Microbial component to obesity

Summaries of newsworthy papers published in Nature on 21 December 2006. Including: Fortnightly tidal oscillations in Antarctic ice stream flow, Starve the tumour, sabotage the blood supply, Gamma-ray burst defies classification, Parasite conundrum solved?, Progeria mutation sheds light on normal ageing, Female meerkats get their claws out ...


This press release is copyright Nature.

VOL.444 NO.7122 DATED 21 DECEMBER 2006

This press release contains:

* Summaries of newsworthy papers:

Obesity: Microbial component to obesity
Glaciology: Fortnightly tidal oscillations in Antarctic ice stream flow
Cancer: Starve the tumour, sabotage the blood supply
Cosmology: Gamma-ray burst defies classification
Infectious disease: Parasite conundrum solved?
Genetics: Progeria mutation sheds light on normal ageing
Ecology: Female meerkats get their claws out
Neuroscience: Neurons group abstract movement
Locomotion: Bungee benefits backpackers
Evolution: Coming up for air
Planetary science: Mercury magnetic field mystery cracked?
Olfaction: How mammals sniff underwater
And finally… A virgin birth for Christmas?

* Mention of papers to be published at the same time with the same embargo
* Geographical listing of authors

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[1] & [2] Obesity: Microbial component to obesity (pp 1027-1031; 1022-1023; N&V)

The microbes living in our guts may influence how prone we are to obesity, a finding that may have implications for the treatment of this worldwide epidemic.

Our gastrointestinal tracts house two dominant groups of beneficial bacteria, the Bacteroidetes and the Firmicutes, which help us to break down otherwise indigestible foods. The relative proportion of Bacteroidetes is decreased in obese compared with lean people, Jeffrey I. Gordon and colleagues report in a Brief Communication in this week's Nature. And the proportion increases as weight is lost on low calorie diets.

The finding suggests that obesity has a microbial component, and an accompanying paper by the collaborating authors suggests a possible explanation. This shows that gut microbes in obese mice are better at harvesting calories from food than those found in their lean littermates. And the effect is transmissible - when 'obese microbes' are transplanted into germ-free mice their total body fat increases more than when 'lean microbes' are transplanted.


Jeffrey I. Gordon (Washington University School of Medicine, St Louis, MO, USA)
Tel: +1 314 362 7243; E-mail: [email protected] <mailto:[email protected]>

Randy J. Seeley (University of Cincinnati, OH, USA) N&V author
Tel: +1 513 558 6664; E-mail: [email protected] <mailto:[email protected]>

[3] Glaciology: Fortnightly tidal oscillations in Antarctic ice stream flow (pp 1063-1064)

The flow of ice through Antarctica's ice streams may be much more variable than was previously thought, a paper in this week's Nature suggests. The finding has implications for estimating the contribution of large ice sheets to global sea-level change, and highlights the pitfalls inherent in measuring ice flow speed.

The ice sheets of Antarctica and Greenland shed much of their ice via fast-flowing ice streams. G. Hilmar Gudmundsson monitored the flow in one such Antarctic stream over a period of two months and found that the surface velocity oscillates by as much as 20 per cent every two weeks, a variation that is linked to the tidal cycle.

Researchers studying ice flow rate often use measurements taken at separate points in time to infer long term changes. So the existence of strong fortnightly variations in flow draws attention to a potential methodological snag.


G. Hilmar Gundmundsson (British Antarctic Survey, Cambridge, UK)
Tel: +44 1223 221 265; E-mail: [email protected] <mailto:[email protected]>

[4] & [5] Cancer: Starve the tumour, sabotage the blood supply (pp 1032-1037; 1083-1087)

A new drug that shrinks tumours by sabotaging their blood supply may work against cancers that have become resistant to standard anti-angiogenic therapies.

Inhibitors of the molecule Delta-like ligand 4 (Dll4) can shrink tumours in a variety of models, two papers in this week’s Nature report. The drug causes an increase in vascularity, but the newly formed blood vessels do not function properly and the tumours become starved of oxygen.

