Abstract
Objectives
The objective of the study was to evaluate whether oral cobalamin supplementation can restore normocobal-aminaemia in cats with hypocobalaminaemia and clinical signs of gastrointestinal disease.
Methods
This was a retrospective study based on a computerised database search for client-owned cats treated at Evidensia Specialist Animal Hospital, Helsingborg, Sweden, during the period December 2013 to August 2016. Inclusion criteria were cats with clinical signs of chronic enteropathy, an initial serum cobalamin concentration ⩽250 pmol/l (reference interval 214–738 pmol/l) and oral treatment with cobalamin tablets.
Results
Twenty-five cats met the inclusion criteria. The cats were treated with 0.25 mg cyanocobalamin tablets once daily. Serum cobalamin concentration was rechecked 27–94 days after continuous oral cobalamin supplementation. All cats had serum cobalamin concentrations above the reference interval after oral cobalamin supplementation. Median (range) serum cobalamin concentration was 128 pmol/l (111–250 pmol/l) prior to treatment and 2701 pmol/l (738–16,359 pmol/l) after supplementation. This difference was statistically significant (P <0.0001).
Conclusions and relevance
Our results suggest that oral cobalamin supplementation is effective in increasing serum cobalamin to supranormal concentrations in cats with hypocobalaminaemia. Thus, oral cobalamin supplementation is a promising alternative to parenteral administration. Prospective comparative studies in cats being treated with parenteral vs oral cobalamin supplementation in a larger number of patients are warranted before oral supplementation can be recommended for routine use.
Introduction
Cobalamin deficiency has been reported in cats with gastrointestinal and pancreatic diseases such as chronic enteropathies, small intestinal lymphoma and exocrine pancreatic insufficiency (EPI).1–6 As cobalamin is required for various biochemical pathways, cobalamin deficiency can have profound metabolic and clinical effects in affected cats.7–9 Reported clinical signs in cats with hypocobalaminaemia are lethargy, weight loss and inappetence. Neurological signs have also been reported, and possibly complications of the underlying gastrointestinal disease. 8
Current supplementation protocols for cobalamin in cats call for repeated parenteral injections. In humans, several studies have reported equal efficacy of oral and parenteral administration of cobalamin.10–13 It has also been demonstrated that humans have an alternative uptake of cobalamin along the entire small intestine that is independent of intrinsic factor. 14 A recently published retrospective study from the present authors supports that oral cobalamin supplementation appears effective in dogs with chronic enteropathies and hypocobalaminaemia, which was also shown in a prospective comparative study in dogs.15,16 Another report demonstrated that oral cobalamin supplementation increased serum cobalamin concentrations in geriatric cats. 17 The reports on successful oral supplementation in humans and encouraging results from the canine studies mentioned has led three of the authors (LT, GO and ML) to start using oral supplementation in cats with hypocobalaminaemia. The purpose of this retrospective study was to evaluate whether oral cobalamin supplementation can restore normocobalaminaemia in cats with hypocobalaminaemia and clinical signs of gastrointestinal disease.
Materials and methods
The medical records of the Evidensia Specialist Animal Hospital, Helsingborg, Sweden, were searched for cats treated with oral cobalamin between December 2013 and August 2016. The database fields for treatment and prescription were searched for the brand name of cobalamin used for tablets (Behepan; Pfizer). Inclusion criteria were cats with clinical signs of gastrointestinal disease, a serum cobalamin concentration below the lower limit of the reference interval (RI) or within the lowest 10% of the RI, treatment with oral cyanocobalamin tablets as prescribed and a follow-up blood sample available. The owners had been instructed not to administer cobalamin on the day of the blood test for the post-treatment blood sample collection. Cats that had received parenteral cobalamin supplementation in parallel with oral supplementation were excluded, as well as cats that had failed therapeutic compliance.
Information regarding breed, age, sex, weight, body condition score, clinical signs, duration of clinical signs, diet, medical treatment and date of cobalamin measurement at baseline and at follow-up were obtained from the medical records. Further, serum concentrations of folate, pancreatic tests (ie, Spec fPL [IDEXX] and feline trypsin-like immunoreactivity [fTLI]) and serum liver enzyme activities were recorded when available, as well as results from abdominal ultrasound and histopathology. Concurrent non-gastrointestinal diseases were reviewed when present.
