Disentangling Dual Threats: Premature Coronary Artery Disease and Early-Onset Type 2 Diabetes Mellitus in South Asians

South Asian individuals (SAs) face heightened risks of premature coronary artery disease (CAD) and early-onset type 2 diabetes mellitus (T2DM), with grave health, societal, and economic implications due to the region's dense population. Both conditions, influenced by cardiometabolic risk factors such as insulin resistance, hypertension, and central adiposity, manifest earlier and with unique thresholds in SAs. Epidemiological, demographic, nutritional, environmental, sociocultural, and economic transitions in SA have exacerbated the twin epidemic. The coupling of premature CAD and T2DM arises from increased obesity due to limited adipose storage, early-life undernutrition, distinct fat thresholds, reduced muscle mass, and a predisposition for hepatic fat accumulation from certain dietary choices cumulatively precipitating a decline in insulin sensitivity. As T2DM ensues, the β-cell adaptive responses are suboptimal, precipitating a transition from compensatory hyperinsulinemia to β-cell decompensation, underscoring a reduced functional β-cell reserve in SAs. This review delves into the interplay of these mechanisms and highlights a prediabetes endotype tied to elevated vascular risk. Deciphering these mechanistic interconnections promises to refine stratification paradigms, surpassing extant risk-prediction strategies.

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

AIM

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.

METHODS

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.

RESULTS

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).

CONCLUSIONS

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.

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

Background

GLP1R agonists provide multiple benefits to patients with type 2 diabetes - including improved glycemic 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.

Methods

Exenatide (5 µg, sc) or saline (0.2 mL, sc) 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 designed as a crossover study in which participants received exenatide and saline in random order.

Results

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 demonstrated that exenatide increased glucose effectiveness (S g ) by 32% (p=0.0008) but did not significantly affect insulin sensitivity (S i ). The exenatide-induced increase in insulin secretion made the largest contribution to inter-individual variation in exenatide-induced acceleration of glucose disappearance while inter-individual variation in the drug effect on S g contributed to a lesser extent (β=0.58 or 0.27, respectively).

Conclusions

This pilot study provides validation for the value of an FSIGT (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 GLP1R agonists' effects on glucose metabolism: first phase insulin secretion, glucose disappearance rates, and glucose effectiveness.

Registration

NCT02462421 (clinicaltrials.gov).

Funding

American Diabetes Association (1-16-ICTS-112); National Institute of Diabetes and Digestive and Kidney Disease (R01DK130238, T32DK098107, P30DK072488).

Lipoprotein Insulin Resistance Index: A Simple, Accurate Method for Assessing Insulin Resistance in South Asians

Context

Identification of insulin resistance (IR) in South Asians, who are at a higher risk for type 2 diabetes, is important. Lack of standardization of insulin assays limits the clinical use of insulin-based surrogate indices. The lipoprotein insulin resistance index (LP-IR), a metabolomic marker, reflects the lipoprotein abnormalities observed in IR. The reliability of the LP-IR index in South Asians is unknown.

Objective

We evaluated the predictive accuracy of LP-IR compared with other IR surrogate indices in South Asians.

Methods

In a cross-sectional study (n = 55), we used calibration model analysis to assess the ability of the LP-IR score and other simple surrogate indices (Homeostatic Model Assessment of Insulin Resistance, Quantitative insulin sensitivity check index, Adipose insulin resistance index, and Matsuda Index) to predict insulin sensitivity (S_I) derived from the reference frequently sampled intravenous glucose tolerance test. LP-IR index was derived from lipoprotein particle concentrations and sizes measured by nuclear magnetic resonance spectroscopy. Predictive accuracy was determined by root mean squared error (RMSE) of prediction and leave-one-out cross-validation type RMSE of prediction (CVPE). The optimal cut-off of the LP-IR index was determined by the area under the receiver operating characteristic curve (AUROC) and the Youden index.

Results

The simple surrogate indices showed moderate correlations with S_I (r = 0.53-0.69, P < .0001). CVPE and RMSE were not different in any of the surrogate indices when compared with LP-IR. The AUROC was 0.77 (95% CI 0.64-0.89). The optimal cut-off for IR in South Asians was LP-IR >48 (sensitivity: 75%, specificity: 70%).

Conclusion

The LP-IR index is a simple, accurate, and clinically useful test to assess IR in South Asians.

Volanesorsen, an antisense oligonucleotide to apolipoprotein C-III, increases lipoprotein lipase activity and lowers triglycerides in partial lipodystrophy

BACKGROUND

Partial lipodystrophy (PL) syndromes involve deficiency of adipose tissue, causing severe insulin resistance and hypertriglyceridemia. Apolipoprotein C-III (apoC-III) is elevated in PL and is thought to contribute to hypertriglyceridemia by inhibiting lipoprotein lipase (LPL).

OBJECTIVE

We hypothesized that volanesorsen, an antisense oligonucleotide to apoC-III, would decrease apoC-III, increase LPL activity, and lower triglycerides in PL.

METHODS

Five adults with PL enrolled in a 16-week placebo-controlled, randomized, double blind study of volanesorsen, 300 mg weekly, followed by 1-year open label extension.

RESULTS

Within-subject effects of volanesorsen before and after 16 weeks of active drug are reported due to small sample size. From week 0 to 16, apoC-III decreased from median (25th, 75th %ile) 380 (246, 600) to 75 (26, 232) ng/mL, and triglycerides decreased from 503 (330, 1040) to 116 (86, 355) mg/dL while activation of LPL by subjects' serum increased from 21 (20, 25) to 36 (29, 42) nEq/mL*min. Although, A1c did not change, peripheral and hepatic insulin sensitivity (glucose disposal and suppression of glucose production during hyperinsulinemic clamp) increased and palmitate turnover decreased. After 32-52 weeks of volanesorsen, liver fat decreased. Common adverse events included injection site reactions and decreased platelets.

CONCLUSIONS

In PL, volanesorsen decreased apoC-III and triglycerides, in part through an LPL dependent mechanism, and may improve insulin resistance and hepatic steatosis.

Management of Hyperglycemia in Hospitalized Adult Patients in Non-Critical Care Settings: An Endocrine Society Clinical Practice Guideline

BACKGROUND

Adult patients with diabetes or newly recognized hyperglycemia account for over 30% of noncritically ill hospitalized patients. These patients are at increased risk for adverse clinical outcomes in the absence of defined approaches to glycemic management.

OBJECTIVE

To review and update the 2012 Management of Hyperglycemia in Hospitalized Patients in Non-Critical Care Settings: An Endocrine Society Clinical Practice Guideline and to address emerging areas specific to the target population of noncritically ill hospitalized patients with diabetes or newly recognized or stress-induced hyperglycemia.

METHODS

A multidisciplinary panel of clinician experts, together with a patient representative and experts in systematic reviews and guideline development, identified and prioritized 10 clinical questions related to inpatient management of patients with diabetes and/or hyperglycemia. The systematic reviews queried electronic databases for studies relevant to the selected questions. The Grading of Recommendations Assessment, Development and Evaluation (GRADE) methodology was used to assess the certainty of evidence and make recommendations.

RESULTS

The panel agreed on 10 frequently encountered areas specific to glycemic management in the hospital for which 15 recommendations were made. The guideline includes conditional recommendations for hospital use of emerging diabetes technologies including continuous glucose monitoring and insulin pump therapy; insulin regimens for prandial insulin dosing, glucocorticoid, and enteral nutrition-associated hyperglycemia; and use of noninsulin therapies. Recommendations were also made for issues relating to preoperative glycemic measures, appropriate use of correctional insulin, and diabetes self-management education in the hospital. A conditional recommendation was made against preoperative use of caloric beverages in patients with diabetes.

CONCLUSION

The recommendations are based on the consideration of important outcomes, practicality, feasibility, and patient values and preferences. These recommendations can be used to inform system improvement and clinical practice for this frequently encountered inpatient population.

A Systematic Review Supporting the Endocrine Society Clinical Practice Guideline for the Management of Hyperglycemia in Adults Hospitalized for Noncritical Illness or Undergoing Elective Surgical Procedures

CONTEXT

Individuals with diabetes or newly recognized hyperglycemia account for over 30% of noncritically ill hospitalized patients. Management of hyperglycemia in these patients is challenging.

OBJECTIVE

To support development of the Endocrine Society Clinical Practice Guideline for management of hyperglycemia in adults hospitalized for noncritical illness or undergoing elective surgical procedures.

METHODS

We searched several databases for studies addressing 10 questions provided by a guideline panel from the Endocrine Society. Meta-analysis was conducted when feasible. The Grading of Recommendations Assessment, Development and Evaluation (GRADE) methodology was used to assess certainty of evidence.

RESULTS

We included 94 studies reporting on 135 553 patients. Compared with capillary blood glucose, continuous glucose monitoring increased the number of patients identified with hypoglycemia and decreased mean daily blood glucose (BG) (very low certainty). Data on continuation of insulin pump therapy in hospitalized adults were sparse. In hospitalized patients receiving glucocorticoids, combination neutral protamine hagedorn (NPH) and basal-bolus insulin was associated with lower mean BG compared to basal-bolus insulin alone (very low certainty). Data on NPH insulin vs basal-bolus insulin in hospitalized adults receiving enteral nutrition were inconclusive. Inpatient diabetes education was associated with lower HbA1c at 3 and 6 months after discharge (moderate certainty) and reduced hospital readmissions (very low certainty). Preoperative HbA1c level < 7% was associated with shorter length of stay, lower postoperative BG and a lower number of neurological complications and infections, but a higher number of reoperations (very low certainty). Treatment with glucagon-like peptide-1 agonists or dipeptidyl peptidase-4 inhibitors in hospitalized patients with type 2 diabetes and mild hyperglycemia was associated with lower frequency of hypoglycemic events than insulin therapy (low certainty). Caloric oral fluids before surgery in adults with diabetes undergoing surgical procedures did not affect outcomes (very low certainty). Counting carbohydrates for prandial insulin dosing did not affect outcomes (very low certainty). Compared with scheduled insulin (basal-bolus or basal insulin + correctional insulin), correctional insulin was associated with higher mean daily BG and fewer hypoglycemic events (low certainty).

CONCLUSION

The certainty of evidence supporting many hyperglycemia management decisions is low, emphasizing importance of shared decision-making and consideration of other decisional factors.

