Solute carrier (SLC) transporters are a superfamily of membrane bound proteins with over 300 identified members. These proteins serve as key regulators of cellular homeostasis by facilitating substrate entry and by‐product elimination across the plasma membrane. Dysregulation of SLC transporter function contributes to numerous diseases such as diabetes, Parkinson's disease and cancer. As SLCs are associated with a disease phenotype they are considered ‘druggable’ i.e., they can be modulated by drugs. Most current drugs that modulate SLC transporters do so by inhibiting transporter activity. For diseases in which decreased transporter activity leads to a potentially beneficial effect, high‐throughput screening (HTS) of large compound libraries using cell lines that overexpress the transporter of interest can be used to discover small molecule inhibitors. However, this is not necessarily a straightforward endeavor for all SLCs. The monocarboxylate transporters (MCTs) are a sub family of SLC transporters comprised of 14 members among which MCT1‐4 facilitate the bidirectional proton‐coupled co‐transport of monocarboxylates such as ketone bodies, pyruvate and lactate. MCT1 is of particular interest for its roles in cancer. Not only is it upregulated in the tumor microenvironment, but has also been identified as a key regulator of angiogenesis, invasion, migration and immune escape. Targeting this protein, MCT1/2 inhibitors are currently in clinical trials as anticancer therapies. More recently, MCT1 has also been identified as a potential drug target for metabolic and CNS disorders. Although MCT1 inhibitors have been identified, they lack selectivity for any given MCT isoform, and have exhibited select off target effects. Typical for this protein class, inhibitors for MCT1 have been difficult to identify, because traditionally, methods for their identification rely on the use of radiolabeled substrate tracking. In addition to the safety concerns associated with radioactivity, this methodology is also expensive and time consuming. Herein, we present a novel, non‐radioactive, cell‐based HTS‐compatible assay for identifying MCT1 inhibitors. Our method utilizes a cell line that endogenously expresses MCT1, and an MCT1 selective cytotoxic substrate, 3‐bromopyruvate (3BrPA). In our assay construct, MCT1 expressing cells are treated with potential MCT1 inhibitors, and then incubated with 3BrPA. In this paradigm, compounds that protect cells from cytotoxicity are identified as MCT1 inhibitors, because only cells treated with an inhibitor have interrupted MCT1 mediated transport and remain viable in the presence of 3BrPA. The screening method described here is robust, reproducible and HTS amenable. Moreover, it establishes a novel technique to identify chemical probes to study the therapeutic potential of MCTs while providing the conceptual framework for further assay development to identify inhibitors for other members of the SLC family. This abstract is from the Experimental Biology 2019 Meeting. There is no full text articl...
Enlarged, hypertrophic adipocytes are less responsive to insulin and are a hallmark feature of obesity, contributing to many of the negative metabolic consequences of excess adipose tissue. Although the mechanisms remain unclear, the adipocyte size appears to be inversely correlated with insulin sensitivity and glucose tolerance, wherein smaller adipocytes are insulin-sensitive and larger adipocytes develop insulin resistance and exhibit an impaired glucose uptake. Thus, pharmacological strategies aimed at regulating adipocyte hypertrophy (increase in adipocyte size) in favor of promoting hyperplasia (increase in adipocyte number) have the potential to improve adipocyte insulin sensitivity and provide therapeutic benefits in the context of metabolic disorders. As white adipose tissue can metabolize large amounts of glucose to lactate, using transcriptomics and in vitro characterization we explore the functional consequences of inhibiting monocarboxylate transporter 1 (MCT1) activity in fully differentiated adipocytes. Our studies show that the pharmacological inhibition of MCT1, a key regulator of the cellular metabolism and proliferation, promotes the re-entry of mature adipocytes into the cell cycle. Furthermore, we demonstrate that inhibitor-treated adipocytes exhibit an enhanced insulin-stimulated glucose uptake as compared with untreated adipocytes, and that this outcome is dependent on the cyclin-dependent kinase 1 (CDK1) activity. In summary, we identify a mechanism though which MCT1 inhibition improves the insulin sensitivity of mature adipocytes by inducing cell cycle re-entry. These results provide the foundation for future studies investigating the role MCT1 plays in adipocyte hyperplasia, and its therapeutic potential as a drug target for obesity and metabolic disease.
Enlarged, hypertrophic, insulin resistant adipocytes are a hallmark feature of obesity and contribute to many of the negative metabolic consequences of excess adipose tissue. Although the precise mechanisms remain unclear, adipocyte size is directly correlated with insulin sensitivity wherein smaller adipocytes retain insulin sensitivity, and larger adipocytes often develop insulin resistance, a phenomenon referred to as hypertrophy. It is well established that preadipocytes become growth arrested prior to differentiation and the accumulation of triglyceride lipid droplets that can expand overtime leading to hypertrophic expansion. Therefore, pharmacological strategies aimed at limiting adipocyte hypertrophy and prolonged lipid accumulation may improve insulin sensitivity and have therapeutic benefits in the context of metabolic disorders characterized by insulin resistance. Here, using RNA sequencing and in vitro characterization, we explore the functional consequences of inhibiting the Monocarboxylate Transporter 1 (MCT1), a key regulator of cellular metabolism and proliferation, in adipocytes. We have identified a mechanism through which MCT1 inhibition improves insulin sensitivity in differentiated adipocytes by inducing the re‐entry of these cells into the cell cycle. Finally, we provide compelling evidence that warrants the need for the further investigation of the role MCT1 plays in adipocyte metabolism and its potential as a therapeutic drug target for insulin resistance in obesity and other metabolic disorders.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.