RESUMEN

Abstract Hibernation in mammals is a physiological and behavioral adaptation to survive intervals of low resource availability through profound decreases in metabolic rate (MR), core body temperature (Tb), and activity. Most small mammalian hibernators thermoconform, with Tb approximating ambient temperature (Ta); arctic species are an exception, since they must actively defend what can be large thermal gradients between Tb and Ta. Here we compare the thermogenic capacity of the arctic ground squirrel (Urocitellus parryii) to that of the golden-mantled ground squirrel (Callospermophilus lateralis), a temperate-zone montane hibernator. We allowed animals to reenter torpor at sequentially lower Ta's and found that arctic ground squirrels maintained steady state torpor at Ta's as low as -26°C, through a 36-fold increase in torpid MR (TMR), compared to their minimum TMR, exhibited at a Ta of 0°C. Golden-mantled ground squirrels are able to maintain steady state torpor at Ta's at least as low as -8°C, through a 13.5-fold increase in MR, compared to their minimum TMR at a Ta of 2°C. In a second experiment, torpid animals were exposed to continuously decreasing Ta's (0.25°C/30 min); individuals of both species increased their metabolism while remaining torpid at low Ta's (as low as -30°C for arctic ground squirrels and -10°C for golden-mantled ground squirrels). Although the capacity to hibernate at subfreezing Ta's is not unique to arctic ground squirrels, their large body size, greater torpid metabolic scope, and previously ascribed capacity to supercool allow them to occupy much colder hibernacula for prolonged seasons of hibernation.

Asunto(s)

Metabolismo Basal/fisiología , Frío , Hibernación/fisiología , Sciuridae/metabolismo , Animales , Regiones Árticas , Regulación de la Temperatura Corporal/fisiología , Especificidad de la Especie

RESUMEN

HYPOTHESES: Consumption of wild ruminant fat represented the primary lipid source for pre-agricultural humans. Hence, the lipid composition of these animals' tissues may provide insight into dietary requirements that offer protection from chronic disease in modern humans. METHOD: We examined the lipid composition of muscle, brain, marrow and subcutaneous adipose tissue (AT) from 17 elk (Cervus elaphus), 15 mule deer (Odocoileus hemionus), and 17 antelope (Antilicapra americana) and contrasted them to wild African ruminants and pasture and grain-fed cattle. RESULTS: Muscle fatty acid (FA) was similar among North American species with polyunsaturated fatty acids/saturated fatty acids (P/S) values from 0.80 to 1.09 and n-6/n-3 FA from 2.32 to 2.60. Marrow FA was similar among North American species with high levels (59.3-67.0%) of monounsaturated FA; a low P/S (0.24-0.33), and an n-6/n-3 of 2.24-2.88. Brain had the lowest n-6/n-3 (1.20-1.29), the highest concentration of 22:6 n-3 (elk, 8.90%; deer, 9.62%; antelope, 9.25%) and a P/S of 0.69. AT had the lowest P/S (0.05-0.09) and n-6/n-3 (2.25-2.96). Conjugated linoleic acid (CLA) isomers were found in marrow of antelope (1.5%), elk (1.0%) and deer (1.0%), in AT (deer, 0.3%; antelope, 0.3%) in muscle (antelope, 0.4%; elk, trace), but not in brain. CONCLUSIONS: Literature comparisons showed tissue lipids of North American and African ruminants were similar to pasture-fed cattle, but dissimilar to grain-fed cattle. The lipid composition of wild ruminant tissues may serve as a model for dietary lipid recommendations in treating and preventing chronic disease.

Asunto(s)

Dieta , Ácidos Grasos/análisis , Rumiantes/metabolismo , Animales , Evolución Biológica , Bovinos

RESUMEN

In preparation for hibernation, golden-mantled ground squirrels (Spermophilus lateralis) must deposit sufficient amounts of lipid during the summer to survive winter hibernation. We conducted an experiment from May 1998 to February 1999 to examine the effects of caloric restriction on the body composition (lipid and fat-free mass) and hibernation of golden-mantled ground squirrels. Ground squirrels were either provided with food ad lib. (controls) or with only enough food to maintain a constant body mass throughout the experiment (calorically restricted). Changes in body composition were followed using total body electrical conductivity (TOBEC). Implanted data loggers that recorded body temperature were used to determine when ground squirrels entered their first torpor bout and the lengths of torpor bouts. Body composition did not change in the calorically restricted ground squirrels between May and September, while both lipid and fat-free mass increased in the controls. However, from September to February, calorically restricted ground squirrels lost only fat-free mass, not lipid mass, but controls lost both lipid and fat-free mass. Calorically restricted ground squirrels entered their first torpor bout about 4 wk after controls, but the torpor bout duration (or length) during hibernation did not differ between the two groups. These results show that ground squirrels maintain body composition during caloric restriction, and the limited quantities of stored lipid have an effect on when hibernation begins but not on torpor bout length.

