Pancreatic triacylglycerol lipase in a hibernating mammal. II. Cold-adapted function and differential expression

2003 ◽  
Vol 16 (1) ◽  
pp. 131-140 ◽  
Author(s):  
Teresa L. Squire ◽  
Mark E. Lowe ◽  
Vernon W. Bauer ◽  
Matthew T. Andrews
Keyword(s):  
Low Temperature ◽  
High Activity ◽  
Ground Squirrel ◽  
Mammalian Cells ◽  
Lipolytic Activity ◽  
Tissue Expression ◽  
Ground Squirrels ◽  
Mrna Levels ◽  
Western Blots ◽  
Triacylglycerol Lipase

Thirteen-lined ground squirrels ( Spermophilus tridecemlineatus) exploit the low-temperature activity of pancreatic triacylglycerol lipase (PTL) during hibernation. Lipolytic activity at body temperatures associated with hibernation was examined using recombinant ground squirrel and human PTLs expressed in yeast. Both the human and ground squirrel enzymes displayed high activity at temperatures as low as 0°C and showed Q10 values of 1.2–1.5 over a range of 37–7°C. These studies indicate that low-temperature lipolysis is a general property of PTL and does not require protein modifications unique to mammalian cells and/or the hibernating state. Western blots show elevated levels of PTL protein during hibernation in both heart and white adipose tissue (WAT). Significant increases in PTL gene expression are seen in heart, WAT, and testes; but not in pancreas, where PTL mRNA levels are highest. Upregulation of PTL in testes is also accompanied by expression of the PTL-specific cofactor, colipase. The multi-tissue expression of PTL during hibernation supports its role as a key enzyme that shows high activity at low temperatures.

Genes controlling the metabolic switch in hibernating mammals

2004 ◽  
Vol 32 (6) ◽  
pp. 1021-1024 ◽  
Author(s):  
M.T. Andrews
Keyword(s):  
Low Temperature ◽  
Pyruvate Dehydrogenase ◽  
Ground Squirrel ◽  
Mammalian Cells ◽  
Lipolytic Activity ◽  
Tricarboxylic Acid Cycle ◽  
Ground Squirrels ◽  
Pyruvate Dehydrogenase Kinase ◽  
Body Temperatures ◽  
Triacylglycerol Lipase

Hibernating mammals have the ability to decrease their metabolic rate and survive up to 6 months without food in an inactive state where body temperatures approach 0°C. In hibernating 13-lined ground squirrels (Spermophilus tridecemlineatus), oxygen consumption holds at 1/30 to 1/50 of the aroused condition and heart rates are as low as 3–10 beats/min, compared with 200–300 beats/min when the animal is active. This seasonal adaptation requires a metabolic shift away from the oxidation of carbohydrates and towards the combustion of stored fatty acids as the primary source of energy. A key element in this fuel switch is the differential expression of the gene encoding pyruvate dehydrogenase kinase isoenzyme 4. Pyruvate dehydrogenase kinase isoenzyme 4 inhibits pyruvate dehydrogenase and thus minimizes carbohydrate oxidation by preventing the flow of glycolytic products into the tricarboxylic acid cycle. Hibernators also exploit the low-temperature activity of PTL (pancreatic triacylglycerol lipase) in both heart and white adipose tissue. Lipolytic activity at body temperatures associated with hibernation was examined using recombinant ground squirrel and human PTL expressed in yeast. Enzymes from both humans and ground squirrel displayed high activity at temperatures as low as 0°C and showed Q10=1.2–1.5 over the temperature range 37–7°C. These studies indicate that low-temperature lipolysis is a general property of PTL and does not require protein modifications unique to mammalian cells and/or the hibernating state.

