Subramaniam Tavintharan

MicroRNA 144 Impairs Insulin Signaling by Inhibiting the Expression of Insulin Receptor Substrate 1 in Type 2 Diabetes Mellitus

Background Dysregulation of microRNA (miRNA) expression in various tissues and body fluids has been demonstrated to be associated with several diseases, including Type 2 Diabetes mellitus (T2D). Here, we compare miRNA expression profiles in different tissues (pancreas, liver, adipose and skeletal muscle) as well as in blood samples from T2D rat model and highlight the potential of circulating miRNAs as biomarkers of T2D. In parallel, we have examined the expression profiles of miRNAs in blood samples from Impaired Fasting Glucose (IFG) and T2D male patients. Methodology/Principal Findings Employing miRNA microarray and stem-loop real-time RT-PCR, we identify four novel miRNAs, miR-144, miR-146a, miR-150 and miR-182 in addition to four previously reported diabetes-related miRNAs, miR-192, miR-29a, miR-30d and miR-320a, as potential signature miRNAs that distinguished IFG and T2D. Of these microRNAs, miR-144 that promotes erythropoiesis has been found to be highly up-regulated. Increased circulating level of miR-144 has been found to correlate with down-regulation of its predicted target, insulin receptor substrate 1 (IRS1) at both mRNA and protein levels. We could also experimentally demonstrate that IRS1 is indeed the target of miR-144. Conclusion We demonstrate that peripheral blood microRNAs can be developed as unique biomarkers that are reflective and predictive of metabolic health and disorder. We have also identified signature miRNAs which could possibly explain the pathogenesis of T2D and the significance of miR-144 in insulin signaling.

Circulating miRNA profiles in patients with metabolic syndrome.

CONTEXT Coordinated interplay of dysregulated microRNAs in isolated metabolic disorder is implicated in the pathogenesis of metabolic syndrome. OBJECTIVE The objective of the study was to characterize microRNA expression in the blood and exosomes of individuals with metabolic syndrome and compare them with those manifesting one of the metabolic vascular risk factors (type 2 diabetes, hypercholesterolemia, or hypertension). RESEARCH DESIGN/SETTING/PARTICIPANTS: A total of 265 participants were recruited in a health screening and characterized into distinct groups as follows: 1) healthy controls (n = 46); 2) metabolic syndrome (n = 50); 3) type 2 diabetes (n = 50); 4) hypercholesterolemia (n = 89); and 5) hypertension (n = 30). Total RNA was subjected to microRNA profiling, and a panel of significantly dysregulated microRNAs was validated using quantitative PCR. MAIN OUTCOME MEASURES Analysis of profiling data characterized unique pools of miRNAs that could categorize the different risk factors of metabolic syndrome. RESULTS We have identified miR-197, miR-23a, and miR-509-5p as potential contributors of dyslipidemia in metabolic syndrome (correlation with body mass index; P = 0.029, 0.021, and 0.042, respectively) and miR-130a and miR-195 as contributors of hypertension (correlation with blood pressure; P = 0.019 and 0.045, respectively). A plausible association of miR-27a and miR-320a with metabolic syndrome and type 2 diabetes patients has also been found because these miRNAs remained dysregulated in both cases (correlation with fasting glucose; P = 0.010 and 0.016, respectively). CONCLUSIONS Significant dysregulation of seven candidate microRNAs has been found to be associated with risks involved in the manifestation of metabolic syndrome.

Metabolic Signature Shift in Type 2 Diabetes Mellitus Revealed by Mass Spectrometry-based Metabolomics

