The epigenetic clock now includes skin

The originator of the 2013 epigenetic clock improved its coverage with this 2018 UCLA human study:

“We present a new DNA methylation-based biomarker (based on 391 CpGs) that was developed to accurately measure the age of human fibroblasts, keratinocytes, buccal cells, endothelial cells, skin and blood samples. We also observe strong age correlations in sorted neurons, glia, brain, liver, and bone samples.

The skin & blood clock outperforms widely used existing biomarkers when it comes to accurately measuring the age of an individual based on DNA extracted from skin, dermis, epidermis, blood, saliva, buccal swabs, and endothelial cells. Thus, the biomarker can also be used for forensic and biomedical applications involving human specimens.

The biomarker applies to the entire age span starting from newborns, e.g. DNAm of cord blood samples correlates with gestational week.

Furthermore, the skin & blood clock confirms the effect of lifestyle and demographic variables on epigenetic aging. Essentially it highlights a significant trend of accelerated epigenetic aging with sub-clinical indicators of poor health.

Conversely, reduced aging rate is correlated with known health-improving features such as physical exercise, fish consumption, high carotenoid levels. As with the other age predictors, the skin & blood clock is also able to predict time to death.

Collectively, these features show that while the skin & blood clock is clearly superior in its performance on skin cells, it crucially retained all the other features that are common to other existing age estimators.”

http://www.aging-us.com/article/101508/text “Epigenetic clock for skin and blood cells applied to Hutchinson Gilford Progeria Syndrome and ex vivo studies”


An introduction to the study highlighted several items:

“Although the skin-blood clock was derived from significantly less samples (~900) than Horvath’s clock (~8000 samples), it was found to more accurately predict chronological age, not only across fibroblasts and skin, but also across blood, buccal and saliva tissue. A potential factor driving this improved accuracy in blood could be related to the approximate 18-fold increase in genomic coverage afforded by using Illumina 450k/850k beadarrays.

It serves as a roadmap for future clock studies, pointing towards the importance of constructing tissue or cell-type specific epigenetic clocks, to more accurately measure biological aging in the given tissue/cell-type, and therefore with the potential to be more informative of disease-risk or the success of disease interventions in the tissue or cell-type of interest.”

http://www.aging-us.com/article/101533/text “Epigenetic clocks galore: a new improved clock predicts age-acceleration in Hutchinson Gilford Progeria Syndrome patients”

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Unindexed comment links?

It’s dawned on me that although links in blog posts are indexed by search engines, links in comments may not be. Here’s a post to elevate links in three comments that may have escaped notice.


From A review of biological variability:

“It is my view that all researchers have a narrow focus on what they want to research, without having an over-riding paradigm in which to fit the research and its results. Janovian Primal Therapy and theory, with its focus and understanding of the three different levels of consciousness would provide for a much needed over-arching paradigm, especially in the area of mental health.”

Congratulations on an excellent podcast, Gil!
59. Gilbert Bates in “Feel It Still” // Love, Primal Therapy & the Three Levels of Consciousness


From Remembering Dr. Arthur Janov:

“You are right on. The Norcross survey, in particular, is utter crap. More than half of those “experts” surveyed were CBT therapists who knew nothing about PT and yet deemed themselves confident to judge “primal scream therapy” as “discredited.” I feel the therapy will never be understood for what it is.”

Thanks for the detailed explanation, Bruce!
The Worst Comparative Psychotherapy Study Ever Published


From How one person’s paradigms regarding stress and epigenetics impedes relevant research:

“There is of course, reversibility. Michael Meaney’s baby rats had their epigenetic changes reversed with loving maternal care. There are several compounds in development which have been shown to reverse methylation. This former physician and researcher says, “Epigenetic changes affect the level of activity of our genes. Genetic activity levels affect our emotions, beliefs, and our bodies. Exploring epigenetics and chronic illness may help us understand causes that many of us suspect have played a role in the onset and evolution of our illnesses. Furthermore, these epigenetic changes have been found to be reversible, at least some of the time, even with a seemingly indirect treatment such as psychotherapy.” Epigenetics and Chronic Illness: Why Symptoms May Be Reversible

I looked up the psychotherapy references and found this: Serotonin tranporter methylation and response to cognitive behaviour therapy in children with anxiety disorders (reversible even with CBT, the weakest therapy of all!)

