[Show abstract][Hide abstract] ABSTRACT: To study whether hypercholesterolemia increases articular damage in a rabbit model of chronic arthritis.
Hypercholesterolemia was induced in eighteen rabbits by administrating a high-fat diet (HFD). Fifteen rabbits were fed normal chow as controls. Chronic arthritis (AIA) was induced in half of the HFD and control rabbits, previously immunized, by intra-articular injections of ovalbumin. After sacrifice, lipid and systemic inflammation markers were analyzed in blood serum. Synovium was analyzed by Krenn score, multinucleated cell counting, immunohistochemistry of RAM11 and CD31, and TNF-alpha and MCP-1 gene expression. Active bone resorption was assessed by protein expression of RANKL, OPG and quantification of cathepsin K, contact surface and invasive area of pannus into bone.
Rabbits receiving HFD showed higher total serum cholesterol, HDL, triglycerides and CRP levels than rabbits fed normal diet. Synovitis score was increased in HFD, and particularly in AIA and AIA+HFD groups. AIA+HFD synovium was characterized by a massive infiltration of RAM11+ cells, higher presence of multinucleated foam cells and bigger vascularization than AIA. Cathepsin K+ osteoclasts and contact surface of bone resorbing pannus were also increased in rabbits with AIA+HFD compared with AIA alone. Synovial TNF-alpha and MCP-1 gene expression was increased in AIA and HFD rabbits compared with healthy animals. RANKL protein expression in AIA and AIA+HFD groups was higher compared with either HFD or normal groups.
This experimental model demonstrates that hypercholesterolemia increments joint tissue damage in chronic arthritis, being foam macrophages key players in this process.
Full-text · Article · Aug 2013 · Arthritis research & therapy
[Show abstract][Hide abstract] ABSTRACT: The receptor activator nuclear factor-kappaB ligand (RANKL) diffuses from articular cartilage to subchondral bone. However, the role of chondrocyte-synthesized RANKL in rheumatoid arthritis-associated juxta-articular bone loss has not yet been explored. This study aimed to determine whether RANKL produced by chondrocytes induces osteoclastogenesis and juxta-articular bone loss associated with chronic arthritis.
Chronic antigen-induced arthritis (AIA) was induced in New Zealand (NZ) rabbits. Osteoarthritis (OA) and control groups were simultaneously studied. Dual X-ray absorptiometry of subchondral knee bone was performed before sacrifice. Histological analysis and protein expression of RANKL and osteoprotegerin (OPG) were evaluated in joint tissues. Co-cultures of human OA articular chondrocytes with peripheral blood mononuclear cells (PBMCs) from healthy donors were stimulated with macrophage-colony stimulating factor (M-CSF) and prostaglandin E2 (PGE2), then further stained with tartrate-resistant acid phosphatase.
Subchondral bone loss was confirmed in AIA rabbits when compared with controls. The expression of RANKL, OPG and RANKL/OPG ratio in cartilage were increased in AIA compared to control animals, although this pattern was not seen in synovium. Furthermore, RANKL expression and RANKL/OPG ratio were inversely related to subchondral bone mineral density. RANKL expression was observed throughout all cartilage zones of rabbits and was specially increased in the calcified cartilage of AIA animals. Co-cultures demonstrated that PGE2-stimulated human chondrocytes, which produce RANKL, also induce osteoclasts differentiation from PBMCs.
Chondrocyte-synthesized RANKL may contribute to the development of juxta-articular osteoporosis associated with chronic arthritis, by enhancing osteoclastogenesis. These results point out a new mechanism of bone loss in patients with rheumatoid arthritis.
