Medium-Chain Triglycerides (8:0 and 10:0) Increase Mini-Mental State Examination (MMSE) Score in Frail Elderly Adults in a Randomized Controlled Trial.

BACKGROUND: Supplementation with medium-chain triglycerides (MCTs) was previously shown to increase muscle function in frail elderly individuals. OBJECTIVE: We aimed to assess effects of MCTs on cognition in such individuals. METHODS: We enrolled 64 elderly nursing home residents (85.5 ± 6.8 y; 13 men, 51 women; BMI 18.6 ± 2.5 kg/m2) in a 3-mo randomized, controlled, single-blinded, intervention trial. Participants were randomly allocated to 3 groups: the first group received supplemental L-leucine (1.2 g) and cholecalciferol (20 µg) enriched with 6 g/d of MCTs (LD + MCT group) as a positive control, the second group received 6 g/d of MCTs (MCT group) as the test nutrient, and the third group received 6 g/d of long-chain triglycerides (LCT group) as a negative control. Cognition (secondary outcome) was monitored 4 times: baseline, 1.5 and 3 mo after initiation of the intervention (intervention), and 1.5 mo after termination of the intervention (postintervention follow-up). Cognition scores were assessed by a linear mixed model (intention-to-treat analysis). RESULTS: MCT supplementation increased the Mini-Mental State Examination (MMSE) score by 3.5 points at the 3-mo intervention from baseline (P < 0.001) [intention-to-treat adjusted means: baseline 17.5 points (95% CI: 14.9, 20.2), 3-mo intervention 21.0 points (18.3, 23.7)], whereas LCT supplementation decreased the MMSE score by -0.7 points [baseline 17.0 points (95% CI: 14.4, 19.6), 3-mo intervention 16.3 points (13.6, 18.9)]. At the 3-mo intervention, the difference in MMSE score between the MCT (21.0 points) and LCT (16.3 points) groups became significant (P < 0.05). The increase in MMSE score in response to MCTs was 2.1-fold greater at 3 mo than at 1.5 mo and had returned to baseline value at the 4.5-mo postintervention follow-up visit. CONCLUSION: Supplementation with 6 g MCTs/d may improve the cognition of frail elderly individuals. This trial was registered at umin.ac.jp as UMIN000023302.

Medium-Chain Triglycerides in Combination with Leucine and Vitamin D Increase Muscle Strength and Function in Frail Elderly Adults in a Randomized Controlled Trial.

BACKGROUND: Sarcopenia, the loss of skeletal muscle mass, strength, and function, is common in elderly individuals but difficult to treat. OBJECTIVE: A combination of nutrients was investigated to treat sarcopenia in very frail elderly adults. METHODS: We enrolled 38 elderly nursing home residents (11 men and 27 women with a mean ± SD age of 86.6 ± 4.8 y) in a 3-mo randomized, controlled, single-blind, parallel group trial. The participants were randomly allocated to 3 groups. The first group received a daily l-leucine (1.2 g) and cholecalciferol (20 µg)-enriched supplement with 6 g medium-chain triglycerides (TGs) (MCTs) (LD + MCT); the second group received the same leucine and cholecalciferol-enriched supplement with 6 g long-chain TGs (LD + LCT); and the third group did not receive any supplements (control). The supplement and oils were taken at dinner, and changes in muscle mass, strength, and function were monitored. RESULTS: The increase in body weight in the LD + MCT (1.1 ± 1.0 kg) and LD + LCT (0.8 ± 1.1 kg) groups was greater than that in the control group (-0.5 ± 0.9 kg) (P < 0.05). After 3 mo, participants in the LD + MCT group had a 13.1% increase in right-hand grip strength (1.2 ± 1.0 kg, P < 0.01), a 12.5% increase in walking speed (0.078 ± 0.080 m/s, P < 0.05), a 68.2% increase in a 10-s leg open-and-close test performance (2.31 ± 1.68 n/10 s, P < 0.001), and a 28.2% increase in peak expiratory flow (53 ± 59 L/min, P < 0.01). No significant improvements in muscle mass, strength, or function were observed in the LD + LCT or control groups. CONCLUSION: The combined supplementation of MCTs (6 g), leucine-rich amino acids, and cholecalciferol at dinner may improve muscle strength and function in frail elderly individuals. This trial was registered at the University Hospital Medical Information Network Clinical Trials Registry as UMIN000017567.

