Volume 488 Number 7410

Editorials

Who calls the shots? p.129

US law-makers need to encourage research on firearms-related violence so that gun laws can be based on facts rather than ideology.

doi: 10.1038/488129a

Take a look p.129

Enjoy Curiosity on Mars. We may not see its like again.

doi: 10.1038/488129b

News

News Features

News & Views

AstrobiologyFrontier or fiction p.160

Astrobiology, the study of life in the Universe, is sometimes criticized as being a fashionable label with which to rebrand existing research fields. Its practitioners, however, argue that the discipline provides a broad framework for developing a better understanding of the frontiers of biology. A biologist and a planetary scientist offer their views.

doi: 10.1038/488160a

PalaeoanthropologyFacing up to complexity p.162

The anatomy of three new fossils, including a face, lends support to the hypothesis that there were at least two parallel lineages early in the evolutionary history of our own genus, Homo. See Letter p.201

doi: 10.1038/488162a

OpticsGain and loss mixed in the same cauldron p.163

The mathematical concept of parity'time symmetry, which was first introduced in field theories of quantum mechanics, has been demonstrated experimentally in a large-scale optical system. See Article p.167

doi: 10.1038/488163a

Atmospheric chemistryThe X factor p.164

Measurements in a forest reveal a previously unknown atmospheric oxidant that acts as a source of sulphuric acid — one of the main precursors for the formation and growth of aerosol particles and clouds. See Letter p. 193

doi: 10.1038/488164a

Structural biologyDynamic binding p.165

Nuclear magnetic resonance spectroscopy has been used to establish a vital role for protein motion in the formation of a protein–DNA complex. The finding potentially opens up fresh approaches for modifying protein function. See Letter p.236

doi: 10.1038/488165a

Articles

Deconstruction of a neural circuit for hunger p.172

Hunger is a complex behavioural state that elicits intense food seeking and consumption. These behaviours are rapidly recapitulated by activation of starvation-sensitive AGRP neurons, which present an entry point for reverse-engineering neural circuits for hunger. Here we mapped synaptic interactions of AGRP neurons with multiple cell populations in mice and probed the contribution of these distinct circuits to feeding behaviour using optogenetic and pharmacogenetic techniques. An inhibitory circuit with paraventricular hypothalamus (PVH) neurons substantially accounted for acute AGRP neuron-evoked eating, whereas two other prominent circuits were insufficient. Within the PVH, we found that AGRP neurons target and inhibit oxytocin neurons, a small population that is selectively lost in Prader–Willi syndrome, a condition involving insatiable hunger. By developing strategies for evaluating molecularly defined circuits, we show that AGRP neuron suppression of oxytocin neurons is critical for evoked feeding. These experiments reveal a new neural circuit that regulates hunger state and pathways associated with overeating disorders.

doi: 10.1038/nature11270

Gut microbiota composition correlates with diet and health in the elderly p.178

Alterations in intestinal microbiota composition are associated with several chronic conditions, including obesity and inflammatory diseases. The microbiota of older people displays greater inter-individual variation than that of younger adults. Here we show that the faecal microbiota composition from 178 elderly subjects formed groups, correlating with residence location in the community, day-hospital, rehabilitation or in long-term residential care. However, clustering of subjects by diet separated them by the same residence location and microbiota groupings. The separation of microbiota composition significantly correlated with measures of frailty, co-morbidity, nutritional status, markers of inflammation and with metabolites in faecal water. The individual microbiota of people in long-stay care was significantly less diverse than that of community dwellers. Loss of community-associated microbiota correlated with increased frailty. Collectively, the data support a relationship between diet, microbiota and health status, and indicate a role for diet-driven microbiota alterations in varying rates of health decline upon ageing.

doi: 10.1038/nature11319

Letters