Sunday, September 18, 2016

Values, Politics and Public Health

The prevalence of obesity and other chronic diseases is quite a problem whether you approach this by looking at the burden on medical systems or simply how they adversely affect the quality of life of many people.  Read a comments section (or be a student in a faculty of health) and you’ll find there’s several different approaches being promoted on how to solve this problem.  These can be summarised as:

  • Personal responsibility
  • Education
  • Taxes/subsidies and bans
  • Pharmaceutical drugs 

A recent piece in the Huffington Post argued for taking politics out of obesity but all proposed public health solution are political, and these political positions are based a set of values

The Political Spectrum

The left-right axis in politics is fairly well known.  But beyond economic policies, the characterisation of this spectrum varies widely on which additional issues this spectrum should include.  Some of the problem here is that the traditional ‘left’ and ‘right’ parties often have opposing positions on various social and other issues.  For the purposes of this post I’ll characterise the left-right spectrum as being related to economics and the beliefs about the world and values that underlie the positions.  I think limiting the left-right divide to economics a good way to broaden our political vocabulary beyond ‘left’ and ‘right’ and to have a more nuanced and accurate conversation

Many of the social issues are best placed on an authoritarian-libertarian axis that is included in some political spectrums (see below).  Of course politics goes beyond this.  It’s become very clear in the last year with Brexit and the US election that some of the major political divisions in society are establishment vs. anti-establishment and globalism vs. nationalism and these divisions don’t fit nicely on the left-right spectrum or the authoritarian-libertarian spectrum.  But they aren’t really relevant to public health, which is the main focus of this post

To give an idea of what this looks like and to disclose any potential biases I have, here are my results* from the political spectrum quiz found here.

The 4 quadrants can be fairly accurately characterised as:

Authoritarian Right                 Conservative
Libertarian Right                     Libertarian
Libertarian Left                       Liberal
Authoritarian Left                   Progressive

To give an idea, here are some of the opposing values in these political axes

Big government
Small government
Economic equity (equality of outcome)
Economic freedom (equality of opportunity)
Government regulation of certain markets
Free market capitalism
Globalisation of markets
Social responsibility
Personal responsibility

Big government
Small government
Ends justify means
Means justify ends
Top down solutions
Bottom up solutions
State sanctioned religion or atheism
Secularism and no special treatment of religion

* I’ve taken the test a few times and get pretty much the same result give or take a box.  I actually thought I would be a bit deeper in the libertarian right quadrant, but there were many questions I answered neutral on because there wasn’t enough information

How This Fits Into Public Health

Most of the public health strategies I mentioned earlier fit very nicely into one of those 4 quadrants:

Personal responsibility fits into the libertarian right quadrant.  The emphasis on personal responsibility itself is a key value of the right.  The right is generally against the expense of government funded programs (education) and interference in the free market (subsidies/taxes/bans).  Leaving it at personal responsibility fits the libertarian perspective where your health is just your business – where everyone has a health project and people are free to choice how well they want to do on it.  This would be the opposite of an authoritarian right strategy where you are responsible for your health but is also someone else’s business too

I didn’t initially think of commonly proposed strategy that fits into the authoritarian right quadrant.  An authoritarian right strategy method might be to emphasise personal responsibility with there being good or bad consequences for meeting or failing to meet certain targets.  Something like fat shaming could fall in this category and you can imagine come other scenarios like government mandated weight/health targets (which you’ll probably only see in a very militaristic society, or economically threatened one with universal healthcare).  (Although, to go a little off topic, these days I’m seeing most of the shaming being done by social justice warriors who are without a doubt very deep in the authoritarian left quadrant)

Education fits into the libertarian left quadrant while taxes/subsidies and bans fit into the authoritarian left quadrant.  The left is less inclined to hold people responsible for bad outcomes and shifts the blame towards society.  Both involve some kind of structural change to society to facilitate the desired outcomes.  The division here is that the libertarian side ultimately want individuals to be free to make their own choices without additional costs while the authoritarian side want to exercise government control

