Plasma proANP and SDMA and microRNAs are associated with chronic mitral regurgitation in a pig model.

OBJECTIVE: NON-ISCHEMIC MITRAL REGURGITATION (MR) IS PRIMARILY CAUSED BY MYXOMATOUS MITRAL VALVE (MV) DISEASE LEADING TO ADAPTIVE REMODELING, ENLARGEMENT, AND DYSFUNCTION OF THE LEFT VENTRICLE. THE AIM OF THIS STUDY WAS TO EXAMINE THE REGULATION OF PLASMA MARKERS AND SEVERAL CARDIAC KEY GENES IN A NOVEL PORCINE MODEL OF NON-ISCHEMIC MR. METHODS AND RESULTS: Twenty-eight production pigs (Sus scrofa) were randomized to experimental MR or sham surgery controls. MR was induced by external suture(s) through the posterior MV leaflet and quantified using echocardiography. The experimental group was subdivided into mild MR (mMR, MR=20-50%, n=10) and moderate/severe MR (sMR, MR >50%, n=6) and compared with controls (CON, MR ≤10%, n=12). Eight weeks postoperatively, follow-up examinations were performed followed by killing. Circulating concentrations of pro-atrial natriuretic peptide (proANP), l-arginine, asymmetric dimethylarginine, and symmetric dimethylarginine (SDMA) were measured. MV, anterior papillary muscle, and left ventricular free wall tissues were collected to quantify mRNA expression of eNOS (NOS3), iNOS (NOS2), MMP9, MMP14, ANP (NPPA), BNP (NPPB), and TGFB1, 2, and 3 and five microRNAs by quantitative real-time PCR. Pigs with sMR displayed markedly increased plasma proANP and SDMA concentrations compared with both controls and mMR (P<0.05). The expression of all genes examined differed significantly between the three localizations in the heart. miR-21 and miR-133a were differently expressed among the experimental groups (P<0.05). CONCLUSIONS: Plasma proANP and SDMA levels and tissue expression of miR-21 and miR-133a are associated with severity of chronic MR in an experimental porcine model.

Circulating cytokine concentrations in dogs with different degrees of myxomatous mitral valve disease.

Cytokines have been associated with the progression of congestive heart failure (CHF) in humans and may be implicated in the pathophysiology of myxomatous mitral valve disease (MMVD) in dogs. The aim of this study was to determine the serum concentrations of cytokines in dogs with MMVD. The study included 16 Cairn terriers with no or minimal mitral regurgitation (MR), 41 Cavalier King Charles Spaniels (CKCS) with different degrees of MR and 11 dogs of different breeds with CHF due to MMVD. Granulocyte-macrophage colony-stimulating factor, interferon-γ, interleukin (IL)-2, IL-6, IL-7, IL-8, IL-10, IL-15, IL-18, keratinocyte-derived chemokine, interferon-γ-induced protein and monocyte chemoattractant protein-1 (MCP-1) were measured using a canine-specific multiplex immunoassay. CHF dogs had significantly higher MCP-1 concentrations than dogs with no or minimal MR. Among the CKCS, IL-2 and IL-7 decreased with increasing left atrial size and IL-7 also decreased with increasing MR. IL-8 decreased with increasing left ventricular end-systolic internal dimensions. MCP-1 was increased in CHF dogs compared to healthy control dogs and IL-2, IL-7 and IL-8 decreased with increasing indices of disease severity. The results suggest a role for these cytokines in canine MMVD and CHF.

Brain-natriuretic peptide and cyclic guanosine monophosphate as biomarkers of myxomatous mitral valve disease in dogs.

Elevations in the plasma concentrations of natriuretic peptides correlate with increased severity of myxomatous mitral valve disease (MMVD) in dogs. This study correlates the severity of MMVD with the plasma concentrations of the biomarkers N-terminal fragment of the pro-brain-natriuretic peptide (NT-proBNP) and its second messenger, cyclic guanosine monophosphate (cGMP). Furthermore, the L-arginine:asymmetric dimethylarginine (ADMA) ratio was measured as an index of nitric oxide availability. The study included 75 dogs sub-divided into five groups based on severity of MMVD as assessed by clinical examination and echocardiography. Plasma NT-proBNP and cGMP concentrations increased with increasing valve dysfunction and were significantly elevated in dogs with heart failure. The cGMP:NT-proBNP ratio decreased significantly in dogs with heart failure, suggesting the development of natriuretic peptide resistance. Although the l-arginine:ADMA ratio decreased with increasingly severe MMVD, this was largely due to the older age of the dogs with heart failure.

Predictive value of natriuretic peptides in dogs with mitral valve disease.

Natriuretic peptides are useful in diagnosing heart failure in dogs. However, their usefulness in detecting early stages of myxomatous mitral valve disease (MMVD) has been debated. This study evaluated N-terminal (NT) fragment pro-atrial natriuretic peptide (NT-proANP) and NT-pro-brain natriuretic peptide (NT-proBNP) in 39 Cavalier King Charles Spaniels (CKCS) with pre-clinical mitral valve regurgitation (MR), sixteen dogs with clinical signs of heart failure (HF) and thirteen healthy control dogs. Twenty seven CKCS and ten control dogs were re-examined 4 years after the initial examination and the status of the dogs 5 years after the initial examination was determined by telephone calls to the owner. All dogs were evaluated by clinical examination and echocardiography. CKCS with severe MR had higher NT-proANP and NT-proBNP compared to controls and CKCS with less severe MR. Dogs with clinical signs of HF had markedly elevated NT-proANP and NT-proBNP. Plasma concentrations of the natriuretic peptides measured at re-examination could predict progression in regurgitant jet size.

Effects of high-fat feeding and fasting on ghrelin expression in the mouse stomach.

Ghrelin is a peptide identified as an endogenous ligand for the growth hormone secretagogue receptor. Studies have shown that ghrelin stimulates growth hormone, promotes food intake and decreases energy expenditure. Furthermore, feeding status seems to influence plasma ghrelin levels, as these are increased during fasting, whereas feeding and oral glucose intake reduce plasma ghrelin. This study examined whether standardized obesity and fasting affect cellular expression of ghrelin. Specimens from the gastrointestinal tract of fed or 18-h fasted, low-fat or high-fat fed (10 weeks on diet) C57BL/6J mice were studied by immunocytochemistry (ICC) for ghrelin and in situ hybridization (ISH) for ghrelin mRNA. Ghrelin was expressed in especially the corpus but also the antrum of the stomach of all groups studied. Cells positive for ghrelin and ghrelin mRNA in the stomach were reduced in high-fat fed mice. In contrast, ghrelin expression was not affected by fasting. The reduction in ghrelin expression in the high-fat fed mice was associated with a reduction in plasma levels of ghrelin, whereas after fasting, when expression rate was not altered, there was an increase in plasma ghrelin. In conclusion, ghrelin is highly expressed in the corpus and antrum of the stomach of C57BL/6J mice. This expression is reduced in obesity, whereas fasting has no effect.