Stanford Medicine researchers have identified a naturally occurring molecule that may suppress appetite and reduce body weight in a way that resembles semaglutide, the active ingredient in Ozempic. In animal studies, the molecule also appeared to avoid several problems associated with the drug, including nausea, constipation and substantial muscle loss. This groundbreaking discovery, detailed in the prestigious journal Nature, could herald a new era in the fight against obesity and metabolic disorders, offering a potentially more targeted and better-tolerated therapeutic avenue.
A Novel Approach to Appetite Regulation
The newly identified molecule, designated as BRP (BRINP2-related-peptide), operates through a distinct yet related metabolic pathway compared to semaglutide. Crucially, BRP activates a separate group of neurons within the brain, a key difference that researchers believe could translate into a more precise and effective tool for controlling appetite and managing body weight.
"The receptors targeted by semaglutide are found in the brain but also in the gut, pancreas and other tissues," explained Katrin Svensson, PhD, an assistant professor of pathology at Stanford Medicine and senior author of the study. "That’s why Ozempic has widespread effects including slowing the movement of food through the digestive tract and lowering blood sugar levels. In contrast, BRP appears to act specifically in the hypothalamus, which controls appetite and metabolism."
The hypothalamus, a small but vital region nestled deep within the brain, serves as the body’s central thermostat for a multitude of critical functions, including the regulation of hunger, body temperature, hormonal activity, and overall energy expenditure. By appearing to exert its primary influence within this localized area, BRP holds the potential to modulate appetite without triggering the cascade of systemic effects often associated with broader-acting medications. This targeted action could significantly mitigate the adverse reactions that have been a hurdle for some patients undergoing treatment with existing weight-management drugs.
Dr. Svensson has co-founded a company poised to advance this discovery into human clinical trials in the near future, signaling a strong commitment to translating these promising preclinical findings into tangible patient benefits. Laetitia Coassolo, PhD, a senior research scientist at Stanford Medicine, served as the lead author of the study, underscoring the collaborative nature of this significant scientific endeavor.
The Power of Artificial Intelligence in Unlocking Biological Secrets
The identification of BRP was not a serendipitous discovery but rather a testament to the transformative power of artificial intelligence in scientific research. The research team leveraged advanced AI algorithms to navigate the complex landscape of prohormones, a class of inactive precursor molecules that require enzymatic cleavage to yield their active peptide fragments.
Prohormones are essentially biological blueprints that, when processed by specific enzymes, are cut into smaller peptides. These peptides then act as crucial signaling molecules, carrying messages that orchestrate a vast array of physiological processes, including metabolism, appetite regulation, and numerous other complex functions throughout the brain and body. The challenge lies in the sheer number of potential peptides that can be generated from a single prohormone, as enzymes can make cuts at various points. This often results in a deluge of fragments, with only a select few possessing the critical biological activity of true peptide hormones.
Traditional laboratory methods for isolating and identifying these peptides, while effective, can generate immense datasets, often requiring researchers to meticulously sift through hundreds of thousands of molecules to pinpoint those with significant biological impact. This laborious process can be a bottleneck in the discovery of novel therapeutic agents.
A Targeted Search for Metabolic Signals
The Stanford team focused their investigation on an enzyme known as prohormone convertase 1/3 (PC1/3). This enzyme plays a pivotal role in cleaving prohormones at specific amino acid sequences, and its link to obesity in humans has been previously established, making it a logical starting point for exploring new metabolic regulators.
Among the well-known peptides generated through PC1/3 processing is glucagon-like peptide 1 (GLP-1). GLP-1 is a key player in regulating hunger and blood sugar levels, and its physiological effects are mimicked by semaglutide. The researchers hypothesized that PC1/3 might also be responsible for producing other, as-yet-undiscovered peptides that influence energy balance and appetite. To uncover these hidden signals, they turned to the predictive power of AI.
The "Peptide Predictor" Algorithm: A Game-Changer
Instead of relying solely on traditional, time-consuming methods of peptide extraction and mass spectrometry, the researchers developed an innovative computer algorithm named "Peptide Predictor." This sophisticated program systematically scanned all approximately 20,000 human protein-coding genes, searching for the specific enzymatic cleavage sites typically recognized by prohormone convertases.
The search was further refined by focusing on genes that produce proteins secreted outside the cell – a common characteristic of hormones – and that possessed at least four potential cleavage sites. This rigorous filtering process dramatically narrowed down the vast number of human genes to a more manageable cohort of 373 prohormones, representing a significant reduction in the scope of the investigation.
"The algorithm was absolutely key to our findings," stated Dr. Svensson, emphasizing the transformative impact of this AI tool.
Peptide Predictor then estimated that PC1/3 could generate an astonishing 2,683 distinct peptides from these 373 prohormones. Drs. Coassolo and Svensson then meticulously narrowed their focus to peptides that exhibited the highest likelihood of influencing brain function. They selected 100 candidate peptides, including GLP-1 itself, for experimental testing.
A Tiny Peptide with a Monumental Impact
The initial laboratory tests involved exposing neuron-like cells to these candidate peptides. As anticipated, GLP-1 demonstrated strong activation of the neuronal cells, increasing their activity by a factor of three compared to untreated control cells. However, a much smaller peptide, BRP, produced an even more remarkable response. Composed of a mere 12 amino acids, BRP triggered a tenfold increase in neuronal activity, far surpassing the effect of GLP-1.
