Noradrenergic projections to the ventromedial hypothalamus regulate fat metabolism during endurance exercise.

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 ß-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.

Increase in transforming growth factor-beta in the brain during infection is related to fever, not depression of spontaneous motor activity.

When viral infection occurs, this information is transmitted to the brain, and symptoms such as fever and tiredness are induced. One of the causes of these symptoms is the secretion of proinflammatory cytokines in blood and the brain. In this study, the i.p. administration of polyinosinic:polycytidylic acid (poly I:C), a synthetic double-stranded RNA, to rats was used as an infection model. Poly I:C decreased spontaneous motor activity (SMA) 2 h after i.p. administration, and this decrease was maintained thereafter. The concentration of active transforming growth factor-beta (TGF-beta) in cerebrospinal fluid (CSF) increased 1 h after the administration. This increase occurred earlier than those in the concentrations of other proinflammatory cytokines, such as interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-alpha), in serum. The intracisternal administration of an anti-TGF-beta antibody partially inhibited fever induced by poly I:C administration; however, this treatment did not affect the decrease in SMA. Furthermore, intracisternal administration of TGF-beta raised the body temperature. These results indicate that TGF-beta in the brain, which was increased by poly I:C administration, is associated with fever but not with a decrease in SMA.

Fluids containing a highly branched cyclic dextrin influence the gastric emptying rate.

The rates of gastric emptying for highly branched cyclic dextrin (HBCD) and other carbohydrate (CHO) solutions were examined using ultrasonograph techniques. Ten healthy volunteers ingested water, physiological saline, or solutions containing various CHO, such as HBCD, glucose, maltose, sucrose, and commercially available dextrin. After a subject drank one of the solutions, the relaxed cross-sectional area of the pylorus antrum was measured at rest by real-time ultrasonography. The time required for gastric emptying was correlated with the relaxed cross-sectional area of the pylorus antrum. Among all of the solutions tested, physiological saline was transferred fastest from the stomach to the small intestine. For solutions of the same CHO, 5 % solution was transferred faster than 10 % solution. For CHO solutions other than HBCD, a low osmotic pressure was associated with rapid transfer from the stomach. The gastric emptying time (GET) of HBCD solution increased with an increase in its concentration. A shorter GET was observed for the CHO solutions at 59 to 160 mOsm regardless of their concentration. A sports drink based on 10 % HBCD adjusted to 150 mOsm by the addition of various minerals, vitamins, and organic acids was evacuated significantly (p < 0.05) faster than a 10 % HBCD solution or a sports drink based on 10 % commercially available dextrin (DE16), which has a higher osmotic pressure (269 mOsm). Our results suggest that a shorter GET could be achieved with CHO solutions with osmotic pressures of 59 - 160 mOsm. Therefore, a sports drink based on 10 % HBCD adjusted to 150 mOsm by the addition of minerals, vitamins, and organic acids could supply adequate quantities of CHO, fluid, and minerals simultaneously in a short time, without increasing GET.

Reduction of diet-induced obesity in transgenic mice overexpressing uncoupling protein 3 in skeletal muscle.

AIMS/HYPOTHESIS: It has been suggested that uncoupling protein 3 (UCP3) can increase energy expenditure, thereby regulating body weight. Although studies on UCP3 knock-out mice suggest that lack of UCP3 function does not cause obesity or Type 2 diabetes, it is possible that up-regulation of UCP3 function improves these disorders or their clinical sequelae. A 10- to 20-fold increase of UCP3 gene expression is achievable through physiological or pharmacological stimuli. We examined the phenotype of transgenic mice with approximately 18-fold overexpression of mouse UCP3 mRNA in skeletal muscle. METHODS: We generated transgenic mice with approximately 18-fold overexpression of mouse UCP3 mRNA in skeletal muscle under control of the skeletal muscle-specific muscle creatine kinase gene promoter. The phenotype of these mice was analysed either on a standard diet or on a 4-week high-fat diet. RESULTS: In mice on standard chow, there was no difference in body weight, oxygen consumption and mitochondrial protonmotive force between transgenic mice and non-transgenic littermates. However, transgenic mice tended to have lower body weight, increased oxygen consumption and decreased mitochondrial protonmotive force than the control mice. Transgenic mice on a 4-week high-fat diet consumed much more oxygen and had noticeably less weight gain and less epididymal fat, as well as better glucose tolerance than non-transgenic littermates. CONCLUSIONS/INTERPRETATION: Our study shows that 18-fold overexpression of UCP3 mRNA in the skeletal muscle reduced diet-induced obesity. An 18-fold increase of UCP3 mRNA can be attained by physiological or pharmacological stimuli, suggesting that UCP3 has therapeutic potential in the treatment of obesity.

