Lori A. Mixson

Prednisone affects inflammation, glucose tolerance, and bone turnover within hours of treatment in healthy individuals

OBJECTIVE Use of glucocorticoids for anti-inflammatory efficacy is limited by their side effects. This study examined, in the same individuals, prednisones acute, dose-dependent effects on inflammation as well as biomarkers of glucose regulation and bone homeostasis. DESIGN In this randomized, double-blind, parallel-design trial of healthy adults demonstrating cutaneous allergen-induced hypersensitivity, patients received placebo or prednisone 10, 25 or 60 mg daily for 7 days. METHODS Effects on peripheral white blood cell (WBC) count, ex vivo whole blood lipopolysaccharide (LPS)-stimulated TNF-α release and response to cutaneous allergen challenge were assessed concurrently with biomarkers for glucose tolerance and bone turnover. RESULTS Differential peripheral WBC counts changed significantly within hours of prednisone administration. Ex vivo, LPS-stimulated TNF-α was significantly reduced by all prednisone doses on days 1 and 7. The late phase cutaneous allergen reaction was significantly reduced with prednisone 60 mg vs placebo on days 1 and 7. Oral glucose tolerance tests revealed significant increases in glycaemic excursion on days 1 and 7, whereas increases in insulin and C-peptide excursions were more notable on day 7 with all doses of prednisone. The bone formation markers osteocalcin, and procollagen I N- and C-terminal peptides decreased significantly on days 1 and 7 vs placebo. CONCLUSIONS In healthy young adults after single doses as low as 10 mg, prednisone treatment has significant effects on glucose tolerance and bone formation markers within hours of treatment, in parallel with anti-inflammatory effects.

Segmental Bioimpedance for Measuring Amlodipine-Induced Pedal Edema: A Placebo-Controlled Study

BACKGROUND The development of antihypertensives requires efficient and accurate tools for identifying pedal edema. Methodologies used to gauge the potential of an agent to induce pedal edema in short-term (<4-week) clinical trials have not been reported in the literature. OBJECTIVE The purpose of this study was to identify a robust and practical method for measuring drug-induced pedal edema for use in the clinical development of antihypertensives. The efficacy of segmental bioimpedance in the detection of increased pedal edema was compared with that of clinical pitting assessment, ankle circumference, and water displacement volumetry. METHODS The study population consisted of male and female healthy subjects and patients with stage 1 or 2 hypertension who were otherwise healthy. Participants were randomly assigned to receive amlodipine 10 mg or placebo once daily in this 6-week, double-blind, parallel-group study. Amlodipine was used as a means of inducing ankle edema, and not for the treatment of hypertension. Patients with hypertension were required to undergo a washout of antihypertensive therapies. Edema was evaluated using segmental bioimpedance at 10 kHz, clinical pitting assessment, ankle circumference, and water displacement at weeks 2, 4, and 6. The ANOVA model used included treatment and baseline values as covariates, with treatment pairs compared via t tests derived from the model. RESULTS A total of 47 individuals were randomized (49% male; 29 [62%] with hypertension; mean [SD] age, 59 [5.9] years; baseline body mass index, 28.6 kg/m(2) [2.8]; blood pressure 146.6 [10.7]/93.5 [6.5] and 139.3 [8.3]/89.5 [4.5] in individuals with and without hypertension, respectively; amlodipine 10 mg, n = 24; placebo, n = 23). At weeks 2, 4, and 6, statistically significant treatment differences in changes from baseline were detected using water displacement (mean [90% CI] treatment differences, +39.0 g [+17.9 to +60.1], +61.9 g [+36.1 to +87.6], and +72.2 g [+42.3 to +102.1], respectively; all, P ≤ 0.001), ankle circumference (+4.74 mm [+2.38 to +7.11; P < 0.001], +2.92 mm [+0.33 to +5.49; P = 0.032], and +5.16 mm [+2.21 to +8.11; P = 0.002]), and bioimpedance (-11.7 Ω [-18.1 to -5.4], -18.3 Ω [-26.2 to -10.4], and -20.9 Ω [-29.7 to -12.0]; all, P≤0.001), but no significant differences were detected using clinical assessment of pitting. CONCLUSION In this population of healthy subjects and patients with hypertension, segmental bioimpedance was comparable to water displacement and ankle circumference and outperformed clinical assessment of pitting for the detection of ankle edema, supporting the use of segmental bioimpedance as a drug-development tool to objectively quantify amlodipine-induced pedal edema.

