Effects of dietary soy isoflavones on health, steroidogenesis, and thyroid gland function in dogs

Evaluation of Soybean Ingredients in Pet Foods Applications: Systematic Review

Soybean use has been low in pet foods, even though they are an excellent source of protein, polyunsaturated fatty acids, and gut fermentable fibers. The purpose of this evaluation was to conduct a systematic review of the public literature to explore how soybeans have been researched for pet food applications since 2000 and to provide strengths, weaknesses, opportunities, and threats for soybeans in the pet food industry. The review covered a total of 44 articles related to soybean ingredients and their potential value in the pet food arena. The articles were categorized by their research contents and narratively summarized to demonstrate useful information to both the pet and soybean industries. When soybean-based products have been adequately processed to reduce the antinutritive factors, they are comparable to processed animal proteins in nutritional value, palatability, and functionality in pet food processing. We conclude that various food processing technologies and the versatility of soybean ingredients allow soybean to have considerable inclusion potential in pet foods. More research on dietary soybean ingredients regarding pet food processing, fermentation benefits on health, and consumer acceptance will be needed to understand soybean's position in the future pet food industry.

Nutrition and Theriogenology: A Glimpse Into Nutrition and Nutritional Supplementation During Gestation, Lactation, Weaning and Breeding Dogs and Cats

Feeding during normal reproduction is often not thought of until there is a problem with conception or gestational losses. Energy demands of lactation and early puppy/kitten are of concern, particularly in large and giant breed dogs where mineral balance is crucial to normal development. There is a paucity of information around optimizing feeding during conception and gestation with many myths around ingredients which will be explored in this article along with supplements that may be able to support spermatogenesis and conception which primarily comes from the human literature and may have validity in times of difficult conception.

Endocrine-Disrupting Chemicals and Their Effects in Pet Dogs and Cats: An Overview

Over the past few decades, several pollutants classified as environmental endocrine-disrupting chemicals (EDCs) have become a matter of significant public health concern. Companion animals play a major role in human society, and pet ownership is substantially increasing worldwide. These intimate human-pet relationships imply sharing much of the same environment, thus including exposure to similar levels of EDCs in daily routine. Here, we review the current knowledge on the sources and routes of exposure to EDCs in domestic indoor and outdoor environments and discuss whether endocrine disruption is a health concern in pets. We summarize the phenomenon of endocrine disruption, providing examples of EDCs with a known impact on dog and cat health. Then, we propose an overview of the literature on the adverse effects of EDCs in domestic pets, with a special focus on the health of reproductive and thyroid systems. Finally, we explore the potential role of companion animals as unintentional sentinels of environmental exposure to EDCs and the implications for public health risk assessment in a "shared risk" scenario. Overall, this review supports the need for an integrated approach considering humans, animals, and the environment as a whole for a comprehensive assessment of the impact of EDCs on human and animal health.

Roles of plant-based ingredients and phytonutrients in canine nutrition and health

Dogs possess the ability to obtain essential nutrients, established by the Association of American Feed Control Officials (AAFCO), from both animal‐ and plant‐based ingredients. There has been a recent increase in the popularity of diets that limit or completely exclude certain plant‐based ingredients. Examples of these diets include ‘ancestral’ or ‘evolutionary’ diets, raw meat‐based diets and grain‐free diets. As compared to animal sources, plant‐derived ingredients (including vegetables, fruits, grains, legumes, nuts and seeds) provide many non‐essential phytonutrients with some data suggesting they confer health benefits. This review aims to assess the strength of current evidence on the relationship between the consumption of plant‐based foods and phytonutrients (such as plant‐derived carotenoids, polyphenols and phytosterols) and biomarkers of health and diseases (such as body weight/condition, gastrointestinal health, immune health, cardiovascular health, visual function and cognitive function) from clinical trials and epidemiological studies. This review highlights the potential nutritional and health benefits of including plant‐based ingredients as a part of balanced canine diets. We also highlight current research gaps in existing studies and provide future research directions to inform the impact of incorporating plant‐based ingredients in commercial or home‐prepared diets.

