Role of insulin and atrial natriuretic peptide in sodium retention in insulin-treated IDDM patients during isotonic volume expansion

Early ICU-acquired hypernatraemia is associated with injury severity and preceded by reduced renal sodium and chloride excretion in polytrauma patients

PURPOSE

To further elucidate the origin of early ICU-acquired hypernatraemia.

MATERIAL AND METHODS

In this retrospective single-centre study, polytrauma patients requiring ICU treatment were analysed.

RESULTS

Forty-eight (47.5%) of 101 included polytrauma patients developed hypernatraemia within the first 7 days on ICU. They were more severely ill as described by higher SAPS III, ISS, daily SOFA scores and initial norepinephrine requirements as well as longer requirements of mechanical ventilation and ICU treatment in general. The development of hypernatraemia was neither attributable to fluid- or sodium-balances nor renal impairment. Although lower in the hypernatraemic group from day 4 onwards, median creatinine clearances were sufficiently high throughout the observation period. However, in the hypernatraemic group, urine sodium and chloride concentrations prior to the evolvement of hypernatraemia (56 (27-87) mmol/l and 39 (23-77) mmol/l) were significantly decreased when compared to i) the time after developing hypernatraemia (94 (58-134) mmol/l and 78 (36-115) mmol/l; p < 0.001) and ii) the non-hypernatraemic group in general (101 (66-143) mmol/l and 75 (47-109) mmol/l; p < 0.001).

CONCLUSIONS

Early ICU-acquired hypernatraemia is associated with injury severity and preceded by reduced renal sodium and chloride excretion in polytrauma patients.

Metabolic and biological changes in children with obesity and diabetes

The World Health Organization has stated that obesity in childhood is one of the most serious public health challenges of the 21^st century. Overweightness and obesity in early childhood lead to a higher risk of overweightness and obesity in adulthood, thus conferring an increased risk of chronic inflammatory conditions, including type 2 diabetes mellitus, cardiovascular diseases, non-alcoholic fatty liver disease, and some cancers. Therefore, metabolome analysis, targeted at screening and intervening in childhood obesity, is very important. Recent studies have indicated that amino acid and lipid metabolism could influence metabolic pathways in children with obesity. For this review, we searched clinical data addressing metabolomic profiles and insulin resistance (IR) in children with obesity from inception to February 2021 in Medline, Web of Science, and Scopus. According to our search, branched-chain amino acids (BCAAs), aromatic amino acids, and acylcarnitines have reportedly been associated with IR as biomarkers for diabetes in children. BCAAs, tyrosine, and phenylalanine could be predictors of the future development of diabetes in nondiabetic subjects. In addition, it is well known that insulin regulates BCAA metabolism, and BCAA is a biomarker for IR. To interpret the mechanism behind metabolic changes in obesity, it is very important to understand the pathways and combinations related with amino acid, lipid and glucose metabolism. In this review, we summarize studies on metabolic changes to understand metabolomics in children with obesity.

High percent body fat mass predicts lower risk of cardiac events in patients with heart failure: an explanation of the obesity paradox

Background

Although high body mass index (BMI) is a risk factor of heart failure (HF), HF patients with a higher BMI had a lower mortality rate than that in HF patients with normal or lower BMI, a phenomenon that has been termed the “obesity paradox”. However, the relationship between body composition, i.e., fat or muscle mass, and clinical outcome in HF remains unclear.

Methods

We retrospectively analyzed data for 198 consecutive HF patients (76 years of age; males, 49%). Patients who were admitted to our institute for diagnosis and management of HF and received a dual-energy X-ray absorptiometry scan were included regardless of left ventricular ejection fraction (LVEF) categories. Muscle wasting was defined as appendicular skeletal muscle mass index < 7.0 kg/m² in males and < 5.4 kg/m² in females. Increased percent body fat mass (increased FM) was defined as percent body fat > 25% in males and > 30% in females.

Results

The median age of the patients was 76 years (interquartile range [IQR], 67–82 years) and 49% of them were male. The median LVEF was 47% (IQR, 33–63%) and 33% of the patients had heart failure with reduced ejection fraction. Increased FM and muscle wasting were observed in 58 and 67% of the enrolled patients, respectively. During a 180-day follow-up period, 32 patients (16%) had cardiac events defined as cardiac death or readmission by worsening HF or arrhythmia. Kaplan-Meier survival curves showed that patients with increased FM had a lower cardiac event rate than did patients without increased FM (11.4% vs. 22.6%, p = 0.03). Kaplan-Meier curves of cardiac event rates did not differ between patients with and those without muscle wasting (16.5% vs. 15.4%, p = 0.93). In multivariate Cox regression analyses, increased FM was independently associated with lower cardiac event rates (hazard ratio: 0.45, 95% confidence interval: 0.22–0.93) after adjustment for age, sex, diabetes, muscle wasting, and renal function.

Conclusions

High percent body fat mass is associated with lower risk of short-term cardiac events in HF patients.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12877-020-01950-9.

Effect of insulin on natriuretic peptide gene expression in porcine heart

Gut hormones affect cardiac function and contractility. In this study, we examined whether insulin affects the cardiac atrial natriuretic peptide (ANP) and B-type natriuretic peptide (BNP) gene expression and release of proANP-derived peptides in pigs. Anaesthetized pigs were included in an experimental study comparing the effect of hyperinsulinemia in 15 pigs submitted to two different protocols versus 11 control pigs receiving saline infusion. Phosphorylation of Akt on Thr308 was determined by western blotting with a pAkt-Thr308 antibody. The mRNA contents of ANP and BNP were determined with real-time PCR; plasma and cardiac tissue proANP was measured with an immunoluminometric assay targeted against the mid-region of the propeptide and a processing-independent assay. Insulin stimulation increased phosphorylation of Akt Thr308 in both left atrium and left ventricle of porcine hearts (p < 0.005). No change was observed in ANP and BNP mRNA contents in the right or left atrium. BNP mRNA contents in the left ventricle, however, decreased 3-fold (p = 0.02) compared to control animals, whereas the BNP mRNA content in the right ventricle as well as ANP mRNA content in the right and left ventricle did not change following hyperinsulinemia. Moreover, the peptide contents did not change in the four cardiac chambers. Finally, proANP concentrations in plasma did not change during the insulin infusion compared to the control animals. These results suggest that insulin does not have direct effect on atrial natriuretic peptide expression but may have a role in the left ventricle.

Do most patients with obesity or type 2 diabetes, and atrial fibrillation, also have undiagnosed heart failure? A critical conceptual framework for understanding mechanisms and improving diagnosis and treatment

Obesity and diabetes can lead to heart failure with preserved ejection fraction (HFpEF), potentially because they both cause expansion and inflammation of epicardial adipose tissue and thus lead to microvascular dysfunction and fibrosis of the underlying left ventricle. The same process also causes an atrial myopathy, which is clinically evident as atrial fibrillation (AF); thus, AF may be the first manifestation of HFpEF. Many patients with apparently isolated AF have latent HFpEF or subsequently develop HFpEF. Most patients with obesity or diabetes who have AF and exercise intolerance have increased left atrial pressures at rest or during exercise, even in the absence of diagnosed HFpEF. Among patients with AF, those who also have latent HFpEF have increased risk for systemic thromboembolism and death. The identification of HFpEF in patients with obesity or diabetes alters the risk-to-benefit relationship of commonly prescribed treatments. Bariatric surgery and statins can ameliorate AF and reduce the risk for HFpEF. Conversely, antihyperglycaemic drugs that promote adipogenesis or cause sodium retention (insulin and thiazolidinediones) may increase the risk for heart failure in patients with an underlying ventricular myopathy. Patients with obesity and diabetes who undergo catheter ablation for AF are at increased risk for AF recurrence and for post-ablation increases in pulmonary venous pressures and worsening heart failure, especially if HFpEF coexists. Therefore, AF may be the earliest indicator of HFpEF in patients with obesity or type 2 diabetes, and recognition of HFpEF alters the management of these patients.

