Broccoli sprouts activate the AMPK pathway, Part 4

Today someone viewed the 2020 Part 3 of Broccoli sprouts activate the AMPK pathway which lacked citations at the time. Checking again, here are three citing 2022 papers, starting with a review:

“Nrf2 is an important transcription factor that regulates expression of a large number of genes in healthy and disease states. Nrf2 regulates expression of several key components of oxidative stress, mitochondrial biogenesis, mitophagy, autophagy, and mitochondrial function in all organs of the human body, and in the peripheral and central nervous systems.

Overall, therapeutic drugs including sulforaphane that target Nrf2 expression and Nrf2/ARE pathway are promising. This article proposes additional research in Nrf2’s role within Parkinson’s disease, Huntington’s disease, and ischemic stroke in preclinical mouse models and humans with age-related neurodegenerative diseases.” “Role of Nrf2 in aging, Alzheimer’s and other neurodegenerative diseases” (not freely available) Thanks to Dr. P. Hemachandra Reddy for providing a copy.

One of the Part 3 study’s coauthors contributed to this very detailed review:

“Due to observed overlapping cellular responses upon AMPK or NRF2 activation and common stressors impinging on both AMPK and NRF2 signaling, it is plausible to assume that AMPK and NRF2 signaling may interdepend and cooperate to readjust cellular homeostasis.


The outcome and underlying signaling events of AMPK-NRF2 crosstalk may diverge between:

  1. in vitro and in vivo studies (one cell type in isolation vs inter-organ crosstalk in living organisms);
  2. Different cell types/organs/organisms of different cultivation conditions, genetic background, age or sex;
  3. Different stress-regimens (chronic vs acute, nature of stress (lipotoxicity, redox stress, xenobiotic, starvation, etc));
  4. Different modes of Nrf2 or AMPK activation and inhibition (genetic vs pharmacological, constitutive vs transient/intermittent, systemic vs organ-specific, electrophilic vs PPI, allosteric vs covalent, or pan vs subtype-specific);
  5. Different target genes with distinct promoter and enhancer structure; or
  6. Different timing of activation.

The latter should deserve increased attention as Nrf2 is one of the most cycling genes under control of the circadian clock. Feeding behavior, metabolism and hence AMPK activity follow and substantiate the biological clock, indicating an entangled circadian regulation of metabolic and redox homeostasis.” “AMPK and NRF2: Interactive players in the same team for cellular homeostasis?”

A third citing paper was a study of lens cells that provided an example of similar metformin effects noted in Part 2 of Broccoli sprouts activate the AMPK pathway:

“Loss of Nrf2 and Nrf2 antioxidant genes expression and activity in aging cells leads to an array of oxidative-induced deleterious responses, impaired function, and aging pathologies. This deterioration is proposed to be the primary risk factor for age-related diseases such as cataracts.

AMPK regulates energy at physiological levels during metabolic imbalance and stress. AMPK is a redox sensing molecule, and can be activated under cellular accumulation of reactive oxygen species, which are endogenously produced due to loss of antioxidant enzymes.

The therapeutic potential of AMPK activation has context-dependent beneficial effects, from cell survival to cell death. AMPK activation was a requisite for Bmal1/Nrf2-antioxidants-mediated defense, as pharmacologically inactivating AMPK impeded metformin’s effect.

Using lens epithelial cell lines (LECs) of human or mouse aging primary LECs along with lenses as model systems, we demonstrated that metformin could correct deteriorated Bmal1/Nrf2/ARE pathway by reviving AMPK-activation and transcriptional activities of Bmal1/Nrf2, resulting in increased antioxidants enzymatic activity and expression of Phase II enzymes. Results uncovered crosstalk between AMPK and Bmal1/Nrf2/antioxidants mediated by metformin for blunting oxidative/aging-linked pathobiology.” “Obligatory Role of AMPK Activation and Antioxidant Defense Pathway in the Regulatory Effects of Metformin on Cellular Protection and Prevention of Lens Opacity”


If you were given a lens to see clearly, would you accept it?

Two papers, starting with a 2022 rodent study of maternal behaviors’ effects on offspring physiologies:

Early life adversity (ELA) is a major risk factor for development of pathology. Predictability of parental care may be a distinguishing feature of different forms of ELA.

We tested the hypothesis that changes in maternal behavior in mice would be contingent on the type of ELA experienced, directly comparing predictability of care in the limited bedding and nesting (LBN) and maternal separation (MS) paradigms. We then tested whether predictability of the ELA environment altered expression of corticotropin-releasing hormone (Crh), a sexually-dimorphic neuropeptide that regulates threat-related learning.

MS was associated with increased expression of Crh-related genes in males, but not females. LBN primarily increased expression of these genes in females, but not males.” “Resource scarcity but not maternal separation provokes unpredictable maternal care sequences in mice and both upregulate Crh-associated gene expression in the amygdala”

I came across this first study by it citing a republished version of 2005 epigenetic research from McGill University:

“Early experience permanently alters behavior and physiology. A critical question concerns the mechanism of these environmental programming effects.

