Incorporating and interpreting regulatory guidance on estimands in diabetes clinical trials: The PIONEER 1 randomized clinical trial as an example

Regulatory guidelines describe the use of estimands in designing and conducting clinical trials. Estimands ensure alignment of the objectives with the design, conduct and analysis of a trial. An estimand is defined by four inter-related attributes: the population of interest, the variable (endpoint) of interest, the way intercurrent events are handled and the population level summary. A trial may employ multiple estimands to evaluate treatment effects from different perspectives in order to address different scientific questions. As estimands may be an unfamiliar concept for many clinicians treating diabetes, this paper reviews the estimand concept and uses the PIONEER 1 phase 3a clinical trial, which investigated the efficacy and safety of oral semaglutide vs placebo, as an example of the way in which estimands can be implemented and interpreted. In the PIONEER 1 trial, two estimands were employed for each efficacy endpoint and were labelled as: (a) the treatment policy estimand, used to assess the treatment effect regardless of use of rescue medication or discontinuation of trial product, and provides a broad perspective of the treatment effect in the population of patients with type 2 diabetes in clinical practice; and (b) the trial product estimand, used to assess the treatment effect if all patients had continued to use trial product for the planned duration of the trial without rescue medication, thereby providing information on the anticipated treatment effect of the medication. Both approaches are complementary to understanding the effect of the studied treatments.

Achieving glycaemic control without weight gain, hypoglycaemia, or gastrointestinal adverse events in type 2 diabetes in the SUSTAIN clinical trial programme

AIM

To evaluate the potential for semaglutide to help people with type 2 diabetes (T2D) achieve glycated haemoglobin (HbA1c) targets while avoiding unwanted outcomes, such as weight gain, hypoglycaemia and gastrointestinal (GI) side effects.

MATERIALS AND METHODS

Data from the phase IIIa SUSTAIN 1 to 5 clinical trials were analysed. Participants had inadequately controlled T2D and were drug-naïve (SUSTAIN 1) or on a range of background treatments (SUSTAIN 2 to 5). The main protocol-specified composite endpoint was the proportion of participants achieving HbA1c <53 mmol/mol (7.0%) at end of treatment (30 or 56 weeks) without weight gain and with no severe or blood glucose (BG)-confirmed symptomatic hypoglycaemia. A post hoc composite endpoint was the proportion of participants achieving the primary composite endpoint without moderate or severe GI adverse events (AEs).

RESULTS

Across the SUSTAIN trials 1 to 5, 3918 participants with T2D were randomized to once-weekly subcutaneous semaglutide 0.5 mg, 1.0 mg, or comparators (placebo, sitagliptin 100 mg, exenatide extended release 2.0 mg or insulin glargine). The proportion of participants achieving HbA1c <53 mmol/mol (7.0%) with no weight gain and no severe/BG-confirmed symptomatic hypoglycaemia was 47% to 66% (semaglutide 0.5 mg) and 57% to 74% (semaglutide 1.0 mg) vs 7% to 19% (placebo) and 16% to 29% (active comparators; all P < .0001). More participants achieved the primary composite endpoint with no moderate or severe GI AEs with semaglutide vs comparators (all P < .0001).

CONCLUSION

Semaglutide helped more people with T2D achieve HbA1c targets than did comparators in the SUSTAIN 1 to 5 trials, while avoiding unwanted outcomes such as weight gain, hypoglycaemia and GI side effects.

A 26-Week Randomized Controlled Trial of Semaglutide Once Daily Versus Liraglutide and Placebo in Patients With Type 2 Diabetes Suboptimally Controlled on Diet and Exercise With or Without Metformin

OBJECTIVE

To investigate the efficacy and safety of once-daily semaglutide in comparison with once-daily liraglutide and placebo in patients with type 2 diabetes.

RESEARCH DESIGN AND METHODS

This 26-week, multicenter, double-blind trial involved patients diagnosed with type 2 diabetes with HbA_1c 7.0-10.0% (53-86 mmol/mol) and treated with diet and exercise with or without metformin. Patients were randomized 2:2:1 to once-daily semaglutide, liraglutide, or placebo in one of four volume-matched doses (semaglutide 0.05, 0.1, 0.2, or 0.3 mg and liraglutide 0.3, 0.6, 1.2, or 1.8 mg, with both compared within each volume-matched dose group). Primary end point was change in HbA_1c from baseline to week 26.

RESULTS

In total, 705 randomized patients were exposed to trial products. At week 26, a dose-dependent change in HbA_1c was observed with semaglutide from -1.1% (0.05 mg) to -1.9% (0.3 mg) and with liraglutide from -0.5% (0.3 mg) to -1.3% (1.8 mg) (all P < 0.001 in favor of volume-matched semaglutide dose). Change with pooled placebo was -0.02% (P < 0.0001 vs. semaglutide). Gastrointestinal (GI) disorders were the most common adverse events (AEs) with semaglutide and liraglutide, occurring in 32.8-54.0% and 21.9-41.5% of patients, respectively.

CONCLUSIONS

Once-daily semaglutide at doses up to 0.3 mg/day resulted in greater reductions in HbA_1c compared with liraglutide or placebo but with a higher frequency of GI AEs.

Exposure-response analysis for evaluation of semaglutide dose levels in type 2 diabetes

AIMS

To evaluate dose levels for semaglutide, a glucagon-like peptide-1 analogue approved for the treatment of type 2 diabetes, by examining the effects of demographic factors on efficacy and safety in an exposure-response analysis.

METHODS

We analysed data from 1552 adults from four randomized phase III trials of 30 to 56 weeks' duration, investigating once-weekly semaglutide doses 0.5 and 1.0 mg. Exposure-response relationships were investigated using graphical and model-based techniques to assess the two dose levels and subgroups with the highest and lowest exposure and response.

