Renin regulation in type II diabetes mellitus: influence of dietary sodium

Insulin, CCAAT/enhancer-binding proteins and lactate regulate the human 11β-hydroxysteroid dehydrogenase type 2 gene expression in colon cancer cell lines

11β-Hydroxysteroid dehydrogenases (11beta-HSD) modulate mineralocorticoid receptor transactivation by glucocorticoids and regulate access to the glucocorticoid receptor. The isozyme 11beta-HSD2 is selectively expressed in mineralocorticoid target tissues and its activity is reduced in various disease states with abnormal sodium retention and hypertension, including the apparent mineralocorticoid excess. As 50% of patients with essential hypertension are insulin resistant and hyperinsulinemic, we hypothesized that insulin downregulates the 11beta-HSD2 activity. In the present study we show that insulin reduced the 11beta-HSD2 activity in cancer colon cell lines (HCT116, SW620 and HT-29) at the transcriptional level, in a time and dose dependent manner. The downregulation was reversible and required new protein synthesis. Pathway analysis using mRNA profiling revealed that insulin treatment modified the expression of the transcription factor family C/EBPs (CCAAT/enhancer-binding proteins) but also of glycolysis related enzymes. Western blot and real time PCR confirmed an upregulation of C/EBP beta isoforms (LAP and LIP) with a more pronounced increase in the inhibitory isoform LIP. EMSA and reporter gene assays demonstrated the role of C/EBP beta isoforms in HSD11B2 gene expression regulation. In addition, secretion of lactate, a byproduct of glycolysis, was shown to mediate insulin-dependent HSD11B2 downregulation. In summary, we demonstrate that insulin downregulates HSD11B2 through increased LIP expression and augmented lactate secretion. Such mechanisms are of interest and potential significance for sodium reabsorption in the colon.

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.

Nonmodulation as the mechanism for salt sensitivity of blood pressure in individuals with hypertension and type 2 diabetes mellitus

CONTEXT

It is assumed that in individuals with type 2 diabetes mellitus (T2DM), blood pressure sensitivity to salt intake and the frequency of a low renin state are both increased compared with the nondiabetic population. However, studies supporting these assumptions may have been confounded by participant inclusion criteria, and study results may reflect target organ damage.

OBJECTIVE

The objective of this study was to examine in a cohort of T2DM 1) the frequency of salt sensitivity of blood pressure and 2) whether alterations of the renin-angiotensin-aldosterone system (RAAS) contribute to salt sensitivity in this population.

DESIGN, PATIENTS, AND METHODS

Within participants of the HyperPATH cohort, four groups were analyzed: 1) T2DM with hypertension (HTN), n=51; 2) T2DM without HTN, n=30; 3) HTN only, n=451; and 4) normotensive, n=209. Phenotype studies were conducted after participants completed two dietary phases: liberal sodium (200 mmol/d) and low sodium (10 mmol/d) for 7 d each. Participants were admitted overnight to a clinical research center after each diet, and supine measurements of the RAAS before and after a 60-min angiotensin II infusion (3 ng/kg·min) were obtained.

RESULTS

Multivariate regression analysis demonstrated that T2DM status (all individuals with T2DM vs. individuals without T2DM) was not associated with the change in mean arterial pressure between the low and liberal sodium diets after accounting for age, gender, body mass index, race, and baseline blood pressure (T2DM status, P=0.5). Furthermore, two intermediate phenotypes of altered RAAS, low renin, and nonmodulation (NMOD), were associated with salt-sensitive blood pressure but occurred at different frequencies in the T2DM-HTN and HTN groups (low renin, 12% T2DM-HTN vs. 29% HTN; NMOD, 41% T2DM-HTN vs. 27% HTN; P=0.01).

CONCLUSION

The frequency of NMOD in participants with T2DM was significantly higher compared with HTN, suggesting that the salt sensitivity often seen in T2DM is driven by NMOD.

Altered dietary salt intake for preventing and treating diabetic kidney disease

BACKGROUND

There is strong evidence that our current consumption of salt is a major factor for increased blood pressure (BP) and a modest reduction in salt intake lowers BP whether BP levels are normal or raised. Tight control of BP in diabetics lowers the risk of strokes, heart attacks and heart failure and slows the progression of diabetic kidney disease (DKD). Currently there is no consensus in restricting salt intake in diabetic patients.

OBJECTIVES

To evaluate the effect of altered salt intake on BP and markers of cardiovascular disease and DKD.

