Treadmill exercise ameliorates apoptotic cell death in the retinas of diabetic rats

Effects of voluntary and forced physical exercise on the retinal health of aging Wistar rats

Aging is accompanied by an increased prevalence of degenerative conditions, including those affecting ocular health, which significantly impact quality of life and increase the burden on healthcare systems. Among these, retinal aging is of particular concern due to its direct link to vision impairment, a leading cause of disability in the elderly. Vision loss in the aging population is associated with heightened risks of cognitive decline, social isolation, and morbidity. This study addresses the critical gap in our understanding of modifiable lifestyle factors, such as physical exercise, that may mitigate retinal aging and its related pathologies. We investigated the effects of different exercise regimens-voluntary (recreational-type) and forced (high-intensity)-on the retinal health of aging Wistar rats (18-month-old), serving as a model for studying the translational potential of exercise interventions in humans. Male Wistar rats were divided into four groups: a young control (3-month-old) for baseline comparison, an aged sedentary control, an aged group engaging in voluntary exercise via a running wheel in their cage, and an aged group subjected to forced exercise on a treadmill for six sessions of 20 min each per week. After a 6-month experimental period, we assessed retinal function via electroretinography (ERG), measured retinal thickness histologically, and analyzed protein expression changes relevant to oxidative stress, inflammation, and anti-aging mechanisms. Our findings reveal that voluntary exercise positively impacts retinal function and morphology, reducing oxidative stress and inflammation markers while enhancing anti-aging protein expression. In contrast, forced exercise showed diminished benefits. These insights underscore the importance of exercise intensity and preference in preserving retinal health during aging. The study highlights the potential of recreational physical activity as a non-invasive strategy to counteract retinal aging, advocating for further research into exercise regimens as preventative therapies for age-related ocular degenerations.

Modulation of pulmonary oxidative status in methamphetamine-withdrawn rats, comparing the effects of continuous training and NBS superfood supplementation

OBJECTIVE

This study aimed to investigate the effects of six weeks of continuous training and Nutrition Bio-shield (NBS) Superfood Supplementation on the state of oxidative stress by the expression of Nrf2, NOX4, superoxide dismutase, and malondialdehyde genes in the lungs of rats after methamphetamine withdrawal.

METHODS

Forty male Wistar rats were randomly divided into five groups (n = 8, per group), undergoing methamphetamine administration (six weeks, 5 mg/kg ip, and once per day) followed by a 21-day withdrawal period. The rats were supplemented NBS superfood at a dosage of 25 g/kg per day for six weeks. The training protocol was 30 minutes of daily continuous training (treadmill running), five days a week for six weeks. The regimen escalated from a pace of 3 m/min for the initial 5 minutes, to 5 m/min for the following 5 minutes, culminating at 8 m/min for the remainder of the session, all at a 0° incline. A one-way analysis of variance was performed to analyze the gene expression of Nrf2, NOX4, MDA, and SOD in the lungs tissue of rats.

RESULTS

The results indicated that, in the experimental groups which underwent continuous training and NBS Superfood supplementation, the expression of the Nrf2 gene exhibited a significant elevation compared to the control group (P < 0.05), while the NOX4, MDA, and SOD genes expression exhibited a significant decline in comparison to the control group (P < 0.05).

CONCLUSION

In general, both exercise interventions and NBS superfood supplementation, when employed separately or in combination after methamphetamine withdrawal, can enhance the state of oxidative stress in the lung.

Protective effects of treadmill exercise on apoptotic neuronal damage and astrocyte activation in ovariectomized and/or diabetic rat prefrontal cortex: molecular and histological aspects

OBJECTIVE

Both estrogen deprivation and diabetes mellitus are known as risk factors for neuronal damage. Using an animal model of ovariectomized and/or streptozotocin (STZ)-induced diabetes mellitus, we examined expression of apoptosis-related proteins, neuronal damage, and astrocyte activation in prefrontal cortex of rats with/without treadmill exercise.

METHODS

Adult female Wistar rats were divided into control, ovariectomized (Ovx, bilateral ovariectomy), diabetic (Dia, STZ 60 mg/kg; i.p.), and ovariectomized diabetic (Ovx + Dia) groups. Next, animals in each group were randomly subdivided into non-exercise and exercise subgroups. Animals in the exercise groups underwent moderate treadmill running for 4 weeks (5 days/week). Thereafter, expression of Bax, Bcl-2, and caspase-3, as apoptosis-related proteins, number of neurons, and number of glial fibrillary acidic protein (GFAP)-positive cells in prefrontal cortex were measured using immunoblotting, cresyl violet staining, and immunohistochemistry, respectively.

RESULTS

In both Dia and Ovx + Dia groups, Bax and caspase-3 protein levels and number of GFAP-positive cells were higher than those in the control group, while Bcl-2 protein level and number of neurons compared were lower than the control group. Beneficial effects of exercise to prevent apoptosis-mediated neuronal damage and astrocyte activation were also observed in the Dia group.

CONCLUSION

Based on our results, physical exercise could be beneficial to attenuate diabetes-induced neuronal damage in the prefrontal cortex via inhibition of apoptosis.

Swimming training reduced inflammation and apoptotic changes in pulmonary tissue in type 1 diabetic mice

Background

Despite the vulnerability of pulmonary tissue to diabetic conditions, there are few reports related to the detrimental effects of hyperglycemia and therapeutic modalities on lung parenchyma. Here, the apoptotic changes were monitored in the diabetic pulmonary tissue of mice (DM1) subjected to a four‒week swimming plan.

Methods

The mice were randomly allocated into Control; Control + Swimming (S); Diabetic group (D); and Diabetic + Swimming (D + S) groups (each in 8 mice). In the D and D + S groups, mice received intraperitoneally 50 mg/kg of streptozotocin (STZ). After 14 days, swimming exercise was done for four weeks. The expression of il-1β, bcl-2, bax, and caspase-3 was investigated using real-time PCR analysis. A histological examination was performed using H&E staining.