RESULTS

The population had the following demographic characteristics: baseline mean age between 53.2 and 58.4 years, glycated haemoglobin (HbA1c) between 64 and 67 mmol/mol (8.0% and 8.3%), body weight between 71.3 and 96.2 kg, and diabetes duration between 4.2 and 8.9 years. Exposure-response analysis showed a clear HbA1c and weight reduction across exposures after 30 weeks, irrespective of baseline values. The exposure-response for HbA1c was influenced by baseline HbA1c, and body weight exposure-response was influenced by sex, with limited impact of other factors. Analyses for relevant subgroups of baseline body weight, baseline HbA1c and sex indicated clinically relevant additional benefits with regard to HbA1c and weight with 1.0 vs 0.5 mg semaglutide. The proportion of participants reporting gastrointestinal (GI) side effects increased with increasing exposure, but was counteracted by tolerance development.

CONCLUSIONS

The analysis showed that all subgroups obtained a clinically relevant benefit with semaglutide 0.5 mg and an additional benefit with semaglutide 1.0 mg. The increase in GI side effects with higher exposure was mitigated by gradually increasing the dose.

Semaglutide s.c. Once-Weekly in Type 2 Diabetes: A Population Pharmacokinetic Analysis

INTRODUCTION

Semaglutide, a new treatment option approved for the treatment of patients with type 2 diabetes mellitus, is a glucagon-like peptide-1 receptor agonist to be injected subcutaneously once weekly. This analysis used a population pharmacokinetic model of semaglutide to identify clinically relevant covariates for exposure.

METHODS

A total of 1612 patients with up to seven pharmacokinetic observations each were included in the analysis. All subjects had type 2 diabetes mellitus and were enrolled in one of five trials in the phase III development program for subcutaneous semaglutide once weekly (the SUSTAIN program). The treatment duration of the trials varied from 30 to 104 weeks.

RESULTS

No clinically relevant effects on the exposure were seen for sex, age, race, ethnicity, renal function, or injection site used, and semaglutide exposure was stable over time. Of the covariates chosen, only body weight had a relevant effect on the exposure of semaglutide. Few subjects developed semaglutide antibodies, and the antibodies had no effect on exposure. Dose proportionality was shown for the 0.5 mg and 1.0 mg maintenance doses of semaglutide.

CONCLUSION

The population pharmacokinetic study showed that semaglutide exposure is not affected by covariates other than body weight at either a maintenance dose of 0.5 or 1.0 mg semaglutide. Therefore, we conclude that no semaglutide dose adjustments are needed in different populations. This finding is to be further explored in an exposure-response analysis.

TRIAL REGISTRATION

The trials were registered at ClinicalTrials.gov (identifiers: NCT02054897, NCT01930188, NCT01885208, NCT01720446 and NCT02207374).

FUNDING

Novo Nordisk A/S, Bagsværd, Denmark.

Safety and efficacy of once-weekly semaglutide vs additional oral antidiabetic drugs in Japanese people with inadequately controlled type 2 diabetes: A randomized trial

AIM

To evaluate the safety and efficacy of once-weekly subcutaneous semaglutide as monotherapy or combined with an oral antidiabetic drug (OAD) vs an additional OAD added to background therapy in Japanese people with type 2 diabetes (T2D) inadequately controlled on diet/exercise or OAD monotherapy.

METHODS

In this phase III, open-label trial, adults with T2D were randomized 2:2:1 to semaglutide 0.5 mg or 1.0 mg, or one additional OAD (a dipeptidyl peptidase-4 inhibitor, biguanide, sulphonylurea, glinide, α-glucosidase inhibitor or thiazolidinedione) with a different mode of action from that of background therapy. The primary endpoint was number of adverse events (AEs) after 56 weeks.

RESULTS

Baseline characteristics were balanced between treatment arms (601 randomized). More AEs were reported in the semaglutide 0.5 mg (86.2%) and 1.0 mg (88.0%) groups than in the additional OAD group (71.7%). These were typically mild/moderate. Gastrointestinal AEs were most frequent with semaglutide, which diminished over time. The mean glycated haemoglobin (HbA1c) concentration (baseline 8.1%) was significantly reduced with semaglutide 0.5 mg and 1.0 mg vs additional OAD (1.7% and 2.0% vs 0.7%, respectively; estimated treatment difference [ETD] vs additional OAD -1.08% and -1.37%, both P < .0001). Body weight (baseline 71.5 kg) was reduced by 1.4 kg and 3.2 kg with semaglutide 0.5 mg and 1.0 mg, vs a 0.4-kg increase with additional OAD (ETD -1.84 kg and -3.59 kg; both P < .0001). For semaglutide-treated participants, >80% achieved an HbA1c concentration <7.0% (Japanese Diabetes Society target).

CONCLUSIONS

Semaglutide was well tolerated, with no new safety issues identified. Semaglutide treatment significantly reduced HbA1c and body weight vs additional OAD treatment in Japanese people with T2D.

A Randomized Trial Investigating the Pharmacokinetics, Pharmacodynamics, and Safety of Subcutaneous Semaglutide Once-Weekly in Healthy Male Japanese and Caucasian Subjects

INTRODUCTION

Semaglutide is a glucagon-like peptide-1 analogue for once-weekly subcutaneous treatment of type 2 diabetes. This trial compared the pharmacokinetics, pharmacodynamics, and safety of semaglutide in Japanese and Caucasian subjects.

METHODS

In this single-center, double-blind, parallel-group, 13-week trial, 44 healthy male subjects (22 Japanese, 22 Caucasian) were randomized within each race to semaglutide 0.5 mg (n = 8), 1.0 mg (n = 8), placebo 0.5 mg (n = 3) or 1.0 mg (n = 3). The primary endpoint was semaglutide exposure at steady state [area under the curve (AUC0-168h)].

RESULTS

Steady-state exposure of semaglutide was similar for both populations: AUC0-168h estimated race ratio (ERR), Japanese/Caucasian: 0.5 mg, 1.06; 1.0 mg, 0.99; maximum concentration (Cmax) ERR: 0.5 mg, 1.06; 1.0 mg, 1.02. Exposure after the first dose (0.25 mg) was slightly higher in Japanese versus Caucasian subjects (AUC0-168h ERR 1.11; Cmax ERR 1.14). Dose-dependent increases in AUC0-168h and Cmax occurred in both populations. Accumulation was as expected, based on the half-life (t1/2, ~ 1 week) and dosing interval of semaglutide. Significant body weight reductions were observed with semaglutide 0.5 mg and 1.0 mg in Japanese (both p ≤ 0.05) and Caucasian (both p ≤ 0.05) subjects versus placebo. No new safety issues were identified.

