Nutrient enrichment induces a shift in dissolved organic carbon (DOC) metabolism in oligotrophic freshwater sediments

Dissolved organic carbon (DOC) turnover in aquatic environments is modulated by the presence of other key macronutrients, including nitrogen (N) and phosphorus (P). The ratio of these nutrients directly affects the rates of microbial growth and nutrient processing in the natural environment. The aim of this study was to investigate how labile DOC metabolism responds to changes in nutrient stoichiometry using ¹⁴C tracers in conjunction with untargeted analysis of the primary metabolome in upland peat river sediments. N addition led to an increase in ¹⁴C-glucose uptake, indicating that the sediments were likely to be primarily N limited. The mineralisation of glucose to ¹⁴CO₂ reduced following N addition, indicating that nutrient addition induced shifts in internal carbon (C) partitioning and microbial C use efficiency (CUE). This is directly supported by the metabolomic profile data which identified significant differences in 22 known metabolites (34% of the total) and 30 unknown metabolites (16% of the total) upon the addition of either N or P. ¹⁴C-glucose addition increased the production of organic acids known to be involved in mineral P dissolution (e.g. gluconic acid, malic acid). Conversely, when N was not added, the addition of glucose led to the production of the sugar alcohols, mannitol and sorbitol, which are well known microbial C storage compounds. P addition resulted in increased levels of several amino acids (e.g. alanine, glycine) which may reflect greater rates of microbial growth or the P requirement for coenzymes required for amino acid synthesis. We conclude that inorganic nutrient enrichment in addition to labile C inputs has the potential to substantially alter in-stream biogeochemical cycling in oligotrophic freshwaters.

Language matters. Addressing the use of language in the care of people with diabetes: position statement of the English Advisory Group

The language used by healthcare professionals can have a profound impact on how people living with diabetes, and those who care for them, experience their condition and feel about living with it day-to-day. At its best, good use of language, both verbal and written, can lower anxiety, build confidence, educate and help to improve self-care. Conversely, poor communication can be stigmatizing, hurtful and undermining of self-care and can have a detrimental effect on clinical outcomes. The language used in the care of those with diabetes has the power to reinforce negative stereotypes, but it also has the power to promote positive ones. The use of language is controversial and has many perspectives. The development of this position statement aimed to take account of these as well as the current evidence base. A working group, representing people with diabetes and key organizations with an interest in the care of people with diabetes, was established to review the use of language. The work of this group has culminated in this position statement for England. It follows the contribution of Australia and the USA to this important international debate. The group has set out practical examples of language that will encourage positive interactions with those living with diabetes and subsequently promote positive outcomes. These examples are based on a review of the evidence and are supported by a simple set of principles.

Language matters: a UK perspective

AIM

To review the existing evidence regarding the use of language in clinical encounters.

BACKGROUND

Awareness of the importance of language in clinical encounters is mostly lacking or located within broader discussions on communication.

METHODS

A scoping study was conducted to review existing research that could increase our understanding of the role language plays as well as identify gaps in knowledge and inform the development of a position statement on language in diabetes care.

RESULTS

Evidence shows that, although carefully chosen language can have a positive effect, there is a potential negative impact of language on people's experiences of diabetes care. The use of stigmatizing and discriminatory words during communication between healthcare practitioners and people with diabetes can lead to disengagement with health services as well as sub-optimal diabetes self-management. Clinical encounters can be compromised where language barriers exist or where there is limited understanding of cultural differences that may have an impact on diabetes self-management. What little empirical evidence there is shows that training can improve language and communication skills.

CONCLUSION

This review raises a number of questions that are being addressed by the NHS England Language Matters Group, which has developed a set of recommendations to support the use of appropriate language in clinical encounters.

Prevalence and correlates of depressive disorders in people with Type 2 diabetes: results from the International Prevalence and Treatment of Diabetes and Depression (INTERPRET-DD) study, a collaborative study carried out in 14 countries

AIMS

To assess the prevalence and management of depressive disorders in people with Type 2 diabetes in different countries.

METHODS

People with diabetes aged 18-65 years and treated in outpatient settings were recruited in 14 countries and underwent a psychiatric interview. Participants completed the Patient Health Questionnaire and the Problem Areas in Diabetes scale. Demographic and medical record data were collected.

RESULTS

A total of 2783 people with Type 2 diabetes (45.3% men, mean duration of diabetes 8.8 years) participated. Overall, 10.6% were diagnosed with current major depressive disorder and 17.0% reported moderate to severe levels of depressive symptomatology (Patient Health Questionnaire scores >9). Multivariable analyses showed that, after controlling for country, current major depressive disorder was significantly associated with gender (women) (P<0.0001), a lower level of education (P<0.05), doing less exercise (P<0.01), higher levels of diabetes distress (P<0.0001) and a previous diagnosis of major depressive disorder (P<0.0001). The proportion of those with either current major depressive disorder or moderate to severe levels of depressive symptomatology who had a diagnosis or any treatment for their depression recorded in their medical records was extremely low and non-existent in many countries (0-29.6%).

CONCLUSIONS

Our international study, the largest of this type ever undertaken, shows that people with diabetes frequently have depressive disorders and also significant levels of depressive symptoms. Our findings indicate that the identification and appropriate care for psychological and psychiatric problems is not the norm and suggest a lack of the comprehensive approach to diabetes management that is needed to improve clinical outcomes.

The INTERPRET-DD study of diabetes and depression: a protocol

AIM

People with diabetes are at an increased risk of developing depression and other psychological disorders. However, little is known about the prevalence, correlates or care pathways in countries other than the UK and the USA. A new study, the International Prevalence and Treatment of Diabetes and Depression Study (INTERPRET-DD) aims to address this dearth of knowledge and identify optimal pathways to care across the globe.

METHOD

INTERPRET-DD is a 2-year longitudinal study, taking place in 16 countries' diabetes outpatients' facilities, investigating the recognition and management of depressive disorders in people with Type 2 diabetes. Clinical interviews are used to diagnose depression, with clinical and other data obtained from medical records and through patient interviews. Pathways to care and the impact of treatment for previously unrecognized (undocumented) depression on clinical outcomes and emotional well-being are being investigated.

RESULTS

Initial evidence indicates that a range of pathways to care exist, with few of them based on available recommendations for treatment. Pilot data indicates that the instruments we are using to measure both the symptoms and clinical diagnosis of depression are acceptable in our study population and easy to use.

CONCLUSIONS

Our study will increase the understanding of the impact of comorbid diabetes and depression and identify the most appropriate (country-specific) pathways via which patients receive their care. It addresses an important public health problem and leads to recommendations for best practice relevant to the different participating centres with regard to the identification and treatment of people with comorbid diabetes and depression.

