African fish may hold key to reversing muscle ageing in humans, scientists say

Scientists have used a 'surprising' new animal model – the African killifish – to show that muscles reverse to an 'early-life' state towards the end of life, an advance which may lead to reversing age-related strength loss in humans.
While previous research has shown that muscles start to waste in old age in a condition called sarcopenia, the precise reason or the mechanism by which this happens has remained elusive.
In the new study, scientists from the Australian Regenerative Medicine Institute (ARMI) at Monash University found, using what they call the 'surprising' new animal model, that towards the end of life, muscles actually reverse to an 'early-life' state that slows death.
The findings, published recently in the journal Aging Cell, offer clues to slowing, halting, or even reversing age-related loss of muscle mass and strength, researchers say.
They highlight that the findings also come at a critical time when the world is witnessing a dramatic increase in the prevalence and severity of sarcopenia throughout the ageing global population.
'There is a pressing need to understand the mechanisms that drive sarcopenia, so that we can identify and implement suitable medical interventions to promote healthy muscle ageing,' study co-author Peter Currie from ARMI said.
The African turquoise killifish, scientifically known as Nothobranchius furzeri, has emerged recently as a new model animal for studying ageing.
This is aided by the fact that the killifish, which live for an average of 4 to 6 months, have the shortest known life span among vertebrates bred in captivity.
Their short life span is also accompanied by symptoms of ageing seen in humans such as the appearance of cancerous lesions in the liver and gonads, reduced regenerative capacity of the limbs (fin), and genetic hallmarks of human ageing as well as shortening of the end of chromosomes.
In the new study, which is the first to use the killifish to study sarcopenia, scientists characterised the cells and molecules of its skeletal muscle from early life, aged and extremely old late-life stages.
The comparisons revealed many similarities to sarcopenia in humans and other mammals, researchers say.
They say the same signature signs of ageing are reversed during the late-life stage in humans and the killifish, 'suggesting that in extremely old animals, there may be mechanisms in place that prevent further deterioration of skeletal muscle health, which may ultimately contribute to an extension of their life span'.
'Importantly, the late-life stage during which we observed improved muscle health perfectly coincides with a stage when mortality rates decline,' Avnika Ruparelia, another author of the study, said.
'We therefore postulate that the improvement in muscle health may be a critical factor contributing to the extension of life span in extremely old individuals,' Dr Ruparelia said.
Scientists also analysed the metabolism of fish at different stages of the ageing process.
They found that some features of the metabolism of the very oldest fish were rejuvenated to resemble those of young fish.
Researchers found a critical role played by lipid metabolism in this rejuvenation process.
'During extreme old age, there is a striking depletion of lipids, which are the main energy reserves in our cells,' Dr Currie explained.
'We believe that this mimics a state of calorie restriction, a process known to extend life span in other organisms, which results in activation of downstream mechanisms ultimately enabling the animal to maintain nutrient balance and live longer. A similar process is seen in the muscle of highly trained athletes,' he explained.
Scientists say the finding that potential drug interventions can manipulate metabolism linked to ageing is an exciting prospect, 'especially given the social, economic and healthcare costs associated with the ever-growing aged population around the world.'

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'Eldest daughter syndrome' to the rebellious youngest sibling: Does your birth order shape your personality?

