GLP-1, Insect Peptides, and Osteoporosis: Emerging Clinical Insights

by Dr. James Ross

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Mealworm-Derived Peptides as Multi-Target Inhibitors Against SARS-CoV-2: An In Silico Evaluation

The emergence of Coronavirus Disease 2019 (COVID-19), triggered by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), has posed a global health crisis. Viral entry occurs through the interaction of the spike glycoprotein’s receptor-binding domain (RBD) with the human angiotensin-converting enzyme 2 (hACE2) receptor. Critical amino acid residues within the RBD—such as Leu455, Phe456, Ser459, Gln474, Ala475, Phe486, Phe490, Gln493, and Pro499—are essential for binding affinity, and mutations at these sites markedly reduce viral attachment to hACE2.

Once inside the host cell, SARS-CoV-2 relies on its main protease (Mpro) and papain-like protease (PLpro) to cleave viral polyproteins into functional units required for replication. Mpro activity depends on its His41–Cys145 catalytic dyad, while PLpro utilizes a catalytic triad of Cys111, His272, and Asp286. Inhibiting RBD–hACE2 interaction as well as proteolysis by Mpro and PLpro are considered effective therapeutic strategies.

Computational analysis indicates that gastrointestinal digestion of mealworm proteins may release peptides capable of blocking viral entry. A recent virtual screening of 1,588 peptide fragments identified two candidates, PKWF and VHRKCF, with strong predicted binding affinity toward the spike RBD, Mpro, and PLpro. Docking simulations and molecular interaction analyses highlighted favorable residue contributions to stability, while physicochemical profiling further supported their therapeutic potential.

These findings suggest that PKWF and VHRKCF may serve as multi-target antiviral peptides with promise for prophylactic or therapeutic development against SARS-CoV-2. Future laboratory and animal studies are needed to validate their efficacy, but the multi-target mechanism is advantageous in combating rapidly mutating RNA viruses.

Walnut Protein Hydrolysates and Their Calcium-Binding Peptides in Osteoporosis Prevention

Bone is a dynamic tissue that undergoes continuous remodeling, balancing bone formation and resorption. During youth, bone accrual surpasses breakdown, but by the third decade of life, peak bone mass is reached. With aging, bone loss accelerates, increasing the risk of osteoporosis. Genetic background and ethnicity influence baseline bone density, and individuals with greater peak bone mass are less likely to develop osteoporosis later in life.

Although current therapeutic agents for osteoporosis are available, they often carry adverse side effects. Calcium remains the cornerstone mineral for skeletal health, comprising 1.5–2% of body weight, with over 99% stored in bone. Despite widespread use of calcium supplements, absorption and bioavailability in vivo are limited, which has prompted interest in natural peptides that enhance calcium uptake.

Walnut protein hydrolysate (WPH), obtained through simulated gastrointestinal digestion, has demonstrated diverse bioactivities including antioxidant, antihypertensive, and lipid-lowering properties. A rat model of retinoic acid–induced osteoporosis was used to evaluate its effects on bone metabolism. WPH showed a degree of hydrolysis of 11.6%, with enrichment in glutamate and proline, and a molecular weight distribution favorable for absorption (average 572 Da).

Experimental results indicated that WPH improved bone structure, modulated serum biomarkers of bone turnover, and promoted bone formation. Fifteen peptide sequences were isolated, many with strong calcium-binding characteristics. These findings highlight WPH as a potential functional ingredient for preventing osteoporosis and advancing nutraceutical applications of walnut protein.

Bacillus-Derived Exopolysaccharides and the Stimulation of GLP-1 via Bitter Taste Receptors

Exopolysaccharides (EPS) are extracellular polymers secreted by bacteria, fungi, and algae, known for their bioactive potential. Bacillus amyloliquefaciens, a Gram-positive bacterium, has been studied for its probiotic effects, including regulation of glucose metabolism, protection against obesity, and support of insulin secretion. EPS from this species (strain amy-1) has demonstrated the ability to enhance glucagon-like peptide-1 (GLP-1) secretion in both in vivo and in vitro models.

GLP-1, an incretin hormone secreted by intestinal L-cells postprandially, plays critical roles in glucose regulation, β-cell preservation, inhibition of glucagon release, delayed gastric emptying, and appetite control. The underlying mechanism of EPS-induced GLP-1 secretion has been linked to bitter taste receptors (TAS2Rs), a family of G protein–coupled receptors.

When activated, TAS2Rs initiate a signaling cascade: Gβγ activation of PLCβ2, production of IP3 and DAG, calcium release from the endoplasmic reticulum, and subsequent activation of TRPM4/5 sodium channels. This leads to membrane depolarization, opening of voltage-gated sodium channels, and ATP release via CALHM1/3 and pannexin1 channels, ultimately generating a bitter taste response. Concurrently, Gα-gustducin lowers intracellular cAMP through phosphodiesterase activation.

Cellular assays showed that EPS induced a calcium influx in NCI-H716 enteroendocrine cells, a response suppressed by inhibitors of G protein–coupled receptor signaling. Heterologous expression studies identified TAS2R14 as the principal mediator of EPS-induced GLP-1 secretion, with additional involvement of TAS2R38.

These findings elucidate a novel mechanism by which bacterial exopolysaccharides enhance GLP-1 secretion through TAS2Rs, supporting their potential use in glycemic modulation and metabolic health.

REFERENCES

1. Ong, J. H., et al. “Multi-target anti-sars-cov-2 peptides from mealworm proteins: An in silico study.” Malaysian Journal of Biochemistry and Molecular Biology (2021): 83-91.
2. Sun, Xiaodong, et al. “Anti-osteoporosis effect and purification of peptides with high calcium-binding capacity from walnut protein hydrolysates.” Food & function.
3. Sung, Wei-Wen, et al. “Bacillus amyloliquefaciens exopolysaccharide preparation induces glucagon-like peptide 1 secretion through the activation of bitter taste receptors.” International Journal of Biological Macromolecules (2021).