SARS-CoV-2 infection of the pancreas promotes thrombofibrosis and is associated with new-onset diabetes

Evidence suggests an association between severe acute respiratory syndrome–cornavirus-2 (SARS-CoV-2) infection and the occurrence of new-onset diabetes. We examined pancreatic expression of angiotensin-converting enzyme 2 (ACE2) and transmembrane serine protease 2 (TMPRSS2), the cell entry factors for SARS-CoV-2, using publicly available single-cell RNA sequencing data sets, and pancreatic tissue from control male and female nonhuman primates (NHPs) and humans. We also examined SARS-CoV-2 immunolocalization in pancreatic cells of SARS-CoV-2–infected NHPs and patients who had died from coronavirus disease 2019 (COVID-19). We report expression of ACE2 in pancreatic islet, ductal, and endothelial cells in NHPs and humans. In pancreata from SARS-CoV-2–infected NHPs and COVID-19 patients, SARS-CoV-2 infected ductal, endothelial, and islet cells. These pancreata also exhibited generalized fibrosis associated with multiple vascular thrombi. Two out of 8 NHPs developed new-onset diabetes following SARS-CoV-2 infection. Two out of 5 COVID-19 patients exhibited new-onset diabetes at admission. These results suggest that SARS-CoV-2 infection of the pancreas may promote acute and especially chronic pancreatic dysfunction that could potentially lead to new-onset diabetes.

A new cell secreting insulin

The pancreatic beta-cell is the only cell in animals that expresses the insulin gene and secretes insulin protein. We have found copious release of immunoreactive and bioactive insulin into the medium from the primary culture of carp adipocytes. Glucose augmented this release to more than 2-fold, and glucose transporter, Glut2, was detected in these cells. These all reflect characteristics of a pancreatic beta-cell. The expression of the adipocyte-specific flotillin gene, the presence of peroxisomal proliferator-activated receptor gamma and Glut4, and the colocalization of insulin and leptin confirmed the identity of these cells as adipocytes. Purified carp adipocyte insulin (AdpInsl) comigrated with porcine and bovine insulin in SDS-PAGE, indicating the similarity of their molecular sizes (5.5 kDa). AdpInsl strongly reduced hyperglycemia in streptozotocin-induced diabetic rats. It also stimulated significantly higher glucose uptake in carp and hamster adipocytes than porcine insulin. Adipocyte RNA hybridized with rat and zebrafish insulin cDNA showing the expression of the insulin gene in this cell. Using oligonucleotide primers designed on the basis of conserved insulin domain, AdpInsl cDNA was reverse transcribed, cloned, and sequenced. The deduced amino acid sequence of AdpInsl A and B chain exhibited 98% homology with zebrafish and more than 70% homology with human, porcine, and murine insulin. To understand the structure-function relationship between AdpInsl and mammalian beta-cell insulin, we have analyzed the amino acid sequences and three-dimensional structure of AdpInsl. In the critical determinant segment for receptor binding, AdpInsl has His at the A8 position instead of Thr in human and porcine insulin, and this attributed greater biological activity to AdpInsl. Our results show that carp adipocyte is a unique cell. As an insulin target cell it can express the insulin gene and secrete highly active insulin protein; thus, it may serve as a natural alternative to pancreatic beta-cell insulin.

Effect of dietary fish oil on platelet aggregability: comparison between two oils with different eicosapentaenoic to arachidonic acid ratio

Rats, acclimatized on a control diet, were fed for 60 days with diets, supplemented with 10% fat of either marine Hilsa fish (Hilsa ilisa) or fresh-water Chital fish (Notopterus chitala). The percentage of eicosapentaenoic acid in chital oil diet was 0.57 times that of the hilsa oil diet, but the eicosapentaenoic to arachidonic acid ratio in the latter (4.08) was 3.2 times that of the former (1.27). Otherwise these two diets were comparable in respect to total saturated, monounsaturated and n-3 polyunsaturated fatty acid contents. Results showed that of the two only hilsa oil diet could significantly lower platelet aggregability and in vitro thromboxane production, through replacement of arachidonic acid in platelet phospholipid by eicosapentaenoic acid. The antithrombic criteria of the oil seems to be a combination of low arachidonic acid content and high eicosapentaenoic to arachidonic acid ratio.