We propose that epigenomic changes serve as an intermediate process that imprints dynamic environmental experiences on the fixed genome resulting in stable alterations in phenotype. These findings demonstrate that structural modifications of DNA can be established through environmental programming and that, in spite of the inherent stability of this epigenomic marker, it is dynamic and potentially reversible.” “Environmental programming of stress responses through DNA methylation: life at the interface between a dynamic environment and a fixed genome”

This post commemorates the five-year anniversary of Dr. Arthur Janov’s death. Its title is taken from my reaction to his comment on Beyond Belief: Symptoms of hopelessness. Search his blog for mentions of the second paper’s coauthors, Drs. Meaney and Szyf.


All about walnuts’ effects

Five 2022 papers focusing on walnuts, starting with a comparison of eight tree nuts:

“The aim of the present study was to examine 8 different popular nuts – pecan, pine, hazelnuts, pistachio, almonds, cashew, walnuts, and macadamia. Total content of phenolic compounds in nuts ranged from 5.9 (pistachio) to 432.9 (walnuts) mg/100 g.

Walnuts had the highest content of polymeric procyanidins, which are of great interest as important compounds in nutrition and biological activity, as they exhibit antioxidant, anti-inflammatory, antimicrobial, cardio- and neuroprotective action. Walnuts are good sources of fatty acids, especially omega-3 and omega-6.” “Nuts as functional foods: Variation of nutritional and phytochemical profiles and their in vitro bioactive properties”

A second study compared the same eight tree nuts plus Brazil nuts and peanuts:

“The highest total content of all analyzed flavonoids was determined in walnuts (114.861 µg/g) with epicatechin the most abundant, while the lowest was in almonds (1.717 µg/g). Epicatechin has antioxidant, anti-inflammatory, antitumor, and anti-diabetic properties. Epicatechin has beneficial effects on the nervous system, enhances muscle performance, and improves cardiac function.” “The Content of Phenolic Compounds and Mineral Elements in Edible Nuts”

Next, two systematic reviews and meta-analyses of human studies:

“We carried out a systematic review of cohort studies and randomized controlled trials (RCTs) investigating walnut consumption, compared with no or lower walnut consumption, including those with subjects from within the general population and those with existing health conditions, published from 2017 to 5 May 2021.

  • Evidence published since 2017 is consistent with previous research suggesting that walnut consumption improves lipid profiles and is associated with reduced CVD risk.
  • Evidence pointing to effects on blood pressure, inflammation, hemostatic markers, and glucose metabolism remains conflicting.
  • Evidence from human studies showing that walnut consumption may benefit cognitive health, which is needed to corroborate findings from animal studies, is now beginning to accumulate.” “Walnut consumption and health outcomes with public health relevance – a systematic review of cohort studies and randomized controlled trials published from 2017 to present”

“We aimed to perform a systematic review and meta-analysis of RCTs to thoroughly assess data concerning effects of walnut intake on selected markers of inflammation and metabolic syndrome in mature adults. Our findings showed that:

  • Walnut-enriched diets significantly decreased TG, TC, and LDL-C concentrations, while HDL-C levels were not significantly affected.
  • No significant changes were noticed on anthropometric, cardiometabolic, and glycemic indices after higher walnut consumption.
  • Inflammatory biomarkers did not record statistically significant results.” “Walnut Intake Interventions Targeting Biomarkers of Metabolic Syndrome and Inflammation in Middle-Aged and Older Adults: A Systematic Review and Meta-Analysis of Randomized Controlled Trials”

Finishing with a rodent study that gave subjects diabetes with a high-fat diet, then mixed two concentrations of walnut extract in with the treatment groups’ chow:

“This study was conducted to evaluate the protective effect of Gimcheon 1ho cultivar walnut (GC) on cerebral disorder by insulin resistance, oxidative stress, and inflammation in HFD-induced diabetic disorder mice. After HFD feed was supplied for 12 weeks, samples were orally ingested for 4 weeks to GC20 and GC50 groups (20 and 50 mg/kg of body weight, respectively).

  • Administration of GC improved mitochondrial membrane potential function, and suppressed oxidative stress in the brain.
  • GC inhibited hepatic and cerebral lipid peroxidation and the formation of serum AGEs, and increased serum antioxidant activity to improve HFD-induced oxidative stress.
  • The HFD group showed significant memory impairment in behavioral tests. On the other hand, administration of GC showed improvement in spatial learning and memory function.

walnut brain effects

Based on these physiological activities, GC showed protective effects against HFD-induced diabetic dysfunctions through complex and diverse pathways.” “Walnut Prevents Cognitive Impairment by Regulating the Synaptic and Mitochondrial Dysfunction via JNK Signaling and Apoptosis Pathway in High-Fat Diet-Induced C57BL/6 Mice”

How do you like my sand art?PXL_20221016_154923750

Another use of a routine blood test

A 2022 human study investigated three measurements of the CBC with Differential/Platelet test:

“This study explored the relationship between the systemic immune-inflammation index (SII) and stroke prognosis. SII was defined as neutrophils × platelets/lymphocytes. Neutrophils and lymphocytes are involved in the inflammatory and immune response, whereas platelets have a primary role in the thrombo-inflammation of stroke.

