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<td><span style="font-family:Helvetica, sans-serif; font-size:20px;font-weight:bold;">NIH Director's Blog Daily Digest (Unofficial)</span></td>
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<td><a href="https://directorsblog.nih.gov/2024/11/07/salivary-enzyme-behind-our-carb-cravings-may-have-unexpectedly-ancient-history/" style="font-family:Helvetica, sans-serif; letter-spacing:-1px;margin:0;padding:0 0 2px;font-weight: bold;font-size: 19px;line-height: 20px;color:#222;">Salivary Enzyme Behind Our Carb Cravings May Have Unexpectedly Ancient History</a>
<div style="font-family:Helvetica, sans-serif; text-align:left;color:#999;font-size:11px;font-weight:bold;line-height:15px;">Nov 7th 2024, 09:00</div>
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<p><figure class="wp-block-image size-large"><img fetchpriority="high" decoding="async" width="1024" height="576" src="https://directorsblog.nih.gov/wp-content/uploads/2024/11/Gene-from-ancient-humans-1024x576.jpg" alt="Illustration of ancient humans walking through grasslands with an illustration of a strand of DNA on top of image. " class="wp-image-26579" srcset="https://directorsblog.nih.gov/wp-content/uploads/2024/11/Gene-from-ancient-humans-1024x576.jpg 1024w, https://directorsblog.nih.gov/wp-content/uploads/2024/11/Gene-from-ancient-humans-300x169.jpg 300w, https://directorsblog.nih.gov/wp-content/uploads/2024/11/Gene-from-ancient-humans-150x84.jpg 150w, https://directorsblog.nih.gov/wp-content/uploads/2024/11/Gene-from-ancient-humans-768x432.jpg 768w, https://directorsblog.nih.gov/wp-content/uploads/2024/11/Gene-from-ancient-humans-1536x864.jpg 1536w, https://directorsblog.nih.gov/wp-content/uploads/2024/11/Gene-from-ancient-humans-180x100.jpg?crop=1 180w, https://directorsblog.nih.gov/wp-content/uploads/2024/11/Gene-from-ancient-humans.jpg 1920w" sizes="(max-width: 1024px) 100vw, 1024px"></figure>
<p class="has-small-font-size"><em>Credit: Donny Bliss/NIH, Natalia/Adobe Stock</em></p>
<p>Digestion involves much more than just your stomach. The <a href="https://www.niddk.nih.gov/health-information/digestive-diseases/digestive-system-how-it-works" target="_blank" rel="noreferrer noopener">digestive process</a> that fuels your body begins in your mouth each time you take a bite of food and chew. An enzyme in your saliva, called amylase, then starts to break down complex carbohydrates—or starches found in many fruits, vegetables, and grains—into simpler sugars to give you their sweet flavor followed by a burst of energy.</p>
<p>Amylase is the reason we’re so good at turning starch into calories, but it isn’t the same for everyone. There’s plenty of genetic variation in the number of salivary amylase genes (<em>AMY1) </em>our cells carry and, therefore, in how much of this essential starch-busting enzyme people have. Studies have suggested a link between changes in amylase gene copy numbers over time and both the rise of agriculture and starch-heavy diets. Now a study in <a href="https://www.science.org/doi/10.1126/science.adn0609" target="_blank" rel="noreferrer noopener"><em>Science</em></a><em>,</em> supported in part by NIH, suggests that extra copies of <em>AMY1</em> are not only connected to our ability to effectively digest carbs, but also may be more ancient than previously known, arising even before modern humans split from Neanderthals and long before the advent of farming.</p>
<p>The new findings come from a research team led by <a href="https://arts-sciences.buffalo.edu/biological-sciences/faculty/faculty-directory/omer-gokcumen.html" target="_blank" rel="noreferrer noopener">Omer Gokcumen</a> at The University of Buffalo, NY, and <a href="https://www.jax.org/research-and-faculty/faculty/charles-lee" target="_blank" rel="noreferrer noopener">Charles Lee</a> of The Jackson Laboratory for Genomic Medicine, Farmington, CT. While an earlier study linked <em>AMY1</em> copy numbers with variation in starchy diets, researchers hadn’t been able to sequence the DNA with sufficient precision to get all the details. Newer methods make it possible to read longer stretches of DNA, bringing variation in the precise number of <em>AMY1 </em>copies into clearer view.</p>
<p>In DNA sequences from 98 individuals, the researchers identified 30 distinct versions of amylase genes known as haplotypes. A haplotype is a collection of genes and their variants that are close enough together on a chromosome that they tend to be inherited together. These collections of amylase genes varied considerably in length and the number of amylase gene copies they contained, ranging from two copies in each cell up to 16.</p>
<p>The researchers then compared the modern-day amylase genes to publicly available DNA sequences from 68 ancient human samples obtained from preserved remains. This revealed that ancient hunter-gatherers already had six to eight <em>AMY1 </em>copies long before people started growing crops and eating high amounts of starch. In fact, genetic variation underlying the production of this enzyme had already spread across Eurasia as far back as 45,000 years ago. However, the new analyses do show an increase in amylase gene copy numbers in the last 4,000 years, as people took up farming.</p>
<p>The study team went on to uncover evidence that the expansion of amylase genes apparently has a longer history than anyone had suspected. Intriguingly, they found three copies of <em>AMY1 </em>in the DNA of three of six Neanderthals and one Denisovan. Neanderthals and Denisovans are both extinct relatives of early humans. The findings suggest that an extra copy of the amylase gene may have arisen as long as 800,000 years ago. The researchers also described how those first extra <em>AMY1 </em>copies could lead to their continued duplications or deletions to produce the wide variation in amylase gene copy numbers seen among modern humans.</p>
<p>This variation in amylase genes would have afforded our ancestors dietary flexibility, allowing them to adapt as diets changed over time. But these discoveries aren’t only fascinating from an evolutionary or historical point of view. They may also lead to new understandings of genetic differences among people today, with potentially important implications for our metabolisms, nutrition, and health.</p>
<p><strong>Reference:</strong></p>
<p>Yılmaz F, <em>et al</em>. <a href="https://pubmed.ncbi.nlm.nih.gov/39418342/" target="_blank" rel="noreferrer noopener">Reconstruction of the human amylase locus reveals ancient duplications seeding modern-day variation</a>. <em>Science</em>. DOI: 10.1126/science.adn0609 (2024).</p>
<p><em>NIH Support: National Human Genome Research Institute, National Institute of General Medical Sciences</em></p></p>
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<p><strong>Forwarded by:<br />
Michael Reeder LCPC<br />
Baltimore, MD</strong></p>
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