Disease-treatment interactions in the management of patients with obesity and diabetes who have atrial fibrillation: the potential mediating influence of epicardial adipose tissue

Both obesity and type 2 diabetes are important risk factors for atrial fibrillation (AF), possibly because they both cause an expansion of epicardial adipose tissue, which is the source of proinflammatory adipocytokines that can lead to microvascular dysfunction and fibrosis of the underlying myocardium. If the derangement of epicardial fat adjoins the left atrium, the result is an atrial myopathy, which is clinically manifest as AF. In patients with AF, there is a close relationship between epicardial fat volume and the severity of electrophysiological abnormalities in the adjacent myocardial tissues, and epicardial fat mass predicts AF in the general population. The expansion of epicardial adipose tissue in obesity and type 2 diabetes may also affect the left ventricle, impairing its distensibility and leading to heart failure with a preserved ejection fraction (HFpEF). Patients with obesity or type 2 diabetes with AF often have HFpEF, but the diagnosis may be missed, if dyspnea is attributed to increased body mass or to the arrhythmia. The expected response to the treatment for obesity, diabetes or AF may be influenced by their effects on epicardial inflammation and the underlying atrial and ventricular myopathy. Bariatric surgery and metformin reduce epicardial fat mass and ameliorate AF, whereas insulin promotes adipogenesis and cardiac fibrosis, and its use is accompanied by an increased risk of AF. Rate control strategies for AF may impair exercise tolerance, because they allow for greater time for ventricular filling in patients who cannot tolerate volume loading because of cardiac fibrosis and HFpEF. At the same time, both obesity and diabetes decrease the expected success rate of rhythm control strategies for AF (e.g., electrical cardioversion or catheter ablation), because increased epicardial adipose tissue volumes and cardiac fibrosis are important determinants of AF recurrence following these procedures.

Continuous Subcutaneous Insulin Infusion Initiation Is Associated With Blood Pressure Reduction in Adults With Type 1 Diabetes

BACKGROUND

In type 1 diabetes (T1D) continuous subcutaneous insulin infusion (CSII) use has been associated with lower risks for mortality and diabetes-related complications when compared to multiple daily injections. There are limited data on the effect of CSII on blood pressure (BP). We aimed to evaluate the relationship between CSII initiation and BP changes.

METHODS

We performed a retrospective, single-center, observational study including all adults with T1D who initiated CSII between 2001 and 2014. Mean systolic BP levels were calculated from values obtained up to 15 months before and up 15 months after CSII initiation.

RESULTS

We studied 436 adults (46% male; mean [95% CI] age: 45 [36, 54] years, duration of diabetes: 20.3 [19.1, 21.5] years). CSII was associated with the following changes (post minus pre CSII levels) in mean (95% CI) SBP and DBP levels, respectively: whole cohort (N = 436): -2 (-1, -3), P < .001 and -2 (-1, -2), P < .001; those taking stable antihypertensive medication (n = 118): -4 (-6, -2), P < .001 and -2 (-3, -1), P < .001; antihypertensive treatment-naïve patients (n = 279): -1 (-2, 0), P = .147 and -1 (-2, 0), P = .002. In multivariate regression analysis including age, sex, diabetes duration, pre-CSII BP, HbA1c and weight changes, only pre-CSII BP showed an independent association with BP drop in all patients' groups. Once adjusted for pre-CSII BP there was no significant difference between those on antihypertensive drugs and antihypertensive treatment-naïve individuals.

CONCLUSIONS

We showed BP reduction in association with CSII therapy particularly in those on antihypertensive medication. These original findings may partly explain the cardiovascular and mortality benefits associated with CSII therapy.

Long-Term Risk of Hypertension in Normoglycemia and Prediabetes, and Their Relation to the Change of Glycemic State

BACKGROUND

Although increasing evidence has suggested the significant association between dysglycemia and hypertension, this association is less well described in prediabetes. Additionally, it is unclear how risk of hypertension varies according to the change of glycemic state.

METHODS

Five thousand four hundred thirteen nondiabetic Koreans were dichotomized into normoglycemia (NG) and prediabetes group and followed-up for 10 years. Cox proportional hazard model was used to evaluate hazard ratios (HRs) with 95% confidence interval (CI) [adjusted HRs (95% CI)] for the development of hypertension. Subgroup analysis was conducted in subdivided glycated hemoglobin (HbA1c) with <5.7%, 5.7-5.9%, and 6.0-6.4% and 2 hour post-load glucose (2 hr-PG) with <140, 140-169, and 170-199 mg/dl. The glycemic states are NG, prediabetes, and diabetes mellitus (DM), which are used in evaluating the change of glycemic state during follow-up in baseline NG (NG → NG, NG → prediabetes, and NG → DM) and baseline prediabetes (prediabetes → prediabetes and prediabetes → DM).

RESULTS

Compared with NG, prediabetes was not significantly associated with the risk of hypertension [1.11 (0.997-1.23)]. HbA1c ≥5.7% [1.13 (1.02-1.26)] and 2 hr-PG ≥140 mg/dl [1.15 (1.004-1.31)] were marginally associated with the risk of hypertension. In subgroup analysis, only 2 hr-PG of 170-199 mg/dl showed the significantly increased risk of hypertension [1.37 (1.09-1.73)]. Compared with the maintaining glycemic state, the progression of glycemic state had the significantly increased risk of hypertension [NG → prediabetes; 1.41 (1.19-1.67), NG→DM; 1.77 (1.36-2.30), and prediabetes → DM; 1.32 (1.13-1.55)].

CONCLUSION

The progression of glycemic state was a strong determinant on the development of hypertension.

Acute effects of insulin on circulating natriuretic peptide levels in humans

Background

The natriuretic peptide hormones play an important role in salt and blood pressure regulation. In observational studies, obesity and insulin resistance have been consistently associated with lower concentrations of natriuretic peptides. It has been proposed that insulin influences natriuretic peptide production.

Objective

We sought to determine the acute effects of insulin administration on natriuretic peptide concentrations.

Methods

31 men and women (11 lean, 10 overweight, and 10 obese), ages 30–70 years, without cardiovascular disease or overt diabetes underwent a hyperinsulinemic-euglycemic insulin clamp. Plasma concentrations of N-terminal pro atrial natriuretic peptide (NT-proANP) and N-terminal pro B-type natriuretic peptide (NT-proBNP) were measured at baseline and steady-state (the final 30 minutes of the clamp protocol).

Results

From baseline to steady-state, insulin levels increased from a mean level of 9.5 to 176.7 μU/ml (p<0.001). Over this period, circulating NT-proANP concentrations decreased by 9% (-1933 ng/L, p = 0.01). The changes in NT-proANP did not differ between lean, overweight, and obese individuals. Steady-state NT-proANP levels, adjusted for baseline, were lower in individuals with greater insulin resistance, independent of BMI. In contrast to NT-proANP, NT-proBNP levels did not change significantly during the clamp (p = 0.41).

Conclusion

Insulin administration was associated with a moderate decrease in circulating NT-proANP, but not NT-proBNP. The lowest NT-proANP concentrations were found in insulin-resistant individuals. Further investigations are warranted to elucidate potential mechanisms underlying the effects of insulin on the cardiac hormonal axis.

Natriuretic peptides in the control of lipid metabolism and insulin sensitivity

Natriuretic peptides have long been known for their cardiovascular function. However, a growing body of evidence emphasizes the role of natriuretic peptides in human substrate and energy metabolism, thereby connecting the heart with several insulin-sensitive organs like adipose tissue, skeletal muscle and liver. Obesity may be associated with an impaired regulation of the natriuretic peptide system, also indicated as a natriuretic handicap. Evidence points towards a contribution of this natriuretic handicap to the development of obesity, type 2 diabetes mellitus and cardiometabolic complications, although the causal relationship is not fully understood. Nevertheless, targeting the natriuretic peptide pathway may improve metabolic health in obesity and type 2 diabetes mellitus. This review will focus on current literature regarding the metabolic roles of natriuretic peptides with emphasis on lipid metabolism and insulin sensitivity. Furthermore, it will be discussed how exercise and lifestyle intervention may modulate the natriuretic peptide-related metabolic effects.

The influence of metabolic syndrome and diabetes mellitus on the N-terminal pro-B-type natriuretic peptide level and its prognostic performance in patients with coronary artery disease

OBJECTIVES

Our aim was to investigate whether the presence of metabolic syndrome (MetS) and diabetes mellitus (DM) influenced the N-terminal pro-B-type natriuretic peptide (NT-proBNP) level and its prognostic performance in coronary artery disease (CAD).

PATIENTS AND METHODS

The present study enrolled a total of 1638 CAD patients. Multivariate regression analyses were carried out to relate NT-proBNP to metabolic components, nondiabetic MetS, DM, and MetS score. Furthermore, we examined the prognostic performance of NT-proBNP in patients with non-MetS, nondiabetic MetS, and DM.

