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Lipid-associated metabolic signalling networks in pancreatic beta cell function Abstract Significant advances have been made in deciphering the mechanisms underlying fuel-stimulated insulin secretion by pancreatic beta cells. The contribution of the triggering/ATP-sensitive potassium (KATP)-dependent Ca2+ signalling and KATP-independent amplification pathways, that include anaplerosis and lipid signalling of glucose-stimulated insulin secretion (GSIS), are well established. A proposed model included a key role for a metabolic partitioning ‘switch’, the acetyl-CoA carboxylase (ACC)/malonyl-CoA/carnitine palmitoyltransferase-1 (CPT-1) axis, in beta cell glucose and fatty acid signalling for insulin secretion. This model has gained overwhelming support from a number of studies in recent years and is now refined through its link to the glycerolipid/NEFA cycle that provides lipid signals through its lipolysis arm. Furthermore, acetyl-CoA carboxylase may also control beta cell growth. Here we review the evidence supporting a role for the ACC/malonyl-CoA/CPT-1 axis in the control of GSIS and its particular importance under conditions of elevated fatty acids (e.g. fasting, excess nutrients, hyperlipidaemia and diabetes). We also document how it is linked to a more global lipid signalling system that includes the glycerolipid/NEFA cycle.

Placebo-controlled randomised trial with liraglutide on magnetic resonance endpoints in individuals with type 2 diabetes: a pre-specified secondary study on ectopic fat accumulation Abstract Aims/hypothesis The aim of this work was to assess the effect of liraglutide on ectopic fat accumulation in individuals with type 2 diabetes mellitus. Methods This study is a pre-specified subanalysis of the MAGNetic resonance Assessment of VICTOza efficacy in the Regression of cardiovascular dysfunction In type 2 diAbetes mellitus (MAGNA VICTORIA) study, with primary endpoints being the effects of liraglutide on left ventricular diastolic and systolic function. The MAGNA VICTORIA study was a single-centre, parallel-group trial in 50 individuals with type 2 diabetes mellitus (BMI >25 kg/m2) who were randomly assigned (1:1, stratified for sex and insulin use) to receive liraglutide 1.8 mg once daily or placebo for 26 weeks, added to standard care. Participants, study personnel and outcome assessors were blinded to treatment allocation. The secondary endpoints of visceral adipose tissue (VAT), abdominal subcutaneous adipose tissue (SAT) and epicardial fat were measured with MRI. Hepatic triacylglycerol content (HTGC) and myocardial triacylglycerol content (MTGC) were quantified with proton MR spectroscopy. Between-group differences (change from baseline) were tested for significance using ANCOVA. Mean differences with 95% CIs were reported. Results The trial was completed in 2016. Twenty-four participants were randomised to receive liraglutide and 26 to receive placebo. One patient in the liraglutide group withdrew consent before having received the study drug and was not included in the intention-to-treat analysis. Liraglutide (n = 23) vs placebo (n = 26) significantly reduced body weight (liraglutide 98.4 ± 13.8 kg to 94.3 ± 14.9 kg; placebo 94.5 ± 13.1 kg to 93.9 ± 13.2 kg; estimated treatment effect −4.5 [95% CI −6.4, −2.6] kg). HbA1c declined in both groups without a significant treatment effect of liraglutide vs placebo (liraglutide 66.7 ± 11.5 mmol/mol to 55.0 ± 13.2 mmol/mol [8.4 ± 1.1% to 7.3 ± 1.2%]; placebo 64.7 ± 10.2 mmol/mol to 56.9 ± 6.9 mmol/mol [8.2 ± 1.0% to 7.5 ± 0.7%]; estimated treatment effect −2.9 [95% CI −8.1, 2.3] mmol/mol or −0.3 [95% CI −0.8, 0.2]%). VAT did not change significantly between groups (liraglutide 207 ± 87 cm2 to 203 ± 88 cm2; placebo 204 ± 63 cm2 to 200 ± 55 cm2; estimated treatment effect −7 [95% CI −24, 10] cm2), while SAT was reduced by a significantly greater extent with liraglutide than with placebo (liraglutide 361 ± 142 cm2 to 339 ± 131 cm2; placebo 329 ± 107 cm2 to 333 ± 125 cm2; estimated treatment effect −29 [95% CI −51, −8] cm2). Epicardial fat did not change significantly between groups (liraglutide 8.9 ± 4.3 cm2 to 9.1 ± 4.7 cm2; placebo 9.6 ± 4.1 cm2 to 9.6 ± 4.6 cm2; estimated treatment effect 0.2 [95% CI −1.5, 1.8] cm2). Change in HTGC was not different between groups (liraglutide 18.1 ± 11.2% to 12.0 ± 7.7%; placebo 18.4 ± 9.4% to 14.7 ± 10.0%; estimated treatment effect −2.1 [95% CI −5.3, 1.0]%). MTGC was not different after treatment with liraglutide (1.5 ± 0.6% to 1.2 ± 0.6%) vs placebo (1.3 ± 0.5% to 1.2 ± 0.6%), with an estimated treatment effect of −0.1 (95% CI −0.4, 0.2)%. There were no adjudicated serious adverse events. Conclusions/interpretation Compared with placebo, liraglutide-treated participants lost significantly more body weight. Liraglutide primarily reduced subcutaneous fat but not visceral, hepatic, myocardial or epicardial fat. Future larger studies are needed to confirm the results of this secondary endpoint study. Trial registration ClinicalTrials.gov NCT01761318. Funding This study was funded by Novo Nordisk A/S (Bagsvaerd, Denmark).

