Low density neutrophils and neutrophil extracellular traps (NETs) are new inflammatory players in heart failure

BACKGROUND

Heart failure with reduced (HFrEF) or preserved ejection fraction (HFpEF) is characterized by low-grade chronic inflammation. Circulating neutrophils regroup two subtypes termed high- and low-density neutrophils (HDNs and LDNs). LDNs represent less than 2% of total neutrophil under physiological conditions, but their count increase in multiple pathologies, releasing more inflammatory cytokines and neutrophil extracellular traps (NETs). The aims of this study were to assess the differential count and role of HDNs, LDNs and NETs-related activities in HF patients.

METHODS

HDNs and LDNs were isolated from human blood by density gradient and purified by FACS and their counts obtained by flow cytometry. NETs formation (NETosis) was quantified by confocal microscopy. Circulating inflammatory and NETosis biomarkers were measured by ELISA. Neutrophil adhesion onto human extracellular matrix (hECM) was assessed by optical microscopy.

RESULTS

A total of 140 individuals were enrolled, including 33 healthy volunteers (HV), 41 HFrEF (19 stable patients and 22 presenting acute decompensated HF; ADHF) and 66 HFpEF patients (36 stable patients and 30 presenting HF decompensation). HDNs and LDNs counts were significantly increased up to 39% and 2740% respectively in HF patients compared to HV. In HF patients, the correlations between LDNs counts and circulating inflammatory (CRP, IL-6 and -8), Troponin T, NT-proBNP and NETosis components were all significant. In vitro, LDNs expressed more H3Cit and NETs and were more pro-adhesive, with ADHFpEF patients presenting the highest pro-inflammatory profile.

CONCLUSIONS

HFpEF patients present higher levels of circulating LDNs and NETs related activities, which are the highest in the context of acute HF decompensation.

Low-Density Neutrophils Contribute to Subclinical Inflammation in Patients with Type 2 Diabetes

Type 2 diabetes (T2D) is characterized by low-grade inflammation. Low-density neutrophils (LDNs) represent normally less than 2% of total neutrophils but increase in multiple pathologies, releasing inflammatory cytokines and neutrophil extracellular traps (NETs). We assessed the count and role of high-density neutrophils (HDNs), LDNs, and NET-related activities in patients with T2D. HDNs and LDNs were purified by fluorescence-activated cell sorting (FACS) and counted by flow cytometry. Circulating inflammatory and NETs biomarkers were measured by ELISA (Enzyme Linked Immunosorbent Assay). NET formation was quantified by confocal microscopy. Neutrophil adhesion onto a human extracellular matrix (hECM) was assessed by optical microscopy. We recruited 22 healthy volunteers (HVs) and 18 patients with T2D. LDN counts in patients with diabetes were significantly higher (160%), along with circulating NETs biomarkers (citrullinated H3 histone (H3Cit), myeloperoxidase (MPO), and MPO-DNA (137%, 175%, and 69%, respectively) versus HV. Circulating interleukins (IL-6 and IL-8) and C-Reactive Protein (CRP) were significantly increased by 117%, 171%, and 79%, respectively, in patients compared to HVs. Isolated LDNs from patients expressed more H3Cit, MPO, and NETs, formed more NETs, and adhered more on hECM compared to LDNs from HVs. Patients with T2D present higher levels of circulating LDN- and NET-related biomarkers and associated pro-inflammatory activities.

Increased Imminent Fracture Risk in Liver Transplant Recipients Despite Bisphosphonate Therapy

BACKGROUND

Bone loss is significant after orthotopic liver transplant (OLT) and is associated with increased fracture risk and decreased quality of life. In post-transplant fracture prevention, the cornerstone of therapeutic management is bisphosphonates.

METHODS

We conducted a retrospective study in a cohort of 155 OLT recipients who received a bisphosphonate prescription at hospital discharge between 2012 and 2016 to investigate post-OLT fragility fracture incidence and predictive risk factors.