What factors influence concordance with medications? Findings from the U.K. Asian Diabetes study

AIMS

To investigate concordance with medication, as assessed at baseline and at 1- and 2-year follow-up, and to examine factors associated with non-concordance in a UK-resident South-Asian population.

METHODS

Data from the UK Asian Diabetes Study were analysed. Concordance with medications was assessed and recorded at three time points during the study. Multiple logistic regression was used to investigate the factors associated with non-concordance; the associations of baseline factors with year 1 concordance and baseline plus year 1 factors with year 2 concordance.

RESULTS

Data for 403 patients from seven practices participating in the UK Asian Diabetes Study were analysed. The numbers of patients who were non-concordant were: 63 (16%) at baseline; 101 (25%) at year 1; and 122 (30%) at year 2. The baseline-measured variables that were significantly associated with year 1 non-concordance included diabetes duration, history of cardiovascular disease, components of the EuroQol quality of life questionnaire, the EQ-5D score, and number of medications prescribed. In multivariable analyses, the most important determinant of year 1 non-concordance was baseline non-concordance: odds ratio 13.6 (95% confidence limits 4.7, 39.9). Number of medications prescribed for blood pressure control was also significant: odds ratio 1.8 (95% confidence limits 1.4, 2.4). Similar results were observed for year 2 non-concordance.

CONCLUSIONS

Non-concordance with medications was common and more likely in people prescribed more medications. The current target-driven management of risk factor levels may lead to increasing numbers and doses of medications. Considering the high cost of medications and the implications of poor health behaviours on morbidity and mortality, further investigation of prescribing behaviours and the factors affecting patient concordance are required.

Kaleidoscope model of diabetes care: time for a rethink?

National Audit Data highlight persistent sub-optimum control among increasing numbers of people living with diabetes, with severe consequences for the individual and the NHS. The aim of the present review was to introduce a new cohesive, holistic model of care, tailored to individual needs to support optimum diabetes outcomes. This model of diabetes is necessary in order to understand the driving forces behind behaviour and their impact on diabetes management. Feelings (an emotional state or reaction) and beliefs (an acceptance that something is true or real) are fundamental behavioural drivers and influence diabetes self-management choices. Individually, these explain some of the complexities of behaviour and, collectively, they impact on personal motivation (rationale/desire to act) to achieve a specific outcome. Inevitably, they independently affect diabetes self-management and the environment in which individuals live. A model of care that proposes the encompassing of environment, intrinsic thought and therapy regimens to provide tailored, personalized healthcare should support enhanced diabetes self-management and outcomes from diagnosis. The Kaleidoscope model of care could be deliverable in routine care, incorporating each of the influences on diabetes self-management, and should benefit both individuals with diabetes and healthcare professionals.

Screening tools used for measuring depression among people with Type 1 and Type 2 diabetes: a systematic review

BACKGROUND

Depression is common in patients with Type 1 or Type 2 diabetes, has a strong negative impact on the quality of life of patients and is associated with poor outcomes and higher mortality rates. Several guidelines encourage screening of patients with diabetes for depression. It is unclear which depression screening tools are currently being used in people with diabetes and which are most appropriate.

METHODS

A systematic review was conducted to examine which depression screening instruments are currently being used in diabetes research, and the operating characteristics of these tools in diabetes populations. Literature searches for the period January 1970 to October 2010 were conducted using MEDLINE, PSYCH-INFO, ASSIA, SCOPUS, ACADEMIC SEARCH COMPLETE, CINAHL and SCIENCE DIRECT.

RESULTS

Data are presented for the 234 published studies that were examined. The Beck Depression Inventory and the Centre for Epidemiologic Studies Depression Scale were the most popular screening tools (used in 24% and 21% of studies). Information on the cultural applicability of screening tools was mostly unavailable and, where reported, included only details of the language translation process. A small number of studies reported reliability data, most of which showed moderate-good sensitivity and specificity but a high rate of false positives.

CONCLUSIONS

Although a range of depression screening tools have been used in research, there remains few data on their reliability and validity. Information on the cultural applicability of these instruments is even scantier. Further research is required in order to determine the suitability of screening tools for use in clinical practice and to address the increasing problem of co-morbid diabetes and depression.

Measuring psychological well-being in South Asians with diabetes; a qualitative investigation of the PHQ-9 and the WHO-5 as potential screening tools for measuring symptoms of depression

BACKGROUND

People from South Asian backgrounds living in the UK have a greatly increased risk of developing Type 2 diabetes. Whether or not this patient group also experience high rates of depressive symptoms (known to be the case in Caucasian populations with diabetes) remains unknown, partly because it is unclear whether the screening tools used are culturally relevant. The aim of this study was to develop culturally competent translations (in both written and audio formats) of two screening tools used to measure symptoms of depression in languages with no written form and establish their face validity.

METHODS

Adults with Type 2 diabetes from two South Asian minority ethnic groups (from Bangladesh and Pakistan) whose main language is only spoken (Sylheti and Mirpuri) were recruited via the Birmingham Heartlands Hospital Diabetes Centre. Participants attended two focus group meetings to consider the content and method of delivery of two questionnaires measuring symptoms of depression, the Patient Health Questionnaire (PHQ-9) and the World Health Organization Well-being Index (WHO-5).

RESULTS

Culturally equivalent content was achieved for both questionnaires in both languages. The Mirpuri men and women groups did not indicate a clear preference for either mode of questionnaire delivery; however, the Sylheti groups' preference was for independent audio-delivery in their spoken language.

CONCLUSIONS

The face validity of the PHQ-9 and the WHO-5 was established for Sylheti and Mirpuri in an audio delivery format. Psychometric testing is now needed among minority ethnic populations so that the feasibility of wider use can be determined.

Modification and validation of the Revised Diabetes Knowledge Scale

OBJECTIVES

To develop a simplified true/false response format of the Revised Diabetes Knowledge Scale and assess scaling assumptions, reliability and validity of the binary response format (the Simplified Diabetes Knowledge Scale) and compare with a multiple-choice version.

METHODS

Ninety-nine respondents attending an outpatient clinic completed the multiple-choice version of the Revised Diabetes Knowledge Scale and the simplified version of the Revised Diabetes Knowledge Scale. The response patterns and psychometric properties of both questionnaires were assessed in order to test the construct validity of the simplified version.

RESULTS

The mean age of the respondents was 57 years (range 21-83 years) and 64% were men. Respondents attained an average score of 65% on the Simplified Diabetes Knowledge Scale, compared with 62% on the Revised Diabetes Knowledge Scale. Overall, the Simplified Diabetes Knowledge Scale appeared to be somewhat easier to complete compared with the Revised Diabetes Knowledge Scale, as indicated by the number of missing responses.

