LXR activation by GW3965 alters fat tissue distribution and adipose tissue inflammation in ob/ob female mice.
ABSTRACT: To investigate the role of liver X receptor (LXR) in adipose tissue metabolism during obesity, ob/ob mice were treated for 5 weeks with the synthetic LXR agonist GW3965. MRI analysis revealed that pharmacological activation of LXR modified fat distribution by decreasing visceral (VS) fat and inversely increasing subcutaneous (SC) fat storage without affecting whole body fat content. This was concordant with opposite regulation by GW3965 of the lipolytic markers hormone-sensitive lipase (HSL) and adipose triglyceride lipase (ATGL) in the two fat depots; moreover, the expression of genes involved in lipogenesis was significantly induced in SC fat. Lipidomic analysis suggested that changes in lipid composition in response to GW3965 also varied between VS and SC fat. In both depots, the observed alteration in lipid composition indicated an overall change toward less lipotoxic lipids. Flow cytometry analysis showed decreased immune cell infiltration in adipose tissue of ob/ob mice in response to GW3965 treatment, which in VS fat mainly affected the macrophage population and in SC fat the lymphocyte population. In line with this, the expression and secretion of proinflammatory markers was decreased in both fat deposits with GW3965 treatment.
Project description:The response to overfeeding is sex dependent, and metabolic syndrome is more likely associated to obesity in men or postmenopausal women than in young fertile women. We hypothesized that obesity-induced metabolic syndrome is sex dependent due to a sex-specific regulation of the fatty acid (FA) synthesis pathways in liver and white adipose depots. We aimed to identify distinctive molecular signatures between sexes using a lipidomics approach to characterize lipid species in liver, perigonadal adipose tissue, and inguinal adipose tissue and correlate them to the physiopathological responses observed. Males had less total fat but lower subcutaneous on visceral fat ratio together with higher liver weight and higher liver and serum triglyceride (TG) levels. Males were insulin resistant compared to females. Fatty acid (FA) and TG profiles differed between sexes in both fat pads, with longer chain FAs and TGs in males compared to that in females. Remarkably, hepatic phospholipid composition was sex dependent with more abundant lipotoxic FAs in males than in females. This may contribute to the sexual dimorphism in response to obesity towards more metaflammation in males. Our work presents an exhaustive novel description of a sex-specific lipid signature in the pathophysiology of metabolic disorders associated with obesity in ob/ob mice. These data could settle the basis for future pharmacological treatment in obesity.
Project description:The effect of acute exposure to cold on the expression of the ob (obese) gene, which encodes a protein that plays a critical role in the regulation of energy balance and body weight, has been examined in epididymal white adipose tissue of mice. Overnight (18 h) exposure of mice to a temperature of 4 degrees C led to the disappearance of ob mRNA in epididymal white fat, and subsequent studies showed that a cold-induced loss of ob mRNA could occur in as little as 2-4 h of exposure to 4 degrees C. When mice exposed to cold for 18 h were returned to the warm (24 degrees C), there was a rapid stimulation of the expression of the ob gene, the mRNA returning within 2.5 h. Administration of noradrenaline led to a reduction in the level of ob mRNA in mice maintained in the warm, while isoprenaline resulted in the disappearance of the mRNA; these changes in ob mRNA were paralleled by similar changes in lipoprotein lipase mRNA. In contrast to white fat, the level of lipoprotein lipase mRNA in brown adipose tissue was increased by noradrenaline and isoprenaline. It is concluded that there is a cold-induced suppression of ob gene expression in white adipose tissue of mice and that this is mediated primarily by the sympathetic system. The profound effect of cold on ob gene expression indicates that the ob system relates to energy expenditure, as well as to satiety.
Project description:Transcriptional regulation of genes in AML12 cells treated with Palmitic acid, LXR lingand (GW3965) and Ulk1 siRNA shows differential effect of Ulk1 KD on LXr responsive genes AML-12 cells co-treated with 0.75mM PA+/- 10ÂµM GW3965 for 24 h +/- Ulk1 SiRNA
Project description:1. Clearing-factor lipase was assayed in acetone-ether-dried powders of heart and epididymal fat-pads of lean and genetically obese mice (ob/ob). In both tissues the enzyme activity in the adult was higher in the obese mice. 2. In heart the enzyme activity was unchanged from 8 to 48 weeks of age in lean mice, but in obese mice it increased between 8 and 12 weeks of age and remained elevated. 3. Starvation produced changes in the heart clearing-factor lipase activity in obese, but not lean, mice. 4. The clearing-factor lipase activity of epididymal fat-pads decreased rapidly during 24h starvation in both lean and obese mice, but the activity in the obese mice remained higher than that in lean mice. 5. Plasma triglyceride and cholesterol concentrations were determined in both lean and obese mice. Triglyceride concentrations were not greatly different, but the obese mice were hypercholesterolaemic. Plasma cholesterol concentrations were not correlated with changes in clearing-factor lipase activity.