RESULTS

Before OLT, 14 patients presented a T score < -2.5 SD, and 23 patients (14.8%) had a history of fracture. During follow-up, the cumulative incidence of fractures on bisphosphonates (99.4% risedronate/alendronate) was 9.7% at 12 months and 13.1% at 24 months. The median time to first fragility fracture was 10 months (IQR, 3-22 months) and thus within the first 2 years of follow-up. Predictive factors of fragility fractures in multivariate Cox regression analyses included age 60 years or older (hazard ratio [HR], 2.61; 95% CI, 1.14-6.01; P = .02), post-transplant diabetes mellitus (HR, 3.82; 95% CI, 1.55-9.44; P = .004), and cholestatic disease (HR, 5.93; 95% CI, 2.30-15.26; P = .0002). Additionally, the female sex was associated with a strong trend toward increased fracture risk in univariate analysis (HR, 2.27; 95% CI, 1.00-5.15; P = .05), as well as a post-transplant absolute decrease in bone mineral density at the femoral neck and total hip (P = .08).

CONCLUSIONS

This real-world study reports a high incidence of fractures post-OLT despite bisphosphonate therapy. Age 60 years or older, post-transplant diabetes mellitus, cholestatic disease, female sex, and femoral neck and/or total hip bone mineral density loss contribute to increased imminent fracture risk in liver transplant recipients.

Neutrophils and Circulating Inflammatory Biomarkers in Diabetes Mellitus and Heart Failure With Preserved Ejection Fraction

Heart failure with preserved ejection fraction (HFpEF) is characterized by low-grade chronic inflammation, which could be exacerbated by type 2 diabetes mellitus (DM). We hypothesized that neutrophils in patients with DM and patients with HFpEF with/without DM contribute to low-grade inflammation through the release of pro-inflammatory cytokines. Venous blood was withdrawn from patients with DM (n = 22), HFpEF (n = 15), HFpEF with DM (n = 13), and healthy controls (CTL) (n = 21). Levels of circulating cytokines and in vitro cytokines released by isolated neutrophils were assessed by enzyme-linked immunosorbent assay. Compared with CTL, there was a significant decrease in circulating nitric oxide in patients with DM (p ≤0.001), HFpEF (p ≤0.05), and HFpEF with DM (p ≤0.001) up to 44%. Circulating soluble intercellular adhesion molecule-1 and vascular cell adhesion molecule-1 levels increased (up to 2.5-fold and 1.9-fold, respectively; p ≤0.001) in patients with HFpEF and patients with HFpEF and DM, whereas soluble E-selectin only increased in patients with HFpEF and DM (1.4-fold, p ≤0.001). Circulating vascular endothelial growth factor levels were similar in CTL and patients with DM but were decreased in patients with HFpEF with/without DM (up to 94%; p ≤0.001). Circulating C-reactive protein, interleukin (IL)-8, IL-6, and IL-receptor antagonist increased in all patient groups with a maximum of 3.3-fold, 4.7-fold, 4.8-fold, and 1.6-fold, respectively, in patients with HFpEF and patients with DM. In vitro, lipopolysaccharide increased neutrophils IL-6 release from HFpEF with DM (3.7-fold; p ≤0.001), and IL-8 release from DM and HFpEF with DM versus CTL (2.8-fold and 10.1-fold, respectively; p ≤0.001). IL-1 receptor antagonist and vascular endothelial growth factor release from HFpEF neutrophils significantly decreased up to 87.0% and 92.2%, respectively, versus CTL. Neutrophils from patients with DM and HFpEF release more cytokines than CTL. This increase in pro-inflammatory status may explain the greater event rate in patients with HFpEF and DM.

Angiopoietin 1 release from human neutrophils is independent from neutrophil extracellular traps (NETs)

Background

Neutrophils induce the synthesis and release of angiopoietin 1 (Ang1), a cytosolic growth factor involved in angiogenesis and capable of inducing several pro-inflammatory activities in neutrophils. Neutrophils also synthesize and release neutrophil extracellular traps (NETs), comprised from decondensed nuclear DNA filaments carrying proteins such as neutrophil elastase (NE), myeloperoxidase (MPO), proteinase 3 (PR3) and calprotectin (S100A8/S100A9), which together, contribute to the innate immune response against pathogens (e.g., bacteria). NETs are involved in various pathological conditions through pro-inflammatory, pro-thrombotic and endothelial dysfunction effects and have recently been found in heart failure (HF) and type 2 diabetes (T2DM) patients. The aim of the present study was to investigate the role of NETs on the synthesis and release of Ang1 by the neutrophils in patients with T2DM and HF with preserved ejection fraction (HFpEF) (stable or acute decompensated; ADHFpEF) with or without T2DM.

