Mesoamerican Nephropathy (MeN): What We Know so Far

Kidney disease characteristics, prevalence, and risk factors in León, Nicaragua: a population-based study

BACKGROUND

CKD of unknown etiology (CKDu) disproportionately affects young people in Central America who lack traditional CKD risk factors (diabetes and hypertension) and has instead been variably linked to heat stress, occupational and environmental exposures, nephrotoxic medications, and/or genetic susceptibility. This study aimed to estimate the prevalence of CKD and identify risk factors for traditional CKD and CKDu in Nicaragua.

METHODS

Surveys and assessment for CKD markers in urine and serum were performed in 15-59 year olds in households of the León municipality of Nicaragua. The survey included questions on demographics, health behaviors, occupation, and medical history. Participants with CKD were subdivided into traditional CKD and suspected CKDu based on history of diabetes, hypertension, or other specified conditions. A multinomial logistic regression model was used to identify factors associated with traditional CKD and suspected CKDu, compared to the non-CKD reference group.

RESULTS

In 1795 study participants, CKD prevalence was 8.6%. Prevalence in males was twofold higher than females (12% vs 6%). Of those with CKD, 35% had suspected CKDu. Both traditional CKD and CKDu were associated with male sex and increasing age. Traditional CKD was associated with a family history of CKD, history of urinary tract infections, and lower socioeconomic status, while CKDu was associated with drinking well water and a lower body mass index.

CONCLUSIONS

Both traditional CKD and CKDu are significant burdens in this region. Our study supports previous hypotheses of CKDu etiology and emphasizes the importance of CKD screening.

Management of traditional risk factors for the development and progression of chronic kidney disease

Chronic kidney disease (CKD) and its downstream complications (i.e. cardiovascular) are a major source of morbidity worldwide. Additionally, deaths due to CKD or CKD-attributable cardiovascular disease account for a sizeable proportion of global mortality. However, the advent of new pharmacotherapies, diagnostic tools, and global initiatives are directing greater attention to kidney health in the public health agenda, including the implementation of effective strategies that (i) prevent kidney disease, (ii) provide early CKD detection, and (iii) ameliorate CKD progression and its related complications. In this Review, we discuss major risk factors for incident CKD and CKD progression categorized across cardiovascular (i.e. hypertension, dyslipidemia, cardiorenal syndrome), endocrine (i.e. diabetes mellitus, hypothyroidism, testosterone), lifestyle (i.e. obesity, dietary factors, smoking), and genetic/environmental (i.e. CKDu/Mesoamerican nephropathy, APOL1, herbal nephropathy) domains, as well as scope, mechanistic underpinnings, and management.

The impact of heat exposures on biomarkers of AKI and plasma metabolome among agricultural and non-agricultural workers

BACKGROUND

Agricultural workers are consistently exposed to elevated heat exposures and vulnerable to acute kidney injury. The underlying pathophysiology and detailed molecular mechanisms of AKI among agricultural workers, and the disproportionate burden of HRI and heat stress exposure are not well understood, especially at the level of cellular metabolism.

OBJECTIVE

The aim of this study was to examine the impact of heat exposures on renal biomarkers and on the human metabolome via untargeted high-resolution metabolomics among agricultural and non-agricultural workers.

METHODS

Blood and urine samples were collected pre- and post-work shift from 63 agricultural workers and 27 non- agricultural workers. We evaluated pre- and post-work shift renal biomarkers and completed untargeted metabolomics using high-resolution mass spectrometry with liquid chromatography. Metabolome-wide association studies (MWAS) models identified the metabolic features differentially expressed between agricultural workers and non-agricultural workers.

RESULTS

Median values of pre-shift creatinine and osteopontin (p < 0.05) were higher for agricultural workers than non-agricultural workers. Metabolic pathway enrichment analyses revealed 27 diverse pathways differed between agricultural workers and non-agricultural workers (p < 0.05) including TCA cycle and urea cycle, carbohydrate metabolism, histidine metabolism and evidence for altered microbiome shikimate pathway.

CONCLUSION

This is the first investigation on the metabolic pathways that are affected among agricultural workers who are exposed to heat compared to non-heat exposed workers. This study shows extensive responses of central metabolic systems to heat exposures that impact human health.

