Fatty acids from fat cell lipolysis do not activate an inflammatory response but are stored as triacylglycerols in adipose tissue macrophages

Abstract

Aims/hypothesis Activation of macrophages by fatty acids (FAs) is a potential mechanism linking obesity to adipose tissue (AT) inflammation and insulin resistance. Here, we investigated the effects of FAs released during adipocyte lipolysis on AT macrophages (ATMs). Methods Human THP-1 macrophages were treated with media from human multipotent adipose-derived stem (hMADS) adipocytes stimulated with lipolytic drugs. Macrophages were also treated with mixtures of FAs and an inhibitor of Toll-like receptor 4, since this receptor is activated by saturated FAs.Levels of mRNA and the secretion of inflammation-related molecules were measured in macrophages. FA composition was determined in adipocytes, conditioned media and macrophages. The effect of chronic inhibition or acute activation of fat cell lipolysis on ATM response was investigated in vivo in mice. Results Whereas palmitic acid alone activates THP-1, conditioned media from hMADS adipocyte lipolysis had no effect on IL, chemokine and cytokine gene expression, and secretion by macrophages. Mixtures of FAs representing de novo lipogenesis or habitual dietary conditions also had no effect. FAs derived from adipocyte lipolysis were taken up by macrophages and stored as triacylglycerol droplets. In vivo, chronic treatment with an antilipolytic drug did not modify gene expression and number of ATMs in mice with intact or defective Tlr4. Stimulation of adipocyte lipolysis increased storage of neutral lipids by macrophages without change in number and phenotype.

Dietary taurine supplementation to a plant protein source‐based diet improved the growth and intestinal immune function of young grass carp (Ctenopharyngodon idella)

“…In rat, taurine could increase liver CD36 expression (Li, Reynolds, Sloboda, Gray, & Vickers, ) that contributed to the uptake of oleate only in the PI and MI, but not in the DI (Nassir, Wilson, Han, Gross, & Abumrad, ). A study reported that oleate could increase IL‐10 secretion in the THP‐1 macrophages of human (Casparbauguil et al, ). Hence, we propose that taurine supplementation might contribute to the uptake of oleate only in the PI and MI (rather than in the DI), leading to the up‐regulated IL‐10 mRNA levels only in the PI and MI (rather than in the DI) of fish.…”

“…In rat, taurine could increase liver CD36 expression (Li, Reynolds, Sloboda, Gray, & Vickers, 2013) that contributed to the uptake of oleate only in the PI and MI, but not in the DI (Nassir, Wilson, Han, Gross, & TA B L E 5 Correlation coefficient of parameters between signal molecules and inflammatory cytokines, as well as signal molecules themselves in proximal intestine (PI), mid intestine (MI) and distal intestine (DI) of young grass carp (Ctenopharyngodon idella) fed the all-plant protein source-based diets containing graded levels of taurine Abumrad, 2007). A study reported that oleate could increase IL-10 secretion in the THP-1 macrophages of human (Casparbauguil et al, 2015). Hence, we propose that taurine supplementation might contribute to the uptake of oleate only in the PI and MI (rather than in the DI), leading to the up-regulated IL-10 mRNA levels only in the PI and MI (rather than in the DI) of fish.…”

Gut microbiota‐derived lipopolysaccharide uptake and trafficking to adipose tissue: implications for inflammation and obesity

“…The authors suggested that other mechanisms may link dietary fat intake with TLR‐associated pathologies . The view that FFAs from adipocytes did not stimulate cytokine release from macrophages has recently been confirmed by experimental observations . Moreover, the RBP4 (a retinol transporter secreted from adipocytes and liver) is also involved in AT inflammation .…”

Adipose tissue macrophages: going off track during obesity

“…Moreover, SFAs and their derivatives, including ceramides, are classified as danger-associated molecular patterns (DAMPs) that are recognised by the NLRP3 inflammasome and lead to IL-1β secretion via caspase 1 activation [ 142 ]. However, the response of macrophages upon lipid uptake does not necessarily have to be proinflammatory in nature [ 143 ]. Although it has been suggested that internalised palmitate, a very well-known SFA, promotes lipid metabolism and limits inflammation [ 57 ], in general only unsaturated FAs, particularly n -3 FAs, are recognised for their anti-inflammatory properties [ 139 , 144 ].…”