Results

DM1 significantly upregulated il-1β, bax, and caspase-3, and down-regulated bcl-2 compared to the non-diabetic mice (p < 0.05). We noted that swimming exercises reversed the expression pattern of all genes in the diabetic mice and closed to basal levels (p < 0.05). Data indicated that swimming exercise could diminish emphysematous changes, and interstitial pneumonitis induced by STZ. Along with these changes, swimming exercise had protective effects to reduce the thickness of the inter-alveolar septum and mean alveolar area in diabetic mice.

Conclusion

These data demonstrated that swimming exercises could decrease DM1-related pathologies in mouse lungs by regulating apoptosis and inflammatory response.

Co-administration of exercise training and melatonin on the function of diabetic heart tissue: a systematic review and meta-analysis of rodent models

PURPOSE

Diabetes mellitus (DM), a hyperglycemic condition, occurs due to the failure of insulin secretion and resistance. This study investigated the combined effects of exercise training and melatonin (Mel) on the function of heart tissue in diabetic rodent models.

METHODS

A systematic search was conducted in Embase, ProQuest, Cochrane library, Clinicaltrial.gov, WHO, Google Scholar, PubMed, Ovid, Scopus, Web of Science, Ongoing Trials Registers, and Conference Proceedings in July 2022 with no limit of date or language. All trials associated with the effect of Mel and exercise in diabetic rodent models were included. Of the 962 relevant publications, 58 studies met our inclusion criteria as follows; Mel and type 1 DM (16 studies), Mel and type 2 DM (6 studies), exercise and type 1 DM (24 studies), and exercise and type 2 DM (12 studies). Meta-analysis of the data was done using the Mantel Haenszel method.

RESULTS

In most of these studies, antioxidant status and oxidative stress, inflammatory response, apoptosis rate, lipid profiles, and glucose levels were monitored in diabetic heart tissue. According to our findings, both Mel and exercise can improve antioxidant capacity by activating antioxidant enzymes compared to the control diabetic groups (p < 0.05). The levels of pro-inflammatory cytokines, especially TNF-α were reduced in diabetic rodents after being treated with Mel and exercise. Apoptotic changes were diminished in diabetic rodents subjected to the Mel regime and exercise in which p53 levels and the activity of Caspases reached near normal levels (p < 0.05). Based on the data, both Mel and exercise can change the lipid profile in diabetic rodents, especially rats, and close it to near-to-control levels.

CONCLUSION

These data showed that exercise and Mel can reduce the harmful effects of diabetic conditions on the heart through the regulation of lipid profile, antioxidant capacity, apoptosis, and inflammation.

Potential Protective Function of Adiponectin in Diabetic Retinopathy

Adiponectin, one of the most ubiquitous adipokines found in the blood, plays a major role in glucolipid metabolism and energy metabolism and regulation. In recent years, a growing body of research indicates that adiponectin also plays a significant role in diabetic retinopathy. In the present review, we specifically address the protective effects of adiponectin on the development and progression of diabetic retinopathy through improvement in insulin resistance, alleviation of oxidative stress, limiting of inflammation, and prevention of vascular remodeling, with the aim to explore new potential approaches and targets for the prevention and treatment of diabetic retinopathy.

Voluntary exercise modulates pathways associated with amelioration of retinal degenerative diseases

Background: Exercise has been shown to promote a healthier and longer life and linked to a reduced risk of developing neurodegenerative diseases including retinal degenerations. However, the molecular pathways underpinning exercise-induced cellular protection are not well understood. In this work we aim to profile the molecular changes underlying exercise-induced retinal protection and investigate how exercise-induced inflammatory pathway modulation may slow the progression of retinal degenerations.

Methods: Female C57Bl/6J mice at 6 weeks old were given free access to open voluntary running wheels for a period of 28 days and then subjected to 5 days of photo-oxidative damage (PD)-induced retinal degeneration. Following, retinal function (electroretinography; ERG), morphology (optical coherence tomography; OCT) and measures of cell death (TUNEL) and inflammation (IBA1) were analysed and compared to sedentary controls. To decipher global gene expression changes as a result of voluntary exercise, RNA sequencing and pathway and modular gene co-expression analyses were performed on retinal lysates of exercised and sedentary mice that were subjected to PD, as well as healthy dim-reared controls.

Results: Following 5 days of PD, exercised mice had significantly preserved retinal function, integrity and reduced levels of retinal cell death and inflammation, compared to sedentary controls. In response to voluntary exercise, inflammatory and extracellular matrix integrity pathways were significantly modulated, with the gene expression profile of exercised mice more closely trending towards that of a healthy dim-reared retina.

Conclusion: We suggest that voluntary exercise may mediate retinal protection by influencing key pathways involved in regulating retinal health and shifting the transcriptomic profile to a healthy phenotype.

The Assessment of Acute Chorioretinal Changes Due to Intensive Physical Exercise in Senior Elite Athletes

Regular physical exercise is known to lower the incidence of age-related eye diseases. We aimed to assess the acute chorioretinal alterations in older adults following intense physical strain. Seventeen senior elite athletes were recruited who underwent an aerobic exercise on a cycle ergometer and macular scanning by optical coherence tomography. A significant thinning of the entire retina was observed 1 min after exercise, followed by a thickening at 5 min, after which the thickness returned to baseline. This trend was similar in almost every single retinal layer, although a significant change was observed only in the inner retina. Choroidal thickness changes were neither significant nor did they correlate with the thickness changes of intraretinal layers. The mechanism of how these immediate retinal changes chronically impact age-related sight-threatening pathologies that, in turn, result in a substantially reduced quality of life warrants further investigation on nontrained older adults as well.

