A biochemical approach for assessing cutoffs at the age thresholds of 14 and 18 years: a pilot study on the applicability of bone specific alkaline phosphatase on an Italian sample

A Three-Year Longitudinal Study Comparing Bone Mass, Density, and Geometry Measured by DXA, pQCT, and Bone Turnover Markers in Children with PKU Taking L-Amino Acid or Glycomacropeptide Protein Substitutes

In patients with phenylketonuria (PKU), treated by diet therapy only, evidence suggests that areal bone mineral density (BMDa) is within the normal clinical reference range but is below the population norm. Aims: To study longitudinal bone density, mass, and geometry over 36 months in children with PKU taking either amino acid (L-AA) or casein glycomacropeptide substitutes (CGMP-AA) as their main protein source. Methodology: A total of 48 subjects completed the study, 19 subjects in the L-AA group (median age 11.1, range 5–16 years) and 29 subjects in the CGMP-AA group (median age 8.3, range 5–16 years). The CGMP-AA was further divided into two groups, CGMP100 (median age 9.2, range 5–16 years) (n = 13), children taking CGMP-AA only and CGMP50 (median age 7.3, range 5–15 years) (n = 16), children taking a combination of CGMP-AA and L-AA. Dual X-ray absorptiometry (DXA) was measured at enrolment and 36 months, peripheral quantitative computer tomography (pQCT) at 36 months only, and serum blood and urine bone turnover markers (BTM) and blood bone biochemistry at enrolment, 6, 12, and 36 months. Results: No statistically significant differences were found between the three groups for DXA outcome parameters, i.e., BMDa (L2–L4 BMDa g/cm²), bone mineral apparent density (L2–L4 BMAD g/cm³) and total body less head BMDa (TBLH g/cm²). All blood biochemistry markers were within the reference ranges, and BTM showed active bone turnover with a trend for BTM to decrease with increasing age. Conclusions: Bone density was clinically normal, although the median z scores were below the population mean. BTM showed active bone turnover and blood biochemistry was within the reference ranges. There appeared to be no advantage to bone density, mass, or geometry from taking a macropeptide-based protein substitute as compared with L-AAs.

Cryptochrome 1 Regulates Osteoblast Differentiation via the AKT Kinase and Extracellular Signal-Regulated Kinase Signaling Pathways

The many circadian clock genes build up a network structure that controls physiological processes, such as the sleep cycle, metabolism, and hormone secretion. Cryptochrome 1 (CRY1), as one of the critical circadian proteins, is closely related to bone formation. However, the regulatory function of CRY1 in osteogenic differentiation remains unclear. In this study, we investigated the role of CRY1 in regulating proliferation and osteoblast differentiation in C3H10 and C2C12 cells after silencing Cry1 using short hairpin RNA interference. In vitro experiments confirmed that the expression level of CRY1 gradually increased during the osteogenic differentiation process, and Cry1 knockdown inhibited the proliferation and differentiation of osteoblastic cells. In addition, Cry1 knockdown inhibited the phosphorylation of AKT kinase (AKT) and extracellular signal-regulated kinase (ERK), which suppressed the phosphatidylinositol-4,5-bisphosphate 3-kinase (PI3K)-AKT and mitogen-activated protein kinase (MAPK)-ERK signaling pathways. Taken together, these findings show that CRY1 regulates the proliferation and differentiation of osteoblastic cells in an AKT and ERK-dependent manner.