Hyperinsulinaemia as long-term predictor of death and ischaemic heart disease in nondiabetic men: The Malmö Preventive Project

Diets with higher insulinaemic potential are associated with increased risk of overall and cardiovascular disease-specific mortality

Hyperinsulinaemia and insulin resistance have been proposed to be associated with mortality risk, and diet can modulate insulin response. However, whether dietary patterns with high insulinaemic potential are associated with mortality remains unknown. We prospectively examined the associations between hyperinsulinaemic diets and the risk of total and cause-specific mortality in a large nationally representative population. Dietary factors were assessed by 24-h recalls. Two empirical dietary indices for hyperinsulinaemia (EDIH) and insulin resistance (EDIR) were developed to identify food groups most predictive of biomarkers for hyperinsulinaemia (C-peptide and insulin) and insulin resistance (homoeostatic model assessment for insulin resistance), respectively. Deaths from date of the first dietary interview until 31 December 2015 were identified by the National Death Index. Multivariable hazard ratios (HR) and 95 % CI were calculated using Cox regression models. During a median follow-up of 7·8 years, 4904 deaths were documented among 40 074 participants. For EDIH, the multivariable-adjusted HR (comparing extreme quintiles) were 1·20 (95 % CI 1·09, 1·32, P-trend<0·001) for overall mortality and 1·41 (95 % CI 1·15, 1·74, P-trend = 0·002) for CVD mortality. Similar associations were observed for EDIR with HR of 1·18 (95 % CI 1·07, 1·29, P-trend < 0·001) for total and 1·35 (95 % CI 1·09, 1·67, P-trend = 0·005) for CVD mortality. After further adjustments for BMI and diabetes, these positive associations were somewhat attenuated. Our findings suggested that diets with higher insulinaemic potential are associated with increased risk of overall and CVD-specific mortality.

Triglyceride-Glucose Index is a Risk Marker of Incident COPD Events in Women

Purpose

The triglyceride-glucose index (TyG index) is a marker of insulin resistance and metabolic dysfunction and has the advantage of being universally available. Although recent evidence suggests the TyG index has relevance to respiratory health, there have been no prospective studies assessing its value as a biomarker for chronic lung diseases. We aim to assess the TyG index as a potential risk marker for future incident COPD events in the general population.

Patients and Methods

Baseline TyG index was assessed in 28,282 middle-aged men and women without previous history of chronic obstructive pulmonary disease (COPD) from the Malmö Preventive Project (men between 1974 and 1982 and women between 1982 and 1992). All subjects were followed up prospectively, and Cox proportional hazards regression was used to assess incident COPD events according to quartiles of TyG index.

Results

After an average of 31 years of follow-up, TyG index was a strong predictor of future COPD events even after adjusting for potential confounders (Q4 (highest TyG index) HR (95% CI): 1.21 (1.09–1.35) vs Q1 (reference), p-trend <0.001). After stratifying by sex, the results remained statistically significant in women only (Q4 vs Q1 HR 1.72 (1.41–2.09)). Additionally, the risk remained significant in a cohort of life-long never smokers (Q4 vs Q1 HR 1.47 (1.08–2.01)).

Conclusion

A raised TyG index is a novel risk marker of future incident COPD events in women. Insulin resistance as reflected by the TyG index can precede the development of obstructive lung disease and as such may be an easily measurable and useful predictor of COPD in women.

Dietary Insulinemic Potential and Risk of Total and Cause-Specific Mortality in the Nurses' Health Study and the Health Professionals Follow-up Study

OBJECTIVE

Insulin response is related to overall health. Diet modulates insulin response. We investigated whether insulinemic potential of diet is associated with risk of all-cause and cause-specific mortality.

RESEARCH DESIGN AND METHODS

We prospectively followed 63,464 women from the Nurses' Health Study (1986-2016) and 42,880 men from the Health Professionals Follow-up Study (1986-2016). Diet was assessed by food frequency questionnaires every 4 years. The insulinemic potential of diet was evaluated using a food-based empirical dietary index for hyperinsulinemia (EDIH), which was predefined based on predicting circulating C-peptide concentrations.

RESULTS

During 2,792,550 person-years of follow-up, 38,329 deaths occurred. In the pooled multivariable-adjusted analyses, a higher dietary insulinemic potential was associated with an increased risk of mortality from all-cause (hazard ratio [HR] comparing extreme quintiles: 1.33; 95% CI 1.29, 1.38; P-trend <0.001), cardiovascular disease (CVD) (HR 1.37; 95% CI 1.27, 1.46; P-trend <0.001), and cancers (HR 1.20; 95% CI 1.13, 1.28; P-trend <0.001). These associations were independent of BMI and remained significant after further adjustment for other well-known dietary indices. Furthermore, compared with participants whose EDIH scores were stable over an 8-year period, those with the greatest increases had a higher subsequent risk of all-cause (HR 1.13; 95% CI 1.09, 1.18; P-trend <0.001) and CVD (HR 1.10; 95% CI 1.01, 1.21; P-trend = 0.006) mortality.

CONCLUSIONS

Higher insulinemic potential of diet was associated with increased risk of all-cause, CVD, and cancer mortality. Adopting a diet with low insulinemic potential might be an effective approach to improve overall health and prevent premature death.

