Ldlr-/- mice display decreased susceptibility to Western-type diet-induced obesity due to increased thermogenesis

Effect of diet and genotype on the lipidome of mice with altered lipoprotein metabolism

The present study describes and compares the impact of PCSK9 and LDLR, two pivotal players in cholesterol metabolism, on the whole lipidome of plasma, liver and aorta in different dietary conditions. This issue is relevant, since several lipid species, circulating at very low concentrations, have the ability to impair lipid metabolism and promote atherosclerosis development. To this aim, wild-type, hypercholesterolemic Ldlr-KO, and hypocholesterolemic Pcsk9-KO mice were fed a standard chow or a Western-type diet up to 30 and 16 weeks of age, respectively. 42 lipids including cholesterol, cholesteryl esters, several sphingolipids, phospholipids, and lysophospholipids, accumulated uniquely in the atherosclerotic aorta of Western-type diet-fed Ldlr-KO mice. In addition, multiple organ/tissue comparisons allowed us to identify 16 lipids whose plasma and hepatic patterns mirrored the lipidome of the atherosclerotic aorta. These lipid species, belonging to cholesteryl esters, glucosyl/galactosylceramide, lactosylceramide, globotriaosylceramide, sphingomyelin, and phosphatidylcholine could be further investigated as circulating biomarkers or therapeutic targets.

Maintenance of thermogenic adipose tissues despite loss of the H3K27 acetyltransferases p300 or CBP

Brown and beige adipose tissues are specialized for thermogenesis and are important for energy balance in mice. Mounting evidence suggests that chromatin-modifying enzymes are integral for the development, maintenance, and functioning of thermogenic adipocytes. p300 and cAMP-response element binding protein (CREB)-binding protein (CBP) are histone acetyltransferases (HATs) responsible for writing the transcriptionally activating mark H3K27ac. Despite their homology, p300 and CBP do have unique tissue- and context-dependent roles, which have yet to be examined in brown and beige adipocytes specifically. We assessed the requirement of p300 or CBP in thermogenic fat using uncoupling protein 1 (Ucp1)-Cre-mediated knockdown in mice to determine whether their loss impacted tissue development, susceptibility to diet-induced obesity, and response to pharmacological induction via β3-agonism. Despite successful knockdown, brown adipose tissue mass and expression of thermogenic markers were unaffected by loss of either HAT. As such, knockout mice developed a comparable degree of diet-induced obesity and glucose intolerance to that of floxed controls. Furthermore, "browning" of white adipose tissue by the β3-adrenergic agonist CL-316,243 remained largely intact in knockout mice. Although p300 and CBP have nonoverlapping roles in other tissues, our results indicate that they are individually dispensable within thermogenic fats specifically, possibly due to functional compensation by one another.NEW & NOTEWORTHY The role of transcriptionally activating H3K27ac epigenetic mark has yet to be examined in mouse thermogenic fats specifically, which we achieved here via Ucp1-Cre-driven knockdown of the histone acetyltransferases (HAT) p300 or CBP under several metabolic contexts. Despite successful knockdown of either HAT, brown adipose tissue was maintained at room temperature. As such, knockout mice were indistinguishable to controls when fed an obesogenic diet or when given a β3-adrenergic receptor agonist to induce browning of white fat. Unlike other tissues, thermogenic fats are resilient to p300 or CBP ablation, likely due to sufficient functional overlap between them.

Activation of β-catenin in mesenchymal progenitors leads to muscle mass loss

Loss of muscle mass is a common manifestation of chronic disease. We find the canonical Wnt pathway to be activated in mesenchymal progenitors (MPs) from cancer-induced cachectic mouse muscle. Next, we induce β-catenin transcriptional activity in murine MPs. As a result, we observe expansion of MPs in the absence of tissue damage, as well as rapid loss of muscle mass. Because MPs are present throughout the organism, we use spatially restricted CRE activation and show that the induction of tissue-resident MP activation is sufficient to induce muscle atrophy. We further identify increased expression of stromal NOGGIN and ACTIVIN-A as key drivers of atrophic processes in myofibers, and we verify their expression by MPs in cachectic muscle. Finally, we show that blocking ACTIVIN-A rescues the mass loss phenotype triggered by β-catenin activation in MPs, confirming its key functional role and strengthening the rationale for targeting this pathway in chronic disease.

