Setting sail for glucose homeostasis with the AKAP150-PP2B-anchor

Protective effects of curcumin on desipramine-induced islet β-cell damage via AKAP150/PKA/PP2B complex

Tricyclic antidepressants (TCAs) are widely used to treat depression and anxiety-related mood disorders. But evidence shows that TCAs elevate blood glucose levels and inhibit insulin secretion, suggesting that TCAs are a risk factor, particularly for individuals with diabetes. Curcumin is a bioactive molecule from the rhizome of the Curcuma longa plant, which has shown both antidepressant and anti-diabetic activities. In the present study, we investigated the protective effect of curcumin against desipramine-induced apoptosis in β cells and the underlying molecular mechanisms. In the mouse forced swimming test (FST), we found that lower doses of desipramine (5 and 10 mg/kg) or curcumin (2.5 mg/kg) alone did not affect the immobility time, whereas combined treatment with curcumin (2.5 mg/kg) and desipramine (5, 10 mg/kg) significantly decreased the immobility time. Furthermore, desipramine dose-dependently inhibited insulin secretion and elevated blood glucose levels, whereas the combined treatment normalized insulin secretion and blood glucose levels. In RIN-m5F pancreatic β-cells, desipramine (10 μM) significantly reduced the cell viability, whereas desipramine combined with curcumin dose-dependently prevented the desipramine-induced impairment in glucose-induced insulin release, most effectively with curcumin (1 and 10 μM). We demonstrated that desipramine treatment promoted the cleavage and activation of Caspase 3 in RIN-m5F cells. Curcumin treatment inhibited desipramine-induced apoptosis, increased mitochondrial membrane potential and Bcl-2/Bax ratio. Desipramine increased the generation of reactive oxygen species, which was reversed by curcumin treatment. Curcumin also inhibited the translocation of forkhead box protein O1 (FOXO1) from the cytoplasm to the nucleus and suppressed the binding of A-kinase anchor protein 150 (AKAP150) to protein phosphatase 2B (PP2B, known as calcineurin) that was induced by desipramine. These results suggest that curcumin protects RIN-m5F pancreatic β-cells against desipramine-induced apoptosis by inhibiting the phosphoinositide 3-kinase/AKT/FOXO1 pathway and the AKAP150/PKA/PP2B interaction. This study suggests that curcumin may have therapeutic potential as an adjunct to antidepressant treatment.

New anti-diabetic drug Morus alba L. (Sangzhi) alkaloids (SZ-A) improves diabetic nephropathy through ameliorating inflammation and fibrosis in diabetic rats

Background

Morus alba L. (Sangzhi) alkaloid (SZ-A) is a new antidiabetic drug approved by the China National Medical Products Administration in 2020. Diabetic nephropathy (DN) is a common diabetic complication and an important cause of morbidity and mortality in patients with diabetes. The effects of SZ-A on DN remain unknown.

Purpose

This study evaluated the effects of SZ-A on DN in Zucker diabetic fatty (ZDF) rats and explored the underlying mechanisms based on nitrosative stress, inflammation, and fibrosis.

Methods

Diabetic ZDF rats were orally administered 100 and 200 mg/kg of SZ-A once daily for 9 weeks. The glucose metabolism and kidney function were assayed. The pathological injury and fibrosis of the kidneys were separately evaluated using hematoxylin and eosin staining and Masson's staining. The oxidative and nitrosative stress and inflammation were assayed by determining the levels of related indices in the blood and kidneys and quantifying the related gene and protein expression. The expression of transforming growth factor β1 (TGFβ1) gene and protein were assayed by quantitative real-time PCR and immunohistochemistry, respectively. The renal transcriptomics was analyzed using RNA sequencing.

Results

Repeated treatment with SZ-A significantly improved glucose metabolism, dose-dependently decreased the levels of blood urea nitrogen, urinary albumin, and β2-microglobulin, and evidently relieved the renal injury in diabetic ZDF rats. As for the mechanisms, SZ-A remarkably ameliorated systemic nitrosative stress through lowering the levels of blood inducible nitric oxide synthase and nitric oxide, and significantly relieved systemic and renal inflammation by reducing the levels of blood interleukin-1β and monocyte chemoattractant protein-1 (MCP-1) and decreasing the levels of renal C-reactive protein content and expression of tumor necrosis factor-α in the kidneys. SZ-A also improved renal fibrosis by lowering the expression of TGFβ1 in the kidneys. Additionally, SZ-A significantly lowered the expression of stimulator of chondrogenesis 1 in the kidneys.

Conclusion

Repeated treatments with SZ-A significantly ameliorates DN by regulating systemic nitrosative stress, renal inflammation, and renal fibrosis partially through inhibition of the cytokine-NO and TGF-β1 signaling in ZDF rats, providing evidence for the additional application of SZ-A in clinical use for the treatment of DN.

Knockout of AKAP150 improves impaired BK channel-mediated vascular dysfunction through the Akt/GSK3β signalling pathway in diabetes mellitus

Vascular dysfunction resulting from diabetes is an important factor in arteriosclerosis. Previous studies have shown that during hyperglycaemia and diabetes, AKAP150 promotes vascular tone enhancement by intensifying the remodelling of the BK channel. However, the interaction between AKAP150 and the BK channel remains open to discussion. In this study, we investigated the regulation of impaired BK channel‐mediated vascular dysfunction in diabetes mellitus. Using AKAP150 null mice (AKAP150^−/−) and wild‐type (WT) control mice (C57BL/6J), diabetes was induced by intraperitoneal injection of streptozotocin. We found that knockout of AKAP150 reversed vascular remodelling and fibrosis in mice with diabetes and in AKAP150^−/− diabetic mice. Impaired Akt/GSK3β signalling contributed to decreased BK‐β₁ expression in aortas from diabetic mice, and the silencing of AKAP150 increased Akt phosphorylation and BK‐β₁ expression in MOVAS cells treated with HG medium. The inhibition of Akt activity caused a decrease in BK‐β₁ expression, and treatment with AKAP150 siRNA suppressed GSK3β expression in the nuclei of MOVAS cells treated with HG. Knockout of AKAP150 reverses impaired BK channel‐mediated vascular dysfunction through the Akt/GSK3β signalling pathway in diabetes mellitus.