Sarcopenia and a physiologically low respiratory quotient in patients with cirrhosis: a prospective controlled study

Abstract

Patients with cirrhosis have increased gluconeogenesis and fatty acid oxidation that may contribute to a low respiratory quotient (RQ), and this may be linked to sarcopenia and metabolic decompensation when these patients are hospitalized. Therefore, we conducted a prospective study to measure RQ and its impact on skeletal muscle mass, survival, and related complications in hospitalized cirrhotic patients. Fasting RQ and resting energy expenditure (REE) were determined by indirect calorimetry in cirrhotic patients (n = 25), and age, sex, and weight-matched healthy controls (n = 25). Abdominal muscle area was quantified by computed tomography scanning. In cirrhotic patients we also examined the impact of RQ on mortality, repeat hospitalizations, and liver transplantation. Mean RQ in patients with cirrhosis (0.63 ± 0.05) was significantly lower (P < 0.0001) than healthy matched controls (0.84 ± 0.06). Psoas muscle area in cirrhosis (24.0 ± 6.6 cm(2)) was significantly (P < 0.001) lower than in controls (35.9 ± 9.5 cm(2)). RQ correlated with the reduction in psoas muscle area (r(2) = 0.41; P = 0.01). However, in patients with cirrhosis a reduced RQ did not predict short-term survival or risk of developing complications. When REE was normalized to psoas area, energy expenditure was significantly higher (P < 0.001) in patients with cirrhosis (66.7 ± 17.8 kcal/cm(2)) compared with controls (47.7 ± 7.9 kcal/cm(2)). We conclude that hospitalized patients with cirrhosis have RQs well below the traditional lowest physiological value of 0.69, and this metabolic state is accompanied by reduced skeletal muscle area. Although low RQ does not predict short-term mortality in these patients, it may reflect a decompensated metabolic state that requires careful nutritional management with appropriate consideration for preservation of skeletal muscle mass.

Treatment to Improve Nutrition and Functional Capacity Evaluation in Liver Transplant Candidates

“…Consistently, a number of abnormalities have been reported in cirrhosis including decreased gluconeogenesis, increased lactate production during exercise, and lower VO 2 max compared to controls [22, 29]. These are accompanied by reduced exercise capacity.…”

“…Overall, the most convincing data supports reduced whole body protein synthesis and conflicting data on protein breakdown in patients with cirrhosis. Cirrhosis is also believed to be a state of accelerated starvation based on whole body studies on substrate utilization [17, 29]. Early postprandial lowering of the respiratory quotient indicates a more rapid shift to fat as a primary fuel for energy [46].…”

“…However, one of the major goals is reversal of sarcopenia and there is a need for rapid assessment of the efficacy of interventions is critical. Based on our studies in cirrhotics in whom low RQ is associated with reduced muscle mass, it could be argued that the goal of interventions is to increase the RQ so that muscle protein synthesis is increased and breakdown is reduced [29]. …”

Nutrition and Alcoholic Liver Disease

“…Skeletal muscle area determined from a single section at the 3 rd or 4 th lumbar vertebra on CT or MRI has been shown to reflect whole body muscle mass 26 . Using these methods, cirrhotic patients have lower muscle mass and fat mass compared to controls 28,29 . Even though most studies to date have included alcoholic cirrhosis as part of the cohort of cirrhotic patients studied, there are no published data on differences in prevalence of sarcopenia defined by direct muscle mass measurements stratified by etiology of cirrhosis.…”

“…Cirrhosis is a state of accelerated starvation that is defined not by appetite, rather by the low respiratory quotient, that is the ratio of the oxygen consumed and carbon dioxide released 28,30 . Unlike that observed in healthy subjects, post-prandial reduction in RQ occurs much earlier in cirrhotics suggesting a more rapid fatty acid and amino acid oxidation as a source of energy 30,31 .…”