Intestinal lymphangiectasia: Understanding the bigger picture

Intestinal lymphangiectasia (IL) is characterized by the dilation of intestinal lymphatic vessels, which can rupture and cause loss of lymph into the intestine. Due to the high content of proteins, lipoproteins, and lymphocytes in the intestinal lymph, loss of lymph might result in hypoproteinemia, hypoalbuminemia, hypogammaglobulinemia, and lymphocytopenia. In addition, there may be a depletion of minerals, lipids, and fat-soluble vitamins. IL can be primary due to inherent malfunctioning of the lymphatic system, or secondly, a result of various factors that may hinder lymphatic drainage either directly or indirectly. This condition has emerged as a subject of significant clinical interest. Given that the intestinal lymphatic system plays an important role in the body's fluid homeostasis, adaptive immunity, nutrient and drug absorption, intestinal transport, and systemic metabolism, its dysfunction may have wider implications. Although primary IL is rare, with varied clinical features, complications, treatment response, and outcomes, secondary IL is more common than previously believed. The definitive diagnosis of IL requires endoscopic demonstration of whitish villi (which frequently resemble snowflakes) and histological confirmation of dilated lacteals in the small intestinal mucosa. Treatment of IL is challenging and involves dietary modifications, managing underlying medical conditions, and using medications such as sirolimus and octreotide. Recognizing its prevalence and diverse etiology is crucial for targeted management of this challenging medical condition. This article provides a comprehensive exploration of the clinical implications associated with IL. In addition, it offers valuable insights into critical knowledge gaps in the existing diagnostic and management landscape.

HDL-small RNA Export, Transport, and Functional Delivery in Atherosclerosis

PURPOSE OF REVIEW

This review highlights recent advances on the mechanisms and impact of HDL-small non-coding RNAs (sRNA) on intercellular communication in atherosclerosis.

RECENT FINDINGS

Studies demonstrate that HDL-microRNAs (miRNA) are significantly altered in atherosclerotic cardiovascular disease (ASCVD), and are responsive to diet, obesity, and diabetes. Immune cells, pancreatic beta cells, and neurons are shown to export miRNAs to HDL. In turn, HDL can deliver functional miRNAs to recipient hepatocytes and endothelial cells regulating adhesion molecule expression, cytokines, and angiogenesis. With high-throughput sRNA sequencing, we now appreciate the full sRNA signature on circulating HDL, including the transport of rRNA and tRNA-derived fragments. Strikingly, HDL were highly enriched with exogenous microbial sRNAs. HDL transport a diverse set of host and non-host sRNAs that are altered in cardiometabolic diseases. Given the bioactivity of these sRNAs, they likely contribute to cellular communication within atherosclerotic lesions, and are potential disease biomarkers and therapeutic targets.

Methylglyoxal-induced miR-223 suppresses rat vascular KATP channel activity by downregulating Kir6.1 mRNA in carbonyl stress

The vascular ATP-sensitive K⁺ (K_ATP) channel composed of Kir6.1 and SUR2B subunits regulates cellular activity by coupling intermediary metabolism to membrane excitability. Our previous studies have shown that both Kir6.1 and SUB2B are post-transcriptionally downregulated by methylglyoxal (MGO) which is a reactive carbonyl specie and can cause disruption of vascular tone regulation under diabetic conditions. We have shown that the SUB2B downregulation is mediated by the microRNA (miR) miR-9a, while the mechanism underlying Kir6.1 inhibition is still unclear. Studying the microRNA databases, we found that miR-223 has sequence similarities to the 3' untranslated sequence (3'UTR) of Kir6.1 mRNA suggesting their potential interactions. Therefore, we explored the role of miR-233 in K_ATP channel regulation by up/down-regulation of miR-223 in smooth muscle cells (SMCs) and mesenteric arterials. Quantitative reverse transcriptase polymerase chain reaction (qRT-PCR) analysis showed augmentation of miR-223 expression in the cultured SMCs after 300 μM MGO exposure by 5-6 folds. miR-223 overexpression down-regulated Kir6.1 mRNA levels by ~2.6 times while miR-223 knockdown diminished the effect of 300 μM MGO by ~50% in the SMCs. Luciferase assay and mutagenesis studies showed that the effect of miR-223 was abolished when the potential interaction site in the 3' UTR was mutated. Studies with Western blot, patch clamp, and perfused mesenteric arterial rings showed that transfection of miR-223 downregulated K_ATP protein expression, inhibited K_ATP channel activity and enhanced vasoconstriction. These results therefore suggest that miR-223 is induced by MGO exposure, which subsequently downregulates the Kir6.1 mRNA, suppresses K_ATP channel function, and impairs functional regulation of vascular tones.

BACKGROUND

Methylglyoxal causes transcriptional inhibition of the vascular K_ATP channel.

RESULTS

Exogenous miR-223 down-regulated Kir6.1. miR-223 knockdown alleviated the effect of MGO.

CONCLUSION

Vascular K_ATP channel is important for miR-223 targeting.

SIGNIFICANCE

Regulation of the miR-223 level may be a novel strategy for clinical treatment of diabetes.

Advances in HDL: Much More than Lipid Transporters

High Density Lipoprotein (HDL) particles, beyond serving as lipid transporters and playing a key role in reverse cholesterol transport, carry a highly variable number of proteins, micro-RNAs, vitamins, and hormones, which endow them with the ability to mediate a plethora of cellular and molecular mechanisms that promote cardiovascular health. It is becoming increasingly evident, however, that the presence of cardiovascular risk factors and co-morbidities alters HDLs cargo and protective functions. This concept has led to the notion that metrics other than HDL-cholesterol levels, such as HDL functionality and composition, may better capture HDL cardiovascular protection. On the other hand, the potential of HDL as natural delivery carriers has also fostered the design of engineered HDL-mimetics aiming to improve HDL efficacy or as drug-delivery agents with therapeutic potential. In this paper, we first provide an overview of the molecules known to be transported by HDL particles and mainly discuss their functions in the cardiovascular system. Second, we describe the impact of cardiovascular risk factors and co-morbidities on HDL remodeling. Finally, we review the currently developed HDL-based approaches.

Niacin induces miR-502-3p expression which impairs insulin sensitivity in human adipocytes

MicroRNAs have been involved in insulin resistance (IR). As the mechanism whereby niacin, an anti-dyslipidemic agent, leads to IR remains elusive, we sought to identify differentially expressed microRNAs in adipose tissue (AT) of individuals receiving niacin and to explore the link between microRNAs, niacin and IR in human adipocytes.In a double-blind controlled study, 22 obese men received extended-release niacin or placebo over 8 weeks. Bioclinical data and subcutaneous AT biopsies were obtained before and after treatment. AT microRNA expression profiles were determined using RTqPCR for 758 human-specific microRNAs. hMADS adipocytes were treated with niacin, or acipimox (a niacin-like drug without effect on IR), or transfected with miR-502-3p. Glucose uptake and Western blotting were performed.In obese men, insulin sensitivity decreased after niacin treatment. In AT, the expression of 6 microRNAs including miR-502-3p was up-regulated. Treatment of hMADS adipocytes with niacin specifically increased miR-502-3p expression. Acipimox had no effect. Overexpression of miR-502-3p in adipocytes led to reduced insulin-induced glucose uptake and lower insulin-stimulated AKT phosphorylation.Long term niacin treatment altered microRNA expression levels in human AT. Increased miR-502-3p expression may play a role in the mediation of IR due to niacin in adipocytes.The study is registered in Clinical Trials NCT01083329 and EudraCT 2009-012124-85.