Compromised endothelial Wnt/ß-catenin signaling mediates the blood-brain barrier disruption and leads to neuroinflammation in endotoxemia.

The blood-brain barrier (BBB) is a critical interface that maintains the central nervous system homeostasis by controlling the exchange of substances between the blood and the brain. Disruption of the BBB plays a vital role in the development of neuroinflammation and neurological dysfunction in sepsis, but the mechanisms by which the BBB becomes disrupted during sepsis are not well understood. Here, we induced endotoxemia, a major type of sepsis, in mice by intraperitoneal injection of lipopolysaccharide (LPS). LPS acutely increased BBB permeability, activated microglia, and heightened inflammatory responses in brain endothelium and parenchyma. Concurrently, LPS or proinflammatory cytokines activated the NF-κB pathway, inhibiting Wnt/ß-catenin signaling in brain endothelial cells in vitro and in vivo. Cell culture study revealed that NF-κB p65 directly interacted with ß-catenin to suppress Wnt/ß-catenin signaling. Pharmacological NF-κB pathway inhibition restored brain endothelial Wnt/ß-catenin signaling activity and mitigated BBB disruption and neuroinflammation in septic mice. Furthermore, genetic or pharmacological activation of brain endothelial Wnt/ß-catenin signaling substantially alleviated LPS-induced BBB leakage and neuroinflammation, while endothelial conditional ablation of the Wnt7a/7b co-receptor Gpr124 exacerbated the BBB leakage caused by LPS. Mechanistically, Wnt/ß-catenin signaling activation rectified the reduced expression levels of tight junction protein ZO-1 and transcytosis suppressor Mfsd2a in brain endothelial cells of mice with endotoxemia, inhibiting both paracellular and transcellular permeability of the BBB. Our findings demonstrate that endotoxemia-associated systemic inflammation decreases endothelial Wnt/ß-catenin signaling through activating NF-κB pathway, resulting in acute BBB disruption and neuroinflammation. Targeting the endothelial Wnt/ß-catenin signaling may offer a promising therapeutic strategy for preserving BBB integrity and treating neurological dysfunction in sepsis.

Serum thrombospondin-2 level changes with liver stiffness improvement in patients with type 2 diabetes.

OBJECTIVE: Baseline circulating thrombospondin-2 (TSP2) level was identified as a potential novel hepatic fibrosis biomarker that associates with development and progression of hepatic fibrosis in patients with nonalcoholic fatty liver disease and type 2 diabetes. Here, we investigated whether circulating TSP2 levels changed with improvement in liver stiffness (LS), which reflects liver fibrosis on transient elastography. DESIGN: Serum TSP2 levels were measured in participants from a randomized, open-label intervention study, at baseline and after 24-weeks treatment of either dapagliflozin 10 mg (N = 30) or sitagliptin 100 mg daily (N = 30). Vibration-controlled transient elastography was performed to evaluate the severity of hepatic fibrosis and steatosis using LS and controlled attenuation parameter (CAP), respectively. PATIENTS AND MEASUREMENTS: Among all 60 participants with similar clinical characteristics at baseline (mean HbA1c 8.9%, CAP 289 dB/m and LS 5.8 kPa), despite similar HbA1c lowering, treatment with dapagliflozin, but not sitagliptin, led to significant improvements in body weight (BW) (p = .012), CAP (p = .015) and LS (p = .011) after 24 weeks. RESULTS: Serum TSP2 level decreased significantly from baseline in dapagliflozin-treated participants (p = .035), whereas no significant change was observed with sitagliptin. In correlation analysis, change in serum TSP2 levels only positively correlated with change in LS (r = .487, p = .006), but not with changes in BW, CAP or HbA1c after dapagliflozin treatment. CONCLUSIONS: Serum TSP2 level decreased with LS after dapagliflozin treatment, and was independent of improvements in BW, glycemic control and hepatic steatosis, further supporting the potential of serum TSP2 level as a novel hepatic fibrosis biomarker in type 2 diabetes.

A-FABP in Metabolic Diseases and the Therapeutic Implications: An Update.

