Exercise Speeds Cutaneous Wound Healing in High-Fat Diet-Induced Obese Mice

Exercise Training for People With Diabetes-related Foot Ulcers---A Systematic Review of Glycemia, Fitness, and Wound-healing Outcomes

OBJECTIVES

Regular physical activity is a key, patient-centred therapy for people with diabetes to manage their glycemia. The International Working Group on the Diabetic Foot recommends optimization of glycemic control for people with/at risk of diabetes-related foot ulcer (DFU); however, people with DFU are commonly instructed by clinicians to avoid physical activity so as not to worsen the ulcer. The effects of exercise on glycemia, fitness, and wound healing in people with active DFU are not clear. In this study we examined the effects of regular exercise (training) on glycemia, cardiorespiratory fitness, muscular strength, metabolic health, and ulcer healing in adults with diabetes and an active foot ulcer.

METHODS

Online databases and reference lists of included studies were searched from earliest records to December 2023. Studies involving adult populations with DFU and incorporating interventions of exercise training were included. Data were extracted independently by 2 reviewers.

RESULTS

Of the 5,592 studies screened, 8 were included, with a total of 213 participants. Exercise interventions involved foot range-of-movement exercises and/or aerobic and/or resistance-type exercise. None of the studies reported on cardiorespiratory fitness or anthropometry and limited data were available for glycemic and muscular strength outcomes. Interpretation of data on safety, wound healing, and adherence to exercise were limited due to inconsistent reporting.

CONCLUSIONS

Despite some data that exercise may have a positive impact on wound healing, evidence regarding its benefits and safety is significantly lacking, despite metabolic (particularly glycemic) and fitness outcomes being core to the rationale for exercise therapy in diabetes. Given the importance of exercise in current management guidelines for diabetes, and the plausibility of positive health effects of exercise training for people with DFU, there is a need for research to move from foot-focussed to person-centred outcomes to better inform the implementation of exercise therapy for people with DFU.

Impact of a High-Fat Diet at a Young Age on Wound Healing in Mice

As the prevalence of juvenile-onset obesity rises globally, the multitude of related health consequences gain significant importance. In this context, obesity is associated with impaired cutaneous wound healing. In experimental settings, mice are the most frequently used model for investigating the effect of high-fat diet (HFD) chow on wound healing in wild-type or genetically manipulated animals, e.g., diabetic ob/ob and db/db mice. However, these studies have mainly been performed on adult animals. Thus, in the present study, we introduced a mouse model for a juvenile onset of obesity. We exposed 4-week-old mice to an investigational feeding period of 9 weeks with an HFD compared to a regular diet (RD). At a mouse age of 13 weeks, we performed excisional and incisional wounding and measured the healing rate. Wound healing was examined by serial photographs with daily wound size measurements of the excisional wounds. Histology from incisional wounds was performed to quantify granulation tissue (thickness, quality) and angiogenesis (number of blood vessels per mm2). The expression of extracellular matrix proteins (collagen types I/III/IV, fibronectin 1, elastin), inflammatory cytokines (MIF, MIF-2, IL-6, TNF-α), myofibroblast differentiation (α-SMA) and macrophage polarization (CD11c, CD301b) in the incisional wounds were evaluated by RT-qPCR and by immunohistochemistry. There was a marked delay of wound closure in the HFD group with a decrease in granulation tissue quality and thickness. Additionally, inflammatory cytokines (MIF, IL-6, TNF-α) were significantly up-regulated in HFD- when compared to RD-fed mice measured at day 3. By contrast, MIF-2 and blood vessel expression were significantly reduced in the HFD animals, starting at day 1. No significant changes were observed in macrophage polarization, collagen expression, and levels of TGF-β1 and PDGF-A. Our findings support that an early exposition to HFD resulted in juvenile obesity in mice with impaired wound repair mechanisms, which may be used as a murine model for obesity-related studies in the future.