Results

Our data show that at basal level (PBS) and upon treatment with LPS, levels of NETs are slightly increased in patients suffering from T2DM, HFpEF ± T2DM and ADHF without (w/o) T2DM, whereas this increase was significant in ADHFpEF + T2DM patients compared to healthy control (HC) volunteers and ADHFpEF w/o T2DM. We also observed that treatments with PMA or A23187 increase the synthesis of Ang1 (from 150 to 250%) in HC and this effect is amplified in T2DM and in all cohorts of HF patients. Ang1 is completely released (100%) by neutrophils of all groups and does not bind to NETs as opposed to calprotectin.

Conclusions

Our study suggests that severely ill patients with HFpEF and diabetes synthesize and release a greater abundance of NETs while Ang1 exocytosis is independent of NETs synthesis.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12865-021-00442-8.

The effects of exercise training in adult solid organ transplant recipients: A systematic review and meta-analysis

Reduced exercise capacity can predispose solid organ transplant (SOT) recipients to higher risk of diabetes, cardiovascular complications, and mortality and impact their quality of life. This systematic review and meta-analysis investigated the effects of exercise training (versus no training) in adult SOT recipients. We conducted an electronic search of randomized controlled trials reporting on exercise interventions in SOT recipients. Primary outcomes were exercise capacity, quadriceps muscle strength, and health-related quality of life (HRQoL). Twenty-nine articles met the inclusion criteria. In 24 studies, there were either high risk of bias or some concerns about the potential risk of bias. There was an increase in exercise capacity (VO₂ peak) (SMD: 0.40; 95%CI 0.22-0.57; P = 0.0) and quadriceps muscle strength (SMD: 0.38; 95%CI 0.16-0.60; P = 0.001) in the exercise vs control groups. There were also improvements in several domains of the SF-36. Diastolic blood pressure improved in the exercise group compared to controls (SMD: -0.22; 95%CI -0.41-0.03; P = 0.02). Despite the considerable variation in exercise training characteristics and high risk of bias in the included studies, exercise training improved maximal exercise capacity, quadriceps muscle strength, HRQoL, and diastolic blood pressure and should be an essential part of the post-transplant care.

Changes in 6-minute walking distance in lung transplant candidates while participating in a home-based pre-habilitation program-A retrospective chart review

Home-based exercise programs may offer a less costly alternative to providing exercise pre-transplant to a large number of patients. We describe the changes in 6-minute walk distance (6MWD) in lung transplant candidates who participated in a home-based exercise program and their relationship to post-transplant outcomes. Retrospectively, we investigated 159 individuals while awaiting transplantation who performed the surgery between 2011 and 2015. Primary outcome was 6MWD at time of assessment for transplant, last test prior to transplant and one-month post-transplant. 6MWD decreased by 28 ± 93.9 m between the time of assessment and the last 6MWD prior to transplantation (P < .001). Forty-one patients (25.8%) increased their 6MWD (mean + 85.8 ± 42.8 m); 72 patients (45.3%) decreased their 6MWD (mean -109.8 ± 71.2 m); and 46 patients (28.9%) had no change in 6MWD (-1.5 ± 15.7 m). There was a moderate correlation (r = .528; P < .001) between the last 6MWD prior to transplant and 6MWD post-transplant. Change in 6MWD prior to transplant weakly correlated with length of time on mechanical ventilation (r = -.185; P = .034). When adjusted for covariates, change in 6MWD prior to transplant was not associated with length of time on mechanical ventilation, total hospital LOS, or intensive care unit LOS. The majority of the patients were able to either increase or maintain their 6MWD while participating in a home-based pre-habilitation program during the waiting list period. Prospective research is needed to evaluate the effects of home-based pre-habilitation program for lung candidates.

