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 hypothalamus and aging

This 2018 Korean review discussed aspects of the hypothalamus and aging:

“A majority of physiological functions that decline with aging are broadly governed by the hypothalamus, a brain region controlling development, metabolism, reproduction, circadian rhythm, and homeostasis. In addition, the hypothalamus is poised to connect the brain and the body so that the environmental information affecting aging can be transmitted through the hypothalamus to affect the systematic aging of the peripheral organs.

The hypothalamus is hypothesized to be a primary regulator of the process of aging of the entire body. This review aims to assess the contribution of hypothalamic aging to the age-related decline in body functions, particularly from the perspective of:

  • energy homeostasis,
  • hormonal balance,
  • circadian rhythm, and
  • reproduction,

and to highlight its underlying cellular mechanisms with a focus on:

  • nutrient sensing
  • inflammation,
  • loss of stem cell,
  • loss of proteostasis, and
  • epigenetic alterations.”

The reviewers didn’t consider aging to be an “unintended consequence” of development. This perspective was found in a reference to A study of DNA methylation and age:

“Aging is not and cannot be programmed. Instead, aging is a continuation of developmental growth, driven by genetic pathways.

Genetic programs determine developmental growth and the onset of reproduction. When these programs are completed, they are not switched off.

Aging has no purpose (neither for individuals nor for group), no intention. Nature does not select for quasi-programs. It selects for robust developmental growth.”

The epigenetic clock theory of aging cited the same author, and modified his point to say:

“The proposed epigenetic clock theory of ageing views biological ageing as an unintended consequence of both developmental programmes and maintenance programmes.”

This review’s opposite paradigm was:

“The hypothalamus is hypothesized to be a primary regulator of the process of aging.”

Almost all of the details discussed were from rodent studies.

I favor the “unintended consequence” explanation of aging. As detailed in How to cure the ultimate causes of migraines? and its references, the hypothalamus is a brain structure that lacks feedback mechanisms for several of its activities.

This structure develops shortly after conception and has an active prenatal role. The hypothalamus plays its part in getting us developed and ready to reproduce, with several feedback loops being evolutionarily unnecessary.

The hypothalamus perfectly illustrates the point of:

“When these programs are completed, they are not switched off.”

Should hypothalamic activity not winding down when its developmental role is over be interpreted to construe a role that has some other meaning or purpose as we age?

https://www.sciencedirect.com/science/article/pii/S0047637418300502 “Role of hypothalamus in aging and its underlying cellular mechanisms” (not freely available)

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 the influence of the sponsor’s biases, and any directed narrative that ignored evidence contradicting the narrative, and any storytelling.

See if you can match the meaning of the review’s last sentence 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 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.

A dietary supplement that reversed age-related hearing problems in the brainstem

This 2018 Nevada rodent study was on acetyl-L-carnitine’s action in the brainstem:

“We examined age-related changes in the efficiency of synaptic transmission at the calyx of Held, from juvenile adults (1-month old) and late middle-age (18- to 21-month old) mice. The calyx of Held synapse has been exploited as a model for understanding excitation-secretion coupling in central glutamatergic neurons, and is specialized for high-frequency transmission as part of a timing circuit for sound localization.

Our observations suggest that during aging, there is neuronal cell loss in the MNTB [Medial nucleus of the trapezoid body, a collection of brainstem nuclei in an area that’s the first recipient of sound and equilibrium information], similar to previous reports. In remaining synapses of the MNTB, we observed severe impairments in transmission timing and SV [synaptic vesicle] recycling, resulting in timing errors and increased synaptic depression in the calyx of Held synapse. These defects reduce the efficacy of this synapse to encode temporally sensitive information and are likely to result in diminished sound localization.

We orally administered ALCAR for 1 month and found that it reversed transmission defects at the calyx of Held synapse in the older mice.

These results support the concept that facilitators of mitochondrial metabolism and antioxidants may be an extremely effective therapy to increase synaptic function and restore short-term plasticity in aged brains, and provide for the first time a clear mechanism of action for ALCAR on activity-dependent synaptic transmission.

