Giving children allergies with pets

This 2021 human study investigated development and persistence of allergies:

“Allergic rhinitis (AR) is a common IgE-mediated disorder involving troublesome symptoms of nasal congestion, nasal itch, sneezing, and associated eye symptoms. Like many chronic health conditions, AR stems from complex gene–environment interactions.

130 subjects with AR were recruited. Control population included 154 healthy children who underwent a regular physical examination in the same ear, nose and throat clinic as AR patients. Individuals with history of asthma or atopic dermatitis were excluded.

AR analysis

Plenty of contradictory associations exist as whether furred pet exposure (cats and dogs) may be a risk or a protective factor for AR development. Discrepancies are likely due to the ubiquitous nature of pet allergens, while pet owners are more concerned about sanitation and many other hygiene-related reasons.

Interaction of early-life pet exposure with methylation level of ADAM33 increased the risk for AR onset 1.423 times more in children. This study provides evidence that:

  • Early-life pet exposure and low methylation level of ADAM33 increase AR risk in children; and
  • The interaction between pet exposure and methylation level of ADAM33 may play an important role in development of AR.”

https://aacijournal.biomedcentral.com/articles/10.1186/s13223-021-00526-5 “Interaction between early-life pet exposure and methylation pattern of ADAM33 on allergic rhinitis among children aged 3–6 years in China”


There’s nothing children can do about who their parents were. Exposing them to pet allergens, though, may be another example of early-life experiences causing lifelong effects.

Happy Mothers Day

This 2021 rodent study investigated effects on offspring of maternal high-fat diet (HFD) during gestation and lactation, and offspring HFD during young adulthood:

“We found that gestation was the most sensitive period to induce obesity in late life, and there was no difference between sexes in chance of obesity. Furthermore, we found that lactation and administration of a HFD post‐weaning increased incidence of lipid metabolism disorders and obesity in offspring.

gestational hfd effects on offspring

There are different windows of opportunity for programming epigenetically labile genes. Some studies support the alteration of epigenetic status during development as an important cause induced adult obesity.

Gestation is considered as the most sensitive period because high DNA synthesis and DNA methylation patterns are established for normal tissue development during the embryonic period. These two programming events are the times when the epigenetic state changes most widely in the life cycle.”

https://onlinelibrary.wiley.com/doi/10.1111/jcmm.16551 “Gestational high-fat diet impaired demethylation of Pparα and induced obesity of offspring”


Hey mothers! Do what you please. But don’t turn around and deny consequences of your behavior and choices on your descendants’ physiology and behavior, and possibly those of further descendants.

Gestation, birth, infancy, and early childhood are critical periods for humans. There’s no going back to correct errors and problems.

Part 2 of Broccoli sprouts activate the AMPK pathway

This 2021 review subject was metformin’s role in autophagy:

“Metformin had been used as the first choice for treating diabetes for almost a century. Autophagy is responsible for recycling and degrading cellular components, which significantly affects cell functions in physiology and pathology.

Effects of metformin on autophagy mainly depend on corresponding signaling pathways in specific organs or tissues. Metformin can induce autophagy in cells of many organs and tissues via affirmed signaling pathways, such as AMPK-related signaling pathways.

1-s2.0-S0753332221000718-gr5_lrg

Different signaling pathways (alone or in combination) mediated the process of metformin affecting autophagy in different organs or tissues. It is necessary to combine effects of metformin on autophagy with pharmacological effects on pathologies in different organs or tissues, which would provide indications for future metformin applications.”

https://www.sciencedirect.com/science/article/pii/S0753332221000718 “The effects of metformin on autophagy”


I characterized this review as Part 2 of Broccoli sprouts activate the AMPK pathway because that study’s experimental evidence showed sulforaphane activation of the AMPK pathway was a predecessor to sulforaphane’s main effects of Nrf2 pathway activation. This review didn’t even mention Nrf2 activation.

Do all of metformin’s cited effects apply to daily intake of broccoli sprouts? Probably not, but most people who take metformin every day aren’t healthy.

