Using Structural Equation Modelling to Untangle Pathways of Factors Associated with Type 2 Diabetes

Background

Risk factors for type 2 diabetes (T2D) are multi-facet and interrelated. We aimed to apply structural equation modelling to examine and quantify pathways of modifiable risk factors related to incident type 2 diabetes.

Methods

Analysis was based on 68 649 participants (35-80 years, without diabetes at baseline) from the Lifelines cohort study. We proposed a conceptual model that illustrates the pathways of risk factors related to incident type 2 diabetes: socio-economic status (income and education) → lifestyle behaviors (diet quality, physical activity, TV watching, and smoking) → clinical markers (blood lipids and obesity status) → incident type 2 diabetes. Structural equation modeling was performed to test this proposed model.

Results

After a median follow-up of 41 months, 1124 new cases of type 2 diabetes were identified. The best-fitting model indicated that among all modifiable risk factors included, waist circumference had the biggest direct effect on type 2 diabetes (β: 0.213 ), followed by HDL-cholesterol (β: -0.141). Less TV watching and more physical activity were found to play an important role in improving clinical markers that were directly associated with type 2 diabetes. Education had the biggest direct effects on all lifestyle behaviors.

Conclusions

Using this innovative approach, our analysis provides a more nuanced assessment of the interplay of type 2 diabetes risk factors, compared to traditional risk estimates. Our results indicated that reducing large waist circumference may be prioritized as the main target for the prevention of type 2 diabetes, and lifestyle interventions are urgently warranted with additional support for those with a low education.

Key messages

Our study elucidated the multiple causal pathways to type 2 diabetes in a prospective setting. Our results identified the most critical targets for future prevention strategies for type 2 diabetes.

Lipophilic index, kidney function, and kidney function decline

BACKGROUND AND AIMS

Unhealthy dietary fats are associated with faster kidney function decline. The cell membrane composition of phospholipid fatty acids (FAs) is a determinant of membrane fluidity and rheological properties. These properties, which have been linked to kidney damage, are thought to be reflected by the lipophilic index (LI). We prospectively investigated the associations of LI with kidney function and its decline.

METHODS AND RESULTS

Observational study from the Prospective Investigation of Vasculature in Uppsala Seniors including 975 men and women with plasma phospholipid FAs composition and cystatin-C estimate glomerular filtration rate (eGFR). Of these, 780 attended re-examination after 5 years, and eGFR changes were assessed. Participants with a 5-year eGFR reduction ≥30% were considered chronic kidney disease (CKD) progressors (n = 198). LI was calculated as the sum of the products of the FA proportions with the respective FAs melting points. Blood rheology/viscosity measurements were performed in a random subsample of 559 subjects at baseline. Increased LI showed a statistically significant but overall weak association with blood, plasma viscosity (both Spearman rho = 0.16, p < 0.01), and erythrocyte deformability (rho = -0.09, p < 0.05). In cross-sectional analyses, LI associated with lower eGFR (regression coefficient 3.00 ml/min/1.73 m² 1-standard deviation (SD) increment in LI, 95% CI: -4.31, -1.69, p < 0.001). In longitudinal analyses, LI associated with a faster eGFR decline (-2.13 [95% CI -3.58, -0.69] ml/min/1.73 m², p < 0.01) and with 32% increased odds of CKD progression (adjusted OR 1.32 [95%, CI 1.05-1.65]).

CONCLUSIONS

A high LI was associated with lower kidney function, kidney function decline, and CKD progression.

Excess protein intake relative to fiber and cardiovascular events in elderly men with chronic kidney disease

BACKGROUND AND AIMS

The elevated cardiovascular (CVD) risk observed in chronic kidney disease (CKD) may be partially alleviated through diet. While protein intake may link to CVD events in this patient population, dietary fiber has shown cardioprotective associations. Nutrients are not consumed in isolation; we hypothesize that CVD events in CKD may be associated with dietary patterns aligned with an excess of dietary protein relative to fiber.

METHODS AND RESULTS

Prospective cohort study from the Uppsala Longitudinal Study of Adult Men. Included were 390 elderly men aged 70-71 years with CKD and without clinical history of CVD. Protein and fiber intake, as well as its ratio, were calculated from 7-day dietary records. Cardiovascular events were registered prospectively during a median follow-up of 9.1 (inter-quartile range, 4.5-10.7) years. The median dietary intake of protein and fiber was 66.7 (60.7-71.1) and 16.6 (14.5-19.1) g/day respectively and the protein-to-fiber intake ratio was 4.0 (3.5-4.7). Protein-to-fiber intake ratio was directly associated with serum C-reactive protein levels. During follow-up, 164 first-time CVD events occurred (incidence rate 54.5/1000 per year). Protein-fiber intake ratio was an independent risk factor for CVD events [adjusted hazard ratio, HR per standard deviation increase (95% confidence interval, CI) 1.33 (1.08, 1.64)]. Although in opposing directions, dietary protein [1.18 (0.97, 1.44)], dietary fiber alone [0.81 (0.64, 1.02)], were not significantly associated with CVD events.

CONCLUSIONS

An excess of dietary protein relative to fiber intake was associated with the incidence of cardiovascular events in a homogeneous population of older men with CKD.

Dietary protein-fiber ratio associates with circulating levels of indoxyl sulfate and p-cresyl sulfate in chronic kidney disease patients

BACKGROUND AND AIMS

Indoxyl sulfate (IS) and p-cresyl sulfate (PCS) are uremic toxins derived solely from colonic bacterial fermentation of protein. Dietary fiber may counteract this by limiting proteolytic bacterial fermentation. However, the influence of dietary intake on the generation of IS and PCS has not been adequately explored in chronic kidney disease (CKD).

