Insulin Resistance Associated Genes and miRNAs

Lychee Seed as a Potential Hypoglycemic Agent, and Exploration of its Underlying Mechanisms

Food is people's primal want. A reasonable diet and healthy food not only provide nutrients for human growth but also contribute to disease prevention and treatment, while following an unhealthy diet can lead to an increased risk of many diseases, especially metabolic disorders, such as diabetes. Nature is enriched with different food sources, and it seems that purely natural products are more in line with the current concept of health, which enhance the formation of the notion that "Food/Diet Supplements from Natural Sources as a Medicine." As a delicious fruit, the medicinal values such as anticancer, antibacterial, antioxidation, and antiglycating properties of lychee have been found. Lychee (Litchi in Chinese) is a subtropical fruit plant belonging to the family Sapindaceae. It has been widely cultivated in warm climates worldwide, particularly in China, for thousands of years. In recent years, various phytochemical components such as quercetin, procyanidin A2, and (2R)-naringenin-7-O-(3-O-αL-rhamnopyranosyl-β-D-glucopyranoside) have been identified in a lychee seed, which may lend a lychee seed as a relatively safe and inexpensive adjuvant treatment for diabetes and diabetic complications. In fact, accumulating evidence has shown that lychee seed, lychee seed extracts, and related compounds have promising antihyperglycemic activities, including improving insulin resistance, anti-inflammatory effect, lipid regulation, neuroprotection, antineurotoxic effect, and renoprotection effect. In this review, we summarized publications on antiglycemic effects and mechanisms of lychee seed, lychee seed extracts, and related compounds, which included their efficacies as a cure for diabetes and diabetic complications in cells, animals, and humans, attempting to obtain a robust evidence basis for the clinical application and value of lychee seed.

Metformin downregulates miR223 expression in insulin-resistant 3T3L1 cells and human diabetic adipose tissue

AIMS AND DESIGNS

Metformin, an anti-diabetic drug, is the first line medication for the treatment of type 2 diabetes mellitus and some studies show its relationship with micro-RNAs. This study set up to determine the effect of metformin on miR223 expression and content of AKT/GLUT4 proteins in insulin resistant signaling in 3T3L1 cells and adipocyte of human diabetic patients.

MATERIALS AND METHODS

Subcutaneous adipose tissues were taken from newly diagnosed diabetic patients (HOMA-IR > 1.8), before and after three months treatment with 500 mg of metformin twice a day. Cellular homogenate was prepared and miR223 expression and AKT/GLUT4 protein expression were determined by quantitative real-time PCR and western blotting. The results were compared to insulin resistant 3T3L1 adipocytes that were treated with 10 mM Metformin.

RESULTS

MiR223 expression was significantly overexpressed both in insulin-resistant 3T3L1 adipocytes compared to non-insulin resistant adipocytes and in human diabetic adipose tissue, compared to non-diabetics (P value < 0.01). Metformin treatment downregulated miR223 expression in both adipocytes and human diabetic adipose tissue. In contrast the IRS/PI3-K/AKT pathway signaling components, Akt and GLUT4 increased in insulin-resistant 3T3L1 adipocytes and human diabetic adipose tissue after three months of metformin treatment.

CONCLUSIONS

Metformin reduced insulin resistance in adipocytes by reduction of miR223 expression and improving of IRS/Akt/GLUT4 signaling pathways. Plasma miR223 expression of human diabetic patients was reduced by metformin treatment. These results point to a novel mechanism of miR223 in insulin resistance.

Descending Expression of miR320 in Insulin-Resistant Adipocytes Treated with Ascending Concentrations of Metformin

Some miRNAs are supposed to play a role in insulin resistance and metabolic disorders. Such miRNAs can be differentially expressed in response to a pharmacologic intervention for insulin resistance as a biomarker/risk factor for insulin resistance. This study aimed at determining the effect of Metformin on miR320 expression in insulin-resistant (IR) adipocytes. The 3T3L1 cells were expanded in DMEM, differentiated into adipocytes by differentiating medium, became resistant to insulin, and then were treated with ascending concentrations of Metformin. Quantitative real-time PCR was performed to profile the miR320 expression in 3T3L1 adipocytes, IR adipocytes, and Metformin-treated IR adipocytes. Compared to the normal adipocytes, IR adipocytes exhibited a significantly higher level of miR320 expression, however, in response to Metformin graded concentrations, IR adipocytes down-regulated miR320 and were almost at normal level. The maximum effect of Metformin was at 10 mM. In IR adipocytes, miR320 expression is over-expressed which can be down-regulated by Metformin treatment. The findings provide some information on a potentially new marker to determine insulin resistance and to predict response to insulin resistance therapy.