Possible Extracellular Signals to Ameliorate Sarcopenia in Response to Medium-Chain Triglycerides (8:0 and 10:0) in Frail Older Adults.

In frail older adults (mean age 85 years old), a 3-month supplementation with a low dose (6 g/day) of medium-chain triglycerides (MCTs; C8:0 and C10:0) given at a meal increased muscle mass and function, relative to supplementation with long-chain triglycerides (LCTs), but it decreased fat mass. The reduction in fat mass was partly due to increased postprandial energy expenditure by stimulation of the sympathetic nervous system (SNS). However, the extracellular signals to ameliorate sarcopenia are unclear. The following three potential extracellular signals to increase muscle mass and function after MCT supplementation are discussed: (1) Activating SNS-the hypothesis for this is based on evidence that a beta2-adrenergic receptor agonist acutely (1-24 h) markedly upregulates isoforms of peroxisomal proliferator-activated receptor gamma coactivator-1alpha (PGC-1alpha) mRNAs, promotes mitochondrial biogenesis, and chronically (~1 month) induces muscle hypertrophy. (2) An increased concentration of plasma acyl-ghrelin stimulates growth hormone secretion. (3) A nitrogen-sparing effect of ketone bodies, which fuel skeletal muscle, may promote muscle protein synthesis and prevent muscle protein breakdown. This review will help guide clinical trials of using MCTs to treat primary (age-related) sarcopenia.

Marked phenotypic differences of endurance performance and exercise-induced oxygen consumption between AMPK and LKB1 deficiency in mouse skeletal muscle: changes occurring in the diaphragm.

LKB1 phosphorylates members of the AMP-activated protein kinase (AMPK) family. LKB1 and AMPK in the skeletal muscle are believed to regulate not only fuel oxidation during exercise but also exercise capacity. LKB1 was also required to prevent diaphragm fatigue, which was shown to affect exercise performance. Using mice expressing dominant negative (DN) mutants of LKB1 and AMPK, specifically in the skeletal muscle but not in the heart, we investigated the roles of LKB1 and AMPK activity in exercise performance and the effects of these kinases on the characteristics of respiratory and locomotive muscles. In the diaphragm and gastrocnemius, both AMPK-DN and LKB1-DN mice showed complete loss of AMPKα2 activity, and LKB1-DN mice showed a reduction in LKB1 activity. Exercise capacity was significantly reduced in LKB1-DN mice, with a marked reduction in oxygen consumption and carbon dioxide production during exercise. The diaphragm from LKB1-DN mice showed an increase in myosin heavy chain IIB and glycolytic enzyme expression. Normal respiratory chain function and CPT I activity were shown in the isolated mitochondria from LKB1-DN locomotive muscle, and the expression of genes related to fiber type, mitochondria function, glucose and lipid metabolism, and capillarization in locomotive muscle was not different between LKB1-DN and AMPK-DN mice. We concluded that LKB1 in the skeletal muscle contributes significantly to exercise capacity and oxygen uptake during exercise. LKB1 mediated the change of fiber-type distribution in the diaphragm independently of AMPK and might be responsible for the phenotypes we observed.

Medium-chain triglycerides (8:0 and 10:0) increase muscle mass and function in frail older adults: a combined data analysis of clinical trials.

Background: Three clinical trials have examined the chronic effects of medium-chain triglycerides (MCTs) on muscle mass and function in frail older adults (mean age 85 years old). However, significant increases in muscle mass and some muscle function relative to long-chain triglycerides (LCTs) have yet to be shown, possibly due to the small number of participants in each trial. Objective: We re-analyzed these previous clinical trials to clarify whether MCT supplementation can increase muscle mass and function. Analysis: After adding post hoc tests to the original report, we compared changes in measurement between the MCT and LCT groups in the first 2 trials and conducted a combined data analysis. Methods: In a combined data analysis, changes from baseline in measurements at the 3 months intervention in the MCTs- and LCTs-containing groups were assessed by analysis of covariance adjusted for baseline values of each measurement, age, sex, BMI, allocation to trial, habitual intakes in energy, protein, leucine, octanoic acid, decanoic acid, and vitamin D during the baseline period. The Mann-Whitney U test was used to analyze data on right and left knee extension times. Results: MCT supplementation for 3 months increased muscle function relative to LCT supplementation with and without an L-leucine (1.2 g) and vitamin D (cholecalciferol, 20 µg)-enriched supplement. In a combined data analysis (n = 29 in MCTs, n = 27 in LCTs), relative to supplementation with 6 g LCTs/day, supplementation with 6 g MCTs/day at dinner for 3 months significantly increased body weight (adjusted mean change from baseline: MCTs 1.2 vs. LCTs 0.2 kg, p = 0.023), right arm muscle area (MCTs 1.4 vs. LCTs-0.7 cm2, p = 0.002), left calf circumference (p = 0.015), right-hand grip strength (MCTs 1.6 vs. LCTs 0.3 kg, p = 0.017), right knee extension time (p = 0.021), left knee extension time (p = 0.034), walking speed (p = 0.002), and number of iterations in leg open and close test (p < 0.001) and decreased right triceps skinfold thickness (p = 0.016). Conclusion: In frail older adults, supplementation for 3 months with a low dose (6 g/day) of MCTs (C8:0 and C10:0) increased muscle mass and function. These findings indicate the potential for the practical use of MCTs in daily life in treating sarcopenia.

