Zinc changes in blood and urine during cyclic parenteral nutrition: relationships with amino acid metabolism

Associations between Zinc Deficiency and Metabolic Abnormalities in Patients with Chronic Liver Disease

Zinc (Zn) is an essential trace element which has favorable antioxidant, anti-inflammatory, and apoptotic effects. The liver mainly plays a crucial role in maintaining systemic Zn homeostasis. Therefore, the occurrence of chronic liver diseases, such as chronic hepatitis, liver cirrhosis, or fatty liver, results in the impairment of Zn metabolism, and subsequently Zn deficiency. Zn deficiency causes plenty of metabolic abnormalities, including insulin resistance, hepatic steatosis and hepatic encephalopathy. Inversely, metabolic abnormalities like hypoalbuminemia in patients with liver cirrhosis often result in Zn deficiency. Recent studies have revealed the putative mechanisms by which Zn deficiency evokes a variety of metabolic abnormalities in chronic liver disease. Zn supplementation has shown beneficial effects on such metabolic abnormalities in experimental models and actual patients with chronic liver disease. This review summarizes the pathogenesis of metabolic abnormalities deriving from Zn deficiency and the favorable effects of Zn administration in patients with chronic liver disease. In addition, we also highlight the interactions between Zn and other trace elements, vitamins, amino acids, or hormones in such patients.

Clinical relevance of trace element measurement in patients on initiation of parenteral nutrition

Background and Aims Serum zinc, copper and selenium are measured in patients prior to commencing on parenteral nutrition; however, their interpretation can be difficult due to acute phase reactions. We assessed (i) the relationship of raised C-reactive protein with trace elements and albumin (ii) benefits of measuring trace elements when C-reactive protein is raised in patients requiring short-term parenteral nutrition. Methods Samples were collected for zinc, copper, selenium and albumin at baseline and then every two weeks and correlated with C-reactive protein results in patients on parenteral nutrition. Results were categorized into four groups based on the C-reactive protein concentrations: (i) <20 mg/L, (ii) 20-39 mg/L, (iii) 40-79 mg/L and (iv) ≥80 mg/L. Results In 166 patients, zinc, selenium and albumin correlated (Spearman's) negatively with C-reactive protein; r = -0.26, P < 0.001 (95% CI -0.40 to -0.11), r = -0.44, P < 0.001 (-0.56 to -0.29) and r = -0.22 P = 0.005 (-0.36 to -0.07), respectively. Copper did not correlate with C-reactive protein (r = 0.09, P = 0.25 [-0.07 to 0.25]). Comparison of trace elements between the four groups showed no difference in zinc and copper (both P > 0.05), whereas selenium and albumin were lower in the group with C-reactive protein > 40 mg/L ( P < 0.05). Conclusion In patients on short-term parenteral nutrition, measurement of C-reactive protein is essential when interpreting zinc and selenium but not copper results. Routine measurement of trace elements prior to commencing parenteral nutrition has to be considered on an individual basis in patients with inflammation.

Zinc: physiology, deficiency, and parenteral nutrition

The essential trace element zinc (Zn) has a large number of physiologic roles, in particular being required for growth and functioning of the immune system. Adaptive mechanisms enable the body to maintain normal total body Zn status over a wide range of intakes, but deficiency can occur because of reduced absorption or increased gastrointestinal losses. Deficiency impairs physiologic processes, leading to clinical consequences that include failure to thrive, skin rash, and impaired wound healing. Mild deficiency that is not clinically overt may still cause nonspecific consequences, such as susceptibility to infection and poor growth. The plasma Zn concentration has poor sensitivity and specificity as a test of deficiency. Consequently, diagnosis of deficiency requires a combination of clinical assessment and biochemical tests. Patients receiving parenteral nutrition (PN) are susceptible to Zn deficiency and its consequences. Nutrition support teams should have a strategy for assessing Zn status and optimizing this by appropriate supplementation. Nutrition guidelines recommend generous Zn provision from the start of PN. This review covers the physiology of Zn, the consequences of its deficiency, and the assessment of its status, before discussing its role in PN.

Role of trace elements in parenteral nutrition support of the surgical neonate

BACKGROUND

Parenteral nutrition (PN) has transformed the outcome for neonates with surgical problems in the intensive care unit. Trace element supplementation in PN is a standard practice in many neonatal intensive care units. However, many of these elements are contaminants in PN solutions, and contamination levels may, in themselves, be sufficient for normal metabolic needs. Additional supplementation may actually lead to toxicity in neonates whose requirements are small.

METHODS

An electronic search of the MEDLINE, Cochrane Collaboration, and SCOPUS English language medical databases was performed for the key words "trace elements," "micro-nutrients," and "parenteral nutrition additives." Studies were categorized based on levels of evidence offered, with randomized controlled trials and meta-analyses accorded the greatest importance at the apex of the data pool and case reports and animal experiments the least importance. Articles were reviewed with the primary goal of developing uniform recommendations for trace element supplementation in the surgical neonate. The secondary goals were to review the physiologic role, metabolic demands, requirements, losses, deficiency syndromes, and toxicity symptoms associated with zinc, copper, chromium, selenium, manganese, and molybdenum supplementation in PN.

RESULTS

Zinc supplementation must begin at initiation of PN. All other trace elements can be added to PN 2 to 4 weeks after initiation. Copper and manganese need to be withheld if the neonate develops PN-associated liver disease. The status of chromium supplementation is currently being actively debated, with contaminant levels in PN being sufficient in most cases to meet neonatal requirements. Selenium is an important component of antioxidant enzymes with a role in the pathogenesis of neonatal surgical conditions such as necrotizing enterocolitis and bronchopulmonary dysplasia. Premature infants are often selenium deficient, and early supplementation has shown a reduction in sepsis events in this age group.

CONCLUSION

Appropriate supplementation of trace elements in surgical infants is important, and levels should be monitored. In certain settings, it may be more appropriate to individualize trace element supplementation based on the predetermined physiologic need rather than using bundled packages of trace elements as is the current norm. Balance studies of trace element requirements should be performed to better establish clinical recommendations for optimal trace element dosing in the neonatal surgical population.

Trace elements in parenteral micronutrition

OBJECTIVE

To update some essential trace metals required in total parenteral nutrition.

CONCLUSION

Essential trace metals, chromium, copper, manganese, molybdenum, selenium, and zinc are added to parenteral fluids to prevent the development of deficiency syndromes. When possible, these metals should be monitored, even in patients on short-term total parenteral nutrition (TPN) to avoid deficiency or toxicity. Many of the nutrients or additives used in parenteral solutions may be contaminated with metals, such as aluminum or chromium. Such trace-metal monitoring becomes more critical in infants, and those on long-term TPN.