Get serious about advanced glycation end products (AGEs)

Ever heard about AGEs? Here are three papers that describe how AGEs affect humans.

First is a 2020 Italian review Common Protective Strategies in Neurodegenerative Disease: Focusing on Risk Factors to Target the Cellular Redox System:

“Neurodegenerative disease is an umbrella term for different conditions which primarily affect the neurons in the human brain. Currently, neurodegenerative diseases are incurable, and the treatments available only control the symptoms or delay the progression of the disease.

Neurotoxicity can be induced by glycation reactions. Since glycation is a nonenzymatic process, proteins characterized by a slow turnover are those that more easily accumulate AGEs.

Methylglyoxal (MG) can occur as glycolysis by-product, but it is also present in foods (especially cooked and baked), beverages (mainly those fermented), and cigarette smoke, and it is considered the most potent precursor of AGE formation. More than 20 different AGEs have been identified in foods and in human tissues.

AGE accumulation, oxidative stress, and inflammation are related to AGE ability to bind specific receptors called RAGE. RAGE expression increases during aging, cancer, cardiovascular diseases, AD [Alzheimer’s], PD [Parkinson’s], and other neurodegenerative diseases.”

A 2015 study by some of the same authors Antiglycative activity of sulforaphane: a new avenue to counteract neurodegeneration? was cited for a treatment in addition to changing one’s diet to be AGE-less.

“When MG production is increased by high glucose or oxidative stress, glycated proteins accumulate in the brain and lead to glycative stress, playing a fundamental role in the establishment of different neurodegenerative disorders.

Our results indicated that SF [sulforaphane] counteracts ROS by two possible mechanisms of action: an increase of intracellular GSH [glutathione] levels and an enhancement of MG-detoxification through the up-regulation of the glyoxalase (GLO1) systems. GLO1 up-regulation is mediated by the transcription factor Nrf2. SF has been demonstrated to activate Nrf2.

Another mechanism by which SF exerts its neuroprotective activity against MG-induced glycative damage is the modulation of mitogen-activated protein kinase (MAPK) signaling pathways involved in apoptotic cell death. All MAPK signaling pathways are activated in AD.

Brain-derived neurotrophic factor (BDNF) is associated with neuronal survival through its interactions with the tyrosine receptor kinase B (TrkB) and p75 cellular receptors. BDNF expression levels are reduced in the brain of AD patients. SF pre-treatment, before MG addition, not only further increased BDNF levels, but also significantly induced TrkB protein levels reverting MG negative effect on this receptor.

SF totally reverts the reduction of glucose uptake caused by MG exposure. SF can be defined as a multitarget agent modulating different cellular functions leading to a pro-survival frame of particular importance in the prevention / counteraction of multifactorial neurodegenerative diseases.”

A 2020 review Non-enzymatic covalent modifications: a new link between metabolism and epigenetics investigated glycation:

“Non-enzymatic covalent modifications (NECMs) by chemically reactive metabolites have been reported to manipulate chromatin architecture and gene transcription. Unlike canonical post-translational modifications (PTMs), NECMs accumulate over time and are much more dependent on the cellular microenvironment.

A. Guanine residues in DNA and RNA can undergo methylglyoxal glycation, thereby inducing DNA and RNA damage. This DNA damage has few corresponding repair pathways.

B. Histones are primary glycation substrates because of their long half-lives and abundant lysine and arginine residues. Histone glycation was found to induce epigenetic dysregulation through three distinct mechanisms:

  1. Competition with essential enzymatic PTMs for sites (e.g., glycation adducts replace H3K4me3 and H3R8me2);
  2. Changing the charge states of histone tails and subsequently affecting the compaction state of the fiber; and
  3. Altering three-dimensional chromatin architecture by inducing both histone-histone and histone-DNA crosslinking.

Epigenetic impacts of histone glycation were shown to be dependent on sugar concentration and exposure time. Histone and DNA glycation may lead to long term epigenetic impacts on immune responses.

C. Glycation of multiple lysine residues of NRF2 inhibits its oncogenic function. Sugar molecules can influence epigenetic events through glycation of transcription factors and/or their associated regulatory proteins.”

