Preventing obesity, insulin resistance and type 2 diabetes by targeting MT1-MMP

Obesity is one of the predominant risk factors for type 2 diabetes. Despite all the modern advances in medicine, an effective drug treatment for obesity without overt side effects has not yet been found. The discovery of growth and differentiation factor 15 (GDF15), an appetite-regulating hormone, created hopes for the treatment of obesity. However, an insufficient understanding of the physiological regulation of GDF15 has been a major obstacle to mitigating GDF15-centric treatment of obesity. Our recent studies revealed how a series of proteolytic events predominantly mediated by membrane-type 1 matrix metalloproteinase (MT1-MMP/MMP14), a key cell-surface metalloproteinase involved in extracellular remodeling, contribute to the pathogenesis of metabolic disorders, including obesity and diabetes. The MT1-MMP-mediated cleavage of the GDNF family receptor-α-like (GFRAL), a key neuronal receptor of GDF15, controls the satiety center in the hindbrain, thereby regulating non-homeostatic appetite and bodyweight changes. Furthermore, increased activation of MT1-MMP does not only lead to increased risk of obesity, but also causes age-associated insulin resistance by cleaving Insulin Receptor in major metabolic tissues. Importantly, inhibition of MT1-MMP effectively protects against obesity and diabetes, revealing the therapeutic potential of targeting MT1-MMP for the management of metabolic disorders.

Artesunate treats obesity in male mice and non-human primates through GDF15/GFRAL signalling axis

Obesity, a global health challenge, is a major risk factor for multiple life-threatening diseases, including diabetes, fatty liver, and cancer. There is an ongoing need to identify safe and tolerable therapeutics for obesity management. Herein, we show that treatment with artesunate, an artemisinin derivative approved by the FDA for the treatment of severe malaria, effectively reduces body weight and improves metabolic profiles in preclinical models of obesity, including male mice with overnutrition-induced obesity and male cynomolgus macaques with spontaneous obesity, without inducing nausea and malaise. Artesunate promotes weight loss and reduces food intake in obese mice and cynomolgus macaques by increasing circulating levels of Growth Differentiation Factor 15 (GDF15), an appetite-regulating hormone with a brainstem-restricted receptor, the GDNF family receptor α-like (GFRAL). Mechanistically, artesunate induces the expression of GDF15 in multiple organs, especially the liver, in mice through a C/EBP homologous protein (CHOP)-directed integrated stress response. Inhibition of GDF15/GFRAL signalling by genetic ablation of GFRAL or tissue-specific knockdown of GDF15 abrogates the anti-obesity effect of artesunate in mice with diet-induced obesity, suggesting that artesunate controls bodyweight and appetite in a GDF15/GFRAL signalling-dependent manner. These data highlight the therapeutic benefits of artesunate in the treatment of obesity and related comorbidities.

Ruminococcus gnavus plays a pathogenic role in diarrhea-predominant irritable bowel syndrome by increasing serotonin biosynthesis

Diarrhea-predominant irritable bowel syndrome (IBS-D), a globally prevalent functional gastrointestinal (GI) disorder, is associated with elevated serotonin that increases gut motility. While anecdotal evidence suggests that the gut microbiota contributes to serotonin biosynthesis, mechanistic insights are limited. We determined that the bacterium Ruminococcus gnavus plays a pathogenic role in IBS-D. Monocolonization of germ-free mice with R. gnavus induced IBS-D-like symptoms, including increased GI transit and colonic secretion, by stimulating the production of peripheral serotonin. R. gnavus-mediated catabolism of dietary phenylalanine and tryptophan generated phenethylamine and tryptamine that directly stimulated serotonin biosynthesis in intestinal enterochromaffin cells via a mechanism involving activation of trace amine-associated receptor 1 (TAAR1). This R. gnavus-driven increase in serotonin levels elevated GI transit and colonic secretion but was abrogated upon TAAR1 inhibition. Collectively, our study provides molecular and pathogenetic insights into how gut microbial metabolites derived from dietary essential amino acids affect serotonin-dependent control of gut motility.