Isovolumetric performance of isolated ground squirrel and rat hearts at low temperature

1984 ◽  
Vol 247 (4) ◽  
pp. R722-R727 ◽  
Author(s):  
D. R. Caprette ◽  
J. B. Senturia
Keyword(s):  
Low Temperature ◽  
Ground Squirrel ◽  
Mechanical Performance ◽  
Cell Communication ◽  
Ventricular Myocardium ◽  
Ground Squirrels ◽  
Rat Hearts ◽  
Pulsus Alternans ◽  
Rate Of Increase ◽  
Developed Pressure

The effects of low temperature on mechanical performance of the isolated left ventricles of the 13-lined ground squirrel (a hibernator) and the rat (a nonhibernator) were studied. In addition, low-temperature performance of hearts from summer-active, winter-hibernating, and winter-active ground squirrels were compared. By measuring pressure (P) generated against a balloon inserted into the left ventricle, maximum developed pressure (DP) and maximum rate of increase of P (peak dP/dt) were determined over a temperature range of 5–20 degrees C. The DP and dP/dt of the rat ventricle exhibited significantly greater reduction in magnitude at reduced temperature, compared with those of ground squirrel ventricle. Rat, but not ground squirrel, hearts exhibited arrhythmias of various kinds, including extra-systoles, tachycardia, pulsus alternans, and periods of asystole. Hearts from winter-active ground squirrels developed greater pressures than those from winter-hibernating and summer-active animals. This evidence suggests that disruption of cell communication in the nonhibernator ventricular myocardium plays an important role in the failure of the nonhibernator heart at low body temperatures. Contractility of the seasonal hibernator's heart is influenced by both season and hibernation itself, possibly through shifts in myocardial metabolism. However, seasonal adaptations appear not to be required to confer the special resistance of the seasonal hibernator's heart to the deleterious effects of low temperature.

scholarly journals Seasonal changes of androgen receptor, estrogen receptors and aromatase expression in the medial preoptic area of the wild male ground squirrels (Citellus dauricus Brandt)

2016 ◽  
Vol 60 (2) ◽  
Author(s):  
F. Zhang ◽  
J. Wang ◽  
Y. Jiao ◽  
L. Zhang ◽  
H. Zhang ◽  
...  
Keyword(s):  
Androgen Receptor ◽  
Estrogen Receptors ◽  
Breeding Season ◽  
Ground Squirrel ◽  
Preoptic Area ◽  
Medial Preoptic Area ◽  
Ground Squirrels ◽  
Mrna Levels ◽  
Wild Male ◽  
Significant Difference

<p>The wild ground squirrel is a typical seasonal breeder. In this study, using RT-PCR, western blot and immunohistochemistry, we investigated the mRNA and protein expressions of androgen receptor (AR), estrogen receptors α and β (ERα and ERβ) and aromatase cytochrome P450 (P450arom) in the medial preoptic area (MPOA) of hypothalamus of the wild male ground squirrel during the breeding season (April), the non-breeding season (June) and pre-hibernation (September). AR, ERα, ERβ and P450arom protein/mRNA were present in the MPOA of all seasons detected. The immunostaining of AR and ERα showed no significant changes in different periods, whereas ERβ and P450arom had higher immunoreactivities during the breeding season and pre-hibernation when compared to those of the non-breeding season. Consistently, both the protein and mRNA levels of P450arom and ERβ were higher in the MPOA of pre-hibernation and the breeding season than in the non-breeding season, whereas no significant difference amongst the three periods was observed for AR and ERα levels. These findings suggested that the MPOA of hypothalamus may be a direct target of androgen and estrogen. Androgen may play important regulatory roles through its receptor and/or the aromatized estrogen in the MPOA of hypothalamus of the wild male ground squirrels.</p>

Enhancement of the lipolytic activity of skeletal muscle in certain physiological states

1970 ◽  
Vol 48 (5) ◽  
pp. 547-552 ◽  
Author(s):  
Donald P. Wallach
Keyword(s):  
Skeletal Muscle ◽  
Ground Squirrel ◽  
Skeletal Muscles ◽  
Specific Activity ◽  
Lipolytic Activity ◽  
Ground Squirrels ◽  
Lipolytic Enzyme ◽  
Rat Skeletal Muscle ◽  
Enzyme Preparations ◽  
Dystrophic Mice