The Transcription factor glycation section referenced a 2011 paper Regulation of the Keap1/Nrf2 system by chemopreventive sulforaphane: implications of posttranslational modifications:

“Nrf2 mRNA level is unaffected by treatment with sulforaphane, suggesting that cellular expression of Nrf2 protein is posttranscriptionally regulated. Posttranslational modifications of Keap1 and Nrf2 proteins seem to play an important role in the regulation of ARE‐dependent gene expression.”

Other curated AGEs papers include:

Eat broccoli sprouts for your hair!

This 2017 review explored broccoli sprout compounds effects on head hair:

“Skin appendages, notably hair follicles (HFs), can be exposed to high levels of reactive oxygen species (ROS), which are generated through metabolic reactions occurring mostly in the mitochondria, peroxisomes and the endoplasmic reticulum as well as in the plasma membrane. Despite their involvement in redox stress and cellular damage, ROS also have key roles in physiological signalling processes, including but not limited to, control of stem cell quiescence / differentiation, regulation of innate and adaptive immune responses and importantly, normal HF development.

HFs are composed of a series of concentric keratinocyte layers with a central hair shaft, all of which are encapsulated by a mesenchymal connective tissue sheath. Within this structure is an area known as the ‘bulge’, housing a population of epithelial and melanocyte stem cells. The hair bulb, the lowermost portion of the HF, contains transient amplifying cells that produce the rapidly proliferating matrix keratinocytes that give rise to the various cell types of the inner root sheath and hair shaft itself.

Putative impact of NRF2 activation on protection against hair disorders:

  1. Accumulation of excess ROS within crucial HF compartments (i.e. bulb and bulge) can be induced by endogenous and exogenous stressors associated with androgenetic alopecia (AGA), alopecia areata (excessive mast cell degranulation), chemotherapy, UV exposure and even physiological processes such as melanogenesis.
  2. In the HFSCs [hair follicle stem cells] of the bulge, this can lead to reduced FOXP1 signaling, increased senescence and P21-mediated telogen retention, contributing the hair ageing.
  3. In the hair bulb, negative consequences of excessive ROS can include reduced matrix keratinocyte proliferation and Bcl-2 expression, coupled to increased p53 activity and apoptosis. This redox imbalance may also stimulate the dermal papilla-derived TGF-b1 release associated with AGA.
  4. NRF2 activation via SFN [sulforaphane] can induce the expression of numerous downstream targets, hence suggesting the potential to counteract excessive ROS and associated pathologies, for example via enhanced clearance of reactive species, detoxification, NADPH generation and GSH maintenance.
  5. In addition, NRF2 may down-regulate genes that would negatively impact on proliferation and stimulate apoptosis.
  6. Ultimately, the activation of NRF2 has the potential to protect against HF miniaturization, chemotherapy-induced apoptosis, HFSC aging and hair greying, through maintenance of normal redox homeostasis.

Whereas eumelanin (black) is involved in natural UV protection by reducing generation of free radicals, pheomelanin (red) can trigger generation of ROS. It would certainly be interesting to determine whether NRF2 activity is therefore higher in individuals with red as opposed to black hair, in order to mitigate any negative impact from higher ROS generation.

Modulation of NRF2 activity is an attractive approach for further study in the prevention of hair greying and HFSC ageing. The remarkable prospect for NRF2 activators in modulating other oxidative stress-linked disease states, strongly advocates for the development of NRF2 targeting as a novel strategy in modulating redox-associated disorders of the HF.” “Oxidative stress management in the hair follicle: Could targeting NRF2 counter age‐related hair disorders and beyond?” (not freely available)

This review was cited in a 2020 Exploring the possibility of predicting human head hair greying from DNA using whole-exome and targeted NGS data:

“This study aimed to assess the potential of genetic data to predict hair greying in a population of nearly 1000 individuals from Poland. Most of the prediction information was brought by age alone. Genetic variants explained < 10% of hair greying variation and the impact of particular SNPs on prediction accuracy was found to be small.

Study population included 673 males (67.4%) and 325 (32.6%) females. The mean age of the participants was 30.5 ± 8.8.

