Daniela Miti Tsukumo

Loss-of-Function Mutation in Toll-Like Receptor 4 Prevents Diet-Induced Obesity and Insulin Resistance

Obesity is associated with insulin resistance and a state of abnormal inflammatory response. The Toll-like receptor (TLR)4 has an important role in inflammation and immunity, and its expression has been reported in most tissues of the body, including the insulin-sensitive ones. Because it is activated by lipopolysaccharide and saturated fatty acids, which are inducers of insulin resistance, TLR4 may be a candidate for participation in the cross-talk between inflammatory and metabolic signals. Here, we show that C3H/HeJ mice, which have a loss-of-function mutation in TLR4, are protected against the development of diet-induced obesity. In addition, these mice demonstrate decreased adiposity, increased oxygen consumption, a decreased respiratory exchange ratio, improved insulin sensitivity, and enhanced insulin-signaling capacity in adipose tissue, muscle, and liver compared with control mice during high-fat feeding. Moreover, in these tissues, control mice fed a high-fat diet show an increase in IκB kinase complex and c-Jun NH2-terminal kinase activity, which is prevented in C3H/HeJ mice. In isolated muscles from C3H/HeJ mice, protection from saturated fatty acid–induced insulin resistance is observed. Thus, TLR4 appears to be an important mediator of obesity and insulin resistance and a potential target for the therapy of these highly prevalent medical conditions.

Saturated Fatty Acids Produce an Inflammatory Response Predominantly through the Activation of TLR4 Signaling in Hypothalamus: Implications for the Pathogenesis of Obesity

In animal models of diet-induced obesity, the activation of an inflammatory response in the hypothalamus produces molecular and functional resistance to the anorexigenic hormones insulin and leptin. The primary events triggered by dietary fats that ultimately lead to hypothalamic cytokine expression and inflammatory signaling are unknown. Here, we test the hypothesis that dietary fats act through the activation of toll-like receptors 2/4 and endoplasmic reticulum stress to induce cytokine expression in the hypothalamus of rodents. According to our results, long-chain saturated fatty acids activate predominantly toll-like receptor 4 signaling, which determines not only the induction of local cytokine expression but also promotes endoplasmic reticulum stress. Rats fed on a monounsaturated fat-rich diet do not develop hypothalamic leptin resistance, whereas toll-like receptor 4 loss-of-function mutation and immunopharmacological inhibition of toll-like receptor 4 protects mice from diet-induced obesity. Thus, toll-like receptor 4 acts as a predominant molecular target for saturated fatty acids in the hypothalamus, triggering the intracellular signaling network that induces an inflammatory response, and determines the resistance to anorexigenic signals.

Inhibition of toll-like receptor 2 expression improves insulin sensitivity and signaling in muscle and white adipose tissue of mice fed a high-fat diet

The aims of the present study were to investigate the expression of toll-like receptor 2 (TLR2) in muscle and white adipose tissue (WAT) of diet-induced obesity (DIO) mice, and also the effects of its inhibition, with the use of TLR2 antisense oligonucleotide (ASON), on insulin sensitivity and signaling. The expression of TLR2 was increased in muscle and WAT of DIO mice, compared with those that received standard chow. Inhibition of TLR2 in DIO mice, by TLR2 ASON, improved insulin sensitivity and signaling in muscle and WAT. In addition, data show that the inhibition of TLR2 expression prevents the activation of IKBKB, MAPK8, and serine phosphorylation of IRS1 in DIO mice, suggesting that TLR2 is a key modulator of the crosstalk between inflammatory and metabolic pathways. We, therefore, suggest that a selective interference with TLR2 presents an attractive opportunity for the treatment of insulin resistance in obesity and type 2 diabetes.

Topical insulin accelerates wound healing in diabetes by enhancing the AKT and ERK pathways: a double-blind placebo-controlled clinical trial.