Project description:The Liver X receptor (LXR) is an important regulator of carbohydrate and lipid metabolism in humans and mice. We have recently shown that activation of LXR regulates cellular fuel utilization in adipocytes. In contrast, the role of LXR in human adipocyte lipolysis, the major function of human white fat cells, is not clear. In the present study, we stimulated in vitro differentiated human and murine adipocytes with the LXR agonist GW3965 and observed an increase in basal lipolysis. Microarray analysis of human adipocyte mRNA following LXR activation revealed an altered gene expression of several lipolysis-regulating proteins, which was also confirmed by quantitative real-time PCR. We show that expression and intracellular localization of perilipin1 (PLIN1) and hormone-sensitive lipase (HSL) are affected by GW3965. Although LXR activation does not influence phosphorylation status of HSL, HSL activity is required for the lipolytic effect of GW3965. This effect is abolished by PLIN1 knockdown. In addition, we demonstrate that upon activation, LXR binds to the proximal regions of the PLIN1 and HSL promoters. By selective knock-down of either LXR isoform, we show that LXR? is the major isoform mediating the lipolysis-related effects of LXR. In conclusion, the present study demonstrates that activation of LXR? up-regulates basal human adipocyte lipolysis. This is at least partially mediated through LXR binding to the PLIN1 promoter and down-regulation of PLIN1 expression.
Project description:We have previously demonstrated that subcutaneous and intra-abdominal adipose tissue show different patterns of expression for developmental genes (Shox2, En1, Tbx15 Hoxa5, Hoxc8, and Hoxc9), and that the expression level of Tbx15 and Hoxa5 in humans correlated with the level of obesity and fat distribution. To further explore the role of these developmental genes in adipose tissue, we have characterized their expression in different adipose depots in mice, and studied their regulation in obesity and by fasting. Developmental and adipogenic gene expression was compared in two subcutaneous and three intra-abdominal white adipose tissue (WAT) depots as well as brown adipose tissue (BAT) from lean or obese mice in a fed or fasting state. Each of these six adipose depots display a unique pattern of developmental gene expression, whereas expression of adipogenic transcription factors PPARgamma2 C/EBPalpha, beta, and Delta showed constant expression levels in all depots. Expression levels of developmental genes were similar in obese (ob/ob and high-fat diet (HFD)) and lean mice in most depots. Fasting systematically decreased expression of Hoxc8, PPARgamma2, and increased C/EBPDelta in both lean and ob/ob mice, but produced only variable changes in the expression of other developmental and adipogenic genes. These data indicate that each fat depot has a unique developmental gene expression signature, which is largely independent of nutritional state. This finding further supports a fundamental role of developmental genes in fat distribution and the development and/or function of specific adipose tissue depots.
Project description:Obesity may result from altered fatty acid (FA) disposal. Altered FA distribution in obese individuals is poorly understood. Lean wild-type C57BL/6J and obese C57BL/6Job/ob mice received an oral dose of [1-(14)C]18:1n-9 (oleic acid), and the radioactivity in tissues was evaluated at various time points. The (14)C concentration decreased rapidly in gastrointestinal tract but gradually increased and peaked at 96 h in adipose tissue, muscle and skin in lean mice. The (14)C concentration was constant in adipose tissue and muscle of obese mice from 4 h to 168 h. (14)C-label content in adipose tissue was significantly affected by genotype, whereas muscle (14)C-label content was affected by genotype, time and the interaction between genotype and time. There was higher total (14)C retention (47.7%) in obese mice than in lean mice (9.0%) at 168 h (P<0.05). The (14)C concentrations in the soleus and gastrocnemius muscle were higher in obese mice than in lean mice (P<0.05). Perirenal adipose tissue contained the highest (14)C content in lean mice, whereas subcutaneous adipose tissue (SAT) had the highest (14)C content and accounted for the largest proportion of total radioactivity among fat depots in obese mice. More lipid radioactivity was recovered as TAG in SAT from obese mice than from lean mice (P<0.05). Gene expression suggested acyl CoA binding protein and fatty acid binding protein are important for FA distribution in adipose tissue and muscle. The FA distribution in major tissues was altered in ob/ob mice, perhaps contributing to obesity. Understanding the disparity in FA disposal between lean and obese mice may reveal novel targets for the treatment and prevention of obesity.
