Dietary protein load affects the energy and nitrogen balance requiring liver glutamate dehydrogenase to maintain physical activity.

Provision of amino acids to the liver is instrumental for gluconeogenesis while it requires safe disposal of the amino group. The mitochondrial enzyme glutamate dehydrogenase (GDH) is central for hepatic ammonia detoxification by deaminating excessive amino acids toward ureagenesis and preventing hyperammonemia. The present study investigated the early adaptive responses to changes in dietary protein intake in control mice and liver-specific GDH KO mice (Hep-Glud1-/-). Mice were fed chow diets with a wide coverage of protein contents; i.e., suboptimal 10%, standard 20%, over optimal 30%, and high 45% protein diets; switched every 4 days. Metabolic adaptations of the mice were assessed in calorimetric chambers before tissue collection and analyses. Hep-Glud1-/- mice exhibited impaired alanine induced gluconeogenesis and constitutive hyperammonemia. The expression and activity of GDH in liver lysates were not significantly changed by the different diets. However, applying an in situ redox-sensitive assay on cryopreserved tissue sections revealed higher hepatic GDH activity in mice fed the high-protein diets. On the same section series, immunohistochemistry provided corresponding mapping of the GDH expression. Cosinor analysis from calorimetric chambers showed that the circadian rhythm of food intake and energy expenditure was altered in Hep-Glud1-/- mice. In control mice, energy expenditure shifted from carbohydrate to amino acid oxidation when diet was switched to high protein content. This shift was impaired in Hep-Glud1-/- mice and consequently the spontaneous physical activity was markedly reduced in GDH KO mice. These data highlight the central role of liver GDH in the energy balance adaptation to dietary proteins.

GCN2 drives diurnal patterns in the hepatic integrated stress response and maintains circadian rhythms in whole body metabolism during amino acid insufficiency.

Disruptions in circadian rhythms are associated with an increased risk of developing metabolic diseases. General control nonderepressible 2 (GCN2), a primary sensor of amino acid insufficiency and activator of the integrated stress response (ISR), has emerged as a conserved regulator of the circadian clock in multiple organisms. The objective of this study was to examine diurnal patterns in hepatic ISR activation in the liver and whole body rhythms in metabolism. We hypothesized that GCN2 activation cues hepatic ISR signaling over a natural 24-h feeding-fasting cycle. To address our objective, wild-type (WT) and whole body Gcn2 knockout (GCN2 KO) mice were housed in metabolic cages and provided free access to either a control or leucine-devoid diet (LeuD) for 8 days in total darkness. On the last day, blood and livers were collected at CT3 (CT = circadian time) and CT15. In livers of WT mice, GCN2 phosphorylation followed a diurnal pattern that was guided by intracellular branched-chain amino acid concentrations (r2 = 0.93). Feeding LeuD to WT mice increased hepatic ISR activation at CT15 only. Diurnal oscillations in hepatic ISR signaling, the hepatic transcriptome including lipid metabolic genes, and triglyceride concentrations were substantially reduced or absent in GCN2 KO mice. Furthermore, mice lacking GCN2 were unable to maintain circadian rhythms in whole body energy expenditure, respiratory exchange ratio, and physical activity when fed LeuD. In conclusion, GCN2 activation functions to maintain diurnal ISR activation in the liver and has a vital role in the mechanisms by which nutrient stress affects whole body metabolism.NEW & NOTEWORTHY This work reveals that the eIF2 kinase GCN2 functions to support diurnal patterns in the hepatic integrated stress response during natural feeding and is necessary to maintain circadian rhythms in energy expenditure, respiratory exchange ratio, and physical activity during amino acid stress.

Effects of Different Protein Sources on Amino Acid Absorption and Plasma Appearance of Tryptophan, Large Neutral Amino Acids, and Tryptophan Metabolites in Pigs.

