Immunohistochemical localization and mRNA expression of matrix Gla protein and fetuin-A in bone biopsies of hemodialysis patients.

Matrix Gla protein (MGP) and fetuin-A are inhibitors of arterial calcifications. In blood of rats, calcium-phosphate-fetuin-MGP complexes, produced in bone, have been identified. Indeed, an association between bone resorption, release of such complexes, and arterial calcifications has been reported. We have investigated the synthesis and localization of fetuin-A and MGP in bone of hemodialysis patients and the possible contribution of bone cells in arterial calcifications. Bone biopsies from 11 hemodialysis patients were used for histology, in situ hybridization of fetuin-A and MGP messenger RNA (mRNA), immunohistochemistry of fetuin-A, and total, carboxylated, and non-carboxylated MGP proteins. Patients showed various types of renal osteodystrophy, or normal bone. MGP was synthesized and expressed (total and carboxylated) by osteoblasts, osteocytes, and most osteoclasts, while fetuin-A by osteoblasts and osteocytes. Fetuin-A and carboxylated MGP proteins were positive in the calcified matrix, while total MGP was negative. Osteoid seams were negative to fetuin-A, lightly positive to carboxylated MGP, and occasionally positive to total MGP. Undercarboxylated MGP was mostly undetectable. In adult humans, fetuin-A is produced also by osteoblasts, and not only by hepatocytes, as previously believed. MGP, essentially carboxylated, is synthesized by osteoblasts and most osteoclasts. Increased bone turnover can be an important contributor to arterial calcifications.

Meat and meat products consumption in Italy: contribution to trace elements, heme iron and selected B vitamins supply.

This study was undertaken to estimate the contribution of meat and meat products consumption to the daily intakes of trace elements (Fe, Zn, Cu, Se), heme iron, and selected B vitamins (thiamine, riboflavin, niacin) in Italy. Meat and meat products were selected on the basis of their consumption frequency reported by the most recent nationwide dietary individual survey carried out in Italy (INN-CA study). The daily intakes of total iron and heme iron were 1.65 and 1.13 mg/person/day. Zinc intake was 3.65 mg/person/day. Beef made the main contribution to iron, heme iron, and zinc daily intakes. Copper daily intake was 107.3 microg/person/day, with meat products provided the highest contribution (40 microg/person/day). Daily intake of selenium (7.14 microg/person/day) was provided mainly by poultry consumption. Thiamine intake was 228 microg/person/day, and meat products were the main source (110 microg/person/day). Riboflavin intake was 136 microg/person/day, with both beef and meat products as the main contributors (40 microg/person/day). Niacin intake was 7.53 mg/person/day, and poultry was the main source (2.28 mg/person/day). Meat and meat products were a valuable source of micronutrients, supplying 47, 48, and 24% of zinc, niacin, and thiamin daily requirements, respectively, and over 10% of iron, copper, selenium, and riboflavin daily average requirement values of the italian RDAs calculated for the population involved in the survey (INN-CA study).