Fish-derived proteins and their potential to improve human health

Molecular Localization of Health-Promoting Peptides Derived from Fish Protein Hydrolyzates on Fish Muscle Proteins

The four previously reported health-promoting dipeptides, valine-tyrosine, lysine-tryptophan, methionine-phenylalanine, and arginine-isoleucine, found in the fish muscle hydrolyzates, were mainly located in the myosin subfragment-1 heavy chain, whereas the health-promoting tripeptide, alanine-lysine-lysine, was found in the fibrous rod consisting of the myosin subfragment-2 and light meromyosin with a regular coiled-coil structure of α-helix, irrespective of the fish species. Furthermore, the localization of these peptides either in the random coil, β-sheet, or α-helix was also examined in the three-dimensional image, showing no specific tendency. Surprisingly, the same trend was observed even for the mammalian rabbit fast muscle myosin heavy chain. Since a trade-off between myofibrillar ATPase and structural stability has been reported for fish living at low environmental temperatures, it is speculated that fish muscle proteins, when ingested, are easily digested by various proteases in the human digestive tract and provide various health-promoting peptides also in vivo. While fish actin contained only two dipeptides, methionine-phenylalanine and valine-tyrosine, glyceraldehyde 3-phosphate dehydrogenase, one of the major components of fish muscle water-soluble protein, contained all of the four dipeptides and one tripeptide mentioned above.

Fish - a scoping review for Nordic Nutrition Recommendations 2023

The aim of this scoping review was to conduct evidence-based documentation between fish intake and health outcomes for food-based dietary guidelines (FBDGs) in the Nordic Nutrition Recommendations (NNR) 2023. For most health outcomes, the evidence for fish oil and n-3 long chain (LC) polyunsaturated fatty acids (PUFA) supplementation was included when examining evidence between fish intake and health. In this review, conclusions from qualified systematic reviews (qSR) approved by NNR2023 are included. In addition, conclusions of a de novo systematic reviews on the topic of n-3 LC-PUFA, asthma, and allergy are included. Finally, a systematic literature search was performed limited to systematic reviews and meta-analysis published between 2011 and September 2021. In total, 21 papers from the systematic literature search, four qSR, and eight reports were included addressing the association between fish intake, fish oil, and n-3 LC-PUFA supplementation on several health outcomes. These included cardiovascular disease (CVD), type 2 diabetes, cancers (colorectal, breast, and prostate), metabolic syndrome, obesity, mortality, cognition and mental health, pregnancy-related outcomes (preterm birth and birth weight), and outcomes specific for children (neurodevelopment, and risk of food allergies, and asthma). In addition, intermediate risk factors such as blood lipids, glucose, C-reactive protein, and blood pressure were reviewed. Based on current evidence, fish consumption can have beneficial effects to prevent coronary heart disease (CHD) and stroke incidence, and lower mortality from CVD, CHD, myocardial infarction (MI), and stroke, as well as total mortality risk. In addition, fish consumption is beneficial for preventing cognitive decline in adults (e.g. dementia and Alzheimer's disease). Fish intake may also prevent metabolic syndrome, supported by an observed association between fish intake and reduction in plasma triglycerides and increase in high-density lipoprotein (HDL) cholesterol levels. Data from fish oil and n-3 LC-PUFA supplementation studies supports the conclusions on the effects of fish consumption on most of the health outcomes.

Effects of diets supplemented with bioactive peptides on nutrient digestibility, immune cell responsiveness, and fecal characteristics, microbiota, and metabolites of adult cats

Bioactive peptides (BP) are recognized for their ability to function as antioxidants and maintain lipid stability. They may have positive health effects, including antihypertensive, anti-inflammatory, antimicrobial, osteoprotective, gut health, and immunomodulatory properties, but are poorly tested in cats. Our primary objective was to determine the apparent total tract digestibility (ATTD) of BP-containing kibble diets and assess how the fecal characteristics, metabolites, and microbiota were affected in adult cats. Our secondary objective was to test whether BP could impact blood oxidative stress markers and cytokine concentrations following transport stress. Twelve adult cats (4.83 ± 0.37 yr; 4.76 ± 0.14 kg) were used in a replicated 4 × 4 Latin square design to test four extruded kibble diets: Control (no BP), Chicken (4% chicken BP), Marine1 (2% marine BP), and Marine2 (4% marine BP). Each experimental period lasted 28 d, with a 20-d adaptation phase, 5 d for fecal collection, 2 d for blood collection, and 1 d for transport stress testing (driven in vehicle in individual carriers for 45 min). Salivary cortisol and blood oxidative stress markers and cytokines were measured after transport. Fecal microbiota data were evaluated using 16S rRNA gene amplicon sequencing and QIIME2. All other data were analyzed using the Mixed Models procedure of SAS, with P < 0.05 being considered significant and P < 0.10 considered trends. No differences were observed in animal health outcomes, with all cats remaining healthy and serum metabolites remaining within reference ranges. Cats fed the Marine2 diet had higher (P < 0.05) ATTD of dry matter (84.5% vs. 80.9%) and organic matter (88.3% vs. 85.8%) than those fed the control diet. The ATTD of protein and energy tended to be higher (P < 0.10) for cats fed the Marine2 diet. Fecal characteristics, metabolites, and bacterial alpha and beta diversity measures were not affected by treatment. However, the relative abundances of six bacterial genera were different (P < 0.05) and two bacterial genera tended to be different (P < 0.10) across treatments. Treatment did not alter salivary cortisol, blood oxidative stress markers, or blood cytokines after transport stress. Our data suggest that BP inclusion may increase nutrient digestibility and modify fecal microbiota and immune measures. More testing is required, however, to determine whether BP may provide additional benefits to cats.

Protein oxidation-mediated changes in digestion profile and nutritional properties of myofibrillar proteins from bighead carp (Hypophthalmichthys nobilis)

Digestibility is an important factor in accessing the nutritional quality and potential health benefits of protein. In this study, exudates were utilized to incubate myofibrillar proteins (MPs) for simulating the oxidation of MPs in frozen-thawed fish fillets. An in vitro gastrointestinal system was used to investigate the effect of protein oxidation on the digestion profile and nutritional properties of MPs. Results showed that exudates treatment caused the moderate oxidation of MPs and its digestibility thus increased, hydroxyl radical generation system treatment reduced the digestibility significantly. The analysis of SDS-PAGE, tricine-SDS-PAGE, amino acid composition, and peptidomics of digestion products indicates that protein oxidation decreases digestibility by causing protein cross-linking, degradation, and amino acid residues conversion. Additionally, protein oxidation reduces nutritional value of MPs via several ways including loss of essential amino acids, the proportion increase of macromolecular peptides (>2 kDa) in digests, and the percentage decrease of potential bioactive peptides in digests. The present study provides an intuitive insight into the impact of protein oxidation in frozen/thawed fillets on the digestibility of MPs, emphasizing the importance of mitigating protein oxidation to preserve their nutritional quality.