The strategy of pharmaceutical drugs doesn’t fit quite so nicely into the political spectrum and doesn’t tap into those key values as much.  Relying on drugs does offload the personal responsibility of adopting a healthy lifestyle, and in many countries the government funds much of the basic science that aids the identification of drug targets and then subsidises the drugs (more left leaning).  Although private business does the rest, and a philosophy of innovating your way out of a problem and using the free market (which isn’t the case) is a very right libertarian one (which can be seen in things like sustainability/climate change as well) 

To finish up, if you disagree with someone politically don’t instantly dismiss their position as ideologically based and think they’re evil.  Everyone has ideologies and many people have similar goals but just disagree on the methods.  They probably just have a different set of values and different experiences to you.  The way to move the conversation forward is by coming out of the echo chambers and having an honest discussion of the advantages and disadvantages of various strategies.  That’s what I’ll attempt to do in some later posts

The 'Thrifty Gene' of Samoa

A recent study conducted a genome-wide association study (GWAS) in 3072 Samoans and found a gene variant of the CREBRF gene that is much more prevalent in Samoans and is strongly associated with higher BMI [1].  The narrative being sold is that this thrifty gene had positive selection in Samoans to help promote storage of fat for periods of food scarcity, like travelling across the Pacific [2]

Unfortunately for the thrifty gene hypothesis (which I’ve previously discussed), the function of CREBRF suggests this gene could scarcely be a worse match for this narrative

The main functions of the endoplasmic reticulum (ER) include Ca2+ homeostasis, the synthesis of proteins and lipids, and ‘folding’ proteins into their tertiary structure.  However, several things (including infection, nutrient stress, oxidative stress, etc) can impair protein folding, leading to an accumulation of unfolded or misfolded proteins and ER stress.  One of the homeostatic responses to ER stress is the unfolded protein response, which attempts to reduce the load on the ER.  If ER stress is prolonged or intense the cell initiates apoptosis [3]

CREBRF stands for ‘cyclic AMP-responsive element-binding protein 3 regulatory factor’ or CREB3 regulatory factor.  CREB3 is part of unfolded protein response [4], while CREBRF is a negative regulator of CREB3, and thus is a negative regulator of the unfolded protein response [5]

This is highly relevant, as endoplasmic reticulum stress is a cause of leptin resistance in diet-induced obesity [6] [7].  Specifically, ER stress increases PTP1B, which mediates the effect of ER stress on leptin resistance [8].  The GWAS paper cites other research showing that knocking out CREBRF lowers body weight in mice and flies [1].  So the chain of mechanisms involved seems to be as follows:

↓ CREBRF > ↑ CREB3 > ↑ homeostatic ER stress response > ↓ ER stress ↓ PTP1B > ↓ leptin resistance > ↓ weight gain

And so for people with the gene variant:

p.Arg457Gln > ↑ CREBRF > ↓ CREB3 > ↓ homeostatic ER stress response > ↑ ER stress ↑ PTP1B > ↑ leptin resistance > ↑ weight gain

The paper provides evidence that the gene variant had positive selection, but that doesn’t explain what outcomes of the gene variant were the source of the positively selection, it doesn’t necessary mean fat storage or that such extreme fat storage as obesity was being selected for.  Going back 100’s of years ago this gene variant doesn’t seem like it would be a problem when ER stress would have been an infrequent transient response to something like infection.  But these days, the average Samoan on a western diet likely has chronic low level ER stress, which leads to higher PTP1B and leptin resistance – and this is being amplified by a weaker homeostatic response

This gene variant fits the certainly fits the outcomes of being thrifty gene, but not the purpose of one.  The thrifty gene hypothesis suggests that overweight/obesity is an evolutionary adaptive physiological condition, whereas this gene variant increases weight by increasing ER stress, a pathological state

Finally, as George Henderson shows below, Samoans were lean and muscular before adopting a western diet.  If you try to explain the leanness by suggesting the picture was taken during a period of scarcity, then why so much muscle mass?  People promoting the thrifty gene hypothesis need to show evidence that ethnic groups who are susceptible to obesity have been overweight during periods of abundance (before adopting a western diet).  Such periods wouldn’t have been uncommon, as we’re talking about tropical Pacific islands, not northern Europe

It’s time for evolutionary medicine to stop looking for reasons why chronic disease may been evolutionary adaptive, and then focus on sources of mismatch