Effect of L-Arginine Treatment in Pregnant Rats with Adriamycin Nephropathy

Prenatal Amino Acid Supplementation to Improve Fetal Growth: A Systematic Review and Meta-Analysis

Aberrant fetal growth remains a leading cause of perinatal morbidity and mortality and is associated with a risk of developing non-communicable diseases later in life. We performed a systematic review and meta-analysis combining human and animal studies to assess whether prenatal amino acid (AA) supplementation could be a promising approach to promote healthy fetal growth. PubMed, Embase, and Cochrane libraries were searched to identify studies orally supplementing the following AA groups during gestation: (1) arginine family, (2) branched chain (BCAA), and (3) methyl donors. The primary outcome was fetal/birth weight. Twenty-two human and 89 animal studies were included in the systematic review. The arginine family and, especially, arginine itself were studied the most. Our meta-analysis showed beneficial effects of arginine and (N-Carbamyl) glutamate (NCG) but not aspartic acid and citrulline on fetal/birth weight. However, no effects were reported when an isonitrogenous control diet was included. BCAA and methyl donor supplementation did not affect fetal/birth weight. Arginine family supplementation, in particular arginine and NCG, improves fetal growth in complicated pregnancies. BCAA and methyl donor supplementation do not seem to be as promising in targeting fetal growth. Well-controlled research in complicated pregnancies is needed before ruling out AA supplements or preferring arginine above other AAs.

Therapeutic Potential of Citrulline as an Arginine Supplement: A Clinical Pharmacology Review

Supplemental arginine has shown promise as a safe therapeutic option to improve endogenous nitric oxide (NO) regulation in cardiovascular diseases associated with endothelial dysfunction. In clinical studies in adults, L-arginine, an endogenous amino acid, was reported to improve cardiovascular function in hypertension, pulmonary hypertension, preeclampsia, angina, and MELAS (mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes) syndrome. L-citrulline, a natural precursor of L-arginine, is more bioavailable than L-arginine because it avoids hepatic first-pass metabolism and has a longer circulation time. Although not yet well-studied, arginine/citrulline has immense therapeutic potential in some life-threatening diseases in children. However, the optimal clinical development of arginine or citrulline in children requires more information about pharmacokinetics and exposure-response relationships at appropriate ages and under relevant disease states. This article summarizes the preclinical and clinical studies of arginine/citrulline in both adults and children, including currently available pharmacokinetic information. The pharmacology of arginine/citrulline is confounded by several patient-specific factors such as variations in baseline arginine/citrulline due to developmental ages and disease states. Currently available pharmacokinetic studies are insufficient to inform the optimal design of clinical studies, especially in children. Successful bench-to-bedside clinical translation of arginine supplementation awaits information from well-designed pharmacokinetic/pharmacodynamic studies, along with pharmacometric approaches.

Animal models of preeclampsia

Some of the maternal symptoms of preeclampsia can be produced by uterine ischemia, although no quadriped spontaneously exhibits this disease. It may be that the combination of upright posture and uteroplacental ischemia are necessary for manifestation of the full syndrome. Chronic nitric oxide synthase inhibition in rats produces a pattern of change that resembles the symptoms of preeclampsia, and the preeclamptic-like response of rats with adriamycin nephropathy and hyperinsulinemia is associated with endothelial dysfunction. These models are definitely of use in preeclampsia research, but because this disease only occurs spontaneously in primates, the definitive studies on preeclampsia will, of necessity, be clinical.

Pregnancy-induced hypertension in rats with adriamycin nephropathy is associated with an inadequate production of nitric oxide

Hypertensive complications are relatively common in pregnancy, particularly in the presence of preexisting renal disease. Although the pathogenesis of such complications is still unknown, recent animal studies have suggested that it may be related to impaired synthesis of nitric oxide (NO). Rats with adriamycin nephropathy develop a "preeclamptic-type" pregnant state characterized by elevated blood pressure, lack of hyperfiltration, and enhanced proteinuria. Preliminary studies with this model have implicated inadequate NO synthesis in the development of preeclamptic-like pregnancy. The aim of the present study was to confirm this hypothesis. Pregnant rats, both normal (PREG) and those with adriamycin nephropathy (AN-PREG), received 100 mg/L N omega-nitro-L-arginine methyl ester PO from the middle of gestation to term (day 11, term approximately 22 days). One group of AN-PREG rats received either L-arginine or D-arginine (2 g/L) from midpregnancy. At term, systolic pressure, mean arterial pressure, urinary metabolites of NO, creatinine clearance, and urinary protein were assessed. At term, compared with virgin rats with adriamycin nephropathy, untreated AN-PREG rats had increased systolic pressure, mean arterial pressure, and proteinuria (mean arterial pressure, 124 +/- 2.5 versus 99.7 +/- 1.6 mm Hg [P < .05]; proteinuria, 434 +/- 58 versus 216 +/- 63 mg/d [P < .05]). Creatinine clearance did not change (1.68 +/- 0.23 versus 1.35 +/- 0.09 mL/min, P = NS). In PREG rats, urinary metabolites of NO increased approximately threefold at term pregnancy compared with control. By contrast, in AN-PREG rats, excretion of urinary metabolites of NO increased only by approximately 1.7-fold (P < .01) versus PREG rats. With the exception of AN-PREG rats, inhibition of NO synthesis with N omega-nitro-L-arginine methyl ester enhanced blood pressure and decreased creatinine clearance but did not influence proteinuria. Excretion of urinary metabolites of NO was similarly inhibited in all rats. In AN-PREG rats, L-arginine normalized blood pressure (91 +/- 2.15 mm Hg) and lowered proteinuria partially but significantly. D-Arginine had no effect. In summary, AN-PREG rats are unable to adequately increase NO synthesis when physiologically required. Correction of this deficit by L-arginine treatment induced a significant clinical improvement.