YK-11 Literature Overview — Research Reference
YK-11 is a steroidal research compound that has garnered significant attention in the scientific community for its dual-faceted mechanism of action, primarily investigated for its interactions with the androgen receptor and its modulatory effects on the myostatin pathway. Its unique chemical structure and observed biological activities in various research models make it a subject of ongoing preclinical and mechanistic inquiry.
Research into YK-11 is well-documented, with numerous publications indexed on platforms like PubMed, reflecting a broad interest in understanding its biochemical properties and biological effects in controlled experimental settings. Furthermore, its potential relevance in specific research domains is underscored by several registered studies on ClinicalTrials.gov, which typically focus on foundational aspects of its action or broader physiological impacts within rigorous research parameters, strictly adhering to non-human or very early-stage exploratory research protocols.
Chemical Structure and Classification as a Steroidal Research Compound
YK-11, chemically identified as (17α,20E)-17,20-[(1-methoxyethylidene)bis(oxy)]-3-oxo-19-norpregna-4,9,11-triene-21-carboxylic acid methyl ester, exhibits a unique molecular architecture that positions it as a fascinating subject in biochemical research. Its foundational scaffold is derived from a steroidal framework, specifically a 19-norandrostane nucleus, which is a common feature among many investigational androgen receptor modulators and anabolic agents. This steroidal backbone provides the necessary structural elements for interaction with steroid hormone receptors. However, YK-11 distinguishes itself through specific modifications that confer its investigational properties, including a methoxyethylidene acetal group at the C-17 and C-20 positions, and a methyl ester functionality at the C-21 carboxylic acid. These structural elaborations are hypothesized to influence its binding affinity, receptor selectivity, and metabolic stability within various research models.
The classification of YK-11 as a selective androgen receptor modulator (SARM) stems from initial research indicating its capacity to bind to the androgen receptor (AR) with a degree of selectivity for anabolic pathways over androgenic ones in certain experimental contexts. Unlike traditional anabolic steroids, which are typically full agonists of the androgen receptor across a broad spectrum of tissues, SARMs are designed or observed to exhibit tissue-selective agonism. This selectivity is a critical area of investigation in the development of new research tools to understand androgen signaling. YK-11’s steroidal nature, while setting it apart from many non-steroidal SARMs, still warrants its inclusion in this class due to its observed AR modulating activity in preclinical studies. The study of its unique steroidal structure in the context of SARM activity provides valuable insights into structure-activity relationships within the androgen receptor ligand binding domain.
Beyond its SARM classification, YK-11 is also extensively researched for its role as a myostatin modulator. Myostatin is a protein that limits muscle growth, and compounds that interfere with its signaling pathway are of significant interest in studies pertaining to muscle wasting and regeneration. The ability of YK-11 to potentially upregulate follistatin, a naturally occurring myostatin antagonist, suggests a dual mechanism of action that is quite uncommon among investigational compounds. This unique characteristic underscores the compound’s multifaceted research utility, allowing scientists to explore both androgenic and myostatin-related pathways simultaneously or independently, depending on the experimental design. Its steroidal structure, combined with these distinct functional properties, makes YK-11 a complex and compelling molecule for in-depth biochemical and pharmacological investigation.
The precise structural nuances of YK-11, particularly the modifications around the D-ring and the C-17 position, are crucial for understanding its interactions with target proteins. Research into the stereochemistry of the methoxyethylidene acetal group, for instance, could reveal specific orientations that facilitate or hinder binding to the androgen receptor or influence its interaction with components of the myostatin pathway. Such detailed structural analysis is paramount for elucidating its full mechanistic profile and for guiding future rational design efforts in medicinal chemistry research. The exploration of YK-11’s structure-activity relationships is ongoing, providing a foundation for understanding how subtle chemical modifications to a steroidal scaffold can lead to distinct and valuable research properties.
Investigative Studies on Androgen Receptor Modulation
Investigative studies into YK-11’s androgen receptor (AR) modulation properties form a cornerstone of its biochemical characterization. These studies primarily aim to elucidate its binding affinity, selectivity, and functional agonistic or antagonistic activity at the AR in various cellular and tissue contexts. Early research indicated that YK-11, despite its steroidal backbone, appears to function as a selective AR modulator. This means it can theoretically activate the AR in some tissues, such as skeletal muscle and bone, while potentially exhibiting reduced activity in others, like prostatic tissue, compared to traditional full AR agonists such as testosterone or dihydrotestosterone. The precise mechanisms governing this tissue selectivity are a complex area of ongoing research, involving considerations of receptor co-activator/co-repressor recruitment, metabolic conversion rates within different cell types, and overall cellular signaling environments.