Hair greying was recorded in 14.3% of individuals aged 18–30 and the prevalence of grey hair was noted to be significantly higher in young males when comparing to young females (17.8 and 9.2%, respectively). The incidence of grey hair increased to 29.5% in the group of people aged 18–40 years and was 84.2% when people aged ≥40 years were considered.

Because pleiotropy is so common, it would be impossible to predict natural phenotypes avoiding genes involved in determination of pathological phenotypes. The penetrance of individual SNP variants is usually low and they altogether can only explain a small fraction of the predisposition to the disease.

Prediction of hair greying status solely based on genetic information is currently impossible.”

A 2020 review had a pertinent evaluation scheme:

“Geroprotectors are pharmacological agents that decrease the rate of aging and extend lifespan. We proposed a set of primary and secondary selection criteria for potential geroprotectors. Primary criteria:

  1. The life extension in experiments with wild type animal models. The geroprotector should prolong the life of the model beyond the intact maximum lifespan, protecting it from one or more mechanisms of aging.
  2. Improvement of molecular, cellular, and physiological biomarkers to a younger state or slow down the progression of age-related changes in humans.
  3. Most potential geroprotectors are preventive only when applied at relatively high concentrations. The lifespan-extending dose should be several orders of magnitude less than the toxic dose.
  4. Minimal side effects at the therapeutic dosage at chronic application.
  5. The potential benefit of taking a geroprotector may come after a long period. Potential geroprotectors should initially improve some parameters of health-related quality of life: physical, mental, emotional, or social functioning of the person.” “Terpenoids as Potential Geroprotectors”


Transgenerational epigenetic inheritance of epimutations

My 600th curation is a 2020 rodent study from Dr. Michael Skinner’s labs at Washington State University:

“Numerous environmental toxicants have been shown to induce the epigenetic transgenerational inheritance of disease and phenotypic variation. Alterations in the germline epigenome are necessary to transmit transgenerational phenotypes.

In previous studies, the pesticide DDT and the agricultural fungicide vinclozolin were shown to promote the transgenerational inheritance of sperm differential DNA methylation regions, non-coding RNAs and histone retention, which are termed epimutations. The current study was designed to investigate the developmental origins of the transgenerational differential histone retention sites (called DHRs) during gametogenesis of the sperm.

In addition to alterations in sperm DNA methylation and ncRNA expression previously identified, the induction of DHRs in the later stages of spermatogenesis also occurs. This novel component of epigenetic programming during spermatogenesis can be environmentally altered and transmitted to subsequent generations.

While the DHR may be consistent and present between the stages of development, the histone modifications may be altered. Several of the core histone retention sites absent in the DHRs had altered histone methylation. This adds a level of complexity to the potential role of histone retention in that it may be not only the retention, but also the alterations in histone epigenetic modifications.

The DHRs had positional associations with genes and the major functional categories were signaling, metabolism and transcription.

In the event the embryo stem cell population has a modified epigenetics and corresponding transcriptome, then all somatic cells derived from the stem cell population will have an altered cascade of epigenetic and gene expression programming to result in adult differentiated cells with altered epigenetics and transcriptomes. Previous observations have demonstrated in older adult human males alterations in histone retention develop and are associated with infertility.

Similar observations have also been provided for the development of differential DNA methylation regions (DMRs) induced by environmental toxicants such as DDT and vinclozolin. Since DHRs have a similar developmental programming, other epigenetic processes such as ncRNA are also anticipated to be similar.” “Developmental origins of transgenerational sperm histone retention following ancestral exposures”

This study, like its dozens of predecessors performed year after year by this research facility, provided evidence for mechanisms of epigenetic transgenerational inheritance. The studied F3 generation members were great-grand-offspring, the first generation to have no direct exposure to DDT and vinclozolin.

As pointed out in A compelling review of epigenetic transgenerational inheritance:

“During the 1950s, the entire North American population was exposed to high levels of the pesticide DDT, when the obesity rate was < 5% of the population. Three generations later, the obesity frequency in North America is now ~45% of the population.”

