Muscle Mass and Composition in Malnourished Infants and Children and Changes Seen after Recovery

Abstract

SummaryA method for measuring muscle mass in children with [15N]creatine has been used to study changes in muscle after recovery from protein-energy malnutrition. Creatine pool size, muscle mass, total muscle cell number, muscle cell size, and total body water have been measured in seven malnourished and eight recovered children. After recovery there was a significant reduction in the muscle concentration (micrograms mg-' wet wt muscle) of creatine (4.21 to 3.12), and a trend towards reduction in noncollagen protein (155 to 136) and DNA (2.13 to 1.34). The fractional turnover rate of creatine did not change but the creatine pool size increased significantly (4.2 to 5.6 g). Average muscle mass almost doubled (1.00 to 1.91 kg) and made up a greater percentage of body weight (16 to 22%). When muscle mass was expressed as a percentage of the expected muscle mass for a normal child of the same height the increase with recovery was from 49% to 92%. Total muscle noncollagen protein (NCP) increased after recovery (153 to 265 g) and accounted for a greater percentage of total body solids (6.6 to 8.5%). The average total muscle DNA was 2.049 g in the malnourished and 2.380 g in the recovered children and the ratio of NCP:DNA increased from 92 to 110 on recovery. Total body water as a percentage of body weight was not significantly different after recovery. Values for muscle mass in recovered children were similar to those reported for normal children of the same weight, height, and age. SpeculationIn children who have recovered from malnutrition by reaching their expected weight for height, muscle mass repletion is achieved by a combination of cellular hypertrophy and hyperplasia.Muscle tissue provides the largest store of potentially available protein in the body (29) and is considerably reduced in the children with severe protein-energy malnutrition (PEM). From cadaver studies of children dying of severe PEM, the deficit in muscle was estimated to be about 70% based on either wet weight (18) or total muscle protein (15,29). Muscle biopsy data showed a 45% reduction in total protein in malnourished as compared to recovered children (31). Both the size and the total number of muscle fibers were considerably smaller in the sartorius muscle, obtained at postmortem, of malnourished as compared to well nourished children (23). During recovery from PEM there is an accelerated rate of weight gain (2), and the daily excretion of creatinine has been used as an indirect index of muscle mass in malnourished and recovered children (1,7,13,27). However, the validity of creatinine excretion as a reliable measure of muscle mass in the malnourished child remains to be established. This is important since changes in muscle cell size and total cell number during recovery from PEM have been based on this method of estimating muscle mass (7).Recently we reported a more direct method of measuring muscle mass in children (25). This method has been used in the present study to determine quantitative changes in muscle mass, total cell number, a...

Quantitative Analysis of Nuclear Population in Muscle from Malnourished and Recovered Children

“…Thus, to reasonably estimate the number of muscle cells from the D N A content of muscle, it is necessary to correct the latter by a factor of one-third. When the total number of muscle cells from biopsy data and a value for total muscle mass are estimated the assumption is made that the composition of the sampled muscle is representative of the (2,3,10,15). A n underlying a s s u m p assumption but studies in normal and malnourished rats suggest tion of this mathematic expression is that nonmuscle cells in the that changes in DNA content of the quadriceps femoris parallel muscle sample contribute insignificantly to the protein and D N A those of other muscles (3,11).…”

“…Sections for light microscontent or concentration is frequently used as a reference to copy (' ml*) were cut On an LKB ultramicrotome and stained express biochemical responses of other muscle constituents to (6). The total number of nuclei in each section was determined protein-energy malnutrition (PEM) (2,3,10,14) and to nutri-at a magnification of 40Ox on an 0 '~~~~s microsco~e. Counts tional rehabilitation (2, The use of DNA as a reference is were made on sections from five different specimen blocks per based on the assumption "that no cells are present in the subject.…”

Consequences of inadequate food energy and negative energy balance in humans

“…Table 1 shows the relative loss of different tissues in atrophic infants 32 , where the brain, viscera and skeleton are relatively preserved when compared to muscle and fat. Indeed, the rate of both muscle and adipose tissue are higher than other tissues during acute under-nutrition 29,34 . Since these tissues have relatively lower metabolic rates than visceral organs 29 and since the organ mass has been shown to be inversely related to the FFM 35 , it is possible that the BMR per kg FFM, would depend largely on these factors.…”

“…The decrease in growth rate results in a lower body size along with changes in body composition. In general, with severe undernutrition, fat and muscle tend to be lost the most 29,34 , followed by thoracic and abdominal organs, while the brain tends to be preserved ( Table 1). The TBW increases 207 , particularly in those children with oedema, and is mainly due to an increase in the extracellular water 208 .…”

A Prospective Study of the Effects of Clinically Severe Protein‐energy Malnutrition on Growth

“…Children recovering from clinically-severe protein-energy malnutrition (PEM) gain both weight and muscle and, after recovery, both of these variables are appropriate for their body length (2,14). However, both weight and length are usually small for age after treatment (5,19).…”