Sustained beta cell apoptosis in patients with long-standing type 1 diabetes: indirect evidence for islet regeneration?

Abstract

Aims/hypothesis: Type 1 diabetes is widely held to result from an irreversible loss of insulin-secreting beta cells. However, insulin secretion is detectable in some people with long-standing type 1 diabetes, indicating either a small population of surviving beta cells or continued renewal of beta cells subject to ongoing autoimmune destruction. The aim of the present study was to evaluate these possibilities. Materials and methods: Pancreatic sections from 42 individuals with type 1 diabetes and 14 non-diabetic individuals were evaluated for the presence of beta cells, beta cell apoptosis and replication, T lymphocytes and macrophages. The presence and extent of periductal fibrosis was also quantified. Results: Beta cells were identified in 88% of individuals with type 1 diabetes. The number of beta cells was unrelated to duration of disease (range 4-67 years) or age at death (range 14-77 years), but was higher (p<0.05) in individuals with lower mean blood glucose. Beta cell apoptosis was twice as frequent in type 1 diabetes as in control subjects (p<0.001), but beta cell replication was rare in both groups. The increased beta cell apoptosis in type 1 diabetes was accompanied by both increased macrophages and T lymphocytes and a marked increase in periductal fibrosis (p<0.001), implying chronic inflammation over many years, consistent with an ongoing supply of beta cells. Conclusions/interpretation: Most people with long-standing type 1 diabetes have beta cells that continue to be destroyed. The mechanisms underlying increased beta cell death may involve both ongoing autoimmunity and glucose toxicity. The presence of beta cells despite ongoing apoptosis implies, by definition, that concomitant new beta cell formation must be occurring, even after long-standing type 1 diabetes. We conclude that type 1 diabetes may be reversed by targeted inhibition of beta cell destruction.

Direct evidence of attempted beta cell regeneration in an 89-year-old patient with recent-onset type 1 diabetes

“…2 and 3), consistent with the clinical diagnosis of recent-onset type 1 diabetes. The extent of islet infiltration was much more pronounced than in the cases of longstanding type 1 diabetes studied previously by our group [7], and appeared similar to that typically found at diabetes onset in NOD mice [9]. Interestingly, the appearance of this infiltration was quite heterogeneous, some islets being completely unaffected and others showing a marked invasion of T lymphocytes.…”

“…These data affirm that increased beta cell apoptosis is present in humans with type 1 diabetes, as previously reported in non-obese diabetic (NOD) mice [8]. The presence of beta cells with ongoing beta cell apoptosis up to 60 years after the onset of type 1 diabetes also provided indirect evidence of ongoing beta cell formation in patients with longstanding type 1 diabetes [7]. These studies were limited because, among other reasons, the pancreas tissue was obtained at autopsy and there were insufficient beta cells to establish whether the source of the putative new beta cell formation was beta cell replication.…”

“…It has long been recognised that a few beta cells can still be identified in pancreas tissue from people with longstanding type 1 diabetes [4][5][6]. We recently reported that beta cells in longstanding type 1 diabetes have increased apoptosis and are associated with a low-grade immune infiltrate [7]. These data affirm that increased beta cell apoptosis is present in humans with type 1 diabetes, as previously reported in non-obese diabetic (NOD) mice [8].…”

“…Specimens from five areas of the pancreas were fixed in formaldehyde and embedded in paraffin for subsequent analysis as described previously [7]. Sequential 5 μm sections from each block were stained as follows: (1) haematoxylin and eosin for light microscopy; (2) insulin (peroxidase staining) and haematoxylin for light microscopy; (3) insulin, terminal deoxynucleotidyl transferasemediated dUTP-biotin nick-end labelling (TUNEL) and 4,6-diamidino-2-phenylindole (DAPI) (immunofluorescence); (4) insulin, Ki67 and DAPI (immunofluorescence); (5) insulin, CD3, CD68 (immunofluorescence); (6) insulin, CD4 and DAPI (immunofluorescence); (7) insulin and CD8 (immunofluorescence); and (8) glucagon (peroxidase staining) and haematoxylin for light microscopy.…”

“…To measure the fractional alpha and beta cell areas, each pancreatic section was imaged at 40× magnification (4× objective), and the ratios of alpha cell area or beta cell area to the exocrine area were quantified digitally as previously described [7] using Image Pro Plus software (Media Cybernetics, Silver Springs, MD, USA).…”