Mohamed Omer - Academia.edu (original) (raw)
Papers by Mohamed Omer
Cell Reports, 2020
Obesity is characterized by adipose tissue inflammation. Because proteoglycans regulate inflammat... more Obesity is characterized by adipose tissue inflammation. Because proteoglycans regulate inflammation, here we investigate their role in adipose tissue inflammation in obesity. We find that adipose tissue versican and biglycan increase in obesity. Versican is produced mainly by adipocytes and biglycan by adipose tissue macrophages. Both proteoglycans are also present in adipose tissue from obese human subjects undergoing gastric bypass surgery. Deletion of adipocyte-specific versican or macrophage-specific biglycan in mice reduces macrophage accumulation and chemokine and cytokine expression, although only adipocyte-specific versican deletion leads to sustained improvement in glucose tolerance. Macrophage-derived biglycan activates inflammatory genes in adipocytes. Versican expression increases in cultured adipocytes exposed to excess glucose, and adipocyte-conditioned medium stimulates inflammation in resident peritoneal macrophages, in part because of a versican breakdown product, versikine. These findings provide insights into the role of adipocyte-and macrophage-derived proteoglycans in adipose tissue inflammation in obesity.
Arteriosclerosis, thrombosis, and vascular biology, 2017
Obesity is associated with insulin resistance and adipose tissue inflammation. Reactive oxygen sp... more Obesity is associated with insulin resistance and adipose tissue inflammation. Reactive oxygen species (ROS) increase in adipose tissue during the development of obesity. We previously showed that in response to excess nutrients like glucose and palmitate, adipocytes generated ROS via NADPH oxidase (NOX) 4, the major adipocyte isoform, instead of using mitochondrial oxidation. However, the role of NOX4-derived ROS in the development of whole body insulin resistance, adipocyte inflammation, and recruitment of macrophages to adipose tissue during the development of obesity is unknown. In this study, control C57BL/6 mice and mice in which NOX4 has been deleted specifically in adipocytes were fed a high-fat, high-sucrose diet. During the development of obesity in control mice, adipocyte NOX4 and pentose phosphate pathway activity were transiently increased. Primary adipocytes differentiated from mice with adipocytes deficient in NOX4 showed resistance against high glucose or palmitate-i...
The Journal of clinical investigation, Jan 7, 2015
HDL from healthy humans and lean mice inhibits palmitate-induced adipocyte inflammation; however,... more HDL from healthy humans and lean mice inhibits palmitate-induced adipocyte inflammation; however, the effect of the inflammatory state on the functional properties of HDL on adipocytes is unknown. Here, we found that HDL from mice injected with AgNO3 fails to inhibit palmitate-induced inflammation and reduces cholesterol efflux from 3T3-L1 adipocytes. Moreover, HDL isolated from obese mice with moderate inflammation and humans with systemic lupus erythematosus had similar effects. Since serum amyloid A (SAA) concentrations in HDL increase with inflammation, we investigated whether elevated SAA is a causal factor in HDL dysfunction. HDL from AgNO3-injected mice lacking Saa1.1 and Saa2.1 exhibited a partial restoration of antiinflammatory and cholesterol efflux properties in adipocytes. Conversely, incorporation of SAA into HDL preparations reduced antiinflammatory properties but not to the same extent as HDL from AgNO3-injected mice. SAA-enriched HDL colocalized with cell surface-ass...