One aspect of research on short-chain fatty acids

To further understand An overlooked gut microbiota product, a 2018 rodent study found:

“Microbial metabolites short-chain fatty acids (SCFAs) have been implicated in gastrointestinal functional, neuroimmune regulation, and host metabolism, but their role in stress-induced behavioural and physiological alterations is poorly understood

SCFAs are primarily derived from fermentation of dietary fibres, and play a pivotal role in host gut, metabolic and immune function. All these factors have previously been demonstrated to be adversely affected by stress.

Administration of SCFAs to mice undergoing psychosocial stress alleviated enduring alterations in anhedonia and heightened stress-responsiveness, as well as stress-induced increases in intestinal permeability.

experimental design

SCFA treatment alleviated psychosocial stress-induced alterations in reward-seeking behaviour, and increased responsiveness to an acute stressor and in vivo intestinal permeability. In addition, SCFAs exhibited behavioural test-specific antidepressant and anxiolytic effects, which were not present when mice had also undergone psychosocial stress.”

https://physoc.onlinelibrary.wiley.com/doi/pdf/10.1113/JP276431 “Short-chain fatty acids: microbial metabolites that alleviate stress-induced brain–gut axis alterations”


One way researchers advance science is to relate aspects of their findings to previous studies. That approach works, but may miss items that weren’t covered in previous research.

This study fed specific quantities of three SCFAs – acetate, butyrate, and propionate – apparently due to previous research findings. If other SCFAs produced by gut microbiota were ignored – like crotonate (aka unsaturated butyrate) – how would that approach advance science?

I found this study from its citation in Harnessing endogenous defenses with broccoli sprouts.

An overlooked gut microbiota product

This 2021 review subject was histone crotonylation:

“Histone crotonylation is a newly identified epigenetic modification that has a pronounced ability to regulate gene expression. It belongs to an expanding group of short chain lysine acylations that also includes the extensively studied mark histone acetylation.

Histone Kcr was first identified in 2011 where it was found to be mainly associated with active chromatin. Kcr occurs on the ε-amino group of the lysine side chain, where it neutralizes the positive charge of this residue. The loss in positive charge on histone Lys residues weakens DNA interaction, thus making chromatin less compact and accessible to DNA-binding factors.

Crotonate, like other short chain fatty acids (SCFAs), is mainly produced by gut microbiota during fermentation of partially and nondigestible carbohydrates. Circulating SCFAs (acetate, crotonate, butyrate, and propionate) can be taken up by tissues and converted into their cognate short-chain acyl-CoAs, the direct donors of histone Lys acylations.

fcell-09-624914-g001

Crotonyl-CoA is generated as a by-product of fatty acid and amino acid metabolism. Synthesis of crotonyl-CoA can occur in mitochondria or the cytoplasm. Evidence suggests that histone acylations are directly sensitive to changes in concentrations of their corresponding acyl-CoA metabolites, and therefore can act as indicators of cellular metabolic state.

Only a small number of Kcr sites in human histones have been identified so far. This is in part due to a lack of commercially available Kcr site-specific antibodies, which has meant much of the research in this field has focused on studying total histone crotonylation. This is likely to limit our understanding of the importance of histone Kcr, as functional impact of modification at specific sites cannot be readily assessed.”

https://www.frontiersin.org/articles/10.3389/fcell.2021.624914/full “The Regulation and Function of Histone Crotonylation”


At first I thought I had missed recent studies of gut microbiota producing crotonate. Searching again for “crotonate” “microbiota” 2020 2021, I didn’t find any that weren’t cited by this paper.

A lack of research could be due to factors mentioned above. It may also be that researchers just don’t look for evidence of the circulating SCFA crotonate.

Broccoli sprouts’ immune effects

Two 2021 papers, with the first’s subject being sulforaphane’s immune effects:

“Effects of sulforaphane (SFN) on immune response generate scientific interest because of its bioavailability, which is much higher than other phytochemicals, and its capacity to induce Nrf2 target genes. Clinical trials suggest that sulforaphane produces favorable results in cases where pharmaceutical products fail.

