Chronic physical activity: hepatic hypertrophy and increased total biotransformation enzyme activity

Is Physical Activity an Efficient Strategy to Control the Adverse Effects of Persistent Organic Pollutants in the Context of Obesity? A Narrative Review

Obesity affects nearly 660 million adults worldwide and is known for its many comorbidities. Although the phenomenon of obesity is not fully understood, science regularly reveals new determinants of this pathology. Among them, persistent organic pollutants (POPs) have been recently highlighted. Mainly lipophilic, POPs are normally stored in adipose tissue and can lead to adverse metabolic effects when released into the bloodstream. The main objective of this narrative review is to discuss the different pathways by which physical activity may counteract POPs' adverse effects. The research that we carried out seems to indicate that physical activity could positively influence several pathways negatively influenced by POPs, such as insulin resistance, inflammation, lipid accumulation, adipogenesis, and gut microbiota dysbiosis, that are associated with the development of obesity. This review also indicates how, through the controlled mobilization of POPs, physical activity could be a valuable approach to reduce the concentration of POPs in the bloodstream. These findings suggest that physical activity should be used to counteract the adverse effects of POPs. However, future studies should accurately assess its impact in specific situations such as bariatric surgery, where weight loss promotes POPs' blood release.

Physical exercise and persistent organic pollutants

Exposure to the legacy and emerging persistent organic pollutants (POPs) incessantly has become an important threat to individual health, which is closely related to neurodevelopment, endocrine and cardiovascular homeostasis. Exercise, on the other hand, has been consistently shown to improve physical fitness. Whereas associations between traditional air pollutants, exercise and lung function have been thoroughly reviewed, reviews on associations between persistent organic pollutants and exercise are scarce. Hence, a literature review focused on exercise, exposure to POPs, and health risk assessment was performed for studies published from 2004 to 2022. The purpose of this review is to provide an overview of exposure pathways and levels of POPs during exercise, as well as the impact of exercise on health concerns attributable to the redistribution, metabolism, and excretion of POPs in vivo. Therein lies a broader array of exercise benefits, including insulin sensitizing, mitochondrial DNA repair, lipid metabolism and intestinal microecological balance. Physical exercise is conducive to reduce POPs body burden and resistant to health hazards of POPs generally. Besides, individual lipid metabolism condition is a critical factor in evaluating potential link in exercise, POPs and health effects.

Biochemical and osmoregulatory responses of the African clawed frog experimentally exposed to salt and pesticide

Salinization and pollution are two main environmental stressors leading deterioration to water quality and degradation of aquatic ecosystems. Amphibians are a highly sensitive group of vertebrates to environmental disturbance of aquatic ecosystems. However, studies on the combined effect of salinization and pollution on the physiology of amphibians are limited. In this study, we measured the standard metabolic rate (SMR) and biochemical parameters of adult males of the invasive frog Xenopus laevis after 45 days of exposure to contrasting salinity environments (400 and 150 mOsm NaCl) with either 1.0 μg/L of the organophosphate pesticide chlorpyrifos (CPF) or pesticide-free medium. Our results revealed a decrease in SMR of animals exposed to the pesticide and in the ability to concentrate the plasma in animals exposed simultaneously to both stressors. The lack of ability to increase plasma concentration in animals exposed to both salt water and CPF, suggests that osmoregulatory response is decreased by pesticide exposure. In addition, we found an increase of liver citrate synthase activity in response to salt stress. Likewise, the liver acetylcholinesterase (AChE) activity decreased by 50% in frogs exposed to salt water and CPF and 40% in those exposed only to CPF, which suggest an additive effect of salinity on inhibition of AChE. Finally, oxidative stress increased as shown by the higher lipid peroxidation and concentration of aqueous peroxides found in the group exposed to salt water and pesticide. Thus, our results revealed that X. laevis physiology is compromised by salinization and pesticide exposure to both environmental stressors join.

