Once-weekly glucagon-like peptide-1 receptor agonists vs dipeptidyl peptidase-4 inhibitors: cardiovascular effects in people with diabetes and cardiovascular disease

BACKGROUND

Glucagon-like peptide-1 receptor agonists (GLP-1 RAs), which have proven cardiovascular benefits, are recommended in people with type 2 diabetes (T2D) and atherosclerotic cardiovascular disease (ASCVD). However, there is limited real-world evidence comparing the effects of once-weekly (OW) GLP-1 RAs and dipeptidyl peptidase-4 inhibitors (DPP-4is). This observational cohort study (1/1/2017-9/30/2021) used data from the Optum Clinformatics® Data Mart to compare time to incident clinical cardiovascular outcomes, health care resource utilization (HCRU), and medical costs in new adult users of OW GLP-1 RAs and DPP-4is with T2D and ASCVD.

METHODS

Time to occurrence of ischemic stroke, myocardial infarction (MI), or their composite and ASCVD-related and all-cause HCRU and medical costs were investigated. Baseline characteristics were balanced using inverse probability of treatment weighting. Survival analyses were conducted to compare risks during exposure.

RESULTS

OW GLP-1 RA users (weighted N = 25,287) had 26%, 22%, and 24% lower risk of ischemic stroke, MI, and their composite, respectively, compared with DPP-4i users (weighted N = 39,684; all P < 0.01). Compared with DPP-4i users, OW GLP-1 RA users had 25% and 26% lower ASCVD-related and all-cause hospitalization costs, 19% and 23% lower ASCVD-related and all-cause medical costs, 23% and 27% fewer ASCVD-related and all-cause hospitalizations, 13% and 8% fewer ASCVD-related and all-cause outpatient visits, and 8% fewer all-cause ER visits (all P < 0.01).

CONCLUSIONS

In adults with T2D and ASCVD, OW GLP-1 RAs are associated with reduced stroke and MI risks and ASCVD-related and all-cause HCRU and costs vs DPP-4is.

Persistence on Novel Cardioprotective Antihyperglycemic Therapies in the United States

Selected glucagon-like peptide-1 receptor agonists (GLP-1RAs) and sodium-glucose cotransporter-2 inhibitors (SGLT-2is) have cardioprotective effects in patients with type 2 diabetes mellitus (T2D) and elevated cardiovascular risk. Prescription and consistent use of these medications are essential to realizing their benefits. In a nationwide deidentified United States administrative claims database of adults with T2D, the prescription practices of GLP-1RAs and SGLT-2i were evaluated across guideline-directed co-morbidity indications from 2018 to 2020. The monthly fill rates were assessed for 12 months after the initiation of therapy by calculating the proportion of days with consistent medication use. Of 587,657 subjects with T2D, 80,196 (13.6%) were prescribed GLP-1RAs and 68,149 (11.5%) SGLT-2i from 2018 to 2020, representing 12.9% and 11.6% of patients with indications for each medication, respectively. In new initiators, 1-year fill rate was 52.5% for GLP-1RAs and 52.9% for SGLT-2i, which was higher for patients with commercial insurance than those with Medicare Advantage plans for both GLP-1RAs (59.3% vs 51.0%, p <0.001) and SGLT-2i (63.4% vs 50.3%, p <0.001). After adjusting for co-morbidities, there were higher rates of prescription fills for patients with commercial insurance (odds ratio 1.17, 95% confidence interval 1.06 to 1.29 for GLP-1RAs, and 1.59 [1.42 to 1.77] for SGLT-2i); and higher income (odds ratio 1.09 [1.06 to 1.12] for GLP-1RAs, and 1.06 [1.03 to 1.1] for SGLT-2i). From 2018 to 2020, the use of GLP-1RAs and SGLT-2i remained limited to fewer than 1 in 8 patients with T2D and indications, with 1-year fill rates around 50%. The low and inconsistent use of these medications compromises their longitudinal health outcome benefits in a period of expanding indications for their use.

ODP154 Reduction of Cardiac Adipose Tissue Volume with Short-Term Empagliflozin in Patients with Type 2 Diabetes: Results from the SIMPLE Randomized Clinical Trial

Background

Sodium-glucose transporter 2 inhibitors (SGLT2-is) appear to have rapid clinical cardiovascular benefits in type 2 diabetes. Furthermore, SGLT2-is have known effects on fat metabolism. Cardiac adipose tissue (CAT) correlates with known markers of cardiovascular risk and left ventricular function. The effects of SGLT2-i treatment on CAT is largely unknown.

