Monosodium Glutamate Consumption Disrupts Vitamin B6 Status in Rat Kidney

Monosodium glutamate (MSG) is widely used as a food additive and flavor enhancer, but concerns have emerged regarding its potential effects on kidney function and vitamin B6 metabolism. This study investigated the impact of varying levels of dietary MSG intake on vitamin B6 status in a rat model. Male Wistar rats were divided into four groups and administered MSG in their drinking water at concentrations of 0, 0.5, 1.5, and 3.0 g % for 12 weeks. Three isoforms of vitamin B6, pyridoxal (PL), pyridoxal 5'-phosphate (PLP), and pyridoxic acid (PA), were measured in plasma, liver, kidney, and urine using HPLC-MS. Kidney metabolites were analyzed by ¹H nuclear magnetic resonance spectroscopy to assess MSG-related metabolic changes. We found that plasma PL and PLP levels were elevated in all MSG-treated groups compared with controls, regardless of dose. This correlated with increased hepatic PLP levels and a decreased PLP catabolic ratio (PAr). In contrast to the liver, PLP levels in the kidney were significantly lower compared to controls. Metabolomics profiling of kidney tissue revealed elevated levels of various amino acids and metabolic intermediates in the MSG-treated rats. In conclusion, MSG consumption cannot induce vitamin B6 deficiency systematically, such as in the liver and plasma, as long as dietary vitamin B6 is adequate. However, depletion of PLP occurred locally in the kidney. Because MSG consumption may affect renal vitamin B6 status, there is a need for further studies to elucidate the underlying mechanisms and assess the potential health implications of habitual MSG intake.