Adiponectin stimulates AMP-activated protein kinase in the hypothalamus and increases food intake.

Adiponectin has been shown to stimulate fatty acid oxidation and enhance insulin sensitivity through the activation of AMP-activated protein kinase (AMPK) in the peripheral tissues. The effects of adiponectin in the central nervous system, however, are still poorly understood. Here, we show that adiponectin enhances AMPK activity in the arcuate hypothalamus (ARH) via its receptor AdipoR1 to stimulate food intake; this stimulation of food intake by adiponectin was attenuated by dominant-negative AMPK expression in the ARH. Moreover, adiponectin also decreased energy expenditure. Adiponectin-deficient mice showed decreased AMPK phosphorylation in the ARH, decreased food intake, and increased energy expenditure, exhibiting resistance to high-fat-diet-induced obesity. Serum and cerebrospinal fluid levels of adiponectin and expression of AdipoR1 in the ARH were increased during fasting and decreased after refeeding. We conclude that adiponectin stimulates food intake and decreases energy expenditure during fasting through its effects in the central nervous system.

The ddY mouse: a model of postprandial hypertriglyceridemia in response to dietary fat.

Postprandial hyperlipidemia (lipemia) is a risk factor for atherosclerosis. However, mouse models of postprandial hyperlipidemia have not been reported. Here, we report that ddY mice display marked postprandial hypertriglyceridemia in response to dietary fat. In ddY mice, the fasting serum total triacylglyceride (TG) concentration was 134 mg/dl, which increased to 571 mg/dl after an intragastric safflower oil load (0.4 ml/mouse). In C57BL/6J mice, these concentrations were 57 and 106 mg/dl, respectively. By lipoprotein analysis, ddY mice showed increases in chylomicron- and VLDL-sized TG fractions (remnants and VLDL) after fat load. In C57BL/6J mice, post-heparin plasma LPL activity after fat load was increased 4.8-fold relative to fasting. However, in ddY mice, the increase of LPL activity after fat load was very small (1.2-fold) and not significant. High fat feeding for 10 weeks led to obesity in ddY mice. A difference in LPL amino acid composition between C57BL/6J and ddY mice was detected but was deemed unlikely to cause hypertriglyceridemia because hypertriglyceridemia was not evident in other strains harboring the ddY-type LPL sequence. These findings indicate that postprandial hypertriglyceridemia in ddY mice is induced by decreased LPL activity after fat load and is associated with obesity induced by a high-fat diet.

Delay of stroke onset by milk proteins in stroke-prone spontaneously hypertensive rats.

BACKGROUND AND PURPOSE: There is an inverse association between dairy food consumption and the incidence of stroke in observational studies. However, it is unknown whether the relationship is causal or, if so, what components in milk are responsible for reducing the incidence of stroke. METHODS: Stroke-prone spontaneously hypertensive rats were fed diets comprising amino acids, proteins from different sources (casein, whey, soybean, or egg white), or fats from different sources (butter, beef tallow, or cocoa butter) and the onset of stroke and lifespan were examined. RESULTS: Increasing the amount of dietary casein (5% to 55% of caloric intake) markedly delayed the onset of stroke. However, when stroke-prone spontaneously hypertensive rats were fed diets containing 55% of caloric intake as protein, rats fed casein or whey protein, a major component of milk, displayed a delayed onset of stroke compared with rats fed soybean or egg white protein. Rats fed an amino acids diet containing the same amino acids composition as casein did not have a delay in the onset of stroke. Increasing dietary fats, including butter as well as beef tallow and cocoa butter, did not affect the onset of stroke. All diets did not affect blood pressure in the early stage. CONCLUSIONS: These data suggest that the inverse association between dairy food consumption and incidence of stroke in epidemiological studies is causal and that peptides in milk protein, but not fat, might be responsible for this effect.

