Author Topic: Testosterone-PPARs-PGC1a-Irisin axis  (Read 346 times)


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Testosterone-PPARs-PGC1a-Irisin axis
« on: September 08, 2021, 03:27:43 PM »
So this thread means yet another shift in the focus of my research as I came to realize that FAAH inhibition is not predominantly involved in my case. Although most FAAH inhibitors seem to have at least some minor benefit, but this doesn't implicate them as major factors. As a further proof recently I have done some preliminary tests on CBD oil, quercetin and galangal (kaempferol) and they just don't have a considerable effect on my symptoms. The same is possibly true for AKR1C3 inhibitors and lucerne/alfalfa probably has another effect that makes it so potent as in the case of saffron.

I also decided to make a kind of supplementation topographic map as this should pinpoint the origin of the problems eventually.

Based on this it became evident that I react well to testosterone boosters as they provide the best general effect. So far these were the most beneficial: Maca (yellow), Tribulus, Ecdysterone, Tongkat Ali. The 5a-reductases I have tried so far usually have a weak or moderate effect. These were: fenugreek, Pygeum, beta-sitosterol, Reishi Ganoderma. Aromatase inhibitors could be considered as another source of free testosterone. Damiana could be tested for this, however Pygeum is both a potent 5a-reductase and aromatase inhibitor and still it only had a weak to moderate effect, which probably means that my problems are not directly related to either DHT or estrogen.
Interestingly medicinal mushrooms also generally work and have a rather good effect: Lion's mane, Reishi ganoderma, beta-glucan (maitake), Cordyceps, which probably indicates a role for beta-glucan, but more medicinal mushrooms have to be tested to claim this with great certainty.
Another major category involves supplements that are supposed to restore hormonal balance and by this I mean even those that target women. These are beneficial so far: Wild yam root, lavender tea, tea tree oil, shatavari.
Adaptogens could be considered as well, however there are many overlaps with previous categories.

So at first it would seem like I am really lucky to have found so many remedies, however the real picture is not so wonderful. I mainly test supplements separately this time, however I tried some combinations and the effects are usually not additive. I also have the problem of supplements losing effectiveness over time, however I am not worried that they will completely lose the benefit. Some supplements seem to have a greater benefit when I am in worse condition, but less when I am feeling relatively well. From the perspective of POIS it is a good thing as I at least can avoid being severely ill, however my aim is to treat the CFS condition as well and it seems to be a more difficult barrier to overcome. Lately I had to work a lot and sometimes I used combinations of the most beneficial supplements. Even so I had exercise intolerance induced POIS symptoms and this was actually in the chronic phase (over 7 days). This made me think that I have to pay more attention to the possible causes of CFS as well.

Of course exercise intolerance is the major symptom of CFS and the cause is still mostly unknown. However recently I have found something that seems to be rather interesting. A few years ago researchers discovered a kind of new myokine hormone called irisin, which is also considered as an exercise hormone. I wonder why none had mentioned this before as irisin seems to be a major factor in regulating the benefits of physical exercise and could be implicated in CFS as well.
Even more interesting is the fact that irisin is mainly regulated by peroxisome-proliferator-activated receptor-gamma co-activator-1 alpha (PGC-1a). PGC-1a has intrigued me for a while now due to its relation to PPARs and studying it a bit more one can easily realize how likely its involvement in POIS pathology. PGC-1a has a considerable role in glucose, lipid and energy homeostasis and is at the nexus to regulate skeletal muscle adaptations to increased work load. As PPAR ligands are likely to have a role in POIS state modification I have to assume that the PPAR - PGC-1a relation must be at the core of our issues. PGC-1a functions kind of like a hub and may even serve to unify earlier theories (e.g. BDNF, calcineurin, lactate, NRF-2, etc).
Some background information on irisin and PGC-1a:
We also observed an independent correlation with serum concentrations of high-sensitivity C-reactive protein (hs-CRP), thus suggesting that inflammation may influence irisin production. The inflamed patients exhibited higher serum irisin concentrations. Irisin concentrations were significantly correlated with age (r=-0.44; p <0.001), creatinine (r=-0.35; p <0.05), and fibrinogen (r=0.40; p <0.05) concentrations. No association was observed between irisin, interleukine-6 and tumor necrosis factor alpha. This study confirms the association between inflammation and irisin concentrations.

