Autism spectrum disorder: advances in diagnosis and evaluationBMJ 2018; 361 doi: https://doi.org/10.1136/bmj.k1674 (Published 21 May 2018) Cite this as: BMJ 2018;361:k1674
All rapid responses
In answer to John Stone, when I say "muscle meats", I am also referring to fish and poultry. These days, they too are generally eaten without the bones (that used to be tossed into the soup pot instead of the trash), not to mention the likes of shrimp, crab and lobster, of which also only the muscle meats are consumed. And although the consumption of bone broth has now gained some popularity, I think the general shift away from eating it in recent generations is common knowledge. Certainly the overall consumption of meats, fish (including shellfish) and poultry is much higher now in the Western world than in previous generations, and the fact that this results in the depletion of glycine specifically has now been clearly demonstrated in the EPIC-Oxford cohort (1) as I pointed out in my previous response in this string. Perhaps it is unfortunate that those cohort members who consume an omnivorous diet were classified as "meat-eaters", in order to contrast their dietary habits to those who consume no meat or poultry (classified as "fish-eaters"), those who consume no meat, fish or poultry (classified as "vegetarians"), and those who consume no animal products at all ("vegans").
Schmidt JA, Rinaldi S, Scalbert A, et al. Plasma concentrations and intakes of amino acids in male meat-eaters, fish-eaters, vegetarians and vegans: a cross-sectional analysis in the EPIC-Oxford cohort. Eur J Clin Nutrition 2016;70:306–12. doi:10.1038/ejcn.2015.144
Competing interests: No competing interests
I am grateful to Joel Brind, but while I would not wish to dismiss out of hand low glycine consumption as a potential factor in autism - among other environmental influences - I also note that his statement:
"There has been in recent years, in the industrialized world, a general dietary shift away from the consumption of whole meats, fish and poultry, toward the consumption of exclusively muscle meats."
is not supported by any cited evidence, though he has twelve footnotes. Meanwhile, I still find on visits to supermarkets that the shelves are still stacked with fish and poultry as well as "muscle meat". I understand that even Macdonald's offer alternatives to burgers, including fish and chicken. Nor, perhaps, would the parents of autistic children like to be stereo-typed as burger eaters!
Competing interests: No competing interests
In response to the new review by Zwaigenbaum and Penner (1) John Stone writes: “We come back in the end to the reality that when it comes to what could be driving these changes to our society the authors neither acknowledge the problem, or have any explanation of it. I fear they may be fiddling as Rome burns.”(2) In the interest of not “fiddling as Rome burns”, I here advance the following explanation, as an eminently testable hypothesis based on the following findings, some of which have only very recently been established:
1)ASD develops in a state of neuroinflammation in the brain. In 2011, Patterson (3) observed “an ongoing, hyper-responsive inflammatory-like state in many young as well as adult autism subjects.” In 2017, Lee et al (4) demonstrated, in postmortem ASD v normal brains, “a shift in microglial phenotype that may indicate impaired synaptic plasticity and a chronic vulnerability to exaggerated immune responses.” Specifically, they observed “a significant increase in primed microglia in gray matter of ASD compared to typically developing individuals.”
2)Microglia are brain macrophages, bone marrow-derived myelocytes that migrate to the brain during embryogenesis (5). Macrophages of all types are resident in a diverse array (perhaps all) organs, and they share not only a common embryonic origin but a common dual functionality:
a)The removal, by phagocytosis, of dead or superfluous cells and cell debris resulting from injury, natural cycles of growth and regression (e.g., in the breasts and uterus during the menstrual cycle), or the unfolding of developmental programs (e.g., normal brain development; 6,7) and
b)The destruction of invading bacteria or other microbes in response to infection, via secretion TNFα and a host of cascading toxins, i.e., inflammation. These two types of macrophage activity are initiated by distinct signaling pathways (6). Activation of inflammation where infection is not present only produces damage to normal tissues. This dual functionality of macrophages may be likened to the action of first responders such as the police. The police are called to the scene of an accident on the highway, and do what is necessary to clear the area of damaged vehicles and persons, to restore the normal flow of traffic. But whilst they are armed (e.g., in the US), they do not draw nor fire their weapons unless bad actors are present. The drawing and use of firearms may be likened to inflammation in the body.
