Overweight and osteoarthritis
Obesity is a public health problem for humans but also for animals. It is estimated that 33% of adult humans in the United States
are obese. In the dog population, up to 41% of individuals are overweight. Canine and feline obesity has reached pandemic proportions in recent years, and is associated with many
other health problems including urinary, skin, endocrine, tumor and osteoarticular diseases
of which osteoarthritis is the most important.
Osteoarthritis is a degenerative disease affecting the joints.
It has a high prevalence in dogs, affecting at least 20% of adults. Prevalence of radiographic signs of osteoarthritis
in cats varies from 16 to 91% according to the publications; this pathology
is particularly present in the older cat. In humans as in
In dogs, osteoarthritis is the most common cause of pain and physical disability.
Obesity has long been considered a factor predisposing to the onset of osteoarthritis and aggravating its clinical signs in men
as in the animal. Many articles report an association
between knee osteoarthritis and obesity in men. In veterinary medicine, the association between osteoarthritis of the hip and overweight is established…
capdouleur.fr. 6 december 2021
Influence of overweight in the development of osteoarthritis
Introduction
Obesity is a public health problem in humans and animals. In the United States, 33% of adults are considered obese, and up to 41% of the canine population is overweight. Canine and feline obesity has reached pandemic proportions in recent years and is associated with many other health problems including urinary, skin, endocrine or tumor pathologies and osteoarticular diseases of which osteoarthritis is the most important. Osteoarthritis is a degenerative disease affecting the joints that is highly prevalent in dogs, affecting at least 20% of adult dogs. Radiographic signs of osteoarthritis in cats vary from 16 to 91% depending on the journal, and are particularly present in older cats. In both humans and dogs, osteoarthritis is the most common cause of pain and physical disability. Obesity has long been considered a predisposing factor in the development of osteoarthritis and aggravates the clinical signs in humans and animals. Many reviews report an association between knee osteoarthritis and obesity in men. In veterinary medicine, the association between osteoarthritis of the hip and overweight is established.
The dog, a model for studying osteoarthritis in humans
The relatively short lifespan of the dog compared to humans allows for a longitudinal comparison of osteoarthritis disease between the two species and of the therapies implemented during clinical signs of osteoarthritis. However, the quadrupedal position of the dog compared to the bipedal position of the man must be taken into account. In the dog, the weight distribution is 60% on the forelimbs and 40% on the hindlimbs, with an angulation of about 20 degrees on the femorotibial joint which could have consequences on the development of osteoarthritis, still unknown. Some epidemiological aspects must also be emphasized, since this disease is influenced in dogs by breed, size, weight, sex, age and sterilization. Obesity, for example, is known to be a risk factor in humans but assessing the importance of its role in the development of osteoarthritis is proving to be a challenge. In dogs, one study showed that when two groups of dogs with identical epidemiological characteristics are fed in different ways (ad libitum or restricted), there is a clear difference in the time to onset of osteoarthritis; 25% of the ad libitum-fed dogs versus 4% of the restricted-fed dogs have radiographic evidence of hip osteoarthritis at 5 years.
Endocrine adipose tissue, a culprit in the aggravation of degenerative joint disease
A recent study of hip and knee joints in dogs shows an increased concentration of adipokines in synovial fluid, intrapatellar pad fat, chondrocytes and synoviocytes, positively associated with the severity of OA. In humans, the expression of leptin and its receptors has been shown to be increased in osteoarthritic cartilage compared to healthy tissue, and in advanced osteoarthritis compared to early osteoarthritis. Leptin, produced by adipocytes, plays a role in regulating appetite by activating hypothalamic receptors, it also participates in other biological systems such as immune function or inflammation. Within the severely affected cartilage, leptin is more present in the obese individual compared to the normal weight individual. This suggests local as well as systemic hyperleptinemia in the overweight individual. Leptin has long-term inhibitory effects on chondrocytes, and induces the production of IL-1, MMP-3 and MMP-9 in a dose-dependent manner, which ultimately contributes to the catabolic effect on chondrocyte metabolism. Adiponectin is another adipokine synthesized by adipocytes and other tissues. It is present in large quantities in the systemic circulation and produced locally by chondrocytes and synovial fibroblasts. In humans and mice, chondrocytes in contact with adiponectin produce local stress factors (NO, MMP-3 and MMP-9), participating in the phenotypic loss of chondrocytes, their apoptosis and the degradation of the extracellular matrix. The progressive discovery of the role of adipokines in the pathophysiology of osteoarthritis represents a new class of target molecules for the therapeutic management of patients.