Physical Activity Participation in People With an Active Diabetic Foot Ulceration: A Scoping Review

BACKGROUND

Being physically active on a regular basis has a favourable impact on diabetes-related complications. With the exception of evidence advising individuals with an active diabetic foot ulceration (DFU) to avoid weight-bearing activity, no physical activity (PA) recommendations are currently provided for this population.

OBJECTIVE

The aim of this scoping review was to examine and map the existing research evidence of PA participation for individuals with an active DFU.

DESIGN

A scoping review using the Arksey and O'Malley framework was conducted in electronic databases and grey literature from inception to June 2020 to identify publications that investigated individuals with type 1 or type 2 diabetes and an active DFU at enrolment in relation to a PA intervention. Reported outcomes had to inform on effects of PA on any health or wound parameters.

RESULTS

Nineteen articles from 17 distinct studies met inclusion criteria. Fourteen of the included studies were published in the last 10 years. Types of exercises and materials used, duration of studies, offloading considerations and provision of wound care varied greatly between studies. Included studies are heterogenous in methodological designs and aims, and reporting was often lacking important components of wound care and PA interventions. A discussion based on descriptive statistics and narrative analysis is provided.

CONCLUSIONS

It is not possible from this scoping review to determine what would be the ideal components of a PA program for this specific population. Conclusions are limited by the quality and design of the included studies. No articles evaluated quality of life, mortality or cardiorespiratory capacity, nor were adverse effects routinely reported.

Prospective exploration of the effect of adiposity and associated microbial factors on healing and progression of diabetic foot ulcers in Tanzania: study protocol of a longitudinal cohort study

BACKGROUND

Diabetic foot ulcers (DFUs) are associated with high morbidity and mortality in low-income countries. This coexists with an increasing prevalence of obesity which has been reported to alter antimicrobial susceptibility and potentially affect the outcome of infected foot ulcers. This study aims to determine whether adiposity and local microbial factors affect the progression and healing of foot ulcers in people with type 2 diabetes in hospital settings in Tanzania.

METHODS AND ANALYSIS

A prospective cohort of 300 individuals with type 2 diabetes presenting with DFUs at an outpatient clinic will be enrolled into the study. At baseline, participants will be stratified into normal and high adiposity groups (150 per group) as measured by bioelectrical impedance analysis (BIA). Both groups will receive DFU management according to locally appropriate standards of care and will be followed up for 24 weeks or until complete wound healing, whichever occurs first. The primary end point is complete wound healing at 24 weeks while secondary end points are ulcer progression (worsening or improving), amputation and death. Enrolling 150 participants per group will have a minimum power of 80% to detect a 20% difference in cumulative incidence of complete ulcer healing (at the 5% level of statistical significance) between the normal and high adiposity groups.

ETHICAL CONSIDERATIONS AND DISSEMINATION OF RESULTS

This study will be conducted in compliance with the independent institutional review boards (IRBs), informed consent guidelines, the declaration of Helsinki and International Conference on Harmonisation, Good Clinical Practice Guidelines. Ethical clearance has been granted by the Muhimbili University of Health and Allied Sciences ethical review board (MUHAS Ref. No. DA.282/298/01 .C/). Permissions to conduct the study have been granted by the Abbas Medical Centre and the Muhimbili Academic Medical Centre (MAMC).Progress and results emanating from this work will be communicated to the scientific community through conference presentations, short communications (using journal letters and interesting case reports) and peer-reviewed publications. When necessary, through proper channels, popular means of communication (newspapers, magazines and online communications) will be used to inform policy and the public.

TRIAL REGISTRATION NUMBER

NCT03960255; Pre-results.

