Nutritional support in advanced lung disease. The pulmonary cachexia syndrome

Practical dietary advices for subjects with alpha-1 antitrypsin deficiency

Congenital alpha-1 antitrypsin deficiency (AATD) is a rare inherited disorder caused by the mutation of the SERPINA1 gene on chromosome 14. At pulmonary level, AAT deficiency leads to an increased risk of chronic obstructive pulmonary disease (COPD) and emphysema, starting from the third-fourth decade of life. At hepatic level, some variants of the allelic, in particular PI*Z, cause a conformational change of the AAT molecule, which polymerizes within the hepatocytes. Excessive hepatic accumulation of these abnormal molecules can lead to liver disease in both adults and children, with clinical presentation ranging from cholestatic jaundice in the newborn to abnormal blood indices of liver function in children and adults, up to fatty liver, cirrhosis and hepatocarcinoma. Nutritional interventions in AATD aim to provide the necessary calories, stop protein catabolism, prevent and treat malnutrition as in the case of common COPD, and even take into account any liver disease that is a distinctive trait, compared to common COPD. Actually, there is a lack of formal research regarding the effects of specific nutritional recommendations in patients with AATD, proper eating habits may help to preserve lung and liver function. For practical dietary advice in patients with AATD and COPD, recently a food pyramid proposal has been published. It has been observed that there is a marked overlap between AATD liver disease and obesity-related liver disease, suggesting shared molecular basis and, therefore, similar nutritional strategies. In this narrative review dietary advice for all possible stages of liver disease have been reported.

Global Deletion of Pannexin 3 Resulting in Accelerated Development of Aging-Induced Osteoarthritis in Mice

OBJECTIVE

Osteoarthritis (OA) results in pathologic changes in the joint tissue. The mechanisms driving disease progression remain largely unclear, and thus disease-modifying treatments are lacking. Pannexin 3 (Panx3) was identified as a potential mediator of cartilage degeneration in OA, and our previous study in mice indicated that deletion of the Panx3 gene delayed surgically induced cartilage degeneration. This study was undertaken to examine the role of Panx3 in other OA subtypes, particularly primary OA during aging, in a mouse model of aging-induced OA.

METHODS

Wild-type (WT) and Panx3^-/- C57BL/6J (Black-6) mice, ages 18-24 months, were analyzed by micro-computed tomography to investigate bone mineral density and body composition. Joints were harvested from the mice, and histopathologic analysis of the joint tissue for OA development was conducted with a specific focus on changes in articular cartilage, subchondral bone, and synovial tissue.

RESULTS

Global loss of Panx3 in aging mice was not associated with increased mortality or changes in body composition. Mice lacking Panx3 had shorter appendicular skeletons than WT mice, but overall the body compositions appeared quite similar. Panx3 deletion dramatically accelerated cartilage degeneration and subchondral bone thickening with aging in both 18-month-old and 24-month-old mice, while promoting synovitis in 18-month-old mice.

CONCLUSION

These observations in a mouse model of OA suggest that Panx3 has a protective role against the development of primary aging-associated OA. It appears that Panx3 has opposing context-specific roles in joint health following traumatic injury versus that associated with aging. These data strongly suggest that there are differences in the molecular pathways driving different subtypes of OA, and therefore a detailed understanding of these pathways could directly improve strategies for OA diagnosis, therapy, and research.

Effect of Megestrol Acetate and Testosterone on Body Composition and Hormonal Responses in COPD Cachexia