CRP Induces NETosis in Heart Failure Patients with or without Diabetes

C-reactive protein (CRP) is recognized as a biomarker of chronic, low-grade inflammation associated with vascular disorders. Lately, the role of neutrophils and neutrophil extracellular traps (NETs) has been investigated as a potential source of chronic inflammation and cardiovascular complications. This study investigated NETs as a marker of inflammation in patients with symptomatic heart failure (HF) with or without type 2 diabetes (T2DM) and examined the correlation between NETs and CRP. We performed a noninterventional study including patients with HF with or without T2DM, T2DM, and a healthy control (HC) group. NETs and other inflammatory markers in serum were measured by ELISA. The release of NETs (NETosis) in vitro under various stimuli was measured by confocal microscopy. The levels of NETs in the serum of HF patients were significantly higher compared with HC (112%). Serum CRP concentrations were significantly increased in HF and HF plus T2DM patients compared with HC, and a positive correlation was observed between serum CRP and NETs levels. Neutrophils from HF and HF plus T2DM patients underwent in vitro NETs release faster than T2DM and HC without any stimuli. In vitro, serum collected from the HF and the HF plus T2DM group induced NETosis in healthy neutrophils significantly more when compared with HC and T2DM, which was prevented by depletion from CRP. We confirmed in vitro that CRP induces a concentration-dependent NETs synthesis. This study proposes a mechanism by which CRP increases the risk of future cardiovascular events and supports mounting evidences on the role of neutrophils in chronic low-grade inflammation associated with HF.

Hypomagnesemia During Teriparatide Treatment in Osteoporosis: Incidence and Determinants

In our clinical experience, we have encountered patients who developed hypomagnesemia after the introduction of teriparatide. Some trials have reported hypomagnesemia as an adverse event during teriparatide treatment, but this issue had never been studied specifically. Our objective was twofold: 1) determine the incidence of hypomagnesemia (serum magnesium <0.7 mmol/L) associated with teriparatide in a retrospective cohort and 2) identify the predisposing factors to hypomagnesemia in this cohort. We reviewed the files of 53 patients treated for severe osteoporosis with teriparatide for 6 to 24 months between May 2008 and January 2016. Serum magnesium levels were measured at 0, 3, 6, 12, 18, and 24 months. In the full cohort, we observed an average decrease of serum magnesium of 0.075 mmol/L, 0.069 mmol/L, 0.085 mmol/L, 0.086 mmol/L (p < 0.001) at 3, 6, 12 months, and at the end of the treatment, respectively. The cumulative incidence of hypomagnesemia during treatment with teriparatide was 35.9% (19 patients). Patients' older age (71.1 versus 65.1 years; p = 0.05) and lower baseline level of magnesium before teriparatide treatment (0.81 mmol/L versus 0.85 mmol/L; p = 0.03) were significant risk factors for teriparatide-induced hypomagnesemia. The average decrease of serum magnesium was greater in the patients who developed hypomagnesemia compared with normomagnesemic patients at 3 months (0.110 mmol/L versus 0.054 mmol/L; p = 0.02), 6 months (0.139 mmol/L versus 0.036 mmol/L; p < 0.001), and 12 months (0.156 mmol/L versus 0.048 mmol/L; p < 0.001). Serum calcium, creatinine, and parathyroid hormone remained normal throughout the treatment period. We observed a statistically significant decrease in the serum magnesium levels in patients treated with teriparatide for severe osteoporosis. Older age and lower baseline magnesium were significant determinants of hypomagnesemia. Closer monitoring of serum magnesium level should be considered in these patients. © 2018 American Society for Bone and Mineral Research.

Physician Practice Patterns and Barriers to Counselling on Physical Activity in Solid Organ Transplant Recipients

Background

Many solid organ transplant (SOT) recipients fail to meet the recommended physical activity (PA) levels. “Physician recommendation” has previously been reported by SOT recipients as a key facilitator to being more physically active. The purpose of this study was to determine the proportion of Canadian SOT physicians providing PA counselling and identify barriers to including such counselling as part of the SOT recipients’ routine care.

Material/Methods

We conducted a cross-sectional web-based survey study to evaluate physicians’ PA counselling practices, including the prevalence and barriers to such practice. A survey link was sent to a convenience sample of transplant physicians who are members of the Canadian Society of Transplantation.

Results

Thirty-four physicians (13.6%) participated in the survey. While 97% (n=33) of the participants reported providing PA counselling to their transplant patients, only 18% (n=6) responded they were very confident in PA counselling. Lack of time (n=19; 56%) and a lack of exercise guidelines (n=18; 53%) were identified as the main barriers to PA counselling.

