Myofiber Baf60c controls muscle regeneration by modulating Dkk3-mediated paracrine signaling.

Obesity and type 2 diabetes (T2D) are the leading causes of the progressive decline in muscle regeneration and fitness in adults. The muscle microenvironment is known to play a key role in controlling muscle stem cell regenerative capacity, yet the underlying mechanism remains elusive. Here, we found that Baf60c expression in skeletal muscle is significantly downregulated in obese and T2D mice and humans. Myofiber-specific ablation of Baf60c in mice impairs muscle regeneration and contraction, accompanied by a robust upregulation of Dkk3, a muscle-enriched secreted protein. Dkk3 inhibits muscle stem cell differentiation and attenuates muscle regeneration in vivo. Conversely, Dkk3 blockade by myofiber-specific Baf60c transgene promotes muscle regeneration and contraction. Baf60c interacts with Six4 to synergistically suppress myocyte Dkk3 expression. While muscle expression and circulation levels of Dkk3 are markedly elevated in obese mice and humans, Dkk3 knockdown improves muscle regeneration in obese mice. This work defines Baf60c in myofiber as a critical regulator of muscle regeneration through Dkk3-mediated paracrine signaling.

Dietary intervention preserves ß cell function in mice through CTCF-mediated transcriptional reprogramming.

Pancreatic ß cell plasticity is the primary determinant of disease progression and remission of type 2 diabetes (T2D). However, the dynamic nature of ß cell adaptation remains elusive. Here, we establish a mouse model exhibiting the compensation-to-decompensation adaptation of ß cell function in response to increasing duration of high-fat diet (HFD) feeding. Comprehensive islet functional and transcriptome analyses reveal a dynamic orchestration of transcriptional networks featuring temporal alteration of chromatin remodeling. Interestingly, prediabetic dietary intervention completely rescues ß cell dysfunction, accompanied by a remarkable reversal of HFD-induced reprogramming of islet chromatin accessibility and transcriptome. Mechanistically, ATAC-based motif analysis identifies CTCF as the top candidate driving dietary intervention-induced preservation of ß cell function. CTCF expression is markedly decreased in ß cells from obese and diabetic mice and humans. Both dietary intervention and AAV-mediated restoration of CTCF expression ameliorate ß cell dysfunction ex vivo and in vivo, through transducing the lipid toxicity and inflammatory signals to transcriptional reprogramming of genes critical for ß cell glucose metabolism and stress response.