Search

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.

Objectives: Supplementation with 6 g/day of medium-chain triglycerides (MCTs) at dinnertime increases muscle function and cognition in frail elderly adults relative to supplementation with long-chain triglycerides. However, suitable timing of MCT supplementation during the day is unknown. Design: We enrolled 40 elderly nursing home residents (85.9 ± 7.7 years) in a 1.5-month randomized intervention trial. Participants were randomly allocated to two groups: one received 6 g/day of MCTs at breakfast (breakfast group) as a test group and the other at dinnertime (dinner group) as a positive control group. Measurements: Muscle mass, strength, function, and cognition were monitored at baseline and 1.5 months after initiation of intervention. Results: Thirty-seven participants completed the study and were included in the analysis. MCT supplementation in breakfast and dinner groups respectively increased right arm muscle area from baseline by 1.1 ± 0.8 cm2 (P

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.

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

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.

Aim: The associations between dietary saturated fatty acids and the risks of stroke subtypes in cohort studies were examined by a meta-analysis of separate ethnic Japanese and non-Japanese cohorts, and causes of their difference were elucidated. Method: Log hazard ratio (HR) with 95% confidence interval (CI) of the highest versus the lowest saturated fat intake from cohort studies were weighed by an inverse variance method to combine HRs. Results: Five studies of intracerebral hemorrhage and 11 studies/comparisons of ischemic stroke were selected. A meta-analysis of intracerebral hemorrhage excluding subarachnoid hemorrhage showed a strong inverse association in Japanese (n = 3, HR = 0.55, 95% CI 0.32–0.94) but not in non-Japanese (n = 2, HR = 0.98, 95% CI 0.62–1.53). A meta-analysis of ischemic stroke showed a mild inverse association in Japanese (n = 4, HR = 0.82, 95% CI 0.71–0.93) but not in non-Japanese (n = 7, HR = 0.93, 95% CI 0.84–1.03). The effect size of saturated fat in reducing the risk of stroke in Japanese was stronger for intracerebral hemorrhage (45% reduction) than for ischemic stroke (18% reduction). Conclusions: In Japanese but not in non-Japanese, a diet high in saturated fat is associated with a low risk of intracerebral hemorrhage and ischemic stroke. This may be due to differences in the range of intake of saturated fat, genetic susceptibility, incidence of lacunar infarction, and/or confounding factors such as dietary proteins. An intervention study targeting Japanese will be required to verify the causality.

Leptin increases glucose uptake and fatty acid oxidation (FAO) in red-type skeletal muscle. However, the mechanism remains unknown. We have investigated the role of β2-adrenergic receptor (AR), the major β-AR isoform in skeletal muscle, and AMPK in leptin-induced muscle glucose uptake of mice. Leptin injection into the ventromedial hypothalamus (VMH) increased 2-deoxy-D-glucose (2DG) uptake in red-type skeletal muscle in wild-type (WT) mice accompanied with increased phosphorylation of the insulin receptor (IR) and Akt as well as of norepinephrine (NE) turnover in the muscle. Leptin-induced 2DG uptake was not observed in β-AR-deficient (β-less) mice despite that AMPK phosphorylation was increased in the muscle. Forced expression of β2-AR in the unilateral hind limb of β-less mice restored leptin-induced glucose uptake and enhancement of insulin signalling in red-type skeletal muscle. Leptin increased 2DG uptake and enhanced insulin signalling in red-type skeletal muscle of mice expressing a dominant negative form of AMPK (DN-AMPK) in skeletal muscle. Thus, leptin increases glucose uptake and enhances insulin signalling in red-type skeletal muscle via activation of sympathetic nerves and β2-AR in muscle and in a manner independent of muscle AMPK.

The combined supplementation of medium-chain triglycerides (MCTs), L-leucine-rich amino acids, and cholecalciferol (vitamin D3) increase muscle strength and function in frail elderly individuals. However, their effects on cognition are unknown. We enrolled 38 elderly nursing home residents (mean age±SD, 86.6±4.8 y) in a 3-mo randomized, controlled, parallel group trial. The participants were randomly allocated to 3 groups: the first group received a L-leucine (1.2 g)- and cholecalciferol (20 μg)-enriched supplement with 6 g of MCT (LD+MCT); the second group received the same supplement with 6 g of long-chain triglycerides (LD+LCT); and the third group did not receive any supplements (control). Cognition was assessed at baseline and after the 3-mo intervention. The difference in changes among the groups was assessed with ANCOVA, adjusting for age and the baseline value as covariates. After 3 mo, the Mini-Mental State Examination (MMSE) score in the LD+MCT group increased by 10.6% (from 16.6 to 18.4 points, p

