Co-activation of VTA DA and GABA neurons mediates nicotine reinforcement.

Smoking is the most important preventable cause of mortality and morbidity worldwide. This nicotine addiction is mediated through the nicotinic acetylcholine receptor (nAChR), expressed on most neurons, and also many other organs in the body. Even within the ventral tegmental area (VTA), the key brain area responsible for the reinforcing properties of all drugs of abuse, nicotine acts on several different cell types and afferents. Identifying the precise action of nicotine on this microcircuit, in vivo, is important to understand reinforcement, and finally to develop efficient smoking cessation treatments. We used a novel lentiviral system to re-express exclusively high-affinity nAChRs on either dopaminergic (DAergic) or γ-aminobutyric acid-releasing (GABAergic) neurons, or both, in the VTA. Using in vivo electrophysiology, we show that, contrary to widely accepted models, the activation of GABA neurons in the VTA plays a crucial role in the control of nicotine-elicited DAergic activity. Our results demonstrate that both positive and negative motivational values are transmitted through the dopamine (DA) neuron, but that the concerted activity of DA and GABA systems is necessary for the reinforcing actions of nicotine through burst firing of DA neurons. This work identifies the GABAergic interneuron as a potential target for smoking cessation drug development.

Evaluation of new leptin fragments on food intake and body weight of normal rats.

Leptin, a protein hormone originating from adipose tissue, circulates in the plasma and affects the energy balance by interacting with the hypothalamus. Leptin plays an important role in the regulation of a variety of physiological functions, including food intake, body temperature and body weight maintenance. Tertiary structure of the leptin molecule reveals the existence of a four-helix bundle that is characteristic of the short-helix cytokines. To identify regions of the leptin molecule responsible for its bioactivity, we have recently synthesized six peptides based on the protein three-dimensional structure. Our results indicated that the fragments Ac-hLEP(92-115)-NH(2) (IV) and Ac-[Ser(117)]-hLEP(116-140)-NH(2) (V) were recognized by leptin receptor present in hp-75 cells validating that this region of the molecule contain the functional epitope of the leptin molecule. In the present study, a new series of decapeptides encompassing the region of fragments IV and V of leptin were synthesized, and their effects on body weight and food intake were assessed when administered into the lateral cerbroventricle of normal rats. Peptides were synthesized by SPPS, purified by RP-HPLC and characterized by LC/ESI-MS. We also performed a conformational study of the peptides by circular dichroism in order to correlate the biological activity and secondary structure of the leptin fragments. Among the fragments tested, we found that Ac-hLEP(110-119)-NH(2) (VI) induce a significant reduction in both body weight and food intake. The use of synthetic leptin-derivate fragments may offer the basis for the development of compounds with potential application in human obesity or to its related metabolic dysfunctions.

Chronic lipoic acid treatment worsens energy imbalances in streptozotocin-induced diabetic rats.

AIM: Our objective was to verify the energy balance in streptozotocin-induced diabetic rats chronically treated with lipoic acid (LA). METHODS: Diabetes was induced in rats by streptozotocin and the animals divided into four groups, comprising controls and diabetic rats, with each group receiving either daily intraperitoneal LA (30 mg/kg) or a buffer solution for 30 days. Body weight, food intake and stool and urine collections were recorded daily. On day 30, animals were sacrificed and the carcasses, faeces and urine collected and processed for calorimetric analysis. Blood glucose and insulin were also determined. RESULTS: All parameters of energy balance were affected by diabetes. LA treatment reduced weight gain, energy gain and gross food efficiency in both control and diabetic animals. However, the LA-treated animals tended to show higher energy expenditure than non-treated animals. Body composition was also affected by diabetes: fat content was impaired by LA treatment in both control and diabetic animals. The latter also showed increased glycaemia and decreased insulinaemia, but LA had no effect on these parameters. CONCLUSION: Our results indicate that chronic treatment with LA aggravates energy imbalances in diabetic animals. Moreover, our data suggest the need to reconsider the use of LA as an adjuvant in the prevention and treatment of type 1 diabetes.

Diet-induced obesity impairs hypothalamic glucose sensing but not glucose hypothalamic extracellular levels, as measured by microdialysis.