Background: Underweight chronic obstructive pulmonary disease (COPD) patients with involuntary weight loss have a poor prognosis; no effective therapy is currently available. We conducted the first clinical trial seeking to determine whether combination therapy with an appetite stimulant and an anabolic steroid would have beneficial effects on body composition for patients with COPD cachexia. Methods: We conducted a 12-week pilot study in which 4 men and 5 women (age 64±10 y, forced expiratory volume in 1 second [FEV₁] 31±9 %pred., body mass index [BMI] 18±3 kg/m²) with low-normal testosterone levels (average 532±45ng/dl in men and 12.4±5.3ng/dl in women) and weight loss ≥10 lbs over the previous year were treated with oral megestrol acetate 800mg/day plus weekly testosterone enanthate injections, initially 125 mg in men and 40 mg in women, with doses subsequently adjusted targeting circulating nadir testosterone levels of 850 and 300 ng/dl, respectively. Results: On treatment, nadir testosterone level increases averaged 160±250 ng/dl (NS) in men and 322±49 (p<0.001) ng/dl in women. Body weight increased in all individuals, with average end-intervention weight gain of 3.1±2.2 kg (p<0.005). Two women and 2 men had COPD exacerbations and did not complete the 12-week study. In the 5 individuals who completed, dual energy x ray absorptiometry (DEXA) scans revealed an average 2.0±1.5 kg lean mass and 2.3±1.7 kg fat mass increase (each p<0.05). No adverse effects of treatment were detected. Conclusions: Combination therapy reversed the trajectory of involuntary weight loss and increased lean mass in cachectic COPD patients. Though the interventions were apparently well tolerated, participant drop-out rate was high. Larger randomized placebo-controlled long-term studies with functional outcomes are needed.

Nutrition in chronic obstructive pulmonary disease: A review

Cachexia and muscle wasting is a frequent but partly reversible complication in patients with chronic obstructive pulmonary disease (COPD), and affects the disease progression and prognosis. Weight loss in COPD is a consequence of increased energy requirements unbalanced by dietary intake. Nutritional supplement therapy has been shown to be effective for maintaining and improving the muscle strength and exercise tolerance in poorly nourished COPD patients, thereby decreasing morbidity and mortality. This mini review discusses the role of nutritional supplement therapy in the treatment of COPD.

Plasma ghrelin levels and weight loss in Chinese Uygur patients with chronic obstructive pulmonary disease

Ghrelin is an important orexigenic hormone that reduces fat oxidation and increases adiposity. This study investigated plasma ghrelin levels in Chinese Uygur patients with chronic obstructive pulmonary disease (COPD). Plasma ghrelin and anabolic and catabolic factors were measured in 38 patients and 24 control subjects. COPD patients were divided into two groups based on body mass index (BMI): underweight (BMI < 20 kg/m(2), n = 18) or normoweight (BMI > or = 20 kg/m(2), n = 20). Plasma ghrelin levels were found to be significantly higher in underweight than in normoweight patients or healthy controls. Circulating tumour necrosis factor-alpha and interleukin-6 concentrations were significantly higher in underweight than in normoweight patients, whereas insulin concentrations were significantly lower. Plasma ghrelin levels correlated negatively with forced expiratory volume in 1 s (FEV(1); r = 0.35), but did not significantly correlate with FEV(1)/forced vital capacity. Plasma ghrelin levels were elevated in underweight COPD patients and were associated with cachexia and abnormal pulmonary function.

Anorexia in chronic obstructive pulmonary disease--association to cachexia and hormonal derangement

BACKGROUND

In patients with chronic obstructive pulmonary disease (COPD) weight loss frequently occurs that may ultimately lead to cachexia as a serious co-morbidity, indicating severely impaired functional capacity, health status and increased mortality. Increased energy expenditure due to mechanic and metabolic inefficiency and systemic inflammation are determinants of a hypermetabolic state that is not balanced by dietary intake. Anorexia may importantly contribute to weight loss in COPD, however, the association between immune and hormonal derangement and altered appetite has not been studied in detail.

AIM

The aim of the present study was to investigate whether anorexia in COPD is related to inflammation and hormonal derangement in association to weight loss.

METHODS

We prospectively enrolled 103 consecutive patients with COPD (age 59.8+/-1.3 years, 35% female, mean FEV1 38.3+/-1.7%) in comparison to healthy controls of similar age (n=15).