Ldlr-Deficient Mice with an Atherosclerosis-Resistant Background Develop Severe Hyperglycemia and Type 2 Diabetes on a Western-Type Diet

Apoe^-/- and Ldlr^-/- mice are two animal models extensively used for atherosclerosis research. We previously reported that Apoe^-/- mice on certain genetic backgrounds, including C3H/HeJ (C3H), develop type 2 diabetes when fed a Western diet. We sought to characterize diabetes-related traits in C3H-Ldlr^-/- mice through comparing with C3H-Apoe^-/- mice. On a chow diet, Ldlr^-/- mice had lower plasma total and non-HDL cholesterol levels but higher HDL levels than Apoe^-/- mice. Fasting plasma glucose was much lower in Ldlr^-/- than Apoe^-/- mice (male: 122.5 ± 5.9 vs. 229.4 ± 17.5 mg/dL; female: 144.1 ± 12.4 vs. 232.7 ± 6.4 mg/dL). When fed a Western diet, Ldlr^-/- and Apoe^-/- mice developed severe hypercholesterolemia and also hyperglycemia with fasting plasma glucose levels exceeding 250 mg/dL. Both knockouts had similar non-HDL cholesterol and triglyceride levels, and their fasting glucose levels were also similar. Male Ldlr^-/- mice exhibited greater glucose tolerance and insulin sensitivity compared to their Apoe^-/- counterpart. Female mice showed similar glucose tolerance and insulin sensitivity though Ldlr^-/- mice had higher non-fasting glucose levels. Male Ldlr^-/- and Apoe^-/- mice developed moderate obesity on the Western diet, but female mice did not. These results indicate that the Western diet and ensuing hyperlipidemia lead to the development of type 2 diabetes, irrespective of underlying genetic causes.

The multifaceted roles of the adipose tissue vasculature

The prevalence of obesity and its associated pathologies continue to increase, which has led to a renewed interest in our major weight-regulating organ, the white adipose tissue. It has become clear that its development, expansion, and physiological function depend on proper crosstalk between each of its cellular constituents, with a central role for the vascular endothelium lining the blood vessels. Although first considered a mere barrier, the endothelium has emerged as a dynamic unit modulating many critical adipose tissue functions. It not only oversees the uptake of all nutrients to be stored in the adipocytes but also provides an important growth niche for adipocyte progenitors and regulates the expandability of the tissue during overfeeding and obesity. In this review, we describe the reciprocal relationship between endothelial cells, adipocytes, and obesity. We present recent studies that support an important role for endothelial cells as central mediators of many of the physiological and pathological functions of the adipose tissue and highlight several unknown aspects of adipose tissue vascular biology. This new perspective could present exciting opportunities to develop new therapeutic approaches against obesity-related pathologies and is thus of great interest in our increasingly obese society.

Pcpe2, a Novel Extracellular Matrix Protein, Regulates Adipocyte SR-BI-Mediated High-Density Lipoprotein Uptake

Objective

To investigate the role of adipocyte Pcpe2 (procollagen C-endopeptidase enhancer 2) in SR-BI (scavenger receptor class BI)-mediated HDL-C (high-density lipoprotein cholesterol) uptake and contributions to adipose lipid storage.

