In vivo metabolic profiling of glioma-initiating cells using proton magnetic resonance spectroscopy at 14.1 Tesla.

In the last decade, evidence has emerged indicating that the growth of a vast majority of tumors including gliomas is sustained by a subpopulation of cancer cells with stem cell properties called cancer initiating cells. These cells are able to initiate and propagate tumors and constitute only a fraction of all tumor cells. In the present study, we showed that intracerebral injection of cultured glioma-initiating cells into nude mice produced fast growing tumors showing necrosis and gadolinium enhancement in MR images, whereas gliomas produced by injecting freshly purified glioma-initiating cells grew slowly and showed no necrosis and very little gadolinium enhancement. Using proton localized spectroscopy at 14.1 Tesla, decreasing trends of N-acetylaspartate, glutamate and glucose concentrations and an increasing trend of glycine concentration were observed near the injection site after injecting cultured glioma-initiating cells. In contrast to the spectra of tumors grown from fresh cells, those from cultured cells showed intense peaks of lipids, increased absolute concentrations of glycine and choline-containing compounds, and decreased concentrations of glutamine, taurine and total creatine, when compared with a contralateral non-tumor-bearing brain tissue. A decrease in concentrations of N-acetylaspartate and γ-aminobutyrate was found in both tumor phenotypes after solid tumor formation. Further investigation is needed to determine the cause of the dissimilarities between the tumors grown from cultured glioma-initiating cells and those from freshly purified glioma-initiating cells, both derived from human glioblastomas.

Relationship of mating systems and metabolic rate with cycle length of spermatogenesis and sperm production rate in shrews

SUMMARY : The shrews are among the most ancient of living eutherian mammals. They represent an interesting comparative model because of their extreme divergent species. The two shrew subfamilies, Soricinae and Crocidurinae are characterized by fundamental differences concerning their metabolic rates, litter size, period of gestation and different mating pattern. In this study we established and compared the sperm characteristics in four species of different genera of shrews (Sorex araneus, Neomys fodiens, Crocidura russula and Suncus murinus) in the context of the sperm competition hypothesis. The sperm competition concerns the competition between ejaculates of different males for fertilization of ova of a female within a single estrus period. As expected, a greater relative testis size (indicating the importance of polyandry) was associated with a higher number of cauda epididymal spermatozoa, higher level of circulating testosterone and a higher percentage of progressive sperm motility. In addition, we investigated if the basal metabolic rate (BMR) and relative testis size (RTS) may be correlated with the cycle length of spermatogenesis. In this purpose, we determined and compared the cycle length of spermatogenesis in six species of shrews belonging to two subfamilies: Soiricinae (Sorex araneus, Sorex coronatus, Sorex minutus, Neomys fodiens) and Crocidurinae (Crocidura russula, Sunctes murinus). Our results indicate that sperm competition and metabolic rate may act independently or together reducing cycle length of spermatogenesis and thus increase sperm production. We finally investigated this correlation across 32 mammalian species. After testing the data for phylogenetic independence, our results showed that BMR explained only 21 % of the variation, while the RTS explained 44% of the variation of the cycle length of spermatogenesis. The level of the sperm competition, indicated by RTS, is thus to our knowledge the most important factor influencing the speed of spermatogenesis in mammals. RESUME : Les musaraignes sont parmi les plus anciens mammifères vivants. Grâce à leurs extrêmes divergences, ils sont souvent utilisés comme modèles dans des études comparatives. Les deux sous-familles Soricinae et Crocidurinae sont caractérisées par des différences fondamentales, notamment en termes d'intensité du métabolisme, des stratégies de reproduction et du comportement social. Dans la première partie de cette étude, nous avons établi et comparé certaines "caractéristiques des spermatozoïdes chez quatre espèces de musaraignes appartenant à des genres différents (Sorex araneus, Neomys fodiens, Crocidura russula et Suncus murinus). Les résultats ont été interprétés dans le contexte de la théorie de la compétition spermatique, c'est-à-dire la compétition entre le sperme de deux ou plusieurs mâles pour féconder un maximum d'ovules de la même femelle. Cette compétition spermatique peut amener à certaines adaptations biologiques afin de produire plus de sperme. Comme attendu, une grande taille relative des testicules est associée à un nombre élevé de spermatozoïdes, dont la majorité présente une mobilité progressive. Un taux élévé de testostérone a également été observé. De plus, nous avons étudié l'influence du métabolisme basal ainsi que l'intensité de la compétition spermatique sur la durée du cycle de la spermatogenèse. Dans ce but, nous avons déterminé et comparé les durées de la spermatogenèse chez six espèces de musaraignes appartenant à deux sous-familles : Soricinae (Sorex araneus, Sorex coronatus, Sorex minutus, Neomys fodiens) et Crocidurinae (Crocidura russula, Suncus murinus). Les résultats obtenus indiquent que ces deux facteurs (l'intensité du métabolisme basal et de la compétition spermatique) agissent d'une manière dépendante ou indépendante dans le même sens. La conséquence de ces actions est une diminution de la durée de la spermatogenèse entraînant une augmentation de la production de spermatozoïdes. Nous avons finalement étudié ce phénomène dans l'ensemble des mammifères. Après avoir testé l'indépendance phylogénétique, nos résultats montrent que l'intensité de la compétition spermatique indiquée par le RTS est mieux corrélée avec la régulation de la durée de la spermatogenèse qu'avec l'intensité du métabolisme.