Full-text · Article · Jun 2012 · Arthritis research & therapy
[Show abstract][Hide abstract] ABSTRACT: Background and objectivesCytotoxic T lymphocyte antigen 4 (CTLA4) is a surface protein on T lymphocytes that binds to the surface of antigen-presenting cells through the CD80/86 molecules regulating their co-stimulation. The authors hypothesised that Abatacept (CTLA4-Ig) might bind to monocyte/macrophages regulating the differentiation of monocytes to macrophages, and the production of pro-inflammatory and anti-inflammatory cytokines by macrophages.Material and methodsHuman peripheral blood mononuclear cells were isolated from buffy coats from four normal donors by Ficoll gradient cell separation. Then, monocytes were purified by CD14 positive selection, and they were differentiated in vitro to classic and alternative macrophages by culturing in the presence of granulocyte-macrophage colony stimulating factor or macrophage-colony stimulating factor (M-CSF) respectively. The authors analysed the CTLA4-Ig binding to classic and alternative macrophages by flow cytometry. After demonstrating that CTLA4-Ig binds to classic and alternative macrophages, the effect of CTLA4-Ig on macrophage differentiation and cytokines production were tested.ResultsCTLA4-Ig binds to human macrophages. In addition, CTLA4-Ig reduced, in a dose-dependent fashion, the macrophage differentiation in monocytes cultures stimulated with M-CSF. This results did not evidence any effect of CTLA4-Ig on the IL-10 or tumour necrosis factor production by neither classical nor alternative macrophages.Conclusion
These data show that CTLA4-Ig directly affects macrophage differentiation in vitro. Therefore, the beneficial effect of Abatacept in rheumatoid arthritis patients could be achieved at least partially through a direct mechanism of action on the monocyte/macrophage line cell.
No preview · Article · Feb 2011 · Annals of the Rheumatic Diseases
[Show abstract][Hide abstract] ABSTRACT: Non-steroidal anti-inflammatory drugs improve inflammatory cachexia in several conditions. Thus, we have explored inhibition of cyclooxygenase-2 (COX-2) in an experimental model of rheumatoid cachexia in rabbits.
Chronic arthritis was induced in immunized rabbits by repeated intra-articular injections of ovalbumin. To increase the degree of systemic inflammation and also to induce atherosclerotic lesions, the animals were fed a hyperlipidaemic diet (2% cholesterol and 6% peanut oil) and were given an endothelial injury of the femoral artery. Rabbits were randomized to receive the COX-2 inhibitor celecoxib (10 mg·kg⁻¹ ·day⁻¹) or no treatment. After 4 weeks, sera, peripheral mononuclear cells and vessel specimens were collected.
Inhibition of COX-2 by celecoxib modulated the systemic inflammatory response and increased total cholesterol and triglyceride levels. Celecoxib also minimized weight loss and prevented serum albumin fall. At a vascular level, celecoxib reduced COX-2 protein in the femoral arterial wall, but did not modify size or the macrophage infiltration of femoral lesions nor the percentage of rabbits with spontaneous aortic plaques.
Our animal model induced a severe inflammatory cachexia, comparable to that of persistently active rheumatoid arthritis. The inhibition of COX-2 by celecoxib improves this state, suggesting that COX products play an important role in its development, without affecting the development or the progression of vascular lesions. Overall, these results suggest that celecoxib might be considered as a new therapeutic tool for the treatment of rheumatoid cachexia.
Full-text · Article · Nov 2010 · British Journal of Pharmacology
[Show abstract][Hide abstract] ABSTRACT: Our aim was to explore the effect of chondroitin sulfate (CS), a natural glycosaminoglycan with attributed anti-inflammatory properties, on synovitis in a rabbit model of chronic arthritis with intense systemic inflammation bolstered by endothelial lesion and atherosclerotic diet.
Chronic arthritis was induced by intraarticular injections of ovalbumin in immunized rabbits. Systemic inflammation was boosted in these rabbits by receiving a hyperlipidemic diet after producing an endothelial lesion in the femoral arteries. A group of these rabbits were treated with CS (100mg/kg/day). At sacrifice, synovial membranes were isolated, and cyclooxygenase-2 (COX-2) and chemokine (C-C motif) ligand 2 (CCL2) mRNA, as well as protein expression were assayed by quantitative real-time polymerase chain reaction (RT-PCR) and western blot studies. Histological synovial examination was also carried out employing the histopathological synovitis score (Krenn scale).
CS diminished both gene expression and protein synthesis of COX-2 and CCL2, and the histopathological score of the synovial membrane, when compared to untreated rabbits. In fact, CS partially prevented the intimal layer proliferation and the inflammatory cell infiltration in the synovial membrane, which was observed in non-treated animals.
CS reduced the inflammatory response of the synovial membrane, as well as decreased the synovial histopathological lesions in our animal model. Further studies are warranted to demonstrate whether CS might be beneficial in the treatment of inflammatory arthritis.
