Gender differences in the laryngectomee experience

BACKGROUND

Laryngectomy is a pivotal event in patients. lives, with pervasive and far-reaching effects. Understanding gender differences in these effects may improve care of laryngectomy patients. This paper describes gender differences in the experience after laryngectomy.

AIM

To explore the similarities and differences in the laryngectomee experience based on gender.

METHODS & PROCEDURES

Four gender-matched focus groups were conducted; dialogue was audio recorded, transcribed and studied using interpretative phenomenological analysis (IPA).

OUTCOMES & RESULTS

A total of 17 laryngectomees, eight female and nine male, age range 41-80 years, participated in focus groups. Laryngectomy represented a turning point in the lives of both genders. Four themes emerged: perception of loss, adjusting to alaryngeal communication, finding a positive outlook and re-establishing the self. Themes applied to both genders, with subthemes demonstrating similarities and differences between men and women.

CONCLUSIONS & IMPLICATIONS

Men and women experienced destabilization after laryngectomy related to perceived losses and shifts in identity. Men described navigating from physical disability toward recovery of function, while women described an emotional journey concerning loss and rediscovery of meaning in their lives. Understanding the laryngectomee experience in better detail, which includes recognizing gender differences and rejecting a one-size-fits-all approach, may facilitate more effective preoperative counselling and post-operative support from providers.

WHAT THIS PAPER ADDS

What is already known on the subject Patients who undergo total laryngectomy often struggle with problems with physical, emotional, and social functioning and decreased quality of life. As the literature currently stands, the understanding of the experience of laryngectomees has primarily focused on the perspective of a singular gender. Thus, this is the first qualitative study specifically investigating differences in the laryngectomee experience between men and women. What this paper adds to existing knowledge This study finds that women and men both endorse significant mental and physical changes following laryngectomy; however, their perception of their experience differed by gender. Women endorsed alteration to meaningful life and men demonstrated distress related to loss of physical functioning; both genders described laryngectomy as a formative event that helped them rediscover joy and redefine themselves for the better. What are the potential or actual clinical implications of this work? Our findings suggest men and women have distinct mental and emotional struggles after laryngectomy despite similar physical changes. This suggests that tailoring care with consideration of these gender differences, including preoperative counselling, post-operative support and gender-matched visitors or support groups, may help beneficial in recovery after laryngectomy.

Epidemiology and Prognostic Indicators of Survival in Tongue Lymphoma

OBJECTIVES

Lymphoma, categorized as either non-Hodgkin's lymphoma or Hodgkin's lymphoma, is the second most common malignancy in the head and neck. Primary tongue lymphoma is exceedingly rare, with only case reports or small case series in the literature. This population-based analysis is the first to report the epidemiology and prognostic factors of survival in patients with primary tongue lymphoma.

METHODS

The Surveillance, Epidemiology, and End Results 18 database from the National Cancer Institute was queried for patients diagnosed between the years 2000 and 2016 with tongue lymphoma. Outcomes of interest were overall and disease-specific survival. Independent variables included age at diagnosis, sex, race, marital status, primary subsite, histologic subtype, stage, and treatment type.

RESULTS AND CONCLUSION

Seven hundred forty patients met criteria; the male-female ratio was 1.5:1 and the mean age at diagnosis was 67.8 years. The majority of lesions localized to the base of tongue (90.0%), were histologically diffuse large B-cell lymphoma (59.5%), and presented at stage I or II (77.9%). Most early-stage lymphomas were treated with chemotherapy only (40.5%) or a combination of both chemotherapy and radiation (31.3%), while late-stage cancers were primarily treated with chemotherapy alone (68.5%). In multivariate analysis, younger age at diagnosis, female sex, married/partnered marital status, mucosa-associated lymphoid tissue histologic subtype, and earlier cancer stage were found to be associated with improved survival. Chemotherapy treatment with or without radiation was also associated with better survival compared to no treatment or radiation alone, though data regarding immunotherapy was unavailable.

Temporal trends in oropharyngeal cancer incidence, survival, and cancer-directed surgery among elderly Americans

OBJECTIVE

This study assesses longitudinal epidemiologic trends in the oldest head and neck cancer (HNC) patients, comparing the oropharynx to other mucosal HNC sites.

MATERIALS AND METHODS

Using data from the Surveillance, Epidemiology, and End Results database, trends in incidence, two-year cancer specific mortality, and percent of cases recommended for and which received surgery from 2000 to 2018 in patients ages ≥85 years were assessed using Joinpoint analysis by HNC site. Trends were quantified as annual percentage change (APC) with 95% confidence intervals (CI).

RESULTS

Among older adults, oropharyngeal cancer (OPC) incidence increased (APC = 1.80% [95% CI: 0.94-2.67]), while mortality decreased (APC = -2.01% [95% CI: -3.26--0.74]) from 2000 to 2018. At other mucosal HNC sites, incidence and mortality remained stable. Percentage of patients who received surgery significantly changed for oropharyngeal (APC = -15.34% from 2000 to 2005 [95% CI: -24.37 to -4.79]) and laryngeal (APC = -4.61% from 2000 to 2008 [95% CI -8.28 to -0.80]) cancers. Trends in recommendation for surgery varied by site with significant decreases at the larynx, oral cavity, and oropharynx.

CONCLUSION

OPC incidence is increasing among the oldest HNC patients. An increasing proportion of HPV-associated tumors could account for associated mortality improvement. There has been a shift towards non-surgical therapy possibly due to known favorable response of HPV-associated OPC to radiation therapy and/or poor surgical candidacy in this age group. The evolving treatment approach has not been detrimental to population-level survival outcomes, but optimal treatment has yet to be established. Future studies with pathologically confirmed HPV status are needed to better understand older adult OPC burden.

Radiation-Associated Sarcoma of the Head and Neck: Incidence, Latency, and Survival

OBJECTIVES/HYPOTHESIS

Radiation-associated sarcomas of the head and neck (RASHN) are known but rare sequelae after radiation for squamous cell carcinoma. The purpose of this study was to characterize RASHN, estimate the risk of RASHN in head and neck squamous cell patients after therapeutic radiation, and compare their survival to that of patients with de novo sarcomas of the head and neck (dnSHN).

STUDY DESIGN

Retrospective database analysis.

METHODS

RASHN and dnSHN cases were collected from the Surveillance, Epidemiology, and End Results Database to identify risk factors and calculate incidence and latency. Survival was compared between RASHN and dnSHN.

RESULTS

The risk of RASHN was 20.0 per 100,000 person-years. The average latency period was 124.2 months (range 38-329). The cumulative incidence of RASHN at 20 years was 0.13%. Oral cavity and oropharynx primaries demonstrate increased risk. Five-year overall survival of RASHN was 22.4% compared to 64.5% for dnSHN.

CONCLUSIONS

RASHN are confirmed to be rare. RASHN have poor overall survival and worse survival compared to dnSHN. The impact of intensity-modulated radiation therapy protocols on this risk is unknown. Modifiable risk factors of smoking and alcohol consumption continue to dwarf radiation therapy as risk factors of second primary head and neck cancers.

LEVEL OF EVIDENCE

3 Laryngoscope, 2021.

Does Subglottic Squamous Cell Carcinoma Warrant a Different Strategy Than Other Laryngeal Subsites?

OBJECTIVES/HYPOTHESIS

Subglottic squamous cell carcinoma (SSCC) is a rare cancer with limited evidence-based treatment guidelines. This study aimed to describe the treatment patterns for SSCC and to determine which treatments provide the best overall survival.

STUDY DESIGN

Retrospective database review.

METHODS

The National Cancer Database (NCDB) was queried for patients treated for SSCC from 2004 through 2014. Overall survival (OS) rates were determined by the Kaplan-Meier method. Clinicopathologic characteristics were assessed by univariable and multivariable Cox proportional hazards models, which corrected for age, sex, race, insurance status, income quartile, residence, Charlson-Deyo comorbidity score, facility type providing treatment, tumor grade, and clinical N and T category.

RESULTS

In this cohort of 549 patients with SSCC, the 5-year OS was 48.2%. SSCC presented at an advanced stage (American Joint Committee on Cancer stage III or IV) in 60.1% of cases; 78.3% of cases had no nodal metastases. Among only stage IV cases, multivariable analysis showed that radiotherapy (RT) (hazard ratio [HR] = 5.944; 95% confidence interval [CI]: 2.76-12.8; P < .001) and chemoradiotherapy (CRT) (HR = 2.321; 95% CI: 1.36-3.97; P = .002) were both associated with decreased 5-year OS compared to a group consisting of all surgeries. When this analysis was repeated for only stage III cases, RT (HR = 1.134; 95% CI: 0.38-3.37; P = .821) and CRT (HR = 1.784; 95% CI: 0.78-4.08; P = .170) were equivalent to surgery.

CONCLUSIONS

Using the NCDB to study the largest cohort of SSCC with known staging and treatment, primary surgery may provide a better 5-year OS in advanced-stage SSCC.

