SUMMARY: ROYAL CANIN Veterinary Diet^TM/MC canine HYPOALLERGENIC HP 19^TM/MC is a highly palatable, highly digestible, complete, and balanced diet formulated to meet the requirements for canine adult maintenance. This diet is a hydrolyzed soy protein isolate, which is lactose and wheat gluten free and indicated in both the diagnosis and management of adverse reactions to food.

back to top

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. Proteins are most commonly implicated in dietary sensitivity in dogs. In dogs, 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 generally manifest as dermatological or gastrointestinal disease. The most common clinical signs are pruritus, vomiting, and diarrhea. Occasionally, dogs 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 dogs. The aim is to feed a complete and balanced diet while strictly limiting the protein and carbohydrate sources by feeding protein sources to which the dog has never been previously exposed.

The reason an immunological response against a specific protein (or food allergen) is mounted in certain individuals is not fully understood. The lipoprotein 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, rather than the typical IgG response, is mounted. The IgE antibodies bind to high affinity receptors on mast cells. With re-exposure, the protein allergen can bind 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 typical of food allergy.

Degranulation of the mast cells requires that the allergenic protein contains two binding sites, or epitopes, which 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 below those commonly eliciting an allergic response.

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 to the residual antigenic proteins and large polypeptides. Highly digestible proteins are completely digested to free amino acids and small peptides which have 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 the growth of beneficial intestinal bacteria and the production of short chain fatty acids. Short chain fatty acids have a trophic role 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 with a lipid matrix consisting of fatty acids, sterols, and ceramides held together in a brick and mortar analogy.

In terms of barrier function, ceramide-1 is thought to be key component. Ceramide-1 contains linoleic acid as one of its major components. In this respect, linoleic acid is believed to play a crucial role in barrier function of the skin. Waltham Science has also shown that the addition of biotin, pantothenic acid, nicotinamide, pyridoxine, choline, inositol, proline, and histadine increases the synthesis of ceramides and lipids. The 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 eicosanoid synthesis; e.g. prostaglandins, thromboxanes, and leukotrienes. With respect to skin disease, both omega-3 and omega-6 appear to be anti-inflammatory. However, the mechanisms of action are different.

The anti-inflammatory effect of the omega-6 fatty acids is related to the synthesis of dihomo-zeta-linolenic acid (DGLA) from dietary GLA (found in high concentrations in borage oil). DGLA can 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 acid 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 acid.

back to top

Special Tips

back to top

REFERENCES:
Biourge VC, Fontaine J, Vroom M. Diagnoses of adverse reactions in dogs: Efficacy of a soy hydrolysate-based diet. Waltham International Science Symposium, Bangkok, Thailand, October 28-31, 2003, p22.

Biourge VC, Fontaine J. Exocrine pancreatic insufficiency (EPI) and adverse reaction to food: A positive response to a high fat, soy isolate hydrolysate based diet. Waltham International Science Symposium, Bangkok, Thailand, October 28-31, 2003 p58.

Dossin O, Semin MO, Raymond I, et al. Soy isolate hydrolysate in the management of inflammatory bowel disease in dogs. J Vet Intern Med 2002;16(3):327.

Vroom M, Swinnen C. A clinical study of a soy protein isolate hydrolysate diet, in dogs and cats with adverse reactions to food. Proc. of Voorjaarsdagen 2002, p252.

Dossin O, Semin MO, Raymond I, et al. Soy hydrolysate in the management of Canine IBD: A preliminary study. Proc. 12th ECVIM-CA/ESVIM congress, Munich September 2002, p167.

Van Pottelberge D, Biourge V, Marniquet P, et al. Efficacy of a hypoallergenic diet containing soy isolate hydrolysate for the diagnosis and management of food hypersensitivity in dogs: a multicentric field study. Proc. Joint Nutrition Symposium, Antwerpen Belgium August 21-25, 2002, p17.

Fontaine J. Réactions cutanées induites par l’alimentation : Intérêt d’un aliment contenant des protéines hydrolysées. Congrès CNVSPA-AFVAC, SAVAB Lille 23-25 Novembre 2001, p160.

back to top