RESULTS

In 34 patients (33%) cachexia was diagnosed (weight loss >7.5%, BMI < or = 24 kg/m2). Cachectic COPD patients had lower BMI (19.0+/-0.5 vs 25.6+/-0.7 kg/m2) and impaired lung function (FEV1 31+/-2% vs 42+/-2%, FVC 51+/-3 vs 59+/-3%, both p<0.001). Inflammatory immune activation (IL-6 and IL-6/IL-10 ratio) was significantly higher in cachectic COPD patients. Analysis of the extent of anorexia (visual analogue scale) revealed that cachectic COPD patients had significantly decreased subjective desire to eat compared to non-cachectic patients (3.5+/-0.3 vs 6.3+/-0.2, p<0.001). Patients with COPD and cachexia showed evidence of acquired GH resistance (decreased IGF-1/GH ratio) and insulin resistance (HOMA). Anorexia showed a direct correlation with the IGF-1/GH ratio (r=0.34, p<0.05) and was further related to BMI and % weight loss (both p<0.001).

CONCLUSION

In COPD anorexia relates to hormonal derangement and inflammatory immune activation. Anorexia contributes to development of cachexia. The concept of appetite stimulating therapy emerges as a novel therapeutic option in cachectic COPD patients.

Body composition in patients with chronic obstructive pulmonary disease: which method to use in clinical practice?

The objective of the present study was to compare anthropometry with bioelectrical impedance (BIA) in relation to densitometry (dual-energy X-ray absorptiometry; DEXA) as methods of nutritional assessment and body composition in out-patients with chronic pulmonary obstructive disease (COPD). We conducted a cross-sectional clinical study with sixty-one patients with COPD (forty-two men and nineteen women), mean age of 66.5 (sd 7.9) years and forced expiratory volume in 1 s of 1.3 (sd 0.6) litres (52.2 (sd 19.8) % predicted), referred to the Pulmonary Rehabilitation Center. The patients were evaluated regarding nutrition status and body composition as determined by anthropometry, BIA and DEXA. In the results, 34.4 % showed mild obstruction, 31.2 %, moderate and 34.4 %, severe obstruction. According to the BMI (mean 24.5 (sd 4.5) kg/m2), 45.9 % of the patients exhibited normal weight, while 27.9 % were underweight and 26.2 % were obese. Related to fat-free mass (FFM), anthropometry and BIA compared with DEXA presented high correlations (r 0.96 and 0.95 respectively; P < 0.001) and high reliability between the methods (alpha 0.98; P < 0.001). Agreement analysis between the methods shows that anthropometry overestimates (0.62 (sd of the difference 2.89) kg) while BIA underestimates FFM (0.61 (sd of the difference 2.82) kg) compared with DEXA. We concluded that according to the nutritional diagnosis, half of our population of patients with COPD showed normal weight, while the other half comprised equal parts obese and underweight patients. Body composition estimated by BIA and anthropometry presented good reliability and correlation with DEXA; the three methods presented satisfactory clinical accuracy despite the great disparity of the limits of agreement.

The pathophysiology of emphysema: considerations for critical care nursing practice

Emphysema is caused by exposure to cigarette smoking as well as alpha(1)-antitrypsin deficiency. It has been estimated to cost the National Health Service (NHS) in excess of 800 million pounds per year in related health care costs. The challenges for Critical Care nurses are those associated with dynamic hyperinflation, Auto-PEEP, malnutrition and the weaning from invasive and non-invasive mechanical ventilation. In this paper we consider the impact of the pathophysiology of emphysema, its effects on other body systems as well as the impact acute exacerbations have when patients are admitted to the Intensive Care Unit.

Dietary problems in patients with severe chronic obstructive pulmonary disease

BACKGROUND AND AIMS

Low body weight and low fat-free mass-index (FFMI) are common in patients with severe chronic obstructive pulmonary disease (COPD). Several factors seem to contribute. The aims of the present observational study were to investigate dietary problems in patients with severe COPD and to compare dietary problems to nutritional status, energy intake and smoking habits.

METHODS

Nutritional status was assessed in 73 stable outpatients using body mass index and FFMI by single-frequency bioelectrical impedance. Lung function, smoking habits, energy intake and dietary problems were also assessed.

