Adipose tissue macrophage (ATM)-driven inflammation plays a key role in insulin resistance; however, factors activating ATMs are poorly understood. Using a proteomics approach, we show that markers of classical activation are absent on ATMs from obese humans, but readily detectable on airway macrophages of patients with cystic fibrosis, a disease of chronic bacterial infection. Moreover, treating macrophages with glucose, insulin, and palmitate – conditions characteristic of the metabolic syndrome – produces a ‘metabolically-activated’ phenotype distinct from classical activation. Markers of metabolic activation are expressed by pro-inflammatory ATMs in obese humans/mice and are positively correlated with adiposity. Metabolic activation is driven by independent pro- and anti-inflammatory pathways, which regulate balance between cytokine production and lipid metabolism. We identify PPARγ and p62/SQSTM1 as two key proteins that promote lipid metabolism and limit inflammation in metabolically-activated macrophages. Collectively, our data provide important mechanistic insights into pathways that drive the metabolic disease-specific phenotype of macrophages.

SUMMARY During obesity, adipose tissue macrophages (ATMs) adopt a ‘metabolically-activated’ (MMe) phenotype. However, the functions of MMe macrophages are poorly understood. Here we combine proteomic and functional methods to demonstrate that in addition to potentiating inflammation, MMe macrophages also promote dead adipocyte clearance through lysosomal exocytosis. We identify NADPH-oxidase-2 (NOX2) as a driver of the inflammatory and adipocyte-clearing properties of MMe macrophages, and show that compared to wild-type, Nox2−/− mice exhibit a time-dependent metabolic phenotype during diet-induced obesity. After 8-weeks of high-fat feeding, Nox2−/− mice exhibit attenuated ATM inflammation and mildly improved glucose tolerance. After 16-weeks of high-fat feeding, Nox2−/− mice develop severe insulin resistance, hepatosteatosis, and visceral lipoatrophy characterized by dead adipocyte accumulation and defective ATM lysosomal exocytosis, a phenotype reproduced in myeloid cell-specific Nox2−/− mice. Collectively, our findings suggest that MMe macrophages perform detrimental and beneficial functions, whose contribution to metabolic phenotypes during obesity is determined by disease progression.

Abstract-It is becoming clear that upregulated protein kinase C (PKC) signaling plays a role in reduced ventricular myofilament contractility observed in congestive heart failure. However, data are scant regarding which PKC isozymes are involved. There is evidence that PKC-␣ may be of particular importance. Here, we examined PKC-␣ quantity, activity, and signaling to myofilaments in chronically remodeled myocytes obtained from rats in either early heart failure or end-stage congestive heart failure. Immunoblotting revealed that PKC-␣ expression and activation was unaltered in early heart failure but increased in end-stage congestive heart failure. Left ventricular myocytes were isolated by mechanical homogenization, Triton-skinned, and attached to micropipettes that projected from a force transducer and motor. Myofilament function was characterized by an active force- [Ca 2ϩ ] relation to obtain Ca 2ϩ -saturated maximal force (F max ) and myofilament Ca 2ϩ sensitivity (indexed by EC 50 ) before and after incubation with PKC-␣, protein phosphatase type 1 (PP1), or PP2a. PKC-␣ treatment induced a 30% decline in F max and 55% increase in the EC 50 in control cells but had no impact on myofilament function in failing cells. PP1-mediated dephosphorylation increased F max (15%) and decreased EC 50 (Ϸ20%) in failing myofilaments but had no effect in control cells. PP2a-dependent dephosphorylation had no effect on myofilament function in either group. Lastly, PP1 dephosphorylation restored myofilament function in control cells hyperphosphorylated with PKC-␣. Collectively, our results suggest that in end-stage congestive heart failure, the myofilament proteins exist in a hyperphosphorylated state attributable, in part, to increased activity and signaling of PKC-␣. Key Words: heart failure Ⅲ protein kinase C-␣ Ⅲ myofilament proteins Ⅲ protein phosphatase type 1 Ⅲ phosphorylation I t has been predicted that the global incidence and prevalence of the clinical syndrome of congestive heart failure (CHF) will continue to rise. 1 The "road" to CHF usually begins with some inciting event (eg, myocardial infarction), which imposes a heightened mechanical strain on the myocardium. Ventricular dysfunction ensues resulting in a decline in cardiac output. In turn, key regulatory neurohormonal signals are recruited, which, in the acute phase, maintain cardiac output and "mask" the underlying ventricular contractile deficit. However, prolonged exposure of the heart to these signals coupled with the prevailing mechanical overload proves deleterious resulting in contractile dysfunction, myocyte hypertrophy, and death, heralding a downward spiral wherein ventricular dysfunction becomes manifest and the clinical features of CHF overt. Not surprisingly, considerable attention is now being focused on unraveling the molecular and cellular complexities that conspire to promote contractile dysfunction of the failing cardiac myocyte, with the underlying aim being identification of novel molecules that may be potential foci for therapeutic inte...

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Tiwari et al. identify metabolically activated macrophages in obese mammary adipose tissue as an important source of IL-6, which fuels triple-negative breast cancer stemness and tumorigenesis through GP130 signaling. These mechanistic insights provide potential targets for treating obesity-associated triple-negative breast cancer.