CGRP blockade by galcanezumab was not associated with reductions in signs and symptoms of knee osteoarthritis in a randomized clinical trial

OBJECTIVE

This study tested whether galcanezumab, a humanized monoclonal antibody with efficacy against migraine, was superior to placebo for the treatment of mild or moderate osteoarthritis (OA) knee pain.

METHOD

In a multicenter, double-blind, placebo- and celecoxib-controlled trial, patients with moderate to severe OA pain were randomized to placebo; celecoxib 200 mg daily for 16 weeks; or galcanezumab 5, 50, 120, and 300 mg subcutaneously every 4 weeks, twice. The primary outcome was change from baseline at Week 8 in Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) pain subscore measured by 100 mm visual analog scale (VAS). The trial was considered positive if ≥1 dose of galcanezumab demonstrated ≥95% Bayesian posterior probability of superiority to placebo and ≥50% posterior probability of superiority to placebo by ≥9 mm. A planned interim analysis allowed termination of the study if posterior probability of superiority to placebo by ≥9 mm was ≤5%. Secondary endpoints included WOMAC function subscore and Patient Global Assessment (PGA) of OA. Safety and tolerability were also assessed.

RESULTS

The study was terminated after interim analysis suggested inadequate efficacy. Celecoxib significantly reduced WOMAC pain subscore compared with placebo [-12.0 mm; 95% confidence interval (CI) -23 to -2 mm]. None of the galcanezumab arms demonstrated clinically meaningful improvement (range: 1.5 to -5.0 mm) or met the prespecified success criteria. No improvement in any secondary objective was observed. Galcanezumab was well tolerated by OA patients.

CONCLUSIONS

This study failed to demonstrate sufficient statistical evidence that galcanezumab was efficacious for treating OA knee pain.

STUDY IDENTIFICATION

NCT02192190.

Coding variants in PNPLA3 and TM6SF2 are risk factors for hepatic steatosis and elevated serum alanine aminotransferases caused by a glucagon receptor antagonist

LY2409021 is a glucagon receptor antagonist that was associated with hepatic steatosis and elevated aminotransferases in phase 2 diabetes studies. We investigated the relationship between selected genetic variants and hepatic steatosis and elevated alanine aminotransferases (ALTs) associated with LY2409021. Patients participated in a 6‐week placebo‐controlled trial (I1R‐MC‐GLDI [GLDI], n = 246) and a 52‐week placebo‐ and active comparator‐controlled trial (I1R‐MC‐GLDJ [GLDJ], n = 158). GLDJ had endpoints at 6 months, including measures of hepatic fat fraction (HFF) by magnetic resonance imaging. The five genes tested were patatin‐like phospholipase domain containing 3 (PNPLA3) (rs738409 and rs738491), transmembrane 6 superfamily member 2 (TM6SF2) (rs58542926), peroxisome proliferative activated receptor gamma coactivator 1 alpha (PPARGC1A) (rs4361373, rs3774921, rs2970849), adenylate cyclase 3 (ADCY3) (rs713586), and insulin‐like growth factor 1 (IGF‐1) (rs1520220). In GLDI, PNPLA3 I148M (P = 0.001) and TM6SF2 E167K (P = 0.001) were significantly associated with an increase in ALT at 6 weeks for LY2409021 but not for placebo. In GLDJ, PNPLA3 I148M showed the same effect (P = 0.007) on ALT at 6 months but the placebo or sitagliptin did not. In GLDJ, both PNPLA3 and TM6SF2 risk‐allele carriers showed increases in HFF that were numerically greater but not statistically significant. The carriers of PNPLA3 and/or TM6SF2 risk alleles showed significantly increased ALT (GLDI, +13.28 U/L in carriers versus +4.84 U/L in noncarriers, P = 4 × 10^–5; GLDJ, +14.6 U/L in carriers versus +1.7 in noncarriers, P = 0.0018) and HFF (GLDJ, +5.35% in carriers versus 2.38% in noncarriers, P = 0.048). Elevation of transaminase and HFF were also noted in the noncarriers but at a significantly lower degree. Conclusion: The carriers of PNPLA3 and/or TM6SF2 variant alleles are at risk for hepatic steatosis and elevated ALT levels caused by LY2409021, a glucagon receptor antagonist. More studies are needed to investigate if our observations are generalizable to hepatic steatosis caused by other medications. (Hepatology Communications 2018;2:561‐570)

Evaluation of the Safety, Pharmacokinetics, Pharmacodynamics, and Efficacy After Single and Multiple Dosings of LY3016859 in Healthy Subjects and Patients With Diabetic Nephropathy

Two phase 1 studies (TGAA and TGAB) evaluated the safety, pharmacokinetics, pharmacodynamics, and efficacy of LY3016859 (LY), a monoclonal antibody that binds epiregulin and transforming growth factor α (TGF-α), administered intravenously or subcutaneously. In TGAA, 56 healthy subjects received a single dose of LY (0.1-750 mg intravenously, 50 mg subcutaneously) or placebo. In TGAB part A, 15 patients with diabetic nephropathy (DN) received 2 doses of LY (10-750 mg intravenously) or placebo, and in TGAB part B, 45 patients with DN received 5 doses of LY (50-750 mg intravenously) or placebo. Pharmacokinetics, pharmacodynamics, anti-LY antibodies, and change in proteinuria and albuminuria were evaluated. Single and multiple doses of LY administered 3 weeks apart were well tolerated. Pharmacokinetics were nonlinear in healthy subjects and patients with DN, indicating target-mediated drug disposition. Epiregulin level increased in both studies, and TGF-α levels increased in the TGAB study, consistent with target engagement; however, LY treatment did not significantly reduce proteinuria or albuminuria in patients with DN. There was no obvious effect of LY on the disease-related biomarkers monocyte chemoattractant protein-1, synaptopodin, or transferrin. Although LY administration resulted in a high frequency of anti-LY antibodies, pharmacokinetics, target engagement, and efficacy were not impacted.

Factors associated with stroke, myocardial infarction, ischemic heart disease, unstable angina, or mortality in patients from real world clinical practice with newly-diagnosed type 2 diabetes and early glycemic control

OBJECTIVES

The objective of this study was to identify factors associated with stroke, myocardial infarction (MI), all-cause mortality, or a diagnosis of ischemic heart disease (IHD) or unstable angina (UA), among patients newly-diagnosed with type 2 diabetes (T2DM) with no recent history of cardiovascular (CV) events who rapidly achieve and maintain HbA_1c ≤8.0%.

METHODS

Data were obtained from the Clinical Practice Research Datalink (CPRD) from January 1990 to December 2012. A nested case-control design was used with Cox proportional hazards analysis. Cases were identified by the first occurrence of stroke, MI, IHD, UA, or death within 5 years after HbA_1c ≤ 8.0% was first reached (index date) following T2DM diagnosis. Controls were selected using a risk-set sampling approach and were matched 4:1 to cases using index date, exposure time, age, gender, and HbA_1c at index date.

RESULTS

A total of 11,426 T2DM patients met the inclusion criteria for cases. Of these, 5,261 experienced a CV event. Stroke was the most frequent CV event (40%), followed by IHD (29%), MI (22%), and UA (9%). Mean HbA1c ≥7.0% over the length of exposure (vs 6.5 to <7.0%) was associated with an increased risk of stroke, MI, and IHD. The use of anti-platelet medications at baseline was also associated with increased risk of stroke (HR = 1.82 [CI = 1.60-2.06]), MI (HR = 1.67 [CI = 1.38-2.03]), and IHD (HR = 1.85 [CI = 1.57-2.17]). Mean HbA1c < 6.0% was associated with increased risk of stroke (HR = 1.29 [CI = 1.02-1.63]) and IHD (HR = 1.65 [CI = 1.25-2.19]). Use of nitrate medications at baseline was associated with increased risk of MI (HR = 2.83 [CI = 2.24-3.57]), IHD (HR = 4.32 [CI = 3.57-5.22]), and UA (HR = 10.38 [CI = 7.67-14.03]).

