Developing and exploring the validity of a patient reported experience measure for adult inpatient diabetes care

AIM

To develop and explore the validity of a Patient Reported Experience Measure (PREM) for adult inpatient diabetes care.

METHOD

27 in-depth interviews were conducted to inform the development of the 42-item PREM which was cognitively tested with 10 people. A refined 38-item PREM was piloted with 228 respondents completing a paper (n = 198) or online (n = 30) version. The performance of the PREM was evaluated by exploring (i) uptake/number of responses and (ii) survey validity by investigating whether the PREM data were of adequate quality and delivered useful information.

RESULTS

The PREM had low drop-out or missing data rates suggesting it was appropriately constructed. Analysis of item frequencies and variances, and problem score calculations concluded that questions provided sufficient score differentiation.

CONCLUSIONS

This new PREM allows for experiences of inpatient diabetes care to be measured, understood and reported on to help identify priority areas for improving care quality.

Prolonged remission followed by low insulin requirements in a patient with type 1 diabetes on a very low-carbohydrate diet

Summary

The use of a low-carbohydrate diet (LCD) reduces insulin requirements in insulinopenic states such as type 1 diabetes mellitus (T1DM). However, the use of potentially ketogenic diets in this clinical setting is contentious and the mechanisms underlying their impact on glycaemic control are poorly understood. We report a case of a patient with a late-onset classic presentation of T1DM who adopted a very low-carbohydrate diet and completely avoided insulin therapy for 18 months, followed by tight glycaemic control on minimal insulin doses. The observations suggest that adherence to an LCD in T1DM, implemented soon after diagnosis, can facilitate an improved and less variable glycaemic profile in conjunction with temporary remission in some individuals. Importantly, these changes occurred in a manner that did not lead to a significant increase in blood ketone (beta-hydroxybutyrate) concentrations. This case highlights the need for further research in the form of randomised controlled trials to assess the long-term safety and sustainability of carbohydrate-reduced diets in T1DM.

Learning points

This case highlights the potential of low-carbohydrate diets (LCDs) in type 1 diabetes mellitus (T1DM) to mediate improved diabetes control and possible remission soon after diagnosis. Could carbohydrate-reduced diets implemented early in the course of T1DM delay the decline in endogenous insulin production? Adherence to an LCD in T1DM can facilitate an improved and less variable glycaemic profile. This case suggests that LCDs in T1DM may not be associated with a concerning supraphysiological ketonaemia.

Type 1 diabetes and low carbohydrate diets-Defining the degree of nutritional ketosis

AIMS

Adopting a low- or very low-carbohydrate (LCD or VLCD) diet in type 1 diabetes mellitus (T1D) is a controversial intervention. The main fear is that these diets may increase the risk of diabetic ketoacidosis. However, there is little data about the ketoacidosis risk and the level of physiological nutritional ketosis in individuals following these diets. We aimed to define the level of ketosis in those with T1D following carbohydrate restricted diets in a real-world observational study.

METHODS

Patients with T1D who had self-selected dietary carbohydrate restriction were enrolled from local clinics and were compared to those following an unrestricted regular carbohydrate control diet (RCCD). Participants completed a 3-day diary, documenting food intake, ketones, and blood/interstitial glucose concentrations.

RESULTS

Participants were divided into three groups according to mean carbohydrate intake: VLCD (<50 g carbohydrates/day) n = 6, LCD (50-130 g carbohydrates/day) n = 6, and RCCD (>130 g carbohydrates/day) n = 3. Mean beta-hydroxybutyrate (BOHB) concentrations were 1.2 mmol/l (SD 0.14), 0.3 mmol/l (SD 0.12) and 0.1mmol/l (SD 0.05) in the VLCD, LCD and RCCD groups, respectively (p = 0.02). Post hoc Dunn test demonstrated this reached statistical significance between the VLCD and RCCD groups (p = 0.02).

CONCLUSION

Carbohydrate restricted diets, in particular VLCDs, are associated with a higher BOHB level. However, the degree of ketosis seen is much lower than we expected, and significantly lower than the level typically associated with diabetic ketoacidosis. This may suggest the risk of ketoacidosis is lower than feared, although safety will need to be evaluated further in large scale randomised trials.

Dietary approaches to the management of type 2 diabetes (DIAMOND) in primary care: A protocol for a cluster randomised trial

INTRODUCTION

There is strong evidence that type 2 diabetes (T2D) remission can be achieved by adopting a low-energy diet achieved through total dietary replacement products. There is promising evidence that low-carbohydrate diets can achieve remission of T2D. The Dietary Approaches to the Management of type 2 Diabetes (DIAMOND) programme combines both approaches in a behaviourally informed low-energy, low-carbohydrate diet for people with T2D, delivered by nurses in primary care. This trial compares the effectiveness of the DIAMOND programme to usual care in inducing remission of T2D and in reducing risk of cardiovascular disease.

METHODS AND ANALYSIS

We aim to recruit 508 people in 56 practices with T2D diagnosed within 6 years, who are demographically representative of the UK population. We will allocate general practices, based on ethnicity and socioeconomic status, to provide usual care for diabetes or offer the DIAMOND programme. Participants in practices offering DIAMOND will see the nurse seven times over 6 months. At baseline, 6 months, and 1 year we will measure weight, blood pressure, HbA1c, lipid profile and risk of fatty liver disease. The primary outcome is diabetes remission at 1 year, defined as HbA1c < 48 mmol/mol and off glucose-lowering medication for at least 6 months. Thereafter, we will assess whether people resume treatment for diabetes and the incidence of microvascular and macrovascular disease through the National Diabetes Audit. Data will be analysed using mixed-effects generalised linear models. This study has been approved by the National Health Service Health Research Authority Research Ethics Committee (Ref: 22/EM/0074).

TRIAL REGISTRATION NUMBER

ISRCTN46961767.

Improved glycaemic control in patients with type 2 diabetes has a beneficial impact on NAFLD, independent of change in BMI or glucose lowering agent

BACKGROUND AND AIM

The current focus of the treatment of Non-Alcoholic Fatty Liver Disease (NAFLD) is lifestyle intervention with the aim of significant weight loss alongside aggressive cardiovascular risk reduction. NAFLD is tightly associated with type 2 diabetes (T2D) and obesity. In patients with T2D, glucose lowering agents that promote weight loss have shown a beneficial impact on NAFLD. However, it remains unclear as to whether glucose lowering can improve NALFD in patients with T2D, independent of weight loss.

METHODS AND RESULTS

In a retrospective analysis of data from 637 people with T2D, we examined the longitudinal impact of optimizing glycaemic control with DPP-IV inhibitors, GLP-1RAs and SGLT2 inhibitors on Fatty liver index (FLI) and Fibrosis score 4 (Fib-4) adjusting for changes in BMI and choice of glucose lowering regimen over a 12-month period. Multiple linear regression analysis demonstrated a significant correlation between the change in glycated haemoglobin and change in FLI after adjustment for change in BMI, age, sex, and drug class (R = 0.467, p = 0.031). The greatest reduction in FLI was observed in patients with the largest reduction in glycated haemoglobin (p < 0.0001). The probability of improvements in FLI with optimization of glycaemic control was similar with all 3 glucose lowering agents, despite differences in weight reduction. Similar relationships were observed examining the changes in glycaemic control and Fib-4.

CONCLUSIONS

Improvements in glucose control that are independent of weight loss are associated with improvement in NAFLD and should form an integral part of the management patients with co-existent NAFLD and T2D.

