Acyl-CoA thioesterase 1 (ACOT1) catalyzes the hydrolysis of long-chain acyl-CoAs to free fatty acids and coenzyme A and is typically upregulated in obesity. Whether targeting ACOT1 in the setting of high-fat diet induced obesity would be metabolically beneficial is not known. Here we report that male and female ACOT1KO mice are partially protected from high-fat diet induced obesity, an effect associated with increased energy expenditure without alterations in physical activity or food intake. In males, ACOT1 deficiency increased mitochondrial uncoupling protein-2 (UCP2) protein abundance, while reducing 4-hydroxynonenal (4-HNE), a marker of oxidative stress, in white adipose tissue and liver of high-fat fed mice. Moreover, concurrent knockdown of UCP2 with ACOT1 in hepatocytes prevented increases in oxygen consumption observed with ACOT1 knockdown during high lipid loading, suggesting that UCP2-induced uncoupling may increase energy expenditure to attenuate weight gain. Together, these data indicate that targeting ACOT1 may be effective for obesity prevention during caloric excess by increasing energy expenditure.
Timothy D. Heden, Mallory P. Franklin, Christina Dailey, Mara T. Mashek, Chen Chen, Douglas G. Mashek
Metabolic mechanisms underlying the heterogeneity of major adverse cardiovascular events (MACE) risk in individuals with type 2 diabetes mellitus (T2D) remain unclear. We hypothesized that circulating metabolites reflecting mitochondrial dysfunction predict incident MACE in T2D. Targeted mass-spectrometry profiling of 60 metabolites was performed on baseline plasma from TECOS (discovery) and EXSCEL (validation) trial biomarker substudy cohorts. A principal components analysis metabolite factor comprised of medium-chain acylcarnitines was associated with MACE in TECOS and validated in EXSCEL, with higher levels associated with higher MACE risk. Meta-analysis showed that long-chain acylcarnitines and dicarboxylacylcarnitines were also associated with MACE. Metabolites remained associated with MACE in multivariate models and favorably changed with exenatide therapy. A third cohort (CATHGEN) with T2D assessed whether these metabolites improved discriminative capability multivariate for MACE; nine metabolites (medium- and long-chain acylcarnitines and one dicarboxylacylcarnitine) were associated with time-to-MACE in CATHGEN. Addition of these metabolites to clinical models minimally improved the discriminative capability for MACE but did significantly down reclassify risk. Thus, metabolites reporting on dysregulated mitochondrial fatty acid oxidation are higher in individuals with T2D who experience subsequent MACE. These biomarkers may improve CV risk prediction models, be therapy responsive, and highlight emerging risk mechanisms.
Jessica A. Regan, Robert J. Mentz, Maggie Nguyen, Jennifer B. Green, Lauren K. Truby, Olga Ilkayeva, Christopher Newgard, John B. Buse, Harald Sourij, C. David Sjöström, Naveed Sattar, Robert W. McGarrah, Yinggan Zheng, Darren K. McGuire, Eberhard Standl, Paul Armstrong, Eric Peterson, Adrian Hernandez, Rury R. Holman, Svati H. Shah
Dyslipidemia in obesity results from excessive production and impaired clearance of triglyceride (TG)-rich lipoproteins, which is particularly pronounced in the postprandial state. Here, we investigated the impact of Roux-en-Y gastric bypass (RYGB) surgery on the postprandial VLDL1 and VLDL2 apoB and TG kinetics and their relationship with insulin responsiveness indices. 24 obese non-diabetic RYGB surgery patients underwent a lipoprotein kinetics study during a mixed meal test and a hyperinsulinemic-euglycemic clamp study before the surgery, and one year later. A physiologically based computational model was developed to investigate the impact of RYGB surgery and plasma insulin on postprandial VLDL kinetics. After the surgery, VLDL1 apoB and TG production rates were significantly decreased, whereas VLDL2 apoB and TG production rates remained unchanged. TG catabolic rate was increased in both VLDL1 and VLDL2 fractions, but only the VLDL2 apoB catabolic rate tended to increase. Furthermore, post-surgery VLDL1 apoB and TG production rates, but not VLDL2, were positively correlated with insulin resistance. Insulin-mediated stimulation of peripheral lipoprotein lipolysis was also improved after the surgery. In summary, RYGB resulted in a reduced hepatic VLDL1 production that correlated with reduced insulin resistance, an elevated VLDL2 clearance, and improved insulin sensitivity in lipoprotein lipolysis pathways.