CONCLUSIONS

Early and sustained HbA_1c control between 6.5 and <7.0% appears to be an important modifiable factor that helps reduce CV risk in patients with newly-diagnosed T2DM in real-world clinical practice.

Clinical Outcomes of Patients with Diabetes Who Exhibit Upper-Quartile Insulin Antibody Responses After Treatment with LY2963016 or Lantus® Insulin Glargine

INTRODUCTION

We compared insulin antibody response (IAR) profiles in patients with type 1 diabetes (T1D) or type 2 diabetes (T2D) who received LY2963016 insulin glargine (LY IGlar) or Lantus^® insulin glargine (IGlar) and evaluated the potential relationship between higher IARs and clinical and safety outcomes with a focus on patients who exhibited antibody responses in the upper quartile.

METHODS

Data from ELEMENT-1 (52-week open-label in T1D) and ELEMENT-2 (24-week, double-blind study in T2D) were analyzed. Maximum postbaseline IAR levels and proportions of patients in the upper quartile of maximum antibody percent binding (UQMAPB; patients with maximum postbaseline percent binding in the highest 25% of maximum values observed) were compared for differential treatment effects on clinical efficacy outcomes and incidence of adverse events. Continuous outcomes were analyzed by analysis of covariance. Categorical data were analyzed by the Cochran-Mantel-Haenszel or Breslow-Day test.

RESULTS

In both studies (N = 532 evaluable patients with T1D; N = 730 with T2D), no statistically significant differences between LY IGlar and IGlar were observed for maximum antibody percent binding (MAPB) levels or for proportions of patients in the respective UQMAPB. No statistically significant differential treatment effects were observed in the relationship between MAPB and clinical efficacy and safety outcomes.

CONCLUSIONS

Maximum postbaseline IAR levels and the proportion of patients with high IAR levels were similar for LY IGlar and IGlar. High antibody levels did not affect clinical outcomes. These results add further evidence supporting similar IARs of LY IGlar and IGlar.

FUNDING

Eli Lilly and Company and Boehringer-Ingelheim.

Evaluation of Efficacy and Safety of the Glucagon Receptor Antagonist LY2409021 in Patients With Type 2 Diabetes: 12- and 24-Week Phase 2 Studies

OBJECTIVE

Type 2 diabetes pathophysiology is characterized by dysregulated glucagon secretion. LY2409021, a potent, selective small-molecule glucagon receptor antagonist that lowers glucose was evaluated for efficacy and safety in patients with type 2 diabetes.

RESEARCH DESIGN AND METHODS

The efficacy (HbA1c and glucose) and safety (serum aminotransferase) of once-daily oral administration of LY2409021 was assessed in two double-blind studies. Phase 2a study patients were randomized to 10, 30, or 60 mg of LY2409021 or placebo for 12 weeks. Phase 2b study patients were randomized to 2.5, 10, or 20 mg LY2409021 or placebo for 24 weeks.

RESULTS

LY2409021 produced reductions in HbA1c that were significantly different from placebo over both 12 and 24 weeks. After 12 weeks, least squares (LS) mean change from baseline in HbA1c was -0.83% (10 mg), -0.65% (30 mg), and -0.66% (60 mg) (all P < 0.05) vs. placebo, 0.11%. After 24 weeks, LS mean change from baseline in HbA1c was -0.45% (2.5 mg), -0.78% (10 mg, P < 0.05), -0.92% (20 mg, P < 0.05), and -0.15% with placebo. Increases in serum aminotransferase, fasting glucagon, and total fasting glucagon-like peptide-1 (GLP-1) were observed; levels returned to baseline after drug washout. Fasting glucose was also lowered with LY2409021 at doses associated with only modest increases in aminotransferases (mean increase in alanine aminotransferase [ALT] ≤10 units/L). The incidence of hypoglycemia in the LY2409021 groups was not statistically different from placebo.

CONCLUSIONS

In patients with type 2 diabetes, glucagon receptor antagonist treatment significantly lowered HbA1c and glucose levels with good overall tolerability and a low risk for hypoglycemia. Modest, reversible increases in serum aminotransferases were observed.

Evaluation of immunogenicity of LY2963016 insulin glargine compared with Lantus® insulin glargine in patients with type 1 or type 2 diabetes mellitus

AIMS

To compare the immunogenicity profiles and the potential effects on clinical outcomes of LY2963016 insulin glargine (LY IGlar) and Lantus® insulin glargine (IGlar), products with identical primary amino acid sequences, in patients with type 1 or type 2 diabetes mellitus (T1DM or T2DM).

METHODS

To assess immunogenicity, anti-insulin glargine antibodies (measured as percent binding) were compared between treatments in 52-week (open-label) and 24-week (double-blind) randomized studies in total study populations of patients with T1DM (N = 535) and T2DM (N = 756), respectively, and two subgroups of patients with T2DM: insulin-naïve patients and those reporting prestudy IGlar treatment (prior IGlar). Relationships between insulin antibody levels and clinical outcomes were assessed using analysis of covariance and partial correlations. Insulin antibody levels were assessed using Wilcoxon rank sum. Treatment comparisons for treatment-emergent antibody response (TEAR) and incidence of detectable antibodies were analysed using Fisher's exact test.

RESULTS

No significant treatment differences were observed for insulin antibody levels, incidence of detectable anti-insulin glargine antibodies, or incidence of TEAR [overall and endpoint, by last-observation-carried-forward (LOCF)] in patients with T1DM or patients with T2DM, including the insulin-naïve subgroup. A statistically significant difference was noted in the overall incidence of detectable antibodies but not at endpoint (LOCF) nor in TEAR for the prior IGlar subgroup of patients with T2DM. Insulin antibody levels were low (<5%) in both treatment groups. Insulin antibody levels or developing TEAR was not associated with clinical outcomes.

CONCLUSIONS

LY IGlar and IGlar have similar immunogenicity profiles; anti-insulin glargine antibody levels were low for both treatments, with no observed effect on efficacy and safety outcomes.

Prognostic and predictive biomarkers of abdominal aortic aneurysm growth rate

OBJECTIVES

To test the utility of clinical and circulating biomarkers to predict abdominal aortic aneurysm (AAA) growth rate and response to doxycycline therapy.

METHODS

Plasma samples were obtained in the Pharmaceutical Aneurysm Stabilization Trial that tested the effect of doxycycline (n = 44) vs. placebo (n = 49) in patients with a 35-50 mm AAA. Approximately 200 biomarkers were evaluated in a candidate approach that included markers of matrix turnover and cathepsin S activity and a broad-based approach of predominantly inflammation-related and clinical biomarkers.

RESULTS

In a recursive partitioning based analysis, total cholesterol, baseline AAA size, and apolipoprotein B were prognostic of AAA growth in the placebo group whereas elastin and biglycan degradation products were predictive of AAA growth with doxycycline treatment. Univariate analysis of these biomarkers showed that baseline total cholesterol (r = 0.38, unadjusted P = 0.011), apolipoprotein B (r = 0.41, unadjusted P = 0.005), and baseline AAA size (r = 0.35, unadjusted P = 0.013) correlated with AAA growth in the placebo but not the doxycycline group. Elastin fragments were associated with 18 month AAA growth (r = 0.33, unadjusted P = 0.031) in the doxycycline group.

LIMITATIONS

Limitations of this study include small sample size, a retrospective growth analysis, and translatability of the method used to measure the analytes.

CONCLUSIONS

This study implies that total cholesterol, baseline AAA size, and apolipoprotein B are predictors of AAA growth. Levels of elastin and biglycan fragments are predictive of doxycycline effects on AAA growth and provide a clue towards this unexpected negative effect.

Pharmacokinetics and pharmacodynamics of the cathepsin S inhibitor, LY3000328, in healthy subjects

AIM

The aim of this study was to assess the safety and tolerability, pharmacokinetics and pharmacodynamics of LY3000328 when administered as single escalating doses to healthy volunteers.

