Growth hormone secretagogues modulate inflammation and fibrosis in mdx mouse model of Duchenne muscular dystrophy

Front Immunol. 2023 Apr 12:14:1119888. doi: 10.3389/fimmu.2023.1119888. eCollection 2023.

Abstract

Introduction: Growth hormone secretagogues (GHSs) exert multiple actions, being able to activate GHS-receptor 1a, control inflammation and metabolism, to enhance GH/insulin-like growth factor-1 (IGF-1)-mediated myogenesis, and to inhibit angiotensin-converting enzyme. These mechanisms are of interest for potentially targeting multiple steps of pathogenic cascade in Duchenne muscular dystrophy (DMD).

Methods: Here, we aimed to provide preclinical evidence for potential benefits of GHSs in DMD, via a multidisciplinary in vivo and ex vivo comparison in mdx mice, of two ad hoc synthesized compounds (EP80317 and JMV2894), with a wide but different profile. 4-week-old mdx mice were treated for 8 weeks with EP80317 or JMV2894 (320 µg/kg/d, s.c.).

Results: In vivo, both GHSs increased mice forelimb force (recovery score, RS towards WT: 20% for EP80317 and 32% for JMV2894 at week 8). In parallel, GHSs also reduced diaphragm (DIA) and gastrocnemius (GC) ultrasound echodensity, a fibrosis-related parameter (RS: ranging between 26% and 75%). Ex vivo, both drugs ameliorated DIA isometric force and calcium-related indices (e.g., RS: 40% for tetanic force). Histological analysis highlighted a relevant reduction of fibrosis in GC and DIA muscles of treated mice, paralleled by a decrease in gene expression of TGF-β1 and Col1a1. Also, decreased levels of pro-inflammatory genes (IL-6, CD68), accompanied by an increment in Sirt-1, PGC-1α and MEF2c expression, were observed in response to treatments, suggesting an overall improvement of myofiber metabolism. No detectable transcript levels of GHS receptor-1a, nor an increase of circulating IGF-1 were found, suggesting the presence of a novel receptor-independent mechanism in skeletal muscle. Preliminary docking studies revealed a potential binding capability of JMV2894 on metalloproteases involved in extracellular matrix remodeling and cytokine production, such as ADAMTS-5 and MMP-9, overactivated in DMD.

Discussion: Our results support the interest of GHSs as modulators of pathology progression in mdx mice, disclosing a direct anti-fibrotic action that may prove beneficial to contrast pathological remodeling.

Keywords: Duchenne muscular dystrophy; fibrosis; growth hormone secretagogues; mdx mouse; skeletal muscle.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Disease Models, Animal
  • Fibrosis
  • Growth Hormone* / pharmacology
  • Growth Hormone* / therapeutic use
  • Inflammation / drug therapy
  • Inflammation / metabolism
  • Inflammation / pathology
  • Insulin-Like Growth Factor I* / pharmacology
  • Insulin-Like Growth Factor I* / therapeutic use
  • Male
  • Mice
  • Mice, Inbred mdx
  • Muscular Dystrophy, Duchenne* / metabolism
  • Muscular Dystrophy, Duchenne* / pathology
  • Secretagogues* / metabolism

Substances

  • Growth Hormone
  • Secretagogues
  • Insulin-Like Growth Factor I

Grants and funding

This work was supported by AFM Téléthon Research Grant Project #22199 to ADL (as PI), AT and SD. Also, partly supported by PRIN-MIUR (Research Projects of Relevant National Interest – Ministry of Education, University and Research) 2017 Prot. 2017FJSM9S_005 to ADL. PM was recipient of MIUR funding PON (National Operational Program) “Research and Innovation 2014-2020” AIM (Attraction and International Mobility) Project AIM1801289-2. BB and AC are recipient of fellowships on BTS grant (2018-PDR-00351) to OC. At the time of experiments, SC was recipient of Research for Innovation (REFIN) POR PUGLIA FESR-FSE 2014-2020 funding Project n. D908ACB4, at the Department of Pharmacy-Drug Sciences, University of Bari “Aldo Moro” (current address: Department of Chemical, Biological, Pharmaceutical and Environmental Sciences, University of Messina, Messina, Italy).