High-fat diet exacerbates postoperative pain and inflammation in a sex-dependent manner

Obesity is often associated with increased pain, but little is known about the effects of obesity and diet on postoperative pain. In this study, effects of diet and obesity were examined in the paw incision model, a preclinical model of postoperative pain. Long-Evans rats were fed high-fat diet (40% calories from butter fat) or low-fat normal chow. Male rats fed high-fat diet starting 6 weeks before incision (a diet previously shown to induce markers of obesity) had prolonged mechanical hypersensitivity and an overall increase in spontaneous pain in response to paw incision, compared with normal chow controls. Diet effects in females were minor. Removing high-fat diet for 2 weeks before incision reversed the diet effects on pain behaviors, although this was not enough time to reverse high-fat diet-induced weight gain. A shorter (1 week) exposure to high-fat diet before incision also increased pain behaviors in males, albeit to a lesser degree. The 6-week high-fat diet increased macrophage density as examined immunohistochemically in lumbar dorsal root ganglion even before paw incision, especially in males, and sensitized responses of peritoneal macrophages to lipopolysaccharide stimuli in vitro. The nerve regeneration marker growth-associated protein 43 (GAP43) in skin near the incision (day 4) was higher in the high-fat diet group, and wound healing was delayed. In summary, high-fat diet increased postoperative pain particularly in males, but some diet effects did not depend on weight gain. Even short-term dietary manipulations, that do not affect obesity, may enhance postoperative pain.

Psychological and Biomechanical Aspects of Patient Adaptation to Diabetic Neuropathy and Foot Ulceration

PURPOSE OF REVIEW

The purpose of this review was to elucidate how psychological and biomechanical factors interrelate in shaping patients' experience with diabetic symmetric polyneuropathy (DSPN) and its sequela-diabetic foot ulceration (DFU).

RECENT FINDINGS

Recent findings emphasize the importance not only of neuropathic pain but also of other DSPN symptoms, such as unsteadiness. We highlight the negative spiral between unsteadiness, falls, and psychological distress. Moreover, unsteadiness is a key determinant of non-adherence to offloading resulting in the delayed DFU healing. While depression is an established predictor of incident DFU, findings linking depression and DFU healing remain inconclusive. Examination of physical activity in DFU development and healing represents the most recent application of research to this field. Research evidence indicates that DSPN markedly impairs physical and emotional functioning and suggests that there is an unmet need for the development of multifaceted interventions that address both psychological distress and biomechanical challenges experienced by patients with this debilitating complication of diabetes.

Exercise prior to, but not concomitant with, stress reverses stress-induced delayed skin wound healing

Stress-induced prolonged inflammation impairs cutaneous wound healing. Exercise may inhibit this effect via an anti-inflammatory mechanism. Our aim was to investigate the effect of moderate exercise on skin wound healing in chronically stressed mice. Mice were trained five times per week on a treadmill or received no training. Mice underwent daily rotational stress from the 6th week until euthanasia. During the 8th week, two wounds were created in the dorsum and collected 10 days later. A control group only received wounds. Exercise was performed prior to and simultaneous with stress for 2 weeks or only prior to stress. Stress increased normetanephrine levels 10 days after wounding, resulting in an increased amount of inflammatory cells and reduced expression of inflammatory cytokines as well as angiogenesis, myofibroblast differentiation and matrix deposition. Concomitant exercise and stress potentiated these effects, intensifying the delayed wound contraction. When exercise was performed only prior to stress, however, the mice showed reduced inflammatory cells in granulation tissue 10 days after wounding and improved wound healing compared with animals with exercise and concomitant stress. Moderate exercise in association with stress potentiates the stress effect; however, when exercise was performed prior to stress, wound healing was improved.

Effect of a high-fat diet and alcohol on cutaneous repair: A systematic review of murine experimental models

BACKGROUND AND PURPOSE

Chronic alcohol intake associated with an inappropriate diet can cause lesions in multiple organs and tissues and complicate the tissue repair process. In a systematic review, we analyzed the relevance of alcohol and high fat consumption to cutaneous and repair, compared the main methodologies used and the most important parameters tested. Preclinical investigations with murine models were assessed to analyze whether the current evidence support clinical trials.