BACKGROUND: Absorption of tryptophan (TRP) across the gut epithelium is potentially modulated by competing large neutral amino acids (LNAAs), which could affect the appearance of TRP and its metabolites in the bloodstream. OBJECTIVES: This study aimed to determine, in a growing pig model of an adult human, the absorption of TRP and other LNAAs from the gastrointestinal tract, and plasma appearance of TRP, LNAAs, and TRP metabolites, in response to dietary proteins varying in TRP content. METHODS: Pigs were adapted for 7 d to each of 4 diets that differed in their protein source and TRP content: 1) alpha-lactalbumin (AL; 9.95 mg TRP/g diet DM), 2) whey protein (6.59 mg TRP/g), 3) casein (3.73 mg TRP/g), or 4) zein (0.14 mg TRP/g). On day 8, pigs were euthanised after a 12-h fast (baseline), or 1, 2, 3, 4, or 6 h after they received a test meal consisting of 45 g protein, or a protein-free meal (n = 6 pigs at each time in each meal group). Tryptophan and LNAA absorption from the small intestine, and appearance of TRP, LNAAs, and TRP metabolites (melatonin, serotonin, kynurenine pathway metabolites), in the portal vein and systemic circulation, were determined. RESULTS: AL intake resulted in sustained elevated plasma TRP concentrations after an overnight fast. The amount of TRP absorbed was dose-dependently related to protein TRP content (P = 0.028), with fastest rates for pigs fed AL (371 mg/h). Portal and systemic plasma TRP, TRP/LNAA, and the TRP metabolites were highest (P ≤ 0.05) after AL intake, and remained above baseline levels for ∼4 h postprandially. Absorption rates of TRP correlated with postprandial plasma TRP and TRP metabolites (P ≤ 0.05). CONCLUSIONS: In adult humans, postprandial plasma TRP and TRP metabolite concentrations can likely be modulated by the TRP content of the meal.

Assessing Muscle Protein Synthesis Rates In Vivo in Humans: The Deuterated Water (2H2O) Method.

Skeletal muscle tissue is in a constant state of turnover, with muscle tissue protein synthesis and breakdown rates ranging between 1% and 2% across the day in vivo in humans. Muscle tissue remodeling is largely controlled by the up- and down-regulation of muscle tissue protein synthesis rates. Research studies generally apply stable isotope-labeled amino acids to assess muscle protein synthesis rates in vivo in humans. Following labeled amino acid administration in a laboratory setting, muscle tissue samples are collected over several hours to assess the incorporation rate of these labeled amino acids in muscle tissue protein. To allow quantification of bulk muscle protein synthesis rates over more prolonged periods, the use of deuterated water methodology has regained much interest. Ingestion of daily boluses of deuterium oxide results in 2H enrichment of the body water pool. The available 2H-atoms become incorporated into endogenously synthesized alanine primarily through transamination of pyruvate in the liver. With 2H-alanine widely available to all tissues, it becomes incorporated into de novo synthesized tissue proteins. Assessing the increase in tissue protein-bound 2H-alanine enrichment in muscle biopsy samples over time allows for the calculation of muscle protein synthesis rates over several days or even weeks. As the deuterated water method allows for the assessment of muscle tissue protein synthesis rates under free-living conditions in nonlaboratory settings, there is an increasing interest in its application. This manuscript describes the theoretical background of the deuterated water method and offers a comprehensive tutorial to correctly apply the method to determine bulk muscle protein synthesis rates in vivo in humans.

Greater Protein Intake Emphasizing Lean Beef Does Not Affect Resistance Training-Induced Adaptations in Skeletal Muscle and Tendon of Older Women: A Randomized Controlled Feeding Trial.

BACKGROUND: Although experimental research supports that resistance training (RT), especially with greater dietary protein intake, improves muscle mass and strength in older adults, comparable research on tendons is needed. OBJECTIVES: We assessed the effects of a protein-rich diet emphasizing lean beef, compared with 2 control diets, on RT-induced changes in skeletal muscle and tendon size and strength in older women. METHODS: We randomly assigned women [age: 66 ± 1 y, body mass index (BMI): 28 ± 1] to groups that consumed 1) 0.8 g total protein/kg body weight/day from mixed food sources (normal protein control, n = 16); 2) 1.4 g/kg/d protein from mixed food sources (high protein control, n = 17); or 3) 1.4 g/kg/d protein emphasizing unprocessed lean beef (high protein experimental group, n = 16). Participants were provided with all foods and performed RT 3 times/wk, 70% of 1-repetition maximum for 12 wk. We measured quadriceps muscle volume via magnetic resonance imaging (MRI). We estimated patellar tendon biomechanical properties and cross-sectional area (CSA) using ultrasound and MRI. RESULTS: Dietary intake did not influence RT-induced increases in quadriceps strength (P < 0.0001) or muscle volume (P < 0.05). We noted a trend for an RT effect on mean tendon CSA (P = 0.07), with no differences among diets (P > 0.05). Proximal tendon CSA increased with RT (P < 0.05) with no difference between dietary groups (P > 0.05). Among all participants, midtendon CSA increased with RT (P ≤ 0.05). We found a decrease in distal CSA in the 0.8 g group (P < 0.05) but no change in the 1.4 g group (P > 0.05). Patellar tendon MRI signal or biomechanical properties were unchanged. CONCLUSIONS: Our findings indicated that greater daily protein intake, emphasizing beef, did not influence RT-induced changes in quadriceps muscle strength or muscle volume of older women. Although we noted trends in tendon CSA, we did not find a statistically significant impact of greater daily protein intake from beef on tendon outcomes. This trial was registered at clinicaltrials.gov as NCT04347447.

