Glucose intolerance with hypokalemia: an increased proportion of circulating proinsulin-like component

Recovery from diabetes mellitus in primary aldosteronism patients after adrenalectomy

BACKGROUND

The prevalence of diabetes mellitus (DM) was higher in primary aldosteronism (PA) patients. We aimed to evaluate the outcome of DM after adrenalectomy and determine the factors associated with that in PA patients.

METHODS

PA patients with DM (PA + DM patients) who received adrenalectomy were recruited into the study. The patients were classified into 3 groups based on their DM conditions after treatment, including "remission", "improved" and "unchanged" groups. Univariate and multivariate logistic regression analysis was conducted to uncover the preoperative factors affecting the outcome of DM after adrenalectomy.

RESULTS

A total of 54 PA + DM patients received adrenalectomy. After adrenalectomy, 16.7%, 33.3% and 50.0% of patients were classified into the "remission", "improved" and "unchanged" groups, respectively. The factors negatively associated with remission or improvement from DM after adrenalectomy were longer duration of hypertension (P = 0.029). Higher concentration of urinary magnesium (P = 0.031) and higher 24 h urinary potassium (P = 0.049) were factors negatively associated with the "remission" from DM after adrenalectomy.

CONCLUSIONS

Adrenalectomy was beneficial for the remission and improvement from DM in the half of PA patients with DM. Longer duration of hypertension, higher concentration of urinary magnesium and higher 24 h urinary potassium may prevent the remission and improvement from DM after adrenalectomy in PA patients. Examination of urinary electrolyte could be considered in PA patients with DM for predicting the outcome of DM after adrenalectomy.

Effects of potassium supplements on glucose metabolism in African Americans with prediabetes: a pilot trial

Background: Low potassium has been identified both as a risk factor for type 2 diabetes and as a mediator of the racial disparity in diabetes risk. Low potassium could be a potentially modifiable risk factor, particularly for African Americans.Objective: We sought to determine the effects of potassium chloride (KCl) supplements, at a commonly prescribed dose, on measures of potassium and glucose metabolism.Design: Among African-American adults with prediabetes, we conducted a double-blinded pilot randomized controlled trial that compared the effects of 40 mEq K/d as KCl supplements with a matching placebo, taken for 3 mo, on measures of potassium and glucose metabolism, with measures collected from frequently sampled oral-glucose-tolerance tests (OGTTs).Results: Twenty-seven of 29 recruited participants completed the trial. Participants had high adherence to the study medication (92% by pill count). Participants in both groups gained weight, with an overall mean ± SD weight gain of 1.24 ± 2.03 kg. In comparison with participants who received placebo, urine potassium but not serum potassium increased significantly among participants randomly assigned to receive KCl (P = 0.005 and 0.258, respectively). At the end of the study, participants taking KCl had stable or improved fasting glucose, with a mean ± SD change in fasting glucose of -1.1 ± 8.4 mg/dL compared with an increase of 6.1 ± 7.6 mg/dL in those who received placebo (P = 0.03 for comparison between arms). There were no significant differences in glucose or insulin measures during the OGTT between the 2 groups, but there was a trend for improved insulin sensitivity in potassium-treated participants.Conclusions: In this pilot trial, KCl at a dose of 40 mEq/d did not increase serum potassium significantly. However, despite weight gain, KCl prevented worsening of fasting glucose. Further studies in larger sample sizes, as well as with interventions to increase serum potassium more than was achieved with our intervention, are indicated to definitively test this potentially safe and inexpensive approach to reducing diabetes risk. This trial was registered at clinicaltrials.gov as NCT02236598.

Influence of West African Ethnicity and Gender on Beta-Cell Function and Insulin Sensitivity in Essential Hypertensives Treated with Hydrochlorothiazide and Hydrochlorothiazide-lisinopril Combination

OBJECTIVE

To assess the effects of hydrochlorothiazide (HCT) given alone and in combination with an angiotensin-converting enzyme inhibitor (ACEI) on beta-cell function in a negroid population to further explore possible ethnic differences in the effect of antihypertensive drugs on homeostasis model assessment - insulin resistance (HOMA-IR).

MATERIALS AND METHODS

A total of 80 newly diagnosed Nigerian essential hypertensive patients were assigned to receive either HCT 25 mg daily or both HCT and lisinopril (Lis; 25/10 mg daily) in an open-label study for 12 weeks. The treatment groups were well matched in clinical and demographic baseline features. Changes in HOMA-IR from baseline to end of study (week 12), fasting plasma glucose (FPG), serum potassium, serum insulin, and blood pressure over the same period were also evaluated.

