Expression Of Insulin-degrading Enzyme Research Articles

Metformin attenuates vascular pathology by increasing expression of insulin-degrading enzyme in a mixed model of cerebral amyloid angiopathy and type 2 diabetes mellitus

Sporadic cerebral amyloid angiopathy (CAA), which is characterized by cerebrovascular amyloid β (Aβ) deposits, causes cerebral hemorrhages and dementia in elderly people. Metformin has been used to treat patients with type 2 diabetes mellitus (T2DM), and animal and clinical studies have reported therapeutic effects of metformin in Alzheimer’s disease (AD). However, the therapeutic effects of metformin in CAA are unclear. Here, we used a mixed mouse model of CAA and T2DM (APP23-ob/ob) to investigate whether metformin has therapeutic effects on cerebrovascular Aβ deposits. We dissolved metformin hydrochloride in water and administered it orally at 350 mg/kg/day. Treatments started when mice were 6 weeks old and continued until they were 15 months old. After we treated APP23-ob/ob mice with metformin, we counted the numbers of vessels with Aβ and measured levels of Aβ40 and Aβ42 (soluble and insoluble), amyloid precursor protein (APP), APP-processing enzymes (α-, β-, and γ-secretases), and Aβ-degrading enzymes (insulin-degrading enzyme [IDE], neprilysin). Metformin significantly reduced cerebrovascular Aβ deposits in APP23-ob/ob mice (p < .05). Compared with controls, metformin-treated APP23-ob/ob mice had significantly reduced Aβ levels in the cerebral cortex (p < .05) and hippocampus (p < .05) and increased levels of IDE in the hippocampus (p < .01). Our results indicate that metformin attenuates the severity of CAA by enhancing Aβ-cleaving IDE expression. The clinical application of metformin may lead to a novel therapeutic strategy in CAA treatment, especially in patients with T2DM.

Influence of Liver Cirrhosis on Blood Glucose, Insulin Sensitivity and Islet Function in Mice

BackgroundThe relationship between cirrhosis and diabetes is controversial. We studied the influence of cirrhosis on glucose levels and islet function and explored its possible mechanisms. Materials and MethodsCirrhosis was induced in male C57BL/6 mice by bile duct ligation (BDL). Serum biochemical parameters were determined, and oral glucose tolerance tests (OGTT) were performed at 4 and 8 weeks after BDL. Histopathology and phospho-NF-κB-p65/I-kappa B α immunohistochemical staining of the liver and islet were observed. The protein levels of the insulin signaling system and the gene expression of insulin-degrading enzyme (IDE) in the liver and muscle were determined. The activity of glucokinase (GCK) and glucose 6-phosphatase (G6P) and glycogen levels in liver homogenates were measured. ResultsAfter BDL, the mice developed cirrhosis, and fasting glucose decreased significantly, but 2 h postprandial glucose increased, and the insulin areas under the curves increased. At 4 weeks of BDL, the ratios of phospho-NF-κB-p65/I-kappa B α accumulation in the liver and islet increased, the activity of G6P and the glycogen content in liver homogenates decreased, the insulin signaling system and the gene expression of IDE in the liver was downregulated, and the islet areas were decreased. After 8 weeks, these changes were more severe. ConclusionsIn different periods of cirrhosis, the levels of fasting glucose and 2 h postprandial glucose changed in different amplitudes. Glycogen concentrations and the activity of G6P in the liver were decreased. The mice developed insulin resistance and the islet areas were decreased. The NF-κB pathway may play a role in the process.

Dietary Curcumin Systemically Maintains Insulin Homeostasis in Diet-Induced Aged Obese Mice via Liver-Pancreas-Brain Axis

