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


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
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.
Meier
J J
JJ
Larry Hillblom Islet Research Center, UCLA David Geffen School of Medicine, Los Angeles, CA 90095-7073, USA.
Bhushan
A
A
Butler
A E
AE
Rizza
R A
RA
Butler
P C
PC
D000293:Adolescent; D000328:Adult; D000368:Aged; D017209:Apoptosis / Q000502:physiology; D001786:Blood Glucose / Q000378:metabolism; D017252:CD3 Complex; D016022:Case-Control Studies; D002452:Cell Count; D003922:Diabetes Mellitus, Type 1 / Q000209:etiology / Q000473:pathology*; D005260:Female; D005355:Fibrosis; D006801:Humans; D066298:In Vitro Techniques; D050417:Insulin-Secreting Cells / Q000473:pathology*; D008264:Macrophages / Q000473:pathology; D008297:Male; D008875:Middle Aged; D010179:Pancreas / Q000502:physiology*; D012038:Regeneration; D013601:T-Lymphocytes / Q000473:pathology
D001786:Blood Glucose; D017252:CD3 Complex