SFN exhibits the highest bioavailability among well-known antioxidant phytochemicals, such as quercetin (20-fold higher) and curcumin (80-fold higher). SFN confers a high potential to be used either as a nutraceutical to improve health status, or as pharmaceutical to treat disease states.

molecules-26-00752-g001

Sulforaphane exerts a pleiotropic effect on immunological response, and the final effect depends on cell type.

  • In lymphocyte T-cells, SFN induces ROS production, GSH depletion, and repression of inflammatory cytokines, resulting in suppression of immune and inflammatory responses.
  • In monocytes and macrophages, SFN stimulates immune response by inducing Nrf2, thus triggering antioxidant and anti-inflammatory responses.”

https://www.mdpi.com/1420-3049/26/3/752/htm “Potential of Sulforaphane as a Natural Immune System Enhancer: A Review”


A second study was Fertilization and Pre-Sowing Seed Soaking Affect Yield and Mineral Nutrients of Ten Microgreen Species:

“Ten tested microgreen species [amaranth, arugula, basil, broccoli, red cabbage, Daikon radish, kale, kohlrabi, mustard, and green pea] in this study varied in fresh and dry shoot weights, shoot height, and mineral nutrient concentrations.”

This study grew sprouts for 6 – 18 days before harvesting. Its study design didn’t require sampling along the way to discover informative compositional changes, as did 2020’s 3-day-old broccoli sprouts have the optimal yields and Broccoli sprout compounds include sinapic acid derivatives.

Their supplier was the same as I used for broccoli and red cabbage seeds. No endorsement is intended.

I’d rather use an unknown broccoli variety than this study’s broccoli cultivar, Waltham 29. It was found to be relatively glucoraphanin-deficient when measured in a 2004 study referenced in Tailoring measurements for broccoli sprouts, 32nd of 34 tested.

Received these today:

PXL_20210424_191628875

I’ve asked for clarification of the red cabbage seed variety I received. Not sure what “Agnostic” means in a “Red Cabbage Microgreen – Agnostic” context. 🙂

Mustard and red cabbage sprouting will follow Improving healthy compounds of broccoli sprouts efforts, minus that study’s laboratory setup and duration. I expect synergistic effects from handling both species’ sprouts with my protocol for microwaved 3-day-old broccoli sprouts.

Improving healthy compounds of broccoli sprouts

This 2020 study investigated known and experimental effects on sprouted broccoli, white mustard, red radish, and red cabbage compounds:

“We planned development of cruciferous sprouts in hydroponics elicited with LED lighting and Methyl-Jasmonate (MeJA) to bio-stimulate production of glucosinolates, comparing effects of two types of LEDs designed for indoor food production systems.

We aimed to gain knowledge on response (germination rate, biomass yield) and phytochemical composition of fresh edible sprouts of cruciferous varieties (broccoli, radish, cabbage and mustard) under these conditions for future food production recommendations:

  • Use of LED lights to grow edible cruciferous sprouts was positive in terms of biomass production and phytochemical content (glucosinolates) without any negative effects.
  • Use of MeJA was positive, confirming previous results. Intensity of response for different species is useful to focus production of sprouts for specific purposes.

3-day old sprouts were placed in a growth chamber with controlled conditions (Photoperiod 18/6 h; temperature 24/18 °C; and relative humidity 60/80%), irrigated every other day to maintain enough humidity in substrate, using 1% bleach in distilled water, and collected on day 7. Trays of germinating seeds were evenly sprayed daily with 10 mL of solution for 4 days.

4 sprouts glusosinolates affected by LED and MeJa

Total Glucosinolates (mg/100 g fresh weight) of White Mustard, Broccoli, Red Cabbage and Red Radish sprouts, under two different LED lightings, and elicited with MeJA (250 μM).

Combining MeJA spraying with different LED light treatment showed clear increases in total glucosinolate contents for all studied sprouts when sprayed for 4 days with MeJA 250 μM.”

https://www.mdpi.com/2504-3900/70/1/67 “The Quality and Glucosinolate Composition of Cruciferous Sprouts under Elicitor Treatments Using MeJA and LED Lights”


The research group of Our model clinical trial for Changing to a youthful phenotype with broccoli sprouts keep ramping it up. They’ve published studies of MeJA effects and LED effects on sprouts separately, but not combined like this one did.

