Among the most frequently used genetic models to study NAFLD are those that exhibit alterations
in feeding behaviour (e.g., hyperphagia), which frequently results from defects in the leptin signalling
pathways. Indeed, the so-called ob/ob mouse carries a spontaneous mutation in the leptin gene, which
results in a leptin deficiency, subsequently leading to a hyperphagic, inactive, obese, and diabetic
phenotype accompanied by the development of NAFLD ([10,11] and Figure 2). This model has been
extensively studied, and is used as a model for various metabolic diseases, among them NAFLD,
despite the fact that the “ob” mutation is rare in humans [12–14]. Furthermore, results of association
studies of leptin levels with the development of NAFLD are somewhat contradictory, as in older
studies leptin levels correlate poorly with the development of NASH, whereas in more recent years, a
positive association was found [12–14].
Furthermore, more recent studies also reported an association of a single nucleotide polymorphism
on the gene encoding for the leptin receptor with the development of NAFLD [15,16]. However, also
unlike the human situation, ob/ob mice do not spontaneously progress from steatosis to steatohepatitis
but rather require some kind of “second hit” (e.g., a dietary intervention such as a methionine- and
choline-deficient (MCD) diet, or a high-fat diet (HFD), or a challenge with small doses of
endotoxin) [17,18].
Contrary to what is seen in ob/ob mice, db/db, mice have a natural mutation in the leptin receptor
(ob-Rb) gene; however, in line with what is found in ob/ob mice, db/db animals also only develop
obesity, insulin resistance, and macrovesicular steatosis and require a “second hit” to progress from
steatosis to steatohepatitis [19]. Similar to the latter, the obese (fa/fa) Zucker rat also exhibits
hyperphagia resulting in hyperinsulinemia, hyperlipidemia and the development of liver steatosis due
to a loss of the leptin receptor