Trial of Carbamylation in Renal Disease-Modulation With Amino Acid Therapy

As human kidney function declines, so does the kidney's ability to excrete urea, the chief end product of nitrogen metabolism. Excess urea may accelerate the pathophysiological consequences of kidney failure. Urea spontaneously dissociates to form cyanate, which, in its unprotonated form can react with protein amino groups in a process known as carbamylation. Carbamylation-induced protein alterations may be involved in the progression of various diseases by changing the structure, charge, and function of enzymes, hormones, receptors, and amino acids. For example, proteins such as collagen and low density lipoproteins (LDLs), when carbamylated, have been shown to induce the characteristic biochemical events of atherosclerosis progression. This research aims to evaluate whether amino acid supplementation can attenuate such processes that are known to contribute to morbidity in patients with ESRD.

Percent carbamylated albumin (C-Alb) level will be used as a measure of overall carbamylation burden. Previous studies conducted by MGH Investigators have shown a negative correlation between %C-Alb and circulating amino acids, suggesting that free amino acids may actively scavenge reactive isocyanate. Further, ex vivo studies show that amino acid supplementation reduces the carbamylation reaction. The MGH Investigators recently demonstrated an association between markers of cardiac stress, heart failure and carbamylation in patients with ESRD and found that %C-Alb was strongly associated with erythropoietin resistance in dialysis patients. Additionally, using validated measures of total-body carbamylation, these and other Investigators have reported that elevated protein carbamylation was linked with higher mortality in several distinct ESRD cohorts. Finally, preliminary data from a recent pilot study at MGH (NCT01612429) suggests that amino acid supplementation in patients with ESRD undergoing maintenance hemodialysis can attenuate carbamylation of proteins.

The proposed randomized study will directly evaluate the impact of amino acid supplementation on: (1) the burden of carbamylation in terms of %C-Alb; and (2) selected intermediate determinants of clinical outcomes, i.e., markers of inflammation, cardiac stress, and erythropoietin responsiveness.

Inclusion criteria

• Informed of the investigational nature of the study and sign written informed consent
• Willing and able to adhere to all study-related procedures, including adherence to study medication regimen
• ≥18 years old
• On stable medical therapy in the last 30 days before the study entry, defined as no change, addition, or removal of medications
• Patients must satisfy the following criteria based on the initial screening laboratory values:

• Serum albumin ≥ 3.0 g/dL (30 g/L)
• Dialysis adequacy recorded as Kt/ V > 1.2
• Carbamylated albumin (C-Alb) > 7.7 mmol/mol
• Women of childbearing potential must be practicing barrier or oral contraception, for the duration of the study-related treatment, or be documented as surgically sterile or one year post-menopausal
• If female, be non-nursing, non-pregnant and have a negative pregnancy test within two weeks of starting study treatment
• On stable hemodialysis therapy for at least 90 days before the study entry, defined as receiving thrice weekly dialysis and carrying a diagnosis of ESRD
• Prescribed a dialysis treatment time of 4 hours per session

Exclusion criteria

• Taking any type of amino acid supplementation within the last 90 days
• Received parenteral nutrition within last 90 days
• History of allergy to any amino acid compound
• Poorly controlled hypertension (systolic blood pressure > 180 mmHg and/or diastolic blood pressure > 110 mmHg during any of the previous 3 dialysis sessions (confirmed by repeat)
• Severe hepatic impairment
• HIV positive
• Condition with prognosis <1 year at time of study entry
• Body Mass Index (BMI) <18 or >30
• Current active treatment in another investigational study or participation in another investigational study in the 1 month prior to screening
• Active malignancies or other serious concurrent or recent medical or psychiatric condition which, in the opinion of the Investigator, makes the patient unsuitable for participation in this study
• Presence of asthma