Currently, major concerns about the safety and efficacy of RNA interference (RNAi)-based bone anabolic strategies still exist because of the lack of direct osteoblast-specific delivery systems for osteogenic siRNAs. Here we screened the aptamer CH6 by cell-SELEX, specifically targeting both rat and human osteoblasts, and then we developed CH6 aptamer–functionalized lipid nanoparticles (LNPs) encapsulating osteogenic pleckstrin homology domain-containing family O member 1 (Plekho1) siRNA (CH6-LNPs-siRNA). Our results showed that CH6 facilitated in vitro osteoblast-selective uptake of Plekho1 siRNA, mainly via macropinocytosis, and boosted in vivo osteoblast-specific Plekho1 gene silencing, which promoted bone formation, improved bone microarchitecture, increased bone mass and enhanced mechanical properties in both osteopenic and healthy rodents. These results indicate that osteoblast-specific aptamer-functionalized LNPs could act as a new RNAi-based bone anabolic strategy, advancing the targeted delivery selectivity of osteogenic siRNAs from the tissue level to the cellular level.
Excessive consumption of diets high in sugars and saturated fat, frequently known as western diet (WD), may lead to obesity and metabolic syndrome. Recent evidence shows that WD-induced obesity impairs cardiac function, but the underlying mechanisms are not fully understood. Trimethylamine N-oxide (TMAO), a gut microbiota-dependent metabolite of specific dietary nutrients, has emerged as a key contributor to cardiovascular disease pathogenesis. We tested the hypothesis that elevated circulating TMAO levels contribute to cardiac dysfunction in WD-induced obesity. CD1 mice were fed a normal diet (ND) or a WD, without or with 1.0% 3,3-Dimethyl-1-butanol (DMB, an inhibitor of trimethylamine formation) in drinking water for 8 weeks. Compared with mice fed a ND, mice fed a WD showed a significant increase in body weight and dyslipidemia, and had markedly higher plasma TMAO levels at the end of the feeding protocol. Echocardiography revealed that cardiac systolic and diastolic function was impaired in mice fed a WD. DMB treatment had no effects on body weight and dyslipidemia, but significantly reduced plasma TMAO levels and prevented cardiac dysfunction in mice fed a WD. In addition, mice fed a WD had elevated expression of pro-inflammatory cytokines tumor necrosis factor-α and interleukin IL-1β, decreased expression of anti-inflammatory cytokine IL-10, and increased interstitial fibrosis in the hearts, all of which were prevented by DMB treatment. Notably, DMB treatment also reduced plasma TMAO levels in mice fed a ND but did not alter other parameters. These results suggest that consumption of a WD increases circulating TMAO levels, which lead to cardiac inflammation and fibrosis, contributing to cardiac dysfunction. Interventions that reduce circulating TMAO levels may be a novel therapeutic strategy for prevention and treatment of WD-induced cardiac dysfunction.
It has been shown that inhibition of de novo sphingolipid synthesis increases insulin sensitivity. For further exploration of the mechanism involved, we utilized two models: heterozygous serine palmitoyltransferase (SPT) subunit 2 (Sptlc2) gene knockout mice and sphingomyelin synthase 2 (Sms2) gene knockout mice. SPT is the key enzyme in sphingolipid biosynthesis, and Sptlc2 is one of its subunits. Homozygous Sptlc2-deficient mice are embryonic lethal. However, heterozygous Sptlc2-deficient mice that were viable and without major developmental defects demonstrated decreased ceramide and sphingomyelin levels in the cell plasma membranes, as well as heightened sensitivity to insulin. Moreover, these mutant mice were protected from high-fat diet-induced obesity and insulin resistance. SMS is the last enzyme for sphingomyelin biosynthesis, and SMS2 is one of its isoforms. Sms2 deficiency increased cell membrane ceramide but decreased SM levels. Sms2 deficiency also increased insulin sensitivity and ameliorated high-fat diet-induced obesity. We have concluded that Sptlc2 heterozygous deficiency-or Sms2 deficiency-mediated reduction of SM in the plasma membranes leads to an improvement in tissue and whole-body insulin sensitivity.Metabolic syndrome is a collection of abnormalities in metabolism, including obesity, nonalcoholic fatty liver disease, macrophage inflammation, impaired fasting glucose clearance, dyslipidemia, and hypertension. Insulin resistance appears to be a key feature in metabolic syndrome (47). The de novo sphingolipid synthesis pathway is considered a promising target for pharmacological intervention in insulin resistance. It has been shown that inhibition of serine palmitoyltransferase (SPT; the first enzyme for sphingolipid biosynthesis) increases insulin sensitivity (17). However, the mechanism is incompletely understood, since such an inhibition decreases many bioactive sphingolipids, including sphingomyelin (44), ceramide, and glycosphingolipids. Ceramide levels appear to be important in mediating inflammation, obesity, and insulin sensitivity (4, 17, 18). Sphingomyelin (SM) levels also appear to be important in mediating inflammation and atherosclerosis (11,27,34). However, few in vivo studies have been conducted to investigate the functions of these two metabolism-related sphingolipids separately, since animal models are lacking.The biochemical synthesis of SM occurs through the actions of SPT, 3-ketosphinganine reductase, ceramide synthase, dihydroceramide desaturase, and sphingomyelin synthase (SMS) (36). Mammalian SPT contains two subunits, Sptlc1 and Sptlc2, encoding 53-and 63-kDa proteins, respectively (13, 64). These subunits are homologous, sharing roughly 20% sequence identity (13, 64), and form a heterodimer. A third subunit, Sptlc3, has also been reported (19), but its function remains to be elucidated. Recently, the discovery of two proteins, ssSPTa and ssSPTb, was reported. Each substantially enhances the activity of mammalian SPT, expressed in either yeast or mammalian cells, and...
