Short term elevation in dietary protein intake does not worsen insulin resistance or lipids in older adults with metabolic syndrome: a randomized-controlled trial

Abstract

BackgroundThere is a great deal of controversy as to whether higher protein intake improves or worsens insulin sensitivity in humans. The purpose of the study was to determine the influence of a short-term elevation in dietary protein on hepatic and peripheral insulin sensitivity in twelve older subjects (51–70 yrs) with metabolic syndrome.MethodsIndividuals were randomly assigned to one of the dietary groups: recommended protein intake (RPI, 10% of daily calorie intake) or elevated protein intake (EPI, 20% of daily calorie intake) for 4 weeks. Prior to and immediately following the dietary intervention, subjects were studied with primed continuous infusion of [6,6-2H2]glucose and [1-3C]glucose dissolved in drink during the dual tracer oral glucose tolerance test (DT OGTT) to determine hepatic and peripheral insulin sensitivity. Plasma lipids were measured pre- and post-dietary intervention.ResultsIn both intervention groups: 1) hepatic insulin sensitivity as assessed by the endogenous glucose rate of appearance (glucose Ra), 2) peripheral insulin sensitivity as assessed by the metabolic clearance rate of glucose normalized to plasma glucose concentration (MCR) and/or the rate of glucose utilization (Rd) or 3) glucose/insulin AUC were unaffected by the diets. Moreover, fasting lipid was not affected by RPI or EPI.ConclusionOur findings suggest that a short-term elevation in EPI with correspondingly higher branched chain amino acid (BCAA) contents has no detrimental impact on hepatic and peripheral insulin sensitivity or plasma lipid parameters in older adults with metabolic syndrome.Trial registrationClinicalTrials.gov Identifier: NCT02885935; This trial was registered retrospectively (Study start date, April 01, 2013, date of registration, August 26, 2016).

Dietary Protein and Muscle Mass: Translating Science to Application and Health Benefit

“…These associations are typically confounded by misrepresentation of foods labeled as “protein-rich” which may, by their nature, be overall less-healthful nutrient-sparse food options, providing high amounts of total and saturated fats and processing additives (e.g., nitrates, nitrites, sodium) [60]. To the best of our knowledge, there are no data demonstrating a well-defined association between dietary protein itself and cardiovascular disease [70,71] or type 2 diabetes mellitus [56]. Similarly, methionine restriction (e.g., vegan dietary pattern) may be a viable approach to limit carcinogenic processes and tumor growth [72,73], yet meta-analyses show no link between overall dietary protein intake and incidence of colorectal [57] or breast [58] cancers.…”

Quantifications of Lipid KineticsIn VivoUsing Stable Isotope Tracer Methodology

“…6C represents the time course changes in enrichments of precursor and product between 2 time points ( t 1 and t 2 ) where tissues (e.g., plasma) are typically harvested to measure changes in product enrichment and precursor enrichments for quantification of TAG FSR. The FSR term is also used in determining various polymers such as protein (from amino acids), 14 18 19 20 27 glucose (from 2 trioses), 28 29 DNA (from bases), 28 30 RNA (from bases), 31 32 and so on. In the following section, we will show flux calculation of selected variables of lipid kinetics using stable isotope tracer methodology and mass spectrometry.…”

“…As stated above, R a tracee is calculated as F divided by E p . Importantly, multiple stable isotope tracers can be simultaneously administered into body for assessing various kinetics of lipids as well as other substrates such as glucose, 8 12 13 14 15 amino acids 16 17 18 19 20 and nitric oxide. 21 22 23 In this review, we will deal only with steady state substrate kinetics due to the complexity and uncertainty of non-steady state kinetics despite much of the real life being more in non-steady state.…”

In Vivo and In Vitro Quantification of Glucose Kinetics: From Bedside to Bench

“…Dynamic information on the metabolic status of substrates including glucose, lipids, amino acids/proteins in organisms (i.e., metabolic flux or kinetics) in vivo and in vitro can be best explored with the introduction of one or more of molecules that are labeled with either a stable or radioactive isotope (i.e., metabolic tracer) into the circulation in the body [11,15,16,[26][27][28].…”

“…GC-MS, gas chromatography mass spectrometry; LC-MS, liquid chromatography mass spectrometry. [6,47,48], glycerol [49][50][51], pyruvate [52], lactate [53][54][55] as well as glucose [8,11,56,57] in steady states and non-steady states.…”