Efavirenz modulation of sleep spindles and sleep spectral profile

Non‐nucleoside reverse transcriptase inhibitors are important antiretroviral agents for the treatment of human immunodeficiency virus. Some non‐nucleoside reverse transcriptase inhibitors, in particular efavirenz, have prominent effects on sleep, cognition and psychiatric variables that limit their tolerability. To avoid confounds due to drug–drug and drug–disease interactions, we assessed the effects of efavirenz in healthy volunteers on sleep, cognition and psychological endpoints during the first week of treatment. Forty healthy male subjects were randomized to receive placebo or efavirenz 600 mg nightly for 7 days after completion of a 3‐day placebo run‐in period. Treatment with efavirenz was associated with reduced time to sleep onset in the Maintenance of Wakefulness Test, an increase in non‐rapid eye movement sleep, a large exposure‐related decrease in sigma band spectral density and sleep spindle density during non‐rapid eye movement sleep, and reduced performance on an attention switching task. Because efavirenz has been shown to have serotonin 2A receptor partial‐agonist properties, we reasoned that antagonism of serotonin 2A receptor signalling in the thalamic reticular nucleus, which generates sleep spindles and promotes attention, may be responsible. Consistent with predictions, treatment of healthy volunteers with a single dose of a serotonin 2A receptor antagonist was found to significantly suppress sigma band spectral density in an exposure‐related manner and modulated the overall spectral profile in a manner highly similar to that observed with efavirenz, consistent with the notion that efavirenz exhibits serotonin 2A receptor partial‐agonist pharmacology in humans.

Quantification, Variability, and Reproducibility of Basal Skeletal Muscle Glucose Uptake in Healthy Humans Using 18F-FDG PET/CT

The quantification and variability of skeletal muscle glucose utilization (SMGU) in healthy subjects under basal (low insulin) conditions are poorly known. This information is essential early in clinical drug development to effectively interrogate novel pharmacologic interventions that modulate glucose uptake. The aim of this study was to determine test–retest characteristics and variability of SMGU within and between healthy subjects under basal conditions. Furthermore, different kinetic modeling strategies were evaluated to find the best-fitting model to assess SMGU studied by 18F-FDG. Methods: Six healthy male volunteers underwent 2 dynamic 18F-FDG PET/CT scans with an interval of 24 h. Subjects were admitted to the clinical unit to minimize variability in daily activities and food intake and restrict physical activity. 18F-FDG PET/CT scans of gluteal and quadriceps muscle area were obtained with arterial input. Regions of interest were drawn over the muscle area to obtain time–activity curves and standardized uptake values (SUVs) between 60 and 90 min. Spectral analysis of the data and kinetic modeling was performed using 2-tissue-irreversible (2T3K), 2-tissue-reversible, and 3-tissue-sequential-irreversible (3T5KS) models. Reproducibility was assessed by intraclass correlation coefficients (ICCs) and within-subject coefficient of variation (WSCV). Results: SUVs in gluteal and quadriceps areas were 0.56 ± 0.09 and 0.64 ± 0.07. ICCs (with 90% confidence intervals in parentheses) were 0.88 (0.64–0.96) and 0.96 (0.82–0.99), respectively, for gluteal and quadriceps muscles, and WSCV for gluteal and quadriceps muscles was 2.2% and 3.6%, respectively. The rate of glucose uptake into muscle was 0.0016 ± 0.0004 mL/mL⋅min, with an ICC of 0.94 (0.93–0.95) and WSCV of 6.6% for the 3T5KS model, whereas an ICC of 0.98 (0.92–1.00) and WSCV of 2.8% was obtained for the 2T3K model. 3T5KS demonstrated the best fit to the measured experimental points. Conclusion: Minimal variability in skeletal muscle glucose uptake was observed under basal conditions in healthy subjects. SUV measurements and rate of glucose uptake values were reproducible, with an average WSCV of less than 5%. Compared with SUV, the 3-tissue model adds information about kinetics between blood, intra- and intercellular compartments, and phosphorylation that may highlight the exact mechanisms of metabolic changes after pharmacologic intervention.