CONCLUSIONS

The Simplified Diabetes Knowledge Scale provides researchers with a brief and simple diabetes knowledge questionnaire with favourable psychometric properties. The scale may require further updating to include other items relevant to diabetes education. This simplified version will now undergo translation and validation for use among minority ethnic groups resident in the UK.

Type 2 diabetes mellitus as a risk factor for the onset of depression: a systematic review and meta-analysis

AIMS/HYPOTHESIS

An earlier meta-analysis showed that diabetes is a risk factor for the development and/or recurrence of depression. Yet whether this risk is different for studies using questionnaires than for those relying on diagnostic criteria for depression has not been examined. This study examined the association of diabetes and the onset of depression by reviewing the literature and conducting a meta-analysis of longitudinal studies on this topic.

METHODS

EMBASE, MEDLINE and PsycInfo were searched for articles published up to September 2009. All studies that examined the relationship between type 2 diabetes and the onset of depression were included. Pooled relative risks were calculated using fixed and random effects models.

RESULTS

Eleven studies met our inclusion criteria for this meta-analysis. Based on the pooled data, including 48,808 cases of type 2 diabetes without depression at baseline, the pooled relative risk was 1.24 (95% CI 1.09-1.40) for the random effects model. This risk was significantly higher for studies relying on diagnostic criteria of depression than for studies using questionnaires. However, this difference was no longer significant when controlled for year of publication.

CONCLUSIONS/INTERPRETATION

Compared with non-diabetic controls, people with type 2 diabetes have a 24% increased risk of developing depression. The mechanisms underlying this relationship are still unclear and warrant further research.

Does diabetes-related distress explain the presence of depressive symptoms and/or poor self-care in individuals with Type 1 diabetes?

AIMS

To examine the relationship between depressive symptomatology, diabetes-related distress and aspects of diabetes self-care in a cohort of individuals with Type 1 diabetes.

METHODS

Individuals with Type 1 diabetes taking part in the Pittsburgh Epidemiology of Diabetes Complications Study completed the Beck Depression Inventory (BDI), the Center for Epidemiologic Studies Depression (CES-D) Scale and the Problem Areas in Diabetes (PAID) scale. Self-care was measured by physical activity in the past week and over the previous year, frequency of blood glucose/urine testing, smoking status and alcohol intake.

RESULTS

Clinically significant levels of depressive symptomatology (i.e. scores >or= 16) were reported by 14% of the study population on the BDI and by 18% on the CES-D. There were strong correlations between depressive symptoms and diabetes-related distress (PAID scores) and physical activity. Multivariate analyses indicated that depression was independently associated with diabetes-related distress scores and with physical activity, but not with frequency of blood glucose testing.

CONCLUSIONS

These findings have implications for clinical practice and treatment of both psychological morbidity and diabetes. There may be significant effects of depression on aspects of diabetes self-care. Further prospective studies are required to confirm these findings.

Development of alternative methods of data collection in South Asians with Type 2 diabetes

AIMS

Previous research in the UK has established the difficulty of recruiting and collecting information from individuals whose main language is spoken and does not have an agreed written form. The aims of this study were (i) to develop culturally competent translations of two questionnaires measuring diabetes self-care in languages with no written form and to establish their face validity and (ii) to develop acceptable methods of delivery with the potential for providing valid and reliable data for use in research studies.

METHODS

Adults with Type 2 diabetes from two minority ethnic groups whose main language is spoken (Sylheti and Mirpuri) were recruited via the Birmingham Heartlands hospital diabetes centre. Participants were invited to attend five focus groups to consider the content and method of delivery of two questionnaires measuring knowledge of diabetes and confidence in diabetes self-care. Delivery methods were (i) pen and paper self-completion in Bengali/Urdu, (ii) pen and paper assisted completion in spoken language, (iii) partially-assisted completion in spoken language, (iv) independent audio delivery in spoken language.

RESULTS

Culturally competent content was achieved for both questionnaires in both languages. The Mirpuri men and women's groups preferred assisted or partially assisted completion in spoken language. The Sylheti groups' preference was for independent audio delivery in spoken language.

CONCLUSIONS

The face validity of two questionnaires measuring diabetes self-care is established for Sylheti and Mirpuri, in four alternative delivery formats. The questionnaires are now ready for psychometric testing in minority ethnic populations and the methods available for use by researchers to establish within-study feasibility.

Systematic literature review: quality of life associated with insulin pump use in Type 1 diabetes

AIM

To review systematically the published literature addressing whether continuous subcutaneous insulin infusion (CSII) provides any quality of life benefits to people with Type 1 diabetes.

METHODS

Electronic databases and published references were searched and a consultation with two professional groups was undertaken to identify relevant studies published up to July 2005. A multistep selection process was then undertaken to identify those articles which met the specific selection criteria, which were then critically reviewed.

RESULTS

Eighty-four potential relevant articles were identified from examination of titles and abstracts published during the specified time frame. Of these, 28 articles were retrieved in full text, of which 17 fulfilled the specific criteria for inclusion. Mixed results emerged from existing literature. Of the five randomized controlled trials, three reported mixed results, with one study reporting quality of life benefits and one reporting no evidence of quality of life benefits.

CONCLUSIONS

There is conflicting evidence reported in the various studies on the quality of life benefits of CSII in Type 1 diabetes. Existing research is flawed, making a judgement about the quality of life benefits of insulin pump use difficult. There is no strong evidence against quality of life benefits associated with CSII or otherwise, with poor methodology and inconsistent assessment of quality of life clouding the issue. The lack of reported benefit is probably a function of this rather than pump therapy not offering any quality of life benefits.

Effect of central administration of interleukin-1 receptor antagonist on protein synthesis in skeletal muscle, kidney, and liver during sepsis

Inflammatory cytokines may mediate the host response to infection via central nervous system (CNS), endocrine, and/or paracrine pathways. The purpose of the present study was to determine whether intracerebroventricular (ICV) infusion of interleukin-1 receptor antagonist (IL-1ra) influences the effects of sepsis on protein metabolism in peripheral organs (skeletal muscle, kidney, and liver). A constant ICV infusion of IL-1ra (100 microg/h) or saline was begun immediately before the induction of sepsis or sterile inflammation and continued for 5 days. ICV infusion of IL-1ra did not alter protein metabolism in animals with a sterile abscess. Sepsis reduced muscle weight, protein content, and rates of protein synthesis in gastrocnemius. ICV infusion of IL-1ra attenuated the sepsis-induced loss of muscle mass and protein and the inhibition of protein synthesis in gastrocnemius by augmenting the translational efficiency. Similar results were observed in kidney, with respect to kidney weight, total protein, rates of protein synthesis, and translational efficiency. However, central infusion of IL-1ra did result in a small (12%) increase in the renal RNA content in either sterile or septic abscess rats. In liver, ICV infusion of IL-1ra prevented the sepsis-induced inhibition of protein synthesis and reduction in translational efficiency. These results suggest that central administration IL-1ra can modulate protein metabolism in peripheral organs during sepsis by preventing the sepsis-induced defects in the translational efficiency.

