[Show abstract][Hide abstract] ABSTRACT: INTRODUCTIONThiazolidinediones (TZDs) enhanced body weight (BW) partially by increased adipogenesis and hyperphagia. Neuronal PPARγ knockout mice on high fat diet (HFD) are leaner because of enhanced leptin response, although it could be secondary to their leanness. Thus, it still is an open question how TZDs may alter energy balance. Multiple factors regulate food intake (FI) and energy expenditure (EE), including anorexigenic hormones as insulin and leptin. Nonetheless, elevated hypothalamic AMPK activity increases FI and TZDs increase AMPK activity in muscle cells. Thus, the aim of the present study was to investigate whether Pioglitazone (PIO) treatment alters hypothalamic insulin and leptin action/signaling, AMPK phosphorylation, and whether these alterations may be implicated in the regulation of FI and EE.METHODS
Swiss mice on HFD (2 months) received PIO (25 mg/kg/day-gavage) or vehicle for 14 days. AMPK and AdipoR1 were inhibited via ICV injections using Compound C and siRNA, respectively. Western Blot, Real Time PCR and CLAMS were done.RESULTSPIO treatment increased BW, adiposity, FI, NPY mRNA and decreased POMC mRNA expression and EE in HFD mice. Despite higher adiposity, PIO treatment improved insulin sensitivity, glucose tolerance, decreased insulin and increased adiponectin serum levels. This result was associated with, improved insulin and leptin action/signaling, decreased α2AMPK(Ser491) phosphorylation and elevated ACC and AMPK(Thr172) phosphorylation in hypothalamus. The inhibition of hypothalamic AMPK with Compound C was associated with decreased adiposity, FI, NPY mRNA and EE in PIO-treated mice. The reduced expression of hypothalamic adiponectin receptor 1 (AdipoR1) with siRNA concomitantly with PIO treatment reverted Pioglitazone induced obesity development, suggesting that adiponectin may be involved in this effect.CONCLUSIONS
These results demonstrated that PIO, despite improving insulin/leptin action in hypothalamus, increases FI and decreases EE, partially, by activating hypothalamic adiponectin/AdipoR1/AMPK axis. Suggesting a novel mechanism in the hypothalamus by which TZDs increase BW.International Journal of Obesity accepted article preview online, 31 July 2015. doi:10.1038/ijo.2015.134.
International journal of obesity (2005) 07/2015; DOI:10.1038/ijo.2015.134 · 5.39 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: IKK epsilon (IKKε) is induced by the activation of NFκB. Whole body IKKε knockout mice on a high fat diet (HFD) were protected from insulin resistance and showed altered energy balance. Here, we demonstrate that IKKε is expressed in neurons and is upregulated in the hypothalamus of obese mice, contributing to insulin and leptin resistance. Blocking IKKε in the hypothalamus of obese mice, using CAYMAN10576 or siRNA, decreased NFκB activation in this tissue, relieving the inflammatory environment. Inhibition of IKKε activity, but not TBK1, reduced IRS-1(Ser) phosphorylation and insulin and leptin resistance by an improvement of IR/IRS-1/Akt and JAK2/STAT3 pathway in the hypothalamus. These improvements were independent of body weight and food intake. Increased insulin and leptin action/signaling in the hypothalamus may contribute to a decrease in adiposity, hypophagia, and enhancement of energy expenditure, accompanied by lower NPY and increased POMC mRNA levels. Improvement of hypothalamic insulin action decreases fasting glycemia, glycemia after pyruvate injection, and PEPCK protein expression in the liver of HFD and db/db mice, suggesting a reduction on hepatic glucose production. We suggest that IKKε may be a key inflammatory mediator in the hypothalamus of obese mice, and its hypothalamic inhibition improves energy and glucose metabolism.
