Diabetes mellitus has become one of the most common chronic diseases, thereby posing a major challenge to global health. Characterized by high levels of blood glucose (hyperglycemia), diabetes usually results from a loss of insulin-producing β-cells in the pancreas, leading to a deficiency of insulin (type 1 diabetes), or loss of insulin sensitivity (type 2 diabetes). Both types of diabetes have serious secondary complications, such as microvascular abnormalities, cardiovascular dysfunction, and kidney failure. Various complex factors, such as genetic and environmental factors, are associated with the pathophysiology of diabetes. Over the past two decades, the role of small, single-stranded noncoding microRNAs in various metabolic disorders, especially diabetes mellitus and its complications, has gained widespread attention in the scientific community. Discovered first as an endogenous regulator of development in the nematode Caenorhabditis elegans, these small RNAs post-transcriptionally suppress mRNA target expression. In this review, we discuss the potential roles of different microRNAs in diabetes and diabetes-related complications.
Animals ; Diabetes Complications ; genetics ; metabolism ; Diabetes Mellitus ; genetics ; metabolism ; Glucose ; metabolism ; Homeostasis ; genetics ; Humans ; Insulin ; metabolism ; MicroRNAs ; biosynthesis ; genetics ; metabolism

OBJECTIVETo study the relationship between insulin resistance and methylation of insulin receptor (INSR) gene in the endometrium of women with polycystic ovary syndrome (PCOS).

METHODSBased on the HOMA index, 35 patients with PCOS were divided into insulin resistant group (IR group, n=18) and non-resistant group (NIR group, n=18). The patients age, serum estriol, testosterone, FSH and LH, fasting insulin and fasting blood glucose were compared between the two groups. The endometrial samples were obtained from the patients to examine DNA methylation status of INSR gene in the endometrial cells using methylation-specific PCR.

RESULTSThe BMI, WHR, fasting glucose, fasting insulin, and HOMA index differed significantly between the two groups (P<0.05). PCR analysis showed partial methylation in the promoter region of INSR gene in 13 samples in IR group and 11 samples in NIR group, without detection of full methylation of the INSR gene in either group. The methylation status showed no significant difference between the two groups (P=0.328).

CONCLUSIONPartial methylation of the INSR gene occurs in the endometria of PCOS patients, but this study does not provide a strong evidence supporting the relationship between insulin resistance and INSR gene methylation in women with PCOS.

Adult ; DNA Methylation ; Endometrium ; metabolism ; Female ; Humans ; Insulin Resistance ; Polycystic Ovary Syndrome ; genetics ; metabolism ; Receptor, Insulin ; genetics ; metabolism

Adaptor Proteins, Signal Transducing ; genetics ; metabolism ; Animals ; Energy Metabolism ; genetics ; Growth Hormone ; metabolism ; Humans ; Insulin ; metabolism ; Longevity ; genetics ; Metabolism ; genetics ; Signal Transduction ; genetics

Breast Neoplasms ; genetics ; metabolism ; Carcinoma, Squamous Cell ; genetics ; metabolism ; Colorectal Neoplasms ; genetics ; metabolism ; Endometrial Neoplasms ; genetics ; metabolism ; Female ; Gene Frequency ; Genetic Predisposition to Disease ; Head and Neck Neoplasms ; genetics ; metabolism ; Humans ; Insulin-Like Growth Factor Binding Protein 1 ; genetics ; metabolism ; Insulin-Like Growth Factor Binding Protein 3 ; genetics ; metabolism ; Insulin-Like Growth Factor Binding Protein 5 ; genetics ; metabolism ; Insulin-Like Growth Factor Binding Proteins ; genetics ; metabolism ; Lung Neoplasms ; genetics ; metabolism ; Male ; Ovarian Neoplasms ; genetics ; metabolism ; Polymorphism, Genetic ; Promoter Regions, Genetic ; Prostatic Neoplasms ; genetics ; metabolism

Type 2 diabetes mellitus is characterized by insulin resistance and failure of pancreatic beta-cells producing insulin. Autophagy plays a crucial role in cellular homeostasis through degradation and recycling of organelles such as mitochondria or endoplasmic reticulum (ER). Here we discussed the role of beta-cell autophagy in development of diabetes, based on our own studies using mice with beta-cell-specific deletion of Atg7 (autophagy-related 7), an important autophagy gene, and studies by others. beta-cell-specific Atg7-null mice showed reduction in beta-cell mass and pancreatic insulin content. Insulin secretory function ex vivo was also impaired, which might be related to organelle dysfunction associated with autophagy deficiency. As a result, beta-cell-specific Atg7-null mice showed hypoinsulinemia and hyperglycemia. However, diabetes never developed in those mice. Obesity and/or lipid are physiological ER stresses that can precipitate beta-cell dysfunction. Our recent studies showed that beta-cell-specific Atg7-null mice, when bred with ob/ob mice, indeed become diabetic. Thus, autophagy deficiency in beta-cells could be a precipitating factor in the progression from obesity to diabetes due to inappropriate response to obesity-induced ER stress.
Animals ; Autophagy/genetics/*physiology ; Diabetes Mellitus/genetics/*metabolism ; Endoplasmic Reticulum Stress/genetics/*physiology ; Humans ; Insulin-Secreting Cells/*metabolism

OBJECTIVETo investigate the relationship between visceral fat depot and adiponectin level in OLETF rats.

