home index by author index by subject

There is a PowerPoint file available to accompany this presentation. The BDA Conference 2001 CD-ROM contains 61 PowerPoint files. For details of how to obtain the CD-ROM, please contact the BDA.

Talk; other LD

Friday stream 1 Session 14.00 - 15.40 Length 25 minutes

Potential aids to diagnosis in neurodevelopmental disorders

L. E. F. MacDonell, A. I. M. Glen, P. E. Ward, M. A. Ross, A. C. A. Glen, D. J. Macdonald, R. M. Boyle and D. F. Horrobin

(1) Highland Psychiatric Research Foundation, The Green House, Beechwood Business Park, Inverness IV2 3ED (2) Biochemistry Dept., South Glasgow University Hospitals NHS Trust, Glasgow G42 9TY. (3) Laxdale Ltd, Laurelhill Business Park, Polmaise Road, Stirling FK7 9JQ. loismac@hprf.sol.co.uk

Abstract

There is good evidence for epidemiological linkage between a variety of neurodevelopmental disorders. These include dyslexia, attention deficit hyperactivity disorder (ADHD), autistic spectrum disorder, dyspraxia and schizophrenia. This may represent a shared underlying biochemical abnormality. Lipid abnormalities have been reported in ADHD, autism and schizophrenia. In dyslexia, others using NMR spectroscopy have previously described a potential incorporation deficit of fatty acids into brain phospholipids. We have investigated the enzyme, phospholipase A2 which releases arachidonic acid (AA) from phospholipids to make it available for cell signalling processes. The role of AA in the central nervous system is well described, both in regard to brain development and in cell signalling. We have found a significant increase in phospholipase A2 in adults with dyslexia. We are currently investigating other potential diagnostics for lipid abnormalities, including a skin patch test, which measures the cyclooxygenase pathway for prostaglandin production, and a breath sampling technique to measure the products of lipid breakdown.

The Foundation's research interests

• the role of fatty acids in psychiatric and neurodevelopmental disorders
• development of fatty-acid-related diagnostic aids and treatments

Epidemiological evidence demonstrates that a variety of conditions may be considered as neurodevelopmental disorders. Schizophrenia, manic-depression, attention deficit hyperactivity disorder, autism, Aspberger's syndrome, dyslexia, dyspraxia and possible some allergic conditions may all be included. These diagnoses are not discrete, there being much overlap, for example (reproduction by kind permission of Dr. Alex Richardson):

Why these connections?

• Genes

- there are already at least 25 genes implicated in schizophrenia and 3 in dyslexia
- a variety of combinations may lead to susceptibility to any of these conditions
- inheritance is far from straightforward

Note: Unaff = unaffected, Schiz = schizophrenic, NSLD = non-specific learning difficulty, OND = other neurodevelopmental disorders, i.e. Aut = Autism, Asp = Asperger's Syndrome, ADD = attention deficit disorder. Grey = spouses without diagnoses. Squares = male, circles = female

This possible family tree demonstrates the ways in which inheritance may take place within one family, including the possibility that one twin might be schizophrenic while the other is unaffected. It also shows that twice as many males are affected by these disorders as females.

Why these connections?

• Brain lipids

- dry weight of brain is around 60% fat
- brain depends on phospholipids, which are made up of this fat
- 3/4 of these fats are arachidonic acid (AA) and docosahexaenoic acid (DHA)

This table shows the essential fatty acids, i.e. those that have to be taken in through the diet, linoleic acid and alpha-linolenic acid, of the n-6 and n-3 series, respectively. Also shown are AA and DHA. LA is principally derived from vegetables and the n-3 from oily fish.

Examples were then given of the presence of:

Phospholipid abnormalities

• dyslexia and other neurodevelopmental disorders - cerebellar impairment, magnocellular and retinal abnormalities, abnormal cerebral phospholipid metabolism
• schizophrenia - red blood cell (RBC) and post-mortem brain fatty acid levels, P31 MRS of living brain
• depression - RBC fatty acids, reduced membrane fluidity

Reference was also made to evidence of fatty acid deficiencies in attention deficit disorder.

These abnormalities were the theme of the Neurodevelopmental Disorders Workshop held in Inverness in September 1999, the proceeding of which were published in Prostaglandins, Leukotrienes and Essential Fatty Acids, Vol. 63, Jul-Aug 2000.