RESULTS

After 12 weeks, mean delta HOMA-IR (and %) was higher in the HCT monotherapy group; although, this change did not reach statistical significance in both groups -0.1 ± 7.1, P = 0.538 (HCT) and 0.6 ± 4.2 P = 0.913 (HCT + Lis); an insignificant increase was observed in FPG and serum insulin in both groups, whereas serum potassium decreased in similar fashion. Blood pressure reduction was similar in both groups. Analysis of HOMA-IR change according to gender in response to HCT mono- or combination therapy with Lis showed no significant difference.

CONCLUSIONS

HCT monotherapy in hypertensive indigenous Nigerians, was not associated with worse metabolic effects when compared with combination therapy using Lis, an ACEI after 12 weeks. Low-dose thiazide diuretic as first-line antihypertensive medication may be safe in the short-term, further larger and long-term studies are needed to corroborate this finding.

The McKittrick-Wheelock syndrome: a rare cause of curable diabetes

McKittrick-Wheelock syndrome (MWS) is a rare consequence of severe dehydration and electrolyte depletion due to mucinous diarrhoea secondary to a rectosigmoid villous adenoma. Reported cases of MWS commonly describe hypersecretion of mucinous diarrhoea in association with dehydration, hypokalaemia, hyponatraemia, hypochloraemia and pre-renal azotemia. Hyperglycaemia and diabetes are rarely reported manifestations of MWS. Herein we describe the case of a 59-year-old woman who presented with new-onset diabetes and severe electrolyte derangement due to a giant rectal villous adenoma. Subsequent endoscopic resection of the tumour cured her diabetes and normalised electrolytes. This case describes a rare cause of 'curable diabetes' and indicates hyperaldosteronism and/or whole-body potassium stores as important regulators of insulin secretion and glucose homeostasis.

LEARNING POINTS

McKittrick-Wheelock syndrome (MWS) is typically characterised by the triad of pre-renal failure, electrolyte derangement and chronic diarrhoea resulting from a secretory colonic neoplasm.Hyperglycaemia and new-onset diabetes are rare clinical manifestations of MWS.Hyperaldosteronism and/or hypokalaemia may worsen glucose tolerance in MWS.Aggressive replacement of fluid and electrolytes is the mainstay of acute management, with definitive treatment and complete reversal of the metabolic abnormalities being achieved by endoscopic or surgical resection of the neoplasm.

Abnormal glucose metabolism and insulin sensitivity in Chinese patients with Gitelman syndrome

BACKGROUND

Gitelman syndrome (GS) is an autosomal recessive disease of renal tubulopathy, primarily characterized by hypokalemic metabolic alkalosis with significant hypomagnesemia, low urinary calcium, secondary aldosteronism and normal blood pressure. Both hypokalemia and hypomagnesemia were reported to cause impaired glucose tolerance and/or insulin resistance, but it is unclear whether impaired glucose tolerance and/or insulin resistance are common in GS patients.

METHODS

An oral glucose tolerance test was performed among 16 GS patients and 12 healthy adults as control subjects. Fasting glucose and serum insulin levels were measured and the values of glucose and serum insulin after 30, 60, 120 and 180 min were also measured after an oral glucose load. The area under curve (AUC) of glucose and insulin was calculated.

RESULTS

One patient had isolated impaired fasting glucose, 2 had isolated impaired glucose tolerance, and 1 had combined impaired fasting glucose and glucose tolerance. Six patients were diagnosed with type 2 diabetes mellitus. Compared with a healthy normal control group, GS patients showed a higher AUC glucose level [16.1 (IQR 12.5-25.4 mEq · h/l) vs. 13.0 (IQR 11.9-13.7 mEq · h/l); p < 0.05] and AUC insulin level [81.0 (IQR 58.9-138 µU · h/ml) vs. 46.4 (IQR 35.6-63.3 µU · h/ml); p < 0.01]. GS patients showed a delay of insulin secretion peak which was observed 120 min after a glucose load. Homeostasis model assessment of insulin resistance in GS patients was significantly higher than in control volunteers. Quantitative insulin sensitivity check index and insulin sensitivity index composite in the GS group were significantly lower than in the control group.

CONCLUSION

Abnormal glucose metabolism and insulin secretion is common in GS patients. It is speculated that hypokalemia and hypomagnesemia may be the main cause.

Renin-angiotensin system polymorphisms and the association between use of angiotensin II receptor blockers or angiotensin-converting enzyme inhibitors and the risk of diabetes

Introduction. We assessed the influence of genetic polymorphisms in the renin-angiotensin system on the risk of diabetes associated with the use of angiotensin II receptor blockers and angiotensin-converting enzyme (ACE) inhibitors.

Materials and methods. We performed a matched case-control study among antihypertensive drug users. Pharmacy records and questionnaires were used to ascertain incident diabetes (cases), antihypertensive drug use, and risk factors. Controls did not (yet) have diabetes.We genotyped ACE (G4656C, which is in complete linkage disequilibrium with the ACE insertion/deletion polymorphism), angiotensinogen (M235T), and angiotensin II type 1 receptor (A1166C).

