The present study was undertaken to investigate the effects of the T-type calcium channel blocker, Mibefradil, on white adipocytes. Unexpected for a T-type channel blocker, Mibefradil was found to increase intracellular calcium levels, cause lipid droplet fusion, and result in cell death. Calcium imaging of white adipocytes showed an increase of calcium concentration by Mibefradil at concentrations ranging from10-50 µM. The elevation in calcium by Mibefradil was significantly reduced by pretreatment of cells with Thapsigargin, an endoplasmic reticulum (ER) specific Ca ATPase inhibitor. Additionally, lipid droplet fusion and cell death were also attenuated by Thapsigargin pretreatment in white adipocytes. We conclude that Mibefradil elevated intracellular calcium levels, induced lipid droplet fusion and cell death in white adipocytes via mobilizing intracellular calcium stores from the ER. These results describe novel effects of Mibefradil on white adipocytes and may provide new insight into how this drug might be repurposed in obesity research.

In this study, I examined the use of mouse (Mus musculus) Fat Specific Protein 27 (FSP27) ectopically expressed in Arabidopsis thaliana and Nicotiana benthamiana as a means to increase lipid droplet (LD) presence in plant tissues. In mammalian cells, this protein induces cytoplasmic LD clustering and fusion and helps prevent breakdown of LDs contributing to the large, single LD that dominates adipocytes. When expressed in Arabidopsis thaliana and Nicotiana benthamiana, FSP27 retained its functionality and supported the accumulation of numerous and large cytoplasmic LDs, although it failed to produce the large, single LD that typifies adipose cells. FSP27 has no obvious homologs in plants, but a search for possible distant homologs in Arabidopsis returned a Tudor/PWWP/MBT protein coded for by the gene AT1G80810 which for the purposes of this study, we have called LIPID REGULATORY TUDOR DOMAIN CONTAINING GENE 1 (LRT1). As a possible homolog of FSP27, LRT1 was expected to have a positive regulatory effect on LDs in cells. Instead, a negative regulatory effect was observed in which disruption of the gene induced an accumulation of cytoplasmic LDs in non-seed tissue. A study of lrt1 mutants demonstrated that disruption this gene is the causal factor of the cytoplasmic LD accumulation observed in the mutants, that this phenotype occurs in above ground tissues and is present throughout the early growth stages of the plant. Further examination of lrt1 mutant plants has allowed a preliminary understanding of the role LRT1 may play in LD regulation. Taken together, the results of this study point towards some promising strategies to increase LD content in plant tissues.