For the festive season, we have a look at the funny side of the biology of Christmas. Enjoy!

1. The DNA Universe
THE BIOLOGY OF CHRISTMAS
2019

2. 2
A funny take on the changes in human
gene expression during Christmas season
Eurofins Genomics - The DNA Universe
Christmas season - the most wonderful time of the year when our thoughts are on
festive relaxation and cosiness, and when we eagerly anticipate the celebration
with our loved ones.
Christmas season is linked to temporal neuronal and hormonal changes that
result in modifications of human behaviour.
Rapid advances in molecular biology
and genetics have led to a greater
understanding of the ‘Biology of
Christmas’.
Research results strongly indicate the
involvement of a circannual rhythm!
Ludwig M. (2011). Christmas: an event driven by our hormones? J. Neuroendocrinol. 23(12):1191-3.

3. 3Eurofins Genomics - The DNA Universe
What are circannual rhythms?
• Endogenous mechanisms of utmost importance for the regulation of the
physiology.
• They have a period length of approximately one year and prepare the organism
to reoccurring events.
• In animals they are involved in migration/
hibernation, fur change of mammals
(summer and winter fur) and seasonal
reproduction for instance.
• Latest research substantiates the
hypothesis that in humans a specific
circannual rhythm evolved for the
reoccurring event of Christmas.
- Harmer, L., Panda, S, Kay, S.A. (2001) Molecular Bases of Circadian Rhythms. Annu. Rev. Cell Dev. Biol. 17:215-53.
- Kumar, V. and Mishra, I. (2018) Circannual Rhythms. In M.K. Skinner (Ed), Encyclopedia of Reproduction. Vol 1, pp. 442-50. Academic Press: Elsevier.
- Lincoln, G. (2019) A brief history of circannual time. J Neuroendocrinol. 31(3):e12694.
- Xie, Y., Tang, Q., Chen, G., Xie, M., Yu, S., Zhao, J., & Chen, L. (2019) New Insights Into the Circadian Rhythm and Its Related Diseases. Front Physiol. 10: 682.

4. 4Eurofins Genomics - The DNA Universe
The Christmas circannual rhythm
The Christmas circannual rhythm is generated in a region of the hypothalamus
labelled “Christmas vivifying centre”.
• This centre is a cluster of neurons that is dormant for 11 months of the year.
• Activity in this centre gradually increases with the beginning of December and
shows peak activity at 25th and 26th
December.
• Thereafter, activity decreases
extremely fast and reaches
dormancy again at 1st of January.

5. 5Eurofins Genomics - The DNA Universe
Activation of the “Christmas vivifying centre” results in an upregulation of liver
enzyme production via the Christmas-stimulating hormone (CSH) in
anticipation of extensive feeding.
Three associated genes have been identified:
• GBF1 (GINGERBREAD FATTENING 1)
• MWG (MULLED WINE GUZZLING) that encodes
a novel class III alcohol dehydrogenase
• IIC (INDULGING IN CHOCOLATE, also known as
I’M IN CONTROL-HONESTLY).
Díaz-Zavala, R. G., Castro-Cantú, M. F., Valencia, M. E., Álvarez-Hernández, G., Haby, M. M., Esparza-Romero, J. (2017) Effect of the Holiday
Season on Weight Gain: A Narrative Review. J Obes. 2017: 2085136.
Effects of activation of the “Christmas vivifying centre”
Upregulation of IIC in particular seems to be associated with body weight gain
in adults during Christmas season. Interestingly, significant weight gains have
been observed in adults during holiday season in general, even when weight
loss was aimed for!

6. 6Eurofins Genomics - The DNA Universe
In order to restore homeostasis,
antagonising mechanisms are activated
that stimulate another cluster of neurons
in the hypothalamus called
”New Year’s Resolution centre”:
Activation of antagonising mechanisms
• Here, the Necessity for
diet-releasing factor (NdRF) is
produced that reaches peak level
around 2nd January.
• Unsurprisingly, NdRF levels decrease rapidly.
• This is associated with terminating any ambitions of dieting as part of
the New Year resolutions by mid-January.

7. 7Eurofins Genomics - The DNA Universe
The bitter truth:
• Investigations showed that 77% of New Year's resolvers broke their pledges
after one week and only 19% successfully kept them for two years.
- Norcross, J. C. and Vangarelli, D. J. (1988) The resolution solution: Longitudinal examination of New Year’s change attempts. J Subst Abuse. 1(2):127-34.
- Ramage, S., Farmer, A., Eccles, K.A., McCargar, L. (2014) Healthy strategies for successful weight loss and weight maintenance: a systematic review. Appl Physiol
Nutr Metab. 39(1):1-20.
- Varkevisser, R.D.M., van Stralen, M.M., Kroeze, W., Ket, J.C.F., Steenhuis, I.H.M. (2019) Determinants of weight loss maintenance: a systematic review. Obes
Rev. 20(2):171-211.
Success of New Year’s resolutions
• For loosing body weight and main-
taining the weight loss long-term, many
strategies exist, but ultimately it comes
down to sustainability.
• The most effective diet is useless when
it is not sustainable as a life style,
especially during stressful times.
• Pick a diet, be it vegan, vegetarian, low
fat, low carb, etc., and test if it is the
right choice and you can stick to it.

8. 8Eurofins Genomics - The DNA Universe
This text has been created for entertainment and most of it has
been made up.
However, gain in body fat, particularly visceral fat, and obesity
have deleterious effects on health and profoundly impact the
quality of life!
On a serious note
- Scully, T. (2014) Public health: Society at large. Nature. 508(7496):S50-1.
- González-Muniesa, P., Mártinez-González, M.A., Hu, F.B., Després, J.P., Matsuzawa, Y., Loos, R.J.F., Moreno, L.A., Bray, G.A., Martinez, J.A. (2017) Obesity. Nat
Rev Dis Primers. 3:17034.

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