Using an epigenetic clock with children

This 2015 UK human study by many of the coauthors of What’s the origin of the problem of being fat? applied the Horvath epigenetic clock method to the same UK mother-child pairs and a Danish cohort:

“There has been no investigation on prenatal and antenatal factors that affect AA [age acceleration] in children. It is possible that the detrimental consequences of a higher AA may accrue over time, initiating in childhood. Conversely, it could be postulated that having a positive AA during early life and childhood is developmentally advantageous. To reflect this, we could refer to AA as an epigenetic measure of development in children.

We found associations between AA and sex, birth weight, caesarean section delivery and several maternal characteristics, namely smoking in pregnancy, weight, BMI, selenium and cholesterol level.

Offspring of non-drinkers had higher AA on average at birth, but this appeared to resolve during childhood. Offspring of smokers had higher AA on average and this difference became larger during childhood and adolescence.

The lack of correlation between AA and several clinical variables may also indicate that AA reflects an ‘intrinsic’ aging rate that is independent of various aging factors.

The observation that the estimated genetic component of AA increased in older study participants may indicate that the AA measure is more biologically meaningful in adults rather than children, though alternatively it could be a reflection of a decreasing environmental influence on DNA methylation patterns over time.

This accords with our finding of strengthening within subject correlation over time, which suggests the period of rapid early life changes in methylation affects epigenetic age during development to a greater extent than adulthood changes in methylation.”

The heritability of age acceleration was analyzed:

“The heritability estimate from our study (h = 0.37) is lower than that reported Horvath (h = 1.0), which was based on a small number of cord blood samples from twin pairs. Both of these heritability estimates were based on relatively few samples. Future large scale studies will be needed to arrive at precise estimates of the heritability of AA in newborns and minors.

While our heritability estimate may seem low, empirical evidence has suggested that fitness related traits tend to have lower heritability than morphological traits because selection acts to purify deleterious genetic variation, and one might consider age accelerated residuals in the former category.”

Like the coauthors’ follow-on study, causality couldn’t be definitively determined:

“Assessing the causal relationship between exposures and AA (through Mendelian randomization) is underpowered in our current data.”

Epigenetic age acceleration at birth seemed to be overall “developmentally advantageous” for offspring of non-drinking mothers. That age acceleration continued for the offspring of smokers at the second and third measurement times (ages 7 and 15-17) seemed to have “detrimental consequences.” I’d guess that the methylation state of specific CpG sites would be more informative than the overall rate in these cases.

The point about “ independent of various aging factors” was similar to one made in Using an epigenetic clock to distinguish cellular aging from senescence:

“Cellular ageing is distinct from cellular senescence and independent of DNA damage response and telomere length.”

The study was a step toward establishing the Horvath epigenetic clock for widespread usage. The Hannum method was also compared and contrasted. “Prenatal and early life influences on epigenetic age in children: a study of mother-offspring pairs from two cohort studies”

What’s the origin of the problem of being fat?

This 2016 UK human study attempted to replicate the DNA methylation and adiposity associations found by studies on a long-term longitudinal UK cohort:

“We tested for replication of associations between previously identified CpG sites at HIF3A [the hypoxia inducible factor 3 alpha subunit gene] and adiposity in ∼1,000 mother-offspring pairs from the Avon Longitudinal Study of Parents and Children.”

The researchers had sufficient data to test the unidirectional and causal findings of previous studies:

“Availability of methylation and adiposity measures at multiple time points, as well as genetic data, allowed us to assess the temporal associations between adiposity and methylation and to make inferences regarding causality and directionality.”

The analyses didn’t replicate the previous studies’ findings, and a new finding was indicated:

“Our results were discordant with those expected if HIF3A methylation has a causal effect on BMI [body mass index, derived from height and weight] and provided more evidence for causality in the reverse direction i.e. an effect of BMI on HIF3A methylation.

These results are based on robust evidence from longitudinal analyses and were also partially supported by Mendelian randomization analysis, although this latter analysis was underpowered to detect a causal effect of BMI on HIF3A methylation.

Our results also highlight an apparent long-lasting inter-generational influence of maternal BMI on offspring methylation at this locus, which may confound associations between own [offspring] adiposity and HIF3A methylation.”

A person’s parents contributed all of their genetic material and the prenatal environment, and usually almost all of their postnatal and childhood development environment. If a person has a health problem that may have genetic and developmental origins, this is where to look for causes and preventive actions.

That these distant causes can no longer be addressed is a hidden assumption of research and treatment of effects of health problems. Aren’t such assumptions testable here in 2016? (pdf) “DNA methylation and body mass index: investigating identified methylation sites at HIF3A in a causal framework”

Epigenetic effects of diet, and reversing DNA methylation

This 2015 French review focused on:

“The role of maternal health and nutrition in the initiation and progression of metabolic and other disorders.

