Metformin shown for the first time to inhibit Zika virus in human umbilical cells: AMPK links virus destruction with Progeria, HIV & Cancer stem cells

By Jim Gathany [Public domain], via Wikimedia Commons; CC-BY-SA-3.0 http://creativecommons.org/licenses/by-sa/3.0/)], via Wikimedia Commons

A study published in the Journal of Virology in December of 2017 by researchers from the University of Southern California showed for the first time that AMPK activators including the anti-diabetic drug metformin caused an approximately 60% to 80% decrease in virus production from human umbilical vein endothelial cells (HUVECs) infected with Zika virus (ZIKV) [1]. ZIKV has been causally linked to microcephaly (head circumference smaller than normal due to abnormal brain development) and has been shown to efficiently infect HUVECs, which directly contact the fetal blood stream [2]. Metformin-induced inhibition of ZIKV replication in HUVECs may thus represent a powerful, safe, and economically viable option to treat and/or prevent conditions associated with ZIKV infection. Interestingly, as further explained below, metformin and AMPK have recently been shown to exert antiviral and anti-parasitic effects against dengue virus (which is transmitted by the same mosquito vector as ZIKV) and different Plasmodium species (the etiological agent of malaria), respectively.

Additionally, metformin activates AMPK and alleviates accelerating aging defects in cells from children with the genetic disorder Hutchinson-Gilford progeria syndrome (HGPS), promotes the differentiation and/or apoptosis of cancer stem cells in an AMPK-dependent manner, and destabilizes the latent HIV-1 reservoir in chronically-infected HIV-1 patients (facilitating virus elimination and potentially contributing to an HIV-1 cure). Also, because AMPK is critical for oocyte maturation and bacteria-derived antibiotics (e.g. ionomycin, A23187) that activate AMPK are used extensively to activate human oocytes to create normal, healthy babies, it is likely that stress-induced AMPK activation (e.g. via reactive oxygen species, intracellular calcium, and/or AMP/ATP ratio increase, etc.) represents a common mechanism linking pathogen elimination with HGPS, caner stem cell elimination, HIV-1 eradication, and the creation of all human life, as I originally proposed in several recent publications (see below) [3-6].   

As noted above, the AMPK activators metformin and AICAR potently inhibited ZIKV replication in HUVECs [1]. Although the authors unexplainably found that compound C (an AMPK inhibitor) also inhibited ZIKV replication, AMPK activation has recently been found to exert significant antiviral effects against Rift Valley Fever virus as well as multiple arbovirus family members including the Flavivirus Kunjin virus, the Togavirus Sindbis virus, and the Rhabdovirus Vesicular stomatitis virus [1,7]. Indeed, several AMPK-activating compounds have also recently demonstrated antiviral effects against ZIKV infection and replication. For example, EGCG (found in green tea) inhibited ZIKV entry in Vero E6 cells, curcumin (derived from the plant Curcuma longa) inhibited ZIKV replication in HeLa cells, NDGA (derived from the plant Larrea tridentate) reduced viral yield in Vero cells infected with a ZIKV strain isolated from a human patient, sophoraflavenone G (isolated from the plant Sophora Flavecens) inhibits ZIKV replication in A549 cells, hemin (an iron-containing porphyrin) significantly inhibited ZIKV replication in primary human monocyte-derived macrophages, quercetin (found in a variety of plants) exerted antiviral activity against ZIKV in both tissue culture and knockout mice, and chloroquine (an anti-malarial compound) inhibited ZIKV infection in vitro and protected fetal mice from ZIKV-induced microcephaly [8-14]. Similar to metformin, each of the aforementioned compounds or the plant extracts from which they are derived activates AMPK in vivo and/or in vitro [15-19].

