Biomedical subjects

Minoru Sugiura

Publications and source records attributed to Minoru Sugiura.

14 recordsLinked to original sources

PubMed2006

Chronic administration of Satsuma mandarin fruit (Citrus unshiu Marc.) improves oxidative stress in streptozotocin-induced diabetic rat liver.

Fruits and vegetables contain numerous antioxidants such as carotenoids, vitamins, and phenolic phytochemicals. Recent studies have demonstrated that antioxidants may reduce the risk for diabetes or its complications. In this study, we investigated the effects of the chronic administration of Satsuma mandarin fruit on an antioxidant defense system in streptozotocin (STZ)-induced diabetic rat liver. After a ten-week administration of Satsuma mandarin, antioxidant enzymes and glutathione levels in the liver were evaluated. The superoxide dismutase (SOD), catalase, and glutathione-peroxidase (GPx) activities, and glutathione level in the STZ-induced diabetic rats liver decreased significantly compared with those in the age-matched normal rats. The glutathione-reductase (GR) activities did not differ significantly between these two groups. In contrast, the SOD, GR, and glutathione levels in the Satsuma mandarin (1% or 3%) diet-fed STZ-diabetic rat livers were significantly higher than those in the normal diet-fed STZ-diabetic rat livers. In addition, although the serum alanine aminotransferase and gamma-glutamyl-aminotransferase concentrations of normal diet-fed STZ-diabetic rats were significantly higher than those of the age-matched normal rats, these increments of serum liver enzymes were diminished by the chronic administration of Satsuma mandarin. These results suggest that Satsuma mandarin may act as a suppressor against liver cell damage and inhibit the progression of liver dysfunction induced by chronic hyperglycemia.

Animals↗

PubMed2006

Effect of chronic administration of fruit extract (Citrus unshiu Marc.) on glucose tolerance in GK rats, a model of type 2 diabetes.

Recent epidemiological studies have demonstrated that high dietary consumption of fruit and vegetables results in lower risks of diabetes. In this study, we investigated the effects of chronic administration of fruit extract (Citrus unshiu Marc.) on glucose tolerance in GK rats, a model of type 2 diabetes. After 10 weeks administration of the fruit extract, intraperitoneal glucose tolerance tests revealed significant decrements of blood glucose levels after glucose loading. Our findings further support an advantageous association of fruit consumption with diabetes.

Animals↗

PubMed2006

The homeostasis model assessment-insulin resistance index is inversely associated with serum carotenoids in non-diabetic subjects.

BACKGROUND: Carotenoids may reduce the risk for diabetes mellitus, but little is known about the association of insulin resistance with serum carotenoids in non-diabetic subjects. This study aimed to investigate whether the homeostasis model assessment-insulin resistance (HOMA-IR) index would be lower in the presence of high serum carotenoid concentrations in non-diabetic subjects. METHODS: A total of 812 subjects (256 males and 556 females) who had received health examinations in 2003 participated in the study. The associations of the serum-carotenoid concentrations and HOMA-IR were evaluated cross-sectionally. The multivariate-adjusted geometric means of HOMA-IR by the tertiles of the serum carotenoid concentration were calculated after adjusting for age, body mass index, systolic blood pressure, total cholesterol, triacylglycerols, current tobacco use, regular alcohol intake, exercise habits and total energy intake. Associations among high HOMA-IR (3.0+mUxmmol/L2) across tertiles of serum carotenoid concentration were assessed by tests for logistic regression analysis. RESULTS: In male subjects, the multivariate adjusted geometric mean of HOMA-IR was inversely associated with the serum beta-cryptoxanthin concentrations. In female subjects, an inverse association of the serum carotenoid concentration and HOMA-IR was observed in lycopene, beta-cryptoxanthin, and zeaxanthin. The confounding factor-adjusted odds ratios (OR) for high HOMA-IR on the highest tertiles of serum alpha-carotene, beta-carotene, beta-cryptoxanthin, and zeaxanthin were 0.18 [95% confidence interval (CI): 0.06-0.52], 0.22 (95% CI: 0.07-0.67), 0.34 (95% CI: 0.12-0.96), and 0.30 (95% CI: 0.11-0.79), respectively, in male subjects. On the other hand, in female subjects, the adjusted OR for high HOMA-IR on the highest tertiles of serum lycopene and beta-cryptoxanthin were 0.39 (95% CI: 0.21-0.73) and 0.51 (95% CI: 0.28-0.95), respectively. CONCLUSIONS: The serum antioxidant carotenoids were inversely associated with HOMA-estimated insulin resistance in non-diabetic subjects.

