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January 1979 - December 2012
Publications
Publications (134)
This review is a tribute to honor Dr Douglas Paddon-Jones by highlighting his career research contributions. Dr Paddon-Jones was a leader in recognizing the importance of muscle health and the interactions of physical activity and dietary protein for optimizing the health span. Aging is characterized by loss of muscle mass and strength associated w...
Background:
Protein quantity and quality at a meal affect muscle protein synthesis (MPS); however, long-term effects of protein distribution at individual meals on adult muscle mass remain unknown.
Objective:
We used a precise feeding protocol in adult rats to determine if optimizing postmeal MPS response by modifying the meal distribution of pr...
The aim of the present study was to investigate the mechanistic basis of protein deficiency during pregnancy in mother that is transduced to offspring. To this end, timed-pregnant Sprague-Dawley rats were fed either a control (20 % of energy from protein) or low-protein (LP, 8 % of energy from protein) diet during gestation. Tissues were collected...
Dietary protein provides essential amino acids (EAAs) for the synthesis of new proteins plus an array of other metabolic functions; many of these functions are sensitive to postprandial plasma and intracellular amino acid concentrations. Recent research has focused on amino acids as metabolic signals that influence the rate of protein synthesis, in...
The RDA for protein describes the quantity that should be consumed daily to meet population needs and to prevent deficiency. Protein consumption in many countries exceeds the RDA; however, intake is often skewed toward the evening meal, whereas breakfast is typically carbohydrate rich and low in protein. We examined the effects of protein distribut...
AQ1 INTRODUCTION The past decade witnessed an emergence of dietary protein in the popular press and nutrition research. Rediscovery of pro-tein as a critical dietary component has been fueled by three distinct areas of research. One area driving intense interest is use of higher-protein diets for weight loss; a second area evolved from concern abou...
Previous research demonstrates that the anabolic response of muscle protein synthesis (MPS) to a meal is regulated at the level of translation initiation with signals derived from leucine (Leu) and insulin to activate mTORC1 signaling. Recent evidence suggests that the duration of the meal response is limited by energy status of the cell and inhibi...
Background
Leucine (Leu) regulates muscle protein synthesis (MPS) producing dose-dependent plasma Leu and MPS responses from free amino acid solutions. This study examined the role of Leu content from dietary proteins in regulation of MPS after complete meals.
Methods
Experiment 1 examined 4 protein sources (wheat, soy, egg, and whey) with differe...
Limited data on sex differences in body composition changes in response to higher protein diets (PRO) compared to higher carbohydrate diets (CARB) suggest that a PRO diet helps preserve lean mass (LM) in women more so than in men.
To compare male and female body composition responses to weight loss diets differing in macronutrient content.
Twelve m...
Obesity is a world-wide epidemic costing billions in health care each year. Research demonstrates that the macronutrient composition of a calorie-controlled meal plan plays a significant role in obesity treatment. Nutrition research suggests that shifts in the American diet to consumption of a high carbohydrate, high glycemic, low protein diet redu...
Muscle protein synthesis (MPS) increases after consumption of a protein-containing meal but returns to baseline values within 3 h despite continued elevations of plasma amino acids and mammalian target of rapamycin (mTORC1) signaling. This study evaluated the potential for supplemental leucine (Leu), carbohydrates (CHO), or both to prolong elevated...
The purpose of this double-blind randomized clinical trial was to compare the relative effectiveness of a higher protein and conventional carbohydrate intake during weight loss on body composition and physical function in older women.
Thirty-one overweight or obese, postmenopausal women (mean ± SD: age 65.2 ± 4.6 years, body mass index 33.7 ± 4.9 k...
Herein we review the efficacy of whey protein consumption in support of skeletal muscle protein health. The essential amino acid leucine has been identified as an important signaling molecule, which regulates skeletal muscle protein anabolism. Whey protein has a uniquely high leucine density. Consequently, whey protein has been shown to increase an...
Current theory on the influence of breast cancer on bone describes metastasis of tumor cells to bone tissue, followed by induction of osteoclasts and bone degradation. Tumor influences on bone health in pre- or nonmetastatic models are unknown. Female rats (n = 48, 52 days old) were injected with N-methyl-N-nitrosourea (MNU) to induce breast cancer...
The Dietary Reference Intakes (DRI) established acceptable macronutrient distribution ranges (AMDR) for carbohydrates and protein, however little is known about differences in glycemic regulations and metabolic signaling across this range. This study examined metabolic outcomes associated with intake of two diets differing in carbohydrate:protein r...
