Minimal Model Analysis Research Articles

The undervalued league of insulin resistance testing: uncovering their importance.

Type 2 diabetes, obesity, and several other metabolic diseases are all largely attributed to the problem known as insulin resistance. Diagnosing insulin resistance promptly and accurately is essential for adequately managing and intervening in metabolic disorders. Several diagnostic methods have been developed to assess insulin resistance. However, each method has advantages and disadvantages. The most precise test is the hyperinsulinemic-euglycemic clamp, which examines the direct impact of insulin on glucose uptake by tissues. However, it is primarily utilized in research due to its complexity and intrusiveness. Homeostatic Model Assessment of Insulin Resistance (HOMA-IR) and the Quantitative Insulin Sensitivity Check Index (QUICKI) are the second most used Insulin resistance tests in the clinical setup. These tests are based on measuring the fasting glucose and insulin levels. The Oral Glucose Tolerance Test (OGTT), Insulin tolerance test, and the Matsuda Index are further diagnostic procedures that shed light on insulin sensitivity. The improved techniques, such as the insulin suppression test and the minimal model analysis, provide substitutes for unique clinical circumstances. Additionally, including extra measurements with these tests, like waist circumference, lipid profiles, and inflammatory markers, can improve the evaluation of insulin resistance. In summary, identifying insulin resistance is essential for the early detection and treatment of various metabolic illnesses. To make educated judgments and improve patient care, healthcare workers should be aware of thedifferent available diagnostic tests and how they are used in each situation. Insulin resistance detection and monitoring will require further study to improve current diagnostic approaches and create novel, less invasive techniques.

Asymmetric response emerges between creation and disintegration of force-bearing subcellular structures as revealed by percolation analysis.

Cells dynamically remodel their internal structures by modulating the arrangement of actin filaments (AFs). In this process, individual AFs exhibit stochastic behavior without knowing the macroscopic higher-order structures they are meant to create or disintegrate, but the mechanism allowing for such stochastic process-driven remodeling of subcellular structures remains incompletely understood. Here we employ percolation theory to explore how AFs interacting only with neighboring ones without recognizing the overall configuration can nonetheless create a substantial structure referred to as stress fibers (SFs) at particular locations. We determined the interaction probabilities of AFs undergoing cellular tensional homeostasis, a fundamental property maintaining intracellular tension. We showed that the duration required for the creation of SFs is shortened by the increased amount of preexisting actin meshwork, while the disintegration occurs independently of the presence of actin meshwork, suggesting that the coexistence of tension-bearing and non-bearing elements allows cells to promptly transition to new states in accordance with transient environmental changes. The origin of this asymmetry between creation and disintegration, consistently observed in actual cells, is elucidated through a minimal model analysis by examining the intrinsic nature of mechano-signal transmission. Specifically, unlike the symmetric case involving biochemical communication, physical communication to sense environmental changes is facilitated via AFs under tension, while other free AFs dissociated from tension-bearing structures exhibit stochastic behavior. Thus, both the numerical and minimal models demonstrate the essence of intracellular percolation, in which macroscopic asymmetry observed at the cellular level emerges not from microscopic asymmetry in the interaction probabilities of individual molecules, but rather only as a consequence of the manner of the mechano-signal transmission. These results provide novel insights into the role of the mutual interplay between distinct subcellular structures with and without tension-bearing capability. Insight: Cells continuously remodel their internal elements or structural proteins in response to environmental changes. Despite the stochastic behavior of individual structural proteins, which lack awareness of the larger subcellular structures they are meant to create or disintegrate, this self-assembly process somehow occurs to enable adaptation to the environment. Here we demonstrated through percolation simulations and minimal model analyses that there is an asymmetry in the response between the creation and disintegration of subcellular structures, which can aid environmental adaptation. This asymmetry inherently arises from the nature of mechano-signal transmission through structural proteins, namely tension-mediated information exchange within cells, despite the stochastic behavior of individual proteins lacking asymmetric characters in themselves.

Insulin's Function in Health and Disease

Insulin is a polypeptide hormone that is primarily released by cells in the pancreatic islets of Langerhans. The hormone may work in tandem with glucagon to control blood sugar levels; glucagon has catabolic properties while insulin has anabolic ones. Insulin controls blood glucose levels and causes the liver, muscles, and adipose tissue to store glucose, which causes total weight gain. Insulin plays a crucial role in the initiation and development of many chronic diseases because it modulates a variety of physiological processes. Other techniques are based on the exogenous infusion of glucose or insulin, or both, either under steady-state (the insulin suppression test) or under dynamic conditions (the insulin tolerance test, intravenous glucose-tolerance test with minimal model analysis, and constant infusion of glucose with model analysis). Homeostatic model assessment uses fasting plasma glucose and insulin concentrations to derive indices of insulin sensitivity and secretion from a mathematical model.