Adult↗

PubMed2005

Serum carotenoid concentrations are inversely associated with serum aminotransferases in hyperglycemic subjects.

Hyperglycemia increases the generation of free radicals by glucose auto-oxidation, and the increment of free radicals may lead to liver cell damage. In this study, we tested the hypothesis that hyperglycemia-induced increases of serum liver enzymes among its physiological concentration would be inversely associated with serum antioxidant carotenoid level. Study subjects were 857 male and female Japanese who had received health examinations in 2003. Those with a history of liver disease and excessive alcohol drinkers were excluded. The associations of serum six-carotenoid concentrations with serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT) stratified by glucose tolerance status were evaluated cross-sectionally. Serum AST and ALT concentrations in the groups of impaired fasting glucose (IFG) and diabetes were significantly higher than those in the normal group. The multivariate-adjusted means of the serum AST and ALT concentrations in IFG and diabetes group were significantly low in accordance with the tertiles of the serum beta-cryptoxanthin and beta-carotene concentrations. The most inverse association of serum liver enzyme and carotenoid concentration was observed in beta-cryptoxanthin. Antioxidant carotenoid, especially beta-cryptoxanthin, may act a deterrent substance against increasing the serum aminotransferase in the earlier pathogenesis of liver dysfunction among hyperglycemic subjects.

Alanine Transaminase↗

PubMed2005

High beta-carotene and beta-cryptoxanthin are associated with low pulse wave velocity.

Antioxidants are potentially beneficial in preventing vascular complications in diabetes because oxidative stress would be enhanced in such a condition and play an important role in vascular disorders. This study aimed to investigate whether brachial-ankle pulse wave velocity (baPWV) would be lower in the presence of high serum carotenoid concentrations stratified according to the glycemic state. A total of 297 men and 579 women between 30 and 70 years of age were analyzed cross-sectionally. Multivariate adjusted mean of baPWV in the highest tertile for beta-carotene (1386 cm/s) was lower than that in the lowest tertile (1432 cm/s) and that in the highest tertile for beta-cryptoxanthin (1382 cm/s) was lower than that in the middle tertile (1424 cm/s) in the case of normal fasting glucose. Similar inverse associations were observed in a group that included subjects with both impaired fasting glucose and diabetes, however, without statistical significance. The highest tertile of carotenoids was associated with a low risk for high baPWV (> or =1680 cm/s). Age, sex and glycemic state adjusted odds ratio was 0.35 (95% CI 0.20-0.60) for beta-carotene and 0.45 (0.27-0.77) for beta-cryptoxanthin. Multivariate adjustment did not alter the results. In conclusion, an inverse association of baPWV with beta-carotene and beta-cryptoxanthin was observed independently of the glycemic state.

Adult↗

PubMed2005

Effects of chronic administration of fruit extract (Citrus unshiu Marc) on endothelial dysfunction in streptozotocin-induced diabetic rats.

We investigated the effects of chronic administration of fruit extract (Citrus unshiu MARC) on the endothelial dysfunction seen in aortae from streptozotocin (STZ)-induced diabetic rats. A ten-week administration of this fruit extract preserved acetylcholine (ACh)-induced endothelium-dependent relaxation, but not sodium nitroprusside (SNP)-induced endothelium-independent relaxation, in the diabetic aorta. In age-matched control rats, chronic administration of the fruit extract had no influence on the ACh- or SNP-induced aortic relaxation. The increased total cholesterol, low-density lipoprotein (LDL) cholesterol, and triglyceride levels seen in STZ-induced diabetic rats were not normalized by fruit-extract treatment. These results suggest that Citrus unshiu MARC extract preserves endothelial function in the aorta in STZ-induced diabetic rats without lowering plasma cholesterol. This beneficial effect may be due to this extract protecting of nitric oxide against inactivation by oxygen free radicals.