Linearity of β-cell response across the metabolic spectrum and to pharmacology: insights from a graded glucose infusion-based investigation series

The graded glucose infusion (GGI) examines insulin secretory response patterns to continuously escalating glycemia. The current study series sought to more fully appraise its performance characteristics. Key questions addressed were comparison of the GGI to the hyperglycemic clamp (HGC), comparison of insulin secretory response patterns across three volunteer populations known to differ in β-cell function (healthy nonobese, obese nondiabetic, and type 2 diabetic), and characterization of effects of known insulin secretagogues in the context of a GGI. Insulin secretory response was measured as changes in insulin, C-peptide, insulin secretion rates (ISR), and ratio of ISR to prevailing glucose (ISR/G). The GGI correlated well with the HGC (r = 0.72 for ISR/G, P < 0.01). The insulin secretory response in type 2 diabetes (T2DM) was significantly blunted (P < 0.001), whereas it was significantly increased in obese nondiabetics compared with healthy nonobese (P < 0.001). Finally, robust (P < 0.001 over placebo) pharmacological effects were observed in T2DM and healthy nonobese volunteers. Collectively, the findings of this investigational series bolster confidence that the GGI has solid attributes for assessing insulin secretory response to glucose across populations and pharmacology. Notably, the coupling of insulin secretory response to glycemic changes was distinctly and uniformly linear across populations and in the context of insulin secretagogues. (Clinical Trial Registration Nos. NCT00782418, NCT01055340, NCT01373450).

Native Oxyntomodulin Has Significant Glucoregulatory Effects Independent of Weight Loss in Obese Humans With and Without Type 2 Diabetes

Oxyntomodulin (OXM), an enteroendocrine hormone, causes appetite suppression, increased energy expenditure, and weight loss in obese humans via activation of GLP-1 and glucagon receptors. However, the effects of OXM on glucose homeostasis remain ill defined. To address this gap, we evaluated the effects of an i.v. infusion of native OXM on insulin secretion rates (ISRs) and glycemic excursion in a graded glucose infusion (GGI) procedure in two separate randomized, placebo (PBO)-controlled, single-dose crossover trials in 12 overweight and obese subjects without diabetes and in 12 obese subjects with type 2 diabetes mellitus (T2DM), using the GLP-1 analog liraglutide (LIRA) as a comparator in T2DM. In both groups, in the GGI, 3.0 pmol/kg/min of OXM significantly increased ISR and blunted glycemic excursion relative to PBO. In T2DM, the effects of OXM were comparable to those of LIRA, including restoration of β-cell glucose responsiveness to that of nonobese subjects without diabetes. Our findings indicate that native OXM significantly augments glucose-dependent insulin secretion acutely in obese subjects with and without diabetes, with effects comparable to pharmacologic GLP-1 receptor activation and independent of weight loss. Native OXM has potential to improve hyperglycemia via complementary and independent induction of insulin secretion and weight loss.

Early Clinical Development Planning via Biomarkers, Clinical Endpoints, and Simulation A Case Study to Optimize for Phase 3 Dose Selection

Background: This study investigated a framework that leverages the relationship between biomarkers and a target clinical endpoint to optimize an early development plan. Methods: Different biomarker designs were assessed for proof of concept (PoC) and dose finding (DF) to improve phase 2b (Ph2b) design as well as phase 3 (Ph3) dose choice. A case study using a Bayesian trivariate normal distribution model for 2 biomarkers and a clinically relevant endpoint was utilized with simulation to assess performance characteristics. Results: We found the following: (1) at typical sample sizes for early development trials, biomarkers appear useful for PoC but not for clinical endpoint DF; and (2) even with large amounts of prior information and near perfect correlation between biomarkers and clinical endpoints, Ph2b variability is only overcome by increased Ph2b sample sizes to improve Ph3 dose choice. Conclusions: For highly variable clinical endpoints, the fastest path should be to demonstrate PoC by biomarkers and then go directly to Ph2b to measure the target clinical endpoint.