RESULTS

The most frequently reported dietary problems were 'anorexia', 'dyspeptic symptoms other than diarrhoea', 'slimming', 'fear of gaining weight', 'dyspnoea', 'diarrhoea', 'depression, anxiety, solitude'. Smoking habits and gender had impact on the kind of dietary problems reported. Reporting two dietary problems correlated to low FFMI, whereas reporting one or more dietary problems correlated to decreased energy intake.

CONCLUSION

Dietary problems are common in the group studied and related to smoking habits and gender. Dietary problems affect energy intake and FFMI negatively. It is important to recognize dietary problems and to offer intervention of the dietary problems as a part of the dietary intervention.

Nutritional management of the patient with chronic obstructive pulmonary disease

The prevalence and prognostic importance of malnutrition in chronic obstructive pulmonary disease (COPD), the factors that contribute to development of nutritional depletion, and the available evidence regarding effects of nutrition support in these patients are the subjects of this review. Nutritional depletion, as indicated by weight loss and loss of lean body mass, is a common complication of advanced COPD (particularly, but not limited to, the emphysematous type). Low body weight or recent weight loss and in particular depleted lean body mass in patients with COPD have been shown to be independent predictors of mortality, outcomes after acute exacerbations, hospital admission rates, and need for mechanical ventilation. The factors thought to contribute to nutritional depletion in these patients include elevated resting and activity-related energy expenditure, reduced dietary intake relative to resting energy expenditure, accelerated negative nitrogen balance, particularly during acute exacerbations of COPD, medication effects, and perhaps most importantly an elevated systemic inflammatory response. Studies to date suggest that, although it can help limit weight loss and negative energy balance in these patients, the effect of nutritional supplementation alone on clinically significant outcomes such as pulmonary function and exercise capacity is minimal. However, nutritional supplementation may have a role in the management of COPD when provided as part of an integrated rehabilitation program incorporating a structured exercise component as an anabolic stimulus.

Investigation into the nutritional status, dietary intake and smoking habits of patients with chronic obstructive pulmonary disease

BACKGROUND AND AIMS

Weight loss and reduced fat-free mass are prevalent amongst patients with chronic obstructive pulmonary disease (COPD). However, the causes of this weight loss are not clear. The aims of this study are to investigate the factors affecting body weight and dietary intake in a group of outpatients with COPD, and to investigate any differences between adequately nourished and malnourished patients.

METHODS

In 103 stable outpatients, nutritional status was assessed using Body Mass Index (BMI) and upper arm anthropometry. Lung function, smoking status, exercise tolerance, dietary intake, dietary problems and health-related quality of life were assessed. Patients were classed as either adequately nourished or malnourished.

RESULTS

Twenty-three per cent of subjects were classed as malnourished. The malnourished subjects had lower lung function measurements, suffered more dietary problems and had lower nutritional intake compared with the adequately nourished subjects. They also had poorer fatigue scores. In linear regression analysis, the factors that had the most effect on BMI were a low transfer factor, presence of early satiety, and being a current smoker.

CONCLUSION

Important differences were found between adequately nourished and malnourished subjects. These differences move us closer to understanding how best to screen and treat this group of patients.

Body composition and resting energy expenditure in clinically stable, non-weight-losing patients with severe emphysema

STUDY OBJECTIVES

To characterize the metabolic status of weight-stable and clinically stable individuals with advanced emphysema.

PATIENTS

Seventy-nine patients with severe emphysema (FEV(1), 29 +/- 13% of predicted [mean +/- SD]) evaluated for enrollment in the National Emphysema Treatment Trial and 20 age-matched healthy subjects were studied.

SETTING

Pulmonary function laboratory of university-affiliated teaching hospital.

INTERVENTIONS

Data collection.

