Hypothalamic TTF-1 orchestrates the sensitivity of leptin

Hypothalamic P62 (SQSTM1) regulates energy balance by modulating leptin signaling

RATIONALE

The multifaceted functions of p62 (SQSTM1) are increasingly recognized, but its role in hypothalamic metabolism-associated neurons for energy balance has yet to be elucidated.

METHODS

Single-nucleus RNA sequencing (snRNA-Seq) was performed on hypothalamic tissues from db/db and db/m mice to explore p62 expression. Overexpression and knockout of p62 in hypothalamic POMC neurons were performed via AAV-mediated gene delivery and Cre-loxP systems. Metabolic outcomes were assessed under normal chow (NCD) and high-fat diet (HFD) conditions. The co-immunoprecipitation and luciferase reporter assays were used to investigate the interaction between p62 and STAT3.

RESULTS

The snRNA-Seq analysis found that p62 was ubiquitously expressed in hypothalamic neurons, with significantly higher levels in POMC neurons of db/db mice compared to db/m controls. Under NCD or HFD conditions, the absence of p62 in POMC neurons led to increased body weight, decreased energy expenditure and leptin sensitivity, while its overexpression in POMC neurons produced the opposite phenotype. Mechanistically, p62 interacts with STAT3, facilitating its phosphorylation to initiate POMC transcription and amplify leptin sensitivity.

CONCLUSION

This study demonstrated the capacity of p62 to monogenically regulate the obesity phenotype and emphasized its dual role in managing energy homeostasis through direct modulation of STAT3/POMC signaling and amplification of leptin sensitivity.

Altered Metabolic Phenotypes and Hypothalamic Neuronal Activity Triggered by Sodium-Glucose Cotransporter 2 Inhibition

BACKGRUOUND

Sodium-glucose cotransporter 2 (SGLT-2) inhibitors are currently used to treat patients with diabetes. Previous studies have demonstrated that treatment with SGLT-2 inhibitors is accompanied by altered metabolic phenotypes. However, it has not been investigated whether the hypothalamic circuit participates in the development of the compensatory metabolic phenotypes triggered by the treatment with SGLT-2 inhibitors.

METHODS

Mice were fed a standard diet or high-fat diet and treated with dapagliflozin, an SGLT-2 inhibitor. Food intake and energy expenditure were observed using indirect calorimetry system. The activity of hypothalamic neurons in response to dapagliflozin treatment was evaluated by immunohistochemistry with c-Fos antibody. Quantitative real-time polymerase chain reaction was performed to determine gene expression patterns in the hypothalamus of dapagliflozin-treated mice.

RESULTS

Dapagliflozin-treated mice displayed enhanced food intake and reduced energy expenditure. Altered neuronal activities were observed in multiple hypothalamic nuclei in association with appetite regulation. Additionally, we found elevated immunosignals of agouti-related peptide neurons in the paraventricular nucleus of the hypothalamus.

CONCLUSION

This study suggests the functional involvement of the hypothalamus in the development of the compensatory metabolic phenotypes induced by SGLT-2 inhibitor treatment.

Sirtuin1-Mediated Deacetylation of Hypothalamic TTF-1 Contributes to the Energy Deficiency Response

TTF-1 stimulates appetite by regulating the expression of agouti-related peptide (AgRP) and proopiomelanocortin (POMC) genes in the hypothalamus of starving animals. However, the mechanism underlying TTF-1's response to decreased energy levels remains elusive. Here, we provide evidence that the NAD+-dependent deacetylase, sirtuin1 (Sirt1), activates TTF-1 in response to energy deficiency. Energy deficiency leads to a twofold increase in the expression of both Sirt1 and TTF-1, leading to the deacetylation of TTF-1 through the interaction between the two proteins. The activation of Sirt1, induced by energy deficiency or resveratrol treatment, leads to a significant increase in the deacetylation of TTF-1 and promotes its nuclear translocation. Conversely, the inhibition of Sirt1 prevents these Sirt1 effects. Notably, a point mutation in a lysine residue of TTF-1 significantly disrupts its deacetylation and thus nearly completely hinders its ability to regulate AgRP and POMC gene expression. These findings highlight the importance of energy-deficiency-induced deacetylation of TTF-1 in the control of AgRP and POMC gene expression.