The antinatriuretic effect of insulin: an unappreciated mechanism for hypertension associated with insulin resistance?

Uromodulin biology

Uromodulin is a kidney-specific glycoprotein which is exclusively produced by the epithelial cells lining the thick ascending limb and early distal convoluted tubule. It is currently recognized as a multifaceted player in kidney physiology and disease, with discrete roles for intracellular, urinary, interstitial and serum uromodulin. Among these, uromodulin modulates renal sodium handling through the regulation of tubular sodium transporters that reabsorb sodium and are targeted by diuretics, such as the loop diuretic-sensitive Na+-K+-2Cl- cotransporter type 2 (NKCC2) and the thiazide-sensitive Na+/Cl- cotransporter (NCC). Given these roles, the contribution of uromodulin to sodium-sensitive hypertension has been proposed. However, recent studies in humans suggest a more complex interaction between dietary sodium intake, uromodulin and blood pressure. This review presents an updated overview of the uromodulin's biology and its various roles, and focuses on the interaction between uromodulin and sodium-sensitive hypertension.

Obesity and hypertension: Obesity medicine association (OMA) clinical practice statement (CPS) 2023

Background

This Obesity Medicine Association (OMA) Clinical Practice Statement (CPS) provides an overview of the mechanisms and treatment of obesity and hypertension.

Methods

The scientific support for this CPS is based upon published citations, clinical perspectives of OMA authors, and peer review by the Obesity Medicine Association leadership.

Results

Mechanisms contributing to obesity-related hypertension include unhealthful nutrition, physical inactivity, insulin resistance, increased sympathetic nervous system activity, renal dysfunction, vascular dysfunction, heart dysfunction, increased pancreatic insulin secretion, sleep apnea, and psychosocial stress. Adiposopathic factors that may contribute to hypertension include increased release of free fatty acids, increased leptin, decreased adiponectin, increased renin-angiotensin-aldosterone system activation, increased 11 beta-hydroxysteroid dehydrogenase type 1, reduced nitric oxide activity, and increased inflammation.

Conclusions

Increase in body fat is the most common cause of hypertension. Among patients with obesity and hypertension, weight reduction via healthful nutrition, physical activity, behavior modification, bariatric surgery, and anti-obesity medications mostly decrease blood pressure, with the greatest degree of weight reduction generally correlated with the greatest degree of blood pressure reduction.

Lab on a Chip Device for Diagnostic Evaluation and Management in Chronic Renal Disease: A Change Promoting Approach in the Patients' Follow Up

Lab-on-a-chip (LOC) systems are miniaturized devices aimed to perform one or several analyses, normally carried out in a laboratory setting, on a single chip. LOC systems have a wide application range, including diagnosis and clinical biochemistry. In a clinical setting, LOC systems can be associated with the Point-of-Care Testing (POCT) definition. POCT circumvents several steps in central laboratory testing, including specimen transportation and processing, resulting in a faster turnaround time. Provider access to rapid test results allows for prompt medical decision making, which can lead to improved patient outcomes, operational efficiencies, patient satisfaction, and even cost savings. These features are particularly attractive for healthcare settings dealing with complicated patients, such as those affected by chronic kidney disease (CKD). CKD is a pathological condition characterized by progressive and irreversible structural or functional kidney impairment lasting for more than three months. The disease displays an unavoidable tendency to progress to End Stage Renal Disease (ESRD), thus requiring renal replacement therapy, usually dialysis, and transplant. Cardiovascular disease (CVD) is the major cause of death in CKD, with a cardiovascular risk ten times higher in these patients than the rate observed in healthy subjects. The gradual decline of the kidney leads to the accumulation of uremic solutes, with negative effect on organs, especially on the cardiovascular system. The possibility to monitor CKD patients by using non-invasive and low-cost approaches could give advantages both to the patient outcome and sanitary costs. Despite their numerous advantages, POCT application in CKD management is not very common, even if a number of devices aimed at monitoring the CKD have been demonstrated worldwide at the lab scale by basic studies (low Technology Readiness Level, TRL). The reasons are related to both technological and clinical aspects. In this review, the main technologies for the design of LOCs are reported, as well as the available POCT devices for CKD monitoring, with a special focus on the most recent reliable applications in this field. Moreover, the current challenges in design and applications of LOCs in the clinical setting are briefly discussed.

Insulin Resistance and High Blood Pressure: Mechanistic Insight on the Role of the Kidney

The metabolic effects of insulin predominate in skeletal muscle, fat, and liver where the hormone binds to its receptor, thereby priming a series of cell-specific and biochemically diverse intracellular mechanisms. In the presence of a good secretory reserve in the pancreatic islets, a decrease in insulin sensitivity in the metabolic target tissues leads to compensatory hyperinsulinemia. A large body of evidence obtained in clinical and experimental studies indicates that insulin resistance and the related hyperinsulinemia are causally involved in some forms of arterial hypertension. Much of this involvement can be ascribed to the impact of insulin on renal sodium transport, although additional mechanisms might be involved. Solid evidence indicates that insulin causes sodium and water retention, and both endogenous and exogenous hyperinsulinemia have been correlated to increased blood pressure. Although important information was gathered on the cellular mechanisms that are triggered by insulin in metabolic tissues and on their abnormalities, knowledge of the insulin-related mechanisms possibly involved in blood pressure regulation is limited. In this review, we summarize the current understanding of the cellular mechanisms that are involved in the pro-hypertensive actions of insulin, focusing on the contribution of insulin to the renal regulation of sodium balance and body fluids.

Glycemia Reduction in Type 2 Diabetes - Microvascular and Cardiovascular Outcomes

BACKGROUND

Data are lacking on the comparative effectiveness of commonly used glucose-lowering medications, when added to metformin, with respect to microvascular and cardiovascular disease outcomes in persons with type 2 diabetes.

METHODS

We assessed the comparative effectiveness of four commonly used glucose-lowering medications, added to metformin, in achieving and maintaining a glycated hemoglobin level of less than 7.0% in participants with type 2 diabetes. The randomly assigned therapies were insulin glargine U-100 (hereafter, glargine), glimepiride, liraglutide, and sitagliptin. Prespecified secondary outcomes with respect to microvascular and cardiovascular disease included hypertension and dyslipidemia, confirmed moderately or severely increased albuminuria or an estimated glomerular filtration rate of less than 60 ml per minute per 1.73 m2 of body-surface area, diabetic peripheral neuropathy assessed with the Michigan Neuropathy Screening Instrument, cardiovascular events (major adverse cardiovascular events [MACE], hospitalization for heart failure, or an aggregate outcome of any cardiovascular event), and death. Hazard ratios are presented with 95% confidence limits that are not adjusted for multiple comparisons.

