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Background: Duchenne muscular dystrophy (DMD) is characterized by the lack of dystrophin in skeletal, cardiac, and smooth muscle. Slow colonic transit and constipation are common in DMD patients and animal models of DMD. However, the cause of this hypocontractility and the expression of contractile proteins in smooth muscle are unknown. The aim of the study was to investigate the expression of contractile proteins in the colonic smooth muscle and the function of the colon in control and mdx mice. Methods: Muscle contraction was measured in muscle strips and isolated muscle cells. Peristaltic activity was measured in ex vivo preparations by spatiotemporal mapping, and gastrointestinal (GI) transit in vivo was measured by the distribution of fluorescent marker along the intestine and colon. mRNA expression of contractile proteins smoothelin, caldesmon, calponin, and tropomyosin was measured by qRT‐PCR. Results: Expression of mRNA for contractile proteins was decreased in colonic smooth muscle of mdx mice compared with control. Contraction in response to acetylcholine and KCl was decreased in colonic muscle strips and in isolated muscle cells of mdx mice. Distension of ex vivo colons with Krebs buffer induced peristalsis in both control and mdx mice; however, significantly fewer full peristaltic waves were recorded in the colons of mdx mice. GI transit was also inhibited in mdx mice. Conclusion and Inferences: The data indicate that the lack of dystrophin causes decrease in colonic smooth muscle contractility, peristalsis, and GI transit and provides the basis for analysis of mechanisms involved in smooth muscle dysfunction in DMD. [ABSTRACT FROM AUTHOR]

Arterial medial calcification (AMC) is associated with crystallization of hydroxyapatite in the extracellular matrix and arterial smooth muscle cells (SMCs) leading to reduced arterial compliance. The study was performed to test whether lysosomal acid sphingomyelinase (murine gene code: Smpd1)‐derived ceramide contributes to the small extracellular vesicle (sEV) secretion from SMCs and consequently leads to AMC. In Smpd1trg/SMcre mice with SMC‐specific overexpression of Smpd1 gene, a high dose of Vit D (500 000 IU/kg/d) resulted in increased aortic and coronary AMC, associated with augmented expression of RUNX2 and osteopontin in the coronary and aortic media compared with their littermates (Smpd1trg/SMwt and WT/WT mice), indicating phenotypic switch. However, amitriptyline, an acid sphingomyelinase (ASM) inhibitor, reduced calcification and reversed phenotypic switch. Smpd1trg/SMcre mice showed increased CD63, AnX2 and ALP levels in the arterial wall, accompanied by reduced co‐localization of lysosome marker (Lamp‐1) with multivesicular body (MVB) marker (VPS16), a parameter for lysosome‐MVB interaction. All these changes related to lysosome fusion and sEV release were substantially attenuated by amitriptyline. Increased arterial stiffness and elastin disorganization were found in Smpd1trg/SMcre mice as compared to their littermates. In cultured coronary arterial SMCs (CASMCs) from Smpd1trg/SMcre mice, increased Pi concentrations led to markedly increased calcium deposition, phenotypic change and sEV secretion compared with WT CASMCs, accompanied by reduced lysosome‐MVB interaction. However, amitriptyline prevented these changes in Pi‐treated CASMCs. These data indicate that lysosomal ceramide plays a critical role in phenotype change and sEV release in SMCs, which may contribute to the arterial stiffness during the development of AMC. [ABSTRACT FROM AUTHOR]

Background and Purpose Enhanced mammalian target of rapamycin (mTOR) signalling contributes to the pathogenesis of diabetes and plays a critical role in myocardial ischaemia/reperfusion (I/R) injury. Rapatar is a novel nanoformulated micellar of rapamycin, a putative inhibitor of mTOR that has been rationally designed to increase water solubility of rapamycin to facilitate p.o. administration and enhance bioavailability. We examined the effect of Rapatar on the metabolic status and protection against myocardial I/R injury in type 2 diabetic mice. Experimental Approach Adult male db/db mice were treated daily for 10 weeks with Rapatar (0.75 mg·kg−1·day−1, p.o.) or vehicle. Isolated hearts were connected to a Langendorff perfusion system and subjected to global ischaemia (30 min) and reperfusion (1 h). Key Results Rapatar reduced fasting plasma glucose and triglyceride levels, prevented the gain in body weight and also improved glucose tolerance and insulin sensitivity in db/db mice compared with control. Cardiac function was improved following Rapatar treatment in db/db mice. Myocardial infarct size was reduced in Rapatar-treated mice with improved post-ischaemic rate-force product. Western blot analyses demonstrated a significant inhibition of phosphorylation of ribosomal protein (downstream target of mTORC1), but not Akt (Ser473, target of mTORC2) following chronic treatment with Rapatar. Rapatar also induced phosphorylation of AMPK, STAT3, ERK1/2 and glycogen synthase kinase 3β, without interfering with phosphorylation of p38. Conclusion and implications Our studies indicate that chronic treatment with Rapatar improves metabolic status and cardiac function with a reduction of infarct size following myocardial I/R injury in diabetic mice. [ABSTRACT FROM AUTHOR]