Patients were divided into four groups according to SII values: quartile (Q)1 <366; Q2 366–533; Q3 534–799; and Q4 ≥800. As the SII quartile increased, patients with acute ischemic stroke were more likely to have poor functional outcomes during follow-up.

Although age, smoking status, and alcohol consumption are risk factors, and female estrogen is a protective factor for stroke, we did not identify subgroups specifically being affected by these factors. Even if we adjusted our model for factors identified by previous studies as immune-inflammation markers that might affect prognosis, such as the high-sensitivity C-reactive protein level, our results still suggested that SII is closely related to short- and long-term prognosis of patients with acute ischemic stroke.

As a new type of immune-inflammation index, the SII integrates neutrophils, platelets, and lymphocytes, and can reflect the balance of the systemic immune response and inflammatory response.” “Correlation of the systemic immune-inflammation index with short- and long-term prognosis after acute ischemic stroke”


Don’t bother eating broccoli sprouts if you’re old?

I try to not curate research that wastes resources. Couldn’t help but present this 2022 rodent study:

“We aimed to evaluate if sulforaphane (SFN) long-term treatment was able to prevent age-associated cognitive decline in adult (15-month-old) and old (21-month-old) female and male rats.

Our results showed that SFN restored redox homeostasis in brain cortex and hippocampus of adult rats, preventing cognitive decline in both sexes. However, redox responses were not the same in males and females.

Old rats were not able to recover their redox state as adults did, but they had a mild improvement. These results suggest that SFN mainly prevents rather than reverts neural damage; though, there might also be a range of opportunities to use hormetins like SFN, to improve redox modulation in old animals.” “Long-term sulforaphane-treatment restores redox homeostasis and prevents cognitive decline in middleaged female and male rats, but cannot revert previous damage in old animals” (not freely available)

These researchers cited Sulforaphane in the Goldilocks zone for hormetic effects of sulforaphane, so I asked:

“Did you develop any preliminary dose/response data for stating ‘there might also be a range of opportunities to use hormetins like SFN to improve redox modulation in old animals’?”

They cited Broccoli sprouts activate the AMPK pathway for long-term effects of a small sulforaphane dose, so I asked:

“Also, the three studies cited for ‘0.5 mg/Kg, i.e. 2.82 μmol/Kg BW for 3 months’ were all mouse studies. Since this was a rat study, wouldn’t there be increased dose and duration equivalencies?”

I’ll update this blog post in the event either of my questions to these researchers are answered.


Sulforaphane nose drops

This 2022 rodent study compared capabilities of intranasal nanoparticle sulforaphane and free sulforaphane to mitigate brain damage caused by a common cancer treatment:

“Non-invasive intranasal (IN) trafficking of therapeutic agents with nanocarriers can enhance efficacy of drug delivery, biodistribution, bioavailability, and absorption against enzymatic degradation and extracellular transportation. Direct IN trafficking of nanocarriers is expected to reduce drug wastage, administration frequency, and undesirable adverse effects.

The nasal route for brain-targeted delivery of sulforaphane (SF) loaded within iron oxide nanoparticles (Fe3O4-NPs) was based on improving physicochemical stability of SF, and to enhance its bioavailability by avoiding oral route drawbacks like extensive first-pass metabolism and intestinal drug degradation.

Cisplatin (CIS) significantly induced a significant increase in acetylcholinesterase activities and lipid peroxides, and a significant decrement in glutathione and nitric oxide contents. We aimed to explore the nanotherapeutic potential of intranasally delivered SF loaded within Fe3O4-NPs (N.SF) against CIS-induced neurotoxicity through different biochemical, behavioral, and histological investigations.

hippocampus damage

Treatment with N.SF was more capable of mitigating both CIS-induced striatal and cortical injuries. IN treatment with either SF or N.SF showed equal alleviative potential regarding CIS-induced hippocampal or cerebellar injury.

These encouraging results demonstrated the potential use of iron-oxide NPs as neurotherapeutic agents, and confirmed the possibility of developing a novel promising and non-invasive intranasal delivery system for treatment of CIS-induced neurotoxicity.” “Neuroprotective Potential of Intranasally Delivered Sulforaphane-Loaded Iron Oxide Nanoparticles Against Cisplatin-Induced Neurotoxicity”

I found this study from it citing a paper in Do broccoli sprouts treat migraines?


If you lose mobility, you lose cognitive function

This 2022 human study used four epigenetic clocks to assess aging:

“This cohort study was a secondary analysis of 3 Women’s Health Initiative (WHI) ancillary studies among 1813 women eligible to survive to age 90 years by end of study period. The study found that increased epigenetic age acceleration (EAA) as measured by 4 epigenetic clocks was associated with lower odds of survival to age 90 years with intact mobility; results were similar when including intact cognitive functioning.