Bariatric surgery increases the rate of major fracture: self-controlled case series study in UK Clinical Practice Research Datalink

Conflicting results exist about the relationship between bariatric surgery and fracture risk. Also, prediction of who is at increased risk of fracture after bariatric surgery is not currently available. Hence, we used a combination of a self-controlled case series (SCCS) study to establish the association between bariatric surgery and fracture, and develop a prediction model for postoperative fracture risk estimation using a cohort study. Patients from UK Primary care records from the Clinical Practice Research Datalink GOLD linked to Hospital Episode Statistics undergoing bariatric surgery with body mass index (BMI) ≥30 kg/m2 between 1997 and 2018 were included in the cohort. Those sustaining one or more fractures in the 5 years before or after surgery were included in the SCCS. Fractures were considered in three categories: (i) any except skull and digits (primary outcome); (ii) major (hip, vertebrae, wrist/forearm, and humerus); and (iii) peripheral (forearm and lower leg). Of 5487 participants, 252 (4.6%) experienced 272 fractures (of which 80 were major and 135 peripheral) and were included in the SCCS analyses. Major fracture risk increased after surgery, incidence rate ratios (IRRs) and 95% confidence intervals (CIs): 2.77 (95% CI, 1.34-5.75) and 3.78 (95% CI, 1.42-10.08) at ≤3 years and 3.1 to 5 years postsurgery when compared to 5 years prior to surgery, respectively. Any fracture risk was higher only in the 2.1 to 5 years following surgery (IRR 1.73; 95% CI, 1.08-2.77) when compared to 5 years prior to surgery. No excess risk of peripheral fracture after surgery was identified. A prediction tool for major fracture was developed using 5487 participants included in the cohort study. It was also internally validated (area under the receiver-operating characteristic curve [AUC ROC] 0.70) with use of anxiolytics/sedatives/hypnotics and female as major predictors. Hence, major fractures are nearly threefold more likely after bariatric surgery. A simple prediction tool with five variables identifies high risk patients for major fracture. © 2021 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

Inpatient hypoglycaemia in older people is associated with a doubling in the increased length of stay compared with the younger population

BACKGROUND

Hypoglycaemia during hospital admission is associated with poor outcomes including increased length of stay. In this study, we compared the incidence of inpatient hypoglycaemia and length of stays among people of three age groups: ≤65 years, 65-80 years and >80 years old.

METHODS

The study was conducted using a 4-year electronic patient record dataset from Oxford University Hospitals NHS Foundation Trust. The dataset contains hospital admission data for people with diabetes. We analysed the blood glucose (BG) measurements and identified all level 1 (BG <4 mmol/l) and level 2 (BG <3 mmol/l) hypoglycaemic episodes. We compared the length of stays between different age groups and with different levels of hypoglycaemia.

RESULTS

We analysed data obtained from 17,658 inpatients with diabetes who underwent 32,758 hospital admissions. The length of stays for admissions with no hypoglycaemia were 3[1,6], 3[1,8] and 4[2,11] (median[interquartile range]) days for age groups ≤65 years, 65-80 years and >80 years, respectively. These were statistically significantly lower (P < 0.01 for all pairwise comparisons) than the length of stays for admissions with level 1 hypoglycaemia, which were 6[3,13], 10[5,20] and 12[6,22] days, and level 2 hypoglycaemia, which were 7[3,14], 11[5,24] and 13[6,24] days.

CONCLUSIONS

In all age groups, admissions with either level 1 or level 2 hypoglycaemia were associated with an increased length of stay. However, in both the older groups, the length of stay increments were much higher (double) than the younger counterparts. The clinical consequences of hypoglycaemia were more severe in older people compared with the younger population.

Inpatient hypoglycaemia: understanding who is at risk

AIMS/HYPOTHESIS

We analysed data obtained from the electronic patient records of inpatients with diabetes admitted to a large university hospital to understand the prevalence and distribution of inpatient hypoglycaemia.

METHODS

The study was conducted using electronic patient record data from Oxford University Hospitals NHS Foundation Trust. The dataset contains hospital admission data for patients coded for diabetes. We used the recently agreed definition for a level 1 hypoglycaemia episode as any blood glucose measurement <4 mmol/l and a level 2 hypoglycaemia episode as any blood glucose measurement <3 mmol/l. Any two or more consecutive low blood glucose measurements within a 2 h time window were considered as one single hypoglycaemic episode.

RESULTS

We analysed data obtained from 17,658 inpatients with diabetes (1696 with type 1 diabetes, 14,006 with type 2 diabetes, and 1956 with other forms of diabetes; 9277 men; mean ± SD age, 66 ± 18 years) who underwent 32,758 hospital admissions between July 2014 and August 2018. The incidence of level 1 hypoglycaemia was 21.5% and the incidence of level 2 hypoglycaemia was 9.6%. Recurrent level 1 and level 2 hypoglycaemia occurred, respectively, in 51% and 39% of hospital admissions in people with type 2 diabetes with at least one hypoglycaemic episode, and in 55% and 45% in those with type 1 diabetes. The incidence of level 2 hypoglycaemia in people with type 2 diabetes, when corrected for the number of people who remained in hospital, remained constant for the first 100 h at approximately 0.15 events per h per admission. With regards to the hypoglycaemia distribution during the day, after correcting for the number of blood glucose tests per h, there were two clear spikes in the rate of hypoglycaemia approximately 3 h after lunch and after dinner. The highest rate of hypoglycaemia per glucose test was seen between 01:00 hours and 05:00 hours. Medication had a significant impact on the incidence of level 2 hypoglycaemia, ranging from 1.5% in people with type 2 diabetes on metformin alone to 33% in people treated with a combination of rapid-acting insulin analogue, long-acting insulin analogue and i.v.-administered insulin.

CONCLUSIONS/INTERPRETATION

Retrospective analysis of data from electronic patient records enables clinicians to gain a greater understanding of the incidence and distribution of inpatient hypoglycaemia. This information should be used to drive evidence-based improvements in the glycaemic control of inpatients through targeted medication adjustment for specific populations at high risk of hypoglycaemia.

Predicting the Risk of Inpatient Hypoglycemia With Machine Learning Using Electronic Health Records

OBJECTIVE

We analyzed data from inpatients with diabetes admitted to a large university hospital to predict the risk of hypoglycemia through the use of machine learning algorithms.

RESEARCH DESIGN AND METHODS

Four years of data were extracted from a hospital electronic health record system. This included laboratory and point-of-care blood glucose (BG) values to identify biochemical and clinically significant hypoglycemic episodes (BG ≤3.9 and ≤2.9 mmol/L, respectively). We used patient demographics, administered medications, vital signs, laboratory results, and procedures performed during the hospital stays to inform the model. Two iterations of the data set included the doses of insulin administered and the past history of inpatient hypoglycemia. Eighteen different prediction models were compared using the area under the receiver operating characteristic curve (AUROC) through a 10-fold cross validation.

RESULTS

We analyzed data obtained from 17,658 inpatients with diabetes who underwent 32,758 admissions between July 2014 and August 2018. The predictive factors from the logistic regression model included people undergoing procedures, weight, type of diabetes, oxygen saturation level, use of medications (insulin, sulfonylurea, and metformin), and albumin levels. The machine learning model with the best performance was the XGBoost model (AUROC 0.96). This outperformed the logistic regression model, which had an AUROC of 0.75 for the estimation of the risk of clinically significant hypoglycemia.

CONCLUSIONS

Advanced machine learning models are superior to logistic regression models in predicting the risk of hypoglycemia in inpatients with diabetes. Trials of such models should be conducted in real time to evaluate their utility to reduce inpatient hypoglycemia.

A food-based, low-energy, low-carbohydrate diet for people with type 2 diabetes in primary care: A randomized controlled feasibility trial

AIM

To examine the feasibility of a food-based, low-energy, low-carbohydrate diet with behavioural support delivered by practice nurses for patients with type 2 diabetes.

MATERIALS AND METHODS

People with type 2 diabetes and a body mass index (BMI) of ≥30 kg/m² were randomized 2:1 to intervention or control (usual care) and assessed at 12 weeks. The intervention comprised an 800-1000 kcal/day, food-based, low-carbohydrate (<26% energy) diet for 8 weeks, followed by a 4-week weight maintenance period and four 15-20-minute appointments with a nurse. Primary outcomes were feasibility of recruitment, fidelity of intervention delivery and retention of participants at 12 weeks. Secondary outcomes included change in weight and HbA1c. Focus groups explored the intervention experience.

