Chlorpropamide alcohol flushing and diabetic retinopathy

[Fundamental Properties of Aldehyde Dehydrogenase 2 (ALDH2) and the Importance of the ALDH2 Polymorphism]

Human aldehyde dehydrogenase 2 (ALDH2) is a 56 kDa mitochondrial protein that forms homodimers through hydrogen bonding interactions between the Glu487 and Arg475 residues of two ALDH2 proteins. Two ALDH2 homodimers can interact to form an ALDH2 tetramer. ALDH2 is widely distributed throughout the organs of the body. In addition to its dehydrogenase activity, ALDH2 also exhibits esterase and reductase activities, with the main substrates for these three activities being aldehydes, 4-nitrophenyl acetate and nitroglycerin, respectively. ALDH2 can be readily inhibited by a wide variety of endogenous and exogenous chemicals, but the induction or activation of this enzyme remains unlikely. The polymorphism of ALDH2 to the corresponding ALDH2*2 variant results in a severe deficiency in ALDH2 activity, and this particular polymorphism is prevalent among people of Mongoloid descent. It seems reasonable to expect that people with the ALDH2*2 variant would be more vulnerable to stress and diseases because ALDH2 defends the human body against toxic aldehydes. However, it has been suggested that people with the ALDH2*2 variant are protected by alternative stress-defending systems. The ALDH2*2 variant has been reported to be associated with many different kinds of diseases, although the mechanisms underlying these associations have not yet been elucidated. ALDH2 polymorphism has a significant impact on human health; further studies are therefore required to determine the practical implications of this polymorphism in the fields of preventive and clinical medicine.

Facial skin temperature in chlorpropamide alcohol flush

Objective methods to study the chlorpropamide alcohol flush (CPAF) have been inadequate. Determination of blood acetaldehyde has proved to be a promising method, but the analysis is difficult and time-consuming. To measure the facial skin temperature is more handy. The results of these measurements can be presented as delta T (skin temperature increase), %T (per cent of maximum possible temperature rise) or delta MTCI (malar thermal circulation index) after calculations. The baseline skin temperature is accounted for in %T and delta MTCI. Blood acetaldehyde determinations and placebo-alcohol tests can be used to separate the CPAF reaction from alcohol flushing. Single dose CPAF tests including facial skin temperature measurements were performed in 133 type 2 (non-insulin dependent) diabetics. Facial flush was observed in 42.9%. The specificity and sensitivity of all three skin temperature methods were high: 88.2, 85.5, 96.1%, and 89.5, 86.0, 86.0%, respectively. Skin temperature measurement, whether expressed as delta T, %T or delta MTCI, provides a method to study CPAF with high accuracy.

Low risk of coronary heart disease in female type II diabetic subjects with diabetic relatives

Possible risk factors for cardiovascular disease were studied in 52 type II diabetic subjects, 19 with and 33 without a history of coronary heart disease (CHD). None of the recognized risk factors, such as hypertension, hyperlipidaemia, smoking and blood glucose imbalance, could be related to CHD. However, all female patients with CHD were lacking a family history of diabetes, while seven of nine female diabetic subjects without a history of CHD had diabetes in the family (p less than 0.02). This was confirmed in a second study of 150 type II diabetic subjects; CHD was more common among female patients without compared to those with diabetes in the family; 9/38 and 1/28, respectively (p less than 0.03). Diabetes increases the risk of CHD, and it does so for women more than it does for men. The finding of a possible low CHD risk in female diabetic subjects with diabetes in the family supports the hypothesis of genetic factors being important for the pathogenesis of cardiovascular disease in diabetes mellitus.

Characterization of patients with chlorpropamide-alcohol flush

One hundred and sixty patients with onset of non-ketotic diabetes at the ages of 35-70 were investigated for chlorpropamide-alcohol flush (CPAF), beta-cell function, insulin sensitivity, human leucocyte antigens (HLA), organ specific antibodies and diabetic complications. A positive flush reaction was defined as an increase in facial skin temperature by at least 1.5 degrees C, which was associated with a visible flush reaction in all patients. In accordance with these criteria, 38% of the patients were considered CPAF-positive with a mean rise in facial skin temperature of 2.3 +/- 0.1 degrees C compared with 0.6 +/- 0.1 degrees C in the CPAF-negative patients (p less than 0.001). The CPAF-positive patients could be distinguished from the CPAF-negative with respect to: 1) higher frequency of first degree family history of diabetes (p less than 0.05), 2) lower basal and glucagon-stimulated C-peptide concentrations (p less than 0.02 and p less than 0.001), 3) increased frequency of HLA-A2 (p less than 0.01) and decreased frequency of HLA-B7 (p less than 0.01). The findings thus support the genetically determined nature of CPAF. Considering the criteria for maturity onset diabetes in the young, it is unlikely that CPAF acts as a genetic marker for this particular form of genetic diabetes.