Abstract Objectives Aging is a condition in which we gradually lose the ability to maintain homeostasis due to dysfunction. There continues to be a knowledge gap in implicating how dietary intervention affects the mechanisms delaying or preventing aging-related chronic diseases. Although curcumin (CUR), a natural antioxidant, shows the putative therapeutic properties such as reinstating insulin homeostasis in obese mice, an aging-associated mechanism in which CUR regulates insulin levels largely remains unclear. Thus, the objective of this study is to determine effects of CUR on anti-aging under obese condition mediated by maintaining insulin homeostasis via cross-talk among liver, pancreas and brain. Methods We examine how dietary CUR improves insulin clearance and maintains a proper range of circulating insulin level in the aged diet-induced obesity (DIO) mouse model. Old male C57BL/6J mice were fed a normal chow diet (NCD) or a NCD containing 0.4% (w/w) curcumin (NCD + CUR), a high fat/high sugar diet (HFHSD) or a HFHSD + CUR (N = 7–9 per group) for 16 weeks. Results Old male C57BL/6J mice were fed a normal chow diet (NCD) or a NCD containing 0.4% (w/w) curcumin (NCD + CUR), a high fat/high sugar diet (HFHSD) or a HFHSD + CUR (N = 7–9 per group) for 16 weeks. Mice given HFHSD + CUR had reduced body weight gain (4.7 ± 1.8 vs 7.8 ± 1.6g) and had lower blood insulin levels (2.24 ± 0.3 vs. 1.53 ± 0.3 ng/ml) under fasting conditions compared to mice on HFHSD alone, resulting from significantly improved insulin clearance via upregulation of hepatic insulin-degrading enzyme (IDE) and circulating IDE levels in serum. On the other hand, the expression of IDE gene in hypothalamus was significantly lower in HFHSD + CUR mice (1.3 folds) than HFHSD animals. Obesity induces hyperglycemic condition in brain by higher IDE expression to excessively break down insulin. We also observed significantly smaller islets of Langerhans (4.53 ± 0.72 vs 7.90 ± 0.34 a.u.) in HFSD + CUR fed mice and increased glucagon contents compared to HFS fed mice, indicating less secretion of insulin in pancreas under obese condition. Conclusions The conclusion of this study is that curcumin is a potent, natural therapeutic agent that can systemically regulate insulin levels in a multifaceted manner to protect against insulin resistance in aged mice. Funding Sources Intramural Research Program of NIAThe OTTOGI HAM TAIHO Foundation

Pharmacological ablation of astrocytes reduces A\u03b2 degradation and synaptic connectivity in an ex vivo model of Alzheimer\u2019s disease

BackgroundAstrocytes provide a vital support to neurons in normal and pathological conditions. In Alzheimer’s disease (AD) brains, reactive astrocytes have been found surrounding amyloid plaques, forming an astrocytic scar. However, their role and potential mechanisms whereby they affect neuroinflammation, amyloid pathology, and synaptic density in AD remain unclear.MethodsTo explore the role of astrocytes on Aβ pathology and neuroinflammatory markers, we pharmacologically ablated them in organotypic brain culture slices (OBCSs) from 5XFAD mouse model of AD and wild-type (WT) littermates with the selective astrocytic toxin L-alpha-aminoadipate (L-AAA). To examine the effects on synaptic circuitry, we measured dendritic spine number and size in OBCSs from Thy-1-GFP transgenic mice incubated with synthetic Aβ42 or double transgenics Thy-1-GFP/5XFAD mice treated with LAAA or vehicle for 24 h.ResultsTreatment of OBCSs with L-AAA resulted in an increased expression of pro-inflammatory cytokine IL-6 in conditioned media of WTs and 5XFAD slices, associated with changes in microglia morphology but not in density. The profile of inflammatory markers following astrocytic loss was different in WT and transgenic cultures, showing reductions in inflammatory mediators produced in astrocytes only in WT sections. In addition, pharmacological ablation of astrocytes led to an increase in Aβ levels in homogenates of OBCS from 5XFAD mice compared with vehicle controls, with reduced enzymatic degradation of Aβ due to lower neprilysin and insulin-degrading enzyme (IDE) expression. Furthermore, OBSCs from wild-type mice treated with L-AAA and synthetic amyloid presented 56% higher levels of Aβ in culture media compared to sections treated with Aβ alone, concomitant with reduced expression of IDE in culture medium, suggesting that astrocytes contribute to Aβ clearance and degradation. Quantification of hippocampal dendritic spines revealed a reduction in their density following L-AAA treatment in all groups analyzed. In addition, pharmacological ablation of astrocytes resulted in a decrease in spine size in 5XFAD OBCSs but not in OBCSs from WT treated with synthetic Aβ compared to vehicle control.ConclusionsAstrocytes play a protective role in AD by aiding Aβ clearance and supporting synaptic plasticity.

Regulatory feedback cycle of the insulin-degrading enzyme and the amyloid precursor protein intracellular domain: Implications for Alzheimer's disease.

