Cardiometabolic and Cellular Adaptations to Multiple vs. Single Daily HIIT Sessions in Wistar Rats: Impact of Short-Term Detraining.

Multiple short daily bouts of HIIT are more effective than single daily sessions in improving cardiometabolic and cellular adaptations in rats. We hypothesize that a short period of detraining is sufficient to abolish the superior adaptive responses to multiple versus single daily sessions of HIIT in rats. Male rats were divided into untrained, 1xHIIT, and 3xHIIT groups. Over eight weeks, the 1xHIIT group performed 115 min single daily sessions of HIIT, while the 3xHIIT group performed three 5 min sessions with 4 h intervals. After training, both groups remained sedentary for four weeks (detraining). Resting oxygen consumption (VO2), body composition, glucose/insulin tolerance, and blood pressure were recorded. After euthanasia, cardiac function/histology and gastrocnemius mitochondrial density were analyzed. After training, both 1xHIIT and 3xHIIT protocols induced similar improvements in VO2, maximal oxygen uptake (VO2max), cardiac function/hypertrophy, and gastrocnemius mitochondrial density. These effects were maintained even after detraining. Only the 3xHIIT protocol improved insulin sensitivity. After detraining, this effect was abolished. After training, both 1xHIIT and 3xHIIT protocols reduced adiposity. After detraining, the adiposity increased in both groups, with a more pronounced increase in the 3xHIIT rats. A four-week detraining period abolishes the superior adaptive responses to multiple versus single daily HIIT sessions in rats.

Intense Caloric Restriction from Birth Prevents Cardiovascular Aging in Rats.

We previously demonstrated that a 50% caloric restriction (CR) from birth improves several cardiometabolic risk factors in young rats. In this study, we investigated in middle-aged rats the consequences of a 50% CR from birth on cardiometabolic risk factors, heart function/morphology, ventricular arrhythmia, and fibrillation incidence, and cardiac intracellular proteins involved with redox status and cell survival. From birth to the age of 18 months, rats were divided into an Ad Libitum (AL18) group, which had free access to food, and a CR18 group, which had food limited to 50% of that consumed by the AL18. Resting metabolic rate, blood pressure, and heart rate were recorded, and oral glucose and intraperitoneal insulin tolerance tests were performed. Blood was collected for biochemical analyses, and visceral fat and liver were harvested and weighed. Hearts were harvested for cardiac function, histological, redox status, and western blot analyses. The 50% CR from birth potentially reduced several cardiometabolic risk factors in 18-month-old rats. Moreover, compared with AL18, the CR18 group showed a ∼50% increase in cardiac contractility and relaxation, nearly three to five times less incidence of ventricular arrhythmia and fibrillation, ∼18% lower cardiomyocyte diameter, and ∼60% lower cardiac fibrosis. CR18 hearts also improved biomarkers of antioxidant defense and cell survival. Collectively, these results reveal several metabolic and cardiac antiaging effects of a 50% CR from birth in middle-aged rats.

Superior cardiometabolic and cellular adaptive responses to multiple versus single daily sessions of high-intensity interval training in Wistar rats.

This study aimed to compare in rats the cardiometabolic and cellular adaptative responses to 8 weeks of high-intensity interval training (HIIT) performed in a single (1xHIIT) or three shorter daily sessions (3xHIIT). Male Wistar rats were assigned to untrained (n = 10), 1xHIIT (n = 10), and 3xHIIT (n = 10) groups. Both HIIT groups performed 15 min of a treadmill run five times per week for 8 weeks. The 1xHIIT performed single daily sessions of 15 min, and the 3xHIIT performed three daily sessions of 5 min with an interval of 4 h between sessions. Resting VO2 and VO2max were measured using a metabolic chamber; blood pressure and heart rate were measured by plethysmography; body composition was estimated by DEXA; Glucose and insulin tolerance tests were performed; after euthanasia, hearts, gastrocnemius, and visceral fat were harvested for analysis of cardiac function, histology, and morphology. Mitochondrial densities of the gastrocnemius and left ventricle muscles were determined by electron microscopy. 3xHIIT induced similar positive adaptative responses to 1xHIIT on resting VO2 and VO2max, cardiac function, and mitochondria density. 3xHIIT was superior to 1xHIIT in reducing visceral fat weight and adipocyte size and improving insulin tolerance. Multiple short daily bouts of HIIT may be superior to single HIIT daily sessions in improving cardiometabolic and cellular adaptations in rats.

Does endurance training prior to ovariectomy protect against myocardial contractility dysfunction in rats?

BACKGROUND: Endurance training prevents cardiac dysfunction induced by menopause, but to date, no studies compared the effects of endurance training prior to menopause versus estrogen replacement therapy during menopause on heart function of rats. METHODS: Female Wistar rats aged three months were randomly assigned into three groups: Untrained ovariectomized rats (UN-OVX), untrained ovariectomized rats treated with estradiol (UN-OVX-E2), and ovariectomized rats previously exercised (EX-OVX). The endurance training protocol consisted of running on a treadmill at 60-70% of maximal aerobic capacity, 60 min per day, five days per week, for eight weeks. Estradiol replacement therapy consisted of silastic capsules containing the hormone for twelve days. After euthanasia, hearts were harvested, weighed and cardiac function was evaluated by the Langendorff technique. RESULTS: Both cardiac contractility and relaxation indexes improved similarly in the EX-OVX and UN-OVX-E2 rats compared to UN-OVX. CONCLUSION: Our findings reveal similar beneficial effects between endurance training previously to menopause and estradiol replacement therapy during menopause on cardiac function of rats.