Analysis of aerobic exercise influence on intraocular pressure and ocular perfusion pressure in patients with primary open-angle glaucoma: A randomized clinical trial

Purpose

To investigate the change pattern of ocular perfusion pressure (OPP) and intra-ocular pressure (IOP) after short-term and long-term aerobic exercise.

Methods

In this prospective, single-masked, randomized clinical trial, 123 patients with a primary open angle glaucoma that locally used prostaglandin analog alone were randomly divided into the exercise and control groups. In the short-term study, all individuals underwent a cycling exercise at moderate intensity (20% Wmax for 10 minutes) and high intensity (60% Wmax for 5 minutes). During the long-term study, the exercise group is characterized by regular jogging exercise lasting for 30 minutes during 6: 00-10: 00 in the morning for 3 months, with the exercise frequency of at least 20 times per month, and with the intensity reflected by the target heart rate. The control group is designed as a group with irregular exercise.

Results

After short-term aerobic exercise, IOP significantly decreased, whereas the ocular perfusion pressure (OPP) significantly increased. The decreasing amplitude of IOP is related to the baseline of IOP, the intensity of exercise, gender, and so on. After 3 months of long-term exercise, the changes in the IOP level of the exercise group indicated a decreasing trend.

Conclusion

The significant decrement of IOP and the increment of OPP suggest that aerobic exercise is beneficial for patients with primary open-angle glaucoma and appropriate aerobic exercise is appropriate in treating glaucoma patients.

Trial registration

ChiCTR, ChiCTR-TRC-10001055. Registered one October 2010-Retrospectively registered, http://www.chictr.org.cn/showproj.aspx?proj = 8483.

Physical Activity Status and Diabetic Retinopathy: A Review

Substantial evidence highlights the association between physical inactivity and diabetes onset and complications. Little is known regarding the link between physical inactivity and diabetic retinopathy in terms of onset, progression, and severity. This review aims to investigate these associations and understand the underlying mechanisms behind these associations. Decreased sedentary times and the inclusion of more physical activity have been linked to the delayed onset and progression of diabetic retinopathy and less severe forms of said condition. Physical activity provides both protective and anti-inflammatory effects on the retina. Further research is needed to understand and elucidate the exact mechanisms by which lack of physical activity affects retinal health and the onset, progression, and severity of diabetic retinopathy.

Unconventional avenues to decelerated diabetic retinopathy

Diabetic retinopathy (DR) is an important microvascular complication of diabetes mellitus (DM), causing significant visual impairment worldwide. Current gold standards for retarding the progress of DR include blood sugar control and regular fundus screening. Despite these measures, the incidence and prevalence of DR and vision-threatening DR remain high. Given its slowly progressive course and long latent period, opportunities to contain or slow DR before it threatens vision must be explored. This narrative review assesses the recently described unconventional strategies to retard DR progression. These include gut-ocular flow, gene therapy, mitochondrial dysfunction-oxidative stress, stem cell therapeutics, neurodegeneration, anti-inflammatory treatments, lifestyle modification, and usage of phytochemicals. These therapies impact DR directly, while some of them also influence DM control. Most of these strategies are currently in the preclinical stage, and clinical evidence remains low. Nevertheless, our review suggests that these approaches have the potential for human use to prevent the progression of DR.

Neuroprotective Effects of Treadmill Exercise in Hippocampus of Ovariectomized and Diabetic Rats

To determine detrimental effects of estrogen and insulin deficiencies on hippocampus, we examined apoptosis-induced neuronal damage and cholinergic system in ovariectomized and/or diabetic rat hippocampus. Possible neuroprotective effects of treadmill exercise were also investigated. Adult female Wistar rats were randomly divided into four groups (n = 5 rats/group) as follows: control, ovariectomized (Ovx), diabetic (Dia, streptozotocin (STZ) 60 mg/kg; i.p.), and Ovx + Dia groups. Each group was further subdivided into exercise and non-exercise groups. Animals in exercise groups were subjected to treadmill training, while those in non-exercise groups were placed on the stationary treadmill for 4 weeks (5 days/week). Apoptosis-related protein levels (i.e. Bax, Bcl-2, and caspase-3), number of survived neurons, and acetylcholinesterase (AChE) activity in the hippocampus were measured using Western blotting, Cresyl Violet staining, and Ellman assay, respectively. Both ovariectomy and diabetes increased expression of Bax and caspase-3 and decreased expression of Bcl-2 at protein levels. In addition, a significant decrease in the number of survived neurons was observed in both Ovx and Dia groups, while AChE activity was lower only in the Dia group. The Ovx + Dia group showed stronger apoptosis-induced neuropathology and inhibition of AChE activity. Treadmill exercise attenuated apoptosis-induced neuropathology in the Ovx and Dia groups and recovered AChE activity in the Dia group. Neuroprotective effects of treadmill exercise were mediated by inhibition of apoptosis. Moderate exercise protocol had no beneficial anti-apoptotic and neuroprotective effects in ovariectomized-diabetic rats.

The assessment of acute chorioretinal changes due to intensive physical exercise in young adults

Purpose

There is abundant evidence on the benefits of physical activity on cardiovascular health. However, there are only few data on the acute effects of physical exercise on the retina and choroid. Our aim was the in vivo examination of chorioretinal alterations following short intense physical activity by spectral domain optical coherence tomography (SD-OCT).

Methods

Twenty-one eyes of 21 healthy, young subjects (mean age 22.5 ± 4.1 years, 15 males and 6 females) were recruited. Macular scanning with a SD-OCT was performed before and following a vita maxima-type physical strain exercise on a rowing ergometer until complete fatigue. Follow-up OCT scans were performed 1, 5, 15, 30 and 60 minutes following the exercise. The OCT images were exported and analyzed using our custom-built OCTRIMA 3D software and the thickness of 7 retinal layers was calculated, along with semi-automated measurement of the choroidal thickness. One-way ANOVA analysis was performed followed by Dunnett post hoc test for the thickness change compared to baseline and the correlation between performance and thickness change has also been calculated. The level of significance was set at 0.001.

