Genetic and environmental factors of schizophrenia and autism spectrum disorder: insights from twin studies.

Twin studies of psychiatric disorders such as schizophrenia and autism spectrum disorder have employed epidemiological approaches that determine heritability by comparing the concordance rate between monozygotic twins (MZs) and dizygotic twins. The basis for these studies is that MZs share 100% of their genetic information. Recently, biological studies based on molecular methods are now being increasingly applied to examine the differences between MZs discordance for psychiatric disorders to unravel their possible causes. Although recent advances in next-generation sequencing have increased the accuracy of this line of research, there has been greater emphasis placed on epigenetic changes versus DNA sequence changes as the probable cause of discordant psychiatric disorders in MZs. Since the epigenetic status differs in each tissue type, in addition to the DNA from the peripheral blood, studies using DNA from nerve cells induced from postmortem brains or induced pluripotent stem cells are being carried out. Although it was originally thought that epigenetic changes occurred as a result of environmental factors, and thus were not transmittable, it is now known that such changes might possibly be transmitted between generations. Therefore, the potential possible effects of intestinal flora inside the body are currently being investigated as a cause of discordance in MZs. As a result, twin studies of psychiatric disorders are greatly contributing to the elucidation of genetic and environmental factors in the etiology of psychiatric conditions.

Impaired feedback regulation of XBP1 as a genetic risk factor for bipolar disorder.

The pathophysiology of bipolar disorder is still unclear, although family, twin and linkage studies implicate genetic factors. Here we identified XBP1, a pivotal gene in the endoplasmic reticulum (ER) stress response, as contributing to the genetic risk factor for bipolar disorder. Using DNA microarray analysis of lymphoblastoid cells derived from two pairs of twins discordant with respect to the illness, we found downregulated expression of genes related to ER stress response in both affected twins. A polymorphism (-116C-->G) in the promoter region of XBP1, affecting the putative binding site of XBP1, was significantly more common in Japanese patients (odds ratio = 4.6) and overtransmitted to affected offspring in trio samples of the NIMH Bipolar Disorder Genetics Initiative. XBP1-dependent transcription activity of the -116G allele was lower than that of the -116C allele, and in the cells with the G allele, induction of XBP1 expression after ER stress was markedly reduced. Valproate, one of three mood stabilizers, rescued the impaired response by inducing ATF6, the gene upstream of XBP1. These results indicate that the -116C-->G polymorphism in XBP1 causes an impairment of its positive feedback system and increases the risk of bipolar disorder.

Inhibition by epsilon-polylysine of fat digestion in the stomach and intestine of rats.

In vitro, the inhibition by epsilon-polylysine depends on how the substrate is presented to the lipase. We therefore examined whether epsilon-polylysine can interact with the lipid emulsion and prevent lipase activity in digestive organs. To confirm lipase inhibition by epsilon-polylysine, a (14)C-trioleoylglycerol emulsion with or without epsilon-polylysine was orally administered to rats, and the radioactive lipid distribution determined at regular intervals. The radioactive plasma lipid was decreased, and radioactive fecal lipid was increased by the administration of epsilon-polylysine. The peak of radioactive lipids in the intestine was delayed by the administration of epsilon-polylysine. We used 20-week-old rats as a model for the middle-aged and elderly to test the effect of epsilon-polylysine on the body weight increase. epsilon-Polylysine significantly prevented any elevation in body weight and weight of the liver and epididymal adipose tissues. These data show that epsilon-polylysine inhibited the lipase activity in the digestive organ and had an anti-obesity function in the middle-aged rats.

Mechanism of the inhibitory action of chestnut astringent skin extract on carbohydrate absorption.

Chestnut astringent skin (CAS) extract inhibited pancreatic alpha-amylase and intestinal alpha-glucosidase in a concentration-dependent manner with the 50% inhibition concentration (IC50) for amylase, maltase and sucrase being 7.5, 650 and 390 microg/mL, respectively. We have investigated the effect of CAS extract on carbohydrate absorption in normal rats. Oral administration of CAS extract to rats fed cornstarch (2 g/kg body weight) significantly suppressed the increase of blood glucose levels and the area under the curve (AUC). Administration of CAS extract to rats fed maltose or sucrose delayed the increase of blood glucose level and slightly suppressed AUC, but not significantly. Administration of CAS extract to rats fed glucose did not affect the increase in blood glucose level or AUC. Similar results were observed with type-2 diabetic model rats (GK/jcl). To test the effect of CAS extract on diabetes, type 2 diabetic model mice (db/db mice) were fed a standard laboratory diet containing 1 or 2% CAS extract. CAS extract prevented increases in body weight and fasting blood glucose concentration. These data suggest that CAS extract has an anti-diabetic function in type 2 diabetic mice that mainly functions through inhibition of alpha-amylase.