The dual incretin co-agonist tirzepatide increases both insulin secretion and glucose effectiveness in model experiments in mice

Tirzepatide is a dual GIP and GLP-1 receptor co-agonist which is approved for glucose-lowering therapy in type 2 diabetes. Here, we explored its effects on beta cell function, insulin sensitivity and insulin-independent glucose elimination (glucose effectiveness) in normal mice. Anesthetized female C57/BL/6 J mice were injected intravenously with saline or glucose (0.125, 0.35 or 0.75 g/kg) with or without simultaneous administration of synthetic tirzepatide (3 nmol/kg). Samples were taken at 0, 1, 5, 10, 20 and 50 min. Glucose elimination rate was estimated by the percentage reduction in glucose from min 5 to min 20 (KG). The 50 min areas under the curve (AUC) for insulin and glucose were determined. Beta cell function was assessed as AUCinsulin divided by AUCglucose. Insulin sensitivity (SI) and glucose effectiveness (SG) were determined by minimal model analysis of the insulin and glucose data. Tirzepatide glucose-dependently reduced glucose levels and increased insulin levels. The slope for the regression of AUCinsulin versus AUCglucose was increased 7-fold by tirzepatide from 0.014 ± 0.004 with glucose only to 0.099 ± 0.016 (P < 0.001). SI was not affected by tirzepatide, whereas SG was increased by 78% (P < 0.001). The increase in SG contributed to an increase in KG by 74 ± 4% after glucose alone and by 67 ± 8% after glucose+ tirzepatide, whereas contribution by SI times AUCinsulin insulin (i.e., disposition index) was 26 ± 4% and 33 ± 8%, respectively. In conclusion, tirzepatide stimulates both insulin secretion and glucose effectiveness, with stimulation of glucose effectiveness being the prominent process to reduce glucose.

OR34-04 Defective FGFR1 Signaling Disrupts Glucose Regulation In Humans: Evidence From Patients With Isolated Hypogonadotropic Hypogonadism Harboring FGFR1 Mutations

Abstract Disclosure: M. Stamou: None. C.J. Chiu: None. S. Jadhav: None. K. Salnikov: None. L. Plummer: None. S.B. Seminara: None. R. Balasubramanian: None. Introduction: Recent studies have shown that antibody-mediated activation of FGFR1 receptor improves metabolic health in rodents, nonhuman primates, and humans. Hence, disruption of the FGFR1 receptor may lead to glucose dysregulation. FGFR1 mutations contribute to 12% of the genetic background of subjects with isolated hypogonadotropic hypogonadism (IHH), a rare Mendelian disease caused by GnRH deficiency. In this study, we examined glucose effectiveness and insulin sensitivity in IHH subjects with rare FGFR1 variants and hypothesized that these subjects will display defective glucose metabolism compared healthy non-carrier controls. Methods: Nine subjects with IHH (7 males and 2 females) with heterozygous rare FGFR1 variants were enrolled [7 subjects with protein truncating variants: p.Q680*, p.R622*, p.Q52*, p.I347Nfs*61, p.R576Pfs*77, p.Q309*, c.1553-2A&amp;gt;G and 2 subjects with deleterious missense variants: p.G97S &amp; p.Y701C. Thirty healthy controls (17 males and 13 females) with no FGFR1 variants were enrolled from the Mass General Brigham Biobank. Medical history, physical exam, laboratory evaluation, a bone density scan, and an intravenous glucose tolerance test (IVGTT) were performed. The area under the curve (AUC) for glucose, insulin, and C-peptide response to 50% dextrose (0.3g/kg, t=0min) and an insulin bolus (0.03u/kg, t=20 min) were estimated for each subject. The glucose effectiveness (Sg), insulin sensitivity (SI), acute insulin response to glucose (AIR), and the disposition index (DI= AIRG*SI) were calculated using the Minimal Model Analysis. Statistical comparisons were performed with t-test and non-parametric Wilcoxon rank sum test. A linear regression model was used to adjust the t-test outcomes for potential confounders. Results: Despite similar BMIs (28 vs. 26.5, p=0.29), IHH FGFR1 positive subjects demonstrated higher % fat mass compared to controls (38 vs. 31, p=0.02). IHH patients were supplemented with sex-steroids at the time of the study. Male patients demonstrated similar testosterone levels compared to controls (385 vs. 451 ng/dL, p=0.52). IHH FGFR1 positive subjects demonstrated a higher AUC for C-peptide compared to controls (167 vs. 92, p=0.001), that remained significant after adjusting for age, gender, BMI, and % fat mass. Non-parametric test showed higher AUC for glucose, insulin, and C-peptide (p 0.01, 0.01 &amp; 0.005 respectively) as well as lower SI (p=0.01) and higher AIRg (p=0.037) in the IHH FGFR1 positive group compared to non-carrier controls. Discussion: This is the first study to evaluate glucose metabolism in humans with naturally occurring FGFR1 variants. IHH FGFR1 positive subjects showed higher insulin response to glucose and lower insulin sensitivity during an IVGTT test compared to the healthy non-carrier controls. These findings confirm that FGFR1 signaling is a key regulator of insulin secretion and action in humans. Presentation: Sunday, June 18, 2023

Kinesin and myosin motors compete to drive rich multiphase dynamics in programmable cytoskeletal composites.

