Antiadipogenic Effects of Loganic Acid in 3T3-L1 Preadipocytes and Ovariectomized Mice.

Obesity is caused by an excess storage of body fat, resulting from a chronic imbalance between energy intake and expenditure. Gentiana lutea L. (GL) root has been reported to reduce lipid accumulation in the aortic wall of diabetic rats. Here, we performed fractionation and isolation of the bioactive constituent(s) that may be responsible for the antiadipogenic effects of the GL root extract. A single compound, loganic acid, was identified as a candidate component in the 30% ethanol extract of GL. Loganic acid treatment significantly decreased the adipocyte differentiation of 3T3-L1 preadipocytes in a dose-dependent manner. The expression of key adipogenesis-related genes such as adiponectin (Adipoq), peroxisome proliferator-activated receptor gamma (Pparg), lipoprotein lipase (Lpl), perilipin1 (Plin1), fatty acid binding protein 4 (Fabp4), glucose transporter type 4 (Slc2a4), CCAAT/enhancer-binding protein alpha (Cebpa), and tumor necrosis factor-alpha (Tnf) were significantly reduced following treatment with loganic acid. In vivo experiments in an ovariectomy-induced obesity mouse model showed that loganic acid (oral administration with 10 and 50 mg/kg/day) significantly inhibited body weight gain, total fat increase, fatty hepatocyte deposition in the liver, and adipocyte enlargement in the abdominal visceral fat tissues. These results suggest that loganic acid in the GL root extract has antiadipogenic effects in vitro and in vivo. Loganic acid may be beneficial for the prevention and treatment of obesity, particularly in menopausal obese women.

Regulation of retinoid X receptor gamma expression by fed state in mouse liver.

Glucose metabolism is balanced by glycolysis and gluconeogenesis with precise control in the liver. The expression of genes related to glucose metabolism is regulated primarily by glucose and insulin at transcriptional level. Nuclear receptors play important roles in regulating the gene expression of glucose metabolism at transcriptional level. Some of these nuclear receptors form heterodimers with RXRs to bind to their specific regulatory elements on the target promoters. To date, three isotypes of RXRs have been identified; RXRα, RXRß and RXRγ. However, their involvement in the interactions with other nuclear receptors in the liver remains unclear. In this study, we found RXRγ is rapidly induced after feeding in the mouse liver, indicating a potential role of RXRγ in controlling glucose or lipid metabolism in the fasting-feeding cycle. In addition, RXRγ expression was upregulated by glucose in primary hepatocytes. This implies that glucose metabolism governed by RXRγ in conjunction with other nuclear receptors. The luciferase reporter assay showed that RXRγ as well as RXRα increased SREBP-1c promoter activity in hepatocytes. These results suggest that RXRγ may play an important role in tight control of glucose metabolism in the fasting-feeding cycle.

Nuclear receptor PPARγ-regulated monoacylglycerol O-acyltransferase 1 (MGAT1) expression is responsible for the lipid accumulation in diet-induced hepatic steatosis.

Recently, hepatic peroxisome proliferator-activated receptor (PPAR)γ has been implicated in hepatic lipid accumulation. We found that the C3H mouse strain does not express PPARγ in the liver and, when subject to a high-fat diet, is resistant to hepatic steatosis, compared with C57BL/6 (B6) mice. Adenoviral PPARγ2 injection into B6 and C3H mice caused hepatic steatosis, and microarray analysis demonstrated that hepatic PPARγ2 expression is associated with genes involved in fatty acid transport and the triglyceride synthesis pathway. In particular, hepatic PPARγ2 expression significantly increased the expression of monoacylglycerol O-acyltransferase 1 (MGAT1). Promoter analysis by luciferase assay and electrophoretic mobility shift assay as well as chromatin immunoprecipitation assay revealed that PPARγ2 directly regulates the MGAT1 promoter activity. The MGAT1 overexpression in cultured hepatocytes enhanced triglyceride synthesis without an increase of PPARγ expression. Importantly, knockdown of MGAT1 in the liver significantly reduced hepatic steatosis in 12-wk-old high-fat-fed mice as well as ob/ob mice, accompanied by weight loss and improved glucose tolerance. These results suggest that the MGAT1 pathway induced by hepatic PPARγ is critically important in the development of hepatic steatosis during diet-induced obesity.

Indices of arterial stiffness in African American and African Caribbean subjects.