Approach and Results

Pcpe2, a glycoprotein devoid of intrinsic proteolytic activity, is believed to participate in extracellular protein-protein interactions, supporting SR-BI- mediated HDL-C uptake. In published studies, Pcpe2 deficiency increased the development of atherosclerosis by reducing SR-BI-mediated HDL-C catabolism, but the biological impact of this deficiency on adipocyte SR-BI-mediated HDL-C uptake is unknown. Differentiated cells from Ldlr-/-/Pcpe2-/- (Pcpe2-/-) mouse adipose tissue showed elevated SR-BI protein levels, but significantly reduced HDL-C uptake compared to Ldlr-/- (control) adipose tissue. SR-BI-mediated HDL-C uptake was restored by preincubation of cells with exogenous Pcpe2. In diet-fed mice lacking Pcpe2, significant reductions in visceral, subcutaneous, and brown adipose tissue mass were observed, despite elevations in plasma triglyceride and cholesterol concentrations. Significant positive correlations exist between adipose mass and Pcpe2 expression in both mice and humans.

Conclusions

Overall, these findings reveal a novel and unexpected function for Pcpe2 in modulating SR-BI expression and function as it relates to adipose tissue expansion and cholesterol balance in both mice and humans.

Lipotoxic Injury Differentially Regulates Brain Microvascular Gene Expression in Male Mice

The Western diet (WD) and hyperlipidemia are risk factors for vascular disease, dementia, and cognitive impairment. However, the molecular mechanisms are poorly understood. This pilot study investigated the genomic pathways by which the WD and hyperlipidemia regulate gene expression in brain microvessels. Five-week-old C57BL/6J wild type (WT) control and low-density lipoprotein receptor deficient (LDL-R-/-) male mice were fed the WD for eight weeks. Differential gene expression, gene networks and pathways, transcription factors, and non-protein coding RNAs were evaluated by a genome-wide microarray and bioinformatics analysis of laser-captured hippocampal microvessels. The WD resulted in the differential expression of 1972 genes. Much of the differentially expressed gene (DEG) was attributable to the differential regulation of cell signaling proteins and their transcription factors, approximately 4% was attributable to the differential expression of miRNAs, and 10% was due to other non-protein coding RNAs, primarily long non-coding RNAs (lncRNAs) and small nucleolar RNAs (snoRNAs) not previously described to be modified by the WD. Lipotoxic injury resulted in complex and multilevel molecular regulation of the hippocampal microvasculature involving transcriptional and post-transcriptional regulation and may provide a molecular basis for a better understanding of hyperlipidemia-associated dementia risk.

Dietary intake of bioactive ingredients impacts liver and adipose tissue transcriptomes in a porcine model of prepubertal early obesity

Global prevalence of obesity has increased to epidemic proportions over the past 40 years, with childhood obesity reaching alarming rates. In this study, we determined changes in liver and adipose tissue transcriptomes of a porcine model for prepubertal early obesity induced by a high-calorie diet and supplemented with bioactive ingredients. A total of 43 nine-weeks-old animals distributed in four pens were fed with four different dietary treatments for 10 weeks: a conventional diet; a western-type diet; and a western-type diet with Bifidobacterium breve and rice hydrolysate, either adding or not omega-3 fatty acids. Animals fed a western-type diet increased body weight and total fat content and exhibited elevated serum concentrations of cholesterol, whereas animals supplemented with bioactive ingredients showed lower body weight gain and tended to accumulate less fat. An RNA-seq experiment was performed with a total of 20 animals (five per group). Differential expression analyses revealed an increase in lipogenesis, cholesterogenesis and inflammatory processes in animals on the western-type diet while the supplementation with bioactive ingredients induced fatty acid oxidation and cholesterol catabolism, and decreased adipogenesis and inflammation. These results reveal molecular mechanisms underlying the beneficial effects of bioactive ingredient supplementation in an obese pig model.