METHODS AND RESULTS

This cross-sectional study included 40 CKD participants (60% male; age 69 ± 10 years; 45% diabetic) with a mean estimated glomerular filtration rate (eGFR) of 24 ± 8 mL/min/1.73 m(2), who enrolled in a randomized controlled trial of synbiotic therapy. Total and free serum IS and PCS were measured at baseline by ultra-performance liquid chromatography. Dietary intake was measured using in-depth diet histories collected by a dietitian. Associations between each toxin, dietary fiber (total, soluble and insoluble), dietary protein (total, and amino acids: tryptophan, tyrosine and phenylalanine), and the protein-fiber index (ratio of protein to fiber) were assessed using linear regression. Dietary fiber was associated with free and total serum PCS (r = -0.42 and r = -0.44, both p < 0.01), but not IS. No significant association was observed between dietary protein and either toxin. The protein-fiber index was associated with total serum IS (r = 0.40, p = 0.012) and PCS (r = 0.43, p = 0.005), independent of eGFR, sex and diabetes.

CONCLUSION

Dietary protein-fiber index is associated with serum IS and PCS levels. Such association, beyond fiber and protein alone, highlights the importance of the interplay between these nutrients. We speculate that dietary modification towards a lower protein-fiber index may contribute to lowering IS and PCS.

Epicardial fat accumulation, cardiometabolic profile and cardiovascular events in patients with stages 3-5 chronic kidney disease

BACKGROUND

It has been hypothesized that epicardial adipose tissue (EAT) exerts pathogenic effects on cardiac structures. We analysed the associations between EAT and both cardiovascular (CV) disease risk factors and CV events in patients with chronic kidney disease (CKD).

PATIENTS AND METHODS

We included 277 nondialysed patients [median age 61, interquartile range (IQR) 53-68 years; 63% men] with stages 3-5 CKD in this cross-sectional evaluation. EAT and abdominal visceral adipose tissue (VAT) were assessed by computed tomography. Patients were followed for median 32 (IQR 20-39) months, and the composite of fatal and nonfatal CV events was recorded.

RESULTS

With increasing EAT quartiles, patients were older, had higher glomerular filtration rate, body mass index, waist, VAT and coronary calcification, higher levels of haemoglobin, triglycerides, albumin, C-reactive protein and leptin and higher prevalence of left ventricular hypertrophy and myocardial ischaemia; total and high-density lipoprotein cholesterol, 25-hydroxy-vitamin D and 1, 25-dihydroxy-vitamin D progressively decreased. Associations between EAT and cardiac alterations were not independent of VAT. During follow-up, 58 CV events occurred. A 1-SD higher EAT volume was associated with an increased risk of CV events in crude [hazard ratio (HR) 1.41, 95% confidence interval (CI) (1.12-1.78) and adjusted (HR 1.55, 95% CI 1.21-1.99) Cox models. However, adding EAT to a standard CV disease risk prediction model did not result in a clinically relevant improvement in prediction.

CONCLUSION

Epicardial adipose tissue accumulation in patients with CKD increases the risk of CV events independent of general adiposity. This is consistent with the notion of a local pathogenic effect of EAT on the heart or heart vessels, or both. However, EAT adds negligible explanatory power to standard CV disease risk factors.

Dietary acid load, kidney function, osteoporosis, and risk of fractures in elderly men and women

SUMMARY

Because kidney dysfunction reduces the ability to excrete dietary acid excess, we hypothesized that underlying kidney function may have confounded the mixed studies linking dietary acid load with the risk of osteoporosis and fractures in the community. In a relatively large survey of elderly men and women, we report that dietary acid load did neither associate with DEXA-estimated bone mineral density nor with fracture risk. Underlying kidney function did not modify these null findings. Our results do not support the dietary acid-base hypothesis of bone loss.

INTRODUCTION

Impaired renal function reduces the ability to excrete dietary acid excess. We here investigate the association between dietary acid load and bone mineral density (BMD), osteoporosis, and fracture risk by renal function status.

METHODS

An observational study was conducted in 861 community-dwelling 70-year-old men and women (49% men) with complete dietary data from the Prospective Investigation of the Vasculature in Uppsala Seniors (PIVUS). The exposure was dietary acid load as estimated from 7-day food records by the net endogenous acid production (NEAP) and potential renal acid load (PRAL) algorithms. Renal function assessed by cystatin C estimated glomerular filtration rate was reduced in 21% of the individuals. Study outcomes were BMD and osteoporosis state (assessed by DEXA) and time to fracture (median follow-up of 9.2 years).

RESULTS

In cross-section, dietary acid load had no significant associations with BMD or with the diagnosis of osteoporosis. During follow-up, 131 fractures were validated. Neither NEAP (adjusted hazard ratios (HR) (95% confidence interval (CI)), 1.01 (0.85-1.21), per 1 SD increment) nor PRAL (adjusted HR (95% CI), 1.07 (0.88-1.30), per 1 SD increment) associated with fracture risk. Further multivariate adjustment for kidney function or stratification by the presence of kidney disease did not modify these null associations.

CONCLUSIONS

The hypothesis that dietary acid load associates with reduced BMD or increased fracture risk was not supported by this study in community-dwelling elderly individuals. Renal function did not influence on this null finding.

Prevalence of sarcopenia in elderly maintenance hemodialysis patients: the impact of different diagnostic criteria

The prevalence of sarcopenia on elderly maintenance hemodialysis (MHD) has been scarcely investigated.

OBJECTIVES

To investigate the prevalence of decreased muscle mass and strength alone or combined (true sarcopenia) in elderly patients on MHD according to different methods and cutoff limits. Additionally, we evaluated the agreement between dual energy x-ray absorptiometry (DXA) and surrogate methods for the assessment of muscle mass.

DESIGN

Observational and cross-sectional study.

PARTICIPANTS

Non-institutionalized 102 elderly (age > 60 years) patients on MHD.

MEASUREMENTS

Sarcopenia was considered when the patient fit one criteria for low muscle mass assessed by DXA, bioelectrical impedance (BIA), sum of skinfold thicknesses (SKF), calf circumference and mid-arm muscle circumference (MAMC) and one for low muscle strength evaluated by handgrip dynamometer.

RESULTS

Decreased muscle strength was found in 85% of the patients. The prevalence of decreased muscle mass varied from 4 to 73.5% and of sarcopenia (decreased muscle mass and strength combined) from 4 to 63%, depending on the method and cutoff limit applied. A small percentage of patients (2 to 15%) were classified as sarcopenic by more than one diagnostic criteria. The agreement between DXA and the surrogate methods to assess muscle mass showed better kappa coefficients with BIA (r=0.36; P<0.01) and SKF (r=0.40; P<0.01).