Physiological and immune profiling of tilapia Oreochromis niloticus gills by high-throughput single-cell transcriptome sequencing

The physiological and immune functions of fish gills are largely recognized, but their following functional heterogeneity at the single cell scale has been rarely reported. Here, we performed single cell RNA sequencing (scRNA-seq) on the gills of tilapia fish Oreochromis niloticus. We identified a total of 12 cell populations and analyzed their functional heterogeneity. To investigate the physiological function of O. niloticus gills, expression patterns of genes encoding ion transporters were selected from the identified H+-ATPase-rich cells (HR cells), Na+/K+-ATPase-rich cells (NaR cells), and pavement cells. Specific enrichment of ca4a, slc9a1a, and LOC100692482 in the HR cells of O. niloticus gills explained their functions in acid-base regulation. Genes encoding Ca2+ transporters, including atp2b1, LOC100696627, and LOC 100706765, were specifically expressed in the NaR cells. Pavement cells were presumably the main sites responsible for ammonia and urea transports in O. niloticus gills with specific enrichment of Rhbg and LOC100693008, respectively. The expression patterns of the four immune cell subtypes varied greatly, with B cells being enriched with the most immune-related GO terms. KEGG enrichment analysis showed that MAPK signaling pathway was the most enriched pathway among the four types of immune cells in O. niloticus gills. Our results are important in understanding the physiological and immune responses of fish gills at the cellular resolution.

Antioxidant and Renin Inhibitory Activities of Peptides from Food Proteins on Hypertension: A Review

Hypertension is a condition induced by oxidative stress causing an alteration in the endothelium, which increases the risk of suffering from other degenerative diseases. This review compiles the findings on peptides from food proteins with antioxidant and antihypertensive activities. Antihypertensive peptides are mainly focused on renin inhibition. Peptides containing hydrophobic amino acids have antioxidant and renin inhibitory activities, as reported by studies on the biological activity of peptides from various food sources evaluated separately and simultaneously. Peptides from food sources can present multiple biological activities. Moreover, antioxidant peptides have the potential to be evaluated against renin, offering an alternative for hypertension therapy without causing adverse side effects.

Identifying Novel Data-Driven Dietary Patterns via Dimensionality Reduction and Associations with Socioeconomic Profile and Health Outcomes in Ireland

Dietary patterns and body mass index (BMI) play a significant role in the development of noncommunicable diseases (NCDs), which are the leading cause of mortality worldwide, including Ireland. A cross-sectional survey was conducted across Ireland to collate respondents' socioeconomic profiles, health status, and dietary patterns with a representative sample size of 957 adult respondents. Principal component analysis (PCA) and statistical analyses were subsequently employed. To the author's knowledge, this is the first study to use recent (2021) nationally representative data to characterise dietary patterns in Ireland via dimensionality reduction. Five distinct dietary patterns ("meat-focused", "dairy/ovo-focused", "vegetable-focused", "seafood-focused", and "potato-focused") were identified and statistically characterised. The "potato-focused" group exhibited the highest mean BMI (26.88 kg/m²), while the "vegetable-focused" group had the lowest (24.68 kg/m²). "Vegetable-focused" respondents were more likely to be associated with a categorically healthy BMI (OR = 1.90) and urban residency (OR = 2.03). Conversely, "meat-focused" respondents were more likely to have obesity (OR = 1.46) and rural residency (OR = 1.72) along with the "potato-focused" group (OR = 2.15). Results show that data-derived dietary patterns may better predict health outcomes than self-reported dietary patterns, and transitioning to diets focusing on vegetables, seafood, and lower meat consumption may improve health.

Physicochemical, technofunctional, in vitro antioxidant, and in situ muscle protein synthesis properties of a sprat (Sprattus sprattus) protein hydrolysate

Introduction

Sprat (Sprattus sprattus) is an underutilized fish species that may act as an economic and sustainable alternative source of protein due to its good amino acid (AA) profile along with its potential to act as a source of multiple bioactive peptide sequences.

Method and results

This study characterized the physicochemical, technofunctional, and in vitro antioxidant properties along with the AA profile and score of a sprat protein enzymatic hydrolysate (SPH). Furthermore, the impact of the SPH on the growth, proliferation, and muscle protein synthesis (MPS) in skeletal muscle (C2C12) myotubes was examined. The SPH displayed good solubility and emulsion stabilization properties containing all essential and non-essential AAs. Limited additional hydrolysis was observed following in vitro-simulated gastrointestinal digestion (SGID) of the SPH. The SGID-treated SPH (SPH-SGID) displayed in vitro oxygen radical antioxidant capacity (ORAC) activity (549.42 μmol TE/g sample) and the ability to reduce (68%) reactive oxygen species (ROS) production in C2C12 myotubes. Muscle growth and myotube thickness were analyzed using an xCELLigence™ platform in C2C12 myotubes treated with 1 mg protein equivalent.mL^-1 of SPH-SGID for 4 h. Anabolic signaling (phosphorylation of mTOR, rpS6, and 4E-BP1) and MPS (measured by puromycin incorporation) were assessed using immunoblotting. SPH-SGID significantly increased myotube thickness (p < 0.0001) compared to the negative control (cells grown in AA and serum-free medium). MPS was also significantly higher after incubation with SPH-SGID compared with the negative control (p < 0.05).

Conclusions

These preliminary in situ results indicate that SPH may have the ability to promote muscle enhancement. In vivo human studies are required to verify these findings.

Congener-specific accumulation of persistent organic pollutants in marine fish from the Northeast Atlantic Ocean

Bioaccumulation of persistent organic pollutants (POPs) in marine fish may pose a health risk to human consumers. Using data from ∼8400 individuals of 15 fish species collected in the North-East Atlantic Ocean (NEAO), we assessed concentrations of individual POP congeners, including dioxins, polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs). POPs analyses were performed with accredited methods using high-resolution gas chromatography/high-resolution mass spectrometry, gas chromatography/tandem mass spectrometry (GC-MS/MS) and GC/MS. The results showed that POPs congener composition profiles were more influenced by fish species than by geography. However, due to long range transport from emissions at lower latitudes, lighter congeners made a larger contribution to the total POPs concentrations in the northernmost areas compared to southern regions. A model was developed to elucidate the relative effects of several factors on POPs concentrations and showed that variation among and within fish species was associated with fat content, fish size, trophic position, and latitude. For the first time, POPs concentrations were shown to increase nonlinearly with fat content, reaching an asymptotic plateau when fat content was > 10%. This study explored detailed POP congener profiles and the factors associated with POPs accumulation in commercially relevant fish harvested from the NEAO.