Four lipolytic enzyme preparations, whose existence was previously demonstrated in rat skeletal muscle, have been shown to be present in preparations from skeletal muscles of the golden hamster, the 13-lined ground squirrel, and three strains of mice. When compared with appropriate controls, statistically significant increases in specific activity of all four lipase preparations were observed in hibernating hamsters and muscular dystrophic mice. In obese hyperglycemic mice, three monoglyceride lipases were significantly increased; there was no significant increase, however, in tricaproin lipase. In hibernating 13-lined ground squirrels and aurothioglucose-treated hyperphagic mice, only the monopalmitin lipase was significantly increased.

Temperature and the Regulation of Enzyme Activity in the Hibernator. Isoenzymes of Liver Pyruvate Kinase from the Hibernating and Non-hibernating Arctic Ground Squirrel

1974 ◽  
Vol 52 (10) ◽  
pp. 894-902 ◽  
Author(s):  
Hans W. Behrisch
Keyword(s):  
Molecular Weight ◽  
Pyruvate Kinase ◽  
Wide Temperature Range ◽  
Ground Squirrel ◽  
Energy Charge ◽  
High Energy ◽  
Ground Squirrels ◽  
The Arctic ◽  
Arctic Ground Squirrel ◽  
Temperature Range

Liver of the hibernating (H) Arctic ground squirrel (Citellus undulatus) contains a single species of pyruvate kinase (PyK) that is distinct from the single isoenzyme of pyK observed in the non-hibernating (NH) ground squirrel, which has been previously described (Behrisch &Johnson (1974) Can. J. Biochem. 52, 547–559). The H-PyK has a pI value of 5.7 and a molecular weight of 241 000 – 243 000. Affinity of the H-PyK for the substrates phosphoenolpyruvate (PEP) and ADP is not affected by changing temperature. It is argued that this stability of the apparent Km's for substrate over a wide temperature range permits the hibernator to take advantage of the Q10 effect in maintaining a low rate of the PyK reaction. Similarly, affinity of H-PyK for the allosteric activator fructose-1,6-phosphate (FDP) and the inhibitor ATP is also conspicuously independent of temperature, suggesting a fine stoichiometry in the relative concentrations of the regulatory ligands in control of H-PyK over a wide temperature range. Further, affinity of H-PyK for the inhibitor ATP is about three- to fourfold lower than that of the NH-PyK, a condition that would favor the maintenance of a high energy charge in the hibernating liver cell. ATP apparently inhibits PyK by causing a dissociation of the enzyme molecule into two "halves" of about 110 000 molecular weight each. This dissociation is offset and reversed by FDP. Removal of the ATP by dialysis does not of itself result in a reassociation of the PyK "halves"; FDP and/or the substrates are required for the two subunits of PyK to reassociate. As the apparent Ki of H-PyK for ATP is higher than that of NH-PyK, substantially higher concentrations of ATP are required to effect the dissociation of H-PyK. Similarly, elevated concentrations of FDP are required to offset the ATP-caused dissociation of the H-PyK.Hibernating Arctic ground squirrels that are preparing to emerge finally from the hibernating state already possess substantial activities of the NH-PyK isoenzyme. This suggests that the animal "anticipates" its transition from one metabolic state from another. On the basis of these data a formal mechanism is proposed for the regulation of liver PyK in the Arctic ground squirrel in both the non-hibernating and hibernating states.