To understand the potential benefits of increased dietary protein during weight loss and the importance of distribution of high-quality protein at each meal.
Popular weight loss diets emphasize use of protein as a substitute for carbohydrates or fat to reduce insulin and minimize hunger and food cravings. These diets produce short-term weight loss,...
Breast cancer is the most prevalent cancer in American women. Dietary factors are thought to have a strong influence on breast cancer incidence. This study utilized a meal-feeding protocol with female Sprague-Dawley rats to evaluate effects of two ratios of carbohydrate:protein on promotion and early progression of breast tissue carcinomas. Mammary...
This study examined the impact of leucine (Leu) derived from complete meals on stimulation of skeletal muscle protein synthesis (MPS). Expt. 1 examined time course changes in translation initiation and MPS after a meal. Male rats ( approximately 300 g) were trained for 5 d to eat 3 meals/d providing 20, 50, and 30% of energy from whey protein, carb...
Dietary Guidelines for Americans provide nutrition advice aimed at promoting healthy dietary choices for life-long health and reducing risk of chronic diseases. With the advancing age of the population, the 2010 Dietary Guidelines confront increasing risks for age-related problems of obesity, osteoporosis, type 2 diabetes, Metabolic Syndrome, heart...
Diets with increased protein and reduced carbohydrates (PRO) are effective for weight loss, but the long-term effect on maintenance is unknown. This study compared changes in body weight and composition and blood lipids after short-term weight loss (4 mo) followed by weight maintenance (8 mo) using moderate PRO or conventional high-carbohydrate (CH...
High-quality proteins make a valuable contribution to the synthesis and maintenance of muscle and indirectly to the regulation of blood glucose levels, thus contributing to power, strength, and energy. Eggs have traditionally been used as the standard of comparison for measuring protein quality because of their essential amino acid (EAA) profile an...
Weight loss causes bone mineral loss. Higher protein diets continue to be criticized for further potential harmful bone effects, including elevated urinary calcium, but may promote bone health if protein sources include dairy. Overweight middle-aged subjects (n = 130, 59 males) were randomized to a diet providing 1.4 g.kg(-1).d(-1) protein and 3 da...
Many factors influence bone mass. Protein has been identified as being both detrimental and beneficial to bone health, depending on a variety of factors, including the level of protein in the diet, the protein source, calcium intake, weight loss, and the acid/base balance of the diet. This review aims to briefly describe these factors and their rel...
Diets with increased protein and reduced carbohydrates have been shown to improve body composition, lipid and lipoprotein profiles, and glycemic regulations associated with treatment of obesity and weight loss. Derived from these outcomes, high-protein, low-carbohydrate diets are also being examined for treatment of heart disease, metabolic syndrom...
Protein quality describes characteristics of a protein in relation to its ability to achieve defined metabolic actions. Traditionally, this has been discussed solely in the context of a protein's ability to provide specific patterns of amino acids to satisfy the demands for synthesis of protein as measured by animal growth or, in humans, nitrogen b...
To evaluate the metabolic effects of two weight loss diets differing in macronutrient composition on features of dyslipidemia and post-prandial insulin (INS) response to a meal challenge in overweight/obese individuals.
This study was a parallel-arm randomized 4 mo weight loss trial. Adults (n = 50, 47 +/- 7 y) matched on BMI (33.6 +/- 0.6 kg/m2, P...
This study examined the interaction of 2 diets (high protein, reduced carbohydrates vs. low protein, high carbohydrates) with exercise on body composition and blood lipids in women (n 48, 46 y old, BMI 33 kg/m 2) during weight loss. The study was a 4-mo weight loss trial using a 2 2 block design (Diet Exercise). Diets were equal in total energy (7....
The dietary reference intakes (DRIs) established an acceptable macronutrient distribution range (AMDR); however, few studies have evaluated differences in metabolic regulations across the DRI range. This study examined differences in glycemic regulations associated with specific ratios of carbohydrate and protein. Male rats ( approximately 200 g) w...
High-performance physical activity and postexercise recovery lead to significant changes in amino acid and protein metabolism in skeletal muscle. Central to these changes is an increase in the metabolism of the BCAA leucine. During exercise, muscle protein synthesis decreases together with a net increase in protein degradation and stimulation of BC...
High-performance physical activity and postexercise recovery lead to significant changes in amino acid and protein metabolism in skeletal muscle. Central to these changes is an increase in the metabolism of the BCAA leucine. During exercise, muscle protein synthesis decreases together with a net increase in protein degradation and stimulation of BC...