Do the daily experiences of healthy men and women vary according to occupational prestige and work strain?

OBJECTIVE

This study evaluated the influence of occupational prestige and work strain on mood, the occurrence of interpersonal conflict, and ambulatory blood pressure and heart rate.

METHODS

Participants were 50 men and 50 women matched for occupational prestige who were healthy and middle-aged and who completed measures of mood and conflict simultaneously with measures of ambulatory blood pressure and heart rate recorded every 30 minutes during waking hours of two workdays and one nonworkday; at the end of each day, overall ratings were made. Work strain was assessed by the Work Section of the Self-Evaluation and Social Support Interview Schedule. Multiple level random regression coefficients analyses were conducted.

RESULTS

Men and women with low-prestige occupations experienced more interpersonal conflict, b = -0.03, p = .04, and higher ambulatory heart rate, b = -4.83, p = .004, throughout the three days of the study. Relative to those with low work strain, those reporting high work strain experienced negative emotion, b = -0.41, p < .0001, and boredom, b = -0.17, p < .0004. End of the day ratings of negative mood were more influenced by work strain among men than among women. No effects of occupational prestige or work strain were obtained for ambulatory blood pressure readings after adjustment for physical activity, posture, and location.

CONCLUSIONS

Individuals in low-prestige occupations experience greater exposure to interpersonal conflict and arousal as indexed by heart rate, which might increase risk for stress-related illnesses often associated with social class. Individuals who report work strain experience negative mood and boredom, both at work and at home. The absence of work effects on ambulatory blood pressure may be due to the participants being healthy.

Prevalence of symptoms of depression and anxiety in a diabetes clinic population

AIMS

To investigate the use of a short questionnaire to measure psychological symptoms in a busy clinic setting, and to examine the prevalence of these symptoms in adults with diabetes. The perceived need for psychological treatment services was also measured.

METHODS

Adults (> 18 years) with either Type 1 or Type 2 diabetes were invited to complete a short demographic form and the Hospital Anxiety and Depression Scale (HADS) whilst waiting for their routine diabetes outpatients appointment. Complication status was measured via patients' medical records. Glycaemic control (HbA(1c)) was also recorded.

RESULTS

A high response rate (96%) was achieved. Prevalence rates of psychological symptoms were high (overall 28% of study participants reported moderate-severe levels of depression or anxiety or both). Men were somewhat more likely to report moderate-severe depressive symptoms, whereas women reported more moderate-severe anxiety. A significant association between depression and poor glycaemic control was observed in the men, but not in the women. Regression analysis demonstrated that the interaction between sex and glycaemic control, HbA(1c) and sex were all significantly associated with depression and anxiety (R2 = 0.16 and 0.19, respectively). One-third of subjects reported that at the moment they would be interested in receiving counselling or psychotherapy if it was currently available at the diabetes clinic.

CONCLUSIONS

This study has shown that the HADS is an appropriate questionnaire to use in a clinic setting in adults with diabetes. There may be a stronger association between glycaemic control and psychological symptomatology in men than in women. There remains a significant proportion of individuals with diabetes who require psychological support, which, if available, might help improve glycaemic control and thus overall wellbeing.

Association between stress and glycemic control in adults with type 1 (insulin-dependent) diabetes

OBJECTIVE

To examine the relationship between stressful life events and alterations in glycemic control in adults with diabetes.

RESEARCH DESIGN AND METHODS

The occurrence of stressful experiences was recorded using the life Events and Difficulties Schedule of Brown and Harris in 55 adults with type 1 diabetes. The two most recent measures of glycemic control (HbA1c) were obtained from medical records, with poor glycemic control defined by the sample median (> or =7.7%).

RESULTS

Subjects whose control deteriorated over time or who remained in poor glycemic control were significantly more likely to report severe personal stressors (SPS) in the month before HbA1c measurement, compared with subjects whose control remained fair or whose control improved (43 and 25% vs. 7 and 0%; P = 0.000). Subjects whose control remained fair or whose control improved were significantly more likely to report only positive life events during the same time period (80 and 11% vs. 0 and 0%, respectively; P = 0.000). Multiple regression analysis demonstrated that SPS, sex, and lack of further education were all significantly associated with either remaining in poor control or deterioration of control.

CONCLUSIONS

The study has shown that recent severe stressors are associated with poorer glycemic control. Positive life events were associated with fair or improved glycemic control. This study has its limitations, and future studies should be prospective in design. While it is not always possible to avoid stress, learning to recognize and cope with stressors may help individuals with diabetes maintain good glycemic control and improve overall quality of life.

Physical and psychological well-being in adults with Type 1 diabetes

The physical and psychological well-being of adults with Type 1 (insulin-dependent) diabetes (n = 397) were investigated using a series of questionnaires, including the Medical Outcomes Survey SF36. Development of diabetes complications and glycaemic control (glyated haemoglobin) were also measured. Results showed that older individuals, those with complications, women, the less physically active and those on lower incomes, were more likely to experience a poorer quality of life. Those who reported at least one hypoglycaemic episode per month also had poorer quality of life. This study, whilst confirming earlier work showing an association between quality of life and diabetes complications, demonstrates that other factors may also be important. Of particular interest is the association with hypoglycaemia, which has implications for diabetes care. Given the importance of reducing blood glucose levels in order to avoid complications, this focus in patient care may overlook the subsequent impact on quality of life.

Factors associated with clinic non-attendance in adults with type 1 diabetes mellitus

In order to examine the causes of non-attendance in a diabetic clinic, a 1-year retrospective casenote review of 259 diabetic patients with no evidence of major complications was undertaken. Frequency of clinic attendance, clinic non-attendance, and glycaemic control (HbA1c) were recorded. In a sub-sample of 82 patients, more detailed demographic data was obtained via questionnaire. During the previous year 39% of patients had failed to attend the clinic on at least one occasion and 10% were recurrent non-attenders. Non-attenders had a significantly higher mean HbA1c compared with those who did attend (8.1 +/- 2.2 vs 7.6 +/- 1.6%; p = 0.03). They were also significantly younger (mean age 27 + 7 vs 29 +/- 9 yrs; p = 0.02) and had a significantly shorter duration of diabetes (12 +/- 8 vs 15 +/- 10 yrs; p = 0.02). Attendance did not differ according to gender or age of onset of diabetes. Sub-sample analysis showed that smokers, those with children at home, and single parents were all more likely to default from their appointments. Non-attendance is a significant problem at our diabetic clinic, however, by addressing the reasons why patients fail to attend clinic we hope to develop strategies to encourage regular attendance. This may be translated into improved glycaemic control and ultimately reduce the risk of late diabetic complications.

