RESUMEN
Bile salt hydrolase (BSH) enzymes are widely expressed by human gut bacteria and catalyze the gateway reaction leading to secondary bile acid formation. Bile acids regulate key metabolic and immune processes by binding to host receptors. There is an unmet need for a potent tool to inhibit BSHs across all gut bacteria to study the effects of bile acids on host physiology. Here, we report the development of a covalent pan-inhibitor of gut bacterial BSHs. From a rationally designed candidate library, we identified a lead compound bearing an alpha-fluoromethyl ketone warhead that modifies BSH at the catalytic cysteine residue. This inhibitor abolished BSH activity in conventional mouse feces. Mice gavaged with a single dose of this compound displayed decreased BSH activity and decreased deconjugated bile acid levels in feces. Our studies demonstrate the potential of a covalent BSH inhibitor to modulate bile acid composition in vivo.
Asunto(s)
Amidohidrolasas/antagonistas & inhibidores , Amidohidrolasas/metabolismo , Microbioma Gastrointestinal/fisiología , Amidohidrolasas/fisiología , Animales , Bacterias/enzimología , Ácidos y Sales Biliares/metabolismo , Diseño de Fármacos , Femenino , Humanos , Masculino , Ratones , Ratones Endogámicos C57BL , Bibliotecas de Moléculas PequeñasRESUMEN
The intestinal epithelium plays an essential role in nutrient absorption, hormone release, and barrier function. Maintenance of the epithelium is driven by continuous cell renewal by stem cells located in the intestinal crypts. The amount and type of diet influence this process and result in changes in the size and cellular make-up of the tissue. The mechanism underlying the nutrient-driven changes in proliferation is not known, but may involve a shift in intracellular metabolism that allows for more nutrients to be used to manufacture new cells. We hypothesized that nutrient availability drives changes in cellular energy metabolism of small intestinal epithelial crypts that could contribute to increases in crypt proliferation. We utilized primary small intestinal epithelial crypts from C57BL/6J mice to study (1) the effect of glucose on crypt proliferation and (2) the effect of glucose on crypt metabolism using an extracellular flux analyzer for real-time metabolic measurements. We found that glucose increased both crypt proliferation and glycolysis, and the glycolytic pathway inhibitor 2-deoxy-d-glucose (2-DG) attenuated glucose-induced crypt proliferation. Glucose did not enhance glucose oxidation, but did increase the maximum mitochondrial respiratory capacity, which may contribute to glucose-induced increases in proliferation. Glucose activated Akt/HIF-1α signaling pathway, which might be at least in part responsible for glucose-induced glycolysis and cell proliferation. These results suggest that high glucose availability induces an increase in crypt proliferation by inducing an increase in glycolysis with no change in glucose oxidation.
Asunto(s)
Proliferación Celular/efectos de los fármacos , Metabolismo Energético/efectos de los fármacos , Glucosa/farmacología , Mucosa Intestinal/efectos de los fármacos , Células Madre/efectos de los fármacos , Animales , Glucosa/metabolismo , Glucólisis/efectos de los fármacos , Mucosa Intestinal/metabolismo , Masculino , Ratones Endogámicos C57BL , Transducción de Señal/efectos de los fármacos , Células Madre/metabolismoRESUMEN
The small intestine is the main organ involved in the digestion and absorption of nutrients. It is in an ideal position to sense the availability of energy in the lumen in addition to its absorptive function. Consumption of a high-fat diet (HFD) influences the metabolic characteristics of the small intestine. Therefore, to better understand the metabolic features of the small intestine and their changes in response to dietary fat, we characterized the metabolism of duodenal, jejunal, and hepatic cell lines and assessed the metabolic changes in the enterocytes and the liver after short-term (3 days) or medium-term (14 days) HFD feeding in mice. Experiments with immortalized enterocytes indicated a higher glycolytic capacity in the duodenal cell line compared to the other two cell lines, whereas the jejunal cell line exhibited a high oxidative metabolism. Short-term HFD feeding induced changes in the expression of glucose and lipid metabolism-related genes in the duodenum and the jejunum of mice, but not in the liver. When focusing on fatty acid oxidation both, short- and medium-term HFD feeding induced an upregulation of 3-hydroxy-3-methylglutaryl-coenzyme A, the key enzyme of ketogenesis, at the protein level in the intestinal epithelial cells, but not in the liver. These results suggest that HFD feeding induces an early adaptation of the small intestine rather than the liver in response to a substantial fat load. This highlights the importance of the small intestine in the adaptation of the body to the metabolic changes induced by HFD exposure. J. Cell. Physiol. 232: 167-175, 2017. © 2016 Wiley Periodicals, Inc.