Hyperinsulinemia and Its Pivotal Role in Aging, Obesity, Type 2 Diabetes, Cardiovascular Disease and Cancer

For many years, the dogma has been that insulin resistance precedes the development of hyperinsulinemia. However, recent data suggest a reverse order and place hyperinsulinemia mechanistically upstream of insulin resistance. Genetic background, consumption of the “modern” Western diet and over-nutrition may increase insulin secretion, decrease insulin pulses and/or reduce hepatic insulin clearance, thereby causing hyperinsulinemia. Hyperinsulinemia disturbs the balance of the insulin–GH–IGF axis and shifts the insulin : GH ratio towards insulin and away from GH. This insulin–GH shift promotes energy storage and lipid synthesis and hinders lipid breakdown, resulting in obesity due to higher fat accumulation and lower energy expenditure. Hyperinsulinemia is an important etiological factor in the development of metabolic syndrome, type 2 diabetes, cardiovascular disease, cancer and premature mortality. It has been further hypothesized that nutritionally driven insulin exposure controls the rate of mammalian aging. Interventions that normalize/reduce plasma insulin concentrations might play a key role in the prevention and treatment of age-related decline, obesity, type 2 diabetes, cardiovascular disease and cancer. Caloric restriction, increasing hepatic insulin clearance and maximizing insulin sensitivity are at present the three main strategies available for managing hyperinsulinemia. This may slow down age-related physiological decline and prevent age-related diseases. Drugs that reduce insulin (hyper) secretion, normalize pulsatile insulin secretion and/or increase hepatic insulin clearance may also have the potential to prevent or delay the progression of hyperinsulinemia-mediated diseases. Future research should focus on new strategies to minimize hyperinsulinemia at an early stage, aiming at successfully preventing and treating hyperinsulinemia-mediated diseases.

Does rearranging meal times at night improve cardiovascular risk factors? An Australian pilot randomised trial in night shift workers

BACKGROUND AND AIMS

Shift workers face an increased risk of cardiovascular disease (CVD), type-2 diabetes and obesity. Eating during the night is a likely contributing factor, as it coincides with the time at which postprandial metabolism is least efficient. In this pilot randomised crossover trial, we examine the effects of a short overnight fast on CVD risk markers (primarily postprandial triglyceride and glucose response) of night shift workers.

METHODS AND RESULTS

Night shift workers with abdominal obesity underwent 4-week intervention and control periods, separated by ≥ 2 weeks washout. In the intervention period, an overnight fast (0100 h-0600 h) was implemented, by redistributing 24-h energy intake. Usual dietary habits were followed in the control period. Outcomes between intervention and control were compared using mixed effects linear regression models. Nineteen adults completed the trial [13 females, mean (±SD) age 41 ± 10 years, BMI 30.7 ± 5.7 kg/m²]. Postprandial triglyceride and glucose response post intervention were not different to post control. The overnight fast was well-tolerated by participants with an adherence rate of 95%, assessed by weekly 24-h dietary recalls. Exploratory analysis indicates lower mean body weight post intervention compared to post control (mean difference: -0.9 kg, 95% CI: -1.3 to -0.4).

CONCLUSIONS

Night shift workers who habitually ate during their night shifts were able to rearrange their meal times to maintain a small overnight fast, which may have promoted small weight changes. This warrants further investigation into the role of meal timing in mitigating the metabolic consequences of night shift work.

TRIAL REGISTRATION

Australian New Zealand Clinical Trials Registry (http://anzctr.org.au/) registered on the 30th May 2017 (ACTRN12617000791336).

Negative associations for fasting blood glucose, cholesterol and triglyceride levels with the development of giant cell arteritis

Objectives

To investigate metabolic features that may predispose to GCA in a nested case–control study.

Methods

Individuals who developed GCA after inclusion in a population-based health survey (the Malmö Preventive Medicine Project; N = 33 346) were identified and validated through a structured review of medical records. Four controls for every validated case were selected from the database.

Results

A total of 76 cases with a confirmed incident diagnosis of GCA (61% female, 65% biopsy positive, mean age at diagnosis 70 years) were identified. The median time from screening to diagnosis was 20.7 years (range 3.0–32.1). Cases had significantly lower fasting blood glucose (FBG) at baseline screening compared with controls [mean 4.7 vs 5.1 mmol/l (S.d. overall 1.5), odds ratio (OR) 0.35 per mmol/l (95% CI 0.17, 0.71)] and the association remained significant when adjusted for smoking [OR 0.33 per mmol/l (95% CI 0.16, 0.68)]. Current smokers had a reduced risk of GCA [OR 0.35 (95% CI 0.18, 0.70)]. Both cholesterol [mean 5.6 vs 6.0 mmol/l (S.d. overall 1.0)] and triglyceride levels [median 1.0 vs 1.2 mmol/l (S.d. overall 0.8)] were lower among the cases at baseline screening, with significant negative associations with subsequent GCA in crude and smoking-adjusted models [OR 0.62 per mmol/l (95% CI 0.43, 0.90) for cholesterol; 0.46 per mmol/l (95% CI 0.27, 0.81) for triglycerides].

Conclusion

Development of GCA was associated with lower FBG and lower cholesterol and triglyceride levels at baseline, all adjusted for current smoking, suggesting that metabolic features predispose to GCA.

Fad Diets: Hype or Hope?

PURPOSE OF REVIEW

Obesity continues to be a growing concern globally due to association with a number of comorbidities and contributing significantly to increase in health care expenditures. Despite availability of a number of treatment modalities, lifestyle modification with dietary modification and exercise continues to be the foundation. However, the standard model of lifestyle modification is not efficacious or sustainable for many patients leading them to seek alternative approaches. We conducted a comprehensive literature review to present the data regarding efficacy and sustainability of many common dietary approaches.

RECENT FINDINGS

Building upon previous work, recent randomized controlled trials have compared many popular diets head to head in varying patient populations. Along with the weight changes, studies have investigated the changes in metabolic parameters, inflammatory markers, and cardiac risk factor reduction. Though the studies do not show superiority of one diet compared to the other, the preventive benefits and other favorable metabolic changes of the diets make them worthy of consideration.

