We examined the effects of three high‐fat diets differing in the percentage of total calories from saturated fat (SF) (6%, 12%, and 24%), but identical in total fat (40%), on body composition, macrophage behavior, inflammation, and metabolic dysfunction in mice. Diets were administered for 16 weeks. Body composition and metabolism (glucose, insulin, triglycerides, LDL‐C, HDL‐C, total cholesterol) were examined monthly. Adipose tissue (AT) expression of marker genes for M1 and M2 macrophages and inflammatory mediators (TLR‐2, TLR‐4, MCP‐1, TNF‐α, IL‐6, IL‐10, SOCS1, IFN‐γ) was measured along with activation of NFκB, JNK and p38‐MAPK. AT macrophage infiltration was examined using immunohistochemistry. Circulating MCP‐1, IL‐6, adiponectin, and leptin were also measured. SF content, independent of total fat, can profoundly affect adiposity, macrophage behavior, inflammation, and metabolic dysfunction. In general, the 12%‐SF diet, most closely mimicking the standard American diet, led to the greatest adiposity, macrophage infiltration, and insulin resistance (IR), whereas the 6%‐SF and 24%‐SF diets produced lower levels of these variables with the 24%‐SF diet resulting in the least degree of IR and the highest TC/HDL‐C ratio. Macrophage behavior, inflammation and IR following HFDs are heavily influenced by dietary SF content, however, these responses are not necessarily proportional to the SF%. This work was supported by an ASPIRE (Advanced Support Programs for Innovative Research Excellence) grant from the University of South Carolina to E.A.M. Grant Funding Source: ASPIRE

Obesity is characterized by chronic low-grade, systemic inflammation, altered gut microbiota, and gut barrier disruption. Additionally, obesity is associated with increased activity of endocannabinoid system (eCB). However, the clear connection between gut microbiota and the eCB system in the regulation of energy homeostasis and adipose tissue inflammation and metabolism, remains to be established. We investigated the effect of treatment of mice with a cannabinoid receptor 1 (CB1) antagonist on Diet-Induced Obesity (DIO), specifically whether such a treatment that blocks endocannabinoid activity can induce changes in gut microbiota and anti-inflammatory state in adipose tissue. Blockade of CB1 attenuated DIO, inflammatory cytokines and trafficking of M1 macrophages into adipose tissue. Decreased inflammatory tone was associated with a lower intestinal permeability and decreased metabolic endotoxemia as evidenced by reduced plasma LPS level, and improved hyperglycemia and insulin resistance. 16S rRNA metagenomics sequencing revealed that CB1 blockade dramatically increased relative abundance of Akkermansia muciniphila and decreased Lanchnospiraceae and Erysipelotrichaceae in the gut. Together, the current study suggests that blocking of CB1 ameliorates Diet-Induced Obesity and metabolic disorder by modulating macrophage inflammatory mediators, and that this effect is associated with alterations in gut microbiota and their metabolites.

Tumor-associated macrophages are associated with poor prognosis in certain cancers. Monocyte chemoattractant protein 1 (MCP-1) is thought to be the most important chemokine for recruitment of macrophages to the tumor microenvironment. However, its role on tumorigenesis in a genetic mouse model of colon cancer has not been explored. We examined the role of MCP-1 on tumor-associated macrophages, inflammation, and intestinal tumorigenesis. Male Apc Min/+, Apc Min/+/MCP-1−/− or wild-type mice were euthanized at 18 wk of age and intestines were analyzed for polyp burden, apoptosis, proliferation, β-catenin, macrophage number and phenotype, markers for cytotoxic T lymphocytes and regulatory T cells, and inflammatory mediators. MCP-1 deficiency decreased overall polyp number by 20% and specifically large polyp number by 45% ( P < 0.05). This was consistent with an increase in apoptotic cells ( P < 0.05), but there was no change detected in proliferation or β-catenin. MCP-1 deficiency decreased F4/80-positive cells in both the polyp tissue and surrounding intestinal tissue ( P < 0.05) as well as expression of markers associated with M1 (IL-12 and IL-23) and M2 macrophages (IL-13, CD206, TGF-β, and CCL17) ( P < 0.05). MCP-1 knockout was also associated with increased cytotoxic T lymphocytes and decreased regulatory T cells ( P < 0.05). In addition, MCP-1−/− offset the increased mRNA expression of IL-1β and IL-6 in intestinal tissue and IL-1β and TNF-α in polyp tissue ( P < 0.05), and prevented the decrease in SOCS1 expression ( P < 0.05). We demonstrate that MCP-1 is an important mediator of tumor growth and immune regulation that may serve as an important biomarker and/or therapeutic target in colon cancer.

BACKGROUND Non-alcoholic fatty liver disease (NAFLD) has become an epidemic largely due to the worldwide increase in obesity. While lifestyle modifications and pharmacotherapies have been used to alleviate NAFLD, successful treatment options are limited. One of the main barriers to finding safe and effective drugs for long-term use in NAFLD is the fast initiation and progression of disease in the available preclinical models. Therefore, we are in need of preclinical models that (1) mimic the human manifestation of NAFLD and (2) have a longer progression time to allow for the design of superior treatments. AIM To characterize a model of prolonged high-fat diet (HFD) feeding for investigation of the long-term progression of NAFLD. METHODS In this study, we utilized prolonged HFD feeding to examine NAFLD features in C57BL/6 male mice. We fed mice with a HFD (60% fat, 20% protein, and 20% carbohydrate) for 80 wk to promote obesity (Old-HFD group, n = 18). A low-fat diet (LFD) (14% fat, 32% protein, and 54% carbohydrate) was administered for the same duration to age-matched mice (Old-LFD group, n = 15). An additional group of mice was maintained on the LFD (Young-LFD, n = 20) for a shorter duration (6 wk) to distinguish between age-dependent and age-independent effects. Liver, colon, adipose tissue, and feces were collected for histological and molecular assessments. RESULTS Prolonged HFD feeding led to obesity and insulin resistance. Histological analysis in the liver of HFD mice demonstrated steatosis, cell injury, portal and lobular inflammation and fibrosis. In addition, molecular analysis for markers of endoplasmic reticulum stress established that the liver tissue of HFD mice have increased phosphorylated Jnk and CHOP. Lastly, we evaluated the gut microbial composition of Old-LFD and Old-HFD. We observed that prolonged HFD feeding in mice increased the relative abundance of the Firmicutes phylum. At the genus level, we observed a significant increase in the abundance of Adercreutzia, Coprococcus, Dorea , and Ruminococcus and decreased relative abundance of Turicibacter and Anaeroplasma in HFD mice. CONCLUSION Overall, these data suggest that chronic HFD consumption in mice can mimic pathophysiological and some microbial events observed in NAFLD patients.

SummaryInflammatory bowel disease (IBD), a chronic intestinal inflammatory condition that affects millions of people worldwide, results in high morbidity and exorbitant health-care costs. The critical features of both innate and adaptive immunity are to control inflammation and dysfunction in this equilibrium is believed to be the reason for the development of IBD. miR-155, a microRNA, is up-regulated in various inflammatory disease states, including IBD, and is a positive regulator of T-cell responses.