Diabetic hypertensive patients: improving their prognosis

Pharmacotherapy of hypertension in patients with pre-dialysis chronic kidney disease

INTRODUCTION

Hypertension is the most common co-morbidity in patients with chronic kidney disease (CKD), with prevalence gradually increasing across CKD Stages to the extent that about 90% of end-stage renal disease (ESRD) patients are hypertensives. Several factors contribute to blood pressure (BP) elevation and guide the therapeutic interventions that should be employed in these patients.

AREAS COVERED

This review summarizes the existing data for the management of hypertension, regarding optimal BP targets and the use of major antihypertensive classes in patients with CKD.

EXPERT OPINION

Management of hypertension in CKD requires both lowering BP levels and reducing proteinuria to minimize the risk of both CKD progression and cardiovascular disease. In this respect, aggressive control of office BP to levels <130/80 mmHg has long been proposed for patients with proteinuric nephropathies. Following evidence from recent studies that confirmed significant reductions in renal and cardiovascular outcomes with strict BP control, most, but not all, of international guidelines, suggest such BP goals for all hypertensive patients, including those with CKD. Use of renin-angiotensin system (RAS) blockers is the treatment of choice for patients with proteinuric nephropathies, while, in most patients with CKD, combination treatment with two, three, or more antihypertensive agents is often required to control BP.

Antihypertensive Therapy in the Presence of Proteinuria

The presence of proteinuria is a well-known risk factor for both the progression of renal disease and cardiovascular morbidity and mortality, and decreases in urine protein excretion level were associated with a slower decrease in renal function and decrease in risk of cardiovascular events. Increased blood pressure has a major role in the development of proteinuria in patients with either diabetic or nondiabetic kidney disease, and all recent guidelines recommend a blood pressure goal less than 130/80 mm Hg in patients with proteinuria to achieve maximal renal and cardiovascular protection. Drugs interfering with the renin-angiotensin system, ie, angiotensin-converting enzyme inhibitors and angiotensin receptor blockers, should be used as first-line antihypertensive therapy in patients with proteinuria because they seem to have a blood pressure-independent antiproteinuric effect, and if blood pressure levels are still out of goal, a diuretic should be added to this regimen. A combination of an angiotensin-converting enzyme inhibitor with an angiotensin receptor blocker or other classes of medications shown to decrease protein excretion, such as nondihydropyridine calcium antagonists or aldosterone receptor blockers, should be considered to decrease proteinuria further. This review provides an extended summary of current evidence regarding the associations of blood pressure with proteinuria, the rationale for currently recommended blood pressure goals, and the use of various classes of antihypertensive agents in proteinuric patients.

Slowing the progression of diabetic nephropathy and its cardiovascular consequences

This paper incorporates the findings from a multidisciplinary meeting on diabetic nephropathy and its renal and cardiovascular complications into a review article. The epidemic of obesity and the growing elderly population in the United States are primary drivers of a secondary epidemic of incipient type 2 diabetes mellitus and diabetic nephropathy. Current therapies aim to treat blood pressure, particularly with agents that block the renin-angiotensin system, to a target of 130/80 mm Hg. However, even lower blood pressure targets may be optimal. Control of hyperglycemia and dyslipidemia, smoking cessation, exercise, and weight loss all compliment blood pressure control and are achieved most effectively when the patient, provider, and health system are aligned with these goals. Once end-stage renal disease (ESRD) is reached, patients enter the highest cardiovascular risk-state appreciated in human medicine. Because of uniform access to care in the United States, advanced data systems, and circulatory system (intravascular) access in most patients, the ESRD population should be the future sampling frame for newer treatments tested in both prospective cohort and randomized trials. Cardiorenal risk, or the degree of excess cardiovascular risk incurred by patients with chronic kidney disease and ESRD, is a state offering considerable research opportunities for novel cardiovascular risk factors. Future studies should fully consider the possibility that improved outcomes would be achieved at a greater cost; thus, cost-effectiveness studies are essential for understanding the economic aspects of implementation. The goal of an ideal clinical trial would be ESRD prevention; however, pragmatic objectives such as a greater understanding of therapeutic toxicities should also be explored in this population.

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.

Hypertension in patients with diabetes. Strategies for drug therapy to reduce complications

Hypertension in diabetic patients must be treated aggressively if patients are to benefit from reduced risk of morbidity and mortality. Diabetes itself must be diagnosed promptly, particularly in at-risk patients, so appropriate lifestyle modifications can be made at the earliest opportunity. Although this may reduce or delay onset of hypertension, antihypertensive drug treatment should be initiated in the diabetic patient with even high-normal blood pressure. Traditional approaches to management of hypertension are inappropriate for most patients with diabetes. While ACE inhibitors, calcium antagonists, angiotensin II receptor blockers, beta blockers, and low-dose diuretics, alone or in combination, all currently have roles in hypertension management, the outcomes of studies now under way may clarify some still unanswered questions about the dangerous combination of high blood pressure and diabetes.

Hypertension in patients with diabetes. Why is aggressive treatment essential?

Hypertension and diabetes are interrelated diseases. Alone, each condition is a risk factor for cardiovascular disease and, together, they strongly predispose to end-stage renal disease, coronary artery disease, and peripheral vascular and cerebrovascular disease. Pharmacologic treatment of hypertension can substantially reduce morbidity and mortality in diabetic patients with hypertension, but adequate control of blood pressure is seldom achieved in a clinical setting. More aggressive treatment is needed to improve the prognosis for this over-expanding patient population.

Imidapril, an angiotensin-converting enzyme inhibitor, improves insulin sensitivity by enhancing signal transduction via insulin receptor substrate proteins and improving vascular resistance in the Zucker fatty rat

Angiotensin-converting enzyme (ACE) inhibitors are antihypertensive agents, that inhibit the conversion of angiotensin I to angiotensin II, resulting in smooth-muscle relaxation and a reduction of vascular resistance. Recently, it has been suggested that ACE inhibitors improve insulin resistance in diabetic patients. To investigate the effect of an ACE inhibitor on insulin sensitivity, insulin signaling, and circulation, imidapril was administered orally or intraduodenally to Zucker fatty rats. Oral administration of imidapril improved insulin sensitivity based on the results of an oral glucose tolerance test (OGTT) and a decrease in urinary glucose secretion. Phosphatidylinositol 3-kinase (PI 3-kinase) activity associated with hepatic insulin receptor substrate-1 (IRS-1) in the insulin-stimulated condition was significantly enhanced 110% without a significant alteration in tyrosine phosphorylation of IRS-1 in the imidapril-treated group. In muscle, IRS-1 tyrosine phosphorylation and PI 3-kinase activity associated with IRS-1 in the insulin-stimulated condition were enhanced 70% and 20%, respectively, in the imidapril-treated group. In contrast, an alteration of the IRS-2 pathway was observed only in liver; a significant insulin-induced increase in the IRS-2-associated PI 3-kinase over the basal level was observed in the imidapril-treated group but not in the control. In addition, treatment with imidapril was shown to significantly reduce blood pressure and increase blood flow in the liver and muscle. These results suggest that the ACE inhibitor imidapril may improve insulin sensitivity not only by acting directly on the insulin signaling pathway but also by increasing blood flow in tissues via normalization of vascular resistance, a major cause of hypertension.