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BACKGROUND & AIMS: Polygenic and environmental factors are underlying causes of inflammatory bowel disease (IBD). We hypothesized that integration of the genetic loci controlling a metabolite's abundance, with known IBD genetic susceptibility loci, may help resolve metabolic drivers of IBD. METHODS: We measured the levels of 1300 metabolites in the serum of 484 patients with ulcerative colitis (UC) and 464 patients with Crohn's disease (CD) and 365 controls. Differential metabolite abundance was determined for disease status, subtype, clinical and endoscopic disease activity, as well as IBD phenotype including disease behavior, location, and extent. To inform on the genetic basis underlying metabolic diversity, we integrated metabolite and genomic data. Genetic colocalization and Mendelian randomization analyses were performed using known IBD risk loci to explore whether any metabolite was causally associated with IBD. RESULTS: We found 173 genetically controlled metabolites (metabolite quantitative trait loci, 9 novel) within 63 non-overlapping loci (7 novel). Furthermore, several metabolites significantly associated with IBD disease status and activity as defined using clinical and endoscopic indexes. This constitutes a resource for biomarker discovery and IBD biology insights. Using this resource, we show that a novel metabolite quantitative trait locus for serum butyrate levels containing ACADS was not supported as causal for IBD; replicate the association of serum omega-6 containing lipids with the fatty acid desaturase 1/2 locus and identify these metabolites as causal for CD through Mendelian randomization; and validate a novel association of serum plasmalogen and TMEM229B, which was predicted as causal for CD. CONCLUSIONS: An exploratory analysis combining genetics and unbiased serum metabolome surveys can reveal novel biomarkers of disease activity and potential mediators of pathology in IBD.
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Acil-CoA Deshidrogenasa/genética , Colitis Ulcerosa/genética , Colitis Ulcerosa/metabolismo , Enfermedad de Crohn/genética , Enfermedad de Crohn/metabolismo , Adolescente , Adulto , Anciano , Anciano de 80 o más Años , Biomarcadores/sangre , Butiratos/sangre , Estudios de Casos y Controles , Niño , Preescolar , Colitis Ulcerosa/sangre , Colitis Ulcerosa/tratamiento farmacológico , Enfermedad de Crohn/sangre , Enfermedad de Crohn/tratamiento farmacológico , Estudios Transversales , Heces/química , Femenino , Estudio de Asociación del Genoma Completo , Genotipo , Células HEK293 , Humanos , Masculino , Análisis de la Aleatorización Mendeliana , Metaboloma , Persona de Mediana Edad , Plasmalógenos/sangre , Plasmalógenos/genética , Sitios de Carácter Cuantitativo , Índice de Severidad de la Enfermedad , Adulto JovenRESUMEN
BACKGROUND & AIMS: Severe malnutrition in young children is associated with signs of hepatic dysfunction such as steatosis and hypoalbuminemia, but its etiology is unknown. Peroxisomes and mitochondria play key roles in various hepatic metabolic functions including lipid metabolism and energy production. To investigate the involvement of these organelles in the mechanisms underlying malnutrition-induced hepatic dysfunction we developed a rat model of malnutrition. METHODS: Weanling rats were placed on a low protein or control diet (5% or 20% of calories from protein, respectively) for four weeks. Peroxisomal and mitochondrial structural features were characterized using immunofluorescence and electron microscopy. Mitochondrial function was assessed using high-resolution respirometry. A novel targeted quantitative proteomics method was applied to analyze 47 mitochondrial proteins involved in oxidative phosphorylation, tricarboxylic acid cycle and fatty acid ß-oxidation pathways. RESULTS: Low protein diet-fed rats developed hypoalbuminemia and hepatic steatosis, consistent with the human phenotype. Hepatic peroxisome content was decreased and metabolomic analysis indicated peroxisomal dysfunction. This was followed by changes in mitochondrial ultrastructure and increased mitochondrial content. Mitochondrial function was impaired due to multiple defects affecting respiratory chain complex I and IV, pyruvate uptake and several ß-oxidation enzymes, leading to strongly reduced hepatic ATP levels. Fenofibrate supplementation restored hepatic peroxisome abundance and increased mitochondrial ß-oxidation capacity, resulting in reduced steatosis and normalization of ATP and plasma albumin levels. CONCLUSIONS: Malnutrition leads to severe impairments in hepatic peroxisomal and mitochondrial function, and hepatic metabolic dysfunction. We discuss the potential future implications of our findings for the clinical management of malnourished children. LAY SUMMARY: Severe malnutrition in children is associated with metabolic disturbances that are poorly understood. In order to study this further, we developed a malnutrition animal model and found that severe malnutrition leads to an impaired function of liver mitochondria which are essential for energy production and a loss of peroxisomes, which are important for normal liver metabolic function.
