The effect of in vitro simulated colonic pH gradients on microbial activity and metabolite production using common prebiotics as substrates.

BACKGROUND: The interplay between gut microbiota (GM) and the metabolization of dietary components leading to the production of short-chain fatty acids (SCFAs) is affected by a range of factors including colonic pH and carbohydrate source. However, there is still only limited knowledge on how the GM activity and metabolite production in the gastrointestinal tract could be influenced by pH and the pH gradient increases along the colon. RESULTS: Here we investigate the effect of pH gradients corresponding to levels typically found in the colon on GM composition and metabolite production using substrates inulin, lactose, galactooligosaccharides (GOS), and fructooligosaccharide (FOS) in an in vitro colon setup. We investigated 3 different pH regimes (low, 5.2 increasing to 6.4; medium, 5.6 increasing to 6.8 and high, 6.0 increasing to 7.2) for each fecal inoculum and found that colonic pH gradients significantly influenced in vitro simulated GM structure, but the influence of fecal donor and substrate was more pronounced. Low pH regimes strongly influenced GM with the decreased relative abundance of Bacteroides spp. and increased Bifidobacterium spp. Higher in vitro simulated colonic pH promoted the production of SCFAs in a donor- and substrate-dependent manner. The butyrate producer Butyricimonas was enriched at higher pH conditions, where also butyrate production was increased for inulin. The relative abundance of Phascolarctobacterium, Bacteroides, and Rikenellaceae also increased at higher colonic pH, which was accompanied by increased production of propionate with GOS and FOS as substrates. CONCLUSIONS: Together, our results show that colonic substrates such as dietary fibres influence GM composition and metabolite production, not only by being selectively utilized by specific microbes, but also because of their SCFA production, which in turn also influences colonic pH and overall GM composition and activity. Our work provides details about the effect of the gradients of rising pH from the proximal to distal colon on fermenting dietary substrates in vitro and highlights the importance of considering pH in GM research.

Maillard reaction products and metabolite profile of plant-based meat burgers compared with traditional meat burgers and cooking-induced alterations.

We are undergoing a food transformation with the introduction of plant-based meat analogues, but little is known about their chemical characteristics. This study aimed to elucidate the Maillard reactions in plant-based meat burger alternatives (PBMBA). For this purpose, NMR-based metabolomics and targeted MS analysis of Maillard and dehydroalanine pathway markers were conducted on six PBMBA prototypes with different proportions of high-moisture protein extrudates, low-moisture extrudates and pea protein on a commercial PBMBA and on a meat burger before and after cooking. Results revealed that higher levels of Maillard reaction markers were present in PBMBAs in the uncooked state, with lower levels formed during cooking compared with conventional meat. The metabolite profile disclosed that the distinct pattern of the Maillard reaction could be attributed to different substrate availability, but data also revealed that pre-processing of the plant protein affects the presence of Maillard reaction products in PBMBAs.

Changes in Plasma, Urine, and Fecal Metabolome after 16 Weeks of Consuming Dairy With Different Food Matrixes - A Randomized Controlled Trial.

SCOPE: Understanding the mode-of-action by which fermented dairy consumption influences health is of interest. The aim of this study is to elucidate the impact of the chemical-physical properties of the dairy matrix and postbiotic effects on the metabolomics response to fermented dairy consumption. METHODS AND RESULTS: Hundred males (Body Mass Index (BMI) 28.0-45.0 kg m-2, waist circumference ≥ 102 cm) are included in the study. During a 16-week intervention, the study subjects are instructed to consume 400 g per day of either 1) milk, 2) yogurt, 3) heat-treated yogurt, or 4) chemically acidified milk as part of their habitual diet. Nuclear Magnetic Resonance (NMR)-based metabolomics is conducted on plasma, urine, and fecal samples collected before and after the intervention. Both consumption of acidified milk and heat-treated yogurt resulted in changes in the fecal metabolome including decreases in the level of amino acids (leucine, valine, and threonine), and the branched-chain fatty acid (BCFA) isobutyrate that indicated an altered protein putrefaction, and proteolytic metabolism in the gut. In the plasma metabolome, an increased citrate is found for yogurt consumption. No difference in the urine metabolome is found. CONCLUSIONS: Our metabolomics analyses indicate that consumption of heat-treated yogurt and acidified milk exerted similar effects on the metabolic activity in the gut as yogurt consumption.