RESULTS

NT-proBNP levels correlated inversely with BMI (β=-0.11, P=0.003) and correlated positively with fasting glucose (β=0.12, P=0.001). There were no significant relationships of NT-proBNP with other metabolic parameters. Compared with non-MetS, the presence of DM significantly increased NT-proBNP levels (P=0.004), whereas nondiabetic MetS did not influence NT-proBNP levels (P=0.954). During the median follow-up of 21 months, 109 all-cause deaths occurred. NT-proBNP levels independently predicted all-cause deaths irrespective of the presence of nondiabetic MetS and DM (Pinteraction=0.43).

CONCLUSION

DM, but not nondiabetic MetS, is associated with higher NT-proBNP levels. NT-proBNP can still predict death in patients with CAD, even with the confounding effect of MetS and diabetes.

Effect of Pancreatic Hormones on pro-Atrial Natriuretic Peptide in Humans

Plasma concentrations of pro-Atrial natriuretic peptide, proANP, are decreased in obesity and diabetes. Decreased proANP concentrations have also been noted after meal intake, and recently, a glucose-mediated regulation of ANP gene expression was reported. Hence, we evaluated the effects of insulin, glucagon and glucose on plasma proANP in a series of observational and experimental studies.

Six healthy men underwent seven days of bed rest. Before and after the bed rest, hyperinsulinemic euglycemic clamps with serial plasma measurements of proANP were performed. Moreover, plasma proANP was quantified in 65 individuals with normal or impaired glucose regulation. Finally, the effects of infusion-induced hyperglucagonemia were examined in ten healthy men.

Bed rest decreased insulin sensitivity and plasma proANP. The decrease in proANP was not associated with insulin sensitivity and the peptide concentrations remained constant during euglycemic hyperinsulinemia and hyperglycemic hyperglucagonemia. Impaired glucose regulation was not associated with decreased proANP concentrations.

Bed rest per se induces a marked decrease in plasma proANP concentrations whereas insulin resistance and impaired glucose regulation was not associated with lower proANP concentrations. Neither acute hyperinsulinemia nor hyperglucagonemia seems to affect plasma proANP. Our findings thus suggest that decreased plasma proANP concentrations occur late in the development of insulin resistance.

•

Plasma proANP is markedly decreased in bedridden patients and should be interpreted in the light of these circumstances.

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Low-grade insulin resistance was not associated with decreased proANP concentrations.

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Neither acute hyperinsulinemia nor hyperglucagonemia seems to affect plasma proANP in lean individuals.

Circulating concentrations of pro-ANP areis used as biomarkers of heart failure, where normal concentrations can exclude a diagnosis of cardiac pump dysfunction. In the present study, bed rest per se induced a decrease in plasma proANP. Notably, bed rest is common in patients submitted to hospitals and our findings may thus interfere with the present diagnostic cut-off values.

In contrast, presence of low-grade insulin resistance and impaired glucose regulation was not associated with decreased plasma proANP. Neither acute hyperinsulinemia nor hyperglucagonemia affected plasma proANP in lean individuals. Decreased plasma proANP may thus not be evident until more progressed insulin resistance.

A cohort study of incident microalbuminuria in relation to HOMA-IR in Korean men

BACKGROUND

Despite the previous studies showing the relationship between microalbuminuria and insulin resistance, longitudinal effect of insulin resistance on development of microalbuminuria is not clearly identified in non-diabetic population.

METHODS

One thousand six hundred three non-diabetic Korean men without microalbuminuria in 2005 had been followed up for the development of microalbuminuria until 2010. Microalbuminuria was evaluated by urine-albumin creatinine ration, and insulin resistance was evaluated by homeostasis model assessment of insulin resistance (HOMA-IR). Cox proportional hazards model was used to estimate the risk for microalbuminuria according to the tertile of HOMA-IR.

RESULTS

During 5465.8 person-y of average follow-up, microalbuminuria developed in 76 (4.7%) participants. Incidence of microalbuminuria increased in proportion to the level of HOMA-IR (tertile 1: 3.0%, tertile 2: 4.1%, tertile 3: 7.1%, P<0.001). When the 1st tertile of HOMA-IR was set as reference, hazard ratios and 95% confidence interval were 1.15 (0.56-2.35) and 2.07 (1.05-4.09) for those in the 2nd and 3rd tertiles of HOMA-IR, even after adjusting multiple covariates, respectively (P for linear trend=0.054).

CONCLUSIONS

Increased insulin resistance was a predictor of microalbuminuria in Korean men.

Elevated fasting insulin level significantly increases the risk of microalbuminuria

BACKGROUND

Microalbuminuria is significantly associated with long-term prognosis in the general population as well as in diabetic patients. It is well known that insulin resistance (IR) can induce microalbuminuria, but an elevated fasting insulin level, which is an early clinical manifestation of IR, as a risk factor for microalbuminuria has not been clarified, so we investigated the association between fasting insulin level and the development of microalbuminuria in a general population.

METHODS AND RESULTS

A total of 1,192 non-diabetic Korean men without microalbuminuria in 2005 were followed until 2010. They were categorized into 3 groups according to their fasting insulin levels and monitored for the development of microalbuminuria. The incidence of microalbuminuria was compared among groups, and Cox proportional hazards models were used to calculate the hazard ratios for microalbuminuria according to the fasting insulin levels. During 4,013.0 person-years of follow-up, 51 incident cases of microalbuminuria developed between 2006 and 2010. The incidence of microalbuminuria increased in proportion to the fasting insulin levels (tertile 1: 1.8%, tertile 2: 4.5%, tertile 3: 6.5%, P<0.001). Hazard ratios for microalbuminuria also increased in proportion to the fasting insulin levels [tertile 1: reference, tertile 2: 2.44 (1.01-5.89), tertile 3: 3.30 (1.40-7.78), respectively, P for trend 0.013].

CONCLUSIONS

Elevated fasting insulin level was associated with the future development of microalbuminuria.

Obesity and natriuretic peptides, BNP and NT-proBNP: mechanisms and diagnostic implications for heart failure

Many advances have been made in the diagnosis and management of heart failure (HF) in recent years. Cardiac biomarkers are an essential tool for clinicians: point of care B-type natriuretic peptide (BNP) and its N-terminal counterpart (NT-proBNP) levels help distinguish cardiac from non-cardiac causes of dyspnea and are also useful in the prognosis and monitoring of the efficacy of therapy. One of the major limitations of HF biomarkers is in obese patients where the relationship between BNP and NT-proBNP levels and myocardial stiffness is complex. Recent data suggest an inverse relationship between BNP and NT-proBNP levels and body mass index. Given the ever-increasing prevalence of obesity world-wide, it is important to understand the benefits and limitations of HF biomarkers in this population. This review will explore the biology, physiology, and pathophysiology of these peptides and the cardiac endocrine paradox in HF. We also examine the clinical evidence, mechanisms, and plausible biological explanations for the discord between BNP levels and HF in obese patients.

Relation of visceral adiposity to circulating natriuretic peptides in ambulatory individuals

Natriuretic peptides have important roles in the regulation of vasomotor tone, salt homeostasis, and ventricular remodeling. Lower natriuretic peptide levels observed in obese individuals may underlie the greater cardiovascular risk associated with obesity. Thus the aim of this study was to determine whether lower natriuretic peptide levels in obesity are attributable to differences in regional fat distribution. We investigated the relation of plasma N-terminal pro-B-type natriuretic peptide (NT-pro-BNP) to regional adiposity in 1,873 community-based individuals (46% women, mean age 45 years). Subcutaneous adipose tissue (SAT) and visceral adipose tissue (VAT) volumes were measured by multidetector computed tomography. In gender-specific multivariable analyses adjusting for age and blood pressure, log NT-pro-BNP was inversely associated with VAT in men (beta -0.11 per standard deviation increment, p <0.001) and women (beta -0.19, p <0.001). Log NT-pro-BNP was inversely associated with SAT in women only (beta -0.14, p <0.001). In models containing VAT and SAT, only VAT was significantly associated with log NT-pro-BNP (men, beta -0.137, p <0.001; women, beta -0.184, p <0.001). VAT remained associated with log NT-pro-BNP even after adjustment for body mass index and waist circumference (beta -0.119, p <0.001) and in analyses restricted to nonobese patients (beta -0.165, p <0.001). Adjustment for insulin resistance attenuated the associations of NT-pro-BNP with VAT and SAT. In conclusion, this study demonstrates that circulating NT-pro-BNP is related to variations in regional and particularly visceral adiposity. These findings suggest that excess visceral adiposity and concomitant hyperinsulinemia may contribute to the natriuretic peptide "deficiency" observed in obesity.

