[Show abstract][Hide abstract] ABSTRACT: Body temperature homoeostasis in mammals is governed centrally through the regulation of shivering and non-shivering thermogenesis and cutaneous vasomotion. Non-shivering thermogenesis in brown adipose tissue (BAT) is mediated by sympathetic activation, followed by PGC-1α induction, which drives UCP1. Here we identify nardilysin (Nrd1 and NRDc) as a critical regulator of body temperature homoeostasis. Nrd1(-/-) mice show increased energy expenditure owing to enhanced BAT thermogenesis and hyperactivity. Despite these findings, Nrd1(-/-) mice show hypothermia and cold intolerance that are attributed to the lowered set point of body temperature, poor insulation and impaired cold-induced thermogenesis. Induction of β3-adrenergic receptor, PGC-1α and UCP1 in response to cold is severely impaired in the absence of NRDc. At the molecular level, NRDc and PGC-1α interact and co-localize at the UCP1 enhancer, where NRDc represses PGC-1α activity. These findings reveal a novel nuclear function of NRDc and provide important insights into the mechanism of thermoregulation.
[Show abstract][Hide abstract] ABSTRACT: Changes in the extracellular concentration of dopamine (DA) in the nucleus accumbens (NAc) shell and the basolateral amygdala (BLA) resulting from the voluntary ingestion of either corn oil, mineral oil, or 1% linoleic acid diluted with mineral oil as a vehicle were measured in rats by using in vivo microdialysis after they had been trained to establish a preference for corn oil. Ingesting the mineral oil caused no significant change in DA level in the NAc shell, whereas corn oil ingestion significantly increased the DA level during 0-15 min of the test session, reaching the maximum level of 129.8 ± 6.2% compared with the baseline after 10 min. Ingesting linoleic acid also resulted in a significant increase in DA level during 0-20 min, reaching 125.9 ± 9.0% after 10 min. Similar results were obtained in the BLA. Despite its very low calorie content, a low concentration of non-esterified fatty acid increased the DA levels equivalent to those resulting from corn oil in the brain's reward system.
Bioscience Biotechnology and Biochemistry 11/2013; · 1.27 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The present study explored the possibility of generating a novel sensory evaluation instrument for describing comprehensive food palatability via its subdomains (rewarding, cultural, and informational) while keeping physiological factors constant. Seventy-five Japanese participants were asked to taste cheese samples and to respond to a questionnaire that was developed to dissect the distinct subdomains of palatability. The subsequent factor analyses revealed that three major factors may serve as distinct subdomains of palatability: rewarding, cultural, and informational, although the informational factor was not sufficiently robust. Multivariate regression analysis on cheese samples with exactly the same ingredients but sold in different packages led to different comprehensive palatability ratings due to the contribution of the cultural, but not the rewarding, factor. These results suggest that palatability is not merely determined by the physical and chemical properties that are intrinsic to a food product itself, but also depends on psychological properties that can arise through interaction between humans and the food product. The current study presents the first experimental demonstration that palatability could be dissociated to its subdomains.
[Show abstract][Hide abstract] ABSTRACT: The present study explored the possibility that aroma components generated by the oxidation of olive oil may enhance the palatability of olive oil. Using a mouse behavioral model, we found that olive oil oxidized at room temperature for 3 weeks after opening the package, and heated olive oil were both significantly preferred over non-oxidized olive oil. Furthermore, this preference was enhanced with an additive of oxidized refined olive oil flavoring preparation at a certain concentration. These results suggest that the aroma of oxidized fat might be present in most fats, and might act as a signal that makes possible the detection of fats or fatty acid sources.
Bioscience Biotechnology and Biochemistry 06/2013; · 1.27 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Matriptase is an epithelial-derived type-II transmembrane serine protease. This protease is expressed prominently in the villus tip of small-intestinal epithelia at which senescent cells undergo shedding and/or apoptosis. The basement membrane of epithelial cells, including small-intestinal epithelial cells, contains extracellular matrix (ECM) proteins such as fibronectin and laminin. We found previously that high concentrations of a recombinant matriptase catalytic domain (r-MatCD) (e.g. 1 μM) caused an increased detachment of and increases in the activity of apoptotic effector caspase-3 in a rat small-intestinal epithelial IEC-6 line cultured on laminin-coated plates and proposed that at sites with its high level of expression, matriptase contributes to promoting shedding and/or detachment-induced death of epithelial cells through a mechanism mediating loss of cell-ECM adhesion. In this study, we found that even without increasing cell detachment, a high concentration of r-MatCD causes an increase in caspase-3 activity in IEC-6 cells cultured on fibronectin-coated plates, suggesting that the recombinant matriptase can cause apoptosis by a mechanism unrelated to cell detachment. Also, r-MatCD-treated IEC-6 cells on fibronectin were found to display spindle-like morphological changes. We suggest that r-MatCD causes apoptosis of IEC-6 on fibronectin by a mechanism involving the disruption of cell integrity.