CONCLUSIONS

The pharmacokinetic, pharmacodynamic, and safety profiles of semaglutide were similar in Japanese and Caucasian subjects, suggesting that no dose adjustment is required for the clinical use of semaglutide in Japanese subjects.

FUNDING

Novo Nordisk A/S, Denmark.

TRIAL REGISTRATION

ClinicalTrials.gov identifier NCT02146079. Japanese trial registration number JapicCTI-142550.

Safety and efficacy of semaglutide once weekly vs sitagliptin once daily, both as monotherapy in Japanese people with type 2 diabetes

AIMS

To assess the safety and efficacy of monotherapy with once-weekly subcutaneous (s.c.) semaglutide vs sitagliptin in Japanese people with type 2 diabetes (T2D).

METHODS

In this phase IIIa randomized, open-label, parallel-group, active-controlled, multicentre trial, Japanese adults with T2D treated with diet and exercise only or oral antidiabetic drug monotherapy (washed out during the run-in period) received once-weekly s.c. semaglutide (0.5 or 1.0 mg) or once-daily oral sitagliptin 100 mg. The primary endpoint was number of treatment-emergent adverse events (TEAEs) after 30 weeks.

RESULTS

Overall, 308 participants were randomized and exposed to treatment, with similar baseline characteristics across the groups. In total, 2.9% of participants in both the semaglutide 0.5 mg and the sitagliptin group prematurely discontinued treatment, compared with 14.7% in the semaglutide 1.0 mg group. The majority of discontinuations in the semaglutide 0.5 and 1.0 mg groups were attributable to adverse events (AEs). More TEAEs were reported in semaglutide- vs sitagliptin-treated participants (74.8%, 71.6% and 66.0% in the semaglutide 0.5 mg, semaglutide 1.0 mg and sitagliptin groups, respectively). AEs were mainly mild to moderate. Gastrointestinal AEs, most frequently reported with semaglutide, diminished in frequency over time. The mean glycated haemoglobin (HbA1c [baseline 8.1%]) decreased by 1.9% and 2.2% with semaglutide 0.5 and 1.0 mg, respectively, vs 0.7% with sitagliptin (estimated treatment difference [ETD] vs sitagliptin -1.13%, 95% confidence interval [CI] -1.32; -0.94, and -1.44%, 95% CI -1.63; -1.24; both P < .0001). Body weight (baseline 69.3 kg) was reduced by 2.2 and 3.9 kg with semaglutide 0.5 and 1.0 mg, respectively (ETD -2.22 kg, 95% CI -3.02; -1.42 and -3.88 kg, 95% CI -4.70; -3.07; both P < .0001).

CONCLUSIONS

In Japanese people with T2D, more TEAEs were reported with semaglutide than with sitagliptin; however, the semaglutide safety profile was similar to that of other glucagon-like peptide-1 receptor agonists. Semaglutide significantly reduced HbA1c and body weight compared with sitagliptin.

Insulin degludec/insulin aspart vs biphasic insulin aspart 30 twice daily in Japanese patients with type 2 diabetes: A randomized controlled trial

AIMS/INTRODUCTION

Insulin degludec/insulin aspart (IDegAsp) is a soluble combination of insulin degludec (70%) and insulin aspart (30%). The present exploratory trial investigated the safety of switching unit-to-unit from twice-daily basal or pre-mix insulin to twice-daily IDegAsp in Japanese patients with type 2 diabetes.

MATERIALS AND METHODS

In this 6-week, open-label, parallel-group, controlled trial, 66 participants were randomized (1:1) to receive either IDegAsp or biphasic insulin aspart 30 (BIAsp 30) twice daily at the same total daily dose as pre-trial insulin. During the trial, insulin doses were adjusted according to a pre-specified algorithm to achieve pre-breakfast and pre-dinner plasma glucose of 4.4-7.2 mmol/L.

RESULTS

No severe hypoglycemic episodes occurred. There were no statistically significant differences in rates of confirmed hypoglycemia (rate ratio IDegAsp/BIAsp 30: 0.63, 95% confidence interval: 0.31-1.30) and confirmed nocturnal hypoglycemia (rate ratio: 0.49, 95% confidence interval: 0.10-2.38) for IDegAsp vs BIAsp 30. The hypoglycemia rate for IDegAsp was constant over the 6 weeks of treatment. IDegAsp and BIAsp 30 were both safe and well tolerated. Reduction in fasting plasma glucose was statistically significantly greater for IDegAsp than for BIAsp 30 (estimated treatment difference, IDegAsp-BIAsp 30: -1.6 mmol/L, 95% confidence interval: -2.4 to -0.8). The apparent decrease in mean postprandial plasma glucose increment (IDegAsp: 4.2-3.8 mmol/L; BIAsp 30: 4.5-2.8 mmol/L) was not statistically significantly different between treatments (estimated treatment difference: 1.0 mmol/L, 95% confidence interval: -0.1 to 2.2).

CONCLUSIONS

Switching unit-to-unit from basal or pre-mix insulin to IDegAsp seems not to be associated with any concerns related to hypoglycemia or general safety in Japanese patients with type 2 diabetes.

Effect of adding insulin degludec to treatment in patients with type 2 diabetes inadequately controlled with metformin and liraglutide: a double-blind randomized controlled trial (BEGIN: ADD TO GLP-1 Study)

AIM

To evaluate the efficacy and safety of adding insulin degludec (IDeg) to treatment in patients with type 2 diabetes receiving liraglutide and metformin and qualifying for treatment intensification because of inadequate glycaemic control.

