It doesn’t appear that men are more likely to contract diabetes than women; the likelier explanation is that women are better than men at following health advice.
Moreover, the actual problem with Type II diabetes (the most common form) is the systemic inflammation caused by the elevated serum insulin levels resulting from insulin resistance (caused, as we might expect, by a high-carbohydrate diet). I believe it is probably this inflammation that makes people more vulnerable to coronavirus. [Edit: The notion that glucose might feed the virus, which several posts mention, also makes a great deal of sense.]
Because Type I diabetes was the first to be noticed and described over two thousand years ago, the customary thinking is that diabetes is a problem with the regulation of serum glucose (since elevated serum glucose is the most noticeable symptom). However, all types of diabetes are better described as problems with insulin regulation.
Type I is an autoimmune disease, in which the immune system selectively attacks and destroys the beta cells of the Islets of Langerhans in the pancreas. These are the cells that synthesise and secrete insulin, and without a certain minimum level of insulin in the bloodstream, we essentially starve to death. This was the usual fate of Type I diabetics until the discovery of insulin in 1921.
Type II and Type III (Alzheimer’s disease) are problems of excessive insulin resulting from insulin resistance, which is the opposite problem from that found in Type I. Typically, insulin resistance is caused by excessive carbohydrate intake.
Type III diabetes is a problem with glucose metabolism in the brain, whereas Type II is a problem with elevated serum insulin, which leads to hypertension, atherosclerosis, glycated haemoglobin (and the associated increase risk of stroke and myocardial infarction), gout, obesity, certain cancers, and the other conditions considered to be part of metabolic syndrome. In Type II diabetes, the problem is not so much that the glucose metabolism doesn’t work, but rather that insulin resistance has increased to the point where high levels of insulin in the bloodstream are no longer as effective at stimulating glucose metabolism as they would be in a healthy person. In other words, cells can still metabolise glucose just fine, but they have shut down most of the insulin receptors that instruct them to do so.
The late Dr. Joseph Kraft, who studied Type II diabetes extensively, believed that it was an error to withhold a diagnosis of Type II until the insulin resistance got to the point where serum glucose was out of control. He believed that it was possible to diagnose Type II as much as twenty years earlier, by conducting an oral glucose tolerance test (OGTT) and analysing the results. The problem is that OGTT’s are labour-intensive and therefore expensive, so doctors don’t like to prescribe them and insurance companies don’t like to pay for them.