Dysregulation of endoplasmic reticulum (ER) Ca2؉ homeostasis triggers ER stress leading to the development of insulin resistance in obesity and diabetes. Impaired function of the sarco/endoplasmic reticulum Ca 2؉ -ATPase (SERCA) has emerged as a major contributor to ER stress. We pharmacologically activated SERCA2b in a genetic model of insulin resistance and type 2 diabetes (ob/ob mice) with a novel allosteric activator, CDN1163, which markedly lowered fasting blood glucose, improved glucose tolerance, and ameliorated hepatosteatosis but did not alter glucose levels or body weight in lean controls. Importantly, CDN1163-treated ob/ob mice maintained euglycemia comparable with that of lean mice for >6 weeks after cessation of CDN1163 administration. CDN1163-treated ob/ob mice showed a significant reduction in adipose tissue weight with no change in lean mass, assessed by magnetic resonance imaging. They also showed an increase in energy expenditure using indirect calorimetry, which was accompanied by increased expression of uncoupling protein 1 (UCP1) and UCP3 in brown adipose tissue. CDN1163 treatment significantly reduced the hepatic expression of genes involved in gluconeogenesis and lipogenesis, attenuated ER stress response and ER stress-induced apoptosis, and improved mitochondrial biogenesis, possibly through SERCA2-mediated activation of AMP-activated protein kinase pathway. The findings suggest that SERCA2b activation may hold promise as an effective therapy for type-2 diabetes and metabolic dysfunction.Obesity and insulin resistance are major causes of type 2 diabetes (T2D), 2 which represents an enormous health burden to societies worldwide. T2D is now one of the most prevalent diseases globally and is the fourth leading cause of death in many developed countries (1). Endoplasmic reticulum stress (ER stress) has emerged as an important cause of the metabolic syndrome and T2D. ER stress and the unfolded protein response have now been described in organs playing key roles in metabolic homeostasis such as liver, pancreatic ␤-cells, adipose tissue, and hypothalamus in both obese and/or diabetic humans and rodents (2-5) and have recently emerged as key pathophysiological pathways triggering insulin resistance and T2D (4). Amelioration of ER stress through chemical chaperones has been demonstrated to be a promising pharmacological strategy for treatment of T2D (6 -10). The ER is the main storage site of intracellular Ca 2ϩ , and alterations in Ca 2ϩ homeostasis have been demonstrated to trigger ER stress and activation of the unfolded protein response (11, 12). The sarco/endoplasmic reticulum Ca 2ϩ -ATPase (SERCA) pumps Ca 2ϩ from the cytoplasm into the ER. Recent studies demonstrate that SERCA dysfunction leads to elevation of cytoplasmic calcium and triggers ER stress. SERCA2 activity and expression is diminished in islets (13), liver (2, 14), and heart (15) in animal models of obesity/ diabetes, highlighting a potential pathological role for SERCA2 dysfunction and disturbed ER Ca 2ϩ homeostasis in the dev...

