Mois : mai 2024

A recent study saw researchers associated with Cellvie demonstrate significant improvements to mitochondria and muscle function in aged mice by injecting additional mitochondria [1].

Mitochondrial dysfunction is a reason we age

Mitochondria are cellular powerhouses that convert nutrients into adenosine triphosphate (ATP), a form of energy that powers cells. It is not an exaggeration to say that without mitochondria, complex life, such as people, would not be possible.

With aging, the mitochondria can become damaged and less efficient over time. This is because producing energy is a dirty business that creates harmful byproducts called free radicals.

These free radicals bounce around inside of cells, damaging things that they strike, particularly mitochondrial DNA. This damage causes mutations, which make energy production less efficient and cause mitochondria to behave in harmful ways.

Mitochondria do not have an efficient DNA repair system like cells’ nuclear DNA. As time passes, the number of mutations in mitochondria increases. This leads to a downward spiral in which mitochondria become increasingly unable to produce energy and function properly.

A number of researchers are now developing therapies to combat this. If they are successful, it may be possible to slow down or even reverse aging in our cells.

Rejuvenating old cells with donated mitochondria

It has been known for some time that mitochondria can transfer between cells and can be absorbed into cells from their environment. This suggests transferring healthy mitochondria to an aged animal or person may be a viable approach for rejuvenation.

This is exactly what the researchers in this new study did. It is interesting that the mitochondria were harvested from mice of the same age and not younger donors.

The mitochondria were separated from the donor tissue and given directly to the test group mice. The animals were then injected directly into the hindleg muscle tissue, meaning delivery was relatively simple.

Compared to the control group, the test group saw improvements to mitochondrial function and muscle function. There was also an improvement in endurance.

Results: The results indicated significant increases (ranging between ~36% and ~65%) in basal cytochrome c oxidase and citrate synthase activity as well as ATP levels in mice receiving mitochondrial transplantation relative to the placebo. Moreover, there were significant increases (approx. two-fold) in protein expression of mitochondrial markers in both glycolytic and oxidative muscles. These enhancements in the muscle translated to significant improvements in exercise tolerance.

A follow-up study to better understand these results

As mentioned, the notable thing about this particular study was that even though the mitochondria were delivered from animals of the same age, the results demonstrate some level of improvement.

Perhaps there is some form of dilution of damaged mitochondria happening here that explains the results. The influx of additional mitochondria may be somewhat offsetting the burden of mutated mitochondria in the recipient.

That said, it is reasonable to assume that delivering mitochondria from a younger donor would be more advantageous. It would make for an ideal follow up experiment using mitochondria harvested from younger animals.

There is also the consideration of if mitochondrial haplotypes need to match between donor and recipient or not. Mitochondrial haplotypes refer to groups of closely linked genetic markers present on mitochondrial DNA. These haplotypes are used to trace maternal lineages and genetic variations in populations.

Understanding the role of haplotypes in a follow-up study would also be beneficial. If they do not need to match to be effective, that would also simplify production at scale.

An inroad for rejuvenation research

Mitochondrial dysfunction is a hallmark of aging, but it’s unlikely that “aging” will be the target of this research. Companies working on mitochondrial transfer will probably initially target frailty and muscle loss in older adults for clinical trials. Once approved, the approach could be used off label for other related conditions and aspects of aging.

The great news is that growing mitochondria in culture is likely a scalable technology. This is very important and directly relates to the ability of people to access and afford therapies.

Many rejuvenation biotechnology supporters are worried about being able to access it in the future. After all, it’s no use if a therapy works but is unaffordable for most people. Hopefully, companies such as Cellvie and Mitrix will use bioreactor-grown mitochondria to cost-effectively produce them en masse.

It’s likely that medical tourism in countries with less regulations will offer mitochondrial transplants to those with the means. Obviously, those first adopters need to consider the risks of doing so. Meanwhile, the rest of us will be waiting for therapies to get through the clinic via the FDA, EMA, etc.

This avenue of research looks promising if the challenges of manufacturing at scale and access can be overcome. We will continue to follow research progress closely and hopefully will have more to report in the near future.

