Post-pituitary surgery copeptin analysis as a 'rule-out' test for post-operative diabetes insipidus

BACKGROUND

Diabetes insipidus (DI) is a recognised complication of pituitary surgery, with diagnosis requiring clinical observation aided by plasma and urine electrolytes and osmolalities. Copeptin is a stable surrogate marker of AVP release and has potential to facilitate prompt diagnosis of post-operative DI. This assay has been shown to accurately predict which patients are likely to develop DI following pituitary surgery.

OBJECTIVE

To determine whether copeptin analysis can be used to predict which patients are at risk of developing DI following trans-sphenoidal surgery (TSS).

METHODS

Seventy-eight patients undergoing TSS had samples taken for copeptin pre-operatively and at day 1 post-TSS. The majority of patients also had samples from day 2, day 8, and week 6 post-TSS. Results from patients who developed post-operative DI (based on clinical assessment, urine and plasma biochemistry and the need for treatment with DDAVP) were compared to those who did not. Patients with any evidence of pre-operative DI were excluded.

RESULTS

Of 78 patients assessed, 11 were clinically determined to have developed DI. Differences were observed between patients with DI and those without in post-operative samples. Of note, there was a significant difference in plasma copeptin at day 1 post-operation (p = 0.010 on Kruskal-Wallis test), with copeptin levels greater than 3.4 pmol/l helping to rule out DI (91% sensitivity, 55% specificity at this cut off).

CONCLUSION

In the post-TSS setting, copeptin is a useful rule-out test in patients with values above a defined threshold, which may facilitate earlier decision making and shorter hospital stays.

Management of cranial diabetes insipidus: clinical outcomes and patient perception of care

OBJECTIVE

There is growing recognition of morbidity and mortality that can occur in patients with cranial diabetes insipidus (CDI) during hospitalisation, due to prescribing errors and dysnatraemia, often related to confusion between CDI and diabetes mellitus among non-specialists. We aimed to investigate this.

METHODS

Data for each hospitalisation in patients with CDI attending Oxford University Hospital (OUH) were collected retrospectively. The same cohort were invited to complete a questionnaire by telephone.

RESULTS

One hundred and nine patients were included, median age was 42 (range: 6-80) years. Route of desmopressin was tablet, melt and nasal spray in 74%, 7% and 17% of patients, respectively, while two patients used a combination of tablet and nasal spray. There were 85 admissions to OUH by 38 patients between 2012 and 2021. Daily measurement of serum sodium was performed in 39% of admissions; hyponatraemia and hypernatraemia occurred in 44 and 15% of admissions, respectively. Endocrine consultation was sought in 63% of admissions post-2018. Forty-five of 78 patients (58%) self-reported ≥1 admission to any hospital since diagnosis. Of these, 53% felt their medical team did not have a good understanding of the management of CDI during hospital admission. Twenty-four per cent reported delay in administration of desmopressin, while 44% reported confusion between CDI and diabetes mellitus, often leading to unnecessary blood glucose monitoring.

CONCLUSION

Dysnatraemia is common in hospitalised patients with CDI. More than half of patients perceived their medical team's understanding of CDI to be poor when admitted with intercurrent illness. A coordinated approach, including early consultation of specialists, frequent serum sodium monitoring, and education of hospital specialists is needed to address this.

Multiple endocrine neoplasia type 1 in children and adolescents: Clinical features and treatment outcomes

BACKGROUND

Clinical manifestations and treatment outcomes in children and adolescents with multiple endocrine neoplasia type 1 are not well characterized.

METHODS

We conducted a retrospective cohort study of 80 patients with multiple endocrine neoplasia type 1 who commenced tumor surveillance at ≤18 years of age.