Results

We observed a significant thinning of the total retina 1 minute post-exercise (-7.3 ± 0.6 μm, p < 0.001) which was followed by a significant thickening by 5 and 15 minutes (+3.6 ± 0.6 μm and +4.0 ± 0.6 μm, respectively, both p <0.001). Post-exercise retinal thickness returned to baseline by 30 minutes. This trend was present throughout the most layers of the retina, with significant changes in the ganglion cell–inner plexiform layer complex, (-1.3 ± 0.1 μm, +0.6 ± 0.1 μm and +0.7 ± 0.1 μm, respectively, p <0.001 for all), in the inner nuclear layer at 1 and 5 minutes (-0.8 ± 0.1 μm and +0.8 ± 0.1 μm, respectively, p <0.001 for both), in the outer nuclear layer–photoreceptor inner segment complex at 5 minute (+2.3 ± 0.4 μm, p <0.001 for all) and in the interdigitation zone–retinal pigment epithelium complex at 1 and 15 minutes (-3.3 ± 0.4 μm and +1.8 ± 0.4 μm, respectively, p <0.001 for both). There was no significant change in choroidal thickness; however, we could detect a tendency towards thinning at 1, 15, and 30 minutes following exercise. The observed changes in thickness change did not correlate with performance. Similar trends were observed in both professional and amateur sportsmen (n = 15 and n = 6, respectively). The absolute changes in choroidal thickness did not show any correlation with the thickness changes of the intraretinal layers.

Conclusions

Our study implies that in young adults, intense physical exercise has an acute effect on the granular layers of the retina, resulting in thinning followed by rebound thickening before normalization. We could not identify any clear correlation with either choroidal changes or performance that might explain our observations, and hence the exact mechanism warrants further clarification. We believe that a combination of vascular and mechanic changes is behind the observed trends.

Exercise training and probiotic supplementation effects on skeletal muscle apoptosis prevention in type-Ι diabetic rats

AIMS

Hyperglycemia occurring in the diabetic condition can cause apoptosis via the mitochondrial pathway with higher pro-apoptotic protein expression. Probiotics are viable microorganisms that have anti-diabetic and antioxidant effects. Also, exercise may affect the signaling pathways of skeletal muscle apoptosis. This study examined the aerobic exercise training and probiotic supplementation effects on some apoptotic indices of the soleus muscle in diabetic rats-induced by streptozotocin.

MAIN METHODS

We examined 32 male Wistar rats (weight: 250-270 g; age: eight weeks old) and divided them into four groups: control, control + probiotics, aerobic training (AT), and AT + probiotics (ATS). The rats in the training groups aerobically exercised using a treadmill five days per week for five weeks. We evaluated the gene expression of Bax, Bcl2, and p53 using the RT-PCR. We also used a one-way ANOVA for statistical analysis and set the significance level at P ≤ 0.05.

KEY FINDINGS

The results showed that the fasting blood sugar was significantly higher in the control and control + probiotics groups (P = 0.008). Moreover, the AT + probiotics group showed lower expression of p53 (P = 0.005), Bax (P = 0.001) and the Bax/Bcl2 ratio (P = 0.001). Conversely, Bcl2 expression was higher after aerobic training and receiving probiotics (P = 0.002). However, the groups revealed no significant difference regarding muscle weight (P = 0.053) and the muscle weight/final body weight ratio of the rats (P = 0.26).

SIGNIFICANCE

It appears that aerobic exercise training with the use of probiotics prevents apoptosis in the muscle with the down-regulation of blood glucose.

Running to save sight: The effects of exercise on retinal health and function

The benefits of exercise to human health have long been recognised. However, only in the past decade have researchers started to discover the molecular benefits that exercise confers, especially to the central nervous system (CNS). These discoveries include the magnitude of molecular messages that are communicated from skeletal muscle to the CNS. Despite these advances in understanding, very limited studies have been conducted to decipher the molecular benefits of exercise in retinal health and disease. Here, we review the latest work on the effects of exercise on the retina and discuss its effects on the wider CNS, with a focus on demonstrating the potential applicability and comparative molecular mechanisms that may be occurring in the retina. This review covers the key molecular pathways where exercise exerts its effects: oxidative stress and mitochondrial health; inflammation; protein aggregation; neuronal health; and tissue crosstalk via extracellular vesicles. Further research on the benefits of exercise to the retina and its molecular messages within extracellular vesicles is highly topical in this field.

Therapeutic effect of curcumin and C60 fullerene against hyperglycemia-mediated tissue damage in diabetic rat lungs

Increasing evidence suggests that diabetes also targets lung tissues resulting in structural and physiological abnormalities. The present study evaluated the impact of pristine C60 fullerene (C60) against diabetes-induced lung damage for the first time. The objective was to evaluate the impacts of Curcumin (Cur), C60 and C60 fullerene+Curcumin (C60 + Cur) combination on oxidative stress (MDA, GSH, CAT, GST, Retinol, α-tocopherol), apoptosis (Caspase-3, Bcl-2), cholesterol and fatty acid profile (16:0,18:0,18:1,18:2, 22:4, 22:6) against changes in the lung tissue of diabetic rats. Streptozotocin (STZ) was used for inducing diabetes with Cur, C60 and C60 + Cur combination administered for eight weeks to treat diabetic and control rats. Increased oxidative stress, apoptosis and significant changes in cell structure were observed in the lung tissues of diabetic rats. The combination of Cur, C60 and C60 + Cur reduced oxidative stress in the lung tissue of diabetic rats while increasing the antioxidant defense capacity of the tissue, exhibiting tissue protective properties against apoptosis. The diabetic rats displayed favorable properties against lipotoxicity-induced tissue damage due to the increase in the fatty acid and cholesterol levels in lung tissue. It was observed that Cur, C60 and C60 + Cur combination displays protective effects against hyperglycemia induced oxidative damage to lung tissue. Oxidative stress, prevention of lipid and cholesterol accumulation, and weakening of lung apoptosis may be associated with these effects.