Objective

In this exploratory sub-study from the SIMPLE-trial, we investigated whether empagliflozin affects CAT volume in patients with type 2 diabetes.

Methods

Between April 4, 2017, and May 11, 2020, we randomized 90 patients with type 2 diabetes and established or high risk of cardiovascular disease to either 25 mg empagliflozin or placebo for 13 weeks. The primary focus of this sub-study was change in CAT evaluated by computer-tomography (CT). The analysis included 78 patients who had at least one CT scan. Furthermore, we investigated the effect of empagliflozin on left ventricular mass (LVM), end-diastolic volume (EDV) and end-systolic volume (ESV) evaluated by rest and stress 82Rubidium Positron Emission Tomography CT and changes in whole-body metabolism evaluated by fat mass distribution via dual x-ray absorptiometry and measurements of various parameters of glucose, ketone and lipid metabolism.

Results

Mean ±SD baseline CAT volume was 258.5 mL ±117.9. Empagliflozin reduced CAT after 13 weeks by 12.41 mL (95%CI [-23.83 to -0.99], P=0. 034) as compared with placebo. LVM (-5.16 g, 95%CI [-8.80 to -1.52], P=0. 006), EDV (-7.90 mL, 95%CI [-13.70 to -2.10], P=0. 008) and ESV (-5.46 mL 95%CI [-9.78 to -1.15], P=0. 014) decreased with empagliflozin when comparing groups at week 13. In addition, improvements were observed in whole body metabolic parameters: mean total body weight (-1.48 kg, 95%CI [-2.41 to -0.55], P=0. 002), total fat mass (-0.81 kg, 95%CI [-1.40 to -0.22], P=0. 008), fasting plasma (-1.82 mmol/L, 95%CI [-2.83 to -0.80], P=0. 001), HbA1c (NGSP: -0.76%, 95%CI [-1. 00 to -0.51], P<0. 001; IFCC: -8.28 mmol/mol, 95%CI [-11. 01 to -5.54], P<0. 001), beta-hydroxybutyrate (0. 07 mmol/L, 95%CI [0. 00 to 0.14], P=0. 044), and triglycerides (-16.1%, 95%CI [-27.3 to -3.2], P=0. 017), when comparing groups at week 13. We observed no significant correlation between changes in CAT and changes in LVM, EDV and ESV.

Conclusion

Treatment with empagliflozin provides an early reduction of CAT and improves myocardial structure and function which may explain some of this SGLT2-i's clinical cardiovascular benefits.

Presentation: No date and time listed

RF16 | PSUN155 Empagliflozin and the risk of nephrolithiasis

Aims

Nephrolithiasis is a common disease, estimated to affect 10% of the US population. In addition to pain, often severe, it can lead to urinary tract infections and acute kidney injury, while contributing to health care costs from emergency room visits and follow-up interventions necessary to relieve stone burden. Type 2 diabetes (T2D) is a well-known risk factor for nephrolithiasis. Recently in an observational study of patients with T2D, use of sodium-glucose transport protein 2 (SGLT2) inhibitors as glucose lowering agents was associated with a 49% lower risk of nephrolithiasis when compared with use of glucagon like peptide 1 (GLP-1) receptor agonists. We examined, prospectively, the association between renal stone disease and the use of the SGLT2 inhibitor empagliflozin, using existing data from randomized clinical trials.

Methods

Pooled data from 15,081 patients with T2D treated with empagliflozin (10,177) or placebo (4,904) from 20 phase I-IV randomized, placebo-controlled trials including the large cardiovascular outcome trial, EMPA-REG OUTCOME, were included in this analysis. Incident urinary tract stone events were captured using a pre-defined collection of MedDRA terms: nephrolithiasis, renal colic, ureterolithiasis, calculus bladder, calculus urinary, calculus urethral, and nephrocalcinosis (MedDRA version 22.1). A sensitivity analysis used a narrower definition by excluding the terms renal colic and nephrocalcinosis. Incidence rate ratios (IRR) and 95% confidence intervals (CI) were calculated using the relative risk estimate stratified by study.

