Too Fat? Try Love

Oxytocin, also called the love hormone, plays an important role in keeping the body in shape. T.V. Jayan on a new study

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A hormone that induces love and trust in human beings may soon be drafted in the battle against the bulge. Nearly 60 years after it was first synthesised in the lab, oxytocin — which evokes a general feeling of contentment as well as triggers the let down of breast milk in nursing mothers — is found to have a role in helping maintain body weight and energy balance. The study closely follows another research which found that oxytocin stimulates the heart to beat more in sync with the breathing cycle in people with healthy social lives.

A neuromodulator, oxytocin has been in the news for both the right and wrong reasons. It’s no secret that it evokes maternal behaviour, epitomised by maternal love and trust. It also influences a number of other physiological and behavioural activities, including social bonding and sexual receptivity — a reason why it’s said to be abused by party animals. Molecules of this hormone are available as pills and recently, as a nasal spray too.

However, it’s for the first time that scientists conjured up a role for oxytocin in keeping the body in shape and through this, a strategy to ward off obesity. “It’s the first study to link oxytocin to body weight. We have demonstrated that defective oxytocin release in the brain can lead to weight gain and thus to obesity,” says Dongsheng Cai of the Albert Einstein College of Medicine, New York.

The study, that appeared recently in the journal Neuron, is significant also because it unravels the mechanism by which the hormone is released in the brain and why its production is stymied in those who indulge in a high-fat diet. Over-nutrition leads to compromised action of oxytocin in the brain, the scientists found.

Digging deep, the researchers identified a protein called synaptotagmin-4 that is directly responsible as it controls the release of oxytocin in the hypothalamus, a brain region that acts as the headquarters for maintaining the energy balance. Experimenting with lab mice, they found the rodents that were fed a high-fat diet had elevated levels of synaptotagmin-4 and this inhibited the release of oxytocin. And also that it further encouraged overeating and weight gain, resulting in obesity. On the other hand, when the protein production was genetically knocked off, the animals maintained a normal oxytocin release, despite the binge eating behaviour.

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Cai and his team had been exploring for some time the role played by the brain in triggering obesity. In yet another path-breaking work in 2008, they had discovered a different message system in the brain that directly affects food intake and body weight. Their insightful study showed how seemingly harmless over nutrition in the early stages of development can trigger an uncontrollable chain reaction. Too much energy consumption, they found, leads to what they call metabolic inflammation. Unlike classical inflammation typically observed in infections, injuries and diseases such as cancer, metabolic inflammation seen in obesity-related diseases is milder and has no overt symptoms. However, the brain reacts to it by marshalling the services of a protein complex, which is an important part of the body’s innate immunity. Once in action, it disrupts the function of the hypothalamus, the master regulator of appetite and energy balance.

Cai’s findings may emerge as an important tool in the big fight against obesity and related diseases such as diabetes and heart disorders. “We have discovered two new anti-obesity strategies,” he says. The scientist hopes that by controlling the production of synaptotagmin-4 or developing molecules with similar action as that of oxytocin, they might be able to find a medical solution to the epidemic.

“As a next stage, we will work to identify applicable approaches to block synaptotagmin-4 or enhance oxytocin release in the brain,” Cai told  the reporter of  The Telegraph (Kolkata, India)

 

The ultimate control of appetite and obesity is through neurochemicals in the brain, says Anoop Misra, head of internal medicine at Fortis Hospital, New Delhi. “Several brain chemicals (such as neuropeptide Y) have been shown to control appetite, but their interactions with others — such as hormones released by taste sensation and in the stomach — make their manipulation difficult and complex. Oxytocin is yet another chemical which has shown promise in the appetite-satiety pathway, but human studies are needed to illustrate its definitive role,” he says.

While a successful oxytocin strategy may help fight obesity, and through that keep related heart complications at bay, a new study by a team of scientists from universities in Ohio and Chicago points out that oxytocin may not protect everyone from a heart failure. The research — led by Greg Norman, a psychologist at Ohio State University — found that socially active people have healthier heart functions when administered a nasal spray of oxytocin. It, however, failed to produce any beneficial effect in those who were stressed, aloof and lonely by nature. Stress and social isolation are reckoned to be cardiovascular risk factors comparable to smoking and obesity.

Call it an alpha-hypophamine or cuddle chemical, oxytocin is truly a hormone to be loved and trusted.

Source:The Telegraph ( Kolkata, India)

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