Other anti-angiogenic drugs that target a different protein called vascular endothelial growth factor (VEGF), or its receptor, are already in the clinic but they are not effective against all tumours. Dll4 blockers may work against these anti-VEGF-resistant cancers, say Gavin Thurston and Minhong Yan; they may also work well in combination with anti-VEGF therapies.


Gavin Thurston (Regeneron Pharmaceuticals, Tarrytown, NY, USA) Author paper [4]
Tel: +1 914 345 7575; E-mail: [email protected] <mailto:[email protected]>

Minhong Yan (Genentech, South San Francisco, CA, USA) Author paper [5]
Tel: +1 650 225 5691; E-mail: [email protected] <mailto:[email protected]>

[6] [7] [8] & [9] Cosmology: Gamma-ray burst defies classification (pp 1044-1046; 1050-1052; 1047-1049; 1053-1055; N&V)

The more it’s studied, the more enigmatic it becomes. Gamma-ray burst GRB 060614 doesn’t fit into the current classification scheme, four papers in this week’s Nature report, leaving researchers to ponder exactly what this huge explosion of energy was.

On 14 June 2006, the Burst Alert Telescope onboard the Swift satellite detected a presumed gamma-ray burst (GRB) that lasted 102 seconds. GRBs can be separated into two classes - short and long - on the basis of their duration, but GRB 060614 displays features of both, say Neil Gehrels and colleagues.

Three further groups, led by Massimo Della Valle, Johan P. U. Fynbo and A. Gal-Yam, report optical data demonstrating that GRB 060614 had no accompanying supernova, as is characteristic of most long-duration bursts. So while the findings may prompt the development of a new GRB classification system, they also highlight just how little we understand about the nature of some of these bursts.


Neil Gehrels (NASA Goddard Spaceflight Center, Greenbelt, MD, USA) Author paper [6]
Tel: +1 301 286 6546; E-mail: [email protected] <mailto:[email protected]>

Massimo Della Valle (Arcetri Astrophysical Observatory, Firenze, Italy) Author paper [7]
Tel: +39 3394 320 350; E-mail: [email protected] <mailto:[email protected]>

Johan P. U. Fynbo (University of Copenhagen Dark Cosmology Centre, Denmark) Author paper [8]
Tel: +45 3532 5983; E-mail: [email protected] <mailto:[email protected]>

Avishay Gal-Yam (California Institute of Technology, Caltech Optical Observatories, Pasadena, CA, USA) Author paper [9]
Tel: +1 626 395 4421; E-mail: [email protected] <mailto:[email protected]>

Bing Zhang (University of Nevada, Las Vegas, NV, USA) N&V author
Tel: +1 702 895 4050; E-mail: [email protected] <mailto:[email protected]>

[10] Infectious disease: Parasite conundrum solved? (AOP)
DOI: 10.1038/nature05395

***This paper will be published electronically on Nature's website on 20 December at 1800 London time / 1300 US Eastern time (which is also when the embargo lifts) as part of our AOP (ahead of print) programme. Although we have included it on this release to avoid multiple mailings it will not appear in print on 21 December, but at a later date.***

When it infects humans, some strains of the parasite Toxoplasma gondii go largely unnoticed, whereas others can kill. Researchers now think they know why.

One strain of the parasite injects an enzyme into the host cell, which travels to the cell’s nucleus and dramatically alters the host’s gene expression. This can then alter the expression of proteins that are involved in the host’s response to infection. Some other strains of Toxoplasma do not possess this enzyme, which may explain why infections manifest disease in different ways, say Jeroen Saeij and colleagues in this week's Nature.

The findings provide a new mechanism for the interaction between an intracellular eukaryotic pathogen and its host, and reveal major differences in how Toxoplasma lineages have evolved to exploit this interaction.

Jeroen Saeij (Stanford University, CA, USA)
Tel: +1 650 723 7296; E-mail: [email protected] <mailto:[email protected]>

[11] Genetics: Progeria mutation sheds light on normal ageing (pp 1038-1043; N&V)

The discovery of a new mutation that causes an unusually severe form of a disease that results in accelerated ageing (progeria), may help to reconcile two seemingly disparate theories of ageing.

Some think that ageing is genetically regulated; others, that it is due to a gradual build up of DNA damage. In this week’s Nature, Jan H. J. Hoeijmakers and colleagues suggest that both theories are correct.