Results

The median exposure to study drug was 543 (placebo) and 549 (empagliflozin 10 or 25 mg) days We found that a total of 183 patients experienced an incident urolithiasis during follow-up (79 in placebo, 104 in pooled empagliflozin) yielding annual incidence rates of 1.01 versus 0.63 events per 100 patient years in placebo and empagliflozin, respectively. All but one event occurred in patients with no prior history of urinary tract stones. The IRR was 0.64 (95% CI 0.48, 0.86), in favor of empagliflozin. In the sensitivity analysis, now restricted to nephrolithiasis, ureterolithiasis, calculus bladder, calculus urinary, and calculus urethral, the results were similar (IRR, empagliflozin vs. placebo, 0.62 [95% CI 0.45, 0.85]).

Conclusion

As compared to placebo, use of empagliflozin was associated with an approximate 40% reduction in the risk of urolithiasis in patients with T2D. Alterations in lithogenic profile of the urine (including dilutional effects) of potential stone formers after SGLT2 inhibition may explain this finding. Based on these initial observations, mechanistic studies to elucidate the mediator(s) of this seemingly protective effect and dedicated randomized prospective clinical trials appear warranted in patients with renal stone disease. As with follow-up SGLT2 inhibitor investigations conducted in patients with heart failure and chronic kidney disease, such trials should include individuals who do not have T2D.

Presentation: Sunday, June 12, 2022 12:30 p.m. - 2:30 p.m., Sunday, June 12, 2022 1:12 p.m. - 1:17 p.m.

Elevated markers of liver function are associated with poorer outcomes in HFREF: an analysis of DAPA-HF

Background

Abnormalities of liver tests in patients with heart failure with reduced ejection fraction (HFrEF) is a well-recognised phenomenon. We examined the prognostic value of measures of liver function in a large contemporary cohort of patients with HFrEF enrolled in the Dapagliflozin and Prevention of Adverse Outcomes in Heart Failure (DAPA-HF) trial

Methods

In this post-hoc analysis of the DAPA-HF trial we studied 4625 patients with liver function tests available at baseline. Cox proportional hazards models were used to assess the association between liver tests (total bilirubin, alkaline phosphatase [ALP], alanine transaminase [ALT], aspartate transaminase [AST]) and the Model for End-stage Liver Disease excluding INR (MELD-XI) score (calculated as 5.11 Ln [total bilirubin as mg/dL] + 11.76 Ln [creatinine as mg/dL] + 9.44), and the risk of the primary composite endpoint (hospitalisation or urgent visit for heart failure or cardiovascular death). Models were adjusted for age, sex, race, region, systolic blood pressure, heart rate, LVEF, eGFR, log-transformed NT-proBNP, NYHA class, history of hypertension, stroke, myocardial infarction, atrial fibrillation, heart failure aetiology and randomized treatment to dapagliflozin and stratified by diabetic status at baseline. An interaction term between each measure and the effect of treatment on the primary composite outcome was tested as a fractional polynomial.

Results

Total bilirubin, ALP, and MELD-XI score were associated with a higher risk of all the primary outcome (Figure 1) but not ALT or AST. These relationships persisted after adjustment: total bilirubin per log unit increase (HR=1.46; 95% CI 1.28 – 1.67, p&lt;0.001), ALP per log unit increase (HR=1.39; 95% CI 1.15 – 1.66, p&lt;0.001), MELD-XI per 1 SD increase (HR 1.27; 95% CI 1.13 – 1.42, p&lt;0.001). The effect of dapagliflozin on the primary outcome was not modified by the baseline levels of either total bilirubin, ALP or MELD-XI score (Figure 2)

Conclusions

Higher total bilirubin, ALP and MELD-XI score were independently associated with a higher risk of cardiovascular death or worsening HF and may be useful routinely available biomarkers to assess prognosis. The efficacy of dapagliflozin was the not modified by baseline levels of any of these markers.

Funding Acknowledgement

Type of funding sources: None. Figure 2

LB005KIDNEY IMPLICATIONS OF THE INITIAL EGFR RESPONSE TO SGLT2 INHIBITION WITH EMPAGLIFLOZIN: THE ‘EGFR DIP’ IN EMPA-REG OUTCOME

Background and Aims

Empagliflozin (EMPA) reduces cardiovascular and renal risk in patients with type 2 diabetes (T2D) and established cardiovascular disease (CVD). EMPA induces an initial ‘dip’ in estimated glomerular filtration rate (eGFR). Although considered to be of haemodynamic origin and largely reversible, this needs to be better understood. We investigated whether the initial eGFR dip after EMPA initiation was influenced by baseline characteristics and/or might have an impact on the EMPA-induced risk reduction in kidney outcomes.

