The protective role of metformin in autophagic status in peripheral blood mononuclear cells of type 2 diabetic patients

• Published in: Cell biology international 2020-08, Vol.44 (8), p.1628-1639
• Main Authors: Bhattacharya, Debalina, Dutta, Moumita, Mukhopadhyay, Mainak, Bhattacharyya, Maitree, Chowdhury, Subhankar, Karmakar, Parimal
• Format: Article
• Language: English
• Subjects: Aged; AMP; Antidiabetics; Apoptosis; Autophagosomes - physiology; Autophagy; Autophagy - drug effects; Caspase; Cell death; Cells, Cultured; Diabetes; Diabetes mellitus (non-insulin dependent); Diabetes Mellitus, Type 2 - metabolism; Diabetes Mellitus, Type 2 - pathology; Diabetes Mellitus, Type 2 - physiopathology; Endoplasmic Reticulum Stress; Female; Humans; Hypoglycemic Agents - pharmacology; Kinases; Leukocytes (mononuclear); Leukocytes, Mononuclear - drug effects; Leukocytes, Mononuclear - metabolism; Leukocytes, Mononuclear - physiology; Leukocytes, Mononuclear - ultrastructure; lysosomal fusion; Lysosomes; Lysosomes - physiology; Male; Membrane Fusion - drug effects; Membrane proteins; Metformin; Metformin - pharmacology; Middle Aged; Peripheral blood mononuclear cells; Phagocytosis; Protein kinase; Proteins; Rapamycin; starvation; TOR protein; Transmission electron microscopy; Tunicamycin; Vacuoles
• ISSN: 1065-6995; 1095-8355
• DOI: 10.1002/cbin.11355

Autophagy plays an important role in the pathophysiology of type 2 diabetes (T2D). Metformin is the most common antidiabetic drug. The main objective of this study was to explore the molecular mechanism of metformin in starvation‐induced autophagy in peripheral blood mononuclear cells (PBMCs) of type 2 diabetic patients. PBMCs were isolated from 10 diabetic patients and 7 non‐diabetic healthy volunteers. The autophagic puncta and markers were measured with the help of monodansylcadaverine staining and western blot. Additionally, transmission electron microscopy was also performed. No significant changes were observed in the initial autophagy marker protein levels in PBMCs of T2D after metformin treatment though diabetic PBMCs showed a high level of phospho‐mammalian target of rapamycin, p62 and reduced expression of phospho‐AMP‐activated protein kinase and lysosomal membrane‐associated protein 2, indicating a defect in autophagy. Also, induction of autophagy by tunicamycin resulted in apoptosis in diabetic PBMCs as observed by caspase‐3 cleavage and reduced expression of Bcl2. Inhibition of autophagy by bafilomycin rendered consistent expression of p62 indicating a defect in the final process of autophagy. Further, electron microscopic studies also confirmed massive vacuole overload and a sign of apoptotic cell death in PBMCs of diabetic patients, whereas metformin treatment reduced the number of autophagic vacuoles perhaps by lysosomal fusion. Thus, our results indicate that defective autophagy in T2D is associated with the fusion process of lysosomes which could be overcome by metformin.