Social deprivation and mortality in adults with diabetes mellitus

To investigate the relationship between measures of social deprivation and mortality in adults with diabetes, data from 2104 randomly selected adults (> 16 years of age) with Type 1 and Type 2 diabetes mellitus from 8 hospital out-patient departments were analysed. A total of 38% of subjects had Type 1 (diagnosed before the age of 36 years and treated with insulin), 55% were male and 85% Caucasian. During a follow-up period (mean (SD) of 8.4 (0.9) years), 293 (14%) of the subjects died, the most commonly recorded cause of death being cardiovascular disease. Duration adjusted odds ratios (OR) and 95% confidence intervals (CI) were calculated separately for Type 1 and Type 2 subjects. The mortality rates for men were higher than for women (Type 1: OR 1.27, CI 0.61-2.62; Type 2: OR 1.79, CI 1.27-2.52); were higher for those of lower vs higher social class (Type 1: OR 1.34, CI 0.61-2.96; Type 2: OR 2.0, CI 1.41-2.85); and were higher for those who left school before 16 years of age compared to those who left school at or after 16 years of age (Type 1: OR 3.98, CI 1.96-8.06; Type 2: OR 2.86, CI 1.93-4.25). Subjects who were unemployed had a higher mortality rate than those employed at the time of the study (Type 1: OR 3.10, CI 1.67-5.79; Type 2: OR 2.88, CI 2.12-3.91) and those living in council housing had a greater mortality than those who were living in other types of housing (Type 1: OR 2.57, CI 1.35-4.91, Type 2: OR 2.76, CI 2.05-3.73). Also for both Type 1 and Type 2 subjects mortality was significantly higher in those subjects who had a least one diabetic complication at baseline and reported one or more hospital admissions in the previous year and in Type 2 subjects with poor glycaemic control. After adjusting for duration of diabetes, hospital admissions, and the presence of diabetic complications, being unemployed, male, in poor glycaemic control (Type 2 only), and less educated were significant risk factors for mortality (p<0.001). These results suggest that there are important indicators of social deprivation which predict mortality over and above diabetic health status itself. Locally targeted action will be required if these inequalities in health experienced by people with diabetes are to be reduced.

Coronary artery disease in IDDM. Gender differences in risk factors but not risk

Insulin-dependent diabetes mellitus (IDDM) increases the risk of developing coronary artery disease (CAD) compared with that seen in the general population, while the sex differential in rates of CAD is considerably reduced in IDDM populations. To further our understanding of these observations, the effects of gender on baseline risk factors for CAD incidence were examined. Participants in the Pittsburgh Epidemiology of Diabetes Complications (EDC) Study were recruited from the Children's Hospital of Pittsburgh IDDM registry and had been diagnosed between 1950 and 1980. Subjects completed a series of questionnaires and were given a full clinical examination at baseline (1986 through 1988) and every subsequent 2 years. This report is based on the first 4 years of follow-up. Similar incidence rates of new CAD events were observed in men and women. In neither sex was glycemic control a predictor of later CAD. Sex-specific Cox proportional hazards models showed that for men, duration of IDDM, HDL cholesterol, fibrinogen, hypertension, and smoking were all significantly associated with the onset of CAD. Hypertension, fibrinogen, and smoking were all replaced by nephropathy when this latter variable was added to the model. For women, duration, hypertension, waist-hip ratio, physical activity, and depressive symptomatology were all significant independent predictors of CAD. Nephropathy status did not enter the model for women. While 4-year incidence of CAD in IDDM varies little by sex in this population, the predictive risk factors vary considerably. In particular, the effect of renal disease was stronger in men, while the cluster of physical activity, waist-to-hip ratio, and depressive symptomatology were more important in women. These results may help explain the relatively greater impact IDDM has on CAD risk for women and suggest new potential preventive approaches.

A comparison of renal disease across two continents; the epidemiology of diabetes complications study and the EURODIAB IDDM Complications Study

OBJECTIVE

To compare prevalence rates of increased albumin excretion in the Epidemiology of Diabetes Complications Study (EDC) (in the U.S.) to similar rates in the EURODIAB study (in Europe) and determine if any differences relate to hypertension, glycemic control, or smoking status.

RESEARCH DESIGN AND METHODS

The study population is made up of two epidemiological clinic-based IDDM populations with comparable ages (chi = 28 years, both studies), sex distribution (50% male, EURODIAB; 49% male, EDC), and duration characteristics. Comparison of two cross-sectional (prevalence) studies was made. Despite different laboratory assays, comparability was established for urinary albumin (r = 0.98) and GHb measures (r = 0.95). Hypertension was measured with an identical protocol. Renal status was determined by 24-h urine albumin excretion (< 20 micrograms/min normal, 20-200 micrograms/min microalbuminuria, > 200 micrograms/min macroalbuminuria) in EURODIAB. Identical cutoffs were used for EDC, though two of three samples (24-h, 4-h clinic, and/or overnight sample) had to be positive in one range. (Main findings are confirmed using only 24-h results from EDC.)

RESULTS

The prevalence of macroalbuminuria was higher in EDC (27%) than in EURODIAB (12%). Rates of microalbuminuria were similar (22 vs. 25%, respectively). These patterns were seen at all durations and ages and in both sexes. Controlling for glycemic control, hypertension, or smoking did not account for the higher rate in EDC, nor did exclusion of subjects with raised serum creatinine.

CONCLUSIONS

Advanced renal disease is more prevalent in IDDM in EDC (Pittsburgh, PA) than in Europe. This is not explained by hypertension, glycemic control, or smoking.

Incidence of complications in insulin-dependent diabetes mellitus: a survival analysis

The authors used 4-year incidence data from the Pittsburgh Epidemiology of Diabetes Complications (EDC) Study to investigate the wider applicability of recent research findings that demonstrate an association between glycemic control and insulin-dependent diabetes mellitus (IDDM) complications. EDC subjects participated in clinical examination at baseline (1986-1988) and were followed up every 2 years. Results demonstrated that, during the first 4 years of follow-up, subjects who were in "poor" control (glycosylated hemoglobin (GHb) > or = 11%) at baseline were significantly (p < 0.001) more likely to develop microalbuminuria, proliferative retinopathy, and distal symmetrical polyneuropathy (DSP), compared with subjects who were in "fair" control (GHb < 11%). Subjects who were in poor control were somewhat more likely to develop overt nephropathy (p = 0.08) and renal failure (p = 0.085) during follow-up; however, no associations were observed with either coronary heart disease or lower extremity arterial disease (LEAD). These results confirm the strong association between prior glycemic control and the onset of microalbuminuria, proliferative retinopathy, and DSP observed in the Diabetes Control and Complications Trial study. However, the results of the study suggest weaker associations for the later stages of renal disease, and little relation was seen between glycemic control and LEAD or coronary disease. Other risk factors may be more important for the development of the later complications of IDDM. Further follow-up is necessary in order to rule out type II error.

