m6A Regulators in Human Adipose Tissue - Depot-Specificity and Correlation With Obesity

BACKGROUND

N⁶-methyladenosine (m6A) is one of the most abundant post-transcriptional modifications on mRNA influencing mRNA metabolism. There is emerging evidence for its implication in metabolic disease. No comprehensive analyses on gene expression of m6A regulators in human adipose tissue, especially in paired adipose tissue depots, and its correlation with clinical variables were reported so far. We hypothesized that inter-depot specific gene expression of m6A regulators may differentially correlate with clinical variables related to obesity and fat distribution.

METHODS

We extracted intra-individually paired gene expression data (omental visceral adipose tissue (OVAT) N=48; subcutaneous adipose tissue (SAT) N=56) of m6A regulators from an existing microarray dataset. We also measured gene expression in another sample set of paired OVAT and SAT (N=46) using RT-qPCR. Finally, we extracted existing gene expression data from peripheral mononuclear blood cells (PBMCs) and single nucleotide polymorphisms (SNPs) in METTL3 and YTHDF3 from genome wide data from the Sorbs population (N=1049). The data were analysed for differential gene expression between OVAT and SAT; and for association with obesity and clinical variables. We further tested for association of SNP markers with gene expression and clinical traits.

RESULTS

In adipose tissue we observed that several m6A regulators (WTAP, VIRMA, YTHDC1 and ALKBH5) correlate with obesity and clinical variables. Moreover, we found adipose tissue depot specific gene expression for METTL3, WTAP, VIRMA, FTO and YTHDC1. In PBMCs, we identified ALKBH5 and YTHDF3 correlated with obesity. Genetic markers in METTL3 associate with BMI whilst SNPs in YTHDF3 are associated with its gene expression.

CONCLUSIONS

Our data show that expression of m6A regulators correlates with obesity, is adipose tissue depot-specific and related to clinical traits. Genetic variation in m6A regulators adds an additional layer of variability to the functional consequences.

Gastric bypass versus sleeve gastrectomy in patients with type 2 diabetes (Oseberg): a single-centre, triple-blind, randomised controlled trial

BACKGROUND

For patients with obesity and type 2 diabetes, weight loss improves insulin sensitivity and β-cell function, and can induce remission of diabetes. The comparative efficacy of various bariatric procedures for the remission of type 2 diabetes has not been fully elucidated. We aimed to compare the effects of the two most common bariatric procedures, gastric bypass and sleeve gastrectomy, on remission of diabetes and β-cell function.

METHODS

We conducted a single-centre, triple-blind, randomised trial at Vestfold Hospital Trust (Tønsberg, Norway), in which patients (aged ≥18 years) with type 2 diabetes and obesity were randomly assigned (1:1) to receive gastric bypass or sleeve gastrectomy (the Oseberg study). Randomisation was performed with a computerised random number generator and a block size of 10. Treatment allocation was masked from participants, study personnel, and outcome assessors and was concealed with sealed opaque envelopes. Surgeons used identical skin incisions during both surgeries and were not involved in patient follow-up. The primary clinical outcome was the proportion of participants with complete remission of type 2 diabetes (HbA_1c of ≤6·0% [42 mmol/mol] without the use of glucose-lowering medication) at 1 year after surgery. The primary physiological outcome was disposition index (a measure of β-cell function) at 1 year after surgery, as assessed by an intravenous glucose tolerance test. Primary outcomes were analysed in the intention-to-treat and per-protocol populations. This trial is ongoing and closed to recruitment, and is registered with ClinicalTrials.gov, NCT01778738.