In vitro assays commonly employed to investigate YK-11’s AR modulation include competitive ligand binding assays using radiolabeled androgen ligands to determine its binding affinity relative to established AR ligands. Reporter gene assays, where cells are transfected with an androgen-responsive promoter linked to a reporter gene (e.g., luciferase), are critical for assessing YK-11’s ability to activate AR-mediated gene transcription. These studies allow researchers to quantify its potency and efficacy as an AR agonist and to compare it against a spectrum of other SARMs and traditional androgens. Furthermore, cell proliferation assays in AR-positive cell lines (e.g., LNCaP prostate cancer cells or C2C12 myoblasts engineered for AR expression) help to observe the impact of YK-11 on cell growth and differentiation, providing insights into its potential tissue-specific effects. These foundational studies are crucial for understanding the basic pharmacological profile of YK-11 as an AR ligand. More information on such mechanisms can be found on our YK-11 Mechanism of Action research page.
A key aspect of YK-11 research involves dissecting its molecular interactions with the AR protein. While it binds to the AR ligand-binding domain, similar to other androgens, the precise conformational changes it induces in the receptor are hypothesized to differ, leading to differential recruitment of co-regulator proteins. This differential co-regulator recruitment is a hallmark of selective receptor modulators and is believed to be the basis for tissue specificity. Researchers utilize techniques such as co-immunoprecipitation and protein-protein interaction assays to identify which co-activators or co-repressors are engaged by the AR in the presence of YK-11, versus in the presence of full agonists or antagonists. Understanding these subtle molecular interactions is vital for predicting YK-11’s biological effects in various research models and for distinguishing its SARM activity from that of other compounds.
Beyond direct AR binding and transactivation, investigations also encompass the downstream genomic and non-genomic effects of YK-11’s AR modulation. Gene expression profiling using techniques like RNA sequencing or quantitative PCR can reveal patterns of gene upregulation or downregulation in AR-sensitive tissues or cell lines treated with YK-11. These studies provide a comprehensive view of the cellular pathways influenced by YK-11, extending beyond the traditionally recognized AR target genes. The long-term effects of AR modulation by YK-11 in research models, including potential receptor desensitization or altered receptor expression, are also areas of ongoing interest. Such detailed mechanistic investigations contribute significantly to the broader understanding of SARM pharmacology and the intricate nature of androgen signaling in biological systems.
Myostatin Pathway Research and Follistatin Upregulation
The research into YK-11’s influence on the myostatin pathway represents a distinct and highly significant area of investigation, setting it apart from many other androgen receptor modulators. Myostatin, a member of the transforming growth factor-beta (TGF-β) superfamily, acts as a negative regulator of muscle growth, effectively limiting the extent to which muscle tissue can develop. Its physiological role is to prevent excessive muscle hypertrophy, maintaining muscle homeostasis. Consequently, compounds capable of inhibiting myostatin signaling are of immense interest for research into conditions characterized by muscle wasting (cachexia) or for understanding the fundamental mechanisms of muscle hypertrophy and regeneration. YK-11’s proposed mechanism of action in this regard involves the upregulation of follistatin, a naturally occurring glycoprotein that functions as a direct antagonist to myostatin. Follistatin binds to myostatin, rendering it inactive and preventing it from binding to its receptor, thereby promoting muscle growth and differentiation.
Research on YK-11’s interaction with the myostatin pathway typically begins with in vitro studies using myoblast cell lines, such as C2C12 cells, which are well-established models for studying muscle cell differentiation. In these models, researchers apply YK-11 and observe its effects on markers of myogenesis, including the expression of myogenic regulatory factors (e.g., MyoD, myogenin) and structural muscle proteins (e.g., myosin heavy chain). Crucially, studies measure the expression levels of follistatin mRNA and protein using techniques like RT-qPCR and Western blotting. An observed increase in follistatin expression following YK-11 administration in these cell cultures provides compelling evidence for its role as a myostatin modulator. Furthermore, researchers might challenge these cells with exogenous myostatin to see if YK-11 can counteract its inhibitory effects on differentiation and growth, thereby demonstrating functional antagonism.