Waist to hip ratio and psychosocial factors in adults with insulin-dependent diabetes mellitus: the Pittsburgh Epidemiology of Diabetes Complications study

The relationship between waist to hip ratio (WHR) and psychosocial factors has seldom been investigated, although both may contribute to cardiovascular risk. Therefore, these variables were examined in adults with insulin-dependent diabetes mellitus ([IDDM] N = 592; mean age, 29 years; mean duration, 20 years), a population at increased risk of developing cardiovascular disease. Moreover, the association between changes in psychosocial factors and change in WHR was considered. After adjusting for body mass index (BMI), WHR in men was correlated with higher levels of depressive symptomatology (r = .19, P < .001), greater anxiety (r = .13, P < .05), less social support (r = -.20, P < .01), and lower type A scores (r = -.25, P < .001). In women, WHR was significantly correlated with higher levels of depressive symptomatology (r = .18, P < .01), greater stress (r = .16, P < .01), and alcohol consumption (r = .12, P < .05). For both sexes, smokers had a significantly greater mean WHR than nonsmokers (P < .01). For men, multiple regression analyses adjusting for BMI and age demonstrated that smoking, lower income, less exercise, and lower type A scores were the most significant variables associated with WHR. In women, the independent predictors of WHR were a history of smoking, lower educational level, and depressive symptomatology. The most significant independent predictors of change in WHR from baseline to 2-year follow-up study were change in weight (men), change in BMI (women), and change in depression scores (both sexes). These results suggest that psychosocial factors may affect cardiovascular disease risk through their influence on body fat distribution, and both may be important in identifying those most at risk for cardiovascular disease in populations with IDDM.

High mortality from unidentified CVD in IDDM: time to start screening?

Mortality in insulin-dependent diabetes is markedly increased compared to the general population. Although strong associations have been found between renal disease and the risk of cardiovascular disease (CVD) the interaction between these two factors is not well understood. This study, which addresses risk factors for mortality in IDDM with a particular focus on the renal-CVD link, is based on the prospective Epidemiology of Diabetes Complications study. Thirty-seven (mean age 36 years, mean duration of IDDM 28 years at baseline) of the 658 IDDM individuals (mean age 28 years, mean duration of IDDM 20 years at baseline) have died in the first 4 years of follow up. A nested case-control study was performed, matching on sex and duration of diabetes. Twenty-two (59%) of the deaths were attributed to coronary heart disease, with an additional 16% attributed to diabetic coma. Only nine (41%) of the 22 individuals who died from cardiovascular disease had clinical evidence of coronary heart disease when seen for their last biennial exam. However, 54% of those who died of CVD without prior evidence did have evidence of lower extremity arterial disease. A strong link with renal disease was confirmed, with 81% of those with a coronary artery disease death having renal disease. Multivariate analyses suggest that smoking history, triglycerides and total platelet count are independent predictors of mortality, while LDL cholesterol best predicted CVD mortality. These results suggest a need for more intensive screening for cardiovascular disease, and correction of cardiovascular risk factors, in order to reduce the increased rate of mortality in this population. Efforts to prevent or delay the onset of renal disease may also be of benefit.

The influence of pregnancy on IDDM complications

OBJECTIVE

Although pregnancy has been associated with an increased progression of certain insulin-dependent diabetes mellitus (IDDM) complications, particularly retinopathy, both the short- and long-term relationships between pregnancy and both neuropathy and macrovascular disease are poorly documented. This study was conducted to comprehensively examine the influence of pregnancy on the development and progression of IDDM complications.

RESEARCH DESIGN AND METHODS

Using the Pittsburgh Epidemiology of Diabetes Complications Study population (childhood-onset IDDM), two nested, pair-matched case-control studies were conducted. Women who had completed at least one successful pregnancy (n = 80) were matched to women with no history of pregnancy by age, duration of IDDM, race, and marital history. The first nested study (study 1) compared the prevalences of five IDDM complications between case and control groups. The second nested study (study 2) compared the incidences of the same five complications over an approximate 2-year interval during which the case subjects (n = 30) completed a successful pregnancy.

RESULTS

There were no significant differences in the prevalence rates of coronary heart disease, neuropathy, proliferative retinopathy, lower extremity arterial disease, and overt nephropathy by case-control status, while parity did not predict any complication in multiple logistic analysis (study 1). In study 2, there were small but nonsignificant differences in incidence rates of overt nephropathy and lower extremity arterial disease between the groups, whereas case subjects had almost 3 times the incidence rate of proliferative retinopathy (P = 0.58) and 10 times the incidence rate of neuropathy (P < 0.001) as did other matched control subjects. In multivariate analysis, parity predicted neuropathy incidence but did not predict the incidence of any other complication, including proliferative retinopathy.

CONCLUSIONS

Women with IDDM who experience a pregnancy may not be at an increased risk of diabetes complications later in life. However, in the short term, pregnancy may accelerate the development of some complications, such as neuropathy.

The progression of retinopathy over 2 years: the Pittsburgh Epidemiology of Diabetes Complications (EDC) Study

This study examined potential risk factors for the incidence and progression of retinopathy in a large representative cohort of childhood onset insulin-dependent diabetic patients. Participants in the Epidemiology of Diabetes Complications (EDC) Study underwent a full clinical examination at baseline and again at a 2-year follow-up. Retinopathy status was ascertained using stereo fundus photographs graded according to the modified Airlie House System. The study population is based on a large cohort of childhood-onset insulin-dependent diabetic patients, seen within 1 year of diagnosis at the Children's Hospital of Pittsburgh between January 1950 and May 1980. A total of 657 subjects participated at baseline (1986-1988), with 80% of eligible survivors taking part in the follow-up examination. This report concerns risk factors associated with the progression of diabetic retinopathy over a 2-year period, and the interaction of these factors with the presence of nephropathy. Analyses showed that baseline diastolic blood pressure was significantly associated with the incidence of any retinopathy, while glycosylated hemoglobin, baseline severity of retinopathy, serum triglycerides, and, to a lesser extent, higher levels of low-density lipoprotein (LDL) cholesterol and fibrinogen were associated with the progression of retinopathy. Progression to proliferative retinopathy was related to higher LDL cholesterol, fibrinogen, serum triglycerides, albumin excretion rate, and glycosylated hemoglobin (GHb). Risk factors varied with the presence of nephropathy. In the absence of nephropathy, GHb was a significant predictor of progression, whilst this was not the case in the presence of nephropathy.(ABSTRACT TRUNCATED AT 250 WORDS)

Predictors of microalbuminuria in individuals with IDDM. Pittsburgh Epidemiology of Diabetes Complications Study

OBJECTIVE

To examine the relationships between microalbuminuria and the development of overt diabetic nephrology, elevated blood pressure, and a more atherogenic lipid profile; and to identify risk factors for the development of microalbuminuria in individuals with IDDM. Microalbuminuria has been associated with the subsequent development of overt diabetic nephropathy in individuals with IDDM. It is associated with elevated blood pressure and a more atherogenic lipid profile, but the temporal relationship between the development of microalbuminuria and the changes in these factors is unclear.

