Abstract
Because of impaired thermogenesis, cold stress is poorly tolerated by hypoxic neonates. Since free fatty acids (FFA) are a major fule for heat production, deficient FFA mobilization could contribute to reduced heat production at low oxygen tensions. In order to determine the effect of hypoxia upon cold-stimulated lipolysis and its potential role in thermogenesis, plasma glycerol and FFA levels, and deep rectal temperature were studied in cooled puppies made hypoxic.
Upon lowering ambient temperature from 30 to 20°C, levels of plasma glycerol and FFA increased in 12 puppies ventilated with air (PaO2 < 75 mm Hg). In contrast to persisting high plasma glycerol and FFA levels with continued cooling in the control group, plasma glycerol fell from 172 ± 8% to 85 ± 10% and FFA from 206=25% to 105±13% mean control values (mean ± S.E.) in six animals made hypoxic (PaO2 25–35 mm Hg) for 45 min. Comparison of core temperatures during cooling revealed that the rate of temperature fall was accelerated by hypoxia, and that the mean peak fall was significantly greater in hypoxic than in control animals (p < 0.005).
These observations indicate that lipolysis stimulated by cold stress is inhibited by hypoxia, which results in the reduction of FFA as a fuel source. This loss of FFA as a fuel may explain the handicap to thermogenesis observed in the hypoxic neonate.
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Baum, D., Anthony, C. & Stowers, C. Inhibited Lipolysis by Hypoxia: Its Potential Role in Neonatal Thermogenesis. Pediatr Res 4, 473 (1970). https://doi.org/10.1203/00006450-197009000-00154
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DOI: https://doi.org/10.1203/00006450-197009000-00154