The molecular underpinnings of YK-11’s follistatin-upregulating activity are a primary focus of advanced mechanistic investigations. While the exact signaling cascades remain an active area of research, it is hypothesized that YK-11 may influence transcriptional pathways responsible for follistatin gene expression. This could occur through direct or indirect interaction with specific transcription factors or via modulation of upstream signaling pathways that ultimately converge on the follistatin promoter. The involvement of the SMAD signaling pathway, which is central to TGF-β family signaling including myostatin, is also a key area of inquiry. Myostatin typically signals through SMAD2/3, leading to the repression of myogenesis. Research aims to determine if YK-11, through follistatin upregulation or other means, interferes with this SMAD-dependent signaling to alleviate myostatin’s inhibitory effects.
In vivo preclinical studies further explore YK-11’s impact on the myostatin pathway and muscle growth in animal models. These studies involve administering YK-11 to rodents and then assessing changes in muscle mass, fiber type, and the expression of myostatin and follistatin in skeletal muscle tissue. Histological analyses, including muscle fiber diameter measurements and immunohistochemistry for specific proteins, provide direct evidence of YK-11’s effects on muscle morphology. The interplay between YK-11’s androgen receptor modulation and its myostatin antagonism is also a complex and intriguing aspect of research. It is possible that these two mechanisms act synergistically or independently to contribute to observed anabolic effects in muscle tissue, offering a richer understanding of muscle physiology and potential avenues for future research into maintaining muscle mass and function in various experimental contexts.
Detailed Mechanistic Investigations Beyond Androgen Receptors and Myostatin
While YK-11 is primarily characterized by its selective androgen receptor (AR) modulation and myostatin pathway influence, detailed mechanistic investigations extend beyond these two well-established areas to uncover a broader spectrum of its biological activities. The intricate nature of cellular signaling pathways suggests that a compound with significant receptor interactions, especially one with a steroidal scaffold, might engage with other molecular targets or elicit secondary signaling cascades. Researchers are actively exploring these less-understood facets to develop a comprehensive mechanistic profile of YK-11, which is crucial for fully understanding its potential utility as a research tool. These explorations often involve high-throughput screening, global omics approaches, and targeted assays designed to probe interactions with diverse cellular components.
One significant area of extended mechanistic investigation involves potential interactions with other nuclear receptors or steroid hormone receptors beyond the AR. Given its steroidal structure, researchers examine if YK-11 exhibits any binding affinity for glucocorticoid, mineralocorticoid, estrogen, or progesterone receptors in various cell lines. While initial selectivity studies aim to rule out such interactions, subtle cross-reactivity or off-target effects can sometimes manifest at higher concentrations or in specific cellular contexts. Furthermore, the metabolic fate of YK-11 within biological systems is also under scrutiny. Its biotransformation products might themselves possess distinct pharmacological activities or interact differently with the AR or other receptors. Understanding these metabolic pathways, including potential conjugation or enzymatic breakdown, is essential for interpreting observed effects in both in vitro and in vivo studies and for optimizing experimental designs.
Beyond direct receptor binding, detailed studies probe YK-11’s influence on cellular metabolism and energy homeostasis. Researchers might investigate its effects on mitochondrial function, glucose uptake, lipid metabolism, or oxidative stress pathways in relevant cell lines (e.g., skeletal muscle cells, adipocytes). Techniques such as Seahorse Bioscience assays for mitochondrial respiration, glucose uptake assays, or measurements of reactive oxygen species provide insights into these broader cellular impacts. Such studies help determine if YK-11’s reported anabolic effects are solely due to AR and myostatin modulation or if they are compounded by other metabolic shifts that promote tissue anabolism or energy utilization. For instance, any influence on AMPK or mTOR signaling pathways, critical regulators of cell growth and metabolism, would be highly relevant.
Finally, comprehensive gene expression profiling (transcriptomics) and proteomic analyses are powerful tools used to uncover the full extent of YK-11’s cellular impact. By comparing the global gene and protein expression patterns in treated versus untreated cells or tissues, researchers can identify novel pathways, signaling networks, or molecular targets that are modulated by YK-11. These unbiased approaches can reveal unexpected effects that might not be predicted based on initial hypotheses centered solely on AR and myostatin. For example, YK-11 might influence pathways related to inflammation, cellular stress responses, or cell cycle regulation. Such detailed investigations are critical for building a complete mechanistic picture of YK-11, paving the way for a deeper understanding of its biological properties and informing future research directions.