METHODS

In this 26-week, double-blind trial, patients who still had inadequate glycaemic control after a 15-week run-in period with initiation and dose escalation of liraglutide to 1.8 mg in combination with metformin (≥1500 mg) were randomized to addition of once-daily IDeg ('IDeg add-on to liraglutide' arm; n = 174) or placebo ('placebo add-on to liraglutide' arm; n = 172), with dosing of both IDeg and placebo based on titration guidelines.

RESULTS

At 26 weeks, the mean change in glycated haemoglobin level was greater in the IDeg add-on to liraglutide arm (-1.04%) than in the placebo add-on to liraglutide arm (-0.16%; p < 0.0001). Similarly, the mean fasting plasma glucose reduction was greater, and self-measured plasma glucose values were lower at all eight time points, with IDeg add-on versus placebo add-on (both p < 0.0001). At 26 weeks, the IDeg dose was 51 U (0.54 U/kg). During the run-in period with liraglutide, body weight decreased by ∼3 kg in both groups. After 26 weeks, the mean change was +2.0 kg (IDeg add-on to liraglutide) and -1.3 kg (placebo add-on to liraglutide). Confirmed hypoglycaemia rates were low in both groups, although higher with IDeg than with placebo (0.57 vs. 0.12 episodes/patient-years of exposure; p = 0.0002). Nocturnal confirmed hypoglycaemia was infrequent in both groups, with no episodes of severe hypoglycaemia, and no marked differences in adverse events with either treatment approach.

CONCLUSION

The addition of liraglutide and IDeg to patients sub-optimally treated with metformin and liraglutide and requiring treatment intensification was found to be effective and well-tolerated.

Twice-daily insulin degludec/insulin aspart provides superior fasting plasma glucose control and a reduced rate of hypoglycaemia compared with biphasic insulin aspart 30 in insulin-naïve adults with Type 2 diabetes

AIM

To evaluate the efficacy and safety of twice-daily insulin degludec/insulin aspart vs. twice-daily biphasic insulin aspart 30 in people with Type 2 diabetes mellitus who were naïve to insulin.

METHODS

In this 26-week, multinational, open-label, controlled, two-arm, parallel-group, treat-to-target trial, participants [mean (± sd) age 58.9 (±8.9) years, duration of diabetes 9.5 (±5.9) years, HbA1c 68 (±8.7) mmol/mol or 8.4 (±0.8)% and BMI 31.2 (±4.2) kg/m(2) ) were randomized (1:1) to insulin degludec/insulin aspart (n = 197) or biphasic insulin aspart 30 (n = 197), administered with breakfast and the main evening meal, titrated to a self-monitored plasma glucose target > 3.9 and ≤ 5.0 mmol/l.

RESULTS

The mean HbA1c was reduced to 49 mmol/mol (6.6%) with insulin degludec/insulin aspart and 48 mmol/mol (6.5%) with biphasic insulin aspart 30. Insulin degludec/insulin aspart achieved the prespecified non-inferiority margin (estimated treatment difference 0.02%; 95% CI -0.12, 0.17). Insulin degludec/insulin aspart was superior in lowering fasting plasma glucose (estimated treatment difference -1.00 mmol/l; 95% CI -1.4, -0.6; P < 0.001) and reducing overall and nocturnal confirmed hypoglycaemia at a similar overall insulin dose compared with biphasic insulin aspart 30. Similar proportions of participants in each arm experienced severe hypoglycaemia. Adverse events were equally distributed.

CONCLUSIONS

Consistent with previous findings, insulin degludec/insulin aspart twice daily effectively improved long-term glycaemic control, with superior reductions in FPG, and significantly less overall and nocturnal confirmed hypoglycaemia compared with biphasic insulin aspart 30 in people with Type 2 diabetes who were insulin-naïve.

Treatment intensification with an insulin degludec (IDeg)/insulin aspart (IAsp) co-formulation twice daily compared with basal IDeg and prandial IAsp in type 2 diabetes: a randomized, controlled phase III trial

AIMS

To evaluate the efficacy and safety of two insulin intensification strategies for patients with type 2 diabetes previously treated with basal insulin--insulin degludec (IDeg) and insulin aspart (IAsp)--administered as a co-formulation (IDegAsp) or as a basal-bolus regimen (IDeg and IAsp in separate injections).

METHODS

This 26-week, open-label, treat-to-target, phase IIIb, non-inferiority trial randomized patients (1 : 1) to IDegAsp twice daily with main meals (n = 138; IDegAsp group) or IDeg once daily and IAsp 2-4 times daily (n = 136; IDeg+IAsp group).

RESULTS

After 26 weeks, the mean glycated haemoglobin (HbA1c) level was 7.0% (53 mmol/mol) for the IDegAsp group and 6.8% (51 mmol/mol) for the IDeg+IAsp group (Δ%HbA1c from baseline -1.31 and -1.50%, respectively). The non-inferiority of IDegAsp versus IDeg+IAsp was not confirmed for mean change in HbA1c [estimated treatment difference (ETD) 0.18, 95% confidence interval (CI) -0.04, 0.41; p = non-significant]. No significant differences were observed in the proportion of patients achieving HbA1c <7.0% (56.5 and 59.6%, respectively). IDegAsp treatment resulted in a significantly lower total daily insulin dose, a smaller change in body weight, numerically lower rates of confirmed hypoglycaemia (self-reported plasma glucose <3.1 mmol/l; rate ratio 0.81; p = non-significant), and nocturnal confirmed hypoglycaemic episodes (rate ratio 0.80; p = non-significant) versus IDeg+IAsp. Patient-reported outcome scores for social functioning were significantly higher for IDegAsp versus IDeg+IAsp (ETD 2.2; 95% CI 0.3, 4.1; p < 0.05).

CONCLUSIONS

Both intensification strategies effectively improved glycaemic control. Although non-inferiority was not confirmed, there were no significant differences between the groups that could affect clinical utility.

Increased Baseline C-Reactive Protein Concentrations Are Associated with Increased Risk of Infections: Results from 2 Large Danish Population Cohorts

BACKGROUND

The acute-phase reactant C-reactive protein (CRP) increases rapidly during an infection. We tested the hypothesis that chronic low-level increases in CRP are associated with an increased risk of infectious disease.