Serum miR-195-5p is upregulated in gestational diabetes mellitus

BACKGROUND

Gestational diabetes mellitus (GDM) is defined as varying degrees of glucose intolerance with an onset or first recognition during pregnancy in women without previously diagnosed diabetes. Accumulating evidence indicates that miRNAs exert crucial roles in the pathogenesis and development of diabetes, including GDM. In the present study, we aimed to determine the clinical performance of miR-195-5p in GDM.

METHODS

First, the miR-195-5p expressions in serum samples from healthy pregnant women and women with GDM at 25 weeks pregnancy were detected using real-time polymerase chain reaction (RT-qPCR). Then, receive characteristic (ROC) curve was used to determine the diagnostic value of miR-195-5p in GDM. Finally, the correlation analysis of miR-195-5p expression with related clinicopathological factors was carried out to determine the clinical value of miR-195-5p in GDM.

RESULTS

In this study, we found that miR-195-5p expression was significantly increased in serum samples from GDM patients as compared with that in healthy pregnancies. Furthermore, miR-195-5p might be a putative biomarker for GDM diagnosis with an area under the curve (AUC) of 0.8451; the cutoff value was 1.598, sensitivity was 73.69%, specificity was 96.85%, accuracy was 81.26%, and Youden index was 70.54%. Expression of miR-195-5p was positively associated with fasting plasma glucose, one-hour plasma glucose, and two-hour plasma glucose.

CONCLUSION

miR-195-5p might function as a putative diagnostic biomarker for GDM and contribute to identifying at-risk mothers in pregnancy.

Circulating miR-135 May Serve as a Novel Co-biomarker of HbA1c in Type 2 Diabetes

Hemoglobin A1c (HbA1c) is a reliable marker of insulin resistance in normal glucose tolerance patients; however, several physiological, environmental, and genetic factors may affect HbA1c and cause false results. Therefore, it is essential to use new biomarkers due to increasing diabetes predictive value. Recently, it has been indicated that microRNAs (miRNAs) are involved in the pathophysiology of diabetes, particularly, in insulin resistance pathways. Therefore, miRNAs have the potential to be introduced as new glycemic control biomarkers. The aim of this study was to investigate the association between plasma level of miRNA-135a and HbA1c in patients with prediabetes and type 2 diabetes. In this case-control study, 120 samples were enrolled (healthy individuals, people with type 2 diabetes, and prediabetes) and HbA1c and miR-135a expression level in their plasma samples were evaluated. Multinomial logistic regression and ROC curve analysis were conducted to assess the diagnostic accuracy of plasma miR-135a in T2D , prediabetes, and healthy control groups. Data analysis indicated that miR-135a was significantly elevated in both diabetes/prediabetes samples. Then, subjects were reclassified based on the calculated cutoff value of miRNA. Logistic Regression analysis showed that an increased level of miRNA positively correlated with HbA1c level in prediabetes (Adjusted OR = 1.14, p value = 0.033) and diabetic status (Adjusted OR = 1.27, p value = 0.024 ). miR-135 may provide an assistant marker for HbA1c to detect type 2 diabetes.

Cytotoxicity Analysis of Morphologically Different Sol-Gel-Synthesized MgO Nanoparticles and Their In Vitro Insulin Resistance Reversal Ability in Adipose cells