Effects of lipid metabolism on mouse incisor dentinogenesis

Tooth formation can be affected by various factors, such as oral disease, drug administration, and systemic illness, as well as internal conditions including dentin formation. Dyslipidemia is an important lifestyle disease, though the relationship of aberrant lipid metabolism with tooth formation has not been clarified. This study was performed to examine the effects of dyslipidemia on tooth formation and tooth development. Dyslipidemia was induced in mice by giving a high-fat diet (HFD) for 12 weeks. Additionally, LDL receptor-deficient (Ldlr^−/−) strain mice were used to analyze the effects of dyslipidemia and lipid metabolism in greater detail. In the HFD-fed mice, incisor elongation was decreased and pulp was significantly narrowed, while histological findings revealed disappearance of predentin. In Ldlr^−/− mice fed regular chow, incisor elongation showed a decreasing trend and pulp a narrowing trend, while predentin changes were unclear. Serum lipid levels were increased in the HFD-fed wild-type (WT) mice, while Ldlr^−/− mice given the HFD showed the greatest increase. These results show important effects of lipid metabolism, especially via the LDL receptor, on tooth homeostasis maintenance. In addition, they suggest a different mechanism for WT and Ldlr^−/− mice, though the LDL receptor pathway may not be the only factor involved.

Hyperlipidaemia and cardioprotection: Animal models for translational studies

Hyperlipidaemia is a well-established risk factor for cardiovascular diseases and therefore, many animal model have been developed to mimic the human abnormal elevation of blood lipid levels. In parallel, extensive research for the alleviation of ischaemia/reperfusion injury has revealed that hyperlipidaemia is a major co-morbidity that attenuates the cardioprotective effect of conditioning strategies (preconditioning, postconditioning and remote conditioning) and that of pharmacological interventions by interfering with cardioprotective signalling pathways. In the present review article, we summarize the existing data on animal models of hypercholesterolaemia (total, low density and HDL abnormalities) and hypertriglyceridaemia used in ischaemia/reperfusion injury and protection from it. We also provide recommendations on preclinical animal models to be used for translations of the cardioprotective strategies into clinical practice. LINKED ARTICLES: This article is part of a themed issue on Risk factors, comorbidities, and comedications in cardioprotection. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v177.23/issuetoc.

The Western Diet Regulates Hippocampal Microvascular Gene Expression: An Integrated Genomic Analyses in Female Mice

Hyperlipidemia is a risk factor for dementia, and chronic consumption of a Western Diet (WD) is associated with cognitive impairment. However, the molecular mechanisms underlying the development of microvascular disease in the memory centers of the brain are poorly understood. This pilot study investigated the nutrigenomic pathways by which the WD regulates gene expression in hippocampal brain microvessels of female mice. Five-week-old female low-density lipoprotein receptor deficient (LDL-R−/−) and C57BL/6J wild type (WT) mice were fed a chow or WD for 8 weeks. Metabolics for lipids, glucose and insulin were determined. Differential gene expression, gene networks and pathways, transcription factors, and non-protein coding RNAs were evaluated by genome-wide microarray and bioinformatics analysis of laser captured hippocampal microvessels. The WD resulted in differential expression of 2,412 genes. The majority of differential gene expression was attributable to differential regulation of cell signaling proteins and their transcription factors, approximately 7% was attributable to differential expression of miRNAs, and a lesser proportion was due to other non-protein coding RNAs, primarily long non-coding RNAs (lncRNAs) and small nucleolar RNAs (snoRNAs) not previously described to be modified by the WD in females. Our findings revealed that chronic consumption of the WD resulted in integrated multilevel molecular regulation of the hippocampal microvasculature of female mice and may provide one of the mechanisms underlying vascular dementia.

