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SUMMARY:
ROYAL CANIN Veterinary DietTM/MC
feline HYPOALLERGENIC HP 23TM/MC
(dry) is a highly palatable, highly digestible, complete, and balanced
diet formulated to meet the requirements for feline growth and maintenance.
This diet is a hydrolyzed soy protein isolate, lactose, and wheat gluten
free diet that is indicated in both the diagnosis and management of adverse
reactions to food.
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| INDICATIONS:
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CONTRAINDICATIONS: |
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Adverse reactions to food (food
hypersensitivity/food allergy) which may present with the following
dermatological signs:
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Soy protein isolate hydrolysate hypersensitivity |
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Intense pruritus and ulcerative
dermatitis of the head and neck |
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Miliary dermatitis-like lesions |
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Eosinophilic granuloma complex
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Bilaterally symmetrical or localized alopecia |
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Or with the following gastrointestinal signs:
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Vomiting |
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Diarrhea |
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Dietary intolerance (e.g., lactose intolerance)
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Pancreatic exocrine insufficiency |
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Inflammatory bowel disease
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Idiopathic diarrhea
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Food elimination trial |
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RATIONALE:
Dietary sensitivity, an adverse reaction to food, is a term used to describe
a clinically abnormal response to the ingestion of a particular food.
Food allergy or hypersensitivity is an immunological response to the food.
Most basic food ingredients, including proteins, lipoproteins, glycoproteins,
and lipopolysaccharides, have the potential to induce an allergic response.
However, proteins are most commonly implicated in dietary sensitivity
in cats. In cats, cow’s milk, beef, and cereal account for many
reported cases.
When an immunological mechanism cannot be demonstrated, food intolerance
is a more appropriate term. Food intolerance may result from pharmacological,
metabolic, toxic reactions, or an inability to digest the food.
Adverse reactions to food can manifest as dermatological or gastrointestinal
signs. The most common dermatological sign is pruritus. Gastrointestinal
signs include vomiting, diarrhea, and/or inflammatory bowel disease. Occasionally
cats will present with signs involving both systems.
Elimination diets, with subsequent re-challenge with the original diet,
are the only way to confirm a diagnosis of food allergies and intolerance
in cats. The aim is to feed a complete and balanced diet while simultaneously
strictly limiting the protein and carbohydrate sources by feeding protein
sources to which the cat has never been previously exposed.
It is not fully understood why some cats will mount an abnormal immunological
response against a specific protein (or food allergen) in the diet. The
glycoprotein fractions of foods are typically implicated in the allergic
response. The predominant allergenic glycoproteins are water-soluble,
largely heat resistant, acid stable, and commonly in the range of 10 to
60 kDa.
Upon initial exposure or sensitization to the allergen, an IgE immune
response is mounted rather than the typical immunological response. The
IgE antibodies bind to high affinity receptors on mast cells. With re-exposure
to the food, the protein allergen binds to the IgE molecules causing mast
cell degranulation and the release of inflammatory mediators including
histamine, prostaglandins, and leukotrienes. These mediators are ultimately
responsible for both the immediate and delayed hypersensitivity reactions
to food allergens.
Degranulation of the mast cells requires that the allergenic protein
contains two binding sites or epitopes that must bind and cross-link two
IgE molecules bound to high affinity receptors on mast cells (and to a
lesser degree, basophils and other inflammatory cells).
The antigenicity of dietary proteins can be minimized by enzymatic hydrolysis
to produce low molecular weight proteins. Decreasing the size of the proteins
that are ingested reduces the chances of immunoglobulin cross-linking
and subsequent mast cell degranulation. Protein hydrolysates typically
have molecular weights less than the 10,000-60,000 kDalton molecular weight
of common allergens.
Genetics, age, poor digestibility of proteins, a defective mucosal barrier,
defective oral tolerance, and increased mucosal permeability are all predisposing
factors for food allergy.
Proteins that are incompletely digested have more potential to incite
an immune response. Highly digestible proteins are completely digested
to free amino acids and small peptides, with less potential to elicit
an allergic response. Hydrolyzed soy isolate protein contains highly digestible
(> 96%), low molecular proteins which are rapidly digested to free
amino acids and small peptides that are likely to evade detection by the
immune system.
