Nutrition and Lifestyle-Related Factors as Predictors of Muscle Atrophy in Hematological Cancer Patients.

BACKGROUND: Cancer and side effects from cytostatic treatment commonly affect nutritional status manifested as a decrease in muscle mass. We aimed to investigate the impact of nutrition and lifestyle-related factors on muscle mass in patients with hematological cancer. METHODS: Dietary intake, food preferences, quality of life (QoL), and physical activity level (PAL) were monitored during 1-2 cytostatic treatment series. Body composition was estimated using bioelectrical impedance analysis (BIA). RESULTS: 61 patients were included. Weight loss and loss of muscle mass were detected in 64% and 59% of the patients, respectively. Muscle mass was significantly positively correlated to increasing PAL (p = 0.003), while negatively correlated to increasing age (p = 0.03), physical QoL (p = 0.007), functional QoL (p = 0.05), self-perceived health (p = 0.004), and self-perceived QoL (p = 0.007). Weight was significantly positively correlated to increased intake of soft drinks (p = 0.02) as well as the favoring of bitter grain and cereal products (p = 0.03), while negatively correlated to increasing age (p = 0.03) and increasing meat intake (p = 0.009) Conclusions: Several nutritional and lifestyle-related factors affected change in body composition. The clinical significance of these changes should be investigated in controlled, interventional studies.

Glycemic profile and quality of recovery after emergency abdominal surgery-A prospective explorative cohort study.

Associations between degrees of postoperative hyperglycemia and morbidity has previously been established. There may be an association between the glycemic profile and patient-reported recovery, and this may be a target for perioperative quality improvements. We aimed to investigate the association between metrics of the 30-day glycemic profile and patient-reported recovery in nondiabetic patients after major abdominal surgery. In a prospective, explorative cohort study, nondiabetic adult patients undergoing acute, major abdominal surgery were included within 24 h after surgery. Interstitial fluid glucose concentration was measured for 30 consecutive days with a continuous glucose measurement device. The validated questionnaire 'Quality of Recovery-15' was used to assess patient-reported quality of recovery on postoperative days 10, 20, and 30. Follow-up time was divided into five-day postoperative intervals using days 26-30 as a reference. Linear mixed models were applied to investigate temporal changes in mean p-glucose, coefficient of variation, time within 70-140 mg/dl, and time above 200 mg/dl in relation to patient-reported recovery. Twenty-seven patients completed the study per protocol. A hyperglycemic event (>200 mg/dl) occurred in 18 of 27 patients (67%) within the first three postoperative days. Compared to the reference period, the coefficient of variation was significantly increased during all time intervals, indicating prolonged postoperative insulin resistance. During 30 days of follow-up, patient-reported recovery was associated with the coefficient of variation measured for 3 and 5 days before the corresponding recovery score assessment (recovery score estimate -1.52 [p < .001] and -0.92 [p = .006], respectively). We did not find an association between the remaining metrics and patient-reported recovery. Alterations in the glycemic profile are frequent and prolonged during the first postoperative month after major surgery probably due to peripheral insulin resistance. Our findings indicate that high-glycemic variation is associated with poorer patient-reported recovery and might represent a proxy for care improvements in the postoperative period.

Prevalence of sarcopenia in patients with chronic intestinal failure-how are SARC-F and the EWGSOP algorithm associated before and after a physical exercise intervention.

INTRODUCTION: Patients with chronic intestinal failure (IF) have a low degree of physical activity, decreased muscle mass, and decreased muscle strength, leading to a high risk of sarcopenia. We aimed to test the prevalence of sarcopenia by the use of SARC-F and EWGSOP and to investigate the association between the two at baseline and after 12 weeks of an exercise intervention. METHODS: Thirty-one patients with chronic IF completed 12 weeks of three weekly home-based individualized exercise sessions. Body composition was measured by bioimpedance analysis and physical function by handgrip strength (HGS) and timed up-and-go (TUG). Sarcopenia was assessed by SARC-F and EWGSOP. Multiple regression analysis was used to test for the association between the two tools. RESULTS: The prevalence of sarcopenia measured by EWGSOP was 59%. This prevalence did not change after the intervention. At baseline, 38.8% of patients were screened as at risk for sarcopenia by SARC-F. This decreased to 29.0% after the intervention (P < 0.001). A statistically significant increase was achieved in muscle mass (P = 0.017) and muscle mass index (P = 0.016). Furthermore, both TUG (P = 0.033) and HGS (P = 0.019) improved. CONCLUSIONS: Sarcopenia is prevalent in patients with chronic IF. EWGSOP finds more patients to be at risk of sarcopenia than SARC-F but was not sufficiently sensitive to measure changes induced by the physical intervention. The significant change in SARC-F may illustrate that patients, themselves, find an improvement in self-perceived health.