Enhancing the Trustworthiness of the Endocrine Society's Clinical Practice Guidelines

In an effort to enhance the trustworthiness of its clinical practice guidelines, the Endocrine Society has recently adopted new policies and more rigorous methodologies for its guideline program. In this Clinical Practice Guideline Communication, we describe these recent enhancements-many of which reflect greater adherence to the Grading of Recommendations, Assessment, Development and Evaluation (GRADE) approach to guideline development-in addition to the rationale for such changes. Improvements to the Society's guideline development practices include, but are not limited to, enhanced inclusion of nonendocrinologist experts, including patient representatives, on guideline development panels; implementation of a more rigorous conflict/duality of interest policy; a requirement that all formal recommendations must be demonstrably underpinned by systematic evidence review; the explicit use of GRADE Evidence-to-Decision frameworks; greater use and explanation of standardized guideline language; and a more intentional approach to guideline updating. Lastly, we describe some of the experiential differences our guideline readers are most likely to notice.

Postprandial Plasma Lipidomics Reveal Specific Alteration of Hepatic-derived Diacylglycerols in Nonalcoholic Fatty Liver Disease

BACKGROUND & AIMS

Hepatic energy metabolism is a dynamic process modulated by multiple stimuli. In nonalcoholic fatty liver disease (NAFLD), human studies typically focus on the static fasting state. We hypothesized that unique postprandial alterations in hepatic lipid metabolism are present in NAFLD.

METHODS

In a prospective clinical study, 37 patients with NAFLD and 10 healthy control subjects ingested a standardized liquid meal with pre- and postprandial blood sampling. Postprandial plasma lipid kinetics were characterized at the molecular lipid species level by untargeted lipidomics, cluster analysis, and lipid particle isolation, then confirmed in a mouse model.

RESULTS

There was a specific increase of multiple plasma diacylglycerol (DAG) species at 4 hours postprandially in patients with NAFLD but not in controls. This was replicated in a nonalcoholic steatohepatitis mouse model, where postprandial DAGs increased in plasma and concomitantly decreased in the liver. The increase in plasma DAGs appears early in the disease course, is dissociated from NAFLD severity and obesity, and correlates with postprandial insulin levels. Immunocapture isolation of very low density lipoprotein in human samples and stable isotope tracer studies in mice revealed that elevated postprandial plasma DAGs reflect hepatic secretion of endogenous, rather than meal-derived lipids.

CONCLUSIONS

We identified a selective insulin-related increase in hepatic secretion of endogenously derived DAGs after a mixed meal as a unique feature of NAFLD. DAGs are known to be lipotoxic and associated with atherosclerosis. Although it is still unknown whether the increased exposure to hepatic DAGs contributes to extrahepatic manifestations and cardiovascular risk in NAFLD, our study highlights the importance of extending NAFLD research beyond the fasting state.

Endogenous Leptin Concentrations Poorly Predict Metreleptin Response in Patients With Partial Lipodystrophy

CONTEXT

Leptin replacement with metreleptin improves glycemia and hypertriglyceridemia in severely hypoleptinemic patients with generalized lipodystrophy (GLD), but its effects are variable in partially leptin-deficient patients with partial lipodystrophy (PLD).

OBJECTIVE

Compare 3 leptin assays (Study I); identify diagnostic performance of leptin assays to detect responders to metreleptin for each assay (Study II).

DESIGN

Study I: cross-sectional analysis of average bias between leptin assays. Study II: retrospective analysis of diagnostic accuracy of potential leptin cut points to detect clinical responders to metreleptin.

SETTING

National Institutes of Health; University of Michigan.

PARTICIPANTS AND INTERVENTIONS

Study I: Metreleptin-naïve patients with lipodystrophy (GLD, n = 33, PLD, n = 67) and healthy volunteers (n = 239). Study II: GLD (n = 66) and PLD (n = 84) patients treated with metreleptin for 12 months.

OUTCOME MEASURES

Leptin concentrations by Millipore radioimmunoassay (RIA), Millipore enzyme-linked immunosorbent assay (MELISA), and R&D Systems enzyme-linked immunosorbent assay (RDELISA). Response to metreleptin therapy was defined as either reduction ≥1.0% in A1c or ≥30% in serum triglycerides.

RESULTS

RDELISA measured 3.0 ± 9.5 ng/mL higher than RIA; MELISA measured 11.0 ± 17.8 and 14.0 ±19.2 less than RIA and RDELISA, respectively. Leptin by RIA, MELISA, and RDELISA modestly predicted metreleptin response in GLD + PLD [receiver operating characteristic (ROC) area under the curve (AUC) 0.74, 0.69, and 0.71, respectively; P < 0.01 for all] with lower predictive power in PLD (ROC AUC 0.63, 0.61 and 0.65, respectively; P > 0.05 for all). The only reproducible cut point identified on sensitivity analyses was RIA leptin 7.2 ng/mL (sensitivity 56%; specificity 78%).

CONCLUSIONS

Three common leptin assays are not interchangeable, and a reliable cut point to select responders to metreleptin was not identified.

Minimal Model-Derived Insulin Sensitivity Index Underestimates Insulin Sensitivity in Black Americans

OBJECTIVE

To examine the ethnic differences in insulin sensitivity (S_I) as measured by the minimal model approach (S_I-MM) and the reference method, the euglycemic-hyperinsulinemic clamp (EHC).

RESEARCH DESIGN AND METHODS

In a prospective study design, thirty Black Americans (BA) were age, sex, and BMI matched with non-Hispanic Whites (NHW). Participants underwent frequently sampled intravenous tolerance test (FSIVGTT) and EHC on 2 separate days during a single visit.

RESULTS

S_I-MM values were significantly lower in BA when compared with NHW (0.035 ± 0.025 vs. 0.058 ± 0.036 [dL/min]/[μU/mL]; P = 0.003). However, there were no ethnic differences in S_I measured by EHC (0.028 ± 0.012 vs. 0.035 ± 0.019 [dL/min]/[μU/mL]; P = 0.18).

CONCLUSIONS

S_I-MM systematically underestimates S_I in BA when compared with NHW. These findings suggest that studies inferring lower S_I in BA based on FSIVGTT and S_I-MM should be interpreted cautiously.

Mifepristone Improves Adipose Tissue Insulin Sensitivity in Insulin Resistant Individuals

BACKGROUND

Increased tissue cortisol availability has been implicated in abnormal glucose and fat metabolism in patients with obesity, metabolic syndrome, and type 2 diabetes (T2DM). Our objective was to evaluate whether blockade of glucocorticoid receptor (GR) with mifepristone ameliorates insulin resistance (IR) in overweight/obese subjects with glucose intolerance.

METHODS

We conducted a randomized, double-blinded, placebo-controlled, crossover study in overweight/obese individuals (n = 16, 44% female) with prediabetes or mild T2DM but not clinical hypercortisolism. Mifepristone (50 mg every 6 h) or placebo was administered for 9 days, followed by crossover to the other treatment arm after a washout period of 6 to 8weeks. At baseline and following each treatment, oral glucose tolerance test (OGTT) and frequently sampled intravenous glucose tolerance test (FSIVGTT) were performed. Insulin sensitivity was measured using FSIVGTT [primary outcome: insulin sensitivity index (SI)] and OGTT [Matsuda index (MI) and oral glucose insulin sensitivity index (OGIS)]. Hepatic and adipose insulin resistance were assessed using hepatic insulin resistance index (HIRI), and adipose tissue insulin sensitivity index (Adipo-SI) and adipo-IR, derived from the FSIVGTT.

RESULTS

Mifepristone administration did not alter whole-body glucose disposal indices of insulin sensitivity (SI, MI, and OGIS). GR blockade significantly improved Adipo-SI (61.7 ± 32.9 vs 42.8 ± 23.9; P = 0.002) and reduced adipo-IR (49.9 ± 45.9 vs 65.5 ± 43.8; P = 0.004), and HIRI (50.2 ± 38.7 vs 70.0 ± 44.3; P = 0.08). Mifepristone increased insulin clearance but did not affect insulin secretion or β-cell glucose sensitivity.

CONCLUSION

Short-term mifepristone administration improves adipose and hepatic insulin sensitivity among obese individuals with hyperglycemia without hypercortisolism.

When MINMOD Artifactually Interprets Strong Insulin Secretion as Weak Insulin Action

We address a problem with the Bergman-Cobelli Minimal Model, which has been used for 40 years to estimate S_I during an intravenous glucose tolerance test (IVGTT). During the IVGTT blood glucose and insulin concentrations are measured in response to an acute intravenous glucose load. Insulin secretion is often assessed by the area under the insulin curve during the first few minutes (Acute Insulin Response, AIR). The issue addressed here is that we have found in simulated IVGTTs, representing certain contexts, Minimal Model estimates of S_I are inversely related to AIR, resulting in artifactually lower S_I. This may apply to Minimal Model studies reporting lower S_I in Blacks than in Whites, a putative explanation for increased risk of T2D in Blacks. The hyperinsulinemic euglycemic clamp (HIEC), the reference method for assessing insulin sensitivity, by contrast generally does not show differences in insulin sensitivity between these groups. The reason for this difficulty is that glucose rises rapidly at the start of the IVGTT and reaches levels independent of S_I, whereas insulin during this time is determined by AIR. The minimal model in effect interprets this combination as low insulin sensitivity even when actual insulin sensitivity is unchanged. This happens in particular when high AIR results from increased number of readily releasable insulin granules, which may occur in Blacks. We conclude that caution should be taken when comparing estimates of S_I between Blacks and Whites.

Insulin sensitivity and pancreatic β-cell function in patients with primary aldosteronism

BACKGROUND

Primary aldosteronism (PA) is associated with an increased risk for dysglycemia. However, the effects of hyperaldosteronism on insulin sensitivity and β-cell function are unclear.

METHODS

Using a cross-sectional study design, we assessed insulin sensitivity and pancreatic β-cell function from an oral glucose tolerance test (OGTT) in patients from two cohorts: subjects with PA (n = 21) and essential hypertension control (EHC) subjects (n = 22). Age, sex, BMI, and mean arterial pressure adjusted measures of insulin sensitivity and β-cell function were compared between the groups.

RESULTS

PA individuals were less insulin sensitive compared to EHC subjects (Quantitative insulin sensitivity check index [QUICKI]: 0.340 ± 0.006 vs. 0.374 ± 0.013, p < 0.001; Matsuda index: 4.14 ± 0.49 vs. 7.87 ± 1.42, p < 0.001; S_I: 11.45 ± 4.85 vs. 21.23 ± 6.11 dL/kg/min per μU/mL, p = 0.02). The hepatic insulin resistance index (HIRI) was higher in PA subjects (PA: 5.61 ± 1.01 vs. EHC: 4.13 ± 0.61, p = 0.002). The insulinogenic index (IGI), an index of β-cell function was higher in the PA cohort (PA: 1.49 ± 0.27 vs. 1.11 ± 0.21 μU/mL/mg/dL, p = 0.03). However, the oral disposition index (DI) was similar between the groups (PA: 4.77 ± 0.73 vs. EHC: 5.46 ± 0.85, p = 0.42), which likely accounts for the similar glucose tolerance between the two cohorts, despite lower sensitivity.