This study benefited from a large, racially and ethnically diverse sample of women who were followed up to at least age 90 years with detailed longitudinal data on a host of lifestyle and health history factors. This study is generalizable to WHI women owing to use of IPW weights, and may be generalizable to a large range of women in the United States.


Among 1813 women, there were:

  • 464 women who survived to age 90 years with intact mobility and cognitive functioning;
  • 420 women who survived to age 90 years without intact mobility and cognitive functioning; and
  • 929 women who did not survive to age 90 years.

Only 29 women were reclassified from the healthy longevity group to surviving to age 90 years without intact mobility and cognitive functioning. Although it was of great interest to investigate the association between EAA and survival to age 90 years with intact cognitive function independently, this study population did not have sufficient numbers of women who experienced loss of cognitive function (without loss of mobility) to do so.” “Analysis of Epigenetic Age Acceleration and Healthy Longevity Among Older US Women”

Early humans who lost mobility in our African savanna ancestral environment during the Pleistocene Epoch (approximately 2.6M to 12K years ago) were prey. I highly doubt that immobile individuals successfully became our ancestors.

I downgraded this study because these researchers misguidedly soiled worthwhile findings with BMI and education level non-causal associations. They intentionally did this, as several of them were coauthors of the execrable Epigenome-wide meta-analysis of BMI in nine cohorts: examining the utility of epigenetic BMI in predicting metabolic health.

See Findings, or fun with numbers? and Does a societal mandate cause DNA methylation? for opposing research.


Broccoli sprouts and your brain

A 2022 review of Nrf2 signaling hilariously avoided mentioning sulforaphane, although of ~4,000 sulforaphane published articles, two were cited. I’ll curate it anyway to highlight referenced brain effects.

“A good stability of NRF2 activity is crucial to maintain redox balance and therefore brain homeostasis. In this review, we have gathered recent data about the contribution of the NRF2 pathway in the healthy brain as well as during metabolic diseases, ageing, and ageing-related neurodegenerative diseases.

A functional NRF2 system is important to regulate both neuroinflammation, i.e., activation of microglia and astrocytes, and oxidative stress in the brain. NRF2 and NF-κB transcription factors regulate cellular responses to inflammation and oxidative stress in order to maintain brain homeostasis. Both pathways have been described to inhibit each other.

Nrf2 brain aging

Future challenges will be to establish novel therapies to:

  • Increase NRF2 activation in specific cell types and/or brain regions; and
  • Modulate NRF2 pathway in senescent cells.

Modulation of NRF2 signalling pathway by using specific food products [like unmentioned broccoli sprouts] and phytochemicals [like unmentioned sulforaphane], dietary supplements [like unmentioned Vitamin D3], drugs, and epigenetic modifiers, alone or in combination, will help to limit inflammatory diseases, ageing process, and subsequently ageing-related diseases.” “Normal and Pathological NRF2 Signalling in the Central Nervous System”


Week 120 of Changing to a youthful phenotype with sprouts

It was time for an annual physical last Wednesday. My focus was to see whether reducing sulforaphane intake per Week 87 had the desired effect on thyroid measurements.

That and other adjustments did! Readings of TSH 2.91 (0.45 – 4.50 uIU/mL), free T4 1.22 (0.82 − 1.77 ng/dL), and free T3 2.4 (2.0 – 4.4 pg/mL) were all in-range. 🙂


I won’t repeat the Week 63 workbook calculations done after last year’s annual physical. To me, that’s another form of magical thinking.

Every one of those reference ranges, and optimal ranges built from all-cause mortality statistics, requires a suffix “of people who didn’t positively change their healthspan and lifespan.” What value is there in optimizing (pick a measurement) against those outcomes? Why compare my efforts, or results, or any other aspect of my life, to people who didn’t actionably care about their one precious life?

I’m not deflecting with poor measurements:

  • 3 of the 5 values in last year’s optimal ranges got better, and the other 2 stayed the same; and
  • 2 of the 4 values that weren’t in last year’s optimal ranges came into those ranges, and the other 2 got better but stayed outside an optimal range.

We each have a lot at stake. Bad things like diseases of old age happen on their own. If we want good things to happen, we have to make them happen.

Consider this from The impact of transgenerational epigenetic inheritance and early life experiences:

“Every disease is connected to the immune system.”

Are people making good choices every day for their immune systems?


Non-CpG methylation

Three 2022 papers on methylation epigenetic modifiers, starting with a human study focused on mitochondrial DNA non-CpG methylation involving nucleobases other than guanine (arginine, cytosine, or thymine):

“We collected brain tissue in the nucleus accumbens and prefrontal cortex from deceased individuals without (n = 39) and with (n = 14) drug use, and used whole-genome bisulfite sequencing to cover cytosine sites in the mitochondrial genome. Epigenetic clocks in illicit drug users, especially in ketamine users, were accelerated in both brain regions by comparison with nonusers.