Asunto(s)

Composición Corporal/fisiología , Ingestión de Alimentos , Hibernación/fisiología , Sciuridae/fisiología , Animales , Dieta , Grasas de la Dieta , Femenino , Lípidos/sangre , Masculino , Estaciones del Año

RESUMEN

The essential fatty acids (EFAs), alpha-linolenic acid (18:3,n-3) and linoleic acid (18:2,n-6) are known to be important for mammalian hibernation. In marmots (Marmota flaviventris), reducing both dietary EFAs alters hibernation patterns by causing an increase in energy expenditure, but hibernation still occurs. In this study, marmots fed a diet high in alpha-linolenic acid, with normal linoleic acid levels, had significantly (p < 0.05) more alpha-18:3 in their WAT and plasma unesterified fatty acids after 4 months than did marmots fed a control diet. During the winter, the control marmots hibernated normally while the marmots fed the alpha-18:3 diet did not hibernate, continued to eat, and lost less mass than the control group during the winter. These results suggest that alpha-18:3 may play a role in regulating normal hibernation behavior in marmots.

Asunto(s)

Hibernación/efectos de los fármacos , Aceite de Linaza/farmacología , Marmota/fisiología , Tejido Adiposo/fisiología , Animales , Temperatura Corporal/fisiología , Peso Corporal/efectos de los fármacos , Dieta , Ingestión de Alimentos , Estradiol/sangre , Ácidos Grasos/sangre , Ácidos Grasos no Esterificados/sangre , Femenino , Masculino , Estaciones del Año , Testosterona/sangre

RESUMEN

During winter, hibernating animals rely on their lipid stores for survival. In vitro lipolytic activity of isolated adipocytes from gonadal and subcutaneous white adipose tissue (WAT) was studied in captive alpine marmots (Marmota marmota) at two different times of their yearly cycle. During the summer, when marmots were eating, adipocyte responsiveness and sensitivity to isoprenaline and noradrenaline were higher in gonadal than in subcutaneous WAT. During hibernation, when marmots were spontaneously fasting. both the response and sensitivity to catecholamines decreased in gonadal WAT to the level of subcutaneous WAT. A similar pattern of response was also observed when lipolysis was stimulated with glucagon but the lipolytic rate was three times lower than with catecholamines. Adenosine deaminase (ADA) had a marked stimulatory effect on lipolysis, especially during the 'feeding' period, suggesting that adenosine may be a potent lipolytic modulator in marmot adipocytes. It is concluded that in marmots, lipolysis could be differentially regulated between fat depots during the annual cycle possibly to optimize either the building-up or the use of fat reserves.

Asunto(s)

Adipocitos/metabolismo , Tejido Adiposo/metabolismo , Lipólisis/fisiología , Marmota/fisiología , Periodicidad , Estaciones del Año , Adenosina Desaminasa/farmacología , Adipocitos/citología , Adipocitos/efectos de los fármacos , Tejido Adiposo/citología , Tejido Adiposo/efectos de los fármacos , Animales , Peso Corporal/fisiología , Separación Celular , Ayuno/fisiología , Femenino , Glucagón/farmacología , Gónadas/citología , Gónadas/efectos de los fármacos , Gónadas/metabolismo , Hibernación/fisiología , Técnicas In Vitro , Isoproterenol/farmacología , Lipólisis/efectos de los fármacos , Masculino , Norepinefrina/farmacología , Piel/citología , Piel/efectos de los fármacos , Piel/metabolismo

