Adherence and eating experiences differ between participants following a flexitarian diet including red meat or a vegetarian diet including plant-based meat alternatives: findings from a 10-week randomised dietary intervention trial.

Background: Flexitarian, vegetarian and exclusively plant-based diets are increasingly popular, particularly amongst young adults. This is the first randomised dietary intervention to investigate the health, wellbeing, and behavioural implications of consuming a basal vegetarian diet that additionally includes low-to-moderate amounts of red meat (flexitarian) compared to one containing plant-based meat alternatives (PBMAs, vegetarian) in young adults (ClinicalTrials.gov NCT04869163). The objective for the current analysis is to measure adherence to the intervention, nutrition behaviours, and participants' experience with their allocated dietary group. Methods: Eighty healthy young adults participated in this 10-week dietary intervention as household pairs. Household pairs were randomised to receive either approximately three serves of red meat (average of 390 g cooked weight per individual, flexitarian group) or PBMAs (350-400 g per individual, vegetarian group) per week on top of a basal vegetarian diet. Participants were supported to adopt healthy eating behaviours, and this intervention was developed and implemented using a behaviour change framework. Adherence (eating allocated red meat or PBMA, abstaining from animal-based foods not provided by researchers) was continuously monitored, with total scores calculated at the end of the 10-week intervention period. Eating experiences were measured by the Positive Eating Scale and a purpose-designed exit survey, and a food frequency questionnaire measured dietary intake. Analyses used mixed effects modeling taking household clustering into account. Results: The total average adherence score was 91.5 (SD = 9.0) out of a possible 100, with participants in the flexitarian group scoring higher (96.1, SD = 4.6, compared to 86.7, SD = 10.0; p < 0.001). Those receiving red meat were generally more satisfied with this allocation compared to those receiving the PBMAs, even though a leading motivation for participants joining the study was an opportunity to try plant-based eating (35% expressed that their interest in taking part was related to trying plant-based eating). Participants in both intervention groups had increased vegetable intake (p < 0.001), and reported more positive eating experiences (p = 0.020) and satisfaction with eating (p = 0.021) at the end of the 10-week intervention relative to baseline values. Conclusion: Methods to encourage engagement with the trial were successful, as participants demonstrated excellent adherence to the intervention. Observed differences in participants' adherence and experiences between flexitarian and vegetarian groups holds implications for the adoption of healthy, sustainable dietary patterns beyond this study alone.

Plasma Amino Acid Appearance and Status of Appetite Following a Single Meal of Red Meat or a Plant-Based Meat Analog: A Randomized Crossover Clinical Trial.

Background: Red meat is a nutrient-dense food and a dietary staple. A new generation of plant-based meat analogs (PBMAs) have been designed to mimic the experience of eating meat, but there is limited evidence about their digestive efficacy and nutritional quality. Objectives: We compared the postprandial digestive response of a single meal containing meat commercially raised in New Zealand, including lamb, on-farm pasture-raised beef (Pasture), or grain-finished beef (Grain) with a PBMA (Beyond Burger; Beyond Meat) sold through consumer retail. The primary outcome was the appearance of amino acids in plasma. Secondary outcomes included glucose and insulin, appetite assessment, and anthropometry. Methods: Thirty healthy men (20-34 y) participated in a double-blinded randomized crossover trial. Each consumed 1 of the 4 test meals on 4 occasions separated by a washout period of at least 1 wk, following an overnight fast. The meal was a burrito-style wrap containing meat or PBMAs, vegetables, salsa, and seasonings in a flour tortilla. The amount of Pasture, Grain, Lamb, or BB was 220 g raw (∼160 g cooked). Venous blood samples were collected over 4 h. Appetite and hunger status was scored with visual analog scales. Results: Pre-meal amino acid concentrations in plasma did not differ by group (P > 0.9), although several nonessential amino acids differed strongly according to participant BMI. Postprandial amino acids peaked at 2-3 h in all groups. The BB meal produced significantly lower plasma concentrations of total, essential, branched-chain, and non-proteogenic amino acids than the Lamb, Pasture, or Grain meals, based on AUC. There were no significant differences between meal groups in scores for hunger, fullness, or cravings. Conclusions: Red meat meals exhibited greater bioavailability of amino acids compared with the PBMA (BB). Pasture versus Grain origins of the beef had little influence on participants' responses. This trial was registered at ClinicalTrials.gov as NCT04545398.