METHODS

This was a phase 1, placebo-controlled, dose escalation study with LY3000328 in 21 healthy male volunteers. Subjects were administered escalating LY3000328 doses up to 300 mg with food in this single dose study. Blood samples were collected at set times post-dose for the assessment of LY3000328 pharmacokinetics and the measurement of cathepsin S (CatS) activity, CatS mass and calculated CatS specific activity.

RESULTS

All doses of LY3000328 were well tolerated, with linear pharmacokinetics up to the 300 mg dose. The pharmacodynamic activity of LY3000328 was measured ex vivo showing a biphasic response to LY3000328, where CatS activity declines, then returns to baseline, and then increases to a level above baseline. CatS mass was also assessed post-dose which increased in a dose-dependent manner, and continued to increase after LY3000328 had been cleared from the body. CatS specific activity was additionally calculated to normalize CatS activity for changes in CatS mass. This demonstrated the increase in CatS activity was attributable to the increase in CatS mass detected in plasma.

CONCLUSION

A specific inhibitor of CatS which is cleared quickly from plasma may produce a transient decrease in plasma CatS activity which is followed by a more prolonged increase in plasma CatS mass which may have implications for the future clinical development of inhibitors of CatS.

Short-term administration of the glucagon receptor antagonist LY2409021 lowers blood glucose in healthy people and in those with type 2 diabetes

AIM

To describe the clinical effects of single and multiple doses of a potent, selective, orally administered, small-molecule antagonist of the human glucagon receptor, LY2409021, in healthy subjects and in patients with type 2 diabetes.

METHODS

LY2409021 was administered in dose-escalation studies to healthy subjects (n = 23) and patients with type 2 diabetes (n = 9) as single doses (Study 1) and daily to patients with type 2 diabetes (n = 47) for 28 days (Study 2). Safety, tolerability, pharmacokinetic (PK) and pharmacodynamic (PD) assessments were made after single doses and in patients receiving once-daily doses of LY2409021 (5, 30, 60 or 90 mg) for 28 days.

RESULTS

LY2409021 was well tolerated at all dose levels in both studies. Fasting and postprandial glucose were reduced and glucagon levels increased after single and multiple dosing, with reductions in fasting serum glucose of up to ∼1.25 mmol/l on day 28. Serum aminotransferases increased in a dose-dependent manner with multiple dosing and reversed after cessation of dosing. Significant glucose-lowering was observed with LY2409021 at dose levels associated with only minor aminotransferase increases.

CONCLUSION

Blockade of glucagon signalling in patients with type 2 diabetes is well tolerated and results in substantial reduction of fasting and postprandial glucose with minimal hypoglycaemia, but with reversible increases in aminotransferases. Inhibition of glucagon signalling by LY2409021 is a promising potential treatment for patients with type 2 diabetes and should be evaluated in longer clinical trials to better evaluate benefits and risks.

Physician preferences for extra-glycemic effects of type 2 diabetes treatments

INTRODUCTION

The purpose of this study was to quantify United States (US) and United Kingdom (UK) physicians' preferences for attributes of type 2 diabetes treatments.

METHODS

Samples of general practitioners (GPs) and endocrinologists in the US (n = 204) and the UK (n = 200) completed a discrete-choice experiment in which respondents chose between pairs of hypothetical type 2 diabetes treatments in a series of trade-off questions. The questions described hypothetical injectable treatments with differing levels of attributes, such as glucose control and treatment side effects. Relative importance of attributes was estimated by a multivariate regression model for limited dependent variables. These results were used to calculate how the predicted probability of choosing hypothetical type 2 diabetes treatments varies with changes in given attributes.

RESULTS

The most important attributes to physicians were glucose control, risk of a fatal myocardial infarction (MI), and weight change. For US physicians, glucose control was about twice as important as gastrointestinal side effects, 5 times more important than changes in depression symptoms, and 20 times more important than liver monitoring. For UK physicians, reduction in MI risk was about 1.5 times more important than glucose control, 2.5 times more important than gastrointestinal side effects, and 10 times more important than liver-monitoring requirements. Preferences were similar among physicians in the US and the UK and among GPs and endocrinologists.

CONCLUSIONS

Physicians valued type 2 diabetes treatments that go beyond glycemic control, although mitigating different complications and comorbidities was not equally as important.

The effects of LY2405319, an FGF21 analog, in obese human subjects with type 2 diabetes

Fibroblast growth factor 21 (FGF21) is a recently discovered metabolic regulator. Exogenous FGF21 produces beneficial metabolic effects in animal models; however, the translation of these observations to humans has not been tested. Here, we studied the effects of LY2405319 (LY), a variant of FGF21, in a randomized, placebo-controlled, double-blind proof-of-concept trial in patients with obesity and type 2 diabetes. Patients received placebo or 3, 10, or 20 mg of LY daily for 28 days. LY treatment produced significant improvements in dyslipidemia, including decreases in low-density lipoprotein cholesterol and triglycerides and increases in high-density lipoprotein cholesterol and a shift to a potentially less atherogenic apolipoprotein concentration profile. Favorable effects on body weight, fasting insulin, and adiponectin were also detected. However, only a trend toward glucose lowering was observed. These results indicate that FGF21 is bioactive in humans and suggest that FGF21-based therapies may be effective for the treatment of selected metabolic disorders.

A novel high-sensitivity electrochemiluminescence (ECL) sandwich immunoassay for the specific quantitative measurement of plasma glucagon

OBJECTIVES

To develop a novel, dual-monoclonal sandwich immunoassay with superior sensitivity that provides a rapid and convenient method for measuring glucagon. Glucagon is a 29-amino acid polypeptide hormone produced in the pancreas by the α-cells of the islets of Langerhans. Working in concert with insulin, glucagon is involved in regulating circulating glucose concentrations.

DESIGN AND METHODS

The immunoassay utilizes Meso Scale Discovery (MSD) electrochemiluminescence (ECL) technology and two affinity-optimized monoclonal antibodies. A series of experiments was performed to determine the linear range of the assay and to evaluate sensitivity, accuracy, recovery, precision, and linearity.

RESULTS

The sandwich assay was specific for glucagon and did not recognize the closely related peptide oxyntomodulin or other incretin peptides. The assay demonstrated excellent recovery, precision, and linearity, and a broad dynamic range of 0.14 pmol/L to 1950 pmol/L. In addition, assay results were highly correlated with those obtained using a previously described competitive RIA employing polyclonal antiserum.

CONCLUSION

The use of affinity-optimized monoclonal antibodies in a sandwich immunoassay format provides a robust, sensitive, and convenient method for measuring concentrations of glucagon that is highly sensitive and specific. This immunoassay should help to improve our understanding of the role of glucagon in the regulation of glucose metabolism.

Genetic variation of GPLD1 associates with serum GPI-PLD levels: a preliminary study

HDL is a heterogeneous mixture of lipoprotein particles varying in composition, size, and function. We and others have described a small (7.0nm), minor (0.1% of total apolipoprotein AI) particle containing apolipoprotein AI, AIV and glycosylphosphatidylinositol-specific phospholipase D (GPI-PLD) in humans the function of which is not entirely known. Circulating GPI-PLD levels are regulated by multiple factors including genetics. To determine if genetic variation in GPLD1 affects circulating GPI-PLD levels, we examined the relationship between 32 SNPS upstream, within, and downstream of GPLD1 and circulating GPI-PLD levels in Caucasians (n=77) and African-Americans (n=99). The genotype distribution among races differed at 13 SNPs. Nine SNPS were associated with circulating GPI-PLD levels in Caucasians but not African-Americans. These results suggest that genetic variation of GPLD1 appears to associate with circulating GPI-PLD levels. This article is part of a Special Issue entitled Advances in High Density Lipoprotein Formation and Metabolism: A Tribute to John F. Oram (1945-2010).

Dual-Monoclonal, Sandwich Immunoassay Specific for Glucose-Dependent Insulinotropic Peptide1-42, the Active Form of the Incretin Hormone

BACKGROUND

Glucose-dependent insulinotropic peptide (GIP) is an incretin peptide secreted by intestinal K cells that stimulates insulin secretion in a glucose-dependent manner. It is secreted as an active, intact 42–amino acid peptide GIP1-42, which is rapidly degraded by dipeptidyl peptidase 4 to GIP3-42, which is inactive. There is currently no described monoclonal antibody–based sandwich immunoassay to quantify concentrations of GIP1-42, the active form of the peptide.