During contractions, regulation of microvascular oxygen partial pressure (Pmvo2), which drives blood-myocyte O2flux, is a function of skeletal muscle fiber type and oxidative capacity and can be altered by exercise training. The kinetics of Pmvo2during contractions in predominantly fast-twitch muscles evinces a more rapid fall to far lower levels compared with slow-twitch counterparts. Peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α) improves endurance performance, in part, due to mitochondrial biogenesis, a fiber-type switch to oxidative fibers, and angiogenesis in skeletal muscle. We tested the hypothesis that improvement of exercise capacity by genetic overexpression of PGC-1α would be associated with an altered Pmvo2kinetics profile of the fast-twitch (white) gastrocnemius during contractions toward that seen in slow-twitch muscles (i.e., slowed response kinetics and elevated steady-state Pmvo2). Phosphorescence quenching techniques were used to measure Pmvo2at rest and during separate bouts of twitch (1 Hz) and tetanic (100 Hz) contractions in gastrocnemius muscles of mice with overexpression of PGC-1α and wild-type littermates (WT) mice under isoflurane anesthesia. Muscles of PGC-1α mice exhibited less fatigue than WT ( P < 0.01). However, except for the Pmvo2response immediately following onset of contractions, WT and PGC-1α mice demonstrated similar Pmvo2kinetics. Specifically, the time delay of the Pmvo2response was shortened in PGC-1α mice compared with WT (1 Hz: WT, 6.6 ± 2.4 s; PGC-1α, 2.9 ± 0.8 s; 100 Hz: WT, 3.3 ± 1.1 s, PGC-1α, 0.9 ± 0.3 s, both P < 0.05). The ratio of muscle force to Pmvo2was higher for the duration of tetanic contractions in PGC-1α mice. Slower dynamics and maintenance of higher Pmvo2following muscle contractions is not obligatory for improved fatigue resistance in fast-twitch muscle of PGC-1α mice. Moreover, overexpression of PGC-1α may accelerate O2utilization kinetics to a greater extent than O2delivery kinetics.

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.

The liver is a major organ of lipid metabolism, which is markedly changed in response to physiological nutritional demand; however, the regulation of hepatic lipogenic gene expression in early life is largely unknown. In this study, we show that expression of glycerol-3-phosphate acyltransferase 1 (GPAT1; Gpam), a rate-limiting enzyme of triglyceride biosynthesis, is regulated in the mouse liver by DNA methylation, an epigenetic modification involved in the regulation of a diverse range of biological processes in mammals. In the neonatal liver, DNA methylation of the Gpam promoter, which is likely to be induced by Dnmt3b, inhibited recruitment of the lipogenic transcription factor sterol regulatory element–binding protein-1c (SREBP-1c), whereas in the adult, decreased DNA methylation resulted in active chromatin conformation, allowing recruitment of SREBP-1c. Maternal overnutrition causes decreased Gpam promoter methylation with increased GPAT1 expression and triglyceride content in the pup liver, suggesting that environmental factors such as nutritional conditions can affect DNA methylation in the liver. This study is the first detailed analysis of the DNA-methylation–dependent regulation of the triglyceride biosynthesis gene Gpam, thereby providing new insight into the molecular mechanism underlying the epigenetic regulation of metabolic genes and thus metabolic diseases.

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.

The microvascular partial pressure of oxygen (Pmvo2) kinetics following the onset of exercise reflects the relationship between muscle O2delivery and uptake (V̇o2). 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 O2delivery and V̇o2at 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 Pmvo2kinetics following onset of muscle contractions. Phosphorescence quenching techniques were used to measure Pmvo2at 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 O2to avoid hypoxemia. Baseline Pmvo2before contractions was not different between groups ( P > 0.05). Both muscle contraction conditions exhibited a delay followed by an exponential decrease in Pmvo2. However, compared with WT, AMPK-DN demonstrated 1) prolongation of the time delay before Pmvo2began 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 O2consumption kinetics (i.e., oxidative phosphorylation response) and impairs the hyperemic response at the onset of contractions thereby sowing the seeds for exercise intolerance.

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-1β-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 β2-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 β2-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 β2-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.

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.

