Genetic determinants of obesity heterogeneity in type II diabetes

Background

Although obesity is considered as the main cause of Type II diabetes (T2DM), non-obese individuals may still develop T2DM and obese individuals may not.

Method

The mRNA expression of PI3K/AKT axis from 100 non-obese and obese participants with insulin sensitivity and insulin resistance states were compared in this study toward the understanding of obesity heterogeneity molecular mechanism.

Result

In present study, there was no statistically significant difference in gene expression levels of IRS1 and PTEN between groups, whereas PI3K, AKT2 and GLUT4 genes were expressed at a lower level in obese diabetic group compared to other groups and were statistically significant. PDK1 gene was expressed at a higher level in non-obese diabetic group compared to obese diabetic and non-obese non-diabetics groups. No statistically significant difference was identified in gene expression pattern of PI3K/AKT pathway between obese non-diabetics and non-obese non-diabetics.

Conclusion

The components of PI3K/AKT pathway which is related to the fasting state, showed reduced expression in obese diabetic group due to the chronic over-nutrition which may induced insensitivity and reduced gene expression. The pathogenesis of insulin resistance in the absence of obesity in non-obese diabetic group could be due to disturbance in another pathway related to the non-fasting state like gluconeogenesis. Therefore, the molecular mechanism of insulin signalling in non-obese diabetic individuals is different from obese diabetics which more investigations are required to study insulin signalling pathways in greater depth, in order to assess nutritional factors, contribute to insulin resistance in obese diabetic and non-obese diabetic individuals.

Genetic Determinants of Obesity Heterogeneity in Type II Diabetes.. [DOI: 10.21203/rs.3.rs-18810/v2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

Background: Although obesity is considered as the main cause of Type II diabetes (T2DM), non-obese individuals may still develop T2DM and obese individuals may not. Method: The mRNA expression of PI3K/AKT axis from 100 non-obese and obese participants with insulin sensitivity and insulin resistance states were compared in this study toward the understanding of obesity heterogeneity molecular mechanism. Result: In present study, there was no statistically significant difference in gene expression levels of IRS1 and PTEN between groups, whereas PI3K, AKT2 and GLUT4 genes were expressed at a lower level in obese diabetic group compared to other groups and were statistically significant. PDK1 gene was expressed at a higher level in non-obese diabetic group compared to obese diabetic and non-obese non-diabetics groups. No statistically significant difference was identified in gene expression pattern of PI3K/AKT pathway between obese non-diabetics and non-obese non-diabetics.Conclusion: The components of PI3K/AKT pathway which is related to the fasting state, showed reduced expression in obese diabetic group due to the chronic over-nutrition which may induced insensitivity and reduced gene expression. The pathogenesis of insulin resistance in the absence of obesity in non-obese diabetic group could be due to disturbance in another pathway related to the non-fasting state like gluconeogenesis. Therefore, the molecular mechanism of insulin signalling in non-obese diabetic individuals is different from obese diabetics which more investigations are required to study insulin signalling pathways in greater depth, in order to assess nutritional factors, contribute to insulin resistance in obese diabetic and non-obese diabetic individuals.

Gene Expression Pattern of PI3K/AKT Pathway Based on Insulin Resistance and Vitamin D Toward the Understanding of T2DM Pathogenesis.. [DOI: 10.21203/rs.3.rs-22403/v1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

Background Insulin-stimulated glucose transport occurs via PI3K/AKT-dependent pathway which results in GLUT4 translocation from intracellular vesicles to plasma membrane and glucose uptake. PTEN, as a phosphatase, is the main antagonist of the PI3K/AKT pathway’s kinases. Present study was performed to investigate underlying mechanism responsible for defects in insulin signaling and the plausible role of vitamin D in pathogenesis of T2DM through the comparison of serum vitamin D and expression of genes involved in insulin signaling in diabetics and non-diabetics.Results RT-PCR was employed to investigate mRNA expression level of IRS1/PI3K/PDK1/AKT2/GLUT4/PTEN in diabetic and non-diabetic participants and serum vitamin D was measured by HPLC. Findings provide evidence that IRS1 expression was preserved while PI3K /AKT2/GLUT4 were expressed significantly lower and PDK1 was expressed significantly higher in diabetics compared to non-diabetics. Albeit there was no significant difference in PTEN expression between groups, it was up-regulated by the years of having diabetes. No significant correlation between serum vitamin D and gene expression of GOIs was observed in either group.Conclusion Since PTEN has been identified as a negative regulator of insulin signaling, it has generated great interest in new therapeutic approaches. This study reveals that insulin resistance is not caused through an alteration in PTEN expression as a primary defect but may be caused by decreased PI3K/AKT2/GLUT4 signalling and dysregulation of feedback loops. Particularly, PTEN expression showed a significant relation with duration of diabetes, suggesting that PTEN may not be the cause of the reduced expression of PI3K/AKT pathway in diabetics while it can be the effect of that. Therefore, the future investigations should be focused on regulators of pathway instead of PTEN. No significant correlation between serum vitamin D and gene expression of GOIs could be due to the non-linearity relationships as insulin signaling is a cascade with amplifying properties.

