Hypokalemia and diabetes mellitus

Magnesium and potassium supplementation in the prevention of diabetic vascular disease

Vascular disease underlies many of the complications of diabetes and includes coronary, cerebral, renal, peripheral and retinal vascular abnormalities. Magnesium (Mg) and potassium (K) deficiencies occur frequently in diabetic patients. Because of the vasoconstrictive effects of hypomagnesemia and hypokalemia and the adverse effects of Mg and K deficiency on carbohydrate metabolism we hypothesize that routine Mg and K supplementation of all hypomagnesemic diabetics will ameliorate or prevent the ravages of diabetic vascular disease.

Potassium regulates plasma testosterone and renal ornithine decarboxylase in mice

Potassium deficiency produced different effects in the kidney of male or female mice. While in female, potassium deficiency caused a marked renal hypertrophy with no significant changes in testosterone-regulated enzymes, such as ornithine decarboxylase and beta-glucuronidase, in the male the same treatment provoked a marked fall of these enzymes owing to a dramatic decrease in plasma testosterone. Potassium replenishment restored plasma testosterone and renal enzymatic activities. These results show for the first time, that potassium modulates circulating testosterone and suggest that this cation could exert an important regulatory role in controlling androgen actions.

Effects of antihypertensive agents on coronary artery disease risk factors

The adverse effects of certain antihypertensive medications, most notably diuretics and beta blockers, on serum lipids, glucose, and potassium may explain why control of hypertension has not been accompanied by declines in coronary artery disease. Evidence indicates that angiotensin-converting enzyme (ACE) inhibitors, including quinapril, the newest member of this class of drugs, have no deleterious effects on these coronary risk factors. In addition to differences in chemical structure, the unique activity of quinapril at the local tissue level might to some degree explain its comparatively favorable clinical profile. Consequently, ACE inhibiting agents may be better choices for the management of patients with mild-to-moderately elevated blood pressure. However, controlled clinical trials with these drugs are needed to determine their impact on events related to coronary artery disease.

Bartter's syndrome and diabetes mellitus

We here report a case of Bartter's syndrome occurring in association with diabetes mellitus. The patient, an insulin-dependent diabetic, presented with hypokalaemia, inappropriate kaliuresis and metabolic alkalosis. He had high plasma renin activity, relatively low plasma aldosterone, and resistance to infused angiotensin II. A high potassium diet raised total body potassium and serum potassium, did not affect plasma renin activity, but raised plasma aldosterone significantly and did not alter the resistance to angiotensin II. Indomethacin administered acutely reduced urinary potassium and kallikrein excretion and, on chronic administration, lowered plasma renin activity, urinary chloride excretion, and raised serum potassium. Salt restriction resulted in a prompt and significant reduction in urinary sodium and chloride excretion. Urinary kallikrein excretion was very high throughout, increased with sodium restriction, and decreased with sodium loading. Oral potassium supplementation partially corrected the hypokalaemia, but did not affect blood sugar control. In this patient the primary defect appears to have been primary urinary potassium wasting, rather than sodium or chloride wasting. The striking effects of indomethacin suggest that prostaglandins may play a fundamental role in the genesis of the syndrome.

A comparison of the effects of hydrochlorothiazide and captopril on glucose and lipid metabolism in patients with hypertension

It has been suggested that the metabolic side effects of antihypertensive drugs are responsible for their failure to reduce cardiovascular morbidity in patients with hypertension. Therefore, in 50 patients with essential hypertension, we performed a randomized, double-blind, crossover study comparing the effects of carbohydrate and lipid metabolism of captopril (mean [+/- SD] dose, 81 +/- 24 mg per day) and hydrochlorothiazide (40 +/- 12 mg per day) over two four-month treatment periods. Captopril increased the insulin-mediated disposal of glucose, as compared with placebo, from 5.7 +/- 2.4 to 6.3 +/- 2.5 mg per kilogram of body weight per minute (P less than 0.05), whereas hydrochlorothiazide caused a decrease from 6.4 +/- 2.0 to 5.7 +/- 1.9 (P less than 0.01). Captopril had no effect on the basal insulin concentration, but it decreased the late (30- to 90-minute) insulin response to glucose and increased the early (2- to 6-minute) insulin peak. Hydrochlorothiazide increased the basal insulin concentration and the late insulin response to glucose. These findings may be explained by an increase in insulin sensitivity with captopril and a decrease with hydrochlorothiazide. Little or no change was seen in serum lipid or lipoprotein levels during treatment with captopril, whereas hydrochlorothiazide caused significant increases in serum total (5 percent) and low-density lipoprotein (6 percent) cholesterol levels and total (15 percent) and very-low-density lipoprotein (25 percent) triglyceride levels, as compared with placebo (P less than 0.01 for all comparisons). We conclude that hydrochlorothiazide for the treatment of essential hypertension has adverse effects on glucose and lipid metabolism. It is possible, but not proved in this study, that these changes may contribute to the risk for diabetes mellitus and coronary heart disease. In contrast, captopril appears to have beneficial or no effects on glucose and lipid metabolism.