Preview · Article · Jun 2010 · Osteoarthritis and Cartilage
[Show abstract][Hide abstract] ABSTRACT: The rheumatic diseases have been associated with accelerated atherosclerosis. Rheumatoid arthritis (RA) is a systemic inflammatory disease characterized by persistent synovial inflammation which leads to disability and structural changes in joints. Epidemiological studies have demonstrated an increased cardiovascular mortality in patients with RA. In these patients, atherosclerotic plaque occurs earlier, and it has a faster evolution than in general population. Atherosclerosis (AT) is also an inflammatory disease partly mediated by cytokines, many of them involved on chronic synovitis. Our group has developed a rabbit experimental model of AT aggravated by chronic arthritis to study inflammatory mechanisms involved on the progression of vascular lesions and their response to drugs. A preliminary study using this model suggests a beneficial effect of chondroitin sulphate (CS), a drug recommended for the treatment of osteoarthritis, in controlling AT lesions. Yet clinical trials should be conducted with this compound to address the same hypothesis in human studies.
Preview · Article · Jun 2010 · Osteoarthritis and Cartilage
[Show abstract][Hide abstract] ABSTRACT: Glucosamine sulfate (GS) is a glycosaminoglycan with anti-inflammatory and immunoregulatory properties. Here we set out to explore the effect of GS administration on markers of systemic and local inflammation in rabbits with atherosclerosis aggravated by chronic arthritis. Atherosclerosis was induced in rabbits by maintaining them on a hyperlipidemic diet after producing an endothelial lesion in the femoral arteries. Simultaneously, chronic arthritis was induced in these animals by repeated intra-articular injections of ovalbumin in previously immunized rabbits. A group of these rabbits was treated prophylactically with oral GS (500 mg.kg(-1).day(-1)), and, when the animals were killed, serum was extracted and peripheral blood mononuclear cells (PBMC) were isolated. Furthermore, the femoral arteries, thoracic aorta, and synovial membranes were examined in gene expression studies and histologically. GS administration reduced circulating levels of the C-reactive protein and of interleukin-6. GS also lowered nuclear factor-kappaB activation in PBMC, and it downregulated the expression of both the CCL2 (monocyte chemoattractant protein) and cyclooxygenase-2 genes in these cells. Lesions at the femoral wall were milder after GS treatment, as reflected by the intimal-to-media thickened ratio and the absence of aortic lesions. Indeed, GS also attenuated the histological lesions in synovial tissue. In a combined rabbit model of chronic arthritis and atherosclerosis, orally administered GS reduced the markers of inflammation in peripheral blood, as well as the femoral and synovial membrane lesions. GS also prevented the development of inflammation-associated aortic lesions. These results suggest an atheroprotective effect of GS.
No preview · Article · Jun 2009 · AJP Heart and Circulatory Physiology
[Show abstract][Hide abstract] ABSTRACT: Recently independent studies, including genome-wide scans, have shown that variation in the fat mass and obesity associated gene (FTO) were significantly associated with obesity in populations of European origin.
In this study we examined the association between rs9939609 FTO variant and obesity related parameters in a population based-study of 732 unrelated individuals (46.9% males and 53.1% females; ages 35-74 years) from the province of Segovia in Central Spain (Castille).
The AA genotype was significantly more frequent in obese individuals (defined as body mass index >or= 30 kg/m(2), n = 207; 80 males and 127 females) than in non-obese (19.9%vs. 13.7%, P = 0.026). In addition to increased obesity, AA homozygous individuals had higher waist circumference than individuals with AT heterozygous and TT homozygous genotypes. The minor A-allele of rs9939609 was associated with an increased odds ratio (OR) for obesity [OR 1.51, 95% confidence interval (CI) 1.10-2.12] as compared to the TT genotype. This difference was also statistically significant even after the adjustment for sex and age (OR 1.46, 95% CI 1.02-2.07).
Our results support the association of FTO gene variants with obesity, including parameters of visceral (abdominal) obesity, in an adult general population from Spain. Overall we confirm the previously reported association studies between variants in FTO gene and the risk of obesity.
