OGT upregulates myogenic IL‐6 by mediating O‐GlcNAcylation of p65 in mouse skeletal muscle under cold exposure

Abstract

Cold exposure is an unavoidable and severe challenge for people and animals residing in cold regions of the world, and may lead to hypothermia, drastic changes in systemic metabolism, and inhibition of protein synthesis. O‐linked‐N‐acetylglucoseaminylation (O‐GlcNAcylation) directly regulates the activity and function of target proteins involved in multiple biological processes by acting as a stress receptor and nutrient sensor. Therefore, our study aimed to examine whether O‐GlcNAcylation affected myogenic IL‐6 expression, regulation of energy metabolism, and promotion of survival in mouse skeletal muscle under acute cold exposure conditions. Total protein was extracted from C2C12 cells that had been cultured at 32°C for 3, 6, 9, and 12 h. Western blot analysis showed that mild hypothermia enhanced O‐GlcNAc transferase (OGT) and O‐GlcNAcase (OGA) expression. Furthermore, global OGT‐dependent glycosylation and interleukin‐6 (IL‐6) levels peaked 3 h after induction of mild hypothermia. Enhanced activation of the NF‐κB pathway was also observed in response to mild hypothermia. Alloxan and Thiamet G were used to reduce and increase global OGT glycosylation levels in C2C12 cells, respectively. Increased O‐GlcNAcylation was associated with significant upregulation of IL‐6 expression, as well as enhanced activity and nuclear translocation of p65, while decreased O‐GlcNAcylation had the opposite effect. In addition, increased O‐GlcNAcylation was associated with significantly increased glucose metabolism, and OGT‐mediated O‐GlcNAcylation of p65. We generated skeletal muscle‐specific OGT knockout mice and exposed them to cold at 4°C for 3 h per day for 1 week. OGT deficiency attenuated the O‐GlcNAcylation, activity, and nuclear translocation of p65, resulting in downregulation of IL‐6 in mouse skeletal muscle of mice exposed to cold conditions. Taken together, our data suggested that O‐GlcNAcylation of p65 enhanced p65 activity and nuclear translocation leading to the upregulation of IL‐6, which maintained energy homeostasis and promotes cell survival in mouse skeletal muscle during cold exposure.

Liuwei Dihuang formula ameliorates chronic stress-induced emotional and cognitive impairments in mice by elevating hippocampal O-GlcNAc modification

“…Various types of research have proved that dynamic protein O-GlcNAc modification is an intracellular signaling mechanism triggered by numerous stressors, including pressure-overload hypertrophy ( Zhu et al, 2021 ), trauma-hemorrhage ( Zou et al, 2007 ), cardiac injury ( Jones et al, 2008 ), as well as a stress response ( Fahie et al, 2022 ). As a stress receptor, O-GlcNAcylated p65 rapidly upregulated RNA binding motif protein 3 ( Liu Y. et al, 2022 ) and interleukin-6 level ( Hu et al, 2022 ) to maintain glucose metabolism and decrease apoptosis in the skeletal muscle of mice under acute cold exposure. Acute exercise stress significantly increased the O-GlcNAc level for cellular adaptation to oxidative stress, and this effect persists for at least 4 h ( Peternelj et al, 2015 ).…”

Regulation of the urea cycle by CPS1O-GlcNAcylation in response to dietary restriction and aging

“…Hypothermia is more threatening to the elderly than to young people ( Young and Lee, 1997 ). O -GlcNAcylation of p65 enhanced p65 activity and nuclear translocation, leading to the upregulation of interleukin-6, which maintains energy homeostasis and promotes cell survival in mouse skeletal muscle during cold exposure ( Hu et al., 2022 ). Deletion of Ogt in brown adipocytes resulted in severe cold intolerance with decreased uncoupling protein 1 expression ( Ohashi et al., 2017 ).…”

O-GlcNAcylation: The Underestimated Emerging Regulators of Skeletal Muscle Physiology

“…The absence of O -GlcNAcylation increases the secretion of IL-15 in skeletal muscle, which serves as a myokines regulating systemic oxidative metabolism [ 198 ]. Similarly, the secretion of myogenic IL-6 is indirectly regulated by O -GlcNAcylated p65 to maintain energy homeostasis in skeletal muscle [ 199 ]. In addition, creatine kinase is O -GlcNAcylated [ 200 ].…”