Insulin resistance is one of the major factors that leads to type 2 diabetes. Although insulin therapies have been shown to overcome insulin resistance, overweight and hypoglycemia are still observed in most cases. The disadvantages of insulin therapies have driven the interest in developing novel curative agents with enhanced insulin resistance reversibility. Magnesium deficiency has also been recognized as a common problem which leads to insulin resistance in both type 1 and 2 diabetes. Oxide nanoparticles demonstrate highly tunable physicochemical properties that can be exploited by engineers to develop unique oxide nanoparticles for tailored applications. Magnesium supplements for diabetic cells have been reported to increase the insulin resistance reversibility. Hence, it is hypothesized that magnesium oxide (MgO) nanoparticles could be molecularly engineered to offer enhanced therapeutic efficacy in reversing insulin resistance. In the present work, morphologically different MgO nanoparticles were synthesized and evaluated for biophysical characteristics, biocompatibility, cytotoxicity, and insulin resistance reversibility. MTT assay revealed that hexagonally shaped MgO nanoparticles are less toxic to 3T3-L1 adipose cells (diabetic) compared with spherically and rod-shaped MgO nanoparticles. MTT assays using VERO cells (normal, non-diabetic) showed that 400 μg/ml of hexagonal MgO nanoparticles were less toxic to both diabetic and non-diabetic cells. DNS glucose assay and western blot showed that hexagonally shaped MgO nanoparticles had reversed 29.5% of insulin resistance whilst fluorescence microscopy studies indicated that the insulin resistance reversal is due to the activation of intracellular enzymes. The probable mechanism for MgO nanoparticles to induce cytotoxic effect and insulin resistance reversal is discussed.

MicroRNA-96 regulates pancreatic β cell function under the pathological condition of diabetes mellitus through targeting Foxo1 and Sox6

To elucidate the potential function of microRNA-96 in protecting pancreatic β cell function under the pathological condition of T2DM and the underlying mechanism. Relative levels of microRNA-96 and genes associated with β cell function in the in vivo and in vitro T2DM and obesity models were detected by qRT-PCR. Insulin functions, including fasting blood glucose, plasma insulin, HOMA-IR, HOMA-%b, glucose tolerance and insulin tolerance, were assessed in microRNA-96 KO mice and wild-type mice fed with normal diet or high-fat diet. Downstream targets of microRNA-96 were verified by dual-luciferase reporter gene assay. Finally, regulatory effects of microRNA-96 on proliferation and apoptosis of MIN6 cells were determined. MicroRNA-96 was upregulated in mice fed with high-fat diet, db/db mice, high-level glucose-treated cells, TNF-α-treated cells, pancreatic cells isolated from the obesity and T2DM patients. Increased fasting blood glucose and HOMA-IR, as well as decreased plasma insulin and HOMA-%b were observed in microRNA-96 KO mice. IPGTT and IPITT results indicated that knockout of microRNA-96 led to pancreatic β cell dysfunction under the pathological condition of T2DM. Dual-luciferase reporter gene assay confirmed that microRNA-96 could bind Foxo1 and Sox6. MicroRNA-96 negatively regulated Foxo1 and Sox6 levels. Moreover, overexpression of microRNA-96 promoted proliferative ability and inhibited apoptosis in MIN6 cells. Relative levels of Pdx1, Nkx6.1, Cyclin D1 and Cyclin E1 were upregulated in MIN6 cells overexpressing microRNA-96. Opposite results were obtained after knockdown of microRNA-96 in MIN6 cells. MicroRNA-96 is upregulated in pancreatic β cells under the pathological condition of T2DM. Overexpression of microRNA-96 promotes proliferative ability and inhibits apoptosis in pancreatic β cells through targeting Foxo1 and Sox6.

Characterization of Glucokinase Catalysis from a Pseudo-Dimeric View

Glucose phosphorylation by glucokinase exhibits a sigmoidal dependency on substrate concentration regardless of its simple structure. Dimorph mechanism suggested the existence of two enzymatic states with different catalytic properties, which has been shown to be plausible by structural analysis. However, the dimorph mechanism gives rise to a complicated or non-explicit non-closed mathematical form. It is neither feasible to apply the dimorph mechanism in effector characterizations. To improve the area of glucokinase study with stronger theoretical support and less complication in computation, we proposed the investigation of the enzyme from a pseudo-dimeric angle. The proposed mechanism started from the idealization of two monomeric glucokinase as a dimeric complex, which significantly simplified the glucose phosphorylation kinetics, while the differences in enzyme reconfiguration caused by variable substrates and effectors have been successfully characterized. The study presented a simpler and more reliable way in studying the properties of glucokinase and its effectors, providing guidelines of effector developments for hyperglycemia and hypoglycemia treatment.