Asunto(s)
Dieta Alta en Grasa , Enterocitos/efectos de los fármacos , Intestino Delgado/efectos de los fármacos , Intestino Delgado/metabolismo , Metabolismo de los Lípidos/efectos de los fármacos , Obesidad/metabolismo , Adaptación Fisiológica/efectos de los fármacos , Composición Corporal/efectos de los fármacos , Composición Corporal/fisiología , Grasas de la Dieta/metabolismo , Enterocitos/metabolismo , Humanos , Hígado/efectos de los fármacos , Hígado/metabolismo , Factores de TiempoRESUMEN
Thylakoids reduce body weight gain and body fat accumulation in rodents. This study investigated whether an enhanced oxidation of dietary fat-derived fatty acids in the intestine contributes to the thylakoid effects. Male Sprague-Dawley rats were fed a high-fat diet with (n = 8) or without thylakoids (n = 8) for 2 wk. Body weight, food intake, and body fat were measured, and intestinal mucosa was collected and analyzed. Quantitative real-time PCR was used to measure gene expression levels of key enzymes involved in fatty acid transport, fatty acid oxidation, and ketogenesis. Another set of thylakoid-treated (n = 10) and control rats (n = 10) went through indirect calorimetry. In the first experiment, thylakoid-treated rats (n = 8) accumulated 25% less visceral fat than controls. Furthermore, fatty acid translocase (Fat/Cd36), carnitine palmitoyltransferase 1a (Cpt1a), and mitochondrial 3-hydroxy-3-methylglutaryl-CoA synthase 2 (Hmgcs2) genes were upregulated in the jejunum of the thylakoid-treated group. In the second experiment, thylakoid-treated rats (n = 10) gained 17.5% less weight compared with controls and their respiratory quotient was lower, 0.86 compared with 0.91. Thylakoid-intake resulted in decreased food intake and did not cause steatorrhea. These results suggest that thylakoids stimulated intestinal fatty acid oxidation and ketogenesis, resulting in an increased ability of the intestine to handle dietary fat. The increased fatty acid oxidation and the resulting reduction in food intake may contribute to the reduced fat accumulation in thylakoid-treated animals.
Asunto(s)
Dieta Alta en Grasa , Ácidos Grasos/metabolismo , Mucosa Intestinal/metabolismo , Grasa Intraabdominal/fisiología , Tilacoides/metabolismo , Regulación hacia Arriba/fisiología , Animales , Masculino , Tamaño de los Órganos/fisiología , Oxidación-Reducción , Ratas , Ratas Sprague-Dawley , Tilacoides/químicaRESUMEN
Hepatic fatty acid oxidation (FAO) has long been implicated in the control of eating. Nevertheless, direct evidence for a causal relationship between changes in hepatic FAO and changes in food intake is still missing. Here we tested whether increasing hepatic FAO via adenovirus-mediated expression of a mutated form of the key regulatory enzyme of mitochondrial FAO carnitine palmitoyltransferase 1A (CPT1mt), which is active but insensitive to inhibition by malonyl-CoA, affects eating and metabolism in mice. CPT1mt expression increased hepatocellular CPT1 protein levels. This resulted in an increase in circulating ketone body levels in fasted CPT1mt-expressing mice, suggesting an increase in hepatic FAO. These mice did not show any significant changes in cumulative food intake, energy expenditure, or respiratory quotient after 4-h food deprivation. After 24-h food deprivation, however, the CPT1mt-expressing mice displayed increased food intake. Thus expression of CPT1mt in the liver increases hepatic FAO capacity, but does not inhibit eating. Rather, it may even stimulate eating after prolonged food deprivation. These data do not support the hypothesis that an increase in hepatic FAO decreases food intake.