METHODS

To create a sandwich ELISA for GIP1-42, we generated a monoclonal antibody specific for the intact N-terminus of the peptide, which was further optimized to increase its affinity. We used this antibody as a conjugate antibody in a sandwich ELISA and paired it with an anti–total GIP capture monoclonal antibody to create a dual monoclonal sandwich ELISA for GIP1-42.

RESULTS

The sandwich ELISA was highly specific for GIP1-42 and did not recognize GIP3-42. The ELISA demonstrated a broad dynamic range and a lower limit of quantification of 5 ng/L. Using the ELISA, we were able to show that GIP1-42 concentrations in healthy volunteers increased dramatically in the postprandial state compared to the fasting state. GIP1-42 values were correlated with total GIP values overall; however, there was substantial interindividual variation.

CONCLUSIONS

The use of an N-terminal–specific monoclonal antibody in a sandwich ELISA format provides a robust and convenient method for measuring concentrations of GIP1-42, the active form of the incretin hormone. This ELISA should help to improve our understanding of the role of GIP1-42 in regulating glucose-dependent insulin secretion.

Glycosylphosphatidylinositol-specific phospholipase D improves glucose tolerance

Insulin regulation of energy metabolism is complex and involves numerous signaling cascades. Insulin has been suggested to stimulate a phospholipase that cleaves glycosylphosphatidylinositols resulting in the generation of an inositol glycan that serves as an insulin mediator. To determine if glycosylphosphatidylinositol-specific phospholipase D (GPI-PLD) may play a role in glucose metabolism, we examined the effect of overexpressing GPI-PLD using adenovirus-mediated gene transfer in C57BL/6 mice. Overexpressing GPI-PLD was associated with a decrease in fasting glucose as well as an improvement in glucose tolerance as determined by an intraperitoneal glucose tolerance test. This effect to improve glucose tolerance does not result from an increase in insulin sensitivity, as overexpressing GPI-PLD does not alter the response to insulin. In contrast, the insulin response during the glucose tolerance test in GPI-PLD-overexpressing mice was increased. Overexpressing GPI-PLD in an insulinoma cell line enhanced glucose-stimulated insulin secretion, suggesting that enhanced insulin secretion in vivo may have contributed to the improved glucose tolerance.

Plasma glycosylphosphatidylinositol-specific phospholipase D predicts the change in insulin sensitivity in response to a low-fat but not a low-carbohydrate diet in obese women

Although circulating glycosylphosphatidylinositol-specific phospholipase D (GPI-PLD), a minor high-density lipoprotein-associated protein, is elevated in patients with insulin resistance or high triglycerides, no information is available on the effect of weight loss or changes in insulin sensitivity on circulating GPI-PLD levels. The objective of the study was to determine the effect of weight loss and changes in insulin sensitivity on plasma GPI-PLD levels. Forty-two nondiabetic obese women were included in the study, which involved a 3-month dietary intervention randomizing patients to a low-fat or a low-carbohydrate diet. The study's main outcome measures were plasma GPI-PLD levels and insulin sensitivity as estimated by the homeostasis model assessment. The very low carbohydrate diet group lost more weight after 3 months (-7.6 +/- 3.2 vs -4.2 +/- 3.5 kg, P < .01), although the decrease in insulin resistance was similar between groups. Weight loss with either diet did not alter plasma GPI-PLD levels. However, baseline GPI-PLD levels correlated with the change in insulin sensitivity in response to the low-fat diet, whereas baseline insulin sensitivity correlated with the change in insulin sensitivity in response to the low-carbohydrate diet. Plasma GPI-PLD may serve as a clinical tool to determine the effect of a low-fat diet on insulin sensitivity.

Development of progressive aortic vasculopathy in a rat model of aging

Recent studies have established that age is the major risk factor for vascular disease. Numerous aberrant changes occur in vascular structure and function during aging, and animal models are the primary means to determine the underlying mechanisms of age-mediated vascular pathology. The Fischer 344/Brown Norway F1 hybrid (F344xBN) rat thoracic aorta has been shown to display age-related pathology similar to what occurs in humans. This study utilized the F344xBN rat aorta and both morphometric and global gene expression analyses to identify appropriate time points to study vascular aging and to identify molecules associated with the development and progression of vascular pathology. In contrast to some previous studies that indicated age-related abrupt changes, a progressive increase in intimal and medial thickness, as well as smooth muscle cell-containing intimal protrusions, was observed in thoracic aorta. This structural vascular pathology was associated with a progressive, but nonlinear, increase in global differential gene expression. Gene products with altered mRNA and protein expression included inflammation-related molecules: specifically, the adhesion molecules ICAM-1 and VCAM-1 and the bone morphogenic proteins osteopontin and bone sialoprotein-1. Intimal-associated macrophages were found to increase significantly in number with age. Both systemic and tissue markers of oxidant stress, serum 8-isoprostane and 3-nitrotyrosine, respectively, were also found to increase during aging. The results demonstrate that major structural abnormalities and altered gene expression develop after 6 mo and that the progressive pathological development is associated with increased inflammation and oxidant stress.

Pioglitazone and rosiglitazone have different effects on serum lipoprotein particle concentrations and sizes in patients with type 2 diabetes and dyslipidemia

OBJECTIVE

Associated with insulin resistance in type 2 diabetes are increased serum triglycerides, decreased HDL cholesterol, and a predominance of large VLDL, small LDL, and small HDL particles. The comparative effects of thiazolidinedione insulin sensitizers on serum lipoprotein particle concentrations and sizes in type 2 diabetes are not known. We studied the effects of pioglitazone (PIO) and rosiglitazone (ROSI) treatments on serum lipoprotein particle concentrations and sizes in type 2 diabetic patients with dyslipidemia.

RESEARCH DESIGN AND METHODS

This is a prospective, randomized, double-blind, multicenter, parallel-group study. After a 4-week placebo washout period, patients randomized to PIO (n = 369) were treated with 30 mg q.d. for 12 weeks followed by 45 mg q.d. for another 12 weeks, while patients randomized to ROSI (n = 366) were treated with 4 mg q.d. followed by 4 mg b.i.d. for the same intervals. Lipoprotein subclass particle concentrations and sizes were determined by proton nuclear magnetic resonance spectroscopy at baseline and end point (PIO [n = 333] and ROSI [n = 325] patients).

RESULTS

PIO treatment increased total VLDL particle concentration less than ROSI treatment and decreased VLDL particle size more than ROSI. PIO treatment reduced total LDL particle concentration, whereas ROSI treatment increased it. Both treatments increased LDL particle size, with PIO treatment having a greater effect. Whereas PIO treatment increased total HDL particle concentration and size, ROSI treatment decreased them; both increased HDL cholesterol levels.

CONCLUSIONS

PIO and ROSI treatments have different effects on serum lipoprotein subclass particle concentrations and sizes in patients with type 2 diabetes and dyslipidemia.

Statin therapy reduces serum levels of glycosylphosphatidylinositol-specific phospholipase D

Statin therapy is associated with changes in low-density, very low-density, and high- density lipoprotein metabolism. The effect of statin therapy on a minor high-density lipoprotein particle containing glycosylphosphatidylinositol-specific phospholipase D has not been examined. Glycosylphosphatidylinositol-specific phospholipase D (GPI-PLD) has been implicated in triglyceride metabolism. A double-blind, crossover design comparing the effect of simvastatin (80 mg) and atorvastatin (80 mg) on serum lipid and glycosylphosphatidylinositol-specific phospholipase D levels was conducted in 13 patients with low high-density lipoproteins. Both statins reduced cholesterol, triglycerides, and apolipoprotein B and significantly lowered serum glycosylphosphatidylinositol-specific phospholipase D levels (16%). This statin effect seems to occur in the plasma compartment as neither statin altered GPI-PLD mRNA levels in HepG2 cells. Serum glycosylphosphatidylinositol-specific phospholipase D levels are regulated by statins and may represent an additional biochemical mechanism for affecting serum triglyceride levels.

