Current therapeutic concepts in diabetic hypertension

Cyclosporine pharmacokinetics and effect in the type I diabetic rat model

Recent clinical studies have demonstrated the potential benefit of the T-cell-specific immunosuppressant, cyclosporine, in the treatment of Type I insulin-dependent diabetes. In the present study, steady-state cyclosporine pharmacokinetics, fasting glucose and insulin levels and renal function were examined in stable insulin-dependent diabetic rats and compared to non-diabetic rats. Mean creatinine clearance 30 days following diabetes induction was not significantly different from saline controls. Cyclosporine treatment (5 mg/kg/day i.v. for 13 days) did not significantly alter creatinine clearance in either group; however, renal function of vehicle-treated diabetic rats was markedly reduced compared to other groups. Serum insulin concentrations were significantly greater in diabetic rats treated with cyclosporine compared to the control group (35.1 +/- 22.7 vs. 16.0 +/- 8.1 microU/ml; P less than 0.05). Glucose levels were proportionately reduced in diabetic rats treated with cyclosporine. Area under the concentration-time curve, half-life and volume of distribution of cyclosporine were significantly reduced in diabetic rats compared to non-diabetic controls. In summary, the pharmacokinetics and pharmacodynamics of cyclosporine were significantly different in the insulin-dependent diabetic rat model compared to normal controls. Furthermore, short-term cyclosporine therapy reduced the extent of experimental diabetic nephropathy observed in this model.

A 1-year follow-up study on the effect of atenolol on serum beta 2-microglobulin level in hypertensive diabetic patients

Hypertensive diabetic patients are particularly prone to renal function impairment. A total of nine out-patients with diabetes and hypertension were, therefore, entered into this single-blind uncontrolled study on the effects of 50 mg/day atenolol on reducing blood pressure and preserving normal kidney functioning. Treatment and evaluations were continued for 12 months. Serum beta 2-microglobulin concentration was used as the index for measuring renal impairment. Atenolol significantly reduced heart rate, systolic and diastolic blood pressure, and serum beta 2-microglobulin concentrations compared with baseline. Plasma glucose and glycosylated haemoglobin levels were unchanged, and blood urea nitrogen levels were increased slightly (non-significant). Serum creatinine showed a tendency (non-significant) to reflect the changes in beta 2-microglobulin concentration. Ways in which atenolol may act to improve kidney functioning are suggested. It is concluded that atenolol is a favourable choice for the treatment of hypertension in diabetic patients with normally functioning kidneys since, even in long-term use, normal renal functioning is preserved.

Effect of nicardipine on insulin secretion, glucose and lipid metabolism in hypertensive, non-insulin dependent diabetics

Certain acute and chronic metabolic effects of nicardipine have been studied in 20 patients with non-insulin dependent diabetes (NIDD). An intravenous glucose tolerance test (i.v. GTT, glucose 0.33 g/kg as a bolus) and the corresponding insulin response were assessed at the end of a 4 week placebo period, after the first dose and on administration for 12 weeks of nicardipine 20 mg t.i.d. The glucose and insulin responses to the i.v.GTT, evaluated as incremental AUCs, did not change significantly (glucose 30.5 mg/dl.90 min on placebo, 33.1 mg/dl.90 min acutely and 31.4 mg/dl.90 min on chronic administration of nicardipine; insulin 2.08 microU/ml.90 min on placebo, 1.87 microU/ml.90 min acutely and 1.93 microU/ml.90 min after chronic nicardipine). Glucose removal rate (KG) following the i.v.GTT was 0.73%/min on placebo 0.75%/min on acute administration and 0.8%.min-1 with chronic nicardipine. Active treatment produced a significant reduction of blood pressure (from 187/96 mm Hg on placebo to 166/89 mm Hg acutely and 152/83 mm Hg after 12 weeks of nicardipine treatment). It is concluded that the calcium antagonist nicardipine was an effective antihypertensive drug, and that it did not cause deterioration of metabolic control in hypertensive patients with NIDD.

Hypertension

The awareness of hypertension as one of the major risk factors for mortality and morbidity in NIDDM has increased greatly in the past few years. It is now accepted practice to measure BP at least yearly in all such patients. Unfortunately, one cannot yet be sure to what extent diabetics benefit from anti-hypertensive therapy, and the simple assumption that treatment of the increased risk reduces that risk must be constantly questioned. No specific data are yet available for NIDDM, though it would be remarkable if the benefits of decreased cerebrovascular mortality and probable reduced total mortality (Sleight, 1987) did not apply to the higher-risk diabetic subject, at least at the higher levels of diastolic pressure (greater than 105 mm Hg). There is, though, no evidence that mortality or morbidity of coronary artery disease, the major killer in NIDDM, is reduced even in non-diabetics and the present author does not consider there to be any evidence suggesting that thresholds for treatment of hypertension in uncomplicated patients with NIDDM should be lower than those for non-diabetics, unless progressive nephropathy is present. Current advice in the non-diabetic is that levels of blood pressure in adults consistently above 95 mm Hg warrant therapy, aiming to reduce it below 90 mm Hg (World Health Organization, 1986). While the importance of hypertension should not be underestimated, it should not deflect attention from the other risk factors. Cessation of smoking, and by implication its reduction, will, for all smoking patients but the most hypertensive, produce a greater reduction in cardiovascular and total mortality risk than will anti-hypertensive therapy. There are also early signs that effective dietary and/or drug treatment of significant hyperlipidaemia lowers cardiovascular mortality. Choice of anti-hypertensive therapy is especially important, not only for efficacy but also for quality of life, in patients who already suffer major restrictions on diet, freedom and life expectancy. While controlled trials in the subject are of immense importance in determining optimum therapy, there is currently no evidence to favour any particular group of drugs, and an individual patient's therapy should be decided on the basis of their own circumstances.