Impact of natriuretic peptide clearance receptor (NPR3) gene variants on blood pressure in type 2 diabetes

OBJECTIVE

Hypertension in diabetes is characterized by abnormal sodium homeostasis, suggesting a particular role of natriuretic peptide pathway. Natriuretic peptides can affect blood pressure (BP) through their plasma concentrations, which are dependent on their receptor activities. We thus assessed the association between nine NPR3 gene polymorphisms and BP levels in patients with type 2 diabetes.

RESEARCH DESIGN AND METHODS

Nine single nucleotide polymorphisms (SNPs) tagging the haplotype structure of the NPR3 gene were genotyped in the 3,126 French Non-insulin-dependent Diabetes, Hypertension, Microalbuminuria or Proteinuria, Cardiovascular Events, and Ramipril (DIABHYCAR) trial participants. We then used a second population (Diabete de type 2, Nephropathie et Genetique [DIAB2NEPHROGENE]/Survie, Diabete de type 2 et Genetique [SURDIAGENE] study) of 2,452 patients for the purpose of replication. Finally, we separately investigated subjects selected according to their rs 2270915SNP genotypes for their BP response to salt restriction.

RESULTS

In DIABHYCAR patients, three SNPs (rs6889608, rs1173773, and rs2270915) were significantly associated with systolic BP (SBP). The effect of the rs2270915 was replicated in the second step population: AA homozygotes had a lower SBP than G carriers (137.4 ± 19.1 vs. 140.0 ± 20.2 mmHg, P = 0.004). The rs2270915 influenced the response of SBP to salt reduction, with AA homozygous patients showing greater reductions after restriction of salt intake compared with G carriers: -20 mmHg (-43 to -8) vs. -3 (-20 to +7); P = 0.006.

CONCLUSIONS

We found a consistent and significant association between the rs2270915 polymorphism of the NPR3 gene and SBP in diabetic patients. This genetic variation may affect pressure response to changes in dietary sodium.

Continuous subcutaneous insulin infusion is more effective than multiple daily insulin injections in preventing albumin excretion rate increase in Type 1 diabetic patients

AIMS

To compare the effect of continuous subcutaneous insulin infusion (CSII) and multiple daily insulin injections (MDI) on albumin excretion rate (AER) in Type 1 diabetic patients.

METHODS

In a 3-year multicentre retrospective observational study, 110 Type 1 diabetic patients treated with CSII were compared with 110 patients treated with MDI matched at baseline for age, sex, diabetes duration and HbA(1c). At entry, 90 patients in each group had normal AER and 20 persistent microalbuminuria. AER, estimated glomerular filtration rate (eGFR), HbA(1c,) lipids and blood pressure were assessed.

RESULTS

HbA(1c) was lower in the CSII than in the MDI group (8.1 +/- 0.9 vs. 8.4 +/- 1.3%; P < 0.005 after 3 years). Blood pressure and eGFR were similar during the study. AER [median (95% confidence interval)], similar at baseline [6.0 microg/min (9, 21) in the CSII group vs. 4.4 (8, 16) in the MDI group, NS] was significantly lower in the patients treated with CSII both at year 2 and at year 3 of follow-up [4.7 microg/min (6, 12) vs. 6.4 (13, 29), P < 0.002]. This difference was observed even when normo- and microalbuminuric patients were analysed separately. Nine patients progressed to microalbuminuria in the MDI group and only one in the CSII group. Nine patients regressed to normoalbuminuria in the CSII group, whereas only two regressed to normoalbuminuria in the MDI group.

CONCLUSIONS

Despite a small benefit in terms of improved glycaemic control, CSII therapy may be useful in decreasing the progressive increase in AER in Type 1 diabetic patients.

Severe hyponatremia due to hypopituitarism with adrenal insufficiency: a case report

OBJECTIVE

Adrenal insufficiency due to hypopituitarism can lead to severe hyponatremia with potentially fatal consequences. Prompt diagnosis and adequate hormonal replacement therapy are essential to block an otherwise unfavorable course and to re-establish a healthy life. Unfortunately, this condition is often misdiagnosed.

DESIGN

Case report.

SETTING

Intensive Care Unit of a teaching hospital.

PATIENT

A 76-yr-old man with refractory hypotension, acute myocardial infarction, and left ventricular dysfunction, secondary to severe chronic pan-hypopituitarism, associated with severe hyponatremia.

METHODS AND MAIN RESULTS

The patient underwent mechanical ventilation and continuous venous-venous hemodiafiltration, for severe respiratory and renal insufficiency. A hormonal replacement therapy with T4, hydrocortisone, and nandrolone was started and the patient was discharged to a rehabilitation facility after 31 days of hospitalization.

CONCLUSIONS

Hypopituitarism with secondary adrenal insufficiency is often misdiagnosed at an early stage and a high degree of suspicion is necessary for early diagnosis. Determination of plasma cortisol level in patients with hyponatremia not explained by other causes should always be obtained.

Blood pressure lowering for the prevention and treatment of diabetic kidney disease

The current pandemic of diabetes mellitus will inevitably be followed by an epidemic of chronic kidney disease. It is anticipated that 25-40% of patients with type 1 diabetes and 5-40% of patients with type 2 diabetes will ultimately develop diabetic kidney disease. The control of blood pressure represents a key component for the prevention and management of diabetic nephropathy. There is a strong epidemiological connection between hypertension in diabetes and adverse outcomes in diabetes. Hypertension is closely linked to insulin resistance as part of the 'metabolic syndrome'. Diabetic nephropathy may lead to hypertension through direct actions on renal sodium handling, vascular compliance and vasomotor function. Recent clinical trials also support the utility of blood pressure reduction in the prevention of diabetic kidney disease. In patients with normoalbuminuria, transition to microalbuminuria can be prevented by blood pressure reduction. This action appears to be significant regardless of whether patients have elevated blood pressure or not. The efficacy of ACE inhibition appears to be greater than that achieved by other agents with a similar degree of blood pressure reduction; although large observational studies suggest the risk of microalbuminuria may be reduced by blood pressure reduction, regardless of modality. In patients with established microalbuminuria, ACE inhibitors and angiotensin receptor antagonists (angiotensin receptor blockers [ARBs]) consistently reduce the risk of progression from microalbuminuria to macroalbuminuria, over and above their antihypertensive actions. The clinical utility of combining these strategies remains to be established. In patients with overt nephropathy, blood pressure reduction is associated with reduced urinary albumin excretion and, subsequently, a reduced risk of renal impairment or end stage renal disease. In addition to actions on systemic blood pressure, it is now clear that ACE inhibitors and ARBs also reduce proteinuria in patients with diabetes. This anti-proteinuric activity is distinct from other antihypertensive agents and diuretics. Although there is a clear physiological rationale for blockade of the renin angiotensin system, which is strongly supported by clinical studies, to achieve the optimal lowering of blood pressure, particularly in the setting of established diabetic renal disease, a number of different antihypertensive agents will always be needed. In the end, the choice of agents should be individualised to achieve the maximal tolerated reduction in blood pressure and albuminuria. Ultimately, no matter how it is achieved, so long as it is achieved, renal risk can be reduced by agents that lower blood pressure and albuminuria.

Lack of evidence of hypervolemia in children with insulin-dependent diabetes mellitus

Hypervolemia is considered to play a major role in the pathogenesis of diabetic vasculo- and nephropathy. The aim of our study is to determine whether children and adolescents with insulin-dependent diabetes mellitus (IDDM) experience alterations in blood volume (BV) before onset of apparent nephropathy. BV (calculated as the sum of measured plasma volume (PV) and red cell volume (RCV)) was determined in 31 children (9-16 yr) with a mean duration of IDDM of 6.6 yr and without microalbuminuria. Due to dependence of these values on age, size and sex, all data were normalised for body size parameters. While no statistical difference for BV normalised for lean body mass (LBM) (86.98+/-9.5 ml/kg) was found in diabetic children compared with our control population (84.91+/-12.08 ml/kg), a difference could be shown when normalised for body surface area (BSA) (diabetic children 2.37+/-0.3 L/m(2); control population 2.15+/-0.38 L/m(2), p=0.002). Increased BV is only present when normalising for BSA and not for the theoretical superior LBM-index. Because the study population exhibited a poor glycemic control (HbA1c 10.2+/-2.4 %), an influence of glucosuria-induced polyuria on BV cannot be excluded. Taking into account these limitations our data do not confirm the presence of hypervolemia before onset of diabetic nephropathy.