LEVEL OF EVIDENCE

4 Laryngoscope, 131:E1117-E1124, 2021.

Metabolic modeling using statistical and spreadsheet software: Application to the glucose minimal model

Kinetic non-linear metabolic models are used extensively in medical research and increasingly for clinical diagnostic purposes. An example of such a model is the Glucose Minimal Model by Bergman and colleagues [1]. This model is similar to pharmacokinetic/pharmacodynamic models in that like pharmacokinetic/pharmacodynamic models, it is based on a small number of fairly simple ordinary differential equations and it aims to determine how the changing concentration of one blood constituent influences the concentration of another constituent. Although such models may appear prima facie, to be relatively simple, they have gained a reputation of being difficult to fit to data, especially in a consistent and repeatable fashion. Consequently, researchers and clinicians have generally relied on dedicated software packages to do this type of modeling. This article describes the use of statistical and spreadsheet software for fitting the Glucose Minimal Model to data from an insulin modified intravenous glucose tolerance test (IM-IVGTT). A novel aspect of the modeling is that the differential equations that are normally used to describe insulin action and the disposition of plasma glucose are first solved and expressed in their explicit forms so as to facilitate the estimation of Glucose Minimal Model parameters using the nonlinear (nl) optimization procedure within statistical and spreadsheet software. The most important clinical parameter obtained from the Glucose Minimal Model is insulin sensitivity (S_I). Using IM-IVGTT data from 42 horses in one experiment and 48 horses in a second experiment, we demonstrate that estimates of S_I derived from the Glucose Minimal Model fitted to data using STATA and Excel, are highly concordant with S_I estimates obtained using the industry standard software, MinMod Millennium. This work demonstrates that there is potential for statistical and spreadsheet software to be applied to a wide range of kinetic non-linear modeling problems.

Does sinonasal cancer survival differ based on human papillomavirus status?

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Background: The sinonasal tract is a lesser known “hot spot” for the human papillomavirus (HPV), compared with the oropharynx. Additionally, unlike the oropharynx, the role of HPV tumor status in the survival and overall prognosis of the sinonasal tract and other non-oropharyngeal head and neck cancer sites remains inconclusive. Understanding differences in survival based on HPV status could be useful clinically, as it has been for HPV-positive oropharyngeal disease. This study examined whether there are survival differences in sinonasal cancer based on HPV status. Methods: This study included adult sinonasal cancer cases diagnosed between 2010 and 2015 in the National Cancer Database. A multivariable Cox proportional hazards model estimated the association between sinonasal cancer HPV status (HPV-positive, HPV-negative) and all-cause mortality while controlling for covariates (sex, age, race/ethnicity, insurance status, urban/rural, county-level household income, county-level percentage without high school diploma, comorbidity score, stage, histology, facility type, and treatment). A second multivariable proportional hazards model stratified HPV-positive tumor status by high-risk HPV (16, 18, 26, 31, 33, 35, 36, 45, 51, 52, 53, 56, 58, 59, 66, 67, 68, 69, 70, 73, 82, and 85) vs. low-risk HPV (6, 11, 32, 34, 40, 42, 44, 54, 61, 62, 64, 71, 72, 74, 81, 83, 84, 87, and 89) and compared their all-cause mortality to HPV-negative patients. Results: There were 1,750 sinonasal cancer patients included in this study, and 484 (27.7%) had HPV-positive disease. Among patients with HPV-positive disease, 75.6% had high-risk types. Mortality risk among all HPV-positive patients combined was 23% lower than HPV-negative patients (aHR = 0.77; 95% CI 0.64, 0.93). After stratifying by high-risk vs. low-risk HPV, high-risk HPV positive patients had 30% lower mortality risk than HPV-negative patients (aHR = 0.70; 95% CI 0.57, 0.88) while risk of mortality did not significantly differ between low-risk HPV-positive patients and HPV-negative sinonasal cancer patients. Conclusions: Sinonasal cancer shows differential survival based on HPV status, and sinonasal cancer patients positive for high-risk HPV had a significantly greater survival advantage than low-risk strains and those with HPV negative disease. HPV status might yet play a role in prognostication of sinonasal cancer, if future studies confirm these findings.

Comparison of the Financial Burden of Survivors of Head and Neck Cancer With Other Cancer Survivors

Importance

Head and neck cancer (HNC) is more common among socioeconomically disenfranchised individuals, making financial burden particularly relevant.

Objective

To assess the financial burdens of HNC compared with other cancers.

Design, Setting, and Participants

In this retrospective review of nationally representative, publicly available survey, data from the Medical Expenditure Panel Survey were extracted from January 1, 1998, to December 31, 2015. A total of 444 867 adults were surveyed, which extrapolates to a population of 221 503 108 based on the weighted survey design. Data analysis was performed from April 18, 2018, to August 20, 2018.

Exposures

Of 16 771 patients with cancer surveyed (weighted count of 10 083 586 patients), 489 reported HNC (weighted count of 261 631).

Main Outcomes and Measures

Patients with HNC were compared with patients with other cancers on demographics, income, employment, and health. Within the HNC group, risk factors for total medical expenses and relative out-of-pocket expenses were assessed with regression modeling. Complex sampling methods were accounted for with weighting using balanced repeated replication.

Results

A total of 16 771 patients (mean [SD] age, 62.3 [18.9] years; 9006 [53.7%] female) with cancer were studied. Compared with patients with other cancers, patients with HNC were more often members of a minority race/ethnicity, male, poor, publicly insured, and less educated, with lower general and mental health status. Median annual medical expenses ($8384 vs $5978; difference, $2406; 95% CI, $795-$4017) and relative out-of-pocket expenses (3.93% vs 3.07%; difference, 0.86%; 95% CI, 0.06%-1.66%) were higher for patients with HNC than for patients with other cancers. Among patients with HNC, median expenses were lower for Asian individuals compared with white individuals ($5359 vs $10 078; difference, $4719; 95% CI, $1481-$7956]), Westerners ($8094) and Midwesterners ($5656) compared with Northwesterners ($10 549), and those with better health status ($16 990 for those with poor health vs $6714 for those with excellent health). Higher relative out-of-pocket expenses were associated with unemployment (5.13% for employed patients vs 2.35% for unemployed patients; difference, 2.78%; 95% CI, 0.6%-4.95%), public insurance (5.35% for those with public insurance vs 2.87% for those with private insurance; difference, 2.48%; 95% CI, -0.6% to 5.55%), poverty (13.07% for poor patients vs 2.06% for high-income patients), and lower health status (10.2% for those with poor health vs 1.58% for those with excellent health).

Conclusions and Relevance

According to this study, HNC adds a substantial, additional burden to an already financially strained population in the form of higher total and relative expenses. The financial strain on individuals, assessed as relative out-of-pocket expenses, appears to be driven more by income than by health factors, and health insurance does not appear to be protective.

Impact of type 2 diabetes on hospitalization and mortality in people with malignancy

AIM

To compare the characteristics of and outcomes for people with malignancies with and without a co-diagnosis of diabetes.

METHODS

Emergency department and hospital discharge data from a single centre for the period between 1 January 2015 and 31 December 2017 were used to identify people with a diagnosis of a malignancy and diabetes. Multivariate Cox regression models were used to estimate the effect of diabetes on all-cause mortality. A truncated negative binomial regression model was used to assess the impact of diabetes on length of hospital inpatient stay. Prentice-Williams-Peterson total time models were used to assess the effect of diabetes on number of emergency department re-presentations and inpatient re-admissions.

RESULTS

Of 7004 people identified with malignancies, 1195 (17.1%) were also diagnosed with diabetes. A diagnosis of diabetes was associated with a greater number of inpatient re-admissions [adjusted hazard ratio 1.13 (95% CI 1.03, 1.24)], a greater number of emergency department re-presentations [adjusted hazard ratio 1.13 (95% CI 1.05, 1.22)] and longer length of stay [adjusted incidence rate ratio 1.14 (95% CI 1.04, 1.25)]. A co-diagnosis of diabetes was also associated with a 48% increased risk of all-cause mortality [adjusted hazard ratio 1.48 (95% CI 1.22-1.76)].

CONCLUSIONS

People with malignancies and diabetes had significantly more emergency department presentations, more inpatient admissions, longer length of hospital stay and higher rates of all-cause mortality compared to people with a malignancy without diabetes.

Basaloid Squamous Cell Carcinoma of the Larynx: A National Cancer Database Analysis

OBJECTIVE

Basaloid squamous cell histology is a rare variant that accounts for about 2% of all head and neck squamous cell laryngeal carcinomas. The purpose of this study was to examine overall survival rates of patients according to treatment, stage, and laryngeal subsite.

STUDY DESIGN

Retrospective analysis.

SETTING

National Cancer Database (NCDB).

SUBJECTS AND METHODS

The NCDB was queried for patients with basaloid squamous cell carcinoma (BSCC) who were treated from 2004 to 2014. Five-year overall survival rates were determined by the Kaplan-Meier method. Univariate and multivariate analysis was used to identify factors correlated with 5-year overall survival.

