Energy restriction but not protein source affects antioxidant capacity in athletes

Supplementation with a putative calorie restriction mimetic micronutrient blend increases glutathione concentrations and improves neuroenergetics in brain of healthy middle-aged men and women

BACKGROUND

Caloric restriction (CR) without micronutrient deficiency has been shown to increase both lifespan and healthspan. In animals, CR has been demonstrated to increase glutathione (GSH), a neuroprotective antioxidant, in the brain and preserve brain mitochondrial function by altering neuroenergetics. In humans it has been associated with improvements in mood states and cognitive function. However, most CR studies have employed a 30-60% reduction in calories which is likely too stringent for most people to adhere to long-term. Thus, there is an unmet need for nutritional supplements which can mimic the biological effects of CR, without the need for calorie limitations.

AIM

The purpose of the present randomized, placebo-controlled clinical trial was to use Proton (¹H) Magnetic Resonance Spectroscopic (MRS) measurements to determine non-invasively whether a blend of micronutrients, a putative CR mimetic, positively modulates metabolites related to neuroprotection and neuroenergetics in the brain.

METHODS

Healthy middle-aged men and women (N = 63 [33 women]; age: 40-60 years) were randomized in a double-blind manner to 6 weeks supplementation with either the putative CR mimetic or placebo. At baseline and 6 weeks, subjects underwent MRS at 3 T to investigate changes in brain chemistry, including the neurometabolites: GSH, Glutamate (Glu), Glutamine (Gln) and N-Acetylaspartate (NAA).

RESULTS

GSH, a marker of antioxidant and cellular redox status, increased in the brain of participants in the supplement group. The supplement group also showed an increase in the Glu/Gln ratio, a marker of excitatory neurotransmission and bioenergetics. A trend for an increase in NAA/H₂O, a marker of neuronal integrity, was observed in females in the supplement group.

CONCLUSIONS

The present study reveals that 6-weeks daily supplementation with a micronutrient blend elicits positive changes in brain neurochemistry. This is the first study to demonstrate that a putative CR mimetic increases brain GSH concentrations and improves neuroprotection and neuroenergetics in the brain of healthy humans. This study was registered at www.clinicaltrials.gov as NCT02439983.

Dietary Energy Restriction Ameliorates Cognitive Impairment in a Mouse Model of Traumatic Brain Injury

Traumatic brain injury (TBI) is one of the most common causes of neurological damage in young people. It was previously reported that dietary restriction, by either intermittent fasting (IF) or daily caloric restriction (CR), could protect neurons against dysfunction and degeneration in animal models of stroke and Parkinson's disease. Recently, several studies have shown that the protein Sirtuin 1 (SIRT1) plays a significant role in the induced neuroprotection following dietary restriction. In the present study, we found a significant reduction of SIRT1 levels in the cortex and hippocampus in a mouse model of mild weight-drop closed head TBI. This reduction was prevented in mice maintained on IF (alternate day fasting) and CR initiated after the head trauma. Hippocampus-dependent learning and memory (measured using a novel object recognition test) was impaired 30 days post-injury in mice fed ad libitum, but not in mice in the IF and CR groups. These results suggest a clinical potential for IF and/or CR as an intervention to reduce brain damage and improve functional outcome in TBI patients.

Oxidative stress, inflammation, psychological status, and severity of respiratory infections are negatively affected during the pre-contest period in amateur bodybuilders