Generation and identification of kokumi compounds and their validation by taste-receptor assay: An example with dry-cured lamb meat.

Kokumi tastants are small γ-glutamyl peptides (GGP) that enhance flavour in foods. We sought to generate GGP from the meat crusts of dry-cured lamb, an underutilised protein resource, identify these using mass spectrometry, and validate their functional activity using a kokumi-calcium sensing receptor (CaSR) assay. The water-soluble extract (WSE) of meat crust was hydrolysed by protease A (PA) and treated with glutaminase (GA). Fifteen GGP were identified, with 14 being significantly increased in PA and GA groups compared to WSE, as were along with free amino acid levels. The GA extract activated CaSR with higher potency and efficacy than PA and WSE suggesting the generation of potent kokumi tastants. The in vitro receptor assay might be an expedient tool for screening kokumi tastants prior to conducting human sensory analysis. Collectively, our findings indicate that the meat crust can be a valuable source to generate kokumi tastants via a two-step enzymatic reaction.

A Modern Flexitarian Dietary Intervention Incorporating Web-Based Nutrition Education in Healthy Young Adults: Protocol for a Randomized Controlled Trial.

BACKGROUND: The trend of flexitarian eating patterns is on the rise, with young adults among the biggest adopters claiming health and environmental reasons to reduce red meat intake. Nutrient-dense meat and animal products are often the lynchpin of these diets, even when consumed only occasionally and in moderate amounts. Red meat provides forms and concentrations of essential proteins, lipids, and micronutrients that are scarce in exclusively vegetarian regimens. OBJECTIVE: The aim of this study is to consider the effects of moderate consumption of lean red meat as part of an otherwise vegetarian balanced diet and its impact on biomarkers of sustained health and well-being. METHODS: A cohort of healthy, young (20-34 years old, n=80) male and female participants will take part in a 2-arm, parallel randomized controlled trial (RCT) for a duration of 12 weeks, with a 3-month posttrial follow-up. The trial will commence with a 2-week assessment period followed by allocation to the intervention arms. The intervention will include the consumption of red meat or meat alternatives 3 times per week for 10 weeks. Blood samples of the participants will be collected to measure changes in erythrocyte fatty acid distribution, circulating amino acids, neurotransmitters, markers of mineral status, and inflammatory markers. Questionnaires to assess well-being and mental health will be undertaken every 2 weeks. Body composition, physical function, and blood parameters will be assessed at allocation (t0), week 5 into the intervention (t5), and post intervention (t10). RESULTS: The protocol has been developed using the SPIRIT (Standard Protocol Items: Recommendations for Interventional Trials) checklist and the outcomes will be reported in accordance with the CONSORT (Consolidated Standards of Reporting Trials) guidelines. The trial was approved by the New Zealand Ministry of Health's Health and Disability Ethics Committees (protocol 20/STH/157). The results of this study will be communicated via publication. CONCLUSIONS: To our knowledge, this is the first RCT investigating the overarching health consequences of consuming pasture-fed red meat or no meat as part of a healthy diet. TRIAL REGISTRATION: ClinicalTrials.gov NCT04869163; https://clinicaltrials.gov/ct2/show/NCT04869163. INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID): PRR1-10.2196/30909.

The Effect of Elevated Protein Intake on DNA Damage in Older People: Comparative Secondary Analysis of Two Randomized Controlled Trials.

