scholarly journals Assessment of Aspartate and Bicarbonate Produced From Hyperpolarized [1-13C]Pyruvate as Markers of Renal Gluconeogenesis

2021 ◽  
Vol 12 ◽  
Author(s):  
Hikari A. I. Yoshihara ◽  
Arnaud Comment ◽  
Juerg Schwitter
Keyword(s):  
Phosphoenolpyruvate Carboxykinase ◽  
Left Kidney ◽  
The Body ◽  
Spin Labels ◽  
Resonance Spectroscopy ◽  
Fasted State ◽  
Renal Gluconeogenesis ◽  
Invasive Techniques ◽  
Fasted Rats ◽  
Marked Drop

As both a consumer and producer of glucose, the kidney plays a significant role in glucose homeostasis. Measuring renal gluconeogenesis requires invasive techniques, and less invasive methods would allow renal gluconeogenesis to be measured more routinely. Magnetic resonance spectroscopy and imaging of infused substrates bearing hyperpolarized carbon-13 spin labels allows metabolism to be detected within the body with excellent sensitivity. Conversion of hyperpolarized 1-13C pyruvate in the fasted rat liver is associated with gluconeogenic flux through phosphoenolpyruvate carboxykinase (PEPCK) rather than pyruvate dehydrogenase (PDH), and this study tested whether this was also the case in the kidney. The left kidney was scanned in fed and overnight-fasted rats either with or without prior treatment by the PEPCK inhibitor 3-mercaptopicolinic acid (3-MPA) following infusion of hyperpolarized 1-13C pyruvate. The 13C-bicarbonate signal normalized to the total metabolite signal was 3.2-fold lower in fasted rats (p = 0.00073) and was not significantly affected by 3-MPA treatment in either nutritional state. By contrast, the normalized [1-13C]aspartate signal was on average 2.2-fold higher in the fasted state (p = 0.038), and following 3-MPA treatment it was 2.8-fold lower in fed rats and 15-fold lower in fasted rats (p = 0.001). These results confirm that, unlike in the liver, most of the pyruvate-to-bicarbonate conversion in the fasted kidney results from PDH flux. The higher conversion to aspartate in fasted kidney and the marked drop following PEPCK inhibition demonstrate the potential of this metabolite as a marker of renal gluconeogenesis.

scholarly journals [13C]bicarbonate labelled from hyperpolarized [1-13C]pyruvate is an in vivo marker of hepatic gluconeogenesis in fasted state

2022 ◽  
Vol 5 (1) ◽  
Author(s):  
Emine Can ◽  
Jessica A. M. Bastiaansen ◽  
Dominique-Laurent Couturier ◽  
Rolf Gruetter ◽  
Hikari A. I. Yoshihara ◽  
...  
Keyword(s):  
Plasma Concentration ◽  
Pyruvate Dehydrogenase ◽  
Pyruvate Carboxylase ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Hepatic Gluconeogenesis ◽  
Fasted State ◽  
Basal Plasma ◽  
Fasted Rats ◽  
In Vivo Assessment

AbstractHyperpolarized [1-13C]pyruvate enables direct in vivo assessment of real-time liver enzymatic activities by 13C magnetic resonance. However, the technique usually requires the injection of a highly supraphysiological dose of pyruvate. We herein demonstrate that liver metabolism can be measured in vivo with hyperpolarized [1-13C]pyruvate administered at two- to three-fold the basal plasma concentration. The flux through pyruvate dehydrogenase, assessed by 13C-labeling of bicarbonate in the fed condition, was found to be saturated or partially inhibited by supraphysiological doses of hyperpolarized [1-13C]pyruvate. The [13C]bicarbonate signal detected in the liver of fasted rats nearly vanished after treatment with a phosphoenolpyruvate carboxykinase (PEPCK) inhibitor, indicating that the signal originates from the flux through PEPCK. In addition, the normalized [13C]bicarbonate signal in fasted untreated animals is dose independent across a 10-fold range, highlighting that PEPCK and pyruvate carboxylase are not saturated and that hepatic gluconeogenesis can be directly probed in vivo with hyperpolarized [1-13C]pyruvate.

