Elevated levels of plasma free fatty acid (FFA) and disturbed mitochondrial dynamics play crucial roles in the pathogenesis of diabetic kidney disease (DKD). However, the mechanisms by which FFA leads to mitochondrial damage in glomerular podocytes of DKD and the effects of Berberine (BBR) on podocytes are not fully understood. Methods : Using the db/db diabetic mice model and cultured mouse podocytes, we investigated the molecular mechanism of FFA-induced disturbance of mitochondrial dynamics in podocytes and testified the effects of BBR on regulating mitochondrial dysfunction, podocyte apoptosis and glomerulopathy in the progression of DKD. Results : Intragastric administration of BBR for 8 weeks in db/db mice significantly reversed glucose and lipid metabolism disorders, podocyte damage, basement membrane thickening, mesangial expansion and glomerulosclerosis. BBR strongly inhibited podocyte apoptosis, increased reactive oxygen species (ROS) generation, mitochondrial fragmentation and dysfunction both in vivo and in vitro . Mechanistically, BBR could stabilize mitochondrial morphology in podocytes via abolishing palmitic acid (PA)-induced activation of dynamin-related protein 1 (Drp1). Conclusions : Our study demonstrated for the first time that BBR may have a previously unrecognized role in protecting glomerulus and podocytes via positively regulating Drp1-mediated mitochondrial dynamics. It might serve as a novel therapeutic drug for the treatment of DKD.

Background and Purpose Disordered lipid metabolism and disturbed mitochondrial bioenergetics play pivotal roles in the initiation and development of diabetic kidney disease (DKD). Berberine is a plant alkaloid, used in Chinese herbal medicine. It has multiple therapeutic actions on diabetes mellitus and its complications, including regulation of glucose and lipid metabolism, improvement of insulin sensitivity, and alleviation of oxidative damage. Here, we investigated the reno‐protective effects of berberine. Experimental Approach We used samples from DKD patients and experiments with models of DKD (db/db mice) and cultured podocytes, to characterize energy metabolism profiles using metabolomics. Molecular targets and mechanisms involved in the regulation of mitochondrial function and bioenergetics by berberine were investigated, along with its effects on metabolic alterations in DKD mice. Key Results Metabolomic analysis suggested altered mitochondrial fuel usage and generalized mitochondrial dysfunction in patients with DKD. In db/db mice, berberine treatment reversed the disordered metabolism, podocyte damage and glomerulosclerosis. Lipid accumulation, excessive generation of mitochondrial ROS, mitochondrial dysfunction, and deficient fatty acid oxidation in DKD mouse models and in cultured podocytes were suppressed by berberine. These protective effects of berberine were accompanied by activation of the peroxisome proliferator‐activated receptor γ coactivator‐1α (PGC‐1α) signalling pathway, which promoted mitochondrial energy homeostasis and fatty acid oxidation in podocytes. Conclusion and Implications PGC‐1α‐mediated mitochondrial bioenergetics could play a key role in lipid disorder‐induced podocyte damage and development of DKD in mice. Restoration of PGC‐1α activity and the energy homeostasis by berberine might be a potential therapeutic strategy against DKD.

BackgroundsInflammation is recognized as the key pathological mechanism of type 2 diabetes. The hypoglyceamic effects of berberine (BBR) are related to the inhibition of the inflammatory response, but the mechanism is not completely clear.MethodsThe inflammatory polarization of Raw264.7 cells and primary peritoneal macrophages were induced by LPS, and then effects and underlying mechanisms of BBR were explored. An inflammatory model was established by LPS treatment at different concentrations for different treatment time. An ELISA assay was used to detect the secretions of TNF-α. RT-PCR was applied to detect M1 inflammatory factors. The F4/80+ ratio and CD11c+ ratio of primary peritoneal macrophages were determined by flow cytometry. The expressions of p-AMPK and TLR4 were detected by Western blot. The cytoplasmic and nuclear distributions of NFκB p65 were observed by confocal microscopy. The binding of TLR4 to MyD88 was tested by CoIP, and the affinity of BBR for TLR4 was assessed by molecular docking.ResultsUpon exposure to LPS, the secretion of TNF-α and transcription of inflammatory factors in macrophages increased, cell morphology changed and protrusions appeared gradually, the proportion of F4/80+CD11c+ M1 macrophages increased, and the nuclear distribution of NFκB p65 increased. BBR pretreatment partially inhibited the changes mentioned above. However, the expression of TLR4 and p-AMPK did not change significantly after LPS intervention for 3 h. Meanwhile, CoIP showed that the interaction between TLR4 and MyD88 increased, and BBR inhibited the binding. Molecular docking suggested that BBR might interact with TLR4.ConclusionsInflammatory changes were induced in macrophages after LPS stimulation for 3 h, and BBR pretreatment inhibited inflammatory polarization. BBR might interact with TLR4 and disturb TLR4/MyD88/NFκB signalling pathway, and it might be the mechanism by which BBR attenuated inflammation in the early phase.