Network of three specific microRNAs influence type 2 diabetes through inducing insulin resistance in muscle cell lines

Insulin resistance has been implicated as one of the best predictors for type 2 diabetes. Growing evidence propose the involvement of microRNAs (miRNAs) as short regulatory molecules in modulating and inducing resistance. In this regard, we have investigated the role of three selected miRNAs in insulin resistance development (miR-135, miR-202, and miR-214), via assessing glucose uptake levels in C2C12 and L6 muscle cell lines. Interestingly, miRNA-transfected cells demonstrated a significantly different glucose uptake compared to the positive control cells. In addition, we evaluated the expression levels of three putative miRNA target genes (Rho-associated coiled-coil containing protein kinase 1, serine/threonine kinase 2, and vesicle-associated membrane protein 2) in transfected cells, recruiting luciferase assay. Our results indicated the targeting and downregulation of Rho-associated coiled-coil containing protein kinase 1 and serine/threonine kinase 2 genes in all miR-transfected cell lines ( P ≤ 0.05), but not for vesicle-associated membrane protein 2. MiRNA upregulation led to the poor stimulation of glucose uptake through insulin and developed insulin-resistant phenotype in both muscle cell lines. Our study showed the role of three miRNAs in the induction of insulin resistance in cell lines and making them prone to type 2 diabetes development.

Molecular epidemiology; New but impressive

Molecular epidemiology is a subdivision of medical science and epidemiology that emphases on the involvement of potential environmental and genetic risk factors, recognized at the molecular level, to the etiology and avoidance of sickness through populations. This arena has developed from the combination of molecular biology and traditional epidemiological research. Molecular epidemiology can improve our knowledge about the precise pathogenesis of disease through recognizing particular pathways that affect the risk of developing the disease. Furthermore, it tries to find how the collaborations between genetic characteristics and environmental exposures works in disease occurrence.

MicroRNA-190b regulates lipid metabolism and insulin sensitivity by targeting IGF-1 and ADAMTS9 in non-alcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is characterized by ectopic lipid accumulation and insulin resistance, yet the underlying molecular mechanisms are poorly understood. MiR-190b is thought to play a role in hepatocellular carcinoma by modulating insulin resistance; however, its role in NAFLD remains unknown. Here, we found that miR-190b expression was significantly increased in the liver tissues of patients with NAFLD, compared to normal tissues. Moreover, miR-190b was upregulated in a high-fat diet NAFLD mouse model and a free fatty acid-induced NAFLD cellular model. Knockdown of miR-190b decreased aspartate transaminase (AST), alanine transaminase (ALT), triglyceride (TG), and total cholesterol (TC). It also reduced expression of the lipogenic genes fatty acid synthase (FAS) and 3-hydroxy-3-methylglutarylCoA reductase (HMGCR), alleviated hepatic steatosis, improved glucose tolerance, elevated insulin sensitivity, and activated insulin receptor substrate (IRS)2/Akt signaling in vivo and/or in vitro. Furthermore, we confirmed that miR-190b directly targeted IGF-1 and ADAMTS9. MiR-190b overexpression suppressed expression of IGF-1 and ADAMTS9, which were increased by miR-190b inhibition. Expression of IGF-1 and ADAMTS9 was inversely correlated with miR-190b in liver tissues of patients with NAFLD, respectively. We also found that IGF-1 or ADAMTS9 inhibition partially reversed the effects of miR-190b on lipid metabolism and insulin signaling in vitro. Taken together, the data reveal that miR-190b inhibition suppressed lipid accumulation and improved insulin sensitivity by targeting IGF-1 and ADAMTS9, suggesting that miR-190b inhibition may be a therapeutic strategy against NAFLD.

Efficiencies of Low-Level Laser Therapy (LLLT) and Gabapentin in the Management of Peripheral Neuropathy: Diabetic Neuropathy