Unlike the predominance of CpG over non-CpG methylation in the nuclear genome, the average CpG and non-CpG methylation levels in the mitochondrial genome were almost equal. The utility of non-CpG methylation was further illustrated by the three indices constructed in this study with non-CpG sites having better distinction between brain areas, age groups, and the presence or absence of drug use than indices consisting of CpG sites only. Results of previous studies on the mitochondrial genome that were solely based on CpG sites should be interpreted cautiously.

The epigenetic clock made up of age-related cytosine sites in mtDNA of the control group was consistently replicated in these two brain regions. One possibility for the correlation is the cycle theory that involves mitochondrial activity, mitochondrial DNA methylation, and alpha-ketoglutarate.

As mitochondrial activity fades with aging, mitochondria gradually lose the ability to eliminate methylation on cytosines through alpha-ketoglutarate. Further investigation of the underlying mechanisms is warranted.

To our knowledge, this is the first report that ketamine might change the mitochondrial epigenetic clock in human brain tissues. We believe this is the first report to elucidate comprehensively the importance of mitochondrial DNA methylation in human brain.” “Mitochondrial DNA methylation profiling of the human prefrontal cortex and nucleus accumbens: correlations with aging and drug use”

A second rodent study focused on RNA methylation:

“We investigated the role of RNA N6-methyladenosine (m6A) in improved resilience against chronic restraint stress. A combination of molecular, behavioral, and in vivo recording data demonstrates exercise-mediated restoration of m6A in the mouse medial prefrontal cortex, whose activity is potentiated to exert anxiolytic effects. To provide molecular explanations, it is worth noting that epigenetic regulation, such as histone modification, microRNA, and DNA methylation all participate in mental and cognitive rehabilitation following exercise.

To generalize these rodent data to humans, we recruited a small group of patients with major depressive disorder with prominent anxiety disorders. Compared to age- and sex-matched healthy individuals, patients displayed decreased circulating methyl donor S-adenosyl methionine (SAM) levels. Serum SAM levels were found to be inversely correlated with the Hamilton Anxiety Scale, suggesting the potential value of SAM as a biomarker for depression or anxiety disorders.

Hepatic biosynthesis of methyl donors is necessary for exercise to improve brain RNA m6A to counteract environmental stress. The dependence on hepatic-brain axis suggests the ineffectiveness of exercise training on people with hepatic dysfunctions.

This novel liver-brain axis provides an explanation for brain network changes upon exercise training, and provides new insights into diagnosis and treatment of anxiety disorders. Exercise-induced anxiolysis might be potentiated by further replenishment of RNA methylation donors, providing a strategy of exercise plus diet supplement in preventing anxiety disorders.” “Physical Exercise Prevented Stress-Induced Anxiety via Improving Brain RNA Methylation”

A third paper was a review of mitochondrial-to-nuclear epigenetic regulation. I’ll highlight one mitochondrial metabolite, alpha-ketoglutarate (α-KG):

“Apart from established roles in bioenergetics and biosynthesis, mitochondria are signaling organelles that communicate their fitness to the nucleus, triggering transcriptional programs to adapt homeostasis stress that is essential for organismal health and aging. Emerging studies revealed that mitochondrial-to-nuclear communication via altered levels of mitochondrial metabolites or stress signals causes various epigenetic changes, facilitating efforts to maintain homeostasis and affect aging.

Metabolites generated by the tricarboxylic acid (TCA) cycle, the electron transport chain (ETC), or one-carbon cycle within mitochondria can act as substrates or cofactors to control epigenetic modification, especially histone acetylation and methylation and DNA methylation. α-KG produced in the TCA cycle serves as an essential cofactor for the chromatin-modifying Jumonji C (JmjC) domain-containing lysine demethylases (JMJDs) and ten-eleven translocation (TETs) DNA demethylases. Changes in α-KG levels are capable of driving nuclear gene expression by affecting DNA and histone methylation profiles.


α-KG deficiency in progenitor stem cells increases with age. For example, the level of α-KG is reduced in follicle fluids of aged humans, and supplementation with α-KG preserves ovarian function in mice.

α-KG extends lifespan in Drosophila by activating AMPK signaling and inhibiting the mTOR pathway. Supplementing α-KG in the form of a calcium salt promoted a longer and healthier life associated with decreased levels of inflammatory cytokines in old mice.

A human study showed a nearly 8-year reversal in DNA methylation clock biological ages of 42 individuals taking an α-KG based formulation for 4–10 months. α-KG supplementation leads to both demethylation and hypermethylation of some CpG sites in the genome, suggesting that α-KG may have a broader effect on methylation-based aging, such as metabolic functions.

