ABSTRACT
Our circadian world shapes much of metabolic physiology. In mice â¼40% of the light and â¼80% of the dark phase time is characterized by bouts of increased energy expenditure (EE). These ultradian bouts have a higher body temperature (Tb) and thermal conductance and contain virtually all of the physical activity and awake time. Bout status is a better classifier of mouse physiology than photoperiod, with ultradian bouts superimposed on top of the circadian light/dark cycle. We suggest that the primary driver of ultradian bouts is a brain-initiated transition to a higher defended Tb of the active/awake state. Increased energy expenditure from brown adipose tissue, physical activity, and cardiac work combine to raise Tb from the lower defended Tb of the resting/sleeping state. Thus, unlike humans, much of mouse metabolic physiology is episodic with large ultradian increases in EE and Tb that correlate with the active/awake state and are poorly aligned with circadian cycling.
Subject(s)
Body Temperature , Circadian Rhythm , Energy Metabolism , Photoperiod , Ultradian Rhythm , Animals , Mice , Adipose Tissue, Brown/metabolism , Adipose Tissue, Brown/physiology , Body Temperature/physiology , Circadian Rhythm/physiology , Energy Metabolism/physiology , Sleep/physiology , Ultradian Rhythm/physiology , Wakefulness/physiologyABSTRACT
While phosphodiesterase-5 inhibition (PED5i) may prevent hypertrophy and failure in pressure-overloaded heart in an experimental model, the impact of PDE5i on volume-overload (VO)-induced hypertrophy is unknown. It is also unclear whether the hypertrophied right ventricle (RV) and left ventricle (LV) differ in their responsiveness to long-term PDE5i and if this therapy affects renal function. The goal of this study was to elucidate the effect of PDE5i treatment in VO due to aorto-caval fistula (ACF) and to compare PDE5i treatment with standard heart failure (HF) therapy with angiotensin-converting enzyme inhibitor (ACEi). ACF/sham procedure was performed on male HanSD rats aged 8 weeks. ACF animals were randomized for PDE5i sildenafil, ACEi trandolapril, or placebo treatments. After 20 weeks, RV and LV function (echocardiography, pressure-volume analysis), myocardial gene expression, and renal function were studied. Separate rat cohorts served for survival analysis. ACF led to biventricular eccentric hypertrophy (LV: +68%, RV: +145%), increased stroke work (LV: 3.6-fold, RV: 6.7-fold), and reduced load-independent systolic function (PRSW, LV: -54%, RV: -51%). Both ACF ventricles exhibited upregulation of the genes of myocardial stress and glucose metabolism. ACEi but not PDE5i attenuated pulmonary congestion, LV remodeling, albuminuria, and improved survival (median survival in ACF/ACEi was 41 weeks vs. 35 weeks in ACF/placebo, p = .02). PDE5i increased cyclic guanosine monophosphate levels in the lungs, but not in the RV, LV, or kidney. PDE5i did not improve survival rate and cardiac and renal function in ACF rats, in contrast to ACEi. VO-induced HF is not responsive to PDE5i therapy.
Subject(s)
Angiotensin-Converting Enzyme Inhibitors , Heart Failure , Phosphodiesterase 5 Inhibitors , Ventricular Remodeling , Animals , Male , Rats , Angiotensin-Converting Enzyme Inhibitors/pharmacology , Cardiomegaly/drug therapy , Heart Failure/drug therapy , Phosphodiesterase 5 Inhibitors/pharmacologyABSTRACT
OBJECTIVE: Physical activity is a major component of total energy expenditure (TEE) that exhibits extreme variability in mice. Our objective was to construct a general, physiology-based model of TEE to accurately quantify the energy cost of physical activity. METHODS: Spontaneous home cage physical activity, body temperature, TEE, and energy intake were measured with frequent sampling. The energy cost of activity was modeled considering six contributors to TEE (basal metabolic rate, thermic effect of food, body temperature, cold induced thermogenesis, physical activity, and body weight). An ambient temperature of 35 °C was required to remove the contribution from cold induced thermogenesis. Basal metabolic rate was adjusted for body temperature using a Q10 temperature coefficient. RESULTS: We developed a TEE model that robustly explains 70-80% of the variance in TEE at 35 °C while fitting only two parameters, the basal metabolic rate and the mass-specific energy cost per unit of physical activity, which averaged 60 cal/km/g body weight. In Ucp1-/- mice the activity cost was elevated by 60%, indicating inefficiency and increased muscle thermogenesis. The diurnal rhythm in TEE was quantitatively explained by the combined diurnal differences in physical activity, body temperature, and energy intake. Incorporating body temperature into human basal metabolic rate measurements significantly reduced the inter-individual variation. CONCLUSIONS: The physiology-based model of TEE allows quantifying the energy cost of physical activity. While applied here to mice, the model should be generally valid across species. Due to the effect of body temperature, we suggest that basal metabolic rate measurements be corrected to a reference body temperature, including in humans. Having an accurate cost of physical activity allows mechanistic dissection of disorders of energy homeostasis, including obesity.
