Silkworms for Medicine & Good Health

A SILKWORM A DAY may not keep the doctor away, but for some in South Korea silkworm proteins are the pathway towards reduced Alzheimer’s disease, less diabetes, less fatigue, stronger muscles and perhaps eventually gold and silver Olympic swimming medals; much the way ghost moth caterpillars naturally infected with cordyceps fungi are used by Chinese athletes and herbal medicine practitioners. Silkworm production dates back several thousand years, and likely came to the Korean Peninsula via China, where over a thousand years ago bolts of silk (30 ft/bolt; one day’s production by a skilled weaver) were equal to silver and gold as hard currencies. A director of the International Dunhuang Project (IDP) investigating ancient Silk Road links between Asia, the Middle East and Europe, Susan Whitfield, wrote in her book, Life Along the Silk Road, that distrust of promissory notes led to demands that horse buyers pay with bolts of silk. According to A Guide to Korean Cultural Heritage (Korean Information Service, 2001): “In Korea, ma (hemp) and ppong (mulberry) trees were cultivated; myeonpo (cotton cloth) and mapo (hemp cloth), as well as hapsa (twisted thread)” and jasu (embroidery) on silk date back well over a thousand years to a time when China imported fine silks from Korea.

Medically, biodegradable silkworm fibers are highly valued for their biocompatiblity (i.e. minimal immune response) when sewn with human tissues as sutures or stitches. Various formulations of silk are also useful in surgical or bioengineering operations such as growing new bones, nerves or blood vessels. “As has been documented over decades, silk protein exhibits high mechanical strength and flexibility, permeability to water and oxygen and can be made into nets, sponges or membranes, being easily handled, manipulated and sterilized…especially in tissue engineering for the generation of artificial bones or ligaments,” write researchers at China’s Nantong University investigating “silk-based or silk-coated materials for peripheral nerve repair.” The idea being to use silk “as scaffold material to prepare the tissue engineered nerve grafts for promoting peripheral nerve regeneration.” Silk scaffolds or blood vessels can also be designed to release various drugs (e.g. anti-coagulants, antimicrobials, anti-inflammatory agents).

Silks can also be naturally colored or made luminescent (fluorescent) by incorporating coloring agents into silkworm mulberry leaf diets: Hence, “novel silk-based material (that) not only maintains the superior properties of natural silk but can also be imbued with additional properties to perform sensing and monitoring functions” such as measuring changes in wound or tissue pH (i.e. acidity, alkalinity), says Dr. Han Mingyong, Senior Scientist at Singapore’s Institute of Materials Research and Engineering (IMRE). “The novel silk material can be used as fabrics in apparel, and furnishing. In biomaterials, it can add function to sutures, wound dressings, and tissue engineering scaffolds.” All this at “minimal cost and with little modification” of centuries-old standard silkworm production practices, but with real environmental benefits because: “The lengthy dyeing process and post-processing steps in conventional silk making are completely removed.”

Silkworm silk production involves getting the adult female silkworm moths, which are flightless and can no longer live in the wild after centuries of domestication, to lay eggs that hatch into caterpillars living on mulberry (some species prefer oak) leaves. When the silkworms pupate, they spin a silken cocoon which is dropped in boiling water so that the outer silk threads unravel and can be spun into the fibers of commerce. “According to legend, 5,000 years ago Chinese Empress Xi Ling-Shi discovered silk when a silkworm cocoon fell into her hot cup of tea,” says Ecoworldly.com. “She unraveled the strange cocoon and, wrapping the thread around her finger, soon realized what an exquisite cloth it would make…If this is true, the silkworm that haplessly fell into the empress’ cup on that fateful day met a fate very similar to that of modern day silkworms.” Being insects, which are animals, they are not vegetarian fare; those concerned with animal cruelty and animal rights activists need to consider that these silkworms are in essence a human-created species (almost a symbiosis) and unable to survive in the wild.