METHODS

We studied 9660 individuals from a prospective general population cohort, including 3592 in whom infectious disease developed, and another 60 896 individuals from a cross-sectional general population study, of whom 13 332 developed infectious disease; 55% were women, and the mean age was 57 years. Hospital diagnoses of infections in 1977-2010 were based on International Classification of Diseases-coded discharge records from the national Danish Patient Registry. We measured CRP concentrations and conducted genotyping for 4 CRP polymorphisms that increase CRP. Individuals with CRP >10 mg/L were excluded because of possible ongoing infection at the time of testing.

RESULTS

Individuals with CRP >3 mg/L had 1.2 and 1.7 times increased risk of infectious disease, in the prospective general population cohort and the cross-sectional general population study, respectively, compared with individuals with CRP <1 mg/L. In the combined populations, individuals in the highest CRP tertile (compared with the lowest) had an increased risk of bacterial diseases (hazard ratio 1.7, 95% CI 1.6-1.8), but not viral, mycosis, and parasitic diseases. The increased risk was mainly carried by pneumonia, sepsis, and particularly gram-negative infections. None of the genotype combinations examined conferred an increased risk of infectious disease.

CONCLUSIONS

Chronic low-level CRP increases were associated with increased risk of bacterial infections, gram-negative infections in particular. Genotypes associated with increases in CRP were not associated with increased risk of infection.

Risk of venous thromboembolism associated with single and combined effects of Factor V Leiden, Prothrombin 20210A and Methylenetethraydrofolate reductase C677T: a meta-analysis involving over 11,000 cases and 21,000 controls

Genetic and environmental factors interact in determining the risk of venous thromboembolism (VTE). The risk associated with the polymorphic variants G1691A of factor V (Factor V Leiden, FVL), G20210A of prothrombin (PT20210A) and C677T of methylentetrahydrofolate reductase (C677T MTHFR) genes has been investigated in many studies. We performed a pooled analysis of case-control and cohort studies investigating in adults the association between each variant and VTE, published on Pubmed, Embase or Google through January 2010. Authors of eligible papers, were invited to provide all available individual data for the pooling. The Odds Ratio (OR) for first VTE associated with each variant, individually and combined with the others, were calculated with a random effect model, in heterozygotes and homozygotes (dominant model for FVL and PT20210A; recessive for C677T MTHFR). We analysed 31 databases, including 11,239 cases and 21,521 controls. No significant association with VTE was found for homozygous C677T MTHFR (OR: 1.38; 95 % confidence intervals [CI]: 0.98-1.93), whereas the risk was increased in carriers of either heterozygous FVL or PT20210 (OR = 4.22; 95 % CI: 3.35-5.32; and OR = 2.79;95 % CI: 2.25-3.46, respectively), in double heterozygotes (OR = 3.42; 95 %CI 1.64-7.13), and in homozygous FVL or PT20210A (OR = 11.45; 95 %CI: 6.79-19.29; and OR: 6.74 (CI 95 % 2.19-20.72), respectively). The stratified analyses showed a stronger effect of FVL on individuals ≤ 45 years (p value for interaction = 0.036) and of PT20210A in women using oral contraceptives (p-value for interaction = 0.045). In this large pooled analysis, inclusive of large studies like MEGA, no effect was found for C677T MTHFR on VTE; FVL and PT20210A were confirmed to be moderate risk factors. Notably, double carriers of the two genetic variants produced an impact on VTE risk significantly increased but weaker than previously thought.

The effect of elevated body mass index on ischemic heart disease risk: causal estimates from a Mendelian randomisation approach

BACKGROUND

Adiposity, assessed as elevated body mass index (BMI), is associated with increased risk of ischemic heart disease (IHD); however, whether this is causal is unknown. We tested the hypothesis that positive observational associations between BMI and IHD are causal.

METHODS AND FINDINGS

In 75,627 individuals taken from two population-based and one case-control study in Copenhagen, we measured BMI, ascertained 11,056 IHD events, and genotyped FTO(rs9939609), MC4R(rs17782313), and TMEM18(rs6548238). Using genotypes as a combined allele score in instrumental variable analyses, the causal odds ratio (OR) between BMI and IHD was estimated and compared with observational estimates. The allele score-BMI and the allele score-IHD associations used to estimate the causal OR were also calculated individually. In observational analyses the OR for IHD was 1.26 (95% CI 1.19-1.34) for every 4 kg/m(2) increase in BMI. A one-unit allele score increase associated with a 0.28 kg/m(2) (95 CI% 0.20-0.36) increase in BMI and an OR for IHD of 1.03 (95% CI 1.01-1.05) (corresponding to an average 1.68 kg/m(2) BMI increase and 18% increase in the odds of IHD for those carrying all six BMI increasing alleles). In instrumental variable analysis using the same allele score the causal IHD OR for a 4 kg/m(2) increase in BMI was 1.52 (95% CI 1.12-2.05).

CONCLUSIONS

For every 4 kg/m(2) increase in BMI, observational estimates suggested a 26% increase in odds for IHD while causal estimates suggested a 52% increase. These data add evidence to support a causal link between increased BMI and IHD risk, though the mechanism may ultimately be through intermediate factors like hypertension, dyslipidemia, and type 2 diabetes. This work has important policy implications for public health, given the continuous nature of the BMI-IHD association and the modifiable nature of BMI. This analysis demonstrates the value of observational studies and their ability to provide unbiased results through inclusion of genetic data avoiding confounding, reverse causation, and bias.

Effect modification by population dietary folate on the association between MTHFR genotype, homocysteine, and stroke risk: a meta-analysis of genetic studies and randomised trials

BACKGROUND

The MTHFR 677C→T polymorphism has been associated with raised homocysteine concentration and increased risk of stroke. A previous overview showed that the effects were greatest in regions with low dietary folate consumption, but differentiation between the effect of folate and small-study bias was difficult. A meta-analysis of randomised trials of homocysteine-lowering interventions showed no reduction in coronary heart disease events or stroke, but the trials were generally set in populations with high folate consumption. We aimed to reduce the effect of small-study bias and investigate whether folate status modifies the association between MTHFR 677C→T and stroke in a genetic analysis and meta-analysis of randomised controlled trials.

