The mechanical and biochemical properties of tail tendon in a rat model of obesity: Effect of moderate exercise and prebiotic fibre supplementation

Saturated fatty acids negatively affect musculoskeletal tissues in vitro and in vivo

Fish oils rank among the world's most popular nutritional supplements and are purported to have numerous health benefits. Previous work suggested that fish oils increase collagen production; however, the effect of fish oils on musculoskeletal health is poorly understood. Further, the divergent effects of omega-3 (Ω3FA) and saturated fatty acids (SFA) remains poorly understood. We tested the effects of Ω3FA and SFAs on in vitro-engineered human ligament (EHL) function. EHLs were treated with bovine serum albumin (BSA)-conjugated eicosapentaenoic acid (EPA, 20:5(n-3)), palmitic acid (PA, 16:0), or a BSA control for 6 days. EPA did not significantly alter, whereas PA significantly decreased EHL function and collagen content. To determine whether this was an in vitro artifact, mice were fed a control or high-lard diet for 14 weeks and musculoskeletal mass, insulin sensitivity, and the collagen content, and mechanics of tendon and bone were determined. Body weight was 40 % higher on a HFD, but muscle, tendon, and bone mass did not keep up with body weight resulting in relative losses in muscle mass, tendon, and bone collagen, as well as mechanical properties. Importantly, we show that PA acutely decreases collagen synthesis in vitro to a similar extent as the decrease in collagen content with chronic treatment. These data suggest that Ω3FAs have a limited effect on EHLs, whereas SFA exert a negative effect on collagen synthesis resulting in smaller and weaker musculoskeletal tissues both in vitro and in vivo.

Metabolic Syndrome and Tendon Disease: A Comprehensive Review

Metabolic syndrome (MS) is a multifaceted pathological condition characterized by the atypical accumulation of various metabolic components such as central obesity or excess weight, hyperlipidemia, low-density lipoprotein (LDL), hypertension, and insulin resistance. Recently, MS has been recognized as a notable contributor to heart and circulatory diseases. In addition, with increasing research, the impact of MS on tendon repair and disease has gradually emerged. Recent studies have investigated the relationship between tendon healing and diseases such as diabetes, dyslipidemia, obesity, and other metabolic disorders. However, diabetes mellitus (DM), hypercholesterolemia, obesity, and various metabolic disorders often coexist and together constitute MS. At present, insulin resistance is considered the major pathological mechanism underlying MS, central obesity is regarded as the predominant factor responsible for it, and dyslipidemia and other metabolic diseases are known as secondary contributors to MS. This review aims to evaluate the current literature regarding the impact of various pathological conditions in MS on tendon recovery and illness, and to present a comprehensive overview of the effects of MS on tendon recovery and diseases, along with the accompanying molecular mechanisms.

A high-fat diet has negative effects on tendon resident cells in an in vivo rat model

BACKGROUND

Tendinopathy is a major complication of diet-induced obesity. However, the effects of a high-fat diet (HFD) on tendon have not been well characterised. We aimed to determine: [1] the impact of a HFD on tendon properties and gene expression; and [2] whether dietary transition to a control diet (CD) could restore normal tendon health.

METHODS

Sprague-Dawley rats were randomised into three groups from weaning and fed either a: CD, HFD or HFD for 12 weeks and then CD thereafter (HF-CD). Biomechanical, histological and structural evaluation of the Achilles tendon was performed at 17 and 27 weeks of age. Tail tenocytes were isolated with growth rate and collagen production determined. Tenocytes and activated THP-1 cells were exposed to conditioned media (CM) of visceral adipose tissue explants, and gene expression was analysed.

RESULTS

There were no differences in the biomechanical, histological or structural tendon properties between groups. However, tenocyte growth and collagen production were increased in the HFD group at 27 weeks. There was lower SOX-9 expression in the HFD and HF-CD groups at 17 weeks and higher expression of collagen-Iα1 and matrix metalloproteinase-13 in the HFD group at 27 weeks. THP-1 cells exposed to adipose tissue CM from animals fed a HFD or HF-CD had lower expression of Il-10 and higher expression of Il-1β.

