Tofu and cognitive impairment — studies
Association of mid-life consumption of tofu with late life
cognitive impairment and dementia: the Honolulu-Asia Aging Study.
White L, Petrovich H, Ross GW, Masaki K.
Fifth International Conference on Alzheimer's Disease, #487, 27 July
1996, Osaka, Japan.
Abstract
Tofu and other soybean foods contain isoflavones - three ringed
molecules bearing structural resemblance to steroidal hormones and
having significant estrogen agonistic or antagonistic activities
apparently related to their interactions with estrogen receptors and/or
with enzymes involved in estrogen metabolism.
There is evidence suggesting that estrogens modulate neural and
synaptic plasticity during aging. Male neurons have both estrogen and
androgen receptors. Further, an enzyme (aromatase) that converts
androgens to estrogens has been demonstrated in the medial forebrain,
limbic system, hippocampus, and hypothalamus.
It was hypothesized that men had consistently high dietary intakes
of tofu during middle life would experience different patterns of
cognitive decline and dementia in late life, compared with men
reporting little or no tofu consumption.
The Honolulu-Asia Aging Study is a longitudinal study of aging and
dementia conducted in Japanese-American men who are members of the
Honolulu Heart Program cohort. Mid-life patterns of consumption of tofu
and several other foods were defined on the basis of food frequency
interviews conducted in 1965 and 1972. The Cognitive Abilities
Screening Instrument was administered to more than three thousand
surviving participants aged 71-93 years during the 1991-93 examination
cycle. DSM-HI-R, NINCDS-ADRDA, and California criteria were use for the
diagnosis of dementia (all cause), AD and VsD.
We found an association of consistently high levels of tofu
consumption in mid-life with low cognitive test scores (p=0.02) and
(independently) with Alzheimer's disease in late life, controlling for
all other relevant variables. The odds ratio for AD in persons who
reported eating tofu at least twice weekly was 2.4 (95% CI 1.14-5.09),
compared with persons reporting tofu consumption rarely or never.
Life-style risk factors for cognitive impairment.
White LR, Foley DJ, Havlik RJ
In: Strategies to prevent cognitive decline in late life,
Fillit H, Butler RN, editors. London: Greenwich Medical Media; 1997. p.
23-32.
Abstract
The EDB Program of NIA is involved in an epidemiological study of
about 3,500 older Japanese-American men in Honolulu, Hawaii. As has
been mentioned, prevalence rates of Alzheimer’s disease
are higher than in Japan. This study offers some unique features, which
should be highlighted. This population has been under observation for
about 25 years; so, data were collected many years earlier, before any
effect of dementia could distort the data. Data were primarily on
cardiovascular risk factors including dietary intake and indicators of
cultural differences (more or less traditional Japanese). Preliminary
results are available on a number of potential risk factors for
Alzheimer’s disease. There is no relationship with alcohol
consumption, smoking, years of education, or low complexity occupations
including working in sugar-cane or pineapple fields. What is
unexpected, and somewhat inconsistent with the hypothesis of
westernization being related to increased Alzheimer’s
disease, is the unexplained finding that components of the traditional
Japanese diet, which include a high intake of green tea, tofu, and miso
soup, are positively associated with Alzheimer’s disease.
This finding is being pursued in further analyses. Also, an unusual
aspect of the study is a high autopsy rate among participants. The
situation will allow study of structure-function relationships,
including correlation of ante-mortem factors with
Alzheimer’s disease-specific findings of plaques and
tangles and brain size. It is quite possible that certain factors will
be related to structural changes and others to the clinical
manifestations of Alzheimer’s disease. It should be
possible to evaluate these complex interrelationships within this
rather unique population.
Long-term potentiation in the hippocampus is blocked by tyrosine
kinase inhibitors.
O'Dell TJ, Kandel ER, Grant SG
Nature 1991 Oct 10 353:6344 558-60
Abstract
Long-term potentiation (LTP) in the hippocampus is thought to
contribute to memory formation. In the Ca1 region, LTP requires the
NMDA (N-methyl-D-aspartate) receptor-dependent influx of Ca2+ and
activation of serine and threonine protein kinases. Because of the high
amount of protein tyrosine kinases in hippocampus and cerebellum, two
regions implicated in learning and memory, we examined the possible
additional requirement of tyrosine kinase activity in LTP. We first
examined the specificity in brain of five inhibitors of tyrosine kinase
and found that two of them, lavendustin A and genistein, showed
substantially greater specificity for tyrosine kinase from hippocampus
than for three serine-threonine kinases: protein kinase A, protein
kinase C, and Ca2+/calmodulin kinase II. Lavendustin A and genistein
selectively blocked the induction of LTP when applied in the bath or
injected into the postsynaptic cell. By contrast, the inhibitors had no
effect on the established LTP, on normal synaptic transmission, or on
the neurotransmitter actions attributable to the actions of protein
kinase A or protein kinase C. These data suggest that tyrosine kinase
activity could be required postsynaptically for long-term synaptic
plasticity in the hippocampus. As Ca2+ calmodulin kinase II or protein
kinase C seem also to be required, the tyrosine kinases could
participate postsynaptically in a kinase network together with serine
and threonine kinases.
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