Administration of N-Acyl-Phosphatidylethanolamine Expressing Bacteria to Low Density Lipoprotein Receptor-/- Mice Improves Indices of Cardiometabolic Disease

Obesity increases the risk for cardiometabolic diseases. N-acyl phosphatidylethanolamines (NAPEs) are precursors of N-acylethanolamides, which are endogenous lipid satiety factors. Incorporating engineered bacteria expressing NAPEs into the gut microbiota retards development of diet induced obesity in wild-type mice. Because NAPEs can also exert anti-inflammatory effects, we hypothesized that administering NAPE-expressing bacteria to low-density lipoprotein receptor (Ldlr)^-/- mice fed a Western diet would improve various indices of cardiometabolic disease manifested by these mice. NAPE-expressing E. coli Nissle 1917 (pNAPE-EcN), control Nissle 1917 (pEcN), or vehicle (veh) were given via drinking water to Ldlr^-/- mice for 12 weeks. Compared to pEcN or veh treatment, pNAPE-EcN significantly reduced body weight and adiposity, hepatic triglycerides, fatty acid synthesis genes, and increased expression of fatty acid oxidation genes. pNAPE-EcN also significantly reduced markers for hepatic inflammation and early signs of fibrotic development. Serum cholesterol was reduced with pNAPE-EcN, but atherosclerotic lesion size showed only a non-significant trend for reduction. However, pNAPE-EcN treatment reduced lesion necrosis by 69% indicating an effect on preventing macrophage inflammatory death. Our results suggest that incorporation of NAPE expressing bacteria into the gut microbiota can potentially serve as an adjuvant therapy to retard development of cardiometabolic disease.

Dual specificity phosphatase 6 deficiency is associated with impaired systemic glucose tolerance and reversible weight retardation in mice

Here, we aimed to investigate the potential role of DUSP6, a dual specificity phosphatase, that specifically inactivates extracellular signal-regulated kinase (ERK), for the regulation of body weight and glucose homeostasis. We further assessed whether metabolic challenges affect Dusp6 expression in selected brain areas or white adipose tissue. Hypothalamic Dusp6 mRNA levels remained unchanged in chow-fed lean vs. high fat diet (HFD) fed obese C57Bl/6J mice, and in C57Bl/6J mice undergoing prolonged fasting or refeeding with fat free diet (FFD) or HFD. Similarly, Dusp6 expression levels were unchanged in selected brain regions of Lep^ob mice treated with 1 mg/kg of leptin for 6 days, compared to pair-fed or saline-treated Lep^ob controls. Dusp6 expression levels remained unaltered in vitro in primary adipocytes undergoing differentiation, but were increased in eWAT of HFD-fed obese C57Bl/6J mice, compared to chow-fed lean controls. Global chow-fed DUSP6 KO mice displayed reduced body weight and lean mass and slightly increased fat mass at a young age, which is indicative for early-age weight retardation. Subsequent exposure to HFD led to a significant increase in lean mass and body weight in DUSP6 deficient mice, compared to WT controls. Nevertheless, after 26 weeks of high-fat diet exposure, we observed comparable body weight, fat and lean mass in DUSP6 WT and KO mice, suggesting overall normal susceptibility to develop obesity. In line with the increased weight gain to compensate for early-age weight retardation, HFD-fed DUSP6 KO displayed increased expression levels of anabolic genes involved in lipid and cholesterol metabolism in the epididymal white adipose tissue (eWAT), compared to WT controls. Glucose tolerance was perturbed in both chow-fed lean or HFD-fed obese DUSP6 KO, compared to their respective WT controls. Overall, our data indicate that DUSP6 deficiency has limited impact on the regulation of energy metabolism, but impairs systemic glucose tolerance. Our data are in conflict to earlier reports that propose protection from diet-induced obesity and glucose intolerance in DUSP6 deficient mice. Reasons for the discrepancies remain elusive, but may entail differential genetic backgrounds, environmental factors such as the type and source of HFD, or alterations in the gut microbiome between facilities.