There are varieties of mischaracterizations and hand-waving denials of epigenetically-inherited diseases. People don’t want to hear about and read proof that something we did or experienced disfavored our children, who unwittingly passed resultant problems on to their children, and which furthered on to their children’s children.

A review of sulforaphane and aging

This 2019 Mexican review stated:

“We describe some of the molecular and physical characteristics of SFN, its mechanisms of action, and the effects that SFN treatment induces in order to discuss its relevance as a ‘miraculous’ drug to prevent aging and neurodegeneration. SFN has been shown to modulate several cellular pathways in order to activate diverse protective responses, which might allow avoiding cancer and neurodegeneration as well as improving cellular lifespan and health span.

NF-κB is in charge of inflammatory response regulation. Under basal conditions, NF-κB is sequestrated into the cytosol by IκB, but when pro-inflammatory ligands bind to its receptors, the IKK protein family phosphorylates IκB to degrade it via proteasome, so NF-κB is able to translocate into the nucleus and transcript several inflammatory mediators. Sulforaphane is capable to inhibit IκB phosphorylation and NF-κB nuclear translocation.

SFN upregulated Nrf2 expression by reducing DNA demethylation levels of the Nrf2 promoter. In another model using the triple-transgenic mouse model of Alzheimer’s disease (3 × Tg-AD), the use of SFN regulates the expression of the Brain-derived neurotrophic factor (BDNF) via HDAC inhibition, thus increasing H3 and H4 acetylation on the BDNF promoter. Enhancing BDNF expression as an effect of SFN treatment increased the neuronal content of several synaptic molecules like MAP 2, synaptophysin, and PSD-95 in primary cortical neurons of 3 × Tg-AD.” “Sulforaphane – role in aging and neurodegeneration”

I came across this review while searching PubMed for sulforaphane commonalities with presentation topics in Part 2 of Reversal of aging and immunosenescent trends with sulforaphane. The review outlined some aging aspects and presented relevant sulforaphane studies. Others such as eye and muscle decline weren’t addressed.

Since sulforaphane’s “a ‘miraculous’ drug” in the Abstract, I expected but didn’t see corresponding excitement in the review body. Just phrases like “it is known” and non-specific “more research is needed.”

Other papers published after this review were found by a PubMed “sulforaphane signal aging” search:

Clearing out the 2019 queue of interesting papers

I’m clearing out the below queue of 27 studies and reviews I’ve partially read this year but haven’t taken the time to curate. I have a pesky full-time job that demands my presence elsewhere during the day. :-\

Should I add any of these back in? Let’s be ready for the next decade!

Early life “Early Behavioral Alterations and Increased Expression of Endogenous Retroviruses Are Inherited Across Generations in Mice Prenatally Exposed to Valproic Acid” (not freely available) “Consolidation of an aversive taste memory requires two rounds of transcriptional and epigenetic regulation in the insular cortex” (not freely available) “Intergenerational transmission of depression: clinical observations and molecular mechanisms” (not freely available)

mother “Epigenomics and Transcriptomics in the Prediction and Diagnosis of Childhood Asthma: Are We There Yet?” epigenetic clocks: estimating gestational age using placental DNA methylation levels” “Mismatched Prenatal and Postnatal Maternal Depressive Symptoms and Child Behaviours: A Sex-Dependent Role for NR3C1 DNA Methylation in the Wirral Child Health and Development Study” “Environmental influences on placental programming and offspring outcomes following maternal immune activation” “5-Hydroxymethylcytosine in cord blood and associations of DNA methylation with sex in newborns” (not freely available) “Paternal diet impairs F1 and F2 offspring vascular function through sperm and seminal plasma specific mechanisms in mice” “Sex differences in the epigenetic regulation of chronic visceral pain following unpredictable early life stress” (not freely available) “Genome-wide DNA methylation data from adult brain following prenatal immune activation and dietary intervention” in depression vulnerability and resilience: novel targets for preventive strategies”

