Histidine-containing dipeptide deficiency links to hyperactivity and depression-like behaviors in old female mice.

Carnosine, anserine, and homocarnosine are histidine-containing dipeptides (HCDs) abundant in the skeletal muscle and nervous system in mammals. To date, studies have extensively demonstrated effects of carnosine and anserine, the predominant muscular HCDs, on muscular functions and exercise performance. However, homocarnosine, the predominant brain HCD, is underexplored. Moreover, roles of homocarnosine and its related HCDs in the brain and behaviors remain poorly understood. Here, we investigated potential roles of endogenous brain homocarnosine and its related HCDs in behaviors by using carnosine synthase-1-deficient (Carns1-/-) mice. We found that old Carns1-/- mice (female 12 months old) exhibited hyperactivity- and depression-like behaviors with higher plasma corticosterone levels on light-dark transition and forced swimming tests, but had no defects in spontaneous locomotor activity, repetitive behavior, olfactory functions, and learning and memory abilities, as compared with their age-matched wild-type (WT) mice. We confirmed that homocarnosine and its related HCDs were deficient across brain areas of Carns1-/- mice. Homocarnosine deficiency exhibited small effects on its constituent γ-aminobutyric acid (GABA) in the brain, in which GABA levels in hypothalamus and olfactory bulb were higher in Carns1-/- mice than in WT mice. In WT mice, homocarnosine and GABA were highly present in hypothalamus, thalamus, and olfactory bulb, and their brain levels did not decrease in old mice when compared with younger mice (3 months old). Our present findings provide new insights into roles of homocarnosine and its related HCDs in behaviors and neurological disorders.

Modelling of salt intake reduction by incorporation of umami substances into Japanese foods: a cross-sectional study.

BACKGROUND: Evidence has demonstrated that excess sodium intake is associated with development of several non-communicable diseases. The main source of sodium is salt. Therefore, reducing salt intake in foods is an important global public health effort to achieve sodium reduction and improve health. This study aimed to model salt intake reduction with 'umami' substances among Japanese adults. The umami substances considered in this study include glutamate or monosodium glutamates (MSG), calcium diglutamate (CDG), inosinate, and guanylate. METHODS: A total of 21,805 participants aged 57.8 years on average from the National Health and Nutrition Survey was used in the analysis. First, we employed a multivariable linear regression approach with overall salt intake (g/day) as a dependent variable, adjusting for food items and other covariates to estimate the contribution of salt intake from each food item that was selected through an extensive literature review. Assuming the participants already consume low-sodium products, we considered three scenarios in which salt intake could be reduced with the additional umami substances up to 30%, 60% and 100%. We estimated the total amount of population-level salt reduction for each scenario by age and gender. Under the 100% scenario, the Japan's achievement rates against the national and global salt intake reduction goals were also calculated. RESULTS: Without compromising the taste, the 100% or universal incorporation of umami substances into food items reduced the salt intake of Japanese adults by 12.8-22.3% at the population-level average, which is equivalent to 1.27-2.22 g of salt reduction. The universal incorporation of umami substances into food items changed daily mean salt intake of the total population from 9.95 g to 7.73 g: 10.83 g to 8.40 g for men and 9.21 g to 7.17 g for women, respectively. This study suggested that approximately 60% of Japanese adults could achieve the national dietary goal of 8 g/day, while only 7.6% would meet the global recommendation of 5.0 g/day. CONCLUSIONS: Our study provides essential information on the potential salt reduction with umami substances. The universal incorporation of umami substances into food items would enable the Japanese to achieve the national dietary goal. However, the reduced salt intake level still falls short of the global dietary recommendation.

Carnosine synthase deficiency in mice affects protein metabolism in skeletal muscle.

