Dietary oleic acid intake increases the proportion of type 1 and 2X muscle fibers in mice.

Skeletal muscle is one of the largest metabolic tissues in mammals and is composed of four different types of muscle fibers (types 1, 2A, 2X, and 2B); however, type 2B is absent in humans. Given that slow-twitch fibers are superior to fast-twitch fibers in terms of oxidative metabolism and are rich in mitochondria, shift of muscle fiber types in direction towards slower fiber types improves metabolic disorders and endurance capacity. We previously had reported that oleic acid supplementation increases type 1 fiber formation in C2C12 myotubes; however, its function still remains unclear. This study aimed to determine the effect of oleic acid on the muscle fiber types and endurance capacity. An in vivo mouse model was used, and mice were fed a 10% oleic acid diet for 4 weeks. Two different skeletal muscles, slow soleus muscle with the predominance of slow-twitch fibers and fast extensor digitorum longus (EDL) muscle with the predominance of fast-twitch fibers, were used. We found that dietary oleic acid intake improved running endurance and altered fiber type composition of muscles, the proportion of type 1 and 2X fibers increased in the soleus muscle and type 2X increased in the EDL muscle. The fiber type shift in the EDL muscle was accompanied by an increased muscle TAG content. In addition, blood triacylglycerol (TAG) and non-esterified fatty acid levels decreased during exercise. These changes suggested that lipid utilization as an energy substrate was enhanced by oleic acid. Increased proliferator-activated receptor γ coactivator-1ß protein levels were observed in the EDL muscle, which potentially enhanced the fiber type transitions towards type 2X and muscle TAG content. In conclusion, dietary oleic acid intake improved running endurance with the changes of muscle fiber type shares in mice. This study elucidated a novel functionality of oleic acid in skeletal muscle fiber types. Further studies are required to elucidate the underlying mechanisms. Our findings have the potential to contribute to the field of health and sports science through nutritional approaches, such as the development of supplements aimed at improving muscle function.

Effects of the dipeptides comprising leucine and lysine on lifespan and age-related stress in Caenorhabditis elegans.

The aging process is affected by various stressors. An increase in oxidative stress is related to the impairment of physiological functions and enhancement of glycative stress. Food-derived bioactive peptides have various physiological functions, including antioxidant activities. Dipeptides comprising Leu and Lys (LK and KL, respectively) have been isolated from foods; however, their physiological properties remain unclear. In this study, we investigated the antioxidant/antiglycation activity of dipeptides and their antiaging effects using Caenorhabditis elegans (C. elegans). Both dipeptides showed antioxidant activities against several reactive oxygen species (ROS) in vitro. In particular, the scavenging activity of LK against superoxide radicals was higher than KL did. Moreover, dipeptides suppressed advanced glycation end products (AGEs) formation in the BSA-glucose model. In the lifespan assays using wild-type C. elegans, both LK and KL significantly prolonged the mean lifespan by 20.9% and 11.7%, respectively. In addition, LK decreased intracellular ROS and superoxide radical levels in C. elegans. Blue autofluorescence, an indicator of glycation in C. elegans with age, was also suppressed by LK. These results suggest that dipeptides, notably LK, show an antiaging effect by suppressing oxidative and glycative stress. Our findings suggest that such dipeptides can be used as a novel functional food ingredient. Food-derived dipeptide Leu-Lys (LK) and Lys-Leu (KL) exert antioxidant and antiglycation activity in vitro. Treatment with LK prolonged the mean lifespan and maximum lifespan of C. elegans more than that of KL. Intracellular ROS and blue autofluorescence levels (indicator of aging) were suppressed by LK.

Dietary olive oil intake induces female-specific hepatic lipid accumulation without metabolic impairment in mice.

