Feeding lactating primiparous sows to establish three divergent metabolic states: II. Effect on nitrogen partitioning and skeletal muscle composition

We established an experimental model to study nitrogen (N) partitioning in lactating primiparous sows alimented to three levels of nutrient intake. Thirty-six sows fitted with a gastric cannula and fed a 15.4 MJ DE/kg and 18.6% CP diet were allocated to one of three treatments after farrowing: 1) ad libitum-fed; 2) restricted-fed to 55% of the ad libitum feed intake; and 3) superalimented to at least 125% of the ad libitum feed intake. These feed intakes were successfully achieved throughout lactation. Nitrogen balance was studied for three 5-d periods starting on d 2, 11, and 19 of lactation, and a triceps muscle biopsy was taken on d 26. For all treatments, N intake increased, milk N production increased, urinary N losses decreased, but fecal N losses increased as the 28-d lactation progressed. Restricted-fed sows had the lowest fecal N and urinary losses and mobilized the most maternal protein (-23.0 vs -7.4 +/- 6.5 g N/d for ad libitum-fed sows) during lactation. As a consequence of these economies, and extensive protein mobilization, restricted-fed sows were able to maintain milk N production similar to that of sows on the other treatments. Superalimented sows did not mobilize protein, had the poorest protein digestibility, directed the least digestible N toward milk (40.1 vs 78.3% in restricted-fed sows), and produced amounts of milk N similar to those produced by sows on the other treatments. The treatment differences in N retention measured by N balance were reflected in differences in skeletal muscle variables and urinary creatinine. Skeletal muscle cell size (protein:DNA ratio) and protein synthetic capacity (RNA:DNA ratio) increased in response to feed intake. The protein:DNA ratio increased (P < .01) linearly and the RNA:DNA ratio increased (P < .05) in a curvilinear manner. These data suggest that primiparous sows partition additional retained N toward their maternal reserves rather than milk N. They also suggest that sows fed inadequate N intakes maintain milk production by mobilizing maternal protein reserves. Such sows also conserve maternal N during lactation, possibly by reducing muscle protein synthesis

Insulin-like growth factor-1 and insulin resistance in skeletal muscles of adult and old rats

International audienc

Swelling of sarcoplasmic reticulum after isometric contractions in rat semimembranosus lateralis muscle

The decline in isometric force, swelling of sarcoplasmic reticulum and loss of desmin was measured in semimembranosus lateralis muscle of male Wistar rats immediately after a short series of brief (500 ms) maximal isometric contractions. For the active muscle, the series ended below (protocol A) and just over muscle optimum length (protocol AA). In one protocol, the muscle remained passive and was extended to lengths just over muscle optimum length (protocol P). After all experimental protocols, no loss of desmin was observed and sarcomere appearance was normal. Protocol A produced swelling (87%) of the sarcoplasmic reticulum but no decline in isometric force. Protocol AA produced larger swelling (147%) of the sarcoplasmic reticulum and an isometric force decline (<49%) at short muscle lengths. Swelling of sarcoplasmic reticulum was observed mainly in the periphery of muscle fibres. Protocol P did not result in swelling of the sarcoplasmic reticulum and isometric force decline. It is concluded that swelling of the sarcoplasmic reticulum in the periphery of muscle fibres after brief maximal isometric contractions is associated with muscle force and not muscle length

Ectopic fat in liver and skeletal muscle is associated with shorter overall survival in patients with colorectal liver metastases

BACKGROUND: Myosteatosis has been associated with shorter overall survival in cancer patients. The increase in ectopic fat might not be limited to skeletal muscle only and might also extend to other sites such as the liver, resulting in non‐alcoholic fatty liver disease (NAFLD). In this study, we assessed the relationship between myosteatosis and NAFLD and their association with overall survival in patients with colorectal liver metastases undergoing partial hepatectomy. METHODS: Patients were selected from a prospective cohort of 289 consecutive patients with colorectal liver metastases. All patients with a preoperative computed tomography (CT)‐scan and liver biopsy obtained during surgery were included. If available a second pre‐operative CT scan was used to calculate changes in body composition over time. Muscle radiation attenuation was defined as the average Hounsfield units on CT of all muscle tissue at the L3 level. Liver biopsies were graded by a liver pathologist using the steatosis, activity, and fibrosis scoring system for NAFLD. RESULTS: Two‐hundred and eighteen patients had an available liver biopsy of which 131 patients had two available pre‐operative CT scans with an average time interval of 3.2 months. One‐hundred and thirty‐five (62%) biopsies were classified as NAFLD. In multivariable Cox‐regression analysis, NAFLD [hazard ratio (HR): 1.8, 95%‐confidence interval (CI) 1.0–3.0, P = 0.037], increase in myosteatosis (HR 1.8, 95%‐CI 1.1–2.9, P = 0.018), and skeletal muscle loss (HR 1.7, 95%‐CI 1.0–2.9, P = 0.035) were independently associated with shorter overall survival while high visceral adipose tissue fat content was associated with longer overall survival (HR: 0.7, 95%‐CI 0.5–0.9, P = 0.014). CONCLUSIONS: Ectopic fat content of liver as well as skeletal muscle tissue is independently associated with shorter overall survival in patients with colorectal liver metastases, while increased visceral adipose tissue fat content is associated with longer overall survival

Ectopic fat in liver and skeletal muscle is associated with shorter overall survival in patients with colorectal liver metastases

Background Myosteatosis has been associated with shorter overall survival in cancer patients. The increase in ectopic fat might not be limited to skeletal muscle only and might also extend to other sites such as the liver, resulting in non-alcoholic fatty liver disease (NAFLD). In this study, we assessed the relationship between myosteatosis and NAFLD and their association with overall survival in patients with colorectal liver metastases undergoing partial hepatectomy.Methods Patients were selected from a prospective cohort of 289 consecutive patients with colorectal liver metastases. All patients with a preoperative computed tomography (CT)-scan and liver biopsy obtained during surgery were included. If available a second pre-operative CT scan was used to calculate changes in body composition over time. Muscle radiation attenuation was defined as the average Hounsfield units on CT of all muscle tissue at the L3 level. Liver biopsies were graded by a liver pathologist using the steatosis, activity, and fibrosis scoring system for NAFLD.Results Two-hundred and eighteen patients had an available liver biopsy of which 131 patients had two available pre-operative CT scans with an average time interval of 3.2 months. One-hundred and thirty-five (62%) biopsies were classified as NAFLD. In multivariable Cox-regression analysis, NAFLD [hazard ratio (HR): 1.8, 95%-confidence interval (CI) 1.0-3.0, P = 0.037], increase in myosteatosis (HR 1.8, 95%-CI 1.1-2.9, P = 0.018), and skeletal muscle loss (HR 1.7, 95%-CI 1.0-2.9, P = 0.035) were independently associated with shorter overall survival while high visceral adipose tissue fat content was associated with longer overall survival (HR: 0.7, 95%-CI 0.5-0.9, P = 0.014).Conclusions Ectopic fat content of liver as well as skeletal muscle tissue is independently associated with shorter overall survival in patients with colorectal liver metastases, while increased visceral adipose tissue fat content is associated with longer overall survival