Regenerating islet-derived protein 3α : A promising therapy for diabetes. Preliminary data in rodents and in humans

Publisher Copyright: © 2022The aim of our study was to test the hypothesis that administration of Regenerating islet-derived protein 3α (Reg3α), a protein described as having protective effects against oxidative stress and anti-inflammatory activity, could participate in the control of glucose homeostasis and potentially be a new target of interest in the treatment of type 2 diabetes. To that end the recombinant human Reg3α protein was administered for one month in insulin-resistant mice fed high fat diet. We performed glucose and insulin tolerance tests, assayed circulating chemokines in plasma and measured glucose uptake in insulin sensitive tissues. We evidenced an increase in insulin sensitivity during an oral glucose tolerance test in ALF-5755 treated mice vs controls and decreased the pro-inflammatory cytokine C-X-C Motif Chemokine Ligand 5 (CXCL5). We also demonstrated an increase in glucose uptake in skeletal muscle. Finally, correlation studies using human and mouse muscle biopsies showed negative correlation between intramuscular Reg3α mRNA expression (or its murine isoform Reg3γ) and insulin resistance. Thus, we have established the proof of concept that Reg3α could be a novel molecule of interest in the treatment of T2D by increasing insulin sensitivity via a skeletal muscle effect.Peer reviewe

Imidazole propionate is increased in diabetes and associated with dietary patterns and altered microbial ecology

Microbiota-host-diet interactions contribute to the development of metabolic diseases. Imidazole propionate is a novel microbially produced metabolite from histidine, which impairs glucose metabolism. Here, we show that subjects with prediabetes and diabetes in the MetaCardis cohort from three European countries have elevated serum imidazole propionate levels. Furthermore, imidazole propionate levels were increased in subjects with low bacterial gene richness and Bacteroides 2 enterotype, which have previously been associated with obesity. The Bacteroides 2 enterotype was also associated with increased abundance of the genes involved in imidazole propionate biosynthesis from dietary histidine. Since patients and controls did not differ in their histidine dietary intake, the elevated levels of imidazole propionate in type 2 diabetes likely reflects altered microbial metabolism of histidine, rather than histidine intake per se. Thus the microbiota may contribute to type 2 diabetes by generating imidazole propionate that can modulate host inflammation and metabolism

The Reg3α (HIP/PAP) Lectin Suppresses Extracellular Oxidative Stress in a Murine Model of Acute Liver Failure

<div><p>Background and Aims</p><p>Acute liver failure (ALF) is a rapidly progressive heterogeneous illness with high mortality rate and no widely accessible cure. A promising drug candidate according to previous preclinical studies is the Reg3α (or HIP/PAP) lectin, which alleviates ALF through its free-radical scavenging activity. Here we study the therapeutic targets of Reg3α in order to gain information on the nature of the oxidative stress associated with ALF.</p><p>Methods</p><p>Primary hepatocytes stressed with the reactive oxygen species (ROS) inducers TNFα and H₂O₂ were incubated with a recombinant Reg3α protein. ALF was induced in C57BL/6J mice by an anti-CD95 antibody. Livers and primary hepatocytes were harvested for deoxycholate separation of cellular and extracellular fractions, immunostaining, immunoprecipitation and malondialdehyde assays. Fibrin deposition was studied by immunofluorescence in frozen liver explants from patients with ALF.</p><p>Results</p><p>Fibrin deposition occurs during experimental and clinical acute liver injuries. Reg3α bound the resulting transient fibrin network, accumulated in the inflammatory extracellular matrix (ECM), greatly reduced extracellular ROS levels, and improved cell viability. Hepatocyte treatment with ligands of death receptors, e.g. TNFα and Fas, resulted in a twofold increase of malondialdehyde (MDA) level in the deoxycholate-insoluble fractions. Reg3α treatment maintained MDA at a level similar to control cells and thereby increased hepatocyte survival by 35%. No antioxidant effect of Reg3α was noted in the deoxycholate-soluble fractions. Preventing fibrin network formation with heparin suppressed the prosurvival effect of Reg3α.</p><p>Conclusions</p><p>Reg3α is an ECM-targeted ROS scavenger that binds the fibrin scaffold resulting from hepatocyte death during ALF. ECM alteration is an important pathogenic factor of ALF and a relevant target for pharmacotherapy.</p></div

Abundant fibrin deposition in human ALFs.

<p>Histological analysis using hematoxylin/eosin (H&E) staining (left), anti-fibrin immunofluorescence (right) of sections of liver explants from patients with end stage acute liver failure of different etiologies. Control: liver explants from patients with amyloid neuropathy. Scale bars: 50 μm.</p

Reg3α fights oxidative stress to extracellular matrix <i>in vitro</i>.

<p>(A and B) Immunofluorescence of primary human hepatocytes (PHHs) incubated with either a recombinant Reg3α without (A, top) or with heparin (A, bottom), or (B) vehicle. DNA: blue. (C) Immunoblotting for Reg3α, fibrinogen (Fbg), and fibronectin (Fn) in DOC-soluble and insoluble extracts from PHHs cultured under the indicated conditions. (D) Anti-Reg3α immunoblotting (IB) in the indicated fractions of lysates immunoprecipitated (IP) with an anti-fibrin/fibrinogen antibody. (E) Immunofluorescence of PHHs stressed with H₂O₂ or TNFα/ActD and treated either with Reg3α or vehicle. (F) Left: Immunofluorescence of PHHs incubated with heparin and then TNFα/ActD and Reg3α. Right: Normalized cell viability. (G) Normalized concentration of malondialdehyde (MDA) in DOC-insoluble and DOC-soluble fractions of PHHs subjected to the same treatments as in (F). Scale bars: 50 μm. Student’s t-test, *P < 0.05; **P <0.01.</p