Villaseñor A

Language: Spanish
References: 35
Page: 135-139
PDF size: 64.84 Kb.

ABSTRACT

Leptin is a 167 amminoacid protein synthesized and secreted by adipocytes which provides a feedback signal from adipose tissue to receptors in the hypothalamus. Visceral adipocytes appear to produce less leptin than their subcutaneous counterpart. Leptin traverses the blood-brain barrier to inhibit the synthesis of neuropeptide Y with powerful stimulatory effects on appetite. Also inhibits other orexigenic neuropeptides. High leptin levels, indicative of an excessive adipose tissue mass, also lead to increased thermogenesis (neuropeptide Y, also inhibits the activity of thermogenic brown adipose tissue in the rat). Concomitantly, neuropeptide Y administration increases the activity of the hypothalamus-pituitary-adrenal axis, with resulting hypercortisolemia and increased susceptibility to stressful situations. These effects serve to limit further weight gain. Animal models in which leptin (ob/ob mouse) or its hypothalamic receptor (db/db mouse, fa/fa rat) are absent are associated with obesity and insulin resistance. Circulating leptin concentrations are elevated in most obese humans implying cellular resistance rather than deficiency. Plasma leptin concentrations correlate with hyperinsulinemia independently of body mass index.

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