Olive oil is one of the most widely researched Mediterranean diet components in both experimental models and clinical studies. However, the relationship between dietary olive oil intake and liver function in a healthy state of the body remains unclear. Because men are at a greater risk of developing hepatic diseases than women, and because hepatic metabolism is regulated by sex hormones, we hypothesized that olive oil-induced changes in hepatic metabolism would differ by sex. To test our hypothesis, 12-week-old C57BL/6JJcl male and female mice were fed an olive oil diet for 4 weeks. Blood was collected and serum biochemical components were analyzed. Hepatic lipid accumulation was determined via histological analysis using Sudan III staining. Finally, transcript expression levels of hepatic metabolism-related genes were analyzed using quantitative polymerase chain reaction. We observed significant increased hepatic lipid droplet accumulation in olive oil-fed female mice. Serum biochemical and liver messenger RNA expression analyses revealed that the hepatic lipid accumulation was nonpathological and did not involve inflammation. Moreover, the expression of genes related to triacylglycerol and fatty acid synthesis (Dgat1, Dgat2, Agpat3, and Fasn) was significantly upregulated in the liver of olive oil-fed female mice compared with control female mice. Our study demonstrates female-specific hepatic lipid accumulation without liver impairment in a dietary olive oil-fed mouse model. These findings provide a deeper mechanistic understanding of sex-dependent hepatic lipid metabolism of dietary oils.

Comparison of 2,5-dimethyl-4-hydroxy-3(2H)-furanone, a volatile odor compound generated by the Maillard reaction, in cooked meat of various animal species and parts.

2,5-Dimethyl-4-hydroxy-3(2H)-furanone (DMHF), a compound having a sweet caramel-like odor, is one of the major compounds generated by the Maillard reaction. DMHF could affect the palatability of cooked and processed foods such as meat, while its inhalation induces several physiological functions. However, basic findings of DMHF generation in meat remain unclear. In this study, we compared the amount of DMHF in cooked meat of various animal meat (Japanese black cattle beef, Australian beef, pork, and chicken) and parts (round, loin, thigh, and breast). Meat samples were heated at 230°C, and then the amount of DMHF was measured using the solvent extraction methods. Moreover, the substrates (total free amino acid and glucose) used for the Maillard reaction were also measured to elucidate the relation between DMHF generation and nutrients in meat. DMHF was detected in all cooked meat samples, suggesting that DMHF is generated in meat regardless of animal species and parts. A significant positive correlation was observed between the DMHF generation and glucose content in the round and thigh parts. Our results suggest that DMHF generation during meat cooking would be regulated by the glucose content.

Impact of oxidation on the cardioprotective properties of the bioactive dipeptide AW in dry-cured ham.

Unbalanced oxidative reactions occurred during the dry-curing period of ham can trigger unpleasant taste. Additionally, salt might mediate in these reactions that cause the oxidation of some of the generated peptides acting as a pro-oxidant. The influence of the processing and oxidation on the release of peptides and bioactivity have been dimly investigated. In this study, the dipeptide AW, and its oxidized form AWox were quantitated in dry-cured ham. AW concentration reached 4.70 mg/g of dry-cured ham at 24 months of traditional dry-curing. The intact and the oxidized peptide forms accumulated to 5.12 and 6.80 µg/g dry-cured ham in 12-months low-salted hams, respectively, while they were undetectable in 12 months-traditionally elaborated hams. Moreover, oxidation affected the antioxidant properties depending on the in vitro assay and reduced the AW potential as antihypertensive. This study reports the potential role of the dry-cured ham-derived peptide AW on cardiovascular health and the relevance of post-oxidation on its bioactivity.

Dietary Olive Oil Intake Improves Running Endurance with Intramuscular Triacylglycerol Accumulation in Mice.