PLoS ONE, 2013
Adipose tissue inflammation and specifically, pro-inflammatory macrophages are believed to contri... more Adipose tissue inflammation and specifically, pro-inflammatory macrophages are believed to contribute to insulin resistance (IR) in obesity in humans and animal models. Recent studies have invoked T cells in the recruitment of pro-inflammatory macrophages and the development of IR. To test the role of the T cell response in adipose tissue of mice fed an obesogenic diet, we used two agents (CTLA-4 Ig and anti-CD40L antibody) that block co-stimulation, which is essential for full T cell activation. C57BL/6 mice were fed an obesogenic diet for 16 weeks, and concomitantly either treated with CTLA-4 Ig, anti-CD40L antibody or an IgG control (300 mg/week). The treatments altered the immune cell composition of adipose tissue in obese mice. Treated mice demonstrated a marked reduction in pro-inflammatory adipose tissue macrophages and activated CD8+ T cells. Mice treated with anti-CD40L exhibited reduced weight gain, which was accompanied by a trend toward improved IR. CTLA-4 Ig treatment, however, was not associated with improved IR. These data suggest that the presence of pro-inflammatory T cells and macrophages can be altered with co-stimulatory inhibitors, but may not be a significant contributor to the whole body IR phenotype.
Diabetes, 2009
OBJECTIVE Obesity is associated with monocyte-macrophage accumulation in adipose tissue. Previous... more OBJECTIVE Obesity is associated with monocyte-macrophage accumulation in adipose tissue. Previously, we showed that glucose-stimulated production by adipocytes of serum amyloid A (SAA), monocyte chemoattractant protein (MCP)-1, and hyaluronan (HA) facilitated monocyte accumulation. The current objective was to determine how the other major nutrient, free fatty acids (FFAs), affects these molecules and monocyte recruitment by adipocytes. RESEARCH DESIGN AND METHODS Differentiated 3T3-L1, Simpson-Golabi-Behmel syndrome adipocytes, and mouse embryonic fibroblasts were exposed to various FFAs (250 μmol/l) in either 5 or 25 mmol/l (high) glucose for evaluation of SAA, MCP-1, and HA regulation in vitro. RESULTS Saturated fatty acids (SFAs) such as laurate, myristate, and palmitate increased cellular triglyceride accumulation, SAA, and MCP-1 expression; generated reactive oxygen species (ROS); and increased nuclear factor (NF) κB translocation in both 5 and 25 mmol/l glucose. Conversely, p...
Circulation Research, 2013
Rationale: Macrophage accumulation in adipose tissue associates with insulin resistance and incre... more Rationale: Macrophage accumulation in adipose tissue associates with insulin resistance and increased cardiovascular disease risk. We previously have shown that generation of reactive oxygen species and monocyte chemotactic factors after exposure of adipocytes to saturated fatty acids, such as palmitate, occurs via translocation of NADPH oxidase 4 into lipid rafts (LRs). The anti-inflammatory effects of apolipoprotein AI (apoAI) and high-density lipoprotein (HDL) on macrophages and endothelial cells seem to occur via cholesterol depletion of LRs. However, little is known concerning anti-inflammatory effects of HDL and apoAI on adipocytes. Objective: To determine whether apoAI and HDL inhibit inflammation in adipocytes and adipose tissue, and whether this is dependent on LRs. Methods and Results: In 3T3L-1 adipocytes, apoAI, HDL, and methyl-β-cyclodextrin inhibited chemotactic factor expression. ApoAI and HDL also disrupted LRs, reduced plasma membrane cholesterol content, inhibited ...
Energy Procedia, 2013
Active interrogation in 235 U was demonstrated with LaBr 3 :Ce scintillation detectors using the ... more Active interrogation in 235 U was demonstrated with LaBr 3 :Ce scintillation detectors using the nuclear resonance fluorescence (NRF) technique. An NRF experiment was performed at the High using quasi-ray beams. Photons scattered at 90 o relative to the incident beam were detected with two different sizes of cylindrical LaBr 3 :Ce detectors. Clear NRF peaks at 1733 and 1815 keV corresponding to de-excitations to the ground state and/or low-lying levels in 235 U were observed within 77 minutes of beam time even under the high background due to the self-activity of LaBr 3 :Ce and the radioactive decay of 214 Bi nuclei existing in the 235 U target. The present study shows a possibility of using LaBr 3 :Ce detector to perform NRF experiments, promoting many options for inspection of special nuclear materials.
