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

The role of acetaldehyde in the actions of alcohol (update 2000)

BACKGROUND

Recent advances in the field of acetaldehyde (AcH) research have raised the need for a comprehensive review on the role of AcH in the actions of alcohol. This update is an attempt to summarize the available AcH research.

METHODS

The descriptive part of this article covers not only recent research but also the development of the field. Special emphasis is placed on mechanistic analyses, new hypotheses, and conclusions.

RESULTS

Elevated AcH during alcohol intoxication causes alcohol sensitivity, which involves vasodilation associated with increased skin temperature, subjective feelings of hotness and facial flushing, increased heart and respiration rate, lowered blood pressure, sensation of dry mouth or throat associated with bronchoconstriction and allergy reactions, nausea and headache, and also reinforcing reactions like euphoria. These effects seem to involve catecholamine, opiate peptide, prostaglandin, histamine, and/or kinin mechanisms. The contribution of AcH to the pathological consequences of chronic alcohol intake is well established for different forms of cancer in the digestive tract and the upper airways. AcH seems to play a role in the etiology of liver cirrhosis. AcH may have a role in other pathological developments, which include brain damage, cardiomyopathy, pancreatitis, and fetal alcohol syndrome. AcH creates both unpleasant aversive reactions that protect against excessive alcohol drinking and euphoric sensations that may reinforce alcohol drinking. The protective effect of AcH may be used in future treatments that involve gene therapy with or without liver transplantation.

CONCLUSIONS

AcH plays a role in most of the actions of alcohol. The individual variability in these AcH-mediated actions will depend on the genetic polymorphism, not only for the alcohol and AcH-metabolizing enzymes but also for the target sites for AcH actions. The subtle balance between aversive and reinforcing, protecting and promoting factors will determine the overall behavioral and pathological developments.

The role of acetaldehyde in the actions of alcohol (update 2000)

BACKGROUND

Recent advances in the field of acetaldehyde (AcH) research have raised the need for a comprehensive review on the role of AcH in the actions of alcohol. This update is an attempt to summarize the available AcH research.

METHODS

The descriptive part of this article covers not only recent research but also the development of the field. Special emphasis is placed on mechanistic analyses, new hypotheses, and conclusions.

RESULTS

Elevated AcH during alcohol intoxication causes alcohol sensitivity, which involves vasodilation associated with increased skin temperature, subjective feelings of hotness and facial flushing, increased heart and respiration rate, lowered blood pressure, sensation of dry mouth or throat associated with bronchoconstriction and allergy reactions, nausea and headache, and also reinforcing reactions like euphoria. These effects seem to involve catecholamine, opiate peptide, prostaglandin, histamine, and/or kinin mechanisms. The contribution of AcH to the pathological consequences of chronic alcohol intake is well established for different forms of cancer in the digestive tract and the upper airways. AcH seems to play a role in the etiology of liver cirrhosis. AcH may have a role in other pathological developments, which include brain damage, cardiomyopathy, pancreatitis, and fetal alcohol syndrome. AcH creates both unpleasant aversive reactions that protect against excessive alcohol drinking and euphoric sensations that may reinforce alcohol drinking. The protective effect of AcH may be used in future treatments that involve gene therapy with or without liver transplantation.

CONCLUSIONS

AcH plays a role in most of the actions of alcohol. The individual variability in these AcH-mediated actions will depend on the genetic polymorphism, not only for the alcohol and AcH-metabolizing enzymes but also for the target sites for AcH actions. The subtle balance between aversive and reinforcing, protecting and promoting factors will determine the overall behavioral and pathological developments.

The effect of ethanol on platelet function and vascular prostanoids

The present review will discuss the effects of ethanol on platelet function and vascular prostanoids. Whenever possible we have considered human studies because there are marked species differences in platelet function and vascular prostanoid release even in the absence of ethanol. Because of the specialised nature of some parts of the text, we have included brief introductions to help readers who are not familiar with this field.