Control of SARS-CoV-2 infection by MT1-MMP-mediated shedding of ACE2

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has caused a global pandemic. Angiotensin-converting enzyme 2 (ACE2) is an entry receptor for SARS-CoV-2. The full-length membrane form of ACE2 (memACE2) undergoes ectodomain shedding to generate a shed soluble form (solACE2) that mediates SARS-CoV-2 entry via receptor-mediated endocytosis. Currently, it is not known how the physiological regulation of ACE2 shedding contributes to the etiology of COVID-19 in vivo. The present study identifies Membrane-type 1 Matrix Metalloproteinase (MT1-MMP) as a critical host protease for solACE2-mediated SARS-CoV-2 infection. SARS-CoV-2 infection leads to increased activation of MT1-MMP that is colocalized with ACE2 in human lung epithelium. Mechanistically, MT1-MMP directly cleaves memACE2 at M706-S to release solACE2_18-706 that binds to the SARS-CoV-2 spike proteins (S), thus facilitating cell entry of SARS-CoV-2. Human solACE2_18-706 enables SARS-CoV-2 infection in both non-permissive cells and naturally insusceptible C57BL/6 mice. Inhibition of MT1-MMP activities suppresses solACE2-directed entry of SARS-CoV-2 in human organoids and aged mice. Both solACE2 and circulating MT1-MMP are positively correlated in plasma of aged mice and humans. Our findings provide in vivo evidence demonstrating the contribution of ACE2 shedding to the etiology of COVID-19.

Clinically relevant small-molecule promotes nerve repair and visual function recovery

Adult mammalian injured axons regenerate over short-distance in the peripheral nervous system (PNS) while the axons in the central nervous system (CNS) are unable to regrow after injury. Here, we demonstrated that Lycium barbarum polysaccharides (LBP), purified from Wolfberry, accelerated long-distance axon regeneration after severe peripheral nerve injury (PNI) and optic nerve crush (ONC). LBP not only promoted intrinsic growth capacity of injured neurons and function recovery after severe PNI, but also induced robust retinal ganglion cell (RGC) survival and axon regeneration after ONC. By using LBP gene expression profile signatures to query a Connectivity map database, we identified a Food and Drug Administration (FDA)-approved small-molecule glycopyrrolate, which promoted PNS axon regeneration, RGC survival and sustained CNS axon regeneration, increased neural firing in the superior colliculus, and enhanced visual target re-innervations by regenerating RGC axons leading to a partial restoration of visual function after ONC. Our study provides insights into repurposing of FDA-approved small molecule for nerve repair and function recovery.

Cerebellar glutamatergic system impacts spontaneous motor recovery by regulating Gria1 expression

Peripheral nerve injury (PNI) often results in spontaneous motor recovery; however, how disrupted cerebellar circuitry affects PNI-associated motor recovery is unknown. Here, we demonstrated disrupted cerebellar circuitry and poor motor recovery in ataxia mice after PNI. This effect was mimicked by deep cerebellar nuclei (DCN) lesion, but not by damaging non-motor area hippocampus. By restoring cerebellar circuitry through DCN stimulation, and reversal of neurotransmitter imbalance using baclofen, ataxia mice achieve full motor recovery after PNI. Mechanistically, elevated glutamate-glutamine level was detected in DCN of ataxia mice by magnetic resonance spectroscopy. Transcriptomic study revealed that Gria1, an ionotropic glutamate receptor, was upregulated in DCN of control mice but failed to be upregulated in ataxia mice after sciatic nerve crush. AAV-mediated overexpression of Gria1 in DCN rescued motor deficits of ataxia mice after PNI. Finally, we found a correlative decrease in human GRIA1 mRNA expression in the cerebellum of patients with ataxia-telangiectasia and spinocerebellar ataxia type 6 patient iPSC-derived Purkinje cells, pointing to the clinical relevance of glutamatergic system. By conducting a large-scale analysis of 9,655,320 patients with ataxia, they failed to recover from carpal tunnel decompression surgery and tibial neuropathy, while aged-match non-ataxia patients fully recovered. Our results provide insight into cerebellar disorders and motor deficits after PNI.