Conclusions

Incorporating sufficient PA knowledge into physicians’ educational curricula system, developing specific PA guidelines as well as establishing an easier referral system to exercise specialists might improve the frequency and quality of PA counselling post-transplant.

Association Between Metformin Adherence and All-Cause Mortality Among New Users of Metformin: A Nested Case-Control Study

BACKGROUND

Metformin presents better survival rates than other oral antidiabetics in the treatment of type 2 diabetes. However, these benefits may be dampened by inadequate treatment adherence.

OBJECTIVE

We aimed to investigate the relationship between adherence level to metformin therapy and all-cause mortality over 10 years in incident metformin users.

METHODS

A nested case-control study was conducted using a large cohort of beneficiaries of the Quebec public drug insurance plan, aged 45 to 85 years, who initiated metformin between 2000 and 2009. Each case of all-cause death during follow-up was matched with up to 10 controls. Adherence to metformin was measured using the medication possession ratio (MPR). Conditional logistic regression models were used to estimate rate ratios (RRs) for mortality between adherent (MPR ≥ 80%) and nonadherent patients (MPR < 80%). Subgroup analyses were conducted according to age (45-64 and 65-85 years) and comedication use (antihypertensive/cardiovascular drugs and statins).

RESULTS

The cohort included 82 720 incident metformin users, followed up for 2.4 [0.8-4.4] years (median [interquartile range]) and 4747 cases of all-cause deaths. Analyses revealed decreased mortality risks after long-term adherence to metformin. Specifically, RRs were 0.84 (95% CI = [0.71-0.98]) and 0.69 [0.57-0.85] after 4 to 6 and ≥6 years of adherence to metformin, respectively. Survival benefits of long-term adherence (≥4 years) were also observed across most subgroups and particularly in patients using neither antihypertensive/cardiovascular drugs nor statins (0.57 [0.41-0.77]).

CONCLUSIONS

Long-term adherence to metformin is associated with decreased risks of all-cause mortality in incident metformin users. Further research should investigate whether survival benefits vary according to the comorbidity burden of patients.

Impact of Resistance Training on Factors Involved in the Development of New-Onset Diabetes After Transplantation in Renal Transplant Recipients: An Open Randomized Pilot Study

OBJECTIVES

New-onsetdiabetes after transplant (NODAT) is a major contributor to cardiovascular disease after transplantation. Kidney transplantation (KT) recipients have low levels of exercise capacity. Resistance training (RT) might be of special benefit in this population because underlying disease and immunosuppressive drugs favour muscle loss and insulin resistance. The aim of this study was to assess the feasibility of implementing an RT program within a population of KT recipients and its impact on the incidence of NODAT and cardiometabolic risk factors.

METHODS

This pilot study was an open-randomized study. We randomized 24 patients with a 1:1 allocation to 2 parallel groups, the exercise group (E) or the control group (C). The E group was submitted to RT 3 times a week for 16 weeks. Anthropometric, body composition, cardiometabolic risk factors, muscle strength, cardiorespiratory fitness and well-being were measured before and after 16 weeks.

RESULTS

Of the 24 recruited participants, 20 completed the study (10 in the E group and 10 in the C group). No injuries were reported. The intervention was associated with a significant increase in muscle strength (p=0.003). A significant group effect, in favour of the E group, was detected for the well-being score (p=0.03). However, no changes in body composition, cardiometabolic risk factors or cardiorespiratory fitness were noted for either group after the intervention.

CONCLUSIONS

This pilot study suggests that RT appears to be secure and feasible and improves strength and well-being in patients after KT. However, it does not improve cardiometabolic risk factors.

Persistence and adherence to oral antidiabetics: a population-based cohort study

AIMS

A population-based cohort study design was used to estimate persistence rate, re-initiation rate after discontinuation, and adherence level among incident users of oral antidiabetics (OADs), and to investigate predictors of non-persistence and non-adherence.

METHODS

Incident OAD users were identified using healthcare databases of residents covered by the public drug insurance plan of the Province of Quebec, Canada. Patients initiated OAD therapy between January 2000 and October 2009 and were aged 45-85 years at cohort entry. Persistence rate, re-initiation after discontinuation, and adherence level were assessed over 2 years. Predictors of non-persistence and non-adherence were analyzed using Cox and logistic regression models, respectively.