Aerobic exercise delays retinal ganglion cell death after optic nerve injury

Aerobic exercise has been shown to play a crucial role in preventing neurological diseases and improving cognitive function. In the present study, we investigated the effect of treadmill training on retinal ganglion cells (RGCs) following optic nerve transection in adult rats. We exercised the rats on a treadmill for 5 d/week (30 min/d at a rate of 9 m/min) or placed control rats on static treadmills. After 3 weeks of exercise, the left optic nerve of each rat was transected. After the surgery, the rat was exercised for another week. The percentages of surviving RGCs in the axotomized eyes of inactive rats were 67% and 39% at 5 and 7 days postaxotomy, respectively. However, exercised rats had significant more RGCs at 5 (74% survival) and 7 days (48% survival) after axotomy. Moreover, retinal brain-derived neurotrophic factor (BDNF) protein levels were significantly upregulated in response to exercise compared with those in the axotomized eyes of inactive rats. Blocking BNDF signaling during exercise by intraperitoneal injections of ANA-12, a BDNF tropomyosin receptor kinase (TrkB) receptor antagonist, reduced the number of RGCs in exercised rats to the level of RGCs in the inactive rats, effectively abolishing the protection of RGCs afforded by exercise. The results suggest that treadmill training effectively rescues RGCs from neurodegeneration following optic nerve transection by upregulating the expression of BDNF.

Low-Intensity Exercise in Mice Is Sufficient to Protect Retinal Function During Light-Induced Retinal Degeneration

Purpose

We previously reported that a specific treadmill running exercise regimen protects against light-induced retinal degeneration (LIRD) in mice. We hypothesized that this protective effect varies with running intensity. To test this, mice undergoing LIRD were run at different treadmill speeds and retinal function was assessed.

Methods

BALB/c mice were assigned to LIRD groups at varying treadmill speeds-0, 5, 10, or 20 m/min labeled inactive, low, medium, and high, respectively-and compared with naïve mice exposed to standard lighting (50 lux; naïve). Following 2 weeks of exercise, a subset of mice were exposed to toxic light (10,000 lux; LIRD) for 4 hours. After 5 additional days of exercise, retinal function was assessed by ERG. Corticosterone levels in serum and cathepsin B (CTSB) protein levels in muscle, brain, serum, and retina were measured. The retinal gene expression of complement factor 1qa (C1qa) and CTSB were measured.

Results

The low+LIRD and medium+LIRD exercise groups had greater a- and b-wave ERG amplitudes when compared with the inactive+LIRD group (P < 0.02). The high+LIRD mice only differed from the inactive+LIRD mice in their dark-adapted b-waves. Serum corticosterone increased in the high+LIRD mice (P < 0.006). Retinal CTSB protein levels were higher in the low+LIRD versus high+LIRD mice (P < 0.004) but were otherwise unchanged. Exercise of any intensity decreased C1qa gene expression.

Conclusions

Faster running did not additionally protect against LIRD, but it did increase serum corticosterone, suggesting stress-induced limits to exercise benefits. Unexpectedly, exercise did not increase CTSB proteins levels in muscle or serum, suggesting that it may not mediate exercise effects. Our results have implications for the use of low-intensity exercise as a vision loss treatment.

Adiponectin, exercise and eye diseases

Adiponectin, one kind of adipokines, has been shown to be neuroprotective in different neurodegenerative diseases. Adiponectin exerts its role through combination with its receptors and activates downstream molecular pathways. In the retinas, the expression of adiponectin can be detected and adiponectin receptors (AdipoRs) locate in different retinal cells. Adiponectin is mainly produced by adipose tissue, enters the circulation and passes through blood-brain barrier (BBB) without injury. It can also be produced locally in the brains as well as in the retinas. Therefore, it is possible that adiponectin from blood as well as that produced locally in the retinas take part in defense of different eye diseases. Here we have summarized the published data about the protective effects of adiponectin in eye diseases. Because exercise can increase the production of adiponectin systemically in the whole body and locally in the brain although no evidence has shown that exercise can increase the production of adiponectin in the eyes until now, we hypothesize that exercise will have a potential protective effect for the eyes via increasing the levels of adiponectin which needs further investigation.

Initial Assessment of Lactate as Mediator of Exercise-Induced Retinal Protection

Physical exercise is protective in rodent models of retinal injury and disease. Data suggest that this is in part mediated by brain-derived neurotrophic factor (BDNF) signal transduction. It has been hypothesized that exercised-induced neuroprotection may be mediated by increases in circulating lactate that in turn alter BDNF secretion. We therefore tested whether mice undergoing a treadmill running regimen previously shown to be protective in a mouse model of retinal degeneration (RD) have increased serum levels of lactate. Lactate levels in exercised and non-exercised mice were statistically indistinguishable. A role for circulating lactate in exercise-induced retinal protection is unsupported.

Compound Danshen Dripping Pill Inhibits Retina Cell Apoptosis in Diabetic Rats

Scope: Diabetic retinopathy (DR) is a severe microvascular complication of diabetes. Previous clinical trials have shown that Compound Danshen Dripping Pill (CDDP) improves DR symptoms. However, the mechanism involved remains unclear.

Procedures: Rats fed a high-fat diet and injected with streptozotocin (STZ) were used as an experimental type 2 diabetes rodent model. CDDP was administered to two groups of diabetic rats at 0.2 and 0.4 g/kg/day via gastric gavage for 12 weeks. After the 12 weeks of treatment, retinal function was evaluated by electroretinography (ERG). Histological staining and TdT-mediated dUTP nick-end labeling (TUNEL) assays were also performed. Retinal genome expression was determined by gene array.