Vehpi Yildirim, Kasper W. ter Horst, Pim W. Gilijamse, Dewi van Harskamp, Henk Schierbeek, Hans Jansen, Alinda W.M. Schimmel, Max Nieuwdorp, Albert K. Groen, Mireille J. Serlie, Natal A.W. van Riel, Geesje M. Dallinga-Thie
Proline and its synthesis enzyme pyrroline-5-carboxylate reductase 1 (PYCR1) are implicated in epithelial-mesenchymal transition (EMT), yet how proline and PYCR1 function in allergic asthmatic airway remodeling via EMT has not yet been addressed. In the present study, increased levels of plasma proline and PYCR1 were observed in asthmatic patients. Similarly, proline and PYCR1 in lung tissues were higher in a murine allergic asthma model induced by house dust mites (HDMs). Pycr1 knockout (KO) decreased proline in lung tissues, with reduced airway remodeling and EMT. Mechanistically, loss of Pycr1 restrained HDM-induced EMT by modulating mitochondrial fission, metabolic reprogramming, and the AKT/mTOR1 and WNT3a/β–catenin signaling pathways in airway epithelial cells. Therapeutic inhibition of PYCR1 in wild-type mice disrupted HDM-induced airway inflammation and remodeling. Deprivation of exogeneous proline partially relieved HDM-induced airway remodeling to some extent. Collectively, this study illuminates that proline and PYCR1 involved with airway remodeling in allergic asthma could be viable targets for asthma treatment.
Tingting Xu, Zhenzhen Wu, Qi Yuan, Xijie Zhang, Yanan Liu, Chaojie Wu, Meijuan Song, Jingjing Wu, Jingxian Jiang, Zhengxia Wang, Zhongqi Chen, Mingshun Zhang, Mao Huang, Ningfei Ji
BACKGROUND Weight-loss diets often target dietary fat or carbohydrates, macronutrients that are sensed via distinct gut-brain pathways and differentially affect peripheral hormones and metabolism. However, the effects of such diet changes on the human brain are unclear. METHODS We investigated whether selective isocaloric reductions in dietary fat or carbohydrates altered dopamine D2/3 receptor binding potential (D2BP) and neural activity in brain-reward regions in response to visual food cues in 17 inpatient adults with obesity as compared with a eucaloric baseline diet using a randomized crossover design. RESULTS On the fifth day of dietary fat restriction, but not carbohydrate restriction, both D2BP and neural activity to food cues were decreased in brain-reward regions. After the reduced-fat diet, ad libitum intake shifted toward foods high in both fat and carbohydrates. CONCLUSION These results suggest that dietary fat restriction increases tonic dopamine in brain-reward regions and affects food choice in ways that may hamper diet adherence. TRIAL REGISTRATION ClinicalTrials.gov NCT00846040 FUNDING. NIDDK 1ZIADK013037.
