Metabolism
Abstract
BACKGROUND. High circulating levels of ceramides (Cer) and sphingomyelins (SM) have been associated with cardiometabolic diseases. The consumption of whole-fat dairy products, which naturally contain such polar lipids (PL), is associated with health benefits, but the impact on sphingolipidome remains unknown. We investigated how milk PL supplementation impacts circulating and intestinal SM and Cer composition in association with improvement of cardiovascular markers. METHODS. In a 4 week-randomized double-blind controlled study, 58 postmenopausal women consumed daily a cream cheese containing 0, 3 or 5 g of milk PL. Postprandial metabolic explorations were performed before and after the supplementation. SM and Cer species were analyzed in serum, intestine-derived chylomicrons and feces. The ileal content of 4 ileostomy patients was also explored after milk PL intake in a crossover double-blind study. RESULTS. Milk PL consumption decreased serum atherogenic C24:1 Cer (Pgroup = 0.033), C16:1 (Pgroup = 0.007) and C18:1 (Pgroup = 0.003) SM species. Changes in serum C16+18 SM species were positively correlated with the reduction of total cholesterol (r = 0.706, P < 0.001), LDL-C (r = 0.666, P < 0.001) and ApoB (r = 0.705, P < 0.001). Milk PL decreased the concentration in chylomicrons of total SM (Pgroup < 0.0001) and of C24:1 Cer (Pgroup = 0.001). Saturated SM and Cer species, which are also the major species found in milk PL-enriched cheeses, increased in ileal efflux and feces. There was a marked increase in total fecal Cer after milk PL supplementation (Pgroup = 0.0002). Milk PL also modulated the abundance of some specific SM and Cer species in ileal efflux and feces, suggesting differential absorption and metabolization processes in the gut. CONCLUSION. These data demonstrate that milk PL supplementation decreases atherogenic SM and Cer species associated with an improvement of cardiovascular risk markers. Our findings bring new insights on sphingolipid metabolism in the gastrointestinal tract, especially Cer as such signaling molecules potentially participating in the beneficial effect of milk PL. ClinicalTrials.gov, NCT02099032, NCT02146339. FUNDINGS. Agence Nationale de la Recherche, ANR-11-ALID-007-01; Regional Hospital Clinical Research Program (PHRCI-2014: VALOBAB, n°14-007); French Dairy Interbranch Organization (CNIEL); Groupe Lipides et Nutrition (GLN 2018-11-07), Hospices Civils de Lyon as sponsor.
Authors
Mélanie Le Barz, Cécile Vors, Emmanuel Combe, Laurie Joumard-Cubizolles, Manon Lecomte, Florent Joffre, Michèle Trauchessec, Sandra Pesenti, Emmanuelle Loizon, Anne-Esther Breyton, Emmanuelle Meugnier, Karène Bertrand, Jocelyne Drai, Chloé Robert, Annie Durand, Charlotte Cuerq, Patrice Gaborit, Nadine Leconte, Annick Bernalier-Donadille, Eddy Cotte, Martine Laville, Stéphanie Lambert-Porcheron, Lemlih Ouchchane, Hubert Vidal, Corinne Malpuech-Brugère, David Cheillan, Marie-Caroline Michalski
Abstract
Macrophage-mediated inflammatory response has been implicated in the pathogenesis of obesity and insulin resistance. Brd4 has emerged as a key regulator in the innate immune response. However, the role of Brd4 in obesity-associated inflammation and insulin resistance remains uncharacterized. Here, we demonstrated that myeloid lineage-specific Brd4 knockout (Brd4-CKO) mice were protected from high-fat diet–induced (HFD-induced) obesity with less fat accumulation, higher energy expenditure, and increased lipolysis in adipose tissue. Brd4-CKO mice fed a HFD also displayed reduced local and systemic inflammation with improved insulin sensitivity. RNA-Seq of adipose tissue macrophages (ATMs) from HFD-fed WT and Brd4-CKO mice revealed that expression of antilipolytic factor Gdf3 was significantly decreased in ATMs of Brd4-CKO mice. We also found that Brd4 bound to the promoter and enhancers of Gdf3 to facilitate PPARγ-dependent Gdf3 expression in macrophages. Furthermore, Brd4-mediated expression of Gdf3 acted as a paracrine signal targeting adipocytes to suppress the expression of lipases and the associated lipolysis in cultured cells and mice. Controlling the expression of Gdf3 in ATMs could be one of the mechanisms by which Brd4 modulates lipid metabolism and diet-induced obesity. This study suggests that Brd4 could be a potential therapeutic target for obesity and insulin resistance.