Chlorpropamide-alcohol flushing in relation to macroangiopathy and peripheral neuropathy in non-insulin dependent diabetes

Seventy patients with non-insulin dependent diabetes (NIDD) were studied for the chlorpropamide-alcohol flush (CPAF), first degree family history of diabetes, macroangiopathy and for peripheral neuropathy. Positive CPAF challenge tests were found in 65% of the tested subjects and in 77% if there was a family history of diabetes. Signs of macroangiopathy (loss of foot pulses) were significantly (p less than 0.05) less common in the CPAF positive than in the CPAF negative diabetics with a duration of diabetes of ten years or less. With a longer duration this difference between the two groups was reduced. Also signs of peripheral neuropathy (abnormal vibration sense) were less common (p less than 0.05) in the CPAF positive diabetics than in the CPAF negative. Previously a low prevalence of retinopathy in teh CPAF positive non-insulin dependent diabetics has been reported. We have shown that this is also true of peripheral macroangiopathy and peripheral neuropathy. Chlorpropamide-alcohol flushing seems to be related to a relative protection against late complications in diabetes and the test might be used to find patients at risk.

Chlorpropamide-alcohol flushing and blood kinins

In a pilot study six patients with noninsulin dependent diabetes, three positive and three negative to chlorpropamide-alcohol flushing (CPAF), were tested. The patients were tested both without and with chlorpropamide premedication. Blood kinin concentrations were determined before and after ingestion of small quantities of alcohol. No rise in blood kinin concentrations were found during the flush suggesting that kinins do not play a major part in chlorpropamide-alcohol flushing.

Association of aldehyde dehydrogenase with inheritance of NIDDM

To investigate the influence of the mitochondrial aldehyde dehydrogenase 2 (ALDH2) genotype on the clinical features of diabetes, 212 Japanese patients with non-insulin-dependent diabetes mellitus (NIDDM) (154 males and 58 females aged 17-83 years; mean age 58.2 years) were investigated. Genotyping of ALDH2 was performed by the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method. The pattern of inheritance of diabetes and various clinical parameters was compared between active and inactive ALDH2 groups. Of the 212 subjects, 120 had active ALDH2 and 92 had inactive ALDH2. The percentage of patients with a diabetic mother was higher in the inactive ALDH2 group (32.6%) than in the active ALDH2 group (19.2%) (p < 0.05). The prevalence of proliferative retinopathy was lower in the inactive ALDH2 group than in the active ALDH2 group (p < 0.05). However, other clinical parameters showed no difference. We conclude that maternal inheritance of diabetes was common in the inactive ALDH2 group. The finding is suggestive of a relationship between alcohol intolerance and inheritance of diabetes. We speculate that the interaction between mitochondrial DNA and ALDH2 inactivity causes an increase of mitochondrial DNA mutations or deletions, thereby inducing the maternal inheritance of diabetes. The relationship of the ALDH2 genotype with proliferative retinopathy is interesting, because it resembles that of chlorpropamide alcohol flushing with severe diabetic retinopathy. The interaction of aldehyde dehydrogenase isoenzymes might have an aetiological role, since aldehyde dehydrogenase 1 plays an important part in oxidation of retinal to retinoic acid. However, the number of affected patients with proliferative retinopathy was small, hence, our result should be considered as a preliminary finding.

Plasma met-enkephalin in type I diabetes

Physiological and pathological evidence suggests that opioid peptides may play a role in glucose homeostasis. We measured plasma levels of beta-endorphin (beta-END) and met-enkephalin (met-ENK) in 22 type I diabetic patients and 15 healthy women (control group). No differences were observed in plasma beta-END levels, whereas plasma met-ENK levels were significantly higher (Student's t test, P less than .005) in diabetics than in controls before (68 +/- 3 pg/mL v 32 +/- 7 pg/mL) and 1 hour after, a standard meal and administration of insulin therapy (81 +/- 9 pg/mL v 32 +/- 7 pg/mL). This is the first report of met-ENK levels in insulin-dependent diabetes mellitus (IDDM), and an impaired feedback of insulin/met-ENK is suggested.

High levels of circulating met-enkephalin in pregnant and menstruating type 1 diabetic women

Plasma met-enkephalin (MET-ENK) levels are increased in type 1 diabetic women and in pregnant diabetic women in comparison with normal women. Plasma MET-ENK levels further increase in the peripartum period both in diabetic and non-diabetic females, probably due to the analgesic and behavioural properties of the opioid system.