RESULTS

During a mean 5.0 years of follow-up in 5047 participants, there were no material differences among the interventions with respect to the development of hypertension or dyslipidemia or with respect to microvascular outcomes; the mean overall rate (i.e., events per 100 participant-years) of moderately increased albuminuria levels was 2.6, of severely increased albuminuria levels 1.1, of renal impairment 2.9, and of diabetic peripheral neuropathy 16.7. The treatment groups did not differ with respect to MACE (overall rate, 1.0), hospitalization for heart failure (0.4), death from cardiovascular causes (0.3), or all deaths (0.6). There were small differences with respect to rates of any cardiovascular disease, with 1.9, 1.9, 1.4, and 2.0 in the glargine, glimepiride, liraglutide, and sitagliptin groups, respectively. When one treatment was compared with the combined results of the other three treatments, the hazard ratios for any cardiovascular disease were 1.1 (95% confidence interval [CI], 0.9 to 1.3) in the glargine group, 1.1 (95% CI, 0.9 to 1.4) in the glimepiride group, 0.7 (95% CI, 0.6 to 0.9) in the liraglutide group, and 1.2 (95% CI, 1.0 to 1.5) in the sitagliptin group.

CONCLUSIONS

In participants with type 2 diabetes, the incidences of microvascular complications and death were not materially different among the four treatment groups. The findings indicated possible differences among the groups in the incidence of any cardiovascular disease. (Funded by the National Institute of Diabetes and Digestive and Kidney Diseases and others; GRADE ClinicalTrials.gov number, NCT01794143.).

SGLT-2 inhibitors and nephroprotection: current evidence and future perspectives

Chronic kidney disease (CKD) is a major public health issue and an independent risk factor for cardiovascular and all-cause mortality. Diabetic kidney disease develops in 30-50% of diabetic patients and it is the leading cause of end-stage renal disease in the Western world. Strict blood pressure control and renin-angiotensin system (RAS) blocker use are the cornerstones of CKD treatment; however, their application in everyday clinical practice is not always ideal and in many patients CKD progression still occurs. Accumulated evidence in the past few years clearly suggests that sodium-glucose co-transporter-2 (SGLT-2) inhibitors present potent nephroprotective properties. In clinical trials in patients with type 2 diabetes mellitus, these agents were shown to reduce albuminuria and proteinuria by 30-50% and the incidence of composite hard renal outcomes by 40-50%. Furthermore, their mechanism of action appears rather solid, as they interfere with the major mechanism of proteinuric CKD progression, i.e., glomerular hypertension and hyperfiltration. The present review summarizes the current evidence from human trials on the effects of SGLT-2 inhibitors on nephroprotection and discusses their position in everyday clinical practice.

Double diabetes: A distinct high-risk group?

The term double diabetes (DD) has been used to refer to individuals with type 1 diabetes (T1D) who are overweight, have a family history of type 2 diabetes and/or clinical features of insulin resistance. Several pieces of evidence indicate that individuals who display features of DD are at higher risk of developing future diabetes complications, independently of average glucose control, measured as glycated haemoglobin (HbA1c) concentration. Given the increased prevalence of individuals with features of DD, pragmatic criteria are urgently required to identify and stratify this group, which will help with subsequent implementation of more effective personalized interventions. In this review, we discuss the potential criteria for the clinical identification of individuals with DD, highlighting the strengths and weaknesses of each definition. We also cover potential mechanisms of DD and how these contribute to increased risk of diabetes complications. Special emphasis is placed on the role of estimated glucose disposal rate (eGDR) in the diagnosis of DD, which can be easily incorporated into clinical practice and is predictive of adverse clinical outcome. In addition to the identification of individuals with DD, eGDR has potential utility in monitoring response to different interventions. T1D is a more heterogeneous condition than initially envisaged, and those with features of DD represent a subgroup at higher risk of complications. Pragmatic criteria for the diagnosis of individuals with DD will help with risk stratification, allowing a more personalized and targeted management strategy to improve outcome and quality of life in this population.

Postprandial effects on electrolyte homeostasis in the kidney

Insulin is known to be an important regulator of a number of different channels and transporters in the kidney, but its role in the kidney to prevent Na⁺ and volume loss during the osmotic load after a meal has only recently been validated. With increasing numbers of people suffering from diabetes and hypertension, furthering our understanding of insulin signaling and renal Na⁺ handling in both normal and diseased states is essential for improving patient treatments and outcomes. The present review is focused on postprandial effects on Na⁺ reabsorption in the kidney and the role of the epithelial Na⁺ channels as an important channel contributing to insulin-mediated Na⁺ reclamation.

Dietary Approaches to Stop Hypertension (DASH): potential mechanisms of action against risk factors of the metabolic syndrome

The metabolic syndrome is a cluster of disorders dominated by abdominal obesity, hypertriacylglycerolaemia, low HDL-cholesterol, high blood pressure and high fasting glucose. Diet modification is a safe and effective way to treat the metabolic syndrome. Dietary Approaches to Stop Hypertension (DASH) is a dietary pattern rich in fruits, vegetables and low-fat dairy products, and low in meats and sweets. DASH provides good amounts of fibre, K, Ca and Mg, and limited quantities of total fat, saturated fat, cholesterol and Na. Although DASH was initially designed for the prevention or control of hypertension, using a DASH diet has other metabolic benefits. In the present review, the effect of each dietary component of DASH on the risk factors of the metabolic syndrome is discussed. Due to limited fat and high fibre and Ca content, individuals on the DASH diet are less prone to overweight and obesity and possess lower concentrations of total and LDL-cholesterol although changes in TAG and HDL-cholesterol have been less significant and available evidence in this regard is still inconclusive. Moreover, high amounts of fruit and vegetables in DASH provide great quantities of K, Mg and fibre, all of which have been shown to reduce blood pressure. K, Mg, fibre and antioxidants have also been effective in correcting glucose and insulin abnormalities. Evidence is provided from cross-sectional investigations, cohort studies and randomised controlled trials, and, where available, from published meta-analyses. Mechanisms are described according to human studies and, in the case of a lack of evidence, from animal and cell culture investigations.

The effect of SGLT-2 inhibitors on blood pressure: a pleiotropic action favoring cardio- and nephroprotection

Strict blood pressure (BP) control in patients with diabetes is associated with reductions in cardiovascular and renal risk. SGLT-2 inhibitors act in the proximal tubule to reduce glucose reabsorption. They also have mild natriuretic and diuretic effects, combining properties of proximal tubule diuretics and osmotic diuretics, which are expected to reduce BP. Several lines of evidence suggests that SGLT-2 inhibitors produce mild but meaningful reductions in BP and also decrease the incidence of renal outcomes, cardiovascular events and mortality. Thus, recent guidelines for type 2 diabetes suggest that among oral agents to use together with metformin, SGLT-2 inhibitors should be preferred in patients at increased cardiovascular risk, kidney disease or heart failure. This review summarizes current literature on the effect of SGLT-2 inhibitors on BP, and its potential relationships with cardio- and nephroprotection.

