INFORMATIVE NOTE: An opinion on the regulation of bone marrow adipose tissue by dietary fatty acids

Obesity has a significant impact on predisposition to various diseases and also affects the viabil­ity and choice of haematopoietic stem cells (HSCs) to favour myeloid cell production and/or turnover, all of which are extremely important for the functioning of immune system. As the production of blood cells and mobilization of HSCs and their progeny are regulated, at least in part, by multifaceted interactions through signals that come from the bone marrow (BM) microenvironment, it does not seem astonishing to assume that circumstances that cause alterations in BM structure will unavoidably cause alterations in mesenchymal cells such as adipocytes and lineages from HSCs. The existence of adipose tissue in BM or marrow fat (BMAT) is well known, although its origin, expansion, and functions are poorly understood. Inspired by other studies showing the potential role for olive oil and omega-3 long chain polyunsaturated fatty acids (omega-3 PUFAs) on BM health, and by our own preliminary findings showing the effects of monounsaturated (olive oil) but not saturated (milk cream) dietary fats to contain neutrophils and CD14 high monocytes in BM during postprandial periods in healthy volunteers, herein we asked whether dietary fats (saturated fatty acids, SFAs, monounsatu­rated fatty acids, MUFAs, and omega-3 PUFAs) may be a candidate lifestyle factor to modulate the expansion, composition, and function of BMAT, the infiltration of adipose tissue macrophages (ATMs) in BMAT and the mobilization of HSCs and mature myeloid cells from BM during high-fat-induced obesity in mice. This is the first time that the interplay between different dietary fatty acids, obesity, and BM is addressed.