Project description:Liver X receptors (LXRs) activate genes that regulate lipid and cholesterol metabolism. LXR agonists were shown recently to also increase murine renin gene expression in vivo. To further examine a link between lipid metabolism, the renin-angiotensin-aldosterone-system and blood pressure regulation, we investigated the effect of a LXR agonist (GW3965) on angiotensin II (Ang II)-mediated vasoreactivity and vascular angiotensin II receptor (ATR) gene expression.Arterial blood pressure (BP) was measured during Ang II infusions (1.5 min duration; 0.001-3 microg kg(-1)) in pentobarbital-anesthetized male Sprague-Dawley rats (n = 6-9) after oral administration of GW3965 (10 mg kg(-1), q.d.) or vehicle for 7 - 15 days. Mesenteric arteries and plasma were collected to analyze ATR gene expression and to measure plasma renin activity (PRA) and lipid profile, respectively.Basal mean arterial pressure (MAP) was similar between groups. GW3965 dosing blunted the vasopressor effect of Ang II, which was significantly different with the 0.3 and 3 microg kg(-1) doses. No difference in heart rate, PRA or lipid profile was observed between groups. A time-course indicated that ATR type 1 and 2 gene expression of GW3965-treated vs. vehicle-treated rats decreased by 50%, reaching significance for ATR type 2, but not for ATR type 1, at time-points coinciding with BP measurements.GW3965 decreased Ang II-mediated vasopressor responses coincident with a trend toward reduced ATR gene expression, suggesting that LXR agonists could affect vascular reactivity.
Project description:Traumatic brain injury (TBI) increases Alzheimer's disease (AD) risk and leads to the deposition of neurofibrillary tangles and amyloid deposits similar to those found in AD. Agonists of Liver X receptors (LXRs), which regulate the expression of many genes involved in lipid homeostasis and inflammation, improve cognition and reduce neuropathology in AD mice. One pathway by which LXR agonists exert their beneficial effects is through ATP-binding cassette transporter A1 (ABCA1)-mediated lipid transport onto apolipoprotein E (apoE). To test the therapeutic utility of this pathway for TBI, we subjected male wild-type (WT) and apoE-/- mice to mild repetitive traumatic brain injury (mrTBI) followed by treatment with vehicle or the LXR agonist GW3965 at 15 mg/kg/day. GW3965 treatment restored impaired novel object recognition memory in WT but not apoE-/- mice. GW3965 did not significantly enhance the spontaneous recovery of motor deficits observed in all groups. Total soluble A?(40) and A?(42) levels were significantly elevated in WT and apoE-/- mice after injury, a response that was suppressed by GW3965 in both genotypes. WT mice showed mild but significant axonal damage at 2 d post-mrTBI, which was suppressed by GW3965. In contrast, apoE-/- mice showed severe axonal damage from 2 to 14 d after mrTBI that was unresponsive to GW3965. Because our mrTBI model does not produce significant inflammation, the beneficial effects of GW3965 we observed are unlikely to be related to reduced inflammation. Rather, our results suggest that both apoE-dependent and apoE-independent pathways contribute to the ability of GW3965 to promote recovery from mrTBI.
Project description:Analysis of differentially expressed genes in response to the LXR agonist GW3965 in the MCF-7, T-47D, SK-BR-3, and MDA-MB-231 breast cancer cell lines. It was previously reported that GW3965 has antiproliferative effects on these 4 different breast cancer cell lines. In the present study, we additionally determine the effects of the LXR ligand on breast cancer cells and determine their mechanism of action in reducing cell proliferation. Total RNA obtained from 4 different breast cancer cell lines (MCF-7, T-47D, SK-BR-3, MDA-MB-231) grown in culture treated with ethanol (control) or GW3965 (GW-treated, experimental) for 48 hours. Triplicates were performed.