Outstanding questions:

  1. How is production of mitochondrial metabolites regulated both spatially and temporally to elicit epigenetic changes in response to mitochondrial dysfunction?
  2. What are specific epigenetic factors involved in mitochondrial-to-nuclear communications, and how do they cooperate with transcription factors in response to various external and internal stimuli?
  3. Do various mitochondrial metabolites act alone or in concert on the epigenome to regulate the aging process?
  4. Are some organs or tissues more at risk than others in maintaining mitochondrial-to-nuclear communication during aging?
  5. Can intervention of mitochondrial-to-nuclear communications mimic beneficial epigenetic changes to delay aging or alleviate age-onset diseases?” “Mitochondrial-to-nuclear communication in aging: an epigenetic perspective”


Taurine week #7: Brain

Finishing a week’s worth of 2022 taurine research with two reviews of taurine’s brain effects:

“We provide a overview of brain taurine homeostasis, and review mechanisms by which taurine can afford neuroprotection in individuals with obesity and diabetes. Alterations to taurine homeostasis can impact a number of biological processes such as osmolarity control, calcium homeostasis, and inhibitory neurotransmission, and have been reported in both metabolic and neurodegenerative disorders.

Models of neurodegenerative disorders show reduced brain taurine concentrations. On the other hand, models of insulin-dependent diabetes, insulin resistance, and diet-induced obesity display taurine accumulation in the hippocampus. Given cytoprotective actions of taurine, such accumulation of taurine might constitute a compensatory mechanism that attempts to prevent neurodegeneration.


Taurine release is mainly mediated by volume-regulated anion channels (VRAC) that are activated by hypo-osmotic conditions and electrical activity. They can be stimulated via glutamate metabotropic (mGluR) and ionotropic receptors (mainly NMDA and AMPA), adenosine A1 receptors (A1R), and metabotropic ATP receptors (P2Y).

Taurine mediates its neuromodulatory effects by binding to GABAA, GABAB, and glycine receptors. While taurine binding to GABAA and GABAB is weaker than to GABA, taurine is a rather potent ligand of the glycine receptor. Reuptake of taurine occurs via taurine transporter TauT.

Cytoprotective actions of taurine contribute to brain health improvements in subjects with obesity and diabetes through various mechanisms that improve neuronal function, such as:

  • Modulating inhibitory neurotransmission, which promotes an excitatory–inhibitory balance;
  • Stimulating antioxidant systems; and
  • Stabilizing mitochondria energy production and Ca2+ homeostasis.” “Taurine Supplementation as a Neuroprotective Strategy upon Brain Dysfunction in Metabolic Syndrome and Diabetes”

A second review focused on taurine’s secondary bile acids produced by gut microbiota:

“Most neurodegenerative disorders are diseases of protein homeostasis, with misfolded aggregates accumulating. The neurodegenerative process is mediated by numerous metabolic pathways, most of which lead to apoptosis. Hydrophilic bile acids, particularly tauroursodeoxycholic acid (TUDCA), have shown important anti-apoptotic and neuroprotective activities, with numerous experimental and clinical evidence suggesting their possible therapeutic use as disease-modifiers in neurodegenerative diseases.

Biliary acids may influence each of the following three mechanisms through which interactions within the brain-gut-microbiota axis take place: neurological, immunological, and neuroendocrine. These microbial metabolites can act as direct neurotransmitters or neuromodulators, serving as key modulators of the brain-gut interactions.

The gut microbial community, through their capacity to produce bile acid metabolites distinct from the liver, can be thought of as an endocrine organ with potential to alter host physiology, perhaps to their own favour. Hydrophilic bile acids, currently regarded as important hormones, exert modulatory effects on gut microbiota composition to produce secondary bile acids which seem to bind a number of receptors with a higher affinity than primary biliary acids, expressed on many different cells.


TUDCA regulates expression of genes involved in cell cycle regulation and apoptotic pathways, promoting neuronal survival. TUDCA:

  • Improves protein folding capacity through its chaperoning activity, in turn reducing protein aggregation and deposition;
  • Reduces reactive oxygen species production, leading to protection against mitochondrial dysfunction;
  • Ameliorates endoplasmic reticulum stress; and
  • Inhibits expression of pro-inflammatory cytokines, exerting an anti-neuroinflammatory effect.

Although Alzheimer’s disease, Huntington’s disease, Parkinson’s disease, amyotrophic lateral sclerosis (ALS), and cerebral ischemia have different disease progressions, they share similar pathways which can be targeted by TUDCA. This makes this bile acid a potentially strong therapeutic option to be tested in human diseases. Clinical evidence collected so far has reported comprehensive data on ALS only.” “Tauroursodeoxycholic acid: a potential therapeutic tool in neurodegenerative diseases”

Taurine week #6: Stress

Two 2022 rodent studies of taurine’s associations with long-term stress, starting with a chronic restraint stress model:

“We show that chronic restraint stress can lead to hyperalgesia accompanied by changes in gut microbiota that have significant gender differences. Corresponding changes of bacteria can further induce hyperalgesia and affect different serum metabolism in mice of the corresponding sex.

Different serum metabolites between pseudo-germ-free mice receiving fecal microbiota transplantation from the chronic restraint stress group and those from the control group were mainly involved in bile secretion and steroid hormone biosynthesis for male mice, and in taurine and hypotaurine metabolism and tryptophan metabolism for female mice.

Effects of gut microbiota transplantation on serum metabolomics of female host: Taurine and hypotaurine metabolism, tryptophan metabolism, serotonergic synapse, arachidonic acid metabolism, and choline metabolism in cancer were the five identified pathways in which these different metabolites were enriched.