The cellular cytoskeleton relies on diverse populations of motors, filaments, and binding proteins acting in concert to enable nonequilibrium processes ranging from mitosis to chemotaxis. The cytoskeleton's versatile reconfigurability, programmed by interactions between its constituents, makes it a foundational active matter platform. However, current active matter endeavors are limited largely to single force-generating components acting on a single substrate-far from the composite cytoskeleton in cells. Here, we engineer actin-microtubule (MT) composites, driven by kinesin and myosin motors and tuned by crosslinkers, to ballistically restructure and flow with speeds that span three orders of magnitude depending on the composite formulation and time relative to the onset of motor activity. Differential dynamic microscopy analyses reveal that kinesin and myosin compete to delay the onset of acceleration and suppress discrete restructuring events, while passive crosslinking of either actin or MTs has an opposite effect. Our minimal advection-diffusion model and spatial correlation analyses correlate these dynamics to structure, with motor antagonism suppressing reconfiguration and demixing, while crosslinking enhances clustering. Despite the rich formulation space and emergent formulation-dependent structures, the nonequilibrium dynamics across all composites and timescales can be organized into three classes-slow isotropic reorientation, fast directional flow, and multimode restructuring. Moreover, our mathematical model demonstrates that diverse structural motifs can arise simply from the interplay between motor-driven advection and frictional drag. These general features of our platform facilitate applicability to other active matter systems and shed light on diverse ways that cytoskeletal components can cooperate or compete to enable wide-ranging cellular processes.

Acute pharmacodynamic responses to exenatide: Drug-induced increases in insulin secretion and glucose effectiveness.

Glucagon-like peptide-1 receptor agonists provide multiple benefits to patients with type 2 diabetes, including improved glycaemic control, weight loss and decreased risk of major adverse cardiovascular events. Because drug responses vary among individuals, we initiated investigations to identify genetic variants associated with the magnitude of drug responses. Exenatide (5 μg, subcutaneously) or saline (0.2 ml, subcutaneously) was administered to 62 healthy volunteers. Frequently sampled intravenous glucose tolerance tests were conducted to assess the impact of exenatide on insulin secretion and insulin action. This pilot study was a crossover design in which participants received exenatide and saline in random order. Exenatide increased first phase insulin secretion 1.9-fold (p = 1.9 × 10-9 ) and accelerated the rate of glucose disappearance 2.4-fold (p = 2 × 10-10 ). Minimal model analysis showed that exenatide increased glucose effectiveness (Sg ) by 32% (p = .0008) but did not significantly affect insulin sensitivity (Si ). The exenatide-induced increase in insulin secretion made the largest contribution to interindividual variation in exenatide-induced acceleration of glucose disappearance while interindividual variation in the drug effect on Sg contributed to a lesser extent (β = 0.58 or 0.27, respectively). This pilot study provides validation for the value of a frequently sampled intravenous glucose tolerance test (including minimal model analysis) to provide primary data for our ongoing pharmacogenomic study of pharmacodynamic effects of semaglutide (NCT05071898). Three endpoints provide quantitative assessments of the effects of glucagon-like peptide-1 receptor agonists on glucose metabolism: first phase insulin secretion, glucose disappearance rates and glucose effectiveness.

LBMON175 Nadir Growth Hormone Concentrations In Patients With Acromegaly Relate To Disease Activity, Glucose Metabolism, BMI And Sex