Regulation of age-associated insulin resistance by MT1-MMP-mediated cleavage of insulin receptor

Insulin sensitivity progressively declines with age. Currently, the mechanism underlying age-associated insulin resistance remains unknown. Here, we identify membrane-bound matrix metalloproteinase 14 (MT1-MMP/MMP14) as a central regulator of insulin sensitivity during ageing. Ageing promotes MMP14 activation in insulin-sensitive tissues, which cleaves Insulin Receptor to suppress insulin signaling. MT1-MMP inhibition restores Insulin Receptor expression, improving insulin sensitivity in aged mice. The cleavage of Insulin Receptor by MT1-MMP also contributes to obesity-induced insulin resistance and inhibition of MT1-MMP activities normalizes metabolic dysfunctions in diabetic mouse models. Conversely, overexpression of MT1-MMP in the liver reduces the level of Insulin Receptor, impairing hepatic insulin sensitivity in young mice. The soluble Insulin Receptor and circulating MT1-MMP are positively correlated in plasma from aged human subjects and non-human primates. Our findings provide mechanistic insights into regulation of insulin sensitivity during physiological ageing and highlight MT1-MMP as a promising target for therapeutic avenue against diabetes.

Deep Brain Stimulation of the Interposed Nucleus Reverses Motor Deficits and Stimulates Production of Anti-inflammatory Cytokines in Ataxia Mice

Cerebellum is one of the major targets of autoimmunity and cerebellar damage that leads to ataxia characterized by the loss of fine motor coordination and balance, with no treatment available. Deep brain stimulation (DBS) could be a promising treatment for ataxia but has not been extensively investigated. Here, our study aims to investigate the use of interposed nucleus of deep cerebellar nuclei (IN-DCN) for ataxia. We first characterized ataxia-related motor symptom of a Purkinje cell (PC)-specific LIM homeobox (Lhx)1 and Lhx5 conditional double knockout mice by motor coordination tests, and spontaneous electromyogram (EMG) recording. To validate IN-DCN as a target for DBS, in vivo local field potential (LFP) multielectrode array recording of IN-DCN revealed abnormal LFP amplitude surges in PCs. By synchronizing the EMG and IN-DCN recordings (neurospike and LFP) with high-speed video recordings, ataxia mice showed poorly coordinated movements associated with low EMG amplitude and aberrant IN-DCN neural firing. To optimize IN-DCN-DBS for ataxia, we tested DBS parameters from low (30 Hz) to high stimulation frequency (130 or 150 Hz), and systematically varied pulse width values (60 or 80 µs) to maximize motor symptom control in ataxia mice. The optimal IN-DCN-DBS parameter reversed motor deficits in ataxia mice as detected by animal behavioral tests and EMG recording. Mechanistically, cytokine array analysis revealed that anti-inflammatory cytokines such as interleukin (IL)-13 and IL-4 were upregulated after IN-DCN-DBS, which play key roles in neural excitability. As such, we show that IN-DCN-DBS is a promising treatment for ataxia and possibly other movement disorders alike.

Body weight regulation via MT1-MMP-mediated cleavage of GFRAL

GDNF-family receptor a-like (GFRAL) has been identified as the cognate receptor of growth/differentiation factor 15 (GDF15/MIC-1), considered a key signaling axis in energy homeostasis and body weight regulation. Currently, little is known about the physiological regulation of the GDF15-GFRAL signaling pathway. Here we show that membrane-bound matrix metalloproteinase 14 (MT1-MMP/MMP14) is an endogenous negative regulator of GFRAL in the context of obesity. Overnutrition-induced obesity increased MT1-MMP activation, which proteolytically inactivated GFRAL to suppress GDF15-GFRAL signaling, thus modulating the anorectic effects of the GDF15-GFRAL axis in vivo. Genetic ablation of MT1-MMP specifically in GFRAL+ neurons restored GFRAL expression, resulting in reduced weight gain, along with decreased food intake in obese mice. Conversely, depletion of GFRAL abolished the anti-obesity effects of MT1-MMP inhibition. MT1-MMP inhibition also potentiated GDF15 activity specifically in obese phenotypes. Our findings identify a negative regulator of GFRAL for the control of non-homeostatic body weight regulation, provide mechanistic insights into the regulation of GDF15 sensitivity, highlight negative regulators of the GDF15-GFRAL pathway as a therapeutic avenue against obesity and identify MT1-MMP as a promising target.