Diabetic neuropathy (DN) is the highly occurred complication of diabetes mellitus; it has been defined as an event of peripheral nerve dysfunction characterized by pain, allodynia, hyperalgesia, and paraesthesia. The current study was conducted to evaluate the efficacy of low-level laser therapy (LLLT) in the management of neuropathy in diabetic rats. The used animals were divided into the following groups: negative control, streptozotocin-induced diabetic rats, and diabetic rats with peripheral neuropathy (DNP) and DNP treated with gabapentin or with LLLT. Behavioral tests were carried out through hotplate test for the determination of pain sensations and the Morris water maze test for spatial reference memory evaluation. Blood samples were collected at the end of treatment for biochemical determinations. In the current study, the latency of hind-paw lick decreased significantly when DNP are treated with gabapentin or LLLT. The Morris water maze test showed that LLLT treatment improved memory that deteriorated in DNP more than gabapentin do. The results of the biochemical study revealed that LLLT could not affect the level of beta-endorphin that decreased in DNP but significantly decreased S100B that rose in DNP. PGE2 and cytokines IL-1β, IL-10, and TNF-α showed significant increase in DNP compared with control group. The gabapentin administration or LLLT application significantly reversed the levels of the mentioned markers towards the normal values of the controls. Levels of serum MDA and nitric oxide increased significantly in the DNP but rGSH showed significant decrease. These markers were improved significantly when the DNP were treated with gabapentin or LLLT. The treatment with gabapentin or LLLT significantly decreased the raised level in total cholesterol in DNP but could not decrease the elevated level of triglycerides, while LDL cholesterol decreased significantly in DNP treated with gabapentin but not affected by LLLT. Values of serum alanine aminotransferase (ALAT), aspartate aminotransferase (ASAT), urea, and creatinine increased significantly in the DPN and diabetic rats without peripheral neuropathy (PN) compared with control group. The treatment of DNP with gabapentin induced significant increases in ALAT and ASAT activities but LLLT treatment induced significant decreases in ALAT and ASAT activities as compared with DNP group. Neither gabapentin nor LLLT could improve the elevated levels of serum urea and creatinine in the DNP. It could be concluded that LLLT is more safe and effective than gabapentin in the management of neuropathy in diabetic rats.

Immunochemical Study of the Effect of F2Glc on Glycogen Synthase Translocation and Glycogen Synthesis in Isolated Rat Hepatocytes

The compound 2-deoxy-2-fluoro-α-D-glucopyranosyl fluoride (F₂Glc), which is a nonmetabolized superior glucose analogue, is a potent inhibitor of glycogen phosphorylase and pharmacological properties are reported. Glycogen phosphorylase (GP) and glycogen synthase (GS) are responsible of the degradation and synthesis, respectively, of glycogen which is a polymer of glucose units that provides a readily available source of energy in mammals. GP and GS are two key enzymes that modulate cellular glucose and glycogen levels; therefore, these proteins are suggested as potential targets for the treatment of diseases related to glycogen metabolism disorders. We studied by Western Blot technique that F₂Glc decreased GP activity, and we also showed that F₂Glc did not affect GS activity and its translocation from a uniform cytosolic distribution to the hepatocyte periphery, which is crucial for glycogen synthesis, using immunoblotting and immunofluorescence labeling techniques. F₂Glc specifically inhibits glycogenolysis pathway and permits a greater deposition of glycogen. These observations open up the possibility of further develop drugs that act specifically on GP. The ability to selectively inhibit GP, which is a key enzyme for the release of glucose from the hepatic glycogen reserve, may represent a new approach for the treatment of hyperglycemia in type 2 diabetes.

miR-101-1 expression pattern in Qinchuan cattle and its role in the regulation of cell differentiation

MiRNAs have emerged as key regulators of skeletal muscle development, but the knowledge of miRNAs in the molecular network of muscle development remains poorly understood. In this study, we designed to examine the biological function of bovine-miR-101-1. The bovine miR-101-1 was detected in the skeletal muscle of fetal, calf and adult cattle. Its abundance was significantly higher in the skeletal muscle of calf cattle than that in fetal and adult cattle. In the course of C2C12 myoblast differentiation, the expression of miR-101-1 gradually increased. Transfected the exogenous miR-101-1 into the C2C12 myoblast could decrease myotube formation, and the mRNA expression levels of the myogenic marker genes MyOD, MyOG and MyHC were up-regulated. The protein level of MyOD, MyOG and MyHC were also up-regulated. Through TargetScan to predict the target gene of bovine miR-101-1, and the dual luciferase system was used for target gene verification. The results show that amyloid precursor protein (APP) is the target gene of miR-101-1. Therefore, our results shed light on miR-101-1 in the regulation of the skeletal muscle development.

Comparison of adjunctive therapy with metformin and acarbose in patients with Type-1 diabetes mellitus

Objective:

All the aforementioned data have stimulated interest in studying other potential therapies for T1DM including noninsulin pharmacological therapies. The present study attempts to investigate the effect of adjunctive therapy with metformin and acarbose in patients with Type-1 diabetes mellitus.

