Kidney aging process and the management of the elderly patient with renal impairment (Review)

Age-related trends in urine specific gravity in apparently healthy cats

OBJECTIVES

Urine specific gravity (USG) is the most common method for the estimation of urine concentration in cats. Utilization of USG as a screening tool is easily accessible and is of low cost to the client if strategically utilized in settings of higher diagnostic value. There is currently minimal population information regarding how USG changes across ages in cats.

METHODS

Data were collected from electronic pet medical records from more than 1000 hospitals and screened for cats with an apparently healthy clinical status and complete diagnostic information. USG was compared with age in multiple analyses to examine the relationship between the variables.

RESULTS

In the absence of other indicators of disease, renal concentrating ability begins to diminish, on average, starting at approximately 9 years of age. By age group, cats aged 11-15 years (1.044, 95% confidence interval [CI] 1.043-1.044) had statistically significantly lower mean USGs compared with cats aged less than 1 year (1.049, 95% CI 1.048-1.051; P <0.001), 1-6 years (1.049, 95% CI 1.049-1.050; P <0.001) or 7-10 years (1.049, 95% CI 1.048-1.049; P <0.001). Cats aged ⩾15 years (1.038, 95% CI 1.036-1.040) had statistically significantly lower mean USGs compared with cats aged less than 1 year (P <0.001), 1-6 years (P <0.001), 7-10 years (P <0.001) or 11-15 years (P <0.001).

CONCLUSIONS AND RELEVANCE

Renal concentrating ability begins to diminish, on average, starting at approximately 9 years of age and is progressive as cat age increases. This study provides important and new information to help improve screening practices for disorders of concentrating ability in cats.

Ageing-Related Alterations in Renal Epithelial Glucose Transport

The kidney plays a crucial role in glucose homeostasis by regulating glucose transport. We aimed to investigate the impact of alterations in glucose transport on glucose metabolism during ageing. Adult male Sprague Dawley rats were divided into five groups: 3-month, 6-month, and 12-month control groups, and 6- and 12-month groups receiving the hydrogen sulfide donor molecule GYY4137. The study found that, as age increased, daily urinary uric acid and protein levels increased in the 12-month group. Blood sugar level and HOMA-IR index increased in the 12-month group, and were partially improved by GYY4137. The kidney tissue showed mild glomerulosclerosis in the 12-month group, which was diminished by GYY4137. Gene expression analysis showed decreased sirtuin and increased p21 expression in the aging groups. Increased SGLT1 and SGLT2 expression was observed in the 12-month group, which was reversed by GYY4137. Both GLUT1 and GLUT2 expression was increased in the 6- and 12-month groups, and reversed by GYY4137 in the 12-month group. The study concluded that aging was associated with increased blood sugar levels and the HOMA-IR index, and the abundance of renal glucose transporters increased as aging progressed. GYY4137 effectively reversed aging-related alterations in glucose homeostasis and renal epithelial transporters.

Multiple pathways and mediation effects of built environment on kidney disease rate via mitigation of atmospheric threats

Air pollution and high temperatures can increase kidney disease rate, especially under climate change. A well-designed urban environment has mediating effects on atmospheric environmental threats and promoting human health, but previous studies have overlooked these effects. This study used partial least squares modeling and urban-scale data from Taiwan to identify the crucial effects (i.e., direct, indirect, and total effects) and pathways of urban form (i.e., urban development intensity, land-use mix, and urban sprawl), urban greening (i.e., green coverage), urban industrial status (e.g., industrial level), atmospheric environment (i.e., high temperature and air pollution), and socioeconomic status (i.e., elderly ratio, medical resources, and economic status) on kidney disease rate. Maximizing land-use mix and green coverage and minimizing urban development intensity, urban sprawl, and industrial levels could help reduce kidney disease rate. Air pollution and high temperature had a mediation effect of built environment on kidney disease rate; with the mediation effect of air pollution was greater than that of high temperature. Furthermore, air pollution, high temperature, and elderly ratio increased kidney disease rate, whereas medical resources decreased kidney disease rate. This study is the first to consider the impact (i.e., direct, indirect, and total effects) and pathways of built environment characteristics on kidney disease rate. The findings revealed that an appropriate urban policy might be a practical strategy and lower kidney disease rate for a healthy city development. Moreover, this study provides a new approach for clarifying complex relationships and identifying crucial factors.

Changes in creatinine-to-cystatin C ratio over 4 years, risk of diabetes, and cardiometabolic control: The China Health and Retirement Longitudinal Study

BACKGROUND

Creatinine-to-cystatin C ratio has attracted substantial interest as a measure to reflect health well-being, but no studies have assessed whether its longitudinal changes are associated with risk of diabetes. We aimed to examine their association, along with the exploration of the relationship of such changes with cardiometabolic control in middle-aged and older adults.

METHODS

We included a total of 3278 participants aged ≥45 years who provided measurements of creatinine and cystatin C at baseline and 4 years later from the China Health and Retirement Longitudinal Study. Diabetes was diagnosed based on glucose, hemoglobin A1c (HbA1c), medical history, or use of antidiabetic mediations. Odds ratio (OR) and 95% confidence interval (CI) were obtained using logistic regression analyses.

RESULTS

After 4-year follow-up, 272 participants developed diabetes. Larger increases in creatinine-to-cystatin C ratio were associated with lower risk of diabetes. The multivariable-adjusted OR for diabetes per 1 SD increase in creatinine-to-cystatin C ratio was 0.84 (95% CI 0.72-0.98). Compared with participants showing decreases in creatinine-to-cystatin C ratio but increases in body mass index (BMI), those experiencing increases in creatinine-to-cystatin C ratio and decreases in BMI had the largest risk reduction (multivariable-adjusted OR 0.52). Changes in creatinine-to-cystatin C ratio showed inverse correlation with blood pressure, HbA1c, lipids, and C-reactive protein at the 4-year follow-up. Moreover, they also correlated inversely with changes in HbA1c and C-reactive protein (all P ≤ 0.004).

CONCLUSIONS

Increases in creatinine-to-cystatin C ratio led to reduced risk of diabetes and may benefit cardiometabolic control.