Hot Literature: What's the relationship between hypertriglyceridemia and pancreatitis in miniature schnauzers?

It has long been suspected that hypertriglyceridemia in miniature schnauzers may predispose them to developing pancreatitis. A recent prospective case-controlled study looked at the possible causal relationship between elevated serum triglyceride concentrations and the development of pancreatitis in this breed.

Miniature schnauzers with and without a recent history of pancreatitis were compared. Inclusion data for both groups were evaluated via a questionnaire given to all dog owners to obtain information regarding each dog's age, sex, weight, current diet, medications, and medical history.

Group 1

Group 1 dogs consisted of 17 miniature schnauzers with a history of pancreatitis. Pancreatitis was diagnosed if the dogs had an elevated specific canine pancreatic lipase immunoreactivity (cPLI) concentration (> 400 µg/L) and at least two of the following clinical signs: vomiting, diarrhea, abdominal pain, anorexia, and depression. Serum triglyceride and cholesterol concentrations were measured at enrollment and again at follow-up examinations.

To ultimately be included in the study, the dogs had to be reevaluated at the time of clinical resolution of their pancreatitis (absence of clinical signs) and demonstrate normalization of their cPLI concentration (< 200 µg/L), free thyroxine (T4) or total T4 concentrations within the reference range, and no history of diseases or current drug use that could alter lipid metabolism.

Group 2

For every group 1 dog, two age-matched control dogs made up group 2. These were all healthy miniature schnauzers with no history of pancreatitis. Inclusion criteria for this group included absence of any clinical signs of disease, cPLI and free T4 or total T4 concentrations within the reference range, and no history of diseases or current drug use that could alter lipid metabolism. Serum cholesterol and triglyceride concentrations were measured for these dogs as well.

Group findings

Perhaps the most notable difference between the two groups was that 71% of the group 1 dogs vs. 11% of the group 2 dogs had hypertriglyceridemia at the time of the follow-up visit. In 10 of the 17 group 1 dogs, the hypertriglyceridemia was classified as moderate to severe (> 500 mg/dl), whereas this was noted in only three of 34 control group dogs. In people, evidence of elevated triglycerides after recovery from pancreatitis is thought to indicate a preexisting lipid metabolism disorder. The authors suspect that the same may be true in dogs and that control of the hypertriglyceridemia may decrease the risk of pancreatitis, as has been shown to occur in people.

Establishing a causal association between hypertriglyceridemia and the development of pancreatitis in miniature schnauzers has been difficult to prove in patients with spontaneously occurring disease. This would require knowing the triglyceride concentrations before the onset of pancreatitis, which is impossible to predict. For this reason, the presence of hypertriglyceridemia after clinical recovery was used as evidence of preexisting hypertriglyceridemia in this study.

It is also interesting to note that 50% of the miniature schnauzers in group 1 were already receiving diets labeled as low-fat, so it is possible that the prevalence of hypertriglyceridemia in this population may in fact be underestimated. If, indeed, there is a causal relationship between hypertriglyceridemia and pancreatitis, the authors postulate that this may be due to individual variations in lipoprotein metabolism or composition. The degree of triglyceride elevation may also play a role since the hypertriglyceridemia documented in most of the control dogs was mild (< 500 mg/dl) and, therefore, may be less likely to be associated with pancreatitis.

Three dogs in group 1 had normal triglyceride concentrations at the time of their diagnosis but had significant elevations after clinical resolution of their disease. One theory for this finding is that these dogs were all anorectic at the time of their diagnosis, which may have led to normalization of their triglyceride concentrations. This same phenomenon has been documented in people and may indicate that triglyceride concentrations during clinical disease may be inaccurate and should be reassessed once clinical recovery has occurred.

The serum cholesterol concentration was higher in the miniature schnauzers with a history of pancreatitis, but the median concentration between the two groups was within the reference range, and in the five dogs in group 1 that had elevated concentrations, these elevations were mild. The authors do not think that cholesterol concentrations play a role in the development of pancreatitis.

The authors also stated that, in the absence of any endocrine diseases, drug administration, or other metabolic abnormalities, it is likely the hypertriglyceridemia seen in this study's dogs was idiopathic.

The authors acknowledge that one limitation of the study was that a normal cPLI concentration does not definitively rule out pancreatitis, but histopathologic evaluation of the pancreas for confirmation would not have been justified in these cases.

Conclusion

This study demonstrates that, in contrast to control dogs, hypertriglyceridemia is a common finding in miniature schnauzers with a history of pancreatitis, but further studies are needed to establish what role this plays in the development of the disease in this and other breeds.

Xenoulis PG, Levinski MD, Suchodolski JS, et al. Serum triglyceride concentrations in Miniature Schnauzers with and without a history of probable pancreatitis. J Vet Intern Med 2010;25(1):20-25.

Link to full text of article: http://onlinelibrary.wiley.com/doi/10.1111/j.1939-1676.2010.0644.x/pdf