DHA in dyslexia

• Stordy (1995) found improvements in dark adaptation in dyslexics supplemented with DHA
• HPRF (1999) found differences in dark adaptation between schizophrenics, dyslexics and controls but the schizophrenia data were not robust and the sample was small

Blood fatty acid estimations

• in the dark-adaptation study, blood fatty acid analyses did not show significant differences between the groups
• this unexpected result led to study of the enzyme, cytosolic phospholipase A2 (cPLA2)
• cPLA2 controls release of AA from membranes

cPLA2

• previous work (e.g. Gattaz et al, 1995) measured activity of cPLA2
• using a new ELISA (enzyme-linked immuno-sorbent assay) developed at the Victoria Infirmary enabled the amount of cPLA2 to be measured for the first time

In a study of amounts of cPLA2:

Inclusion criteria

Dyslexic types:

• pro-rated WAIS-R (shortened)/WRAT3 discrepancy equivalent > 1 SD
  
  and/or
  
• Bangor Dyslexia Test score > 7

Controls:

• Age and sex matched, no known dyslexia-type problems

Exclusion criteria

All
psychiatric problems excluded by use of:

• Brief Symptom Inventory (BSI)
• Controls
• dark-adaptation participants (n=11); already screened by Quick, WRAT3 and Bangor Test
• others (n=43); informal screening only

Demographics

Amounts of cPLA2

cPLA2 findings:

The significant differences between dyslexics and controls demonstrated clearly they were from different opoulations. A similar comparison between schizophrenics (n=49) and the same controls revealed an even more striking difference (p<0.0001). The schizophrenics had even greater amounts of cPLA2, suggesting that they are all on a continuum.

In order to demonstrate that the dyslexic group had a different amount of cPLA2 from other groups, the chart below also shows bipolars (manic depressives) and unipolars (depressives).

cPLA2 assay

• Currently this new ELISA only used for research and the method has not yet been published
• Potential for development into a quick, cheap, point-of-care diagnostic aid, e.g. a drop of blood on a strip such as now used for blood glucose measurement

A second possible diagnostic aid is the:

Niacin skin patch test

• small amounts of methyl nicotinate induce skin reddening
• this is secondary to release of prostaglandin D2, metabolite of AA
• the niacin skin patch test - developed in Inverness - is a topical test which uses a range of doses of methyl nicotinate

Shown below are examples of the skin patch test results at fifteen minutes, after the patch has been held against the skin for one minute. Previously niacin had been administered orally, which caused a whole body flush and could be very unpleasant.

Healthy control	Patient with schizophrenia

Niacin skin patch test

• failure to flush associated with phospholipid metabolism abnormalities in schizophrenia
• may have a role in developmental disorders
• unpublished report (Gordon Bell, Stirling) is of reduced flushing in children with autism
• adult dyslexics tend to show increased flushing but detailed analysis yet to be done

Niacin skin patch test

• advantages
  -non-invasive
  -quick
  -cheap
  -anyone can administer
• ocurrently being commercially developed

The third possible diagnostic aid is:

Breath analysis

oanother indicator of phospholipid metabolism abnormality is increased breath hydrocarbons omeasured using mass spectrometry with breath capture - developed in Inverness obreath capture technique is simple and allows samples to be posted widely

Breath test applications

• increased cPLA2 level would suggest increased lipid peroxidation which would lead to raised alkanes in breathoabnormal levels of butane found in some schizophrenia patients
• as there is an increased cPLA2 level in some dyslexic adults there may be a role for breath testing

Summary

• EFAs have a role in neurodevelopmental disorder
• so physiological measures could come to complement existing diagnostic tools
• the assessments - cPLA2, skin patch test and breath analysis - would be quick and easy to administer

Acknowledgements

• HPRF
  -Iain Glen
  -Pauline Ward
  -Marion Ross
• Victoria Infirmary, Glasgow
  -Alistair Glen
  -Donald Macdonald
  -Rose Mary Boyle
• David Horrobin
• Inverness College
• Highland Dyslexia Association

Highland Psychiatric Research Foundation, The Green House, Beechwood Business Park North, Inverness IV2 3ED
e-mail: hprf@hprf.sol.co.uk