Glycerol metabolism in the hibernating black bear

Ahlquist, David A.; Nelson, Ralph A.; Steiger, Dianne L.; Jones, James D.; Ellefson, Ralph D.

doi:10.1007/bf00688794

Cited by 46 publications

(40 citation statements)

References 8 publications

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“…Urea, creatinine, uric acid, and glucose levels presented were similar to those reported by others (Nelson et al 1975Ahlquist et al 1984;Storm et al 1988;Hellgren et al 1993; Table 5: Changes in concentrations of free amino acids calculated from mean values presented in Table 1 and their possible fate as glucogenic or ketogenic precursors In recent studies, Tinker et al (1998) reported that lactating black bears lose a significant amount of muscle protein during hibernation. Consequently, one might expect a corresponding increase in plasma total amino acids and the N end products, urea, ammonia, and creatinine, in lactating compared with nonlactating female denning bears, but for the most part, this was not observed ( Table 2).…”

Section: Nitrogen End Products and Other Plasma Metabolitessupporting

confidence: 84%

“…Glutamine is believed to play an important role in regulating substrate and energy metabolism in fasted animals (Cersosimo et al 1986). During hibernation in bears, when amino acids and urea are recycled (Nelson et al 1975;Ahlquist et al 1984;Nelson and Jones 1987;Barboza et al 1997), the steady release of ammonia requires detoxification, which is possibly achieved by the action of glutamine synthetase in various tissues. The reciprocal levels of plasma glutamine (Table 1) and ammonia (Table 2) suggest that perhaps glutamate binds ammonia during dormancy in female bears.…”

Section: Hibernationmentioning

confidence: 99%

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Lactation during Hibernation in Wild Black Bears: Effects on Plasma Amino Acids and Nitrogen Metabolites

Wright

Obbard²,

Battersby³

et al. 1999

Physiological and Biochemical Zoology

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This study examined the seasonal and reproductive influences on individual plasma amino acid concentrations and nitrogen metabolites in a black bear population (Ontario, Canada). During hibernation, 11 of 23 plasma amino acids were significantly higher (13%-108%) in lactating than in nonlactating females, without an alteration in plasma total protein or total essential or nonessential amino acid levels. The greatest changes were observed in glutamine, arginine, and glycine levels. Plasma urea, urea/creatinine, and ammonia levels were significantly lower in hibernating compared with active female bears, but lactation had no effect on these parameters. Taken together these results show that lactation during hibernation is an additional metabolic challenge that results in increased mobilization of individual plasma amino acids and no accumulation of nitrogen end products, underlining the remarkable efficiency of amino acid and urea recycling in denning female black bears.

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Section: Nitrogen End Products and Other Plasma Metabolitessupporting

confidence: 84%

Section: Hibernationmentioning

confidence: 99%

Lactation during Hibernation in Wild Black Bears: Effects on Plasma Amino Acids and Nitrogen Metabolites

Wright

Obbard²,

Battersby³

et al. 1999

Physiological and Biochemical Zoology

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“…Lean body mass, calculated using measurements of total body water based on the dilution of deuterated water, is preserved in part because the ammonia nitrogen liberated by protein catabolism or by the breakdown of urea is reincorporated into new protein. Thus, in denning bears, 14 C label from injected [U- 14 C]glycerol was found in alanine, serine, and plasma proteins, and nitrogen from administered doubly labeled 15 N urea appeared in the amino acids ornithine, arginine, glycine, tyrosine, phenylalanine, and threonine (1,24,25). Since urea is a major determinant of urinary volume and since there is no net synthesis of urea, urine is not excreted.…”

mentioning

confidence: 99%

Seasonal regulation of the growth hormone-insulin-like growth factor-I axis in the American black bear (Ursus americanus)