No preview · Article · Jun 2008 · Clinical Endocrinology
[Show abstract][Hide abstract] ABSTRACT: The metabolic syndrome (MS), a cluster of several metabolic disorders, is increasingly being recognized as a risk factor for cardiovascular disease. Ectonucleotide pyrophosphatase/phosphodiesterase 1 (ENPP1), originally described as a plasma cell allo-antigen and named plasma cell membrane glycoprotein (PC-1), is an inhibitor of insulin-induced activation of the insulin receptor. The single nucleotide polymorphism (SNP) K121Q in the ENPP1 gene has been studied in relation to obesity, insulin resistance and other features of MS in several populations with conflicting results. We therefore investigate the role of the K121Q SNP in the ENPP1 gene in MS in Caucasians from the province of Segovia in Central Spain (Castille).
We recruited 794 unrelated persons (46.5% males and 53.5% females), ages 35-74 years from a cross-sectional population-based epidemiological survey in the province of Segovia in Central Spain (Castille). Obesity-related anthropometric measurements included BMI, waist circumference, blood pressure and lipid profile. MS was defined by International Diabetes Federation (IDF) guidelines. K121Q PC-1 genotypes were determined by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP).
The 121Q allele was associated with an increased BMI and waist circumference among subjects fulfilling the criteria for MS. These differences remained statistically significant even after the adjustment for sex, age and degree of glucose tolerance (beta = 1.347, P = 0.017 and beta = 2.824, P = 0.046; for BMI and waist circumference, respectively). Moreover, among type 2 diabetic patients those carrying the 121Q allele had higher BMI and higher leptin levels than subjects carrying the K121K genotype.
Our results suggest that the ENPP1121Q allele might contribute to the genetic susceptibility to abdominal obesity among subjects with MS.
No preview · Article · Jun 2008 · Clinical Endocrinology
[Show abstract][Hide abstract] ABSTRACT: Sexual dimorphism in blood pressure (BP) regulation has been observed both in humans and experimental animals, and estrogens have been shown to contribute to this epidemiological observation. A key enzyme in determining estrogen levels is aromatase cytochrome P450. The aim of this study was to evaluate the role of the gene encoding aromatase, CYP19A1, as an independent risk factor for hypertension and its relationship with systolic and diastolic BP measures. We genotyped 2 polymorphisms within the CYP19A1 gene, IVS4 rs11575899 and 3'UTR rs10046, in 3448 individuals. In quantitative analysis, we observed significant associations between the 2 polymorphisms and BP values in women, being these associations dependent on BMI and independent of menopause status. The case-control analysis revealed that the most prominent associations were found for nonobese women in diastolic hypertension (DHT): the IVS4_22 and 3'UTR_11 are risk genotypes (OR=1.61, P=0.027 and OR=1.59, P=0.012, respectively), whereas IVS4_11 and 3'UTR_22 genotypes have a protective effect against DHT (OR=0.63, P=0.009, and OR=0.61, P=0.020, respectively). Haplotype analysis confirmed the above associations: among nonobese women the haplotype 21 is overrepresented in hypertensive women (OR=1.33, P=0.004, for DHT and OR=1.25, P=0.026, for systolic hypertension, SHT) and, conversely, the haplotype 12 protects against hypertension (OR=0.78, P=0.015 for DHT and OR=0.82, P=0.04 for SHT). Our study has shown that the CYP19A1 gene may be involved in the genetic regulation of BP in women. This effect is dependent on BMI and independent of menopause status, suggesting that this action is mainly driven by aromatase activity in fat tissue.
[Show abstract][Hide abstract] ABSTRACT: C-reactive protein (CRP) is a marker of systemic inflammation significantly associated with an increased risk of cardiovascular disease in the general population. The aim of our current work was to study those clinical and genetic variables potentially associated with interindividual variability in serum CRP levels. A random sample of 844 participants (450 women, mean age 55 years) from a study carried out on the general Spanish population (The Segovia Study) was studied. Our results showed that age, gender, waist circumference, leptin, impaired glucose tolerance and smoking were the clinical variables significantly associated with variations in serum CRP levels. Among those, leptin showed the strongest association, explaining 11% of the interindividual variability in circulating CRP levels (p<0.001). To study the effect of genetic variants on serum CRP levels, 10 SNPs within the CRP locus were genotyped in 756 participants. Four of these SNPs (rs1417938, rs1800947, rs1130864, rs1205) were significantly associated with CRP levels after adjustment for clinical variables. Among the common haplotypes inferred from eight SNPs, two (CCATGCCT, p=0.025; CTATCCTT, p=0.004) explained 2.9% of the total variation in serum CRP. The results here reported show that 2.9% of the total variation in circulating CRP levels seems to be explained by genetics variations within CRP locus. Furthermore, serum leptin levels are strongly associated with serum CRP levels in our Spanish population.