This minuscule peptide, BRP, derived from the parent prohormone BPM/retinoic acid inducible neural specific 2 (BRINP2), was named for its origin. Amino acids, the fundamental building blocks of proteins and peptides, are assembled in specific sequences to create these functional molecules. A peptide as small as BRP, with only 12 amino acids, is considered remarkably compact yet it elicited the most potent response in these initial cellular assays, underscoring its significant biological potential.
Preclinical Efficacy: Significant Weight Loss and Metabolic Improvements
The promising results in cell cultures prompted the researchers to move to in vivo studies, testing BRP in both lean mice and minipigs. Minipigs were chosen for their metabolic and eating patterns, which more closely mirror those of humans than do those of mice, providing a more robust preclinical model.
In these studies, an intramuscular injection of BRP administered prior to feeding led to a substantial reduction in food intake, decreasing it by as much as 50% within the hour following administration in both species. This immediate and pronounced appetite-suppressing effect was a critical early indicator of BRP’s potential.
Further extending these observations, the research team conducted a 14-day study in obese mice. Daily BRP injections resulted in an average weight loss of 3 grams in the treated animals, with nearly all of this reduction attributed to body fat loss. In stark contrast, mice in the control group experienced an average weight gain of approximately 3 grams during the same period, highlighting BRP’s efficacy in promoting fat reduction.
Beyond weight loss, the BRP-treated obese mice also exhibited significant improvements in glucose and insulin tolerance. These measures are critical indicators of metabolic health, reflecting the body’s efficiency in regulating blood sugar and its responsiveness to insulin, the hormone essential for transporting glucose from the bloodstream into cells for energy. These findings suggest that BRP may not only aid in weight management but also contribute to overall metabolic well-being.
A Favorable Side Effect Profile in Animal Models
One of the most encouraging aspects of the BRP research is its apparent lack of common side effects associated with existing weight-loss medications. Behavioral testing in the animal models revealed no significant differences between BRP-treated and untreated animals in key areas such as movement, water consumption, anxiety-like behavior, or fecal production.
The absence of altered fecal production is particularly noteworthy, given that semaglutide and similar drugs are known to slow digestion and can lead to constipation in some individuals. Furthermore, the researchers did not observe any signs of nausea-related responses or substantial muscle loss, which have been reported with certain other weight-loss treatments. This suggests that BRP might offer a more palatable and less burdensome therapeutic experience.
Detailed analyses of brain activity and body function further supported these observations, indicating that BRP operates through distinct metabolic and neuronal pathways compared to GLP-1 or semaglutide. This difference in mechanism of action is believed to be responsible for its potentially more targeted and favorable side effect profile. While these findings are currently limited to animal studies, they provide a strong foundation for optimism regarding BRP’s potential in human applications.
Navigating the Path to Human Clinical Trials
Despite the promising preclinical data, the journey from laboratory discovery to approved human therapy is complex and rigorous. The Stanford team is actively pursuing several critical research avenues to further elucidate BRP’s mechanism of action and optimize its therapeutic potential.
A primary focus is the identification of the specific cell-surface receptors that BRP binds to. Receptors act as molecular docking stations, receiving signals from hormones, drugs, and other chemical messengers. Understanding which receptor BRP interacts with is paramount to precisely deciphering how it influences appetite and metabolism at a cellular level.
The researchers are also working to map the complete sequence of events that occur after BRP binds to its target receptor. This detailed understanding will provide a comprehensive picture of its biological impact and inform the development of the most effective therapeutic strategies.
Another significant challenge for small peptides like BRP is their inherent stability in the body. Small molecules can be rapidly broken down by enzymes, which can limit the duration of their therapeutic effects. The team is actively investigating methods to enhance BRP’s stability and prolong its activity, aiming to enable a more practical dosing schedule for potential human use.
"The lack of effective drugs to treat obesity in humans has been a problem for decades," Dr. Svensson acknowledged, highlighting the urgent unmet medical need. "Nothing we’ve tested before has compared to semaglutide’s ability to decrease appetite and body weight. We are very eager to learn if it is safe and effective in humans."
The success of this research was made possible through a collaborative effort involving researchers from the University of California, Berkeley; the University of Minnesota; and the University of British Columbia. Funding for this groundbreaking work was provided by a consortium of prestigious institutions, including the National Institutes of Health (grants R01DK125260, P30DK116074, K99AR081618 and GM113854), the SPARK Translational Research Program at Stanford, Stanford Bio-X, the Stanford Maternal and Child Health Research Institute, the American Heart Association, a Stanford Medicine Dean’s Fellowship Award, the Carlsberg Foundation, and the Wu Tsai Human Performance Alliance.
Drs. Svensson and Coassolo are listed as inventors on patents pertaining to BRP peptides for metabolic disorders, and Dr. Svensson is a co-founder of Merrifield Therapeutics, the company established to further develop this promising molecule. The potential implications of this research are vast, offering a beacon of hope for millions worldwide struggling with obesity and its associated health complications. As BRP progresses towards human trials, the scientific and medical communities will be watching closely, eager to see if this novel molecule can indeed deliver on its extraordinary promise.