Meals containing equivalent total protein from foods providing complete, complementary, or incomplete essential amino acid profiles do not differentially affect 24-hour skeletal muscle protein synthesis in healthy, middle-aged women.

BACKGROUND: Dietary protein quality can be assessed by skeletal muscle protein synthesis (MPS) stimulation. Limited knowledge exists on how consuming isonitrogenous meals with varied protein qualities affect postprandial and 24-h MPS. OBJECTIVE: We assessed the effects of protein quality and complementary proteins on MPS. We hypothesized that meals containing a moderate amount of high-quality, complete protein would stimulate postprandial and 24-h MPS. Meals with two complementary, plant-based incomplete proteins would stimulate MPS less, and meals with plant-based incomplete proteins at each meal, but complementary over 24 h would not stimulate MPS. DESIGN: This quasi-experimental study included a randomized, crossover design to assess protein quality and a non-randomized low-protein control. We measured postprandial and 24-h MPS responses of healthy middle-aged women (n=9, age 56±4 y), to three dietary conditions: isonitrogenous meals containing 23 g protein/meal from i) complete protein (lean beef); ii) two incomplete, but complementary protein sources (navy/black beans and whole wheat bread); and iii) single incomplete protein sources (black beans or whole wheat bread at a meal), but providing a complete amino acid profile over 24 h. In the low-protein group women (n=8, 54 ± 5 y) consumed a single breakfast meal containing 5 g of protein. Venous blood and vastus lateralis samples were obtained during primed, constant infusions of L-[ring-13C6] phenylalanine to measure mixed muscle fractional synthetic rates (FSR). RESULTS: Meals with complete, complementary, or incomplete proteins did not differentially influence FSR responses after breakfast (p=0.90) or 24 h (p=0.38). At breakfast, the complete (p=0.030) and complementary (p=0.031) protein meals, but not the incomplete protein meal (p=0.38), had greater FSR responses, compared to the low-protein control meal. CONCLUSIONS: Isonitrogenous meals containing a moderate serving of total protein from foods providing complete, complementary, or incomplete essential amino acid profiles do not differentially stimulate muscle protein synthesis after a meal and daily. CLINICAL TRIALS REGISTRY: This clinical trial was registered at clinicaltrials.gov as NCT03816579. URL:; https://www. CLINICALTRIALS: gov/ct2/show/NCT03816579?term=NCT03816579&draw=2&rank=1.

Mice Regulate Dietary Amino Acid Balance and Energy Intake by Selecting between Complementary Protein Sources.

BACKGROUND: A balanced intake of protein and constituent amino acids (AAs) requires adjustments to total food intake (protein leverage [PL]) and food selection to balance deficits and excesses (complementary feeding). We provided mice with choices of casein and whey, 2 protein sources that are complementary in AA balance, across a range of protein concentrations (P%) of digestible energy (DE). OBJECTIVES: We aimed to determine if: 1) PL operates similarly for casein and whey; 2) one protein source is preferred at control P%; 3) the preference changes as P% falls; and 4) AA intakes under control and low P% levels identify AAs that drive changes in protein selection. METHODS: Food intake and plasma fibroblast growth factor-21 (FGF21) concentrations were measured in mice at various P% (P7.5%-P33%). For direct comparisons, defined diets were used in which the protein source was either casein or whey. In food choice studies, mice had access to foods in which both casein and whey were provided at the same P% level at the same time. RESULTS: PL operated at different P% thresholds in casein (13%)- and whey (10%)-based diets, and the magnitude of PL was greater for casein. Although mice preferred casein under control conditions (P23%), a pronounced preference shift to whey occurred as P% fell to P13% and P10%. At low P%, increases in food intake were accompanied by increases in plasma FGF21, a protein hunger signal. Among AAs deficient in casein and enriched in whey, the intake of Cys was the most invariant as P% changed between P23% and P10%, appearing to drive the switch in protein preference. CONCLUSIONS: Mice selected between complementary protein sources, casein and whey, achieving stable total energy intake and regulated intake of AAs as P% varied. Supplementation of low P% casein diets with one whey-enriched AA, Cys, suppressed plasma FGF21 and total food intake.