Asunto(s)
Carnitina O-Palmitoiltransferasa/metabolismo , Ingestión de Alimentos/fisiología , Ácidos Grasos/metabolismo , Metabolismo de los Lípidos/fisiología , Hígado/metabolismo , Mitocondrias/metabolismo , Animales , Metabolismo Energético/fisiología , Privación de Alimentos/fisiología , Masculino , Ratones Endogámicos C57BL , Modelos Animales , Oxidación-ReducciónRESUMEN
The endogenous lipid messenger oleoylethanolamide (OEA) inhibits eating and modulates fat metabolism supposedly through the activation of peroxisome proliferator-activated receptor-α (PPARα) and vagal sensory fibers. We tested in adult male rats whether OEA stimulates fatty acid oxidation (FAO) and ketogenesis and whether it increases plasma levels of the satiating gut peptides glucagon-like peptide-1 (GLP-1) and peptide YY (PYY). We also explored whether OEA still inhibits eating after subdiaphragmatic vagal deafferentation (SDA). We found that intraperitoneally injected OEA (10 mg/kg body wt) reduced (P < 0.05) food intake mainly by increasing meal latency and that this effect was stronger in rats fed a 60% high-fat diet (HFD) than in chow-fed rats. OEA increased (P < 0.05) postprandial plasma nonesterified fatty acids and ß-hydroxybutyrate (BHB) in the hepatic portal vein (HPV) and vena cava (VC) 30 min after injection, which was more pronounced in HFD- than in chow-fed rats. OEA also increased the protein expression of the key ketogenetic enzyme, mitochondrial 3-hydroxy-3-methylglutaryl-CoA synthase, in the jejunum of HFD-fed rats, but not in the liver or duodenum of either diet group. Furthermore, OEA decreased GLP-1 and PYY concentrations (P < 0.05) in the HPV and VC 30 min after administration. Finally, OEA reduced food intake in SDA and sham-operated rats similarly. Our findings indicate that neither intact abdominal vagal afferents nor prandial increases in GLP-1 or
Asunto(s)
Ingestión de Alimentos/efectos de los fármacos , Tracto Gastrointestinal/efectos de los fármacos , Metabolismo de los Lípidos , Ácidos Oléicos/farmacología , Saciedad/efectos de los fármacos , Animales , Dieta Alta en Grasa/efectos adversos , Ingestión de Alimentos/fisiología , Endocannabinoides , Tracto Gastrointestinal/inervación , Tracto Gastrointestinal/metabolismo , Péptido 1 Similar al Glucagón/efectos de los fármacos , Metabolismo de los Lípidos/efectos de los fármacos , Metabolismo de los Lípidos/fisiología , Hígado/efectos de los fármacos , Hígado/metabolismo , Masculino , Ácidos Oléicos/administración & dosificación , Ratas , Ratas Sprague-Dawley , Saciedad/fisiología , Nervio Vago/cirugíaRESUMEN
OBJECTIVE: This study was performed to determine the effect of fasting on reproducibility of the glucose tolerance test. Due to individual variation in animal feeding behaviors, fasting animals prior to metabolic and behavioral experiments is widely held to reduce inter-subject variation in glucose and metabolic parameters of preclinical rodent models. Reducing variability is especially important for studies where initial metabolite levels can influence the magnitude of experimental interventions, but fasting also imposes stress that may distort the variables of interest. One such intervention is the glucose tolerance test (GTT) which measures the maximum response and recovery following a bolus of exogenous glucose. We sought to investigate how fasting affects the response of individual mice to a GTT. METHODS: Using simultaneous continuous glucose monitoring (CGM) and indirect calorimetry, we quantified blood glucose, physical activity, body temperature, metabolic rates, and food consumption levels on a minute-to-minute basis in adult male mice for 4 weeks. We tested the effects of a 4-h or 18-h fast on the GTT to examine the effect of food withdrawal in light or dark photoperiods. Studies were also performed with 4-h fasting in additional mice without implanted CGM probes. RESULTS: Contrary to our expectations, a 4-h fast during the light photoperiod promotes a paradoxical increase in inter-animal variation in metabolic rate, physical activity, body temperature, glycemia, and glucose tolerance. This hyperglycemic and hyper-metabolic phenotype promotes increased corticosterone levels and is consistent with a behavioral stress response to food deprivation, even in well-fed mice. We find that mice undergoing an 18-h fast entered torpor, a hibernation-like state. In addition to low body temperature and metabolic rate, torpor is also associated with glucose levels 56 mg/dl lower than those seen in mice with ad libitum access to food. Moreover, the time spent in torpor affects the response to a GTT. CONCLUSION: Our results suggest fasting mice before glucose tolerance testing, and perhaps other experiments, can have the opposite of the intended effect where fasting can increase, rather than decrease, experimental variability.