scholarly journals Modeling the eye as a window on the body

2020 ◽  
Vol 2 (4) ◽  
pp. 4-10
Author(s):  
Lucia Carichino ◽  
Simone Cassani ◽  
Sergey Lapin ◽  
Alice Verticchio Vercellin
Keyword(s):  
The Body ◽  
Systemic Diseases ◽  
Non Invasive ◽  
Structural Functions ◽  
Invasive Techniques

Systemic pathologies such as diabetes and hypertension affect different organs and systems in the body. However, the first signs of these pathologies often emerge as alterations in visual and structural functions in the eye. As a consequence, the ophthalmologist is often the first physician to make a diagnosis of systemic diseases. In fact, the eye represents a unique organ where signs of systemic diseases may be assessed with non-invasive techniques.

Endurance training attenuates stress hormone responses to exercise in fasted rats

1982 ◽  
Vol 243 (1) ◽  
pp. R179-R184 ◽  
Author(s):  
W. W. Winder ◽  
M. A. Beattie ◽  
R. T. Holman
Keyword(s):  
Blood Glucose ◽  
Plasma Concentrations ◽  
Liver Glycogen ◽  
Stress Hormone ◽  
Glucose Levels ◽  
Blood Glucose Levels ◽  
Fasted State ◽  
Hormone Responses ◽  
Exercise Muscle ◽  
Fasted Rats

Endurance exercise training produces major adaptations in hormonal and metabolic responses to exercise. This study was designed to determine whether the differences in hormone response persist in the fasted condition when liver glycogen is depleted. Rats were run on a motor-driven rodent treadmill 5 days/wk for periods up to 2 h/day for 10 wk. Trained and nontrained rats were then fasted 24 h and were run for periods ranging from 0- to 60 min. At the end of 60 min of exercise muscle glycogen was higher in trained rats (2.9 +/- 0.3 vs. 1.1 +/- 0.1 mg/g). Blood glucose was maintained at higher levels in trained rats throughout the course of the exercise (3.2 +/- 0.1 vs. 2.3 +/- 0.1 mM after 60 min). Plasma concentrations of glucagon and epinephrine increased in both groups during the exercise but were significantly lower in trained animals. Differences between trained and nontrained animals in stress hormone responses to exercise persist in the fasted state and appear to be a consequence of the capacity of trained animals to maintain higher blood glucose levels.

scholarly journals Unusual MR Imaging Features in CT Hyperdense Posterior Fossa Dermoids: Report of Two Cases

2020 ◽  
Vol 09 (01) ◽  
pp. 63-66
Author(s):  
Anbazhagan Sathiaprabhu ◽  
Nichanametla Sravani ◽  
Krishnan Nagarajan ◽  
Sekar Sabarish ◽  
Kapil Patil
Keyword(s):  
Magnetic Resonance ◽  
Posterior Fossa ◽  
Magnetization Transfer ◽  
The Body ◽  
Resonance Spectroscopy ◽  
Imaging Features ◽  
Signal Loss ◽  
Mri Features ◽  
Magnetic Resonance Imaging Mri ◽  
T2 Hyperintensity

AbstractDermoids, either intracranial or in the rest of the body, usually have typical imaging findings due to their fat contents as fat density in computed tomography (CT) and T1- and T2-hyperintensity in magnetic resonance imaging (MRI). Variable imaging appearances have been described due to soft tissue contents, hair, calcification, or even tooth. Posterior fossa dermoids have been reported as a specific variant that shows hyperdensity in CT and mixed signal intensity in MRI. We report two cases of posterior fossa CT hyperdense dermoids that showed unusual MRI features in the form of signal loss in magnetization transfer images and lipid peak in magnetic resonance spectroscopy. Both patients underwent surgical resection and histopathological confirmation and the causes of this unusual imaging appearance are discussed.

