Effect of chlorella and its fractions on blood pressure, cerebral stroke lesions, and life-span in stroke-prone spontaneously hypertensive rats.

Effects of Chlorella regularis (dried cell powder)--cultured axenically under heterotrophic conditions, and provided as a dietary supplement--and its fractions on the blood pressure, cerebral stroke lesions, and life-span of stroke-prone spontaneously hypertensive rats (SHRSP/Izm) were investigated. When SHRSP were fed on diets with supplemented Chlorella to a commercial diet (Funabashi SP), elevation of blood pressure was significantly lower in the Chlorella groups than in the control group. At 21 wk of feeding, serum total cholesterol was significantly lower in the Chlorella groups than in the control group. Histopathological examination revealed cerebral vascular accidents in the brains of the control group, but those of Chlorella groups showed apparently low incidence compared to the control group. The average life-span of the Chlorella groups were significantly longer than that of the control group (p < 0.001). Chlorella powder was fractionated into three fractions, lipid-soluble, hot water-soluble, and residual fractions. The diets supplemented with lipid or residual fractions equivalent to 10% Chlorella significantly suppressed elevation of blood pressure in SHRSP, and then decreased the incidence rate of cerebral vessel lesions compared to the control group. Chemical analysis revealed that the lipid fraction contained large quantities of antioxidants, including carotenoids (especially lutein) and others, and phospholipids involved in aorta collagen and elastin metabolism; the residual fraction contained high concentrations of arginine, enhancing the function of blood vessels. The control diet contained only a little these substances. These experimental results suggest that the beneficial effect of Chlorella on SHRSP is caused by the synergistic action of several ingredients of Chlorella, which play a role in sustention of a vascular function of rats.

Effect of a gamma-aminobutyric acid-enriched dairy product on the blood pressure of spontaneously hypertensive and normotensive Wistar-Kyoto rats.

We investigated the blood-pressure-lowering effects of gamma-aminobutyric acid (GABA) and a GABA-enriched fermented milk product (FMG) by low-dose oral administration to spontaneously hypertensive (SHR/Izm) and normotensive Wistar-Kyoto (WKY/Izm) rats. FMG was a non-fat fermented milk product produced by lactic acid bacteria, and the GABA contained in FMG was made from the protein of the milk during fermentation. A single oral dose of GABA or FMG (5 ml/kg; 0.5 mg GABA/kg) significantly (P<0.05) decreased the blood pressure of SHR/Izm from 4 to 8 h after administration, but did not increase that of WKY/Izm rats. The hypotensive activity of GABA was dose-dependent from 0.05 to 5.00 mg/kg in SHR/Izm. During the chronic administration of experimental diets to SHR/Izm, a significantly slower increase in blood pressure with respect to the control group was observed at 1 or 2 weeks after the start of feeding with the GABA or FMG diet respectively (P<0.05) and this difference was maintained throughout the period of feeding. The time profile of blood-pressure change due to administration of FMG was similar to that of GABA. FMG did not inhibit angiotensin 1-converting enzyme. Furthermore, an FMG peptide-containing fraction from reverse-phase chromatography lacked a hypotensive effect in SHR/Izm rats. The present results suggest that low-dose oral GABA has a hypotensive effect in SHR/Izm and that the hypotensive effect of FMG is due to GABA.

Production of intracellular phytochemicals in Chlorella under heterotrophic conditions.