Results. Among 495 cases of incident diabetes and 2,624 controls, homozygous 1166C carriers of angiotensin II type 1 receptor who used angiotensin II receptor blockers had an increased risk of diabetes compared to 1166A carriers (interaction odds ratio 5.3 [95% confidence interval: 1.8-16.1]). Homozygous ACE GG subjects who used ACE inhibitors ≥ 1 defined daily dose/day had a higher risk of diabetes compared to subjects with the ACE C allele (interaction odds ratio 2.3 [95% confidence interval: 1.2-4.5]).

Conclusions. Angiotensin II receptor blockers increase the occurrence of diabetes in homozygous 1166C carriers of angiotensin II type 1 receptor, but not in 1166A carriers. ACE inhibitors at doses ≥ 1 defined daily dose/day increase the risk of diabetes among homozygous ACE GG carriers, but not in 4656C carriers.

Variation in Renin-Angiotensin system and salt-sensitivity genes and the risk of diabetes mellitus associated with the use of thiazide diuretics

BACKGROUND

Variation in the renin-angiotensin system (RAS) and salt-sensitivity genes may influence the effect of thiazides on the risk of diabetes. We assessed whether polymorphisms in RAS and salt-sensitivity genes influenced the risk of diabetes associated with thiazides.

METHODS

Nested case-control study was conducted among antihypertensive drug users. Pharmacy records and questionnaires were used to assess new onset diabetes (cases), to ascertain antihypertensive use and risk factors for diabetes. Cases were matched to controls (up to five) who were not (yet) diagnosed with diabetes mellitus. We genotyped angiotensin-converting enzyme (ACE) (G4656C), angiotensinogen (AGT) (M235T), angiotensin II type 1 receptor, (AGTR1) (A1166C), adducin 1 (alpha) (ADD1) (G460T), guanine nucleotide binding protein (G protein), beta-polypeptide 3 (GNB3) (C825T).

RESULTS

Among 497 incident cases of type 2 diabetes and 2,633 controls, AGTR1 CC genotype carriers had no increased risk of diabetes due to thiazides (odds ratio (OR) 0.63 (95% confidence interval (CI): 0.28-1.40)) compared to AGTR1 1166A allele carriers (OR 1.79 (95% CI: 1.43-2.23)) receiving thiazides (synergy index (SI) for interaction 0.32 (95% CI: 0.15-0.68)). Although homozygous ACE GG subjects and ACE C allele carriers both had an increased risk of diabetes associated with thiazide use, this risk was more increased for ACE GG subjects (SI 1.70 (95% CI: 1.08-2.66)), particularly at doses > or =1 daily defined dose (DDD) (=25 mg hydrochlorothiazide)/day (SI 2.0 (95% CI: 1.20-3.32)). Among GNB3 T allele carriers, the risk of diabetes due to thiazide use was less increased than among homozygous GNB3 CC subjects (SI 0.62 (95% CI: 0.41-0.93)).

CONCLUSION

The risk of diabetes due to thiazide use was not increased among AGTR1 1166 CC homozygous subjects and less increased among GNB3 T allele carriers. The ACE 4656 GG genotype enhanced the risk of diabetes due to thiazides.

Insulin secretion in alcoholics in a withdrawal state

Insulin secretion was studied after stimulation with oral glucose and intravenous glucagon in 23 chronic alcoholics in a withdrawal state. Each subject was studied twice at one week's interval between the examinations. The insulin and C-peptide responses to glucagon were lower in the early withdrawal state. Moreover, the insulin and C-peptide increments were, when related to the magnitude of the glycemic stimulus, lower in the early than in the late withdrawal state. The fasting values of blood glucose, insulin and C-peptide and the blood glucose and C-peptide levels after oral glucose were higher in the early withdrawal state. These findings indicate that glucose metabolism in alcoholics in a withdrawal state can be disturbed by impaired insulin secretion and insulin resistance.

Potassium-sparing diuretics

The hemodynamic and the endocrine disturbances in congestive heart failure (CHF) impose major changes in electrolyte balance with a retention of sodium and concomitant losses of potassium and magnesium from the body. These changes are of great importance for the development of cardiac dysrhythmias, a diminished glucose tolerance and for the well-being of the patient. The use of conventional diuretics imposes further burdens on the already deranged electrolyte balance. On long-term therapy with conventional diuretics in CHF we observed that approximately 50% of the 297 patients studied had potassium and magnesium deficiencies and an increased sodium content as judged by skeletal muscle biopsies. The magnesium deficiency is especially dangerous since it prevents the cells from keeping their high intracellular potassium concentration unchanged. Potassium substitution is without effect in a magnesium deficiency since magnesium is necessary for the transportation of potassium over the cell membrane against the concentration gradient. In case of magnesium depletion, potassium substitution may even have negative effects on the body potassium content. The reason for this is probably the increase of p-potassium concentration induced by the substitution, leading to an increase of aldosterone secretion. An increase of p-potassium levels by 0.2-0.4 mmol/l may thus result in a 50-100% rise in p-aldosterone concentration. These changes promote further urinary losses of potassium and magnesium. Several studies have demonstrated the positive effects of the potassium-sparing diuretics amiloride, spironolactone and triamterene on p-potassium concentration, but also on the body potassium content.(ABSTRACT TRUNCATED AT 250 WORDS)