Primary care physician treatment of low HDL: Rational approach or Pandora's Box?

BACKGROUND

Guidelines for treating high low-density lipoproteins are clear, whereas guidelines for treating low high-density lipoproteins (HDL) are less so. Physicians approach to treating low HDL cholesterol is not known.

OBJECTIVE

To determine primary care physicians approach to managing low HDL.

METHODS

Three-thousand, nine-hundred and nineteen surveys were mailed to all primary care physicians in the State of Indiana, asking questions regarding demographics, case studies to assess the provider's approach to managing low HDL, and direct questions regarding management of HDL levels and general lipid knowledge questions.

RESULTS

Seven-hundred and eighty-one surveys were returned, for a response rate of 19.9%. Fifty-eight percent of participants would initiate HDL-raising therapy after achieving the appropriate low-density lipoprotein cholesterol goal. The approaches used to raise HDL included lifestyle changes (diet, exercise, smoking cessation) (85%), niacin (83%), fibric acid derivative (61%), and alcohol (31%). Reasons inhibiting initiating therapy for raising HDL included concern over side effects (56%), perceived lack of effectiveness of currently available drugs (24%), lack of clear guidelines (22%), and lack of evidenced-based trials demonstrating benefit of raising HDL (14%). For men, 40% of physicians use 40 mg/dL as a cutoff for initiating HDL-raising therapy, while 25% using a cutoff of 35 mg/dL. For women, 24% use a cutoff of 50 mg/dL for initiating HDL-raising therapy, while 12% use 45 mg/dL as a cutoff.

CONCLUSIONS

The majority of primary care physicians in the State of Indiana treated low HDL with appropriate approaches, although use of alcohol to raise HDL raises concerns.

Safety and Efficacy of Extended-Release Niacin for the Treatment of Dyslipidaemia in Patients with HIV Infection: Aids Clinical Trials Group Study A5148

Background

Dyslipidaemia is very common in patients with HIV infection, but current therapies are often suboptimal. Since niacin may cause insulin resistance and hepatotoxicity, it has generally been avoided in this setting.

Methods

Non-diabetic male subjects ( n=33) who had well-controlled HIV infection on antiretroviral therapy, fasting triglycerides ≥2.26 mmol/l and non-high density lipoprotein cholesterol (non-HDL-C) ≥4.66 mmol/l received escalating doses of extended-release niacin (ERN) up to 2,000 mg nightly for up to 44 weeks.

Results

Fourteen subjects (42%) had pre-diabetes at entry. Twenty-three subjects (70%) received the maximum dose, eight (24%) received 1,500 mg. Niacin was well-tolerated. Only four subjects (12%) discontinued study treatment. There were small increases in fasting glycaemia and insulin resistance estimated by the homeostasis model assessment, but insulin resistance measures from the 2-h oral glucose tolerance test only transiently worsened. No subject developed persistent fasting hyperglycaemia; one had persistently elevated 2-h glucose >11.1 mmol/l. There were no significant changes in serum transaminases or uric acid. At week 48, the median change in fasting lipid levels in mmol/l (interquartile range) were: total cholesterol -0.21 (-1.35, -0.05), HDL-C +0.013 (-0.03,+0.28), non-HDL-C -0.49 (-1.37, +0.08) and triglycerides -1.73 (-3.68, -0.72). Favourable changes in large HDL and large very low density lipoprotein particle concentration were observed by nuclear magnetic resonance spectroscopy.

Conclusions

ERN in doses up to 2,000 mg daily was safe, well-tolerated and efficacious in HIV-infected subjects with atherogenic dyslipidaemia. Increases in glycaemia and insulin resistance tended to be transient.

Glycosylphosphatidylinositol-specific phospholipase d in nonalcoholic Fatty liver disease: a preliminary study

CONTEXT

Recent studies demonstrated that de novo lipogenesis is increased in patients with nonalcoholic fatty liver disease (NAFLD). Patients with NAFLD also have plasma lipid abnormalities. These lipid abnormalities may in part be related to insulin resistance, which is common in patients with NAFLD. Insulin resistance is associated with alterations in proteins involved in lipid metabolism including glycosylphosphatidylinositol-specific phospholipase D (GPI-PLD), which is involved in triglyceride metabolism.

OBJECTIVE

The objective of the study was to determine whether alterations in serum and hepatic levels of GPI-PLD occur in patients with NAFLD.

DESIGN AND PATIENTS

We examined the following: 1) levels of serum GPI-PLD in nondiabetics with nonalcoholic steatohepatitis, compared with matched controls; 2) hepatic expression of GPI-PLD mRNA in patients with normal liver or NAFLD; and 3) effect of overexpressing GPI-PLD vs. beta-galactosidase (control) on global gene expression in a human hepatoma cell line.

RESULTS

The serum levels of GPI-PLD were significantly higher in patients with nonalcoholic steatohepatitis than in matched controls (119 +/- 24 vs.105 +/- 15 microg/ml, P = 0.047). The hepatic expression of GPI-PLD mRNA was increased nearly 3-fold in NAFLD patients, compared with patients with normal liver (3.1 +/- 2.6 vs. 1.1 +/- 1.0 arbitrary units per microgram total RNA, P = 0.026). Finally, overexpressing GPI-PLD was associated with an increase in de novo lipogenesis genes.

CONCLUSIONS

Patients with NAFLD have elevated serum levels and hepatic expression of GPI-PLD, and its overexpression in vitro is associated with increased expression of de novo lipogenesis genes. These results suggest that GPI-PLD may play a role in the pathogenesis of NAFLD and/or its metabolic features and warrants further investigation.

Glycosylphosphatidylinositol-specific phospholipase D influences triglyceride-rich lipoprotein metabolism

Glycosylphosphatidylinositol-specific phospholipase D (GPI-PLD) is a minor HDL-associated protein. Because many minor HDL-associated proteins exchange between different lipoprotein classes during the postprandial state and are also involved in triglyceride (TG) metabolism, we hypothesized that GPI-PLD may play a role in the metabolism of TG-rich lipoproteins. To test this hypothesis, we examined the distribution of GPI-PLD among lipoprotein classes during a fat tolerance test in C57BL/6 and LDL receptor-deficient (LDLR(-/-)) mice fed either a chow or high-fructose diet. In the fasting state in wild-type mice fed a chow diet, GPI-PLD was only present in HDL, whereas in LDLR(-/-) mice GPI-PLD was present in HDL and intermediate-density lipoproteins (IDL)/LDL. During the fat tolerance test, there was no change in total serum GPI-PLD levels in either model; however, a significant amount of GPI-PLD appeared in both VLDL (0.5-1% of total GPI-PLD) and IDL/LDL (5-10% of total GPI-PLD) in both models. The high-fructose diet increased both fasting and postprandial TG and serum GPI-PLD levels in both strains as well as the amount of GPI-PLD in VLDL. To determine whether GPI-PLD plays a direct role in TG metabolism, we increased liver GPI-PLD expression in C57BL/6 mice by adenovirus-mediated gene transfer, which resulted in a sevenfold increase in serum GPI-PLD levels. This change was associated with an increase in fasting (30%) and postprandial TG (50%) and a twofold reduction in TG-rich lipoprotein catabolism compared with saline or control adenovirus-treated mice. These studies demonstrate that GPI-PLD affects serum TG levels by altering catabolism of TG-rich lipoproteins.

Safety and efficacy of extended-release niacin for the treatment of dyslipidaemia in patients with HIV infection: AIDS Clinical Trials Group Study A5148

BACKGROUND

Dyslipidaemia is very common in patients with HIV infection, but current therapies are often suboptimal. Since niacin may cause insulin resistance and hepatotoxicity, it has generally been avoided in this setting.

METHODS

Non-diabetic male subjects (n=33) who had well-controlled HIV infection on antiretroviral therapy, fasting triglycerides > or =2.26 mmol/l and non-high density lipoprotein cholesterol (non-HDL-C) > or =4.66 mmol/l received escalating doses of extended-release niacin (ERN) up to 2,000 mg nightly for up to 44 weeks.