Transgenic overexpression of brain natriuretic peptide prevents the progression of diabetic nephropathy in mice

AIMS/HYPOTHESIS

Brain natriuretic peptide (BNP) is a potent vasorelaxing and natriuretic peptide that is secreted from the heart and has cardioprotective properties. We have previously generated hypotensive transgenic mice (BNP-Tg mice) that overproduce BNP in the liver, which is released into the circulation. Using this animal model, we successfully demonstrated the amelioration of renal injury after renal ablation and in proliferative glomerulonephritis. Glomerular hyperfiltration is an early haemodynamic derangement, representing one of the key mechanisms of the pathogenesis of diabetic nephropathy. Based on the suggested involvement of increased endogenous natriuretic peptides, the aim of this study was to investigate their role in the development and progression of diabetic nephropathy.

MATERIALS AND METHODS

We evaluated the progression of renal injury and fibrogenesis in BNP-Tg mice with diabetes induced by streptozotocin. We also investigated the effect of BNP on high glucose-induced signalling abnormalities in mesangial cells.

RESULTS

After induction of diabetes, control mice exhibited progressively increased urinary albumin excretion with impaired renal function, whereas these changes were significantly ameliorated in BNP-Tg mice. Notably, diabetic BNP-Tg mice revealed minimal mesangial fibrogenesis with virtually no glomerular hypertrophy. Glomerular upregulation of extracellular signal-regulated kinase, TGF-beta and extracellular matrix proteins was also significantly inhibited in diabetic BNP-Tg mice. In cultured mesangial cells, activation of the above cascade under high glucose was abrogated by the addition of BNP.

CONCLUSIONS/INTERPRETATION

Chronic excess of BNP prevents glomerular injury in the setting of diabetes, suggesting that renoprotective effects of natriuretic peptides may be therapeutically applicable in preventing the progression of diabetic nephropathy.

Elevated plasma concentrations of atrial and brain natriuretic peptide in type 1 diabetic subjects

BACKGROUND

The intravenous infusion of atrial (ANP) and brain (BNP) natriuretic peptides have been shown to increase urinary albumin excretion in type 1 diabetes.

AIMS

To measure plasma ANP and BNP concentrations in patients with type 1 diabetes and to examine the parameters associated with elevated plasma concentrations. Methods We measured plasma ANP and BNP concentrations, UAER, HbA1C systolic blood pressure, and left ventricular mass index. Plasma ANP and BNP were also measured in non-diabetic control subjects for comparison.

RESULTS

Using multivariate regression analysis plasma ANP correlated positively with HbA1C (1.9 + 0.47, p = 0.0002), UAER (0.37 + 0.05, p = 0.00001), SBP (1.26 + 0.5, p = 0.01) and LVMI (00.46 + 0.25, p = 0.07). BNP was positively related with LVMI (0.95 + 0.4, p = 0.02), and UAER (0.56 + 0.08, p = 0.001).

CONCLUSIONS

Plasma concentrations of ANP and BNP are elevated in some patients with type 1 diabetes. Plasma ANP concentrations are closely related to UAER and elevated plasma concentrations are associated with poor glycaemic control and systemic hypertension. Plasma BNP concentration is related to LVMI.

Glomerular hyperfiltration in type 1 diabetes mellitus results from primary changes in proximal tubular sodium handling without changes in volume expansion

BACKGROUND

Glomerular hyperfiltration plays a role in the pathophysiology of diabetic nephropathy. An increase in the glomerular filtration rate (GFR) could result from primary actions at the glomerular/vascular level or could be the consequence of a primary increase in proximal tubular sodium reabsorption resulting in systemic volume expansion. Recently it was hypothesized that an increase in sodium reabsorption may lead to glomerular hyperfiltration through the tubulo-glomerular feedback mechanism (tubular-hypothesis) without volume expansion.

DESIGN

We have studied 54 normoalbuminuric patients with type 1 diabetes. The GFR was measured by inulin clearance. Proximal and distal sodium reabsorption were calculated according to standard formulas using the free water clearance technique. Plasma volume, measured by the (125)I-albumin method, atrial natriuretic peptide (ANP) and the second messenger cyclic guanosine-3,5-monophosphate (c-GMP) were used as markers of extracellular volume expansion.

RESULTS

Glomerular hyperfiltration (GFR >or= 130 mL min(-1) 1.73 m(-2)) was present in 14 out of 55 patients with diabetes (25%). There were no differences in plasma volume between normo-(NF) and hyper-filtrating (HF) patients (2933 +/- 423 in NF vs. 3026 +/- 562 mL in HF, NS). Also plasma ANP and c-GMP levels were not significantly different between the groups. The fractional proximal reabsorption of sodium was significantly increased in HF [fPRNa(+) (%) 90.1 +/- 2.0 vs. 91.5 +/- 1.6, P = 0.02]. There were no differences in distal sodium reabsorption or distal sodium load (approximately macula densa concentration of NaCl) in both groups.

CONCLUSIONS

Our data suggest that the primary event in diabetic glomerular hyperfiltration is an increase in proximal tubular sodium reabsorption. They do not support the hypothesis that systemic volume expansion or ANP mediate glomerular hyperfiltration in patients with normoalbuminuric type 1 diabetes. As such, changes in tubular sodium handling most probably influence tubulo-glomerular feedback.

A case of insulin edema with inappropriate hyperaldosteronism

Edema of variable severity is an uncommon complication of insulin treatment. Increased sodium reabsorption, transient proteinuria and hypoalbuminemia are the most frequently reported laboratory disorders at the time of edema formation. This case report describes a 44-yr-old man with a 4-month history of anorexia, polyuria, polydipsia and weight loss of 25 kg who presented with diabetic ketoacidosis. On admission, there were no clinical or laboratory signs of volume depletion. Following insulin treatment he developed marked insulin edema and a cluster of abnormalities, including decreased sodium excretion, hypokalemia, hypouricemia, proteinuria, hypoalbuminemia and anemia. The diagnostic work-up showed the presence of high renin and aldosterone values despite the absence of evident hypovolemia and no evidence of gastrointestinal, cardiovascular, renal, thyroid, hepatic or other endocrine disorder. Complement values were normal; autonomic neuropathy and venoocclusive intraabdominal lesions were excluded and no other drugs except insulin were administered. Initiation of spironolactone was associated with prompt resolution of the edema and gradual correction of the laboratory abnormalities. Our findings show that hyperaldosteronism may occur in patients with insulin edema, even in the absence of volume depletion, contributing to the development of increased sodium reabsorption and of other laboratory disorders.

Effect of sodium intake on blood pressure and albuminuria in Type 2 diabetic patients: the role of insulin resistance

AIMS/HYPOTHESIS

This study was done to measure the effect of Na+ intake on blood pressure and albuminuria, in relation with insulin sensitivity and kidney haemodynamics, in Type 2 diabetic patients with and without microalbuminuria.

METHODS

Type 2 diabetic patients, 20 with microalbuminuria, 21 without, spent two consecutive 7-day periods, one on a high (250 mmol), the other on a low-Na+ (20 mmol) diet. Body weight, 24-h blood pressure and albuminuria were measured at the end of each period. At the end of high-Na+ diet insulin sensitivity (euglycaemic insulin clamp; 2 mU.kg(-1).min(-1)) and kidney haemodynamics were measured in nine patients from each group.

RESULTS

Switching from low to high-Na+ diet resulted in an increase in blood pressure (7.4+/-4.7 mmHg; p<0.001), body weight (1.9+/-0.4 kg; p<0.05) and albuminuria [from 80 (31-183) microg/min to 101 (27-965) microg/min; p<0.01) in patients with microalbuminuria. No changes occurred in patients without microalbuminuria. Patients with microalbuminuria also had greater intraglomerular pressure (44+/-1 mmHg vs 36+/-1; p<0.001), calculated from glomerular filtration rate, renal plasma flow, plasma protein concentration and the relationship between pressure and natriuresis. In these patients insulin sensitivity was lower (5.16+/-49 vs 7.36+/-0.63 mg.kg(-1).min(-1); p=0.007). Urinary albumin excretion (r=0.40; p=0.009) and insulin sensitivity (r=-0.59; p=0.01) were correlated with intraglomerular pressure.

CONCLUSION/INTERPRETATION

High salt intake increases blood pressure and albuminuria in Type 2 diabetic patients with microalbuminuria. These responses are associated with insulin resistance and increased glomerular pressure. Insulin resistance could contribute to greater salt sensitivity, increased glomerular pressure and albuminuria.