Fermentable fiber such as beet pulp and fructo-oligosaccharides may have
a positive effective on the mucosal barrier by stimulating both the growth
of beneficial intestinal bacteria and the production of short chain fatty
acids. Short chain fatty acids have a trophic effect on the intestinal
mucosa. Zeolite (sodium silico aluminate), a tetrahedral clay, is capable
of absorbing bacterial toxins, bile acids, and gases. By forming a protective
film on the intestinal mucosa, zeolite helps to enhance the mucosal barrier
against allergen invasion.
Fatty acids such as linolenic (LA), gamma linoleic (GLA), eicosapentaenoic
(EPA), and docosahexaenoic (DHA) acid have several important structural,
biochemical, and beneficial effects on the skin and hair coat.
It has long been known that the skin provides a barrier to protect the
body from potentially damaging environmental influences including contact
with allergens. The cornified stratum corneum plays the principal role
of barrier defense. The stratum corneum consists of protein rich corneocytes
held together with a lipid matrix consisting of fatty acids, sterols,
and ceramides, similar to the brick and mortar analogy.
In terms of barrier function, ceramide-1 is thought to be the key component.
Ceramide-1 contains linoleic acid as one of its major components. It is
in this respect that linoleic acid is believed to play a crucial role
in barrier function of the skin. In addition, Waltham Science has shown
that the synthesis of ceramides and skin lipids can be enhanced by dietary
supplementation with biotin, pantothenic acid, nicotinamide, pyridoxine,
choline, inositol, proline, and histadine. The main result is an improvement
in the barrier effect of the epidermis and a reduction in transepidermal
water loss.
Long chain omega-3 and omega-6 polyunsaturated fatty acids are essential
for the maintenance of membrane integrity as constituents of membrane
phospholipids and the provision of substrates for eicosenoid synthesis
e.g.; prostaglandins, thromboxanes, and leukotrienes.
With respect to skin disease, both omega-3 and omega-6 fatty acids appear
to be anti-inflammatory. However, the mechanisms of action are different.
The anti-inflammatory effect of the w-6 fatty acids is related to the
synthesis of dihomo-zeta-linolenic acid (DGLA) from dietary gamma-linoleic
acid (GLA), found in high concentrations in borage oil. DGLA can eventually
be converted to arachidonic acid, a potent inflammatory mediator. However,
the conversion process is slow.
DGLA can also be converted to the less inflammatory PGE1. In addition,
DGLA can be converted to a potent anti-inflammatory hydroxy fatty acid
that blocks the lipoxygenase pathway.
Long chain omega-3 fatty acids, such as eicosapentaenoic and docosahexaenoic
acid, directly compete with arachidonic acid for the lipoxygenase and
cycloxygenase enzymes. Subsequent metabolism of eicosapentaenoic acid
generates less inflammatory mediators such as LTB5, and PGE3 compared
to the metabolism of arachidonic acids. In addition, the metabolism of
eicosapentaenoic acid produces hydroxy fatty acids that block the production
of LTB4, a potent chemotatic factor, from arachidonic acids.
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Special
Tips:
| 1. |
Many diets which are labeled "hypoallergenic"
are not really true elimination diets. They may contain many other
protein sources, including those antigens the owner is trying to avoid.
It is important to counsel owners about true elimination diets and
advise them to verify a product’s ingredients by checking the
ingredient list on the label. |
| 2. |
During the initial diagnostic period, it is important that the cat
be fed exclusively HYPOALLERGENIC HP 23TM/MC.
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| 3. |
Snacks, treats, dietary supplements, and flavored medications may
contain antigens. It is important that the owner understands that
even minor deviations from a strict limited antigen diet can lead
to a recurrence of allergic symptoms. |
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REFERENCES:
Vroom MW, Swinnen CA. A clinical study of a soy
protein isolate hydrolysate diet in dogs and cats with adverse reactions
to food. Scientific Proceedings Voorjaarsdagen Amsterdam 2002, p 252.
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