Cell Reports, 2020
Obesity is characterized by adipose tissue inflammation. Because proteoglycans regulate inflammat... more Obesity is characterized by adipose tissue inflammation. Because proteoglycans regulate inflammation, here we investigate their role in adipose tissue inflammation in obesity. We find that adipose tissue versican and biglycan increase in obesity. Versican is produced mainly by adipocytes and biglycan by adipose tissue macrophages. Both proteoglycans are also present in adipose tissue from obese human subjects undergoing gastric bypass surgery. Deletion of adipocyte-specific versican or macrophage-specific biglycan in mice reduces macrophage accumulation and chemokine and cytokine expression, although only adipocyte-specific versican deletion leads to sustained improvement in glucose tolerance. Macrophage-derived biglycan activates inflammatory genes in adipocytes. Versican expression increases in cultured adipocytes exposed to excess glucose, and adipocyte-conditioned medium stimulates inflammation in resident peritoneal macrophages, in part because of a versican breakdown product, versikine. These findings provide insights into the role of adipocyte-and macrophage-derived proteoglycans in adipose tissue inflammation in obesity.
Arteriosclerosis, thrombosis, and vascular biology, 2017
Obesity is associated with insulin resistance and adipose tissue inflammation. Reactive oxygen sp... more Obesity is associated with insulin resistance and adipose tissue inflammation. Reactive oxygen species (ROS) increase in adipose tissue during the development of obesity. We previously showed that in response to excess nutrients like glucose and palmitate, adipocytes generated ROS via NADPH oxidase (NOX) 4, the major adipocyte isoform, instead of using mitochondrial oxidation. However, the role of NOX4-derived ROS in the development of whole body insulin resistance, adipocyte inflammation, and recruitment of macrophages to adipose tissue during the development of obesity is unknown. In this study, control C57BL/6 mice and mice in which NOX4 has been deleted specifically in adipocytes were fed a high-fat, high-sucrose diet. During the development of obesity in control mice, adipocyte NOX4 and pentose phosphate pathway activity were transiently increased. Primary adipocytes differentiated from mice with adipocytes deficient in NOX4 showed resistance against high glucose or palmitate-i...
The Journal of clinical investigation, Jan 7, 2015
HDL from healthy humans and lean mice inhibits palmitate-induced adipocyte inflammation; however,... more HDL from healthy humans and lean mice inhibits palmitate-induced adipocyte inflammation; however, the effect of the inflammatory state on the functional properties of HDL on adipocytes is unknown. Here, we found that HDL from mice injected with AgNO3 fails to inhibit palmitate-induced inflammation and reduces cholesterol efflux from 3T3-L1 adipocytes. Moreover, HDL isolated from obese mice with moderate inflammation and humans with systemic lupus erythematosus had similar effects. Since serum amyloid A (SAA) concentrations in HDL increase with inflammation, we investigated whether elevated SAA is a causal factor in HDL dysfunction. HDL from AgNO3-injected mice lacking Saa1.1 and Saa2.1 exhibited a partial restoration of antiinflammatory and cholesterol efflux properties in adipocytes. Conversely, incorporation of SAA into HDL preparations reduced antiinflammatory properties but not to the same extent as HDL from AgNO3-injected mice. SAA-enriched HDL colocalized with cell surface-ass...
