Yoshinobu Kiso

Dietary supplementation of arachidonic and docosahexaenoic acids improves cognitive dysfunction

Age-dependent increase of peroxidation of membrane fatty acids such as arachidonic acid (ARA) and docosahexaenoic acid (DHA) in neurons was reported to cause a decline of the hippocampal long-term potentiation (LTP) and cognitive dysfunction in rodents. Although supplementation of ARA and DHA can improve LTP and cognitive function in rodents, their effects in humans are unknown. The present work was undertaken to study whether ARA and DHA have beneficial effects in human amnesic patients. The subjects were 21 mild cognitive dysfunction (12 MCI-A with supplementation and 9 MIC-P with placebo), 10 organic brain lesions (organic), and 8 Alzheimers disease (AD). The cognitive functions were evaluated using Japanese version of repeatable battery for assessment of neuropsychological status (RBANS) at two time points: before and 90 days after the supplementation of 240 mg/day ARA and DHA, or 240 mg/day of olive oil, respectively. MCI-A group showed a significant improvement of the immediate memory and attention score. In addition, organic group showed a significant improvement of immediate and delayed memories. However, there were no significant improvements of each score in AD and MCI-P groups. It is suggested from these data that ARA and DHA supplementation can improve the cognitive dysfunction due to organic brain damages or aging.

Altered emotional behavioral responses in mice lacking brain-type fatty acid-binding protein gene

Brain‐type fatty acid‐binding protein (B‐FABP) belongs to a family of intracellular lipid‐binding proteins. B‐FABP exhibits a binding affinity to long‐chain fatty acids (FAs) whose effects on brain functions including development, emotion, learning and memory have been proposed. B‐FABP is localized in the ventricular germinal cells in embryonic brain and astrocytes in developing and mature brain of rodents. In the present study we generated the mouse harboring a null mutation in the B‐FABP gene and studied its phenotype. B‐FABP mutant mice exhibited the enhanced anxiety and increased fear memory as well as the decreased content of docosahexaenoic acid (DHA) in their brain during the neonatal period without detection of any histological changes in the brain. In the adult brain, B‐FABP was localized more numerously to the astrocytes in the amygdala and septal area than to those in the hippocampal area. Analysis of FA content in the amygdala of adult brain revealed that arachidonic and palmitic acids increased significantly in the mutant mice compared with wild‐type. Furthermore, the response of N‐methyl‐d‐aspartate receptor‐mediated current to DHA in isolated neurons from B‐FABP mutant brain was significantly decreased compared with that of wild‐type, while no significant differences were detected in behavioral responses related to the spatial learning/memory or in the hippocampal long‐term potentiation. These data indicate that B‐FABP is crucially involved in the fear memory and anxiety through its binding with FAs and/or its own direct effects on pertinent metabolism/signaling of FAs.

Arachidonic acid drives postnatal neurogenesis and elicits a beneficial effect on prepulse inhibition, a biological trait of psychiatric illnesses.

Prepulse inhibition (PPI) is a compelling endophenotype (biological markers) for mental disorders including schizophrenia. In a previous study, we identified Fabp7, a fatty acid binding protein 7 as one of the genes controlling PPI in mice and showed that this gene was associated with schizophrenia. We also demonstrated that disrupting Fabp7 dampened hippocampal neurogenesis. In this study, we examined a link between neurogenesis and PPI using different animal models and exploring the possibility of postnatal manipulation of neurogenesis affecting PPI, since gene-deficient mice show biological disturbances from prenatal stages. In parallel, we tested the potential for dietary polyunsaturated fatty acids (PUFAs), arachidonic acid (ARA) and/or docosahexaenoic acid (DHA), to promote neurogenesis and improve PPI. PUFAs are ligands for Fabp members and are abundantly expressed in neural stem/progenitor cells in the hippocampus. Our results are: (1) an independent model animal, Pax6 (+/−) rats, exhibited PPI deficits along with impaired postnatal neurogenesis; (2) methylazoxymethanol acetate (an anti-proliferative drug) elicited decreased neurogenesis even in postnatal period, and PPI defects in young adult rats (10 weeks) when the drug was given at the juvenile stage (4–5 weeks); (3) administering ARA for 4 weeks after birth promoted neurogenesis in wild type rats; (4) raising Pax6 (+/−) pups on an ARA-containing diet enhanced neurogenesis and partially improved PPI in adult animals. These results suggest the potential benefit of ARA in ameliorating PPI deficits relevant to psychiatric disorders and suggest that the effect may be correlated with augmented postnatal neurogenesis.