CONCLUSIONS

In this rodent model, a HFD negatively altered tendon cell characteristics. Dietary intervention restored some gene expression changes; however, adipose tissue secretions from the HF-CD group promoted an increased inflammatory state in macrophages. These changes may predispose tendon to injury and adverse events later in life.

Prebiotic and Exercise Do Not Alter Knee Osteoarthritis in a Rat Model of Established Obesity

OBJECTIVE

Metabolic disturbance is a known risk factor for cardiovascular disease and has been identified as a risk factor for the development of knee osteoarthritis. In this study, we sought to determine the effects of prebiotic fiber supplementation, aerobic exercise, and the combination of the 2 interventions, on the progression of knee osteoarthritis in a high-fat/high-sucrose diet-induced rat model of metabolic disturbance.

DESIGN

Twelve-week-old male CD-Sprague-Dawley rats were either fed a standard chow diet, or a high-fat/high-sucrose diet. After 12 weeks on diets, rats consuming the high-fat/high-sucrose diet were randomized into 4 subgroups: a sedentary, an aerobic exercise, a prebiotic fiber supplementation, and an aerobic exercise combined with prebiotic fiber supplementation group. The aerobic exercise intervention consisted of a progressive treadmill training program for 12 weeks, while the prebiotic fiber was added to the high-fat/high-sucrose diet at a dose of 10% by weight for 12 weeks. Outcome measures included knee joint damage, body mass, percent body fat, bone mineral density, insulin sensitivity, and serum lipid profile.

RESULTS

Aerobic exercise, or the combination of prebiotic fiber and aerobic exercise, improved select markers of metabolic disturbance, but not knee joint damage. However, these results need to be considered in view of the fact that the chow-fed rats had similar knee OA-like damage as the high-fat/high-sucrose-fed rats.

CONCLUSION

Exercise or prebiotics did not increase joint damage and might be good strategies for populations with metabolic knee osteoarthritis to alleviate other health-related problems, such as diabetes or cardiovascular disorders.

Obesity Impairs Enthesis Healing After Rotator Cuff Repair in a Rat Model

BACKGROUND

Being overweight or obese is associated with poor outcomes and an increased risk of failure after rotator cuff (RC) surgery. However, the effect of obesity on enthesis healing has not been well characterized.

HYPOTHESES

Diet-induced obesity (DIO) would result in inferior enthesis healing in a rat model of RC repair, and a dietary intervention in the perioperative period would improve enthesis healing.

STUDY DESIGN

Controlled laboratory study.

METHODS

Male Sprague-Dawley rats were divided into 3 weight-matched groups (n = 26 per group): control diet (CD), high-fat diet (HFD), or HFD until surgery and then CD thereafter (HF-CD). After 12 weeks, the left supraspinatus tendon was detached, followed by immediate repair. Animals were sacrificed, and RCs were harvested at 2 and 12 weeks after surgery for biomechanical and histological evaluations. Metabolic end points were assessed using dual-energy X-ray absorptiometry and plasma analyses.

RESULTS

DIO was established in the HFD and HF-CD groups before surgery and subsequently reversed in the HF-CD group after surgery. At 12 weeks after surgery, the body fat percentage (P = .0021) and plasma leptin concentration (P = .0025) were higher in the HFD group compared with the CD group. Histologically, the appearance of the repaired entheses was poorer in both the HFD and HF-CD groups compared with the CD group at 12 weeks after surgery, with semiquantitative scores of 6.20 (P = .0078), 4.98 (P = .0003), and 8.68 of 15, respectively. The repaired entheses in the HF-CD group had a significantly lower load to failure (P = .0278) at 12 weeks after surgery compared with the CD group, while the load to failure in the HFD group was low but not significantly different (P = .0960). There were no differences in the biomechanical and histological results between the groups at 2 weeks after surgery. Body mass at the time of surgery, plasma leptin concentration, and body fat percentage were negatively correlated with histology scores and plasma leptin concentration was correlated with load to failure at 12 weeks after surgery.