Method

In the EMPA-REG OUTCOME trial, patients with T2D and established CVD were treated (1:1:1) with EMPA 10 mg, 25 mg or placebo (PBO), in addition to standard of care. In this post hoc analysis, 6,668 participants who received at least one dose of study drug and had an available eGFR value at both baseline and Week 4 were categorised by initial percentage eGFR change from baseline. A multivariate logistic regression model was used to identify which baseline characteristics are predictive of an initial eGFR dip &gt;10% in EMPA-treated participants versus PBO. Across these predictive baseline factors, we investigated the occurrence of incident or worsening nephropathy, hard kidney outcomes (defined as doubling of serum creatinine with eGFR [MDRD] ≤45 ml/min/1.73 m2 or initiation of renal replacement therapy or death from renal disease), and kidney safety (narrow standardized MedDRA query acute renal failure). The impact of an eGFR dip &gt;10% on the risk reduction with EMPA for incident or worsening nephropathy was assessed using Cox regression analysis adjusting for such eGFR dip.

Results

In the EMPA-REG OUTCOME trial cohort, an initial eGFR dip of &gt;10% from baseline at Week 4 occurred in more than twice as many participants on EMPA (28.3%) compared to PBO (13.4%). However, a more pronounced eGFR dip of &gt;30% was uncommon, occurring in only 1.4% and 0.9%, respectively. Within the EMPA group, participants with an eGFR dip &gt;10% were significantly older, had longer diabetes duration and showed a higher KDIGO (Kidney Disease: Improving Global Outcomes) risk category. Diuretic use and/or higher KDIGO risk category at baseline were predictive of an initial eGFR dip of &gt;10% in EMPA vs. PBO. The average odds ratio [OR; 95% CI] for an eGFR dip &gt;10% with EMPA was 2.7 [2.3–3.0]. In subgroups with a dipping odds ratio below vs. above that average, beneficial treatment effects with EMPA on incident or worsening nephropathy and the hard kidney outcome were consistent (panel A). Also, an eGFR dip &gt;10% did not affect risk reduction for the primary kidney outcome (panel B). Acute renal failure rates were generally lower or similar in EMPA vs. PBO, regardless of baseline predictive factors for an eGFR dip.

Conclusion

T2D patients with more advanced kidney disease and/or on diuretic therapy at baseline were more likely to have an initial eGFR dip &gt;10% with EMPA. However, EMPA treatment appeared to be safe and was associated with improved kidney outcomes, regardless of these baseline predictive factors or an initial eGFR dip &gt;10%.

Design of a randomised controlled trial of the effects of empagliflozin on myocardial perfusion, function and metabolism in type 2 diabetes patients at high cardiovascular risk (the SIMPLE trial)

INTRODUCTION

A diagnosis of type 2 diabetes (T2D) more than doubles the risk of cardiovascular disease (CVD), with heart failure (HF) being one of the most common complications with a severe prognosis. The landmark Empagliflozin Cardiovascular Outcome Event Trial in Type 2 Diabetes Mellitus Paitients (EMPA-REG OUTCOME) study demonstrated that treatment with the sodium glucose cotransporter-2 (SGLT-2) inhibitor empagliflozin rapidly and significantly reduces CVD mortality and admission rates for HF. However, the mechanisms behind this reduction in clinical events are unknown.This study was designed to investigate the effects of the SGLT-2 inhibitor empagliflozin on myocardial perfusion and function in patients with T2D and high CVD risk.

METHODS AND ANALYSIS

In this investigator-initiated, randomised, double-blind controlled clinical trial, 92 patients with T2D and established CVD or high CVD risk will be randomised to treatment with empagliflozin 25 mg or a matching placebo for 13 weeks. The primary outcome measure is change in myocardial flow reserve measured quantitatively by Rubidium-82 position emission tomography. In a substudy, invasive haemodynamics at rest and during exercise will be measured at baseline and following the intervention, using right heart catheterisation.

