Whereas visceral adipose tissue (VAT) primarily stores excess energy, brown adipose tissue (BAT) dissipates it in a process termed nonshivering thermogenesis. Several key VAT features, particularly murine epidydimal VAT, are regulated by a distinct population of regulatory T (T _reg ) cells, raising the question of whether BAT hosts an analogous population. Although T _reg cells have been observed in BAT, their properties and mechanisms of action require elucidation. We found BAT T _reg cells to be heterogeneous in subtissular localization and subtype composition. Punctual depletion of T _reg cells unleashed interferon-γ (IFN-γ)–producing lymphocytes in BAT, but not in subcutaneous or visceral fat depots, leading to IFN-γ–dependent mitochondrial dysfunction and metabolic dysregulation, thereby impeding nonshivering thermogenesis. Cold challenge selectively expanded the IL-18R1 ⁺ T _reg subtype in BAT; stripping this receptor specifically from T _reg cells unleashed IFN-γ–producing lymphocytes and compromised temperature control. Thus, control of local IFN-γ production is a core feature of T _reg cell control of tissue homeostasis.

Adipose browning and atrophy are early events of cachexia, a lethal metabolic disorder affecting nearly half of the population with cancer. Here, using individual-derived specimens and mouse models, we identified an iron-dependent pathway that initiates adipose browning in both physiological and cachectic settings. Upon adrenergic stimulation of adipocytes, an influx of iron induces the activity of methionine sulfoxide reductase A (MSRA), an enzyme that reverses the oxidation of proteinaceous methionine residues. Mechanistically, iron coordination by the conserved iron-binding EXXH motif of two MSRA polypeptides serves to dimerize, stabilize and elevate its reductase activity. Iron-bound MSRA dimers in turn promote adipose browning by maintaining the reduced state of select substrates, including the catalytic subunit of protein kinase A. Remarkably, in mouse models, MsrA deletion impairs adipose browning, mitigates cachexia and prolongs the survival of tumor-bearing animals. Thus, as a key nexus of cancer-associated cachexia, the β3 adrenergic receptor–iron–MSRA axis is a promising target for clinical intervention.

Previous reports have described a statistical association between high-density lipoproteins (HDL) subclasses and the expression of genes coding for pro-calcifying proteins in the epicardial adipose tissue of patients with coronary artery disease (CAD) and aortic valvular stenosis (AVS). These results suggest a causal relationship between HDL and the regulation of gene expression in epicardial adipose tissue. However, there is no experimental evidence that supports this causal relationship. Therefore, we explored the effect of HDL isolated from CAD or AVS patients on the expression of OPN, BMP2, and BMP4, genes coding for proteins related to calcification, osteopontin, and bone morphogenetic proteins -2 and -4, respectively, and LEP, UCP, and PER, coding for leptin, uncoupling protein-1, and perilipin-2, respectively, proteins that confer phenotypic characteristics to adipocytes. The experiments were performed using a novel model of cardiac adipocytes differentiated in vitro from stromal cells of rabbit cardiac adipose tissue. AVS or CAD patients’ HDL differentially modulated the expression of BMP4 and LEP, whereas HDL from both kinds of patients upregulated the OPN gene expression. A high concentration of triglycerides associated to small HDL and a higher concentration of phospholipids of large HDL from CAD patients than those from AVS individuals were the most remarkable structural differences. Finally, we demonstrated that cholesterol from reconstituted HDL was internalized to the adipocytes. The regulation of genes related to the secretory activity of cardiac adipocytes mediated by HDL has clinical implications as a potential therapeutic target for the prevention and treatment of CAD and AVS. In summary, the HDL isolated from the CAD and AVS patients differentially regulated gene expression in adipocytes by a mechanism that seems to be dependent on HDL lipid internalization to the cells and structural characteristics of the lipoproteins.

Breast cancer (BCa) is a heterogeneous disease, initially responsive to hormone therapy but often developing resistance to both hormonal and chemotherapy treatments. Novel therapeutic strategies are needed for drug-resistant BCa. Genistein, a phytoestrogen structurally similar to estrogen, competes with estrogen for receptor binding and exhibits anti-cancer effects. In this study, we investigated the cellular and metabolic impacts of genistein, alone or in combination with chemotherapy, in two human BCa cell lines—one estrogen receptor-positive (ER+) and one estrogen receptor-negative (ER−). We observed a strong synergistic effect on cell viability at low concentrations of genistein and chemotherapy, resulting in reduced clonogenic capacity and impaired cell migration. Genistein alone modulated cellular energy metabolism, notably reducing ATP production in MCF7 (ER+) cells. This metabolic shift was linked to a decreased dependence on fatty acids for energy, coupled with a decrease in the rate-limiting mitochondrial translocase CPT1 required for fatty acid oxidation, alongside with an increase in intracellular fatty acid levels. While the most significant changes occurred in ER+ cells, ER− cells also showed responses to genistein treatment. Collectively, our findings suggest that low dose genistein, in combination with conventional chemotherapy, induces synergistic anti-cancer effects, promoting cellular senescence. This effect may be partly mediated by a reduced reliance on fatty acid metabolism in BCa cells.