Risk of diabetes in offspring of parents with non-insulin-dependent diabetes

Type 2 diabetes and inheritance: what information do diabetes organizations provide on the Internet?

AIMS

The worldwide epidemic of Type 2 diabetes necessitates preventive actions. Providing information to high-risk populations is key. In an international comparison of websites, we aimed to investigate the presence and quality of information provided by diabetes organizations on inheritance of Type 2 diabetes and the benefits of a healthy lifestyle targeted at those with a family history or belonging to a specific ethnic population.

METHODS

All websites included in the International Diabetes Federation member list in English, German, French, Dutch, Spanish, Portuguese, Swedish, Norwegian, Finnish, Danish and Japanese were included for assessment. Using qualitative content analysis, we reviewed 34 websites which provided health-related information on diabetes.

RESULTS

Most websites mention family history as a risk factor. However, an explanation of the interaction of lifestyle factors and increased genetic susceptibility is lacking. Ethnicity is mentioned in only half of the sites describing risk factors. Although most websites do provide information on the importance of a healthy lifestyle, they do not address specific high-risk groups. Only two websites encourage Type 2 diabetic patients to inform family members of the familial character of diabetes.

CONCLUSIONS

Information on inheritance of Type 2 diabetes and prevention specifically targeted at high-risk groups on the Internet by diabetes organizations is often of poor quality or indeed is lacking. Efforts should be made to disseminate information on heredity of Type 2 diabetes and preventive options to the general public and high-risk populations.

[Genetics of type 2 diabetes]

In the last years type 2 diabetes has reached almost epidemic proportions. More than 170 million individuals are affected worldwide, about 6 million in Germany. Manifestation of type 2 diabetes is determined by both environmental factors such as lack of physical exercise and overeating and a genetic predisposition. Despite enormous efforts in medical research to identify susceptibility loci and high risk alleles, the genetics of common type 2 diabetes (non-MODY) remain unknown. To date, only a few susceptibility genes have been identified (such as PPARG, KCNJ11, CAPN10). However, replication of initial studies is often difficult. This can be explained by both locus and allelic heterogeneity as well as ethnic differences between different populations. Studies in genetically isolated populations such as the Pima Indians are advantageous to identify susceptibility alleles. Despite some recent advances, it is not possible to predict an individual's risk of type 2 diabetes based on the presence of a certain disease-risk allele.

Type 2 diabetes: principles of pathogenesis and therapy

Type 2 diabetes mellitus has become an epidemic, and virtually no physician is without patients who have the disease. Whereas insulin insensitivity is an early phenomenon partly related to obesity, pancreas beta-cell function declines gradually over time already before the onset of clinical hyperglycaemia. Several mechanisms have been proposed, including increased non-esterified fatty acids, inflammatory cytokines, adipokines, and mitochondrial dysfunction for insulin resistance, and glucotoxicity, lipotoxicity, and amyloid formation for beta-cell dysfunction. Moreover, the disease has a strong genetic component, but only a handful of genes have been identified so far: genes for calpain 10, potassium inward-rectifier 6.2, peroxisome proliferator-activated receptor gamma, insulin receptor substrate-1, and others. Management includes not only diet and exercise, but also combinations of anti-hyperglycaemic drug treatment with lipid-lowering, antihypertensive, and anti platelet therapy.

The impact of screening for Type 2 diabetes in siblings of patients with established diabetes

BACKGROUND

Targeted screening for Type 2 diabetes has been proposed as a method of identifying people with, or at risk of, the disease in order to implement preventive care.

AIM

To assess the changes in anxiety, well-being, and cognitions associated with screening for Type 2 diabetes in people at increased risk of diabetes after 1 year; and to identify potential predictors of increased anxiety and lower well being over this period.

DESIGN AND SETTING

One-year follow up of a cohort of non-diabetic siblings of those with Type 2 diabetes registered with general practitioners in Oxfordshire and Northamptonshire who were identified for participation in a programme to undertake sib-pair genetic analysis.