Olive oil is a functional food shown to have a variety of bioactive effects. Therefore, we expect it to be a novel functional food with an exercise-mimetic effect on skeletal muscles. This study aimed to investigate the effect of olive oil on the endurance capacity and muscle metabolism in mice. Mice fed a 7% (w/w) olive oil diet for eight weeks showed improved treadmill running endurance and increased intramuscular triacylglycerol (IMTG) accumulation in the gastrocnemius muscle compared to soybean oil diet-fed controls. The increase in running endurance with olive oil intake was independent of the muscle fiber type. To elucidate underlying the mechanism of elevated IMTG levels, we examined the expression levels of the genes related to lipid metabolism. We found that the expression of diacylglycerol O-acyltransferase1 (DGAT1) was significantly upregulated in the muscle of olive oil diet-fed mice. In addition, the olive oil diet-fed mice showed no metabolic impairment or differences in growth profiles compared to the controls. These results suggest that dietary olive oil intake affects muscle metabolism and muscle endurance by increasing energy accumulation.

Skeletal Muscle Fibre Type Changes in an Avian Model of Hepatic Fibrosis.

We investigated the susceptibility of type I and type II skeletal myofibres to atrophy in hens with hepatic fibrosis induced by bile duct ligation (BDL). Seven hens, approximately 2 years old, were randomly assigned to BDL (n = 4) and sham surgery (SHAM) (n = 3) groups. Mean body weight and mean liver weight as a percentage of mean body weight were significantly lower in the BDL group than in the SHAM group at 4 weeks post surgery (P = 0.002, P = 0.005, respectively). Mean plasma aspartate aminotransferase activity was slightly higher, while total cholesterol (P <0.001), total bilirubin (P = 0.022) and NH3 (P = 0.048) concentrations were significantly higher in the BDL group than in the SHAM group. Liver lesions were induced in all hens in the BDL group. The weights of the pectoralis (PCT) (P = 0.049) and flexor perforans et perforatus digiti III (FPPD III) muscles (P = 0.006) as a percentage of body weight were significantly decreased in the BDL group. A significantly reduced mean myofibre cross-sectional area in the PCT of BDL hens (P = 0.005) was indicative of atrophy. No significant differences were observed in the fibre type composition of the PCT, supracoracoideus or FPPD III muscles between the SHAM and BDL groups. However, there was an approximate 43% increase in the number of type I fibres in the femorotibialis lateralis of the BDL group and small angular type II fibres and large round type I fibres in this muscle were characteristic of peripheral neuropathy. The results suggest that type II fibres are more susceptible to atrophy than type I fibres in this model of hepatic fibrosis.

Inhalation of odors containing DMHF generated by the Maillard reaction affects physiological parameters in rats.

The effects of odors generated by the Maillard reaction from amino acids and reducing sugars on physiological parameters (blood pressure, heart rate, and oxidative stress levels) in Wistar rats were investigated in the present study. The Maillard reaction samples were obtained from glycine, arginine, or lysine of 1.0 mol/L and glucose of 1.0 mol/L with heat treatment. The odor-active compounds in the Maillard reaction samples were identified using the aroma extract dilution analysis. Among the odor-active compounds identified, 2,5-dimethyl-4-hydroxy-3(2H)-furanone (DMHF, FURANEOL and strawberry furanone) had the highest odor activity and its concentration was affected by amino acid types. The Maillard reaction odors generated from glycine or arginine significantly decreased systolic blood pressure and heart rate in rats when inhaled. These physiological effects were associated with DMHF. Furthermore, oxidative stress marker levels in rat plasma were decreased by the inhalation of DMHF. The inhalation of DMHF appears to at least partly affect physiological parameters by decreasing oxidative stress.

Correlation between skeletal muscle fiber type and responses of a taste sensing system in various beef samples.

The difference of muscle fiber type composition affects several parameters related to meat quality; however, the relationship between muscle fiber types and meat taste is unclear. To elucidate this relationship, we determined the taste of various beef samples using a taste sensor (INSENT SA402B) and analyzed its correlation with different muscle fiber type composition. We used 22 kinds of beef samples and measured nine tastes, including the relative and change of membrane potential caused by adsorption (CPA) values, using six sensors (GL1, CT0, CA0, AAE, C00, and AE1). The taste sensor analysis indicated positive value outputs for the relative C00, AAE, and GL1 values as well as for the CPA value of AAE, which corresponded to bitterness, umami, sweetness, and richness, respectively. We found significant positive correlations of the myosin heavy chain 1 (MyHC1) composition with umami taste, and with richness. This result suggests that high levels of slow MyHC1 can induce strong umami taste and richness in beef. We expect that our results will contribute to the elucidation of the relationship between muscle fiber types and meat palatability.