Acute changes in the metabolome following resistance exercise combined with intake of different protein sources (cricket, pea, whey).

INTRODUCTION: Separately, both exercise and protein ingestion have been shown to alter the blood and urine metabolome. This study goes a step further and examines changes in the metabolome derived from blood, urine and muscle tissue extracts in response to resistance exercise combined with ingestion of three different protein sources. METHODS: In an acute parallel study, 52 young males performed one-legged resistance exercise (leg extension, 4 × 10 repetitions at 10 repetition maximum) followed by ingestion of either cricket (insect), pea or whey protein (0.25 g protein/kg fat free mass). Blood and muscle tissue were collected at baseline and three hours after protein ingestion. Urine was collected at baseline and four hours after protein ingestion. Mixed-effects analyses were applied to examine the effect of the time (baseline vs. post), protein (cricket, pea, whey), and time x protein interaction. RESULTS: Nuclear magnetic resonance (NMR)-based metabolomics resulted in the annotation and quantification of 25 metabolites in blood, 35 in urine and 21 in muscle tissue. Changes in the muscle metabolome after combined exercise and protein intake indicated effects related to the protein source ingested. Muscle concentrations of leucine, methionine, glutamate and myo-inositol were higher after intake of whey protein compared to both cricket and pea protein. The blood metabolome revealed changes in a more ketogenic direction three hours after exercise reflecting that the trial was conducted after overnight fasting. Urinary concentration of trimethylamine N-oxide was significantly higher after ingestion of cricket than pea and whey protein. CONCLUSION: The blood, urine and muscle metabolome showed different and supplementary responses to exercise and ingestion of the different protein sources, and in synergy the summarized results provided a more complete picture of the metabolic state of the body.

1H-NMR based-metabolomics reveals alterations in the metabolite profiles of chickens infected with ascarids and concurrent histomonosis infection.

BACKGROUND: Gut infections of chickens caused by Ascaridia galli and Heterakis gallinarum are associated with impaired host performance, particularly in high-performing genotypes. Heterakis gallinarum is also a vector of Histomonas meleagridis that is often co-involved with ascarid infections. Here, we provide a first insight into the alteration of the chicken plasma and liver metabolome as a result of gastrointestinal nematode infections with concomitant histomonosis. 1H nuclear magnetic resonance (1H-NMR) based-metabolomics coupled with a bioinformatics analysis was applied to explore the variation in the metabolite profiles of the liver (N = 105) and plasma samples from chickens (N = 108) experimentally infected with A. galli and H. gallinarum (+H. meleagridis). This was compared with uninfected chickens at different weeks post-infection (wpi 2, 4, 6, 10, 14, 18) representing different developmental stages of the worms. RESULTS: A total of 31 and 54 metabolites were quantified in plasma and aqueous liver extracts, respectively. Statistical analysis showed no significant differences (P > 0.05) in any of the 54 identified liver metabolites between infected and uninfected hens. In contrast, 20 plasma metabolites including, amino acids, sugars, and organic acids showed significantly elevated concentrations in the infected hens (P < 0.05). Alterations of plasma metabolites occurred particularly in wpi 2, 6 and 10, covering the pre-patent period of worm infections. Plasma metabolites with the highest variation at these time points included glutamate, succinate, trimethylamine-N-oxide, myo-inositol, and acetate. Differential pathway analysis suggested that infection induced changes in (1) phenylalanine, tyrosine, and tryptophan metabolism, (2) alanine, aspartate and glutamate metabolism; and 3) arginine and proline metabolism (Pathway impact > 0.1 with FDR adjusted P-value < 0.05). CONCLUSION: In conclusion, 1H-NMR based-metabolomics revealed significant alterations in the plasma metabolome of high performing chickens infected with gut pathogens-A. galli and H. gallinarum. The alterations suggested upregulation of key metabolic pathways mainly during the patency of infections. This approach extends our understanding of host interactions with gastrointestinal nematodes at the metabolic level.

