The persistence of epigenetic marks in Type 1 diabetes

This 2016 California human study found:

“A persistency of DNA methylation over time at key genomic loci associated with diabetic complications. Two sets of DNAs collected at least 16–17 years apart from the same participants are used to show the persistency of DNA-me over time.

Twelve annotated differentially methylated loci were common in both WB [whole blood] and Monos [blood monocytes], including thioredoxin-interacting protein (TXNIP), known to be associated with hyperglycemia and related complications.

The top 38 hyperacetylated promoters in cases included 15 genes associated with the nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) inflammatory pathway, which is strongly associated with diabetic complications.”

The researchers built on a series of studies that showed how subjects with early intensive interventions didn’t develop further complications, whereas subjects with later intensive interventions:

“Continued to develop complications, such as nephropathy, retinopathy, and macrovascular diseases, at significantly higher rates.

This persistence of benefit from early application of intensive therapy, called ‘metabolic memory,’ is an enigma.”

I’d say that the researchers needed to also consider a point of Enduring memories? Or continuous toxic stimulation? that:

“The lasting epigenomic effect would not be due to memory, but continuous stimulation by persistent pathogens or persistent components.”

Other studies that involved specific genes of this study include: “Epigenomic profiling reveals an association between persistence of DNA methylation and metabolic memory in the DCCT/EDIC type 1 diabetes cohort”


Using epigenetic outliers to diagnose cancer

This 2016 Chinese/UK human cancer cell study tested five algorithms and found:

“Most of the novel proposed algorithms lack the sensitivity to detect epigenetic field defects at genome-wide significance. In contrast, algorithms which recognise heterogeneous outlier DNA methylation patterns are able to identify many sites in pre-neoplastic lesions, which display progression in invasive cancer.

Many DNA methylation outliers are not technical artefacts, but define epigenetic field defects which are selected for during cancer progression.”

The usual method of epigenetic studies involves:

“Identify genomic sites where the mean level of DNAm [DNA methylation] differs as much as possible between the two phenotypes. As we have seen however, such an approach is seriously underpowered in cancer studies where tissue availability is a major obstacle.

In addition to allelic frequency, we also need to take the magnitude of the alteration into consideration. As shown here, infrequent but bigger changes in DNAm (thus defining outliers) are more likely to define cancer field defects, than more frequent yet smaller DNAm changes.”

A similar point was made in Genetic statistics don’t necessarily predict the effects of an individual’s genes:

“Epigenomic analyses are limited by averaging of population-wide dynamics and do not inform behavior of single cells.”

One of the five tested algorithms was made freely available by the researchers. The limitations on its use were discussed, and included:

“Studies conducted in a surrogate tissue such as blood are scenarios where DNAm outliers are probably not of direct biological relevance to cancer development.” “Stochastic epigenetic outliers can define field defects in cancer”

Using salivary microRNA to diagnose autism

This 2016 New York human study found:

“Measurement of salivary miRNA in this pilot study of subjects with mild ASD [autism spectrum disorder] demonstrated differential expression of 14 miRNAs that are:

  • expressed in the developing brain,
  • impact mRNAs related to brain development, and
  • correlate with neurodevelopmental measures of adaptive behavior.”

Some problems with current diagnostic methods for autism are:

“The first sign of ASD commonly recognized by pediatricians is a deficit in communication and language that does not manifest until 18–24 months of age.

The mean age of diagnosis for children with ASD is 3 years, and approximately half of these are false-positives.

Despite a substantial genetic component, no single gene variant accounts for >1 % of ASD incidence.

Nearly 2000 individual genes have been implicated in ASD, but none are specific to the disorder.”

Study limitations included:

“Aside from the sample size and cross-sectional nature of this pilot study, another limitation is the age of ASD and control subjects it describes (4–14 years) which are not representative of the target population in which ASD biomarkers would ideally be utilized (0–2 years). However, selecting a homogenous group of subjects with mild ASD (as measured by ADOS) that was well-established and diagnosed by a developmental specialist requires subjects with long-standing diagnoses.”

Regarding other later-life consequences of disrupted neurodevelopment, an understanding of these processes is critical for tracing symptoms back to their causes, as noted in Grokking an Adverse Childhood Experiences (ACE) score.

I wonder how long it will take for researchers in other fields to stop wasting resources and do what this study did: focus on epigenetic biomarkers that have developmental origins. “Salivary miRNA profiles identify children with autism spectrum disorder, correlate with adaptive behavior, and implicate ASD candidate genes involved in neurodevelopment”

Observing pain in others had long-lasting brain effects

This 2016 Israeli human study used whole-head magnetoencephalography (MEG) to study pain perception in military veterans:

Our findings demonstrate alterations in pain perception following extreme pain exposure, chart the sequence from automatic to evaluative pain processing, and emphasize the importance of considering past experiences in studying the neural response to others’ states.