Results: We found that CDDP moderated ERG and histological abnormalities in diabetic rats, independent of blood glucose level. A gene array showed that CDDP changed 262 genes significantly in the diabetic retina. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis indicated that differentially expressed genes in the CDDP-treated groups were involved mainly in the apoptosis pathway. Moreover, CDDP reduced the number of TUNEL-positive cells in the diabetic retinas. CDDP prevented the reduction in Bcl-2 expression and the increase in BCL-2 associated X (Bax) and caspase-3 (Casp3) expression in diabetic rats.

Conclusion: Our results suggest that CDDP exerts its neuroprotective functions by inhibiting cell apoptosis in diabetic rats.

Physical exercise and glaucoma: a review on the roles of physical exercise on intraocular pressure control, ocular blood flow regulation, neuroprotection and glaucoma-related mental health

The benefits of physical exercise on health and well-being have been studied in a wide range of systemic and ocular diseases, including glaucoma, a progressive optic neuropathy characterized by accelerated apoptosis of retinal ganglion cells (RGCs). Elevated intraocular pressure (IOP) and insufficient ocular perfusion have been postulated to be the two main theories in glaucoma development and progression. The effects of exercise in these two aspects have been demonstrated by numerous researches. A review in 2009 focusing on these two theories concluded that exercise results in transient IOP reduction but an inconsistent elevation in ocular perfusion. However, the majority of the studies had been conducted in healthy subjects. Over the past decade, technological advancement has brought forth new and more detailed evidence regarding the effects of exercise. Moreover, the neuroprotective effect of exercise by upregulation of neurotrophin and enhancement of mitochondrial function has been a focus of interest. Apart from visual impairment, the mental health issues in patients with glaucoma, which include anxiety and depression, should also be addressed. In this review, we mainly focus on publications from the recent years, so as to provide a comprehensive review on the impact of physical exercise on IOP, ocular perfusion, neuroprotection and mental health in patients with glaucoma.

Neuroprotective strategies for retinal disease

Diseases that affect the eye, including photoreceptor degeneration, diabetic retinopathy, and glaucoma, affect 11.8 million people in the US, resulting in vision loss and blindness. Loss of sight affects patient quality of life and puts an economic burden both on individuals and the greater healthcare system. Despite the urgent need for treatments, few effective options currently exist in the clinic. Here, we review research on promising neuroprotective strategies that promote neuronal survival with the potential to protect against vision loss and retinal cell death. Due to the large number of neuroprotective strategies, we restricted our review to approaches that we had direct experience with in the laboratory. We focus on drugs that target survival pathways, including bile acids like UDCA and TUDCA, steroid hormones like progesterone, therapies that target retinal dopamine, and neurotrophic factors. In addition, we review rehabilitative methods that increase endogenous repair mechanisms, including exercise and electrical stimulation therapies. For each approach, we provide background on the neuroprotective strategy, including history of use in other diseases; describe potential mechanisms of action; review the body of research performed in the retina thus far, both in animals and in humans; and discuss considerations when translating each treatment to the clinic and to the retina, including which therapies show the most promise for each retinal disease. Despite the high incidence of retinal diseases and the complexity of mechanisms involved, several promising neuroprotective treatments provide hope to prevent blindness. We discuss attractive candidates here with the goal of furthering retinal research in critical areas to rapidly translate neuroprotective strategies into the clinic.

TrkB signalling pathway mediates the protective effects of exercise in the diabetic rat retina

Diabetic retinopathy is a leading cause of vision loss. Treatment options for early retinopathy are sparse. Exercise protects dying photoreceptors in models of retinal degeneration, thereby preserving vision. We tested the protective effects of exercise on retinal and cognitive deficits in a type 1 diabetes model and determined whether the TrkB pathway mediates this effect. Hyperglycaemia was induced in Long Evans rats via streptozotocin injection (STZ; 100 mg/kg). Following confirmed hyperglycaemia, both control and diabetic rats underwent treadmill exercise for 30 min, 5 days/week at 0 m/min (inactive groups) or 15 m/min (active groups) for 8 weeks. A TrkB receptor antagonist (ANA-12), or vehicle, was injected 2.5 h before exercise training. We measured spatial frequency and contrast sensitivity using optokinetic tracking biweekly post-STZ; retinal function using electroretinography at 4 and 8 weeks; and cognitive function and exploratory behaviour using Y-maze at 8 weeks. Retinal neurotrophin-4 was measured using ELISA. Compared with non-diabetic controls, diabetic rats showed significantly reduced spatial frequency and contrast sensitivity, delayed electroretinogram oscillatory potential and flicker implicit times and reduced cognitive function and exploratory behaviour. Exercise interventions significantly delayed the appearance of all deficits, except for exploratory behaviour. Treatment with ANA-12 significantly reduced this protection, suggesting a TrkB-mediated mechanism. Despite this, no changes in retinal neurotrohin-4 were observed with diabetes or exercise. Exercise protected against early visual and cognitive dysfunction in diabetic rats, suggesting that exercise interventions started after hyperglycaemia diagnosis may be a beneficial treatment. The translational potential is high, given that exercise treatment is non-invasive, patient controlled and inexpensive.

