A novel dynamic proteomics approach for the measurement of broiler chicken protein fractional synthesis rate.

RATIONALE: The study of protein synthesis in farm animals is uncommon despite its potential to increase knowledge about metabolism and discover new biomarkers of health and growth status. The present study describes a novel dynamic proteomics approach for the measurement of protein fractional synthesis rate (FSR) in broiler chickens. METHODS: Chickens received a 10 g/kg oral dose of 2 H2 O at day 21 of their life. Body water 2 H abundance was measured in plasma samples using a portable Fourier transform infrared spectrometer. Free and protein-bound amino acids (AAs) were isolated and had their 2 H enrichment measured by gas chromatography with mass spectrometry (GC/MS). Peptide 2 H enrichment was measured by proteomics analysis of plasma and muscle samples. Albumin, fibrinogen and muscle protein FSR were calculated from GC/MS and proteomics data. RESULTS: Ala appeared to be more enriched at the site of protein synthesis than in the AA free pools. Glu was found to be the AA closest to isotopic equilibrium between the different AA pools. Glu was used as an anchor to calculate n(AA) values necessary for chicken protein FSR calculation in dynamic proteomics studies. FSR values calculated using proteomics data and GC/MS data showed good agreement as evidenced by a Bland-Altman residual plot. CONCLUSIONS: A new dynamic proteomics approach for the measurement of broiler chicken individual protein FSR based on the administration of a single 2 H2 O oral bolus has been developed and validated. The proposed approach could facilitate new immunological and nutritional studies on free-living animals.

Improved measurement of protein synthesis in human subjects using 2H-phenylalanine isotopomers and gas chromatography/mass spectrometry.

Sensitive methods to measure protein synthetic rate in vivo are required to assess changes in protein expression, especially when comparing healthy with infirm subjects. We have previously applied a 'flooding dose' procedure using (2)H(5)-phenylalanine ((2)H(5)-phe) and (2)H(8)-phe isotopomers as tracers, which has proven successful in measuring albumin and fibrinogen synthesis in response to feeding in cancer patients. Using tert-butyldimethylsilyl derivatives, we have observed that (2)H(7)-phe is formed with time in vivo from (2)H(8)-phe, probably during transamination. This increases errors when estimating the fractional synthetic rate (FSR) using the (2)H(8)-phe isotopomer compared with the (2)H(5)-phe isotopomer. We sought to improve this situation by use of an alternative derivative that overcomes this problem whilst also streamlining sample preparation. When using N-ethoxycarbonyltrifluoroethyl (ECTFE) amino acid esters, (2)H(8)-phe is effectively converted into (2)H(7)-phe through fragmentation under electron ionisation (EI), allowing both (2)H(8)-phe and (2)H(7)-phe isotopomers to be measured as a single intense C(7)(2)H(7)(+) fragment at 98 Th. To illustrate the improved situation, the mean RMS residual was calculated for all albumin data, for each isotopomer and for each derivative. Albumin-bound Phe was analysed as ECTFE-phe with improved precision, independent of the isotopomer used, confirming that the new derivative is superior.

Habitual Myofibrillar Protein Synthesis Is Normal in Patients with Upper GI Cancer Cachexia.

PURPOSE: Skeletal muscle wasting and weight loss are characteristic features of cancer cachexia and contribute to impaired function, increased morbidity, and poor tolerance of chemotherapy. This study used a novel technique to measure habitual myofibrillar protein synthesis in patients with cancer compared with healthy controls. EXPERIMENTAL DESIGN: An oral heavy water (87.5 g deuterium oxide) tracer was administered as a single dose. Serum samples were taken over the subsequent week followed by a quadriceps muscle biopsy. Deuterium enrichment was measured in body water, serum alanine, and alanine in the myofibrillar component of muscle using gas chromatography-pyrolysis-isotope ratio mass spectrometry and the protein synthesis rate calculated from the rate of tracer incorporation. Net change in muscle mass over the preceding 3 months was calculated from serial CT scans and allowed estimation of protein breakdown. RESULTS: Seven healthy volunteers, 6 weight-stable, and 7 weight-losing (≥5% weight loss) patients undergoing surgery for upper gastrointestinal cancer were recruited. Serial CT scans were available in 10 patients, who lost skeletal muscle mass preoperatively at a rate of 5.6%/100 days. Myofibrillar protein fractional synthetic rate was 0.058%, 0.061%, and 0.073%/hour in controls, weight-stable, and weight-losing patients, respectively. Weight-losing patients had higher synthetic rates than controls (P = 0.03). CONCLUSION: Contrary to previous studies, there was no evidence of suppression of myofibrillar protein synthesis in patients with cancer cachexia. Our finding implies a small increase in muscle breakdown may account for muscle wasting.

Patient-focused endpoints in advanced cancer: criterion-based validation of accelerometer-based activity monitoring.

BACKGROUND & AIMS: Objective assessment of daily physical activity (PA) by body-worn accelerometers offers potential as a novel endpoint in the clinical management of advanced cancer patients. This study aimed to assess criterion-based validity of an accelerometer-based activity monitoring system (AM-system), ActivPAL™, using two different methods. METHODS: Advanced cancer in patients and outpatients (Karnofsky Performance Status (KPS) 40-100). ActivPAL™ measurements were validated against (i) observations and (ii) energy expenditure (EE) measured by 2-week doubly-labelled water (DLW) protocol. RESULTS: Absolute errors for mean time spent in different body positions (<0.1%) and number of transfers (0%) were low. Step count error was significantly higher in patients with KPS 40-60 (non-self caring) compared to KPS 70-100 (self-caring) (33 vs. 24%, p = 0.006). Post-hoc mathematical analysis demonstrated that absolute errors for the mean energy expenditure of activity (EEA) (1.4%) and mean total EE (0.4%) were low, but agreement was also low. CONCLUSIONS: AM-systems provide valid estimates of body positions and transfers, but not step count, especially in non-self caring patients. ActivPAL™ can derive estimates of EE but there is considerable variability in results, which is consistent, in part, with the inaccuracy in step count. Further studies are required to assess the validity of different endpoints derived from AM-systems in advanced cancer patients.