Targeted pharmacological therapy restores β-cell function for diabetes remission

Dedifferentiation of insulin-secreting β cells in the islets of Langerhans has been proposed to be a major mechanism of β-cell dysfunction. Whether dedifferentiated β cells can be targeted by pharmacological intervention for diabetes remission, and ways in which this could be accomplished, are unknown as yet. Here we report the use of streptozotocin-induced diabetes to study β-cell dedifferentiation in mice. Single-cell RNA sequencing (scRNA-seq) of islets identified markers and pathways associated with β-cell dedifferentiation and dysfunction. Single and combinatorial pharmacology further show that insulin treatment triggers insulin receptor pathway activation in β cells and restores maturation and function for diabetes remission. Additional β-cell selective delivery of oestrogen by Glucagon-like peptide-1 (GLP-1-oestrogen conjugate) decreases daily insulin requirements by 60%, triggers oestrogen-specific activation of the endoplasmic-reticulum-associated protein degradation system, and further increases β-cell survival and regeneration. GLP-1-oestrogen also protects human β cells against cytokine-induced dysfunction. This study not only describes mechanisms of β-cell dedifferentiation and regeneration, but also reveals pharmacological entry points to target dedifferentiated β cells for diabetes remission.

Leukocyte telomere length is associated with elevated plasma glucose and HbA1c in young healthy men independent of birth weight

Telomeres are protein-bound regions of repetitive nucleotide sequences (TTAGGG) at the end of human chromosomes, and their length is a marker of cellular aging. Intrauterine growth restriction is associated with shorter blood cell telomeres at birth and individuals with type 2 diabetes have shorter telomeres. Individuals with a low birth weight (LBW) have an increased risk of metabolic disease and type 2 diabetes. Therefore, we aimed to investigate the relationship between birth weight and telomere length and the association between birth weight, telomere length and cardiometabolic phenotype in adulthood. Young, healthy men with LBW (n = 55) and normal birth weight (NBW) (n = 65) were examined including blood pressure, blood samples and body composition. Leukocyte telomere length was determined using a high-throughput qPCR method. The LBW men were more insulin resistant as determined by the HOMA-IR index. There was no difference in telomere length between LBW and NBW subjects. When adjusting for birth weight and cohort effect, significant negative associations between telomere length and fasting glucose (P = 0.003) and HbA1c (P = 0.0008) were found. In conclusion, no significant difference in telomere length was found between LBW and NBW men. The telomere length was negatively associated with glucose concentrations and HbA1c levels within the normal non-diabetic range independent of birth weight.

Impact of Liraglutide on Amylase, Lipase, and Acute Pancreatitis in Participants With Overweight/Obesity and Normoglycemia, Prediabetes, or Type 2 Diabetes: Secondary Analyses of Pooled Data From the SCALE Clinical Development Program

OBJECTIVE

To describe amylase/lipase activity levels and events of acute pancreatitis (AP) in the SCALE (Satiety and Clinical Adiposity-Liraglutide Evidence in individuals with and without diabetes) weight-management trials.

RESEARCH DESIGN AND METHODS

Secondary analyses were performed on pooled data from four trials (N = 5,358 with BMI ≥30, or 27 to <30 kg/m² with ≥1 comorbidity). Of these, 1,723 had normoglycemia, 2,789 had prediabetes, and 846 had type 2 diabetes. Participants were randomized to liraglutide 3.0 mg (n = 3,302), liraglutide 1.8 mg (n = 211, only type 2 diabetes), or placebo (n = 1,845). Relationships between baseline characteristics and amylase/lipase activity at baseline and during treatment were investigated.

RESULTS

Over 56 weeks, liraglutide 3.0 mg versus placebo was associated with increases in mean levels of 7% (amylase) and 31% (lipase), respectively. Similar changes in amylase/lipase levels were observed with liraglutide 1.8 mg. More participants receiving liraglutide 3.0 mg versus placebo experienced amylase (9.4% vs. 5.9%) and lipase (43.5% vs. 15.1%) elevations greater than or equal to the upper limit of normal (ULN); few had elevations ≥3 × ULN for amylase (<0.1% with liraglutide 3.0 mg or placebo) or lipase (2.9% vs. 1.5%, respectively). After liraglutide discontinuation, enzymes returned to baseline levels. Thirteen participants developed AP: 12 on (n = 9, 0.3%) or after (n = 3, 0.1%) liraglutide 3.0 mg treatment and one (0.1%) with placebo. A total of 6/13 participants with AP (5/12 liraglutide; 1 placebo) had gallstone disease evident at AP onset. Amylase/lipase elevations either 1 × ULN or ≥3 × ULN before AP onset had very low positive predictive value for AP (<1%).

CONCLUSIONS

Liraglutide resulted in dose-independent, reversible increases in amylase/lipase activity, unrelated to baseline characteristics, not predicting AP onset. Gallstones possibly contributed to 50% of AP cases. Data provide no basis for amylase/lipase level monitoring in liraglutide treatment except in suspected AP.

Liraglutide 3.0 mg for weight management: weight-loss dependent and independent effects

OBJECTIVE

As an adjunct to a reduced-calorie diet and increased physical activity, treatment with liraglutide 3.0 mg for weight management provides a statistically significant and clinically meaningful weight loss of 5.7%-8.0% compared to 1.6%-2.6% with placebo. The objective of this post hoc analysis was to quantify the relative contribution of weight loss to the treatment effects of liraglutide 3.0 mg on key efficacy endpoints.

METHODS

The analysis utilized data from 4725 participants across three randomized, placebo-controlled, double-blind trials that evaluated the efficacy and safety of liraglutide 3.0 mg versus placebo, as an adjunct to a reduced-calorie diet and increased physical activity (ClinicalTrials.gov identifiers: NCT01272219, NCT01272232 and NCT01557166). The duration of two of the trials was 56 weeks; one trial was of 32 weeks' duration. A mediation analysis was performed, which ranked the relative contribution of weight loss to the treatment effects of liraglutide 3.0 mg on key cardiometabolic efficacy endpoints, Apnea-Hypopnea Index (AHI) and health-related quality of life (QoL). A limitation of this type of analysis is that it cannot conclusively prove a causal relationship.

RESULTS

In individuals without type 2 diabetes mellitus (T2DM), endpoints predominantly driven by liraglutide-induced weight loss included waist circumference, diastolic blood pressure, triglycerides, high density lipoprotein cholesterol, AHI, and Impact of Weight on Quality of Life-Lite total and physical function scores. Endpoints predominantly independent of weight loss included the glycemic endpoints hemoglobin A1c and fasting plasma glucose in individuals with and without T2DM. Regardless of the degree of dependence on weight loss according to the mediation analysis, greater weight loss was associated with greater improvement in all endpoints.

CONCLUSION

Treatment with liraglutide 3.0 mg contributes to improved cardiometabolic parameters, AHI and health-related QoL through both weight-loss dependent and weight-loss independent mechanisms.

Liraglutide 3.0 mg for Weight Management: A Population Pharmacokinetic Analysis

BACKGROUND AND OBJECTIVES

This analysis used a population pharmacokinetic approach to identify covariates that influence plasma exposure of liraglutide 3.0 mg, a glucagon-like peptide-1 (GLP-1) receptor agonist approved for weight management in overweight and obese individuals.

METHODS

Samples for pharmacokinetic analysis were drawn at weeks 2, 12 and 28 of the phase IIIa SCALE Obesity and Prediabetes (N = 2339) and SCALE Diabetes (N = 584) trials. Dose proportionality of liraglutide in obese subjects was investigated using data from a phase II dose-finding study (N = 331).

RESULTS

Dose-proportional exposure of liraglutide up to and including 3.0 mg was confirmed. Body weight and sex influenced exposure of liraglutide 3.0 mg, while age ≥70 years, race, ethnicity and baseline glycaemic status did not. Compared with a reference subject weighing 100 kg, exposure of liraglutide 3.0 mg was 44 % lower for a subject weighing 234 kg (90 % CI 41-47), 41 % higher for a subject weighing 60 kg (90 % CI 37-46), and 32 % higher (90 % CI 28-35) in females than males with the same body weight. Neither injection site nor renal function significantly influenced exposure of liraglutide 3.0 mg (post hoc analysis).