Animals↗

PubMed2005

High serum carotenoids are inversely associated with serum gamma-glutamyltransferase in alcohol drinkers within normal liver function.

BACKGROUND: Many studies have reported that the consumption of alcohol induces the generation of free radicals. Moreover, recent studies suggest that serum gamma-glutamyltransferase (gamma-GTP) within its normal range might be an early marker of oxidative stress. In this study, we tested the hypothesis that serum antioxidant carotenoids would be inversely associated with serum gamma-GTP in alcohol drinkers within normal liver function. METHODS: A total of 266 Japanese men who had received health examination in 2003 participated in the study. The associations of serum gamma-GTP and serum-carotenoid concentrations stratified by alcohol intake levels were evaluated cross-sectionally. The participants were divided into three groups according to their ethanol intake level (non-drinker, less than 1 g/day; light drinker, 1-25 g/day; and moderate and heavy drinkers, 25+ g/day). The multivariate-adjusted geometric means of the serum gamma-GTP concentrations in each tertile of the serum-carotenoid concentrations were calculated after adjustment for ethanol intake, age, body mass index, total cholesterol, triacylglycerols, current tobacco use, and habitual exercise. RESULTS: The serum gamma-GTP concentrations were significantly high in accordance with the ethanol intake level. In moderate and heavy drinkers, the multivariate-adjusted geometric means of serum gamma-GTP concentrations were significantly low in accordance with the tertiles of the serum lycopene, alpha-carotene, beta-carotene, and beta-cryptoxanthin concentrations. CONCLUSIONS: The serum antioxidant carotenoids were inversely associated with alcohol-induced increases of serum gamma-GTP in moderate and heavy drinkers within normal liver function.

Adult↗

PubMed2004

Effect of sucrose on ascorbate level and expression of genes involved in the ascorbate biosynthesis and recycling pathway in harvested broccoli florets.

The relationship between sucrose (Suc) and ascorbate (AA) metabolism was investigated in harvested broccoli (Brassica oleracea L. var. italica) florets. Decreases in both Suc and AA content were observed in broccoli florets 48 h after all the leaves were excised, but none were observed when the plants were kept intact or with leaves attached in a room at 20 degrees C. In harvested broccoli plants without leaves and roots, continuous absorption of a 10% (w/v) Suc solution from the cut surface of the stem suppressed the degreening of sepals and the loss of AA content in florets. The expression of the genes related to AA metabolism in chloroplasts and its biosynthesis were up-regulated by Suc feeding in broccoli florets. These data suggest that a decline in Suc leads to considerable damage not only to AA biosynthesis but also to the hydrogen peroxide-scavenging system in chloroplasts. In addition, the cessation of the Suc supply from leaves can be the main factor of AA degradation in harvested broccoli florets.

Ascorbic Acid↗

PubMed2004

Identification and quantification of the conjugated metabolites derived from orally administered hesperidin in rat plasma.

Hesperidin is a biologically effective flavonoid. Several studies have reported that dietary hesperidin was converted to conjugated metabolites, such as hesperetin-glucuronides and sulfoglucuronides, during absorption and metabolism. However, the chemical structures of the conjugated metabolites, especially the sites of glucuronidation and sulfoglucuronidation in plasma, were unconfirmed. Therefore, the concentrations of the metabolites conjugated at various sites in plasma could not be individually quantified. In the present study, we identified the chemical structures and concentrations of the major conjugated metabolites in rat plasma after oral administration of hesperidin. Two hesperetin-glucuronides were prepared and identified as hesperetin-7-O-beta-D-glucuronide and hesperetin-3'-O-beta-D-glucuronide. Using these authentic compounds, the concentrations of hesperetin-7-O-beta-D-glucuronide and hesperetin-3'-O-beta-D-glucuronide in rat plasma were individually determined by liquid chromatography-mass spectrometry. In rat plasma, hesperetin-glucuronides were primarily comprised of hesperetin-7-O-beta-D-glucuronide and hesperetin-3'-O-beta-D-glucuronide. The concentration of hesperetin-7-O-beta-D-glucuronide was slightly higher than that of hesperetin-3'-O-beta-D-glucuronide. Furthermore, not only hesperetin conjugates but also homoeriodictyol conjugates were observed in rat plasma. The present study is the first report elucidating the chemical structures and changes in individual concentrations in rat plasma of glucuronides derived from orally administered hesperidin.

