Fenretinide Reduces Intestinal Mucin-2-Positive Goblet Cells in Chronic Alcohol Abuse.

INTRODUCTION: Alcohol-induced thickening of the gut mucosal layer and increased expression of goblet cell gel-forming mucins, such as mucin-2 (MUC2) are associated with disruptions to the gut barrier in alcoholic liver disease (ALD). Interest in drugs that can target gut mucins in ALD has grown; however to date, no studies have examined the properties of drugs on expression of gut mucins in models of ALD. We previously demonstrated that at 10 mg/kg/day, the drug fenretinide (N-[4-hydroxyphenyl] retinamide [Fen]), a synthetic retinoid, mitigates alcohol-associated damage to the gut barrier and liver injury in a murine model of ALD. METHODS: In this study, we specifically sought to examine the effects of Fen on gut goblet cells, and expression of mucins, including MUC2 using a 25-day Lieber-DeCarli model of chronic alcohol intake. RESULTS: Our results show that chronic alcohol intake increased gut-mucosal thickening, goblet cell numbers, and mRNA and protein expression of MUC2 in both the ileum and colon. Alcohol intake was associated with marked decreases in ileal and colonic Notch signaling, levels of Notch ligands Dll1 and Dll4, and increases in the expression of Notch-associated genes indispensable for goblet cell specification, including Math1 and Spdef. Interestingly, ileal and colonic expression of KLF4, which is involved in terminal differentiation of goblet cells, was reduced in mice chronically fed alcohol. Coadministration of alcohol with Fen at 10 mg/kg/day significantly reduced alcohol-associated increases in ileal and colonic mucosal thickening, ileal Muc2, colonic Muc2, Muc5ac and Muc6 mRNAs, and goblet cell numbers. We also found that Fen strongly prevented alcohol-mediated suppression of the Notch ligand Dll1, Notch signaling, and alcohol-induced increases in expression of Notch-associated goblet cell specification genes in both the ileum and colon. In the absence of alcohol, Fen treatments alone at 10 mg/kg/day had no effects on any of the goblet cell-related endpoints. CONCLUSION: These data show for the first time that the drug Fen possesses mucosal layer-modulating properties in response to chronic alcohol abuse. These data warrant further preclinical examination of Fen given the need for anti-ALD drugs and emerging evidence of a role for intestinal goblet cell mucins in the progression of ALD.

mTOR1c Activation with the Leucine "Trigger" for Prevention of Sarcopenia in Older Adults During Lockdown.

Sarcopenia and muscle wasting have many negative impacts on health and well-being. Evidence suggests that high rates of COVID-19 hospitalizations and lockdown conditions will lead to a marked increase in musculoskeletal disorders associated with sarcopenia in older adults. The molecular etiology of sarcopenia is complex, but physical inactivity, poor diet, and age diminished ability to stimulate muscle protein synthesis (MPS) remain important drivers. A body of evidence shows that, acting through the highly conserved nutrient sensor pathway mTORc1, the branch chain amino acid leucine can trigger and enhance MPS in older adults, and thus has a role in the medical management of sarcopenia. Whey protein-enriched enteral supplements are a low cost, easily accessible source of highly bioavailable leucine used clinically in older adults for preservation of lean body mass in long-term care setting. Therefore, given the evidence of leucine's ability to stimulate MPS in older adults, we argue that meal supplementation with whey-enriched enteral products, which can provide the 3-5 g of leucine necessary to trigger MPS in older adults, should be given serious consideration by medical and nutrition professionals to potentially mitigate muscle wasting and sarcopenia risk associated with prolonged COVID-19 lockdown measures.

Fenretinide Improves Intestinal Barrier Function and Mitigates Alcohol Liver Disease.

Alcohol liver disease (ALD) is a major cause of liver-related mortality globally, yet there remains an unmet demand for approved ALD drugs. The pathogenesis of ALD involves perturbations to the intestinal barrier and subsequent translocation of bacterial endotoxin that, acting through toll-like receptor 4 (TLR4), promotes hepatic inflammation and progression of ALD. In the present study we investigated the ability of fenretinide (Fen) [N-(4-hydroxyphenyl) retinamide], a synthetic retinoid with known anti-cancer and anti-inflammatory properties, to modulate intestinal permeability and clinical hallmarks of ALD in a mouse model of chronic ethanol (EtOH) exposure. Our results show that EtOH-treated mice had reductions in mRNA and protein expression of intestinal tight junction proteins, including claudin one and occludin, and increases in intestinal permeability and endotoxemia compared to pair-fed mice. Also, EtOH-treated mice had marked increases in hepatic steatosis, liver injury, and expression of pro-inflammatory mediators, including TNF-α, and TLR4-positive macrophages, Kupffer cells, and hepatocytes in the intestines and liver, respectively. In contrast, EtOH + Fen-treated mice were resistant to the effects of EtOH on promoting intestinal permeability and had higher intestinal protein levels of claudin one and occludin. Also, EtOH + Fen-treated mice had significantly lower plasma levels of endotoxin, and reductions in expression of TNF-α and TLR4 positive macrophages, Kupffer cells, and hepatocytes in the intestine and liver. Lastly, we found that EtOH + Fen-treated mice exhibited major reductions in hepatic triglycerides, steatosis, and liver injury compared to EtOH-treated mice. Our findings are the first to demonstrate that Fen possesses anti-ALD properties, potentially through modulation of the intestinal barrier function, endotoxemia, and TLR4-mediated inflammation. These data warrant further pre-clinical investigations of Fen as a potential anti-ALD drug.