Risk factor assessment for new onset diabetes: literature review

Metabolic syndrome (MS), typified by hypertension, abdominal obesity, dyslipidaemia and impaired glucose metabolism, is a precursor of type 2 diabetes. Thiazide diuretics (TD) and beta-blockers are associated with increased risk of diabetes in patients with hypertension; however, the role of these agents in development of diabetes in MS patients is unknown. We reviewed the literature regarding risk factors for diabetes development and compared this with data from the Study of Trandolapril/Verapamil SR And Insulin Resistance (STAR), which investigated the effects of two fixed-dose combinations (FDCs) [trandolapril/verapamil SR and losartan/hydrochlorothiazide (L/H)] on glucose control and new diabetes in MS patients. In STAR, logistic regression modelling identified haemoglobin A1c [odds ratio (OR) 4.21 per 1% increment; p = 0.003), L/H treatment (OR 4.04; p = 0.002) and 2-h oral glucose tolerance test glucose levels (OR 1.39 per 10 mg/dl increments; p < 0.001) as baseline predictors of diabetes. These data support prior analyses and suggest that choice of antihypertensive agent is important. Patients with MS may be at lower risk of diabetes when using a FDC calcium channel blocker + angiotensin-converting enzyme inhibitor compared with an angiotensin receptor blocker + TD.

Bartter's syndrome with type 2 diabetes mellitus

We report a rare case of Bartter's syndrome in a 35-year-old woman with type 2 diabetes mellitus. The patient presented with leg weakness, fatigue, polyuria and polydipsia. Hypokalemia, metabolic alkalosis, and high renin and aldosterone concentrations were present, but the patient was normotensive. Gitelman's syndrome was excluded because of the presence of hypercalciuria, secondary hyperparathyroidism and bilateral nephrocalcinosis. The patients condition improved upon administration of a prostaglandin synthetase inhibitor (acemetacin), oral potassium chloride and potassium-sparing diuretics. Five months later, the patient discontinued acemetacin because of epigastric discomfort; at the same time, severe hypokalemia and hyperglycemia developed. Glucagon stimulation and water deprivation tests were performed. Type 2 diabetes mellitus with nephrogenic diabetes insipidus was diagnosed. To avoid further gastrointestinal complications, the patient was treated with celecoxib, a selective cyclooxygenase 2 inhibitor. This case serves as a reminder that Bartter's syndrome is associated with various metabolic derangements including nephrogenic diabetes insipidus, nephrocalcinosis and diabetes mellitus. When treating Bartter's syndrome, it is also prudent to remember that the long-term use of nonsteroidal anti-inflammatory drugs and potassium-sparing diuretics may result in serious adverse reactions.

Abdominal obesity is associated with potassium depletion and changes in glucose homeostasis during diuretic therapy

The activation of the renin-angiotensin system (RAS) is an important mechanism that contributes to hypertension in obese individuals. Thiazide diuretics also activate the RAS in response to volume contraction and can lead to a decrease in serum potassium values and glucose metabolism abnormalities. To evaluate the impact of abdominal obesity on potassium depletion and glucose homeostasis in hypertensive patients receiving thiazide therapy, the authors studied 329 hypertensive patients without known diabetes or impaired renal function. Patients were stratified into 2 major groups according to whether they used thiazide diuretic therapy, and each group was further divided in 2 subgroups according to the presence of abdominal obesity. The authors demonstrated that obese patients receiving diuretic therapy had lower plasma potassium levels and higher glucose values compared with nonobese patients receiving diuretic therapy. In conclusion, abdominal obesity predisposes to potassium depletion during diuretic therapy in association with effects on glucose homeostasis.

Treating hypertension while protecting the vulnerable islet in the cardiometabolic syndrome

Hypertension, a multifactorial-polygenic disease, interacts with multiple environmental stressors and results in functional and structural changes in numerous end organs, including the cardiovascular system. This can result in coronary heart disease, stroke, peripheral vascular disease, congestive heart failure, end-stage renal disease, insulin resistance, and damage to the pancreatic islet. Hypertension is the most important modifiable risk factor for major health problems encountered in clinical practice. Whereas hypertension was once thought to be a medical condition based on discrete blood pressure readings, a new concept has emerged defining hypertension as part of a complex and progressive metabolic and cardiovascular disease, an important part of a cardiometabolic syndrome. The central role of insulin resistance, oxidative stress, endothelial dysfunction, metabolic signaling defects within tissues, and the role of enhanced tissue renin-angiotensin-aldosterone system activity as it relates to hypertension and type 2 diabetes mellitus are emphasized. Additionally, this review focuses on the effect of hypertension on functional and structural changes associated with the vulnerable pancreatic islet. Various classes of antihypertensive drugs are reviewed, especially their roles in delaying or preventing damage to the vulnerable pancreatic islet, and thus delaying the development of type 2 diabetes mellitus.