RESULTS

Fifty-six patients (70%) developed an endocrine tumor by age ≤18 years (median age = 14 years, range = 6-18 years). Primary hyperparathyroidism occurred in >80% of patients, with >70% undergoing parathyroidectomy, in which less-than-subtotal (<3-gland) resection resulted in decreased disease-free outcomes versus subtotal (3-3.5-gland) or total (4-gland) parathyroidectomy (median 27 months versus not reached; P = .005). Pancreaticoduodenal neuroendocrine tumors developed in ∼35% of patients, of whom >70% had nonfunctioning tumors, >35% had insulinomas, and <5% had gastrinomas, with ∼15% having metastases and >55% undergoing surgery. Pituitary tumors developed in >30% of patients, and ∼35% were macroprolactinomas. Tumor occurrence in male patients and female patients was not significantly different. Genetic analyses revealed 38 germline MEN1 mutations, of which 3 were novel.

CONCLUSION

Seventy percent of children aged ≤18 years with multiple endocrine neoplasia type 1 develop endocrine tumors, which include parathyroid tumors for which less-than-subtotal parathyroidectomy should be avoided; pancreaticoduodenal neuroendocrine tumors that may metastasize; and pituitary macroprolactinomas.

Cell proliferation, apoptosis, and angiogenesis in non-functional pituitary adenoma: association with tumor invasiveness

PURPOSE

Non-functioning pituitary adenoma (NFPA) is the most prevalent pituitary macroadenoma. No prognostic marker has been found to explain the behavior of these tumors. We aimed to explore cell proliferation, apoptosis, proangiogenic markers, and microvascular density (MVD) in noninvasive and invasive NFPAs.

METHODS

Adenoma invasiveness was defined according to Knosp and Hardy classifications based on preoperative magnetic resonance imaging scans. Cell proliferation was examined using Ki67 and P53. Tissue expression of Bcl-2 was used to assess the antiapoptosis pathway. CD34 and CD105 were measured to evaluate MVD, while VEGF expression was assessed as an indicator of pro-angiogenesis. Moreover, VEGF, bFGF, endocan, and endostatin were measured on preoperative serum samples.

RESULTS

Tissue and serum markers were examined in 18 patients with invasive and 21 patients with noninvasive NFPAs. Ki67 less than 3% was reported in 10 invasive and 14 noninvasive NFPAs (P = 0.752). P53 staining was negative in all subjects. In addition, Bcl-2 staining was negative in 15 and 20 subjects, respectively (P = 0.718). VEGF-A expression 2+ or 3+ was reported in 9 invasive and 11 noninvasive macroadenomas (P = 0.83). Moreover, CD34 and CD105 positivity were comparable between the two groups. Furthermore, the comparison of serum markers showed no significant differences.

CONCLUSION

Cell proliferation, apoptosis, and angiogenesis play a limited role in NFPA behavior.

Random 'spot' urinary metanephrines compared with 24-h-urinary and plasma results in phaeochromocytomas and paragangliomas

BACKGROUND

In patients with phaeochromocytomas or paragangliomas (PPGLs), 24-h urine collections for metanephrines (uMNs) are cumbersome.

OBJECTIVE

To evaluate the diagnostic utility of ratios to creatinine of 'spot' uMNs.

METHODS

Concentrations of uMNs and plasma metanephrines (pMNs) were measured by HPLC-mass-spectrometry. We retrospectively compared correlations of 24-h-urine output and ratio to creatinine in historical specimens and prospectively assessed 24-h and contemporaneous spot urines and, where possible, pMNs. Using trimmed log-transformed values, we derived reference intervals based on age and sex for spot urines. We used multiples of upper limit of normal (ULNs) to compare areas under curves (AUCs) for receiver-operator characteristic curves of individual, and sum and product of, components.

RESULTS

In 3143 24-h-urine specimens on 2416 patients, the correlation coefficients between the ratios and outputs of metanephrine, normetanephrine and 3-methoxytyramine in 24-h urines were 0.983, 0.905 and 0.875, respectively. In 96 patients, the correlations between plasma concentrations, urine output and ratios in spot specimens were similar to those for raw output or ratios in 24-h specimens. Of the 160 patients with PPGLs, the CIs for AUCs for individual metabolites overlapped for all four types of measurement, as did those for the sum of the multiple ULNs although these were slightly higher (AUC for spot urine: 0.838 (0.529-1), plasma: 0.929 (0.874-0.984) and output: 0.858 (0.764-0.952)).