Protective effect of sesamin administration on exercise-induced lipid peroxidation.

To investigate the mechanism of antioxidative effects of sesamin in vivo, 32 male ddY mice were administered with 10 mg/kg or 100 mg/kg of sesamin (S10, S100), 100 mg/kg of vitamin E (VE100) or control sample (C). They were subjected to 30 min of swimming exercise 2 h after the sample administration by using a new forced-swimming apparatus, i. e. an adjustable-current swimming pool. Exercise resulted in a significant increase in plasma lipid peroxides (LPO) in C and VE100 (p < 0.01), but not in S10 and S100. S100 showed significantly higher total glutathione peroxidase activity and glutathione S-transferase activity in liver compared to C (p < 0.05). In conclusion, sesamin may enhance LPO degradation in the liver resulting in the strong protective effects against exercise-induced plasma lipid peroxidation.

TRPV1 activation and induction of nociceptive response by a non-pungent capsaicin-like compound, capsiate.

Capsiate is a capsaicin-like ingredient of a non-pungent cultivar of red pepper, CH-19 sweet. To elucidate the mechanisms underlying the non-pungency of capsiate, we investigated whether capsiate activates the cloned capsaicin receptor, TRPV1 (VR1). In patch-clamp experiments, capsiate was found to activate TRPV1 expressed transiently in HEK293 cells with a similar potency as capsaicin. Capsiate induced nociceptive responses in mice when injected subcutaneously into their hindpaws with a similar dose dependency as capsaicin. These data indicate that the non-pungent capsiate is an agonist for TRPV1 and could excite peripheral nociceptors. In contrast to this, capsiate did not induce any significant responses when applied to the skin surface, eye or oral cavity of mice, suggesting that capsiate requires direct access to nerve endings to exhibit its effects. Capsiate was proved to have high lipophilicity and to be easily broken down in normal aqueous conditions, leading to less accessibility to nociceptors. Another highly lipophilic capsaicin analogue, olvanil, was similar to capsiate in that it did not produce irritant responses when applied to the skin surface, although it could activate TRPV1. Taken together, high lipophilicity and instability might be critical determinants for pungency and so help in understanding the effects of capsaicin-related compounds.

Effect of diazepam binding inhibitor (DBI) on the fluid intake, preference and the taste reactivity in mice.

We have reported that a diazepam binding inhibitor (DBI)-like peptide is released by the aversive quinine stimuli 'Chem. Senses 25 (2000) 739'. To determine the effect of DBI on the fluid intake, we injected a DBI peptide fragment into the fourth ventricle in mice. DBI suppressed the intake of 5% sucrose, water and 0.9 mM quinine-HCl and the preference for 0.05% saccharin. Administration (i.p.) of flumazenil, a benzodiazepine receptor antagonist, 20 min before the injection of DBI (i.c.v.) antagonized the suppressive effect of DBI on the intake and the preference for saccharin. We also studied the dose dependency of the effect of DBI on the intake of 5% sucrose. Injection of DBI in excess of 3 microg suppressed the intake of 5% sucrose in mice. Furthermore, injection of DBI (i.c.v.) increased the aversive response to 0.9% NaCl in the taste reactivity in mice. These results suggest that DBI affect the preference to food.

CH-19 sweet, a non-pungent cultivar of red pepper, increased body temperature and oxygen consumption in humans.

We investigated the effect of CH-19 Sweet, a non-pungent cultivar of red pepper, on body temperature and oxygen consumption in humans. CH-19 Sweet was given to 11 healthy volunteers, and core body temperature, body surface temperature and oxygen consumption were measured. The control group ingested California-Wandar, which contained neither capsaicin nor capsiate. The core body temperature in the CH-19 Sweet group was significantly higher than that in the control group (P<0.01). The forehead temperature measured by infrared thermography in the CH-19 Sweet group was significantly higher than that in the control group. The body surface temperature was increased for about 20 min after consumption of CH-19 Sweet intake, and the neck temperature was significantly higher (P<0.001) than when the subjects consumed California-Wandar. We also measured respiratory gas by indirect calorimetry while subjects wore a face mask. A significant difference was detected in oxygen consumption between the two groups, and the value was significantly higher in the CH-19 Sweet group (P<0.03). These results suggest that CH-19 Sweet increased thermogenesis and energy consumption.