Inhibitory effect of pectin from the segment membrane of citrus fruits on lipase activity.

Segment membranes from 4 citrus species selected from 4 sections were treated with water to obtain polysaccharides containing pectin. The extracts, which inhibited pancreatic lipase activity in a concentration-dependent manner, were divided into high molecular weight fractions [molecular weight (M.W.) >300,000], which inhibited the activity strongly, and low molecular weight fractions (M.W. <300,000), which did not show such strong inhibition. The high molecular weight fractions were composed mainly of a characteristic sugar of pectin, namely, galacturonic acid. A galacturonic acid-rich fraction purified by anion exchange chromatography from a water extract also strongly inhibited the activity. The inhibitory activity of the high molecular weight fraction was much stronger than that of commercial citrus pectin. The results suggest that pectin from segment membranes of citrus fruits might be useful as a functional food, especially as a fat-reducing material.

Chestnut astringent skin extract, an alpha-amylase inhibitor, retards carbohydrate absorption in rats and humans.

Inhibitors of carbohydrate-hydrolyzing enzyme play an important role to control postprandial blood glucose levels. In this paper, we investigated the effect of an ethanol extract from chestnut astringent skin (CAS) on alpha-amylase. Chestnut astringent skin extract strongly inhibited human and porcine pancreatic alpha-amylase. We also investigated the effect of CAS extract on carbohydrate absorption in rats and humans. Oral administration of CAS extract to normal rats fed corn starch (2 g/kg body weight), significantly suppressed the increase of blood glucose levels after starch loading in a dose-dependent manner. The effective dose of CAS extract required to achieve 20 and 40% suppression of the rise in blood glucose level was estimated to be 40 and 155 mg/kg body weight, respectively. Chestnut astringent skin extract also suppressed the rise in plasma insulin level and the fall in plasma non-esterified fatty acid level. In the type 2 diabetic rat model, CAS extract significantly suppressed the rise in blood glucose level after starch loading in a dose-dependent manner. Chestnut astringent skin extract also suppressed the rise in plasma glucose level after boiled rice loading in a dose-dependent manner in humans. The amount of CAS extract required to achieve 11 and 23% suppression in the rise in plasma glucose level was 300 and 600 mg/person, respectively. These results suggest that CAS extract retards absorption of carbohydrate and reduces post-prandial hyperglycemia.

Global hypomethylation of peripheral leukocyte DNA in male patients with schizophrenia: a potential link between epigenetics and schizophrenia.

Genetic and epigenetic factors can potentially alter susceptibility to psychiatric disorders such as schizophrenia. In order to explore the effect of epigenetics on the pathogenesis of schizophrenia, we examined the global methylation level of leukocyte DNA from 210 patients with schizophrenia (124 males and 86 females) and 237 healthy subjects (108 males and 129 females). Methylated deoxycytidine (mC) content in peripheral leukocyte DNA was measured by high performance liquid chromatography (HPLC). We confirmed in the healthy subjects our previous finding that there are sex-dependent differences in mC content (males>females; beta=0.319, p<0.001), in addition to the effect of age (beta=-0.141, p=0.022). We therefore used multiple regression to analyze the data from all subjects by sex, with age as a co-variant. In males, a tendency was observed toward lower mC content in patients than in controls (beta=-0.115, p=0.075), with a significant effect of age (beta=-0.212, p<0.001). This difference was more prominent in younger individuals. In females, no effect of age or disease status on mC content was observed. These results established that there is significant sex-dependent difference in the mC content of human peripheral leukocyte DNA, and raise the possibility that alterations in DNA methylation state are present in patients with schizophrenia.

Lipolysis induced by segment wall extract from Satsuma mandarin orange (Citrus unshu Mark).