Mapping and functional analysis of an instability element in phosphoenolpyruvate carboxykinase mRNA

2000 ◽  
Vol 279 (5) ◽  
pp. F866-F873 ◽  
Author(s):  
Omar F. Laterza ◽  
Lynn Taylor ◽  
Shashikala Unnithan ◽  
Ly Nguyen ◽  
Norman P. Curthoys
Keyword(s):  
Phosphoenolpyruvate Carboxykinase ◽  
Luciferase Activity ◽  
Specific Protein ◽  
Luciferase Reporter ◽  
Reporter Construct ◽  
Luciferase Reporter Construct ◽  
Functional Studies ◽  
Renal Gluconeogenesis ◽  
Shift Analysis ◽  
Nontranslated Region

Phosph oenolpyruvate carboxykinase (PEPCK) is a key regulatory enzyme of renal gluconeogenesis. The 3′-nontranslated region of the PEPCK mRNA contains an instability element that facilitates its rapid turnover and contributes to the regulation of PEPCK gene expression. Such processes are mediated by specific protein-binding elements. Thus RNA gel shift analysis was used to identify proteins in rat renal cortical cytosolic extracts that bind to the 3′-nontranslated region of the PEPCK mRNA. Deletion constructs were then used to map the binding interactions to two adjacent RNA segments (PEPCK-6 and PEPCK-7). However, competition experiments established that only the binding to PEPCK-7 was specific. Functional studies were performed by cloning similar segments in a luciferase reporter construct, pLuc/Zeo. This analysis indicated that both PEPCK-6 and PEPCK-7 segments were necessary to produce a decrease in luciferase activity equivalent to that observed with the full-length 3′-nontranslated region. Thus the PEPCK-7 segment binds a specific protein that may recruit one or more proteins to form a complex that mediates the rapid decay of the PEPCK mRNA.

scholarly journals 2′-Alkynyl spin-labelling is a minimally perturbing tool for DNA structural analysis

2020 ◽  
Vol 48 (6) ◽  
pp. 2830-2840 ◽  
Author(s):  
Jack S Hardwick ◽  
Marius M Haugland ◽  
Afaf H El-Sagheer ◽  
Denis Ptchelkine ◽  
Frank R Beierlein ◽  
...  
Keyword(s):  
Epr Spectroscopy ◽  
Spin Labels ◽  
Resonance Spectroscopy ◽  
Conformational Ensemble ◽  
Dna Duplexes ◽  
Paramagnetic Resonance ◽  
Dynamics Simulations ◽  
Electron Paramagnetic ◽  
Spin Labelling

Abstract The determination of distances between specific points in nucleic acids is essential to understanding their behaviour at the molecular level. The ability to measure distances of 2–10 nm is particularly important: deformations arising from protein binding commonly fall within this range, but the reliable measurement of such distances for a conformational ensemble remains a significant challenge. Using several techniques, we show that electron paramagnetic resonance (EPR) spectroscopy of oligonucleotides spin-labelled with triazole-appended nitroxides at the 2′ position offers a robust and minimally perturbing tool for obtaining such measurements. For two nitroxides, we present results from EPR spectroscopy, X-ray crystal structures of B-form spin-labelled DNA duplexes, molecular dynamics simulations and nuclear magnetic resonance spectroscopy. These four methods are mutually supportive, and pinpoint the locations of the spin labels on the duplexes. In doing so, this work establishes 2′-alkynyl nitroxide spin-labelling as a minimally perturbing method for probing DNA conformation.

Canine gallbladder cyclic motor activity

1988 ◽  
Vol 255 (4) ◽  
pp. G409-G416 ◽  
Author(s):  
T. Matsumoto ◽  
S. K. Sarna ◽  
R. E. Condon ◽  
W. J. Dodds ◽  
N. Mochinaga
Keyword(s):  
Motor Activity ◽  
Short Duration ◽  
Sphincter Of Oddi ◽  
The Body ◽  
Phase Iii ◽  
Fasted State ◽  
Long Duration ◽  
The Mean ◽  
Esophageal Sphincter