Biomarkers of seafood intake during pregnancy - Pollutants versus fatty acids and micronutrients

Intake of fish and seafood during pregnancy may have certain beneficial effects on fetal development, but measurement of intake using questionnaires is unreliable. Here, we assessed several candidate biomarkers of seafood intake, including long-chain omega 3 fatty acids (n-3 LCPUFA), selenium, iodine, methylmercury, and different arsenic compounds, in 549 pregnant women (gestational week 29) in the prospective birth cohort NICE (Nutritional impact on Immunological maturation during Childhood in relation to the Environment). Proportions of the fatty acids eicosapentaenoic acid (EPA), docosapentaenoic acid (DPA), and docosahexaenoic acid (DHA) in erythrocytes were measured using gas chromatography with flame ionization detector. Selenium was measured in blood plasma and erythrocytes, mercury and arsenic in erythrocytes, and iodine and several arsenic compounds in urine, using inductively coupled plasma mass spectrometry, arsenic compounds after first being separated by ion exchange high-performance liquid chromatography (HPLC). Each biomarker was related to intake of total seafood and to intake of fatty and lean fish, and shellfish in third trimester, estimated from a semi-quantitative food frequency questionnaire filled out in gestational week 34. The pregnant women reported a median total seafood intake of 184 g/week (5th-95th percentiles: 34-465 g/week). This intake correlated most strongly with erythrocyte mercury concentrations (rho = 0.49, p < 0.001), consisting essentially of methylmercury, followed by total arsenic in erythrocytes (rho = 0.34, p < 0.001), and arsenobetaine in urine (rho = 0.33, p < 0.001), the main form of urinary arsenic. These biomarkers correlated well with intake of both fatty fish, lean fish, and shellfish. Erythrocyte DHA and plasma selenium correlated, although weakly, mainly with fatty fish (rho = 0.25 and 0.22, respectively, both p < 0.001). In conclusion, elevated concentrations of erythrocyte mercury and urinary arsenobetaine can be useful indicators of seafood intake, more so than the n-3 LCPUFAs. However, the relative importance of the biomarkers may differ depending on the type and amount of seafood consumed.

A Cell-Based Assessment of the Muscle Anabolic Potential of Blue Whiting (Micromesistius poutassou) Protein Hydrolysates

Blue whiting (BW) represents an underutilised fish species containing a high-quality protein and amino acid (AA) profile with numerous potentially bioactive peptide sequences, making BW an economic and sustainable alternative source of protein. This study investigated the impact of three different BW protein hydrolysates (BWPH-X, Y and Z) on growth, proliferation and muscle protein synthesis (MPS) in skeletal muscle (C2C12) myotubes. BWPHs were hydrolysed using different enzymatic and heat exposures and underwent simulated gastrointestinal digestion (SGID), each resulting in a high degree of hydrolysis (33.41-37.29%) and high quantities of low molecular mass peptides (86.17-97.12% <1 kDa). C2C12 myotubes were treated with 1 mg protein equivalent/mL of SGID-BWPHs for 4 h. Muscle growth and myotube thickness were analysed using an xCelligence™ platform. Anabolic signalling (phosphorylation of mTOR, rpS6 and 4E-BP1) and MPS measured by puromycin incorporation were assessed using immunoblotting. BWPH-X significantly increased muscle growth (p < 0.01) and myotube thickness (p < 0.0001) compared to the negative control (amino acid and serum free media). Muscle protein synthesis (MPS), as measured by puromycin incorporation, was significantly higher after incubation with BWPH-X compared with the negative control, but did not significantly change in response to BWPH-Y and Z treatments. Taken together, these preliminary findings demonstrate the anabolic potential of some but not all BWPHs on muscle enhancement, thus providing justification for human dietary intervention studies to confirm and translate the results of such investigations to dietary recommendations and practices.

Protein Characteristics and Bioactivity of Fish Protein Hydrolysates from Tra Catfish (Pangasius hypophthalmus) Side Stream Isolates

Enzymatic hydrolysis is a novel method to recover highly potent bioactive fish protein hydrolysates (FPHs) from fish processing side-streams. The common way of producing FPHs directly from fish side-streams may be inappropriate due to the excess of lipids and pro-oxidants, especially in lipid-rich streams, as obtained from Tra catfish. This study aimed to optimise the hydrolysis conditions for a commercial enzyme (Alcalase® 2.4 L) (enzyme concentrate, temperature, and time) in FPH production from the fish protein isolate obtained from Tra catfish dark muscle (DM-FPI) using the pH-shift method. The degree of hydrolysis (DH), protein recovery (PR), and antioxidant properties, including DPPH radical scavenging activity (DPPH-RSA) and total reducing power capacity (TRPC), were measured to evaluate the effects of the hydrolysis conditions on the FPHs. Optimal hydrolysis was obtained at an enzyme/substrate protein ratio of 3% (v/w) and a hydrolysis temperature of 50 °C for 3 h. The FPHs obtained from different substrates, including DM-FPI, abdominal cut-off (ACO) FPI, and head and backbone blend (HBB) FPI, had similar DHs under these optimum conditions, ranging from 22.5% to 24.0%. However, the FPH obtained from abdominal cut-off isolate (ACO-FPH) showed the highest PR of 81.5 ± 4.3% and the highest antioxidant properties, with a DPPH-RSA of 86.1 ± 1.6% and a TRPC of 6.4 ± 0.4 equivalent mg vitamin C/g protein. The resulting FPHs present a natural source of antioxidants with great potential for food applications, especially the ACO-FPH. In addition, all FPHs had excellent amino acid profiles, indicating strong potential for their use as supplements. Tra catfish protein-rich side-streams can thus be processed into high-value bioactive FPHs using Alcalase for human consumption.

Physiopathological mechanisms involved in the development of hypertension associated with gut dysbiosis and the effect of nutritional/pharmacological interventions

The gut microbiota dysbiosis represents a triggering factor for cardiovascular diseases, including hypertension. In addition to the harmful impact caused by hypertension on different target organs, gut dysbiosis is capable of causing direct damage to critical organs such as the brain, heart, blood vessels, and kidneys. In this sense, it should be noted that pharmacological and nutritional interventions may influence gut microbiota composition, either inducing or preventing the development of hypertension. Some of the most important nutritional interventions at this level are represented by pro-, pre-, post- and/or syn-biotics, as well as polysaccharides, polyunsaturated fatty acids ω-3, polyphenols and fiber contained in different foods. Meanwhile, certain natural and synthetic active pharmaceutical ingredients, including antibiotics, antihypertensive and immunosuppressive drugs, vegetable extracts and vitamins, may also have a key role in the modulation of both gut microbiota and cardiovascular health. Additionally, gut microbiota may influence drugs and food-derived bioactive compounds metabolism, positively or negatively affecting their biological behavior facing established hypertension. The understanding of the complex interactions between gut microbiome and drug/food response results of great importance to developing improved pharmacological therapies for hypertension prevention and treatment. The purpose of this review is to critically outline the most relevant and recent findings on cardiovascular, renal and brain physiopathological mechanisms involved in the development of hypertension associated with changes in gut microbiota, besides the nutritional and pharmacological interventions potentially valuable for the prevention and treatment of this prevalent pathology. Finally, harmful food/drug interventions on gut microbiota are also described.