CONCLUSIONS

Ratios of fractionated metanephrines to creatinine in spot urine samples appear to have a similar diagnostic power to other measurements. The ease of spot urine collection may facilitate diagnosis and follow-up of PPGLs through improved patient compliance.

Recovery of the Hypothalamo-Pituitary-Adrenal Axis After Transsphenoidal Adenomectomy for Non-ACTH-Secreting Macroadenomas

CONTEXT

Secondary adrenal insufficiency is a potential complication of transsphenoidal adenomectomy (TSA). Most centers test recovery of the hypothalamo-pituitary-adrenal (HPA) axis after TSA, but, to our knowledge, there are no data predicting likelihood of recovery or the frequency of later recovery of HPA function.

OBJECTIVE

To assess timing and predictors of HPA axis recovery after TSA.

DESIGN

Single-center, retrospective analysis of consecutive pituitary surgeries performed between February 2015 and September 2018.

PATIENTS

Patients (N = 109) with short Synacthen test (SST) data before and at sequential time points after TSA.

MAIN OUTCOME MEASURES

Recovery of HPA axis function at 6 weeks, and 3, 6, and 9 to12 months after TSA.

RESULTS

Preoperative SST indicated adrenal insufficiency in 21.1% Among these patients, 34.8% recovered by 6 weeks after TSA. Among the 65.2% (n = 15) remaining, 13.3% and 20% recovered at 3 months and 9 to 12 months, respectively. Of the 29% of patients with adrenal insufficiency at the 6-week SST, 16%, 12%, and 6% subsequently recovered at 3, 6, and 9 to 12 months, respectively. Preoperative SST 30-minute cortisol, postoperative day 8 cortisol, and 6-week postoperative SST baseline cortisol levels above or below 430 nmol/L [15.5 μg/dL; AUC ROC, 0.86]; 160 nmol/L (5.8 μg/dL; AUC ROC, 0.75); and 180 nmol/L (6.5 μg/dL; AUC ROC, 0.88), were identified as cutoffs for predicting 6-week HPA recovery. No patients with all three cutoffs below the threshold recovered within 12 months after TSA, whereas 92% with all cutoffs above the threshold recovered HPA function within 6 weeks (OR, 12.200; 95% CI, 5.268 to 28.255).

CONCLUSION

HPA axis recovery can occur as late as 9 to 12 months after TSA, demonstrating the need for periodic reassessment of patients who initially have SST-determined adrenal insufficiency after TSA. Pre- and postoperative SST values can guide which patients are likely to recover function and potentially avoid unnecessary lifelong glucocorticoid replacement.

MON-454 Recovery of the Hypothalamic-Pituitary-Adrenal, Gonadal, and Thyroid Axes Following Trans-Sphenoidal Adenomectomy: A Single Center Experience

