Posted: 14 June 2012
Aspartame impairment of spatial cognition and insulin sensitivity in mice, focus on phenylalanine and aspartate [ methanol also crosses placenta into fetus, turning into teratogenic formaldehyde], Kate S. Collision et al, PLoS One 2012.04.03: Rich
Aspartame impairment of spatial cognition and insulin sensitivity in mice, focus on phenylalanine and aspartate [methanol also crosses placenta into fetus, turning into teratogenic formaldehyde], Kate S. Collision et al, PLoS One 2012.04.03: Rich Murray 2012.04.29
[See also: 40. Collison KS, Makhoul NJ, Inglis A, Al-Johi M, Zaidi MZ, et al.
Dietary trans-fat combined with monosodium glutamate induces dyslipidemia and impairs spatial memory.
Physiol Behav. 2010;99(3):334–342. [PubMed]
http://www.biomedcentral.com/1471-2164/12/555 free full text]
Aspartame is 11% methanol, 22 mg per can of diet drink -- in humans only, the ADH enzyme turns methanol into formaldehyde adjacent to and within cells in blood vessels, brain, retina, and many other tissues, including breast, prostate, womb and fetus -- killing cells, forming cumulative micro lesions, mutating DNA, and leading to later cancers.
Methanol sources also include wood and cigarette smoke, canned fruits juices vegetables, fermented and smoked foods, some wines and liquors, and more...
Methanol/formaldehyde paradigm for multiple sclerosis, free full 56 page chapter 9 pdf, While Science Sleeps, 146 full text references online, Prof. Woodrow C. Monte: Rich Murray 2012.03.20
"We used a dosage of aspartame [testing mice] which approximated the ADI for aspartame in the US (approx. 50 mg/kg body weight)." [WC Monte notes that humans are uniquely vulnerable to aspartame (methanol/formaldehyde) toxicity, about 100X worse than for rodents. While Science Sleeps, 2012 January pages 23, 59]
"Whilst the neurological effects of methanol have been well documented,  [ in human brain MRIs in 7 studies ] aspartate, like glutamate, has been shown to cause brain lesions , obesity  and impaired memory retention  in rodents exposed to these excitatory amino acids (EAA)."
[3. Blanco M, Casado R, Vázquez F, Pumar JM.
CT and MR imaging findings in methanol intoxication.
AJNR Am J Neuroradiol. 2006; 27(2):452–454. [PubMed]]
AJNR Am J Neuroradiol. 2006 Feb;27(2):452-4.
CT and MR imaging findings in methanol intoxication.
Blanco M, a, Casado R, b, Vázquez F, a, Pumar JM. a.
a. From the Radiology Department Hospital Clínico Universitario de Santiago, Santiago de Compostela, Spain
b. Intensive Care Unit, Hospital Clínico Universitario de Santiago, Santiago de Compostela, Spain
We present the CT and MR imaging findings in acute methanol intoxication in a 35-year-old man who was admitted to the emergency department with weakness, blurred vision, mild bilateral areactive mydriasis, and a progressive decrease in the level of consciousness. CT and MR imaging showed bilateral putaminal hemorrhagic necrosis and subcortical white matter lesions with peripheral contrast enhancement. There was only partial improvement in patient's Glasgow Coma Scale score during follow-up. PMID: 16484428 [PubMed - indexed for MEDLINE] Free full text
http://www.ajnr.org/content/27/2/452.long free full text
The most characteristic MR findings in methanol toxicity are bilateral putaminal necroses, which may have varying degrees of hemorrhage. This finding is by no means specific to methanol toxicity but is seen also in a variety of conditions, including Wilson disease and Leigh disease.4 Putaminal necrosis and hemorrhage probably result from the direct toxic effects of methanol metabolites and metabolic acidosis in the basal ganglia.5 Cerebral and intraventricular hemorrhage, cerebellar necrosis, diffuse cerebral edema, bilateral subcortical white matter necrosis or edema, and optic nerve necrosis all have been described in severe methanol intoxication.3,5 Optic nerve demyelination secondary to myelinoclastic effect of formic acid has been suggested as responsible for optic nerve damage with or without axonal loss.5 It is possible that direct toxic effects of methanol metabolites also were responsible for the subcortical and putaminal lesions.5,6 It has also been suggested that putamen is particularly at risk to various pathologic processes because of its high metabolic demand and because it lies in the boundary zones of vascular perfusion,4 though for some authors the nature of the distribution of the lesions seems to be counterevidence of a vascular cause.5 The basis for the selective vulnerability in these regions remains unknown.5
It is probably a combination of factors, including cerebral microvascular anatomy and direct toxic effects of methanol metabolites, that causes the characteristic distribution of pathologic findings, including severe alterations of subcortical white matter and central gray matter alteration with sparing of peripheral gray matter.