Authors
Xiangming Hu, Xingchen Dong, Guo Li, Yanheng Chen, Jinjing Chen, Xiaoxin He, Hao Sun, Dong-Hyun Kim, Jongsook Kim Kemper, Lin-Feng Chen
Abstract
Perilipin 2 (PLIN2) is the lipid droplet (LD) protein in β cells that increases under nutritional stress. Down-regulation of PLIN2 is often sufficient to reduce LD accumulation. To determine whether PLIN2 positively or negatively affects β cell function under nutritional stress, PLIN2 was down-regulated in mouse β cells, INS1 cells, and human islet cells. β cell specific deletion of PLIN2 in mice on a high fat diet reduced glucose-stimulated insulin secretion (GSIS) in vivo and in vitro. Down-regulation of PLIN2 in INS1 cells blunted GSIS after 24 h incubation with 0.2 mM palmitic acids. Down-regulation of PLIN2 in human pseudoislets cultured at 5.6 mM glucose impaired both phases of GSIS, indicating that PLIN2 is critical for GSIS. Down-regulation of PLIN2 decreased specific OXPHOS proteins in all three models and reduced oxygen consumption rates in INS1 cells and mouse islets. Moreover, we found that PLIN2 deficient INS1 cells increased the distribution of a fluorescent oleic acid analog to mitochondria and showed signs of mitochondrial stress as indicated by susceptibility to fragmentation and alterations of acyl-carnitines and glucose metabolites. Collectively, PLIN2 in β cells have an important role in preserving insulin secretion, β cell metabolism, and mitochondrial function under nutritional stress.
Authors
Akansha Mishra, Siming Liu, Joseph Promes, Mikako Harata, William I. Sivitz, Brian D. Fink, Gourav Bhardwaj, Brian T. O'Neill, Chen Kang, Rajan Sah, Stefan Strack, Samuel B. Stephens, Timothy H. King, Laura Jackson, Andrew S. Greenberg, Frederick Anokye-Danso, Rexford S. Ahima, James A. Ankrum, Yumi Imai
Abstract
Sphingosine-1-phosphate lyase insufficiency syndrome (SPLIS) is a rare metabolic disorder caused by inactivating mutations in SGPL1, which is required for the final step of sphingolipid metabolism. SPLIS features include steroid-resistant nephrotic syndrome (SRNS) and impairment of neurological, endocrine, and hematopoietic systems. Many affected individuals die within the first two years. No targeted therapy for SPLIS is available. We hypothesized that SGPL1 gene replacement would address the root cause of SPLIS, thereby serving as a universal treatment for the condition. As proof of concept, we evaluated the efficacy of adeno-associated virus 9-mediated transfer of human SGPL1 (AAV-SPL) given to newborn Sgpl1 KO mice that model SPLIS and die in the first weeks of life. Treatment dramatically prolonged survival and prevented nephrosis, neurodevelopmental delay, anemia, and hypercholesterolemia. STAT3 pathway activation and elevated pro-inflammatory and fibrogenic cytokines observed in KO kidneys were attenuated by treatment. Plasma and tissue sphingolipids were reduced in treated compared to untreated KO pups. SGPL1 expression and activity were measurable for at least 40 weeks. In summary, early AAV-SPL treatment prevents nephrosis, lipidosis and neurological impairment in a mouse model of SPLIS. Our results suggest that SGPL1 gene replacement holds promise as a durable and universal targeted treatment for SPLIS.