Clinically significant diuretic-induced glucose intolerance

Diuretic-induced glucose intolerance is cited frequently as a problem of only limited clinical significance. In certain populations, such as Mexican-Americans, this effect may be much more dramatic. A 50-year-old obese Mexican-American woman presented with a three-month history of increased thirst and frequent urination. A fasting blood glucose concentration of 365 mg/dL prompted initiation of chlorpropamide therapy. A review of her medical history revealed that a thiazide diuretic was started six months previously. A reduction in thiazide dose and potassium supplementation together with chlorpropamide therapy controlled the patient's blood glucose. Subsequently, all three medications were discontinued, and the patient remained normoglycemic during a full year of follow-up. The temporal relationship between symptomatic diabetes and hydrochlorothiazide therapy incriminates the diuretic as the most probable cause.

Modifications of the pancreatic beta-cell function after lowering their potassium content

beta-cell-rich pancreatic islets from ob/ob-mice were kept for 3 days in a culture medium and analysed for their content of potassium. In a normal ionic milieu intracellular potassium was calculated as 190-260 mM. Whereas this concentration remained essentially unaffected after lowering extracellular K+ to 1.5 mM, further reduction to 0.15 mM depressed islet potassium to 5% or less of its original value. Irrespective of its medium concentration, potassium in the islets increased when glucose was raised from 1 to 20 mM. Depression of the islet potassium was associated with a rise of intracellular calcium. Despite profound depletion of potassium, the beta-cells maintained their insulin content and could still oxidize glucose at a substantial rate. When potassium was suppressed to 25% or less of the original content, the beta-cells responded to glucose with a paradoxical inhibition of insulin release. After 3 days of potassium depletion, exposure to a normal ionic milieu neither restored the intracellular content of potassium nor a stimulated insulin secretory response to glucose.

Diuretic-induced hypokalemia

Diuretic therapy is the most common cause of potassium deficiency. Although the extent of potassium deficiency usually does not exceed 200 or 300 mEq, under appropriate circumstances such modest deficiency may have important consequences. Factors that tend to increase the incidence or severity of potassium deficiency in patients who take diuretics include high salt diets, large urine volumes, metabolic alkalosis, increased aldosterone production, and the simultaneous use of two diuretics that act on different sites in the renal tubule. There are many serious complications of potassium deficiency, including cardiac arrhythmias, muscle weakness, rhabdomyolysis, glucose intolerance, and several complications that result directly from increased ammonia production, such as protein and nitrogen wasting and hepatic coma. Emphasized herein are those conditions that impose potential danger in patients with mild hypokalemia. Important factors that identify specific causes of potassium deficiency and its treatment are discussed briefly.

Elevated hemoglobin A1c and low-density lipoprotein cholesterol levels in thiazide-treated diabetic patients

Despite the well-known hyperglycemic effect of thiazide diuretics, these agents are often administered to diabetic patients. This study compared 89 insulin-treated diabetic patients receiving hydrochlorothiazide, 57 receiving furosemide, and 255 receiving no diuretic. Hemoglobin A1c level was 7.2 +/- 1.8 percent (mean +/- SD) with hydrochlorothiazide, significantly higher than the levels of 5.9 +/- 2.3 percent with furosemide and 6.4 +/- 2.0 percent with no diuretic. Low-density lipoprotein cholesterol level was 154 +/- 43 mg/dl with hydrochlorothiazide, but 134 +/- 42 mg/dl with furosemide and 130 +/- 42 mg/dl with no diuretic. Multivariate analysis showed that the associations remained significant after adjustment for age, sex, race, type and duration of diabetes, body mass index, blood pressure, serum potassium level, insulin dose, and treatment with other medications. These findings suggest that treatment with thiazide diuretics in the diabetic population may increase low-density lipoprotein cholesterol and hemoglobin A1c levels.

Diuretic therapy for mild hypertension: the "real" cost of treatment

The benefit of any medical intervention, particularly drug therapy, must be weighed against its cost. These costs are not only dollar expenditures but effects on lifestyle and overall health. Diuretic therapy for hypertension has been in use long enough to allow long-term clinical evaluation. It is clear from the numerous prospective drug intervention trials involving hypertensive patients that diuretic therapy is not free of "costs." Aside from the fact that 15 to 20% of diuretic-treated patients reportedly drop out of trials because of side effects, including exertional dyspnea, fatigability, lethargy and impotence, numerous metabolic derangements have been reported with these drugs, i.e., potassium, uric acid, lipid, sodium, glucose and magnesium alterations. Perhaps most important are the changes in lipid fractions, which may be responsible for the failure of antihypertensive therapy to decrease the risk of coronary heart disease. Thus, although diuretics are somewhat less expensive than other antihypertensive drugs in terms of dollars, their overall costs are high. The major alternatives, such as the alpha-blocker prazosin or the central nervous system agent clonidine, are preferable, do not impair a patient's lifestyle and are recommended to be used along with changes in diet and an exercise program for control of mild to moderate hypertension.