Fish Allergenicity Modulation Using Tailored Enriched Diets—Where Are We?

Food allergy is an abnormal immune response to specific proteins in a certain food. The chronicity, prevalence, and the potential fatality of food allergy, make it a serious socio-economic problem. Fish is considered the third most allergenic food in the world, affecting part of the world population with a higher incidence in children and adolescents. The main allergen in fish, responsible for the large majority of fish-allergic reactions in sensitized patients, is a small and stable calcium-binding muscle protein named beta-parvalbumin. Targeting the expression or/and the 3D conformation of this protein by adding specific molecules to fish diets has been the innovative strategy of some researchers in the fields of fish allergies and nutrition. This has shown promising results, namely when the apo-form of β-parvalbumin is induced, leading in the case of gilthead seabream to a 50% reduction of IgE-reactivity in fish allergic patients.

Postprandial Effects of Salmon Fishmeal and Whey on Metabolic Markers in Serum and Gene Expression in Liver Cells

Fish is considered an important part of a healthy diet, in part due to the content of long chain omega-3 fatty acids. However, both lean and fatty fish have beneficial health effects, suggesting that micronutrients and proteins may play a role. In a randomised, controlled, cross-over trial, five healthy male participants consumed 5.2 g of protein from either salmon fishmeal or whey. Blood samples were taken before and 30 and 60 min after intake. The concentration of glucose, lipids, hormones and metabolites, including 28 different amino acids and derivatives, were measured in serum or plasma. Cultured HepG2 cells were incubated with or without serum from the participants, and transcriptomic profiling was performed using RNA sequencing. The ingestion of both salmon fishmeal and whey reduced the glucose and triglyceride levels in serum. Protein intake, independent of the source, increased the concentration of 22 amino acids and derivatives in serum. Fishmeal increased the concentration of arginine, methionine, serine, glycine, cystathionine and 2-aminobutyric acid more than whey did. Incubation with postprandial serum resulted in large transcriptomic alterations in serum-fasted HepG2 cells, with the differential expression of >4500 protein coding genes. However, when comparing cells cultivated in fasting serum to postprandial serum after the ingestion of fishmeal and whey, we did not detect any differentially regulated genes, neither with respect to the protein source nor with respect to the time after the meal. The comparable nutrigenomic effects of fishmeal and whey do not change the relevance of fish by-products as an alternative food source.

How Do Italian Consumers Value Sustainable Certifications on Fish?—An Explorative Analysis

Sustainable certifications communicate the environmental benefits of food products to consumers, and allow producers to differentiate their products from conventional ones. This study expands existing knowledge on fish consumers by assessing the importance of sustainable certifications in fish selection. A best–worst analysis was applied to a convenient sample of Italian household members responsible for food shopping, segmented with a latent class clustering model based on their socio-demographic characteristics, fish purchase behaviors, as well as attitudinal features. The results show that sustainable certifications were of interest to consumers, as more than 1 out of 10 respondents valued sustainable certifications in purchasing fish. Respondents interested in sustainable certifications on fish were medium-aged consumers, with high working status, well educated, as well as living in a medium-size household without children. These consumers were more interested in organic foods and had an interest in food nutritional information; they likely have a healthy holistic lifestyle, and may purchase organic food, including fish, to improve their health by increasing their physical well-being.

Valorization of fish byproducts: Sources to end-product applications of bioactive protein hydrolysate

Fish processing industries result in an ample number of protein-rich byproducts, which have been used to produce protein hydrolysate (PH) for human consumption. Chemical, microbial, and enzymatic hydrolysis processes have been implemented for the production of fish PH (FPH) from diverse types of fish processing byproducts. FPH has been reported to possess bioactive active peptides known to exhibit various biological activities such as antioxidant, antimicrobial, angiotensin-I converting enzyme inhibition, calcium-binding ability, dipeptidyl peptidase-IV inhibition, immunomodulation, and antiproliferative activity, which are discussed comprehensively in this review. Appropriate conditions for the hydrolysis process (e.g., type and concentration of enzymes, time, and temperature) play an important role in achieving the desired level of hydrolysis, thus affecting the functional and bioactive properties and stability of FPH. This review provides an in-depth and comprehensive discussion on the sources, process parameters, purification as well as functional and bioactive properties of FPHs. The most recent research findings on the impact of production parameters, bitterness of peptide, storage, and food processing conditions on functional properties and stability of FPH were also reported. More importantly, the recent studies on biological activities of FPH and in vivo health benefits were discussed with the possible mechanism of action. Furthermore, FPH-polyphenol conjugate, encapsulation, and digestive stability of FPH were discussed in terms of their potential to be utilized as a nutraceutical ingredient. Last but not the least, various industrial applications of FPH and the fate of FPH in terms of limitations, hurdles, future research directions, and challenges have been addressed.

Fish protein hydrolysates as a health-promoting ingredient-recent update

Dietary habits and lifestyle-related diseases indicate that food has a direct impact on individual health. Hence, a diet containing essential nutrients is important for healthy living. Fish and fish products are important in diets worldwide because of their nutritional value, especially their easily digestible proteins with essential amino acids. Similarly, fish protein hydrolysate (FPH) obtained from fish muscle and by-products has been reported to exhibit various biological activities and to have functional properties, which make FPH a suitable nutraceutical candidate. This review focuses on the health-promoting ability of FPH in terms of skin health, bone and cartilage health, blood lipid profile, and body-weight management studied in rats and human model systems. The absorption and bioavailability of FPH in humans is discussed, and challenges and obstacles of FPH as a functional food ingredient are outlined.

