Glucocorticoids improve myogenic differentiation in vitro by suppressing the synthesis of versican, a transitional matrix protein overexpressed in dystrophic skeletal muscles

In Duchenne muscular dystrophy (DMD), a dysregulated extracellular matrix (ECM) directly exacerbates pathology. Glucocorticoids are beneficial therapeutics in DMD, and have pleiotropic effects on the composition and processing of ECM proteins in other biological contexts. The synthesis and remodelling of a transitional versican-rich matrix is necessary for myogenesis; whether glucocorticoids modulate this transitional matrix is not known. Here, versican expression and processing were examined in hindlimb and diaphragm muscles from mdx dystrophin-deficient mice and C57BL/10 wild type mice. V0/V1 versican (Vcan) mRNA transcripts and protein levels were upregulated in dystrophic compared to wild type muscles, especially in the more severely affected mdx diaphragm. Processed versican (versikine) was detected in wild type and dystrophic muscles, and immunoreactivity was highly associated with newly regenerated myofibres. Glucocorticoids enhanced C2C12 myoblast fusion by modulating the expression of genes regulating transitional matrix synthesis and processing. Specifically, Tgfβ1, Vcan and hyaluronan synthase-2 (Has2) mRNA transcripts were decreased by 50% and Adamts1 mRNA transcripts were increased three-fold by glucocorticoid treatment. The addition of exogenous versican impaired myoblast fusion, whilst glucocorticoids alleviated this inhibition in fusion. In dystrophic mdx muscles, versican upregulation correlated with pathology. We propose that versican is a novel and relevant target gene in DMD, given its suppression by glucocorticoids and that in excess it impairs myoblast fusion, a process key for muscle regeneration

A study of the relationship between C-type natriuretic peptide and pregnancy in sheep and red deer

C-type natriuretic peptide (CNP) is a signaling molecule with important roles in mammalian growth and vascular function. Unexpectedly high plasma CNP concentrations have been reported in late gestation ewes, suggesting a possible role during pregnancy. However, the temporal pattern of CNP in maternal circulation, site/s of production and function during pregnancy have not been identified. Consequently, the aim of this PhD project was to address these unexplored aspects of CNP biology in order to improve our understanding of CNP’s role in pregnancy. To characterise the temporal pattern of maternal circulating CNP during pregnancy, a longitudinal survey was conducted in two representative species of ruminant: sheep and red deer. Plasma concentrations of both CNP and a presumed bio-inactive fragment of its precursor (NTproCNP) increased in twin-bearing ewes at 40-50 days of gestation with peak values attained (CNP 31 ± 5 pmol l⁻¹, NTproCNP 270 ± 16 pmol l-1) at about day 120. A similar temporal pattern was evident in red deer hinds. In pregnant ewes studied at day 120, there was a positive relationship between maternal CNP forms and fetal number (P < 0.01). Collectively, these results strongly implicated the uteroplacental unit as the major source of CNP during pregnancy. Therefore, studies were conducted to determine the relative contribution of uterine and placental tissues to circulating CNP concentration. The concentration of both CNP forms in the placenta exceeded that in intercaruncular uterine tissue throughout pregnancy (P < 0.05), with the highest concentrations measured in the fetal cotyledon. Immunohistochemistry revealed staining of CNP and NTproCNP around placental blood vessels and in trophoblast binucleate cells (BNC), identifying these cells as a probable source of maternal circulating CNP during pregnancy. Having identified the source of CNP during pregnancy, further studies were undertaken to test the hypothesis that CNP production by the ovine uteroplacental unit is homeostatically regulated by nutritional status, using models of nutrient restriction (3-day fast) or nutrient abundance (caloric loading or mid-pregnancy shearing). Maternal circulating NTproCNP concentration, expressed as a percentage of pre-fasting concentration, was significantly elevated in ewes fasted in late pregnancy compared with controls (117 ± 5.1 % vs 107 ± 3.5 %, P < 0.05). In contrast, there was no effect of nutrient abundance on the concentration of either CNP form, suggesting that CNP production is selectively upregulated during situations of fetal restriction. CNP’s localisation to the BNC and high circulating concentrations in the pregnant ruminant suggest a novel endocrine role for the peptide during pregnancy, in addition to likely paracrine actions within the placental vasculature. The strong relationship between maternal circulating CNP and placental peptide production identified in this thesis makes the pregnant ewe a unique in vivo model for studying the regulation of CNP during pregnancy, and may reveal potential applications for this peptide as a marker of maternal and/or fetal health and wellbeing in both human medicine and animal production