Maturity-onset diabetes of the young (MODY)

This review summarized aspects of the widening scope, phenotypic expression, natural history, recognition, pathogeneses, and heterogenous nature of maturity-onset diabetes of the young (MODY), an autosomal dominant inherited subtype of NIDDM, which can be recognized at a young age. There are differences in metabolic, hormonal, and vascular abnormalities in different ethnic groups and even among Caucasian pedigrees. In MODY patients with low insulin responses, there is a delayed and decreased insulin and C-peptide secretory response to glucose from childhood or adolescence, even before glucose intolerance appears; it may represent the basic genetic defect. The nondiabetic siblings have had normal insulin responses for decades. The fasting hyperglycemia of some MODY has been treated successfully with sulfonylureas for more than 30 years. In a few, after years or decades of diabetes, the insulin and C-peptide responses to glucose are so low that they may resemble those of early Type I diabetes. The rate of progression of the insulin secretory defect over time does distinguish between these two types of diabetes. In contrast are patients from families who have very high insulin responses to glucose despite glucose intolerance and fasting hyperglycemia similar to those seen in patients with low insulin responses. In many of these patients, there is in vivo and in vitro evidence of insulin resistance. Whatever its mechanism, the compensatory insulin responses to nutrients must be insufficient to maintain normal carbohydrate tolerance. This suggests that diabetes occurs only in those patients who have an additional islet cell defect, i.e., insufficient beta cell reserve and secretory capacity. In a few MODY pedigrees with high insulin responses to glucose and lack of evidence of insulin resistance, an insulin is secreted which is a structurally abnormal, mutant insulin molecule that is biologically ineffective. No associations have been found between specific HLA antigens and MODY in Caucasian, black, and Asian pedigrees. Linkage studies of the insulin gene, the insulin receptor gene, the erythrocyte/Hep G2 glucose transporter locus, and the apolipoprotein B locus have shown no association with MODY. Vascular disease may be as prevalent as in conventional NIDDM. Because of autosomal dominant transmission and penetrance at a young age, MODY is a good model for further investigations of etiologic and pathogenetic factors in NIDDM, including the use of genetic linkage strategies to identify diabetogenic genes.

Alcohol and treatment of diabetes

The effects of alcohol on diabetic patients controlled on insulin are reviewed and the associated risks of hypoglycaemia, insulin resistance and ketosis are commented on. The impact of alcohol intake in patients with maturity onset diabetes is also considered and potential interactions with oral hypoglycaemic agents highlighted.

Adverse cardiovascular effects of sulphonylurea drugs. Clinical significance

Sulphonylureas are widely used in the treatment of diabetes mellitus. Since the publication of the University Groups Diabetes Program (UGDP) results the discussion on their possible cardiovascular side effects has been lively and sometimes even passionate. The initial UGDP findings about the adverse effects of tolbutamide on the cardiovascular system have been criticised, particularly for shortcomings in the study design. The results of other epidemiological studies of the sulphonylurea effects on cardiovascular morbidity and mortality published this far have been contradictory. This is understandable because the factors involved are very complex. Most of these studies have used tolbutamide only, and the findings cannot necessarily be directly extrapolated to other sulphonylureas. Only properly performed prospective studies may provide further information on this issue. High concentrations of several sulphonylureas may have inotropic effects on heart muscle in in vitro animal models, but human studies performed in vivo do not support the view of clinically significant inotropy for sulphonylureas. High concentrations of tolbutamide or glibenclamide (glyburide) may affect the myocardial metabolism in isolated organs, but the possible clinical significance of these findings remains unknown. Some epidemiological and experimental studies have associated oral antidiabetic treatment with the occurrence of cardiac arrhythmias or increased digitalis toxicity. Only a few results are available, and there may be differences between the sulphonylureas in this respect. Antiaggregatory properties have been postulated for some sulphonylureas. Gliclazide, in particular, has been studied, but some other compounds of this class have also been effective in short term studies. If confirmed, these effects on haemostasis would be noteworthy. The sulphonylurea effects on serum lipids, especially on HDL-cholesterol, have been discussed widely during the last few years. Decreases in HDL-cholesterol concentrations were suggested to be associated with sulphonylurea therapy. However, these findings were not confirmed in recent cross-sectional and longitudinal studies performed with different sulphonylureas. Chlorpropamide, and to a lesser extent tolbutamide, may cause dilutional hyponatraemia and aggravate existing heart failure. Glibenclamide may increase the clearance of water in the kidney.