RESULTS

The NCDB identified 440 patients meeting inclusion criteria. Median follow-up time was 31.2 months. On univariate analysis, the treatment modalities assessed (surgery alone, surgery with radiotherapy, surgery with chemoradiotherapy, radiotherapy, chemoradiotherapy) did not differ in their survival benefit. On multivariate analysis, only chemoradiotherapy (hazard ratio, 0.587; 95% CI, 0.37-0.93; P = .022) was associated with improved survival. All treatment modalities performed similarly between stage I and II tumors ( P = .340) and stage III and IV tumors ( P = .154).

CONCLUSION

This study represents the largest laryngeal BSCC series to date. We found that chemoradiotherapy was associated with improved 5-year overall survival of laryngeal BSCC on multivariate analysis.

Asymmetric changes in circulating insulin levels after an increase compared with a reduction in insulin pump basal rate in people with Type 1 diabetes

AIMS

To investigate circulating insulin profiles after a clinically relevant insulin pump basal rate increase vs a reduction, and the associated glucose responses.

METHODS

A cohort of 12 adults with Type 1 diabetes undertook this two-stage university hospital study using Accu-Chek pumps (Roche Diagnostics, Mannheim, Germany) and insulin aspart. An insulin basal rate change of 0.2 unit/h (increase in first stage, reduction in second stage) was implemented at ~09:30 h, after a single overnight basal rate (without bolus insulin), while fasting participants rested. Frequent venous samples for the assessment of plasma free insulin, glucose and cortisol were collected from 60 min before until 300 min after rate change. The primary outcome was time to steady-state insulin.

RESULTS

The 0.2-unit/h rate change represented a mean ± sd alteration of 23 ± 6%. After the rate increase, the median (interquartile range) times to 80% and 90% steady-state insulin were 170 (45) min and 197 (87) min, respectively. By contrast, after rate reduction, 80% steady-state insulin was not achieved. After the rate increase, mean ± se insulin levels increased by 4.3 ± 3.1%, 12.0 ± 2.9% and 25.6 ± 2.6% at 60, 120 and 300 min, respectively (with no significant difference until 180 min). After the rate reduction, insulin decreased by 8.3 ± 3.0% at 300 min (with no significant difference until 300 min). After rate reduction, glucose levels paradoxically declined by 17.4 ± 3.7% after 300 min; cortisol levels also fell during observation (P = 0.0003).

CONCLUSIONS

The time to circulating insulin change after a 0.2-unit/h basal rate change was substantial, and was greater after a reduction than after an increase. Counter-regulatory hormone circadian variation may affect glycaemia when implementing minor changes at low basal rates. Both direction of basal rate change, and time of day, warrant consideration when anticipating the clinical effects of basal rate changes.

Multicenter Australian trial of islet transplantation: improving accessibility and outcomes

Whilst initial rates of insulin independence following islet transplantation are encouraging, long-term function using the Edmonton Protocol remains a concern. The aim of this single-arm, multicenter study was to evaluate an immunosuppressive protocol of initial antithymocyte globulin (ATG), tacrolimus and mycophenolate mofetil (MMF) followed by switching to sirolimus and MMF. Islets were cultured for 24 h prior to transplantation. The primary end-point was an HbA1c of <7% and cessation of severe hypoglycemia. Seventeen recipients were followed for ≥ 12 months. Nine islet preparations were transported interstate for transplantation. Similar outcomes were achieved at all three centers. Fourteen of the 17 (82%) recipients achieved the primary end-point. Nine (53%) recipients achieved insulin independence for a median of 26 months (range 7-39 months) and 6 (35%) remain insulin independent. All recipients were C-peptide positive for at least 3 months. All subjects with unstimulated C-peptide >0.2 nmol/L had cessation of severe hypoglycemia. Nine of the 17 recipients tolerated switching from tacrolimus to sirolimus with similar graft outcomes. There was a small but significant reduction in renal function in the first 12 months. The combination of islet culture, ATG, tacrolimus and MMF is a viable alternative for islet transplantation.

β-blockers protect against dispersion of repolarization during exercise in congenital long-QT syndrome type 1

INTRODUCTION

β-Blocker therapy reduces syncope and sudden death in long-QT syndrome type 1 (LQT1), but the mechanism of protection is incompletely understood. This study tested the hypothesis that β-blockade reduces QT prolongation and dispersion of repolarization, measured as the T peak-to-end interval (T(pe) ), during exercise and recovery in LQT1 patients.

METHODS AND RESULTS

QT and T(pe) were measured in 10 LQT1 patients (33 ± 13 years) and 35 normal subjects (32 ± 12 years) during exercise tests on and off β-blockade. In LQT1 patients, β-blockade reduced QT (391 ± 25 milliseconds vs 375 ± 26 milliseconds, P = 0.04 during exercise; 419 ± 41 milliseconds vs 391 ± 39 milliseconds, P = 0.02 during recovery) and markedly reduced T(pe) (91 ± 26 milliseconds vs 67 ± 19 milliseconds, P = 0.03 during exercise; 103 ± 26 milliseconds vs 78 ± 11 milliseconds, P = 0.02 during recovery). In contrast, in normal subjects, β-blockade had no effect on QT (320 ± 17 milliseconds vs 317 ± 16 milliseconds, P = 0.29 during exercise; 317 ± 13 milliseconds vs 315 ± 14 milliseconds, P = 0.15 during recovery) and mildly reduced T(pe) (69 ± 13 milliseconds vs 61 ± 11 milliseconds, P = 0.01 during exercise; 77 ± 19 milliseconds vs. 68 ± 14 milliseconds, P < 0.001 during recovery).

CONCLUSION

In LQT1 patients, β-blockers reduced QT and T(pe) during exercise and recovery, supporting the theory that β-blocker therapy protects LQT1 patients by reducing dispersion of repolarization during exercise and recovery.

Application of the intravenous glucose tolerance test and the minimal model to patients with insulinoma: insulin sensitivity (Si) and glucose effectiveness (Sg) before and after surgical excision

BACKGROUND

The unmodified frequently sampled intravenous glucose tolerance test (FSIGT) has not previously been used to assess insulin/glucose kinetics in patients with insulinoma.

OBJECTIVE

To measure insulin sensitivity (Si) and glucose effectiveness (Sg) by means of the FSIGT in patients with insulinoma, before and after surgical removal of the tumour.

SUBJECTS AND METHODS

FSIGTs were performed in five patients, before and approximately 3 months post-surgery, and in 11 controls. Si and Sg were estimated using Minimal Model computer analysis of dynamic glucose and insulin data.

RESULTS

Si was lower in insulinoma patients before, compared with after surgery (3.37 +/- 0.62 vs. 6.24 +/- 1.09 SE [x10(-4)] min(-1)microU(-1) ml, P < 0.05). Sg was similar in patients pre- and post-surgery (3.0 +/- 0.67 vs. 2.4 +/- 0.6 [x10(-2)] min(-1), NS).

CONCLUSIONS

Insulin sensitivity improves after excision of an insulinoma. Glucose effectiveness is not influenced by chronic hyperinsulinaemia and hypoglycaemia.

Insulin secretion and insulin sensitivity are normal in non-diabetic subjects from maternal inheritance diabetes and deafness families

BACKGROUND

The pathophysiological mechanism of diabetes mellitus in the presence of the 3243 A-G tRNALEU(UR) mitochondrial DNA mutation is thought to result from deficient insulin secretion. However, few subjects with normal glucose tolerance have been studied to determine the sequence of events resulting in the development of diabetes mellitus.

AIM

To determine whether abnormalities of insulin sensitivity, insulin secretion or glucose effectiveness are present in non-diabetic subjects with the 3243 A-G tRNALEU(UUR) mitochondrial DNA mutation.

METHODS

Twelve non-diabetic subjects with the mutation were compared with 12 controls, matched for age and anthropometric parameters, using both oral and intravenous glucose tolerance tests, the latter with Minimal Model analysis.

RESULTS

Following an oral glucose load we found significantly higher blood glucose levels at 90 min and 120 min and significantly higher insulin levels at 120 min and 180 min in non-diabetic subjects with the mutation but no difference in the insulinogenic indices at 30 min and 180 min. From the intravenous glucose tolerance test there was no difference in overall glucose tolerance, insulin sensitivity, first- or second-phase insulin secretion, proinsulin secretion or glucose effectiveness. Insulin-independent glucose disposal was increased in subjects with lower insulin sensitivity and declined with increasing age in subjects with the mutation but not in controls.

CONCLUSIONS

While there appear to be subtle defects of glucose handling in non-diabetic subjects with the 3243 mutation, these could not be explained by differences in insulin sensitivity or secretion.