CONCLUSION

Population pharmacokinetics of liraglutide up to and including 3.0 mg daily in overweight and obese adults demonstrated dose-proportional exposure, and limited effect of covariates other than sex and body weight. These findings were similar to those previously observed with liraglutide up to 1.8 mg in subjects with type 2 diabetes mellitus. Further analysis of exposure-response relationship and its effect on dose requirements is addressed in a separate publication.

A Phase 2, Randomized, Dose-Finding Study of the Novel Once-Weekly Human GLP-1 Analog, Semaglutide, Compared With Placebo and Open-Label Liraglutide in Patients With Type 2 Diabetes

OBJECTIVE

To investigate the dose-response relationship of semaglutide versus placebo and open-label liraglutide in terms of glycemic control in patients with type 2 diabetes.

RESEARCH DESIGN AND METHODS

This was a 12-week, randomized, double-blind phase 2 trial. Patients (n = 415) were randomized to receive a subcutaneous injection of semaglutide once weekly without dose escalation (0.1-0.8 mg) or with dose escalation (E) (0.4 mg steps to 0.8 or 1.6 mg E over 1-2 weeks), open-label liraglutide once daily (1.2 or 1.8 mg), or placebo. The primary end point was change in HbA1c level from baseline. Secondary end points included change in body weight, safety, and tolerability.

RESULTS

Semaglutide dose-dependently reduced the level of HbA1c from baseline (8.1 ± 0.8%) to week 12 by up to -1.7%, and body weight by up to -4.8 kg (1.6 mg E, P < 0.001 vs. placebo). Up to 81% of patients achieved an HbA1c level of <7%. HbA1c level and weight reductions with semaglutide 1.6 mg E were greater than those with liraglutide 1.2 and 1.8 mg (based on unadjusted CIs), but adverse events (AEs) and withdrawals occurred more frequently. The incidence of nausea, vomiting, and withdrawal due to gastrointestinal AEs increased with the semaglutide dose; most events were mild to moderate, transient, and ameliorated by dose escalation. There were no major episodes of hypoglycemia and few cases of injection site reactions.

CONCLUSIONS

After 12 weeks, semaglutide dose-dependently reduced HbA1c level and weight in patients with type 2 diabetes. No unexpected safety or tolerability concerns were identified; gastrointestinal AEs typical of glucagon-like peptide 1 receptor agonists were mitigated by dose escalation. On this basis, weekly semaglutide doses of 0.5 and 1.0 mg with a 4-week dose escalation were selected for phase 3.

Semaglutide, a once-weekly human GLP-1 analog, does not reduce the bioavailability of the combined oral contraceptive, ethinylestradiol/levonorgestrel

The effect of semaglutide, a once-weekly human glucagon-like peptide-1 (GLP-1) analog in development for type 2 diabetes (T2D), on the bioavailability of a combined oral contraceptive was investigated. Postmenopausal women with T2D (n = 43) on diet/exercise ± metformin received ethinylestradiol (0.03 mg)/levonorgestrel (0.15 mg) once daily for 8 days before (semaglutide-free) and during (steady-state 1.0 mg) semaglutide treatment (subcutaneous once weekly; dose escalation: 0.25 mg 4 weeks; 0.5 mg 4 weeks; 1.0 mg 5 weeks). Bioequivalence of oral contraceptives was established if 90%CI for the ratio of pharmacokinetic parameters during semaglutide steady-state and semaglutide-free periods was within prespecified limits (0.80-1.25). The bioequivalence criterion was met for ethinylestradiol area under the curve (AUC0-24 h ) for semaglutide steady-state/semaglutide-free; 1.11 (1.06-1.15). AUC0-24 h was 20% higher for levonorgestrel at semaglutide steady-state vs. semaglutide-free (1.20 [1.15-1.26]). Cmax was within bioequivalence criterion for both contraceptives. Reductions (mean ± SD) in HbA1c (-1.1 ± 0.6%) and weight (-4.3 ± 3.1 kg) were observed. Semaglutide pharmacokinetics were compatible with once-weekly dosing; the semaglutide dose and dose-escalation regimen were well tolerated. Adverse events, mainly gastrointestinal, were mild to moderate in severity. Asymptomatic increases in mean amylase and lipase were observed. Three subjects had elevated alanine aminotransferase levels ≥3x the upper limit of normal during semaglutide/oral contraceptive coadministration, which were reported as adverse events, but resolved during follow-up. Semaglutide did not reduce the bioavailability of ethinylestradiol and levonorgestrel.

Increased nocturnal fat oxidation in young healthy men with low birth weight: results from 24-h whole-body respiratory chamber measurements

OBJECTIVE

Low birth weight (LBW), a marker of disturbed fetal growth, is associated with adiposity and increased risk of type 2 diabetes (T2D). The aim of the study was to investigate whether LBW is associated with changes in 24-h energy expenditure (EE) and/or substrate utilization rates, potentially contributing to the development of adiposity and/or T2D compared to matched control subjects.

MATERIALS/METHODS

Forty-six young, healthy men were included in the study; 20 with LBW (≤ 10th percentile) and 26 control subjects with normal birth weight (NBW) (50th-90th percentile). The subjects were fed a weight maintenance diet and 24-h energy expenditure (EE), respiratory quotient (RQ), and substrate oxidation were assessed in a respiratory chamber.

RESULTS

No differences in 24-h EE, RQ or substrate oxidation were observed between LBW and controls. Interestingly, the LBW group exhibited lower nocturnal RQ compared to controls (0.81 ± 0.01 vs. 0.85 ± 0.01 (mean ± SE), P = 0.01), and hence higher nocturnal fat oxidation (2.55 ± 0.13 vs. 2.09 ± 0.12 kJ/min (mean ± SE), P = 0.02).

CONCLUSIONS

Young LBW men do not exhibit reductions in 24-h EE. However, LBW subjects display increased nocturnal fat oxidation at the expense of reduced glucose oxidation. We speculate that this may be associated with insufficient capability to retain fat in subcutaneous adipose tissue after meals during day time, with an increased rate of nocturnal and morning lipolysis, and potentially with subtle elevations of gluconeogenesis and of fasting glucose levels in the LBW subjects.

Deoxyribonucleic acid methylation and gene expression of PPARGC1A in human muscle is influenced by high-fat overfeeding in a birth-weight-dependent manner

CONTEXT

Low birth weight (LBW) and unhealthy diets are risk factors of metabolic disease including type 2 diabetes (T2D). Genetic, nongenetic, and epigenetic data propose a role of the key metabolic regulator peroxisome proliferator-activated receptor gamma, coactivator 1alpha (PPARGC1A) in the development of T2D.

OBJECTIVE

Our objective was to investigate gene expression and DNA methylation of PPARGC1A and coregulated oxidative phosphorylation (OXPHOS) genes in LBW and normal birth weight (NBW) subjects during control and high-fat diets. DESIGN, SUBJECTS, AND MAIN OUTCOME MEASURES: Twenty young healthy men with LBW and 26 matched NBW controls were studied after 5 d high-fat overfeeding (+50% calories) and after a control diet in a randomized manner. Hyperinsulinemic-euglycemic clamps were performed and skeletal muscle biopsies excised. DNA methylation and gene expression were measured using bisulfite sequencing and quantitative real-time PCR, respectively.

RESULTS

When challenged with high-fat overfeeding, LBW subjects developed peripheral insulin resistance and reduced PPARGC1A and OXPHOS (P < 0.05) gene expression. PPARGC1A methylation was significantly higher in LBW subjects (P = 0.0002) during the control diet. However, PPARGC1A methylation increased in only NBW subjects after overfeeding in a reversible manner. DNA methylation of PPARGC1A did not correlate with mRNA expression.

CONCLUSIONS

LBW subjects developed peripheral insulin resistance and decreased gene expression of PPARGC1A and OXPHOS genes when challenged with fat overfeeding. The extent to which our finding of a constitutively increased DNA methylation in the PPARGC1A promoter in LBW subjects may contribute needs to be determined. We provide the first experimental support in humans that DNA methylation induced by overfeeding is reversible.