One-hour glucose value as a long-term predictor of cardiovascular morbidity and mortality: the Malmö Preventive Project

OBJECTIVE

To examine the predictive capability of a 1-h vs 2-h postload glucose value for cardiovascular morbidity and mortality.

DESIGN

Prospective, population-based cohort study (Malmö Preventive Project) with subject inclusion 1974-1992.

METHODS

4934 men without known diabetes and cardiovascular disease, who had blood glucose (BG) measured at 0, 20, 40, 60, 90 and 120 min during an OGTT (30 g glucose per m² body surface area), were followed for 27 years. Data on cardiovascular events and death were obtained through national and local registries. Predictive capabilities of fasting BG (FBG) and glucose values obtained during OGTT alone and added to a clinical prediction model comprising traditional cardiovascular risk factors were assessed using Harrell's concordance index (C-index) and integrated discrimination improvement (IDI).

RESULTS

Median age was 48 (25th-75th percentile: 48-49) years and mean FBG 4.6 ± 0.6 mmol/L. FBG and 2-h postload BG did not independently predict cardiovascular events or death. Conversely, 1-h postload BG predicted cardiovascular morbidity and mortality and remained an independent predictor of cardiovascular death (HR: 1.09, 95% CI: 1.01-1.17, P = 0.02) and all-cause mortality (HR: 1.10, 95% CI: 1.05-1.16, P < 0.0001) after adjusting for various traditional risk factors. Clinical risk factors with added 1-h postload BG performed better than clinical risk factors alone, in predicting cardiovascular death (likelihood-ratio test, P = 0.02) and all-cause mortality (likelihood-ratio test, P = 0.0001; significant IDI, P = 0.0003).

CONCLUSION

Among men without known diabetes, addition of 1-h BG, but not FBG or 2-h BG, to clinical risk factors provided incremental prognostic yield for prediction of cardiovascular death and all-cause mortality.

Fasting insulin, insulin resistance, and risk of cardiovascular or all-cause mortality in non-diabetic adults: a meta-analysis

Studies on elevated fasting insulin or insulin resistance (IR) and cardiovascular or all-cause mortality risk in non-diabetic individuals have yielded conflicting results. This meta-analysis aimed to evaluate the association of elevated fasting insulin levels or IR as defined by homeostasis model assessment of IR (HOMA-IR) with cardiovascular or all-cause mortality in non-diabetic adults. We searched for relevant studies in PubMed and Emabse databases until November 2016. Only prospective observational studies investigating the association of elevated fasting insulin levels or HOMA-IR with cardiovascular or all-cause mortality risk in non-diabetic adults were included. Risk ratio (RR) with its 95% confidence intervals (CIs) was pooled for the highest compared with the lowest category of fasting insulin levels or HOMA-IR. Seven articles involving 26976 non-diabetic adults were included. The pooled, adjusted RR of all-cause mortality comparing the highest with the lowest category was 1.13 (95% CI: 1.00–1.27; P=0.058) for fasting insulin levels and 1.34 (95% CI: 1.11–1.62; P=0.002) for HOMA-IR, respectively. When comparing the highest with the lowest category, the pooled adjusted RR of cardiovascular mortality was 2.11 (95% CI: 1.01–4.41; P=0.048) for HOMA-IR in two studies and 1.40 (95% CI: 0.49–3.96; P=0.526) for fasting insulin levels in one study. IR as measured by HOMA-IR but not fasting insulin appears to be independently associated with greater risk of cardiovascular or all-cause mortality in non-diabetic adults. However, the association of fasting insulin and HOMA-IR with cardiovascular mortality may be unreliable due to the small number of articles included.

High salt intake does not aggravate glucose dysregulation and dyslipidemia induced by estrogen-progestin oral contraceptive

BACKGROUND

Estrogen-progestogen combined oral contraceptive (OC) use has been associated with increased cardiometabolic risk factors, including glucose dysregulation, dyslipidemia, hypertension, and pro-inflammatory state. However, the effect of a high-salt diet on these risk factors during OC use is not yet investigated. We therefore hypothesized that a high-salt diet would increase cardiometabolic risk factors in female rats treated with a combination of OC steroids, levonorgestrel (L) and ethinylestradiol (EE), and that elevated plasma levels of pro-inflammatory markers are associated with the cardiometabolic effects.

METHODS

Female Wistar rats were given (p.o.) vehicle, high-dose (1.0μg EE plus 5.0μgL) or low-dose (0.1μg EE plus 0.5μgL) OC with or without a high-salt diet (8%) daily for 8 weeks. Insulin resistance (IR) was estimated using the homeostatic model of assessment (HOMA).

RESULTS

Results showed that OC treatment or high salt diet led to significant increases in insulin resistance, plasma insulin, total cholesterol (TC), triglyceride (TG), TC/HDL-cholesterol, uric acid levels, and decreased glucose tolerance. OC treatment but not a high-salt diet resulted in increased plasma C-reactive protein and TG/HDL-cholesterol. However, a high-salt diet did not aggravate the effects of OC treatment.

CONCLUSION

The results from the present study indicate that glucose dysfunction and dyslipidemia induced by OC use, but not those induced by increased dietary salt are associated with elevated plasma C-reactive protein. Besides, increased dietary salt does not worsen abnormal cardiometabolic impact of OC use.

Follow-up duration influences the relative importance of OGTT and optimal timing of glucose measurements for predicting future type 2 diabetes

OBJECTIVE

To examine the impact of follow-up duration on the incremental prognostic yield of a baseline oral glucose tolerance test (OGTT) for predicting type 2 diabetes and to assess the discrimination ability of blood glucose (BG) obtained at different time points during OGTT.

DESIGN

A prospective, population-based cohort study (Malmö Preventive Project) with inclusion of subjects from 1974 to 1992.