Asunto(s)
Automonitorización de la Glucosa Sanguínea , Glucemia , Ratones , Masculino , Animales , Glucemia/metabolismo , Prueba de Tolerancia a la Glucosa , Reproducibilidad de los Resultados , GlucosaRESUMEN
Modern indirect calorimetry systems allow for high-frequency time series measurements of the factors affected by thermogenesis: energy intake and energy expenditure. These indirect calorimetry systems generate a flood of raw data recording oxygen consumption, carbon dioxide production, physical activity, and food intake among other factors. Analysis of these data requires time-consuming manual manipulation for formatting, data cleaning, quality control, and visualization. Beyond data handling, analyses of indirect calorimetry experiments require specialized statistical treatment to account for differential contributions of fat mass and lean mass to metabolic rates.Here we describe how to use the software package CalR version 1.2, to analyze indirect calorimetry data from three examples of thermogenesis, cold exposure, adrenergic agonism, and hyperthyroidism in mice, by providing standardized methods for reproducible research. CalR is a free online tool with an easy-to-use graphical user interface to import data files from the Columbus Instruments' CLAMS, Sable Systems' Promethion, and TSE Systems' PhenoMaster. Once loaded, CalR can quickly visualize experimental results and perform basic statistical analyses. We present a framework that standardizes the data structures and analyses of indirect calorimetry experiments to provide reusable and reproducible methods for the physiological data affecting body weight.
Asunto(s)
Obesidad , Termogénesis , Animales , Peso Corporal , Calorimetría Indirecta , Metabolismo Energético , RatonesRESUMEN
Cellular processes such as proliferation, differentiation and death are intrinsically dependent upon the redox status of a cell. Among other indicators of redox flux, cellular NAD(H) levels play a predominant role in transcriptional reprogramming. In addition to this, normal physiological functions of a cell are regulated in response to perturbations in NAD(H) levels (for example, due to alterations in diet/metabolism) to maintain homeostatic conditions. Cells achieve this homeostasis by reprogramming various components that include changes in chromatin structure and function (transcription). The interdependence of changes in gene expression and NAD(H) is evolutionarily conserved and is considered crucial for the survival of a species (by affecting reproductive capacity and longevity). Proteins that bind and/or use NAD(H) as a co-substrate (such as, CtBP and PARPs/Sirtuins respectively) are known to induce changes in chromatin structure and transcriptional profiles. In fact, their ability to sense perturbations in NAD(H) levels has been implicated in their roles in development, stress responses, metabolic homeostasis, reproduction and aging or age-related diseases. It is also becoming increasingly clear that both the levels/activities of these proteins and the availability of NAD(H) are equally important. Here we discuss the pivotal role of NAD(H) in controlling the functions of some of these proteins, the functional interplay between them and physiological implications during calorie restriction, energy homeostasis, circadian rhythm and aging.