A high protein intake at old age is important for muscle protein synthesis, however, this could also trigger protein oxidation with the potential risk for DNA damage. The aim of this study was to investigate whether an increased protein intake at recommended level or well above would affect DNA damage or change levels of reduced (GSH) and oxidised glutathione (GSSG) in community-dwelling elderly subjects. These analyses were performed in two randomized intervention studies, in Austria and in New Zealand. In both randomized control trials, the mean protein intake was increased with whole foods, in the New Zealand study (n = 29 males, 74.2 ± 3.6 years) to 1.7 g/kg body weight/d (10 weeks intervention; p < 0.001)) in the Austrian study (n = 119 males and females, 72.9 ± 4.8 years) to 1.54 g/kg body weight/d (6 weeks intervention; p < 0.001)). In both studies, single and double strand breaks and as formamidopyrimidine-DNA glycosylase-sensitive sites were investigated in peripheral blood mononuclear cells or whole blood. Further, resistance to H2O2 induced DNA damage, GSH, GSSG and CRP were measured. Increased dietary protein intake did not impact on DNA damage markers and GSH/GSSG levels. A seasonal-based time effect (p < 0.05), which led to a decrease in DNA damage and GSH was observed in the Austrian study. Therefore, increasing the protein intake to more than 20% of the total energy intake in community-dwelling seniors in Austria and New Zealand did not increase measures of DNA damage, change glutathione status or elevate plasma CRP.

Objective Measurements Associated with the Preferred Eating Qualities of Fermented Salamis.

The development of new food products can be expedited by understanding the physicochemical attributes that are most relevant to consumers. Although many objective analyses are possible, not all are a suitable proxy to serve as quality markers associated with sensory preferences. In this work, we selected nine candidate laboratory assays to use on six commercial salamis, which were also eaten and informally described by a consumer discussion group familiar with China-sourced meat products. Several objective measures were strongly related to the flavour perceptions: (i) texture: instrumental texture values, fat release at oral temperature and fat saturation ratios, (ii) aroma: volatile compounds (e.g., alcohols and esters) associated with microbial fermentation and spices (terpenes and sulphur compounds) and (iii) taste: kokumi taste receptor responses. The fat released at oral temperature was associated with unsaturated fatty acids (r = 0.73). However, there was less explanatory worth for associations between sensory perceptions and proximate composition, water activity, pH or L*, a*, b* colourimetry.

Responsiveness of one-carbon metabolites to a high-protein diet in older men: Results from a 10-wk randomized controlled trial.

OBJECTIVES: Dietary strategies to promote successful aging are divergent. Higher-protein diets are recommended to preserve skeletal muscle mass and physical function. Conversely, increased B-vitamin intake, supporting one-carbon (1C) metabolism, reduces the risk of cognitive decline and cardiovascular disease. On the hypothesis that higher protein intake through animal-based sources will benefit 1C regulation by the supply of B vitamins (folate, riboflavin, and vitamins B6 and B12) and methyl donors (choline) despite higher methionine intake, this study explored the effect of a higher-protein diet on 1C metabolite status in older men compared to current protein recommendations. METHODS: Older men (age, 74 ± 3 y) were randomized to receive a diet for 10 wk containing either the recommended dietary allowance (RDA) of protein (0.8 g/kg body weight/d, n = 14), or double that amount (2RDA, n = 15), with differences in protein accounted for by modifying carbohydrate intake. Intervention diets were matched to each individual's energy requirements based on the Harris-Benedict equation and adjusted fortnightly as required depending on physical activity and satiety. Fasting plasma 1C metabolite concentrations were quantified by liquid chromatography coupled with mass spectrometry at baseline and after 10 wk of intervention. RESULTS: Plasma homocysteine concentrations were reduced from baseline to follow-up with both diets. Changes in metabolite ratios reflective of betaine-dependent homocysteine remethylation were specific to the RDA diet, with an increase in the betaine-to-choline ratio and a decrease in the dimethylglycine-to-betaine ratio. Comparatively, increasing folate intake was positively associated with a change in choline concentration and inversely with the betaine-to-choline ratio for the 2RDA group. CONCLUSIONS: Adding to the known benefits of higher protein intake in older people, this study supports a reduction of homocysteine with increased consumption of animal-based protein, although the health effects of differential response of choline metabolites to a higher-protein diet remain uncertain.

The effects of blanching on composition and modification of proteins in navy beans (Phaseolus vulgaris).