We investigated whether the gallbladder has cyclic motor activity similar to that of the stomach, lower esophageal sphincter, and sphincter of Oddi in the fasted state. We found that the canine gallbladder infundibulum exhibited a cyclic burst of short duration (69 +/- 3 s) contractions that were closely associated with phase III activity of the antrum. The cyclic motor activity was sometimes less prominent or absent in the body and the fundus of the gallbladder. The mean period of gallbladder cyclic motor activity was not significantly different from the mean period of phase III activity in the stomach and the duodenum. The cyclic bursts of gallbladder contractions lasted for 21 +/- 2 min. The gallbladder cyclic motor activity started at about the same time as the antral phase III activity, and both of these activities started approximately 12 min earlier than the duodenal phase III activity. In addition to the aforementioned cyclic bursts of contractions, the gallbladder sometimes exhibited long duration (6.4 +/- 0.6 min) contractions that occurred irregularly and unpredictably during the duodenal migrating motor complex cycle. We conclude that during fasting the canine gallbladder has a cyclic motor activity that is temporally related to phase III activity of the stomach and the duodenum. The role of short duration phasic contractions during cyclic motor activity may be to periodically stir gallbladder contents, whereas the long duration contractions may partially empty the gallbladder in the fasted state.

High-frequency pulsed electron–electron double resonance spectroscopy on DNA duplexes using trityl tags and shaped microwave pulses

2018 ◽  
Vol 20 (41) ◽  
pp. 26140-26144 ◽  
Author(s):  
A. Kuzhelev ◽  
D. Akhmetzyanov ◽  
V. Denysenkov ◽  
G. Shevelev ◽  
O. Krumkacheva ◽  
...  
Keyword(s):  
Pump Pulse ◽  
High Frequency ◽  
Double Resonance ◽  
Spin Labels ◽  
Resonance Spectroscopy ◽  
Dna Duplexes ◽  
Microwave Pulses ◽  
Double Resonance Spectroscopy

Distances between trityl spin labels attached to DNA duplexes were determined by 180 GHz and 260 GHz PELDOR spectroscopy applying broadband pump pulse at higher frequency.

cAMP-dependent stabilization of phosphoenolpyruvate carboxykinase mRNA in LLC-PK1-F+ kidney cells

2006 ◽  
Vol 290 (2) ◽  
pp. F313-F318 ◽  
Author(s):  
Purabi S. Dhakras ◽  
Sachin Hajarnis ◽  
Lynn Taylor ◽  
Norman P. Curthoys
Keyword(s):  
Phosphoenolpyruvate Carboxykinase ◽  
Luciferase Activity ◽  
Kidney Cells ◽  
Reporter Construct ◽  
Pronounced Increase ◽  
Rate Limiting Step ◽  
Renal Gluconeogenesis ◽  
Limiting Step ◽  
The Individual ◽  
Rate Limiting

Phospho enolpyruvate carboxykinase (PEPCK) catalyzes a rate-limiting step in hepatic and renal gluconeogenesis. In the kidney, PEPCK expression is enhanced during metabolic acidosis and in response to ANG II and parathyroid hormone. The effect of the latter hormone is mediated, in part, by cAMP. Treatment of subconfluent cultures of LLC-PK1-F+ cells, a gluconeogenic line of porcine proximal tubule-like cells, with cAMP produces a pronounced increase in the level of PEPCK mRNA. The luciferase activity of pLuc/3′-PCK-1, a reporter construct that contains the 3′-UTR of the PEPCK mRNA, was increased three- to fourfold by coexpression of the catalytic subunit of protein kinase A (PKA). This result indicates that cAMP-dependent stabilization may contribute to the increased expression of PEPCK mRNA in LLC-PK1-F+ cells. Various pLuc/3′ constructs containing different segments of the 3′-UTR of PEPCK mRNA were used to map the cAMP response to two segments that were previously shown to bind AUF1 and to function as instability elements. A tetracycline-responsive promoter system was used to quantify the effect of forskolin on the half-lives of chimeric β-globin-PEPCK (TβG-PCK) mRNAs. The half-life of the labile βG-PCK-1 mRNA was increased eightfold by addition of forskolin. In contrast, the half-lives of the constructs containing the individual instability elements were increased only twofold. Therefore, the multiple instability elements present within the 3′-UTR may function synergistically to mediate both the rapid degradation and the cAMP-induced stabilization of PEPCK mRNA. The latter process may result from a PKA-dependent phosphorylation of AUF1.

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