Consequences of low birthweight on urinary excretion of DNA markers of oxidative stress in young men

OBJECTIVE

Low birthweight (LBW) has been associated with an increased risk of development of type 2 diabetes in adult life. Both type 1 and type 2 diabetes mellitus are characterized by increased oxidative stress. The purpose of this study was to investigate whether young healthy adults born with LBW showed differences in oxidative stress under normal conditions and during the added challenge of a physiological Intralipid infusion.

MATERIAL AND METHODS

Urinary excretion of DNA markers of oxidative stress were analyzed by LC-MS/MS in 19 men (aged 19 years) with LBW and in 19 age matched, normal birthweight (NBW) controls pre- and post a 3-fold increase of plasma free fatty acids.

RESULTS

Mean excretion rates of 8-oxo-guanine (8oxoGua), 8-oxo-guanosine (8oxoGuo), 8-oxo-2'deoxyguanosine (8oxodG), and 1,N6-ethenodeoxyadenosine (epsilon dA) did not statistically differ between subjects with LBW and NBW (66.9 versus 73.9 nmol/15 h, 17.8 versus 18.5 nmol/15 h, 11.9 versus 14.4 nmol/15 h and 44.0 versus 43.2 pmol/15 h, respectively). Furthermore, Intralipid infusion did not affect excretion of DNA adducts in LBW or NBW subjects. Statistically significant correlations were found between body mass index and urinary excretion of 8oxoGua (r = 0.64, p = 0.003) and 8oxoGuo (r = 0.64, p = 0.003) in the LBW group only.

CONCLUSIONS

These findings suggest that oxidative stress may be a consequence of diabetes and is not, or at least only partly, involved in the early pathogenesis of type 2 diabetes.

The T allele of rs7903146 TCF7L2 is associated with impaired insulinotropic action of incretin hormones, reduced 24 h profiles of plasma insulin and glucagon, and increased hepatic glucose production in young healthy men

AIMS/HYPOTHESIS

We studied the physiological, metabolic and hormonal mechanisms underlying the elevated risk of type 2 diabetes in carriers of TCF7L2 gene.

METHODS

We undertook genotyping of 81 healthy young Danish men for rs7903146 of TCF7L2 and carried out various beta cell tests including: 24 h glucose, insulin and glucagon profiles; OGTT; mixed meal test; IVGTT; hyperglycaemic clamp with co-infusion of glucagon-like peptide (GLP)-1 or glucose-dependent insulinotropic polypeptide (GIP); and a euglycaemic-hyperinsulinaemic clamp combined with glucose tracer infusion to study hepatic and peripheral insulin action.

RESULTS

Carriers of the T allele were characterised by reduced 24 h insulin concentrations (p < 0.05) and reduced insulin secretion relative to glucose during a mixed meal test (beta index: p < 0.003), but not during an IVGTT. This was further supported by reduced late-phase insulinotropic action of GLP-1 (p = 0.03) and GIP (p = 0.07) during a 7 mmol/l hyperglycaemic clamp. Secretion of GLP-1 and GIP during the mixed meal test was normal. Despite elevated hepatic glucose production, carriers of the T allele had significantly reduced 24 h glucagon concentrations (p < 0.02) suggesting altered alpha cell function.

CONCLUSIONS/INTERPRETATION

Elevated hepatic glucose production and reduced insulinotropic effect of incretin hormones contribute to an increased risk of type 2 diabetes in carriers of the rs7903146 risk T allele of TCF7L2.

Impact of short-term high-fat feeding on glucose and insulin metabolism in young healthy men

A high-fat, high-calorie diet is associated with obesity and type 2 diabetes. However, the relative contribution of metabolic defects to the development of hyperglycaemia and type 2 diabetes is controversial. Accumulation of excess fat in muscle and adipose tissue in insulin resistance and type 2 diabetes may be linked with defective mitochondrial oxidative phosphorylation. The aim of the current study was to investigate acute effects of short-term fat overfeeding on glucose and insulin metabolism in young men. We studied the effects of 5 days' high-fat (60% energy) overfeeding (+50%) versus a control diet on hepatic and peripheral insulin action by a hyperinsulinaemic euglycaemic clamp, muscle mitochondrial function by (31)P magnetic resonance spectroscopy, and gene expression by qrt-PCR and microarray in 26 young men. Hepatic glucose production and fasting glucose levels increased significantly in response to overfeeding. However, peripheral insulin action, muscle mitochondrial function, and general and specific oxidative phosphorylation gene expression were unaffected by high-fat feeding. Insulin secretion increased appropriately to compensate for hepatic, and not for peripheral, insulin resistance. High-fat feeding increased fasting levels of plasma adiponectin, leptin and gastric inhibitory peptide (GIP). High-fat overfeeding increases fasting glucose levels due to increased hepatic glucose production. The increased insulin secretion may compensate for hepatic insulin resistance possibly mediated by elevated GIP secretion. Increased insulin secretion precedes the development of peripheral insulin resistance, mitochondrial dysfunction and obesity in response to overfeeding, suggesting a role for insulin per se as well GIP, in the development of peripheral insulin resistance and obesity.

Altered PI3-kinase/Akt signalling in skeletal muscle of young men with low birth weight

BACKGROUND

Low birth weight (LBW) is associated with increased future risk of insulin resistance and type 2 diabetes mellitus. The underlying molecular mechanisms remain poorly understood. We have previously shown that young LBW men have reduced skeletal muscle expression of PI3K p85alpha regulatory subunit and p110beta catalytic subunit, PKCzeta and GLUT4 in the fasting state. The aim of this study was to determine whether insulin activation of the PI3K/Akt and MAPK signalling pathways is altered in skeletal muscle of young adult men with LBW.

METHODS

Vastus lateralis muscle biopsies were obtained from 20 healthy 19-yr old men with BW< or = 10th percentile for gestational age (LBW) and 20 normal birth weight controls (NBW), matched for physical fitness and whole-body glucose disposal, prior to (fasting state) and following a 4-hr hyperinsulinemic euglycemic clamp (insulin stimulated state). Expression and phosphorylation of selected proteins was determined by Western blotting.

PRINCIPAL FINDINGS

Insulin stimulated expression of aPKCzeta (p<0.001) and Akt1 (p<0.001) was decreased in muscle of LBW men when compared to insulin stimulated controls. LBW was associated with increased insulin stimulated levels of IRS1 (p<0.05), PI3K p85alpha (p<0.001) and p110beta (p<0.05) subunits, while there was no significant change in these proteins in insulin stimulated control muscle. In addition LBW had reduced insulin stimulated phospho-Akt (Ser 473) (p<0.01), indicative of reduced Akt signalling. Insulin stimulated expression/phosphorylation of all the MAPK proteins studied [p38 MAPK, phospho-p38 MAPK (Thr180/Tyr182), phospho-ERK (Thr 202/Tyr204), JNK1, JNK2 and phospho-JNK (Thr 183/Tyr185)] was not different between groups.

CONCLUSIONS

We conclude that altered insulin activation of the PI3K/Akt but not the MAPK pathway precedes and may contribute to development of whole-body insulin resistance and type 2 diabetes in men with LBW.

Mitochondrial function in skeletal muscle is normal and unrelated to insulin action in young men born with low birth weight

OBJECTIVE

Low birth weight (LBW) is an independent risk factor of insulin resistance and type 2 diabetes. Recent studies suggest that mitochondrial dysfunction and impaired expression of genes involved in oxidative phosphorylation (OXPHOS) may play a key role in the pathogenesis of insulin resistance in aging and type 2 diabetes. The aim of this study was to determine whether LBW in humans is associated with mitochondrial dysfunction in skeletal muscle.

METHODS

Mitochondrial capacity for ATP synthesis was assessed by (31)phosphorus magnetic resonance spectroscopy in forearm and leg muscles in 20 young, lean men with LBW and 26 matched controls. On a separate day, a hyperinsulinemic euglycemic clamp with excision of muscle biopsies and dual-energy x-ray absorptiometry scanning was performed. Muscle gene expression of selected OXPHOS genes was determined by quantitative real-time PCR.

RESULTS

The LBW subjects displayed a variety of metabolic and prediabetic abnormalities, including elevated fasting blood glucose and plasma insulin levels, reduced insulin-stimulated glycolytic flux, and hepatic insulin resistance. Nevertheless, in vivo mitochondrial function was normal in LBW subjects, as was the expression of OXPHOS genes.

