Lipotoxicity-polarised macrophage-derived exosomes regulate mitochondrial fitness through Miro1-mediated mitophagy inhibition and contribute to type 2 diabetes development in mice.

AIMS/HYPOTHESIS: Insulin resistance is a major pathophysiological defect in type 2 diabetes and obesity. Numerous experimental and clinical studies have provided evidence that sustained lipotoxicity-induced mitophagy deficiency can exacerbate insulin resistance, leading to a vicious cycle between mitophagy dysfunction and insulin resistance, and thereby the onset of type 2 diabetes. Emerging evidence suggests that exosomes (Exos) from M2 macrophages play an essential role in modulating metabolic homeostasis. However, how macrophages are affected by lipotoxicity and the role of lipotoxicity in promoting macrophage activation to the M1 state have not been determined. The objective of this study was to determine whether M1 macrophage-derived Exos polarised by lipopolysaccharide (LPS) + palmitic acid (PA)-induced lipotoxicity contribute to metabolic homeostasis and impact the development of insulin resistance in type 2 diabetes. METHODS: Lipotoxicity-polarised macrophage-derived M1 Exos were isolated from bone marrow (C57BL/6J mouse)-derived macrophages treated with LPS+PA. Exos were characterised by transmission electron microscopy, nanoparticle tracking analysis and western blotting. Flow cytometry, H&E staining, quantitative real-time PCR, immunofluorescence, glucose uptake and output assays, confocal microscopy imaging, western blotting, GTTs and ITTs were conducted to investigate tissue inflammation, mitochondrial function and insulin resistance in vitro and in vivo. The roles of miR-27-3p and its target gene Miro1 (also known as Rhot1, encoding mitochondrial rho GTPase 1) and relevant pathways were predicted and assessed in vitro and in vivo using specific miRNA mimic, miRNA inhibitor, miRNA antagomir and siRNA. RESULTS: miR-27-3p was highly expressed in M1 Exos and functioned as a Miro1-inactivating miRNA through the miR-27-3p-Miro1 axis, leading to mitochondria fission rather than fusion as well as mitophagy impairment, resulting in NOD-like receptor 3 inflammatory activation and development of insulin resistance both in vivo and in vitro. Inactivation of miR-27-3p induced by M1 Exos prevented type 2 diabetes development in high-fat-diet-fed mice. CONCLUSIONS/INTERPRETATION: These findings suggest that the miR-27-3p-Miro1 axis, as a novel regulatory mechanism for mitophagy, could be considered as a new therapeutic target for lipotoxicity-related type 2 diabetes disease development.

A high fat diet in glutamate 3-/Y mice causes changes in behavior that resemble human intellectual disability.

Cognitive impairment in individuals with intellectual disability (ID) is characterized by developmental delay and deficits in language and memory. Ionotropic AMPA mediate the majority of excitatory synaptic transmission in the central nervous system and are essential for the induction and maintenances of long-term potentiation (LTP) and long-term depression (LTD), two cellular models of learning and memory underlie many the symptoms of ID. Clinical research has found obese male patients with GluA3 interrupted underlie the symptom of ID. We tested GluA3-/Y mice under high fat diet (HFD) stress on a series of behavioral paradigms associated with symptoms of ID: wild type mice showed significant levels of sociability, while GluA3-/Y mice did not. Wild type mice showed significant preference for social novelty, while GluA3-/Y mice did not. Normal scores on relevant control measures confirmed general health and physical abilities in both GluA3-/Y and wild type mice (WT), ruling out artifactual explanations for social deficits. GluA3-/Y mice also showed working spatial memory behavior impairment in Y-maze test and abnormal anxiety in open-field test, compared to wild-type littermate controls. GluA3-/Y mice had a significantly reduced spontaneous activities tested by elevated plus maze, display both low social approach and resistance to change in routine on the T-maze, consistent with an ID-like phenotype. These findings demonstrate that selective gene deletion of GluA3 receptor in male mice under oxidative stress induced phenotypic abnormalities related to ID-like symptoms.