title: Impaired autophagic function in rat islets with aging.
abstract: Type 2 diabetes is characterized by a deficit in β-cell function and mass, and its incidence increases with age. Autophagy is a highly regulated intracellular process for degrading cytoplasmic components, particularly protein aggregates and damaged organelles. Impaired or deficient autophagy is believed to cause or contribute to aging and age-related disease. Autophagy may be necessary to maintain structure, mass, and function of pancreatic β-cells. In this study, we investigated the effects of age on β-cell function and autophagy in pancreatic islets of 4-month-old (young), 14-month-old (adult), and 24-month-old (old) male Wistar rats. We found that islet β-cell function decreased gradually with age. Protein expression of the autophagy markers LC3/Atg8 and Atg7 exhibited a marked decline in aged islets. The expression of Lamp-2, a good indicator of autophagic degradation rate, was significantly reduced in the islets of old rats, suggesting that autophagic degradation is decreased in the islets of aged rats. However, protein expression of beclin-1/Atg6, which plays an important role in the induction and formation of the pre-autophagosome structure by associating with a multimeric complex of autophagy regulatory proteins (Atg14, Vps34/class 3 PI3 kinase, and Vps15), was most prominent in the islets of adult rats, and was higher in 24-month-old islets than in 4-month-old islets. The levels of p62/SQSTM1 and polyubiquitin aggregates, representing the functions of autophagy and proteasomal degradation, were increased in aging islets. 8-Hydroxydeoxyguanosine, a marker of mitochondrial and nuclear DNA oxidative damage, exhibited strong immunostaining in old islets. Analysis by electron microscopy demonstrated swelling and disintegration of cristae in the mitochondria of aged islets. These results suggest that β-cell and autophagic function in islets decline simultaneously with increasing age in Wistar rats, and that impaired autophagy in the islets of older rats may cause accumulation of misfolded and aggregated proteins and reduce the removal of abnormal mitochondria in β-cells, leading to reduced β-cell function. Dysfunctional autophagy in islets during the aging process may be an important mechanism leading to the development of type 2 diabetes.
authors: Department of Geriatric Endocrinology, Chinese PLA General Hospital, 28 Fuxing Road, Beijing, 100853, China.
authors: Yu
authors: Y
authors: Liu
authors: Suozhu
authors: S
authors: Shi
authors: Zhaoyan
authors: Z
authors: Gu
authors: Yingzhen
authors: Y
authors: Du
authors: Minyan
authors: M
authors: Liu
authors: Shuangtong
authors: S
authors: Yan
authors: Jianjun
authors: J
authors: Gao
authors: Jian
authors: J
authors: Li
authors: Yinghong
authors: Y
authors: Shao
authors: Wenwen
authors: W
authors: Zhong
authors: Xiangmei
authors: X
authors: Chen
authors: Chunlin
authors: C
authors: Li
mesh_terms: D000375:Aging / Q000378:metabolism* / Q000473:pathology; D000818:Animals; D001343:Autophagy; D000071193:Autophagy-Related Protein 7; D015153:Blotting, Western; D003921:Diabetes Mellitus, Experimental / Q000378:metabolism* / Q000473:pathology; D018450:Disease Progression; D007150:Immunohistochemistry; D050417:Insulin-Secreting Cells / Q000378:metabolism* / Q000648:ultrastructure; D008297:Male; D008854:Microscopy, Electron; D008869:Microtubule-Associated Proteins / Q000096:biosynthesis; D051381:Rats; D017208:Rats, Wistar; D044764:Ubiquitin-Activating Enzymes / Q000096:biosynthesis
chemical_list: D000071193:Autophagy-Related Protein 7; D008869:Microtubule-Associated Proteins; D044764:Ubiquitin-Activating Enzymes; C561242:Atg7 protein, rat; C526109:Anxa3 protein, rat