Epigenetic mechanisms are likely to be involved in the development of obesity. This study was designed to examine the role of a DNA methyltransferase (Dnmt3a), in obese adipose tissue. The gene expression of Dnmts was examined by quantitative real-time PCR analysis. Transgenic mice overexpressing Dnmt3a in the adipose tissue driven by the aP2 promoter were created (Dnmt3a mice). DNA methylation of downregulated genes was examined using bisulfite DNA methylation analysis. Dnmt3a mice were fed a methyl-supplemented or high-fat diet, and subjected to body weight measurement and gene expression analysis of the adipose tissue. Expression of Dnmt3a was markedly upregulated in the adipose tissue of obese mice. The complementary DNA (cDNA) microarray analysis of Dnmt3a mice revealed a slight decrease in the gene expression of secreted frizzled-related protein 1 (SFRP1) and marked increase in that of interferon responsive factor 9 (IRF9). In the SFRP1 promoter, DNA methylation was not markedly increased in Dnmt3a mice relative to wild-type mice. In experiments with a high-fat diet or methyl-supplemented diet, body weight did not differ significantly with the genotypes. Gene expression levels of inflammatory cytokines such as tumor necrosis factor-alpha (TNF-alpha) and monocyte chemoattractant protein-1 (MCP-1) were higher in Dnmt3a mice than in wild-type mice on a high-fat diet. This study suggests that increased expression of Dnmt3a in the adipose tissue may contribute to obesity-related inflammation. The data highlight the potential role of Dnmt3a in the adult tissue as well as in the developing embryo and cancer.

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.

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.

Caloric restriction (CR) is the most robust and reproducible intervention that can extend lifespan in rodents. Studies in invertebrates have led to the identification of genes that regulate lifespan, some of which encode components of the insulin or insulin-like signaling pathway, including DAF-16 (C. elegans) and dFOXO (Drosophila). Mice subjected to CR for 8 weeks showed an increase in FOXO1 mRNA and other longevity-related genes: Gadd 45alpha, glutamine synthase, and catalase in skeletal muscle. To investigate whether FOXO1 expression affects longevity in mammals, transgenic mice were studied that over-express FOXO1 in their skeletal muscle (FOXO1 mice), and in which muscle atrophy occurs. FOXO1 mice showed increases in Gadd 45alpha, and glutamine synthase proteins in skeletal muscle. In FOXO1 mice, the phosphorylation/dephosphorylation state of the p70 S6K and 4E-BP1 proteins were not altered, suggesting that translation initiation of protein synthesis might not be suppressed. The lifespan of FOXO1 mice was similar to their wild-type littermates. FOXO1 overexpression could not prevent aging-induced reduction in catalase, CuZu-SOD, and Mn-SOD mRNA in skeletal muscle. These data suggest that an increase in FOXO1 protein and its activation in skeletal muscle does not extend lifespan in mice.

Uncoupling protein 2 (UCP2) is a possible target molecule for energy dissipation. Many dietary fats, including safflower oil and lard, induce obesity in C57BL/6 mice, whereas fish oil does not. Fish oil increases UCP2 expression in hepatocytes and may enhance UCP2 activity by activating the UCP2 molecule or altering the lipid bilayer environment. To examine the role of liver UCP2 in obesity, we created transgenic mice that overexpressed human UCP2 in hepatocytes and examined whether UCP2 transgenic mice showed less obesity when fed a high-fat diet (safflower oil or lard). In addition, we examined whether fish oil had antiobesity effects in UCP2 knockout mice. UCP2 transgenic and wild-type mice fed a high-fat diet (safflower oil or lard) developed obesity to a similar degree. UCP2 knockout and wild-type mice fed fish oil had lower rates of obesity than mice fed safflower oil. Remarkably, safflower oil did not induce obesity in female UCP2 knockout mice, an unexpected phenotype for which we presently have no explanation. However, this unexpected effect was not observed in male UCP2 knockout mice or in UCP2 knockout mice fed a high-lard diet. These data indicate that liver UCP2 is not essential for fish oil-induced decreases in body fat.

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.

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 (PPARγ) 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 PPARγ. (HEPATOLOGY 2007.)

