Protein metabolism in obese subjects during a very low energy diet (original) (raw)
Clinical Nutrition, 2007
Background & aims: Patients with type 2 diabetes (T2DM) tend to loose more lean body mass during both long-term weight reduction and short-term very-low-calorie diet. We ask what factors influence protein loss during acute starvation in T2DM. Methods: In a prospective in-hospital observational study, we compared 10 subjects with T2DM and 10 age-weight-sex matched obese controls (OB) during 60 h of fasting and used frequent blood sampling and indirect calorimetry to describe metabolic and endocrine response. We analyzed factors influencing nitrogen balance using stepwise multiple regressions. Results: Despite comparable pattern of plasma insulin, free fatty acid, 3-hydroxybutyrate and almost identical behavior of growth hormone axis, our T2DM subjects remained hyperglycaemic and in contrast to OB subjects they failed to reduce the rate of protein oxidation, even though muscle protein breakdown rate declined similarly in both groups. Regression analysis revealed that protein oxidation rate in T2DM group was enhanced by hyperglycemia and sympathetic activity and suppressed by circulating insulin and 3hydroxybutyrate. Liver insulin resistance increases peripheral insulin concentrations and enhances the conversion of non-esterified fatty acids (NEFA) to ketones and thus it might be a protein-saving factor.
Nitrogen metabolism at chronic low energy intakes
Nutrition Research, 1993
The response of animals adapted to moderate or severe energy restriction to supplements of free amino acids or protein is unknown. Lysine supplementation was examined because it is an amino acid frequently limiting in cereal-based diets. Male rats weighing ]15 g were assigned to one of seven diet groups. Animals were fed either a gluten-based diet or the gluten diet supplemented with adequate levels of lysine for 8 weeks. These diets were fed ad libitum or at 40% or 75% restricted levels. An additional group was fed a high gluten diet at the same energy level as the 75% restricted rats. Body weight, muscle weights, and adipose tissue were reduced relative to the level of restriction. Restricted groups adapted to the energy restrictions and exhibited either slow growth or stable body weight after 4 weeks on the respective treatments. Lysine supplementation increased muscle mass and improved nitrogen balance in the ad libitum and 40% restricted groups, but had no effect on the 75% restricted group. Excretion of 3-methylhistidine (3MH) was higher in the energy restricted animals after 7 weeks on the respective diets, and lysine supplements further increased 3MH losses. Plasma lysine levels were reduced by the food restrictions and unaffected by lysine supplements in the restricted animals. These findings indicate that the efficacy of lysine supplementation depends on the absolute level of energy intake, and a lysine supplemented diet may be detrimental to skeletal muscle mass at very low energy intakes. The data also showed that rats adapt to a 75% food restriction by achieving and maintaining nitrogen balance despite the increase in myofibrillar protein breakdown.
Protein intake regulation and nitrogen retention in young obese and lean mice
Journal of Nutrition
Young female obese (ob/ob) and lean mice were fed a single diet containing 10 or 20% casein or were allowed to self-select from two diets containing 10 and 50, 20 and 60, or 30 and 70% casein for 3 weeks. Obese and lean mice offered a choice of two diets varying in protein-consumed 36% and 32%, respectively, of energy from protein. Although both obese and lean mice consumed more protein when allowed to self-select, each group maintained the same energy intake as observed when a single diet was fed. Because obese mice consumed more energy than lean mice, their self-selected intake of protein was 55% greater than observed in lean mice. The increased protein intake in self-selected obese mice was associated with a decreased tryptophan:large neutral amino acid ratio in their plasma. Average nitrogen retention was only slightly less in obese mice than in lean mice, but the sites of nitrogen deposition differed considerably. Obese mice retained only 35% of their nitrogen in the carcass (s...
Low protein diets produce divergent effects on energy balance
Scientific Reports, 2016
Diets deficient in protein often increase food consumption, body weight and fat mass; however, the underlying mechanisms remain poorly understood. We compared the effects of diets varying in protein concentrations on energy balance in obesity-prone rats. We demonstrate that protein-free (0% protein calories) diets decreased energy intake and increased energy expenditure, very low protein (5% protein) diets increased energy intake and expenditure, whereas moderately low protein (10% protein) diets increased energy intake without altering expenditure, relative to control diet (15% protein). These diet-induced alterations in energy expenditure are in part mediated through enhanced serotonergic and β-adrenergic signaling coupled with upregulation of key thermogenic markers in brown fat and skeletal muscle. The protein-free and very low protein diets decreased plasma concentrations of multiple essential amino acids, anorexigenic and metabolic hormones, but these diets increased the tissu...