CONCLUSIONS

These data support and expand previous findings of abnormal glucose metabolism in young men with LBW. In addition, we found that the young, healthy men with LBW exhibited hepatic insulin resistance. However, the study does not support the hypothesis that muscle mitochondrial dysfunction per se is the underlying key metabolic defect that explains or precedes whole body insulin resistance in LBW subjects at risk for developing type 2 diabetes.

Altered skeletal muscle fiber composition and size precede whole-body insulin resistance in young men with low birth weight

CONTEXT

Low birth weight (LBW), a surrogate marker of an adverse fetal milieu, is linked to muscle insulin resistance, impaired insulin-stimulated glycolysis, and future risk of type 2 diabetes. Skeletal muscle mass, fiber composition, and capillary density are important determinants of muscle function and metabolism, and alterations have been implicated in the pathogenesis of insulin resistance.

OBJECTIVE

The aim of this study was to investigate whether an adverse fetal environment (LBW) induces permanent changes in skeletal muscle morphology, which may contribute to the dysmetabolic phenotype associated with LBW.

DESIGN AND SUBJECTS

Vastus lateralis muscle was obtained by percutaneous biopsy from 20 healthy 19-yr-old men with birth weights at 10th percentile or lower for gestational age (LBW) and 20 normal birth weight controls, matched for body fat, physical fitness, and whole-body glucose disposal. Myofibrillar ATPase staining was used to classify muscle fibers as type I, IIa, and IIx (formerly type IIb), and double immunostaining was performed to stain capillaries (LBW, n=8; normal birth weight, n=12).

RESULTS

LBW was associated with increased proportion of type IIx fibers (+66%; P=0.03), at the expense of decreased type IIa fibers (-22%; P=0.003). No significant change was observed in proportion of type I fibers (+16%; P=0.11). In addition, mean area of type IIa fibers was increased (+29%; P=0.01) and tended to be increased for type I fibers as well (+17%; P=0.08). Capillary density was not significantly different between groups.

CONCLUSION

Alterations in fiber composition and size may contribute to development of type 2 diabetes in individuals with LBW.

Decreased protein levels of key insulin signalling molecules in adipose tissue from young men with a low birthweight: potential link to increased risk of diabetes?

AIMS/HYPOTHESIS

Individuals with low birthweight are at increased risk of type 2 diabetes mellitus. However, the underlying molecular mechanisms are unknown. Previously we have shown that low birthweight is associated with changes in muscle insulin signalling proteins. Here we determined whether low birthweight is associated with changes in insulin signalling proteins in adipose tissue.

METHODS

Men (age 23 years) with either a low (bottom 10th percentile) (n = 17) or a normal (50th-90th percentile) (n = 17) birthweight were recruited from the Danish Medical Birth Registry and subcutaneous adipose biopsies were taken.

RESULTS

Between the two groups there was no difference in protein level of the insulin receptor, protein kinase C zeta, glycogen synthase kinase-3 (GSK3) alpha, GSK3 beta, protein kinase B alpha and beta, peroxisome proliferative activated receptor gamma coactivator 1 or Src-homology-2-containing protein. However, the levels of GLUT4 (also known as solute carrier family 2 [facilitated glucose transporter], member 4 [SLC2A4]) (52 +/- 10.9% reduction, p < 0.01), p85alpha subunit of phosphoinositide 3-kinase (PI3K) (45 +/- 9% reduction, p < 0.01), p110ss subunit of PI3K (48 +/- 17% reduction, p = 0.06) and IRS1 (59 +/- 24% reduction, p < 0.05) were reduced in men of low birthweight.

CONCLUSIONS/INTERPRETATION

These findings show that low birthweight is associated with reduced levels of adipose insulin signalling proteins, thus providing a potential molecular framework to explain why people with low birthweight are at increased risk of developing type 2 diabetes. These differences precede the development of diabetes and thus may help predict disease risk.

Young, low-birth-weight men are not more susceptible to the diabetogenic effects of a prolonged free fatty acid exposure than matched controls

Low birth weight (LBW) is associated with increased risk of developing type 2 diabetes later in life. Progression from normal to impaired glucose tolerance and overt diabetes may depend, to some extent, on elevation of plasma free fatty acids (FFAs). We undertook this study to elucidate whether a prolonged physiological lipid load could unmask or augment existing metabolic defects in otherwise healthy young LBW subjects. Forty 19-year-old men (LBW [n = 20], controls [normal birth weight, NBW] [n = 20]) without a family history of diabetes underwent an intravenous glucose tolerance test (0.3 g kg(-1)), followed by 2-step hyperinsulinemic-euglycemic clamps (2 x 120 minutes: 10 and 40 mU m(-2) min(-1)) in combination with [3-3H]-glucose and indirect calorimetry. The tests were preceded, in randomized order, by a 24-hour continuous intralipid (20%, 0.4 mg mL(-1) h(-1)) or saline infusion. Estimates of cellular glucose metabolism were obtained and a disposition index calculated. Clamp FFA concentrations were 4- to ten-fold higher during lipid infusion. Both groups experienced a similar decrease in insulin-stimulated glucose disposal in response to lipid infusion (approximately 15%; P < .05), which was mainly accounted for by reduced glucose oxidation (approximately 30%; P < .001). Glycolysis, glucose storage, and glucose production were not significantly altered by lipid infusion. Nevertheless, the LBW group had significantly lower insulin-stimulated glycolysis during lipid infusion (approximately 27%; P < .05) than the NBW group. An appropriate increase in insulin secretion matched the decline in insulin sensitivity in both groups. A 24-hour low-grade intralipid infusion has similar effects on whole-body glucose metabolism and first-phase insulin secretion in 19-year-old, healthy, lean, LBW men with normal glucose tolerance and in NBW controls. We reproduced our previous finding of lower insulin-stimulated glycolysis in this population.

Normal secretion and action of the gut incretin hormones glucagon-like peptide-1 and glucose-dependent insulinotropic polypeptide in young men with low birth weight

CONTEXT

Low birth weight (LBW) is associated with increased risk of type 2 diabetes mellitus. An impaired incretin effect was reported previously in type 2 diabetic patients.

OBJECTIVE

We studied the secretion and action of glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) in young LBW men (n = 24) and matched normal birth weight controls (NBW) (n = 25).

RESULTS

LBW subjects were 5 cm shorter but had a body mass index similar to NBW. LBW subjects had significantly elevated fasting and postprandial plasma glucose, as well as postprandial (standard meal test) plasma insulin and C-peptide concentrations, suggestive of insulin resistance. Insulin secretion in response to changes in glucose concentration ("beta-cell responsiveness") during the meal test was similar in LBW and NBW but inappropriate in LBW relative to insulin sensitivity. Fasting and postprandial plasma GLP-1 and GIP levels were similar in the groups. First- and second-phase insulin responses were similar in LBW and NBW during a hyperglycemic clamp (7 mm) with infusion of GLP-1 or GIP, respectively, demonstrating normal action of these hormones on insulin secretion.

CONCLUSION

Reduced secretion or action of GLP-1 or GIP does not explain a relative reduced beta-cell responsiveness to glucose or the slightly elevated plasma glucose concentrations observed in young LBW men.

Low birthweight is associated with specific changes in muscle insulin-signalling protein expression

AIMS/HYPOTHESIS

People with low birthweight have an increased risk of developing type 2 diabetes mellitus in adulthood. The mechanistic basis of this phenomenon is not known. Here we investigate the effect of early growth restriction on the expression of insulin-signalling proteins in skeletal muscle in a human cohort and a rat model.

METHODS

We recruited 20 young men with low birthweight (mean birthweight 2702+/-202 g) and 20 age-matched control subjects (mean birthweight 3801+/-99 g). Biopsies were obtained from the vastus lateralis muscle and protein expression of selected insulin-signalling proteins was determined. Rats used for this study were male offspring born to dams fed a standard (20%) protein diet or a low (8%) protein diet during pregnancy and lactation. Protein expression was determined in soleus muscle from adult offspring.

RESULTS

Low-birthweight subjects showed reduced muscle expression of protein kinase C (PKC)zeta, p85alpha, p110beta and GLUT4. PKCzeta, GLUT4 and p85 were also reduced in the muscle of rats fed a low-protein diet. Other proteins studied were unchanged in low-birthweight humans and in rats fed a low-protein diet when compared with control groups.