Background Hypopituitarism is a potential sequelea of pituitary macroadenoma or trans-sphenoidal adenomectomy (TSA). Recovery of pituitary function can occur post-TSA, and reassessment is required to avoid needless hormonal replacement. The timing and frequency of re-testing is variable across centres and the aim of this study was to determine rate of, and time to recovery of hypothalamic-pituitary adrenal (HPA), gonadal and thyroid axes postTSA. Methods We performed a single-centre retrospective analysis of TSA patients from February 2015 to September 2018. Patients with apoplexy, corticotroph adenomas, redo-surgery, emergency TSA, craniotomy or pituitary radiotherapy were excluded. Thyroid, gonadal and HPA axis adequacy was respectively assessed with TSH/freeT4, FSH/LH/estradiol or testosterone measurement and short synacthen test (SST), performed pre-TSA and at 6-weeks, 3-, 6-, and 9 to 12-months post-TSA. Results Data on 135 patients (mean age 54±17 years; 80M) were analysed. Macroadenomas occurred in 118 (87.4%), microadenoma in 8 (5.9%). Histology confirmed gonadotroph (53%), somatotroph (10.4%), plurihormonal (13.3%), lactotroph (5.2%), meningioma (1.5%), craniopharyngioma (12.6%), thyrotroph (1.5%) and metastatic malignancy (2.2%). 53.7%, 30.2% and 19.1% of patients had pre-op gonadal, thyroid and HPA function deficit respectively. 59% of patients had at least one deficit at baseline. Age was associated with the number of deficits manifested (F=6.026, p<0.001). 6-weeks post-TSA, 31.4%, 20.6% and 32% showed gonadal, thyroid and HPA axis deficit respectively. 35.7% of patients with normal pre-op pituitary function developed at least one new hormonal axis deficit at 6-weeks. Of 19.1% patients with abnormal pre-op HPA function, 30.4 % (7/23) recovered at 6-weeks. Among patients with abnormal HPA function at 6 weeks, 12.2%, 7.3% and 4.9% recovered at 3-, 6-, and 9 to 12-months respectively. 31.6% of patients with abnormal pre-op thyroid and 20% of patients with abnormal pre-op gonadal axes recovered at 6-weeks. Among patients recovering HPA axis function at 6-weeks, the majority also recovered thyroid axis (85.1% vs 14.9%, χ2=4.839, OR 2.643, p=0.03), whereas no association was found between gonadal and HPA axis recovery (54.1% vs 45.9%, p=0.16). Conclusions We demonstrate a significant rate of recovery of pre-operative pituitary deficit following TSA. 6-weeks post-operatively, gonadal failure is the most prevalent deficit. Regaining HPA axis function is a positive predictor for thyroid axis recovery but not gonadal axis recovery. HPA axis normalization can even occur at 9 to 12-months post-TSA, emphasizing the importance of periodic reassessment to avoid unnecessary hydrocortisone replacement in those who could eventually regain function. More longitudinal data are needed to assess the potential for recovery of thyroid and gonadal axes at >6 weeks post-op.

The Short Synacthen (Corticotropin) Test Can Be Used to Predict Recovery of Hypothalamo-Pituitary-Adrenal Axis Function

CONTEXT

The 250-μg short Synacthen (corticotropin) test (SST) is the most commonly used tool to assess hypothalamo-pituitary-adrenal (HPA) axis function. There are many potentially reversible causes of adrenal insufficiency (AI), but no data to guide clinicians as to the frequency of repeat testing or likelihood of HPA axis recovery.

OBJECTIVE

To use the SST results to predict adrenal recovery.

DESIGN

A retrospective analysis of 1912 SSTs data.

PATIENTS

Seven hundred seventy-six patients with reversible causes of AI were identified who had at least two SSTs performed. A subgroup analysis was performed on individuals previously treated with suppressive doses of glucocorticoids (n = 110).

MAIN OUTCOME MEASURES

Recovery of HPA axis function.

RESULTS

SST 30-minute cortisol levels above or below 350 nmol/L (12.7 μg/dL) best predicted HPA axis recovery [area under the curve (AUC) receiver operating curve (ROC) = 0.85; median recovery time: 334 vs 1368 days, P = 8.5 × 10-13]: 99% of patients with a 30-minute cortisol >350 nmol/L recovered adrenal function within 4 years, compared with 49% in those with cortisol levels <350 nmol/L. In the subgroup analysis, delta cortisol (30-minute-basal) best predicted the recovery (AUC ROC = 0.77; median recovery time: 262 vs 974 days, P = 7.0 × 10-6). No patient with a delta cortisol <100 nmol (3.6 μg/dL) and a subsequent 1-year random cortisol <200 nmol/L (7.3 μg/dL) recovered HPA axis function.

CONCLUSIONS

Cortisol levels across an SST can be used to predict recovery of AI and may guide the frequency of repeat testing and inform both clinicians and patients as to the likelihood of restoration of HPA axis function.