What is interesting in our case is the presence of intense peripheral enhancement in subcortical and putaminal lesions, a result of brain-blood barrier damage.
Previous studies have linked aspartame consumption to impaired retention of learned behavior in rodents. Prenatal exposure to aspartame has also been shown to impair odor-associative learning in guinea pigs; and recently, aspartame-fed hyperlipidemic zebrafish exhibited weight gain, hyperglycemia and acute swimming defects.
We therefore investigated the effects of chronic lifetime exposure to aspartame, commencing in utero, on changes in blood glucose parameters, spatial learning and memory in C57BL/6J mice.
Morris Water Maze (MWM) testing was used to assess learning and memory, and a random-fed insulin tolerance test was performed to assess glucose homeostasis. Pearson correlation analysis was used to investigate the associations between body characteristics and MWM performance outcome variables. At 17 weeks of age, male aspartame-fed mice exhibited weight gain, elevated fasting glucose levels and decreased insulin sensitivity compared to controls (P<0.05). Females were less affected, but had significantly raised fasting glucose levels. During spatial learning trials in the MWM (acquisition training), the escape latencies of male aspartame-fed mice were consistently higher than controls, indicative of learning impairment. Thigmotactic behavior and time spent floating directionless was increased in aspartame mice, who also spent less time searching in the target quadrant of the maze (P<0.05). Spatial learning of female aspartame-fed mice was not significantly different from controls.
Reference memory during a probe test was affected in both genders, with the aspartame-fed mice spending significantly less time searching for the former location of the platform.
Interestingly, the extent of visceral fat deposition correlated positively with non-spatial search strategies such as floating and thigmotaxis, and negatively with time spent in the target quadrant and swimming across the location of the escape platform. These data suggest that lifetime exposure to aspartame, commencing in utero, may affect spatial cognition and glucose homeostasis in C57BL/6J mice, particularly in males.
PMID: 22509243 [PubMed - in process] PMCID: PMC3317920
Free PMC Article
> Free full text Journal List > PLoS One v.7(4); 2012
Formats: Abstract | Full Text | PDF (1.0M)
PLoS One. 2012; 7(4): e31570.
Published online 2012 April 3. doi: 10.1371/journal.pone.0031570
Copyright Collison et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Conceived and designed the experiments: KSC NJM FAA. Performed the experiments: NJM MZZ SMS BA AI RAR. Analyzed the data: KSC NJM MZZ.
Wrote the paper: KSC.
Received October 15, 2011; Accepted January 11, 2012.
[Rich Murray: I increased line spacing to improve readability and highlight facets.]
Previous studies have shown that chronic consumption of the dipeptide artificial sweetener aspartame may affect the T-maze cognitive performance of male rats, promoting impairment of retention of learned behavior when compared to the performance of controls .
The Acceptable Daily Intake for aspartame currently stands at 50 mg/Kg body weight in the United States, and 40 mg/Kg in Europe.