CONCLUSIONS

In summary, insulin sensitivity is significantly lower in PA with an appropriately compensated β-cell function. These results suggest that excess aldosterone and/or other steroids in the context of PA may negatively affect insulin action without adversely impacting β-cell function.

Apolipoprotein CIII and Angiopoietin-like Protein 8 are Elevated in Lipodystrophy and Decrease after Metreleptin

Context

Lipodystrophy syndromes cause hypertriglyceridemia that improves with leptin treatment using metreleptin. Mechanisms causing hypertriglyceridemia and improvements after metreleptin are incompletely understood.

Objective

Determine relationship of circulating lipoprotein lipase (LPL) modulators with hypertriglyceridemia in healthy controls and in patients with lipodystrophy before and after metreleptin.

Methods

Cross-sectional comparison of patients with lipodystrophy (generalized lipodystrophy n = 3; partial lipodystrophy n = 11) vs age/sex-matched healthy controls (n = 28), and longitudinal analyses in patients before and after 2 weeks and 6 months of metreleptin. The study was carried out at the National Institutes of Health, Bethesda, Maryland. Outcomes were LPL stimulators apolipoprotein (apo) C-II and apoA-V and inhibitors apoC-III and angiopoietin-like proteins (ANGPTLs) 3, 4, and 8; ex vivo activation of LPL by plasma.

Results

Patients with lipodystrophy were hypertriglyceridemic and had higher levels of all LPL stimulators and inhibitors vs controls except for ANGPTL4, with >300-fold higher ANGPTL8, 4-fold higher apoC-III, 3.5-fold higher apoC-II, 1.9-fold higher apoA-V, 1.6-fold higher ANGPTL3 (P < .05 for all). At baseline, all LPL modulators except ANGPLT4 positively correlated with triglycerides. Metreleptin decreased apoC-II and apoC-III after 2 weeks and 6 months, and decreased ANGPTL8 after 6 months (P < 0.05 for all). Plasma from patients with lipodystrophy caused higher ex vivo LPL activation vs hypertriglyceridemic control plasma (P < .0001), which did not change after metreleptin.

Conclusion

Elevations in LPL inhibitors apoC-III and ANGPTL8 may contribute to hypertriglyceridemia in lipodystrophy, and may mediate reductions in circulating and hepatic triglycerides after metreleptin. These therefore are strong candidates for therapies to lower triglycerides in these patients.

Metabolic Syndrome and COVID 19: Endocrine-Immune-Vascular Interactions Shapes Clinical Course

The ongoing coronavirus disease 2019 (COVID-19) pandemic is caused by the novel coronavirus, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Individuals with metabolic syndrome are at increased risk for poor disease outcomes and mortality from COVID-19. The pathophysiologic mechanisms for these observations have not been fully elucidated. A critical interaction between SARS-CoV-2 and the angiotensin-converting enzyme 2 (ACE2) facilitates viral entry into the host cell. ACE2 is expressed in pancreatic islets, vascular endothelium, and adipose tissue, and the SARS-CoV-2 -ACE2 interaction in these tissues, along with other factors, governs the spectrum and the severity of clinical manifestations among COVID-19 patients with metabolic syndrome. Moreover, the pro-inflammatory milieu observed in patients with metabolic syndrome may contribute toward COVID-19-mediated host immune dysregulation, including suboptimal immune responses, hyperinflammation, microvascular dysfunction, and thrombosis. This review describes the spectrum of clinical features, the likely pathophysiologic mechanisms, and potential implications for the management of metabolic syndrome in COVID-19 patients.

A Pragmatic Approach to Inpatient Diabetes Management during the COVID-19 Pandemic

The pandemic of COVID-19 has presented new challenges to hospital personnel providing care for infected patients with diabetes who represent more than 20% of critically ill patients in intensive care units. Appropriate glycemic management contributes to a reduction in adverse clinical outcomes in acute illness but also requires intensive patient interactions for bedside glucose monitoring, intravenous and subcutaneous insulin administration, as well as rapid intervention for hypoglycemia events. These tasks are required at a time when minimizing patient interactions is recommended as a way of avoiding prolonged exposure to COVID-19 by health care personnel who often practice in settings with limited supplies of personal protective equipment. The purpose of this manuscript is to provide guidance for clinicians for reconciling recommended standards of care for infected hospitalized patients with diabetes while also addressing the daily realities of an overwhelmed health care system in many areas of the country. The use of modified protocols for insulin administration, bedside glucose monitoring, and medications such as glucocorticoids and hydroxychloroquine that may affect glycemic control are discussed. Continuous glucose monitoring systems have been proposed as an option for reducing time spent with patients, but there are important issues that need to be addressed if these are used in hospitalized patients. On-site and remote glucose management teams have potential to provide guidance in areas where there are shortages of personnel who have expertise in inpatient glycemic management.

Endothelial dysfunction due to selective insulin resistance in vascular endothelium: insights from mechanistic modeling

Previously, we have used mathematical modeling to gain mechanistic insights into insulin-stimulated glucose uptake. Phosphatidylinositol 3-kinase (PI3K)-dependent insulin signaling required for metabolic actions of insulin also regulates endothelium-dependent production of the vasodilator nitric oxide (NO). Vasodilation increases blood flow that augments direct metabolic actions of insulin in skeletal muscle. This is counterbalanced by mitogen-activated protein kinase (MAPK)-dependent insulin signaling in endothelium that promotes secretion of the vasoconstrictor endothelin-1 (ET-1). In the present study, we extended our model of metabolic insulin signaling into a dynamic model of insulin signaling in vascular endothelium that explicitly represents opposing PI3K/NO and MAPK/ET-1 pathways. Novel NO and ET-1 subsystems were developed using published and new experimental data to generate model structures/parameters. The signal-response relationships of our model with respect to insulin-stimulated NO production, ET-1 secretion, and resultant vascular tone, agree with published experimental data, independent of those used for model development. Simulations of pathological stimuli directly impairing only insulin-stimulated PI3K/Akt activity predict altered dynamics of NO and ET-1 consistent with endothelial dysfunction in insulin-resistant states. Indeed, modeling pathway-selective impairment of PI3K/Akt pathways consistent with insulin resistance caused by glucotoxicity, lipotoxicity, or inflammation predict diminished NO production and increased ET-1 secretion characteristic of diabetes and endothelial dysfunction. We conclude that our mathematical model of insulin signaling in vascular endothelium supports the hypothesis that pathway-selective insulin resistance accounts, in part, for relationships between insulin resistance and endothelial dysfunction. This may be relevant for developing novel approaches for the treatment of diabetes and its cardiovascular complications.

Leptin decreases de novo lipogenesis in patients with lipodystrophy

De novo lipogenesis (DNL) plays a role in the development of hepatic steatosis. In humans with lipodystrophy, reduced adipose tissue causes lower plasma leptin, insulin resistance, dyslipidemia, and ectopic triglyceride (TG) accumulation. We hypothesized that recombinant leptin (metreleptin) for 6 months in 11 patients with lipodystrophy would reduce DNL by decreasing insulin resistance and glycemia, thus reducing circulating TG and hepatic TG. The percentage of TG in TG-rich lipoprotein particle (TRLP-TG) derived from DNL (%DNL) was measured by deuterium incorporation from body water into palmitate. At baseline, DNL was elevated, similar to levels previously shown in obesity-associated nonalcoholic fatty liver disease (NAFLD). After metreleptin, DNL decreased into the normal range. Similarly, absolute DNL (TRLP-TG × %DNL) decreased by 88% to near-normal levels. Metreleptin improved peripheral insulin sensitivity (hyperinsulinemic-euglycemic clamp) and lowered hemoglobin A1c and hepatic TG. Both before and after metreleptin, DNL positively correlated with insulin resistance, insulin doses, and hepatic TG, supporting the hypothesis that hyperinsulinemia stimulates DNL and that elevated DNL is integral to the pathogenesis of lipodystrophy-associated NAFLD. These data suggest that leptin-mediated improvement in insulin sensitivity increases clearance of blood glucose by peripheral tissues, reduces hepatic carbohydrate flux, and lowers insulinemia, resulting in DNL reductions and improvements in hepatic steatosis and dyslipidemia.

Increased β-Cell Responsivity Independent of Insulin Sensitivity in Healthy African American Adults

BACKGROUND

Primary insulin hypersecretion predicts type 2 diabetes (T2DM) independent of insulin resistance. Enhanced β-cell glucose responsivity contributes to insulin hypersecretion. African Americans (AAs) are at a higher risk for T2DM than non-Hispanic Whites (NHWs). Whether AAs manifest primary insulin hypersecretion is an important topic that has not been examined systematically.

OBJECTIVE

To examine if nondiabetic AA adults have a higher β-cell glucose responsivity compared with NHWs.

METHODS

Healthy nondiabetic AA (n = 18) and NHW (n=18) subjects were prospectively recruited. Indices of β-cell function, acute C-peptide secretion (X0); basal (Φ B), first-phase (Φ 1), second-phase (Φ 2), and total β-cell responsivity to glucose (Φ TOT), were derived from modeling of insulin, C-peptide, and glucose concentrations during an intravenous glucose tolerance test. Insulin sensitivity was assessed by the hyperinsulinemic-euglycemic glucose clamp technique.

RESULTS

Glucose disposal rate (GDR) during clamp was similar in AAs and NHWs (GDR: [AA] 12.6 ± 3.2 vs [NHW] 12.6 ± 4.2 mg/kg fat free mass +17.7/min, P = .49). Basal insulin secretion rates were similar between the groups. AA had significantly higher X0 (4423 ± 593 vs 1807 ± 176 pmol/L, P = .007), Φ 1 [377.5 ± 59.0 vs 194.5 ± 26.6 (109) P = 0.03], and Φ TOT [76.7 ± 18.3 vs 29.6 ± 4.7 (109/min), P = 0.03], with no significant ethnic differences in Φ B and Φ 2.