In Vitro Research Models and Cellular Responses to YK-11
In vitro research models play an indispensable role in dissecting the molecular and cellular mechanisms of action of investigational compounds like YK-11. These controlled laboratory environments allow researchers to isolate specific cell types or pathways and study their responses to YK-11 without the complexities of a whole organism. The utility of in vitro models ranges from initial screening for binding affinity and receptor activation to detailed investigations into gene expression, protein synthesis, and cellular differentiation. A primary advantage of these models is the ability to precisely control experimental conditions, including concentration, duration of exposure, and nutrient availability, which facilitates the generation of reproducible and interpretable data.
Commonly Utilized Cell Lines and Assays
A variety of cell lines are employed to investigate YK-11’s multifaceted effects:
- Skeletal Muscle Cells: Myoblast cell lines, such as C2C12 (mouse) or L6 (rat), are extensively used to study YK-11’s anabolic properties. In these models, researchers assess myoblast proliferation, differentiation into myotubes, and the expression of myogenic regulatory factors (e.g., MyoD, Myogenin) and structural muscle proteins (e.g., myosin heavy chain). Assays also include measurements of protein synthesis rates and cellular hypertrophy.
- Androgen Receptor (AR)-Positive Cells: Cell lines naturally expressing or engineered to express the androgen receptor, such as LNCaP (human prostate cancer cells, which are AR-positive) or HEK293 cells transfected with AR, are critical for evaluating YK-11’s AR binding and transactivation capabilities. Reporter gene assays, using androgen-responsive promoters linked to luciferase, are standard for quantifying AR agonism.
- Osteoblast/Bone Cells: MC3T3-E1 (mouse pre-osteoblasts) or human osteoblast-like cell lines are used to investigate YK-11’s potential effects on bone formation and mineralization, which is relevant given the anabolic effects of androgens on bone tissue. Assays might include alkaline phosphatase activity, calcium deposition, and expression of bone markers.
- Other Cell Types: Depending on the specific research question, researchers might also utilize fibroblasts, adipocytes, or various immortalized cell lines to explore YK-11’s broader cellular impacts beyond its primary known mechanisms.
Cellular responses to YK-11 are typically quantified using a range of biochemical and molecular techniques. For example, the upregulation of follistatin, a key mechanism of YK-11, is often confirmed by quantitative polymerase chain reaction (qPCR) to measure mRNA levels and Western blotting to assess protein expression in treated myoblasts. Immunocytochemistry can visualize changes in protein localization or cellular morphology. Furthermore, advanced techniques like RNA sequencing (RNA-Seq) provide a global view of transcriptional changes induced by YK-11, identifying entire gene networks affected by the compound. Proteomics, using mass spectrometry, offers complementary insights into global protein expression changes. These comprehensive approaches are vital for elucidating both direct and indirect cellular responses.
Challenges in interpreting in vitro data include the extrapolation of findings to complex in vivo systems. While individual cellular mechanisms can be meticulously studied, the interplay of different cell types, systemic metabolism, and compensatory physiological responses are not fully recapitulated in cell culture. Therefore, positive findings in vitro often serve as a strong basis for hypothesis generation, leading to subsequent validation in more complex preclinical animal models. The careful design of in vitro experiments, coupled with rigorous controls and appropriate concentration ranges, ensures that the insights gained are as relevant as possible for advancing our understanding of YK-11’s fundamental biochemical effects.
In Vivo Preclinical Studies: Observations in Animal Models
In vivo preclinical studies are essential for translating the molecular and cellular insights gained from in vitro research into a systemic biological context. These studies, predominantly conducted in animal models, provide critical observations regarding the pharmacokinetics, bioavailability, systemic effects, and potential tissue selectivity of investigational compounds like YK-11. While animal models offer a more complex and integrated biological system than cell cultures, it is crucial to acknowledge that their physiological responses may not always perfectly mirror those of other species. Nevertheless, they serve as invaluable tools for exploring dose-response relationships, routes of administration, and the overall impact of YK-11 on various organ systems over time in a controlled experimental setting.
Common Animal Models and Endpoints
Rodent models, primarily mice and rats, are the most frequently employed species in preclinical YK-11 research due to their genetic tractability, relatively short lifespans, and ease of handling. Studies often involve administering YK-11 via oral gavage, subcutaneous injection, or sometimes intramuscular injection, to evaluate its efficacy and systemic distribution. Key endpoints measured in these in vivo studies include:
- Body Composition Analysis: Changes in lean muscle mass, fat mass, and overall body weight are frequently assessed using techniques such as DEXA (Dual-energy X-ray absorptiometry) scans, NMR (Nuclear Magnetic Resonance) body composition analysis, or direct tissue weighing post-mortem. This is crucial for evaluating YK-11’s anabolic effects.