The time course study revealed that circulating irisin increased immediately after high-intensity interval exercise and declined 1 hour thereafter. In vitro experiments showed that irisin facilitates glucose and lipid metabolism in human muscle through AMP kinase phosphorylation.
Exercise is considered a cornerstone in the prevention and treatment of chronic metabolic diseases such as obesity, type 2 diabetes mellitus, and age-related muscle wasting.
Irisin regulates gene expression of metabolic enzymes in human muscle. Gene modulation was followed by enhanced lactate production.
We confirmed that irisin-mediated gene regulation is dependent on AMPK.
Irisin induces mitochondrial biogenesis and uncoupling.
The role of irisin in metabolic regulation indicates the existence of an irisin receptor that has yet to be identified, which triggers downstream AMPK activation.

Irisin may enhance NO production and phosphorylation of AMPK, Akt, and eNOS.
Irisin mediates the beneficial effects of exercise on metabolism, inducing the browning of adipocytes and thermogenesis by stimulating uncoupling protein 1 expression (UCP-1).
Circulating irisin is significantly lower in individuals with type 2 diabetes and obesity compared with controls.
Irisin significantly enhances endothelium-dependent vasodilatation (EDV).
Irisin is a novel endothelium-dependent and NO-mediated vasorelaxive agent.

Genetic deletion of irisin impairs cognitive function in exercise, aging and Alzheimer’s disease.
Irisin protects against neuroinflammation by acting directly on glia cells in the brain.

Irisin exhibits antiinflammatory properties via the downregulation of toll-like receptor 4 (TLR4)/myeloid differentiation primary response 88 in macrophages, and reduces the expression of inflammatory genes via inhibiting the p38 mitogen-activated protein kinase (p38 MAPK)/NF-kB in endothelial cells. Furthermore, irisin reduces oxidative stress in macrophages and endothelial cells.
Endurance exercise activates the peroxisome proliferator activated receptor (PPAR)-gamma coactivator 1a (PGC1a) which in turn stimulates the FNDC5 expression in SKMs (skeletal muscle) leading to increased levels of circulating irisin. Myocytes treated with irisin in vitro showed increased PGC1a, nuclear respiratory factor 1 (NRF-1), mitochondrial transcription factor A (TFAM), glucose transporter 4 (GLUT4), UCP-3 and irisin itself, indicating the existence of a positive autoregulatory loop between FNDC5 and PGC1a and suggesting that irisin positively regulates muscle metabolism in an autocrine manner.
This activation of FNDC5 positively regulates the hippocampal expression of BDNF, the master regulator of neuronal cells proliferation and differentiation. This PGC1a/FNDC5/BDNF axis that ultimately leads to improved cognitive function, learning and memory, suggests the existence of a direct SKM-brain cross-talk that further contributes to the beneficial effects of exercise on the brain.
Irisin is released into the circulation during exercise and when exposed to cold.
Muscle-specific PGC-1a overexpression renders mice resistant to age-related obesity and diabetes and increases lifespan.
Overexpression of irisin led to an increase in total body energy expenditure and modest improvements in glucose intolerance. Irisin stimulates glucose uptake in muscles.
Acute exercise did not affect expression of the Fndc5 gene, although PGC1-a was substantially (7.4-fold) upregulated under these conditions.
Cells were treated with exercise-mimicking agents such as caffeine, ionomycin, and forskolin. Although PGC1-a was substantially induced in response to these agents, the level of Fndc5 mRNA was even decreased under these conditions.
Fndc5 gene expression is regulated by a Pgc1alpha/ERRalpha (a Pgc1alpha cofactor) complex.
The findings that peripheral delivery of FNDC5 is sufficient to induce CNS expression of Bdnf suggest that a circulating form of FNDC5, possibly irisin, travels to CNS targets (including BDNF-producing retina cells) and in a Pgc1alpha-dependent manner, directly and in addition with local FNDC5 pathway, enhances BDNF production with subsequent TrkB activation. It may be that similar pathways mediate exercise-induced retinal neuroprotection.

