Effect of Brassica rapa var. rapifera on Insulin Resistance and Inflammatory Analysis of Visceral Adipose Tissue of Obese Wistar Rats Under Glucolipotoxicity Condition / Efecto de Brassica rapa var. rapifera sobre la Resistencia a la Insulina y el Análisis Inflamatorio del Tejido Adiposo Visceral de Ratas Wistar Obesas en Condiciones de Glucolipotoxicidad

SUMMARY: Obesity-related pathophysiologies such as insulin resistance and the metabolic syndrome show a markedly increased risk for type 2 diabetes and atherosclerotic cardiovascular disease. This risk appears to be linked to alterations in adipose tissue function, leading to chronic inflammation and the dysregulation of adipocyte-derived factors. Brassica rapa have been used in traditional medicine for the treatment of several diseases, including diabetes. This study aimed to investigate the effect of nutritional stress induced by a high-fat and high-sucrose diet on the pathophysiology of visceral adipose tissue and the therapeutic effect of Brassica rapa in male Wistar rats. We subjected experimental rats to a high-fat (10 %) high-sucrose (20 %)/per day for 11 months and treated them for 20 days with aqueous extract Br (AEBr) at 200 mg/kg at the end of the experiment. At the time of sacrifice, we monitored plasma and tissue biochemical parameters as well as the morpho-histopathology of visceral adipose tissue. We found AEBr corrected metabolic parameters and inflammatory markers in homogenized visceral adipose tissue and reduced hypertrophy, hyperplasia, and lipid droplets. These results suggest that AEBr enhances anti-diabetic, anti-inflammatory and a protective effect on adipose tissue morphology in type 2 diabetes and obesity.

La fisiopatología relacionadas con la obesidad, como la resistencia a la insulina y el síndrome metabólico, muestran un riesgo notablemente mayor de diabetes tipo 2 y enfermedad cardiovascular aterosclerótica. Este riesgo parece estar relacionado con alteraciones en la función del tejido adiposo, lo que lleva a una inflamación crónica y a la desregulación de los factores derivados de los adipocitos. Brassica rapa se ha utilizado en la medicina tradicional para el tratamiento de varias enfermedades, incluida la diabetes. Este estudio tuvo como objetivo investigar el efecto del estrés nutricional inducido por una dieta rica en grasas y sacarosa sobre la fisiopatología del tejido adiposo visceral y el efecto terapéutico de Brassica rapa en ratas Wistar macho. Sometimos a ratas experimentales a una dieta rica en grasas (10 %) y alta en sacarosa (20 %)/por día durante 11 meses y las tratamos durante 20 días con extracto acuoso de Br (AEBr) a 200 mg/kg al final del experimento. En el momento del sacrificio, monitoreamos los parámetros bioquímicos plasmáticos y tisulares, así como la morfohistopatología del tejido adiposo visceral. Encontramos parámetros metabólicos corregidos por AEBr y marcadores inflamatorios en tejido adiposo visceral homogeneizado y reducción de hipertrofia, hiperplasia y gotitas de lípidos. Estos resultados sugieren que AEBr mejora el efecto antidiabético, antiinflamatorio y protector sobre la morfología del tejido adiposo en la diabetes tipo 2 y la obesidad.

Hypothyroidism increases angiotensinogen gene expression associated with vascular smooth muscle cells cholesterol metabolism dysfunction and aorta remodeling in Psammomys obesus.

It has been previously shown that clinical cardiovascular manifestations can be caused by mild changes in thyroid function. However, the implication of angiotensinogen (Agt) and vascular smooth muscle cells (VSMCs) dysfunction in the pathophysiology of cardiovascular manifestations in hypothyroidism have not yet been investigated. We induced experimental hypothyroidism in Psammomys obesus by administering carbimazole for five months. At the end of the experiment, the animals were sacrificed and histopathological analysis was performed using Masson's trichrome staining of the aorta and thyroid gland. The expression of the Agt gene and the genes implicated in cholesterol metabolism regulation in the liver and VSMCs was determined by qRT-PCR. Histological observations revealed profound remodeling of the aorta structure in animals with hypothyroidism. In addition, Agt gene expression in the liver was significantly increased. In vitro study, showed that VSMCs from hypothyroid animals overexpressed 3-hydroxy-3-methylglutaryl coenzyme A reductase (Hmgcr) and Acyl CoA:cholesterol acyltransferase (Acat) 1, with failure to increase the efflux pathway genes (ATP-binding cassette subfamily G member (Abcg) 1 and 4). These results suggest that hypothyroidism leads to vascular alterations, including structural remodeling, VSMCs cholesterol metabolism dysfunction, and their switch to a synthetic phenotype, together with hepatic Agt gene overexpression.

TRα inhibits arterial renin-angiotensin system expression and prevents cholesterol accumulation in vascular smooth muscle cells.