Heterogeneous metabolic adaptation of C57BL/6J mice to high-fat diet.

C57BL/6J mice were fed a high-fat, carbohydrate-free diet (HFD) for 9 mo. Approximately 50% of the mice became obese and diabetic (ObD), approximately 10% lean and diabetic (LD), approximately 10% lean and nondiabetic (LnD), and approximately 30% displayed intermediate phenotype. All of the HFD mice were insulin resistant. In the fasted state, whole body glucose clearance was reduced in ObD mice, unchanged in the LD mice, and increased in the LnD mice compared with the normal-chow mice. Because fasted ObD mice were hyperinsulinemic and the lean mice slightly insulinopenic, there was no correlation between insulin levels and increased glucose utilization. In vivo, tissue glucose uptake assessed by 2-[(14)C]deoxyglucose accumulation was reduced in most muscles in the ObD mice but increased in the LnD mice compared with the values of the control mice. In the LD mice, the glucose uptake rates were reduced in extensor digitorum longus (EDL) and total hindlimb but increased in soleus, diaphragm, and heart. When assessed in vitro, glucose utilization rates in the absence and presence of insulin were similar in diaphragm, soleus, and EDL muscles isolated from all groups of mice. Thus, in genetically homogenous mice, HFD feeding lead to different metabolic adaptations. Whereas all of the mice became insulin resistant, this was associated, in obese mice, with decreased glucose clearance and hyperinsulinemia and, in lean mice, with increased glucose clearance in the presence of mild insulinopenia. Therefore, increased glucose clearance in lean mice could not be explained by increased insulin level, indicating that other in vivo mechanisms are triggered to control muscle glucose utilization. These adaptive mechanisms could participate in the protection against development of obesity.

Smoking offsets the metabolic benefits of parental longevity in women : the CoLaus study