Low plasma aldosterone despite normal plasma renin activity in uncomplicated type 1 diabetes mellitus: effects of RAAS stimulation

BACKGROUND

Data on levels and responsiveness of PRA and aldosterone in type 1 diabetes mellitus are conflicting. Earlier studies were not standardized with respect to the type of diabetes mellitus, the presence of diabetic complications or sodium intake. Therefore, we studied plasma renin activity and plasma aldosterone in uncomplicated type 1 diabetes mellitus by evaluating the effects of endogenous (sodium restriction) and exogenous (angiotensin I infusion) stimulation.

DESIGN

Twenty-four type 1 diabetic patients and 24 matched healthy subjects were studied after 1 week of liberal sodium diet (200 mmol 24 h-1) and 1 week of low sodium diet (50 mmol 24 h-1). Angiotensin (Ang)I was infused at 4 and 8 ng kg-1 min-1 during both study days.

RESULTS

During liberal and low sodium intake, plasma aldosterone was lower in type 1 diabetic patients compared with healthy subjects both at 08:00 h (P < 0.05) and after a 2-h euglycaemic clamp (P < 0.05), despite similar PRA levels. The correlations between changes in PRA and changes in plasma aldosterone when shifting sodium intake were similar in both groups. During liberal sodium intake, the aldosterone levels after AngI infusion were lower in type 1 diabetic patients, whereas during low sodium they were not different.

CONCLUSIONS

Plasma aldosterone was deceased relative to PRA in uncomplicated type 1 diabetic patients, irrespective sodium intake. The responsiveness to sodium restriction was adequate and sodium restriction was able to overcome the decreased plasma aldosterone response to exogenous AngI, which was observed during liberal sodium in diabetic patients. The lower aldosterone is not secondary to diabetic complications and does not depend on the level of sodium intake.

Acute hyperglycaemia causes elevation in plasma atrial natriuretic peptide concentrations in Type 1 diabetes mellitus

AIMS

To examine the effect of acute hyperglycaemia on atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) concentrations in Type 1 diabetes.

METHODS

The study was two limb, randomized, and single-blind. Eight Type 1 diabetes subjects were clamped at euglycaemia by intravenous infusion of insulin. When euglycaemia was established, the insulin infusion rate was left unaltered for the remainder of the protocol, and an intravenous infusion of either 500 ml 0.9% saline or 500 ml 10% dextrose was administered over 1 h. Blood was collected for estimation of plasma glucose, ANP and BNP concentrations at 30 min intervals for 2 h from the start of the infusion period. One week later, each subject received the alternate infusion. Results are expressed as mean +/- standard deviation, and were analysed by ANOVA.

RESULTS

Baseline plasma glucose (P = 0.8), ANP (P = 0.8) and BNP (P = 0.8) concentrations were similar on the study days. Plasma glucose rose with dextrose (6.1 + 0.5-15.1 + 2.8 mmol/l, P = 0.9). Plasma ANP concentrations were unaltered by saline infusion (76.5 +/- 14.7-77.7 +/- 15.2 pg/ml, P = 0.9), but increased with dextrose infusion (79 +/- 14-134 +/- 17.1 pg/ml, P < 0.0001), and were higher with dextrose than saline infusion (P < 0.0001). Plasma concentrations of BNP were not significantly altered by infusion of either dextrose (5.1 +/- 3.9-9.3 +/- 5.4 pg/ml, P = 0.63) or saline (4.3 +/- 3.5-6 +/- 5.2 pg/ml, P = 0.84).

CONCLUSIONS

Plasma concentrations of ANP, but not BNP, rise in response to acute hyperglycaemia in Type 1 diabetes.

Atrial natriuretic peptide increases albuminuria in type I diabetic patients: evidence for blockade of tubular protein reabsorption

BACKGROUND

It has been suggested that atrial natriuretic peptide (ANP) contributes to the glomerular hyperfiltration of diabetes mellitus. Infusion of ANP increases the urinary excretion of albumin in patients with type I diabetes mellitus (IDDM). Although the increased albuminuria is attributed to a rise in glomerular pressure, alterations in tubular protein handling might be involved.

PATIENTS AND METHODS

We have studied the effects of ANP in nine microalbuminuric IDDM patients. After obtaining baseline parameters, ANP was infused over a 1-h period (bolus 0.05 microgram kg-1, infusion rate 0.01 microgram kg-1 min-1). Renal haemodynamics, sodium and water clearance and tubular protein handling were studied.

RESULTS

The glomerular filtration rate (GFR) increased from 116.4 +/- 8.9 to 128.3 +/- 8.8 mL min-1 1.73 m-2, whereas the effective renal plasma flow (ERPF) decreased from 534.3 +/- 44.3 to 484.9 +/- 33.3 mL min-1 1.73 m-2 (P < 0.05). As a result, the filtration fraction was significantly higher during infusion of ANP. ANP attenuated proximal tubular sodium reabsorption. Urinary albumin excretion rose from 87.57 +/- 21.03 to 291.40 +/- 67.86 micrograms min-1 (P < 0.01). Changes in the urinary excretion of beta 2-microglobulin and free kappa light chains were more marked, the excretion of beta 2-microglobulin increasing from 0.28 +/- 0.21 to 51.87 +/- 10.51 micrograms min-1 (P < 0.01), and of free kappa-light chains from 4.73 +/- 1.74 to 46.14 +/- 6.19 micrograms min-1 (P < 0.01).

CONCLUSIONS

The observed rise in albuminuria during infusion of ANP does not simply reflect a change in glomerular pressure, but might at least partly result from an attenuation of tubular protein reabsorption.

Effects of insulin and lipid emulsion on renal haemodynamics and renal sodium handling in IDDM patients

To evaluate the role of insulin and hypertriglyceridaemia in the regulation of renal haemodynamics and sodium handling in insulin-dependent diabetes mellitus (IDDM), 11 IDDM patients without microalbuminuria and 13 weight-, age-, protein intake- and sex-matched healthy control subjects were studied. Clearances of inulin (Cin), para-amino-hippuric acid (CPAH), sodium (CNa), and lithium (CLi) were measured in four 60-min clearance periods (periods I, II, III and IV) during isoinsulinaemia with lipid emulsion infusion (study 1), a hyperinsulinaemic isoglycaemic clamp with Intralipid infusion (study 2), and during time-controlled isoinsulinaemia (study 3). We found that Cin, CPAH and filtration fraction were comparable in IDDM and control subjects, whereas CNa was decreased in diabetic subjects (2.01 +/- 1.11 vs 3.03 +/- 1.32 ml/min; p < 0.05) due to elevations of proximal tubular fractional and absolute reabsorptions of sodium (p < 0.05). Insulin infusion did not affect Cin, increased CPAH (p < 0.05) and, consequently, lowered the filtration fraction (p < 0.01) in both groups. While acute hyperinsulinaemia resulted in increases in distal tubular fractional and absolute reabsorptions of sodium (p < 0.01) contributing to a fall in CNa (p < 0.01) in control subjects, in diabetic subjects the sodium-retaining effect of insulin was not significant. The lipid emulsion did not alter any of the estimated parameters. We conclude that IDDM without microalbuminuria is associated with a tendency to sodium retention which is not aggravated by insulin when compared to control subjects. Acutely induced hypertriglyceridaemia does not alter renal haemodynamics or renal sodium handling.

Salt sensitivity in hypertensive type-1 diabetes mellitus

As sodium retention has been proposed as a causal factor in the development of hypertension in diabetic patients, a high incidence of salt sensitivity has been suggested. To evaluate the influence of dietary sodium intake on blood pressure, casual and 24-h blood pressure was measured in 30 hypertensive type-1 diabetic patients aged 24-67 (mean 46) years while they were on habitual diet, after 6 days of low-sodium diet (50 mmol/day), and after 6 days of high-sodium diet (250 mmol/day). Nine patients (30%) who increased their 24-h mean blood pressure by more than 10% when going from low- to high-sodium intake were classified as salt sensitive; the others as salt resistant. The salt sensitive group had a significantly lower urinary excretion of dopamine at baseline, and a higher diuresis and a more pronounced decrease in 24-h blood pressure during salt depletion (all p < 0.01). Low-sodium diet reduced casual and 24-h blood pressure by 4% in the total study population compared with 9% in the salt sensitive group (p < 0.01). There was no difference in glomerular filtration rate, filtration fraction, proteinuria or urinary sodium excretion between the groups.

