This 2018 US government rodent study used extreme dosages to achieve its directed goals of demonizing nicotine and extolling the biomarker paradigm:
“This study examined whether adolescent nicotine exposure alters adult hippocampus-dependent learning, involving persistent changes in hippocampal DNA methylation and if choline, a dietary methyl donor, would reverse and mitigate these alterations.
Mice were chronically treated with nicotine (12.6mg/kg/day) starting at post-natal day 23 (pre-adolescent), p38 (late adolescent), or p54 (adult) for 12 days followed by a 30-day period during which they consumed either standard chow or chow supplemented with choline (9g/kg).
Our gene expression analyses support this model and point to two particular genes involved in chromatin remodeling, Smarca2 and Bahcc1. Both Smarca2 and Bahcc1 showed a similar inverse correlation pattern between promoter methylation and gene expression.
Our findings support a role for epigenetic modification of hippocampal chromatin remodeling genes in long-term learning deficits induced by adolescent nicotine and their amelioration by dietary choline supplementation.”
Let’s use the average weight of a US adult male – published by the US Centers for Disease Control as 88.8 kg – to compare the study’s dosages with human equivalents:
Neither of these dosages are even remotely connected to human realities:
The human-equivalent dosage of nicotine used in this study would probably kill an adult human before the end of 12 days.
What effects would an adult human suffer from exceeding the choline “Tolerable Upper Intake Level” BY 228 TIMES for 30 days?
Isn’t the main purpose of animal studies to help humans? What’s the justification for performing animal studies simply to promote an agenda?
A funding source of this study was National Institute on Drug Abuse (NIDA) Identification of Biomarkers for Nicotine Addiction award (T-DA-1002 MG). Has the biomarker paradigm been institutionalized to the point where research proposals that don’t have biomarkers as goals aren’t funded?
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:
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.
“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:
EWAS coverage is sufficient for complex psychiatric problems;
Peripheral tissue is meaningful for mental health problems; and
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.
“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.
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:
circadian rhythm, and
and to highlight its underlying cellular mechanisms with a focus on:
“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.”
Hypothalamic activity not winding down when its developmental role is over shouldn’t be interpreted to construe a role that has some other meaning or purpose.
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 phenotypicprogramming 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.
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.
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 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.”
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.
This 2018 Washington rodent study subject was transgenerational epigenetic inheritance of disease caused by a fungicide that’s been phased out or banned for over a decade:
“This study was designed to help understand how three different epigenetic processes in sperm are correlated with vinclozolin-induced epigenetic transgenerational inheritance of disease.
Most DMRs [differential DNA-methylated regions] identified in this study are unique between the F1, F2, and F3 generations.
The number of lncRNA was much higher than the number of sncRNA [small noncoding RNA, including microRNA]. The overlap between each generation was very low or nonexistent.
The F1 and the F2 generation control versus vinclozolin lineage sperm had negligible DHRs [differential histone retention sites]. This observation suggests that the direct vinclozolin exposure does not alter histone retention or trigger any changes. However, the F3 generation control versus vinclozolin lineage sperm DHRs increased considerably.
It appears that the phenomenon is more complex than just a direct exposure triggering the formation of epimutations that are then simply maintained in the subsequent generations.”
I asked the coauthors why a third of the cited references were self-referencing. The lead author replied:
“The field in epigenetic transgenerational inheritance is expanding, however it is still hard for us to find relevant studies in rodents or human that we can cite. Most of the time DNA methylation, ncRNA and histone modifications are investigated from a direct exposure and/or from a purely mechanistic angle (e.g. DNA methylation of specific genes).
In contrast, transgenerational phenotypes and toxicology by definition excludes direct exposure and must be transmitted through multiple generations (the F3 generation is the first transgenerational one). We are not looking at specific genes but using whole genome sequencing technologies which is a broader approach.
Besides, if you do a pubmed search with the keywords “epigenetics” and “transgenerational”, you will probably find that more than 50% of the studies have been done by Dr Michael K. Skinner. He is also one of the first researcher who started to work on the epigenetic transgenerational inheritance phenomenon 15 years ago. Not citing his previous work is challenging.
We hope to see other labs contributing to this particular field and we will be delighted to cite them. In the meantime, our only option is to reference our previous work.”
“Thank you for your reply! It must be exasperating to see other researchers stop their studies short of the F3 generation for no apparent or disclosed reason.
Have you seen even one scientifically adequate human study of transgenerational epigenetic inheritance?”