Method:

In a single-center, placebo-controlled study (IRCT201102165844N1) we compared the results of two clinical trials conducted in two different time periods on 40 patients with Type-1 diabetes mellitus. In the first section, metformin was given to the subjects. After six months, metformin was replaced with acarbose in the therapeutic regimen. In both studies, subjects were checked for their BMI, FBS, HbA1C, TGs, Cholesterol, LDL, HDL, 2hpp, unit of NPH and regular insulin variations.

Results:

Placebo-controlled evaluation of selected factors has showna significant decrease in FBS and TG levels in the metformin group during follow up but acarbose group has shown substantial influence on two hour post prandial (2hpp) and regular insulin intake decline. Moreover, Comparison differences after intervention between two test groups has shown that metformin has had superior impact on FBS and HbA1C decline in patients. Nonetheless, acarbose treatment had noteworthy influence on 2hpp, TGs, Cholesterol, LDL, and regular insulin intake control.

Conclusion:

The results of this experiment demonstrate that the addition of acarbose or metformin to patients with Type-1 diabetes mellitus who are controlled with insulin is commonly well tolerated and help to improve metabolic control in patients.

Comprehensive functional screening of miRNAs involved in fat cell insulin sensitivity among women

The key pathological link between obesity and type 2 diabetes is insulin resistance, but the molecular mechanisms are not entirely identified. micro-RNAs (miRNA) are dysregulated in obesity and may contribute to insulin resistance. Our objective was to detect and functionally investigate miRNAs linked to insulin sensitivity in human subcutaneous white adipose tissue (scWAT). Subjects were selected based on the insulin-stimulated lipogenesis response of subcutaneous adipocytes. Global miRNA profiling was performed in abdominal scWAT of 18 obese insulin-resistance (OIR), 21 obese insulin-sensitive (OIS), and 9 lean women. miRNAs demonstrating differential expression between OIR and OIS women were overexpressed in human in vitro-differentiated adipocytes followed by assessment of lipogenesis and identification of miRNA targets by measuring mRNA/protein expression and 3'-untranslated region analysis. Eleven miRNAs displayed differential expression between OIR and OIS states. Overexpression of miR-143-3p and miR-652-3p increased insulin-stimulated lipogenesis in human in vitro differentiated adipocytes and directly or indirectly affected several genes/proteins involved in insulin signaling at transcriptional or posttranscriptional levels. Adipose expression of miR-143-3p and miR-652-3p was positively associated with insulin-stimulated lipogenesis in scWAT independent of body mass index. In conclusion, miR-143-3p and miR-652-3p are linked to scWAT insulin resistance independent of obesity and influence insulin-stimulated lipogenesis by interacting at different steps with insulin-signaling pathways.

Urinary chromium is associated with changes in leukocyte miRNA expression in obese subjects

BACKGROUND/OBJECTIVES

Epidemiological studies suggest a link between chromium (Cr) status and cardiovascular disease. Increased urinary excretion of Cr was reported in subjects with diabetes compared with non-diabetic controls and those with non-diabetic insulin resistance. Epigenetic alterations have been linked to the presence of Cr, and microRNA (miRNA) expression has been implicated in the pathogenesis of metabolic diseases and cardiovascular diseases (CVDs). We investigated the association between Cr excretion and miRNA expression in leukocytes from obese subjects. We also examined the relationship between altered miRNA expression and selected clinical parameters to further investigate mechanisms linking Cr to metabolic diseases and CVDs.

SUBJECTS/METHODS

We analyzed urinary Cr in 90 Italian subjects using inductively coupled plasma-mass spectrometry. Peripheral blood miRNA levels were screened with TaqMan Low-Density Array Human MicroRNA A. Cr level-associated expression of miRNAs was detected with multivariate regression analyses, and the top 10 candidate miRNAs were selected for validation. We also used multivariate regression analyses to assess possible associations between validated miRNAs and glycated hemoglobin (A1c) and blood pressure (BP). The validated miRNAs were further investigated by functional analysis with Ingenuity Pathway Analysis software.

RESULTS

Urinary Cr levels (mean: 0.35 μg/l; s.d.=0.24) ranged from 0.05 to 1.27 μg/l. In the screening phase, 43 miRNAs were negatively associated with Cr. Of the top 10 miRNAs selected for validation, nine (miR-451, miR-301, miR-15b, miR-21, miR-26a, miR-362-3p, miR-182, miR-183 and miR-486-3p) were downregulated in association with Cr (P-false discovery rate (FDR)<0.10). miR-451 expression was associated with A1c (β=-0.06; P=0.0416), whereas miR-486-3p expression was associated both with diastolic (β=2.1; P=0.004) and systolic BP (β=3.3; P=0.003).