Later life “Effect of Flywheel Resistance Training on Balance Performance in Older Adults. A Randomized Controlled Trial” “Eccentric Overload Flywheel Training in Older Adults” “Epigenetic regulation of the innate immune response to infection” (not freely available) “Hair Cell Regeneration” (not freely available) Modifications as an Intersection Between Diet and Longevity” “Serotonin transporter gene methylation predicts long-term cortisol concentrations in hair” (not freely available) “Frailty biomarkers in humans and rodents: Current approaches and future advances” (not freely available) “Neural mechanisms underlying adaptive and maladaptive consequences of stress: Roles of dopaminergic and inflammatory responses “In Search of Panacea—Review of Recent Studies Concerning Nature-Derived Anticancer Agents” “Reversal of oxycodone conditioned place preference by oxytocin: Promoting global DNA methylation in the hippocampus” (not freely available) “Different epigenetic clocks reflect distinct pathophysiological features of multiple sclerosis” “The Beige Adipocyte as a Therapy for Metabolic Diseases” “Bone adaptation: safety factors and load predictability in shaping skeletal form” (not freely available) “Successful treatment of post-traumatic stress disorder reverses DNA methylation marks” (not freely available) “Editing the Epigenome to Tackle Brain Disorders” (not freely available)

Epigenetic inheritance and microRNAs

This 2019 Canadian rodent study found:

“Folic acid (FA) supplementation mitigates sperm miRNA profiles transgenerationally following in utero paternal exposure to POPs [persistent organic pollutants]. Across the F1 – F4 generations, sperm miRNA profiles were less perturbed with POPs + FA compared to sperm from descendants of dams treated with POPs alone..and only in F1 sperm.

The POPs mixture represents the pollutant composition found in Ringed seal blubber of Northern Quebec which is a traditional food of Inuit people in that region.

F0 founder dams were gavaged with the POPs mixture corresponding to 500 µg PCBs/kg body weight or corn oil (CTRL) thrice weekly and were fed the AIN-93G diet containing either 2 mg/kg (1X) or 6 mg/kg (3X) of FA ad libitum. Treatments were only administered to F0 founder dams for 9 weeks in total; 5 weeks before mating to untreated males at postnatal day 90 and until parturition. Subsequent lineages, F1 through F4, were neither exposed to POPs nor 3X FA – instead they received 1X FA diet ad libitum.”

Folic acid’s mechanisms weren’t clear:

“The protective role of FA supplementation in the F1 sperm may be partly explained by its antioxidant activity if the miRNA changes are caused by oxidative stress induced by POPs exposure. If, however, the miRNA changes in POPs exposed sperm are due to an altered methylation capacity or dysregulated nucleotide synthesis or mutations, then the increased availability of methyl groups provided by FA supplementation may mitigate the POPs effect by supporting DNA repair through nucleotide synthesis. Additional studies of the interaction between POPs and FA are required.”

Epigenetic inheritance mechanisms were also unclear:

“It remains puzzling how environmentally perturbed paternal miRNAs can persist across multiple generations. To become heritable, parts of the sperm chromatin must escape reprogramming, leading to the possibility that sperm miRNA profiles are subsequently modified by environmental factors. There are clear examples of sperm DNA methylation that escape reprogramming and histones can be involved.”

The study may have produced more clarity had its design investigated DNA methylation as Epigenetic transgenerational inheritance extends to the great-great-grand offspring did. That study also had an intercross breeding scheme with the populations for the F1 – F3 generations before an outcross for the F4 generation because:

“An intercross within the exposure lineage population (with no sibling or cousin breeding to avoid inbreeding artifacts) provides the optimal phenotypes (i.e. pathology) and germline epigenetic alterations.”

Which breeding scheme do you think would more fairly represent the humans of this study? I’d guess that intercross would – if all Inuits eat Ringed seal blubber and have children with other Inuits. “Folic acid supplementation reduces multigenerational sperm miRNA perturbation induced by in utero environmental contaminant exposure”

A transgenerational view of the rise in obesity

This 2019 Washington State University rodent study found epigenetically inherited transgenerational effects in great-grand offspring due to their great-grandmothers’ toxicant exposures during pregnancy:

“Previous studies found an increased susceptibility to obesity in F3 generation rats ancestrally exposed to the pesticide DDT, and an increase in a lean phenotype in the F3 generation rats ancestrally exposed to the herbicide atrazine. The present study investigated whether there were common DMR [differential DNA methylated region] and associated genes between the control, DDT, and atrazine lineage male and female adipocytes in order to identify potential novel gene pathways modulated by DNA methylation.