Atherogenesis and metabolic dysregulation in LDL receptor-knockout rats

Mechanisms of atherogenesis have been studied extensively in genetically engineered mice with disturbed cholesterol metabolism such as those lacking either the LDL receptor (Ldlr) or apolipoprotein E (apoe). Few other animal models of atherosclerosis are available. WT rabbits or rats, even on high-fat or high-cholesterol diets, develop sparse atherosclerotic lesions. We examined the effects of Ldlr deletion on lipoprotein metabolism and atherosclerotic lesion formation in Sprague-Dawley rats. Deletion of Ldlr resulted in the loss of the LDLR protein and caused a significant increase in plasma total cholesterol and triglycerides. On normal chow, Ldlr-KO rats gained more weight and were more glucose intolerant than WT rats. Plasma proprotein convertase subtilisin kexin 9 (PCSK9) and leptin levels were higher and adiponectin levels were lower in KO than WT rats. On the Western diet, the KO rats displayed exaggerated obesity and age-dependent increases in glucose intolerance. No appreciable aortic lesions were observed in KO rats fed normal chow for 64 weeks or Western diet for 16 weeks; however, after 34-52 weeks of Western diet, the KO rats developed exuberant atherosclerotic lesions in the aortic arch and throughout the abdominal aorta. The Ldlr-KO rat may be a useful model for studying obesity, insulin resistance, and early-stage atherosclerosis.

A maternal high-fat, high-sucrose diet has sex-specific effects on fetal glucocorticoids with little consequence for offspring metabolism and voluntary locomotor activity in mice

Maternal overnutrition and obesity during pregnancy can have long-term effects on offspring physiology and behaviour. These developmental programming effects may be mediated by fetal exposure to glucocorticoids, which is regulated in part by placental 11β-hydroxysteroid dehydrogenase (11β-HSD) type 1 and 2. We tested whether a maternal high-fat, high-sucrose diet would alter expression of placental 11β-HSD1 and 2, thereby increasing fetal exposure to maternal glucocorticoids, with downstream effects on offspring physiology and behaviour. C57BL/6J mice were fed a high-fat, high-sucrose (HFHS) diet or a nutrient-matched low-fat, no-sucrose control diet prior to and during pregnancy and lactation. At day 17 of gestation, HFHS dams had ~20% lower circulating corticosterone levels than controls. Furthermore, there was a significant interaction between maternal diet and fetal sex for circulating corticosterone levels in the fetuses, whereby HFHS males tended to have higher corticosterone than control males, with no effect in female fetuses. However, placental 11β-HSD1 or 11β-HSD2 expression did not differ between diets or show an interaction between diet and sex. To assess potential long-term consequences of this sex-specific effect on fetal corticosterone, we studied locomotor activity and metabolic traits in adult offspring. Despite a sex-specific effect of maternal diet on fetal glucocorticoids, there was little evidence of sex-specific effects on offspring physiology or behaviour, although HFHS offspring of both sexes had higher circulating corticosterone at 9 weeks of age. Our results suggest the existence of as yet unknown mechanisms that mitigate the effects of altered glucocorticoid exposure early in development, making offspring resilient to the potentially negative effects of a HFHS maternal diet.

Prolonged Intake of Dietary Lipids Alters Membrane Structure and T Cell Responses in LDLr-/- Mice

Although it is recognized that lipids and membrane organization in T cells affect signaling and T cell activation, to what extent dietary lipids alter T cell responsiveness in the absence of obesity and inflammation is not known. In this study, we fed low-density lipoprotein receptor knockout mice a Western high-fat diet for 1 or 9 wk and examined T cell responses in vivo along with T cell lipid composition, membrane order, and activation ex vivo. Our data showed that high levels of circulating lipids for a prolonged period elevated CD4(+) and CD8(+) T cell proliferation and resulted in an increased proportion of CD4(+) central-memory T cells within the draining lymph nodes following induction of contact hypersensitivity. In addition, the 9-wk Western high-fat diet elevated the total phospholipid content and monounsaturated fatty acid level, but decreased saturated phosphatidylcholine and sphingomyelin within the T cells. The altered lipid composition in the circulation, and of T cells, was also reflected by enhanced membrane order at the activation site of ex vivo activated T cells that corresponded to increased IL-2 mRNA levels. In conclusion, dietary lipids can modulate T cell lipid composition and responses in lipoprotein receptor knockout mice even in the absence of excess weight gain and a proinflammatory environment.

