Role of alcohol metabolism in chronic pancreatitis

Alcohol abuse is the major cause of chronic inflammation of the pancreas (i.e., chronic pancreatitis). Although it has long been thought that alcoholic pancreatitis is a chronic disease from the outset, evidence is accumulating to indicate that chronic damage in the pancreas may result from repeated attacks of acute tissue inflammation and death (i.e., necroinflammation). Initially, research into the pathogenesis of alcoholic pancreatitis was related to ductular and sphincteric abnormalities. In recent years, the focus has shifted to the type of pancreas cell that produces digestive juices (i.e., acinar cell). Alcohol now is known to exert a number of toxic effects on acinar cells. Notably, acinar cells have been shown to metabolize alcohol (i.e., ethanol) via both oxidative (i.e., involving oxygen) and nonoxidative pathways. The isolation and study of pancreatic stellate cells (PSCs)-the key effectors in the development of connective tissue fibers (i.e., fibrogenesis) in the pancreas-has greatly enhanced our understanding of the pathogenesis of chronic pancreatitis. Pancreatic stellate cells become activated in response to ethanol and acetaldehyde, a toxic byproduct of alcohol metabolism. In addition, PSCs have the capacity to metabolize alcohol via alcohol dehydrogenase (the major oxidizing enzyme for ethanol). The fact that only a small percentage of heavy alcoholics develop chronic pancreatitis has led to the search for precipitating factors of the disease. Several studies have investigated whether variations in ethanol-metabolizing enzymes may be a trigger factor for chronic pancreatitis, but no definite relationship has been established so far.

Differential impact of recent heavy drinking on first and recurrent acute pancreatitis

BACKGROUND

While alcohol is known to sensitize the pancreas to acute injury, the role of short-term episodic drinking in regular drinkers is unknown.

METHODS

We conducted a case-crossover study to (1) determine the hazardous period of drinking prior to a first episode of acute pancreatitis (FAP) or recurrent acute pancreatitis (RAP) and (2) evaluate the dose-response association between short-term drinking and FAP/RAP. Patients hospitalized for FAP/RAP with an AUDIT-C score of ≥3 were enrolled. Recent and lifetime drinking history were collected through interviews. Drinking prior to the index pancreatitis attack was compared to that of an asymptomatic control period. Conditional logistic regression quantified the association of heavy drinking and FAP/RAP.

RESULTS

Of 141 patients who completed a short-term drinking questionnaire, 77 had RAP, and 64 experienced FAP. We found that both FAP and RAP patients drank at moderate-to-heavy levels regularly, with modest day-to-day variation (intraclass correlation of drinks/day 67%-82%). Alcohol consumption increased 2 days preceding the onset of the index pancreatitis attack as compared to the week prior. Stratifying by prior AP history, heavy drinking in the hazard period was associated with RAP (OR = 3.79, 95% confidence interval [CI] 1.57-9.12). Each drink was associated with 1.22-fold (95%CI 1.10-1.35) increased odds of RAP. Short-term heavy drinking was not associated with a FAP (OR = 1.06, 95%CI 0.43-2.57).

CONCLUSION

In summary, we found that patients with a prior history of AP face a higher risk of RAP due to excess drinking. Drinking intensity did not increase prior to a FAP, which may have been triggered by other cofactors warranting further examination.

Individual susceptibility to alcoholic pancreatitis: still an enigma

Evidence is increasing that individuals vary in their susceptibility to alcoholic pancreatitis. Numerous investigators have attempted to account for this individual susceptibility by studying associations between alcoholic pancreatitis and potential risk factors. Those studies, reviewed here, have focused on the amount, type, and pattern of alcohol consumption, genetic markers (such as blood groups, HLA phenotypes, alpha 1-antitrypsin, and alcohol dehydrogenase isoenzyme distribution), diet, hypertriglyceridemia, tobacco consumption, and pancreatic ischemia. Associations between pancreatitis and several of these factors have been reported, but many studies offer conflicting conclusions. A number of studies are difficult to interpret because of methodologic problems, particularly with regard to inadequate controls and small numbers of index subjects. At present, the evidence is insufficient for one to conclude that any of the above-mentioned factors are well-established risk factors for pancreatitis. As a result, individual susceptibility to alcoholic pancreatitis remains unexplained. Clarification of potential risk factors may ultimately lead to the ability to prevent this relatively common disorder, but additional, appropriately designed studies are required.