Subject(s)
Basal Metabolism , Energy Metabolism , Humans , Animals , Mice , Energy Metabolism/physiology , Body Weight/physiology , Basal Metabolism/physiology , Obesity , Thermogenesis/physiologyABSTRACT
Type 2 diabetes mellitus represents a major health problem with increasing prevalence worldwide. Limited efficacy of current therapies has prompted a search for novel therapeutic options. Here we show that treatment of pre-diabetic mice with mitochondrially targeted tamoxifen, a potential anti-cancer agent with senolytic activity, improves glucose tolerance and reduces body weight with most pronounced reduction of visceral adipose tissue due to reduced food intake, suppressed adipogenesis and elimination of senescent cells. Glucose-lowering effect of mitochondrially targeted tamoxifen is linked to improvement of type 2 diabetes mellitus-related hormones profile and is accompanied by reduced lipid accumulation in liver. Lower senescent cell burden in various tissues, as well as its inhibitory effect on pre-adipocyte differentiation, results in lower level of circulating inflammatory mediators that typically enhance metabolic dysfunction. Targeting senescence with mitochodrially targeted tamoxifen thus represents an approach to the treatment of type 2 diabetes mellitus and its related comorbidities, promising a complex impact on senescence-related pathologies in aging population of patients with type 2 diabetes mellitus with potential translation into the clinic.
Subject(s)
Diabetes Mellitus, Experimental , Diabetes Mellitus, Type 2 , Aged , Animals , Diabetes Mellitus, Experimental/complications , Diabetes Mellitus, Experimental/drug therapy , Diabetes Mellitus, Type 2/complications , Diabetes Mellitus, Type 2/drug therapy , Glucose/metabolism , Humans , Mice , Obesity/complications , Obesity/drug therapy , Obesity/metabolism , Tamoxifen/pharmacology , Tamoxifen/therapeutic useABSTRACT
(1) Background: empagliflozin, sodium-glucose co-transporter 2 (SGLT-2) inhibitor, is an effective antidiabetic agent with strong cardio- and nephroprotective properties. The mechanisms behind its cardio- and nephroprotection are still not fully clarified. (2) Methods: we used male hereditary hypertriglyceridemic (hHTG) rats, a non-obese model of dyslipidaemia, insulin resistance, and endothelial dysfunction fed standard diet with or without empagliflozin for six weeks to explore the molecular mechanisms of empagliflozin effects. Nuclear magnetic resonance (NMR)-based metabolomics; quantitative PCR of relevant genes involved in lipid and glucose metabolism, or senescence; glucose and palmitic acid oxidation in isolated tissues and cell lines of adipocytes and hepatocytes were used. (3) Results: empagliflozin inhibited weight gain and decreased adipose tissue weight, fasting blood glucose, and triglycerides and increased HDL-cholesterol. It also improved insulin sensitivity in white fat. NMR spectroscopy identified higher plasma concentrations of ketone bodies, ketogenic amino acid leucine and decreased levels of pyruvate and alanine. In the liver, adipose tissue and kidney, empagliflozin up-regulated expression of genes involved in gluconeogenesis and down-regulated expression of genes involved in lipogenesis along with reduction of markers of inflammation, oxidative stress and cell senescence. (4) Conclusion: multiple positive effects of empagliflozin, including reduced cell senescence and oxidative stress, could contribute to its long-term cardio- and nephroprotective actions.
Subject(s)
Adipose Tissue/metabolism , Benzhydryl Compounds/administration & dosage , Cellular Senescence/drug effects , Gluconeogenesis/drug effects , Glucosides/administration & dosage , Hypertriglyceridemia/drug therapy , Hypertriglyceridemia/metabolism , Hypoglycemic Agents/administration & dosage , Kidney/metabolism , Lipogenesis/drug effects , Liver/metabolism , Oxidative Stress/drug effects , Sodium-Glucose Transporter 2 Inhibitors/administration & dosage , 3T3-L1 Cells , Administration, Oral , Animals , Cell Survival/drug effects , Disease Models, Animal , Down-Regulation/drug effects , Dyslipidemias/drug therapy , Gluconeogenesis/genetics , Hep G2 Cells , Humans , Insulin Resistance , Lipogenesis/genetics , Male , Mice , Rats , Treatment Outcome , Up-Regulation/drug effects , Weight Gain/drug effectsABSTRACT
OBJECTIVE: To improve understanding of mouse energy homeostasis and its applicability to humans, we quantitated the effects of housing density on mouse thermal physiology in both sexes. METHODS: Littermate wild type and Brs3-null mice were single- or group- (three per cage) housed and studied by indirect calorimetry with continuous measurement of core body temperature, energy expenditure, physical activity, and food intake. RESULTS: At 23 °C, below thermoneutrality, single-housed males had a lower body temperature and unchanged metabolic rate compared to group-housed controls. In contrast, single-housed females maintained a similar body temperature to group-housed controls by increasing their metabolic rate. With decreasing ambient temperature below 27 °C, only group-housed mice decreased their heat conductance, likely due to huddling, thus interfering with the energy expenditure vs ambient temperature relationship described by Scholander. In a hot environment (35 °C), the single-housed mice were less heat stressed. Upon fasting, single-housed mice had larger reductions in body temperature, with male mice having more torpor episodes of similar duration and female mice having a similar number of torpor episodes that lasted longer. Qualitatively, the effects of housing density on thermal physiology of Brs3-null mice generally mimicked the effects in controls. CONCLUSIONS: Single housing is more sensitive than group housing for detecting thermal physiology phenotypes. Single housing increases heat loss and amplifies the effects of fasting or a cold environment. Male and female mice utilize different thermoregulatory strategies to respond to single housing.
