GCG and COVID-19: At the protein level, immunostaining in tissue samples from five COVID-19 patients and in SARS-CoV-2-infected human primary islets, confirmed an increased percentage of GCG (+)/INS(+) and Trypsin1 (+)/INS(+) cells, with lower INS and higher GCG and Trypsin1 (acinar cell marker) fluorescence intensity in β-cells (Tang et al., 2021).