Increased circulating progranulin is not sufficient to induce cardiac dysfunction or supraventricular arrhythmia

Figures

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  Figure 1. AAV8-Grn bGH vector results in significantly elevated levels of circulating progranulin 20 weeks post-injection. Mice received retro-orbital injections of AAV8-Grn bGH vector at 1.25 × 1012 (Grn Low) and 4.17 × 1012 (Grn High) VG/kg and plasma levels of progranulin quantified by ELISA. (a) Plasma progranulin levels 10 weeks post-injection (Control/Chow and Grn Low, n = 12, Control/HFD, and Grn High, n = 11). Plasma progranulin levels 20 weeks post-injection (Control/Chow and Grn High, n = 11; Control/HFD, n = 9; Grn Low, n = 12). (b) % Change in body weight measured weekly for 20 weeks. (c) Area under the curve of (b). (d) Hex A activity measured in liver homogenates from controls and progranulin overexpressing mice with the fluorogenic substrate 4-methylumbelliferyl-6-sulfo-N-acetyl-beta-D-glucosaminide (n = 6). *p = 0.02, **p = 0.0023, ****p < 0.0001. Data are presented as individual values, bars represent mean ± SD.

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  Figure 2. Chronic overexpression of circulating progranulin does not alter cardiac structure or function. After 20 weeks of progranulin overexpression, echocardiography was performed on all groups to determine systolic function and degree of left ventricular remodeling. Progranulin overexpression does not alter: (a) left ventricular ejection fraction, (b) atria weight/tibia length, (c) heart weight/tibia length, (d) left ventricular mass, (e,f) or left ventricular internal diameter at systole and diastole. Control/Chow n = 11, Control/HFD n = 9, Grn Low n = 12, and Grn High n = 11. p > 0.05 for all comparisons. Data are presented as individual values, bars represent mean ± SD.

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  Figure 3. Chronic overexpression of circulating progranulin does not affect cardiac electrical activity. At 20 weeks chronic progranulin overexpression surface ECGs were recorded to quantify cardiac electrical activity. Baseline measures represent averaged values from a 5-min recording under 1.5% isoflurane. Following baseline, mice received a 3mg/kg bolus of the β-adrenergic agonist isoproterenol. (a,b) Representative traces of one cardiac cycle at baseline (a) and following isoproterenol challenge (b). (c) Chronotropic response to isoproterenol challenge (beats/minute). (d) RR interval. (e) Atrial conduction time (P duration). (f) PR interval. (g) QRS interval. (h) P wave amplitude. Control/Chow n = 11, Control/HFD n = 9, Grn Low n = 12, and Grn High n = 11. p > 0.05 for all comparisons. Data are presented as individual values, bars represent mean ± SD.

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  Figure 4. 20 weeks of elevated plasma progranulin does not result in increased ectopic beats/cardiac rhythms. (a,b) Representative ECG traces of ectopic events at baseline (a) and following isoproterenol challenge (b) irrespective of treatment group. (c) Percentage of mice with ectopic beats/cardiac rhythms at baseline. (d) Percentage of mice with ectopic beats/cardiac rhythms following isoproterenol challenge. SR sinus rhythm, PVC premature ventricular contraction, PAC premature atrial contraction, AV Dissociation: atrioventricular dissociation.

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  Figure 5. Elevated levels of circulating progranulin do not alter the expression of fibrosis-related genes. RNA was isolated from the atria of control mice and mice receiving AAV8-Grn bGH vector at indicated doses 6 weeks post-injection and markers of fibrosis was evaluated by qPCR. No changes were observed in mRNA levels of (a) Col1a2, (b) Col3a1, (c) Postn, (d) Acta2, and (e) Tgfb1. n = 6 for all groups. p > 0.05 for all comparisons. Data are presented as individual values, bars represent mean ± SD.

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  Figure 6. Increased circulating progranulin does not affect atrial expression levels of pro-inflammatory genes. RNA was isolated from the atria of all groups at 20 weeks and expression levels of pro-inflammatory genes evaluated by qPCR. No significant changes in expression levels of Il1b, Il6, Il18, Tnf, or Nlrp3 were observed (a–e). n = 6 for all groups. p > 0.05 for all comparisons. Data are presented as individual values, bars represent mean ± SD.