CONCLUSION

A wide prevalence of sarcopenia is observed depending on the method and cutoff limit applied. This may limit extrapolate on to clinical practice. BIA and SKF were the surrogate methods to assess muscle mass with the best concordance with DXA in elderly MHD patients.

Immunoglobulin (Ig)M antibodies against oxidized cardiolipin but not native cardiolipin are novel biomarkers in haemodialysis patients, associated negatively with mortality

The risk of premature death is high in haemodialysis (HD) patients. Antibodies against cardiolipin (anti-CL) are thrombogenic in diseases such as systemic lupus erythematosus (SLE). CL is easily oxidized (Ox) and plays a role in apoptosis. In this work we studied immunoglobulin (Ig)M anti-CL and anti-OxCL in HD-patients. We conducted an observational study with a prospective follow-up examining the relationship between anti-CL, anti-OxCL and mortality risk in a well-characterized cohort of 221 prevalent HD patients [56% men, median age 66 (interquartile range 51-74) years, vintage time 29 (15-58) months] with a mean follow-up period of 41 (20-48 months). According to the receiver operator characteristic (ROC) analysis, anti-OxCL [area under the curve (AUC) 0·62, P < 0·01], but not anti-CL (AUC 0·52, P = 0·2), is associated with mortality. In crude and adjusted Cox analysis, every log increase in anti-OxCL inversely predicted all-cause [adjusted hazard ratios (HR) 0·62 (0·43-0·89)] and CVD-related [adjusted HR 0·56 (0·32-0·98)] mortality. Patients with anti-OxCL levels below median also had increased all-cause and cardiovascular disease (CVD)-related mortality. Although anti-OxCL and anti-phosphorylcholine (PC) were related positively to each other (ρ = 0·57, P < 0·01), patients with one or two of these autoantibody levels below the median were associated with an incrementally increased death risk. Anti-OxCL were co-factor β2-GPI-independent; anti-CL from patients with anti-phospholipid antibody syndrome were β2-GPI-dependent, while sera from HD-patients less so. Sera from healthy donors was not β2-GPI-dependent. Anti-OxCL IgM is β2-glycoprotein 1 (GPI)-independent and a novel biomarker; low levels are associated with death among HD patients (and high levels with decreased risk). Combination with anti-PC increases this association. Putative therapeutic implications warrant further investigation.

Serum fatty acid patterns, insulin sensitivity and the metabolic syndrome in individuals with chronic kidney disease

OBJECTIVES

The causes of the multiple metabolic disorders of individuals with chronic kidney disease (CKD) are not fully known. We investigated the relationships between dietary fat quality, the metabolic syndrome (MetS), insulin sensitivity and inflammation in individuals with CKD.

SUBJECTS

Two population-based surveys were conducted in elderly Swedish individuals (aged 70 years) with serum cystatin C-estimated glomerular filtration rate <60 mL min(-1) /1.73 m2: the Uppsala Longitudinal Study of Adult Men (ULSAM) and the Prospective Investigation of the Vasculature in Uppsala Seniors (PIVUS) surveys. The present population comprised 274 men and 187 subjects (63% women) from the ULSAM and PIVUS cohorts, respectively.

DESIGN

Factor analyses of serum fatty acids were used to evaluate dietary fat quality. Insulin sensitivity was measured by homeostasis model assessment of insulin resistance (IR) and, in ULSAM, also by euglycaemic clamp.

RESULTS

Factor analyses generated two fatty acid patterns of (i) low linoleic acid (LA)/high saturated fatty acid (SFA) or (ii) high n-3 polyunsaturated fatty acid (n-3 PUFA) levels. In both surveys, the low LA/high SFA pattern increased the odds of having MetS [adjusted odds ratio 0.60 [95% confidence interval (CI) 0.44-0.81] and 0.45 (95% CI 0.30-0.67) per SD decrease in factor score in the ULSAM and PIVUS surveys, respectively] and was directly associated with both IR and C-reactive protein. The n-3 PUFA pattern was not consistently associated with these risk factors.

CONCLUSIONS

A serum fatty acid pattern reflecting low LA and high SFA was strongly associated with MetS, IR and inflammation in two independent surveys of elderly individuals with CKD. At present, there are no specific dietary guidelines for individuals with CKD; however, these findings indirectly support current recommendations to replace SFAs with PUFAs from vegetable oils.

Visceral obesity assessed by computed tomography predicts cardiovascular events in chronic kidney disease patients

BACKGROUND AND AIM

Cardiovascular disease is the leading cause of death among patients with chronic kidney disease (CKD). Although there is emerging evidence that excess visceral fat is associated with a cluster of cardiometabolic abnormalities in these patients, the impact of visceral obesity evaluated by a gold-standard method on future outcomes has not been studied. We aimed to investigate whether visceral obesity assessed by computed tomography was able to predict cardiovascular events in CKD patients.

METHODS AND RESULTS

We studied 113 nondialyzed CKD patients [60% men; 31% diabetics; age 55.3 ± 11.3 years; body mass index (BMI) 27.2 ± 5.3 kg/m(2); estimated glomerular filtration rate (GFR) 33.7 ± 13.6 ml/min/1.73 m(2)]. Visceral and subcutaneous abdominal fat were assessed by computed tomography at L4-L5. Visceral to subcutaneous fat ratio >0.55 (highest tertile cut-off) was defined as visceral obesity. Cardiovascular events including acute myocardial infarction, angina, arrhythmia, uncontrolled blood pressure, stroke and cardiac failure were recorded during 24 months. Cardiovascular events were 3-fold higher in patients with visceral obesity than in those without visceral obesity. The Kaplan-Meier analysis indicated that patients with visceral obesity had shorter cardiovascular event-free time than those without visceral obesity (P = 0.021). In the univariate Cox analysis, visceral obesity was associated with higher risk of cardiovascular events (hazard ratio = 3.4; 95% confidence interval = 1.1-10.5; P = 0.03). The prognostic power of visceral obesity for cardiovascular events remained significant after adjustments for sex, age, diabetes, previous cardiovascular disease, smoking, sedentary lifestyle, BMI, GFR, hypertension, dyslipidemia and inflammation.