[Show abstract][Hide abstract] ABSTRACT: CD36 binds oxidized low-density lipoprotein (oxLDL). A synthetic peptide comprising amino-acid residues 149-168 of mouse CD36 was recently found to bind fluorescence-labeled oxLDL particles. Based on our oxLDL-binding analysis of various synthetic CD36 peptides, we suggest that not only hydrophilic residues (e.g., Lys164 and Lys166) but also hydrophobic ones (e.g., Phe153, Leu158, and Leu161) are critical to binding.
Bioscience Biotechnology and Biochemistry 05/2013; · 1.27 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: CD36 is an integral membrane protein that mediates the cellular uptake of oxidized low-density lipoprotein (oxLDL) through recognition of the oxidized glycerophospholipids (oxPLs) formed during LDL oxidation. We aimed to devise an assay system to detect binding between CD36 and oxLDL/oxPL without using recombinant proteins. A peptide corresponding to amino-acid residues 149-168 of mouse CD36 with biotin at its N-terminus (named biotin-CD36(149-168)) and variants of it were synthesized and immobilized onto streptavidin-coated plates. oxLDL labeled with Alexa-Fluor-488 bound specifically and saturably to immobilized biotin-CD36(149-168), but poorly or not at all to the variants, such as that with a scrambled amino-acid sequence. The binding of fluorescence-labeled oxLDL to biotin-CD36(149-168) was inhibited efficiently by an oxPL species, but not by a nonoxidized glycerophospholipid. This assay system using biotin-CD36(149-168) provides a convenient means not only of characterizing binding profiles between CD36 and oxLDL/oxPL but also of finding competitors for the binding.
Bioscience Biotechnology and Biochemistry 01/2013; · 1.27 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We investigated the effects of allyl isothiocyanate (AITC) on the blood glucose levels of mice using an intraperitoneal glucose tolerance test. The intragastric administration of 25 mg/kg body weight AITC reduced the increase in blood glucose level after 2 g/kg body weight glucose was given intraperitoneally, compared with that of control mice. To elucidate the mechanism responsible for the reduction, respiratory gas analysis employing (13)C-labeled glucose was performed. The intragastrically administering AITC increased (13)CO2 emission, compared to vehicle, after intraperitoneal administration of (13)C-labeled glucose. This indicated that AITC increased the utilization of exogenously administered glucose, which was excessive glucose in the blood. To examine whether transient receptor potential (TRP) channels mediated this reduction in the blood glucose levels, we used TRPA1 and TRPV1 knockout (KO) mice. Intragastrically administering AITC reduced the increase in the blood glucose level in TRPA1 KO mice but not in TRPV1 KO mice. These findings suggest that dietary AITC might reduce the increases in blood glucose levels by increasing the utilization of excessive glucose in the blood by activating TRPV1.
Journal of Nutritional Science and Vitaminology 01/2013; 59(1):56-63. · 0.99 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Milk is an effective post-exercise rehydration drink that maintains the net positive fluid balance. However, it is unclear which components are responsible for this effect. We assessed the effect of milk protein solution (MPS) obtained by dialysis on body fluid retention. Milk, MPS, milk electrolyte solution (MES), sports drink and water were administered to male Wistar rats at a dose of 6 ml/rat after treadmill exercise. Total body fluid retention was assessed by urine volume 4 h after administration of hydrating liquids. The rate of gastric emptying was evaluated by a tracer method using 13C-labelled acetate. Plasma osmolality, Na and K levels, and urinary Na and K were measured by HPLC and osmometry, respectively. The gastric emptying rate was not delayed by MPS. During 4 h of rehydration, cumulative urine volumes differed significantly between treatment groups (P < 0·05) with 4·9, 2·2 and 3·4 ml from water-, milk- and MPS-fed rats, respectively. Thus, MPS elicited 50 % of the total body fluid retention of milk. Plasma aldosterone levels were significantly higher in MPS- and milk-fed rats compared with water-fed rats. Plasma osmolality was maintained at higher levels in MPS-fed rats than in water- and MES-fed rats (P < 0·05). Cumulative urine Na excretion was also suppressed in the milk- and MPS-fed groups compared with the MES-fed group. Our results demonstrate that MPS obtained by dialysis clearly affects net body water balance without affecting gastric emptying after exercise. This effect was attributed to retention of Na and water, and maintenance of plasma osmolality.
