TOP NUTRITION NEWSLETTER VOLUME 3, NO 1: JANUARY 2000  

Editorial  

This is the first issue of TOP NUTRITION NEWSLETTER in 2000. In this issue  the following topics are updated for your interest. 
 
Taurine improves insulin sensitivity in the Otsuka Long-Evans Tokushima Fatty rat, a model of spontaneous type 2 diabetes

Grape Juice, But Not Orange Juice or Grapefruit Juice, Inhibits Human Platelet Aggregation

A Prospective, Randomized Clinical Trial on Perioperative Feeding With an Arginine-, Omega-3 Fatty Acid, and RNA-Enriched Enteral Diet: Effect on Host Response and Nutritional Status 

Total Parenteral Nutrition in the Critically Ill Patient: A Meta-Analysis 

Any comments or suggestions to include the interesting topics are welcomed for future issues. 
 

Dr Shwe Win  

Editor  

Taurine improves insulin sensitivity in the Otsuka Long-Evans Tokushima Fatty rat, a model of spontaneous type 2 diabetes

Reference: Am J Clin Nutr 2000;71:54-58.

Background: Taurine, a potent antioxidant, has been reported to improve streptozotocin-induced diabetes mellitus, in which the development of diabetes results from an attack by oxygen free radicals on pancreatic ß cells. However, taurine also increases the excretion of cholesterol via conversion to bile acid and would be expected to improve insulin resistance. 

Objective: The effects of taurine on insulin sensitivity were examined in a model rat of insulin resistance and type 2 diabetes—the Otsuka Long-Evans Tokushima Fatty (OLETF) rat. 

Design: Male OLETF rats were divided into 2 groups at the age of 16 wk: a taurine-supplemented group and an unsupplemented group. As a nondiabetic control, Long-Evans-Tokushima-Otsuka rats were used. An oral-glucose-tolerance test and hyperinsulinemic euglycemic clamp were performed at the ages of 23 and 25 wk. 

Results: The OLETF rats had hyperglycemia and insulin resistance and they had a greater accumulation of abdominal fat than did control rats. Abdominal fat accumulation, hyperglycemia, and insulin resistance were significantly lower in the taurine-supplemented group than in the unsupplemented group. Serum and liver concentrations of triacylglycerol and cholesterol were significantly higher in the OLETF rats than in the control rats and were significantly lower in the taurine-supplemented group than in the unsupplemented group, presumably because of the increased secretion of cholesterol into bile acid. Taurine-supplemented rats also showed higher nitric oxide secretion, evidenced by increased urinary excretion of nitrite. 

Conclusion: Taurine effectively improves metabolism in OLETF rats by decreasing serum cholesterol and triacylglycerol, presumably via increased secretion of cholesterol into bile acid and decreased production of cholesterol because of increased nitric oxide production. 

Grape Juice, But Not Orange Juice or Grapefruit Juice, Inhibits Human Platelet Aggregation

Reference: J Nutr 2000;130:53-56.

Coronary artery disease is responsible for much mortality and morbidity around the world. Platelets are involved in atherosclerotic disease development and the reduction of platelet activity by medications reduces the incidence and severity of disease. Red wine and grapes contain polyphenolic compounds, including flavonoids, which can reduce platelet aggregation and have been associated with lower rates of cardiovascular disease. Citrus fruits contain different classes of polyphenolics that may not share the same properties. This study evaluated
whether commercial grape, orange and grapefruit juices, taken daily, reduce ex vivo platelet activity. In a randomized cross-over design, ten healthy human subjects (ages 26–58 y, five of each gender) drank 5–7.5 mL/(kg · d) of purple grape juice, orange juice or grapefruit juice for 7–10 d each. Platelet aggregation (whole blood impedance aggregometry, Chronolog Model #590) at baseline was compared to results after consumption of each juice. Drinking purple grape juice for one week reduced the whole blood platelet aggregation response to 1 mg/L of collagen by 77% (from 17.9 ± 2.3 to 4.0 ± 6.8 ohms, P = 0.0002). Orange juice and grapefruit juice had no effect on platelet aggregation. The purple grape juice had approximately three times the total polyphenolic concentration of the citrus juices and was a potent platelet inhibitor in healthy subjects while the citrus juices showed no effect. The platelet inhibitory effect of the flavonoids in grape juice may
decrease the risk of coronary thrombosis and myocardial infarction. 

A Prospective, Randomized Clinical Trial on Perioperative Feeding With an Arginine-, Omega-3 Fatty AcidB, and RNA-Enriched Enteral Diet: Effect on Host Response and Nutritional Status 

J P E N 1999;23(6):314-320.

Background: The use of immune-enhancing enteral diets in the postoperative period has given contrasting results. The purpose of this prospective, randomized, double-blinded clinical study was to evaluate the effect of immunonutrition given perioperatively on cytokine release and nutritional parameters. 