Bile acids induce energy expenditure by promoting intracellular thyroid hormone activation.

While bile acids (BAs) have long been known to be essential in dietary lipid absorption and cholesterol catabolism, in recent years an important role for BAs as signalling molecules has emerged. BAs activate mitogen-activated protein kinase pathways, are ligands for the G-protein-coupled receptor (GPCR) TGR5 and activate nuclear hormone receptors such as farnesoid X receptor alpha (FXR-alpha; NR1H4). FXR-alpha regulates the enterohepatic recycling and biosynthesis of BAs by controlling the expression of genes such as the short heterodimer partner (SHP; NR0B2) that inhibits the activity of other nuclear receptors. The FXR-alpha-mediated SHP induction also underlies the downregulation of the hepatic fatty acid and triglyceride biosynthesis and very-low-density lipoprotein production mediated by sterol-regulatory-element-binding protein 1c. This indicates that BAs might be able to function beyond the control of BA homeostasis as general metabolic integrators. Here we show that the administration of BAs to mice increases energy expenditure in brown adipose tissue, preventing obesity and resistance to insulin. This novel metabolic effect of BAs is critically dependent on induction of the cyclic-AMP-dependent thyroid hormone activating enzyme type 2 iodothyronine deiodinase (D2) because it is lost in D2-/- mice. Treatment of brown adipocytes and human skeletal myocytes with BA increases D2 activity and oxygen consumption. These effects are independent of FXR-alpha, and instead are mediated by increased cAMP production that stems from the binding of BAs with the G-protein-coupled receptor TGR5. In both rodents and humans, the most thermogenically important tissues are specifically targeted by this mechanism because they coexpress D2 and TGR5. The BA-TGR5-cAMP-D2 signalling pathway is therefore a crucial mechanism for fine-tuning energy homeostasis that can be targeted to improve metabolic control.

Effect of exercise intensity and AICAR on isoform-specific expressions of murine skeletal muscle PGC-1α mRNA: a role of ß2-adrenergic receptor activation.

There are three isoforms of peroxisome proliferator-activated receptor-γ coactivator 1α (PGC-1α) mRNA, which promotes mitochondrial biogenesis in skeletal muscles. Compared with PGC-1α-a mRNA, PGC-1α-b or PGC-1α-c mRNA is transcribed by a different exon 1 of the PGC-1α gene. In this study, effects of exercise intensity and 5-aminoimidazole-4-carboxamide-1ß-d-ribofuranoside (AICAR) on isoform-specific expressions of PGC-1α were investigated. All isoforms were increased in proportion to exercise intensity of treadmill running (10-30 m/min for 30 min). Preinjection of ß2-adrenergic receptor (AR) antagonist (ICI 118551) inhibited the increase in PGC-1α-b and PGC-1α-c mRNAs, but not the increase in PGC-1α-a mRNA, in response to high-intensity exercise. Although high-intensity exercise activated α2-AMP-activated protein kinase (α2-AMPK) in skeletal muscles, inactivation of α2-AMPK activity did not affect high-intensity exercise-induced mRNA expression of all PGC-1α isoforms, suggesting that activation of α2-AMPK is not mandatory for an increase in PGC-1α mRNA by high-intensity exercise. A single injection in mice of AICAR, an AMPK activator, increased mRNAs of all PGC-1α isoforms. AICAR increased blood catecholamine concentrations, and preinjection of ß2-AR antagonist inhibited the increase in PGC-1α-b and PGC-1α-c mRNAs but not the increase in PGC-1α-a mRNA. Direct exposure of epitrochlearis muscle to AICAR increased PGC-1α-a but not the -b isoform. These data indicate that exercise-induced PGC-1α expression was dependent on the intensity of exercise. Exercise or AICAR injection increased PGC-1α-b and PGC-1α-c mRNAs via ß2-AR activation, whereas high-intensity exercise increased PGC-1α-a expression by a multiple mechanism in which α2-AMPK is one of the signaling pathways.

Control of microvascular PO2 kinetics following onset of muscle contractions: role for AMPK.