FINDINGS

Between Oct 15, 2012, and Sept 1, 2017, 1305 patients who were preparing for bariatric surgery were screened, of whom 319 consecutive patients with type 2 diabetes were assessed for eligibility. 109 patients were enrolled and randomly assigned to gastric bypass (n=54) or sleeve gastrectomy (n=55). 107 (98%) of 109 patients completed 1-year follow-up, with one patient in each group withdrawing after surgery (per-protocol population). In the intention-to-treat population, diabetes remission rates were higher in the gastric bypass group than in the sleeve gastrectomy group (risk difference 27% [95% CI 10 to 44]; relative risk [RR] 1·57 [1·14 to 2·16], p=0·0054); results were similar in the per-protocol population (risk difference 27% [95% CI 10 to 45]; RR 1·57 [1·14 to 2·15], p=0·0036). In the intention-to-treat population, disposition index increased in both groups (between-group difference 55 [-111 to 220], p=0·52); results were similar in the per-protocol population (between-group difference 21 [-214 to 256], p=0.86). In the gastric bypass group, ten of 54 participants had early complications and 17 of 53 had late side-effects. In the sleeve gastrectomy group, eight of 55 participants had early complications and 22 of 54 had late side-effects. No deaths occurred in either group.

INTERPRETATION

Gastric bypass was found to be superior to sleeve gastrectomy for remission of type 2 diabetes at 1 year after surgery, and the two procedures had a similar beneficial effect on β-cell function. The use of gastric bypass as the preferred bariatric procedure for patients with obesity and type 2 diabetes could improve diabetes care and reduce related societal costs.

FUNDING

Morbid Obesity Centre, Vestfold Hospital Trust.

Single-centre, triple-blinded, randomised, 1-year, parallel-group, superiority study to compare the effects of Roux-en-Y gastric bypass and sleeve gastrectomy on remission of type 2 diabetes and β-cell function in subjects with morbid obesity: a protocol for the Obesity surgery in Tønsberg (Oseberg) study

INTRODUCTION

Bariatric surgery is increasingly recognised as an effective treatment option for subjects with type 2 diabetes and obesity; however, there is no conclusive evidence on the superiority of Roux-en-Y gastric bypass or sleeve gastrectomy. The Oseberg study was designed to compare the effects of gastric bypass and sleeve gastrectomy on remission of type 2 diabetes and β-cell function.

METHODS AND ANALYSIS

Single-centre, randomised, triple-blinded, two-armed superiority trial carried out at the Morbid Obesity Centre at Vestfold Hospital Trust in Norway. Eligible patients with type 2 diabetes and obesity were randomly allocated in a 1:1 ratio to either gastric bypass or sleeve gastrectomy. The primary outcome measures are (1) the proportion of participants with complete remission of type 2 diabetes (HbA1c≤6.0% in the absence of blood glucose-lowering pharmacologic therapy) and (2) β-cell function expressed by the disposition index (calculated using the frequently sampled intravenous glucose tolerance test with minimal model analysis) 1 year after surgery.

ETHICS AND DISSEMINATION

The protocol of the current study was reviewed and approved by the regional ethics committee on 12 September 2012 (ref: 2012/1427/REK sør-øst B). The results will be disseminated to academic and health professional audiences and the public via publications in international peer-reviewed journals and conferences. Participants will receive a summary of the main findings.

TRIAL REGISTRATION NUMBER

NCT01778738;Pre-results.

Associations between Lifetime Adversity and Obesity Treatment in Patients with Morbid Obesity

BACKGROUND

Bariatric surgery is associated with greater and more sustainable weight loss compared with lifestyle intervention programs. On the other hand, bariatric surgery may also be associated with physical and psychosocial complications. The influence of psychological evaluation on treatment choice, however, is not known. We aimed to examine variables associated with treatment choice and, specifically, if self-reported lifetime adversity influenced obesity treatment, i.e. bariatric surgery, high-intensive lifestyle treatment or low-intensive lifestyle treatment in primary care.

METHODS

We consecutively included 924 patients from the registry study of patients with morbid obesity at Akershus University Hospital, Lørenskog, Norway. Treatment selection was made through a shared decision-making process. Self-reported lifetime adversity was registered by trained personnel. Logistic regression models were used to assess the associations between obesity treatment and possible predictors.