Favorable Effects of a Ketogenic Diet on Physical Function, Perceived Energy, and Food Cravings in Women with Ovarian or Endometrial Cancer: A Randomized, Controlled Trial

Ketogenic diets (KDs) are gaining attention as a potential adjuvant therapy for cancer, but data are limited for KDs’ effects on quality of life. We hypothesized that the KD would (1) improve mental and physical function, including energy levels, (2) reduce hunger, and (3) diminish sweet and starchy food cravings in women with ovarian or endometrial cancer. Participants were randomized to a KD (70:25:5 energy from fat, protein, and carbohydrate) or the American Cancer Society diet (ACS: high-fiber, lower-fat). Questionnaires were administered at baseline and after 12 weeks on the assigned diet to assess changes in mental and physical health, perceived energy, appetite, and food cravings. We assessed both between-group differences and within-group changes using ANCOVA and paired t-tests, respectively. After 12 weeks, there was a significant between-group difference in adjusted physical function scores (p < 0.05), and KD participants not receiving chemotherapy reported a significant within-group reduction in fatigue (p < 0.05). There were no significant between-group differences in mental function, hunger, or appetite. There was a significant between-group difference in adjusted cravings for starchy foods and fast food fats at 12 weeks (p < 0.05 for both), with the KD group demonstrating less frequent cravings than the ACS. In conclusion, in women with ovarian or endometrial cancer, a KD does not negatively affect quality of life and in fact may improve physical function, increase energy, and diminish specific food cravings. This trial was registered at ClinicalTrials.gov as NCT03171506.

High glucose stimulates expression of aldosterone synthase (CYP11B2) and secretion of aldosterone in human adrenal cells

Aldosterone synthase is the key rate‐limiting enzyme in adrenal aldosterone production, and induction of its gene (CYP11B2) results in the progression of hypertension. As hypertension is a frequent complication among patients with diabetes, we set out to elucidate the link between diabetes mellitus and hypertension. We examined the effects of high glucose on CYP11B2 expression and aldosterone production using human adrenal H295R cells and a stable H295R cell line expressing a CYP11B2 5′‐flanking region/luciferase cDNA chimeric construct. d‐glucose (d‐glu), but not its enantiomer l‐glucose, dose dependently induced CYP11B2 transcription and mRNA expression. A high concentration (450 mg·dL⁻¹) of d‐glu time dependently induced CYP11B2 transcription and mRNA expression. Moreover, high glucose stimulated secretion of aldosterone into the media. Transient transfection studies using deletion mutants/nerve growth factor‐induced clone B (NGFIB) response element 1 (NBRE‐1) point mutant of CYP11B2 5′‐flanking region revealed that the NBRE‐1 element, known to be activated by transcription factors NGFIB and NURR1, was responsible for the high glucose‐mediated effect. High glucose also induced the mRNA expression of these transcription factors, especially that of NURR1, but NURR1 knockdown using its siRNA did not affect high glucose‐induced CYP11B2 mRNA expression. Taken together, it is speculated that high glucose may induce CYP11B2 transcription via the NBRE‐1 element in its 5′‐flanking region, resulting in the increase in aldosterone production although high glucose‐induced NURR1 is not directly involved in the effect. Additionally, glucose metabolism and calcium channels were found to be involved in the high glucose effect. Our observations suggest one possible explanation for the high incidence of hypertension in patients with diabetes.

Paroxysmal Hypertension Induced by an Insulinoma

Insulinoma is a rare, usually benign, pancreatic neuroendocrine tumor. The clinical features of an insulinoma are fasting hypoglycemia with neuroglycopenic symptoms including confusion and unusual behavior, while hypertension is usually not associated with the disease. We herein report a patient with insulinoma who manifested paroxysmal hypertension and neuroglycopenic symptoms. The possible etiology of hypertension induced by an insulinoma is catecholamine release in response to hypoglycemia, which may cause acute hypertension through activation of the sympatho-adrenal system. This case implies that sustained hyperinsulinemia due to insulinoma can be functionally linked to the induction of paroxysmal hypertension.

The effects of physical therapeutic agents on serum levels of stress hormones in patients with osteoarthritis

To investigate the effects of physical agents on the levels of stress hormones in patients with osteoarthritis (OA).Transcutaneous electrical nerve stimulation, hot packs, and therapeutic ultrasound were applied to the lumbar region and knees of patients with OA. Blood samples were taken for the measurement of the serum levels of glucose, insulin (INS), growth hormone (GH), prolactin (PRL), cortisol (COR), and plasma adrenocorticotropic hormone (ACTH) immediately before and after the 1st session, to investigate the acute effects of those physical agents on the endocrine system. The hormone levels were also measured every 5 sessions in a total of 10 sessions. The treatment response was also evaluated by using the visual analogue scale (VAS), Roland Morris Disability Questionnaire (RMDQ), and Western Ontario and McMaster Universities Arthritis Index (WOMAC) throughout the therapy period.After the 1st session, there was a decrease in INS levels and a mild decrease in PRL levels (P = 0.001 and P < 0.05, respectively). Throughout the 10-session therapy period, the INS levels increased, whereas the ACTH and COR levels decreased (P < 0.05 for all). The VAS-spine, RMDQ, VAS-knee, and WOMAC scores decreased (P = 0.001 for VAS-spine and P < 0.001 for all others). A positive correlation was detected between the changes in serum COR and WOMAC-pain score (P < 0.05).Although the combination therapy caused changes in INS level accompanied with steady glucose levels, the application of physical agents did not adversely affect the hormone levels. The decrease in ACTH and COR levels may be attributed to the analgesic effect of agents and may be an indicator of patient comfort through a central action.

Obesity-related glomerulopathy: clinical and pathologic characteristics and pathogenesis

The prevalence of obesity-related glomerulopathy is increasing in parallel with the worldwide obesity epidemic. Glomerular hypertrophy and adaptive focal segmental glomerulosclerosis define the condition pathologically. The glomerulus enlarges in response to obesity-induced increases in glomerular filtration rate, renal plasma flow, filtration fraction and tubular sodium reabsorption. Normal insulin/phosphatidylinositol 3-kinase/Akt and mTOR signalling are critical for podocyte hypertrophy and adaptation. Adipokines and ectopic lipid accumulation in the kidney promote insulin resistance of podocytes and maladaptive responses to cope with the mechanical forces of renal hyperfiltration. Although most patients have stable or slowly progressive proteinuria, up to one-third develop progressive renal failure and end-stage renal disease. Renin-angiotensin-aldosterone blockade is effective in the short-term but weight loss by hypocaloric diet or bariatric surgery has induced more consistent and dramatic antiproteinuric effects and reversal of hyperfiltration. Altered fatty acid and cholesterol metabolism are increasingly recognized as key mediators of renal lipid accumulation, inflammation, oxidative stress and fibrosis. Newer therapies directed to lipid metabolism, including SREBP antagonists, PPARα agonists, FXR and TGR5 agonists, and LXR agonists, hold therapeutic promise.