One of the major pathological hallmarks of Alzheimer´s disease (AD) is an accumulation of amyloid‐β (Aβ) in brain tissue leading to formation of toxic oligomers and senile plaques. Under physiological conditions, a tightly balanced equilibrium between Aβ‐production and ‐degradation is necessary to prevent pathological Aβ‐accumulation. Here, we investigate the molecular mechanism how insulin‐degrading enzyme (IDE), one of the major Aβ‐degrading enzymes, is regulated and how amyloid precursor protein (APP) processing and Aβ‐degradation is linked in a regulatory cycle to achieve this balance. In absence of Aβ‐production caused by APP or Presenilin deficiency, IDE‐mediated Aβ‐degradation was decreased, accompanied by a decreased IDE activity, protein level, and expression. Similar results were obtained in cells only expressing a truncated APP, lacking the APP intracellular domain (AICD) suggesting that AICD promotes IDE expression. In return, APP overexpression mediated an increased IDE expression, comparable results were obtained with cells overexpressing C50, a truncated APP representing AICD. Beside these genetic approaches, also AICD peptide incubation and pharmacological inhibition of the γ‐secretase preventing AICD production regulated IDE expression and promoter activity. By utilizing CRISPR/Cas9 APP and Presenilin knockout SH‐SY5Y cells results were confirmed in a second cell line in addition to mouse embryonic fibroblasts. In vivo, IDE expression was decreased in mouse brains devoid of APP or AICD, which was in line with a significant correlation of APP expression level and IDE expression in human postmortem AD brains. Our results show a tight link between Aβ‐production and Aβ‐degradation forming a regulatory cycle in which AICD promotes Aβ‐degradation via IDE and IDE itself limits its own production by degrading AICD.

Insulin degrading enzyme (IDE) expressed by Chinese hamster ovary (CHO) cells is responsible for degradation of insulin in culture media

Chinese hamster ovary (CHO) cells cultured in serum-free chemically-defined media (CDM) are used for manufacturing of therapeutic proteins. Growth factors, such as insulin are commonly utilized in manufacturing platforms to enhance CHO cell viability and growth. Here we report that insulin is degraded in the culture media over time mainly due to the activity of the insulin degrading enzyme (IDE). Insulin degradation was faster in cell lines that released more IDE, which negatively impacted cell growth and in turn, production titers. Deletion of the IDE gene in a representative CHO cell line nearly abolished insulin degradation in seed train and end-of-production media. In summary, our data suggests that selecting cell lines that have lower IDE expression or targeted-deletion of the IDE gene can improve culture viability and growth for insulin-dependent CHO production platforms.

Perindopril ameliorates experimental Alzheimer's disease progression: role of amyloid β degradation, central estrogen receptor and hyperlipidemic-lipid raft signaling.

Accumulating evidence indicates that over-stimulation of angiotensin-converting enzyme 1 (ACE1) activity is associated with β-amyloid (Aβ) and phosphorylated tau (p-tau)-induced apoptosis, oxido-nitrosative neuroinflammatory stress and neurodegeneration in Alzheimer's disease (AD). Alternatively, activation of the ACE2, the metalloprotease neprilysin (Neutral Endopeptidase; NEP) and the insulin-degrading enzyme (IDE) could oppose the effects of ACE1 activation. We aim to investigate the relationship between ACE1/ACE2/NEP/IDE and amyloidogenic/hyperlipidemic-lipid raft signaling in hyperlipidemic AD model. Induction of AD was performed in ovariectomized female rats with high-fat high fructose diet (HFFD) feeding after 4weeks following D-galactose injection (150mg/kg). The brain-penetrating ACE1 inhibitor perindopril (0.5mg/kg/day, p.o.) was administered on a daily basis for 30days. Perindopril significantly decreased hippocampal expression of ACE1 and increased expression of ACE2, NEP and IDE. Perindopril markedly decreased Aβ1-42, improved lipid profile and ameliorated the lipid raft protein markers caveolin1 (CAV1) and flotillin 1 (FLOT1). This was accompanied by decreased expression of p-tau and enhancement of cholinergic neurotransmission, coupled with decreased oxido-nitrosative neuroinflammatory stress, enhancement of blood-brain barrier (BBB) functioning and lower expression of the apoptotic markers glial fibrillary acidic protein (GFAP), Bax and β-tubulin. In addition, perindopril ameliorated histopathological damage and improved learning, cognitive and recognition impairment as well as depressive behavior in Morris water maze, Y maze, novel object recognition and forced swimming tests, respectively. Conclusively, perindopril could improve cognitive defects in AD rats, at least through activation of ACE2/NEP/IDE and inhibition of ACE1 and subsequent modulation of amyloidogenic/hyperlipidemic-lipid raft signaling and oxido-nitrosative stress.