Differences in brain activation to ‘pain’ and ‘no pain’ in the PCC [posterior cingulate cortex] emerged only among controls. This suggests that prior exposure to extreme pain alters the typical brain response to pain by blurring the distinction between painful and otherwise identical but nonpainful stimuli, and that this blurring of the ‘pain effect’ stems from increased responses to ‘no pain’ rather than from attenuated response to pain.”

Limitations included:

  • “The pain-exposed participants showed posttraumatic symptoms, which may also be related to the observed alterations in the brain response to pain.
  • We did not include pain threshold measurements. However, the participants’ sensitivity to experienced pain may have had an effect on the processing of observed pain.
  • The regions of interest for the examination of pain processing in the pain-exposed group were defined on the basis of the results identified in the control group.
  • We did not detect pain-related activations in additional regions typically associated with pain perception, such as the anterior insula and ACC. This may be related to differences between the MEG and fMRI neuroimaging approaches.”

The subjects self-administered oxytocin or placebo per the study’s design. However:

“We chose to focus on the placebo condition and to test group differences at baseline only, in light of the recent criticism on underpowered oxytocin administration studies, and thus all following analyses are reported for the placebo condition.”

A few questions:

  1. If observing others’ pain caused “increased responses to ‘no pain’,” wouldn’t the same effect or more be expected from experiencing one’s own pain?
  2. If there’s evidence for item 1, then why aren’t “increased responses to ‘no pain'” of affected people overtly evident in everyday life?
  3. If item 2 is often observed, then what are the neurobiological consequences for affected people’s suppression of “increased responses to ‘no pain’?”
  4. Along with the effects of item 3, what may be behavioral, emotional, and other evidence of this suppressed pain effect?
  5. What would it take for affected people to regain a normal processing of others’ “‘pain’ and ‘no pain’?” “Prior exposure to extreme pain alters neural response to pain in others” Thanks to one of the authors, Ruth Feldman, for providing the full study

A study of how genetic factors determined diet-induced epigenetic changes

This 2016 California rodent study found:

“HF [high fat] diet leads to persistent alterations of chromatin accessibility that are partially mediated by transcription factors and histone post-translational modifications. These chromatin alterations are furthermore strain specific, indicating a genetic component to the response.

These results suggest that persistent epigenetic modifications induced by HF diet have the potential to impact the long-term risk for metabolic diseases.”

The experimental procedure was that 7-8 week old subjects of two mice strains “were placed on three diet regimens:

  1. control diet for sixteen weeks,
  2. HF diet for sixteen weeks, or
  3. HF diet for an initial eight weeks followed by control diet for eight weeks (diet reversal).”

On diet regimen 3, one of the mouse strains wasn’t able to reverse the epigenetic changes caused by eight weeks of a high-fat diet. The symptoms included:

  • Elevated lipid accumulation and triglyceride levels
  • 15% of chromatin sites were more accessible, with the HNF4α transcription factor implicated
  • 6% of chromatin sites were less accessible due to H3K9 methylation
  • Persistently up-regulated genes were more likely to be in the vicinity of a persistently accessible site
  • A set of persistently up-regulated genes enriched for mitochondrial genes was present only with diet regimen 3 subjects.

A second mouse strain “known to display differences in metabolic dysfunction under HF diet” compared to the first strain didn’t experience the same symptoms on diet regimen 3:

  • Lipid accumulation and triglyceride levels weren’t elevated
  • The majority of diet-induced chromatin remodeling [was] reversible
  • Little overlap with the first strain in the set of genes that changed expression.

The study didn’t suggest any specific human applicability. (pdf) “Persistent chromatin modifications induced by high fat diet”


The epigenetic influence of obese parents at conception

This 2016 German rodent study found:

“Using in vitro fertilization to ensure exclusive inheritance via the gametes, we show that a parental high-fat diet renders offspring more susceptible to developing obesity and diabetes in a sex- and parent of origin–specific mode.”

It would have benefited the researchers to have made the full study freely available. As it is, an interested reader has to ferret out information such as the basic study design provided in this link:

which had in the caption that both the parental and offspring diets were normal until:

  • “Between 9 [young adult] and 15 weeks of age.
  • This experiment was replicated at least three times for each F1 cohort, using sperm and oocytes from independent donors.”