Valerie L. Darcey, Juen Guo, Amber B. Courville, Isabelle Gallagher, Jason A. Avery, W. Kyle Simmons, John E. Ingeholm, Peter Herscovitch, Alex Martin, Kevin D. Hall
The mineralocorticoid aldosterone, secreted by the adrenal zona glomerulosa (ZG), is critical for life, maintaining ion homeostasis and blood pressure. Therapeutic inhibition of protein phosphatase 3 (Calcineurin (Cn)) results in inappropriately low plasma aldosterone levels despite concomitant hyperkalemia and hyperreninemia. We tested the hypothesis that Cn participates in the signal transduction pathway regulating aldosterone synthesis. Inhibition of Cn with tacrolimus abolished the potassium (K+)-stimulated expression of aldosterone synthase, encoded by CYP11B2, in the NCI-H295R human adrenocortical cell line as well as ex vivo in mouse and human adrenal tissue. ZG-specific deletion of the regulatory Cn subunit CnB1 diminished Cyp11b2 expression in vivo and disrupted K+-mediated aldosterone synthesis. Phosphoproteomic analysis identified Nuclear factor of activated T-cells, cytoplasmic 4 (NFATc4) as a target for Cn-mediated dephosphorylation. Deletion of NFATc4 impaired K+-dependent stimulation of CYP11B2 expression and aldosterone production while expression of a constitutively active form of NFATc4 increased expression of CYP11B2 in NCI-H295R cells. Chromatin immunoprecipitation revealed NFATc4 directly regulates CYP11B2 expression. Thus, calcineurin controls aldosterone production via the Cn-NFATc4 pathway. Inhibition of Cn-NFATc4 signaling may explain low plasma aldosterone levels and hyperkalemia in patients treated with tacrolimus and the Cn-NFATc4 pathway may provide novel molecular targets to treat primary aldosteronism.
Mesut Berber, Sining Leng, Agnieszka Wengi, Denise V. Winter, Alex Odermatt, Felix Beuschlein, Johannes Loffing, David T. Breault, David Penton
Insulin secretion from pancreatic β cells is essential to the maintenance of glucose homeostasis. Defects in this process result in diabetes. Identifying genetic regulators that impair insulin secretion is crucial for the identification of novel therapeutic targets. Here, we show that reduction of ZNF148 in human islets, and its deletion in stem cell–derived β cells (SC–β cells), enhances insulin secretion. Transcriptomics of ZNF148-deficient SC–β cells identifies increased expression of annexin and S100 genes whose proteins form tetrameric complexes involved in regulation of insulin vesicle trafficking and exocytosis. ZNF148 in SC–β cells prevents translocation of annexin A2 from the nucleus to its functional place at the cell membrane via direct repression of S100A16 expression. These findings point to ZNF148 as a regulator of annexin-S100 complexes in human β cells and suggest that suppression of ZNF148 may provide a novel therapeutic strategy to enhance insulin secretion.
Eleonora de Klerk, Yini Xiao, Christopher H. Emfinger, Mark P. Keller, David I. Berrios, Valentina Loconte, Axel A. Ekman, Kate L. White, Rebecca L. Cardone, Richard G. Kibbey, Alan D. Attie, Matthias Hebrok
Fatty acid binding protein 4 (FABP4) is a lipid chaperone secreted from adipocytes upon stimulation of lipolysis. Circulating FABP4 levels strongly correlate with obesity and metabolic pathologies in experimental models and humans. While adipocytes have been presumed to be the major source of hormonal FABP4, this question has not been addressed definitively in vivo. We generated mice with Fabp4 deletion in cells known to express the gene; adipocytes (Adipo-KO), endothelial cells (Endo-KO), myeloid cells (Myeloid-KO), and the whole body (Total-KO) to examine the contribution of these cell types to basal and stimulated plasma FABP4 levels. Unexpectedly, baseline plasma FABP4 was not significantly reduced in Adipo-KO mice, whereas Endo-KO mice showed ~87% reduction versus wildtype controls. In contrast, Adipo-KO mice exhibited ~62% decreased induction of FABP4 responses to lipolysis, while Endo-KO mice showed only mildly decreased induction, indicating that adipocytes are the main source of increases in FABP4 during lipolysis. We did not detect any myeloid contribution to circulating FABP4. Surprisingly, despite the nearly intact induction of FABP4, Endo-KO mice showed blunted lipolysis-induced insulin secretion, identical to Total-KO mice. We conclude that the endothelium is the major source of baseline hormonal FABP4 and is required for the insulin response to lipolysis.