CONCLUSIONS

Independent of insulin sensitivity, AAs showed significantly higher first-phase and total β-cell responsivity than NHWs. We propose that this difference reflects increased β-cell responsivity specifically to first-phase readily releasable insulin secretion. Future studies are warranted to identify mechanisms leading to primary β-cell hypersensitivity in AAs.

MON-593 Single-Dose Effects of Anti-Obesity Drugs on Human Basal Metabolic Rate

Design and rationale: Obesity results from energy intake exceeding energy expenditure (EE) over a prolonged period. Many anti-obesity drugs are designed to decrease energy intake. However, their potential impact on EE is not well documented. We designed a placebo-controlled, double-blind, randomized cross-over study to determine the acute effects of several FDA-approved anti-obesity drugs on basal metabolic rate (BMR) under well-controlled conditions.

Protocol and inclusion criteria: This ongoing study is limited to healthy males of all ethnicities aged 18–35 years with a BMI of 18.5 to 25.0 kg/m². Following an overnight stay in the Metabolic Clinical Research Unit, fasting subjects were measured from 8:00am to 12:00pm in a whole-room indirect calorimeter, which was maintained at a thermoneutral temperature (26.7±0.9°C) to prevent non-shivering thermogenesis. The six treatments include placebo, caffeine as the positive control (300 mg), phentermine (37.5 mg), topiramate (200 mg), Qsymia (phentermine 15 mg / topiramate 92 mg), and naltrexone (100 mg), with a 1-week outpatient washout period after each treatment. Drug-naïve subjects received a single dose of each drug to minimize potential metabolic adaptations that may occur with weight-loss or chronic use. The prespecified primary outcome was a ≥5% increase in BMR vs. placebo for each drug. This difference can be detected for 16 subjects with 0.83 power at α=0.05 allowing for ≤25% dropout. Secondary outcomes include respiratory quotient (RQ), heart rate (HR), mean arterial pressure (MAP), and self-reported hunger.

Preliminary data: To date, 7 subjects were recruited and 6 have completed the study (26.1±4.3 years, BMI 23.1±1.4 kg/m², body fat percentage 18.4±4.1%). Interim analysis using paired t-tests shows, compared to placebo, caffeine trended towards increasing EE (1.17±0.07 vs. 1.27±0.12 kcal/min; p=0.07) and increased MAP by 5.5±4.2% (88±2 vs. 93±4; p<0.05), but did not change heart rate (59±10 vs. 61±13 bpm). Naltrexone increased EE by 5.9±4.3% (p<0.05). No treatments altered resting RQ compared to placebo (0.83±0.05). Phentermine increased resting HR, both alone (15.7±7.9%, p<0.01) and in Qsymia (9.2±3.6%, p<0.05), compared to placebo. Of the five drug-treatments, only Qsymia reduced self-reported hunger scores compared to placebo.

Summary and future directions: Anti-obesity drugs may increase energy expenditure by upregulating sympathetic nervous system activity. Combined with appetite suppression, the impact on energy balance can lead to weight loss. We aim to complete our study to determine whether these drugs can acutely increase EE with minimal cardiovascular side-effects and compare our findings with long-term interventions.

SUN-128 Impaired Fasting Glucose Is Associated with Insulin Resistance in Patients with Germline Mutations in the Multiple Endocrine Neoplasia Type 1 (MEN1) Gene

BACKGROUND: Multiple endocrine neoplasia type 1 (MEN1) is an autosomal dominant syndrome characterized by hyperparathyroidism, pituitary adenomas, and gastro-entero-pancreatic neuroendocrine tumors. Patients with MEN1 mutations have impaired glucose homeostasis, but the role of insulin resistance and beta-cell function is unclear.

METHODS: Using a case-control study design, a retrospective analysis of germline mutation-positive MEN 1 patients (n=289) seen at our institution between 1991-2019 was performed. Patients with diabetes and/or insulinoma were excluded. Subjects were age, BMI, sex and race matched 1:1 to unrelated, healthy controls. Fasting glucose, insulin, c-peptide, calcium, PTH, 25-OH vitamin D, cholesterol, LDL, HDL and triglycerides (TG) were compared between two groups. Homeostasis model assessment (HOMA-IR) and HOMA-beta cell function (HOMA-b) were used as surrogate measures of insulin resistance and beta-cell function, respectively. Data is presented as mean ± SD.

RESULTS: MEN1 subjects (n=40; age 41±11 years; BMI 29.2±7.2 kg/m²) were matched to healthy controls (age 41±11 years; BMI 29.1±7.5 kg/m²). Only 3 MEN1 patients had no evidence of pancreatic neuroendocrine tumors. Impaired fasting glucose was more prevalent in MEN1 compared with controls (53% vs 10%, p<0.0001). HOMA-IR was positively associated with BMI, but not age, sex, calcium or vitamin D levels in either cohort. HOMA-IR adjusted for age, BMI, and sex was higher in patients with MEN1 compared with controls (4.01 vs. 2.44, adjusted ratio of means 1.54, 95% CI [1.14, 2.07], p=0.005). HOMA-b was not significantly different between the groups (177 vs. 129, adjusted ratio of means 1.17, 95% CI [0.86, 1.58], p=0.23). There were no significant differences in total cholesterol, LDL, HDL, and TG between the groups.

CONCLUSION: Lower insulin sensitivity, but not impaired beta cell function may contribute to the higher prevalence of impaired fasting glucose in MEN1 patients compared with controls. Mechanistic studies into the role of menin loss in glucose homeostasis are warranted.

SAT-651 Ethnic Differences in the Relationship Between Uric Acid Clearance and Insulin Sensitivity

Background: Hyperuricemia is associated with gout, type-2 diabetes, hypertriglyceridemia, and other insulin resistant (IR) states. Impaired clearance of uric acid (UA) has been proposed to play a role in hyperuricemia in IR. In a small study, urinary UA clearance was negatively associated with IR. African-Americans (AA) are more insulin resistant than Caucasians (CA). However, plasma UA levels are lower in AA. Ethnic differences underlying the relationship between UA clearance and insulin sensitivity (Si) remain unknown.

Objective: To compare the relationships between UA production, clearance, and Si in AA and CA.

Design: In a cross-sectional study, AA (n = 40; age 43 ± 10 years; BMI 41.3 ± 9.7 kg/m2) and CA (n = 88; age 44 ± 13 years; BMI 32.9 ± 8.2 kg/m2) subjects underwent an intravenous glucose tolerance test (IVGTT) to derive Si using the Minimal Model. Plasma UA and creatinine (Cr), were measured in the NIH Department of Laboratory Medicine. Urinary UA and Cr levels in spot urine samples were measured using a colorimetric assay. Fractional Excretion (FE) of UA and urine urate-to-creatinine ratio (UUCR), a measure of uric acid production, were calculated.

Results: AA had a significantly higher BMI (p &lt; 0.0001), percent body fat (45.8 ± 8.9 vs. 39.7 ± 11.5 %, p = 0.0007), A1C (5.8 ± 0.4 vs. 5.5 ± 0.3 %, p = 0.0006), diastolic BP (74 ± 9 vs. 71 ± 8 mm of Hg, p = 0.02), and lower Si (2.36 ± 2.7 vs. 4.43 ± 3.4 min−1·μU·ml−1, p = 0.0004) compared to CA. Stepwise multiple regression analysis was performed with independent variables A1c, fasting glucose, fasting insulin, triglycerides, and Si. Among these, Si was a significant predictor of FE of UA in CA (r = 0.33, p=0.001), but not AA (r = - 0.02, p=0.92).There was also a negative association between Si and plasma UA in CA (r = 0.48, p &lt; 0.0001), but not in AA (r = 0.06, p = 0.70). There was no association between Si and UA production in both groups (AA: p = 0.33, CA: p = 0.69).

Conclusion: These findings suggest that reduced insulin sensitivity may not play a major role in the pathogenesis of hyperuricemia in AA in insulin-resistant states.

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.

OR17-01 Leptin Decreases De Novo Lipogenesis in Lipodystrophic Patients

De novo lipogenesis (DNL) plays a role in the development of hepatic steatosis and non-alcoholic fatty liver disease (NAFLD). In rodent models of both health and lipodystrophy (LD), leptin decreases DNL. In human patients with LD, reduced adipose tissue results in adipokine deficiencies, including lower plasma leptin, which contributes to insulin resistance, dyslipidemia and ectopic accumulation of triglycerides (TG). The mechanisms by which leptin regulates serum and hepatic-TG are not well elucidated. Studying patients with LD before and after leptin therapy provides an important clinical model for understanding leptin’s effect on DNL. We hypothesized that leptin treatment in lipodystrophic patients would decrease DNL by decreasing insulin resistance and glycemia, resulting in reduced circulating and hepatic-TG.

Leptin-naïve patients with LD (n=11) were treated with recombinant leptin (metreleptin) for 6 months. All measurements were performed after an 8–12 hr fast. The % of TG in TG-rich lipoproteins (TRLP-TG) derived from DNL (% DNL) was measured using body water labeling (oral D₂O) of TG and mass spectrometry analysis. Absolute DNL was calculated as the product of TRLP-TG and % DNL. HbA1c and serum-TG were measured biochemically, hepatic-TG by MRI, and total body and hepatic insulin sensitivity measured during a hyperinsulinemic-euglycemic clamp.

DNL decreased after metreleptin: % DNL from 22.8±6.8 to 9.1±5.1% (p=0.0008) and absolute DNL from 54.2±32.1 to 8.6±6.5 mg/dl (p=0.003). TRLP-TG decreased from (median [interquartile range]) 160 [107, 280] to 98 [66, 147] mg/dl (p=0.01). Total body and hepatic insulin sensitivity increased from 3.7 [3.0, 7.3] to 8.4 [5.1,10.6] mg/kg_FFM/min (p=0.03) and from 61.0 [48.5, 69.3] to 84.7 [75.2, 107.6] % (p =0.01), respectively. HbA1c decreased from 8.6±1.8 to 7.1±1.4% (p=0.04), hepatic-TG decreased from 17.6±11.9 to 10.3±9.1% (p=0.02), and serum-TG from 386 [216, 686] to 223 [118, 497] mg/dl (p=0.06). DNL correlated negatively with insulin sensitivity both before (r=-0.73, p=0.03) and after (r=-0.85, p=0.004) metreleptin. DNL correlated positively with hepatic-TG before (r=0.70 p=0.03) and tended to correlate after metreleptin (r=0.65, p=0.06). The change in DNL correlated with change in serum-TG (r=0.77, p=0.04) but not the change in hepatic-TG (p=0.80).