Beondegi (번데기), the boiled or steamed silkworm chrysalis, are served as a snack food on the streets in Korea, and University of Florida, Gainesville, entomology professor Nan-Yao Su, who donated termite trap (Sentricon) royalties to establish the Entomological Society of America’s (ESA) “Nan-Yao Su Award for Innovation and Creativity in Entomology,” told me of eating silkworm snacks as a student in Japan. Dr. Su was not that impressed, an opinion shared by a South Korean and her Brazilian guest’s “gag me with a spoon response” on Izumislife vlog on YouTube; though an older Korean lady in the background, presumably more well-versed in beondegi’s medicinal properties was gulping down the boiled insects sold by the street vendor like there was no tomorrow (increased longevity may indeed be a beondegi benefit). Evidently, silkworms or beondegi (번데기) are a cultivated taste. But Dr. Su, with Professor Marjorie Hoy as my witness, professed not to be a Trader Joe’s fan either. So, I kept to my plan to attend the Tuesday night ESA Annual Meeting Korean Young Entomologists networking meeting, which led off with drones for delivering biocontrol insects and concluded with a trio of researchers fresh off the plane from South Korea to talk (in Korean; with slides in English) about their impressive latest research on the medical benefits of eating silkworm proteins. I was impressed with the research, and spent the last few months reading the English language scientific literature on silkworms for medicine and good health. The result is an overly long blog, like those 3-hour articles I used to read in the New Yorker instead of going to sleep at night; but since the blog readers mainly come here via search engines looking for information on a topic, I figure overly long is okay.

The Korean Young Entomologists (KYE) Member Symposium led off with Yong-Lak Park’s “Shooting insects from the sky: Aerial delivery of natural enemies using aerospace engineering,” and finally sometime between 9 and 10 at night (some time changes from ESA Internet site) came the silkworm presentations by Eunyoung Ahn, Hyobin Seo, and Yiseol Kim from South Korea’s Kyungpook National University. Researchers Sungpil Ryu, Taedong Kwon, Yunghi Yeo, and Mihee Cho contributed to the work, but were not present. The researchers made the point that silkworm pupae had a higher protein and amino acid content than soybeans, and were high in desirable unsaturated fatty acids that lowered blood lipid levels (anti-obesity). In rat feeding trials, powdered, freeze-dried silkworm proteins increased skeletal muscle volume when swimming was the exercise. This has obvious appeal to body builders and others involved in exercise and training seeking to increase muscle mass, strength and energy. Specific amino acids (glutamine, branched-chain amino acids, cysteine) were singled out as most important to the immune systems of athletes. A combination of silkworm proteins and exercise had multiple beneficial effects: increased antioxidants; decreased MDA and inflammatory cytokines. Swimming plus silkworm pupae also improved fat metabolism, leading to lower blood lipid levels; so a combination of silkworm protein and exercise was deemed good for promoting weight loss or combating the worldwide epidemic of obesity caused by “excess nutrition” (e.g. the trend towards super-sized portions). Other research indicated benefits involving blood cholesterol, reduced fat synthesis and accumulation, and preventing liver cirrhosis in high-fat diets. Thus, silkworm pupae are potential weight-loss foods or food supplements.

The 25-volume Dong-eui-bo-gam (동의보감) (Mirror of Eastern Medicine), published in 1613 by the legendary Korean royal physician Heo Jun (허준), called silkworm pupa a natural healthy food and nontoxic remedy for diabetes, ischemic disease and “thinning.” Modern medical research indicates Heo Jun knew what he was talking about, and was actually a couple of centuries ahead of modern Western medicine. Our knowledge of the potential medical benefits of silkworms is rapidly expanding, particularly in South Korea, China and Japan; and to a lesser degree in India, where the silkworms are often a different species feeding on oak tree leaves. We have only scratched the surface of the medical benefits of silkworms in this blog.

The Mysteries of Colony Collapse

COLONY COLLAPSE DISORDER (CCD) of honey bees is one of the lingering mysteries of early 21st Century science in more ways than one: from its microbial, immune system and genetic components to an amorphous almost Orwellian terminology as imprecise and ambiguous as climate change (a slogan wide enough to encompass warming up, cooling down, and even staying the same temperature while the numbers fluctuate around the mean or average). The ambiguous language says both nothing and everything simultaneously, though underlying CCD is a quest for as yet unknown changes in insect rearing circumstances that will produce non-collapsing honey bee colonies. During the 19th century (1800s), a century marked by worldwide famines in the the old colonial empires and phylloxera-ravaged wine-grape vineyards collapsing in France, a revolution in modern medicine was being birthed in the mysteriously collapsing silkworm colonies. Fortunately for lovers of silk fabrics, fashion and textiles, 19th century silkworm farmers had the services of the real-life scientific Sherlock Holmes of the era, the famous French freelance scientist and sometime entomologist, Louis Pasteur.