Breast, cervical and colorectal cancer screening in adults with diabetes: a systematic review and meta-analysis Abstract Aims/hypothesis Individuals with diabetes are at increased risk of developing and dying from cancer. Evidence-based guidelines recommend universal screening for breast, cervical and colorectal cancer; however, evidence on the uptake of these tests in individuals with diabetes is mixed. We conducted a meta-analysis to quantify the association between diabetes and participation in breast, cervical and colorectal cancer screening. Methods MEDLINE, EMBASE and CINAHL were searched systematically for publications between 1 January 1997 and 18 July 2018. The search was supplemented by handsearching of reference lists of the included studies and known literature reviews. Abstracts and full texts were assessed in duplicate according to the following eligibility criteria: study conducted in the general population; diabetes included as a predictor vs a comparison group without diabetes; and breast (mammography), cervical (Papanicolaou smear) or colorectal (faecal and endoscopic tests) cancer screening uptake included as an outcome. Random-effects meta-analyses were performed using the most-adjusted estimates for each cancer site. Results Thirty-seven studies (25 cross-sectional, 12 cohorts) were included, with 27 studies on breast, 19 on cervical and 18 on colorectal cancer screening. Having diabetes was associated with significantly lower likelihood of breast (adjusted OR 0.83 [95% CI 0.77, 0.90]) and cervical (OR 0.76 [95% CI 0.71, 0.81]) cancer screening, relative to not having diabetes. Colorectal cancer screening was comparable across groups with and without diabetes (OR 0.95 [95% CI 0.86, 1.06]); however, women with diabetes were less likely to receive a colorectal cancer screening test than women without diabetes (OR 0.86 [95% CI 0.77, 0.97]). Conclusions/interpretation Our findings suggest that women with diabetes have suboptimal breast, cervical and colorectal cancer screening rates, compared with women without diabetes, although the absolute differences might be modest. Given the increased risk of cancer in this population, higher quality prospective evidence is necessary to evaluate the contribution of diabetes to cancer screening disparities in relation to other patient-, provider- and system-level factors. Registration PROSPERO registration ID CRD42017073107.

Association between glucose variation and lower extremity amputation incidence in individuals with type 2 diabetes: a nationwide retrospective cohort study Abstract Aims/hypothesis Elevated glucose level is one of the risk factors for lower extremity amputation (LEA), but whether glycaemic variability confers independent risks of LEA remains to be elucidated. This study aimed to investigate the association between visit-to-visit glycaemic variability and minor and major LEA risks during 8 years of follow-up in type 2 diabetic individuals aged 50 years and older. Methods This retrospective cohort study included 27,574 ethnic Chinese type 2 diabetic individuals aged ≥50 years from the National Diabetes Care Management Program in Taiwan. Glycaemic variability measures were presented as the CVs of fasting plasma glucose (FPG-CV) and of HbA1c (A1c-CV). The effect of glycaemic variability on the incidence of LEA events was analysed using Cox proportional hazards models. Results After a median follow-up of 8.9 years, 541 incident cases of LEA with a crude incidence density rate of 2.4 per 1000 person-years were observed. After multivariate adjustment, FPG-CV and A1c-CV were found to be significantly associated with minor LEA, with corresponding HRs of 1.53 (95% CI 1.15, 2.04) and 1.34 (95% CI 1.02, 1.77) for the third tertiles of FPG-CV and A1c-CV, respectively. In addition, these associations were stronger amongst older adults with longer diabetes duration (≥3 years) than amongst those with shorter duration (<3 years) (pinteraction < 0.01). Conclusions/interpretation Our study suggests that visit-to-visit variations in HbA1c and FPG are important predictors of minor LEA amongst older adults with type 2 diabetes, particularly for those with more than 3 years of diabetes duration.