Diet-induced ketosis in adult patients with subacute acquired brain injury: a feasibility study.

Background: Research in animal models on cerebral metabolism after brain injury highlights the potential benefits of ketosis in reducing secondary brain injury, but studies in humans are lacking. Aim: This study aimed to examine if a 6-week ketogenic diet intervention with added medium-chain triglycerides (MCT) was feasible in adult patients with acquired brain injury in the subacute phase, whether ketosis could be achieved and maintained, and to what extent serious adverse reactions, adverse reactions, serious adverse events, and adverse events occured. Methods: Patients ≥18 years of age diagnosed with subacute acquired brain injury and an expectation of hospitalisation ≥6 weeks were included in the intervention group. Patients not included in the intervention group were included in a standard care reference group. The intervention consisted of a ketogenic diet supplemented with MCT to obtain a plasma concentration of ß-hydroxybutyrate (BHB) ≥0.5 mmol/L. Patients who were enterally fed were given KetoCal® 2.5:1 LQ MCT Multi Fiber (Nutricia A/S, Allerød, Denmark), supplemented with Liquigen® (Nutricia A/S, Allerød, Denmark). Patients consuming oral nutrition were given KetoCal® 2.5:1 LQ MCT Multi Fiber supplemented with Liquigen®, in addition to ketogenic meals. Results: During a 13-week inclusion period, 12 of 13 eligible patients (92% [95% CI: 67% to 99%]) were included in the intervention group, and 17 of 18 excluded patients (94% [95% CI: 74% to 99%]) were included in the reference group. Eight patients (67%) completed the 6-week intervention. It took a median of 1 day to achieve ketosis from starting a 100% MCT ketogenic diet, and it was maintained for 97% of the intervention period after ketosis was obtained. There were no serious adverse reactions to the MCT ketogenic diet, and patients experienced adverse reactions not considered serious in 9.5% of days with the intervention. The MCT ketogenic diet was accepted by patients on all intervention days, and in the two patients transitioning from enteral feeding to oral intake, there were no complications related to transitioning. Conclusion: Intervention with MCT ketogenic diet is feasible and tolerated for 6 weeks in hospitalised adult patients with subacute acquired brain injury. Randomised controlled trials are needed to assess the benefits and harms of the MCT ketogenic diet and the effect on patients' recovery.Clinical trial registration: ClinicalTrials.gov, identifier [NCT04308577].

Personalized exercise intervention in HPN patients - A feasibility study.

BACKGROUND: Physical health status may be predictive of readmissions, psychological health and mortality in patients with short bowel syndrome. AIMS: This study aimed to investigate the feasibility and effect of an individualized exercise intervention and secondary, oral nutrition intake counseling on Timed-Up-and-Go (TUG) and 30 s Chair Stand Test (CST) as well as body-composition and EuroQol (EQ)-5D-5L, in patients with chronic intestinal failure (IF) type III receiving HPN and/or fluid therapy. METHODS: A 12-week individualized exercise intervention consisting on three weekly home based sessions, and nutrition counselling focusing on protein intake and reducing high stoma output, was performed. Weekly follow-up by phone was done on motivation to exercise. RESULTS: The study invited 71 patients, 44 accepted the invitation (62%), 37(52%) were included, and 31 (84%) completed the intervention. The exercise intervention was well tolerated. TUG improved from 8.9(SD 5.5) to 7.7(SD 3.8) (p = 0.033). CST improved by four repetitions (<0.001∗). A statistical, however not clinically relevant improvement was seen in muscle mass. No improvement was seen in (EQ)-5D-5L total, but insignificantly (p = 0.055) for physical function only. Protein intake improved by 10.6 g/day (p = 0.008). CONCLUSIONS: A 12 weeks individualized exercise intervention showed very feasible and beneficial in HPN patients. Physical function improved statistically and clinically, and oral protein intake improved. QoL overall did not improve, however COVID-19 was an uninvited partner throughout the study period, which may have influenced general QoL. As only 62% accepted the invitation to participate, home based exercise intervention may not apply to all patients.

A high-protein diet during hospitalization is associated with an accelerated decrease in soluble urokinase plasminogen activator receptor levels in acutely ill elderly medical patients with SIRS.