The effects of acute and chronic ingestion of ethanol on the autonomic nervous system

Evidence is reviewed linking clinical effects of ethanol with actions on the sympathetic and parasympathetic nervous systems. The studies reported include a series of investigations by the authors. Acutely, ethanol causes peripheral vasodilation and may also result in changes in heart rate and blood pressure. Ethanol may contribute to acute problems which may present clinically, including micturition syncope, accidental hypothermia and facial flushing. However, increased sympathetic nervous activity plays a role in causing hypertension and other symptoms during ethanol withdrawal in chronic alcoholics. Some chronic alcoholics may have neuropathy involving sympathetic nerves, and this can result in distal sweating loss and occasionally in orthostatic hypotension. Also, hypothalamic lesions associated with Wernicke's encephalopathy may result in hypothermia. Neuropathy involving parasympathetic nerves in not uncommon in alcoholics with other evidence of nervous system damage, but it is generally asymptomatic. Occasionally, vagal neuropathy may cause disorder of gastrointestinal motility, and neuropathy affecting the sacral innervation may be a factor in alcoholic impotence.

Genetic and metabolic risk factors for the development of late complications in type I (insulin-dependent) diabetes

The genetic background seems to be involved in the development of type I diabetes and it might also be involved in the development of diabetic complications, but studies carried out so far have yielded conflicting results. The aim of this study was to evaluate the influence of some genetic markers and metabolic factors in the development of late diabetic complications. One hundred and twenty-seven patients (69 males, 58 females) with type I diabetes were evaluated for ABO and Rh blood groups, chlorpropamide alcohol flush (CPAF) and acetylator phenotype (AP) as well as for life-habits (smoking, alcohol use, diet and drug compliance), metabolic indexes (M-value, HbA1, cholesterol and triglyceride levels) and late complications of diabetes [coronary heart disease (CHD), arterial hypertension (AH), retinopathy and nephropathy]. Diabetic patients were more frequently fast acetylators and CPAF positive than controls and CPAF was more frequent among females than among males. None of the genetic markers used in this study appeared as a risk factor for the development of diabetic complications. At multiple logistic analysis different risk factors appeared for each microangiopathic complication. For retinopathy: female sex, duration of disease and triglyceride levels; for nephropathy: male sex, cholesterol levels and hypertension. These risk factors have already been recognized in previous studies, while the genetic markers evaluated in our study do not identify a greater or smaller risk for the development of late complications.

Heterogeneity within type II and MODY diabetes

The heterogeneity within Type II diabetes (NIDDM) and within Maturity-Onset type Diabetes of Young people (MODY), a subset of NIDDM which is inherited in an autosomal dominant fashion, is discussed. Aspects of the definition and phenotypic expression of MODY are reviewed. Within NIDDM there are differences in patterns of inheritance between subgroups. HLA antigen associations are not found in most NIDDM populations but exist in three specific population groups with Type II diabetes. Within NIDDM and within MODY there are differences in the magnitude of insulin responses to glucose, differences in target tissue responsiveness to insulin in vivo, and differences in receptor and post-receptor effects of insulin. Structurally abnormal variant and biologically defective insulin molecules have been found in some Type II diabetic patients and in members of certain MODY families. The presence or absence of obesity may mark heterogeneous groups of Type II diabetic patients, in addition to the importance of obesity in uncovering an insulin secretory defect by causing insulin resistance. There is heterogeneity in susceptibility to vascular disease within NIDDM and MODY. The natural history of carbohydrate metabolism and of insulin secretory responses to glucose in early Type I diabetes and in MODY with low insulin secretory responses are illustrated and similarities and dissimilarities compared and contrasted. Failure to recognize young patients with MODY may contribute to incorrect diagnosis, management, and assignment of prognosis of this form of diabetes in the young by many practicing physicians. The recognition that Type I or insulin-dependent diabetes (IDDM) and Type II or noninsulin-dependent (NIDDM) differ from each other not only phenotypically but also in etiology and pathogenesis led the National Diabetes Data Group (NDDG) to devise the present nomenclature and classification of diabetes mellitus. These were adopted by the World Health Organization. As suggested by the NDDG report, the classification should be reexamined periodically to reflect improved understanding of the disease, to stimulate further research, and to be of help to practicing physicians.

[Facial vasomotor flushing due to alcohol-chlorpropamide. Prevalence in diabetic and non-diabetic patients]

Using a standard test (sherry 40 ml 12 hours and 36 hours after 250 mg chlorpropamide), chlorpropamide-alcohol flush (CPAF) prevalence was 34 p. 100 (19/56) in non insulin-dependent diabetics (NIDD), 10 p. 100 (3/30) in insulin-dependent diabetics and 7 p. 100 (2/27) in controls. Family history of diabetes was not associated with CPAF trait. Conflicting results in the literature might be explained by bias in patients selection or methodology.

