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1. Introduction
Obesity is currently declared a global pandemic by the World Health Organization (WHO; http://www.who.int/mediacentre/factsheets/fs311/en/index.html/), with at least 2.6 millions of people dying each year as a result of being overweight or obese. The incidence of overweight and obesity is dramatically rising and, according to WHO predictions, approximately 2.3 billion of people will be overweight and more than 700 million will be obese by the year 2015 (http://www.who.int/features/factfiles/obesity/en/index.html). Furthermore, obesity predisposes to the development of metabolic abnormalities, clustered in the term metabolic syndrome. The metabolic syndrome is characterized by the presence of at least three of five symptoms: central obesity, insulin resistance, impaired glucose tolerance, dyslipidemia (increased triglyceridemia and low plasma high-density lipoproteins (HDL) cholesterol), and/or hypertension [1–5]. Moreover, metabolic syndrome is the main risk factor for developing type 2 diabetes [6, 7]. From these considerations, there is an urgent necessity for increasing knowledge about obesity and its effects. However, mechanistical experimentation is not affordable in human beings and animal models are needed.
Most of the experimental studies on obesity and metabolic disorders are carried out on laboratory rodents despite the marked differences in metabolism and adipose tissue biology between rodents and humans [8]. However, different species of large animals offer numerous profitable characteristics [9]. The pig is emerging rapidly as a biomedical model for energy metabolism and obesity in humans because it shares several similarities with humans: omnivorous habits, propensity to sedentary behaviour and fattening, and similar metabolic and cardiovascular features [10–13].
The objective of the present study was to determine the propensity of a swine breed with predisposition to obesity (the Iberian pig) for developing features of metabolic syndrome and type 2 diabetes. The Iberian pig is worldwide known for the production of a unique highly priced dry-cured product, the Iberian ham, with a unique taste due to its abundance in intramuscular fat. In fact, the Iberian pig has a high potential for fat accumulation under its skin and among the muscular fibres [14], due to a polymorphism of the leptin receptor gene (LEPR) with effects on food intake, body weight, and fat deposition [15, 16]. As a consequence, Iberian LEPR allele increases insatiability and obesity. Such state in human medicine is called leptin resistance, the failure, in...