METHODS

A total of 5256 men without diabetes, who had BG measured at 0, 20, 40, 60, 90, and 120 min during OGTT (30 g/m2 glucose), were followed for 30 years. Incident type 2 diabetes was recorded using registries. The performance of OGTT added to a clinical prediction model (age, body mass index (BMI), diastolic blood pressure, fasting BG, triglycerides, and family history of diabetes) was assessed using Harrell's concordance index (C-index) and integrated discrimination improvement (IDI).

RESULTS

Median age was 48 years, mean BMI 24.9 kg/m2, and mean fasting BG 4.7 mmol/L. Models with added post-load BG performed better than the clinical model (C-index: P = 0.08 for BG at 120 min at 5 years, otherwise P ≤ 0.045; IDI: P ≥ 0.06 for BG at 60 and 90 min at 5 years, otherwise P ≤ 0.01). With a longer follow-up duration, C-index decreased, and the C-index increase associated with OGTT was attenuated. Models including BG at 60 or 90 min performed significantly better than the model with BG at 120 min, evident beyond follow-up of 10 and 5 years, respectively.

CONCLUSIONS

OGTT provided incremental prognostic yield for type 2 diabetes prediction. BG measured at 60 or 90 min provided better discrimination than BG at 120 min.

Glycaemic and insulin responses, glycaemic index and insulinaemic index values of rice between three Asian ethnic groups

Asians exhibit larger glycaemic response (GR) and insulin response (IR) than Caucasians, predisposing to an increased risk of type 2 diabetes mellitus (T2DM). We aimed to determine the GR and IR as well as the glycaemic index (GI) and insulinaemic index (II) of two rice varieties among three ethnic groups in Singapore. A total of seventy-five healthy males (twenty-five Chinese, twenty-five Malay and twenty-five Asian-Indians) were served the available equivalent carbohydrate amounts (50 g) of test foods (Jasmine rice and Basmati rice) and a reference food (glucose) on separate occasions. Postprandial blood glucose and plasma insulin concentrations were measured at fasting ( -5 and 0 min) and at 15, 30, 45, 60, 90 and 120 min after food consumption. Using the trapezoidal rule, GR, IR, GI and II values were determined. The GR did not differ between ethnic groups for Jasmine rice and Basmati rice. The IR was consistently higher for Jasmine rice (P=0·002) and Basmati rice (P=0·002) among Asian-Indians, probably due to compensatory hyperinsulinaemia to maintain normoglycaemia. The GI and II of both rice varieties did not differ significantly between ethnicities. The overall mean GI for Jasmine rice and Basmati rice were 91 (sd 21) and 59 (sd 15), respectively. The overall mean II for Jasmine rice was 76 (sd 26) and for Basmati rice was 57 (sd 24). We conclude that the GI values presented for Jasmine rice and Basmati rice were applicable to all three ethnic groups in Singapore. Future studies should include deriving the II for greater clinical utility in the prevention and management of T2DM.

Low fasting plasma insulin is associated atrial fibrillation in men from a cohort study--the Malmö preventive project

Background

Type 2 diabetes has been associated with increased incidence of atrial fibrillation (AF) and cardiovascular disease. Controversy remains regarding the role of insulin in the epidemiology of AF risk. The aim of the present study was to study the association between fasting plasma insulin (FPI) and incidence of AF, as well as any effect modification by fasting blood glucose (FBG) or 2 h post-load blood glucose and body mass index (BMI).

Methods

The study population consisted of 6052 men and 1014 women followed for an average of 26.2 years. There were 983 cases of incident AF. Analysis was performed using Cox regression and competing risks regression approaches. The population was analysed as a whole, and by subgroups according to glucose levels and BMI.

Results

After adjustment for age, height, weight, systolic blood pressure and smoking there was a significant inverse association between FPI and AF (hazard ratio; HR) for 4th vs. 1st quartile: 0.69 (95% confidence interval (CI): 0.57-0.83, p < 0.0001) in the cohort as a whole. Among men the corresponding values were HR 0.64 (95% CI 0.52-0.78, p < 0.001) and among women HR 1.16 (95% CI 0.69-1.93, p = 0.58); p-value for interaction 0.06. The protective effects of insulin tended to be weaker in subjects with elevated fasting glucose, implying that the relation between FPI and incident AF could be dependent on the status of individual’s glucose metabolism.

Conclusions

High levels of FPI are associated with lower risk of incident AF in a middle-aged population with a long follow-up.

The zone diet: an anti-inflammatory, low glycemic-load diet

The Zone Diet was developed on the concept that the hormonal responses of macronutrients could be orchestrated to maintain key hormones within therapeutic zones to control inflammatory responses. In particular, the two hormonal systems that are directly affected by dietary macronutrients are (1) the insulin/glucagon axis and (2) eicosanoids. Each of these hormonal systems can have a significant impact on the inflammatory process. This hormonal approach to optimizing an anti-inflammatory diet has significant ramifications in treatment of those chronic diseases (obesity, type 2 diabetes, and cardiovascular disease) that are known to produce inflammatory responses. On the other hand, an inappropriate balance of macronutrients (especially high glycemic- load carbohydrates) can lead to increased inflammation. A primary example of this is the promotion of the United States Department of Agriculture's Food Guide Pyramid. Since its adoption, the prevalence of obesity and type 2 diabetes has risen substantially. Both conditions also demonstrate a significant increase in inflammatory markers. The purpose of this article is to review the historical factors that led to the development of the Zone Diet, to understand how the Zone Diet can alter inflammatory responses, and to review the published literature on its ability to affect hormonal and metabolic responses.

Are the glycemic and insulinemic index values of carbohydrate foods similar in healthy control, hyperinsulinemic and type 2 diabetic patients?