C-type natriuretic peptide forms in pregnancy: maternal plasma profiles during ovine gestation correlate with placental and fetal maturation

Circulating concentrations of C-type natriuretic peptide (CNP) and a related amino terminal fragment (NTproCNP) were measured at weekly intervals from preconception to 3 wk postpartum in ewes with twins (n = 8) and nonpregnant ewes (n = 8). In contrast to low and stable values in nonpregnant ewes (CNP, 0.75 ± 0.08; NTproCNP, 22 ± 2 pmol/liter), CNP forms increased abruptly at 40–50 d of gestation and rose to peak values (CNP, 31 ± 5, NTproCNP, 270 ± 16 pmol/liter) at about d 120. Approximately 7 d prepartum, the concentration of both CNP forms fell precipitously to preconception values immediately postpartum. In separate studies, circulating maternal CNP forms were positively related to fetal number at d 120. Consistent with a major contribution from the placenta to circulating levels, the concentrations of CNP forms were elevated in the placentome (cotyledon: CNP, 18 ± 4, NTproCNP, 52 ± 10 pmol/g; caruncle: CNP, 13 ± 3, NTproCNP, 31 ± 6 pmol/g) and much higher than those of intercaruncular uterine tissue (CNP, 0.19 ± 0.05, NTproCNP, 0.98 ± 0.2 pmol/g) in late-gestation ewes (P < 0.001, n = 4). These distinctive patterns of maternal plasma CNP forms, positive relation with fetal number, and greatly elevated protein concentrations in the placentome demonstrate the hormone's strong relation to placental and fetal maturation. The findings provide a firm basis for future studies of the functional role of CNP in fetal-maternal welfare

Advanced Glycation End-Products and Their Effects on Gut Health

Dietary advanced glycation end-products (AGEs) are a heterogeneous group of compounds formed when reducing sugars are heated with proteins, amino acids, or lipids at high temperatures for a prolonged period. The presence and accumulation of AGEs in numerous cell types and tissues are known to be prevalent in the pathology of many diseases. Modern diets, which contain a high proportion of processed foods and therefore a high level of AGE, cause deleterious effects leading to a multitude of unregulated intracellular and extracellular signalling and inflammatory pathways. Currently, many studies focus on investigating the chemical and structural aspects of AGEs and how they affect the metabolism and the cardiovascular and renal systems. Studies have also shown that AGEs affect the digestive system. However, there is no complete picture of the implication of AGEs in this area. The gastrointestinal tract is not only the first and principal site for the digestion and absorption of dietary AGEs but also one of the most susceptible organs to AGEs, which may exert many local and systemic effects. In this review, we summarise the current evidence of the association between a high-AGE diet and poor health outcomes, with a special focus on the relationship between dietary AGEs and alterations in the gastrointestinal structure, modifications in enteric neurons, and microbiota reshaping

Erratum: Treatment of dystrophic mdx mice with an ADAMTS-5 specific monoclonal antibody increases the ex vivo strength of isolated fast twitch hindlimb muscles (Biomolecules, (2020) 10, 10.3390/biom10030416)

The authors wish to make a change to this published paper [1]. In the original manuscript, there was a mistake in the labeling of the y-axis for Figure 5B,D. To assess muscle fatiguability, extensor digitorum longus (EDL) and soleus muscles were subjected to 4 min of intermittent (1 contraction every 5 s), submaximal stimulation at 60 Hz. The force output of every fifth contraction is statistically presented as a data point. The revision to Figure 5B,D now reflects the correct stimulation number. The authors apologize for any inconvenience caused, and we wish to stress that this change does not affect the presented scientific results and statistical analyses. The manuscript with be updated and the original will remain online on the article webpage at https://www.mdpi.com/2218-273X/10/3/416