Human brainstem research is neglected, as noted by Advance science by including emotion in research. Evidence from such research doesn’t play well with beliefs in the popular models and memes of human cerebral dominance.

Do you know any “late middle-age” people who have obvious auditory and synaptic deficits? What if some of the neurobiological causes of what’s wrong in their brains could be “reversed by ALCAR?”

Before using this study as a guide, however, I asked the study’s researchers to calculate the human-equivalent dosage. When I translated the “daily dose of ~2.9 g/kg/d” it worked out to several hundred times the 500 mg to 1 g dietary supplement dosage of acetyl-L-carnitine.

The study’s corresponding coauthor replied:

“This is indeed much larger than that normally consumed by humans via dietary supplementation. We are currently working to determine the effective ‘minimal’ dose of ALCAR and alpha lipoic acid, to better assist guidelines for human application of this supplement.”

https://www.researchgate.net/publication/323941877_Age-related_defects_in_short-term_plasticity_are_reversed_by_acetyl-L-carnitine_at_the_mouse_calyx_of_Held “Age-related defects in short-term plasticity are reversed by acetyl-L-carnitine at the mouse calyx of Held”

A trio of epigenetic clock studies

The first 2018 epigenetic clock human study was from Finland:

“We evaluated the association between maternal antenatal depression and a novel biomarker of aging at birth, namely epigenetic gestational age (GA) based on fetal cord blood methylation data. We also examined whether this biomarker prospectively predicts and mediates maternal effects on early childhood psychiatric problems.

Maternal history of depression diagnosed before pregnancy and greater antenatal depressive symptoms were associated with child’s lower epigenetic GA. Child’s lower epigenetic GA, in turn, prospectively predicted total and internalizing problems and partially mediated the effects of maternal antenatal depression on internalizing problems in boys.”

Listening to a podcast by one of the coauthors, although the researchers’ stated intent was to determine the etiology of the findings, I didn’t hear any efforts to study the parents in sufficient detail to be able to detect possible intergenerational and transgenerational epigenetic inheritance causes and effects. There were the usual “associated with” and “it could be this, it could be that” hedges, which were also indicators of the limited methods employed toward the study’s limited design.

Why was an opportunity missed to advance human research in this area? Are researchers satisfied with non-causal individual differences non-explanations instead of making efforts in areas that may produce etiological findings?

https://www.jaacap.org/article/S0890-8567(18)30107-2/pdf “The Epigenetic Clock at Birth: Associations With Maternal Antenatal Depression and Child Psychiatric Problems” (not freely available)

The second 2018 epigenetic clock human study was from Alabama:

“We estimated measures of epigenetic age acceleration in 830 Caucasian participants from the Genetics Of Lipid Lowering Drugs and diet Network (GOLDN) considering two epigenetic age calculations.

Both DNA methylation age estimates were highly correlated with chronological age. We found that the Horvath and Hannum measures of epigenetic age acceleration were moderately correlated.

The Horvath age acceleration measure exhibited marginal associations with increased postprandial [after eating a meal] HDL [high-density lipoprotein], increased postprandial total cholesterol, and decreased soluble interleukin 2 receptor subunit alpha (IL2sRα). The Hannum measure of epigenetic age acceleration was inversely associated with fasting HDL and positively associated with postprandial TG [triglyceride], interleukin-6 (IL-6), C-reactive protein (CRP), and tumor necrosis factor alpha (TNFα).

Overall, the observed effect sizes were small.

https://clinicalepigeneticsjournal.biomedcentral.com/track/pdf/10.1186/s13148-018-0481-4 “Metabolic and inflammatory biomarkers are associated with epigenetic aging acceleration estimates in the GOLDN study”

The third 2018 epigenetic clock human study was a meta-analysis of cohorts from the UK, Italy, Sweden, and Scotland:

“The trajectories of Δage showed a declining trend in almost all of the cohorts with adult sample collections. This indicates that epigenetic age increases at a slower rate than chronological age, especially in the oldest population.

