Metabolites are the substances made and used during the body’s metabolic processes – or, as a new discovery out of Scripps Research and its drug development arm, Calibr, indicates, they could also be potent molecules for treating severe diseases.
In a study published in the journal Metabolites, the researchers used novel drug discovery technologies to uncover a metabolite that converts white adipocytes (‘bad’ fat cells) to brown adipocytes (‘good’ fat cells). This discovery suggests a pathway to treating metabolic disorders such as obesity, type 2 diabetes and cardiovascular disease. This creative drug discovery method could also identify countless other potential therapeutics.
“The reason many types of molecules don’t go to market is because of toxicity,” said co-senior author Gary Siuzdak, PhD. “With our technology, we can pull out endogenous metabolites – meaning the ones that the body makes on its own – that can have the same impact as a drug with less side effects. The potential of this approach is even evidenced by the FDA’s recent approval of Relyvrio, the combination of two endogenous metabolites for the treatment of amyotrophic lateral sclerosis (ALS).”
Metabolic diseases are often caused by an imbalance in energy homeostasis. This is why certain therapeutic approaches have centred around converting white adipocytes into brown adipocytes. White adipocytes store excess energy and can eventually result in metabolic diseases like obesity, while brown adipocytes dissolve this stored energy into heat – ultimately increasing the body’s energy expenditure and helping bring balance.
To uncover a therapy that could stimulate the production of brown adipocytes, the researchers searched through Calibr’s ReFRAME drug-repurposing collection – a library of 14 000 known drug compounds that have been approved by the FDA for other diseases or have been extensively tested for human safety. Using high-throughput screening – an automated drug discovery method for searching through large pools of information –the scientists scanned ReFRAME for a drug with these specific capabilities.
This is how they uncovered zafirlukast, an FDA-approved drug used for treating asthma. Through a set of cell culture experiments, they found zafirlukast could turn adipocyte precursor cells (known as preadipocytes) into predominantly brown adipocytes, as well as convert white adipocytes into brown adipocytes.
Unfortunately, zafirlukast is toxic at higher doses, and it wasn’t entirely clear how zafirlukast was converting the adipocytes. This is when the researchers partnered with Dr Siuzdak and his team of metabolite experts.
“We needed to use additional tools to break down the chemicals in zafirlukast’s mechanism,” explained Kristen Johnson, PhD, co-senior author of the paper. “Framed another way, could we find a metabolite that was providing the same functional effect that zafirlukast was, but without the side effects?”
Dr Siuzdak and his team designed a novel set of experiments, known as drug-initiated activity metabolomics (DIAM) screening, to help answer Johnson’s question. DIAM uses technologies such as liquid chromatography (a tool that separates components in a mixture) and mass spectrometry (an analytical technique that separates particles by weight and charge) to pool through thousands of molecules and identify specific metabolites. In this case, the researchers were searching through adipose tissue for metabolites that could lead to brown adipocyte cell production.
After reducing 30 000 metabolic features to just 17 metabolites, they came upon myristoylglycine – an endogenous metabolite that prompted the creation of brown adipocytes, without harming the cell. Of the thousands of metabolic features measured in the analysis, only myristoylglycine had this special characteristic, even among nearly structurally identical metabolites.
“Identifying myristoylglycine among the thousands of other molecules speaks to the power of Siuzdak’s approach and these technologies,” added Dr Johnson. “Our findings illustrate what happens when an analytical chemistry team and a drug discovery group closely collaborate with each other.”
Source: Scripps Research