BACKGROUND/OBJECTIVES

a criticism of glycemic index (GI) is that it does not indicate the insulin response of foods (insulinemic index, II). However, it is unknown if the GI and II values of foods are equivalent in all subjects, a necessary criterion for clinical utility. We compared GI and II values in non-diabetic subjects with fasting-serum-insulin (FSI) <40 pmol/l (healthy control) or with FSI ≥ 40 pmol/l (hyper[I]) and subjects with type 2 diabetes (T2DM), and to see whether GI and II were related to the serum-glucose concentrations, insulin sensitivity, β-cell function and hepatic insulin extraction (HIE) of the subjects.

SUBJECTS/METHODS

Serum-glucose, -insulin and -C-peptide responses after 50 g available-carbohydrate portions of glucose (tested three times by each subject), sucrose, instant mashed-potato, white-bread, polished-rice and pearled-barley were measured in healthy control (n=9), hyper[I] (n=12) and T2DM (n=10) subjects.

RESULTS

Food GI values did not differ significantly among the three subject groups, whereas II values were higher in T2DM (100±7) than healthy controls (78±5) and hyper[I] subjects (70±5) (mean±s.e.m., P=0.05). II was inversely associated with insulin sensitivity (r=-0.66, P<0.0001) and positively related to fasting- and postprandial-glucose (both r=0.68, P<0.0001) and HIE (r=0.62, P=0.0002). In contrast, GI was not related to any of the biomarkers (P>0.05).

CONCLUSION

The GI is a valid property of foods because its value is similar in healthy control, hyper [I] and T2DM subjects, and is independent of subjects' metabolic status. However, II may depend upon the glycaemic control, insulin sensitivity and HIE of the subjects.

Salt sensitivity is associated with insulin resistance, sympathetic overactivity, and decreased suppression of circulating renin activity in lean patients with essential hypertension

BACKGROUND

The mechanisms by which a derangement of glucose metabolism causes high blood pressure are not fully understood.

OBJECTIVES

This study aimed to clarify the relation between salt sensitivity of blood pressure and insulin resistance, which are important subcharacteristics of hypertension and impaired glucose metabolism, respectively. Effects on the renin-angiotensin and sympathetic nervous systems were also studied.

DESIGN

The state of glucose metabolism was assessed by a hyperinsulinemic euglycemic glucose clamp technique and a 75-g oral-glucose-tolerance test in 24 essential hypertensive patients who were lean and without diabetes or chronic kidney disease. The subjects were classified as salt-sensitive or salt-resistant on the basis of the difference (Delta mean blood pressure > or =5%) between 24-h ambulatory blood pressure monitoring results on the seventh day of low-salt (34 mmol/d) and high-salt (252 mmol/d) diets. Urine and blood samples were collected for analyses.

RESULTS

There was a robust inverse relation between the glucose infusion rate (GIR) and the salt sensitivity index. The GIR correlated directly with the change in urinary sodium excretion and was inversely related to the change in hematocrit when the salt diet was changed from low to high, which is indicative of salt and fluid retention in salt-sensitive subjects. The GIR also showed an inverse correlation compared with the changes in urinary norepinephrine excretion, plasma renin activity, and plasma aldosterone concentration.

CONCLUSIONS

Salt sensitivity of blood pressure is strongly associated with insulin resistance in lean, essential hypertensive patients. Hyperinsulinemia, sympathetic overactivation, and reduced suppression of the renin-angiotensin system may play a role in this relation.

Demographic and cardiovascular risk factors modify association of fasting insulin with incident coronary heart disease and ischemic stroke (from the Atherosclerosis Risk In Communities Study)

Previous studies have reported an association between circulating insulin and incident cardiovascular disease, but limited knowledge is available on the association across subgroups. We examined the associations of fasting insulin with incident coronary heart disease (CHD) and ischemic stroke in multiple subgroups of a biracial, middle-age cohort. A total of 12,323 subjects were included in the analysis. The incidence of CHD (n = 960) and ischemic stroke (n = 445) through 2005 was determined through annual interviews, repeat examinations, and community surveillance. Serum insulin was measured at baseline. Cox regression analysis was used to estimate the hazard ratios by quintile of fasting insulin at baseline and to determine the significance of effect modification. In the minimally adjusted models (age, gender, race, and field center), the baseline fasting insulin quintile was positively associated with both incident CHD (hazard ratio per quintile insulin = 1.12, p-trend <0.0001) and ischemic stroke (hazard ratio per quintile insulin = 1.11, p = 0.0018). The adjustment for high-density lipoprotein completely attenuated the association of insulin with CHD but not with stroke. The associations of insulin with CHD were stronger in nonsmokers (p-interaction = 0.018) and in those without hypertension (p-interaction = 0.0087). The associations of insulin with stroke were stronger in women (p-interaction = 0.037), whites (compared to blacks; p-interaction = 0.036), and those without hypertension (p-interaction = 0.0027).

HOMA insulin sensitivity index and the risk of all-cause mortality and cardiovascular disease events in the general population: the Australian Diabetes, Obesity and Lifestyle Study (AusDiab) study

AIMS/HYPOTHESIS

We assessed whether the relationships between insulin sensitivity and all-cause mortality as well as fatal or non-fatal cardiovascular disease (CVD) events are independent of elevated blood glucose, high blood pressure, dyslipidaemia and body composition in individuals without diagnosed diabetes.

METHODS

Between 1999 and 2000, baseline fasting insulin, glucose and lipids, 2 h plasma glucose, HbA(1c), anthropometrics, blood pressure, medication use, smoking and history of CVD were collected from 8,533 adults aged >35 years from the population-based Australian Diabetes, Obesity and Lifestyle study. Insulin sensitivity was estimated by HOMA of insulin sensitivity (HOMA-%S). Deaths and fatal or non-fatal CVD events were ascertained through linkage to the National Death Index and medical records adjudication.