2,3-Dimethylpyrazine (3DP) and 2,5-dimethyl-4-hydroxy-3(2H)-furanone (DMHF) generated by the Maillard reaction in foods affect autonomic nervous activity and central nervous activity in human.

This study investigated the effect of the odors generated by the glycine/glucose Maillard reaction and the potent odorants 2,3-dimethylpyrazine (3DP) and 2,5-dimethyl-4-hydroxy-3(2H)-furanone (DMHF) on the human mood and integrative physiological activity. The score of certain subjective moods, especially anger-hostility, and tension-anxiety were decreased significantly after inhalation of the Maillard reaction sample and DMHF, and fatigue-inertia mood was also significantly decreased by DMHF, suggesting a sedative effect of these odors on mood, while 3DP had no effect. Miosis rate and fingertip temperature increased significantly following inhalation of the odor from the Maillard reaction sample and both potent odorants, suggesting that the parasympathetic nervous system dominates through suppression of the sympathetic activity. The physiological relaxing effect of these odors was also confirmed by decreased flicker frequency value and decreased oxyhemoglobin in the prefrontal cortex.

DMHF (2,5-dimethyl-4-hydroxy-3(2H)-furanone), a volatile food component generated by the Maillard reaction, promotes appetite and changes gene expression in the rat brain through inhalation.

Inhalation of odors can affect physiological parameter and change gene expression-related specific function. 2,5-Dimethyl-4-hydroxy-3(2H)-furanone (DMHF) is one of the major odor compounds generated by the Maillard reaction. We previously reported that the inhalation of DMHF decreased systolic blood pressure via the autonomic nervous system in rats. The autonomic nervous system is also closely related to appetite regulation. The present study investigated the effects of DMHF on dietary intake and gene expression. The inhalation of DMHF increased the dietary intake of rats during the feeding period. However, body weight did not change after 6 weeks feeding. A DNA microarray analysis showed that DMHF altered gene expression associated with feeding behavior and neurotransmission in the rat brain. DMHF inhalation promotes appetite and changes gene expression in rats. Furthermore, phenotypic changes may regulate neurotransmission and appetite at the mRNA level in addition to controlling the autonomic nervous system. PRACTICAL APPLICATION: DMHF is an important flavor component in the food industry. In this study, we first observed that the inhalation of DMHF promotes appetite. This finding is directly connected with the industrial application.

Oleic acid up-regulates myosin heavy chain (MyHC) 1 expression and increases mitochondrial mass and maximum respiration in C2C12 myoblasts.

Skeletal muscle is divided into type 1 and type 2 fibers. Type 1 fibers are rich in mitochondria, have high oxidative metabolism, and are resistant to fatigue. Muscle-specific overexpression of peroxisome proliferator-activated receptor (PPAR)δ drastically increases the number of type 1 fibers. We focused on oleic acid, an omega-9 monounsaturated fatty acid, as a factor that activates PPARδ. In this study, we examined the effects of oleic acid on the muscle fiber type of C2C12 myotubes and its relationship with PPARδ. Our results showed that oleic acid treatment increased the levels of myosin heavy chain (MyHC)1, a known type 1 fiber marker, as well as mitochondrial mass and maximum respiration in C2C12 cells. To confirm the relationship between PPARδ activation and oleic acid-induced MyHC1 increase, we examined the effects of oleic acid in PPARδ knockdown C2C12 myoblasts. We found that oleic acid supplementation increased the mRNA expression of MyHC1 in PPARδ-knockdown C2C12 cells. Our data suggest that oleic acid increases type 1 fiber levels in C2C12 myotubes in a PPARδ-independent manner.

