Chemical Chaperone PBA Attenuates ER Stress and Upregulates SOCS3 Expression as a Regulator of Leptin Signaling

Angiotensin(1-7) attenuates visceral adipose tissue expansion and lipogenesis by suppression of endoplasmic reticulum stress via Mas receptor

BACKGROUND

White adipose tissue can be classified based on its location as subcutaneous and visceral fat, and the latter accumulation is reported to be more detrimental to metabolism. Endoplasmic reticulum (ER) stress has been demonstrated to regulate lipogenesis. The peptide angiotensin(1-7) [Ang(1-7)], which can be produced from angiotensin II (AngII) by angiotensin-converting enzyme 2 (ACE2), plays its role through Mas receptor, also participates in the regulation of lipid metabolism in adipose tissue, however, whether ER stress is involved in the mechanism remains unclear. Therefore, we aimed to explore the role of Ang(1-7) pathway in regulating visceral adipose tissue expansion and ER stress.

METHODS

ACE2 knockout (KO), Mas KO and C57BL/6 J mice were fed with high fat diet. Db/db mice were treated with either normal saline, Ang(1-7) or Ang(1-7) combined with Mas receptor inhibitor A779 using mini osmotic pumps. Fat mass was weighted, fat distribution was evaluated by MRI, and lipid profile and adipokines in epididymal adipose tissue were measured by ELISA kits, and histology of epididymal adipose tissue was also analyzed in multiple animal models. Additionally, differentiated 3T3-L1 cells were pre-loaded with palmitic acid to induce ER stress, then treated with drugs as those administrated to db/db mice. ER stress and lipogenesis related proteins in mice adipose and differentiated 3T3L-1 cells were analyzed by Western blot.

RESULTS

ACE2 or Mas KO mice exhibited increased visceral adipose tissue, adipocyte size and protein expression of lipogenesis and ER stress related markers in epididymal adipose tissue compared to wild-type mice. Db/db mice treated with Ang(1-7) displayed decreased visceral fat mass, adipocyte size and protein expression of lipogenesis and ER stress markers in epididymal adipose tissue compared to those treated with normal saline, while A779 partly attenuated these effects. Additionally, Ang(1-7) improved ER stress and lipogenesis markers in differentiated 3T3-L1 cells pre-loaded with palmitic acid.

CONCLUSIONS

Our findings indicated that Ang(1-7) attenuated visceral adipose tissue expansion and lipogenesis by suppression of ER stress via Mas receptor. The present study provides a potential perspective for Ang(1-7) for the therapeutics of obesity and related disorders.

Gut Microbiota Restores Central Neuropeptide Deficits in Germ-Free Mice

Recent work has demonstrated the ability of the gut microbiota (GM) to alter the expression and release of gut peptides that control appetite and regulate energy homeostasis. However, little is known about the neuronal response of these hormones in germ-free (GF) animals, especially leptin, which is strikingly low in these animals. Therefore, we aimed to determine the response to exogenous leptin in GF mice as compared to conventionally raised (CONV-R) mice. Specifically, we injected and measured serum leptin in both GF and CONV-R mice and measured expression of orexigenic and anorexigenic peptides NPY, AgRP, POMC, and CART in the hypothalamus and hindbrain to examine whether the GM has an impact on central nervous system regulation of energy homeostasis. We found that GF mice had a significant increase in hypothalamic NPY and AgRP mRNA expression and a decrease in hindbrain NPY and AgRP mRNA, while mRNA expression of POMC and CART remained unchanged. Administration of leptin normalized circulating levels of leptin, GLP-1, PYY, and ghrelin, all of which were significantly decreased in GF mice. Finally, brief conventionalization of GF mice for 10 days restored the deficits in hypothalamic and hindbrain neuropeptides present in GF animals. Taken together, these results show that the GM regulates hypothalamic and hindbrain orexigenic/anorexigenic neuropeptide expression. This is in line with the role of gut microbiota in lipid metabolism and fat deposition that may contribute to excess fat in conventionalized animals under high feeding condition.

Fibrosis, the Bad Actor in Cardiorenal Syndromes: Mechanisms Involved

Cardiorenal syndrome is a term that defines the complex bidirectional nature of the interaction between cardiac and renal disease. It is well established that patients with kidney disease have higher incidence of cardiovascular comorbidities and that renal dysfunction is a significant threat to the prognosis of patients with cardiac disease. Fibrosis is a common characteristic of organ injury progression that has been proposed not only as a marker but also as an important driver of the pathophysiology of cardiorenal syndromes. Due to the relevance of fibrosis, its study might give insight into the mechanisms and targets that could potentially be modulated to prevent fibrosis development. The aim of this review was to summarize some of the pathophysiological pathways involved in the fibrotic damage seen in cardiorenal syndromes, such as inflammation, oxidative stress and endoplasmic reticulum stress, which are known to be triggers and mediators of fibrosis.