Carnosine and anserine are abundant peptides found in the skeletal muscle and nervous system in many vertebrates. Several in vitro and in vivo studies have demonstrate that exogenously administered carnosine improves exercise performance. Furthermore, carnosine is an antioxidant and antifatigue supplement. However, the physiological functions of endogenous carnosine and its related histidine-containing dipeptides in a living organism remain unclear. We aimed to clarify the physiological roles of endogenous carnosine by investigating the characteristics of carnosine synthase gene-deficient mice and the effects of carnosine on skeletal muscle protein metabolism. We discovered that carnosine and anserine were undetectable in the skeletal muscle of carnosine synthase knockout mice. We also quantified protein gene expression and enzyme levels in muscle protein metabolism. Gene and protein levels of the muscle protein synthesizer insulin-like growth factor-1 (IGF-1) and the degrading enzyme cathepsin B were markedly lower in carnosine synthase gene-deficient mice than those in wild-type mice. The amount of 3-methylhistidine (a marker for muscle proteolysis) in forced exercise and the weight of the gastrocnemius muscle were considerably lower in carnosine synthase gene-deficient mice than in wild-type mice. Consequently, we showed that carnosine deficiency affects weight maintenance and protein metabolism in skeletal muscle, suggesting that carnosine regulates skeletal muscle protein metabolism.

Pharmacokinetics and tissue distribution of orally administrated imidazole dipeptides in carnosine synthase gene knockout mice.

Imidazole dipeptides (ID) are abundant in skeletal muscle and the brain and have various functions, such as antioxidant, pH-buffering, metal-ion chelation. However, the physiological significance of ID has not been fully elucidated. In this study, we orally administered ID to conventional carnosine synthase gene-deficient mice (Carns-KO mice) to investigate the pharmacokinetics. Carnosine or anserine was administered at a dose of 500 mg (∼2 mmol) per kilogram of mouse body weight, and ID contents in the tissues were measured. No ID were detected in untreated Carns-KO mice. In the ID treatment groups, the ID concentrations in the tissues increased in a time-dependent manner in the gastrocnemius muscle, soleus muscle, and cerebrum after ID administration. Our findings suggest that the Carns-KO mice are a valuable animal model for directly evaluating the effects of dietary ID and for elucidating the physiological functions of oral ID administration.

Salt intake reduction using umami substance-incorporated food: a secondary analysis of NHANES 2017-2018 data.

OBJECTIVE: Excessive salt intake raises blood pressure and increases the risk of non-communicable diseases (NCD), such as CVD, chronic kidney disease and stomach cancer. Reducing the Na content of food is an important public health measure to control the NCD. This study quantifies the amount of salt reduced by using umami substances, i.e. glutamate, inosinate and guanylate, for adults in the USA. DESIGN: The secondary data analysis was performed using data of the US nationally representative cross-sectional dietary survey, the National Health and Nutrition Examination Survey (NHANES) 2017-2018. Per capita daily salt intake corresponding to the NHANES food groups was calculated in the four hypothetical scenarios of 0 %, 30 %, 60 % and 90 % market share of low-Na foods in the country. The salt reduction rates by using umami substances were estimated based on the previous study results. SETTING: The USA. PARTICIPANTS: 4139 individuals aged 20 years and older in the USA. RESULTS: Replacing salt with umami substances could help the US adults reduce salt intake by 7·31-13·53 % (7·50-13·61 % for women and 7·18-13·53 % for men), which is equivalent to 0·61-1·13 g/d (0·54-0·98 g/d for women and 0·69-1·30 g/d for men) without compromising the taste. Approximately, 21·21-26·04 % of the US adults could keep their salt intake below 5 g/d, the WHO's recommendation in the scenario where there is no low-Na product on the market. CONCLUSIONS: This study provides essential information that the use of umami substances as a substitute for salt may help reduce the US adults' salt intake.

Current status of clinical proteogenomics in lung cancer.

