Exercise training reduces fatty acid availability and improves the insulin sensitivity of glucose metabolism

Aims/hypothesis - It is not known whether the beneficial effects of exercise training on insulin sensitivity are due to changes in hepatic and peripheral insulin sensitivity or whether the changes in insulin sensitivity can be explained by adaptive changes in fatty acid metabolism, changes in visceral fat or changes in liver and muscle triacylglycerol content. We investigated the effects of 6 weeks of supervised exercise in sedentary men on these variables. Subjects and methods - We randomised 17 sedentary overweight male subjects (age 50 ± 2.6 years, BMI 27.6 ± 0.5 kg/m2) to a 6-week exercise programme (n = 10) or control group (n = 7). The insulin sensitivity of palmitic acid production rate (Ra), glycerol Ra, endogenous glucose Ra (EGP), glucose uptake and glucose metabolic clearance rate were measured at 0 and 6 weeks with a two-step hyperinsulinaemic–euglycaemic clamp [step 1, 0.3 (low dose); step 2, 1.5 (high dose) mU kg−1 min−1]. In the exercise group subjects were studied >72 h after the last training session. Liver and skeletal muscle triacylglycerol content was measured by magnetic resonance spectroscopy and visceral adipose tissue by cross-sectional computer tomography scanning. Results - After 6 weeks, fasting glycerol, palmitic acid Ra (p = 0.003, p = 0.042) and NEFA concentration (p = 0.005) were decreased in the exercise group with no change in the control group. The effects of low-dose insulin on EGP and of high-dose insulin on glucose uptake and metabolic clearance rate were enhanced in the exercise group but not in the control group (p = 0.026; p = 0.007 and p = 0.04). There was no change in muscle triacylglycerol and liver fat in either group. Conclusions/interpretation - Decreased availability of circulating NEFA may contribute to the observed improvement in the insulin sensitivity of EGP and glucose uptake following 6 weeks of moderate exercise.

Enhanced bio-decolourisation of acid orange 7 by Shewanella oneidensis through co-metabolism in a microbial fuel cell

The decolourisation of acid orange 7 (AO7) (C.I.15510) through co-metabolism in a microbial fuel cell by Shewanella oneidensis strain 14063 was investigated with respect to the kinetics of decolourisation, extent of degradation and toxicity of biotransformation products. Rapid decolourisation of AO7 (>98% within 30 h) was achieved at all tested dye concentrations with concomitant power production. The aromatic amine degradation products were recalcitrant under tested conditions. The first-order kinetic constant of decolourisation (k) decreased from 0.709 ± 0.05 h−1 to 0.05 ± 0.01 h−1 (co-substrate – pyruvate) when the dye concentration was raised from 35 mg l−1 to 350 mg l−1. The use of unrefined co-substrates such as rapeseed cake, corn-steep liquor and molasses also indicated comparable or better AO7 decolourisation kinetic constant values. The fully decolourised solutions indicated increased toxicity as the initial AO7 concentration was increased. This work highlights the possibility of using microbial fuel cells to achieve high kinetic rates of AO7 decolourisation through co-metabolism with concomitant electricity production and could potentially be utilised as the initial step of a two stage anaerobic/aerobic process for azo dye biotreatment.

Production of Polyhydroxyalkanoates by Pseudomonas mendocina using vegetable oils and their characterisation

Synthesis of Polyhydroxyalkanoates (PHAs) by Pseudomonas mendocina, using different vegetable oils such as, coconut oil, groundnut oil, corn oil and olive oil, as the sole carbon source was investigated for the first time. The PHA yield obtained was compared with that obtained during the production of PHAs using sodium octanoate as the sole carbon source. The fermentation profiles at shaken flask and bioreactor levels revealed that vegetable oils supported the growth of Pseudomonas mendocina and PHA accumulation in this organism. Moreover, when vegetable oil (coconut oil) was used as the sole carbon source, fermentation profiles showed better growth and polymer production as compared to conditions when sodium octanoate was used as the carbon source. In addition, comparison of PHA accumulation at shaken flask and fermenter level confirmed the higher PHA yield at shaken flask level production. The highest cell mass found using sodium octanoate was 1.8 g/L, whereas cell mass as high as 5.1 g/L was observed when coconut oil was used as the feedstock at flask level production. Moreover, the maximum PHA yield of 60.5% dry cell weight (dcw) was achieved at shaken flask level using coconut oil as compared to the PHA yield of 35.1% dcw obtained using sodium octanoate as the sole carbon source. Characterisations of the chemical, physical, mechanical, surface and biocompatibility properties of the polymers produced have been carried out by performing different analyses as described in the second chapter of this study. Chemical analysis using GC and FTIR investigations showed medium chain length (MCL) PHA production in all conditions. GC-MS analysis revealed a unique terpolymer production, containing 3-hydroxyoctanoic acid, 3-hydroxydecanoic acid and 3-hydroxydodecanoic acid when coconut oil, groundnut oil, olive oil, and corn oil were used as the carbon source. Whereas production of the homopolymer containing 3-hydroxyoctanoic acid was observed when sodium octanoate was used as the carbon source. MCL-PHAs produced in this study using sodium octanoate, coconut oil, and olive oil exhibited melting transitions, indicating that each of the PHA was crystalline or semi-crystalline polymer. In contrast, the thermal properties of PHAs produced from groundnut and corn oils showed no melting transition, indicating that they were completely amorphous or semi-crystalline, which was also confirmed by the X-Ray Diffraction (XRD) results obtained in this study. Mechanical analysis of the polymers produced showed higher stiffness of the polymer produced from coconut oil than the polymer from sodium octanoate. Surface characterisation of the polymers using Scanning Electron Microscopy (SEM) revealed a rough surface topography and surface contact angle measurement revealed their hydrophobic nature. Moreover, to investigate the potential applicability of the produced polymers as the scaffold materials for dental pulp regeneration, multipotent human Mesenchymal stem cells (hMSCs) were cultured onto the polymer films. Results indicated that these polymers are not cytotoxic towards the hMSCs and could support their attachment and proliferation. Highest cell growth was observed on the polymer samples produced from corn oil, followed by the polymer produced using coconut oil. In conclusion, this work established, for the first time, that vegetable oils are a good economical source of carbon for production of MCL-PHA copolymers effectively by Pseudomonas mendocina. Moreover, biocompatibility studies suggest that the produced polymers may have potential for dental tissue engineering application.