Subject(s)
Body Composition/physiology , Body Temperature , Receptors, Bombesin/metabolism , Temperature , Animals , Female , Male , Mice , Mice, Inbred C57BL , Mice, Knockout , Receptors, Bombesin/deficiencyABSTRACT
The preoptic area (POA) is a key brain region for regulation of body temperature (Tb), dictating thermogenic, cardiovascular, and behavioral responses that control Tb. Previously characterized POA neuronal populations all reduced Tb when activated. Using mice, we now identify POA neurons expressing bombesin-like receptor 3 (POABRS3) as a population whose activation increased Tb; inversely, acute inhibition of these neurons reduced Tb. POABRS3 neurons that project to either the paraventricular nucleus of the hypothalamus or the dorsomedial hypothalamus increased Tb, heart rate, and blood pressure via the sympathetic nervous system. Long-term inactivation of POABRS3 neurons caused increased Tb variability, overshooting both increases and decreases in Tb set point, with RNA expression profiles suggesting multiple types of POABRS3 neurons. Thus, POABRS3 neuronal populations regulate Tb and heart rate, contribute to cold defense, and fine-tune feedback control of Tb. These findings advance understanding of homeothermy, a defining feature of mammalian biology.
Subject(s)
Body Temperature Regulation , Heart Rate , Neurons/physiology , Preoptic Area/metabolism , Receptors, Bombesin/metabolism , Animals , Body Temperature/genetics , Body Temperature Regulation/genetics , Heart Rate/genetics , Male , Mice , Mice, 129 Strain , Mice, Inbred C57BL , Mice, Transgenic , Neurons/cytology , Neurons/metabolism , Preoptic Area/cytology , Receptors, Bombesin/genetics , Signal Transduction/genetics , Sympathetic Nervous System/physiology , Thermogenesis/geneticsABSTRACT
Understanding mouse thermal physiology informs the usefulness of mice as models of human disease. It is widely assumed that the mouse tail contributes greatly to heat loss (as it does in rat), but this has not been quantitated. We studied C57BL/6J mice after tail amputation. Tailless mice housed at 22°C did not differ from littermate controls in body weight, lean or fat content, or energy expenditure. With acute changes in ambient temperature from 19 to 39°C, tailless and control mice demonstrated similar body temperatures (Tb), metabolic rates, and heat conductances and no difference in thermoneutral point. Treatment with prazosin, an α1-adrenergic antagonist and vasodilator, increased tail temperature in control mice by up to 4.8 ± 0.8°C. Comparing prazosin treatment in tailless and control mice suggested that the tail's contribution to total heat loss was a nonsignificant 3.4%. Major heat stress produced by treatment at 30°C with CL316243, a ß3-adrenergic agonist, increased metabolic rate and Tb and, at a matched increase in metabolic rate, the tailless mice showed a 0.72 ± 0.14°C greater Tb increase and 7.6% lower whole body heat conductance. Thus, the mouse tail is a useful biomarker of vasodilation and thermoregulation, but in our experiments contributes only 5-8% of whole body heat dissipation, less than the 17% reported for rat. Heat dissipation through the tail is important under extreme scenarios such as pharmacological activation of brown adipose tissue; however, non-tail contributions to heat loss may have been underestimated in the mouse.
Subject(s)
Body Temperature Regulation/physiology , Models, Animal , Tail/physiology , Adrenergic alpha-1 Receptor Antagonists , Amputation, Surgical , Animals , Body Composition/physiology , Body Surface Area , Body Temperature Regulation/drug effects , Body Weight/physiology , Energy Metabolism/physiology , Heat-Shock Response , Mice , Mice, Inbred C57BL , Prazosin/pharmacology , Rats , Tail/surgery , Vasodilation/physiologyABSTRACT
Human and mouse thermal physiology differ due to dissimilar body sizes. Unexpectedly, in mice we found no ambient temperature zone where both metabolic rate and body temperature were constant. Body temperature began increasing once cold-induced thermogenesis was no longer required. This result reproduced in male, female, C57BL/6J, 129, chow-fed, diet-induced obese, and ob/ob mice as well as Trpv1-/-;Trpm8-/-;Trpa1-/- mice lacking thermal sensory channels. During the resting-light phase, the energy expenditure minimum spanned â¼4°C of ambient temperature, whereas in the active-dark phase it approximated a point. We propose the concept of a thermoneutral point (TNP), a discrete ambient temperature below which energy expenditure increases and above which body temperature increases. Humans do not have a TNP. As studied, the mouse TNP is â¼29°C in light phase and â¼33°C in dark phase. These observations inform how thermoneutrality is defined and how mice are used to model human energy physiology and drug development.