Acute illness and hospitalization in elderly individuals are often accompanied by the systemic inflammatory response syndrome (SIRS) and malnutrition, both associated with wasting and mortality. Nutritional support and resistance training were shown to increase muscle anabolism and reduce inflammation in healthy elderly. We hypothesized that nutritional support and resistance training would accelerate the resolution of inflammation in hospitalized elderly patients with SIRS. Acutely admitted patients aged >65 years with SIRS were randomized to an intervention consisting of a high-protein diet (1.7 g/kg per day) during hospitalization, and daily protein supplement (18.8 g) and 3 weekly resistance training sessions for 12 weeks after discharge (Intervention, n=14), or to standard-care (Control, n=15). Plasma levels of the inflammatory biomarkers soluble urokinase plasminogen activator receptor (suPAR), interleukin-6, C-reactive protein (CRP), and albumin were measured at admission, discharge, and 4 and 13 weeks after discharge. The Intervention group had an earlier decrease in suPAR levels than the Control group: -15.4% vs. +14.5%, P=.007 during hospitalization, and -2.4% vs. -28.6%, P=.007 between discharge and 4 weeks. There were no significant effects of the intervention on the other biomarkers. All biomarkers improved significantly between admission and 13 weeks, although with different kinetics (suPAR: -22%, interleukin-6: -86%, CRP: -89%, albumin: +11%). Nutritional support during hospitalization was associated with an accelerated decrease in suPAR levels, whereas the combined nutrition and resistance training intervention after discharge did not appear to affect the inflammatory state. Our results indicate that improved nutritional care during hospitalization may accelerate recovery in acutely ill elderly medical patients.

The influence of carbohydrate consumption on glycemic control in pregnant women with type 1 diabetes.

AIMS: To study the influence of the quantity and the quality of carbohydrate consumption on glycemic control in early pregnancy among women with type 1 diabetes. METHODS: A retrospective study of 107 women with type 1 diabetes who completed 1-3days of diet recording before first antenatal visit, as a part of routine care. The total daily carbohydrate consumption from the major sources (e.g. bread, potatoes, rice, pasta, dairy products, fruits, candy) was calculated. A dietician estimated the overall glycemic index score (scale 0-7). RESULTS: At least two days of diet recording were available in 75% of the 107 women at mean 64 (SD±14) gestational days. The quantity of carbohydrate consumption from major sources was 180 (±51)g/day. HbA1c was positively associated with the quantity of carbohydrate consumption (ß=0.41; 95% CI 0.13-0.70, P=0.005), corresponding to an increase of 0.4% in HbA1c per 100g carbohydrates consumed daily, when adjusted for insulin dose/bodyweight and use of insulin pump treatment. The median (IQR) glycemic index score was 2 (0-3). An adjusted association between HbA1c and glycemic index score was not demonstrated. The women using carbohydrate counting daily (45%) had lower HbA1c compared to the remaining women (6.4 (±0.5) vs. 6.8 (±0.9)% (47±6 vs. 51±10mmol/mol), P=0.01). CONCLUSIONS: HbA1c in early pregnancy was positively associated with the quantity of carbohydrate consumption regardless of insulin treatment. Carbohydrate counting is probably important for glycemic control in pregnant women with type 1 diabetes.

Marine Oil Supplements for Arthritis Pain: A Systematic Review and Meta-Analysis of Randomized Trials.

Arthritis patients often take fish oil supplements to alleviate symptoms, but limited evidence exists regarding their efficacy. The objective was to evaluate whether marine oil supplements reduce pain and/or improve other clinical outcomes in patients with arthritis. Six databases were searched systematically (24 February 2015). We included randomized trials of oral supplements of all marine oils compared with a control in arthritis patients. The internal validity was assessed using the Cochrane Risk of Bias tool and heterogeneity was explored using restricted maximum of likelihood (REML)-based meta-regression analysis. Grading of Recommendations Assessment, Development and Evaluation (GRADE) was used to rate the overall quality of the evidence. Forty-two trials were included; 30 trials reported complete data on pain. The standardized mean difference (SMD) suggested a favorable effect (-0.24; 95% confidence interval, CI, -0.42 to -0.07; heterogeneity, I² = 63%. A significant effect was found in patients with rheumatoid arthritis (22 trials; -0.21; 95% CI, -0.42 to -0.004) and other or mixed diagnoses (3 trials; -0.63; 95% CI, -1.20 to -0.06), but not in osteoarthritis patients (5 trials; -0.17; 95% CI, -0.57-0.24). The evidence for using marine oil to alleviate pain in arthritis patients was overall of low quality, but of moderate quality in rheumatoid arthritis patients.