Link between insulin resistance and hypertension: What is the evidence from evolutionary biology?

Insulin resistance and hypertension are considered as prototypical "diseases of civilization" that are manifested in the modern environment as plentiful food and sedentary life. The human propensity for insulin resistance and hypertension is a product, at least in part, of our evolutionary history. Adaptation to ancient lifestyle characterized by a low sodium, low-calorie food supply and physical stress to injury response has driven our evolution to shape and preserve a thrifty genotype, which is favorite with energy-saving and sodium conservation. As our civilization evolved, a sedentary lifestyle and sodium- and energy-rich diet, the thrifty genotype is no longer advantageous, and may be maladaptive to disease phenotype, such as hypertension, obesity and insulin resistance syndrome. This article reviews human evolution and the impact of the modern environment on hypertension and insulin resistance.

Pathophysiology of the diabetic kidney

Diabetes mellitus contributes greatly to morbidity, mortality, and overall health care costs. In major part, these outcomes derive from the high incidence of progressive kidney dysfunction in patients with diabetes making diabetic nephropathy a leading cause of end-stage renal disease. A better understanding of the molecular mechanism involved and of the early dysfunctions observed in the diabetic kidney may permit the development of new strategies to prevent diabetic nephropathy. Here we review the pathophysiological changes that occur in the kidney in response to hyperglycemia, including the cellular responses to high glucose and the responses in vascular, glomerular, podocyte, and tubular function. The molecular basis, characteristics, and consequences of the unique growth phenotypes observed in the diabetic kidney, including glomerular structures and tubular segments, are outlined. We delineate mechanisms of early diabetic glomerular hyperfiltration including primary vascular events as well as the primary role of tubular growth, hyperreabsorption, and tubuloglomerular communication as part of a "tubulocentric" concept of early diabetic kidney function. The latter also explains the "salt paradox" of the early diabetic kidney, that is, a unique and inverse relationship between glomerular filtration rate and dietary salt intake. The mechanisms and consequences of the intrarenal activation of the renin-angiotensin system and of diabetes-induced tubular glycogen accumulation are discussed. Moreover, we aim to link the changes that occur early in the diabetic kidney including the growth phenotype, oxidative stress, hypoxia, and formation of advanced glycation end products to mechanisms involved in progressive kidney disease.

Enhanced phosphorylation of Na(+)-Cl- co-transporter in experimental metabolic syndrome: role of insulin

In the present study, we investigated the activity of the thiazide-sensitive NCC (Na(+)-Cl(-) co-transporter) in experimental metabolic syndrome and the role of insulin in NCC activation. Renal responses to the NCC inhibitor HCTZ (hydrochlorothiazide), as a measure of NCC activity in vivo, were studied in 12-week-old ZO (Zucker obese) rats, a model of the metabolic syndrome, and in ZL (Zucker lean) control animals, together with renal NCC expression and molecular markers of NCC activity, such as localization and phosphorylation. Effects of insulin were studied further in mammalian cell lines with inducible and endogenous expression of this molecule. ZO rats displayed marked hyperinsulinaemia, but no differences in plasma aldosterone, compared with ZL rats. In ZO rats, natriuretic and diuretic responses to NCC inhibition with HCTZ were enhanced compared with ZL rats, and were associated with a decrease in BP (blood pressure). ZO rats displayed enhanced Thr(53) NCC phosphorylation and predominant membrane localization of both total and phosphorylated NCC, together with a different profile in expression of SPAK (Ste20-related proline/alanine-rich kinase) isoforms, and lower expression of WNK4. In vitro, insulin induced NCC phosphorylation, which was blocked by a PI3K (phosphoinositide 3-kinase) inhibitor. Insulin-induced reduction in WNK4 expression was also observed, but delayed compared with the time course of NCC phosphorylation. In summary, we report increased NCC activity in hyperinsulinaemic rodents in conjunction with the SPAK expression profile consistent with NCC activation and reduced WNK4, as well as an ability of insulin to induce NCC stimulatory phosphorylation in vitro. Together, these findings indicate that hyperinsulinaemia is an important driving force of NCC activity in the metabolic syndrome with possible consequences for BP regulation.

Sodium-retaining effect of insulin in diabetes

Insulin has long been hypothesized to cause sodium retention, potentially of enough magnitude to contribute to hypertension in obesity, metabolic syndrome, and Type II diabetes. There is an abundance of supportive evidence from correlational analyses in humans, acute insulin infusion studies in humans and animals, and chronic insulin infusion studies in rats. However, the absence of hypertension in human insulinoma patients, and negative results for sodium-retaining or blood pressure effects of chronic insulin infusion in a whole series of dog studies, strongly refute the insulin hypothesis. We recently questioned whether the euglycemic, hyperinsulinemia model used for most insulin infusion studies, including the previous chronic dog studies, was the most appropriate model to test the renal actions of insulin in obesity, metabolic syndrome, and Type II diabetes. In those circumstances, hyperinsulinemia coexists with hyperglycemia. Therefore, we tested the sodium-retaining effect of insulin in chronically instrumented, alloxan-treated diabetic dogs. We used 24 h/day intravenous insulin infusion to regulate plasma insulin concentration. Induction of diabetes (∼400 mg/dl) caused sustained natriuresis and diuresis. However, if we clamped insulin at baseline, control levels, i.e., prevented it from decreasing, then the sustained natriuresis and diuresis were completely reversed, despite the same level of hyperglycemia. We also found that 24 h/day intrarenal insulin infusion had the same effect in diabetic dogs but had no sodium-retaining action in normal dogs. This new evidence that insulin has a sodium-retaining effect during hyperglycemia may have implications for maintaining sodium balance in uncontrolled Type II diabetes.

Influence of high glycemic index and glycemic load diets on blood pressure during adolescence

We aimed to prospectively examine the association between the glycemic index and glycemic load of foods consumed and the dietary intakes of carbohydrates, sugars, fiber, and principal carbohydrate-containing food groups (eg, breads, cereals, and sugary drinks) with changes in blood pressure during adolescence. A total of 858 students aged 12 years at baseline (422 girls and 436 boys) were examined from 2004-2005 to 2009-2011. Dietary data were assessed from validated semiquantitative food frequency questionnaires. Blood pressure was measured using a standard protocol. In girls, after adjusting for age, ethnicity, parental education, parental history of hypertension, baseline height, baseline blood pressure, change in body mass index, and time spent in physical and sedentary activities, each 1-SD (1-SD = 7.10 g/d) increase in baseline dietary intake of total fiber was associated with a 0.96-, 0.62-, and 0.75-mmHg decrease in mean systolic (P = 0.02), diastolic (P = 0.01), and arterial blood pressures (P = 0.002), respectively, 5 years later. In girls, each 1-SD increase in dietary glycemic index, glycemic load, carbohydrate, and fructose was concurrently related to increases of 1.81 (P = 0.001), 4.02 (P = 0.01), 4.74 (P = 0.01), and 1.80 mm Hg (P = 0.03) in systolic blood pressure, respectively, >5 years. Significant associations between carbohydrate nutrition variables and blood pressure were not observed among boys. Excessive dietary intake of carbohydrates, specifically from high glycemic index/glycemic load foods, could adversely influence blood pressure, particularly in girls, whereas fiber-rich diets may be protective against elevated blood pressure during adolescence.