Antihypertensive Effect of Angiotensin I-Converting Enzyme Inhibitory Peptides from a Sesame Protein Hydrolysate in Spontaneously Hypertensive Rats

Sesame peptide powder (SPP) exhibited angiotensin I-converting enzyme (ACE) inhibitory activity, and significantly and temporarily decreased the systolic blood pressure (SBP) in spontaneously hypertensive rats (SHRs) by a single administration (1 and 10 mg/kg). Six peptide ACE inhibitors were isolated and identified from SPP. The representative peptides, Leu-Val-Tyr, Leu-Gln-Pro and Leu-Lys-Tyr, could competitively inhibit ACE activity at respective Ki values of 0.92 μM, 0.50 μM, and 0.48 μM. A reconstituted sesame peptide mixture of Leu-Ser-Ala, Leu-Gln-Pro, Leu-Lys-Tyr, Ile-Val-Tyr, Val-Ile-Tyr, Leu-Val-Tyr, and Met-Leu-Pro-Ala-Tyr according to their content ratio in SPP showed a strong antihypertensive effect on SHR at doses of 3.63 and 36.3 μg/kg, which accounted for more than 70% of the corresponding dosage for the SPP-induced hypotensive effect. Repeated oral administration of SPP also lowered both SBP and the aortic ACE activity in SHR. These results demonstrate that SPP would be a beneficial ingredient for preventing and providing therapy against hypertension and its related diseases.

Possible role of L-carnosine in the regulation of blood glucose through controlling autonomic nerves

Mammalian muscles synthesize L-carnosine, but its roles were unknown. Previously, we found in rats that the administration of a certain amount of L-carnosine elicited an inhibition of the hyperglycemia induced by the Injection of 2-deoxy-D-glucose (2DG) into the lateral cerebral ventricle (LCV), and that intravenous injection of L-carnosine inhibited sympathetic nerves and facilitated the parasympathetic nerve. Moreover, the suppressive effect of L-carnosine on the hyperglycemia induced by 2DG was eliminated by thioperamide, a histaminergic H3 receptor. These findings suggested that L-carnosine might control the blood glucose level through regulating autonomic nerves via H3 receptor. To further clarify the function of L-carnosine, we examined its role in the control of the blood glucose. In this experiment, the following results were observed in rats: (i) A certain amount (0.01% or 0.001%) but not a larger amount (0.1%) of L-carnosine given as a diet suppressed the hyperglycemia induced by LCV-injection of 2DG (2DG-hyperglycemia); (ii) LCV-injection but not the injection into the intraperitoneal space (IP) of a certain amount of L-histidlne suppressed the 2DG-hyperglycemia; (iii) treatments of diphenhydramine, an H1 antagonist, and α-fluoromethylhistidine, an inhibitor of histamine-synthesizing enzyme, reduced the 2DG-hyperglycemia; (iv) the plasma L-carnosine concentration and carnosinase activity showed daily changes; (v) the plasma L-carnosine concentration was significantly lower in the streptozotocin-dlabetic rats; (vi) exercise by a running wheel tended to increase carnosine synthase activity in the gastrocnemius muscle and elevated the plasma L-carnosine concentration in the dark (active) period, and enbanced the plasma carnosinase activity in the light period; (vii) IP-injection of certain amount of L-carnosine stimulated the feeding response to IP-injection of 2DG. These findings suggest a possibility that L-carnosine released from muscles due to exercise functions to reduce the blood glucose level through the regulation of the autonomic nerves.

