CRIC-Visceral Adiposity and Physical Fitness in Chronic Kidney Disease

Obesity and chronic kidney disease (CKD) are major public health problems. In contrary to observations in general population, higher body mass index in those with pre-existing CKD is associated with lower mortality. Chronic Renal Insufficiency Cohort (CRIC) is an ongoing observational study to examine the consequences of CKD with a particular focus on cardiovascular illness like myocardial infarction (heart attack) and stroke. Among CRIC study participants, the investigators propose to obtain visceral and subcutaneous adiposity and physical fitness measures and study its associations with patient-centered outcomes. This study will help the investigators understand the independent and combined effects of visceral adiposity and physical fitness on cardiovascular disease, renal disease progression and death among those with CKD. Further, it will identify mechanisms that could be targeted to reduce the detrimental effects of visceral adiposity in those with kidney disease.

Obesity and chronic kidney disease (CKD) are major public health problems. Obesity independent of its relationship with diabetes and hypertension is associated with the development and progression of kidney disease. However, higher body mass index (BMI) in those with pre-existing CKD is associated with lower mortality (obesity paradox). This may be due to the inability of BMI to differentiate fat mass and muscle mass, which may have opposite relationship with cardiovascular disease and death. Body fat distribution is a major factor of metabolic health with metabolic abnormalities correlating better with visceral than subcutaneous adipose tissue. Further, higher fitness levels among those with higher BMI is associated with a lower prevalence of cardiovascular risk factors and mortality that might explain this obesity paradox. Therefore, among Chronic Renal Insufficiency Cohort (CRIC) study participants, the investigators propose (a) to examine whether visceral adiposity is associated with a higher incidence of composite outcomes (i.e., mortality, cardiovascular events, end stage renal disease, and 50% decline in estimated glomerular filtration rate), (b) to determine if physical fitness modifies the association between adiposity and outcomes, and (c) to study whether visceral adiposity and physical fitness are associated with altered adipokine profile, inflammation, insulin resistance, and oxidative stress. The study proposes to enroll 526 patients with varying degrees of kidney disease from 7 clinical centers involved in the CRIC study. Visceral adiposity will be measured by magnetic resonance imaging (MRI) of the abdomen using a standard protocol, and physical fitness will be measured using a 400 m walk test during routine CRIC study visits. Results from this study will help the Investigators understand the independent and combined effects of visceral adiposity and physical fitness on cardiovascular disease and kidney disease progression among CKD patients. This study will also highlight potential pathways that mediate the relationship between adiposity and outcomes, which will become the focus of future therapeutic investigations in CKD.

Eligibility Criteria:
Inclusion Criteria:

* Age 21-79
* Estimated Glomerular Filtration Rate 20-74 ml/min/1.73m\^2

Exclusion Criteria:

* Pacemaker
* Metallic prosthesis or foreign body (joints, heart valves, clips)

  \*Sites may include patients with cardiac stents and/or dental implants based on the local Radiology department criteria i.e. if there are no restrictions, they can include patients with stents and/or dental implants. If the Radiology department mandates the type of stent details and/or dental implants, site coordinator should provide this to the local Radiology department and obtain permission before enrolling the subject.
* Severe claustrophobia
* Severe osteoarthritis (use of walker or other assisted devices)

  \*Sites may include patients with cane (single or quad).
* Recent cardiovascular or cerebrovascular events (within 6 months prior to enrollment)
* Kidney transplant
* Currently on dialysis
* Peripheral vascular disease limiting long distance walking