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Desnutrición , Adenosina Trifosfato , Animales , Niño , Hígado Graso , Humanos , Hígado , Mitocondrias , Oxidación-Reducción , RatasRESUMEN
AIM: Acylcarnitines are fatty acid oxidation (FAO) intermediates, which have been implicated in diet-induced insulin resistance. Elevated acylcarnitine levels are found in obese, insulin resistant humans and rodents, and coincide with lower free carnitine. We hypothesized that increasing free carnitine levels by administration of the carnitine precursor γ-butyrobetaine (γBB) could facilitate FAO, thereby improving insulin sensitivity. METHODS: C57BL/6N mice were fed with a high fat or chow diet with or without γBB supplementation (n=10 per group). After 8weeks of diet, indirect calorimetry, glucose tolerance and insulin sensitivity tests were performed. AC profiles and carnitine biosynthesis intermediates were analyzed in plasma and tissues by tandem mass spectrometry (MS) and liquid chromatography tandem MS. RESULTS: γBB supplementation did not facilitate FAO, was unable to curb bodyweight and did not prevent impaired glucose homeostasis in the HFD fed mice in spite of marked alterations in the acylcarnitine profiles in plasma and liver. Remarkably, γBB did not affect the acylcarnitine profile in other tissues, most notably muscle. Administration of a bolus acetylcarnitine also caused significant changes in plasma and liver, but not in muscle acylcarnitine profiles, again without effect on glucose tolerance. CONCLUSION: Altogether, increasing carnitine availability affects acylcarnitine profiles in plasma and liver but does not modulate glucose tolerance or insulin sensitivity. This may be due to the lack of an effect on muscle acylcarnitine profiles, as muscle tissue is an important contributor to whole body insulin sensitivity. These results warrant caution on making associations between plasma acylcarnitine levels and insulin resistance.
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Carnitina/análogos & derivados , Metabolismo Energético , Intolerancia a la Glucosa/sangre , Resistencia a la Insulina , Obesidad/sangre , Animales , Betaína/análogos & derivados , Betaína/farmacología , Carnitina/sangre , Carnitina/farmacología , Grasas de la Dieta/efectos adversos , Grasas de la Dieta/farmacología , Intolerancia a la Glucosa/inducido químicamente , Intolerancia a la Glucosa/patología , Hígado/metabolismo , Hígado/patología , Ratones , Ratones Obesos , Músculo Esquelético/metabolismo , Músculo Esquelético/patología , Obesidad/inducido químicamente , Obesidad/patologíaRESUMEN
Muscle lipid overload and the associated accumulation of lipid intermediates play an important role in the development of insulin resistance. Carnitine insufficiency is a common feature of insulin-resistant states and might lead to incomplete fatty acid oxidation and impaired export of lipid intermediates out of the mitochondria. The aim of the present study was to test the hypothesis that carnitine supplementation reduces high-fat diet-induced lipotoxicity, improves muscle mitochondrial function, and ameliorates insulin resistance. Wistar rats were fed either normal chow or a high-fat diet for 15 wk. One group of high-fat diet-fed rats was supplemented with 300 mg·kg(-1)·day(-1) L-carnitine during the last 8 wk. Muscle mitochondrial function was measured in vivo by (31)P magnetic resonance spectroscopy (MRS) and ex vivo by high-resolution respirometry. Muscle lipid status was determined by (1)H MRS (intramyocellular lipids) and tandem mass spectrometry (acylcarnitines). High-fat diet feeding induced insulin resistance and was associated with decreases in muscle and blood free carnitine, elevated levels of muscle lipids and acylcarnitines, and an increased number of muscle mitochondria that showed an improved capacity to oxidize fat-derived substrates when tested ex vivo. This was, however, not accompanied by an increase in muscle oxidative capacity in vivo, indicating that in vivo mitochondrial function was compromised. Despite partial normalization of muscle and blood free carnitine content, carnitine supplementation did not induce improvements in muscle lipid status, in vivo mitochondrial function, or insulin sensitivity. Carnitine insufficiency, therefore, does not play a major role in high-fat diet-induced muscle mitochondrial dysfunction in vivo.