Adipocyte fatty acid-binding protein (A-FABP), which is also known as ap2 or FABP4, is a fatty acid chaperone that has been further defined as a fat-derived hormone. It regulates lipid homeostasis and is a key mediator of inflammation. Circulating levels of A-FABP are closely associated with metabolic syndrome and cardiometabolic diseases with imminent diagnostic and prognostic significance. Numerous animal studies have elucidated the potential underlying mechanisms involving A-FABP in these diseases. Recent studies demonstrated its physiological role in the regulation of adaptive thermogenesis and its pathological roles in ischemic stroke and liver fibrosis. Due to its implication in various diseases, A-FABP has become a promising target for the development of small molecule inhibitors and neutralizing antibodies for disease treatment. This review summarizes the clinical and animal findings of A-FABP in the pathogenesis of cardio-metabolic diseases in recent years. The underlying mechanism and its therapeutic implications are also highlighted.

The Novel Perspectives of Adipokines on Brain Health.

First seen as a fat-storage tissue, the adipose tissue is considered as a critical player in the endocrine system. Precisely, adipose tissue can produce an array of bioactive factors, including cytokines, lipids, and extracellular vesicles, which target various systemic organ systems to regulate metabolism, homeostasis, and immune response. The global effects of adipokines on metabolic events are well defined, but their impacts on brain function and pathology remain poorly defined. Receptors of adipokines are widely expressed in the brain. Mounting evidence has shown that leptin and adiponectin can cross the blood-brain barrier, while evidence for newly identified adipokines is limited. Significantly, adipocyte secretion is liable to nutritional and metabolic states, where defective circuitry, impaired neuroplasticity, and elevated neuroinflammation are symptomatic. Essentially, neurotrophic and anti-inflammatory properties of adipokines underlie their neuroprotective roles in neurodegenerative diseases. Besides, adipocyte-secreted lipids in the bloodstream can act endocrine on the distant organs. In this article, we have reviewed five adipokines (leptin, adiponectin, chemerin, apelin, visfatin) and two lipokines (palmitoleic acid and lysophosphatidic acid) on their roles involving in eating behavior, neurotrophic and neuroprotective factors in the brain. Understanding and regulating these adipokines can lead to novel therapeutic strategies to counteract metabolic associated eating disorders and neurodegenerative diseases, thus promote brain health.

Development of a therapeutic monoclonal antibody against circulating adipocyte fatty acid binding protein to treat ischaemic stroke.

BACKGROUND AND PURPOSE: Adipocyte fatty acid-binding protein (A-FABP) exacerbates cerebral ischaemia injury by disrupting the blood-brain barrier (BBB) through inducing expression of MMP-9. Circulating A-FABP levels positively correlate with infarct size in stroke patients. We hypothesized that targeting circulating A-FABP by a neutralizing antibody would alleviate ischaemic stroke outcome. EXPERIMENTAL APPROACH: Monoclonal antibodies (mAbs) against A-FABP were generated using mouse hybridoma techniques. Binding affinities of a generated mAb named 6H2 towards various FABPs were determined using Biacore. Molecular docking studies were performed to characterize the 6H2-A-FABP complex structure and epitope. The therapeutic potential and safety of 6H2 were evaluated in mice with transient middle cerebral artery occlusion (MCAO) and healthy mice, respectively. KEY RESULTS: Replenishment of recombinant A-FABP exaggerated the stroke outcome in A-FABP-deficient mice. 6H2 exhibited nanomolar to picomolar affinities to human and mouse A-FABP, respectively, with minimal cross-reactivities with heart and epidermal FABPs. 6H2 effectively neutralized JNK/c-Jun activation elicited by A-FABP and reduced MMP-9 production in macrophages. Molecular docking suggested that 6H2 interacts with the "lid" of the fatty acid binding pocket of A-FABP, thus likely hindering the binding of its substrates. In mice with transient MCAO, 6H2 significantly attenuated BBB disruption, cerebral oedema, infarction, neurological deficits, and decreased mortality associated with reduced cytokine and MMP-9 production. Chronic 6H2 treatment showed no obvious adverse effects in healthy mice. CONCLUSION AND IMPLICATIONS: These results establish circulating A-FABP as a viable therapeutic target for ischaemic stroke, and provide a highly promising antibody drug candidate with high affinity and specificity.