SEARCH STRATEGY

In January 2010, we searched the Cochrane Renal Group's Specialised Register, CENTRAL (in The Cochrane Library), MEDLINE (from 1966) and EMBASE (from 1980) to identify appropriate articles.

SELECTION CRITERIA

We included all randomised controlled trials of salt reduction in individuals with type 1 and type 2 diabetes.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed studies and resolved differences by discussion with a third independent author. We calculated mean effect sizes using both the fixed-effect and random-effects models.

MAIN RESULTS

Thirteen studies (254 individuals) met our inclusion criteria. These included 75 individuals with type 1 diabetes and 158 individuals with type 2 diabetes. The median reduction in urinary sodium was 203 mmol/24 h (11.9 g/day) in type 1 diabetes and 125 mmol/24 h (7.3 g/day) in type 2 diabetes. The median duration of salt restriction was one week in both type 1 and type 2 diabetes. BP was reduced in both type 1 and type 2 diabetes. In type 1 diabetes (56 individuals), salt restriction reduced BP by -7.11/-3.13 mm Hg (systolic/diastolic); 95% CI: systolic BP (SBP) -9.13 to -5.10; diastolic BP (DBP) -4.28 to -1.98). In type 2 diabetes (56 individuals), salt restriction reduced BP by -6.90/-2.87 mm Hg (95% CI: SBP -9.84 to -3.95; DBP -4.39 to -1.35). There was a greater reduction in BP in normotensive patients, possibly due to a larger decrease in salt intake in this group.

AUTHORS' CONCLUSIONS

Although the studies are not extensive, this meta-analysis shows a large fall in BP with salt restriction, similar to that of single drug therapy. All diabetics should consider reducing salt intake at least to less than 5-6 g/day in keeping with current recommendations for the general population and may consider lowering salt intake to lower levels, although further studies are needed.

The renin-angiotensin system and diabetic nephropathy

The renin-angiotensin system (RAS) has key regulatory functions for blood pressure and fluid homeostasis. In addition, dysregulation of the system can have maladaptive effects to promote tissue injury in chronic diseases such as hypertension, heart failure, and kidney disease. These actions for the RAS to promote disease pathogenesis are especially apparent in diabetic nephropathy, the most common cause of end-stage renal disease in the United States. Evidence of a role for the RAS in diabetic nephropathy comes from studies in animal models and randomized clinical trials showing efficacy of angiotensin-converting enzyme inhibitors and angiotensin-receptor blockers to slow the progression of renal disease. Widespread applications of these therapies to a range of renal diseases may have contributed to the recent reduction in the incidence rates for end-stage renal disease. We provide a general review of the RAS and its role in diabetic nephropathy.

The renin-angiotensin system in blacks: active, passive, or what?

Plasma renin activity in blacks has been consistently reported to be lower than in whites. Many mechanisms for the low plasma renin activity have been proposed, including volume status, renal sodium handling, and the reduction of renin release. The status of the RAS is paramount in the regulation of salt and water balance and its implications in disease processes such as hypertension and renal failure. In this review, we present data to suggest that low systemic plasma renin activity in blacks may not be the primary abnormality, but rather the reflection of an overactive RAS at the tissue level in the kidney.

Salt intake, hypertension and diabetes mellitus

Diabetes mellitus affects approximately 135 million people in the world. Diabetes and hypertension are both relatively common diseases in westernised countries. Both entities increase with age. Essential hypertension accounts for the majority of hypertension in people with type 2 diabetes, who constitute more than 90% of those with a dual diagnosis of diabetes and hypertension. The benefit conferred per mm Hg blood pressure reduction appears to be greater in persons with type 2 diabetes than in those with hypertension and non-coexistent diabetes mellitus. Similar to a subset of patients with essential hypertension, type 2 diabetic patients manifest dietary NaCl-induced exacerbation of hypertension. Recent guidelines have emphasised that the target blood pressure levels for patients with diabetes should be lower than in other hypertensive groups. An increased total body sodium and enhanced vascular reactivity are found in people with diabetes and most type 2 diabetic patients are salt sensitive. Type 2 diabetes with hypertension is associated with reduced renal plasma flow when dietary salt intake is high. Experimental, observational and interventional evidence support the benefits of sodium restriction in hypertensives. However, the full effects of sodium restriction are usually not obvious for at least 5 weeks. Other favourable effects of moderate reduction in sodium intake are a regress left ventricular hypertrophy, decrease in diuretic-induced potassium wastage, reduction in proteinuria, protection against stroke and from osteoporosis and renal stones, and enhancement of the antihypertensive effect of the antihypertensive agents.