Is routine electrolyte testing necessary for diabetic patients who present to the emergency department with moderate hyperglycemia?

OBJECTIVES

No consensus standard is established for the workup of diabetic patients with moderate hyperglycemia [fingerstick glucose of 11.00-33.00 mmol/l (200-600 mg/dl)]. We measured the incidence of serious electrolyte abnormalities in patients with moderate hyperglycemia and attempted to identify a subset of these patients who can safely forego routine electrolyte testing.

METHODS

Prospective cohort study in two affiliated emergency departments.

INCLUSION CRITERIA

Moderate hyperglycemia.

EXCLUSION CRITERIA

new onset diabetes or renal failure. The composite outcome was defined as an abnormal potassium K >5.00 or <3.50 mmol/l or diabetic ketoacidosis. Univariate analyses were performed using t-test and Fisher's exact test (alpha=0.05, two-tails). Logistic regression models were generated to identify variables that could predict the composite outcome.

RESULTS

Three hundred and ninety-nine adults were enrolled (294 type II, 38% men). Mean age was 59+/-15 (20-97 years) years. The incidence of the composite outcome was 22% (95% confidence interval, 17.8-26.0%, n=86). The univariate analysis identified potassium-altering medications and insulin use as risk factors for the composite outcome. Logistic regression analysis identified potassium-altering medications as an increased risk (relative risk: 1.64, 95% confidence interval, 1.14-2.37) and use of oral hypoglycemics as a decreased risk (relative risk: 0.62, 95% confidence interval, 0.43-0.90) of the composite outcome. Cross-validation of the model demonstrated poor sensitivity (76%) and even worse accuracy (51%).

CONCLUSION

We failed to identify any subgroup of patients with moderate hyperglycemia who can be safely excluded from routine electrolyte testing. We recommend routine electrolyte testing for all moderate hyperglycemia patients in the emergency department.

Thiazide diuretics, potassium, and the development of diabetes: a quantitative review

National guidelines and a recent clinical trial have supported the use of thiazide diuretics as the preferred initial pharmacological treatment for hypertension. However, evidence from this and other clinical trials have also found an increased incidence of new onset diabetes among those patients receiving thiazide diuretics. The mechanisms responsible for the increased incidence of diabetes with thiazide diuretics have not been fully elucidated. This article provides a review of intervention studies that included data on the relation between thiazide-induced hypokalemia and glucose intolerance. We conducted a literature search from 1966 to June 2004 to identify clinical trials using thiazide diuretics where the metabolic effects on potassium and glucose are reported. A total of 59 clinical trials constituting 83 thiazide diuretic study arms were identified. Trial size, length, type of thiazide diuretic, and dose varied substantially among the studies. The association between average changes in potassium and glucose in the study arms is considered jointly in a weighted statistical model. The Pearson's correlation coefficient, weighted by study sample size, for the relationship between glucose and potassium was -0.54 (95% CI, -0.67 to -0.36; P < 0.01). A sensitivity analysis, which considered subset analyses and effect of covariates, as well as inverse-variance weighting, supported this finding. These data suggest that thiazide-induced hypokalemia is associated with increased blood glucose. Treatment of thiazide-induced hypokalemia may reverse glucose intolerance and possibly prevent the future development of diabetes.

Effect of antihypertensive agents on the development of type 2 diabetes mellitus

People with hypertension have a high prevalence of insulin resistance and are at relatively high risk of developing type 2 diabetes mellitus. It is becoming increasingly evident that antihypertensive agents have disparate metabolic effects. For example, recent clinical trials indicate that agents that interrupt the renin-angiotensin axis reduce the risk of developing diabetes compared with other classes of antihypertensive agents. Blockade of the effects of angiotensin II might improve blood flow to insulin-sensitive tissues. Furthermore, interruption of the renin-angiotensin system might provide metabolic benefit through such mechanisms as reduced oxidative stress and restored nitric oxide production, which could lead to improved insulin signaling. Alternatively, collective trials suggest that both diuretics and beta-blockers accelerate the appearance of new-onset type 2 diabetes mellitus in patients with hypertension. Therefore, the risk of new-onset diabetes-associated cardiovascular risks should be factored into future treatment recommendations for patients who require antihypertensive therapy. This will become even more important as the number of insulin-resistant patients with hypertension increases in parallel with the steady growth in the number of sedentary, obese, and aged persons in our population.