ETHICS AND DISSEMINATION

The study protocol (v7, 02/08/2018) has been approved by the Ethics Committee of the Capital Region, Danish Data Protection Board and the Danish Medicines Agency, and it will be monitored according to the Good Clinical Practice regulations from the International Conference on Harmonization. The results be submitted to international peer-reviewed journals and be presented at conferences. The data will be made available to the public via EudraCT and www.clinicaltrials.gov.

TRIAL REGISTRATION NUMBER

NCT03151343.

SUN-149 Cardiologist vs. Endocrinologist Encounters in Patients with T2D and CVD: Potential Implications for Glucose-Lowering Therapy Use and Education

Background: A large proportion of patients with type 2 diabetes (T2D) have established cardiovascular (CV) disease (D). Recent large CV outcome trials demonstrated clear CV benefits of 2 novel classes of glucose-lowering agents (GLA), SGLT2 inhibitors and GLP-1 receptor agonists. Guidelines now stipulate that these should be favored in patients with T2D and overt CVD. Not surprisingly, endocrinologists prescribe these GLAs more frequently than cardiologists. Some, however, have proposed that cardiologists should take a more active role in prescribing these GLAs for CV risk reduction. We therefore endeavored to compare prescribing opportunities for these GLAs, by assessing the likelihood that a patient with T2D and CVD had an outpatient encounter with a cardiologist vs. an endocrinologist over a 1-year period in a large academic healthcare system in New England. Methods: We reviewed electronic health records of adult patients (age ≥18) with T2D who had outpatient encounters within the Yale New Haven Hospital System (YNHHS) during 2017. We analyzed demographic information, CVD diagnostic categories (coronary artery disease [CAD], congestive heart failure [CHF], cerebrovascular disease [CBD], peripheral vascular disease [PVD]), number of cardiology and endocrinology encounters, provider types, and visit diagnoses. Results: Of 78,878 T2D patients (mean age 66.7 ±14.4 years; 51% female), 31,639 (40.1%) had established CVD. The ratio of cardiologist:endocrinologist outpatient encounters was 2.6 (51,954 vs. 20,337 encounters) for all T2D patients and 5.3 (43,482 vs. 8,264 encounters) for those with T2D and CVD. Of the 4 CVD diagnostic categories, patients with CHF had the highest cardiologist:endocrinologist encounter ratio at 8.4 (24,477 vs. 2,931 encounters), followed by patients with CAD at 6.0 (33,722 vs 5,579 encounters). Conclusion: In our health system, over the course of a single year, a patient with T2D was nearly 3 times more likely to have an outpatient encounter with a cardiologist than an endocrinologist. With coexisting CVD, the likelihood increased to greater than 5-fold. In order to capitalize on the CV benefits of the newer GLAs, prescriptions by cardiologists are apt to hasten adherence to the latest guidelines and improve patient outcomes. Educational programs pertaining to these emerging treatment paradigms should target cardiologists in addition to endocrinologists (and primary care physicians).

Pioglitazone: The forgotten, cost-effective cardioprotective drug for type 2 diabetes

Type 2 diabetes individuals are at high risk for macrovascular complications: myocardial infarction, stroke and cardiovascular mortality. Recent cardiovascular outcome trials have demonstrated that agents in two antidiabetic classes (SGLT2 inhibitors and GLP-1 receptor agonists) reduce major adverse cardiovascular events. However, there is strong evidence that an older and now generically available medication, the thiazolidinedione, pioglitazone, can retard the atherosclerotic process (PERISCOPE and Chicago) and reduce cardiovascular events in large randomized prospective cardiovascular outcome trials (IRIS and PROactive). Pioglitazone is a potent insulin sensitizer, preserves beta-cell function, causes durable reduction in HbA1c, corrects multiple components of metabolic syndrome and improves nonalcoholic fatty liver disease/nonalcoholic steatohepatitis. Adverse effects (weight gain, fluid retention, fractures) must be considered, but are diminished with lower doses and are arguably outweighed by these multiple benefits. With healthcare expenses attributable to diabetes increasing rapidly, this cost-effective drug requires reconsideration in the therapeutic armamentarium for the disease.