The microvascular partial pressure of oxygen (Pmv(o(2))) kinetics following the onset of exercise reflects the relationship between muscle O(2) delivery and uptake (Vo(2)). Although AMP-activated protein kinase (AMPK) is known as a regulator of mitochondria and nitric oxide metabolism, it is unclear whether the dynamic balance of O(2) delivery and Vo(2) at exercise onset is dependent on AMPK activation level. We used transgenic mice with muscle-specific AMPK dominant-negative (AMPK-DN) to investigate a role for skeletal muscle AMPK on Pmv(o(2)) kinetics following onset of muscle contractions. Phosphorescence quenching techniques were used to measure Pmv(o(2)) at rest and across the transition to twitch (1 Hz) and tetanic (100 Hz, 3-5 V, 4-ms pulse duration, stimulus duration of 100 ms every 1 s for 1 min) contractions in gastrocnemius muscles (each group n = 6) of AMPK-DN mice and wild-type littermates (WT) under isoflurane anesthesia with 100% inspired O(2) to avoid hypoxemia. Baseline Pmv(o(2)) before contractions was not different between groups (P > 0.05). Both muscle contraction conditions exhibited a delay followed by an exponential decrease in Pmv(o(2)). However, compared with WT, AMPK-DN demonstrated 1) prolongation of the time delay before Pmv(o(2)) began to decline (1 Hz: WT, 3.2 ± 0.5 s; AMPK-DN, 6.5 ± 0.4 s; 100 Hz: WT, 4.4 ± 1.0 s; AMPK-DN, 6.5 ± 1.4 s; P < 0.05), 2) a faster response time (i.e., time constant; 1 Hz: WT, 19.4 ± 3.9 s; AMPK-DN, 12.4 ± 2.6 s; 100 Hz: WT, 15.1 ± 2.2 s; AMPK-DN, 9.0 ± 1.7 s; P < 0.05). These findings are consistent with the presence of substantial mitochondrial and microvascular dysfunction in AMPK-DN mice, which likely slows O(2) consumption kinetics (i.e., oxidative phosphorylation response) and impairs the hyperemic response at the onset of contractions thereby sowing the seeds for exercise intolerance.

The cathepsin L gene is a direct target of FOXO1 in skeletal muscle.

FOXO1 (forkhead box O1), a forkhead-type transcription factor whose gene expression is up-regulated in the skeletal muscle during starvation, appears to be a key molecule of energy metabolism and skeletal muscle atrophy. Cathepsin L, a lysosomal proteinase whose expression is also up-regulated in the skeletal muscle during starvation, is induced in transgenic mice overexpressing FOXO1 relative to wild-type littermates. In the present study, we conducted in vivo and in vitro experiments focusing on FOXO1 regulation of Ctsl (cathepsin L gene; CTSL1 in humans) expression in the skeletal muscle. During fasting and refeeding of C57BL/6 mice, Ctsl was regulated in parallel with FOXO1 in the skeletal muscle. Fasting-induced Ctsl expression was attenuated in transgenic mice overexpressing a dominant-negative form of FOXO1 or in skeletal-muscle-specific Foxo1-knockout mice relative to respective wild-type controls. Using C2C12 mouse myoblasts overexpressing a constitutively active form of FOXO1, we showed that FOXO1 induces Ctsl expression. Moreover, we found FOXO1-binding sites in both the mouse Ctsl and human CTSL1 promoters. The luciferase reporter analysis revealed that the mouse Ctsl and human CTSL1 promoters are activated by FOXO1, which is abolished by mutations in the consensus FOXO1-binding sites. Gel mobility-shift and chromatin immunoprecipiation assays showed that FOXO1 is recruited and binds to the Ctsl promoter. The present study provides in vivo and in vitro evidence that Ctsl is a direct target of FOXO1 in the skeletal muscle, thereby suggesting a role for the FOXO1/cathepsin L pathway in fasting-induced skeletal muscle metabolic change and atrophy.

Effects of fenofibrate and its combination with lovastatin on the expression of genes involved in skeletal muscle atrophy, including FoxO1 and its targets.