The Impact of Diet and Exercise on Drug Responses

It is well known that lifestyle changes can alter several physiological functions in the human body. For exercise and diet, these effects are used sensibly in basic therapies, as in cardiovascular diseases. However, the physiological changes induced by exercise and a modified diet also have the capacity to influence the efficacy and toxicity of several drugs, mainly by affecting different pharmacokinetic mechanisms. This pharmacological plasticity is not clinically relevant in all cases but might play an important role in altering the effects of very common drugs, particularly drugs with a narrow therapeutic window. Therefore, with this review, we provide insights into possible food–drug and exercise–drug interactions to sharpen awareness of the potential occurrence of such effects.

Can Habitual Exercise Help Reduce Serum Concentrations of Lipophilic Chemical Mixtures? Association between Physical Activity and Persistent Organic Pollutants

BACKGROUND

Low-dose persistent organic pollutants (POPs), especially organochlorine pesticides (OCPs), have emerged as a new risk factor of many chronic diseases. As serum concentrations of POPs in humans are mainly determined by both their release from adipose tissue to circulation and their elimination from circulation, management of these internal pathways may be important in controlling the serum concentrations of POPs. As habitual physical activity can increase the elimination of POPs from circulation, we evaluated whether chronic physical activity is related to low serum POP concentrations.

METHODS

A cross-sectional study of 1,850 healthy adults (age ≥20 years) without cardio-metabolic diseases who participated in the U.S. National Health and Nutrition Examination Survey 1999 to 2004 was conducted. Information on moderate or vigorous leisure-time physical activity was obtained based on questionnaires. Serum concentrations of OCPs and polychlorinated biphenyls were investigated as typical POPs.

RESULTS

Serum concentrations of OCPs among physically active subjects were significantly lower than those among physically inactive subjects (312.8 ng/g lipid vs. 538.0 ng/g lipid, P<0.001). This difference was maintained after adjustment for potential confounders. When analyses were restricted to physically active subjects, there were small decreases in the serum concentrations of OCPs with increasing duration of physical activity, showing a curvilinear relationship over the whole range of physical activity (Pquadratic <0.001). In analyses stratified by age, sex, body mass index, and smoking status, a strong inverse association was similarly observed among all subgroups.

CONCLUSION

Physical activity may assist in decreasing serum concentrations of lipophilic chemical mixtures such as OCPs.

New approaches to cope with possible harms of low-dose environmental chemicals

Low-dose environmental chemicals including endocrine-disrupting chemicals can disturb endocrine, nervous and immune systems. Traditional chemical-focused approaches, strict regulation and avoidance of exposure sources, can help protect humans from individual or several chemicals in the high-dose range, but their value in the low-dose range is questionable. First, exposure sources to problematic environmental chemicals are omnipresent, and many common pollutants present no safe level. In this situation, the value of any effort focusing on individual chemicals is very limited. Second, critical methodological issues, including the huge number of environmental chemicals, biological complexity of mixtures and non-linearity, make it difficult for risk assessment-based regulation to provide reliable permissible levels of individual chemicals. Third, the largest exposure source is already internal; human adipose tissue contains the most complex chemical mixtures. Thus, in the low-dose range, a paradigm shift is required from a chemical-focused to a human-focused approach for health protection. Two key questions are (1) how to control toxicokinetics of chemical mixtures to decrease their burden in critical organs and (2) how to mitigate early harmful effects of chemical mixtures at cellular levels. Many lifestyles can be evaluated for these purposes. Although both the chemical-focused and human-focused approaches are needed to protect humans, the human-focused holistic approach must be the primary measure in the low-dose range of environmental chemicals.