Effect of dietary fish oil intake on ubiquitin ligase expression during muscle atrophy induced by sciatic nerve denervation in mice.

Dietary fish oil intake improves muscle atrophy in several atrophy models however the effect on denervation-induced muscle atrophy is not clear. Thus, the aim of this study was to investigate the effects of dietary fish oil intake on muscle atrophy and the expression of muscle atrophy markers induced by sciatic nerve denervation in mice. We performed histological and quantitative mRNA expression analysis of muscle atrophy markers in mice fed with fish oil with sciatic nerve denervation. Histological analysis indicated that dietary fish oil intake slightly prevented the decrease of muscle fiber diameter induced by denervation treatment. In addition, dietary fish oil intake suppressed the MuRF1 (tripartite motif-containing 63) expression up-regulated by denervation treatment, and this was due to decreased tumor necrosis factor-alpha (TNF-α) production in skeletal muscle. We concluded that dietary fish oil intake suppressed MuRF1 expression by decreasing TNF-α production during muscle atrophy induced by sciatic nerve denervation in mice.

Investigation of potent odorants generated during the production of whey protein hydrolysates.

Whey protein hydrolysates (WPH) were prepared from whey protein concentrate (WPC) by partial or extensive hydrolysis. WPC and two WPH types were characterized by a descriptive sensory analysis. WPC exhibited a "milky", "sweet", and "mild milk fat" odor, whereas extensively hydrolyzed whey protein (E-WPH) demonstrated "cheese-like", "acrid odor", and "sour" olfactory characteristics. In E-WPH, 3-(methylthio)-propanal, phenylacetaldehyde, and 3-methylbutanoic acid were specifically detected with high flavor dilution factors upon aroma extract dilution analysis. These odor-active compounds likely contributed to the olfactory characteristics of E-WPH, and their concentration increased together with that of their respective putative precursors: free methionine, phenylalanine, and leucine.

Odors generated from the Maillard reaction affect autonomic nervous activity and decrease blood pressure through the olfactory system.

BACKGROUND: Systolic blood pressure (SBP) of rats decreases significantly following exposure to the odor generated from the Maillard reaction of protein digests with xylose. This study identified active odorants that affect blood pressure and demonstrated the mechanism of action. RESULTS: Among the four potent odorants that contribute most to the odor of the Maillard reaction sample, 2,5-dimethyl-4-hydroxy-3(2H)-furanone (DMHF) and 5-methyl-2-pyrazinemethanol (MPM) decreased SBP significantly. The earliest decrease in blood pressure was observed 5 min after exposure to DMHF. Application of zinc sulfate to the nasal cavity eliminated the effect. Furthermore, gastric vagal (parasympathetic) nerve activity was elevated and renal sympathetic nerve activity was lowered after exposure to DMHF. CONCLUSION: It is indicated that DMHF affects blood pressure through the olfactory system, and the mechanism for the effect of DMHF on blood pressure involves the autonomic nervous system. © 2017 Society of Chemical Industry.

Identification of two novel antioxidant peptides from edible bird's nest (Aerodramus fuciphagus) protein hydrolysates.

Edible bird's nest (EBN) is widely consumed as a delicacy and traditional medicine amongst the Chinese. In the present study, for the first time, the antioxidant properties of an EBN pepsin-trypsin hydrolysate of the swiftlet species Aerodramus fuciphagus and its ultrafiltration fractions were investigated. Thirteen peptides with molecular weights between 514.29 and 954.52 Da were identified in the EBN fraction with the use of mass spectrometry. Two novel pentapeptides Pro-Phe-His-Pro-Tyr and Leu-Leu-Gly-Asp-Pro, corresponding to f134-138 and f164-168 of cytochrome b of A. fuciphagus, indicated the highest ORAC values of 14.95 and 14.32 µM of TE µM-1 peptide, respectively. Both purified peptides showed resistance against simulated gastrointestinal proteases. In addition, both peptides had no in vitro cytotoxicity on human lung MRC-5 cells and prevented human liver carcinoma HepG2 cellular damage caused by hydroxyl radicals. Therefore, it is suggested that EBN protein hydrolysates are a good source of natural antioxidants and could be applied as nutraceutical compounds.