RESULTS

Patients who chose bariatric surgery were more likely to have type 2 diabetes (DM2) compared with patients who chose lifestyle treatment (bariatric surgery: 35%, high-intensive lifestyle treatment: 26%, and low-intensive lifestyle treatment: 26%; p = 0.035). Patients who chose bariatric surgery were less likely than patients who chose lifestyle intervention to report lifetime adversity (bariatric surgery: 39%, high-intensive lifestyle treatment: 47%, and low-intensive lifestyle treatment: 51%; p = 0.004). After multivariable adjustments, increasing BMI, having DM2, and joint pain were associated with choosing bariatric surgery over non-surgical obesity treatment (odds ratio [95% CI]: BMI 1.03 [1.01-1.06], DM2 1.47 [1.09-1.99], and joint pain 1.46 [1.08-1.96]). Self-reported lifetime adversity was furthermore associated with lower odds of choosing bariatric surgery in patients with morbid obesity (0.67 [0.51-0.89]).

CONCLUSION

This study shows that increasing BMI, DM2, and joint pain were all associated with treatment choice for obesity. In addition, self-reported lifetime adversity was associated with the patients' treatment choice for morbid obesity. Consequently, we suggest that decisions concerning obesity treatment should include dialogue-based assessments of the patients' lifetime adversity.

The association of early post-transplant glucose levels with long-term mortality

AIMS/OBJECTIVE

We aimed to assess the long-term effects of post-transplant glycaemia on long-term survival after renal transplantation.

METHODS

Study participants were 1,410 consecutive transplant recipients without known diabetes who underwent an OGTT 10 weeks post-transplant and were observed for a median of 6.7 years (range 0.3-13.8 years). The HRs adjusted for age, sex, traditional risk factors and transplant-related risk factors were estimated.

RESULTS

Each 1 mmol/l increase in fasting plasma glucose (fPG) or 2 h plasma glucose (2hPG) was associated with 11% (95% CI -1%, 24%) and 5% (1%, 9%) increments in all-cause mortality risk and 19% (1%, 39%) and 6% (1%, 12%) increments in cardiovascular (CV) mortality risk, respectively. Including both fPG and 2hPG in the multi-adjusted model the HR for 2hPG remained unchanged, while the HR for fPG was attenuated (1.05 [1.00, 1.11] and 0.97 [0.84, 1.14]). Compared with recipients with normal glucose tolerance, patients with post-transplant diabetes mellitus had higher all-cause and CV mortality (1.54 [1.09, 2.17] and 1.80 [1.10, 2.96]), while patients with impaired glucose tolerance (IGT) had higher all-cause, but not CV mortality (1.39 [1.01, 1.91] and 1.04 [0.62, 1.74]). Conversely, impaired fasting glucose was not associated with increased all-cause or CV mortality (0.79 [0.52, 1.23] and 0.76 [0.39, 1.49]). Post-challenge hyperglycaemia predicted death from any cause and infectious disease in the multivariable analyses (1.49 [1.15, 1.95] and 1.91 [1.09, 3.33]).

CONCLUSIONS/INTERPRETATION

For predicting all-cause and CV mortality, 2hPG is superior to fPG after renal transplantation. Also, early post-transplant diabetes, IGT and post-challenge hyperglycaemia were significant predictors of death. Future studies should determine whether an OGTT helps identify renal transplant recipients at increased risk of premature death.

Undiagnosed diabetes in kidney transplant candidates: a case-finding strategy

BACKGROUND AND OBJECTIVES

Guidelines recommend that candidates for kidney transplantation (KTx) who do not have diabetes perform a pretransplantation oral glucose tolerance test (OGTT) when fasting plasma glucose (FPG) is <110 mg/dl (<6.1 mmol/L); however, the OGTT is potentially costly and cumbersome. We studied the role of the OGTT for diagnosing diabetes and the accuracy of FPG and glycated hemoglobin (HbA(1c)) for predicting a diabetic OGTT before KTx.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

In this cross-sectional study, 889 first single-kidney transplant candidates without diabetes, mainly white, performed an OGTT during the transplantation workup. Results were studied using receiver operating characteristic analysis.