3)Physiologically, the priming or activation of macrophages of all types, to produce inflammation, is naturally regulated by the amino acid glycine (8). This has now been confirmed experimentally in the brain in rats (9). The glycine receptor is a glycine-gated chloride channel which allows for chloride ion influx, thus stabilizing (by hyperpolarization) the macrophage plasma membrane, thus rendering them less susceptible to depolarization by various stimuli (8). The depolarization of the macrophage plasma membrane initiates calcium ion influx and the cascade of inflammatory events. These days, plasma glycine levels are normally in the range of 150 – 350 μM, whereas glycine concentrations optimal for macrophage regulation are in the range of 0.5-1mM (8), well in excess of biochemical requirements for protein synthesis, etc.
4)There has been in recent years, in the industrialized world, a general dietary shift away from the consumption of whole meats, fish and poultry, toward the consumption of exclusively muscle meats. This has gone unnoticed, in my view, because of glycine’s long having been considered “nonessential”, the presumption being that the amino acid content of muscle meat provides an optimal mix of “essential” amino acids.
5)However, muscle meats are relatively methionine-rich and glycine-poor, whereas collagen is exceedingly glycine-rich (one third mole fraction) and methionine-poor (less than 1%). Metabolically, methionine and glycine have a reciprocal relationship. When a methionine-rich meal is absorbed (e.g., after a typical meat, fish or poultry meal) hepatic metabolism is switched from methionine salvage mode to methionine clearance mode, by the activation of glycine-N-methyltransferase, the main enzyme of the only clearance pathway for methionine. Each mole of methionine requires at least two moles of glycine to be cleared (10).
6)The general dietary shift toward exclusively muscle meat consumption and away from collagen (gelatin) consumption, has therefore resulted in a reduction in plasma glycine levels in the general population. While this may seem paradoxical because the typical modern omnivorous diet is rich in all the protein amino acids, the concomitant increase in dietary glycine consumption and decrease in plasma concentration has recently been demonstrated in the Oxford cohort of the EPIC study. Thus, Schmidt et al. (11) observed that while meat-eaters in the UK consumed 20% more glycine each day than vegans (3.12 v 2.61 g/day, respectively), their mean plasma free glycine level was 14% lower (390 v 452 μM, respectively) than that of vegans.
7)Hence, if there is a critical threshold concentration of plasma glycine that must be maintained for the overall optimal regulation of the innate immune system (i.e., macrophages body-wide, including microglia in the brain), it may be suggested that most in the general population (save for vegans and those who consume significant collagen) suffer a functional glycine deficiency.
8)Glycine infusion has now been shown to prevent microglial activation (8), just as earlier studies showed in animal models (9), and at least one human clinical trial, in which glycine supplementation reversed type 2 diabetes (12).
The foregoing may be distilled down to the following simple hypothesis: ASD (among many other conditions, including arthritis, diabetes, cardiovascular disease and cancer) is a manifestation of systemic glycine deficiency, resulting from consumption of a typical diet high in essential amino acids (ie., in muscle meats), but lacking in glycine (a main constituent of bone and connective tissue, which, in contrast to diets of previous generations, is typically discarded.) It may be easily corrected by supplementing the diet with either free glycine, or foods rich in gelatin (collagen), such as bone broths of any kind. It is really the extension of the whole foods approach to meat, fish and poultry as well as grains.
1. Zwaigenbaum L, Penner M. Autism spectrum disorder: advances in diagnosis and evaluation (State of the Art Review). BMJ 2018;361:k1674 doi: https://doi.org/10.1136/bmj.k1674 21 May, 2018.