Animals↗

PubMed2004

Accumulation of carotenoids and expression of carotenoid biosynthetic genes during maturation in citrus fruit.

The relationship between carotenoid accumulation and the expression of carotenoid biosynthetic genes during fruit maturation was investigated in three citrus varieties, Satsuma mandarin (Citrus unshiu Marc.), Valencia orange (Citrus sinensis Osbeck), and Lisbon lemon (Citrus limon Burm.f.). We cloned the cDNAs for phytoene synthase (CitPSY), phytoene desaturase (CitPDS), zeta-carotene (car) desaturase (CitZDS), carotenoid isomerase (CitCRTISO), lycopene beta-cyclase (CitLCYb), beta-ring hydroxylase (CitHYb), zeaxanthin (zea) epoxidase (CitZEP), and lycopene epsilon-cyclase (CitLCYe) from Satsuma mandarin, which shared high identities in nucleotide sequences with Valencia orange, Lisbon lemon, and other plant species. With the transition of peel color from green to orange, the change from beta,epsilon-carotenoid (alpha-car and lutein) accumulation to beta,beta-carotenoid (beta-car, beta-cryptoxanthin, zea, and violaxanthin) accumulation was observed in the flavedos of Satsuma mandarin and Valencia orange, accompanying the disappearance of CitLCYe transcripts and the increase in CitLCYb transcripts. Even in green fruit, high levels of beta,epsilon-carotenoids and CitLCYe transcripts were not observed in the juice sacs. As fruit maturation progressed in Satsuma mandarin and Valencia orange, a simultaneous increase in the expression of genes (CitPSY, CitPDS, CitZDS, CitLCYb, CitHYb, and CitZEP) led to massive beta,beta-xanthophyll (beta-cryptoxanthin, zea, and violaxanthin) accumulation in both the flavedo and juice sacs. The gene expression of CitCRTISO was kept low or decreased in the flavedo during massive beta,beta-xanthophyll accumulation. In the flavedo of Lisbon lemon and Satsuma mandarin, massive accumulation of phytoene was observed with a decrease in the transcript level for CitPDS. Thus, the carotenoid accumulation during citrus fruit maturation was highly regulated by the coordination of the expression among carotenoid biosynthetic genes. In this paper, the mechanism leading to diversity in beta,beta-xanthophyll compositions between Satsuma mandarin and Valencia orange was also discussed on the basis of the substrate specificity of beta-ring hydroxylase and the balance of expression between upstream synthesis genes (CitPSY, CitPDS, CitZDS, and CitLCYb) and downstream synthesis genes (CitHYb and CitZEP).

Alkyl and Aryl Transferases↗

PubMed2004

Multiple linear regression analysis of the seasonal changes in the serum concentration of beta-cryptoxanthin.

Beta-cryptoxanthin (beta-CRX) is a carotenoid pigment found in Satsuma mandarin (Citrus unshiu Marc.) fruit, which is heavily produced in Japan. In this study, we evaluated the seasonal changes in the serum beta-CRX level and investigated predictors of serum beta-CRX level by multiple linear regression analysis. Blood tests and self-administered questionnaires were used every other month for one year. The subjects were healthy volunteers, 15 males and 12 females. The serum beta-CRX levels increased dramatically as the intake of Satsuma mandarin increased; the maximum increase was noted in January. Multiple linear regression analysis showed that, in males, the serum beta-CRX level could be predicted by Satsuma mandarin intake, age and the month of blood sampling; however, it was inversely associated with alcohol and smoking habits. Conversely, in females, the serum beta-CRX concentration could be predicted by Satsuma mandarin intake, the month of blood sampling and age; however, it was inversely associated with body mass index. The results of multiple linear regression analysis suggest that the serum beta-CRX levels can be used to evaluate the intake volume of Satsuma mandarin. Furthermore, beta-CRX is a useful biomarker to estimate the beneficial effects of Satsuma mandarin intake in epidemiological studies.

