Impact of age on host responses to diet-induced obesity:Development of joint damage and metabolic set points

Background:Osteoarthritis is one of the leading causes of pain and disability worldwide,and a large percentage of patients with osteoarthritis are individuals who are also obese.In recent years,a series of animal models have demonstrated that obesity-inducing diets can result in synovial joint damage(both with and without the superimposition of trauma),which may be related to changes in percentage of body fat and a series of low-level systemic inflammatory mediators.Of note,there is a disparity between whether the dietary challenges commence at weaning,representing a weanling onset,or at skeletal maturity,representing an adult onset of obesity.We wished to evaluate the effect ofthe dietary exposure time and the age at which animals are exposed to a high-fat and high-sucrose(HFS) diet to determine whether these factors may result in disparate outcomes,as there is evidence suggesting that these factors result in differential metabolic disturbances.Based on dietary exposure time,we hypothesized that rats fed an HFS diet for 14 weeks from weaning(HFS Weanling) would demonstrate an increase in knee joint damage scores,whereas rats exposed to the HFS diet for 4 weeks,starting at 12 weeks of age(HFS Adult) and rats exposed to a standard chow diet(Chow)would not display an increase in knee joint damage scores.Methods:Male Sprague-Dawley rats were fed either an HFS diet for 14 weeks from weaning(HFS Weanling) or an HFS diet for 4 weeks,starting at 12 weeks of age(HFS Adult).At sacrifice,joints were scored using the modified Mankin Criteria,and serum was analyzed for a defined subset of inflammatory markers(Interleukin-6,leptin,monocyte chemoattractant protein-1,and tumor necrosis factorα).Results:When the HFS Weanling and HFS Adult groups were compared,both groups had a similar percent of body fat,although the HFS Weanling group had a significantly greater body mass than the HFS Adult group.The HFS Weanling and HFS Adult animals had a significant increase in body mass and percentage of body fat when compared to the Chow group.Although knee joint damage scores were low in all 3 groups,we found,contrary to our hypothesis,that the HFS Adult group had statistically significant greater knee joint damage scores than the Chow and HFS Weanling groups.Furthermore,we observed that the HFS Weanling group did not have significant differences in knee joint damage scores relative to the Chow group.Conclusion:These findings indicate that the HFS Weanling animals were better able to cope with the dietary challenge of an HFS diet than the HFS Adult group.Interestingly,when assessing various serum proinflammatory markers,no significant differences were detected between the HTS Adult and HFS Weanling groups.Although details regarding the mechanisms underlying an increase in knee joint damage scores in the HFS Adult group remain to be elucidated,these findings indicate that dietary exposure time maybe less important than the age at which an HFS diet is introduced.Moreover,increases in serum proinflammatory mediators do not appear to be directly linked to knee joint damage scores in the HFS Weanling group animals but may be partially responsible for the observed knee joint damage in the adults over the very short time of exposure to the HFS diet.

Potential Impact of Space Environments on Developmental and Maturational Programs Which Evolved to Meet the Boundary Conditions of Earth: Will Maturing Humans Be Able to Establish a Functional Biologic System Set Point under Non-Earth Conditions?

Mammalian development and maturation, particularly processes for humans have evolved in the context of the boundary conditions of Earth (i.e. 1 g gravity, geomagnetic field, background radiation) to yield functional individuals, although the process is not perfect and “errors” do occur. With the advent of spaceflight to low Earth orbit (the International Space Station), humans are now exposed to microgravity and increased exposure to radiation. However, thus far, only adult humans have served as astronauts, but this will likely change with plans to explore deep space and colonize planets. Thus, conception, fetal development, post-birth maturation, puberty and skeletal maturity will occur in the context of boundary conditions that did not shape human evolution and influence physiological and biomechanical systems designed to function within the Earth’s boundary conditions. Thus, processes utilizing the 1 g environment (i.e. walking upright) and the geomagnetic field (i.e. the electrical/biomagnetic basis of neural interactions) will have to adapt to new boundary conditions, providing opportunity for additional errors or alterations in processing during development which could impact functional outcomes at multiple levels. This review/perspective will discuss some of these issues and attempt to provide direction for addressing the potential issues to be encountered.

Would Adding Low Doses of Lithium Salts and/or Prebiotic Fibre Interventions to an Effective Exercise Protocol Further Enhance Retention of Cognitive Integrity? Potential for Preventing Loss of Cognition with Aging Using Combinations of Low Cost Regimens

It is clear that loss of cognition is becoming epidemic in our aging society. Onset of dementia and diseases such as Alzheimer’s are very prevalent and the prognosis is not optimistic that numbers will decrease in the coming decades. Thus, this epidemic is impacting the quality of life of a large number of people, primarily females, as well as the health care systems of many countries. Of relevance is the fact that large clinical trials of candidate drugs to treat these conditions have not been overwhelming successes, indicating that we may need to take new directions or focus on prevention. One conservative approach in this regard has been the use of exercise protocols to both retain cognition and inhibit progression of loss. With the optimization of exercise protocols, it may be time to step back and ask “how can these successes be augmented to further inhibit risk and stabilize loss early in the development of these conditions?” An example of how this could be approached is via supplementation with low doses of minerals such as lithium salts, or supplementation of the diet with prebiotics in patients with obesity and metabolic syndrome. Regarding the former, recent epidemiological studies have indicated that the content of Li in the drinking water is associated with lower incidences of cognitive diseases/conditions. While not definitive, such clues may warrant performing controlled studies using low doses of lithium salts plus exercise to further optimize impact on retention of cognition in those at risk, or those with early disease. Similarly, patients with obesity are at higher risk to develop dementia, and prebiotics can correct some of the metabolic derangements associated with the microbiome in such patients to impact risk. Thus, multiple low cost interventions plus exercise could further enhance retention of cognitive integrity in specific populations.