Flvcr1a deficiency promotes heme-based energy metabolism dysfunction in skeletal muscle

lncRNA AK159072 Promotes Myoblast Proliferation and Muscle Regeneration Through Activation of Akt/Foxo1 Pathway

Long non-coding RNAs (lncRNAs) are significant regulators of myoblast proliferation, migration and regeneration. In our previous research, we identified that lncRNA AK159072 was differentially expressed during myoblast development. In this study, we would like to explore the regulatory role and the mechanisms of AK159072 in proliferation. We discovered that AK159072 was increasingly expressed during myoblast proliferation and was located in both the nucleus and cytoplasm of proliferating C2C12 myoblasts. Overexpression of AK159072 promoted the expression of proliferation-related genes c-Myc, cyclin-dependent kinase 2 (CDK2), CDK4, and CDK6 in C2C12 myoblasts. Additionally, the cell viability and EdU-positive cells were increased, while the wound size was decreased after overexpression AK159072. In contrast, cell proliferation was attenuated when AK159072 was successfully silenced. Furthermore, the cross sectional area (CSA) and proliferative markers were decreased after knockdown of AK159072 in the mouse hind leg muscles with CTX-induced injury in vivo, indicating that knockdown of AK159072 may delay muscle regeneration. The study further demonstrated that Akt/Foxo1 pathway mediated the effects of AK159072 overexpression and knockdown in myoblasts. Taken together, our results suggested that AK159072 may regulate myoblast proliferation and muscle regeneration via Akt/Foxo1 pathway. The study suggestd that modulating the expression of AK159072 could be a potential therapeutic strategy for muscle injuries, this could have significant clinical relevance for conditions such as muscular dystrophy, sarcopenia, and other muscle disorders.

Haem biosynthesis regulates BCAA catabolism and thermogenesis in brown adipose tissue

The distinctive colour of brown adipose tissue (BAT) is attributed to its high content of haem-rich mitochondria. However, the mechanisms by which BAT regulates intracellular haem levels remain largely unexplored. Here we demonstrate that haem biosynthesis is the primary source of haem in brown adipocytes. Inhibiting haem biosynthesis results in an accumulation of the branched-chain amino acids (BCAAs) valine and isoleucine, owing to a haem-associated metabolon that channels BCAA-derived carbons into haem biosynthesis. Haem synthesis-deficient brown adipocytes display reduced mitochondrial respiration and lower UCP1 levels than wild-type cells. Although exogenous haem supplementation can restore intracellular haem levels and mitochondrial function, UCP1 downregulation persists. This sustained UCP1 suppression is linked to epigenetic regulation induced by the accumulation of propionyl-CoA, a byproduct of disrupted haem synthesis. Finally, disruption of haem biosynthesis in BAT impairs thermogenic response and, in female but not male mice, hinders the cold-induced clearance of circulating BCAAs in a sex-hormone-dependent manner. These findings establish adipose haem biosynthesis as a key regulator of thermogenesis and sex-dependent BCAA homeostasis.

Unearthing FLVCR1a: tracing the path to a vital cellular transporter

The Feline Leukemia Virus Subgroup C Receptor 1a (FLVCR1a) is a member of the SLC49 Major Facilitator Superfamily of transporters. Initially recognized as the receptor for the retrovirus responsible of pure red cell aplasia in cats, nearly two decades since its discovery, FLVCR1a remains a puzzling transporter, with ongoing discussions regarding what it transports and how its expression is regulated. Nonetheless, despite this, the substantial body of evidence accumulated over the years has provided insights into several critical processes in which this transporter plays a complex role, and the health implications stemming from its malfunction. The present review intends to offer a comprehensive overview and a critical analysis of the existing literature on FLVCR1a, with the goal of emphasising the vital importance of this transporter for the organism and elucidating the interconnections among the various functions attributed to this transporter.