The functional variant V433M of the CYP4F2 and the metabolic syndrome in Swedes

BACKGROUND AND AIM

The genetic basis of Metabolic syndrome (MetS) is largely unknown but a link with salt sensitivity is recognized. The cytochrome P450 isoform 4F2 (CYP4F2) is involved in renal production of 20-hydroxyeicosatethraenoic acid (20-HETE), a natriuretic substance associated with salt sensitivity. The same enzyme is implicated in ω-hydroxylation of very long and medium chain fatty acids in the liver suggesting its possible influence on gluco-metabolic components of MetS. The aim of the present study was to evaluate the effect of CYP4F2 V433M, a functional polymorphism previously associated with hypertension via renal salt reabsorption, on the individual components of MetS and MetS itself.

METHODS

The polymorphism was genotyped in the cardiovascular cohort of the Malmö Diet and Cancer (MDC-CVA) study and successively in the Malmö Preventive Project (MPP) cohort. Different definitions of the MetS were applied.

RESULTS

In the MDC-CVA, male, but not female, CYP4F2 M433 carriers had significantly higher levels of waist, triglycerides, BP and a composite sum of MetS phenotypes (MetS score) beside lower HDL-cholesterol respect to V-homozygotes. MetS, as defined in the ATPIII and the AHA/NHLBI definitions, was more prevalent in M-carriers with respect to V-homozygotes. In the MPP cohort, significant association was detectable only for triglycerides at baseline and for Diastolic BP at reinvestigation in male M-carriers.

CONCLUSION

The initial positive association of the CYP4F2 V433M polymorphism with components of MetS and MetS itself, found in MDC-CVA, was partially denied in another large cohort. The first association either could be due to a false positive result or alternatively, different genetic background or population stratification could have hidden the effect of the polymorphism in the replication cohort.

Chronic intrarenal insulin replacement reverses diabetes mellitus-induced natriuresis and diuresis

We showed recently that sustained natriuresis in type 1 diabetic dogs was attributed to the decrease in insulin rather than the hyperglycemia alone. The sodium-retaining action of insulin appeared to require hyperglycemia, and it completely reversed the diabetic natriuresis and diuresis. This study tested whether the sodium-retaining effect was attributed to direct intrarenal actions of insulin. Alloxan-treated dogs (D; n=7) were maintained normoglycemic using 24-h/d IV insulin replacement. After control measurements, IV insulin was decreased to begin a 6-day diabetic period. Blood glucose increased from 84±6 mg/dL to an average of 428 mg/dL on days 5 and 6, sodium excretion increased from 74±8 to 98±7 meq/d over the 6 days, and urine volume increased from 1645±83 to 2198±170 mL/d. Dir dogs (n=7) were subjected to the same diabetic regimen, but, in addition, insulin was infused continuously into the renal artery at 0.3 mU/kg per minute during the 6-day period. This did not affect plasma insulin. Blood glucose increased from 94±10 mg/dL to an average of 380 mg/dL on days 5 and 6, but sodium excretion averaged 76±5 and 69±8 meq/d during control and diabetes mellitus, respectively. The diuresis also was prevented. Glomerular filtration rate increased only in Dir dogs, and there was no change in mean arterial pressure in either group. This intrarenal insulin infusion had no effect on sodium or volume excretion in normal dogs. Intrarenal insulin replacement in diabetic dogs caused a sustained increase in tubular reabsorption that completely reversed diabetic natriuresis. Insulin plus glucose may work to prevent salt wasting in uncontrolled type 2 diabetes mellitus.

Association of body mass index with glomerular filtration rate in Japanese: a cross-sectional study in work-site population

It has been shown that aging and hypertension are important risk factors to promote renal damage. However, little data are available on the effect of obesity on the progression of renal damage, especially in young and middle-aged individuals. The aim of this study was to determine the association between body mass index (BMI) and renal function evaluated by estimated glomerular filtration rate (eGFR) in Japanese men. We studied the cross-sectional association of BMI with eGFR in 3872 Japanese men in a work-site population (18-64 y; mean age 42.1 ± 0.2 y). Estimated glomerular filtration rate was calculated by a novel equation for Japanese men. Estimated glomerular filtration rate was negatively correlated with age, systolic blood pressure (SBP), hemoglobin A1c (HbA1c), and BMI. We performed multiple regression analysis, controlling for factors, such as SBP, low-density lipoprotein-cholesterol, gamma-glutamyl transpeptidase, age, HbA1c, and uric acid. The association between age and eGFR was highly statistically significant. In addition, BMI was still significantly associated with eGFR independently of SBP. Moreover, mean eGFR, which was adjusted for age, SBP, HbA1c, serum uric acid, and gamma-glutamyl transpeptidase, decreased from 88.9 mL/min/1.73 m(2) in the first quartile of BMI to 87.5 mL/min/1.73 m(2) in the second, 86.9 mL/min/1.73 m(2) in the third, and 85.9 mL/min/1.73 m(2) in the fourth quartile (test for trend, P < .0001). These results show that a close relationship is present between obesity and decreased eGFR in Japanese men. Keeping appropriate body weight, in addition to appropriate blood pressure, in young and middle age may be important to prevent renal damage in older age.

Differential effects of various fish proteins in altering body weight, adiposity, inflammatory status, and insulin sensitivity in high-fat-fed rats

Mounting evidence suggests that the benefits of fish consumption are not limited to the well-appreciated effects of omega-3 fatty acids. We previously demonstrated that cod protein protects against the development of diet-induced insulin resistance. The goal of this study was to determine whether other fish protein sources present similar beneficial effects. Rats were fed a high-fat, high-sucrose diet containing protein from casein or fish proteins from bonito, herring, mackerel, or salmon. After 28 days, oral glucose tolerance tests or hyperinsulinemic-euglycemic clamps were performed; and tissues and plasma were harvested for biochemical analyses. Despite equal energy intake among all groups, the salmon-protein-fed group presented significantly lower weight gain that was associated with reduced fat accrual in epididymal white adipose tissue. Although this reduction in visceral adiposity was not associated with improved glucose tolerance, we found that whole-body insulin sensitivity for glucose metabolism was improved using the very sensitive hyperinsulinemic-euglycemic clamp technique. Importantly, expression of both tumor necrosis factor-α and interleukin-6 was reduced in visceral adipose tissue of all fish-protein-fed groups when compared with the casein-fed control group, suggesting that fish proteins carry anti-inflammatory properties that may protect against obesity-linked metabolic complications. Interestingly, consumption of the salmon protein diet was also found to raise circulating salmon calcitonin levels, which may underlie the reduction of weight gain in these rats. These data suggest that not all fish protein sources exert the same beneficial properties on the metabolic syndrome, although anti-inflammatory actions appear to be common.