Levofloxacin alleviates blood-brain barrier disruption following cerebral ischemia and reperfusion via directly inhibiting A-FABP.

Reperfusion therapy is currently the most effective treatment for acute ischemic stroke, but often results in secondary brain injury. Adipocyte fatty acid-binding protein (A-FABP, FABP4, or aP2) was shown to critically mediate cerebral ischemia/reperfusion (I/R) injury by exacerbating blood-brain barrier (BBB) disruption. However, no A-FABP inhibitors have been approved for clinical use due to safety issues. Here, we identified the therapeutic effect of levofloxacin, a widely used antibiotic displaying A-FABP inhibitory activity in vitro, on cerebral I/R injury and determined its target specificity and action mechanism in vivo. Using molecular docking and site-directed mutagenesis, we showed that levofloxacin inhibited A-FABP activity through interacting with the amino acid residue Asp76, Gln95, Arg126 of A-FABP. Accordingly, levofloxacin significantly inhibited A-FABP-induced JNK phosphorylation and expressions of proinflammatory factors and matrix metalloproteinase 9 (MMP-9) in mouse primary macrophages. In wild-type mice with transient middle cerebral artery occlusion, levofloxacin substantially mitigated BBB disruption and neuroinflammation, leading to reduced cerebral infarction, alleviated neurological outcomes, and improved survival. Mechanistically, levofloxacin decreased MMP-9 expression and activity, and thus reduced degradation of extracellular matrix and endothelial tight junction proteins. Importantly, the BBB- and neuro-protective effects of levofloxacin were abolished in A-FABP or MMP-9 knockout mice, suggesting that the therapeutic effects of levofloxacin highly depended on specific targeting of the A-FABP-MMP-9 axis. Overall, our study demonstrates that levofloxacin alleviates A-FABP-induced BBB disruption and neural tissue injury following cerebral I/R, and unveils its therapeutic potential for the treatment of ischemic stroke.

Illicit drug use is associated with lower bone mineral density and bone strength.

Objectives: To evaluate the association of illicit drug use with bone mineral density (BMD) and hip geometric parameters at the narrow neck. Methods: This is a cross-sectional matched cohort study conducted in the Hong Kong Chinese population. Associations with illicit drug use were estimated using linear regression for BMD (lumbar spine and femoral neck) and hip geometrical parameters (cross-sectional area [CSA], cross-sectional moment of inertia [CSMI], section modulus [SM], average cortical thickness [ACT] and BMD at the narrow neck) after adjusting for age, body mass index (BMI), smoking status, drinking status, physical activity, and history of antipsychotic and antidepressant use. Mean difference and 95% confidence intervals (95% CI) were calculated between 108 illicit drug users and 108 controls using an adjusted linear model and cluster-robust standard errors after matching by age and sex. The false discovery rate was used to correct for multiple testing. Results: Illicit drug users had a significantly lower BMD (g/cm2) at the lumbar spine (mean difference: -0.062; 95% CI: -0.108 to -0.015), and femoral neck (mean difference: -0.058; 95% CI: -0.106 to -0.010) in the fully adjusted model. Illicit drug users also had a significantly lower CSA (mean difference: -0.238 cm2; 95% CI: -0.462 to -0.013), ACT (mean difference: -0.018 cm; 95% CI: -0.030 to -0.006) and BMD (mean difference: -0.070 g/cm2; 95% CI: -0.128 to -0.012) at the narrow neck. Conclusions: Illicit drug use is associated with lower BMD and bone strength. Future studies evaluating the risk of illicit drug use with fragility fracture are warranted.

Growth hormone induces hepatic production of fibroblast growth factor 21 through a mechanism dependent on lipolysis in adipocytes.

