Mesoamerican Nephropathy is a CKD epidemic in Central America affecting predominantly outdoor agricultural workers. The pattern of injury is a chronic tubulo-interstitial nephropathy with a variety of etiologic mechanisms proposed (see recent Test your Knowledge post). In a part of the world with limited nephrology services, the mortality risk of this kidney disease is high. A recent study in AJKD examined whether job category and self-reported hydration status in Nicaraguan sugarcane workers were related to short-term changes in tubular injury biomarkers, specifically neutrophil gelatinase-associated lipocalin (NGAL), interleukin-18 (IL-18), and N-acetyl-beta-D-glucosaminidase (NAG).
A total of 284 workers from seven different types of labor-intensive jobs in the sugarcane industry had pre- and post-harvest urine and serum samples examined. The mean age of workers was 33.6 years, and 88% were men. Workers reported drinking an average 5 liters of water and 2.4 electrolyte solution packets (each 100 mL) while at work each day. The following was observed during the 6 month harvest:
- The overall late-harvest mean eGFR was 112 mL/min in men and 118 mL/min in women. Albuminuria was generally low or absent.
- Workers with the most strenuous jobs (especially cane cutters) had increases in urinary NGAL and IL-18.
- Self-reported hydration did not appear to offer a protective benefit from kidney injury in the overall cohort. However, when stratified by job, a protective effect of consuming electrolyte solution packets was evident among cane and seed cutters.
- Workers with the largest increases in NGAL and NAG had declines in eGFR of 4.6 mL/min and 3.1 mL/min, respectively (adjusted for age, sex, and years worked).
This study demonstrates that in a population at risk for Mesoamerican Nephropathy, biomarkers of kidney injury varied throughout the harvest season and depending on the job performed (this may be a surrogate for heat exposure). Future studies and in the field should focus on these workers, with limits on work hours and aggressive education regarding fluid ingestion. The tubular biomarkers provide additional evidence, in a disease where renal histology has been lacking, that this is a tubulo-interstitial process. It also tantalisingly suggests that fluid and electrolyte consumption may protect against kidney injury in this setting. It is worth noting that workers in this study consumed water and electrolyte solutions, but not sugary beverages that may be harmful if the uric acid/fructose hypothesis is true (see Roncal-Jimenez et al). The story of Mesoamerican Nephropathy continues to evolve. With several research groups focussing on this condition, we appear to be edging closer to understanding the pathogenesis of this recently identified epidemic kidney disease.
Dr. Paul Phelan
AJKD Blog Contributor