CONCLUSION

DIO impaired enthesis healing in this rat RC repair model, with inferior biomechanical and histological outcomes. Restoring a normal weight with dietary changes after surgery did not improve healing outcomes.

CLINICAL RELEVANCE

Obesity is a potentially modifiable factor that impairs RC healing and increases the risk of failure after surgery. Exploring interventions that improve the metabolic state of obese patients and counseling patients appropriately about their modest expectations after repair should be considered.

Moderate aerobic exercise, but not dietary prebiotic fibre, attenuates losses to mechanical property integrity of tail tendons in a rat model of diet-induced obesity

The purpose of this study was to investigate the alterations with obesity, and the effects of moderate aerobic exercise or prebiotic dietary-fibre supplementation on the mechanical and biochemical properties of the tail tendon in a rat model of high-fat/high-sucrose (HFS) diet-induced obesity. Thirty-two male Sprague-Dawley rats were randomized to chow (n = 8) or HFS (n = 24) diets. After 12-weeks, the HFS fed rats were further randomized into sedentary (HFS sedentary, n = 8), exercise (HFS + E, n = 8) or prebiotic fibre supplementation (HFS + F, n = 8) groups. After another 12-weeks, rats were sacrificed, and one tail tendon was isolated and tested. Stress-relaxation and stretch-to-failure tests were performed to determine mechanical properties (peak, steady-state, yield and failure stresses, Young's modulus, and yield and failure strains) of the tendons. The hydroxyproline content was also analyzed. The HFS sedentary and HFS + F groups had higher final body masses and fat percentages compared to the chow and HFS + E groups. Yield strain was reduced in the HFS sedentary rats compared to the chow rats. Peak and steady-state stresses, failure strain, Young's modulus, and hydroxyproline content were not different across groups. Although the HFS + E group showed higher failure stress, yield stress, and yield strain compared to the HFS sedentary group, HFS + F animals did not produce differences in the properties of the tail tendon compared to the HFS sedentary group. These results indicate that exposure to a HFS diet led to a reduction in the yield strain of the tail tendon and aerobic exercise, but not fibre supplementation, attenuated these diet-related alterations to tendon integrity.

A Maternal High Fat Diet Leads to Sex-Specific Programming of Mechanical Properties in Supraspinatus Tendons of Adult Rat Offspring

Background: Over half of women of reproductive age are now overweight or obese. The impact of maternal high-fat diet (HFD) is emerging as an important factor in the development and health of musculoskeletal tissues in offspring, however there is a paucity of evidence examining its effects on tendon. Alterations in the early life environment during critical periods of tendon growth therefore have the potential to influence tendon health that cross the lifespan. We hypothesised that a maternal HFD would alter biomechanical, morphological and gene expression profiles of adult offspring rotator cuff tendon. Materials and Methods: Female Sprague-Dawley rats were randomly assigned to either: control diet (CD; 10% kcal or 43 mg/g from fat) or HFD (45% kcal or 235 mg/g from fat) 14 days prior to mating and throughout pregnancy and lactation. Eight female and male offspring from each maternal diet group were weaned onto a standard chow diet and then culled at postnatal day 100 for tissue collection. Supraspinatus tendons were used for mechanical testing and histological assessment (cellularity, fibre organisation, nuclei shape) and tail tendons were collected for gene expression analysis. Results: A maternal HFD increased the elasticity (Young's Modulus) in the supraspinatus tendon of male offspring. Female offspring tendon biomechanical properties were not affected by maternal HFD. Gene expression of SCX and COL1A1 were reduced in male and female offspring of maternal HFD, respectively. Despite this, tendon histological organisation were similar between maternal diet groups in both sexes. Conclusion: An obesogenic diet during pregnancy increased tendon elasticity in male, but not female, offspring. This is the first study to demonstrate that maternal diet can modulate the biomechanical properties of offspring tendon. A maternal HFD may be an important factor in regulating adult offspring tendon homeostasis that may predispose offspring to developing tendinopathies and adverse tendon outcomes in later life.