Effects of ethanol and acetaldehyde on cultured rabbit aortic myocytes and human platelets in vitro

The recently reported finding that a moderate alcohol consumption may lower the risk of cardiovascular disease prompted a study of the effects of ethanol and acetaldehyde on proliferation, viability and collagen secretion of rabbit aortic myocytes in culture and on the spontaneous efflux reaction of human platelets in vitro. Ethanol had no effects on any of the systems and acetaldehyde did not influence platelets significantly. Fifty mumol 1(-1) acetaldehyde diminished the proliferation and collagen secretion of arterial myocytes by 20% (P less than 0.01) and 100 mumol 1(-1) acetaldehyde by 39% (P less than 0.001) without affecting cell mass or cell death. A metabolic degradation, and some evaporation, of acetaldehyde was taking place and 50 mumol 1(-1) acetaldehyde was halved after approximately 2 h. The more 'physiological' concentration of acetaldehyde (5 mumol 1(-1] influenced cell proliferation significantly (P less than 0.001) if the concentration was restored by 6-h intervals and the incubation time increased from 24 to 48 h. The weak aldehydedehydrogenase inhibitor chlorpropamide did not accentuate the effects of acetaldehyde.

Roles of chlorpropamide, alcohol and acetaldehyde in determining the chlorpropamide-alcohol flush

The value and reproducibility of the chlorpropamide-alcohol flush (CPAF) have been questioned, and objective measures of the test are required. Recording of facial skin temperature, measurement of chlorpropamide, ethanol and acetaldehyde concentrations have been proposed for this purpose. The present study was designed to evaluate the relative contributions of these variables in determining CPAF. Twenty-one Type 2 (non-insulin-dependent) diabetic patients (11 CPAF-positive and 10 CPAF-negative according to previous tests with standard amounts of alcohol and chlorpropamide) were investigated in a random fashion with either chlorpropamide or placebo given on three subsequent evenings before a two-step alcohol challenge with increasing body-weight-matched amounts of alcohol. Higher rises in facial skin temperature and heart rate, higher flush-score and higher acetaldehyde levels resulted from chlorpropamide therapy than followed placebo. After smaller alcohol challenges (with chlorpropamide pretreatment) there were positive intercorrelations between flush-score, rise in facial skin temperature, and plasma concentrations of chlorpropamide and blood acetaldehyde. The increased alcohol dose abolished most of these correlations and a minimum temperature rise of 1.8 degrees C appeared in all but two subjects regardless of previous CPAF classification. During the current experimental conditions, the previously-classified CPAF-positive and CPAF-negative patients did not differ with respect to flush-score, rise in skin temperature, heart rate, blood acetaldehyde or ethanol concentrations, whereas they differed with respect to chlorpropamide concentrations. The present results support the view that CPAF is associated with elevated blood acetaldehyde levels due to inhibition of aldehyde dehydrogenase by chlorpropamide.(ABSTRACT TRUNCATED AT 250 WORDS)

Chlorpropamide-alcohol flush: significance of body weight, sex and serum chlorpropamide level

Chlorpropamide-alcohol flush (CPAF) tests were carried out in 15 male and 15 female Type 2 diabetics. Twelve subjects were CPAF-positive and 18 were -negative. The two groups did not differ in age or duration of diabetes, but the CPAF-positive subjects weighed less (mean difference 13 kg) and had higher plasma chlorpropamide levels. There was a negative correlation between plasma chlorpropamide and body weight, and a positive correlation between plasma chlorpropamide and the increase in facial skin temperature. Females had higher plasma chlorpropamide, a greater skin temperature increase and lower body weight than males; there were 11 females and only 1 male amongst the 12 CPAF-positive subjects. The findings confirm that plasma chlorpropamide is a major determinant of the CPAF reaction and also show that body weight strongly influences the chlorpropamide level and, consequently, the outcome of the CPAF test. The sex difference in body weight probably accounts for most, if not all, of the sex difference in the incidence of the CPAF.

Chlorpropamide-ethanol induced met-enkephalin secretion in dogs: release mechanisms and biochemical characterisation