Subject(s)
Body Temperature Regulation/physiology , Energy Metabolism/physiology , Thermogenesis/physiology , Adipose Tissue/metabolism , Adipose Tissue, Brown/metabolism , Animals , Body Composition/physiology , Body Size/physiology , Body Temperature/physiology , Body Weight/physiology , Cold Temperature , Energy Intake , Male , Mice , Mice, 129 Strain , Mice, Inbred C57BL , Obesity/metabolism , TemperatureABSTRACT
Nicotinamide phosphoribosyltransferase (NAMPT) is located in both the nucleus and cytoplasm and has multiple biological functions including catalyzing the rate-limiting step in NAD synthesis. Moreover, up-regulated NAMPT expression has been observed in many cancers. However, the determinants and regulation of NAMPT's nuclear transport are not known. Here, we constructed a GFP-NAMPT fusion protein to study NAMPT's subcellular trafficking. We observed that in unsynchronized 3T3-L1 preadipocytes, 25% of cells had higher GFP-NAMPT fluorescence in the cytoplasm, and 62% had higher GFP-NAMPT fluorescence in the nucleus. In HepG2 hepatocytes, 6% of cells had higher GFP-NAMPT fluorescence in the cytoplasm, and 84% had higher GFP-NAMPT fluorescence in the nucleus. In both 3T3-L1 and HepG2 cells, GFP-NAMPT was excluded from the nucleus immediately after mitosis and migrated back into it as the cell cycle progressed. In HepG2 cells, endogenous, untagged NAMPT displayed similar changes with the cell cycle, and in nonmitotic cells, GFP-NAMPT accumulated in the nucleus. Similarly, genotoxic, oxidative, or dicarbonyl stress also caused nuclear NAMPT localization. These interventions also increased poly(ADP-ribosyl) polymerase and sirtuin activity, suggesting an increased cellular demand for NAD. We identified a nuclear localization signal in NAMPT and amino acid substitution in this sequence (424RSKK to ASGA), which did not affect its enzymatic activity, blocked nuclear NAMPT transport, slowed cell growth, and increased histone H3 acetylation. These results suggest that NAMPT is transported into the nucleus where it presumably increases NAD synthesis required for cell proliferation. We conclude that specific inhibition of NAMPT transport into the nucleus might be a potential avenue for managing cancer.
Subject(s)
Cell Nucleus/metabolism , Nicotinamide Phosphoribosyltransferase/metabolism , 3T3-L1 Cells , Acrylamides/pharmacology , Active Transport, Cell Nucleus , Animals , Cell Cycle Checkpoints , Cell Proliferation , Cell Survival/drug effects , Cytoplasm/metabolism , Hep G2 Cells , Histones/metabolism , Humans , Mice , Mutagenesis, Site-Directed , NAD/metabolism , Nicotinamide Phosphoribosyltransferase/chemistry , Nicotinamide Phosphoribosyltransferase/genetics , Oxidative Stress , Piperidines/pharmacology , Poly(ADP-ribose) Polymerases/metabolism , Recombinant Fusion Proteins/chemistry , Recombinant Fusion Proteins/genetics , Recombinant Fusion Proteins/metabolism , Sirtuins/metabolismABSTRACT
Bombesin-like receptor 3 (BRS3) is an orphan G-protein-coupled receptor that regulates energy homeostasis and heart rate. We report that acute activation of Brs3-expressing neurons in the dorsomedial hypothalamus (DMHBrs3) increased body temperature (Tb), brown adipose tissue temperature, energy expenditure, heart rate, and blood pressure, with no effect on food intake or physical activity. Conversely, activation of Brs3 neurons in the paraventricular nucleus of the hypothalamus had no effect on Tb or energy expenditure, but suppressed food intake. Inhibition of DMHBrs3 neurons decreased Tb and energy expenditure, suggesting a necessary role in Tb regulation. We found that the preoptic area provides major input (excitatory and inhibitory) to DMHBrs3 neurons. Optogenetic stimulation of DMHBrs3 projections to the raphe pallidus increased Tb. Thus, DMHBrs3âraphe pallidus neurons regulate Tb, energy expenditure, and heart rate, and Brs3 neurons in the paraventricular nucleus of the hypothalamus regulate food intake. Brs3 expression is a useful marker for delineating energy metabolism regulatory circuitry.