Abstract TMP92: Pioglitazone for Secondary Stroke Prevention in Pre-diabetes: Implications for Real-world Practice

Pioglitazone reduces insulin resistance and cardiovascular risk among patients with type 2 diabetes. The Insulin Resistance Intervention after Stroke (IRIS) trial randomized 3876 non-diabetic participants with recent stroke/TIA and insulin resistance based on the Homeostasis Model of Insulin Resistance (HOMA-IR) score to pioglitazone (PIO) vs. placebo (PLA). Over 4.8 years, the relative risk reduction (RRR) with PIO was 27% for stroke/myocardial infarction, 25% for stroke, 29% for acute coronary syndrome (ACS), and 52% for new-onset diabetes. PIO could therefore be considered a new therapy for secondary stroke prevention before diabetes onset. However, it is not in widespread use, not only because of increased fracture risk, but perhaps also because HOMA-IR is not commonly assessed in clinical practice. In contrast, the presence of prediabetes is often identified in this population. We therefore analyzed the intention-to-treat (ITT) and the on-treatment effect of PIO (defined as adherence of > 80%) in IRIS participants with prediabetes by the American Diabetes Association criteria: HbA1C 5.7%-6.4%, or fasting glucose 100-125 mg/dL (n=2885; PIO 1456, PLA 1429). By ITT, for pioglitazone the hazard ratio and 95% confidence interval in Cox regression for stroke/MI was 0.70 (0.56-0.88, p=0.002), for stroke 0.72 (0.56-0.93, p=0.013), for ACS 0.72 (0.52-1.00, p = 0.052), for stroke/MI/hospitalized heart failure (HHF) 0.78 (0.63-0.96, p=0.02), and for new-onset diabetes HR 0.46 (0.34-0.61, p <0.0001). Among participants with good adherence, pioglitazone participants (n=644) were more likely to be men (76.2% vs 70.6%, p=0.02) and more likely to be smokers (15.9% vs. 11.7%, p=0.02) compared to PLA participants (n=810). In this subgroup, the HR for stroke/MI was 0.57 (0.39-0.84, p=0.004), for stroke 0.64 (0.42-0.99, p=0.04), for ACS 0.47 (0.26-0.85, p=0.01), for stroke/MI/HHF 0.61 (0.42-0.88, p=0.008), and for new-onset diabetes HR 0.18 (0.10-0.33, p<0.0001)

Conclusion: Pioglitazone should be considered efficacious for secondary prevention in stroke/TIA participants with prediabetes, simply assessed by fasting plasma glucose or A1C.

Improving Type 2 Diabetes Patient Health Outcomes with Individualized Continuing Medical Education for Primary Care

INTRODUCTION

This study provided physicians with continuing medical education (CME) related to type 2 diabetes and evaluated the effect on patient health outcomes.

METHODS

Physicians participated in multi-platform CME (live and online programs) and completed a 25 item questionnaire for patient baseline (3-months pre-CME activity) and follow-up visits (≥6-months post-CME activity). Changes in physician knowledge and patient health outcomes were evaluated.

RESULTS

34 physicians completed both phases of the CME curricula and submitted data for 264 patients. Significant improvements were observed in physician knowledge after the live (p < 0.05) and online programs (p < 0.0005). Mean patient glycated hemoglobin (HbA1c) absolute reduction of 1.15% (p < 0.0001) was reported.

CONCLUSIONS

CME is an effective tool to close established practice gaps and potentially help improve patient health outcomes.

Glycemic targets: what is the evidence?

Hyperglycemia is the unifying metabolic abnormality for all forms of diabetes mellitus, forming the basis for its diagnosis and treatment. The strong epidemiologic associations between hyperglycemia and the complications of diabetes have given rise to the glucose hypothesis-that the complications of diabetes are caused by hyperglycemia and that they can be prevented by normalizing glucose levels. Herein the authors review the epidemiologic relationships between hyperglycemia and the complications of diabetes, the major trials of glucose lowering, and the extent to which the glucose hypothesis is supported by these studies and how this information can be translated into clinical practice.

BRIEF REPORT: nutrition and weight loss information in a popular diet book: is it fact, fiction, or something in between?

BACKGROUND/OBJECTIVE

Diet books dominate the New York Times Advice Best Seller list and consumers cite such books as an important source of nutrition information. However, the scientific support for nutrition claims presented as fact (nutrition facts) in diet books is not known.

