In vivo glycation-interplay between oxidant and carbonyl stress in bone.

Metabolic syndromes (eg, obesity, type 2 diabetes (T2D), atherosclerosis, and neurodegenerative diseases) and aging, they all have a strong component of carbonyl and reductive-oxidative (redox) stress. Reactive carbonyl (RCS) and oxidant (ROS) stress species are commonly generated as products or byproducts of cellular metabolism or are derived from the environment. RCS and ROS can play a dual role in living organisms.

Techniques for advanced glycation end product measurements for diabetic bone disease: pitfalls and future directions.

Purpose Of Review: Multiple biochemical and biophysical approaches have been broadly used for detection and quantitation of posttranslational protein modifications associated with diabetic bone, yet these techniques present a variety of challenges. In this review, we discuss recent advancements and complementary roles of analytical (UPLC/UPLC-MS/MS and ELISA) and biophysical (Raman and FTIR) techniques used for characterization of glycation products, measured from bone matrix and serum, and provide recommendations regarding the selection of a technique for specific study of diabetic bone.

Recent Findings: Hyperglycemia and oxidative stress in diabetes contribute to the formation of a large subgroup of advanced glycation end products (AGEs) known as glycoxidation end products (AGOEs).

Non-Obese MKR Mouse Model of Type 2 Diabetes Reveals Skeletal Alterations in Mineralization and Material Properties.

Obesity is a common comorbidity of type 2 diabetes (T2D). Therefore, increased risk of fragility fractures in T2D is often confounded by the effects of obesity. This study was conducted to elucidate the mechanistic basis by which T2D alone leads to skeletal fragility.

Induction and rescue of skeletal fragility in a high-fat diet mouse model of type 2 diabetes: An in vivo and in vitro approach.

Poor bone quality is associated with Type 2 Diabetes (T2D), with patients having a higher risk of fracture despite normal to high bone mineral density (BMD). Diabetes contributes to modifications of the mineral and organic matrix of bone. Hyperglycemia has been linked to the formation of advanced glycation end-products (AGEs) which increase the risk for skeletal fragility fractures.

Controlled Formation of Carboxymethyllysine in Bone Matrix through Designed Glycation Reaction.

It has been a challenge to establish a link between specific advanced glycation end products (AGEs) as causal agents of different pathologies and age-related diseases, primarily because of the lack of suitable in vitro experimental strategies facilitating increased formation of a specific AGE, here carboxymethyllysine (CML), over other AGEs under controlled conditions. CML is of considerable importance to various oxidative stress-related diseases, because in vivo formation of this AGE is connected with cellular oxidative/carbonyl metabolism. The mechanistic implications of CML accumulation in bone remain to be elucidated.

Circadian rhythm disruption with high-fat diet impairs glycemic control and bone quality.

Biological functions, including glycemic control and bone metabolism, are highly influenced by the body's internal clock. Circadian rhythms are biological rhythms that run with a period close to 24 hours and receive input from environmental stimuli, such as the light/dark cycle. We investigated the effects of circadian rhythm disruption (CRD), through alteration of the light/dark schedule, on glycemic control and bone quality of mice.

The role of extracellular matrix phosphorylation on energy dissipation in bone.

Protein phosphorylation, critical for cellular regulatory mechanisms, is implicated in various diseases. However, it remains unknown whether heterogeneity in phosphorylation of key structural proteins alters tissue integrity and organ function. Here, osteopontin phosphorylation level declined in hypo- and hyper- phosphatemia mouse models exhibiting skeletal deformities.

Individuals with type 2 diabetes mellitus show dimorphic and heterogeneous patterns of loss in femoral bone quality.

Type 2 diabetes mellitus (T2DM), a metabolic disease on the rise, is associated with substantial increase in bone fracture risk. Because individuals with T2DM have normal or high bone mineral density (BMD), osteodensitometric measurements of BMD do not predict fracture risk with T2DM. Here, we aim to identify the underlying mechanism of the diabetes-induced fracture risk using a high-resolution multi-scale analysis of human cortical bone with special emphasis on osseous cellular activity.

Altered Tissue Composition, Microarchitecture, and Mechanical Performance in Cancellous Bone From Men With Type 2 Diabetes Mellitus.

People with type 2 diabetes mellitus (T2DM) have normal-to-high BMDs, but, counterintuitively, have greater fracture risks than people without T2DM, even after accounting for potential confounders like BMI and falls. Therefore, T2DM may alter aspects of bone quality, including material properties or microarchitecture, that increase fragility independently of bone mass. Our objective was to elucidate the factors that influence fragility in T2DM by comparing the material properties, microarchitecture, and mechanical performance of cancellous bone in a clinical population of men with and without T2DM.

Phosphorylation of Extracellular Bone Matrix Proteins and Its Contribution to Bone Fragility.

Phosphorylation of bone matrix proteins is of fundamental importance to all vertebrates including humans. However, it is currently unknown whether increase or decline of total protein phosphorylation levels, particularly in hypophosphatemia-related osteoporosis, osteomalacia, and rickets, contribute to bone fracture. To address this gap, we combined biochemical measurements with mechanical evaluation of bone to discern fracture characteristics associated with age-related development of skeletal fragility in relation to total phosphorylation levels of bone matrix proteins and one of the key representatives of bone matrix phosphoproteins, osteopontin (OPN).

Accumulation of carboxymethyl-lysine (CML) in human cortical bone.

Advanced glycation end-products (AGEs) are a category of post translational modification associated with the degradation of the structural properties of multiple different types of tissues. Typically, AGEs are the result of a series of post-translational modification reactions between sugars and proteins through a process known as non-enzymatic glycation (NEG). Increases in the rate of NEG of bone tissue are associated with type 2 diabetes and skeletal fragility.