Comparative effect of vitamin E compounds on HSP70 expression in response to acute redox imbalance in Chang liver cells.. [DOI: 10.21203/rs.3.rs-22336/v1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

Abstract

Background: HSP70 represents the most highly induced member of the stress protein family which is constitutively expressed in normal cell conditions as chaperon and rapidly upregulated in response to stress conditions. Vitamin E compounds are considered to be the most potent oxidation chain breaking compounds. Although α-tocopherol, has been long considered as the most potent antioxidant among the vitamin E isomers, many studies have recently suggested a higher antioxidant potency of tocotrienols compared to tocopherols. Present study was carried out to investigate the effects of tocotrienol supplementation compared to α-tocopherol on HSP70 expression.Methods: To assess whether the increase in HSP70 secondary to the stress caused by the oxidant could decrease in the presence of vitamin E; two groups of cells were incubated for 4 hours with α-tocopherol and palm tocotrienol-rich fraction respectively with concentration of 10, 20 and 30 μg/ml after the cells were pre-exposed to oxidative stress.Results: The comparison between the negative control which represents the basal expression of HSP70 and the positive control that represents the expression of HSP70 as a response to the oxidant, has clearly indicated that treatment with 100 μM copper sulphates for 24 hours resulted in a significant up-regulation of HSP70 expression. The present study has shown that the overall effect of vitamin E compounds seems to reduce the increase in HSP70 expression. α-tocopherol tended to trigger a more constant rate of response to the dose given but unable to significantly induced the decrease of the HSP70 expression as compared to tocotrienol.Conclusion: Treatment with vitamin E has conferred significant protection against stress induced cellular damage. Whether the reduction of HSP70 by vitamin E is deleterious or beneficial is still controversial and needs to be considered.

Genetic Determinants of Obesity Heterogeneity in Type II Diabetes.. [DOI: 10.21203/rs.3.rs-18810/v1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

Background: Although obesity is considered as the main cause of Type II diabetes (T2DM), non-obese individuals may still develop T2DM and obese individuals may not. Method: The mRNA expression of insulin signalling components (PI3K/AKT axis) from 100 non-obese and obese participants with insulin sensitivity and insulin resistance states were compared in this study toward the understanding of obesity heterogeneity molecular mechanism. Result: In present study, there was no statistically significant difference in gene expression levels of IRS1 and PTEN between groups, whereas PI3K, AKT2 and GLUT4 genes were expressed at a lower level in obese diabetic group compared to other groups. PDK1 gene was expressed at a higher level in non-obese diabetic group compared to obese diabetic and non-obese non-diabetics groups. No statistically significant difference was identified in gene expression pattern of PI3K/AKT pathway between obese non-diabetics and non-obese non-diabetics. Conclusion: The components of PI3K/AKT pathway which is related to the fasting state, showed reduced expression in obese diabetic group due to the chronic over-nutrition which may induced insensitivity and reduced gene expression. The pathogenesis of insulin resistance in the absence of obesity in non-obese diabetic group could be due to disturbance in another pathway related to the non-fasting state like gluconeogenesis. Therefore, the molecular mechanism of insulin signalling in non-obese diabetic individuals is different from obese diabetics which more investigations are required to study insulin signalling pathways in greater depth, in order to assess nutritional factors contribute to insulin resistance in obese diabetic and non-obese diabetic individuals.

Vitamins D and E Stimulate the PI3K-AKT Signalling Pathway in Insulin-Resistant SK-N-SH Neuronal Cells

This study investigated the effects of vitamins D and E on an insulin-resistant model and hypothesized that this treatment would reverse the effects of Alzheimer’s disease (AD) and improves insulin signalling. An insulin-resistant model was induced in SK-N-SH neuronal cells with a treatment of 250 nM insulin and re-challenged with 100 nM at two different incubation time (16 h and 24 h). The effects of vitamin D (10 and 20 ng/mL), vitamin E in the form of tocotrienol-rich fraction (TRF) (200 ng/mL) and the combination of vitamins D and E on insulin signalling markers (IR, PI3K, GLUT3, GLUT4, and p-AKT), glucose uptake and AD markers (GSK3β and TAU) were determined using quantitative real-time polymerase chain reaction (qRT-PCR) and enzyme-linked immunosorbent assay (ELISA). The results demonstrated an improvement of the insulin signalling pathway upon treatment with vitamin D alone, with significant increases in IR, PI3K, GLUT3, GLUT4 expression levels, as well as AKT phosphorylation and glucose uptake, while GSK3β and TAU expression levels was decreased significantly. On the contrary, vitamin E alone, increased p-AKT, reduced the ROS as well as GSK3β and TAU but had no effect on the insulin signalling expression levels. The combination of vitamins D and E only showed significant increase in GLUT4, p-AKT, reduced ROS as well as GSK3β and TAU. Thus, the universal role of vitamin D, E alone and in combinations could be the potential nutritional agents in restoring the sensitivity of neuronal cells towards insulin and delaying the pathophysiological progression of AD.