Fibrates and statins have been widely used to reduce triglyceride and cholesterol levels, respectively. Besides its lipid-lowering effect, the side effect of muscle atrophy after fibrate administration to humans has been demonstrated in some studies. Combination therapy with fibrates and statins also increases the risk of rhabdomyolysis. FoxO1, a member of the FoxO forkhead type transcription factor family, is markedly upregulated in skeletal muscle in energy-deprived states and induces muscle atrophy via the expression of E3-ubiquitine ligases. In this study, we investigated the changes in FoxO1 and its targets in murine skeletal muscle with fenofibrate treatment. High doses of fenofibrate (greater than 0.5% (wt/wt)) over one week increased the expression of FoxO1 and its targets in the skeletal muscles of mice and decreased skeletal muscle weight. These fenofibrate-induced changes were diminished in the PPARα knockout mice. When the effect of combination treatment with fenofibrate and lovastatin was investigated, a significant increase in FoxO1 protein levels was observed despite the lack of deterioration of muscle atrophy. Collectively, our findings suggest that a high dose of fenofibrate over one week causes skeletal muscle atrophy via enhancement of FoxO1, and combination treatment with fenofibrate and lovastatin may further increase FoxO1 protein level.

Dietary restriction suppresses inflammation and delays the onset of stroke in stroke-prone spontaneously hypertensive rats.

Subjects with high blood levels of inflammatory markers and patients with chronic inflammatory disorders are at high risk for stroke. Dietary restriction (DR) suppresses systemic inflammation to deter age-related chronic diseases. To examine whether DR delays the onset of stroke, 10-week-old stroke-prone spontaneously hypertensive rats (SHRSP) were assigned to either a control (ad libitum) or DR (50% diet of control) group, and day of stroke onset and lifespan were observed. DR markedly delayed the onset of stroke in SHRSP compared to control without affecting blood pressure. Day of stroke onset (median) in the control group was 34days, whereas it was 70days in the DR group. After 2weeks of DR and before the onset of stroke, plasma levels of interleukin-1beta (IL-1beta), tumor necrosis factor-alpha (TNF-alpha), and monocyte chemoattractant protein-1 (MCP-1) and their mRNA expression levels in adipose tissue were significantly lower in the DR rats than in the control rats. Intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) mRNA expression levels in cerebrovascular endothelial cells (CVECs), and macrophage infiltration into brain were lower in the DR rats than in the control rats. IL-1beta and TNF-alpha treatment in CVECs increased MCP-1, C-reactive protein, ICAM-1, and VCAM-1 mRNA and their protein levels in vitro. In conclusion, suppression of inflammation in response to DR may lead to a delay in the onset of stroke independent of any effect on blood pressure in SHRSP.

Ubiquitin C-terminal hydrolase-L3-knockout mice are resistant to diet-induced obesity and show increased activation of AMP-activated protein kinase in skeletal muscle.

Obesity results from the dysregulation of energy balance throughout the entire body. Although the ubiquitin system participates in many cellular processes, its contribution to the balance of energy in the body remains poorly understood. Here, we show that ubiquitin C-terminal hydrolase (UCH)-L3, one of the deubiquitinating enzymes, contributes to the regulation of metabolism. Uchl3(-/-) mice displayed a reduction of adipose tissue mass and were protected against high-fat diet (HFD)-induced obesity and insulin resistance. Uchl3(-/-) mice given both a normal chow and an HFD had an increased whole-body energy expenditure accounting for the reduction of adipose tissue mass. Activation of AMP-activated protein kinase (AMPK) in skeletal muscle has been reported to increase fatty acid beta-oxidation, leading to the elevation of the whole-body energy expenditure. Consistently, increased activation of AMPK and fatty acid beta-oxidation was observed in skeletal muscle of Uchl3(-/-) mice. Mouse embryonic fibroblasts derived from Uchl3(-/-) mice also showed increased activation of AMPK, indicating that UCH-L3 is involved in a cell-autonomous down-regulation of AMPK. These results suggest a role for UCH-L3 in the regulation of AMPK activity and whole-body energy metabolism.

Dietary protein, but not carbohydrate, is a primary determinant of the onset of stroke in stroke-prone spontaneously hypertensive rats.