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Carnitina/administración & dosificación , Dieta Alta en Grasa , Lípidos/efectos adversos , Mitocondrias Musculares/efectos de los fármacos , Enfermedades Mitocondriales/dietoterapia , Animales , Carnitina/análogos & derivados , Carnitina/metabolismo , Carnitina/farmacología , Suplementos Dietéticos , Metabolismo de los Lípidos/efectos de los fármacos , Masculino , Mitocondrias Musculares/metabolismo , Enfermedades Mitocondriales/metabolismo , Músculo Esquelético/efectos de los fármacos , Músculo Esquelético/metabolismo , Ratas , Ratas WistarRESUMEN
Acylcarnitines are derived from mitochondrial acyl-CoA metabolism and have been associated with diet-induced insulin resistance. However, plasma acylcarnitine profiles have been shown to poorly reflect whole body acylcarnitine metabolism. We aimed to clarify the individual role of different organ compartments in whole body acylcarnitine metabolism in a fasted and postprandial state in a porcine transorgan arteriovenous model. Twelve cross-bred pigs underwent surgery where intravascular catheters were positioned before and after the liver, gut, hindquarter muscle compartment, and kidney. Before and after a mixed meal, we measured acylcarnitine profiles at several time points and calculated net transorgan acylcarnitine fluxes. Fasting plasma acylcarnitine concentrations correlated with net hepatic transorgan fluxes of free and C2- and C16-carnitine. Transorgan acylcarnitine fluxes were small, except for a pronounced net hepatic C2-carnitine production. The peak of the postprandial acylcarnitine fluxes was between 60 and 90 min. Acylcarnitine production or release was seen in the gut and liver and consisted mostly of C2-carnitine. Acylcarnitines were extracted by the kidney. No significant net muscle acylcarnitine flux was observed. We conclude that liver has a key role in acylcarnitine metabolism, with high net fluxes of C2-carnitine both in the fasted and fed state, whereas the contribution of skeletal muscle is minor. These results further clarify the role of different organ compartments in the metabolism of different acylcarnitine species.