We show here for the first time that 6 months of metreleptin treatment in humans with LD decreased DNL by 84% and was associated with reductions in glycemia and improved peripheral and hepatic insulin sensitivity. These data indicate a strong link between metreleptin’s effects to increase clearance of blood glucose by peripheral tissues and reduce hepatic carbohydrate flux, resulting in DNL reductions. This led to lowered hepatic steatosis and dyslipidemia and suggests treatments that target multi-organ insulin resistance may lead to decreased NAFLD and cardiovascular risk.

OR08-05 Sex and Ethnic Differences in Advanced Lipoprotein Profiles in South Asians, African-Americans, and Caucasians

Background: African-Americans (AA) and South Asians (SA) are known to have higher risk for T2D and cardiovascular disease (CVD) compared to Caucasians (CA). Advanced analysis of lipoprotein particles with nuclear magnetic resonance (NMR) spectroscopy can offer insights into CVD risk and lipid metabolism beyond a standard lipid panel. Insulin resistance (IR) is known to be associated with atherogenic lipoprotein profile.

Objective: To characterize the lipoprotein profile in AA, CA, and SA men and women.

Design: A cross-sectional study of 182 healthy, non-diabetic SA, AA and CA patients was conducted at NIH. Subjects underwent an intravenous glucose tolerance test from which insulin sensitivity (Si) was derived using the Minimal Model. Lipoprotein profiles were measured by NMR with the LP4 deconvolution algorithm, which reports triglyceride-rich lipoprotein particles (TRLPs), high-density lipoprotein particles (HDLPs), and low-density lipoprotein particles (LDLPs). For group comparisons, Si was adjusted for age and fat free mass. Lipoprotein parameters were adjusted for age and body fat %.

Results: Fifty-nine non-diabetic SA (33 males, 26 females), 49 AA (26 males, 23 females), and 74 CA (29 males, 45 females) were included in the study. Ethnic differences in Si were observed in men (p=0.002) but not in women (p=0.43). SA men had a significantly lower Si than both AA and CA men (p=0.02). TG concentrations and TRL particle number were significantly higher in CA men and women when compared with AA. TRLP size was not different between the ethnic groups in either sex. LDL particle number and ApoB concentration was significantly higher in SA men and women compared to AA and CA. There were no ethnic or sex differences in LDL size. HDL concentration, HDL particle number, and ApoA-I levels were not different between the groups in both sexes. However, in SA, large HDL particle number and HDL particle size was significantly lower than CA. Cholesteryl ester transfer protein (CETP) activity was significantly higher in SA men, but not women, when compared with AA and CA. Ethnic differences in LDLP and L-HDLP number remained even after adjusting for Si.

Conclusions: In SA men and women, the lipoprotein phenotype (higher LDLP and lower L-HDLP) is independent of insulin sensitivity. Increased CETP activity may contribute to the lower large HDL particle number in this group. In AA, TG and TRLP number were lower as previously reported. Further investigation is needed to determine the factors mediating the atherogenic profile in SA.

COVID-19 pandemic, coronaviruses, and diabetes mellitus

The pandemic of coronavirus disease (COVID-19), a disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is causing substantial morbidity and mortality. Older age and presence of diabetes mellitus, hypertension, and obesity significantly increases the risk for hospitalization and death in COVID-19 patients. In this Perspective, informed by the studies on SARS-CoV-2, Middle East respiratory syndrome (MERS-CoV), and the current literature on SARS-CoV-2, we discuss potential mechanisms by which diabetes modulates the host-viral interactions and host-immune responses. We hope to highlight gaps in knowledge that require further studies pertinent to COVID-19 in patients with diabetes.

Reduced Insulin Clearance and Insulin-Degrading Enzyme Activity Contribute to Hyperinsulinemia in African Americans

BACKGROUND

African Americans (AAs) are at a higher risk for developing type 2 diabetes compared with non-Hispanic whites (NHWs). The causal role of β-cell glucose sensitivity (β-GS) and insulin clearance in hyperinsulinemia in AA adults is unclear.

OBJECTIVE

Using a cross-sectional study design, we compared β-cell function and insulin clearance in nondiabetic AAs (n = 36) and NHWs (n = 47) after a mixed meal test (MMT).

METHODS

Insulin secretion rate, glucose sensitivity, rate sensitivity, and insulin sensitivity during MMT were derived from a mathematical model. Levels of insulin-degrading enzyme (IDE) and carcinoembryonic antigen-related cell adhesion molecule-1 (CEACAM1), key players in insulin clearance, were measured (by enzyme-linked immunosorbent assay) in hepatic cytosolic fractions from age-, sex-, and body mass index-matched AA and NHW cadaveric donors (n = 10).

RESULTS

Fasting and mean postprandial plasma glucose levels were similar in both ethnic groups. AAs had significantly higher fasting and mean postprandial plasma insulin levels. However, fasting ISR, total insulin output, and insulin sensitivity during MMT were not different between the groups. β-GS and rate sensitivity were higher in AAs. Fasting and meal plasma insulin clearance were lower in AAs. Hepatic levels of IDE and CEACAM-1 were similar in AAs and NHWs. Hepatic IDE activity was significantly lower in AAs.

CONCLUSIONS

In this study, lower insulin clearance contributes to higher plasma insulin levels in AAs. Reduced insulin clearance may be explained by lower IDE activity levels in AAs. Further confirmatory studies are needed to investigate diminished insulin clearance in AAs as a result of lower IDE activity levels.

Metabolomic Analysis of the Effects of Leptin Replacement Therapy in Patients with Lipodystrophy

Context and Objective

Leptin treatment has dramatic clinical effects on glucose and lipid metabolism in leptin-deficient patients with lipodystrophy. Further elucidation of metabolic effects of exogenous leptin therapy will shed light on understanding leptin physiology in humans. Our objective was to utilize metabolomic profiling to examine the changes associated with administration of short-term metreleptin therapy in patients with lipodystrophy.

Study Design

We conducted a pre-post-treatment study in 19 patients (75% female) with varying forms of lipodystrophy (congenital generalized lipodystrophy, n = 10; acquired generalized lipodystrophy, n = 1; familial partial lipodystrophy, n = 8) who received daily subcutaneous metreleptin injections for a period of 16 to 23 weeks. A 3-hour oral glucose tolerance test and body composition measurements were conducted before and after the treatment period, and fasting blood samples were used for metabolomic profiling. The study outcome aimed at measuring changes in physiologically relevant metabolites before and after leptin therapy.

Results

Metabolomic analysis revealed changes in pathways involving branched-chain amino acid metabolism, fatty acid oxidation, protein degradation, urea cycle, tryptophan metabolism, nucleotide catabolism, vitamin E, and steroid metabolism. Fold changes in pre- to post-treatment metabolite levels indicated increased breakdown of fatty acids, branched chain amino acids proteins, and nucleic acids.

Conclusions

Leptin replacement therapy has significant effects on important metabolic pathways implicated in patients with lipodystrophy. Continued metabolomic studies may provide further insight into the mechanisms of action of leptin replacement therapy and provide novel biomarkers of lipodystrophy.Abbreviations: 1,5-AG, 1,5-anhydroglucitol; 11βHSD1, 11-β hydroxysteroid dehydrogenase 1; BCAA, branched-chain amino acid; FFA, free fatty acid; GC-MS, gas chromatography mass spectrometry; IDO, indoleamine 2,3-dioxygenase; IFN-γ, interferon-γ; m/z, mass to charge ratio; OGTT, oral glucose tolerance test; TDO, tryptophan 2,3-dioxygenase; TNF-α, tumor necrosis factor-α; UPLC-MS/MS, ultra-performance liquid chromatography-tandem mass spectrometry.

Advanced Lipoprotein Analysis Shows Atherogenic Lipid Profile That Improves After Metreleptin in Patients with Lipodystrophy

Context

Patients with lipodystrophy have dyslipidemia and insulin resistance. Leptin treatment with metreleptin in lipodystrophy decreases insulin resistance and lowers triglycerides without changing high-density lipoprotein. Detailed measurement of lipoprotein particles with nuclear magnetic resonance (NMR) spectroscopy can offer insights into cardiovascular disease (CVD) risk and lipid metabolism beyond a standard lipid panel. We hypothesized that patients with lipodystrophy would have a more atherogenic lipid profile than controls at baseline, which would be ameliorated with metreleptin treatment.

Objective

To characterize the lipoprotein profile in patients with lipodystrophy compared with controls and to evaluate effects of metreleptin treatment.

Design Setting Patients and Intervention

Patients with lipodystrophy (N = 17) were studied before and after metreleptin for 2 weeks and 6 months and compared with 51 insulin-sensitive sex-matched controls.

Main Outcome Measures

Lipoprotein profiles were measured by NMR with the LP4 deconvolution algorithm, which reports triglyceride-rich lipoprotein particles (TRLPs), high-density lipoprotein particles (HDLPs), and low-density lipoprotein particles (LDLPs).

Results

Patients with lipodystrophy had elevated large TRLPs and smaller HDLPs and LDLPs compared with controls. Five patients with lipodystrophy had chylomicrons, compared with zero controls. Metreleptin decreased the size and concentration of TRLPs, eliminated chylomicrons in all but one patient, decreased LDLPs, and increased LDLP size. Metreleptin treatment did not have major effects on HDLPs.

Conclusions

Patients with lipodystrophy had an atherogenic lipoprotein profile at baseline consistent with elevated CVD risk, which improved after metreleptin treatment. The presence of fasting chylomicrons in a subset of patients with lipodystrophy suggests saturation of chylomicron clearance by lipoprotein lipase.

Sexual Dimorphism of Coronary Artery Disease in a Low- and Intermediate-Risk Asymptomatic Population: Association with Coronary Vessel Wall Thickness at MRI in Women

Purpose

To demonstrate the association between coronary vessel wall thickness (VWT) measured at MRI and coronary artery disease (CAD) risk in asymptomatic groups at low and intermediate risk on the basis of Framingham score.

Materials and Methods

A total of 131 asymptomatic adults were prospectively enrolled. All participants underwent CT angiography for scoring CAD, and coronary VWT was measured at 3.0-T MRI. Nonlinear single and multivariable regression analyses with consideration for interaction with sex were performed to investigate the association of traditional atherosclerotic risk factors and VWT with CT angiography-based CAD scores.

Results

The analysis included 62 women and 62 men with low or intermediate Framingham score of less than 20%. Age (mean age, 45.0 years ± 14.5 [standard deviation]) and body mass index were not different between the groups. Age, sex, and VWT were individually significantly associated with all CT angiography-based CAD scores (P < .05). Additionally, sex was a significant effect modifier of the associations with all CAD scores. In men, age was the only statistically significant independent risk factor of CAD; in women, VWT was the only statistically significant independent surrogate associated with increased CAD scores (P < .05).