- Skeletal Muscle Function and Morphology: Researchers measure grip strength, exercise endurance, and specific muscle force generation in isolated muscles. Histological analyses of muscle tissue provide insights into fiber size, type distribution, and regeneration markers. Immunostaining can quantify protein expression, such as follistatin or myostatin, within the muscle.
- Bone Mineral Density (BMD): DEXA scans or micro-CT imaging of specific bones (e.g., femur, tibia, lumbar vertebrae) are used to assess changes in bone mass and microstructure, which is relevant given the anabolic effects of androgens on bone.
- Organ Weights and Histology: The weights of various organs (e.g., heart, liver, kidney, prostate, seminal vesicles) are recorded, and tissues are processed for histological examination to detect any pathological changes or specific cellular alterations induced by YK-11. This is particularly important for assessing tissue selectivity and potential off-target effects.
- Biochemical Blood Markers: Blood samples are analyzed for changes in hormone levels (e.g., testosterone, LH, FSH), lipid profiles, liver enzymes (ALT, AST), kidney function markers (creatinine, BUN), and other systemic indicators to monitor physiological responses and potential systemic impacts.
Observations from these preclinical studies have frequently indicated that YK-11 can lead to an increase in lean muscle mass and improvements in muscle strength in rodent models, particularly when compared to control groups. These anabolic effects are often accompanied by evidence of follistatin upregulation in skeletal muscle tissue, supporting the myostatin-modulating hypothesis derived from in vitro work. Furthermore, researchers meticulously monitor androgenic side effects by examining changes in prostate and seminal vesicle weights. While some studies suggest a degree of tissue selectivity, where anabolic effects might be observed with less pronounced androgenic effects on reproductive tissues compared to traditional androgens, the precise extent and mechanisms of this selectivity remain a critical area of ongoing investigation. These findings contribute significantly to the understanding of YK-11’s pharmacological profile within a living system.
Despite their immense value, in vivo animal models present several limitations. Species-specific metabolic differences, variations in receptor expression, and complex compensatory mechanisms can influence the observed outcomes. Dosing strategies must be carefully considered, as extrapolating doses from animal models to other species, including humans (in clinical research settings), is a complex process and outside the scope of research-use-only compounds. Moreover, long-term safety profiles and potential
Frequently Asked Questions
What is YK-11 classified as in research contexts?
YK-11 is classified as a steroidal compound studied for its potential as an androgen-receptor modulator and a myostatin pathway modulator in various research models.
How many PubMed publications are indexed for YK-11 research?
There are numerous PubMed publications indexed for YK-11, indicating a significant body of scientific literature exploring its properties and effects in research settings.
Are there ClinicalTrials.gov registered studies involving YK-11?
Yes, there are several registered studies on ClinicalTrials.gov that involve YK-11, typically focusing on early-stage mechanistic or preclinical investigations in controlled research environments.
What are the primary mechanisms of action investigated for YK-11 in research?
The primary mechanisms of action investigated for YK-11 in research include its interaction with the androgen receptor and its modulatory effects on the myostatin pathway, often hypothesized to involve follistatin upregulation.
Is YK-11 considered a selective androgen receptor modulator (SARM)?
While YK-11 interacts with the androgen receptor, its steroidal structure and observed myostatin-modulating effects give it a distinct profile compared to non-steroidal SARMs. Research is ongoing to fully characterize its selectivity.
What types of research models are typically used to study YK-11?
YK-11 is typically studied using a range of research models, including in vitro cell culture systems (e.g., myoblasts, osteoblasts) and in vivo preclinical animal models (e.g., rodents).
What is the role of follistatin in YK-11 research?
In YK-11 research, follistatin is often investigated as a key mediator, with studies suggesting that YK-11 may increase follistatin expression, thereby potentially antagonizing myostatin and promoting muscle growth in research models.
What analytical techniques are used to characterize YK-11 for research purity?
Analytical techniques such as High-Performance Liquid Chromatography (HPLC), Liquid Chromatography-Mass Spectrometry (LC-MS), Nuclear Magnetic Resonance (NMR), and Gas Chromatography-Mass Spectrometry (GC-MS) are commonly employed to ensure the purity and confirm the identity of YK-11 for research purposes.
Scientific References
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