FXR agonists are used to treat non-alcoholic fatty liver disease (NAFLD), in part because they reduce hepatic lipids. Here, we show that FXR activation with the FXR agonist GSK2324 controls hepatic ...lipids via reduced absorption and selective decreases in fatty acid synthesis. Using comprehensive lipidomic analyses, we show that FXR activation in mice or humans specifically reduces hepatic levels of mono- and polyunsaturated fatty acids (MUFA and PUFA). Decreases in MUFA are due to FXR-dependent repression of Scd1, Dgat2, and Lpin1 expression, which is independent of SHP and SREBP1c. FXR-dependent decreases in PUFAs are mediated by decreases in lipid absorption. Replenishing bile acids in the diet prevented decreased lipid absorption in GSK2324-treated mice, suggesting that FXR reduces absorption via decreased bile acids. We used tissue-specific FXR KO mice to show that hepatic FXR controls lipogenic genes, whereas intestinal FXR controls lipid absorption. Together, our studies establish two distinct pathways by which FXR regulates hepatic lipids.
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•Non-steroidal agonists of FXR significantly decrease intestinal lipid absorption•FXR decreases hepatic triglycerides independently of SHP and SREBP1C•FXR activation reduces expression of three key lipogenic genes, Scd1, Lpin1, and Dgat2•Intestinal and hepatic FXR are both required to decrease hepatic triglycerides
The nuclear receptor FXR lowers hepatic triglycerides to protect against the onset of NAFLD. Clifford et al. demonstrate that activation of FXR decreases hepatic triglycerides through two distinct mechanisms. First, via bile-acid-dependent decreases in intestinal lipid absorption and second, through selective changes in lipogenesis.
Dysregulation of lipid homeostasis is a precipitating event in the pathogenesis and progression of hepatosteatosis and metabolic syndrome. These conditions are highly prevalent in developed societies ...and currently have limited options for diagnostic and therapeutic intervention. Here, using a proteomic and lipidomic-wide systems genetic approach, we interrogated lipid regulatory networks in 107 genetically distinct mouse strains to reveal key insights into the control and network structure of mammalian lipid metabolism. These include the identification of plasma lipid signatures that predict pathological lipid abundance in the liver of mice and humans, defining subcellular localization and functionality of lipid-related proteins, and revealing functional protein and genetic variants that are predicted to modulate lipid abundance. Trans-omic analyses using these datasets facilitated the identification and validation of PSMD9 as a previously unknown lipid regulatory protein. Collectively, our study serves as a rich resource for probing mammalian lipid metabolism and provides opportunities for the discovery of therapeutic agents and biomarkers in the setting of hepatic lipotoxicity.
Objective The purpose of this study was to characterize the urinary microbiota in women who are planning treatment for urgency urinary incontinence and to describe clinical associations with urinary ...symptoms, urinary tract infection, and treatment outcomes. Study Design Catheterized urine samples were collected from multisite randomized trial participants who had no clinical evidence of urinary tract infection; 16S ribosomal RNA gene sequencing was used to dichotomize participants as either DNA sequence-positive or sequence-negative. Associations with demographics, urinary symptoms, urinary tract infection risk, and treatment outcomes were determined. In sequence-positive samples, microbiotas were characterized on the basis of their dominant microorganisms. Results More than one-half (51.1%; 93/182) of the participants’ urine samples were sequence-positive. Sequence-positive participants were younger (55.8 vs 61.3 years old; P = .0007), had a higher body mass index (33.7 vs 30.1 kg/m2 ; P = .0009), had a higher mean baseline daily urgency urinary incontinence episodes (5.7 vs 4.2 episodes; P < .0001), responded better to treatment (decrease in urgency urinary incontinence episodes, –4.4 vs –3.3; P = .0013), and were less likely to experience urinary tract infection (9% vs 27%; P = .0011). In sequence-positive samples, 8 major bacterial clusters were identified; 7 clusters were dominated not only by a single genus, most commonly Lactobacillus (45%) or Gardnerella (17%), but also by other taxa (25%). The remaining cluster had no dominant genus (13%). Conclusion DNA sequencing confirmed urinary bacterial DNA in many women with urgency urinary incontinence who had no signs of infection. Sequence status was associated with baseline urgency urinary incontinence episodes, treatment response, and posttreatment urinary tract infection risk.