2. Stone J. Rapid Response re: Autism spectrum disorder: advances in diagnosis and evaluation. BMJ 2018;361:k1674 doi: https://doi.org/10.1136/bmj.k1674/rapid responses. 21 May, 2018.
3. Patterson PH. Maternal infection and immune involvement in autism. Trends Mol Med 2011;17: 389–394. doi:10.1016/j.molmed.2011.03.001.
4. Lee AS , Azmitia EC, Whitaker-Azmitia PM. Developmental microglial priming in postmortem autism spectrum disorder temporal cortex. Brain Behav Immun.2017;62:193-202. doi: 10.1016/j.bbi.2017.01.019.
5. Bolton JL, Marinero S, Hassanzadeh T, et al. Gestational Exposure to Air Pollution Alters Cortical Volume, Microglial Morphology, and Microglia-Neuron Interactions in a Sex-Specific Manner. Front Synaptic Neurosci 2017;9:1-16. doi: 10.3389/fnsyn.2017.00010.
6. Schafer DP, Lehrman EK, Kautzman AG, et al. Microglia sculpt postnatal neural circuits in an activity and complement-dependent manner. Neuron.2012 May 24;74(4):691-705. doi: 10.1016/j.neuron.2012.03.026.
7.Cunningham CL, Martinez-Cerdeno V, Noctor SC. Microglia regulate the number of neural precursor cells in the developing cerebral cortex J Neurosci 2013;33:4216–4233. doi:10.1523/JNEUROSCI.3441-12.2013.
8. Wheeler MD, Ikejema K, Enomoto N, et al. Glycine: a new anti-inflammatory immunonutrient (Review). Cell Mol Life Sci 1999;56:843–856
9. Mori H, Momosaki K, Kido J, et al. Amelioration by glycine of brain damage in neonatal rat brain following hypoxia-ischemia. Pediatr Int. 2017 Mar;59:321-327. doi: 10.1111/ped.13164.
10. Martinov MV, Vitvitsky VM, Banerjee R, Ataullakhanov FIl. Review: The logic of the hepatic methionine metabolic cycle. Biochim Biophys Acta 2010; 1804: 89–96. doi:10.1016/j.bbapap.2009.10.004
11. Schmidt JA, Rinaldi S, Scalbert A, et al. Plasma concentrations and intakes of amino acids in male meat-eaters, fish-eaters, vegetarians and vegans: a cross-sectional analysis in the EPIC-Oxford cohort. Eur J Clin Nutrition 2016;70:306–12. doi:10.1038/ejcn.2015.144
12. Cruz M, Maldonado-Bernal C, R. Mondragón-Gonzalez R, et al. Glycine treatment decreases proinflammatory cytokines andincreases interferon- in patients with Type 2 diabetes. J Endocrinol Invest 2008;31:694-99
Competing interests: No competing interests
The article on autism spectrum disorders, presented as “State of the art review”, does not address an important and significant area of research that has provided a biomarker and a treatment for ASD. Even though a whole section is devoted to “advances in biomarker research” there is no mention of folate receptor autoantibodies. In this context, the authors as well as reviewers of this article, have failed the readers.
Folate plays a prominent role in fertility, pregnancy, pregnancy outcome, fetal development and brain development during fetal as well as neonatal life. Folate deficiency has been attributed to many of the pregnancy and fetal development disorders. The identification of folate receptor autoantibodies in a majority of mothers with a history of neural tube defect pregnancy (1) and more recently in mothers with an autistic child (2) has provided an explanation for folate deficiency in the fetus due to the autoantibody blocking folate transport from the mother to the fetus as well as antibody-mediated inflammation as factors contributing to abnormalities in fetal brain development. These autoantibodies in children have been associated with cerebral folate deficiency syndrome (3). Recent studies have identified the autoantibody in 70% of children diagnosed with ASD and folinic acid treatment has shown significant improvement in the core deficits associated with ASD (4). These initial observations were recently confirmed in a double-blind placebo-controlled trial, which showed significant improvement in language and speech in children positive for the folate receptor autoantibody (5). Thus identifying folate receptor autoantibodies in parents and children provides a marker for early intervention to treat as well as potentially prevent the pathological consequences, as recently shown in a rat model (6).