Chronic Kidney Disease of Non-traditional Etiology in a Young Man From Central America: Geography, Poverty, and Uncertain Pathophysiology Create a Formidable Medical Challenge

A man in his early 20s with kidney biopsy-confirmed focal segmental glomerulosclerosis (FSGS) was admitted with one month of nausea and vomiting, intermittent episodes of confusion, shortness of breath, and dysuria. He reported that many people from his native village in Central America, where he harvested sugarcane as a child, have died from kidney disease, including his father and cousin. He believed the source of disease to be agrochemicals found in the village's water supply. Although FSGS would be a rare manifestation, the patient's risk factors strongly suggested chronic kidney disease of unknown etiology (CKDu) - also known as Mesoamerican nephropathy (MeN) - a phenomenon he had never previously heard of. He took lisinopril for the last six years to manage his kidney disease. Due to uremic symptoms and abnormal electrolytes, he was initiated on hemodialysis.

Environmental and Social Factors Associated with High Chronic Kidney Disease Mortality Rates in Municipalities of Guatemala: An Ecological Study of Municipal-Level Mortality Data

The purpose of this study was to determine the association between social and environmental indicators and high mortality rates from chronic kidney disease (CKD) in municipalities of Guatemala. An ecological study of municipal-level factors associated with CKD mortality in Guatemala was conducted. Crude mortality rates were calculated for the 2009-2019 period for each of the country's 340 municipalities, by gender and age groups. Municipal-level social and environmental indicators were used as independent variables. Linear regression was used for bivariate and multivariate analysis. A total of 28,723 deaths from CKD were documented for the 2009-2019 period. Average crude mortality rate for all ages for the country's 340 municipalities was 70.66 per 100,000 [0-502.99]. Very highly positive associations with high mortality rates were found in two agrarian territories where land use is mainly for permanent crops (e.g., sugar cane, coffee, rubber, banana, plantain, African palm) and pastures for cattle, with very low percentages of land covered by forests or protected areas. Social factors related to poverty and environmental factors related to agricultural use of land may play a role in the high CKD mortality rates documented in a cluster of municipalities of Guatemala.

Acute Presentation of Mesoamerican Nephropathy in an Agricultural Worker From Panama

Mesoamerican nephropathy (MeN) is Central America's growing endemic renal disorder. No single cause is established, but many risk factors are hypothesized, such as young and medium-aged adults, male sex, work environment, heavy metals and agrochemicals exposure, occupational heat stress, nephrotoxic drug use, and low socioeconomic status. The diagnosis is confirmed by renal biopsy with chronic tubular atrophy and tubulointerstitial nephritis. If biopsies are unavailable, MeN is clinically suspected in patients residing in hotspot regions with a reduced estimated glomerular filtration rate (eGFR) and the absence of defining etiology, such as hypertension, diabetes, or glomerulonephritis. Currently, there is no specific treatment for which early diagnosis and intervention on risk factors is the primary strategy to improve prognosis. We report a case of a young male with agricultural labor exposure who presented with acute abdominal pain, back pain, and renal dysfunction that later progressed to chronic kidney disease (CKD) due to MeN. This case is significant because, although MeN is well-described in the literature, few cases of acute presentation have been documented.

Global, Regional, and National Burden of CKD due to Glomerulonephritis from 1990 to 2019: A Systematic Analysis from the Global Burden of Disease Study 2019

BACKGROUND

CKD is becoming a major human health concern. Limited quantitative assessments of the burden of CKD due to glomerulonephritis have been performed. We performed a comprehensive analysis of the disease burden to update the epidemiology of this disease.

METHODS

Incidence, prevalence, deaths, and disability-adjusted life-years (DALYs) data and percent changes in these indicators were extracted from Global Burden of Disease Study 2019 to analyze the burden of CKD due to glomerulonephritis.

RESULTS

Globally, there were 606,300 (95% uncertainty interval [UI], 560,100 to 658,100) incident patients, 17,300,000 (95% UI, 16,100,000 to 18,600,000) prevalent patients, 183,700 (95% UI, 146,300 to 228,900) deaths, and 6,900,000 (95% UI, 5,900,000 to 8,100,000) DALYs of CKD due to glomerulonephritis in 2019. Compared with those in 1990, the numbers of incident patients, prevalent patients, deaths, and DALYs increased by 77%, 81%, 100%, and 66%, respectively. Most of the disease burden was concentrated in countries with lower sociodemographic index. In Central Latin America, the disease burden was much higher than expected on the basis of its sociodemographic index. Decomposition analysis showed that population aging and growth were the two major drivers of the increase in DALYs. Frontier analysis revealed considerable opportunities to reduce the age-standardized DALYs in the middle of the sociodemographic-index spectrum. Although middle-aged and elderly individuals accounted for the majority of the disease burden, the highest incidence rate was observed in children aged 1-4 years.