Sesamin Metabolites Induce an Endothelial Nitric Oxide-Dependent Vasorelaxation through Their Antioxidative Property-Independent Mechanisms: Possible Involvement of the Metabolites in the Antihypertensive Effect of Sesamin

Sesamin, a major lignan in sesame seeds and oil, has been known to lower blood pressure in several types of experimental hypertensive animals. A recent study demonstrated that sesamin metabolites had in vitro radical-scavenging activities. Thus, we determined whether the antioxidative effect of sesamin metabolites modulate the vascular tone and contribute to the in vivo antihypertensive effect of sesamin. We used four demethylated sesamin metabolites: SC-1m (piperitol), SC-1 (demethylpiperitol), SC-2m [(1R,2S,5R,6S)-6-(4-hydroxy-3-methoxyphenyl)-2-(3,4-dihydroxyphenyl)-3,7-dioxabicyclo[3,3,0]octane], and SC-2 [(1R,2S,5R, 6S)-2,6-bis(3,4-dihydroxyphenyl)-3,7-dioxabicyclo-[3,3,0]octane]. SC-1, SC-2m, and SC-2, but not SC-1m, exhibited potent radical-scavenging activities against the xanthine/xanthine oxidase-induced superoxide production. On the other hand, SC-1m, SC-1, and SC-2m produced endothelium-dependent vasorelaxation in phenylephrine-precontracted rat aortic rings, whereas SC-2 had no effect. The SC-1m- and SC-1-induced vasorelaxations were markedly attenuated by pretreatment with a nitric oxide synthase (NOS) inhibitor, NG-nitro-l-arginine (NOARG), or a soluble guanylate cyclase inhibitor, 1H-[1,2,4]oxadiazolo-[4,3-a]quinoxalin-1-one. Neither SC-1m nor SC-1 changed the expression level of endothelial NOS protein in aortic tissues. The antihypertensive effects of sesamin feeding were not observed in chronically NOARG-treated rats or in deoxycorticosterone acetate-salt-treated endothelial NOS-deficient mice. These findings suggest that the enhancement of endothelium-dependent vasorelaxation induced by sesamin metabolites is one of the important mechanisms of the in vivo antihypertensive effect of sesamin.

Effect of L-carnosine on the hyperglycemia caused by intracranial injection of 2-deoxy-D-glucose in rats

Effects of a chicken essence and one of its components, L-carnosine, on the hyperglycemia caused by intracranial injection of 2-deoxy-D-glucose (2DG-hyperglycemia) in unanesthetized rats were examined. The chicken essence inhibited the 2DG-hyperglycemia. Central or peripheral administration of specific doses of L-carnosine reduced the 2DG-hyperglycemia. L-carnosine inhibited neural activities of sympathetic efferent nerves innervating the adrenal gland and liver and facilitated the activity of vagal celiac nerve innervating the pancreas in urethane anesthetized rats. Specific doses of histamine also suppressed the 2DG-hyperglycemia, and thioperamide eliminated the inhibiting actions of both histamine and L-carnosine on the 2DG-hyperglycemia. Considering mammalian muscles contain L-carnosine, these facts suggest a possibility that L-carnosine might be an endogenous control factor of the blood glucose level through autonomic nerves via H3-receptor.