Association between visit-to-visit variability of HbA 1c and cognitive decline: a pooled analysis of two prospective population-based cohorts Abstract Aims/hypothesis The aim of this study was to investigate the association between visit-to-visit variability in HbA1c and cognitive function decline in the elderly population. Methods We performed a pooled analysis of two prospective population-based cohorts (the Health Retirement Study [HRS] and the English Longitudinal Study of Ageing [ELSA]). Cognitive function, including memory and executive function, were assessed at baseline and every 2 years, while HbA1c levels were assessed at baseline and every 4 years. Visit-to-visit variability (VVV) in HbA1c was calculated using the CV, SD and variation independent of the mean (VIM) during the follow-up period. Linear mixed models were used to evaluate the association between HbA1c variability and cognitive function decline with adjustment for demographics, mean HbA1c, education, smoking, alcohol consumption, BMI, baseline hypertension, baseline diabetes status and HDL-cholesterol. Results The study enrolled 6237 participants (58.23% women, mean age 63.38 ± 8.62 years) with at least three measurements of HbA1c. The median follow-up duration was 10.56 ± 1.86 years. In the overall sample, compared with the lowest quartile of HbA1c variability, participants in the highest quartile of HbA1c variability had a significantly worse memory decline rate (−0.094 SD/year, 95% CI −0.185, −0.003) and executive function decline rate (−0.083 SD/year, 95% CI −0.125, −0.041), irrespective of mean HbA1c values over time. Among individuals without diabetes, each 1-SD increment in HbA1c CV was associated with a significantly higher rate of memory z score decline (−0.029, 95% CI −0.052, −0.005) and executive function z score decline (−0.049, 95% CI −0.079, −0.018) in the fully adjusted model. Conclusions/interpretation We observed a significant association between long-term HbA1c variability and cognitive decline among the non-diabetic population in this study. The effect of maintaining steady glucose control on the rate of cognitive decline merits further investigation.

Potential impact of diabetes prevention on mortality and future burden of dementia and disability: a modelling study Abstract Aims/hypothesis Diabetes is associated with an increased risk of dementia. We estimated the potential impact of trends in diabetes prevalence upon mortality and the future burden of dementia and disability in England and Wales. Methods We used a probabilistic multi-state, open cohort Markov model to integrate observed trends in diabetes, cardiovascular disease and dementia to forecast the occurrence of disability and dementia up to the year 2060. Model input data were taken from the English Longitudinal Study of Ageing, Office for National Statistics vital data and published effect estimates for health-state transition probabilities. The baseline scenario corresponded to recent trends in obesity: a 26% increase in the number of people with diabetes by 2060. This scenario was evaluated against three alternative projected trends in diabetes: increases of 49%, 20% and 7%. Results Our results suggest that changes in the trend in diabetes prevalence will lead to changes in mortality and incidence of dementia and disability, which will become visible after 10–15 years. If the relative prevalence of diabetes increases 49% by 2060, expected additional deaths would be approximately 255,000 (95% uncertainty interval [UI] 236,000–272,200), with 85,900 (71,500–101,600) cumulative additional cases of dementia and 104,900 (85,900–125,400) additional cases of disability. With a smaller relative increase in diabetes prevalence (7% increase by 2060), we estimated 222,200 (205,700–237,300) fewer deaths, and 77,000 (64,300–90,800) and 93,300 (76,700–111,400) fewer additional cases of dementia and disability, respectively, than the baseline case of a 26% increase in diabetes. Conclusions/interpretation Reducing the burden of diabetes could result in substantial reductions in the incidence of dementia and disability over the medium to long term.

Characterising nitric oxide-mediated metabolic benefits of low-dose ultraviolet radiation in the mouse: a focus on brown adipose tissue Abstract Aims/hypothesis Exposure to sunlight has the potential to suppress metabolic dysfunction and obesity. We previously demonstrated that regular exposure to low-doses of ultraviolet radiation (UVR) reduced weight gain and signs of diabetes in male mice fed a high-fat diet, in part via release of nitric oxide from skin. Here, we explore further mechanistic pathways through which low-dose UVR exerts these beneficial effects. Methods We fed mice with a luciferase-tagged Ucp1 gene (which encodes uncoupling protein-1 [UCP-1]), referred to here as the Ucp1 luciferase transgenic mouse (‘Thermomouse’) a high-fat diet and examined the effects of repeated exposure to low-dose UVR on weight gain and development of metabolic dysfunction as well as UCP-1-dependent thermogenesis in interscapular brown adipose tissue (iBAT). Results Repeated exposure to low-dose UVR suppressed the development of glucose intolerance and hepatic lipid accumulation via dermal release of nitric oxide while also reducing circulating IL-6 (compared with mice fed a high-fat diet only). Dietary nitrate supplementation did not mimic the effects of low-dose UVR. A single low dose of UVR increased UCP-1 expression (by more than twofold) in iBAT of mice fed a low-fat diet, 24 h after exposure. However, in mice fed a high-fat diet, there was no effect of UVR on UCP-1 expression in iBAT (compared with mock-treated mice) when measured at regular intervals over 12 weeks. More extensive circadian studies did not identify any substantial shifts in UCP-1 expression in mice exposed to low-dose UVR, although skin temperature at the interscapular site was reduced in UVR-exposed mice. The appearance of cells with a white adipocyte phenotype (‘whitening’) in iBAT induced by consuming the high-fat diet was suppressed by exposure to low-dose UVR in a nitric oxide-dependent fashion. Significant shifts in the expression of important core gene regulators of BAT function (Dio2, increased more than twofold), fatty acid transport (increased Fatp2 [also known as Slc27a2]), lipolysis (decreased Atgl [also known as Pnpla2]), lipogenesis (decreased Fasn) and inflammation (decreased Tnf), and proportions of macrophages (increased twofold) were observed in iBAT of mice exposed to low-dose UVR. These effects were independent of nitric oxide released from skin. Conclusions/interpretation Our results suggest that non-burning (low-dose) UVR suppresses the BAT ‘whitening’, steatotic and pro-diabetic effects of consuming a high-fat diet through skin release of nitric oxide, with some metabolic and immune pathways in iBAT regulated by UVR independently of nitric oxide.