Early development of calcific aortic valve disease and left ventricular hypertrophy in a mouse model of combined dyslipidemia and type 2 diabetes mellitus

OBJECTIVE

This study aimed to determine the potential impact of type 2 diabetes mellitus on left ventricular dysfunction and the development of calcified aortic valve disease using a dyslipidemic mouse model prone to developing type 2 diabetes mellitus.

APPROACH AND RESULTS

When compared with nondiabetic LDLr(-/-)/ApoB(100/100), diabetic LDLr(-/-)/ApoB(100/100)/IGF-II mice exhibited similar dyslipidemia and obesity but developed type 2 diabetes mellitus when fed a high-fat/sucrose/cholesterol diet for 6 months. LDLr(-/-)/ApoB(100/100)/IGF-II mice showed left ventricular hypertrophy versus C57BL6 but not LDLr(-/-)/ApoB(100/100) mice. Transthoracic echocardiography revealed significant reductions in both left ventricular systolic fractional shortening and diastolic function in high-fat/sucrose/cholesterol fed LDLr(-/-)/ApoB(100/100)/IGF-II mice when compared with LDLr(-/-)/ApoB(100/100). Importantly, we found that peak aortic jet velocity was significantly increased in LDLr(-/-)/ApoB(100/100)/IGF-II mice versus LDLr(-/-)/ApoB(100/100) animals on the high-fat/sucrose/cholesterol diet. Microtomography scans and Alizarin red staining indicated calcification in the aortic valves, whereas electron microscopy and energy dispersive x-ray spectroscopy further revealed mineralization of the aortic leaflets and the presence of inflammatory infiltrates in diabetic mice. Studies showed upregulation of hypertrophic genes (anp, bnp, b-mhc) in myocardial tissues and of osteogenic genes (spp1, bglap, runx2) in aortic tissues of diabetic mice.

CONCLUSIONS

We have established the diabetes mellitus -prone LDLr(-/-)/ApoB(100/100)/IGF-II mouse as a new model of calcified aortic valve disease. Our results are consistent with the growing body of clinical evidence that the dysmetabolic state of type 2 diabetes mellitus contributes to early mineralization of the aortic valve and calcified aortic valve disease pathogenesis.

Distinct metabolic and vascular effects of dietary triglycerides and cholesterol in atherosclerotic and diabetic mouse models

Cholesterol and triglyceride-rich Western diets are typically associated with an increased occurrence of type 2 diabetes and vascular diseases. This study aimed to assess the relative impact of dietary cholesterol and triglycerides on glucose tolerance, insulin sensitivity, atherosclerotic plaque formation, and endothelial function. C57BL6 wild-type (C57) mice were compared with atherosclerotic LDLr(-/-) ApoB(100/100) (LRKOB100) and atherosclerotic/diabetic IGF-II × LDLr(-/-) ApoB(100/100) (LRKOB100/IGF) mice. Each group was fed either a standard chow diet, a 0.2% cholesterol diet, a high-fat diet (HFD), or a high-fat 0.2% cholesterol diet for 6 mo. The triglyceride-rich HFD increased body weight, glucose intolerance, and insulin resistance but did not alter endothelial function or atherosclerotic plaque formation. Dietary cholesterol, however, increased plaque formation in LRKOB100 and LRKOB100/IGF animals and decreased endothelial function regardless of genotype. However, cholesterol was not associated with an increase of insulin resistance in LRKOB100 and LRKOB100/IGF mice and, unexpectedly, was even found to reduce the insulin-resistant effect of dietary triglycerides in these animals. Our data indicate that dietary triglycerides and cholesterol have distinct metabolic and vascular effects in obese atherogenic mouse models resulting in dissociation between the impairment of glucose homeostasis and the development of atherosclerosis.