Cardioprotective effects of severe calorie restriction from birth in adult ovariectomized rats.

AIMS: Menopause is a female condition induced by a reduction of ovarian hormone and is related to an increase in cardiovascular diseases in women. We have shown that severe calorie restriction (SCR) from birth reduces the cardiometabolic risk in adult male Wistar rats. In this study, we investigated the effects of SCR from birth to adulthood on cardiovascular function of ovariectomized rats. MAIN METHODS: From birth to adulthood, rats were daily fed ad libitum (control group - C) or with 50% of the amount consumed by the control group (calorie-restricted group - R). At 90 days, half of the rats in each group underwent bilateral ovariectomy (OVX), totaling 4 groups: C-Sham, C-OVX, R-Sham, R-OVX. Systolic blood pressure (SBP), heart rate (HR) and, double product (DP) index were recorded by tail-cuff plethysmography. Cardiac function was analyzed by the Langendorff technique and cardiomyocyte diameter was accessed by histologic analysis. Additionally, cardiac SERCA2 content and redox status were evaluated. KEY FINDINGS: C-OVX rats exhibited reduced cardiac function and cardiac non-enzymatic total antioxidant capacity (TAC). R-Sham animals showed reduced SBP, DP, HR, improved cardiac function, reduced cardiac protein carbonyl derivatives and increased TAC, catalase, and superoxide dismutase activities. R-OVX rats maintained reduced SBP, DP, HR, and increased contractility and relaxation indexes. R-Sham and R-OVX rats exhibited preserved heart mass and reduced cardiomyocyte diameter. Cardiac SERCA2 content did not differ between the groups. SIGNIFICANCE: Taken together, our findings show cardioprotective effects of SCR from birth in adult ovariectomized rats.

Caryocar brasiliense oil improves cardiac function by increasing Serca2a/PLB ratio despite no significant changes in cardiovascular risk factors in rats.

BACKGROUND: Caryocar brasiliense (pequi) oil is high in monounsaturated fat acids (MUFA), especially oleic, and in carotenoids, which have been associated with protection against cardiovascular disease. However, this food is poorly studied in this context, especially in the cardiac function. Therefore, we investigated the effects of a long-term intake of pequi oil in systemic cardiovascular risk factors and in the ex vivo cardiac function of rats. METHODS: Previously, we determined fatty acids and carotenoids in pequi oil. Next, male rats were divided in C - control group feed a standard diet, and PO - pequi oil group fed the same diet added pequi oil (+2.25 g.100 g-1). After 15 weeks, plasma lipids, glucose, insulin, blood pressure, heart rate, hepatic lipids were accessed and visceral fat pads were harvested. Hearts were used for the ex vivo cardiac function, histologic assays, SERCA2a and phospholanban (PLB) determinations. RESULTS: In agreement with scientific data, pequi oil had expressive amounts MUFA, especially oleic acid, and carotenoids. Hepatic triglycerides (TG) were reduced by pequi oil intake (p < 0.05). All others cardiovascular risk factors were not changed. The intrinsic heart rate was lower in PO group (p < 0.05). SERCA2a content was higher in this group (p < 0.05), without affecting PLB. Also, SERCA2a/PLB ratio increased in PO group (p < 0.05). CONCLUSION: Pequi oil intake improved cardiac function ex vivo, despite no significant changes in systemic cardiovascular risk factors. The higher lipid offer in pequi oil diet, its composition in oleic acid and carotenoids could be related to those effects.

Severe Calorie Restriction Reduces Cardiometabolic Risk Factors and Protects Rat Hearts from Ischemia/Reperfusion Injury.

BACKGROUND AND AIMS: Recent studies have proposed that if a severe caloric restriction (SCR) is initiated at the earliest period of postnatal life, it can lead to beneficial cardiac adaptations later on. We investigated the effects of SCR in Wistar rats from birth to adult age on risk factors for cardiac diseases (CD), as well as cardiac function, redox status, and HSP72 content in response to ischemia/reperfusion (I/R) injury. METHODS AND RESULTS: From birth to the age of 3 months, CR50 rats were fed 50% of the food that the ad libitum group (AL) was fed. Food intake was assessed daily and body weight were assessed weekly. In the last week of the SCR protocol, systolic blood pressure and heart rate were measured and the double product index was calculated. Also, oral glucose and intraperitoneal insulin tolerance tests were performed. Thereafter, rats were decapitated, visceral fat was weighed, and blood and hearts were harvested for biochemical, functional, tissue redox status, and western blot analyzes. Compared to AL, CR50 rats had reduced the main risk factors for CD. Moreover, the FR50 rats showed increased cardiac function both at baseline conditions (45% > AL rats) and during the post-ischemic period (60% > AL rats) which may be explained by a decreased cardiac oxidative stress and increased HSP72 content. CONCLUSION: SCR from birth to adult age reduced risk factors for CD, increased basal cardiac function and protected hearts from the I/R, possibly by a mechanism involving ROS.