Physiologic modeling of the intravenous glucose tolerance test in type 2 diabetes: a new approach to the insulin compartment

The minimal model of Bergman et al has been used to yield estimates of insulin sensitivity (Si) and glucose effectiveness (Sg) in type 2 diabetes by incorporating exogenous insulin protocols into the regular intravenous glucose tolerance test (IVGTT). These estimates, however, are influenced by the degree to which the dose of exogenous insulin is greater than the physiologic response to a glucose load. Moreover, most studies have related to type 2 diabetes subjects whose diabetes was relatively mild in terms of therapeutic requirements. To develop a "minimal disturbance" approach in estimating Si and Sg in type 2 diabetes, we have used a reduced glucose load (200 mg/kg) and a "physiologic" insulin infusion throughout the IVGTT in a series of 8 patients, 5 of whom were insulin-requiring. Data from this approach were analyzed using the modelling program CONSAM to apply the Bergman model, either unmodified (BMM), or incorporating an additional delay element between the plasma and "remote" insulin compartments (MMD). Application of the MMD and extension of the IVGTT from 3 to 5 hours improved successful resolution of Si and Sg from 37.5% (BMM, 3-hour IVGTT) to 100% (MMD, 5-hour IVGTT). Si was reduced in these type 2 diabetes patients compared with normal subjects (1.86 +/- 0.60 v. 8.65 +/- 2.27 min(-1) x microU(-1) x mL x 10(4) P <.01). The results were validated in the type 2 diabetes group using a 2-stage euglycemic clamp ((Si)CLAMP = 2.02 +/- 0.42 min(-1) x microU(-1) x mL x 10(4) P >.4). Sg was not significantly reduced (2.00 +/- 0.25 type 2 diabetes v. 1.55 +/- 0.26 normal min(-1) x 10(2)). Data from a group of normal nondiabetic subjects was then analyzed using the MMD, but this approach did not enhance the fit of the model compared with the BMM. This result indicates that the delay in insulin action in type 2 diabetes represents an abnormality whereby the onset of insulin action cannot be described as a single phase in the transfer of insulin from plasma to the remote compartment. It is postulated that the physiologic basis for this delayed action may relate to transcapillary endothelial transfer of insulin, this process limiting the rate of onset of insulin action.

The Melbourne Pre-Diabetes Study: prediction of type 1 diabetes mellitus using antibody and metabolic testing

OBJECTIVES

To determine the utility of various autoantibodies in predicting progression to clinical diabetes in first-degree relatives of patients with type 1 diabetes mellitus.

PARTICIPANTS

3315 first-degree relatives of patients with type 1 diabetes (1161 parents, 1206 siblings and 948 offspring) recruited through diabetes clinics, private endocrinologists, Diabetes Australia and the Juvenile Diabetes Foundation.

MAIN OUTCOME MEASURES

Prevalence of islet cell antibodies (ICA) levels > or = 20 JDFu, insulin autoantibodies (IAA) levels > 100 nU/mL, and antibodies to glutamic acid decarboxylase (GADAb) and tyrosine phosphatase IA2 (IA2Ab); change in beta cell function over time; and development of clinical diabetes.

RESULTS

2.6% of relatives had elevated ICA levels, 1.3% had elevated IAA levels and 0.3% had both. High ICA levels were significantly more frequent in siblings than in offspring or parents, and were more frequent in relatives younger than 20 years. GADAb were detected in 68% and IA2Ab in 57% of relatives with elevated ICA and/or IAA levels. Diabetes developed in 33 relatives (25 siblings, 2 offspring and 6 parents). Before diagnosis of clinical diabetes, high ICA levels were detected in 18 (58%), high IAA levels in 7 (23%), both in 5 (15%), and either in 19 (61%); GADAb were detected in 26 (84%), IA2Ab in 13 (42%), both in 11 (35%), and either in 28 (90%). First phase insulin release (FPIR) less than 50 mU/L was very strongly associated with progression to diabetes. In relatives with FPIR initially greater than 50 mU/L who eventually developed diabetes, there was a gradual and continuous reduction in FPIR over time before diagnosis.

CONCLUSIONS

Type 1 diabetes can be diagnosed in the preclinical stage. The recently described antibodies to glutamic acid decarboxylase and tyrosine phosphatase IA2 appear superior to ICA as screening tools for the preclinical diagnosis of type 1 diabetes.

Impact of family history of diabetes on the assessment of beta-cell function

Numerous factors impinge on beta-cell function, and include the genetic background and insulin sensitivity of the individual. The aim of the present study was to evaluate the impact of a family history of non-insulin-dependent diabetes mellitus (NIDDM) on beta-cell function and to determine whether the relationships between beta-cell function and insulin sensitivity and age are influenced by a family history of diabetes. Thirty-three healthy control subjects (CON), 20 normal glucose-tolerant first-degree relatives of known NIDDM patients (REL), and 12 nondiabetic identical twins with an identical twin with known NIDDM were studied. Insulin and C-peptide responses to an acute intravenous glucose (AIRg) and glucagon bolus (at euglycemia [AIR[G.GON]]) were measured, as well as each individual's insulin sensitivity. Fasting insulin and C-peptide levels were similar in all groups. AIRg was significantly reduced by 65% in the nondiabetic twins compared with the CON and REL groups, with the latter group being similar to CON, whereas for the AIR[G.GON], the insulin responses in the twin subjects were reduced only by 35% compared with CON. Following stepwise (default) multiple regression analysis, three independent variables (insulin sensitivity, 23%; family history of NIDDM, 20%; and fasting glucose, 7%) were identified, and these combined to fit a model for prediction of acute beta-cell responses to glucose that yielded an R2 (adjusted) value of 50%. Following analysis of covariance (ANCOVA), a positive family history of NIDDM and insulin sensitivity but not the age of the subject were confirmed as separate factors affecting AIRg. In conclusion, in subjects with normal or mild glucose intolerance, the individual's genetic background and insulin sensitivity are important determinants of insulin secretion.

Risk and mechanism of dexamethasone-induced deterioration of glucose tolerance in non-diabetic first-degree relatives of NIDDM patients

We tested the hypothesis that glucose intolerance develops in genetically prone subjects when exogenous insulin resistance is induced by dexamethasone (dex) and investigated whether the steroid-induced glucose intolerance is due to impairment of beta-cell function alone and/or insulin resistance. Oral glucose tolerance (OGTT) and intravenous glucose tolerance tests with minimal model analysis were performed before and following 5 days of dex treatment (4 mg/day) in 20 relatives of non-insulin-dependent diabetic (NIDDM) patients and in 20 matched control subjects (age: 29.6 +/- 1.7 vs 29.6 +/- 1.6 years, BMI: 25.1 +/- 1.0 vs 25.1 +/- 0.9 kg/m2). Before dex, glucose tolerance was similar in both groups (2-h plasma glucose concentration (PG): 5.5 +/- 0.2 [range: 3.2-7.0] vs 5.5 +/- 0.2 [3.7-7.4] mmol/l). Although insulin sensitivity (Si) was significantly lower in the relatives before dex, insulin sensitivity was reduced to a similar level during dex in both the relatives and control subjects (0.30 +/- 0.04 vs 0.34 +/- 0.04 10(-4) min(-1) per pmol/l, NS). During dex, the variation in the OGTT 2-h PG was greater in the relatives (8.5 +/- 0.7 [3.9-17.0] vs 7.5 +/- 0.3 [5.7-9.8] mmol/l, F-test p < 0.05) which, by inspection of the data, was caused by seven relatives with a higher PG than the maximal value seen in the control subjects (9.8 mmol/l). These "hyperglycaemic" relatives had diminished first phase insulin secretion (O1) both before and during dex compared with the "normal" relatives and the control subjects (pre-dex O1: 12.6 +/- 3.6 vs 26.4 +/- 4.2 and 24.6 +/- 3.6 (p < 0.05), post-dex O1: 22.2 +/- 6.6 vs 48.0 +/- 7.2 and 46.2 +/- 6.6 respectively (p < 0.05) pmol x l(-1) x min(-1) per mg/dl). However, Si was similar in "hyperglycaemic" and "normal" relatives before dex (0.65 +/- 0.10 vs 0.54 +/- 0.10 10(-4) x min(-1) per pmol/l) and suppressed similarly during dex (0.30 +/- 0.07 vs 0.30 +/- 0.06 10(-4) x min(-1) per pmol/l). Multiple regression analysis confirmed the unique importance of low pre-dex beta-cell function to subsequent development of high 2-h post-dex OGTT plasma glucose levels (R2 = 0.56). In conclusion, exogenous induced insulin resistance by dex will induce impaired or diabetic glucose tolerance in those genetic relatives of NIDDM patients who have impaired beta-cell function (retrospectively) prior to dex exposure. These subjects are therefore unable to enhance their beta-cell response in order to match the dex-induced insulin resistant state.