Adult↗

PubMed2004

Seasonal changes in the relationship between serum concentration of beta-cryptoxanthin and serum lipid levels.

Beta-cryptoxanthin (beta-CRX) is a carotenoid pigment found especially in Satsuma mandarin (Citrus unshiu Marc.) fruit, which is mainly produced in Japan. Previously, we found that serum beta-CRX concentrations rose to extreme levels as the frequency of consumption of Satsuma mandarin increases. Using 94 non-smoking female volunteers, the present study evaluated the relationship between serum concentration of beta-CRX and serum lipid levels in September, when the Satsuma mandarin is not in season, and in January of the next year, when it is in season. The mean of increment in serum beta-CRX concentrations from September to January was 95.9 +/- 84.0 microg/dl (mean +/- SD). Although the changes in serum lipid levels did not correlate with the changes in serum beta-CRX, the serum HDL-cholesterol and apo-lipoprotein A1 levels in the highest quartile of the increment in serum beta-CRX from September to January were significantly higher than those in the lowest quartile in both September and January. In cross-sectional analyses, serum beta-CRX concentrations were correlated positively with those of LDL-cholesterol and apo-lipoprotein B levels in September, but these correlations were not observed in January. In contrast, serum beta-CRX concentrations were correlated positively with those of HDL-cholesterol and apo-lipoprotein A1 levels in January. These results suggest that habitual eating of Satsuma mandarin while it is in season may influence lipid metabolism throughout the year.

Apolipoprotein A-I↗

PubMed2003

Ascorbate metabolism in harvested broccoli.

The ascorbate content declined rapidly in broccoli (Brassica oleracea L. var. italica) florets, but not in the stem tissue, during post-harvest senescence. Ascorbate peroxidase (APX), ascorbate oxidase (AO), l-galactono-1,4-lactone dehydrogenase (GLDH), monodehydroascorbate reductase (MDAR), dehydroascorbate reductase (DHAR), and glutathione reductase (GR) were investigated in gene expression after harvest in both florets and the stem tissue of broccoli. Cytosolic gene expressions (BO-APX 1, BO-APX 2, BO-AO, BO-MDAR 2, and BO-GR) were stimulated actively in broccoli florets after harvest. By contrast, it was observed that mRNA levels of chloroplastic APX, BO-sAPX and BO-tbAPX, had decreased by 12 h after harvest in broccoli florets, suggesting that the active oxygen species (AOS) scavenging system in chloroplasts was largely abolished in florets during the early hours of the post-harvest period. In addition, gene expressions in GLDH and other chloroplastic enzymes such as BO-MDAR 1 and BO-DHAR decreased rapidly within 24 h after harvest. Ethylene treatment had no effect on the ascorbate level and the expression of all genes investigated. The expressions of BO-GLDH and chloroplastic genes (BO-sAPX, BO-tbAPX, BO-MDAR 1, and BO-DHAR) mRNA were suppressed by treatment with methyl jasmonate (MJ) and abscisic acid (ABA) and were accompanied by the acceleration of ascorbate degradation. These data suggest that ascorbate metabolism tends to be inactivated in chloroplasts by transcriptional regulation, but not in the cytosol, when ascorbate decreases under stress conditions.

Ascorbate Oxidase↗

PubMed2003

Hepatoprotective and antihyperliposis activities of in vitro cultured Anoectochilus formosanus.

The pharmacological effects of an aqueous extract of the whole plants of in vitro cultured Anoectochilus formosanus were investigated experimentally for hepatoprotective and antihyperliposis activities. The extract showed significant antihepatotoxic activity against carbon tetrachloride induced cytotoxicity in primary cultured rat hepatocytes. In an assay for antihyperliposis using aurothioglucose-induced obese mice, the extract suppressed significantly the increase in the weights of body and liver, ameliorated triglyceride levels in the liver and serum, and also significantly reduced the deposition of adipose tissue.

Adipose Tissue↗