Abstract Background In healthy subjects, nadir growth hormone (GH) concentrations following an oral glucose load are related to BMI, gender and estrogen use. To date, very few data exist on factors influencing nadir GH in patients with acromegaly. Methods Glucose suppression tests (2h-75g) were performed in 166 patients with acromegaly not receiving any acromegaly-specific medical therapy: 132 OGTTs were performed at the initial disease diagnosis and 126 after at least one pituitary surgery. Glucose, insulin and C-peptide were measured every 30 minutes and the metabolic response was evaluated by minimal model analysis. Uni- and multivariate regression analysis was performed to test the relationship between nadir GH concentrations, patient characteristics and parameters of disease activity, lipid and glucose metabolism. Results In patients with active acromegaly (46% males), nadir glucose concentrations positively correlated to fasting IGF-1 (expressed as fold-ULN; p&amp;lt;0. 001), fasting insulin and C-peptide (both p=0. 004), HOMA-insulin resistance index (p=0. 016), and prehepatic beta-cell function (p=0. 002), but not to BMI and gender. In multivariate analysis, fasting C-peptide and IGF-1 were both independent predictors of nadir GH levels in patients with newly diagnosed acromegaly (p&amp;lt;0. 001). When testing for sex-specific predictors of nadir GH, we found a negative relationship between nadir GH and age in male patients, but not in females. After surgery, IGF-1 decreased from 805.5 (3.2 xULN, IQR 437.8) to 277.5 ng/ml (1.1 xULN, IQR 234. 0) and nadir GH after glucose suppression decreased from 8.8 (IQR 16.2) to 0.5 ng/ml (IQR 1.9). The decrease in biomarkers of disease activity following surgery leads to changes in predictors of nadir GH: postoperatively nadir GH relates to IGF-1 (p&amp;lt;0. 001), prehepatic beta-cell function (p=0. 02), weight (p=0. 031) and BMI (p=0. 044), with beta-cell-function being the only independent predictor in multivariate analysis (p=0. 003). When postoperative OGTTs performed in men and women were separately analyzed, nadir GH remained in a positive relationship to GH and IGF-1 in both sexes, but the relationship with beta-cell-function and other parameters of glucose metabolism remained significant only in male patients. In addition, postoperative nadir GH in male patients positively relates to LDL-cholesterol and triglycerides, and negatively to gonadal axis activity. Conclusion Here we describe that nadir GH concentrations in patients with acromegaly are mainly determined by parameters of disease activity and beta-cell function, but not by BMI and sex. A positive relationship between nadir GH and weight/BMI is only observed following improvement of disease activity after surgery, but appears mainly influenced by morphologic gender differences, as it disappears when male and female cohorts are analyzed separately. Presentation: Monday, June 13, 2022 12:30 p.m. - 2:30 p.m.

On the existence and uniqueness analysis of fractional blood glucose-insulin minimal model

In our research work, we suggest the modified minimal model of fractional order and analyze it using the homotopy decomposition method (HDM). The minimal model is quite a useful mathematical model which describes the behavior of glucose-insulin metabolism. The original model was given in the 80s and has been updated over a different period. In this modified model, we add a one-factor diet which plays an important role in the blood-glucose analysis. We obtained the numerical results by using the homotopy decomposition method. HDM is extremely useful, significant, and very simple. We also discuss the existence and uniqueness of the fractional model.

Age, Body Mass Index, and Waist-to-Hip Ratio Related Changes in Insulin Secretion and Insulin Sensitivity in Women with Polycystic Ovary Syndrome: Minimal Model Analyses.

Insulin resistance is believed to be an integral component of the polycystic ovary syndrome (PCOS). Beta (ß) cell dysfunction is also found in PCOS. In the study, we determined the influence of age, body mass index (BMI), and waist-to-hip ratio (WHR) on insulin response to oral glucose load (OGTT) and on insulin sensitivity (Si) and ß-cell function in young women with PCOS. One hundred fourteen patients with PCOS and 41 controls with normal basal plasma glucose were studied. A 75-g OGTT was performed to determine glucose tolerance and insulin response. Insulin sensitivity and ß-cell function were studied using a modified frequently sampled IV glucose tolerance test (FISGTT) to determine the acute insulin response (AIRG), as well as Si by minimal model analysis. Si was decreased in PCOS women (2.49 0.18 vs. 3.41 ± 0.36, p < 0.05), but no difference in AIRG existed between the PCOS and control group (75.1 ± 4.6 vs. 63.4 ± 4.6, p < 0.05). BMI and WHR correlated negatively with Si (r = −0.43; r = −0.289, p < 0.001, respectively), but not with AIRG (r = 0.116; r = −0.02, p > 0.05, respectively). Increasing age correlated negatively with AIRG (r = −0.285, p < 0.001). There was a significant interaction between disease (PCOS), BMI, and WHR on Si as well as between age and PCOS on AIRG. Thus, patients below the age of 25 with PCOS showed enhanced AIRG (89.5 ± 7.1 vs. 65.1 ± 6.7, p < 0.05) and decreased Si (2.43 ± 0.25 vs. 4.52 ± 0.62, p < 0.05) compared to age-matched controls. In conclusion, these data suggest that not all patients with PCOS have basal and stimulated hyperinsulinemia, insulin resistance, and impaired glucose tolerance. Based on these data in young PCOS subjects, the development of insulin resistance and T2DM may be prevented with appropriate treatment strategies.

Insulin-resistance in paediatric age: Its magnitude and implications.