Literature

[1] Arroum, T., Hish, G. A., Burghardt, K. J., McCully, J. D., Hüttemann, M., & Malek, M. H. (2024). Mitochondrial Transplantation’s Role in Rodent Skeletal Muscle Bioenergetics: Recharging the Engine of Aging. Biomolecules, 14(4), 493.

A placebo-controlled Phase 1/2 trial conducted in East Shanghai has found that administering umbilical cord-derived mesenchymal stem cells reduces frailty in older people.

Stem cells against frailty

These researchers begin by defining frailty as “a state of heightened vulnerability to potential stressors as a consequence of reduction in physiological reserves across multiple systems” [1]. This vulnerability destroys the strength and endurance of older people, exhausting their stamina and greatly increasing their risks of death and disability, and a metric has been determined to measure this [2]. However, while vitamin supplements may help people with nutritional deficiencies, there are no medically approved drugs to treat frailty [3].

As stem cell exhaustion has been pinpointed as a cause of frailty [4], replacement stem cells have been investigated as a possible treatment. In particular, mesenchymal stem cells (MSCs), which are naturally attracted to injury sites [5], appear to be the most promising. MSCs have multiple potential sources for derivation [6], and previous trials have been conducted to treat frailty by using MSCs derived from bone marrow (BM-MSCs), with positive results [7, 8].

This study, however, was conducted on stem cells that were originally derived from the human umbilical cord (HUC-MSCs). These cells are easy to mass produce [9], have been successfully clinically tested against other diseases such as heart failure [10] and arthritis [11], and fight inflammation [12]. This, however, is the first trial of HUC-MSCs for frailty.

Frail adults only

All participants had to meet three criteria: to be between the ages of 60 and 80, to score between 1 and 4 on the Fried frailty scale [2], and to be expected to live another year. A large variety of co-morbidities were screened out, such as uncontrolled diabetes, serious cardiovascular problems, infections, and viral diseases. This was a double-blinded trial from which 80 potential candidates were excluded. 15 patients received placebo, and 15 received MSCs, for 6 months.

This study measured physical performance by testing grip strength, the timed up-and-go test, walking speed, and the ability to stand up and sit back down. Inflammatory cytokines such as interleukins were also measured, and sleep quality, quality of life, and mental health were also assessed.

Only good significant effects

There were no significant adverse effects. Three participants had suffered from ailments during the trial, two of which were in the placebo group and the third of which had dizziness not related to the MSCs.

Physical function, the primary endpoint of the study, was strongly affected by the MSCs. Even with only 30 total participants, not all of which participated in every assessment, the researchers were able to obtain, against baseline, a p-value of .003 after only one week of treatment and p-values under .001 for 1 and 6 months. Against placebo, the p-value at the end of the 6-month study was .042.

There were possible effects on mental health and sleep quality but those could be statistically attributed to the placebo effect. However, the treatment improved total quality of life with a p-value of 0.002 against placebo at the end of the study.

Cytokines had less clear effects; the placebo group spiked in TNF-α and IL-17 at 6 months while the MSC group did not.

While not all of the endpoints were hit, this study was against frailty, and it is clear from these results that MSCs have beneficial impacts on frailty in human beings. However, this study was conducted in one country among 30 people. Further work, with a larger sample size and more testing sites, will need to be conducted to determine if these results hold up under further scrutiny.

Literature

[1] Clegg, A., Young, J., Iliffe, S., Rikkert, M. O., & Rockwood, K. (2013). Frailty in elderly people. The lancet, 381(9868), 752-762.

[2] Fried, L. P., Tangen, C. M., Walston, J., Newman, A. B., Hirsch, C., Gottdiener, J., … & McBurnie, M. A. (2001). Frailty in older adults: evidence for a phenotype. The Journals of Gerontology Series A: Biological Sciences and Medical Sciences, 56(3), M146-M157.

[3] Dent, E., Morley, J. E., Cruz-Jentoft, A. J., Woodhouse, L., Rodríguez-Mañas, L., Fried, L. P., … & Vellas, B. (2019). Physical frailty: ICFSR international clinical practice guidelines for identification and management. The Journal of nutrition, health and aging, 23(9), 771-787.