Diets with total protein intake >1.5 g.kg(-1).d(-1) and carbohydrate intake <150 g/d are effective for treatment of obesity, type 2 diabetes, and the Metabolic Syndrome. These diets improve body composition and enhance glycemic control. During weight loss, protein-rich diets reduce loss of lean tissue and increase loss of body fat. Specific mechani...
This study examined the interaction of 2 diets (high protein, reduced carbohydrates vs. low protein, high carbohydrates) with exercise on body composition and blood lipids in women (n = 48, approximately 46 y old, BMI = 33 kg/m(2)) during weight loss. The study was a 4-mo weight loss trial using a 2 x 2 block design (Diet x Exercise). Diets were eq...
Leucine (Leu) is known to stimulate translation initiation of protein synthesis at mammalian target of rapamycin (mTOR) in the insulin signaling pathway. However, potential feedback from mTOR to upstream aspects of the insulin signaling pathway remains controversial. This study evaluates the impact of a physiological oral dose of Leu and/or carbohy...
Evidence is accumulating that diets with reduced carbohydrates and increased levels of high quality protein are effective for weight loss. These diets appear to provide a metabolic advantage during restricted energy intake that targets increased loss of body fat while reducing loss of lean tissue and stabilizing regulations of blood glucose. We hav...
Evidence is accumulating that diets with reduced carbohydrates and increased levels of high quality protein are effective for weight loss. These diets appear to provide a metabolic advantage during restricted energy intake that targets increased loss of body fat while reducing loss of lean tissue and stabilizing regulations of blood glucose. We hav...
Diets with higher protein (1.5 g x kg(-1) x d(-1)) and reduced carbohydrates (120 to 200 g/d) appear to enhance weight loss due to a higher loss of body fat and reduced loss of lean body mass. While studies of prolonged use of moderate protein diets are not available, short-term studies report beneficial effects associated with increased satiety, i...
Debate about the optimum balance of macronutrients for adult weight maintenance or weight loss continues to expand. Often this debate centers on the relative merits or risks of carbohydrates vs. fats; however, there is increasing interest in the optimal level of dietary protein for weight loss. Diets with a reduced ratio of carbohydrates/protein ar...
Amino acids interact with glucose metabolism both as carbon substrates and by recycling glucose carbon via alanine and glutamine; however, the effect of protein intake on glucose homeostasis during weight loss remains unknown. This study tests the hypothesis that a moderate increase in dietary protein with a corresponding reduction of carbohydrates...
Claims about the merits or risks of carbohydrate (CHO) vs. protein for weight loss diets are extensive, yet the ideal ratio of dietary carbohydrate to protein for adult health and weight management remains unknown. This study examined the efficacy of two weight loss diets with modified CHO/protein ratios to change body composition and blood lipids...
Exercise produces changes in protein and amino acid metabolism. These changes include degradation of the branched-chain amino acids, production of alanine and glutamine, and changes in protein turnover. One of the amino acid most affected by exercise is the branched-chain amino acid leucine. Recently, there has been an increased understanding of th...
Prolonged exercise increases circulating insulin-like growth factor binding protein-1 (IGFBP-1) in humans and animals, but its physiological significance is unknown. This study examined 1) time-course changes in plasma IGFBP-1 and hepatic IGFBP-1 mRNA expression after exercise, 2) changes in IGFBP-1 in relation to plasma glucose, insulin, and IGF-I...
This study was designed to determine the ability of leucine to enhance muscle recovery after exercise. Male rats (200 g) were divided into five groups: sedentary, food-deprived (SF); exercised, food-deprived (EF); exercised, fed a carbohydrate meal (EC); exercised, fed a leucine meal (EL); and exercised, fed a combination of carbohydrate and leucin...
The efficacy of recombinant human growth hormone (GH) and/or a diet enriched in protein and energy to improve growth recovery following prolonged malnutrition was examined in male rats food-restricted from birth until 120 d of age. At d 121, restricted rats were randomly assigned to recovery groups receiving either a control or enriched diet with o...
We examined the response of the IGF-I system to prolonged undernutrition and its involvement in somatic and skeletal muscle growth retardation. Male rats were food-restricted to 50% of freely-fed controls (C) from birth to 120 days postpartum. Serum and tissues were collected at d 50 and d 120 postpartum. Somatic growth of food-restricted animals (...