The effective storage of lipids in white adipose tissue (WAT) critically impacts whole body energy homeostasis. Many genes have been implicated in WAT lipid metabolism, including tripartite motif ...containing 28 (Trim28), a gene proposed to primarily influence adiposity via epigenetic mechanisms in embryonic development. However, in the current study we demonstrate that mice with deletion of Trim28 specifically in committed adipocytes, also develop obesity similar to global Trim28 deletion models, highlighting a post-developmental role for Trim28. These effects were exacerbated in female mice, contributing to the growing notion that Trim28 is a sex-specific regulator of obesity. Mechanistically, this phenotype involves alterations in lipolysis and triglyceride metabolism, explained in part by loss of Klf14 expression, a gene previously demonstrated to modulate adipocyte size and body composition in a sex-specific manner. Thus, these findings provide evidence that Trim28 is a bona fide, sex specific regulator of post-developmental adiposity and WAT function.
Both as a component of metabolic syndrome and as an independent entity, hypertension poses a continued challenge with regard to its diagnosis, pathogenesis, and treatment. Previous studies have ...documented connections between hypertension and indicators of lipid metabolism. Novel technologies, such as plasma lipidomic profiling, promise a better understanding of disorders in which there is a derangement of the lipid metabolism. However, association of plasma lipidomic profiles with hypertension in a high-risk population, such as Mexican Americans, has not been evaluated before. Using the rich data and sample resource from the ongoing San Antonio Family Heart Study, we conducted plasma lipidomic profiling by combining high-performance liquid chromatography with tandem mass spectroscopy to characterize 319 lipid species in 1192 individuals from 42 large and extended Mexican American families. Robust statistical analyses using polygenic regression models, liability threshold models, and bivariate trait analyses implemented in the SOLAR software were conducted after accounting for obesity, insulin resistance, and relative abundance of various lipoprotein fractions. Diacylglycerols, in general, and the DG 16:0/22:5 and DG 16:0/22:6 lipid species, in particular, were significantly associated with systolic blood pressure (SBP), diastolic blood pressure (DBP), and mean arterial pressure (MAP), as well as liability of incident hypertension measured during 7140.17 person-years of follow-up. Four lipid species, including the DG 16:0/22:5 and DG 16:0/22:6 species, showed significant genetic correlations with the liability of hypertension in bivariate trait analyses. Our results demonstrate the value of plasma lipidomic profiling in the context of hypertension and identify disturbance of diacylglycerol metabolism as an independent biomarker of hypertension.
Objective
Waist circumference (WC), the clinical marker of central obesity, is gaining popularity as a screening tool for type 2 diabetes (T2D). While there is epidemiologic evidence favoring the ...WC‐T2D association, its biological substantiation is generally weak. Our objective was to determine the independent association of plasma lipid repertoire with WC.
Methods
Samples and data from the San Antonio Family Heart Study of 1208 Mexican Americans from 42 extended families were used. Association of plasma lipidomic profiles with the cross‐sectionally assessed WC was determined. Plasma lipidomic profiling entailed liquid chromatography with mass spectrometry. Statistical analyses included multivariable polygenic regression models and bivariate trait analyses using the SOLAR software.
Results
After adjusting for age and sex interactions, body mass index, homeostasis model of assessment—insulin resistance, total cholesterol, triglycerides, high density lipoproteins and use of lipid lowering drugs, dihydroceramides as a class were associated with WC. Dihydroceramide species 18:0, 20:0, 22:0, and 24:1 were significantly associated and genetically correlated with WC. Two sphingomyelin species (31:1 and 41:1) were also associated with WC.
Conclusions
Plasma dihydroceramide levels independently associate with WC. Thus, high resolution plasma lipidomic studies can provide further credence to the biological underpinnings of the association of WC with T2D.
Plasma lipidome is now increasingly recognized as a potentially important marker of chronic diseases, but the exact extent of its contribution to the interindividual phenotypic variability in family ...studies is unknown. Here, we used the rich data from the ongoing San Antonio Family Heart Study (SAFHS) and developed a novel statistical approach to quantify the independent and additive value of the plasma lipidome in explaining metabolic syndrome (MS) variability in Mexican American families recruited in the SAFHS. Our analytical approach included two preprocessing steps: principal components analysis of the high-resolution plasma lipidomics data and construction of a subject-subject lipidomic similarity matrix. We then used the Sequential Oligogenic Linkage Analysis Routines software to model the complex family relationships, lipidomic similarities, and other important covariates in a variance components framework. Our results suggested that even after accounting for the shared genetic influences, indicators of lipemic status (total serum cholesterol, TGs, and HDL cholesterol), and obesity, the plasma lipidome independently explained 22% of variability in the homeostatic model of assessment-insulin resistance trait and 16% to 22% variability in glucose, insulin, and waist circumference. Our results demonstrate that plasma lipidomic studies can additively contribute to an understanding of the interindividual variability in MS.