Insulin secretory effect of sitagliptin: assessment with a hyperglycemic clamp combined with a meal challenge

Sitagliptin, a dipeptidyl peptidase-IV inhibitor (DPP-4), sustains activity of the incretin hormones GLP-1 and GIP and improves hyperglycemia in Type 2 diabetes mellitus (T2DM). It has however proven challenging to quantify the effect of sitagliptin on rates of insulin secretion (ISR) during a prandial challenge. The tight feedback governance of ISR by plasma glucose means that in the face of treatment-related lowering of postprandial glycemia, corresponding stimulation of ISR is lessened. We postulated that sustaining a stable level of moderate hyperglycemia before and during a meal challenge (MC) would be a platform that enables greater clarity to assess the effect of sitagliptin on ISR and an approach that could be valuable to evaluate novel targets that increase insulin secretion directly and by augmenting incretins. A hyperglycemic clamp (HGC) at 160 mg/dl was conducted in 12 healthy volunteers (without diabetes) for 6 h; 3 h into the HGC, MC was administered while maintaining stable hyperglycemia of the HGC for an additional 3 h. Modeling of C-peptide response was used to calculate ISR. In crossover design of three periods (sitagliptin twice and placebo once), the effect of sitagliptin vs. placebo on ISR and the reproducibility of the response to sitagliptin were assessed. Sitagliptin increased ISR compared with placebo by 50% and 20% during the HGC alone and the HGC-MC phases, respectively ( P < 0.001 for both). There was an associated significant treatment-based increase in circulating insulin, as well as active levels of GLP-1. Robust reproducibility of the sitagliptin-mediated ISR response was observed; the intraclass correlation value was 0.94. The findings delineate the effect of sitagliptin to stimulate insulin secretion, and these benchmark data also demonstrate that an HGC-MC can be a useful platform for interrogating therapeutic targets that could potentially modulate ISR via direct action on beta-cells as well as by augmenting release or action of incretins.

Dose-dependent quantitative effects of acute fructose administration on hepatic de novo lipogenesis in healthy humans

Fructose feeding increases hepatic de novo lipogenesis (DNL) and is associated with nonalcoholic fatty liver disease. Little is known, however, about individual variation in susceptibility to fructose stimulation of DNL. In this three-period crossover study, 17 healthy male subjects were enrolled to evaluate the within- and between-subject variability of acute fructose feeding on hepatic fractional DNL. During each assessment, [1-13C1]acetate was infused to measure DNL in the fasting state and during fructose feeding. Subjects randomly received a high dose of fructose (10 mg·kg fat-free mass-1·min-1) on two occasions and a low dose (5 mg·kg fat-free mass-1·min-1) on another. Fructose solutions were administered orally every 30 min for 9.5 h. Ten subjects completed all three study periods. DNL was assessed as the fractional contribution of newly synthesized palmitate into very-low-density lipoprotein triglycerides using mass isotopomer distribution analysis. Mean fasting DNL was 5.3 ± 2.8%, with significant within- and between-subject variability. DNL increased dose dependently during fructose feeding to 15 ± 2% for low- and 29 ± 2% for high-dose fructose. The DNL response to high-dose fructose was very reproducible within an individual ( r = 0.93, P < 0.001) and independent of fasting DNL. However, it was variable between individuals and significantly correlated to influx of unlabeled acetyl-CoA ( r = 0.7, P < 0.001). Unlike fasting DNL, fructose-stimulated DNL is a robust and reproducible measure of hepatic lipogenic activity for a given individual and may be a useful indicator of metabolic disease susceptibility and treatment response.