CONCLUSIONS/INTERPRETATION

We found decreased expression of specific insulin-signalling proteins in low-birthweight subjects compared to controls. These changes precede the onset of impaired glucose tolerance. The similarity of protein expression profile in the men with low birthweight compared to that of the offspring of rats fed a low-protein diet suggests that the rodent model is an accurate representation of the human situation. It also provides a potential mechanistic explanation as to why the fetal environment plays an important role in determining risk of developing type 2 diabetes.

Dissociation between fat-induced in vivo insulin resistance and proximal insulin signaling in skeletal muscle in men at risk for type 2 diabetes

The effect of short- (2 h) and long-term (24 h) low-grade Intralipid infusion on whole-body insulin action, cellular glucose metabolism, and proximal components of the insulin signal transduction cascade was studied in seven obese male glucose intolerant first degree relatives of type 2 diabetic patients [impaired glucose tolerance (IGT) relatives] and eight matched control subjects. Indirect calorimetry and excision of vastus lateralis skeletal muscle biopsies were performed before and during hyperinsulinemic euglycemic clamps combined with 3[(3)H]glucose. Clamps were performed after 0, 2, or 24 h Intralipid infusion (0.4 ml.kg(-1).min(-1)). Insulin-stimulated glucose disposal decreased approximately 25% after short- and long-term fat infusion in both IGT relatives and controls. Glucose oxidation decreased and lipid oxidation increased after both short- and long-term fat infusion in both groups. Insulin-stimulated glucose oxidation was higher after long-term as compared with short-term fat infusion in control subjects. Short- or long-term infusion did not affect the absolute values of basal or insulin-stimulated insulin receptor substrate-1 tyrosine phosphorylation, tyrosine-associated phosphoinositide 3-kinase (PI 3-kinase) activity, insulin receptor substrate-1-associated PI 3-kinase activity, or Akt serine phosphorylation in IGT relatives or matched controls. In fact, a paradoxical increase in both basal and insulin-stimulated PI 3-kinase activity was noted in the total study population after both short- and long-term fat infusion. Short- and long-term low-grade Intralipid infusion-induced (or enhanced) whole-body insulin resistance and impaired glucose metabolism in IGT relatives and matched control subjects. The fat-induced metabolic changes were not explained by impairment of the proximal insulin signaling transduction in skeletal muscle.

Insulin secretion after short- and long-term low-grade free fatty acid infusion in men with increased risk of developing type 2 diabetes

We studied the effect of a low-grade short- and long-term 20% Intralipid infusion (0.4 mL(-1) x kg(-1) x h(-1)) on insulin secretion and insulin action in 15 elderly obese men; 7 glucose intolerant first-degree relatives of type 2 diabetic patients (impaired glucose tolerance [IGT] relatives) and 8 healthy controls of similar age and body mass index (BMI). Intravenous glucose tolerance test (IVGTT) and a graded glucose infusion (dose-response test [DORE]) were performed to determine first phase insulin response and to explore the dose response relationship between glucose concentration and insulin secretion rates (ISR). ISR were calculated by deconvolution of plasma C-peptide concentrations. Insulin action was determined by performing a 120-minute hyperinsulinemic euglycemic clamp. All tests were performed 3 times, preceded by 0, 2, or 24 hours Intralipid infusion. Disposition indices (DI) were calculated for the IVGTT. Insulin action was reduced 25% after 2 and 24 hours Intralipid infusion in both groups. In IGT relatives, the beta-cell responsiveness to glucose (measured during DORE) decreased after 2 and 24 hours Intralipid infusion (P=.02), whereas first phase insulin response (measured during IVGTT) decreased after 24 hours Intralipid infusion. Insulin secretion measured during DORE and IVGTT was not affected by Intralipid infusion in controls. DI decreased after 2 and 24 hours Intralipid infusion in the total study population. In conclusion, insulin resistance induced by low-grade short- and long-term Intralipid infusion is not balanced by an adequate compensatory increase in insulin secretion in IGT relatives or in matched controls. IGT relatives appear to be more sensitive to the deleterious effects of low-grade fat infusion on insulin secretion than normal glucose tolerant control subjects.

Insulin secretion and cellular glucose metabolism after prolonged low-grade intralipid infusion in young men

We examined the simultaneous effects of a 24-h low-grade Intralipid infusion on peripheral glucose disposal, intracellular glucose partitioning and insulin secretion rates in twenty young men, by 2-step hyperinsulinemic euglycemic clamp [low insulin clamp (LI), 10 mU/m(2) x min; high insulin clamp (HI), 40 mU/m(2) x min], 3-(3)H-glucose, indirect calorimetry, and iv glucose tolerance test. Free fatty acid concentrations were similar during basal steady state but 3.7- to 13-fold higher during clamps. P-glucagon increased and the insulin/glucagon ratio decreased at both LI and HI during Intralipid infusion. At LI, glucose oxidation decreased by 10%, whereas glucose disposal, glycolytic flux, glucose storage, and glucose production were not significantly altered. At HI, glucose disposal, and glucose oxidation decreased by 12% and 24%, respectively, during Intralipid infusion. Glycolytic flux, glucose storage, and glucose production were unchanged. Insulin secretion rates increased in response to Intralipid infusion, but disposition indices (DI = insulin action.insulin secretion) were unchanged. In conclusion, a 24-h low-grade Intralipid infusion caused insulin resistance in the oxidative (but not in the nonoxidative) glucose metabolism in young healthy men. Moreover, insulin hypersecretion perfectly countered the free-fatty acid-induced insulin resistance. Future studies are needed to determine the role of a prolonged moderate lipid load in subjects at increased risk of developing diabetes.

Normal insulin-stimulated endothelial function and impaired insulin-stimulated muscle glucose uptake in young adults with low birth weight

Low birth weight has been linked to insulin resistance and cardiovascular disease. We hypothesized that insulin sensitivity of both muscle and vascular tissues were impaired in young men with low birth weight. Blood flow was measured by venous occlusion plethysmography during dose-response studies of acetylcholine and sodium nitroprusside in the forearm of fourteen 21-yr-old men with low birth weight and 16 controls of normal birth weight. Glucose uptake was measured during intraarterial insulin infusion. Dose-response studies were repeated during insulin infusion. The maximal blood flow during acetylcholine infusion was 14.1 +/- 2.7 and 14.4 +/- 2.1 [ml x (100 ml forearm)(-1) x min(-1)] in low and normal birth weight subjects, respectively. Insulin coinfusion increased acetylcholine-stimulated flow in both groups: 18.0 +/- 3.1 vs. 17.9 +/- 3.1 [ml x (100 ml forearm)(-1) x min(-1)], NS. Insulin infusion increased glucose uptake significantly in the normal birth weight group, compared with the low birth weight group: 0.40 +/- 0.09 to 1.00 +/- 0.16 vs. 0.44 +/- 0.09 to 0.59 +/- 0.1 [ micro mol glucose x (100 ml forearm)(-1) x min(-1)], P = 0.04. Young men with low birth weight have normal insulin-stimulated endothelial function and impaired insulin-stimulated forearm glucose uptake. Thus, endothelial dysfunction does not necessarily coexist with metabolic alterations in subjects with low birth weight.

The 'Seamless Web': the development of the electronic patient record in Aarhus region, Denmark

OBJECTIVES

The article surveys the organization of the current project to develop an electronic patient record in the Aarhus Region, Denmark.

METHODS

The article is based on various policy documents and reports as well as a number of semi-structured interviews with project managers from the EPR organization in Aarhus County and with participants in the development process at local hospitals. This material is used to present and discuss the framing of the project in a 'discourse coalition'.

RESULTS

The stabilization of a specific discourse coalition has been an important factor in ensuring the success of the development project up to the present moment. This coalition became relatively stable by integrating a diverse set of actors in a story-line about the relationships between co-operation, management and technology in the medial sector, and has influenced the modular organization of the project.