Transsphenoidal surgery for pituitary tumours: frequency and predictors of delayed hyponatraemia and their relationship to early readmission

OBJECTIVE

A major cause of readmission after transsphenoidal surgery (TSS) is delayed hyponatraemia. The purpose of this study was to identify predictors of hyponatraemia one week post surgery and predictors of 30-day readmissions for hyponatraemia.

DESIGN

A retrospective cohort study including patients who had TSS performed for pituitary lesions.

METHOD

The risk of readmission for hyponatraemia was assessed in consecutive patients between January 2008 and March 2016. The risk of hyponatraemia one week post surgery was assessed in patients admitted for TSS between July 2011 and March 2016.

RESULTS

Of all included patients, 56/522 (10.7%) were readmitted within 30 days. Hyponatraemia was found in 14/56 (25%) of 30-day readmissions. We did not identify any predictive variable for hyponatraemia on readmission. The number of patients with hyponatraemia on the seventh post-operative day was 26/314 (8.3%). The risk of hyponatraemia one week post surgery was increased by an odds ratio of 2.40 (95% CI: 1.06-5.40) in patients with a tumour abutting the optic chiasm and by an odds ratio of 1.16 (1.04-1.31) per mmol/L decrease in sodium levels on the first post-operative day.

CONCLUSIONS

Hyponatraemia occurred in 25% of readmissions; however, we did not identify any predictive variable for readmission with hyponatraemia. One week post surgery, 8.9% had hyponatraemia. Tumours pressing on the optic chiasm as well as a fall in sodium levels on the first post-operative day were associated with an increased risk of hyponatraemia one week post surgery. We suggest that a day 7 serum sodium <130 nmol/L should lead to concern and the provision of patient advice.

INITIATION OF PATIENTS ONTO LONG-ACTING SOMATOSTATIN ANALOGUE THERAPY FOR NEUROENDOCRINE TUMORS: A SINGLE-CENTER REVIEW OF PRACTICE

OBJECTIVE

Neuroendocrine tumors (NETs) are being seen increasingly frequently, and recent data show that long-acting somatostatin analogues have become a major initial treatment, regardless of whether the tumors are functioning or not. However, test dosing with subcutaneous (sc) octreotide is usually advised to assess longer-term tolerability, although this advice is mainly based on results with functioning tumors. The aim of the study was to assess the value of an initiating test dose of sc octreotide on the prediction of subsequent adverse events after treatment with the long-acting analogue.

METHODS

In a single, large Centre of Excellence for NETs, a first cohort of patients (n = 24) was admitted overnight after an sc injection of octreotide, and then administered the analogue; a subsequent group (n = 53) had the test dose performed on an outpatient basis. Side effects were recorded after the test dose and subsequent treatment with the long-acting analogue.

RESULTS

The test dose injection was of little value in predicting adverse events following the long-acting somatostatin analogue.

CONCLUSION

Unless there are serious symptoms associated with a functioning NET, it is unnecessary to carry out a test dose; a change to this procedure will improve resource allocation and should enhance early initiation onto maintenance therapy.

ABBREVIATIONS

CLARINET = Controlled study of lanreotide antiproliferative response in neuroendocrine tumors LAR = long-acting repeatable NET = neuroendocrine tumor PROMID = Placebo-controlled, double-blind, prospective, randomized study on the effect of octreotide LAR in the control of tumor growth in patients with meta-static neuroendocrine midgut tumors.

Routine genetic screening with a multi-gene panel in patients with pheochromocytomas

PURPOSE

Several new gene mutations have been reported in recent years to be associated with a risk of familial pheochromocytoma. However, it is unclear as to whether extensive genetic testing is required in all patients.

METHODS

The clinical data of consecutive patients operated for pheochromocytoma over a decade in a tertiary referral center were reviewed. Genetic screening was performed using a 10-gene panel: RET, VHL, SDHB, SDHD, SDHA, SDHC, SDHAF2, MAX, TMEM127 and FH.