The lipolysis induced by Satsuma mandarin orange (Citrus unshu Mark) was investigated using rat fat cells. Peel or segment wall extract from Satsuma mandarin orange induced the lipolysis in a concentration-dependent manner, whereas juice sac extract did not induce the lipolysis. High concentration of synephrine, which is an adrenergic amine, was detected in the peel or segment wall extract, whereas it was not detected in the juice sac extract. The segment wall extracts from Iyokan and orange had high lipolytic activity, whereas the extracts from grapefruit and lemon did not have lipolytic activity. The beta-antagonist inhibited the lipolysis elicited by the segment wall extract from Satsuma mandarin orange, whereas alpha-antagonist did not inhibit the lipolysis induced by the segment wall. The lipolysis induced by the segment wall was considerably higher in the visceral fat cells when compared to the subcutaneous fat cells. These results suggest that the segment wall, an edible fraction, from Satsuma mandarin orange might be useful as a functional food, especially as a fat-reducing material.

Basal lipolysis in epididymal fat cells from streptozotocin-induced diabetic rats.

The level of free fatty acid (FFA) in plasma is increased by diabetes. The increase in plasma FFA levels accompanied the stimulation of basal lipolysis (i.e. lipolysis in the absence of lipolytic agents) in fat cells. Injection of streptozotocin with rats resulted in a significant increase in basal FFA production (5.5 fold) in fat cells. However, basal glycerol production in fat cells was increased only 1.5 fold by streptozotocin-induced diabetes, implying that FFA re-esterification in fat cells was decreased by streptozotocin-induced diabetes. The FFA re-esterification in fat cells was also decreased by 1 d of fasting. Although basal lipolysis was increased by streptozotocin-induced diabetes or 1-d fasting, neutral triacylglycerol lipase activity and the immunoreactive HSL protein content in fat cells from streptozotocin-induced diabetic rats or 1-d fasting rats were not significantly changed. Although beta-blockers inhibited lipolysis induced by norepinephrine at a concentration of 10(-4) M, it failed to inhibit the basal lipolysis and FFA re-esterification in fat cells from streptozotocin-induced diabetic rats. Nor did insulin or H-89, another antilipolytic agent, affect basal lipolysis or FFA re-esterification in fat cells from streptozotocin-induced diabetic rats. These results indicate that basal FFA production may be induced by a decrease of re-esterification of FFA in diabetic rats and is not affected by antilipolytic agents such as insulin, beta-blockers or H-89.

Persimmon-Tannin, an α-Amylase Inhibitor, Retards Carbohydrate Absorption in Rats.

Inhibitors of carbohydrate-hydrolyzing enzymes play an important role in controlling postprandial blood glucose levels. Thus the effect of persimmon tannin on pancreatic α-amylase and intestinal α-glucosidase has been investigated. Persimmon tannin inhibits pancreatic α-amylase and intestinal α-glucosidase in a concentration-dependent manner with the 50% inhibition concentration (IC50) for amylase, maltase and sucrase being 1.7 µg/mL, 632 µg/mL and 308 µg/mL, respectively. The effect of persimmon-tannin extract on carbohydrate absorption in rats has also been investigated. Oral administration of persimmon tannin to normal rats fed cornstarch (2 g/kg body weight) significantly suppressed the increase in blood glucose levels and the area under the curve (AUC) after starch loading in a dose-dependent manner. The effective dose of persimmon tannin required to achieve 50% suppression of the rise in blood glucose level was estimated to be 300 mg/kg body weight. Administration of persimmon tannin to rats fed maltose or sucrose delayed the increase of blood glucose level and slightly suppressed AUC, but not significantly. These results suggest that persimmon tannin retards absorption of carbohydrate and reduces post-prandial hyperglycemia mainly through inhibition of α-amylase.

Anti-obese action of raspberry ketone.

Raspberry ketone (4-(4-hydroxyphenyl) butan-2-one; RK) is a major aromatic compound of red raspberry (Rubus idaeus). The structure of RK is similar to the structures of capsaicin and synephrine, compounds known to exert anti-obese actions and alter the lipid metabolism. The present study was performed to clarify whether RK helps prevent obesity and activate lipid metabolism in rodents. To test the effect on obesity, our group designed the following in vivo experiments: 1) mice were fed a high-fat diet including 0.5, 1, or 2% of RK for 10 weeks; 2) mice were given a high-fat diet for 6 weeks and subsequently fed the same high-fat diet containing 1% RK for the next 5 weeks. RK prevented the high-fat-diet-induced elevations in body weight and the weights of the liver and visceral adipose tissues (epididymal, retroperitoneal, and mesenteric). RK also decreased these weights and hepatic triacylglycerol content after they had been increased by a high-fat diet. RK significantly increased norepinephrine-induced lipolysis associated with the translocation of hormone-sensitive lipase from the cytosol to lipid droplets in rat epididymal fat cells. In conclusion, RK prevents and improves obesity and fatty liver. These effects appear to stem from the action of RK in altering the lipid metabolism, or more specifically, in increasing norepinephrine-induced lipolysis in white adipocytes.