RESULTS

Forty-eight people were screened, 33 enrolled and 32 followed-up. Mean (±SD) weight loss in the intervention group was 9.5 kg (± 5.4 kg) compared with 2 kg (± 2.5 kg) in the control group (adjusted difference - 7.5 kg [-11.0 to -4.0, P < 0.001]). Mean reduction in HbA1c in the intervention group was 16.3 mmol/mol (± 13.3 mmol/mol) compared with 0.7 mmol/mol (±4.5 mmol/mol) in the control group (difference - 15.7 mmol/mol [-24.1 to -7.3, P < 0.001]).

CONCLUSIONS

It is feasible to recruit participants to a food-based, low-energy, low-carbohydrate intervention, for practice nurses to deliver the programme in primary care, and to retain participants in both groups. There is evidence of clinically significant short-term improvements in weight and glycaemic control.

Importance of inpatient hypoglycaemia: impact, prediction and prevention

Hypoglycaemia is a key barrier to achieving euglycaemic control in people who are hospitalized. Inpatient hypoglycaemia has been linked to adverse clinical outcomes, including mortality and longer stay in hospital. A number of studies have applied mathematical tools and statistical models to predict inpatient hypoglycaemia and identify factors that may result in hypoglycaemic events. Several different approaches have been tested to prevent inpatient hypoglycaemia. These can be categorized as human intervention, computerized methods or application of medical devices. In this review we provide an overview of the epidemiology of inpatient hypoglycaemia and its impact on patients and hospitals. We also discuss the existing methodology used to predict inpatient hypoglycaemia and the limited number of trials performed to prevent inpatient hypoglycaemia. The review highlights the urgent need for evidence-based methods to reduce inpatient hypoglycaemia.

Dietary Approaches to the Management Of type 2 Diabetes (DIAMOND): protocol for a randomised feasibility trial

INTRODUCTION

Some clinicians have observed that low-carbohydrate, low-energy diets can improve blood glucose control, with reports of remission from type 2 diabetes in some patients. In clinical trials, support for low-carbohydrate, low-energy diets has been provided by specialist staff and these programmes are unsuitable for widespread deployment in routine primary care. The aim of this trial is to test whether a newly developed behavioural support programme can effectively deliver a low-energy, low-carbohydrate diet in a primary care setting.

METHODS AND ANALYSIS

This is a feasibility randomised controlled trial (RCT) with embedded qualitative study. Thirty adult patients with type 2 diabetes and body mass index ≥30 kg/m² in 2-4 general practices will be randomised 2:1 intervention or control and followed up over 12 weeks. The intervention diet comprises 8 weeks of a low-carbohydrate food-based diet providing around 800 kcal/day, followed by 4 weeks of weight maintenance. This programme will be delivered by practice nurses, who will also support patients through goal-setting, motivation and self-monitoring across four appointments, and provide a self-help booklet with recipes, shopping lists and other behavioural support. Primary outcome measures of feasibility will be met if CIs do not cross the following proportions: that 60% of intervention group participants attempt the dietary intervention, healthcare professionals conduct the intervention delivery session with at least 60% of essential elements present and 60% of participants attend the final follow-up session. Secondary outcome measures will assess process and qualitative measures, as well as exploratory outcomes including change in haemoglobin A1c and change in weight.

ETHICS AND DISSEMINATION

This study has been granted ethical approval by the National Research Ethics Service, South Central Oxford B Research Ethics Committee (ref: 18/SC/0071). The study results will inform whether to progress to a full-scale RCT to test the efficacy of offering this programme for patients with type 2 diabetes in primary care.

TRIAL REGISTRATION NUMBER

ISRCTN62452621; Pre-results.

Barriers and facilitators to integrating primary and specialist healthcare in the United Kingdom: a narrative literature review

Many national policies propose integration between primary and specialist care to improve the care of people with long-term conditions. There is an increasing need to understand how to practically implement such service redesign. This paper reviews the literature on the barriers to, and facilitators of, integrating primary and specialist healthcare for people with long-term conditions in the UK, with the aim of informing the development and implementation of similar initiatives in integration. MEDLINE and CINAHL databases were searched and 14 articles discussing factors hindering or enabling integration were identified. The factors were extracted and synthesised and key lessons were tabulated. Successful integration of care requires synchronised changes on different levels, a well-resourced team, a well-defined and evidence-based service, agreed and articulated new roles and responsibilities, and a willingness among healthcare professionals to co-work and co-learn. Barriers to successful implementation of integrated care include a lack of commitment across organisations, limited resources, poorly functioning information technology (IT), poor coordination of finances and care pathways, conflicting objectives, and conflict within teams. The examples of integrated working provide insights into problems and solutions around interorganisational and interprofessional working that will guide those planning integration in the future.

Single Sensor Gait Analysis to Detect Diabetic Peripheral Neuropathy: A Proof of Principle Study

This study explored the potential utility of gait analysis using a single sensor unit (inertial measurement unit [IMU]) as a simple tool to detect peripheral neuropathy in people with diabetes. Seventeen people (14 men) aged 63±9 years (mean±SD) with diabetic peripheral neuropathy performed a 10-m walk test instrumented with an IMU on the lower back. Compared to a reference healthy control data set (matched by gender, age, and body mass index) both spatiotemporal and gait control variables were different between groups, with walking speed, step time, and SDa (gait control parameter) demonstrating good discriminatory power (receiver operating characteristic area under the curve >0.8). These results provide a proof of principle of this relatively simple approach which, when applied in clinical practice, can detect a signal from those with known diabetes peripheral neuropathy. The technology has the potential to be used both routinely in the clinic and for tele-health applications. Further research should focus on investigating its efficacy as an early indicator of or effectiveness of the management of peripheral neuropathy. This could support the development of interventions to prevent complications such as foot ulceration or Charcot's foot.

Prevalence and severity of non-alcoholic fatty liver disease are underestimated in clinical practice: impact of a dedicated screening approach at a large university teaching hospital

AIMS

To define the attitudes and current clinical practice of diabetes specialists with regard to non-alcoholic fatty liver disease and, based on the results, implement an evidenced-based pathway for non-alcoholic fatty liver disease assessment.

METHODS

An online survey was disseminated to diabetes specialists. Based on findings from this survey, we sought a local solution by launching an awareness campaign and implementing a screening algorithm across all diabetes clinics at a secondary/tertiary referral centre.

RESULTS

A total of 133 diabetes specialists responded to the survey. Fewer than 5% of responders correctly assessed the prevalence and severity of advanced fibrotic non-alcoholic fatty liver disease in people with diabetes as 50-75%. Whilst most clinicians performed liver function tests, only 5.7% responded stating that they would use, or had used, a non-invasive algorithm to stage the severity of non-alcoholic fatty liver disease. Implementing a local non-alcoholic fatty liver disease awareness campaign and screening strategy using pre-printed blood request forms, we ensured that 100% (n=395) of all people with Type 1 and Type 2 diabetes mellitus attending secondary/tertiary care diabetes clinics over a 6-month period were appropriately screened for advanced fibrotic non-alcoholic fatty liver disease using the Fib-4 index; 17.9% required further investigation or assessment.

CONCLUSIONS

The prevalence and severity of non-alcoholic fatty liver disease are underestimated among diabetes specialists. The Fib-4 index can easily be incorporated into clinical practice in secondary/tertiary care to identify those individuals at risk of advanced fibrosis who require further assessment and who may benefit from a dedicated multidisciplinary approach to their management.

A single dose of cannabidiol reduces blood pressure in healthy volunteers in a randomized crossover study

BACKGROUND

Cannabidiol (CBD) is a nonpsychoactive phytocannabinoid used in multiple sclerosis and intractable epilepsies. Preclinical studies show CBD has numerous cardiovascular benefits, including a reduced blood pressure (BP) response to stress. The aim of this study was to investigate if CBD reduces BP in humans.

METHODS

Nine healthy male volunteers were given 600 mg of CBD or placebo in a randomized, placebo-controlled, double-blind, crossover study. Cardiovascular parameters were monitored using a finometer and laser Doppler.