Circulating met-enkephalin-like immunoreactivity (MLI) rises in man after chlorpropamide and ethanol although the origin and molecular forms of circulating MLI are not well defined. We have studied the response to oral ethanol in conscious and anaesthetised dogs pretreated with chlorpropamide. In conscious dogs MLI rose from a basal level of 29 +/- 7 pg/ml to a peak of 55 +/- 14 pg/ml 10 min after ethanol (P less than 0.001). In anaesthetised animals, following ethanol, plasma MLI rose in caval (35 +/- 6 pg/ml to a peak of 70 +/- 10 pg/ml), in portal (28 +/- 6 pg/ml to 51 +/- 6 pg/ml) and in adrenal blood (897 +/- 316 pg/ml to 1483 +/- 298 pg/ml; P less than 0.001). Biogel P-4 chromatography of caval and portal basal plasma showed 87% of MLI measured coeluted with the synthetic pentapeptide, while chromatography of peak plasma showed that only 65% coeluted with the pentapeptide and the remaining 35% was of larger molecular size. Sephadex G75 chromatography of adrenal vein plasma revealed three peaks of MLI of differing molecular sizes (8 k = 69.7%; 3-5 k = 12.1% and the pentapeptide = 18.2%). Treatment of the column fractions with trypsin and carboxypeptidase B resulted in the generation of new MLI with peaks of approximate molecular sizes 31 k (10.4%), and 18 k (37.1%) in addition to 8 k (40.0%), 3-5 k (5.0%) and the pentapeptide (7.5%). Acetaldehyde involvement in MLI release was investigated. Following acetaldehyde infusion, plasma MLI rose both in caval (35 +/- 9 pg/ml to 86 +/- 8 pg/ml) and adrenal vein (417 +/- 121 pg/ml to 1768 +/- 433 pg/ml) bloods. Thus we have established an animal model which enables further study of the mechanisms of MLI release and characterisation of the molecular forms. The adrenal medulla, unlike the gut, may be an important source of circulating met-enkephalin and acetaldehyde formation an essential intrinsic component of chlorpropamide-ethanol induced met-enkephalin release.

Glomerular manifestations of diabetes in the BB rat

Morphologic characteristics of the renal glomeruli and tubules of BB rats with spontaneous diabetes mellitus were studied at 30 weeks' duration of diabetes. Whereas the glomerular basement membrane (GBM) was significantly thickened, no changes in the diabetic glomeruli were seen in the peripheral capillary wall area and in the fractional volumes of the mesangial cells or of the mesangial matrix. Light microscopy of the diabetic kidneys were normal, and immunofluorescent examination of diabetic glomeruli showed no increased accumulation of albumin, C3, or IgG. Diabetic rats had increased renal blood flow and glomerular filtration rates. Diabetic rats at 7, 17, and 30 weeks excreted normal amounts of urinary albumin. Thus kidneys of the BB diabetic rat differ from other experimental models of diabetes in that GBM thickening occurs in the absence of mesangial changes and of increased albuminuria. These studies suggest that the mesangium may influence glomerular permeability in diabetes, while thickening of the GBM in diabetes does not necessarily coincide with increased urinary albumin excretion. Furthermore, these results are consonant with the hypothesis that genetic factors may influence the pathological expression of diabetic nephropathy in rats.

Plasma chlorpropamide: a critical factor in chlorpropamide-alcohol flush

The chlorpropamide-alcohol flush (CPAF) phenomenon was quantitatively related to blood levels of acetaldehyde and chlorpropamide in 105 Type II diabetics, of whom 74 had not previously taken the drug and 31 were on chronic treatment. Standardized skin temperature recordings were made with a sensitive probe. Plasma ethanol and acetaldehyde concentrations were determined by gas chromatography, and those of chlorpropamide by high-pressure liquid chromatography. There were significant positive correlations between plasma acetaldehyde and the skin temperature increase, between plasma chlorpropamide and plasma acetaldehyde, and between plasma chlorpropamide and the skin temperature increase. CPAF-positive patients became CPAF-negative and vice versa following reduction and increase, respectively, in the dose of chlorpropamide. Thus, the CPAF reaction is a consequence of chlorpropamide inhibition of the oxidation of ethanol-generated acetaldehyde, and it appears that the plasma concentration of chlorpropamide is critical. It remains an open question whether the CPAF test has any prognostic value.

Chlorpropamide-alcohol flushing, aldehyde dehydrogenase activity, and diabetic complications

Many diabetics who take chlorpropamide (a sulphonylurea compound) experience facial flushing after drinking even small amounts of alcohol. These flushers have a noticeably lower prevalence of late complications of diabetes (microangiopathy, macroangiopathy, and neuropathy) than non-flushers. This flush reaction is accompanied by increased blood acetaldehyde concentrations, suggesting an inhibition of aldehyde dehydrogenase activity. In the present study the activity of this enzyme in erythrocytes was assessed in the absence of chlorpropamide. Erythrocyte homogenates obtained from flushers and non-flushers were incubated with acetaldehyde and the rate of metabolism studies. Flushers eliminated acetaldehyde more slowly at a low range of concentrations (0--30 mumol/l), suggesting a difference in aldehyde dehydrogenase activity. Further studies are needed to clarify the role of this enzyme in the pathogenesis of diabetic complications.