Polymorphic 33-bp repeats with promoter-like activity in synaptotagmin 11 gene.

In the immediate upstream region of the transcription initiation site of human synaptotagmin 11 gene, we found a tandem repeat of a 33-bp unit with a promoter-like activity. The tandem repeat is apparently polymorphic in the Japanese population as two DNA samples from 60 schizophrenia patients exhibited an increased number (three) of the unit. In a transfection assay using constructs with different numbers of repeats, the promoter-like activity was found to increase with the number of repeating unit.

HLA class I distribution in Japanese patients with schizophrenia.

Several Caucasian studies and one Japanese study have observed associations between human leukocyte antigen (HLA) class I specificities, including A24 (9) and A26 (10) and schizophrenia. Most of those studies were conducted in 1970s and early 1980s, when the typing technique of HLA was not adequately reliable. Also, an operational diagnostic system was not employed in many of the studies. The present study investigated frequencies of HLA-A specificities in schizophrenia patients (ICD-10 and DSM-III-R, n=98) and sex-matched healthy controls (n=392) from population in the southwestern part of Japan. HLA-B and -C specificities were studied in addition. Frequencies of subjects possessing A24 and A26 were not different between the patients and controls (54% and 24% in the patients and 62% and 24% in the controls, respectively). No significant difference was found in frequencies of other class I (A, B, and C) specificities between the patients and the controls. Thus, the present study provided no evidence for an association between the HLA class I specificities, including A24, A26, and others, and schizophrenia in the Japanese population.

Effect of ultrasound application on fat mobilization.

The aim of this experimental trial was to study the effect of ultrasound application on the lipolysis in adipose tissue. Rats were administered to pentobarbital (Nembutal) anesthesia and their abdomens were shaved. Rat abdomen was subjected to 24 kHz-1 MHz ultrasound for 10 min to investigate frequency and power-intensity dependency for fat mobilization. Blood was taken from the tail vein to estimate plasma free fatty acids (FFA). For frequency dependency two regions around 100 kHz and 300-500 kHz were effective for fat mobilization. For power-intensity dependency, effective regions were found to be from 24 to 1090 kHz. In the effective regions on frequency and power-intensity, application of ultrasound caused increases in plasma FFA and norepinephrine concentration of extra-cellular fluid of perirenal adipose tissue. These results suggest that ultrasound application stimulates fat mobilization through a local increase in norepinephrine secretion under the conditions of effective frequency and intensity.

Adequate evaluation of HSL mass and activity in rat adipose tissue in fasting and aging-related obesity.

Adipose tissue is a unique tissue because its mass is readily changed by altering nutritional conditions. Therefore the activity and content of enzyme in the adipose tissue is significantly differed according to the way of their presentation: per g tissue, per whole tissue, or per cell number. In the present study, the effects of the ways of expressing the hormone sensitive lipase (HSL) activity and content were studied in rat by decreasing or increasing adipose tissue. Fasting caused a progressive decline in body weight and in the weight of the epididymal fat pad. When the HSL content was expressed per g of adipose tissue, the lipase activity and immunoreactive HSL protein content in fasting rats were higher than those in fed rats. On the other hand, when they were expressed as per fat pad, the lipase activity and immunoreactive HSL protein in fasting rats were lower than those in fed rats. The opposite results were observed in obesity. When the HSL content was expressed per g of adipose tissue, the lipase activity and immunoreactive HSL protein in obese rats were lower than in control rats. However, when the HSL content was expressed per fat pad, the lipase activity and immunoreactive HSL protein in the obese rats were higher than in the control rats. Therefore we must pay careful attention to the way of presentation of adipose tissue enzyme contents.

Inhibition of lipase activities by citrus pectin.