The question of whether siblings' birth order shapes their personality has puzzled families and psychologists for years. But the evidence isn't as straightforward as you might think. As the eldest daughter of two, I often identify with the traits stereotypically associated with being the oldest sibling: responsible, conscientious, a perfectionist. My mum is an eldest daughter, too, and also shares those traits. My younger sister, on the other hand, is a bit more carefree – even though she and I grew up in the same household with the same parents, and are close, our personalities are quite different. I wondered whether that difference could be due to our birth order – is there any science to the idea that being the oldest, the youngest, or an only child, shapes who we are, and how we navigate the world? A century-long mystery Despite fascinating the scientific community and public for more than 100 years, the question of whether our birth order amongst siblings shapes our personalities is very much still up for debate. Historically, research has produced inconsistent findings. There are several reasons why this is, though to put it simply: it's hard to measure. Rodica Damian, an associate professor in psychology at the University of Houston, Texas, in the US, explains that previous studies have often included small sample sizes. In addition, since personality tests are often self-reported, they may be affected by bias. Recent studies point out that a number of confounding variables can make it hard to investigate if birth order is systematic, meaning that it affects every person in the same way. The total number of siblings may be a factor, for example: one would expect the overall dynamics to be different in a family with two siblings compared to a family with seven siblings. Being the eldest or youngest child in these differently-sized families might be a very different experience, and not directly comparable. Family size and the experience of being a child in any given family may in turn be entangled with many other factors, such as a family's socioeconomic status (wealthier families with higher socioeconomic status tend to have fewer children, for example). And then there is a person's age and gender, which could influence their experience within the family and beyond. Within this context, researchers have not been able to conclude that birth order has any consistent, universal impacts on our personalities. But that doesn't mean birth order is irrelevant. It could play a role within certain families, or cultures. "I think people have a lot of beliefs that are kind of outdated, or that were never well supported in the first place," says Julia Rohrer, a personality researcher at Leipzig University in Germany. "For example, the 'eldest daughter syndrome' thing is a big one – of course, women often still have different roles and are expected to provide more care. And then, first-borns are expected to take care of younger siblings," she says. "For some women, this might perfectly match their experience but for others it doesn't because every family is different." In other words, not every eldest daughter will be responsible and caring – but for some, the idea of an "eldest daughter syndrome" may ring true because they really did grow up having to look after their younger siblings and feel that this experience shaped them. Rohrer and her colleagues have found that birth order "does not have a lasting effect on broad personality traits" after examining three large datasets from surveys in the UK, US and Germany, each comprising data from several thousand people. However, the study did confirm previous findings on the impact of birth order on one specific trait: intelligence. Intelligence is a complex phenomenon and the study only measures it in the form of performance in intelligence tests, and self-reported intellect. "We confirmed the effect that firstborns score higher on objectively measured intelligence and additionally found a similar effect on self-reported intellect," Rohrer and her colleagues wrote in the study. Previous research had documented that performances in intelligence tests "decline slightly from firstborns to later-borns". As for birth order and other personality traits, Rohrer says reflecting on one's experience can still be meaningful, even if there is no universal pattern: "It does provide a label where you can find other people who grew up in a similar situation, and you can exchange experiences and so on," she says of terms such as "eldest daughter syndrome". There is nothing wrong with framing your experience that way, "as long as you don't assume that this experience is universal," she says. Damian echoes this: "While we don't find differences in personality that are systematic, that doesn't mean that there aren't social processes within each family or within each culture that can lead to different outcomes based on birth order." For example, the UK has a historically (male-preferring) primogeniture culture, meaning the eldest child would be the first in line to inherit family wealth, estate or titles. Only in 2013, with the passing of the Succession to the Crown Act did primogeniture within the monarchy end, removing the power of a male heir to displace an elder daughter in their right to the Crown. The idea of primogeniture is surprisingly widespread and persistent: in Succession, the HBO satirical comedy-drama, about a family's fight to take over a media empire, one character shouts "I'm the eldest boy!" in the finale. He believes his birth position should give him the right to take over his father's position of CEO. (He is actually the second-eldest son, but we won't get into that). "If the social practice is based on birth order, then yes, birth order will impact your outcomes," says Damian. Age is just a number? Age-related experiences can easily be mistaken for a personality trait or behaviour influenced by birth order, the researchers explain. Take the older, "responsible" sibling as an example: "As people grow older, they become more responsible, more self-controlled. So, the firstborn is always going to be older than the later born, and as you observe your children grow, the firstborn will always be more responsible," says Damian. "Another thing is that people become more self-conscious as they grow older," she adds. "So the second-born might appear more sociable and less neurotic, because a 10-year-old is much more happy and full of themselves… compared to the 14-year-old, who's freaking out about everything. That's because they have different challenges." 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But when there are more siblings born into a family, levels of intellectual stimulation might decrease. "So it's not so much that they're genetically smarter or that they have more potential – it's more that they translate into a higher verbal IQ score on the test which could be due to knowing more words, because more adults versus children spoke to them," she says. "With two children, maybe some of that reading time is taken by managing sibling interactions where the verbal input is a little bit less elevated." There are also suggestions that as older siblings tutor younger siblings, or explain things to them, they use "more cognitive resources". Interestingly, these patterns of intelligence aren't replicated globally. Data from developing countries differs to data from developed countries, for example. 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