OBJECTIVE Metabolic profiling of small molecules offers a snapshot of physiological processes. To identify metabolic signatures associated with type 2 diabetes and impaired fasting glucose (IFG) beyond differences in glucose, we used mass spectrometry-based metabolic profiling. RESEARCH DESIGN AND METHODS Individuals attending an institutional health screen were enrolled. IFG (n = 24) was defined as fasting glucose (FG) of 6.1 to 6.9 mmol/L and 2-hour post glucose load <11.1 mmol/L or glycosylated hemoglobin <6.5%, type 2 diabetes (n = 27), FG ≥7.0 mmol/L, or 2-hour post glucose load ≥11.1 mmol/L, or glycosylated hemoglobin ≥6.5%, and healthy controls (n = 60), FG <6.1 mmol/L. Fasting serum metabolomes were profiled and compared using gas chromatography/mass spectrometry and liquid chromatography/mass spectrometry. RESULTS Compared to healthy controls, those with IFG and type 2 diabetes had significantly raised fructose, α-hydroxybutyrate, alanine, proline, phenylalanine, glutamine, branched-chain amino acids (leucine, isoleucine, and valine), low carbon number lipids (myristic, palmitic, and stearic acid), and significantly reduced pyroglutamic acid, glycerophospohlipids, and sphingomyelins, even after adjusting for age, gender, and body mass index. CONCLUSIONS Using 2 highly sensitive metabolomic techniques, we report distinct serum profile change of a wide range of metabolites from healthy persons to type 2 diabetes mellitus. Apart from glucose, IFG and diabetes mellitus are characterized by abnormalities in amino acid, fatty acids, glycerophospholipids, and sphingomyelin metabolism. These early broad-spectrum metabolic changes emphasize the complex abnormalities present in a disease defined mainly by elevated blood glucose levels.

Circulating MicroRNAs as Biomarkers of Acute Stroke

MicroRNAs have been identified as key regulators of gene expression and thus their potential in disease diagnostics, prognosis and therapy is being actively pursued. Deregulation of microRNAs in cerebral pathogenesis has been reported to a limited extent in both animal models and human. Due to the complexity of the pathology, identifying stroke specific microRNAs has been a challenge. This study shows that microRNA profiles reflect not only the temporal progression of stroke but also the specific etiologies. A panel of 32 microRNAs, which could differentiate stroke etiologies during acute phase was identified and verified using a customized TaqMan Low Density Array (TLDA). Furthermore we also found 5 microRNAs, miR-125b-2*, -27a*, -422a, -488 and -627 to be consistently altered in acute stroke irrespective of age or severity or confounding metabolic complications. Differential expression of these 5 microRNAs was also observed in rat stroke models. Hence, their specificity to the stroke pathology emphasizes the possibility of developing these microRNAs into accurate and useful tools for diagnosis of stroke.

Is There a Clear Threshold for Fasting Plasma Glucose That Differentiates Between Those With and Without Neuropathy and Chronic Kidney Disease? The Singapore Prospective Study Program

Recent studies suggest that no distinct glycemic threshold consistently differentiates individuals with or without retinopathy. The authors sought to determine whether the same was true for other microvascular complications. They studied 5,094 participants with fasting plasma glucose values and concurrent microvascular complications from 4 previous cross-sectional surveys carried out in Singapore (1982-1998) who attended a follow-up examination in 2004-2007. Peripheral neuropathy was diagnosed based on abnormal responses to a 10-g monofilament or neurothesiometer test. Chronic kidney disease was defined in various ways by using albuminuria (urine albumin:creatinine ratio >30 microg/mg) and estimated glomerular filtration rate, alone and in combination. Prevalence of peripheral neuropathy was 7.5%. For chronic kidney disease, prevalence of albuminuria only was 10.5%, estimated glomerular filtration rate of <60 mL/minute per 1.73 m(2) only was 4.1%, and both was 2.1%. Prevalence of peripheral neuropathy and chronic kidney disease gradually increased in relation to fasting plasma glucose, beginning at levels below the existing diagnostic threshold for diabetes mellitus of 7.0 mmol/L (126 mg/dL). For chronic kidney disease, these associations persisted after adjustment for age, gender, ethnic group, and hypertension. Current diagnostic thresholds for diabetes mellitus have limited sensitivity for identifying individuals with these microvascular complications. Ascertaining these individuals may require development and application of novel screening strategies.