CONCLUSIONS

Sodium restriction more effectively reduces blood pressure in the salt sensitive minority of hypertensive type-1 diabetic patients irrespective of renal function. The incidence of salt sensitivity is not increased in hypertensive type-1 diabetic patients compared with essential hypertensive patients.

Effects of dietary sodium on blood pressure in IDDM patients with nephropathy

The objectives of the study were to assess the effects of moderate sodium restriction on blood pressure in insulin-dependent diabetic (IDDM) patients with nephropathy and high normal or mildly hypertensive blood pressure (primary objective), and to document possible associated changes of exchangeable body sodium, body volumes, components of the renin-angiotensin-aldosterone system, atrial natriuretic peptide, and catecholamines (secondary objective). Sixteen patients with untreated systolic blood pressure > or = 140 < 160 mmHg and/or diastolic blood pressure > or = 85 < 100 mmHg were included in a double-blind, randomized, placebo-controlled trial. After a 4-week run-in period on their usual diet and a 2-week dietary training period to reduce sodium intake to about 90 mmol/day, eight patients received 100 mmol/day sodium supplement (group 2) and eight patients a matching placebo (group 1) for 4 weeks while continuing on the reduced-sodium diet. Patients were examined at weekly intervals. Main response variables were mean values of supine and sitting systolic and diastolic blood pressure as measured in the clinic and by the patients at home. The differences in blood pressure between the beginning and the end of the blinded 4-week study period were calculated and the differences in changes between the two patient groups were regarded as the main outcome parameters. During the blinded 4-week study period, average urinary sodium excretion was 92 +/- 33 (mean +/- SD) mmol/day in group 1 and 199 +/- 52 mmol/day in group 2 (p = 0.0002). The differences in blood pressure changes between the two patient groups were 3.9(-1.2 to 9) mmHg [mean (95% confidence intervals)] for systolic home blood pressure, 0.9(-3.7 to 5.5) mmHg for diastolic home blood pressure, 4.9(-3.3 to 13.1) mmHg for clinic systolic blood pressure and 5.3(1 to 9.7 mmHg, p = 0.02) for clinic diastolic blood pressure. Combining all patients, there were relevant associations between changes of urinary sodium excretion and blood volume (Spearman correlation coefficient r = 0.57), blood pressure and angiotensin II (diastolic: r = -0.7; systolic: r = -0.48), and exchangeable body sodium and renin activity (r = -0.5). In conclusion, in this study of IDDM patients with nephropathy and high normal or mildly hypertensive blood pressure, a difference in sodium intake of about 100 mmol/day for a period of 4 weeks led to a slight reduction of clinic diastolic blood pressure. Studies including larger numbers of patients with various stages of nephropathy and hypertension are needed to definitely clarify the effects of sodium restriction in IDDM.

Effect of insulin on renal sodium handling and renal haemodynamics in insulin-dependent (type 1) diabetes mellitus patients

The effects of insulin on renal haemodynamics and renal sodium handling were studied in eight insulin-dependent (type 1) diabetic patients (aged 30 +/- 3 years). Seven healthy men (aged 38 +/- 4 years) served as controls. The type 1 diabetic patients were resistant to insulin-stimulated glucose disposal as estimated by a 45% lower metabolic (P < 0.01) clearance of glucose as compared with controls. However, type 1 diabetic patients were still sensitive to the distal tubular antinatriuretic effect of insulin, as indicated by an increase in distal sodium reabsorption (95.5 +/- 0.5% to 96.9% +/- 0.4%; P < 0.05) during insulin infusion compared with controls (95.5% +/- 0.6% to 97.4% +/- 0.3%; P < 0.05). In control subjects insulin infusion was associated with 9% increases (P < 0.05) in lithium clearance and in renal plasma flow, whereas no significant increases in lithium clearance and in renal plasma flow were observed in the type 1 diabetic patients. In both groups, the changes in renal plasma flow in response to insulin infusion were positively correlated with that in lithium clearance (r = 0.80 and r = 0.90, respectively; P < 0.05-0.01). In conclusion, the present result demonstrates an intact distal tubular sodium retaining effect in conjunction with a blunted decrease in proximal tubular sodium reabsorption following insulin infusion, which could be the result of an impaired renal vasodilation in type 1 diabetes mellitus.

Increased prevalence of salt sensitivity of blood pressure in IDDM with and without microalbuminuria

In insulin-dependent diabetes mellitus (IDDM) elevated exchangeable sodium (Na) levels are found even in the absence of hypertension, but it is not known whether this is associated with increased sensitivity of blood pressure to sodium level. To clarify this issue we compared 30 patients with IDDM (19 without and 11 with microalbuminuria, i.e. more than 30 mg albumin/day) and 30 control subjects matched for age, gender and body mass index. The subjects were studied on the 4th day of a low-salt diet (20 mmol/day) under in-patient conditions and were subsequently changed to the same diet with a high-salt supplement, yielding a total daily intake of 220 mmol Na/day. Circadian blood pressure, plasma renin activity (PRA), plasma atrial natriuretic factor (p-ANF), plasma cyclic guanosine 5'-phosphate (p-cGMP) and urinary albumin were measured. The proportion of salt-sensitive subjects, i.e. showing increment of mean arterial pressure > or = 3 mmHg on high-salt diet, was 43% in diabetic patients (50% of diabetic patients with and 37% without microalbuminuria) and 17% in control subjects (p < 0.05). Lying and standing PRA levels on low- or high-salt diet were significantly lower in diabetic patients than in control subjects. Salt-sensitive diabetic patients had significantly higher lying ANF on high-salt (38.7 +/- 4.2 pmol/l vs 20.1 +/- 2.3 pmol/l, p < 0.005) than on low-salt diet. The results suggest that (i) the prevalence of sodium sensitivity is high in IDDM (ii) sodium sensitivity is found even in the absence of nephropathy as indicated by albuminuria.

Serum insulin levels, 24-hour blood pressure profile, and left ventricular mass in nonobese hypertensive patients

In essential hypertensive patients, considered to be insulin-resistant, a blunted decline in nocturnal blood pressure is associated with increased adrenergic tone and left ventricular mass. Since insulin stimulates the sympathetic system, we tested whether insulin resistance and insulinemia influence left ventricular mass and the 24-hour blood pressure profile. We studied 29 nonobese hypertensive patients with office diastolic pressure between 95 and 110 mm Hg and normal oral glucose tolerance test after a 4-month washout period. They were then assigned to M-mode echocardiographic evaluation and 24-hour ambulatory blood pressure monitoring. The glucose and insulin responses to a 75-g oral glucose load were compared with those obtained in 16 weight-matched normotensive control subjects. During the oral glucose tolerance test the hypertensive patients compared with control subjects presented higher levels of glucose at 60 minutes (138.7 +/- 30.3 versus 108.7 +/- 35.7 mg/dL; P < .05) and 90 minutes (114.0 +/- 23.8 versus 94.8 +/- 31.1 mg/dL; P < .05) and insulin at 60 minutes (287.1 +/- 259.4 versus 142.1 +/- 83.9 pmol/L; P < .05). However, peak insulin levels after glucose load did not correlate with ambulatory blood pressure values or left ventricular mass index. Left ventricular mass index showed significant correlation with mean sleeping systolic pressure (rs = 56, P < .05) and diurnal systolic pressure (rs = .37, P < .05) but not with mean diurnal or sleeping diastolic pressures. In conclusion, our results indicate that in nonobese hypertensive patients, insulin resistance does not have any influence on the 24-hour blood pressure profile or on left ventricular mass index.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of administration of insulin on streptozotocin-induced diabetic hypertension in rat

We have reported that streptozotocin-induced insulin-dependent diabetes mellitus in 25% reduced renal mass rats is associated with low-renin, volume-expanded hypertension and that the development of the hypertension can be prevented with insulin. In this study we examined the effect of insulin after the animals had developed sustained hypertension. Normotensive 25% reduced renal mass rats were treated with streptozotocin and, as expected, developed insulin-dependent diabetes mellitus and hypertension. After 4 weeks of sustained hypertension, neutral protamine Hagedorn insulin (6 to 8 IU/d) was administered subcutaneously for 4 weeks. As expected, insulin treatment decreased plasma glucose and increased body weight gain relative to untreated diabetic rats. On the other hand, insulin treatment did not reverse the hypertension and albuminuria. It also did not normalize extracellular fluid volume and plasma renin activity. Furthermore, insulin treatment did not reverse the increase in plasma Na+,K(+)-ATPase inhibitory activity (determined by both radioimmunoassay and bioassay) and the inhibition of myocardial microsomal Na+,K(+)-ATPase activity observed in the untreated diabetic hypertensive rats. 5'-Nucleotidase, a membrane marker, was not different between insulin-treated and untreated diabetic rats. These results show that insulin, given as here described, does not reverse the insulin-dependent diabetes mellitus hypertension in 25% reduced renal mass rats once it is established, perhaps because it does not reverse the albuminuria, volume expansion, increase in endogenous digitalis-like substance, and inhibition of cardiovascular muscle cell Na+,K(+)-ATPase activity.