A role for membrane-type serine protease (MT-SP1) in intestinal epithelial turnover.

Membrane type-serine protease 1 (MT-SP1) plays potential roles in the process of invasion and metastasis of carcinomas. In the present study, we cloned a rat MT-SP1 cDNA and investigated the intestinal distribution and proteolytic properties of the enzyme. By in situ hybridization we found the prominent expression of the mRNA in the epithelial layer of the small intestinal upper villi and of the colon, where cells are loosely attached to the basement membrane. When MT-SP1 was expressed in Caco-2, a colonic carcinoma cell line, the protein was localized exclusively on the basolateral side. A secreted form of the enzyme produced in COS-1 cells digested fibronectin and laminin. These findings suggest that MT-SP1 participates in the control of intestinal epithelial turnover by regulating the cell-substratum adhesion.

Preference for corn oil in olfactory-blocked mice in the conditioned place preference test and the two-bottle choice test.

We studied the effects of olfactory stimuli on preference for corn oil in mice. In the conditioned place preference test, voluntary intake of 100% corn oil by both olfactory normal and ZnSO4-induced olfactory-blocked (anosmic) mice resulted in their place preference for the corn oil-related box. In the olfactory normal mice, place preference was also observed by voluntary intake of linoleic acid as well as of corn oil. In the two-bottle choice test, normal mice showed significant preference for test fluids that contained corn oil at all concentrations (1-10%) tested relative to vehicle alone. However, the lower concentrations (1 and 3%) of corn oil were not preferred in the anosmic mice. These results suggested that stimuli other than olfaction contributed to the rewarding effects of corn oil, but at lower concentrations olfactory stimuli might act as a signal for the oil.

A single oral administration of conjugated linoleic acid enhanced energy metabolism in mice.

We investigated the effect of a single oral administration of conjugated linoleic acid (CLA) on energy metabolism in mice. Male Std ddY mice were orally administered CLA (5 mL/kg weight) or linoleic acid (5 mL/kg weight) (both solutions at concentrations of 73.5%) as a control. Oxygen consumption was significantly greater in the CLA-administered mice than in the control mice. Respiratory quotient was slightly lower in the CLA-adminis-tered mice than in the control mice. We calculated fat and carbohydrate oxidation from oxygen consumption and respiratory quotient. Fat oxidation in the CLA-administered mice was significantly higher than in the control mice, and there was no difference in carbohydrate oxidation. Serum concentrations of noradrenalin and adrenalin in the CLA administered mice were significantly higher than in the control mice. These results suggested that CLA enhanced sympathetic nervous activity and energy metabolism.

Elevation of blood NAD level after moderate exercise in young women and mice.

We previously reported that the blood NAD levels are decreased by severe exercise, and administration of nicotinamide, a precursor of NAD, improves the endurance capacity of mice. In the present study, we determined whether moderate exercise changes the blood NAD levels in humans and mice. College female students exercised moderately with bike-ergometers. The blood NAD levels elevated after moderate exercise. Mice were forced to swim in a running water pool for 5 min as a moderate exercise, 15 min as a strong exercise, and until exhaustion as a severe exercise (average swimming time was 28.7 min). A 5 min swim gave a result similar to that of moderate exercise by human subjects. However, the blood NAD levels decreased after all-out exercise. The changes in whole blood tryptophan (a precursor of pyridine nucleotides) levels were similar to that in NAD. The glucose levels in whole blood and the non-esterified fatty acid levels in serum decreased according to exercising time. These data are the first demonstration of moderate exercise raising the blood NAD levels in human and mice. Elevation of the blood NAD levels may reflect changes in niacin metabolism that occur in response to exercise.

Capsaicin increases modulation of sympathetic nerve activity in rats: measurement using power spectral analysis of heart rate fluctuations.

We assessed the sympatho-vagal activities of the heart after administration of capsaicin by measuring the power spectral analysis in rats. There were major two frequency components of heart rate variability, which we defined as high (1.0 Hz <, HF) and low (LF, < 1.0 Hz) frequency components. Vagal blockade by atropine abolished the high frequency component, and lowered the amplitude of the low frequency component. On the other hand, under conditions of sympathetic blockade by propranolol, the low frequency component was reduced. Combined vagal and sympathetic blockade abolished all heart rate fluctuations. We analyzed the low and high frequency components by integrating the spectrum for the respective band width. The rats administered capsaicin had a higher heart rate and sympathetic nervous system index (LF/HF) than the control group of rats. These results suggest that power spectral analysis is an effective and noninvasive method for detecting subtle changes in autonomic activity in response to the intake of foods or drugs.