Blanching is an important process in the preparation of navy beans (Phaseolus vulgaris L.) for canning. We here explore the effect of blanching which can profoundly affect protein composition and introduce protein-primary-level modifications. Amino acid analysis showed significantly decreased protein abundance (58.5%) in blanched beans compared to raw beans. Proteomic analyses revealed a decrease in high molecular weight isoforms of the major storage globulin proteins phaseolin (mean fold-change -3.7) and legumin (mean fold-change -2.5) and concomitant increase in their low molecular weight isoforms (mean fold-change 6.4 and 8.3, respectively). Blanched beans also had decreased abundance of lipoxygenase (mean fold-change -13.1), an enzyme responsible for product spoilage during storage. Increased lysinoalanine (up to 47%) and highly modified protein fragments were found in the processing waters, indicating heat- induced modifications. Correlating these molecular level changes thus provides a basis for evaluating how processing parameters can be modified to increase protein food quality.

Quality, nutrient and sensory characteristics of aged meat from lambs supplemented with selenomethionine.

Selenium (Se) as a co-factor of antioxidant enzymes is metabolically essential for animals. Its presence in muscle can improve the oxidative stability of meat and is a desirable nutrient for consumers. A novel approach to Se supplementation for meat-producing livestock was demonstrated in a 95-day study of young lambs. DL-selenomethionine (SeMet) was administered by subcutaneous injection at day 0 (3-4 weeks of age) and again at day 54. A Control group (n = 9) received carrier only, whilst Medium and High groups (n = 10) received graded levels of Se. Physicochemical attributes of meat quality and sensory characteristics were measured at 1, 3, 14 and 42 days of ageing (vacuum packaged at -1.5 °C), followed by instrumental colour measurements after 7 days of simulated retail display. There were no significant interactions between SeMet treatment and ageing. Muscle pH, drip and cooking losses, initial display colour and sensory evaluations by trained and consumer panels were unaffected by treatment. Smaller changes in colour during display were observed for the Medium group compared to Control (P < 0.05). The shorter range of ageing times improved meat tenderness however extended ageing decreased colour stability. SeMet markedly increased Se concentrations in muscle, blood, kidney and liver (P < 0.05), resulting in Se enriched meat without appreciable changes in meat quality.

Comparable Postprandial Amino Acid and Gastrointestinal Hormone Responses to Beef Steak Cooked Using Different Methods: A Randomised Crossover Trial.

Cooking changes the texture and tenderness of red meat, which may influence its digestibility, circulatory amino acids (AA) and gastrointestinal (GI) hormonal responses in consumers. In a randomised crossover intervention, healthy males (n = 12) consumed a beef steak sandwich, in which the beef was cooked by either a pan-fried (PF) or sous-vide (SV) method. Plasma AA were measured by ultrahigh performance liquid chromatography (UPLC), while plasma GI hormones were measured using a flow cytometric multiplex array. Following meat ingestion, the circulatory concentrations of some of the essential AA (all the branched-chain AA: leucine, isoleucine and valine; and threonine), some of the nonessential AA (glycine, alanine, tyrosine and proline) and some of the nonproteogenic AA (taurine, citrulline and ornithine) were increased from fasting levels by 120 or 180 min (p < 0.05). There were no differences in circulating AA concentrations between cooking methods. Likewise, of the measured GI hormones, glucose-dependent insulinotropic peptide (GIP) and glucagon-like peptide-1 (GLP-1) concentrations increased from fasting levels after consumption of the steak sandwich (p < 0.05), with no differences between the cooking methods. In the healthy male adults, protein digestion and circulating GI hormone responses to a beef-steak breakfast were unaltered by the different cooking methods.

Analysis of Human Faecal Host Proteins: Responsiveness to 10-Week Dietary Intervention Modifying Dietary Protein Intake in Elderly Males.

Faecal proteomics targeting biomarkers of immunity and inflammation have demonstrated clinical application for the identification of changes in gastrointestinal function. However, there are limited comprehensive analyses of the host faecal proteome and how it may be influenced by dietary factors. To examine this, the Homo sapiens post-diet proteome of older males was analysed at the completion of a 10-week dietary intervention, either meeting the minimum dietary protein recommendations (RDA; n = 9) or twice the recommended dietary allowance (2RDA, n = 10). The host faecal proteome differed markedly between individuals, with only a small subset of proteins present in ≥ 60% of subjects (14 and 44 proteins, RDA and 2RDA, respectively, with only 7 common to both groups). No differences were observed between the diet groups on the profiles of host faecal proteins. Faecal proteins were detected from a wide range of protein classes, with high inter-individual variation and absence of obvious impact in response to diets with markedly different protein intake. This suggests that well-matched whole food diets with two-fold variation in protein intake maintained for 10 weeks have minimal impact on human faecal host proteins.