RESULTS

A total of 166 patients were analyzed: 87 of them had genetic screening performed (39 M: 44.8%, 48 F: 55.2%, age range 6-81 years, mean 45±16.8 years). In total, 22/87 (25.3%) patients had germline mutations, while 65/87 (74.7%) patients presented with apparently sporadic tumors. Germline VHL mutations were identified in 11.7% of patients, RET in 6.8% (five MEN2A/MEN2 and one MEN2B/MEN3), SDHD in 2.3%, MAX in 2.3%, SDHB in 1.1%, and TMEM127 in 1.1% of patients. At diagnosis, 15.1% of patients with unilateral non-syndromic pheochromocytoma showed germline mutations. We identified 19.7% of mutations in patients with unilateral-non-recurrent pheochromocytomas within 5 years vs. 50% in the recurrent-bilateral-metastatic group (p = 0.01). Germline mutations were more frequently seen with bilateral pheochromocytomas (p = 0.001): 80% of patients with bilateral disease had germline mutations (4 VHL, 3 RET, 1 MAX).

CONCLUSIONS

The advent of rapid genetic screening using a gene-panel makes it feasible to screen large cohorts of patients and provides a valuable tool to contribute to the prediction of bilateral and malignant disease and to screen family members.

Baseline morning cortisol level as a predictor of pituitary-adrenal reserve: a comparison across three assays

CONTEXT

The short ACTH stimulation test (250 μg) is the dynamic test most frequently used to assess adrenal function. It is possible that a single basal cortisol could be used to predict the dynamic response, but research has been hampered by the use of different assays and thresholds.

OBJECTIVE

To propose a morning baseline cortisol criterion of three of the most commonly used modern cortisol immunoassays - Advia Centaur (Siemens), Architect (Abbott) and the Roche Modular System (Roche) - that could predict adrenal sufficiency.

DESIGN

Observational, retrospective cross-sectional study at two centres.

PATIENTS AND MEASUREMENTS

Retrospective analysis of the results of 1019 Short Synacthen tests (SSTs) with the Advia Centaur, 449 SSTs with the Architect and 2050 SSTs with the Roche Modular System assay. Serum cortisol levels were measured prior to injection of 250 μg Synacthen and after 30 min. Overall, we were able to collate data from a total of 3518 SSTs in 3571 patients.

RESULTS

Using receiver-operator curve analysis, baseline cortisol levels for predicting passing the SST with 100% specificity were 358 nmol/l for Siemens, 336 nmol/l for Abbott and 506 nmol/l for Roche. Utilizing these criteria, 589, 158 and 578 SSTs, respectively, for Siemens, Abbott and Roche immunoassays could have been avoided.

CONCLUSIONS

We have defined assay-specific morning cortisol levels that are able to predict the integrity of the hypothalamo-pituitary-adrenal axis. We propose that this represents a valid tool for the initial assessment of adrenal function and has the potential to obviate the need for dynamic testing in a significant number of patients.

Pituitary stalk thickening: the role of an innovative MRI imaging analysis which may assist in determining clinical management

CONTEXT

Disease processes that affect the pituitary stalk are broad; the diagnosis and management of these lesions remains unclear.

OBJECTIVE

The aim was to assess the clinical, biochemical and histopathological characteristics of pituitary stalk lesions and their association with specific MRI features in order to provide diagnostic and prognostic guidance.

DESIGN AND METHODS

Retrospective observational study of 36 patients (mean age 37years, range: 4-83) with pituitary stalk thickening evaluated at a university hospital in Oxford, UK, 2007-2015. We reviewed morphology, signal intensity, enhancement and texture appearance at MRI (evaluated with the ImageJ programme), along with clinical, biochemical, histopathological and long-term follow-up data.

RESULTS

Diagnosis was considered certain for 22 patients: 46% neoplastic, 32% inflammatory and 22% congenital lesions. In the remaining 14 patients, a diagnosis of a non-neoplastic disorder was assumed on the basis of long-term follow-up (mean 41.3months, range: 12-84). Diabetes insipidus and headache were common features in 47 and 42% at presentation, with secondary hypogonadism the most frequent anterior pituitary defect. Neoplasia was suggested on size criteria or progression with 30% sensitivity. However, textural analysis of MRI scans revealed a significant correlation between the tumour pathology and pituitary stalk heterogeneity in pre- and post-gadolinium T1-weighted images (sensitivity: 88.9%, specificity: 91.7%).

