Effects of prolonged fasting on plasma cortisol and TH in postweaned northern elephant seal pups

2001 ◽  
Vol 280 (3) ◽  
pp. R790-R795 ◽  
Author(s):  
Rudy M. Ortiz ◽  
Charles E. Wade ◽  
C. Leo Ortiz
Keyword(s):  
Fat Metabolism ◽  
Plasma Concentrations ◽  
Primary Source ◽  
Elephant Seal ◽  
Mirounga Angustirostris ◽  
Hormone Metabolism ◽  
Northern Elephant Seal ◽  
Fasting Period ◽  
Total Triiodothyronine ◽  
Fat Stores

Northern elephant seal ( Mirounga angustirostris) pups rely on the oxidation of fat stores as their primary source of energy during their 8- to 12-wk postweaning fast; however, potential endocrine mechanisms involved with this increased fat metabolism have yet to be examined. Therefore, 15 pups were serially blood sampled in the field during the first 7 wk of their postweaning fast to examine the changes in plasma concentrations of cortisol and thyroid hormones (TH), which are involved in fat metabolism in other mammals. Cortisol increased, indicating that it contributed to an increase in lipolysis. Increased total triiodothyronine (tT3) and thyroxine (tT4) may not reflect increased thyroid gland activity, but rather alterations in hormone metabolism. tT3-to-tT4 ratio decreased, suggesting a decrease in thyroxine (T4) deiodination, whereas the negative correlation between total proteins and free T4 suggests that the increase in free hormone is attributed to a decrease in binding globulins. Changes in TH are most similar to those observed during hibernation than starvation in mammals, suggesting that the metabolic adaptations to natural fasting are more similar to hibernation despite the fact these animals remain active throughout the fasting period.

scholarly journals GH and ghrelin increase with fasting in a naturally adapted species, the northern elephant seal (Mirounga angustirostris)

2003 ◽  
Vol 178 (3) ◽  
pp. 533-539 ◽  
Author(s):  
RM Ortiz ◽  
DP Noren ◽  
CL Ortiz ◽  
F Talamantes
Keyword(s):  
Elephant Seal ◽  
Mirounga Angustirostris ◽  
Prolonged Fasting ◽  
Northern Elephant Seal ◽  
Factor I ◽  
Esterified Fatty Acids ◽  
Igf I ◽  
Fat Stores ◽  
The Relationship ◽  
Natural Component

After nursing, pups of the northern elephant seal (Mirounga angustirostris) are approximately 46% body fat and rely almost entirely on the oxidation of their large fat stores to sustain their metabolism for the ensuing 8-12 week postweaning fast, which is a natural component of their life history. Thus, fasting pups provide an ideal opportunity to examine the hormonal alterations associated with prolonged food deprivation in a naturally adapted model. Cortisol, ghrelin, glucagon, growth hormone (GH), insulin-like growth factor-I (IGF-I), insulin, blood urea nitrogen (BUN), glucose and non-esterified fatty acids (NEFA) were examined in 20 male and 20 female pups blood sampled early (<1 week postweaning) and late (6-8 weeks postweaning) during the fast. Mean cortisol, ghrelin, GH, and glucagon increased 1.8-, 1.8-, 1.4-, and 2.3-fold between early and late periods, while mean IGF-I and insulin decreased 97% and 38%, respectively. NEFA increased 2.3-fold, while BUN and glucose decreased 46% and 11%, respectively. NEFA was significantly and positively correlated with cortisol and GH; individually; however, when the relationship was examined as a multiple regression the correlation improved suggesting that cortisol and GH act synergistically to promote lipolysis during the fast. GH and BUN were negatively and significantly correlated between early and late fasting suggesting that GH may promote protein sparing as well. The decrease in glucose may be responsible for stimulating glucagon, resulting in the maintenance of relative hyperglycemia. The increases in cortisol, ghrelin, glucagon, and GH suggest that these hormones may be integral in mediating the metabolism of seal pups during prolonged fasting.

A new perspective on adiposity in a naturally obese mammal

2001 ◽  
Vol 281 (6) ◽  
pp. E1347-E1351 ◽  
Author(s):  
Rudy M. Ortiz ◽  
Dawn P. Noren ◽  
Beate Litz ◽  
C. Leo Ortiz
Keyword(s):  
Body Fat ◽  
Marine Mammals ◽  
Tritiated Water ◽  
Elephant Seal ◽  
Mirounga Angustirostris ◽  
Prolonged Fasting ◽  
Northern Elephant Seal ◽  
Fat Stores ◽  
New Perspective ◽  
Water Dilution