[4] Schulman, I. H., Balkan, W., & Hare, J. M. (2018). Mesenchymal stem cell therapy for aging frailty. Frontiers in Nutrition, 5, 108.

[5] Golpanian, S., Wolf, A., Hatzistergos, K. E., & Hare, J. M. (2016). Rebuilding the damaged heart: mesenchymal stem cells, cell-based therapy, and engineered heart tissue. Physiological reviews, 96(3), 1127-1168.

[6] Zhang, J., Huang, X., Wang, H., Liu, X., Zhang, T., Wang, Y., & Hu, D. (2015). The challenges and promises of allogeneic mesenchymal stem cells for use as a cell-based therapy. Stem cell research & therapy, 6, 1-7.

[7] Golpanian, S., DiFede, D. L., Khan, A., Schulman, I. H., Landin, A. M., Tompkins, B. A., … & Hare, J. M. (2017). Allogeneic human mesenchymal stem cell infusions for aging frailty. Journals of Gerontology Series A: Biomedical Sciences and Medical Sciences, 72(11), 1505-1512.

[8] Tompkins, B. A., DiFede, D. L., Khan, A., Landin, A. M., Schulman, I. H., Pujol, M. V., … & Hare, J. M. (2017). Allogeneic mesenchymal stem cells ameliorate aging frailty: a phase II randomized, double-blind, placebo-controlled clinical trial. Journals of Gerontology Series A: Biomedical Sciences and Medical Sciences, 72(11), 1513-1522.

[9] Sarugaser, R., Lickorish, D., Baksh, D., Hosseini, M. M., & Davies, J. E. (2005). Human umbilical cord perivascular (HUCPV) cells: a source of mesenchymal progenitors. Stem cells, 23(2), 220-229.

[10] Bartolucci, J., Verdugo, F. J., González, P. L., Larrea, R. E., Abarzua, E., Goset, C., … & Khoury, M. (2017). Safety and efficacy of the intravenous infusion of umbilical cord mesenchymal stem cells in patients with heart failure: a phase 1/2 randomized controlled trial (RIMECARD trial [randomized clinical trial of intravenous infusion umbilical cord mesenchymal stem cells on cardiopathy]). Circulation research, 121(10), 1192-1204.

[11] Wang, L., Huang, S., Li, S., Li, M., Shi, J., Bai, W., … & Liu, Y. (2019). Efficacy and safety of umbilical cord mesenchymal stem cell therapy for rheumatoid arthritis patients: a prospective phase I/II study. Drug design, development and therapy, 4331-4340.

[12] Uccelli, A., Pistoia, V., & Moretta, L. (2007). Mesenchymal stem cells: a new strategy for immunosuppression?. Trends in immunology, 28(5), 219-226.

A study published in Human Nutrition & Metabolism found that prolonged intermittent fasting causes the expression of genes involved in autophagy, the inflammasome, and senescence to change [1].

Fasting your way to better health and longevity?

Previous research has linked fasting to delaying the onset of age-related diseases and longevity along with positive outcomes in several diseases [2]. It has been documented to benefit patients with type 1 and 2 diabetes, cancer, cardiovascular disease, and major depressive disorder [2, 3, 4].

The authors of this paper were particularly interested in what fasting does to the human body on the molecular level, attempting to determine the impacts of prolonged intermittent fasting on health and longevity markers in humans. Therefore, they recruited 25 healthy young men who intended “to fast for the whole month of Ramadan from dawn to dusk.” They measured gene expression levels one week before Ramadan, in the middle of Ramadan, in the last days of Ramadan, and one week after Ramadan.

Fasting induces autophagy

Intermittent fasting activates autophagy, a cellular process through which cells break down their components. Studies have linked the activation of autophagy to longevity, and there are many proteins involved in this process. These researchers tested ULK1, a sensor of nutrient levels and autophagy signals [5]; ATG5, a gene encoding a protein that serves in autophagy induction [6]; and BECN1, a gene encoding a protein necessary in the early steps of autophagy for autophagosome formation [7].