I ordered a pound of red cabbage seeds to see how I like their 3-day-old sprouts. I started soaking mustard seeds purchased from a grocery store’s spice section last year to see if they’ll sprout.

Although effects in the above graphic are compelling, I don’t want to turn my kitchen into a laboratory with LED lights and MeJA treatments. I’ll first see if red cabbage and mustard sprouts are tolerable.

Repositioning DNA methylation

This 2021 human study found:

“We report on a randomized controlled clinical trial conducted among 43 healthy adult males between the ages of 50-72. The 8-week treatment program included diet, sleep, exercise and relaxation guidance, and supplemental probiotics and phytonutrients.

This is the first randomized controlled study to suggest that specific diet and lifestyle interventions may reverse Horvath DNAmAge (2013) epigenetic aging in healthy adult males. Larger-scale and longer duration clinical trials are needed to confirm these findings, as well as investigation in other human populations.

aging-v13iundefined-202913-figure-f3

In both treatment and control groups, there was no net increase or decrease in methylation of 353 sites that compose the Horvath clock. This finding suggests that intervention did not lead to an overall increase in methylation of Horvath clock sites, but rather it prompted a repositioning of clock CpG methylation patterns consistent with a younger biological age.

One significant limitation of this pilot trial is limited statistical power due to relatively small sample size. It is not yet fully established whether interventions that slow any methylation clocks necessarily curtail risks of age-related disease.”

https://www.aging-us.com/article/202913/text “Potential reversal of epigenetic age using a diet and lifestyle intervention: a pilot randomized clinical trial”


Baffled as to why these researchers relied on 2013 research rather than at least Dr. Horvath’s improved 2018 skin and blood clock, a review of which noted:

“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.”

Which would you prefer? A 2013 flip phone, or a 2018 smartphone?

A bat epigenetic clock

This 2021 study subject was bats:

“Exceptionally long-lived species, including many bats, rarely show overt signs of aging, making it difficult to determine why species differ in lifespan. Here, we use DNA methylation (DNAm) profiles from 712 known-age bats, representing 26 species, to identify epigenetic changes associated with age and longevity.

Hypermethylated age- and longevity-associated sites are disproportionately located in promoter regions of key transcription factors (TF) and enriched for histone and chromatin features associated with transcriptional regulation. Predicted TF binding site motifs and enrichment analyses indicate that:

  • Age-related methylation change is influenced by developmental processes, while
  • Longevity-related DNAm change is associated with innate immunity or tumorigenesis genes, suggesting that
  • Bat longevity results from augmented immune response and cancer suppression.

Molossus molossus [a short-lived species] age genes are not enriched for immunity genes or genes that frequently mutated in cancer. However, M. molossus longevity genes exhibit significant overlap with genes involved in immunity and genes frequently mutated in human tumors.

Similar overlap patterns among immunity, longevity, and tumor-mutated genes also exist for long-lived bats.

Two species’ genetic adaptations for tumor suppression have been described to help explain their extreme longevity. Bats also have genetic mechanisms that enable strong antiviral immune responses without inducing damaging inflammatory reactions that may enable them to tolerate high levels of viral exposure.

Our results are consistent with an epigenetic clock theory of aging that connects beneficial developmental and cell maintenance processes to detrimental processes causing tissue dysfunction.”

https://www.nature.com/articles/s41467-021-21900-2 “DNA methylation predicts age and provides insight into exceptional longevity of bats”


The founder of the epigenetic clock has been busy, coauthoring more published studies than there have been weeks in this year! I’ve read five other 2021 studies he’s coauthored on dogs, horses, mammals (2), and humans in DNA methylation biomarker for cumulative lead exposure is associated with Parkinson’s disease. This one stood out for its “longevity results from augmented immune response and cancer suppression” findings.