Fibroblast growth factor (FGF) 21 and growth hormone (GH) are metabolic hormones that play important roles in regulating glucose and lipid metabolism. Both hormones are induced in response to fasting and exert their actions on adipocytes to regulate lipolysis. However, the molecular interaction between these two hormones remains unclear. Here we demonstrate the existence of a feedback loop between GH and FGF21 on the regulation of lipolysis in adipocytes. A single bolus injection of GH into C57 mice acutely increases both mRNA and protein expression of FGF21 in the liver, thereby leading to a marked elevation of serum FGF21 concentrations. Such a stimulatory effect of GH on hepatic FGF21 production is abrogated by pretreatment of mice with the lipolysis inhibitor niacin. Direct incubation of either liver explants or human HepG2 hepatocytes with GH has no effect on FGF21 expression. On the other hand, FGF21 production in HepG2 cells is significantly induced by incubation with the conditioned medium harvested from GH-treated adipose tissue explants, which contains high concentrations of free fatty acids (FFA). Further analysis shows that FFA released by GH-induced lipolysis stimulates hepatic FGF21 expression by activation of the transcription factor PPARα. In FGF21-null mice, both the magnitude and duration of GH-induced lipolysis are significantly higher than those in their wild type littermates. Taken together, these findings suggest that GH-induced hepatic FGF21 production is mediated by FFA released from adipose tissues, and elevated FGF21 in turn acts as a negative feedback signal to terminate GH-stimulated lipolysis in adipocytes.

Amauroderma rugosum Protects PC12 Cells against 6-OHDA-Induced Neurotoxicity through Antioxidant and Antiapoptotic Effects.

Amauroderma rugosum (AR) is a dietary mushroom in the Ganodermataceae family whose pharmacological activity and medicinal value have rarely been reported. In this study, the antioxidant capacity and neuroprotective effects of AR were investigated. The aqueous extract of AR was confirmed to contain phenolic compounds, polysaccharides, and triterpenes. The results of 2,2-diphenyl-1-picryl-hydrazyl-hydrate (DPPH) and total antioxidant capacity assays revealed that AR extract scavenged reactive oxygen species. Moreover, AR extract decreased the cytotoxicity, oxidative stress, mitochondrial dysfunction, and apoptosis of PC12 cells induced by 6-hydroxydopamine (6-OHDA). In addition, 6-OHDA upregulated the expressions of proapoptotic proteins and downregulated the Akt (protein kinase B)/mTOR- (mammalian target of rapamycin-) and MEK (mitogen-activated protein kinase kinase)/ERK- (extracellular signal-regulated kinases-) dependent signaling pathways. These effects of 6-OHDA were abolished or partially reversed by AR extract. Furthermore, the neuroprotective effects of AR in 6-OHDA-treated PC12 cells were significantly abolished by Akt and MEK inhibitor. Thus, AR extract possesses neuroprotective effects, probably through its antioxidant and antiapoptotic effects. These findings suggest the potential application of AR in the prevention or treatment of oxidative stress-related neurodegenerative diseases such as Parkinson's disease.

The APPL1-Rab5 axis restricts NLRP3 inflammasome activation through early endosomal-dependent mitophagy in macrophages.

Although mitophagy is known to restrict NLRP3 inflammasome activation, the underlying regulatory mechanism remains poorly characterized. Here we describe a type of early endosome-dependent mitophagy that limits NLRP3 inflammasome activation. Deletion of the endosomal adaptor protein APPL1 impairs mitophagy, leading to accumulation of damaged mitochondria producing reactive oxygen species (ROS) and oxidized cytosolic mitochondrial DNA, which in turn trigger NLRP3 inflammasome overactivation in macrophages. NLRP3 agonist causes APPL1 to translocate from early endosomes to mitochondria, where it interacts with Rab5 to facilitate endosomal-mediated mitophagy. Mice deficient for APPL1 specifically in hematopoietic cell are more sensitive to endotoxin-induced sepsis, obesity-induced inflammation and glucose dysregulation. These are associated with increased expression of systemic interleukin-1ß, a major product of NLRP3 inflammasome activation. Our findings indicate that the early endosomal machinery is essential to repress NLRP3 inflammasome hyperactivation by promoting mitophagy in macrophages.

Adipocyte-secreted exosomal microRNA-34a inhibits M2 macrophage polarization to promote obesity-induced adipose inflammation.