RESULTS

The cohort included 160,231 incident OAD users at entry. One year after OAD initiation, persistence rate was 51 % and adherence level 67 %. Among those deemed non-persistent, 80.6 % re-initiated OAD therapy within 12 months of discontinuation; a proportion increasing with primary persistence duration. The 1-year persistence rate varied according to OAD classes; being the highest for thiazolidinediones (62 %) and the lowest for alpha-glucosidase inhibitors (30 %). The likelihood for non-persistence was 39-54 % higher when drug copayments were required. Conversely, OAD discontinuation was least likely for patients with schizophrenia [hazard ratio 0.70 (95 % CI 0.67-0.73)], dyslipidemia [0.85 (0.84-0.87)], anticoagulation [0.86 (0.83-0.88)], hypertension [0.87 (0.85-0.88)], and ≥7 medications [0.90 (0.88-0.91)]. Predictors of non-adherence were similar.

CONCLUSIONS

Non-persistence and non-adherence to OAD therapy were common, although re-initiation rate was high. OAD classes, drug copayments, comorbidities and co-medications may help identifying those who were more likely to benefit from counseling.

Weight gain after orthotopic liver transplantation: is nonalcoholic fatty liver disease cirrhosis a risk factor for greater weight gain?

Posttransplant weight gain is common after orthotopic liver transplantation. We sought to determine the extent of weight gain at 5 years after transplantation in patients with nonalcoholic fatty liver disease (NAFLD) cirrhosis versus patients with other types of cirrhosis (non-NAFLD). We studied 126 liver transplants performed between 2005 and 2007 at Saint Luc Hospital, University of Montreal. Seventeen of the 126 patients (13.5%) had NAFLD cirrhosis. Ascites volume was difficult to assess, so we used the body mass index (BMI) at 3 months as the reference BMI. All patients gained weight after transplantation, but BMI increased significantly more and earlier among the NAFLD patients [4.8 versus 1.5 kg/m(2) at 1 year (P = 0.001), 5.0 versus 2.3 kg/m(2) at 2 years (P = 0.01), and 5.6 versus 2.6 kg/m(2) at 5 years (P = 0.009)] in comparison with non-NAFLD patients in unadjusted analyses. The greatest BMI increase over time was investigated with univariate and multivariate logistic regression analyses. The BMI increase was divided into tertiles for each period of time observed. The greatest BMI increase over time was defined as the top tertile of BMI increase. After adjustments for potential confounders (ie, total cholesterol, diabetes, and length of hospital stay), NAFLD was no longer associated with a risk of a greater BMI increase [odds ratio (OR) = 3.73 at 1 year (P = 0.11), OR = 2.15 at 2 years (P = 0.34), and OR = 2.87 at 5 years (P = 0.30)]. These findings suggest the need for multidisciplinary, early, and close weight monitoring for all patients. All patients could benefit from pretransplant counseling regarding weight gain and its consequences.

Role of zoledronic acid in the prevention and treatment of osteoporosis

Taken once a year, intravenous zoledronic acid (Zol) (Reclast® or Aclasta®) is a third-generation nitrogen-containing bisphosphonate that is effective compared with placebo in reducing the risk of fractures in patients with postmenopausal osteoporosis and recent low-trauma hip fracture. In glucocorticoid-induced osteoporosis, there is no significant difference between Zol and risedronate for new fractures. Improvements in bone mineral density and early reduction of bone remodeling markers are observed in postmenopausal osteoporosis, recent low-trauma hip fracture, and glucocorticoid-induced osteoporosis. Given that Zol is generally well tolerated and very convenient, it is an interesting therapeutic option for aging patients who take multiple oral drugs, who have adherence or gastrointestinal tolerance issues, and who have an indication for oral bisphosphonates. Zol is not recommended for patients with severe renal impairment. Vitamin D deficiency should be corrected before the administration of Zol.