A phenylalanine-free recombinant nutritional protein for the dietary management of phenylketonuria.

Phenylketonuria (PKU) is a congenital metabolic disorder that causes the systemic elevation of phenylalanine (Phe), which is neurotoxic and teratogenic. PKU is currently incurable, and management involves lifelong adherence to an unpalatable protein-restricted diet based on Phe-free amino acid mixtures. Seeking a palatable dietary alternative, we identified a Bacillus subtilis protein (GSP16O) with a well-balanced but low-Phe amino acid profile. We optimized the sequence and expressed a modified Phe-free version (GSP105) in Pseudomonas fluorescens, achieving yields of 20 g/L. The purified GSP105 protein has a neutral taste and smell, is highly soluble, and remains stable up to 80°C. Homozygous enu2 mice, a model of human PKU, were fed with diets containing either GSP105 or normal protein. The GSP105 diet led to normalization of blood Phe levels and brain monoamine neurotransmitter metabolites, and prevented maternal PKU. The GSP105 diet thus provides an alternative and efficacious dietary management strategy for PKU.

The cross-sectional association between dietary total, animal, and plant-based protein intake and the prevalence and severity of depressive symptoms in Dutch adults with type 2 diabetes: The Hoorn Diabetes Care System cohort.

OBJECTIVE: This study aimed to investigate cross-sectional associations of total, animal, and plant-based protein intake and depressive symptoms in Dutch adults with type 2 diabetes (T2D). METHODS: We included 1137 individuals with T2D (aged 68.6 ± 9.0) from the Hoorn Diabetes Care System cohort. Energy-adjusted protein intake was assessed using a validated Food Frequency Questionnaire. The nine-item Patient Health Questionnaire (PHQ-9) was used to assess the prevalence of depressive symptoms (PHQ-9 ≥ 10 and/or anti-depressant use) and the severity of depressive symptoms (continuous PHQ-9 score). Associations between total, animal, and plant-based protein (quartiles) with depressive symptoms were assessed using multiple logistic and linear regression. RESULTS: Highest intake of total, animal, and plant-based protein was not associated with the prevalence of depressive symptoms, compared to lowest intake (e.g., total protein, ORQ4vsQ1:0.75, 95%CI 0.42;1.32). For the severity of depressive symptoms, highest total protein intake was significantly associated with lower PHQ-9 scores (ORQ4vsQ1:0.87, 95%CI 0.75;1.00), compared to lowest intake. Animal protein was not associated with the severity of depressive symptoms (ߠ∼ 1), while the association for plant-based protein was marginally non-significant (ßQ4vsQ1:0.88, 95%CI 0.76;1.02). CONCLUSION: In individuals with T2D, higher total protein intake was associated with reduced severity of depressive symptoms, but not with the prevalence of depressive symptoms. Further prospective research with a larger sample size is needed to confirm these associations.

The comparison of total energy and protein intake relative to estimated requirements in chronic spinal cord injury.

In chronic spinal cord injury (SCI), individuals experience dietary inadequacies complicated by an understudied research area. Our objectives were to assess (1) the agreement between methods of estimating energy requirement (EER) and estimated energy intake (EEI) and (2) whether dietary protein intake met SCI-specific protein guidelines. Persons with chronic SCI (n = 43) completed 3-day food records to assess EEI and dietary protein intake. EER was determined with the Long and Institute of Medicine (IOM) methods and the SCI-specific Farkas method. Protein requirements were calculated as 0·8-1·0 g/kg of body weight (BW)/d. Reporting accuracy and bias were calculated and correlated to body composition. Compared with IOM and Long methods (P < 0·05), the SCI-specific method did not overestimate the EEI (P = 0·200). Reporting accuracy and bias were best for SCI-specific (98·9 %, -1·12 %) compared with Long (94·8 %, -5·24 %) and IOM (64·1 %, -35·4 %) methods. BW (r = -0·403), BMI (r = -0·323) and total fat mass (r = -0·346) correlated with the IOM reporting bias (all, P < 0·05). BW correlated with the SCI-specific and Long reporting bias (r = -0·313, P = 0·041). Seven (16 %) participants met BW-specific protein guidelines. The regression of dietary protein intake on BW demonstrated no association between the variables (ß = 0·067, P = 0·730). In contrast, for every 1 kg increase in BW, the delta between total and required protein intake decreased by 0·833 g (P = 0·0001). The SCI-specific method for EER had the best agreement with the EEI. Protein intake decreased with increasing BW, contrary to protein requirements for chronic SCI.