Inulin Supplementation Modulates the Hepatic Transcriptome, Metabolome, and Ferritin Content in Ovariectomized Rats.

SCOPE: Liver is an important metabolic organ regulating whole-body homeostasis. This study aims to investigate how prebiotic-induced changes in the metabolic activity of the gut microbiome (GM) and dietary calcium depletion modulates the hepatic metabolome and transcriptome. METHODS AND RESULTS: The serum metabolome, liver metabolome, and transcriptome are determined on samples from ovariectomized (OVX) rats fed a control diet (Control, n = 7), a control diet supplemented with 5% w/w inulin (Inulin, n = 7), or a calcium-deficient diet (CaDef, n = 7). Inulin fortification is associated with higher serum concentrations of acetate, 3-hydroxybutyrate, and reduced concentration of dimethyl sulfone, revealing that changes in the metabolic activity of the GM are reflected in circulating metabolites. Metabolomics also reveal that the inulin-fortified diet results in lower concentrations of hepatic glutamate, serine, and hypoxanthine while transcriptomics reveal accompanying effects on the hepatic expression of ferric iron binding-related genes. Inulin fortification also induces effects on the hepatic expression of genes involved in olfactory transduction, suggesting that prebiotics regulate liver function through yet unidentified mechanisms involving olfactory receptors. CONCLUSION: Inulin ingestion impacts hepatic gene expression and is associated with an upregulation of ferritin synthesis-related genes and liver ferritin content.

NMR foodomics in the assessment of diet and effects beyond nutrients.

PURPOSE OF REVIEW: This review provides an overview of most recent research studies employing nuclear magnetic resonance (NMR)-based metabolomics in the assessment of effects of diet and food ingestion. RECENT FINDINGS: NMR metabolomics is a useful tool in the elucidation of specific diets, for example, the Mediterranean diet, the New Nordic diet types, and also for comparing vegan, vegetarian and omnivore diets where specific diet-linked metabolite perturbations have been identified. Another core area where NMR metabolomics is employed involves research focused on examining specific food components or ingredients, including dietary fibers and other functional components. In several cases, NMR metabolomics has aided to document how specific food components exert effects on the metabolic activity of the gut microbiota. Research has also demonstrated the potential use of NMR metabolomics in assessing diet quality and interactions between specific food components such as meat and diet quality. The implications of these findings are important as they address that background diet can be decisive for if food items turn out to exert either harmful or health-promoting effects. SUMMARY: NMR metabolomics can provide important mechanistic insight and aid to biomarker discovery with implications for compliance and food registration purposes.

Influence of protein source (cricket, pea, whey) on amino acid bioavailability and activation of the mTORC1 signaling pathway after resistance exercise in healthy young males.

PURPOSE: New dietary proteins are currently introduced to replace traditional animal protein sources. However, not much is known about their bioaccessibility and ability to stimulate muscle protein synthesis compared to the traditional protein sources. We aimed to compare effects of ingesting a protein bolus (0.25 g/kg fat free mass) of either cricket (insect), pea, or whey protein on circulating amino acid levels and activation of the mTORC1 signaling pathway in the skeletal muscle at rest and after exercise. METHODS: In a randomized parallel controlled trial, young males (n = 50) performed a one-legged resistance exercise followed by ingestion of one of the three protein sources. Blood samples were collected before and in the following 4 h after exercise. Muscle biopsies were obtained at baseline and after 3 h from the non-exercised and exercised leg. RESULTS: Analysis of blood serum showed a significantly higher concentration of amino acids after ingestion of whey protein compared to cricket and pea protein. No difference between protein sources in activation of the mTORC1 signaling pathway was observed either at rest or after exercise. CONCLUSION: Amino acid blood concentration after protein ingestion was higher for whey than pea and cricket protein, whereas activation of mTORC1 signaling pathway at rest and after exercise did not differ between protein sources. TRIAL REGISTRATION NUMBER: Clinicaltrials.org ID NCT04633694.