Conclusion

In asymptomatic women, VWT MRI was the primary independent surrogate of CAD, whereas age was the strongest risk factor in men. This study suggests that VWT may be used as a CAD surrogate in women at low or intermediate risk of CAD. Further longitudinal studies are required to determine the potential implication and use of this MRI technique for the preventative management of CAD in women.© RSNA, 2019.

OR28-6 Short-Term Mifepristone Treatment Improves Hepatic and Adipose Tissue Insulin Sensitivity in Overweight and Obese Subjects with Glucose Intolerance

Background: Increased tissue cortisol availability and enhanced glucocorticoid action have been implicated in abnormal glucose and fat metabolism in patients with obesity, metabolic syndrome, and type 2 diabetes. Objective: To test the hypothesis that blockade of glucocorticoid receptor (GR) with mifepristone ameliorates insulin resistance in overweight/obese subjects with glucose intolerance. Design: We conducted a randomized, placebo-controlled, double-blind, crossover trial of mifepristone (50 mg orally, every six hr) in overweight/obese subjects (BMI 25-37 kg/m²), with abnormal glucose tolerance (n=16, women=7). Participants (age:56 ± 8 yr) had prediabetes (n=12) or mild type 2 DM (n=4, A1c < 7%) on diet control or stable dose of metformin for 3 months (n=2). Mifepristone or placebo treatment for one week was followed by a 6-8-week washout and crossover to the other arm. At baseline, and after each treatment period, insulin sensitivity was assessed by a frequently sampled intravenous glucose tolerance test (FSIVGTT) and an oral glucose tolerance test (OGTT). Whole body glucose disposal index of insulin sensitivity (S_I) was derived using a Minimal model analysis. Adipose tissue-S_I, which reflects insulin-induced free fatty acid (FFA) suppression, was estimated by the log-linear slope of FFA levels during the FSIVGTT. Matsuda index, oral glucose insulin sensitivity index (OGIS, ml/min/m²), and hepatic insulin resistance index (HIRI, mg/dL×µU/mL×10⁵) were derived from OGTT. Adipo-IR, a surrogate measure of adipocyte insulin resistance, was calculated by multiplying fasting concentrations of FFA and insulin (mmol×pmol/L). Comparison of various post-treatment parameters was performed using crossover ANOVA. This analysis takes into account specific treatment arm, treatment order, and treatment effects. Thus, we explicitly tested for carryover effects in our crossover study. Results: GR blockade did not affect body weight (p=0.56) or fasting glucose (p=0.67), but significantly decreased fasting insulin levels when compared with placebo [mean (95%CI): -40.7 (-68.53 to -12.91), p=0.007]. Mifepristone administration for one week did not alter whole body glucose disposal indices of insulin sensitivity (FSIVGTT-S_i: p=0.52, Matsuda Index: p=0.74; and OGIS: p=0.75). However, GR blockade reduced HIRI [-19.80 (-40.76 to 1.15), p=0.05], Adipo-IR [-15.54 (-31.47 to 0.37), p=0.04], and improved Adipose-S_I [-19.75 (-31.41 to -8.08), p=0.003]. Conclusions: In patients with abnormal glucose tolerance, short-term GR blockade improved hepatic and adipose tissue insulin sensitivity without significantly altering whole-body insulin sensitivity. These findings suggest that GR may be a therapeutic target in insulin-resistant states. Unless otherwise noted, all abstracts presented at ENDO are embargoed until the date and time of presentation. For oral presentations, the abstracts are embargoed until the session begins. Abstracts presented at a news conference are embargoed until the date and time of the news conference. The Endocrine Society reserves the right to lift the embargo on specific abstracts that are selected for promotion prior to or during ENDO.

OR31-6 Insulin Sensitivity and Pancreatic Beta-Cell Function in Patients with Primary Aldosteronism

Insulin sensitivity and pancreatic beta-cell function are primary determinants of glucose tolerance. Primary aldosteronism (PA) is associated with increased risk for glucose intolerance. However, its effects on insulin sensitivity and β-cell function have shown mixed results. In this study, we compared indices of insulin sensitivity and pancreatic β-cell function derived from an oral glucose tolerance test (OGTT) in patients from two cohorts: subjects with PA (n=25) and essential hypertension control (EHC) subjects. The EHC controls (n=25) were similar in age and BMI range, gender composition (female, n=14), and number of subjects with type 2 diabetes (n=3). Group comparisons were performed after adjusting for age, sex, and BMI; data is presented as unadjusted mean ± SD. As expected, the PA group show lower potassium concentrations compared to the EHC group, as well as elevated aldosterone and reduced renin levels. Mean arterial pressure was not significantly different between the groups (PA:100.6 ± 11.7, EHC: 96.7 ± 15.5 mm Hg, p=0.22). The area under the curve (AUC) for insulin during an OGTT, but not glucose, was higher in the PA group (insulin AUC: 14831 ± 9545 vs. 8582 ± 4948, μU/mL∙min, p<0.05). Whole-body and hepatic insulin sensitivity were determined using surrogate indices and oral minimal model (SI_MM) analysis. PA individuals were found to be less insulin sensitive compared to EHC subjects (Quantitative insulin sensitivity check index (QUICKI): 0.337 ± 0.035 vs. 0.367 ± 0.062, p<0.001; Matsuda Index: 3.98 ± 2.33 vs. 7.24 ± 6.50, p<0.001; and SI_MM: 1.01x10^-3 ± 2.01x10^-3 vs. 1.87x10^-3 ± 2.71x10^-3, min^-1 per μU/mL, p=0.08). The hepatic insulin resistance index (HIRI) was significantly higher in PA individuals (HIRI: 5.62 ± 4.52 vs. 4.02 ± 2.78, mg/dL∙ μU/mL ∙ 10⁶, p<0.001), suggesting decreased hepatic insulin sensitivity. Insulinogenic index (IGI), a measure of β -cell function is calculated as change in insulin concentrations divided by change in glucose from 0 to 30 min (ΔI_0-30/ΔG_0-30). IGI was slightly higher in the PA cohort (169 ± 150 vs. 124 ± 122, pmol/mmol, p=0.06). Oral disposition index (DI), a marker of integrated islet β-cell function, is the product of insulin secretion and sensitivity derived from OGTT. DI was similar between the groups (561 ± 434 vs. 605 ± 517, p=0.80). This accounts for the similar glucose tolerance between the groups. In summary, insulin sensitivity is significantly lower in PA and is accompanied by a compensatory increase in β-cell function. These results suggest that excess aldosterone and/or other steroids in the context of PA may negatively affect insulin action without adversely impacting beta-cell function.

SAT-081 Advanced Lipoprotein Analysis Demonstrates Atherogenic Lipid Profile in Patients with Lipodystrophy That Improves after Metreleptin Treatment

Lipodystrophies (LD) are defined by deficient adipose tissue, causing low leptin and metabolic disease including severe insulin resistance and hypertriglyceridemia. Recombinant leptin (metreleptin, ML) treatment in LD improves insulin resistance and lowers triglycerides without changing HDL. Detailed measurement of lipoprotein particles using NMR spectroscopy can offer insights into cardiovascular disease (CVD) risk and lipid metabolism beyond a standard lipid panel and has never been performed in LD. We hypothesized that patients with LD would have a more atherogenic lipid profile than controls at baseline, which would be ameliorated with ML treatment secondary to improvements in insulin sensitivity. Patients with LD (N=17) were enrolled in a study evaluating short- and long-term effects of ML on metabolic disease and compared to 51 insulin sensitive (SI<3 on IV glucose tolerance test) sex-matched controls. Lipoprotein profiles were assessed on samples obtained after a 10-12 hour fast using a new deconvolution algorithm, LP4, which reports 27 triglyceride rich lipoprotein particles (TRLP) and 7 HDL particles (HDLP). The major categories are small, medium, and large HDLP and LDL particles (LDLP) and very small, small, medium, large, and very large TRLP. LP4 was compared in controls vs. patients with LD prior to ML. LP4 was compared in patients with LD before vs. after 14 days and 6 months of ML. Particle size, concentration, and concentration of subclasses by size were measured for LDLP, HDLP, and TRLP. Insulin sensitivity before and after ML was measured as glucose disposal (mg/kgFFM/min) during hyperinsulinemic euglycemic clamp. Patients and controls did not differ by age, weight, or BMI. Patients with LD had elevated large TRLP and smaller sized HDLP and LDLP, all associated with increased atherogenicity, vs. controls. Five of 17 patients with LD had chylomicrons present, vs. 0 of 51 controls. ML treatment in LD decreased size and concentration of TRLP, eliminated chylomicrons in all but 1 patient, decreased LDLP concentration, and increased LDLP size. ML treatment did not have major effects on HDLP. Prior to ML in patients with LD, insulin sensitivity negatively correlated with very large TRLP (r= -0.76, p= 0.0007), TRLP size (r= -0.52, p= 0.04), and TRLP TG (r= -0.58, p= 0.02). Short term (Day 0 to Day 14) and long-term changes (Day 0 to 6 months) in insulin sensitivity were not significantly correlated with changes in any lipoprotein parameter. In conclusion, patients with LD had an atherogenic lipoprotein profile at baseline consistent with increased CVD risk, which improved after ML treatment. The presence of fasting chylomicrons in a subset of patients with LD suggests saturation of chylomicron clearance by lipoprotein lipase. Improvements in lipoprotein parameters with ML were independent of improved insulin sensitivity, possibly due to direct effects of ML on lipoprotein metabolism.