If we’re interested in longevity, this clarity can direct efforts to both improve our immune systems and avoid problems like cancer. Symptoms may be subclinical, but that doesn’t provide adequate rationale to not address causes.

Peer review comments and responses were informative:

Reviewer #1 – “Developing an aging clock that works for a diverse set of bat species is a spectacular achievement.”

Reviewer #2 – “This is a tour de force study.”

Replies to Reviewer #3:

“Difference in recorded lifespans between three long-lived species and two short-lived species that we used to identify longevity DMPs [differentially methylated positions] is 20 years or more, even though they have similar body sizes (20-40 g). The three long-lived species [maximum ages 29.9, 30.5, and 37.1 years] also represent three different phylogenetic lineages.

CpG sites that undergo hypomethylation with age do so largely at random. In contrast, sites that undergo hypermethylation with age are highly nonrandom, and as has been noted before, are near genes associated with development. So yes, we believe there are predictable methylation changes with age.”

Gut microbiota topics

Here are thirty 2019 and 2020 papers related to Switch on your Nrf2 signaling pathway topics. Started gathering research on this particular theme three months ago.

There are more researchers alive today than in the sum of all history, and they’re publishing. I can’t keep up with the torrent of interesting papers.

on

2020 A prebiotic fructo-oligosaccharide promotes tight junction assembly in intestinal epithelial cells via an AMPK-dependent pathway

2019 Polyphenols and Intestinal Permeability: Rationale and Future Perspectives

2020 Prebiotic effect of dietary polyphenols: A systematic review

2019 Protease‐activated receptor signaling in intestinal permeability regulation

2020 Intestinal vitamin D receptor signaling ameliorates dextran sulfate sodium‐induced colitis by suppressing necroptosis of intestinal epithelial cells

2019 Intestinal epithelial cells: at the interface of the microbiota and mucosal immunity

2020 The Immature Gut Barrier and Its Importance in Establishing Immunity in Newborn Mammals

2019 Prebiotics and the Modulation on the Microbiota-GALT-Brain Axis

2019 Prebiotics, Probiotics, and Bacterial Infections

2020 Vitamin D Modulates Intestinal Microbiota in Inflammatory Bowel Diseases

2020 Microbial tryptophan metabolites regulate gut barrier function via the aryl hydrocarbon receptor

2019 Involvement of Astrocytes in the Process of Metabolic Syndrome

2020 Intestinal Bacteria Maintain Adult Enteric Nervous System and Nitrergic Neurons via Toll-like Receptor 2-induced Neurogenesis in Mice (not freely available)

2019 Akkermansia muciniphila ameliorates the age-related decline in colonic mucus thickness and attenuates immune activation in accelerated aging Ercc1−/Δ7 mice

2020 Plasticity of Paneth cells and their ability to regulate intestinal stem cells

2020 Coagulopathy associated with COVID-19 – Perspectives & Preventive strategies using a biological response modifier Glucan

2020 Synergy between Cell Surface Glycosidases and Glycan-Binding Proteins Dictates the Utilization of Specific Beta(1,3)-Glucans by Human Gut Bacteroides

2020 Shaping the Innate Immune Response by Dietary Glucans: Any Role in the Control of Cancer?

2020 Systemic microbial TLR2 agonists induce neurodegeneration in Alzheimer’s disease mice

2019 Prebiotic supplementation in frail older people affects specific gut microbiota taxa but not global diversity

2020 Effectiveness of probiotics, prebiotics, and prebiotic‐like components in common functional foods

2020 Postbiotics-A Step Beyond Pre- and Probiotics

2019 Pain regulation by gut microbiota: molecular mechanisms and therapeutic potential

2020 Postbiotics: Metabolites and mechanisms involved in microbiota-host interactions

2020 Postbiotics against Pathogens Commonly Involved in Pediatric Infectious Diseases

2019 Glutamatergic Signaling Along The Microbiota-Gut-Brain Axis

2019 Lipoteichoic acid from the cell wall of a heat killed Lactobacillus paracasei D3-5 ameliorates aging-related leaky gut, inflammation and improves physical and cognitive functions: from C. elegans to mice