The team discovered a new mutation in the XPF gene of a human patient that causes a dramatic form of progeria. Young mice that have been genetically engineered to model this syndrome show many features of normal old mice. These include reduced insulin signalling; increased cell death, anti-oxidant and DNA repair pathways; and a shift towards anabolism - the building up of new tissues. The results suggest that an accumulation of DNA damage induces metabollic changes aimed at extending life rather than maintaining growth.

They conclude that DNA damage drives the functional decline associated with ageing. But genetics, and in particular the insulin signalling pathway, influence how rapidly damage accumulates and function is lost.


Jan H. J. Hoeijmakers (Erasmus MC, Rotterdam, The Netherlands)
Tel: +31 10 408 7199; E-mail: [email protected] <mailto:[email protected]>

Tom Kirkwood (Newcastle University, UK) N&V author

Tel: +44 191 256 3319; E-mail: [email protected] <mailto:[email protected]>

[12] Ecology: Female meerkats get their claws out (pp 1065-1068)

Cute and fluffy they may be, but female meerkats have a dark side. They'll scrap readily in order to obtain access to mates and resources, and researchers now think they know why.

In most animals, the sex that invests least in its offspring competes more intensely for access to the opposite sex. However, in meerkats (Suricata suricatta) and other animals where females are the primary care givers, females compete more with each other than males. One reason, say Tim H. Clutton-Brock and colleagues in this week's Nature, is that in the arid savannahs of southern Africa, meerkat resources are heavily concentrated.

Meerkats are unusual because one female tends to monopolize reproduction, producing up to four litters - each of up to seven pups - per year for up to a decade. Most of the pups are born to a dominant male, but it's the females who provide most of the child care and who have most to gain by acquiring dominant status.


Tim H. Clutton-Brock (University of Cambridge, UK)
Tel: +44 1223 336 605; E-mail: [email protected] <mailto:[email protected]>

[13] Neuroscience: Neurons group abstract movement (AOP)

DOI: 10.1038/nature05470

***This paper will be published electronically on Nature's website on 20 December at 1800 London time / 1300 US Eastern time (which is also when the embargo lifts) as part of our AOP (ahead of print) programme. Although we have included it on this release to avoid multiple mailings it will not appear in print on 21 December, but at a later date.***

Neuroscientists have identified neurons in monkey brains that may be involved in grouping different types of movements into abstract categories.

It’s hard to remember a large number of individual complex movements, but grouping them into general categories can make a task easier. Online in this week’s Nature, Jun Tanji and colleagues describe neurons in the lateral prefrontal cortex that become active before certain categories of movement.

Their presence suggests that the monkeys use a ‘grouping’ strategy to help remember complex sequences of movements. And alongside previous work, the current study suggests that abstract grouping may be a general property of the prefrontal cortex.


Jun Tanji (Tohoku University School of Medicine, Sendai, Japan)
Tel: +81 22 717 8071; E-mail: [email protected] <mailto:[email protected]>

[14] Locomotion: Bungee benefits backpackers (pp 1023-1024)

Backpackers might have a new use for bungee cord besides providing an aerial adrenaline rush. New research shows that using the springy rope to suspend a backpack from its frame reduces the energetic cost of carrying the load.

Conventional backpacks, which are attached tightly to their frames and therefore to the wearer's body, move up and down in time with the walker's footsteps - and this vertical movement costs the walker energy, explain researchers led by Lawrence Rome in a Brief Communication in this week's Nature. By hanging the backpack load from springy cords, a 27-kilogram backpack can be transported using the same energy required to carry a conventional pack weighing just 21.7 kilograms, they calculate.

The principle is the same as that used by traditional Asian merchants who carry their wares using flexible bamboo poles, the authors point out. Designing springy backpacks could prevent injuries to children who carry backpacks, and could allow emergency personnel such as soldiers and medics to run more easily while carrying packs, allowing them to get to disaster sites more quickly.