RESULTS

CBD reduced resting systolic BP (-6 mmHg; P < 0.05) and stroke volume (-8 ml; P < 0.05), with increased heart rate (HR) and maintained cardiac output. Subjects who had taken CBD had lower BP (-5 mmHg; P < 0.05, especially before and after stress), increased HR (+10 bpm; P < 0.01), decreased stroke volume (-13 ml; P < 0.01), and a blunted forearm skin blood flow response to isometric exercise. In response to cold stress, subjects who had taken CBD had blunted BP (-6 mmHg; P < 0.01) and increased HR (+7 bpm; P < 0.05), with lower total peripheral resistance.

CONCLUSIONS

This data shows that acute administration of CBD reduces resting BP and the BP increase to stress in humans, associated with increased HR. These hemodynamic changes should be considered for people taking CBD. Further research is required to establish whether CBD has a role in the treatment of cardiovascular disorders.

Efficacy and Safety of Cannabidiol and Tetrahydrocannabivarin on Glycemic and Lipid Parameters in Patients With Type 2 Diabetes: A Randomized, Double-Blind, Placebo-Controlled, Parallel Group Pilot Study

OBJECTIVE

Cannabidiol (CBD) and Δ(9)-tetrahydrocannabivarin (THCV) are nonpsychoactive phytocannabinoids affecting lipid and glucose metabolism in animal models. This study set out to examine the effects of these compounds in patients with type 2 diabetes.

RESEARCH DESIGN AND METHODS

In this randomized, double-blind, placebo-controlled study, 62 subjects with noninsulin-treated type 2 diabetes were randomized to five treatment arms: CBD (100 mg twice daily), THCV (5 mg twice daily), 1:1 ratio of CBD and THCV (5 mg/5 mg, twice daily), 20:1 ratio of CBD and THCV (100 mg/5 mg, twice daily), or matched placebo for 13 weeks. The primary end point was a change in HDL-cholesterol concentrations from baseline. Secondary/tertiary end points included changes in glycemic control, lipid profile, insulin sensitivity, body weight, liver triglyceride content, adipose tissue distribution, appetite, markers of inflammation, markers of vascular function, gut hormones, circulating endocannabinoids, and adipokine concentrations. Safety and tolerability end points were also evaluated.

RESULTS

Compared with placebo, THCV significantly decreased fasting plasma glucose (estimated treatment difference [ETD] = -1.2 mmol/L; P < 0.05) and improved pancreatic β-cell function (HOMA2 β-cell function [ETD = -44.51 points; P < 0.01]), adiponectin (ETD = -5.9 × 10(6) pg/mL; P < 0.01), and apolipoprotein A (ETD = -6.02 μmol/L; P < 0.05), although plasma HDL was unaffected. Compared with baseline (but not placebo), CBD decreased resistin (-898 pg/ml; P < 0.05) and increased glucose-dependent insulinotropic peptide (21.9 pg/ml; P < 0.05). None of the combination treatments had a significant impact on end points. CBD and THCV were well tolerated.

CONCLUSIONS

THCV could represent a new therapeutic agent in glycemic control in subjects with type 2 diabetes.

Validity of simplified protocols to estimate glomerular filtration rate using iohexol clearance

Background: Iohexol clearance is an accurate and precise exogenous marker of glomerular filtration rate (GFR), but protocols are generally lengthy or require multiple sampling. Shorter or simpler protocols would be more practicable.

Methods: Two clearance estimates, two weeks apart, were undertaken in 11 healthy individuals and 26 diabetic patients with minimal to moderate renal impairment (chronic kidney disease stages 1-3). Blood specimens withdrawn at 60, 90, 120, 150, 180 and 240 min post-iohexol were analysed for iohexol.

Results: Visit 1 demonstrated excellent correlation with visit 2 (slope 1.00, confidence interval [CI] 0.88 to 1.13, intercept 0.94 mL/min/1.73 m2, CI -9.9 to 11.8, P=0.43). The within-individual coefficient of variation (CV) of the 240 min reference method was 5.4% at a mean GFR of 84.1 mL/min/1.73 m2. Single point estimates between 120 and 240 min had CVs of 4.5-7.0%, and did not differ from the reference method CV by more than 2.0 mL/min/1.73 m2. Two and three point estimates in the interval 60-120 min post iohexol injection offered no advantages over these single-point estimates and overestimated at lower GFRs.

Conclusions: An iohexol clearance estimate of GFR derived from a single sample taken between 2 to 4 h after infusion may provide a suitable tool for routine clinical use.

The effects of obesity, diabetes and metabolic syndrome on the hydrolytic enzymes of the endocannabinoid system in animal and human adipocytes

Background

Circulating endocannabinoid levels are increased in obesity and diabetes. We have shown that fatty acid amide hydrolase (FAAH, an endocannabinoid hydrolysing enzyme) in subcutaneous adipose tissue positively correlates with BMI in healthy volunteers. The aim of the present study was to investigate whether the hydrolytic enzymes of the endocannabinoid system are affected by diabetes or metabolic syndrome in obesity.

Methods

Using radiolabelled substrates, FAAH and monoacylglycerol lipase (MGL) activities were assessed in adipocytes from various adipose depots in Zucker rats (n = 22, subcutaneous abdominal, visceral and epididymal) and bariatric patients (n = 28, subcutaneous abdominal and omental).

Results

FAAH activity was significantly increased in adipocytes of obese (Zucker Fatty) compared to Zucker lean rats (P < 0.05) but was not raised in the Zucker Diabetic Fatty rats (ZDF). MGL activity was raised in both Zucker Fatty (P < 0.001-0.01) and ZDF rats (P < 0.05) and was positively correlated with body weight and plasma glucose levels (P < 0.01). In bariatric patients (BMI range 37–58 kg.m²), there was a trend for MGL activity to correlate positively with BMI, reaching significance when type 2 diabetic patients were removed. FAAH and MGL activities in obese humans were not correlated with blood pressure, skinfold thicknesses, fasting glucose, insulin, HbA1c, triglycerides or cholesterol levels.

Conclusions

FAAH in adipocytes is differentially altered in animal models of obesity and diabetes, while MGL activity is increased by both. However, in obese humans, FAAH or MGL activity in adipocytes is not affected by diabetes, dyslipidaemia or other markers of metabolic dysfunction. This suggests increased circulating levels of endocannabinoids are not a result of altered degradation in adipose tissue.

The activity of the endocannabinoid metabolising enzyme fatty acid amide hydrolase in subcutaneous adipocytes correlates with BMI in metabolically healthy humans

Background

The endocannabinoid system (ECS) is a ubiquitously expressed signalling system, with involvement in lipid metabolism and obesity. There are reported changes in obesity of blood concentrations of the endocannabinoids anandamide (AEA) and 2-arachidonoylglcyerol (2-AG), and of adipose tissue expression levels of the two key catabolic enzymes of the ECS, fatty acid amide hydrolase (FAAH) and monoacylglycerol lipase (MGL). Surprisingly, however, the activities of these enzymes have not been assayed in conditions of increasing adiposity. The aim of the current study was to investigate whether FAAH and MGL activities in human subcutaneous adipocytes are affected by body mass index (BMI), or other markers of adiposity and metabolism.

Methods

Subcutaneous abdominal mature adipocytes, fasting blood samples and anthropometric measurements were obtained from 28 metabolically healthy subjects representing a range of BMIs. FAAH and MGL activities were assayed in mature adipocytes using radiolabelled substrates. Serum glucose, insulin and adipokines were determined using ELISAs.

Results

MGL activity showed no relationship with BMI or other adiposity indices, metabolic markers (fasting serum insulin or glucose) or serum adipokine levels (adiponectin, leptin or resistin). In contrast, FAAH activity in subcutaneous adipocytes correlated positively with BMI and waist circumference, but not with skinfold thickness, metabolic markers or serum adipokine levels.