Antihypertensive drugs and incidence of type 2 diabetes: Evidence and implications for clinical practice

The major antihypertensive drug classes appear to exert differing effects on glycemic control and diabetes incidence. Thiazide diuretic and beta-blockers are potentially diabetogenic, whereas calcium channel blockers appear neutral. Inhibitors of the renin-angiotensin system are associated with improvements in glycemic control and may lower diabetes incidence, but it is not clear if this represents a truly preventive effect. Also, it should be noted that previous studies have reported inconsistent results, and the data to date are not definitive. We suggest that inhibitors of the renin-angiotensin system be used as first-line agents in uncomplicated hypertensive patients who are at high risk for developing type 2 diabetes. Thiazides and beta-blockers should not be avoided in patients with compelling indications for these drugs. Many hypertensive patients (particularly those who are obese or have prediabetes) require several agents to achieve target blood pressure levels. Therefore, the choice of initial agent is far less important than ensuring that target blood pressure goals are reached.

Antihypertensive therapy and incidence of type 2 diabetes: a systematic review

OBJECTIVE

To systematically review the available evidence examining the effects of the major antihypertensive drug classes on the incidence of type 2 diabetes.

RESEARCH DESIGN AND METHODS

The Cochrane Controlled Trials Register, Medline, and Embase were searched for English-language case-control, cohort, and randomized controlled trials involving the major antihypertensive classes and reporting type 2 diabetes as an end point. Reference lists of original studies and narrative reviews were also hand searched. One reviewer (R.P.) performed the electronic searches. Both reviewers independently extracted data and assessed all potentially relevant studies for inclusion and methodological quality. Abstracts were not included, and unpublished studies were not sought.

RESULTS

One case-control study, 8 cohort studies, and 14 randomized controlled trials met inclusion criteria. No study examined diabetes incidence as a primary end point. Poor methodological quality limits the conclusions that can be drawn from most nonrandomized trials. Evidence from randomized studies is also potentially limited by several sources of bias, including treatment contamination and bias inherent in post hoc analyses. Data from the highest-quality studies suggest that diabetes incidence is unchanged or increased by thiazide diuretics and beta-blockers and unchanged or decreased by ACE inhibitors, calcium channel blockers, and angiotensin receptor blockers.

CONCLUSIONS

The major antihypertensive classes may exert differential effects on diabetes incidence, although current data are far from conclusive. Ongoing placebo-controlled randomized trials involving potentially beneficial drug classes and examining diabetes incidence as a primary end point should provide more definitive evidence.

Circulating proinsulin-like molecules

An improved understanding of the characteristics of proinsulin and its intermediate conversion products has resulted from the use of novel assays for distinguishing these molecules from insulin. Use of such assays may help clarify the role of insulin deficiency in non-insulin-dependent diabetes mellitus (NIDDM). Levels of proinsulin-like molecules are elevated in subjects who have NIDDM or impaired glucose tolerance. However, the observation that hyperproinsulinemia may occur in individuals without hyperglycemia suggests that elevated proinsulin levels may be a manifestation of beta-cell dysfunction rather than of increased demand on the beta cell. Although the metabolic effects of proinsulin-like molecules have yet to be elucidated, some studies indicate that the effect of these molecules on hepatocytes is greater than that on other insulin-sensitive cells. A potential therapeutic role of proinsulin in NIDDM thus has been envisioned, in that suppression of hepatic glucose output might reduce the risk of hypoglycemia caused by increased peripheral glucose uptake. Clinical study of proinsulin has been discontinued, however, owing to the finding of an association between use of human proinsulin and cardiovascular adverse events in one study. In NIDDM subjects, associations have been reported between elevated des 31,32 proinsulin concentrations and such cardiovascular risk factors as elevated blood pressure, increased serum triglyceride and total cholesterol values, and elevated plasminogen-activator inhibitor levels, suggesting a role of proinsulin in cardiovascular risk. Epidemiologic data, however, indicate that elevated levels of proinsulin-like molecules are related to low birth weight and that low birth weight is associated with increased risk of cardiovascular events, suggesting that inadequate intrauterine nutrition may be the common antecedent of augmented proinsulin levels and cardiovascular risk.