Detection of type 2 diabetes (T2D) is routinely based on the presence of dysglycemia. Although disturbed lipid metabolism is a hallmark of T2D, the potential of plasma lipidomics as a biomarker of ...future T2D is unknown. Our objective was to develop and validate a plasma lipidomic risk score (LRS) as a biomarker of future type 2 diabetes and to evaluate its cost-effectiveness for T2D screening.
Plasma LRS, based on significantly associated lipid species from an array of 319 lipid species, was developed in a cohort of initially T2D-free individuals from the San Antonio Family Heart Study (SAFHS). The LRS derived from SAFHS as well as its recalibrated version were validated in an independent cohort from Australia--the AusDiab cohort. The participants were T2D-free at baseline and followed for 9197 person-years in the SAFHS cohort (n = 771) and 5930 person-years in the AusDiab cohort (n = 644). Statistically and clinically improved T2D prediction was evaluated with established statistical parameters in both cohorts. Modeling studies were conducted to determine whether the use of LRS would be cost-effective for T2D screening. The main outcome measures included accuracy and incremental value of the LRS over routinely used clinical predictors of T2D risk; validation of these results in an independent cohort and cost-effectiveness of including LRS in screening/intervention programs for T2D.
The LRS was based on plasma concentration of dihydroceramide 18:0, lysoalkylphosphatidylcholine 22:1 and triacyglycerol 16:0/18:0/18:1. The score predicted future T2D independently of prediabetes with an accuracy of 76%. Even in the subset of initially euglycemic individuals, the LRS improved T2D prediction. In the AusDiab cohort, the LRS continued to predict T2D significantly and independently. When combined with risk-stratification methods currently used in clinical practice, the LRS significantly improved the model fit (p < 0.001), information content (p < 0.001), discrimination (p < 0.001) and reclassification (p < 0.001) in both cohorts. Modeling studies demonstrated that LRS-based risk-stratification combined with metformin supplementation for high-risk individuals was the most cost-effective strategy for T2D prevention.
Considering the novelty, incremental value and cost-effectiveness of LRS it should be used for risk-stratification of future T2D.
Cardiovascular disease (CVD) is the most common cause of death in the United States and is associated with a high economic burden. Prevention of CVD focuses on controlling or improving the lipid ...profile of patients at risk. The human lipidome is made up of thousands of ubiquitous lipid species. By studying biologically simple canonical lipid species, we investigated whether the lipidome is genetically redundant and whether its genetic influences can provide clinically relevant clues of CVD risk.
We performed a genetic study of the human lipidome in 1212 individuals from 42 extended Mexican American families. High-throughput mass spectrometry enabled rapid capture of precise lipidomic profiles, providing 319 unique species. Using variance component-based heritability analyses and bivariate trait analyses, we detected significant genetic influences on each lipid assayed. Median heritability of the plasma lipid species was 0.37. Hierarchical clustering based on complex genetic correlation patterns identified 12 genetic clusters that characterized the plasma lipidome. These genetic clusters were differentially but consistently associated with risk factors of CVD, including central obesity, obesity, type 2 diabetes mellitus, raised serum triglycerides, and metabolic syndrome. Also, these clusters consistently predicted occurrence of cardiovascular deaths during follow-up.
The human plasma lipidome is heritable. Shared genetic influences reduce the dimensionality of the human lipidome into clusters that are associated with risk factors of CVD.
In a previous simulation study, we demonstrated the feasibility of using coded apertures together with pixelated detectors tors for small animal SPECT. In this paper; we further explore the potential ...of this approach with a prototype detector and simulated multipinhole apertures. We also investigated the effect of multiplexing due to overlapped projections on convergence properties, image signal-to-noise ratio (SNR) and spatial resolution. The detector comprises a 48/spl times/44 array of NaI(Tl) crystals, each 1 mm/spl times/1 mm/spl times/5 mm on a 1.25-mm pitch. The crystal array is directly coupled to a Hamamatsu R3941 8 cm position sensitive photomultiplier tube. Multipinhole apertures were simulated by performing repeated SPECT acquisitions of the same object with a single tungsten pinhole translated to different positions in the aperture plane. Image reconstruction is based on a three-dimensional ray driven projector which is an extension of a method described for single pinhole SPECT with a displaced center of rotation. Image estimates are updated using the maximum likelihood expectation maximization (ML-EM) algorithm. The effect of multiplexing was to slow convergence and reduce the achievable SNR by approximately 15% compared with nonmultiplexed data (but the result may be achieved in a fraction of the time). The reconstructed resolution obtained with a resolution phantom was 1.5-mm full width at half maximum and there was no appreciable difference between the resolution of multiplexed and nonmultiplexed data. These results encourage us to develop a prototype coded aperture system for high sensitivity, high resolution small animal SPECT.
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