A fat lot of good
Gail Vines talks to Caroline Pond, the zoologist who has uncovered the benefits of adipose tissue. We think of adipose tissue as an ill-defined repository for excess calories - as something to be grudgingly tolerated at best, and then only in small amounts.
Researchers, too, see fat in an exclusively pathological light: nearly all contemporary research on adipose tissue focuses on obesity for diabetes, ignoring its role in healthy bodies. But one British zoologist, Caroline Pond, has now routed this age-old dogma. Her "critical breakthrough" was to see that fat is strategically placed around the body to perform a variety of vital tasks: to supply rare nutrients to our muscles, heart and immune system, and to regulate their activities. "Singlehandedly she has challenged the centuries-old view that 'fat is just fat'", says Andrew Prentice, head of obesity research at the Medical Research Council's Dunn Nutrition Unit in Cambridge.
Pond has worked in this field at the Open University for about a decade without the support of any major outside funding. Working mostly on her own, she has established that adipose tissue has an evolutionary history and a multiplicity of roles: "She can take the credit for virtually all the current rethink in this direction," says Prentice. "Adipose tissue was adipose tissue was adipose tissue until she came along." agrees Eric Newsholme, a biochemist at the University of Oxford.
The mystery is why she is not yet a household name. "She has not got the recognition she deserves," says Richard Dawkins of Oxford University. In this era of increasing specialisation and molecularistion, "Caroline Pond is a modern survivor of that endangered species, the true scholar of zoology". She has "a huge knowledge which she deploys in a very powerful way, with great intelligence", says Dawkins, who often rings Pond with esoteric zoological queries.
Growing up in London, Pond used to ride her bike to the Natural History Museum or London Zoo after school and in the holidays. Drawn to the life sciences by a fascination with the beauty and diversity of animals, Pond took a first in zoology at Oxford in the early 1960s. Yet in a course then heavily devoted to comparative anatomy and phylogeny, adipose tissue was conspicuous by its absence, Pond now recalls. "We learnt nothing about it, and it never appeared on the diagrams. If this tissue had the affrontery to be present, your first act in dissections was to remove it into the bin. It certainly was not regarded as a valid object for study. It was not accorded that dignity."
The neglect of adipose tissue struck home only some years later, however, long after she had completed her DPhil at Oxford on insect flight, when she was at the University of Pennsylvania, teaching gross anatomy in the veterinary school. "We were dissecting all these fat old sheep and fat old dogs and fat old donkeys and it struck me as odd that the most abundant tissue in the body was barely mentioned in the textbooks. I felt it was time to put the record straight."
After the traumatic break-up of her marriage to the equally original American ecologist Dan Janzen, Pond arrived in Milton Keynes in 1979 to lecture in biology at the Open University. She set up house with Madge, her African grey parrot. Required to devote the next three years to teaching and still heavily involved in writing OU courses Pond began research at last in 1982, "in a very small way", by "picking up 'junk' animals as 19th-century anatomists would have done".
"Milton Keynes was still being built," she remembers, "and new roads were put through areas that were formerly farmland or woodland. I cycled round at night and picked up all sorts of mammals along the roadside: badgers, hedgehogs, foxes and muntjac deer descendants of escapees from the Duke of Bedford's estate at Woburn." Gamekeepers, zookeepers and police officers also passed mammalian corpses her way.
Dissecting her finds, Pond began to realise that adipose tissue, in a mammal's body at least, is highly and quite intricately organised. "A really very simple observation makes the point," she remarks. Look inside most fish, reptiles and amphibians and you find all the fat arranged into one or two large fat bodies located in the abdomen, as close as possible to the centre of gravity. "This arrangement is by far the most sensible, if the principal function of the tissue is simply as a storage organ," Pond points out. Tucked away in the abdomen, it can safely expand and contract, as the vagaries of the food supply dictate, without creating any mechanical problems for the animals. Yet, says Pond, you never find that arrangement in mammals.
In humans and other mammals, in contrast, fat is distributed in about a dozen discrete depots, some of which are carefully lodged around lymph nodes of the immune system, in muscle and on the heart. Through meticulous laboratory studies of guinea pigs, she and her OU colleague Christ Mattacks have now established that some fat depots act as "nurse and nanny" to the immune system - providing white blood cells with valuable polyunsaturated fats and regulating their proliferation.
Pond supplemented this laboratory work with ground-breaking research in the field. She surmised that wild animals that naturally become obese, the "professional fatties", would shed light on the many and varied roles adipose tissue plays. "Rats and people are mere novices in being obese, compared to many polar animals," she says. Arctic animals - polar bears, reindeer and arctic foxes are the real pros. Combining fatness and fitness, a polar bear can outrun a man despite a body mass that is sometimes 50 per cent fat.
Through fieldwork in the Canadian Arctic and on the island of Svalbard, north of Norway, in the space of just five years Pond has established herself as an accomplished arctic biologist, says Nicholas Tyler of the University of Tromso in Norway who worked with Pond on Svalbard. "It was remarkable to see someone adapt to circumstances they couldn't have anticipated through sheer willpower." With no previous experience of the extreme cold and the perpetual darkness of a winter at 78 degrees North, she plunged herself into life in a small, remote field station.
"People either take to it like ducks to water, or they absolutely hate it'', says Tyler. "But Caroline was in the unheard-of middle: enormously strong-willed, she said to herself, I am going to do this, I will now instantly programme myself into polar explorer mode and enjoy it." Through her studies of adipose tissue in arctic mammals, "she carved out an area of science all by herself," Tyler says.
Yet, despite her achievements, Pond languishes in relative obscurity. She explores unfashionable waters, investigating topics that have little to do with the human genome or the brain. Tyler, lamenting the decline of comparative physiology in Britain today, funded by pharmaceutical companies and devoted to making women skinnier, says it is is based "on research on fat cells in rats, and not just in rats, but in male rats, and not just in male rats but in juvenile male rats, and not just in juvenile male rats but in their testicular fat pad. It's amazing, it's absurd. So Caroline is saying, let's go comparative, let's do research on more sorts of fat and more sorts of animals. But she's St John shouting away in the wilderness and no one is listening."
It is a depressing message, but Pond remains optimistic. She says her long-term aim is "to halt the division of biology into two narrow camps: cellular and molecular biology, with loyalties directed to medicine and food technology, and ecology and behaviour, oriented mainly towards conservation and evolutionary theory. I hope my work has shown that adipose tissue is more interesting than it looks and tastes, and that it might even persuade molecular biologists and immunologists that ecologists with snow on their boots can provide them with important new ideas."