CONCLUSIONS

These results indicate that miR-451 and miR-486-3p are involved in the link between Cr levels and metabolic diseases and CVDs.

Metabolite Variation in Lean and Obese Streptozotocin (STZ)-Induced Diabetic Rats via 1H NMR-Based Metabolomics Approach

Diabetes mellitus (DM) is considered as a complex metabolic disease because it affects the metabolism of glucose and other metabolites. Although many diabetes studies have been conducted in animal models throughout the years, the pathogenesis of this disease, especially between lean diabetes (ND + STZ) and obese diabetes (OB + STZ), is still not fully understood. In this study, the urine from ND + STZ, OB + STZ, lean/control (ND), and OB + STZ rats were collected and compared by using ¹H NMR metabolomics. The results from multivariate data analysis (MVDA) showed that the diabetic groups (ND + STZ and OB + STZ) have similarities and dissimilarities for a certain level of metabolites. Differences between ND + STZ and OB + STZ were particularly noticeable in the synthesis of ketone bodies, branched-chain amino acid (BCAA), and sensitivity towards the oral T2DM diabetes drug metformin. This finding suggests that the ND + STZ group was more similar to the T1DM model and OB + STZ to the T2DM model. In addition, we also managed to identify several pathways and metabolism aspects shared by obese (OB) and OB + STZ. The results from this study are useful in developing drug target-based research as they can increase understanding regarding the cause and effect of DM.

Development of Insulin Resistance through Induction of miRNA-135 in C2C12 Cells

Objective

Micro-RNAs (miRNAs) are a class of posttranscriptional regulators that play crucial roles in various biological processes. Emerging evidence suggests a direct link between miRNAs and development of several diseases including type 2 diabetes (T2D). In this study, we aimed to investigate the effect of predicted miRNA and target genes on insulin resistance.

Materials and Methods

This experimental study was conducted on the C2C12 cell line. Using bioinformatics tools miRNA-135 and two respective target genes-insulin receptor (Insr) and vesicle associated membrane protein 2 (Vamp2)were selected as potential factors involved in insulin resistance process. Levels of glucose uptake miRNA expression and respective gene targets were determined after cell transfaction by miR-135.

Results

It was determined that Insr gene expression was significantly down-regulated in miR-135 transfected C2C12 cell line (P≤0.05). Interestingly; these transfected cells have shown a significant difference in glucose uptake incomparision the positive control cells, while it was similar to the insulin resistant cell line (P≤0.05). In contrast, no significant alteration of Vamp2 gene expression was observed.

Conclusion

Our data indicated no change on the Vamp2 expression level after miRNA transfection, while expression level of Insr was reduced and miR-135 expression was contrarily increased leading to poor stimulation of glucose uptake through insulin, and development of insulin resistance phenotype in C2C12 cell line.

Chronic pistachio intake modulates circulating microRNAs related to glucose metabolism and insulin resistance in prediabetic subjects

PURPOSE

To assess the effects of a pistachio-enriched diet on the profile of circulating microRNAs (miRNAs) related to glucose metabolism and insulin resistance (IR).

METHODS

Randomized crossover clinical trial in 49 subjects with prediabetes was performed. Subjects consumed a pistachio-supplemented diet (PD, 50 % carbohydrates, 33 % fat, including 57 g/day of pistachios) and an isocaloric control diet (CD, 55 % carbohydrates and 30 % fat) for 4 months each, separated by a 2-week washout period. The plasma profile of a set of seven predefined miRNAs related to glucose and insulin metabolism was analyzed by quantitative RT-PCR.

RESULTS

After the PD period, subjects have shown significant lower circulating levels of miR-192 and miR-375 compared to CD period, whereas miR-21 nonsignificantly increased after PD compared with CD (47 vs. 2 %, P = 0.092). Interestingly, changes in circulating miR-192 and miR-375 were positively correlated with plasma glucose, insulin and HOMA-IR.

CONCLUSION

Chronic pistachio consumption positively modulates the expression of some miRNA previously implicated on insulin sensitivity.