2091-P: Effects of Caveolin-1 on the Synthesis and Decomposition of Islet ß-Cell IAPP and Its Mechanism

Objective: Islet amyloid polypeptide(IAPP) is a major component of islet amyloid deposition in type 2 diabetic patients. Our preliminary study showed that membrane protein Caveolin-1 (Cav1) silencing inhibited β-cell apoptosis and promote insulin secretion. The purpose of this study was to investigate the regulation of Cav1 on islet β-cell IAPP and its mechanism. Materials and Methods: Firstly, IAPP secretion of each group of primary islets was detected by ELISA, then Western blot and real-time quantitative PCR (qPCR) were used to detect the expression levels of IAPP, PAM(Peptidyl-glycine alpha-amidating monooxygenase), PC1(Prohormone Convertase-1), BACE2(Beta-secretase 2), IDE(Insulin-Degrading Enzyme), TXNIP(Thioredoxin interacting protein), and finally, it confirmed that Cav1 interacted with the protein of TXNIP by immunofluorescence confocal and co-immunoprecipitation (Co-IP). Results: The secretion of IAPP was decreased in primary pancreatic islets and Cav1 deficiency significantly down-regulated the expression of IAPP in NIT-1 cells, while over-expression of Cav1 in βTC-6 cells significantly up-regulated the expression of IAPP. This effect correlated with Cav1 silencing leading to down-regulation of PAM expression associated with IAPP synthesis and over-expression of Cav1 leading to up-regulation of PC1 associated with IAPP synthesis. On the other hand,Cav1 deficiency resulted in the up-regulation of the expression of BACE2 and IDE, the enzymes associated with IAPP decomposition. While over-expression of Cav1 leaded to down-regulation of BACE2 and IDE. Further studies indicated that Cav1 co-localized with TXNIP, and it interacted with and regulated the expression of TXNIP, which regulates IAPP gene transcription. Conclusion: Cav-1 can regulate the synthesis and decomposition of IAPP in islet β cell by interacting with TXNIP. This study suggests that Cav-1 may protect diabetic islet beta cells by reducing islet amyloid deposition. Disclosure K. Liu: None. W. Zeng: None. S. Lin: None. C. Lin: None. F. Xu: None. N. Cai: None. L. Zeng: None. Funding National Natural Science Funding of China (51873071); Natural Science Foundation of Guangdong Province (2018B030311012)

Topical insulin application accelerates diabetic wound healing by promoting anti-inflammatory macrophage polarization.

Besides regulating glucose levels, insulin has been reported to participate actively in many other functions, including modulating inflammatory reactions. In this study we investigated how topical insulin application would affect the diabetic wound healing process. We found that the excessive expression of insulin-degrading enzyme led to insufficient insulin levels in diabetic skin during wound healing, which ultimately reduced the recovery rate of diabetic wounds. We confirmed that topical insulin application could reverse the impaired inflammation reaction in the diabetic wound environment and promote healing of diabetic wounds. Our study revealed that insulin promoted apoptosis of neutrophils and subsequently triggered polarization of macrophages. Both in vivo and in vitro studies verified that insulin re-established phagocytosis function and promoted the process of phagocytosis-induced apoptosis in neutrophils. Furthermore, we found that insulin treatment also promoted efferocytosis of the apoptosed neutrophils by macrophages, and thus induced macrophages to change their polarization state from M1 to M2. In conclusion, our studies proved that the exogenous application of insulin could improve diabetic wound healing via the restoration of the inflammatory response.

CDK5 Participates in Amyloid-β Production by Regulating PPARγ Phosphorylation in Primary Rat Hippocampal Neurons

Cyclin-dependent kinase 5 (CDK5) in adipose tissue mediates peroxisome proliferator-activated receptor γ (PPARγ) phosphorylation at Ser273 to inhibit its activity, causing PPARγ target gene expression changes. Among these, insulin-degrading enzyme (IDE) degrades amyloid-β peptide (Aβ), the core pathological product of Alzheimer's disease (AD), whereas β-amyloid cleavage enzyme 1 (BACE1) hydrolyzes amyloid-β protein precursor (AβPP). Therefore, we speculated that CDK5 activity in the brain might participate in Aβ production, thereby functioning as a key molecule in AD pathogenesis. To confirm this hypothesis, we transduced primary rat hippocampal neurons using CDK5-expressing lentiviral vectors. CDK5 overexpression increased PPARγ Ser273 phosphorylation, decreased IDE expression, increased BACE1 and AβPP expression, increased Aβ levels, and induced neuronal apoptosis. The CDK5 inhibitor roscovitine effectively reversed these CDK5 overexpression-mediated effects. Moreover, silencing of the Cdk5 gene via CDK5 shRNA-expressing lentiviral vectors in primary hippocampal neurons did not exert any protective effect against normal neuronal apoptosis, nor were significant effects observed on Aβ levels, PPARγ phosphorylation, or PPARγ target gene expression in the cells. However, Cdk5 gene silencing exhibited a neuroprotective effect in the Aβ-induced AD neuron model by effectively inhibiting the Aβ-induced neuronal apoptosis, PPARγ phosphorylation, PPARγ expression downregulation, and PPARγ target gene expression changes, and reducing Aβ levels. In conclusion, this study demonstrated that CDK5 played an important role in the pathogenesis of AD. Specifically, CDK5 participated in Aβ production by regulating PPARγ phosphorylation. Targeted therapy against CDK5 could effectively reduce and reverse the neurotoxic effects of Aβ and may represent a novel approach for AD treatment.