CONCLUSION

Visceral obesity assessed by computed tomography was a predictor of cardiovascular events in CKD patients.

Clinical determinants and mortality predictability of stearoyl-CoA desaturase-1 activity indices in dialysis patients

BACKGROUND

Stearoyl-CoA desaturase-1 (SCD-1) converts dietary saturated fatty acids to monounsaturated fatty acids. Elevated SCD-1 activity thus signifies impaired fatty acid metabolism and excess saturated fat intake. In the general population, increased SCD-1 activity is associated with cardiovascular disease and mortality. The determinants and implications of SCD-1 activity in dialysis patients are unknown.

SUBJECTS

A total of 222 dialysis patients (39% women) with prospective follow-up, median age of 57 years and an average of 12 months of dialysis.

DESIGN

Fatty acid compositions in plasma phospholipids and free fatty acids (FFAs) were assessed by gas-liquid chromatography. SCD-1 activity indices were calculated as the product-to-precursor fatty acid ratio (palmitoleic acid/palmitic acid) in each fraction to reflect SCD-1 activities in the liver and adipose tissue.

RESULTS

Median hepatic and adipose tissue SCD-1 activity indices were 0.016 and 0.150, respectively. In multivariate analyses, SCD-1 was positively associated with age, female sex and serum interleukin-6 level. During 18.4 (interquartile range 5.5-37.3) months of follow-up, there were 61 deaths and 115 kidney transplants. The cut-off level for high SCD-1 indices was determined by receiver operating characteristic curve analyses. In fully adjusted competing risk models, patients with high SCD-1 indices in both phospholipids and FFAs had more than twofold increased mortality risk before kidney transplantation [hazard ratio (HR) 2.29, 95% confidence interval (CI) 1.28-4.11 and HR 2.36, 95% CI 1.38-4.03, respectively], compared with patients with low SCD-1 indices.

CONCLUSIONS

Both hepatic and adipose tissue SCD-1 activity indices independently predict mortality in dialysis patients. Further studies are warranted to determine whether reducing SCD-1 activity by dietary intervention (limiting saturated fat) could improve survival in dialysis patients.

Sandfly saliva of Lutzomyia ovallesi (Diptera: Psychodidae) as a possible marker for the transmission of Leishmania in Venezuela Andes region

BACKGROUND & OBJECTIVES

The saliva of the Phlebotominae is highly immunogenic to the vertebrate host and is a determining factor in the Leishmania infection. The aim of this work was to study the saliva of Lutzomyia ovallesi as a possible risk marker for the transmission of Leishmania.

METHODS

Two populations of L. ovallesi from different geographical areas and subjected to different environmental conditions were compared by geometric morphometry of the wings, by protein profile analysis of salivary glands and by assessing the presence of anti-saliva protein in human sera confronted with laboratory L. ovallesi saliva.

RESULTS

The results showed differences in the isometric size and structure of the wings but no allometric effects. Protein profiles of salivary glands of both the L. ovallesi populations studied were found to be similar, based on 11 protein bands with molecular weights ranging from 16 to 99 kDa. Anti-saliva antibodies were present in human sera, but human sera infected and uninfected with leishmaniasis could not be differentiated.

INTERPRETATION & CONCLUSION

We conclude that the saliva of laboratory-reared L. ovallesi is representative of that of the wild population. It is suggested to study the presence of anti-saliva antibodies in other species of sandflies and mosquitoes.

The newly identified anorexigenic adipokine nesfatin-1 in hemodialysis patients: Are there associations with food intake, body composition and inflammation?

Nesfatin-1 is a recently identified anorexigenic peptide that has been implicated in appetite regulation, weight loss and/or malnutrition. Anorexia and malnutrition are common features of chronic kidney disease (CKD) that predispose patients to worse outcomes. However, the reasons for the occurrence of anorexia in CKD patients are not fully elucidated. The aim of this study was to investigate the association between nesfatin-1 and protein intake and body composition in patients undergoing hemodialysis (HD). Twenty five HD patients from a private Clinic in Rio de Janeiro, Brazil were studied and compared with 15 healthy subjects that were matched for body mass index (BMI), % body fat mass (by anthropometrics) and age. Appetite was measured using a specific questionnaire, and food intake was evaluated based on 3-day food records. Nesfatin-1 levels were measured by ELISA and leptin, TNF-α and IL-6 levels were determined by a multiplex assay kit. Serum nesfatin-1 levels did not differ between HD patients (0.16±0.07ng/mL) and healthy subjects (0.17±0.10ng/mL). Nesfatin-1 levels showed significant negative correlations with protein intake (r=-0.42; p=0.03), but did not associate with inflammatory markers or appetite scores. Combining patients and controls, we observed positive correlations with BMI (r=0.33; p=0.03), % body fat (r=0.35; p=0.03), leptin (r=0.45; p=0.006) and the triceps skinfold thickness (r=0.36; p=0.02). In multivariate analysis % body fat was the main determinant of nesfatin-1 variance. In conclusion, nesfatin-1 levels did not differ between HD patients and healthy subjects and negatively correlated with protein intake. This pathway is likely not dysregulated in uremia.

The effect of immunosuppressive treatment on arterial stiffness and matrix Gla protein levels in renal transplant recipients

INTRODUCTION

Arterial stiffness is a risk marker for cardiovascular events. In this study we aimed to compare the effect on calcineurin inhibitors (CNI) and mammalian Target of Rapamycine inhibitors (mTORi) on arterial stiffness in renal transplant patients.

PATIENTS AND METHODS

81 renal transplant patients under CNI-based or mTORi-based protocol for at least 6 months were included in the study. Arterial stiffness was measured by using the SphygmoCor device (AtCor Medical, Sydney, Australia). Vitamin K-dependent, calcification inhibitor matrix Gla protein (MGP) concentrations were quantified by ELISA methods (Biomedica, Vienna, Austria).

RESULTS

34 patients were on mTORi-based and 47 on CNI-based immunosuppression. Mean age was 37.9 ± 10.8 (18 - 71) years and 45% were female. Age, gender, graft functions and follow-up period of the groups were similar. Augmentation index was 15.2 ± 12.6% in CNI and 18.8 ± 14.0% in mTORi groups (p > 0.05). There was no difference regarding carotid-femoral pulse wave velocity between groups. Arterial stiffness was positively correlated with age, total cholesterol, LDL cholesterol, mean arterial pressure (MAP) and proteinuria. MGP levels were higher in the mTORi group but were not predictors for carotid-femoral pulse wave velocity.