1: Rothenberg SP, da Costa MP, Sequeira JM, Cracco J, Roberts JL, Weedon J, Quadros EV. Autoantibodies against folate receptors in women with a pregnancy complicated by a neural-tube defect. N Engl J Med. 2004 Jan 8;350(2):134-42. PubMed PMID: 14711912.
2: Quadros EV, Sequeira JM, Brown WT, Mevs C, Marchi E, Flory M, Jenkins EC, Velinov MT, Cohen IL. Folate receptor autoantibodies are prevalent in children diagnosed with autism spectrum disorder, their normal siblings and parents. Autism Res. 2018 Feb 2. doi: 10.1002/aur.1934. [Epub ahead of print] PubMed PMID: 29394471.
3: Ramaekers VT, Rothenberg SP, Sequeira JM, Opladen T, Blau N, Quadros EV, Selhub J. Autoantibodies to folate receptors in the cerebral folate deficiency syndrome. N Engl J Med. 2005 May 12;352(19):1985-91. PubMed PMID: 15888699.
4: Ramaekers VT, Blau N, Sequeira JM, Nassogne MC, Quadros EV. Folate receptor autoimmunity and cerebral folate deficiency in low-functioning autism with neurological deficits. Neuropediatrics. 2007 Dec;38(6):276-81. doi: 10.1055/s-2008-1065354. PubMed PMID: 18461502.
5: Frye RE, Slattery J, Delhey L, Furgerson B, Strickland T, Tippett M, Sailey A, Wynne R, Rose S, Melnyk S, Jill James S, Sequeira JM, Quadros EV. Folinic acid improves verbal communication in children with autism and language impairment: a randomized double-blind placebo-controlled trial. Mol Psychiatry. 2018 Feb;23(2):247-256. doi: 10.1038/mp.2016.168. Epub 2016 Oct 18. PubMed PMID: 27752075; PubMed Central PMCID: PMC5794882.
6: Desai A, Sequeira JM, Quadros EV. Prevention of behavioral deficits in rats exposed to folate receptor antibodies: implication in autism. Mol Psychiatry. 2017 Sep;22(9):1291-1297. doi: 10.1038/mp.2016.153. Epub 2016 Sep 20. PubMed PMID: 27646260.
Competing interests: Dr. Quadros is an inventor listed in a US patent for the folate receptor autoantibody test issued to the State University of New York.
Diagnosing and evaluating Autistic Spectrum Disorder especially very early in a child’s life can be a confusing and daunting process for a clinician and as confusing and daunting to the parent/s too. In spite of several guidelines and innovative tools it appears that we still have a long way to go to fully get our heads round this fast growing malady and to get to grips with its onslaught that continues to devastate families and societies the world over, recently in epidemic proportions. Early diagnosis so as to facilitate early intervention is perhaps easier said than done. It is heart breaking each time we hear a mother saying, “he was so easy as an infant to look-after, so undemanding but now…”. Or to hear, “He was so lovely till he turned three, and then…”. Or, “he was so curious. He used to speak, but now he seems to have gone backwards after he had his….”. (I am sure one can guess and forgive my attempt at political correctness). And all this, in spite of regular and religious visits and encounters with healthcare professionals. We do of course rejoice though at glimmers of hope through the valiant efforts of highly engaged parent/s and the compassionate efforts of determined carers, but they seem to be few and far between.
