Highlights of the BMC Series – July 2022

Do dolphins adapt to their environment? What is the impact of glyphosate exposure on oxidative stress, inflammation and lung function? Does the presence of bacterial DNA in blood impact the risk of cardiovascular disease (CVD) mortality? What is the effect of daily temperature on the risk of preeclampsia? How does the spotted cat fish adapt to an environment with highly fluctuating salt concentrations?

Seascape genomics of common dolphins (Delphinus delphis) reveals adaptive diversity linked to regional and local oceanography | BMC Ecology and Evolution | Full Text

The common dolphin is a well-known inhabitant of marine waters worldwide. But how do the various environments and ever changing conditions faced by these small cetacean impact their genetic diversity and have they adapted to their specific environment? This BMC Ecology and Evolution seascape genomic study uses genome wide and environmental data at the population level to look at selective pressure, adaptive population structure and population diversity in the common dolphin in southern Australia. Four key variables are identified to have an impact on genomic variation:  sea surface temperature, primary productivity, current velocity and salinity. These data can in turn help to inform on the impact of specific factors such as pollution and assist in the conservation efforts. This study lead to the identification of five populations of common dolphin to be considered as priority for population management and conservation. As a near top predator, dolphins are key players in their environments and a vital part of the food chain. Thus, impacts from anthropogenic activities such as fisheries or climatic disruptions on dolphin populations could have long standing effects on the whole of the marine ecosystem.


Effects of exposure to glyphosate on oxidative stress, inflammation, and lung function in maize farmers, Northern Thailand | BMC Public Health | Full Text

Thailand is one of the world’s largest food exporter and sees a high usage of pesticides to boost productivity, especially herbicides.  The highest imported herbicide is Glyphosate. Glyphosate is a weak organic acid, often supplemented by adjuvants to increase its herbicidal properties. It is generally composed of an isopropylamine salt and a surfactant that is toxic to humans. Upon entrance into the body, Glyphosate is absorbed through the cell membrane and enters the bloodstream eventually spreading to the tissues and organs before being excreted by the body, primarily through urination and defecation.  Primary exposure to Glyphosate is through the skin and respiratory system while using herbicides and it has been linked to various illnesses, especially respiratory system afflictions. This BMC Public Health longitudinal pre-post study was conducted in maize farmer in Thailand using information from questionnaires, urine, blood samples and lung function assessment a day before and a day after glyphosate usage. As expected, exposure to glyphosate had negative impacts on oxidative stress, inflammation and lung function.

Oxidative stress can cause damage to cells and tissues and thus impact the body leading to increased inflammation. One of the by-product of oxidative damage is the accumulation of malondialdehyde (MDA). Upon oxidative stress, cells defend themselves by producing antioxidants in order to destroy damaging free radicals. Glutathione (GHS) plays a vital role in this process and acts to protect cells from oxidative stress. Glyphosate was shown to negatively impact the regulation of oxidative stress at different levels as exposure to glyphosate was shown to lead to a significant increase in the level of serum MDA and oxidative stress as well as a significant decrease in serum level of GHS. Furthermore, a statistically significant increase in inflammation was identified after glyphosate exposure as well as an increase in C-reactive protein (CRP), a key marker of inflammation which increases upon tissue injury, causes monocyte activation as well as the generation of reactive oxygen species and activation of complement. Last but not least, lung function was significantly decreased after application of glyphosate.

This study focused on the short term effects of acute exposure thus further studies on the long-term effect of glyphosate exposure are warranted.


The blood microbiome and its association to cardiovascular disease mortality: case-cohort study | BMC Cardiovascular Disorders | Full Text

Despite the popularity of microbiome studies, little is known about the impact of the presence of bacterial DNA in human blood and the risk of cardiovascular disease (CVD) mortality. The association between chronic diseases and CVD has been extensively studied and a number of risk factors are known to be associated an increase in CVD mortality such as tobacco use, obesity, diet, physical activity, history of heart diseases etc… In this BMC Cardiovascular Disorders case-cohort study spanning over nearly 10 years, blood samples from men of a mean age of 70 were collected and their microbiome analysed in order to investigate a putative association with CVD mortality. Over 80% of the blood samples collected contained bacterial DNA from a whole range of bacteria originating from the gut, skin, oral cavity or the environment. Three genera were significantly associated with CVD mortality but the two most prevalent genera isolated, Streptococcus and Staphylococcus were not and are part of the commensal microbiota.  The presence of two genera in blood, Kocuria and Enhydrobacter, was associated with an increased CVD mortality whereas it was the opposite for the third genera, Paracoccus. Interestingly, these correlations were identified independently of other know health and lifestyle risk factors for CVD mortality. This study reflects on the risk through a lifetime as it looks at older men and it will be useful to inform on of which genera to pursue in future research projects.


Short-term effects of ambient temperature on the risk of preeclampsia in Nanjing, China: a time-series analysis | BMC Pregnancy and Childbirth | Full Text

Preeclampsia is a complication of pregnancy that occurs in 3-5% of pregnant women. This condition was traditionally diagnosed upon observation of an increase in blood pressure and high level of proteins in urine. Recent studies have found an association between temperature and the risk of preeclampsia. Indeed, it has now been shown that the risk of preeclampsia increases for women who have conceived in warmth months and delivered in cold months based on the study of seasonal or monthly temperature data. In this BMC Pregnancy and Childbirth study, the effect of short-term temperature exposure on the risk of preeclampsia was investigated using daily temperature data. The authors reported that there was a significantly larger number of hospital admissions for preeclampsia on cold days than on hot ones. Indeed, the highest number of admissions to hospital for preeclampsia was observed on days where the mean temperature was lower than 10°C. Furthermore, the lowest number of admissions to hospital for preeclampsia was on days where the mean temperature was higher than 30°C. The lag effect of low temperature preeclampsia risk was also identified as a significant risk factor.  Thus the recommendation was that in low temperature, pregnant women should stay warm and pay attention to their blood pressure and go to the hospital if it raises. This information could be used in order for governments to increase publicity on the impact of low temperature on the risk of preeclampsia and thus help to reduce that risk.


Osmoregulatory strategies of estuarine fish Scatophagus argus in response to environmental salinity changes | BMC Genomics | Full Text

Estuaries are changing environments characterised by large variations in salinity levels due to the mixture of marine and fluvial waters. Thus their inhabitants have had to develop strategies to adapt to such fluctuations. This BMC Genomics study set out to unravel the molecular mechanism responsible for the strong salinity tolerance of Scatophagus argus, the spotted cat fish, a recently developed mariculture specie by looking at differentially expressed proteins. They uncovered that cellular ion regulation transport as well as ATP synthesis are key players in the osmoregulatory process of its specialised gills that act as the main osmoregulatory organ. These gills have developed different strategies to enable the fish to adapt to different salinity level. Under hypo saline conditions, Na+ efflux is maintained through Na+-K+-ATPase (NKA) increased activity leading to a reduction in the intracellular osmotic pressure. Simultaneously, an increased NKA internalisation prevents excessive ion loss. Upon hypersaline stress, excess ions are excreted through active transport and reduced NKA activity resulting in an increased intracellular osmotic pressure. Thus this fish has developed different osmoregulatory strategies in order to handle hypoosmotic as well as hyperosmotic stresses and thus adapt to an environment subject to large fluctuations in salinity levels. These result provide valuable insights on Scatophagus argus and the strategies used by estuarine fishes that should prove helpful to the expansion of commercial aquaculture.

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