Serum samples for cobalamin assay were refrigerated within 2 h of collection, stored at −20ºC within 1–3 days and sent to the Laboratory Department of Evidensia Specialist Animal Hospital, Strömsholm, Sweden, with cold packs, using a priority delivery service. It has been shown previously that cobalamin is stable in these storage conditions. 18 The samples were analysed using an automated chemiluminescence immunoassay (Immulite 2000; Siemens Healthcare Diagnostics). Serum cobalamin concentrations were compared before and after oral cobalamin supplementation. For statistical analysis, a commercially available software package (GraphPad Prism 6.0; GraphPad Software) was used. Data were tested for normality using the D’Agostino and Pearson omnibus normality test. As data were not normally distributed, the Wilcoxon matched-pairs signed rank test was used for comparison. The significance threshold was set at 0.05.
Results
Twenty-five cats aged 1–16 years (median 10 years) met the inclusion criteria. Additional baseline data are shown in Table 1. All cats were fed commercial pet food kibble from major pet food manufacturers. The most common presenting complaints at time of diagnosis were vomiting, diarrhoea and weight loss (Table 1). Concurrent exocrine pancreatic disease was common (Table 2).
Baseline data at inclusion for 25 cats with hypocobalaminaemia
Ragdoll, Siamese or British Shorthair
Meloxicam, mirtazapine or chlorambucil
Verified with intestinal biopsies
Based on increased Serum Spec fPL concentration
Based on histopathology or cytology
Euthyroid with treatment at inclusion
Feline asthma, degenerative joint disease or urinary tract infection (one cat each)
EPI = exocrine pancreatic insufficiency
Selected serum biochemistry parameters
IDEXX
Two cats had a serum feline trypsin-like immunoreactivity (fTLI) concentration consistent with exocrine pancreatic insufficiency and one cat had an equivocal fTLI result
None of the cats had a decreased serum folate concentration
ALT = alanine aminotransferase
Two of the cats had previously been supplemented with parenteral cobalamin according to the medical records. The supplementation ended 30–45 days prior to study inclusion. Recurrence of hypocobalaminaemia following withdrawal of the cobalamin supplementation had been documented prior to study inclusion in both cats.
The most common concurrent medication administered at the time of diagnosis of hypocobalaminaemia was prednisolone (Table 1). Two cats were under treatment with methimazole at inclusion. All cats had an abdominal ultrasound performed, of which 21/25 had evidence of gastrointestinal changes, such as mild-to-moderate thickening of the small intestinal wall, thickening of the intestinal muscularis layer, poor definition of intestinal wall layers and/or enlargement of the mesenteric lymph nodes.
Histopathology and cytology
Histopathological reports from evaluation of endoscopic biopsies of the stomach, small intestine and large intestine were available from 9/25 cats. One of those cats was diagnosed with small intestinal lymphoma, and the remaining eight cats with chronic gastrointestinal inflammation of varying severity (Table 3). Intestinal biopsies were collected prior to study inclusion in four of the cats.
Intestinal histopathology results and concurrent disease in nine cats
One cat had a serum feline trypsin-like immunoreactivity (fTLI) concentration consistent with exocrine pancreatic insufficiency (EPI) and one cat had an equivocal fTLI result
LP = lymphocytic-plasmacytic
One additional cat had histopathological changes of the liver consistent with chronic hepatitis and hepatic lipidosis. All biopsies were analysed by board-certified pathologists at the veterinary pathology laboratory Biovet in Sollentuna, Sweden. One of the cats had a fine-needle aspirate of the liver consistent with hepatic lipidosis.
Cobalamin
Serum cobalamin concentration for follow-up was analysed 28–94 days after initiation of continuous oral cobalamin supplementation. Ten cats had undetectable serum cobalamin concentrations at inclusion, reported as <111 pmol/l (<150 ng/l). Those results were truncated to 111 pmol/l for statistical analysis. The median (range) serum cobalamin concentration was 128 pmol/l (111–250 pmol/l; 173 ng/l [150–339 ng/l]) prior to treatment (RI 214–738 pmol/l [290–1000 ng/l]) and 2701 pmol/l (738–16,359 pmol/l; 3660 ng/l [1000–22167 ng/l]) after treatment (Figure 1). This difference was statistically significant (P <0.0001). Samples were diluted to exact numbers in all but seven cats, for which the laboratory reported cobalamin >738 pmol/1; these were truncated to 738. Thus, the full magnitude of the increase was not available for all cats.