Hepatic PGC-1α has minor regulatory effect on the liver transcriptome and metabolome during high fat high fructose diet and exercise training.

The prevalence of non-alcoholic fatty liver diseases (NAFLD) has reached epidemic levels during recent years and a major driver of NAFLD are diets high in fat and fructose. A common practice in the treatment of NAFLD are life-style interventions including for example increased physical activity. The transcriptional coactivator peroxisome proliferator-activated receptor gamma coactivator 1α (PGC-1α) has been shown to be central in mediating the beneficial effects of exercise training by regulating the expression of key metabolic genes. However, the significance of hepatic PGC-1α for high fat high fructose (HFFD) induced changes in gene expression and metabolites associated with NAFLD has not been elucidated. Therefore the aim of the present study was to investigate the effect of hepatic PGC-1α on HFFD and exercise-induced changes in the hepatic transcriptome and metabolome in mice. Using gene-arrays and 1H NMR spectroscopy, the liver transcriptome and metabolome of liver-specific PGC-1α knock-out mice receiving either standard chow, HFFD or HFFD + exercise (HFFD + Ex) were determined. In total 122 genes were identified as differently expressed in mice receiving HFFD for 13 weeks compared to chow, while the loss of hepatic PGC-1α only had very minor effects on the transcriptome. The same was observed for the liver metabolome. The effect of 4 weeks exercise training in combination with 13 weeks of HFFD, had small effects on the transcriptome and metabolome compared to HFFD alone. Together our results highlight a minor regulatory effect of hepatic PGC-1α on the liver transcriptome during high fat high fructose diet and exercise training.

NMR-Based Metabolomics to Decipher the Molecular Mechanisms in the Action of Gut-Modulating Foods.

Metabolomics deals with uncovering and characterizing metabolites present in a biological system, and is a leading omics discipline as it provides the nearest link to the biological phenotype. Within food and nutrition, metabolomics applied to fecal samples and bio-fluids has become an important tool to obtain insight into how food and food components may exert gut-modulating effects. This review aims to highlight how nuclear magnetic resonance (NMR)-based metabolomics in food and nutrition science may help us get beyond where we are today in understanding foods' inherent, or added, biofunctionalities in relation to gut health.

The Diurnal Blood Metabolome and Effects of Vitamin D Supplementation: A Randomised Crossover Trial in Postmenopausal Women.

A way to maintain an adequate vitamin D status is through supplementation. Demonstration of blood-metabolome rhythmicity of vitamin D3 post-dosing effects is lacking in the pharmaco-metabonomics area. Thus, the overall aim of this study was to investigate the diurnal changes in the blood metabolome and how these are affected by vitamin D3 supplementation. The study was conducted as a crossover study, and the treatment included 200 µg (8000 IU) of vitamin D3 as compared with placebo with a washout period of at least 10 days. The participants were postmenopausal women aged 60−80 years (N = 29) with vitamin D insufficiency (serum 25-hydroxyvitamin D < 50 nmol/L) but otherwise healthy. During the intervention day, blood samples were taken at 0 h, 2 h, 4 h, 6 h, 8 h, 10 h, 12 h, and 24 h, and plasma was analysed by proton nuclear magnetic resonance (NMR) spectroscopy as a metabolomics approach. In general, diurnal effects were identified for the majority of the 20 quantified metabolites, and hierarchical cluster analysis revealed a change in the overall plasma metabolome around 12 AM (6 h after intervention), suggesting that the diurnal rhythm is reflected in two diurnal plasma metabolomes; a morning metabolome (8−12 AM) and an afternoon/evening metabolome (2−8 PM). Overall, the effect of vitamin D supplementation on the blood metabolome was minor, with no effect on the diurnal rhythm. However, a significant effect of the vitamin D supplementation on plasma acetone levels was identified. Collectively, our findings reveal an influence of diurnal rhythm on the plasma metabolome, while vitamin D supplementation appears to have minor influence on fluctuations in the plasma metabolome.