RESUMEN

Alpine marmots (Marmota marmota) were maintained on a laboratory diet, and the fatty acid composition of gonadal and subcutaneous white adipose tissues (WAT) was studied during a yearly cycle. Fatty acids (FA) released from isolated adipocytes were also identified after stimulation of in vitro lipolysis. Analysis of the FA composition of WAT depots showed that marmot WAT mainly contained monounsaturated FA (65%, mostly oleic acid, 18:1n-9) although laboratory food contained 45% of linoleic acid (18:2n-6) and only 21% of 18:1n-9. During stimulated lipolysis, saturated FA were preferentially released from isolated adipocytes whereas unsaturated FAs were retained. Despite this selective release of FA from isolated WAT cells in vitro, and despite the FA composition of the food, marmots maintained a constant FA composition in both WAT depots throughout the year. Six months of hibernation and fasting as well as an intense feeding period did not affect this composition. The potential adaptive benefit of such regulation of WAT composition, based on a high level of monounsaturated FA, might be to maintain fat with appropriate physical properties allowing animals to accommodate to and survive the wide range of body temperatures experienced during hibernation.

Asunto(s)

Tejido Adiposo/metabolismo , Ácidos Grasos/metabolismo , Marmota/fisiología , Animales , Dieta , Ácidos Grasos/análisis , Femenino , Hibernación/fisiología , Ácidos Linoleicos/análisis , Ácidos Linoleicos/metabolismo , Masculino , Ácidos Oléicos/análisis , Ácidos Oléicos/metabolismo , Estaciones del Año

RESUMEN

In order to determine whether critical enzyme activities of glycerolipid synthesis change seasonally in the golden-mantled ground squirrel (Spermophilus lateralis), we collected summer and winter samples of liver, brown adipose tissue (BAT), and white adipose tissue (WAT). Compared with fatty acid synthase activity during hibernation, summer activities were 2.5- to 8-fold higher in adipose tissue and liver. Diacylglycerol acyltransferase (DGAT) activity was 2.6-fold higher in WAT during the summer, consistent with increased seasonal triacylglycerol storage, but the activity did not change in liver or BAT, suggesting that in these tissues, triacylglycerol synthesis is equally active in summer and winter. Lack of change in acyl-CoA synthetase in liver and BAT may reflect high synthetic rates for acyl-CoAs that are destined in the summer for glycerolipid synthesis and in the winter for beta-oxidation. Monoacylglycerol acyltransferase (MGAT) activity increased significantly in both liver and WAT during the summer but decreased in BAT. Although the changes were consistent with active year-round triacylglycerol synthesis, the higher summer MGAT activity observed in the squirrel liver and WAT suggest that MGATs function may not be limited to conserving essential fatty acids during physiological states of lipolysis. Seasonal changes observed in the ground squirrel were similar to those previously reported in the yellow-bellied marmot (Marmota flaviventris), confirming that important adjustments occur in energy metabolism necessitated by long seasonal hibernation.

Asunto(s)

Hibernación , Metabolismo de los Lípidos , Proteínas Represoras , Proteínas de Saccharomyces cerevisiae , Sciuridae/fisiología , Triglicéridos/biosíntesis , Aciltransferasas/metabolismo , Tejido Adiposo/metabolismo , Animales , Coenzima A Ligasas/metabolismo , Colorado , Diacilglicerol Colinafosfotransferasa/metabolismo , Diacilglicerol O-Acetiltransferasa , Ácido Graso Sintasas/metabolismo , Hígado/metabolismo , Estaciones del Año , Triglicéridos/metabolismo

RESUMEN

The aim of the present study was to estimate insulin secretion, insulin sensitivity (SI), and glucose effectiveness (SG) in non-obese Japanese subjects with impaired glucose tolerance (IGT). Ten IGT subjects (five men, five women) and 15 normal-tolerance subjects (seven men, eight women) without a family history of diabetes were studied. They underwent a modified frequently sampled intravenous glucose tolerance test (FSIGT); glucose (300 mg/kg body weight) was administered, and insulin (20 mU/kg over 5 minutes) was infused from 20 to 25 minutes after the administration of glucose. SI and SG were estimated by Bergman's minimal model method. No significant difference was observed in body mass index ([BMI] 22.1 +/- 0.8 v 21.1 +/- 0.5 kg/m2), fasting plasma glucose (5.19 +/- 0.18 v 5.07 +/- 0.11 mmol/L), and insulin levels (50.7 +/- 7.3 v 45.2 +/- 4.5 pmol/L) of subjects with IGT and normal controls. The glucose disappearance rate (KG) was significantly lower in subjects with IGT than in normal-tolerance subjects (1.57 +/- 0.20 v 2.09 +/- 0.15%/min, P < .05). Pancreatic insulin secretion expressed as the integrated area of plasma insulin above the basal level during the first 20 minutes was lower in IGT subjects (2,556 +/- 572 pmol/L x min) than in normal-tolerance subjects (4,957 +/- 800 pmol/L x min, P < .05). SI was not statistically different between the two groups (0.84 +/- 0.13 x 10(-4) v 1.14 +/- 0.15 x 10(-4).min-1.pmol/L-1). However, SG was significantly lower in subjects with IGT than in normal controls (0.013 +/- 0.002 v 0.023 +/- 0.002 min-1, P < .01).(ABSTRACT TRUNCATED AT 250 WORDS)

