OTR-AC

Potential Health Benefits of OTR-AC

• Increases muscle mass and strength [1-9]
• Reduces body fat [5, 10-12]
• Improves bone health [13-15]
• Lowers cholesterol levels [10, 13]
• Improves blood sugar levels [2, 7]

What is OTR-AC?

OTR-AC, also called MK-2866 Ester, is MK-2866 (Ostarine) which has undergone esterification (the process of combining an organic acid with an alcohol). This chemical process is used to maximize the potency and increase the half-life (the time required for a quantity to reduce to half of its initial value) of a substance. Because of this process, the ester version of ostarine has the capacity to remain bioactive ten times longer. This in turn achieves more benefits such as decreased dosing frequency and more stable blood levels.

How OTR-AC Works

As the ester version of the selective androgen receptor modulator (SARM) ostarine, OTR-AC is more potent and has longer effects. By attaching to proteins in the body known as androgen receptors, it stimulates the formation of muscle tissue. This in turn increases muscle mass and strength.

Chemical Structure of OTR-AC

Research on OTR-AC

Increases Muscle Mass and Strength

Studies suggest that OTR-AC along with other SARMs increases muscle mass and strength by stimulating the formation of muscle tissue:

1. In older adults, the administration of SARMs including OTR-AC resulted in increased lean muscle mass and decreased body fat percentage. [1]
2. In elderly men and women, OTR-AC administration resulted in increased lean muscle mass, decreased fat mass, and significant improvements in their ability to climb stairs. [2-4]
3. Studies showed that OTR-AC may help increase muscle mass in patients with cancer cachexia (muscle wasting). [5-6]
4. In elderly men and postmenopausal women, OTR-AC significantly improved total lean body mass and physical function. [7]
5. In rats that had surgical removal of the ovaries, OTR-AC improved muscle tissue. [8]
6. In rats, OTR-AC increased muscle mass by increasing the production of muscle cells. [9]

Reduces Body Fat

Aside from helping gain muscle mass, OTR-AC has also been found to reduce overall body fat:

1. In Phase I and II clinical trials, OTR-AC has demonstrated promising results in increasing total lean body mass, decreasing total tissue percent fat, and enhancing functional performance. [5]
2. A review of studies showed that OTR-AC can help increase lean body mass and decrease body fat in overweight patients. [10]
3. In a phase 2a study, the administration of OTR-AC along with other SARMs resulted in increased lean fat mass and decreased body fat percentage. [11]
4. In male rats, OTR-AC increased fat cell breakdown by improving lipid metabolism and affecting the release of adiponectin (a hormone that regulates fatty acid breakdown). [12]

Improves Bone Health

Studies suggest that OTR-AC can help stimulate bone formation and protect against bone disorders:

1. In rats that had surgical removal of the ovaries, OTR-AC administration resulted in improved bone healing. [13]
2. In a rat model for aged male osteoporosis, both OTR-AC and testosterone treatments improved bone healing by increasing callus volume and area, bone volume and density, and bone width [14]
3. In a rat model of postmenopausal osteoporosis, high doses of OTR-AC for 5 weeks resulted in increased bone volume, density, and bone mineral density. [15]

Lowers Cholesterol Levels

Evidence suggests that OTR-AC can help lower cholesterol levels especially low-density lipoprotein (bad cholesterol):

1. In elderly men and postmenopausal women, OTRC-AC administration resulted in significant reduction in low-density lipoprotein levels. [10]
2. In rats that had surgical removal of the ovaries, OTR-AC treatment reduced the blood levels of cholesterol. [13]

Improves Blood Sugar Levels

Studies also found that OTR-AC can help improve blood sugar levels in older people:

1. In elderly men and women, OTR-AC administration decreased fasting blood glucose and insulin resistance (a condition in which the body does not respond to the effects of insulin) while increasing muscle mass. [2]
2. In elderly men and postmenopausal women, OTR-AC treatment improved blood sugar levels by correcting insulin resistance. [7]

Associated Side Effects of OTR-AC

OTR-AC side effects are very uncommon. There have been some side effects associated with the use of this SARM wherein the patient had one of the issues listed below at some point while being on OTR-AC. However, the issue wasn’t’ confirmed to be caused by the treatment and could have been a coincidence and not related to the use of OTR-AC. Despite this, it was listed as a side effect associated with OTR-AC even though these associated side effects are very uncommon.
Side effects associated with OTR-AC may include the following:

• Headache
• Nausea
• Fatigue
• Back pain
• Elevation in liver enzymes such as alanine transaminase (ALT)
• Reductions in high-density lipoprotein
• Low blood sugar
• Insulin resistance