Relationship between circulating irisin, renal function and body composition in type 2 diabetes ☆ ☆☆

AIMS Chronic kidney disease (CKD) secondary to type 2 diabetes mellitus (T2DM) is associated with multifaceted energy dysmetabolism. We aim to study the relationship between renal function, body composition and irisin, the recently identified myokine which is involved in energy regulation, in T2DM. METHODS Circulating irisin and body composition were measured in 365 T2DM subjects across a wide range of renal function. RESULTS Circulating irisin was significantly decreased in T2DM with renal insufficiency (77.4 ± 13.7 ng/ml in T2DM with eGFR ≥ 60 ml/min/1.73 m(2) versus 72.5 ± 14.9 ng/ml in those with eGFR<60 ml/min/1.73 m(2), p = 0.001) and the reduction in irisin was most pronounced in stage 5 CKD patients. In T2DM with preserved renal function, irisin was correlated with age (r = -0.242, p = 0.001) and pulse pressure (r = -0.188, p = 0.002). Among those with renal insufficiency, irisin was correlated with BMI (r = 0.171, p = 0.022), fat mass (r = 0.191, p = 0.013), percentage of fat mass (r = 0.210, p = 0.007) and eGFR (r = 0.171, p = 0.020). Multivariate linear regression models revealed that variations in circulating irisin were mainly attributable to eGFR and age in T2DM with and without renal impairment, respectively. CONCLUSION Our observations suggest that the level of circulating irisin may be associated with renal function in T2DM. The role of reduced irisin in energy dysmetabolism in diabetic patients with renal insufficiency deserves further investigation.

Associations between complications and health‐related quality of life in individuals with diabetes

Type 2 diabetes and associated complications adversely affect health‐related quality of life (HRQoL). However, it is unclear whether different complications have the same or different associations with HRQoL. We examined associations between retinopathy, nephropathy, peripheral neuropathy (microvascular), coronary heart disease, stroke and peripheral arterial disease (macrovascular) in diabetes and HRQoL.

High normal albuminuria is independently associated with aortic stiffness in patients with Type 2 diabetes

High normal albuminuria is associated with higher cardiovascular risk in patients with diabetes. Increased aortic stiffness is an established risk factor of vascular events. However, the relationship between albuminuria within the normal range (0–30 mg/g) and aortic stiffness in patients with Type 2 diabetes is unknown.

Diagnosis of Diabetes Mellitus Using HbA1c in Asians: Relationship Between HbA1c and Retinopathy in a Multiethnic Asian Population

CONTEXT Hemoglobin A1c (HbA1c) ≥ 6.5% (47.5 mmol/mol) has recently been included as a criterion for the diagnosis of diabetes mellitus. It is unclear whether this criterion is appropriate in Asians. OBJECTIVE To examine the relationship between HbA1c and diabetes-specific moderate retinopathy in Asian ethnic groups. DESIGN, SETTING, AND PARTICIPANTS Four independent population-based cross-sectional studies (2004-2011) in Singapore representing the three major Asian ethnic groups (n = 13 170 adults aged ≥ 25 y: Chinese, 5834; Malays, 3596; and Indians, 3740). MAIN OUTCOME Moderate retinopathy was assessed from digital retinal photographs and defined as a level >43 using the Early Treatment Diabetic Retinopathy Study (ETDRS) scale. Sensitivity, specificity, positive and negative predictive values, and the area under the receiver operating characteristic curve for detecting moderate retinopathy were compared across ethnic groups at different HbA1c cut-points. RESULTS HbA1c levels were higher in Indians and Malays compared to Chinese (P < .001). The prevalence of moderate retinopathy below HbA1c <6.5% was <1% in all ethnic groups. At HbA1c ≥ 6.5%, the sensitivity for detecting moderate retinopathy was lower in Chinese subjects compared to Indians and Malays (75.8 vs 86.0 and 85.3%), but specificity (89.7 vs 71.9 and 76.3%) was higher; however, positive predictive value and negative predictive value were similar among Chinese, Indians, and Malays (10.5, 12.3, 12.4%; and 99.6, 99.1, 99.2%, respectively). The AUCs were similar across all three ethnic groups (0.861, 0.851, and 0.853). CONCLUSIONS Our study supports the use of HbA1c for diagnosing diabetes in Asians. Despite some interethnic variation in the relationship of HbA1c and retinopathy, a cut-point of 6.5% performs reasonably well in the three major Asian ethnic groups.

Ethnic disparities in risk of cardiovascular disease, end-stage renal disease and all-cause mortality: a prospective study among Asian people with Type 2 diabetes.

To study prospectively the ethnic‐specific risks of cardiovascular disease, end‐stage renal disease and all‐cause mortality in patients with Type 2 diabetes mellitus among native Asian subpopulations.