Quantitative assessment of ground squirrel mRNA levels in multiple stages of hibernation

2002 ◽  
Vol 10 (2) ◽  
pp. 93-102 ◽  
Author(s):  
L. Elaine Epperson ◽  
Sandra L. Martin
Keyword(s):  
Steady State ◽  
Core Body Temperature ◽  
Ground Squirrels ◽  
Apolipoprotein A1 ◽  
Mrna Levels ◽  
Cdna Subtraction ◽  
Global Issues ◽  
Α2 Macroglobulin ◽  
Steady State Levels ◽  
Molecular Components

Hibernators in torpor dramatically reduce their metabolic, respiratory, and heart rates and core body temperature. These extreme physiological conditions are frequently and rapidly reversed during the winter hibernation season via endogenous mechanisms. This phenotype must derive from regulated expression of the hibernator’s genome; to identify its molecular components, a cDNA subtraction was used to enrich for seasonally upregulated mRNAs in liver of golden-mantled ground squirrels. The relative steady-state levels for seven mRNAs identified by this screen, plus five others, were measured and analyzed for seasonal and stage-specific differences using kinetic RT-PCR. Four mRNAs show seasonal upregulation in which all five winter stages differ significantly from and are higher than summer (α2-macroglobulin, apolipoprotein A1, cathepsin H, and thyroxine-binding globulin). One of these mRNAs, α2-macroglobulin, varies during the winter stages with significantly lower levels at late torpor. None of the 12 mRNAs increased during torpor. The implications for these newly recognized upregulated mRNAs for hibernation as well as more global issues of maintaining steady-state levels of mRNA during torpor are discussed.

scholarly journals Primase p49 mRNA expression is serum stimulated but does not vary with the cell cycle.

1989 ◽  
Vol 9 (5) ◽  
pp. 1940-1945 ◽  
Author(s):  
B Y Tseng ◽  
C E Prussak ◽  
M T Almazan
Keyword(s):  
Cell Cycle ◽  
Dna Synthesis ◽  
Mammalian Cells ◽  
Cell Cycle Progression ◽  
Small Subunit ◽  
Mrna Levels ◽  
Proliferating Cells ◽  
Restriction Point ◽  
Serum Stimulation ◽  
G1 Cells

Expression of the small-subunit p49 mRNA of primase, the enzyme that synthesizes oligoribonucleotides for initiation of DNA replication, was examined in mouse cells stimulated to proliferate by serum and in growing cells. The level of p49 mRNA increased approximately 10-fold after serum stimulation and preceded synthesis of DNA and histone H3 mRNA by several hours. Expression of p49 mRNA was not sensitive to inhibition by low concentrations of cycloheximide, which suggested that the increase in mRNA occurred before the restriction point control for cell cycle progression described for mammalian cells and was not under its control. p49 mRNA levels were not coupled to DNA synthesis, as observed for the replication-dependent histone genes, since hydroxyurea or aphidicolin had no effect on p49 mRNA levels when added before or during S phase. These inhibitors did have an effect, however, on the stability of p49 mRNA and increased the half-life from 3.5 h to about 20 h, which suggested an interdependence of p49 mRNA degradation and DNA synthesis. When growing cells were examined after separation by centrifugal elutriation, little difference was detected for p49 mRNA levels in different phases of the cell cycle. This was also observed when elutriated G1 cells were allowed to continue growth and then were blocked in M phase with colcemid. Only a small decrease in p49 mRNA occurred, whereas H3 mRNA rapidly decreased, when cells entered G2/M. These results indicate that the level of primase p49 mRNA is not cell cycle regulated but is present constitutively in proliferating cells.

Analysis by mRNA levels of the expression of six G protein α-subunit genes in mammalian cells and tissues

1991 ◽  
Vol 1094 (2) ◽  
pp. 193-199 ◽  
Author(s):  
Jermelina Linor R. Garibay ◽  
Tohru Kozasa ◽  
Hiroshi Itoh ◽  
Toshihiko Tsukamoto ◽  
Masaaki Matsuoka ◽  
...  
Keyword(s):  
G Protein ◽  
Mammalian Cells ◽  
Mrna Levels ◽  
Α Subunit ◽  
G Protein Α Subunit

