A high activity index of stearoyl-CoA desaturase is associated with increased risk of fracture in men

Osteoporosis: A role for lipids

An inverse relationship between bone marrow (BM) adiposity and bone mass has been described in different physiological and pathological conditions, including osteoporosis (OP). In osteoporotic patients, lower bone mass density is indeed associated with higher BM fat content, suggesting a potential role for bone lipids in the OP pathogenesis. Nevertheless, some questions remain. Is that BM adiposity a cause or a consequence of the bone loss? What kinds of lipids are involved? Human data are somehow contradictories regarding bone lipid signature related to OP, and animal data are needed to support on one or another way the human observations. Bone lipid signature associated to OP needs to be clarified if we want to understand better their roles in OP. In that context, by using an ovariectomy-induced OP murine model and looking at lipids in two bone compartments: BM and mineralized tissue (MT), our first challenge was to identify local lipid changes in relation to OP, in view to explore later the mechanisms by which those compounds could alter bone quality, particularly during the mineralization process. As the most striking data, long-term OP resulted in an accumulation of triglycerides, reduced levels of arachidonic and docosahexaenoic acids, an increase of stearoyl-CoA desaturase indices and a reduction of sphingomyelin in the MT, and potential consequences on bone properties and cell activities are discussed. The reader will appreciate that we are at an early stage of understanding the roles of lipids in the OP development and more investigations will be necessary.

Alterations in DNA methylation profiles in cancellous bone of postmenopausal women with osteoporosis

Osteoporosis is characterized by systemic microarchitecture impairment and bone loss, which ultimately lead to fragility fractures. This disease is most common in older people, especially in postmenopausal women. Cancellous bone is affected by osteoporosis earlier than cortical bone, and DNA methylation microarray analysis of the hip cancellous bone of patients with osteoarthritis revealed differential methylation. In view of the important role of cancellous bone in bone development, we examined genome‐wide DNA methylation profiles in the cancellous bone from patients with postmenopausal osteoporosis versus healthy postmenopausal women using Illumina 850K methylation microarray analysis. Under a threshold of P < 0.05, we obtained a total of 8973 differentially methylated genes, such as SOX6, ACE, SYK and TGFB3. Under a threshold of P < 0.05 and |△β| > 0.2, a total of 17 and 34 key differentially methylated genes were further identified at the promoter region and cytosine‐ phosphate‐ guanine (CpG) islands (such as PRKCZ, GNA11 and COL4A1), respectively. PLEKHA2, PLEKHB1, PNPLA7, SCD, MGST3 and TSNAX were the most common differentially methylated genes at both the promoter region and CpG islands. Five important signaling pathways, including the calcium signaling pathway, the cyclic guanosine phospho‐protein kinase G (cGMP‐PKG) signaling pathway, endocytosis, the Rap1 signaling pathway and the AMPK signaling pathway were identified. Our study may be suitable as a basis for exploring the mechanisms underlying osteoporosis in postmenopausal women.

Long Term Ovariectomy-Induced Osteoporosis is Associated with High Stearoyl-CoA Desaturase Indexes in Rat Femur