Pasteur had a knack for solving applied problems like fermentation (beer, wine, vinegar) and silkworm colony collapse, and then using the results to develop broader theories like germ theory, which taught modern doctors to wash their hands and sterilize their instruments so as to stop spreading the germs that commonly killed their patients. How Pasteur almost single-handedly accomplished so much more than whole scientific institutes seemed able to do in the 20th century was the subject of an illuminating mid-20th century book, Louis Pasteur Free Lance of Science, by French-borne microbiologist Rene Dubos. “Toward the middle of the nineteenth century a mysterious disease began to attack the French silkworm nurseries,” wrote Dubos. “In 1853, silkworm eggs could no longer be produced in France, but had to be imported from Lombardy; then the disease spread to Italy, Spain and Austria. Dealers procuring eggs for the silkworm breeders had to go farther and farther east in an attempt to secure healthy products; but the disease followed them, invading in turn Greece, Turkey, the Caucasus–finally China and even Japan. By 1865, the silkworm industry was near ruin in France, and also, to a lesser degree, in the rest of Western Europe.”

“The first triumphs of microbiology in the control of epidemics came out of the genius and labors of two men, Agostino Bassi and Louis Pasteur, both of whom were untrained in medical or veterinary sciences, and both of whom first approached the problems of pathology by studying the diseases of silkworms,” wrote Dubos, who between World Wars I and II worked at the League of Nations’ Bureau of Agricultural Intelligence and Plant Diseases as an editor of the International Review of the Science and Practice of Agriculture. “A disease known as mal del segno was then causing extensive damage to the silkworm industry in Lombardy. Bassi demonstrated that the disease was infectious and could be transmitted by inoculation, by contact, and by infected food. He traced it to a parasitic fungus, called after him Botrytis bassiana (since renamed Beauveria bassiana, a widely used biocontrol agent)…An exact understanding…allowed Bassi to work out methods to prevent its spread through the silkworm nurseries. After twenty years of arduous labor, he published in 1836…Although unable to see the bacterial agents of disease because of blindness, Bassi envisioned from his studies on the mal del segno the bacteriological era which was to revolutionize medicine two decades after his death.”

Chemist Jean Baptiste Dumas, Pasteur’s mentor, prevailed upon the reluctant free lance scientist to head a mission of the French Ministry of Agriculture. “Although Pasteur knew nothing of silkworms or their diseases, he accepted the challenge,” wrote Dubos. “To Pasteur’s remark that he was totally unfamiliar with the subject, Dumas had replied one day: ‘So much the better! For ideas, you will have only those which shall come to you as a result of your observations!’”

A way of life was also at stake. As described in 19th century France by Emile Duclaux, Pasteur’s student and intimate collaborator (in Dubos’ book): “…the cocoons are put into a steam bath, to kill the chrysalids by heat. In this case, scarcely six weeks separate the time of egg-hatching from the time when the cocoons are carried to market, from the time the silk grower sows to the time when he reaps. As, in former times, the harvest was almost certain and quite lucrative, the Time of the Silkworm was a time of festival and of joy, in spite of the fatigues which it imposed, and, in gratitude, the mulberry tree had received the name of arbre d’or, from the populations who derived their livelihood from it.”

“The study of silkworm diseases constituted for Pasteur an initiation into the problem of infectious diseases,” wrote Dubos, who was influenced by the famous Russian soil microbiologist, Serge Winogradsky, who favored studying microbial interactions in natural environments rather than in pure laboratory cultures. “Instead of the accuracy of laboratory procedures he encountered the variability and unpredictability of behavior in animal life, for silkworms differ in their response to disease as do other animals. In the case of flacherie (a disease), for example, the time of death after infection might vary from 12 hours to 3 weeks, and some of the worms invariably escaped death…Time and time again, he discussed the matter of the influence of environmental factors on susceptibility, on the receptivity of the ‘terrain’ for the invading agent of disease. So deep was his concern with the physiological factors that condition infection that he once wrote, ‘If I had to undertake new studies on silkworms, I would investigate conditions for increasing their vigor, a problem of which one knows nothing. This would certainly lead to techniques for protecting them against accidental diseases.’”

“Usually, the public sees only the finished result of the scientific effort, but remains unaware of the atmosphere of confusion, tentative gropings, frustration and heart-breaking discouragement in which the scientist often labors while trying to extract, from the entrails of nature, the products and laws which appear so simple and orderly when they finally reach textbooks and newspapers,” wrote Dubos. “In many circumstances, he developed reproducible and practical techniques that in other hands failed, or gave such erratic results as to be considered worthless. His experimental achievements appear so unusual in their complete success that there has been a tendency to explain them away in the name of luck, but the explanation is in reality quite simple. Pasteur was a master experimenter with an uncanny sense of the details relevant to the success of his tests. It was the exacting conscience with which he respected the most minute details of his operations, and his intense concentration while at work, that gave him an apparently intuitive awareness of all the facts significant for the test, and permitted him always to duplicate his experimental conditions. In many cases, he lacked complete understanding of the reasons for the success of the procedures that he used, but always he knew how to make them work again, if they had once worked in his hands.”

