Reversal of spontaneous Type 2 Diabetes by bone marrow transplant

Abstract

Hyperglycemia causes epigenetic changes associated with persistent activation of inflammatory pathways, a phenomenon known as 'metabolic memory'. Given the nature of the differentiation and the relatively short half-lives of leukocytes, particularly monocytes/macrophages in inflammation, memory of the innate immune system results from epigenetic imprint on bone marrow hematopoietic stem progenitor cells. An important epigenetic mark is the post-translational modification of histone proteins in their unstructured tails (acetylation, methylation, phosphorylation, and / or sumoilation) that influence their interaction with DNA and facilitate or repress gene transcription. Mono- or trimethylation of histone-H3 amino terminal tails in lysine-4 and 36 (H3K4me1, H3K36me3) are associated in vitro and in vivo with the persistence of hyperglycemia-induced proinflammatory condition. Reduction in H3K9 acetylation and H3K27 trimethylation also occurs by exposure to hyperglycemia in macrophages and is associated with increased proinflammatory gene expression. Given the key role of leukocyte recruitment in chronic inflammation present in DM, we hypothesized the existence of a proinflammatory metabolic memory in bone marrow progenitor cells in this condition. To support our hypothesis, we will perform bone marrow stem cell transplantation from normoglycemic Wistar (WT) rats to Goto-Kakizaki (GK) animals. These latter rats are spontaneously diabetic and do not develop obesity that could in itself promote inflammation. The opposite will also be done, as bone marrow transplantation of GK rats in WT. Recipient animals will be immunosuppressed by busulfan and cyclophosphamide. The following parameters will be evaluated in recipient animals: 1) circulating leukocyte recomposition after 7, 15 and 50 days post-transplantation, by blood count and flow cytometry using cell staining with specific antibodies (CD34, CD45RA, CD3, CD4, CD8, and CD11b); 2) glycemic profile by glucose and insulin tolerance tests; 3) femoral and tibial bone marrow for analysis inflammatory markers (IL-1² and CxCl2) by gene expression and IL-1² gene interaction with PU.1 and NF-ºB transcription factors and histones proteins (H3K4me, H3K36me3 , H3K27me3, H3K9ac) by western blot and chromatin immunoprecipitation (ChIP); and 4) hepatic tissue for its inflammatory profile (gene expression of IL-6 and IL-10) and metabolic assessed by glycogen content (sulfuric acid-phenol method) and liver enzyme activity (OGT and PGT). Bone marrow transplantation with stem cells from normoglycemic WT animals to GK may reverse or attenuate the diabetic condition of recipient animals. In turn, the bone marrow of GK animals can induce a diabetic condition in WT recipient animals. These results would prove that the diabetic state is associated with an inflammatory condition established in bone marrow leukocyte progenitor cells by epigenetic reprogramming. (AU)