[Sodium intake and metabolic syndrome: a systematic review]

Recent studies have shown that sodium intake restrictions may increase insulin resistance (IR) and induce changes on serum lipoproteins and on inflammation markers that are similar to those found in metabolic syndrome (MS). We performed a systematic review of literature regarding the effects of restricting sodium intake on MS or on IR. Nine articles were included in the review. Restriction of sodium consumption was associated with increase insulin resistance in two articles and with decrease in three others. In seven of nine articles, salt intake restriction determined blood pressure reduction, and in two articles adverse effects on markers of MS were found. Most studies showed beneficial effects of moderate sodium intake restriction, associated or not to others nutritional modifications or increased physical activity. Further studies are needed to evaluate the effects of moderate sodium consumption reductions on MS and IR.

Chronic sodium-retaining action of insulin in diabetic dogs

Insulin-mediated sodium retention is implicated as a mechanism for hypertension in metabolic syndrome and type II diabetes. However, there is no direct experimental evidence for a sustained antinatriuretic effect of insulin outside of rodents, and all previous studies in dogs have been negative. This study used a novel approach to test for a chronic sodium-retaining action of insulin in dogs, by testing the hypothesis that natriuresis in type I diabetes is dependent on the decrease in insulin, rather than being due solely to osmotic actions of hyperglycemia. Dogs were chronically instrumented and housed in metabolic cages. Fasting blood glucose in alloxan-treated dogs was maintained at ~65 mg/dl by continuous intravenous insulin infusion. Then, a 6-day diabetic period was induced by either 1) decreasing the insulin infusion to induce type I diabetes (D; blood glucose = 449 ± 40 mg/dl) or 2) clamping the insulin infusion and infusing glucose continuously (DG; blood glucose = 470 ± 56 mg/dl). Control urinary sodium excretion (UnaV) averaged 70 ± 5 (D) and 69 ± 5 (DG) meq/day and increased on day 1 in both groups. UnaV remained elevated in the D group (115 ± 15 meq/day days 2-6), but it returned to control in the DG group (69 ± 11 meq/day days 2-6) and was accompanied by decreased lithium clearance. Thus, insulin had a sustained antinatriuretic action that was triggered by increased glucose, and it was powerful enough to completely block the natriuresis caused by hyperglycemia. These data may reveal an unrecognized physiologic function of insulin as a protector against hyperglycemia-induced salt wasting in diabetes.

Relationship of insulin resistance in chronic haemodialysis patients with inflammatory indicators, malnutrition, echocardiographic parameters and 24 hour ambulatory blood pressure monitoring

OBJECTIVE

The relationship between malnutrition, echocardiographic parameters, 24 h ambulatory blood pressure (ABP) parameters and decreased insulin sensitivity index (ISI-S) in chronic haemodialysis patients was investigated.

MATERIAL AND METHODS

ISI-S and inflammatory indicators were measured. The nutritional state was assessed by malnutrition score. Echocardiography and 24 h ABP were performed 1 day before the second haemodialysis session of the week.

RESULTS

ISI-S was inversely correlated with the night-time mean blood pressure (BP)/day-time mean BP ratio (p = 0.021) and malnutrition score (p < 0.01). High-sensitivity C-reactive protein, night-time mean BP/day-time mean BP and vena cava collapse index were independent risk factors affecting ISI-S (p < 0.001; beta = 0.412, p = 0.025; beta = -0.204, p < 0.001; beta = -0.465).

CONCLUSIONS

The decrease in ISI-S along with the hypervolaemia suggests that volume overload is a contributory factor in the pathogenesis of insulin resistance in patients with chronic renal failure. This study indicates that, in addition to the traditional cardiovascular risk factors in these patients, insulin resistance can be regarded as a risk factor, but not an independent one, mainly a reflection of the underlying culprit, hypervolaemia.

Analytic review: glucose controversies in the ICU

Hyperglycemia is common in critical illness and has been associated with increased morbidity and mortality. An era of tight glucose control began when intensive insulin therapy was shown to improve outcomes in a single-center randomized trial. More recently, with the publication of additional studies, questions have been raised regarding the efficacy and safety of intensive glycemic management. This article will review the biologic mechanisms that may help us understand why and how hyperglycemia and insulin are relevant in critical illness. We will then explore insights gleaned from available clinical trials. Finally, we will discuss specific areas of controversy that relate to the implementation of glycemic control in the intensive care unit, such as the ideal glucose target and the importance of hypoglycemia.

Characteristic clinical and biochemical profile of recurrent calcium-oxalate nephrolithiasis in patients with metabolic syndrome

BACKGROUND

Metabolic syndrome is a risk factor for nephrolithiasis. This study was performed to evaluate the clinical and biochemical profile of calcium-oxalate nephrolithiasis in stone formers with metabolic syndrome.

METHODS

A total of 526 recurrent stone formers, 184 of them with metabolic syndrome, and 214 controls were examined on a free diet and after a sodium-restricted diet (sodium intake < 100 mmol/24 h).

RESULTS

On free diet, stone formers with metabolic syndrome showed higher sodium excretion [mean (95% confidence interval), 196 (176-218) vs 160 (150-168) mmol/24 h; P < 0.01] and lower citrate excretion [2.23 (1.99-2.58) vs 2.84 (2.51-3.17) mmol/24 h; P < 0.01] compared to controls, whereas stone formers without metabolic syndrome showed higher calcium and oxalate excretion [5.43 (5.01-5.82) vs 3.58 (2.84-4.19) and 0.34 (0.32-0.36) vs 0.26 (0.20-0.31)m mmol/24 h for calcium and oxalate, respectively; P < 0.01] and lower citrate excretion [2.18 (1.98-2.38) vs 2.84 (2.51-3.17) mmol/24 h; P < 0.01] compared to controls. The ion activity product of urinary calcium-oxalate salts was similar between stone formers with and without metabolic syndrome [1.41 (1.31-1.59) vs 1.40 (1.35-1.45); P > 0.05]. After the test diet, this index was lower in diet-compliant stone formers with metabolic syndrome compared to diet-compliant stone formers without metabolic syndrome [1.15 (1.10-1.21) vs 1.39 (1.31-1.45); P < 0.01].

CONCLUSIONS

The biochemical profiles and responses to the sodium-restricted diet were significantly different between stone formers with metabolic syndrome and those without. Dietary habits play a central role in the pathogenesis of nephrolithiasis in stone formers with metabolic syndrome.