Insulin resistance (IR) is insulin failure in normal plasma levels to adequately stimulate glucose uptake by the peripheral tissues. IR is becoming more common in children and adolescents than before. There is a strong association between obesity in children and adolescents, IR, and the metabolic syndrome components. IR shows marked variation among different races, crucial to understanding the possible cardiovascular risk, specifically in high-risk races or ethnic groups. Genetic causes of IR include insulin receptor mutations, mutations that stimulate autoantibody production against insulin receptors, or mutations that induce the formation of abnormal glucose transporter 4 molecules or plasma cell membrane glycoprotein-1 molecules; all induce abnormal energy pathways and end with the development of IR. The parallel increase of IR syndrome with the dramatic increase in the rate of obesity among children in the last few decades indicates the importance of environmental factors in increasing the rate of IR. Most patients with IR do not develop diabetes mellitus (DM) type-II. However, IR is a crucial risk factor to develop DM type-II in children. Diagnostic standards for IR in children are not yet established due to various causes. Direct measures of insulin sensitivity include the hyperinsulinemia euglycemic glucose clamp and the insulin-suppression test. Minimal model analysis of frequently sampled intravenous glucose tolerance test and oral glucose tolerance test provide an indirect estimate of metabolic insulin sensitivity/resistance. The main aim of the treatment of IR in children is to prevent the progression of compensated IR to decompensated IR, enhance insulin sensitivity, and treat possible complications. There are three main lines for treatment: Lifestyle and behavior modification, pharmacotherapy, and surgery. This review will discuss the magnitude, implications, diagnosis, and treatment of IR in children.

Comparison of insulin sensitivity between healthy neonatal foals and horses using minimal model analysis.

The equine neonate is considered to have impaired glucose tolerance due to delayed maturation of the pancreatic endocrine system. Few studies have investigated insulin sensitivity in newborn foals using dynamic testing methods. The objective of this study was to assess insulin sensitivity by comparing the insulin-modified frequently sampled intravenous glucose tolerance test (I-FSIGTT) between neonatal foals and adult horses. This study was performed on healthy neonatal foals (n = 12), 24 to 60 hours of age, and horses (n = 8), 3 to 14 years of age using dextrose (300 mg/kg IV) and insulin (0.02 IU/kg IV). Insulin sensitivity (SI), acute insulin response to glucose (AIRg), glucose effectiveness (Sg), and disposition index (DI) were calculated using minimal model analysis. Proxy measurements were calculated using fasting insulin and glucose concentrations. Nonparametric statistical methods were used for analysis and reported as median and interquartile range (IQR). SI was significantly higher in foals (18.3 L·min-1· μIU-1 [13.4–28.4]) compared to horses (0.9 L·min-1· μIU-1 [0.5–1.1]); (p < 0.0001). DI was higher in foals (12 × 103 [8 × 103−14 × 103]) compared to horses (4 × 102 [2 × 102−7 × 102]); (p < 0.0001). AIRg and Sg were not different between foals and horses. The modified insulin to glucose ratio (MIRG) was lower in foals (1.72 μIUinsulin2/10·L·mgglucose [1.43–2.68]) compared to horses (3.91 μIU insulin2/10·L·mgglucose [2.57–7.89]); (p = 0.009). The homeostasis model assessment of beta cell function (HOMA-BC%) was higher in horses (78.4% [43–116]) compared to foals (23.2% [17.8–42.2]); (p = 0.0096). Our results suggest that healthy neonatal foals are insulin sensitive in the first days of life, which contradicts current literature regarding the equine neonate. Newborn foals may be more insulin sensitive immediately after birth as an evolutionary adaptation to conserve energy during the transition to extrauterine life.

Effects of colchicine on lipolysis and adipose tissue inflammation in adults with obesity and metabolic syndrome.

The aim of this study was to examine whether colchicine's anti-inflammatory effects would improve measures of lipolysis and distribution of leukocyte populations in subcutaneous adipose tissue (SAT). A secondary analysis was conducted for a double-blind, randomized, placebo-controlled pilot study in which 40 adults with obesity and metabolic syndrome (MetS) were randomized to colchicine 0.6 mg or placebo twice daily for 3 months. Non-insulin-suppressible (l0 ), insulin-suppressible (l2 ), and maximal (l0 +l2 ) lipolysis rates were calculated by minimal model analysis. Body composition was determined by dual-energy x-ray absorptiometry. SAT leukocyte populations were characterized by flow cytometry analysis from biopsied samples obtained before and after the intervention. Colchicine treatment significantly decreased l2 and l0 +l2 versus placebo (p < 0.05). These changes were associated with a significant reduction in markers of systemic inflammation, including high-sensitivity C-reactive protein, resistin, and circulating monocytes and neutrophils (p < 0.01). Colchicine did not significantly alter SAT leukocyte population distributions (p > 0.05). In adults with obesity and MetS, colchicine appears to improve insulin regulation of lipolysis and reduce markers of systemic inflammation independent of an effect on local leukocyte distributions in SAT. Further studies are needed to better understand the mechanisms by which colchicine affects adipose tissue metabolic pathways in adults with obesity and MetS.

