Amylase activity is associated with AMY2B copy numbers in dog: implications for dog domestication, diet and diabetes

Abstract

High amylase activity in dogs is associated with a drastic increase in copy numbers of the gene coding for pancreatic amylase, AMY2B, that likely allowed dogs to thrive on a relatively starch-rich diet during early dog domestication. Although most dogs thus probably digest starch more efficiently than do wolves, AMY2B copy numbers vary widely within the dog population, and it is not clear how this variation affects the individual ability to handle starch nor how it affects dog health. In humans, copy numbers of the gene coding for salivary amylase, AMY1, correlate with both salivary amylase levels and enzyme activity, and high amylase activity is related to improved glycemic homeostasis and lower frequencies of metabolic syndrome. Here, we investigate the relationship between AMY2B copy numbers and serum amylase activity in dogs and show that amylase activity correlates with AMY2B copy numbers. We then describe how AMY2B copy numbers vary in individuals from 20 dog breeds and find strong breed-dependent patterns, indicating that the ability to digest starch varies both at the breed and individual level. Finally, to test whether AMY2B copy number is strongly associated with the risk of developing diabetes mellitus, we compare copy numbers in cases and controls as well as in breeds with varying diabetes susceptibility. Although we see no such association here, future studies using larger cohorts are needed before excluding a possible link between AMY2B and diabetes mellitus.

Amy2Bcopy number variation reveals starch diet adaptations in ancient European dogs

“…These dogs come from regions with no, or recent, agricultural practices [17,18,37]. This supports the hypothesis that the development of a dog's capability to digest starch efficiently does not result from a relaxation of the natural selection pressures related to domestication.…”

“…Both fragment sequences were amplified using dog specific primers [16,18,37]: —  Amy2B —fragment of 76 bp: forward 5′-CCAAACCTGGACGGACATCT-3′ and reverse 5′-TATCGTTCGCATTCAAGAGCAA-3′.—  C7orf28b-3 —fragment of 60 bp: forward 5′-GGGAAACTCCACAAGCAATCA-3′ and reverse 5′-GAGCCCATGGAGGAAATCATC-3′. Both fragments matched in size and were designed to exclude a potential amplification bias in degraded DNA. These two pairs of primers were then mixed in a single tube.…”

“…The following probes matched the target Amy2B gene and reference housekeeping gene C7orf28b  [16,18,37]: Amy2B probe-6FAM–TTTGAGTGGCGCTGGG-MGBNFQ [33,34]; C7orf28b-3 probe-VIC-CACCTGCTAAACAGC-MGBNFQ.…”

“…We followed the same experimental design as previously published [16,18]: the reaction was performed in a 25 µl reaction volume containing 12.5 µl of Taqman Genotyping master mix (Applied Biosystems), 0.9 µM of each primer, 0.25 µM of each probe and 2 ng of DNA. The cycling conditions were one step at 50°C for 2 min, one step at 95°C for 10 min, followed by 40 cycles of one step at 95°C for 15 s and one step at 60°C for 1 min.…”

“…This led to a several fold copy number increase in modern dog breeds in comparison with their wild ancestor, the wolf, that is associated with a higher amylase activity [16,17]. Whereas Amy2B copy numbers vary widely in dogs (4–34 copies), both at a breed and individual level [18], the copy number range is much lower (two to eight copies) across wolf populations with 60% of the wolves bearing only two copies [17]. This suggests that dogs have adapted to a diet richer in starch, relative to the carnivorous wolf diet [16].…”