Pivotal Roles of Peroxisome Proliferator-Activated Receptors (PPARs) and Their Signal Cascade for Cellular and Whole-Body Energy Homeostasis

Peroxisome proliferator-activated receptors (PPARs), members of the nuclear receptor superfamily, are important in whole-body energy metabolism. PPARs are classified into three isoforms, namely, PPARα, β/δ, and γ. They are collectively involved in fatty acid oxidation, as well as glucose and lipid metabolism throughout the body. Importantly, the three isoforms of PPARs have complementary and distinct metabolic activities for energy balance at a cellular and whole-body level. PPARs also act with other co-regulators to maintain energy homeostasis. When endogenous ligands bind with these receptors, they regulate the transcription of genes involved in energy homeostasis. However, the exact molecular mechanism of PPARs in energy metabolism remains unclear. In this review, we summarize the importance of PPAR signals in multiple organs and focus on the pivotal roles of PPAR signals in cellular and whole-body energy homeostasis.

Hypoxia-dependent mitochondrial fission regulates endothelial progenitor cell migration, invasion, and tube formation

Tumor undergo uncontrolled, excessive proliferation leads to hypoxic microenvironment. To fulfill their demand for nutrient, and oxygen, tumor angiogenesis is required. Endothelial progenitor cells (EPCs) have been known to the main source of angiogenesis because of their potential to differentiation into endothelial cells. Therefore, understanding the mechanism of EPC-mediated angiogenesis in hypoxia is critical for development of cancer therapy. Recently, mitochondrial dynamics has emerged as a critical mechanism for cellular function and differentiation under hypoxic conditions. However, the role of mitochondrial dynamics in hypoxia-induced angiogenesis remains to be elucidated. In this study, we demonstrated that hypoxia-induced mitochondrial fission accelerates EPCs bioactivities. We first investigated the effect of hypoxia on EPC-mediated angiogenesis. Cell migration, invasion, and tube formation was significantly increased under hypoxic conditions; expression of EPC surface markers was unchanged. And mitochondrial fission was induced by hypoxia time-dependent manner. We found that hypoxia-induced mitochondrial fission was triggered by dynamin-related protein Drp1, specifically, phosphorylated DRP1 at Ser637, a suppression marker for mitochondrial fission, was impaired in hypoxia time-dependent manner. To confirm the role of DRP1 in EPC-mediated angiogenesis, we analyzed cell bioactivities using Mdivi-1, a selective DRP1 inhibitor, and DRP1 siRNA. DRP1 silencing or Mdivi-1 treatment dramatically reduced cell migration, invasion, and tube formation in EPCs, but the expression of EPC surface markers was unchanged. In conclusion, we uncovered a novel role of mitochondrial fission in hypoxia-induced angiogenesis. Therefore, we suggest that specific modulation of DRP1-mediated mitochondrial dynamics may be a potential therapeutic strategy in EPC-mediated tumor angiogenesis.

Evaluation of anti-secretory and anti-ulcerogenic activities of avipattikar churna on the peptic ulcers in experimental rats

BACKGROUND

Avipattikar churna, a poly-herbal formulation, is one of the popular ayurvedic formulations which is used for peptic ulcer diseases but the scientific documentation with regards to its effect for the indication is lacking.

AIMS

This study was carried out to evaluate the anti-secretory and the anti-ulcerogenic activities of the churna and to compare its activity with that of ranitidine in a pyloric ligated model of rats.

MATERIAL AND METHODS

Four groups of rats with 6 animals in each served as the ulcer controls, churna low dose (500 mg/kg), churna high dose (750mg/kg) and ranitidine (25mg/kg). The control group rats received only vehicle (2% (v/v) gum acacia), while the rats of the other groups received the respective dose of the churna or ranitidine which was suspended in the vehicle. The treatments were given twice a day, orally, for two days. After 1 hour of the last dose, pyloric ligations were performed and the rats were sacrificed for evaluation after four hours of the ligations. The gastric contents were collected and its volume, pH and acidity were measured. The numbers of ulcers and their lengths were measured which were used to calculate the gastric irritancy index and the curative ratio. The histological examinations of the gastric tissues were also performed.

RESULTS

The churna, in both doses, significantly decreased the volumes of the gastric contents, the ulcer score, the length of the ulcer, the gastric irritancy index and pH increased as compared to those in the control group. The effects of the churna were comparable to that of ranitidine. The histopathological evaluation of the gastric tissue also supported the results.

CONCLUSION

Avipattikar churna has anti-secretory and anti-ulcerogenic effects which are comparable to those of ranitidine in peptic ulcer diseases.