Molecular Heterogeneities of Adipose Depots - Potential Effects on Adipose-Muscle Cross-Talk in Humans, Mice and Farm Animals

Abstract

Adipose tissue is considered as a major endocrine organ that secretes numerous proteins called adipokines. The heterogeneous nature of adipose tissue in different parts of the body suggests respective heterogeneity of proteomes and secretomes. This review consolidates knowledge from recent studies targeting the diversity of different adipose depots affecting the pattern of secreted adipokines and discusses potential consequences for the cross-talk between adipose and skeletal muscle in humans, rodent models and farm animals. Special attention is paid to muscle-associated fat depots like inter- and intramuscular fat that become focus of attention in the context of the rather new notion of skeletal muscle as a major endocrine organ. Understanding the complexity of communication between adipocytes and skeletal muscle cells will allow developing strategies for improvement of human health and for sustainable production of high quality meat.

Invited review: Pre- and postnatal adipose tissue development in farm animals: from stem cells to adipocyte physiology

“…), some under the skin (subcutaneous depots) and some within the musculature (inter-and intramuscular depots), these depots having large differences in size and in relative quantitative importance depending on age and species (Komolka et al, 2014). For instance, the predominant adipose tissue depot is subcutaneous AT in growing pigs (Kouba et al, 1999;Kouba and Bonneau, 2009) whereas it is intermuscular adipose tissue in cattle (Robelin, 1981;Cianzio et al, 1985).…”

“…Over the past years, the identification of multiple other secretory products termed adipokines or adipocytokines, has now allowed considering the WAT as a true secretory or endocrine organ (Romacho et al, 2014). It is important to note that the list of proteins secreted by WAT is still expanding including in livestock species (Komolka et al, 2014;Restelli et al, 2014).…”

Review: Animal model and the current understanding of molecule dynamics of adipogenesis

“…Although research in humans and farm animals ultimately have different goals -identification of potential drug targets for metabolic diseases v. optimization of meat quality -the same tissue can be the focus of both research efforts (Komolka et al, 2014). Bovine adipocytes are a cell model for studying adipogenesis and lipid metabolism for improving animal production and also serving human health .…”

“…Adipose cells derived from VAT, in particular, have higher levels of metabolic activity and have been shown to hypertrophy in obese individuals. In addition to VAT and SAT, intermuscular adipose tissue and IMF are also measured in farm animal species such as swine and cattle (Komolka et al, 2014).…”

“…Myostatin, a growth differentiation factor secreted by myoblasts, suppresses proliferation of preadipocytes in muscle tissue through direct down-regulation of adipogenic transcription factors, thus decreasing the overall IMF (Komolka et al, 2014). Furthermore, co-culture of myoblasts and adipocytes results in an upregulation of peroxisome proliferator activating receptor γ (PPARγ), CCAAT enhancer binding protein α (C/EBPα) and fatty acid binding protein 4 (FABP4), possibly indicating myoblasts' promotion of adipogenic specific transcription factors leading to increased IMF or allowing for MSC transdifferentiation as a mechanism for increasing IMF (Muthuraman, 2014).…”