New-onset diabetes after transplantation: risk factors and clinical impact

With improvements in patient and graft survival, increasing attention has been placed on complications that contribute to long-term patient morbidity and mortality. New-onset diabetes after transplantation (NODAT) is a common complication of solid-organ transplantation, and is a strong predictor of graft failure and cardiovascular mortality in the transplant population. Risk factors for NODAT in transplant recipients are similar to those in non-transplant patients, but transplant-specific risk factors such as hepatitis C (HCV) infection, corticosteroids and calcineurin inhibitors play a dominant role in NODAT pathogenesis. Management of NODAT is similar to type 2 diabetes management in the general population. However, adjusting the immunosuppressant regimen to improve glucose tolerance must be weighed against the risk of allograft rejection. Lifestyle modification is currently the strategy with the least risk and the most benefit.

Osteoporosis among patients with type 1 and type 2 diabetes

Both diabetes and fractures are prevalent in adults. The relationship between diabetes and osteoporosis is complex and, although it has been investigated extensively, the subject remains controversial. While low bone mineral density (BMD) is consistently observed in type 1 diabetes, the relationship is less clear in type 2 diabetes, with some studies reporting modestly increased or unchanged BMD. Both type 1 and type 2 diabetes have been associated with a higher risk of fractures. Despite discrepancies between BMD and fracture rates, clinical trials uniformly support the fact that new bone formation and bone microarchitecture and, thus, bone quality, are altered in both types of diabetes. Although a causal association between diabetes and osteoporosis cannot be established on the basis of existing data, it is possible to conclude from many studies and from a better understanding of the physiopathology of diabetes that it can increase the risk of fractures through skeletal (decreased BMD and bone quality) and extraskeletal (increased risk of falls) factors. Even though osteoporosis screening or prophylactic treatment in all patients with type 1 and type 2 diabetes is not being recommended at present, such patient populations should be given general guidelines regarding calcium and vitamin D intakes, exercise and the avoidance of potential risk factors for osteoporosis. The extent of diagnostic and therapeutic interventions should be based on the individual's risk profile for fractures.

Acute regulation of circulating parathyroid hormone (PTH) molecular forms by calcium: utility of PTH fragments/PTH(1-84) ratios derived from three generations of PTH assays

CONTEXT

The quantitative evaluation of circulating PTH peaks revealed by PTH assays after HPLC separation constitutes the best way to study the behavior of PTH molecular forms, but it is also impractical.

OBJECTIVE

The objective of the study was to investigate the regulation of circulating PTH molecular forms by calcium through the use of PTH fragments/PTH (1-84) ratios derived from PTH assays with different specificities before and after HPLC separation of circulating PTH.

DESIGN

CaCl2 and Na citrate were infused in eight volunteers. PTH was measured in serum and HPLC fractions at different calcium concentrations in PTH assays reacting with regions 1-2 (CA), 12-18 (T), and 65-69 (C) of the PTH structure.

RESULTS

From hypo- to hypercalcemia, the C/CA ratio had the highest range (1.92 to 9.75; P < 0.001), and the C/T ratio had a higher range (1.69 to 6.11; P < 0.01) than the T/CA ratio (1.15 to 1.86). Human (h) PTH (1-84) represented 32.7 and 4.3% of circulating PTH in hypo- and hypercalcemic HPLC profiles, respectively. These numbers were 5 and 0.9% for amino-terminal (N)-PTH, an amino-terminal form of PTH distinct from hPTH (1-84), 7.3 and 6.8% for non-(1-84) PTH or large C-PTH fragments with a partially preserved N structure, and 54.9 and 88.1% for C-PTH fragments missing a N structure. The HPLC C-PTH fragments to hPTH (1-84) ratio had the most extensive range (1.67 to 20.58). Despite their quantitative differences, all ratios identified identical behavior of PTH fragments relative to PTH (1-84).

CONCLUSIONS

PTH assay ratios are an adequate tool to investigate the modulation of PTH molecular forms, even if all PTH assays show some undesirable cross-reactivity with certain circulating forms of PTH.

Overproduction of an amino-terminal form of PTH distinct from human PTH(1-84) in a case of severe primary hyperparathyroidism: influence of medical treatment and surgery

OBJECTIVE

Rare patients with severe primary hyperparathyroidism present with large parathyroid tumours, severe hypercalcaemia, very high PTH levels and osteitis fibrosa cystica. Some of these patients display a large amount of C-PTH fragments in circulation and present with a higher C-PTH/I-PTH ratio than seen in less severe cases of primary hyperparathyroidism. We wanted to determine how PTH levels and circulating PTH high-performance liquid chromatography (HPLC) profiles analysed with PTH assays having different epitopes could be affected by medical and surgical treatment in such patients.

