TABLE 1.
Summary of factors in macrophages that protect from (green) or promote (red) adipose tissue inflammation and insulin resistance.
| Factor | Function | References | |
|---|---|---|---|
| Lipid handling | PPARγ | Regulates metabolic processes such as lipid production, storage and metabolism. Promotes pro-resolving polarization and efferocytosis | Luo et al. (2019), Montaigne et al. (2021) |
| TREM2 | Marker for foam cell like macrophages, involved in phagocytosis and lipid catabolism | Kober and Brett (2017), Jaitin et al. (2019) | |
| LPL | Uptake and metabolism of cholesterol and fatty acids from lipoproteins, as well as the synthesis of cholesterol esters and triglycerides | Mead et al. (2002), Aouadi et al. (2014) | |
| Cytokine | IL-1β | Reprograms adipocyte metabolism, promotes myelopoiesis and adipocyte insulin resistance | Larsen et al. (2007), Vandanmagsar et al. (2011), Gao et al. (2014), Nagareddy et al. (2014), Zhou et al. (2020) |
| IL-13 | inhibit inflammatory activation of ATMs and improve glucose and insulin tolerance | Kwon et al. (2014) | |
| IL-33 | induces the production of IL-5, IL-6 and IL-13 which can exert protection against insulin resistance, also reduces obesity | Miller et al. (2010) | |
| IL-10 | Suppress the production of pro-inflammatory cytokines and increases sensitivity to insulin | Lumeng et al. (2007), Hong et al. (2009) | |
| Lipid mediators | COX-2 | Inhibits accumulation of fat in ATMs and their local proliferation, as well as monocyte recruitment | Pan et al. (2022) |
| BLT1 | Promotes trafficking of monocyte to AT and increases hepatic triglyceride levels | Spite et al. (2011) | |
| RvD1, RvE1 | Improve hyperglycemia and hyperinsulinemia. RvD1 promotes reparative macrophage polarization | Hellmann et al. (2011), Pal et al. (2020) | |
| miRNAs | miR-155 | Inhibits insulin signaling through suppression of Pparg | Tryggestad et al. (2019) |
| miR-17–92 | Upregulates Il10 and suppresses Tnfa | Zhang et al. (2020) | |
| miR-30 | Reduces inflammatory polarization, including TNFa and CCL2 production | Miranda et al. (2018) | |
| Efferocytosis/phagocytosis | MERTK | Crucial role in the recognition and subsequent ingestion of apoptotic cells | Suresh Babu et al. (2016) |
| ADAM9 | Cleaves and inactivates Mertk | Suresh Babu et al. (2016) | |
| EPO | Elevates PPARγ levels | Luo et al. (2019) |