Effects of odor generated from the glycine/glucose Maillard reaction on human mood and brainwaves.

Effects of the odor generated from the glycine/glucose Maillard reaction on human mood and brainwaves were investigated in the present study. Equimolar solutions of glucose and glycine were adjusted to pH 7 and pH 9 and heated at 90 °C for 30 min. The odor generated from the glycine/glucose Maillard reaction significantly decreased negative moods. Its effects on brainwaves differed according to pH; alpha brainwave distribution was increased after inhalation of the odor generated at pH 7, whereas it was decreased by the odor generated at pH 9. The effects on mood and brainwaves were also measured after inhalation of model solutions, which comprised of potent odorants determined by aroma extract dilution analysis (AEDA), and the results were similar to those obtained with the Maillard reaction samples. Therefore, odors constructed by potent odorants could influence human mood and brainwaves. Among all potent odorants, 2,3-dimethylpyrazine and 2,5-dimethyl-4-hydroxy-3(2H)-furanone (DMHF) were identified as the strongest, and high pH values resulted in higher yields of these odorants. Furthermore, DMHF was identified as the putative agent responsible for the decrease in alpha brainwave distribution after smelling the pH-9 Maillard reaction sample since higher concentrations of DMHF resulted in a similar effect.

Antioxidant activity of fermented meat sauce and isolation of an associated antioxidant peptide.

The present study was carried out to investigate the radical scavenging and antioxidant activities of fermented meat sauce (FMS) against 1,1-diphenyl-2-picrylhydrazyl (DPPH) and the hydroxyl radical (OH-radical), as well as to isolate substances in FMS related to its antioxidant activity. FMS was prepared by mixing ground pork, koji (rice fermented with koji mold such as Aspergillus), and salt, and fermenting for 24weeks. High antioxidant activities against the DPPH radical and the OH-radical in FMS were observed as about 0.55µmolTroloxeq./ml and 61.2%, respectively. DPPH radical scavenging activities were related to time-dependent changes in proteolysis and antioxidant peptides could be generated in FMS by proteolysis. Liquid chromatography-mass spectrometry analysis detected a substance of molecular weight 406.26g/mol from the purified peptide fraction, which showed an extremely high antioxidant activity against the OH-radical that was greater than 90%. This substance was anticipated to be the tripeptide Gln-Tyr-Pro.

Angiotensin converting enzyme (ACE) inhibitory and antihypertensive activities of protein hydrolysate from meat of Kacang goat (Capra aegagrus hircus).

BACKGROUND: The meat of Kacang goat has potential for production of a protein hydrolysate. Functional ingredients from protein hydrolysate of Kacang goat meat were determined by the consistency of angiotensin-converting enzyme (ACE) inhibitory activity and antihypertensive effect. This study examined the potency of Kacang goat protein hydrolysate in ACE inhibition and antihypertensive activity. RESULT: Protein hydrolysates of Kacang goat meat were prepared using sequential digestion of endo-proteinase and protease complex at several concentrations and hydrolysis times. The highest ACE inhibitory activity resulted from a hydrolysate that was digested for 4 h with 5 g kg(-1) of both enzymes. An ACE inhibitory peptide was purified and a novel peptide found with a sequence of Phe-Gln-Pro-Ser (IC50 value of 27.0 µmol L(-1) ). Both protein hydrolysates and a synthesised peptide (Phe-Gln-Pro-Ser) demonstrated potent antihypertensive activities in spontaneously hypertensive rats. CONCLUSION: Protein hydrolysate of Kacang goat meat produced by sequential digestion with endo-proteinase and protease complex has great potential as a functional ingredient, particularly as an antihypertensive agent. © 2015 Society of Chemical Industry.