METHODS

Potential families were selected through identification of people with Type 2 diabetes. Family members aged 35-74 years, who did not have diabetes and who were willing to participate in the study, completed measures before receiving the results of a fasting plasma glucose test, and 1 year later. Measures included the Spielberger State Anxiety Scale-short form (SSAI-SF), the Well-Being Questionnaire 12 item scale (WBQ-12), and measures of cognitions about developing diabetes. The Health Anxiety Inventory (HAI) was completed before receiving the results of the tests to assess its relationship with anxiety at 1 year.

RESULTS

A cohort of 431 individuals was identified, of whom 328 (76%) returned fully completed WBQ scales both initially and at 1 year. State anxiety measured with the SSAI-SF fell from 34.5 (95% CI 33.4-35.6) to 32.3 (31.2-33.4) at 1 year (P < 0.0001). Mean WBQ-12 scores rose (i.e. improved) from 26.8 (26.0-27.4) to 27.4 (26.7-28.1) (P = 0.008). SSAI-SF and WBQ-12 mean scores over 1 year did not differ between participants receiving a normal or an at-risk test result. However, those receiving an at-risk test result were more likely, at 1 year, to consider themselves at increased likelihood of developing diabetes (P < 0.001) and to report thinking about what it would be like to develop diabetes (P = 0.006). A score in the upper tertile of the initial HAI was associated with an increased level of anxiety at 1 year (adjusted odds ratio 2.0, 95% CI 1.2-3.4, P = 0.006).

CONCLUSIONS

There is no evidence that an 'at-risk' test result leads to sustained anxiety or reduced well being at 1 year compared with those receiving a normal test result. However, further studies are required to clarify levels of anxiety prior to screening to assess the overall impact of the process.

Central fat predicts deterioration of insulin secretion index and fasting glycaemia: 6-year follow-up of subjects at varying risk of Type 2 diabetes mellitus

AIMS

To examine the relationships between body composition and changes in fasting glycaemia, and in indices of insulin secretion and insulin action over 6 years in females with a family history of Type 2 diabetes with or without prior gestational diabetes ('at risk' group, AR) and control females (control group, C).

METHODS

At baseline and at follow-up, an oral glucose tolerance test and dual energy X-ray absorptiometry assessment of body composition were performed. Indices of insulin resistance (HOMA R') and insulin secretion (HOMA beta') were obtained from fasting insulin and glucose concentrations.

RESULTS

At baseline, the groups were similar for age, body mass index, fasting levels of plasma glucose and insulin, HOMA R' and HOMA beta'. Despite similar total body fatness, AR had significantly greater waist circumference and central fat (both P < 0.02) compared with C. At follow-up there was a significant increase in central adiposity only in AR, and the fasting plasma glucose (FPG) level was higher in AR compared with C (5.0 +/- 0.2 vs. 4.3 +/- 0.2 mmol/l, P = 0.02). This rise in plasma glucose in AR was related to a decline in HOMA beta' (r = 0.45, P = 0.0065). Both the baseline and the increments in total and central abdominal fat mass were associated with the time-related decline in HOMA beta'.

CONCLUSIONS

Six years after initial assessment, AR showed deterioration in FPG levels due predominantly to a decline in insulin secretion index without major change in insulin resistance index. Importantly, baseline body fatness (especially central adiposity), as well as increases in fatness with time, were the major predictors of the subsequent decline of insulin secretion index and the consequent rise in FPG.

Early disturbances in insulin secretion in the development of type 2 diabetes mellitus

After a short description of normal glucose homeostasis, recent findings in relation to insulin release in three groups with a high risk of future development of type 2 diabetes are described. Hyperglycemic clamps in subjects with impaired glucose tolerance (IGT) clearly indicate that pancreatic beta cell function is decreased, in addition to the decreased insulin sensitivity. In women with former gestational diabetes mellitus (GDM), insulin release is also lower than in controls. In Caucasian first-degree relatives (FDRs) with normal glucose tolerance, various studies have shown that beta cell function is lower than in controls, while on the average insulin sensitivity is normal. This implies that beta cell function is disturbed earlier in subjects at risk of developing diabetes than is often appreciated. In the near future, the genetic studies currently underway will presumably unravel the pathogenesis of disturbances both in insulin secretion and in insulin action, in type 2 diabetes mellitus.