Blunted suppression of plasma renin activity in diabetes

We have documented, contrary to expectation, that the renin-angiotensin-aldosterone system (RAAS) is stimulated normally by restriction of sodium intake inpatients with Type 2 diabetes mellitus (DM) and hypertension. Conversely, plasma renin activity (PRA)is suppressed less than in normal subjects by a high-salt diet in these patients. Increasing plasma angiotensin II (Ang II) concentration through intravenous Ang II infusion also suppresses renin release, via the short feedback loop. In this study, we sought to ascertain whether the limited renin suppression in Type 2 diabetes mellitus via high-salt intake is a unique defect or part of a more generalised abnormality of PRA suppression. We studied 38 patients with Type 2 DM and hypertension, 158 hypertensive control patients, and 61 normotensive controls. All patients were studied while in metabolic balance on a 10 mEq sodium (Na) diet. The response to the Ang II infusion at 3 ng/kg/min for 45 minutes was measured. We found that PRA fell significantly in normal subjects, from 4.0 +/- 0.33 to 2.5 +/- 0.23 ngAngI/ml/hr (p=0.0056). In patients with essential hypertension, the Ang II infusion also led to a fall in PRA from 3.51 +/- 0.23 to 2.76 +/- 0.17 ng Angl/ml/hr(p=0.014). In patients with DM, despite a similar basal PRA (3.7 +/- 0.40 ng AngI/ml/hr), the infusion of Ang II did nor influence PRA significantly (3.43 +/- 0.42ng AngI/ml/hr; p > 0.77), though these patients had the most robust mean arterial pressure response. Our data are in complete accord with the concept of high intrarenal Ang II in DM and suggest lower systemic Ang II despite comparable PRA.

The paradox of the low-renin state in diabetic nephropathy

Although diabetic nephropathy is often a low renin state, the renin system appears to be implicated in its pathogenesis. In this study, it was hypothesized that the low plasma renin activity (PRA) is misleading, masking and perhaps reflecting an activated intrarenal renin system. PRA and renal vascular responses (inulin and para-aminohippurate clearance) to graded doses of an angiotensin II (AngII) antagonist, irbesartan, were assessed in eight healthy volunteers and 12 patients with type 2 diabetes mellitus and nephropathy on a 10 mmol Na intake, to activate the renin system. Basal PRA was suppressed in type 2 diabetes mellitus compared with the healthy subjects (0.58 +/- 0.14 versus 1.58 +/- 0.28 ng/L per s, mean +/- SEM; P < 0.01). Despite the low PRA, renal perfusion rose more in response to irbesartan in type 2 diabetes mellitus (714 +/- 83 to 931 +/- 116 ml/min; P = 0.002) than normal (624 +/- 29 to 772 +/- 49 ml/min; P = 0.008). The youngest patients were hyperfiltrating and showed the largest rise in renal plasma flow in response to irbesartan, whereas renal plasma flow rose less and GFR fell in patients with low basal GFR. PRA rose in response to irbesartan more gradually in the patients with type 2 diabetes mellitus, but ultimately matched the normal response. To account for the apparent paradox of a heightened renal hemodynamic response to an AngII antagonist in the face of a low PRA in type 2 diabetes mellitus, and the rise in PRA following the AngII antagonist, it is proposed that there is increased intrarenal AngII production in type 2 diabetes mellitus. This increase could account for suppressed circulating renin, the exaggerated renal vasodilator response to irbesartan, and the therapeutic effectiveness of interrupting the renin system in diabetic nephropathy.

High plasma prorenin in non diabetic siblings of non insulin-dependent diabetes mellitus patients

In a large cohort (no. = 361) of NIDDM probands and their concordant/discordant siblings from no. = 132 families we studied: 1. the levels of plasma prorenin in non affected siblings of NIDDM probands as opposed to normal subjects without family history of diabetes, and 2. whether plasma prorenin raises in parallel to urinary protein loss in NIDDM patients. Prorenin (solid-phase trypsin) and micro-macroalbuminuria (radioimmunoassay) were evaluated. Plasma prorenin was higher in NIDDM probands and siblings than in non NIDDM siblings (37+/-31 vs. 25+/-15 ng/ml/h, p<0.0005) who, in turn, showed higher plasma prorenin than non diabetic controls without family history of diabetes (25+/-15 vs. 17+/-8 ng/ml/h, p<0.005). Plasma prorenin was higher in NIDDM siblings of micro-macroalbuminuric probands than in NIDDM siblings of non micro-macroalbuminuric probands (40+/-26 vs. 29+/-20 ng/ml/h, mean +/- SD, p = 0.0058) whereas no difference was found among non diabetic siblings (24+/-14 vs. 22+/-11 ng/ml/h, NS). Our data confirm that plasma prorenin is elevated in NIDDM patients, and show: 1. that the raise of plasma prorenin in non-NIDDM siblings of a diabetic patient does not depend entirely from the presence of diabetes, and 2. that plasma prorenin in NIDDM probands and their concordant siblings goes along with micro-macroalbuminuria.