METHODS

We established a collaboration of genetic studies consisting of 237 datasets including 59,995 individuals with data for homocysteine and 20,885 stroke events. We compared the genetic findings with a meta-analysis of 13 randomised trials of homocysteine-lowering treatments and stroke risk (45,549 individuals, 2314 stroke events, 269 transient ischaemic attacks).

FINDINGS

The effect of the MTHFR 677C→T variant on homocysteine concentration was larger in low folate regions (Asia; difference between individuals with TT versus CC genotype, 3·12 μmol/L, 95% CI 2·23 to 4·01) than in areas with folate fortification (America, Australia, and New Zealand, high; 0·13 μmol/L, -0·85 to 1·11). The odds ratio (OR) for stroke was also higher in Asia (1·68, 95% CI 1·44 to 1·97) than in America, Australia, and New Zealand, high (1·03, 0·84 to 1·25). Most randomised trials took place in regions with high or increasing population folate concentrations. The summary relative risk (RR) of stroke in trials of homocysteine-lowering interventions (0·94, 95% CI 0·85 to 1·04) was similar to that predicted for the same extent of homocysteine reduction in large genetic studies in populations with similar folate status (predicted RR 1·00, 95% CI 0·90 to 1·11). Although the predicted effect of homocysteine reduction from large genetic studies in low folate regions (Asia) was larger (RR 0·78, 95% CI 0·68 to 0·90), no trial has evaluated the effect of lowering of homocysteine on stroke risk exclusively in a low folate region.

INTERPRETATION

In regions with increasing levels or established policies of population folate supplementation, evidence from genetic studies and randomised trials is concordant in suggesting an absence of benefit from lowering of homocysteine for prevention of stroke. Further large-scale genetic studies of the association between MTHFR 677C→T and stroke in low folate settings are needed to distinguish effect modification by folate from small-study bias. If future randomised trials of homocysteine-lowering interventions for stroke prevention are undertaken, they should take place in regions with low folate consumption.

FUNDING

Full funding sources listed at end of paper (see Acknowledgments).

Using genetic loci to understand the relationship between adiposity and psychological distress: a Mendelian Randomization study in the Copenhagen General Population Study of 53,221 adults

OBJECTIVE

We used genetic variants that are robustly associated with adiposity to examine the causal association of adiposity with psychological distress.

METHODS

We examined the association of adiposity with psychological distress in a large (N = 53,221) general population cohort of 20- to 99-year-old adults from Copenhagen, Denmark. Psychological distress was assessed using four questions that asked about: feeling stressed; not accomplishing very much; wanting to give up; and regular use of antidepressants/sedatives. We used the genetic loci FTO rs9939609 and MC4R rs17782313 as instrumental variables for adiposity quantified by body mass index (BMI) and waist to hip ratio (WHR).

RESULTS

In conventional multivariable analyses, BMI and WHR were positively associated with distress. For example, the odds ratio of reporting not accomplishing for each additional standard deviation increase for BMI was 1.11 (95% CI: 1.09, 1.13) and for WHR was 1.10 (95% CI: 1.08, 1.13) in the fully adjusted analyses. In contrast, instrumental variable analyses showed an inverse association of adiposity on distress; corresponding odds ratio in instrumental variable analyses was 0.64 (95% CI: 0.46, 0.89) for BMI and 0.49 (95% CI: 0.25, 0.94) for WHR (P-values for difference between the two approaches both = 0.001).

CONCLUSION

The inverse associations of adiposity and psychological distress when genetic variants are used as instrumental variables could be explained by biological pathways linking adiposity and distress. The positive associations of adiposity with distress in multivariable analyses might be explained by residual confounding or reverse causality.

C-reactive protein levels and body mass index: elucidating direction of causation through reciprocal Mendelian randomization

CONTEXT

The assignment of direction and causality within networks of observational associations is problematic outside randomized control trials, and the presence of a causal relationship between body mass index (BMI) and C-reactive protein (CRP) is disputed.

OBJECTIVE

Using reciprocal Mendelian randomization, we aim to assess the direction of causality in relationships between BMI and CRP and to demonstrate this as a promising analytical technique.

PARTICIPANTS AND METHODS

The study was based on a large, cross-sectional European study from Copenhagen, Denmark. Genetic associates of BMI (FTO(rs9939609)) and circulating CRP (CRP(rs3091244)) have been used to reexamine observational associations between them.

RESULTS

Observational analyses showed a strong, positive association between circulating CRP and BMI (change in BMI for a doubling in log CRP of 1.03 kg m(-2) (95% confidence interval (95% CI): 1.00, 1.07), P<0.0001). Analysis using CRP(rs3091244) to re-estimate the causal effect of circulating CRP on BMI yielded null effects (change in BMI for a doubling in log CRP of -0.24 kg m(-2) (95% CI: -0.58, 0.11), P=0.2). In contrast, analysis using FTO(rs9939609) to assess the causal effect of BMI on circulating CRP confirmed observational associations (ratio of geometric means of CRP per s.d. increase in BMI 1.41 (95% CI: 1.10, 1.80), P=0.006).

CONCLUSIONS

Taken together, these data suggest that the observed association between circulating CRP and measured BMI is likely to be driven by BMI, with CRP being a marker of elevated adiposity. More generally, the method of reciprocal randomization has general applicability in determining the direction of causation within inter-correlated networks of metabolic components.