The effects of various in utero exposures and maternal nutritional status may have different effects on the epigenome. However, critical windows of exposure that seem to exist during development need to be better defined.

The epigenome can be considered as an interface between the genome and the environment that is central to the generation of phenotypes and their stability throughout the life course.”

The reviewer used the term “transgenerational” to refer to effects that were more appropriately termed parental or intergenerational. Per the definition in A review of epigenetic transgenerational inheritance of reproductive disease, for the term to apply there needed to be evidence in subsequent generations of:

“Altered epigenetic information between generations in the absence of continued environmental exposure.”

The review had separate sections for animal and human studies. “Impact of Maternal Diet on the Epigenome during In Utero Life and the Developmental Programming of Diseases in Childhood and Adulthood”

I arrived at the above review as a result of it citing the 2014 Harvard Reversing DNA Methylation: Mechanisms, Genomics, and Biological Functions. I’ll quote a few items from that review’s informative “Role of DNA demethylation in neural development” section:

“Distinct parts of mammalian brains, including frontal cortex, hippocampus, and cerebellum, all exhibit age-dependent acquisition of 5hmC [an oxidized derivative of 5mC [methylation of the fifth position of cytosine]].

In fact, the genome of mature neurons in adult central nervous system contains the highest level of 5hmC of any mammalian cell-type (~40% as abundant as 5mC in Purkinje neurons in cerebellum). These observations indicate that 5mC oxidation and potentially DNA demethylation may be functionally important for neuronal differentiation and maturation processes.

A comprehensive base-resolution analyses of 5mC and 5hmC in mammalian frontal cortex in both fetal and adult stages indicate that non-CpG methylation (mCH) and CpG hydroxymethylation (hCG) drastically build up in cortical neurons after birth, coinciding with the peak of synaptogenesis and synaptic pruning in the cortex. This study demonstrated that mCH could become a dominant form of cytosine modifications in adult brains, accounting for 53% in adult human cortical neuronal genome.

In mature neurons, intragenic mCH is preferentially enriched at inactive non-neuronal lineage-specific genes, indicating a role in negative regulation of the associated transcripts. By contrast, genic hCG is positively correlated with gene expression levels.”

The link between scientific value and content is broken at

Should we expect content posted on the Proceedings of the National Academy of Sciences of the United States of America to have scientific value?

This 2016 Singapore study was a “PNAS Direct Submission” that claimed:

“This paper makes a singular contribution to understanding the association between biological aging indexed by leukocyte telomeres length (LTL) and delay discounting measured in an incentivized behavioral economic task.

LTL is an emerging marker of aging at the cellular level, but little is known regarding its link with poor decision making that often entails being overly impatient.”

The study wasn’t freely available on but the Supplementary material was. The full study was available here.

Whether measured at the level of a human or of a blood cell, in 2016 there wasn’t incontrovertible evidence to support:

  • “Biological aging indexed by leukocyte telomeres length
  • LTL is an emerging marker of aging at the cellular level”

Using an epigenetic clock to distinguish cellular aging from senescence found:

Cellular ageing is distinct from cellular senescence and independent of DNA damage response and telomere length.”

If that study was too recent, the researchers and reviewer knew or should have known of studies such as this 2009 study that found the correlation between a person’s chronological age and blood cell telomere length was r = −0.51 in women and r = −0.55 in men.

A study of biological aging in young adults with limited findings was cited for evidence that “the seeds of biological aging are widely thought to be planted early in life.” That study didn’t elucidate the point, however, as it didn’t fully link its measurements when the subjects were 38 years old with measurements taken during the subjects’ early lives.

Problematic research with telomere length was cited for evidence that “other factors, such as the early family environment, lifestyle, and stress, also have considerable impact on cellular aging.” The researchers had to be willing to overlook that study’s multiple questionable practices in order to cite it as evidence for anything.

Nevertheless, the study used a one-to-one correspondence of telomere length and cellular aging.

The researchers speciously modeled a relationship between telomere length and the behavioral trait “poor decision making that often entails being overly impatient.” That overreach was further stretched to the breaking point:

“We then asked if genes possibly modulate the effect of impatient behavior on LTL.

The oxytocin receptor gene (OXTR) polymorphism rs53576, which has figured prominently in investigations of social cognition and psychological resources, and the estrogen receptor β gene (ESR2) polymorphism rs2978381, one of two gonadal sex hormone genes, significantly mitigate the negative effect of impatience on cellular aging in females.”

The “significantly mitigate” finding was “fun with numbers” that produced false effects rather than solid evidence. Consider that:

  1. The study’s model disregarded the probability that “Cellular ageing is independent of telomere length.”
  2. The researchers provided no mechanisms that plausibly linked performance “in an incentivized behavioral economic task” with telomere length.
  3. The researchers didn’t characterize any causal mechanisms whereby two gene variants affected the task performance’s purported effect on telomere length.

What’s the real reason the reviewer forwarded this paper to “Delay discounting, genetic sensitivity, and leukocyte telomere length”

What’s a good substitute for feeling loved?