The researchers observed an increase in ULK1 levels caused by fasting two weeks and one month after starting fasting. However, cessation of fasting caused ULK1 to return to its basal levels. Another autophagy protein, ATG5, has shown a similar pattern. The observed pattern is consistent with the function of ULK1 and ATG5 in nutrient sensing and autophagy induction.

BECN1 has shown a different pattern, which included an increase in BECN1 two weeks after starting the fast and a subsequent reduction in its expression levels. Since BECN1’s role in autophagy is more dynamic, this might influence more complex changes in its levels. Additionally, BECN1’s role in apoptosis suggests a hypothesis that “reduction of BECN1 expression level at later time points is to avoid unnecessary apoptosis in healthy individuals” while simultaneously keeping autophagy processes induced, as suggested by the expression of other autophagy genes.

Inflammation and senescence

As part of the immune system, the inflammasome, in response to stimuli, “regulates the activation of many pathways resulting in the secretion of cytokines” [8]. However, the inflammasome can also contribute to inflammaging, a process associated with aging and age-related diseases. The authors measured the expression of genes connected to the inflammasome: NLRP3, a core protein of the inflammasome complex [9]; ASC, a marker of an activated inflammasome complex [10]; and IL-1β, a proinflammatory cytokine [11].

The researchers didn’t find TNF-α levels to change in a statistically significant way, which is contrary to a previous study that found TNF-α upon intermittent fasting.

Other examined genes showed changes in expression. NLRP3 and IL-1β expression was increased two weeks and one month after the start of the intermittent fasting, and the levels decreased one week after the end of fasting. The authors point out that those results contradict other studies. However, they point out that autophagy promotes inflammation in a way that depends on Atg5 [12], connecting it to their results regarding autophagy genes.

On the other hand, they observed that expression of ASC was lower than basal levels one month after the start of intermittent fasting, suggesting that despite higher levels of NLRP3 and IL-1β, most likely caused by ATG5 induction, the inflammasome is not activated. They suggest that prolonged fasting might have activated some non-canonical pathways.

The authors also tested markers of senescence, a cellular process that is a hallmark of aging. Previous research suggests that fasting might reduce senescence by activating autophagy [13]. The senescence markers they used included the senescence mediator p16INK4a, which is essential in senescence initiation through p21 induction [14]. p21 can induce cell cycle arrest, and p53 activation can lead to senescence [15].

The researchers didn’t observe statistically significant changes in the p16INK4a expression levels until the end of their observation. Nevertheless, they observed that p16INK4A expression tends to increase after the start of fasting and then decrease.

The authors observed p21 levels decreasing during and after the fasting. However, those observations are not statistically significant and contradict what was previously reported in animal models. The authors also point out p21’s role as an injury marker required for proliferation and regeneration [16], leading to the hypothesis that p21 levels might be increased during acute fasting but reduced during longer fasting periods.

The final marker was p53 expression, which was increased during fasting. Its levels decreased after fasting cessation. These results align with previous research showing p53 responding to nutrient depletion [17]. p53 can also act as an autophagy activator, which aligns with ATG5 and ULK1 expression during fasting. The authors explain that since they saw an increase in p53 expression but not a significant increase in p16INK4a and p21, they hypothesized this increase to be related to p53’s role in DNA repair but not senescence.

More population variables are needed for future studies

This study has demonstrated that markers of autophagy, inflammasome, and senescence are related in complex ways. While the authors provided many hypothesized explanations, further research is necessary to confirm or refute them.

The authors point out some of this study’s limitations. One is that food intake, physical activity, and sleeping patterns were not recorded, and the authors believe that these variables could have an impact on gene expression patterns. Additionally, only young males were included in this study, making these results questionable for other demographic groups. While the authors recorded the levels of gene expression, the levels of actual proteins may differ, and future studies are needed to assess them.

Literature

[1] Erlangga, Z., Ghashang, S. K., Hamdan, I., Melk, A., Gutenbrunner, C., & Nugraha, B. (2023). The effect of prolonged intermittent fasting on autophagy, inflammasome and senescence genes expressions: An exploratory study in healthy young males. Human Nutrition & Metabolism, 32, 200189.

