Insulin Receptor Genetic Variants Causal Association with Type 2 Diabetes: A Mendelian Randomization Study

Background

Type 2 diabetes (T2D) is a prevalent chronic disease associated with several comorbidities.

Objectives

This study investigated whether the risk of T2D varied with genetically predicted insulin (INS), insulin receptor (INS-R), or insulin-like growth factor 1 receptor (IGF-1R) using genetic variants in a Mendelian randomization (MR) study.

Methods

A 2-sample MR study was conducted using summary statistics from 2 genome-wide association studies (GWASs). Genetic predictors of the exposures (INS, INS-R, and IGF-1R) were obtained from a publicly available proteomics GWAS of the INTERVAL randomized controlled trial of blood donation in the United Kingdom. For T2D, the study leveraged the DIAbetes Meta-ANalysis of Trans-Ethnic association studies (DIAMANTE) consortium. The estimated associations of INS, INS-R, and IGF-1R proteins with T2D were based on independent single nucleotide polymorphisms (SNPs) strongly (P < 5 × 10-6) predicting each exposure. These SNPs were applied to publicly available genetic associations with T2D from the DIAMANTE case (n = 74,124) and control (n = 824,006) study of people of European descent. SNP-specific Wald estimates were meta-analyzed using inverse variance weighting with multiplicative random effects. Sensitivity analysis was conducted using the weighted median (WM) and MR-Egger.

Results

INS-R (based on 13 SNPs) was associated with a lower risk of T2D (OR: 0.95 per effect size; 95% CI: 0.92, 0.98; P = 0.001), with similar estimates from the WM and MR-Egger. Insulin (8 SNPs) and IGF-1R (10 SNPs) were not associated with T2D. However, 1 of the SNPs for INS-R was from the ABO blood group gene.

Conclusions

This study is consistent with a causally protective association of the INS-R with T2D. INS-R in RBCs regulates glycolysis and thus may affect their functionality and integrity. However, a pleiotropic effect via the blood group ABO gene cannot be excluded. The INS-R may be a target for intervention by repurposing existing therapeutics or otherwise to reduce the risk of T2D.

miR-497 may enhance the sensitivity of non-small cell lung cancer cells to gefitinib through targeting the insulin-like growth factor-1 receptor

Background

Recently, studies have demonstrated that microRNA-497 (miR-497) plays an important role in modulating tumor cell sensitivity to chemotherapeutic drugs; however, its role in cellular resistance to the effects of epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) in treatment of non-small cell lung cancer (NSCLC) is not fully understood. In this study, we explored the potential of miR-497 in targeting the insulin-like growth factor-1 receptor (IGF-1R) signaling pathways to overcome gefitinib resistance.

Methods

A gefitinib resistant human lung adenocarcinoma A549 cell line (A549/GR) was established by the method of gefitinib mutagenesis culture. Next, the A549/GR cells were transfected with miR-497 mimics to establish an miR-497 overexpression model, designated A549/GR-miR497-mimic. MTT assay was used to assess cell resistance to gefitinib, and western blot assay was employed to evaluate alterations of IGF-1R and the AKT1 signaling pathway.

Results

We found that A549/GR-miR497-mimic cells (IC50 =33.76±0.97 µmol/L) were more sensitive to gefitinib than the control group (P<0.01). In addition, the expression levels of IGF-1R and phosphorylated AKT1 (p-AKT1) in A549/GR-miR497-mimic cells were reduced.

Conclusions

We demonstrated that miR-497 may have the effect of reversing gefitinib resistance and increasing the sensitivity of NSCLC cells to EGFR-TKIs by inhibiting the expression of IGF-1R and reducing activation of the downstream AKT signaling pathway. Thus, miR-497 plays a vital role in the acquired resistance to EGFR-TKIs, and it may represent a potential therapeutic strategy to treat NSCLC exhibiting resistance to EGFR-TKIs.

[Effects of electroacupuncture at "Zhongliao" (BL 33) and "Tianshu" (ST 25) on ovarian function in rats with premature ovarian insufficiency]

OBJECTIVE

To explore the effects of electroacupuncture (EA) at "Zhongliao" (BL 33) and "Tianshu" (ST 25) on ovarian function in rats with premature ovarian insufficiency (POI).