A friend of mine sent a link to this TED talk yesterday. The speaker inspired my friend to change their life along the speaker’s guidelines:

“The very act of doing the thing that scared me undid the fear.

That feeling, you can’t help but strive for greatness at any cost.

The more I work to be successful, the more I need to work.”

I wasn’t similarly inspired. Evidence doesn’t support that a fear memory is undone by behavior that covers it over and tamps it down. What I saw expressed in the TED talk was an exhausting pursuit of substitutes for feeling loved.

This February 18 blog post by Dr Arthur Janov framed the TED talk in the context that I understood the speaker:

“Most of us thought that once we choose a profession and follow it and succeed at it, becoming an expert and well known, that would be fulfilling. We would feel like a success.

Success is not a feeling, loved is.

Fame is other people’s idea of success; it is in a way their feeling…admiration, humbling, important, etc.

And why does the person, even most accomplished, never feel satisfied nor fulfilled?”

What do you feel is the appropriate context of the TED talk? What do you think are likely outcomes of a person following the speaker’s guidelines?

Using an epigenetic clock to distinguish cellular aging from senescence

The 2016 UK/UCLA human study found:

“Induction of replicative senescence (RS) and oncogene-induced senescence (OIS) are accompanied by ageing of the cell. However, senescence induced by DNA damage is not, even though RS and OIS activate the cellular DNA damage response pathway, highlighting the independence of senescence from cellular ageing.

We used primary endothelial cells (ECs) that were derived from the human coronary artery of a 19 year old male.

The fact that maintenance of telomere length by telomerase did not prevent cellular ageing defines the singular role of telomeres as that of a means by which cells restrict their proliferation to a certain number; which was the function originally ascribed to it. Cellular ageing on the other hand proceeds regardless of telomere length.

Collectively, our results reveal that cellular ageing is distinct from cellular senescence and independent of DNA damage response and telomere length.”

The following was the closest the study came to a Limitations statement:

“Although the characteristics of cellular ageing are still not well known, the remarkable precision with which the epigenetic clock can measure it and correlate it to biological ageing remove any doubt of its existence, distinctiveness and importance. This inevitably raises the question of what is the nature of this cellular ageing, and what are its eventual physical consequences.

Admittedly, the observations above do not purport to provide the answer, but they have however, cleared the path to its discovery by unshackling cellular ageing from senescence, telomeres and DNA damage response, hence inviting fresh perspectives into its possible mechanism.”

The epigenetic clock method was the same used by:[]=7383&path[]=21162 “Epigenetic clock analyses of cellular senescence and ageing”

What’s the underlying question for every brain study to answer?

Is it:

  • How do our brains internally represent the external world?

Is it:

  • How did we learn what we know?
  • How do we forget or disregard what we’ve learned?
  • What keeps us from acquiring and learning newer or better information?

How about:

  • What affects how we pay attention to our environments?
  • How do our various biochemical states affect our perceptions, learning, experiences, and behavior?
  • How do these factors in turn affect our biology?

Or maybe:

  • Why do we do what we do?
  • How is our behavior affected by our experiences?
  • How did we become attracted and motivated toward what we like?
  • How do we develop expectations?
  • Why do we avoid certain situations?

Not to lose sight of:

  • How do the contexts affect all of the above?
  • What happens over time to affect all of the above?

This 2015 UCLA paper reviewed the above questions from the perspective of Pavlovian conditioning:

“The common definition of Pavlovian conditioning, that via repeated pairings of a neutral stimulus with a stimulus that elicits a reflex the neutral stimulus acquires the ability to elicit that the reflex, is neither accurate nor reflective of the richness of Pavlovian conditioning. Rather, Pavlovian conditioning is the way we learn about dependent relationships between stimuli.

Pavlovian conditioning is one of the few areas in biology in which there is direct experimental evidence of biological fitness.”

The most important question unanswered by the review is:

  • How can its information be used to help humans?

How does Pavlov conditioning answer:

  • What can a human do about the thoughts, feelings, behavior, epigenetic effects – the person – that they’ve been shaped into?

One relevant hypothesis of Dr. Arthur Janov’s Primal Therapy is that a person will continue to be their conditioned self until they address the sources of their pain. A corollary is that addressing symptoms will seldom address causes.

How could it be otherwise? A problem isn’t cured by ameliorating its effects.

As an example, the review pointed out in a section about fear extinction that it doesn’t involve unlearning. Fear extinction instead inhibits the symptoms of fear response. The fear memory is still intact, awaiting some other context to be reactivated and expressed.

How can that information be used to help humans?

  • Is inhibiting the symptoms and leaving the fear memory in place costless with humans?
  • Or does this practice have both potential and realized adverse effects?
  • Where’s the human research on methods that may directly address a painful emotional memory? “The Origins and Organization of Vertebrate Pavlovian Conditioning”