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.

Pioglitazone Attenuates Palmitate-Induced Inflammation and Endoplasmic Reticulum Stress in Pancreatic β-Cells

BACKGROUND: The nuclear receptor peroxisome proliferator-activator gamma (PPARγ) is a useful therapeutic target for obesity and diabetes, but its role in protecting β-cell function and viability is unclear. METHODS: To identify the potential functions of PPARγ in β-cells, we treated mouse insulinoma 6 (MIN6) cells with the PPARγ agonist pioglitazone in conditions of lipotoxicity, endoplasmic reticulum (ER) stress, and inflammation. RESULTS: Palmitate-treated cells incubated with pioglitazone exhibited significant improvements in glucose-stimulated insulin secretion and the repression of apoptosis, as shown by decreased caspase-3 cleavage and poly (adenosine diphosphate [ADP]-ribose) polymerase activity. Pioglitazone also reversed the palmitate-induced expression of inflammatory cytokines (tumor necrosis factor α, interleukin 6 [IL-6], and IL-1β) and ER stress markers (phosphor-eukaryotic translation initiation factor 2α, glucose-regulated protein 78 [GRP78], cleaved-activating transcription factor 6 [ATF6], and C/EBP homologous protein [CHOP]), and pioglitazone significantly attenuated inflammation and ER stress in lipopolysaccharide- or tunicamycin-treated MIN6 cells. The protective effect of pioglitazone was also tested in pancreatic islets from high-fat-fed KK-Ay mice administered 0.02% (wt/wt) pioglitazone or vehicle for 6 weeks. Pioglitazone remarkably reduced the expression of ATF6α, GRP78, and monocyte chemoattractant protein-1, prevented α-cell infiltration into the pancreatic islets, and upregulated glucose transporter 2 (Glut2) expression in β-cells. Moreover, the preservation of β-cells by pioglitazone was accompanied by a significant reduction of blood glucose levels. CONCLUSION: Altogether, these results support the proposal that PPARγ agonists not only suppress insulin resistance, but also prevent β-cell impairment via protection against ER stress and inflammation. The activation of PPARγ might be a new therapeutic approach for improving β-cell survival and insulin secretion in patients with diabetes mellitus

Low glibenclamide concentrations affect endoplasmic reticulum stress in INS-1 cells under glucotoxic or glucolipotoxic conditions

BACKGROUND/AIMS: beta-Cell apoptosis caused by increased endoplasmic reticulum (ER) stress is an important pathogenic component of type 2 diabetes mellitus. In theory, sulfonylureas, used for the treatment of diabetes, can contribute to ER stress. We assessed changes in ER stress in pancreatic beta-cells under glucotoxic or glucolipotoxic conditions using low concentrations of the sulfonylurea, glibenclamide (GB). METHODS: Low concentrations of GB (10 or 100 nM) were added to INS-1 cells cultured under glucotoxic or glucolipotoxic conditions. The degree of viability, level of apoptosis and levels of markers associated with ER stress were measured. RESULTS: Apoptosis decreased in response to low concentrations of GB under glucolipotoxic but not glucotoxic conditions. Most ER stress markers decreased upon the addition of GB. Under glucotoxic conditions, changes in the levels of ER stress markers were not consistent. However, all decreased significantly under glucolipotoxic conditions. CONCLUSIONS: Low concentrations of GB exerted antiapoptotic effects through the attenuation of ER stress under glucolipotoxic conditions.

Glucolipotoxicity in Pancreatic beta-Cells

The recent epidemic of type 2 diabetes in Asia differs from that reported in other regions of the world in several key areas: it has evolved over a much shorter time, in an earlier stage of life, and in people with lower body mass indices. These phenotypic characteristics of patients strongly suggest that insulin secretory defects may perform a more important function in the development and progression of diabetes. A genetic element clearly underlies beta-cell dysfunction and insufficient beta-cell mass; however, a number of modifiable factors are also linked to beta-cell deterioration, most notably chronic hyperglycemia and elevated free fatty acid (FFA) levels. Neither glucose nor FFAs alone cause clinically meaningful beta-cell toxicity, especially in patients with normal or impaired glucose tolerance. Thus the term "glucolipotoxicity" is perhaps more appropriate in describing the phenomenon. Several mechanisms have been proposed to explain glucolipotoxicity-induced beta-cell dysfunction and death, but its major factors appear to be depression of key transcription factor gene expression by altered intracellular energy metabolism and oxidative stress. Therefore, stabilization of metabolic changes induced by glucolipotoxicity in beta-cells represents a new avenue for the treatment of type 2 diabetes mellitus.

ERS response mediates glucolipotoxicity-induced β-cell apoptosis / 基础医学与临床

As one of the most sensitive cells of endoplasmic retieulum stress (ERS), pancreatic β-cells have an a-bundance of endoplasmic reticulum. Fatty acids cause apoptosis of β-cells and might contribute to β-cell loss in type 2 diabetes mellitus via the induction of ERS. Glucose is an amplifier of the ERS response to fatty acid, leading to increased β-cell apoptosis. ERS response mediates glucolipotoxicity-induced β-cell apoptosis.