The demonstration of irisin presence in central and peripheral areas as the testes suggests that this peptide may play a role in the gonadal axis by regulating some reproductive processes.
PPARG, a nuclear receptor that regulates fatty acid deposition, glucose metabolism and adipocyte differentiation. Together with PGC-1a, PPARG is involved in the regulation of irisin. Furthermore, the expression of FNDC5 strictly depends on increased levels of PPARG, which is known to regulate the genes in response to nutritional and physiological signals, particularly during exercise.
Studies showed the expression of FNDC5 in the human and rat ovaries, as well as in different areas of the brain, muscle, both cardiac and skeletal, brown adipose tissue, pituitary, placenta and testis.
Since these discrepancies are apparently unrelated to irisin dosages used in these different experiments, varying from physiological to pharmacological concentrations, we can speculate that species as well as cell type play a fundamental role.
Irisin has been shown to play a role in the control of reproduction by modulating pituitary gonadotropin secretion in different species by means of a classical endocrine effect.

In this study, we demonstrated that serum irisin levels were significantly higher in the T2DM patients with hypertriglyceridemia compared with the controls, and serum irisin was positively correlated with BMI, FBG, TC, and HDL, suggesting that irisin could play an important role in the delicate balance of energy metabolism and insulin resistance.
Our findings are in contrast to some recent studies indicating that circulating irisin was significantly lower in patients with T2DM. However, our results align with other studies indicating that circulating irisin was significantly higher in patients with insulin resistant diseases, such as metabolic syndrome and polycystic ovary syndrome, and that it was associated with an increased risk of metabolic syndrome, cardiometabolic variables, and cardiovascular diseases in humans. There may be a compensatory increase of irisin to overcome insulin resistance. We hypothesize that the increased irisin levels in T2DM with hypertriglyceridemia in our study might have represented irisin resistance, reflecting a compensatory result to counterbalance the increasing needs for irisin (similar to the increased insulin levels in insulin resistance) and to improve metabolic features. Additionally, we also hypothesize that, at different stages of T2DM, irisin levels might change from overcompensating to failing to compensate (similar to different insulin levels in different stages of T2DM).
Accumulating evidence has demonstrated that PPARA is an important modulator of metabolic syndrome and that it might be a therapeutic target for treating some of its features. Its known that target genes are involved in most aspects of lipid metabolism and lipid transport. PPARA agonist fenofibrate has been proven to be effective at improving lipid parameters. Importantly, we report for the first time here that fenofibrate treatment administered to T2DM patients with hypertriglyceridemia for 8 weeks resulted in a significant decrease in serum irisin levels, although fenofibrate was reported to increase irisin gene expression in diet-induced male obese mice. We hypothesize that the PPARA agonist fenofibrate could induce the increase of UCP1 and browning of WAT by activating PPARA and that the increased UCP1 levels and browning programme might compensatively inhibit the FNDC5 expression and then reduce the irisin levels.

As irisin is a novel myokine secreted in response to PGC-1a activation. Studies suggest that PGC-1a is important for mitochondrial homeostasis for it regulates mitochondrial biogenesis and oxidative metabolism, and mitochondrial function also plays a role in IR. Furthermore, expression and activity of PGC1-a are lower in patients with T2DM.
The association between irisin and glucose homeostasis was confirmed by several studies, indicating that irisin may be a predictor and protective factor for developing diabetes. However, whether it is negatively or positively concerned, still remains controversial.