BACKGROUND/OBJECTIVES: Glucose from the diet may signal metabolic status to hypothalamic sites controlling energy homeostasis. Disruption of this mechanism may contribute to obesity but its relevance has not been established. The present experiments aimed at evaluating whether obesity induced by chronic high-fat intake affects the ability of hypothalamic glucose to control feeding. We hypothesized that glucose transport to the hypothalamus as well as glucose sensing and signaling could be impaired by high-fat feeding. SUBJECTS/METHODS: Female Wistar rats were studied after 8 weeks on either control or high-lard diet. Daily food intake was measured after intracerebroventricular (i.c.v.) glucose. Glycemia and glucose content of medial hypothalamus microdialysates were measured in response to interperitoneal (i.p.) glucose or meal intake after an overnight fast. The effect of refeeding on whole hypothalamus levels of glucose transporter proteins (GLUT) 1, 2 and 4, AMPK and phosphorylated AMPK levels was determined by immunoblotting. RESULTS: High-fat rats had higher body weight and fat content and serum leptin than control rats, but normal insulin levels and glucose tolerance. I.c.v. glucose inhibited food intake in control but failed to do so in high-fat rats. Either i.p. glucose or refeeding significantly increased glucose hypothalamic microdialysate levels in the control rats. These levels showed exacerbated increases in the high-fat rats. GLUT1 and 4 levels were not affected by refeeding. GLUT2 levels decreased and phosphor-AMPK levels increased in the high-fat rats but not in the controls. CONCLUSIONS: The findings suggest that, in the high-fat rats, a defective glucose sensing by decreased GLUT2 levels contributed to an inappropriate activation of AMPK after refeeding, despite increased extracellular glucose levels. These derangements were probably involved in the abolition of hypophagia in response to i.c.v. glucose. It is proposed that 'glucose resistance' in central sites of feeding control may be relevant in the disturbances of energy homeostasis induced by high-fat feeding.

Beneficial effects of Ginkgo biloba extract on insulin signaling cascade, dyslipidemia, and body adiposity of diet-induced obese rats.

Ginkgo biloba extract (GbE) has been indicated as an efficient medicine for the treatment of diabetes mellitus type 2. It remains unclear if its effects are due to an improvement of the insulin signaling cascade, especially in obese subjects. The aim of the present study was to evaluate the effect of GbE on insulin tolerance, food intake, body adiposity, lipid profile, fasting insulin, and muscle levels of insulin receptor substrate 1 (IRS-1), protein tyrosine phosphatase 1B (PTP-1B), and protein kinase B (Akt), as well as Akt phosphorylation, in diet-induced obese rats. Rats were fed with a high-fat diet (HFD) or a normal fat diet (NFD) for 8 weeks. After that, the HFD group was divided into two groups: rats gavaged with a saline vehicle (HFD+V), and rats gavaged with 500 mg/kg of GbE diluted in the saline vehicle (HFD+Gb). NFD rats were gavaged with the saline vehicle only. At the end of the treatment, the rats were anesthetized, insulin was injected into the portal vein, and after 90s, the gastrocnemius muscle was removed. The quantification of IRS-1, Akt, and Akt phosphorylation was performed using Western blotting. Serum levels of fasting insulin and glucose, triacylglycerols and total cholesterol, and LDL and HDL fractions were measured. An insulin tolerance test was also performed. Ingestion of a hyperlipidic diet promoted loss of insulin sensitivity and also resulted in a significant increase in body adiposity, plasma triacylglycerol, and glucose levels. In addition, GbE treatment significantly reduced food intake and body adiposity while it protected against hyperglycemia and dyslipidemia in diet-induced obesity rats. It also enhanced insulin sensitivity in comparison to HFD+V rats, while it restored insulin-induced Akt phosphorylation, increased IRS-1, and reduced PTP-1B levels in gastrocnemius muscle. The present findings suggest that G. biloba might be efficient in preventing and treating obesity-induced insulin signaling impairment.

Lipid profile and cardiovascular risk factors among first-year Brazilian university students in São Paulo.