We examined whether off-season (OffS) and pre-contest (PreC) periods affect blood oxidative stress, inflammatory, immunological, and psychological markers in 20 bodybuilders. The athletes recorded their food intake (3-day record), physical activities, mood states (Profile of Mood States, POMS), recovery-stress (Recovery-Stress Questionnaire for Athletes, RESTQ-Sport), and upper respiratory symptoms (Wisconsin Upper Respiratory Symptom Survey, WURSS-21), and blood was obtained for biochemical analysis. Almost all athletes were in positive energy balance during OffS, while bodybuilders presented markedly restricted energy intake (∼45%) leading to loss of weight (-9%) and fat mass (-45%) with preservation of fat-free mass in PreC. Protein intake was high during both periods, while lipid and carbohydrate intakes were reduced ∼50% in PreC. Almost all athletes consumed 100% of the Recommended Dietary Allowance (RDA) for micronutrients in OffS, while 45% and 75% of the athletes had intakes below the RDA for vitamins A and E in PreC. Oxidative damage to lipids (thiobarbituric acid reactive substances, TBARS), protein carbonyls, and the TBARS/total antioxidant capacity ratio increased in PreC (32%, 27%, 60%), as did plasma tumor necrosis factor α (4-fold) and WURSS-21 scores (25%). There were no significant changes in serum catalase, glutathione reductase, and superoxide dismutase activities nor in interleukin 1β and immunoglobulins. In PreC, POMS showed negative changes in vigor (-20%), fatigue (23%), and total mood disturbance (35%), and RESTQ-Sport showed alterations for general and sport stress (34% and 50%, respectively) and sport recovery (-23%). Thus, PreC negatively affects nutrient intake, which may worsen oxidative stress, inflammation, psychological status, and the severity of respiratory infections in bodybuilders.

Antinociceptive effects of caloric restriction on post-incisional pain in nonobese rats

Caloric restriction (CR) increases lifespan, retards physiological signs of aging, and delays a variety of diseases. Reduction of inflammatory response was proposed as one of the molecular mechanisms for how CR exerts beneficial effects. The present study investigated the effects of CR on postoperative pain in rats. Adult nonobese rats were divided into two dietary groups, an ad libitum fed group (AL) and a caloric restriction group (CR) that was provided with 60% of the food intake of AL rats. After 6 weeks, the effects of CR on pain behaviors and inflammation induced by plantar incision were examined. CR rats displayed significantly reduced nonevoked pain, mechanical allodynia and thermal hyperalgesia induced by incision, and showed decreased levels of pro-inflammatory cytokines in serum, peri-incisional skin tissue and ipsilateral spinal cord dorsal horn at 6 h and 24 h after incision. The analgesic efficiency of parecoxib and morphine, two agents widely used for the management of postoperative pain clinically, was reinforced by CR. Together, CR generates antinociceptive effects on postoperative incisional pain in rats, perhaps providing some improvement of QOL in patients with postoperative pain, and the beneficial effects may be attributable to the inhibition of excessive inflammation induced by surgical injury.

The DAF-2 insulin-like signaling pathway independently regulates aging and immunity in C. elegans

The Caenorhabditis elegans DAF-2 insulin-like signaling pathway, which regulates lifespan and stress resistance, has also been implicated in resistance to bacterial pathogens. Loss-of-function daf-2 and age-1 mutants have increased lifespans and are resistant to a variety of bacterial pathogens. This raises the possibility that the increased longevity and the pathogen resistance of insulin-like signaling pathway mutants are reflections of the same underlying mechanism. Here we report that regulation of lifespan and resistance to the bacterial pathogen Pseudomonas aeruginosa is mediated by both shared and genetically distinguishable mechanisms. We find that loss of germline proliferation enhances pathogen resistance and this effect requires daf-16, similar to the regulation of lifespan. In contrast, the regulation of pathogen resistance and lifespan is decoupled within the DAF-2 pathway. Long-lived mutants of genes downstream of daf-2, such as pdk-1 and sgk-1, show wildtype resistance to pathogens. However, mutants of akt-1 and akt-2, which we find to individually have modest effects on lifespan, show enhanced resistance to pathogens. We also demonstrate that pathogen resistance of daf-2, akt-1, and akt-2 mutants is associated with restricted bacterial colonization, and that daf-2 mutants are better able to clear an infection after challenge with P. aeruginosa. Moreover, we find that pathogen resistance among insulin-like signaling mutants is associated with increased expression of immunity genes during infection. Other processes that affect organismal longevity, including Jun kinase signaling and caloric restriction, do not affect resistance to bacterial pathogens, further establishing that aging and innate immunity are regulated by genetically distinct mechanisms.

