Brains have a gut feeling about fat storage

Speijer, Dave

doi:10.1002/bies.201200002

Cited by 8 publications

(7 citation statements)

References 11 publications

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“…Despite this they do not use the most energy rich substrate: FAs. This fact might explain an observed inverse correlation between fat deposits and brain size in mammals [73,74]. Neurons have to combine high ATP generation with low ROS formation by using substrates with low F/N ratios, with little variation.…”

Section: Breakdown Of Ketone Bodies and Lactate In Brain Illustrates mentioning

confidence: 99%

How the mitochondrion was shaped by radical differences in substrates

Speijer

2014

BioEssays

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As free-living organisms, alpha-proteobacteria produce reactive oxygen species (ROS) that diffuse into the surroundings; once constrained inside the archaeal ancestor of eukaryotes, however, ROS production presented evolutionary pressures - especially because the alpha-proteobacterial symbiont made more ROS, from a variety of substrates. I previously proposed that ratios of electrons coming from FADH2 and NADH (F/N ratios) correlate with ROS production levels during respiration, glucose breakdown having a much lower F/N ratio than longer fatty acid (FA) breakdown. Evidently, higher endogenous ROS formation did not hinder eukaryotic evolution, so how were its disadvantages mitigated? I propose that the resulting selection pressures favoured the evolution of a variety of eukaryotic 'innovations': peroxisomes for FA breakdown, carnitine shuttles, the linkage of beta-oxidation to antioxidant properties, uncoupling proteins (UCPs) and using mitochondrial uncoupling during beta-oxidation to reduce ROS. Recently observed relationships between peroxisomes and mitochondria further support the model.

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Section: Breakdown Of Ketone Bodies and Lactate In Brain Illustrates mentioning

confidence: 99%

How the mitochondrion was shaped by radical differences in substrates

Speijer

2014

BioEssays

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“…Indeed, several comparative studies have demonstrated negative associations between brain size and gut size (Aiello & Wheeler, ; Aiello et al ., ; Tsuboi et al ., ). This hypothesis assumes that any reduction in gut size is coupled to a switch in diet to higher quality or more easily digestible food, and the hypothesis has recently been extended to explain negative associations found between brain size and other energetically costly organs such as fat storage (Navarrete et al ., ; but see Speijer, ), muscle tissue (Isler & van Schaik, ) or reproductive effort (Isler & van Schaik, ). An experimental study in guppies further showed that individuals artificially selected for larger brains exhibited reduced gut size and also reduced fecundity compared to individuals selected for smaller brains (Kotrschal et al ., ).…”

Section: Introductionmentioning

confidence: 99%

Positive genetic correlation between brain size and sexual traits in male guppies artificially selected for brain size

Kotrschal

Corral‐Lopez

Zajitschek

et al. 2015

J of Evolutionary Biology

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Brain size is an energetically costly trait to develop and maintain. Investments into other costly aspects of an organism's biology may therefore place important constraints on brain size evolution. Sexual traits are often costly and could therefore be traded off against neural investment. However, brain size may itself be under sexual selection through mate choice on cognitive ability. Here, we use guppy (Poecilia reticulata) lines selected for large and small brain size relative to body size to investigate the relationship between brain size, a large suite of male primary and secondary sexual traits, and body condition index. We found no evidence for trade‐offs between brain size and sexual traits. Instead, larger‐brained males had higher expression of several primary and precopulatory sexual traits – they had longer genitalia, were more colourful and developed longer tails than smaller‐brained males. Larger‐brained males were also in better body condition when housed in single‐sex groups. There was no difference in post‐copulatory sexual traits between males from the large‐ and small‐brained lines. Our data do not support the hypothesis that investment into sexual traits is an important limiting factor to brain size evolution, but instead suggest that brain size and several sexual traits are positively genetically correlated.

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“…The central argument in this critique was that brain tissue generally do not use fatty acid breakdown for energy generation, presumably due to high oxygen radical formation (Speijer 2011). However, brain tissue can use fat as energy source through conversion to ketone bodies such as acetoacetate and β ‐hydroxybutyrate in the liver (Henderson and Tocher 1987; Soengas and Aldegunde 2002; Speijer 2012). This process is most important during energetically active periods and situations that are presumably common for females of S. schlegeli during the reproductive season.…”

Section: Discussionmentioning

confidence: 99%

“…This may imply the existence of a direct energetic connection between brain maintenance and fat storage. However, following the study of Navarrete et al (2011), the metabolic connection between fat and brain was challenged by Speijer (2012). The central argument in this critique was that brain tissue generally do not use fatty acid breakdown for energy generation, presumably due to high oxygen radical formation (Speijer 2011).…”

Section: The Expensive Tissue Hypothesismentioning

confidence: 99%

Within species support for the expensive tissue hypothesis: a negative association between brain size and visceral fat storage in females of the Pacific seaweed pipefish

Tsuboi

Shoji

Sogabe

et al. 2016

Ecology and Evolution

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The brain is one of the most energetically expensive organs in the vertebrate body. Consequently, the high cost of brain development and maintenance is predicted to constrain adaptive brain size evolution (the expensive tissue hypothesis, ETH). Here, we test the ETH in a teleost fish with predominant female mating competition (reversed sex roles) and male pregnancy, the pacific seaweed pipefish Syngnathus schlegeli. The relative size of the brain and other energetically expensive organs (kidney, liver, heart, gut, visceral fat, and ovary/testis) was compared among three groups: pregnant males, nonpregnant males and egg producing females. Brood size in pregnant males was unrelated to brain size or the size of any other organ, whereas positive relationships were found between ovary size, kidney size, and liver size in females. Moreover, we found that the size of energetically expensive organs (brain, heart, gut, kidney, and liver) as well as the amount of visceral fat did not differ between pregnant and nonpregnant males. However, we found marked differences in relative size of the expensive organs between sexes. Females had larger liver and kidney than males, whereas males stored more visceral fat than females. Furthermore, in females we found a negative correlation between brain size and the amount of visceral fat, whereas in males, a positive trend between brain size and both liver and heart size was found. These results suggest that, while the majority of variation in the size of various expensive organs in this species likely reflects that individuals in good condition can afford to allocate resources to several organs, the cost of the expensive brain was visible in the visceral fat content of females, possibly due to the high costs associated with female egg production.

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Brains have a gut feeling about fat storage

Cited by 8 publications

References 11 publications

How the mitochondrion was shaped by radical differences in substrates

How the mitochondrion was shaped by radical differences in substrates

Positive genetic correlation between brain size and sexual traits in male guppies artificially selected for brain size

Within species support for the expensive tissue hypothesis: a negative association between brain size and visceral fat storage in females of the Pacific seaweed pipefish

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