Asunto(s)
Regulación de la Expresión Génica/fisiología , Homeostasis/fisiología , NAD/metabolismo , Transcripción Genética/fisiología , Envejecimiento/fisiología , Animales , Metabolismo Energético/fisiología , HumanosRESUMEN
Bile acids play crucial roles in host physiology by acting both as detergents that aid in digestion and as signaling molecules that bind to host receptors. Gut bacterial bile salt hydrolase (BSH) enzymes perform the gateway reaction leading to the conversion of host-produced primary bile acids into bacterially modified secondary bile acids. Small molecule probes that target BSHs will help elucidate the causal roles of these metabolites in host physiology. We previously reported the development of a covalent BSH inhibitor with low gut permeability. Here, we build on our previous findings and describe the development of a second-generation gut-restricted BSH inhibitor with enhanced potency, reduced off-target effects, and durable in vivo efficacy. Structure-activity relationship (SAR) studies focused on the bile acid core identified a compound, AAA-10, containing a C3-sulfonated lithocholic acid scaffold and an alpha-fluoromethyl ketone warhead as a potent pan-BSH inhibitor. This compound inhibits BSH activity in mouse and human fecal slurry, bacterial cultures, and purified BSH proteins and displays reduced toxicity against mammalian cells compared to first generation compounds. Oral administration of AAA-10 to wild-type mice for 5 days resulted in a decrease in the abundance of the secondary bile acids deoxycholic acid (DCA) and lithocholic acid (LCA) in the mouse GI tract with low systemic exposure of AAA-10, demonstrating that AAA-10 is an effective tool for inhibiting BSH activity and modulating bile acid pool composition in vivo.
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Amidohidrolasas/antagonistas & inhibidores , Proteínas Bacterianas/antagonistas & inhibidores , Inhibidores Enzimáticos/farmacología , Microbioma Gastrointestinal/efectos de los fármacos , Ácido Litocólico/análogos & derivados , Ácido Litocólico/farmacología , Animales , Bacterias/efectos de los fármacos , Ácidos y Sales Biliares/metabolismo , Línea Celular Tumoral , Inhibidores Enzimáticos/síntesis química , Inhibidores Enzimáticos/toxicidad , Heces/química , Heces/enzimología , Humanos , Ácido Litocólico/toxicidad , Masculino , Ratones Endogámicos C57BL , Estructura Molecular , Relación Estructura-ActividadRESUMEN
Maintaining a healthy body weight requires an exquisite balance between energy intake and energy expenditure. To understand the genetic and environmental factors that contribute to the regulation of body weight, an important first step is to establish the normal range of metabolic values and primary sources contributing to variability. Energy metabolism is measured by powerful and sensitive indirect calorimetry devices. Analysis of nearly 10,000 wild-type mice from two large-scale experiments revealed that the largest variation in energy expenditure is due to body composition, ambient temperature, and institutional site of experimentation. We also analyze variation in 2329 knockout strains and establish a reference for the magnitude of metabolic changes. Based on these findings, we provide suggestions for how best to design and conduct energy balance experiments in rodents. These recommendations will move us closer to the goal of a centralized physiological repository to foster transparency, rigor and reproducibility in metabolic physiology experimentation.
Maintaining a healthy weight requires the body to balance energy intake and expenditure. The body converts food to energy through a process called energy metabolism. Genetic and environmental factors can affect energy metabolism and energy balance contributing to conditions like obesity. To better understand metabolism, scientists often study mice in laboratories, but mice from different laboratories appear to convert food to energy at different rates. This makes it hard to determine what is 'normal' for mouse metabolism. These discrepancies could be due to small differences between how mice are kept in different laboratories. For example, the temperatures of the mouse cages or how active the mice are might differ depending on the laboratory. Identifying the effects of such differences is essential, but it requires looking at data from hundreds of mice. Corrigan et al. examined data from more than 30,000 mice at laboratories around the world to show that room temperatures and the amount of muscle and fat in a mouse's body have the biggest influence on energy balance. These two factors affected the metabolism of both typical mice and mice with mutations that affect their energy balance. These results suggest that it is important for scientists to report factors like room temperatures, the body make-up of the mice, or the animals' activity levels in metabolism studies. This can help scientists compare results and repeat experiments, which could speed up research into mouse metabolism. Corrigan et al. also found that other unknown factors also affect mouse metabolism in different laboratories. Further studies are needed to identify these factors.