A role of low dose chemical mixtures in adipose tissue in carcinogenesis

The Halifax project recently hypothesized a composite carcinogenic potential of the mixture of low dose chemicals which are commonly encountered environmentally, yet which are not classified as human carcinogens. A long neglected but important fact is that adipose tissue is an important exposure source for chemical mixtures. In fact, findings from human studies based on several persistent organic pollutants in general populations with only background exposure should be interpreted from the viewpoint of chemical mixtures because serum concentrations of these chemicals can be seen as surrogates for chemical mixtures in adipose tissue. Furthermore, in conditions such as obesity with dysfunctional adipocytes or weight loss in which lipolysis is increased, the amount of the chemical mixture released from adipose tissue to circulation is increased. Thus, both obesity and weight loss can enhance the chance of chemical mixtures reaching critical organs, however paradoxical this idea may be when fat mass is the only factor considered. The complicated, interrelated dynamics of adipocytes and chemical mixtures can explain puzzling findings related to body weight among cancer patients, including the obesity paradox. The contamination of fat in human diet with chemical mixtures, occurring for reasons similar to contamination of human adipose tissue, may be a missing factor which affects the association between dietary fat intake and cancer. The presence of chemical mixtures in adipose tissue should be considered in future cancer research, including clinical trials on weight management among cancer survivors.

Exercise Is Medicine, But Does It Interfere With Medicine?

Exercise frequently is prescribed therapeutically, either on its own or combined with drugs. A drug's absorption, distribution, metabolism, and excretion can be affected by the user's anatomy and physiology, which are both changed by the myriad of complex adaptations to acute and chronic exercise. This article reviews the research that suggests exercise may influence a drug's plasma concentration, and thus its efficacy and safety.

Endurance swimming stimulates transepithelial calcium transport and alters the expression of genes related to calcium absorption in the intestine of rats

Endurance impact exercise, e.g., running, is known to enhance the intestinal calcium absorption. However, nonimpact exercise, e.g., swimming, is more appropriate for osteoporotic patients with cardiovascular diseases or disorders of bone and joint, but the effect of swimming on the intestinal calcium transport was unknown. This study, therefore, aimed to investigate the transepithelial calcium transport and the expression of related genes in the intestine of rats trained to swim nonstop 1 h/day, 5 days/wk for 2 wk. We found that endurance swimming stimulated calcium transport in the duodenum, proximal jejunum, and cecum, while decreasing that in the proximal colon. Swimming affected neither the transepithelial potential difference nor resistance. As demonstrated by real-time PCR, the small intestine, especially the duodenum, responded to swimming by upregulating a number of genes related to the transcellular calcium transport, i.e., TRPV5, TRPV6, calbindin-D9k, PMCA1b, and NCX1, and the paracellular calcium transport, i.e., ZO-1, ZO-2, ZO-3, cingulin, occludin, and claudins, as well as nuclear receptor of 1,25(OH)2D3. In contrast, swimming downregulated those genes in the colon. Microarray analysis showed that swimming also altered the expression of duodenal genes related to the transport of several ions and nutrients, e.g., Na+, K+, Cl-, glucose, and amino acids. In conclusion, endurance swimming enhanced intestinal calcium absorption, in part, by upregulating the calcium transporter genes. The present microarray study also provided relevant information for further investigations into the intestinal nutrient and electrolyte transport during nonimpact exercise.