Establishing the role of gene-environment interactions in the etiology of type 2 diabetes

The descriptive epidemiology of type 2 diabetes and findings from cohort studies suggest that this disorder originates in large part from a complex interaction between genetic and environmental factors. Determining the details of these interactions using the nested case-control design may be optimal, but is a long-term and expensive strategy. Quicker and cheaper results may be obtained by studying interaction on the quantitative traits that underlie diabetes; however, the power of such studies to detect interaction is highly dependent on the precision with which non-genetic exposures are measured. Unraveling these interactions will undoubtedly shed light on the etiology of diabetes and will, we hope, lead to opportunities for targeted prevention. Recent studies in high-risk groups such as people with impaired glucose tolerance suggest that the incidence of diabetes can be reduced by more than 50% by interventions aimed at changing dietary and physical activity behavior [39,40]; however, it may be that individuals with a particular genotype are particularly susceptible to the negative metabolic consequences of sedentary living, and that they conversely, therefore, would have most to gain from a targeted preventive intervention program. Understanding how to detect these individuals and which environmental factors a program should attempt to manipulate is a major goal of studies that attempt to unravel gene-environment interaction.

A family history of Type 2 diabetes is associated with increased plasma levels of C-reactive protein in non-smoking healthy adult women

AIMS

The aim of our study was to test whether a family history of Type 2 diabetes (FH) in women is associated with plasma C-reactive protein (CRP).

METHODS

CRP plasma levels were measured in 162 women, aged 18-60 years; 95 had a positive family history of Type 2 diabetes in a parent or grandparent (FH+), and 67 gave no family history of this disease (FH-). Other measurements included: central fat accumulation, as evaluated by waist circumference; insulin resistance, as calculated by homeostatic model assessment (HOMAIR); systolic and diastolic blood pressure; and fasting concentrations of glucose, insulin, and lipids.

RESULTS

CRP plasma levels were significantly higher in FH+ than in FH- subjects. Moreover, CRP was independently associated with age, body mass index, waist circumference, HOMAIR, and FH.

CONCLUSIONS

Our study, performed in a selected population of women free from well-known risk factors for atherothrombosis, demonstrates that subjects with a family history of Type 2 diabetes have higher CRP plasma levels than age- and BMI-matched controls with no family history. Our results show that a family history of Type 2 diabetes is an independent contributor of CRP concentrations, in addition to age, total fatness, central fat accumulation, and insulin resistance.

Perception of risk of developing diabetes in offspring of type 2 diabetic patients

BACKGROUND

The risk of developing diabetes is high in the offspring of patients with type 2 diabetes. There have been no studies to assess the offspring's awareness of the risk of developing diabetes. The aim of this study was to investigate how the male offspring of type 2 diabetic patients assess their likelihood of developing diabetes.

METHODS

One hundred and one non-diabetic men with one or both parents having type 2 diabetes, aged 19-28 years, were recruited.

RESULTS

Thirty-nine subjects (38.6%) were concerned about diabetes and 85 (84.2%) considered diabetes a serious problem. However, only 10 (9.9%) thought they might develop diabetes and 9 (8.9%) had previously attended diabetes education programs with their parents. The educational level amongst the diabetic parents was the only independent predictor of perception of the increased risk. Age, body mass index, waist-to-hip ratio, educational level and the perception of diabetes as a serious problem were not associated with perception of the increased risk.

CONCLUSION

Most offspring of diabetic parents lacked knowledge about the increased risk amongst family members. We suggest that physicians and diabetic educators should provide knowledge about the increased risk of developing diabetes in offspring and the benefit of lifestyle modification to delay or prevent the development of the disease.