References

1. Bhasin S. Selective Androgen Receptor Modulators as Function Promoting Therapies. J Frailty Aging. 2015;4(3):121-122. doi:10.14283/jfa.2015.65.
2. Dalton JT 2007 Development and potential uses of selective androgen receptor modulators (SARMs). American Society of Andrology.
3. Dalton JT, Therapeutic promise of selective androgen receptor modulators (SARMs): preclinical and clinical proof-of-concept studies. Program of the 89th Annual Meeting of The Endocrine Society, Toronto, Canada, 2007 (Abstract 41-42).
4. Steiner M. S.; Barnette K. G.; Hancock M. L.; Dodson S. T.; Rodriguez D.; Morton R. A. Effect of GTx-024, a selective androgen receptor modulator (SARM), on stair climb performance and quality of life (QOL) in patients with cancer cachexia. ASCO Meeting Abstracts 2010, 28, 9147.
5. Zilbermint, M. F., & Dobs, A. S. (2009). Nonsteroidal selective androgen receptor modulator Ostarine in cancer cachexia. Future oncology (London, England), 5(8), 1211–1220. https://doi.org/10.2217/fon.09.106.
6. Zilbermint, M. F., & Dobs, A. S. (2009). Nonsteroidal selective androgen receptor modulator Ostarine in cancer cachexia. Future oncology (London, England), 5(8), 1211–1220. https://doi.org/10.2217/fon.09.106.
7. Dalton JT, Barnette KG, Bohl CE, Hancock ML, Rodriguez D, Dodson ST, Morton RA, Steiner MS. The selective androgen receptor modulator GTx-024 (enobosarm) improves lean body mass and physical function in healthy elderly men and postmenopausal women: results of a double-blind, placebo-controlled phase II trial. J Cachexia Sarcopenia Muscle. 2011 Sep;2(3):153-161. doi: 10.1007/s13539-011-0034-6. Epub 2011 Aug 2. PMID: 22031847; PMCID: PMC3177038.
8. Roch PJ, Henkies D, Carstens JC, Krischek C, Lehmann W, Komrakova M, Sehmisch S. Ostarine and Ligandrol Improve Muscle Tissue in an Ovariectomized Rat Model. Front Endocrinol (Lausanne). 2020 Sep 17;11:556581. doi: 10.3389/fendo.2020.556581. PMID: 33042018; PMCID: PMC7528560.
9. Leciejewska, N., Kołodziejski, P. A., Sassek, M., Nogowski, L., Małek, E., & Pruszyńska-Oszmałek, E. (2022). Ostarine-Induced Myogenic Differentiation in C2C12, L6, and Rat Muscles. International journal of molecular sciences, 23(8), 4404. https://doi.org/10.3390/ijms23084404.
10. Solomon ZJ, Mirabal JR, Mazur DJ, Kohn TP, Lipshultz LI, Pastuszak AW. Selective Androgen Receptor Modulators: Current Knowledge and Clinical Applications. Sex Med Rev. 2019;7(1):84-94. doi:10.1016/j.sxmr.2018.09.006.
11. Narayanan R, Mohler ML, Bohl CE, Miller DD, Dalton JT. Selective androgen receptor modulators in preclinical and clinical development. Nucl Recept Signal. 2008;6:e010.
12. Leciejewska, N., Pruszynska-Oszmalek, E., Bien, J., Nogowski, L., & Kolodziejski, P. A. (2019). Effect of ostarine (enobosarm/GTX024), a selective androgen receptor modulator, on adipocyte metabolism in Wistar rats. Journal of physiology and pharmacology : an official journal of the Polish Physiological Society, 70(4), 10.26402/jpp.2019.4.04. https://doi.org/10.26402/jpp.2019.4.04.
13. Komrakova M, Furtwängler J, Hoffmann DB, Lehmann W, Schilling AF, Sehmisch S. The Selective Androgen Receptor Modulator Ostarine Improves Bone Healing in Ovariectomized Rats. Calcif Tissue Int. 2020 Feb;106(2):147-157. doi: 10.1007/s00223-019-00613-1. Epub 2019 Sep 17. PMID: 31531719.
14. Komrakova M, Nagel J, Hoffmann DB, Lehmann W, Schilling AF, Sehmisch S. Effect of Selective Androgen Receptor Modulator Enobosarm on Bone Healing in a Rat Model for Aged Male Osteoporosis. Calcif Tissue Int. 2020;107(6):593-602. doi:10.1007/s00223-020-00751-x.
15. Hoffmann DB, Komrakova M, Pflug S, et al. Evaluation of ostarine as a selective androgen receptor modulator in a rat model of postmenopausal osteoporosis. J Bone Miner Metab 2019;37:243-55. 10.1007/s00774-018-0929-9.