CONCLUSIONS

The successful maintenance of the discourse coalition allows the project to appear 'seamless' from the outside. Conversely, the project is likely to be continually reviewed as successful only to the extent that it is able to flexibly keep the fluctuating set of relevant actors in alignment. If the practical work of keeping a coalition in place remains invisible it becomes easy to imagine an ideal way of planning large socio-technical projects, like developing an ECR. But practical success is more likely to be achieved if one takes seriously the thorough intertwining of discursive, organizational and technical aspects of development projects.

Early differential defects of insulin secretion and action in 19-year-old caucasian men who had low birth weight

Several studies have linked low birth weight (LBW) and type 2 diabetes. We investigated hepatic and peripheral insulin action including intracellular glucose metabolism in 40 19-year-old men (20 LBW, 20 matched control subjects), using the hyperinsulinemic-euglycemic clamp technique at two physiological insulin levels (10 and 40 mU/m(2) per min), indirect calorimetry, and [3-(3)H]glucose. Insulin secretion was examined during an oral and intravenous glucose tolerance test. Fasting p-glucose was higher in the LBW group (5.6 +/- 0.1 vs. 5.4 +/- 0.1; P < 0.05). Basal plasma glycerol concentrations were significantly lower in the LBW group. Insulin-stimulated glycolytic flux was significantly reduced, and suppression of endogenous glucose production was enhanced in the LBW group. Nevertheless, basal and insulin-stimulated rates of whole-body peripheral glucose disposal, glucose oxidation, lipid oxidation, exogenous glucose storage, and nonoxidative glucose metabolism were similar in the two groups. Insulin secretion was reduced by 30% in the LBW group, when expressed relative to insulin sensitivity (disposition index = insulin secretion x insulin action). We propose that reduced insulin-stimulated glycolysis precedes overt insulin resistance in LBW men. A lower insulin secretion may contribute to impaired glucose tolerance and ultimately lead to diabetes.

Insulin signal transduction in skeletal muscle from glucose-intolerant relatives of type 2 diabetic patients [corrected]

To determine whether defects in the insulin signal transduction cascade are present in skeletal muscle from prediabetic individuals, we excised biopsies from eight glucose-intolerant male first-degree relatives of patients with type 2 diabetes (IGT relatives) and nine matched control subjects before and during a euglycemic-hyperinsulinemic clamp. IGT relatives were insulin-resistant in oxidative and nonoxidative pathways for glucose metabolism. In vivo insulin infusion increased skeletal muscle insulin receptor substrate-1 (IRS-1) tyrosine phosphorylation (P = 0.01) and phosphatidylinositide 3-kinase (PI 3-kinase) activity (phosphotyrosine and IRS-1 associated) in control subjects (P < 0.02) but not in IGT relatives (NS). The incremental increase in insulin action on IRS-1 tyrosine phosphorylation was lower in IGT relatives versus control subjects (P < 0.05). The incremental defects in signal transduction noted for IRS-1 and PI 3-kinase may be attributed to elevated basal phosphorylation/activity of these parameters, because absolute phosphorylation/activity under insulin-stimulated conditions was similar between IGT relatives and control subjects. Insulin increased Akt serine phosphorylation in control subjects and IGT relatives, with a tendency for reduced phosphorylation in IGT relatives (P = 0.12). In conclusion, aberrant phosphorylation/activity of IRS-1, PI 3-kinase, and Akt is observed in skeletal muscle from relatives of patients with type 2 diabetes with IGT. However, the elevated basal activity of these signaling intermediates and the lack of a strong correlation between these parameters to glucose metabolism suggests that other defects of insulin signal transduction and/or downstream components of glucose metabolism may play a greater role in the development of insulin resistance in skeletal muscle from relatives of patients with type 2 diabetes.

The effects of antirhino- and enteroviral vinylacetylene benzimidazoles on cytochrome P450 function and hepatic porphyrin levels in mice

In an ongoing effort to identify an orally bioavailable compound for the treatment of rhino- and enteroviral infections, a series of vinylacetylene benzimidazoles was recently examined. Previous studies demonstrated the potential for these compounds to possess both good in vitro antiviral activity as well as acceptable oral plasma concentrations in mice. Optimization of these properties led to four compounds as candidates for further evaluation. In view of the recognized potential for certain acetylenic drugs both to inhibit cytochrome P450 enzymes by mechanism-based inactivation and to possibly perturb heme metabolism, information regarding drug effects on cytochromes P450 and hepatic porphyrin levels was sought. In an initial single-dose pharmacokinetic study, the four selected compounds were given orally to mice, and both plasma concentrations and porphyrin levels were determined. Two of the compounds, 4 and 5, caused a pronounced increase in liver porphyrin levels whereas compounds 6 and 7 exhibited almost no effect on porphyrin levels. Analysis of plasma concentrations showed that only 4 and 5 gave significant exposure and that 6 and 7 produced negligible levels of drug in the plasma even at the highest dose tested (500 mg/kg). A multiple dose study was then initiated in which compounds 4 and 5 were given for 1 week in daily oral doses to mice. Upon completion of dosing, liver was analyzed for cytochrome P450-dependent 7-ethoxyresorufin O-deethylase (EROD) and benzphetamine N-demethylase (BND) activities, total cytochrome P450 content, and porphyrin levels. Both vinylacetylenes showed dose dependent inhibitory and induction effects on EROD and BND activities. In addition, these compounds caused a marked increase in hepatic porphyrin levels. Therefore, while all four selected compounds displayed potent antiviral activity and two of the compounds exhibited acceptable pharmacokinetic properties, the hepatic effects of these latter two compounds suggest the potential for drug induced porphyria with multidose therapeutic use.

Role of lipid peroxidation in dapsone-induced hemolytic anemia

Dapsone hydroxylamine (DDS-NOH) is a direct-acting hemolytic agent responsible for dapsone-induced hemolytic anemia in the rat. The hemolytic activity of DDS-NOH is associated with the formation of disulfide-linked hemoglobin adducts on membrane skeletal proteins. We have postulated that this membrane protein "damage" is a consequence of DDS-NOH-induced oxidative stress within the red cell and that it serves as the trigger for premature removal of injured but intact red cells from the circulation by splenic macrophages. Oxidative stress has also been associated with the induction of lipid peroxidation, and it is possible that direct damage to the lipoidal membrane may play a role in the premature sequestration of the damaged cells in the spleen. To investigate this possibility, rat and human red cells were incubated with hemolytic concentrations of DDS-NOH and examined for evidence of lipid peroxidation using two independent assays: thiobarbituric acid-reactive substances formation and cis-paranaric acid degradation. Phenylhydrazine, which is known to induce lipid peroxidation in red cells, was used as a positive control. The extent of thiobarbituric acid-reactive substances formation and cis-paranaric acid degradation in DDS-NOH-treated rat and human red cells was not significantly different from that in control cells. In contrast, thiobarbituric acid-reactive substances formation and cis-paranaric acid degradation were significantly increased in red cells treated with hemolytic concentrations of the positive control, phenylhydrazine. These data suggest that lipid peroxidation is not involved in the mechanism underlying dapsone-induced hemolytic anemia.

Alterations of the catalytic activities of drug-metabolizing enzymes in cultures of human liver slices

Precision-cut human liver slices are an important tool for defining the metabolism and hepatotoxicity of drug candidates early in development. Because of the frequent use of this in vitro tool, a knowledge of the catalytic activities of the drug-metabolizing enzymes during human liver slice culture is necessary. Therefore, marker catalytic activities for various cytochrome P450 (P450 or CYP) forms, as well as phase II activities (glucuronidation and sulfation of 7-hydroxycoumarin), were measured in slices from three different human livers during 96 hr in culture. Standard viability measures were found to be stable from 8 to 24 hr and then declined to 96 hr. Catalytic activities measured for the P450s were ethoxyresorufin O-deethylase (CYP1A2), coumarin 7-hydroxylase (CYP2A6), (S)-mephenytoin N-demethylase (CYP2B6), diclofenac 4'-hydroxylase (CYP2C9), (S)-mephenytoin 4'-hydroxylase (CYP2C19), bufuralol 1'-hydroxylase (CYP2D6), chlorzoxazone 6-hydroxylase (CYP2E1), and midazolam 1'-hydroxylase (CYP3A). The P450 activities decreased by approximately 20% by 4 hr and by at least 65% by 24 hr and were not measurable by 96 hr. In contrast to the phase I activities, 7-hydroxycoumarin glucuronosyltransferase activity was increased at the 8-hr time point by approximately 100% and then decreased to approximately initial values by 96 hr. The 7-hydroxycoumarin sulfotransferase activity of the slices decreased significantly more slowly than did the P450 activities. In conclusion, using conventional methods of liver slice preparation and culture, most of the metabolic capabilities of human liver slices are rapidly lost with time. Therefore, the development of culture methods for human liver slices that can improve the preservation of the drug-metabolizing capabilities may be required.

