Dietary γ-amino butyric acid (GABA) has been suggested to decrease systolic blood pressure. This study aimed to ex-amine the effects of dietary GABA on the life span of stroke-prone spontaneously hypertensive rats (SHRSPs). In this study, life span was determined for SHRSPs provided 1% NaCl solution or 0.01% GABA in 1% NaCl solution as drinking water. The life span of the GABA-fed group (76.3 ± 1.65 days) was significantly shorter than that of the control group (81.6 ± 0.88 days). The results of this study may not be applicable to humans. Future studies will be necessary to elucidate the mechanism underlying this phenomenon.
γ-Aminobutyric acid (GABA) is an amino acids, found in unpolished rice, fermented food such as tempe, and vegetables. In humans, it is well recognized as an inhibitory transmitter. Moreover GABA is present in the peripheral organs such as the intestinal tract; [
SHRSPs aged 3 weeks were purchased from Japan SLC Inc. (Shizuoka, Japan). The animals were housed individually in stainless steel cages in a room with controlled lighting (lights on: 0800 - 2000 hours) and a constant temperature (20 - 25˚C). They were fed a commercial nonpurified chow diet (CRF-1; CLEA Japan Co. Ltd.; Tokyo, Japan) and distilled water for 1 week. They were then divided into 2 experimental groups of 5 rats each. The food remained the same, but the water was replaced with 1% NaCl solution in 1 group and with 0.01% GABA solution in 1% NaCl in the other group. GABA (special-grade reagent) was purchased from Wako pure chemical industries, Ltd. (Osaka, Japan). The concentration of the GABA solution was the same as that in Gabaron Tea [
Data are represented as means ± standard error. The differences between the experimental groups were evaluated by Student’s t test. P < 0.05 was considered statistically significant.
Until the onset of stroke, the body weights of all animals increased well, and no significant differences were observed between the 2 groups (
As shown in
Although several animal studies, including those on
spontaneously hypertensive rat (SHRs), have shown that dietary GABA decreases systolic blood pressure [
The results of this animal study might not be applicable to humans because the brain uptake of GABA is suggested to be a characteristic of SHRs [6,7]. Generally, it has been reported that polar molecules such as dietary GABA cannot cross the brain because of the blood-brain barrier (BBB). However, the volume of 14C-GABA distribution in the cerebrospinal fluid and brain regions was significantly greater in SHRs than in Wistar Kyoto (WKY) rats. Moreover, a study on BBB integrity showed that the paracellular permeability of the brain capillaries was higher in SHRs than in WKY rats [
Another difference between human and SHRSP is the excessively high absorption of phytosterol induced by mutation of ATP-binding cassette transporter G5 [
Therefore, if SHRSP was used in a nutritional experiment, specific consideration might be needed.
Although the abnormality of the BBB in SHRSPs has not been examined in this respect, a BBB disorder may be related to the short life span observed for GABA-fed SHRSPs in this study. The underlying mechanism should be elucidated in future studies.
We observed the life span of SHRSP fed GABA because dietary GABA reduces systolic blood pressure. Unexpectedly, dietary GABA decreased the life span of SHRSP. The results of this animal study might not be applicable to humans because the brain uptake of GABA is a characteristic of SHRs. The underlying mechanism for this phenomenon will be elucidated in future studies.