Conclusions

In this study, novel evidence is provided that FAAH activity in subcutaneous mature adipocytes increases with BMI, whereas MGL activity does not. These findings support the hypothesis that some components of the ECS are upregulated with increasing adiposity in humans, and that AEA and 2-AG may be regulated differently.

RANTES release by human adipose tissue in vivo and evidence for depot-specific differences

Obesity is associated with elevated inflammatory signals from various adipose tissue depots. This study aimed to evaluate release of regulated on activation, normal T cell expressed and secreted (RANTES) by human adipose tissue in vivo and ex vivo, in reference to monocyte chemoattractant protein-1 (MCP-1) and interleukin-6 (IL-6) release. Arteriovenous differences of RANTES, MCP-1, and IL-6 were studied in vivo across the abdominal subcutaneous adipose tissue in healthy Caucasian subjects with a wide range of adiposity. Systemic levels and ex vivo RANTES release were studied in abdominal subcutaneous, gastric fat pad, and omental adipose tissue from morbidly obese bariatric surgery patients and in thoracic subcutaneous and epicardial adipose tissue from cardiac surgery patients without coronary artery disease. Arteriovenous studies confirmed in vivo RANTES and IL-6 release in adipose tissue of lean and obese subjects and release of MCP-1 in obesity. However, in vivo release of MCP-1 and RANTES, but not IL-6, was lower than circulating levels. Ex vivo release of RANTES was greater from the gastric fat pad compared with omental (P = 0.01) and subcutaneous (P = 0.001) tissue. Epicardial adipose tissue released less RANTES than thoracic subcutaneous adipose tissue in lean (P = 0.04) but not obese subjects. Indexes of obesity correlated with epicardial RANTES but not with systemic RANTES or its release from other depots. In conclusion, RANTES is released by human subcutaneous adipose tissue in vivo and in varying amounts by other depots ex vivo. While it appears unlikely that the adipose organ contributes significantly to circulating levels, local implications of this chemokine deserve further investigation.

Transcriptional control of human adipose tissue blood flow

Adipose tissue is highly vascularized and expresses several genes involved in vasodilatory and vasoconstrictive regulation. We took a transcriptional approach to study the relationships between adipose tissue blood flow (ATBF) and genes involved in vasoactive processes. As ATBF is impaired in obesity, we tested whether body weight interfered with the transcriptional regulation of ATBF. The mRNA content (real-time PCR) of 26 genes was quantified in subcutaneous adipose tissue biopsies from 28 healthy men with a wide range of BMI. ATBF was measured by 133Xe washout. None of the transcripts was related to fasting ATBF (ATBFF). However, the expression levels of two transcripts involved in vasodilation (natriuretic peptide receptor A/guanylate cyclase A (NPRA) and endothelial nitric oxide synthase (eNOS)) were positively associated with postprandial ATBF (r = 0.53 and r = 0.55, P < 0.01, respectively). Although BMI was negatively related to the mRNA content of NPRA and eNOS (r = -0.78 and r = -0.63, P < 0.01, respectively), the strong associations found between postprandial ATBF and the two transcripts were not affected by obesity. Several genes were subject to coordinated regulation of expression. This study demonstrates for the first time that ATBF responsiveness to nutrient intake is related to the transcription of two genes expressed in adipose tissue and directly involved in vasodilatory actions (eNOS and NPRA), suggesting that part of the regulation of ATBF is at a transcriptional level. Interestingly, these associations were not secondary to changes in BMI. We also found that certain genes involved in the regulation of ATBF are subject to coordinate regulation of expression suggesting physiological autoregulation.

Fatty acid metabolism in patients with PPARgamma mutations

CONTEXT

PPARG mutations may cause insulin resistance and dyslipidemia, but little is known about the mechanisms of the abnormalities of lipid metabolism.

OBJECTIVE

We hypothesized that in PPARG mutations, abnormal adipose tissue triglyceride storage causes insulin resistance.

DESIGN, PATIENTS, AND MAIN OUTCOME MEASURES

Whole-body and adipose tissue-specific metabolic phenotyping through arteriovenous blood sampling was made before and after a mixed meal including 13C-palmitic acid. Studies were performed in a 32-yr-old male with partial lipodystrophy and type 2 diabetes, heterozygous for the PPARG P467L mutation and in an apparently phenotypically normal 32-yr-old male heterozygous for the PPARG n.AAA553T mutation. Comparator groups were age- and sex-matched healthy participants (n=10) and type 2 diabetes sex-matched participants (n=6).

RESULTS

The P467L patient had elevated unmodulated fasting and postprandial plasma nonesterified fatty acid (NEFA) concentrations, despite a low adipose tissue NEFA output. Instead, NEFA appeared to originate directly from triglyceride-rich lipoproteins: 13C-palmitic acid accumulated rapidly in the NEFA fraction, as a sign of impaired fatty acid trapping in tissues. In contrast to the Pparg haploinsufficient mouse, the patient with n.AAA553T mutation did not exhibit paradoxically insulin sensitive and showed a mostly normal metabolic pattern.

CONCLUSIONS

The lipodystrophic PPARG P467L phenotype include excessive and uncontrolled generation of NEFA directly from triglyceride-rich lipoproteins, explaining high systemic NEFA concentrations, whereas the human PPARG haploinsufficiency is metabolically almost normal.

Tissue-specific stable isotope measurements of postprandial lipid metabolism in familial combined hyperlipidaemia

OBJECTIVE

The metabolic defects underlying familial combined hyperlipidaemia (FCHL) are not clearly understood. We used stable isotope techniques combined with tissue-specific measurements in adipose tissue and forearm muscle to investigate fatty acid handling by these tissues in the fasting and postprandial states.

RESULTS

Patients were insulin resistant as shown by higher glucose and insulin concentrations and lower muscle glucose extraction than controls. Plasma triacylglycerol (TAG) concentrations were higher in patients. Adipose tissue TAG extraction was not lower in patients than controls, although TAG clearance was lower, probably representing saturation. Following a test meal, patients showed a greater increase in chylomicron-TAG concentrations. There were no differences between FCHL patients and controls in postprandial suppression of non-esterified fatty acid (NEFA) concentrations or postprandial NEFA release, but patients had greater trapping of exogenous fatty acids in adipose tissue. 3-Hydroxybutyrate concentrations were lower in patients indicative of decreased hepatic fatty acid oxidation.

CONCLUSIONS

In this group of patients with FCHL, the major defect appeared to be overproduction of TAG by the liver due to decreased fatty acid oxidation, with fatty acids directed to TAG synthesis. We found no evidence of decreased lipoprotein lipase action or impaired fatty acid re-esterification in adipose tissue.

Adipose tissue: a key target for diabetes pathophysiology and treatment?

Excess adipose tissue brings with it a number of adverse consequences, many of which may stem from the development of insulin resistance. An emerging view is that inflammatory changes occurring in expanding adipose tissue are associated with the secretion of peptide and other factors that can adversely affect metabolic processes in other key insulin-target tissues, especially liver and skeletal muscle. However, there is still a commonly-expressed view that the adverse changes in other tissues are ultimately due to an excess of fatty acids, liberated by a metabolically-challenged adipose tissue. Our own studies of adipose tissue metabolism and physiological function (especially blood flow) IN VIVO suggest that these two views of adipose tissue function may be closely linked. Enlarged adipocytes are less dynamic in their responses, just as 'enlarged adipose tissue' is less dynamic in blood flow regulation. Adipocytes seem to be able to sense the appropriate level of fat storage. If the normal mechanisms regulating adipocyte fat storage are interfered with (either in genetically-modified animals or by increasing the size of the adipocytes), then perhaps some sort of cellular stress sets in, leading to the inflammatory and endocrine changes. Some evidence for this comes from the effects of the thiazolidinediones, which improve adipose tissue function and in parallel reduce inflammatory changes.