Multi-frequency bioelectrical impedance analysis (BIA) compared to magnetic resonance imaging (MRI) for estimation of fat-free mass in colorectal cancer patients treated with chemotherapy.

BACKGROUND: Changes in body composition in cancer patients during chemotherapy are associated with treatment related toxicities or mortalities. Thus, it is relevant to identify accessible, relatively inexpensive, portable and reliable tools for evaluation of body composition in cancer patients during the course of their treatments. OBJECTIVE: To examine relationships between single cross-sectional thighs magnetic resonance imaging (MRI), skeletal muscle mass (SM) as reference and multi-frequency bioelectrical impedance analysis (BIA) fat free mass (FFM) in patients with colorectal cancer undergoing chemotherapy. DESIGN: In an observational, prospective study we examine the relationships between single cross-sectional thighs MRI (T1-weighted (1.5 T) SM compared to FFM BIA (8-electrodes multi-frequency Tanita MC780MA)) and FFM skin-fold thickness (ST) (4-points (Harpenden, Skinfold Caliper)) and SM equation for non-obese persons from Lee et al. 2000 (L2000) (based on age, height, weight, sex and race). FFM and SM (kg) were calculated based on either area (MRI) or weight. RESULTS: 18 CRC patients (10 males and 8 females) with mean (SD) age 67 yr (6) were measured at baseline, and 13 were available for follow-up. BIA overestimated FFM kg for all 31 measurements with mean (SD) 18.0 kg (6.0) compared to the MRI. ST overestimated FFM kg with mean 12.4 kg (6.2) and L2000 underestimated SM kg in 18 measurements and overestimated in 13 with a total mean of -4.3 kg (6.8). CONCLUSIONS: BIA and ST were the best alternatives to MRI as they showed constant and thereby correctable errors. The equation, L2000, carried the smallest average measurement error but it was non-constant.

The effect of protein intake and resistance training on muscle mass in acutely ill old medical patients - A randomized controlled trial.

BACKGROUND & AIM: Stress metabolism is associated with accelerated loss of muscle that has large consequences for the old medical patient. The aim of this study was to investigate if an intervention combining protein and resistance training was more effective in counteracting loss of muscle than standard care. Secondary outcomes were changes in muscle strength, functional ability and body weight. METHODS: 29 acutely admitted old (>65 years) patients were randomly assigned to the intervention (n = 14) or to standard care (n = 15). The Intervention Group received 1.7 g protein/kg/day during admission and a daily protein supplement (18.8 g protein) and resistance training 3 times per week the 12 weeks following discharge. Muscle mass was assessed by Dual-energy X-ray Absorptiometry. Muscle strength was assessed by Hand Grip Strength and Chair Stand Test. Functional ability was assessed by the de Morton Mobility Index, the Functional Recovery Score and the New Mobility Score. Changes in outcomes from time of admission to three-months after discharge were analysed by linear regression analysis. RESULTS: The intention-to-treat analysis showed no significant effect of the intervention on lean mass (unadjusted: ß-coefficient = -1.28 P = 0.32, adjusted for gender: ß-coefficient = -0.02 P = 0.99, adjusted for baseline lean mass: ß-coefficient = -0.31 P = 0.80). The de Morton Mobility Index significantly increased in the Control Group (ß-coefficient = -11.43 CI: 0.72-22.13, P = 0.04). No other differences were found. CONCLUSION: No significant effect on muscle mass was observed in this group of acutely ill old medical patients. High compliance was achieved with the dietary intervention, but resistance training was challenging. Clinical trials identifier NCT02077491.

A mixed diet supplemented with L-arabinose does not alter glycaemic or insulinaemic responses in healthy human subjects.