202-LB: Reduced Glucose Effectiveness Exacerbates Impaired Glucose Tolerance in Prediabetic Dogs

The prodromal prediabetic state is characterized by glucose intolerance. Both insulin-dependent (sensitivity, secretion, clearance) and -independent factors (“glucose effectiveness”) contribute to glucose homeostasis. The relative importance of glucose effectiveness is not known. Healthy dogs (n=18) were tested at baseline (BL), after 6 wk on a high-fat diet (HFD), and 2 wk, after a sub-diabetogenic dose of streptozotocin (STZ, 18.5 mg/kg); HFD was continued. We performed intravenous glucose tolerance tests (IVGTTs)at 0, 6, and 8 wks. Minimal model analysis quantified insulin sensitivity (SI), acute insulin response to glucose (AIRg), disposition index (DI, = SI x AIRg), and glucose tolerance (KG). Glucose effectiveness (SG) was measured both by minimal model analysis and directly by multi-step hyperglycemic clamps at basal insulin in a subset of the dogs (n=5). Consumption of HFD induced 7.7±1.0% weight gain (P&amp;lt;0.001) and reduced SI (BL: 3.33±0.35; HFD: 2.01±0.38 x 104 min-1 per µU/ml; P=0.02). HFD elicited an increased AIRg (BL: 596±42; HFD: 1865±476 µU/ml, P=0.03) while maintaining KG (BL: 3.33±0.25; HFD: 3.67±0.33 min-1, P=0.69) as well as β-cell function expressed as DI (BL: 1939±236; HFD: 1882±199, P=0.97). SG was not changed by fat feeding per se (P=0.88). Prediabetes (STZ) conserved fasting glucose, but KG deteriorated (-45% from HFD to STZ) due to sustained insulin resistance with compromised β-cell function (DI decreased by 45±8%, P&amp;lt;0.01). Additionally, minimal model-based SG declined 37±8% from HFD to STZ (0.044±0.003 vs. 0.027±0.003 min-1, P&amp;lt;0.01), a result confirmed by glucose clamps (-30%). Impairments in both insulin-dependent and insulin-independent factors contribute to the glucose intolerance of experimental prediabetes. Rather than compensating for insulin resistance and beta-cell dysfunction, glucose effectiveness also declines, demonstrating that it exacerbates and contributes to glucose intolerance in the canine model of prediabetes. Disclosure C. M. Kolka: Research Support; Self; AstraZeneca. J. Porter: None. M. Ader: None. R. N. Bergman: None. Funding National Institutes of Health (DK27619, DK29867)

Effects of Colchicine on Measures of Lipolysis in Adults With Obesity

Background: Obesity-associated inflammation promotes adipose tissue (AT) dysfunction and contributes to the progression of type 2 diabetes and cardiovascular disease. Recent clinical studies have demonstrated that colchicine may improve metabolic and cardiovascular outcomes; however, colchicine’s effects on metabolic and inflammatory measures within AT remain unclear. Methods: The aim of this study was to examine if colchicine’s anti-inflammatory effects would improve measures of lipolysis and immune cell populations in subcutaneous AT (SAT). This is a secondary analysis of a double-blind, randomized, placebo-controlled pilot study in which 40 nondiabetic adults with obesity and metabolic syndrome (MetS) were randomized to colchicine 0.6mg or placebo twice daily for 3 months. Blood samples for insulin, glucose, and free fatty acids were collected in the fasted state and during a frequently-sampled intravenous glucose tolerance test. Noninsulin-suppressible (l0), insulin-suppressible (l2), and maximal (l0+l2) lipolysis rates were calculated by minimal model analysis. Body composition was determined by DXA. SAT immune cell populations were characterized by flow cytometry fluorescence-activated single cell sorting of the stromovascular fractions obtained after collagenase digestion of SAT samples obtained using a mini-liposuction technique pre- and post-intervention. Results: Data from 18 subjects in the colchicine group (Mean ± SD: age 48.4 ± 13.5 y; BMI 39.3 ± 6.3 kg/m2; sex: female 72.2%) and 18 subjects in the placebo group (age 44.7 ± 10.2 y; BMI 41.8 ± 8.2 kg/m2; sex: female 77.8%) were available for this study. Colchicine treatment significantly reduced l2 (p = 0.04) and l0+l2 (p = 0.04) versus placebo. These changes were significantly associated with reductions in systemic inflammation, including the changes in high-sensitivity C-reactive protein concentrations, white blood cell count, circulating monocyte and neutrophil populations, and the neutrophil-lymphocyte ratio (p’s < 0.015). Colchicine did not significantly alter SAT immune cell population distributions (p’s > 0.05). Conclusions: In adults with obesity and MetS, colchicine may improve insulin action at the level of AT. These improvements were positively associated with the suppression of systemic inflammation. However, no local AT inflammatory cell populations were significantly affected by colchicine use in our study, suggesting that colchicine’s systemic, rather than local, anti-inflammatory effects may be more consequential in ameliorating AT metabolic pathways in MetS. Further studies are warranted to elucidate the biological mechanisms underlying colchicine’s effects in AT, as these investigations could potentially shed light on treatments to improve metabolic outcomes in human obesity.