Rapport de synthèse : Objectif: nous avons regardé si les sujets dont les parents vivaient plus longtemps présentaient des niveaux plus faibles de facteurs de risques cardiovasculaires, y compris pour le syndrome métabolique. Méthodes: nous avons analysé les données d'un échantillon représentatif de la population suisse (1163 hommes et 1398 femmes) âgé de 55 à 75 ans, de la ville de Lausanne. Les participants ont été stratifiés par nombre de parents (0, 1, 2) qui ont vécu jusqu'à 85 ans ou plus. Les associations entre la longévité parentale et les facteurs de risques cardiovasculaires ou les variables métaboliques associées ont été analysées au moyen de régressions linéaires multiples. Résultats: la prévalence ajustée pour l'âge du syndrome métabolique varie de 24.8%, 20.5% à 13.8% chez les femmes (P<0.05) et de 28.8%, 32.1 % à 27.6% chez les hommes (non significatif) pour 0, 1 et 2 parents à forte longévité. L'association entre la longévité parentale et la prévalence du syndrome métabolique est particulièrement forte pour les femmes qui n'ont jamais fumé. Dans ce groupe, les femmes qui ont 2 parents à forte longévité ont un BMI plus faible et un tour de taille moins grand. Chez les gens qui n'ont jamais fumé, pour les deux sexes, les niveaux moyens (95% d'intervalle de confiance) et ajustés de cholestéro-HDL étaient de 1.64(1.61-1.67), 1.67(1.65-1.70) et 1.71(1.65-1.76) mmol/L pour 0, 1 et 2 parents à forte longévité (P<0.01), respectivement. La tendance n'était pas significative chez les anciens fiuneurs et fumeurs actuels. Conclusions: la longévité parentale est associée à un meilleur profil métabolique chez les femmes, mais pas chez les hommes. Les avantages métaboliques du fait d'avoir des parents âgés sont fortement atténués par le tabagisme.

Potential of education-based insulin therapy for achievement of good metabolic control: a real-life experience.

Diabet. Med. 28, 539-542 (2011) ABSTRACT: Aims  Achievement of good metabolic control in Type 1 diabetes is a difficult task in routine diabetes care. Education-based flexible intensified insulin therapy has the potential to meet the therapeutic targets while limiting the risk for severe hypoglycaemia. We evaluated the metabolic control and the rate of severe hypoglycaemia in real-life clinical practice in a centre using flexible intensified insulin therapy as standard of care since 1990. Methods  Patients followed for Type 1 diabetes (n = 206) or those with other causes of absolute insulin deficiency (n = 17) in our outpatient clinic were analysed in a cross-sectional study. Mean age (± standard deviation) was 48.9 ± 15.7 years, with diabetes duration of 21.4 ± 14.4 years. Outcome measures were HbA(1c) and frequency of severe hypoglycaemia. Results  Median HbA(1c) was 7.1% (54 mmol/mol) [interquartile range 6.6-7.8 (51-62 mmol/mol)]; a good or acceptable metabolic control with HbA(1c) < 7.0% (53 mmol/mol) or 7.5% (58 mmol/mol) was reached in 43.5 and 64.6% of the patients, respectively. The frequency of severe hypoglycaemic episodes was 15 per 100 patient years: 72.3% of the patients did not experience any such episodes during the past 5 years. Conclusions  Good or acceptable metabolic control is achievable in the majority of patients with Type 1 diabetes or other causes of absolute insulin deficiency in routine diabetes care while limiting the risk for severe hypoglycaemia.

Cerebral metabolic effects of exogenous lactate supplementation on the injured human brain.

PURPOSE: Experimental evidence suggests that lactate is neuroprotective after acute brain injury; however, data in humans are lacking. We examined whether exogenous lactate supplementation improves cerebral energy metabolism in humans with traumatic brain injury (TBI). METHODS: We prospectively studied 15 consecutive patients with severe TBI monitored with cerebral microdialysis (CMD), brain tissue PO2 (PbtO2), and intracranial pressure (ICP). Intervention consisted of a 3-h intravenous infusion of hypertonic sodium lactate (aiming to increase systemic lactate to ca. 5 mmol/L), administered in the early phase following TBI. We examined the effect of sodium lactate on neurochemistry (CMD lactate, pyruvate, glucose, and glutamate), PbtO2, and ICP. RESULTS: Treatment was started on average 33 ± 16 h after TBI. A mixed-effects multilevel regression model revealed that sodium lactate therapy was associated with a significant increase in CMD concentrations of lactate [coefficient 0.47 mmol/L, 95% confidence interval (CI) 0.31-0.63 mmol/L], pyruvate [13.1 (8.78-17.4) μmol/L], and glucose [0.1 (0.04-0.16) mmol/L; all p < 0.01]. A concomitant reduction of CMD glutamate [-0.95 (-1.94 to 0.06) mmol/L, p = 0.06] and ICP [-0.86 (-1.47 to -0.24) mmHg, p < 0.01] was also observed. CONCLUSIONS: Exogenous supplemental lactate can be utilized aerobically as a preferential energy substrate by the injured human brain, with sparing of cerebral glucose. Increased availability of cerebral extracellular pyruvate and glucose, coupled with a reduction of brain glutamate and ICP, suggests that hypertonic lactate therapy has beneficial cerebral metabolic and hemodynamic effects after TBI.