Removal of triacylglycerols from chylomicrons and VLDL by capillary beds: the basis of lipoprotein remnant formation

The triacylglycerol content of chylomicrons and VLDL (very-low-density lipoprotein) compete for the same lipolytic pathway in the capillary beds. Although chylomicron triacylglycerols appear to be the favoured substrate for lipoprotein lipase, VLDL particles compete in numbers. Methods to quantify the specific triacylglycerol removal from VLDL and chylomicrons may involve endogenous labelling of the triacylglycerol substrate with stable isotopes in combination with arteriovenous blood sampling in humans. Arteriovenous quantification of remnant lipoproteins suggests that adipose tissue with its high lipoprotein lipase activity is a principal site for generation of remnant lipoproteins. Under circumstances of reduced efficiency in the removal of triacylglycerols from lipoproteins, there is accumulation of remnant lipoproteins, which are potentially atherogenic.

Rosiglitazone decreases postprandial production of acylation stimulating protein in type 2 diabetics

Background

We evaluated plasma ASP and its precursor C3 in type 2 diabetic men with/without rosiglitazone (ROSI) treatment compared to healthy non-obese men. We tested (1) whether plasma ASP or C3 are altered postprandially in subcutaneous adipose tissue or forearm muscle effluent assessed by arteriovenous (A-V) differences in healthy lean men and older obese diabetic men and (2) whether treatment with ROSI changes the arteriovenous gradient of ASP and/or C3.

Methods

In this ongoing placebo-controlled, crossover, double-blinded study, AV differences following a mixed meal were measured in diabetic men (n = 6) as compared to healthy men (n = 9).

Results

Postprandial arterial and adipose venous TG and venous NEFA were increased in diabetics vs. controls (p < 0.05–0.0001). ROSI treatment decreased postprandial arterial TG (p < 0.001), adipose venous NEFA (p < 0.005), reduced postprandial glucose (p < 0.0001) and insulin concentrations (p < 0.006). In healthy men, there was no change in postprandial C3, but an increase in adipose venous ASP vs. arterial ASP (p < 0.02), suggesting ASP production, with no change in forearm muscle. In older, obese diabetic subjects, arterial C3 was greater than in controls (p < 0.001). Arterial C3 was greater than venous C3 (p < 0.05), an effect that was lost with ROSI treatment. In diabetics, postprandial venous ASP was greater than arterial (p < 0.05), indicating ASP production, an effect that was lost with ROSI treatment (p < 0.01).

Conclusion

Increased postprandial venous production of ASP is specific for adipose tissue (absent in forearm muscle). Increased postprandial C3 and ASP in diabetic subjects is consistent with an ASP resistant state, this state is partially normalized by treatment with ROSI.

Effects of peroxisome proliferator-activated receptor-alpha and -gamma agonists on 11beta-hydroxysteroid dehydrogenase type 1 in subcutaneous adipose tissue in men

CONTEXT

In animals, peroxisome proliferator-activated receptor-alpha (PPARalpha) and PPARgamma agonists down-regulate 11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD1) mRNA and activity in liver and adipose tissue, respectively, and PPARgamma agonists reduce ACTH secretion from corticotrope cells.

OBJECTIVE

Our objective was to test whether PPAR agonists alter cortisol secretion and peripheral regeneration by 11beta-HSD1 in humans and whether reduced cortisol action contributes to metabolic effects of PPARgamma agonists.

DESIGN AND SETTING

Three randomized placebo-controlled crossover studies were conducted at a clinical research facility.

PATIENTS AND PARTICIPANTS

Healthy men and patients with type 2 diabetes participated. INTERVENTIONS, OUTCOME MEASURES, AND RESULTS: In nine healthy men, 7 d of PPARalpha agonist (fenofibrate) or PPARgamma agonist (rosiglitazone) had no effect on cortisol secretion, hepatic cortisol generation after oral cortisone administration, or tracer kinetics during 9,11,12,12-[(2)H](4)-cortisol infusion, although rosiglitazone marginally reduced cortisol generation in sc adipose tissue measured by in vivo microdialysis. In 12 healthy men, 4-5 wk of rosiglitazone increased insulin sensitivity during insulin infusion but did not change 11beta-HSD1 mRNA or activity in sc adipose tissue, and insulin sensitization was unaffected by glucocorticoid blockade with a combination of metyrapone and RU38486. In 12 men with type 2 diabetes 12 wk of rosiglitazone reduced arteriovenous cortisone extraction across abdominal sc adipose tissue and reduced 11beta-HSD1 mRNA in sc adipose tissue but increased plasma cortisol concentrations.

CONCLUSIONS

Neither PPARalpha nor PPARgamma agonists down-regulate 11beta-HSD1 or cortisol secretion acutely in humans. The early insulin-sensitizing effect of rosiglitazone is not dependent on reducing intracellular glucocorticoid concentrations. Reduced adipose 11beta-HSD1 expression and increased plasma cortisol during longer therapy with rosiglitazone probably reflect indirect effects, e.g. mediated by changes in body fat.

Acute and selective regulation of glyceroneogenesis and cytosolic phosphoenolpyruvate carboxykinase in adipose tissue by thiazolidinediones in type 2 diabetes

AIMS/HYPOTHESIS

Regulation of glyceroneogenesis and its key enzyme cytosolic phosphoenolpyruvate carboxykinase (PEPCK-C) plays a major role in the control of fatty acid release from adipose tissue. Here we investigate the effect of rosiglitazone on the expression of genes involved in fatty acid metabolism and the resulting metabolic consequences.

MATERIALS AND METHODS

Rosiglitazone was administered to Zucker fa/fa rats for 4 days and to 24 diabetic patients for 12 weeks, then mRNA expression for the genes encoding PEPCK-C, mitochondrial PEPCK, adipocyte lipid-binding protein, glycerol kinase, lipoprotein lipase and glycerol-3-phosphate dehydrogenase was examined in s.c. adipose tissue by real-time RT-PCR. Glyceroneogenesis was determined using [1-(14)C]pyruvate incorporation into lipids. Cultured adipose tissue explants from overweight women undergoing plastic surgery were incubated with rosiglitazone for various times before mRNA determination and analysis of PEPCK-C protein, activity and glyceroneogenesis.

RESULTS

Rosiglitazone administration to rats induced the expression of the gene encoding PEPCK-C mRNA (PCK1) and PEPCK-C activity in adipose tissue with a resulting 2.5-fold increase in glyceroneogenesis. This was accompanied by an improvement in dyslipidaemia as demonstrated by the decrease in plasma NEFAs and triacylglycerol. In rosiglitazone-treated diabetic patients, PCK1 mRNA was raised 2.5-fold in s.c. adipose tissue. Rosiglitazone treatment of adipose tissue explants from overweight women caused a selective augmentation in PCK1 mRNA which reached a maximum of 9-fold at 14 h, while mRNA for other genes remained unaffected. Experiments with inhibitors showed a direct and transcription-only effect, which was followed by an increase in PEPCK-C protein, enzyme activity and glyceroneogenesis.

CONCLUSIONS/INTERPRETATION

These results favour adipocyte glyceroneogenesis as the initial thiazolidinedione-responsive pathway leading to improvement in dyslipidaemia.

Insulin sensitisation affects lipoprotein lipase transport in type 2 diabetes: role of adipose tissue and skeletal muscle in response to rosiglitazone

AIMS/HYPOTHESIS

Lipoprotein lipase (LPL) is produced by adipose tissue and skeletal muscle, but acts on plasma lipoproteins after being transported to endothelial binding sites. Insulin resistance is associated with decreased plasma LPL mass. We investigated the effects of insulin sensitisation on tissue-specific LPL expression and transport in patients with type 2 diabetes.

MATERIALS AND METHODS

Arterio-venous gradients of plasma LPL activity and mass across adipose tissue and skeletal muscle were measured in 16 type 2 diabetic patients in a double-blind, placebo-controlled, cross-over randomised trial of rosiglitazone. In vivo LPL rate of action was assessed by tissue-specific arterio-venous triglyceride concentration gradients. LPL mRNA was quantified in adipose tissue and skeletal muscle biopsies.

