The global prevalence of obesity is increasing across most ages in both sexes. This is contributing to the early emergence of type 2 diabetes and its related epidemic. Having either parent obese is ...an independent risk factor for childhood obesity. Although the detrimental impacts of diet-induced maternal obesity on adiposity and metabolism in offspring are well established, the extent of any contribution of obese fathers is unclear, particularly the role of non-genetic factors in the causal pathway. Here we show that paternal high-fat-diet (HFD) exposure programs β-cell 'dysfunction' in rat F(1) female offspring. Chronic HFD consumption in Sprague-Dawley fathers induced increased body weight, adiposity, impaired glucose tolerance and insulin sensitivity. Relative to controls, their female offspring had an early onset of impaired insulin secretion and glucose tolerance that worsened with time, and normal adiposity. Paternal HFD altered the expression of 642 pancreatic islet genes in adult female offspring (P < 0.01); genes belonged to 13 functional clusters, including cation and ATP binding, cytoskeleton and intracellular transport. Broader pathway analysis of 2,492 genes differentially expressed (P < 0.05) demonstrated involvement of calcium-, MAPK- and Wnt-signalling pathways, apoptosis and the cell cycle. Hypomethylation of the Il13ra2 gene, which showed the highest fold difference in expression (1.76-fold increase), was demonstrated. This is the first report in mammals of non-genetic, intergenerational transmission of metabolic sequelae of a HFD from father to offspring.
Aims/hypothesis
Hypoxia may contribute to beta cell failure in type 2 diabetes and islet transplantation. The adaptive unfolded protein response (UPR) is required for endoplasmic reticulum (ER) ...homeostasis. Here we investigated whether or not hypoxia regulates the UPR in beta cells and the role the adaptive UPR plays during hypoxic stress.
Methods
Mouse islets and MIN6 cells were exposed to various oxygen (O
2
) tensions. DNA-damage inducible transcript 3 (DDIT3), hypoxia-inducible transcription factor (HIF)1α and HSPA5 were knocked down using small interfering (si)RNA;
Hspa5
was also overexpressed.
db/db
mice were used.
Results
Hypoxia-response genes were upregulated in vivo in the islets of diabetic, but not prediabetic,
db/db
mice. In isolated mouse islets and MIN6 cells, O
2
deprivation (1–5% vs 20%; 4–24 h) markedly reduced the expression of adaptive UPR genes, including
Hspa5
,
Hsp90b1
,
Fkbp11
and spliced
Xbp1
. Coatomer protein complex genes (
Copa
,
Cope
,
Copg
also known as
Copg1
,
Copz1
and
Copz2
) and ER-to-Golgi protein trafficking were also reduced, whereas apoptotic genes (
Ddit3
,
Atf3
and
Trb3
also known as
Trib3
), c-Jun N-terminal kinase (JNK) phosphorylation and cell death were increased. Inhibition of JNK, but not HIF1α, restored adaptive UPR gene expression and ER-to-Golgi protein trafficking while protecting against apoptotic genes and cell death following hypoxia. DDIT3 knockdown delayed the loss of the adaptive UPR and partially protected against hypoxia-induced cell death. The latter response was prevented by HSPA5 knockdown. Finally,
Hspa5
overexpression significantly protected against hypoxia-induced cell death.
Conclusions/interpretation
Hypoxia inhibits the adaptive UPR in beta cells via JNK and DDIT3 activation, but independently of HIF1α. Downregulation of the adaptive UPR contributes to reduced ER-to-Golgi protein trafficking and increased beta cell death during hypoxic stress.
It is well established that regular physiological stimulation by glucose plays a crucial role in the maintenance of the beta-cell differentiated phenotype. In contrast, prolonged or repeated exposure ...to elevated glucose concentrations both in vitro and in vivo exerts deleterious or toxic effects on the beta-cell phenotype, a concept termed as glucotoxicity.
OBJECTIVECytokines contribute to I2-cell destruction in type 1 diabetes. Endoplasmic reticulum (ER) stressamediated apoptosis has been proposed as a mechanism for I2-cell death. We tested whether ER ...stress was necessary for cytokine-induced I2-cell death and also whether ER stress gene activation was present in I2-cells of the NOD mouse model of type 1 diabetes. RESEARCH DESIGN AND METHODSINS-1 I2-cells or rat islets were treated with the chemical chaperone phenyl butyric acid (PBA) and exposed or not to interleukin (IL)-1I2 and I3-interferon (IFN-I3). Small interfering RNA (siRNA) was used to silence C/EBP homologous protein (CHOP) expression in INS-1 I2-cells. Additionally, the role of ER stress in lipid-induced cell death was assessed. RESULTSCytokines and palmitate triggered ER stress in I2-cells as evidenced by increased phosphorylation of PKR-like ER kinase (PERK), eukaryotic initiation factor (EIF)2I-, and Jun NH sub(2)-terminal kinase (JNK) and increased expression of activating transcription factor (ATF)4 and CHOP. PBA treatment attenuated ER stress, but JNK phosphorylation was reduced only in response to palmitate, not in response to cytokines. PBA had no effect on cytokine-induced cell death but was associated with protection against palmitate-induced cell death. Similarly, siRNA-mediated reduction in CHOP expression protected against palmitate- but not against cytokine-induced cell death. In NOD islets, mRNA levels of several ER stress genes were reduced (ATF4, BiP binding protein, GRP94 glucose regulated protein 94, p58, and XBP-1 X-box binding protein 1 splicing) or unchanged (CHOP and Edem1 ER degradation enhancer, mannosidase I-alike 1). CONCLUSIONSWhile both cytokines and palmitate can induce ER stress, our results suggest that, in contrast to lipoapoptosis, the PERK-ATF4-CHOP ER stressasignaling pathway is not necessary for cytokine-induced I2-cell death.
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