Pathogenesis of osteoarthritis
The initiating cause of osteoarthritis, in humans or animals, remains unknown. Two types of osteoarthritis can be distinguished: primary or secondary diseases of the articular cartilage. Primary osteoarthritis may be due to repeated impacts on the joint, to age or to a genetic predisposition (e.g. hip dysplasia found in certain human or animal populations). Secondary osteoarthritis may result from orthopedic disease, injury or abnormal joint congruence. More precisely: the predisposing factors for the development of osteoarthritis in dogs are elbow and hip dysplasia, orthopedic surgeries, rupture of the cranial cruciate ligament, joint fractures or incongruities due to limb deformities in particular. In these contexts, the inflammation of the joint is permanent and the body tries to maintain the stability of the joint through bone proliferation.tabilité de l’articulation grâce à une prolifération osseuse. This corresponds to an articular inflammatory process where degradation or even loss of the proteoglycans of the extracellular matrix predominates, resulting in a general modification of the anatomy of the articular cartilage. The pathogenesis is based on the destruction of cartilage and subchondral bone, histologically appear cartilage cracks. The osteoarthritic joint is characterized by a decrease in its elastic capacities despite the attempts of the chondrocytes to repair it and by a densification of the subchondral bone which increases the ossification of the joint. Several markers of this degenerative process have been identified: prostaglandins E2 (PGE2), metalloproteinases (MMPs), substance P, tumor necrosis factor (TNF-alpha), pro-inflammatory interleukins such as IL1, IL6, IL10, and leukotrienes accompany these changes; due to their action on oxidative stress, they participate in the advancement of the destruction of the osteoarthritis joint.
Obesity, a predisposing and aggravating factor?
The etiology of osteoarthritis associated with obesity therefore remains unclear. The effect of excess weight on the biomechanics of the compressed joint in humans and animals is the primary suspected cause of degenerative joint disease. Néanmoins, une étude chez l’homme montre une prévalence augmentée de l’arthrose des articulations de la main chez l’individu obèse. Since these joints do not support the weight of the body, it is assumed that obesity is accompanied by a systemic inflammatory state that becomes a risk factor for the development of osteoarthritis. Indeed, adipose tissue in both humans and animals secretes a wide variety of adipokines, suggesting that metabolic factors associated with obesity are present, independent of the risk of developing OA. Inflammatory mediators produced by adipose tissue include cytokines (MMPs, IL1, IL6, and TNF-alpha), and adipokines (leptin, vistafine, adiponectin and resistin). The exact role of cytokines is not yet clear, but they are found in the inflamed tissues of the synovial joint during osteoarthritis, and they mediate the degeneration of the cartilage.
Diseases associated with obesity and their participation in the aggravation of osteoarthritis
Other pathologies associated with obesity seem to participate in the aggravation of arthrosic disease. In humans, it has been hypothesized that atherosclerosis of the subchondral bone and associated ischemia may contribute to disease progression. This raises the question of whether treatment of hypercholesterolemic states in these patients would slow its progression. An association has also been established between diabetes mellitus in men and osteoarthritis of the joints of the hand. The deposition of glucagon metabolism products is accelerated in diabetic patients in the articular cartilage. This increases the fragility of collagen, increases the degradation of the extracellular matrix and slows the production of proteoglycans. In the event that these degradation products of glucagon metabolism promote the progression of osteoarthritis, it may be worthwhile to prevent and manage human type 2 diabetes to reduce the prevalence of osteoarthritis in these individuals.
Conclusion
The relationship between osteoarthritis and obesity is complex and clinical and therapeutic findings are still recent. It is commonly accepted that 4 potential risk factors present in the overweight individual are associated with the development of osteoarthritis: the biomechanical component, adipokines, vascular and endocrine diseases. These are all potential therapeutic targets for reducing the progression of osteoarthritis in humans and animals. In addition to these risk factors, there is a complex interaction between the environment, genetics and possible osteoarticular trauma.
Osteoarthritis is a degenerative disease that cannot be treated, so it is essential to prevent its appearance and slow its progression. Managing the patient’s weight helps to reduce mechanical and organic stress within the affected joints. Once osteoarthritis develops, it is important to take a multi-modal approach to managing the animal/owner pair. This is based on the evaluation of the animal’s quality of life, on the management of its pain, on the maintenance of its activity but also on the provision of an adapted diet to maintain an optimal weight.