DESIGN

A 55-year-old man with severe hypercalcaemia (Ca(2+): 2.01 mmol/l), very high PTH levels (CA-PTH 82.1 and T-PTH 72 pmol/l) caused by a large parathyroid tumour (7.35 g) and accompanied by significant bone involvement (alkaline phosphatase of 185 UI/l and subperiostal bone resorption of hands) was referred to us. Blood was obtained at various time points during his medical treatment, before and after surgery, to measure parameters of calcium and phosphorus metabolism, and of bone turnover. HPLC separations of circulating PTH molecular forms were performed and analysed with PTH assays having 1-4 (CA), 12-18 (T), 26-32 (E) and 65-84 (C) epitopes.

RESULTS

Before surgery, serum Ca2+ was nearly normalized with hydratation, intravenous (IV) pamidronate and oral vitamin D administration. Despite a decrease in Ca2+ to 1.31 mmol/l, CA-PTH and T-PTH levels decreased by half in relation to a threefold increase in basal 1,25-dihydroxyvitamin D [1,25(OH)2D] level (94 to 337 pmol/l). After this initial positive response, hypercalcaemia and elevated CA- and T-PTH levels recurred even if 1,25(OH)2D levels remained elevated. The tumour was removed surgically and proved to be poorly differentiated with nuclear atypia and mitosis. After surgery, the Ca2+ level and PTH secretion normalized. The higher CA-PTH level relative to the T-PTH level observed before surgery in this patient was related to the oversecretion of an amino-terminal (N) form of PTH recognized by PTH assays with (1-4) or (26-32) epitopes but not by the T-PTH assay with a (12-18) epitope. This molecular form represented 50% of CA-PTH measured in this patient, but only 7% in less severe cases of primary hyperparathyroidism. It was unaffected by medical therapy and disappeared after surgery.

CONCLUSION

The relationship between the overexpression of this N-PTH molecular form and severe primary hyperparathyroidism remains unclear. Further studies will be required in these rare patients to see whether N-PTH is a marker of less well differentiated parathyroid tumours and/or relates to the overproduction of C-PTH fragments in the presence of severe hypercalcaemia.

Evidence that the amino-terminal composition of non-(1-84) parathyroid hormone fragments starts before position 19

BACKGROUND

Non-(1-84) parathyroid hormone (PTH) fragments are large C-terminal fragments of PTH with a partially preserved N-terminal structure. They differ from other C-terminal PTH fragments, which do not have an N-terminal structure and do not react in intact PTH assays. We aimed to identify the minimal N-terminal structure common to all non-(1-84) PTH fragments.

METHODS

Sera obtained from six healthy individuals and six patients with primary hyperparathyroidism, and six serum pools from dialysis patients with different PTH concentrations were fractionated by HPLC and analyzed by four different PTH assays. Each assay was characterized by saturation analysis of its detection antibody and capacity to react with different PTH fragments. Human PTH(1-84) [hPTH(1-84)] calibrators were normalized to an in-house hPTH(1-84) calibrator.

RESULTS

The cyclase-activating PTH (CA-PTH) assay had an early (1, 2,) epitope and reacted only with hPTH(1-84). The other assays had epitopes in region (13-34). Total and intact PTH assays had epitopes proximal to position 18 and reacted equally well with hPTH(1-84) and hPTH(7-84), and the Elecsys PTH assay had an epitope distal to position 19, being saturable by hPTH(18-48) and also reacting with [Tyr(34)]hPTH(19-84). The HPLC profiles obtained with these assays showed that non-(1-84) PTH fragments did not react in the CA-PTH assay, as expected. The amount of non-(1-84) PTH detected by the other three assays was similar when the assay results were normalized to a common calibrator.

CONCLUSIONS

The results suggest that the amount of non-(1-84) PTH detected by epitopes proximal or distal to position 19 of the PTH structure is identical, indicating a common minimum structure starting before position 19. This in turn points to a probable high-affinity interaction with the C-PTH receptor, as observed previously with [Tyr(34)]hPTH(19-84) in various cell lines and in mouse osteocytes with PTH/PTHrP type I receptor ablation.