CONCLUSIONS

The disease burden of CKD due to glomerulonephritis has increased worldwide, especially in regions and countries with lower sociodemographic indexes.

Mesoamerican Endemic Nephropathy (MeN): A Disease Reported in Adults That May Start Since Childhood?

Mesoamerican endemic nephropathy (MeN) is a type of chronic kidney disease (CKD) of uncertain etiology that occurs along the Pacific coast of the southern part of Mexico and Central America. During the past 20 years MeN has become a leading cause of death in the region, clamming close to 50,000 lives, with 40% of these deaths occurring in young people. The cause remains unknown, but most researchers believe in a multifactorial etiology that includes social determinants of poverty. Existing evidence suggests that subclinical kidney injury begins early in life and leads to a higher than expected prevalence of CKD among children in Central America. Access to health services in the region, specifically kidney replacement therapy, remains limited. We proposed a strategy to address the perceived needs and urge coordinated efforts of governments, academic organizations, and international bodies to develop a comprehensive plan of action to mitigate this situation among the vulnerable and economically disadvantaged population.

Fluid Intake and Hydration Status Among North Carolina Farmworkers: A Mixed Methods Study

BACKGROUND

Agricultural workers are disproportionately at risk for heat-related morbidity and mortality. The purpose of this study was to explore how sociocultural and occupational factors, and environmental heat stress influenced fluid intake and hydration status among Latino farmworkers working in eastern North Carolina.

METHODS

A community-informed, mixed methods research study was conducted in partnership with staff at a federally qualified health center. In summer 2020, we recruited Latino farmworkers at migrant camps. Twenty-eight male, migrant farmworkers participated in focus group discussions and 30 completed surveys and provided urine specimens. Wet bulb globe temperatures were measured in fields where workers labored. Content analysis and parametric analyses were performed. Data integration was completed using a meta-matrix.

RESULTS

Prior to work, 46.7% of farmworkers' urine specific gravity measurements indicated dehydration, which increased to 100% after work. The farmworkers spent between 2 and 7.5 hours of their day working in conditions above the recommended limits for workplace heat exposure. Farmworkers described exposure to extreme heat and inconsistent occupational policy compliance. Farmworkers expressed the opportunity to drink water but accessibility and poor water quality limited hydration. The integrated data supported congruent findings of extreme heat, few work breaks, and substandard housing.

CONCLUSION/APPLICATION TO PRACTICE

Farmworkers are dehydrated at work, placing them at higher risk for heat-related illness (HRI). By engaging with agricultural stakeholders, occupational health nurses can combine efforts and advocate for effective health and safety work policies to reduce HRIs and deaths among farmworkers. Legislation stipulating cooling and hydration practices would support safer work environments.

High prevalence of chronic kidney disease of unknown etiology among workers in the Mesoamerican Nephropathy Occupational Study

BACKGROUND

Mortality from chronic kidney disease of unknown etiology (CKDu) is extremely high along the Pacific coast of Central America, particularly among sugarcane workers. The Mesoamerican Nephropathy Occupational Study (MANOS) is a prospective cohort study of CKDu among agricultural and non-agricultural workers in El Salvador and Nicaragua. The objective of this manuscript is to describe the MANOS cohort recruitment, baseline data collection, and CKDu prevalence after two rounds.

METHODS

Workers with no known diabetes, hypertension, or CKD were recruited from sugarcane, corn, plantain, brickmaking, and road construction industries (n = 569). Investigators administered questionnaires, collected biological samples, and observed workers for three consecutive workdays at the worksite. Serum specimens were analyzed for kidney function parameters, and used to calculate estimated glomerular filtration rate (eGFR). At six months, serum was collected again prior to the work shift. CKD at baseline is defined as eGFR ≤ 60 ml/min/1.73m² at both timepoints. Age-standardized prevalence was calculated by industry, country, and demographic measures. Kidney function parameters were compared by CKD status.

RESULTS

Prevalence of CKD at baseline was 7.4% (n = 42). Age-standardized prevalence was highest in Salvadoran sugarcane (14.1%), followed by Salvadoran corn (11.6%), and Nicaraguan brickmaking (8.1%). Nicaraguan sugarcane had the lowest prevalence, likely due to kidney function screenings prior to employment.

CONCLUSION

Despite efforts to enroll participants without CKD, our identification of prevalent CKD among agricultural and non-agricultural workers in the MANOS cohort indicates notable kidney disease in the region, particularly among sugarcane workers.