Chlorpropamide-alcohol flushing, malar thermal circulation index, and baseline malar temperature

Chlorpropamide-alcohol flushing (CPAF) has been advanced and challenged as a specific marker for familial noninsulin dependent diabetes mellitus. The previous studies assay flushing reactions employing arbitrarily defined critical threshold values of rise and rate of rise in facial temperature. Since these methods ignore the curvilinear relationship between skin temperature and cutaneous blood flow, errors of analysis obtained, Further, the role of baseline facial temperature is obfuscated. The method of malar thermal circulation index derived from the relationship between skin temperature and cutaneous blood flow provides a more accurate assay method and permits the characterization of the role of baseline facial temperature. Baseline facial temperature is less in subjects with CPAF and noninsulin dependent diabetes than in normal subjects. The lower baseline facial temperature alone may account for the reported differences in the parameters of the CPAF test.

Chlorpropamide-alcohol flushing in non insulin-dependent diabetes: prevalence of small and large vessel disease and or risk factors for angiopathy

One hundred and eight non insulin-dependent diabetics were tested for alcohol flushing after chlorpropamide administration (CPAF test). The overall prevalence of patients who flushed at the first challenge was 32%. However, nearly half of them still flushed after alcohol administration, when placebo was given instead of chlorpropamide, so that the prevalence of 'true' flushers was only 17%. Even though the distribution of retinal lesions was similar in 'true' flushers and in non flushers, severe loss of visual acuity was confined to the non flushers and aspecific flushers. The frequency of pathological ECG findings and of peripheral pulse reduction or abolition was significantly higher in the non flushers and aspecific flushers. Blood pressure, serum lipids and hemostatic parameters were similar in the two groups, and therefore do not explain the differences in prevalence of lesions. This study confirms the previous findings of a lower prevalence of large vessel lesions in flushers; however, the prevalence of 'true' CPAF phenomenon in our out-patient population appears to be much lower than previously reported.

Circulating prostanoid levels, both basal and during the chlorpropamide alcohol flush, in non-insulin dependent diabetes

Circulating basal levels of prostanoids were measured in non-insulin dependent diabetics (NIDDs) who showed chlorpropamide alcohol flushing (CPAF), with and without diabetic complications, and in non-diabetic controls. Prostanoids were also measured during CPAF in those diabetics in whom CPAF is or is not blocked by indomethacin and also in CPAF-negative patients. There was no significant difference in circulating prostanoids between diabetics with and without severe vascular disease. The level of prostaglandin F, however, was significantly higher in the diabetic than in the non-diabetic subjects (mean +/- SEM PGFM 521 +/- 23 v. 414 +/- 18 pmol/l respectively P less than 0.01). In the group in whom CPAF could be blocked by indomethacin there was a significant rise in thromboxane during CPAF when compared with basal values (mean +/- SEM 905 +/- 48 v. 688 +/- 46 pmol/l respectively P less than 0.01) which was abolished by prior administration of indomethacin. There was no significant rise in prostacyclin or PGF. The group in which CPAF could not be blocked by indomethacin and the CPAF negative group showed no rise in any of the prostanoids measured. These findings support the concept of at least two different groups of CPAF positive NIDDs, one in which prostanoids are involved in CPAF and one in which they are not. It is the group in which prostanoids are involved in CPAF who seem to be highly protected against vascular disease.

Chlorpropamide alcohol flush and circulating met-enkephalin: a positive link

Chlorpropamide-alcohol flushing may be due to sensitivity to endogenous opiates. To investigate this possibility the plasma met-enkephalin and beta-endorphin responses to sherry with and without chlorpropamide were studied in six patients with non-insulin dependent diabetes and in six normal subjects. After chlorpropamide all patients showed a rise in met-enkephalin concentrations from a basal level of 50 +/- 7.2 ng/l to a peak of 75 +/- 8.1 ng/l (p less than 0.001). In contrast, before chlorpropamide treatment was started met-enkephalin values did not change after alcohol. No significant changes in beta-endorphin values were observed. In six normal subjects pretreated with chlorpropamide the met-enkephalin concentration also rose from a basal level of 72 +/- 15 ng/l to a peak of 103 +/- 9.4 ng/l (p less than 0.002). Again, the met-enkephalin rise was not observed after placebo. Neither beta-endorphin concentrations nor facial temperature changed significantly. These data suggest that endogenous opiates may be implicated in CPAF. Furthermore, this is the first study in which a significant change in circulating met-enkephalin values has occurred.