Yogurt Benefits Bone Mineralization in Ovariectomized Rats with Concomitant Modulation of the Gut Microbiome.

SCOPE: Evidence supports that gut-modulating foods potentially can suppress bone loss in postmenopausal women. This study aims to investigate the effect of milk calcium-enriched milk, yogurt, and yogurt-inulin combination on the gut-bone association. METHODS AND RESULTS: A 6-week intervention study is conducted in ovariectomized rats. Four pastes containing milk calcium-fortified milk (M-Ca), milk calcium-fortified yogurt (Y-Ca), inulin-fortified Y-Ca (Y-I-Ca), or an isoconcentration of calcium carbonate (Ca-N), and a calcium-deficient paste are provided. M-Ca does not influence bone mineral density and content (BMD and BMC), femur mechanical strength, or femoral microstructure compared to Ca-N, but Y-Ca increases spine BMD. The serum metabolome reveals that Y-Ca modulated glycine-related pathways with reduced glycine, serine, and threonine. No additive effects of yogurt and inulin are found on bone parameters. Correlation analysis shows that increased lactobacilli and reduced Clostridiaceae members in Y-Ca is associated with an increased spine BMD. Increases in Bifidobacterium pseudolongum, Turicibacter, Blautia, and Allobaculum and gut short-chain fatty acids in Y-I-Ca are not reflected in bone parameters. CONCLUSION: Yogurt as calcium vehicle contributes to increased spine BMD concomitant with changes in the gut microbiome and glycine-related pathways, while adding inulin to yogurt does not affect bone mineralization in ovariectomized rats.

Effects of Calcium Source, Inulin, and Lactose on Gut-Bone Associations in an Ovarierectomized Rat Model.

SCOPE: Osteoporosis poses a health challenge especially for postmenopausal women. This study aims to explore nutritional strategies to counteract bone demineralization in ovarierectomized (OVX) rats. METHODS AND RESULTS: OVX rats (n = 49) are fed with one of six different diets, where two different calcium sources (dairy calcium or calcium carbonate) are provided alone or in combination with either inulin (5%) or lactose (0.5%). In addition, a calcium-deficient diet is included. Calcium supplementation increases intestinal concentrations of short-chain fatty acids (SCFAs) and the abundance of fecal Acinetobacter and Propionibacterium. Accompanied with these effects, rats fed with calcium-fortified diets have higher bone mineral density, bone mineral content and femur mechanical strength, lower serum levels of bone markers, and lower expression of calcium absorption-related genes (transient receptor potential vanilloid type 6 (TRPV6), calcium-binding protein (CaBP) compared with control. Inulin supplementation results in a markedly increased production of intestinal SCFAs, a decreased intestinal pH, an increased abundance of Allobaculum and Bifidobacterium, and an increased expression of Trpv6. Inulin and lactose show beneficial effects on spine bone. CONCLUSION: Calcium modulates gut microbiome composition and function. A pronounced effect of inulin on metabolic activity in the gastrointestinal tract is evident, and lactose supplementation decreases jejunal pH that might be associated with slightly enhanced bone mineralization.

Fluctuations in Metabolites and Bone Markers Across the Menstrual Cycle in Eumenorrheic Women and Oral Contraceptive Users.