Effect of oophorosalpingo-hysterectomy on serum antioxidant enzymes in female dogs

There are few studies evaluating the oxidant-antioxidant status after oophorosalpingohysterectomy (OSH) in female dogs. Here we determined the effect of OSH on antioxidant enzymes in serum, and quantified morphological changes in subcutaneous adipocytes. Lateral OSH was performed in 12 female dogs. The concentration of 17β-estradiol (17β-E₂), the activities of extracellular superoxide dismutase (SOD-ec), glutathione peroxidase (GPx), glutathione-S-transferase (GST) and glutathione reductase (GR) were determined. Glutathione (GSH), glutathione disulfide (GSSG), lipid peroxidation (LPO), total antioxidant capacity (TAC), carbonylation and vitamin C were measured in serum. Subcutaneous adipose tissue was obtained to determine morphological changes and cell number, under basal conditions and six months after OSH. The SOD-ec, GPx and GST activities increased significantly (p ≤ 0.05), LPO, carbonylation and GSSG also increased. GSH and vitamin C decreased (p = 0.03). 17β-E₂ tended to decrease six months after OSH. Hypertrophy of subcutaneous adipocytes was observed after OSH from the first month and was accentuated after six months (p = 0.001). The results suggest that 17β-E₂ decreases after OSH and alters the antioxidant enzyme activities in serum thus, redox balance is altered. These changes are associated with an increase in body weight and hypertrophy of subcutaneous adipose tissue.

Dietary phytoestrogens, intestinal microflora and human health

With the growth of age, the amount of estrogens produced by the human body will get less and less. Studies have shown that estrogen deficiency may cause many kinds of diseases, such as cardiovascular diseases, osteoporosis, and syndrome of menopause. Estrogens are also distributed extensively in numerous types of plants. Since there is a trace amount of natural estrogen in plants, our body can achieve continuous phytoestrogen supplementation while our health will not be influenced or damaged by the absorbed phytoestrogens in diets. After being absorbed, the phytoestrogens in diets may be converted by intestinal microflora to different metabolites with higher estrogenic activity. This review summarizes the types and distributions of phytoestrogens in diets, their metabolism, metabolites and bioactivities, with an aim to provide some guidelines for further study and utilization of microbial biotransforming metabolites of phytoestrogens.

Bioactivation of Phytoestrogens: Intestinal Bacteria and Health

Phytoestrogens are polyphenols similar to human estrogens found in plants or derived from plant precursors. Phytoestrogens are found in high concentration in soya, flaxseed and other seeds, fruits, vegetables, cereals, tea, chocolate, etc. They comprise several classes of chemical compounds (stilbenes, coumestans, isoflavones, ellagitannins, and lignans) which are structurally similar to endogenous estrogens but which can have both estrogenic and antiestrogenic effects. Although epidemiological and experimental evidence indicates that intake of phytoestrogens in foods may be protective against certain chronic diseases, discrepancies have been observed between in vivo and in vitro experiments. The microbial transformations have not been reported so far in stilbenes and coumestans. However, isoflavones, ellagitanins, and lignans are metabolized by intestinal bacteria to produce equol, urolithins, and enterolignans, respectively. Equol, urolithin, and enterolignans are more bioavailable, and have more estrogenic/antiestrogenic and antioxidant activity than their precursors. Moreover, equol, urolithins and enterolignans have anti-inflammatory effects and induce antiproliferative and apoptosis-inducing activities. The transformation of isoflavones, ellagitanins, and lignans by intestinal microbiota is essential to be protective against certain chronic diseases, as cancer, cardiovascular disease, osteoporosis, and menopausal symptoms. Bioavailability, bioactivity, and health effects of dietary phytoestrogens are strongly determined by the intestinal bacteria of each individual.

Soy isoflavone metabolism in cats compared with other species: urinary metabolite concentrations and glucuronidation by liver microsomes

1. Soybean is a common source of protein in many pet foods. Slow glucuronidation of soy-derived isoflavones in cats has been hypothesized to result in accumulation with adverse health consequences. Here, we evaluated species' differences in soy isoflavone glucuronidation using urine samples from cats and dogs fed a soy-based diet and liver microsomes from cats compared with microsomes from 12 other species. 2. Significant concentrations of conjugated (but not unconjugated) genistein, daidzein and glycitein, and the gut microbiome metabolites, dihydrogenistein and dihydrodaidzein, were found in cat and dog urine samples. Substantial amounts of conjugated equol were also found in cat urine but not in dog urine. 3. β-Glucuronidase treatment showed that all these compounds were significantly glucuronidated in dog urine while only daidzein (11%) and glycitein (37%) showed any glucuronidation in cat urine suggesting that alternate metabolic pathways including sulfation predominate in cats. 4. Glucuronidation rates of genistein, daidzein and equol by cat livers were consistently ranked within the lowest 3 out of 13 species' livers evaluated. Ferret and mongoose livers were also ranked in the lowest four species. 5. Our results demonstrate that glucuronidation is a minor pathway for soy isoflavone metabolism in cats compared with most other species.