And this:
MAOA gene hypomethylation in panic disorder—reversibility of an epigenetic risk pattern by psychotherapy (also CBT)

So what gives? I suspect that your researcher is working with his/her head in the sand, hamstrung by their ideological biases. If CBT can effect epigenetic changes, imagine what primal therapy can do.”


And a seven-year anniversary repost of events that affect me every day:

Reflections on my four-year anniversary of spine surgery

Prenatal programming of human HPA axis development

This 2017 UC Irvine human review subject provided details of how fetal hypothalamic-pituitary-adrenal components and systems develop, and how they are epigenetically changed by the mother’s environment:

“The developmental origins of disease or fetal programming model predicts that intrauterine exposures have life-long consequences for physical and psychological health. Prenatal programming of the fetal hypothalamic-pituitary-adrenal (HPA) axis is proposed as a primary mechanism by which early experiences are linked to later disease risk.

Development of the fetal HPA axis is determined by an intricately timed cascade of endocrine events during gestation and is regulated by an integrated maternal-placental-fetal steroidogenic unit. Mechanisms by which stress-induced elevations in hormones of maternal, fetal, or placental origin influence the structure and function of the emerging fetal HPA axis are discussed.

Human gestational physiology and fetal HPA axis development differ even from that of closely related nonhuman primates, thereby limiting the generalizability of animal models. This review will focus solely on studies of prenatal stress and fetal HPA axis development in humans.”


Every time I read a prenatal study I’m in awe of all that has to go right, and at the appropriate time, and in sequence, for a fetus to be undamaged. Add in what needs to happen at birth, during infancy, and throughout early childhood, and it seems impossible for a human to escape epigenetic damage.


1. The reviewers referenced human research performed with postnatal subjects, as well as animal studies, despite the disclaimer:

This review will focus solely on studies of prenatal stress and fetal HPA axis development in humans.”

This led to blurring of what had been studied or not with human fetuses regarding the subject.

2. The reviewers uncritically listed many dubious human studies that had both stated and undisclosed severe limitations on their findings. It’s more appropriate for reviewers to offer informed reviews of cited studies, as Sex-specific impacts of childhood trauma summarized with cortisol:

“Findings are dependent upon variance in extenuating factors, including but not limited to, different measurements of:

  • early adversity,
  • age of onset,
  • basal cortisol levels, as well as
  • trauma forms and subtypes, and
  • presence and severity of psychopathology symptomology.”

3. It would have been preferable had the researchers stayed with their stated intention and critically reviewed only a few dozen studies with solid evidence of the review title: “Developmental origins of the human hypothalamic-pituitary-adrenal axis.” Let other reviews cover older humans, animals, and questionable evidence.

I asked the reviewers to provide a searchable file so that their work could be better used as a reference.

https://www.researchgate.net/publication/318469661_Developmental_origins_of_the_human_hypothalamic-pituitary-adrenal_axis “Developmental origins of the human hypothalamic-pituitary-adrenal axis” (registration required)

How do memories transfer?

This 2018 Chinese study electronically modeled the brain’s circuits to evaluate memory transfer mechanisms:

“During non-rapid-eye-movement (NREM) sleep, thalamo-cortical spindles and hippocampal sharp wave-ripples have been implicated in declarative memory consolidation. Evidence suggests that long-term memory consolidation is coordinated by the generation of:

  • Hierarchically nested hippocampal ripples (100-250 Hz),
  • Thalamo-cortical spindles (7-15 Hz), and
  • Cortical slow oscillations (<1 Hz)

enabling memory transfer from the hippocampus to the cortex.

Consolidation has also been demonstrated in other brain tasks, such as:

  • In the acquisition of motor skills, where there is a shift from activity in prefrontal cortex to premotor, posterior parietal, and cerebellar structures; and
  • In the transfer of conscious to unconscious tasks, where activity in initial unskilled tasks and activity in skilled performance are located in different regions, the so-called ‘scaffolding-storage’ framework.

By separating a neural circuit into a feedforward chain of gating populations and a second chain coupled to the gating chain (graded chain), graded information (i.e. information encoded in firing rate amplitudes) may be faithfully propagated and processed as it flows through the circuit. The neural populations in the gating chain generate pulses, which push populations in the graded chain above threshold, thus allowing information to flow in the graded chain.