Gastrointestinal weight-loss surgery: glimpses at the molecular level

Pharmacotherapy for obesity remains a key challenge, and gastrointestinal weight-loss surgery remains a preferred option to help reduce excess body weight along with resolution of several comorbidities associated with obesity. This offers a unique opportunity to study the underlying mechanisms of gastro-intestinal weight-loss surgery to develop effective and less invasive long-term therapeutic interventions potentially mimicking the benefits of gastrointestinal weight-loss surgery. Here, we present an integrative analysis of currently available human transcriptomics data sets pre- and post-surgery and propose a computational biology strategy for selecting putative drug targets. We anticipate that approaches similar to the one that we outline here, would help elucidate underlying mechanisms that result in metabolic improvements and provide guidance on pharmaceutical targets to develop effective and less invasive therapies for obesity and related comorbidities.

The LDLR deficient mouse as a model for aortic calcification and quantification by micro-computed tomography

OBJECTIVE

Patients with familial hypercholesterolemia (FH) due mutations in the low-density lipoprotein receptor (LDLR) suffer premature aortic calcification, an effect that is age- and gene dosage-dependent and cholesterol level independent later in life. To better understand this process, we examined a murine model.

METHODS

We compared chow fed Ldlr(-/-) mice to controls at 6, 12 and 18 months and on a Western diet (WD) at 6 months. Additionally, we compared controls to Ldlr(-/-) mice and transgenic mice Tg(Pcsk9) overexpressing PCSK9, which promotes LDLR degradation. Aortas were perfused-fixed, embedded in paraffin, and sections were stained with alizarin red. Micro-computerized tomography (micro-CT) was used to quantify vascular calcification.

RESULTS

Ldlr(-/-) mice develop calcification in the ascending, transverse aorta and neck vessels with a distribution similar to that of human. Calcification was most prominent in 18-month-old Ldlr(-/-) mice fed a chow diet and in 6-month-old Ldlr(-/-) mice fed a WD. Interestingly, Tg(Pcsk9) mice fed a WD develop aortic calcifications as well. Histology confirmed that the calcification were predominantly sub-intimal. Marked expression of LRP5 and WNT was observed in the Ldlr(-/-) and Tg(Pcsk9) models, but not in age-matched controls.

CONCLUSIONS

The two mouse models develop aortic calcification in an age- and diet-dependent manner. Abnormal regulation of the LRP5/Wnt pathway may play a role in the calcification process. Further analysis of these aortic calcification models using this micro-CT imaging technique may provide a better understanding of the link between FH and arterial calcification.

Lipid and hematological parameters in hyperleptinemic healthy Arab male youth in Jordan

To analyze the influence ofhyperleptinemia on fasting lipid and hematological parameters in healthy Arab male youth in Jordan, this cross-sectional study was carried out in April 2009 on a sample of 120 students aged 18-24 years. Subjects were stratified by fasting leptin into two groups (control, <12.7 ng mL(-1) vs. hyperleptenimic, e_< 12.7 ng mL(-1)) and BMI (normal weight, < 25 kgm(-2) vs. overweight/obese, BMI e_< 25 kg m(-2)). Fasting serum leptin, blood glucose, lipid profile and hematological parameters values were determined by standard kit methods. Mean serum leptin concentrations were more than five times as high in hyperleptenemic subjects than in control subjects (p < 0.001). Compared with control group, significant elevations (p < 0.01) were observed in the means total cholesterol, LDL cholesterol and triglyceride levels of hyperleptenemic group whereas no significant differences was detected in HDL-cholesterol. Except the changes of WBC count, MCH and slightly MCHC, there were no differences between both groups in any other term of hematological parameters. In conclusion, changes in lipid variables and some hematological parameters may increase plasma viscosity as a step during atherosclerosis pathogenesis in male youth at risk for dyslipidemia and cardiovascular diseases. Thus, hyperleptinemia could be a useful index in identifying healthy youth male subjects but this hypothesis needs further investigation.