Inhaled Silica Nanoparticles Causes Chronic Kidney Disease in Rats

INTRODUCTION

Silica nanoparticles (SiNPs) released during the burning of sugarcane have been postulated to have a role in chronic kidney disease of unknown etiology. We tested the hypothesis that pristine SiNPs of the size present in sugarcane might cause chronic kidney injury when administered through the lung in rats.

METHODS

We administered 200 nm or 300 nm amorphous SiNPs twice weekly (4 mg/dose) or vehicle by oropharyngeal aspiration for 13 weeks to rats followed by sacrifice after an additional 13 weeks (26 weeks total). Tissues were evaluated for presence of SiNPs and evidence of histologic injury.

RESULTS

Both sizes of SiNPs caused kidney damage, with early tubular injury and inflammation (at week 13) that continued to inflammation and chronic fibrosis at week 26 despite discontinuing the SiNP administration. Both sizes of SiNPs caused local inflammation in the lung and kidney and were detected in the serum and urine at week 13, and the 200 nm particles also localized to the kidney with no evidence of retention of the 300 nm particles. At week 26 there was some clearance of the 200 nm silica from the kidneys, and urinary levels of SiNPs were reduced but still significant in both the 200 and 300 nm exposed rats.

CONCLUSIONS

Inhaled SiNPs causes chronic kidney injury that progresses despite stopping the SiNP administration. These findings are consistent with the hypothesis that human exposure to amorphous silica nanoparticles found in burned sugarcane fields could have a participatory role in chronic kidney disease of unknown etiology.

THIRSTY FOR FRUCTOSE: Arginine Vasopressin, Fructose, and the Pathogenesis of Metabolic and Renal Disease

We review the pathways by which arginine vasopressin (AVP) and hydration influence the sequelae of the metabolic syndrome induced by high fructose consumption. AVP and inadequate hydration have been shown to worsen the severity of two phenotypes associated with metabolic syndrome induced by high fructose intake-enhanced lipogenesis and insulin resistance. These findings have implications for those who frequently consume sweeteners such as high fructose corn syrup (HFCS). Patients with metabolic syndrome are at higher risk for microalbuminuria and/or chronic kidney disease; however, it is difficult to discriminate the detrimental renal effects of the metabolic syndrome from those of hypertension, impaired glucose metabolism, and obesity. It is not surprising the prevalence of chronic renal insufficiency is growing hand in hand with obesity, insulin resistance, and metabolic syndrome in those who consume large amounts of fructose. Higher AVP levels and low hydration status worsen the renal insufficiency found in patients with metabolic syndrome. This inter-relationship has public health consequences, especially among underserved populations who perform physical labor in environments that place them at risk for dehydration. MesoAmerican endemic nephropathy is a type of chronic kidney disease highly prevalent in hot ambient climates from southwest Mexico through Latin America. There is growing evidence that this public health crisis is being spurred by greater fructose consumption in the face of dehydration and increased dehydration-dependent vasopressin secretion. Work is needed at unraveling the mechanism(s) by which fructose consumption and increased AVP levels can worsen the renal disease associated with components of the metabolic syndrome.

Documenting Disease in the Undocumented Migrants: A Case Report of Chronic Kidney Disease of Unknown Origin in a Central American Migrant

Mesoamerican nephropathy (MeN) or chronic kidney disease of unknown origin (CKDu) is a rising epidemic in hotspot regions of El Salvador and Nicaragua. MeN is often defined in patients who exhibit a clinically reduced estimated glomerular filtration rate (eGFR) but lack a defining etiology such as diabetes or hypertension. A multitude of risk factors for MeN have been identified, including physical labor demands in a hot climate, exposure to pesticides, and poverty. Additionally, social determinants such as limited access to health care and the cost of disease burden often contribute to overall poor prognosis and progression of the disease.

We present a case of a 39-year-old male with a past medical history of gout who presented to the emergency room with abdominal pain radiating to the flanks and bilateral great toe pain. Social history revealed the patient recently moved to the United States from Central America (Nicaragua), was unemployed, and did not have health insurance. Prior to the presentation, the patient admitted he was not compliant with his gout medications for about one month. The symptoms first began two to three weeks prior to his evaluation in the emergency department; the patient also endorsed decreased oral intake during this time period. He was noted to have abnormally elevated creatinine along with elevated uric acid levels, low potassium and magnesium levels. Abdominal imaging revealed nephrolithiasis without hydronephrosis. Initial differentials included acute kidney injury (AKI) from dehydration, non-steroidal anti-inflammatory drug (NSAID) induced nephropathy, and uric acid nephropathy. This patient was eventually found to have a biopsy-proven findings of CKDu. We want to highlight the need to keep MeN high in the differential with a low threshold to perform a renal biopsy for accurate diagnosis and management of the disease, especially in the rising immigrant population in the United States.