Lawrence C. Rome (University of Pennsylvania, Philadelphia, PA, USA)
Tel: +1 215 898 9915; E-mail: [email protected] <mailto:[email protected]>

[15] Evolution: Coming up for air (AOP; N&V)

DOI: 10.1038/nature05450

***This paper will be published electronically on Nature's website on 20 December at 1800 London time / 1300 US Eastern time (which is also when the embargo lifts) as part of our AOP (ahead of print) programme. Although we have included it on this release to avoid multiple mailings it will not appear in print on 21 December, but at a later date.***

Biologists now have a new tool to help them trace evolutionary change over geological time, and it’s hidden in the fundamental biochemistry of the cell.

In this week’s Nature, Claudia Acquisti and colleagues report systematic variation in the ways in which various organisms incorporate oxygen in membrane-spanning proteins. The membrane proteins of eukaryotes and compartmentalized prokaryotes tend to contain more oxygen than those of simpler prokaryotes - a sign, say the authors, of evolution on the early Earth when the concentration of oxygen in the atmosphere was rising from a low level to its present-day abundance.


Claudia Acquisti (Max Planck Institute for Plant Breeding Research, Koln, Germany)
Tel: +49 221 506 2467; E-mail: [email protected] <mailto:[email protected]>

Peggy Baudouin-Cornu (CEA-Saclay, Gif-sur-Yvette, France) N&V author

Tel: +33 1 69 08 97 18; E-mail: [email protected] <mailto:[email protected]>

[16] Planetary science: Mercury magnetic field mystery cracked? (pp 1056-1058)

Mercury's magnetic field is one hundred times weaker than Earth's, and researchers now think they know why.

Just like Earth, Mercury's magnetic field is probably generated by a dynamo as molten iron swirls around in the core of the planet. But unlike Earth, the dynamo may only operate in the deep part of the core, says Ulrich R. Christensen in this week's Nature. He thinks this is because material in the core’s outer regions is stably stratified and so is not able to convect heat.

The model explains both the strength and morphology of Mercury's magnetic field and its validity should be testable by upcoming missions to the planet.


Ulrich R. Christensen (Max Planck Institute for Solar System Research, Katlenburg-Lindau, Germany)
Tel: +49 5556 979 542; E-mail: [email protected] <mailto:[email protected]>

[17] Olfaction: How mammals sniff underwater (pp 1024-1025)

Most land mammals are unable to smell underwater, because the nose requires odours to be carried by air. But two semi-aquatic mammals, the star-nosed mole and the water shrew, have now demonstrated a neat way around the problem.

The two animals both use an underwater sniffing technique in which they breathe out a small bubble of air and then re-inhale it to detect odours, reports Kenneth Catania in a Brief Communication in this week's Nature.

Catania tested this trick by training star-nosed moles (Condylura cristata) to follow a scent trail underneath a mesh that prevented them from using their sensitive tactile 'star-nose' appendages. Despite not being able to use touch to aid their detection of prey, they still caught worms with a success rate of 85% using only their underwater sniffing prowess. Water shrews (Sorex palustris) enjoyed a similar success rate.


Kenneth Catania (Vanderbilt University, Nashville, TN, USA)

Tel: +1 615 343 1079; E-mail: [email protected] <mailto:[email protected]>

[18] And finally… A virgin birth for Christmas? (pp 1021-1022)

As you raise a glass of Christmas cheer, spare a thought for Flora the Komodo dragon. The anxious mother-to-be is waiting for eight offspring to hatch, each and every one a virgin conception.

Parthenogenesis, the production of offspring without fertilization by a male, is rare in vertebrate species. Now Phillip C. Watts and colleagues have used genetic fingerprinting to identify parthenogenetic offspring produced by two female Komodo dragons (Varanus komodoensis) that had been kept at separate institutions away from males. Their findings are reported in Nature this week, as the Brief Communications bow out with a Christmas theme.

Flora, who lives at Chester Zoo in the UK, produced a clutch of eleven viable eggs earlier this year. Three collapsed early during incubation, providing embryonic material for DNA tests. The remaining eight eggs are developing normally and are expected to hatch in January 2007.

Another captive-bred female, London Zoo's Sungai, managed to produce four viable offspring more than two years after her last contact with a male, and subsequently has produced additional offspring sexually.

