Abstract
Obesity is a complex condition that increases the risk of life threatening diseases such as cardiovascular disease and diabetes. Studying the gene regulation of obesity is important for understanding the molecular mechanisms behind the obesity derived diseases and may lead to better intervention and treatment plans. MicroRNAs (miRNAs) are short non-coding RNAs regulating target mRNA by binding to their 3’UTR. They are involved in numerous biological processes and diseases, including obesity. In this study we use a mixed breed pig model designed for obesity studies to investigate differentially expressed miRNAs in subcutaneous adipose tissue by RNA sequencing (RNAseq). Both male and female pigs are included to explore gender differences. The RNAseq study shows that the most highly expressed miRNAs are in accordance with comparable studies in pigs and humans. A total of six miRNAs are differentially expressed in subcutaneous adipose tissue between the lean and obese group of pigs, and in addition gender specific significant differential expression is observed for a number of miRNAs. The differentially expressed miRNAs have been verified using qPCR. The results of these studies in general confirm the trends found by RNAseq. Mir-9 and mir-124a are significantly differentially expressed with large fold changes in subcutaneous adipose tissue between lean and obese pigs. Mir-9 is more highly expressed in the obese pigs with a fold change of 10 and a p-value < 0.001. Mir-124a is more highly expressed in the obese pigs with a fold change of 114 and a p-value < 0.001. In addition, mir-124a is significantly higher expressed in abdominal adipose tissue in male pigs with a fold change of 119 and a p-value < 0.05. Both miRNAs are also significantly higher expressed in the liver of obese male pigs where mir-124a has a fold change of 12 and mir-9 has a fold change of 1.6, both with p-values < 0.05.
Highlights
Obesity is a risk factor for various complications and diseases such as hypertension, cardiovascular disease, dyslipidemia, inflammation, insulin resistance and type II diabetes
Retroperitoneal fat was bluntly excised at slaughter and the weight of it was corrected for body length; Body Mass Index (BMI) was calculated as weight/(length)2; Body Adiposity Index (BAI) was calculated as abdominal circumference divided by length1.5; the abdominal circumference (ABC) was measured around the largest circumference of the body
Sequencing of the small RNA fraction isolated from subcutaneous adipose tissue from the 14 samples produced 52,883,376 reads
Summary
Obesity is a risk factor for various complications and diseases such as hypertension, cardiovascular disease, dyslipidemia, inflammation, insulin resistance and type II diabetes. The obese state, characterized by excess fat accumulation, is in itself a burden to the affected subject with minor complications such as back pain, respiratory symptoms and difficulties in physical activity, but the secondary complications such as type 2 diabetes and coronary heart disease are expensive in terms of health-care costs as well as being life threatening [1]. The excess fat, in form of lipids, is stored in specialized cells (adipocytes) in the adipose tissue. Apart from storing lipids for later use as an energy source, adipose tissue functions as an endocrine organ secreting cytokines and interleukins involved in energy metabolism and inflammation. The endocrine activity derives from the adipocytes, and from immune cells present in the adipose tissue. Macrophages are recruited to, and accumulate in the adipose tissue where they contribute to the inflammation seen in these subjects [2]
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