PGC-1a is the master regulator of mitochondrial biogenesis. PGC-1a is also the primary regulator of liver gluconeogenesis, inducing increased gene expression for gluconeogeneis.
PGC-1a is a transcriptional coactivator that regulates the genes involved in energy metabolism.
This protein can interact with, and regulate the activity of, cAMP response element-binding protein (CREB) and nuclear respiratory factors (NRFs).
Endurance exercise has been shown to activate the PGC-1a gene in human skeletal muscle. Exercise-induced PGC-1a in skeletal muscle increases autophagy and unfolded protein response.
PGC-1a protein may be also involved in controlling blood pressure, regulating cellular cholesterol homoeostasis, and the development of obesity.
PGC-1a upregulation of sirtuin 3 makes mitochondria healthier.
PGC-1a is known to be activated by:
- Reactive oxygen species (ROS) and reactive nitrogen species (RNS)
- Cold exposure
- Endurance exercise: prevents high lactate levels and makes lactate as an energy source more efficient
- cAMP response element-binding (CREB) proteins
- Protein kinase B / Akt is thought to downregulate PGC-1a, but upregulate its downstream effectors, NRF1 and NRF2. Akt itself is activated by PIP3, often upregulated by PI3K after G-protein signals.
- PGC-1a may have positive feedback on upstream regulators:
1. PGC-1a increases Akt (PKB) and Phospho-Akt (Ser 473 and Thr 308) levels in muscle
2. PGC-1a leads to calcineurin activation
Akt and calcineurin are both activators of NF kappa B (p65).Through their activation PGC-1a seems to activate NF kappa B. Increased activity of NF kappa B in muscle has recently been demonstrated following induction of PGC-1a. The finding seems to be controversial. Other groups found that PGC-1s inhibit NF kappa B activity. The effect was demonstrated for PGC-1 alpha and beta.
PGC-1a and beta has furthermore been implicated in polarization to anti-inflammatory M2 macrophages by interaction with PPARG with upstream activation of STAT6.
PGC-1a has been recently proposed to be responsible for B-aminoisobutyric acid secretion by exercising muscles. The effect of B-aminoisobutyric acid. Hence, the B-aminoisobutyric acid could act as a messenger molecule of PGC-1a and explain the effects of PGC-1a increase in other tissues such as white fat.

To observe the effect of electroacupuncture (EA) of "Zusanli" (ST 36) on mitochondrial oxidative stress of skeletal muscle in rats with chronic fatigue syndrome (CFS) based on adenosine 5'-monophosphate (AMP)-activated protein kinase (AMPK)/ peroxisome proliferator-activated receptor-gamma coactivator-1 alpha (PGC-1a) signaling, in order to reveal its mechanism underlying improvement of CFS.
Compared with the normal group, the grabbing force, and the expression levels of ATP synthase and PGC-1a proteins and mRNAs were significantly decreased (P<0.05, P<0.01), while the expression of SIRT 1 protein was significantly up-regulated (P<0.05) in the CFS model group. Following EA intervention, the grabbing force and the expression levels of ATP synthase mRNA, SIRT 1 and PGC-1a proteins and mRNAs, and p-AMPK/AMPK were significantly up-regulated in the EA-Zusanli (ST 36) group (P<0.05, P<0.01).
EA of ST 36 can raise the grabbing force of CFS rats, which may be related to its effects in up-regulating the expression of ATP synthase mRNA, SIRT 1 and PGC-1a proteins and mRNAs, and p-AMPK/AMPK to reduce mitochondrial oxidative stress reaction and in increasing ATP synthesis.

