4-Phenylbutyric acid and rapamycin improved diabetic status in high fat diet/streptozotocin-induced type 2 diabetes through activation of autophagy

An accumulating body of evidence supports the role of autophagy in the pathophysiology of T2DM. Also, abnormal endoplasmic reticulum (ER) stress response that has been implicated as a cause of insulin resistance (IR) could also be affected by the autophagic status in β-cells. The present study was designed to investigate whether autophagy is regulated in T2DM as well as to investigate the modulatory effect of the ER stress inhibitor 4-phenylbutyric acid (4-PBA) and the autophagy inducer rapamycin (Rapa) on the autophagic and diabetic status using type 2 diabetic animal model with IR. Treatment of diabetic rats with either 4-PBA or Rapa improved significantly the states of hyperglycaemia and dyslipidaemia, increased the antioxidant capacity, reduced the levels of lipid peroxidation and ER stress and increased the autophagic flux. The obtained improvements were attributed mainly to the induction of autophagy with subsequent regulation of ER stress-oxidative activation and prevention of β-cell apoptosis.

Sirtuin 1 promotes autophagy and proliferation of endometrial cancer cells by reducing acetylation level of LC3

Endometrial cancer (EC) constitutes a common female genital tract tumor with a rising incidence rate. Sirtuin 1 (SIRT1) is a member of histone deacetylase, which extensively participates in the progression of aging, cell death, and tumorigenesis. This study explored the effect of SIRT1-mediated LC3 acetylation on autophagy and proliferation of EC cells. SIRT1 expression in EC tissues and adjacent tissues, EC cell lines and normal human epithelial cells was detected. SIRT1 expression was elevated in EC cell lines and tissues. Knockdown of SIRT1 inhibited proliferation, migration, and invasion of EC cells. Then, EC cells were starved in serum-free medium, and levels of autophagy-related proteins were detected. Starvation induced autophagy of EC cells. The starvation-treated EC cells showed an increased SIRT1 expression, a decreased LC3 acetylation level and an increased autophagy level. The proliferation and autophagy of EC cells under different treatments were evaluated. In EC cells transfected with overexpressing SIRT1, LC3 acetylation was inhibited and cell proliferation was promoted. Moreover, overexpressing SIRT1 facilitated growth and autophagy of transplanted tumors in nude mice. In conclusion, SIRT1 promoted autophagy and proliferation of EC cells by reducing acetylation level of LC3.

[LAP (LC3-associated phagocytosis): phagocytosis or autophagy?]

Phagocytosis and macroautophagy, named here autophagy, are two essential mechanisms of lysosomal degradation of diverse cargos into membrane structures. Both mechanisms are involved in immune regulation and cell survival. However, phagocytosis triggers degradation of extracellular material whereas autophagy engulfs only cytoplasmic elements. Furthermore, activation and maturation of these two processes are different. LAP (LC3-associated phagocytosis) is a form of phagocytosis that uses components of the autophagy pathway. It can eliminate (i) pathogens, (ii) immune complexes, (iii) threatening neighbouring cells, dead or alive, and (iv) cell debris, such as POS (photoreceptor outer segment) and the midbody released at the end of mitosis. Cells have thus optimized their means of elimination of dangerous components by sharing some fundamental elements coming from the two main lysosomal degradation pathways.

A journey into the retina: Müller glia commanding survival and death

Müller glial cells (MGCs) are known to participate actively in retinal development and to contribute to homoeostasis through many intracellular mechanisms. As there are no homologous cells in other neuronal tissues, it is certain that retinal health depends on MGCs. These macroglial cells are located at the centre of the columnar subunit and have a great ability to interact with neurons, astrocytes, microglia and endothelial cells in order to modulate different events. Several investigations have focused their attention on the role of MGCs in diabetic retinopathy, a progressive pathology where several insults coexist. As expected, data suggest that MGCs display different responses according to the severity of the stimulus, and therefore trigger distinct events throughout the course of the disease. Here, we describe physiological functions of MGCs and their participation in inflammation, gliosis, synthesis and secretion of trophic and antioxidant factors in the diabetic retina. We invite the reader to consider the protective/deleterious role of MGCs in the early and late stages of the disease. In the light of the results, we open up the discussion around and ask the question: Is it possible that the modulation of a single cell type could improve or even re-establish retinal function after an injury?

Autophagy and its link to type II diabetes mellitus

Autophagy, a double-edged sword for cell survival, is the research object on 2016 Nobel Prize in Physiology or Medicine. Autophagy is a molecular mechanism for maintaining cellular physiology and promoting survival. Defects in autophagy lead to the etiology of many diseases, including diabetes mellitus (DM), cancer, neurodegeneration, infection disease and aging. DM is a metabolic and chronic disorder and has a higher prevalence in the world as well as in Taiwan. The character of diabetes mellitus is hyperglycemia resulting from defects in insulin secretion, insulin action, or both. Type 2 diabetes mellitus (T2DM) is characterized by insulin resistance and failure of producing insulin on pancreatic beta cells. In T2DM, autophagy is not only providing nutrients to maintain cellular energy during fasting, but also removes damaged organelles, lipids and miss-folded proteins. In addition, autophagy plays an important role in pancreatic beta cell dysfunction and insulin resistance. In this review, we summarize the roles of autophagy in T2DM.