Lívia Bitencourt Pascoal

Inhibition of Hypothalamic Inflammation Reverses Diet-Induced Insulin Resistance in the Liver

Defective liver gluconeogenesis is the main mechanism leading to fasting hyperglycemia in type 2 diabetes, and, in concert with steatosis, it is the hallmark of hepatic insulin resistance. Experimental obesity results, at least in part, from hypothalamic inflammation, which leads to leptin resistance and defective regulation of energy homeostasis. Pharmacological or genetic disruption of hypothalamic inflammation restores leptin sensitivity and reduces adiposity. Here, we evaluate the effect of a hypothalamic anti-inflammatory approach to regulating hepatic responsiveness to insulin. Obese rodents were treated by intracerebroventricular injections, with immunoneutralizing antibodies against Toll-like receptor (TLR)4 or tumor necrosis factor (TNF)α, and insulin signal transduction, hepatic steatosis, and gluconeogenesis were evaluated. The inhibition of either TLR4 or TNFα reduced hypothalamic inflammation, which was accompanied by the reduction of hypothalamic resistance to leptin and improved insulin signal transduction in the liver. This was accompanied by reduced liver steatosis and reduced hepatic expression of markers of steatosis. Furthermore, the inhibition of hypothalamic inflammation restored defective liver glucose production. All these beneficial effects were abrogated by vagotomy. Thus, the inhibition of hypothalamic inflammation in obesity results in improved hepatic insulin signal transduction, leading to reduced steatosis and reduced gluconeogenesis. All these effects are mediated by parasympathetic signals delivered by the vagus nerve.

Defective Regulation of the Ubiquitin/Proteasome System in the Hypothalamus of Obese Male Mice

In both human and experimental obesity, inflammatory damage to the hypothalamus plays an important role in the loss of the coordinated control of food intake and energy expenditure. Upon prolonged maintenance of increased body mass, the brain changes the defended set point of adiposity, and returning to normal weight becomes extremely difficult. Here we show that in prolonged but not in short-term obesity, the ubiquitin/proteasome system in the hypothalamus fails to maintain an adequate rate of protein recycling, leading to the accumulation of ubiquitinated proteins. This is accompanied by an increased colocalization of ubiquitin and p62 in the arcuate nucleus and reduced expression of autophagy markers in the hypothalamus. Genetic protection from obesity is accompanied by the normal regulation of the ubiquitin/proteasome system in the hypothalamus, whereas the inhibition of proteasome or p62 results in the acceleration of body mass gain in mice exposed for a short period to a high-fat diet. Thus, the defective regulation of the ubiquitin/proteasome system in the hypothalamus may be an important mechanism involved in the progression and autoperpetuation of obesity.

Resolvin Rvd2 Reduces Hypothalamic Inflammation And Rescues Mice From Diet-induced Obesity

BackgroundDiet-induced hypothalamic inflammation is an important mechanism leading to dysfunction of neurons involved in controlling body mass. Studies have shown that polyunsaturated fats can reduce hypothalamic inflammation. Here, we evaluated the presence and function of RvD2, a resolvin produced from docosahexaenoic acid, in the hypothalamus of mice.MethodsMale Swiss mice were fed either chow or a high-fat diet. RvD2 receptor and synthetic enzymes were evaluated by real-time PCR and immunofluorescence. RvD2 was determined by mass spectrometry. Dietary and pharmacological approaches were used to modulate the RvD2 system in the hypothalamus, and metabolic phenotype consequences were determined.ResultsAll enzymes involved in the synthesis of RvD2 were detected in the hypothalamus and were modulated in response to the consumption of dietary saturated fats, leading to a reduction of hypothalamic RvD2. GPR18, the receptor for RvD2, which was detected in POMC and NPY neurons, was also modulated by dietary fats. The substitution of saturated by polyunsaturated fats in the diet resulted in increased hypothalamic RvD2, which was accompanied by reduced body mass and improved glucose tolerance. The intracerebroventricular treatment with docosahexaenoic acid resulted in increased expression of the RvD2 synthetic enzymes, increased expression of anti-inflammatory cytokines and improved metabolic phenotype. Finally, intracerebroventricular treatment with RvD2 resulted in reduced adiposity, improved glucose tolerance and increased hypothalamic expression of anti-inflammatory cytokines.ConclusionsThus, RvD2 is produced in the hypothalamus, and its receptor and synthetic enzymes are modulated by dietary fats. The improved metabolic outcomes of RvD2 make this substance an attractive approach to treat obesity.

Transcriptional and Molecular Pathways Activated in Mesenteric Adipose Tissue and Intestinal Mucosa of Crohn’s Disease Patients

Crohns disease (CD) is a chronic inflammatory disorder, characterized by cytokine imbalance and transcription signaling pathways activation. In addition, the increase of mesenteric adipose tissue (MAT) near the affected intestinal area is a hallmark of CD. Therefore, we evaluated the transcription signaling pathways and cytokines expression in intestinal mucosa and MAT of active CD patients. Ten patients with ileocecal CD and eight with noninflammatory diseases were studied. The biopsies of intestinal mucosa and MAT were snap-frozen and protein expression was determined by immunoblotting. RNA levels were measured by qPCR. The pIkB/IkB ratio and TNFα level were significantly higher in intestinal mucosa of CD when compared to controls. However, STAT1 expression was similar between intestinal mucosa of CD and controls. Considering the MAT, the pIkB/IkB ratio was significantly lower and the anti-inflammatory cytokine IL10 was significantly higher in CD when compared to controls. Finally, the protein content of pSTAT1 was higher in MAT of CD compared to controls. These findings reinforce the predominance of the proinflammatory NF-kB pathway in CD intestinal mucosa. For the first time, we showed the activation of STAT1 pathway in MAT of CD patients, which may help to understand the physiopathology of this immune mediated disease.

Ileal pouch of ulcerative colitis and familial adenomatous polyposis patients exhibit modulation of autophagy markers

Total retocolectomy with ileal pouch-anal anastomosis (IPAA) is the surgery of choice for patients with ulcerative colitis (UC) that are refractory to clinical treatment. Pouchitis is one of the most common complications after this procedure. Defects in autophagy have been reported in inflammatory bowel diseases. However, there are no studies on the IP. Therefore, we studied markers for autophagy in the IP mucosa of UC and FAP patients comparing them to controls with a normal distal ileum. Sixteen patients with IP in “J” shape, asymptomatic and with endoscopically normal IP were evaluated. The control group consisted of eight patients with normal colonoscopy. There was a significant decrease in the transcriptional levels of ATG5, MAP1LC3A and BAX in the FAP group. There was also a decrease in the protein level of Beclin-1 in the UC and FAP compared to the control group. Although the LC3II levels by immunoblot were higher in the UC group, LC3/p62 co-localization were lower in the immunofluorescence analysis in the UC and FAP compared to the control group. Corroborating these results, there was an increase of p62 by immunoblot in the UC group. These findings indicated a modulation of macroautophagy markers in the IP, which may explain the mucosa inflammation predisposition.