Peroxisome proliferator-activated receptor (PPAR) γ coactivator 1α (PGC-1α) is a coactivator of various nuclear receptors and other transcription factors whose expression increases in the skeletal muscle during exercise. We have previously made transgenic mice overexpressing PGC-1α in the skeletal muscle (PGC-1α-Tg mice). PGC-1α upregulates the expression of genes associated with red fibers, mitochondrial function, fatty acid oxidation, and branched chain amino acid (BCAA) degradation. However, global analyses of the actual metabolic products have not been investigated. In this study, we conducted metabolomic analysis of the skeletal muscle in PGC-1α-Tg mice by capillary electrophoresis with electrospray ionization time-of-flight mass spectrometry. Principal component analysis and hierarchical cluster analysis showed clearly distinguishable changes in the metabolites between PGC-1α-Tg and wild-type control mice. Changes were observed in metabolite levels of various metabolic pathways such as the TCA cycle, pentose phosphate pathway, nucleotide synthesis, purine nucleotide cycle, and amino acid metabolism, including BCAA and β-alanine. Namely, metabolic products of the TCA cycle increased in PGC-1α-Tg mice, with increased levels of citrate (2.3-fold), succinate (2.2-fold), fumarate (2.8-fold), and malate (2.3-fold) observed. Metabolic products associated with the pentose phosphate pathway and nucleotide biosynthesis also increased in PGC-1α-Tg mice. Meanwhile, BCAA levels decreased (Val, 0.7-fold; Leu, 0.8-fold; and Ile, 0.7-fold), and Glu (3.1-fold) and Asp (2.2-fold) levels increased. Levels of β-alanine and related metabolites were markedly decreased in PGC-1α-Tg mice. Coordinated regulation of the TCA cycle and amino acid metabolism, including BCAA, suggests that PGC-1α plays important roles in energy metabolism. Moreover, our metabolomics data showing the activation of the purine nucleotide pathway, malate–aspartate shuttle, as well as creatine metabolism, which are known to be active during exercise, further suggests that PGC-1α regulates metabolism in exercise. Thus, we demonstrated the roles of PGC-1α in the skeletal muscle at the metabolite level.

The relation between blood taurine (2-aminoethanesulfonic acid) concentrations and obesity was investigated. Taurine is supplied to the body by dietary ingestion as well as by de novo synthesis; it is anabolized by cysteine dioxygenase (CDO), which is abundantly expressed in liver and white adipose tissue. Overexpression of CDO in 3T3-L1 preadipocytes caused a decrease in the level of cysteine (precursor of taurine) and an increase in the level of taurine in the culture medium, suggesting that CDO is involved in biosynthesis and secretion of taurine in white adipose tissue. In high-fat diet-induced and/or genetically obese mice, a decrease in the blood taurine concentration was observed along with a decrease in CDO expression in adipose tissue but not in liver. Dietary taurine supplementation prevented high-fat diet-induced obesity with increased resting energy expenditure. Thus, taurine deficiency observed in association with obesity may create a vicious circle promoting obesity. Dietary taurine supplementation interrupts this vicious circle and may prevent obesity.

日本人のn-3系多価不飽和脂肪酸 (以下n-3系脂肪酸と略す) の摂取基準策定 (2005年版) に用いた論文をエビデンステーブル (表) として提示し, 策定の基本的な考え方を詳しく述べた。n-3系脂肪酸は一定量以下のある摂取量で皮膚炎, 成長障害が認められる必須脂肪酸であるので, 下限の設定 (最低必要量) が必要である。しかし, 報告症例が少なく, 一定量以下のある摂取量を求めることができないため, 摂取量の中央値で表される目安量を用いた。すなわち, 大部分の日本人では皮膚炎は認められていないので, 日本人の各年齢階層における男女別にみたn-3系脂肪酸摂取量の中央値を日本人の大多数で欠乏症状が認められない十分な量と考え, 目安量とした。このように安全幅が広めに設定されているため, 実際の摂取量が目安量より少なくても欠乏症状はあらわれないと思われる。n-3系脂肪酸を多く摂取すると, 虚血性心疾患罹患が少なくなることを示す欧米の報告は多い。しかし, 現在の日本人のn-3系脂肪酸摂取量の中央値は, 欧米人の検討成績の中で, 虚血性心疾患罹患率の最も低い, 最高分位のn-3系脂肪酸摂取量のグループの中央値よりも多い。このため, 日本人のn-3系脂肪酸摂取量の中央値程度を摂取していれば, 虚血性心疾患罹患率を十分低くできると考えられる。そこで, 18歳以上に対し, n-3系脂肪酸摂取量の中央値を, 目標量 (生活習慣病予防を目的とした食事摂取基準の一つ) の下限と設定した。設定された18歳以上の目標量は2.0-2.9g/day以上となる。この値は必須脂肪酸としての目安量と一致するため, 18歳以上については目標量のみの設定となっている。n-3系脂肪酸を多く摂取した場合の弊害についても検討した。出血時間の延長, LDL-コレステロール値の増加が多く報告されているが, 臨床的に問題となる出血例の増加は報告されていないし, 虚血性心疾患罹患率が増加したことを示す報告もない。このため, 今回の策定では, 目標量の上限値設定は行わなかった。しかしながら, 日本人のおもなn-3系脂肪酸摂取源である魚介類には, 水銀, カドニウムなどの重金属, ダイオキシン, PCBなどの環境汚染物質が微量ながら含まれる。食事摂取基準では, 有害物質の摂取量について取り扱っていないため, これらの影響については考慮されていない。この点を補完するために, 本稿では水銀摂取の影響についてエビデンスの収集を行い, 妊婦が魚を摂取する場合の注意点についても言及した。