Opiate antagonist nalmefene inhibits ethanol-induced flushing in Asians: a preliminary study

Ethanol-induced flushing (EIF) occurs in up to 80% of Asians and is characterized by facial flushing, tachycardia, and increased cardiac output. Since endogenous opiates and prostaglandins may be mediators of flushing syndromes, we attempted to block EIF in four Asian flushers with single doses of either the opiate antagonist nalmefene, or the prostaglandin synthesis inhibitor indomethacin. Nonflushers (2 Caucasian, 2 Asian) and four Asian flushers were given on separate days water, ethanol (0.4 g/kg p.o.), ethanol plus nalmefene (2 mg i.v.), or ethanol plus indomethacin (50 mg p.o.). Ethanol concentrations of flushers and nonflushers were similar. Mean (+/- SEM) plasma acetaldehyde concentrations of flushers (28.2 +/- 11.8 microM) were significantly greater than nonflushers (1.4 +/- 0.5 microM) following ethanol ingestion (p less than 0.001). Ethanol alone always induced a significant rise in facial skin temperature [mean area under the curve (AUC) = 5142 +/- 648 % delta T x min, p less than 0.01] and of pulse (mean AUC = 1622 +/- 120 bpm x min, p less than 0.001) in flushers compared to water ingestion. A single dose of nalmefene (2 mg i.v.) but not indomethacin (50 mg p.o.), reduced the mean (+/- SEM) ethanol-induced rise in facial skin temperature of flushers by 58 +/- 14% (p less than 0.05) without changing plasma acetaldehyde concentrations. These data are preliminary evidence that the opiate antagonist, nalmefene, blocks some of the vascular manifestations of EIF without altering the elevated plasma concentrations of acetaldehyde.

Opiate-prostaglandin interactions in the regulation of insulin secretion from rat islets of Langerhans in vitro

The inadequate insulin secretory response to glucose stimulation in non-insulin dependent diabetes has been attributed to many factors including high PGE2 levels blunting the secretory response, and to the existence of inhibitory opiate activity in vivo. The purpose of the present work was to see if there was a connection between these two independent theories. Radioimmunoassayable PGE2 in islets of Langerhans was found to be proportional to islet number and protein content and was typically 4 to 5pg/micrograms islet protein. Indomethacin (2.8 X 10(-5) M), sodium salicylate (1.25 X 10(-3) M) and chlorpropamide (7.2 X 10(-5) M) all lowered islet PGE2 levels and stimulated insulin release in vitro. Dynorphin (1-13), stimulated insulin release at a concentration of 6 X 10(-9) M, while lowering islet PGE2. Conversely, at a higher concentration, (6 X 10(-7) M), dynorphin had no stimulatory effect on insulin secretion and did not lower PGE2 levels in islets or in the incubation media. The stimulatory effects of dynorphin and sodium salicylate on insulin secretion were blocked by exogenous PGE2 (10(-5) M). PGE2 at a lower concentration (10(-9) M) did not exert any inhibitory effect on dynorphin- or sodium salicylate-induced insulin release. This concentration of exogenous PGE2 stimulated insulin release in the presence of 6mM glucose. Results from these experiments suggest that since an opioid peptide can lower endogenous PGE2 production in islets and since the stimulatory effects of the opioid peptide are reversed by exogenous PGE2 there may be interactions between these two modulators of insulin secretion.

Association between chlorpropamide-alcohol flushing and fast acetylator phenotype in type I and type II diabetes

Different prevalences of chlorpropamide alcohol flushing (CPAF) have been reported by different authors in either type I or type II diabetics or in normal subjects and this could be due to different methodological approaches or to different criteria of evaluation of CPAF. Previous studies in small series of patients have also suggested the existence of an association between type I diabetes and the fast acetylator phenotype (AP). The first aim of this study was to find reliable criteria for the assessment of CPAF. The second was to evaluate the prevalence of CPAF and of AP in a large series of type I and type II diabetics; and the third was to evaluate possible associations of CPAF and AP. AP and CPAF were evaluated separately in 256 diabetics (110 with type I and 146 with type II diabetes) and in 183 diabetics (74 with type I and 109 with type II diabetes), respectively. In 156 of these subjects, the two markers were evaluated together. The occurrence of CPAF was studied by subjective and objective assessment and by thermographic recording; CPAF was quantified by the differential value of skin temperature increase [delta T(C-P)] and by the value of differential speed of ascent, expressed in angle-degrees [delta a(C-P)], after treatment with placebo and with chlorpropamide. The fast AP was more frequent in type I than in type II diabetics, was not related to family history of diabetes, sex of the patients, age at onset and duration of diabetes or metabolic control. The most reliable assessment of CPAF was represented by thermographic recording of speed of ascent of skin temperature. CPAF was more frequent in females than in males, more frequent in diabetics than in healthy controls, similarly frequent in type I and in type II diabetes and showed no relationship with family history of diabetes, age at onset, duration of diabetes or metabolic control. An association between fast AP and CPAF was found in type II, but not in type I diabetics: fast acetylators were more frequently CPAF-positive, while slow acetylators were more frequently CPAF-negative. In addition, a linear relationship was found between rate of acetylation and speed of ascent of facial skin temperature after chlorpropamide and alcohol in type II diabetics, not in type I diabetics. The meaning of this association is not clear and deserves further investigations.