Glyoxalase phenotypes in patients with diabetes mellitus

Caucasian diabetic patients in Australian surveys showed a significant difference in the distribution of glyoxalase phenotypes. Insulin dependent diabetic patients with age of onset less than 40 years had a relative excess of glyoxalase homozygote 1-1 and a deficiency of types 2-1 and 2-2. Non-insulin dependent diabetic patients were not significantly different from non-diabetic subjects in the distribution of glyoxalase phenotypes. Insulin dependent diabetic patients without the complications of retinopathy or neuropathy also showed a significant excess of glyoxalase type 1-1 in relation to the control group. Genes controlling glyoxalase polymorphism appear to be associated with the variations of diabetes and its complications.

The genetics of the glucose intolerance disorders

Genetic heterogeneity, the concept that diabetes can have many different causes, was first suggested by the existence of rare genetic syndromes with diabetes, ethnic differences in clinical features and genetic heterogeneity of animal models. Genetic heterogeneity is now considered to be firmly established by family, twin, metabolic, immunologic and HLA disease association studies that separate idiopathic diabetes into insulin-dependent types (juvenile-onset type) and noninsulin-dependent types (maturity-onset type). Further heterogeneity is being demonstrated within each of these broad groups of disorders--within insulin-dependent diabetes using the HLA antigens and immunologic studies, and within noninsulin-dependent diabetes using such criteria as obesity, insulin response, age of onset and chlorpropamide-primed alcohol-induced flushing. This heterogeneity has major implications for the research and care of our diabetic patients since the precise etiology, risk of complications and genetic counseling are likely to vary among these different disorders that result in diabetes.

Effect of enkephalins and morphine on insulin secretion from isolated rat islets

The direct effects of an enkephalin analogue, (D-Ala2/MePhe4/Met/(O)-o1) enkephalin (DAMME), on insulin release from isolated islets of Langerhans of the rat have been investigated. DAMME had a dose-dependent effect on insulin secretion: low concentrations (10(-10) to 10(-8) mol/l) were stimulatory while high concentrations (10(-5) mol/l) were inhibitory in the presence of 8 mmol/l glucose. Similar effects were found with met-enkephalin, and with the longer acting alanine substituted met-enkephalin. Morphine sulphate (5 X 10(-7) mol/l) also stimulated insulin release. The effects of enkephalin and morphine were blocked by the specific opiate antagonist naloxone hydrochloride (1.2 X 10(-6) mol/l). The insulin secretory response of perifused islets to enkephalins and morphine was rapid, corresponding to the first phase of glucose induced insulin release. These observations suggest that there may be opiate receptors in islets, and that opioid peptides could modulate insulin release.

Blockade of chlorpropamide-alcohol flushing by indomethacin suggests an association between prostaglandins and diabetic vascular complications

Chlorpropamide/alcohol flushing (CPAF), found in many patients with non-insulin-dependent diabetes (NIDD), can be blocked by indomethacin in most patients who are free of vascular complications but not in those with such complications. Since indomethacin is a prostaglandin inhibitor this finding suggests that prostaglandins may be involved in the aetiology of vascular diseases in NIDD. All 6 pairs of identical twins with CPAF, of whom 2 pairs were disocrdant for diabetes, were concordant for indomethacin blocking, which suggests that the block has a genetic basis. The difference in the response of CPAF to indomethacin in diabetic patients with and without vascular complications is probably the first indication of a metabolic difference between these two types of patient.

Chlorpropamide-alcohol flushing and large-vessel disease in non-insulin-dependent diabetes

A total of 220 non-insulin-dependent diabetics aged over 45 (139 with a history of chlorpropamide-alcohol flushing and 81 without such a history) were examined for the prevalence of large-vessel disease. Large-vessel disease was significantly more common in the group without a history of flushing (41% v 24% of the two groups respectively; p < 0.05). A history of myocardial infarction was found in 14 (17%) of the patients without flushing but in only 10 (7%) patients with flushing. Similar differences were detected in the prevalences of angina, intermittent claudication, and absent foot pulses. There were, however, no significant differences in the prevalence of cerebrovascular disease or hypertension between the two groups. These results suggest that patients with non-insulin-dependent diabetes who flush in response to chlorpropamide and alcohol are significantly less likely to develop large-vessel disease than those who do not. Hence such flushing is probably related to the pathogenesis not only of small-vessel but also of large-vessel disease.

Blockade of chlorpropamide alcohol flush by aspirin

The blocking effects of aspirin, chlorpheniramine, and cimetidine were tested against the flush provoked by alcohol in twenty-four chlorpropamide-treated patients with non-insulin-dependent diabetes mellitus. Active preparations were compared in a double-blind manner with an indistinguishable placebo. Aspirin significantly decreased the number of patients who flushed. Five patients studied in detail all showed suppression of chlorpropamide/alcohol flush by aspirin, with a mean facial temperature increase during the flush of 2.4 degrees C after pretreatment with placebo and an increase of 0.4 degrees C after pretreatment with aspirin.