The study of renin-angiotensin-aldosterone in experimental diabetes mellitus

It is generally accepted that hypertension and other vascular pathologies increase in diabetes mellitus (DM) patients as a result of the renin-angiotensin-aldosterone (RAA) system. In this study, changes in the renin-angiotensin-aldosterone (RAA) system level was determined in Streptozotocin (STZ)-injected rats. A total of 46 female Wistar albino rats (180-220 g body weight) was utilized in these experiments. STZ was given intraperitoneally to induce diabetes in rats. Streptozotocin (60 mg kg(-1) body weight) was dissolved in 0.1 m citrate--phosphate buffer (pH 4-5). The non-diabetic rats were injected with sterilized buffer alone to act as a control group. Blood glucose levels were 398+/-8.2 mg dl(-1), 488+/-11.75 mg dl(-1) and 658+/-29.6 mg dl(-1) at days 3, 12 and 30 respectively. The level of plasma renin activity (PRA) was measured as 7.69+/-1.07 ng ml(-1) h(-1); 1.82+/-0.22 ng ml(-1) h(-1) and 0. 67+/-0.12 ng ml(-1) h(-1) at days 3, 12 and 30, respectively. These values showed that the PRA levels are decreased with increased time period. Serum angiotensin converting enzyme (ACE, E.C. 3.4.15.1) levels were increased at days 12 and 30 (p<0.05 and p<0.005), whereas serum aldosterone levels were increased at days 3 and 12 (p<0.05). The level of urea and creatinine increased at days 12 and 30 (p<0.05 and p<0.005, respectively) when compared to the control group. The data from these experiments indicate that the PRA level decreased whereas ACE activity level increased in diabetic rats compared with the control. Aldosterone levels increased at the first stage of the experiment, but then decreased by the end of the experiment as a result of changes in renin and ACE levels.

Autonomy of the renin system in type II diabetes mellitus: dietary sodium and renal hemodynamic responses to ACE inhibition

Recognition that non-insulin-dependent diabetes mellitus (NIDDM) is a leading cause of end-stage renal disease (ESRD), and a focus of recent therapeutic and genetic studies on the renin system have rekindled interest in mechanisms by which angiotensin converting enzyme (ACE) inhibitors influence the diabetic kidney. We evaluated the renal hemodynamic status of 19 hypertensive patients with NIDDM under controlled sodium balance, low (10 mmol/day for 5 to 7 days) or high (200 mmol/day for 5 to 7 days). The renal plasma flow (RPF) response to ACE inhibition and to angiotensin II (Ang II) infusion was measured as para-aminohippurate (PAH) clearance before and during enalapril administration (10 mg b.i.d. for 3 days). Our premise was that if renal vasodilation induced by ACEI involves kinins, prostaglandins, and/or nitric oxide, vasoconstrictor responses to Ang II would be blunted. Conversely, if the dominant ACE inhibitor action were a reduction in Ang II formation, the consequence would be up-regulation and an enhanced vasoconstrictor response to exogenous Ang II. RPF in NIDDM on a high-salt diet was lower than in age-matched controls (477 +/- 25 vs. 551 +/- 25 ml/min/1.73 m2; P = 0.02). Enalapril increased RPF in NIDDM to 511 +/- 29 ml/min/1.73 m2 (P < 0.05) and enhanced renal vasoconstrictor responses to Ang II infusion, from -68 +/- 9 to -106 +/- 18 ml/min/1.73 m2 (P = 0.03). Baseline plasma renin activity (PRA) and plasma aldosterone significantly exceeded matched normotensive controls (1.1 +/- 0.5 vs. 0.3 +/- 0.1 ng AI/ml/hr and 10 +/- 0.9 vs. 4.1 +/- 0.5 ng/dl, P < 0.01, respectively). Conversely all measures in studies on a low-salt diet were normal. Our findings indicate that: (1) NIDDM with hypertension is associated with reduced RPF when dietary salt intake is high, (2) reduced Ang II formation is the dominant mechanism of ACEI-induced renal vasodilation in hypertensives with NIDDM; and (3) the sustained renal hemodynamic responses to ACE inhibition despite high-salt balance, and the increased PRA suggest an autonomous renin-angiotensin system suppressed subnormally by a high salt diet in patients with NIDDM despite greater volume expansion.