SUN-087 Effects of Leptin Replacement on Circulating Plasma Inhibitors of Lipoprotein Lipase in Patients with Lipodystrophy

Lipodystrophy syndromes (LD) result from selective deficiency of adipose tissue, leading to low leptin. Low leptin leads to hyperphagia and ectopic lipid storage, causing severe insulin resistance and metabolic complications including high triglycerides (TG) and subsequent pancreatitis. Replacement of leptin using metreleptin (ML) in LD decreases TG. TG are broken down to non-esterified fatty acids (NEFA) by lipoprotein lipase (LPL). We previously demonstrated that patients with LD had high apoCIII and ANGPLT8 (inhibitors of LPL) that decreased with ML, suggesting that ML may lower TG by reducing inhibition of LPL activity. We hypothesized that plasma from patients with LD would cause greater inhibition of LPL compared to controls, and that ML would ameliorate this. We further hypothesized that net inhibition of LPL in LD would be reflected by a decreased ratio of apoCII (an LPL stimulator) to apoCIII (an LPL inhibitor) vs. controls. METHODS: Plasma from ML-naive patients with LD (n=14) and a pooled high-TG control group (651 mg/dL, n=10) were diluted to the same concentration of TG. Samples were incubated with bovine LPL, and NEFA produced was measured enzymatically over 1hr at 37⁰C. Because the concentrations of added LPL and TG were equal in each patient sample, NEFA generation (nmole) reflected the net effect of LPL stimulators and inhibitors in plasma. To test the effects of ML, the same method was applied to samples from patients with LD after ML 5 mg Q12h for 2 weeks and 6 months. ApoCII and apoCIII were compared in patients with LD (n=14) versus healthy controls (TG = 74 [54, 97] mg/dL, n=28). RESULTS: Patients with LD had baseline TG 492 [208, 1016] mg/dL which decreased to 279 [171, 648] after 2 weeks of ML (n=14, p=.0023) and to 223 [118, 335] after 6 months of ML (n=11, p=0.15). Prior to ML, patients with LD had higher NEFA generation vs. controls (patients 0.79 ± 0.08; controls 0.59 ± 0.1; p<0.0001), consistent with less net inhibition of LPL. NEFA generation did not change with ML therapy after 2 weeks (0.77 ± 0.09) or 6 months (0.78 ± 0.12) compared to baseline (p>0.05). ApoCII:apoCIII ratio did not differ in LD vs controls (0.63±0.31 vs 0.54±0.17, p=0.6), and did not change after ML. CONCLUSIONS: Counter to our hypothesis, patients with LD had higher NEFA generation compared to high TG controls, consistent with less net inhibition of LPL, while the ratio of LPL activator (apoCII) to inhibitor (apoCIII) did not differ in LD vs normal TG controls. Furthermore, NEFA generation and apoCII:apoCIII ratio did not change after ML therapy, suggesting no net change in inhibition of LPL with ML. These findings suggest that changes in circulating activators and inhibitors of LPL are not a major mechanism by which ML lowers TG in LD. Studies including direct measurement of LPL activity after heparin stimulation are needed to further explore the role of LPL in regulating TG in LD.

Sweet taste perception is greater in non-Hispanic black than in non-Hispanic white adults

OBJECTIVE

Research suggests a difference in sweet taste perception between non-Hispanic black (NHB) and non-Hispanic white (NHW) adults; however, limited research has examined sweet taste perception in relation to the dietary intake of sweet products. The aim of this study was to examine sweet taste perception and the consumption of sweet foods, beverages, and sugar in NHB and NHW adults, and to evaluate whether sweet taste perception is associated with dietary intake.

METHODS

This cross-sectional study examined the association between race, sweet taste perception and sweet food, beverages, and sugar consumption in healthy, NHB and NHW adults. Seven day food records were analyzed in Nutrition Data System for Research software. Intensity of sweet taste perception was tested and the general labeled magnitude scale method was used to facilitate group comparisons. Independent t tests, Mann-Whitney tests, and Pearson correlations were used to assess associations.

RESULTS

Participants were NHB (n = 98) and NHW (n = 90) adults, 41 ± 1 y of age (mean ± SEM) with energy intake of 2271 ± 53 kcal. Body mass index was higher in NHBs than in NHWs (36 ± 1 versus 32 ± 1 kg/m2, P = 0.048), but no differences were observed in age, energy consumption, or total sugar intake. Sweet taste perception rating (median [interquartile range] NHB: 73.5 [63.9-83], NHW: 52.1 [46.4-57.7]; P = 0.001) and added sugar intake (NHB: 39.4 g/1000 kcal [36.3-42.4], NHW: 30 g/1000 kcal [26.7-33.4]; P < 0.001) were greater in NHB. Perceived sweet taste intensity was positively associated with consumption of servings of sweet products among NHBs (R2 = 0.057, P = 0.018) but not NHWs (R2 = -0.012, P = 0.314).

CONCLUSIONS

NHBs have a higher intensity of sweet taste perception than NHWs. The positive association of sweet taste perception and sweet product consumption in NHBs suggests that a higher intensity of sweet taste perception may be associated with an increased proportion of energy consumption from added sugars.

Effects of growth hormone on hepatic insulin sensitivity and glucose effectiveness in healthy older adults

PURPOSE

Growth hormone (GH) replacement decreases insulin sensitivity in healthy individuals. However, the effects of GH on organ-specific insulin sensitivity and glucose effectiveness are not well characterized. The purpose of this study was to evaluate the effects of GH administration for 26 weeks on muscle and hepatic insulin sensitivity and glucose effectiveness in healthy older individuals.

METHODS

This report is from a 26-week randomized, double-blind, placebo-controlled parallel-group trial in healthy, ambulatory, community-dwelling older women and men. We compared surrogate indices of insulin sensitivity [quantitative insulin-sensitivity check index (QUICKI), muscle insulin sensitivity index (MISI), hepatic insulin resistance index (HIRI)] and glucose effectiveness [oral glucose effectiveness index (oGE)] derived from oral glucose tolerance tests (OGTTs) in subjects before and after 26 weeks of administration of GH (n = 17) or placebo (n = 15) as an exploratory outcome.

RESULTS

GH administration for 26 weeks significantly increased fasting insulin concentrations and HIRI but did not significantly change MISI or oGE compared to placebo.

CONCLUSIONS

GH administration for 26 weeks in healthy older subjects impairs insulin sensitivity in the liver but not skeletal muscle and does not alter glucose effectiveness.

Assessing the predictive accuracy of oral glucose effectiveness index using a calibration model

PURPOSE

Current reference methods for measuring glucose effectiveness (GE) are the somatostatin pancreatic glucose clamp and minimal model analysis of frequently sampled intravenous glucose tolerance test (FSIVGTT), both of which are laborious and not feasible in large epidemiological studies. Consequently, surrogate indices derived from an oral glucose tolerance test (OGTT) to measure GE (oGE) have been proposed and used in many studies. However, the predictive accuracy of these surrogates has not been formally validated. In this study, we used a calibration model analysis to evaluate the accuracy of surrogate indices to predict GE from the reference FSIVGTT (Sg_MM).

METHODS

Subjects (n = 123, mean age 48 ± 11 years; BMI 35.9 ± 7.3 kg/m²) with varying glucose tolerance (NGT, n = 37; IFG/IGT, n = 78; and T2DM, n = 8) underwent FSIVGTT and OGTT on two separate days. Predictive accuracy was assessed by both root mean squared error (RMSE) of prediction and leave-one-out cross-validation-type RMSE of prediction (CVPE).

RESULTS

As expected, insulin sensitivity, Sg_MM, and oGE were reduced in subjects with T2DM and IFG/IGT when compared with NGT. Simple linear regression analyses revealed a modest but significant relationship between oGE and Sg_MM (r = 0.25, p < 0.001). However, using calibration model, measured Sg_MM and predicted Sg_MM derived from oGE were modestly correlated (r = 0.21, p < 0.05) with the best fit line suggesting poor predictive accuracy. There were no significant differences in CVPE and RMSE among the surrogates, suggesting similar predictive ability.

CONCLUSIONS

Although OGTT-derived surrogate indices of GE are convenient and feasible, they have limited ability to robustly predict GE.

"Fat Shadows" From DXA for the Qualitative Assessment of Lipodystrophy: When a Picture Is Worth a Thousand Numbers

OBJECTIVE

Lipodystrophy syndromes are a heterogeneous group of disorders associated with selective absence of fat. Currently, the diagnosis is established only clinically.

RESEARCH DESIGN AND METHODS

We developed a new method from DXA scans called a "fat shadow," which is a color-coded representation highlighting only the fat tissue. We conducted a blinded retrospective validation study to assess its usefulness for the diagnosis of lipodystrophy syndromes.

RESULTS

We evaluated the fat shadows from 16 patients (11 female and 5 male) with generalized lipodystrophy (GL), 57 (50 female and 7 male) with familial partial lipodystrophy (FPLD), 2 (1 female and 1 male) with acquired partial lipodystrophy, and 126 (90 female and 36 male) control subjects. FPLD was differentiated from control subjects with 85% sensitivity and 96% specificity (95% CIs 72-93 and 91-99, respectively). GL was differentiated from nonobese control subjects with 100% sensitivity and specificity (95% CIs 79-100 and 92-100, respectively).

CONCLUSIONS

Fat shadows provided sufficient qualitative information to infer clinical phenotype and differentiate these patients from appropriate control subjects. We propose that this method could be used to support the diagnosis.

Predictive Accuracy of Surrogate Indices for Hepatic and Skeletal Muscle Insulin Sensitivity

Context

Surrogate indices of muscle and hepatic insulin sensitivity derived from an oral glucose tolerance test (OGTT) are frequently used in clinical studies. However, the predictive accuracy of these indices has not been validated.

Design

In this cross-sectional study, hyperinsulinemic-euglycemic glucose clamp with tritiated glucose infusion and a 75-g OGTT were performed in individuals (n = 659, aged 18 to 49 years, body mass index of 16 to 64 kg/m²) with varying degrees of glucose tolerance. A calibration model was used to assess the ability of OGTT-derived, tissue-specific surrogate indices [hepatic insulin resistance index (HIRI) and muscle insulin sensitivity index (MISI)] to predict insulin sensitivity/resistance indices derived from the reference glucose clamp [Hepatic-IR_basal, a product of fasting plasma insulin and hepatic glucose production (HGP), Hepatic-IR_clamp, reciprocal of the percent suppression of HGP during the insulin clamp corrected for plasma insulin concentration, and Muscle-IS_clamp, a measure of peripheral glucose disposal]. Predictive accuracy was assessed by root mean squared error of prediction and leave-one-out, cross-validation-type square root of the mean squared error of prediction.

Results

HIRI and MISI were correlated with their respective clamp-derived indices. HIRI was negatively related to Muscle-IS_clamp (r = -0.62, P < 0.0001) and MISI correlated with Hepatic-IR derived from the clamp (Hepatic-IR_basal: r = -0.48, P < 0.0001 and Hepatic-IR_clamp: r = -0.41, P < 0.0001). However, the accuracy of HIRI and MISI to predict Hepatic-IR (basal or during clamp) was not significantly different. Likewise, the ability of HIRI and MISI to predict Muscle-IS_clamp was also similar.

Conclusion

Our findings indicate that the surrogate indices derived from an OGTT are accurate in predicting insulin sensitivity but are not tissue specific.