RESULTS

Of 72 (8.1%) patients with undiagnosed diabetes, only 16 (22%) had a diabetic FPG (> or =126 mg/dl [> or =7.0 mmol/L]). In patients with a nondiabetic FPG, diabetes (2-hour plasma glucose [2h-PG] > or =200 mg/dl [> or =11.1 mmol/L]) was predicted by FPG but not by HbA(1c). Performing the OGTT in patients with FPG 92 to 125 mg/dl (5.1 to 6.9 mmol/L) identified 65 (90%) patients with diabetes (16 by FPG, 49 by 2h-PG) and required seven OGTTs per patient identified. Subjecting all patients with FPG <110 mg/dl (<6.1 mmol/L) to the OGTT identified 60 (83%) patients with diabetes (16 by FPG, 44 by 2h-PG) but required 14 OGTTs per patient.

CONCLUSIONS

The OGTT was paramount in finding most cases of undiagnosed diabetes before KTx. FPG but not HbA(1c) predicted a diabetic OGTT. We suggest that white KTx candidates without diabetes perform a pretransplantation OGTT when FPG is 92 to 125 mg/dl (5.1 to 6.9 mmol/L).

Impaired glucose homeostasis in renal transplant recipients receiving basiliximab

BACKGROUND

The pathogenesis of new onset diabetes after transplantation (NODAT) is multifactorial. Suppression of regulatory T lymphocytes may have a negative impact on pancreatic beta-cells. Induction with basiliximab affects regulatory T-cell function and may therefore, theoretically, also affect glucose homeostasis in renal transplant recipients.

METHODS

All kidney recipients > or =50 years of age without diabetes mellitus transplanted from 1 January 2005 to 31 December 2007 were included in a single-centre retrospective study. Immunosuppression consisted of steroids, mycophenolate mofetil and cyclosporine. Basiliximab was introduced as induction therapy 1 January 2007. An oral glucose tolerance test (OGTT) was performed in all patients 10 weeks post-transplant.

RESULTS

A total of 264 patients were recruited. One hundred and thirty-four patients received basiliximab. In the basiliximab group, 51.5% developed NODAT, impaired glucose tolerance (IGT) or impaired fasting glucose (IFG) versus 36.9% in the group without induction therapy (P = 0.017). In recipients with normal OGTT, the mean fasting glucose at 10 weeks was 5.18 mmol/l (SD: 0.54) in the basiliximab group (n = 65) and 4.84 mmol/l (SD: 0.64) in the no induction group (n = 82) (P = 0.001).

CONCLUSION

Use of basiliximab as induction therapy may be associated with impaired glucose homeostasis after kidney transplantation.

Glucose tolerance before and after renal transplantation

BACKGROUND

Renal insufficiency predisposes to insulin resistance, hyperparathyroidism and derangements in calcium phosphate and nitrogenous compound balance, leading to pre-transplant hyperglycaemia. These metabolic risk factors are not fully corrected after renal transplantation. The present study aimed to assess the role of pre-transplant glycaemia and the named metabolic risk factors in post-transplant hyperglycaemia [PHYG; impaired fasting glucose (IFG), impaired glucose tolerance (IGT) or diabetes mellitus (DM)].

METHODS

This is a retrospective cohort study involving 301 patients without pre-transplant DM. Measurements included a pre- and post-transplant oral glucose tolerance test (OGTT) as well as glomerular filtration rate (GFR), parathyroid hormone (PTH), phosphate, calcium and urea measured 10 weeks post-transplant. The risk of PHYG at 10 weeks post-transplant was analysed using multiple logistic regression.

RESULTS

Ninety-three patients (31%) had PHYG (two IFG, 52 IGT, 39 DM). Variables associated with PHYG included pre-transplant 2-h glycaemia [OR 1.26, 95% CI (1.09, 1.46)] and post-transplant urea levels [OR 1.14, 95% CI (1.02, 1.27)]. Older age, non-Caucasian ethnicity, previous transplants, >or=3 HLA class 1 mismatches and high prednisolone doses were likewise associated with an increased PHYG risk (all P < 0.05).

CONCLUSIONS

Pre-transplant glycaemia and high post-transplant levels of urea were associated with a greater risk of PHYG. This seemed to be independent of GFR, PTH, phosphate, calcium and traditional risk factors such as age and glucocorticoid load.