Background Wound healing is impaired in diabetes mellitus, but the mechanisms involved in this process are virtually unknown. Proteins belonging to the insulin signaling pathway respond to insulin in the skin of rats. Objective The purpose of this study was to investigate the regulation of the insulin signaling pathway in wound healing and skin repair of normal and diabetic rats, and, in parallel, the effect of a topical insulin cream on wound healing and on the activation of this pathway. Research Design and Methods We investigated insulin signaling by immunoblotting during wound healing of control and diabetic animals with or without topical insulin. Diabetic patients with ulcers were randomized to receive topical insulin or placebo in a prospective, double-blind and placebo-controlled, randomized clinical trial (NCT 01295177) of wound healing. Results and Conclusions Expression of IR, IRS-1, IRS-2, SHC, ERK, and AKT are increased in the tissue of healing wounds compared to intact skin, suggesting that the insulin signaling pathway may have an important role in this process. These pathways were attenuated in the wounded skin of diabetic rats, in parallel with an increase in the time of complete wound healing. Upon topical application of insulin cream, the wound healing time of diabetic animals was normalized, followed by a reversal of defective insulin signal transduction. In addition, the treatment also increased expression of other proteins, such as eNOS (also in bone marrow), VEGF, and SDF-1α in wounded skin. In diabetic patients, topical insulin cream markedly improved wound healing, representing an attractive and cost-free method for treating this devastating complication of diabetes. Trial Registration ClinicalTrials.gov NCT01295177

Double-Stranded RNA-Activated Protein Kinase Is a Key Modulator of Insulin Sensitivity in Physiological Conditions and in Obesity in Mice

The molecular integration of nutrient- and pathogen-sensing pathways has become of great interest in understanding the mechanisms of insulin resistance in obesity. The double-stranded RNA-dependent protein kinase (PKR) is one candidate molecule that may provide cross talk between inflammatory and metabolic signaling. The present study was performed to determine, first, the role of PKR in modulating insulin action and glucose metabolism in physiological situations, and second, the role of PKR in insulin resistance in obese mice. We used Pkr(-/-) and Pkr(+/+) mice to investigate the role of PKR in modulating insulin sensitivity, glucose metabolism, and insulin signaling in liver, muscle, and adipose tissue in response to a high-fat diet. Our data show that in lean Pkr(-/-) mice, there is an improvement in insulin sensitivity, and in glucose tolerance, and a reduction in fasting blood glucose, probably related to a decrease in protein phosphatase 2A activity and a parallel increase in insulin-induced thymoma viral oncogene-1 (Akt) phosphorylation. PKR is activated in tissues of obese mice and can induce insulin resistance by directly binding to and inducing insulin receptor substrate (IRS)-1 serine307 phosphorylation or indirectly through modulation of c-Jun N-terminal kinase and inhibitor of κB kinase β. Pkr(-/-) mice were protected from high-fat diet-induced insulin resistance and glucose intolerance and showed improved insulin signaling associated with a reduction in c-Jun N-terminal kinase and inhibitor of κB kinase β phosphorylation in insulin-sensitive tissues. PKR may have a role in insulin sensitivity under normal physiological conditions, probably by modulating protein phosphatase 2A activity and serine-threonine kinase phosphorylation, and certainly, this kinase may represent a central mechanism for the integration of pathogen response and innate immunity with insulin action and metabolic pathways that are critical in obesity.

Translational research into gut microbiota: new horizons in obesity treatment

1 , Bruno M. Carvalho 1 , AbstrAct Obesity is a pandemic which has been rapidly developing for three decades. When a popula- tion is submitted to the same nutritional stress, some individuals are less susceptible to diet- induced weight gain and hyperglycemia. This observation suggests that other mechanisms are involved which are not directly related to the human genome. The human gut contains an immense number of microorganisms, collectively known as the microbiota. Evidence that gut microbiota composition can differ between obese and lean humans has led to the speculation that gut microbiota can participate in the pathophysiology of obesity. Different mechanisms have been proposed to explain the link between gut flora and obesity. The first mechanism consists in the role of the gut microbiota to increase energy extraction from indigestible dietary polysaccharides. The second, consists in the role of gut flora to modulate plasma lipopolysac- charide levels which triggers chronic low-grade inflammation leading to obesity and diabetes. A third mechanism proposes that gut microbiota may induce regulation of host genes that modulate how energy is expended and stored. However, further studies are needed to clarify a number of issues related to the relationship between the gut microbiota and obesity.