BACKGROUND AND PURPOSE: Previously, an inverse association has been found between the dietary proportion of protein or fat and incidence of intracerebral hemorrhage. A positive association has been found with respect to carbohydrate intake. To examine what changes in macronutrient intake are causative, animal studies were conducted. METHODS: Stroke-prone spontaneously hypertensive rats (SHRSP) were fed diets with varying ratios of macronutrients ad libitum, and the onset of stroke was examined. RESULTS: When 10% of calories were from fat, rats fed a high-protein/low-carbohydrate diet (55% calories from protein) had a delayed onset of stroke, whereas rats fed a low-protein/high-carbohydrate diet (5% calories from protein) had an accelerated onset of stroke. When 30% of calories were from carbohydrate, a marked delay in the onset of stroke was observed when the diet was high in protein. When 85% of calories were from carbohydrate, rats fed 7.5% of calories as protein displayed an accelerated onset of stroke. When 20% of calories were from protein, increased fat content did not affect the onset of stroke. However, with a fat-free diet, when 20% of calories were from protein, the onset of stroke was delayed, whereas when 10% of calories were from protein, the onset of stroke was accelerated. CONCLUSIONS: The amount of protein, but not of carbohydrate and fat, is a primary determinant of the onset of stroke. However, when calories from protein are relatively low in the diet (10%), fat is necessary to delay the onset of stroke in SHRSP.

Medium-chain triglycerides (8:0 and 10:0) are promising nutrients for sarcopenia: a randomized controlled trial.

BACKGROUND: The combined supplementation of medium-chain triglycerides (MCTs), l-leucine-rich amino acids, and cholecalciferol was previously shown to increase muscle strength and function in frail elderly individuals. OBJECTIVE: We examined whether treatment with MCTs alone is sufficient to increase muscle strength and function and activities of daily living (ADL) in such individuals. METHODS: We enrolled 64 elderly nursing home residents (85.5 ± 6.8 y) in a 3-mo randomized, controlled, single-blinded intervention trial. The participants were randomly assigned to 3 groups: the first group received supplemental l-leucine (1.2 g) and cholecalciferol (20 µg) enriched with 6 g/d of MCTs (LD + MCT group) as a positive control, the second group received 6 g/d of MCTs (MCT group) as a target, and the third group received 6 g/d of long-chain triglycerides (LCT group) as a negative control. Changes in muscle mass, strength, function, and ADL were monitored 4 times: at baseline, at 1.5 and 3 mo after initiation of the intervention (intervention), and 1.5 mo after termination of the intervention (washout). RESULTS: The 64 participants randomly assigned to the 3 groups were included in an intention-to-treat analysis. Forty-eight participants completed the study and were included in a per-protocol analysis. At 3 mo, participants in the MCT group had a 48.1% increase in 10-s leg open and close test performance [intention-to-treat adjusted means: MCT 2.28 n/10 s (1.37, 3.19) compared with LCT -0.59 n/10 s (-1.52, 0.35), P < 0.05], a 27.8% increase in a 30-s repetitive saliva swallowing test [MCT 0.5 n/30 s (0.1, 1.0) compared with LCT -0.5 n/30 s (-0.9, 0.0), P < 0.05], and a 7.5% increase in Functional Independence Measure score, a questionnaire for assessing ADL [MCT 5.6 points (1.3, 9.9) compared with LCT -6.6 points (-11.3, -2.0), P < 0.05]. CONCLUSION: MCTs (6 g/d) could increase the muscle strength and function of frail elderly individuals and also improve their ADL. This trial was registered at the University Hospital Medical Information Network Clinical Trial Registry as UMIN000023302.

Isoform-specific increases in murine skeletal muscle peroxisome proliferator-activated receptor-gamma coactivator-1alpha (PGC-1alpha) mRNA in response to beta2-adrenergic receptor activation and exercise.

Adrenergic receptor (AR) activation increases expression of peroxisome proliferator-activated receptor (PPAR)-gamma coactivator 1alpha (PGC-1alpha) mRNA, which may promote mitochondrial biogenesis in skeletal muscles. An AR-activated increase in PGC-1alpha mRNA was observed in exercise. PGC-1alpha mRNA is considered a single transcript (PGC-1alpha-a); however, a transcript search of PGC-1alpha in expressed sequence tag libraries revealed that two novel isoforms of PGC-1alpha mRNA, named PGC-1alpha-b and PGC-1alpha-c, were expressed in mice tissues. Compared with PGC-1alpha-a mRNA (a previously described isoform), PGC-1alpha-b or PGC-1alpha-c mRNA was transcribed by a different exon 1 of the PGC-1alpha gene and produced slightly smaller-sized proteins. PGC-1alpha-b or PGC-1alpha-c protein was functional; both isoforms possessed transcriptional activity and could coactivate PPARs, similar to those in PGC-1alpha-a in vitro. Transgenic mice overexpressing PGC-1alpha-b or PGC-1alpha-c in skeletal muscles showed increased gene expression related to mitochondrial biogenesis and fatty acid oxidation. In C57BL/6J mice, injection of the beta2-AR agonist clenbuterol increased PGC-1alpha-b and PGC-1alpha-c mRNA expression more than 350-fold, but not PGC-1alpha-a, in skeletal muscle. A single bout of exercise also increased PGC-1alpha-b and PGC-1alpha-c mRNAs, but not PGC-1alpha-a, in skeletal muscles. The increases in skeletal muscles in response to exercise were inhibited by pretreatment with the beta2-AR-specific inhibitor ICI 118,551. However, in liver, fasting increased PGC-1alpha-a mRNA, but not PGC-1alpha-b and PGC-1alpha-c mRNAs. These data indicate that AR activation is a major mechanism of an increase in PGC-1alpha expression in skeletal muscles, and the increase in PGC-1alpha mRNAs was isoform specific.

