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A Journal on Dermatology
Esperienze Dermatologiche 2010 June;12(2):63-8
Histophysiology and histopathology of adipose organ
Dipartimento di Patologia Molecolare e terapie Innovative, Università Politecnica delle Marche, Ancona
Mammals have two types of adipose tissues, white and brown, and their anatomy and physiology is different. White adipose tissues store lipids, and brown adipose tissue burn them to produce heat. We demonstrated that they are mixed in many fat depots, raising the concept of adipose organ. In fact organs are formed by different tissues cooperating for functional purposes. We explain the reason for their cohabitation with the hypothesis of reversible physiological transdifferentiation: they are able to convert one into each other. If needed, the brown component of the organ could increase at the expense of the white component and vice versa. This plasticity is important because the brown phenotype of the organ associates with resistance to obesity and related disorders. This is relevant because a brown phenotype of the adipose organ induce obesity resistance. Recent data suggest that the adipose organ of humans have similar properties. Another example of physiological transdifferetiation of adipocytes is offered by the mammary gland: the pregnancy hormonal stimuli seems to trigger a reversible transdifferentiation of adipocytes into milk-secreting epithelial glands. The obese adipose organ is infiltrated by macrophages inducing chronic inflammation that is widely considered as a causative factor for insulin resistance. We showed that the vast majority of macrophages infiltrating the obese organ are arranged around dead adipocytes, forming characteristic “crown-like structures”. This could be caused by the excess of enlargement reached by adipocytes in obese status. Visceral adipocytes seems to be more susceptible to death offering a possible explanation to the more pathogenic effects of visceral fat accumulation.