Risk assessment for developing type 1 diabetes: intentions of behavioural changes prior to risk notification

BACKGROUND

Recent progress in predictive techniques allows people at risk of developing type 1 diabetes to be identified in a pre-symptomatic stage and prevention trials to be implemented. The present study examined prospectively whether participants in a screening programme anticipated behavioural changes in the event of having a high risk.

METHODS

Four hundred and three first-degree relatives of people with type 1 diabetes completed a self-administered questionnaire about their views on screening and diabetes, and questionnaires on well-being and locus of control.

RESULTS

Prior to risk notification, 73% reported that they intended to introduce lifestyle changes if at high risk. The vast majority of the respondents (87%) reported that eating habits would be the main changes made. Those anticipating changes believed they could take actions to reduce their risk of type 1 diabetes (p<0.001) and to have personal control over diabetes onset (p<0.001). They were also more worried about developing diabetes (p<0.01) and preoccupied with diabetes-related symptoms (p<0.01).

CONCLUSIONS

Prior to risk notification, the process of being screened raised concerns and expectations about future changes. Despite the lack of any evidence, people believed lifestyle changes would be effective in reducing their risk. Since the impact of lifestyle in the development of type 1 diabetes is not yet established, accurate information about the role of health behaviour in the progression to overt diabetes is needed to avoid unrealistic expectations on the benefit of these changes and unnecessary impairment to quality of life. Personally initiated changes should be monitored since they could importantly influence the progress and outcome of prevention trials.

Apolipoprotein E polymorphism and lipid levels differ by gender and family history of diabetes: the Rancho Bernardo Study

Association between apolipoprotein E (apoE) gene polymorphism and lipid levels was studied in 164 nondiabetic first-degree relatives of persons with diabetes and 962 nondiabetic persons with no family history of diabetes. Sex-specific genotypic distribution of apoE polymorphism did not differ between persons with and without a family history of diabetes. In first-degree relatives, lipid levels did not differ among persons with apoE2 (E2/2, E2/3), apoE3/3, and apoE4 (E4/4, E3/4) after adjusting for age, waist circumference, smoking, and alcohol and estrogen use. In persons without a family history of diabetes, both men (p<0.01) and women (p<0.001) with apoE2 showed lower levels of total and low density lipoprotein cholesterol compared with persons with apoE3/3 and apoE4. In women with a family history of diabetes, persons with apoE4 had larger waist circumference (p<0.05). ApoE2 allele is associated with more favorable levels of total and low density lipoprotein cholesterol in men and women without a family history of diabetes. ApoE4 allele is associated with obesity independent of dyslipidemia in women but not men with a family history of diabetes. ApoE polymorphism is not associated with lipids in men or women with a family history of diabetes.

Autonomic neuropathy in nondiabetic offspring of type 2 diabetic subjects is associated with urinary albumin excretion rate and 24-h ambulatory blood pressure: the Fredericia Study

The aim of this study was to examine the impact of parental type 2 diabetes on the autonomic nervous system and to determine whether autonomic neuropathy is present and associated with changes in 24-h ambulatory blood pressure (AMBP) and urinary albumin excretion rate (UAER) in nondiabetic subjects with parental type 2 diabetes. We examined 223 nondiabetic offspring of type 2 diabetic subjects and a control group of 258 offspring of nondiabetic subjects. The autonomic nervous system was assessed by three cardiovascular reflex tests, 24-h AMBP was measured with an oscillometric recorder (90207; Spacelabs, Redmond, WA), and UAER was determined through three overnight urine samples. The subjects with parental type 2 diabetes had significantly lower heart rate variation in all three bedside tests (P < 0.01) than subjects without parental diabetes. The prevalence of autonomic neuropathy in the nondiabetic offspring with parental type 2 diabetes (6.7%) was significantly (P < 0.01) higher compared with the control group (1.6%). Autonomic neuropathy was associated with a higher fasting insulin level (P < 0.05), higher UAER (P < 0.001), higher 24-h mean AMBP (P < 0.01), and reduced diurnal blood pressure variation (P < 0.001) after adjustment for age, sex, and BMI. In conclusion, parental type 2 diabetes was found to be associated with alterations in the autonomic nervous system in nondiabetic subjects. The presence of autonomic neuropathy in subjects with parental type 2 diabetes was associated with higher UAER, fasting insulin level, and 24-h AMBP and a reduced diurnal blood pressure variation. This study indicates that parental type 2 diabetes has an impact on the cardiac autonomic function in nondiabetic subjects.