Associations of GlycA and high-sensitivity C-reactive protein with measures of lipolysis in adults with obesity

Obesity-associated inflammation promotes metabolic dysfunction. However, it is unclear how different inflammatory biomarkers predict dysregulation in specific tissues/organs, particularly adipose tissue. The aim of our study was to examine whether GlycA, a nuclear magnetic resonance-measured biomarker of inflammation, is a better predictor of insulin-suppressible lipolysis and other measures of metabolic dysfunction compared with high-sensitivity C-reactive protein (hsCRP) in human obesity. This was a cross-sectional study of 58 nondiabetic adults with obesity (body mass index: 39.8±7.0kg/m2, age 46.5±12.2years, 67.2% female) who underwent a frequently sampled intravenous glucose tolerance test in the fasted state. Noninsulin-suppressible (l0), insulin-suppressible (l2), and maximal (l0+l2) lipolysis rates, as well as insulin sensitivity and acute insulin response to glucose, were calculated by minimal model analysis. Nuclear magnetic resonance was used to measure GlycA. Body composition was determined by dual-energy X-ray absorptiometry. GlycA was strongly correlated with hsCRP (r=+0.46; P<.001). GlycA and hsCRP were positively associated with l2, l0+l2, and fat mass (Ps<.01). In linear regression models accounting for age, race, sex, and fat mass, GlycA remained significantly associated with l2 and l0+l2 (Ps<.05), whereas hsCRP did not (Ps≥.20). Neither GlycA nor hsCRP was associated with l0, insulin sensitivity, or acute insulin response to glucose. GlycA was associated with elevated lipolysis, independent of adiposity, in adults with obesity. Our findings suggest that GlycA and hsCRP have distinct inflammation-mediated metabolic effects, with GlycA having a greater association with adipose tissue dysfunction. Further studies are warranted to investigate the mechanisms underlying these associations.

Visual food cues decrease blood glucose and glucoregulatory hormones following an oral glucose tolerance test in normal-weight and obese men

Previous experiments of our group have demonstrated that preprandial processing of food cues attenuates postprandial blood glucose excursions. Here we systematically re-evaluated the glucose-lowering effect of visual food cues by submitting 40 healthy fasted men (20 normal-weight men, mean age 24.8 ± 3.7 years, BMI 21.9 ± 0.3 kg/m2; 20 obese men, 26.8 ± 4.2 years, 34.3 ± 1.3 kg/m2) to an oral glucose tolerance test (OGTT) following exposure to pictures of high-calorie food items versus neutral items. OGTT-related changes in blood concentrations of glucose and relevant glucoregulatory hormones including GLP-1 were assessed and analyzed according to the oral minimal model. Independent of body weight, food-cue compared to neutral stimulus presentation reduced postprandial concentrations of glucose (p = 0.041), insulin (p = 0.026) and C-peptide (p = 0.007); accordingly, oral minimal model analyses yielded a food-cue induced decrease of dynamic-phase insulin secretion (p = 0.036). We also observed a trend towards lower GLP-1 levels directly after food cue stimulation in both body weight groups (p = 0.057), as well as a trend towards decreased heart rate (p = 0.093) and significantly decreased diastolic blood pressure (p = 0.019). While we did not detect indicators of an early rise in insulin levels in terms of a ‘cephalic phase insulin response’, our findings support the assumption that preprandial processing of food cues exerts marked effect on postprandial glucose regulation, with possible contributions of changes in GLP-1. The mechanisms linking food cue exposure and glucoregulatory improvements should be investigated in greater detail, to potentially open new treatment options for metabolic dysfunctions.

SAT-624 Predictive Ability of Lipoprotein Insulin Resistance (LPIR) Score in South Asians: A Comparison of Surrogate Indices of Insulin Sensitivity/Resistance