PLoS ONE, 2013
Adipose tissue inflammation and specifically, pro-inflammatory macrophages are believed to contri... more Adipose tissue inflammation and specifically, pro-inflammatory macrophages are believed to contribute to insulin resistance (IR) in obesity in humans and animal models. Recent studies have invoked T cells in the recruitment of pro-inflammatory macrophages and the development of IR. To test the role of the T cell response in adipose tissue of mice fed an obesogenic diet, we used two agents (CTLA-4 Ig and anti-CD40L antibody) that block co-stimulation, which is essential for full T cell activation. C57BL/6 mice were fed an obesogenic diet for 16 weeks, and concomitantly either treated with CTLA-4 Ig, anti-CD40L antibody or an IgG control (300 mg/week). The treatments altered the immune cell composition of adipose tissue in obese mice. Treated mice demonstrated a marked reduction in pro-inflammatory adipose tissue macrophages and activated CD8+ T cells. Mice treated with anti-CD40L exhibited reduced weight gain, which was accompanied by a trend toward improved IR. CTLA-4 Ig treatment, however, was not associated with improved IR. These data suggest that the presence of pro-inflammatory T cells and macrophages can be altered with co-stimulatory inhibitors, but may not be a significant contributor to the whole body IR phenotype.
Diabetes, 2009
OBJECTIVE Obesity is associated with monocyte-macrophage accumulation in adipose tissue. Previous... more OBJECTIVE Obesity is associated with monocyte-macrophage accumulation in adipose tissue. Previously, we showed that glucose-stimulated production by adipocytes of serum amyloid A (SAA), monocyte chemoattractant protein (MCP)-1, and hyaluronan (HA) facilitated monocyte accumulation. The current objective was to determine how the other major nutrient, free fatty acids (FFAs), affects these molecules and monocyte recruitment by adipocytes. RESEARCH DESIGN AND METHODS Differentiated 3T3-L1, Simpson-Golabi-Behmel syndrome adipocytes, and mouse embryonic fibroblasts were exposed to various FFAs (250 μmol/l) in either 5 or 25 mmol/l (high) glucose for evaluation of SAA, MCP-1, and HA regulation in vitro. RESULTS Saturated fatty acids (SFAs) such as laurate, myristate, and palmitate increased cellular triglyceride accumulation, SAA, and MCP-1 expression; generated reactive oxygen species (ROS); and increased nuclear factor (NF) κB translocation in both 5 and 25 mmol/l glucose. Conversely, p...
Circulation Research, 2013
Rationale: Macrophage accumulation in adipose tissue associates with insulin resistance and incre... more Rationale: Macrophage accumulation in adipose tissue associates with insulin resistance and increased cardiovascular disease risk. We previously have shown that generation of reactive oxygen species and monocyte chemotactic factors after exposure of adipocytes to saturated fatty acids, such as palmitate, occurs via translocation of NADPH oxidase 4 into lipid rafts (LRs). The anti-inflammatory effects of apolipoprotein AI (apoAI) and high-density lipoprotein (HDL) on macrophages and endothelial cells seem to occur via cholesterol depletion of LRs. However, little is known concerning anti-inflammatory effects of HDL and apoAI on adipocytes. Objective: To determine whether apoAI and HDL inhibit inflammation in adipocytes and adipose tissue, and whether this is dependent on LRs. Methods and Results: In 3T3L-1 adipocytes, apoAI, HDL, and methyl-β-cyclodextrin inhibited chemotactic factor expression. ApoAI and HDL also disrupted LRs, reduced plasma membrane cholesterol content, inhibited ...
Energy Procedia, 2013
Active interrogation in 235 U was demonstrated with LaBr 3 :Ce scintillation detectors using the ... more Active interrogation in 235 U was demonstrated with LaBr 3 :Ce scintillation detectors using the nuclear resonance fluorescence (NRF) technique. An NRF experiment was performed at the High using quasi-ray beams. Photons scattered at 90 o relative to the incident beam were detected with two different sizes of cylindrical LaBr 3 :Ce detectors. Clear NRF peaks at 1733 and 1815 keV corresponding to de-excitations to the ground state and/or low-lying levels in 235 U were observed within 77 minutes of beam time even under the high background due to the self-activity of LaBr 3 :Ce and the radioactive decay of 214 Bi nuclei existing in the 235 U target. The present study shows a possibility of using LaBr 3 :Ce detector to perform NRF experiments, promoting many options for inspection of special nuclear materials.