Spontaneous diabetes mellitus in transgenic mice expressing human islet amyloid polypeptide.

Abstract

The islet in non-insulin-dependent diabetes mellitus (NIDDM) is characterized by loss of ,B cells and large local deposits of amyloid derived from the 37-amino acid protein, islet amyloid polypeptide (IAPP Non-insulin-dependent diabetes mellitus (NIDDM) is characterized by (3-cell destruction and islet amyloid derived from islet amyloid polypeptide (IAPP) (1, 2). IAPP is a 37-amino acid protein that possesses amyloidogenic properties in species that spontaneously develop NIDDM (humans, monkeys, cats), but is non-amyloidogenic in mice that do not develop NIDDM (3, 4). Overexpression of human IAPP (h-IAPP), but not rat IAPP, in COS cells resulted in intracellular IAPP amyloidosis that was associated with cell death (5). Thus far, hemizygous transgenic mice for h-IAPP have not been reported to develop islet amyloid or diabetes mellitus spontaneously (6-8). Induction of marked insulin resistance in hemizygous mice transgenic for h-IAPP provokes intra-and extracellular IAPP amyloid formation, which is associated with 13-cell death and hyperglycemia (9).Based on these observations, we hypothesized that sufficiently increased rates of h-IAPP expression and synthesis results in intracellular IAPP amyloidosis and (3-cell death, which results in diabetes mellitus (10). To examine this further, we developed a homozygous line of mice transgenic for h-IAPP, thereby doubling the h-IAPP gene copy number. We report here that these mice spontaneously developed diabetes mellitus due to (3-cell death, which was associated with abnormal intra-and extracellular aggregates of h-IAPP. We conclude that overproduction of IAPP in vulnerable species (humans, monkeys, cats) may cause (3-cell destruction and diabetes mellitus. MATERIALS AND METHODSPreparation of Transgenic Construct. The RIPHAT transgene (2395 bp) is described elsewhere (9). It consists of a PCR-generated cDNA encompassing the h-IAPP coding sequence (270 bp) under the regulation of the rat insulin II promoter/5' untranslated region and followed by intron I (728 bp) from the human albumin gene and the polyadenylylation site/RNA termination region (525 bp) from the human glyceraldehyde-3-phosphate gene (GAPDH). Use of the albumin intron I and GAPDH polyadenylylation site in transgenic constructs has been described (11).Generation of Transgenic Mice. Hemizygotes of the RHF line described in Couce et al. (9) were self-crossed to generate Fl offspring. Transgenic offspring were identified by PCR amplification of RIPHAT from tail DNA. Hemizygotes were distinguished from homozygotes by backcross breeding to nontransgenic FVB/N mice. Homozygotes were defined as those mice that generated more than 20 transgenic and no nontransgenic offspring. Four such homozygotes were used to establish the core RHF breeding colony.Northern Blot Analysis. Total RNA was prepared from whole pancreata of FVB/N, RHF hemizygote, and RHF homozygote males and females. Gels and blots were prepared and hybridized as described (9)

Long-term effect of maternal obesity on pancreatic beta cells of offspring: reduced beta cell adaptation to high glucose and high-fat diet challenges in adult female mouse offspring

“…Whatever the mechanism of damage, it was evident that female offspring were significantly and reproducibly more sensitive than male offspring. Other type 2 diabetes models exhibit a sex bias; however, this is generally towards greater sensitivity of males [37,38]. Maternal obesity must have a different mode of damage to beta cells.…”

Islet amyloid: a complication of islet dysfunction or an aetiological factor in Type 2 diabetes?

“…Transgenic mice overexpressing the gene for human IAPP (hIAPP TM) have increased circulating IAPP which can be up to 30 times higher than the endogenous mouse IAPP [49, 91,92,93,94]; these are not necessarily associated with amyloidosis suggesting that increased concentration is not adequate alone to induce changes in peptide conformation [95,96]. Amyloid deposition in obese or fat-fed hIAPP TM is more frequent in males [96,97], is reversed by oestrogen treatment in obese male animals [98] and is increased in hIAPP females by oophorectomy despite no change in circulating concentrations of IAPP [99].…”

Peptide Conformation and Supramolecular Organization in Amylin Fibrils: Constraints from Solid-State NMR

“…It has been suggested that the toxicity of human amylin aggregates may be attributed to soluble oligomeric species and not to fibrils, based in part on the findings that certain transgenic mice (homozygous males that overexpress human amylin) develop hyperglycemia and insulin deficits prior to the appearance of detectable islet amyloid (94), and that rifampicin (a drug that may inhibit fibril formation but not oligomer formation) does not protect cultured β-cells from amylin-induced apoptosis (95). The interpretation of the rifampicin studies is unclear, given that Tomiyama et al show that rifampicin binds to, but does not inhibit or dissociate, amylin fibrils (96).…”