Absorption

In recent years, significant progress has been made in transdermal drug delivery systems, but there is still a search for enhancers that can improve the absorption of active substances through the stratum corneum. Although permeation enhancers have been described in the scientific literature, the use of naturally occurring substances in this role is still of particular interest, because they can offer a high level of safety of use, with a low risk of skin irritation, and high efficiency. In addition, these ingredients are biodegradable, easily available, and widely accepted by consumers due to the growing trust in natural compounds. This article provides information on the role of naturally derived compounds in transdermal drug delivery systems that help them penetrate the skin. The work focuses on the components found in the stratum corneum such as sterols, ceramides, oleic acid, and urea. Penetration enhancers found in nature, mainly in plants, such as terpenes, polysaccharides, and fatty acids have also been described. The mechanism of action of permeation enhancers in the stratum corneum is discussed, and information on the methods of assessing their penetration efficiency is provided. Our review mainly covers original papers from 2017 to 2022, supplemented with review papers, and then older publications used to supplement or verify the data. The use of natural penetration enhancers has been shown to increase the transport of active ingredients through the stratum corneum and can compete with synthetic counterparts.

Chronic alcohol use has been attributed to the development of malnutrition. This is in part due to the inhibitory effect of ethanol on the absorption of vital nutrients, including glucose, amino acids, lipids, water, vitamins, and minerals within the small intestine. Recent advances in research, along with new cutting-edge technologies, have advanced our understanding of the mechanism of ethanol's effect on intestinal nutrient absorption at the brush border membrane (BBM) of the small intestine. However, further studies are needed to delineate how ethanol consumption could have an impact on altered nutrient absorption under various disease conditions. Current research has elucidated the relationship of alcohol consumption on glucose, glutamine, vitamins B1 (thiamine), B2 (riboflavin), B9 (folate), C (ascorbic acid), selenium, iron, and zinc absorption within the small intestine. We conducted systematic computerized searches in PubMed using the following keywords: (1) "Alcohol effects on nutrient transport"; (2) "Alcohol mediated malabsorption of nutrients"; (3) "Alcohol effects on small intestinal nutrient transport"; and (4) "Alcohol mediated malabsorption of nutrients in small intestine". We included the relevant studies in this review. The main objective of this review is to marshal and analyze previously published research articles and discuss, in-depth, the understanding of ethanol's effect in modulating absorption of vital macro and micronutrients in health and disease conditions. This could ultimately provide great insights in the development of new therapeutic strategies to combat malnutrition associated with alcohol consumption.

In this study, the transdermal fate of vesicular nanosystems was investigated. Particularly, ethosomes based on phosphatidylcholine 0.9% w/w and transethosomes based on phosphatidylcholine 0.9 or 2.7% w/w plus polysorbate 80 0.3% w/w as an edge activator were prepared and characterized. The vesicle mean size, morphology and deformability were influenced by both phosphatidylcholine and polysorbate 80. Indeed, the mean diameters of ethosome were around 200 nm, while transethosome's mean diameters were 146 or 350 nm in the case of phosphatidylcholine 0.9 or 2.7%, w/w, respectively. The highest deformability was achieved by transethosomes based on phosphatidylcholine 0.9%, w/w. The three types of vesicular nanosystems were applied on explanted human skin maintained in a bioreactor. Transmission electron microscopy demonstrated that all vesicles were able to enter the skin, keeping their structural integrity. Notably, the vesicle penetration capability was influenced by their physical-chemical features. Indeed, ethosomes reached keratinocytes and even the dermis, phosphatidylcholine 0.9% transethosomes were found in keratinocytes and phosphatidylcholine 2.7% transethosomes were found only in corneocytes of the outer layer. These findings open interesting perspectives for a differentiated application of these vesicles for transdermal drug delivery as a function of the cutaneous pathology to be addressed.

IntroductionKlotho acts as a coreceptor for the phosphaturic hormone fibroblast growth factor-23 (FGF-23) and exists in both a membrane-bound and a soluble form (sKlotho) found in blood and urine. Klotho protein is moderately expressed in kidney proximal tubule and more abundant in the distal convolution (DC), which includes the distal convoluted tubule (DCT) and connecting tubule (CNT). However, the function of Klotho in the DC, particularly its role in sKlotho release and regulation of mineral metabolism, remains unclear.MethodsscRNA-seq was performed on isolated mouse DC cells. Four novel gene-modified mouse models were generated with Klotho deleted in the entire DC, the late DCT/CNT, the DCT only, and pan-tubular.ResultsUsing scRNA-seq on isolated mouse DC tubules, we showed that Klotho is more abundant in the late-DCT/CNT than in the early DCT. The composite data from three DC specific Klotho knockout mice support DC to be the primary source of urinary sKlotho, with 80% coming from the late-DCT/CNT and only 20% from the DCT. Notably, mice lacking Klotho in the entire DC (Kl-KODC) maintained normal serum sKlotho, FGF-23, and phosphate homeostasis. Bulk RNA-seq of isolated fluorescent DC segments from Kl-KODC_Tomato mice revealed suppressed signaling by mitogen activated protein kinase and downregulation of several genes involved in kidney calcium ion handling (Trpv5, Vdr, Pth1r, Klk1). Consistently, the Kl-KODC mice exhibited profound hypercalciuria and reduced bone density. On the other hand, pan-tubular Klotho deficiency in mice led to severe phosphate imbalance and loss of both serum/urine sKlotho.ConclusionsDC-derived Klotho regulates urinary sKlotho levels and controls calcium ion reabsorption, while Klotho in proximal tubule maintains phosphate homeostasis and likely regulates circulating sKlotho levels.