Physical activity and cancer prevention : pathways and targets for intervention

The prevalence of obesity, an established epidemiological risk factor for many cancers, has risen steadily for the past several decades in the US and many other countries. Particularly alarming are the increasing rates of obesity among children, portending continuing increases in the rates of obesity and obesity-related cancers for many years to come. Modulation of energy balance, via increased physical activity, has been shown in numerous comprehensive epidemiological reviews to reduce cancer risk. Unfortunately, the effects and mechanistic targets of physical activity interventions on the carcinogenesis process have not been thoroughly characterized. Studies to date suggest that exercise can exert its cancer-preventive effects at many stages during the process of carcinogenesis, including both tumour initiation and progression. As discussed in this review, exercise may be altering tumour initiation events by modifying carcinogen activation, specifically by enhancing the cytochrome P450 system and by enhancing selective enzymes in the carcinogen detoxification pathway, including, but not limited to, glutathione-S-transferases. Furthermore, exercise may reduce oxidative damage by increasing a variety of anti-oxidant enzymes, enhancing DNA repair systems and improving intracellular protein repair systems. In addition to altering processes related to tumour initiation, exercise may also exert a cancer-preventive effect by dampening the processes involved in the promotion and progression stages of carcinogenesis, including scavenging reactive oxygen species (ROS); altering cell proliferation, apoptosis and differentiation; decreasing inflammation; enhancing immune function; and suppressing angiogenesis. A paucity of data exists as to whether exercise may be working as an anti-promotion strategy via altering ROS in initiated or preneoplastic models; therefore, no conclusions can be made about this possible mechanism. The studies directly examining cell proliferation and apoptosis have shown that exercise can enhance both processes, which is difficult to interpret in the context of carcinogenesis. Studies examining the relationship between exercise and chronic inflammation suggest that exercise may reduce pro-inflammatory mediators and reduce the state of low-grade, chronic inflammation. Additionally, exercise has been shown to enhance components of the innate immune response (i.e. macrophage and natural killer cell function). Finally, only a limited number of studies have explored the relationship between exercise and angiogenesis; therefore, no conclusions can be made currently about the role of exercise in the angiogenesis process as it relates to tumour progression. In summary, exercise can alter biological processes that contribute to both anti-initiation and anti-progression events in the carcinogenesis process. However, more sophisticated, detailed studies are needed to examine each of the potential mechanisms contributing to an exercise-induced decrease in carcinogenesis in order to determine the minimum dose, duration and frequency of exercise needed to yield significant cancer-preventive effects, and whether exercise can be used prescriptively to reverse the obesity-induced physiological changes that increase cancer risk.

Influence of 4-week and 8-week exercise training on the pharmacokinetics and pharmacodynamics of intravenous and oral azosemide in rats

Cytochrome P450 expression was determined in the livers of control, 4-week exercised (4WE) and 8-week exercised (8WE) rats. Even though the 4-week and 8-week exercise training caused 53 and 25% increases, respectively, in total cytochrome P450 contents in the liver, exercise training did not cause any changes in the levels of P450 1A2 (which primarily metabolizes azosemide), 2E1 and 3A23 in the liver, as assessed by both Western and Northern blot analyses. Also, exercise training failed to alter the activity of NADPH-dependent cytochrome P450 reductase. The plasma concentrations of norepinephrine and epinephrine were significantly (2 to 3 folds) higher in 4WE rats than in controls, presumably due to physical stress, but the catecholamine levels in 8 WE rats returned to control levels. After intravenous administration (10 mg/kg of azosemide), the amount of unchanged azosemide excreted in 8-h urine (Ae(Azo, 0-8 h)) was significantly greater (46% increase) in 4WE rats than that in control rats. This resulted in a significantly faster (82% increase) renal clearance of azosemide. However, the nonrenal clearances were not significantly different between control and 4WE rats. The significantly greater Ae(Azo, 0-8 h) in 4WE rats was mainly due to a significant increase in intrinsic active secretion of azosemide in renal tubules and not due to a decrease in the metabolism of azosemide. After oral administration (20 mg/kg), Ae(Azo, 0-8 h) was also significantly greater (264%) in 4WE rats and this again was due to a significant increase in intrinsic active renal secretion of azosemide and not due to an increase in gastrointestinal absorption. After both intravenous and oral administration, the 8-h urine output was not significantly different between control and 4WE rats although Ae(Azo, 0-8 h) increased significantly in 4WE rats. This could be due to the fact that the urine output reached a plateau at 10 mg/kg after intravenous administration and 20 mg/kg after oral administration of azosemide to rats and possibly due to increase in plasma antidiuretic hormone levels and aldosterone production in 4WE rats.

Wheel running attenuates the antinociceptive properties of morphine and its metabolite, morphine-6-glucuronide, in rats