Novel mutation in the MYOC gene in primary open angle glaucoma patients

Editor—Glaucoma is the worlds leading cause of irreversible blindness1 and is characterised by progressive optic disc cupping with corresponding visual field loss. Both intraocular pressure (IOP) and positive family history are risk factors for the development of the disease.2 Juvenile open angle glaucoma (JOAG) is a subtype of open angle glaucoma characterised by an early onset (10 to 35 years of age) and autosomal dominant inheritance with high penetrance,3 a characteristic which has led several authors to investigate affected families in an attempt to identify a gene or genes associated with this condition.4-10 With the use of genetic linkage analysis in families with JOAG, a genetic locus (GLC1A) was recognised on chromosome 1q21-q31.4 The gene associated with GLC1A has been identified and it codifies a 57 kDa protein named trabecular meshwork induced glucocorticoid response protein (TIGR),10also known as myocilin (MYOC).11 The MYOC gene is composed of three exons of 604, 126, and 785 bp, respectively.12 During screening for mutations in the MYOC gene in 25 unrelated Brazilian patients with JOAG, an unreported mutation (Cys433Arg) was detected, present in seven of them. Patients were followed at the Glaucoma Service of the State University of Campinas, Brazil. They underwent an ocular examination, including gonioscopy by Posner lens, applanation tonometry, slit lamp biomicroscopy, optic nerve evaluation, and automated perimetry (Humphrey 630, program 30-2). JOAG was defined as the presence of characteristic bilateral optic nerve damage and visual field loss in the presence of an open angle in subjects younger than 36 years of age. Each patient included in this study came from different families according to interview data. The study was approved by the Ethics Committee of the State University of Campinas. At the time of the ocular examination, the mean age …

[RETRACTION]Translational research into gut microbiota: new horizons in obesity treatment

Obesity is a pandemic which has been rapidly developing for three decades. When a population is submitted to the same nutritional stress, some individuals are less susceptible to diet-induced weight gain and hyperglycemia. This observation suggests that other mechanisms are involved which are not directly related to the human genome. The human gut contains an immense number of microorganisms, collectively known as the microbiota. Evidence that gut microbiota composition can differ between obese and lean humans has led to the speculation that gut microbiota can participate in the pathophysiology of obesity. Different mechanisms have been proposed to explain the link between gut flora and obesity. The first mechanism consists in the role of the gut microbiota to increase energy extraction from indigestible dietary polysaccharides. The second, consists in the role of gut flora to modulate plasma lipopolysaccharide levels which triggers chronic low-grade inflammation leading to obesity and diabetes. A third mechanism proposes that gut microbiota may induce regulation of host genes that modulate how energy is expended and stored. However, further studies are needed to clarify a number of issues related to the relationship between the gut microbiota and obesity.

Translational research into gut microbiota: new horizons on obesity treatment: updated 2014

Obesity is currently a pandemic of worldwide proportions affecting millions of people. Recent studies have proposed the hypothesis that mechanisms not directly related to the human genome could be involved in the genesis of obesity, due to the fact that, when a population undergoes the same nutritional stress, not all individuals present weight gain related to the diet or become hyperglycemic. The human intestine is colonized by millions of bacteria which form the intestinal flora, known as gut flora. Studies show that lean and overweight human may present a difference in the composition of their intestinal flora; these studies suggest that the intestinal flora could be involved in the development of obesity. Several mechanisms explain the correlation between intestinal flora and obesity. The intestinal flora would increase the energetic extraction of non-digestible polysaccharides. In addition, the lipopolysaccharide from intestinal flora bacteria could trigger a chronic sub-clinical inflammatory process, leading to obesity and diabetes. Another mechanism through which the intestinal flora could lead to obesity would be through the regulation of genes of the host involved in energy storage and expenditure. In the past five years data coming from different sources established causal effects between intestinal microbiota and obesity/insulin resistance, and it is clear that this area will open new avenues of therapeutic to obesity, insulin resistance and DM2.

Hypercalcemia in a patient with disseminated paracoccidioidomycosis: a case report

IntroductionHypercalcemia is well described in various granulomatous disorders, such as sarcoidosis, tuberculosis, berylliosis, leprosy and fungal infections. However, the association of Paracoccidioides brasiliensis and hypercalcemia is rare: to the best of our knowledge, only two cases have previously been reported, and neither had a clear documentation of the etiology of the hypercalcemia.Case presentationWe report the case of a 22-year-old man in whom disseminated infection with paracoccidioidomycosis was associated with hypercalcemia. The patient had a high normal serum level of 1,25-dihydroxyvitamin D and a suppressed parathyroid hormone value, an indication that the hypercalcemia was not mediated by parathyroid hormone and might be associated with 1,25-dihydroxyvitamin D.ConclusionThe episode resolved readily with administration of corticosteroids, an outcome suggesting that this is an effective treatment of hypercalcemia of this origin. On follow-up, while receiving antifungal therapy for P. brasiliensis the patients calcium values remained normal.