Interestingly, as both ZIKV and dengue virus (DENV) are transmitted by the same mosquito vector, a study recently published in the journal PLoS Pathogens in April of 2017 demonstrated for the first time that metformin exerted significant antiviral effects in DENV-infected human liver cells that was dependent on activation of the master metabolic regulator AMPK [20]. The authors showed that an increase in HMG-CoA reductase (HMGCR) activity, a target of AMPK, was associated with DENV-infected cells, AMPK activation was reduced in DENV-infected cells at 12 and 24 hours post infection (hpi), and metformin significantly decreased the number of infected cells, viral yield, and viral genome copies, leading the authors to conclude that metformin-induced AMPK activation generates a strong antiviral effect against DENV [20]. Recent efforts funded by the U.S. and British governments, the Bill & Melinda Gates Foundation, and the Google health spin-off Verily have sought to decrease the spread of dengue and Zika viruses through the coordinated release of female and/or male mosquitoes (called Aedes aegypti) that were purposely infected with a bacterium that inhibits the mosquito’s ability to transmit the two viruses to humans [21,22]. Studies have shown that this bacterium, called Wolbachia, enhances the mosquito’s immune response by increasing the levels of reactive oxygen species (ROS), thus enhancing inhibition of DENV replication [23]. Because AMPK is activated by cellular stress (e.g. ROS increase, intracellular calcium [Ca2+] increase, AMP/ATP ratio increase, etc.), has been found in Aedes aegypti (Ae. aegypti), and AMPK activation by stress-inducing compounds (e.g. resveratrol) increased average life span and enhanced the immune response in Ae. aegypti in an AMPK-dependent manner, the recent finding that metformin also inhibits DENV replication in human cells in an AMPK-dependent manner provides compelling evidence that the anti-viral and antimicrobial effects of AMPK activation likely crosses species boundaries [24]. 

Moreover, a study published in the journal Cell Reports in September of 2016 by researchers from the Massachusetts Institute of Technology (MIT) and the University of Lisbon also showed for the first time that metformin and other AMPK activators significantly reduced parasite load in human liver cells of different species of Plasmodium, a protozoan parasite that is the etiological agent of malaria [25]. Importantly, the authors also showed that AMPK activation inhibits growth and replication of different Plasmodium spp. (species) and AMPK activators as well as dietary restriction, which activates AMPK, reduces Plasmodium berghei (malaria-causing species in rodents often used as a model for the study of human malaria) infection in mice [25]. The AMPK-activating compounds salicylate and A769662 also reduced P. berghei and P. falciparum (malaria parasite that infects humans) merozoite formation (infectious parasites generated through replication in erythrocytes) in vitro while salicylate decreased parasitaemia in mice in vivo [26].

Cellular stress-induced AMPK activation has also been shown to exert antiviral effects against HIV-1. AMPK activation and several AMPK-activating compounds, including EGCG, curcumin, tanshinone II A (derived from the plant Salvia miltiorrhiza), byrostatin-1 (isolated from the marine organism Bugula neritina), and resveratrol (found in grapes and in the plant Polygonum cuspidatum) have been shown to exhibit antiviral activity in vitro against HIV-1 [27-31].

An active area among HIV-1 cure researchers, known as the “shock and kill” approach, involves reactivating (i.e. “shock”) a T cell (or another immune cell) that harbors dormant HIV-1, hence reactivating the virus itself and thus inducing destruction of the T cell along with the virus or enhancing recognition and destruction of the virus-infected T cell by the immune system (i.e. “kill”) [4]. Strikingly, AMPK is also critical for the activation of T cells and the mounting of an effective immune response to eliminate viruses, bacteria, and cancer cells [5,32,33]. A recent study demonstrated that metformin, when combined with the protein kinase C modulator bryostatin, induced reactivation of latent HIV-1 in a monocytic cell line in an AMPK-dependent manner. Bryostatin was also shown to induce phosphorylation and activation of AMPK in that study, implying that bryostatin is an indirect AMPK activator as well [30]. Furthermore, the calcium ionophores ionomycin and A23187, both of which activate AMPK and induce human oocyte activation, are often combined with phorbol 12-myristate 13-acetate (PMA) and are extremely efficient in promoting T cell activation-induced latent HIV-1 reactivation [34-36].