BackgroundMicroRNAs (miRNAs) play a key role in the development of heart failure, and recent studies have shown that the muscle‐specific miR‐1 is a key regulator of cardiac hypertrophy. We tested the hypothesis that chronic restoration of miR‐1 gene expression in vivo will regress hypertrophy and protect against adverse cardiac remodeling induced by pressure overload.Methods and ResultsCardiac hypertrophy was induced by left ventricular pressure overload in male Sprague‐Dawley rats subjected to ascending aortic stenosis. When the hypertrophy was established at 2 weeks after surgery, the animals were randomized to receive either an adeno‐associated virus expressing miR‐1 (AAV9.miR‐1) or green fluorescent protein (GFP) as control (AAV9.GFP) via a single‐bolus tail‐vein injection. Administration of miR‐1 regressed cardiac hypertrophy (left ventricular posterior wall thickness,; 2.32±0.08 versus 2.75±0.07 mm, P<0.001) and (left ventricular septum wall thickness, 2.23±0.06 versus 2.54±0.10 mm, P<0.05) and halted the disease progression compared with control‐treated animals, as assessed by echocardiography (fractional shortening, 37.60±5.01% versus 70.68±2.93%, P<0.05) and hemodynamic analyses (end‐systolic pressure volume relationship/effective arterial elastance, 1.87±0.46 versus 0.96±0.38, P<0.05) after 7 weeks of treatment. Additionally, miR‐1 replacement therapy lead to a marked reduction of myocardial fibrosis, an improvement in calcium handling, inhibition of apoptosis, and inactivation of the mitogen‐activated protein kinase signaling pathways, suggesting a favorable effect on preventing the maladaptive ventricular remodeling. We also identified and validated a novel bona fide target of miR‐1, Fibullin‐2 (Fbln2), a secreted protein implicated in extracellular matrix remodeling.ConclusionsTaken together, our findings suggest that restoration of miR‐1 gene expression is a potential novel therapeutic strategy to reverse pressure‐induced cardiac hypertrophy and prevent maladaptive cardiac remodeling.

Resistin has been suggested to be involved in the development of diabetes and insulin resistance. We recently reported that resistin is expressed in diabetic hearts and promotes cardiac hypertrophy; however, the mechanisms underlying this process are currently unknown. Therefore, we wanted to elucidate the mechanisms associated with resistin-induced cardiac hypertrophy and myocardial insulin resistance. Overexpression of resistin using adenoviral vector in neonatal rat ventricular myocytes was associated with inhibition of AMP-activated protein kinase (AMPK) activity, activation of tuberous sclerosis complex 2/mammalian target of rapamycin (mTOR) pathway, and increased cell size, S6K , a downstream kinase target of mTOR, and increased phosphorylation of the IRS1 serine 636/639 residues, whereas treatment with rapamycin reduced the phosphorylation of these residues. Interestingly, these in vitro signaling pathways were also operative in vivo in ventricular tissues from adult rat hearts overexpressing resistin. These data demonstrate that resistin induces cardiac hypertrophy and myocardial insulin resistance, possibly via the AMPK/mTOR/p70 S6K and apoptosis signal-regulating kinase 1/JNK/IRS1 pathways.

Recent studies have demonstrated that TNF-related apoptosis-inducing ligand (TRAIL) is a modulator of the immune response. The relation between TRAIL and type 1 diabetes (T1D) as an autoimmune inflammatory disease in vivo is relatively unknown. To explore the potential role of TRAIL in the development of T1D, we examined its in vivo effects in nonobese diabetic (NOD) mice. NOD mice at 7 wk of age were iv injected with an adenovirus carrying either human TRAIL (Ad.hTRAIL) or β-galactosidase genes. Blood glucose was monitored weekly, and the expression of hTRAIL was evaluated in plasma and liver of mice. To investigate whether hTRAIL elicits its effect through the induction of tissue inhibitor of metalloproteinase-1 (TIMP-1), we examined the concentration of plasma TIMP-1 by ELISA and the inhibition of matrix metalloproteinase (MMP) by gelatin zymography. Here, we show that Ad.hTRAIL-transduced mice had significantly reduced blood glucose levels and markedly increased production of TIMP-1 compared with control β-galactosidase animals. Pancreatic tissue isolated from Ad.hTRAIL-treated NOD mice showed reduced MMP activities associated with significantly improved insulitis. In addition, TIMP-1 in vitro suppressed cytokine-induced apoptosis in insulin-producing INS-1 cells. These results indicate that T1D can be prevented by TRAIL overexpression through enhancement of TIMP-1 function. Elevated TIMP-1 production inhibits the activity of MMPs, which may contribute to suppress the transmigration of diabetogenic T cells into the pancreatic islets and protects pancreatic β-cells from cytokine-induced apoptosis. Therefore, TRAIL and TIMP-1 induction may be potential targets to prevent development of T1D.