Upregulation of miR-497 induces hepatic insulin resistance in E3 rats with HFD-MetS by targeting insulin receptor

OBJECTIVE

The study aims to find regulatory microRNA(s) responsible for down-regulated insulin receptor (InsR) in the liver of HFD-MetS E3 rats with insulin resistance.

METHODS

Firstly, hepatic insulin resistance in HFD-MetS E3 rats was evaluated by RT-qPCR, western blotting, immunohistochemistry and PAS staining. Secondly, the candidate miRNAs targeting rat InsR were predicted through online softwares and detected in the liver of HFD-MetS E3 rats with insulin resistance. Then, the expression of InsR, phosphorylated IRS-1 (pIRS-1) at Tyr632, phosphorylated AKTs (pAKTs) at Ser473 and Thr308, phosphorylated GSK-3β (p GSK-3β) at Ser9, phosphorylated GS (pGS) at Ser641 and the glycogen content were detected in CBRH-7919 cells treated with 100 nM insulin for different time periods by western blotting or PAS staining respectively, after transient transfection with miR-497 mimics or inhibitors for 24 h. Lastly, the relation between miR-497 and InsR was further determined using dual luciferase reporter assay.

RESULTS

Elevated miR-497 was negatively related with down-regulated InsR in the liver of HFD-MetS E3 rats with insulin resistance. Comparing with the mNC group, glycogen content and the expression of InsR, pIRS-1 (Tyr632), pAKTs (Ser473 and Thr308) and pGSK-3β (Ser9) decreased significantly in CBRH-7919 cells, while pGS (Ser641) increased significantly, after transient transfection with miR-497 mimics for 24 h and treatment with 100 nM insulin for corresponding time periods, counter to those results in CBRH-7919 cells after similar procedures with miR-497 inhibitors and insulin. In addition, dual luciferase reporter assay further confirmed that miR-497 can bind to the 3'UTR of rat InsR.

CONCLUSION

Insulin receptor is the target gene of miR-497, and elevated miR-497 might induce hepatic insulin resistance in HFD-MetS E3 Rats through inhibiting the expression of insulin receptor and confining the activation of IRS-1/PI3K/Akt/GSK-3β/GS pathway to insulin.

Expression Change of miR-214 and miR-135 during Muscle Differentiation

Objective

MicroRNAs (miRNAs) are a class of small non-coding RNAs that play pivotal roles in many biological processes such as regulating skeletal muscle development where alterations in miRNA expression are reported during myogenesis. In this study, we aimed to investigate the impact of predicted miRNAs and their target genes on the myoblast to myocyte differentiation process.

Materials and Methods

This experimental study was conducted on the C2C12 cell line. Using a bioinformatics approach, miR-214 and miR-135 were selected according to their targets as potential factors in myoblast to myocyte differentiation induced by 3% horse serum. Immunocytochemistry (ICC) was undertaken to confirm the differentiation process and quantitative real-time polymerase chain reaction (PCR) to determine the expression level of miRNAs and their targets.

Results

During myoblast to myocyte differentiation, miR-214 was significantly down- regulated while miRNA-135, Irs2, Akt2 and Insr were overexpressed during the process.

Conclusion

miR-214 and miR-135 are potential regulators of myogenesis and are involved in skeletal muscle development through regulating the IRS/PI3K pathway.

MicroRNA regulatory networks in human adipose tissue and obesity

MicroRNAs (miRNAs) are small noncoding RNAs that regulate gene expression and, therefore, biological processes in different tissues. A major function of miRNAs in adipose tissue is to stimulate or inhibit the differentiation of adipocytes, and to regulate specific metabolic and endocrine functions. Numerous miRNAs are present in human adipose tissue; however, the expression of only a few is altered in individuals with obesity and type 2 diabetes mellitus or are differentially expressed in various adipose depots. In humans, obesity is associated with chronic low-grade inflammation that is regulated by signal transduction networks, in which miRNAs, either directly or indirectly (through regulatory elements such as transcription factors), influence the expression and secretion of inflammatory proteins. In addition to their diverse effects on signalling, miRNAs and transcription factors can interact to amplify the inflammatory effect. Although additional miRNA signal networks in human adipose tissue are not yet known, similar regulatory circuits have been described in brown adipose tissue in mice. miRNAs can also be secreted from fat cells into the circulation and serve as markers of disturbed adipose tissue function. Given their role in regulating transcriptional networks, miRNAs in adipose tissue might offer tangible targets for treating metabolic disorders.