[Show abstract][Hide abstract] ABSTRACT: Matriptase is a type II transmembrane serine protease containing two complement proteases C1r/C1s-urchin embryonic growth factor-bone morphogenetic protein domains (CUB repeat) and four low-density lipoprotein receptor class A domains (LDLRA repeat). The single-chain zymogen of matriptase has been found to exhibit substantial protease activity, possibly causing its own activation (i.e., conversion to a disulfide-linked two-chain fully active form), although the activation appears to be mediated predominantly by two-chain molecules. Our aim was to assess the roles of CUB and LDLRA repeats in zymogen activation. Transient expression studies of soluble truncated constructs of recombinant matriptase in COS-1 cells showed that the CUB repeat had an inhibitory effect on zymogen activation, possibly because it facilitated the interaction of two-chain molecules with a matriptase inhibitor, hepatocyte growth factor activator inhibitor type-1. By contrast, the LDLRA repeat had a promoting effect on zymogen activation. The effect of the LDLRA repeat appears to reflect its ability to increase zymogen activity. The proteolytic activities were higher in pseudozymogen forms of recombinant matriptase containing the LDLRA repeat than in a pseudozymogen without the repeat. Our findings provide new insights into the roles of these non-catalytic domains in the generation of active matriptase.
Journal of biochemistry 10/2012; · 1.95 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Lipid droplets (LDs) are ubiquitous organelles storing neutral lipids, including triacylglycerol (TAG) and cholesterol ester. The properties of LDs vary greatly among tissues, and LD-binding proteins, the perilipin family in particular, play critical roles in determining such diversity. Overaccumulation of TAG in LDs of non-adipose tissues may cause lipotoxicity, leading to diseases such as diabetes and cardiomyopathy. However, the physiological significance of non-adipose LDs in a normal state is poorly understood. To address this issue, we generated and characterized mice deficient in perilipin 5 (Plin5), a member of the perilipin family particularly abundant in the heart. The mutant mice lacked detectable LDs, containing significantly less TAG in the heart. Particulate structures containing another LD-binding protein, Plin2, but negative for lipid staining, remained in mutant mice hearts. LDs were recovered by perfusing the heart with an inhibitor of lipase. Cultured cardiomyocytes from Plin5-null mice more actively oxidized fatty acid than those of wild-type mice. Production of reactive oxygen species was increased in the mutant mice hearts, leading to a greater decline in heart function with age. This was, however, reduced by the administration of N-acetylcysteine, a precursor of an antioxidant, glutathione. Thus, we conclude that Plin5 is essential for maintaining LDs at detectable sizes in the heart, by antagonizing lipase(s). LDs in turn prevent excess reactive oxygen species production by sequestering fatty acid from oxidation and hence suppress oxidative burden to the heart.
Journal of Biological Chemistry 04/2012; 287(28):23852-63. · 4.65 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The opioid system regulates food choice, consumption, and reinforcement processes, especially for palatable meals such as fatty food. β-Endorphin is known as an endogenous opioid peptide produced in neurons of the hypothalamus. In this study, we found that Intralipid (fat emulsion) ingestion increased c-fos expression in β-endorphin neurons. However, intragastric infusion of Intralipid only slightly increased c-fos expression 2h after infusion. Further, dissection of glossopharyngeal nerve, innervating posterior tongue taste buds, partially but significantly decreased the Intralipid-induced c-fos expression. These results indicate that mainly the orosensory stimulation from fat may activate β-endorphin neurons, thereby promoting β-endorphin release.