Nitric oxide enhancement and blood pressure decrease in patients with metabolic syndrome using soy protein or fish oil

OBJECTIVE: To verify the effects of fish oil and soy on nitric oxide (NO) and blood pressure in patients with metabolic syndrome (MS). SUBJECTS AND METHODS: Sixty women with MS were investigated in a parallel randomized design study. The first group maintained their usual diet; the second group received 25 g/day of soy; the third group received 3 g/day of n-3 fatty acids, and the fourth group the same amount previously cited of n-3 fatty acids and soy. RESULTS: Serum nitric oxide metabolites showed significant increase after 90 days in the fish oil and soy groups. Systolic pressure reduced after 45 days of treatment with fish oil, whereas diastolic pressure decreased significantly throughout the study in the soy group. CONCLUSIONS: NO increase and blood pressure reduction with fish oil or soy protein reinforce the importance of the influence of NO on blood pressure in patients with MS.

Obesity and impaired renal function: potential for lifestyle intervention?

Obesity is recently acknowledged as an important independent risk factor for kidney disease, in which epidemiological evidence played a crucial role. This risk is probably explained by intracellular lipid accumulation in the kidney. Lifestyle factors such as physical activity and diet play a role in the development of kidney disease in several stages: development of obesity and the metabolic syndrome, occurrence of obesity-related glomerulopathy, improvement of hemodialysis patients, and prevention of graft dysfunction and graft loss after renal transplantation. After the recent success of lifestyle intervention to prevent diabetes, further research is needed to show the effects of lifestyle changes to prevent and reduce obesity-related morbidity, including chronic kidney disease.

Progress and controversies: treating obesity and insulin resistance in the context of hypertension

Improvements in hypertension treatment and control are challenged by the increasing incidence of metabolic risk factors for hypertension, in particular, obesity and insulin resistance. Such risk factors can increase the severity of hypertension and can interact via a multitude of hormonal and inflammatory pathways. Their presence may affect antihypertensive agent choice with regard to antihypertensive efficacy as well as potential synergistic or antagonistic effects on inflammatory status and progression to diabetes. Furthermore, an increasing number of pharmacologic options are available to promote weight loss and insulin sensitivity that may affect blood pressure directly and indirectly. This review considers the metabolic basis for the complex interactions of hypertension with obesity and insulin resistance, and it assesses the clinical evidence for an impact of weight loss and insulin-sensitizing treatment on blood pressure. Awareness of these pathophysiologic interrelations and their implications for treatment are likely to be of increasing importance for successful blood pressure management.

Chronic glucose infusion causes sustained increases in tubular sodium reabsorption and renal blood flow in dogs

This study tested the hypothesis that inducing hyperinsulinemia and hyperglycemia in dogs, by infusing glucose chronically intravenously, would increase tubular sodium reabsorption and cause hypertension. Glucose was infused for 6 days (14 mg.kg(-1).min(-1) iv) in five uninephrectomized (UNX) dogs. Mean arterial pressure (MAP) and renal blood flow (RBF) were measured 18 h/day using DSI pressure units and Transonic flow probes, respectively. Urinary sodium excretion (UNaV) decreased significantly on day 1 and remained decreased over the 6 days, coupled with a significant, sustained increase in RBF, averaging approximately 20% above control on day 6. Glomerular filtration rate and plasma renin activity (PRA) also increased. However, although MAP tended to increase, this was not statistically significant. Therefore, the glucose infusion was repeated in six dogs with 70% surgical reduction in kidney mass (RKM) and high salt intake. Blood glucose and plasma insulin increased similar to the UNX dogs, and there was significant sodium retention, but MAP still did not increase. Interestingly, the increases in PRA and RBF were prevented in the RKM dogs. The decrease in UNaV, increased RBF, and slightly elevated MAP show that glucose infusion in dogs caused a sustained increase in tubular sodium reabsorption by a mechanism independent of pressure natriuresis. The accompanying increase in PRA, together with the failure of either RBF or PRA to increase in the RKM dogs, suggests the site of tubular reabsorption was before the macula densa. However, the volume retention and peripheral edema suggest that systemic vasodilation offsets any potential renal actions to increase MAP in this experimental model in dogs.

Co-associations between insulin sensitivity and measures of liver function, subclinical inflammation, and hematology

Clustering of risk factors for coronary heart disease and diabetes is well established, particularly in relation to insulin resistance. To determine whether evaluation of risk factor clustering will contribute to risk assessment, it is first necessary to discriminate co-association between risk factors from correlation. We undertook this in a large homogenous group, using a sophisticated measure of insulin sensitivity and a broad range of risk factors. Cross-sectional analysis of an occupational cohort using regression and factor analyses was performed. Subjects were 472 apparently healthy white men. The main outcome measures were insulin sensitivity, S(I), by minimal model analysis of the intravenous glucose tolerance test plus liver function and hematologic variables, including the inflammation indices, leukocyte count, and erythrocyte sedimentation rate. The S(I) correlated independently with serum gamma-glutamyl transferase (GGT), aspartate transaminase, and alkaline phosphatase activities; blood pressure; leukocyte count; and erythrocyte sedimentation rate (P < .01). On factor analysis, the factor that explained the greatest proportion of the variance (56.7%) included, in decreasing order of factor loading, triglycerides, S(I) (negative), body mass index, high-density lipoprotein cholesterol (negative), insulin, uric acid, and GGT activity (loadings >0.40). Mean arterial pressure was not a feature (loading 0.29), neither were indices of subclinical inflammation. In apparently healthy men, blood pressure and indices of subclinical inflammation do not cluster with other insulin resistance-related risk factors, despite correlating with insulin sensitivity. In contrast, both GGT activity and uric acid concentrations correlated with insulin sensitivity and co-associated with insulin resistance-related risk factors and are therefore components of a true risk factor cluster.

Association of heart rate with microalbuminuria in cardiovascular risk patients: data from I-SEARCH

BACKGROUND

Microalbuminuria (MAU) is an indicator of impaired renal function and a relevant risk predictor for cardiovascular events. An increased heart rate is closely correlated with increased cardiovascular mortality. The International Survey Evaluating Microalbuminuria Routinely by Cardiologists in Patients with Hypertension (I-SEARCH) investigated 21 050 patients with hypertension and risk factors for cardiovascular disease. In patients in sinus rhythm (n = 18 900) the relationship between increased heart rate and the prevalence of MAU was analysed.

METHODS AND RESULTS

The study was performed in 26 countries worldwide from September 2005 to March 2006. Heart rate, blood pressure, urine albumin and serum creatinine were measured as key parameters. With increasing heart rate (> 80 bpm to < 120 bpm) the proportion of patients with MAU increased from 63 to 69% (P < 0.0001). The odds ratio (OR) for MAU increased with increasing heart rate [heart rate 80-100 bpm compared with 60 bpm: OR, 1.47; 95% confidence interval (CI), 1.29-1.68; P < 0.0001; and heart rate 100-120 bpm compared with 60 bpm: OR, 1.56; 95% CI, 1.22-1.99; P = 0.0004]. The prevalence of MAU was similar whether or not patients were receiving beta-blockers; but MAU was significantly reduced in physically active patients compared with sedentary patients (OR, 0.78; 95% CI, 0.73-0.84; P < 0.0001).