Some of the effect is likely driven by survival bias, where healthy individuals are those maintained within a longitudinal study, although other factors like underlying training population for the respective clocks may also have influenced this trend. It may also be possible that there is a ceiling effect for Δage whereby epigenetic clock estimates plateau.”

https://academic.oup.com/biomedgerontology/advance-article/doi/10.1093/gerona/gly060/4944478 “Tracking the Epigenetic Clock Across the Human Life Course: A Meta-analysis of Longitudinal Cohort Data”

Immune memory in the brain

This 2018 German rodent study was a proof-of-principle for immune epigenetic memory in the brain:

“Innate immune memory is a vital mechanism of myeloid [bone marrow] cell plasticity that occurs in response to environmental stimuli and alters subsequent immune responses.

Two types of immunological imprinting can be distinguished – training and tolerance. These are epigenetically mediated and enhance or suppress subsequent inflammation, respectively.

Certain immune stimuli train blood monocytes to generate enhanced immune responses to subsequent immune insults. By contrast, other stimuli induce immune tolerance — suppression of inflammatory responses to subsequent stimuli.

Microglia (brain-resident macrophages) are very long-lived cells. This makes them particularly interesting for studying immune memory, as virtually permanent modification of their molecular profile appears possible.

In a mouse model of Alzheimer’s pathology, immune training exacerbates cerebral β-amyloidosis and immune tolerance alleviates it; similarly, peripheral immune stimulation modifies pathological features after stroke. Our results identify immune memory in the brain as an important modifier of neuropathology.

Immune memory in the brain is predominantly mediated by microglia..Immune memory in the brain could conceivably affect the severity of any neurological disease that presents with an inflammatory component, but this will need to be studied for each individual condition.”

The researchers performed multiple experiments to test different hypotheses about how immune-response experiences are remembered. Modifications to histone methylation and acetylation were targeted. The dosage of the stimulus needed to produce immune tolerance was usually four times the immune training dosage.

https://www.nature.com/articles/s41586-018-0023-4 “Innate immune memory in the brain shapes neurological disease hallmarks” (not freely available)

Faith-tainted epigenetics

This 2018 Loma Linda review subject was epigenetic interventions for aging:

“Epigenomic markers of aging, global DNA hypomethylation and promoter-specific hypermethylation may be engendered by iron and HCys [homocysteine] retention.

MiR-29/p53 axis may reverse age-related methylomic shifts, stabilizing both the genome and the epigenome, therefore removing a major risk factor of neurodegeneration. Lowering iron and HCys overload can be accomplished via chelation, blood donation and maintaining an adequate omega-6/omega-3 ratio.”

Sometimes it’s difficult to detect researchers’ biases. If a reader didn’t know about the funding sponsor’s mission:

“Each day we seek to extend the teaching and healing ministry of Jesus Christ”

they may view this paper as unbiased rather than as a directed narrative.

Consider the sponsor’s influence from the perspective of someone seeking treatment for Alzheimer’s disease. If a doctor in this review sponsor’s hospital system recommended chelation treatment, hope would be generated for the patient. Adopting the doctor’s belief about the treatment, though, would be contrary to other evidence per this review:

“In 2008, the NIH chelation trial stopped enrolling patients, approximately two years early.

There is no indication for exposing patients with dementia to the risks of chelation therapy because current chelators cannot help them.”

After reading another review that had this sponsor – The lack of oxygen’s epigenetic effects on a fetus – which also reflected the influence of the sponsor’s biases, and had a directed narrative that ignored evidence contradicting the narrative, and involved storytelling, I’m done curating any paper sponsored by this institution.

http://www.nrronline.org/downloadpdf.asp?issn=1673-5374;year=2018;volume=13;issue=4;spage=635;epage=636;aulast=Sfera;type=2 “Epigenetic interventions for brain rejuvenation: anchoring age-related transposons” (click the pdf button)