[Show abstract][Hide abstract] ABSTRACT: Moderate-intensity running (treadmill velocity of 21 m/min) increased blood lactate and actived transforming growth factor-β (TGF-β) concentration in rat cerebrospinal fluid (CSF). On the other hand, low-intensity running (15 m/min) did not increase blood lactate and caused no change in CSF TGF-β. Intraperitoneal (i.p.) administration of lactate to anesthetized rats caused an increase in blood lactate similar to that observed after a 21 m/min running exercise and increased the level of active TGF-β in CSF. Intraperitoneal administration of lactate at the same dose to awake and unrestricted rats caused a decrease in the respiratory exchange ratio, that is, enhancement of fatty acid oxidation and depression of spontaneous motor activity (SMA). Given that intracisternal administration of TGF-β to rats has been reported to enhance fatty acid metabolism and to depress SMA, we surmise that the observed changes caused by i.p. lactate administration in this study were mediated, at least in part, by TGF-β in the brain.
Journal of Nutritional Science and Vitaminology 01/2012; 58(2):88-95. · 0.99 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We investigated to determine whether dried bonito broth flavor induces a reinforcing effect using the conditioned place preference (CPP) test. Only dried bonito broth did not induce CPP. Sucrose induced CPP in 20% solution. A 21.86% dextrin solution, with the same calorie content as the 20% sucrose solution, did not induce CPP, but a dextrin solution flavored with dried bonito broth (BD) induced CPP. An AD solution containing the same concentrations of dextrin, NaCl, IMP, GMP, and amino acids as found in BD tended to increase the time spent in the conditioned box but did not significantly. Aromatic compounds, such as citral, vanillin, and menthol flavored AD solutions did not induce CPP, whereas an AD solution supplemented with dried bonito flavoring agent induced CPP. In mice with transected olfactory nerves, CPP was not induced by voluntary intake of BD. These results suggest that the aromatic profile of the dried bonito broth plays an important role in BD-induced CPP.
Bioscience Biotechnology and Biochemistry 12/2011; 75(12):2288-92. · 1.27 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Capsiate is produced by 'CH-19 Sweet' (Capsicum annuun L.), a non-pungent cultivar of red pepper. Like capsaicin, capsiate is thought to enhance energy metabolism by activating the sympathetic nervous system and suppressing inflammation, but the underlying mechanisms for this are uncertain. We previously reported that capsiate could activate transient receptor potential vanilloid 1 (TRPV1), a capsaicin receptor. The purpose of the present study is to investigate whether capsinoids activate other TRP channels.
Using Ca(2+) imaging and whole-cell patch-clamp methods, we analysed the response of TRP channels to three kinds of capsinoids, capsiate, dihydrocapsiate and nordihydrocapsiate, in HEK293T cells expressing TRP channels or in primary cultures of mouse dorsal root ganglion neurons.
We found that in both cell types TRP ankyrin 1 (TRPA1) had a slightly weaker response to capsinoids compared with TRPV1, with the capsiate EC(50) for TRPA1 activation being more than that for TRPV1 activation, and that the capsinoid-evoked action was blocked by a specific TRPA1 antagonist. TRPA1 was activated by capsinoids, but not by their degradation products. Amino acids known to participate in TRPA1 activation following cysteine covalent modification or zinc treatment were not involved in the activation of TRPA1 by capsinoid.
Taken together, these results indicate that capsinoids activate TRPA1 by an as yet unknown mechanism, and TRPA1 could be involved in physiological phenomena associated with capsinoid treatment.
British Journal of Pharmacology 08/2011; 165(5):1476-86. · 5.07 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The regulation of energy metabolism by the central nervous system during endurance exercise was examined. We conducted respiratory gas analysis by functionally paralyzing the ventromedial hypothalamus (VMH), the lateral hypothalamic area, and the paraventricular nucleus of the hypothalamus with local anaesthetic (lidocaine) during treadmill running at a velocity that allowed for efficient fatty acid oxidation. Our results showed that only the lidocaine treatment of the VMH attenuated fatty acid oxidation during endurance exercise. The monoaminergic neural activities at these nuclei during in vivo microdialysis in rats under the same conditions indicated a significant increase in the extracellular concentration of noradrenaline in all nuclei. Similarly, a significant increase in dopamine occurred at some points during exercise, but no change in serotonin concentration occurred regardless of exercise. Disruption of noradrenergic projections to the VMH by 6-hydroxydopamine attenuated the enhancement of fat oxidation during running. Blocker treatments clarified that noradrenergic inputs to the VMH are mediated by β-adrenoceptors. These data indicate that information about peripheral tissues status is transmitted via noradrenergic projections originating in the medulla oblongata, which may be an important contribution by the VMH and its downstream mechanisms to enhanced fatty acid oxidation during exercise.