[89Zr]A2cDb Immuno-PET of Prostate Cancer in a Human Prostate Stem Cell Antigen Knock-in (hPSCA KI) Syngeneic Model.

PURPOSE: A great challenge in the diagnosis and treatment of prostate cancer is distinguishing between indolent or local disease and aggressive or metastatic disease. Antibody-based positron emission tomography (immuno-PET) as a cancer-specific imaging modality could improve diagnosis of primary disease, aid the detection of metastases to regional lymph nodes as well as to distant sites (e.g., bone), and monitor response to therapy. PROCEDURE: In search for a more physiologically relevant disease model, a human prostate stem cell antigen knock-in (hPSCA KI) mouse model was generated. The use of a syngeneic prostate cancer cell line transduced to express human PSCA (RM-9-hPSCA) enabled the evaluation of anti-PSCA immuno-PET in immunocompetent mice and in the context of normal tissue expression of PSCA. Two PSCA-specific humanized antibody fragments, A11 minibody and A2 cys-diabody, were radiolabeled with positron emitters iodine-124 and zirconium-89, respectively ([124I]A11 Mb and [89Zr]A2cDb), and used for immuno-PET in wild-type, hPSCA KI and tumor-bearing mice. RESULTS: The hPSCA KI mice express PSCA at low levels in the normal prostate, bladder and stomach, reproducing the expression pattern seen in humans. [124I]A11 Mb immuno-PET detected increased levels of PSCA expression in the stomach, and because I-124 is non-residualizing, very little activity was seen in organs of clearance (liver, kidney, spleen). However, due to the longer half-life of the 80 kDa protein, blood activity (and thus urine activity) at 20 h postinjection remains high. The smaller 50 kDa [89Zr]A2cDb cleared faster, resulting in lower blood and background activity, despite the use of a residualizing radiometal. Importantly, [89Zr]A2cDb immuno-PET showed antigen-specific targeting of PSCA-expressing tumors and minimal nonspecific uptake in PSCA-negative controls. CONCLUSION: Tracer biodistribution was not significantly impacted by normal tissue expression of PSCA. [89Zr]A2cDb immuno-PET yielded high tumor-to-blood ratio at early time points. Rapid renal clearance of the 50 kDa tracer resulted in an unobstructed view of the pelvic region at 20 h postinjection that would allow the detection of cancer in the prostate.

Impact of a High Protein Intake on the Plasma Metabolome in Elderly Males: 10 Week Randomized Dietary Intervention.

High protein diets may improve the maintenance of skeletal muscle mass in the elderly, although it remains less clear what broader impact such diets have on whole body metabolic regulation in the elderly. Non-targeted polar metabolomics analysis using HILIC HPLC-MS was used to profile the circulating plasma metabolome of elderly men (n = 31; 74.7 ± 4.0 years) who were randomized to consume for 10 weeks a diet designed to achieve either protein (RDA; 0.8·g-1·kg-1) or that doubled this recommend intake (2RDA; 1.6.g.kg-1). A limited number of plasma metabolites (n = 24) were significantly differentially regulated by the diet. These included markers of protein anabolism, which increased by the 2RDA diet, including; urea, creatine, and glutarylcarnitine. Whilst in response to the RDA diet; glutamine, glutamic acid, and proline were increased, relative to the 2RDA diet (p < 0.05). Metaboanalyst identified six major metabolic pathways to be influenced by the quantity of protein intake, most notably the arginine and proline pathways. Doubling of the recommended protein intake in older males over 10 weeks exerted only a limited impact on circulating metabolites, as determined by LC-MS. This metabolomic response was almost entirely due to increased circulating abundances of metabolites potentially indicative of altered protein anabolism, without evidence of impact on pathways for metabolic health. Trial Registration: This trial was registered on 3rd March 2016 at the Australia New Zealand Clinical Trial Registry (www.anzctr.org.au) at ACTRN 12616000310460.