2020 Live and heat-killed cells of Lactobacillus plantarum Zhang-LL ease symptoms of chronic ulcerative colitis induced by dextran sulfate sodium in rats

2019 Health Benefits of Heat-Killed (Tyndallized) Probiotics: An Overview

2020 New Horizons in Microbiota and Metabolic Health Research (not freely available)

Long-lasting benefits of a common vaccine

This 2021 review subject was effects of the 100-year-old tuberculosis vaccine:

“Bacillus Calmette-Guerin (BCG) vaccine is one of the most widely used vaccines. It protects against many non-mycobacterial infections secondary to its nonspecific immune effects.

The mechanism for these effects includes modification of innate and adaptive immunity. BCG vaccine is known to not only boost immune responses to many vaccines when they are co-administered, but also decreases severity of these infections when used alone.

Alteration in innate immunity is through histone modifications and epigenetic reprogramming of monocytes to develop an inflammatory phenotype, a process called trained immunity. Memory T cells of adaptive immunity are also responsible for resistance against secondary infections after administration of BCG vaccine, a process called heterologous immunity.

The PI3K/AKT pathway, another pathway for mediating immunity, was upregulated. This was supported by recent studies demonstrating its involvement in induction of trained immunity by both BCG and β-glucan.

BCG vaccine can modify both innate and adaptive immunity, and provide immunity not only against Mycobacterium tuberculosis but also other pathogens. Heterologous immunity and trained immunity contribute to pathophysiologic mechanisms which explain how a vaccine protects against unrelated pathogens.”

https://www.amjmedsci.org/article/S0002-9629(21)00092-6/fulltext “Bacillus Calmette-Guerin Vaccine and Nonspecific Immunity”


As inferred by “induction of trained immunity by both BCG and β-glucan” many of these findings also apply to yeast cell wall β-glucan treatments. See Choosing your future with β-glucan for a representative study.

Our first 1000 days

This 2021 review subject was a measurable aspect of our early lives:

“The first 1000 days from conception are a sensitive period for human development programming. During this period, environmental exposures may result in long-lasting epigenetic imprints that contribute to future developmental trajectories.

The present review reports on effects of adverse and protective environmental conditions occurring on glucocorticoid receptor gene (NR3C1) regulation in humans. Thirty-four studies were included.

The hypothalamic-pituitary-adrenal (HPA) axis is key in regulating mobilization of energy. It is involved in stress reactivity and regulation, and it supports development of behavioral, cognitive, and socio-emotional domains.

The NR3C1 gene encodes for specific glucocorticoid receptors (GRs) in the mammalian brain, and it is epigenetically regulated by environmental exposures.

When mixed stressful conditions were not differentiated for their effects on NR3C1 methylation, no significant results were obtained, which speaks in favor of specificity of epigenetic vestiges of different adverse conditions. Specific maternal behaviors and caregiving actions – such as breastfeeding, sensitive and contingent interactive behavior, and gentle touch – consistently correlated with decreased NR3C1 methylation.

If the neuroendocrine system of a developing fetus and infant is particularly sensitive to environmental stimulations, this model may provide the epigenetic basis to inform promotion of family-centered prevention, treatment, and supportive interventions for at-risk conditions. A more ambiguous picture emerged for later effects of NR3C1 methylation on developmental outcomes during infancy and childhood, suggesting that future research should favor epigenome-wide approaches to long-term epigenetic programming in humans.”

https://www.sciencedirect.com/science/article/abs/pii/S0149763421001081 “Glucocorticoid receptor gene (NR3C1) methylation during the first thousand days: Environmental exposures and developmental outcomes” (not freely available). Thanks to Dr. Livio Provenci for providing a copy.


I respectfully disagree with recommendations for an EWAS approach during infancy and childhood. What happened to each of us wasn’t necessarily applicable to a group. Group statistics may make interesting research topics, but they won’t change anything for each individual.

Regarding treatment, our individual experiences and needs during our first 1000 days should be repeatedly sensed and felt in order to be therapeutic. Those memories are embedded in our needs because cognitive aspects of our brains weren’t developed then.