RESULTS

After a median of 5.0 years there were 277 deaths and 225 CVD events. HOMA-%S was not associated with all-cause mortality. Compared with the most insulin-sensitive quintile, the combined fatal or non-fatal CVD HR (95% CI) for quintiles of decreasing HOMA-%S were 1.1 (0.6-1.9), 1.4 (0.9-2.3), 1.6 (1.0-2.5) and 2.0 (1.3-3.1), adjusting for age and sex. Smoking, CVD history, hypertension, lipid-lowering medication, total cholesterol and waist-to-hip ratio moderately attenuated this relationship. However, the association was rendered non-significant by adding HDL. Fasting plasma glucose, but not HOMA-%S significantly improved the prediction of CVD, beyond that seen with other risk factors.

CONCLUSIONS/INTERPRETATION

In this cohort, HOMA-%S showed no association with all-cause mortality and only a modest association with CVD events, largely explained by its association with HDL. Fasting plasma glucose was a better predictor of CVD than HOMA-%S.

Fasting serum insulin and the homeostasis model of insulin resistance (HOMA-IR) in the monitoring of lifestyle interventions in obese persons

OBJECTIVES

Lifestyle changes with increased physical activity and balanced energy intake are recognized as the principal interventions in obesity and insulin resistance. Only few prospective studies, however, have so far addressed the potential role of routine biochemical markers of insulin sensitivity in the monitoring of respective interventions.

DESIGN AND METHODS

Fasting insulin and glucose was measured in 33 obese individuals undergoing a lifestyle modification program (MOBILIS) at baseline and after 1 year. The HOMA-IR index (homeostasis model of insulin resistance) was calculated as [fasting serum glucose*fasting serum insulin/22.5], with lower values indicating a higher degree of insulin sensitivity.

RESULTS

While the median body mass index (BMI) and waist circumference decreased by 10% and 11%, respectively, the HOMA-IR index decreased in an over-proportional manner by 45% within 1 year (BMI baseline, median 35.7, interquartile range (IQR) 33.7-37.7; after 1 year, median 32.2, IQR 29.6-35.1. HOMA-IR baseline, median 2.9, IQR 1.5-4.6; after 1 year 1.6, IQR 0.9-2.7). In contrast to HOMA-IR and fasting serum insulin, no significant changes in fasting serum glucose were observed. Baseline and post-intervention HOMA-IR showed a high degree of inter-individual variation with eight individuals maintaining high HOMA-IR values despite weight loss after 1 year of intervention.

CONCLUSIONS

Individual changes in the carbohydrate metabolism achieved by a lifestyle intervention program were displayed by fasting serum insulin concentrations and the HOMA-IR but not by fasting glucose measurement alone. Therefore, assessment of the HOMA-IR may help to individualize lifestyle interventions in obesity and to objectify improvements in insulin sensitivity after therapeutic lifestyle changes.

Insulin resistance is associated with increased risk of major cardiovascular events in patients with preexisting coronary artery disease

BACKGROUND

Over the past years it has been recognized that insulin resistance (IR) is an independent risk factor for the development of diabetes, whereas its association with cardiovascular events remains controversial. The aim of our study was to explore the association between IR per se and cardiovascular events among patients with preexisting coronary artery disease.

METHODS

The mean follow-up period of this prospective study was 6.2 years. Metabolic and inflammatory parameters were analyzed from stored frozen plasma samples obtained at baseline from 2938 patients aged 45 to 74 years. The homeostatic index of IR (HOMA-IR) was calculated according to the homeostasis model assessment.

RESULTS

New major cardiovascular events (fatal and nonfatal myocardial infarction and sudden death) were recorded in 108 (11.1%) patients from the lowest IR tertile, in 147 (14.7%) from the intermediate tertile, and in 166 (17.2%) from the highest tertile (P = .0002). The linear trend for total and cardiac death across the tertiles of HOMA-IR was significant as well (P = .02 and P = .009, respectively). The highest age-adjusted rates for major cardiovascular events and new diabetes were found among patients within the top tertile of HOMA-IR (57% and 130% higher rates, respectively, tertile 3 vs tertile 1, P < .0001 for both). Multivariable analysis identified HOMA-IR (tertile 3 vs tertile 1) as an independent predictor of increased risk of major cardiovascular events and new diabetes with hazard ratios (95% CI) of 1.4 (1.1-1.8) and 1.5 (1.1-2.0), respectively.

CONCLUSIONS

Insulin resistance per se is an independent risk factor for cardiovascular events and new diabetes in patients with preexisting coronary artery disease.

Metabolic syndrome: why the controversy?

As originally conceived, the metabolic syndrome defined a clustering of cardiovascular disease risk factors with insulin resistance as the common, underlying pathophysiologic determinant. The definition of the syndrome has evolved since then, with several groups proposing somewhat differing definitions. Partly, this has been motivated by efforts to make the syndrome a clinically useful entity. However, recent articles have called the clinical use of the metabolic syndrome into question. In this review, some of these concerns and counterarguments for the continued use of the metabolic syndrome are reviewed.