Pioglitazone Reduces β Amyloid Levels via Inhibition of PPARγ Phosphorylation in a Neuronal Model of Alzheimer's Disease.

It has been demonstrated that peroxisome proliferator-activated receptor γ (PPARγ) can regulate the transcription of its target gene, insulin-degrading enzyme (IDE), and thus enhance the expression of the IDE protein. The protein can degrade β amyloid (Aβ), a core pathological product of Alzheimer’s disease (AD). PPARγ can also regulate the transcription of other target gene, β-amyloid cleavage enzyme 1 (BACE1), and thus inhibit the expression of the BACE1 protein. BACE1 can hydrolyze amyloid precursor protein (APP), the precursor of Aβ. In adipose tissue, PPARγ agonists can inhibit the phosphorylation of PPARγ by inhibiting cyclin-dependent kinase 5 (CDK5), which in turn affects the expression of target genes regulated by PPARγ. PPARγ agonists may also exert inhibitory effects on the phosphorylation of PPARγ in the brain, thereby affecting the expression of the aforementioned PPARγ target genes and reducing Aβ levels. The present study confirmed this hypothesis by showing that PPARγ agonist pioglitazone attenuated the neuronal apoptosis of primary rat hippocampal neurons induced by Aβ1–42, downregulated CDK5 expression, weakened the binding of CDK5 to PPARγ, reduced PPARγ phosphorylation, increased the expression of PPARγ and IDE, decreased the expression of BACE1, reduced APP production, and downregulated intraneuronal Aβ1–42 levels. These effects were inhibited by the PPARγ antagonist GW9662. After CDK5 silencing with CDK5 shRNA, the above effect of pioglitazone was not observed, except when upregulating the expression of PPARγ in Aβ1–42 treated neurons. In conclusion, this study demonstrated that pioglitazone could inhibit the phosphorylation of PPARγ in vitro by inhibiting CDK5 expression, which in turn affected the expression of PPARγ target genes Ide and Bace1, thereby promoting Aβ degradation and reducing Aβ production. This reduced Aβ levels in the brain, thereby exerting neuroprotective effects in an AD model.

Memantine, a Noncompetitive N-Methyl-D-Aspartate Receptor Antagonist, Attenuates Cerebral Amyloid Angiopathy by Increasing Insulin-Degrading Enzyme Expression.

Sporadic cerebral amyloid angiopathy (CAA) is characterized by cerebrovascular amyloid beta (Aβ) deposits and causes cerebral hemorrhages and dementia in elderly people. Memantine is used in Alzheimer's disease to inhibit the glutamatergic system by blocking N-methyl-D-aspartate receptors. Its therapeutic effects in CAA are unclear, however. Here, we used APP23 transgenic mice (CAA model) to investigate whether memantine has direct therapeutic effects on cerebrovascular Aβ deposits. We treated APP23 mice and age-matched wild-type littermates with memantine at ages 6-18months. We counted the numbers of vessels with Aβ and hemosiderin deposits. We measured soluble and insoluble Aβ40 and Aβ42 levels and levels of amyloid precursor protein (APP), APP-processing enzymes (α-, β-, γ-secretase), and Aβ-degrading enzymes (insulin-degrading enzyme [IDE], neprilysin). Memantine reduced cerebrovascular Aβ and hemosiderin deposits in APP23 mice. Compared with controls, memantine-treated APP23 mice had reduced Aβ40 levels and increased levels of hippocampal and vascular IDE. Our results suggest that memantine reduces cerebrovascular Aβ deposits by enhancing Aβ-cleaving IDE expression. The clinical availability of memantine may allow its use as a novel therapeutic agent in CAA.

