Relation of alleles of the collagen type Ialpha1 gene to bone density and the risk of osteoporotic fractures in postmenopausal women

Association of polymorphism at the type I collagen (COL1A1) locus with reduced bone mineral density, increased fracture risk, and increased collagen turnover

OBJECTIVE

To examine the relationship between a common polymorphism within intron 1 of the COL1A1 gene and osteoporosis in a nested case-control study.

METHODS

We studied 185 healthy women (mean +/- SD age 54.3+/-4.6 years). Bone mineral density (BMD) was measured using dual x-ray absorptiometry, and fractures were determined radiographically. The COL1A1 genotype was assessed using the polymerase chain reaction and Bal I endonuclease digestion.

RESULTS

Genotype frequencies were similar to those previously observed and in Hardy-Weinberg equilibrium: SS 61.1%, Ss 36.2%, and ss 2.7%. Carriage of at least one copy of the "s" allele was associated with a significant reduction in lumbar spine BMD (P = 0.02) and an increased risk of total fracture (P = 0.04). Urinary pyridinoline levels were significantly elevated in those with the risk allele (P < 0.05).

CONCLUSION

These data support the findings that the COL1A1 gene polymorphism is associated with low BMD and fracture risk, and suggest a possible physiologic effect on total body turnover of type I collagen.

Linkage, association, and the genetic analysis of bone mineral density and related phenotypes: an overview for clinicians

Most medical genetic studies seek to answer one of two questions: What genes are important in determining disease risk? and What alleles of a candidate gene confer excess risk? This article seeks to provide physicians with a practical approach to assessing articles on genetic topics, using examples from bone mineral density and related areas. First, this article reviews the essential features of meiosis, crossing over, and allele detection. Second, mapping strategies are described and illustrated. Third, this article considers studies of the association between alleles of specific candidate genes and bone phenotypes. Linkage without association and association without linkage are both possible. Fourth, the ability of studies using inbred mice to establish both linkage and association is explained. Fifth, the transmission disequilibrium test is proposed as a superior design for investigating the association of alleles with bone phenotypes. Sixth and last, a systematic approach to reading medical genetic studies critically is developed. Common shortcomings in published articles include insufficient evidence for candidate choice, confusion between functionally significant alleles and markers, and failure to distinguish between identity by descent and identity by state.

Role of polypeptides in the treatment and diagnosis of osteoporosis

Osteoporosis is a common disorder characterized by reduced bone mineral density, deterioration of the microarchitecture of bone tissue and increased risk of fracture. The aim of treatment of osteoporosis is to maintain and, ideally, to restore bone strength safely. In recent years the role of polypeptide growth factors in bone metabolism has begun to appear. It has been proposed that alterations in the expression or production of growth factor can modulate the proliferation and activity of bone forming cells. In this direction, the role of structurally diverse peptides for the management and diagnosis of osteoporosis has attracted the attention of many investigators. This paper reviews numerous findings concerning the use of polypeptides, hormones, and growth factors, for the management of osteoporosis. Many of the compounds mentioned here are experimental prototypes of new therapeutic classes. Though it is unlikely that some of the compounds may ever be used clinically, development of safe and efficacious agents in each class will define the future course of therapy for osteoporosis.

Osteoporosis in the corticosteroid-treated patient with asthma

Osteoporosis affects 40% of white women older than 45 years of age and 15% of white men older than 50 years of age, resulting in approximately 1.5 million annual fractures in the United States. Systemic corticosteroid therapy increases the probability of osteoporosis, even with alternate-day dosing and with dosages sufficiently low so as not to affect the hypothalamic-pituitary-adrenal axis. Inhaled corticosteroid therapy may affect bone density if high-dose therapy is given to select individuals. The potential of increasing osteoporosis with inhaled corticosteroid asthma therapy is a concern because of the availability of more potent inhaled corticosteroid agents and recommendations that inhaled corticosteroid therapy be initiated earlier in the course of asthma. This article provides suggestions, on the basis of the medical literature and consensus of the authors when specific information was not available, for assessing and treating osteoporosis in subjects with asthma. Suggested risk categories are "low risk" (inhaled corticosteroid dosage of < or =800 microg of heclomethasone dipropionate [BDP]/day in adults or < or =400 microg BDP or equivalent in children), "moderate risk" (inhaled BDP >800 microg/day in adults or >400 microg/day in children), and "high risk" (systemic corticosteroid therapy 4 times a year or daily or alternate-day systemic corticosteroid therapy). Dosage of nasal corticosteroid probably should be added to the orally inhaled corticosteroid for total burden of inhaled corticosteroid. Potential treatment strategies based on risk factors and bone density if indicated are offered to assist physicians treating patients with asthma.

Phenotype and genotype of osteoporosis

A top priority in osteoporosis research is the identification of the structural basis and the genetic factors that contribute to variations in the risk for fragility fractures. This review summarizes current knowledge regarding the genetic determination of fragility fractures and bone mass measurements, and the complex phenotypes and genotypes of osteoporosis.