AJP: Endocrinology and Metabolism, 2007
It is unclear whether the rate of weight loss, independent of magnitude, affects whole body protein metabolism and the synthesis and plasma concentrations of specific hepatic secretory proteins. We examined 1) whether lean men losing weight rapidly (starvation) show greater changes in whole body protein kinetics, synthesis, and circulating concentrations of selected hepatic secretory proteins than those losing the same amount of weight more slowly [very low energy diet (VLED)]; and 2) whether plasma concentrations and synthetic rates of these proteins are related. Whole body protein kinetics were measured using [1-13C]leucine in 11 lean men (6 starvation, 5 VLED). Fractional and absolute synthetic rates of HDL-apolipoprotein A1 (apoA1), retinol binding protein, transthyretin, α1-antitrypsin (α1-AT), and transferrin were measured using a prime-constant intravenous infusion of [13C2]glycine. Compared with VLED group, the starvation group showed greater increases (at a 5% weight loss) ...
Obesity and Protein Metabolism
Journal of Pharmacy and Pharmacology 6 (2018) 956-964, 2018
A conceptual model of the interdependence between the metabolism of proteins, fats and carbohydrates taking into account the transport of the carbon skeleton and the stages of the relationship between the processes of formation and utilization of ATP (Adenosine Triphosphate) energy, which demonstrates the key role of protein metabolism and the maintenance of glucose homeostasis with different organism availability in energy was proposed. In supporting the processes of vital activity of the body, two periods should be analyzed. The first one is absorptive period, which is for providing rehabilitation processes, the expression of which is the "food pyramid" and the second one is postabsorptive period, which is for the energetic provision of physical and mental work, the expression of which is the "energy pyramid". These pyramids differ in the ratio of macronutrients, and in their composition, which must be taken into account when developing the principles of human nutrition. Although obesity is seen as a simple discrepancy between the amount of intake of food calories and their utilization for physical activity, however, do not take into account the large energy expenditure on volatile processes, in particular, the process of protein synthesis. The process of protein synthesis depends on the availability in the substrate (amino acids), the intensity of mRNA expression (transcription) and the speed of reproduction (translation), so the violation at each of these stages will affect the energy balance and promote the development of obesity. Half of the protein mass is muscle, so it largely determines the homeostasis of glucose and the development of energy balance, which is presented in the form of an interdisciplinary model for the development of diabetes, obesity and cardiovascular diseases. In conclusion, technologies were proposed to support the process of protein synthesis and ways of preventing and treating obesity.
Protein sparing during treatment of obesity: ketogenic versus nonketogenic very low calorie diet
Metabolism, 1992
Although it is generally agreed that both ketogenic and nonketogenic very low calorie diets promote weight reduction, there is no consensus on a preference of one diet over the other in regard to protein sparing. In the present study, we compared the effects of isocaloric (600 kcal/d) and isonitrogenous (6 g nitrogen/d) ketogenic (low carbohydrate) and nonketogenic diets on parameters of protein and amino acid metabolism, in 16 morbidly obese women maintained on these diets for 4 weeks while confined to a metabolic ward. Cumulative urinary nitrogen excretion (g/4 wk) was significantly (P < .Ol) greater (246 f 6 w 207-C 12, mean-C SEM, n = 8). and cumulative nitrogen balance significantly (P < .02) more negative (-50.4 f 4.4 Y-18.8-C 5.7), during treatment with the ketogenic than with the nonketogenic diet. Plasma leucine concentration (pmol/ L) was significantly higher (P < .05) during treatment with the ketogenic than with the nonketogenic diet at day 14 (210 f 17 Y 160 f S), but not at day 28 (174 f 9 Y 148 f 8). Whole-body rates of leucine oxidation (mmol/h) were significantly higher (P < .05) during treatment with the ketogenic than with the nonketogenic diet at day 14 (1.29 f 0.20~0.92 f 0.10) and at day 28 (1.00 + 0.16 Y 0.75 f 0.10). Conversely, proteolysis, as measured by leucine turnover rate and urinary excretion of 3-methylhistidine, was not significantly different between the diets. We conclude that there is greater protein sparing by the nonketogenic than by the ketogenic very low calorie diet, and the mechanism appears to be greater protein synthesis.