Abstract Body (Do not enter title and authors here):
Introduction: Metabolic syndrome (MS) is an important predisposing factor for atrial fibrillation, and is highly related to the autonomic nervous system. Triglyceride-rich very-low-density lipoprotein (VLDL) has specific VLDL receptors (VLDLR), which are abundantly expressed in cardiomyocytes.
Hypothesis: VLDL affects neuronal growth through cardiomyocyte-secreted exosomes in metabolic syndrome.
Goals/Aims: To determine whether exosomes from VLDL-incubated cardiomyocytes can alter neuronal proliferation.
Methods/ Approach: HL-1 cardiomyocytes were incubated with VLDL isolated from human subjects with MS, and exosomes were extracted at the end of the incubation period. VLDLR knockdown HL-1 cells were used to determine the role of VLDLR in exosome secretion. The molecular contents of exosomes were determined by mass spectrometry, which identified neurotropic proteins only detected in the exosomes of MS VLDL-incubated cardiomyocytes. We selected transmembrane protein 14B (TMEM14B) to investigate its effect on neuronal proliferation in P19 cells.
Results: Regardless of the knockdown or overexpression of VLDLR in HL-1 cardiomyocytes, exosomes isolated from after VLDL incubation were shown to cause 2.062-fold and 2.084-fold expression of tyrosine hydroxylase (TH) in P19 cells, relative to P19 cells induced by non-VLDL-treated HL-1 cardiomyocyte-secreted exosomes. A similar trend could be seen with HL-1 cardiomyocytes without VLDLR editing, as VLDL-incubated HL-1 cardiomyocytes produced exosomes that could cause 1.926-fold increase in P19 TH expression, relative to treatment by exosomes from HL-1 cardiomyocytes without VLDL-incubation. The P19 cells incubated with TMEM14B demonstrated increased neurite length, with an average of 2.342-fold neurite length when compared with that of control cells.
Conclusions: VLDL in MS induced HL-1 cardiomyocytes to secrete exosomes containing neurotrophic molecules and increased dendritic growth of neuronal cells. This effect was VLDLR-independent and was partially caused by TMEM14B in the exosomes.