In addition to a yet-to-be published study showing arabinose to have an inhibiting effect on maltase, in vitro studies have shown L-arabinose to exert an inhibiting effect on small-intestinal sucrase and maltase and the consumption of a sucrose-rich drink containing L-arabinose to exert positive effects on postprandial blood glucose, insulin and C-peptide responses in humans. However, the effects of adding L-arabinose to mixed meals on the indices of glucose control are unknown. The purpose of the present study was to investigate whether the positive effects of L-arabinose added to a sugar drink could be reproduced in subjects consuming a mixed meal containing sucrose and/or starch from wheat flour. A total of seventeen healthy men participated in study 1, a randomised, double-blind, cross-over trial. In this study, the subjects consumed two different breakfast meals containing sucrose and starch from wheat flour (meal A) or starch from wheat flour (meal B) supplemented with 0, 5 and 10 % L-arabinose by weight after a 12 h fast. A total of six healthy men participated in study 2, a randomised, double-blind, cross-over trial. In this study, the subjects also consumed meal B served in two different textures and a liquid meal with maltose supplemented with 0 and 20% L-arabinose. In addition, 1·5 g of paracetamol was chosen as an indirect marker to assess gastric emptying. Postprandial plasma glucose, insulin and C-peptide concentrations were measured regularly for 3 h. The results of the present study showed that the peak plasma concentration, time to reach peak plasma concentration or AUC values of glucose, insulin and C-peptide were not altered after consumption of the test meals. Overall, it was not possible to reproduce the beneficial effects of L-arabinose added to sucrose drinks when L-arabinose was mixed in a solid or semi-solid mixed meal.

Randomized trial of the effects of individual nutritional counseling in cancer patients.

BACKGROUND & AIMS: Cancer-related malnutrition is multifactorial and related to a bad prognosis. The aim of this study was to investigate the effect of intensive, individual dietary counseling of patients in radiotherapy and/or chemotherapy for gynecologic-, gastric-, or esophageal cancer. METHODS: 61 outpatients were stratified by diagnoses and randomly assigned to one of two groups (G1; n = 32 and G2; n = 29). The basic regimen, applied to both groups, included measurement of body weight, 24-h dietary recall interview, micronutrient status and quality of life. In addition G1 received intensive, individual dietary counseling one hour per week and, if the patient accepted, a daily oral nutritional supplement containing 2531 kJ, 33.8 g protein and 2.2 g EPA. RESULTS: At the end of the treatment period, significantly fewer patients had lost weight in the intervention group (mean: 44% vs. 72%, p < 0.05), and the fulfillment of estimated energy requirements was better during treatment (mean: 107% vs. 95%, p < 0.05). A significant positive effect was observed on the fulfillment of protein requirement, both during the treatment period (mean: 92% vs. 71%, p < 0.001) and at follow-up (mean: 86% vs. 71%, p < 0.05). CONCLUSION: In these cancer patients, intensive, individual dietary counseling was associated with a better weight maintenance and a higher provision of adequate amounts of protein and energy. The intervention had no significant effects on patients' quality of life, incidence of treatment-related side effects or appearance of micronutrient deficiencies.

Quantitative proteomic profiling of membrane proteins from the mouse brain cortex, hippocampus, and cerebellum using the HysTag reagent: mapping of neurotransmitter receptors and ion channels.

Analysis of the brain proteome and studying brain diseases through clinical biopsies and animal disease models require methods of quantitative proteomics that are sensitive and allow identification and quantification of low abundant membrane proteins from minute amount of tissue. Taking advantage of recently developed methods for isolation of membrane proteins from 10-20 mg brain tissue [Nielsen, P.Aa., Olsen, J.V., Podtelejnokov, A.V., Andersen, J.R., Mann, M., Wisniewski, J.R., 2005. Proteomic mapping of brain plasma membrane proteins. Mol. Cell. Proteomics 4, 402--408] and the HysTag-quantification method [Olsen, J.V., Andersen, J.R., Nielsen, P.Aa., Nielsen, M.L., Figeys, D., Mann, M., Wisniewski, J.R., 2004. HysTag---A novel proteomic qualification tool applied to differential analysis of membrane proteins from distinct areas of mouse brain. Mol. Cell. Proteomics 3, 82--92] we performed quantitative proteomic analysis of three functionally distinct compartments of mouse brain: cortex, hippocampus, and cerebellum. In total, 976 unique peptides corresponding to 555 unique proteins were quantified. Up to 20-fold differences in the levels of some proteins between brain areas were measured. For many quantified proteins--as for glutamate receptors, calcium channel subunits, and ATP-ases--an excellent correlation between our proteomic data and previously published mRNA expression levels or intensity of immunostaining was found. Our results clearly demonstrate differences in levels of membrane proteins mapped in distinct brain compartments and offer a technology that allows in depth study of brain membrane proteomes, such as mouse models of neurological diseases.

Proteomic mapping of brain plasma membrane proteins.