Antidiabetic effect of glycyrrhizin in genetically diabetic KK-Ay mice.

We, previously demonstrated that one shot administration of glycyrrhizin (Grz) reduced the postprandial blood glucose rise, using Std ddY mice. Subsequently, we evaluated the effects of long-term Grz treatment (2.7, 4.1 g/kg diet) on diabetic symptoms using genetically non-insulin dependent diabetic model mice (KK-Ay). Male KK-Ay mice were divided into 3 groups: the control group, 0.27% Grz diet (2.7 g of Grz/kg diet) group and 0.41% Grz diet (4.1 g of Grz/kg diet) group. The elevation of blood glucose concentration was almost entirely suppressed in mice fed the 0.41% Grz diet 7 weeks after the beginning of test feeding, although it was not suppressed in mice fed the control diet or the 0.27% Grz diet. Water intake in the control and 0.27% Grz diet groups increased gradually, whereas, this was not true in the 0.41% Grz diet group. Grz treatment significantly lowered blood insulin level. Throughout the experiment, Grz did not affect the food intake or body weight among the three groups. The mice fed the 0.41% Grz diet also improved their tolerance to oral glucose loading 9 weeks after the beginning of test feeding. This study shows that Grz has an antidiabetic effect in noninsulin-dependent diabetes model mice.

Biochemical and physiological characteristics of fat cell.

Since animals are under constant threat of starvation, storage of energy sources inside the body is essential for various activities. Therefore, animals exhibit highly sophisticated mechanisms for storing energy inside their bodies in adipose tissue. However, in humans it has been clarified that fat cell (adipocyte, which comprises adipose tissues) differentiation and the extent of subsequent fat accumulation (hypertrophy of cells) are closely associated with the occurrence and advancement of various diseases resulting from obesity. Moreover, progress in biochemical studies with respect to adipocyte in recent years has rapidly clarified new functions and differentiation mechanisms of adipocytes. Interesting points, in particular, are the function of white adipocytes as "secreting cells" and the molecular mechanism of adipocyte differentiation via the nuclear receptors. Consequently, adipose tissue is being targeted to prevent or treat many common diseases. This paper summarizes recent knowledge on characteristics, differentiation and proliferation of adipocytes and the mechanisms by which adipocytes are regulated.

Opioidergic contribution to conditioned place preference induced by corn oil in mice.

We previously reported that voluntary intake of corn oil in the light box showed place preference in the conditioned place preference (CPP) test in mice. In the present study, we investigated the contribution of opioidergic systems to the corn oil-induced CPP in mice. Acquisition of the place preference by corn oil intake was blocked by i.p. injections of an opioid mu antagonist, naloxone (0.1 and 0.3 mg/kg), and delta antagonists, 7-benzylidenenaltrexone (0.5 mg/kg) and naltriben (0.5 mg/kg) 15 min before conditioning. The opioid kappa agonist U-50488H (1 and 3 mg/kg i.p.) also blocked corn oil-induced CPP. Naloxone (1 mg/kg, i.p.) and naltriben (0.5 mg/kg, i.p.) did not affect corn oil intake in the home cage. However, 7-benzylidenenaltrexone (0.5 mg/kg, i.p.) and U-50488H (1 mg/kg i.p.) decreased and increased the corn oil intake, respectively. These results suggested that the rewarding effects of corn oil in the CPP test are at least partially mediated via opioidergic systems through mu and delta receptors. Further, we showed that an opioid kappa agonist reduced the rewarding effects of corn oil in the CPP test in mice, although it increased corn oil intake.

Long-term optional ingestion of corn oil induces excessive caloric intake and obesity in mice.

Corn oil is well tolerated by mice but tolerance may decrease with excessive ingestion. In the present study, we compared the effects of optional ingestion of excessive corn oil with ingestion of water (control) or a 20% sucrose solution in mice. During the entire study, mice consistently ingested 100% corn oil and incrementally ingested 20% sucrose. Food intake in the corn-oil group was approximately constant but that in the sucrose group was slightly decreased. Body-weight gains in the corn-oil group were higher than those in the control and sucrose groups. At the end of the study, hepatic hypertrophy and fatty liver were present, especially in the corn-oil group, and the visceral fat of mice fed corn oil increased significantly compared with the other two groups. These results suggest that mice, when given a choice, will continue to overeat corn oil over the long term, inducing excessive caloric intake and obesity.