Karen E. Inouye, Kacey J. Prentice, Alexandra Lee, Zeqiu B. Wang, Carla Dominguez-Gonzalez, Mu Xian Chen, Jillian K. Riveros, M. Furkan Burak, Grace Y. Lee, Gokhan S. Hotamisligil
Central glucose-dependent insulinotropic polypeptide (GIP) receptor (GIPR) signaling is critical in GIP-based therapeutics’ ability to lower body weight, but pathways leveraged by GIPR pharmacology in the brain remain incompletely understood. We explored the role of Gipr neurons in the hypothalamus and dorsal vagal complex (DVC) — brain regions critical to the control of energy balance. Hypothalamic Gipr expression was not necessary for the synergistic effect of GIPR/GLP-1R coagonism on body weight. While chemogenetic stimulation of both hypothalamic and DVC Gipr neurons suppressed food intake, activation of DVC Gipr neurons reduced ambulatory activity and induced conditioned taste avoidance, while there was no effect of a short-acting GIPR agonist (GIPRA). Within the DVC, Gipr neurons of the nucleus tractus solitarius (NTS), but not the area postrema (AP), projected to distal brain regions and were transcriptomically distinct. Peripherally dosed fluorescent GIPRAs revealed that access was restricted to circumventricular organs in the CNS. These data demonstrate that Gipr neurons in the hypothalamus, AP, and NTS differ in their connectivity, transcriptomic profile, peripheral accessibility, and appetite-controlling mechanisms. These results highlight the heterogeneity of the central GIPR signaling axis and suggest that studies into the effects of GIP pharmacology on feeding behavior should consider the interplay of multiple regulatory pathways.
Alice Adriaenssens, Johannes Broichhagen, Anne de Bray, Julia Ast, Annie Hasib, Ben Jones, Alejandra Tomas, Natalie Figueredo Burgos, Orla Woodward, Jo Lewis, Elisabeth O’Flaherty, Kimberley El, Canqi Cui, Norio Harada, Nobuya Inagaki, Jonathan Campbell, Daniel Brierley, David J. Hodson, Ricardo Samms, Fiona Gribble, Frank Reimann
BACKGROUND/AIMS. The effects of diet-induced weight loss (WL) and WL after Roux-en-Y gastric bypass (RYGB) surgery on β-cell function are unclear because of conflicting results from different studies, presumably because of differences in the methods used to measure β-cell function, the amount of WL between treatment groups, and baseline β-cell function. The goal of this study was to evaluate the effect of WL after RYGB surgery or reduced energy intake alone on β-cell function in people with obesity with and without type 2 diabetes. METHODS. β-cell function (insulin secretion in relationship to plasma glucose) was assessed before and after glucose or mixed-meal ingestion before and after: i) progressive amounts (6%, 11%, 16%) of WL induced by a low-calorie diet (LCD) in people with obesity without diabetes, ii) ~20% WL after RYGB surgery or laparoscopic adjustable gastric banding (LAGB) in people with obesity without diabetes, and iii) ~20% WL after RYGB surgery or LCD alone in people with obesity and diabetes. RESULTS. Diet-induced progressive WL in people without diabetes progressively decreased β-cell function. Marked WL after LAGB or RYGB in people without diabetes did not alter β-cell function. Marked WL after LCD or RYGB in people with diabetes markedly increased β-cell function, without a difference between the two groups. CONCLUSION. Marked WL increases β-cell function in people with obesity and diabetes but not in people with obesity without diabetes. The effect of RYGB-induced WL on β-cell function is not different from the effect of matched WL after LAGB or LCD alone. CLINICAL TRIAL REGISTRATION NUMBERS. NCT00981500, NCT02207777, NCT01299519 FUNDING. This study was supported by NIH grants R01 DK037948, R01 DK101578, P30 DK056341 (Washington University Nutrition and Obesity Research Center), P30 DK020579 (Washington University Diabetes Research Center), and UL1 TR002345 (Washington University Institute of Clinical and Translational Sciences), and grants from the American Diabetes Association (1-18-ICTS-119), the Longer Life Foundation (2019-011).
Bettina Mittendorfer, Bruce W. Patterson, Faidon Magkos, Mihoko Yoshino, David P. Bradley, J. Christopher Eagon, Samuel Klein
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