運動は, 肥満や糖尿病を予防する。筋肉のAMP-キナーゼ活性が減弱したマウスの研究から, 筋肉のAMP-キナーゼが, 運動の体脂肪減少効果に必要であることがわかった。AMP-キナーゼは細胞内エネルギー不足を感知し, 糖や脂質の代謝を亢進させる酵素である。一方, 運動を繰り返すと糖輸送体GLUT4量が増加し, 運動をしないとGLUT4量は減少する。GLUT4は糖の筋肉への取り込みに関与するタンパク質で, GLUT4量増加は運動の糖尿病予防効果の主因と考えられる。ミニジーンGLUT4欠失ミュータントのトランスジェニックマウスを用いた研究から, 運動に反応するシスエレメントの存在部位も推定されている。魚の摂取は心筋梗塞を予防する。魚油のSREBP-1c活性化阻害による脂肪合成抑制, PPARα活性化による脂肪燃焼亢進作用が肝臓で認められた。SREBP-1c活性化抑制は絶食時にも認められるが, 魚油は絶食とは異なる機序でSREBP-1c活性化を阻害した。SREBP-1c活性化の阻害が, 心筋梗塞の予防に関与するかどうかは明らかでない。一方, PPARα活性化は, 血中中性脂肪低下剤フィブレートのおもな作用であり, フィブレートにも心筋梗塞予防作用があることから, 魚油の心筋梗塞予防作用は, 一部にはPPARα活性化作用を介していることが推定される。このように運動, 魚の摂取は生体でのエネルギー代謝に大きな影響を与え, 生活習慣病予防機序の一部として働いていると考えられる。これらの機序を明らかにすることは, 運動のできない人の疾病予防薬の開発, テーラーメイドの疾患予防の理論構築のために重要である。

Acyl-CoA:diacylglycerol acyltransferases (DGATs) catalyze the last step in triglyceride (TG) synthesis. The genes for two DGAT enzymes, DGAT1 and DGAT2, have been identified. To examine the roles of liver DGAT1 and DGAT2 in TG synthesis and very low density lipoprotein (VLDL) secretion, liver DGAT1- and DGAT2-overexpressing mice were created by adenovirus-mediated gene transfection. DGAT1-overexpressing mice had markedly increased DGAT activity in the presence of the permeabilizing agent alamethicin. This suggests that DGAT1 possesses latent DGAT activity on the lumen of the endoplasmic reticulum. DGAT1-overexpressing mice showed increased VLDL secretion, resulting in increased gonadal (epididymal or parametrial) fat mass but not subcutaneous fat mass. The VLDL-mediated increase in gonadal fat mass might be due to the 4-fold greater expression of the VLDL receptor protein in gonadal fat than in subcutaneous fat. DGAT2-overexpressing mice had increased liver TG content, but VLDL secretion was not affected. These results indicate that DGAT1 but not DGAT2 has a role in VLDL synthesis and that increased plasma VLDL concentrations may promote obesity, whereas increased DGAT2 activity has a role in steatosis.

Isomerized hop extract (IHE), which consists mainly of isohumulones and is required in the beer brewing process, was investigated for its effects on diet-induced obesity in two strains of mice. C57BL/6N and KK-Ay mice were fed a standard or high-fat diet containing IHE and their body and tissue weights were measured at various time points. Oral glucose tolerance tests (OGTT) and insulin tolerance tests (ITT) were carried out in high-fat diet-fed C57BL/6N mice. The effects of IHE on intestinal lipid absorption were examined in Wistar rats using a plasma triacylglycerol assay after oral administration of a lipid emulsion. Fecal lipid levels were also measured in these animals after they were fed a high-fat diet containing IHE for 15 days. The effects of IHE on pancreatic lipase activity and the expression of genes involved in hepatic lipid metabolism were also examined using an in vitro assay and quantitative RT-PCR, respectively. Supplementation of high-fat-containing chow with IHE reduced body weight gain and improved glucose tolerance in our experimental mice. A reduction in body weight gain was also observed in C57BL/6N mice fed a standard diet containing IHE. Wistar rats fed a high-fat diet containing IHE showed reduced plasma triacylglycerol levels and an increase in their fecal lipid excretion. Similarly, their pancreatic lipase activity was inhibited and their elevation in plasma triacylglycerol levels seen after the oral administration of lipid emulsion was significantly suppressed. IHE-fed mice showed an increased expression in their lipid oxidation genes and a decreased expression in genes involved in triacylglycerol biosynthesis. The inhibition of intestinal dietary fat absorption may be the mechanism by which IHE induces its weight-lowering effects in high-fat diet-fed mice. The modulatory effect of IHE on lipid metabolism may also, at least partly, be responsible for its beneficial effects on body weight gain. These results suggest that IHE may be helpful in humans in preventing diet-induced obesity and perhaps even metabolic syndrome, the latter of which is known to be associated with obesity.