BACKGROUND/AIMS: The surveillance of cardiovascular risk factors has been recommended worldwide. The current study is aimed to estimate the prevalence of cardiovascular risk factors among first-year students from a public university in the city of Sao Paulo, Brazil. METHODS: A cross-sectional study of 56 first-year students, of both genders, was performed. Information about demographic characteristics, family history of chronic diseases, smoking, and physical activity was obtained by means of a standardised questionnaire. Anthropometrical parameters (BMI, waist circumference, body fat percentage), metabolic parameters (glycaemia, serum lipid profile), and dietary data (total energy intake, percentage of total energy from macronutrients, cholesterol and dietary fiber) were assessed. RESULTS: The risk of cardiovascular diseases was characterised by family history of cardiovascular diseases (44.6%), smoking (10.7%), physical inactivity (35.7%), borderline high total cholesterol and LDL-c levels (16.1% and 5.4, respectively), decreased HDL-c levels (8.9%), increased triglyceride levels (8.9%), and overweight and obesity (17.8% and 7.1%, respectively). The diet of the students was inadequate: it was high in fat and protein, and low in carbohydrate and dietary fibre. CONCLUSIONS: The prevalence of risk factors for cardiovascular diseases in young adults draws attention to the need to adopt preventive plans in the university setting.

Beneficial effects of Ginkgo biloba extract on insulin signaling cascade, dyslipidemia, and body adiposity of diet-induced obese rats

Ginkgo biloba extract (GbE) has been indicated as an efficient medicine for the treatment of diabetes mellitus type 2. It remains unclear if its effects are due to an improvement of the insulin signaling cascade, especially in obese subjects. The aim of the present study was to evaluate the effect of GbE on insulin tolerance, food intake, body adiposity, lipid profile, fasting insulin, and muscle levels of insulin receptor substrate 1 (IRS-1), protein tyrosine phosphatase 1B (PTP-1B), and protein kinase B (Akt), as well as Akt phosphorylation, in diet-induced obese rats. Rats were fed with a high-fat diet (HFD) or a normal fat diet (NFD) for 8 weeks. After that, the HFD group was divided into two groups: rats gavaged with a saline vehicle (HFD+V), and rats gavaged with 500 mg/kg of GbE diluted in the saline vehicle (HFD+Gb). NFD rats were gavaged with the saline vehicle only. At the end of the treatment, the rats were anesthetized, insulin was injected into the portal vein, and after 90s, the gastrocnemius muscle was removed. The quantification of IRS-1, Akt, and Akt phosphorylation was performed using Western blotting. Serum levels of fasting insulin and glucose, triacylglycerols and total cholesterol, and LDL and HDL fractions were measured. An insulin tolerance test was also performed. Ingestion of a hyperlipidic diet promoted loss of insulin sensitivity and also resulted in a significant increase in body adiposity, plasma triacylglycerol, and glucose levels. In addition, GbE treatment significantly reduced food intake and body adiposity while it protected against hyperglycemia and dyslipidemia in diet-induced obesity rats. It also enhanced insulin sensitivity in comparison to HFD+V rats, while it restored insulin-induced Akt phosphorylation, increased IRS-1, and reduced PTP-1B levels in gastrocnemius muscle. The present findings suggest that G. biloba might be efficient in preventing and treating obesity-induced insulin signaling impairment.

Differential diagnosis of common female genitourinary complaints.

The symptoms and diagnosis of the three most common female bladder-urethral dysfunctions (infection, stress incontinence, and irritable bladder syndrome) are examined so that the practitioner may better differentiate between these problems and some of their counterparts. Cystitis cystica, urethritis, and radiation cystitis are among the less common infections and are frequently missed. Other conditions can be mistaken for infections: urethral diverticulum, Hunner's ulcer, atrophic vaginitis, urethral stenosis. Stress urinary incontinence, arising from abnormal bladder-urethral unit physiology or from obesity, can benefit from Kegel's exercise to strengthen the external sphincter and pubococcygeus muscles. For irritable bladder syndrome, which is often misdiagnosed, a bladder drill with increasing voiding intervals is useful. Patient understanding of bladder function and the need for retraining is also important.