In vitro and in vivo ultrastructural changes induced by macrolide antibiotic LY281389

High doses of LY281389 (9-N-(n-propyl)-erythromycylamine) cause cytoplasmic vacuolar changes in striated and smooth muscle characteristic of drug-induced phospholipidosis. This study characterized phospholipidosis in striated and smooth muscle of rats and dogs, compared in vivo observations with those in a cultured rat myoblast model, and attempted to confirm the lysosomal origin of the drug-induced vacuoles. Standard transmission electron microscopy and acid phosphatase cytochemistry techniques were used to evaluate ultrastructural changes in vivo and in vitro. Rats and dogs exposed to LY281389 had a time- and dose-related increase in number and size of vacuoles containing concentric lamellar figures in cardiac and skeletal muscle. Cytochemical staining of dog stomach smooth muscle for acid phosphatase, a lysosomal enzyme, stained the periphery of vacuoles that contained concentric lamellar figures. Cultured rat L6 myoblast cells were exposed to 0.25 mg LY281389/ml for 2.5, 5, 10, 20, 30, or 90 min and 2, 6, 12, 24, or 48 hr. Cell cultures exposed for 2 hr had several predominantly large, clear, membrane-bound vacuoles, and at 6 and 12 hr there were greater numbers of large vacuoles that contained increased amounts of membranous figures. Following 24- or 48-hr exposures, vacuoles occupied most of the cytoplasmic volume, and were engorged predominantly with amorphous or granular material. These findings indicate that LY281389 can induce similar phospholipidosis-like vacuolar changes in rat and dog muscle and in a cultured rat muscle cell line. Further, positive acid phosphatase staining of drug-induced vacuolar structures, in conjunction with standard transmission electron microscopy techniques, strongly suggests that vacuoles seen in vitro and in vivo are lysosomal in origin.

Nafenopin-induced peroxisome proliferation in vitamin A deficient rats

Induction of peroxisome proliferator responsive genes is thought to be mediated through binding of a peroxisome proliferator-activated receptor (PPAR) to specific peroxisome proliferator response elements in the upstream region of these genes. Binding of PPAR to the acyl-CoA oxidase promoter requires heterodimerization with the retinoid X receptor (RXR), and subsequent transactivation is strongest when ligands for both PPAR and RXR are present. Therefore, we hypothesized that depletion of ligand for the retinoid receptor would limit the induction of peroxisome proliferation in rats. Hepatic retinol content was reduced by more than 90% by feeding weanling rats a vitamin A deficient (VAD) diet for approximately 3 months. Nafenopin treatment for 7 days induced peroxisomal beta-oxidation 18-fold in VAD rats compared with 16-fold in rats fed a vitamin A sufficient (VAS) diet. Nafenopin induced microsomal laurate hydroxylase and mitochondrial beta-oxidation to comparable rates of specific activity in both VAD and VAS rats. However, the activities in VAD controls were significantly lower than in VAS controls, so the magnitude of the nafenopin-induced increases was greater in the VAD rats. Relative liver weights were increased nearly 2-fold in both VAS and VAD rats treated with nafenopin. Ultrastructural examination of the livers demonstrated that nafenopin increased the number and size of peroxisomes in both VAD and VAS rats. These data demonstrate that rats with severely depleted vitamin A stores remained responsive to the peroxisome proliferator nafenopin. Whether critical retinoid pools that supply RXR ligand (9-cis-retinoic acid) are spared in the vitamin A deficient rats remains to be determined.

First web space contracture and hand function

We studied 125 normal volunteers to determine the normal first web space angle and to evaluate the influence of thumb-index finger web space contracture on hand function. One hundred ninety-five hands were measured and found to have a mean web space angle of 100 degrees. There was no significant difference in the mean angle in relation to sex or hand dominance. The mean angle was significantly smaller for persons 50 to 79 years of age than for the two younger age groups. Twenty-five normal volunteers (50 hands) took the Jebsen-Taylor test three times: first, with no restrictions; second, with splints simulating a 60-degree web space contracture; and third, with splints simulating a 30-degree contracture. More than half of the volunteers had abnormal small-object subtests. Other abnormal subtests included card turning, feeding, and stacking checkers. Grasping large light and heavy objects was less difficult because of compensatory techniques used by the volunteers.

The role of N-hydroxyphenetidine in phenacetin-induced hemolytic anemia

Phenacetin is well known to cause hemolytic anemia and methemoglobinemia in humans. Early mechanistic studies clearly established a causal role for active/reactive drug metabolites in the process but did not unequivocally identify these metabolite(s) or resolve the question of whether these two hemotoxicities are mechanistically linked. As part of ongoing studies on the mechanism underlying arylamine-induced hemotoxicities, we have recently shown that the arylhydroxylamine metabolites of aniline and dapsone mediate the hemolytic activity of aniline and dapsone, respectively. The present study was undertaken to determine if N-hydroxyphenetidine (PNOH), the known arylhydroxylamine metabolite of phenacetin, is responsible for phenacetin-induced hemolytic anemia. As measured by decreased survival of 51Cr-labeled erythrocytes in rats, phenacetin, p-phenetidine, and PNOH were all hemolytic in vivo, with PNOH being significantly the most potent of the three. In vitro exposure of 51Cr-tagged erythrocytes to PNOH, followed by transfusion into isologous rats, resulted in a concentration-dependent reduction in erythrocyte survival, indicating that PNOH is a direct-acting hemolytic agent. Phenacetin and p-phenetidine were inactive. Phenacetin, p-phenetidine, and PNOH all produced dose-dependent methemoglobinemia in rats. In parallel in vitro studies, PNOH elevated methemoglobin levels, p-phenetidine and phenacetin did not. However, attempts to identify PNOH in the blood of phenacetin- and p-phenetidine-treated rats were unsuccessful, despite the use of a highly sensitive analytical method. Hemotoxic concentrations of PNOH were found to be highly unstable in the presence of red cells, though relatively stable in the buffer vehicle alone. Inhibitors of acetylation (p-aminobenzoic acid [PABA]) and deacetylation (bis-[p-nitrophenyl]phosphate [BNPP]), used to alter the cyclic interconversion of phenacetin and p-phenetidine, caused changes in phenacetin hemotoxicity that indicated the hemotoxin was a deacetylated metabolite distal to p-phenetidine. These data are consistent with the hypothesis that PNOH, formed during the metabolic clearance of phenacetin, mediates phenacetin-induced hemolytic anemia and methemoglobinemia through direct toxic actions in the erythrocyte.

Two ubiquitin-long-tail fusion genes arranged as closely spaced direct repeats in barley

Ubiquitin (Ubi) genes encode two types of fusion proteins: polyUbi with a varying number of direct repeats of Ubi, and Ubi-tail fusions with long or short basic C-terminal extensions. A barley (Hordeum vulgare) genomic clone has been isolated with two very similar, intronless genes encoding monoUbi-long-tail fusion peptides. The genes are arranged as direct repeats separated by 3 kb of DNA and account for two of the probable three long-tail genes in the haploid barley genome. Both genes are active and give rise to messengers about 800 nt long. The sequence of the encoded Ubi moieties is identical to the sequence of Ubi repeats of polyUbi precursors from barley and other plants. The basic tails of the peptides are 79 aa long and 71-72% homologous to corresponding sequences from yeast and man. Recently, it was found that the long and short tails are ribosomal proteins in yeast [Finley et al., Nature 338 (1989) 394-401] and the evolutionary conservation of the structure of the Ubi-tail fusion genes suggests that they serve the same function in plants. The similarity between yeast and barley Ubi-long-tail fusion genes may extend to the regulatory regions, since upstream activating sites characteristic of ribosomal protein-encoding genes in yeast (UASrpg) were found in the barley genes.