To become curative, we first sense and feel early needs and experiences. Later, we understand their contributions and continuations in our emotions, behavior, and thinking.

And then we can start to change who we were made into.

Rhythmicity

This 2021 review subject was circadian signaling in the digestive system:

“The circadian system controls diurnal rhythms in gastrointestinal digestion, absorption, motility, hormones, barrier function, and gut microbiota. The master clock, located in the suprachiasmatic nucleus (SCN) region of the hypothalamus, is synchronized or entrained by the light–dark cycle and, in turn, synchronizes clocks present in peripheral tissues and organs.

Rhythmic clock gene expression can be observed in almost every cell outside the SCN. These rhythms persist in culture, indicating that these cells also contain an endogenous circadian clock system.

Processes in the gastrointestinal tract and its accessory digestive organs display 24-hour rhythmicity:

Clock disruption has been associated with disturbances in gut motility. In an 8-day randomized crossover study, in which 14 healthy young adults were subjected to simulated day-shift or night-shift sleeping schedules, circadian misalignment increased postprandial hunger hormone ghrelin levels by 10.4%.

Leptin, a satiety hormone produced by white adipose tissue, peaks at night in human plasma. A volunteer ate and slept at all phases of the circadian cycle by scheduling seven recurring 28-hour ‘days’ in dim light and eating four isocaloric meals every ‘day’. Plasma leptin levels followed the forced 28-hour behavioural cycle, while their endogenous 24-hour rhythm was lost. However, since meal timing can entrain the circadian system, this forced desynchrony study could not exclude a potential role of the circadian system.

Another constant routine protocol study with 20 healthy participants showed that rhythms in plasma lipids differed substantially between individuals, suggesting the existence of different circadian metabolic phenotypes.

Composition, function, and absolute abundance of gut microbiota oscillate diurnally. For example, microbial pathways involved in cell growth, DNA repair and energy metabolism peaked during the dark phase, while detoxification, environmental sensing and motility peaked during the day.

It is unclear how phase information is communicated to gut microbiota. However, human commensal bacterium Enterobacter aerogenes showed an endogenous, temperature-compensated 24-hour pattern of swarming and motility in response to melatonin, suggesting that the host circadian system might regulate microbiota by entraining bacterial clocks.

With increasing popularity of time-restricted eating as a dietary intervention, which entrains peripheral clocks of the gastrointestinal tract, studies investigating circadian clocks in the human digestive system are highly needed. Additionally, further research is needed to comprehend shifts in temporal relationships between different gut hormones during chronodisruption.”

https://www.nature.com/articles/s41575-020-00401-5 “Circadian clocks in the digestive system” (not freely available). Thanks to Dr. Inge Depoortere for providing a copy.


This review included many more human examples. I mainly quoted gut interactions.

A long time ago I was successively stationed on four submarines. An 18-hour schedule while underwater for weeks and months wiped out my circadian rhythms.

The U.S. Navy got around to studying 18-hour schedule effects this century. In 2014, submarine Commanding Officers were reportedly authorized to switch their crews to a 24-hour schedule.

Surface! Surface! Surface!

Adaptive and innate immunity

Two 2021 reviews presented aspects of human immune systems:

“The adaptive immune system’s challenge is to protect the host through generation and differentiation of pathogen‐specific short‐lived effector T cells, while in parallel developing long‐lived memory cells to control future encounters with the same pathogen.

The system highly relies on self‐renewal of naïve and memory T cells, which is robust, but eventually fails. Genetic and epigenetic modifications contribute to functional differences in responsiveness and differentiation potential.

Less than 20% of nascent T cells are produced from the thymus in young adults, which dwindles to less than 1% after the age of 50 years. Even in young adults, the majority of T cells are produced in the periphery. A pickup in proliferation has been described in late life, possibly as a consequence of increased cell death and evolving lymphopenia.

One challenge of the aging process is to replenish cells while keeping integrity of the organ. The dynamic lymphoid system employs a vast number of T cells (>1011) and maintains a balance between cell production, death, and differentiation.