CONCLUSION

Rather than specific immunosuppressive drug effects, conventional risk factors, blood pressure and proteinuria are the most important predictors for arterial stiffness in renal transplant patients.

Plasma osteoprotegerin, arterial stiffness, and mortality in normoalbuminemic Japanese hemodialysis patients

A high circulating osteoprotegerin (OPG) level may be a risk factor for vascular calcification and mortality in hemodialysis patients. OPG and pulse wave velocity (PWV) were measured at baseline in 151 normoalbuminemic, long-term (>3 years) Japanese hemodialysis patients who were prospectively followed for 6 years. In long-term normoalbuminemic Japanese hemodialysis patients, OPG levels were strongly linked with both arterial stiffness and worse outcome.

INTRODUCTION

A high circulating OPG level is reported to be a risk factor for vascular calcification and mortality in Western chronic kidney disease (CKD) patients but it is not known if this is true for Japanese CKD patients, where a different risk profile may operate.

METHODS

OPG and PWV were measured at baseline in 151 normoalbuminemic, long-term (>3 years) Japanese hemodialysis patients (median age 62 years) who were prospectively followed for 6 years.

RESULTS

OPG levels were associated in multivariate analysis with age, dialysis vintage, history of cardiovascular disease (CVD) and parathyroid hormone levels. C-reactive protein levels did not correlate with OPG. Patients with clinical history of CVD had significantly higher OPG levels and OPG levels were positively correlated to PWV, an index of arterial stiffness. These associations were independent of age, sex, dialysis vintage, and diabetes. During the follow-up period, 40 deaths, including 25 cardiovascular deaths, were recorded. In crude analysis, each unit of increase in OPG was associated with increased all-cause (hazard ratios 1.14, 95% confidence interval 1.08-1.20) and CVD mortality (1.14 [1.07-1.21]), which persisted after adjustment for age, sex, dialysis vintage, diabetes, and baseline CVD (1.12 [1.05-1.19] and 1.11 [1.02-1.19], all-cause and CVD mortality, respectively).

CONCLUSIONS

In long-term normoalbuminemic Japanese hemodialysis patients, with low prevalence of inflammation, OPG levels were strongly linked with both arterial stiffness and worse outcome.

Increased expression of pro-inflammatory genes in abdominal subcutaneous fat in advanced chronic kidney disease patients

OBJECTIVES

Low-grade systemic inflammation, oxidative stress and peripheral insulin resistance are intimately associated and contribute to the increased risk of cardiovascular complications in advanced chronic kidney disease (CKD). Because altered adipose tissue activities have previously been linked to pathophysiological processes in various inflammatory and metabolic diseases we hypothesized that the uraemic milieu in patients with CKD may interact with the adipose tissue, provoking an unfavourable shift in its transcriptional output.

DESIGN

Twenty-one adipokine mRNAs were quantified in abdominal subcutaneous adipose tissue (SAT) biopsies and serum/plasma concentrations of inflammatory markers and related protein products were measured.

SETTING

The study was conducted at the Karolinska University Hospital, Huddinge, and Karolinska Institutet, Stockholm, Sweden.

SUBJECTS

Thirty-seven patients with CKD [15 women, median 58 (interquartile range 49-65) years] and nine nonuraemic individuals [four women, age 62 (45-64) years] were recruited prior to initiation of peritoneal dialysis catheter insertion or elective hernia repair/laparoscopic cholecystectomy, respectively.

RESULTS

Even after correction for body mass index, SAT from patients showed a significant upregulation of inflammatory pathway genes interleukin 6 (3.0-fold, P=0.0002) and suppressor of cytokine signalling 3 (2.5-fold, P=0.01), as well as downregulation of leptin (2.0-fold, P=0.03) and the oxidative stress genes uncoupling protein 2 (1.5-fold, P=0.03) and cytochrome b-245, alpha polypeptide (1.5-fold, P=0.005), in relation to controls.

CONCLUSIONS

These gene expression differences suggest that inflammatory and oxidative stress activities may be important features of the intrinsic properties of uraemic adipose tissue, which may have significant effects on the uraemic phenotype.

Temporal discrepancies in the association between the apoB/apoA-I ratio and mortality in incident dialysis patients

BACKGROUND

In the general population, a high apoB/apoA-I ratio is a strong risk factor for cardiovascular disease and mortality. However, whether this is the case in chronic kidney disease (CKD) patients is currently unknown.

STUDY DESIGN

The apoB/apoA-I ratio was evaluated in 391 incident CKD stage 5 patients examined close to dialysis initiation, and again after 1 year of dialysis in a subgroup of 182 patients, subsequently followed for up to 3 years.

RESULTS

Baseline values of the apoB/apoA-I ratio as well as changes in the ratio during the first year of dialysis correlated with body mass index (BMI) and fat mass. The baseline apoB/apoA-I ratio showed no association with 4-year mortality. However, after adjustment for confounders, a high apoB/apoA-I ratio (>0.9) predicted short-term (first year) survival [hazard ratio (HR): 0.35; 95% confidence interval (CI): 0.13-0.85)] and long-term (next 3 years) mortality (HR: 1.72; 95% CI: 1.01-2.96). An increase in the apoB/apoA-I ratio during the first year of dialysis was linked to a survival advantage thereafter (HR: 0.48; 95% CI: 0.22-0.98). However, this association lost its significance (HR: 0.62; 95% CI: 0.26-1.36) after adjustment for indices of protein-energy wasting.

CONCLUSIONS

A high apoB/apoA-I ratio and an increase in this ratio during the first year on dialysis were associated with short-term survival advantage in CKD patients. This paradoxical relationship represents an example of the so-called reverse epidemiology phenomenon in CKD patients and suggests that the apoB/apoA-I ratio should always be interpreted with caution in this patient population.