Autophagy dysfunction is a common feature in neurodegenerative disorders characterized by accumulation of toxic protein aggregates. Increasing evidence has demonstrated that activation of TFEB (transcription factor EB), a master regulator of autophagy and lysosomal biogenesis, can ameliorate neurotoxicity and rescue neurodegeneration in animal models. Currently known TFEB activators are mainly inhibitors of MTOR (mechanistic target of rapamycin [serine/threonine kinase]), which, as a master regulator of cell growth and metabolism, is involved in a wide range of biological functions. Thus, the identification of TFEB modulators acting without inhibiting the MTOR pathway would be preferred and probably less deleterious to cells. In this study, a synthesized curcumin derivative termed C1 is identified as a novel MTOR-independent activator of TFEB. Compound C1 specifically binds to TFEB at the N terminus and promotes TFEB nuclear translocation without inhibiting MTOR activity. By activating TFEB, C1 enhances autophagy and lysosome biogenesis in vitro and in vivo. Collectively, compound C1 is an orally effective activator of TFEB and is a potential therapeutic agent for the treatment of neurodegenerative diseases.
BACKGROUND Remote ischemic preconditioning (RIPC) can inhibit recurrent ischemic events effectively in patients with acute or chronic cerebral ischemia. However, it is still unclear whether RIPC can impede ischemic injury after carotid artery stenting (CAS) in patients with severe carotid artery stenosis. METHODS Subjects with severe carotid artery stenosis were recruited in this randomized controlled study, and assigned to RIPC, sham, and no intervention (control) groups. All subjects received standard medical therapy. Subjects in the RIPC and sham groups underwent RIPC and sham RIPC twice daily, respectively, for 2 weeks before CAS. Plasma neuron-specific enolase and S-100B were used to evaluate safety, hypersensitive C-reactive protein, and new ischemic diffusion-weighted imaging lesions were used to determine treatment efficacy. The primary outcomes were the presence of ≥1 newly ischemic brain lesions on diffusion-weighted imaging within 48 hours after stenting and clinical events within 6 months after stenting. RESULTS We randomly assigned 189 subjects in this study (63 subjects in each group). Both RIPC and sham RIPC procedures were well tolerated and completed with high compliance (98.41% and 95.24%, respectively). Neither plasma neuron-specific enolase levels nor S-100B levels changed significantly before and after treatment. No severe adverse event was attributed to RIPC and sham RIPC procedures. The incidence of new diffusion-weighted imaging lesions in the RIPC group (15.87%) was significantly lower than in the sham group (36.51%; relative risk, 0.44; 96% confidence interval, 0.20–0.91; P<0.01) and the control group (41.27%; relative risk, 0.39; 96% confidence interval, 0.21–0.82; P<0.01). The volumes of lesions were smaller in the RIPC group than in the control and sham groups (P<0.01 each). Ischemic events that occurred after CAS were 1 transient ischemic attack in the RIPC group, 2 strokes in the control group, and 2 strokes and 1 transient ischemic attack in the sham group, but these results were not significantly different among the 3 groups (P=0.597). CONCLUSIONS RIPC is safe in patients undergoing CAS, which may be able to decrease ischemic brain injury secondary to CAS. However, the mechanisms and effects of RIPC on clinical outcomes in this cohort of patients need further investigation. CLINICAL TRIAL REGISTRATION URL: http://www.clinicaltrials.gov. Unique identifier: NCT01654666
Support for data collection and analysis was provided by grants from the National Science Foundation of China. None of the authors has anything to disclose.
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