BACKGROUND: African American and African Caribbeans have high cardiovascular morbidity/mortality. Increased arterial stiffness is a marker of subclinical atherosclerosis, predicts higher cardiovascular risk, and causes isolated systolic hypertension. The objectives of the study were to compare arterial stiffness indices in African Americans and African Caribbeans and obtain reference values. METHODS/RESULTS: We prospectively studied 449 African Americans and 454 African Caribbeans. Using applanation tonometry, mean augmentation index and carotid-to-radial pulse-swave velocity were similar between the 2 groups (23 +/- 15 vs 24 +/- 14%, p = .20) and (9.0 +/- 1.9 vs 9.0 +/- 2.0 m/s, p = .86). On multivariate analysis, age, weight, gender, mean arterial pressure, heart rate, and family history of coronary artery disease were independently associated with augmentation index in African Americans (R2, 0.46) and African Caribbeans (R2, 0.49). Among 94 African American and 98 African Caribbean healthy subjects without cardiovascular risk factors/disease, augmentation index (20 +/- 14 vs 18 +/- 16%, p = .43) and pulse-wave velocity (8.9 +/- 1.9 vs 9.0 +/- 1.5 m/s, p = .92) were similar. Age-based normative values were determined. CONCLUSION: Augmentation index and pulse-wave velocity and their related clinical factors are similar between African Americans and African Caribbeans. Age, weight, female gender, mean arterial pressure, heart rate, and family history of coronary artery disease are independent predictors of higher augmentation index in African Americans and African Caribbeans. Whether increased arterial stiffness improves risk stratification in these populations merits further study.

Delineating the relationships among the formation of reactive oxygen species, cell membrane instability and innate autoimmunity in intestinal reperfusion injury.

Acute intestinal ischemia is a medical emergency with a high mortality rate, attesting to the need for a better understanding of its pathogenesis and the development of effective therapies. The goal of this study was to delineate the relationships among intracellular and extracellular events in intestinal ischemia/reperfusion (I/R) injury, particularly the formation of reactive oxygen species (ROS), cell membrane instability associated with lipid peroxidation and the innate autoimmune response mediated by natural IgM and complement. A murine model of natural IgM-mediated intestinal I/R was used. Mice overexpressing anti-oxidant enzyme SOD1 were found to have significantly reduced intestinal tissue damage and complete blockage of IgM-mediated complement activation compared with WT controls. To determine if cell membrane instability was an event intermediate between ROS formation and natural IgM-mediated innate autoimmune response, the cell membrane stabilizer (trehalose) was administered to WT mice prior to the induction of intestinal ischemia. Treatment with trehalose significantly protected animals from I/R injury and inhibited IgM-mediated complement activation although it did not prevent membrane lipid peroxidation. These data indicate that in normal mice subjected to I/R injury, intracellular ROS formation is an event upstream of the lipid peroxidation which results in cell membrane instability. The membrane instability leads to an innate autoimmune response by natural IgM and complement. Trehalose, a nontoxic disaccharide tolerated well by animals and humans, has promise as a protective agent for patients with medical conditions related to acute intestinal ischemia.

Mayne's sign is mainly related to younger age and not to aortic regurgitation.

BACKGROUND: An exaggerated decrease in diastolic blood pressure (DBP) upon raising the upper extremity is a sign of severe chronic aortic regurgitation (AR) (Mayne's sign). However, this finding was proposed prior to the widespread use of Doppler echocardiography. OBJECTIVE: To determine the relation between Doppler echo determined AR and changes in DBP. METHODS: We prospectively studied 30 controls without AR and 40 patients (69±15 years) with AR ranging from mild to severe and measured DBP before and during upper extremity raising. RESULTS: The change in DBP was inversely correlated with age (r=-0.41, P<0.001) but not to the presence or severity of AR on Doppler echocardiography (r=-0.10, P=0.42). CONCLUSION: Greater decreases in DBP upon arm raising appear to be related to younger age but not to the presence or severity of AR. Therefore, Mayne's sign should not be considered a reliable finding of regurgitant aortic valve flow.

Effect of reactive hyperemia on carotid-radial pulse wave velocity in hypertensive participants and direct comparison with flow-mediated dilation: a pilot study.

