Effects of polyunsaturated fatty acids on hibernation and torpor: a review and hypothesis

Abstract

Polyunsaturated fatty acids (PUFAs) can have strong effects on hibernation and daily torpor in mammals. High dietary PUFA contents were found to increase proneness for torpor, decrease body temperatures, prolong torpor bout duration, and attenuate hibernation mass loss. The mechanism by which PUFAs enhance torpor and hibernation is unknown, however. On the basis of a review of the literature, and on reexamining our own data on alpine marmots, we propose that effects on hibernation are not due to PUFAs in general, but to shifts in the ratio of n-6 PUFAs to n-3 PUFAs in membrane phospholipids. Specifically, high ratios of n-6 to n-3 PUFAs increase the activity of the Ca2+-Mg2+ pump in the sarcoplasmic reticulum of the heart (SERCA) and counteract Q10 effects on SERCA activity at low tissue temperatures. Therefore, high n-6 to n-3 PUFA ratios in cardiac myocyte membranes appear to protect the hibernating heart from arrhythmia, which in hypothermic nonhibernators is caused by massive increases in cytosolic Ca2+. The resulting reduced risk of cardiac arrest during hypothermia may explain why increased dietary uptake of n-6 PUFAs, but not of n-3 PUFAs, can strongly enhance the propensity for hibernation, and allows heterotherms to reach lower body temperatures, with associated increased energy savings. Therefore, at least for herbivorous hibernators, such as marmots, linoleic acid (C18:2 n-6)--the dietary source of all n-6 PUFAs--appears to represent a crucial and limited resource in natural environments.

Helpers influence on territory use and maintenance in Alpine marmot groups

“…Indeed, alpine meadows at higher altitude are physiologically younger and consequently enriched of α-linolenic acid (Hawke, J.C. 1973) which has been demonstrated affecting hibernation and torpor in mammals (Ruf & Arnold 2008). In accordance our results show that groups inhabiting alpine meadows at lower altitude share larger part of their territory with neighbours underlining the need of incorporating data on vegetation quality to increase our knowledge on inter group competition in this species.…”

Phenotypic flexibility in migrating bats: seasonal variation in body composition, organ sizes and fatty acid profiles

“…To interpret exercise performance effects we would need to understand sex differences in the energetic cost or energetic strategies associated with migratory flight. However, sexbased variation in the muscle PL n-6:n-3 ratio is consistent with the Ruf and Arnold (Ruf and Arnold, 2008) hypothesis that an increased n-6:n-3 ratio is associated with torpor use. During spring migration, male hoary bats readily use torpor while females rarely lower their body temperature (Cryan and Wolf, 2003), and accordingly we observed an increased n-6:n-3 ratio in males and a decreased ratio in females.…”

“…Based on the Munro and Thomas (Munro and Thomas, 2004) framework, migrating insectivorous bats should seek to maximize PUFAs. However, another review suggested that a high n-6:n-3 ratio is important for maintaining membrane function at low body temperatures (Ruf and Arnold, 2008). Male hoary bats are more likely to use torpor during spring migration than females (Cryan and Wolf, 2003), and therefore we predicted that sexes would differ in muscle PL composition during migration.…”

“…Male hoary bats are more likely to use torpor during spring migration than females (Cryan and Wolf, 2003), and therefore we predicted that sexes would differ in muscle PL composition during migration. Specifically, we predicted that males would have either greater total PUFAs or greater n-6:n-3 if the Munro and Thomas (Munro and Thomas, 2004) or Ruf and Arnold (Ruf and Arnold, 2008) hypotheses were supported, respectively.…”

Obese super athletes: fat-fueled migration in birds and bats

“…If this is true for n-3 and n-6 PUFA, then selection for diets high in PUFA could be important for successful migration. Similar arguments have been made for diet shifts in mammals preparing to hibernate (Ruf and Arnold, 2008). The evidence regarding the effects of unsaturation in general, and PUFA in particular, on migratory birds has been reviewed previously (Guglielmo, 2010;Pierce and McWilliams, 2014;Price, 2010;Weber, 2009), so I will only cover this briefly here and discuss new findings.…”