Ectopic expression of PGC-1a in muscle results in increased mitochondrial number and function as well as an increase in oxidative, fatigue-resistant muscle fibers. Moreover, skeletal muscle-specific PGC-1a knock-out animals (MKO) have reduced endurance capacity and exhibit fiber damage and elevated markers of inflammation following treadmill running.
Interestingly, MEF2 and PGC-1a also control PGC-1a gene transcription in an autoregulatory loop. Metabolic genes, including those responsible for mitochondrial oxidative phosphorylation, are induced by a transcriptional cascade with coactivation of the estrogen-related receptor alpha (ERRa, official nomenclature NR3B1), the nuclear respiratory factor 2 (NRF-2, alternatively called GA-binding protein, GABP), and the nuclear respiratory factor 1 (NRF-1) by PGC-1a and subsequent increase in the levels of mitochondrial transcription factor A (TFAM) and mitochondrial transcription specificity factors TFB1M and TFB2M.
PGC-1a apparently controls most if not all of the transcriptional changes induced by motor neuron signaling in skeletal muscle.
Whole body PGC-1a knock-out animals have a dominant central nervous system phenotype that might mask the effects of loss-of-function of PGC-1a in peripheral tissues. These mice are hyperactive, show circadian abnormalities, and have constitutively activated AMP-activated kinase in skeletal muscle, all of which might compensate for the loss of PGC-1a in this tissue.
Strikingly, skeletal muscle of MKOs has a low level of damaged and regenerating fibers. This compromised skeletal muscle integrity is dramatically exacerbated by physical exercise and accompanied by elevated markers of systemic inflammation.
PGC-1a transcription is induced by exercise and repressed by disuse.
However, MKOs are hypoactive compared with control mice. These findings are in stark contrast to the hyperactive PGC-1a total knock-out animals. Interestingly, the decrease in physical activity in MKOs is similar in the light and the dark period. The hyperactivity of PGC-1a total knock-out mice was predominantly caused by abnormal activity during the light period.
Lack of skeletal muscle PGC-1a leads to a 60% reduction in grip strength performance in MKOs.
Interestingly, PGC-1a total knock-out animals performed even worse than MKOs in treadmill running. This might reflect additional defects in heart function and the motor neuron system in whole body PGC-1a knock-out mice that also contribute to physical endurance.
Increased muscle fiber regeneration is often a sign of muscle damage in mice, and muscle damage leads to higher serum creatine kinase levels in the blood leaking from muscle fibers.
MKOs exhibit low grade muscle damage, even in the basal state.
Skeletal muscle PGC-1a is required in maintaining muscle fiber integrity in the sedentary state; this is even more so during and following physical exertion.
In addition, circulating interleukin 6 levels in the blood were elevated in MKOs compared with controls, but we did not see a significant difference in circulating TNFa levels in the non-exercised context.
Remarkably, transcript levels of TNFa were massively increased in exercised MKOs compared with pre-exercised MKOs, whereas no change in TNFa expression was observed in control mice before and after physical activity.
Thus, increased cytokine levels, in particular those for TNFa in MKOs, likely contribute to fiber damage by inducing an inflammatory myopathy.
Despite the protection observed in PGC-1a muscle transgenic animals against denervation-induced muscle atrophy, MKOs show no increased propensity for disuse-mediated muscle atrophy.
Reactive oxygen species detoxification is crucially regulated by PGC-1a and the levels of a number of reactive oxygen species detoxification genes are reduced in MKOs, including superoxide dismutase 1, superoxide dismutase 2, adenine nucleotide transporter, and glutathione peroxidase 1.
In addition, we recently found that PGC-1a regulates the gene program involved in postsynaptic neuromuscular junction plasticity. MKOs have a lower number of acetylcholine clusters on muscle fiber membranes and thus might be insufficiently innervated.
The decrease in body weight and fat mass, reduced physical activity, skeletal muscle damage, increased body temperature and basal metabolic rate, and diminished food intake4 are compatible with symptoms observed in animal models and human patients suffering from chronic inflammation.