The NLRP3 inflammasome: a sensor for metabolic danger?

Interleukin-1beta (IL-1beta), reactive oxygen species (ROS), and thioredoxin-interacting protein (TXNIP) are all implicated in the pathogenesis of type 2 diabetes mellitus (T2DM). Here we review mechanisms directing IL-1beta production and its pathogenic role in islet dysfunction during chronic hyperglycemia. In doing so, we integrate previously disparate disease-driving mechanisms for IL-1beta, ROS, and TXNIP in T2DM into one unifying model in which the NLRP3 inflammasome plays a central role. The NLRP3 inflammasome also drives IL-1beta maturation and secretion in another disease of metabolic dysregulation, gout. Thus, we propose that the NLRP3 inflammasome contributes to the pathogenesis of T2DM and gout by functioning as a sensor for metabolic stress.

Deletion of Sirt3 does not affect atherosclerosis but accelerates weight gain and impairs rapid metabolic adaptation in LDL receptor knockout mice: implications for cardiovascular risk factor development.

Sirt3 is a mitochondrial NAD(+)-dependent deacetylase that governs mitochondrial metabolism and reactive oxygen species homeostasis. Sirt3 deficiency has been reported to accelerate the development of the metabolic syndrome. However, the role of Sirt3 in atherosclerosis remains enigmatic. We aimed to investigate whether Sirt3 deficiency affects atherosclerosis, plaque vulnerability, and metabolic homeostasis. Low-density lipoprotein receptor knockout (LDLR(-/-)) and LDLR/Sirt3 double-knockout (Sirt3(-/-)LDLR(-/-)) mice were fed a high-cholesterol diet (1.25 % w/w) for 12 weeks. Atherosclerosis was assessed en face in thoraco-abdominal aortae and in cross sections of aortic roots. Sirt3 deletion led to hepatic mitochondrial protein hyperacetylation. Unexpectedly, though plasma malondialdehyde levels were elevated in Sirt3-deficient mice, Sirt3 deletion affected neither plaque burden nor features of plaque vulnerability (i.e., fibrous cap thickness and necrotic core diameter). Likewise, plaque macrophage and T cell infiltration as well as endothelial activation remained unaltered. Electron microscopy of aortic walls revealed no difference in mitochondrial microarchitecture between both groups. Interestingly, loss of Sirt3 was associated with accelerated weight gain and an impaired capacity to cope with rapid changes in nutrient supply as assessed by indirect calorimetry. Serum lipid levels and glucose tolerance were unaffected by Sirt3 deletion in LDLR(-/-) mice. Sirt3 deficiency does not affect atherosclerosis in LDLR(-/-) mice. However, Sirt3 controls systemic levels of oxidative stress, limits expedited weight gain, and allows rapid metabolic adaptation. Thus, Sirt3 may contribute to postponing cardiovascular risk factor development.