METHODS

The studies were selected from MEDLINE/PubMed and Scopus databases, according to Fig 1. All 15 identified articles had their data extracted. The reporting bias was investigated according to the ARRIVE (Animal Research: Reporting of in Vivo Experiments) strategy.

RESULTS

In general, animals offered a high-fat diet and alcohol showed decreased cutaneous wound closure, delayed skin contraction, chronic inflammation and incomplete re-epithelialization.

CONCLUSION

In further studies, standardized experimental design is needed to establish comparable study groups and advance the overall knowledge background, facilitating data translatability from animal models to human clinical conditions.

Beneficial Effect of Voluntary Exercise on Experimental Colitis in Mice Fed a High-Fat Diet: The Role of Irisin, Adiponectin and Proinflammatory Biomarkers

Inflammatory bowel diseases (IBDs) are a heterogeneous group of disorders exhibited by two major phenotypic forms: Crohn's disease and ulcerative colitis. Although the aetiology of IBD is unknown, several factors coming from the adipose tissue and skeletal muscles, such as cytokines, adipokines and myokines, were suggested in the pathogenesis of ulcerative colitis; however, it has not been extensively studied whether voluntary exercise can ameliorate that disorder. We explored the effect of moderate exercise (i.e., voluntary wheel running) on the disease activity index (DAI), colonic blood flow (CBF), plasma irisin and adiponectin levels and real-time PCR expression of proinflammatory markers in mesenteric fat in mice with 2,4,6-trinitrobenzenesulfonic acid (TNBS) colitis fed a high-fat diet (HFD) compared to those on a standard chow diet (SD). Macroscopic and microscopic colitis in sedentary SD mice was accompanied by a significant fall in CBF, some increase in colonic tissue weight and a significant increase in the plasma levels of tumour necrosis factor-alpha (TNF-α), IL-6, monocyte chemotactic protein 1 (MCP-1) and IL-13 (p < 0.05). In sedentary HFD mice, colonic lesions were aggravated, colonic tissue weight increased and the plasma TNF-α, IL-6, MCP-1, IL-1β and leptin levels significantly increased. Simultaneously, a significant decrease in the plasma irisin and adiponectin levels was observed in comparison with SD mice (p < 0.05). Exercise significantly decreased macroscopic and microscopic colitis, substantially increased CBF and attenuated the plasma TNF-α, IL-6, MCP-1, IL-1β and leptin levels while raising the plasma irisin and the plasma and WAT concentrations of adiponectin in HFD mice (p < 0.05). We conclude that: (1) experimental colitis is exacerbated in HFD mice, possibly due to a fall in colonic microcirculation and an increase in the plasma and mesenteric fat content of proinflammatory biomarkers; and (2) voluntary physical activity can attenuate the severity of colonic damage in mice fed a HFD through the release of protective irisin and restoration of plasma adiponectin.

Voluntary exercise improves murine dermal connective tissue status in high-fat diet-induced obesity

Obesity is a risk factor for several cardiovascular and metabolic diseases. Its influence on the skin is less obvious, yet certain negative effects of adipose tissue inflammation on the dermis have been suggested. Excess weight is closely associated with sedentary behavior, so any increase in physical activity is considered beneficial against obesity. To investigate the effects of obesity and physical exercise on the skin, we established a mouse model in which mice were kept either on a high-fat diet or received standard chow. After the two groups achieved a significant weight difference, physical exercise was introduced to both. Animals were given the opportunity to perform voluntary exercise for 40 min daily in a hamster wheel for a period of 8 weeks. We evaluated the status of the dermis at the beginning and at the end of the exercise period by in vivo nonlinear microscopy. Obese mice kept on high-fat diet lost weight steadily after they started to exercise. In the high-fat diet group, we could detect significantly larger adipocytes and a thicker layer of subcutaneous tissue; both changes started to normalize after exercise. Nonlinear microscopy revealed an impaired collagen structure in obese mice that improved considerably after physical activity was introduced. With the ability to detect damage on collagen structure, we set out to address the question whether this process is reversible. With the use of a novel imaging method, we were able to show the reversibility of connective tissue deterioration as a benefit of physical exercise.