Previous studies have suggested that docosahexaenoic acid (DHA), contained in fish oil, prevents brain disease. In the current study, the effect of fish oil feeding on gene expression in the brain was investigated by suppression subtractive hybridization. We found that pyruvate dehydrogenase E1 alpha (PDHE1alpha) mRNA expression is down-regulated by fish oil feeding. We examined whether the expression of PDHE1alpha mRNA is altered by DHA treatment in differentiated PC12 cells. PDHE1alpha mRNA was reduced by supplementation of DHA with a significant decrease in cellular ATP level. These results indicate that fish oil feeding might modulate energy metabolism in the brain.

日本人の食事摂取基準 (2005年版) のコレステロールに関する基本的考え方を解説した。至適コレステロール摂取量は, 疾病の罹患率, 死亡率が低くなるように, 今までの大規模観察研究や介入研究の報告を基に, 日本人のコレステロール摂取量を考慮して設定されるべきである。食事性コレステロール摂取量は血中コレステロール値に一般的には大きな影響を与えないが, 個人差があり, 欧米人に比べ, 肥満が少なく, 飽和脂肪酸摂取量の少ない日本人では, 食事性コレステロールによる血中コレステロール値の影響が欧米人に比べ, 大きい可能性がある。日本人も欧米人と同様, 血中総コレステロール値が高くても, 低くても死亡率は増加する。血中総コレステロール高値による死亡率増加はLDL-コレステロール値増加によって生じる動脈硬化が主因と考えられるが, 血中総コレステロール低値による死亡率増加は, 基盤にある消耗性疾患 (がん, 呼吸器疾患, 貧血, 感染症等) が原因と考えられる。観察研究では, 食事性コレステロール摂取量と総死亡率, 虚血性心疾患発症率, 脳卒中発症率との関連は認められていない。しかし, 日本人高齢者の糖尿病罹患率はこの5年間で増加しているため, 今後血中コレステロール値が増加すると, 糖尿病等の動脈硬化性疾患の危険因子をもった人では, 動脈硬化性疾患が増加する可能性が高い。また, 食事性コレステロール摂取量は肺がん, 消化器がん (膵臓がんや大腸/直腸がん) と正の関連を示す報告がある。以上の結果から, 多量のコレステロール摂取は好ましくなく, 成人ではコンステロール摂取量の上限値設定が必要と考えられた。

Obesity is a common and serious metabolic disorder in the developed world that is occasionally accompanied by type II diabetes, atherosclerosis, hypertension, and hyperlipidemia. We have found that mesoderm-specific transcript (Mest)/paternally expressed gene 1 (Peg1) gene expression was markedly enhanced in white adipose tissue of mice with diet-induced and genetically caused obesity/diabetes but not with streptozotocin-induced diabetes, which does not cause obesity. Administration of pioglitazone, a drug for type II diabetes and activator of peroxisome proliferator-activated receptor (PPAR)γ, in obese db/ db mice reduced the enhanced expression of Mest mRNA in adipose tissue, concomitant with an increase in body weight and a decrease in the size of adipose cells. Ectopic expression of Mest in 3T3-L1 cells caused increased gene expression of adipose markers such as PPARγ, CCAAT/enhancer binding protein (C/EBP)α, and adipocyte fatty acid binding protein (aP)2. In transgenic mice overexpressing Mest in adipose tissue, enhanced expression of the adipose genes was observed. Moreover, adipocytes were markedly enlarged in the transgenic mice. Thus Mest appears to enlarge adipocytes and could be a novel marker of the size of adipocytes.