Osteoporosis is characterized by a bone loss associated to an increased bone marrow adiposity; however, it is still unclear what kind of lipids are involved. Therefore, the main purpose of this study was to see if there is any local bone lipid changes related to osteoporosis, by using the ovariectomy-induced osteoporosis (OVX) rat model. Female SD rats (operated at 6 months of age for skeletal maturity) were divided in control SHAM and OVX groups (n = 6/group) and maintained for 9 month post-surgery. Lipids were analyzed in two compartments of femoral diaphyses: bone marrow (BM) and mineralized tissue (MT), by chromatographic methods. As expected, osteoporotic femurs had a larger BM mass associated with a two-fold increase of lipid content. The MT had a similar lipid enrichment, indicating that adiposity affected the mineral part as well. The main lipids concerned were triglycerides, sphingomyelin, phosphatidylcholine and phosphatidylserine in BM, and triglycerides and cholesterol esters in MT. The increase of both energy-storage and membrane-associated lipids in BM suggested that cell number and/or size was enhanced to allow more triglyceride storage. Interestingly, in MT of osteoporotic femurs, sphingomyelin was decreased, suggesting that its catabolism could be linked to osteoporosis. In both femoral compartments, fatty acid profiles were enriched in 14:0 and 16:1, lowered in 18:0 and 20:4 n-6, and two-fold higher stearoyl-CoA desaturase indexes (16:1/16:0 and 18:1/18:0 ratios), suggesting an increased de novo lipogenesis in osteoporotic femurs. Thus, the present study is first to report local changes of individual lipids in rat osteoporotic femurs and suggests that osteoporosis is a pathologic condition associated with an enhanced de novo lipogenesis. Further studies will be needed to better understand the consequences of these lipid changes in osteoporotic bones.

Is the Fatty Acids Profile in Blood a Good Predictor of Liver Changes? Correlation of Fatty Acids Profile with Fatty Acids Content in the Liver

BACKGROUND

Existing data show a correlation between the profile of fatty acids, liver, and blood. Therefore, the aim of our study was to investigate the correlation between the fatty acids profile in blood pallets and the liver.

METHODS

The experiment was performed on 60 eight-week-old male Sprague-Dawley rats. The study group (n = 30, 5 groups, 6 rats each) received a cholesterol diet; the control group (n = 30, 5 groups, 6 rats each) received standard food for laboratory rats. The rats from both the study and control groups were sacrificed after 2, 4, 8, 12, and 16 weeks of dietary exposure. The fatty acids profile was measured using gas chromatography (GC).

RESULTS

In both the control and study group, the highest correlations were observed in palmitoleic acid (RHO = 0.68), heptadecanoic acid (RHO = 0.65), vaccenic acid (RHO = 0.72), eicosapentaenoic acid (RHO = 0.68), docosapentaenoic acid (RHO = 0.77), and docosahexaenoic (RHO = 0.77). Among liver indexes, the highest correlations were desaturase-18 (0.61).

CONCLUSIONS

Fatty acids profile is a sensitive marker of the development of potentially pathological changes in the liver. The potential markers of fatty liver are: oleic acid, vaccenic acid, EPA, DHA, docosapentaenoic acid, and desaturase index (SCD-18 index).

The effect of antiresorptives on bone quality

BACKGROUND

Currently, antiresorptive therapy in the treatment and prevention of osteoporosis includes bisphosphonates, estrogen replacement, selective estrogen receptor modulators (raloxifene), and denosumab (a human antibody that inactivates RANKL). The original paradigm driving the development of antiresorptive therapy was that inhibition of bone resorption would allow bone formation to continue and correct the defect. However, it is now clear increases in bone density account for little of the antifracture effect of these treatments.

QUESTIONS/PURPOSES

We examined the antifracture benefit of antiresorptives deriving from bone quality changes.

METHODS

We searched the archive of nearly 30,000 articles accumulated over more than 40 years in our research center library using a software program (Refman™). Approximately 250 publications were identified in locating the 69 cited here.

RESULTS

The findings document antiresorptive agents are not primarily anabolic. All cause a modest increase in bone density due to a reduction in the bone remodeling space; however, the majority of their efficacy is due to suppression of the primary cause of osteoporosis, ie, excessive bone remodeling not driven by mechanical need. All of them improve some element(s) of bone quality.

CONCLUSIONS

Antiresorptive therapy reduces risk of fracture by improving bone quality through halting removal of bone tissue and the resultant destruction of microarchitecture of bone and, perhaps to some extent, by improving the intrinsic material properties of bone tissue. Information presented here may help clinicians to improve selection of patients for antiresorptive therapy by avoiding them in cases clearly not due to excessive bone remodeling.