The role of endogenous opioids in the chlorpropamide alcohol flush

The response of plasma immunoreactive met-enkephalin (IR-met-enkephalin) to ethanol (8 g by mouth) after chlorpropamide (250 mg daily for 14 d) was studied in three groups of non-insulin dependent diabetics (a) six diabetics who showed chlorpropamide alcohol flush (CPAF) and in whom the reaction could be blocked by indomethacin, (b) five diabetics who showed CPAF but in whom the flush could not be blocked by indomethacin and (c) five diabetics who did not show CPAF. A rise in plasma IR-met-enkephalin was observed in all three groups. When the two groups of flushers were re-tested with the addition of an infusion of naloxone a rise in plasma IR-met-enkephalin was still demonstrated in both groups regardless of whether the flush was blocked by naloxone. Naloxone blocked the flush only in those six subjects whose flush could be blocked by indomethacin. In five subjects, all flushers, CPAF was tested using intravenous and oral ethanol in doses producing similar plasma ethanol levels. A facial flush was induced by both intravenous and oral ethanol. In three flushers, plasma IR-met-enkephalin levels were measured during CPAF testing with both intravenous and oral ethanol. None showed a rise in plasma IR-met-enkephalin after intravenous ethanol, despite the appearance of a facial flush, whereas all showed a rise after oral ethanol. We therefore conclude that CPAF is unlikely to be caused by a rise in plasma IR-met-enkephalin.

[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.

Epidemiological study of prevalence of chlorpropamide alcohol flushing in insulin dependent diabetics, non-insulin dependent diabetics, and non-diabetics

An epidemiological study was carried out to compare the prevalence of facial flushing in non-diabetics, patients with insulin dependent diabetes, and patients with non-insulin dependent diabetes in response to 40 ml sherry taken 12 hours after 250 mg chlorpropamide or placebo, administered double blind in randomised order. A flush after chlorpropamide but not placebo was reported by 6.2% of non-diabetics (17/273), 9.7% of insulin-dependent diabetics (14/145), and 10.5% of non-insulin dependent diabetics (25/239), excluding those receiving long term chlorpropamide treatment. The differences were not significant. This response was unrelated to age, sex, body mass index, and family history of diabetes in all three groups. Patients taking long term chlorpropamide, however, showed a significantly (p less than 0.01) higher prevalence of flushing after both chlorpropamide and placebo (56.3%; 9/16) compared with the rest of the non-insulin dependent diabetics (16.7%; 40/239), the insulin dependent diabetics (6.9%; 10/145), and the non-diabetics (5.9%; 16/273). Patients receiving long term chlorpropamide would be expected to flush with sherry after a placebo tablet because of therapeutic plasma concentrations of the drug. It is concluded that there is no evidence of an increased prevalence of chlorpropamide alcohol flushing in response to the single challenge test in non-insulin dependent diabetics compared with insulin dependent diabetics and non-diabetics except in selected patients taking chlorpropamide long term. This study does not support the hypothesis that the chlorpropamide alcohol flush is a specific marker for a subtype of non-insulin dependent diabetes.