The role of angiotensin II in diabetic nephropathy: emphasis on nonhemodynamic mechanisms

Several systemic or intrarenal networks of cytokines and growth factors can be modulated by the diabetic state. We summarize the status of the renin-angiotensin system in diabetes mellitus and review the evidence of its involvement in the pathogenesis of diabetic nephropathy. Particular emphasis is placed on the nonhemodynamic properties of this vasoactive agent as both a renal growth factor and a profibrogenic peptide. Antagonizing the effects of angiotensin II with converting enzyme inhibitors is an established protective strategy in the management of diabetic nephropathy even in the absence of systemic hypertension. This and other indirect evidence from experimental animal studies suggest that the intrarenal concentration of angiotensin II may be increased as a result of increased synthesis and despite enhanced breakdown, that this peptide participates in the progression of diabetic nephropathy. However, down-regulation of angiotensin type 1 (AT1)-receptors is one of the abnormalities of both tubules and glomeruli in diabetic renal disease. A heightened bioactivation of the intrarenal angiotensin II system is therefore likely but not certain. Studies in cultured proximal tubular and glomerular mesangial cells have disclosed striking similarities between the effects of high glucose-containing medium and of treatment with angiotensin II on the growth properties and the induction of cytokines in these cells. There may also exist additive effects of angiotensin II and high glucose on signal-transduction pathways, such as activation of protein kinase C, although the contractile response to angiotensin II may be blunted by high glucose in mesangial cells. An important downstream mediator of the effects of both angiotensin II and high glucose is the activation of transforming growth factor-beta that can mediate at least some of the hypertrophic and profibrotic effects of either angiotensin II or high glucose in the diabetic kidney.

Plasma prorenin as an early marker of nephropathy in diabetic (IDDM) adolescents

We studied a group of 50 adolescents, average age 16 years, with diagnosed IDDM present for about seven years. Twenty-five had microalbuminuria (MA) averaging 111.0 +/- 34.0 (SEM) micrograms/min albumin excretion rate versus 6.7 +/- 7.4 micrograms/min in the 25 without MA. In other respects, such as sex ratio, age, body mass index, duration of IDDM, hemoglobin A1c, and normotensive systolic, diastolic and mean blood pressures (BP), these subgroups were closely matched. We compared them with a control group of 39 normotensive adolescents, of whom 18 were carefully matched siblings of the IDDM subjects with MA and 21 were similarly matched siblings of the IDDM non-MA subjects. Plasma renin concentration was determined by a direct radioimmunoassay method (Sanofi-Pasteur) and found to be virtually the same in the control and IDDM adolescents as a whole. There was also no real difference between the MA and non-MA subgroups. In contrast, plasma prorenin was significantly higher in the combined IDDM group (197.5 +/- 9.3 vs. control, 134.0 +/- 7.9 pg/ml, P < 0.0001). It was also higher in the MA subgroup than in the non-MA subgroup (226.4 +/- 13.6 vs. 168.5 +/- 10.1 pg/ml, P < 0.001). Interestingly, the 18 control siblings matching the MA subgroup had higher plasma prorenin than the 21 control siblings matching the non-MA subgroup (P < 0.001), suggesting a familial predisposition that precedes detectable diabetes and nephropathy. Our findings confirm and extend reports by other workers that elevated plasma prorenin is associated with incipient nephropathy, manifested by MA. The exclusive renal origin of this prorenin, its role in plasma, and the mechanism responsible for its elevation in IDDM with MA, are yet to be demonstrated, as is the general applicability of these findings to different populations of diabetics, with a higher incidence and severity of complications.

