Day: April 25, 2008

Dopamine and Eating

In an earlier post The Sugar Made Me Do It, I covered recent research by de Araujo, Oliveira-Maia et al. on how food, specifically sucrose, can reinforce eating by activating mid-brain dopamine circuitry, even in the absence of taste. In the accompanying editorial essay by Andrews and Horvath, this great graphic appeared, representing what is known about how eating can act on the hypothalamus and on the mesolimbic dopamine system (ventral tegmental area, nucleus accumbens, and prefrontal cortex).

Here is a much more convincing link to how eating can become appetite-driven, which previous posts on Genetics and Obesity and On the Causes of Obesity had raised as an important issue in the obesity problem.

Just one more note on the graphic: in terms of how taste can affect dopamine function, see some thoughts in the post on the neuropeptide orexin.

Figure 1. Schematic Illustration Depicting Some of the Major Findings of de Araujo and Oliveira-Maia et al

Taste alone (noncaloric sweetener), taste with caloric value (sucrose solution), or caloric value only (in the absence of taste receptors) can all equally activate the midbrain reward circuitry. To date, major emphasis has been placed on the hypothalamus and its various circuits, including orexin (ORX/Hcrt)- and melanin concentrating hormone (MCH)-producing neurons in the lateral hypothalamus as well as neuropeptide Y (NPY)/agouti-related protein (AgRP)- and -melanocyte-stimulating hormone (-MSH)-producing neurons in the arcuate nucleus, as a homeostatic center for feeding, responding to various peripheral metabolic hormones and fuels. The mesencephalic dopamine system is also targeted by peripheral hormones that affect and alter behavioral (and potentially endocrine) components of energy homeostasis. The results by de Araujo and Oliveira-Maia et al. highlight, however, that without classical hedonic signaling associated with reward-seeking behavior, the midbrain dopamine system can be entrained by caloric value arising from the periphery. While the precise signaling modality that mediates caloric value on dopamine neuronal activity remains to be deciphered, overall it is reasonable to suggest that distinction between hedonic and homeostatic regulation of feeding is redundant. DA, dopamine; GABA, γ-aminobutyric acid; Glut, glutamate.

Guns and Public Health

The New England Journal of Medicine has an informative podcast of an interview with David Hemenway on “gun violence in the United States and the likely effects of the Supreme Court case D.C. v. Heller.”

Hemenway covers the effect of gun control laws from the public health point of view. He provides a good international perspective, based both on variation in policy and research. One thing I did not know was how the US has become a major supplier of guns to Mexico, Japan and elsewhere–sold here, then imported illegally there. He also describes the impact of major gun control in Australia, where there was a significant reduction in violence post legislation.

The New England Journal of Medicine also provides a full-length editorial, Handgun Violence, Public Health, and the Law, by Gregory Curfman, Stephen Morrissey, and Jeffrey Drazen. Here is the opening: “Firearms were used to kill 30,143 people in the United States in 2005, the most recent year with complete data from the Centers for Disease Control and Prevention. A total of 17,002 of these were suicides, 12,352 homicides, and 789 accidental firearm deaths. Nearly half of these deaths occurred in people under the age of 35. When we consider that there were also nearly 70,000 nonfatal injuries from firearms, we are left with the staggering fact that 100,000 men, women, and children were killed or wounded by firearms in the span of just one year. This translates into one death from firearms every 17 minutes and one death or nonfatal injury every 5 minutes. By any standard, this constitutes a serious public health issue that demands a response not only from law enforcement and the courts, but also from the medical community.”

The same issue of NEJM also has a free-access article on this topic, Guns, Fear, the Constitution, and the Public’s Health, by Garen Wintemute. Focusing specifically on the Washington DC statute being challenged in the Supreme Court, Wintemute writes, “In 1976, Washington, D.C., took action that was consistent with such evidence. Having previously required that guns be registered, the District prohibited further registration of handguns, outlawed the carrying of concealed guns, and required that guns kept at home be unloaded and either disassembled or locked. These laws worked. Careful analysis linked them to reductions of 25% in gun homicide and 23% in gun suicide, with no parallel decrease (or compensatory increase) in homicide and suicide by other methods and no similar changes in nearby Maryland or Virginia.”

Encephalon Past, Future, and Present

Encephalon is the always-stimulating blog carnival of neuroscience/brain related blogging. For those of you interested in exploring recent Encephalon round up’s, Sharp Brains has the on-going list of the hosting sites dating from February 2008.

For older editions, Neurophilosophy has the list of older Encephalon editions from the very first in July 2006 running through 2007.

Finally, we are truly honored that we will be hosting a forthcoming edition of Encephalon on June 8th, so look for more on that as we get closer to summer.

Red meat, Neandertals were meant to eat it

The Meat and Livestock Association (MLA) of Australia has these great television commercials featuring actor Sam Neill (and by ‘great,’ I don’t mean ‘scientifically accurate’). They’re all about how we humans were ‘meant’ to eat red meat. They’re obviously meant to counteract growing concern about red meat in our diet, in the environmental impact of livestock, and other issues, and they use evolutionary arguments to try to get Australians to ‘beef up’ the amount of red meat in their diet, because of course, Australians don’t eat enough meat (trust me if you’re not in Australia — that’s probably not the biggest health issue here, ‘lack’ of red meat in the Aussie diet). For more information on the campaign, check out the MLA’s webpage, ‘Red Meat. We were meant to eat it.’ (You can download the video of the ads from that site if, like me, you want to incorporate it into your lecture on human evolution and diet.)

Especially interesting is the third ad in the campaign, ‘Evolution.’ The text of that ad is:

‘Evolution’ set the scene for the story of red meat and its role in human evolution. It also highlights the bundle of nutrients in red meat making it a foundation food essential for brain development and function. Red meat. We were meant to eat it.

But an article by M. P. Richards and colleagues soon to appear in the Journal of Human Evolution suggests that the evolutionary prize for red meat-eating should have gone, not to Homo sapiens sapiens but to Homo sapiens neanderthalensis (or H. neanderthalensis). Richards and the research team examined carbon and nitrogen ratios in Neandertal bone collagen to figure out what the Neandertals were eating.

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