Once ingested, aspartame (L-aspartyl-phenylalanine methyl ester) is rapidly metabolized to its metabolic components phenylalanine, aspartate, and methanol in the ratio of 50-40-10 w/w/w .
Whilst the neurological effects of methanol have been well documented, [3 aspartate, like glutamate, has been shown to cause brain lesions , obesity  and impaired memory retention  in rodents exposed to these excitatory amino acids (EAA).
3. Blanco M, Casado R, Vázquez F, Pumar JM. CT and MR imaging findings in methanol intoxication.
AJNR Am J Neuroradiol. 2006; 27(2):452–454. [PubMed]]
The aspartame metabolite phenylalanine is an essential amino acid which occurs naturally in the breast milk of mammals; however high levels of phenylalanine are a health hazard to those born with phenylketonuria (PKU), a metabolic disorder caused by an inherited mutation in the phenylalanine hydroxylase (PAH) gene which prevents phenylalanine from being metabolized correctly. This results in a detrimental accumulation of the amino acid, leading to developmental defects, seizures and mental retardation .
Normal mammalian plasma levels of phenylalanine are approx. 30–50 µM (0.5–0.8 mg/dL), however 1 in 50 individuals are heterozygous for the mutation in the phenylalanine hydroxylase gene , resulting in significantly higher levels of fasting plasma phenylalanine compared to non-carriers , together with a reduced phenylalanine clearance rate after intravenous loading .
Repeated ingestion of 8 servings of aspartame-sweetened beverages by PAH heterozygous individuals incurred plasma phenylalanine levels of up to 165 µM , although this was still well below the levels reported to cause neurotoxicity during acute administration in primates. Additionally, genetically mutated PAH-deficient homozygous Pah enu2 PKU BTBR mice have six times the level of brain phenylalanine compared to their heterozygous counterparts , resulting in abnormal CNS synapses and dendritic spines  together with pathological cognitive impairment .
In vitro, phenylalanine has been demonstrated to specifically and reversibly attenuate glutamatergic synaptic transmission by competing with the glycine binding site of N-methyl D-aspartate (NMDA) receptor , .
Additionally, the ratio of GluN2A/GluN2B NMDA receptor subunit expression is significantly increased in the hyperphenylalaninemic Pah enu2 PKU mouse model, suggesting a potential mechanism whereby elevated levels of phenylalanine may impair brain development and function , . Since their discovery in the early 1950s, NMDA receptors have been implicated in many crucial functions of central importance, including learning and memory, neuronal plasticity and neurotoxicity , ; and they are the only known receptor that is regulated both by a ligand (usually glutamate) and also by voltage . There are at least five binding sites on the NMDA receptor which regulate its activity including glutamate, glycine, magnesium, zinc and a fifth site that binds to the hallucinogenic substance phencyclidine . The central role of NMDA receptors in the process of learning and memory has been confirmed by the extensive use of NMDA receptor agonists and antagonists to study long term potentiation in memory acquisition and maintenance .
Whereas it is generally agreed that aspartate crosses the placenta only to a limited degree , phenylalanine is actively transported across the placenta , resulting in an increase in this aromatic amino acid at the expense of the maternal concentration .
During pregnancy, aspartame administration by gavage resulted in impaired performance of the offspring in an odor-aversion test administered to guinea-pigs within the first month of life . This insightful study confirms previous reports in a second species, that aspartame administered pre- and postnatally to rats can result in impaired cognitive performance of the offspring .
Furthermore, aspartame has been shown to cause brain inflammation, hyperglycemia and fatalities in a third species: the hyperlipidemic zebrafish model . Aspartame-fed zebrafish also exhibited swimming defects which were interpreted as possibly due to damage in the brain and neurons (28).
The timing, dosage and route of EAA administration in vivo appears to be of critical importance, since acute exposure to high doses of dipeptide aspartame during adulthood has no effect on cognitive ability in either humans  or rodents .