CONCLUSIONS

New techniques of MRI imaging analysis may identify clinically significant neoplastic lesions, thus directing future therapy. We propose possible textural heterogeneity criteria of the pituitary stalk on pre- and post-gadolinium T1 images with the aim of differentiating between neoplastic and non-neoplastic lesions with a high degree of accuracy.

Diabetic ketoacidosis in the setting of HNF1A-maturity onset diabetes of the young

A female patient was treated for type 1 diabetes following presentation at 12 years of age with hyperglycaemia, polydipsia and weight loss. Eleven years later, while screening relatives attending a genetic diabetes clinic, she was identified as potentially harbouring a mutation in the hepatocyte nuclear factor 1A (HNF1A) gene. Biochemical testing supported the diagnosis of HNF1A-maturity onset diabetes of the young (MODY) and genetic screening was positive for a heterozygous mutation in the HNF1A gene. The patient transitioned from insulin to sulfonylurea therapy. Three years later, in the setting of poor metabolic control, the patient presented to the emergency department with a history of nausea, vomiting and palpitations. A diagnosis of diabetic ketoacidosis (DKA) was confirmed and successfully treated. Although a diagnosis of HNF1A-MODY is rarely considered in a patient with a history of DKA, we demonstrate that DKA is possible in the setting of non-compliance with sulfonylurea therapy.

A role for coding functional variants in HNF4A in type 2 diabetes susceptibility

AIMS/HYPOTHESIS

Rare mutations in the gene HNF4A, encoding the transcription factor hepatocyte nuclear factor 4α (HNF-4A), account for ~5% of cases of MODY and more frequent variants in this gene may be involved in multifactorial forms of diabetes. Two low-frequency, non-synonymous variants in HNF4A (V255M, minor allele frequency [MAF] ~0.1%; T130I, MAF ~3.0%)-known to influence downstream HNF-4A target gene expression-are of interest, but previous type 2 diabetes association reports were inconclusive. We aimed to evaluate the contribution of these variants to type 2 diabetes susceptibility through large-scale association analysis.

METHODS

We genotyped both variants in at least 5,745 cases and 14,756 population controls from the UK and Denmark. We also undertook an expanded association analysis that included previously reported and novel genotype data obtained in Danish, Finnish, Canadian and Swedish samples. A meta-analysis incorporating all published association studies of the T130I variant was subsequently carried out in a maximum sample size of 14,279 cases and 26,835 controls.

RESULTS

We found no association between V255M and type 2 diabetes in either the initial (p = 0.28) or the expanded analysis (p = 0.44). However, T130I demonstrated a modest association with type 2 diabetes in the UK and Danish samples (additive per allele OR 1.17 [95% CI 1.08-1.28]; p = 1.5 × 10⁻⁴), which was strengthened in the meta-analysis (OR 1.20 [95% CI 1.10-1.30]; p = 2.1 × 10⁻⁵).

CONCLUSIONS/INTERPRETATION

Our data are consistent with T130I as a low-frequency variant influencing type 2 diabetes risk, but are not conclusive when judged against stringent standards for genome-wide significance. This study exemplifies the difficulties encountered in association testing of low-frequency variants.

Genetic association analysis of LARS2 with type 2 diabetes

AIMS/HYPOTHESIS

LARS2 has been previously identified as a potential type 2 diabetes susceptibility gene through the low-frequency H324Q (rs71645922) variant (minor allele frequency [MAF] 3.0%). However, this association did not achieve genome-wide levels of significance. The aim of this study was to establish the true contribution of this variant and common variants in LARS2 (MAF > 5%) to type 2 diabetes risk.