RESULTS

Adipose tissue released large quantities of inactive LPL (p<0.001); skeletal muscle released small amounts of active LPL (p<0.01). Rosiglitazone increased adipose tissue release of LPL mass (+35%, p=0.04) and decreased the release of active LPL from skeletal muscle (-57%, p=0.03). Rosiglitazone increased adipose tissue and skeletal muscle LPL mRNA, but did not affect adipose tissue LPL rate of action or activity. Adipose tissue release of LPL mass correlated with systemic LPL mass concentrations (r=0.47, p=0.007), suggesting that the rate of adipose tissue release of LPL mass is a major determinant of systemic LPL mass concentrations.

CONCLUSIONS/INTERPRETATION

LPL transport from adipose tissue and skeletal muscle are regulated differently. In adipose tissue, rosiglitazone increases LPL mRNA abundance and LPL transport rate and possibly increases endothelial binding sites for LPL, but affects neither tissue LPL activity nor LPL rate of action.

The in vivo effects of the Pro12Ala PPARgamma2 polymorphism on adipose tissue NEFA metabolism: the first use of the Oxford Biobank

AIMS/HYPOTHESIS

To investigate the phenotypic effects of common polymorphisms on adipose tissue metabolism and cardiovascular risk factors, we set out to establish a biobank with the unique feature of allowing a prospective recruit-by-genotype approach. The first use of this biobank investigates the effects of the peroxisome proliferator-activated receptor (PPAR) Pro12Ala polymorphism on integrative tissue-specific physiology. We hypothesised that Ala12 allele carriers demonstrate greater adipose tissue metabolic flexibility and insulin sensitivity.

MATERIALS AND METHODS

From a comprehensive population register, subjects were recruited into a biobank, which was genotyped for the Pro12Ala polymorphism. Twelve healthy male Ala12 carriers and 12 matched Pro12 homozygotes underwent detailed physiological phenotyping using stable isotope techniques, and measurements of blood flow and arteriovenous differences in adipose tissue and muscle in response to a mixed meal containing [1,1,1-(13)C]tripalmitin.

RESULTS

Of 6,148 invited subjects, 1,072 were suitable for inclusion in the biobank. Among Pro12 homozygotes, insulin sensitivity correlated with HDL-cholesterol concentrations, and inversely correlated with blood pressure, apolipoprotein B, triglyceride and total cholesterol concentrations. Ala12 carriers showed no such correlations. In the meal study, Ala12 carriers had lower plasma NEFA concentrations, higher adipose tissue and muscle blood flow, and greater insulin-mediated postprandial hormone-sensitive lipase suppression along with greater insulin sensitivity than Pro12 homozygotes.

CONCLUSIONS/INTERPRETATION

This study shows that a recruit-by-genotype approach is feasible and describes the biobank's first application, providing tissue-specific physiological findings consistent with the epidemiological observation that the PPAR Ala12 allele protects against the development of type 2 diabetes.

Adipose tissue function in the insulin-resistance syndrome

Insulin resistance is often seen as a consequence of obesity and there are several possible links between adipose tissue function and insulin resistance determined in other organs such as skeletal muscle or liver. One such link is the regulation of NEFA (non-esterified fatty acid) delivery to the rest of the body. Simplistically, an expanded adipose tissue mass delivers more NEFA to the systemic circulation and these fatty acids compete for substrate utilization in skeletal muscle, which in turn reduces glucose utilization. This increases blood glucose concentration and provides the stimulus for increased insulin secretion and hyperinsulinaemia is a key feature of the insulin-resistance syndrome. However, there is abundant evidence that adipose tissue is exquisitely insulin sensitive and hyperinsulinaemia may therefore lead to a constant lipolytic inhibition in adipose tissue. Consequently, the main function of adipose tissue, to rapidly switch between fat uptake and fat release, will be hampered. Adipose tissue blood flow is the conveyor of signals and substrates to and from the adipose tissue. In healthy people adipose tissue blood flow is much enhanced by food intake, whereas in insulin-resistant subjects this response is blunted. This is another facet of unresponsiveness of adipose tissue in the insulin-resistance syndrome.

A unique role of monocyte chemoattractant protein 1 among chemokines in adipose tissue of obese subjects

CONTEXT

Low-grade inflammation in adipose tissue may contribute to insulin resistance in obesity. However, the roles of individual inflammatory mediators in adipose tissue are poorly understood.

OBJECTIVES

The objective of this study was to determine which inflammation markers are most overexpressed at the gene level in adipose tissue in human obesity and how this relates to corresponding protein secretion.

DESIGN

We examined gene expression profiles in 17 lean and 20 obese subjects. The secretory pattern of relevant corresponding proteins was examined in human s.c. adipose tissue or isolated fat cells in vitro and in vivo in several obese or lean cohorts.

RESULTS

In ranking gene expression, defined pathways associated with obesity and immune and defense responses scored high. Among seven markedly overexpressed chemokines, only monocyte chemoattractant protein 1 (MCP1) was released from adipose tissue and isolated fat cells in vitro. In obesity, the secretion and expression of MCP1 in adipose tissue pieces were more than 6- and 2-fold increased, respectively, but there was no change in circulating MCP1 levels. There was no net release of MCP1, but there was a net release of leptin, in vivo from adipose tissue into the circulation.

CONCLUSIONS

Obesity is associated with the increased expression of several chemokine genes in adipose tissue. However, only MCP1 is secreted into the extracellular space, where it primarily acts as a local factor, because little or no spillover into the circulation occurs. MCP1 influences the function of adipocytes, is a recruitment factor for macrophages, and may be a crucial link among chemokines between adipose tissue inflammation and insulin resistance.

Changes in adiponectin receptor expression in muscle and adipose tissue of type 2 diabetic patients during rosiglitazone therapy

AIMS/HYPOTHESIS

Adiponectin is important in the regulation of insulin sensitivity in man. Its receptors, adipoR1 and R2, have recently been identified, but their expression in adipose tissue and their regulation in response to insulin sensitisation of diabetic patients have never been assessed. We therefore explored the regulation of adipoR1/R2 and adiponectin expression in adipose tissue and skeletal muscle, and of adiponectin plasma concentrations in response to insulin sensitisation by rosiglitazone.

METHODS

Patients with type 2 diabetes were studied in a double-blind, placebo-controlled crossover study, using in vivo arteriovenous techniques of measuring adipose tissue and muscle blood flow, combined with measurement of adipose tissue and skeletal muscle gene expression.

RESULTS

Rosiglitazone treatment increased adiponectin concentrations by 69%. Skeletal muscle adipoR1 expression was down-regulated from 109.0 (70.1-165.7) (median [interquartile range]) to 82.8 (63.6-89.3) relative units (p=0.04), but adipose tissue adipoR1 expression was up-regulated from 5.3 (4.4-9.4) to 11.2 (4.8-15.3) relative units (p=0.02) by rosiglitazone. In contrast to adipoR1 expression, adipoR2 expression was not altered by rosiglitazone in either of the tissues. The increase in adipose tissue adipoR1 expression with rosiglitazone was associated with increased postprandial triglyceride clearance (r=0.67, p=0.05), and increased fasting fatty acid output (r=0.78, p=0.01) measured in subcutaneous adipose tissue.

CONCLUSIONS/INTERPRETATION

AdipoR1 expression is up-regulated in adipose tissue but down-regulated in skeletal muscle by rosiglitazone. These data suggest that adipoR1 plays a role in mediating the effects of adiponectin in specific tissues in relation to insulin sensitisation.