DESIGN/MEASUREMENTS

We assessed the quality of nutrition facts in the best-selling South Beach Diet using support in peer-reviewed literature as a measure of quality. We performed structured literature searches on nutrition facts located in the books' text, and then assigned each fact to 1 of 4 categories (1) fact supported, (2) fact not supported, (3) fact both supported and not supported, and (4) no related papers. A panel of expert reviewers adjudicated the findings.

RESULTS

Forty-two nutrition facts were included. Fourteen (33%) facts were supported, 7 (17%) were not supported, 18 (43%) were both supported and not supported, and 3 (7%) had no related papers, including the fact that the diet had been "scientifically studied and proven effective."

CONCLUSIONS

Consumers obtain nutrition information from diet books. We found that over 67% of nutrition facts in a best-seller diet book may not be supported in the peer-reviewed literature. These findings have important implications for educating consumers about nutrition information sources.

Mechanism by which high-dose aspirin improves glucose metabolism in type 2 diabetes

Recent studies have implicated fatty acid-dependent activation of the serine kinase IKKbeta, which plays a key role in tissue inflammation, in the pathogenesis of insulin resistance. High doses of salicylates have recently been shown to inhibit IKKbeta activity and might therefore ameliorate insulin resistance and improve glucose tolerance in patients with type 2 diabetes. To test this hypothesis, we studied nine type 2 diabetic subjects before and after 2 weeks of treatment with aspirin ( approximately 7 g/d). Subjects underwent mixed-meal tolerance tests and hyperinsulinemic-euglycemic clamps with [6,6-(2)H2]glucose to assess glucose turnover before and after treatment. High-dose aspirin treatment resulted in a approximately 25% reduction in fasting plasma glucose, associated with a approximately 15% reduction in total cholesterol and C-reactive protein, a approximately 50% reduction in triglycerides, and a approximately 30% reduction in insulin clearance, despite no change in body weight. During a mixed-meal tolerance test, the areas under the curve for plasma glucose and fatty acid levels decreased by approximately 20% and approximately 50%, respectively. Aspirin treatment also resulted in a approximately 20% reduction in basal rates of hepatic glucose production and a approximately 20% improvement in insulin-stimulated peripheral glucose uptake under matched plasma insulin concentrations during the clamp. In conclusion, these data support the hypothesis that IKKbeta represents a new target for treating type 2 diabetes mellitus.

Mechanism of troglitazone action in type 2 diabetes

To examine the metabolic pathways by which troglitazone improves insulin responsiveness in patients with type 2 diabetes, the rate of muscle glycogen synthesis was measured by 13C-nuclear magnetic resonance (NMR) spectroscopy. The rate-controlling steps of insulin-stimulated muscle glucose metabolism were assessed using 31P-NMR spectroscopic measurement of intramuscular glucose-6-phosphate (G-6-P) combined with a novel 13C-NMR method to assess intracellular glucose concentrations. Seven healthy nonsmoking subjects with type 2 diabetes were studied before and after completion of 3 months of troglitazone (400 mg/day) therapy. After troglitazone treatment, rates of insulin-stimulated whole-body glucose uptake increased by 58+/-11%, from 629+/-82 to 987+/-156 micromol x m(-2) x min(-1) (P = 0.008), which was associated with an approximately 3-fold increase in rates of insulin-stimulated glucose oxidation (from 119+/-41 to 424+/-70 micromol x m(-2) x min(-1); P = 0.018) and muscle glycogen synthesis (26+/-17 vs. 83+/-35 micromol x l(-1) muscle x min(-1); P = 0.025). After treatment, muscle G-6-P concentrations increased by 0.083+/-0.019 mmol/l (P = 0.008 vs. pretreatment) during the hyperglycemic-hyperinsulinemic clamp, compared with no significant changes in intramuscular G-6-P concentrations in the pretreatment study, reflecting an improvement in glucose transport and/or hexokinase activity. The concentrations of intracellular free glucose did not differ between the pre- and posttreatment studies and remained >50-fold lower in concentration (<0.1 mmol/l) than what would be expected if hexokinase activity was rate-controlling. These results indicate that troglitazone improves insulin responsiveness in skeletal muscle of patients with type 2 diabetes by facilitating glucose transport activity, which thereby leads to increased rates of muscle glycogen synthesis and glucose oxidation.