RESEARCH DESIGN AND METHODS

Baseline characteristics were examined in 256 individuals with IDDM who had normal albumin excretion (urinary AER < or = 20 micrograms/min in > or = 2 timed urine collections) and were re-examined 2 yr later.

RESULTS

At follow-up, 24 had developed microalbuminuria (AER 20-200 micrograms/min in > or = 2 timed urine collections) and 1 had developed overt nephropathy (AER > 200 micrograms/min). Overall, the significant independent predictors of microalbuminuria were HbA1 (P < 0.001), low-density lipoprotein (P < 0.01), duration of IDDM (P < 0.05), and systolic blood pressure (P = 0.05). Sex-specific analyses showed HbA1, age, and baseline AER were particularly important for men; whereas, for women, the main predictors were duration of IDDM and triglycerides. Duration-specific analyses showed that HbA1 was an important predictor both for individuals with < and > 20-yr duration. Low-density lipoprotein cholesterol was more important for subjects with shorter durations; whereas triglycerides were important for those with longer durations.

CONCLUSIONS

These results suggest that glycemic control, age or duration of IDDM, disturbed lipids, and possibly elevated blood pressure all may contribute to the development of microalbuminuria; and, further, that the adverse cardiovascular risk profile seen in individuals with overt nephropathy may begin to develop even before the detection of microalbuminuria.

Psychosocial correlates of glycemic control: the Pittsburgh Epidemiology of Diabetes Complications (EDC) Study

The psychosocial correlates of glycemic control were examined in an incident cohort of childhood onset insulin-dependent diabetic subjects aged 18 years or older (n = 592). Glycosylated hemoglobin was measured at subjects' clinical examination, and questionnaires on diabetes self-care activity, barriers to regimen adherence and social support were completed. Demographic information was also collected. Glycosylated hemoglobin (GHb) was correlated with age, income and educational attainment (correlations coefficients between -0.1 and -0.2; P < 0.01), suggesting that older, more educated and wealthier patients have better glycemic control. GHb was also inversely associated with the degree of self-care activity (r = -0.11; P < 0.01), in particular administering injections at the recommended times and the frequency of performing blood/urine tests. Factors related to self-care behavior were identified, and included degree of social support (r = 0.14; P < 0.001) and patients' reports of difficulties adhering to their self-care regimen (r = -0.3; P < 0.0001). Gender was also related to self-care activities, with women reporting more self-care behavior than men (mean self-care scores 17.9 +/- 3.7 vs. 16.9 +/- 4.0; P < 0.01). Thus psychosocial factors (e.g. low income and education) may have an important effect on glycemic control in adults, and also (e.g. social support and adherence difficulties) seem particularly important in influencing the performance of self-care. As good metabolic control may help avoid the progression of diabetic complications, efforts need to be directed towards patients with these characteristics who are more likely to experience difficulties with self-care.

Are the social relationships of young insulin-dependent diabetic patients affected by their condition?

In order to compare the social relationships of young adults with Type 1 diabetes with those of healthy controls, 80 young people aged 16-25 years were interviewed in-depth with a semi-structured questionnaire. Results demonstrated that subjects with diabetes had an equally high commitment to social arenas, but were significantly more likely to be socially isolated and were less likely to have very close relationships. Subjects had more attitudinal constraints with regard to having close relationships, and were more likely to report a fear of intimacy. They were less likely to have children, and many voiced their concerns regarding the impact their diabetes might have on both marriage and future parenthood. This study suggests that young adults with diabetes have more negative social experiences which may affect their feelings with regard to having close relationships. The absence of supportive relationships may impact on diabetes management; however this has yet to be fully ascertained in a young adult population.

Education and employment experiences in young adults with type 1 diabetes mellitus

Educational attainment, employment experiences, and self-esteem were measured using semi-structured questionnaires in young adults with Type 1 diabetes mellitus and in a group of age/sex matched healthy controls. Results showed that subjects with diabetes and their matched controls obtained comparable qualifications at all levels. However, subjects with diabetes were less likely to feel competent with regard to their educational performance, and many of this group reported experiencing difficulties at school. There were no differences in the proportion of each group who had experienced unemployment, although this was explained more by social class and educational attainment. Whereas only a minority had decided to withhold information about their condition from their employers, one-third of those with diabetes had experienced health-related problems in obtaining employment. This study suggests that the educational achievements and employment experiences of young adults with diabetes may not differ from those of healthy controls. However subjective reports of difficulties in these areas may be associated with reduced self-esteem. Confirmation of these findings should be carried out in a larger sample, using a prospective design.

Psychosocial factors and complications of IDDM. The Pittsburgh Epidemiology of Diabetes Complications Study. VIII

OBJECTIVE

To investigate whether psychosocial factors are associated with diabetic complications.

RESEARCH DESIGN AND METHODS

Questionnaires on quality of life, depressive symptomatology, and personality type were completed and a clinical assessment was performed. The study population was an incident cohort of childhood-onset insulin-dependent diabetic (IDDM) subjects whose duration of IDDM was greater than or equal to 25 yr (n = 175).

RESULTS

Patients with macrovascular disease (P less than 0.01) or nephropathy (P less than 0.05) reported significantly poorer quality of life compared with those who were free from all complications. Patients with macrovascular disease also reported greater depressive symptomatology (P less than 0.05). Quality of life significantly deteriorated according to the presence of multiple (greater than or equal to 4) complications (P less than 0.001). Higher depression symptom scores were also related to the presence of greater than or equal to 4 complications (P less than 0.001). Those with multiple complications reported less type A behavior than those without any complications (P less than 0.05).

CONCLUSIONS

This study shows that psychosocial differences exist according to both the number and the type of diabetic complications present. Because poorer quality of life and symptoms of depression may both result form complications, prospective follow-up is needed to clarify their temporal interrelationships, and to determine whether type A personality affords any protection against complications or is diminished as a result of developing complications.

The relationship between stress and the development of diabetic complications

Using the Life Events and Difficulties Schedule of Brown and Harris, the relationship between preceding stress and the onset of diabetic complications and premature death was investigated prospectively in a random sample of 130 patients with diabetes, aged 35-59 years. The presence of stress, assessed as severe life-events and severe long-term difficulties, was not significantly associated with premature death or the onset of macrovascular disease over the relatively short period of follow-up (4 years). Those who commenced anti-hypertensive therapy during the follow-up period were significantly more likely to have experienced five or more severe life-events during the previous 5 years (40 vs 6%, p less than 0.01), and also to have experienced one or more severe long-term difficulties during the same time period (60 vs 28%, p less than 0.05). A multiple Cox regression analysis showed that the effects of stress were independent of other factors such as baseline blood pressure, type of diabetes, sex, and ethnic group.