OBJECTIVES: The tissue renin-angiotensin system (tRAS) plays a key role in the maintenance of cellular homeostasis but is also implicated in atherosclerosis. Thyroid hormone (TH) contributes, via genomic effects, to control of tRAS gene expression in the arterial wall and vascular smooth muscle cells (VSMCs). We investigated the specific functions of TH receptors-α and -ß (TRα and TRß) on tRAS gene expression in the aorta and VSMCs, and the potential protective effect of TRα against atherosclerosis. MATERIAL AND METHODS: Using aorta and cultured aortic VSMCs from TRα and TRß deficient mice, tRAS gene expression was analyzed by determining mRNA levels on real-time PCR. Gene regulation under cholesterol loading mimicking atherosclerosis conditions was also examined in VSMCs in vitro. RESULTS: TRα deletion significantly increased expression of angiotensinogen (AGT) and angiotensin II receptor type 1 subtype a (AT1Ra) at transcriptional level in aorta, a tissue with high TRα expression level. TRα activity thus seems to be required for maintenance of physiological levels of AGTand AT1Raexpression in the arterial wall. In addition, during cholesterol loading, TRα deletion significantly increased cholesterol content in VSMCs, with a weaker decrease in AGTexpression. CONCLUSION: TRα seems to have an inhibitory impact on AGTand AT1Raexpression, and loss of TRα function in TRα0/0 mice increases tRAS expression in the aortic wall. More importantly, TRα deletion significantly increases VSMC cholesterol content. Our results are consistent with a protective role of TRα against atherosclerosis.

Thyroid Hormone Receptor Alpha Deletion in ApoE-/- Mice Alters the Arterial Renin-Angiotensin System and Vascular Smooth Muscular Cell Cholesterol Metabolism.

Thyroid hormone (TH) regulates gene transcription by binding to TH receptors (TRs). TRs regulate the genes of lipid metabolism and the renin-angiotensin system (RAS). We examined the effect of TRα deletion in ApoE-/- mice (DKO mice) on the following: (i) the expression of genes controlling cholesterol metabolism and tissue (t)RAS in the liver and aorta and (ii) the expression of these genes and the regulation of cholesterol content in cultured vascular smooth muscle cells (VSMCs). TRα deletion in ApoE-/- mice led to the repression of genes involved in the synthesis and influx of cholesterol in the liver. However, TRα deletion in the arterial wall suppressed the expression of genes involved in the esterification and excretion of cholesterol and enhanced the expression of angiotensinogen (AGT). The VSMCs of the ApoE-/- and DKO mice increased their cholesterol content during cholesterol loading, but failed to increase the expression of ATP-binding cassette transporter A1 (ABCA1). T3 addition partially corrected these abnormalities in the cells of the ApoE-/- mice but not those of the DKO mice. In conclusion, TRα deletion in ApoE-/- mice slightly increases the expression of tRAS in the aorta and aggravates the dysregulation of cholesterol content in the VSMCs.

Perilipin 1 ablation in mice enhances lipid oxidation during exercise and does not impair exercise performance.

Perilipin 1 is involved in the control of adipose tissue triacylglycerol hydrolysis. Its ablation in mice decreases fat mass and induces a partial resistance to diet-induced and genetic obesity. However, the consequences of perilipin 1 invalidation on energy balance are not fully defined. Moreover, the impact of perilipin 1 ablation on exercise performance and on fatty acids mobilization and utilization during exercise has not been studied. We compared energy balance (food intake, energy expenditure, spontaneous physical activity) and response to exercise of Plin1(-/-) and wild-type mice receiving a chow diet. The Plin1(-/-) mice had less fat, comparable food intake, comparable or slightly decreased energy expenditure, and no change in spontaneous physical activity. Mean 24-hour respiratory quotient was slightly lower, suggesting enhanced fatty acid oxidation. Exercise performance (both acute and endurance) was not impaired. Changes in nonesterified fatty acid levels during exercise were comparable, showing that triacylglycerol mobilization was unimpaired. Oxygen consumption increased faster (both tests) and to higher values (acute exercise) in Plin1(-/-) mice. Respiratory quotient increased during both types of exercise in Plin1(-/-) and control mice, but less in Plin1(-/-) mice. These lower respiratory quotient values show that Plin1(-/-) mice rely more on fatty acid oxidation during exercise. This is probably related to an overexpression in liver and muscle of genes for fatty acids oxidation. Perilipin 1 ablation has limited consequences on energy balance. It does not impair exercise performance; fatty acids mobilization during exercise is not impaired, whereas their oxidation is enhanced.

Lipogenesis in arterial wall and vascular smooth muscular cells: regulation and abnormalities in insulin-resistance.

BACKGROUND: Vascular smooth muscular cells (VSMC) express lipogenic genes. Therefore in situ lipogenesis could provide fatty acids for triglycerides synthesis and cholesterol esterification and contribute to lipid accumulation in arterial wall with aging and during atheroma. METHODS: We investigated expression of lipogenic genes in human and rat arterial walls, its regulation in cultured VSMC and determined if it is modified during insulin-resistance and diabetes, situations with increased risk for atheroma. RESULTS: Zucker obese (ZO) and diabetic (ZDF) rats accumulated more triglycerides in their aortas than their respective control rats, and this triglycerides content increased with age in ZDF and control rats. However the expression in aortas of lipogenic genes, or of genes involved in fatty acids uptake, was not higher in ZDF and ZO rats and did not increase with age. Expression of lipogenesis-related genes was not increased in human arterial wall (carotid endarterectomy) of diabetic compared to non-diabetic patients. In vitro, glucose and adipogenic medium (ADM) stimulated moderately the expression and activity of lipogenesis in VSMC from control rats. LXR agonists, but not PXR agonist, stimulated also lipogenesis in VSMC but not in arterial wall in vivo. Lipogenic genes expression was lower in VSMC from ZO rats and not stimulated by glucose or ADM. CONCLUSION: Lipogenic genes are expressed in arterial wall and VSMC; this expression is stimulated (VSMC) by glucose, ADM and LXR agonists. During insulin-resistance and diabetes, this expression is not increased and resists to the actions of glucose and ADM. It is unlikely that this metabolic pathway contribute to lipid accumulation of arterial wall during insulin-resistance and diabetes and thus to the increased risk of atheroma observed in these situations.