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Carnitina/análogos & derivados , Metabolismo de los Lípidos , Hígado/metabolismo , Modelos Biológicos , Acetilcarnitina/sangre , Acetilcarnitina/metabolismo , Animales , Carnitina/biosíntesis , Carnitina/sangre , Carnitina/metabolismo , Catéteres de Permanencia , Cruzamientos Genéticos , Femenino , Mucosa Intestinal/metabolismo , Intestinos/irrigación sanguínea , Riñón/irrigación sanguínea , Riñón/metabolismo , Hígado/irrigación sanguínea , Aceite de Oliva , Especificidad de Órganos , Palmitoilcarnitina/sangre , Palmitoilcarnitina/metabolismo , Aceites de Plantas/administración & dosificación , Aceites de Plantas/metabolismo , Periodo Posprandial , Sus scrofaRESUMEN
PURPOSE: Elevation of long-chain acylcarnitine levels is a hallmark of long-chain mitochondrial ß-oxidation (FAO) disorders, and can be accompanied by secondary carnitine deficiency. To restore free carnitine levels, and to increase myocardial export of long-chain fatty acyl-CoA esters, supplementation of L-carnitine in patients has been proposed. However, carnitine supplementation is controversial, because it may enhance the potentially lipotoxic buildup of long-chain acylcarnitines in the FAO-deficient heart. In this longitudinal study, we investigated the effects of carnitine supplementation in an animal model of long-chain FAO deficiency, the long-chain acyl-CoA dehydrogenase (LCAD) knockout (KO) mouse. METHODS: Cardiac size and function, and triglyceride (TG) levels were quantified using proton magnetic resonance imaging (MRI) and spectroscopy ((1)H-MRS) in LCAD KO and wild-type (WT) mice. Carnitine was supplemented orally for 4 weeks starting at 5 weeks of age. Non-supplemented animals served as controls. In vivo data were complemented with ex vivo biochemical assays. RESULTS: LCAD KO mice displayed cardiac hypertrophy and elevated levels of myocardial TG compared to WT mice. Carnitine supplementation lowered myocardial TG, normalizing myocardial TG levels in LCAD KO mice. Furthermore, carnitine supplementation did not affect cardiac performance and hypertrophy, or induce an accumulation of potentially toxic long-chain acylcarnitines in the LCAD KO heart. CONCLUSION: This study lends support to the proposed beneficial effect of carnitine supplementation alleviating toxicity by exporting acylcarnitines out of the FAO-deficient myocardium, rather than to the concern about a potentially detrimental effect of supplementation-induced production of lipotoxic long-chain acylcarnitines.
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Acil-CoA Deshidrogenasa de Cadena Larga/genética , Carnitina/farmacología , Metabolismo de los Lípidos/efectos de los fármacos , Miocardio/metabolismo , Acil-CoA Deshidrogenasa de Cadena Larga/deficiencia , Acil-CoA Deshidrogenasa de Cadena Larga/metabolismo , Animales , Carnitina/análogos & derivados , Carnitina/sangre , Suplementos Dietéticos , Modelos Animales de Enfermedad , Evaluación Preclínica de Medicamentos , Corazón/efectos de los fármacos , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Triglicéridos/metabolismoRESUMEN
BACKGROUND: During heart failure (HF), cardiac metabolic substrate preference changes from fatty acid (FA) toward glucose oxidation. This change may cause progression toward heart failure. We hypothesize that a diet rich in FAs may prevent this process, and that dietary ω3-FAs have an added antiarrhythmic effect based on action potential (AP) shortening in animals with HF. METHODS AND RESULTS: Rabbits were fed a diet containing 1.25% (w/w) high oleic sunflower oil (HF-ω9, N=11), 1.25% fish oil (HF-ω3, N=11), or no supplement (HF-control, N=8). Subsequently, HF was induced by volume and pressure overload. After 4 months, HF-parameters were assessed, electrocardiograms were recorded, and blood and ventricular tissue were collected. Myocytes were isolated for patch clamp or intracellular Ca(2+)- recordings to study electrophysiologic remodeling and arrhythmogenesis. Both the HF-ω9 and the HF-ω3 groups had larger myocardial FA oxidation capacity than HF control. The HF-ω3 group had significantly lower mean (± SEM) relative heart and lung weight (3.3±0.13 and 3.2±0.12 g kg(-1), respectively) than HF control (4.8±0.30 and 4.5±0.23), and shorter QTc intervals (167±2.6 versus 182±6.4). The HF-ω9 also displayed a significantly reduced relative heart weight (3.6±0.26), but had similar QTc (179±4.3) compared with HF control. AP duration in the HF-ω3 group was ≈20% shorter due to increased I(to1) and I(K1) and triggered activity, and Ca(2+)-aftertransients were less than in the HF-ω9 group. CONCLUSIONS: Dietary unsaturated FAs started prior to induction of HF prevent hypertrophy and HF. In addition, fish oil FAs prevent HF-induced electrophysiologic remodeling and arrhythmias.