[Show abstract][Hide abstract] ABSTRACT: The transient receptor potential (TRP) channel family is composed of a wide variety of cation-permeable channels activated polymodally by various stimuli and is implicated in a variety of cellular functions. Recent investigations have revealed that activation of TRP channels is involved not only in nociception and thermosensation but also in thermoregulation and energy metabolism. We investigated the effect of intragastric administration of TRP channel agonists on changes in energy substrate utilization of mice. Intragastric administration of allyl isothiocyanate (AITC; a typical TRPA1 agonist) markedly increased carbohydrate oxidation but did not affect oxygen consumption. To examine whether TRP channels mediate this increase in carbohydrate oxidation, we used TRPA1 and TRPV1 knockout (KO) mice. Intragastric administration of AITC increased carbohydrate oxidation in TRPA1 KO mice but not in TRPV1 KO mice. Furthermore, AITC dose-dependently increased intracellular calcium ion concentration in cells expressing TRPV1. These findings suggest that AITC might activate TRPV1 and that AITC increased carbohydrate oxidation via TRPV1.
[Show abstract][Hide abstract] ABSTRACT: Enhancement of energy expenditure and reducing energy intake are crucial for weight control. Capsiate, a non-pungent capsaicin analog, is known to suppress body fat accumulation and reduce body weight by enhancing of energy expenditure in both mice and humans. However, it is poorly understood whether suppressing body fat accumulation by capsiate administration is equal to exercise or not. The aim of this study is to compare the effects of repeated administration of capsiate and exercise and to investigate the weight rebound after repeated capsiate administration and/or exercise. In the present study, we report that 2 weeks treatment of capsiate and exercise increased energy metabolism and suppressed body fat accumulation during 4 more weeks of ad libitum feeding. The body weight in capsiate and exercise groups was significantly lower than that of control group. The oxygen consumption was significanlty increased in capsiate and exercise groups than in the vehicle administered mice. In addition, the abdominal adipose tissue weight in capsiate and exercise groups was significantly lower than that of control group. These results indicate that suppressing body fat accumulation by capsiate intake is beneficial for maintaining an ideal body weight as exercise.
Biomedical Research 01/2011; 32(4):279-84. · 1.15 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Enhancing energy expenditure and reducing energy intake are both crucial for weight control. Capsinoids, which are non-pungent capsaicin analogs, are known to suppress body fat accumulation and reduce body weight by enhancing energy expenditure in both mice and humans. However, it is poorly understood whether the suppression of body fat accumulation by capsinoids has an advantage over dietary restriction. This study shows that the oxygen consumption was increased in mice administered with capsinoids but not in dietary-restricted mice, although there was a similar suppression of body fat accumulation in both groups. The weight rebound was more notable in the dietary-restricted mice than in the mice administered with capsinoids. These results indicate that suppressing body fat accumulation by capsinoids was more beneficial than a restricted diet for maintaining body weight.
Bioscience Biotechnology and Biochemistry 01/2011; 75(1):95-9. · 1.27 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Matriptase is a type-II transmembrane serine protease that is expressed strongly in the epithelial elements of various organs. In the small intestine, it is expressed prominently at the villus tip where aged epithelial cells undergo shedding and/or apoptosis. This observation, together with the ability of matriptase to cleave laminin (a basement membrane component critical for epithelial cell attachment), prompted us to hypothesize that it plays an important part in the removal of aged epithelial cells in the small intestine. We tested this hypothesis by determining whether a recombinant catalytic domain of rat matriptase (His(6)t-S-CD) causes detachment and/or apoptosis of small-intestinal epithelial IEC-6 cells. His(6)t-S-CD caused detachment of cells attached to laminin-coated plates but did not detach cells attached to fibronectin- or type-IV collagen-coated plates. Pre-treatment of laminin-coated plates with His(6)t-S-CD decreased the attachment of cells, suggesting that the recombinant matriptase caused detachment through a mechanism involving a direct effect on laminin. His(6)t-S-CD was also found to induce apoptosis in the cells cultured on laminin-coated plates, as assessed by annexin-V staining, DNA fragmentation and caspase-3 activity assays. These findings support our hypothesis regarding the role of matriptase in the small intestine.
Journal of biochemistry 12/2010; 148(6):721-32. · 1.95 Impact Factor