A long noncoding RNA, LOC157273, is the effector transcript at the chromosome 8p23.1-PPP1R3B metabolic traits and type 2 diabetes risk locus

AbstractAimsCausal transcripts at genomic loci associated with type 2 diabetes are mostly unknown. The chr8p23.1 variant rs4841132, associated with an insulin resistant diabetes risk phenotype, lies in the second exon of a long non-coding RNA (lncRNA) gene, LOC157273, located 175 kilobases from PPP1R3B, which encodes a key protein regulating insulin-mediated hepatic glycogen storage in humans. We hypothesized that LOC157273 regulates expression of PPP1R3B in human hepatocytes.MethodsWe tested our hypothesis using Stellaris fluorescent in-situ hybridization to assess subcellular localization of LOC157273; siRNA knockdown of LOC157273, followed by RT-PCR to quantify LOC157273 and PPP1R3B expression; RNA-seq to quantify the whole-transcriptome gene expression response to LOC157273 knockdown and an insulin-stimulated assay to measure hepatocyte glycogen deposition before and after knockdown.ResultsWe found that siRNA knockdown decreased LOC157273 transcript levels by approximately 80%, increased PPP1R3B mRNA levels by 1.7-fold and increased glycogen deposition by >50% in primary human hepatocytes. An A/G heterozygous carrier (vs. three G/G carriers) had reduced LOC157273 abundance due to reduced transcription of the A allele and increased PPP1R3B expression and glycogen deposition.ConclusionWe show that the lncRNA LOC157273 is a negative regulator of PPP1R3B expression and glycogen deposition in human hepatocytes and the causal transcript at an insulin resistant type 2 diabetes risk locus.

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Degradation of IRS1 leads to impaired glucose uptake in adipose tissue of the type 2 diabetes mouse model TALLYHO/Jng

Journal of Endocrinology ◽

10.1677/joe-09-0026 ◽

2009 ◽

Vol 203 (1) ◽

pp. 65-74 ◽

Cited By ~ 25

Author(s):

Yun Wang ◽

Patsy M Nishina ◽

Jürgen K Naggert

Keyword(s):

Insulin Resistance ◽

Type 2 Diabetes ◽

Adipose Tissue ◽

Glucose Uptake ◽

Molecular Mechanisms ◽

Glucose Transporter ◽

Cytokine Signaling ◽

Mrna Levels ◽

Insulin Resistant

The TALLYHO/Jng (TH) mouse strain is a polygenic model for type 2 diabetes (T2D) characterized by moderate obesity, impaired glucose tolerance and uptake, insulin resistance, and hyperinsulinemia. The goal of this study was to elucidate the molecular mechanisms responsible for the reduced glucose uptake and insulin resistance in the adipose tissue of this model. The translocation and localization of glucose transporter 4 (GLUT4) to the adipocyte plasma membrane were impaired in TH mice compared to control C57BL6/J (B6) mice. These defects were associated with decreased GLUT4 protein, reduced phosphatidylinositol 3-kinase activity, and alterations in the phosphorylation status of insulin receptor substrate 1 (IRS1). Activation of c-Jun N-terminal kinase 1/2, which can phosphorylate IRS1 on Ser307, was significantly higher in TH mice compared with B6 controls. IRS1 protein but not mRNA levels was found to be lower in TH mice than controls. Immunoprecipitation with anti-ubiquitin and western blot analysis of IRS1 protein revealed increased total IRS1 ubiquitination in adipose tissue of TH mice. Suppressor of cytokine signaling 1, known to promote IRS1 ubiquitination and subsequent degradation, was found at significantly higher levels in TH mice compared with B6. Immunohistochemistry showed that IRS1 colocalized with the 20S proteasome in proteasomal structures in TH adipocytes, supporting the notion that IRS1 is actively degraded. Our findings suggest that increased IRS1 degradation and subsequent impaired GLUT4 mobilization play a role in the reduced glucose uptake in insulin resistant TH mice. Since low-IRS1 levels are often observed in human T2D, the TH mouse is an attractive model to investigate mechanisms of insulin resistance and explore new treatments.

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