In this paper, we will describe how a set of previously learned synapses may in turn be copied to another module with a pulse-gated transmission paradigm that operates internally to the circuit and is independent of the learning process.”


The study has neither been peer-reviewed, nor have the mechanisms been tested in living beings.

https://www.biorxiv.org/content/early/2018/07/27/351114 “A Mechanism for Synaptic Copy between Neural Circuits”

Hidden hypotheses of epigenetic studies

This 2018 UK review discussed three pre-existing conditions of epigenetic genome-wide association studies:

“Genome-wide technology has facilitated epigenome-wide association studies (EWAS), permitting ‘hypothesis-free’ examinations in relation to adversity and/or mental health problems. Results of EWAS are in fact conditional on several a priori hypotheses:

  1. EWAS coverage is sufficient for complex psychiatric problems;
  2. Peripheral tissue is meaningful for mental health problems; and
  3. The assumption that biology can be informative to the phenotype.

1. CpG sites were chosen as potentially biologically informative based on consultation with a consortium of DNA methylation experts. Selection was, in part, based on data from a number of phenotypes (some medical in nature such as cancer), and thus is not specifically targeted to brain-based, stress-related complex mental health phenotypes.

2. The assumption is often that distinct peripheral tissues are interchangeable and equally suited for biomarker detection, when in fact it is highly probable that peripheral tissues themselves correspond differently to environmental adversity and/or disease state.

3. Analyses result in general statements such as ‘neurodevelopment’ or the ‘immune system’ being involved in the aetiology of a given phenotype. Whether these broad categories play indeed a substantial role in the aetiology of the mental health problem is often hard to determine given the post hoc nature of the interpretation.”


The reviewers mentioned in item #2 the statistical flaw of assuming that measured entities are interchangeable with one another. They didn’t mention that the problem also affected item #1 methodologies of averaging CpG methylation measurements in fixed genomic bins or over defined genomic regions, as discussed in:

The reviewers offered suggestions for reducing the impacts of these three hypotheses. But will doing more of the same, only better, advance science?

Was it too much to ask of researchers whose paychecks and reputations depended on a framework’s paradigm – such as the “biomarker” mentioned a dozen and a half times – to admit the uselessness of gathering data when the framework in which the data operated wasn’t viable? They already knew or should have known this.

Changing an individual’s future behavior even before they’re born provided one example of what the GWAS/EWAS framework missed:

“When phenotypic variation results from alleles that modify phenotypic variance rather than the mean, this link between genotype and phenotype will not be detected.”

DNA methylation and childhood adversity concluded that:

“Blood-based EWAS may yield limited information relating to underlying pathological processes for disorders where brain is the primary tissue of interest.”

The truth about complex traits and GWAS added another example of how this framework and many of its paradigms haven’t produced effective explanations of “the aetiology of the mental health problem”

“The most investigated candidate gene hypotheses of schizophrenia are not well supported by genome-wide association studies, and it is likely that this will be the case for other complex traits as well.”

Researchers need to reevaluate their framework if they want to make a difference in their fields. Recasting GWAS as EWAS won’t make it more effective.

https://www.sciencedirect.com/science/article/pii/S2352250X18300940 “Hidden hypotheses in ‘hypothesis-free’ genome-wide epigenetic associations”

A mid-year selection of epigenetic topics

Here are the most popular of the 65 posts I’ve made so far in 2018, starting from the earliest:

The pain societies instill into children

DNA methylation and childhood adversity

Epigenetic mechanisms of muscle memory

Sex-specific impacts of childhood trauma

Sleep and adult brain neurogenesis

This dietary supplement is better for depression symptoms than placebo

The epigenetic clock theory of aging

A flying human tethered to a monkey

Immune memory in the brain

The lack of oxygen’s epigenetic effects on a fetus

The lack of oxygen’s epigenetic effects on a fetus

This 2018 Loma Linda review subject was gestational hypoxia:

“Of all the stresses to which the fetus and newborn infant are subjected, perhaps the most important and clinically relevant is that of hypoxia. This review explores the impact of gestational hypoxia on maternal health and fetal development, and epigenetic mechanisms of developmental plasticity with emphasis on the uteroplacental circulation, heart development, cerebral circulation, pulmonary development, and the hypothalamic-pituitary-adrenal axis and adipose tissue.

