We tested the hypothesis that hepatic nitric oxide (NO) and glutathione (GSH) are involved in the synthesis of a putative hormone referred to as hepatic insulin-sensitizing substance HISS. Insulin action was assessed in Wistar rats using the rapid insulin sensitivity test (RIST). Blockade of hepatic NO synthesis with N ^G-nitro-l-arginine methyl ester (l-NAME, 1.0 mg/kg intraportal) decreased insulin sensitivity by 45.1 ± 2.1% compared with control (from 287.3 ± 18.1 to 155.3 ± 10.1 mg glucose/kg, P < 0.05). Insulin sensitivity was restored to 321.7 ± 44.7 mg glucose/kg after administration of an NO donor, intraportal SIN-1 (5 mg/kg), which promotes GSH nitrosation, but not after intraportal sodium nitroprusside (20 nmol · kg⁻¹ · min⁻¹), which does not nitrosate GSH. We depleted hepatic GSH using the GSH synthesis inhibitor l-buthionine-[ S,R]-sulfoximine (BSO, 2 mmol/kg body wt ip for 20 days), which reduced insulin sensitivity by 39.1%. Insulin sensitivity after l-NAME was not significantly different between BSO- and sham-treated animals. SIN-1 did not reverse the insulin resistance induced by l-NAME in the BSO-treated group. These results support our hypothesis that NO and GSH are essential for insulin action.

Anaplastic thyroid carcinoma (ATC) is a very rare subtype of thyroid carcinoma and one of the most lethal malignancies. Poor prognosis is mainly associated with its undifferentiated nature, inoperability, and failing to respond to the typically used therapies for thyroid cancer. Photothermal Therapy (PTT) entails using light to increase tissues’ temperature, leading to hyperthermia-mediated cell death. Tumours are more susceptible to heat as they are unable to dissipate it. By using functionalized gold nanoparticles (AuNPs) that transform light energy into heat, it is possible to target the heat to the tumour. This study aims to formulate ATC-targeted AuNPs able to convert near-infrared light into heat, for PTT of ATC. Different AuNPs were synthetized and coated. Size, morphology, and surface plasmon resonances band were determined. The optimized coated-AuNPs were then functionalized with ligands to assess ATC’s specificity. Safety, efficacy, and selectivity were assessed in vitro. The formulations were deemed safe when not irradiated (>70% cell viability) and selective for ATC. However, when irradiated, holo-transferrin-AuNPs were the most cytotoxic (22% of cell viability). The biodistribution and safety of this formulation was assessed in vivo. Overall, this novel formulation appears to be a highly promising approach to evaluate in a very near future.

Carvedilol is known to be an adrenoreceptor blocker and free radical scavenger, used in hypertension and cardiac failure. However, its therapeutic actions cannot be fully explained by these mechanisms. In these studies, we tested the hypothesis that carvedilol action is associated with the synthesis/release of nitric oxide (NO). Male Wistar rats (n = 22), 9 weeks old, were anesthetized with an intraperitoneal injection of sodium pentobarbital. Mean arterial pressure and arterial NO levels were monitored throughout the experiments. Carvedilol (1 mg/kg, intravenously [iv]) effects were evaluated before and after NO synthase (NOS) inhibitor N(omega)-nitro-L-arginine methyl ester (L-NAME, 5 mg/kg, iv). Carvedilol induced a significant decrease in basal arterial pressure (from 126.6 +/- 4.3 mm Hg to 75.9 +/- 3.0 mm Hg, P < .001) and significant increase in NO levels (from 17.9 +/- 1.7 micromol/L to 32.2 +/- 2.5 micromol/L, P < .001). After administration of L-NAME the arterial pressure increased (129.9 +/- 5.0 mm Hg, P < .001) with concomitant decrease in NO levels (13.4 +/- 1.6 micromol/L, P < .01). The second carvedilol administration (post-L-NAME) did not affect either arterial pressure (108.3 +/- 8.0 mm Hg) or NO levels (22.1 +/- 1.3 micromol/L). Our results suggest that the carvedilol-induced decrease of blood pressure is associated with an increase of plasma NO levels. Furthermore, NOS inhibition results in impairment of carvedilol hemodynamic effects and plasma NO levels. Therefore, these results are consistent with the hypothesis that the hemodynamic effect of carvedilol is in part dependent on endogenous NO production.

