The inhibitory effects of himeukogi (Acanthopanax sieboldianus) leaf tea on postprandial blood glucose elevation were investigated in normal rats and healthy human volunteers. First, extraction methods for himeukogi leaf tea were examined in vitro using the decrease of α-glucosidase activity as an indicator. The decrease of α-glucosidase activity of himeukogi leaf tea was enhanced by extraction with hot water containing 2% himeukogi leaf (w/v). In sugar tolerance tests in rats, himeukogi leaf tea significantly suppressed the increase in the blood glucose level after oral administration of maltose or starch. In human subjects, the postprandial blood glucose level after ingestion of boiled rice was measured after oral administration of himeukogi leaf tea. Himeukogi leaf tea suppressed the increase of blood glucose at 30 min after the meal, and the effect was especially marked in subjects whose postprandial blood glucose levels were higher than the mean (144 mg/dL) at this time point. These results suggest that intake of himeukogi leaf tea prevents the increase in the postprandial blood glucose level by decreasing the digestion of sugars in the gastrointestinal tract.

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Diabetes mellitus (DM) has been shown to enhance oxidative stress, leading to aggravation of cerebral ischemic injury following stroke. In this study, we examined the effects of daily administration of a water-soluble extract from culture medium of Ganoderma lucidum mycelia (WER) on total plasma oxidative stress, antioxidant capacity and activity of antioxidant enzymes (superoxide dismutase and catalase) in the brain of rats with streptozotocin (STZ)-induced diabetes. We also investigated whether WER ameliorates the exacerbation of neuronal damage induced by middle cerebral artery occlusion (MCAO) followed by reperfusion in a diabetic state. Male SD rats were treated with STZ (60 mg/kg, i.p.) and housed for 5 weeks for induction of an experimental diabetic state. WER (1 g/kg) was then administered orally for an additional 2 weeks. DM rats had increased oxidative stress and decreased plasma antioxidant capacity in comparison with non-DM rats. Furthermore, the activity of antioxidant enzymes was decreased in the DM rat brain. DM rats treated with WER showed normal levels of all these parameters. The diabetic state markedly aggravated MCAO/reperfusion-induced neurological deficits and cerebral injury assessed by infarct volume. Treatment with WER markedly improved both of these parameters in diabetic rats. These results show that daily intake of WER relieves the exacerbation of cerebral ischemic injury in a diabetic state, and that this may be attributable to amelioration of augmented oxidative stress.

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The purpose of the present study was to investigate the acute effect of orally administered GABA on changes in autonomic nervous system (ANS) activity in young healthy males. Using a double-blind, random crossover design, 12 males (aged 21.7±0.8 yr) consumed a placebo or GABA-containing (30 mg per meal) capsules after an overnight fast. ANS activity was evaluated by means of heart rate variability power spectral analysis before and after administration for 30 and 60 min. There were significant increases in overall ANS and parasympathetic nervous system activities after GABA ingestion. The present results suggest that GABA may induce relaxation effects by modulating ANS activity.

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