Prostaglandins in alcohol intolerance and hangover

The effects of alcohol on the formation of prostaglandins (PGs) and the blockade of some actions of alcohol by PG-inhibitors suggest that PGs may be involved in the action of ethyl alcohol. Regulation of lipid peroxidation and synthesis and release of precursor fatty acids may affect the overall formation of PGs. The effect of alcohol may be qualitative for several reasons: (i) the possible preferred formation of 1-series of PGs would mean an important qualitative change in PG-impact in some tissues; (ii) inhibition of PG-metabolism in the lung might affect mostly the plasma levels of PGE; (iii) a selective blockade of certain PG-effects and a potentiation of some others gives rise to qualitative changes in the actions of PGs. PGs may be involved in several acute or short-term reactions caused by alcohol. Chlorpropamide-alcohol flush, alcohol intolerance and hangover are effectively alleviated by a prophylactic use of PG-inhibitors. Speculatively PGs might also be involved in migraine attacks provoked by alcohol and in antabuse in reaction. The roles of PGs in the regulation of vascular tone, water and electrolyte balance as well as in certain secretory and metabolic processes may be important in the generation of alcohol related reactions.

Clinical pathology of alcohol

There is good though not conclusive evidence that a small to modest average daily intake of alcohol--that is, 20-30 g/day is associated with increased longevity due mainly to a reduction in death from cardiovascular disease. Larger average daily alcohol intakes--especially those in excess of 60 g/day for men and 40 g/day for women--are associated with gradually increasing morbidity and mortality rates from a variety of diseases. Alcohol may be unrecognised as the cause of somatic disease, which can occur without overt psychosocial evidence of alcohol abuse, unless the index of suspicion is high and a thorough drink history obtained. Laboratory tests for the detection and/or confirmation of alcohol abuse are useful but subject to serious limitations being neither as sensitive nor specific as sometimes believed. The value of random blood and/or breath alcohol measurements, in outpatients, as an aid to diagnosis of alcohol-induced organic disease is probably not sufficiently appreciated and, though relatively insensitive, is highly specific.

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.

A quantitative, non-invasive method for the characterization of flushing reactions

A new method for the characterization of flushing reactions is established based on the curvilinear relationship between malar skin temperature and an index of cutaneous blood flow in the face. Previous studies relied on the absolute change in malar temperature which overlooks the curvilinear aspect of this relationship. The change in malar thermal circulation index (delta MTCI) is derived from the mathematical model of this curvilinear relationship. There were 71 positive flushing reactions in 162 challenges to a variety of agents. The peak malar temperature, change in malar temperature, and delta MTCI significantly correlated with flushing (p less than 0.001). For the commonly used threshold values for change in malar temperature of 1.1 degrees C and 1.2 degrees C, sensitivity was only 63.4 and 54.9, respectively. The sensitivity, specificity, and predictive value of a positive result for the delta MTCI were 90.1, 95.6 and 94.1, respectively. delta MTCI did not appear to be related to the baseline malar temperature, suggesting that a low malar temperature did not predispose to flushing. Thus, the inverse relationship between change in malar temperature and baseline malar temperature results solely from the curvilinear relationship between malar skin temperature and cutaneous blood flow in the face. Data from 2 previously reported studies are reevaluated employing the delta MTCI method; in both studies the new method is more sensitive without loss in specificity. The results indicate that delta MTCI may be useful as an accurate, noninvasive method for the quantitative characterization of flushing reactions.

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.

Impaired insulin secretion in human diabetes mellitus. II. A possible role for prostaglandins

Human diabetes mellitus is characterized by impaired insulin response to intravenous glucose. In search of possible endogenous factors which impair insulin release, we have investigated the effect of lysine acetylsalicylate (LAS), an inhibitor of endogenous prostaglandin (PGs) synthesis, upon insulin responses to glucose and arginine in subjects with type II (adult-on-set) diabetes mellitus. Acute insulin response to glucose (20 g) was significantly increased by LAS (response before LAS=26 +/- 10%; during LAS=77+15%, mean+/-SEM, mean change 3-10 min insulin, % basal, n=8, p 0.01), as well as second phase insulin secretion (before LAS=1437+/-316%; during LAS=3960+/-550%, change 10-60 min, uU/ml-min, % basal, p less than 0.01). This effect was associated with an increase in glucose disappearance rates (p less than 0.01). Acute insulin response to arginine (5 g iv) was also increased by LAS infusion. These results suggest that endogenous PGs may be one of the factors which impair insulin secretion in human diabetes.