Asunto(s)
Ciclo Celular/efectos de los fármacos , Fibroblastos/citología , Aceites de Pescado/farmacología , Terapia de Inmunosupresión/métodos , Bromodesoxiuridina , Células Cultivadas , Aceite de Maíz/farmacología , Inhibidores de la Ciclooxigenasa/farmacología , Citometría de Flujo , Humanos , Indometacina/farmacología , Fase SRESUMEN
Cellular proliferation is regulated by cell cycle progression which, in turn, is controlled by sequential activation of various cyclin-dependent kinases (CDKs). To explore the mechanism(s) by which long chain polyunsaturated fatty acids (PUFAs) influence the growth of tumor cells, we compared the effects of different n-3 and n-6 fatty acids on the activity of CDKs. Docosahexaenoic acid (DHA), a major component of fish oil diets, is able to reduce serum-stimulated cyclin D1-, E-, and A- associated kinases activity in synchronized-HT-29 cells. The inhibitory effect of DHA on cyclin A-associated kinase activity is time-dependent, and is probably modulated by down-regulation of cyclin A protein expression. In addition, DHA inhibits the phosphorylation of pRb and DNA-binding activity of E2F-1 in response to serum stimulation, and prevents the serum-stimulated entry of S-phase in HT-29 cells. These results indicate that DHA may exert its negative effect on the growth of tumor cells by inhibiting the activation and expression of G1-associated cell cycle regulatory proteins. Since the synthetic antioxidant BHT is able to reverse the inhibition of serum-stimulated activation of cyclin A/CDK by DHA in a dose-dependent manner, endogenous oxidative stress produced by lipid peroxidation in HT-29 cells may be involved in the control of cell cycle progression.
Asunto(s)
Proteínas Portadoras , Proteínas de Ciclo Celular , Quinasas Ciclina-Dependientes/antagonistas & inhibidores , Proteínas de Unión al ADN , Ácidos Docosahexaenoicos/farmacología , Aceites de Pescado/administración & dosificación , Proteínas Fúngicas , Proteínas Quinasas , Fase S/efectos de los fármacos , Quinasas Ciclina-Dependientes/metabolismo , Grasas Insaturadas en la Dieta/farmacología , Relación Dosis-Respuesta a Droga , Factores de Transcripción E2F , Factor de Transcripción E2F1 , Ácidos Grasos Insaturados/farmacología , Citometría de Flujo , Células HT29 , Humanos , Immunoblotting , Fosforilación/efectos de los fármacos , Inhibidores de Proteínas Quinasas , Subunidades de Proteína , Proteína 1 de Unión a Retinoblastoma , Serina Endopeptidasas/metabolismo , Factor de Transcripción DP1 , Factores de Transcripción/efectos de los fármacosRESUMEN
This study was conducted to characterize the effects of fish oil and sunflower oil on hepatic glucose production and peripheral glucose utilization during infusion of saline or tumor necrosis factor (TNF), using the euglycemic-hyperinsulinemic clamp technique combined with a primed-constant tracer infusion of high-performance liquid chromatography-purified 3H-3-glucose for estimation of whole-body glucose appearance and utilization rates. Insulin 10 mU/kg.min was infused to reach a plasma insulin level of 200 microU/mL. 14C-1-deoxyglucose (14C-DG) uptake was also measured in specific tissues following intravenous bolus administration. The results showed that during a hyperinsulinemic-euglycemic clamp, infusion of TNF 20 micrograms/kg for 3 hours resulted in a significant reduction of glucose infusion and a significant increase of hepatic glucose production in both dietary groups as compared with saline infusion, indicating a state of insulin resistance induced by TNF. The results also showed that TNF infusion significantly decreased the rate of 14C-DG uptake in muscle in the sunflower oil group but not in the fish oil group, suggesting that fish oil is able to restore to normal the glucose utilization impaired by TNF. These observations suggest that in hyperinsulinemic and euglycemic conditions, prefeeding with fish oil significantly improves glucose uptake in muscle tissue, but does not alter the increase in hepatic glucose production during TNF infusion.