Changes in Cardiac Levels of Caspase-8, Bcl-2 and NT-proBNP Following 4 Weeks of Aerobic Exercise in Diabetic Rats

Introduction: Cardiac apoptosis is one of the most important cardiovascular complications of diabetes. We aimed to investigate the changes of caspase-8, Bcl-2, and N-terminal pro B-type natriuretic peptide (NT-proBNP) in cardiac tissue after 4 weeks of aerobic exercise in male rats with diabetes. Methods: Forty adult male rats were randomly allocated to healthy control, diabetes, control + exercise and exercise + diabetes groups. Diabetes was induced by intraperitoneal injection of streptozotocin (STZ) solution (55 mg/kg). Two weeks after injection, fasting blood glucose levels were measured. After the induction of diabetes, the exercise program was performed for 4 weeks (5 sessions per week) at a speed of 15 to 18 m/min for 25 to 44 minutes. Forty-eight hours after the last training session, the subjects were anesthetized and the heart muscle was removed. Caspase-8, Bcl-2 and NT-proBNP levels were measured by ELISA method. Results: The induction of diabetes in the control group resulted in a significant increase in caspase-8, and NT-proBNP levels while an insignificant increase was observed for Bcl-2 levels (P<0.05). In non-diabetic groups, exercise caused no changes in caspase-8, NT-proBNP and Bcl-2 (P<0.05). Exercise in diabetic groups significantly decreased NT-proBNP while no changes were observed in caspase-8 and Bcl-2 (P<0.05). Conclusion: Our findings showed that diabetes increases the pro-apoptotic and anti-apoptotic agent. In addition, 4 weeks of regular aerobic exercises can be used as a non-pharmacological strategy to reduce the complications of apoptosis in diabetic cardiomyocytes.

The Comparison between Effects of 12 weeks Combined Training and Vitamin D Supplement on Improvement of Sensory-motor Neuropathy in type 2 Diabetic Women

Background:

Peripheral neuropathy is a common complaint of diabetes. This study aimed to determine the effects of 12 weeks combined training with Vitamin D supplement on improvement of sensory-motor neuropathy in women with diabetic neuropathy.

Materials and Methods:

This clinical trial study conducted on 90 patients were selected and randomly divided into two groups. Finally, 81 adult females with diabetes type II (20–55 years old) were interred in this study. The control group had no training, but received Vitamin D. The experimental group received Vitamin D and 12 weeks training program (3 days a week, 60 min/session) including aerobic exercises, strength, and flexibility. Aerobic exercise intensity was set at 60–70% maximum heart rate and resistance training intensity was determined by 10 R.M. Michigan neuropathy questionnaire, reflex hammer and tuning fork 128 Hz used to screening tense of neuropathy (Michigan Neuropathy Screening Instrument) that were used for pretest and posttest.

Results:

Following 3 months combined training and supplementation with Vitamin D, had observed a significant reduction in numbness (P = 0.001), pain (0.002), tingling (P = 0.001), and weakness (P = 0.002) in the lower limb and also increases in sense of touch intervention (P = 0.005), detects the position of the fingers (P = 0.001) and vibration perception (P = 0.001) in tissues. Knee reflexes (P = 0.77) and ankles reflexes (P = 0.47) did not significantly change after interventions.

Conclusion:

It seems that taking part in combined training and supplementation with Vitamin D can improve the symptoms of sensory-motor neuropathy.

Neurodegeneration and Neuroinflammation in Diabetic Retinopathy: Potential Approaches to Delay Neuronal Loss

In spite of the extensive research the complex pathogenesis of diabetic retinopathy (DR) has not been fully elucidated. For many years it has been thought that diabetic retinopathy manifests only with microangiopathic lesions, which are totally responsible for the loss of vision in diabetic patients. In view of the current knowledge on the microangiopathic changes in the fundus of the eye, diabetic retinopathy is perceived as a neurodegenerative disease. Several clinical tools are available to detect neuronal dysfunction at early stages of diabetes. Many functional changes in the retina can be identified before vascular pathology develops, suggesting that they result from a direct effect of diabetes on the neural retina. In the course of diabetes there is a chronic loss of retinal neurons due to increased frequency of apoptosis. The neuronal apoptosis begins very early in the course of diabetes. This observation has led to suggestions that precautions against DR should be implemented immediately after diabetes is diagnosed. Neurodegeneration cannot be reversed; therefore treatments preventing neuronal cell loss in the retina need to be developed to protect diabetic patients. This review is an attempt to summarize what is currently known about the mechanisms of neuronal apoptosis in the context of diabetic retinopathy and vascular degeneration as well as about potential treatments of DR

Effects of voluntary exercise on apoptosis and cortisol after chronic restraint stress in mice

[Purpose]

To determine whether voluntary exercise (wheel running) has the potential of relieving stress.

[Methods]

In this study, restraint stress with or without voluntary wheel running was performed for mice housed in individual cages. A total of 21 ICR male mice were assigned into control (CON), restraint stress with voluntary exercise (RSVE), or restraint stress (RS) without voluntary exercise groups (n = 7 each).

[Results]

No significant difference in body weight increase was found among the three groups, although CON and RS groups had a tendency of having smaller body weight increase compared to the RSVE group. No significant difference in the expression level of liver heat shock protein 70, Bcl-2, or p53 was found among the three groups. However, caspase-3 protein level in RS group was significantly higher than that in the other two groups. Blood cortisol concentration in RS was higher (p < 0.05) than that in RSVE or CON group. It was the lowest (p < 0.05) in the RSVE group.

[Conclusion]

Our findings suggest that apoptosis caused by chronic restraint stress might be suppressed by voluntary exercise in mice.