Ultrafiltration of Saithe (Pollachius virens) Protein Hydrolysates and Its Effect on Antioxidative Activity

The whitefish industry generates a huge amount of rest raw material, which is currently wasted or underutilized in the production of low-value products such as animal feed. While fish muscle is the primary product of use for human consumption, rest raw material has great potential as a source of protein and bioactive peptides for the production of food ingredients and nutraceuticals. Enzymatic hydrolysis is a biotechnological processing method that can be used to extract protein from fish rest raw material into a protein hydrolysate. This study aimed at investigating the functionality of ultrafiltration as an industrial processing method and its effect on the bioactivity of protein hydrolysates. Protein hydrolysates were produced by enzymatic hydrolysis of saithe (Pollachius virens) head and backbone caught at two separate occasions to investigate the effect of seasonal variations. Ultrafiltration effectively concentrated larger peptides (>4 kDa) and smaller peptides (<4 kDa) in separate fractions, with a protein yield of 31% in the fraction <4 kDa. The unfiltered hydrolysate was found to have a higher antioxidative activity compared to the <4 kDa fraction in ABTS, FRAP, and ORAC assays. These results indicate that ultrafiltration does not effectively increase bioactivity by concentrating small peptides and that bioactivity is dependent on several properties, including interaction with larger peptides.

Tracing the heavy metals zinc, lead and nickel in banana shrimp (Penaeus merguiensis) from the Persian Gulf and human health risk assessment

Seafood has long been considered a unique source of nutrition. However, increasing trends in consumption of marine products must be considered, especially in potentially polluted environments such as the Persian Gulf. This study was undertaken to analyse the level of heavy metal contamination of nickel (Ni), zinc (Zn), and lead (Pb) in shrimp (Penaeus merguiensis) captured from the northern Persian Gulf. The concentration of heavy metals in the muscle of shrimp followed the order Zn > Ni > Pb. The content of Zn and Ni was higher than recommended standard limits by the FAO/WHO. The combined impact of all metals was lower than the acceptable limit of 1 in shrimp. The carcinogenic risk for Ni was higher than the unacceptable value. In total, our finding indicated no potential health risk from the daily consumption of this species. However, long-term consumption of shrimp can pose a risk of carcinogenic effects of nickel. Continuous monitoring of these trace metals in seafood is necessary to ensure the quality of seafood and food safety.

Anti-Atherogenic Effect of 10% Supplementation of Anchovy (Engraulis encrasicolus) Waste Protein Hydrolysates in ApoE-Deficient Mice

Fish protein consumption exerts beneficial metabolic effects on human health, also correlating with a decreased risk for cardiovascular disease. Fish waste contains high amount of proteins and utilization may offer the opportunity for generating compounds advantageous for human health. Especially, fish waste protein hydrolysates beneficially influence pathways involved in body composition, exerting anti-inflammatory and antioxidant activities, making their potential supplementation in human disorders of increased interest. This study assessed the effect of a 10% (w/w) anchovy waste protein hydrolysate (APH) diet for 12 weeks in reducing atherosclerosis in ApoE^-/- mice, through histological and immunohistochemical methods. In addition, monitoring of plaque development was performed, using high-frequency ultrasound and magnetic resonance imaging. Overall, the APH diet attenuated atherosclerotic plaque development, producing a regression of arterial lesions over time (p < 0.05). Twelve weeks on an APH diet had an anti-obesity effect, improving lipid metabolism and reducing hepatic enzyme activity. A significant reduction in plaque size and lipid content was observed in the aortic sinus of APH-fed mice, compared to the control (p < 0.001), whereas no differences in the extracellular matrix and macrophage recruitment were observed. Supplementation of APH significantly attenuates atherosclerosis in ApoE^-/- mice, exerting a lipid-lowering activity. The opportunity to use fish waste protein hydrolysates as a nutraceutical in atherosclerosis is worthy of future investigations, representing a low cost, sustainable, and nutritional strategy with minimal environmental impact.

Lipid-modifying effects of lean fish and fish-derived protein consumption in humans: a systematic review and meta-analysis of randomized controlled trials

CONTEXT

Consumption of lean fish and fish-derived proteins were effective for improving lipid profiles in published studies; however, evidence remains inconclusive.

OBJECTIVE

To evaluate the effectiveness of lean fish or fish-derived protein on serum/plasma lipid and lipoprotein levels by conducting a systematic review of the literature and meta-analysis of available randomized controlled trials (RCTs).

DATA SOURCES

Medline (Ovid), Scopus, CINAHL, and Food and Nutritional Sciences databases were searched from the start date of each database to September 2019 to identify RCTs determining the effect of lean fish on lipid profile.

STUDY SELECTION INCLUDED

RCTs investigated lean fish and fish-derived proteins intake and determined at least 1 major lipid or lipoprotein measurement.

DATA EXTRACTION

Two reviewers independently evaluated 1217 studies against the inclusion and exclusion criteria. Relevant studies were assessed for risks of bias, and random-effects meta-analysis was conducted to generate average estimates of effect.

RESULTS

A total of 24 studies met the inclusion criteria. Meta-analysis of data from 18 to 21 eligible crossover and parallel-design RCTs with a total of 1392 to 1456 participants found triacylglycerol-lowering effects for lean fish compared with no fish consumption. Lean fish intake showed no significant differences related to total cholesterol or lipoprotein levels. Subanalysis showed that parallel-group RCTs tended to find greater reduction effects on circulating triacylglycerol than did crossover RCTs.

CONCLUSION

Additional better-designed, longer, and larger RCTs, particularly crossover RCTs, are needed to clarify the impact of lean fish and fish proteins on the serum/plasma lipid profile. Findings from such studies would enable practitioners to provide their patients evidence-based recommendations to meet the American Heart Association guidelines for fish consumption to reduce cardiovascular disease risk.

n-3 Fatty Acid Biomarkers and Incident Type 2 Diabetes: An Individual Participant-Level Pooling Project of 20 Prospective Cohort Studies

OBJECTIVE

Prospective associations between n-3 fatty acid biomarkers and type 2 diabetes (T2D) risk are not consistent in individual studies. We aimed to summarize the prospective associations of biomarkers of α-linolenic acid (ALA), eicosapentaenoic acid (EPA), docosapentaenoic acid (DPA), and docosahexaenoic acid (DHA) with T2D risk through an individual participant-level pooled analysis.

RESEARCH DESIGN AND METHODS

For our analysis we incorporated data from a global consortium of 20 prospective studies from 14 countries. We included 65,147 participants who had blood measurements of ALA, EPA, DPA, or DHA and were free of diabetes at baseline. De novo harmonized analyses were performed in each cohort following a prespecified protocol, and cohort-specific associations were pooled using inverse variance-weighted meta-analysis.