Proteomics is potentially a powerful technology for elucidating brain function and neurodegenerative diseases. So far, the brain proteome has generally been analyzed by two-dimensional gel electrophoresis, which usually leads to the complete absence of membrane proteins. We describe a proteomic approach for profiling of plasma membrane proteins from mouse brain. The procedure consists of a novel method for extraction and fractionation of membranes, on-membrane digestion, diagonal separation of peptides, and high-sensitivity analysis by advanced MS. Breaking with the classical plasma membrane fractionation approach, membranes are isolated without cell compartment isolation, by stepwise depletion of nonmembrane molecules from entire tissue homogenate by high-salt, carbonate, and urea washes followed by treatment of the membranes with sublytic concentrations of digitonin. Plasma membrane is further enriched by of density gradient fractionation and protein digested on-membrane by endoproteinase Lys-C. Released peptides are separated, fractions digested by trypsin, and analyzed by LC-MS/MS. In single experiments, the developed technology enabled identification of 862 proteins from 150 mg of mouse brain cortex. Further development and miniaturization allowed analysis of 15 mg of hippocampus, revealing 1,685 proteins. More that 60% of the identified proteins are membrane proteins, including several classes of ion channels and neurotransmitter receptors. Our work now allows in-depth study of brain membrane proteomes, such as of mouse models of neurological disease.

HysTag--a novel proteomic quantification tool applied to differential display analysis of membrane proteins from distinct areas of mouse brain.

A novel isotopically labeled cysteine-tagging and complexity-reducing reagent, called HysTag, has been synthesized and used for quantitative proteomics of proteins from enriched plasma membrane preparations from mouse fore- and hindbrain. The reagent is a 10-mer derivatized peptide, H(2)N-(His)(6)-Ala-Arg-Ala-Cys(2-thiopyridyl disulfide)-CO(2)H, which consists of four functional elements: i) an affinity ligand (His(6)-tag), ii) a tryptic cleavage site (-Arg-Ala-), iii) Ala-9 residue that contains four (d(4)) or no (d(0)) deuterium atoms, and iv) a thiol-reactive group (2-thiopyridyl disulfide). For differential analysis cysteine residues in the compared samples are modified using either (d(4)) or (d(0)) reagent. The HysTag peptide is preserved in Lys-C digestion of proteins and allows charge-based selection of cysteine-containing peptides, whereas subsequent tryptic digestion reduces the labeling group to a di-peptide, which does not hinder effective fragmentation. Furthermore, we found that tagged peptides containing Ala-d(4) co-elute with their d(0)-labeled counterparts. To demonstrate effectiveness of the reagent, a differential analysis of mouse forebrain versus hindbrain plasma membranes was performed. Enriched plasma membrane fractions were partially denatured, reduced, and reacted with the reagent. Digestion with endoproteinase Lys-C was carried out on nonsolubilized membranes. The membranes were sedimented by ultra centrifugation, and the tagged peptides were isolated by Ni(2+) affinity or cation-exchange chromatography. Finally, the tagged peptides were cleaved with trypsin to release the histidine tag (residues 1-8 of the reagent) followed by liquid chromatography tandem mass spectroscopy for relative protein quantification and identification. A total of 355 unique proteins were identified, among which 281 could be quantified. Among a large majority of proteins with ratios close to one, a few proteins with significant quantitative changes were retrieved. The HysTag offers advantages compared with the isotope-coded affinity tag reagent, because the HysTag reagent is easy to synthesize, economical due to use of deuterium instead of (13)C isotope label, and allows robust purification and flexibility through the affinity tag, which can be extended to different peptide functionalities.

Systematic identification of protein complexes in Saccharomyces cerevisiae by mass spectrometry.

The recent abundance of genome sequence data has brought an urgent need for systematic proteomics to decipher the encoded protein networks that dictate cellular function. To date, generation of large-scale protein-protein interaction maps has relied on the yeast two-hybrid system, which detects binary interactions through activation of reporter gene expression. With the advent of ultrasensitive mass spectrometric protein identification methods, it is feasible to identify directly protein complexes on a proteome-wide scale. Here we report, using the budding yeast Saccharomyces cerevisiae as a test case, an example of this approach, which we term high-throughput mass spectrometric protein complex identification (HMS-PCI). Beginning with 10% of predicted yeast proteins as baits, we detected 3,617 associated proteins covering 25% of the yeast proteome. Numerous protein complexes were identified, including many new interactions in various signalling pathways and in the DNA damage response. Comparison of the HMS-PCI data set with interactions reported in the literature revealed an average threefold higher success rate in detection of known complexes compared with large-scale two-hybrid studies. Given the high degree of connectivity observed in this study, even partial HMS-PCI coverage of complex proteomes, including that of humans, should allow comprehensive identification of cellular networks.