RESUMO
While the 3T3-L1 adipocyte model is routinely used for the study of obesity and diabetes, the mitochondrial respiratory profile in normal versus high glucose has not been examined in detail. We matured adipocytes in normal (5mM) or high (30 mM) glucose and insulin and examined the mitochondrial bioenergetics. We also assessed the requirement for the Unfolded Protein Response (UPR) and ER stress under these conditions. Basal respiration was ~1.7-fold greater in adipocytes that had matured in 30 mM glucose; however, their ability to increase oxygen consumption in response to stress was impaired. Adipogenesis proceeded in both normal and high glucose with concomitant activation of the UPR, but only high glucose was associated with increased levels of ER stress and mitochondrial stress as observed by parallel increases in CHOP and protein succination. Treatment of adipocytes with sodium phenylbutyrate relieved mitochondrial stress through a reduction in mitochondrial respiration. Our data suggests that mitochondrial stress, protein succination and ER stress are uniquely linked in adipocytes matured in high glucose.
Assuntos
Estresse do Retículo Endoplasmático/efeitos dos fármacos , Metabolismo Energético/efeitos dos fármacos , Glucose/farmacologia , Mitocôndrias/efeitos dos fármacos , Fenilbutiratos/farmacologia , Células 3T3-L1 , Adipogenia/efeitos dos fármacos , Animais , Potencial da Membrana Mitocondrial/efeitos dos fármacos , Camundongos , Mitocôndrias/metabolismo , Consumo de Oxigênio , Dobramento de Proteína , Fator de Transcrição CHOP/análise , Resposta a Proteínas não DobradasRESUMO
Many observational epidemiologic studies suggest an association between exercise and colon cancer risk. The mechanisms contributing to a preventative effect of exercise on colon cancer are complex and multifaceted. Altered immune system function is one possible mechanism that has been largely unexplored. Therefore, the purpose of this study was to examine the effects of exercise on markers associated with macrophages and select T cell populations in a mouse model of intestinal tumorigenesis and to relate this to polyp characteristics. Male Apc(Min/+) mice were randomly assigned to either sedentary (Sed) or exercise (Ex) treatment (n=6-9/group). The exercise treatment consisted of treadmill running for 1 h/day and 6 days a week at 15 m/min from 4 until 16 weeks of age. Intestinal polyps were counted and categorized by size. Mucosal tissue was analyzed for mRNA expression of overall macrophages (F4/80), for genes associated with M1 (IL-12, IL-23 and Nos2) and M2 (CD206, IL-10, IL-4, CCL17, CCL22 and Arg-1) macrophages and the macrophage chemoattractants MCP-1, fetuin A and CXCL14. Markers for cytotoxic T cells (CTLs) and regulatory T cells were also examined by measuring mRNA expression of CD8 and Foxp3, respectively. While there was no significant difference in overall polyp number between the groups (Sed, 23.3±4.3; and Ex, 16.5±4.3), Ex did have a reduction in the number of large polyps (Sed, 6.1±1.1; and Ex, 3.0±0.6) (P<0.05). This was consistent with a decrease in spleen weight (P<0.05). Similarly, Ex reduced mRNA expression of overall macrophages (F4/80) as well as markers associated with both M1 (IL-12) and M2 (CD206, CCL22 and Arg-1) subtypes (P<0.05) but there was no significant decrease in macrophage chemoattractants. CD8 expression was increased while Foxp3 expression was decreased with Ex (P<0.05). Overall the data provide important new information on immune regulation as a possible mechanism for the documented benefits of exercise training on reducing colon cancer progression.
Assuntos
Pólipos Intestinais/imunologia , Atividade Motora/fisiologia , Animais , Transformação Celular Neoplásica , Neoplasias do Colo/imunologia , Modelos Animais de Doenças , Progressão da Doença , Macrófagos/imunologia , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Mutantes , Lesões Pré-Cancerosas/imunologia , Subpopulações de Linfócitos T/imunologia , Linfócitos T/imunologiaRESUMO
Many observational epidemiologic studies suggest an association between high-fat-diet (HFD) and colon cancer risk. However, the lack of controlled experimental studies that examine this relationship and the mechanisms involved weaken the basis for inferring a causal relationship. Inflammation plays a role in colon cancer progression and HFDs have been reported to increase inflammation; however, the inflammatory effects of HFD in colon cancer have yet to be firmly established. We examined the effects of a novel HFD that closely mimics the standard American diet (12% and 40% of total caloric intake from saturated fat and total fat, respectively) on macrophage markers and inflammatory mediators in a mouse model of intestinal tumorigenesis and relate this to polyp characteristics as well as measures of adiposity. Male Apc(Min/+) mice (7-8/group) were fed a Control Diet (Con) or novel high-fat-diet (HFD) from 4 to 12weeks of age. Body weight and body composition were measured weekly and monthly, respectively. Intestinal tissue was analyzed for polyp burden (number and size). Gene expression of macrophage markers and inflammatory mediators were examined in the adipose tissue and polyps. The HFD increased the expression of macrophage markers and inflammatory mediators in the adipose tissue (F4/80, CD11c, TLR-4 and MCP-1) and tumor microenvironment (IL-12, MCP-1, IL-6 and TNF-α). As expected, the HFD increased body weight, body fat percent, fat mass and blood glucose (P<0.05), and was associated with an increase in the number of large polyps (P<0.05) but not total polyps. In summary, consumption of a HFD, similar in macronutrient composition to the standard American diet, altered the expression of macrophage phenotypic markers and inflammatory mediators in adipose tissue and intestinal polyps and this was associated with increased tumorigenesis.