This reproductive plasticity suggests that female Komodo dragons can switch between asexual and sexual reproduction, depending on the availability of a mate - a finding that has implications for breeding this threatened species in captivity. Most zoos keep only females, and males are moved between zoos for mating, but perhaps they should be kept together to avoid triggering parthenogenesis and decreasing genetic diversity.


Phillip C. Watts (University of Liverpool, UK)
Please note that this author is unavailable, please contact:

Richard Gibson (Zoological Society of London, UK) Co-author
Please contact through Emma Kenly (Press Office, Zoological Society of London, UK)
Tel: +44 20 7449 6280; E-mail: [email protected] <mailto:[email protected]>

Kevin R. Buley (Chester Zoo, Upton-by-Chester, UK) Co-author
Please contact through Rachael Ashton (PR and Media Manager, Chester Zoo, UK)
Tel: +44 1244 389460 or 07958 103515; E-mail: [email protected] <mailto:[email protected]>


[19] Observation of the radiative decay mode of the free neutron (pp 1059-1062; N&V)


***These papers will be published electronically on Nature's website on 20 December at 1800 London time / 1300 US Eastern time (which is also when the embargo lifts) as part of our AOP (ahead of print) programme. Although we have included them on this release to avoid multiple mailings they will not appear in print on 21 December, but at a later date.***

[20] Termination of asymmetric cell division and differentiation of stomata
DOI: 10.1038/nature05467

[21] Transcription factor control of asymmetric cell divisions that establish the stomatal lineage
DOI: 10.1038/nature05491

[22] Evidence of giant sulphur bacteria in Neoproterozoic phosphorites
DOI: 10.1038/nature05457


The following list of places refers to the whereabouts of authors on the papers numbered in this release. For example, London: 4 - this means that on paper number four, there will be at least one author affiliated to an institute or company in London. The listing may be for an author's main affiliation, or for a place where they are working temporarily. Please see the PDF of the paper for full details.

Buenos Aires: 7

Western Creek: 9

Santiago: 7, 8
Vitacura: 8

Copenhagen: 8

Paris: 8

Berlin: 15
Heidelberg: 8
Katlenburg-Lindau: 16
Koln: 15
Tautenberg: 8

Dublin: 8

Jerusalem: 9
Tel Aviv: 9

Como: 7
Firenze: 7
Florence: 18
Frascati: 7
Merate: 7
Milan: 7
Palermo: 7
Trieste: 7

Saitama: 22
Sendai: 13
Tokyo: 13

Amsterdam: 8
Rotterdam: 11

Matieland: 12
Pretoria: 12

Granada: 8

Stockholm: 8
Uppsala: 12

Zurich: 12

Birkenhead: 8
Brighton: 19
Cambridge: 3, 12
Hatfield: 8
Leicester: 6
Liverpool: 18
London: 6, 18
Sheffield: 12
St Andrews: 8
Upton-by-Chester: 18

Huntsville: 6
Tempe: 15
Berkeley: 7, 8
Claremont: 9
Los Angeles: 22
Novato: 11
Pasadena: 6, 9
San Diego: 9
San Francisco: 5
Santa Cruz: 6, 8
Stanford: 6, 10
Boulder: 19
Athens: 22
Honolulu: 8, 9
Baltimore: 7, 8
College Park: 6, 19
Gaithersburg: 19
Greenbelt: 6
Woods Hole: 14
Ann Arbor: 19
St Louis: 1, 2
Bozeman: 10
New Jersey
Princeton: 8, 9
New Mexico
Los Alamos: 6
Socorro: 9
New Orleans
Louisiana: 19
New York
New York: 9
Tarrytown: 4
Philadelphia: 14
Pittsburgh: 11
University Park: 6, 9
Nashville: 17
Oak Ridge: 6
Charlottesville: 6, 9
Seattle: 20


For North America and Canada

Katie McGoldrick, Nature Washington
Tel: +1 202 737 2355; E-mail: [email protected]

From Japan, Korea, China, Singapore and Taiwan

Itsumi Kitahara, Nature Tokyo
Tel: +81 3 3267 8751; E-mail: [email protected]

For the UK/Europe/other countries not listed above

Helen Jamison, Nature London
Tel: +44 20 7843 4658; E-mail: [email protected]

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Published: 20 Dec 2006

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