Project description:The relationship between loss of hypothalamic function and onset of diabetes mellitus remains elusive. Therefore, we generated a targeted oxidative-stress murine model utilizing conditional knockout of selenocysteine-tRNA (Trsp) using rat insulin promoter-driven-Cre (RIP-Cre). These Trsp-knockout (TrspRIPKO) mice exhibit deletion of Trsp in both hypothalamic cells and pancreatic β-cells leading to increased hypothalamic oxidative stress and severe insulin resistance. Leptin signals were suppressed and numbers of proopiomelanocortin-positive neurons in the hypothalamus were decreased. In contrast, a Trsp-knockout mouse (TrspIns1KO) expressing Cre specifically in pancreatic β-cells, but not in the hypothalamus, did not display insulin and leptin resistance, demonstrating a critical role of the hypothalamus in the onset of diabetes mellitus. Nrf2 (NF-E2-related-factor-2) regulates antioxidant gene expression. Gene-driven increase in Nrf2 signaling suppressed hypothalamic oxidative stress and improved insulin and leptin resistance in TrspRIPKO mice. Thus, Nrf2 harbors the potential to prevent the onset of diabetic mellitus by reducing hypothalamic oxidative damage.
Project description:The relationship between loss of hypothalamic function and onset of diabetes mellitus remains elusive. Therefore, we generated a targeted oxidative-stress murine model utilizing conditional knockout of selenocysteine-tRNA (Trsp) using rat insulin promoter-driven-Cre (RIP-Cre). These Trsp-knockout (TrspRIPKO) mice exhibit deletion of Trsp in both hypothalamic cells and pancreatic β-cells leading to increased hypothalamic oxidative stress and severe insulin resistance. Leptin signals were suppressed and numbers of proopiomelanocortin-positive neurons in the hypothalamus were decreased. In contrast, a Trsp-knockout mouse (TrspIns1KO) expressing Cre specifically in pancreatic β-cells, but not in the hypothalamus, did not display insulin and leptin resistance, demonstrating a critical role of the hypothalamus in the onset of diabetes mellitus. Nrf2 (NF-E2-related-factor-2) regulates antioxidant gene expression. Gene-driven increase in Nrf2 signaling suppressed hypothalamic oxidative stress and improved insulin and leptin resistance in TrspRIPKO mice. Thus, Nrf2 harbors the potential to prevent the onset of diabetic mellitus by reducing hypothalamic oxidative damage.
Project description:Purpose: 1. Bulk-RNA-Seq was performed to identify tancytye-enriched genes. 2. scRNA-Seq was performed to profile hypothalamic cells following leptin treatment Conclusions: Leptin receptor expression in tanycytes is either absent or undetectably low, that tanycytes do not directly regulate hypothalamic leptin signaling, and that leptin regulates gene expression in diverse hypothalamic cell types through both direct and indirect mechanisms.
Project description:Leptin monotherapy (i.e. without the use of administered insulin and/or any other molecule) corrects ID-induced metabolic aberrancies and promotes survival of insulin deficient rodents. These results generated great interest in the possibility of treating insulin deficient patients with leptin and/or molecule(s) underlying its beneficial effects. Hence, with the goal of identifying circulating molecule(s) underlying the advantageous effect of leptin we performed quantitative proteomic analysis of plasma and identified S100A9 as a putative peripheral mediator of leptin action. Here, to identify circulating molecule(s) underlying the advantageous effect of leptin we compared the results obtained by quantitative proteomic analysis of plasma between 2 groups of mice: streptozotocin (STZ)-treated mice that underwent intracerebroventricular (icv) leptin treatment for 12 days (STZ-Leptin) and ii) STZ-treated mice that underwent icv leptin treatment for 10 days and were withdrawn from leptin treatment for the following two days (STZ-Leptin-STOP). STZ treatment led to a massive loss of pancreatic insulin-producing β-cells, diminished pancreatic Proinsulin mRNA level, and caused severe insulinopenia, and hyperglycemia. icv leptin administration normalized hyperglycemia. However, two days after leptin delivery was halted hyperglycemia reappeared. We hypothesized that change in plasmatic protein(s) content could underlie re-emergence of hyperglycemia following decrease of leptin action.
Project description:Modulating leptin sensitivity in hypothalamic neurons is critical for metabolic regulation and plays a key role in the development of obesity. This study examines the effects of three distinct approaches—leptin exposure (LEPA), leptin antagonist administration (LANTA), and palmitate treatment (PA)—on adult-derived mHypoA-2/12 neurons. Transcriptomic analysis using 3' mRNA-Seq revealed significant downregulation of several pathways, including the NOD-like receptor signaling pathway, C-type lectin receptor signaling pathway, NF-κB signaling pathway, and IL-17 signaling pathway. These pathways are closely linked to neuroinflammatory processes, suggesting that modulating leptin sensitivity may influence inflammation in the hypothalamus. The observed downregulation indicates a complex interaction between leptin signaling and cellular stress responses, which may represent an adaptive mechanism to prolonged exposure to leptin or fatty acids. Understanding these dynamics is crucial for gaining insight into how neuroinflammation contributes to the development of leptin resistance and related metabolic disorders.
Project description:Timed-feeding leads to adipose browning, although the integrative mechanisms for the same remain unclear. Here we show that twice-a-nocturnal (TAN) feeding causes biphasic oscillations of circulating insulin and leptin, representing their entrainment by timed-feeding. Insulin and leptin surges lead to marked cellular, functional and metabolic remodeling of sWAT resulting in increased energy expenditure. Single-cell RNAseq analyses and flow cytometry reveal a role for insulin and leptin surges in ILC2 recruitment and sWAT browning, since depleting leptin or blocking insulin receptor signaling or ILC2 cell recruitment, each dampens TAN feeding-induced sWAT remodeling and energy expenditure. Consistently, recreating insulin and leptin oscillations via once-a-day co-injections is sufficient to favorably remodel innervated sWAT. Indeed, innervation is necessary for sWAT remodeling since denervation of sWAT, but not BAT, blocks TAN-induced sWAT remodeling and resolution of inflammation. In sum, timed feeding reorganizes nutrient-sensitive pathways to remodel sWAT, which drives the metabolic benefits of timed-feeding.