Hyperhomocysteinemia, methylenetetrahydrofolate reductase c.677C>T polymorphism and risk of cancer: cross-sectional and prospective studies and meta-analyses of 75,000 cases and 93,000 controls

Global DNA hypomethylation associates with development of cancer. DNA hypomethylation also associates with hyperhomocysteinemia and MTHFR c.677C>T homozygosity, both of which may associate with increased risk of cancer. We tested the putative association of hyperhomocysteinemia with cancer and the association of the MTHFR c.677TC>T variant with hyperhomocysteinemia and with cancer. We performed a cross-sectional study of 5,949 Danish general population adults, a prospective study of 9,235 Danish general population adults with up to 60 years of registry surveillance, and meta-analyses of 231 studies including 74,671 cases and 93,344 controls. Cross-sectionally, plasma homocysteine levels were 12.9 and 11.6 μmol/L in those with and without cancer (p < 0.0001). However, homocysteine levels increased with age and age-adjusted odds ratio for any cancer in those with homocysteine levels >12.4 versus < 9.4 μmol/L did not differ from 1.0. In cancer-free participants, plasma homocysteine levels were 14.7 and 11.7 μmol/L in MTHFR c.677C>T homozygtes and noncarriers (p < 0.0001). Prospectively, hazard ratios for any cancer and for cancer subtypes in MTHFR c.677C>T homozygotes versus noncarriers did not differ from 1.0. However, in meta-analyses odds ratio for MTHFR c.677C>T homozygotes versus noncarriers were 1.07 (95% CI: 1.01-1.12) for any cancer, 1.77 (1.17-2.68) for esophagus cancer, 1.40 (1.19-1.66) for gastric cancer and 0.85 (0.77-0.94) for colorectal cancer. Increased plasma homocysteine levels are not associated with an increased age-adjusted risk of any cancer. However, MTHFR c.677C>T homozygosity with lifelong hyperhomocysteinemia and hence hypomethylation associate with increased risk of esophagus and gastric cancer, and with decreased risk of colorectal cancer.

Bayesian methods for meta-analysis of causal relationships estimated using genetic instrumental variables

Genetic markers can be used as instrumental variables, in an analogous way to randomization in a clinical trial, to estimate the causal relationship between a phenotype and an outcome variable. Our purpose is to extend the existing methods for such Mendelian randomization studies to the context of multiple genetic markers measured in multiple studies, based on the analysis of individual participant data. First, for a single genetic marker in one study, we show that the usual ratio of coefficients approach can be reformulated as a regression with heterogeneous error in the explanatory variable. This can be implemented using a Bayesian approach, which is next extended to include multiple genetic markers. We then propose a hierarchical model for undertaking a meta-analysis of multiple studies, in which it is not necessary that the same genetic markers are measured in each study. This provides an overall estimate of the causal relationship between the phenotype and the outcome, and an assessment of its heterogeneity across studies. As an example, we estimate the causal relationship of blood concentrations of C-reactive protein on fibrinogen levels using data from 11 studies. These methods provide a flexible framework for efficient estimation of causal relationships derived from multiple studies. Issues discussed include weak instrument bias, analysis of binary outcome data such as disease risk, missing genetic data, and the use of haplotypes.

C-reactive protein and risk of venous thromboembolism in the general population

OBJECTIVE

To examine the robustness of the association between C-reactive protein (CRP) levels and increased risk of venous thromboembolism (VTE) and to examine whether genetically elevated CRP levels cause VTE.

METHODS AND RESULTS

In the prospective Copenhagen City Heart Study, we observed 10 388 participants for longer than 16 years, of whom 484 developed a VTE. In the cross-sectional Copenhagen General Population Study, we studied 36 616 participants, of whom 903 previously had a VTE. Levels of CRP greater than 3 mg/L versus less than 1 mg/L were associated with a 2.3- and 2.4-fold increased risk of VTE in the Copenhagen City Heart Study and the Copenhagen General Population Study, respectively. CRP levels in tertiles, quintiles, and octiles associated with a stepwise increase in VTE risk. CRP genotypes associated with an increase in plasma CRP levels up to 59% but did not associate consistently with risk of VTE in either study. The causal odds ratio for VTE for a doubling in genetically elevated CRP on instrumental variable analyses was lower than the odds ratio for VTE observed for a doubling in plasma CRP on logistic regression ([odds ratio and 95% CI] 0.80 [0.56 to 1.12] versus 1.17 [1.08 to 1.27]; P=0.04).

CONCLUSIONS

We observed 47,000 participants from the general population, of whom 1387 developed VTE. Although elevated CRP levels robustly associated with increased risk of VTE, this may not necessarily be a causal association because genetically elevated CRP did not associate with VTE risk.

C-reactive protein and the risk of cancer: a mendelian randomization study

Elevated plasma levels of C-reactive protein (CRP), a marker of inflammation, are associated with an increased risk of cancer, but it is unclear whether this association is causal. We examined whether four common single-nucleotide polymorphisms (SNPs) in the CRP gene that are associated with altered plasma CRP levels are causally associated with an increased risk of cancer. The study population included participants in a prospective study (n = 10 215) and a cross-sectional study (n = 36 403) of the adult general population in Denmark, all of whom were genotyped for the CRP SNPs. The association between plasma CRP levels measured by a high-sensitivity turbidimetry assay and the risk of cancer was examined for 8224 participants in the prospective study. The hazard ratio of cancer for a doubling of the plasma CRP level was 1.09 (95% confidence interval [CI] = 1.03 to 1.14). The nine most common genotype combinations of the four CRP SNPs were associated with up to a 72% increase (95% CI = 58% to 87%) in CRP levels but not with an increased risk of cancer. The estimated causal odds ratio for cancer associated with a genetically induced doubling in CRP level was 0.94 (95% CI = 0.81 to 1.08). This finding suggests that elevated CRP levels do not cause cancer.

Lipids, atherosclerosis and CVD risk: is CRP an innocent bystander?

AIM

To evaluate recent human studies with respect to the interpretation of whether elevated plasma levels of C-reactive protein (CRP) cause cardiovascular disease (CVD), or whether elevated CRP levels more likely is an innocent bystander.

