Overexpression of the obese (ob) gene in adipose tissue of human obese subjects

Abstract

Obesity is accompanied by complications such as hypertension, non-insulin-dependent diabetes mellitus and atherosclerosis, which in turn cause ischaemic heart disease, stroke and premature death. The underlying mechanisms behind imbalance in energy intake and energy expenditure that lead to obesity are still controversial. In most populations, obesity is more common among women than men and is a multifactorial phenotype, which may result from a complex network of genetic and nongenetic factors. The relative importance of genetic factors for obesity is under debate. Genome searches using polymorphic markers in inbred mice with phenotypes that result in extreme obesity and studies of human candidate genes are being performed in an attempt to identify genes that contribute to obesity. There is evidence that body weight is physiologically regulated and it has been postulated that the storage of fat may provide signals to the brain that the body is obese, which in turn may make the subject eat less and burn more fuel. One of the molecules that may be involved in such signalling is the obese (ob) gene product. Mutations in ob result in profound obesity and type II diabetes in mice. The mouse ob gene and its human homologue have been cloned and sequenced. The gene is expressed in adipose tissue and the product has features of a secreted protein. We have investigated human ob expression in subcutaneous and omental adipose tissue obtained from non-obese and massively obese subjects using in situ hybridization histochemistry and report on overexpression in obese people.

Assessment of selected nutrient intake and adipocytokine profile among Saudi children and adults

“…The circulating levels of leptin have been shown to be influenced by amount of body fat, with higher levels in obese than in lean individuals [29]. However, conflicting findings are reported for leptin concentration differences with similar fat mass [30,31]. Another study found high plasma leptin levels in obese humans [32], suggesting release of leptin from the adipose tissue in relation to adiposity.…”

Role of leptin in hypothalamic–pituitary function

“…Leptin causes weight loss in mice by reducing food intake and increasing energy expenditure (2)(3)(4)(5). Furthermore, ob gene expression is increased in human obesity (6)(7)(8)(9) and in various animal models of obesity (10). The accumulated evidence suggests that leptin is important in controlling body weight.…”

Obesity and related consequences to ageing

“…Recent studies have shown that although the complete absence of leptin leads to obesity (Ahima and Flier 2000;Zhang et al 1994), leptin at excessive levels does not prompt a lean phenotype (Ahima and Flier 2000;Myers et al 2012). Leptin expression occurs at high levels in animal models of obesity (Frederich et al 1995;Sinha et al 1996) and in human obesity (Lonnqvist et al 1995). This phenomenon is called leptin resistance and is described as a reduced sensitivity with respect to the anorectic response to exogenously administered leptin (Carter et al 2013).…”