Comparison of epigenetic alterations indicated that there were substantial overlaps between the different treatment lineage groups for both the lean and obese phenotypes. Novel correlated genes and gene pathways associated with DNA methylation were identified, and may aid in the discovery of potential therapeutic targets for metabolic diseases such as obesity.

Given that the first widespread [DDT] exposures to gestating human females started in the 1950s, the majority of the subsequent F3 generation are adults today. Ancestral exposures to environmental toxicants like DDT may have had a role in the dramatic rise in obesity rates worldwide.”

This same research group noted in Transgenerational diseases caused by great-grandmother DDT exposure:

“DDT was banned in the USA in 1973, but it is still recommended by the World Health Organization for indoor residual spray. India is by far the largest consumer of DDT worldwide.

India has experienced a 5-fold increase of type II diabetes over the last three decades with a predisposition to obesity already present at birth in much of the population. Although a large number of factors may contribute to this increased incidence of obesity, the potential contribution of ancestral toxicant exposures in the induction of obesity susceptibility requires further investigation.” “Adipocyte epigenetic alterations and potential therapeutic targets in transgenerationally inherited lean and obese phenotypes following ancestral exposures”

Epigenetic transgenerational inheritance extends to the great-great-grand offspring

This 2019 rodent study by the Washington State University labs of Dr. Michael Skinner continued to F4 generation great-great-grand offspring, and demonstrated that epigenetic inheritance mechanisms are similar to imprinted genes:

“Epigenetic transgenerational inheritance potentially impacts disease etiology, phenotypic variation, and evolution. An increasing number of environmental factors from nutrition to toxicants have been shown to promote the epigenetic transgenerational inheritance of disease.

Imprinted genes are a special class of genes since their DNA methylation patterns are unchanged over the generation and are not affected by the methylation erasure occurring early in development. The transgenerational epigenetic alterations in the germline appear to be permanently reprogrammed like imprinted genes, and appear protected from this DNA methylation erasure and reprogramming at fertilization in the subsequent generations. Similar to imprinted genes, the epigenetic transgenerational germline epimutations appear to have a methylation erasure in the primordial germ cells involving an epigenetic molecular memory.

Comparison of the transgenerational F3 generation, with the outcross to the F4 generation through the paternal or maternal lineages, allows an assessment of parent-of-origin transmission of disease or pathology. Observations provided examples of the following:

  1. Pathology that required combined contribution of both paternal and maternal alleles to promote disease [testis and ovarian disease];
  2. Pathology that is derived from the opposite sex allele such as father to daughter [kidney disease] or mother to son [prostate disease];
  3. Pathology that is derived from either parent-of-origin alleles independently [obesity];
  4. Pathology that is transmitted within the same sex, such as maternal to daughter [mammary tumor development]; and
  5. Pathology that is observed only following a specific parent-of-origin outcross [both F4 male obesity and F4 female kidney disease in the vinclozolin lineage].”

The study showed that epigenetically inherited legacies extend to the fifth generation. Do any of us know our ancestors’ medical histories back to our great-great-grandparents?

Will toxicologists take their jobs seriously, catch up to the current science, and investigate possible effects in at least the F3 generation that had no direct toxicant exposure? “Epigenetic transgenerational inheritance of parent-of-origin allelic transmission of outcross pathology and sperm epimutations”

Maternal obesity causes heart disease in every offspring generation

This 2019 St. Louis rodent study found:

“We hypothesized that maternal obesity induces cardiac mitochondrial dysfunction in the offspring via transgenerational inheritance of abnormal oocyte mitochondria. All F1 to F3 descendants bred via the female in each generation were nonobese and demonstrated cardiac mitochondrial abnormalities.