RESULTS

Fourteen subjects (42%) had pre-diabetes at entry. Twenty-three subjects (70%) received the maximum dose, eight (24%) received 1,500 mg. Niacin was well-tolerated. Only four subjects (12%) discontinued study treatment. There were small increases in fasting glycaemia and insulin resistance estimated by the homeostasis model assessment, but insulin resistance measures from the 2-h oral glucose tolerance test only transiently worsened. No subject developed persistent fasting hyperglycaemia; one had persistently elevated 2-h glucose >11.1 mmol/l. There were no significant changes in serum transaminases or uric acid. At week 48, the median change in fasting lipid levels in mmol/l (interquartile range) were: total cholesterol -0.21 (-1.35, -0.05), HDL-C +0.013 (-0.03,+0.28), non-HDL-C -0.49 (-1.37,+0.08) and triglycerides -1.73 (-3.68, -0.72). Favourable changes in large HDL and large very low density lipoprotein particle concentration were observed by nuclear magnetic resonance spectroscopy.

CONCLUSIONS

ERN in doses up to 2,000 mg daily was safe, well-tolerated and efficacious in HIV-infected subjects with atherogenic dyslipidaemia. Increases in glycaemia and insulin resistance tended to be transient.

Basic approach to managing hyperglycemia for the nonendocrinologist

The prevalence of type 2 diabetes mellitus is growing rapidly worldwide. Reducing the complications of diabetes requires aggressive management of multiple risk factors, including elevated blood pressure, abnormal plasma lipid levels, and elevated plasma glucose. Fortunately, numerous agents are available to control these risk factors. This review discusses the therapeutic options in managing hyperglycemia, including lifestyle, oral agents, and insulin.

A comparison of lipid and glycemic effects of pioglitazone and rosiglitazone in patients with type 2 diabetes and dyslipidemia

OBJECTIVE

Published reports suggest that pioglitazone and rosiglitazone have different effects on lipids in patients with type 2 diabetes. However, these previous studies were either retrospective chart reviews or clinical trials not rigorously controlled for concomitant glucose- and lipid-lowering therapies. This study examines the lipid and glycemic effects of pioglitazone and rosiglitazone.

RESEARCH DESIGN AND METHODS

We enrolled subjects with a diagnosis of type 2 diabetes (treated with diet alone or oral monotherapy) and dyslipidemia (not treated with any lipid-lowering agents). After a 4-week placebo washout period, subjects randomly assigned to the pioglitazone arm (n = 400) were treated with 30 mg once daily for 12 weeks followed by 45 mg once daily for an additional 12 weeks, whereas subjects randomly assigned to rosiglitazone (n = 402) were treated with 4 mg once daily followed by 4 mg twice daily for the same intervals.

RESULTS

Triglyceride levels were reduced by 51.9 +/- 7.8 mg/dl with pioglitazone, but were increased by 13.1 +/- 7.8 mg/dl with rosiglitazone (P < 0.001 between treatments). Additionally, the increase in HDL cholesterol was greater (5.2 +/- 0.5 vs. 2.4 +/- 0.5 mg/dl; P < 0.001) and the increase in LDL cholesterol was less (12.3 +/- 1.6 vs. 21.3 +/- 1.6 mg/dl; P < 0.001) for pioglitazone compared with rosiglitazone, respectively. LDL particle concentration was reduced with pioglitazone and increased with rosiglitazone (P < 0.001). LDL particle size increased more with pioglitazone (P = 0.005).

CONCLUSIONS

Pioglitazone and rosiglitazone have significantly different effects on plasma lipids independent of glycemic control or concomitant lipid-lowering or other antihyperglycemic therapy. Pioglitazone compared with rosiglitazone is associated with significant improvements in triglycerides, HDL cholesterol, LDL particle concentration, and LDL particle size.

Changes in thrombolytic and inflammatory markers after initiation of indinavir- or amprenavir-based antiretroviral therapy

HIV-infected subjects who have lipodystrophy and insulin resistance on prolonged antiretroviral therapy have elevated levels of tissue plasminogen activator (tPA) and plasminogen activator inhibitor-1 (PAI-1) antigens, markers of impaired thrombolysis that are associated with hyperinsulinemia and increased cardiovascular risk. We studied HIV-infected, protease inhibitor (PI)-naive adults treated with indinavir (n = 11) or amprenavir (n = 14) plus two nucleoside reverse transcriptase inhibitors enrolled in two independent prospective trials. Antiretroviral and immune responses were similar in both studies. Over 8 wk, indinavir was associated with decreased insulin sensitivity, whereas amprenavir was not. Levels of tPA antigen declined by approx 25% with both treatments (p < 0.05 for each); levels of PAI-1 antigen did not change. Levels of the inflammatory marker soluble tumor necrosis factor-alpha receptor II (sTNFr2) correlated positively with tPA antigen (r = 0.33, p = 0.02), and mean (SD) plasma concentrations of sTNFr also declined with treatment (4.44 +/- 1.11 ng/mL pretherapy, 3.75 +/- 1.21 posttherapy, p = 0.007). Short-term improvement in a marker of impaired thrombolysis and increased vascular risk can occur during PI-based antiretroviral therapy, perhaps as a consequence of improvement in HIV-related inflammation. This improvement occurred independent of development of insulin resistance, which occurred only with indinavir.

Systemic levels of lipid peroxidation and its metabolic and dietary correlates in patients with nonalcoholic steatohepatitis

BACKGROUND AND AIM

Products of systemic lipid peroxidation are important in the pathogenesis of cardiovascular disease. Subjects with NASH have increased hepatic lipid peroxidation, but it is unknown if they have increased oxidative stress and lipid peroxidation systemically. Therefore, we conducted a study to measure the circulating levels of lipid peroxidation products and their metabolic and nutritional correlates in patients with NASH and controls.

METHODS

Systemic lipid peroxidation was assessed by measuring the levels of oxidized LDL (ox-LDL) and thiobarbituric acid-reacting substances (TBARS) in 21 subjects with NASH and 19 controls. Correlations were made between serum lipid peroxidation and nutritional determinants of oxidative stress and defense, serum lipids, insulin resistance, transaminases, and liver histology. The short-term nutrient intake was analyzed by maintaining a 3-wk dietary diary.

RESULTS

The serum levels of ox-LDL were significantly higher in NASH patients compared to controls (56 +/- 16 U/L vs 40 +/- 12 U/L, respectively, p < 0.001). Similarly, serum TBARS were significantly higher in NASH patients compared to controls (3.4 +/- 1.3 vs 1.8 +/- 0.9 nmols/ml, respectively, p= 0.0001). Insulin resistance was independently associated with ox-LDL (p= 0.01) and TBARS levels (p= 0.01). We found no differences in the intake of various macro- and micronutrients between the two groups and there was no association between nutrient intake and ox-LDL or TBARS.

CONCLUSION

Subjects with NASH have significantly higher systemic levels of lipid peroxidation products and this could indicate an increased risk of cardiovascular disease. More studies are needed to evaluate this possibility.

Effect of glycosylphosphatidylinositol (GPI)-phospholipase D overexpression on GPI metabolism

GPI-PLD [glycosylphosphatidylinositol (GPI)-specific phospholipase D (PLD)] is a secreted mammalian enzyme that specifically cleaves GPI-anchored proteins. In addition, the enzyme has been shown to cleave GPI anchor intermediates in cell lysates. The biosynthesis of the GPI anchor is well characterized; however, the mechanisms by which the levels of GPI anchor intermediates are regulated are still unknown. To investigate whether GPI-PLD plays a role in this regulation, we isolated stable HeLa cells overexpressing the enzyme. GPI-PLD-HeLa (GPI-PLD-transfected HeLa) cells showed a 3-fold increase in intracellular GPI-PLD activity and drastically decreased the levels of GPI-anchored proteins when compared with untransfected HeLa controls. Intracellular cleavage of GPI-anchored proteins has been suggested to occur early in the secretory pathway and, in agreement with this proposal, GPI-PLD activity in GPI-PLD-HeLa cells was detected not only in the endoplasmic reticulum and Golgi apparatus, but also in the plasma membrane. The enzyme was also active in lipid rafts, membrane microdomains in which GPI-anchored proteins and GPI anchor intermediates are concentrated, indicating that intracellular GPI-PLD cleavage may also occur in this compartment. Pulse-chase paradigms revealed the turnover rate of the last intermediate of the GPI anchor pathway in GPI-PLD-HeLa cells to be accelerated compared with the controls. Furthermore, 1,10-phenanthroline, a GPI-PLD inhibitor, reversed this effect. Our studies demonstrated that GPI-PLD can cleave not only GPI-anchored proteins, but also GPI anchor intermediates intracellularly. This observation opens the possibility that GPI-PLD can influence the steady-state levels of GPI-anchored proteins by hydrolysing the anchor before and after its attachment to proteins.