The oral administration of pectin to rats reduced and delayed the peak plasma triacylglycerol concentration. Pectin inhibited the hydrolysis of trioleoylglycerol emulsified with soybean phosphatidylcholine by pancreatic, carboxylester, and lingual lipases in a concentration-dependent manner. However, the effective concentration of pectin for lingual lipase was 100 times lower than that for pancreatic lipase. Pectin did not inhibit the tributyrin- and p-nitrophenylbutyrate-hydrolyzing activities by pancreatic and carboxylester lipase. When low molecular weight pectin was assayed, pectin at a molecular weight of 90,000 (MW 90) most strongly inhibited three lipase activities. When the effect of pH on pectin inhibition was analyzed using pancreatic lipase, strong inhibition was observed at an acidic pH (below pH 7.0). In the assay system, the pancreatic lipase protein levels in the supernatant and fat layer were estimated by Western blotting with an anti-pancreatic lipase antibody. Pectin reduced the amount of pancreatic lipase protein in the fat layer in a concentration-dependent manner and concomitantly increased that in the supernatant. These results suggest that pectin may interact with emulsified substrates and inhibit the adsorption of lipase to the surface of substrate emulsion.

Preparation and characterisation of peanut seed skin polyphenols.

Using α-amylase inhibition as a separation guide, polyphenolic compounds from peanut seed skin were prepared. During preparation, specific α-amylase inhibitory activities were increased about 4-fold. High-resolution MALDI-TOF mass spectra showed that the structure of this sample was a series of polyflavan-3-ols, up to 15-mer, composed of catechin/epicatechin units together with several afzelechin/epiafzelechin units and gallocatechin/epigallocatechin units. The observed precious mass values suggest that the polymers consist of both interflavanoid C-C linkages (A-type) and interflavanoid ether linkages (B-type). Oral administration of the polyphenol fraction to rats fed corn starch significantly suppressed an increase in blood glucose levels in a dose dependent manner. Administration of the polyphenol fraction to rats fed maltose or sucrose delayed the increase in blood glucose levels. These results suggest peanut seed skin contains polyphenols with strong α-amylase inhibitory activity, which retard absorption of carbohydrates and mainly function through inhibition of α-amylase.

α-Amylase inhibitory activity from nut seed skin polyphenols. 1. Purification and characterization of almond seed skin polyphenols.

Using α-amylase inhibition as a separation guide, polyphenolic compounds from almond ( Prunus dulcis ) seed skin were purified using ultrafiltration and Sephadex LH-20 and ODS columns. The purified fraction specifically and strongly inhibited α-amylase; the IC50 value was 2.2 µg/mL for pig pancreatic α-amylase. The fraction contained about 62% of the total polyphenols, 33.8% flavanol-type tannins and 30% procyanidins. Oral administration of the polyphenol fraction to rats fed corn starch significantly suppressed an increase in blood glucose levels and area under the curve (AUC), in a dose-dependent manner. High-resolution MALDI-TOF mass spectra showed that the structure of this sample is a series of polyflavan-3-ol polymers composed of catechin/epicatechin units and gallocatechin/epigallocatechin units up to 11-mer with several interflavanoid ether linkages. The results suggest almond seed skin contains highly polymerized polyphenols with strong α-amylase inhibitory activity, which retard absorption of carbohydrate.

Purification and characterization of polyphenols from chestnut astringent skin.

Polyphenolic compounds from chestnut astringent skin (CAS) were purified by dialysis, using Diaion HP-20 and Sephadex LH-20 columns. During purification, specific α-amylase inhibitory activities were increased about 3.4-fold, and the 50% inhibition value was 5.71 µg/mL in the Sephadex LH-20 fraction (SE-fraction). The SE-fraction contained about 67% of the total polyphenols, 57.3% of the flavanol-type tannins, and 51.3% of the procyanidins. Strong antioxidant activity was observed in the SE-fraction. Oral administration of the SE-fraction in rats fed corn starch significantly suppressed an increase in blood glucose levels. The SE-fraction contained gallic acid and ellagic acid. The MALDI-TOF spectrum showed a peak series exhibiting a mass increment of 288 Da, reflecting the variation in the number of catechin/epicatechin units. Our results suggest CAS contains polyphenols with strong α-amylase inhibitory activity. The data also suggest CAS polyphenols might be oligomeric proanthocyanidins with gallic acid and ellagic acid.