Increased NHE2 expression in rat intestinal epithelium during ontogeny is transcriptionally mediated

1998 ◽  
Vol 275 (4) ◽  
pp. C1143-C1150 ◽  
Author(s):  
James F. Collins ◽  
Pawel R. Kiela ◽  
Hua Xu ◽  
Jiamin Zeng ◽  
Fayez K. Ghishan
Keyword(s):  
Northern Blot ◽  
Membrane Vesicle ◽  
Mrna Levels ◽  
Rat Intestine ◽  
Functional Protein ◽  
Adult Rats ◽  
Specific Staining ◽  
Western Blots ◽  
Intestinal Membrane ◽  
Old Rats

We have previously described changes in intestinal brush-border membrane vesicle (BBMV) Na+/H+exchange activity and characterized Na+/H+exchanger (NHE3) expression during rat ontogeny. The current studies were designed to investigate developmental changes in NHE2 expression in rat intestine. In previous studies, pH-dependent uptake of Na+ in jejunal BBMV utilizing HOE-694 inhibition demonstrated that NHE2 functional protein levels were lowest in 2-wk-old rats, higher in 3-wk-old and adult rats, and highest in 6-wk-old rats [Collins et al. Am. J. Physiol. 273 ( Cell Physiol. 42): C1937–C1946, 1997]. In the current investigation, Northern blot analyses showed that NHE2 mRNA levels in the jejunum were similar in 6-wk-old, adult, and 3-wk-old rats and three- to fivefold lower in 2-wk-old rats. In situ hybridization of 2- and 6-wk-old rat intestine with NHE2-specific probes confirmed Northern blot observations. Polyclonal antibodies were developed against an NHE2-specific peptide from amino acids 652–661. Western blots with NHE2 antiserum showed that the intensity of a specific 90-kDa band was lowest in 2-wk-old animals and four- to sixfold higher in 3- and 6-wk-old and adult animals. Immunohistochemical analysis showed specific staining of NHE2 antiserum to only the apical intestinal membrane. Furthermore, nuclear run-on analyses showed a 1.7-fold higher NHE2 transcription rate in 6-wk-old rats than in 2-wk-old rats. Overall, the current data suggest that increases in NHE2 expression upon weaning are mediated by increased gene transcription.

Regulation of Na+ pump expression by vascular smooth muscle cells

2001 ◽  
Vol 280 (4) ◽  
pp. H1869-H1874 ◽  
Author(s):  
Aslihan Aydemir-Koksoy ◽  
Julius C. Allen
Keyword(s):  
Smooth Muscle ◽  
Vascular Smooth Muscle ◽  
Smooth Muscle Cells ◽  
Vascular Smooth Muscle Cells ◽  
Mammalian Cells ◽  
Muscle Cells ◽  
Transport Processes ◽  
Western Blots ◽  
Cytoplasmic Transport ◽  
Low K

The Na+ pump and its regulation is important for maintaining membrane potential and transmembrane Na+gradient in all mammalian cells and thus is essential for cell survival and function. Vascular smooth muscle cells (VSMC) have a relatively low number of pump sites on their membrane compared with other cells. We wished to determine the mechanisms for regulating the number of pump sites in these cells. We used canine saphenous vein VSMC cultured in 10% serum and passaged one time. These cells were subcultured in 5% serum media with low K+ (1 mM vs. control of 5 mM), and their pump expression was assessed. These VSMC upregulated their pump sites as early as 4 h after treatment (measured by [3H]ouabain binding). At this early time point, there was no detectable increase in protein expression of either α1- or β1-subunits of the pump shown by Western blots. When the cells were treated with the phosphoinositide 3-kinase (PI-3-K) inhibitor LY-294002 (which is known to inhibit cytoplasmic transport processes) in low-K+ media, the pump site upregulation was inhibited. These data suggest that the low-K+-induced upregulation of Na+ pump number can occur by translocation of preformed pumps from intracellular stores.

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