Though famed for disproving the spontaneous generation of life, immunization via attenuated living vaccines and the germ theory of infectious disease: “Pasteur often emphasized the great importance of the environment, of nutrition, and of the physiological and even psychological state of the patient, in deciding the outcome of the infectious process,” wrote Dubos. “Had the opportunity come for him to undertake again the study of silkworm diseases, he once said, he would have liked to investigate the factors which favor the general robustness of the worms, and thereby increase their resistance to infectious disease…A logic of Pasteur’s life centered on physiological problems is just as plausible as that which resulted from the exclusive emphasis on the germ theory of contagious disease.”

The 21st century is riddled with insect colony conundrums and mysteries. For example, why among the social insects are honey bees plagued by Colony Collapse Disorder, while “Colony Expansion Disorder” prevails for other social insects in the USA. Rather than collapsing, USA colonies of Argentine ants are forming “super-colonies,” and red imported fire ant colonies are growing stronger by the day and annually expanding their North American geographic range; this despite being deliberately dosed with pesticides and attacked by biocontrol organisms (perhaps even more so than the beleaguered honey bees). And quite independently of mortgage rates and housing sales, Formosan subterranean termite colonies damaging billions of dollars of USA housing stock are happily munching away at both live trees and “dead-tree” wooden housing assets with little collective danger of colony collapse, though individual colonies come and go.

Perhaps beekeeping and crop pollination would be easier if Colony Collapse Disorder were an actual “disorder” as defined by the Diagnostic and Statistical Manual of Mental Disorders (DSM), and honey bees were endowed with sufficient consciousness and behaviors amenable to bee psychology or psychiatry.

The very real plight of honey bee colonies or hives is still in what Dubos would call the “atmosphere of confusion, tentative gropings, frustration.” At the most recent Entomological Society of America annual meeting, roughly a century and a half after silkworm colony collapse was eliminated by better more sanitary rearing practices, honey bee health was still puzzling. Honey bee colony loss in Virginia increased to 30% from 5-10% in recent years, possibly due to disease pathogens, pesticides and immune system suppression, say Virginia Tech researchers (e.g. Brenna Traver) studying glucose oxidase (GOX), an indicator of immunity in social insects. Honey bee social immunity is complex, involving factors as diverse as pheromones and grooming, and honey bee production of hydrogen peroxide (H2O2), which sterilizes food for the colony.

Nosema ceranae, a global gut pathogen, was seen all around the USA in 2007 at the same time as Colony Collapse Disorder. Black queen cell virus is another culprit, along with deformed wing virus, which is spread among honey bees by varroa mites. Then it is hard to overlook that over 120 different pesticides and their metabolites have been found in honey; including common beekeeper-applied pesticides such as coumaphos, fluvalinate, chlorothalonil and the antibiotic fumagillin. At the University of Puerto Rico, Gloria Dominguez-Bello is testing oxytetracycline and other commonly used antibiotics for their effects on honey bee microbes similar to those known to affect everything from obesity and brain function to organ transplants.

Those familiar with Pasteur’s entomological research on silkworm colony collapse in the 1800s would have experienced a sense of deja vu at the most recent Entomological Society of America meetings listening to Gloria DeGrandi-Hoffman, a research leader at the USDA-ARS Carl Hayden Bee Research Center in Tucson, Arizona. Nutrition, stress and pesticides may indeed be involved, but more focus is warranted for honey bee microbial health and gut microbes. Honey bee nutrition and microbiology is complicated by seasonal variations with changing food sources. According to DeGrandi-Hoffman, a lack of beneficial microbes may set honey bees up for infectious diseases like chalkbrood.

For example, pesticides used for Varroa mite control and potent beekeeping antibiotics like thymol and formic acid can affect the Lactobacillus microbes bees need for digestion and preservation of pollen as beebread, said DeGrandi-Hoffman. When bacterial plasmids found in high numbers in beebread are plated with the pathogen Aspergillus flavus, the pathogen rapidly loses virulence.

It is likely honey bees rely on beneficial microbes to protect from harmful pathogens, as honey bees have among the fewest immune system genes of any insect. Thus, when California almond growers spray fungicides, insecticides and miticides, a side effect could be fewer beneficial microbes in honey bee guts and in beebread. Thus, the honey bees would be less healthy and more susceptible to diseases like chalkbrood. Probiotic supplements designed to add beneficial microbes to honey bee diets are being tested in some California orchards. No doubt a familiar concept to those shopping for probiotic yogurts.