Asunto(s)

Intolerancia a la Glucosa/metabolismo , Resistencia a la Insulina/fisiología , Insulina/metabolismo , Administración Oral , Adulto , Glucemia/análisis , Diabetes Mellitus Tipo 2/etiología , Femenino , Glucosa/administración & dosificación , Prueba de Tolerancia a la Glucosa/métodos , Humanos , Inyecciones Intravenosas , Insulina/sangre , Secreción de Insulina , Masculino , Modelos Biológicos

RESUMEN

In the suckling rat, chick embryo, and hibernating marmot, fatty acids provide the major source of energy, and despite the high rate of hepatic beta-oxidation, these animals selectively retain long-chain polyunsaturated derivatives of C18:2n-6 and C18:3n-3. To determine whether the hepatic microsomal activity monoacylglycerol acyltransferase (MGAT) (EC 2.3.1.22) could provide a mechanism to selectively acylate monoacylglycerols that contain essential fatty acids, we tested the ability of MGAT activity from each of the three species to acylate sn-2-monoC18:1-, sn-2-monoC18:2-, sn-2-monoC18:3-, and sn-2-monoC20:4-glycerols. Hepatic MGAT activity acylated sn-2-monoC18:3-glycerol and sn-2-monoC18:2-glycerol in preference to sn-2-monoC18:1-glycerol in each of the three different lipolytic animals. MGAT's acyl group specificity could not be explained by invoking differences in membrane fluidity because the apparent affinity for sn-2-monoC20:4-glycerol was not increased. Further, sn-2-monoC18:3-glycerol remained a preferred substrate under assay conditions when both the C18:3 and C18:1 species were present in equal amounts. As would be predicted in the presence of high activity of a selective MGAT, the hepatic glycerolipids from neonatal rats showed increases in dienoic, trienoic, and C22:6 fatty acids and relative decreases in monoenoic, saturated, and C20:4 fatty acids. We hypothesize that, during lipolysis, the reacylation of sn-2-monoacylglycerols by MGAT may provide a mechanism by which essential fatty acids are retained within specific tissues.

Asunto(s)

Aciltransferasas/metabolismo , Ácidos Grasos Esenciales/metabolismo , Hígado/metabolismo , Acilación , Animales , Animales Lactantes , Callithrix , Embrión de Pollo , Ácidos Grasos/análisis , Glicéridos/metabolismo , Hibernación , Lípidos/química , Microsomas Hepáticos/metabolismo , Fosfolípidos/química , Ratas , Ratas Sprague-Dawley

RESUMEN

We investigated the effect of an essential fatty acid (EFA)-deficient diet on hibernation patterns in yellow-bellied marmots (Marmota flaviventris). Fatty acid (FA) analysis of white adipose tissue (WAT) from animals maintained for 2 mo on the EFA-deficient diet suggested that little or no EFAs were present in the gonadal or omental fat depots. Hibernation about lengths of the EFA-deficient animals were significantly shorter (P < 0.01) than control animals. Stated another way, these animals aroused twice as frequently compared with control animals and used more energy to survive winter. Analysis of WAT composition and blood samples revealed that animals were highly lipolytic during winter. Furthermore, the release of FAs was not random: linoleate (cis-9,cis-12-octadecadienoic acid; 18:2, a diene EFA) was significantly (P < 0.05) under-represented in venous outflow from the gonadal WAT pad based on the percentage of this species in WAT. The concentration of saturated FAs was higher than that predicted from the WAT-FA composition. We conclude that linoleate is preferentially retained within WAT and that concentrations of this EFA may influence hibernation behavior. Thus EFAs may have a thermoregulatory role in hibernation in addition to their role as essential precursors for physiologically important lipids after hibernation is over.

