Figure 3 

Metformin treatment of Mtb infected guinea pigs resolve lung lesions in the chronic stages of infection. Guinea pigs were treated orally with mock treatment (OraSweet) (A, C, E) or metformin (B, D, F) and euthanized during the acute (A, B), subacute (C, D) or chronic (E, F) stages of infection with the H37Rv strain of Mtb. The progression of disease from the acute to chronic stages of infection in mock treated animals showed progressive perilesional inflammation (arrows) that corresponded to a higher lung lesion burden. In contrast, in metformin treated guinea pigs, inflammatory cells in the acute and subacute stages of infection are predominately lymphocytes (L) with less peri-leional spread (arrowheads). In the chronic stages of infection in metformin treated animals the decreased overall lung lesion burden was accompanied by well-encapsulated granulomas that were sharply demarcated from the more normal lung parenchyma (arrowheads). (H) and (E) stain, 100× magnification.