[Show abstract][Hide abstract] ABSTRACT: Insulin acts in the hypothalamus, decreasing food intake (FI) by the IR/PI3K/Akt pathway. This pathway is impaired in obese animals and endoplasmic reticulum (ER) stress and low-grade inflammation are possible mechanisms involved in this impairment. Here, we highlighted the amygdala as an important brain region for FI regulation in response to insulin. This regulation was dependent on PI3K/AKT pathway similar to the hypothalamus. Insulin was able to decrease neuropeptide Y (NPY) and increase oxytocin mRNA levels in the amygdala via PI3K, which may contribute to hypophagia. Additionally, obese rats did not reduce FI in response to insulin and AKT phosphorylation was decreased in the amygdala, suggesting insulin resistance. Insulin resistance was associated with ER stress and low-grade inflammation in this brain region. The inhibition of ER stress with PBA reverses insulin action/signaling, decreases NPY and increases oxytocin mRNA levels in the amygdala from obese rats, suggesting that ER stress is probably one of the mechanisms that induce insulin resistance in the amygdala.
FEBS Open Bio 12/2013; 3:443-9. DOI:10.1016/j.fob.2013.09.002 · 1.52 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Mutation of tub gene in mice induces obesity, suggesting that tub could be an important regulator of energy balance. In the current study, we investigated whether insulin, leptin, and obesity can modulate Tub in vivo in hypothalamic nuclei, and we investigated possible consequences on energy balance, neuropeptide expression, and hepatic glucose metabolism. Food intake, metabolic characteristics, signaling proteins, and neuropeptide expression were measured in response to fasting and refeeding, intracerebroventricular insulin and leptin, and Tub antisense oligonucleotide (ASO). Tub tyrosine phosphorylation (Tub-p-tyr) is modulated by nutritional status. Tub is a substrate of insulin receptor tyrosine kinase, (IRTK) and leptin receptor (LEPR)-Janus kinase 2 (JAK2) in hypothalamic nuclei. After leptin or insulin stimulation, Tub translocates to the nucleus. Inhibition of Tub expression in hypothalamus by ASO increased food intake, fasting blood glucose, and hepatic glucose output, decreased O(2) consumption, and blunted the effect of insulin or leptin on proopiomelanocortin, thyroid-releasing hormone, melanin-concentrating hormone, and orexin expression. In hypothalamus of mice administered a high-fat diet, there is a reduction in leptin and insulin-induced Tub-p-tyr and nuclear translocation, which is reversed by reducing protein tyrosine phosphatase 1B expression. These results indicate that Tub has a key role in the control of insulin and leptin effects on food intake, and the modulation of Tub may contribute to insulin and leptin resistance in DIO mice.
[Show abstract][Hide abstract] ABSTRACT: Topiramate (TPM) treatment has been shown to reduce adiposity in humans and rodents. The reduction in adiposity is related to decreased food intake and increased energy expenditure. However, the molecular mechanisms through which TPM induces weight loss are contradictory and remain to be clarified. Whether TPM treatment alters hypothalamic insulin, or leptin signaling and action, is not well established. Thus, we investigate herein whether short-term TPM treatment alters energy balance by affecting insulin and leptin signaling, action, or neuropeptide expression in the hypothalamus of mice fed with a high-fat diet. As expected, short-term treatment with TPM diminished adiposity in obese mice mainly due to reduced food intake. TPM increased anorexigenic signaling by enhancing the leptin-induced leptin receptor/Janus kinase 2/signal transducer and activator of transcription 3 pathway and the insulin-induced insulin receptor substrate/Akt/forkhead box O1 pathway in parallel to reduced phosphatase protein expression in the hypothalamus of obese mice. These effects were independent of body weight. TPM also raised anorexigenic neuropeptides such as POMC, TRH, and CRH mRNA levels in obese mice. In addition, TPM increased the activation of the hypothalamic MAPK/ERK pathway induced by leptin, accompanied by an increase in peroxisome proliferator-activated receptor-coactivator α and uncoupling protein 1 protein levels in brown adipose tissue. Furthermore, TPM increased AMP-activated protein kinase and acetyl-coenzyme A carboxylase phosphorylation in peripheral tissues, which may help improve energy metabolism in these tissues. Together, these results provide novel insights into the molecular mechanisms through which TPM treatment reduces adiposity.