MEASUREMENTS AND RESULTS

We measured lung function, body composition, serum leptin levels, serum tumor necrosis factor receptors (sTNF-Rs), resting oxygen consumption (RVO(2)) normalized to weight in kilograms (RVO(2)/kg), and RVO(2) normalized to fat-free mass (FFM) [RVO(2)/FFM]. The patient group and healthy group had similar age, body mass index (BMI), and body composition. RVO(2)/kg, RVO(2)/FFM, and sTNF-R levels were higher in patients compared to healthy subjects. There were no differences in serum leptin levels between emphysematous and healthy subjects, and there was no correlation between leptin and sTNF-R and RVO(2)/kg. Furthermore, both groups had similar gender-related differences in FFM, percentage of body fat, and serum leptin levels. Patients with lower BMI showed the greatest differences from control subjects in RVO(2)/kg.

CONCLUSION

In weight-stable subjects with advanced emphysema, RVO(2)/kg and RVO(2)/FFM were higher compared to healthy subjects, especially in those with BMI in the lower end of the normal range. RVO(2)/kg and RVO(2)/FFM did not correlate with leptin or sTNF-R levels. These data show that a higher metabolic rate is found in patients with emphysema who are clinically and weight stable. Thus, hypermetabolism is a feature of the disease and not sufficient to lead to weight loss.

Megestrol acetate stimulates weight gain and ventilation in underweight COPD patients

STUDY OBJECTIVES

To assess the effect of megestrol acetate (MA), a progestational appetite stimulant commonly used in patients with AIDS and cancer, on body weight and composition, respiratory muscle strength, arterial blood gas levels, and subjective perceptions in COPD patients.

DESIGN AND SETTING

Prospective, double-blind, randomized, placebo-controlled trial conducted on an outpatient basis at 18 sites.

PATIENTS

Underweight (< 95% ideal body weight) COPD patients > or = 40 years old.

INTERVENTIONS

Either MA, 800 mg/d oral suspension, or placebo at a 1:1 ratio for 8 weeks.

RESULTS

Of 145 randomized patients (63% men), 128 patients completed the trial. Body weight increased by 3.2 kg in the MA group and 0.7 kg in the placebo group (p < 0.001). Anthropometric and dual-energy radiograph absorptiometry assessments confirmed that weight gain was mainly fat. Spirometry and maximal voluntary ventilation showed no significant changes from baseline in either group, and the difference in the change in maximum inspiratory pressure between groups was not significant. The 6-min walk distances did not differ statistically between groups at week 2 and week 4, but were greater in the placebo group at week 8 (p = 0.012). Consistent with the known ability of MA to stimulate ventilation, PaCO(2) decreased (4.6 mm Hg, p < 0.001) and PaO(2) increased (2.8 mm Hg, p < 0.04) in the MA group. Questionnaires revealed that body image and appetite improved in the MA group but not the placebo group. Adverse event frequency and type were similar in both groups, but cortisol and testosterone (in men) levels decreased substantially in the MA group.

CONCLUSIONS

We conclude that MA safely increased appetite and body weight, stimulated ventilation, and improved body image in underweight COPD patients, but did not improve respiratory muscle function or exercise tolerance.

A critical approach to nutritional assessment in critically ill patients

BACKGROUND AND AIMS

Nutritional assessment enhances quality of nutritional care, however, its practice bemuses professionals. This prospective study aimed to identify a feasible/informative nutritional parameter in intensive care.

METHODS

44 patients (APACHE II: 23.8+/-10.1), age 58.4+/-18.6 years, were evaluated at admission: clinical data, height, weight, body mass index (BMI), tricep skinfold thickness, mid-arm circumference (MAC), mid-arm muscle circumference (MAMC), albumin, total protein and lymphocyte count. Anthropometric parameters' performance was evaluated isolated or assembled according to Blackburn and McWhirter criteria.

RESULTS

Oedema increased %IW and BMI (P<0.01); muscle depletion was frequent and agreed with MAC or MAMC ranked by both criteria, P=0.02. %IW and BMI overestimated well-nourished/overweight patients, whilst arm anthropometry, mostly MAC/MAMC, shifted towards +/-50% malnutrition. Patients were not equally ranked by both criteria; McWhirter's by using percentiles clarified the distribution and showed agreement between MAC and MAMC, P=0.007, unlike Blackburn's. Mortality was higher in patients with MAC<5th percentile, P=0.003; MAC;<15th percentile was able to predict mortality and major complications. In invasive ventilated patients, severe muscle depletion was associated with mortality, P=0.05.