Heat shock protein is a key therapeutic target for nerve repair in autoimmune peripheral neuropathy and severe peripheral nerve injury

Guillain-Barré syndrome (GBS) is an autoimmune peripheral neuropathy and a common cause of neuromuscular paralysis. Preceding infection induces the production of anti-ganglioside (GD) antibodies attacking its own peripheral nerves. In severe proximal peripheral nerve injuries that require long-distance axon regeneration, motor functional recovery is virtually nonexistent. Damaged axons fail to regrow and reinnervate target muscles. In mice, regenerating axons must reach the target muscle within 35 days (critical period) to reform functional neuromuscular junctions and regain motor function. Successful functional recovery depends on the rate of axon regeneration and debris removal (Wallerian degeneration) after nerve injury. The innate-immune response of the peripheral nervous system to nerve injury such as timing and magnitude of cytokine production is crucial for Wallerian degeneration. In the current study, forced expression of human heat shock protein (hHsp) 27 completely reversed anti-GD-induced inhibitory effects on nerve repair assessed by animal behavioral assays, electrophysiology and histology studies, and the beneficial effect was validated in a second mouse line of hHsp27. The protective effect of hHsp27 on prolonged muscle denervation was examined by performing repeated sciatic nerve crushes to delay regenerating axons from reaching distal muscle from 37 days up to 55 days. Strikingly, hHsp27 was able to extend the critical period of motor functional recovery for up to 55 days and preserve the integrity of axons and mitochondria in distal nerves. Cytokine array analysis demonstrated that a number of key cytokines which are heavily involved in the early phase of innate-immune response of Wallerian degeneration, were found to be upregulated in the sciatic nerve lysates of hHsp27 Tg mice at 1 day postinjury. However, persistent hyperinflammatory mediator changes were found after chronic denervation in sciatic nerves of littermate mice, but remained unchanged in hHsp27 Tg mice. Taken together, the current study provides insight into the development of therapeutic strategies to enhance muscle receptiveness (reinnervation) by accelerating axon regeneration and Wallerian degeneration.

Ciguatoxin reduces regenerative capacity of axotomized peripheral neurons and delays functional recovery in pre-exposed mice after peripheral nerve injury

Ciguatera fish poisoning (CFP) results from consumption of tropical reef fish containing ciguatoxins (CTXs). Pacific (P)-CTX-1 is among the most potent known CTXs and the predominant source of CFP in the endemic region responsible for the majority of neurological symptoms in patients. Chronic and persistent neurological symptoms occur in some CFP patients, which often result in incomplete functional recovery for years. However, the direct effects of exposure to CTXs remain largely unknown. In present study, we exposed mice to CTX purified from ciguatera fish sourced from the Pacific region. P-CTX-1 was detected in peripheral nerves within hours and persisted for two months after exposure. P-CTX-1 inhibited axonal regrowth from axotomized peripheral neurons in culture. P-CTX-1 exposure reduced motor function in mice within the first two weeks of exposure before returning to baseline levels. These pre-exposed animals exhibited delayed sensory and motor functional recovery, and irreversible motor deficits after peripheral nerve injury in which formation of functional synapses was impaired. These findings are consistent with reduced muscle function, as assessed by electromyography recordings. Our study provides strong evidence that the persistence of P-CTX-1 in peripheral nerves reduces the intrinsic growth capacity of peripheral neurons, resulting in delayed functional recovery after injury.

Dissecting the Role of Anti-ganglioside Antibodies in Guillain-Barré Syndrome: an Animal Model Approach

Guillain-Barré syndrome (GBS) is an autoimmune polyneuropathy disease affecting the peripheral nervous system (PNS). Most of the GBS patients experienced neurological symptoms such as paresthesia, weakness, pain, and areflexia. There are also combinations of non-neurological symptoms which include upper respiratory tract infection and diarrhea. One of the major causes of GBS is due largely to the autoantibodies against gangliosides located on the peripheral nerves. Gangliosides are sialic acid-bearing glycosphingolipids consisting of a ceramide lipid anchor with one or more sialic acids attached to a neutral sugar backbone. Molecular mimicry between the outer components of oligosaccharide of gangliosides on nerve membrane and lipo-oligosaccharide of microbes is thought to trigger the autoimmunity. Intra-peritoneal implantation of monoclonal ganglioside antibodies secreting hybridoma into animals induced peripheral neuropathy. Recent studies demonstrated that injection of synthesized anti-ganglioside antibodies raised by hybridoma cells into mice initiates immune response against peripheral nerves, and eventually failure in peripheral nerve regeneration. Accumulating evidences indicate that the conjugation of anti-ganglioside monoclonal antibodies to activating FcγRIII present on the circulating macrophages inhibits axonal regeneration. The activation of RhoA signaling pathways is also involved in neurite outgrowth inhibition. However, the link between these two molecular events remains unresolved and requires further investigation. Development of anti-ganglioside antagonists can serve as targeted therapy for the treatment of GBS and will open a new approach of drug development with maximum efficacy and specificity.

