Self-assembling polymer-based short chain fatty acid prodrugs ameliorate non-alcoholic steatohepatitis and liver fibrosis.

With the preponderance of a high-calorie diet and sedentary lifestyle, the prevalence of non-alcoholic steatohepatitis (NASH), a state of abnormally elevated lipid accumulation in the liver with chronic inflammation, is increasing at an alarming rate worldwide. Hence, cost-effective therapeutic interventions are required to manage this disease at an early stage. Numerous reports have suggested a link between gut microbial dysbiosis, particularly a decrease in the abundance of short-chain fatty acids (SCFA)-producing microbiota and NASH pathogenesis. Considering these low molecular weight (LMW) SCFAs such as acetic, propionic, and butyric acids have been used to inhibit hepatic steatosis in mouse models. However, the poor pharmacokinetic (PK) profile of SCFAs, caused due to their LMW, renders them therapeutically ineffective. Thus, to improve the PK characteristic-based therapeutic efficacy of LMW SCFAs, we designed SCFA-based prodrugs that possess self-assembling characteristics in aqueous media. The designed SCFA prodrugs consist of enzyme-metabolizable amphiphilic block copolymers, [poly(ethylene glycol)-b-poly(vinyl ester)s] conjugated to propionic acid (PA) or butyric acid (BA) by an ester linkage, which self-assemble into stable nanosized micelles several tens of nanometers in diameter (NanoPA and NanoBA). Via pharmacological analysis, we confirmed that, after oral administration, LMW BA decreased to a physiological level within 24 h in the liver, whereas BA liberated from NanoBA was observed until 72 h post-administration, implying a sustained release profile. Here, we evaluated the therapeutic efficacy of NanoSCFA in a choline-deficient, L-amino acid-defined high-fat diet (CDAHFD)-induced NASH and liver fibrosis mouse model by ad libitum drinking. NanoSCFA, particularly NanoBA, exhibited the remarkable potential to ameliorate the phenotypic features of fatty liver disease by reducing hepatic lipogenesis and fibrosis, with negligible adverse effects. In contrast, conventional LMW SCFAs failed to prevent the pathogenesis of fatty liver disease, which plausibly can be explained by their rapid clearance and discernible adverse effects. Mechanistic studies revealed that NanoBA restored the nuclear expression of PPARα, a transcriptional factor regulating mitochondrial fatty acid oxidation, in the periportal hepatocytes and decreased the CPT1A expression level in the hepatic tissues, reflecting the therapeutic effects of NanoBA. Taken together, we confirmed that our NanoSCFA potentially improved the PK properties of SCFAs, and it consequently alleviated NASH symptoms and fibrotic liver compared to LMW SCFAs. Our study establishes NanoSCFA as a suitable nano-assembled prodrug for NASH treatment.

Retinoic acid receptor activity is required for the maintenance of type 1 innate lymphoid cells.

Group 1 innate lymphoid cells (G1-ILCs) are innate immune effectors critical for the response to intracellular pathogens and tumors. G1-ILCs comprise circulating natural killer (NK) cells and tissue-resident type 1 ILCs (ILC1s). ILC1s mainly reside in barrier tissues and provide the initial sources of interferon-γ (IFN-γ) to prime the protecting responses against infections, which are followed by the response of recruited NK cells. Despite such distribution differences, whether local environmental factors influence the behavior of NK cells and ILC1s is unclear. Here, we show that the signaling of retinoic acid (RA), active metabolites of vitamin A, is essential for the maintenance of ILC1s in the periphery. Mice expressing RARα403, a truncated form of retinoic acid receptor α (RARα) that exerts dominant negative activity, in a lymphoid cell- or G1-ILC-specific manner showed remarkable reductions of peripheral ILC1s while NK cells were unaffected. Lymphoid cell-specific inhibition of RAR activity resulted in the reduction of PD-1+ ILC progenitors (ILCPs), but not of common lymphoid progenitors (CLPs), suggesting the impaired commitment and differentiation of ILC1s. Transcriptome analysis revealed that RARα403-expressing ILC1s exhibited impaired proliferative states and declined expression of effector molecules. Thus, our findings demonstrate that cell-intrinsic RA signaling is required for the homeostasis and the functionality of ILC1s, which may present RA as critical environmental cue targeting local type 1 immunity against infection and cancer.

Design of self-assembling anti-epileptic drug for long-acting drug delivery in vivo.

Valproic acid (VPA) has been extensively used for the treatment of seizures in epilepsy. The recommended VPA concentration in the blood is in the range of 50-100 µg mL-1 and its therapeutic efficiency is well recognized. Since its therapeutic range is relatively narrow, strict scheduling of daily self-medication is required to optimize therapeutic outcomes and avoid adverse effects. To facilitate patient convenience in long-term and chronic therapies, the development of a sustained drug delivery system for VPA is a promising strategy. In this study, an enzyme-metabolizable block copolymer possessing a valproate ester, poly(ethylene glycol)-b-poly(vinyl valproate), was synthesized. The synthesized block copolymers formed stable nanoparticles (denoted NanoVPA) by self-assembly under physiological conditions and released VPA via enzymatic hydrolysis. NanoVPA showed improved pharmacokinetics compared to sodium valproate in vivo, and therapeutic efficacy in a pentylenetetrazol (PTZ)-induced kindling mouse model after once-weekly administration.

Design of enzyme-responsive short-chain fatty acid-based self-assembling drug for alleviation of type 2 diabetes mellitus.

Short-chain fatty acids (SCFAs), such as propionic and butyric acids have been touted as potential therapeutic interventions that can ameliorate diabetic pathogenesis. However, SCFAs are low-molecular-weight (LMW) compounds that have limited clinical use due to unfavorable pharmacokinetics, off-target effects, poor palatability and unpleasant odor. Hence, to improve the therapeutic utilization of SCFAs, the enzyme metabolizable block copolymers, [poly(ethylene glycol)-b-poly(vinyl ester)s], possessing propionate and butyrate esters were synthesized, which formed stable nanoparticles by self-assembling under physiological conditions. In this study, the therapeutic efficacy of propionic acid- and butyric acid-based self-assembling nanoparticles (PNP/BNP) was evaluated in a mouse model of type 2 diabetes mellitus through ad libitum drinking. The conventional antidiabetic drug, exenatide- and BNP-treated mice showed the highest glucose tolerance, whereas LMW SCFAs remained ineffective in normalizing glucose homeostasis. The better efficacy of BNP over the LMW SCFAs was attributable to (i) higher consumption of BNP than the LMW SCFAs by the mice (good palatability and odorless), (ii) prolonged residence time of BNP (48 h) in the gastro-intestinal tract (muco-adhesion) contributing to intestinal enzyme-mediated sustained release of butyric acid, and (iii) negligible off-target effects (no abrupt rise in the bloodstream). The aforementioned data suggest that SCFA-based nanoparticles are more potential therapeutic interventions than LMW SCFAs for metabolic diseases such as diabetes.