Impaired glucose transport as a cause of decreased insulin-stimulated muscle glycogen synthesis in type 2 diabetes

BACKGROUND

Insulin resistance, a major factor in the pathogenesis of type 2 diabetes mellitus, is due mostly to decreased stimulation of glycogen synthesis in muscle by insulin. The primary rate-controlling step responsible for the decrease in muscle glycogen synthesis is not known, although hexokinase activity and glucose transport have been implicated.

METHODS

We used a novel nuclear magnetic resonance approach with carbon-13 and phosphorus-31 to measure intramuscular glucose, glucose-6-phosphate, and glycogen concentrations under hyperglycemic conditions (plasma glucose concentration, approximately 180 mg per deciliter [10 mmol per liter]) and hyperinsulinemic conditions in six patients with type 2 diabetes and seven normal subjects. In vivo microdialysis of muscle tissue was used to determine the gradient between plasma and interstitial-fluid glucose concentrations, and open-flow microperfusion was used to determine the concentrations of insulin in interstitial fluid.

RESULTS

The time course and concentration of insulin in interstitial fluid were similar in the patients with diabetes and the normal subjects. The rates of whole-body glucose metabolism and muscle glycogen synthesis and the glucose-6-phosphate concentrations in muscle were approximately 80 percent lower in the patients with diabetes than in the normal subjects under conditions of matched plasma insulin concentrations. The mean (+/-SD) intracellular glucose concentration was 2.0+/-8.2 mg per deciliter (0.11+/-0.46 mmol per liter) in the normal subjects. In the patients with diabetes, the intracellular glucose concentration was 4.3+/-4.9 mg per deciliter (0.24+/-0.27 mmol per liter), a value that was 1/25 of what it would be if hexokinase were the rate-controlling enzyme in glucose metabolism.

CONCLUSIONS

Impaired insulin-stimulated glucose transport is responsible for the reduced rate of insulin-stimulated muscle glycogen synthesis in patients with type 2 diabetes mellitus.

Metabolic effects of troglitazone monotherapy in type 2 diabetes mellitus. A randomized, double-blind, placebo-controlled trial

BACKGROUND

Troglitazone is a new insulin-sensitizing agent used to treat type 2 diabetes mellitus. The mechanism by which troglitazone exerts its effect on systemic glucose metabolism is unknown.

OBJECTIVE

To determine the effects of 6 months of troglitazone monotherapy on glucose metabolism in patients with type 2 diabetes mellitus.

DESIGN

Randomized, double-blind, placebo-controlled trial.

SETTING

Six general clinical research centers at university hospitals.

PATIENTS

93 patients (mean age, 52 years) with type 2 diabetes mellitus (mean fasting plasma glucose level, 11.2 mmol/L) who were being treated with diet alone or who had discontinued oral antidiabetic medication therapy.

INTERVENTION

Patients were randomly assigned to one of five treatment groups (100, 200, 400, or 600 mg of troglitazone daily or placebo) and had metabolic assessment before and after 6 months of treatment.

MEASUREMENTS

Plasma glucose and insulin profiles during a meal tolerance test; basal hepatic glucose production and insulin-stimulated glucose disposal rate during a hyperinsulinemic-euglycemic clamp procedure.

RESULTS

Troglitazone at 400 and 600 mg/d decreased both fasting (P < 0.001) and postprandial (P = 0.016) plasma glucose levels by approximately 20%. All four troglitazone dosages also decreased fasting (P = 0.012) and postprandial (P < 0.001) triglyceride levels; 600 mg of the drug per day decreased fasting free fatty acid levels (P = 0.018). Plasma insulin levels decreased in the 200-, 400-, and 600-mg/d groups (P < 0.001), and C-peptide levels decreased in all five study groups (P < 0.001). Basal hepatic glucose production was suppressed in the 600-mg/d group compared with the placebo group (P = 0.02). Troglitazone at 400 and 600 mg/d increased glucose disposal rate by approximately 45% above pretreatment levels (P = 0.003). Stepwise regression analysis showed that troglitazone therapy was the strongest predictor of a decrease in fasting (P < 0.001) or postprandial (P = 0.01) glucose levels. Fasting C-peptide level was the next strongest predictor (higher C-peptide level equaled greater glucose-lowering effect).

CONCLUSION

Troglitazone monotherapy decreased fasting and postprandial glucose levels in patients with type 2 diabetes, primarily by augmenting insulin-mediated glucose disposal.