Energetic interventions for healthspan and resiliency with aging

Several behavioral and pharmacological strategies improve longevity, which is indicative of delayed organismal aging, with the most effective interventions extending both life- and healthspan. In free living creatures, maintaining health and function into old age requires resilience against a multitude of stressors. Conversely, in experimental settings, conventional housing of rodents limits exposure to such challenges, thereby obscuring an accurate assessment of resilience. Caloric restriction (CR) and exercise, as well as pharmacologic strategies (resveratrol, rapamycin, metformin, senolytics), are well established to improve indices of health and aging, but some paradoxical effects have been observed on resilience. For instance, CR potently retards the onset of age-related diseases, and improves lifespan to a greater extent than exercise in a variety of models. However, exercise has proven more consistently beneficial to organismal resilience against a broad array of stressors, including infections, surgery, wound healing and frailty. CR can improve cellular stress defenses and protect from frailty, but also impairs the response to infections, bed rest and healing. How an intervention will impact not only longevity, health and function, but also resiliency, is critical to better understanding translational implications. Thus, organismal robustness represents a critical, albeit understudied aspect of aging, which needs more careful attention in order to better inform on how putative age-delaying strategies will impact preservation of health and function in response to stressors with aging in humans.

Low-intensity treadmill exercise promotes rat dorsal wound healing

In order to investigate the promoting effect of low-intensity treadmill exercise on rat dorsal wound healing and the mechanism, 20 Sprague-Dawley rats were randomly divided into two groups: exercise group (Ex) and non-exercise group (non-ex). The rats in Ex group were given treadmill exercise for one month, and those in non-ex group raised on the same conditions without treadmill exercise. Both groups received dorsal wound operation with free access to food and water. By two-week continuous observation and recording of the wound area, the healing rate was analyzed. The blood sample was collected at day 14 post-operation via cardiac puncture for determination of the number of endothelial progenitor cells (EPCs) by flow cytometry, and the concentrations of relevant cytokines such as basic fibroblast growth factor (bFGF), endothelial nitric oxide synthase (eNOS) and vascular endothelial growth factor (VEGF) were measured by ELISA. The skin tissue around the wound was dissected to observe the vascular density under the microscope after HE staining, to detect the mRNA level of VEGFR2 and angiopoietin-1 (Ang-1) receptor using RT-qPCR, and protein expression of a-smooth muscle actin (αSMA) and type III collagen (ColIII) using Western blotting. It was found that the wound area in Ex group was smaller at the same time point than in non-ex group. The number of circulating EPCs was greater and the concentrations of vasoactive factors such as VEGF, eNOS and bFGF were higher in Ex group than in non-ex group. HE staining displayed a higher vessel density in Ex group than in non-ex group. Moreover, the mRNA expression of VEGFR2 and Ang-1 detected in the wound tissue in Ex group was higher than in non-ex group. Meanwhile, the protein expression of αSMA and ColIII was more abundant in Ex group than in non-ex group. Conclusively, the above results demonstrate Ex rats had a higher wound healing rate, suggesting low-intensity treadmill exercise accelerates wound healing. The present work may provide some hint for future study of treating refractory wound.