Taurine and hypotaurine play essential roles in anti-inflammation, anti-hypertension, anti-hyperglycemia, and analgesia. Taurine can be used as a diagnostic index for fibromyalgia syndrome and neuropathic pain.

These findings improve our understanding of sexual dimorphism in gut microbiota in stress-induced hyperalgesia and the effect of gut microbiota on blood metabolic traits. Follow-up research will investigate causal relationships between them.” “Gut microbiota and its role in stress-induced hyperalgesia: Gender-specific responses linked to different changes in serum metabolites”

Human equivalents:

  • A 7-8 month-old mouse would be a 38-42 year-old human.
  • A 14-day stress period is about two years for humans.

A second study used a chronic social defeat stress model:

“The level of taurine in extracellular fluid of the cerebral medial prefrontal cortex (mPFC) was significantly reduced in mice with chronic social defeat stress (CSDS)-induced depression. We found that taurine supplementation effectively rescued immobility time during a tail suspension assay and improved social avoidance behaviors in CSDS mice.

Male C57BL/6 J mice (∼ 23 g) and male CD-1 mice aged 7–8 months (∼ 45 g) were used. CD-1 mice were screened for aggressive behavior during social interactions for three consecutive days before the start of the social defeat sessions. Experimental C57BL/6 J mice were subjected to physical interactions with a novel CD-1 mouse for 10 min once per day over 10 consecutive days.

We found significant reductions in taurine and betaine levels in mPFC interstitial fluid of CSDS mice compared with control mice.

csds taurine betaine

We additionally investigated levels of interstitial taurine in chronic restraint stress (CRS) mice, another depressive animal model. After 14 days of CRS treatment, mice showed typical depression-like behaviors, including decreased sucrose preference and increased immobility time. mPFC levels of interstitial taurine were also significantly decreased in CRS mice.

Taurine treatment protected CSDS mice from impairments in dendritic complexity, spine density, and proportions of different types of spines. Expression of N-methyl D-aspartate receptor subunit 2A, an important synaptic receptor, was largely restored in the mPFC of these mice after taurine supplementation.

These results demonstrated that taurine exerted an antidepressive effect by protecting cortical neurons from dendritic spine loss and synaptic protein deficits.” “Taurine Alleviates Chronic Social Defeat Stress-Induced Depression by Protecting Cortical Neurons from Dendritic Spine Loss”

Human equivalents:

  • A 7-8 month-old mouse would be a 38-42 year-old human.
  • A 500 mg/kg taurine dose injected intraperitoneally is (.081 x 500 mg) x 70KG = 2.835 g.
  • A 10-day stress period is about a year and a half for humans.

Don’t think aggressive humans would have to be twice as large to stress those around them. There may be choices other than enduring a year and a half of that.

The misnomer of nonessential amino acids

Three papers, starting with a 2022 review:

“Ideal diets must provide all physiologically and nutritionally essential amino acids (AAs).

Proposed optimal ratios and amounts of true digestible AAs in diets during different phases of growth and production. Because dynamic requirements of animals for dietary AAs are influenced by a plethora of factors, data below as well as the literature serve only as references to guide feeding practices and nutritional research.


Nutritionists should move beyond the ‘ideal protein’ concept to consider optimum ratios and amounts of all proteinogenic AAs in diets for mammals, birds, and aquatic animals, and, in the case of carnivores, also taurine. This will help formulate effectively low-protein diets for livestock (including swine and high-producing dairy cattle), poultry, fish, and crustaceans, as well as zoo and companion animals.” “The ‘ideal protein’ concept is not ideal in animal nutrition”

A second 2022 review focused on serine:

“The main dietary source of L-serine is protein, in which L-serine content ranges between 2 and 5%. At the daily intake of ~1 g protein per kg of body weight, the amount of serine obtained from food ranges between 1.4 and 3.5 g (13.2–33.0 mmol) per day in an adult.

Mechanisms of potential benefits of supplementing L-serine include increased synthesis of sphingolipids, decreased synthesis of 1-deoxysphingolipids, decrease in homocysteine levels, and increased synthesis of cysteine and its metabolites, including glutathione. L-serine supplementation has been suggested as a rational therapeutic approach in several disorders, particularly primary disorders of L-serine synthesis, neurodegenerative disorders, and diabetic neuropathy.

Unfortunately, the number of clinical studies evaluating dietary supplementation of L-serine as a possible therapy is small. Studies examining therapeutic effects of L-serine in CNS injury and chronic renal diseases, in which it is supposed that L-serine weakens glutamate neurotoxicity and lowers homocysteine levels, respectively, are missing.” “Serine Metabolism in Health and Disease and as a Conditionally Essential Amino Acid”

A 2021 review subject was D-serine, L-serine’s D-isoform:

“The N-methyl-D-aspartate glutamate receptor (NMDAR) and its co-agonist D-serine are currently of great interest as potential important contributors to cognitive function in normal aging and dementia. D-serine is necessary for activation of NMDAR and in maintenance of long-term potentiation, and is involved in brain development, neuronal connectivity, synaptic plasticity, and regulation of learning and memory.