Introduction: Lung cancer is the leading cause of cancer death worldwide. Proteogenomics, a way to integrate genomics, transcriptomics, and proteomics, have emerged as a way to understand molecular causes in cancer tumorigenesis. This understanding will help identify therapeutic targets that are urgently needed to improve individual patient outcomes. Areas covered: To explore underlying molecular mechanisms of lung cancer subtypes, several efforts have used proteogenomic approaches that integrate next generation sequencing (NGS) and mass spectrometry (MS)-based technologies. Expert opinion: A large-scale, MS-based, proteomic analysis, together with both NGS-based genomic data and clinicopathological information, will facilitate establishing extensive databases for lung cancer subtypes that can be used for further proteogenomic analyzes. Proteogenomic strategies will further be understanding of how major driver mutations affect downstream molecular networks, resulting in lung cancer progression and malignancy, and how therapy-resistant cancers resistant are molecularly structured. These strategies require advanced bioinformatics based on a dynamic theory of network systems, rather than statistics, to accurately identify mutant proteins and their affected key networks.

Clinical protein science in translational medicine targeting malignant melanoma.

Melanoma of the skin is the sixth most common type of cancer in Europe and accounts for 3.4% of all diagnosed cancers. More alarming is the degree of recurrence that occurs with approximately 20% of patients lethally relapsing following treatment. Malignant melanoma is a highly aggressive skin cancer and metastases rapidly extend to the regional lymph nodes (stage 3) and to distal organs (stage 4). Targeted oncotherapy is one of the standard treatment for progressive stage 4 melanoma, and BRAF inhibitors (e.g. vemurafenib, dabrafenib) combined with MEK inhibitor (e.g. trametinib) can effectively counter BRAFV600E-mutated melanomas. Compared to conventional chemotherapy, targeted BRAFV600E inhibition achieves a significantly higher response rate. After a period of cancer control, however, most responsive patients develop resistance to the therapy and lethal progression. The many underlying factors potentially causing resistance to BRAF inhibitors have been extensively studied. Nevertheless, the remaining unsolved clinical questions necessitate alternative research approaches to address the molecular mechanisms underlying metastatic and treatment-resistant melanoma. In broader terms, proteomics can address clinical questions far beyond the reach of genomics, by measuring, i.e. the relative abundance of protein products, post-translational modifications (PTMs), protein localisation, turnover, protein interactions and protein function. More specifically, proteomic analysis of body fluids and tissues in a given medical and clinical setting can aid in the identification of cancer biomarkers and novel therapeutic targets. Achieving this goal requires the development of a robust and reproducible clinical proteomic platform that encompasses automated biobanking of patient samples, tissue sectioning and histological examination, efficient protein extraction, enzymatic digestion, mass spectrometry-based quantitative protein analysis by label-free or labelling technologies and/or enrichment of peptides with specific PTMs. By combining data from, e.g. phosphoproteomics and acetylomics, the protein expression profiles of different melanoma stages can provide a solid framework for understanding the biology and progression of the disease. When complemented by proteogenomics, customised protein sequence databases generated from patient-specific genomic and transcriptomic data aid in interpreting clinical proteomic biomarker data to provide a deeper and more comprehensive molecular characterisation of cellular functions underlying disease progression. In parallel to a streamlined, patient-centric, clinical proteomic pipeline, mass spectrometry-based imaging can aid in interrogating the spatial distribution of drugs and drug metabolites within tissues at single-cell resolution. These developments are an important advancement in studying drug action and efficacy in vivo and will aid in the development of more effective and safer strategies for the treatment of melanoma. A collaborative effort of gargantuan proportions between academia and healthcare professionals has led to the initiation, establishment and development of a cutting-edge cancer research centre with a specialisation in melanoma and lung cancer. The primary research focus of the European Cancer Moonshot Lund Center is to understand the impact that drugs have on cancer at an individualised and personalised level. Simultaneously, the centre increases awareness of the relentless battle against cancer and attracts global interest in the exceptional research performed at the centre.

Development of drug discovery screening system by molecular interaction kinetics-mass spectrometry.