RESULTS

A total of 16,693 incident T2D cases were identified during follow-up (median follow-up ranging from 2.5 to 21.2 years). In pooled multivariable analysis, per interquintile range (difference between the 90th and 10th percentiles for each fatty acid), EPA, DPA, DHA, and their sum were associated with lower T2D incidence, with hazard ratios (HRs) and 95% CIs of 0.92 (0.87, 0.96), 0.79 (0.73, 0.85), 0.82 (0.76, 0.89), and 0.81 (0.75, 0.88), respectively (all P < 0.001). ALA was not associated with T2D (HR 0.97 [95% CI 0.92, 1.02]) per interquintile range. Associations were robust across prespecified subgroups as well as in sensitivity analyses.

CONCLUSIONS

Higher circulating biomarkers of seafood-derived n-3 fatty acids, including EPA, DPA, DHA, and their sum, were associated with lower risk of T2D in a global consortium of prospective studies. The biomarker of plant-derived ALA was not significantly associated with T2D risk.

Synthesis of grafted polybutyl acrylate copolymer on fish collagen

Increasingly, scientists are turning to the study of marine, or fish, collagen, which is increasingly replacing collagen of terrestrial animals, due to the fact that it is hypoallergenic, since it is 96% identical to human protein. Materials based on fish collagen have a number of advantages over their analogue of animal origin: it is not a carrier of infectious diseases of animals transmitted to humans, it has a greater structural similarity to human collagen, which provides a higher level of biocompatibility. Materials based on collagen copolymers with synthetic monomers are promising. The use of hybrid materials also helps to reduce the consumption of non-renewable natural resources. Synthesis of grafted collagen copolymers with polybutyl acrylate was carried out at azobisisobutyronitrile initiation and triethyl borane – oxygen system initiation under comparable conditions under intensive stirring of aqueous solution dispersion of collagen and butyl acrylate. After the synthesis, the aqueous and organic phases of the reaction mixture were analyzed by composition and molecular weight parameters using infrared spectroscopy and size-exclusion chromatography. Changes indicating the formation of a copolymer are observed in the copolymer isolated from the aqueous phase, more pronounced in the triethyl borane – oxygen system. It is assumed that the formation of copolymer macromolecules for azobisisobutyronitrile and organoelement initiator takes place according to different schemes. Schemes for the formation of copolymer macromolecules for AIBN and an organoelement initiator are proposed. Only polybutyl acrylate is present in the organic phase. Biological studies were carried out for fungal resistance and bactericidal activity of the obtained copolymers.

Functional and Bioactive Properties of Peptides Derived from Marine Side Streams

In fish processing, a great amount of side streams, including skin, bones, heads and viscera, is wasted or downgraded as feed on a daily basis. These side streams are rich sources of bioactive nitrogenous compounds and protein, which can be converted into peptides through enzymatic hydrolysis as well as bacterial fermentation. Peptides are short or long chains of amino acids differing in structure and molecular weight. They can be considered as biologically active as they can contribute to physiological functions in organisms with applications in the food and pharmaceutical industries. In the food industry, such bioactive peptides can be used as preservatives or antioxidants to prevent food spoilage. Furthermore, peptides contain several functional qualities that can be exploited as tools in modifying food ingredient solubility, water-holding and fat-binding capacity and gel formation. In the pharmaceutical industry, peptides can be used as antioxidants, but also as antihypertensive, anticoagulant and immunomodulatory compounds, amongst other functions. On the basis of their properties, peptides can thus be used in the development of functional foods and nutraceuticals. This review focuses on the bioactive peptides derived from seafood side streams and discusses their technological properties, biological activities and applications.

Limited Benefit of Marine Protein Hydrolysate on Physical Function and Strength in Older Adults: A Randomized Controlled Trial

Age-related muscle wasting can compromise functional abilities of the elderly. Protein intake stimulates muscle protein synthesis; however, ageing muscle is more resistant to stimuli. This double-blinded, randomized, controlled trial is one of the first registered studies to evaluate the effects of a supplement of marine protein hydrolysate (MPH) on measures of physical function and strength. Eighty-six older adults received nutritional supplements containing 3 g of MPH or a placebo for up to 12 months. Short Physical Performance Battery (SPPB), grip strength and gait speed were measured, and dietary intake was registered at baseline, 6 months, and 12 months. No difference was found between the intervention and control groups in mean change in SPPB (independent sample t-test, p = 0.41) or regarding time trend in SPPB, grip strength, or gait speed (linear mixed model). The participants in our study were well functioning, causing a ceiling effect in SPPB. Further, they had sufficient protein intake and were physically active. Differences in physical function between those completing the intervention and the dropouts might also have created bias in the results. We recommend that future studies of MPH be carried out on a more frail or malnourished population.

Novel monoclonal antibody-sandwich immunochromatographic assay based on Fe3O4/Au nanoparticles for rapid detection of fish allergen parvalbumin

In this study, a rapid sandwich immunochromatographic assay (ICA) was developed to detect parvalbumin (PV). Firstly, two optimum primary monoclonal antibody (mAb) against PV had been screened out: mAb1 was used as the capture antibody, and mAb2 conjugated to Fe₃O₄/Au nanoparticles (Fe₃O₄/AuNPs) that served as a detection reagent. Using this pair of mAbs, a sandwich ICA strip based on Fe₃O₄/AuNPs was developed. The results showed that the color intensity of test line positively correlated with the PV concentration in the standard or spiked sample. The limit of detection for qualitative (LOD) and quantitative detection (LOQ) were 2 ng/mL and 0.691 ng/mL, respectively. Besides, the detection time of this ICA strip was within 15 min. The recovery rates ranged from 104.0% to 117.4%, within an acceptable level (80-120%). Moreover, the developed assay also showed high cross reaction in different fish species. These results demonstrated that the established test strip has the potential to be used as a rapid screening tool for large scale determination of PV in foodstuffs.

New Bioactive Peptides Identified from a Tilapia Byproduct Hydrolysate Exerting Effects on DPP-IV Activity and Intestinal Hormones Regulation after Canine Gastrointestinal Simulated Digestion

Like their owners, dogs and cats are more and more affected by overweight and obesity-related problems and interest in functional pet foods is growing sharply. Through numerous studies, fish protein hydrolysates have proved their worth to prevent and manage obesity-related comorbidities like diabetes. In this work, a human in vitro static simulated gastrointestinal digestion model was adapted to the dog which allowed us to demonstrate the promising effects of a tilapia byproduct hydrolysate on the regulation of food intake and glucose metabolism. Promising effects on intestinal hormones secretion and dipeptidyl peptidase IV (DPP-IV) inhibitory activity were evidenced. We identify new bioactive peptides able to stimulate cholecystokinin (CCK) and glucagon-like peptide 1 (GLP-1) secretions, and to inhibit the DPP-IV activity after a transport study through a Caco-2 cell monolayer.