Protein Intake at Twice the RDA in Older Men Increases Circulatory Concentrations of the Microbiome Metabolite Trimethylamine-N-Oxide (TMAO).

Higher dietary protein intake is increasingly recommended for the elderly; however, high protein diets have also been linked to increased cardiovascular disease (CVD) risk. Trimethylamine-N-oxide (TMAO) is a bacterial metabolite derived from choline and carnitine abundant from animal protein-rich foods. TMAO may be a novel biomarker for heightened CVD risk. The purpose of this study was to assess the impact of a high protein diet on TMAO. Healthy men (74.2 ± 3.6 years, n = 29) were randomised to consume the recommended dietary allowance of protein (RDA: 0.8 g protein/kg bodyweight/day) or twice the RDA (2RDA) as part of a supplied diet for 10 weeks. Fasting blood samples were collected pre- and post-intervention for measurement of TMAO, blood lipids, glucose tolerance, insulin sensitivity, and inflammatory biomarkers. An oral glucose tolerance test was also performed. In comparison with RDA, the 2RDA diet increased circulatory TMAO (p = 0.002) but unexpectedly decreased renal excretion of TMAO (p = 0.003). LDL cholesterol was increased in 2RDA compared to RDA (p = 0.049), but no differences in other biomarkers of CVD risk and insulin sensitivity were evident between groups. In conclusion, circulatory TMAO is responsive to changes in dietary protein intake in older healthy males.

Comprehensive Profiling of the Circulatory miRNAome Response to a High Protein Diet in Elderly Men: A Potential Role in Inflammatory Response Modulation.

SCOPE: MicroRNA are critical to the coordinated post-transcriptional regulation of gene expression, yet few studies have addressed the influence of habitual diet on microRNA expression. High protein diets impact cardiometabolic health and body composition in the elderly suggesting the possibility of a complex systems response. Therefore, high-throughput small RNA sequencing technology is applied in response to doubling the protein recommended dietary allowance (RDA) over 10 weeks in older men to examine alterations in circulating miRNAome. METHODS AND RESULTS: Older men (n = 31; 74.1 ± 0.6 y) are randomized to consume either RDA (0.8 g kg-1  day-1 ) or 2RDA (1.6 g kg-1  day-1 ) of protein for 10 weeks. Downregulation of five microRNAs (miR-125b-5p, -100-5p, -99a-5p, -23b-3p, and -203a) is observed following 2RDA with no changes in the RDA. In silico functional analysis highlights target gene enrichment in inflammation-related pathways. qPCR quantification of predicted inflammatory genes (TNFα, IL-8, IL-6, pTEN, PPP1CB, and HOXA1) in peripheral blood mononuclear cells shows increased expression following 2RDA diet (p ≤ 0.05). CONCLUSION: The study findings suggest a possible selective alteration in the post-transcriptional regulation of the immune system following a high protein diet. However, very few microRNAs are altered despite a large change in the dietary protein.

The effects of a wool hydrolysate on short-chain fatty acid production and fecal microbial composition in the domestic cat (Felis catus).

Novel animal-derived fibers are of interest for the pet food industry. We here introduce a method for extracting wool proteins using controlled hydrolysis of wool. This results in an appropriate form and we demonstrate its application in pet food using the domestic cat. The effect of the wool hydrolysate on biomarkers of digestive health (e.g., fecal short-chain fatty acids and fecal microbial composition, apparent amino acid (AA) and protein digestibility), are also described. In a feeding study, a cohort of cats (n = 8 per treatment) were fed a basal diet (Control), or the basal diet supplemented with 2% wool hydrolysate, 2% inulin (Synergy1; as is) or 2% cellulose (Novagel; as is). The concentration of butyric acid was not significant (P = 0.102) between treatment groups. The concentration of fecal lactic acid was greatest (P = 0.007) in cats on the Novagel diet. Valeric acid was increased (P = 0.001) in cats fed Synergy1. Supplementation of cat diet with a wool hydrolysate showed similarities to Novagel supplementation in terms of its effects on fecal short-chain fatty acid concentrations and fecal microbiota composition. Wool hydrolysate increased apparent cysteine digestibility compared to Synergy 1 or Novogel. In terms of fecal health, intake, and palatability, the diet supplemented with wool hydrolysate was not detrimental, being similar to currently used dietary fiber supplements. These findings indicate that wool hydrolysates offer promise as an animal-derived supplement source for pet diets.