‘Autism Spectrum Disorder: Advances in Diagnosis and Evaluation’ (BMJ 2018;361:k1674) provides a comprehensive review of the subject collating information from diverse English language sources for which the efforts of the authors are to be complemented. The article may certainly be of good value to many clinicians in training and those revising for higher examinations and perhaps some determined parents. The article does a good job of stating a problem at hand and elaborating on past and present struggles with the solutions. But, as a front end foot soldier, was I any wiser? Did I gain new insights? Did I become aware of newer strategies? Was I empowered to try something different? Was I equipped with new ammunition? Well, I would not go so far as John Stone (Rapid response 21 May 2018) as to say that it was a case of fiddling as Rome burnt, but I find that Rome is still a city of bricks and alas, miles to go before I can leave it a city of marble (with apologies to Augustus 27 bce – 14 ce).
Competing interests: No competing interests
I have read this review with interest but disquiet . There is perhaps little point in talking about a global prevalence of autism, which Zwaigenbaum and Penner place according to literature at between 1 and 1.5% if autism is rising dynamically in many parts of the world including the United Kingdom - as I have been recently detailing in the columns of BMJ on-line . For instance, recent data from Northern Ireland showed an overall prevalence in schools there of 2.9%, having risen from 1.2% nine years ago, but there are also big disparities between economic classes and town and country, while in Belfast the rate was 4.7% [3,4]. Unfortunately, as Zwaigenbaum and Penner point out diagnosis is characteristically delayed so the true rates are likely much higher.
The rate that be can be established for England from education figures may be at the top end of official estimates at 1.5% but is rising steeply year on year - the rate of Pervasive Development Disorder (the widest possible category of Autistic Spectrum Disorders) for those born between 1984 and 1988 in the United Kingdom was recorded in official data as being 0.2% in 1999. The present figure from Scottish schools data is around 2.2%. However, dramatic reports appear from around the country , notably a report from S.W. London where five London boroughs geared to already diagnosing 750 cases a year were confronting almost double that number a year ago . Extrapolated across the capital that might be 10,000 cases a year, which would possibly be in the 10% region . I have argued that still without any officially accepted explanation for this phenomenon - and certainly Zwaigenbaum and Penner provide none - we are on the brink of population catastrophe. They state:
"Lifetime societal costs related to services and lost productivity by patients and their parents average $1.4m (£1.0m; €1.1m) to $2.4m in the United States and £0.9-£1.5m per child in the United Kingdom, depending on comorbid intellectual disability. When the prevalence of ASD is factored in, the annual estimated societal costs of ASD are $236bn in the US and $47.5bn in the UK."
However, most autism parents know from experience that these are very modest or even delusorily low estimates. Even in 2001 Järbrink and Knapp estimated an average lifetime cost per case in the UK as £2.4m (perhaps £3.8m in today's money) though they thought the overall prevalence was 5 in 10,000, which it perhaps still was in the adult population .
We come back in the end to the reality that when it comes to what could be driving these changes to our society the authors neither acknowledge the problem, or have any explanation of it. I fear they may be fiddling as Rome burns.
 Zwaigenbaum L, Penner M, 'Autism spectrum disorder: advances in diagnosis and evaluation', BMJ 2018; 361 doi: https://doi.org/10.1136/bmj.k1674 (Published 21 May 2018)
 Responses to Viner RM, 'NHS must prioritise health of children and young people', https://www.bmj.com/content/360/bmj.k1116/rapid-responses
 John Stone, 'Re: NHS must prioritise health of children and young people - 1 in 21 children in Belfast now have an autism diagnosis' 13 May 2018, https://www.bmj.com/content/360/bmj.k1116/rr-6
 Information Analysis Directorate 'The Prevalence of Autism (including Asperger Syndrome) in School Age Children in Northern Ireland 2018', published 10 May 2018, https://www.health-ni.gov.uk/sites/default/files/publications/health/asd...
 John Stone, 'Re: NHS must prioritise health of children and young people - what about autism?' , 19 March 2018, https://www.bmj.com/content/360/bmj.k1116/rr
 Järbrink K, Knapp M, 'The economic impact of autism in Britain', Autism. 2001 Mar;5(1):7-22.
Competing interests: No competing interests