The metabolic syndrome: metabolic changes with vascular consequences

Despite criticism regarding its clinical relevance, the concept of the metabolic syndrome improves our understanding of both the pathophysiology of insulin resistance and its associated metabolic changes and vascular consequences. Free fatty acids (FFA) and tumour necrosis factor-alpha (TNF-alpha) play prominent roles in the development of insulin resistance by impairing the intracellular insulin signalling transduction pathway. Obesity is an independent risk factor for cardiovascular disease and strongly related to insulin resistance. In case of obesity, FFAs and TNF-alpha are produced in abundance by adipocytes, whereas the production of adiponectin, an anti-inflammatory adipokine, is reduced. This imbalanced production of pro- and anti-inflammatory adipokines, as observed in adipocyte dysfunction, is thought to be the driving force behind insulin resistance. The role of several recently discovered adipokines such as resistin, visfatin and retinol-binding protein (RBP)-4 in the pathogenesis of insulin resistance is increasingly understood. Insulin resistance induces several metabolic changes, including hyperglycaemia, dyslipidaemia and hypertension, all leading to increased cardiovascular risk. In addition, the dysfunctional adipocyte, reflected largely by low adiponectin levels and a high TNF-alpha concentration, directly influences the vascular endothelium, causing endothelial dysfunction and atherosclerosis. Adipocyte dysfunction could therefore be regarded as the common antecedent of both insulin resistance and atherosclerosis and functions as the link between obesity and cardiovascular disease. Targeting the dysfunctional adipocyte may reduce the risk for both cardiovascular disease and the development of type 2 diabetes. Although lifestyle intervention remains the cornerstone of therapy in improving insulin sensitivity and its associated metabolic changes, medical treatment might prove to be important as well.

Effects of chili consumption on postprandial glucose, insulin, and energy metabolism

BACKGROUND

Animal and some human studies have indicated that the consumption of chili-containing meals increases energy expenditure and fat oxidation, which may help to reduce obesity and related disorders. Because habitual diets affect the activity and responsiveness of receptors involved in regulating and transporting nutrients, the effects of regular consumption of chili on metabolic responses to meals require investigation.

OBJECTIVE

The objective was to investigate the metabolic effects of a chili-containing meal after the consumption of a bland diet and a chili-blend (30 g/d; 55% cayenne chili) supplemented diet.

DESIGN

Thirty-six subjects with a mean (+/-SD) age of 46 +/- 12 y and a body mass index (in kg/m2) of 26.3 +/- 4.6 participated in a randomized, crossover, intervention study with 2 dietary periods (chili and bland) of 4 wk each. The postprandial effects of a bland meal after a bland diet (BAB), a chili meal after a bland diet (CAB), and a chili meal after a chili-containing diet (CAC) were evaluated. Serum insulin, C-peptide, and glucose concentrations and energy expenditure (EE) were measured at fasting and up to 120 min postprandially.

RESULTS

Significant heterogeneity was observed between the meals for the maximum increase in insulin and the incremental area under the curve (iAUC) for insulin (P = 0.0002); the highest concentrations were with the BAB meal and the lowest with the CAC meal. When separated at the median BMI (26.3), the subjects with a BMI > or = 26.3 also showed heterogeneity in C-peptide, iAUC C-peptide, and net AUC EE (P < 0.02 for all); the highest values occurred after the BAB meal and the lowest after the CAC meal. Conversely, the C-peptide/insulin quotient (an indicator of hepatic insulin clearance) was highest after the CAC meal (P = 0.002).

CONCLUSION

Regular consumption of chili may attenuate postprandial hyperinsulinemia.

Impaired fibrinolysis and risk for cardiovascular disease in the metabolic syndrome and type 2 diabetes

Patients with the metabolic syndrome are insulin resistant and manifest a cluster of risk factors for cardiovascular disease. Impaired fibrinolysis and increased concentrations in blood of plasminogen activator inhibitor-1 (PAI-1) are related to insulin resistance and abdominal obesity and may contribute to the increased risk for cardiovascular disease in this group. Weight loss, metformin, and thiazolidinediones ameliorate insulin resistance and decrease concentrations of PAI-1. Thus, they may lower risk in patients with the metabolic syndrome.

Insulin resistance, the metabolic syndrome, and incident cardiovascular events in the Framingham Offspring Study

The metabolic syndrome and insulin resistance have been related to incident cardiovascular disease (CVD), but it is uncertain if metabolic syndrome predicts CVD independent of insulin resistance. Our study sample included 2,898 people without diabetes or CVD at baseline. Metabolic syndrome was defined by the National Cholesterol Education Program (NCEP) Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults (Adult Treatment Panel III) criteria. Insulin resistance was defined by the homeostasis model assessment (HOMA-IR) and by Gutt et al.'s insulin sensitivity index (ISI(0,120)). Age- and sex-adjusted proportional hazards regression models assessed the association of baseline metabolic syndrome and insulin resistance to 7-year CVD risk (186 events). Metabolic syndrome and both measures of insulin resistance were individually related to incident CVD (age- and sex-adjusted hazard ratio [HR] for metabolic syndrome [present versus absent]: 2.0 [95% CI 1.5-2.6], P = 0.0001; for HOMA-IR: 1.9 [1.2-2.9], P = 0.003; and for ISI(0,120) [both highest versus lowest quartile]: 0.5 [0.3-0.7], P = 0.001). In models adjusted for age, sex, LDL cholesterol, and smoking status and including metabolic syndrome, ISI(0,120) levels were independently related to incident CVD (0.5 [0.3-0.8], P = 0.004), whereas HOMA-IR levels were not (1.3 [0.8-2.1], P = 0.24); metabolic syndrome was associated with increased CVD risk in both models (HR 1.6, P < or = 0.007 in both). In conclusion, metabolic syndrome and ISI(0,120) but not HOMA-IR independently predicted incident CVD. Metabolic syndrome may not capture all the CVD risk associated with insulin resistance.

