Metformin is a widely used antidiabetic drug for type 2 diabetes that can play a cardioprotective role through multiple pathways. It is a recognized agonist of AMP-activated protein kinase (AMPK) that blocks mitochondrial complex I. The NLRP3 inflammasome has been demonstrated to be activated in diabetic cardiomyopathy (DCM). However, the role of metformin in regulating the NLRP3 signaling pathway in DCM remains unclear. It has been reported that AMPK can inhibit NLRP3 by activating autophagy. The aim of this study was to investigate whether metformin can inhibit the NLRP3 inflammasome by activating the AMPK/mTOR pathway in DCM. In this study, streptozotocin-induced C57BL/6 mice and high glucose-treated primary cardiomyocytes from neonatal mice were treated with metformin or an AMPK inhibitor compound C. Echocardiography, hematoxylin-eosin and Masson staining showed that the function and morphology of the diabetic hearts were improved after metformin treatment, whereas these parameters deteriorated after intervention with an AMPK inhibitor. Immunohistochemical staining, immunofluorescence staining and western blot assays indicated that the expression levels of mTOR, NLRP3, caspase-1, IL-1β and GSDMD-N were decreased in the diabetic model treated with metformin and were reversed after the administration of an AMPK inhibitor in vivo and in vitro . Mechanistically, our results demonstrated that metformin can activate AMPK, thus improving autophagy via inhibiting the mTOR pathway and alleviating pyroptosis in DCM. Thus, we provide novel information for the treatment of DCM.

Diabetes cardiomyopathy (DCM) is a critical complication of long-term chronic diabetes mellitus and is characterized by myocardial fibrosis and myocardial hypertrophy. It has been suggested that DCM is related to pyroptosis, a programmed cell death associated with inflammation. The long non-coding RNA Kcnq1ot1 is involved in different pathophysiological mechanisms of multiple diseases, including acute myocardial damage and arrhythmia. Our previous study found that Kcnq1ot1 was elevated in left ventricular tissue of diabetic mice. However, whether Kcnq1ot1 is capable of regulating pyroptosis and fibrosis in high glucose-treated cardiac fibroblasts remains unknown. The aim of the study was to investigate the mechanisms of Kcnq1ot1 in DCM. Our study revealed that silencing Kcnq1ot1 by a lentivirus-shRNA improved cardiac function and fibrosis, ameliorated pyroptosis, and inhibited TGF-β1/smads pathway in C57BL/6 mice. In vitro, experiments revealed that Kcnq1ot1 and pyroptosis were activated in cardiac fibroblasts treated with 30 mmol/l glucose. Furthermore, Kcnq1ot1 knockdown by a small interfering RNA decreased caspase-1 expression. Bioinformatic prediction and luciferase assays showed that Kcnq1ot1 functioned as a competing endogenous RNA to regulate the expression of caspase-1 by sponging miR-214-3p. In addition, silencing Kcnq1ot1 promoted gasdermin D cleavage and the secretion of IL-1β, thus repressing the TGF-β1/smads pathway in high glucose-treated cardiac fibroblasts through miR-214-3p and caspase-1. Therefore, Kcnq1ot1/miR-214-3p/caspase-1/TGF-β1 signal pathway presents a new mechanism of DCM progression and could potentially be a novel therapeutic target.