Subject(s)
Body Temperature/physiology , Dorsomedial Hypothalamic Nucleus/metabolism , Eating/physiology , Energy Metabolism/physiology , Heart Rate/physiology , Neurons/metabolism , Receptors, Bombesin/metabolism , Animals , Male , MiceABSTRACT
Brown adipose tissue (BAT) has been suggested to play an important role in lipid and glucose metabolism in rodents and possibly also in humans. In the current study, we used genetic and correlation analyses in the BXH/HXB recombinant inbred (RI) strains, derived from Brown Norway (BN) and spontaneously hypertensive rats (SHR), to identify genetic determinants of BAT function. Linkage analyses revealed a quantitative trait locus (QTL) associated with interscapular BAT mass on chromosome 4 and two closely linked QTLs associated with glucose oxidation and glucose incorporation into BAT lipids on chromosome 2. Using weighted gene coexpression network analysis (WGCNA) we identified 1,147 gene coexpression modules in the BAT from BXH/HXB rats and mapped their module eigengene QTLs. Through an unsupervised analysis, we identified modules related to BAT relative mass and function. The Coral4.1 coexpression module is associated with BAT relative mass (includes Cd36 highly connected gene), and the Darkseagreen coexpression module is associated with glucose incorporation into BAT lipids (includes Hiat1, Fmo5, and Sort1 highly connected transcripts). Because multiple statistical criteria were used to identify candidate modules, significance thresholds for individual tests were not adjusted for multiple comparisons across modules. In summary, a systems genetic analysis using genomic and quantitative transcriptomic and physiological information has produced confirmation of several known genetic factors and significant insight into novel genetic components functioning in BAT and possibly contributing to traits characteristic of the metabolic syndrome.
Subject(s)
Adipose Tissue, Brown/metabolism , Animals , Genetic Predisposition to Disease/genetics , Glucose/metabolism , Male , Metabolic Syndrome/genetics , Metabolic Syndrome/metabolism , Quantitative Trait Loci/genetics , Rats , Rats, Inbred BN , Rats, Inbred SHRABSTRACT
Chronic low-grade inflammation plays an important role in the pathogenesis of insulin resistance. In the current study, we tested the effects of salsalate, a non-steroidal anti-inflammatory drug, in an animal model of inflammation and metabolic syndrome using spontaneously hypertensive rats (SHR) that transgenically express human C-reactive protein (SHR-CRP rats). We treated 15-month-old male transgenic SHR-CRP rats and nontransgenic SHR with salsalate (200 mg/kg/day) mixed as part of a standard diet for 4 weeks. A corresponding untreated control group of male transgenic SHR-CRP and SHR rats were fed a standard diet without salsalate. In the SHR-CRP transgenic strain, salsalate treatment decreased circulating concentrations of the inflammatory markers TNF-α and MCP-1, reduced oxidative stress in the liver and kidney, increased sensitivity of skeletal muscles to insulin action and improved tolerance to glucose. In SHR controls with no CRP-induced inflammation, salsalate treatment reduced body weight, decreased concentrations of serum free fatty acids and total and HDL cholesterol and increased palmitate oxidation and incorporation in brown adipose tissue. Salsalate regulated inflammation by affecting the expression of genes from MAPK signalling and NOD-like receptor signalling pathways and lipid metabolism by affecting hepatic expression of genes that favour lipid oxidation from PPAR-α signalling pathways. These findings suggest that salsalate has metabolic effects beyond suppressing inflammation.
Subject(s)
C-Reactive Protein/biosynthesis , Hypertension/drug therapy , Inflammation/drug therapy , Salicylates/administration & dosage , Adipose Tissue, Brown/metabolism , Animals , Animals, Genetically Modified/genetics , C-Reactive Protein/genetics , Fatty Acids, Nonesterified/metabolism , Humans , Hypertension/genetics , Hypertension/pathology , Inflammation/genetics , Inflammation/pathology , Insulin Resistance/genetics , Lipid Metabolism/drug effects , Liver/metabolism , Metabolic Syndrome/drug therapy , Metabolic Syndrome/genetics , Metabolic Syndrome/pathology , NLR Proteins/biosynthesis , Oxidative Stress/drug effects , PPAR alpha/biosynthesis , Rats , Tumor Necrosis Factor-alpha/biosynthesisABSTRACT
The spontaneously hypertensive rat (SHR), one of the most widely used model of essential hypertension, is predisposed to left ventricular hypertrophy, myocardial fibrosis, and metabolic disturbances. Recently, quantitative trait loci influencing blood pressure, left ventricular mass, and heart interstitial fibrosis were genetically isolated within a minimal congenic subline that contains only 7 genes, including mutant Plzf (promyelocytic leukemia zinc finger) candidate gene. To identify Plzf as a quantitative trait gene, we targeted Plzf in the SHR using the transcription activator-like effector nuclease technique and obtained SHR line harboring targeted Plzf gene with a premature stop codon. Because the Plzf targeted allele is semilethal, morphologically normal heterozygous rats were used for metabolic and hemodynamic analyses. SHR-Plzf+/- heterozygotes versus SHR wild-type controls exhibited reduced body weight and relative weight of epididymal fat, lower serum and liver triglycerides and cholesterol, and better glucose tolerance. In addition, SHR-Plzf+/- rats exhibited significantly increased sensitivity of adipose and muscle tissue to insulin action when compared with wild-type controls. Blood pressure was comparable in SHR versus SHR-Plzf+/-; however, there was significant amelioration of cardiomyocyte hypertrophy and cardiac fibrosis in SHR-Plzf+/- rats. Gene expression profiles in the liver and expression of selected genes in the heart revealed differentially expressed genes that play a role in metabolic pathways, PPAR (peroxisome proliferator-activated receptor) signaling, and cell cycle regulation. These results provide evidence for an important role of Plzf in regulation of metabolic and cardiac traits in the rat and suggest a cross talk between cell cycle regulators, metabolism, cardiac hypertrophy, and fibrosis.
