Diabetes mellitus, tuberculosis and the mycobacteria: two millenia of enigma.

The thought that tuberculosis and the mycobacteria could cause diabetes seems farfetched, but is not. The peculiar relationship and frequent association of diabetes mellitus and tuberculosis has been observed for more than 2000 years, yet the reason for this correlation is, to this day, not known. Before the discovery of insulin, a diagnosis of diabetes was a death sentence within 5 years, and the usual cause of that death was tuberculosis. Despite this, in the 5th century, tuberculosis was already being portrayed as a "complication" of diabetes, a view little changed to this day, parroting Root's original 1934 description of "a one-sided relationship": tuberculosis still seen as a common complication of diabetes, while diabetes is thought to be no more common among TB patients than in the population at large. To Nichol's, this was "not logically tenable" and in his study of 178 otherwise healthy, non-diabetic military men with tuberculosis at Fitzsimmons Army Hospital, one-third had abnormal glucose screening tests. But despite his findings and those of Reaud in New York and others, this was not being recognized elsewhere, and Nichols wanted to know why. Nichols concluded that the incidence of diabetes among tuberculosis patients was considerably underestimated and that in tuberculosis patients, diabetes develops quite commonly. Diabetes was easy to detect. Tuberculosis and the mycobacteria were not. The evidence for a mycobacterial cause of diabetes is mounting rapidly. Schwartz and Haas both linked Type-2 diabetes to tuberculosis. And the pancreatic islet amyloid deposits that they found as a by-product of systemic tubercular infection have recently been dissolved by rifampicin, a first line drug against tuberculosis. Engelbach spoke of "transitory" diabetes in TB and Karachunskii noted changes in carbohydrate metabolism in patients with tuberculosis which commonly led to insulin deficiency with persistent hyperglycemia. Furthermore, mycobacterial elements have been shown recently not only to cause "autoimmune" Type-1 diabetes in NOD (non-obese diabetic) mice, but act as a vaccine to stop the inevitable diabetes that would otherwise materialize. The documentation of patient cases where TB has preceded and come before the development of diabetes is extensive yet underplayed and both Lin's and Tsai's studies speak of tuberculosis complicated by diabetes. Diabetes has been around since the first century AD, in a perpetual state of coping and managing. It is time, it is long past time, to cure diabetes. But current models as to its cause are not equipping us to do so.