Circadian blood pressure levels in normotensive normoalbuminuric type 1 diabetic patients

Increase in blood pressure and its circadian alterations in Type 1 diabetes are usually associated with diabetic nephropathy. To evaluate if diabetes itself could be responsible for the observed increase in blood pressure levels, we studied a group of 17 normotensive, normoalbuminuric Type 1 diabetic patients with a disease duration more than 15 years, with no clinical evidence of autonomic neuropathy or ischaemic heart disease, and without any known determinant of hypertension, and a control group of 17 normal subjects, normotensive, each matched for sex, age, BMI, albumin excretion rate, and clinical blood pressure to a diabetic subject. In both groups an ambulatory blood pressure monitoring was performed through an oscillometric recorder. The mean systolic and diastolic ambulatory blood pressure values were significantly higher in diabetic patients (p < 0.001) in the 24-h analysis and during waking and sleeping periods. The night/day ratio of systolic and diastolic blood pressure were not significantly different in patients and controls, as well as heart rate values and heart rate variability. We conclude that mechanism(s) inherent to the diabetic condition other than diabetic nephropathy or autonomic neuropathy could be responsible for blood pressure evaluation in normotensive Type 1 diabetes with normoalbuminuria.

Sodium retention and insulin treatment in insulin-dependent diabetes mellitus

The hypothesis that total body exchangeable sodium (ENa) is elevated in type 1 (insulin-dependent) diabetic patients with short-duration diabetes and no signs of microangiopathy was tested. Also tested was whether peripheral hyperinsulinaemia, in terms of the amounts of insulin injected subcutaneously, contributes to the increased ENa. Three studies were performed. Study 1 was a cross-sectional study comprising 28 type 1 diabetic men (aged 18-35 years) with short-duration diabetes (< 5 years) and no signs of diabetic complications, and 22 control subjects. Study 2 was a prospective study of 17 newly diagnosed diabetic patients (aged 20-35 years, median 27 years) who were studied on two occasions on different insulin doses. Study 3 was a 12-month prospective intervention study of 21 type 1 diabetic patients with incipient nephropathy, who had been randomized either to receive continuous subcutaneous insulin infusion for improvement of glycaemic control or to remain on conventional insulin treatment. In study 1, ENa was higher in short-duration type 1 diabetic men than in controls (3003 +/- 325 vs 2849 +/- 207 mEq/1.73 m2, P < 0.05) and was correlated significantly with the insulin dose (r = 0.38, P < 0.05). In study 2, of the newly diagnosed diabetic patients, 11 received a reduced insulin dose and 6 an increased dose as compared with the initial study. ENa was reduced in all patients receiving less insulin (P < 0.001) and remained unchanged in patients receiving more insulin.(ABSTRACT TRUNCATED AT 250 WORDS)

Salt-regulating hormones in young normotensive obese subjects. Effects of saline load

To investigate whether the response of salt-regulating hormones to volume expansion is impaired in obese subjects, we assessed the effects of saline load (0.25 mL/kg.min.120 min) in 9 young, healthy, normotensive obese subjects (body mass index, > 30 kg/m2) and in 10 lean control subjects (body mass index, < 25 kg/m2) matched for age, gender, height, and mean blood pressure. Hematocrit, plasma renin activity (PRA), plasma aldosterone (PA), atrial natriuretic factor (ANF), and urinary sodium excretion (UNaV) were evaluated. Saline load increased ANF levels significantly (P < .001) in lean subjects at both 60 and 120 minutes, whereas they decreased in obese subjects. Such decreases became significant (P < .01) at 120 minutes. Suppression of PRA and PA by saline load were more marked in lean than obese subjects. Hematocrit decreased in both groups, and UNaV increased more in lean than obese subjects during saline load. Comparisons of percent changes in ANF, PRA, and PA after saline load showed that the responses of lean and obese subjects were significantly different (P < .001 for ANF at both 60 and 120 minutes; P < .05 for PRA and PA at both 60 and 120 minutes). In conclusion, the lack of ANF response and the reduced suppression of PRA and PA to saline load indicate a dysfunction of these systems in obese subjects. This alteration may be involved in the higher susceptibility of obese subjects to developing hypertension.

Increased red cell sodium lithium countertransport activity, total exchangeable sodium, and hormonal control of sodium balance in normoalbuminuric type 1 diabetes

The relationship between erythrocyte sodium lithium countertransport activity (SLC), total exchangeable sodium (NaE), and hormonal control of renal function was examined in 40 normotensive, normoalbuminuric, non-neuropathic Type 1 diabetic subjects, of whom 8 had elevated SLC (> 0.40 mmol Li h-1l-1 rbc). Eleven health controls with normal SLC, who were of comparable age, body mass, and blood pressure were also studied. By contrast with healthy controls, SLC in Type 1 diabetes was not associated with plasma renin activity (PRA), aldosterone, systolic blood pressure or lean body mass. SLC was also unrelated to atrial natriuretic peptide (ANP) (Type 1 diabetes only) and NaE. NaE was not correlated with any other variables. The relationships between PRA and aldosterone in healthy controls were retained in Type 1 diabetes (R2 0.37 supine, p = 0.00001, and 0.27 ambulant, p = 0.0005), as were respective direct and inverse relations between vasopressin and ANP and both PRA (rs 0.54 to 0.57, rs -0.43 to -0.53), and aldosterone (rs 0.78 to 0.80, rs -0.71 to -0.80). Fasting free serum insulin and vasopressin were both inversely related to ANP (rs -0.91 and -0.71, respectively). In the absence of autonomic dysfunction, hypertension or early nephropathy in Type 1 diabetes, increased SLC or exchangeable sodium were unrelated to each other or with hormonal control of sodium balance, but the homeostatic factors controlling hormonal interaction appear to be maintained. The interaction between insulin and hormonal control of sodium and water balance may be modified by circulating free insulin concentrations.

Hypertension and diabetes

Co-presentation of hypertension and diabetes leads to a significantly greater increase of cardiovascular mortality than each disease separately. Hypertension appears to be not only a complication of diabetes but apparently also shares a common pathogenetic mechanism, particularly in non-insulin dependent diabetes. Recent data suggest alterations in the nocturnal decline of blood pressure in diabetics, which together with microalbuminuria, may prove to be a predictor of nephropathy and hypertension. When hypertension occurs in diabetics, it requires a vigorous therapeutic approach. Nevertheless, the presence of diabetes modifies the requirement for first line therapy, particularly with respect to potential alterations of metabolic homeostasis in order to effectively prevent cardiovascular complications.

Insulin resistance is an important determinant of left ventricular mass in the obese

BACKGROUND

Obesity in adults is associated with increased left ventricular (LV) mass. The mechanism for this is unclear, however. We tested the hypothesis that insulin resistance is an important independent contributing factor to LV mass in the healthy obese population.

METHODS AND RESULTS

The study population consisted of 40 normotensive, nondiabetic, otherwise healthy obese subjects with body mass index (BMI) > 25 kg/m2. LV mass was echocardiographically determined according to the Penn convention, using the formula of Devereux and Reichek. Insulin resistance was assessed using indices derived from Intravenous Glucose Tolerance Test (IVGTT): insulin level at baseline, insulin level at 90 minutes of IVGTT (insulin-90), insulin integration over 90 minutes of IVGTT, and rate of glucose disposal (k value). Insulin-90 (r = .61, P = .0001), k value (r = .55, P = .003), insulin integration over 90 minutes (r = .46, P = .003), basal insulin (r = .44, P = .005), and BMI (r = .59, P = .0001) were all strongly correlated with LV mass by univariate analysis. No significant correlation was found with blood pressure or age. In multivariate regression analysis, only insulin-90 and k value correlated significantly with LV mass (P = .03, P = .02, respectively), accounting for 50% of the variance of LV mass, whereas the association with BMI became insignificant (P = .2).

CONCLUSIONS

LV mass in the normotensive nondiabetic obese population is strongly associated with, and may be mediated by, the degree of insulin resistance and its associated hyperinsulinemia, independent of BMI and blood pressure.