Impaired stimulation of glucose transport in cardiac myocytes exposed to very low-density lipoproteins.

We recently observed that free fatty acids impair the stimulation of glucose transport into cardiomyocytes in response to either insulin or metabolic stress. In vivo, fatty acids for the myocardium are mostly obtained from triglyceride-rich lipoproteins (chylomicrons and Very Low-Density Lipoproteins). We therefore determined whether exposure of cardiac myocytes to VLDL resulted in impaired basal and stimulated glucose transport. Primary adult rat cardiac myocytes were chronically exposed to VLDL before glucose uptake was measured in response to insulin or metabolic stress, provoked by the mitochondrial ATP synthase inhibitor oligomycin. Exposure of cardiac myocytes to VLDL reduced both insulin-and oligomycin-stimulated glucose uptake. The reduction of glucose uptake was associated with a moderately reduced tyrosine phosphorylation of the insulin receptor. No reduction of the phosphorylation of the downstream effectors of insulin signaling Akt and AS160 was however observed. Similarly only a modest reduction of the activating phosphorylation of the AMP-activated kinase (AMPK) was observed in response to oligomycin. Similar to our previous observations with free fatty acids, inhibition of fatty acid oxidation restored oligomycin-stimulated glucose uptake. In conclusions, VLDL-derived fatty acids impair stimulated glucose transport in cardiac myocytes by a mechanism that seems to be mediated by a fatty acid oxidation intermediate. Thus, in the clinical context of the metabolic syndrome high VLDL may contribute to enhancement of ischemic injury by reduction of metabolic stress-stimulated glucose uptake.

Reaction of bone to methacrylate: interface remodelling.

Histologic findings of the bone-cement junction are presented for 10 implants in rabbits and 12 human specimens. Nondecalcified sections were made, employing embedding techniques that conserve the cement. Different time periods from operation were considered. The histological approach considers mainly the distribution of the osseous elements, with a description of the sites of new and old bone, of resorptive lacunae and of fibrous tissue. Fluorescent sequential labelling of bone tissue allowed a dynamic evaluation of the viability of bone after insertion of the cement. Histologic features may be summarized as follows: In the initial phase after PMMA implantation a zone of necrosis is present around the cement. In a second phase there is very active bone formation and remodelling in the tissue adjacent to the cement, with fibrous tissue formation. Long-term adaptive bone remodelling leads to extensive resorption of cortical bone and new bone formation producing a shell around the cement with new trabeculae radiating towards the cortex.

Mineralometry of the lumbar spine and histomorphometry of the iliac crest: preliminary results of a comparison of several parameters in the same individual.

Twelve patients affected with various bone pathologies (osteoporosis, renal osteodystrophy, osteogenesis imperfecta, hyperparathyroidism) were submitted to mineralometry of the lumbar spine with double photonic ray and transiliac biopsy for histomorphometry. A comparison of the values obtained for the mineralometric and histomorphometric parameters--despite the small number of cases--revealed a correlation between bone mineral content of the lumbar spine and trabecular and cortical bone volume of the iliac crest. The correlation is even more significant for the sum of these last two parameters. It may be concluded that: 1) both the methods have predictive values for an evaluation of osteopenia; 2) the measurement of cortical and subcortical bone volume increases the significance of the histomorphometric finding (which is usually limited to the trabecular bone volume); 3) there is a correlation between histomorphometry (iliac crest bone volume) and mineralometry (lumbar spine with double photonic ray) in the same individual.