Blumenthal

Morgan-Boyd

Nelson

et al. 2011

American Journal of Physiology-Endocrinology and Metabolism

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The American black bear maintains lean body mass for months without food during winter denning. We asked whether changes in the growth hormone/insulin-like growth factor-I (GH-IGF-I) axis may contribute to this remarkable adaptation to starvation. Serum IGF-I levels were measured by radioimmunoassay, and IGF-binding proteins (IGFBPs) were analyzed by ligand blotting. Initial studies in bears living in the wild showed that IGF-I levels are highest in summer and lowest in early winter denning. Detailed studies in captive bears showed that IGF-I levels decline in autumn when bears are hyperphagic, continue to decline in early denning, and later rise above predenning levels despite continued starvation in the den. IGFBP-2 increased and IGFBP-3 decreased in early denning, and these changes were also reversed in later denning. Treatment with GH (0.1 mg·kg−1·day−1 × 6 days) during early denning increased serum levels of IGF-I and IGFBP-3 and lowered levels of IGFBP-2, indicating that denning bears remain responsive to GH. GH treatment lowered blood urea nitrogen levels, reflecting effects on protein metabolism. GH also accelerated weight loss and markedly increased serum levels of free fatty acids and β-hydroxybutyrate, resulting in a ketoacidosis (bicarbonate decreased to 15 meq/l), which was reversed when GH was withdrawn. These results demonstrate seasonal regulation of GH/IGF-I axis activity in black bears. Diminished GH activity may promote fat storage in autumn in preparation for denning and prevent excessive mobilization and premature exhaustion of fat stores in early denning, whereas restoration of GH/IGF activity in later denning may prepare the bear for normal activity outside the den.

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“…It is related to how many turns of the cycle occur before an intermediate is withdrawn for amino acid biosynthesis. However, the radio-labeling experiment showed that only 6% of the label in glycerol was released as CO 2 (Ahlquist et al 1984). Thus, it follows that glycerol only has a minor contribution (via acetyl-CoA) to the biosynthesis of amino acids originating from the tricarboxylic acid cycle.…”

Section: Discussionmentioning

confidence: 99%

“…Jones et al (1999) suggest instead that the quantity of glycerol released from triglycerides may be sufficient to provide normal levels of glucose during hibernation without employing the glyoxylate cycle. Ahlquist et al (1984) used 14 C radiolabeling to follow the fate of glycerol in both active and hibernating black bears. Irrespective of the bear's status, glycerol contributed directly to glucose biosynthesis.…”

Section: Discussionmentioning

confidence: 99%

Changes in the intramolecular stable carbon isotope ratios with age of the European cave bear (Ursus spelaeus)

Keeling¹,

Nelson²

2001

Oecologia

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Changes with age in the diet and metabolism of the extinct European cave bear (Ursus spelaeus) from the Divje Babe archaeological site in northwestern Slovenia were investigated by comparing the stable carbon isotope ratio of whole bone collagen with that of the peptide-bonded carboxyl carbons in collagen. These carboxyl carbons were selectively released by decarboxylation of the collagen hydrolysate with ninhydrin (2,2-dihydroxy-1,3-indanedione). The stable carbon isotope ratio increased with age for both the peptide-bonded and other carbons. Although only one-third of the carbon atoms in collagen are peptide-bonded, they account for most of the observed change with age of the stable carbon isotope ratio of the whole collagen. Stable nitrogen isotope ratios decreased with age and were negatively correlated with changes in the stable carbon isotope ratios. These observations support previous investigations on the unique metabolism of hibernating bears.

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Glycerol metabolism in the hibernating black bear

Cited by 46 publications

References 8 publications

Lactation during Hibernation in Wild Black Bears: Effects on Plasma Amino Acids and Nitrogen Metabolites

Lactation during Hibernation in Wild Black Bears: Effects on Plasma Amino Acids and Nitrogen Metabolites

Seasonal regulation of the growth hormone-insulin-like growth factor-I axis in the American black bear (Ursus americanus)

Changes in the intramolecular stable carbon isotope ratios with age of the European cave bear (Ursus spelaeus)

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