Perhaps most convincingly, at the International AIDS Society’s (IAS) HIV Cure and Cancer Forum held in Paris, France in July of 2017, researchers from the University of Hawaii demonstrated for the first time that metformin decreased the percentage of CD4+ T cells expressing the immune checkpoint receptors PD-1, TIGIT, and TIM-3 in HIV-1 patients, receptors that are positively associated with T cells that harbor latent HIV-1. Metformin also destabilized the latent viral reservoir in chronically-infected HIV-1 patients, indicating that metformin may indeed contribute to HIV-1 eradication by inducing an AMPK-mediated reactivation of latent HIV-1, as I initially proposed in 2015 and 2016 [4,5, 37-41].

Also, stress-induced AMPK activation likely also links latent HIV-1 reactivation with alleviation of accelerated aging defects in cells derived from children with the genetic disorder Hutchinson-Gilford progeria syndrome (HGPS). Studies have shown that efficient reactivation of latent HIV-1 involves a reduction in the splicing of the HIV-1 genome by the gene splicing factor SRSF1 [42-44]. Accelerated cellular aging-like phenotypes in HGPS are primarily linked to aberrant splicing of the LMNA gene, leading to the over production of a toxic protein called progerin [3]. Evidence has also shown that inhibition of the splicing factor SRSF1 leads to a reduction in progerin at both the mRNA and protein levels [4,45].

A recent study published online in the Journal npj Aging and Mechanisms of Disease in November of 2016 provided startling evidence that metformin decreased the expression of progerin and SRSF1 and alleviated pathological defects in cells derived from HGPS patients [46]. Another study published online in the Journal Experimental Dermatology in February of 2017 confirmed that metformin alleviated nuclear defects and premature aging phenotypes and activated AMPK in fibroblasts derived from HGPS patients, substantiating my original hypotheses from 2014 and 2015 proposing that AMPK activators including metformin would improve accelerated aging defects in HGPS cells by inhibiting SRSF1 and activating AMPK [3,4,47]. Temsirolimus, an analog of the macrolide rapamycin (which activates AMPK in vivo), also partially rescued the HGPS cellular phenotype but significantly increased the levels of ROS and superoxide within the first hour of treatment, providing further indication that the induction of cellular stress and subsequent AMPK activation links virus and pathogen elimination with alleviation of accelerated cellular aging defects in HGPS [48,49].

Furthermore, ROS and calcium are well-studied mediators of cellular stress-induced differentiation of embryonic and adult stem cells, AMPK has recently been shown to be essential for mouse embryonic stem cell differentiation, and metformin targets and promotes differentiation and/or apoptosis of cancer stem cells in the deadliest of cancers in an AMPK-dependent manner, including glioblastoma and pancreatic cancer [6]. Such evidence strongly suggests that cellular stress-induced AMPK activation by compounds including metformin links pathogen and virus elimination with HGPS and cancer stem cell differentiation and/or apoptosis, a hypothesis that I first proposed in 2017 [6].

Lastly, AMPK activation also promotes oocyte meiotic induction and maturation (processes that are critical for efficient oocyte activation) and AMPK has recently been found localized across the entire acrosome in human spermatozoa [5,50,51]. The induction of cellular stress (e.g. increases in ROS, intracellular calcium, and/or AMP/ATP ratio increase), which activates AMPK, also promotes oocyte meiotic induction/maturation, oocyte activation, and the acrosome reaction in human sperm, processes critical for the creation of all human life [50,52,53]. Indeed, oocyte activation is indispensable for the creation of all human life and the bacteria-derived calcium ionophore ionomycin, which activates AMPK, is commonly used to promote latent HIV-1 reactivation and is extensively used to activate human oocytes, creating normal healthy children (i.e. the “shock and live” approach) [53-57]. Such evidence indicates and further substantiates the novel and provocative assertion that AMPK activation links Zika virus inhibition and pathogen elimination with the amelioration of accelerated aging defects in HGPS cells, HIV-1 latency and replication, adult and cancer stem cells, and the creation of all human life [1,3-6]. 

https://www.linkedin.com/pulse/metformin-shown-first-time-inhibit-zika-virus-human-umbilical-finley/

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