Authors
Piming Zhao, Gizachew B. Tassew, Joanna Y. Lee, Babak Oskouian, Denise P. Muñoz, Jeffrey B. Hodgin, Gordon L. Watson, Felicia Tang, Jen-Yeu Wang, Jinghui Luo, Yingbao Yang, Sarah M. King, Ronald M. Krauss, Nancy Keller, Julie D. Saba
Abstract
Choroideremia (CHM) is a X-linked recessive chorioretinal dystrophy caused by mutations in CHM, encoding for Rab escort protein 1 (REP1). Loss of functional REP1 leads to the accumulation of unprenylated Rab proteins and defective intracellular protein trafficking, the putative cause for photoreceptor, retinal pigment epithelium (RPE) and choroidal degeneration. CHM is ubiquitously expressed, but adequate prenylation is considered to be achieved, outside the retina, through the isoform REP2. Recently, the possibility of systemic features in CHM has been debated, hence, in this study whole metabolomic analysis of plasma samples from 25 CHM patients versus age and gender matched controls was performed. Results showed plasma alterations in oxidative stress-related metabolites, coupled with alterations in tryptophan metabolism leading to significantly raised serotonin levels. Lipid metabolism was disrupted with decreased branched fatty acids and acylcarnitines, suggestive of dysfunctional lipid oxidation, and imbalances of several sphingolipids and glycerophospholipids. Targeted lipidomics of the chmru848 zebrafish provided further evidence for dysfunction, with the use of Fenofibrates over Simvastatin circumventing the prenylation pathway to improve the lipid profile and increase survival. This study provides strong evidence for systemic manifestations of CHM and proposes novel pathomechanisms and targets for therapeutic consideration.
Authors
Dulce Lima Cunha, Rose Richardson, Dhani Tracey-White, Alessandro Abbouda, Andreas Mitsios, Verena Horneffer-van der Sluis, Panteleimon Takis, Nicholas Owen, Jane Skinner, Ailsa A. Welch, Mariya Moosajee
Abstract
Autoimmune diseases are characterized by a breakdown of immune tolerance partly due to environmental factors. The short-chain fatty acid acetate, derived mostly from gut microbial fermentation of dietary fiber, promotes anti-inflammatory regulatory T cells and protects mice from type 1 diabetes, colitis and allergies. Here, we show that the effects of acetate extend to another important immune subset involved in tolerance, the IL-10 producing regulatory B cells (B10 cells). Acetate directly promoted B10 cell differentiation from mouse B1a cells both in vivo and in vitro. These effects were linked to metabolic changes through the increased production of acetyl-CoA, which fueled the tricarboxylic acid cycle and promoted post-translational lysine acetylation. Acetate also promoted B10 cells from human blood cell through similar mechanisms. Finally, we identified that dietary fiber supplementation in healthy individuals was associated with increased blood B10 cells. Direct delivery of acetate or indirectly via acetate-producing diets or -bacteria might be a promising approach to restore B10 cells in non-communicable diseases.
Authors
Claire I. Daïen, Jian Tan, Rachel Audo, Julie Mielle, Lake-Ee Quek, James R. Krycer, Alexandra S. Angelatos, Martha Duares, Gabriela V. Pinget, Duan Ni, Remy Robert, Md Jahangir Alam, Carmen Balguerías Amián, Frederic Sierro, Arvind Parmar, Gary J. Perkins, Sumaiya Hoque, Alison K. Gosby, Stephen J. Simpson, Rosilene V. Ribeiro, Charles R. Mackay, Laurence Macia
Abstract
Despite studies implicating adipose tissue T cells (ATT) in the initiation and persistence of adipose tissue inflammation, fundamental gaps in knowledge regarding ATT function impedes progress towards understanding how obesity influences adaptive immunity. We hypothesized ATT activation and function would have tissue-resident specific properties and that obesity would potentiate their inflammatory properties. We assessed ATT activation and inflammatory potential within mouse and human stromal vascular fraction (SVF). Surprisingly, murine and human ATTs from obese visceral white adipose tissue exhibited impaired inflammatory characteristics. Both environmental and cell-intrinsic factors are implicated in ATT dysfunction. Soluble factors from obese SVF inhibit ATTs activation. Additionally, chronic signaling through the T cell receptor is necessary for ATT impairment in obese adipose tissue but is independent of increased PD1 expression. To assess intracellular signaling mechanisms responsible for ATT inflammation impairments, single-cell RNA sequencing of ATTs was performed. ATTs in obese adipose tissue exhibit gene expression resembling T cell exhaustion and increased expression of co-inhibitory receptor Btla. In sum, this work suggests that obesity-induced ATT cells have functional characteristics and gene expression resembling T cell exhaustion, which is dependent upon localized soluble factors and cell-to-cell interactions in adipose tissue.