The effect of norepinephrine on insulin secretion and glucose effectiveness in non-insulin-dependent diabetes

It has previously been shown that in normal subjects, physiological elevation of norepinephrine (NE) impairs insulin sensitivity (Si) but does not influence insulin secretion. The aim of this study was to determine the effect of short-term physiological elevation of NE on insulin secretion, Si, and glucose-mediated glucose disposal, or the glucose effectiveness index (Sg), in non-insulin-dependent diabetes mellitus (NIDDM). Two intravenous glucose tolerance tests (IVGTTs) were performed in eight well-controlled NIDDM patients, using a supplemental exogenous insulin infusion to achieve an approximation of normal endogenous insulin secretion. The IVGTTs were performed in random order after 30 minutes of either the saline (SAL) or NE (25 ng/kg/min) infusions, which were continued throughout the 3-hour IVGTT. Sg and Si were estimated by minimal model analysis of the IVGTT data as previously described. Plasma C-peptide was used to estimate insulin secretion rate using the ISEC program. NE infusion produced approximately a threefold increase in plasma NE, associated with (1) a significant reduction in glucose disposal ([KG] SAL v NE, 0.73 +/- 0.06 v 0.61 +/- 0.06 x 10(-2).min-1, P < .05), (2) no reduction in Si (2.33 +/- 0.8 v 2.62 +/- 0.9 x 10(-4).min-1/mU/L, NS), (3) a reduced mean second-phase insulin secretion rate (1.21 +/- 0.19 v 1.01 +/- 0.16 x 10(-3) pmol/kg/min per mmol/L glucose, P < .05), (4) a significant increase in Sg (0.89 +/- 0.08 v 1.63 +/- 0.2 x 10(-2).min-1, P < .05), and (5) a corresponding increase in glucose effectiveness at zero insulin ([GEZI] 0.55 +/- 0.13 v 1.30 +/- 0.33 x 10(-2).min-1, P < .05). These results show that in contrast to normal subjects, physiological elevation of NE in NIDDM does not result in a reduction in Si, but causes a reduction in glucose disposal related to inhibition of insulin secretion that is only partially compensated for by increased Sg.

A review of countermeasures to reduce radioiodine in milk of dairy animals

The most effective countermeasure for radioiodine contamination of milk is to provide dairy animals with uncontaminated feed, with the added advantage that it will be effective for other radionuclides in the fallout. Another effective response is to process the milk into storable dairy products for an appropriate length of time to allow for physical decay. The use of additives given to ruminants to reduce radioiodine in milk is an alternative countermeasure which could be effective. Stable iodine administration is a practically feasible option which has the potential to reduce radioiodine levels in milk by at most a factor of three. Stable iodine supplementation should be at sufficiently high rates to be effective (and at least 1 g d-1 for dairy cows), particularly for ruminants already receiving high amounts of iodine in the diet. Currently available data are inadequate to recommend a suitable stable iodine administration rate for different species of ruminants. Other compounds, such as perchlorate and thiocyanate, also reduce the transfer to radioiodine to milk (and thyroid). Some of these compounds seem to be potentially equally as effective as stable iodine. However, currently there is inadequate information on their effectiveness and possible toxicity to both ruminants and humans for these compounds to be considered as suitable countermeasure additives.

Estimates of animal methane emissions

The enteric methane emissions into the atmospheric annually from domestic animals total about 77 Tg. Another 10 to 14 Tg are likely released from animal manure disposal systems. About 95% of global animal enteric methane is from ruminants, a consequence of their large populations, body size and appetites combined with the extensive degree of anaerobic microbial fermentation occurring in their gut. Accurate methane estimates are particularly sensitive to cattle and buffalo census numbers and estimated diet consumption. Since consumption is largely unknown and must be predicted, accuracy is limited often by the information required, i.e., distribution of animals by class, weight and productivity. Fraction of the diet lost as enteric methane mostly falls into the range of 5.5-6.5% of gross energy intake for the world's cattle, sheep and goats. Manure methane emissions are heavily influenced by fraction of disposal by anaerobic lagoon. Non-ruminants, i.e., swine, become major contributors to these emissions.

Insulinopenia and hyperglycemia influence the in vivo partitioning of GE and SI

We determined the impact of variable insulinemia and glycemia on the in vivo partitioning of glucose effectiveness (GE) and insulin sensitivity (SI) and the in vitro intracellular processing of glucose metabolism. Six somatostatin- and [3-3H]glucose-infused dogs underwent euglycemic and hyperglycemic clamps at four physiological insulin (Ins) levels before a muscle biopsy. From the rates of glucose infusion (GINF), total glucose disposal (Rd), total glycolysis (GF), and glucose storage (GS), plots of delta GINF, delta Rd, delta GS vs. delta log Ins concentration were found to be linear for each dog, allowing calculation of the partitioning of GE and SI into their major in vivo sites (periphery vs. liver) and intracellular metabolic pathways (GS vs. GF). Insulinopenia induced a significant reduction in total GE. From insulinopenia to high insulinemia, the 2.3-fold increase in total GE was due to the increased peripheral glucose responsiveness of the GS pathway. Hyperglycemia induced a significant reduction in total SI, with approximately one-half of this reduction due to the decreased peripheral insulin responsiveness of the GF pathway. In skeletal muscle, both glycogen content and glycogen synthase fractional activity were positively correlated with log Ins concentration, Rd, and GS but negatively correlated with glucose 6-phosphate concentration. Moreover, both Rd and GS were negatively correlated with lactate concentration. We conclude that 1) the inhibition of GE and SI induced by insulinopenia and hyperglycemia, respectively, is due mainly to the reduced peripheral responsiveness of contrasting intracellular metabolic pathways; and 2) hyperinsulinemia and/or hyperglycemia stimulates glycogen synthesis and GF but not nonoxidative glycolysis.

The effect of 3 months of recombinant human growth hormone (GH) therapy on insulin and glucose-mediated glucose disposal and insulin secretion in GH-deficient adults: a minimal model analysis

The effect of 3 months of low dose (120 micrograms/kg.week or 0.24 IU/kg.week) recombinant human GH (rhGH) treatment on glucose tolerance, insulin secretion, and insulin- and glucose-mediated glucose disposal was examined in 10 GH-deficient adults. The frequently sampled iv glucose tolerance test was performed at baseline and after 1 week and 3 months of rhGH therapy and analyzed by the minimal model method of Bergman to provide estimates of the glucose decay rate, first and second phase insulin secretion (phi 1 and phi 2), fractional clearance of insulin, and glucose-mediated and insulin-mediated glucose disposal. Fasting glucose, insulin, C-peptide, nonesterified fatty acids (NEFA), and serum cholesterol and triglycerides were also measured. When the 1 week data were compared to baseline, there was a small but significant rise in mean (+/- SE) fasting glucose (4.62 +/- 0.17 vs. 5.1 +/- 0.15 mmol/L; P < 0.01), NEFA (0.70 +/- 0.09 vs. 1.1 +/- 0.12 mmol/L; P < 0.005), insulin (93.6 +/- 8.9 vs. 238.9 +/- 9.2 pmol/L; P < 0.0001), C-peptide (0.32 +/- 0.13 vs. 0.66 +/- 0.13 nmol/L; P < 0.005), and phi 1 (11.9 +/- 1.3 vs. 16.2 +/- 1.8 pmol/L.min/mmol.L x 10(2)) and phi 2 (1.43 +/- 0.17 vs. 3.15 +/- 0.25 pmol/L.min/mmol.L x 10(3); P < 0.05). Conversely, there were associated decreases in glucose decay rate (1.83 +/- 0.26 vs. 1.28 +/- 0.12 min-1; P < 0.05) and insulin-mediated glucose disposal (0.36 +/- 0.08 vs. 0.18 +/- 0.06 min/pmol.L x 10(-4); P < 0.005). There was no change in glucose-mediated glucose disposal or the fractional clearance of insulin. By 3 months, fasting insulin and C-peptide levels remained significantly elevated, whereas other parameters had returned to baseline. There was a minor reduction in serum cholesterol at 1 week (5.1 +/- 0.15 vs. 4.62 +/- 0.17 mmol/L; P < 0.01), which was not maintained at 3 months. Serum triglycerides remained unchanged throughout the study. We conclude that short term low dose rhGH treatment of GH-deficient adults induces a temporary state of mild glucose intolerance, hyperinsulinemia, insulin resistance, and raised NEFA levels at 1 week. By 3 months, these metabolic disturbances had returned to baseline for a persisting modest hyperinsulinemia. Whether this hyperinsulinemia will last over the longer term and/or has distant detrimental metabolic consequences in the individual must await further studies.

Increased glucose effectiveness in normoglycemic but insulin-resistant relatives of patients with non-insulin-dependent diabetes mellitus. A novel compensatory mechanism

20 normoglycemic first degree relatives of non-insulin-dependent diabetes mellitus (NIDDM) patients were compared with 20 matched subjects without any family history of diabetes using the intravenous glucose tolerance test with minimal model analysis of glucose disappearance and insulin kinetics. Intravenous glucose tolerance index (Kg) was similar in both groups (1.60 +/- 0.14 vs 1.59 +/- 0.18, x 10(-2) min-1, NS). However, insulin sensitivity (Si) was reduced (3.49 +/- 0.43 vs 4.80 +/- 0.61, x 10(-4) min-1 per mU/liter, P = 0.05), whereas glucose effectiveness (Sg) was increased (1.93 +/- 0.14 vs 1.52 +/- 0.16, x 10(-2) min-1, P < 0.05) in the relatives. Despite insulin resistance neither fasting plasma insulin concentration (7.63 +/- 0.48 vs 6.88 +/- 0.45, mU/liter, NS) nor first phase insulin responsiveness (Phi1) (3.56 +/- 0.53 vs 4.13 +/- 0.62, mU/liter min-1 per mg/dl, NS) were increased in the relatives. Phi1 was reduced for the degree of insulin resistance in the relatives so that the Phi1 x Si index was lower in the relatives (11.5 +/- 2.2 vs 16.7 +/- 2.0, x 10(-4) min-2 per mg/dl, P < 0.05). Importantly, glucose effectiveness correlated with Kg and with basal glucose oxidation but not with total glucose transporter 4 (GLUT4) content in a basal muscle biopsy. In conclusion we confirm the presence of insulin resistance in first degree relatives of NIDDM patients. However, insulin secretion was altered and reduced for the degree of insulin resistance in the relatives, whereas glucose effectiveness was increased. We hypothesize that increased glucose effectiveness maintains glucose tolerance within normal limits in these "normoinsulinemic" relatives of NIDDM patients.