A heterotrophic synchronous culture (HSC) of Chlorella regularis S-50, a strain with a high growth rate, and one for its mutant were established by alternately culturing for 6 h on medium containing glucose and for 3 h on medium without glucose. The changes in cellular components and respiratory activity during the course of cell cycling in the HSC were investigated. The synchronized daughter cells (small cells) produced by the HSC contained 2-3 times as much intracellular phytochemicals (carotenoids, chlorophyll, tocopherols, and others typical of green plants) as the glucose-metabolizing cells or the non-synchronous cell mass. To attain the HSC at high cell density, the effects of glucose and oxygen on growth rate, synchronous growth, and production of intracellular phytochemicals were revealed. During the increase in cell mass, when a glucose concentration of 0.5-10 g l(-1) in the culture fluid was maintained by glucose feeding, and the (Qo2)(max) in cells was kept constant by supplying oxygen, cell mass increased synchronously with a specific growth rate, mu, of over 0.2 h(-1). In the HSC, when the late glucose-metabolizing cells were aerated by supplying oxygen to maintain over a half of the (Qo2)(max) under glucose-deficient conditions, intracellular phytochemicals increased rapidly in parallel with cell division. On the basis of these results, the HSC system at high cell density was attained by a glucose-limited fed-batch culture that involves three controlled conditions; glucose concentration, glucose feeding time, and oxygen supply. The system maintained synchronous growth for more than three generations until the cell density reached about 90 g l(-1) with a mu of 0.2 h(-1). In the HSC system, synchronized daughter cells were obtained at a cell productivity of 84 g l(-1) (30 h)(-1). The cell yield for glucose was 0.45. A weight of 100 g of dry cells contained 710 mg carotenoids, 350 mg lutein, 50 mg alpha-carotene, 60 mg beta-carotene, 3.3 g chlorophylls, 23 mg tocopherols, and others, with 63 g of protein rich in essential amino acids. Industrial-scale HSC systems made it possible to steadily produce Chlorella, containing 10-50 times as much phytochemicals as green and yellow vegetables, regardless of the weather.

Antioxidant and anti-cataract effects of Chlorella on rats with streptozotocin-induced diabetes.

The antioxidant activities of Chlorella in vitro and in vivo were investigated. Chlorella showed a strong antioxidant effect compared to various vegetables in a 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging assay. To evaluate the antioxidant and anti-cataract effects in vivo, a 7.3% Chlorella powder was fed to rats with streptozotocin-induced diabetes for 11 wk. At the end of the experiment, Chlorella had decreased the blood glycated hemoglobin (hemoglobin A1c) and serum cholesterol levels significantly, however, it had not affected the serum glucose concentration. The serum lipid peroxide value (TBARS value) in the rats fed Chlorella was lower than that of the control rats. In the liver and kidney, Chlorella also reduced chemiluminescent intensities. In addition, it delayed the development of lens opacities. The lens lipid peroxide content of the rats fed Chlorella was lower than that of the control rats, however the differences were not significant. These results indicate that Chlorella has antioxidant activity and may be beneficial for the prevention of diabetic complications such as cataracts.

Involvement of gamma-aminobutyric acid (GABA) B receptors in the hypotensive effect of systemically administered GABA in spontaneously hypertensive rats.

We investigated the effects of intraduodenally (i.d.) administered gamma-aminobutyric acid (GABA) on blood pressure (BP) in anesthetized spontaneously hypertensive rats (SHR) and the mechanism underlying this effect, especially the type of GABA receptor involved in the depressive effect of this amino acid. GABA (0.3 to 300 mg/kg, i.d.) caused a dose-related decrease in the BP of 9.20 +/- 3.96 to 35.0 +/- 5.34 mmHg (mean +/- S.E.M.) that lasted for 30 to 50 min. The minimum effective i.d. dose of GABA was 0.3 to 1.0 mg/kg. Results pertaining to the mechanism underlying the GABA-induced effects on BP were as follows: a) GABA did not alter the BP-related effects of exogenous noradrenaline and acetylcholine; b) pretreatment with hexamethonium decreased the GABA-induced fall in BP, and GABA tended to reduce the pressor response associated with injection of dimethyl phenylpiperazinium; and c) pretreatment with 2-hydroxysaclofen markedly reduced the GABA-induced drop in BP, whereas pretreatment with bicuculline did not. In conclusion, in SHR, low-dose (0.3 to 1.0 mg/kg, i.d.) GABA had a hypotensive effect, which may result from attenuation of sympathetic transmission through the activation of GABA(B) receptors at presynaptic or ganglionic sites.