Insulin resistance is associated with increased serum levels of glycosylphosphatidylinositol-specific phospholipase D

The dyslipidemia of the metabolic syndrome is associated with alterations in triglyceride and high-density lipoprotein (HDL) metabolism. We examined the serum levels of glycosylphosphatidylinositol-specific phospholipase D (GPI-PLD), a minor HDL-associated protein, in a cohort with a wide range of insulin sensitivity. The mean serum GPI-PLD mass from 109 subjects was 58.9 +/- 18.4 microg/mL (mean +/- SD). GPI-PLD levels directly correlated with cholesterol, apolipoprotein AI, triglycerides, insulin, and homeostasis model assessment (HOMA) but not C-reactive protein. These results suggest that increased serum GPI-PLD is associated with the insulin resistance.

Characterization of human brain nicotinamide 5'-mononucleotide adenylyltransferase-2 and expression in human pancreas

NMNAT (nicotinamide 5'-mononucleotide adenylyltransferase; EC 2.7.7.1) catalyses the transfer of the adenylyl group from ATP to NMN to form NAD. We have cloned a novel human NMNAT cDNA, designated hNMNAT-2, from human brain. The cDNA contains a 924 bp open reading frame that encodes a 307 amino acid peptide that was expressed as a histidine-patch-containing thioredoxin fusion protein. Expressed hNMNAT-2 shared only 35% amino acid sequence homology with the human NMNAT enzyme (hNMNAT-1), but possessed enzymic activity comparable with hNMNAT-1. Using human genomic databases, hNMNAT-2 was localized to chromosome 1q25 within a 171 kb gene, whereas hNMNAT-1 is on chromosome 1p32-35. Northern blot analysis revealed highly restricted expression of hNMNAT-2 to brain, heart and muscle tissues, which contrasts with the wide tissue expression of hNMNAT-1; different regions of the brain exhibited differential expression of hNMNAT-2. Substitution mutations of either of two invariant residues, His-24 or Trp-92, abolished enzyme activity. Anti-peptide antibody to a unique epitope within hNMNAT-2 was produced, and immunohistochemical analysis of sections of normal adult human pancreas revealed that hNMNAT-2 protein was markedly expressed in the islets of Langerhans. However, the pancreatic exocrine cells exhibited weak expression of hNMNAT-2 protein. Sections of pancreas from insulinoma patients showed strong expression of hNMNAT-2 protein in the insulin-producing tumour cells, whereas acinar cells exhibited relatively low expression of hNMNAT-2 protein. These data suggest that the unique tissue-expression patterns of hNMNAT-2 reflect distinct functions for the isoforms in the regulation of NAD metabolism.

Glycosylphosphatidylinositol-specific phospholipase D immunoreactivity is present in islet amyloid in type 2 diabetes

Numerous apolipoproteins associate with amyloid plaques. A minor high-density lipoprotein-associated protein, glycosylphosphatidylinositol-specific phospholipase D (GPI-PLD), has recently been described by the authors and others. Since GPI-PLD is synthesized by, and secreted from, pancreatic islet beta cells, the present study examined the hypothesis that GPI-PLD associates with islet amyloid. GPI-PLD immunoreactivity was examined in pancreatic tissues from type 2 diabetic and non-diabetic humans. GPI-PLD binding to heparan sulphate proteoglycan was determined in the absence or presence of heparan sulphate or heparin. Fibril formation from human islet amyloid polypeptide was determined in the absence or presence of GPI-PLD. In non-diabetics, GPI-PLD immunoreactivity was present and co-localized with insulin, as opposed to co-localizing with amyloid in diabetics. No immunoreactivity for apolipoprotein A-I was present in islet cells or islet amyloid. Heparan sulphate proteoglycan, which is commonly present in most amyloid, bound GPI-PLD in vitro. GPI-PLD inhibited the formation of amyloid fibrils from synthetic islet amyloid polypeptide in vitro. GPI-PLD is therefore present in islet amyloid and appears to derive from local production from islets. This localization likely derives from interaction between GPI-PLD and heparan sulphate proteoglycan. Since GPI-PLD also inhibited islet amyloid polypeptide fibril formation in vitro, it is concluded that GPI-PLD may play a role in islet amyloid formation in type 2 diabetes.

Dietary Cholate Is Required for Antiatherogenic Effects of Ethanol in Mouse Models

BACKGROUND

Human consumption of moderate amounts of ethanol is associated with reduced cardiovascular events. Studies examining the effect of ethanol on atherosclerosis in mouse models have yielded conflicting results that may be due to differences in dietary fat and cholate content. To determine if dietary cholate influences ethanol's effect on atherosclerosis, we fed apolipoprotein E-/- and low-density lipoprotein receptor (LDLR)-/- mice different liquid diets with or without ethanol.

METHODS

Apolipoprotein E-/- mice were fed a low-fat or high saturated fat, cholate-containing diet with or without ethanol for 3 to 10 weeks, and LDLR-/- mice were fed a low-fat, high saturated fat, or high saturated fat diet with cholate with or without ethanol for 7 weeks. At the end of the feeding study, aortic root lesion size was determined and compared with serum cholesterol, triglycerides, and high-density lipoprotein cholesterol. Because dietary cholate increases hepatic nuclear factor (NF)-kappaB and ethanol inhibits NF-kappaB, we also examined the effect of ethanol on aortic NF-kappaB binding activity.

RESULTS

Adding ethanol to a low-fat diet had no effect on lesion size. Similarly, ethanol had no effect on lesion size in LDLR-/- mice consuming a high saturated fat diet. Adding ethanol to a high-fat, cholate-containing diet for either strain resulted in a 25% to 50% reduction in lesion size. Dietary cholate increased and ethanol reduced NF-kappaB binding activity in the aorta.

CONCLUSIONS

These results suggest that ethanol inhibits atherosclerosis in the presence of dietary cholate, which may occur via an anti-inflammatory mechanism.

Metabolic and anthropometric evaluation of insulin resistance in nondiabetic patients with nonalcoholic steatohepatitis

OBJECTIVES

Insulin resistance is nearly universal in patients with nonalcoholic steatohepatitis (NASH) when tested by glucose tolerance tests or clamp methods. However, the pattern of insulin resistance in these patients after a physiological challenge is unknown. We conducted a study to characterize the metabolic response to a mixed meal in nondiabetic patients with NASH (NDN) and to identify anthropometric determinants of insulin resistance in these patients.

METHODS

Serum insulin, C-peptide, glucose, and free fatty acid (FFA) levels were measured at 0, 30, 60, 90, and 120 min after a 500-kcal standard meal in 18 NDN and 18 age-, gender-, and body mass index (BMI)-matched controls. Correlations were made between insulin resistance and various anthropometric, calorimetric, and serological variables.

RESULTS

Compared with controls, NDN had significantly higher levels of insulin and C-peptide at baseline and after the mixed meal. However, glucose levels were not different either at baseline or after the meal. NDN had higher fasting levels of FFA than the controls (459 +/- 190 vs 339 +/- 144 micro mol/L, respectively, p = 0.03); however, meal-induced suppression in lipolysis was similar between the two groups (39 +/- 113% vs 46 +/- 60%, p = 0.8). Insulin resistance was significantly correlated with BMI (r = 0.39, p = 0.02) and visceral fat (r = 0.50, p = 0.004). Whereas BMI, percent total body fat, and subcutaneous abdominal fat were similar between the groups, the NASH group had significantly higher percent visceral fat compared with controls (28 +/- 10% vs 22 +/- 14%, p = 0.02).