Impact of variable insulinemia and glycemia on in vivo glycolysis and glucose storage in dogs

To determine the impact of variable plasma insulin concentrations and glycemia on the partitioning of whole body glucose metabolism between glycolysis and glucose storage, we estimated endogenous hepatic glucose production and rates of in vivo glycolytic flux (GF) and glucose storage (GS) in six normal dogs from the generation of plasma tritiated water (3H2O) and [3-3H]glucose specific activity during 150 min of somatostatin euglycemic (E) and hyperglycemic (H) clamps at hypoinsulinemic, basal, intermediate, and high insulin levels. During both E and H clamps, overall rates of GF and GS increased with the rising insulin levels, but the relative contributions to in vivo glucose disposal of GF decreased, whereas GS rose progressively with increasing insulin levels. The relative contribution of GS during H to overall glucose disposal was greater at the lower insulin level. In addition, in absolute terms, GF and GS were significantly higher (P < 0.05) during H than during E at all insulin levels. Moreover, the incremental rise in GF induced by H was equal for the low to intermediate insulin levels tested, independent of the prevailing free fatty acid (FFA) levels. However, when whole body glucose disposal rates were matched, GF and GS rates were independent of the coexisting glycemia, insulin, and/or FFA levels. We conclude that 1) insulin has a major impact on the intracellular fate of infused glucose, with a lesser but significant effect of hyperglycemia per se on these processes; 2) the magnitude of the hyperglycemia-induced increase in GF is independent of the prevailing insulin level from low to intermediate levels; and 3) in vivo GF and GS are dependent on the net rate of glucose uptake into cells but independent of absolute FFA levels or whether glucose uptake is stimulated by raised insulin or glucose levels.

Impaired glucose tolerance after endurance exercise is associated with reduced insulin secretion rather than altered insulin sensitivity

Paired frequently sampled intravenous glucose tolerance tests (FSIGT) were performed on five highly trained athletes within 2 hours of completing a 6-day ultramarathon run (E) and after 2 weeks of complete rest (R). Severe exercise increased free fatty acid (FFA) levels (E 1.2 +/- 0.16 v 0.42 +/- 0.07 mmol/L, P < .01) and norepinephrine levels (E 573 +/- 141 v 224 +/- 33 pg/mL, P < .01), with only moderate reductions in glucose tolerance (glucose disappearance [Kg] E 1.06 +/- 0.2 v R 1.7 +/- 0.3 min-1 x 10(2), P < .05). The minimal model analysis of FSIGT data using the method of Bergman et al (Endocr Rev 6:45-86, 1985) showed a reduced second-phase insulin secretion ([phi 2] E 5.2 +/- 1.3 v 13 +/- 2.2 microU/mL.min-2 per mg/dL, P < .05) and glucose disposition index ([SI x phi 2] E 33.8 +/- 10 v 73.9 +/- 11 mg-1.dL.min-3 x 10(4), P < .02). Insulin sensitivity (SI) and glucose-mediated glucose disposal (SG) were unchanged (SI E 6.9 +/- 1.0 v 6.0 +/- 0.6 min-1 per microU/mL x 10(4); SG E 1.8 +/- 0.6 v 1.4 +/- 0.3 min-1 x 10(2)). Reduced glucose tolerance after prolonged extreme physical exercise was accompanied by reduced phi 2 and not by alterations of SI or SG, despite the marked increase of FFA levels. Elevated norepinephrine levels, reflecting activation of the sympathetic noradrenergic system, was also associated with the reduction in Kg. The reduction in phi 2 would promote mobilization of FFA, the predominant metabolic substrate in these endurance events.

Effects of acute and chronic counterregulatory hormone infusions on glucose tolerance and insulin sensitivity in diabetic dogs

The effects of elevated EPI and CORT levels on KG, SI, and SG were studied in dogs with alloxan-induced diabetes. Conscious dogs received SAL, EPI 20 ng.kg-1.min-1 for 30 min (short EPI) or 72 h (long EPI), or CORT 200 micrograms.kg-1.min-1 for 60 min (short CORT) or 72 h (long CORT) before assessment of glucose metabolism by rapid sampling for glucose and insulin levels after 300 mg/kg i.v. glucose and exogenous insulin infusion designed to simulate the normal secretory pattern. With EPI infusion, KG fell acutely from 2.9 +/- 0.4 to 2.0 +/- 0.2%/min (SAL vs. short EPI, P < 0.05), but rose to 3.4 +/- 0.4%/min during long EPI. Minimal-model analysis of the glucose response with the insulin data as input showed that SI decreased acutely from 4.7 +/- 1.8 to 2.5 +/- 0.6 x 10(-5) min-1/pM (SAL vs. short EPI, P < 0.05), but rose to 4.5 +/- 2.5 x 10(-5) min-1/pM during long EPI. The effects of EPI on SG paralleled the results for KG and SI, with acute decline from 3.9 +/- 0.4 to 2.1 +/- 0.4 x 10(-2) min-1 (SAL vs. short EPI, P < 0.05) and recovery to 3.3 +/- 0.3 x 10(-2) min-1 during long EPI. During CORT infusion, KG tended to fall (SAL 2.9 +/- 0.4 vs. short CORT 2.5 +/- 0.5 vs. long CORT 2.2 +/- 0.5%/min).(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of epinephrine on glucose-mediated and insulin-mediated glucose disposal in insulin-dependent diabetes

The aim of this study was to determine the relative roles of changes in glucose-mediated glucose disposal (SG) and insulin sensitivity (SI) on the impairment of glucose disposal caused by epinephrine (EPI) infusion in type I (insulin-dependent) diabetes mellitus (IDDM). Seven non-obese young adult diabetics with minimal endogenous insulin secretion had EPI infusions at 25 ng/kg/min for 5.5 hours, after a basal overnight insulin infusion (12 mU/kg/h), and glucose infusion as required to maintain euglycemia. The EPI infusion produced approximately an eightfold increase in plasma EPI. At 2.5 hours, an intravenous glucose tolerance test (IVGTT) was performed with supplemental exogenous insulin infusion to achieve an approximation of normal endogenous insulin secretion. In random order, each subject also had a control (CTR) infusion of basal insulin before the IVGTT. The results were analyzed according to a modification of the minimal model of Bergman et al. EPI infusion was associated with (1) elevated basal plasma glucose (EPI v CTR, 9.8 +/- 0.3 SE v 7.7 +/- 0.7 mmol/L, P less than .05); (2) elevated plasma nonesterified fatty acids (NEFA, 0.9 +/- 0.1 v 0.3 +/- 0.1 mmol/L, P less than .05); and (3) profoundly reduced glucose disposal (KG 0.59 +/- 0.1 v 1.91 +/- 0.33 min-1 x 10(2), P less than .02). Further analysis showed that the reduced glucose disposal was attributable to a marked decrease in SI (EPI 0.9 +/- 0.5 v CTR 7.03 +/- 3.2 min-1.mU-1.L x 10(4), P less than .05) with no significant change in SG (EPI 2.5 +/- 0.2 v CTR 3.1 +/- 0.5 min-1 x 10(2), NS).(ABSTRACT TRUNCATED AT 250 WORDS)

Masking of diabetic phenotype on a low-energy diet despite persistence of impaired insulin response

Type 2 diabetes has been postulated to be a "thrifty genotype" that aids fuel conservation; to investigate this hypothesis, type 2 diabetic and nondiabetic subjects, normal weight and obese, were studied after both 6 days on a 700-calorie diet and 6 days on a 2,800-calorie diet. On 2,800 calories per day, the median basal plasma glucose was raised in diabetics compared with nondiabetic subjects (median, 5.5 and 4.5 mmol/L, respectively; P = .003), but on the low-energy diet there was no difference (4.1 and 3.7 mmol/L, respectively; P greater than .05). Basal plasma insulin levels were similar in the diabetic and nondiabetic subjects and were twofold to threefold higher on the high- than low-energy diet in both diabetic (median, 7.8 and 3.1 mU/L on high- and low-energy diets, respectively; P = .007) and nondiabetic subjects (6.8 and 2.6 mU/L, respectively; P = .005). Similarly, the postprandial insulin concentrations increased to the same degree on the high- compared with the low-energy diet in diabetic (median postprandial increment, 14.9 and 3.4 mU/L; P = .005) and nondiabetic patients (9.5 and 3.0 mU/L; P = .005) and the beta cells in type 2 diabetes appeared to modulate normally to different calorie intakes. On both diets, the diabetic subjects had an impaired first-phase insulin response to an intravenous glucose load compared with nondiabetic subjects (high-energy diet median first-phase increment, 4.3 and 21.2 mU/L in diabetic and nondiabetic subjects, P = .0007; low-energy diet, 4.0 and 20.4 mU/L, respectively, P = .003).(ABSTRACT TRUNCATED AT 250 WORDS)