Background/Aims: Diabetic cardiomyopathy (DCM) is a common complication of diabetes and can cause heart failure, arrhythmia and sudden death. The pathogenesis of DCM includes altered metabolism, mitochondrial dysfunction, oxidative stress, inflammation, cell death and extracellular matrix remodeling. Recently, pyroptosis, a type of programmed cell death related to inflammation, was proven to be activated in DCM. However, the molecular mechanisms underlying pyroptosis in DCM remain elusive. The long non-coding RNA (lncRNA) Kcnq1ot1 participates in many cardiovascular diseases. This study aims to clarify whether Kcnq1ot1 affects cardiac pyroptosis in DCM. Methods: AC16 cells and primary cardiomyocytes were incubated with 5.5 and 50 mmol/L glucose. Diabetic mice were induced with streptozotocin (STZ). Kcnq1ot1 was silenced both in vitro and in vivo. qRT-PCR was used to detect the expression level of Kcnq1ot1. Immunofluorescence, qRT-PCR and western blot analyses were used to detect the degree of pyroptosis. Echocardiography, hematoxylin and eosin staining, and Masson’s trichrome staining were used to detect the cardiac function and morphology in mice. Cell death and function were detected using TUNEL staining, immunofluorescence staining and Ca²⁺ measurements. Results: The expression of Kcnq1ot1 was increased in patients with diabetes, high glucose-induced cardiomyocytes and diabetic mouse cardiac tissue. Silencing Kcnq1ot1 alleviated pyroptosis by targeting miR-214-3p and caspase-1. Furthermore, silencing Kcnq1ot1 reduced cell death, cytoskeletal structure abnormalities and calcium overload in vitro and improved cardiac function and morphology in vivo. Conclusion: Kcnq1ot1 is overexpressed in DCM, and silencing Kcnq1ot1 inhibits pyroptosis by influencing miR-214-3p and caspase-1 expression. We clarified for the first time that Kcnq1ot1 could be a new therapeutic target for DCM.

Diabetic cardiomyopathy (DCM) is a vital cause of fatalities in diabetic patients. The programmed death of cardiomyocytes and inflammation critically contribute to cardiac hypertrophy and fibrosis in DCM. Furthermore, circular RNA (circRNA) is a key regulator of various diseases. However, the role of circRNAs in DCM remains to be elucidated. Our previous study found that pyroptosis was markedly activated in the cardiomyocytes subjected to high-glucose conditions, and miR-214-3p regulated the expression of caspase-1. The aim of this study was to elucidate whether circRNA is involved in DCM pyroptosis via the miR-214-3p/caspase-1 pathway. Herein, we identified that hsa_circ_0076631, named caspase-1-associated circRNA (CACR), was increased both in high-glucose-treated cardiomyocytes and in the serum of diabetic patients. CACR also sponged an endogenous miR-214-3p to sequester and inhibit its expression. CACR knockdown in cardiomyocytes counteracted highglucose-induced caspase-1 activation. Conversely, miR-214-3p knockdown partially abolished the beneficial effects of CACR silencing on pyroptosis in cardiomyocytes. Therefore, this study elucidated that CACR might be a novel therapeutic target via the CACR/miR-214-3p/caspase-1 pathway in DCM.

Melatonin is a hormone produced by the pineal gland, and it has extensive beneficial effects on various tissue and organs; however, whether melatonin has any effect on cardiac fibrosis in the pathogenesis of diabetic cardiomyopathy (DCM) is still unknown. Herein, we found that melatonin administration significantly ameliorated cardiac dysfunction and reduced collagen production by inhibiting TGF‐β1/Smads signaling and NLRP3 inflammasome activation, as manifested by downregulating the expression of TGF‐β1, p‐Smad2, p‐Smad3, NLRP3, ASC, cleaved caspase‐1, mature IL‐1β, and IL‐18 in the heart of melatonin‐treated mice with diabetes mellitus (DM). Similar beneficial effects of melatonin were consistently observed in high glucose (HG)‐treated cardiac fibroblasts (CFs). Moreover, we also found that lncRNA MALAT1 (lncR‐MALAT1) was increased along with concomitant decrease in microRNA‐141 (miR‐141) in DM mice and HG‐treated CFs. Furthermore, we established NLRP3 and TGF‐β1 as target genes of miR‐141 and lncR‐MALAT1 as an endogenous sponge or ceRNA to limit the functional availability of miR‐141. Finally, we observed that knockdown of miR‐141 abrogated anti‐fibrosis action of melatonin in HG‐treated CFs. Our findings indicate that melatonin produces an antifibrotic effect via inhibiting lncR‐MALAT1/miR‐141‐mediated NLRP3 inflammasome activation and TGF‐β1/Smads signaling, and it might be considered a potential agent for the treatment of DCM.

