Hepatitis C virus clearance by direct-acting antiviral treatments and impact on insulin resistance in chronic hepatitis C patients.

BACKGROUND AND AIM: Chronic hepatitis C virus (HCV), particularly genotype 1, is associated with insulin resistance (IR) and diabetes. This study evaluated the impact of HCV clearance by all-oral direct-acting antiviral treatments on IR and glycemic control. METHODS: Included in this prospective case-control study were 133 consecutive HCV-genotype 1 patients with advance liver fibrosis (F3-F4) without type 2 diabetes. Sixty eight were treated with direct-acting antiviral and 65 were untreated. Liver fibrosis was assessed by transient elastography. Pre-treatment, end-treatment, and 3 months post-treatment withdrawal IR homeostasis was assessed by homeostatic model assessment (HOMA)-IR, HOMA-S, and HOMA-B. RESULTS: At baseline, treated, and untreated patients showed similar liver fibrosis levels, HOMA-IR was 4.90 ± 4.62 and 4.64 ± 5.62, respectively. HOMA-IR correlated with HCV RNA levels. At the end of treatment, all patients cleared HCV RNA, regardless of liver fibrosis and body mass index, and a reduction in HOMA-IR at 2.42 ± 1.85 was showed (P < 0.001); in addition, increased insulin sensitivity, decreased insulin secretion, reduction of serum glucose, and insulin levels were observed. Data were confirmed 3 months after treatment withdrawal in the 65 patients who cleared HCV. No variation occurred in untreated patients. Overall, 76.5% of sustained virologic response patients showed IR improvements, of which 41.2% normalized IR. Improvement of IR was strictly associated with HCV clearance; however, patients with the highest levels of fibrosis remain associated with some degree of IR. CONCLUSIONS: The data underline a role of HCV in development of IR and that viral eradication reverses IR and improves glycemic control and this could prevent IR-related clinical manifestations and complications.

Open-system chamber for measurements of gas exchanges at plant level.

Gas exchanges of whole canopy can be studied by covering entire plants with a chamber and using portable infrared gas analyzers (IRGAs) to measure CO2 and H2O exchanged with the air blown through the chamber enclosure. The control of temperature rise inside the chamber, which should be kept low, and the accurate measurement of the air flow are two crucial aspects for realistic and precise estimation of photosynthesis and transpiration. An automated open-system plant chamber (clear flexible balloon enclosure) for small plants was developed to ameliorate such a technique. The temperature rise is here predicted by heat balance analysis inside the chamber. The analysis shows that when as much as 500 W m2 of solar radiation is converted to sensible heat, a flow rate of 0.98 mol s(-1) (approximately = 20 L s(-1)) of air blown into a cylinder-shaped enclosure (0.8 m high, 0.5 m wide) is adequate to limit temperature increase to 2 K. An improved calibration for the measurement of the chamber airflow was obtained by combining the use of a Pitot tube anemometer with the classical CO2 injection approach. The concentration increase due to the injection of CO2 at a known rate into the chamber was predicted by the air flow calculated from the "Pitot" air velocity. The turbulent regime of air assured that a single-point Pitot measurement was enough for a good estimation (slope = 0.99; R2 = 0.999) of the actual air flow. The open-system chamber was tested on potted sunflower (Helianthus annuus, L.) and maize (Zea mays, L.) plants under variable solar radiation, temperature, and air humidity during the daytime. As expected, similar rates of maximal leaf-area based photosynthesis (about 40 micromol m(-2) s(-1)) were observed in the two species confirming the reliability of our system. The consistency of data also resulted from the typical relationships observed between photosynthetic rate and light.

Experimental and numerical test of the micrometeorological mass difference technique for the measurement of trace gas emissions from small plots.

Micrometeorological methods for measuring fluxes of gases between the land surface and the atmosphere are non-invasive: in fact, they do not interfere with natural processes of gas exchange. The Micrometeorological Mass Difference (MMD) approach can be used for many environmental monitoring purposes, such as to measure methane and carbon dioxide emission from landfills, methane production by grazing animals, trace gas emission from waste products and from agricultural soils, photosynthesis, and transpiration of plant canopies. The purpose of this study is to adapt the MMD technique, originally developed in Australia, to monitor CO2 and trace gases exchange rate at the plot level. Comparison of different treatments in replicated experiments requires plots of few rather than tens of meters. The tests reported here were performed on a square area (4 m x 4 m) in the meteorological field of the experimental farm of CNR-ISAFOM located in Vitulazio, province of Caserta, Italy (40 degrees 07' N, 14 degrees 50' E, 25 m above sea level) and consisted of the release of pure CO2 at different rates (1.7, 1.3, 0.6 L min(-1)) from a single source on the ground in the center of the experimental area and the consequent measurement of the environmental variables (wind speed and direction, CO2 concentration) at different times at four heights (up to 1.2 m) in order to compute the mass balance according to MMD technique. Measured flow rates well accounted for the mass of CO2 released. A flow underestimation occurred when wind speed dropped below 1.5 m s(-1), in accord with the previous findings obtained in Australia: this happened because anemometers can stall at low speeds, and their measurements are unreliable and because of significant loss of mass from the top of the apparatus. The experimental results were compared with outputs of Computational Fluid Dynamic (CFD) simulations. The commercial CFD package Fluent was used to evaluate performances and sources of errors. According to the experimental and numerical results, the MMD apparatus in our present configuration is suitable to be used for the monitoring of trace gas emissions of experimental plots. Advantages and limits of the present approach are discussed.