The Nature of the Dietary Protein Impacts the Tissue-to-Diet 15N Discrimination Factors in Laboratory Rats

Due to the existence of isotope effects on some metabolic pathways of amino acid and protein metabolism, animal tissues are 15N-enriched relative to their dietary nitrogen sources and this 15N enrichment varies among different tissues and metabolic pools. The magnitude of the tissue-to-diet discrimination (Δ15N) has also been shown to depend on dietary factors. Since dietary protein sources affect amino acid and protein metabolism, we hypothesized that they would impact this discrimination factor, with selective effects at the tissue level. To test this hypothesis, we investigated in rats the influence of a milk or soy protein-based diet on Δ15N in various nitrogen fractions (urea, protein and non-protein fractions) of blood and tissues, focusing on visceral tissues. Regardless of the diet, the different protein fractions of blood and tissues were generally 15N-enriched relative to their non-protein fraction and to the diet (Δ15N>0), with large variations in the Δ15N between tissue proteins. Δ15N values were markedly lower in tissue proteins of rats fed milk proteins compared to those fed soy proteins, in all sampled tissues except in the intestine, and the amplitude of Δ15N differences between diets differed between tissues. Both between-tissue and between-diet Δ15N differences are probably related to modulations of the relative orientation of dietary and endogenous amino acids in the different metabolic pathways. More specifically, the smaller Δ15N values observed in tissue proteins with milk than soy dietary protein may be due to a slightly more direct channeling of dietary amino acids for tissue protein renewal and to a lower recycling of amino acids through fractionating pathways. In conclusion, the present data indicate that natural Δ15N of tissue are sensitive markers of the specific subtle regional modifications of the protein and amino acid metabolism induced by the protein dietary source

Differential preservation of endogenous human and microbial DNA in dental calculus and dentin

Dental calculus (calcified dental plaque) is prevalent in archaeological skeletal collections and is a rich source of oral microbiome and host-derived ancient biomolecules. Recently, it has been proposed that dental calculus may provide a more robust environment for DNA preservation than other skeletal remains, but this has not been systematically tested. In this study, shotgun-sequenced data from paired dental calculus and dentin samples from 48 globally distributed individuals are compared using a metagenomic approach. Overall, we find DNA from dental calculus is consistently more abundant and less contaminated than DNA from dentin. The majority of DNA in dental calculus is microbial and originates from the oral microbiome; however, a small but consistent proportion of DNA (mean 0.08 ± 0.08%, range 0.007–0.47%) derives from the host genome. Host DNA content within dentin is variable (mean 13.70 ± 18.62%, range 0.003–70.14%), and for a subset of dentin samples (15.21%), oral bacteria contribute \u3e 20% of total DNA. Human DNA in dental calculus is highly fragmented, and is consistently shorter than both microbial DNA in dental calculus and human DNA in paired dentin samples. Finally, we find that microbial DNA fragmentation patterns are associated with guanine-cytosine (GC) content, but not aspects of cellular structure

Diet and food strategies in a southern al-Andalusian urban environment during Caliphal period, ecija, Sevilla

The Iberian medieval period is unique in European history due to the widespread socio-cultural changes that took place after the arrival of Arabs, Berbers and Islam in 711 AD. Recently, isotopic research has been insightful on dietary shifts, status, resource availability and the impact of environment. However, there is no published isotopic research exploring these factors in southern Iberian populations, and as the history of this area differs to the northern regions, this leaves a significant lacuna in our knowledge. This research fills this gap via isotopic analysis of human (n = 66) and faunal (n = 13) samples from the 9th to the 13th century Écija, a town renowned for high temperatures and salinity. Stable carbon (δ13C) and nitrogen (δ15N) isotopes were assessed from rib collagen, while carbon (δ13C) values were derived from enamel apatite. Human diet is consistent with C3 plant consumption with a very minor contribution of C4 plants, an interesting feature considering the suitability of Écija to C4 cereal production. δ15N values vary among adults, which may suggest variable animal protein consumption or isotopic variation within animal species due to differences in foddering. Consideration of δ13C collagen and apatite values together may indicate sugarcane consumption, while moderate δ15N values do not suggest a strong aridity or salinity effect. Comparison with other Iberian groups shows similarities relating to time and location rather than by religion, although more multi-isotopic studies combined with zooarchaeology and botany may reveal subtle differences unobservable in carbon and nitrogen collagen studies alone.OLC is funded by Plan Galego I2C mod.B (ED481D 2017/014). The research was partially funded by the projects “Galician Paleodiet” and by Consiliencia network (ED 431D2017/08) Xunta de GaliciaS

The evolution of dog diet and foraging: Insights from archaeological canids in Siberia

Research on the evolution of dog foraging and diet has largely focused on scavenging during their initial domestication and genetic adaptations to starch-rich food environments following the advent of agriculture. The Siberian archaeological record evidences other critical shifts in dog foraging and diet that likely characterize Holocene dogs globally. By the Middle Holocene, body size reconstruction for Siberia dogs indicates that most were far smaller than Pleistocene wolves. This contributed to dogs' tendencies to scavenge, feed on small prey, and reduce social foraging. Stable carbon and nitrogen isotope analysis of Siberian dogs reveals that their diets were more diverse than those of Pleistocene wolves. This included habitual consumption of marine and freshwater foods by the Middle Holocene and reliance on C4 foods by the Late Holocene. Feeding on such foods and anthropogenic waste increased dogs' exposure to microbes, affected their gut microbiomes, and shaped long-term dog population history

Boom and bust at a medieval fishing port: dietary preferences of fishers and artisan families from Pontevedra (Galicia, NW Spain) during the Late Medieval and Early Modern Period

Here, we present an investigation of dietary habits in a town whose history is strongly connected to a single food product: fish. Pontevedra (Galicia, Spain) controlled a big part of fish commerce in the Iberian Peninsula during the Late Medieval period, only losing its position with the beginning of modern era. Burials from the churches of Santa María (thirteenth to seventeenth centuries AD), the necropolis of fishers, and San Bartolomé (thirteenth to fifteenth centuries AD), with a parish mostly made up of craftspeople, were studied to address questions of diet and subsistence practices. A total of 89 samples, including 63 humans, 18 terrestrial and 8 marine animals, were analysed for isotopic composition of bone collagen (δ13C and δ15N). The results show that domestic herbivores were fed a fodder almost exclusively based on C3 plants, while dogs and a cat consumed significant quantities of fish. Humans ate a similar, mixed terrestrial/marine diet, but probably also with an important contribution from C4 plants, most likely millet, or, from c. AD 1600 onwards, maize. Fishermen and their families buried at Santa María could have had preferential access to exported target sea products enriched in 15N (salted sardine, conger eel, hake and octopus), while other marine products may have been more common on the rest of the town’s tables. The decline in fishing activity in the sixteenth–seventeenth centuries appears to have been accompanied by a diversification of diet. The dietary habits of the middle-class urban inhabitants of Pontevedra are closely connected to its economic history and environmental changes