We previously demonstrated that insulin receptor substrate 2 (Irs2) KO mice develop diabetes associated with hepatic insulin resistance, lack of compensatory beta cell hyperplasia, and leptin resistance. To more precisely determine the roles of Irs2 in beta cells and the hypothalamus, we generated beta cell-specific Irs2 KO and hypothalamus-specific Irs2 knockdown (betaHT-IRS2) mice. Expression of Irs2 mRNA was reduced by approximately 90% in pancreatic islets and was markedly reduced in the arcuate nucleus of the hypothalamus. By contrast, Irs2 expression in liver, muscle, and adipose tissue of betaHT-IRS2 mice was indistinguishable from that of control mice. The betaHT-IRS2 mice displayed obesity and leptin resistance. At 4 weeks of age, the betaHT-IRS2 mice showed normal insulin sensitivity, but at 8 and 12 weeks, they were insulin resistant with progressive obesity. Despite their normal insulin sensitivity at 8 weeks with caloric restriction, the betaHT-IRS2 mice exhibited glucose intolerance and impaired glucose-induced insulin secretion. beta Cell mass and beta cell proliferation in the betaHT-IRS2 mice were reduced significantly at 8 and 12 weeks but not at 10 days. Insulin secretion, normalized by cell number per islet, was significantly increased at high glucose concentrations in the betaHT-IRS2 mice. We conclude that, in beta cells and the hypothalamus, Irs2 is crucially involved in the regulation of beta cell mass and leptin sensitivity.

FOXO1, a member of the FOXO forkhead type transcription factors, is markedly up-regulated in skeletal muscle in energy-deprived states such as fasting and severe diabetes, but its functions in skeletal muscle have remained poorly understood. In this study, we created transgenic mice specifically overexpressing FOXO1 in skeletal muscle. These mice weighed less than the wild-type control mice, had a reduced skeletal muscle mass, and the muscle was paler in color. Microarray analysis revealed that the expression of many genes related to the structural proteins of type I muscles (slow twitch, red muscle) was decreased. Histological analyses showed a marked decrease in size of both type I and type II fibers and a significant decrease in the number of type I fibers in the skeletal muscle of FOXO1 mice. Enhanced gene expression of a lysosomal proteinase, cathepsin L, which is known to be up-regulated during skeletal muscle atrophy, suggested increased protein degradation in the skeletal muscle of FOXO1 mice. Running wheel activity (spontaneous locomotive activity) was significantly reduced in FOXO1 mice compared with control mice. Moreover, the FOXO1 mice showed impaired glycemic control after oral glucose and intraperitoneal insulin administration. These results suggest that FOXO1 negatively regulates skeletal muscle mass and type I fiber gene expression and leads to impaired skeletal muscle function. Activation of FOXO1 may be involved in the pathogenesis of sarcopenia, the age-related decline in muscle mass in humans, which leads to obesity and diabetes.

The peroxisome proliferator-activated receptors (PPARs) are dietary lipid sensors that regulate fatty acid and carbohydrate metabolism. The hypolipidemic effects of fibrate drugs and the therapeutic benefits of the thiazolidinedione drugs are due to their activation of PPARalpha and -gamma, respectively. In this study, isohumulones, the bitter compounds derived from hops that are present in beer, were found to activate PPARalpha and -gamma in transient co-transfection studies. Among the three major isohumulone homologs, isohumulone and isocohumulone were found to activate PPARalpha and -gamma. Diabetic KK-Ay mice that were treated with isohumulones (isohumulone and isocohumulone) showed reduced plasma glucose, triglyceride, and free fatty acid levels (65.3, 62.6, and 73.1%, respectively, for isohumulone); similar reductions were found following treatment with the thiazolidinedione drug, pioglitazone. Isohumulone treatment did not result in significant body weight gain, although pioglitazone treatment did increase body weight (10.6% increase versus control group). C57BL/6N mice fed a high fat diet that were treated with isohumulones showed improved glucose tolerance and reduced insulin resistance. Furthermore, these animals showed increased liver fatty acid oxidation and a decrease in size and an increase in apoptosis of their hypertrophic adipocytes. A double-blind, placebo-controlled pilot study for studying the effect of isohumulones on diabetes suggested that isohumulones significantly decreased blood glucose and hemoglobin A1c levels after 8 weeks (by 10.1 and 6.4%, respectively, versus week 0). These results suggest that isohumulones can improve insulin sensitivity in high fat diet-fed mice with insulin resistance and in patients with type 2 diabetes.

