Multiple Routes and Milestones in the Folding of HIV–1 Protease Monomer

Proteins fold on a time scale incompatible with a mechanism of random search in conformational space thus indicating that somehow they are guided to the native state through a funneled energetic landscape. At the same time the heterogeneous kinetics suggests the existence of several different folding routes. Here we propose a scenario for the folding mechanism of the monomer of HIV–1 protease in which multiple pathways and milestone events coexist. A variety of computational approaches supports this picture. These include very long all-atom molecular dynamics simulations in explicit solvent, an analysis of the network of clusters found in multiple high-temperature unfolding simulations and a complete characterization of free-energy surfaces carried out using a structure-based potential at atomistic resolution and a combination of metadynamics and parallel tempering. Our results confirm that the monomer in solution is stable toward unfolding and show that at least two unfolding pathways exist. In our scenario, the formation of a hydrophobic core is a milestone in the folding process which must occur along all the routes that lead this protein towards its native state. Furthermore, the ensemble of folding pathways proposed here substantiates a rational drug design strategy based on inhibiting the folding of HIV–1 protease

Fluid intake and hydration status in obese vs normal weight children

Background/Objectives:Little is known on the relationship between obesity and hydration levels in children. This study assessed whether and by which mechanisms hydration status differs between obese and non-obese children.Subjects/Methods:Hydration levels of 86 obese and 89 normal weight children (age: 7-11 years) were compared. Hydration was measured as the average free water reserve (FWR=urine output/24 h minus the obligatory urine output total 24 h excreted solutes/97th percentile of urine osmolality of children with adequate water intake, that is, 830 mOsm/kg) over 2 days. Three days of weighed dietary and fluid intakes were recorded. Non-parametric tests were used to compare variables that were skewed and to assess which variables correlated with hydration. Variables mediating the different hydration levels of obese and normal weight children were assessed by co-variance analysis.Results:Obese children were less hydrated than normal weight peers FWR=median (IQR): 0.80 (-0.80-2.80) hg/day vs 2.10 (0.10-4.45) hg/day, P<0.02; 32% of obese children vs 20% of non-obese peers had negative FWR, P<0.001. Body mass index (BMI) z-score (z-BMI) and water intake from fluids correlated with FWR (ρ=-0.18 and 0.45, respectively, both P<0.05). Water intake from fluids completely explained the different hydration between obese and normal weight children FWR adjusted for water from fluids and z-BMI=2.44 (0.44) hg vs 2.10 (0.50) hg, P=NS; B coefficient of co-variation between FWR (hg/day) and water intake from fluids (hg/day)=0.47, P<0.001.Conclusions:Obese children were less hydrated than normal weight ones because, taking into account their z-BMI, they drank less. Future prospective studies are needed to explore possible causal relationships between hydration and obesity

Nutritional education and carbohydrate counting in children with type 1 diabetes treated with continuous subcutaneous insulin infusion: the effects on dietary habits, body composition and glycometabolic control.

Carbohydrate counting (CHC) in combination with nutritional education has been used to optimize the insulin dose in patients with type 1 diabetes (T1D). The aim of this study was to test the impact of CHC and nutritional education on changes in dietary habits, body composition and body fat distribution in children with T1D treated with insulin pumps (CSII). Twenty-five children with T1D and CSII were recruited and valuated at baseline and after 18 months of follow-up. They were trained in CHC and following standard nutrition education program (based on American Diabetes Association and International Society of Pediatric and Adolescent Diabetes guidelines); clinical, biochemical and nutritional variables were measured. In the total population, body composition, body fat distribution and biochemical variables did not change, at follow-up; HbA1c was significantly reduced (8.50 \ub1 0.77 vs 7.92 \ub1 0.74 %; p < 0.001) without changing insulin/kg/day requirement. In the sub-group of patients with a significant HbA1c reduction (\u394HbA1c 65 0.5 %, n = 12), the carbohydrate (CHO) intake was significantly higher at follow-up (53.0 \ub1 4.0 vs 57.6 \ub1 2.5 %; p < 0.01); on the contrary, fat (31.3 \ub1 3.6 vs 28.5 \ub1 1.6 %; p < 0.05) and protein intake (15.4 \ub1 1.8 vs 13.3 \ub1 1.6 %; p < 0.01) significantly decreased. Patients without a significant HbA1c reduction did not show any difference. CHC, in combination with nutritional education, does not affect dietary habits, body composition and body fat distribution in children with T1D treated with CSII. Moreover, the sub-group of subjects showing a significant improvement in glycometabolic control reported an increase in CHO intake and a reduction in fat and protein intake

Diet, physical, and biochemical characteristics of children and adolescents with type 1 diabetes: relationship between dietary fat and glucose control.

Maffeis C, Morandi A, Ventura E, Sabbion A, Contreas G, Tomasselli F, Tommasi M, Fasan I, Costantini S, Pinelli L. Diet, physical, and biochemical characteristics of children and adolescents with type 1 diabetes: relationship between dietary fat and glucose control. Background: Nutritional habits may significantly influence glycemic control and cardiovascular risk factors in youth with type 1 diabetes (T1D). Aims: To assess dietary intake, cardiovascular risk factors, and the association between diet composition and glycemic control in Italian youth with T1D. Methods: Subjects included 114 youth aged 6-16 yr with T1D receiving a routine treatment program with nutrition counseling and 448 controls. Cross-sectional measures included dietary intake, anthropometry, blood pressure, lipid profile, and, in children with diabetes, HbA1c. Results: In prepubertal children, BMI, subcutaneous skinfolds, the prevalence of overweight/obesity, and LDL cholesterol (LDL-CH) were significantly lower in patients than in controls, whereas HDL cholesterol (HDL-CH) was higher. Pubertal boys with T1D did not differ significantly from controls in either anthropometry or lipid profile. Pubertal girls with T1D had a higher BMI and higher triceps skinfolds than controls but not significantly different prevalence of overweight/obesity or lipid profile. Compared to controls, participants with T1D had a lower intake of lipids and simple carbohydrates, a higher ratio of unsaturated/saturated fats and fibre, and a dietary intake closer to the National Reference Dietary Intakes (RDIs). The odds of having an HbA1c higher than 7.5, adjusted for BMI, lipid, and fibre intake, increases by 53\% for every 1\% increase of energy intake from saturated fat in the diet and by 30\% for every year of duration of diabetes. Conclusions: Youth with T1D having regular nutritional counseling had a diet closer to RDIs than controls and not different cardiovascular risk factors. High saturated fatty acid intake was associated with poor blood glucose control