ABSTRACT
Background: A major consequence of COVID-19 is long-term metabolic complications (metabolic PASC or Long COVID) following acute disease resolution leading to hyperglycemia, increased risk of diabetes or defects in glucose metabolism. However, the mechanisms underlying the links between COVID-19 and glycometabolic disruptions remain unclear. Method(s): 15 African green monkeys (AGM;Chlorocebus aethiops) were infected with SARS-CoV-2 (Wuhan stain) and divided into two groups: unvaccinated (n=10) and vaccinated (BNT162b2 (Pfizer) 4-days post infection;n=5). Subgenomic SARS-CoV-2 mRNA (sgRNA) reflecting active replication was quantified in nasal and pharyngeal swabs, and blood chemistry analysis was performed longitudinally up to 18 weeks post-infection. We quantified liver glycogen at necropsy using Periodic acid-Schiff staining. Finally, we longitudinally analyzed 96 plasma proteins using a proximity extension assay (Olink). STRING was used to identify enriched protein networks. Comparisons between the two groups over time were performed using PERMANOVA. Result(s): All animals had detectable sgRNA ( >3.64x106) at day 3, and only two were undetectable at week 5. Post-infection BNT162b2 vaccination partially inhibited the SARS-CoV-2 mediated disruption of glucose levels (P=0.001, Fig. 1A). Liver glycogen levels following necropsy correlated positively with blood glucose levels at week 12 (r=0.74, P =0.003). Histopathological analysis revealed no marked evidence of long-term inflammation or fibrosis of pancreatic islets. Using the plasma proteomic data, we identified a signature of 15 SARS-CoV-2-modulated plasma proteins coinciding with early onset hyperglycemia during acute infection (P=0.001, Fig. 1B). These proteins are enriched for biological processes linked to chemotaxis (FDR=1.38E-06), and viral protein interaction with cytokines (FDR=1.01E-12) (Fig. 1C). Of these, CCL25 and glial cell derived neurotrophic factor (GDNF) remained persistently elevated post-acute infection and correlated with blood glucose levels (r=0.57, P=0.0003;and r=0.64, P<0.0001, respectively, Fig. 1D). Conclusion(s): Our AGM model validates phenotypes of metabolic PASC and offers an opportunity to mechanistically study the manifestations of PASC. Our preliminary data suggest that vaccine-preventable early insults by metabolicregulating immune factors may contribute to long-term dysregulated liver and systemic glucose homeostasis during PASC. These immune factors warrant further investigation for their mechanistic links to PASC. (Figure Presented).
ABSTRACT
Drug addiction is a serious problem globally, recently exacerbated by the COVID-19 pandemic. Glial cell-derived neurotrophic factor (GDNF) is considered a potentially effective strategy for the treatment of addiction. Previous animal experiments have proven that GDNF has a good therapeutic effect on drug addiction, but its clinical application is limited due to its poor blood-brain barrier (BBB) permeability. Low-frequency focused ultrasound, combined with microbubbles, is a non-invasive and reversible technique for locally-targeted BBB opening. In the present study, magnetic resonance imaging-guided low-frequency focused ultrasound, combined with GDNF microbubbles, was used to target BBB opening in the ventral tegmental area (VTA) region. The effects of GDNF on morphine-induced conditioned place preference (CPP) and acute withdrawal symptoms in rats after a partially opened BBB were evaluated by behavioral observation. Western blot was used to detect changes in tyrosine hydroxylase (TH) expression levels in the VTA region after different treatments, and high performance liquid chromatography was used to detect the changes in monoamine neurotransmitter content. The results showed that ultrasound combined with GDNF microbubbles targeted and opened the BBB in the VTA region, and significantly increased GDNF content, destroyed morphine-induced CPP, and reduced the withdrawal symptoms of morphine addiction in rats. Furthermore, the up-regulation of TH expression and the increase of norepinephrine and dopamine content induced by morphine were significantly reversed, and the increase of 5-hydroxytryptamine content was partially reversed. Therefore, ultrasound combined with GDNF microbubbles to target and open the BBB can effectively increase the content of central GDNF, thus playing a therapeutic role in morphine addiction. Our study provides a new approach to locally open the BBB and target delivery of neurotrophic factors, such as GDNF, to treat brain diseases like addiction.