Effects of chronic angiotensin converting enzyme inhibition on glucose tolerance and insulin sensitivity in essential hypertension

The relation between the renin-angiotensin-aldosterone (RAA) system and carbohydrate metabolism and insulin sensitivity in essential hypertension has not been investigated systematically. Twenty nondiabetic patients (age, 49 +/- 1 years; body mass index (BMI), 26.1 +/- 0.4 kg/m2) with essential hypertension (blood pressure, 155 +/- 3/105 +/- 1 mm Hg) received an oral glucose tolerance test (OGTT) at the end of a 1-month placebo period and again monthly during 3 months of angiotensin converting enzyme (ACE) inhibition (cilazapril, 5 mg/day). Furthermore, a two-step euglycemic insulin clamp was performed after placebo and again at the end of treatment. Blood pressure fell by 7 +/- 4/10 +/- 3 mm Hg (p less than 0.001), while BMI remained stable. On the euglycemic clamp, insulin-mediated (plasma insulin, 470 pM) whole body glucose use averaged 42.5 +/- 1.6 mumol.min-1.kg-1 before and 43.6 +/- 1.9 after ACE inhibition (p = NS). Substrate concentrations and oxidative rates and energy expenditure (as estimated by indirect calorimetry) were not altered by ACE inhibition, either in the fasting state or in response to insulin. In contrast, oral glucose tolerance was significantly (p less than 0.05) improved after treatment (area under OGTT curve (AUC), 240 +/- 24 versus 282 +/- 23 mmol 2 hr.l-1). The latter change was associated with enhanced (+16%, p less than 0.05) insulin responsiveness to glucose (estimated as the insulin AUC divided by the glucose AUC) throughout the 3 months of ACE inhibition. At baseline, both the OGTT and the clamp had a marked hypokalemic effect (mean decrements in plasma potassium of 0.75 +/- 0.05 and 0.92 +/- 0.05 mmol/l, respectively) in association with plasma aldosterone reductions of 30% and 50%. Chronic ACE inhibition caused a further 20% (p less than 0.03) lowering of plasma aldosterone concentrations but attenuated insulin-induced hypokalemia. Plasma sodium, which was unaltered by the pretreatment tests, fell during the posttreatment tests (by 3 mmol/l, p less than 0.001). In the urine, the ratio of the fractional excretion of potassium to that of sodium was decreased by both oral glucose (-22%, p less than 0.01) and ACE inhibition (-21%, p less than 0.001). Higher plasma potassium levels before treatment predicted a better blood pressure response to ACE inhibition (r = 0.60, p less than 0.005).(ABSTRACT TRUNCATED AT 400 WORDS)

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.

Effects of dexamethasone on glucose-induced insulin and proinsulin release in low and high insulin responders

We compared the effects of dexamethasone-induced insulin resistance on B-cell secretory performance in 12 low insulin responders (LIR) and in eight high insulin responders (HIR). A hyperglycemic clamp (120 minutes) was performed before and after the subjects had ingested dexamethasone 3 mg x 2 for 2 1/2 days. Fasting levels of blood glucose increased from 4.60 +/- 0.13 to 5.74 +/- 0.23 mmol/L after dexamethasone in LIR and from 4.37 +/- 0.18 to 5.26 +/- 0.13 mmol/L in HIR. Dexamethasone treatment increased fasting levels of total immunoreactive insulin (IRI), C-peptide, and proinsulin, as well as the proinsulin to IRI ratio to a similar degree in LIR and HIR. The amount of glucose infused to uphold hyperglycemia during the clamp decreased by 54% after dexamethasone in LIR and by 46% in HIR. Mean level of stimulated IRI during the clamp increased after dexamethasone by 43% in LIR and by 53% in HIR. Mean level of stimulated C-peptide increased by 11% (not significant) in LIR and by 24% in HIR. Mean level of stimulated proinsulin increased by 86% in LIR and by 93% in HIR. The effects of dexamethasone on insulin secretion varied among individuals, since steroid treatment failed to affect IRI responses to glucose in two LIR and two HIR. The magnitude of dexamethasone effects on secretion was not correlated to pre-dexamethasone insulin sensitivity as assessed by a somatostatin-insulin-glucose infusion test (SIGIT) or by M/I (glucose infused/insulin level) ratios of the control clamp.(ABSTRACT TRUNCATED AT 250 WORDS)