Non-: alcoholic fatty liver disease (NAFLD) is prevalent worldwide, especially in patients with type 2 diabetes. Liver enzymes are the main warning signs of liver injury and insulin resistance (IR) is critical to NAFLD. This study was aimed to investigate the association between liver enzymes and insulin resistance in type 2 diabetes patients with NAFLD. Data from 212 diabetes patients with NAFLD were analyzed, including 118 males and 94 females who received care from 2014 to 2015. The patients were divided into three groups by severity (mild n=87, moderate n=89, severe n=36). All patients underwent standard clinical and laboratory examinations. Liver enzymes including alanine aminotransferase (ALT), aspartate aminotransferase (AST), and γ-glutamyl transferase (GGT) were measured, serum fasting glucose and serum fasting insulin were obtained. IR was assessed using the homeostasis model assessment insulin resistance index (HOMA-IR). Age, sex, and BMI did not significantly differ in patients (p>0.05). Compared with normal levels, elevated ALT and AST were associated with a higher HOMA-IR (p=0.0035, p=0.0096, respectively). HOMA-IR did not significantly differ (p>0.05) between patients with normal and elevated GGT. HOMA-IR increased as the levels of liver enzymes increased, and each enzyme showed a significant association with HOMA-IR (p=0.0166, p<0.0001, and p <0.0001). HOMA-IR differs between normal and elevated ALT and AST. Liver enzymes are associated with HOMA-IR in type 2 diabetes patients with NAFLD. These findings can help evaluate the degree of IR and hepatocellular steatosis in patients and prevent the progression of type 2 diabetes and NAFLD in clinical practice.

Diabetic cardiomyopathy (DCM) is the leading cause of morbidity and mortality in diabetes mellitus (DM) patients. Previous studies have shown that the transforming growth factor-beta 1 (TGF-b1)/Smad signaling pathway plays a key role in the development of myocardial fibrosis in DCM. Silymarin (SMN) is used clinically to treat liver disorders and acts by influencing TGF-b1. However, the possible effects of silymarin on DCM remain to be elucidated. In our study, the DM animal model was induced by streptozotocin (STZ) injection. Fasting blood glucose level was measured, and the structure and function of the heart were measured by hematoxylin and eosin (H&E) and Masson staining, echocardiography, and transmission electron microscopy (TEM). Western blot was used to detect the expression of TGF-b1, Smad2/3, phosphorylation Smad2/3(p-Smad2/ 3), and Smad7. Our results showed that silymarin downregulated blood glucose level and significantly improved cardiac fibrosis and collagen deposition in DM rats detected by H&E, Masson staining, and TEM assays. The echocardiography results showed that silymarin administration attenuated cardiac dysfunction in DM rats. Additionally, compared with untreated DM rats, levels of TGF-b1 and p-Smad2/3 were decreased, whereas Smad7 was increased following silymarin administration. These data demonstrate that silymarin ameliorates DCM through the inhibition of TGF-b1/Smad signaling, suggesting that silymarin may be a potential target for DCM treatment.

Hyperglycemia‐induced cardiac fibrosis is a prominent characteristic of diabetic cardiomyopathy. Changes in proinflammatory cytokines have been shown to lead to cardiac fibrosis in patients with diabetes mellitus. This study aimed to investigate the role of miR‐150‐5p in mediating cardiac inflammation and fibrosis in cardiac fibroblasts (CFs). Herein, we found that high‐glucose (HG) treatment significantly induced cardiac inflammation, as manifested by increased proinflammatory cytokine production (IL‐1β) and NF‐κB activity in CFs. Moreover, HG markedly aggravated cardiac fibrosis and increased levels of fibrotic markers (CTGF, FN, α‐SMA) and extracellular matrix proteins (Col‐I, Col‐III) in CFs. At the same time, HG disturbed the TGF‐β1/Smad signaling pathway, as evidenced by increases in TGF‐β1 and p‐Smad2/3 levels and decreases in Smad7 levels in CFs. Furthermore, we found that miR‐150‐5p was upregulated by HG, which negatively regulated Smad7 expression at the posttranscription level. Further study demonstrated that cardiac inflammation and fibrosis in CFs were corrected following miR‐150‐5p knockdown, but exacerbated by miR‐150‐5p overexpression. These data indicated that miR‐150‐5p inhibition could ameliorate NF‐κB‐related inflammation and TGF‐β1/Smad‐induced cardiac fibrosis through targeting Smad7. Thus, miR‐150‐5p may be a novel promising target for treating diabetic cardiomyopathy.