RATIONALE: Drug discovery studies invariably require qualitative and quantitative analyses of target compounds at every stage of drug discovery. We have developed a system combining molecular interaction analysis and mass spectrometry (LC-MS) using the principle of nanopore optical interferometry (nPOI) called molecular interaction kinetics-mass spectrometry (MIK-MS). Since nPOI has high binding capacity, the bond-dissociated compound can be directly detected using LC-MS. In this study, we use carbonic anhydrase II (CAII) as a ligand and apply six small compounds as analytes and report the affinity analysis using MIK-MS. METHODS: CAII was immobilized onto a COOH sensor chip using standard amine coupling. A reference surface was prepared by activating and subsequently blocking the surface under identical conditions. An amount of 50 µL of mix solution was injected over the reference channel and sample channel for CAII immobilization. The solutions eluting from the sensor chip were collected from the waste-line of the SKi Pro system every 30 s. Reconstructed elution samples were then injected into the LC-MS/MS system. RESULTS: A mixture containing furosemide, acetazolamide, 4-sulfamoylbenzoic acid, 5-(dimethylamino)-1-naphthalene sulfonamide (DNSA), sulfanilamide and sulpiride (15 µM each) was injected into the CAII-immobilized sensor chip, and the fractions eluted from the SKi Pro system were collected and subjected to selected reaction monitoring LC-MS characterization. Specific results were obtained for acetazolamide, DNSA, furosemide and sulpiride. The results suggest that the association-dissociation curve of a mixed sample can be obtained by one-time MIK-MS analysis. CONCLUSIONS: Six small-molecule binders of CAII were analyzed quantitatively using nPOI and MIK-MS, and the results were compared to published surface plasmon resonance (SPR) results. The nPOI and SPR results show good agreement, confirming the reliability of the analysis. Time-dependent binding results may be obtained by our MS sensorgram approach. Drugs that meet medical needs in a short period are required; this nPOI-LC-MS system is considered an important tool for rapid drug discovery.

Remote ischemic preconditioning protects human neural stem cells from oxidative stress.

In previous clinical trials, we showed that remote ischemic preconditioning (rIPC) reduced myocardial damage in children undergoing treatment for congenital heart defects and postoperative renal failure in patients undergoing abdominal aortic aneurysm surgery. In rabbit experiments, pre-treatment with plasma and plasma dialysate (obtained using 15-kDa cut-off dialysis membrane) from donor rabbits subjected to rIPC similarly protected against cardiac infarction. However, the protective substances containing in rIPC plasma have been unknown. In the present study, we showed that rIPC plasma exerted anti-apoptotic and anti-oxidative effects on human neural stem cells under oxygen glucose deprivation (OGD) that mimics brain ischemia. Additionally, we applied the sample to the liquid chromatography integrated with mass spectrometry to identify candidate key molecules in the rIPC plasma and determine its role in protecting neural stem cells from OGD-induced cell death. Thioredoxin increased significantly after rIPC compared to pre-IPC. Pretreatment with thioredoxin, the antioxidant protein, markedly protected human neural stem cells from OGD-induced cell death. The effect of thioredoxin on brain ischemia in animals should be further evaluated. However, the present study first evaluated the effect of rIPC in the ischemic cellular model.

Recent mass spectrometry-based proteomics for biomarker discovery in lung cancer, COPD, and asthma.

INTRODUCTION: Lung cancer and related diseases have been one of the most common causes of deaths worldwide. Genomic-based biomarkers may hardly reflect the underlying dynamic molecular mechanism of functional protein interactions, which is the center of a disease. Recent developments in mass spectrometry (MS) have made it possible to analyze disease-relevant proteins expressed in clinical specimens by proteomic challenges. Areas covered: To understand the molecular mechanisms of lung cancer and its subtypes, chronic obstructive pulmonary disease (COPD), asthma and others, great efforts have been taken to identify numerous relevant proteins by MS-based clinical proteomic approaches. Since lung cancer is a multifactorial disease that is biologically associated with asthma and COPD among various lung diseases, this study focused on proteomic studies on biomarker discovery using various clinical specimens for lung cancer, COPD, and asthma. Expert commentary: MS-based exploratory proteomics utilizing clinical specimens, which can incorporate both experimental and bioinformatic analysis of protein-protein interaction and also can adopt proteogenomic approaches, makes it possible to reveal molecular networks that are relevant to a disease subgroup and that could differentiate between drug responders and non-responders, good and poor prognoses, drug resistance, and so on.