Dietary Advanced Glycation End Products Have Sex- and Age-Dependent Effects on Vertebral Bone Microstructure and Mechanical Function in Mice.

Back pain is a leading cause of global disability that can arise from vertebral fracture and osteoporosis. Although poor general health and obesity are among the strongest risk factors for back pain, there is remarkably little known about how diet influences spinal diseases. Advanced glycation end-products (AGEs) are implicated in increased fracture risk, yet no studies investigated how dietary AGEs affect spinal health.

Correction: Advanced Glycation Endproducts and Bone Material Properties in Type 1 Diabetic Mice.

[This corrects the article DOI: 10.1371/journal.pone.

A strategy to quantitate global phosphorylation of bone matrix proteins.

Current studies of protein phosphorylation focus primarily on the importance of specific phosphoproteins and their landscapes of phosphorylation in the regulation of different cellular functions. However, global changes in phosphorylation of extracellular matrix phosphoproteins measured "in bulk" are equally important. For example, correct global phosphorylation of different bone matrix proteins is critical to healthy tissue biomineralization.

A direct role of collagen glycation in bone fracture.

Non-enzymatic glycation (NEG) is an age-related process accelerated by diseases like diabetes, and causes the accumulation of advanced glycation end-products (AGEs). NEG-mediated modification of bone's organic matrix, principally collagen type-I, has been implicated in impairing skeletal physiology and mechanics. Here, we present evidence, from in vitro and in vivo models, and establish a causal relationship between collagen glycation and alterations in bone fracture at multiple length scales.

Glycation of human cortical and cancellous bone captures differences in the formation of Maillard reaction products between glucose and ribose.

To better understand some aspects of bone matrix glycation, we used an in vitro glycation approach. Within two weeks, our glycation procedures led to the formation of advanced glycation end products (AGEs) at the levels that corresponded to approx. 25-30 years of the natural in vivo glycation.

Insulin-like growth factor 1, glycation and bone fragility: implications for fracture resistance of bone.

Despite our extensive knowledge of insulin-like growth factor 1 (IGF1) action on the growing skeleton, its role in skeletal homeostasis during aging and age-related development of certain diseases is still unclear. Advanced glycation end products (AGEs) derived from glucose are implicated in osteoporosis and a number of diabetic complications. We hypothesized that because in humans and rodents IGF1 stimulates uptake of glucose (a glycation substrate) from the bloodstream in a dose-dependent manner, the decline of IGF1 could be associated with the accumulation of glycation products and the decreasing resistance of bone to fracture.

Dilatational band formation in bone.

Toughening in hierarchically structured materials like bone arises from the arrangement of constituent material elements and their interactions. Unlike microcracking, which entails micrometer-level separation, there is no known evidence of fracture at the level of bone's nanostructure. Here, we show that the initiation of fracture occurs in bone at the nanometer scale by dilatational bands.

Solid state NMR investigation of intact human bone quality: balancing issues and insight into the structure at the organic-mineral interface.

Age-related bone fragility fractures present a significant problem for public health. Measures of bone quality are increasingly recognized to complement the conventional bone mineral density (BMD) based assessment of fracture risk. The ability to probe and understand bone quality at the molecular level is desirable in order to unravel how the structure of organic matrix and its association with mineral contribute to the overall mechanical properties.

Effects of bone matrix proteins on fracture and fragility in osteoporosis.

Bone mineral density alone cannot reliably predict fracture risk in humans and laboratory animals. Therefore, other factors including the quality of organic bone matrix components and their interactions may be of crucial importance to understanding of fragility fractures. Emerging research evidence shows, that in addition to collagen, certain noncollagenous proteins (NCPs) play a significant role in the structural organization of bone and influence its mechanical properties.

Biochemical characterization of major bone-matrix proteins using nanoscale-size bone samples and proteomics methodology.

There is growing evidence supporting the need for a broad scale investigation of the proteins and protein modifications in the organic matrix of bone and the use of these measures to predict fragility fractures. However, limitations in sample availability and high heterogeneity of bone tissue cause unique experimental and/or diagnostic problems. We addressed these by an innovative combination of laser capture microscopy with our newly developed liquid chromatography separation methods, followed by gel electrophoresis and mass spectrometry analysis.

UPLC methodology for identification and quantitation of naturally fluorescent crosslinks in proteins: a study of bone collagen.

Methods used to determine collagen crosslinks in different connective tissues require a relatively large amount of material and include a number of experimental steps. We addressed these issues by developing the first ultrahigh-pressure liquid chromatography (UPLC) methodology for detection and quantification of naturally fluorescent enzymatic (pyridinoline, deoxypyridinoline) and senescent (pentosidine) crosslinks using nanogram amounts of acid-hydrolyzed bone and purified bone collagen. Not only the developed set of UPLC methods relies on a single column analysis of all three fluorescent crosslinks in one separation step, but under different separation conditions, the same column is also used to determine hydroxyproline concentration necessary to calculate collagen contents in the samples making this a unique feature of our methodology.

Controlled hierarchical assembly of switchable DNA-multiprotein complexes.

Directed, biologically-driven self-assembly has the potential to yield hybrid multicomponent architectures with applications ranging from sensors and diagnostics to catalysts and responsive materials. To enable these applications, it is critical to gain control over the precise orientation and geometry of biomolecules interacting with one-another and with surfaces. Such control has thus far been difficult to achieve in even the simplest biomolecular designs.