Quercetin mediated reduction of angiogenic markers and chaperones in DLA-induced solid tumours

Diet-derived flavonoids, in particular quercetin, may play advantageous roles by preventing or/and inhibiting oncogenesis. Evidence suggests that quercetin can elicit various properties depending on the cell type. The aim of this study was to evaluate its effects on Dalton's lymphoma ascites (DLA) induced solid tumours and to identify the target(s) of action. We addressed this question by inducing subcutaneous solid tumours in Swiss albino mice and investigated whether the quercetin affects essential biological processes that are responsible for tumour growth, morphology, angiogenesis and apoptosis. We also studied influence on several heat shock proteins (HSPs). Our findings demonstrate that intra-tumour administration of quercetin results in decreased volume/weight. Furthermore, we demonstrate that quercetin promotes apoptosis of cancer cells by down-regulating the levels of Hsp90 and Hsp70. Depletion of these two chaperones by quercetin might result in triggering of caspase-3 in treated tumours. Moreover, it also down-regulated the expression of major key angiogenic or pro-angiogenic factors, like HIF-1α and VEGF In addition, H and E staining together with immunofluorescence of fixed tumour tissue provided evidence in support of increased cell death in quercetin-treated mice.

Response of Mycobacterium habana vaccine in patients with lepromatous leprosy and their household contacts. A pilot clinical study

Single dose vaccination was carried out with Mycobacterium habana vaccine, 31 lepromatous leprosy cases receiving 1.5 mg (1.5 mg = 6.27 x 10(8) bacilli) and 36 household contacts randomly receiving 1.5, 2.0, 2.5 mg vaccine intradermally. Duration of study was 18 weeks. Vaccination induced lepromin conversion in 100% of lepromatous leprosy cases and lepromin negative household contacts and augmentation of lepromin reactivity in 100% of lepromin positive household contacts, which was stable for the 15 weeks duration of follow-up. The maximum augmentation in lepromin reactivity was obtained with 1.5 mg of vaccine, which is probably the supramaximal dose. Overall, post-vaccination, those without prior BCG vaccination scars showed higher mean values of lepromin augmentation. Local vaccination site changes included induration, ulceration, itching, pain and uncomplicated regional lymphadenopathy, all of which remitted spontaneously by 15 weeks. Systemic side-effects noted were pyrexia, ENL and jaundice, and were seen with no greater frequency than that reported in other vaccine trials. Overall, systemic side-effects were easily controlled and were not accompanied by clinically detectable nerve or ocular damage. The safety profile investigations revealed an increase in the mean values of Hb%, RBC count and PCV in household contacts and of PCV in lepromatous patients, post-vaccination. Alterations in the liver function tests were also observed in patients of lepromatous leprosy. Thus, M. habana vaccine appears to be useful in stimulating specific CMI against M. leprae as evidenced by increased lepromin reactivity.

Analysis of weighted fan-out/fan-in volume holographic optical interconnections

The feasibility of employing volume holographic techniques for the implementation of highly multiplexed weighted fan-out/fan-in interconnections is analyzed on the basis of interconnection fidelity, optical throughput, and complexity of recording schedule or implementation hardware. These feasibility criteria were quantitatively evaluated using the optical beam propagation method to numerically simulate the diffraction characteristics of volume holographic interconnections recorded in a linear holographic material. We find that conventional interconnection architectures (that are based on a single coherent optical source) exhibit a direct trade-off between interconnection fidelity and optical throughput on the one hand, and recording schedule or hardware complexity on the other. In order to circumvent this trade-off we describe and analyze in detail an incoherent/coherent double angularly multiplexed interconnection architecture that is based on the use of multiple-source array of individually coherent but mutually incoherent sources. This architecture either minimizes or avoids several key sources of cross talk, permits simultaneous recording of interconnection weights or weight updates, and provides enhanced fidelity, interchannel isolation, and thróughput performance.