History, molecular features, and clinical importance of conventional serum biomarkers in lung cancer.

Serum biomarkers provide valuable information about the diagnosis and prognosis of a wide variety of malignant tumors. Despite the identification of several useful serum biomarkers in lung cancer, consensus on their utility has not yet been reached. Furthermore, guidelines and standard protocols to implement their use for patients with lung cancer are lacking, despite the accumulation of much data on the efficacy of several serum biomarkers over recent decades. In this review, we discuss the molecular features, functions, and clinical relevance of the conventional serum biomarkers for lung cancer, including carcinoembryonic antigen (CEA), cytokeratin 19 fragment 21-1 (CYFRA 21-1), tissue polypeptide antigen (TPA), carbohydrate antigen 19-9 (CA19-9), sialyl Lewisx (sLex), carbohydrate antigen 125 (CA-125), squamous cell carcinoma-related antigen (SCC-Ag), neuron-specific enolase (NSE), and pro-gastrin-releasing peptide (proGRP), aiming to provide a snapshot of the current landscape and their potential combined utility in the diagnosis and prognosis of lung cancer.

Erratum to: Association of chromosome 19 to lung cancer genotypes and phenotypes.

Erratum to: Cancer and Metastasis Review, DOI 10.1007/s10555-015-9556-2. There are changes in authors' affiliations and a new affiliations for Carol L. Nilsson and Thomas E. Fehniger has been added. The corresponding author also missed out to include Peter Horvatovich as a co-author of this work. The complete list of authors is now listed above.

Association of chromosome 19 to lung cancer genotypes and phenotypes.

The Chromosome 19 Consortium, a part of the Chromosome-Centric Human Proteome Project (C-HPP, http://www.C-HPP.org ), is tasked with the understanding chromosome 19 functions at the gene and protein levels, as well as their roles in lung oncogenesis. Comparative genomic hybridization (CGH) studies revealed chromosome aberration in lung cancer subtypes, including ADC, SCC, LCC, and SCLC. The most common abnormality is 19p loss and 19q gain. Sixty-four aberrant genes identified in previous genomic studies and their encoded protein functions were further validated in the neXtProt database ( http://www.nextprot.org/ ). Among those, the loss of tumor suppressor genes STK11, MUM1, KISS1R (19p13.3), and BRG1 (19p13.13) is associated with lung oncogenesis or remote metastasis. Gene aberrations include translocation t(15, 19) (q13, p13.1) fusion oncogene BRD4-NUT, DNA repair genes (ERCC1, ERCC2, XRCC1), TGFß1 pathway activation genes (TGFB1, LTBP4), Dyrk1B, and potential oncogenesis protector genes such as NFkB pathway inhibition genes (NFKBIB, PPP1R13L) and EGLN2. In conclusion, neXtProt is an effective resource for the validation of gene aberrations identified in genomic studies. It promises to enhance our understanding of lung cancer oncogenesis.

Developments for Personalized Medicine of Lung Cancer Subtypes: Mass Spectrometry-Based Clinical Proteogenomic Analysis of Oncogenic Mutations.