Chronic kidney disease of unknown etiology in India: a comparative study with Mesoamerican and Sri Lankan nephropathy

Chronic kidney disease of unknown etiology [CKDu] is a condition characterized by decline in kidney function and is not associated with diabetic nephropathy or hypertensive nephropathy. In this review, we have done a detailed literature analysis on CKDu in India, and then had a comparison with that of Mesoamerica and Sri Lanka. In India, CKDu became the second most common type of CKD after diabetic nephropathy. Silica was seen in the groundwater of both India and Sri Lanka, whereas in Mesoamerica silica exposure through particulate matter was seen among CKDu communities. DDE is a common agrochemical seen in both India and Sri Lanka. The risk factors vary from region to region and it is important to categorize CKDu population based on the risk factors to avoid misinterpretation of the condition as non-CKDu category and to evade further complications. More studies have to be conducted to reveal the detailed pathophysiological mechanisms and its relation with irrational exploitation of environmental resources.

Mesoamerican nephropathy: A not so unknown chronic kidney disease

From 2000, Mesoamerican region has reached an important rate of chronic kidney disease of unknown etiology. Under the name of Meroamerican Nephropathy (MeN) several hypotheses (including dehydration, heat stress, environmental or toxic exposure or even infections) have tried to explain the etiology this new disease. MeN affects young men, agricultural workers exposed to high temperatures. MeN courses with unspecific symptoms as low-grade fever and dysuria and progressive kidney disease with impaired renal function and hydroelectrolyte disturbances. The diagnosis requires kidney biopsy showing tubule-interstitial nephritis (usually at chronic stage). Although MeN conditions a high morbi-mortality in endemic regions, there is a lack of specific treatment and only preventive measures have demonstrated some effect of prognosis (avoid heat stress, constant hydration). In this review we aim to summarize the available information of MeN, illustrating the information in a case report.

Mesoamerican nephropathy: A not so unknown chronic kidney disease

From 2000, Mesoamerican region has reached an important rate of chronic kidney disease of unknown etiology. Under the name of Meroamerican Nephropathy (MeN) several hypotheses (including dehydration, heat stress, environmental or toxic exposure or even infections) have tried to explain the etiology this new disease. MeN affects young men, agricultural workers exposed to high temperatures. MeN courses with unspecific symptoms as low-grade fever and dysuria and progressive kidney disease with impaired renal function and hydroelectrolyte disturbances. The diagnosis requires kidney biopsy showing tubule-interstitial nephritis (usually at chronic stage). Although MeN conditions a high morbi-mortality in endemic regions, there is a lack of specific treatment and only preventive measures have demonstrated some effect of prognosis (avoid heat stress, constant hydration). In this review we aim to summarize the available information of MeN, illustrating the information in a case report.

Purposeful Review to Identify Risk Factors, Epidemiology, Clinical Features, Treatment and Prevention of Chronic Kidney Disease of Unknown Etiology

The global burden of chronic kidney disease (CKD) has risen, and chronic kidney disease of unknown etiology (CKDu) contributes considerably to the national burden of CKD. It is characterized by irreversible, slowly advancing disease, and symptoms often appear in the late stages of the disease. It is a serious, novel cause of kidney failure and leads to premature deaths. Many hypotheses have emerged; however, the etiology of CKDu continues to be elusive and debatable and it is claimed that the etiology is multifactorial, encompassing environmental, genetic, occupational, and social factors. The dominant histopathological feature is chronic tubulointerstitial nephritis. It predominantly affects individuals with low socio-economic status, of working age, largely without chronic comorbidities, who perform strenuous labor in extreme conditions in various tropical areas of the world. It is often fatal due to fast progression and limited access to dialysis or transplant options in the involved geographic areas. Early recognition and appropriate interventions at the earliest possible stage are imperative for decreasing its associated morbidity and mortality. In this review, I tried to summarize available evidence on the risk factors, epidemiology, clinical features, treatment, and prevention of CKDu. The literature search for this review was conducted comprehensively by using different electronic databases and by using appropriate search terms.