Saturday, 12 November 2011

Cholesterol levels in autism: Vader or Skywalker?

Cholesterol is a substance with a bad reputation. Blamed for everything from causing an increased risk of coronary heart disease to upping the risk of stroke via things like the very curiously titled metabolic syndrome, high total cholesterol levels are the Darth Vader of health, the dark side incarnate (at least episode IV & V dark side). As a result, modern society has been mobilised to do everything it can to reduce cholesterol; be it through food, medication, or exercise.

I have discussed the concept of risk quite a few times on this blog and how risk, whilst generally important, takes little account of our individual differences and circumstances. I don't feel that I am suitably qualified to contribute too much to any general debate about cholesterol and health, although my reading around this topic would perhaps suggest that the relationship between cholesterol and health is perhaps not as simple as many people might believe; a point highlighted by this recent post in Scientific American. Indeed Anakin Skywalker (episodes II, III and VI) over Darth Vader might be a better description of cholesterol: a bit of good and a bit of the dark side.

There are a few findings emerging in the area of cholesterol and developmentally-defined conditions which are worthy of some comment, some of which have already been discussed in the blogosphere. Fairly recently cholesterol featured in a post about chronic illness risk and autism. I will at this point repeat my well-chanted mantra: no medical advice is intended or given and please consult with your physician before making any changes to any dietary or medication regime.

Not surprisingly quite a bit of the literature on cholesterol and autism focuses on lifestyle issues like being overweight / levels of obesity and the possible physical side-effects from various medications associated with autism spectrum conditions. Whilst not wishing to downplay such health inequalities, I will instead focus on a few other areas of interest: measured levels of cholesterol and autism's association with other cholesterol-linked conditions.

When it comes to measured cholesterol levels in autism, there are a few, mixed trends appearing including this one pointing towards higher total cholesterol levels and higher low-density lipoprotein (LDL) levels (LDL = the 'bad' cholesterol) in a small trial of people with Asperger syndrome. This is contrasted with this study reporting values from children with autism where no significant difference was noted in either total or LDL levels compared to controls. This study based on samples from the AGRE dataset, found that about a fifth of participants with autism studied actually had low levels of cholesterol, defined as below the 5th centile in population terms. There are some obvious differences between these studies in terms of age, diagnosis and ethnicity which perhaps should be kept in mind before getting too carried away. One should perhaps also realise that measuring cholesterol on its own might mean very little without any other correlations related to symptom presentation or other health-related factors going back to metabolic syndrome.

One condition linked to cholesterol seems to crop up quite a lot in the various searches: the association between autism and Smith-Lemli Opitz syndrome (SLOS). SLOS is a genetic condition which biochemically, is characterised by a failure to make enough cholesterol and the subsequent knock-on effects this has. Interestingly, vitamin D is synthesised from cholesterol, going back to my previous post on the sunshine chemical. The limited research on vitamin D status in SLOS is however a little mixed regarding any deficiency being potentially present.

There is quite a lot of evidence for the appearance of autism or rather autistic symptoms occurring in many cases of SLOS, although as per the study previously highlighted by Tierney and colleagues, the reverse - SLOS appearing in many cases of autism - does not appear to be true. Having said that in those cases of autism where cholesterol is low, discussions have centred on the use of cholesterol supplements to increase circulating levels. Given that Mr Vader reputation for cholesterol, many people might find the idea of giving cholesterol slightly counter-intuitive to our modern-day health messages. This is probably why, at the time of writing, there is a bit of a hole in the research literature when it comes to cholesterol supplementation for autism. I did find this article reviewing its potential use and there are apparently trials on-going with regards to its potential effectiveness for cases of autism. This paper (full-text) again featuring Elaine Tierney offers a few other ideas. We wait and see what they report.

I don't want anyone to assume that from this post I am anti- anti-cholesterol because I am not (?). I do however believe that our modern-day relationship with cholesterol, like so many other things, is complicated. It was not so long ago for example that we were talking about violent deaths being associated with the lowering of cholesterol, in particular suicide attempts and low cholesterol in things like bipolar disorder, something which has resurfaced in discussions this year. Perhaps counter to my previous posts trying to assert the importance of environment alongside genes to many conditions including cases of autism, here I suggest that genes are also potentially as important as environment when it comes to cholesterol and autism and perhaps lots of other things too.

So then, Vader or Skywalker?