21 research outputs found
Lower Fasting Muscle Mitochondrial Activity Relates to Hepatic Steatosis in Humans
OBJECTIVE
Muscle insulin resistance has been implicated in the development of steatosis and dyslipidemia by changing the partitioning of postprandial substrate fluxes. Also, insulin resistance may be due to reduced mitochondrial function. We examined the association between mitochondrial activity, insulin sensitivity, and steatosis in a larger human population.
RESEARCH DESIGN AND METHODS
We analyzed muscle mitochondrial activity from ATP synthase flux (fATP) and ectopic lipids by multinuclei magnetic resonance spectroscopy from 113 volunteers with and without diabetes. Insulin sensitivity was assessed from M values using euglycemic-hyperinsulinemic clamps and/or from oral glucose insulin sensitivity (OGIS) using oral glucose tolerance tests.
RESULTS
Muscle fATP correlated negatively with hepatic lipid content and HbA1c. After model adjustment for study effects and other confounders, fATP showed a strong negative correlation with hepatic lipid content and a positive correlation with insulin sensitivity and fasting C-peptide. The negative correlation of muscle fATP with age, HbA1c, and plasma free fatty acids was weakened after adjustment. Body mass, muscle lipid contents, plasma lipoproteins, and triglycerides did not associate with fATP.
CONCLUSIONS
The association of impaired muscle mitochondrial activity with hepatic steatosis supports the concept of a close link between altered muscle and liver energy metabolism as early abnormalities promoting insulin resistance
Bending Crash Behaviour of Foam-Filled Rectangular Magnesium Alloy AZ31 B Tubes
Quasi-static/dynamic three-point bending tests were conducted to assess the crash
performance of magnesium alloy AZ31B extruded and sheet tubes at the German Aerospace Centre
(DLR) – Institute of Vehicle Concepts in Stuttgart. Different foam-filled AZ31B beams with a
variation of foam density and thickness were fabricated through several manufacturing processes:
cold bending, tungsten inert gas welding, cathodic dip painting and polyurethane foam injection. The
experimental results were compared with those from mild steel DC04 tubes. It shows that empty
magnesium alloy AZ31B outperforms steel DC04 in terms of specific energy absorption for the empty
tubes with equivalent volume when subjected to bending loads. It was found that the foam-filled tubes
achieved much higher load carrying capacity and specific energy absorption than the empty tubes.
Moreover, there is a tendency showing that a foam-filled beam with a higher foam density reaches
higher load carrying capacity, but fractures earlier. The foam-filled AZ31B tube with 0.20 g/cm3 foam
obtained the highest specific energy absorption, but this outperformance was weakened due to the
earlier fracture. In addition, the numerical simulation utilising material model MAT_124 in
LS-DYNA explicit FEA package was performed. The simulation results indicate that using calibrated
stress-strain curves and failure parameters, material model MAT_124 yields a general good
agreement with the experimental results