Recent work has shown that chronic exercise is associated with a reduction in the pain-relieving actions of opioid drugs in experimental animals. To determine whether this reduction represents an interaction between exogenously administered opioids and the endogenous opioid system, or is the result of altered drug pharmacokinetics, the antinociceptive actions of morphine and its metabolite, morphine-6-glucuronide (M6G), were compared in active and inactive female Long-Evans rats. Active animals were housed in running wheels and inactive animals in standard laboratory cages for 3 weeks preceding determinations of antinociception using the tail-flick test. At the end of the 3-week period, active rats were running the equivalent of 9-11 km a day. Antinociceptive responses, determined following subcutaneous injections of either morphine (0.625-20 mg/kg) or M6G (0.3-10.0 mg/kg), were significantly reduced in active rats relative to inactive rats. This reduction was manifested by both a lower magnitude of antinociception, and a shorter duration of antinociception after drug administration in active compared to inactive rats. This reduction was not associated with alterations in the estrous cycle or with differences in body weight between the active and inactive animals. The present results support the hypothesis that cross-tolerance develops between endogenous opioid peptides released in response to exercise and exogenously administered opioid drugs.

The effects of chronic exercise on anesthesia induced hepatotoxicity

A hypoxic rat model of halothane-induced hepatotoxicity, which is known to produce liver damage, was used to determine the effects of chronic exercise on halothane-induced hepatotoxicity and on reduced hepatic glutathione (GSH) levels. Metabolism of volatile anesthetics may generate metabolites that can cause mild and transient hepatotoxicity.

METHODS

Six male Sprague-Dawley rats completed a 10-wk (5 d x wk(-1)) treadmill running protocol. Twelve age-matched animals were used as sedentary controls. After the completion of exercise training, rats were exposed for 2 h to 1% halothane in 14% O2. Twenty-four hours later, animals were anesthetized with sodium pentobarbital and sacrificed. Livers were excised, stained, and evaluated for hepatotoxicity using a histopathological 0 (normal) to 5 (severe damage) point categorical scale and for the determination of GSH levels.

RESULTS

Median histopathologic scores revealed significantly lower indications of hepatotoxicity in exercise animals as compared with control animals (score = 0.25 vs 1.50; P < 0.05). Liver damages scores between 1 and 5 were observed in 75% (9 of 12) of the control animals, whereas only 1 of 6 exercise animals had a score greater than 1 (P < 0.05). No significant difference was observed in reduced GSH levels.

CONCLUSIONS

Chronic exercise improves the detoxicant ability of the liver for halothane anesthesia as noted by the ameliorated liver damage and reduced incidence of halothane-induced hepatotoxicity in the exercise animals.

Review of the metabolic fate of styrene

Styrene and styrene oxide have been implicated as reproductive toxicants, neurotoxicants, or carcinogens in vivo or in vitro. The use of these chemicals in the manufacture of plastics and polymers and in the boat-building industry has raised concerns related to the risk associated with human exposure. This review describes the literature to date on the metabolic fate of styrene and styrene oxide in laboratory animals and in humans. Many studies have been conducted to assess the metabolic fate of styrene in rats, and investigations on the metabolism of styrene in humans have been of considerable interest. Limited research has been done to assess metabolism in the mouse. The metabolism of styrene to styrene oxide and further conversion to styrene glycol (via epoxide hydrolase), mandelic acid, and phenylglyoxylic acid has been given considerable attention, and is considered to be the major pathway of activation and detoxication for humans. While the hydrolysis of styrene oxide to styrene glycol historically has been the favored pathway for the rat, studies in more recent years have indicated that glutathione conjugation also is a viable and significant pathway for both the rat and the mouse. This pathway has not been established in humans. Mandelic acid and phenylglyoxylic acid have been used as urinary markers of exposure in humans exposed to styrene. Extensive investigations have been conducted on the kinetics of styrene and styrene oxide in rodents. In people, the kinetics of styrene and styrene oxide in the blood of occupationally exposed workers and volunteers have been determined. Pharmacokinetic models developed in the last decade have become increasingly complex, with the most recent physiologically based model describing the kinetics of styrene and styrene oxide. This model shows pronounced species differences in sensitivity coefficients for styrene or styrene oxide between mice, rats, and humans, where mice are the more sensitive species to the Vmax for both epoxide hydrolase and monooxygenase. This result is particularly interesting in light of the recent findings of extensive mortality and hepatotoxicity for mice exposed to relatively low levels of styrene (250 to 500 ppm), while rats and humans exhibit only nasal and eye irritations at exposure concentrations well above 500 ppm.