Contrary to our hypothesis, male F1 also transmitted these effects to their offspring, ruling out maternal mitochondria as the primary mode of transmission. We conclude that transmission of obesity-induced effects in the oocyte nucleus rather than abnormal mitochondria underlie transgenerational inheritance of cardiac mitochondrial defects in descendants of obese females.”

For some reason, the researchers didn’t cite any of Dr. Michael Skinner’s research on epigenetic transgenerational inheritance. Their time, efforts, and resources would have been more productive had they used Dr. Skinner’s studies – such as the 2018 Epigenetic transgenerational inheritance of ovarian disease – as guides.

A podcast with the researchers is available here. “Maternal High-Fat, High-Sucrose Diet Induces Transgenerational Cardiac Mitochondrial Dysfunction Independent of Maternal Mitochondrial Inheritance” (not freely available)

Transgenerational epigenetic inheritance of thyroid hormone sensitivity

My 500th curation is a 2019 Portuguese human study of Azorean islanders:

“This study demonstrates a transgenerational epigenetic inheritance in humans produced by exposure to high TH [thyroid hormone] in fetal life, in the absence of maternal influences secondary to thyrotoxicosis. The inheritance is along the male line.

The present work took advantage of the relatively frequent occurrence of fetal exposure to high TH levels in the Azorean island of São Miguel. This is the consequence of a missense mutation in the THRB gene causing the amino-acid replacement R243Q, resulting in reduced affinity of the TH receptor beta (TRβ) for TH and thus RTHβ.

Its origin has been traced to a couple who lived at the end of the 19th century. F0 represented the third generation and F3 the sixth and seventh generation descendant.”

These researchers provided the first adequately evidenced human transgenerational epigenetic inheritance study! However, the lead sentence in its Abstract wasn’t correct:

“Evidence for transgenerational epigenetic inheritance in humans is still controversial, given the requirement to demonstrate persistence of the phenotype across three generations.”

Although found in this study, there is no “requirement to demonstrate persistence of the phenotype.” Observing the same phenotype in each generation is NOT required for human transgenerational epigenetic inheritance to exist!

Animal transgenerational studies have shown that epigenetic inheritance mechanisms may both express different phenotypes for each generation:

and entirely skip a phenotype in one or more generations!

  • Transgenerational pathological traits induced by prenatal immune activation found a F2 and F3 generation phenotype of impaired sociability, abnormal fear expression and behavioral despair – effects that weren’t present in the F1 offspring;
  • The transgenerational impact of Roundup exposure “Found negligible impacts of glyphosate on the directly exposed F0 generation, or F1 generation offspring pathology. In contrast, dramatic increases in pathologies in the F2 generation grand-offspring, and F3 transgenerational great-grand-offspring were observed.” (a disease phenotype similarly skipped the first offspring generation);
  • Epigenetic transgenerational inheritance mechanisms that lead to prostate disease “There was also no increase in prostate histopathology in the directly exposed F1 or F2 generation.” (a prostate disease phenotype skipped the first two male offspring generations before it was observed in the F3 male offspring); and
  • Epigenetic transgenerational inheritance of ovarian disease “There was no increase in ovarian disease in direct fetal exposed F1 or germline exposed F2 generation. The F3 generation can have disease while the F1 and F2 generations do not, due to this difference in the molecular mechanisms involved.” (an ovarian disease phenotype similarly skipped the first two female offspring generations before it was observed in the F3 female offspring).

Details of epigenetic inheritance mechanisms were provided in Another important transgenerational epigenetic inheritance study. Mechanisms from fetal exposure to the fungicide vinclozolin were compared with mechanisms from fetal DDT exposure, and summarized as:

The fetal exposure initiates a developmental cascade of aberrant epigenetic programming, and does NOT simply induce a specific number of DMRs [DNA methylation regions] that are maintained throughout development.

I emailed references to the studies in the first five above curations to the current study’s corresponding coauthor. They replied “What is the mechanism for the transgenerational inheritance you describe?” and my reply included a link to the sixth curation’s study.

Are there still other transgenerational epigenetically inherited effects due to fetal exposure to high thyroid hormone levels? “Reduced Sensitivity to Thyroid Hormone as a Transgenerational Epigenetic Marker Transmitted Along the Human Male Line”