Many mammals seasonally reduce body fat due to inherent periods of fasting, which is associated with decreased leptin concentrations. However, no data exist on the correlation between fat mass (FM) and circulating leptin in marine mammals, which have evolved large fat stores as part of their adaptation to periods of prolonged fasting. Therefore, FM was estimated (by tritiated water dilution), and serum leptin and cortisol were measured in 40 northern elephant seal ( Mirounga angustirostris) pups early (<1 wk postweaning) and late (6–8 wk postweaning) during their natural, postweaning fast. Body mass (BM) and FM were reduced late; however, percent FM (early: 43.9 ± 0.5, late: 45.5 ± 0.5%) and leptin [early: 2.9 ± 0.1 ng/ml human equivalents (HE), late: 3.0 ± 0.1 ng/ml HE] did not change. Cortisol increased between early (9.2 ± 0.5 μg/dl) and late (16.3 ± 0.9 μg/dl) periods and was significantly and negatively correlated with BM ( r = 0.426; P < 0.0001) and FM ( r = 0.328; P = 0.003). FM and percent FM were not correlated ( P > 0.10) with leptin at either period. The present study suggests that these naturally obese mammals appear to possess a novel cascade for regulating body fat that includes cortisol. The lack of a correlation between leptin and FM may reflect the different functions of fat between terrestrial and marine mammals.

scholarly journals In-air hearing in Hawaiian monk seals: implications for understanding the auditory biology of Monachinae seals

2021 ◽  
Author(s):  
Brandi Ruscher ◽  
Jillian M. Sills ◽  
Beau P. Richter ◽  
Colleen Reichmuth
Keyword(s):  
Marine Mammals ◽  
Elephant Seal ◽  
Critical Ratio ◽  
Mirounga Angustirostris ◽  
Northern Elephant Seal ◽  
Hearing Ability ◽  
Highly Sensitive ◽  
Monk Seals ◽  
Management And Conservation ◽  
Hearing Abilities

AbstractThe auditory biology of Monachinae seals is poorly understood. Limited audiometric data and certain anatomical features suggest that these seals may have reduced sensitivity to airborne sounds compared to related species. Here, we describe the in-air hearing abilities of a Hawaiian monk seal (Neomonachus schauinslandi) trained to participate in a psychophysical paradigm. We report absolute (unmasked) thresholds for narrowband signals measured in quiet conditions across the range of hearing and masked thresholds measured in the presence of octave-band noise at two frequencies. The behavioral audiogram indicates a functional hearing range from 0.1 to 33 kHz and poor sensitivity, with detection thresholds above 40 dB re 20 µPa. Critical ratio measurements are elevated compared to those of other seals. The apparently reduced terrestrial hearing ability of this individual—considered with available auditory data for a northern elephant seal (Mirounga angustirostris)—suggests that hearing in Monachinae seals differs from that of the highly sensitive Phocinae seals. Exploration of phylogenetic relationships and anatomical traits support this claim. This work advances understanding of the evolution of hearing in amphibious marine mammals and provides updated information that can be used for management and conservation of endangered Hawaiian monk seals.

Ultrastructural, Sensory and Functional Anatomy of the Northern Elephant Seal (Mirounga angustirostris) Facial Vibrissae

2017 ◽  
Vol 46 (5) ◽  
pp. 487-496
Author(s):  
H. Smodlaka ◽  
I. Galex ◽  
L. Palmer ◽  
J. A. Borovac ◽  
W. A. Khamas
Keyword(s):  
Functional Anatomy ◽  
Elephant Seal ◽  
Mirounga Angustirostris ◽  
Northern Elephant Seal

Directionality of male northern elephant seal (Mirounga angustirostris) threat calls and how it influences receiver behavior.

2011 ◽  
Vol 129 (4) ◽  
pp. 2505-2505
Author(s):  
Marla M. Holt ◽  
Brandon L. Southall ◽  
Stephen J. Insley ◽  
Ronald J. Schusterman
Keyword(s):  
Elephant Seal ◽  
Mirounga Angustirostris ◽  
Northern Elephant Seal

Relationships between plasma ketones and fasting duration in neonatal elephant seals

1990 ◽  
Vol 259 (5) ◽  
pp. R1086-R1089 ◽  
Author(s):  
M. A. Castellini ◽  
D. P. Costa
Keyword(s):  
Ketone Bodies ◽  
Elephant Seal ◽  
Northern Elephant Seal ◽  
Elephant Seals ◽  
Long Duration ◽  
Fat Stores ◽  
Low Levels ◽  
Beta Hydroxybutyrate ◽  
Fasting Duration ◽  
Circulating Levels

Long-duration fasting in mammals can ultimately lead to stage three terminal starvation, which is characterized by depleted fat stores, a metabolic shift away from fat metabolism toward lean tissue catabolism, and a sharp decline in circulating levels of plasma fatty acids and ketone bodies. However, this biochemical shift has never been observed outside of the laboratory in a naturally fasting, nonhibernating mammal. In the current study, plasma levels of the ketone body D-beta-hydroxybutyrate (beta-HBA) were assayed in 10 Northern elephant seal pups during suckling and the postweaning fast and in 12 fasting adult seals. Plasma beta-HBA concentration in the pups was minimal during suckling (0.09 +/- 0.06 mM; n = 10) and began to increase immediately after weaning. The concentration rose until about 55 days into the fast (1.34 +/- 0.36 mM; n = 10) and then declined sharply. Within 10 days of this deflection point, the seal pups left for sea. By contrast, adult elephant seals showed consistently low levels of beta-HBA after several months of fasting (0.06 +/- 0.07 mM; n = 12). The data suggest that the duration of fasting in elephant seal pups may be determined, in part, by biochemical shifts that occur near the end of the fast and that the regulation of ketone concentration is different in fasting neonatal and adult elephant seals.

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