Currently, insulin can only be administered through the subcutaneous route. Due to the flaws associated with this route, it is of interest to orally deliver this drug. However, insulin delivered orally has several barriers to overcome as it is degraded by the stomach’s low pH, enzymatic content, and poor absorption in the gastrointestinal tract. Polymers with marine source like chitosan are commonly used in nanotechnology and drug delivery due to their biocompatibility and special features. This work focuses on the preparation and characterization of mucoadhesive insulin-loaded polymeric nanoparticles. Results showed a suitable mean size for oral administration (<600 nm by dynamic laser scattering), spherical shape, encapsulation efficiency (59.8%), and high recovery yield (80.6%). Circular dichroism spectroscopy demonstrated that protein retained its secondary structure after encapsulation. Moreover, the mucoadhesive potential of the nanoparticles was assessed in silico and the results, corroborated with ex-vivo experiments, showed that using chitosan strongly increases mucoadhesion. Besides, in vitro and in vivo safety assessment of the final formulation were performed, showing no toxicity. Lastly, the insulin-loaded nanoparticles were effective in reducing diabetic rats’ glycemia. Overall, the coating of insulin-loaded nanoparticles with chitosan represents a potentially safe and promising approach to protect insulin and enhance peroral delivery.

In animal studies, the whole-body glucose disposal effect of insulin is low in the fasted state or after atropine infusion, but doubles after a meal, consistent with the hepatic insulin-sensitizing substance (HISS) hypothesis. We tested how a standardized test meal and atropine affected the dynamic response to insulin in humans. Insulin sensitivity was assessed in healthy male subjects (aged 28.9 +/- 1.9 years, body mass index 23.3 +/- 0.8 kg.m-2) by using the rapid insulin sensitivity test (RIST), which is a transient euglycemic clamp. After a 24-hour fasting period, dynamic insulin sensitivity was assessed and then repeated 100 min after the test meal. In a second protocol, the volunteers were fed the standardized test meal and intravenous atropine (0.5 mg) or saline (control group) was administered 50 min before insulin sensitivity assessment. Insulin sensitivity increased in the fed state (232.1% +/- 46.3%, n = 7) in comparison with the 24-hour fasted state. In the atropine protocol, the drug partially blocked (56.5% +/- 11.6%, n = 6) insulin sensitivity. In humans, feeding resulted in increased insulin sensitivity. The low dose of atropine in humans lead to a partial HISS-dependent decrease in insulin sensitivity. Meal-induced insulin sensitization occured in humans by a similar mechanism as that reported in other species. The sensitization process was regulated by a cholinergic 'feeding signal.'

We have recently shown that meal-induced insulin sensitization (MIS) occurs after feeding and decreases progressively to insignificance after 24h of fasting and is caused by action of a hepatic insulin sensitizing substance (HISS). In order to carry out quantitative studies of MIS, some standardized meal intake is required. Our objective was to establish animal models to be tested in both the conscious and anaesthetized state using intragastric injection of liquid meals in order to quantify MIS. Insulin sensitivity was assessed before and 90min after the meal using the rapid insulin sensitivity test (RIST) which is a transient euglycaemic clamp. Rats tested in the conscious state were instrumented under anaesthesia 6–9d prior to testing with catheters in the carotid artery, jugular vein and stomach. Meals, injected into the stomach, consisted of a liquid mixed meal, sucrose, glucose or water. The glucose sequestration in response to insulin increased by 90% and 61% following the liquid mixed meal (10ml/kg) in conscious and anaesthetized rats, respectively. Glucose, sucrose and water did not effectively activate MIS. MIS was completely reversed in the conscious model by atropine and completely prevented from developing in the anaesthetized model that had previously undergone hepatic denervation. Gastric administration of a liquid mixed meal but not glucose or sucrose is capable of activating MIS for purposes of mechanistic studies and quantification of the MIS process. The feeding signal is mediated by the hepatic parasympathetic nerves.