DATA SYNTHESIS

Elevated CRP concentrations are consistently associated with CVD risk. A recent study showed that aggressive statin treatment caused reductions of 50% in LDL cholesterol, 37% in CRP, 44% in CVD events, and 20% in total mortality, and that the highest treatment benefits were obtained in those with the lowest achieved levels of both LDL cholesterol and CRP. However, a reduction in CRP levels after statin treatment could be secondary to the reduced LDL cholesterol levels, and thereby less inflammation in atherosclerotic plaques. We recently performed 4 large Mendelian randomization studies, studies that demonstrated that elevated CRP associate with increased risk of CVD, that genetic variation in the CRP gene associate with increased CRP levels, but that this genetic variation in the CRP gene do not associate with increased risk of CVD. In contrast to previous studies, these new studies had enough statistical power to effectively exclude that genetically elevated CRP cause CVD.

CONCLUSION

These data suggest that elevated CRP per se does not cause CVD; however, inflammation per se possibly contributes to CVD. Elevated CRP levels more likely is a marker for the extent of atherosclerosis or for the inflammatory activity and vulnerability of atherosclerotic plaques, and thus simply an innocent bystander in CVD.

Does greater adiposity increase blood pressure and hypertension risk?: Mendelian randomization using the FTO/MC4R genotype

Elevated blood pressure increases the risk of experiencing cardiovascular events like myocardial infarction and stroke. Current observational data suggest that body mass index may have a causal role in the etiology of hypertension, but this may be influenced by confounding and reverse causation. Through the use of instrumental variable methods, we aim to estimate the strength of the unconfounded and unbiased association between body mass index/adiposity and blood pressure. We explore these issues in the Copenhagen General Population Study. We used instrumental variable methods to obtain estimates of the causal association between body mass index and blood pressure. This was performed using both rs9939609 (FTO) and rs17782313 (MC4R) genotypes as instruments for body mass index. Avoiding the epidemiological problems of confounding, bias, and reverse causation, we confirmed observational associations between body mass index and blood pressure. In analyses including those taking antihypertensive drugs, but for whom appropriate adjustment had been made, systolic blood pressure was seen to increase by 3.85 mm Hg (95% CI: 1.88 to 5.83 mm Hg) for each 10% increase in body mass index (P=0.0002), with diastolic blood pressure showing an increase of 1.79 mm Hg (95% CI: 0.68 to 2.90 mm Hg) for each 10% increase in body mass index (P=0.002). Observed associations are large and illustrate the considerable benefits in terms of reductions in blood pressure-related morbidity that could be achieved through a reduction in body mass index.

[C-reactive protein and risk of ischaemic vascular and cerebrovascular disease--secondary publication]

Elevated levels of C reactive protein (CRP) are associated with increased risk of ischaemic vascular disease. We tested whether this is a causal association. CRP > 3 vs < 1 mg/l were associated with an increased risk of ischaemic heart- and cerebrovascular disease of 1.6 and 1.3, respectively. Four CRP polymorphisms were associated with a 64% increase in CRP levels, resulting in a theoretically predicted increased risk of 32% and 25% for ischemic heart- and ischemic cerebrovascular disease, respectively. However, these genotype combinations were not associated with an increased risk of ischaemic vascular disease.

Genetically elevated C-reactive protein and ischemic vascular disease

BACKGROUND

Elevated levels of C-reactive protein (CRP) are associated with increased risks of ischemic heart disease and ischemic cerebrovascular disease. We tested whether this is a causal association.

METHODS

We studied 10,276 persons from a general population cohort, including 1786 in whom ischemic heart disease developed and 741 in whom ischemic cerebrovascular disease developed. We examined another 31,992 persons from a cross-sectional general population study, of whom 2521 had ischemic heart disease and 1483 had ischemic cerebrovascular disease. Finally, we compared 2238 patients with ischemic heart disease with 4474 control subjects and 612 patients with ischemic cerebrovascular disease with 1224 control subjects. We measured levels of high-sensitivity CRP and conducted genotyping for four CRP polymorphisms and two apolipoprotein E polymorphisms.

RESULTS

The risk of ischemic heart disease and ischemic cerebrovascular disease was increased by a factor of 1.6 and 1.3, respectively, in persons who had CRP levels above 3 mg per liter, as compared with persons who had CRP levels below 1 mg per liter. Genotype combinations of the four CRP polymorphisms were associated with an increase in CRP levels of up to 64%, resulting in a theoretically predicted increased risk of up to 32% for ischemic heart disease and up to 25% for ischemic cerebrovascular disease. However, these genotype combinations were not associated with an increased risk of ischemic vascular disease. In contrast, apolipoprotein E genotypes were associated with both elevated cholesterol levels and an increased risk of ischemic heart disease.

CONCLUSIONS

Polymorphisms in the CRP gene are associated with marked increases in CRP levels and thus with a theoretically predicted increase in the risk of ischemic vascular disease. However, these polymorphisms are not in themselves associated with an increased risk of ischemic vascular disease.

The methylenetetrahydrofolate reductase C677T genotype and the risk of obesity in three large population-based cohorts

OBJECTIVE

Epidemiological studies have shown that low folate levels are associated with a high body mass index (BMI). These findings have potentially important health implications and warrant further investigation to determine whether a causal relationship exists and the direction of this relationship. The methylenetetrahydrofolate reductase (MTHFR) C677T TT genotype is associated with reduced folate availability and may be a surrogate for measuring folate levels. We sought to determine whether MTHFR C677T genotype was associated with obesity.

DESIGN

We carried out our study on four populations from three longitudinal studies based in the UK and Denmark in which DNA for genotyping was obtained along with measures of obesity.

METHODS

Our subjects were taken from the British Women's Heart and Health Study (BWHHS), the Avon Longitudinal Study of Parents and Children (two populations: mothers and children) and the Copenhagen City Heart Study. We performed analyses separately by population, and then carried out a meta-analysis, combining similar populations.

RESULTS

Initial findings in the BWHHS suggested that the TT genotype may be associated with an increased risk of obesity BMI > or =30, however, no association was found with BMI or central adiposity in this cohort. This genotype was not associated with obesity in our other cohorts.

CONCLUSIONS

Our results suggest that the initial positive finding with obesity in the BWHHS was a chance finding. Our findings do not support a causal effect of low folate on obesity.