Zinc Transporter ZnT1 mRNA Expression Is Negatively Associated with Leptin Serum Concentrations but Is not Associated with Insulin Resistance or Inflammatory Markers in Visceral Adipose Tissue.

The aim of this study was to evaluate the relationship between biomarkers of chronic inflammation, insulin resistance, and zinc transporter ZnT1 expression in human visceral adipose tissue. Visceral adipose tissue obtained from 47 adults undergoing laparoscopic surgery for cholecystectomy was used to analyze ZnT1 mRNA expression by RT-qPCR. ZnT1 mRNA levels were compared between subjects with normal weight, overweight, and obesity. A significantly lower ZnT1 expression was observed in overweight and obesity compared with normal-weight subjects (p = 0.0016). Moreover, subjects with normal weight had significantly higher serum zinc concentration (97.7 ± 13.1 mg/L) than subjects with overweight (87.0 ± 12.8 mg/L) and obesity (83.1 ± 6.6 mg/L) (p = 0.002). Pearson test showed a positive correlation between serum zinc concentrations and ZnT1 mRNA expression in visceral adipose tissue (r = 0.323; p = 0.031) and a negative correlation with body mass index (r = - 0.358; p = 0.013). A linear regression model was used to analyze the associations between ZnT1 mRNA expression and serum zinc levels, insulin resistance (HOMA2-IR), serum adipokines (leptin and adiponectin), and serum inflammation biomarkers (tumor necrosis factor alpha, interleukin-6, and C-reactive protein). Interestingly, leptin concentrations were negatively associated with ZnT1 mRNA expression (p = 0.012); however, no significant associations were found for the rest of the analyzed variables. Future research is needed to analyze the causality of negative association between ZntT1 expression in visceral adipose tissue and leptin.

Low miR-222 expression in human visceral adipose tissue is associated with insulin resistance and PTEN and p53 mRNA levels.

INTRODUCTION: The aim of this is study was to analyse the expression of miR-193b, miR-378, miR-Let7-d, and miR-222 in human visceral adipose tissue (VAT), as well as their association with obesity, insulin resistance (IR), and their role in the regulation of genes controlling adipose tissue homeostasis, including adipocytokines, the phosphatase and tension homologue (PTEN), and tumour protein 53 (p53). MATERIAL AND METHODS: VAT was obtained from normal-weight (NW), overweight, and obese (OW/OB) subjects with and without IR. Stem-loop RT-qPCR was used to evaluate miRNA expression levels. miRTarBase 4.0, miRWalk, and DIANA-TarBase v8 were used for prediction of validated target gene of the miRNA analysed. A qPCR was used to evaluate PTEN, p53, leptin (LEP), and adiponectin (ADIPOQ) mRNA. RESULTS: miR-222 was lower in IR subjects, and miR-222 and miR-378 negatively correlated with HOMA-IR. PTEN and p53 are miR-222 direct targets according to databases. mRNA expression of PTEN and p53 was lower in OW/OB subjects with and without IR, compared to NW group and its levels positively associated with miR-222. Additionally, p53 and PTEN are positively associated with serum leptin levels. On the other hand, miR-193b and miR-378 negatively correlated with serum leptin but not with mRNA levels. Moreover, miR-Let-7d negatively correlated with serum adiponectin but not with adiponectin mRNA levels. CONCLUSIONS: Lower miR-222 levels are associated with IR, and PTEN and p53 expression; the implication of these genes in adipose tissue homeostasis needs more research.

Expression of miRNA in obesity and insulin resistance: a review.

MicroRNAs (miRNAs) are part of the epigenetic mechanisms that regulate gene expression at a post-transcriptional level. This review describes some miRNAs whose expression is modified in obesity and that may be involved in the development of insulin resistance. The metabolic alterations associated with obesity are due to an adipose tissue dysfunction. miRNAs are a mechanism that regulates gene expression, one miRNA can regulate the expression up to a thousand genes, and at the same time one gene can be regulated by several miRNAs; moreover, miRNA expression is tissue specific. Obesity leads to a dysregulation of miRNA expression in adipose tissue, and changes in miRNA expression relate to changes in gene expression related to the development of insulin resistance. However, because miRNA can be exported to the extracellular medium through exosomes, proteins, and lipoproteins, miRNA can be found in extracellular fluids like blood, urine, saliva, and cerebrospinal fluid. Considering the above, miRNA have been proposed as biological markers of different diseases, and also as potential therapeutic targets.