Molecular therapies targeting lung cancers with mutated epidermal growth factor receptor (EGFR) by EGFR-tyrosin kinase inhibitors (EGFR-TKIs), gefitinib and erlotinib, changed the treatment system of lung cancer. It was revealed that drug efficacy differs by race (e.g., Caucasians vs. Asians) due to oncogenic driver mutations specific to each race, exemplified by gefitinib / erlotinib. The molecular target drugs for lung cancer with anaplastic lymphoma kinase (ALK) gene translocation (the fusion gene, EML4-ALK) was approved, and those targeting lung cancers addicted ROS1, RET, and HER2 have been under development. Both identification and quantification of gatekeeper mutations need to be performed using lung cancer tissue specimens obtained from patients to improve the treatment for lung cancer patients: (1) identification and quantitation data of targeted mutated proteins, including investigation of mutation heterogeneity within a tissue; (2) exploratory mass spectrometry (MS)-based clinical proteogenomic analysis of mutated proteins; and also importantly (3) analysis of dynamic protein-protein interaction (PPI) networks of proteins significantly related to a subgroup of patients with lung cancer not only with good efficacy but also with acquired resistance. MS-based proteogenomics is a promising approach to directly capture mutated and fusion proteins expressed in a clinical sample. Technological developments are further expected, which will provide a powerful solution for the stratification of patients and drug discovery (Precision Medicine).

A proteomic profile of synoviocyte lesions microdissected from formalin-fixed paraffin-embedded synovial tissues of rheumatoid arthritis.

BACKGROUND: Rheumatoid arthritis (RA) is a systemic autoimmune disease characterized by chronic inflammation of the synovial joints. Early intervention followed by early diagnosis can result in disease remission; however, both early stage diagnosis and provision of effective treatment have been impeded by the heterogeneity of RA, which details of pathological mechanism are unclear. Regardless of numerous investigations of RA by means of genomic and proteomic approaches, proteins interplaying in RA synovial tissues that contain various types of synoviocytes, are not yet sufficiently understood. Hence we have conducted an HPLC/mass spectrometry-based exploratory proteomic analysis focusing on synoviocyte lesions laser-microdissected (LMD) from formalin-fixed paraffin-embedded (FFPE) synovial tissues (RA, n = 15; OA, n = 5), where those of Osteoarthritis (OA) were used as the control. RESULTS: A total of 508 proteins were identified from the RA and OA groups. With the semi-quantitative comparisons, the spectral index (SpI), log2 protein ratio (R SC ) based on spectral counting, and statistical G-test, 98 proteins were found to be significant (pair-wise p < 0.05) to the RA synovial tissues. These include stromelysin-1 (MMP3), proteins S100-A8 and S100-A9, plastin-2, galectin-3, calreticulin, cathepsin Z, HLA-A, HLA-DRB1, ferritin, neutrophil defensin 1, CD14, MMP9 etc. CONCLUSIONS: Our results confirmed the involvement of known RA biomarkers such as stromelysin-1 (MMP3) and proteins S100-A8 and S100-A9, and also that of leukocyte antigens such as HLA-DRB1. Network analyses of protein-protein interaction for those proteins significant to RA revealed a dominant participation of ribosome pathway (p = 5.91 × 10(-45)), and, interestingly, the associations of the p53 signaling (p = 2.34 × 10(-5)). An involvement of proteins including CD14, S100-A8/S100-A9 seems to suggest an activation of the NF-kB/MAPK signaling pathway. Our strategy of laser-microdissected FFPE-tissue proteomic analysis in Rheumatoid Arthritis thus demonstrated its technical feasibility in profiling proteins expressed in synovial tissues, which may play important roles in the RA pathogenesis.

An improvement on mass spectrometry-based epigenetic analysis of large histone-derived peptides by using the Ionization Variable Unit interface.

Highly protonated histone-derived peptides impede a sufficient mass spectrometry (MS)-based epigenetic analysis because their relatively low m/z, due to a high degree of proton addition to peptides, would make it difficult to analyze the resulting complex MS/MS spectra. To reduce the degree of protonations, we have developed a new interface, the Ionization Variable Unit (IVU), in which peptides are ionized under a vaporized organic solvent. It is demonstrated that the doubly charged histone tail H2B peptide, PEPAKSAPAPKKGSKKAVTKAQKK (m/z 1238.243, +2), which was not detectable before, can be detected by using the IVU interface and sequenced.

A new look at drugs targeting malignant melanoma--an application for mass spectrometry imaging.

