Indirect and Direct Effects of SARS-CoV-2 on Human Pancreatic Islets
Recent studies have shown that SARS-CoV-2 infection may induce metabolic distress, leading to hyperglycemia in patients affected by COVID-19. We investigated the potential indirect and direct effects of SARS-CoV-2 on human pancreatic islets in 10 patients who became hyperglycemic after COVID-19. While there was no evidence of peripheral anti-islet autoimmunity, the serum of these patients displayed toxicity on human pancreatic islets, which can be abrogated by the use of anti-IL1b, anti-IL-6 and anti-TNF-a, cytokines known to be highly upregulated during COVID-19. Interestingly, the receptors of those aforementioned cytokines were highly expressed on human pancreatic islets. An increase in peripheral unmethylated INS DNA, a marker of cell death, was evident in several patients with COVID-19. Pathology of the pancreas from deceased hyperglycemic patients who had COVID-19, revealed mild lymphocytic infiltration of pancreatic islets and pancreatic lymph nodes. Moreover, SARS-CoV-2-specific viral RNA, along with the presence of several immature insulin granules or proinsulin, were detected in post-mortem pancreatic tissues, suggestive of β-cell altered proinsulin processing, as well as β-cell degeneration and hyperstimulation. These data demonstrate that SARS-CoV-2 may negatively affect human pancreatic islets function and survival by creating inflammatory conditions and possibly with a direct tropism, which may in turn lead to metabolic abnormalities observed in patients with COVID-19.