The source of D-amino acids in mammals was historically attributed to diet or intestinal bacteria until racemization of L-serine by serine racemase was identified as the endogenous source of D-serine. The enzyme responsible for catabolism (breakdown) of D-serine is D-amino acid oxidase; this enzyme is most abundant in cerebellum and brainstem, areas with low levels of D-serine.

Activation of the NMDAR co-agonist-binding site by D-serine and glycine is mandatory for induction of synaptic plasticity. D-serine acts primarily at synaptic NMDARs whereas glycine acts primarily at extrasynaptic NMDARs.

In normal aging there is decreased expression of serine racemase and decreased levels of D-serine and down-regulation of NMDARs, resulting in impaired synaptic plasticity and deficits in learning and memory. In contrast, in AD there appears to be activation of serine racemase, increased levels of D-serine and overstimulation of NMDARs, resulting in cytotoxicity, synaptic deficits, and dementia.” “An Overview of the Involvement of D-Serine in Cognitive Impairment in Normal Aging and Dementia”


Young gut, young eyes

I’ll highlight this 2022 rodent study findings of effects on eye health:

“We tested the hypothesis that manipulating intestinal microbiota influences development of major comorbidities associated with aging and, in particular, inflammation affecting the brain and retina. Using fecal microbiota transplantation, we exchanged intestinal microbiota of young (3 months), old (18 months), and aged (24 months) mice.

Transfer of aged donor microbiota into young mice accelerates age-associated central nervous system inflammation, retinal inflammation, and cytokine signaling. It promotes loss of key functional protein in the eye, effects which are coincident with increased intestinal barrier permeability.

These detrimental effects can be reversed by transfer of young donor microbiota.

young and aged fmt

We provide the first direct evidence that aged intestinal microbiota drives retinal inflammation, and regulates expression of the functional visual protein RPE65. RPE65 is vital for maintaining normal photoceptor function via trans-retinol conversion. Mutations or loss of function are associated with retinitis pigmentosa, and are implicated in age-related macular degeneration.

Our finding that age-associated decline in host retinal RPE65 expression is induced by an aged donor microbiota, and conversely is rescued by young donor microbiota transfer, suggests age-associated gut microbiota functions or products regulate visual function.” “Fecal microbiota transfer between young and aged mice reverses hallmarks of the aging gut, eye, and brain”


Exercise substitutes?

Two papers, starting with a 2022 abstract of an ongoing in vitro study with rodent cells:

“Exercise mimetics may target and activate the same mechanisms that are upregulated with exercise administration alone. This is particularly useful under conditions where contractile activity is compromised due to muscle disuse, disease, or aging.

Sulforaphane and Urolithin A represent our preliminary candidates for antioxidation and mitophagy, respectively, for maintaining mitochondrial turnover and homeostasis. Preliminary results suggest that these agents may be suitable candidates as exercise mimetics, and set the stage for an examination of synergistic effects.” “Exercise mimicry: Characterization of nutraceutical agents that may contribute to mitochondrial homeostasis in skeletal muscle” (study not available)

A second 2022 paper reviewed what’s known todate regarding urolithins:

“Urolithins (Uros) are metabolites produced by gut microbiota from the polyphenols ellagitannins (ETs) and ellagic acid (EA). ETs are one of the main groups of hydrolyzable tannins. They can occur in different plant foods, including pomegranates, berries (strawberries, raspberries, blackberries, etc.), walnuts, many tropical fruits, medicinal plants, and herbal teas, including green and black teas.

Bioavailability of ETs and EA is very low. Absorption of these metabolites could be increased by co-ingestion with dietary fructooligosaccharides (FOS).

Effects of other experimental factors: post-intake time, duration of administration, diet type (standard and high-fat), and ET dosage (without, low, and high ET intake) in ETs metabolism were evaluated in blood serum and urine of rats consuming strawberry phenolics. Highest concentrations were obtained after 2–4 days of administration.

Various crucial issues need further research despite significant evolution of urolithin research. Overall, whether in vivo biological activity endorsed to Uros is due to each specific metabolite and(or) physiological circulating mixture of metabolites and(or) gut microbial ecology associated with their production is still poorly understood.

  • Ability of Uros to cross the blood-brain barrier and the nature of metabolites and concentrations reached in brain tissues need to be clarified.
  • Specific in vivo activity for each free and conjugated Uro metabolite is unknown. Studies on different Uro metabolites and their phase-II conjugates are needed to understand their role in human health.
  • Evidence on safety and impact of Uros on human health is still scarce and only partially available for Uro-A.
  • It is unknown whether there are potential common links between gut microbial ecologies of the two unambiguously described metabotypes so far, i.e., equol (isoflavones) and Uros (ellagitannins).
  • Gut microbes responsible for producing different Uros still need to be better identified and characterized, and biochemical pathways and enzymes involved.” “Urolithins: a Comprehensive Update on their Metabolism, Bioactivity, and Associated Gut Microbiota”