Asunto(s)
Aceites de Pescado/farmacología , Glucosa/farmacocinética , Músculo Esquelético/metabolismo , Factor de Necrosis Tumoral alfa/farmacología , Animales , Glucemia/análisis , Cromatografía Líquida de Alta Presión , Desoxiglucosa/metabolismo , Ácidos Grasos/análisis , Ácidos Grasos/farmacología , Glucosa/metabolismo , Prueba de Tolerancia a la Glucosa , Helianthus , Insulina/sangre , Insulina/farmacología , Masculino , Músculo Esquelético/química , Aceites de Plantas/farmacología , Distribución Aleatoria , Ratas , Ratas Sprague-Dawley , Aceite de Girasol , TritioRESUMEN
In vivo bromodeoxyuridine (BrdUrd) labelling and bivariate BrdUrd/DNA analysis was used to evaluate cell cycle kinetics in a rat tumor model known to be sensitive to dietary fatty acid manipulation. Fish oil supplementation significantly reduced the rate of BrdUrd movement relative to DNA content, indicating prolongation of the DNA replication time. This finding, which accounted for most of the decrease in tumor growth rate in the fish oil-fed group, represents the first description of an alteration in S phase duration by an extrinsic factor. The significance of this finding is discussed in relation to current understanding of cell cycle regulation. Fish oil feeding is associated with slower growth rate in certain tumors (1,2). According to current concepts of cellular proliferation (3), regulation of growth by extrinsic factors is thought to precede the S phase. This statement is based on the notion that, within a given cell type, DNA replication time (S phase duration) is constant (4-6). Extensive evidence also supports an on/off mechanism of cell cycle regulation at the level of entry into the S phase (3). In this report, we present evidence showing, for the first time, that the S phase duration of fat-responsive tumor cells can be altered by dietary manipulation of fatty acids. Furthermore, these differences in S phase duration appear to account for all the in vivo variation in tumor growth resulting from fish oil feeding. Although the mechanism of this phenomenon remains unclear, our observations support increasing evidence for a regulatory step at the level of the nucleus. They are also important for understanding the relationship between dietary fat and tumor growth.
Asunto(s)
División Celular , Grasas de la Dieta/administración & dosificación , Aceites de Pescado/administración & dosificación , Neoplasias Mamarias Experimentales/patología , Animales , ADN/biosíntesis , Femenino , Cinética , Trasplante de Neoplasias , Ratas , Fase S , Aceite de Cártamo/administración & dosificación , Células Tumorales CultivadasRESUMEN
Female Fischer rats were pair-fed on diets containing either safflower oil (SO) or fish oil (FO) for 6 weeks. Implanted breast 13762 MAT tumors had a doubling times of 35.4 and 55.5 h in SO and FO rats, respectively (P < 0.001). Proliferation kinetics were measured in vivo by bromedeoxyuridine (BrdUrd) labeling and bivariate DNA/BrdUrd analysis by flow cytometry. After 1 h of pulsing, the labeling index was similar in both groups. However, 6 h later, tumor cells from FO rats had significantly lower relative movement of BrdUrd-labeled cells (0.78 vs. 0.91, P < 0.001). These results reflected a significantly longer S phase duration (15.0 vs. 9.1 h, P < 0.001) in FO rats and accounted for all the difference in tumor growth rates. This mechanism, which has not previously been reported, implies a significant role for fatty acids in DNA replication.
Asunto(s)
Replicación del ADN , Grasas de la Dieta/farmacología , Neoplasias Mamarias Experimentales/patología , Animales , Peso Corporal , División Celular , Femenino , Aceites de Pescado , Citometría de Flujo , Modelos Biológicos , Trasplante de Neoplasias , Ratas , Ratas Endogámicas F344 , Fase S , Aceite de Cártamo , Factores de TiempoRESUMEN
The notion that tumors act as "nitrogen traps" has led to the belief that nutrition support of the cancer-bearing patient can enhance tumor growth. Proponents of this theory consider the provision of energy and essential nutrients as well as the influence of hormones and growth factors as responsible for this effect. On the other hand, nutrition administration in the debilitated cancer patient may improve antitumor host defense mechanisms and reduce tumor growth. This paper reviews methodologic issues related to the study of nutrition and cancer growth with emphasis on in vivo methods for measuring tumor protein turnover and cytokinetics. Using this combined approach, we previously demonstrated that dietary fat may significantly regulate tumor growth during chronic feeding as well as with short-term intravenous nutrition support in experimental models. Although the mechanism of this effect remains unclear, we have reasoned that by altering arachidonic acid metabolism and prostaglandin synthesis, omega-3 fatty acids could change tumor protein breakdown rates and inhibit the proliferation potential of these tumors. Acknowledging alternative hypotheses, we now present cytokinetic evidence that intracellular protein degradation may regulate tumor cell proliferation. Additional studies relating dietary fat, tumor protein metabolism and tumor proliferation potential are currently in progress. We propose that the effect of nutrition administration on tumor growth is complex and involves several regulatory systems. Thus, based on available evidence, an a priori tumor-enhancing effect for nutrition support is clearly not warranted. Intracellular protein breakdown and host defense mechanisms, both of which are energy dependent, are important loci at which nutrition and tumor growth regulation could interact.