Compare that information with the description provided by the study’s most thorough news coverage:

“Researchers raised genetically similar mice for six weeks [beginning at 9 weeks of age] on one of three diets: standard mouse chow [13.5% fat], a low-fat diet [11% fat], or a high-fat [60% fat], high-calorie diet. The latter became obese and developed severe glucose intolerance (a precursor to type 2 diabetes), while the other mice stayed slim.

Harvesting the eggs and sperm from mice in each of the diet groups, the researchers then used in vitro fertilization to make specific, controlled crosses. All of the embryos were transferred to healthy, skinny [actually, the foster mothers were on the standard mouse chow diet] foster mothers . To see if the diet of their biological parents affected their metabolism, all of the pups [actually, young adults at age 9 weeks] were challenged with a high-fat, high-calorie diet [beginning at 9 weeks of age].

Unsurprisingly, the female pups with two obese parents had a high degree of insulin resistance and gained at least 20 percent more weight than the offspring of parents on standard or low-fat diets. Female pups with only one obese parent, either the mother or the father, also gained more weight than the control groups—but only between 8 and 14 percent. The result suggests that the metabolic influence of each parent may be additive.

But in a puzzling finding, the male pups didn’t have the same pattern. The male pups of obese parents did tend to be a bit heavier than those from the control groups, but the difference wasn’t statistically significant, the authors report. They did, however, also have a high degree of insulin resistance.

Examining the glucose intolerance more closely, the researchers noted that offspring (both male and female) tended to have more severe glucose intolerance if their mothers were obese. This backs up epidemiological data in humans that suggests a stronger maternal influence over type 2 diabetes development.”

The study didn’t determine causal biological mechanisms for the observed epigenetic effects. No measurements of DNA methylation, histone modifications, or microRNA molecules were taken.

I look forward to further research into epigenetic contributions at conception to adulthood symptoms. “Epigenetic germline inheritance of diet-induced obesity and insulin resistance” Thanks to the lead author Peter Huypens for providing a copy of the full study

Problematic research into epigenetic effects of paternal stress on male offspring

This 2016 Chinese rodent study and its accompanying commentary Don’t stress dad — it’s bad for your kids’ health were caught up in an agenda.

The first problem I noticed was that the hyperglycemic effects found only in the male offspring weren’t consistently labelled as sex-specific. Try to find that fact in the paywalled commentary with its intentionally misleading headline, or in the news coverage with headlines such as “Stressed mouse dads give their offspring high blood sugar.”

That the effects were male-only was briefly noted in the study, yet “male” was absent from the “stress-F1 mice” label used after the initial mention. The male and female symbols in the diagrams were likewise applied to the parents but not the offspring in the study, and its misleading graphic was subsequently used by the news coverage.

The researchers provided no mechanisms that plausibly linked the effects to offspring sex. There was plenty of time between the May 3, 2015 submission and the February 18, 2016 publication to clarify this and other items. I wonder what the reviewer noted.

The second problem was that the highest number of male “stress-F1 mice” tested was 6. I didn’t see any disclosures of what led to the scarcity of subjects, or of the likely impact of using so few.

A related limitation was that the male “stress-F1 mice” were killed as young adults. Whether or not the hyperglycemic effects carried through to old age or to another generation wasn’t determined.

I’m leery of studies like this one that didn’t have a Limitations section, and especially so when the news coverage overlooked obvious limitations. It was difficult to place the findings in a context other than promoting that a male’s stress may also adversely affect their offspring.

One of the problems that research caught up in an agenda create is that non-headline findings are overlooked. Other than sex-specific effects, the study found that the putative preconception cause of hyperglycemia didn’t cause other symptoms:

  • “No significant growth defects were observed in male offspring from stress-F0 fathers (stress-F1 mice) during their early lives.
  • Insulin sensitivity was not changed in stress-F1 mice.
  • Serum glucagon, leptin, and pro-inflammatory cytokines (tumor necrosis factor α [TNFα], interleukin-6 [IL-6]) were unaffected.
  • Body weight, food intake, locomotor activity, CO2 production, O2 consumption, and respiratory exchange ratios also remained unchanged.
  • Liver weight, liver weight/body weight ratios, hepatic triglyceride content, and the histological phenotypes were also comparable.
  • The methylation pattern and expression of microRNAs were not affected in the fetal brains of stress-F1 mice.”

The handling of the study reminded me of Transgenerational epigenetic programming with stress and microRNA where most of the news coverage similarly focused on it being a male’s stress, not a female’s, that affected the developing embryo. The important part lost from news coverage of that study was it demonstrated how a damaging influence can begin immediately after conception, but the symptoms didn’t present until adulthood. “Paternal Psychological Stress Reprograms Hepatic Gluconeogenesis in Offspring”