Enormous TCR ( T cell receptor) diversity is required to be able to respond to the universe of possible peptides (>209). Only T cell generation in the thymus can add new TCR specificities. Homoeostatic proliferation at best maintains diversity, >108 unique TCRs in a given adult.

Antigen-specific memory T cells adopt several fates with age:

  • Decrease in stem-like memory T cells;
  • Increase in NK (natural killer) cell-like TEMRA (terminally differentiated effector T cells);
  • Increase in exhausted T cells;
  • Increase in short-lived effector memory T cells; and
  • Decrease in tissue-residing T memory cells.

Virtual memory T cells without prior experience of antigen encounter also increase with age.”

https://febs.onlinelibrary.wiley.com/doi/epdf/10.1111/febs.15770 “Hallmarks of the aging T cell system”


“Trained immunity is characterized by long‐term functional reprogramming of innate immune cells following challenge with pathogens or microbial ligands during infection or vaccination. This cellular reprogramming leads to increased responsiveness upon re‐stimulation, and is mediated through epigenetic and metabolic modifications.

Trained immunity has been shown to last for at least 3 months and up to 1 year, while heterologous protection against infections can last for at least 5 years. These long-term effects are mediated through reprogramming of myeloid progenitor cells in bone marrow, which in turn generate myeloid cells with a trained immunity phenotype.

Molecular mechanisms underlying trained immunity, for example induced by β‐glucan or Bacille Calmette‐Guérin (BCG) vaccination, can be investigated by using and integrating different layers of information, including genome, epigenome, transcriptome, proteome, metabolome, microbiome, immune cell phenotyping and function. Interplay between epigenetic and metabolic reprogramming is necessary for induction of trained immunity, as certain metabolites have a direct effect on enzymes involved in epigenetic remodeling.

High-throughput methods allow researchers to use an unbiased approach examining many potential genes or markers in relation to health and disease, rather than examining a limited number of candidate genes or markers.

One strength of integrating multiple levels of data is an increased power to identify key regulatory molecular networks driving trained immunity. For example, results obtained from one level (i.e. genes) can be used to reduce the number of traits to test in a second level (i.e. proteins), thereby increasing power.

One important pitfall when it comes to designing effective omics studies, is sample size. With a large number of markers measured, and the relatively small contributing effect size of individual analytes, the risks of both type 1 and 2 errors are high without sufficient sample sizes for both discovery and validation cohorts.”

https://onlinelibrary.wiley.com/doi/pdf/10.1002/eji.202048882 “Resolving trained immunity with systems biology”

Eat broccoli sprouts to prevent lung infections

A 2021 rodent study investigated lung infections:

“Mycobacterium avium complex (MAC) is the most common cause of pulmonary nontuberculous mycobacteria disease worldwide. It is thought that both environmental exposure and host susceptibility are required for the establishment of pulmonary MAC disease, because pulmonary MAC diseases are most commonly observed in slender, postmenopausal women without a clearly recognized immunodeficiency.

Host factors that regulate MAC susceptibility have not been elucidated until now. The Nrf2 system is activated in alveolar macrophages, the most important cells during MAC infection, as both the main reservoir of infection and bacillus-killing cells.

Treatment with sulforaphane (SFN) decreases Mycobacterium growth upregulating the expression of Nramp1 (natural resistance-associated macrophage protein 1, a susceptibility gene for pulmonary nontuberculous mycobacteria disease) and HO-1 (heme oxygenase 1). Mycobacterial counts in the lung, liver, and spleen were reduced after SFN treatment.

These results indicate that Nramp1 and HO-1, regulated by Nrf2, are essential in defending against MAC infection due to the promotion of phagolysosome fusion and granuloma formation, respectively. Nrf2 is thought to be a critical determinant of host resistance to MAC infection.”

https://mbio.asm.org/content/12/1/e01947-20 “Nrf2 Regulates Granuloma Formation and Macrophage Activation during Mycobacterium avium Infection via Mediating Nramp1 and HO-1 Expressions”