Macrophage Phenotypes and Gene Expression Patterns Are Unique in Naturally Occurring Metabolically Healthy Obesity

Abstract

Obesity impacts 650 million individuals globally, often co-occurring with metabolic syndrome. Though many obese individuals experience metabolic abnormalities (metabolically unhealthy obese [MUO]), ~30% do not (metabolically healthy obese [MHO]). Conversely, >10% of lean individuals are metabolically unhealthy (MUL). To evaluate the physiologic drivers of these phenotypes, a 44-animal African green monkey cohort was selected using metabolic syndrome risk criteria to represent these four clinically defined health groups. Body composition imaging and subcutaneous adipose tissue (SQ AT) biopsies were collected. Differences in adipocyte size, macrophage subtype distribution, gene expression, vascularity and fibrosis were analyzed using digital immunohistopathology, unbiased RNA-seq, endothelial CD31, and Masson’s trichrome staining, respectively. MHO AT demonstrated significant increases in M2 macrophages (p = 0.02) and upregulation of fatty acid oxidation-related terms and transcripts, including FABP7 (p = 0.01). MUO AT demonstrated downregulation of these factors and co-occurring upregulation of immune responses. These changes occurred without differences in AT distributions, adipocyte size, AT endothelial cells, collagen I deposition, or circulating cytokine levels. Without unhealthy diet consumption, healthy obesity is defined by an increased SQ AT M2/M1 macrophage ratio and lipid handling gene expression. We highlight M2 macrophages and fatty acid oxidation as targets for improving metabolic health with obesity.

Visceral adipose microbial and inflammatory signatures in metabolically healthy and unhealthy nonhuman primates

“…A total of 150 middle‐aged to older female monkeys (6.7–23.5 years) in the Vervet Research Colony at Wake Forest University School of Medicine, Winston‐Salem, North Carolina, were screened using MetS criteria described for NHPs (waist circumference > 40 cm; hemoglobin A 1c > 6%; blood glucose > 100 mg/dL; systolic blood pressure > 135 mm Hg; diastolic blood pressure > 85 mm Hg; triglycerides > 125 mg/dL; high‐density lipoprotein cholesterol < 50 mg/dL) to identify each metabolic health grouping (44 animals total; n = 9–13 per group) [15, 16]. All animals were maintained on ad libitum feeding, and MetS criteria developed spontaneously; MetS scores were calculated as the sum of each criterion met, as previously described [16]. To date, there is no consensus on the definitions of MHO and MUL phenotypes.…”

“…High‐quality RNA with RNA integrity values ranging from 7.2 to 8.9 was used for RNA sequencing analyses. Copy DNA libraries were prepared, assessed, sequenced, and mapped as previously described, and they are provided in the online Supporting Information Methods [16]. On average, 32.11 ± 5.24 million reads in the RNA sequencing analyses were uniquely mapped to the genome and used for downstream analyses including transcript quantifications and gene pathway identifications.…”

“…Negative and positive controls were unstained sections and lung tissue, respectively. Adipocyte analyses on hematoxylin and eosin‐stained tissue sections determined total tissue area, adipocyte number, and individual cell areas [16]. Sections of adipose tissue were stained with Masson's Trichrome (Abcam) and CD31 (Biocare Medical LLC).…”

“…Staining marked four macrophage phenotypes [16] using fluorescent CD68 and CD163 to evaluate total macrophage infiltration (AbD Serotec, Bio-Rad Laboratories, Inc.), co-stained with pSTAT1 (Cell Signaling Technology) and C-macrophage activation factor (CMAF) (Abcam) to identify undefined (CD68 + CD163 + ), M1 (CD68 + CD163 + pSTAT1 + ), intermediate (CD68 + CD163 + pSTAT1 + CMAF + ), and M2 macrophages (CD68 + CD163 + CMAF + ). Visiopharm software (version 2019.02.1.6005, Visiopharm A/S) distinguished macrophage types by 4 0 , 6-diamidino-2-phenylindole (DAPI)-stained nuclei and the respective macrophage-specific overlaying stains (Supporting Information Figure S2A).…”

Obesity as a Risk Factor for Breast Cancer—The Role of miRNA

“…Due to obesity and secretion of selected cytokines (IL-6 and TNF- α), the anti-inflammatory phenotype of macrophages changes into a proinflammatory phenotype [ 50 ]. The percentage of M1 macrophages increases from 5% to 50% in AT of obese people compared to lean patients [ 51 , 52 , 53 ]. Additionally, primary tumors also secrete cytokines to recruit inflammatory response cells (e.g., monocytes, granulocytes) into the tumor and, consequently, promote chronic inflammation.…”