Exercise can significantly influence PGC-1a and AMPK-SIRT1 pathway, as it is involved in the regulation of energy metabolism and mitochondrial biogenesis.
Studies have shown that various organelles within the cell can generate ROS such as mitochondria, sarcoplasmic reticulum and peroxisomes in exercise condition.
Prolonged exercise increases the NO production, resulting in vasodilation in the heart and skeletal muscles. However, strenuous exercise increases the chances of superoxide production, thereby decreasing the bioavailability of NO, as superoxide combines with NO to produce peroxynitrite—a potent cellular damager. In this scenario, we mainly review about PGC-1 alpha and AMPK, and how NO can act with AMPK synergistically to upregulate the PGC-1 alpha.
Fiber-type switching toward the oxidative type by PGC-1a is characterized by increased mitochondrial production, density, and oxidative metabolism. Conversely, glycolytic fiber of muscles decreased the endurance activity. Taken together, PGC-1a is a key mediator of several cellular processes required for endurance capacity.
Conversely, ROS are involved in the regulation of PGC-1a. For example, H2O2 regulates the expression PGC-1a via AMPK pathway and indirectly it is involved in upregulation of PGC-1a by lactate, a by-product of glycolytic pathway. Therefore, it is a multi-dependent process of PGC-1a, antioxidants, and ROS. Ample evidence supported that muscle contraction during exercise increased the production of ROS in the form of superoxide (O2), hydrogen peroxide (H2O2), and hydroxyl (OH) radicals. H2O2 is an important signaling molecule for muscle adaptation. However, ROS have been shown to increase the expression of PGC-1a and metabolic adaptation in the muscles, but at what level the production of ROS could help regulate PGC-1a during exercise needs more study. Additionally, reactive nitrogen species (RNS) play an important role in the regulation of PGC-1a; particularly, NO increases the PGC-1a expression via AMPK activation and Ca2+/calmodulin. Nitric oxide production is increased during physical exercise. Several studies have suggested the role of NO in the PGC-1a regulation, mitochondrial biogenesis, and fiber type changes.
Exercise like stimuli induces the PGC-1a expression, which contributes the muscular contraction activity. This contraction activates the Ca2+ channels leading to increased amount of Ca2+ in the cytosol. This increased amount of Ca2+ stimulates the calcium/calmodulin-dependent protein kinase, which further phosphorylates the PGC-1a. In another way, muscle contraction-mediated AMPK and p38 MAPK induces PGC-1a expression. PGC-1a can also regulate the homeostasis of oxidants and antioxidants by increasing the stimulation of superoxide dismutase-2, catalase, and GPx expression. Taken together, PGC-1a plays a crucial role in response to external stimuli like exercise to increase the mitochondrial biogenesis by mimicking the many metabolic responses and transcription factors including NRF.
A single bout of exercise can activate AMPK, resulting in stimulation of many metabolic pathways and
also its activation leads to mimic several signaling factors in response to muscle adaptation.
In addition to physical exercise, other forms of stresses including hypoxia also increased the AMPK level in the skeletal and cultured muscles.
Interestingly, AMPK and SIRT1 mediate the PGC-1a expression in mitochondrial biogenesis and glucose metabolism. Altogether, SIRT1, AMPK, and PGC-1a have an imperative role to increase the mitochondrial adaptation to exercise.

Pharmacological activation of the nuclear receptor PPARG is linked to numerous beneficial effects in the contexts of inflammation, lipid homeostasis, Type-2 Diabetes (T2D) and atherosclerosis. These beneficial effects include priming of circulating monocytes for differentiation towards an ‘alternative’ anti-inflammatory M2 macrophage phenotype.
Changes in expression of PPARs and the PPARG co-activators PGC-1a and PGC-1B; Th2 (IL-4; IL-10) and Th1 (IL-6) cytokines; and markers for the M2 (AMAC1, CD14, MR, IL-4) and the ‘classical’ pro-inflammatory M1 (MCP-1, TNFa, IL-6) phenotypes were determined.
Exercise was associated with upregulation of M2 markers, PGC-1a and PGC-1B, and with downregulation of M1 markers. Moreover, plasma levels of Th2 cytokines increased after exercise, while those of Th1 cytokines decreased. However, other PPARs (PPARA; PPARB/D) did not undergo marked exercise-induced activation or upregulation. Thus, participation in low-intensity exercise may prime monocytes for differentiation towards an M2 macrophage phenotype via PPARG/PGC-1a/B

Taken together some of these facts suggest that I have a very low expression of irisin/PGC-1a or a KO genotype, however other facts point towards an overexpression, so based on scientific data alone a clear correlation can't be drawn.
Hormone balance modifiers may have yet unknown effects on irisin level and hopefully studies will uncover this in the near future.

The downregulation of PPARG by testosterone was indicated earlier as a possible mechanism, but at the time I was more concerned with FAAH inhibition. Some beneficial supplements I take also downregulate PPARG activity (testosterone itself, crocin (saffron), papaya, beta-glucan (medicinal mushrooms), garlic, apigenin(?)), however there are beneficial PPARG agonists (e.g. berberine) as well, so it is not a definitive answer. Metformin is indicated to be an agonist of PPARG however a study claims that it downregulates PPARG which makes it a good idea to try.
Testosterone also changes the activity of PGC-1a, but the studies I found are unfortunately controversial in this regard. One study indicates downregulation while two others show PGC-1a upregulation by testosterone.
Saffron (crocin) can also significantly increase PGC-1a. Biotin significantly decreases PGC-1a.
A lowered PGC-1a thus seems very likely, however it is not clear how PPARG antagonism would correlate to this.

I will provide links in a later post.
Now I have a lot more to read and test, but at least this seems a prospective path.