CONCLUSION

In intensive care most nutritional assessment methods are useless; MAC is simple, feasible and if classified by percentiles may prove functional with prognostic value.

The impact of nutritional depletion in chronic obstructive pulmonary disease

Nutritional depletion is prevalent in patients with advanced chronic obstructive pulmonary disease (COPD). These nutritional abnormalities are pronounced in patients with the "emphysematous" form of COPD on chronic corticosteroid therapy. The pathophysiologic mechanisms for the involuntary weight loss appear to be multifactorial. Clinical research has revealed that nutritional depletion in advanced COPD is associated with an increased morbidity and mortality. This review will address the implications of nutritional depletion in addition to potential therapeutic options.

Nutritional intervention in COPD: a systematic overview

OBJECTIVE

We conducted a systematic overview of randomized controlled trials (RCTs) to clarify the contribution of nutritional supplementation for patients with stable COPD.

METHODS

RCTs were identified from several sources, including the Cochrane Airways Group register of RCTs, a hand search of abstracts presented at international meetings, and consultation with experts. Two reviewers independently selected trials for inclusion, assessed quality, and extracted the data.

RESULTS

Twenty-one reports were classified according to the type, duration of supplementation, and the presence of anabolic substances. High carbohydrate meals were associated with an increase in carbon dioxide production and a decrease in exercise capacity. Short-term crossover studies in which diets of various compositions were administered supported the notion that high carbohydrate loads increase the stress on the ventilatory system. The influence of longer-term supplementation (> 2 weeks) on weight, anthropometry, and exercise capacity varied, without there being a consistent effect. Lean body weight was only occasionally reported and health-related quality of life too rarely to be included as an outcome. The influence of recombinant human growth hormone was disappointing. Anabolic steroids increased body weight and lean body mass, but had little influence on exercise capacity.

CONCLUSION

This systematic overview in patients with COPD supports the notion that those with marginal ventilatory reserve might benefit from a dietary regimen in which a high percentage of calories are supplied by fat. Although there are reports of the benefits of nutritional repletion, trials of > 2 weeks failed to show consistent benefit on body weight. Evaluating nutritional repletion is hampered by the absence of information regarding body composition, exercise, and health-related quality of life. Growth hormone has not been shown to be useful. Further studies are needed to refine the beneficial effects of anabolic steroids as adjunctive agents together with nutritional support and exercise.

Peripheral muscle dysfunction in chronic obstructive pulmonary disease

Peripheral muscle dysfunction is a common systemic complication of moderate to severe COPD and may contribute to disability, handicap, and premature mortality. In contrast to the lung impairment, which is largely irreversible, peripheral muscle dysfunction is potentially remediable with exercise training, nutritional intervention, oxygen, and anabolic drugs. Therapeutic success is often incomplete, however, and a better understanding of the mechanisms involved in the development of peripheral muscle dysfunction in COPD is needed to help develop innovative and more effective therapeutic strategies.

Weight gain after lung volume reduction surgery is not correlated with improvement in pulmonary mechanics

STUDY OBJECTIVES

Malnutrition and low body weight are common in patients with emphysema. Previous work has demonstrated correlation between severity of airflow obstruction and body weight. Lung volume reduction surgery (LVRS) is a recent advance in the treatment of patients with severe emphysema that results in improved pulmonary function. We formed the hypothesis that improved lung mechanics after LVRS would result in body weight gain.

DESIGN

Retrospective chart review.

PATIENTS

All patients who underwent bilateral LVRS for severe emphysema at the University of Michigan between January 1995 and April 1996 were eligible for the study.