No preview · Article · Nov 2007 · Thrombosis and Haemostasis
[Show abstract][Hide abstract] ABSTRACT: Studies in humans and mice suggest that plasminogen activator inhibitor-1 (PAI-1) might be a candidate gene for arterial hypertension. Our aims were to analyse whether the functional 4G/5G PAI-1 polymorphism represents a risk marker for the development of arterial hypertension regardless of hypertension-related metabolic variables.
Eight hundred and fifteen unrelated individuals (387 men, age 35-74 years) from a cross-sectional, population-based, epidemiological survey in the province of Segovia (Spain) were studied. Anthropometric/biochemical parameters--body mass index, waist circumference, diastolic and systolic blood pressures, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, triglycerides, fasting glucose, insulin, C-reactive protein, and PAI-1 levels--were analysed. The 4G/5G PAI-1 genotypes were established by restriction fragment length polymorphism. Insulin resistance was estimated by the homeostasis model assessment. Tobacco consumption data were obtained using a standard questionnaire.
The 4G/4G PAI-1 genotype was significantly associated with a high prevalence of arterial hypertension. This association remained statistically significant even after adjustment for hypertension-related metabolic variables in our population (adjusted odds ratio, 1.858; 95% confidence interval, 1.135-3.018; P = 0.013).
Our results show that the 4G/4G PAI-1 genotype appears to be associated with an elevated relative risk of developing arterial hypertension, regardless of PAI-1 levels and other hypertension-related factors, in a representative sample of the Spanish population.
No preview · Article · May 2007 · Journal of Hypertension
[Show abstract][Hide abstract] ABSTRACT: The metabolic syndrome, a cluster of several metabolic disorders, is increasingly being recognized as a risk factor for cardiovascular disease. Endothelium-derived nitric oxide facilitates skeletal muscle glucose uptake, and data from animal models indicate that endothelial nitric oxide synthase (eNOS) gene-null mice present with a phenotype of insulin resistance, hypertension, and hypertriglyceridemia, much like that observed in humans with metabolic syndrome. We used haplotype tagging single nucleotide polymorphisms (htSNPs) to investigate the role of genetic variation in the eNOS gene (NOS3) in metabolic syndrome in humans.
We recruited 738 unrelated persons from a cross-sectional population-based epidemiological survey in the province of Segovia in Central Spain (Castille). Metabolic syndrome was defined according to the recently modified National Cholesterol Education Program Adult Treatment Panel III guidelines.
Haplotype analysis showed a statistically significant association between some NOS3 gene variants and features of metabolic syndrome. Relative to the most common haplotype, 121, the haplotype 212 was associated with an increased odds ratio (OR) for metabolic syndrome [OR = 1.81, 95% confidence interval (CI) 1.15-2.84], and for decreased HDL-cholesterol concentrations (OR 1.52, 95% CI 1.01-2.29), and with increased mean values for the homeostasis model assessment of insulin resistance (P = 0.043), and triglycerides (P = 0.026).
Our results suggest that genetic variation at the eNOS locus is associated with features of metabolic syndrome, and might represent a new genetic susceptibility component for insulin resistance, hypertriglyceridemia, and low HDL-cholesterol concentrations.
[Show abstract][Hide abstract] ABSTRACT: Genes implicated in common complex disorders such as obesity, type 2 diabetes mellitus (T2DM) or cardiovascular diseases are not disease specific, since clinically related disorders also share genetic components. Cysteine protease Calpain 10 (CAPN10) has been associated with T2DM, hypertension, hypercholesterolemia, increased body mass index (BMI) and polycystic ovary syndrome (PCOS), a reproductive disorder of women in which isunlin resistance seems to play a pathogenic role. The calpain 5 gene (CAPN5) encodes a protein homologue of CAPN10. CAPN5 has been previously associated with PCOS by our group. In this new study, we have analysed the association of four CAPN5 gene variants(rs948976A>G, rs4945140G>A, rs2233546C>T and rs2233549G>A) with several cardiovascular risk factors related to metabolic syndrome in general population.