METHODS

A total of 48 SD female rats with regular estrus were divided into a blank group (n=8), a model group (n=10), an EA group (n=10), a binding group (n=10) and a tamoxifen (TAM) group (n=10). The rats in the model group, EA group, binding group and TAM group were all treated with intraperitoneal injection of 4-vinylcyclohexene diepoxide (VCD, 160 mg/kg) for 15 consecutive days to establish the model of POI; the rats in the blank group were treated with normal diet. After the model was established successfully, the rats in the EA group were treated with EA at "Zhongliao" (BL 33) and "Tianshu" (ST 25) with continuous wave (1 to 3 Hz, 0.1 to 1 mA) for 20 minutes, once a day (five times a week) for the first two weeks and once every other day (three times a week) for the following two weeks. The rats in the TAM group were treated with subcutaneous injection of tamoxifen (1mg/kg), once a day (five times a week) for the first two weeks and once every other day (three times a week) for the following two weeks. The rats in the binding group were bound by a small sack as the EA group. The rats in the blank group and the model group were treated with normal diet. After four weeks, the sexual gland weight and index were tested in each group; the ELISA method was applied to test the level of anti-mllerian hormone (AMH) and inhibin B; the morphology of ovary was observed; the number of primordial follicles, primary follicle, antral follicle and atretic follicle was counted; the expression of insulin-like growth factor-1 (IGF-1) and insulin-like growth factor-1 receptor (IGF-1R) were measured.

RESULTS

(1) Compared with the blank group, the ovary weight, ovary index, uterus weight and uterus index were significantly decreased after treatment in the model group, EA group, binding group and TAM group (all P<0.01); but the differences between the model group and the EA group, binding group, TAM group were not significant (all P>0.05). (2) Compared with the blank group, the levels of serum AMH, inhibin B and E₂ were significantly reduced; the levels of FSH and LH were significantly increased in the model group; EA group, binding group and TAM group (all P<0.01). Compared with the model group, the levels of serum AMH, inhibin B and E₂ were significantly increased, the level of FSH and LH were significantly reduced in the EA group and TAM group (all P<0.01). (3) Compared with the blank group, in the model group, EA group, binding group and TAM group the ovary was dark red and pale, surrounded by particle or not; the morphology was small and atrophic; the primordial follicles was reduced even vanished; the structure of primary follicle was damaged and loosely arranged; the mature follicle was few; the atretic follicle and interstitial gland were increased. (4) Compared with the blank group, the expressions of IGF-1 mRNA and IGF-1R mRNA were increased in the model group (all P<0.01); compared with the blank group, the expression of IGF-1 mRNA was increased in the binding group (P<0.05), but that of IGF-1R mRNA was not significantly different (P>0.05); compared with the model group, the expression of IGF-1 mRNA was not significantly different in the EA group, binding group and TAM group (all P>0.05), but that of IGF-1R mRNA was reduced (P<0.05, P<0.01).

CONCLUSION

EA at "Zhongliao" (BL 33) and "Tianshu" (ST 25) has improvement effect on ovarian function in rats with VCD-induced POI, which is likely to be related to regulating the IGF-1R mRNA expression to improve the IGF-1/ IGF-1R axis.

Targeting the insulin growth factor-1 receptor with fluorescent antibodies enables high resolution imaging of human pancreatic cancer in orthotopic mouse models

The goal of the present study was to determine whether insulin-like growth factor-1 receptor (IGF-1R) antibodies, conjugated with bright fluorophores, could enable visualization of pancreatic cancer in orthotopic nude mouse models. IGF-1R antibody (clone 24-31) was conjugated with 550 nm or 650 nm fluorophores. Western blotting confirmed the expression of IGF-1R in Panc-1, BxPC3, and MIAPaCa-2 human pancreatic cancer cell lines. Labeling with fluorophore-conjugated IGF-1R antibody demonstrated fluorescent foci on the membrane of the pancreatic cancer cells. Subcutaneous Panc-1, BxPC-3, and MIA PaCa-2 tumors became fluorescent after intravenous administration of fluorescent IGF-1R antibodies. Orthotopically-transplanted BxPC-3 tumors became fluorescent with the conjugated IGF-1R antibodies, and were easily visible with intravital imaging. Gross and microscopic ex vivo imaging of resected pancreatic tumor and normal pancreas confirmed that fluorescence indeed came from the membrane of cancer cells, and it was stronger from the tumor than the normal tissue. The present study demonstrates that fluorophore-conjugated IGF-1R antibodies can visualize pancreatic cancer and it can be used with various imaging devices such as endoscopy and laparoscopy for diagnosis and fluorescence-guided surgery.