Ablation of GLUT4 in adipose tissues results in whole body insulin resistance and high-fat feeding down-regulates GLUT4 mRNA in white adipose tissues. Previous studies demonstrated that adipose tissue specific element(s) (ASE) of the murine GLUT4 gene is located between -551 and -442 relative to transcription start site and that high-fat responsive element(s) (HFRE) for down-regulation of the GLUT4 gene is located between bases -1001 and -442. To further characterize these regulatory elements, the regulation of GLUT4 minigenes containing -701, -551, and -506 bp of 5(')-flanking region was studied in transgenic mice. GLUT4 minigene mRNA from -506 transgenic mice did not express in adipose tissues, indicating that ASE located within 45 bp is located between bases -551 and -506. An 80-kDa of nuclear DNA binding protein was found to bind to a -TCCTCGTGGGAAGCG- element located between bases -551 and -537. High-fat diet feeding down-regulated GLUT4 minigene mRNA in -701 transgenic mice, but not in -551 transgenic mice, indicating that HFRE is located within 150 bp between bases -701 and -551 of the GLUT4 gene and is distinct from ASE.

A well balanced body energy budget controlled by limitation of calorie uptake and/or increment of energy expenditure, which is typically achieved by proper physical exercise, is most effective against obesity and diabetes mellitus. Recently, peroxisome proliferator-activated receptor (PPAR) γ, a member of the nuclear receptor, and its cofactors have been shown to be involved in lipid metabolism and in the control of energy expenditure. Here we show that PPARγ coactivator 1 (PGC-1) β functions as ERRL1 (for ERR l igand 1 ), which can bind and activate orphan ERRs (estrogen receptor-related receptors) in vitro . Consistently, PGC-1β/ERRL1 transgenic mice exhibit increased expression of the medium-chain acyl CoA dehydrogenase, a known ERR target and a pivotal enzyme of mitochondrial β-oxidation in skeletal muscle. As a result, the PGC-1β/ERRL1 mice show a state similar to an athlete; namely, the mice are hyperphagic and of elevated energy expenditure and are resistant to obesity induced by a high-fat diet or by a genetic abnormality. These results demonstrate that PGC-1β/ERRL1 can function as a protein ligand of ERR, and that its level contributes to the control of energy balance in vivo , and provide a strategy for developing novel antiobesity drugs.

Lipoprotein lipase (LPL) plays a role in lipid usage in skeletal muscle by hydrolyzing plasma triglycerides into fatty acids, which are further utilized for β-oxidation. Lipid usage is stimulated during fasting, diabetes mellitus and exercise, concomitant with enhanced LPL expression in skeletal muscle. Here we show that the forkhead type transcription factor FKHR is strongly induced in skeletal muscle in fasting mice, in mice with streptozotocin-induced diabetes and in mice after treadmill running. Ectopic expression of FKHR enhanced LPL gene expression in C2C12 muscle cells in culture. These results implicate FKHR as an important modulator of lipid metabolism in skeletal muscle.

Objectives In spite of accumulating evidences suggesting an inverse association between insulin resistance and plasma B-type natriuretic peptide (BNP) levels, the effect of daily physical activity on plasma BNP in individuals with glucose intolerance remains unknown. We investigated the association of physical activity level (PAL) with plasma BNP in patients with impaired fasting glucose, impaired glucose tolerance and type 2 diabetes. Design Cross-sectional study. Setting Outpatients visiting the National Center for Global Health and Medicine Kohnodai Hospital. Participants A total of 60 patients with glucose intolerance who did not take any hypoglycaemic agents, cholesterol-lowering agents and antihypertensive agents were recruited. Patients who were diagnosed as having heart failure and renal impairment, engaged in sports-like exercise and resistance training were excluded. Primary outcome measures PAL was objectively measured by a triaxial accelerometer. The association between PAL and plasma BNP levels was assessed by multiple regression analysis. Results PAL was positively correlated with plasma BNP levels (r=0.296, p=0.021). PAL was still significantly correlated with plasma BNP levels after adjustment for age (β=0.290, p=0.014), and adjustment for age and body mass index (β=0.282, p=0.018). Plasma BNP levels were inversely correlated with serum insulin levels (r=−0.350, p=0.006) and homeostasis model assessment-estimated insulin resistance (HOMA-IR; r=−0.363, p=0.004). Serum insulin levels (mean±SD, 8.1±6.4 μU/mL) and HOMA-IR (2.4±1.9) in the high-BNP group were significantly lower than those (11.2±7.4 μU/mL and 3.7±3.0, respectively) in the low-BNP group. Conclusions Our findings propose the possibility that plasma BNP may be increased by daily physical activity and BNP is associated with insulin resistance.