Cross-sectional relationship between dietary protein intake, energy intake and protein energy wasting in chronic kidney disease patients.

The potential threshold for dietary energy intake (DEI) that might prevent protein-energy wasting (PEW) in chronic kidney disease (CKD) is uncertain. The subjects were non-dialysis CKD patients aged ≥ 14 years who were hospitalised from September 2019 to July 2022. PEW was measured by subjective global assessment. DEI and dietary protein intake (DPI) were obtained by 3-d diet recalls. Patients were divided into adequate DEI group and inadequate DEI group according to DEI ≥ 30 or < 30 kcal/kg/d. Logistic regression analysis and restricted cubic spline were used in this study. We enrolled 409 patients, with 53·8 % had hypertension and 18·6 % had diabetes. The DEI and DPI were 27·63 (sd 5·79) kcal/kg/d and 1·00 (0·90, 1·20) g/kg/d, respectively. 69·2 % of participants are in the inadequate DEI group. Malnutrition occurred in 18·6 % of patients. Comparing with patients in the adequate DEI group, those in the inadequate DEI group had significantly lower total lymphocyte count, serum cholesterol and LDL-cholesterol and a higher prevalence of PEW. For every 1 kcal/kg/d increase in DEI, the incidence of PEW was reduced by 12·0 % (OR: 0·880, 95 % CI: 0·830, 0·933, P < 0·001). There was a nonlinear curve relationship between DEI and PEW (overall P < 0·001), and DEI ≥ 27·6 kcal/kg/d may have a preventive effect on PEW in CKD. Low DPI was also significantly associated with malnutrition, but not when DEI was adequate. Decreased energy intake may be a more important factor of PEW in CKD than protein intake.

Dietary amino acids and risk of stroke subtypes: a prospective analysis of 356,000 participants in seven European countries.

PURPOSE: Previously reported associations of protein-rich foods with stroke subtypes have prompted interest in the assessment of individual amino acids. We examined the associations of dietary amino acids with risks of ischaemic and haemorrhagic stroke in the EPIC study. METHODS: We analysed data from 356,142 participants from seven European countries. Dietary intakes of 19 individual amino acids were assessed using validated country-specific dietary questionnaires, calibrated using additional 24-h dietary recalls. Multivariable-adjusted Cox regression models were used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) of ischaemic and haemorrhagic stroke in relation to the intake of each amino acid. The role of blood pressure as a potential mechanism was assessed in 267,642 (75%) participants. RESULTS: After a median follow-up of 12.9 years, 4295 participants had an ischaemic stroke and 1375 participants had a haemorrhagic stroke. After correction for multiple testing, a higher intake of proline (as a percent of total protein) was associated with a 12% lower risk of ischaemic stroke (HR per 1 SD higher intake 0.88; 95% CI 0.82, 0.94). The association persisted after mutual adjustment for all other amino acids, systolic and diastolic blood pressure. The inverse associations of isoleucine, leucine, valine, phenylalanine, threonine, tryptophan, glutamic acid, serine and tyrosine with ischaemic stroke were each attenuated with adjustment for proline intake. For haemorrhagic stroke, no statistically significant associations were observed in the continuous analyses after correcting for multiple testing. CONCLUSION: Higher proline intake may be associated with a lower risk of ischaemic stroke, independent of other dietary amino acids and blood pressure.

Distribution of daily protein intake and appendicular skeletal muscle mass in healthy free-living Chinese older adults.