Authors
Cara E. Porsche, Jennifer B. DelProposto, Lynn Geletka, Robert O’Rourke, Carey N. Lumeng
Abstract
Liver regeneration is critical to survival after traumatic injuries, exposure to hepatotoxins, or surgical interventions, yet the underlying signaling and metabolic pathways remain unclear. Here we show that hepatocyte-specific loss of the mitochondrial deacetylase SIRT3 drastically impairs regeneration and worsens mitochondrial function after partial hepatectomy. Sirtuins, including SIRT3, require nicotinamide adenine dinucleotide (NAD) as a cosubstrate. We previously showed that the NAD precursor nicotinamide riboside (NR) promotes liver regeneration, but whether this involves sirtuins has not been tested. Here we show that despite their NAD-dependence and critical roles in regeneration, neither SIRT3 nor its nuclear counterpart SIRT1 is required for NR to enhance liver regeneration. NR improves mitochondrial respiration in regenerating wild type or mutant livers and rapidly increases oxygen consumption and glucose output in cultured hepatocytes. Our data support a direct enhancement of mitochondrial redox metabolism as the mechanism mediating improved liver regeneration after NAD supplementation and exclude signaling via SIRT1 and SIRT3. Thus, we provide the first evidence for an essential role for a mitochondrial sirtuin during liver regeneration and insight into the beneficial effects of NR.
Authors
Sarmistha Mukherjee, James Mo, Lauren M. Paolella, Caroline E. Perry, Jade Toth, Mindy M. Hugo, Qingwei Chu, Qiang Tong, Karthikeyani Chellappa, Joseph A. Baur
Abstract
A maternal Western-style diet (WSD) is associated with poor reproductive outcomes, but whether this is from the diet itself or underlying metabolic dysfunction is unknown. Here, we performed a longitudinal study using regularly cycling female rhesus macaques (n = 10) that underwent 2 consecutive in vitro fertilization (IVF) cycles, one while consuming a low-fat diet and another 6–8 months after consuming a high-fat WSD. Metabolic data were collected from the females prior to each IVF cycle. Follicular fluid (FF) and oocytes were assessed for cytokine/steroid levels and IVF potential, respectively. Although transition to a WSD led to weight gain and increased body fat, no difference in insulin levels was observed. A significant decrease in IL-1RA concentration and the ratio of cortisol/cortisone was detected in FF after WSD intake. Despite an increased probability of isolating mature oocytes, a 44% reduction in blastocyst number was observed with WSD consumption, and time-lapse imaging revealed delayed mitotic timing and multipolar divisions. RNA sequencing of blastocysts demonstrated dysregulation of genes involved in RNA binding, protein channel activity, mitochondrial function and pluripotency versus cell differentiation after WSD consumption. Thus, short-term WSD consumption promotes a proinflammatory intrafollicular microenvironment that is associated with impaired preimplantation development in the absence of large-scale metabolic changes.
Authors
Sweta Ravisankar, Alison Y. Ting, Melinda J. Murphy, Nash Redmayne, Dorothy Wang, Carrie A. McArthur, Diana L. Takahashi, Paul Kievit, Shawn L. Chavez, Jon D. Hennebold
Abstract
BACKGROUND Metabolic flexibility (MF) refers to the relative ability to utilize lipid and carbohydrate substrates and to transition between them. It is not clear whether MF is impaired in obese youth and what the determining factors are.METHODS We investigated the determinants of MF (increased respiratory exchange ratio [ΔRER] under insulin-stimulated conditions) in pubertal youth (n = 104; 15.6 ± 1.8 years) with obesity across the spectrum of glucose tolerance compared with normal weight (NW) controls, including body composition (fat-free mass [FFM], %body fat), visceral adipose fat (VAT) (MRI), glycemia, and insulin sensitivity (IS) [3-hour hyperinsulinemic-euglycemic clamp with measurement of lipolysis ([2H5] glycerol), free fatty acids (FFAs), and RER (indirect calorimetry)].RESULTS Youth with prediabetes and type 2 diabetes had lower ΔRER and oxidative and nonoxidative glucose disposal compared with NW, with no significant difference in ΔRER between NW and obese with normal glucose tolerance. In multiple regression analysis, ISFFM (β = 0.4, P = 0.004), percentage suppression of FFAs (r = 0.26, P = 0.007), and race/ethnicity (β = –0.23, P = 0.02) contributed to the variance in ΔRER (R2 = 0.30, P < 0.001) independent of percentage body fat (or VAT), sex, Tanner stage, and hemoglobin A1c.Conclusion MF is defective at the extreme of the metabolic phenotype in obese youth with dysglycemia related to a defect in IS limiting substrate utilization.FUNDING USDA/ARS Project Number 3092-51000-057.
Authors
Fida Bacha, Sara Klinepeter Bartz, Maurice Puyau, Anne Adolph, Susan Sharma
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