Assuntos
Carcinogênese/imunologia , Neoplasias do Colo/etiologia , Pólipos do Colo/metabolismo , Dieta Hiperlipídica , Inflamação/imunologia , Tecido Adiposo/metabolismo , Animais , Antígenos de Diferenciação/metabolismo , Biomarcadores/metabolismo , Glicemia , Composição Corporal , Peso Corporal , Antígeno CD11c/metabolismo , Quimiocina CCL2/metabolismo , Dieta , Expressão Gênica , Mediadores da Inflamação/metabolismo , Interleucina-12/metabolismo , Interleucina-6/metabolismo , Macrófagos/imunologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Receptor 4 Toll-Like/metabolismo , Fator de Necrose Tumoral alfa/metabolismoRESUMO
We examined the effects of three high-fat diets (HFD), 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-cholesterol (LDL-C), HDL-cholesterol (HDL-C), total cholesterol (TC)] were examined monthly. Adipose tissue (AT) expression of marker genes for M1 and M2 macrophages and inflammatory mediators [Toll-like receptor (TLR)-2, TLR-4, MCP-1, tumor necrosis factor (TNF)-α, interleukin (IL)-6, IL-10, suppressor of cytokine signaling (SOCS)1, IFN-γ] was measured along with activation of nuclear factor kappa-B (NFκB), c-Jun N-terminal kinase (JNK), and p38- mitogen-activated protein kinase (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 HFD are heavily influenced by dietary SF content; however, these responses are not necessarily proportional to the SF percentage.
Assuntos
Adiposidade/efeitos dos fármacos , Gorduras na Dieta/efeitos adversos , Ácidos Graxos/efeitos adversos , Macrófagos/efeitos dos fármacos , Macrófagos/metabolismo , Tecido Adiposo/citologia , Tecido Adiposo/efeitos dos fármacos , Tecido Adiposo/imunologia , Tecido Adiposo/metabolismo , Animais , Peso Corporal/efeitos dos fármacos , Dieta Hiperlipídica/efeitos adversos , Ingestão de Energia/efeitos dos fármacos , Inflamação/sangue , Inflamação/etiologia , Inflamação/metabolismo , Resistência à Insulina , Leptina/sangue , Macrófagos/imunologia , Masculino , CamundongosRESUMO
The etiology of colon cancer is a complex phenomenon that involves both genetic and environmental factors. However, only about 20% have a familial basis with the largest fraction being attributed to environmental causes that can lead to chronic inflammation. While the link between inflammation and colon cancer is well established, the temporal sequence of the inflammatory response in relation to tumorigenesis has not been characterized. We examined the timing and magnitude of the intestinal inflammatory cytokine response in relation to tumorigenesis in the Apc(Min/+) mouse. Apc(Min/+) mice and wildtype mice were sacrificed at one of 4 time-points: 8, 12, 16, and 20 weeks of age. Intestinal tissue was analyzed for polyp burden (sections 1, 4 and 5) and mRNA expression and protein concentration of MCP-1, IL-1ß, IL-6 and TNF-α (sections 2 and 3). The results show that polyp burden was increased at 12, 16 and 20 weeks compared to 8 weeks (P<0.05). Gene expression (mRNA) of MCP-1, IL-1ß, IL-6 and TNF-α was increased in sections 2 and 3 starting at week 12 (P<0.05), with further increases in MCP-1, IL-1ß and IL-6 at 16 weeks (P<0.05). Protein concentration for these cytokines followed a similar pattern in section 3. Similarly, circulating MCP-1 was increased at 12 weeks (P<0.05) and then again at 20 weeks (P<0.05). In general, overall polyp number and abundance of large polyps were significantly correlated with the inflammatory cytokine response providing further support for a relationship between polyp progression and these markers. These data confirm the association between intestinal cytokines and tumorigenesis in the Apc(Min/+) mouse and provide new information on the timing and magnitude of this response in relation to polyp development. These findings may lead to the development of inflammatory mediators as important biomarkers for colon cancer progression. Further, these data may be relevant in the design of future investigations of therapeutic interventions to effectively target inflammatory processes in rodent models.