Renoprotective Effects of l-Carnosine on Ischemia/Reperfusion-Induced Renal Injury in Rats

We examined the renoprotective effects of l-carnosine (β-alanyl-l-histidine) on ischemia/reperfusion (I/R)-induced acute renal failure (ARF) in rats. Ischemic ARF was induced by occlusion of the left renal artery and vein for 45 min followed by reperfusion, 2 weeks after contralateral nephrectomy. In vehicle (0.9% saline)-treated rats, renal sympathetic nerve activity (RSNA) was significantly augmented during the renal ischemia, and renal function was markedly decreased at 24 h after reperfusion. Intracerebroventricular injection of l-carnosine (1.5 and 5 pmol/rat) to ischemic ARF rats dose-dependently suppressed the augmented RSNA during ischemia and the renal injury at 24 h after reperfusion. N-α-Acetyl-l-carnosine [N-acetyl-β-alanyl-l-histidine; 5 pmol/rat intracerebroventricular (i.c.v.)], which is resistant to enzymatic hydrolysis by carnosinase, did not affect the renal injury, and l-histidine (5 pmol/rat i.c.v.), a metabolite cleaved from l-carnosine by carnosinase, ameliorated the I/R-induced renal injury. Furthermore, a selective histamine H3 receptor antagonist, thioperamide (30 nmol/rat i.c.v.) eliminated the preventing effects by l-carnosine (15 nmol/rat intravenously) on ischemic ARF. In contrast, a selective H3 receptor agonist, R-α-methylhistamine (5 pmol/rat i.c.v.), prevented the I/R-induced renal injury as well as l-carnosine (5 pmol/rat) did. These results indicate that l-carnosine prevents the development of I/R-induced renal injury, and the effect is accompanied by suppressing the enhanced RSNA during ischemia. In addition, the present findings suggest that the renoprotective effect of l-carnosine on ischemic ARF is induced by its conversion to l-histidine and l-histamine and is mediated through the activation of histamine H3 receptors in the central nervous system.

Synaptic plasticity preserved with arachidonic acid diet in aged rats

We examined whether synaptic plasticity was preserved in aged rats administered an arachidonic acid (AA) containing diet. Young male Fischer-344 rats (2 mo of age), and two groups of aged rats of the same strain (2 y of age) who consumed either a control diet or an AA ethyl ester-containing diet for at least 3 mo were used. In the Morris water maze task, aged rats on the AA diet had tendency to show better performance than aged rats on the control diet. Long-term potentiation induced by tetanic stimulation was recorded from a 300 microm thick hippocampal slice with a 36 multi-electrode-array positioned at the dendrites of CA1 pyramidal neurons. The degree of potentiation after 1 h in aged rats on the AA diet was comparable as that of young controls. Phospholipid analysis revealed that AA and docosahexaenoic acid were the major fatty acids in the hippocampus in aged rats. There was a correlation between the behavioral measure and the changes in excitatory postsynaptic potential slope and between the physiologic measure and the total amount of AA in hippocampus.

Essential role of Toll-like receptors for dendritic cell and NK1.1(+) cell-dependent activation of type 1 immunity by Lactobacillus pentosus strain S-PT84.

Activation of type 1 immunity plays a critical role in host defense mechanisms against infectious disease and tumor. Lactic acid bacteria, existing in the gastrointestinal tract, are one of the powerful tools to induce a type-1-dominant immunity, which may improve Th2-dependent allergic diseases. In the present work, we found that an oral intake of Lactobacillus pentosus strain, S-PT84 into mice significantly enhanced NK activity of spleen cells in vivo. We further revealed that NK1.1 positive NK cells and NKT cells are responsible cells for producing IFN-gamma after stimulation with S-PT84 in vitro. S-PT84 induced IFN-gamma-producing cells through activation of IL-12 production by CD11c(+)DCs in Toll-like receptor (TLR) 2- and/or TLR4-dependent manner. Interestingly, direct interaction between DCs and NK1.1(+) cells was also essential for the IFN-gamma production in response to the S-PT84 stimulation. Therefore, we concluded that S-PT84 effectively promoted type 1 immunity through IL-12 and IFN-gamma which were produced by DCs and NK1.1(+) cells, respectively. Thus, S-PT84 would be a nice immune modulator for improving immunobalance, which plays a pivotal role for controlling allergy, infectious diseases and tumor.