Global Provisioning of Red Meat for Flexitarian Diets.

Although not always labeled as such, flexitarianism is the default lifestyle for much of the world, whereby meals based on plant materials provide the bulk of people's calories. The rich nutrition of meat and animal products is often the lynchpin of these diets, even when only consumed occasionally. It provides forms and concentrations of essential proteins, lipids, and micronutrients that are otherwise scarce. However, the production of this meat is resource intensive. It requires large quantities of arable land and water, and typically has lower conversion efficiency of farm inputs to edible outputs compared with crops, poultry, aquaculture, dairy, and eggs. An additional complication is that the quantity of ancillary products produced during slaughterhouse operations is large and underutilized. Each year, approximately 190 million metric tons (MMT) of red meat, including pork, lamb, sheep, veal, beef, and goats are produced globally, half of which will be consumed by less than 25% of the population living in developed countries. With demand for meat expected to exceed 376 MMT by 2030, an increase in the adoption of plant-based diets presents an opportunity for the world to re-evaluate how meat can be sustainably produced, with greater emphasis on animal welfare, nutritional value, product safety, better utilization, and distribution channels. In this article we consider the role meat plays in the modern diet, its production and consumption, opportunities to improve utilization of the animal, the benefits of incorporating a diverse range of red meat into diets, and the strategies that the meat industry should consider in response to flexitarianism.

Dual-Modality Immuno-PET and Near-Infrared Fluorescence Imaging of Pancreatic Cancer Using an Anti-Prostate Stem Cell Antigen Cys-Diabody.

Pancreatic cancer has a high mortality rate due to late diagnosis and the tendency to invade surrounding tissues and metastasize at an early stage. A molecular imaging agent that enables both presurgery antigen-specific PET (immuno-PET) and intraoperative near-infrared fluorescence (NIRF) guidance might benefit diagnosis of pancreatic cancer, staging, and surgical resection, which remains the only curative treatment. Methods: We developed a dual-labeled probe based on A2 cys-diabody (A2cDb) targeting the cell-surface prostate stem cell antigen (PSCA), which is expressed in most pancreatic cancers. Maleimide-IRDye800CW was site-specifically conjugated to the C-terminal cys-tag (A2cDb-800) without impairing integrity or affinity (half-maximal binding, 4.3 nM). Direct radioiodination with 124I (124I-A2cDb-800) yielded a specific activity of 159 ± 48 MBq/mg with a radiochemical purity exceeding 99% and 65% ± 4.5% immunoreactivity (n = 3). In vivo specificity for PSCA-expressing tumor cells and biodistribution of the dual-modality tracer were evaluated in a prostate cancer xenograft model and compared with single-labeled 124I-A2cDb. Patient-derived pancreatic ductal adenocarcinoma xenografts (PDX-PDACs) were grown subcutaneously in NSG mice and screened for PSCA expression by immuno-PET. Small-animal PET/CT scans of PDX-PDAC-bearing mice were obtained using the dual-modality 124I-A2cDb-800 followed by postmortem NIRF imaging with the skin removed. Tumors and organs were analyzed ex vivo to compare the relative fluorescent signals without obstruction by other organs. Results: Specific uptake in PSCA-positive tumors and low nonspecific background activity resulted in high-contrast immuno-PET images. Concurrent with the PET studies, fluorescent signal was observed in the PSCA-positive tumors of mice injected with the dual-tracer 124I-A2cDb-800, with low background uptake or autofluorescence in the surrounding tissue. Ex vivo biodistribution confirmed comparable tumor uptake of both 124I-A2cDb-800 and 124I-A2cDb. Conclusion: Dual-modality imaging using the anti-PSCA cys-diabody resulted in high-contrast immuno-PET/NIRF images of PDX-PDACs, suggesting that this imaging agent might offer both noninvasive whole-body imaging to localize PSCA-positive pancreatic cancer and fluorescence image-guided identification of tumor margins during surgery.