Low-intensity vibration improves angiogenesis and wound healing in diabetic mice

Chronic wounds represent a significant health problem, especially in diabetic patients. In the current study, we investigated a novel therapeutic approach to wound healing – whole body low-intensity vibration (LIV). LIV is anabolic for bone, by stimulating the release of growth factors, and modulating stem cell proliferation and differentiation. We hypothesized that LIV improves the delayed wound healing in diabetic mice by promoting a pro-healing wound environment. Diabetic db/db mice received excisional cutaneous wounds and were subjected to LIV (0.4 g at 45 Hz) for 30 min/d or a non-vibrated sham treatment (controls). Wound tissue was collected at 7 and 15 d post-wounding and wound healing, angiogenesis, growth factor levels and wound cell phenotypes were assessed. LIV increased angiogenesis and granulation tissue formation at day 7, and accelerated wound closure and re-epithelialization over days 7 and 15. LIV also reduced neutrophil accumulation and increased macrophage accumulation. In addition, LIV increased expression of pro-healing growth factors and chemokines (insulin-like growth factor-1, vascular endothelial growth factor and monocyte chemotactic protein-1) in wounds. Despite no evidence of a change in the phenotype of CD11b+ macrophages in wounds, LIV resulted in trends towards a less inflammatory phenotype in the CD11b− cells. Our findings indicate that LIV may exert beneficial effects on wound healing by enhancing angiogenesis and granulation tissue formation, and these changes are associated with increases in pro-angiogenic growth factors.

High-fat diet from perilla oil induces insulin resistance despite lower serum lipids and increases hepatic fatty acid oxidation in rats

Background

The purpose of this study is to investigate the effects of a high-fat diet from perilla oil on serum lipids, hepatic lipid metabolism and insulin sensitivity.

Methods

Male Sprague–Dawley (SD) rats were fed either a control (CT) diet or a diet high in perilla oil (HP). After 16 weeks of feeding, the serum lipids were measured, and the gene expressions involved in hepatic fatty acid oxidation and synthesis were determined. In addition, hepatic fat deposition was detected, and insulin sensitivity was evaluated by means of euglycemic-hyperinsulinemic clamp.

Results

Compared with the rats in the CT group, the HP-feeding significantly decreased the levels of triglyceride (TG), total cholesterol (TCH) and HDL-cholesterol (HDL-c). HP-feeding did not change the levels of LDL-cholesterol (LDL-c), free fatty acid (FFA), intrahepatic lipids or body weight. Moreover, the HP-feeding dramatically increased the mRNA expressions of fatty acid oxidation markers (PPAR-alpha, CPT1A) and fatty acid synthesis markers (SREBP-1, FASN and ACC) in the liver. The HP-feeding induced increased protein levels of CPT1A, while reducing the protein levels of FASN and ACC in the liver. However, the glucose infusion rate significantly increased in the HP group compared with the CT group.

Conclusions

Our data show that, in rats, excessive perilla oil intake may significantly lower serum lipids, strengthen hepatic fatty acid oxidation, and inhibit hepatic fatty acid synthesis, but at the same time may also lead to insulin resistance.

Exercise, Obesity, and Cutaneous Wound Healing: Evidence from Rodent and Human Studies

Significance: Impaired cutaneous wound healing is a major health concern. Obesity has been shown in a number of studies to impair wound healing, and chronic nonhealing wounds in obesity and diabetes are a major cause of limb amputations in the United States. Recent Advances: Recent evidence indicates that aberrant wound site inflammation may be an underlying cause for delayed healing. Obesity, diabetes, and other conditions such as stress and aging can result in a chronic low-level inflammatory state, thereby potentially affecting wound healing negatively. Critical Issues: Interventions which can speed the healing rate in individuals with slowly healing or nonhealing wounds are of critical importance. Recently, physical exercise training has been shown to speed healing in both aged and obese mice and in older adults. Exercise is a relatively low-cost intervention strategy which may be able to be used clinically to prevent or treat impairments in the wound-healing process. Future Directions: Little is known about the mechanisms by which exercise speeds healing. Future translational studies should address potential mechanisms for these exercise effects. Additionally, clinical studies in obese humans are necessary to determine if findings in obese rodent models translate to the human population.