Psychosocial factors and the onset of type 1 diabetes

Stress has been proposed as a possible precipitating factor for the development of Type 1 diabetes in genetically susceptible individuals. A validated in-depth psychometric instrument (The Life Events and Difficulties Schedule) was used to investigate the role of psychosocial factors in the onset of Type 1 diabetes in islet cell antibody (ICA)-positive family members. Families with ICA-positive members had higher scores for subject focused severe life events in the 5-year period prior to the diagnosis of diabetes in a second family member compared with matched control families (1.50 +/- 0.68 (+/- SD) vs 0.32 +/- 0.37; p less than 0.03). In the same time period, these families also experienced a higher mean number of severe long-term difficulties compared with control families (1.34 +/- 0.52 vs 0.14 +/- 0.17; p less than 0.01). Scores for current total visual social contacts were greater for control families compared with case family members (12.10 +/- 1.90 vs 9.64 +/- 2.70; p less than 0.05). These results suggest that global family stress possibly in conjunction with a reduced number of social contacts may act as a trigger for the development of diabetes in a second family member and that social support may act as a buffer to stress and disease onset.

Stimulation of albumin gene transcription by insulin in primary cultures of rat hepatocytes

The first goal of the work reported here was to prepare single-stranded DNA sequences for use in studies on the regulation of albumin gene expression. A double-stranded rat albumin cDNA clone was subcloned into the bacteriophage vector M13mp7. Single-stranded recombinant clones were screened for albumin sequences containing either the mRNA strand or the complementary strand. Two clones were selected that contained the 1,200 nucleotide long 3' end of the albumin sequence. DNA from the clone containing the mRNA strand was used as a template for DNA polymerase I to prepare a radiolabeled, single-stranded cDNA to albumin mRNA. This radiolabeled cDNA probe was used to quantitate the relative abundance of albumin mRNA in samples of total cellular RNA. DNA from the clone containing the complementary strand was used to measure relative rates of albumin gene transcription in isolated nuclei. The second goal was to use the single-stranded DNA probes to investigate the mechanism of the insulin-mediated stimulation of albumin synthesis in primary cultures of rat hepatocytes. Addition of insulin to hepatocytes maintained in hepatocytes. Addition of insulin to hepatocytes maintained in a chemically defined, serum-free medium for 40 h in the absence of any hormones resulted in a specific 1.5- to 2.5-fold stimulation of albumin gene transcription that was maximal at 3 h and was maintained above control values for at least 24 h. The relative abundance of albumin mRNA and albumin secretion increased correspondingly within 24 to 30 h. These parameters remained above control levels for at least 60 h after addition of insulin. Maximal responses were attained at an insulin concentration of 100 nM and there was a close correspondence between albumin gene transcription and albumin secretion at each concentration tested. The rate of albumin gene transcription in nuclei isolated from livers of diabetic rats was reduced to 50% of the value recorded in control nuclei. Taken together, these findings demonstrate that insulin regulates synthesis of albumin at the level of gene transcription.

Direct effect of insulin on albumin gene expression in primary cultures of rat hepatocytes

The purpose of this study was to identify a cell culture system in which the role of insulin in regulating albumin gene expression could be investigated. The system selected was rat hepatocytes maintained in primary culture in a chemically defined, serum-free medium. Under control conditions albumin secretion was nearly the same as the rate recorded in vivo and in perfused liver and was reasonably well maintained during 8 days of culture. Deletion of insulin from the culture medium for 3-6 days resulted in 40-60% reductions in albumin secretion. Furthermore, albumin secretion relative to the rate of total protein synthesis was reduced by approximately 50% as a result of insulin deficiency. Readdition of the hormone to insulin-deficient cultures restored secretion to the control rate. A maximal effect of insulin was observed within 3 days after readdition of the hormone, and a half-maximal response was obtained with a hormone concentration of approximately 3.0 nM. The relative abundance of albumin mRNA, as measured by solution hybridization using a complementary DNA probe, responded in a parallel fashion to the changes in albumin secretion. Thus rat hepatocytes maintained under appropriate culture conditions reflect the effects of diabetes and insulin treatment on albumin gene expression observed in vivo and provide an excellent model system in which to study the mechanism(s) of insulin action.

On the mechanisms involved in the regulation of the cell-surface receptors for human choriogonadotropin and mouse epidermal growth factor in cultured Leydig tumor cells

The MA-10 cells are a clonal strain of mouse Leydig tumor cells that have receptors for human choriogonadotropin (hCG) and mouse epidermal growth factor (mEGF). Exposure of the cells to hCG results in a reduction in the number of surface hCG receptors, and little or no change in the number of surface mEGF receptors. On the other hand, exposure of the cells to mEGF results in a reduction in the number of both surface mEGF receptors and surface hCG receptors. In order to study these phenomena, we assumed that the number of surface receptors is determined by the rate at which receptors appear at the surface and by the rate of receptor internalization. When these rates were measured, we found that hCG and mEGF reduce their respective surface receptors by increasing the rate of receptor internalization, and that mEGF reduces the surface hCG receptors by decreasing the rate of appearance of the receptor.

Degradation of intra- and extrahepatic protein by livers of normal and diabetic mice: differential responses to starvation

Rates of total hepatic proteolysis were measured in normal and streptozotocin-diabetic mice during feeding and over 48 hr of starvation, during which livers in the two groups lost 37% and 54% of their protein content, respectively. Measurements were made in 15-min in situ cyclic perfusions from the linear accumulation of free valine in the presence of cycloheximide; rates were corrected for turnover of short-lived proteins because these components contribute negligibly to alterations in liver protein content. During deprivation, corrected rates, expressed on a per liver basis, remained constant in normal mice but increased markedly in the diabetic group, attaining twice prestarvation values by 48 hr. By contrast, degradation rates of long-lived intracellular proteins, calculated from the sum of their synthesis and the linear decrease in protein content, decreased predictably in both groups and in parallel with absolute rates of protein synthesis. The extra proteolysis, representing the difference between total and long-lived protein degradation, was small in fed animals but increased progressively during starvation. With diabetic mice, however, the increase was approximately 5 times that of the normal and, in absolute terms, roughly equaled the total loss of liver protein. We suggest that this fraction arose from intrahepatic breakdown of proteins that were ultimately derived from sources outside the liver. Acceleration of this novel process could play an important interim role in providing endogenous glucogenic substrate under conditions in which the demand for this substrate is high.