[2] Longo, V. D., Di Tano, M., Mattson, M. P., & Guidi, N. (2021). Intermittent and periodic fasting, longevity and disease. Nature aging, 1(1), 47–59.

[3] Grajower, M. M., & Horne, B. D. (2019). Clinical Management of Intermittent Fasting in Patients with Diabetes Mellitus. Nutrients, 11(4), 873.

[4] Berthelot, E., Etchecopar-Etchart, D., Thellier, D., Lancon, C., Boyer, L., & Fond, G. (2021). Fasting Interventions for Stress, Anxiety and Depressive Symptoms: A Systematic Review and Meta-Analysis. Nutrients, 13(11), 3947.

[5] Ganley, I. G., Lam, duH., Wang, J., Ding, X., Chen, S., & Jiang, X. (2009). ULK1.ATG13.FIP200 complex mediates mTOR signaling and is essential for autophagy. The Journal of biological chemistry, 284(18), 12297–12305.

[6] Zheng, W., Xie, W., Yin, D., Luo, R., Liu, M., & Guo, F. (2019). ATG5 and ATG7 induced autophagy interplays with UPR via PERK signaling. Cell communication and signaling : CCS, 17(1), 42.

[7] Menon, M. B., & Dhamija, S. (2018). Beclin 1 Phosphorylation – at the Center of Autophagy Regulation. Frontiers in cell and developmental biology, 6, 137.

[8] Zheng, D., Liwinski, T., & Elinav, E. (2020). Inflammasome activation and regulation: toward a better understanding of complex mechanisms. Cell discovery, 6, 36.

[9] Swanson, K. V., Deng, M., & Ting, J. P. (2019). The NLRP3 inflammasome: molecular activation and regulation to therapeutics. Nature reviews. Immunology, 19(8), 477–489.

[10] Schroder, K., & Tschopp, J. (2010). The inflammasomes. Cell, 140(6), 821–832.

[11] Kaneko, N., Kurata, M., Yamamoto, T., Morikawa, S., & Masumoto, J. (2019). The role of interleukin-1 in general pathology. Inflammation and regeneration, 39, 12.

[12] Dupont, N., Jiang, S., Pilli, M., Ornatowski, W., Bhattacharya, D., & Deretic, V. (2011). Autophagy-based unconventional secretory pathway for extracellular delivery of IL-1β. The EMBO journal, 30(23), 4701–4711.

[13] Shetty, A. K., Kodali, M., Upadhya, R., & Madhu, L. N. (2018). Emerging Anti-Aging Strategies – Scientific Basis and Efficacy. Aging and disease, 9(6), 1165–1184.

[14] Song, S., Lam, E. W., Tchkonia, T., Kirkland, J. L., & Sun, Y. (2020). Senescent Cells: Emerging Targets for Human Aging and Age-Related Diseases. Trends in biochemical sciences, 45(7), 578–592.

[15] Mijit, M., Caracciolo, V., Melillo, A., Amicarelli, F., & Giordano, A. (2020). Role of p53 in the Regulation of Cellular Senescence. Biomolecules, 10(3), 420.

[16] Sturmlechner, I., Zhang, C., Sine, C. C., van Deursen, E. J., Jeganathan, K. B., Hamada, N., Grasic, J., Friedman, D., Stutchman, J. T., Can, I., Hamada, M., Lim, D. Y., Lee, J. H., Ordog, T., Laberge, R. M., Shapiro, V., Baker, D. J., Li, H., & van Deursen, J. M. (2021). p21 produces a bioactive secretome that places stressed cells under immunosurveillance. Science (New York, N.Y.), 374(6567), eabb3420.

[17] Schupp, M., Chen, F., Briggs, E. R., Rao, S., Pelzmann, H. J., Pessentheiner, A. R., Bogner-Strauss, J. G., Lazar, M. A., Baldwin, D., & Prokesch, A. (2013). Metabolite and transcriptome analysis during fasting suggest a role for the p53-Ddit4 axis in major metabolic tissues. BMC genomics, 14, 758.