Subject(s)
Gene Expression Profiling , Hypertension/genetics , Hypertension/pathology , Hypertrophy, Left Ventricular/genetics , Kruppel-Like Transcription Factors/genetics , Alleles , Analysis of Variance , Animals , Blood Pressure Determination , Blotting, Western , Cells, Cultured , Down-Regulation , Essential Hypertension , Fibrosis/genetics , Hypertrophy, Left Ventricular/physiopathology , Lipid Metabolism/genetics , Male , Myocytes, Cardiac/metabolism , Phenotype , Promyelocytic Leukemia Zinc Finger Protein , Quantitative Trait Loci , Rats , Rats, Inbred SHR , Real-Time Polymerase Chain Reaction/methodsABSTRACT
Resistin has been originally identified as an adipokine that links obesity to insulin resistance in mice. In our previous studies in spontaneously hypertensive rats (SHR) expressing a nonsecreted form of mouse resistin (Retn) transgene specifically in adipose tissue (SHR-Retn), we have observed an increased lipolysis and serum free fatty acids, ectopic fat accumulation in muscles, and insulin resistance. Recently, brown adipose tissue (BAT) has been suggested to play an important role in the pathogenesis of metabolic disturbances. In the current study, we have analyzed autocrine effects of transgenic resistin on BAT glucose and lipid metabolism and mitochondrial function in the SHR-Retn vs. nontransgenic SHR controls. We observed that interscapular BAT isolated from SHR-Retn transgenic rats compared with SHR controls showed a lower relative weight (0.71 ± 0.05 vs. 0.91 ± 0.08 g/100 g body wt, P < 0.05), significantly reduced both basal and insulin stimulated incorporation of palmitate into BAT lipids (658 ± 50 vs. 856 ± 45 and 864 ± 47 vs. 1,086 ± 35 nmol/g/2 h, P ≤ 0.01, respectively), and significantly decreased palmitate oxidation (37.6 ± 4.5 vs. 57 ± 4.1 nmol/g/2 h, P = 0.007) and glucose oxidation (277 ± 34 vs. 458 ± 38 nmol/g/2 h, P = 0.001). In addition, in vivo microPET imaging revealed significantly reduced (18)F-FDG uptake in BAT induced by exposure to cold in SHR-Retn vs. control SHR (232 ± 19 vs. 334 ± 22 kBq/ml, P < 0.05). Gene expression profiles in BAT identified differentially expressed genes involved in skeletal muscle and connective tissue development, inflammation and MAPK and insulin signaling. These results provide evidence that autocrine effects of resistin attenuate differentiation and activity of BAT and thus may play a role in the pathogenesis of insulin resistance in the rat.
Subject(s)
Adipose Tissue, Brown/metabolism , Autocrine Communication/physiology , Glucose/metabolism , Palmitates/metabolism , Resistin/genetics , Adipose Tissue, Brown/physiology , Animals , Autocrine Communication/genetics , Fatty Acids, Nonesterified/metabolism , Insulin/metabolism , Insulin Resistance/physiology , Lipid Metabolism/physiology , Male , Mice , Mice, Inbred BALB C , Mitochondria/genetics , Mitochondria/physiology , Muscle, Skeletal/metabolism , Muscle, Skeletal/physiology , Obesity/metabolism , Obesity/physiopathology , Oxidation-Reduction , Rats , Rats, Inbred SHR , Rats, Transgenic , Transcriptome/geneticsABSTRACT
Inflammation and oxidative and dicarbonyl stress play important roles in the pathogenesis of type 2 diabetes. Metformin is the first-line drug of choice for the treatment of type 2 diabetes because it effectively suppresses gluconeogenesis in the liver. However, its "pleiotropic" effects remain controversial. In the current study, we tested the effects of metformin on inflammation, oxidative and dicarbonyl stress in an animal model of inflammation and metabolic syndrome, using spontaneously hypertensive rats that transgenically express human C-reactive protein (SHR-CRP). We treated 8-month-old male transgenic SHR-CRP rats with metformin (5 mg/kg/day) mixed as part of a standard diet for 4 weeks. A corresponding untreated control group of male transgenic SHR-CRP rats were fed a standard diet without metformin. In a similar fashion, we studied a group of nontransgenic SHR treated with metformin and an untreated group of nontransgenic SHR controls. In each group, we studied 6 animals. Parameters of glucose and lipid metabolism and oxidative and dicarbonyl stress were measured using standard methods. Gene expression profiles were determined using Affymetrix GeneChip Arrays. Statistical significance was evaluated by two-way ANOVA. In the SHR-CRP transgenic strain, we found that metformin treatment decreased circulating levels of inflammatory response marker IL-6, TNFα and MCP-1 while levels of human CRP remained unchanged. Metformin significantly reduced oxidative stress (levels of conjugated dienes and TBARS) and dicarbonyl stress (levels of methylglyoxal) in left ventricles, but not in kidneys. No significant effects of metformin on oxidative and dicarbonyl stress were observed in SHR controls. In addition, metformin treatment reduced adipose tissue lipolysis associated with human CRP. Possible molecular mechanisms of metformin action-studied by gene expression profiling in the liver-revealed deregulated genes from inflammatory and insulin signaling, AMP-activated protein kinase (AMPK) signaling and gluconeogenesis pathways. It can be concluded that in the presence of high levels of human CRP, metformin protects against inflammation and oxidative and dicarbonyl stress in the heart, but not in the kidney. Accordingly, these cardioprotective effects of metformin might be especially effective in diabetic patients with high levels of CRP.