However a single i.p. injection 500 mg/Kg aspartate was sufficient to cause memory impairment and neuronal damage in adult mice undergoing passive avoidance testing ; and intracranial injections of phenylalanine caused permanent amnesia in 1 day old chicks .
Similarly, perinatal exposure to glutamate results in delayed onset neuroendocrine dysfunction together with cognitive deficiencies  -- , whereas exposure to considerable amounts of dietary glutamate in adulthood is apparently without effect .
Interestingly, we  and others  have noted gender-specific differences in behavior in response to Monosodium Glutamate (MSG).
Gender dimorphism in MSG-induced impairment of the growth hormone / IGF-1 axis has also been investigated , and it would be of interest to ascertain whether gender dimorphism in glucose homeostasis exists in response to aspartame consumption.
The aims of the present study were therefore to examine the effect of lifetime exposure to aspartame, commencing in utero, on weight gain, spatial cognition, insulin sensitivity and glucose parameters of male and female C57BL/6J mice.
We used a dosage of aspartame which approximated the ADI for aspartame in the US (approx. 50 mg/kg body weight). [WC Monte notes that humans are uniquely vulnerable to aspartame (methanol/formaldehyde) toxicity, about 100X worse than for rodents.]
Insulin sensitivity was assessed by a random fed insulin tolerance test (ITT), together with measurements of fasting glucose and insulin levels; and cognitive performance was assessed in the Morris Water Maze (MWM). The relationship between visceral fat deposition and cognitive function was determined by analyzing the correlation between body characteristics, glucose and insulin parameters and performance targets in the MWM test, using Pearson correlation analysis......
Our results suggest that neonatal exposure to aspartame consumed as part of the diet of pregnant mice, together with continued chronic exposure of the offspring to dietary aspartame throughout the first 20 weeks of life, may result in increased weight gain compared to controls together with impairment of insulin sensitivity and cognitive performance, most notably in males. Food and water intake was not affected by aspartame administration within the ADI. The results of our analysis support previous observations that aspartame may cause impairment in learning and memory particularly when administered chronically ,  or neonatally . Additionally, damage to hypothalamic morphology has been reported in neonatal rodents ingesting high amounts of aspartame .
Aspartame is metabolized rapidly into methanol, phenylalanine and aspartate ; and oral administration of aspartame (200 mg/Kg) has been shown to increase levels of rat brain phenylalanine and its metabolite tyrosine, whilst decreasing levels of leucine, isoleucine and valine . Whereas it is generally accepted that aspartate does not readily cross the placenta, phenylalanine and tryosine are readily transported to the fetal tissues; resulting in an increase in phenylalanine at the expense of the maternal concentration .
In rodents, phenylalanine is readily converted into the neurotransmitter precursor tyrosine by the hepatic enzyme PAH ; however if the activity of this enzyme is reduced or absent, the high levels of accumulated phenylalanine may be converted into other metabolites such as phenylpyruvate, phenylacetate and phenyllactate , . Crucially, studies have shown that in rodents, PAH activity is undetectable until the final days of gestation and birth, whereupon the gene is activated by glucocorticoids and cyclic AMP –.
Experimentally induced hyperphenylalaninemia has been shown to result in spatial and non-spatial deficits in cognition and learning that are not related to impairment of locomotor skills , .
In humans, deficiency of PAH due to genetic mutations in the gene results in phenylketonuria (PKU), which is characterized by neurotoxic hyperphenylalaninemia and microcephaly, together with visuo-spatial, executive and attention deficits , .
The mechanisms responsible for the hyperphenylalaninemia-induced brain damage are still largely unknown; however hyperphenylalaninemia has recently been shown to promote oxidative stress in rodent brains, which may contribute to the neurotoxicity in phenylketonuria , .
Oxidative stress is the result of the aberrant production of reactive oxygen and / or nitrogen species, or a decrease in the capacity of antioxidant defenses for example glutathione; and has been linked to a number of neurodegenerative diseases and to the cognitive decline associated with aging .