Recruited fibroblasts reconstitute the peri-islet membrane: a longitudinal imaging study of human islet grafting and revascularisation Abstract Aims/hypothesis Rapid and adequate islet revascularisation and restoration of the islet–extracellular matrix (ECM) interaction are significant factors influencing islet survival and function of the transplanted islets in individuals with type 1 diabetes. Because the ECM encapsulating the islets is degraded during islet isolation, understanding the process of revascularisation and engraftment after transplantation is essential and needs further investigation. Methods Here we apply a longitudinal and high-resolution imaging approach to investigate the dynamics of the pancreatic islet engraftment process up to 11 months after transplantation. Human and mouse islet grafts were inserted into the anterior chamber of the mouse eye, using a NOD.ROSA-tomato.Rag2−/− or B6.ROSA-tomato host allowing the investigation of the expansion of host vs donor cells and the contribution of host cells to aspects such as promoting the encapsulation and vascularisation of the graft. Results A fibroblast-like stromal cell population of host origin rapidly migrates to ensheath the transplanted islet and aid in the formation of a basement membrane-like structure. Moreover, we show that the vessel network, while reconstituted by host endothelial cells, still retains the overall architecture of the donor islets. Conclusions/interpretation In this transplantation situation the fibroblast-like stromal cells appear to take over as main producers of ECM or act as a scaffold for other ECM-producing cells to reconstitute a peri-islet-like basement membrane. This may have implications for our understanding of long-term graft rejection and for the design of novel strategies to interfere with this process.

Trends in cancer mortality among people with vs without diabetes in the USA, 1988–2015 Abstract Aims/hypothesis Cancer-related death is higher among people with vs without diabetes. However, it is not known if this excess risk has changed over time or what types of cancer may be driving these changes. Methods To estimate rates of site-specific cancer mortality in adults with vs without self-reported diagnosed diabetes, we used data from adults aged ≥18 years at the time of the interview who participated in the 1985—2012 National Health Interview Survey. Participants’ data were linked to the National Death Index by the National Center for Health Statistics to determine vital status and cause of death through to the end of 2015. Cancer deaths were classified according to underlying cause of death. Death rates for five time periods (1988–1994, 1995–1999, 2000–2004, 2005–2009, 2010–2015) were estimated using discrete Poisson regression models adjusted for age, sex and race/ethnicity with p for linear trend reported (ptrend). Site-specific cancer mortality rates were stratified by diabetes status and period, and total cancer mortality rates were additionally stratified by sex, race/ethnicity, education and BMI status. Results Among adults with diabetes, age-adjusted cancer mortality rates (per 10,000 person-years) declined 25.5% from 39.1 (95% CI 30.1, 50.8) in 1988–1994 to 29.7 (26.6, 33.1) in 2010–2015, ptrend < 0.001. Among adults without diabetes, rates declined 25.2% from 30.9 (28.6, 33.4) in 1988–1994 to 23.2 (22.1, 24.2) in 2010–2015, ptrend < 0.01. Adults with diabetes remained approximately 30% more likely to die from cancer than people without diabetes, and this excess risk did not improve over time. In adults with diabetes, cancer mortality rates did not decline in some population subgroups (including black people, people with lower levels of education and obese people), and the excess risk increased for obese adults with vs without diabetes. Declines in total cancer mortality rates in adults with diabetes appear to be driven by large relative declines in cancers of the pancreas (55%) and breast (65%), while for lung cancer, declines are modest (7%). Conclusions/interpretation Declines in cancer mortality rates were observed in adults with and without diabetes. However, adults with diabetes continue to be more likely to die from cancer than people without diabetes. This study highlights the continued need for greater cancer risk-factor mitigation, especially in adults with diabetes.