Accuracy, patient acceptance and clinical application of capillary HbA1c monitoring

HbA1c values in capillary blood (50 microliters) were compared with venous samples, assayed by HPLC (normal less than 6.6%) in 64 Type 1 and Type 2 diabetic patients. One group (n = 43) collected capillary blood in the Outpatient Department simultaneously with a venous sample. The capillary sample collection was not supervised. A second group (n = 21) obtained two capillary samples during routine home blood glucose monitoring in Unistep containers within 2 days of the venous sample and posted them to the laboratory with a questionnaire about the ease of use and acceptance of the method. In the home collection group, 97% returned samples, there were no postal losses, and 75% returned questionnaires. Although 18% of patients had difficulty collecting the samples, all preferred the Unistep method to venepuncture. Correlation of capillary and venous samples was good for patients (r = 0.97, n = 53). The mean absolute difference between the two methods was 0.36 +/- 0.04 (+/- SE) %Hb. Eleven samples had to be excluded (insufficient blood; samples undated). The standard deviation for capillary duplicates was 0.14%, at a mean of 8.7%. During laboratory storage capillary HbA1c was initially slightly higher than corresponding venous values with some decrease (7.7% to 7.2%) over 7 days. HbA1c values in home-collected samples are accurate and reproducible when compared with venous samples assayed by HPLC, and the method was acceptable to patients.

A modified minimal model analysis of insulin sensitivity and glucose-mediated glucose disposal in insulin-dependent diabetes

Although glucose utilization is impaired in insulin-dependent diabetes mellitus (IDDM), it is unclear whether this is due to reductions in insulin sensitivity (Si) and/or glucose-mediated glucose disposal (SG). The minimal model of Bergman et al can be applied to a frequently sampled intravenous glucose tolerance test (FSIGT) to simultaneously estimate Sl and SG, but cannot accommodate data from diabetics. Exogenous insulin approximating the normal pattern of insulin secretion was infused during FSIGTs in eight young non-obese C-peptide-negative IDDM subjects, but with the total dose modified to achieve sufficient glucose disappearance rates (KG) to allow analysis of data. The minimal model was modified to model the effects of the exogenous insulin on glucose kinetics to estimate SI and SG. Despite deliberately achieving supranormal plasma-free insulin levels during the FSIGT ("first-phase insulin" = 62 +/- 9 SE mU/L; "second phase insulin" = 34 +/- 9 mU/L), the diabetics showed low-normal KG values (1.3 +/- 0.29 min-1 X 10(2). Using the model, good parameter resolution (fractional SD [FSD] less than .5) was achieved (IDDM v controls: SI = 2.5 +/- 0.6 v 8.3 +/- 1.5 min-1.mU-1.L-1 X 10(4); SG = 1.6 +/- 0.5 v 2.6 +/- 0.2 min-1 X 10(2); P less than .05). This reduction in SG was confirmed in the same IDDM subjects by FSIGT during basal insulin infusion only (SG = 1.0 +/- 0.3 min-1 X 10(2)).(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of prolonged pulsatile hyperinsulinemia in humans. Enhancement of insulin sensitivity

Prolonged near-physiological pulsatile insulin infusion has a greater hypoglycemic effect than continuous insulin infusion. We have previously shown that continuous hyperinsulinemia induces insulin insensitivity. This study examines the mechanisms responsible for the greater hypoglycemic effect of pulsatile insulin administration, in particular, whether prolonged pulsatile hyperinsulinemia induces insulin insensitivity. Basally and 1 h after cessation of a 20-h pulsatile infusion of insulin (0.5 mU.kg-1.min-1), eight nondiabetic human subjects were assessed for 1) glucose turnover with [3-3H]glucose, 2) insulin sensitivity by minimal-model analysis of intravenous glucose tolerance tests, and 3) monocyte insulin-receptor binding. The time-averaged plasma insulin levels were 30 +/- 5 mU/L (mean +/- SE) during the infusion, which was similar to the levels achieved in our previous continuous hyperinsulinemia study. However, the average rate of glucose infusion to maintain euglycemia was 55% greater than in the previous study. Hepatic glucose production was -5.2 +/- 1.4 mumol.kg-1.min-1 during the infusion but returned to preinfusion levels 1 h after the infusion was stopped. Insulin sensitivity (Sl) and glucose tolerance (rate of glucose disappearance, Kg) showed changes opposite in direction to our previous continuous hyperinsulinemia study (pre- vs. postinfusion Kg 1.5 +/- 0.1 vs. 1.7 +/- 0.2 min-1 x 10(2), NS; pre- vs. postinfusion Sl 8.4 +/- 2.3 vs. 11.8 +/- 3.7 min-1.mU-1.L x 10(4), P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Fenfluramine increases insulin action in patients with NIDDM

These studies examined the effect of fenfluramine on insulin action and insulin secretion in healthy subjects and patients with non-insulin-dependent diabetes mellitus (NIDDM). In the first study, a double-blind crossover design was used in healthy subjects to compare the effect of short-term fenfluramine therapy (60 mg orally for 3 days) with placebo. Insulin secretion and whole-body insulin sensitivity (determined by frequently sampled intravenous glucose tolerance tests with analysis by the minimal-model method) were unchanged by fenfluramine. In the second study, involving patients with NIDDM inadequately controlled on submaximal to maximal doses of oral hypoglycemic agents, a double-blind crossover strategy was used to compare baseline studies (conducted after a run-in period) with fenfluramine (60 mg orally) or placebo for 4 wk. There was a significant fall in fasting blood glucose after therapy with fenfluramine compared with the baseline study period (13.0 +/- 1.2 vs. 8.4 +/- 0.89 mM, mean +/- SE, P less than .01) with no significant fall in fasting serum insulin (20 +/- 2 vs. 24 +/- 3 microU/ml) or C-peptide (1.3 +/- 0.2 vs. 1.3 +/- 0.1 nM). During euglycemic-hyperinsulinemic (1 mU.kg-1.min-1) clamp studies there was a significant increase in insulin action from 12.7 +/- 2.3 to 17.3 +/- 1.8 min-1.10(3) microU.ml-1 (P less than .05), although clamp insulin levels were lower after fenfluramine treatment (136 +/- 14 vs. 96 +/- 9 microU/ml, P less than .02), reflecting an enhanced metabolic clearance rate for insulin (12.7 +/- 1.5 vs. 20.1 +/- 2.1 ml.kg-1.min-1, P less than .025).(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of short-term pulsatile and continuous insulin delivery on glucagon secretion and insulin secretion and action

In six normal nonobese subjects, hyperinsulinemic euglycemic clamps were performed during paired sequential two-hour intravenous (IV) insulin infusions separated by an hour washout period. Each infusion was either 32 mU/kg/h of continuous insulin (CI) or 75% of this dose as 40-second pulses delivered every 13 minutes (PI). Six studies were performed with each of the following sequences in random order: PI-CI, CI-PI, and CI-CI. Based on the initial infusions, the insulin-dependent fractional glucose disappearance rate (X) during pulsatile insulin delivery (3.0 +/- 0.4 min-1 X 10(2), n = 6) was 73% of that of the continuous infusions (4.1 +/- 0.3 min-1 X 10(2), n = 12). This ratio was similar to that of the measured time-averaged plasma insulin areas (PI = 24.7 +/- 3.8 v CI = 31.4 +/- 3.5 mU/L). There was an average 23% enhancement of insulin's hypoglycemic effect during the second 12 CI infusions compared with the 12 initial CI infusions (X = 5.1 +/- 0.5 v 4.1 +/- 0.3 min-1 X 10(2), P less than .05). There was no significant difference between the enhancing effects of PI and CI infusions on insulin action in the subsequent CI's (X = 4.9 +/- 0.9 for PI-CI v X = 5.3 +/- 0.2 min-1 X 10(2) for CI-CI). First infusion PI significantly (P less than .05) decreased plasma C-peptide levels (0.34 +/- 0.05 to 0.20 +/- 0.06 mumol/L), whereas CI did not (0.33 +/- 0.02 to 0.32 +/- 0.07).(ABSTRACT TRUNCATED AT 250 WORDS)

Chronic renal failure and growth

Growth was assessed in 38 prepubertal children with chronic renal failure for a mean (range) of 2.3 (1-4) years. At first clinic visit their mean (range) glomerular filtration rate was 17 (7-35) ml/min/1.73 m2, their mean (range) age was 3.4 (0.2-9.1) years, and 23 (61%) were greater than two standard deviations below the mean for height. After intensive medical management of their chronic renal failure, half of the children who presented before 2 years of age showed appreciable catch up growth. Only a slow improvement in growth occurred in most children presenting over 2 years of age. At final assessment, the mean (range) glomerular filtration rate was 15 (6-42) ml/min/1.73(2) and 20 (53%) were greater than two standard deviations below the mean for height. There was no correlation between glomerular filtration rate and growth. There remained a group of children who continued to grow poorly. Many of these were of low birth weight, and had dysplastic kidneys.