Importantly, subcutaneous injections of aspartame have recently been shown to increase rat brain thiobarbituric acid-reactive substances (TBARS; markers of lipid peroxidation) and decrease glutathione levels .
[62. Abdel-Salam OM, Salem NA, Hussein JS. Neurotox Res. Aug 6. [Epub ahead of print]; 2011. Effect of Aspartame on Oxidative Stress and Monoamine Neurotransmitter Levels in Lipopolysaccharide-Treated Mice. ]
Collectively, these observations may provide clues as to a mechanism whereby aspartame metabolites; phenylalanine in particular, may contribute to the impairment in spatial learning and memory that we observed in mice exposed to aspartame in utero and during the first months of life.
During acquisition of the water maze task, young rodents typically improve their performance as indicated by a progressive reduction in escape latencies over successive training sessions. Upon introduction to the maze, mice initially adopt non-spatial behaviors including thigmotaxis, scanning and chaining , . As training progresses, this behavior gives way to spatial learning, resulting in more cued swimming towards the hidden platform, more time spent in the target quadrant, and shorter escape latencies. Within the context of this paradigm, aspartame-fed mice exhibited significant differences in learning strategies at four months of age, which resulted in longer escape latencies compared to controls, together with quantitative and qualitative differences in behavioral strategies employed. Towards the end of acquisition training, aspartame-fed mice spent significantly more time swimming around the periphery of the pool and passively floating compared to control mice, which may be indicative of an ineffectual non-spatial swim strategy . Increased thigmotaxis behavior linked to a deficit in responding to visual cues has previously been noted after experimentally induced lesions to the dorsal-striatum: a compound structure of the brain believed to be involved in stimulus-response learning . Additionally, lesions to the hippocampus  and NMDA receptor blockade using specific antagonists have also shown to result in increased thigmotactic behavior , .
Impairment of spatial memory in the aspartame diet group was suggested by a significant reduction in time spent swimming towards the former platform location during the probe test. Additionally, thigmotactic behavior and passive floating during the probe test was increased in male aspartame-fed mice compared to controls. Taken together this suggests that chronic exposure to aspartame may impair rodent spatial memory. It has previously been suggested that exposure to high doses of aspartame at a late stage of pregnancy may result in a delay in visual placing response in the offspring, which is a measure of sensorimotor activity . However, a second study failed to duplicate these findings .
In addition to the effects of aspartame on rodent cognitive performance in the water maze, aspartame appeared to raise fasting blood glucose levels in both sexes. The relationship between peripheral blood glucose levels and cognition has been well-documented and suggests that there is a homeostatic neuroglycemic range within which optimal cognitive function occurs . Hyperglycemia may damage the microvasculature of the blood-brain barrier and/or modify insulin availability in the brain, disrupting normal brain function and cognition. Interestingly hyperglycemia, increased body weight and swimming defects were recently observed in hyperlipidic zebrafish exposed to aspartame , which tends to support our present observations. However, our data using doses of aspartame approximating the current ADI contrasts with a previous report which concluded that long term consumption of aspartame from six weeks onwards did not increase weight gain . This apparent contradiction could conceivably be due to the fact the aspartame in that toxicology study was administered from the 6th week of life onwards at a dose of 2–4 g/Kg body weight (40–80 times the current ADI), resulting in a significant reduction in food intake for animals consuming the higher quantity of the dipeptide sweetener. Interestingly human studies have found a positive correlation between the consumption of artificial sweeteners and weight gain , ; and surprisingly in diabetic subjects, aspartame-containing meals elevated blood glucose and insulin levels to the same extent as that of higher-calorie sucrose-containing meals .
A third novel observation in our study relates to gender-specific differences in insulin sensitivity and cognitive performance, with males apparently exhibiting a greater adiposity, weight gain, glucose dysregulation and cognitive impairment compared to females.