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Adiposidad , Macrodatos , Metabolismo Energético , Obesidad/metabolismo , Adiposidad/genética , Alimentación Animal , Crianza de Animales Domésticos , Animales , Calorimetría Indirecta , Modelos Animales de Enfermedad , Metabolismo Energético/genética , Femenino , Genotipo , Masculino , Ratones Endogámicos C57BL , Ratones Noqueados , Obesidad/genética , Fenotipo , TemperaturaRESUMEN
The thiazolidinediones (TZDs) are ligands of PPARγ that improve insulin sensitivity, but their use is limited by significant side effects. Recently, we demonstrated a mechanism wherein TZDs improve insulin sensitivity distinct from receptor agonism and adipogenesis: reversal of obesity-linked phosphorylation of PPARγ at serine 273. However, the role of this modification hasn't been tested genetically. Here we demonstrate that mice encoding an allele of PPARγ that cannot be phosphorylated at S273 are protected from insulin resistance, without exhibiting differences in body weight or TZD-associated side effects. Indeed, hyperinsulinemic-euglycemic clamp experiments confirm insulin sensitivity. RNA-seq in these mice reveals reduced expression of Gdf3, a BMP family member. Ectopic expression of Gdf3 is sufficient to induce insulin resistance in lean, healthy mice. We find Gdf3 inhibits BMP signaling and insulin signaling in vitro. Together, these results highlight the diabetogenic role of PPARγ S273 phosphorylation and focus attention on a putative target, Gdf3.
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Factor 3 de Diferenciación de Crecimiento/metabolismo , Obesidad/tratamiento farmacológico , PPAR gamma/metabolismo , Tiazolidinedionas/farmacología , Alelos , Animales , Células Cultivadas , Factor 3 de Diferenciación de Crecimiento/genética , Humanos , Resistencia a la Insulina , Masculino , Ratones , Ratones Endogámicos C57BL , Obesidad/metabolismo , PPAR gamma/genética , Fosforilación/efectos de los fármacosRESUMEN
Studies indicate that modulating enterocyte metabolism might affect whole body glucose homeostasis and the development of diet-induced obesity (DIO). We tested whether enhancing enterocyte fatty acid oxidation (FAO) could protect mice from DIO and impaired glycemic control. To this end, we used mice expressing a mutant form of carnitine palmitoyltransferase-1a (CPT1mt), insensitive to inhibition by malonyl-CoA, in their enterocytes (iCPT1mt) and fed them low-fat control diet (CD) or high-fat diet (HFD) chronically. CPT1mt expression led to an upregulation of FAO in the enterocytes. On CD, iCPT1mt mice had impaired glycemic control and showed concomitant activation of lipogenesis, glycolysis and gluconeogenesis in their enterocytes. On HFD, both iCPT1mt and control mice developed DIO, but iCPT1mt mice showed improved glycemic control and reduced visceral fat mass. Together these data indicate that modulating enterocyte metabolism in iCPT1mt mice affects glycemic control in a body weight-independent, but dietary fat-dependent manner.
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Dieta Alta en Grasa , Ácidos Grasos/química , Peroxidación de Lípido , Animales , Carnitina O-Palmitoiltransferasa/genética , Carnitina O-Palmitoiltransferasa/metabolismo , Células Cultivadas , Duodeno/patología , Enterocitos/citología , Enterocitos/metabolismo , Prueba de Tolerancia a la Glucosa , Glucólisis , Lipogénesis , Ratones , Ratones Endogámicos C57BL , Ratones Transgénicos , Mitocondrias/metabolismo , Obesidad/patología , Regulación hacia ArribaRESUMEN
The conserved NAD+-dependent deacylase SIRT1 plays pivotal, sometimes contrasting, roles in diverse physiological and pathophysiological conditions. In this study, we uncover a tissue-restricted isoform of SIRT1 (SIRT1-ΔE2) that lacks exon 2 (E2). Candidate-based screening of SIRT1 substrates demonstrated that the domain encoded by this exon plays a key role in specifying SIRT1 protein-protein interactions. The E2 domain of SIRT1 was both necessary and sufficient for PGC1α binding, enhanced interaction with p53, and thus downstream functions. Since SIRT1-FL and SIRT1-ΔE2 were found to have similar intrinsic catalytic activities, we propose that the E2 domain tethers specific substrate proteins. Given the absence of SIRT1-ΔE2 in liver, our findings provide insight into the role of the E2 domain in specifying "metabolic functions" of SIRT1-FL. Identification of SIRT1-ΔE2 and the conserved specificity domain will enhance our understanding of SIRT1 and guide the development of therapeutic interventions.