UNLABELLED: This pilot study assessed the effects of hyperemia on carotid-radial pulse wave velocity (PWV) in 39 normotensive (NT) and 23 hypertensive (HT) participants using applanation tonometry. Pulse wave velocity was measured at 1- and at 2-minute intervals. Baseline PWV was similar between the groups (P = .59). At 1 minute, PWV decreased (8.5 +/- 1.2 to 7.1 +/- 1.4 m/s, P < .001) in NT but not in HT (P = .83). Hyperemic PWV (DeltaPWV) response differed between the groups (-16% vs + 1.0%, P < .001). On multivariate analysis, HT, not age or blood pressure was independently related to DeltaPWV (R(2) = .43, P < .01). Among patients with cardiovascular risk factors/disease, DeltaPWV was inversely related to flow-mediated dilation (FMD; R( 2) = .43, P < .003). CONCLUSION: hyperemia decreases PWV(1min) in NT but not in HT. DeltaPWV is inversely related to FMD. Blunted hyperemic PWV response may represent impaired vasodilatory reserve.

Reactive oxygen species facilitate adipocyte differentiation by accelerating mitotic clonal expansion.

Growth-arrested 3T3-L1 preadipocytes rapidly express CCAAT/enhancer-binding protein-beta (C/EBPbeta) upon hormonal induction of differentiation. However, the DNA binding activity of C/EBPbeta is not activated until the cells synchronously reenter S phase during the mitotic clonal expansion (MCE) phase of differentiation. In this period, C/EBPbeta is sequentially phosphorylated by MAPK and glycogen synthase kinase-3beta, inducing C/EBPbeta DNA binding activity and transcription of its target genes. Because the DNA binding activity of C/EBPbeta is further enhanced by oxidation in vitro, we investigated how redox state affects C/EBPbeta DNA binding and MCE during adipogenesis. When 3T3-L1 cells were treated with H(2)O(2) and hormonal stimuli, differentiation was accelerated with increased expression of peroxisome proliferator-activated receptor gamma. Interestingly, cell cycle progression (S to G(2)/M phase) was markedly enhanced by H(2)O(2), whereas antioxidants caused an S phase arrest during the MCE. H(2)O(2) treatment resulted in the early appearance of a punctate pattern observed by immunofluorescent staining of C/EBPbeta, which is a hallmark for C/EBPbeta binding to regulatory elements, whereas a short antioxidant treatment rapidly dispersed the centromeric localization of C/EBPbeta. Consistently, reactive oxygen species production was increased during 3T3-L1 differentiation. Our results indicate that redox-induced C/EBPbeta DNA binding activity, along with the dual phosphorylation of C/EBPbeta, is required for the MCE and terminal differentiation of adipocytes.

The effects of passive leg raising on arterial wave reflection in healthy adults.

BACKGROUND: Passive leg raising (PLR) produces hemodynamic and physiological changes related to centralizing blood volume and baroreceptor activation. METHODS/RESULTS: To evaluate the effects of PLR on central hemodynamics, we prospectively studied 50 healthy participants (80% male, age 37 +/- 12 years). Central aortic blood pressures (CA-BPs) and reflected wave properties were evaluated using applanation tonometry at baseline and upon 1 min of PLR. Heart rate (HR) was unchanged. Brachial artery (BA)-systolic BP, BA-diastolic BP, and BA-pulse pressure (PP) all decreased from baseline to PLR. Changes in BA-PP were significantly greater than changes in CA-PP. Reflected wave augmentation pressure (P(s)-P(i)), HR corrected augmentation index (AIx@75), and augmentation index decreased significantly [(P(s)-P(i)): 5 +/- 6 vs. 4 +/-5, P < 0.001; AIx@75%: 10 +/- 13 vs. 7 +/- 12, P = 0.004; AI%: 14 +/- 12 vs. 12 +/- 12, P = 0.014, respectively]. HR corrected ejection duration (ED(c)), round trip travel time (deltat(p)), and reflected wave systolic duration (deltat(r)) all increased upon PLR [ED(c): 433 +/- 15 vs. 444 +/- 17, P < 0.001; deltat(p): 149 +/- 18 vs. 156 +/- 20, P = 0.003; deltat(r): 174 +/- 33 vs. 179 +/- 32, P = 0.046, respectively]. Indices of left ventricular (LV) workload including wasted LV energy and tension-time index decreased upon PLR. CONCLUSION: PLR decreases the amplitude and delays the onset of the reflected aortic pressure wave. This decreases wasted LV pressure energy and workload.