The
db gene homozygous, but not heterozygous, mice develop diabetes with severe β-cell damage. We investigated the molecular mechanism underlying
db gene-associated pancreatic β-cell dysfunction. Islet morphology, β-cell function, and gene expression profiles specific for pancreatic islet cells were compared among
db gene homozygous(
db/db), heterozygous (
db/m) and unrelated
m/m mice. The β-cell ratio decreased in
db/db mice with age, but not in non-diabetic
db/m and
m/m mice. The islet insulin content was lower, but the triglyceride content was higher in
db/db than other mice. The islet cell specific gene expression profiles analyzed by laser capture microdissection method and morphological findings suggested an augmentation of β-cell apoptosis, oxidative stress and ER stress in
db/db mice. Interestingly, insulin I and II, anti-apoptotic bcl-2, and proliferation promoting ERK-1 gene expressions were significantly upregulated in
db/m mice. An impaired glucose tolerance was shown in
m/m mice fed a high fat diet, but not in
db/m mice, in which a higher insulin response and increased β-cell mass were observed. Expressions of insulin I and II, bcl-2, and ERK-1 gene were increased in
db/m mice, but not in
m/m fed a high fat diet. The present results strongly suggest that the
db gene heterozygote, but not homozygote, acquires a compensatory mechanism suppressing β-cell apoptosis and augmenting the capacity of β-cell function.
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