In some cases, initial therapy for high blood pressure should consist of lifestyle modifications, such as losing weight, cutting back on sodium and alcohol consumption, and getting more exercise. One of the most effective lifestyle changes would be to follow the DASH (Dietary Approaches to Stop Hypertension) eating plan, which is a diet low in saturated fat, total fat, and cholesterol that emphasizes fruits, vegetables, and low-fat dairy products. The DASH diet is most effective when combined with a reduction in sodium intake. You can download a copy of “Facts About the DASH Eating Plan” that includes a week’s worth of menus from www.nhlbi.nih.gov/health/public/heart/hbp/dash or call (301) 592-8573 for a free copy.
For treating high blood pressure in people with diabetes — or for treating anyone with diabetes and microalbuminuria or overt nephropathy — specific blood-pressure-lowering drugs called angiotensin-converting enzyme (ACE) inhibitors and angiotensin- II receptor blockers (ARBs) are the drugs of choice. ACE inhibitors include quinapril (Accupril), perindopril (Aceon), ramipril (Altace), captopril (Capoten), benazepril (Lotensin), trandolapril (Mavik), lisinopril (Prinivil, Zestril), and enalapril (Vasotec, Renitec). ARBs include candesartan (Atacand), irbesartan (Avapro), olmesartan (Benicar), losartan (Cozaar), valsartan (Diovan), telmisartan (Micardis), and eprosartan (Teveten). These drugs appear to have a protective effect on kidneys above and beyond blood pressure control.
ACE normally converts a hormone called angiotensin I to a related hormone called angiotensin II, which constricts blood vessels, increases sodium and water retention, activates the sympathetic nervous system, stimulates fibrosis (stiffening) of the heart and blood vessels, and promotes heart cell growth. The immediate net effect of these changes is to raise blood pressure, but over time this hormone can cause damage to the heart and kidneys. ACE inhibitors block the action of ACE, thus decreasing the amount of angiotensin II and in turn minimizing its effects.
ARBs also work to decrease the effects of angiotensin II, but at a different point in the process. For angiotensin II to exert its effects throughout the body, it must bind to certain receptors (much as a key fits into a lock) on cell surfaces. ARBs prevent angiotensin II from binding to its receptors and thus reduce its effects.
Large numbers of studies have shown that in people with diabetes, ACE inhibitors can have a number of beneficial effects, including preventing or delaying the progression of nephropathy in people with microalbuminuria or overt diabetic nephropathy, decreasing the risk of heart attack and stroke, and decreasing mortality, so people with diabetes and hypertension are routinely prescribed ACE inhibitors.
Like ACE inhibitors, ARBs decrease levels of albumin in the urine and have been shown to effectively prevent progression of nephropathy in people with microalbuminuria or overt diabetic nephropathy. If an ACE inhibitor or ARB used alone is not sufficient to lower blood pressure, other blood-pressure-lowering drugs such as diuretics may need to be added; ACE inhibitors and ARBs can even be used together. (Read “Analgesics and Kidney Health” for information on how various over-the-counter medicines affect the kidneys.)
The effectiveness of dietary protein restriction in protecting the kidneys remains somewhat controversial. Dietary protein restriction has been shown to slow the progression of kidney disease in some animal models. Small clinical studies in people with diabetic kidney disease have shown that people who were able to restrict their dietary protein to 0.8 grams per kilogram of body weight per day (which is actually also the Recommended Dietary Allowance of protein for adults) were able to modestly slow the rate of fall in GFR. That level of protein consumption works out to about 54 grams of protein per day for a person weighing 150 pounds.