Persistent, unresolved inflammation in adipose tissue is a major contributor to obesity-associated metabolic complications. However, the molecular links between lipid-overloaded adipocytes and inflammatory immune cells in obese adipose tissues remain elusive. Here we identified adipocyte-secreted microRNA-34a (miR-34a) as a key mediator through its paracrine actions on adipose-resident macrophages. The expression of miR-34a in adipose tissues was progressively increased with the development of dietary obesity. Adipose-selective or adipocyte-specific miR-34a-KO mice were resistant to obesity-induced glucose intolerance, insulin resistance, and systemic inflammation, and this was accompanied by a significant shift in polarization of adipose-resident macrophages from proinflammatory M1 to antiinflammatory M2 phenotype. Mechanistically, mature adipocyte-secreted exosomes transported miR-34a into macrophages, thereby suppressing M2 polarization by repressing the expression of Krüppel-like factor 4 (Klf4). The suppressive effects of miR-34a on M2 polarization and its stimulation of inflammatory responses were reversed by ectopic expression of Klf4 in both bone marrow-derived macrophages and adipose depots of obese mice. Furthermore, increased miR-34a expression in visceral fat of overweight/obese subjects correlated negatively with reduced Klf4 expression, but positively with the parameters of insulin resistance and metabolic inflammation. In summary, miR-34a was a key component of adipocyte-secreted exosomal vesicles that transmitted the signal of nutrient overload to the adipose-resident macrophages for exacerbation of obesity-induced systemic inflammation and metabolic dysregulation.

Chronic adiponectin deficiency leads to Alzheimer's disease-like cognitive impairments and pathologies through AMPK inactivation and cerebral insulin resistance in aged mice.

BACKGROUND: Insulin resistance is the major pathogenesis underlying type 2 diabetes mellitus (T2DM) and these patients have doubled risk of Alzheimer's disease (AD). Increasing evidence suggests that insulin resistance plays an important role in AD pathogenesis, possibly due to abnormal GSK3ß activation, causing intra- and extracellular amyloid-beta (Aß) accumulation. Adiponectin (APN) is an adipokine with insulin-sensitizing and anti-inflammatory effects. Reduced circulatory APN level is associated with insulin resistance and T2DM. The role of APN in AD has not been elucidated. In this study, we aim to examine if adiponectin deficiency would lead to cerebral insulin resistance, cognitive decline and Alzheimer's-like pathology in mice. METHODS: To study the role of adiponectin in cognitive functions, we employed adiponectin-knockout (APN-KO) mice and demonstrated chronic APN deficiency in their CNS. Behavioral tests were performed to study the cognitions of male APN-KO mice. Brains and tissue lysates were collected to study the pathophysiological and molecular changes in the brain of APN-KO mice. SH-SY5Y neuroblastoma cell line was used to study the molecular mechanism upon APN and insulin treatment. RESULTS: Aged APN-deficient mice displayed spatial memory and learning impairments, fear-conditioned memory deficit as well as anxiety. These mice also developed AD pathologies including increased cerebral Aß42 level, Aß deposition, hyperphosphorylated Tau proteins, microgliosis and astrogliosis with increased cerebral IL-1ß and TNFα levels that associated with increased neuronal apoptosis and reduced synaptic proteins levels, suggesting APN deficiency may lead to neuronal and synaptic loss in the brain. AD pathologies-associated APN-KO mice displayed attenuated AMPK phosphorylation and impaired insulin signaling including decreased Akt induction and increased GSK3ß activation in the hippocampus and frontal cortex. Aged APN-KO mice developed hippocampal insulin resistance with reduced pAkt induction upon intracerebral insulin injection. Consistently, APN treatment in SH-SY5Y cells with insulin resistance and overexpressing Aß induce higher pAkt levels through AdipoR1 upon insulin treatment whereas the induction was blocked by compound C, indicating APN can enhance neuronal insulin sensitivity through AMPK activation. CONCLUSION: Our results indicated that chronic APN deficiency inactivated AMPK causing insulin desensitization and elicited AD-like pathogenesis in aged mice which also developed significant cognitive impairments and psychiatric symptoms.