(ABSTRACT TRUNCATED AT 250 WORDS)
Asunto(s)
Dieta/efectos adversos , Proteínas de Neoplasias/metabolismo , Neoplasias/patología , Nutrición Parenteral Total/efectos adversos , Animales , División Celular , Grasas de la Dieta/efectos adversos , Humanos , Neoplasias/metabolismo , Neoplasias Experimentales/patologíaRESUMEN
This study examined the short-term effects of three total parenteral nutrition solutions, each containing a different lipid source, on host and tumor protein metabolism in a rat cancer model. Each diet contained 220 kcal/kg per day, including 2 g of nitrogen/kg per day and 50% of nonprotein calories as either a structured lipid of medium-chain triglycerides and fish oil, a physical mix of medium-chain triglycerides and fish oil, or Liposyn II, a long-chain triglyceride. A 3-day intravenous feeding infusion began on day 7 after tumor implantation. Tumor growth rate, nitrogen balance, energy expenditure, and plasma albumin, glucose, and free fatty acids were measured, and whole body protein kinetics and fractional synthetic rates in liver, muscle, and tumor tissues were assessed using a constant infusion of 14C-leucine. The results revealed that tumor growth rate was slowed in structured lipid-fed animals (p = .06, one-way analysis of variance) with significant increases in rates of tumor protein synthesis and tumor protein breakdown (p < .001, one-way analysis of variance). Although muscle fractional synthetic rates were significantly decreased in tumor-bearing animals (p < .05, two-way analysis of variance), the rates in structured lipid-fed animals were restored. Nitrogen balance improved significantly in structured lipid-fed animals. The results demonstrate that the source of lipid in total parenteral nutrition solutions can influence tumor and host protein metabolism, and that a structured lipid composed of medium-chain triglycerides and fish oil seems to improve protein metabolism in host tissue without stimulating tumor growth.
Asunto(s)
Proteínas de Neoplasias/metabolismo , Nutrición Parenteral Total , Sarcoma de Yoshida/metabolismo , Triglicéridos/administración & dosificación , Animales , Emulsiones , Emulsiones Grasas Intravenosas/administración & dosificación , Aceites de Pescado/administración & dosificación , Cinética , Masculino , Modelos Biológicos , Trasplante de Neoplasias , Fosfolípidos , Distribución Aleatoria , Ratas , Ratas Sprague-Dawley , Aceite de Cártamo , Sarcoma de Yoshida/patología , Aceite de Soja , Factores de TiempoRESUMEN
Alteration in regional blood flow is important in the pathogenesis of organ failure during endotoxemia and sepsis. In particular, intestinal ischemia is thought to enhance the translocation of bacteria into the systemic circulation. We used radioactive microspheres to measure the influence of two intravenous (IV) dietary fats (vegetable oil containing high levels of omega-6 fatty acids, and fish oil containing high levels of omega-3 fatty acids) on regional blood flow during low-dose Escherichia coli endotoxin infusion (0.1 mg/100 g body weight [BW]) in a rat model. Despite absence of changes in the cardiac output, blood flow rates to the small and large intestines, stomach, and pancreas, and also to the skin and skeletal muscle were significantly reduced after 18 hours of endotoxin infusion in the rats fed standard vegetable oil. Short-term IV feeding during a period of 40 hours with an isonitrogenous, isocaloric nutrient solution containing fish oil as the only lipid source normalized intestinal perfusion and increased blood flow to the liver and spleen. Low-dose endotoxin infusion also resulted in significant increases in glucose, lactate, and pyruvate concentrations. In comparison to standard vegetable fat emulsion, fish oil significantly reduced these parameters. A second experiment was conducted to measure lactate kinetics. Based on the dilution of U-14C-lactate, fish oil feeding was associated with higher lactate clearance than standard vegetable oil feeding during the endotoxin infusion. We conclude that short-term IV feeding with fish oil improves intestinal perfusion and portal blood flow, improves glucose tolerance, and increases lactate clearance in a low-dose endotoxin rat model.