AIMS: Evidence regarding impact of protein intake distribution on skeletal muscle mass in older adults is limited and inconsistent. This study aims to investigate the relationship of evenness of dietary protein distribution and number of meals exceeding a threshold with appendicular skeletal muscle mass (ASM) in healthy and free-living Chinese older adults. METHODS: Repeated measured data of 5689 adult participants aged ≥ 60 years from the China Health and Nutrition Survey (CHNS) 2015 and 2018 waves were analyzed. Mixed-effects linear regression model was performed to examine the relationship between coefficient of variance (CV) of protein intake across meals, number of meals ≥ 0.4 g protein/kg BW and ASM, respectively. Analyses were conducted separately for male and female. RESULTS: The average CV of protein intake in each wave was in the range of 0.34-0.35. More than 40% male and female participants in each wave had no meal reaching 0.4 g protein/kg BW. Female participants in the highest quartile of protein intake CV had significantly lower ASM (ß = -0.18, 95%CI = -0.32, -0.04) compared with those in the lowest quartile, after adjustment for multiple confounders. Significant negative trends were observed across dietary protein CV quartiles with ASM both in male (P trend = 0.043) and female (P trend = 0.007). Significant positive association between number of meals exceeding 0.4 g protein /kg BW and relative ASM were observed in females (2 meals vs. 0 meal: ß = 0.003, 95%CI = 0.0007,0.006;≥3 meals vs. 0 meal: ß = 0.008, 95%CI = 0.003,0.013), after adjusting for multiple covariates. CONCLUSIONS: A more even-distributed protein intake pattern and more meals reaching protein intake threshold were respectively associated with higher appendicular skeletal muscle mass in healthy and free-living older Chinese adults. Prospective studies and intervention trials are needed to confirm these cross-sectional findings.

Association between plant and animal protein and biological aging: findings from the UK Biobank.

PURPOSE: This study aimed to evaluate the relationship between plant protein, animal protein and biological aging through different dimensions of biological aging indices. Then explore the effects of substitution of plant protein, animal protein, and their food sources on biological aging. METHODS: The data came from 79,294 participants in the UK Biobank who completed at least two 24-h dietary assessments. Higher Klemera-Doubal Method Biological Age (HKDM-BA), higher PhenoAge (HPA), higher allostatic load (HAL), and longer telomere length (LTL) were estimated to assess biological aging. Logistic regression was used to estimate protein-biological aging associations. Substitution model was performed to assess the effect of dietary protein substitutions. RESULTS: Plant protein intake was inversely associated with HKDM-BA, HPA, HAL, and positively associated with LTL (odds ratios after fully adjusting and comparing the highest to the lowest quartile: 0.83 (0.79-0.88) for HKDM-BA, 0.86 (0.72-0.94) for HPA, 0.90 (0.85-0.95) for HAL, 1.06 (1.01-1.12) for LTL), while animal protein was not correlated with the four indices. Substituting 5% of energy intake from animal protein with plant protein, replacing red meat or poultry with whole grains, and replacing red or processed meat with nuts, were negatively associated with HKDM-BA, HPA, HAL and positively associated with LTL. However, an inverse association was found when legumes were substituted for yogurt. Gamma glutamyltransferase, alanine aminotransferase, and aspartate aminotransferase mediated the relationship between plant protein and HKDM-BA, HPA, HAL, and LTL (mediation proportion 11.5-24.5%; 1.9-6.7%; 2.8-4.5%, respectively). CONCLUSION: Higher plant protein intake is inversely associated with biological aging. Although there is no association with animal protein, food with animal proteins displayed a varied correlation.

Dietary protein and blood pressure: an umbrella review of systematic reviews and evaluation of the evidence.

INTRODUCTION: This umbrella review aimed to investigate the evidence of an effect of dietary intake of total protein, animal and plant protein on blood pressure (BP), and hypertension (PROSPERO: CRD42018082395). METHODS: PubMed, Embase and Cochrane Database were systematically searched for systematic reviews (SRs) of prospective studies with or without meta-analysis published between 05/2007 and 10/2022. The methodological quality and outcome-specific certainty of evidence were assessed by the AMSTAR 2 and NutriGrade tools, followed by an assessment of the overall certainty of evidence. SRs investigating specific protein sources are described in this review, but not included in the assessment of the overall certainty of evidence. RESULTS: Sixteen SRs were considered eligible for the umbrella review. Ten of the SRs investigated total protein intake, six animal protein, six plant protein and four animal vs. plant protein. The majority of the SRs reported no associations or effects of total, animal and plant protein on BP (all "possible" evidence), whereby the uncertainty regarding the effects on BP was particularly high for plant protein. Two SRs addressing milk-derived protein showed a reduction in BP; in contrast, SRs investigating soy protein found no effect on BP. The outcome-specific certainty of evidence of the SRs was mostly rated as low. DISCUSSION/CONCLUSION: This umbrella review showed uncertainties whether there are any effects on BP from the intake of total protein, or animal or plant proteins, specifically. Based on data from two SRs with milk protein, it cannot be excluded that certain types of protein could favourably influence BP.

