Abstract
Obesity is a major risk factor of preventable deaths worldwide, with increasing rates being observed in adults and children. To understand the mechanisms of obesity development, genetically lean (Duroc strain) and obese (Rongchang strain) pigs were used to identify potential differences in muscle and adipose development patterns following consumption of an identical diet for 180 days. Lean pigs had a significantly higher lean percentage (67.79% versus 44.71%) and lower obesity index (0.68 versus 0.84) than obese pigs. They also exhibited significantly lower adipocyte volumes and higher myofibre cross-sectional areas. Quantitative polymerase chain reaction showed that lean pigs had a significantly higher expression of muscle growth-related genes and lower expression of lipogenesis-related genes. By contrast, obese pigs had higher expression of a myostatin-related gene and lower expression of lipolysis-related genes. Additionally, the mitochondrial DNA copy number was higher in the muscle and lower in adipose tissue in lean compared with obese pigs. These results indicate that lean pigs have a distinct development pattern from obese pigs, involving lipogenesis, muscle growth, and energy metabolism. This study provides a basis for exploring the mechanisms of adipose deposition and muscle growth in obesity. Keywords: Obesity, mitochondrial DNA, Sus scrofa
Highlights
Obesity and overweightness are prevalent in developed and developing countries, and are increasing at an alarming rate (Abelson & Kennedy, 2004; Haslam & James, 2005)
Duroc breed has been selected for lean meat for more than 60 years in the USA, whereas the Rongchang breed has not been genetically improved and has a tendency towards obesity
The lean percentage (LP), which correlates negatively with the percentage of fat, was significantly higher in Duroc pigs than in Rongchang pigs (Student’s t-test, 67.8% versus 44.7%, P = 2.05 × 10−5, Figure 1A), which is consistent with the definition of lean (LP > 60%) and obese pigs (LP
Summary
Obesity and overweightness are prevalent in developed and developing countries, and are increasing at an alarming rate (Abelson & Kennedy, 2004; Haslam & James, 2005). By 2030, up to 58% of the world’s adult population are predicted to be obese or overweight (Kelly et al, 2008). These are major risk factors for type 2 diabetes, cardiovascular diseases, hypertension, stroke, certain types of cancer, osteoarthritis and associated metabolic syndromes (Caballero, 2007), and are recognized as major worldwide public health problems, which lead to reduced life expectancy, poor quality of life, depression, and premature death. The major changes of adipokine and myokine production have a wide range of physiological functions, which result in the expansion of the adipose tissue and muscle mass that defines obesity and overweightness. Adipose tissue plays an important role in the regulation of energy metabolism, including storage and dissipation (Li et al, 2012), and skeletal muscle can have direct beneficial effects on the control of bodyweight and metabolism (Satoor et al, 2011)
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