The Modulation of NMDA and AMPA/Kainate Receptors by Tocotrienol-Rich Fraction and Α-Tocopherol in Glutamate-Induced Injury of Primary Astrocytes

Astrocytes are known as structural and supporting cells in the central nervous system (CNS). Glutamate, as a main excitatory amino acid neurotransmitter in the mammalian central nervous system, can be excitotoxic, playing a key role in many chronic neurodegenerative diseases. The aim of the current study was to elucidate the potential of vitamin E in protecting glutamate-injured primary astrocytes. Hence, primary astrocytes were isolated from mixed glial cells of C57BL/6 mice by applying the EasySep^® Mouse CD11b Positive Selection Kit, cultured in Dulbecco's modified Eagle medium (DMEM) and supplemented with special nutrients. The IC₂₀ and IC₅₀ values of glutamate, as well as the cell viability of primary astrocytes, were assessed with 100 ng/mL, 200 ng/mL, and 300 ng/mL of tocotrienol-rich fraction (TRF) and alpha-tocopherol (α-TCP), as determined by an 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The mitochondrial membrane potential (MMP) detected in primary astrocytes was assessed with the same concentrations of TRF and α-TCP. The expression levels of the ionotropic glutamate receptor genes (Gria2, Grin2A, GRIK1) were independently determined using RT-PCR. The purification rate of astrocytes was measured by a flow-cytometer as circa 79.4%. The IC₂₀ and IC₅₀ values of glutamate were determined as 10 mM and 100 mM, respectively. Exposure to 100 mM of glutamate in primary astrocytes caused the inhibition of cell viability of approximately 64.75% and 61.10% in pre- and post-study, respectively (p < 0.05). Both TRF and α-TCP (at the lowest and highest concentrations, respectively) were able to increase the MMP to 88.46% and 93.31% pre-treatment, and 78.43% and 81.22% post-treatment, respectively. Additionally, the findings showed a similar pattern for the expression level of the ionotropic glutamate receptor genes. Increased extracellular calcium concentrations were also observed, indicating that the presence of vitamin E altered the polarization of astrocytes. In conclusion, α-TCP showed better recovery and prophylactic effects as compared to TRF in the pre-treatment of glutamate-injured primary astrocytes.

The neuroprotective effects of tocotrienol rich fraction and alpha tocopherol against glutamate injury in astrocytes

Tocotrienol rich fraction (TRF) is an extract of palm oil, which consists of 25% alpha tocopherol (α-TCP) and 75% tocotrienols. TRF has been shown to possess potent antioxidant, anti-inflammatory, anticancer, neuroprotection, and cholesterol lowering activities. Glutamate is the main excitatory amino acid neurotransmitter in the central nervous system of mammalian, which can be excitotoxic, and it has been suggested to play a key role in neurodegenerative disorders like Parkinson's and Alzheimer's diseases. In this present study, the effects of vitamin E (TRF and α-TCP) in protecting astrocytes against glutamate injury were elucidated. Astrocytes induced with 180 mM of glutamate lead to significant cell death. However, glutamate mediated cytotoxicity was diminished via pre and post supplementation of TRF and α-TCP. Hence, vitamin E acted as a potent antioxidant agent in recovering mitochondrial injury due to elevated oxidative stress, and enhanced better survivability upon glutamate toxicity.

Cytoprotective Effect of Tocotrienol-Rich Fraction and α-Tocopherol Vitamin E Isoforms Against Glutamate-Induced Cell Death in Neuronal Cells

Glutamate is the major mediator of excitatory signals in the mammalian central nervous system. Extreme amounts of glutamate in the extracellular spaces can lead to numerous neurodegenerative diseases. We aimed to clarify the potential of the following vitamin E isomers, tocotrienol-rich fraction (TRF) and α-tocopherol (α-TCP), as potent neuroprotective agents against glutamate-induced injury in neuronal SK-N-SH cells. Cells were treated before and after glutamate injury (pre- and post-treatment, respectively) with 100 - 300 ng/ml TRF/α-TCP. Exposure to 120 mM glutamate significantly reduced cell viability to 76 % and 79 % in the pre- and post-treatment studies, respectively; however, pre- and post-treatment with TRF/α-TCP attenuated the cytotoxic effect of glutamate. Compared to the positive control (glutamate-injured cells not treated with TRF/α-TCP), pre-treatment with 100, 200, and 300 ng/ml TRF significantly improved cell viability following glutamate injury to 95.2 %, 95.0 %, and 95.6 %, respectively (p < 0.05).The isomers not only conferred neuroprotection by enhancing mitochondrial activity and depleting free radical production, but also increased cell viability and recovery upon glutamate insult. Our results suggest that vitamin E has potent antioxidant potential for protecting against glutamate injury and recovering glutamate-injured neuronal cells. Our findings also indicate that both TRF and α-TCP could play key roles as anti-apoptotic agents with neuroprotective properties.