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PR interval is the period from the onset of P wave to the start of the QRS complex on electrocardiograms. A recent genomewide association study (GWAS) suggested that GAREM1 was linked to the PR interval on electrocardiograms. This study was designed to validate this correlation using additional subjects and examined the function of Garem1 in a mouse model. We analyzed the association of rs17744182, a variant in the GAREM1 locus, with the PR interval in 5646 subjects who were recruited from 2 Korean replication sets, Yangpyeong (n = 2471) and Yonsei (n = 3175), and noted a significant genomewide association by meta-analysis (P = 2.39 × 10 -8 ). To confirm the function of Garem1 in mice, Garem1 siRNA was injected into mouse tail veins to reduce the expression of Garem1. Garem1 transcript levels declined by 53% in the atrium of the heart (P = 0.029), and Garem1-siRNA injected mice experienced a significant decrease in PR interval (43.27 ms vs. 44.89 ms in control, P = 0.007). We analyzed the expression pattern of Garem1 in the heart by immunohistology and observed specific expression of Garem1 in intracardiac ganglia. Garem1 was expressed in most neurons of the ganglion, including cholinergic and adrenergic cells. We have provided evidence that GAREM1 is involved in the PR interval of ECGs. These findings increase our understanding of the regulatory signals of heart rhythm through intracardiac ganglia of the autonomic nervous system and can be used to guide the development of a therapeutic target for heart conditions, such as atrial fibrillation.

The use of topiramate (TPM) in the treatment of binge-eating disorder, bulimia nervosa, and antipsychotic-induced weight gain has recently increased, however, the exact molecular basis for its effects on body weight reduction and improved glucose homeostasis, is yet to be elucidated. Here we investigated the effect and signaling pathway of TPM on glucose uptake in L6 rat skeletal muscle cells, which account for >70% of glucose disposal in the body. Intriguingly, we found that TPM (10 microM) stimulated the rate of glucose uptake up to twofold increase. And TPM-stimulated glucose transport was inhibited with the overexpression of dominant-negative form of AMP-activated protein kinase (AMPK), an important mediator in glucose transport, implicating that AMPK-mediated pathway is involved. The TPM-stimulated glucose transport was blocked by SB203580, a specific inhibitor of AMPK downstream mediator, p38 mitogen-activated protein kinase (MAPK) protein. LY294002, an inhibitor of phosphatidylinositol (PI) 3-kinase, which is another crucial mediator in independent glucose transport pathway, did not inhibit TPM-stimulated glucose transport. We also found that TPM increased the phosphorylation level of AMPK and p38 MAPK, whereas no effect on the activity of PI 3-kinase of TPM, when assessed by PI 3-kinase assay, was observed. These results together suggest that TPM stimulates glucose transport, not via PI 3-kinase mediated, but via AMPK-mediated pathway in skeletal muscle cells, thereby contributing to the body weight regulation and glucose homeostasis.