METHODSTwenty male OLETF rats and 10 male Long-Evans Tokushima Otsuka (LETO) rats were subjected to regular oral glucose tolerance test (OGTT). The rats were sacrificed at the ages of 8, 32 and 40 weeks for measurements of the body weight, blood glucose, blood lipid level, blood insulin, and weight of the visceral fat.

RESULTSCompared with LETO rats, OLETF rats had significantly higher body weight and visceral fat with impaired glucose tolerance (P<0.05). OLETF rats also had higher blood insulin, TG, FFA and CHOL levels (P<0.05). The plasma adiponectin level was significantly lower in OLETF rats than in LETO rats at different ages (P<0.05). The adiponectin mRNA level in the adipose tissue of OLETF rats was comparable with that in LETO rats, but significantly decreased at 32 and 40 weeks of age (P<0.01).

CONCLUSIONPlasma adiponectin level is significantly correlated to insulin sensitivity and visceral fat depots in OLETF rats, but a lowered APN mRNA expression level is not the main reason for a decreased plasma adiponectin level in the early stage.

Adiponectin ; blood ; genetics ; metabolism ; Animals ; Insulin Resistance ; Intra-Abdominal Fat ; metabolism ; Male ; RNA, Messenger ; genetics ; metabolism ; Rats ; Rats, Inbred OLETF

Animals ; Cell Cycle Proteins/metabolism* ; Insulin Resistance/genetics* ; Liver/physiopathology* ; Mice ; Sirtuin 1/metabolism*

Animals ; Hypoxia ; metabolism ; physiopathology ; Insulin-Like Growth Factor I ; genetics ; metabolism ; Male ; Muscle, Skeletal ; metabolism ; Myostatin ; genetics ; metabolism ; RNA, Messenger ; genetics ; metabolism ; Rats ; Rats, Sprague-Dawley

BACKGROUNDPolycystic ovary syndrome (PCOS) is the commonest endocrinopathy in women of reproductive age. The patients often develop insulin resistance (IR) or hyperinsulinemia despite manifesting anovulation and signs of hyperandrogenism. The cause and effect relationship of hyperinsulinemia and hyperandrogenemia (HA) is still debated. Micro-ribonucleic acids (miRNAs) have recently been shown to play a role in regulation of ovarian function. Our current study focused on the altered expression of miRNAs with PCOS.

METHODSOvarian theca interna tissues were obtained from 10 PCOS patients and 8 controls that were non-PCOS and had normal insulin sensitivity undergoing laparoscopy and/or ovarian wedge resection. Total RNA of all samples was extracted. We studied the repertoire of miRNAs in both PCOS and non-PCOS women by microarray hybridization. Bioinformatic analysis was performed for predicting targets of the differentially expressed miRNAs. Furthermore, selected miRNAs were validated by quantitative reverse transcriptase polymerase chain reaction (qRT-PCR).

RESULTSA total of 27 miRNAs were differentially expressed in PCOS patients with respect to the controls in our discovery evaluationand two (miR-92a and miR-92b) of them were significantly downregulated in PCOS women in followed validation (P < 0.05). Targets prediction revealed that miR-92a targeted both GATA family of zinc finger transcription factor GATA-binding factor 6 (GATA6) and insulin receptor substrate proteins 2 (IRS-2).

CONCLUSIONSMiRNAs are differentially expressed between PCOS patients and controls. We identified and validated two miRNAs-miR-92a and miR-92b. They are significantly downregulated and may be involved in the pathogenesis of PCOS.

Adult ; Female ; Humans ; Hyperandrogenism ; genetics ; Insulin Resistance ; genetics ; physiology ; Male ; MicroRNAs ; genetics ; Ovary ; metabolism ; Polycystic Ovary Syndrome ; genetics

OBJECTIVETo investigate the relationship between insulin resistance (IR) and adiponectin gene expression in patients with nonalcoholic fatty liver disease (NAFLD).

METHODSSubcutaneous (SC) and omental (OM) adipose tissues were obtained from 21 NAFLD patients with obesity (n=10) and nonobesity (n=11) and also from 24 subjects (without NAFLD) with obesity (n=11) and nonobesity (n=13) who served as controls. Adiponectin mRNA expression levels in subcutaneous and omental adipose tissues were measured using SYBR Green I quantitative real-time PCR. The levels of plasma adiponectin and insulin were measured with ELISA. IR was estimated using the homeostasis assessment (HOMA).

RESULTSThe scores of HOMA-IR levels of the NAFLD patients and the controls with obesity and nonobesity were: 3.0+/-0.8, 2.8+/-0.9, 2.0+/-0.6, 1.2+/-0.5 respectively. The relative mRNA expression of adiponectin and blood adiponectin levels in NAFLD patients differed significantly from those of the controls. The HOMA-IR negatively correlated with the adiponectin mRNA expression levels of adipose tissues (r = -0.5) and blood adiponectin; it positively correlated with body mass index (r = 0.4), waist-hip-ratio (r = 0.4) and serum triglyceride (r = 0.3), but did not correlate with serum total cholesterol (r = 0.2).

CONCLUSIONIR of NAFLD patients was linked to low adiponectin gene expression in their adipose tissues. This finding suggests that low adiponectin gene expression may play a role in the pathogenesis of insulin resistance and NAFLD.

Adiponectin ; genetics ; metabolism ; Adipose Tissue ; metabolism ; Body Mass Index ; Case-Control Studies ; Fatty Liver ; genetics ; metabolism ; Female ; Gene Expression ; Humans ; Insulin ; metabolism ; Insulin Resistance ; Lipid Metabolism ; Male ; Obesity ; genetics ; metabolism