Gender-specific differences in behavior have also been documented in response to Monosodium Glutamate (MSG) a commonly consumed food additive. MSG-treated males appear to be more adversely affected than females , , and have a greater increase in adipose tissue deposition  and insulin resistance  than females.
Therefore the possibility exists that although both males and females showed equal increases in fasting glucose levels in response to aspartame, the gender-specific differences in cognitive performance may be due to differences in the extent of adiposity and insulin resistance, both of which are associated with cognitive performance .
A final intriguing outcome from our study was the correlation we found between visceral adiposity and the adoption of non-spatial escape strategies (thigmotaxis and floating behavior) during the MWM test. In general, non-spatial behavior in the MWM test is associated with an inability to adopt spatial cognitive abilities , and others have found that high-fat diets which promote obesity also impair spatial memory in rodents , .
Our study terminated when the mice were 20 weeks of age (mature adulthood); however it would be of interest to ascertain whether the effects that we noted resulting from lifetime exposure to aspartame will still be apparent in an aging mouse model.
Our unpublished observation, together with previous studies  suggests that the water maze performance of older C57Bl/6J mice decreases markedly with aging.
Further studies are warranted to assess the effects of aspartame on metabolism and cognition in aging mice, and in mice from different strains.
In conclusion, we have demonstrated that compared to controls, neonatal exposure of rodents to dietary aspartame, combined with chronic aspartame consumption throughout early life, may result in impairment of glucose and insulin homeostasis, together with a reduction in cognitive performance. Several gender differences were observed, with males exhibiting greater sensitivity to aspartame exposure. Our data supports previous observations that chronic exposure to aspartame may result in memory deficits in rodents.
Correlations between body characteristics and spatial memory variables in the MWM test. (PDF)
We thank Jonathan Caigas, Rhea Mondreal, Rosario Ubungen, Razan Bakheet and Qammar Al-Haffar for excellent technical assistance; and our gratitude goes to Mr Hakim Al-Enazi for his unparalleled help in coordinating research resources.
Competing Interests: The authors have declared that no competing interests exist.
Funding: This work was funded with the support of the National Comprehensive Plan for Science and Technology, Kingdom of Saudi Arabia (#08-MED490-20). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Murray, full plain text & critique: chronic aspartame in rats affects memory, brain cholinergic receptors, and brain chemistry, Christian B, McConnaughey M et al, 2004 May: 2004.06.05 rmforall
Direct and indirect cellular effects of aspartame on the brain, Humphries P, Pretorius E, Naude H, U. Pretoria, South Africa, Eur J Clin Nutr. 2007 Aug 8: Murray 2007.08.12
Methanol from smoking and aspartame, in humans alone, is always made into formaldehyde via the ADH enzyme inside the cells of blood vessels and many tissues -- a little alcohol protects.
Many novel diseases of civilization result since 1800 -- heart, stroke, Alzheimers, cancers, MS, autism, spina bifida – increasing rapidly with aspartame since 1981.
4 more positive reviews for While Science Sleeps, Prof. Woodrow C. Monte, on Amazon.com: Rich Murray 2012.02.26
While Science Sleeps, methanol from cigarettes and aspartame becomes formaldehyde inside human cells -- Table of Contents, WC Monte bio, Kindle electronic book version $ 9.80 Amazon.com: Rich Murray 2012.01.26
New book, concise opus "While Science Sleeps" life saving facts re aspartame (methanol, formaldehyde) -- 740 full text references are free online -- Woodrow "Woody" C. Monte, retired Prof. of Nutrition, Arizona State University: Rich Murray 2012.01.03
$ 37.98 text 236 pages -- 740 full text references free online -- Kindle electronic book, $ 9.80
See slide show of 18 research studies re huge increases of MS in women in warm countries since aspartame diet drinks started in USA July, 1983, especially in hot summer months:
MA Boston University Graduate School 1967 psychology,
BS MIT 1964 history and physics,
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