CONTEXT: Little is known about changes in circulating metabolites during the menstrual cycle and how use of oral contraceptives (OCs) affects these changes. OBJECTIVES: To study fluctuations in circulating metabolite and bone marker levels during the menstrual/pill cycle in eumenorrheic women and OC users. METHODS: Plasma samples were collected from 28 eumenorrheic women and 10 OC users at 7 to 9 time points across a menstrual/pill cycle. Longitudinal and cross-sectional analyses were performed to examine the cycle- and OC-induced variations in the plasma metabolite and bone turnover marker levels. RESULTS: In eumenorrheic women, plasma levels of alanine, glutamine, threonine, and tyrosine varied significantly across the menstrual cycle, and all dropped to the lowest level around day 21 of the menstrual cycle. These amino acid concentrations were negatively correlated with fluctuations in progesterone and/or estrogen levels. A between-group analysis showed that plasma levels of alanine, glutamine, glycine, proline, and tyrosine were lower in OC users than in nonusers. Concomitantly, plasma C-terminal telopeptide of type I collagen (CTX) and N-terminal propeptide of type I procollagen (PINP) levels were lower in OC users. Intriguingly, when all data were pooled, variations in CTX and PINP levels were positively correlated with fluctuations in proline and glycine concentrations (r > 0.5 or 0.3 < r < 0.5, P < 0.05). CONCLUSIONS: The menstrual cycle and the use of OCs alter plasma levels of metabolites and bone turnover markers in young women. While the impact of these findings remains to be established, the lower glycine level among OC users and the accompanying lower CTX level supports that the use of OCs lowers collagen turnover in young women and may thereby have long-term implications for bone health among OC users.

Dual nuclear magnetic resonance for probing intrinsic bone structure and a potential gut-bone axis in ovariectomized rats.

Currently, the existence of a gut-bone axis receives massive attention, and while sound premises and indirect proofs exist for the gut-bone axis concept, few studies have provided actual data linking the gut and bone physically. This study aimed to exploit the versatile nature of nuclear magnetic resonance (NMR) to link NMR relaxometry data on bone mineralization with NMR spectroscopic profiling of gut metabolites. For this purpose, sample material was obtained from a 6-week intervention study with ovariectomized (OVX) rats (n = 49) fed with seven different diets varying in calcium content (0.2-6.0 mg/kg) and prebiotic fiber content (0-5.0% w/w). This design ensured a span in (i) calcium available for bone mineralization and (ii) metabolic activity in the gut. After termination of the intervention, longitudinal (T1 ), transverse (T2 ) relaxation, and mechanical bone strength were measured on the excised femur bones. A PLS model with high predictability (Q2 = 0.86, R2 = 0.997) was demonstrated between T2 decay curves and femur mechanical strength. Correlations were established between bone T2 populations and gut short-chain fatty acids. In conclusion, the present dual NMR approach showed strong correlation between T2 relaxation and mechanical strength of the bone, and when metabolic activity in the gut was modulated by inulin, the potential existence of a gut-bone axis was demonstrated.

Effect of Dairy Matrix on the Postprandial Blood Metabolome.

This study investigated the postprandial plasma metabolome following consumption of four dairy matrices different in texture and structure: cheddar cheese (Cheese), homogenized cheddar cheese (Hom. Cheese), and micellar casein isolate (MCI) with cream (MCI Drink) or a MCI Gel. An acute, randomized, crossover trial in male participants (n = 25) with four test days was conducted. Blood samples were collected during an 8-h postprandial period after consumption of a meal similar in micro- and macronutrients containing one of the four dairy matrices, and the metabolome was analyzed using nuclear magnetic resonance (NMR) spectroscopy. A liquid dairy matrix (MCI Drink) resulted in a faster absorption of amino acids compared to products, representing either a semi-solid (MCI Gel and Hom. Cheese) or solid (Cheese) dairy matrix. For the MCI Gel, plasma concentration of acetic acid and formic acid increased approximately 2 h following consumption, while 3-hydroxybyturate and acetoacetic acid increased approximately 6 h after consumption. The structure and texture of the dairy matrix affected the postprandial absorption of amino acids, as revealed by the plasma metabolome. Our study furthermore pointed at endogenous effects associated with consumption of dairy products containing glucono-δ-lactone.