Family history of diabetes identifies a group at increased risk for the metabolic consequences of obesity and physical inactivity in EPIC-Norfolk: a population-based study. The European Prospective Investigation into Cancer

OBJECTIVE

To investigate the interaction of a family history of diabetes with obesity and physical inactivity on diabetes prevalence in middle-aged and elderly men and women.

DESIGN

A cross-sectional population-based study.

SUBJECTS

2,912 men and 3,561 women, aged 45-74y.

MEASUREMENTS

Body mass index (BMI), HbA1C, self-administered questionnaire including questions on occupational physical activity and personal and family history of diabetes as part of the Norfolk arm of the European Prospective Investigation into Cancer (EPIC-Norfolk).

RESULTS

The prevalence of diabetes increased in a dose-response relationship with increasing BMI. There was an interaction between family history and obesity on diabetes risk in subjects with a BMI of greater than 27.5kg/m2 (P= 0.049). Crude prevalence in individuals without a family history and BMI of 22.5-24.9 kg/m2 was 2.2% compared to 33.3% in those with a family history and BMI over 35 kg/m2. Thirty-eight percent of the excess risk of diabetes in people with a family history could be avoided if their BMI did not exceed 30 kg/m2. Individuals who reported sedentary occupations were at greater risk of diabetes compared to those reporting more active occupations. There was a synergistic effect of family history and self-reported occupational physical activity on diabetes risk.

CONCLUSION

Individuals with a family history of diabetes are at increased risk for the metabolic consequences of obesity and form an easily identifiable group who may benefit from targeted intervention to prevent the development of obesity through increased physical activity.

Bivariate genetic analysis of fasting insulin and glucose levels

The main aim of this study was to estimate the relative influence of genes and environment on fasting insulin levels, which were considered a proxy of insulin resistance. Possible sex differences in genetic and environmental influences, and the origin of the covariance between fasting insulin and glucose were investigated. Subjects were 209 pairs of middle-aged twins, divided into 5 sex-by-zygosity groups. A general bivariate model and a reciprocal causation model including fasting insulin and glucose were used in the analyses. For both quantitative genetic models, a model specifying additive genetic and unique environmental factors, which were the same in males and females, showed the best fit to the data. Heritability estimates were modest and highly similar in both models: 20-25% of the variance in fasting insulin, and around 50% of the variance in fasting glucose levels could be attributed to genetic factors. The two models could not be discriminated on the basis of their fit to the data. A submodel of the general bivariate model suggested that the covariance between glucose and insulin has a unique environmental basis, whereas for the reciprocal causation model both causal paths were needed to explain the phenotypic correlation between insulin and glucose and estimates of the reciprocal paths were of opposite sign, an indication for the expected negative feedback loop.

Diabetes mellitus in the family: perceptions of offspring's risk

AIMS

The study aimed to explore the beliefs and concerns of people with Type 2 diabetes mellitus (DM) about their children's risk of developing the disease and the possibilities for prevention.

METHODS

Questionnaires were posted to all patients with Type 2 DM in four randomly selected general practices in South London. Two hundred and thirteen (73%) responded. The main outcome measures were: estimated risk of Type 2 DM in their offspring; worry about diabetes in their offspring; knowledge about the possibilities for prevention of Type 2 DM and its complications.

RESULTS

Of the 159 respondents with children, at least 35% and perhaps as many as 64% underestimated the risk of their offspring developing Type 2 DM; 44% thought it possible to reduce the risk of Type 2 DM and its complications; 28% thought altering diet and 6% taking exercise might be useful preventive strategies; 49% worried about their children developing diabetes.