[Retrorectal cystic hamartoma (tailgut cyst): radiologic and pathologic findings]

Cystic hamartoma is a rare congenital lesion that presents as a presacral mass. It arises from remnants of the embryonic postanal gut. It is more common in women and usually presents in middle age. It is usually asymptomatic. It is difficult to distinguish the imaging appearance of cystic hamartoma from that of many other presacral cysts; therefore, histologic analysis is essential for the definitive diagnosis. Complete surgical excision is indicated to establish the diagnosis and avoid complications (infection and malignant transformation).

Low serum fetuin-A concentration predicts poor outcome only in the presence of inflammation in prevalent haemodialysis patients

BACKGROUND

Fetuin-A, a negative acute phase protein that inhibits vascular calcification, has a controversial association with mortality in chronic kidney disease (CKD) patients. Chronic inflammation, which is common in CKD, may promote vascular calcification.

MATERIALS AND METHODS

We investigated the impact of inflammation on the relationship between serum fetuin-A and mortality (42 months) in 222 prevalent haemodialysis (HD) patients.

RESULTS

Serum fetuin correlated negatively with comorbidity score (assessed by Davies score) and circulating inflammatory markers. Patients with low fetuin-A levels (< median) had higher mortality (Hazard ratio 'HR' 2.2; CI 1.4-3.5, P < 0.001), but this association was lost after adjustment for age, gender, comorbidities score, dialysis vintage and inflammation (CRP > median). In inflamed patients with low fetuin a significantly independent association with mortality (HR 2.3; CI 1.2-4.5, P = 0.01) was observed compared to non-inflamed patients with high fetuin-A, after adjusting for the same variables. Non-inflamed patients with low fetuin-A and inflamed patients with high fetuin-A did not have increased mortality compared to non-inflamed patients with high fetuin-A.

CONCLUSIONS

The results show that low levels of serum fetuin-A are associated with increased mortality in HD patients only in the presence of inflammation. This suggests that coexistence of a low serum fetuin-A level and low-grade inflammation exerts an additive effect on the risk of death in HD patients.

The long pentraxin PTX-3 in prevalent hemodialysis patients: associations with comorbidities and mortality

BACKGROUND

Pentraxin (PTX)-3, a new candidate marker for inflammation is expressed in a variety of cell types. Recently, we have shown that increase in PTX-3 level is associated with clinical outcome in incident CKD stage 5 patients at start of renal replacement therapy. However, no data are available on PTX-3 and its relationship with clinical outcome in prevalent dialysis patients.

METHODS

We analyzed plasma PTX-3 concentrations in relation to comorbidities (Davies score), protein-energy wasting (PEW) and inflammation markers in 200 prevalent hemodialysis (HD) patients, aged 64 +/- 14 years, who had been on HD treatment for a median period of 36 months. Survival (42 months) was analyzed in relation to PTX-3 levels (high PTX-3 tertile vs. low two tertiles).

RESULTS

Plasma PTX-3 correlated positively with C-reactive protein and interleukin-6, and negatively with s-albumin and fetuin-A. Patients with cardiovascular disease (CVD) and PEW had higher levels of PTX-3 than their counterparts and PTX-3 was associated with comorbidity score. In multiple logistic regression analysis, the high comorbidity score and PEW were the significant predictive variables of high PTX-3. In unadjusted analysis high PTX-3 was significantly associated with all-cause mortality. After adjustment for sex, age, dialysis vintage, comorbidity score, PEW and CRP using the multivariate Cox regression analysis, death rate was still significantly higher in patients with high PTX-3 (HR 1.7; CI 1.1-2.7, P = 0.03).

CONCLUSION

Markedly increased levels of PTX-3 were found in HD patients with signs of CVD and PEW. In addition, the concentration of PTX-3 was associated with inflammation markers and comorbidity score. Our data also shows that high PTX-3 level was independently associated with all-cause mortality.

Telomere attrition is associated with inflammation, low fetuin-A levels and high mortality in prevalent haemodialysis patients

INTRODUCTION

Chronic kidney disease (CKD) predisposes to a 10- to 20-fold increased cardiovascular risk. Patients undergo accelerated atherogenesis and vascular ageing. We investigated whether telomere attrition, a marker of cell senescence, contributes to this increased mortality risk.

METHODS

This is a cross-sectional study in prevalent haemodialysis patients [n = 175; 98 Males; median (range) age: 66 (23-86) years]. Biochemical markers of oxidative stress and inflammatory status were measured in relation to the patient's leucocyte telomere length. Overall mortality was assessed after a median of 31 (range 2-42) months.

RESULTS

Telomere length was shorter in CKD men, despite women being older (average +/- SD 6.41 +/- 1.23 vs. 6.96 +/- 1.48 kb, P = 0.002). Telomere length was associated with age (rho = -0.18, P = 0.01), fetuin-A (rho = 0.26, P = 0.0004), high-sensitivity C-reactive protein (rho = -0.21, P = 0.005) and IL-6 (rho = -0.17, P = 0.02). In a multivariate logistic regression (pseudo r(2) = 0.14), telomere length was associated with age >65 years (odds ratio: 2.11; 95% CI: 1.10, 4.06), sex (2.01; 1.05, 3.86), fetuin-A (1.85; 0.97, 3.50) and white blood cell count (2.04; 1.02, 4.09). Receiver operating characteristic curves identified a telomere length < 6.28 kb as a fair predictor of mortality. Finally, reduced telomere length was associated with increased mortality, independently of age, gender and inflammation (likelihood ratio 41.6, P < 0.0001), but dependently on fetuin-A levels.

CONCLUSION

Age and male gender seem to be important contributors to reduced telomere length in CKD patients, possibly via persistent inflammation. Reduced telomere length also contributes to the mortality risk of these patients through pathways that could involve circulating levels of fetuin-A.

Clinical and biochemical implications of low thyroid hormone levels (total and free forms) in euthyroid patients with chronic kidney disease

OBJECTIVES

In this study, we explore the associations of decreased thyroid hormone levels with inflammation, wasting and survival in biochemically euthyroid patients with end-stage renal disease (ESRD).

DESIGN

After exclusion of 23 patients with thyroid-stimulating hormone (TSH) values outside the normal range (0.1-4.5 mIU L(-1)), 187 clinically and biochemically euthyroid incident ESRD stage 5 patients starting dialysis were followed for a median of 20 (range 1-60) months. Measurements of total and free forms of thyroid hormones, s-albumin, hs-CRP, interleukin (IL)-6, vascular adhesion molecule (VCAM)-1 and insulin-like growth factor 1 (IGF-1) were performed at baseline.

