CPEB alteration and aberrant transcriptome-polyadenylation lead to a treatable SLC19A3 deficiency in Huntington's disease.

Huntington's disease (HD) is a hereditary neurodegenerative disorder of the basal ganglia for which disease-modifying treatments are not yet available. Although gene-silencing therapies are currently being tested, further molecular mechanisms must be explored to identify druggable targets for HD. Cytoplasmic polyadenylation element binding proteins 1 to 4 (CPEB1 to CPEB4) are RNA binding proteins that repress or activate translation of CPE-containing transcripts by shortening or elongating their poly(A) tail. Here, we found increased CPEB1 and decreased CPEB4 protein in the striatum of patients and mouse models with HD. This correlated with a reprogramming of polyadenylation in 17.3% of the transcriptome, markedly affecting neurodegeneration-associated genes including PSEN1, MAPT, SNCA, LRRK2, PINK1, DJ1, SOD1, TARDBP, FUS, and HTT and suggesting a new molecular mechanism in neurodegenerative disease etiology. We found decreased protein content of top deadenylated transcripts, including striatal atrophy­linked genes not previously related to HD, such as KTN1 and the easily druggable SLC19A3 (the ThTr2 thiamine transporter). Mutations in SLC19A3 cause biotin-thiamine­responsive basal ganglia disease (BTBGD), a striatal disorder that can be treated with a combination of biotin and thiamine. Similar to patients with BTBGD, patients with HD demonstrated decreased thiamine in the cerebrospinal fluid. Furthermore, patients and mice with HD showed decreased striatal concentrations of thiamine pyrophosphate (TPP), the metabolically active form of thiamine. High-dose biotin and thiamine treatment prevented TPP deficiency in HD mice and attenuated the radiological, neuropathological, and motor HD-like phenotypes, revealing an easily implementable therapy that might benefit patients with HD.

Adding Branched-Chain Amino Acids to an Enhanced Standard-of-Care Treatment Improves Muscle Mass of Cirrhotic Patients With Sarcopenia: A Placebo-Controlled Trial.

INTRODUCTION: The effect of branched-chain amino acid (BCAA) supplementation on muscle mass in patients with cirrhosis and sarcopenia is unknown. METHODS: This is a pilot, prospective, randomized, and double-blind study of a cohort of 32 patients with cirrhosis and sarcopenia diagnosed by computed tomography scan who underwent a nutritional and physical activity intervention for 12 weeks. They were divided into 2 groups (placebo: 17 patients; BCAA: 15 patients). The study protocol was registered at ClinicalTrials.gov (NCT04073693). RESULTS: Baseline characteristics were similar in both groups. After treatment, only the BCAA group presented a significant improvement in muscle mass (43.7 vs 46 cm2/m2; P = 0.023). Seventeen patients (63%) presented improvement in muscle mass overall, which was more frequent in the BCAA group (83.3 vs 46.7%; P = 0.056). Regarding frailty, there was a significant improvement in the Liver Frailty Index in the global cohort (n = 32) after the 12 weeks (4.2 vs 3.9; P < 0.001). This difference was significant in both groups: in the placebo group (4.2 vs 3.8; P < 0.001) and in the BCAA group (4.2 vs 3.9; P < 0.001). After treatment, the BCAA group had a higher increase in zinc levels than the placebo group (Δzinc: 12.3 vs 5.5; P = 0.026). In addition, there was a trend for greater improvement of albumin levels in the BCAA group (Δalbumin: 0.19 vs 0.04; P = 0.091). DISCUSSION: BCAA supplementation improves muscle mass in cirrhotic patients with sarcopenia.