Methods: Patients with cancer of the stomach or colo-rectum were eligible. Subjects consumed 1 L/d of either a control enteral formula (n = 25; control group) or a formula supplemented with arginine, omega-3 fatty acids, and RNA (n = 25; verum group) for 1 week before surgery. Both formulas were given by mouth. Six hours after the operation, jejunal infusion with the same diets was started and maintained for 7 days. Blood was drawn at different time points to assess albumin, prealbumin (PA), transferrin, cholinesterase activity, retinol binding protein (RBP), interleukin-2 receptors alpha (IL-2R<alpha>), IL-6, and IL-1 soluble receptors (IL-1RII). The composite score of delayed hypersensitivity response (DHR) to skin test also was determined (the higher the score, the lower the immune response).

Results: During the 7 days of presurgical feeding, none of the above parameters changed in either group. Eight days after operation, in the control group, the concentration of PA and RBP was lower than in the verum group (0.18 vs 0.26 g/L for PA and 30.5 vs 38.7 mg/L for RBP; p < .05). IL-2R<alpha> concentration was 507 pg/mL in the verum group vs 238 pg/mL in the control group (p < .001), whereas IL-6 and IL-1RII were higher in the control group than in the verum group (104 vs 49 and 328 vs 183 pg/mL, respectively; p < .01). The DHR score was 0.68 in the control group vs 0.42 in the verum group (p < .05). 

Conclusions: Perioperative feeding with a supplemented enteral diet modulates cytokine production and
enhances cell-mediated immunity and the synthesis of short half-life proteins. 

Total Parenteral Nutrition in the Critically Ill Patient: A Meta-Analysis 

Reference: http://www.clinnutr.org/publications/ncpabstracts/NCPAB1099.htm

ABSTRACT: Context: Nutritional support has become a standard of care for hospitalized patients, but whether total parenteral nutrition (TPN) affects morbidity and mortality is unclear. 

Objective: To examine the relationship between TPN and complication and mortality rates in critically ill patients. 

Data Sources: Computerized search of published research on MEDLINE from 1980 to 1998, personal files, and review of relevant reference lists. 

Study Selection: We reviewed 210 titles, abstracts, and papers. Primary studies were included if they were randomized clinical trials of critically ill or surgical patients that evaluated the effect of TPN (compared with standard care) on complication and mortality rates. We excluded studies comparing TPN with enteral nutrition. 

Data Extraction: Relevant data were abstracted on the methodology and outcomes of primary studies. Data were abstracted in duplicate, independently. 

Data Synthesis: There were 26 randomized trials of 2211 patients comparing the use of TPN with standard care (usual oral diet plus intravenous dextrose) in surgical and critically ill patients. When the results of these trials were aggregated, TPN had no effect on mortality (risk ratio [RR], 1.03; 95% confidence interval [CI], 0.81B1.31). Patients who received TPN tended to have a lower complication rate, but this result was not statistically significant (RR, 0.84; 95% CI, 0.64B1.09). We examined several a priori hypotheses and found that studies including only malnourished patients were associated with lower complication rates but no difference in mortality when compared with studies of nonmalnourished patients. Studies published since 1989 and studies with a higher methods score showed no treatment effect, while studies published in 1988 or before and studies with a lower methods score demonstrated a significant treatment effect. Complication rates were lower in studies that did not use lipids; however, there was no difference in mortality rates between studies that did not use lipids and those studies that did. Studies limited to critically ill patients demonstrated a significant increase in complication and mortality rates compared with studies of surgical patients. 

Conclusions: Total parenteral nutrition does not influence the overall mortality rate of surgical or critically ill patients. It may reduce the complication rate, especially in malnourished patients, but study results are influenced by patient population, use of lipids, methodological quality, and year of publication.(JAMA 280:2013B2019, 1998) 

COMMENT: Meta-analysis is a process whereby studies that appear to be similar are combined to increase the power to define a true difference between the treatment and control groups. All 26 trials in this meta-analysis compared parenteral nutrition (PN) with standard therapy (ie, no nutritional support [NS]). Although the intent of Heyland and his colleagues was to assess the impact of PN in the critically ill, the vast majority of the trials involved one particular segment: surgical patients. 

It was disappointing that, even when data from 2211 patients were combined, PN was not found to have any favorable effect on mortality or morbidity. This conclusion should not have been surprising, however; one needs only to review past meta-analyses to read similar perspectives. In fact, PN has been associated with higher rates of infectious morbidity in patients undergoing cancer chemotherapy. 

When Heyland et al only assessed the higher quality studies, the relative risks for both mortality and morbidity exceeded 1.0; that is, the PN may even have been of net harm. Hence, even if one believes that enteral nutrition is superior to PN in critically ill patients, one cannot thereby assume that this form of NS is better than no NS at all. One lesson to be gleaned from this meta-analysis is that future trials of critically ill patients must include a true control group, namely, one not systematically provided with any NS.