Pre- and post-treatment serum cobalamin concentrations in 25 cats with hypocobalaminaemia supplemented with oral cobalamin. Log10 scale, long horizontal line represents median. *Results reported as >738 pmol/l for seven cats, which has been truncated to 738. Remaining samples were diluted to exact numbers
Discussion
In this study, serum cobalamin concentrations increased significantly after oral cobalamin supplementation in cats with hypocobalaminaemia. At follow-up, all cats had supranormal serum cobalamin concentrations. As cobalamin is a water-soluble vitamin, supranormal serum cobalamin concentrations are not considered harmful, and current treatment protocols recommend supranormal serum concentrations before stopping supplementation. 8
All cats had signs of gastrointestinal disease, of which one cat was diagnosed with small intestinal lymphoma and two cats had a decreased fTLI concentration consistent with EPI. One cat had an equivocal fTLI concentration at time of inclusion. As intestinal biopsies were not available for the majority of the cats, more could have suffered from small intestinal lymphoma. Likewise, more cats could have been affected with EPI, as serum fTLI concentrations had not been analysed in 12/25 cats. However, in this group of cats, supplementation appeared effective, regardless of the initiating cause of cobalamin deficiency.
Hypocobalaminaemia has previously been described in association with feline hyperthyroidism. 19 A recent study suggests that hypocobalaminaemia in feline hyperthyroidism is not a functional deficiency in need of supplementation unless concurrent gastrointestinal disease is present. 20 The two cats under treatment with methimazole at inclusion had previously been diagnosed with hyperthyroidism, but were euthyroid at time of inclusion and at previous consultations 2–8 months prior to inclusion. Both cats were vomiting and had ultrasonographic changes of the small intestine consistent with feline chronic enteropathy,3,21,22 making gastrointestinal disease a more likely cause of cobalamin deficiency than hyperthyroidism.
The cat with lymphoma had a serum cobalamin concentration of 6430 pmol/l after supplementation and the two cats with EPI had serum cobalamin concentrations of 4360 and 3553 pmol/l, respectively, which were above the median increase of 2701 pmol/l. Furthermore, generally the cats showed strikingly higher serum cobalamin concentrations after supplementation compared with the dogs studied in the authors’ previously reported retrospective study. 15 Comparing the median dose in cats of this study to the median dose in dogs of the retrospective study, 15 the dose in mg/m2 body surface area of cats was with 0.91 mg/m2, only slightly higher than for the dogs, which was 0.85 mg/m2. Thus, the difference in response to supplementation most likely reflects species-dependent metabolic pathways or transport mechanisms. Whether lower doses or every-other-day treatment are sufficient to correct feline hypocobalaminaemia needs to be studied.
Owing to the retrospective nature of this study, no additional serum samples were stored for most of these cats to evaluate intracellular cobalamin status before and after supplementation. However, serum methylmalonic acid (MMA) concentrations were analysed pre- and post-cobalamin supplementation from two of the cats using stable isotope dilution gas chromatography–mass spectrometry method at the Gastrointestinal Laboratory at Texas A&M University. In those two cats, serum MMA concentrations were 23,945 nmol/l and 852 nmol/l (RI 139–898 nmol/l), respectively, prior to supplementation and decreased to 865 nmol/l and 233 nmol/l, respectively, after supplementation.
In humans, an alternative absorptive pathway for cobalamin beyond receptor-mediated transport in the ileum has been demonstrated using oral radioactive cobalamin. 14 This absorption only accounts for 1% of the total amount of unbound cobalamin in humans. We are not aware of any similar studies in cats, but the same mechanism may exist in cats.
Daily oral cobalamin supplementation offers a less-invasive alternative to weekly cobalamin injections. It is also substantially cheaper than parenteral supplementation. Although cats can be difficult to pill, none of the owners reported any problems giving the tablet.
The study has several limitations, such as the small number of cats and unknown serum fTLI concentrations in 12/25 cats. Also, owners may have given cobalamin on the day of the blood test, potentially causing falsely elevated results. Furthermore, serum concentrations of homocysteine and MMA were not measured for this study, with the exception of MMA results from two cats. These assays are a prerequisite in many countries to diagnose and treat cobalamin deficiency in humans.23,24
Conclusions
Despite its limitations, this study shows very encouraging results for oral cobalamin supplementation in cats. Prospective studies in cats being treated with parenteral vs oral cobalamin supplementation in larger numbers of patients are, however, warranted before oral supplementation can be recommended for routine use.
Footnotes
Acknowledgements
We would like to thank Mia Nilsson, Line Elmgren, Eva Spodsberg, Mariana Cigut, Emese Barabas, Annika Andersson and Britta Andersson at Evidensia Specialist Animal Hospital, Helsingborg, as well as Annelie Rundquist and Louise Baurén at the Laboratory Department of Evidensia Specialist Animal Hospital, Strömsholm.
Conflict of interest
The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Funding
The study was partially financed by the Swedish Veterinary Care Foundation.