People Have Gene to Produce Chitin Digesting Enzyme - Please Pass the Stinkbugs

A study in Molecular Biology and Evolution shows that people do have the enzyme that can break down insect casings.  Primates, including humans do have the gene that breaks down chitin, the substance that forms the exoskeleton of bugs.  Most of us were taught that chitin would not be broken down in our digestive systems.  Not so.

An article in National Geographic from 2013,  U.N. Urges Eating Insects; 8 Popular Bugs to Try, suggests these bug species:
1. Beetles
2. Butterflies and Moths
3. Bees and wasps
4. Ants
5. Grasshoppers, crickets, and locusts
6. Flies and mosquitos
7. Water boatmen and backswimmers
8. Stinkbugs

Yes, Stinkbugs....from the article  "If you can get past the funky smell, these insects apparently add an apple flavor to sauces and are a valuable source of iodine. They're also known to have anesthetic and analgesic properties. Who would have thought?"  Not me, that is for sure.

So what wine should we pair with our bowl of crunchy crickets.....a nice grassy sauvignon blanc perhaps?  An article on the subject in Food and Wine magazine suggests pairing a Riesling with honey mustard crickets. 


IFT Weekly Newsletter
http://www.ift.org/Food-Technology/Newsletters/IFT-Weekly-Newsletter/2018/February/021418.aspx
Study finds most primates, including humans, can digest insects



The thought of eating an insect makes most people cringe—at least those who live in the United States, Canada, and Europe, a minority of the world’s population who would not let a cricket, grasshopper, or beetle near their dinner table. The “yuck” factor, however, does not have anything to do with nutrition, digestion, or evolution. In fact, according to a Rutgers study, insects—the food choice for our early primate ancestors—could still be eaten and digested by almost all primates today, including humans.

“For a long time, the prevailing wisdom was that mammals didn’t produce an enzyme that could break down the exoskeletons of insects, so they were considered to be very difficult to digest,” said Mareike Janiak, a doctoral candidate in Rutgers’ Dept. of Anthropology and lead author of the study published recently in Molecular Biology and Evolution. “We now know from research on bats and mice, and now my research on primates, that this isn’t true.”

Janiak and collaborators from Kent State University discovered that almost all living primates still have working versions of the gene needed to produce a stomach enzyme that breaks down exoskeletons. The scientists looked at the genomes of 34 primates, searching for copies of a gene called CHIA, the stomach enzyme that breaks down chitin, which is part of the outer covering of an insect.

What they discovered is that while most living primates have only one copy of the CHIA gene, early primates, which tended to be very small, had at least three working copies. This shows that insects were an extremely important food source for our early ancestors. Some living primates, like the tarsier, which eats more insects than any other primates, and today exists only on islands in Southeast Asia, have five copies of the gene, because it was duplicated specifically in this lineage.

“As some primates evolved to be larger and more active during the day than at night, their diets shifted a bit to other foods like fruits and leaves,” Janiak said. “Insects became less important and their digestive enzymes changed, but most living primates still have at least one working CHIA gene.”

Molecular Biology and Evolution, msx312, https://doi.org/10.1093/molbev/msx312
https://academic.oup.com/mbe/advance-article/doi/10.1093/molbev/msx312/4693806
Evolution of Acidic Mammalian Chitinase Genes (CHIA) Is Related to Body Mass and Insectivory in Primates 
 Mareike C Janiak,    Morgan E Chaney,    Anthony J Tosi 
Published: 05 December 2017

Abstract

Insects are an important food resource for many primates, but the chitinous exoskeletons of arthropods have long been considered to be indigestible by the digestive enzymes of most mammals. However, recently mice and insectivorous bats were found to produce the enzyme acidic mammalian chitinase (AMCase) to digest insect exoskeletons. Here, we report on the gene CHIA and its paralogs, which encode AMCase, in a comparative sample of nonhuman primates. Our results show that early primates likely had three CHIA genes, suggesting that insects were an important component of the ancestral primate diet. With some exceptions, most extant primate species retain only one functional CHIA paralog. The exceptions include two colobine species, in which all CHIA genes have premature stop codons, and several New World monkey species that retain two functional genes. The most insectivorous species in our sample also have the largest number of functional CHIA genes. Tupaia chinensis and Otolemur garnettii retain three functional CHIA paralogs, whereas Tarsius syrichta has a total of five, two of which may be duplications specific to the tarsier lineage. Selection analyses indicate that CHIA genes are under more intense selection in species with higher insect consumption, as well as in smaller-bodied species (<500 g), providing molecular support for Kay’s Threshold, a well-established component of primatological theory which proposes that only small primates can be primarily insectivorous. These findings suggest that primates, like mice and insectivorous bats, may use the enzyme AMCase to digest the chitin in insect exoskeletons, providing potentially significant nutritional benefits.


Keywords: digestive enzymes, acidic mammalian chitinase, insectivory, dietary adaptations


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