Herring Milt and Herring Milt Protein Hydrolysate Are Equally Effective in Improving Insulin Sensitivity and Pancreatic Beta-Cell Function in Diet-Induced Obese- and Insulin-Resistant Mice

Although genetic predisposition influences the onset and progression of insulin resistance and diabetes, dietary nutrients are critical. In general, protein is beneficial relative to carbohydrate and fat but dependent on protein source. Our recent study demonstrated that 70% replacement of dietary casein protein with the equivalent quantity of protein derived from herring milt protein hydrolysate (HMPH; herring milt with proteins being enzymatically hydrolyzed) significantly improved insulin resistance and glucose homeostasis in high-fat diet-induced obese mice. As production of protein hydrolysate increases the cost of the product, it is important to determine whether a simply dried and ground herring milt product possesses similar benefits. Therefore, the current study was conducted to investigate the effect of herring milt dry powder (HMDP) on glucose control and the associated metabolic phenotypes and further to compare its efficacy with HMPH. Male C57BL/6J mice on a high-fat diet for 7 weeks were randomized based on body weight and blood glucose into three groups. One group continued on the high-fat diet and was used as the insulin-resistant/diabetic control and the other two groups were given the high-fat diet modified to have 70% of casein protein being replaced with the same amount of protein from HMDP or HMPH. A group of mice on a low-fat diet all the time was used as the normal control. The results demonstrated that mice on the high-fat diet increased weight gain and showed higher blood concentrations of glucose, insulin, and leptin, as well as impaired glucose tolerance and pancreatic β-cell function relative to those on the normal control diet. In comparison with the high-fat diet, the replacement of 70% dietary casein protein with the same amount of HMDP or HMPH protein decreased weight gain and significantly improved the aforementioned biomarkers, insulin sensitivity or resistance, and β-cell function. The HMDP and HMPH showed similar effects on every parameter except blood lipids where HMDP decreased total cholesterol and non-HDL-cholesterol levels while the effect of HMPH was not significant. The results demonstrate that substituting 70% of dietary casein protein with the equivalent amount of HMDP or HMPH protein protects against obesity and diabetes, and HMDP is also beneficial to cholesterol homeostasis.

The Potential Role of Fish-Derived Protein Hydrolysates on Metabolic Health, Skeletal Muscle Mass and Function in Ageing

Fish protein represents one of the most widely consumed dietary protein sources by humans. The processing of material from the fishing industry generates substantial unexploited waste products, many of which possess high biological value. Protein hydrolysates, such as fish protein hydrolysates (FPH), containing predominantly di- and tripeptides, are more readily absorbed than free amino acids and intact protein. Furthermore, in animal models, FPH have been shown to possess numerous beneficial properties for cardiovascular, neurological, intestinal, renal, and immune health. Ageing is associated with the loss of skeletal muscle mass and function, as well as increased oxidative stress, compromised vascularisation, neurological derangements, and immunosenescence. Thus, there appears to be a potential application for FPH in older persons as a high-quality protein source that may also confer additional health benefits. Despite this, there remains a dearth of information concerning the impact of FPH on health outcomes in humans. The limited evidence from human interventional trials suggests that FPH may hold promise for supporting optimal body composition and maintaining gut integrity. FPH also provide a high-quality source of dietary protein without negatively impacting on subjective appetite perceptions or regulatory hormones. Further studies are needed to assess the impact and utility of FPH on skeletal muscle health in older persons, ideally comparing FPH to ‘established’ protein sources or a non-bioactive, nitrogen-matched control. In particular, the effects of acute and chronic FPH consumption on post-exercise aminoacidaemia, skeletal muscle protein synthesis, and intramyocellular anabolic signalling in older adults are worthy of investigation. FPH may represent beneficial and sustainable alternative sources of high-quality protein to support skeletal muscle health and anabolism in ageing, without compromising appetite and subsequent energy intake.

Tilapia Skin Peptides Ameliorate Diabetic Nephropathy in STZ-Induced Diabetic Rats and HG-Induced GMCs by Improving Mitochondrial Dysfunction

Diabetic nephropathy (DN) is one of the major microvascular complications of diabetes, and mitochondrial dysfunction has been observed in the kidneys of diabetic patients. Tilapia skin peptides (TSPs) are mixtures of small-molecular-weight peptides derived from tilapia skin. Rising evidence suggests that bioactive peptides from marine sources are beneficial for DN. This study aimed to investigate whether TSPs can alleviate the pathological progress in experimental DN by improving mitochondrial dysfunction through the activation of Bnip3/Nix signaling. In the current study, TSPs treatment alleviated the metabolic parameters and renal morphology in streptozotocin-induced diabetic rats. Additionally, TSPs treatment significantly activated Bnip3/Nix signaling and improved the mitochondrial morphology, reversed the over-production of mitochondrial superoxide and cellular reactive oxygen species and the decreased mitochondrial membrane potential, thereby inhibiting the expressions of fibronectin, collagen IV and intercellular cell adhesion molecule-1 in glomerular mesangial cells induced by high glucose. Collectively, our results suggest that TSPs show the renoprotective effect on DN by improving mitochondrial dysfunction, and they can be a potential therapeutic strategy for DN.

Supplementation with Low Doses of a Cod Protein Hydrolysate on Glucose Regulation and Lipid Metabolism in Adults with Metabolic Syndrome: A Randomized, Double-Blind Study

The risk of cardiovascular diseases and type 2 diabetes mellitus are increased in subjects with metabolic syndrome (MetS), and hydrolyzed fish protein may have favorable effects on metabolic health. Here, we investigated the effect of 8 weeks supplementation with 4 g of cod protein hydrolysate (CPH) on glucose metabolism, lipid profile and body composition in individuals with MetS in a double-blind, randomized intervention study with a parallel-group design. Subjects received a daily supplement of CPH (n = 15) or placebo (n = 15). Primary outcomes were serum fasting and postprandial glucose levels. Secondary outcomes were fasting and postprandial insulin and glucagon-like peptide 1 (GLP-1), fasting lipid concentrations and body composition. No difference was observed between CPH and placebo for insulin, glucose or GLP-1 after 8 weeks intervention. Fasting triacylglycerol decreased in both the CPH group and placebo group, with no change between groups. Fasting total cholesterol and low-density lipoprotein cholesterol decreased significantly within both groups from baseline to study end, but no difference was observed between the two groups. In conclusion, supplementing with a low dose of CPH in subjects with MetS for 8 weeks had no effect on fasting or postprandial levels of insulin, glucose or GLP-1, lipid profile or body composition.

