Objective We evaluated the effect of a reduction in the systemic ratio of n-6:n-3 polyunsaturated fatty acids (PUFAs) on changes in inflammation, glucose metabolism, and the idiopathic development of knee osteoarthritis (OA) in mice. We hypothesized that a lower ratio of n-6:n-3 PUFAs would protect against OA markers in cartilage and synovium, but not bone. Design Male and female fat-1 transgenic mice (Fat-1), which convert dietary n-6 to n-3 PUFAs endogenously, and their wild-type (WT) littermates were fed an n-6 PUFA enriched diet for 9-14 months. The effect of gender and genotype on serum PUFAs, IL-6, TNF-α, and glucose tolerance was tested by 2-factor analysis of variance. Cortical and trabecular subchondral bone changes were documented by micro-focal computed tomography, and knee OA was assessed by semi-quantitative histomorphometry grading. Results The n-6:n-3 ratio was reduced 12-fold and 7-fold in male and female Fat-1 mice, respectively, compared to WT littermates. IL-6 and TNF-α levels were reduced modestly in Fat-1 mice. However, these systemic changes did not reduce osteophyte development, synovial hyperplasia, or cartilage degeneration. Also the fat-1 transgene did not alter subchondral cortical or trabecular bone morphology or bone mineral density. Conclusions Reducing the systemic n-6:n-3 ratio does not slow idiopathic changes in cartilage, synovium, or bone associated with early-stage knee OA in mice. The anti-inflammatory and anti-catabolic effects of n-3 PUFAs previously reported for cartilage may be more evident at later stages of disease or in post-traumatic and other inflammatory models of OA.

Background Early, sensitive and reproducible evaluation of left ventricular (LV) function is imperative for diagnosis of cardiac dysfunction in Duchene muscular dystrophy (DMD) patients. We hypothesized that combining 2D-strain analysis with catecholamine stress could be a sensitive method for detecting early cardiac dysfunction. Methods mdx (C57BL/10ScSn-Dmdmdx/J, a mouse model of DMD) and control (C57BL/10ScSn) mice were studied with conventional M-mode and high frequency ultrasound based 2D speckle tracking echocardiography (STE)using long- and short-axis images of LV at baseline and after isoprenaline (2μg/g BW, i.p.). Results Conventional M-mode analysis showed no differences in LV fractional shortening, wall thickness or internal diameter at diastole between mdx and control mice before the age of 6 months. Isoprenaline increased LV ejection fraction and fractional shortening to the same extent in mdx and control mice at young ages (3, 4 and 5 months). No differences in basal peak systolic strain (PSS) but increased standard deviations of times to PSS between young mdx and control mice were found. After isoprenaline, PSS and percentile changes of PSS were significantly diminished in mdx mice compared to control mice at young ages. Isoprenaline increased normalized maximum difference of times to PSS in young mdx mice but not in young control mice, suggesting isoprenaline reduces cardiac contractile synchrony in young mdx mice. Conclusions Our study suggests that catecholamine stress coupled with 2D strain analysis is a feasible and sensitive approach for detecting early onset of cardiac dysfunction, which is instrumental for early diagnosis of cardiac dysfunction and early treatment.

Background MicroRNAs regulate cardiac hypertrophy development, which precedes and predicts the risk of heart failure. microRNA‐204‐5p (miR‐204) is well expressed in cardiomyocytes, but its role in developing cardiac hypertrophy and cardiac dysfunction (CH/CD) remains poorly understood. Methods: We performed RNA‐sequencing, echocardiographic, and molecular/morphometric analysis of the heart of mice lacking or overexpressing miR‐204 five weeks after trans‐aortic constriction (TAC). The neonatal rat cardiomyocytes, H9C2, and HEK293 cells were used to determine the mechanistic role of miR‐204. Results The stretch induces miR‐204 expression, and miR‐204 inhibits the stretch‐induced hypertrophic response of H9C2 cells. The mice lacking miR‐204 displayed a higher susceptibility to CH/CD during pressure overload, which was reversed by the adeno‐associated virus serotype‐9‐mediated cardioselective miR‐204 overexpression. Bioinformatic analysis of the cardiac transcriptomics of miR‐204 knockout mice following pressure overload suggested deregulation of apelin‐receptor (APJ) signalling. We found that the stretch‐induced extracellular signal‐regulated kinase 1/2 (ERK1/2) activation and hypertrophy‐related genes expression depend on the APJ, and both of these effects are subject to miR‐204 levels. The dynamin inhibitor dynasore inhibited both stretch‐induced APJ endocytosis and ERK1/2 activation. In contrast, the miR‐204‐induced APJ endocytosis was neither inhibited by dynamin inhibitors (dynasore and dyngo) nor associated with ERK1/2 activation. We find that the miR‐204 increases the expression of ras‐associated binding proteins (e.g., Rab5a, Rab7) that regulate cellular endocytosis. Conclusions Our results show that miR‐204 regulates trafficking of APJ and confers resistance to pressure overload‐induced CH/CD, and boosting miR‐204 can inhibit the development of CH/CD.

Background: In type 2 diabetic (T2D) patients, the sympathoadrenergic system (SAS) is chronically activated, resulting in chronic protein kinase A (PKA) activation. T2D causes cardiac dysfunction. Objective: To test the hypothesis that PKA plays an important role in diabetic cardiac dysfunction. Methods: PKA inhibition (PKI) transgenic (TG, n=18) and nontransgenic littermate control (NLC, n=20) mice (3-month old) were fed with high fat food (D12451, Research Diet) for 6 months. The body weight (BW) was measured twice a week. Intra-LV hemodynamic, heart weight, liver weight, lung weight, and tibia length were determined at the end point. Myocyte contraction was analyzed. The lean body weight was measured after removing water and fat content of the entire carcass. Inflammatory cell infiltration and fibrosis were determined with MAO staining and Masson’s trichrome staining respectively. Results: 1. The BW of both groups was increased similarly (NLC: from 23.8±3.6g to 45.8±5.6g; TG: from 24.2±3.9g to 46.4±5.6g). Lean body weight and fat composition were not different. 2. The PKI TG group had better cardiac function when examined with intra-LV hemodynamic measurements: (1). The maximal systolic pressure (mmHg) of TG (107.8±4.49) was significantly higher than that of NLC (83.0±8.1) mice. (2). The end diastolic pressure (EDP, mmHg) of TG (2.7 ± 2.2) was significantly lower compared to WT mice (11.5 ± 3.3); (3). Maximum dp/dt (mmHg/s) was significantly higher in PKI TG (7628.0 ± 537.5) than in NLC mice (5021.4 ± 806.2); (4). The relaxation rate of the heart (minimum -dp/dt in mmHg/s) was significantly better in TG (-7159.5 ± 543.0) than in NLC mice (-5334.7 ± 516.2); (5). The HW/BW (mg/g) was significantly less in TG mice (4.6 ± 0.2) than in control mice (5.2 ± 0.2). (6). The lung weight/BW and liver Weight/BW were also reduced in TG mice. (7). At the myocyte level, myocyte contraction amplitude was slightly but significantly greater in TG myocytes than in NLC myocytes. Myocyte relaxation rate was significantly faster in TG myocytes. (8). TG hearts had less inflammatory cell infiltration and fibrosis than control hearts. Conclusion: PKA inhibition ameliorates cardiac remodeling and preserves cardiac function in high fat feeding-induced diabetic mice.