Asunto(s)

Ácidos Grasos Esenciales/farmacología , Alimentos Formulados , Hibernación/fisiología , Marmota/fisiología , Tejido Adiposo/química , Tejido Adiposo/metabolismo , Animales , Peso Corporal/fisiología , Ácidos Grasos Esenciales/administración & dosificación , Femenino , Ácidos Linolénicos/análisis , Ácidos Linolénicos/metabolismo , Masculino , Factores de Tiempo

RESUMEN

Fatty acid metabolism and triacylglycerol synthesis are critical processes for the survival of hibernating mammals that undergo a prolonged fasting period. Fatty acid synthase, fatty-acid-CoA ligase, diacylglycerol acyltransferase, and monoacylglycerol acyltransferase activities were measured in liver and in white and brown adipose tissue, in order to determine whether enzymes of lipogenesis and triacylglycerol synthesis vary seasonally during hibernation in the yellow-bellied marmot (Marmota flaviventris). Compared with mid-winter hibernation, fatty acid synthase activity was higher in all three tissues during early spring when marmots emerged from hibernation and in mid-summer when they were feeding, consistent with the synthesis of fatty acids from the carbohydrate-rich summer diet. Fatty-acid-CoA ligase and diacylglycerol acyltransferase activities were highest in summer in white adipose tissue when triacylglycerol synthesis would be expected to be high; diacylglycerol acyltransferase activity was also high in brown adipose tissue during spring and summer. In liver, however, diacylglycerol acyltransferase specific activity was highest during hibernation, suggesting that triacylglycerol synthesis may be prominent in liver in winter. Monoacylglycerol acyltransferase activity, which may aid in the retention of essential fatty-acids, was 80-fold higher in liver than in white or brown adipose tissue, but did not vary seasonally. Its dependence on palmitoyl-CoA suggests that a divalent cation might play a role in enzyme activation. The high hepatic diacylglycerol acyltransferase activity during hibernation suggests that the metabolism of very low density lipoprotein may be important in the movement of adipose fatty acids to brown adipose tissue and muscle during the rewarming that occurs periodically during hibernation.(ABSTRACT TRUNCATED AT 250 WORDS)

Asunto(s)

Tejido Adiposo/enzimología , Hibernación/fisiología , Hígado/enzimología , Marmota/metabolismo , Proteínas Represoras , Proteínas de Saccharomyces cerevisiae , Estaciones del Año , Triglicéridos/biosíntesis , Aciltransferasas/metabolismo , Animales , Coenzima A Ligasas/metabolismo , Ácido Graso Sintasas/metabolismo , Hígado/metabolismo

RESUMEN

White adipose tissue (WAT) and plasma samples were obtained from yellow-bellied marmots (Marmota flaviventris) throughout the year. Mean plasma triacylglycerol (TG), free fatty acids (FFAs), and glycerol were determined. There was a clear increase in FFAs and decrease in mean TG and glycerol during the hibernation period when animals were fasting, suggesting increased lipolysis. RNA was isolated from WAT biopsies at four times in the year: spring, summer, fall, and winter. There were significant changes in the relative levels of mRNA for lipoprotein lipase (LPL) and hormone-sensitive lipase (HSL) during the body mass cycle of the marmot. The relative levels of LPL mRNA are high during the mass gain phase of the year and that of HSL mRNA are high during the fasting period when endogenous lipid is utilized. These results suggest that the genes for LPL and HSL are regulated seasonally to control the adipose mass depot in marmots.

Asunto(s)

Tejido Adiposo/metabolismo , Hormonas/fisiología , Lipoproteína Lipasa/genética , Marmota/fisiología , ARN Mensajero/metabolismo , Estaciones del Año , Tejido Adiposo/fisiología , Animales , Ácido Graso Sintasas/genética , Ácidos Grasos no Esterificados/sangre , Glicerol/sangre , Marmota/sangre , Concentración Osmolar , Triglicéridos/sangre

Asunto(s)

Hibernación/fisiología , Insulina/líquido cefalorraquídeo , Marmota/fisiología , Saciedad/fisiología , Sciuridae/fisiología , Animales , Química Encefálica , Glucosa/líquido cefalorraquídeo , Insulina/sangre