Anthropometric measurements, blood pressure, insulin, glucose and lipid profiles were determined in 606 individuals randomly chosen from a cross-sectional population-based epidemiological survey in the province of Segovia in Central Spain (Castille), recruited to investigate the prevalence of anthropometric and physiological parameters related to obesity and other components of the metabolic syndrome. Genotypes at the four polymorphic loci in CAPN5 gene were detected by polymerase chain reaction (PCR).
Genotype association analysis was significant for BMI (p < or = 0.041), diastolic blood pressure (p = 0.015) and HDL-cholesterol levels (p = 0.025). Different CAPN5 haplotypes were also associated with diastolic blood pressure (DBP) (0.0005 < or = p < or = 0.006) and total cholesterol levels (0.001 < or = p < or = 0.029). In addition, the AACA haplotype, over-represented in obese individuals, is also more frequent in individuals with metabolic syndrome defined by ATPIII criteria (p = 0.029).
As its homologue CAPN10, CAPN5 seems to influence traits related to increased risk for cardiovascular diseases. Our results also may suggest CAPN5 as a candidate gene for metabolic syndrome.
Full-text · Article · Feb 2007 · BMC Medical Genetics
[Show abstract][Hide abstract] ABSTRACT: Reported data about the effect of the 4G/5G PAI-1 polymorphism on plasma PAI-1 levels are controversial. This study was designed to determine the relative effect of the 4G/5G PAI-1 polymorphism on high plasma PAI-1 levels after adjustment for metabolic syndrome - related variables, and to test if this effect is modified by the smoking status. Six hundred and thirty one unrelated subjects (292 men; 35-74 years), from a cross-sectional population-based epidemiological survey in the province of Segovia (Spain) were studied. The higher frequency of high PAI-1 levels was found in 4G/4G subjects (5G/5G 19.4%, 4G/5G 21.6%, 4G/4G 33.7%, p = 0.003). A multiple regression model, adjusted for gender, age, BMI, waist circumference, triglycerides, HDL-cholesterol, HOMA IR and leptin, showed this adjOR: 4G/4G vs 5G/5G: 2.22, p = 0.008. When smoking status - 4G/5G PAI-1 interaction was included as an independent variable these results were not modified. Our results indicate that the 4G/4G PAI-1 genotype might be strongly associated with high PAI-1 levels regardless of metabolic syndrome-related variables and smoking status.
No preview · Article · Feb 2007 · Diabetes Obesity and Metabolism
[Show abstract][Hide abstract] ABSTRACT: We investigated whether interactions of the -308G/A polymorphism in the promoter region of the tumor necrosis factor-alpha (TNF-alpha) gene with single-nucleotide polymorphisms (SNPs) 45 and 276 of the adiponectin gene are associated with circulating adiponectin and soluble TNF-alpha receptor 2 (sTNFR2) concentrations in a Spanish population.
We performed anthropometric and physiologic measurements in 809 unrelated participants recruited with a simple random sampling approach from respondents to a cross-sectional population-based epidemiologic survey in the province of Segovia in central Spain (Castille).
The 2-h postload glucose and serum insulin concentrations were higher in -308A allele carriers than in -308G/G individuals homozygous for the TNF-alpha gene. Plasma concentrations of sTNFR2 were positively correlated with body mass index, waist-to-hip ratio, and sagittal abdominal diameter among individuals with type 2 diabetes. Individuals with type 2 diabetes and the -308A allele had higher sTNFR2 and lower adiponectin concentrations than -308G homozygotes. Moreover, individuals carrying both the TNF-alpha -308A allele and the G allele of SNP 45 in the adiponectin gene had the highest prevalence of impaired glucose tolerance (adjusted odds ratio, 1.26; 95% confidence interval, 1.01-1.56; P = 0.038) and had lower adiponectin concentrations (beta = -0.090; P = 0.005) than individuals without these genotypes.
Our findings are the first to indicate that a higher incidence of impaired glucose tolerance and low circulating adiponectin concentration may be associated with interaction between the -308G/A promoter polymorphism of the TNF-alpha gene and SNP 45 in the adiponectin gene.
No preview · Article · Feb 2006 · Clinical Chemistry