CONCLUSIONS

NDN are significantly hyperinsulinemic, both at fasting and after the mixed meal; however, their glucose homeostasis and suppression in lipolysis after a meal challenge are maintained. Insulin resistance in these patients is likely related to their higher visceral fat mass.

Phosphorylation decreases trypsin activation and apolipoprotein al binding to glycosylphosphatidylinositol-specific phospholipase D

Glycosylphosphatidylinositol-specific phospholipase D (GPI-PLD) is present in plasma as an apolipoprotein and as a cell-associated lipase. GPI-PLD mRNA levels are regulated, but it is unclear if posttranslational mechanisms also regulate GPI-PLD function. We examined the effect of protein kinase A phosphorylation on human serum GPI-PLD activity, trypsin activation, and apolipoprotein AI binding. Protein kinase A phosphorylation did not activate GPI-PLD activity in vitro, nor did phosphorylated GPI-PLD cleave a GPI-anchored protein from intact porcine erythrocytes. Trypsin cleaves the C-terminal beta propeller of purified human serum GPI-PLD to generate three immunodetectable fragments (75, 28, and 18 kDa) in association with a 12-fold increase in enzyme activity. After phosphorylation, the amounts of 28- and 18-kDa fragments were markedly decreased with trypsin treatment, and activity was only increased five-fold. Phosphorylation also inhibits binding of GPI-PLD to apolipoprotein AI. These data are the first demonstrating that phosphorylation may regulate GPI-PLD interaction with other proteins.

Ethanol induces fatty acid synthesis pathways by activation of sterol regulatory element-binding protein (SREBP)

Alcoholic fatty liver is the earliest and most common response of the liver to alcohol and may be a precursor of more severe forms of liver injury. The mechanism by which ethanol causes fatty liver and liver injury is complex. We found that in both rat H4IIEC3 and McA-RH7777 hepatoma cell lines, ethanol induced transcription of a sterol regulatory element-binding protein (SREBP)-regulated promoter via increased levels of mature SREBP-1 protein. This effect of ethanol was blocked by addition of sterols. This effect is likely mediated by acetaldehyde, because the effect was only seen in cell lines expressing alcohol dehydrogenase, and inhibition of ethanol oxidation by 4-methylpyrazole blocked the effect in the hepatoma cells. Furthermore, the aldehyde dehydrogenase inhibitor cyanamide enhanced the effect of ethanol in the hepatoma cells. Consistent with these in vitro findings, feeding mice a low fat diet with ethanol for 4 weeks resulted in a significant increase in steady-state levels of the mature (active) form of SREBP-1. Activation of SREBP-1 by ethanol feeding was associated with increased expression of hepatic lipogenic genes as well as the accumulation of triglyceride in the livers. These finding suggest that metabolism of ethanol increased hepatic lipogenesis by activating SREBP-1 and that this effect of ethanol may contribute to the development of alcoholic fatty liver.

Glucose and insulin regulate glycosylphosphatidylinositol-specific phospholipase D expression in islet beta cells

Insulin resistance is associated with a compensatory islet hyperactivity to sustain adequate insulin biosynthesis and secretion to maintain near euglycemia. Both glucose and insulin are involved in regulating proteins required for insulin synthesis and secretion within the islet and islet hypertrophy. We have determined that glycosylphosphatidylinositol-specific phospholipase D (GPI-PLD) is present within the secretory granules of islet beta cells. To determine if GPI-PLD is regulated in islet beta cells, we examined the effect of glucose and insulin on GPI-PLD expression in rat islets and murine insulinoma cell lines. Glucose (16.7 mmol/L) increased cellular GPI-PLD activity and mRNA levels 2- to 7-fold in isolated rat islets and betaTC3 and betaTC6-F7 cells. Insulin (10(-7) mol/L) also increased GPI-PLD mRNA levels in rat islets and betaTC6-F7 cells 2- to 4-fold commensurate with an increase in GPI-PLD biosynthesis. To determine if islet GPI-PLD expression is increased in vivo under conditions of islet hyperactivity, we compared GPI-PLD mRNA levels in islets and liver from ob/ob mice and their lean littermates. Islet GPI-PLD mRNA was increased 5-fold while liver mRNA and serum GPI-PLD levels were reduced 30% in ob/ob mice compared with lean littermate controls. These results suggest that glucose and insulin regulate GPI-PLD mRNA levels in isolated islets and beta-cell lines. These regulators may also account for the increased expression of GPI-PLD mRNA in islets from ob/ob mice, a model of insulin resistance and islet hyperactivity.

Increased expression of GPI-specific phospholipase D in mouse models of type 1 diabetes

Glycosylphosphatidylinositol-specific phospholipase D (GPI-PLD) is a high-density lipoprotein-associated protein. However, the tissue source(s) for circulating GPI-PLD and whether serum levels are regulated are unknown. Because the diabetic state alters lipoprotein metabolism, and liver and pancreatic islets are possible sources of GPI-PLD, we hypothesized that GPI-PLD levels would be altered in diabetes. GPI-PLD serum activity and liver mRNA were examined in two mouse models of type 1 diabetes, a nonobese diabetic (NOD) mouse model and low-dose streptozotocin-induced diabetes in CD-1 mice. With the onset of hyperglycemia (2- to 5-fold increase over nondiabetic levels), GPI-PLD serum activity and liver mRNA increased 2- to 4-fold in both models. Conversely, islet expression of GPI-PLD was absent as determined by immunofluorescence. Insulin may regulate GPI-PLD expression, because insulin treatment of diabetic NOD mice corrected the hyperglycemia along with reducing serum GPI-PLD activity and liver mRNA. Our data demonstrate that serum GPI-PLD levels are altered in the diabetic state and are consistent with liver as a contributor to circulating GPI-PLD.

GPI-specific phospholipase D associates with an apoA-I- and apoA-IV-containing complex

Glycosylphosphatidylinositol-specific phospholipase D (GPI-PLD) is abundant in serum and associates with high density lipoproteins (HDL). We have characterized the distribution of GPI-PLD among lipoproteins in human plasma. Apolipoprotein (apo)-specific lipoproteins containing apoB (Lp[B]), apoA-I and A-II (Lp[A-I, A-II]), or apoA-I only (Lp[A-I]) were isolated using dextran sulfate and immunoaffinity chromatography. In six human plasma samples with HDL cholesterol ranging from 39 to 129 mg/dl, 79 +/- 14% (mean +/- SD) of the total plasma GPI-PLD activity was associated with Lp[A-I], 9 +/- 12% with Lp[A-I, A-II], and 1 +/- 1% with Lp[B]; and 11 +/- 10% was present in plasma devoid of these lipoproteins. Further characterization of the GPI-PLD-containing lipoproteins by gel-filtration chromatography and nondenaturing polyacrylamide and agarose gel electrophoresis revealed that these apoA-I-containing particles/complexes were small (8 nm) and migrated with pre-beta particles on agarose electrophoresis. Immunoprecipitation of GPI-PLD with a monoclonal antibody to GPI-PLD co-precipitated apoA-I and apoA-IV but little or no apoA-II, apoC-II, apoC-III, apoD, or apoE. In vitro, apoA-I but not apoA-IV or bovine serum albumin interacted directly with GPI-PLD, but did not stimulate GPI-PLD-mediated cleavage of a cell surface GPI-anchored protein. Thus, the majority of plasma GPI-PLD appears to be specifically associated with a small, discrete, and minor fraction of lipoproteins containing apoA-I and apoA-IV. -- Deeg, M. A., E. L. Bierman, and M. C. Cheung. GPI-specific phospholipase D associates with an apoA-I- and apoA-IV-containing complex. J. Lipid Res. 2001. 42: 442--451.