus abdominis and vastus lateralis muscle groups while other biomarkers demonstrated tissue-specific expression patterns. Candidates selected from the pre-clinical literature, including FOXO protein and ubiquitin E3 ligases, were not related to weight loss in this human clinical study. Furthermore, promoter analysis identified that the 83 weight loss-associated genes had fewer FOXO binding sites than expected by chance.

Conclusion

We were able to discover and validate new molecular biomarkers of human cancer cachexia. The exercise activated genes CaMKIIβ and TIE1 related positively to weight-loss across muscle groups, indicating that this cachexia signature is not simply due to patient inactivity. Indeed, excessive CaMKIIβ activation is a potential mechanism for reduced muscle protein synthesis. Our genomics analysis also supports the view that the available preclinical models do not accurately reflect the molecular characteristics of human muscle from cancer cachexia patients.