Chemically acidified, live and heat-inactivated fermented dairy yoghurt show distinct bioactive peptides, free amino acids and small compounds profiles.

Previous studies found variations in the health-promoting effects of consuming different dairy products. This study aims at investigating the chemical composition of microbial fermented yogurt, chemically acidified yogurt and whole milk to understand the differences in the effects these products exert on human health. For this purpose, peptides and small compounds present in the products were examined using a combination of liquid chromatography mass spectrometry and nuclear magnetic resonance spectroscopic techniques. Results revealed that each product had its own characteristic peptide, free amino acid and small compound profile, and database search for bioactivity disclosed that fermented yogurt manufactured using a starter culture is associated with a higher bioactivity potential than chemically acidified yogurt or whole milk. Additional cold storage (14 days) further enhances the bioactivity potential of fermented yogurt while heat-inactivation, ensuring long shelf-life, modulates the proteins available for proteolysis and thereby the peptide profile generated.

Krill Protein Hydrolysate Provides High Absorption Rate for All Essential Amino Acids-A Randomized Control Cross-Over Trial.

BACKGROUND: adequate protein intake is essential to humans and, since the global demand for protein-containing foods is increasing, identifying new high-quality protein sources is needed. In this study, we investigated the acute postprandial bioavailability of amino acids (AAs) from a krill protein hydrolysate compared to a soy and a whey protein isolate. METHODS: the study was a randomized, placebo-controlled crossover trial including ten healthy young males. On four non-consecutive days, volunteers consumed water or one of three protein-matched supplements: whey protein isolate, soy protein isolate or krill protein hydrolysate. Blood samples were collected prior to and until 180 min after consumption. Serum postprandial AA concentrations were determined using 1H NMR spectroscopy. Hunger and satiety were assessed using visual analogue scales (VAS). RESULTS: whey and krill resulted in significantly higher AA concentrations compared to soy between 20-60 min and 20-40 min after consumption, respectively. Area under the curve (AUC) analyses revealed that whey resulted in the highest postprandial serum concentrations of essential AAs (EAAs) and branched chain AAs (BCAAs), followed by krill and soy, respectively. CONCLUSIONS: krill protein hydrolysate increases postprandial serum EAA and BCAA concentrations in a superior manner to soy protein isolate and thus might represent a promising future protein source in human nutrition.

Partial Substitution of Meat with Insect (Alphitobius diaperinus) in a Carnivore Diet Changes the Gut Microbiome and Metabolome of Healthy Rats.

Insects are suggested as a sustainable protein source of high nutritional quality, but the effects of insect ingestion on processes in the gastrointestinal tract and gut microbiota (GM) remain to be established. We examined the effects of partial substitution of meat with insect protein (Alphitobius diaperinus) in a four-week dietary intervention in a healthy rat model (n = 30). GM composition was characterized using' 16S rRNA gene amplicon profiling while the metabolomes of stomach, small intestine, and colon content, feces and blood were investigated by 1H-NMR spectroscopy. Metabolomics analyses revealed a larger escape of protein residues into the colon and a different microbial metabolization pattern of aromatic amino acids when partly substituting pork with insect. Both for rats fed a pork diet and rats fed a diet with partial replacement of pork with insect, the GM was dominated by Lactobacillus, Clostridium cluster XI and Akkermansia. However, Bray-Curtis dissimilarity metrics were different when insects were included in the diet. Introduction of insects in a common Western omnivore diet alters the gut microbiome diversity with consequences for endogenous metabolism. This finding highlights the importance of assessing gastrointestinal tract effects when evaluating new protein sources as meat replacements.