CONCLUSIONS

Although risk of Type 2 DM was underestimated for their children and little was known about prevention, about half of the respondents worried about their children developing diabetes. Education and counselling about risk and prevention are needed. This is important in view of growing interest in and opportunities for both the primary and secondary prevention of Type 2 DM.

Knowledge of risk of developing diabetes mellitus among siblings of Type 2 diabetic patients

AIMS

We set out to investigate the extent to which siblings of diabetic subjects perceived themselves likely to develop Type 2 diabetes mellitus (DM) when offered screening tests.

METHODS

Nondiabetic siblings, aged 35-74 years, of Type 2 diabetic patients who were more than 35 years old at diagnosis had fasting plasma glucose measured in a study to determine heritability of diabetes. Questionnaires assessing perceived likelihood of developing, seriousness and knowledge about diabetes were completed. Logistic regression assessed factors predicting perceptions of diabetes risk.

RESULTS

Factors predicting diabetes on screening were male sex, increasing age and body mass index (BMI) > or = 30. Eighty-nine per cent of 540 eligible siblings completed questionnaires. Thirty-eight per cent saw themselves at increased risk of diabetes and 34% thought diabetes a serious problem. Predictors of perceiving an increased likelihood of developing diabetes were female sex, age 35-54 years vs. 55-74 years and having a parent with diabetes. BMI did not affect perceptions of likelihood.

CONCLUSION

A perception of reduced vulnerability to diabetes may occur due to unawareness of risk or minimization of risk. Feelings of invulnerability may affect emotional response to a subsequent result. It is not known whether providing more information about the risk of developing diabetes prior to screening would affect outcomes

Macrophages and pancreatic islet amyloidosis

Islet amyloid formed from islet amyloid polypeptide (IAPP, amylin) is found in spontaneously diabetic monkeys and cats. Islet amyloidosis is progressive, apparently irreversible and is associated with destruction of insulin-secreting cells. The role of macrophages in the destruction and removal of islet amyloid is unknown. Therefore, the presence and morphology of macrophages were determined by electron and quantitative light microscopy in islets of diabetic and nondiabetic man and monkeys and in transgenic mice expressing the gene for human IAPP. Tissue macrophages were present in all pancreatic sections and tissue distribution was similar in exocrine and endocrine areas. There was no difference in macrophage density in amyloidotic and amyloid-free islets in monkeys and man. Macrophage density was similar in islets of transgenic mice expressing human IAPP which do not contain amyloid in vivo but in which fibrils are formed in vitro following islet isolation compared to islets from mice expressing rat IAPP which is not amyloidogenic. IAPP amyloid fibrils were visible by electron microscopy in lysosomes of pancreatic macrophages in man, monkeys and human IAPP transgenic mice. Thus, human IAPP is internalised but inefficiently degraded by tissue macrophages. Diabetes-associated amyloidosis is not associated with visible recruitment of macrophages for removal of amyloid or islet debris.

Reduction in body weight helps to delay the onset of diabetes even in non-obese with strong family history of the disease

Of the 1200 non-diabetic offspring of non-insulin-dependent diabetic patients registered under the prevention programme, 262 (M:F 189:73) were available for analysis with greater than or equal to 4 years of follow-up. All of them had been prescribed a calorie restricted diet to suit their body weight, occupation and age, and were advised to restrict the use of refined carbohydrates and fats. Regular exercise was also advised. Compliance with these prescriptions was assessed at each follow up. At the time of analysis, it was noted that only 14.5% had developed diabetes in a period of 8 +/- 4.2 years even though many of them had impaired glucose tolerance at entry in the programme. Multiple regression analysis showed that initial 2 h plasma glucose, initial glucose tolerance and gain in body weight were strong predictors of diabetes. Weight loss occurred in persons who adhered to diet and exercise programmes and conversion to diabetes was lower in them compared to those who gained weight (P < 0.002). Although the rate and degree of obesity is less among Indians, it has been observed in several earlier studies that even a minor increase in body mass index increased the risk of diabetes. This study highlights the fact that measures to control weight helps to delay the onset of diabetes even in the non-obese despite a strong family history of the disorder.