RESUMEN

Plasma insulin (PI) reportedly crosses the blood-brain barrier in mammals and acts with the central nervous system (CNS) to reduce food intake. Animals that hibernate (hibernators) eat little or no food from early winter (November) to spring (April). This lack of food intake may be due to elevated PI concentrations acting within the CNS. In this study, we determined whether hibernators have altered insulin levels within the CNS at different times during the circannual cycle of metabolism and feeding. Plasma and cerebrospinal fluid (CSF) immunoreactive insulin concentrations were measured in marmots (Marmota flaviventris) during the feeding phase of the body weight cycle and during the fasting period (hibernation). Basal plasma and CSF samples were collected in September, November, January, and April. In addition, plasma and CSF insulin levels were monitored during a 2-h intravenous infusion of glucose (20% wt/vol) that stimulated pancreatic B-cell production of insulin. During the spring feeding period, we found that as PI levels rise, so do CSF insulin concentrations. However, in fall and winter when marmots are fasting, very little insulin entered the CSF even when PI levels were significantly elevated. Furthermore, the longer the fast, the lower was the CSF insulin under both basal and infusion conditions. These results lead us to conclude that elevated CSF insulin is not a likely cause of suppressed food intake in fasting marmots.

Asunto(s)

Ayuno , Hibernación/fisiología , Insulina/líquido cefalorraquídeo , Marmota/líquido cefalorraquídeo , Saciedad/fisiología , Estaciones del Año , Animales , Glucemia/metabolismo , Frío , Ingestión de Alimentos , Glucosa/farmacología , Insulina/sangre , Cinética

RESUMEN

The study presented below describes experiments that investigate the ability of insulin to inhibit food intake in awake, active marmots during the summer season. Our results suggest that increasing intraventricular insulin concentration during the summer active feeding period will cause a decrease in food intake and body weight of marmots. When infused with insulin into their lateral ventricles (Alzet #2002 minipumps), animals had significantly lower food intake as compared to their food intake during the control period. In addition, these animals lost body weight during the period of the insulin infusion. We suggest that during the summer when marmots are not hibernating and are actively feeding, brain insulin levels may play a role in regulating food intake.

Asunto(s)

Peso Corporal/efectos de los fármacos , Conducta Alimentaria/efectos de los fármacos , Insulina/farmacología , Estaciones del Año , Tejido Adiposo/efectos de los fármacos , Animales , Callitrichinae , Inyecciones Intraventriculares , Periodicidad

RESUMEN

1. Glucose uptake was measured throughout the year in marmots (Marmota flaviventris) by the hyperglycemic clamp technique. During each 2 hr experiment, the plasma glucose level was maintained at 215 mg/dl while blood samples were collected and analysed for glucose, insulin, glucagon, cortisol and catecholamines. 2. Glucose uptake was calculated from the glucose infusion rate, changes in the glucose pool (using a correction factor), and urinary glucose excretion. 3. In autumn, animals peaked in body weight (greater than 4.0 kg) and ceased to feed. Basal plasma insulin levels in autumn were significantly elevated over all other seasons (P less than 0.01) and glucose uptake in autumn was 9.7 +/- 2.4 mg/min which was significantly lower (P less than 0.05) than summer (21.7 +/- 2.4 mg/min) during the steady state phase of the glucose clamp (90-120 min). 4. Plasma glucagon levels declined during the clamp in all seasons but there was no significant difference between seasons. Plasma cortisol and catecholamine (norepinephrine and epinephrine) levels remained unchanged under basal and experimental conditions throughout the seasons. 5. During glucose infusion, beta-hydroxybutyrate levels were suppressed suggesting that lipolysis was reduced during the experiment. 6. These results suggest that the marmot exhibits seasonal changes in glucose uptake; the lowest rate of glucose uptake occurring in the autumn after the animals peak in body weight and cease to feed.

Asunto(s)

Glucosa/farmacocinética , Marmota/fisiología , Hormonas Pancreáticas/fisiología , Estaciones del Año , Ácido 3-Hidroxibutírico , Animales , Glucemia/análisis , Catecolaminas/sangre , Femenino , Técnica de Clampeo de la Glucosa , Hidroxibutiratos/sangre , Masculino , Marmota/metabolismo , Concentración Osmolar , Hormonas Pancreáticas/sangre