Altered expression of insulin-degrading enzyme and regulator of calcineurin in the rat intracerebral streptozotocin model and human apolipoprotein E-ε4–associated Alzheimer's disease

IntroductionThis study assesses insulin-degrading enzyme (IDE) and regulator of calcineurin 1 (RCAN1) as potential mediators of brain insulin deficiency and neurodegeneration in experimental and human Alzheimer's disease (AD). MethodsTemporal lobes from Long Evans rats treated with intracerebral streptozotocin or vehicle and postmortem frontal lobes from humans with normal aging AD (Braak 0-2), moderate (Braak 3-4) AD, or advanced (Braak 5-6) AD were used to measure IDE and RCAN mRNA and protein. ResultsIntracerebral streptozotocin significantly increased IDE and RCAN mRNA and protein. In humans with apolipoprotein E (ApoE) ε3/ε4 or ε4/ε4 and AD, IDE was elevated at Braak 3-4, but at Braak 5-6, IDE expression was significantly reduced. RCAN1 mRNA was similarly reduced in ApoE ε4+ patients with moderate or severe AD, whereas RCAN1 protein declined with the severity of AD and ApoE ε4 dose. DiscussionThe findings suggest that IDE and RCAN1 differentially modulate brain insulin signaling in relation to AD severity and ApoE genotype.

4,5-dicaffeyolquinic acid improves high-fat diet-induced cognitive dysfunction through the regulation of insulin degrading enzyme.

This study was performed to investigate the effects of Artemisia argyi and 4,5-dicaffeyolquinic acid (4,5-diCQA) as a main compound of ethyl acetate fraction from Artemisia argyi (EFAA) on high-fat diet (HFD)-induced cognitive dysfunction. Both EFAA and 4,5-diCQA were effective in improving cognitive function on HFD-induced cognitive dysfunction. In brain tissue analysis, it was confirmed that EFAA and 4,5-diCQA inhibited the reduction of neurotransmitters as well as oxidative stress and mitochondrial dysfunction. In addition, they inhibited amyloid β (Aβ) accumulation by increasing the expression of insulin-degrading enzyme and consequently prevented apoptosis. In conclusion, it is presumed that Artemisia argyi may help to improve the cognitive impairment due to the HFD, and it is considered that this effect is closely related to the physiological activity of 4,5-diCQA. PRACTICAL APPLICATIONS: Artemisia argyi is used in traditional herbal medicine in Asia. Type 2 diabetes mellitus has been proven by a variety of epidemiological studies to be a risk factor for cognitive impairment, such as Alzheimer's disease. This study confirmed that 4,5-diCQA is a bioactive compound of Artemisia argyi on improving HFD-induced cognitive dysfunction. Therefore, this study can provide useful information to the effect of Artemisia argyi and related substance.

Notoginseng Saponin Rg1 Prevents Cognitive Impairment through Modulating APP Processing in Aβ1-42-injected Rats.

With the intensification of the aging process of the world, Alzheimer's disease (AD), which is the main type of senile dementia, has become a primary problem in the present society. Lots of strategies have been used to prevent and treat AD in animal models and clinical trials, but most of them ended in failure. Panax notoginseng saponins (PNS) contain a variety of monomer compositions which have been separated and identified. Among of the monomer compositions, notoginseng saponin Rg1 (Rg1) accounts for 20% of the cultivation of panax notoginseng roots. And now PNS have been reported to be widely used to treat cardio-cerebrovascular diseases and have neuroprotective effects to restrain the β-amyloid peptide (Aβ)25-35-mediated apoptosis. Moreover, it is reported that PNS could accelerate the growth of nerve cells, increase the length of axons and promote synaptic plasticity. Whether Rg1 can ameliorate the cognitive impairment and the underlying mechanism has not been elucidated. To study the preventive effect of Rg1 on cognitive impairment and the possible mechanism, we established the cognitive impairment model in rats through Aβ1-42 (2.6 µg/µL, 5 µL) injection and then treated the rats with Rg1 (25, 50 and 100 mg/kg) administered intragastrically for 4 weeks. We observed that Aβ1-42 could induce spatial learning and memory deficits in rats. Simultaneously, Aβ1-42 injection also resulted in the reduced neuron number in cornuammonis 1 (CA1) and dentate gyrus (DG) of hippocampus, as well as the increased level of hyperphosphorylated β-amyloid precursor protein (APP) at Thr668 site with up-regulation of β-APP cleaving enzyme 1 (BACE1) and presenilin 1 (PS1) and down-regulation of a disintegrin and metalloprotease domain-containing protein 10 (ADAM10) and insulin-degrading enzyme (IDE). Administration of Rg1 effectively rescued the cognitive impairment and neuronal loss, and inhibited the β-secretase processing of APP through reducing APP-Thr668 phosphorylation and BACE1/PS1 expression, and increasing the expression of ADAM10 and IDE. We concluded that Rg1 might have neuroprotective effects and could promote learning and memory ability, which might be a viable candidate in AD therapy probably through reducing the generation of Aβ and increasing the degradation of Aβ.