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Arritmias Cardíacas/prevención & control , Cardiomegalia/prevención & control , Grasas Insaturadas en la Dieta/uso terapéutico , Ácidos Grasos Insaturados/uso terapéutico , Insuficiencia Cardíaca/prevención & control , Insuficiencia Cardíaca/fisiopatología , Potenciales de Acción/fisiología , Administración Oral , Animales , Arritmias Cardíacas/patología , Arritmias Cardíacas/fisiopatología , Calcio/metabolismo , Cardiomegalia/patología , Cardiomegalia/fisiopatología , Grasas Insaturadas en la Dieta/administración & dosificación , Electrocardiografía , Técnicas Electrofisiológicas Cardíacas , Ácidos Grasos Insaturados/administración & dosificación , Insuficiencia Cardíaca/patología , Masculino , Modelos Animales , Miocitos Cardíacos/metabolismo , Miocitos Cardíacos/patología , Técnicas de Placa-Clamp , ConejosRESUMEN
Obesity and its associated conditions such as type 2 diabetes mellitus are major causes of morbidity and mortality. The iminosugar N-(5-adamantane-1-yl-methoxy-pentyl)-deoxynojirimycin (AMP-DNM) improves insulin sensitivity in rodent models of insulin resistance and type 2 diabetes mellitus. In the current study, we characterized the impact of AMP-DNM on substrate oxidation patterns, food intake, and body weight gain in obese mice. Eight ob/ob mice treated with 100 mg/(kg d) AMP-DNM mixed in the food and 8 control ob/ob mice were placed in metabolic cages during the first, third, and fifth week of the experiment for measurement of substrate oxidation rates, energy expenditure, activity, and food intake. Mice were killed after 6 weeks of treatment. Initiation of treatment with AMP-DNM resulted in a rapid increase in fat oxidation by 129% (P = .05), a decrease in carbohydrate oxidation by 35% (P = .01), and a reduction in food intake by approximately 26% (P < .01) compared with control mice. Treatment with AMP-DNM decreased hepatic triglyceride content by 66% (P < .01) and, in line with the elevated fat oxidation rates, increased hepatic carnitine palmitoyl transferase 1a expression. Treatment with AMP-DNM increased plasma levels of the appetite-regulating peptide YY compared with control mice. Treatment with AMP-DNM rapidly reduces food intake and increases fat oxidation, resulting in improvement of the obese phenotype. These features of AMP-DNM, together with its insulin-sensitizing capacity, make it an attractive candidate drug for the treatment of obesity and its associated metabolic derangements.
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1-Desoxinojirimicina/análogos & derivados , Adamantano/análogos & derivados , Peso Corporal/efectos de los fármacos , Ingestión de Alimentos/efectos de los fármacos , Obesidad/tratamiento farmacológico , Obesidad/metabolismo , 1-Desoxinojirimicina/farmacología , Adamantano/farmacología , Tejido Adiposo/metabolismo , Animales , Metabolismo de los Hidratos de Carbono/efectos de los fármacos , Carnitina O-Palmitoiltransferasa/metabolismo , Ghrelina/metabolismo , Glucosa/metabolismo , Iminoazúcares/farmacología , Hígado/efectos de los fármacos , Hígado/metabolismo , Ratones , Ratones Endogámicos C57BL , Ratones Obesos , Obesidad/genética , Oxidación-Reducción , Péptido YY/metabolismo , Triglicéridos/metabolismo , Regulación hacia Arriba/efectos de los fármacos , Aumento de Peso/efectos de los fármacosRESUMEN
Transporters present in the epithelium of the small intestine determine the efficiency by which dietary and biliary cholesterol are taken up into the body and thus control whole-body cholesterol balance. Niemann-Pick C1 Like Protein 1 (Npc1l1) transports cholesterol into the enterocyte, whereas ATP-binding cassette transporters Abca1 and Abcg5/Abcg8 are presumed to be involved in cholesterol efflux from the enterocyte toward plasma HDL and back into the intestinal lumen, respectively. Abca1, Abcg5, and Abcg8 are well-established liver X receptor (LXR) target genes. We examined the effects of a high-fat diet on expression and function of cholesterol transporters in the small intestine in mice. Npc1l1, Abca1, Abcg5, and Abcg8 were all downregulated after 2, 4, and 8 wk on a cholesterol-free, high-fat diet. The high-fat diet did not affect biliary cholesterol secretion but diminished fractional cholesterol absorption from 61 to 42% (P < 0.05). In an acute experiment in which triacylglycerols of unsaturated fatty acids were given by gavage, we found that this downregulation occurs within a 6-h time frame. Studies in LXRalpha-null mice, confirmed by in vitro data, showed that fatty acid-induced downregulation of cholesterol transporters is LXRalpha independent and associated with a posttranslational increase in 3-hydroxy-3-methylglutaryl-coenzyme A reductase activity that reflects induction of cholesterol biosynthesis as well as with a doubling of neutral fecal sterol loss. This study highlights the induction of adaptive changes in small intestinal cholesterol metabolism during exposure to dietary fat.