Asunto(s)
Endotoxinas/toxicidad , Ácidos Grasos Omega-3/farmacología , Lactatos/metabolismo , Circulación Esplácnica/efectos de los fármacos , Toxemia/fisiopatología , Animales , Gasto Cardíaco/efectos de los fármacos , Aceites de Pescado/farmacología , Glucosa/metabolismo , Ácido Láctico , Masculino , Ratas , Ratas Endogámicas , Tromboxano A2/fisiologíaRESUMEN
The comparative effects of diets containing 20% (wt/wt) of either fish oil (FO) or safflower oil (SO) on protein synthesis and catabolism were determined in rats bearing the 7,12-dimethylbenz(a)anthracene (DMBA) 13762 mammary adenocarcinoma in vivo using a 6-hour constant infusion of L-(1-14C)-leucine. Tumor-bearing animals fed FO had significantly lower tumor growth rate (36 +/- 0.5 v 53 +/- 0.7%/d, P less than .05), total tumor protein synthesis (Ts) (1.25 +/- 0.1 v 1.85 +/- 0.1 mumol/h, P less than .05), and tumor protein concentration (12.0 +/- 0.5 v 14.0 +/- 0.7%/d, P less than 0.01). Tumor fractional synthetic rate and total protein breakdown rate of the tumor were unaffected by FO feeding. Both tumor-bearing and saline-control animals fed FO had significantly (P less than .01) lower liver fractional synthetic rate and total protein breakdown rate, and higher liver total protein compared with SO-fed rats. Muscle protein kinetics were unaffected by either treatment or diet. Whole body protein kinetics were not affected by dietary treatment, but the presence of tumor significantly (P less than .001) reduced whole body flux, synthesis, breakdown, and oxidation. Chronic FO feeding for 7 weeks significantly (P less than .001) lowered omega-6 polyunsaturated fatty acids (omega-6 PUFAs) and significantly elevated omega-3 polyunsaturated fatty acids (omega-3 PUFAs) (P less than .001) in both plasma phospholipid and triglycerides. The present study indicates that dietary FO can modulate mammary tumor growth in a manner that reflects changes in protein metabolism in both host and tumor tissues.
Asunto(s)
Adenocarcinoma/metabolismo , Grasas de la Dieta/farmacología , Ácidos Grasos Omega-3/farmacología , Ácidos Grasos Insaturados/farmacología , Neoplasias Mamarias Experimentales/metabolismo , 9,10-Dimetil-1,2-benzantraceno , Adenocarcinoma/irrigación sanguínea , Adenocarcinoma/inducido químicamente , Adenocarcinoma/patología , Animales , Radioisótopos de Carbono , Ácidos Grasos no Esterificados/sangre , Ácidos Grasos Omega-6 , Femenino , Aceites de Pescado/farmacología , Cinética , Leucina/metabolismo , Hígado/efectos de los fármacos , Hígado/metabolismo , Neoplasias Mamarias Experimentales/irrigación sanguínea , Neoplasias Mamarias Experimentales/patología , Proteínas Musculares/metabolismo , Músculos/irrigación sanguínea , Músculos/efectos de los fármacos , Músculos/metabolismo , Proteínas/metabolismo , Técnica de Dilución de Radioisótopos , Ratas , Ratas Endogámicas F344 , Flujo Sanguíneo Regional , Aceite de Cártamo/farmacologíaRESUMEN
The influence of dietary lipid manipulation with menhaden or safflower oil on changes in protein metabolism in rats receiving recombinant interleukin-1 beta (IL-1 beta), tumor necrosis factor alpha/cachectin (TNF), or both combined (COINF) was examined. Whole-body protein kinetics, energy expenditure, nitrogen excretion, and liver and muscle protein synthesis were studied using tracer quantities of L-[1-14C]-leucine. Rats fed menhaden oil, high in omega-3 fatty acids, had significantly lower rates of leucine oxidation compared to safflower-fed rats after monokine infusion (P less than .05). However, muscle protein synthetic rates and the specific activity of free leucine in plasma and muscle indicated greater net muscle-protein breakdown in animals fed fish oil or receiving monokines. Rats fed omega-3 fatty acids had significantly larger livers as percent of body weight and more total liver protein than safflower oil controls (P less than .0001). Liver weight was further increased by monokines, particularly TNF and COINF (P less than .001) in both diet groups, suggesting that net hepatic anabolism occurred at the expense of net skeletal protein catabolism. Monokines as a group and COINF significantly decreased whole-body leucine flux and incorporation into protein; no effect of menhaden oil was noted. In addition, monokines increased nitrogen excretion during the 24-hour experimental period (P less than .05), and total energy expenditure rose significantly in all groups receiving IL-1 beta and COINF. The recombinant monokines IL-1 beta and TNF, particularly when coinfused, are able to reproduce many of the protein anabolic and catabolic consequences seen following infection and injury.(ABSTRACT TRUNCATED AT 250 WORDS)