Rosiglitazone increases indexes of stearoyl-CoA desaturase activity in humans: link to insulin sensitization and the role of dominant-negative mutation in peroxisome proliferator-activated receptor-gamma

Fatty acid desaturases such as steaoryl-CoA desaturase (SCD) convert saturated to unsaturated fatty acids and are involved in lipogenesis. Observational and animal data suggest that SCD-1 activity is related to insulin sensitivity. However, the effects of insulin-sensitizing drugs on SCD gene expression and desaturase activities are unknown in humans. In a randomized, placebo-controlled, double-blind, crossover study, 24 subjects with type 2 diabetes and one subject with partial lipodystrophy and diabetes due to dominant-negative mutation in the peroxisome proliferator-activated receptor-gamma (PPARgamma) gene (P467L) received placebo and rosiglitazone for 3 months. SCD gene expression in adipose tissue was determined in 23 subjects, and in a representative subgroup (n = 10) we assessed fatty acid composition in fasting plasma triglycerides to estimate SCD and delta6- and delta5-desaturase activity, using product-to-precursor indexes. SCD mRNA expression increased by 48% after rosiglitazone (P < 0.01). SCD and delta5-desaturase but not delta6-desaturase activity indexes were increased after rosiglitazone versus placebo (P < 0.01 and P < 0.05, respectively). The change in activity index but not the expression of SCD was associated with improved insulin sensitivity (r = 0.73, P < 0.05). In the P467L PPARgamma carrier, SCD and delta5-desaturase activity indexes were exceptionally low but were restored (52- and 15-fold increases, respectively) after rosiglitazone treatment. This study shows for the first time that rosiglitazone increases SCD activity indexes and gene expression in humans. An increased SCD activity index may reflect increased lipogenesis and might contribute to insulin sensitization by rosiglitazone. The restored SCD activity index after rosiglitazone in PPARgamma mutation supports a pivotal role of PPARgamma function in SCD regulation.

The effects of rosiglitazone on fatty acid and triglyceride metabolism in type 2 diabetes

AIMS/HYPOTHESIS

We investigated the effects of rosiglitazone on NEFA and triglyceride metabolism in type 2 diabetes.

METHODS

In a double-blind, placebo-controlled, cross-over study of rosiglitazone in diet-treated type 2 diabetic subjects, we measured arteriovenous differences and tissue blood flow in forearm muscle and subcutaneous abdominal adipose tissue, used stable isotope techniques, and analysed gene expression. Responses to a mixed meal containing [1,1,1-(13)C]tripalmitin were assessed.

RESULTS

Rosiglitazone induced insulin sensitisation without altering fasting NEFA concentrations (-6.6%, p=0.16). Postprandial NEFA concentrations were lowered by rosiglitazone compared with placebo (-21%, p=0.04). Adipose tissue NEFA release was not decreased in the fasting state by rosiglitazone treatment (+24%, p=0.17) and was associated with an increased fasting hormone-sensitive lipase rate of action (+118%, p=0.01). Postprandial triglyceride concentrations were decreased by rosiglitazone treatment (-26%, p<0.01) despite unchanged fasting concentrations. Rosiglitazone did not change concentrations of triglyceride-rich lipoprotein remnants. Adipose tissue blood flow increased with rosiglitazone (+32%, p=0.03). Postprandial triglyceride [(13)C]palmitic acid concentrations were unchanged, whilst NEFA [(13)C]palmitic acid concentrations were decreased (p=0.04). In muscle, hexokinase II mRNA expression was increased by rosiglitazone (+166%, p=0.001) whilst the expression of genes involved in insulin signalling was unchanged. Adipose tissue expression of FABP4, LPL and FAT/CD36 was increased.

CONCLUSIONS/INTERPRETATION

Rosiglitazone decreases postprandial NEFA and triglyceride concentrations. This may represent decreased spillover of NEFAs from adipose tissue depots. Decreased delivery of NEFAs to the liver may lead to lowered postprandial triglyceride concentrations. Upregulation of hexokinase II expression in muscle may contribute to insulin sensitisation by rosiglitazone.

Upper and lower body adipose tissue function: a direct comparison of fat mobilization in humans

OBJECTIVES

Fat in the lower body is not associated with the same risk of cardiovascular disease as fat in the upper body. Is this explained by differences in the physiological functioning of the two depots? This study had two objectives: 1) to determine whether fat mobilization and blood flow differ between gluteal and abdominal adipose tissues in humans, and 2) to develop a new technique to assess gluteal adipose tissue function directly.

RESEARCH METHODS AND PROCEDURES

We performed detailed in vivo studies of adipose tissue function involving the assessment of fat mobilization by measurement of adipose tissue blood flows, arterio-venous differences of metabolites across each depot, and gene expression in tissue biopsies in a small-scale physiological study.

RESULTS

Gluteal adipose tissue has a lower blood flow (67% lower, p < 0.05) and lower hormone-sensitive lipase rate of action (87% lower, p < 0.05) than abdominal adipose tissue. Lipoprotein lipase rate of action and mRNA expression are not different between the depots. This is the first demonstration of a novel technique to directly investigate gluteal adipose tissue metabolism.

DISCUSSION

Direct assessment of fasting adipose tissue metabolism in defined depots show that the buttock is metabolically "silent" in terms of fatty acid release compared with the abdomen.

Human metabolic syndrome resulting from dominant-negative mutations in the nuclear receptor peroxisome proliferator-activated receptor-gamma

We previously reported a syndrome of severe hyperinsulinemia and early-onset hypertension in three patients with dominant-negative mutations in the nuclear hormone receptor peroxisome proliferator-activated receptor (PPAR)-gamma. We now report the results of further detailed pathophysiological evaluation of these subjects, the identification of affected prepubertal children within one of the original families, and the effects of thiazolidinedione therapy in two subjects. These studies 1) definitively demonstrate the presence of severe peripheral and hepatic insulin resistance in the affected subjects; 2) describe a stereotyped pattern of partial lipodystrophy associated with all the features of the metabolic syndrome and nonalcoholic steatohepatitis; 3) document abnormalities in the in vivo function of remaining adipose tissue, including the inability of subcutaneous abdominal adipose tissue to trap and store free fatty acids postprandially and the presence of very low circulating levels of adiponectin; 4) document the presence of severe hyperinsulinemia in prepubertal carriers of the proline-467-leucine (P467L) PPAR-gamma mutation; 5) provide the first direct evidence of cellular resistance to PPAR-gamma agonists in mononuclear cells derived from the patients; and 6) report on the metabolic response to thiazolidinedione therapy in two affected subjects. Although the condition is rare, the study of humans with dominant-negative mutations in PPAR-gamma can provide important insight into the roles of this nuclear receptor in human metabolism.

Clinical usefulness of cystatin C for the estimation of glomerular filtration rate in type 1 diabetes: reproducibility and accuracy compared with standard measures and iohexol clearance

OBJECTIVE-Assessment and follow-up of early renal dysfunction is important in diabetic nephropathy. Plasma creatinine is insensitive for a glomerular filtration rate (GFR) >50 ml/min and creatinine clearance is unwieldy and subject to collection inaccuracies. We aimed to assess the reproducibility, reliability, and accuracy of plasma cystatin C as a measure of GFR ranging from normal to moderate impairment due to type 1 diabetes in the presence of a normal plasma creatinine concentration. RESEARCH DESIGN AND METHODS-A sensitive immunoturbidimetric cystatin C assay was examined in 29 subjects with type 1 diabetes and 11 nondiabetic subjects. Duplicate measurements of the following were collected from each subject, 2 weeks apart: cystatin C, enzymatic plasma creatinine, 24-h creatinine clearance, GFR estimated from plasma creatinine by the Cockcroft-Gault equation, and iohexol clearance as a gold standard. RESULTS-Iohexol clearance ranged from 35 to 132 ml. min(-1). 1.73 m(-2). Plasma cystatin C compared well with the other clinically used tests. The reliability of cystatin C, as assessed by the discriminant ratio, was superior to creatinine clearance (3.4 vs. 1.5, P < 0.001) and the correlation of cystatin C with iohexol clearance (Rs -0.80) was similar to that of creatinine clearance (Rs -0.74) and superior to that of plasma creatinine and the Cockcroft-Gault estimate (Rs -0.54 and 0.66, respectively). Duplicate estimations were used to provide an unbiased equation to convert plasma cystatin C to GFR. CONCLUSIONS-Based on this study, cystatin C is a more reliable measure of GFR than creatinine clearance, is more highly correlated with iohexol clearance than plasma creatinine, and is worthy of further investigation as a clinical measure of GFR in type 1 diabetes.