Recent research involving the transfer of radionuclides to milk

The radionuclides in milk, which result from exposure of dairy cows to radioactive fallout, are a major factor in assessment of internal radiation of humans. To evaluate the radionuclide intake of people from fallout-contaminated milk requires information about feed sources and milk distribution. Pasture intake and the shelf-life of milk are important factors in the case of a short-lived radionuclide like 131I. Large-scale human radiation assessment studies are underway, all of which consider the dairy food chain as a critical component. These include retrospective studies of fallout from nuclear weapons testing at the Nevada site in the 1950s and the impact of the Chernobyl accident on April 26, 1986.

The influence of energy intake and percentage of body fat on the reproductive performance of nonpregnant mares

Sixty mares in transition from winter anestrus to normal cyclicity were assigned to a 3 x 2 factorial experiment to determine the effect of energy intake and percentage of body fat on the interval to first ovulation. The factors were 1) percentage of body fat--thin (<11.5), good (11.5 to 15), or fat (>15); and 2) energy intake--maintenance (100% of National Research Council (NRC) digestible energy requirement for maintenance) or high energy (150% of NRC digestible energy requirement for maintenance). Percentage of body fat was estimated by ultrasonographic scanning of rump fat thickness. Energy treatments began on April 2 and ended on June 4. Mares were teased daily with a stallion and their ovaries were palpated per rectum daily or every third day. A high energy intake was effective in hastening ovulation for mares in the thin group (P < 0.05) but not for mares in the moderate or fat groups. Mares in the fat group had a shorter (P < 0.05) interval from April 2 to ovulation (26.4 +/- 4.2 d) than those in the good or high energy-thin groups (48.7 +/- 2.8 and 49.1 +/- 4.2 d, respectively). Duration of the initial estrus was shorter (P < 0.05) for mares in the fat group (16.2 +/- 5.7 d) compared with mares in the good group (34.7 +/- 3.9 d) and tended (P<0.12) to be shorter than mares in the high energy-thin group (29.0 +/- 5.7 d).

The insulin receptor concept and its relation to the treatment of diabetes

The initial step in insulin action is binding to specific receptors. Two covalent receptor modifications possibly involved in producing pharmacodynamic effects as a result of insulin receptor binding are autophosphorylation and disulphide insulin binding. Insulin receptor numbers are 'down regulated' by insulin, but this effect may be minimised by pulsatile insulin secretion. Insulin receptor affinity is modulated rapidly by fasting, exercise and dietary composition. In non-insulin-dependent diabetes coupling of receptor binding to bioeffects is impaired. Binding is also reduced in those subjects with hyperinsulinaemia and non-insulin-dependent diabetes. Insulin-dependent diabetics have reduced insulin sensitivity, which is only partially reversed by conventional insulin therapy. 'Post-binding defects' in some diabetics could be related to defective covalent receptor modifications resulting from genetic receptor defects. High carbohydrate diets improve diabetes control through effects on the binding and coupling defects. In addition to stimulating insulin secretion, oral hypoglycaemics stimulate post-binding insulin action in vivo and in vitro. Insulin therapy in diabetes also tends to reverse post-binding defects. Pulsatile insulin delivery is more effective in lowering blood sugar than continuous administration, and produces less 'down regulation' of receptors. Combined insulin and sulphonylurea drugs reduce insulin requirements only in insulin-dependent diabetics with some endogenous insulin secretion, whereas metformin reduces insulin requirement in C-peptide negative insulin-dependent diabetes mellitus.

Net energy value of ammoniated wheat straw

Eight steers (327 kg average) were fed diets containing either nontreated or anhydrous NH3-treated wheat straw in a two-period crossover design. Intake and digestibilities of dry matter, gross energy, neutral detergent fiber, acid detergent fiber and crude protein were measured by total collection. Energy losses in urine and methane were determined. Heat production was determined by indirect respiration calorimetry on steers fed both diets and after they were fasted. Ammoniation of the straw raised its N content from .49 to 1.59% (P less than .001). Dry matter (DM) intake was increased (P less than .01) by the process from 1.0 to 1.3% of body weight. Digestibility coefficients of dry matter and energy, as well as those for fiber, were increased (P less than .001) by four percentage units or more. Crude protein digestibility, however, was depressed (P less than .001) from 67.8% to 53.5% by ammoniation. Urinary energy as a percentage of gross energy intake (GEI) was reduced (P less than .05) by NH3 treatment from 4.10 to 3.74%. Methane energy was not different (P greater than .10). Metabolizable energy was improved (P less than .001) by ammoniation, increasing from 45.2 to 50.0% of GEI. Daily heat production was higher (P less than .01) for steers consuming the ammoniated straw diet, increasing from 113.7 to 125.3 kcal/wt.75), and was due to higher metabolizable energy intake (MEI) since partial efficiency of MEI used for maintenance did not differ (P greater than .10) between diets. The higher net energy value of the ammoniated wheat straw diet (1.45 vs 1.26 kcal/g DM) was due mainly to decreased fecal loss and a slight decline in urinary loss.

Structure of the human erythrocyte insulin receptor

The structure of the insulin receptor in intact human erythrocytes was defined using the techniques of disuccinimidyl suberate (DSS) cross-linking of 125I-insulin and surface [125I]iodination followed by receptor immunoprecipitation. In contrast to a recent report, we found the erythrocyte insulin receptor to be similar in structure to that in classic target tissues for insulin, consisting of at least three species of molecular weight approximately 295,000, 265,000, and 245,000, containing disulfide-linked subunits of molecular weight approximately 130,000 and 95,000. The interconversion of the three oligomeric forms could mediate changes in receptor affinity as postulated in other tissues. The 95,000 subunit was detected by immunoprecipitation only if surface iodination was performed in a Tris/Hepes buffer using lodogen and not if phosphate-buffered saline or lactoperoxidase iodination was used. These findings indicate that the lack of a bioeffect of insulin in erythrocytes is not explained by a gross defect in the structure of their insulin receptors. The apparent identity of the insulin receptor structure in erythrocytes and insulin target tissues provides a firmer basis for the use of erythrocytes in some circumstances to reflect insulin receptor status.

An anomalous postprandial increase in erythrocyte insulin receptor affinity associated with hyperinsulinemia

Whereas the expected decrease in the binding of 125I-insulin to erythrocytes 4.5 h after a standard mixed breakfast was seen in six young nonobese normoglycemic controls (delta % bound/free = 2.0 +/- 0.5 SEM), 10 obese hyperglycemic subjects showed an increase (0.54 +/- 0.43) and eight obese normoglycemic subjects of similar age and weight, no change in binding (0 +/- 0.31), both being significantly different from the controls (p less than 0.05) but not from each other. Of the total 18 obese subjects, the 11 with fasting hyperinsulinemia (23 +/- 1.4 mU/l) showed an increase in binding of 0.82 +/- 0.40, significantly different (p less than 0.05) from the decrease of 0.30 +/- 0.25 shown by the seven normoinsulinemic (11 +/- 1.4 mU/l) subjects, despite their similar age, weight, and blood glucose concentrations. These changes in binding were explained by alterations in receptor affinity. Thus, an anomalous postprandial increase in erythrocyte insulin receptor affinity occurs in some obese subjects with or without diabetes, and is related to hyperinsulinemia rather than hyperglycemia.

Absence of covalent binding by insulin to erythrocyte and reticulocyte insulin receptors

We investigated whether insulin forms covalent bonds with its receptors on erythrocytes and reticulocytes, as it does in adipocytes (1). Of the [125I]-insulin specifically bound at 37 degrees C to human and rat erythrocytes and rat reticulocytes, only 1.5-2.3% was non-dissociable on extensive washing. When ghosts prepared from the washed cells were solubilized in Triton X-100, only 0.6-1.5% of the specifically bound radioactivity appeared in the void volume of a Sephadex G-50 column. Moreover in contrast to adipocytes, this high molecular weight radioactivity was not immunoprecipitable by antibodies to the insulin receptor and was dissociated during chromatography in sodium dodecyl sulphate. Thus we have been unable to demonstrate the formation of covalent bonds between insulin and its receptors on erythrocytes and reticulocytes. This finding is consistent with the hypothesis that covalent binding of insulin is a necessary receptor modification for insulin's metabolic effects.

Body composition. Methods of estimation and effect upon performance

The assumption that is implicit in nearly all methods for determining body composition is that the fat-free body has a constant composition and that fat content can vary from some minimal amount to over 70 per cent. Fat estimations, however, are almost always indirect and are based upon estimating some fat-free component of the body. Some fifteen different methods are described in terms of the principle involved, the cost, and the applicability for routine use. A review is presented of a large number of regression equations that have been developed to predict body density from many types of anthropometric equations. The accuracy or comparative accuracy of body composition methods cannot be evaluated with human subjects. Methods can be validated only by using the method on an animal model, then performing chemical analyses on the same animal. Data of this type are limited.