Personalized Statin Therapy and Coronary Atherosclerotic Plaque Burden in Asymptomatic Low/Intermediate-Risk Individuals

BACKGROUND

Current guidelines for the primary prevention of atherosclerotic cardiovascular disease are based on the estimation of a predicted 10-year cardiovascular disease risk and the average relative risk reduction estimates from statin trials. In the clinical setting, however, decision-making is better informed by the expected benefit for the individual patient, which is typically lacking. Consequently, a personalized statin benefit approach based on absolute risk reduction over 10 years (ARR10 benefit threshold ≥2.3%) has been proposed as a novel approach. However, how this benefit threshold relates with coronary plaque burden in asymptomatic individuals with low/intermediate cardiovascular disease risk is unknown.

AIMS

In this study, we compared the predicted ARR10 obtained in each individual with plaque burden detected by coronary computed tomography angiography.

METHODS AND RESULTS

Plaque burden (segment volume score, segment stenosis score, and segment involvement score) was assessed in prospectively recruited asymptomatic subjects (n = 70; 52% male; median age 56 years [interquartile range 51-64 years]) with low/intermediate Framingham risk score (< 20%). The expected ARR10 with statin in the entire cohort was 2.7% (1.5-4.6%) with a corresponding number needed to treat over 10 years of 36 (22-63). In subjects with an ARR10 benefit threshold ≥2.3% (vs. < 2.3%), plaque burden was significantly higher (p = 0.02).

CONCLUSION

These findings suggest that individuals with higher coronary plaque burden are more likely to get greater benefit from statin therapy even among asymptomatic individuals with low cardiovascular risk.

Plasma serpinB1 is related to insulin sensitivity but not pancreatic β-Cell function in non-diabetic adults

Pancreatic β‐cell dysfunction because of reduced β‐cell mass and function is a primary determinant in the progression of diabetes. Increase in β‐cell mass and compensatory hyperinsulinaemia is frequently associated with insulin‐resistant states. Although the humoral factors mediating this compensatory response are unknown, serpinB1, a protease inhibitor, has recently been proposed to be one such factor. In this study, we examine the relationships between plasma serpinB1, insulin sensitivity, and pancreatic β‐cell function in non‐diabetic individuals. 117 subjects (women, n = 50, men, n = 67; age= 37.6 ± 10.8; BMI=31.1 ± 7.7 kg/m²) underwent an insulin‐modified frequently sampled intravenous glucose tolerance test (FSIVGTT) at the NIH Clinical Research Center. Acute insulin response (AIR) and insulin sensitivity index (SI) were obtained from the FSIVGTT with MINMOD analysis. The Quantitative Insulin Sensitivity Check Index (QUICKI) was calculated from fasting insulin and glucose values. Plasma serpinB1 levels were measured using an ELISA assay. Simple linear correlation analyses were performed to evaluate the relationship between serpinB1 and measures of insulin sensitivity and β‐cell function. Circulating serpinB1 levels were unrelated to age, sex, race, BMI, or percent body fat. SI but not AIR significantly correlated with circulating serpinB1 levels (r = 0.23, P < 0.05). QUICKI tended to positively correlate with serpinB1 (r = 0.16, P = 0.09). Circulating serpinB1 is directly associated with insulin sensitivity but not β‐cell function in non‐diabetic adults. Whether this modest association plays a role in insulin sensitivity in humans remains to be clarified.

Effects of growth hormone administration on luteinizing hormone secretion in healthy older men and women

The known interactions between the somatotropic and hypothalamic-pituitary-gonadal (HPG) axes have not been well delineated in older individuals. Aging-associated decline in insulin like growth factor-1 (IGF-1) levels has been proposed to play a role in reproductive senescence in animals. However, the effects of GH on LH secretion are unknown in older individuals. Our objective was to determine whether GH modulates LH secretion or levels of sex steroids (SS) in healthy older (ages 65-88 years) men (n = 24) and women (n = 24) with low-normal plasma IGF-1 levels. In a double-masked, placebo-controlled (n = 24), randomized study, we evaluated the effects of GH (n = 24, 20 μg/kg sc 3×/week) for 26 weeks on nocturnal LH secretory dynamics [(8 pm to 8 am, Q20) min sampling and analyzed by multiparameter deconvolution algorithm]. Indices of LH secretion [frequency, mass per burst, pulsatile production rate, and approximate entropy (ApEn)] and fasting serum IGF-1, SHBG, and SS (TT, fT, or E2) were measured. At baseline, all indices of LH secretion (frequency, mass per burst, pulsatile production rate) were inversely (P < 0.05) related to IGF-1, but not to mean nocturnal serum GH concentrations. GH administration for 26 weeks increased serum IGF-1, but exerted no significant effects on LH secretory dynamics, or concentrations of SSs (TT, fT, or E2) or SHBG in older women or men. These data suggest that GH-mediated increases in IGF-1 do not modulate the HPG axis in older individuals.

Metreleptin therapy lowers plasma angiopoietin-like protein 3 in patients with generalized lipodystrophy

BACKGROUND

Reduced triglyceride clearance due to impaired lipoprotein lipase-mediated lipolysis contributes to severe hypertriglyceridemia in lipodystrophy. Angiopoietin-like protein 3 (ANGPTL3) and 4 (ANGPTL4) impair clearance of triglycerides by inhibiting lipoprotein lipase. Whether circulating ANGPTL3/4 levels are altered in lipodystrophy and the effects of leptin replacement on these ANGPTLs are unknown.

OBJECTIVE

To examine if ANGPTL3/4 levels are elevated in patients with generalized lipodystrophy and assess the effects of leptin replacement on these ANGPTLs.

METHODS

Preleptin treatment plasma levels of ANGPTLs in patients with generalized lipodystrophy (n = 22) were compared with healthy controls (n = 39) using a post hoc case-control study design. In a prospective open-label study, we studied the effects of metreleptin therapy (16-32 weeks) on plasma ANGPTL3/4 in patients with generalized lipodystrophy.

RESULTS

Plasma ANGPTL3 (geometric mean [95% confidence interval]; 223 [182-275] vs 174 ng/mL [160-189], P = .02) but not ANGPTL4 levels (55 [37-81] vs 44 ng/mL [37-52], P = .26) were higher in patients with lipodystrophy compared with healthy controls. There was a significant decrease in total cholesterol, triglycerides, and glycosylated hemoglobin (A1C) levels following metreleptin therapy. After metreleptin, ANGPTL3 concentrations decreased significantly (223 [182-275] vs 175 ng/mL [144-214], P = .01) with no change in ANGPTL4 (55 [37-81] vs 48 ng/mL [32-73], P = .11).

CONCLUSIONS

These findings suggest that elevated plasma levels of ANGPTL3 in leptin-deficient states is attenuated with leptin therapy.

Acute vascular and metabolic actions of the green tea polyphenol epigallocatechin 3-gallate in rat skeletal muscle

Epidemiological studies show a dose-dependent relationship between green tea consumption and reduced risk for type 2 diabetes and cardiovascular disease. Bioactive compounds in green tea including the polyphenol epigallocatechin 3-gallate (EGCG) have insulin-mimetic actions on glucose metabolism and vascular function in isolated cell culture studies. The aim of this study is to explore acute vascular and metabolic actions of EGCG in skeletal muscle of Sprague-Dawley rats. Direct vascular and metabolic actions of EGCG were investigated using surgically isolated constant-flow perfused rat hindlimbs. EGCG infused at 0.1, 1, 10 and 100 μM in 15 min step-wise increments caused dose-dependent vasodilation in 5-hydroxytryptamine pre-constricted hindlimbs. This response was not impaired by the phosphatidylinositol 3-kinase (PI3K) inhibitor wortmannin or the AMP-kinase inhibitor Compound C. The nitric oxide synthase (NOS) inhibitor N^G-Nitro-l-Arginine Methyl Ester (L-NAME) completely blocked EGCG-mediated vasodilation at 0.1-10 μM, but not at 100 μM. EGCG at 10 μM did not alter muscle glucose uptake nor did it augment insulin-stimulated muscle glucose uptake. The acute metabolic and vascular actions of 10 μM EGCG in vivo were investigated in anaesthetised rats during a hyperinsulinemic-euglycemic clamp (10 mU min^-1 kg^-1 insulin). EGCG and insulin both stimulated comparable increases in muscle microvascular blood flow without an additive effect. EGCG-mediated microvascular action occurred without altering whole body or muscle glucose uptake. We concluded that EGCG has direct NOS-dependent vasodilator actions in skeletal muscle that do not acutely alter muscle glucose uptake or enhance the vascular and metabolic actions of insulin in healthy rats.

Effect of Leptin Administration on Circulating Apolipoprotein CIII levels in Patients With Lipodystrophy

CONTEXT

Apolipoprotein CIII (apoCIII), an inhibitor of lipoprotein lipase, plays an important role in triglyceride metabolism. However, the role of apoCIII in hypertriglyceridemia in lipodystrophy and the effects of leptin replacement on apoCIII levels are unknown.

OBJECTIVE

The objective of the study was to test the hypotheses that apoCIII is elevated in hypertriglyceridemic patients with lipodystrophy and that leptin replacement in these patients lowers circulating apoCIII.

DESIGN, SETTING, STUDY PARTICIPANTS, INTERVENTION, AND OUTCOME MEASURES

Using a post hoc cross-sectional case-control design, we compared serum apoCIII levels from patients with lipodystrophy not associated with HIV (n = 60) and age-, gender-, race-, and ethnicity-matched controls (n = 54) participating in ongoing studies at the National Institutes of Health. In a prospective, open-label, ongoing study, we studied the effects of 6–12 months of leptin replacement on apoCIII in lipodystrophy patients as an exploratory outcome.

RESULTS

ApoCIII was higher in lipodystrophy patients (geometric mean [25th and 75th percentiles]) (23.9 mg/dL [14.6, 40.3]) compared with controls (14.9 mg/dL [12.3, 17.7]) (P < .0001). ApoCIII and triglyceride levels were positively correlated in patients with lipodystrophy (R = 0.72, P < .0001) and healthy controls (R = 0.6, P < .0001). Leptin replacement (6–12 mo) did not significantly alter apoCIII (before leptin: 23.4 mg/dL [14.5, 40.1]; after leptin: 21.4 mg/dL [16.7, 28.3]; P = .34).

CONCLUSIONS

Leptin replacement in lipodystrophy did not alter serum apoCIII levels. Elevated apoCIII may play a role in the hypertriglyceridemia of lipodystrophy independent of leptin deficiency and replacement.