SUMMARY

These results show that heart rate is an independent predictor for the prevalence of MAU in hypertensive patients with cardiovascular risk factors. In contrast to beta-blocker therapy, physical activity markedly decreased MAU with increasing heart rates. Further controlled and prospective studies are needed to show that lowered heart rates in combination with MAU can significantly reduce kidney damage, as well as cardiovascular events.

Obesity-induced glomerular hyperfiltration: its involvement in the pathogenesis of tubular sodium reabsorption

BACKGROUND

Obesity is associated with hypertension and glomerular hyperfiltration. A major mechanism responsible for the obesity-associated hypertension is renal salt retention. An increased glomerular filtration fraction (FF) is expected to raise postglomerular oncotic pressure and to increase proximal tubular sodium reabsorption. The aim of the present study was to verify whether obesity-associated hyperfiltration leads to increased postglomerular oncotic pressure and increased proximal sodium reabsorption.

METHODS

Twelve obese subjects (BMI >36) and 19 lean subjects participated in the study. They underwent measurement of glomerular filtration rate (GFR), renal plasma flow (RPF) and fractional excretion of lithium (FE Li).

RESULTS

GFR, RPF and FF were 61%, 28% and 29% higher, respectively, in the obese than in the control group (P < 0.00001 for GFR, P < 0.005 for RPF and P < 0.00005 for FF). Half of the obese group had increased FF with increased GFR, while the other half had normal FF with high-normal or increased GFR. Postglomerular oncotic pressure was 13% higher (P < 0.03) and FE Li was 33% lower (P < 0.005) in the obese group with high FF than in the lean group. Postglomerular oncotic pressure and FE Li were normal in the obese group with normal FF.

CONCLUSIONS

These results suggest that glomerular hyperfiltration may lead to increased proximal tubular sodium reabsorption in the obese.

The underlying mechanisms for development of hypertension in the metabolic syndrome

High blood pressure is an important constituent of the metabolic syndrome. However, the underlying mechanisms for development of hypertension in the metabolic syndrome are very complicated and remain still obscure. Visceral/central obesity, insulin resistance, sympathetic overactivity, oxidative stress, endothelial dysfunction, activated renin-angiotensin system, increased inflammatory mediators, and obstructive sleep apnea have been suggested to be possible factors to develop hypertension in the metabolic syndrome. Here, we will discuss how these factors influence on development of hypertension in the metabolic syndrome.

Temperature and blood pressure following amlodipine overdose

The cardiovascular system participates in both blood pressure (BP) and temperature regulation. As a result, salt ingestion creates conflict between BP and temperature homeostasis, as vasodilatation that would promptly lower the BP would simultaneously increase cutaneous blood flow, thereby accelerating heat loss. If temperature homeostasis has precedence over blood pressure homeostasis, as postulated by the thermoregulatory-vascular remodeling (TVR) hypothesis, then in order to minimize heat loss, BP remains elevated following salt ingestion until the kidneys excrete the excess salt. A case of amlodipine overdose offered an opportunity to test a corollary of the TVR hypothesis: vasodilators should cause a drop in body temperature and/or an increase in the metabolic rate. Following the ingestion of 1000 mg of amlodipine, the temperature and BP of a single patient were monitored during the initial 36 hours and during the 13th day of hospitalization. The BP dropped markedly between the fifth and seventh hours postingestion, but then rose steadily and normalized by 28 hours postingestion. The temperature was normal at 7 hours postingestion, declined gradually between the seventh and 26th hours postingestion, stabilized between the 26th and 31st hours postingestion, then began to rise. During this case of amlodipine overdose, a modest temperature decline lagged behind a marked BP decline. As the BP rose, the temperature also rose, but lagged behind the BP increases. These findings suggest that there is a relationship between BP and temperature and are consistent with the TVR hypothesis.

Treatment of type 2 diabetes with combined therapy: what are the pros and cons?

Type 2 diabetes is a progressive syndrome that evolves toward complete insulin deficiency during the patient's life. A stepwise approach for its treatment should be tailored according to the natural course of the disease, including adding insulin when hypoglycemic oral agent failure occurs. Treatment with insulin alone should eventually be considered in a relevant number of cases. Experience has shown the protective effects of insulin on beta-cell survival and function, resulting in more stable metabolic control. On the contrary, treatment with most insulin secretagogues has been associated with increased beta-cell apoptosis, reduced responsiveness to high glucose, and impairment of myocardial function during ischemic conditions. In addition, macrovascular complications are associated with postprandial hyperglycemia, indicating the need for tight glycemic control. Insulin treatment, especially with rapid-acting analogs, has been demonstrated to successfully control postprandial glucose excursions. Finally, a reason for concern with regard to combined therapy is represented by the evidence that polipharmacy reduces compliance to the treatment regimen. This can be particularly relevant in patients with type 2 diabetes usually taking drugs for complications and for concomitant diseases with consequent deterioration not only of metabolic control but also of other conditions. In conclusion, therapy with insulin alone immediately after hypoglycemic oral agent failure may be a useful and safe therapeutic approach in type 2 diabetes.

Cardiovascular actions of insulin

Insulin has important vascular actions to stimulate production of nitric oxide from endothelium. This leads to capillary recruitment, vasodilation, increased blood flow, and subsequent augmentation of glucose disposal in classical insulin target tissues (e.g., skeletal muscle). Phosphatidylinositol 3-kinase-dependent insulin-signaling pathways regulating endothelial production of nitric oxide share striking parallels with metabolic insulin-signaling pathways. Distinct MAPK-dependent insulin-signaling pathways (largely unrelated to metabolic actions of insulin) regulate secretion of the vasoconstrictor endothelin-1 from endothelium. These and other cardiovascular actions of insulin contribute to coupling metabolic and hemodynamic homeostasis under healthy conditions. Cardiovascular diseases are the leading cause of morbidity and mortality in insulin-resistant individuals. Insulin resistance is typically defined as decreased sensitivity and/or responsiveness to metabolic actions of insulin. This cardinal feature of diabetes, obesity, and dyslipidemia is also a prominent component of hypertension, coronary heart disease, and atherosclerosis that are all characterized by endothelial dysfunction. Conversely, endothelial dysfunction is often present in metabolic diseases. Insulin resistance is characterized by pathway-specific impairment in phosphatidylinositol 3-kinase-dependent signaling that in vascular endothelium contributes to a reciprocal relationship between insulin resistance and endothelial dysfunction. The clinical relevance of this coupling is highlighted by the findings that specific therapeutic interventions targeting insulin resistance often also ameliorate endothelial dysfunction (and vice versa). In this review, we discuss molecular mechanisms underlying cardiovascular actions of insulin, the reciprocal relationships between insulin resistance and endothelial dysfunction, and implications for developing beneficial therapeutic strategies that simultaneously target metabolic and cardiovascular diseases.