The Effect of Salt on Serum Glycemic Response and Gastric Emptying after Oral Glucose Loading

Kim, Jung Min; Park, Jae Hong; Kim, Myung Soo; Kim, Ji Youn; Kim, Yong Joo; Lee, Dae Bae; Yang, Seung Won; Jin, Dong Jin; Chung, Min Young; Lee, Tai Hee

Abstract

When studied in vitro, active transport of glucose across the intestinal mucosa is absolutely dependent upon the presence of sodium in the gut lumen, the role of intraluminal sodium in glucose absorption in vivo is less clear and many studied continues on this. Gastric emptying is an important factor on glucose absorption and glycemic response. There are a lot of reports that salt addition increases glycemic response and gastric emptying after glucose load, inversely, hyperglycemia and hyperinsulinemis decrease gastric emptying. Healthy 8 non-smoker were practiced in this study to evaluate the effect of salt ingestion on glycemic response and gastric emptying in Korean population. Overnight fasting 8 volunteers drank each of 2 solution(300mL) a week interval for 2 weeks, one contained glucose(75g glucola) and 99mTc-DTPA 1 mCi in water and the other contained glucose(75g glucola ), 99mTc-DTPA 1 mCi and salt(3.0g) in water. Venous samples were drawn at 0, 15, 30, 45, 60, 90, 120 min after the ingestion of the test solutions. Serum glucose and insulin levels were measured by means of glucose oxidase method, RIA(radioimmunoassay) respectively and gastric emptying times were measured via the detection of radionuclide with gamma-cemera. The results were as follows, 1) After oral gloucose load, the serum glucose concentration was 144.0+/-11.1mg/dL(mean+/-SEM) before salt addition, 155.0+/-15.6mg/dL after salt addition at 45min, 125.4+/-10.7mg/dL before salt addition, 149.8+/-20.1mg/dL after salt addition at 60min, 104.4+/-11.1mg/dL before salt addition, 121.2+/-11.7mg/dL after salt addition at 90min, therefore it showed the trends of increase at 45, 60, 90 min. 2) There were the trends of increase on serum insulin concentrations from 45 min after salt addition compared to before salt addition during 75g oral glucose load, and there were statistical significances at 60, 90, 120min. After oral glucose load, the serum insulin concentration was 56.1+/-16.4micro U/mL before salt addition, 64.3+/-5.9micro U/mL after salt addition at 60min(p<0.05), 28.9+/-8.0micro U/mL before salt addition, 52.6+/-8.5micro U/mL after salt addition at 90min(p<0.01), 12.8+/-4.0micro U/mL before salt addition, 28.8+/-8.5micro U/mL after salt addition at 120 min(p<0.01). 3) Gastric emptying time is shortened after salt addition(70.6+/-17.1min) compared to before salt addition(53.6+/-6.4min), but there was no statistical significance (p=0.231). Serum glucose level and gastric emptying time after salt addition was not statistically different than those before salt addition, in this study. In healthy subjects, it is predicted that salt addition increase insulin needs and is tend to cause glucose intolerance, increase gastric emptying after glucose loading.