Subject(s)
C-Reactive Protein/biosynthesis , Lipolysis/drug effects , Metformin/pharmacology , Myocardium/metabolism , Oxidative Stress/drug effects , Pyruvaldehyde/metabolism , AMP-Activated Protein Kinases/genetics , AMP-Activated Protein Kinases/metabolism , Animals , C-Reactive Protein/genetics , Cytokines/metabolism , Gene Expression , Glucose/metabolism , Heart Ventricles/metabolism , Humans , Lipolysis/genetics , Male , Oxidative Stress/genetics , Rats , Rats, Inbred SHR , Rats, TransgenicABSTRACT
Metabolism of homocysteine and other sulfur amino acids is closely associated with metabolism of folates. In this study, we analyzed the possible role of folates and sulfur amino acids in the development of features of the metabolic syndrome in the BXH/HXB recombinant inbred strains derived from the spontaneously hypertensive rat (SHR) and Brown Norway progenitors. We mapped a quantitative trait locus for cysteine concentrations to a region of chromosome 1 that contains a cis-acting expression quantitative trait locus regulating mRNA levels of folate receptor 1 (Folr1) in the kidney. Sequence analysis revealed a deletion variant in the Folr1 promoter region of the SHR. Transfection studies demonstrated that the SHR-promoter region of Folr1 is less effective in driving luciferase reporter gene expression than the Brown Norway promoter region of Folr1. Results in the SHR.BN-chr.1 congenic strain confirmed that the SHR variant in Folr1 cosegregates with markedly reduced renal expression of Folr1 and renal folate reabsorption, decreased serum levels of folate, increased serum levels of cysteine and homocysteine, increased adiposity, ectopic fat accumulation in liver and muscle, reduced muscle insulin sensitivity, and increased blood pressure. Transgenic rescue experiments performed by expressing a Folr1 transgene in the SHR ameliorated most of the metabolic disturbances. These findings are consistent with the hypothesis that inherited variation in the expression of Folr1 in the kidney influences the development of the metabolic syndrome and constitutes a previously unrecognized genetic mechanism that may contribute to increased risk for diabetes mellitus and cardiovascular disease.
