Elizabeth Wuorinen

Publications (3) View all

• Source

  Available from: Katarina Borer

  Article: Two bouts of exercise before meals, but not after meals, lower fasting blood glucose.

  Katarina T Borer, Elizabeth C Wuorinen, Jamie R Lukos, John W Denver, Stephen W Porges, Charles F Burant
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  ABSTRACT: Reduced counterregulatory responses to a next-day hypoglycemic challenge and hypoglycemia result from two spaced episodes of moderate-intensity exercise and have been characterized as exercise-associated autonomic failure. We hypothesized that this phenomenon is caused by postabsorptive state at the time of exercise rather than by autonomic failure. Participants were nine healthy postmenopausal women in a crossover study. Two hours of treadmill exercise at 43% of maximal effort were performed twice a day, separated by 5 h, either 1 h before (Before-Meals trial) or 1 h after a meal (After-Meals trial). Plasma insulin, counterregulatory hormones (glucagon, growth hormone, cortisol), and metabolites (glucose, free fatty acids, ketones) were measured to evaluate the effects of nutritional timing. Analyses of HR and vagal tone were measured to assess autonomic function. Before-Meals exercise, but not After-Meals exercise, reduced postabsorptive plasma glucose by 20.2% during a 16-h period, without a change in counterregulatory response, and elicited postexercise ketosis. A 49% increase in insulin-glucagon ratio during meals, a 1 mM decline in glucagon glycemic threshold, and a reduced vagal tone during exercise were associated with Before-Meals but not with After-Meals trials. These results demonstrate that exercise performed in postabsorptive, but not in postprandial state, lowers glucoregulatory set point and glucagon glycemic threshold and is accompanied by reduced vagal tone, counterregulatory responses, and glucagon glycemic threshold and by increased insulin-glucagon ratio. Reduced counterregulatory response, altered neuroendocrine function, and sustained lowering of blood glucose are most likely the consequences of reduced carbohydrate availability during exercise.
  Medicine and science in sports and exercise 07/2009; 41(8):1606-14. · 3.71 Impact Factor
• Article: Appetite responds to changes in meal content, whereas ghrelin, leptin, and insulin track changes in energy availability.

  Katarina T Borer, Elizabeth Wuorinen, Kimberly Ku, Charles Burant
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  ABSTRACT: It is uncertain how between-meal variations in energy availability and physiological changes in ghrelin, leptin, and insulin affect appetite. Objective: The aim of the study was to examine the influence on human appetite of the meal size and its nutrient content or changes in energy availability and concentrations of ghrelin, leptin, and insulin. We conducted a crossover study manipulating meal size and energy availability through exercise energy expenditure and iv nutrient replacement (TPN). Setting: The study was performed at a Clinical Research Center. Ten healthy postmenopausal women (age, 59.7 +/- 1.5 yr; mean body mass index, 26 kg/m(2)) were studied. Interventions: We conducted trials based on different morning meal size (418 vs. 2090 KJ), presence or absence of exercise energy expenditure (2273 to 2361 KJ), energy replacement by TPN (1521 to 1538 KJ), and a midday ad libitum meal. Main Outcome Measures: Changes in hunger, fullness, midday ad libitum food consumption, and concentrations of ghrelin, leptin, insulin, and metabolic fuels were measured. We also performed midday meal tests for the presence of caloric compensation. Appetite was influenced by the size and energy content of the meals, but not by variation in energy availability which also did not trigger consummatory compensation. Exercise reduced hunger and increased fullness. Ghrelin, leptin, and insulin responded to changes in energy availability but not to meal size. Appetite was unaffected by physiological changes in ghrelin, leptin, or insulin. During rest, appetite is influenced by the size and energy content of meals, but it bears no homeostatic relationship to between-meal changes in energy availability due to small meals, exercise, or TPN, or concentrations of ghrelin, leptin, and insulin.
  The Journal of clinical endocrinology and metabolism 05/2009; 94(7):2290-8. · 6.50 Impact Factor
• Article: Exercise energy expenditure is not consciously detected due to oro-gastric, not metabolic, basis of hunger sensation.

  Katarina T Borer, Elizabeth Wuorinen, Cewin Chao, Charles Burant
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  ABSTRACT: We tested the hypothesis that exercise energy expenditure (EEE) will elicit reflex metabolic compensations but no increases in hunger. Exercise expended 800 kcal once when fasted and at another time in a post-prandial state. During fasting exercise, pre-meal ratings of hunger were unaffected by EEE, but plasma concentrations of ghrelin, growth hormone and free fatty acids were higher than in the absence of EEE. We propose that the perception of hunger is based on the vagal, lateral hypothalamic and cortical projections of oral and gastro-intestinal (GI) stimuli and that EEE triggers neuroendocrine compensations and influences hunger indirectly by affecting GI functions.
  Appetite 11/2005; 45(2):177-81. · 2.59 Impact Factor