Investigation of AGRP neurons' role on cognitive abilities

Açlık durumunda insan beyninde birçok aktivite değişimi oluşur ve bunlara bağlı olarak vücudun farklı organlarından hormonsal salınımlar gerçekleşir. Bu aktivite değişimleri fizyolojik veya kognitif yetilerde aktive edici, inhibe edici ya da nötr etkilere yol açmaktadır. Fizyolojik açlık sırasında vücutta salınan ghrelinin veya analoglarının rodent deney modellerinde vücuda enjeksiyonları ile elde edilen literatür bilgisi ghrelinin öğrenme, bellek veya diğer kognitif yetilere pozitif bir etkisi olduğunu göstermektedir. Ghrelin hormonunun salınımının tetikleyen açlık mekanizmasında öncül rol oynayan nöronlardan biri Agrp nöronlarıdır. Bu çalışmada açlık nöronları olarak geçen hipotalamik Agrp nöronlarının spatial öğrenme ve bellek gibi temel kognitif yetiler üzerindeki etkisi araştırılmıştır. Agrp-cre transgenik fare ile yapılan deneylerde, Agrp nöronları kemogenetik ajanlar ile uyarılmış, kognitif yetiler Morris Water Maze ve Novel Object Recognition Test uygulanarak incelenmiştir. Yapılan deneyler sonucu Agrp nöronlarının öğrenmeye bir etkisinin bulunmadığının ancak spatial bellek üzerindeki arttırıcı bir etkisinin gözlenebilmesi için öğrenme safhasında Agrp aktivitesinin gerekli olduğu (p<0,005) ve eğer öğrenme fazında Agrp nöron ateşlemesi yok ise nöron aktivitesinin bellek üzerinde negatif bir etkisi olduğu (p<0,001) ortaya konmuştur.During hunger state, activity changes occur throughout the brain, which in turn lead to hormone release. Changes in these activities might have activating or inhibiting effects on physiological or cognitive abilities or they might not have any influence. One of the hormones released during physiological hunger state is ghrelin. Agrp neurons are one of the precursor neurons that play an important role in hunger mechanism which leads to ghrelin release. Previous studies using administrations of ghrelin or its analogous on rodents demonstrated that ghrelin-stimulated-hunger state has a positive effect on cognitive abilities including learning and memory. In this project, we initially studied the effect of hypothalamic Agrp neurons, which are active at the hunger state on cognitive abilities such as spatial learning and spatial memory. For this purpose, we applied chemogenetic methods on Agrp-cre mice in order to stimulate Agrp neurons specifically. Morris Water Maze and Novel Object Recognition Test were conducted for behavioral studies. The results indicate that Agrp activity is necessary during training process for the enhancer effect on memory (p<0,005) and after training without Agrp firing, neuron activity decreases the memory retention (p<0,001), nonetheless there is no influence on learning

Human Biomonitoring Data in Health Risk Assessments Published in Peer-Reviewed Journals between 2016 and 2021: Confronting Reality after a Preliminary Review

Human biomonitoring (HBM) is a rapidly developing field that is emphasized as an important approach for the assessment of health risks. However, its value for health risk assessment (HRA) remains to be clarified. We performed a review of publications concerned with applications of HBM in the assessment of health risks. The selection of publications for this review was limited by the search engines used (only PubMed and Scopus) and a timeframe of the last five years. The review focused on the clarity of 10 HRA elements, which influence the quality of HRA. We show that the usage of HBM data in HRA is limited and unclear. Primarily, the key HRA elements are not consistently applied or followed when using HBM in such assessments, and secondly, there are inconsistencies regarding the understanding of fundamental risk analysis principles and good practices in risk analysis. Our recommendations are as follows: (i) potential usage of HBM data in HRA should not be non-critically overestimated but rather limited and aligned to a specific value for exposure assessment or for the interpretation of health damage; (ii) improvements to HRA approaches, using HBM information or not, are needed and should strictly follow theoretical foundations of risk analysis