Following 2 diet-restricted male outdoor rock climbers: impact on oxidative stress and improvements in markers of cardiovascular risk

Lower body fat percentage is positively associated with climbing performance. This may lead climbers to practice unhealthy diet restriction when no sport-specific nutrition information exists. This study examined whether prolonged diet restriction affects body composition, oxidative stress, or other potential health risks in outdoor rock climbers. Two healthy male climbers conducted a 5 week rock climbing trip with a limited food budget ($1 each per day). Subjects underwent an energy restriction of approximately 40%. Loss of body weight and fat mass at week 5 were 5.8% and 16.1%, respectively, and were accompanied by significant subcutaneous fat loss in the iliac crest and abdomen. Triacylglycerols (TG), free fatty acids and C-reactive protein (CRP) dramatically decreased from baseline to week 2, and then maintained the lower level until week 5. Plasma vitamin C was below the normal range, and F2-isoprostanes, a marker of oxidative stress, continuously increased to week 5. Superoxide dismutase and glutathione peroxidase increased to week 2, but had returned to baseline levels at week 5. These results indicate that prolonged reduced energy intake while climbing may have an impact on weight loss and fat mass loss, which may contribute to low circulating TG and CRP, indicating improvements in markers of cardiovascular risk, and may lead to increased oxidative stress and reduced circulating antioxidants. Further studies are warranted to determine whether antioxidant supplementation or increased energy intake reduce oxidative stress.

The neuroprotective properties of calorie restriction, the ketogenic diet, and ketone bodies

Both calorie restriction and the ketogenic diet possess broad therapeutic potential in various clinical settings and in various animal models of neurological disease. Following calorie restriction or consumption of a ketogenic diet, there is notable improvement in mitochondrial function, a decrease in the expression of apoptotic and inflammatory mediators and an increase in the activity of neurotrophic factors. However, despite these intriguing observations, it is not yet clear which of these mechanisms account for the observed neuroprotective effects. Furthermore, limited compliance and concern for adverse effects hamper efforts at broader clinical application. Recent research aimed at identifying compounds that can reproduce, at least partially, the neuroprotective effects of the diets with less demanding changes to food intake suggests that ketone bodies might represent an appropriate candidate. Ketone bodies protect neurons against multiple types of neuronal injury and are associated with mitochondrial effects similar to those described during calorie restriction or ketogenic diet treatment. The present review summarizes the neuroprotective effects of calorie restriction, of the ketogenic diet and of ketone bodies, and compares their putative mechanisms of action.

Is dietary restriction beneficial for human health, such as for immune function?

PURPOSE OF REVIEW

The impact of dietary restriction on physiologic function in humans is now beginning to be examined. The clinical trials are fueled by decades of animal experiments showing that dietary restriction delays the aging process and decreases the incidence of many age-associated diseases. The critical issue addressed in this article is whether or not dietary restriction long term is feasible or beneficial in humans.

RECENT FINDINGS

Short-term dietary restriction in humans does appear to have beneficial effects at lowering metabolism, especially when examining carbohydrates and weight loss. Dietary restriction long term does, however, have detrimental psychological effects in humans, making its feasibility questionable. Even short-term dietary restriction can negatively impact physical activity and potentially some aspects of immunity. The best avenue for humans to benefit from dietary restriction would be for pharmacological or bioactive food ingredient mimetics to be developed which would be more applicable for long-term use.

SUMMARY

Dietary restriction per se is unlikely to emerge as a feasible long-term strategy to improve human health. Developing dietary restriction mimetics targeting energy metabolism may prove beneficial, not only in aging, but also in diabetes and obesity.