HIGHLY PHAGOCYTIC LIPID-ASSOCIATED MACROPHAGES (LAMs) ARE INCREASED 2 IN COLONIC LAMINA PROPRIA IN OBESITY
Little is known about the effects of high fat diet (HFD)-induced obesity on resident colonic lamina propria (LP) macrophages (LPMs) function and metabolism. Here, we report that obesity and diabetes resulted in increased macrophage infiltration in the colon. These macrophages exhibited the residency phenotype CX3CR1hiMHCIIhi, and were CD4-TIM4-. During HFD, resident colonic LPM exhibited a lipid metabolism gene expression signature that overlapped that used to define lipid associated macrophages (LAMs). Via single cell RNA sequencing, we identified a sub-cluster of macrophages, increased in HFD, that were responsible for the LAM signature. Compared to other macrophages in the colon, these cells were characterized by elevated glycolysis, phagocytosis and efferocytosis signatures. CX3CR1hiMHCIIhi colonic resident LPMs had fewer lipid droplets (LD) and decreased triacylglycerol (TAG) content compared to equivalent cells in lean mice, and exhibited increased phagocytic capacity, suggesting that HFD induces adaptive responses in LPMs to limit bacterial translocation. Overall design: Obesity was induced by ad libitum feeding of C57/BL6 CX3CR1 GFP heterozygous mice for 12 weeks with irradiated high fat diet (Rodent Diet 60% kcal from fat). Control diet (chow) containing 24% protein, 47.5% 438 carbohydrate, and 4.9% fat, was given to age and sex matched animals as a control group. Lamina propria cells from 4 animals from each group were prepared for cell sorting and incubated in anti-CD16/32, stained with Live/Dead, and fluorochrome-conjugated antibody to CD45, CD11b, CD64 , MHCII.  FACS-sorted CX3CR1hi MHCIIhi LPMs using a BD FACS ARIATM III, were prepared for RNA extraction.