Sophisticated tests for susceptibility to atherosclerosis: an added value for heart hospitals

Coronary atherosclerosis is the result of multiple complex metabolic disorders acting alone or in combination. Metabolic cardiology has advanced considerably in the past decade and now offers cardiologists a sophisticated approach to treating the underlying cause(s) of coronary artery disease in patients seen in invasive cardiology practices. Disorders which have now been powerfully linked to coronary artery disease include the small low-density lipoprotein trait, impaired reverse cholesterol transport, homocysteinemia, insulin resistance, aspects of inflammation, and infectious burden. These disorders are common and alone, or in combination, are found in over 90% of patients with coronary artery disease. Treatments for these disorders are well elucidated and have been associated with cardiovascular benefit. Incorporation of a sophisticated metabolic atherosclerosis management unit into existing invasive cardiology practices offers the cardiologist and patient many benefits. The cardiologist obtains a powerful tool that complements invasive cardiology, provides patients with access to cutting-edge diagnosis and treatment, and provides a forum that allows incorporation of clinically valid advances in metabolic cardiovascular care in a time frame far shorter than the traditional consensus recommendation approach. Incorporation of such a clinical service is consistent with the recent American College of Cardiology focus on the "CardioTeam."

FFAs: do they play a role in vascular disease in the insulin resistance syndrome?

The insulin resistance syndrome, otherwise known as the metabolic syndrome, describes a cluster of cardiovascular and metabolic abnormalities, which are strongly associated with overweight and obesity. The importance of the syndrome is due to its increased rates of cardiovascular morbidity and mortality. Insulin resistance is also characterized by elevated free fatty acid (FFA) levels. In otherwise healthy human subjects, elevation of FFA impairs endothelial function. This appears to be largely the result of blunting of nitric oxide-dependent tone, most likely at the level of the endothelial isoform of nitric oxide synthase (eNOS). Some of the potential mediatory mechanisms include oxidative stress, proinflammatory cytokines, C-reactive protein, or endogenous inhibitors of eNOS. Regardless of the mechanism(s) that mediates the effects of increased FFA on the vasculature, impaired vascular function is likely to account, at least in part, for the increase in cardiovascular mortality in subjects with the insulin resistance syndrome.

Risk factors for cardiovascular disease in pediatric renal transplant recipients

About 1,000 children develop end-stage renal disease (ESRD) each year in the United States and about 5,000 children are currently receiving dialysis. Children who develop ESRD are eligible to receive renal replacement therapy, including renal transplantation. There are inherent risks associated with transplantation, including renal insufficiency, infections, post-transplant lymphoproliferative disorder, and cardiovascular disease (CVD). Potential risk factors for CVD in pediatric renal transplant recipients include renal insufficiency, hyperlipidemia, hyperhomocysteinemia, inflammation, malnutrition, anemia, and hyperglycemia/insulin resistance. Despite evidence that many children may possess various risk factors for CVD post-renal transplantation, there are very few studies that have attempted to assess the link between these risk factors and CVD in pediatric renal transplant recipients.

Plasma insulin and cardiovascular mortality in non-diabetic European men and women: a meta-analysis of data from eleven prospective studies

AIMS/HYPOTHESIS

We examined the association between plasma insulin and cardiovascular mortality in non-diabetic European men and women based on data from eleven prospective studies.

METHODS

The study population comprised 6156 men and 5351 women aged 30-89 years. Baseline measurements included oral glucose tolerance test, fasting and 2-h plasma insulin, and conventional risk factors. Cox models were used to calculate hazard ratios (HRs) and their 95% confidence intervals, and overall HRs were assessed by meta-analyses.

RESULTS

During the 8.8-year follow-up, 362 men and 70 women died from cardiovascular disease. The age- and smoking-adjusted overall HR of cardiovascular mortality for the highest vs the lower quartiles of fasting insulin was 1.58 (95% CI: 1.26-1.97) in men and 2.64 (1.54-4.51) in women. Adjusting for other risk factors in addition, the HR was 1.54 (1.16-2.03) in men and 2.66 (1.45-4.90) in women. For 2-h insulin these HRs were 1.28 (0.99-1.66), 1.87 (0.87-4.02), and 0.85 (0.60-1.21), 1.36 (0.53-3.45). The overall HRs for interquartile ranges for fasting and 2-h insulin, with full adjustment, were 1.13 (1.05-1.22) and 1.11 (1.01-1.23) in men, and 1.25 (1.08-1.45) and 1.11 (0.91-1.36) in women.

CONCLUSIONS/INTERPRETATION

Hyperinsulinaemia, defined by the highest quartile cut-off for fasting insulin, was significantly associated with cardiovascular mortality in both men and women independently of other risk factors. Associations between high 2-h insulin and cardiovascular mortality were weaker and non-significant. Weak positive associations of fasting and 2-h insulin with cardiovascular mortality over interquartile ranges were, however, more similar.

Endocrine changes in critical illness

The homeostatic corrections that have emerged in the course of human evolution to cope with catastrophic events involve a complex multisystem endeavor, of which the endocrine contribution is an integral component. Although the repertoire of endocrine changes has been probed in some detail, discerning the vulnerabilities and failure of this system is far more challenging. The ensuing endocrine topics illustrate some of the current issues reflecting attempts to gain an improved insight and clinical outcome for critical illness.

Hypofibrinolysis in the insulin resistance syndrome: implication in cardiovascular diseases

Insulin resistance syndrome (IRS) is associated with increased cardiovascular morbidity and mortality. IRS is becoming one of the major health problems as its prevalence grows rapidly. Accelerated atherothrombotic process in the IRS is attributed to metabolic abnormalities, inflammation and to impaired fibrinolysis due to increased plasma plasminogen activator inhibitor type 1 (PAI-1) levels. Proinflammatory cytokines may have an important role in PAI-1 overexpression, particularly in the adipose tissue. Studies in genetically modified mice indicate that PAI-1 might be involved in the aetiopathogenesis of obesity. Modifying PAI-1 expression by PAI-1 inhibitors may open a new field of research and may reveal the true role of PAI-1 in atherosclerotic and insulin resistance processes.