Influence of electroacupuncture therapy of tonifying the kidney and regulating governor vessel on Aβ related degradation enzymes in the hippocampus of a rat model of Alzheimer's disease induced by Aβ1-42

ObjectiveTo explore influence of electroacupuncture (EA) therapy of tonifying the kidney and regulating governor vessel on amyloid beta (Aβ) related degradation enzymes in the hippocampus of a rat model of Alzheimer's disease (AD) induced by Aβ1-42. MethodsForty Wistar male rats were randomly divided into 4 groups: a normal group, a sham operation group, a model group and an EA group, 10 rats in each one. The rats in normal group were normally fed. The rats in sham operation group were bilaterally injected in the hippocampus with 5 µL of saline and they were normally fed after the injection. The rats in the model group and the EA group were bilaterally injected in the hippocampus with 5 µL of Aβ1-42 on each side. Rats in the EA group received EA of 5 Hz continuous wave at the “Băihuì (百会 GV20)” and bilateral “Shènshū (肾俞 BL23)” for a duration of 15 min per time every day and continuously for 15 days. After 15 days, the hippocampal expression levels of insulin degrading enzyme (IDE), lipoprotein (LPL), transthyretin (TTR), apolipoprotein E (APoE), α2 macroglobulin (α2M) and Aβ1-42 of the 4 groups were tested by Western blot. ResultsCompared with the sham operation group, the expression levels of IDE, LPL, TTR, APoE and α2M in the hippocampus were significantly lower (P < 0.05, P < 0.01) and the expression of Aβ1-42 was significantly higher(P < 0.01) in the model group. Compared with the model group, the expression levels of IDE, LPL, TTR, APoE and α2M in the hippocampus of these rats were significantly lower (P < 0.05, P < 0.01), the expression of Aβ1-42 was significantly higher(P < 0.01) in the EA group. ConclusionEA therapy of tonifying the kidney and regulating governor vessel can enhance the expression of IDE, LPL, TTR, APoE, and α2M in the hippocampus of AD rats injected by Aβ1-42, and may consequently promote the degradation of aβ1-42 to help improve the pathological manifestations of AD and therefore delay its progression.

Expression of inflammatory and fibrogenetic markers in acne hypertrophic scar formation: focusing on role of TGF-β and IGF-1R.

Acne vulgaris is a universal skin disease and it may leave a scar when the original skin lesion disappears. These scars can cause cosmetic problems and psychological burden, leading to poor quality of life of patients. Acne scars are classified into atrophic scars and hypertrophic scars. As most of the acne scars are atrophic, many studies have been conducted focusing on the treatment of atrophic lesions. This study was conducted to investigate the underlying pathogenesis of acne hypertrophic scars by identifying roles of fibrogenetic and inflammatory markers. Skin biopsy samples were obtained from hypertrophic scars of face and back and from adjacent normal tissues as control group. Some samples from back were immature hypertrophic scars and the other samples were in mature stages. Immunohistochemistry staining and quantitative PCR were performed for fibrogenetic and inflammatory markers. Both in mature and immature hypertrophic scars, vimentin and α-SMA were increased. Production of TGF-β3 protein as well as transcription of TGF-β3 was also significantly elevated. In contrast, expression of TGF-β1 showed no increase. Instead, expression levels of SMAD2 and SMAD4 were increased. Elevations of CD45RO, TNF-α and IL-4 and reduction of IL-10 were observed. In immature hypertrophic scars, IGF-1R and insulin-degrading enzyme expression were increased. Increased apoptosis was observed in immature stages of hypertrophic scars but not in mature stages. Elevations of TGF-β3, SMAD2 and SMAD4 in hypertrophic scars and increase of IGF-1R in immature stages may give some clues for acne hypertrophic scar formation.

GLP-1 receptor regulates cell growth through regulating IDE expression level in Aβ1-42-treated PC12 cells.