Do high-protein diets have the potential to reduce gut barrier function in a sex-dependent manner?

PURPOSE: Impaired gut barrier function is associated with systemic inflammation and many chronic diseases. Undigested dietary proteins are fermented in the colon by the gut microbiota which produces nitrogenous metabolites shown to reduce barrier function in vitro. With growing evidence of sex-based differences in gut microbiotas, we determined whether there were sex by dietary protein interactions which could differentially impact barrier function via microbiota modification. METHODS: Fermentation systems were inoculated with faeces from healthy males (n = 5) and females (n = 5) and supplemented with 0.9 g of non-hydrolysed proteins sourced from whey, fish, milk, soya, egg, pea, or mycoprotein. Microbial populations were quantified using fluorescence in situ hybridisation with flow cytometry. Metabolite concentrations were analysed using gas chromatography, solid phase microextraction coupled with gas chromatography-mass spectrometry and ELISA. RESULTS: Increased protein availability resulted in increased proteolytic Bacteroides spp (p < 0.01) and Clostridium coccoides (p < 0.01), along with increased phenol (p < 0.01), p-cresol (p < 0.01), indole (p = 0.018) and ammonia (p < 0.01), varying by protein type. Counts of Clostridium cluster IX (p = 0.03) and concentration of p-cresol (p = 0.025) increased in males, while females produced more ammonia (p = 0.02), irrespective of protein type. Further, we observed significant sex-protein interactions affecting bacterial populations and metabolites (p < 0.005). CONCLUSIONS: Our findings suggest that protein fermentation by the gut microbiota in vitro is influenced by both protein source and the donor's sex. Should these results be confirmed through human studies, they could have major implications for developing dietary recommendations tailored by sex to prevent chronic illnesses.

Dietary amino acid patterns and cardiometabolic risk factors among subjects with obesity; a cross-sectional study.

BACKGROUND: The prevalence of obesity is a growing global public health concern. Certain dietary amino acids have been shown to have a potential therapeutic role in improving metabolic syndrome parameters and body composition in individuals with obesity. However, some amino acids have been linked to an increased risk of cardiometabolic disorders. This cross-sectional study aims to investigate the association between dietary amino acid patterns and cardiometabolic risk factors in individuals with obesity. METHODS: This cross-sectional study included 335 participants with obesity (57.9% males and 41.5% females) from Tabriz and Tehran, Iran. The participants were between the ages of 20-50, with a body mass index (BMI) of 30 kg/m2 or higher, and free from certain medical conditions. The study examined participants' general characteristics, conducted anthropometric assessments, dietary assessments, and biochemical assessments. The study also used principal component analysis to identify amino acid intake patterns and determined the association between these patterns and cardiometabolic risk factors in individuals with obesity. RESULTS: Upon adjusting for potential confounders, the study found that individuals in the third tertiles of pattern 1 and 2 were more likely to have lower LDL levels (OR = 0.99 and 95% CI (0.98-0.99)) for both. Additionally, a significant decrease in total cholesterol was observed in the third tertiles of pattern 2 in model II (OR = 0.99, 95% CI (0.98-0.99)). These findings suggest a potential cardioprotective effect of these amino acid patterns in managing cardiometabolic risk factors in individuals with obesity. CONCLUSIONS: This study found that two identified amino acid patterns were associated with lower serum LDL and total cholesterol levels, while a third pattern was associated with higher serum triglycerides. The specific amino acids contributing to these patterns highlight the importance of targeted dietary interventions in managing cardiometabolic risk factors in individuals with obesity.

Screening for protein energy wasting in children with chronic kidney disease using dual energy x-ray absorptiometry as an additional tool.