Developmental, metabolic and immunological costs of flea infestation in the common vole

Parasites use resources from their hosts, which can indirectly affect a number of host functions because of trade-offs in resource allocation. In order to get a comprehensive view of the costs imposed by blood sucking parasites to their hosts, it is important to monitor multiple components of the development and physiology of parasitized hosts over long time periods. The effect of infestation by fleas on body mass, body length growth, haematocrit, resistance to oxidative stress, resting metabolic rate and humoral immune response were experimentally evaluated. During a 3-month period, male common voles, Microtus arvalis, were either parasitized by rat fleas (Nosopsyllus fasciatus), which are naturally occurring generalist ectoparasites of voles, or reared without fleas. Then voles were challenged twice by injecting Keyhole Limpet Haemocyanin (KLH) to assess whether the presence of fleas affects the ability of voles to produce antibodies against a novel antigen. During the immune challenge we measured the evolution of body mass, haematocrit, resistance to oxidative stress and antibody production. Flea infestation negatively influenced the growth of voles. Moreover, parasitized voles had reduced haematocrit, higher resting metabolic rate and lower production of antibodies against the KLH. Resistance to oxidative stress was not influenced by the presence of fleas. During the immune challenge with KLH, body mass decreased in both groups, while the resistance to oxidative stress remained stable. In contrast, the haematocrit decreased only in parasitized voles. Our experiment shows that infestation by a haematophageous parasite negatively affects multiple traits like growth, energy consumption and immune response. Fleas may severely reduce the survival probability and reproductive success of their host in natural conditions.

Omega-3 fatty acids prevent inflammation and metabolic disorder through inhibition of NLRP3 inflammasome activation.

Omega-3 fatty acids (ω-3 FAs) have potential anti-inflammatory activity in a variety of inflammatory human diseases, but the mechanisms remain poorly understood. Here we show that stimulation of macrophages with ω-3 FAs, including eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and other family members, abolished NLRP3 inflammasome activation and inhibited subsequent caspase-1 activation and IL-1β secretion. In addition, G protein-coupled receptor 120 (GPR120) and GPR40 and their downstream scaffold protein β-arrestin-2 were shown to be involved in inflammasome inhibition induced by ω-3 FAs. Importantly, ω-3 FAs also prevented NLRP3 inflammasome-dependent inflammation and metabolic disorder in a high-fat-diet-induced type 2 diabetes model. Our results reveal a mechanism through which ω-3 FAs repress inflammation and prevent inflammation-driven diseases and suggest the potential clinical use of ω-3 FAs in gout, autoinflammatory syndromes, or other NLRP3 inflammasome-driven inflammatory diseases.

Cytochrome P4503A4 metabolic activity, methadone blood concentrations, and methadone doses.

We examined in vivo the influence of cytochrome P4503A4 (CYP3A4) activity, measured by the 30 min plasma 1'OH-midazolam/midazolam ratio after oral administration of 7.5 mg midazolam, on the methadone steady-state trough plasma concentrations in a group of 32 patients in methadone maintenance treatment. Patients were grouped as receiving 'low' (up to 99 mg/day, n = 10), 'high' (100-199 mg/day, n = 11) and 'very high' (> or = 200 mg/day, n = 11) doses of methadone, and the CYP3A4 metabolic activity was compared between the three groups. (S)-methadone and (R,S)-methadone, but not (R)-methadone, concentrations to dose ratios significantly correlated with the midazolam ratios (r(2) = -0.17, P = 0.018; r(2) = -0.14, P = 0.032; r(2) = -0.10, P = 0.083, respectively), with a 76% higher CYP3A4 activity in the very high-dose group as compared with the low-dose group. Significant differences in the CYP3A4 activity were calculated between the three groups (P = 0.0036), and group-to-group comparisons, using the Bonferroni correction, showed a significant difference between the low-dose and the very high-dose group (P = 0.0039), between the high-dose and the very high-dose group (P = 0.0064), but not between the low-dose and the high-dose group (P = 0.070). The higher CYP3A4 activity measured in patients receiving very high methadone doses could contribute to the need for higher doses in some patients, due to an increased metabolic clearance. This, however, must be confirmed by a prospective study.

Relation between atherogenic dyslipidemia and the Adult Treatment Program-III definition of metabolic syndrome (Genetic Epidemiology of Metabolic Syndrome Project).