An understanding of the specific hypoxia-induced environmental and epigenetic adaptations linked to specific organ systems will enhance the development of target-specific inhibition of DNA methylation, histone modifications, and noncoding RNAs that underlie hypoxia-induced phenotypic programming of disease vulnerability later in life.

A potential stumbling block to these efforts, however, relates to timing of the intervention. The greatest potential effect would be accomplished at the critical period in development for which the genomic plasticity is at its peak, thus ameliorating the influence of hypoxia or other stressors.

With future developments, it may even become possible to intervene before conception, before the genetic determinants of the risk of developing programmed disease are established.”

Table 3 “Antenatal hypoxia and developmental plasticity” column titles were Species | Offspring Phenotypes of Disorders and Diseases | Reference Nos.

Hypoxia phenotypes


This review was really an ebook, with 94 pages and 1,172 citations in the pdf file. As I did with Faith-tainted epigenetics, I read it with caution toward recognizing 1) the influence of the sponsor’s biases, 2) any directed narrative that ignored evidence contradicting the narrative, and 3) any storytelling.

See if you can match the meaning of the review’s last sentence (“intervene before conception” quoted above) with the meaning of any sentence in its cited reference Developmental origins of noncommunicable disease: population and public health implications.

One review topic that was misconstrued was transgenerational epigenetic inheritance of hypoxic effects. The “transgenerational” term was used inappropriately by several of the citations, and no cited study provided evidence for gestational hypoxic effects through the  F2 grandchild and F3 great-grandchild generations.

One omitted topic was gestational hypoxic effects of caffeine. The first paper that came up for my PubMed search of “caffeine pregnancy hypoxia” was an outstanding 2017 Florida rodent review Long-term consequences of disrupting adenosine signaling during embryonic development that had this paragraph and figure:

“One substance that fetuses are frequently exposed to is caffeine, which is a non-selective adenosine receptor antagonist. We discovered that in utero alteration in adenosine action leads to adverse effects on embryonic and adult murine hearts. We find that cardiac A1ARs [a type of adenosine receptor] protect the embryo from in utero hypoxic stress, a condition that causes an increase in adenosine levels. 

After birth in mice, we observed that in utero caffeine exposure leads to abnormal cardiac function and morphology in adults, including an impaired response to β-adrenergic stimulation. Recently, we observed that in utero caffeine exposure induces transgenerational effects on cardiac morphology, function, and gene expression.”

The timing of in utero caffeine treatment leads to differences in adult cardiac function, gene expression, and phenotype. Exposure to caffeine from E6.5–9.5 leads the F1 generation to develop dilated cardiomyopathy with decrease % FS and increased Myh7 expression. In utero caffeine exposure from E10.5–13.5 leads to a hypertrophic cardiomyopathy in the F2 generation along with increased % FS and decreased Myh7 expression

Why was this review and its studies omitted? It was on target for both gestational hypoxia and transgenerational epigenetic inheritance of hypoxic effects!

It was alright to review smoking, cocaine, methamphetamine, etc., but the most prevalent drug addiction – caffeine – couldn’t be a review topic?


The Loma Linda review covered a lot, but I had a quick trigger due to the sponsor’s bias. I started to lose “faith” in the reviewers after reading the citation for the review’s last sentence that didn’t support the statement.

My “faith” disappeared after not understanding why a few topics were misconstrued and omitted. Why do researchers and sponsors ignore, misrepresent, and not continue experiments through the F3 generation to produce evidence for and against transgenerational epigenetic inheritance? Where was the will to follow evidence trails regardless of socially acceptable beverage norms?

The review acquired the taint of storytelling with the reviewers’ assertion:

“..timing of the intervention. The greatest potential effect would be accomplished at the critical period in development for which the genomic plasticity is at its peak, thus ameliorating the influence of hypoxia or other stressors.”

Contradictory evidence was in the omitted caffeine study’s graphic above which described two gestational critical periods where an “intervention” had opposite effects, all of which were harmful to the current fetus’ development and/or to following generations. Widening the PubMed link’s search parameters to “caffeine hypoxia” and “caffeine pregnancy” returned links to human early life studies that used caffeine in interventions, ignoring possible adverse effects on future generations.

This is my final curation of any paper sponsored by this institution.

https://www.physiology.org/doi/abs/10.1152/physrev.00043.2017 “Gestational Hypoxia and Developmental Plasticity” (not freely available) Thanks to coauthor Dr. Xiang-Qun Hu for providing a copy.