RESUMEN

White adipose tissue biopsies and plasma samples were obtained from hibernating yellow-bellied marmots (Marmota flaviventris) maintained in the laboratory. In addition, biopsies and plasma samples were obtained from normothermic animals in the field and laboratory. Measurement of plasma free fatty acid (FA) levels indicated that winter laboratory animals exhibited increased lipolysis. Additionally, analysis of white adipose tissue triacylglycerol revealed that the FA composition of the storage fat in animals maintained on the standard laboratory diet is remarkably simple and uniform between different adipose depots in the same animal. Three FAs (palmitic, oleic, and linoleic acids) made up greater than 95% of the total. Triene (alpha-linolenate) was found in newly captured animals, but the percentage of this FA decreased rapidly when the animals were maintained on the standard laboratory diet. Throughout the hibernation season (October to April), white adipose tissue-saturated FA percentage decreased, monoene percentage remained constant, and diene percentage increased. Analysis of plasma FA composition suggested that these animals tended to metabolize saturated FAs from stored lipid during hibernation and that dienes were mobilized briefly after the last arousal from hibernation in spring. From these observations, we hypothesize that marmots preferentially metabolize saturated fats during the hibernation period and that essential FAs of the omega 6 series tend to be metabolized more slowly than other FAs. These characteristics suggest that marmots are a valuable animal model in which to study lipid metabolism.

Asunto(s)

Tejido Adiposo/metabolismo , Metabolismo de los Lípidos , Marmota/metabolismo , Sciuridae/metabolismo , Animales , Animales de Laboratorio/sangre , Animales de Laboratorio/metabolismo , Animales Salvajes/sangre , Animales Salvajes/metabolismo , Peso Corporal , Ácidos Grasos/sangre , Lípidos/sangre , Marmota/anatomía & histología , Marmota/sangre , Triglicéridos/clasificación , Triglicéridos/metabolismo

RESUMEN

1. The effect of hibernation on cerebral cortical concentrations of cholecystokinin and vasoactive intestinal peptide was investigated in the golden mantled ground squirrel (Citellus lateralis). 2. During hibernation, cortical brain weight decreased to 83% of the non-hibernating weight. 3. The concentration of the small form of CCK was significantly reduced. The concentration of the large forms of immunoreactive CCK did not significantly change during hibernation. The molecular forms of CCK appeared the same both before and during hibernation. 4. Of note, the concentration of vasoactive intestinal peptide significantly increased during hibernation. 5. Since there was a three-fold reduction in the ratio of large to small forms of CCK during hibernation, this suggests that post-translational processing of the precursor peptides are markedly reduced during hibernation.

Asunto(s)

Colecistoquinina/metabolismo , Hibernación , Sciuridae/metabolismo , Péptido Intestinal Vasoactivo/metabolismo , Animales , Corteza Cerebral/metabolismo , Femenino , Masculino , Procesamiento Proteico-Postraduccional

RESUMEN

The amino acid sequence of the alpha-chain from the arctic ground squirrel Citellus parryii) is reported. The tryptic peptides prepared from the hemoglobin were isolated by reverse phase HPLC and sequenced. Data from the tryptic peptides were supported by that from cyanogen bromide peptides and acid cleavage peptides which were partially sequenced. Comparison with other rodent alpha-chains shows 15 differences with mouse, 20 with rat, 25 with muskrat, 16 with mole rat, 33 with the guinea-pig and 23 with the hamster. Comparison of arctic ground squirrel hemoglobin alpha-chain with the amino-terminal 25 residues of the marmot shows one amino acid difference at position 13.

Asunto(s)

Hemoglobinas/análisis , Sciuridae/sangre , Alaska , Secuencia de Aminoácidos , Animales , Cricetinae , Cobayas , Marmota/sangre , Ratones , Ratas , Valores de Referencia

RESUMEN

The effects of hibernation on pancreatic insulin, glucagon, somatostatin, and pancreatic polypeptide was investigated in the golden mantled ground squirrel (Citellus lateralis). During hibernation, pancreatic organ weight decreased to 57% of the nonhibernating weight. The content of all four pancreatic hormones during hibernation was significantly reduced. The concentrations of insulin, pancreatic polypeptide and somatostatin, but not of glucagon, were significantly reduced during hibernation. The maintenance of the pancreatic glucagon concentration during hibernation may be related to its role in counter-regulation and carbohydrate homeostasis during fasting.

Asunto(s)

Glucagón/análisis , Hibernación , Insulina/análisis , Marmota/fisiología , Páncreas/análisis , Polipéptido Pancreático/análisis , Sciuridae/fisiología , Somatostatina/análisis , Animales , Tamaño de los Órganos , Especificidad de la Especie