Subject(s)
Folate Receptor 1/genetics , Gene Expression Regulation , Genetic Predisposition to Disease , Hypertension/complications , Kidney/metabolism , Metabolic Syndrome/genetics , RNA/genetics , Animals , Blood Pressure/physiology , Folate Receptor 1/biosynthesis , Genetic Variation , Hypertension/genetics , Hypertension/metabolism , Male , Metabolic Syndrome/etiology , Metabolic Syndrome/metabolism , Rats , Rats, Inbred BN , Rats, Inbred SHR , Real-Time Polymerase Chain ReactionABSTRACT
BACKGROUND: The marine n-3 fatty acids, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) exert numerous beneficial effects on health, but their potency to improve treatment of type 2 diabetic (T2D) patients remains poorly characterized. We aimed to evaluate the effect of a combination intervention using EPA + DHA and the insulin-sensitizing drug pioglitazone in overweight/obese T2D patients already treated with metformin. METHODS: In a parallel-group, four-arm, randomized trial, 69 patients (66 % men) were assigned to 24-week-intervention using: (i) corn oil (5 g/day; Placebo), (ii) pioglitazone (15 mg/day; Pio), (iii) EPA + DHA concentrate (5 g/day, containing ~2.8 g EPA + DHA; Omega-3), or (iv) pioglitazone and EPA + DHA concentrate (Pio& Omega-3). Data from 60 patients were used for the final evaluation. At baseline and after intervention, various metabolic markers, adiponectin and cytokines were evaluated in serum using standard procedures, EPA + DHA content in serum phospholipids was evaluated using shotgun lipidomics and mass spectrometry, and hyperinsulinemic-euglycemic clamp and meal test were also performed. Indirect calorimetry was conducted after the intervention. Primary endpoints were changes from baseline in insulin sensitivity evaluated using hyperinsulinemic-euglycemic clamp and in serum triacylglycerol concentrations in fasting state. Secondary endpoints included changes in fasting glycemia and glycated hemoglobin (HbA1c), changes in postprandial glucose, free fatty acid and triacylglycerol concentrations, metabolic flexibility assessed by indirect calorimetry, and inflammatory markers. RESULTS: Omega-3 and Pio& Omega-3 increased EPA + DHA content in serum phospholipids. Pio and Pio& Omega-3 increased body weight and adiponectin levels. Both fasting glycemia and HbA1c were increased by Omega-3, but were unchanged by Pio& Omega-3. Insulin sensitivity was not affected by Omega-3, while it was improved by Pio& Omega-3. Fasting triacylglycerol concentrations and inflammatory markers were not significantly affected by any of the interventions. Lipid metabolism in the meal test and metabolic flexibility were additively improved by Pio& Omega-3. CONCLUSION: Besides preventing a modest negative effect of n-3 fatty acids on glycemic control, the combination of pioglitazone and EPA + DHA can be used to improve lipid metabolism in T2D patients on stable metformin therapy. TRIAL REGISTRATION: EudraCT number 2009-011106-42.
ABSTRACT
1. To compare the effectiveness of different drug forms of silymarin: standardized extract of silymarin (SS), micronized silymarin (MS) and silymarin in the form of phytosome (PS) on dyslipidemia and liver fat accumulation in a model of metabolic syndrome, in non-obese hereditary hypertriglyceridemic rats. The second aim of this study was to slightly uncover the silymarin action on enzymes and proteins involved in cholesterol metabolism and excretion. 2. Silymarin administered to hereditary hypertriglyceridemic rats as dietary supplements (1%) for 4 weeks significantly lowered the plasma levels of triglycerides, total cholesterol and markedly increased HDL cholesterol level. Western blot analyses showed significant increase in the protein expression of CYP7A1 and CYP4A and increase in protein expression of selected ABC transporters. Silymarin in the form of phytosome and micronized silymarin were more effective forms of silymarin. 3. These findings suggest that silymarin may favorably affect the metabolism of cholesterol and triglycerides in rats with metabolic syndrome. Raising HDL levels suggests potentially important anti-atherogenic effect of silymarin. The changes in expression of cytochromes P450 and ABC transporters involved in cholesterol metabolism and excretion could be partially responsible for the hypolipidemic effect of silymarin.
Subject(s)
Dyslipidemias/complications , Dyslipidemias/drug therapy , Metabolic Syndrome/complications , Metabolic Syndrome/drug therapy , Silymarin/therapeutic use , ATP-Binding Cassette Transporters/metabolism , Animals , Biological Availability , Blotting, Western , Cholesterol 7-alpha-Hydroxylase/metabolism , Cytochrome P-450 CYP4A/metabolism , Dyslipidemias/blood , Lipids/blood , Liver/drug effects , Liver/enzymology , Metabolic Syndrome/blood , Rats, Wistar , Silymarin/pharmacologyABSTRACT
The aim of this study was to estimate the effect of carnitine supplementation on lipid disorders and peripheral tissue insulin sensitivity in a non-obese animal model of insulin resistance, the hereditary hypertriglyceridemic (HHTg) rat. Male HHTg rats were fed a standard diet, and half of them received daily doses of carnitine (500 mg·kg(-1) body weight) for 8 weeks. Rats of the original Wistar strain were used for comparison. HHTg rats exhibited increased urinary excretion of free carnitine and reduced carnitine content in the liver and blood. Carnitine supplementation compensated for this shortage and promoted urinary excretion of acetylcarnitine without any signs of (acyl)carnitine accumulation in skeletal muscle. Compared with their untreated littermates, carnitine-treated HHTg rats exhibited lower weight gain, reduced liver steatosis, lower fasting triglyceridemia, and greater reduction of serum free fatty acid content after glucose load. Carnitine treatment was associated with increased mitochondrial biogenesis and oxidative capacity for fatty acids, amelioration of oxidative stress, and restored substrate switching in the liver. In skeletal muscle (diaphragm), carnitine supplementation was associated with significantly higher palmitate oxidation and a more favorable complete to incomplete oxidation products ratio. Carnitine supplementation further enhanced insulin sensitivity ex vivo. No effects on whole-body glucose tolerance were observed. Our data suggest that some metabolic syndrome-related disorders, particularly fatty acid oxidation, steatosis, and oxidative stress in the liver, could be attenuated by carnitine supplementation. The effect of carnitine could be explained, at least partly, by enhanced substrate oxidation and increased fatty acid transport from tissues in the form of short-chain acylcarnitines.