Canine and feline obesity: a review of pathophysiology, epidemiology, and clinical management

Canine and feline obesity rates have reached pandemic proportions and are similar to those in humans, with approximately 30%-40% of dogs and cats being overweight to obese. Obesity has been associated with other health problems, including osteoarthritis, renal disease, skin disease, insulin resistance, and neoplasia in dogs, while in cats obesity is associated with dermatological issues, diabetes mellitus, neoplasia, and urolithiasis. The health issues appear to be slightly different across the two species, which may be due to some inherent differences in the hormonal milieu involved in obesity that differs between the dog and the cat. In this review, we discuss the complicated nature of the pathogenesis of obesity, the hormonal stimulus for orexigenic and anorexigenic behavior, adipose tissue as an endocrine organ, and most importantly, clinical management of the number one disease in canine and feline medicine.

Evaluation of estrogenic activity in animal diets using in vitro assay

A yeast estrogen bioassay (RIKILT REA) was in-house validated for feed on the 5μg 17β-estradiol-equivalents per kg level according to EC Decision 2002/657/EC. All the performance characteristics met the criteria as defined in the Decision and the REA is able to detect 17β-estradiol in animal feed at a low level of 1.15-2μgkg(-1). Subsequently, the developed and validated procedure was applied to determine the estrogenic activity in 24 feed samples intended for food producing animals, pets and laboratory animals. Two batches of rodent diet Murigran and one dog feed have been presented as a suspect, i.e. gave responses above the determined decision limit (CCα) and detection capability (CCβ). In assessing the performance of the estrogenic activity in these diets evaluated by comparison with the 17β-estradiol calibration curve, 17β-estradiol-equivalence levels of 7.07μg EEQkg(-1) and 9.54μg EEQkg(-1) in two batches of rodent diet and 5.3μg EEQkg(-1) in dog feed have been established. The activities observed in the rodent feed could be explained by chemical analysis, revealing high amounts of genistein, daidzein and trace amounts of zearalenone. In addition, the estrogenic activity in one of rodent feed was above the established CCα, but below the CCβ values established and all other samples showed no estrogenic activity with responses below the CCα value, which corresponds to levels below 2μg EEQkg(-1).

Impact of flavonoids on thyroid function

Flavonoids are polyphenolic compounds of natural occurrence produced by plants that are largely consumed both for therapeutic purposes and as food. Experimental data have shown that many flavonoids could inhibit thyroperoxidase activity, decreasing thyroid hormones levels thus increasing TSH and causing goiter. In humans, infants fed with soy formula have been shown to develop goiter. However, in post-menopausal women soy intake did not affect thyroid function. In thyroid tumor cell line, flavonoids were shown to inhibit cell growth, but they can also decrease radioiodine uptake, that could reduce the efficacy of radioiodine therapy. Flavonoids could also affect the availability of thyroid hormones to target tissues, by inhibiting deiodinase activity or displacing T4 from transthyretin. Thus, flavonoids have been shown to interfere with many aspects of the thyroid hormones synthesis and availability in in vivo and in vitro models. In the present article, we review and synthesize the literature on the effects of flavonoids on thyroid and discuss the possible relevance of these effects for humans.

Effects of dietary soy intake on maternal thyroid functions and serum anti-thyroperoxidase antibody level during early pregnancy

Soy and its isoflavones have been suggested to suppress thyroperoxidase (TPO), induce goiter, inhibit deiodinase, and modulate immune functions. This study initially investigated the effects of dietary soy consumption on maternal thyroid functions and anti-TPO antibody (TPOAb) production during early pregnancy. Data were collected through questionnaire from 505 women enrolled during early pregnancy by random sampling in Shenyang, China. Based on soy intake frequency, the subjects were divided into three groups (frequent [three or more times per week], conventional [more than twice per month but less than three times per week], and occasional [two or fewer times per month]). Serum thyrotropin (TSH), free thyroxine (FT(4)), and TPOAb were measured by chemiluminescence immunoassay. Additionally, the concentrations of two primary isoflavones (daidzein and genistein) and creatinine were assessed in the spot urine samples from representative subjects (about 20%) randomly selected from the three groups. The percentages of frequent, conventional, and occasional consumers were 18.6%, 62.6%, and 18.8%, respectively. No difference was found in age, medical records, family history of thyroid diseases, serum FT(4), TSH, and TPOAb levels, TPOAb-positive percentages, or prevalence of thyroid dysfunctions among the groups. Both urinary daidzein and genistein levels were significantly higher in the frequent consumers compared with the other two groups. No correlations were found between urinary isoflavone levels and serum FT(4) or TSH. Urinary isoflavone levels were not significantly different between TPOAb-positive and -negative women among the randomly selected representative subjects. On the whole, our findings suggest dietary soy consumption during early pregnancy is not associated with the development of thyroid dysfunction or autoimmunity.