RESULTS

In this population, 17 out of 210 patients (8%) were defined as subclinically hypothyroid. Multivariate analysis, according to receiver operating characteristic (ROC) curves, showed that mortality was best predicted by total triiodothyronine (T3). When using the cut-off levels derived from ROC, low T3 levels were associated with increased inflammation (higher hs-CRP, IL-6 and VCAM-1) and lower concentration of both s-albumin and IGF-1. Finally, low T3 but not low free triiodothyronine was associated with worse all-cause (Likelihood ratio = 45.4; P < 0.0001) and cardiovascular mortality (Likelihood ratio = 47.8; P < 0.0001) after adjustment for confounding factors.

CONCLUSION

This study showed that low T3 levels are independent predictors of all-cause and also cardiovascular disease mortality in biochemically euthyroid patients, perhaps due to an intimate association with inflammation. Based on these results, the use of T3 levels in studies assessing the relationship between thyroid dysfunction and mortality risk is recommended.

Low-grade inflammation in chronic kidney disease patients before the start of renal replacement therapy: sources and consequences

Low-grade inflammation is a common feature of chronic kidney disease (CKD) already before the start of renal replacement therapy, and evidence suggests that persistent inflammation may also be per se a risk factor for progression of CKD and vascular disease. Many factors, including retention of pro-inflammatory cytokines, advanced glycation end products, reactive oxygen species, autonomic dysfunctions and volume overload may contribute to inflammation when renal function declines. The aim of the present review is to summarize the causes and consequences of a chronic inflammatory state in the CKD population before start of renal replacement therapy, with special emphasis in polymorphnuclear leukocyte priming, which may be a key mediator in the induction of a vicious circle of oxidative stress and inflammation in CKD. A more thorough characterization of uremic retention solutes with regard to their specific pro- and anti-inflammatory properties is needed.

One-month administration of hydroxytyrosol, a phenolic antioxidant present in olive oil, to hyperlipemic rabbits improves blood lipid profile, antioxidant status and reduces atherosclerosis development

The present study analysed the effects of hydroxytyrosol (HT) on blood lipids, antioxidant status and the progression of aortic lesions in hyperlipemic rabbits. Sixty-four rabbits were distributed into eight groups of animals (n = 8). Animal groups C, A and H were fed for 1-month with a control diet containing sunflower oil (C), an atherogenic diet (A) high in saturated fat and cholesterol or the A diet together with HT, respectively. The other five groups were fed for 2-months with diets C or A (groups CC or AA, respectively), or for 1-month with the A-diet followed by a further month with diet C, extra virgin olive oil diet (O) or diet C with HT (groups AC, AO and AH, respectively). Four milligram of HT/kg body weight were used in the study. Fifty and 42% decrease in total cholesterol and triacylglycerols, respectively, and a 2.3-fold increase in HDL-cholesterol were observed in the AH group but not in the H group. The HT-supplemented groups improved their antioxidant status and reduced the size of atherosclerotic lesions measured as intimal layer areas of the aortic arch when compared with control animals. We conclude that HT supplementation may have cardioprotective effects in vivo.

[Cardiovascular effects of omega-3-fatty acids and alternatives to increase their intake]

Cardiovascular diseases are the main mortality cause in Europe, the USA and a great extent of Asia. There are several risk factors associated with cardiovascular diseases, such as increased total cholesterol, homocysteine and triglycerides, hypertension, diabetes, and reduced levels of HDL-cholesterol. Many of these risk factors are diet influenced. In spite of the great amount of foods enriched with n-3 fatty acids available at the market, the knowledge about the effects produced by regular intake of these foods still is a challenge in the majority of cases. It appears that intake of foods enriches with n-3 polyunsatured fatty acids is an option that may be effective in reducing risk factors for diseases, by substituting supplements without modifying consumer's alimentary habits. Also shown are the outcomes from a nutritional study undergone with a functional milk-bases food that contains n-3 fatty acids, oleic acid and vitamins.

Two-photon fluorescence lifetime imaging microscopy of macrophage-mediated antigen processing

Two-photon fluorescence lifetime imaging microscopy was used noninvasively to monitor a fluorescent antigen during macrophage-mediated endocytosis, intracellular vacuolar encapsulation, and protease-dependent processing. Fluorescein-conjugated bovine serum albumin (FITC-BSA) served as the soluble exogenous antigen. As a relatively nonfluorescent probe in the native state, the antigen was designed to reflect sequential intracellular antigen processing events through time-dependent changes in fluorescence properties. Using two-photon lifetime imaging microscopy, antigen processing events were monitored continuously for several hours. During this time, the initial fluorescein fluorescence lifetime of 0.5 ns increased to approximately 3.0 ns. Control experiments using fluorescein conjugated poly-L-lysine and poly-D-lysine demonstrated that the increase in fluorescence parameters observed with FITC-BSA were due to intracellular proteolysis since addition of the inert D-isomer did not promote an increase in fluorescence lifetime or intensity. Comparisons of intravacuolar and extracellular FITC-dextran concentration suggested active localization of dextran in the vacuoles by the macrophage. In addition, the kinetics of degradation observed using two-photon microscopy were similar to results obtained on the flow cytometer, thus validating the use of flow cytometry for future studies.