Seasonal Changes in Free Amino Acid and Fatty Acid Compositions of Sardines, Sardina pilchardus (Walbaum, 1792): Implications for Nutrition

The aim of this study was to clarify the seasonal variation in the proximate composition of the free amino acid (AA) and fatty acid (FA) profiles of the European sardine (Sardina pilchardus) from the Adriatic Sea and to better understand the nutritive value needed to organize more effective industrial processing, aquaculture use and to ensure the health benefits for consumers through available bioactive compounds such as omega-3 FA and essential AA. The lipid content ranged from 1.18 to 10.58% during the year, being the highest from July to September. For the first time, this paper reports the monthly variation in AA content in sardines. The highest total AA content was measured during the winter period, from January (843 mg/100 g fillet) to March (953 mg/100 g) with histidine, arginine and threonine being the most dominant. The total content of essential free AA (histidine, threonine, valine, methionine, isoleucine, leucine, phenylalanine, tryptophan and lysine) ranged from 137 to 571 mg/100 g fillet (wet weight), recorded in May and March, respectively. The fatty acid profile analyses revealed the major saturated FA as palmitic (C16:0), followed by myristic (C14:0), and stearic (C18:0) acids, and the predominant monosaturated FA as oleic (C18:1n–9) and palmitoleic (C16:1n–7). The high concentrations of polyunsaturated FA in sardines were omega-3 FA, particularly eicosapentaenoic (EPA; 20:5n-3) and docosahexaenoic (DHA; 20:6n-3) FA. From July to September, their content was the highest (>3.5 g/100 g of sardine fillets), confirming that these species are excellent sources of bioactive lipids.

Taurine and cardiac disease: state of the art and perspectives

Taurine is a nonessential amino acid that has received much attention. Two organs, the heart and the brain, are known to produce their own taurine, but in very limited quantities. It is for this reason that supplementation with this amino acid is necessary. Today, taurine is present in almost all energy drinks. A very vast literature reported beneficial effects of taurine in hepatic dysfunction, gastrointestinal injury, kidney diseases, diabetes, and cardiovascular diseases. Most of its effects were attributed to its modulation of Ca2+homeostasis as well as to its antioxidant properties. In this review, we will focus on the current status of taurine modulation of the cardiovascular system and discuss future avenues for its use as a supplement therapy in a specific cardiovascular disease, namely hypertrophy, and heart failure.

Basophil Activation Test Based on CD203c Expression in the Diagnosis of Fish Allergy

Purpose

The basophil activation test (BAT) has been reported to be useful for the diagnosis of various food allergies, such as allergy to peanut, but not to fish. This study aimed to evaluate the diagnostic performance of the BAT for fish allergy.

Methods

We performed a retrospective review of patients with fish allergy who underwent the BAT using a panel of fish extracts (15 kinds) to examine the differential reactivity to several species of fish. The BAT score for each extract was expressed as the ratio of CD203c^high% with the extract to that with anti-IgE antibody. Clinical reactivity to each fish was confirmed by positive oral food challenge or a typical history of fish-induced immediate allergy symptoms. Receiver-operating-characteristic (ROC) analysis was performed to evaluate the diagnostic performance.

Results

Fifty-one patients with fish allergy were analyzed. Using extracts of 15 species of fish, the BAT was performed a total of 184 times on the patients. Clinical allergy to each species of fish was confirmed in 90 (48.9%) of those tests. ROC analysis yielded high areas under the curve for the BAT scores for the 5 most common fish species (0.72–0.88). The diagnostic accuracy ranged from 0.74 to 0.86. Using a tentative cutoff value of 0.3 deduced from the ROC analyses of the 5 fish species, the accuracy for other fish allergic reactions was generally high (0.6–1.0), except the fish tested in a small number of patients.

Conclusions

The BAT score based on CD203c expression may be useful for fish allergy diagnosis, especially since a large variety of fish can be tested by the BAT using fish extracts prepared by a simple method.

Supplementation with cod protein hydrolysate in older adults: a dose range cross-over study

A large proportion of older adults are affected by impaired glucose metabolism. Previous studies with fish protein have reported improved glucose regulation in healthy adults, but the evidence in older adults is limited. Therefore, we wanted to assess the effect of increasing doses of a cod protein hydrolysate (CPH) on postprandial glucose metabolism in older adults. The study was a double-blind cross-over trial. Participants received four different doses (10, 20, 30 or 40 mg/kg body weight (BW)) of CPH daily for 1 week with 1-week washout periods in between. The primary outcome was postprandial response in glucose metabolism, measured by samples of serum glucose and insulin in 20 min intervals for 120 min. The secondary outcome was postprandial response in plasma glucagon-like peptide 1 (GLP-1). Thirty-one subjects aged 60–78 years were included in the study. In a mixed-model statistical analysis, no differences in estimated maximum value of glucose, insulin or GLP-1 were observed when comparing the lowest dose of CPH (10 mg/kg BW) with the higher doses (20, 30 or 40 mg/kg BW). The estimated maximum value of glucose was on average 0·28 mmol/l lower when the participants were given 40 mg/kg BW CPH compared with 10 mg/kg BW (P = 0·13). The estimated maximum value of insulin was on average 5·14 mIU/l lower with 40 mg/kg BW of CPH compared with 10 mg/kg BW (P = 0·20). Our findings suggest that serum glucose and insulin levels tend to decrease with increasing amounts of CPH. Due to preliminary findings, the results require further investigation.

Herring Milt Protein Hydrolysate Improves Insulin Resistance in High-Fat-Diet-Induced Obese Male C57BL/6J Mice

Protein consumption influences glucose homeostasis, but the effect depends on the type and origin of proteins ingested. The present study was designed to determine the effect of herring milt protein hydrolysate (HPH) on insulin function and glucose metabolism in a mouse model of diet-induced obesity. Male C57BL/6J mice were pretreated with a low-fat diet or a high-fat diet for 6 weeks. Mice on the high-fat diet were divided into four groups where one group continued on the high-fat diet and the other three groups were fed a modified high-fat diet where 15%, 35%, and 70%, respectively, of casein was replaced with an equal percentage of protein derived from HPH. After 10 weeks, mice that continued on the high-fat diet showed significant increases in body weight, blood glucose, insulin, and leptin levels and exhibited impaired oral glucose tolerance, insulin resistance, and pancreatic β-cell dysfunction. Compared to mice fed the high-fat diet, the 70% replacement of dietary casein with HPH protein reduced body weight, semi-fasting blood glucose, fasting blood glucose, insulin, leptin, and cholesterol levels and improved glucose tolerance, homeostasis model assessment of insulin resistance (HOMA-IR), and homeostasis model assessment of β-cell function (HOMA-β) indices. The 35% replacement of dietary casein with HPH protein showed moderate effects, while the 15% replacement of dietary casein with HPH protein had no effects. This is the first study demonstrating that replacing dietary casein with the same amount of protein derived from HPH can prevent high-fat-diet-induced obesity and insulin resistance.