Genetic Epidemiology of Metabolic Syndrome is a multinational, family-based study to explore the genetic basis of the metabolic syndrome. Atherogenic dyslipidemia (defined as low plasma high-density lipoprotein cholesterol with elevated triglycerides (&lt;25th and &gt;75th percentile for age, gender, and country, respectively) identified affected subjects for the metabolic syndrome. This report examines the frequency at which atherogenic dyslipidemia predicts the metabolic syndrome of the National Cholesterol Education Program Adult Treatment Panel III (ATP-III). One thousand four hundred thirty-six (854 men/582 women) affected patients by our criteria were compared with 1,672 (737 men/935 women) unaffected persons. Affected patients had more hypertension, obesity, and hyperglycemia, and they met a higher number of ATP-III criteria (3.2 +/- 1.1 SD vs 1.3 +/- 1.1 SD, p &lt;0.001). Overall, 76% of affected persons also qualified for the ATP-III definition (Cohen's kappa 0.61, 95% confidence interval 0.59 to 0.64), similar to a separate group of 464 sporadic, unrelated cases (75%). Concordance increased from 41% to 82% and 88% for ages &lt; or =35, 36 to 55, and &gt; or =55 years, respectively. Affected status was also independently associated with waist circumference (p &lt;0.001) and fasting glucose (p &lt;0.001) but not systolic blood pressure (p = 0.43). Thus, the lipid-based criteria used to define affection status in this study substantially parallels the ATP-III definition of metabolic syndrome in subjects aged &gt;35 years. In subjects aged &lt;35 years, atherogenic dyslipidemia frequently occurs in the absence of other metabolic syndrome risk factors.

Genetic and phenotypic architecture of metabolic syndrome-associated components in dyslipidemic and normolipidemic subjects: the GEMS Study.

Atherogenic dyslipidemia, manifest by low HDL-cholesterol and high TG levels, is an important component of ATP-III defined metabolic syndrome. Here, we dissected the phenotypic and genetic architecture of these traits by assessing their relationships with other metabolically relevant measures, including plasma adipo-cytokines, highly sensitive C-reactive protein (hsCRP) and LDL particle size, in a large family data set (n=2800) and in an independent set of dyslipidemic cases (n=716) and normolipidemic controls (n=1073). We explored the relationships among these phenotypes using variable clustering and then estimated their genetic heritabilities and cross-trait correlations. In families, four clusters explained 61% of the total variance, with one adiposity-related cluster (including hsCRP), one BP-related cluster, and two lipid-related clusters (HDL-C, TG, adiponectin and LDL particle size; apoB and non-HDL-C). A similar structure was observed in dyslipidemic cases and normolipidemic controls. The genetic correlations in the families largely paralleled the phenotype clustering results, suggesting that common genes having pleiotropic effects contributed to the correlations observed. In summary, our analyses support a model of metabolic syndrome with two major components, body fat and lipids, each with two subcomponents, and quantifies their degree of overlap with each other and with metabolic-syndrome related measures (adipokines, LDL particle size and hsCRP).

Unraveling the complex metabolic nature of astrocytes.

Since the initial description of astrocytes by neuroanatomists of the nineteenth century, a critical metabolic role for these cells has been suggested in the central nervous system. Nonetheless, it took several technological and conceptual advances over many years before we could start to understand how they fulfill such a role. One of the important and early recognized metabolic function of astrocytes concerns the reuptake and recycling of the neurotransmitter glutamate. But the description of this initial property will be followed by several others including an implication in the supply of energetic substrates to neurons. Indeed, despite the fact that like most eukaryotic non-proliferative cells, astrocytes rely on oxidative metabolism for energy production, they exhibit a prominent aerobic glycolysis capacity. Moreover, this unusual metabolic feature was found to be modulated by glutamatergic activity constituting the initial step of the neurometabolic coupling mechanism. Several approaches, including biochemical measurements in cultured cells, genetic screening, dynamic cell imaging, nuclear magnetic resonance spectroscopy and mathematical modeling, have provided further insights into the intrinsic characteristics giving rise to these key features of astrocytes. This review will provide an account of the different results obtained over several decades that contributed to unravel the complex metabolic nature of astrocytes that make this cell type unique.