Renal physiology and pathophysiology of aging

Analyzing Blood Pressure Ascent during Aging in Non-Diabetics: Focusing on Links to Insulin Resistance and Body Fat Mass

BACKGROUND

A gradual upward progression of blood pressure (BP) occurs regularly in most humans during aging. This is unfortunate, because it is generally recognized that elevation of BP, even when relatively mild, is eventually detrimental to human health. Accordingly, considerably more understanding of the pathophysiology behind such a phenomenon is important in order to institute the correct remedies. Two components of the ubiquitous metabolic syndrome (MS) with nutritional implications, elevated insulin resistance (IR) and excess body fat mass (FM), are often postulated to be critical driving forces behind the elevated BP that is common with aging. The current study, therefore, focuses on the presence and importance of IR and/or body FM in BP regulation of non-diabetics over the lifespan.

METHODOLOGY

In cross sectional analyses, baseline data obtained from healthy, non-diabetic volunteers involved in prior clinical studies were analyzed by examining links between FBG measurements used as a surrogate for IR and body FM through their individual and combined effects on BP.

RESULTS

A significant positive correlation was found between FBG and FM and also between each employed individually as independent variables to the dependent BP and heart rate (HR) variables. In volunteers with higher body FM compared to lower, average systolic BP (SBP) values are increased to some extent at the same FBG measurement suggesting that other factors related to FM in addition to IR are the basis for slight pressure differences. Considering quartiles based upon levels of FM and FBG, low FM-low FBG display significantly reduced average SBP, diastolic blood pressure (DBP), and HR compared to the upper FM-FBG quartiles. While readings of FBG and FM display a decline in elderly subjects after age 70 years (aging paradox), such does not occur with SBP.

CONCLUSIONS

IR is a major driving force behind BP regulation even in non-diabetics. FM influences BP substantially through its relationship with IR and also via other mechanisms directly linked to FM.

Prevalence and risk factors of acute kidney injury in polytrauma patients at Muhimbili Orthopedic Institute, Tanzania

Background

Polytrauma can lead to multi-organ dysfunction in addition to the local injuries. Acute kidney injury (AKI) is one of the most common causes and contributors to the high morbidity and mortality. Prevalence of acute kidney injury in trauma patients is as reported to be as high as 40.3%. Early detection and management leads to better outcomes. The prevalence of AKI among polytrauma patients remains unknown in our setting.

Methodology

A cross-sectional study involving all adults with polytrauma who presented at the emergency department at Muhimbili Orthopedic Institute (MOI) was designed. A score of ≥18 on the New Injury Severity Score (NISS) screening tool was used to identify polytrauma patients. The Kidney Disease Improving Global Outcomes (KDIGO) criteria was used to identify patient with polytrauma who developed acute kidney injury. Descriptive statistics were then obtained followed by hypothesis testing between variables with the chi squared test. Logistic regression models were used to determine factors associated with acute kidney injury.

Results

More than half (56.4%) of the patients were between 26 and 40 years and 92.3% of the polytrauma patients were males. Almost 2/5th (38.5%) of the polytrauma patients had acute kidney injury – half of these had stage 1 AKI, 33.3% had stage 2 AKI and the remaining 16.7% had stage 3 AKI. On multivariate logistic regression, it was found that patients who were older than 45 years (OR 8.53, CI 1.65–43.89, p = 0.01) and those patients with Systemic Inflammatory Response Syndrome (SIRS) (OR 21.83, CI 1.66–286.2, p = 0.019) had higher risk of acute kidney injury.

Conclusion

There is high prevalence of AKI among polytrauma patients. Elderly patients and those with SIRS were seen to have higher likelihood of AKI.

The elderly as a sensitive population in environmental exposures: making the case

The US population is aging. CDC has estimated that 20% of all Americans will be 65 or older by the year 2030. As a part of the aging process, the body gradually deteriorates and physiologic and metabolic limitations arise. Changes that occur in organ anatomy and function present challenges for dealing with environmental stressors of all kinds, ranging from temperature regulation to drug metabolism and excretion. The elderly are not just older adults, but rather are individuals with unique challenges and different medical needs than younger adults. The ability of the body to respond to physiological challenge presented by environmental chemicals is dependent upon the health of the organ systems that eliminate those substances from the body. Any compromise in the function of those organ systems may result in a decrease in the body's ability to protect itself from the adverse effects of xenobiotics. To investigate this issue, we performed an organ system-by-organ system review of the effects of human aging and the implications for such aging on susceptibility to drugs and xenobiotics. Birnbaum (1991) reported almost 20 years ago that it was clear that the pharmacokinetic behavior of environmental chemicals is, in many cases, altered during aging. Yet, to date, there is a paucity of data regarding recorded effects of environmental chemicals on elderly individuals. As a result, we have to rely on what is known about the effects of aging and the existing data regarding the metabolism, excretion, and adverse effects of prescription medications in that population to determine whether the elderly might be at greater risk when exposed to environmental substances. With increasing life expectancy, more and more people will confront the problems associated with advancing years. Moreover, although proper diet and exercise may lessen the immediate severity of some aspects of aging, the process will continue to gradually degrade the ability to cope with a variety of injuries and diseases. Thus, the adverse effects of long-term, low-level exposure to environmental substances will have a longer time to be manifested in a physiologically weakened elderly population. When such exposures are coupled with concurrent exposure to prescription medications, the effects could be devastating. Public health officials must be knowledgeable about the sensitivity of the growing elderly population, and ensure that the use of health guidance values (HGVs) for environmental contaminants and other substances give consideration to this physiologically compromised segment of the population.

Renal senescence in 2008: progress and challenges

Kidneys are significantly affected by profound anatomic and functional changes with senescence. These changes lead to decline in glomerular filtration rate, decreased urinary concentrating and diluting ability, diminished urinary acidification, and impaired potassium clearance, to list a few. Such changes make the elderly prone to drug toxicity and serious fluid and electrolyte imbalance. While the entire mystery of aging is far from being clear, the role of oxidative stress, telomere length, Klotho gene expression, and the renin angiotensin system seem to be the key mechanisms involved in aging. Aging, being a complex process, involves an array of intertwined molecular pathways. Simultaneous study of multiple molecular pathways in parallel could provide invaluable information in understanding the clinical course of kidney aging and elucidating mechanisms that play key roles in the aging process. A better understanding of these mechanisms may help to preserve renal function, improve morbidity and mortality, and hopefully reduce healthcare costs for the aging population.