Regulation of SREBP1c gene expression in skeletal muscle: role of retinoid X receptor/liver X receptor and forkhead-O1 transcription factor.

Sterol regulatory element binding protein 1c (SREBP1c) is a master regulator of lipogenic gene expression in liver and adipose tissue, where its expression is regulated by a heterodimer of nuclear receptor-type transcription factors retinoid X receptor-alpha (RXRalpha) and liver X receptor-alpha (LXRalpha). Despite the potential importance of SREBP1c in skeletal muscle, little is known about the regulation of SREBP1c in that setting. Here we report that gene expression of RXRgamma is markedly decreased by fasting and is restored by refeeding in mouse skeletal muscle, in parallel with changes in gene expression of SREBP1c. RXRgamma or RXRalpha, together with LXRalpha, activate the SREBP1c promoter in vitro. Moreover, transgenic mice overexpressing RXRgamma specifically in skeletal muscle showed increased gene expression of SREBP1c with increased triglyceride content in their skeletal muscles. In contrast, transgenic mice overexpressing the dominant-negative form of RXRgamma showed decreased SREBP1c gene expression. The expression of Forkhead-O1 transcription factor (FOXO1), which can suppress the function of multiple nuclear receptors, is negatively correlated to that of SREBP1c in skeletal muscle during nutritional change. Moreover, transgenic mice overexpressing FOXO1 specifically in skeletal muscle exhibited decreased gene expression of both RXRgamma and SREBP1c. In addition, FOXO1 suppressed RXRalpha/LXRalpha-mediated SREBP1c promoter activity in vitro. These findings provide in vivo and in vitro evidence that RXR/LXR up-regulates SREBP1c gene expression and that FOXO1 antagonizes this effect of RXR/LXR in skeletal muscle.

Fish oil prevents sucrose-induced fatty liver but exacerbates high-safflower oil-induced fatty liver in ddy mice.

UNLABELLED: Diets high in sucrose/fructose or fat can result in hepatic steatosis (fatty liver). We analyzed the effects of dietary fish oil on fatty liver induced by sucrose, safflower oil, and butter in ddY mice. In experiment I, mice were fed a high-starch diet [70 energy% (en%) starch] plus 20% (wt/wt) sucrose in the drinking water or fed a high-safflower oil diet (60 en%) for 11 weeks. As a control, mice were fed a high-starch diet with drinking water. Fish oil (10 en%) was either supplemented or not. Mice supplemented with sucrose or fed safflower oil showed a 1.7-fold or 2.2-fold increased liver triglyceride content, respectively, compared with that of control mice. Fish oil completely prevented sucrose-induced fatty liver, whereas it exacerbated safflower oil-induced fatty liver. Sucrose increased SREBP-1c and target gene messenger RNAs (mRNAs), and fish oil completely inhibited these increases. In experiment II, mice were fed a high-safflower oil or a high-butter diet, with or without fish oil supplementation. Fish oil exacerbated safflower oil-induced fatty liver but did not affect butter-induced fatty liver. Fish oil increased expression of peroxisome proliferator-activated receptor gamma (PPARgamma) and target CD36 mRNA in safflower oil-fed mice. These increases were not observed in sucrose-supplemented or butter-fed mice. CONCLUSION: The effects of dietary fish oil on fatty liver differ according to the cause of fatty liver; fish oil prevents sucrose-induced fatty liver but exacerbates safflower oil-induced fatty liver. The exacerbation of fatty liver may be due, at least in part, to increased expression of liver PPARgamma.