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Colesterol/metabolismo , Grasas de la Dieta/farmacología , Intestino Delgado/metabolismo , Proteínas de Transporte de Membrana/genética , Transportador 1 de Casete de Unión a ATP , Transportador de Casetes de Unión a ATP, Subfamilia G, Miembro 5 , Transportador de Casete de Unión a ATP, Subfamilia G, Miembro 8 , Transportadoras de Casetes de Unión a ATP/genética , Animales , Ácidos y Sales Biliares/análisis , Colesterol/sangre , Proteínas de Unión al ADN/genética , Proteínas de Unión al ADN/fisiología , Grasas de la Dieta/administración & dosificación , Células Epiteliales/efectos de los fármacos , Células Epiteliales/metabolismo , Heces/química , Regulación de la Expresión Génica/efectos de los fármacos , Hidroxicolesteroles/farmacología , Hidroximetilglutaril-CoA Reductasas/genética , Hidroximetilglutaril-CoA Reductasas/metabolismo , Absorción Intestinal/efectos de los fármacos , Absorción Intestinal/fisiología , Intestino Delgado/citología , Intestino Delgado/efectos de los fármacos , Lipoproteínas/genética , Receptores X del Hígado , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Modelos Biológicos , Análisis de Secuencia por Matrices de Oligonucleótidos , Receptores Nucleares Huérfanos , Receptores Citoplasmáticos y Nucleares/genética , Receptores Citoplasmáticos y Nucleares/fisiología , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Triglicéridos/farmacologíaRESUMEN
OBJECTIVE: In cells from patients with the autoinflammatory disorder mevalonate kinase (MK) deficiency, which includes the hyperimmunoglobulin D with periodic fever syndrome, MK becomes the rate-limiting enzyme in the isoprenoid biosynthesis pathway. This suggests that up-regulation of residual MK activity in these patients could be a way in which to prevent or alleviate the associated symptoms. We studied the effect of 2 specific inhibitors of isoprenoid biosynthetic enzymes on the residual activity of MK in cells from patients with MK deficiency. METHODS: Skin fibroblasts from MK-deficient patients and from controls were cultured for 7 days with either simvastatin, an inhibitor of 3-hydroxy-3-methylglutaryl coenzyme A reductase, or zaragozic acid A, an inhibitor of squalene synthase. Following culture, MK activity, MK protein levels, MVK messenger RNA levels, and the effect on the pathway flux toward non-sterol isoprenoid biosynthesis were determined. RESULTS: Treatment of the fibroblasts with either of the inhibitors led to a marked increase in residual MK enzyme activity, which was largely attributable to increased MVK gene transcription. This effect was even more pronounced when the cells were cultured in lipoprotein-depleted medium. The flux toward nonsterol isoprenoid end-product synthesis was reduced when cells were treated with simvastatin but was partly restored by concomitant treatment with zaragozic acid A. CONCLUSION: Our results indicate that manipulations of the isoprenoid biosynthesis pathway that promote the synthesis of nonsterol isoprenoids may provide an interesting therapeutic option for the treatment of MK deficiency.