Malignant melanoma (MM) patients are being treated with an increasing number of personalized medicine (PM) drugs, several of which are small molecule drugs developed to treat patients with specific disease genotypes and phenotypes. In particular, the clinical application of protein kinase inhibitors has been highly effective for certain subsets of MM patients. Vemurafenib, a protein kinase inhibitor targeting BRAF-mutated protein, has shown significant efficacy in slowing disease progression. In this paper, we provide an overview of this new generation of targeted drugs, and demonstrate the first data on localization of PM drugs within tumor compartments. In this study, we have introduced MALDI-MS imaging to provide new information on one of the drugs currently used in the PM treatment of MM, vemurafenib. In a proof-of-concept in vitro study, MALDI-MS imaging was used to identify vemurafenib applied to metastatic lymph nodes tumors of subjects attending the regional hospital network of Southern Sweden. The paper provides evidence of BRAF overexpression in tumors isolated from MM patients and localization of the specific drug targeting BRAF, vemurafenib, using MS fragment ion signatures. Our ability to determine drug uptake at the target sites of directed therapy provides important opportunity for increasing our understanding about the mode of action of drug activity within the disease environment.

Characterization of the key aroma compounds in pork soup stock by using an aroma extract dilution analysis.

The aroma extract dilution analysis of an extract prepared from pork stock and subsequent experiments led to the identification of 15 aroma-active compounds in the flavor dilution factor range of 64-2048. Omission experiments to select the most aroma-active compounds from the 15 odor compounds suggested acetol, octanoic acid, δ-decalactone, and decanoic acid as the main active compounds contributing to the aroma of pork stock. Aroma recombination, addition, and omission experiments of these four aroma compounds in taste-reconstituted pork stock showed that each compound had an individual aroma profile. A comparison of the overall aroma between this recombined mixture and pork stock showed strong similarity, suggesting that the key aroma compounds had been successfully identified.

The Role of Lipids in Enhancing the Koku Perception of Pork Sausage.

This study was investigated the effect of adding fat to pork sausage on taste and aroma persistence. Sensory evaluation indicated that increasing fat content intensified umami and saltiness perception, enhancing the mouthfulness and flavor persistence, leading to Koku enhancing effect. Gas chromatography/mass spectrometry (GC/MS) analysis identified aroma compounds such as ß-pinene, 3-carene, D-limonene, octanal, nonanal, caryophyllene, and methyl eugenol, which were consistently present regardless of fat content. These aroma compounds were less likely to be released as the fat content increased. Furthermore, the release of these aroma compounds from the sausage with addition of fat was larger than that without addition of fat in the presence of saline, indicating that the added fat retained these aroma compounds and released them in the presence of saline. This suggests that sausages with added fat release more aroma compounds during consumption, resulting in a more intense flavor and flavor persistence of Koku perception. These seven compounds detected in pork sausage were found to be easily retained by cholesterol and lecithin, likely due to differences in their log P values (octanol/water partition coefficients), which were greater than 3.

Cholesterol-Lowering and Antioxidant Effects of Pork-Liver Protein Hydrolysate in Otsuka Long-Evans Tokushima Fatty Rats.

In this study, we investigated the effects of a porcine liver protein hydrolysate (PLH) diet on lipid metabolism in Otsuka Long-Evans Tokushima Fatty (OLETF) rats, a model of type II diabetes. OLETF rats (20-wk-old males) were pair-fed with either a PLH diet containing 20% PLH or a casein diet for 14 wk. Dietary PLH significantly lowered serum cholesterol and phospholipid concentrations, mainly by decreasing low-density lipoprotein and high-density lipoprotein fractions. Fecal cholesterol was significantly increased in the PLH diet group; however, the total bile acid concentration in the feces was not significantly different between the groups. In addition, the PLH diet significantly decreased serum thiobarbituric acid reactive substance concentrations. These results suggest that dietary PLH exerts hyperlipidemic and antioxidant effects, indicating that it is a novel functional food ingredient.