Endosomal proteolysis of insulin-like growth factor-I at its C-terminal D-domain by cathepsin B

AbstractIGF-I is degraded within the endosomal apparatus as a consequence of receptor-mediated endocytosis. However, the nature of the responsible protease and the position of the cleavage sites in the IGF-I molecule remain undefined. In vitro proteolysis of IGF-I using an endosomal lysate required an acidic pH and was sensitive to CA074, an inhibitor of the cathepsin B enzyme. By nondenaturing immunoprecipitation, the acidic IGF-I-degrading activity was attributed to the luminal species of endosomal cathepsin B with apparent molecular masses of 32- and 28-kDa. The cathepsin B precursor, procathepsin B, was processed in vitro within isolated endosomes at pH 5 or at 7 in the presence of ATP, the substrate of the vacuolar H+-ATPase. The rate of IGF-I hydrolysis using an endosomal lysate or pure cathepsin B was found to be optimal at pH 5–6 and moderate at pH 4 and 7. Competition studies revealed that EGF and IGF-I share a common binding site on the cathepsin B enzyme, with native IGF-I displaying the lowest affinity for the protease (IC50≈1.5μM). Hydrolysates of IGF-I generated at low pH by endosomal IGF-I-degrading activity and analyzed by reverse-phase HPLC and mass spectrometry revealed cleavage sites at Lys68-Ser69, Ala67-Lys68, Pro66-Ala67 and Lys65-Pro66 within the C-terminal D-domain of IGF-I. Treatment of human HepG2 hepatoma cells with the cathepsin B proinhibitor CA074-Me reduced, in vivo, the intracellular degradation of internalized [125I]IGF-I and, in vitro, the degradation of exogenous [125I]IGF-I incubated with the cell-lysates at pH 5. Inhibitors of cathepsin B and pro-cathepsin B processing, which abolish endosomal proteolysis of IGF-I and alter tumor cell growth and IGF-I receptor signalling, merit investigation as antimetastatic drugs

RETAKAFUL CONTRIBUTIONS MODEL USING MACHINE LEARNING TECHNIQUES

Driven by the need to manage risk by the newly created Moroccan Takaful operators, the Moroccan Insurance and Social Welfare Control Authority has authorized the Central Reinsurance Company to create a ReTakaful window for the purpose of reinsuring Takaful operations. Nevertheless, the main challenge is determining the appropriate ReTakaful model for the Moroccan Islamic insurance sector by ensuring compliance with Shariah. With this in mind, this article aims to determine the optimal ReTakaful contributions model for the Moroccan Takaful industry via Machine Learning algorithms. We select the best model by comparing the performance of each algorithm. The achieved results of this study demonstrate the potential of using Machine Learning algorithms to compute ReTakaful contributions that are more suitable for Takaful operators and more optimal for the ReTakaful operator

Chemical reactivity and uses of 1-phenyl-3-methyl-5-pyrazolone (PMP), also known as edaravone

International audienc

Harnessing slaughterhouse by-products: from wastes to high-added value natural food preservative

International audienceBlood, from slaughterhouses, is an inevitable part of meat production, causing environmental problems due to the large volumes recovered and its low valorization. However, the α137-141 peptide, a natural antimicrobial peptide, can be obtained after hydrolysis of hemoglobin, the main constituent of blood red part. To recover it at a sufficient concentration for antimicrobial applications, a new sustainable technology, called electrodialysis with ultrafiltration membrane (EDUF), was investigated. The α137-141 concentration was increased about 4-fold at a feed peptide concentration of 8% with an enrichment factor above 24-fold. This feed peptide concentration also needed the lowest relative energy consumption. Moreover, this peptide fraction protected meat against microbial growth, as well as rancidity, during 14 days under refrigeration. This peptide fraction was validated as a natural preservative and substitute for synthetic additives against food spoilage. Finally, producing antimicrobial/antioxidant peptide from wastes by EDUF fits perfectly with the concept of circular economy

Electroseparation of Slaughterhouse By-Product: Antimicrobial Peptide Enrichment by pH Modification.

International audienceThe fractionation of bioactive peptides from hydrolysate is a main challenge to produce efficient alternative for synthetic additives. In this work, electrodialysis with ultrafiltration membrane (EDUF) was proposed to increase the purity of one antimicrobial peptide from slaughterhouse by-product hydrolysate. This targeted-peptide, α137–141 (653 Da, TSKYR), inhibits a large spectrum of microbial growths and delays meat rancidity; therefore, if concentrated, it could be used as food antimicrobial. In this context, three pH values were investigated during EDUF treatment to increase the α137–141 purity: 4.7, 6.5, and 9. pH 9 showed the highest purity increase—75-fold compared to the initial hydrolysate. Although the whole hydrolysate contains more than 100 peptides, only six peptides were recovered at a significant concentration. In this fraction, the α137–141 peptide represented more than 50% of the recovered total peptide concentration. The EDUF α137–141-enriched fraction obtained in this optimized condition would be a promising natural preservative to substitute synthetic additives used to protect food

Behavior of Regular Insulin in a Parenteral Nutrition Admixture: Validation of an LC/MS-MS Assay and the In Vitro Evaluation of Insulin Glycation

Parenteral-nutrition (PN)-induced hyperglycemia increases morbidity and mortality and must be treated with insulin. Unfortunately, the addition of insulin to a ternary PN admixture leads to a rapid decrease in insulin content. Our study’s objective was to determine the mechanistic basis of insulin’s disappearance. The literature data suggested the presence of a glycation reaction; we therefore validated an LC-MS/MS assay for insulin and glycated insulin. In a 24-h stability study, 20 IU/L of insulin was added to a binary PN admixture at pH 3.6 or 6.3. When the samples were diluted before analysis with a near-neutral diluent, insulin was fully stable at pH 3.6, while a loss of around 50% was observed at pH 6.3. Its disappearance was shown to be inversely correlated with the appearance of monoglycated insulin (probably a Schiff base adduct). Monoglycated insulin might also undergo a back-reaction to form insulin after acidic dilution. Furthermore, a second monoglycated insulin species appeared in the PN admixture after more than 24 h at high temperature (40 °C) and a high insulin concentration (1000 IU/L). It was stable at acidic pH and might be an Amadori product. The impact of insulin glycation under non-forced conditions on insulin’s bioactivity requires further investigation

Protein digestion and energy homeostasis: How generated peptides may impact intestinal hormones?

International audienceThe aim of the present study is to investigate how peptides released by gastrointestinal (GI) digestion of one dietary protein can interact with regulating processes of food intake. An in vitro GI digestion of bovine haemoglobin was carried out and the bioactivity of the digests on CCK and GLP-1 secretion and dipeptidyl peptidase IV (DPP-IV) activity was measured. Intestinal digests exhibited the most potent action on gut hormone release and DPP-IV activity inhibition. They also had the ability to promote hormone gene expression. As a conclusion, two fractions from final intestinal digest led to the greatest GLP-1 secretion increase and DPP-IV activity inhibition. These findings could be very useful in obesity and T2D management research