Treadmill Exercise Attenuates Retinal Oxidative Stress in Naturally-Aged Mice: An Immunohistochemical Study

In the retina, a number of degenerative diseases, including glaucoma, diabetic retinopathy, and age-related macular degeneration, may occur as a result of aging. Oxidative damage is believed to contribute to the pathogenesis of aging as well as to age-related retinal disease. Although physiological exercise has been shown to reduce oxidative stress in rats and mice, it is not known whether it has a similar effect in retinal tissues. The aim of this study was to evaluate retinal oxidative stress in naturally-aged mice. In addition, we evaluated the effects of aerobic training on retinal oxidative stress by immunohistochemically evaluating oxidative stress markers. A group of twelve-week-old male mice were not exercised (young control). Two groups of twenty-two-month-old male mice were created: an old control group and a treadmill exercise group. The old control group mice were not exercised. The treadmill exercise group mice ran on a treadmill (5 to 12 m/min, 30 to 60 min/day, 3 days/week for 12 weeks). The retinal thickness and number of cells in the ganglion cell layer of the naturally-aged mice were reduced compared to those in the young control mice. However, treadmill exercise reversed these morphological changes in the retinas. We evaluated retinal expression of carboxymethyllysine (CML), 8-hydroxy-2'-deoxyguanosine (8-OHdG) and nitrotyrosine. The retinas from the aged mice showed increased CML, 8-OHdG, and nitrotyrosine immunostaining intensities compared to young control mice. The exercise group exhibited significantly lower CML levels and nitro-oxidative stress than the old control group. These results suggest that regular exercise can reduce retinal oxidative stress and that physiological exercise may be distinctly advantageous in reducing retinal oxidative stress.

Betaine inhibits vascularization via suppression of Akt in the retinas of streptozotocin-induced hyperglycemic rats

Diabetic retinopathy is a severe microvascular complication amongst patients with diabetes, and is the primary cause of visual loss through neovascularization. Betaine is one of the components of Fructus Lycii. In the present study, the effects of betaine on the expression levels of vascular endothelial growth factor (VEGF) and hypoxia-inducible factor (HIF)-1α in association with the Akt pathway were investigated in the retinas of streptozotocin (STZ)-induced diabetic rats using western blot and immunohistochemical analyses. The results of the present study revealed that the expression levels of VEGF, HIF-1α, and Akt were increased in the retinas of the STZ-induced diabetic rats. Betaine treatment attenuated this increase in VEGF and HIF-1α expression via suppression of diabetes-induced Akt activation in the retinas of the diabetic rats. The results suggested that betaine may potentially be used to delay the onset of complications associated with diabetic retinopathy via inhibition of retinal neovascularization in patients with diabetes.

Beneficial mechanisms of aerobic exercise on hepatic lipid metabolism in non-alcoholic fatty liver disease

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) refers to any fatty liver disease that is not due to excessive use of alcohol. NAFLD probably results from abnormal hepatic lipid metabolism and insulin resistance. Aerobic exercise is shown to improve NAFLD. This review aimed to evaluate the molecular mechanisms involved in the beneficial effects of aerobic exercise on NAFLD.

DATA SOURCE

We searched articles in English on the role of aerobic exercise in NAFLD therapy in PubMed.

RESULTS

The mechanisms of chronic aerobic exercise in regulating the outcome of NAFLD include: (i) reducing intrahepatic fat content by down-regulating sterol regulatory element-binding protein-1c and up-regulating peroxisome proliferator-activated receptor gamma expression levels; (ii) decreasing hepatic oxidative stress through modulating the reactive oxygen species, and enhancing antioxidant enzymes such as catalase and glutathione peroxidase; (iii) ameliorating hepatic inflammation via the inhibition of pro-inflammatory mediators such as tumor necrosis factor-alpha and interleukin-1 beta; (iv) attenuating mitochondrial dependent apoptosis by reducing cytochrome C released from the mitochondria to the cytosol; and (v) inducing hepato-protective autophagy.

CONCLUSION

Aerobic exercise, via different mechanisms, significantly decreases the fat content of the liver and improves the outcomes of patients with NAFLD.

Treadmill exercise inhibits apoptotic neuronal cell death with suppressed vascular endothelial growth factor expression in the retinas of the diabetic rats

Diabetic retinopathy is one of the most important microvascular complications in diabetes, and it is the major cause of visual loss. Physical exercise is known to ameliorate the symptoms of metabolic syndromes such as diabetic mellitus. In the present study, we investigated the effects of treadmill exercise on vascular endothelial growth factor (VEGF) expression and apoptotic cell death in the retinas of streptozotocin (STZ)-induced diabetic rats. The male Sprague-Dawley rats were randomly divided into three groups (n = 10 in each group): control group, STZ-induce diabetes group, STZ-induced diabetes and treadmill exercise group. To induce diabetes in the experimental animals, a single intraperitioneal injection of STZ (50 mg/kg) was given to each animal. The rats in the exercise group were forced to run on a motorized treadmill for 30 min once a day during 1 week starting 6 weeks after STZ injection. In the present results, VEGF expression in the retinas was increased by induction of diabetes. The numbers of caspase-3-positive and terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL)-positive cells in the retinas were also enhanced by induction of diabetes. Treadmill exercise significantly decreased VEGF expression and suppressed the number of TUNEL-positive and caspase-3-positive cells in the retinas of diabetic rats. In the present study, we have shown that treadmill exercise might alleviate the progression of diabetic retinopathy through suppressing VEGF expression and apoptotic cell death in the retinas of the diabetic rats.

Painful Diabetic Peripheral Neuropathy: Presentations, Mechanisms, and Exercise Therapy

Diabetic peripheral neuropathy (DPN) is a frequent complication of diabetes and a major cause of morbidity and increased mortality. It is typically characterized by significant deficits in tactile sensitivity, vibration sense, lower-limb proprioception, and kinesthesia. Painful diabetic neuropathy (P-DPN) is a common phenotype of DPN that affects up to one-third of the general diabetic population. P-DPN has been shown to be associated with significant reductions in overall quality of life, increased levels of anxiety and depression, sleep impairment, and greater gait variability. The purpose of this review is to examine proposed mechanisms of P-DPN, summarize current treatment regimen, and assess exercise as a potential therapy for P-PDN.

Although exercise has been shown to be an effective therapeutic modality for diabetes, its specific effects on DPN and especially the painful phenotype have not been sufficiently investigated in current literature. Several rodent models and clinical trials have presented promising results in this area, and warrant further investigations examining the effect of exercise on P-DPN.