This study aimed to validate whether glucagon-like peptide-1 receptor (GLP-1R) / cyclic adenosine monophosphate (cAMP) / protein kinase (PKA) / insulin-degrading enzyme (IDE) signaling pathway was associated with neuronal apoptosis. We developed an animal model presenting both Alzheimer’s disease (AD) and type 2 diabetes (T2D), by crossing APP/PS1 mice (AD model) with streptozotocin (STZ)-treated mice (a T2D model). Neuronal apoptosis was detected by TUNEL staining and the expression levels of apoptosis-related proteins were examined by Western blotting. The viability of PC12 cells was analyzed by MTT assay and apoptosis of PC12 cells was detected by flow cytometry. The mRNA expression level was detected by qRT-PCR. T2D contributes to AD progress by prompting neuronal apoptosis and increasing expression of pro-apoptotic protein. β-Amyloid peptide1–42 (Aβ1–42) was shown to exert effects on inhibiting cell viability and prompting cell apoptosis of PC12 cells. However, GLP-1R agonist geniposide (Gen) significantly reversed them, exerting a protective role on PC12 cells. And IDE antagonist bacitracin (Bac) markedly reversed the protective effects of Gen on Aβ1–42-treated PC12 cells. Besides, Gen significantly reversed the effects of Aβ1–42 treatment on IDE expression, and the inhibitor of cAMP/PKA signaling pathway markedly reversed the effects of Gen on IDE expression level in Aβ1–42-treated PC12 cells. In conclusion, GLP-1R regulates cell growth, at least partially, through regulating cAMP/PKA/IDE signaling pathway in Aβ1–42-treated PC12 cells.

Insulin-signaling Pathway Regulates the Degradation of Amyloid β-protein via Astrocytes

Alzheimer’s disease (AD) has been considered as a metabolic dysfunction disease associated with impaired insulin signaling. Determining the mechanisms underlying insulin signaling dysfunction and resistance in AD will be important for its treatment. Impaired clearance of amyloid-β peptide (Aβ) significantly contributes to amyloid accumulation, which is typically observed in the brain of AD patients. Reduced expression of important Aβ-degrading enzymes in the brain, such as neprilysin (NEP) and insulin-degrading enzyme (IDE), can promote Aβ deposition in sporadic late-onset AD patients. Here, we investigated whether insulin regulates the degradation of Aβ by inducing expression of NEP and IDE in cultured astrocytes. Treatment of astrocytes with insulin significantly reduced cellular NEP levels, but increased IDE expression. The effects of insulin on the expression of NEP and IDE involved activation of an extracellular signal-regulated kinase (ERK)-mediated pathway. The reduction in cellular NEP levels was associated with NEP secretion into the culture medium, whereas IDE was increased in the cell membranes. Moreover, insulin-treated astrocytes significantly facilitated the degradation of exogenous Aβ within the culture medium. Interestingly, pretreatment of astrocytes with an ERK inhibitor prior to insulin exposure markedly inhibited insulin-induced degradation of Aβ. These results suggest that insulin exposure enhanced Aβ degradation via an increase in NEP secretion and IDE expression in astrocytes, via activation of the ERK-mediated pathway. The inhibition of insulin signaling pathways delayed Aβ degradation by attenuating alterations in NEP and IDE levels and competition with insulin and Aβ. Our results provide further insight into the pathological relevance of insulin resistance in AD development.

Treadmill Exercise Ameliorates Spatial Learning and Memory Deficits Through Improving the Clearance of Peripheral and Central Amyloid-Beta Levels.

Aggregated amyloid beta (Aβ) peptides are believed to play a decisive role in the pathology of Alzheimer's disease (AD). Previous evidence suggested that exercise contributes to the improvement of cognitive decline and slows down pathogenesis of AD; however, the exact mechanisms for this have not been fully understood. Here, we evaluated the effect of a 4-week moderate treadmill exercise on spatial memory via central and peripheral Aβ clearance mechanisms following developed AD-like neuropathology induced by intra-hippocampal Aβ1-42 injection in male Wistar rats. We found Aβ1-42-treated animals showed spatial learning and memory impairment which was accompanied by increased levels of amyloid plaque load and soluble Aβ1-42 (sAβ1-42), decreased mRNA and protein expression of neprilysin (NEP), insulin degrading enzyme (IDE) and low-density lipoprotein receptor-related protein-1 (LRP-1) in the hippocampus. Aβ1-42-treated animals also exhibited a higher level of sAβ1-42 and a lower level of soluble LRP-1 (sLRP-1) in plasma, as well as a decreased level of LRP-1 mRNA and protein content in the liver. However, exercise training improved the spatial learning and memory deficits, reduced both plaque load and sAβ1-42 levels, and up-regulated expression of NEP, IDE, and LRP-1 in the hippocampus of Aβ1-42-treated animals. Aβ1-42-treated animals subjected to treadmill exercise also revealed decreased levels of sAβ1-42 and increased levels of sLRP-1 in plasma, as well as increased levels of LRP-1 mRNA and protein in the liver. In conclusion, our findings suggest that exercise-induced improvement in both of central and peripheral Aβ clearance are likely involved in ameliorating spatial learning and memory deficits in an animal model of AD. Future studies need to determine their relative contribution.