Influenza A virus enhances Staphylococcus aureus-induced basophil histamine release in normal individuals and patients with intrinsic asthma

Influenza A virus was found to enhance Staphylococcus aureus-induced histamine release in human leukocyte suspensions, but did not per se release histamine. This potentiating effect was found to be similar in cells from normal individuals and from patients with intrinsic asthma. The enhancement of mediator release could be due to viral neuraminidase on the surface of the virus, since a similar potentiating effect was caused by a purified neuraminidase preparation obtained from Vibrio cholerae, and the effect of virus as well as of the purified neuraminidase was completely abolished by a potent neuraminidase inhibitor. The potentiating effect of virus on bacteria-induced mediator release might be of importance for the conversion from latent to manifest asthma in upper respiratory tract infections.

Virus enhances histamine release from human basophils

Histamine release from human basophil leukocytes was triggered by Staph. aureus or by complement activation caused by endotoxins isolated from E. coli or Salmonella bacteria. Influenza A virus was found to enhance the mediator release and the effect was caused by synergism, since the virus itself did not release histamine. The potentiating effect of the virus was abolished by a potent neuraminidase inhibitor. Furthermore, a purified neuraminidase preparation obtained from Vibrio cholerae caused a similar potentiating effect, which was also abolished by the neuraminidase inhibitor. These findings indicate that the neuraminidase on the surface of influenza A virus is responsible for the potentiating effect of the virus on basophil histamine release.

Influenza A virus potentiates basophil histamine release caused by endotoxin-induced complement activation. Examination of normal individuals and patients with intrinsic asthma

Histamine release from human basophil leukocytes was triggered by complement activation by means of endotoxins isolated from E. coli and Salmonella bacteria. Influenza A virus was found to enhance the mediator release, and the effect was caused by synergism, since virus itself did not release histamine. The potentiating effect was similar in cells from normal individuals and from patients with intrinsic asthma. The involvement of viral neuraminidase was examined by a potent neuraminidase inhibitor and this inhibitor completely abolished the potentiating effect by virus. A purified neuraminidase preparation obtained from Vibrio cholerae caused a similar potentiating effect in mediator release and the effect was abolished by the neuraminidase inhibitor. These findings indicate that viral neuraminidase is responsible for the potentiating effect of virus on the histamine release. This effect might play a role in septic conditions and possibly contribute to asthmatic attacks by infections.

Bacteria and their products peptidoglycan and teichoic acid potentiate antigen-induced histamine release in allergic patients

Histamine release was examined in leukocyte suspensions from patients allergic to grass pollen, mite or cat dander or to bacteria (antigen). When the cells were challenged with specific antigen plus bacteria to which the person was not sensitized, these bacteria were found to potentiate the allergic histamine release. The potentiating effect by bacteria might be due to the bacterial cell wall components, peptidoglycan and teichoic acid, which mimic the effect of bacteria.

Influence of nimodipine, verapamil and lanthanum on histamine release from human basophils: effect of pretreatment with sialidase

Our previous studies suggest that the membrane content of sialic acid influences histamine release from human basophils by interfering with the transmembraneous calcium fluxes preceding histamine release. In this study we investigated a possible interaction between membrane sialic acid and the calcium channels, using the calcium antagonists nimodipine, verapamil and lanthanum. Anti-IgE-induced histamine release was inhibited by verapamil, nimodipine and lanthanum. When cells were pretreated with sialidase in order to remove sialic acid from the cell membrane, the inhibitory action of nimodipine was abolished, whereas the inhibition by verapamil or lanthanum was unaffected. This difference may be explained by the different mode of action of the calcium channel antagonists, and the results suggest an association between membrane sialic acid and the calcium channel.

Determination of liothyronine and levothyroxine in thyroid preparations by liquid chromatography

Liothyronine and levothyroxine were quantitatively determined in samples of commercial thyroid tablets and bulk powders. Samples were first hydrolyzed using a bacterial protease and then analyzed by high-performance liquid chromatography. Various hydrolysis conditions were investigated. The liothyronine and levothyroxine contents of commercial tablets and bulk powders were found to be approximately 8-11 micrograms and 25-43 micrograms, respectively, per 65 mg of thyroid. The stability of the iodothyronines in thyroid tablets was also investigated.

Improved method for determination of cellular thiols, disulfides and protein mixed disulfides using HPLC with electrochemical detection

The role of glutathione in cellular responses to toxic insult is well established in the literature and is largely based on chemical determinations of GSH. Although these methods have proved to be adequate to demonstrate the relationships between cellular levels of GSH and xenobiotic toxicity, they may be inadequate for careful investigations regarding the regulation of cellular concentrations of GSH, GSSG and GSSProt. Enzymatic and chromatographic methods provide increased specificity and sensitivity, but the problems of variable accuracy or tedious derivitization steps remain. The HPLC-EC method constitutes a significant improvement over previous methods by satisfying the requirements for selectivity, sensitivity, accuracy and convenience. The utility of the HPLC-EC method has been described in two systems of toxicological interest, particularly with regard to the determination of GSSProt. In further studies, the HPLC-EC method has been useful in investigating the mechanism(s) of alternate nucleophiles, such as cysteamine. The capability to determine various thiols simultaneously in a given biological sample greatly facilitates these investigations. In view of its power as an analytical tool, the HPLC-EC method has the potential for widespread application to the study of cellular thiols.

Swallowing problems in patients with head and neck cancer:

The restoration of swallowing skills in head and neck cancer surgery patients demands a two-pronged approach: thorough and systematic evaluation and simple, fundamental treatments. Therapists should begin with an assessment of their own biases and their knowledge of head and neck cancer and its surgeries. The patients themselves should be evaluated presurgically-to determine food preferences, other medical conditions, nutritional status, and current swallowing abilities, and postsurgically-to assess facial symmetry, oral mobility and strength, saliva management, aspiration risk, and altered swallowing skills. Treatment approaches should generally be basic, stressing oral exercises, positioning techniques, the use of feeding aids, and teaching the supraglottic swallow. Attention to special considerations, like problems with cuffed tracheostomies and the controversies over using variable food consistencies, will refine the treatment.

Stimulation of mitochondrial functions by glucagon treatment. Evidence that effects are not artifacts of mitochondrial isolation

(1) Activation of rat liver mitochondrial functions following glucagon treatment was demonstrated in mitochondria that had not been isolated by the conventional technique of differential centrifugation and washing in sucrose solutions. Crude liver homogenates in 0.3 M-sucrose or 0.15 M-KCl prepared from rats treated with glucagon showed stimulation of State-3 and uncoupled respiration, carboxylation of pyruvate, and citrulline synthesis comparable with those previously reported in isolated mitochondria. (2) During the isolation procedure of mitochondria the hormonal stimulations of pyruvate carboxylation and citrulline formation were shown not to be enhanced by sequential washing. (3) Mitochondria isolated from glucagon-treated rats by differential centrifugation and washing in 0.3 M-mannitol/1 mM-EGTA, pH 7.0, exhibited a mean rate of citrulline synthesis that was greater than twice that of the control. Liver homogenates prepared in 0.3 M-sucrose or 0.3 M-mannitol showed identical rates of State-3 respiration and percentage stimulations of respiration by glucagon treatment. (4) Addition of glucagon led to a rapid accumulation of malate and aspartate and decreased the amounts of glutamate and citrate in isolated hepatocytes incubated with L-lactate. When gluconeogenesis was inhibited at the phosphoenolpyruvate carboxykinase (EC 4.1.1.32) reaction these phenomena were accentuated, lending support to the interpretation that they are the direct result of stimulation of carboxylation and oxidation reactions in the mitochondria. These results do not support the proposal [Siess, Fahimi & Wieland (1981) Hoppe-Seyler's Z. Physiol. Chem. 362. 1643-1651] that the mitochondrial effects of glucagon treatment result from a stabilization of mitochondria to detrimental effects of sucrose during their isolation. (5) The mean hormonal stimulation of pyruvate carboxylation in mitochondria isolated in 0.3 M-sucrose was shown to be approx. 2.5-fold when assayed either at 37 degrees C or 25 degrees C. In contrast, on the basis of similar experiments, Siess et al. (1981) concluded that the effects of glucagon on hepatic mitochondria are not characteristic of a true hormonal stimulation. Our data indicate this conclusion to be unjustified.