MEASUREMENTS AND RESULTS

Pulmonary function and body weight were measured preoperatively and at 3, 6, and 12 months postoperatively for patients who underwent bilateral LVRS between January 1995 and April 1996. The average weight gain in 38 patients returning for 12 months of follow-up was 3.8 +/- 0.9 kg, or 6.2% of the preoperative weight. Women gained significantly more weight than men (9.2 vs 2.2%, respectively) at 1 year. Interestingly, there was no correlation between change in weight and postoperative change in FEV(1), FVC, residual volume (RV), total lung capacity (TLC), or RV/TLC at 12 months. However, there was a statistically significant correlation between weight gained and improvement in diffusion of carbon monoxide measured 12 months postoperatively.

CONCLUSIONS

This study shows that patients with severe emphysema gain weight after LVRS. These changes were independent of changes in pulmonary mechanics but may be a result of improved gas exchange. These findings provide further information about benefits of LVRS in patients with advance emphysema that are beyond simple changes in pulmonary function.

Growth hormone improves body mass recovery with refeeding after chronic undernutrition-induced muscle atrophy in aging male rats

The effects of growth hormone (GH) administration and refeeding after chronic undernutrition (UN) were investigated in Fischer 344 male rats aging into senescence (24.5 mo of age) during UN initiated at 12.5 mo of age that produced muscle atrophy and a 50% decrease in body mass. Muscle mass, protein, myosin heavy-chain (MHC) composition and circulating testosterone levels were measured and compared to controls with free access to food. Within 9 wk, refeeding + GH restored body mass to control levels, whereas it was still decreased with refeeding alone. By 24.5 mo of age, refeeding alone restored body mass, while addition of GH resulted in overshoot. UN uniformly decreased mass of the gastrocnemius, extensor digitorum longus, soleus and diaphragm muscles to 50-60% of controls. Refeeding and refeeding + GH restored these losses with some overshoot of gastrocnemius muscle suggesting hypertrophy. UN more than doubled slow Type I MHC composition and approximately halved fast Type IIB and IIX MHC in the deep gastrocnemius muscle while it increased Type IIA MHC in the diaphragm. Refeeding and refeeding + GH reversed these shifts. MHC shifts in the extensor digitorum longus and soleus muscles were not statistically significant, whereas UN increased fast Type IIA MHC followed by decrease with refeeding + GH. UN decreased testosterone levels to nearly zero followed by restoration with refeeding and refeeding + GH. We conclude that the phenotype of mixed-MHC muscles such as the gastrocnemius and diaphragm are most affected by chronic UN, which is reversible with refeeding and refeeding + GH. These alterations were associated with changes in circulating testosterone, which may be a key regulatory element in these processes.

Growth hormone restores aged diaphragm myosin composition and performance after chronic undernutrition

The effects of growth hormone (GH) on diaphragm muscle myosin heavy chain (MHC) composition and mechanical performance were investigated in Fischer 344 male rats aged to senescence (24.5 mo of age). Chronic undernutrition (UN), refeeding (RF), and RF+GH were compared with ad libitum feeding by using a model of UN that produced a 50% decrease in body weight over a 12-mo period. The effect of aging was assessed by comparing MHC composition of ad libitum-fed rats at 12 and 24.5 mo of age. At senescence, significant decreases in slow type I (-23%) and fast type IIA (-31%) MHC had occurred with aging. Conversely, UN over this aging period increased types I (32-73%) and IIA (22-23%) MHC and decreased fast types IIB (32-54%) and IIX (30-31%) MHC. RF and RF+GH reversed these shifts back toward control values. At senescence, maximal specific force, maximal velocity, and specific power capacity were not different across treatment groups. During repetitive isotonic contraction trials, the diaphragms of UN rats maintained power production over time (54% of initial power at 60 s), whereas the power production of diaphragms of ad libitum-fed rats fell to 0% (P < 0.05). In comparison with UN rats, the diaphragms of RF and RF+GH rats produced 23 (not significant) and 11% (P < 0.05) of initial power, respectively, suggesting that RF+GH treatment restored performance characteristics after UN. We conclude that RF+GH can reverse alterations in MHC composition and mechanical performance produced by chronic UN in the aged rat diaphragm.