Systemic hypertension and the renin-angiotensin system in diabetic vascular complications

Antihypertensive treatment in the diabetic patient is a critical issue because hypertension has an impact on all of the vascular complications of diabetes, including nephropathy, retinopathy, atherosclerosis, and left ventricular hypertrophy. These complications are a consequence of altered endothelial-vascular smooth muscle interrelations that ultimately enhance vasoconstriction and alter the remodeling processes in the vascular wall. Several observations suggest that the renin-angiotensin system (RAS) may be an important contributor to these processes in diabetes mellitus. In both animal and human studies, angiotensin-converting enzyme (ACE) inhibitors have been demonstrated to slow the progression of glomerulosclerosis, prevent abnormal remodeling processes in the heart following injury, and slow the progression of atherosclerosis. In particular, ACE inhibitors appear to protect the kidney more than would be expected from simply the lowering of blood pressure and decreasing of intraglomerular pressure, possibly because angiotensin II has both hemodynamic and direct effects on the glomerulus. Paradoxically, however, the activity of the circulating RAS is low in diabetic patients. Part of these seemingly inconsistent observations may be due to (1) potential activity of tissue RASs, (2) increased sensitivity to angiotensin II in diabetes, or (3) an effect of ACE inhibition on other systems in addition to the RAS. Investigation of these mechanisms will be important in determining the therapeutic role of inhibition of the RAS in diabetes mellitus.

Diabetes mellitus and hypertension

Diabetes mellitus and hypertension are common diseases that coexist at a greater frequency than chance alone would predict. Hypertension in the diabetic individual markedly increases the risk and accelerates the course of cardiac disease, peripheral vascular disease, stroke, retinopathy, and nephropathy. Our understanding of the factors that markedly increase the frequency of hypertension in the diabetic individual remains incomplete. Diabetic nephropathy is an important factor involved in the development of hypertension in diabetics, particularly type I patients. However, the etiology of hypertension in the majority of diabetic patients cannot be explained by underlying renal disease and remains "essential" in nature. The hallmark of hypertension in type I and type II diabetics appears to be increased peripheral vascular resistance. Increased exchangeable sodium may also play a role in the pathogenesis of blood pressure in diabetics. There is increasing evidence that insulin resistance/hyperinsulinemia may play a key role in the pathogenesis of hypertension in both subtle and overt abnormalities of carbohydrate metabolism. Population studies suggest that elevated insulin levels, which often occurs in type II diabetes mellitus, is an independent risk factor for cardiovascular disease. Other cardiovascular risk factors in diabetic individuals include abnormalities of lipid metabolism, platelet function, and clotting factors. The goal of antihypertensive therapy in the patient with coexistent diabetes is to reduce the inordinate cardiovascular risk as well as lowering blood pressure.

Effect of the renin-angiotensin system in the vascular disease of type II diabetes mellitus

A universal underlying abnormality in the pathogenesis of hypertension, atherosclerosis, myocardial dysfunction, and diabetic glomerulosclerosis involves alteration in smooth muscle cell structure, function, and growth. Angiotensin II, through its effects on contractility, growth, and the sympathetic nervous system, may potentially play a key role in this pathologic process and, thus, contribute to the development of these cardiovascular and renal complications of diabetes mellitus. Angiotensin-converting enzyme inhibitors and some direct renin inhibitors prevent or slow the progression of some of these complications, which further suggests a pathologic role for the reninangiotensin system in diabetes mellitus.

Acromegaly and hypertension: prevalence and relationship to the renin-angiotensin-aldosterone system

The prevalence of arterial hypertension was evaluated in a retrospective study of 158 patients with acromegaly, and results were compared to control populations, namely, the Munich Blood Pressure Study (MBPS) and the Framingham Study. The prevalence of hypertension (defined according to WHO criteria) was significantly increased in female patients but not in men; hypertensive acromegalics were older and tended to have higher body weight compared to normotensive patients. Hypertension was not related to serum concentrations of growth hormone. After successful treatment of acromegaly, growth hormone levels and systolic and diastolic blood pressure fell only in female hypertensive acromegalics; this did not occur in normotensives. The rise in plasma renin activity in response to upright posture was diminished in 57.9% of acromegalic patients. The prevalence of low-renin hypertension in our group of patients was 31.6%, which is similar to figures reported for unselected non-acromegalic subjects with essential hypertension. Orthostatic renin activity was weakly and inversely related (r = -0.3) to blood pressure. No relationship between plasma aldosterone concentration and blood pressure could be detected; however, in acromegalic women, aldosterone rose higher after ambulation than in men. In conclusion, hypertension is a common problem in acromegaly and at least in part related to similar risk factors in control populations. The association with abnormalities of the renin-angiotensin-aldosterone system is difficult to interpret and does not offer an explanation for the slight increase in the prevalence of hypertension.