Asunto(s)
Especificidad de Órganos , Sirtuina 1/química , Sirtuina 1/metabolismo , Animales , Biocatálisis , Bovinos , Secuencia Conservada , Evolución Molecular , Exones/genética , Ácidos Grasos/metabolismo , Regulación de la Expresión Génica , Ratones , Proteínas Mutantes/metabolismo , Oxidación-Reducción , Unión Proteica , Dominios Proteicos , Isoformas de Proteínas/química , Isoformas de Proteínas/genética , Isoformas de Proteínas/metabolismo , Multimerización de Proteína , Sirtuina 1/genética , Relación Estructura-Actividad , Fracciones Subcelulares/metabolismo , Transcripción Genética , Proteína p53 Supresora de Tumor/metabolismoRESUMEN
OBJECTIVE: Intestinal metabolism might play a greater role in regulating whole body metabolism than previously believed. We aimed to enhance enterocyte metabolism in mice and investigate if it plays a role in diet-induced obesity (DIO) and its comorbidities. METHODS: Using the cre-loxP system, we overexpressed the mitochondrial NAD+ dependent protein deacetylase SIRT3 in enterocytes of mice (iSIRT3 mice). We chronically fed iSIRT3 mice and floxed-SIRT3 control (S3fl) mice a low-fat, control diet (CD) or a high-fat diet (HFD) and then phenotyped the mice. RESULTS: There were no genotype differences in any of the parameters tested when the mice were fed CD. Also, iSIRT3 mice were equally susceptible to the development of DIO as S3fl mice when fed HFD. They were, however, better able than S3fl mice to regulate their blood glucose levels in response to exogenous insulin and glucose, indicating that they were protected from developing insulin resistance. This improved glucose homeostasis was accompanied by an increase in enterocyte metabolic activity and an upregulation of ketogenic gene expression in the small intestine. CONCLUSION: Enhancing enterocyte oxidative metabolism can improve whole body glucose homeostasis.
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Peso Corporal/fisiología , Enterocitos/metabolismo , Glucosa/metabolismo , Mucosa Intestinal/metabolismo , Sirtuina 3/biosíntesis , Animales , Glucemia/metabolismo , Metabolismo Energético , Enterocitos/enzimología , Intolerancia a la Glucosa/metabolismo , Homeostasis , Humanos , Insulina/metabolismo , Resistencia a la Insulina/fisiología , Mucosa Intestinal/enzimología , Ratones , Ratones Endogámicos C57BL , Ratones Transgénicos , Obesidad/genética , Obesidad/metabolismo , Sirtuina 3/genética , Sirtuina 3/metabolismoAsunto(s)
Investigación Biomédica/tendencias , Investigación Biomédica/economía , Investigación Biomédica/educación , Investigación Biomédica/normas , Educación Profesional/normas , Organización de la Financiación/normas , Revisión de la Investigación por Pares/normas , Control de Calidad , Proyectos de Investigación/normasRESUMEN
MicroRNA mir-9 is speculated to be involved in insulin secretion because of its ability to regulate exocytosis. Sirt1 is an NAD-dependent protein deacetylase and a critical factor in the modulation of cellular responses to altered metabolic flux. It has also been shown recently to control insulin secretion from pancreatic ß-islets. However, little is known about the regulation of Sirt1 and mir-9 levels in pancreatic ß-cells, particularly during glucose-dependent insulin secretion. In this article, we report that mir-9 and Sirt1 protein levels are actively regulated in vivo in ß-islets during glucose-dependent insulin secretion. Our data also demonstrates that mir-9 targets and regulates Sirt1 expression in insulin-secreting cells. This targeting is relevant in pancreatic ß-islets, where we show a reduction in Sirt1 protein levels when mir-9 expression is high during glucose-dependent insulin secretion. This functional interplay between insulin secretion, mir-9 and Sirt1 expression could be relevant in diabetes. It also highlights the crosstalk between an NAD-dependent protein deacetylase and microRNA in pancreatic ß-cells.