Anti-metatype antibody stabilization of Fv 4-4-20 variable domain dynamics

Anti-metatype (anti-Met) antibodies are immunoglobulins that specifically recognize and stabilize antibodies in their liganded or metatypic state, but lack specificity for either the hapten or the unliganded antibody. Autologous anti-Met antibodies were previously observed in vivo, suggesting that a metatypic autoantibody response could play a physiological role in the immune network, e.g. controlling the clearance of immune complexes from circulation. The first elicited anti-Met antibodies were against the fluorescein-liganded high affinity murine anti-fluorescein monoclonal antibody 4-4-20. The fluorescein-hapten system has proved to be an invaluable tool for both the recognition and characterization of the metatypic response by utilization of its spectral properties. In this investigation, hydrostatic pressure measurements, in conjunction with fluorescence spectroscopy, were performed on the recombinant Fv derivative (Fv 4-4-20) of the high affinity anti-fluorescein monoclonal antibody 4-4-20 complexed to anti-Met antibodies to study the influence of anti-Met antibodies of Fv 4-4-20 intervariable domain interactions. Anti-Met antibodies bound to liganded Fv 4-4-20 were observed to cause a change in the fluorescence properties of fluorescein that was not observed when anti-Met antibodies were bound to the liganded parent immunoglobulin. The variation of these spectral properties upon addition of anti-Met antibodies was shown to be correlated with dissociation of the variable domains in Fv 4-4-20 in response to its interaction with the anti-Met antibody. The ability to cause variable domain dissociation was dependent on whether monoclonal or polyclonal anti-Met antibodies were bound to the metatype. A model was proposed that elucidated the interaction of anti-Met antibodies, polyclonal and monoclonal, with variable domains of the primary anti-antigen antibody.

Temperature and pH dependence of fluorescein binding within the monoclonal antibody 9-40 active site as monitored by hydrostatic pressure

In a comparative study, the thermodynamic parameter, DeltaV, was obtained using hydrostatic pressure-induced dissociation of fluorescein (Fl) from the active site of monoclonal antibody (mAb) 9-40 and its mutant and native derivatives equilibrated at six pH values (8.0, 7.5, 7.0, 6.5, 6.0, and 5.5) and four temperatures (35, 25, 15, and 5 degrees C). mAb 9-40 and its Fab and single-chain Fv (scFv) derivatives at pH 8.0 were found to have identical Fl dissociation behavior under pressure as a function of temperature. The pressure dissociation at 25 degrees C as a function of pH showed a sigmoidal dependence of DeltaV with a midpoint value at pH 7.4 for mAb 9-40. Comparison of experimental results for scFv 9-40/212 with its mutant scFv 9-40/212Arg-34L indicated that the pH dependence of mAb 9-40 was due to the titration of His-34L in the active site. Iodide quenching of bound Fl showed that the hapten in this active site was solvent accessible. Imperfect packing, which leads to increased conformational dynamics, was determined as a possible cause of the low affinity for mAb 9-40.

Comparative properties of the single chain antibody and Fv derivatives of mAb 4-4-20. Relationship between interdomain interactions and the high affinity for fluorescein ligand

Recombinant Fv derivative of the high affinity murine anti-fluorescein monoclonal antibody 4-4-20 was constructed and expressed in high yields, relative to the single chain antibody (SCA) derivative (2 3-fold), in Escherichia coli. Both variable heavy (VH) and variable light (VL) domains, that accumulated as insoluble inclusion bodies, were isolated, denatured, mixed, refolded, and affinity-purified to yield active Fv 4-4-20. Affinity-purified Fv 4-4-20 showed identical ligand binding properties compared with the SCA construct, both were slightly lower than the affinities expressed by Fab or IgG 4-4-20. Proper protein folding was shown to be domain-independent by in vitro mixing of individually refolded variable domains to yield functional Fv protein. In solid phase and solution phase assays, Fv 4-4-20 closely approximated the SCA derivative in terms of both idiotype and metatype, confirming identical active site structures and conformations. The equilibrium dissociation constant (Kd) for the VL/VH association (1.43 x 10(-7) M), which was determined using the change in fluorescein spectral properties upon ligand binding, was relatively low considering the high affinity displayed by the Fv protein for fluorescein (Kd, 2.9 x 10(-10) M). Thus, domain-domain stability in the Fv and SCA 4-4-20 proteins cannot be the sole cause of reduced affinity (2-3-fold) for fluorescein as compared with the Fab or IgG form of 4-4-20. With their identical ligand binding and structural properties, the decreased SCA or Fv affinity for fluorescein must be an ultimate consequence of deletion of the CH1 and CL constant domains. Collectively, these results verify the importance of constant domain interactions in antibody variable domain structure-function analyses and future antibody engineering endeavors.

Relative conformational stabilities of single-chain pocket and groove-shaped antibody active sites including HCDR transplant intermediates

Stability measurements of SCA 04-01/212 (anti-ssDNA) which possesses a groove-shaped active site were performed by Gdn-HCl-induced unfolding, analyzed assuming a simple two-state equilibrium, and expressed as the free energy of unfolding, delta Gn-u. A delta Gn-u of 1.44 +/- 0.13 kcal/mol was determined experimentally for SCA 04-01/212. In addition, the conformational stabilities of HCDR transplants, hybrid antibody molecules resulting from the transplantation of HCDRs from SCA 4-4-20 (anti-fluorescein) into the corresponding regions of 04-01 in all combinations, were determined using the identical protocol applied to SCA 04-01. On the basis of the results of these stability experiments, the HCDR transplants were categorized into three groups, representing low, intermediate, and high stability. Data were discussed in terms of the relationships between structure-function and conformational stability pertaining to the groove-shaped antibody active site of SCA 04-01/212 and the pocket-shaped active site of SCA 4-4-20/212.

Oxygen penetration and diffusion into myoglobin revealed by quenching of zincprotoporphyrin IX fluorescence

Oxygen quenching experiments were carried out on zincprotoporphyrin IX reconstituted myoglobin (MbFe-->Zn) at different temperatures and two solvent viscosities. The data were fit to a dynamic model for quenching of fluorophores in protein interiors previously presented (Biophysical J., 45 (1984) 789-794). The parameters associated with the oxygen entry rate (k+), exit rate (k-), and migration rate (chi) in the protein were obtained at six temperatures and two viscosities (1 and 8 cp), along with the activation enthalpies associated with the above rates (k+ and k-). The partition coefficient (alpha) was calculated at each temperature along with the free energy, delta G0, associated with this partition. The rate parameters (k+, k-, chi) and the partition coefficient (alpha) have also been determined for the sample in 40% sucrose (8 cp), to evaluate the effect of bulk solvent viscosities on these values. The steady-state Stern-Volmer quenching plot was calculated using the rate parameters obtained from the analysis (of the dynamic model). Comparison of the Stern-Volmer points obtained using the dynamic model and those obtained experimentally showed excellent agreement.