METHODS

We combined genome-wide association data (n = 10,128) from the DIAGRAM consortium with independent data derived from a tagging single nucleotide polymorphism (SNP) approach in Dutch individuals (n = 999) and took forward two SNPs of interest to replication in up to 11,163 Dutch participants (rs17637703 and rs952621). In addition, because inspection of genome-wide association study data identified a cluster of low-frequency variants with evidence of type 2 diabetes association, we attempted replication of rs9825041 (a proxy for this group) and the previously identified H324Q variant in up to 35,715 participants of European descent.

RESULTS

No association between the common SNPs in LARS2 and type 2 diabetes was found. Our replication studies for the two low-frequency variants, rs9825041 and H324Q, failed to confirm an association with type 2 diabetes in Dutch, Scandinavian and UK samples (OR 1.03 [95% CI 0.95-1.12], p = 0.45, n = 31,962 and OR 0.99 [0.90-1.08], p = 0.78, n = 35,715 respectively).

CONCLUSIONS/INTERPRETATION

In this study, the largest study examining the role of sequence variants in LARS2 in type 2 diabetes susceptibility, we found no evidence to support previous data indicating a role in type 2 diabetes susceptibility.

Low frequency variants in the exons only encoding isoform A of HNF1A do not contribute to susceptibility to type 2 diabetes

Background

There is considerable interest in the hypothesis that low frequency, intermediate penetrance variants contribute to the proportion of Type 2 Diabetes (T2D) susceptibility not attributable to the common variants uncovered through genome-wide association approaches. Genes previously implicated in monogenic and multifactorial forms of diabetes are obvious candidates in this respect. In this study, we focussed on exons 8–10 of the HNF1A gene since rare, penetrant mutations in these exons (which are only transcribed in selected HNF1A isoforms) are associated with a later age of diagnosis of Maturity onset diabetes of the young (MODY) than mutations in exons 1–7. The age of diagnosis in the subgroup of HNF1A-MODY individuals with exon 8–10 mutations overlaps with that of early multifactorial T2D, and we set out to test the hypothesis that these exons might also harbour low-frequency coding variants of intermediate penetrance that contribute to risk of multifactorial T2D.

Methodology and Principal Findings

We performed targeted capillary resequencing of HNF1A exons 8–10 in 591 European T2D subjects enriched for genetic aetiology on the basis of an early age of diagnosis (≤45 years) and/or family history of T2D (≥1 affected sibling). PCR products were sequenced and compared to the published HNF1A sequence. We identified several variants (rs735396 [IVS9−24T>C], rs1169304 [IVS8+29T>C], c.1768+44C>T [IVS9+44C>T] and rs61953349 [c.1545G>A, p.T515T] but no novel non-synonymous coding variants were detected.

Conclusions and Significance

We conclude that low frequency, nonsynonymous coding variants in the terminal exons of HNF1A are unlikely to contribute to T2D-susceptibility in European samples. Nevertheless, the rationale for seeking low-frequency causal variants in genes known to contain rare, penetrant mutations remains strong and should motivate efforts to screen other genes in a similar fashion.

Genetics of type 2 diabetes mellitus and obesity--a review

Type 2 diabetes (T2D) and obesity are recognized as conditions of growing biomedical importance to societies worldwide. Despite this, lack of understanding concerning the processes which normally serve to maintain weight and to regulate glucose concentrations, and ignorance about the mechanisms by which these homeostatic processes fail, remains a significant obstacle to the development of improved tools for management and prevention. There has been a long-standing belief that the identification of the specific genes influencing development of these conditions has the potential to reveal these fundamental processes, thereby providing vital clues to support clinical advances. Furthermore, there has been the hope that this information will translate into the capacity to deliver more 'personalized' medical care, whereby management can be tailored in accordance with an appreciation of individual molecular pathogenesis. As this review indicates, these developments are already a reality for selected monogenic forms of diabetes and obesity. Recent advances in the identification of genes underlying multifactorial forms of these conditions will accelerate efforts to effect similar clinical translation across the full spectrum of disease.