Diabetes, obesity, and insulin resistance in COVID-19: molecular interrelationship and therapeutic implications

Background Our understanding of the pathophysiology of the COVID-19 manifestations and evolution has improved over the past 10 months, but the reasons why evolution is more severe in obese and diabetic patients are not yet completely understood. Main text In the present review we discuss the different mechanisms that may contribute to explain the pathophysiology of COVID-19 including viral entrance, direct viral toxicity, endothelial dysfunction, thromboinflammation, dysregulation of the immune response, and the renin–angiotensin–aldosterone system. Conclusions We show that the viral infection activates an integrated stress response, including activations of serine kinases such as PKR and PERK, which induce IRS-1 serine phosphorylation and insulin resistance. In parallel, we correlate and show the synergy of the insulin resistance of COVID-19 with this hormonal resistance of obesity and diabetes, which increase the severity of the disease. Finally, we discuss the potential beneficial effects of drugs used to treat insulin resistance and diabetes in patients with COVID-19.

Genome-wide, CRISPR-Cas9-based genetic screening for regulators of interferon-induced PD-L1 expression in AML cells.

116 Background: Expression of PD-L1 in AML cells is induced by pro-inflammatory signals, but how the induction is regulated is incompletely known. Genome-wide screening using the CRISPR-Cas9 technology could provide a strategy to interrogate the regulators of PD-L1 expression. Methods: A lentiviral CRISPR-Cas9 library, containing 3 sgRNA targeting each of 19,050 human genes (Nat Methods 2014, 11:783), was used to transduce THP-1 AML cells. Transduced cells were treated with IFN-γ and stained with an anti-PD-L1 antibody. Two subsets of cells were isolated by cell sorting according to their levels of PD-L1 expression. One subset consisted of cells that showed the median 5% of PD-L1 expression and the other subset, the lowest 5%. sgRNA integrated in the sorted subsets were amplified and their frequencies quantified by deep sequencing. Results: As expected, sgRNA targeting the PD-L1 gene itself were highly enriched in the subset that expressed a low level of PD-L1. sgRNA that targeted IFNGR2, β-chain of the IFN-γ receptor, were also enriched in this subset, whereas those for IFNGR1 were not. sgRNA targeting both JAK1 and JAK2 were enriched. By contrast, those for JAK3 and TYK2 were not. Enrichment was seen for sgRNA that targeted STAT1, a transcriptional activator downstream of JAK1/2, whereas sgRNA targeting the other STAT activators (STAT-2, 3, 4, 5A, 5B and 6) showed no enrichment. sgRNA targeting several serine kinases that regulate STAT1 phosphorylation (PKCδ, PKCε, PKCα, CAMKII, ERK, JNK, and CDK8) were not enriched. Nor were sgRNA targeting several phosphatases that modulate STAT1 activity (TC-PTP, PTPN1, SHP1 and SHP2). sgRNA targeting IRF1 (IFN regulatory transcription factor 1) were highly enriched, whereas sgRNA for IRF-2 to IRF-9 were not. In each of the affected genes, at least 2 out of the 3 sgRNA targeting the gene were enriched, indicating a generality of the findings. Conclusions: A CRISPR-Cas9-based screening strategy provided an unbiased interrogation of genes essential for PD-L1 expression on AML cells. It confirmed the importance of the IFNGR2-JAK1/2-STAT1-IRF1 axis, which could serve as targets for the development of drugs to suppress the ability of AML cells to evade host immunity.

Potential Roles ofStevia rebaudianaBertoni in Abrogating Insulin Resistance and Diabetes: A Review

Insulin resistance is a key factor in metabolic disorders like hyperglycemia and hyperinsulinemia, which are promoted by obesity and may later lead to Type II diabetes mellitus. In recent years, researchers have identified links between insulin resistance and many noncommunicable illnesses other than diabetes. Hence, studying insulin resistance is of particular importance in unravelling the pathways employed by such diseases. In this review, mechanisms involving free fatty acids, adipocytokines such as TNFαand PPARγand serine kinases like JNK and IKKβ, asserted to be responsible in the development of insulin resistance, will be discussed. Suggested mechanisms for actions in normal and disrupted states were also visualised in several manually constructed diagrams to capture an overall view of the insulin-signalling pathway and its related components. The underlying constituents of medicinal significance found in theStevia rebaudianaBertoni plant (among other plants that potentiate antihyperglycemic activities) were explored in further depth. Understanding these factors and their mechanisms may be essential for comprehending the progression of insulin resistance towards the development of diabetes mellitus.

Astaxanthin prevents loss of insulin signaling and improves glucose metabolism in liver of insulin resistant mice

This study investigates the effects of astaxanthin (ASX) on insulin signaling and glucose metabolism in the liver of mice fed a high fat and high fructose diet (HFFD). Adult male Mus musculus mice of body mass 25–30 g were fed either normal chow or the HFFD. After 15 days, mice in each group were subdivided among 2 smaller groups and treated with ASX (2 mg·(kg body mass)–1) in olive oil for 45 days. At the end of 60 days, HFFD-fed mice displayed insulin resistance while ASX-treated HFFD animals showed marked improvement in insulin sensitivity parameters. ASX treatment normalized the activities of hexokinase, pyruvate kinase, glucose-6-phosphatase, fructose-1,6-bisphosphatase, glycogen phosphorylase, and increased glycogen reserves in the liver. Liver tissue from ASX-treated HFFD-fed animals showed increased tyrosine phosphorylation and decreased serine phosphorylation of insulin receptor substrates (IRS)-1 and -2. ASX increased IRS 1/2 and phosphatidylinositol 3-kinase (PI3K) association and serine phosphorylation of Akt. In addition, ASX decreased HFFD-induced serine kinases (c-jun N-terminal kinase-1 and extracellular signal-regulated kinase-1). The results suggest that ASX treatment promotes the IRS–PI3K–Akt pathway of insulin signaling by decreasing serine phosphorylation of IRS proteins, and improves glucose metabolism by modulating metabolic enzymes.