Primary cortisol resistance: a familial syndrome and an animal model

Primary cortisol resistance in man is a familial disease. It is characterized by increased plasma cortisol concentrations, high urinary free cortisol excretion, a normal circadian pattern of cortisol secretion, resistance to adrenal suppression by dexamethasone and absence of clinical stigmata of Cushing's syndrome. In its severe form, hypertension and hypokalemic alkalosis are present, owing to increased secretion of the sodium-retaining corticoids, corticosterone and deoxycorticosterone. In subjects with a less severe resistance to cortisol, there are no clinical abnormalities and the disease is revealed only by detailed examination of several parameters of cortisol metabolism. In the whole-cell assay (peripheral mononuclear leukocytes or fibroblasts) the glucocorticoid receptor shows a low affinity for dexamethasone. The receptor may be unsaturable as suggested by decreased receptor concentrations in broken-cell systems. Thus, generalized target-tissue resistance to cortisol, including the pituitary gland and the hypothalamus, is accompanied by a decreased negative feedback of the cortisol-ACTH feedback system resulting in increased ACTH secretion. This causes higher plasma cortisol to compensate for the end-organ resistance and also increases the production of adrenal mineralocorticoids, as by-products. Thus hypertension and hypokalemic alkalosis depends on the degree of the resistance. Cortisol resistance in many New World primate species is characterized by greatly increased plasma cortisol concentrations, decreased cortisol binding globulin capacity and affinity, high levels of plasma and urinary free cortisol, marked resistance of ACTH suppression by dexamethasone, and no physiologic evidence of glucocorticoid hormone excess. Target tissues have normal concentrations of glucocorticoid receptors with decreased affinity for dexamethasone. The New World primates, unlike man, have compensated for this cortisol resistance with intra-adrenal adaptations over the 50 million years of their evolutionary development. These primates also have abnormalities of other steroid hormone-receptor systems such as progesterone, estrogen, androgen and mineralocorticoid. In contrast, the human syndrome appears to be a recent mutation with pathophysiologic consequences.

Indapamide in the treatment of essential arterial hypertension: results of a controlled study

A double-blind trial was carried out in 24 patients with mild hypertension to compare the efficacy and tolerability of indapamide with that of a standard thiazide diuretic, hydrochlorothiazide. After a 6-week washout period on placebo, patients received either 2.5 mg indapamide or 50 mg hydrochlorothiazide per day for 12 weeks. Blood pressure and pulse rate in the recumbent and upright positions were monitored at regular intervals. Laboratory measurements of plasma electrolytes, other biochemical and haematological parameters were made before and after active treatment. The results showed that indapamide treatment produced a statistically significant reduction from placebo levels in diastolic pressure in both the upright and recumbent positions, whereas the reduction was significant only in the upright diastolic pressure with hydrochlorothiazide. There were no significant changes in pulse rate in either active-treatment period. Both drugs produced small but significant reductions in mean plasma chloride and potassium levels, and there was a significant increase in mean serum uric acid in patients receiving hydrochlorothiazide. None of these changes, however, were of clinical importance and all of the patients completed the study.

Evaluation of three commercially available C-peptide kits

Three commercially available methods for the determination of C-peptide in human serum were evaluated. All kits were found to be acceptable with respect to precision and analytical recovery, while differences were observed with respect to sensitivity and cross-reactivity to human proinsulin. Furthermore an intermethod comparison was performed. It is pointed out that, before C-peptide determination on serum from insulin-treated diabetic subjects, a PEG precipitation, to remove antibody-bound proinsulin, should be done.

Primary cortisol resistance in man. A glucocorticoid receptor-mediated disease

We have studied a man suspected of having primary cortisol resistance on the basis of high 24-h mean plasma cortisol levels (27.4 micrograms/dl) and no stigmata of Cushing's syndrome. His son had slightly elevated 24-h mean plasma cortisol levels (9.9 micrograms/dl; normal 7.52 micrograms/dl). Both had high plasma protein unbound cortisol and increased urinary free cortisol. Plasma ACTH concentration was high, and both were resistant to adrenal suppression by dexamethasone. The father appeared to have mineralocorticoid excess resulting in hypertension, hypokalemia, and metabolic alkalosis. This was found to be due to markedly elevated plasma levels of deoxycorticosterone and corticosterone. The son, who was normotensive, had mildly increased plasma corticosterone and normal deoxycorticosterone levels. To study the apparent end-organ resistance to cortisol, we examined the glucocorticoid receptor in the white cells and fibroblasts of these patients. In both tissues, using both whole cell and cytosol assays, the glucocorticoid receptor was found to have reduced affinity for dexamethasone. In the cytoxol assays, a reduced receptor number was found as well. We conclude that cortisol resistance is a rare familial syndrome owing to an abnormal glucocorticoid receptor with a decreased affinity for cortisol.

Proinsulin and C-peptide in diabetes

The availability of C-peptide measurement continues to provide new and useful information about the state of beta cell secretory function and the natural history of diabetes. Measurement of proinsulin is of value in the diagnosis of insulin-secreting tumors.

Insulin and proinsulin in normal and chemical diabetic children

Plasma levels of total immunoreactive insulin and immunoreactive proinsulin were studied in 10 normal children and 15 children with chemical diabetes ranging in age from 5 to 13 years. Eleven of the children with chemical diabetes demonstrated significantly elevated TIRI during fasting and following glucose administration. There was a delay in the increment of plasma TIRI in four children with chemical diabetes, but otherwise their TIRI levels were normal. In these four children IRP was not significantly different from normal; however, in the remaining children with chemical diabetes, those with elevated TIRI, the IRP was elevated following glucose administration. Although the IRP was significantly elevated in the hyperinsulinemic group, the TIRI was also increased to such an extent that the glucose intolerance demonstrated in these patients could not be attributed to the elevated IRP.