South Asians (SA) are at higher risk for developing insulin resistance (IR) and type 2 diabetes. Consequently, identifying IR in this population is important. Lack of standardization and harmonization of insulin assays limit the clinical use of insulin-based surrogate indexes of insulin resistance. The lipoprotein insulin resistance (LPIR) score, a metabolomic marker, reflects the lipoprotein abnormalities observed in insulin-resistant states. The reliability of the LPIR score to predict IR in South Asians is currently unknown. In this study, we aimed to evaluate the predictive accuracy of LPIR compared to other fasting-based surrogate indices in SA.In a cross-sectional study of 59 non-diabetic SA subjects (age 36 ± 8 years, BMI 26.5 ± 5.2 kg/m2), we used calibration model analysis to assess the ability of the LPIR score and other simple surrogate indices [homeostasis model assessment (HOMA-IR), quantitative insulin sensitivity check index (QUICKI) and Adipose tissue insulin sensitivity (Adipo-SI)] to predict insulin sensitivity derived from the reference frequently sampled intravenous glucose tolerance test (FSIVGTT) and Minimal Model analysis (SiMM). LPIR scores were calculated using six lipoprotein particle concentrations and sizes measured by nuclear magnetic resonance (NMR) spectroscopy. Further, quantitative predictive accuracy and index comparisons were determined by root mean squared error (RMSE) of prediction and leave-one-out cross-validation-type RMSE of prediction (CVPE). Receiver operating characteristic (ROC) curve analysis was performed to determine how well LPIR distinguished insulin resistant individuals, categorized as an SiMM < 3.As determined by calibration model analysis, Adipo-SI, HOMA-IR, and QUICKI showed moderate correlations with for SiMM (Adipo-SI: r = 0.66; HOMA-IR: r = 0.60; QUICKI: r = 0.57, p = <0.0001). No significant differences were noted among CVPE or RMSE from any of the routinely used surrogate indices when compared with LPIR. The ROC area under the curve was 0.76 (95% CI 0.64–0.87) suggesting that LPIR performed well in identifying insulin resistant subjects. The optimal cut-off in IR individuals was LPIR >46 (sensitivity: 75.9 %, specificity: 70.0%). We conclude that NMR-derived LPIR may be an appropriate index to assess insulin resistance in South Asians.

Glucose Effectiveness from Short Insulin-Modified IVGTT and Its Application to the Study of Women with Previous Gestational Diabetes Mellitus

BackgroundThis study aimed to design a simple surrogate marker (i.e., predictor) of the minimal model glucose effectiveness (SG), namely calculated SG (CSG), from a short insulin-modified intravenous glucose tolerance test (IM-IVGTT), and then to apply it to study women with previous gestational diabetes mellitus (pGDM).MethodsCSG was designed using the stepwise model selection approach on a population of subjects (n=181) ranging from normal tolerance to type 2 diabetes mellitus (T2DM). CSG was then tested on a population of women with pGDM (n=57). Each subject underwent a 3-hour IM-IVGTT; women with pGDM were observed early postpartum and after a follow-up period of up to 7 years and classified as progressors (PROG) or non-progressors (NONPROG) to T2DM. The minimal model analysis provided a reference SG.ResultsCSG was described as CSG=1.06×10−2+5.71×10−2×KG/Gpeak, KG being the mean slope (absolute value) of loge glucose in 10–25- and 25–50-minute intervals, and Gpeak being the maximum of the glucose curve. Good agreement between CSG and SG in the general population and in the pGDM group, both at baseline and follow-up (even in PROG and NONPROG subgroups), was shown by the Bland-Altman plots (<5% observations outside limits of agreement), and by the test for equivalence (equivalence margin not higher than one standard deviation). At baseline, the PROG subgroup showed significantly lower SG and CSG values compared to the NONPROG subgroup (P<0.03).ConclusionCSG is a valid SG predictor. In the pGDM group, glucose effectiveness appeared to be impaired in women progressing to T2DM.

Increasing the proportion of plasma MUFA, as a result of dietary intervention, is associated with a modest improvement in insulin sensitivity.

The effect of modifying dietary fatty acid (FA) composition on insulin sensitivity remains unclear. We aimed to investigate whether changes in plasma phospholipid (PL) FA composition, as a result of dietary intervention, correspond with changes in insulin sensitivity. The RISCK study was a 6-month randomised controlled dietary intervention study, which assessed the effect of modifying dietary fat and the glycaemic index (GI) of carbohydrates on insulin sensitivity. Total NEFA levels, fasting plasma PL FA profiles and an insulin sensitivity index (Si), derived from intravenous glucose tolerance minimal-model analysis, were available from 533 participants, all at elevated risk of type 2 diabetes. Bivariate correlations between changes in saturated PL FA (SFA), MUFA (as a percentage of total plasma NEFA) and changes in Si were assessed according to treatment group. Age, sex, ethnicity, percentage change in body mass and change in dietary GI were controlled for. Increasing total NEFA concentration was associated with worsening Si (r -0·152; P = 0·001). In the high-MUFA/low-GI diet group, change in PL-MUFA was positively and independently associated with change in Si (r 0·297; P = 0·002). Among MUFA, change in oleic acid (18 : 1) was most strongly correlated with change in Si (r 0·266; P = 0·005), as was change in minor FA 24 : 1 (r 0·244; P = 0·011) and 17 : 1 (r 0·196; P = 0·042). In the high-SFA/high-GI group, change in SFA concentration was not significantly associated with change in Si. In conclusion, increases in the proportion of plasma PL-MUFA following a high-MUFA dietary intervention were associated with improvements in insulin sensitivity.