BACKGROUND: The current diagnosis of protein energy wasting (PEW) is based on scoring systems that lack precision in measuring muscle deficits. We undertook this cross-sectional study to determine the prevalence of PEW in children with chronic kidney disease (CKD) using a scoring system that included dual energy x-ray absorptiometry (DEXA) for measuring lean body mass (LBM) and to determine the prevalence of selected markers in PEW. METHODS: Thirty CKD and 20 healthy children (1-18 years) were evaluated for (1) reduced dietary protein intake (DPI); (2) BMI < fifth centile for height age (BMI/HA); (3) serum albumin < 3.8 g/dl, cholesterol < 100 mg/dl, or CRP > 3 mg/L; (4) LBM < fifth centile for height age [LBMr] on DEXA. PEW was scored as minimal-one parameter positive in 2/4 categories; standard-one parameter positive in 3/4 categories; or modified-standard plus height < 2 SD. RESULTS: Twenty children with CKD (66.7%) had PEW, (5/9) 55% in CKD 3, and (15/21) 71% in advanced CKD; minimal 12, standard 1, and modified 7. LBMr was seen in 20 (100%), reduced DPI in 16 (80%), and BMI/HA in 6 (30%) children with PEW. LBMr had 100% sensitivity and BMI/HA 100% specificity. LBMr was seen in 8 who had no other criteria for PEW. None of the parameters were positive in controls (p < 0.01). CONCLUSIONS: PEW prevalence in CKD was high. Both prevalence and severity were higher in advanced CKD. LBMr was a highly sensitive marker to detect PEW. LBMr seen in some children with CKD who were negative for other markers could represent subclinical PEW.

Interactive effects of water temperature and dietary protein on Nile tilapia: growth, immunity, and physiological health.

Optimizing fish performance depends on several factors, with dietary protein levels and rearing temperature playing important roles. In this study, Nile tilapia fingerlings (Oreochromis niloticus) weighing an average of 20.00 ± 1.26 g were divided into nine groups (in three replicates). Each group was subjected to different water temperatures (26 °C, 28 °C, and 30 °C) and received one of three dietary protein levels (20%, 25%, and 30%) for two months. Our findings indicate that higher temperatures, particularly at 30 °C, increased water electrical conductivity and total dissolved salts, especially noticeable in fish fed 25% or 30% crude protein (CP). Lower total ammonia nitrogen levels were observed at 28 °C with 25% CP, 30 °C with 30% CP, and 26 °C with 30% CP. Hepatic growth hormone receptor 1 and insulin-like growth factor 1 expression gradually rose with higher dietary CP percentages in fish at 26 °C but declined in those at 30 °C, albeit remaining higher than in the 28 °C groups with 25% CP. Fish at 28 °C showed the best final body weights and growth performance when fed 20% or 25% CP, with no significant difference between these groups. Hepatic leptin expression did not differ significantly among groups, but hepatic fatty acid binding protein expression notably increased in fish fed 30% CP at both 26 °C and 30 °C compared to those at 28 °C with 25% CP. Within the same temperature group, fish fed 30% CP exhibited higher globulin levels, particularly thriving at 28 °C or 30 °C. Hepatic mucin-like protein expression significantly increased across all groups, especially in fish at 30 °C with 30% CP compared to those at 28 °C with 25% CP. Hepatic lysozyme expression also increased notably in fish at 30 °C with 30% CP. Notable changes in superoxide dismutase, catalase, and glutathione peroxidase expression were observed, with the highest serum superoxide dismutase and catalase activities recorded in fish at 30 °C with 25% CP. Overall, dietary protein levels of 25% and 30%, combined with temperatures of 28 °C and 30 °C, yielded favorable outcomes, particularly favoring 28 °C with 25% protein.

Not feeling the heat? Effects of dietary protein on satiation and satiety in mice are not due to its impact on body temperature.

Dietary protein modulates food intake (FI) via unclear mechanism(s). One possibility is that higher protein leads to greater post-ingestive heat production (Specific dynamic action: SDA) leading to earlier meal termination (increased satiation), and inhibition of further intake (increased satiety). The influence of dietary protein on feeding behaviour in C57BL/6J mice was tested using an automated FI monitoring system (BioDAQ), simultaneous to body temperature (Tb). Total FI, inter meal intervals (IMI, satiety) and meal size (MS, satiation) were related to changes in Tb after consuming low (5%, LP), moderate (15%, MP) and high (30%, HP) protein diets. Diets were tested over three conditions: 1) room temperature (RT, 21 ± 1 °C), 2) room temperature and running wheels (RTRW) and 3) low temperature (10 °C) and running wheels (LTRW). The differences between diets and conditions were also compared using mixed models. Mice housed at RT fed HP diet, reduced total FI compared with LP and MP due to earlier meal termination (satiation effect). FI was lowered in RTRW conditions with no differences between diets. FI significantly increased under LTRW conditions for all diets, with protein content leading to earlier meal termination (satiation) but not the intervals between feeding bouts (satiety). Tb fell immediately after feeding in all conditions. Despite a reduction in total FI in mice fed HP, mediated via increased satiation, this effect was not linked to increased Tb during meals. We conclude effects of dietary protein on intake are not mediated via SDA and Tb.